There can be few other mathematical models in any branch of engineering which are so well suited to computer solution and that have prompted the development of so many truly different algorithms. Since the late 1950s, hardly a year has gone by without the publication of at least one (and usually more than one) new algorithm. The evolution of algorithms for solving the MESH equations has been influenced by, among many other things, the availability (or lack) of sufficient computer storage and power. Not so very long ago a distillation column simulation had to be performed on a mainframe or mini computer. However, the remarkable increase in the capabilities of personal computers throughout the 1980s has meant that distillation columns often can be more effectively simulated on such machines.
Our own interest in computer simulation in general and of distillation in particular is due in part to the fact that we find distillation calculations quite fascinating. We are involved with students who need to simulate distillation operations either as part of a course on separation processes or as part of a large scale design project that all students must do in their final year of study. In the past these design studies were performed with simulation systems that were installed on a mainframe computer.
In our view, much of the software capable of solving distillation problems that existed when we were planning ChemSep was not suitable for use in the first undergraduate course that deals with stagewise separation processes. For one thing, the comprehensive flowsheeting packages of the time lacked interfaces that were as easy to use and as flexible as we thought they could be. In addition, very few such programs could be run on the kinds of computers that students might possess. Finally, most such programs were not available at prices low enough for students to acquire their own copy.
With these (and other) thoughts in mind Arno Haket and ourselves began the ChemSep project in February 1988 at the University of Technology in Delft (TU Delft) in The Netherlands. Version 0.92 of ChemSep was first introduced to graduate and undergraduate level students at Delft in September 1988 by Professor Hans Wesselingh of the TU Delft (he moved to the RijksUniversiteit Groningen in The Netherlands). The use of ChemSep by Professor Hans in the courses he taught was of enormous value to us in improving the programs.
As a result of the success enjoyed by the program during those first courses at Delft, we continued to develop ChemSep. A series of improved versions (numbered 1.0 to 1.5) was developed by Arno Haket and Harry Kooijman in Delft and Ross Taylor in Potsdam, New York. This development would have been difficult if it were not for the international computer networks that allowed us to hold intercontinental computerised conversations. Many pages of electronic mail testify to our progress (and lack of progress) over the last few years. We find it interesting to look back on our mail and discover the things that we argued about so long ago in our efforts to make things "just right".
In March 1991 we began writing ChemSep 2.0. This version is a completely new set of programs and data files with many new and improved features. Version 2.0 was first used in courses at the University of Amsterdam and at Clarkson University in Potsdam, New York in September 1991.
Some of the features of ChemSep include:
ChemSep 2.0 is the result of too many hours of coding, testing and recoding. It consists of several executable files plus a number of small data files for recording various bits and pieces of information. The driver and interface are written in Borland Pascal (version 7.0) and involve over 50,000 lines of code. The flash and column simulation programs are written in standard Fortran 77. The source code is also over 50,000 lines in length. The code has been developed on mostly PC's with the help of the Multi-Edit programmers editor and WATCOM F77 and F77/386 compilers (versions 10.5). The source code for the column and flash calculations has also been succesfully compiled (unchanged) and executed on a VAX 11/750 and on Sun Workstations. Several of the executable files have been compressed using a public domain utility called LZEXE written by Fabrice Bellard of France. We try to improve the ChemSep software as time permits. We welcome your suggestions for new features and improvements and will try to incorporate as many of your ideas as possible.
Our thanks above all to Professor Hans and to Peter Verheijen who contributed in many ways. Our thanks also to our friends and colleagues at universities in The Netherlands and in the USA who have used earlier versions of ChemSep in their courses or who have tested the program for us. Last, but not least, our thanks to the many students on both sides of the Atlantic Ocean that were forced to use this program or risk failing one of their required courses.
Ross Taylor and Harry Kooijman, 1998
WATCOM F-77 and F-77/386 are products of WATCOM Inc. Borland Pascal is a product of Borland International Inc. Multi-Edit is a product of American Cybernetics.
ChemSep User's Guide
This User's Guide was initially prepared using Word Perfect 5.1 (Word Perfect Corp.) and is now translated to HTML for viewing "online" in a web browser. Key strokes are printed in italics, F5 for example. Bold Face words are used to indicate key words or phrases. With few exceptions, bold face words represent topics that are described elsewhere in the User's Guide. Bold face words often represent words displayed on screen by the ChemSep interface. The name of our software is printed in bold face and italic!
The authors would like to extend their thanks to Sharon Sweeney for reading this document. Any remaining typographical and grammatical errors are, of course, hers!
ChemSep User's Guide
The opening screen identifies the name of program in large bright letters that can be seen from a great distance. We made the opening screen look like this so that anyone who can see your computer screen will know exactly what program you are about to run. The screen lets you know our names and which version of ChemSep you are using. Any limits on the size of problem you can solve with this version of the software are displayed here as well.
Now, do what it says at the bottom of the opening screen and press Any key. Don't worry if your keyboard does not have an Any key, just press some other key instead (but not the Shift, Alt or Ctrl keys) to see the following (extremely boring) screen.
In fact, what you see above the line with the ChemSep v3.60 label is ChemSep's Main menu which is fully described in Chapter 4. At the bottom of the screen is the F-key bar listing the uses of some of the F-keys (as many of them are listed here as we could squeeze in). The F-keys, along with other keyboard assignments, are described in Chapter 3.
cs deproptyped at the system prompt would cause ChemSep to execute and to display the opening screen shown above. However, when Any key was pressed, ChemSep would immediately load the file DEPROP.SEP. If the file contained a solved problem, ChemSep would immediately jump to the Results menu.
There are two command line switches that ChemSep recognizes. Although none of them is necessary to developing a mastery over the program, you may find them useful on occasion.
/k causes ChemSep to execute a Macro that follows. For example:
cs deprop /kisf
jumps to the feed spreadsheet after the startup screen has been
cleared.
/o causes ChemSep to start with a specific configuration (CNF) file. For example:
cs /oset2.cnf
causes ChemSep to load its configuration from the file SET2.CNF.
Notethatyoumustnotuseanyspaces between the switch and the character
string that follows it. In place of the / character used to identify
the switch, you may use - or char '134. For example, the following
three command lines are all equivalent:
cs deprop /kisf cs deprop -kisf cs deprop \kisfThe latter was added to keep unix fans happy.
ChemSep User's Guide
With these seven keys you can go anywhere in the ChemSep interface. Other keys that perform special functions include:
Each menu item has one of its letters highlighted. Pressing that letter will execute the corresponding option. In the illustration above, pressing I while in the main menu would result in the screen image shown. Also, one option in the menu will be under the cursor. When the cursor is on the option you wish to select, press Enter. The arrow keys, as well as Home and End, move the cursor according to the following rules:
The Return option is part of ChemSep's autopilot that will take you through the next option in a predefined sequence. In many cases, the Return option acts in much the same way as Escape except that the cursor may be located in a different place. In the above screen, for example, Escape would clear the specifications menu and leave the cursor on the specifications option in the input menu. The Return option will also go back to the input menu but the cursor will be located one line down on the solve option because that is the next option in the input sequence. In some submenus the Return option may jump to a different branch of the menu tree. Pressing R (or locating the cursor on Return and pressing Enter) will exercise the Return option.
There are a few subtle differences between menus and lists that must be explained. Lists may be distinguished from menus by the lack of highlighted letters. Also, it is possible that not all of the list will fit in the window. It should always be obvious if the list cannot be contained in the displayed window because the word More will appear at the bottom right corner and/or in the top right corner of the list box. The following keys are useful in lists:
This particular spreadsheet serves to illustrate the various features
of ChemSep's spreadsheets. Numerical or character data is entered in
fields. In the spreadsheet shown above the data entry fields are those
in the right hand column. Usually, there will be a label to the left
of the data entry field that identifies or explains the entry to its
right. Some spreadsheets have more than one column of data entry
fields. The feed spreadsheet has a number of columns equal to the
number of feeds.
Many ChemSep spreadsheets have action fields in a line at the bottom
of the spreadsheet. In this example we may Insert a second feed (this
would result in an additional column being inserted in the
spreadsheet, Delete the feed we already have (not a good idea here) or
Return to the previous screen. To exercise these actions place the
cursor on the relevant field and press Enter.
Some of ChemSep's spreadsheet fields require you to press
Enter to bring up a list of options from which you must select
one. The State field is of this kind.
Many of ChemSep's spreadsheets have semi-active fields. That is, a
particular field may not be available in all cases. The three fields
adjacent to the labels Pressure, Vapour fraction and Temperature are
semi-active fields. Only two of these fields are active at any time,
which two depends on the field State.
The following keys are used to move around a spreadsheet:
It may sometimes be more convenient to change an existing data entry.
With the cursor on the relevant field, press Enter to get into
Edit mode. An asterisk (*) in a spreadsheet field indicates an Unset
parameter. With the cursor on a spreadsheet field displaying a *,
press Enter to display the default value and Enter
again to accept it.
In addition to the alpha-numeric keys, the following keys can be used
in a spreadsheet data entry field:
Here are some examples of numerical formula entry:
Formula entry can be useful in the feed spreadsheet where you are
asked to enter the component flows. Perhaps you know the total flow
rate and the mole fractions rather than the component flows. Instead
of using your calculator to compute the component flows, you can let
ChemSep do the calculations for you. By way of an example consider a
column with a feed flow of 573 mol/s containing 36.5 mole percent
ethanol, the rest being water. The component feed flows of ethanol and
water could be typed in as:
ChemSep recognizes the standard prefixes for multiples of 10. For
example:
A numerical formula and a unit string can be entered in the same field
at the same time. All results of formula and unit entry are displayed
in the default set of units.
Notice the prompt box with the invitation to type in the file mask. A
default response, *.SEP, is already available. Pressing Enter
after the prompt for a file mask or by entering wild cards (* and ?)
in the file name prompt box followed by Enter will bring up a
directory of all files meeting the desired file specification. For
example: Typing L*.sep and pressing Enter will bring
up a list of all files with the .SEP extension beginning with the
letter L. Entering *.* after the prompt for a file mask will
bring up a directory of ALL files in the current directory. If
the default response is accepted you will see a screen that looks
something like this:
Pressing any key with a letter or number will make the cursor jump to
the next file or directory whose name begins with that letter. If no
match has been found by the end of the list the search begins again
from the top of the directory list. When you have the name of the data
file you wish to Load, Save, View,or Edit under the cursor, press
Enter.
Rarely are the entire contents of a Table or file displayed in a
single view window. The following keys are useful in a view window:
ChemSep User's Guide
Press Escape to clear any Help message. A second press of F1 while the
help window is displayed brings up the index to the Help system.
The Help system is extensively cross-referenced. Many help messages
and the help index contain one or more words printed in inverse video.
These are keywords and you may use the arrow keys to place the cursor
over one of these keywords. Press Enter to display a new help message
that relates to the highlighted keyword.
F2 displays the last help message shown on screen. ChemSep
remembers the last 16 help pages shown and repeated pressing of
F2 will cause one of the last sixteen help messages to be dislayed
in turn.
A prompt box appears below the Load option asking you for the name of
the file to load. The prompt box contains the default file mask,
*.SEP. SEP is the default extension used by ChemSep for all problem
files. Press Enter to bring up a Directory list of all files
with the extension SEP.
If you know the name of the file you wish to load, type it in the
prompt box. The default file mask will disappear and the file name
being typed will appear in its place. When you have typed in the
complete name including the file extension, press Enter to
load it. If the file has no extension you must end the file name with
a period (.). Consult the section on the Directory facility of ChemSep
for more information on using directory lists to select the file you
wish to load.
The only difference between F4 and the Save option of the File
menu is that Save always prompts you for a file name (mask). F4 only
asks for a file name if no name has been entered. With F4 the prompt
box will appear on the screen close to the last location of the
cursor. Also, when the file has been saved, the cursor will return to
screen location it had prior to the press of F4.
In the left hand column is the name of the quantity whose units you
can set. To the right is the currently selected unit. To change a
currently selected unit use the cursor control keys to move to the
unit you wish to change. Press Enter to display a list of
alternative units that ChemSep recognizes. Use the cursor keys (or
first letters) and Enter to choose the new unit. All
quantities that require this unit will be displayed in the newly
selected unit until you change it again. Selected units are saved in
ChemSep files so the currently selected units may be changed when you
load another file.
Let us illustrate with a specific example. Below is the screen image
of the stream summary table for the Depropanizer example discussed in
Chapter 9 of this User's Guide. In the original problem statement
flows were specified in mol/s, temperatures in Celcius, pressures in
bar, and Enthalpy in kJ/kmol.
To change the Flow Units, press F5 to bring up the Units
spreadsheet. Move the cursor to Flow and press Enter. A list
of alternative units will appear, from whcih we select lbmol/s. In a
similar way change the temperature units to degrees F, the pressure
units to psia, and the enthalpy units to Btu/lbmol. Press
Escape to clear the Units spreadsheet and display the stream
summary in the new set of units. Here is the same stream summary table
in the new set of units:
Press Enter to bring up a Directory list of all files in the
current directory. If you know the name of the file you wish to view,
type it in the prompt box. The default file mask will disappear and
the file name being typed will appear in its place. When you have
typed in the complete name including the file extension, press Enter
to View it. If the file you wish to view has no extension you must end
the file name with a period (.). Consult the section on the Directory
facility of ChemSep for more information on using directory lists to
select the file you wish to view. Press Escape to clear the view
window. The cursor will return to the same location prior to the press
of F7.
The last item in the list are the solve options which are assigned
default values. These are set in the option file which was loaded at
the start of ChemSep (they are saved for each sep-file though!). Here
is an example of a summary screen after the components have been
selected. This particular screen image was obtained while setting up
the Depropanizer illustrative example from Section 10 of this User's
Guide.
Notice the list of components is shown but the other main entries,
Operation, Properties, and Specifications, remain empty. The problem
has also been given a name, TEST.SEP, as indicated on the file name
line.
All the keys available to a View window may be used in a Summary
screen to scroll, Edit, or print the contents of the window. In fact,
it is now necessary to scroll this View window in order to see what
items remain unspecified. The complete summary can be printed and, at
this point in the Input, is reproduced below. Notice the asterisks (*)
that indicate an unspecified item. Also, the Condenser and Reboiler
items remain unspecified. The complete summary specification for this
example is provided in Section 10.
Each macro consists of a sequence of highlighted letters, special
symbols, and key codes. The letters are the ones highlighted in each
menu item. Do not use spaces when entering a new sequence of
characters. You may include Escape and Enter, using
the special symbols shown below. When you have completed the string
press Enter. The new key assignments can be made available
every time you run ChemSep by saving the setup in the "Save options"
item of the Options menu.
The main menu has the following branches:
The file menu contains the following items:
The first four items of the Input menu are concerned with entering
data:
The three items are:
In this case the Results menu is a list of the kinds of Tables that
ChemSep can display for flash problems.
The items in this branch of the main menu are:
ChemSep User's Guide
The File menu can be reached from anywhere in ChemSep using either
F10, F or with
<> .
<> The File menu contains the following items:
A prompt box appears below the Load option asking you for the name of
the file to load. The prompt box contains the default file mask,
*.SEP. SEP is the default extension used by ChemSep for all problem
files. Press Enter to bring up a Directory list of all files
with the extension SEP.
If you know the name of the file you wish to load, type it in the
prompt box. The default file mask will disappear and the file name
being typed will appear in its place. When you have typed in the
complete name including the file extension, press Enter to
Load it. If the file has no extension you must end the file name with
a period (.) otherwise the default extenision, .SEP, is appended.
Consult Directory facility for more information
on using directory lists. F3 jumps directly to the Load option
of the File menu from anywhere in the interface (unless defined
differently under macro's).
The prompt box contains the default file name, NewFile. Type in a new
file name and press Enter if you don't want to use the default
name. All files are given the extension SEP unless you type in a
period (.) followed by an alternative extension. If any existing Input
had been changed but not saved you will be asked if you wish to save
the old Input before the data is reset and the results cleared.
The prompt box contains the default file mask, *.SEP. SEP is the
default extension used by ChemSep for all problem files. Press
Enter to bring up a Directory list of all files with the extension
SEP. Use the cursor control keys to locate the cursor on the name you
wish to use. Press Enter to overwrite the existing file with
the new data. You will be asked to confirm that you wish to overwrite
an old file.
If you don't wish to overwrite an old file simply type a new name in
the prompt box. The default file mask will disappear and the file name
being typed will appear in its place. When you have typed in the
complete name including the file extension, press Enter to
Save it. The file will be given the extension SEP unless you end the
file name with a period (.). Consult Directory
facility for more information on using directory lists.
F4 can also be used to Save the current Input data in a file.
F4 can be pressed anywhere in the interface. Pressing
F4 will result in the immediate overwriting of your file. If no
file name has been given you will be asked to provide one in a prompt
box similar to the one shown above. The only difference is that the
prompt box will appear on the screen close to the last location of the
cursor. Also, when the file has been saved, the cursor will return to
the same location prior to the press of F4.
The prompt box contains the current directory name terminated by char
'134*. Press Enter to bring up a Directory list of directories
on your disk. Use the cursor keys to walk around the directory tree on
your disk. Press Enter when the cursor is over the name of the
directory to which you wish to move. If you know the name of the
directory to which you wish to move, type it in the prompt box. The
default directory name will disappear and the directory name being
typed will appear in its place. When you have typed in the complete
name press Enter to change to that directory. Consult Directory facility for more information on using
directory lists.
If you know the name of the file you wish to view, type it in the
prompt box. The default file mask will disappear and the file name
being typed will appear in its place. When you have typed in the
complete name including the file extension, press Enter to View it. If
the file you wish to view has no extension you must end the file name
with a period (.). Consult the section on View
Windows for further details of how to move around.
F7 can also be used to View a file. F7 can be pressed
anywhere in the interface. Pressing F7 will result in the
display of a prompt box similar to the one shown above. The only
difference is that the prompt box will appear on the screen close to
the last location of the cursor. Also, when the view window has been
cleared (by pressing Escape), the cursor will return to the
same location prior to the press of F7.
If you know the name of the file you wish to edit, you may type it in
the prompt box. The default file mask will disappear and the file name
being typed will appear in its place. When you have typed in the
complete name including the file extension, press Enter to Edit it. If
the file you wish to view has no extension you must end the file name
with a period (.). Consult the section on Edit
Windows for further details of how to move around in and edit a
file displayed in an Edit Window.
If you know the name of the file you wish to copy, type it in the
prompt box. The default file mask will disappear and the file name
being typed will appear in its place. When you have typed in the
complete name including the file extension, press Enter. If
the file you wish to copy has no extension you must end the file name
with a period (.).
A second prompt box will appear asking you for the name to be given to
the copy of the file. Type in the new name and press Enter.
You will be asked to confirm that you wish to copy the file. Press
Y to agree to this suggestion and initiate the copying process.
Press N if you don't want to copy the file. Consult Directory facility for more information on using
directory lists.
A prompt box appears below the Rename option asking you for the name
of the file you wish to rename. The prompt box contains the default
extension *.*. Press Enter to bring up a Directory list of all
files in the current directory. Use the cursor keys and Enter to
select the name of the file you wish to rename. If you know the name
of the file you wish to rename, type it in the prompt box. The default
file mask will disappear and the file name being typed will appear in
its place. When you have typed in the complete name including the file
extension, press Enter. If the file you wish to rename has no
extension you must end the file name with a period (.).
A second prompt box will appear asking you for the new name to be
given to the file. Type in the new name and press Enter. You will be
asked to confirm that you wish to give the selected file a new name.
Press Y to agree to this suggestion and rename the file. Press
N if you don't want to give the file a new name. Consult Directory facility for more information on using
directory lists.
The prompt box contains the default extension *.*. Press Enter to
bring up a Directory list of all files in the current directory. If
you know the name of the file you wish to erase, type it in the prompt
box. When you have typed in the complete name including the file
extension, press Enter. If the file you wish to delete has no
extension you must end the file name with a period (.).
You will be asked to confirm that you wish to erase the selected file.
Press Y to agree to this suggestion and rename the file. Press
N if you don't want to give the file a new name. Consult Directory facility for more information on using
directory lists.
Under no circumstances should you use this option to terminate your
ChemSep session. Shelling to DOS leaves a portion of memory tied up
with a program that will restore ChemSep when you "exit" the shell. To
quit ChemSep use the Exit.
ChemSep User's Guide
This menu may be reached from anywhere in the ChemSep interface using
either F10, I or Alt-I. The first four items of the
input menu are concerned with entering data:
Select Components using the cursor keys and Enter or by pressing the
highlighted letter, C. The screen will look like this:
The box in the upper right hand corner lists the components that have
already been selected. If this is a new problem (or if all previously
selected components have been deleted) the box contains the word None.
The menu lists the actions you can perform.
After the accepting the default library (CHEMSEP1.PCD) or when
searching for all PCD files (the default setting) a new menu will
appear:
The new menu lists the ways in which it is possible to find components
in ChemSep's databanks.
This is an example of a list that was created using the Search by
Class option. All components in the class Alkanes are listed in a
window on the screen. Component(s) can be added to the selected list
using the cursor control keys to position the cursor on the name of
the component you wish to select and pressing Enter. The names
of the selected components are displayed in the window on the upper
right of the screen. ChemSep will prevent you from loading the same
component more than once.
If the list contains more names than can fit on the screen the word
"More" appears at the bottom of the list. As you scroll down the list
using the cursor control keys, the word More will appear at both the
bottom and the top of the list. You will know when you have reached
the end of the list because the cursor will not go any further and the
word More appears only at the top. As in all ChemSep lists, you can
use PgUp, PgDn, Home, End to move more
quickly through the list. You may also type a few characters to move
directly to the first line with a component name that matches the
characters you typed.
By default, ChemSep lists the components in the order they appear in
the datafile. To see the list in order of the last criterion selected
you must go to the Interface item of the Options menu and turn on Sort
lists.
Component lists contain, in addition to component names (and other
information depending on the search criteria), two, or possibly three,
other lines. The additional lines of the component list are ->
Previous Search, -> Begin again, and -> additional
search. The purpose of these items is to allow you to refine the
list of components if the displayed list is too long to search by hand
or does not include the components you want. Press Esc to
clear the component list when all components have been loaded.
First, we used Search by Family to list the components in the databank
that are n-Alkanes. After that we used the "additional search" and
"search by property" to list those components that have a Normal
Boiling Point between 300 and 400 K.
Type in the prompt box the name (or any part of the name) of the
component(s) you wish to load and press Enter. ChemSep will
search its databanks and display a list of all components whose names
contain the string you entered in the prompt box. For example, typing
eth in the prompt box and pressing Enter will bring up
a list containing methane, ethane and ethanol as well as any other
components whose name contains the string eth. If you do not type
anything at all in the prompt box and press Enter, ChemSep
will display a list of the names of all the components in the
databank(s).
and select Search. Notice that the list displays the index
numbers to the left of the component names.
Notice that the list displays the structural formulae to the right of
the component names.
For example, if we select the "vapour pressure" ChemSep displays the
following prompt box:
prompting you to specify the minimum and maximum values of the
property selected. Move the cursor to the Search keyword and press
Enter to begin the search. Property searches may be conducted in
any of the units recognized by ChemSep. For properties that are a
function of temperature you will also need to provide the temperature
at which the property is to be evaluated. The search on components
with a vapour pressure between 1.0 and 1.3 bar at 100 C as specified
above results in:
A list of properties that can be used in a Search by Property Value
follows:
None of the Input information for the other components is lost by this
action. Results, however, while retained until you Solve the problem
again, do not pertain to the current set of components and are not
Saved in the problem file.
Use Reorder as many times as you need until you see the components in
the order you like them to remain. None of the Input information for
any of the components is lost by this action. Results, however, while
retained until you Solve the problem again, do not pertain to the
current ordering of components and are not Saved in the problem file.
The menu contains the following items:
Any flash should have at least one feed in order to calculate anything
useful. The maximum number of feeds is 10. After entering the number
of feeds for the flash and ChemSep continues to the property model
selection.
The nonequilibrium column and dynamic column option also use the
column spreadsheet for defining the column configuration. The
asterisks (*) indicate the fields that must be completed:
Type numbers in the Stages, Feed stages and Sidestream stages fields.
The last named is optional and may be left empty if the column has no
Sidestreams. Multiple feeds and sidestreams must be separated by a
space or by a comma. For example, if a column has two feeds to stages
12 and 25 the Feed stages line of the Operation spreadsheet should
look like this:
The cursor keys (Up, Down, Home, End) and Enter may be used to select
the operation type. The operation types determine the basic column
configuration and the K-models available. A brief summary of each
operation type as it is understood by ChemSep is given below:
The basic Condenser types are as follows:
The basic Reboiler types are as follows:
The flowsheet shows the column with the feeds and side streams as well
as the top and bottom products, selected reboiler and condenser, and
possible pumparounds. Upon completion of the operation configuration
select the Return option and ChemSep continues to the property
model selection.
The menu contains three options: Thermodynamic models,
Physical Properties and Load data. The first option lets
you select the thermodynamic models and the second the physical
property models. The latter is only required for nonequilibrium column
simulations and therefore, will not be present for flash or
equilibrium columns. The Load data option prompts you for necessary
property model data such as interaction parameters for equations of
state etc.
The validity of any results obtained with a program like ChemSep
depends on the proper selection of thermodynamic models and their
parameters. This Users Guide will not go into the technical merits of
the methods available in ChemSep. There is on-line Help available (by
pressing F1) and a technical reference file that can also be
viewed within ChemSep (with F9) that covers some basic
thermodynamics. In the rather likely event that there is insufficient
information available in the on-line help and information files we
strongly suggest you consult a thermodynamics textbook or your
friendly neighbourhood thermodynamicist (is that last word spelled
correctly). For the thermodynamically perplexed we recommend the
following sources of information:
Upon selecting the thermodynamic models option, you will see the above
window for regular columns where we contact a vapor with a liquid. The
asterisks indicate the models that need to be specified. The K-model
and enthalpy model are always needed whereas the other model
selections are only required if you select property models that use
them. After completion of the model selection
Each item in this menu represents a method of computing K-values:
Each of the options in this list represents a model for calculating
activity coefficients:
This menu appears only if EOS, Gamma-Phi or DECHEMA were selected as
K-models. Each of the options in this menu represents a model for
calculating fugacity coefficients for the vapour phase. Liquid
fugacities can only be calculated with cubic equations of state and,
therefore, they are the only available models if the EOS K-model was
selected.
The two-term virial equation is included in ChemSep:
Pv/RT=1+B. The virial model is useful for nonideal chemical
mixtures at low and moderate pressures (up to a few atmospheres).
Cubic equations of state are very widely used for computing properties
of mixtures. They are most often used for hydrocarbon mixtures (with
or without light gases) but extensions now being developed may mean
that we will soon be using this class of model for non-ideal phase
equilibrium calculations.
There are five models available in ChemSep for computing the Vapour
Pressure:
ChemSep incorporates the following methods for estimating the
enthalpy:
All the asterisks indicate unspecified models. Unlike to the
thermodynamic models, it is possible to leave the models for the
physical properties unselected! ChemSep uses a default selection of
models which is sufficient for most purposes. This selection will
depend on the selected components and operating conditions. To force a
default selection of models use the Default option on the bottom of
the screen:
You can now alter this selection by selecting each specific property.
Each has its own models associated with it. Only the selection of the
liquid diffusion coefficients is a bit different as you specify a
model for each binary component pair individually:
If left unspecified the Wilke-Chang method is default method. The
available models for liquid diffusivities are:
If you select the default option, binary diffusivity supplied, you can
enter a constant diffusivity (0 indicates no diffusivity selected!)
for the component pair.
Models (or classes of models) that might appear in the Load Data menu
include:
where, for example, the interaction parameters for the
Peng-Robinson are defined. Note that all the parameters are
left unspecified (asterisks). If you do not enter any
interaction parameters they are assumed to be zero during the
simulation. The interaction parameters can be read from a
library. Selecting the library option gives a listing of the
available interaction parameter libraries:
where the Peng-Robinson library (PR.IPD, an ASCII text file) is
preselected automatically. if you select this file then ChemSep
reads it and scans for parameters appropiate for the selected
components (using the component index numbers). If any
parameters are found a listing will be shown or an error
message:
As can be seen from this list, multiple interaction parameters
for the same pair of components can be present. All the
parameters are selected to be loaded by default, which will
result into loading the second interaction parameter (0.0374)
for C2/nC4 instead of the first one (0.0089). To (un)select use
the space bar. After the selection of the parameters load them
by pressing Enter. Note that the selected parameters
will be set regardles whether they were previously specified.
The cubic equations also contain a correlation option. Any
unspecified interaction parameter is calculated through a
correlation (see the help how this is done).
Upon selecting the library option you get a listing of the
parameter files:
where the file with extended Antoine parameters is preselected.
Pressing Enter accepts and reads this file after which
the parameters for the components found in the library are
shown:
(De)select any of the parameter sets. The listing uses the
component library index (in the first column).
WARNING: Unit conversions are performed automatically for
almost all parameters whenever they are changed using F5. The
units of Activity coefficient parameters, however, are NOT changed
following any use if F5. Believe it or not, we have some good
reasons for doing things this way but we aren'tgoing to tell you why.
If no interaction parameters are required ChemSep will inform you this
with a message and advance you further in the input specifications.
The function of these menu items is as follows:
This first field of this spreadsheet identifies the flash type by two
letters that identify the two specified variables. Locate the cursor
on the top field and press Enter to bring up a list of
available flash types.
When the flash type has been selected, a two letter code will be
written in the Flash type field. Two asterisks (*) will appear in the
fields adjacent to the variables identified by the two letters. For
example, if the pressure and temperature are to be specified the
spreadsheet will look like this:
The two variables marked by the asterisks must be specified. Each line
of this list identifies two variables from among the following list:
The numbers in parentheses represent the numbers of degrees of
freedom. The total number of degrees of freedom is the sum of the
numbers in parentheses. The method used to calculate the number of
degrees of freedom is described below. In what follows, c represents
the number of components.
Start with 1 for the total number of stages and add two for each stage
that is not a condenser or reboiler. The pressure and heat duty must
be specified for all such stages.
Add 2 degrees of freedom for condensers and reboilers. The necessary
specification is the stage pressure. One additional quantity must also
be specified (for example, reflux ratio for the condenser and bottoms
flow rate for the reboiler).
For total condensers and two-product condensers, the "stage" is, in
fact, the condenser and the reflux divider together. The temperature
and pressure in the reflux divider is assumed to be the same as the
temperature and pressure in the condenser and the heat loss from the
divider is assumed to be negligible. Analogous arguments apply to
stream dividers adjacent to total reboilers.
Add 1 more degree of freedom for subcooled and superheated streams.
Unless the product streams from a total condenser or reboiler are
specified as superheated or subcooled, they are assumed to be
saturated. That is, the condensate is at its bubble point and the
vapour leaving a reboiler is at its dew point.
Add (c+3) for each free feed. Component feed flows, two of
temperature, pressure and vapour fraction and the stage location must
be specified for each free feed.
Add (c+2) for each fixed feed. Fixed feeds are those that enter on the
top stage if it is NOT a condenser and the bottom stage if it is NOT a
reboiler. The location of these streams is fixed and so one degree of
freedom is lost compared to the free feeds.
Add 2 degrees for each sidestream (location and flow rate or ratio). A
sidestream from a two product condenser does not have a free location
and is considered in the condenser specification. This additional
product stream is not counted in the number of sidestreams.
To clear the Analysis window press Esc to go back to the
Specifications menu with the cursor located on Analysis. Press
Enter to go back to the same menu but with the cursor located one
line down.
The pressure spreadsheet allows you to specify the column pressure
profile in one of several different ways. When invoked for a new
problem the window contains asterisks (*) to indicate items that must
be completed. The default units used to display pressures are shown in
parentheses on the top line of this spreadsheet. Use F5 to change the
default Units. You may also type in pressures in other units as long
as you use one of the pressure Units recognized by ChemSep after the
numerical value. Consult the section on Entering and Editing Data in
Spreadsheets for more information on Units entry.
The first asterisk may be for the Condenser pressure. The condenser
pressure must be specified (if the column has one). If the column has
no condenser the condenser pressure field will not be present in this
spreadsheet.
The Column pressure field allows you to select the method used to
specify the column pressure profile. With the cursor on the Column
pressure field press Enter to bring up the Column pressure
list.
Use the cursor keys and Enter to select one of these options.
When you have selected the column pressure mode additional asterisks
(*) will appear to indicate any other values that must be entered.
If you select a Constant pressure profile you need enter nothing in
this window other than the Top pressure. The value entered for the Top
pressure will be assigned to all stages. The Top pressure need not be
the same as the Condenser pressure.
If you specify the Bottom and top pressures, two asterisks (*) will
appear in the Top pressure and Bottom pressure fields in the pressure
spreadsheet. The pressure of the remaining stages will be calculated
by linear interpolation between the two end values.
If you opt for Fixed pressure drop then an asterisk (*) will appear
against the Top pressure and Pressure drop fields. The pressure of the
remaining stages will be calculated by adding the specified Pressure
drop to the pressure of the stage above.
The estimated pressure drop option is only available for
nonequilibrium models where we can actually calculate the pressure
drop with hydraulic equations and models. If you select this option
you only need to specify the pressure at the top of the column. You
will need to select the estimate pressure drop options under the
column Design.
The spreadsheet has three parts to it. In the upper portion the
thermal condition of each feed is specified. In the middle section the
component flows are entered. A maximum of five component flows can be
displayed in this central section of the spreadsheet. If the number of
components is more than five you can scroll the list with Up,
Down, Alt--, Alt-+, PgDn,
PgUp, Ctrl-Home and Ctrl-End. The component flows
are added together to give the total flow that is printed in the
bottom of the spreadsheet. Each feed appears in a separate column.
When invoked for a new problem the feed spreadsheet appears as shown
above.
The locations of any feed streams were specified in the Operation
spreadsheet but you may change the location of the feeds here. Any
changes made in this spreadsheet will be reflected in the Operation
spreadsheet if you return there. To change the feed stage number,
locate the cursor on the Stage field and type in the new stage
location. Press Enter to accept the new stage number. For each
feed stream you must specify two of the following three variables:
Pressure, Vapour fraction, and Temperature. Locate the cursor on the
State field and press Enter to bring up a list that allows you
to select one of two options:
Use the cursor control keys and Enter to select one of these
two options. Two asterisks (*) will appear in the fields adjacent to
the variables you have opted to specify. For example, if Pressure and
vapour fraction are to be specified the spreadsheet will now appear
as:
Locate the cursor on the Pressure field and type in the pressure.
Press Enter to accept it. Note the default units are displayed
in parentheses. Use F5 to change the Units.
Locate the cursor on the Vapour fraction field and type in the vapour
fraction. Press Enter to accept it. A vapour fraction of zero
means the feed is a liquid at its boiling point. A vapour fraction of
unity means the feed is a vapour at its dew point. Vapour fractions
between zero and unity indicate a partially vapourized feed. Vapour
fractions less than zero mean the feed is a subcooled liquid. Vapour
fractions greater than unity indicate a superheated vapour. ChemSep
will determine the extent of subcooling or superheating when the
problem is Solved.
Type in the component feed flows in the central section of the feed
spreadsheet. Note the default units. If there are more components in
the feed than will fit into the window you can press PgDn to
access the remaining fields. When all the component flows have been
entered, the Total flow will be displayed. Once the total flow is
calculated it becomes a field that can be specified. You can use this
to specify a feed where you know the feed mole fractions and the total
feed flow. If you change the total flow all the component flows are
adjusted in proportion to the change in the total flow. The
composition (in mole fractions) of the feed is not changed.
ChemSep always displays the component feed flows in molar units. Note
that the Streams table in the Results menu displays flows in both mass
and molar units. ChemSep can accept component feed flows in mass units
rather than molar units. Type in the numerical value of the mass flow
and follow the number by the character string that represents the
appropriate mass unit. Press Enter to accept the mass flow.
For example, we know the mole fractions and entered these:
where the default flow units are mol/s. But we know the feed flows in
lb/min, and simply type that in the total feed flow as
Spaces are ignored when evaluating the expression with units. Any
combination of the units listed under Other Units may be used. ChemSep
checks the dimensions of the unit combination you enter and displays a
warning message if it does not have the correct dimensions. If you
know the total mass flow and the mass fractions: enter the mass
fractions in the component flow fields and the total mass flow in the
total flow field. Enter ALL with the appropriate mass flow
units!
There are three action fields at the bottom of the feeds spreadsheet:
The asterisk (*) on the left in this spreadsheet indicate that two
specifications must be made (we used a condenser and a reboiler here).
Locate the cursor on the top asterisk (press Home if the
cursor is not there) and press Enter to bring up the Top
product / Condenser Specifications. Use the cursor control keys and
Enter to select ONE of the available options.
When you have selected the type of specification you will see
additional asterisks (*) on the line of the spreadsheet corresponding
to the specification you selected. There may be one, two, or three
asterisks depending on the specification you wish to make. Those
options that require you to identify one or two component names from
the list of selected components will have more than one asterisk.
Locate the cursor on the first (and/or second) asterisk and press
Enter to display a List of components. Use the cursor control keys and
Enter to choose one of the component names.
These specification options are explained below:
This spreadsheet identifies the stage from which the sidestream is
withdrawn, the phase of the sidestream, whether the total flow or flow
ratio is specified, and the numerical value of the specification (a
flow in this case). The location of any sidestreams was specified in
the Operation spreadsheet but you may change the location of the
sidestream here. Any changes made in this spreadsheet will be
reflected in the Operation spreadsheet if you return there. To change
the sidestream stage locate the cursor on the Stage field and type in
the new stage location.
Select the Phase of the sidestream by placing the cursor on the phase
field and pressing Enter. Select the desired phase, vapour, or
liquid from the list that appears.
Specification of sidestream flow rates is possible, or you may specify
the flow ratio between the sidestream flow and the interstage flow
rate. Locate the cursor on the Specification field and press
Enter to bring up a list with these two options. Use the cursor
control keys and Enter to select one of these options. An astersik (*)
will appear in the field adjacent to the option you selected. Type the
numerical value of the sidstream flow specification in that field. The
liquid product of a two-product condenser is considered by ChemSep to
be a liquid sidestream from stage 1.
Place the cursor on the Insert field and press Enter if you
wish to add a sidestream, or use the Delete field and to eliminate a
sidestream. The Return field and press Enter to return to the Input
menu.
ChemSep allows you to specify the heat duty of any stage. The default
value of the heat duties is zero. The Heaters/Coolers spreadsheet
shown here has no an asterisk for the unspecified column heat duty
(which will therefore be taken as zero). This is how the spreadsheet
appears when invoked for a New problem. If you enter a value for the
column heat duty it will be spread out over all the stages in the
column with the exception of the condenser and reboiler stages. To add
or remove heat from any specific stage, locate the cursor on Insert
and press Enter to bring up a prompt box as follows:
Type in the number of the stage where the heater or cooler is located
and press Enter. Here is the heaters/coolers spreadsheet after
stages 2 and 3 have been identified as having a heater or cooler.
The asterisks (*) indicate the fields where you must enter numerical
values for the heat duties. In the above illustration, heat duties are
to be entered in J/s. Use F5 to change the default Units. If
the number of heaters/coolers in the spreadsheet is large (more than
10) you can scroll the list with Up, Down,
Alt--, Alt-+, PgDn, PgUp,
Ctrl-Home and Ctrl-End. Locate the cursor on each of these
fields and type in the values of each heat duty. Press Enter
to accept them. Note that quantities of heat removed from a stage
should be given a NEGATIVE sign.
If you leave the heat duties unspecified they will be taken as zero.
ChemSep will not let you specify the heat duties of Condensers and
Reboilers which, if they are specified at all, are specified in their
own spreadsheets. If you try and specify the heat duty of stage 1 when
the column is equipped with a condenser you will see the following
warning:
Locate the cursor on the Delete field and press Enter to be
presented with a box that allows you to eliminate a heater or cooler
from the spreadsheet. Locate the cursor on the Return field and press
Enter to go back to the Specifications menu.
This spreadsheet lets you know that the default value of the Murphree
efficiency is unity for all stages. Additional lines appear in this
spreadsheet whenever you wish to specify unequal efficiencies on
different stages. Locate the cursor on the Default field and type in
the default value of the efficiency. Press Enter to accept the
new value. Here is an example where the default value is 0.75. Note
that that the Murphree efficiency will normally lie between zero and
one.
To specify a different value for any stage, locate the cursor on
Insert and press Enter to bring up a prompt box. Type in the
number of the stage for which the efficiency to be specified is
located and press Enter. Here is the efficiencies spreadsheet
after stages 2 - 5 have been identified as having efficiencies
different from the default value:
The asterisks (*) indicate the fields where you must enter numerical
values for the efficiencies. Locate the cursor on each of these fields
and type in the values of each efficiency. Press Enter to
accept them.
ChemSep will not you specify the efficiencies of Condensers and
Reboilers. These units are assumed to have an efficiency of unity. If
you try and specify the efficiency of stage 1 when the column is
equipped with a condenser you will see a warning that mentions the
valid range of stages. If the number of lines in the spreadsheet is
large (more than 10) you can scroll the list with Up,
Down, Alt--, Alt-+, PgDn, PgUp,
Ctrl-Home and Ctrl-End. Locate the cursor on the
Delete field and press Enter to be presented with a box that
allows you to eliminate a stage from the efficiency spreadsheet.
Locate the cursor on the Return field to go back to the Specifications
menu.
where for each column section we need to specify a type of internals
(here the list for distillation columns. Liquid-liquid extraction
columns can have other types of internals, such as RDC's, spray
columns, etc.):
After selecting a type of internals, for example sieve trays, the
detailed internals layout specification input spreadsheet will pop up:
Here you must enter the detailed layout parameters of the sieve trays
that are in the column section you want to simulate. Some of these
parameters are essential, such as the column diameter and tray
spacing, as they determine the tray's capacity. Others, such as weir
height and hole diameter, can be left unspecified and ChemSep will
supply default values which will often work fine. To accurately
simulate your column you must enter all the layout parameters you
know.
However, if you are designing a column with sieve trays, you
can't specify the layout as nothing is still know of the internal
column flows. Without these, you can't do any calculations to come up
with a reasonable tray layout. For this reason Chemsep has a
design mode. If you leave the column diameter of a section
unspecified (*) the design mode is automatically initiated during the
simulation. This facilitates an initial tray layout design and
additional designs when the internal column flows change during the
iterations. This will guarantee that the trays will handle the column
internal flows and come up with a resonable tray layout. The result is
not themost optimum design, however.
Of course, you can also have valve trays:
or bubble-cap trays
or dumped packing
where the type of packing needs to be specified. You can do this by
loading the data of a specific packing by selecting the packing type
field. This allows you to load the data from a packing library, which
shows you the available dumped packings:
The structured packing specification works just like the dumped
packing
Alternatively, a section can consist of equilibrium stages. This might
be useful if you have a piece of hardware, such as a distributor,
where some vapor-liquid equilibrium will persist but for which no
nonequilibrium model is available. The stage efficiency and pressure
drop are the required inputs:
After specifying the section internals, the design menu will show you
the available models for this type of internal:
Here we enter the section height (only for packed sections), the mass
transfer coefficient model (MTC, used to calculate the mass transfer
rate), the liquid resistance (can be included or ignored), the vapor
and liquid flow models (mixed or plug flow), the pressure drop model
(fixed, or estimated for trays, specific models are available for
packigns, dependent on the type), entrainment (neglected or
estimated), holdup model (only for dynamic simulations), and the
design method which defines the design method used for this section
when the design mode is activated.
The mass transfer coefficient model determines the method used to
calculate the vapor and liquid mass transfer rates. usually there are
several models available for an internals type, for example for sieve
trays:
There are different design methods for the design mode: fraction of
flood, pressure drop, and optimizing.
The first designs the column internal to operate at a certain fraction
of the flood conditions, for example 75 %. This allows the column to
handle some additional capacity or increased reflux (for a higher
purity). For trays, you also need to specify the weep fraction, which
is the fraction of the operating conditions where weeping of the trays
would occur. Weeping is detrimental to the efficiency of the trays.
The flexibility of operation is determined by the fraction of flood
and weep fraction and allows a window for proper column operation.
Note that the weep fraction is not a specification but an upper bound
(thus, the tray can only start to weep at lower fractions than
specified).
Other design philosophies are design for a specific pressure drop and
the optimizing design. The design for a specific pressure drop is one
typically used for packed columns, especially where high pressure
drops are to be avoided (vaccuum distillation). Note that the tray
design pressure drop is again an upper bound instead of a
specification. The optimizing design method tries to optimize the
internals design for a low pressure drop, high average mass transfer
rate, low diameter (cost) and height, as well as high flexibility
(which is inverse proportional to the fraction of flood and the weep
factor). This method is not (yet) available.
For each section the internals type and models must be selected. You
can add sections by selecting "Insert" and specifiying the starting
stage of the section. Peruse multiple sections by using the arrow
keys. section can also deleted by selecting "Delete" and specifying
the number of the section. After you exit the design menu the sections
are ordered by the starting stage number, so the order of the sections
can be changed. Also if you go to the feed specification the sections
stages might be automatically adapted (unless this option is turned
off in the interface options).
The last item in the design menu is the system factor. This factor is
used in many design calculations as a derating factor correcting for
foam formation. Press F1 to obtain help on this parameter and
to see some examples for the system factor values dependent on the
type of operation.
Here you can specify the stages of the pumparound (these are already
filled in), the phase to pump around (for liquids a pump would be
used, for vapors a compressor), the type of flow specification (total
flowrate or flowratio with respect to the internal column flow at the
stage of withdraw), the flow specification, and the type of heat
specification (a heat duty or a temperature) together with the
specification. Often, liquid pumparounds are installed with coolers to
increase the liquid reflux in that secion (introducing subcooled
liquid will condense some of the internal vapor flow).
Unless you press Alt-Q, ChemSep checks for any missing or
obviously inconsistent data. Message boxes informing you of any such
oversights will appear only as needed and you will be taken directly
to the place where you should enter the missing data. If you changed
something (either by accident or by design) you may see a warning
message if your change leads to some inconsistency that the program
can detect. Once the data are verified (or the checks are bypassed
with Alt-Q), ChemSep writes it to a file.
The next thing that will happen is that the ChemSep shell, CS, calls
up the appropriate simulation program to solve the problem. A window
appears in the center of the screen and the simulation program writes
messages there to let you know the current status of the calculations.
If you have a color monitor the window will appear in red over a blue
background. The size of the window depends on how much information you
have requested be written to the screen. Consult the Solve options for
more information on this topic. If you are using the default settings
(only iteration numbers written to the screen) the window will look
something like it does here.
This illustration is from the Depropanizer example in Chapter 10. When
the calculations are complete, the program will inform you of this
fact, the interface reloads the input data together with the results
and jumps to the Results menu (the subject of Chapter 7).
The three items are:
In this case the Results menu is a list of the kinds of Table that
ChemSep can display for flash problems.
This is what the screen looks like for the Depropanizer example
(Chapter 10) when you select the Streams table:
All Tables are written to a View window. Usually, there is
insufficient space on the screen to display the entire table. Use the
cursor control keys, Up, Down, PgUp,
PgDn, Home, and End, to see more of these tables.
Notice that the Function key bar at the foot of the screen has been
replaced by a list of a few keys that have a special purpose in the
Tables menu window.
Continue to press Alt-N or Alt-P until you have
seen the tables in turn. Press Escape to clear the current
table and return to the previous menu.
For nonequilibrium simulations run with the design mode the calculated
column internals design is also available as a table:
The following graphs are predefined by ChemSep:
The items in this list lead to other lists or to spreadsheets where
such things as the color, line style, and point style for each profile
can be selected. The items in this list are discussed below.
The plot spreadsheet allows the specification of the plot
title, orientation (whether the stages are on the vertical or
horizontal axis), axis color and the presence of labels for the
displayed profiles. Boxes around the labels and plot are also
optional.
The stage axis setup spreadsheet allows you to specify the
title, start and ending stage, tic interval, the number of small tics
in an interval, and the selection of a grid, logarithmic mode, and
scientific number labeling. Note that the stage axis specification is
not limited to whole numbers. This is to facilitate plotting two
variables against each other using the "advanced" profile plot option
(see below).
The left/right or top/bottom axis setup spreadsheets define
the same items for the other axis. The plot can has only one stage
axis but can have both a left and right axis or a top and bottom axis
(depending on the orientation selected under the plot setup). ChemSep
uses by default linear axis for all its plots (except the key ratio
plot) but logarithmic axis are useful when plot values take on small
values or span several decades.
The settings for each line in a profile are shown in a profile
setup spreadsheets. Press Enter with the cursor located on
any of the items in the Profiles list to bring up a spreadsheet
similar to the one shown here:
The label, color, point type (Circle, square, etc.), line thickness
(no line, normal, thick), line style (solid, dotted, centered, dashed)
can be set. The axis selection, left/right or top/bottom (dependent on
the plot orientation), selects which axis is used to plot the profile.
The profile is then drawn with values starting from the specified
first to the last stage (thus, though the plot might cover stages
1-50, the profile might only show stages 1-10). The clear
option will clear the profile from the graph and the write
option allows you to write the profile to a file on disk.
It is possible to display, for example, both mole fractions and
temperatures on the same graph, one set using the left axis, the other
using the right axis. To add a profile to a graph select an "empty"
field in the list of profiles and press Enter. You will be
shown a list of available profiles:
Use the cursor keys and Enter to select a new profile.
Compositions, K-values, efficiencies, and mass transfer rates require
a component selection for the profile to add. The advanced profile
allows you to specify the variables used for the X and Y values:
The stage plot string is default set to "S" which is the stage number.
The Y plot string is left empty and needs to be specified. This would
plot the Y variable against the stage number. To plot two variables
against eachother enter one as X variable and the other as Y variable.
You can enter any variable identifier from the following list:
Title Pressing Enter with the cursor located on the Title field
allows you to edit the default title. The title is displayed over
the top of the figure on screen. Press Ctrl-Backspace to delete the
title. Key components ChemSep chooses the two components to be used
in the modified McCabe-Thiele diagram by searching for the two
components whose average K-values are closest to, but on either side
of unity. The components used in the diagram can be changed if desired
by locating the cursor on the key-component fields and pressing Enter.
A list of components will be displayed. Use the cursor control keys
and Enter to select one of the components. Press Escape to remove the
list of components without making a selection. Flip It is
traditional for a McCabe-Thiele diagram to be displayed with the
construction above the 45 degree diagonal that is drawn across the
diagram. It is possible for the construction to appear below the
diagonal. Use the Flip field in the McCabe-Thiele window to obtain a
diagram with the consruction in the desired location. Press Enter
with the cursor located on the Flip field to toggle between Yes and
No. X and Y axes The colour, tic spacing, label, and axis titles may
be changed from the default settings if desired. It is also
possible to change the range of either axis to zoom in any
particularly interesting portion of the diagram. Lines The colour
and line style of the stages lines (the steps of the staircase), the
equilibrium line, the operating line, and the Q-lines may be changed.
Press Enter with the cursor on any Lines field to bring up a list of
alternatives. Use the cursor keys and Enter to select any of the
options displayed. Use Escape to go back to the spreadsheet and use
the prior selection. Printer Setup The McCabe-Thiele diagram may be
printed from ChemSep or to a file for printing from the operating
system. Locate the cursor on the Printer Setup field and press Enter
to bring up the Printer selection and setup spreadsheet.
Print Locate the cursor on Print and press Enter to print the
diagram to the chosen destination.
Title Pressing Enter with the cursor located on the Title field
allows you to edit the default title. The title is displayed over
the top of the figure on screen. Press Ctrl-Backspace to delete the
title. Key Components ChemSep chooses the two components to be used
in the ternary diagram. The components used in the diagram can be
changed if desired by locating the cursor on the key component
fields and pressing Enter. A list of components will be displayed.
Use the cursor control keys and Enter to select one of the
components. Press Escape to remove the list of components without
making a selection. X and Y axes The color, tic spacing, label, and
axis titles may be changed from the default settings if desired.
Locate the cursor on any field and press Enter to see a list of
alternative settings or to edit the previously entered string. Press
Escape to exit any list or data entry field without making any
changes. Points Locate the cursor on the Points field and press
Enter to bring up the Points list. Use the cursor keys and Enter to
select a point style. Line thickness Locate the cursor on the Line
thickness field and press Enter to bring up the Line thickness
list. Use the cursor keys and Enter to select from No line, Normal,
and Thick. Line Style Locate the cursor on the Line style field and
press Enter to bring up the Line style list. Use the cursor keys
and Enter to select one. Printer Setup The ternary diagram may be
printed from ChemSep or to a file for printing from the operating
system. Locate the cursor on the Printer Setup field and press
Enter to choose the printer type and destination. Locate the cursor
on the Print field and press Enter to print the diagram to the chosen
destination.
Title Pressing Enter with the cursor located on the Title field
allows you to edit the default title. The title is displayed over
the top of the figure on screen. Press Ctrl-Backspace to delete the
title. Labels Pressing Enter with the cursor located on any Label
field allows you to edit the default label. Labels are displayed at
the corners of the tetrahedron Press Ctrl-Backspace to delete the
label. Avoid using too many characters in a Label. Depending on the
orientation of the tetrahedron, the Labels may not fit on the screen
and may not be printed completely. Axis color Locate the cursor on
the Axis color field and press Enter to bring up the Colors list.
Use the cursor keys (or first letters) and Enter to select one. Line
color Locate the cursor on the Line color field and press Enter to
bring up the Colors list. Use the cursor keys (or first letters)
and Enter to select one. Line thickness Locate the cursor on the
Line thickness field and press Enter to bring up the Line thickness
list. Use the cursor keys and Enter to select from No line, Normal,
and Thick. Line Style Locate the cursor on the Line style field and
press Enter to bring up the Line style list. Use the cursor keys
and Enter to select one. Points Locate the cursor on the Points
field and press Enter to bring up the Points list. Use the cursor
keys and Enter to select a point style. Printer Setup The quaternary
diagram may be printed from ChemSep or to a file for printing from
the operating system. Locate the cursor on the Printer Setup field
and press Enter to choose the printer type and destination. Locate
the cursor on the Print field and press Enter to print the diagram
to the chosen destination.
The items in this branch of the main menu are: Solve options This item
gives you some control over the simulation programs (F6 jumps here)
Units Engineering problems require units. This is where you change
them (see F5). Macros Here you can assign special duties to 30
two-key combinations. Interface This option leads to a spreadsheet
where you can specify the default settings for text printing,
graphical displays, and numerical formatting. Directories Where you
tell ChemSep where to look for its data files. Video device This item
allows you to choose the video device driver you want to use. Output
device Here you let ChemSep know what kind of printer you have. Save
options Save all of the above options so that ChemSep can use them
again. Load options You can have more than one options file. Use this
option to pick and load the settings you want. You may place the
Options menu on the screen using one of the following key sequences:
Alt-O F10, O Macros are described in detail in Section 3.4. Units
are discussed in Section 3.1.4.
The Solve Options spreadsheet is for specifying options related to the
simulation programs. As a general rule you should not need to change
any of the default settings but ChemSep provides the flexibility if
you require it.
If you select User supplied you must provide your own initial
estimates of the temperatures and/or of the vapour and liquid flows.
You may provide estimates of the temperature profile, the flow
profiles, or of both flow and temperature profiles. If you supply
estimates of the flows then you MUST estimate BOTH vapour AND liquid
flows. Estimates of temperatures and flows will be computed
automatically if you selected User supplied but forgot to provide any
numerical values. Press Enter with the cursor on User supplied to
bring up a spreadsheet where you may enter your initial guesses.
Previous run is an option that uses the results printed in the SEP
file. Naturally, this option will not work for a New problem. However,
if the simulation programs fail to find any Old results, they will
automatically invoke the Automatic Initialization. Problems with
slightly changed specifications are solved much quicker if previous
results are used as starting values for a new run. You cannot use
Previous run if you change the number of stages in a column
simulation.
In the interface spreadsheet, you may toggle between a set of options
that give you a measure of control over the use of the ChemSep
interface.
ChemSep's files may be stored in different directories or on different
disk drives. This facility was added to make it possible to run
ChemSep on computers with no hard disk drive. If you used ChemSep's
install program you should not need to change these settings. It is
recommended (but not required) that you store the ChemSep files in
different directories. It is very important that the directory names
be correctly specified otherwise ChemSep will not work as intended.
The complete path including the drive letter and colon (:) must be
typed in each of these fields.
ChemSep uses the Borland graphics drivers for any drawing on the
screen. The BGI files must be in the directory specified in the
directories spreadsheet. For Olivetti users: use the ATT400 option to
get a higher resolution picture. The list will display only those
drivers that were copied to the hard disk when you installed ChemSep.
If the driver you need is not shown you can copy the required driver
from the original diskette or run the install program again. Available
video drivers are:
The fields of this spreadsheet are reviewed below:
The following device drivers are available
Use the cursor control keys and Enter to select a destination for
printed output. If File is selected you will see a prompt box for you
to type in the name of the file. Press Enter to accept the new File.
Use the cursor control keys and Enter to select a printer mode. Many
printers have three basic modes: Full Full page portrait orientation
Half half page portrait orientation Land Landscape orientation
Other modes may be available for certain printers. Consult the file
TECH.MAN for further information on printer modes.
To create a new configuration file type in the new file name. Press
Enter to write the file. If you wish to overwrite an existing CNF
file, press Enter a second time to bring up a directory list of all
files with a CNF extension. ChemSep will confirm overwriting any
existing configuration file. The CHEMSEP.CNF file is the default
configuration file which will be loaded at startup. You can specify a
different configuration file at startup with the "-cFILENAME"
commandline option. If there is no CHEMSEP.CNF in the current
directory, the program loads the configuration file from the path
where the program resides.
To load this configuration file press Enter or to load a
different file type the path and full name. If you use any wildcards
(for example "*.CNF") a file listing will appear from where you can
select the configuration file to load. The default extension for
configuration files is CNF.
ChemSep User's Guide
Locate the cursor on the Graphs option of the Results menu and press
Enter to bring up a list of graphs that can be viewed.
Spreadsheet Files
As a service to our users that would like to use the results of a
ChemSep simulation in a spreadsheet program such as Lotus Development
Corporation's Lotus 123 or Borland International's Quattro (Pro)
ChemSep can print a file that can be imported into these programs. The
spreadsheet file created by ChemSep is a simple text file so it could
be loaded into any text editor if you so desire. It does not use any
special spreadsheet file format. To exercise this option go to the
Spreadsheet option of the Results menu and Press Enter. A prompt box
will invite you to provide a name for the file. Type in the name you
would like (including any drive and directory names if you wish) and
press Enter.
Exercise
Just to make sure that you have been paying attention we have devised
this exercise to see how much you remember about ChemSep. The feed to
our depropanzer and the separation we desire is given below:
ChemSep User's Guide
2.4 Spreadsheets
ChemSep makes good use of simple spreadsheets for entering data. Here
is an example of the spreadsheet used for entering information
concerning the feeds.
Some spreadsheets are too large to fit in the available window. If
this happens you can use PgUp and PgDn to scroll (part
of) the spreadsheet up or down. A spreadsheet that is too large to fit
on the screen can be easily identified. The F-key bar at the bottom of
the screen is replaced by a line that tells you to use PgUp
and PgDn. The F-keys will work as described elsewhere, even
when the F-key bar is not displayed.
2.4.1 Entering and Editing Data in Spreadsheets
While using ChemSep you often have to enter a string of characters;
the title of a graph, for example, or the numerical value of some
quantity in a spreadsheet field. Position the cursor over the field
where you wish to type in a new entry (or change an old one). Simply
start typing the new value and you immediately enter Edit mode.
2.4.2 Formula Entry
ChemSep can process algebraic calculations wherever numerical input is
required. This is useful since, if you don't know the actual numerical
value that should be entered but you know how to calculate it, you may
enter the calculation. Numerical formulae may include the four basic
arithmetic operations, +, -, *, and /. Operations may be nested within
parentheses () as well. When you have typed in the formula, press
Enter to evaluate the result and Enter a second time to accept
that result. ChemSep does not remember formula entries, only the final
result so you may edit the formula until you press Enter.
3 Enter
5-2 Enter
(2-1) * (5-2) Enter
All of these result in the number 3.
573 * 0.365 Enter
573 * (1 - 0.365) Enter
2.4.3 Units Entry
ChemSep data entry fields also accept units. This feature is
particularly useful if you know a quantity in some units other than
the current set of units. You don't have to change the units (using
F5), type in the input quantity in the default unit set, and then use
F5 to change the units back again. Simply type in the numerical value
of the quantity and follow the number with its units. The number will
be displayed in the default units. For example, what if the default
flow units are kmol/s but we know the feed flows in lbmol/h? Simply
type in the feed flow as, for example,
375 lbmol/h Enter
and ChemSep will automatically convert the number to the correct value
in the default set of units. You can use this feature in any data
entry field in ChemSep. Spaces are ignored when evaluating the
expression with units. Any combination of the units listed under Other
Units may be used. ChemSep checks the dimensions of the units you
enter and displays a warning message if they do not have the correct
dimensions.
mmol/s
is recognized as (mol/s) / 1000.
2.5 Directory Facility
You will want to use the directory facility of ChemSep when, for
example, you want to load, save, view, or edit files. For example,
going to the Load option of the File menu and pressing Enter will
bring up the following screen:
%t2h!2.6 View Windows
ChemSep can display Results in Tables or in Graphs. Tables are written
in a View Window. ChemSep allows you to View text files (as long as
they fit into available memory). The contents of a file being viewed
are displayed in a View window. Here, for example, is the Streams
table for the Depropanizer illustrative example.
In a view window the cursor is positioned on an entire line. The
cursor line is displayed in a different colour from the rest of the
text in the window. If all of the lines of text appear in the same
colour it means that the cursor is on an empty line. There are four
Two-keys that have a special purpose in a View window:
2.7 Edit Windows
ChemSep allows you to Edit any Tables that are written in a View
Window. ChemSep also allows you to Edit text files (as long as they
fit into available memory). To edit a Table, you must have the table
displayed on the screen. Press Alt-E to Edit the contents of
the window. To edit a file use the Edit option of the File menu to
bring up a directory list of the file(s) you wish to Edit. In an Edit
window the cursor line is displayed in a different colour from the
rest of the text in the window. If all of the lines of text appear in
the same color it means that the cursor is on an empty line. The
cursor itself is a blinking underscore. The following keys may be used
to move the cursor in an Edit window:
Characters may be deleted using the following keys:
Other useful keys are:
Press Escape when you have finished editing the contents of
the window. Tables in an Edit window cannot be saved in their modified
form. You must Print the window (by pressing Ctrl-P) to a file
or to a printer if you want to save the contents of the edit window.
Files can be saved in their modified form. If you were editing a file
when you pressed Escape, you will be asked if you wish to save the
file. Press Y to save it (and overwrite the old version). If
you press N the file will not be saved and the Edit window
will be removed from the screen. Any changes you may have made will be
lost.
Chapter 3. The Keys to ChemSep
As noted in Chapter 2, the most important keys in ChemSep are
Up, Down, Left, Right, Enter,
Escape, and the Spacebar. To make life easier for our
users we have assigned special functions to the F-keys and a
number of Alt-key and Ctrl-key combinations. In
addition, it is possible to assign your own functions to the
Alt, Shift and Ctrl F-keys. In this chapter of the
User's Guide we review the following key assignments:
3.1 The F-keys
The keys, F1 to F10, have special functions assigned
to them. Here is a summary:
These keys can be pressed wherever you are within the ChemSep
interface. F6 causes the cursor to jump to the Solve options
item of the Options menu and is described in detail in that section of
this User's Guide. F10 causes the cursor to return to the Main
menu and needs no further discussion here or anywhere else. The
functions of the remaining F-keys are described in detail below.
3.1.1 F1 and F2 - Help
F1 may be pressed any time you are in the ChemSep interface to
display a window containing help messages. The message displayed when
F1 is pressed depends on where you are in ChemSep. Almost all
menu items have their own help message. Here, for example, is the
screen image after F1 is pressed when the cursor is on the
Name item of the Select option of the Components menu:
3.1.2 F3 - Load
F3 jumps directly to the Load option of the File menu and
executes it so that the screen looks like this:
3.1.3 F4 - Save
F4 saves the current Input data immediately. F4 can be
pressed anywhere in the interface. Pressing F4 will result in
the immediate overwriting of your file. If no file name has
been given you will be asked to provide one in a prompt box similar to
the one shown below:
3.1.4 F5 - Units
ChemSep is an engineering program and, therefore, requires units to
express numerical results. ChemSep allows you to use a wide variety of
units for entering and displaying results. All internal calculations
are carried out in SI units but are converted to the units of your
choice for display purposes. Units are selected in the Units item of
the Options menu. You may also change the default units set by
pressing F5 anywhere in Chemsep. In either case, the
spreadsheet below is displayed on the screen.
3.1.5 Unit lists
Below we list the units of all quantities that can be selected with
F5. Note that many of these unit lists contain the unit Other. This
option covers units not in the lists of recognized units and will be
explained later.
3.1.6 Other Units
Several of the unit lists contain the other unit. This option allows
you to choose some other unit that is not in the list of alternatives.
Select other to be presented with a data entry field where you type in
the abbreviation of the unit you wish to use. ChemSep recognises the
following units
Abbreviation Unit
kg kilogram
m meter
s seconds
K Kelvin
kmol kilomole
rad radian
N Newton
Pa Pascal
J Joule
W Watt
degree
lb pound
g gram
min minute
h hour
day day
UKgal UK gallon
USgal US gallon
l liter
cal calorie
Btu British Thermal Unit
in inch
" inch
ft feet
torr torr
bar bar
barg bar in gauge
lbf pound force
kgf kilogram force
atm atmosphere
psia lbf/square inch
psig lbf/sq in gauge
yd yard
ton ton
USton US ton
oz ounce
lbmol poundmole
mol mole
erg erg
dyn dyne
P Poise
mi mile
F Fahrenheit
C Celcius
F Fahrenheit
C Celcius
R Rankine
bbl barrel
Ž dimensionless
% percent
%% per thousand
ppm parts/million
ppb parts/billion
Suppose, for example, that you wanted to display molar flows in
kmol/day. This unit is not included in the list of molar flow units
although kmol and day are recognized by Chemsep. To display molar
flows in kmol/day, press F5 to bring up the units spreadsheet.
Use the cursor keys and Enter to select Flows. Use the cursor keys and
Enter to select other and type kmol/day in the field provided.
Press Enter to accept the new unit. Please note that you must
type the abbreviation and not the full name and that abbreviations are
case sensititive. ChemSep does a dimensional analysis of any unit you
type and will not let you use units (or combinations of units) with
incorrect dimensions.
3.1.7 Unit Prefixes
ChemSep recognizes the standard prefixes for multiples of 10 and they
can be used in Other units. For example: "mm" is interpreted as
"m/1000". The complete list of prefixes and their abbeviations
recognized by Chemsep is as follows:
Abbreviation Full name Power of 10
T Tera 12
G Giga 9
M Mega 6
k kilo 3
h hecto 2
da deka 1
d deci -1
c centi -2
m milli -3
m micro -6
n nano -9
p pico -12
f femto -15
All units and their prefixes can be typed in data entry fields as well
as selected to be part of the default unit set. See the section on
Entering and Editing Data for a discussion of how to use units in data
entry fields.
3.1.8 F7 - View
F7 allows you to inspect the contents a file in a View Window.
Press F7 to display a prompt box similar to that shown below
asking you for the name of the file to view. The prompt box contains
the default file mask, *.*.
3.1.9 F8 - Summary
The F8 key can be pressed anytime you are in the ChemSep
interface in order to bring up a View window containing a summary of
the problem specifications. This is a useful way to determine if the
problem has been completely specified as the necessary sections of
input data will be empty if incomplete. Here is an example of an empty
problem summary. Notice the main sections of this summary include:
Components, Operation, Properties, and Specifications. These are also
the options of the Input menu.
3.1.10 F9 - Information
The F9 key can be pressed anywhere in the ChemSep interface in
order to bring up the ChemSep Book which consists of technical
documentation of all the models and correlations used in ChemSep. This
information is stored in the "chemsep.txt" file and viewed with the
file viewer. Use the cursor control keys to scroll the file in the
window (see the section on Viewing files for a list of keys) and press
Escape to clear the window.
3.2 Alt-Key assignments
As is more or less standard practice in menu-driven software, the
various items on the main menu can be accessed by holding down the Alt
key and pressing the highlighted letter associated with that item:
Some other special functions have been assigned to Alt-key
combinations:
The difference between these last two two-keys is that if you press
Alt-S you will be asked to verify the data file name before
any existing file is overwritten. If you press Alt-Q,
automatic data checking is ignored and the current file name is
overwritten immediately. The Alt-keys can be pressed from anywhere
within ChemSep.
3.3 Control key assignments
Some special functions have been assigned to Ctrl-key combinations:
The Ctrl-keys can be pressed from anywhere within ChemSep.
3.4 User Defined Keys
One of the most useful features of the ChemSep interface is that you
have the power to assign particular tasks to no less than 30 keys. The
Alt, Shift and Ctrl -Function keys can be
programmed by the user. We consider this feature to be very useful and
use it all the time in our own work. To assign one of these key
combinations go to the Macros option of the Options menu and press
Enter. You will see a spreadsheet that lists all the current
user-defined key assignments.
3.4.1 Special Symbols for use in Macros
@ Enter
~ Escape
#aaa ASCII character where aaa is the three digit numeric code for
the ASCII character to be entered (see below for examples)
$xxx Turbo Pascal extended key code where xxx is the three digit
code used to identify certain keys in the Turbo Pascal
programming language
! Execute the macro from the current cursor position.
Macros that do not begin with this symbol are executed from
the main menu
^1 Help
^2 Last help
^3 Save file
^4 Units menu
^5 Solve options
^6 View file
^7 Units converter
^8 Edit file
^9 Summary
^0 Go to main menu
3.4.2 Turbo Pascal Extended Key Codes
$071 Home
$072 Up
$073 Page Up
$075 Left
$077 Right
$079 End
$080 Down
$081 Page Down
$059 - $068 F1 - F10
$084 - $093 Shift F1 - Shift F10
$094 - $103 Ctrl F1 - Ctrl F10
$104 - $103 Alt F1 - Alt F10
$016 Alt-Q
$031 Alt-S
$045 Alt-X
3.4.3 Examples of Macros
ChemSep User's Guide
Chapter 4. The Main Menu
Let us begin our exploration of ChemSep's interface with a quick look
at the Main menu:
In the main menu (and only in the main menu) you can use the
left and right arrow keys to move from branch to branch of
the main menu. You can use the left and right arrows
even when the submenus are hanging down from the main branch. With the
screen as shown above (just after you started ChemSep), Press
Enter and use Left and Right to look at each of
these branches.
4.1 The File Menu
If you press Enter with the cursor on File, the screen will look like
this:
Each of these items is described in detail in Chapter 5.
4.2 The Input Menu
The Input menu is the first branch of a long and complicated menu
tree. If you go to the input option of the main menu and press Enter,
the screen may look like this:
There are two more item in the Input menu:
The first four items in the Input menu are the start of a
complicated menu tree and the way the tree grows depends on how you
walk through it. We shall take a longer look at the Input menu after
we complete our look at the Main menu (Chapter 6).
4.3 The Results Menu
The Results menu allows you to inspect the results of a simulation. If
you have simulated a Column, the Results menu looks like this:
These items are discussed in more detail in Chapter 7. If you
have solved a Flash problem, the Results menu looks like this:
4.4 The Options Menu
If you go to the Options item of the main menu and press
Enter, the screen may look like this:
The Options menu is the subject of Chapter 8.
Chapter 5. The File Menu
If you press Enter with the cursor on File, the screen will look like
this:
A couple of the file menu options have short cuts assigned to
them, such as F3 for load, F4 for save, F7 for
view, and Alt-D for the DOS shell. Let us examine these
options in more detail.
5.1 Load
The Load option of the File menu allows you to load files created by
ChemSep. To exercise the Load option locate the cursor on Load and
press Enter. Alternatively, you can press L. The
screen will look something like this:
5.2 New
The New option of the File menu resets all Input data to their default
values and clears all Results. To exercise the New option locate the
cursor on New and press Enter or press N. You will be
prompted to name the new problem file:
5.3 Save
The Save option of the File menu allows you to save the Input data and
computed Results in files created by ChemSep. To exercise the Save
option locate the cursor on Save and press Enter (or you can
press S). A prompt box appears below the Save option asking
you for the name of the file to save.
5.4 Directory
The Directory option of the File menu allows you to change the current
active directory. The current directory is where ChemSep looks for and
saves files with the SEP extension. A prompt box appears below the
Directory option asking you for the name of the new current directory.
5.5 View
The View option of the File menu allows you to view files on your
disk. After selecting the view option a prompt box appears below the
View option asking you for the name of the file to view. The prompt
box contains the default file mask, *.*. Press Enter to bring up a
Directory list of all files in the current directory.
5.6 Edit
The edit option works very similar to the view option. A prompt box
asks you for the name of the file to edit. The prompt box contains the
default file mask, *.*. Press Enter to bring up a Directory
list of all files in the current directory.
5.7 Copy
The Copy option of the File menu allows you to copy a file on your
disk. You will be prompted you for the name of the file you wish to
copy. The prompt box contains the default extension *.*. Press
Enter to bring up a Directory list of all files in the current
directory. Use the cursor keys and Enter to select the name of
the file you wish to copy.
5.8 Rename
The Rename option of the File menu allows you to give any file on your
disk a new name. To Rename a file locate the cursor on Rename and
press Enter. Alternatively, you can press R. The
screen will look something like this:
5.9 Erase
The Erase option of the File menu allows you to erase any file on your
disk. You are prompted for the file to erase:
5.10 DOS Shell
The last option of the File menu allows you to shell out to the
operating system (in our case DOS). This is particularly useful if you
want to execute a DOS command that cannot be executed from the File
menu. To shell to DOS, press O or select the DOS Shell option.
ChemSep will write the contents of memory to a hidden file on the disk
and return you to the DOS prompt. Type "exit" and press Enter
to return to ChemSep. You can also make shell to DOS at any point
within ChemSep with the Alt-D.
Chapter 6. The Input Menu
The Input menu is the first branch of a long and complicated menu
tree. If you go to the input option of the main menu and press
Enter, the screen may look like this:
There are two more item in the Input menu:
The first four items in the Input menu are the start of a
complicated menu tree and the way the tree grows depends on how you
walk through it. This chapter of the User's Guide discusses all of the
various menus and spreadsheets associated with Input. Some particular
routes through Input are illustrated in Sections 9 to 11.
6.1 Components
To obtain the Components menu, go the Input option of the main menu
and press Enter. The following menu will appear:
Of course, if no components are listed in the upper right box,
the only actions you can perform are Select and Load set. Let us look
at how these actions work.
6.1.1 Select
To add components to the list choose the Select option. You will be
prompted for the PCD (=Pure Component Data) library name unless you
have selected the search all PCD files option under options -
interface.
You can use just one of these methods to find all of the
components or a combination of selection procedures. You can even use
these methods recursively. Use the Search by Name option to see a list
of all the components in ChemSep's databanks.
6.1.2 Component Lists
Here is an example of a list of components displayed by ChemSep.
To jump to the first of these three items, press Home or the
minus (-) key. Here is an example of the use of Additional Search.
6.1.3 Name
Components can be listed based on their names or any fragment of their
names. To exercise this option locate the cursor on Name and press
Enter or press the highlighted letter, N. ChemSep will
display a prompt box as shown below:
6.1.4 Index
Each component has its own index number within a specific library
file. You can display a list of components whose index numbers fall
within a range of values you choose. To exercise this option locate
the cursor on Index and press Enter or press the highlighted
letter, I. ChemSep will display a prompt box. You must enter
the minimum and maximum index numbers. The default values are 1 and
10000 respectively. Locate the cursor on Search and press
Enter. A list of all components with index numbers between these
limits will be shown on the screen. For example, if we enter 10 and
200 as the minimum and maximum index numbers as shown below:
6.1.5 Structure
Components can be listed according to their structure. To exercise
this option locate the cursor on Structure and press Enter.
ChemSep will display a prompt box for the (part of the) structure.
Entering, for example, OH in the prompt box and pressing Enter will
bring up a list of all components having an OH group in their
structure:
6.1.6 Formula
Components may be listed according to their chemical formula or part
of their formula. For example, typing C4 and pressing
Enter will result in the display of a list of all components whose
molecules contain four carbon atoms. Typing C3H6 and pressing
Enter will result in the display of a list of all components
whose molecules contain three carbon atoms and six hydrogen atoms.
6.1.7 Class
ChemSep allows you to find components that belong in certain groups or
classes. For example, alkanes and alcohols are two of the classes that
ChemSep recognizes. Locate the cursor on Class and press Enter
to display a list of classes that ChemSep recognizes. These are the
classes recognized by ChemSep:
Alkanes
Alkenes
Aromatics
Alcohols
Acids
Esters
Halogen compounds
Amines/imines
Inorganics
Use the cursor control keys and Enter to select the class of
interest. All components in the selected class will be displayed on
the screen. For example, selecting Alkanes from the list of classes
might result in the following list:
6.1.8 Family
ChemSep allows you to list components that belong in certain groups or
families. ChemSep recognises 56 different families. Water belongs to a
family of one. Several families may fall into just one class.
n-Alkanes and other alkanes are families in ChemSep both of which fall
in the alkanes class. Locate the cursor on Family and press
Enter to display a list of families that ChemSep recognizes:
1 n-Alkanes
2 Methylalkanes
3 Cycloalkanes
4 Other alkanes
5 1-Alkenes
6 Other alkenes
7 Alkadienes
8 Alkynes
9 n-Alkylbenzenes
10 Other alkylbenzenes
11 Other monoaromatics
12 Polyaromatics
13 Miscellaneous hydrocarbon rings
14 Inorganic gases
15 Aldehydes
16 Ketones
17 n-Alcohols
18 Other alcohols (phenols)
19 Aromatic alcohols
20 Polyols
21 n-Aliphatic acids
22 Other aliphatic acids
23 Aromatic carboxylic acids
24 Anhydrides
25 Formates & acetates
26 Other saturated aliphatic esters
27 Unsaturated aliphatic esters
28 Aromatic esters
29 Ethers
30 Epoxides and peroxides
31 Aliphatic chlorides
32 Aromatic chlorides
33 C/H/Br compounds
34 C/H/I compounds
35 C/H/F compounds
36 C/H multihalogen compounds
37 Aliphatic amines
38 Aromatic amines
39 Other amines and imines
40 Nitriles
41 C/H/NO2 compounds
42 Other C/H/O/N monofunctional compounds
43 C/H/S compounds
44 Polyfunctional C/H/O
45 Polyfunctional C/H/O/N
46 Polyfunctional C/H/O/S
47 Polyfunctional C/H/O/halide
48 Polyfunctional C/H/N/halide (O)
49 Organic-Inorganic compounds
50 Inorganic acids
51 Inorganic bases
52 Sodium salts
53 Other salts
54 Elements
55 Inorganic halides
56 Other inorganics
57 Water
6.1.9 Property Value
ChemSep even allows you to list components that have some desirable
property value. Any of the several tens of pure component data values
recorded in the data bank may be used as a basis for selecting
components. Even temperature dependant properties can be used. For
example, the vapour phase heat capacity at 450 K. If you press
Enter with the cursor on the Property option you will see a list
of properties that are recorded in the data bank. Select the property
you wish to use as a basis for listing components and press
Enter.
Fundamental Properties
1 Critical temperature
2 Critical pressure
3 Critical volume
4 Critical compressibility factor
5 Normal boiling point
6 Melting temperature
7 Triple temperature
8 Triple pressure
9 Molecular weight
10 Liquid molar volume
11 Acentric factor
12 Radius of gyration
13 Solubility parameter
14 Dipole moment
15 Van der Waals volume
16 Van der Waals area
17 IG heat of formation
18 IG Gibbs energy of formation
19 IG absolute entropy
20 Heat of fusion melting point
21 Heat of vaporization at the normal boiling point
22 Standard net heat of combustion
Temperature Dependent Properties
23 Solid density
24 Liquid density
25 Vapour pressure
26 Heat of vaporisation
27 Solid heat capacity
28 Liquid heat capacity
29 Ideal gas heat capacity
30 Second virial coefficient
31 Liquid viscosity
32 Vapour viscosity
33 Liquid thermal conductivity
34 Vapour thermal conductivity
35 Surface tension
36 Ideal gas heat capacity (Reid et al.)
37 Heat of formation
38 Antoine
39 Liquid viscosity (Reid et al.)
Miscellaneous Properties (not available for all components)
40 V* (parameter in COSTLD liquid density model)
41 Lennard Jones diameter
42 Lennard Jones energy
43 Rackett parameter
44 Fuller Schettler Giddings diffusion volume
45 Surface tension at the normal boiling point
46 Parachor
47 Specific gravity
48 Chung association parameter
49 SRK Acentric factor
50 Wilson Volume
51 UNIQUAC R
52 UNIQUAC Q
53 UNIQUAC Q'
54 Peng-Robinson-Stryjek-Vera (PRSV) EOS k1
55 PRSV EOS k2
56 PRSV EOS k3
57 Chao Seader acentric factor
58 Chao Seader solubility parameter
59 Chao Seader liquid volume
6.1.10 Delete
To delete a component from previously selected components, locate the
cursor on the Delete option of the Components menu and press
Enter. This brings up a list of components that you can delete
plus an extra option which will delete all the components.
Use the cursor keys (or first letters) to select one component to be
removed from the list. Press Enter to delete that component.
You will see a message box asking you to confirm your decision.
You may delete all the components in one step using the All option at
the end of the components list.
6.1.11 Substitute
Locate the cursor on the Substitute option of the Components menu and
press Enter to bring up a list of components. Use the cursor
control keys (or first letters) to select a component you wish to
replace with another. Press Enter to bring up the Search menu,
where you can use any of the Search methods to find another component
to take the place of the selected component. The list in the top right
corner of the screen will show that one component name is different.
6.1.12 Reorder
Locate the cursor on the Reorder option of the Components menu and
press Enter to bring up a list of components under the heading
"Swap". Use the cursor keys (or first letters) to select one of the
components from the list. Press Enter and you will see the
same list of components under the heading Swap with. Use the cursor
keys (or first letters) to select another of the components from the
list. Press Enter to see the two selected components
interchanged in the list in the top right corner of the screen.
6.1.13 Save Set
Any set of selected components can be saved in a text file for use on
a different occasion. This can save you the trouble of searching the
databanks for the components you want. To save a set of components
locate the cursor on Save set and press Enter. You will be
prompted for the name of the file you wish to use to record the names
(and library information) of the components you have selected. Type in
the name you wish to use for recording the list of selected
components. If you do not use an extension the file will be given the
extension .PCS. If you wish to overwrite a PCS file that already
exist, press Enter to bring up a Directory list with the names
of all files with a PCS extension. Use the cursor control keys and
Enter to select the name of the file you wish to overwrite.
6.1.14 Load Set
Any set of components that was saved using the Save set option of the
Components menu may be reloaded into ChemSep. This will save the time
needed to Search the databanks for the components you wish to use. You
may add to and delete components from any list of selected components
once they have been loaded. To load a component set locate the cursor
on Load set and press Enter. A prompt box will ask you for the
name of the file you wish to load: The default file mask is *.PCS.
Press Enter to bring up a directory of all files with the .PCS
extension. Use the cursor control keys to select the name of the file
you wish to load and press Enter to perform the load operation. If you
know the name of the file you wish to load, you may type the name in
the prompt box. Any wild card characters (* or ?) will bring up a
Directory list of all files matching the file mask. Once the
components have been loaded, their names will appear in the Components
box in the top right hand corner of the screen.
6.1.15 ChemLib
The ChemLib option allows you to switch to the ChemLib program
which allows you to check and edit pure component data libraries.
6.2 The Operation Menu
The Operation menu contains up to three items:
The default Operation is Column. This means that if a New
problem is being created the cursor will initially be located on
Column when the Operation menu is invoked.
6.2.1 The Flash Operation
Locate the cursor on the Flash option, and press Enter to
select the flash operation. The only configuration that is necessary
for the flash operation is the specification of the number of feeds:
6.2.2 Column Spreadsheet
With the cursor on Column, press Enter (or press C) to
bring up the Column spreadsheet:
To choose the Operation, Condenser, and Reboiler types, locate
the cursor on the appropriate field indicated by the asterisk and
press Enter. The lists of allowable choices will be displayed
(see below for details).
Feed Stages 12,25
or like this:
Feed Stages 12 25
Examples of completed spreadsheets may be found in the Depropanizer
and Extractive distillation examples. Pumparounds (only available for
complex columns) are also entered here. To handle a liquid pumparound
from stage 20 to 10 enter:
Pumparounds 20>10
where the larger than sign indicates the flow direction. Separate
multiple pumparounds by spaces or comma's.
6.2.3 Operation List
Locate the cursor on the Operation field of the Operation spreadsheet
and press Enter to bring up the Operation list:
6.2.4 The Condenser List
Locate the cursor on the Condenser field of the Operation spreadsheet
and press Enter to bring up the Condenser list:
Two product condensers can be simulated in ChemSep by selecting
a Partial condenser and withdrawing a Sidestream from Stage 1.
6.2.5 The Reboiler List
Locate the cursor on the Condenser field of the Operation spreadsheet
and press Enter to bring up the Reboiler list:
6.2.6 Show Flowsheet
Locate the cursor on the "Show Flowsheet" field of the Operation
spreadsheet and press Enter to see the column configuration:
6.3 The Properties Menu
The Properties menu is accessed from the Input menu by pressing
P:
6.3.1 Thermodynamic model selection
6.3.2 Equilibrium Models (K-values)
To bring up the list of K-models available in ChemSep, locate the
cursor on the asterisk next to the K-models and press Enter:
Use the Help system ( F1) or the technical information
( F9) to learn more about these models.
6.3.3 Activity coefficient models
The Margules, Van Laar, NRTL and UNIQUAC models require binary
interaction parameters. These parameters can be entered from the
keyboard or loaded from a file on disk in the Load data option of the
Properties menu. If you select one of these models but fail to specify
a complete set of the interaction parameters, then UNIFAC is used
automatically to compute any unspecified parameters.
6.3.4 Equation of state
The Cubic and Hayden-O'Connell Virial models require binary
parameters. These parameters can be entered from the keyboard or
loaded from a file on disk in the Load data option of the Properties
menu. If you select one of these models but fail to specify a complete
set of the interaction parameters, then any unspecified parameters are
set equal to zero.
6.3.5 Vapour pressure models
6.3.6 Enthalpy models
Consult the Help system ( F1) and the technical reference
file ( F9), for further information. The default option is
Excess.
6.3.7 Physical properties
The nonequlibrium model requires physical properties such as
densities, viscosities, and surface tensions, to calculate mass
transfer coefficients and operating parameters such as pressure drops.
By default, ChemSep doesn't select any method:
6.3.8 Load Data
Load Data is a menu that lists all the models for which parameters
must be entered. For example:
Each of these models (or classes of model) leads to a spreadsheet
where you can enter the required parameters from the keyboard or load
them from a file. Several examples of typical spreadsheets are shown
below:
The spreadsheet identifies the model on the top line. If the model is
a polynomial or similar equation, the equation form used in ChemSep is
displayed. The units of the parameters (or of the result of the
equation) are displayed in parentheses on the top line. An asterisk
(*) indicates each place where parameters must be entered. There are
one, two, or three parameters per binary pair for EOS or Activity
coefficient models. There are up to 6 parameters per component for
Polynomials. Consult the section Editing and Entering data in
spreadsheets for more information on this topic. The action fields on
the bottom line are as follows:
The default value of EOS parameters is zero. Unset activity
coefficient parameters are estimated using UNIFAC. Unset polynomial
parameters result in termination of execution as the program cannot
continue without them.
6.4 Specifications
Locate the cursor on the Specifications option of the Input menu and
press Enter (or press S) to bring up the specification
menu. You will see one of the following menu's:
The sidestreams and pumarounds options only appear as needed
(that is, if you specified any in the operation menu).
6.4.1 Flash Specifications
Locate the cursor on the Flash option, and press Enter to
bring up the Flash specification spreadsheet. When invoked for a New
problem the spreadsheet looks like this:
The cursor control keys (or first letters) and Enter may
be used to select the flash type and set the specifications.
6.4.2 Degrees of Freedom Analysis
Locate the cursor on Analysis and press Enter (or press
A) to display a window containing a degrees of freedom analysis.
This window cannot be edited and the only way to print it is to use
the Print Screen key on your keyboard (or a utility that writes screen
images to a file). Here is an example of a degrees of freedom
analysis:
6.4.3 Column Pressures
Locate the cursor on Pressures and press Enter to bring up the
Column Pressure Spreadsheet:
6.4.4 Feeds Specifications
The feed spreadsheet is for specifying the thermal condition and
component flows in all feed streams. Here is an example of its
appearance when invoked for a New problem.
375 lb/min Enter
and ChemSep will automatically convert the number to the correct value
in mol/s:
If you want to add a feed you will be prompted for the feed
stage number. If you want to eliminate a feed you will be prompted for
which feed you want to delete (by the number in the top line). The
spreadsheet will be adjusted automatically after deleting or inserting
a feed. Use the Return option when you are done with the feed
specification. If you change the feed stages and exit the feeds
specifications, ChemSep re-orders the feeds in ascending stage number.
6.4.5 Operation specifications
In the operation specifications you can define specifications for the
condenser and or reboiler (if they are present!). On entry the
operation specifications are unspecified:
Once we have specified the first specification we need to
specify the next specification by selecting the asterisk and pressing
Enter. In this case the Bottom product / Reboiler
Specifications. Use the cursor control keys and Enter or the
highlighted letters in that menu to select ONE of the available
options.
RR = 2.5 or D = [400 mol/s]
The specification is done in SI units. See the help ( F1) for
more information.
As example, we can specify a reflux ratio of 2 for the condenser
and a bottoms flow as a fraction of the feeds, of 0.6. Use the Return
option to return to the specifications menu.
B = [600 mol/s]
The specification is done in SI units. See the help ( F1) for
more information.
6.4.6 Sidestreams
If you specified a sidestream at stage 5 under the column operation
you can select the sidestreams option from the specifications menu and
get:
6.4.7 Heater / Coolers
Locate the cursor on Heaters/Coolers in the Specifications menu and
press Enter (or press H) to bring up the following
spreadsheet:
6.4.8 Efficiencies
If you are setting up a equilibrium column simulation, you can specify
the efficiencies of the stages in the column. Locate the cursor on
Efficiencies in the Specifications menu and press Enter (or press H)
to bring up the following spreadsheet:
6.4.9 Design
If you are setting up a nonequilibrium column simulation, the
column layout must be known (unless you run the column in design
mode). The column layout contains detailed information about the
tray or packing installed in the column. Generally, the layout of
trays or packed beds remains the same between column feeds and
sidestreams. These areas or "sections" are how the column layout is
handled in ChemSep. A section can consist of one simulation stage or
several stages. Each stage represent one tray or a unit height of
packing. ChemSep automatically divides tge stages over the sections.
For an ordinary distillation column with a feed in the middle, the
column has two sections: the rectification and the stripping section:
6.4.10 Pumparounds
If you specified a pumparound in the operation, there will be a
pumparound option in the specifications. Selecting it will load the
pumparound specification which works similar to the sidestream
specification. For example, if you specified a pumparound from stage
20 to stage 10 the input spreadsheet looks like:
6.5 Solve
When you have completed the Input of all data, you are ready to Solve
the problem. To execute the calculation program you may carry out one
of the following actions:
The difference between these last two two-keys is that if you press
Alt-S all input data will be checked for completeness and you
will be asked to verify the data file name before any existing file is
overwritten. If you press Alt-Q, automatic data checking is
ignored and the current file name is overwritten immediately. These
Alt-key combinations can be pressed from anywhere within ChemSep.
6.6 ChemProp
The ChemProp option allows you to switch to the ChemProp
program with a temporary file loaded that contains the component
selection in the current simulation. ChemSep User's Guide
Chapter 7. The Results Menu
The Results menu allows you to inspect the results of a simulation. If
you have simulated a Column, the Results menu looks like this:
If you have solved a Flash problem, the Results menu looks like
this:
7.1 The Tables Menu
If you have carried out a Column simulation, you may bring up the menu
of Tables by locating the cursor on the Tables option and pressing
Enter:
7.2 The Graphs Menu
Locate the cursor on the Graphs option of the Results menu and press
Enter to bring up the Graphs menu:
There are basically four different kinds of graph. Profiles,
which covers the first six items in the above list, the McCabe-Thiele
diagram, the Right triangular diagram and the Quaternary diagram.
Occasionally we will refer to the latter as a Pyramid plot (or, more
properly, a tetrahedron diagram). These graphs can be configured by
ChemSep users. To configure a graph, press Spacebar while the graph is
displayed on the screen.
7.2.1 Profiles
When Spacebar is pressed with a Profile displayed a list similar to
that shown here will be displayed:
Available identifiers:
X# Liquid mole fraction
Y# Vapour mole fraction
K# K-value
T Temperature (see also TL)
P Pressure
V Vapour flow
L Liquid flow
S Stage number
Z Stage height
HV Vapour entHalpy
HL Liquid entHalpy
where # = Component index
Additional identifiers for the Non-equilibrium model:
M# Murphree efficiency
R# mass transfer Rate
TB Bubble point Temperature
TD Dew point Temperature
TV Vapour Temperature
TL Liquid Temperature
TI Interface Temperature
XI# Liquid Interface mole fraction
YI# Vapour Interface mole fraction
FF Fraction of Flooding
WF Fraction of Weeping
$DsV $DsL densities (kg/m3)
$VisV $VisL viscosities (Pa.s)
$MwV $MwL molar weights (kg/kmol)
$CpV $CpL heat capacities (J/kmol.K)
$TcV $TcL thermal conductivities (J/K/m/s)
$Sigma surface tension (Pa.m)
$Dv#,# $Dl#,# diffusivities (m2/s)
$Atot $Avap $Aliq areas (m2, m2/m3)
$tV $tL residense times (s)
$NTUv $NTUl number of transfer units
$HTCv $HTCl heat transfer coefficients (/)
$Mv $Ml mass flows (kg/s)
$Qv $Ql volume flows (m3/s)
$Uv $Ul superfical velocities (m/s)
$Flv $Vload flow parameter, vapor loading
$Qlw vol. weir flow (m3/m.s)
$Ud downcomer velocity (m/s)
$Fs $Csf F-factor, capacity factor
$FF $Hwt Fraction of flooding, wet tray h (m)
$Hcl $Hr clear liquid and residual height (m)
$Hd $How dry tray and height over weir (m)
$Hg $Hf liquid gradient and froth h (m)
$Hdb $PhiL downcomer height (m) liq. entrain.
$Ae $PhiV mass fraction liq entrain, vap.
$Alpha $Eps liquid and vapor fractions froth
$Tv $Tl residense times (s)
$Uh $Fr-h hole velocity (m/s), froude number
$WF $Wflx fraction of weeping, weep flux
$AlphaD $TimeD liquid fraction downcomer, time
$Qmw $Pd packing minimum vol. rate, dp/dz
The Printer setup option will allow the setup of the output
device (also avaliable under the options menu). The Print
option will print the current graph to the printer (as set up under
the printer setup). This can be done as well by pressing
Ctrl-P when viewing the graph. The Reset option restores
the profiel to the original state (undoing any changes in the settings
made by the user).
7.2.2 McCabe-Thiele Diagram Spreadsheet
Press M in the Graphs menu bring up the McCabe-Thiele diagram.
Examples are provided in Chapters 10 and 11. The diagram is
constructed from the mole fractions of any two components in a
multicomponent mixture. The mole fractions on each axis are normalized
so that each axis extends from 0 to 1. ChemSep chooses the two
components to be used in the modified McCabe-Thiele diagram by
searching for the two components whose average K-values are closest
to, but either side of unity. The components used in the diagram can
be changed if desired. To adapt the diagram press the Spacebar while
the graph is displayed on the screen:
7.2.3 Right Triangular diagram spreadsheet
Press I in the Graphs menu (or locate the cursor on Right triangular
diagram and press Enter) to bring up the triangular diagram. An
example is provided in Chapter 11. The diagram is constructed by
plotting the liquid phase mole fractions of any two components in a
multicomponent mixture on the vertical and horizontal axes. ChemSep
chooses the two components to be used in the triangular diagram by
searching for the two components whose average K-values are closest to
but on either side of unity. The components used in the diagram can be
changed if desired. To adapt the diagram press the Spacebar while the
graph is displayed on the screen. A spreadsheet similar to that shown
here will be displayed.
7.2.4 Quaternary diagram spreadsheet
The Quaternary diagram is available only for four component systems.
We first became aware of this type of diagram after reading a paper by
Julka and Doherty in Chem. Eng. Sci. We believe (hope) that ChemSep is
the first simulation program to include these diagrams. Locate the
cursor on Quaternary diagram and press Enter to bring up a quaternary
diagram. These diagrams can be rotated using thee arrow keys. Press
the Spacebar to adapt the diagram. You will see a spreadsheet that
looks something like this:
7.2.5 Miscellaneous Lists
Some of the fields in the spreadsheets discussed above lead to one of
the miscellaneous lists illustrated here. Use the cursor keys (or
first letters) and Enter to select one of the items on the list.
7.3 Spreadsheet output
Spreadsheet output can be written to disk. ChemSep User's
Guide
Chapter 8. The Options Menu
If you go to the Options item of the main menu and press
Enter, the screen may look like this:
8.1 The Solve Options
Press F6 (or locate the cursor on the Solve options item of
the Options menu and press Enter) to bring up the Solve
options Spreadsheet:
8.1.1 Initialization
Locate the cursor on the Initialization line and press Enter
to bring up a list of available options. Use the cursor keys and
Enter to select one of these methods. There are three methods
available Initializing the calculations:
The default method is Automatic because it requires no user supplied
estimates of any quantity. Read the technical information ( F9)
for a discussion of how the initialization is performed for Column
simulations.
8.1.2 Method
Column and Flash problems are solved using Newton's method to solve
the equations. However, flows, temperatures, and mole fractions are
prevented from taking impossible values (i.e. negative values).
Technical details of the implementation of Newton's method are
available in the files COLUMN.MAN and FLASH.MAN.
8.1.3 Damping
If the straightforward implementation of Newton's method fails you may
want to try Damping the corrections that Newton's method would
otherwise make if left alone. You may specify different damping
factors for each of the quantities listed below:
The adjustments made by the calculation program are mutiplied with the
damping factor. Thus, a damping factor of 0.5 causes the calculations
to change the variables only half as much as the algorithm would
otherwise change them. Do NOT use damping unless you are sure you need
it. The number of iterations will increase.
8.1.4 Accuracy
The accuracy is the value of the norm of the function vector below
which calculations are considered converged. In view of the fact that
SI units are used in COLUMN and FLASH, the default value of the
convergence tolerance is 0.000001. You may wish to change this in
certain cases to obtain better results for mass and heat balance.
ChemSep provides a warning if you specify a value larger than this but
will not prevent you from using any value you choose. A value of 0.001
may be sufficient for problems that involve an Enthalpy calculation
(i.e. as long as as the selected enthalpy model is not 'None'). Note
that TP, PV, and TV flashes do not involve the enthalpy balance.
8.1.5 Number of iteratons
The number of iterations fixes the maximum number of iterations
allowed in COLUMN and FLASH before the calculations are terminated.
The default number is 30. This should be more than sufficient for most
problems. In the event that the maximum number of iterations is
exceeded, the most recent set of flows, temperatures, and mole
fractions will be written to the SEP file. To enter a value for the
convergence tolerance, move the cursor to the accuracy line and type
in a new value. The higher the value, the fewer iterations will be
needed but the problem may not be truly converged. If you are not
certain if a problem has converged, rerun it and print the iteration
history to a file. Inspection of the flows, temperatures, and
compositions will reveal if the problem has converged or not.
8.1.6 Write History
The central section of the Solve options spreadsheet is concerned with
what you see on the screen or is written to a file by the simulation
programs. The following items can be printed on the screen or to a
file:
The default responses for all of these items is off except for the
iteration count and sum of squares. It is probably not a good idea to
suppress writing of all items otherwise you might not know if the
program is working. Printing the variable and function vectors and the
Jacobian matrix is provided for development purposes only and should
not be used unless you are very very curious. The Jacobian matrix is
printed in block format. Printing the Jacobian matrix will require
quite a bit of disk space (or screen time). The iteration history can
be printed to the screen, a file, or both. You may select the location
for the iteration history to be printed by moving the cursor to the
History field pressing Enter and selecting one of the options from the
list displayed. Note that if you select file you will have very little
idea as to how the calculations are proceeding until the problem has
been solved. The name of the file to contain the iteration history
should be typed in the History file field. We suggest you use the name
of the current SEP file, but use a different extension: ".HIS".
8.1.7 Feeds Type
8.1.8 Temporary file
The column simulation program might need to use a file on disk to
write information for temporary use only during the simulation.
Specify the name you would like to use for the temporary file in the
Temporary file field of the Solve options spreadsheet. The file is
deleted automatically when the simulation is complete.
8.1.9 User Program
ChemSep allows you to run a program other than COLUMN or FLASH. You
may enter the name of a program that you would like executed in place
of these two programs. Enter the full path and extension and any
command line parameters. By default, this field is left empty.
8.1.10 User Data
Locate the cursor on the User data field and press Enter to bring up
an Edit window. You may type whatever you like in this window. It will
be saved in the SEP file but the simulation program will not use any
information in this section of the file. For example, you may wish to
write what the weather was like when you ran this simulation or which
teams won hockey games last weekend. A more practical purpose of User
data is to provide a place for you to record problem specific
information; the origin of the problem, for example. Any text entered
in User data edit window will be saved in the SEP file between the
delimiters [User Data] and [End User Data]. The information can be
displayed by returning to the User data field of the Solve options
spreadsheet.
8.1.11 DOS Extender
Personal computers can operate in two different modes: Protected mode
and Real mode. The 286 based PCs usually operate in Real mode. 386
based machines can run protected mode versions of the ChemSep
simulation programs if you recieved them when you ordered ChemSep.
Protected mode programs require a DOS extender. Protected mode
versions of the simulation programs are available for four
commercially available DOS extenders: Rational, Phar Lap, Ergo, and
CauseWay (the current default). Locate the cursor on the DOS Extender
field and press Enter to bring up a list from which you can select the
DOS Extender. For 286 machines you should select None.
8.2 Interface settings
Locate the cursor on the Interface item of the Options menu and press
Enter to bring up the Interface spreadsheet:
8.2.1 Mouse
The ChemSep interface supports the use of a mouse. Press Enter to
toggle between these options. An error message will be generated if
you attempt to enable the mouse if a mouse-driver has not been loaded.
8.2.2 Directory facility
Directory listings always include the file name and extension. You may
also display the file date and time and the file size. In addition,
the directory list may include alternative drive letters so that you
can load, edit or view files on other disk drives. Locate the cursor
on the appropriate fields and press Enter to turn these options on or
off. File names in a directory list may be sorted by name or by date &
time. Locate the cursor on the Sort by field and press Enter to toggle
between these two options.
8.2.3 Data Checks
The data is checked automatically by selecting the Solve option unless
you have elected to suppress this feature. You may turn off the
automatic data checking before running a simulation. Data checking
does not take very long and although we cannot guarantee to catch all
errors, we do not recommend turning off the check facility. Locate the
cursor on the appropriate line and press Enter to toggle between these
options.
8.2.4 Pure Component Data (PCD) file search
Options to control the searching of pure component data files (those
with a PCD extension) can be set in the Interface spreadsheet. ChemSep
will search all PCD files unless the Search All option is turned off.
ChemSep usually is supplied with just one databank and the Search all
option is On. The displayed list of components is not sorted unless
the option to do so is turned on. In the event that sorting is
enabled, the displayed list of components will be sorted according to
the last search criterion. For example, if components are found by
name they will be listed in alphabetical order. On the other hand, if
they are found by property value, they will be listed in order of
increasing value of that property value. The PCD files record just one
of the many possible names for any given component. If the PCD file is
searched by component name it may not find the component you are
looking for if you entered one of the components synonyms. Most common
synonyms are recorded in files with a SYN extension. To enable ChemSep
to search the SYN file for possible components matching the search
criterion (name or name fragment), turn on the Synonym search by
specifying the SYN file in the Synonyms File item in the interface
window. Locate the cursor on this field and press Enter twice to bring
up a directory of SYN files.
8.2.5 Screen lines
8.2.6 Initialization guess
8.2.7 Numeric format
Real number output can be shown in E-format (scientific notation) or
in a variable decimal format. Locate the cursor on the scientific
notation field and press Enter to toggle between these options.
Numbers that will not fit within the decimal format will be printed in
scientfic notation. Trailing zeroes can be removed or displayed.
Locate the cursor on the trailing zeroes field and press Enter to
toggle between these options. The number of significant digits may
also be set in this spreadsheet. To make permanent any change in the
numeric format you must Save the configuration file.
8.2.8 Default graphs settings
All Graphs can be configured to your liking after pressing Spacebar
when a graph is displayed on the screen. A few options can be set
here, however, so that, if you don't like the default settings, you
won't have to change them each time you view a graph.
8.2.9 Text printing
All tables of results are printed in view windows that can be edited
in ChemSep and printed to files or to a printer. Three items in this
spreadsheet control how these text windows are printed.
8.2.10 Sections defaults
8.2.11 Postscript default settings
8.3 Directories
Locate the cursor on the Directories item of the Options menu and
press Enter to bring up the spreadsheet that records where ChemSep's
files are stored:
Move the cursor to the name of the directory you wish to change.
Press Enter and type in the name of the new directory. Press Enter
again when you have typed in the new name completely. When you have
made all the changes you wish to make press Escape to go back to the
settings menu. Use save options to save the directory names and other
ChemSep settings.
8.4 Video Device
Locate the cursor on the Video device item of the Options menu and
press Enter to bring up a list of video devices supported by ChemSep:
CGA
MCGA
EGA
EGA64
EgaMono
IBM8514
HercMono
ATT400
VGA
PC3270
8.5 Output Device
Locate the cursor on the Output device item of the Options menu and
press Enter to bring up the Output device spreadsheet:
8.5.1 Output Devices List
ChemSep uses the device drivers from Fleming software for printing
graphic images. BGI files (printer or graphic drivers) available are
summarized in the list below. The BGI files must be in the directory
specified in the directories spreadsheet.
Epson 9-pin dot matrix
Color Epson 9-pin dot matrix
Epson 24-pin dot matrix
Color Epson 24-pin dot matrix
IBM Proprinter X24
IBM Quietwriter
Toshiba 24-pin dot matrix
Okidata ML-92 dot matrix
LaserJet II
LaserJet III
DeskJet
Color DeskJet
PaintJet
Postscript
Hewlett-Packard 7090
Hewlett-Packard 7470
Hewlett-Packard 7475
Hewlett-Packard 7550
Hewlett-Packard 7585
Hewlett-Packard 7595
ZSoft PCX
Windows 3 BMP
GEM IMG
TIFF compressed
TIFF uncompressed
ANSI CGM
AutoCAD DXF
Video Show
Word Perfect Graphics
Use the cursor keys and Enter to select one of these
printers/plotters. Note that if you normally use a Postscript printer
for printing graphs and want to save Tables for editing later with
your usual editor or word processor you will want to save the Tables
in text format rather than as a Postscript file. Use one of the other
printer emulations for saving Tables as text files. We use the Epson
dot matrix printer drivers. The list above includes all of the drivers
supported by ChemSep. However, the list that you will see includes
only those drivers that were copied to the hard disk when you
installed ChemSep. If the driver you need is not shown you can copy
the required driver from the original diskette or run the install
program again.
8.5.2 Printer Port List
8.5.3 Printer Mode list
8.6 save Options
Locate the cursor on the Save options item of the Options menu in
order to save the current settings for future use. ChemSep's
configuration file records the:
To save a ChemSep configuration (CNF) file locate the cursor on Save
options and press Enter to bring up a file name prompt box with the
default file mask *.CNF:
8.7 Load Options
At startup ChemSep loads the default file CHEMSEP.CNF if it is present
in the directory from which ChemSep was started. To load a different
configuration locate the cursor on the Load options item of the
Options menu and press Enter to bring up a file name prompt
box with the default configuration file and path.
Chapter 9. Example 1. Equilibrium Flash of an Eight Component Mixture
An important problem in chemical engineering is to determine the phase
of a mixture at a particular temperature and pressure. Related
problems include the calculation of the boiling point or dew point
temperatures (or pressures) of a particular mixture. With help of an
example from the chemical engineering literature we explore ChemSep's
Input and Results menus for Flash problems. The problem is from a
paper by T. Gundersen, "Numerical Aspects of the Implementation of
Cubic Equations of State in Flash Calculation Routines" (Comp. Chem.
Eng., 6, pp245-255, 1982) although many others have used the problem
for testing methods of performing flash calculations. We are asked to
determine the vapour fraction of an eight component natural gas
mixture at a pressure of 100 atm and a temperature of 250 K. The
composition of the mixture is given below in the ChemSep summary of
the complete problem specification. Compare the information printed
below with what you will see in the ChemSep menus and spreadsheets.
Flash C:\CS2\8COMP.SEP
Components:
Nitrogen
Methane
Ethane
Propane
n-Butane
n-Pentane
n-Hexane
n-Heptane
Operation:
Flash
Properties:
EOS K model
Soave-RK Cubic EOS
Excess Enthalpy
Specifications:
Feed 1
Pressure (atm) 1.0000
Vapour fraction (Ä)
Temperature (K) 298.15
Component flows (mol/s)
Nitrogen 0.0054000
Methane 0.72800
Ethane 0.054600
Propane 0.030200
n-Butane 0.030700
n-Pentane 0.068800
n-Hexane 0.043800
n-Heptane 0.038500
Flash Pressure & temperature
Pressure 100.00 (atm)
Temperature 250.00 (K)
Press F3 to bring up the Load option of the File menu. Type *.SEP (if
that is not displayed at the end of the path) and press Enter to bring
up a Directory of the SEP files on disk. This particular problem is
contained in the file 8COMP.SEP. Press 8 to bring the cursor to the
first file whose name begins with an 8 and press Enter to Load the
file. Since this file contains results, the cursor jumps to the
Results menu. We will explore the results to this flash problem
shortly. First, however, we will review the Input. Press Alt-I and
then C to go the Components menu. On the right hand side of the screen
we see the list of selected components.
ChemSep 2.0
File Input Results Options Quit
C:8COMP.SEP
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ÚÄ< Components >Ä¿
³ Components ³ ³ Nitrogen ³
³ÚÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ³ ³ Methane ³
³³ Select ³ ³ ³ Ethane ³
³³ Delete ³ ³ ³ Propane ³
³³ Substitute ³ ³ ³ n-Butane ³
À³ Reorder ³ÄÙ ³ n-Pentane ³
³ Save set ³ ³ n-Hexane ³
³ Load set ³ ³ n-Heptane ³
ÃÄÄÄÄÄÄÄÄÄÄÄÄÄ´ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
F1:Help F2:Last help F3:Load F4:Save F5:Units F6:Options F9:Info F10:Main menu
Press R to clear the list and go back to the previous menu. Now go to
Operation and press Enter. The screen will look like this (with the
cursor located on Flash).
ChemSep 2.0
File Input Results Options Quit
C:8COMP.SEP
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Components ³
³ Operation ³
ÚÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄ¿
³ Flash ³
³ Column ³
ÃÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
F1:Help F2:Last help F3:Load F4:Save F5:Units F6:Options F9:Info F10:Main menu
With the cursor on Flash press Enter to accept the Flash operation. A
small prompt box appears asking for the number of feeds. The answer we
gave when setting up this problem was 1 (as it would normally be).
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Flash ³
³ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³³ Number of feeds: 1 ³
³ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Entering a number of feeds greater than one is useful for carrying out
mass and energy balances for stream mixers. Press R to Return to the
Input menu. The cursor should be located on Properties. Press Enter to
bring up the K-models menu:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ K model ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Raoult's law ³
³ EOS ³
³ Gamma-Phi ³
³ DECHEMA ³
³ Chao-Seader ³
³ Polynomial ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
As with the depropanizer, we have selected the EOS model as this was
the model used by Gundersen (it is, of course, the most appropriate
model for this system). Pressing Enter brings up the EOS menu:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Cubic EOS ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Soave-RK ³
³ API-SRK ³
³ Peng-Robinson ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Gundersen used the Soave-Redlich-Kwong (SRK) EOS. With the cursor on
Soave-RK, press Enter and return to the Properties menu. The cursor
should now be located on the Enthalpy option. Press Enter to bring up
the Enthalpy menu and Enter another time to accept the Excess enthalpy
model. The cursor should now be located on Load data. Press Enter to
bring up the following menu:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Load data for: ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Cubic EOS ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
In this case there is only one model in this list, the Cubic EOS.
Press Enter to go to the spreadsheet where you can enter the data:
ChemSep 2.0
File Input Results Options Quit
C:8COMP.SEP
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Cubic EOS: Soave-RK (Ä) ³
ÃÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ Component i Component j kij ³
³ Nitrogen Methane * ³
³ Nitrogen Ethane * ³
³ Nitrogen Propane * ³
³ Nitrogen n-Butane * ³
³ Nitrogen n-Pentane * ³
³ Nitrogen n-Hexane * ³
³ Nitrogen n-Heptane * ³
³ Methane Ethane * ³
³ Methane Propane * ³
³ Methane n-Butane * ³
³ Methane n-Pentane * ³
³ Methane n-Hexane * ³
³ Methane n-Heptane * ³
ÃÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ Reset Library Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
F1:Help F2:Last help F3:Load F4:Save F5:Units F6:Options F9:Info F10:Main menu
Not all of the interaction parameters that can be entered for this
system are listed in this screen image. The window simply is not large
enough to show the entire spreadsheet on one screen. Press PgDn to see
some more of the spreadsheet.
ChemSep 2.0
File Input Results Options Quit
C:8COMP.SEP
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Cubic EOS: Soave-RK (Ä) ³
ÃÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ Component i Component j kij ³
³ Methane n-Hexane * ³
³ Methane n-Heptane * ³
³ Ethane Propane * ³
³ Ethane n-Butane * ³
³ Ethane n-Pentane * ³
³ Ethane n-Hexane * ³
³ Ethane n-Heptane * ³
³ Propane n-Butane * ³
³ Propane n-Pentane * ³
³ Propane n-Hexane * ³
³ Propane n-Heptane * ³
³ n-Butane n-Pentane * ³
³ n-Butane n-Hexane * ³
ÃÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ Reset Library Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
F1:Help F2:Last help F3:Load F4:Save F5:Units F6:Options F9:Info F10:Main menu
As in the previous example, it is possible to set all of these
parameters to zero and obtain acceptable results. This means we can
leave the * as the default zeroes. Move the cursor to the Return field
and press Enter twice. The cursor should now be located on the
Specifications option of the Input menu. Press Enter to bring up this
screen:
ChemSep 2.0
File Input Results Options Quit
C:8COMP.SEP
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Components ³
³ Operation ³
³ Properties ³
³ Specifications ³
³ SoÚÄÄÄÄÄÄÄÄ¿ ³
ÀÄÄÄ´ Feeds ÃÄÄÄÙ
³ Flash ³
ÃÄÄÄÄÄÄÄÄ´
³ Return ³
ÀÄÄÄÄÄÄÄÄÙ
F1:Help F2:Last help F3:Load F4:Save F5:Units F6:Options F9:Info F10:Main menu
Press F to bring up the feed spreadsheet:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Feed 1 ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ State: T & P ³
³ Pressure (atm) 1.00000 ³
³ Vapour fraction (Ä) ³
³ Temperature (K) 298.150 ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Flowrates (mol/s) ³
³ Propane 0.030200 ³
³ n-Butane 0.030700 ³
³ n-Pentane 0.068800 ³
³ n-Hexane 0.043800 ³
³ n-Heptane 0.038500 ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Total flowrate 1.00000 ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Insert Delete Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
The central portion of this spreadsheet lists the component feed
flows. In fact, we have entered the mole fractions (the actual flows
and their units are not relevant when it comes to determining the
vapour fraction of this mixture). This spreadsheet is not long enough
to show the feed flows for all eight components. Use PgUp and PgDn to
see all the component flows (mole fractions). Note that the actual
flow rates are not particularly relevant in this problem. We need to
determine the phase condition of the eight component mixture so we
have entered the mole fractions of all components as the feed flows
(in whatever units were last selected). The mole fractions sum to
unity (as they must). Remove this spreadsheet from the screen, locate
the cursor on the Flash option, and press Enter to bring up the Flash
specification spreadsheet:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Flash ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Flash type PT ³
³ Pressure (atm) 100.00 ³
³ Temperature (K) 250.00 ³
³ Vapour flow (mol/s) ³
³ Liquid flow (mol/s) ³
³ Heat duty (J/s) ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
This window summarizes the two important specifications for the flash;
the pressure and temperature. The first field of this spreadsheet
indicates the flash type. The other two fields are adjacent to the two
variables indicated on the top line. Locate the cursor on the top
field and press Enter. You will see this list of available flash
types:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Pressure & temperature ³
³ Pressure & vapour flow ³
³ Pressure & liquid flow ³
³ Pressure & heat duty ³
³ Temperature & vapour flow ³
³ Temperature & liquid flow ³
³ Temperature & heat duty ³
³ Vapour flow & heat duty ³
³ Liquid flow & heat duty ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Each line of this list identifies two variables from among the vapour
flow, the liquid flow, the flash temperature, the flash pressure, and
the heat duty. The cursor control keys and Enter may be used to select
the flash type. With the cursor on the top line of this list press
Enter to accept the option already selected. With the Pressure &
temperature specified as shown above, the input is complete. Now we
should be ready to Solve this problem. We could locate the cursor on
Solve and press Enter to initiate the solution process. On the other
hand, we could try holding down the Alt key and pressing S. ChemSep
will ask us if we want to overwrite the current file. Press Y to agree
to this suggestion. ChemSep's shell program, CS, will load the
simulation program, Flash, a window will appear in the center of the
screen, and you will see something like this:
ChemSep 2.00
File Input Results Options Quit
C:8COMP.SEP 8 seconds 6 iterations
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Components ³
³ Operation ³
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ ³
³ ³
³ ChemSep / Flash Version 2.0A ³
³ Copyright(c) H.Kooijman, A. Haket, R.Taylor, 1989-91 ³
³ ³
³ Checking data file C:\CS2\8COMP.SEP ³
³ Reading pure component property libraries ³
³ Reading thermodynamic property options and data ³
³ Determining feed conditions ³
³ ³
³ ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
F1:Help F2:Last help F3:Load F4:Save F5:Units F6:Options F9:Info F10:Main menu
A very short time later, after Flash has completed its reading of the
data files and input information, it will begin the calculations. This
calculation does not take very long at all (even on a slow computer).
When the calculations are complete you should see something like this:
ChemSep 2.00
File Input Results Options Quit
C:8COMP.SEP 8 seconds 6 iterations
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Components ³
³ Operation ³
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ ³
³ 2 4.9549E-03 ³
³ 3 1.5876E-03 ³
³ 4 6.9533E-06 ³
³ 5 2.3463E-10 ³
³ 6 4.2639E-16 ³
³ ³
³ Convergence obtained in 6 iterations ³
³ ³
³ ³
³ ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
F1:Help F2:Last help F3:Load F4:Save F5:Units F6:Options F9:Info F10:Main menu
The shell program will reload the interface and read in both input and
results and the cursor will jump to the Results menu:
ChemSep 2.0
File Input Results Options Quit
C:8COMP.SEP
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Mass and Energy Balances ³
³ K-Values ³
³ Streams ³
³ Specifications ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
F1:Help F2:Last help F3:Load F4:Save F5:Units F6:Options F9:Info F10:Main menu
Locate the cursor on Streams and press Enter to bring up the stream
table:
ChemSep 2.00
File Input Results Options Quit
C:8COMP.SEP 8 seconds 6 iterations
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ L1 C1 ³
³ ³
³ Stream Feed 1 Top Bottom ³
³ ³
³ Pressure (atm) 1.0000 100.00 100.00 ³
³ Vapour fraction (Ä) 1.0000 1.0000 0.0000 ³
³ Temperature (K) 298.15 250.00 250.00 ³
³ Enthalpy (J/mol) -41.226 -5073.4 -16157 ³
³ ³
³ Mole flows (mol/s) ³
³ Nitrogen 0.005400 0.003421 0.001980 ³
³ Methane 0.7280 0.3404 0.3876 ³
³ Ethane 0.05460 0.01233 0.04227 ³
³ Propane 0.03020 0.003616 0.02658 ³
³ n-Butane 0.03070 0.001841 0.02886 ³
³ n-Pentane 0.06880 0.002044 0.06676 ³
³ n-Hexane 0.04380 0.0006458 0.04315 ³
³ n-Heptane 0.03850 0.0002899 0.03821 ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Alt-N:Next Alt-P:Previous Alt-E:Edit Ctrl-P:Print
The results window is not large enough to accommodate all of this
table. Use Up, Down, PgUp, and PgDn to scroll the table. You can Edit
this table after pressing Alt-E and print it by pressing Ctrl-P. The
complete set of Tables are reproduced below. You will see from the
Stream table that this particular mixture is 36.41% vapour at 100 atm
and 250 K. As an exercise in the use of ChemSep, determine the vapour
fraction at several other temperatures. It is important to know that
there are certain combinations of temperature and pressure (or other
variables) where ChemSep will not be able to find a solution.
Sometimes this is due to limitations of our program. More often,
however, it will be because there is no solution.
Mass and Energy Balances
Stream / Apparatus Mass (mol/s) Energy (J/s)
Feed 1 1.0000 -41.226
Top -0.36461 1849.8
Bottom -0.63539 10266
Flash Duty -12075
ÄÄÄÄÄÄÄÄÄÄÄ + ÄÄÄÄÄÄÄÄÄÄÄ +
Balance 5.8208E-08 -0.0078125
Component discrepancies (mol/s)
Nitrogen -6.104E-10
Methane 1.6772E-07
Ethane 2.1872E-08
Propane 3.3630E-08
n-Butane 2.4888E-08
n-Pentane 1.8051E-07
n-Hexane 1.3717E-08
n-Heptane 2.0399E-08
K-Values
Nitrogen 3.0113
Methane 1.5307
Ethane 0.50812
Propane 0.23701
n-Butane 0.11114
n-Pentane 0.053366
n-Hexane 0.026077
n-Heptane 0.013220
Stream Summary Table
Stream Feed 1 Top Bottom
Pressure (atm) 1.0000 100.00 100.00
Vapour fraction (Ä) 1.0000 1.0000 0.00000
Temperature (K) 298.15 250.00 250.00
Enthalpy (J/mol) -41.226 -5073.4 -16157
Mole flows (mol/s)
Nitrogen 0.0054000 0.0034205 0.0019795
Methane 0.72800 0.34043 0.38757
Ethane 0.054600 0.012326 0.042274
Propane 0.030200 0.0036156 0.026584
n-Butane 0.030700 0.0018406 0.028859
n-Pentane 0.068800 0.0020443 0.066756
n-Hexane 0.043800 0.00064575 0.043154
n-Heptane 0.038500 0.00028986 0.038210
Total molar flow 1.0000 0.36461 0.63539
Mole fractions (Ä)
Nitrogen 0.0054000 0.0093813 0.0031154
Methane 0.72800 0.93367 0.60998
Ethane 0.054600 0.033806 0.066532
Propane 0.030200 0.0099164 0.041839
n-Butane 0.030700 0.0050482 0.045420
n-Pentane 0.068800 0.0056068 0.10506
n-Hexane 0.043800 0.0017711 0.067918
n-Heptane 0.038500 0.00079499 0.060136
Mass flows (kg/s)
Nitrogen 0.00015127 9.5820E-05 5.5453E-05
Methane 0.011679 0.0054614 0.0062178
Ethane 0.0016418 0.00037064 0.0012712
Propane 0.0013317 0.00015944 0.0011723
n-Butane 0.0017844 0.00010698 0.0016774
n-Pentane 0.0049639 0.00014749 0.0048164
n-Hexane 0.0037746 5.5649E-05 0.0037189
n-Heptane 0.0038579 2.9045E-05 0.0038288
Total mass flow 0.029185 0.0064264 0.022758
Mass fractions (Ä)
Nitrogen 0.0051833 0.014910 0.0024366
Methane 0.40018 0.84983 0.27321
Ethane 0.056256 0.057674 0.055855
Propane 0.045631 0.024809 0.051510
n-Butane 0.061141 0.016647 0.073705
n-Pentane 0.17009 0.022951 0.21163
n-Hexane 0.12933 0.0086594 0.16341
n-Heptane 0.13219 0.0045196 0.16824
ChemSep User's Guide
Chapter 10. Example 2. A Depropanizer
This example is based on a problem coined by Professor Hans
Wesselingh. The depropanizer is a high pressure column for separating
propane (and more volatile components) from butane (and heavier
components). The complete problem specification is given below. It may
be worth noting here that this summary was produced by ChemSep (by
pressing F8, deleting a few lines of irrelevant information, and
pressing Ctrl-P).
Column C:\CHEMSEP\DEPROP.SEP
Components:
Ethane
Propane
n-Butane
n-Pentane
Operation:
Simple Distillation
Partial (Vapour product) Condenser
Partial (Liquid product) Reboiler
20 Stages
Feeds to stages 10
Properties:
EOS K model
Peng-Robinson Cubic EOS
Excess Enthalpy
Specifications:
Column pressure
Condenser pressure 20.000 (bar)
Top pressure 20.000 (bar)
Default efficiency = 1.0000 (Ä)
Feed 1
Stage 10
Pressure (bar) 20.000
Vapour fraction (Ä)
Temperature (K) 298.15
Component flows (mol/s)
Ethane 100.00
Propane 300.00
n-Butane 500.00
n-Pentane 100.00
Condenser
Reflux ratio = 2.0000 (Ä)
Reboiler
Bottom product flow rate = 600.00 (mol/s)
Load the file DEPROP.SEP as described in the section on ChemSep's
Directory Facility. Before we begin the tour of the Input menu, press
F8 to display a window containing the summary shown above. Use
PgUp and PgDn to scroll the summary window. Press
Escape to clear the summary. Use the cursor control keys to go the
Input menu. The screen should look like this:
ChemSep 2.0
File Input Results Options
Quit
C:DEPROP.SEP
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Components ³
³ Operation ³
³ Properties ³
³ Specifications ³
³ Solve ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
F1:Help F2:Last help F3:Load F4:Save F5:Units F6:Options F9:Info F10:Main menu
With the cursor positioned on Components, press Enter (or C) to obtain
the following screen:
ChemSep 2.0
File Input Results Options
Quit
C:DEPROP.SEP (New problem)
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ÚÄ< Components >Ä¿
³ Components ³ ³ Ethane ³
³ÚÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ³ ³ Propane ³
³³ Select ³ ³ ³ n-Butane ³
³³ Delete ³ ³ ³ n-Pentane ³
³³ Substitute ³ ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
À³ Reorder ³ÄÙ
³ Save set ³
³ Load set ³
³ÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
F1:Help F2:Last help F3:Load F4:Save F5:Units F6:Options F9:Info F10:Main menu
The box in the upper right hand corner lists the components that have
already been selected. Adding (or removing) components from the list
in the top right is fully described in the Components section of the
User's Guide. We used Select by Family to load the four components in
this problem. Remember to use the Escape key if you think you are
stuck somewhere with nowhere to go. Escape will always let you go back
one level (until you get to the Main menu). Now accept the Return
option in the Components menu. This will send you back one menu level
and place the cursor on the next item in that menu. Press Enter to
bring up the Operation menu:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Flash ³
³ Column ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
The cursor should be on Column. Remember that the cursor is located on
the last menu option accepted when we go to a new menu. That is why we
can walk through the input menu simply by pressing Enter. With the
cursor on Column, press Enter (or press C) to bring up the Operation
spreadsheet:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Operation Simple Distillation ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Condenser Partial (Vapour product) ³
³ Reboiler Partial (Liquid product) ³
³ Stages 20 ³
³ Feed stages 10 ³
³ Sidestream stages ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
The Operation spreadsheet summarizes the column configuration and its
basic purpose. Locate the cursor on each of the fields in this window
and press Enter. You will find that, in common with many other ChemSep
spreadsheets, some of the fields lead to other menus or lists from
which you must select an appropriate option. Other fields require you
to type in a number. In the Operation window, the first three items
lead to lists whereas the last three require you to type in numbers.
In this case, there is no need to enter anything in the last field
which explains why it is empty (see, however, the extractive
distillation example). Compare the information in this window to that
listed in the summary specification given at the start of this
problem. Use the Help system (F1, F2) to learn more about the items in
this spreadsheet. When you are clear on the purpose of all of these
items, move the cursor to the Return field and press Enter. This
action will return you to the Input menu with the cursor located on
the Properties option. Press Enter to display the following menu:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Equilibrium models ³
³ Enthalpy ³
³ Load data ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Locate the cursor on the Equilibrium Models option (it should be
there) and press Enter (or press E) to obtain the K-models menu:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ K model ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Raoult's law ³
³ EOS ³
³ Gamma-Phi ³
³ DECHEMA ³
³ Chao-Seader ³
³ Polynomial ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Each item in this menu represents a method for computing K-values. In
this case we selected the EOS model as the most appropriate so the
cursor should be on that line. Press Enter to bring up the Cubic EOS
menu:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Cubic EOS ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Soave-RK ³
³ API-SRK ³
³ Peng-Robinson ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Any of these models can be used for this simulation. We selected the
Peng-Robinson model. It is left as an exercise for you to see if the
other models make a difference. Selection of the EOS brings you back
to the Properties menu with the cursor on Enthalpy. Press Enter to see
the list of enthalpy models:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Enthalpy ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ None ³
³ Ideal ³
³ Excess ³
³ Polynomial ³
³ User defined ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
We have selected Excess (as we do in most cases) as it is the most
complete method of calculating enthalpies available in ChemSep. Use
the Help system (F1) to learn more about these models. With the cursor
on Excess press Enter (or press E) to accept the enthalpy model and
return to the properties menu. To complete our review of the
Properties menu go to the Load data option (the cursor should be
there) and press Enter. This brings up a menu that lists the models
for which you must enter parameters.
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Load data for: ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Cubic EOS ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
In this case there is only one model in this list, the Cubic EOS.
Press Enter to bring up a spreadsheet where you can enter the
necessary data:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Cubic EOS: Peng-Robinson (Ä) ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Component i Component j kij ³
³ Ethane Propane * ³
³ Ethane n-Butane * ³
³ Ethane n-Pentane * ³
³ Propane n-Butane * ³
³ Propane n-Pentane * ³
³ n-Butane n-Pentane * ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Reset Library Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Notice that this window identifies the model selected earlier
(Peng-Robinson). The Units of the parameters are shown between ()
after the model name. (-) means the parameters are dimensionless.
There is an asterisk (*) in each place where parameters must be
entered. ChemSep recognizes the * as the default value when it does
its calculations. In this particular spreadsheet the default value for
the * is zero (note that * does not mean zero in all spreadsheets). As
it happens, it is possible to set all of these parameters to zero to
obtain acceptable results. Since it is not actually necessary to enter
zeroes in this spreadsheet, use the cursor control keys to go to the
Return field and press Enter. This will bring us to the Specifications
menu:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Analysis ³
³ Pressures ³
³ Heaters/Coolers ³
³ Efficiencies ³
³ Feeds ³
³ Condenser ³
³ Reboiler ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Use the cursor control keys and F1 (Help) to explore each of these
items. You do not need to read the Analysis screen although it may be
interesting. For this example it looks like this:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ ChemSep requires the following to be specified: ³
³ - The number of stages (1) ³
³ - The location of all feeds (1) ³
³ - The location of all sidestreams (0) ³
³ - For each feed stream you must specify ³
³ the component flows (4) and ³
³ two of the temperature, pressure and vapor fraction (2) ³
³ - The pressure in each stage (18) ³
³ - The heat duty on each stage except reboilers and condensers (18), ³
³ the heat duty will be assumed to be zero unless specified differently ³
³ - The pressure in the condenser (1) ³
³ - For the condenser you must select one variable to specify (1) ³
³ - The pressure in the reboiler (1) ³
³ - For the reboiler you must select one variable to specify (1) ³
³ ³
³ Therefore, the total number of degrees of freedom is 48. ³
³ ³
³ Press
The numbers in parentheses represent the numbers of degrees of
freedom. The total number of degrees of freedom is the sum of the
numbers in parentheses. Press F1 to find out how the number of degrees
of freedom has been calculated. The Pressure spreadsheet looks like
this:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Pressures (bar) ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Condenser pressure 20.000 ³
³ Column pressure Constant pressure ³
³ Top pressure 20.000 ³
³ Pressure Drop ³
³ Bottom pressure ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
The second line in this window indicates the method of determining the
pressure profile in the column. Locate the cursor on line two and
press Enter to bring up the following list of options:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Constant pressure ³
³ Bottom & top pressures ³
³ Fixed pressure drop ³
³ Estimated pressure drop ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Press Enter to accept our choice of Constant pressure. The choice you
make here determines how many fields in the Pressure spreadsheet need
to be filled in. In this case, only the pressure at the top of the
column need be specified so only the Top pressure field is active.
With the cursor on the Return field, press Enter to return to the
Specifications menu. Press H to display the Heaters/Coolers
spreadsheet:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Heaters/Coolers ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Stage Duty (J/s) ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Insert Delete Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
ChemSep allows you to specify the heat duty of any stage. The default
value of the heat duties is zero (except for the heat duties of
Condensers and Reboilers which, if they are specified at all, are
specified in their own spreadsheets). The Heaters/Coolers spreadsheet
shown here has no numerical entries. This means that the default value
is used for all stages. The cursor should be located on the Return
field. Press Enter to go back to the Specifications menu. With the
cursor on Efficiencies press Enter to display the following
spreadsheet:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Murphree Efficiencies ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Stage Efficiency (Ä) ³
³ Default 1.0000 ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Insert Delete Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
This spreadsheet lets you know that the default value of the Murphree
efficiency is unity for all stages. Additional lines appear in this
spreadsheet whenever you wish to specify unequal efficiencies on
different stages. Consult the Efficiencies spreadsheet for a more
detailed description of how to specify differing efficiencies. Locate
the cursor on the Return field and press Enter to go back to the
Specification menu. The cursor should be located on Feeds. Press Enter
to bring up the Feeds spreadsheet looks like this.
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Feed 1 ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Feed stage 10 ³
³ State: T & P ³
³ Pressure (bar) 20.000 ³
³ Vapour fraction (Ä) ³
³ Temperature (K) 298.15 ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Flowrates (mol/s) ³
³ Ethane 100.00 ³
³ Propane 300.00 ³
³ n-Butane 500.0 ³
³ n-Pentane 100.00 ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Total flowrate 1000.0 ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Insert Delete Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Use the cursor control keys and Enter to explore this spreadsheet.
Notice that you can Insert and Delete feeds here as well as in the
Operation spreadsheet. Changes to feed numbers and stage locations
made in this menu are reflected in the Operations spreadsheet. When
you are sure you understand all of the items in the Feeds spreadsheet,
locate the cursor on the Return field and press Enter. You will be
returned to the Specifications menu and the cursor will be located on
Condenser. Press Enter once more to bring up the Top product /
condenser specification spreadsheet:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Top product / condenser Reflux ratio ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Reflux ratio (Ä) 2.5000 ³
³ Heat duty of condenser (J/s) ³
³ Temperature of condensate ( C) ³
³ Distillate flow rate (mol/s) ³
³ Reflux flow rate (mol/s) ³
³ Component flow (mol/s) ³
³ Mole fraction of a component (Ä) ³
³ Component recovery (Ä) ³
³ Fraction of combined feeds recovered (Ä) ³
³ Split between two components (Ä) ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
The left hand column of this spreadsheet lists the top product
condenser specifications that can be selected. The top field in right
hand column identifies which of these options has been selected. In
the field to the right of the appropriate option is the numerical
value of the specified quantity. With the cursor on the top right
field press Enter to display the menu of possible specifications:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Reflux ratio ³
³ Heat duty of condenser ³
³ Temperature of condensate ³
³ Distillate flow rate ³
³ Reflux flow rate ³
³ Component flow ³
³ Mole fraction of a component ³
³ Component recovery ³
³ Fraction of combined feeds recovered ³
³ Split between two components ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Press F1 to learn more about each of these options. With the cursor on
the top line, press Enter (or press R) to accept the Reflux ratio
specification. You will return to the top product / condesner
specification spreadsheet and the cursor should be located on the
field where the numerical value of the specification is entered. In
this example we have chosen to specify the Reflux ratio at 2.5. Locate
the cursor on the Return field and press Enter to return to the
Specifications menu. The cursor should be located on Reboiler. Press
Enter to bring up the Bottom product / reboiler specification
spreadsheet:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Bottom product / reboiler Bottom product flow rate ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Boilup ratio (Ä) ³
³ Heat duty of reboiler (J/s) ³
³ Temperature of reboiler ( C) ³
³ Bottom product flow rate (mol/s) 600.00 ³
³ Reboiled vapour flow (mol/s) ³
³ Component flow (mol/s) ³
³ Mole fraction of a component (Ä) ³
³ Component recovery (Ä) ³
³ Fraction of combined feeds recovered (Ä) ³
³ Split between two components (Ä) ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
This spreadsheet is organized in the same way as the top product /
condenser specification spreadsheet. The top right field identifies
the chosen specification. With the cursor on the top right field,
press Enter to display the menu of options:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Boilup ratio ³
³ Heat duty of reboiler ³
³ Temperature of reboiler ³
³ Bottom product flow rate ³
³ Reboiled vapour flow ³
³ Component flow ³
³ Mole fraction of a component ³
³ Component recovery ³
³ Fraction of combined feeds recovered ³
³ Split between two components ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
As in the condenser specification menu, the cursor is located on the
last specification made. In this example, the Bottom product flow rate
is specified (consult the summary again). With the cursor on the
fourth option of this list, press Enter (or press o) to select this
option and return to the Bottom product/ reboiler specification
spreadsheet. The cursor should be located on a field adjacent to
Bottom product in the spreadsheet. In this example, the bottom product
rate has been set to 600 mol/s. With the cursor on the Return field,
press Enter to return to the Specifications menu. We have completed
our review of the input procedure. The cursor should be located on the
Return option so press Enter (or R) to return to the Input menu. The
cursor will be located on the Solve item and that is the only thing
left for us to do. Press Enter one more time. This last action
initiates the solution process. The first thing done is that ChemSep
checks for any missing or obviously inconsistent data. Message boxes
informing you of any such oversights will appear only as needed and
you will be taken directly to the place where you should enter the
missing data. In this case there should be no messages of this kind
since we created the example for you. If you changed something (either
by accident or by design) you may see a warning message if your change
leads to some inconsistency that the program can detect. Once the data
are verified, ChemSep writes it to a file. You may be asked to verify
if a file name is to be overwritten or not. If not, you need to go to
the File menu and save the file under a new name. The next thing that
will happen is that the ChemSep shell, CS, calls up the appropriate
simulation program to solve the problem. A window appears in the
center of the screen and the simulation program writes messages there
to let you know the current status of the calculations. A short time
after loading the simulation program the screen will look something
like this:
ChemSep 2.0
File Input Results Options Quit
C:DEPROP.SEP
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Components ³
³ Operation ³
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ ³
³ ChemSep / Column Version 2.0A ³
³ Copyright(c) A.Haket, H.Kooijman, R.Taylor, 1989-91 ³
³ ³
³ Checking data file C:\CS2\DEPROP.SEP ³
³ Reading column configuration ³
³ Reading pure component property libraries ³
³ Reading thermodynamic property options and data ³
³ Parameters missing - set to zero ³
³ Reading column specifications ³
³ ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
F1:Help F2:Last help F3:Load F4:Save F5:Units F6:Options F9:Info F10:Main menu
Later on, when the simulation program is doing calculations (rather
than reading the input files and databanks) the screen might look
something like this:
ChemSep 2.0
File Input Results Options Quit
C:DEPROP.SEP
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Components ³
³ Operation ³
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ ³
³ ³
³ Iteration Sum of squares ³
³ ³
³ 0 9.0628E+06 ³
³ 1 7.4113E+04 ³
³ 2 2.4542E+03 ³
³ 3 4.6203E+01 ³
³ 4 1.4788E-01 ³
³ 5 1.0237E-05 ³
³ ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
F1:Help F2:Last help F3:Load F4:Save F5:Units F6:Options F9:Info F10:Main menu
When the calculations are complete, the program will inform you of
this fact, the interface reloads the input data together with the
results and jumps to the Results menu. In this example the screen
looks like this:
C:DEPROP.SEP 78 seconds 6 iterations
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Graphs ³
³ Tables ³
³ Spreadsheet ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Notice that the file line now includes the number of iterations
required to obtain convergence and the time taken. It should be
pointed out that the time reported on the file line should not be used
as a measure of the time taken to perform the numerical calculations.
The time reported also includes the time taken to load the simulation
program and reload the interface into memory. The time taken for these
two actions varies from computer to computer. With the cursor located
on the Tables option press Enter to obtain a list of the tables that
can be reviewed:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Mass and Energy Balances ³
³ T/P/Flow profiles ³
³ Component profiles ³
³ Streams ³
³ Specifications ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
This is what the screen looks like for the depropanizer when you go
the Streams option and press Enter.
ChemSep 2.0
File Input Results Options Quit
C:DEPROP.SEP 78 seconds 6 iterations
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ L1 C1 ³
³ ³
³ Stream Feed 1 Top Bottom ³
³ ³
³ Stage 10 1 20 ³
³ Pressure (bar) 20.000 20.000 20.000 ³
³ Vapour fraction (Ä) 0.0000 1.0000 0.0000 ³
³ Temperature (K) 298.15 321.5 392.6 ³
³ Enthalpy (J/mol) -19280 -449.22 -6217.1 ³
³ ³
³ Mole flows (mol/s) ³
³ Ethane 100.00 100.00 0.003601 ³
³ Propane 300.00 290.13 9.874 ³
³ n-Butane 500.0 9.876 490.1 ³
³ n-Pentane 100.00 0.0010369 100.00 ³
³ ³
³ Total molar flow 1000.0 400.0 600.0 ³
³ ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Alt-N:Next Alt-P:Previous Alt-E:Edit Ctrl-P:Print
All Tables are written to a View window. There is insufficient space
on the screen to display the entire table. Use the cursor control
keys, Up, Down, PgUp, PgDn, Home and End to see more of these tables.
Notice that the Function key bar at the foot of the screen has been
replaced by a list of a few keys that have a special purpose in a View
window.
Alt-N View the next table.
Alt-P View the previous table.
Alt-E Edit the displayed window
Ctrl-P Print the displayed window to a file or a printer
Continue to press Alt-N or Alt-P until you have seen the tables in
turn. The Edit mode is quite useful because it allows you to customize
the tables to the form and content you like before you print them
(either in a file or directly to the printer). The edit keys that you
can use in single spreadsheet fields can be used in an edit window.
Ctrl-Backspace, for example, deletes the line the cursor is on. Note
that ChemSep cannot read these windows (it only writes them) so it
cannot read any changes you make. Further those changes are lost as
soon as you go to another window or press Escape. Make sure you print
the table (if you have made any changes to it and want to keep the
changed format) before you clear the window. Several of these tables
are reproduced below. Press Escape to clear the current table and
return to the list of tables.
Mass and Energy Balances
Stream / Apparatus Mass (mol/s) Energy (MW)
Feed 1 1000.0 -19.280
Top -400.00 0.17969
Bottom -600.00 3.7303
Condenser Duty -10.371
Reboiler Duty 25.741
ÄÄÄÄÄÄÄÄÄÄÄ + ÄÄÄÄÄÄÄÄÄÄÄ +
Balance 0.00000 -2.200E-05
Component discrepancies (mol/s)
Ethane -2.977E-05
Propane 0.00011656
n-Butane -2.517E-04
n-Pentane 0.00010033
Flow, Temperature and Pressure Profiles
Stage Temperature Pressure Flow rates (mol/s)
(K) (bar) Liquid Vapour Feed
Product
1 322.89 20.000 800.00 400.00 V 400.00
2 330.21 20.000 782.49 1200.0
3 335.49 20.000 759.87 1182.5
4 340.04 20.000 739.77 1159.9
5 344.02 20.000 725.04 1139.8
6 347.29 20.000 714.87 1125.0
7 349.86 20.000 706.98 1114.9
8 351.89 20.000 698.82 1107.0
9 353.67 20.000 687.71 1098.8
10 355.58 20.000 2255.7 1087.7 1000.0
11 361.44 20.000 2300.8 1655.7
12 366.23 20.000 2331.4 1700.8
13 370.48 20.000 2356.5 1731.4
14 374.35 20.000 2381.0 1756.5
15 377.85 20.000 2405.7 1781.0
16 380.93 20.000 2428.8 1805.7
17 383.63 20.000 2447.2 1828.8
18 386.11 20.000 2456.7 1847.2
19 388.69 20.000 2451.9 1856.7
20 391.92 20.000 600.00 1851.9 L 600.00
An Example of a Profile for one of the Components
Profile for Propane
Stage Liquid (Ä) Vapour (Ä) K (Ä)
1 0.78474 0.71217 0.90752
2 0.75806 0.76055 1.0033
3 0.69122 0.74254 1.0742
4 0.61423 0.69845 1.1371
5 0.54367 0.64860 1.1930
6 0.48693 0.60358 1.2396
7 0.44479 0.56774 1.2764
8 0.41458 0.54140 1.3059
9 0.39249 0.52291 1.3323
10 0.37472 0.51005 1.3612
11 0.34774 0.50138 1.4418
12 0.30620 0.46151 1.5072
13 0.25793 0.40357 1.5647
14 0.20877 0.33742 1.6162
15 0.16285 0.27061 1.6617
16 0.12264 0.20859 1.7009
17 0.089123 0.15460 1.7346
18 0.062233 0.10988 1.7656
19 0.041251 0.074193 1.7986
20 0.025222 0.046444 1.8414
Stream Summary Table
Stream Feed 1 Top Bottom
Stage 10 1 20
Pressure (bar) 20.000 20.000 20.000
Vapour fraction (Ä) 0.00000 1.0000 0.00000
Temperature (K) 298.15 322.89 391.92
Enthalpy (J/mol) -19280 -449.22 -6217.1
Mole flows (mol/s)
Ethane 100.00 99.994 0.0056326
Propane 300.00 284.87 15.133
n-Butane 500.00 15.137 484.86
n-Pentane 100.00 0.0020952 99.998
Total molar flow 1000.0 400.00 600.00
Mole fractions (Ä)
Ethane 0.10000 0.24999 9.3877E-06
Propane 0.30000 0.71217 0.025222
n-Butane 0.50000 0.037842 0.80811
n-Pentane 0.10000 5.2380E-06 0.16666
Mass flows (kg/s)
Ethane 3.0070 3.0068 0.00016937
Propane 13.229 12.562 0.66732
n-Butane 29.062 0.87979 28.182
n-Pentane 7.2150 0.00015117 7.2149
Total mass flow 52.513 16.448 36.064
Mass fractions (Ä)
Ethane 0.057262 0.18280 4.6963E-06
Propane 0.25192 0.76370 0.018504
n-Butane 0.55342 0.053488 0.78144
n-Pentane 0.13740 9.1906E-06 0.20006
Graphs
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Liquid phase composition profiles ³
³ Vapour phase composition profiles ³
³ K-value profiles ³
³ Temperature profile ³
³ Pressure profile ³
³ Flow profiles ³
³ McCabe-Thiele diagram ³
³ Right triangular diagram ³
³ Quaternary diagram ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Use the cursor keys and Enter (or the highlighted letters) to bring up
the various graphs. On the following pages we have reproduced a number
of these graphs (the Vapour phase composition profiles, the
Temperature profiles, the Flow profiles, the McCabe-Thiele diagram,
and the Quaternary diagram. Note that the latter can be viewed from
different angles; use the arrow keys to change the orientation of the
tetrahedron. Three very important keys that may be used when a graph
is displayed are:
Escape Clears the current graph and returns you to the above menu
Spacebar Clears the graph and brings up a menu (or spreadsheet) that
allows you to configure the graph as you like.
Ctrl-P Prints the graph to the predetermined output device
(printer or file)
The graphs can be configured in many ways. Colors, line styles, point
styles and so on can all be changed. Also, the orientation of the
profiles can be changed. It is possible to plot profiles with the
stages used as either the horizontal axis or as the vertical axis. Our
preference is to plot the stages on the vertical axis but you may make
your own choice in the Interface item of the Options menu and save it
in the configuration file so that all profiles appear with the same
orientation every time (at least until you change the orientation).
Bring up one of these graphs, press the Spacebar, and change
something. Press Escape to redraw the graph.
Component Feed Flow (mol/s) Top Bottom
ethane 100 100 -
propane 300 285 15
n-butane 500 25 475
n-pentane 100 - 100
Although our column comes close to making this separation, we are not
quite there. You are asked to use ChemSep to come up with a column
design that does meet the desired separation. You can change any and
all of the following:
The number of theoretical stages
The location of the feed stage
The reflux ratio
The bottoms flow rate
The column pressure
Don't make the pressure so low that the top product temperature falls
below 25 Celcius. Use the Input menu to make changes. Until you are an
expert, however, we suggest that you do not change more than one thing
at a time. For each change you make to the column configuration you
will have to exercise the Solve option of the Input menu. Look at the
results (the stream summary table will be particularly helpful as will
the McCabe-Thiele diagram) and compare them to the desired results
above. Note that you will not be able to match all the desired results
exactly. Look for a column design that gives at least the desired
amounts of propane in the top product and of n-butane in the bottom
product. Be prepared to spend a little time on this exercise.
Remember, this program is performing real engineering calculations and
they are not done instantly, even on a fast computer.
Chapter 11. Example 3. Extractive Distillation of Methanol and Ethanol
For certain types of hard-to-separate mixtures the process of
Extractive Distillation can be used. In extractive distillation we add
a third component to the system, the solvent, that changes the
relative volatility of the components we wish to separate. Here we
illustrate the use of ChemSep with an extractive distillation of a
mixture of methanol and ethanol. Our objectives in sharing this
example with you are as follows:
The column has 76 stages including a total condenser (stage 1). The
feed containing methanol and ethanol (together with a certain amount
of water) is fed to stage 24 (counting from the top). The solvent,
water, is fed in a large excess to stage 12. This column has no
reboiler and the energy requirements for the column are supplied by
injecting live saturated steam at the base of the column. There is a
liquid sidestream withdrawn from stage 71. The ChemSep input summary
is reproduced below for convenience. Thermodynamic data (the
interaction parameters) comes from Computer Calculations for
Multicomponent Vapor-Liquid and Liquid-Liquid Equilibria by J.
Prausnitz, T. Anderson, E. Grens, C. Eckert, R. Hsieh, and J.
O'Connell (Prentice-Hall, 1980).
Column C:\CHEMSEP\METH-ETH.SEP
Components:
Methanol
Ethanol
Water
Operation:
Complex Column
Total (Liquid product) Condenser
76 Stages
Feeds to stages 12,24,76
SideStreams from stages 71
Properties:
DECHEMA K model
Q' UNIQUAC model
Antoine Vapour pressure
Excess Enthalpy
Thermo data (K):
[UNIQUAC Data]
i j Aij Aji Component Component
1 2 660.19 -292.39 Methanol Ethanol
1 3 -50.82 148.27 Methanol Water
2 3 -64.56 380.68 Ethanol Water
Specifications:
Column pressure
Condenser pressure 1.0000 (atm)
Top pressure 1.0000 (atm)
Default efficiency = 1.0000 (Ä)
Feed 1 2 3
Stage 12 24 76
Pressure (atm) 1.0000 1.0000 1.0000
Vapour fraction (Ä) 0.00000 0.00000 1.0000
Temperature (K)
Component flows (mol/h)
Methanol 0.00000 16.000 0.00000
Ethanol 0.00000 16.000 0.00000
Water 3220.0 68.000 650.00
Condenser
Reflux ratio = 32.000 (Ä)
SideStream 1
Stage 71
Phase Liquid
Flow (mol/h) 224.00
Flow ratio (Ä)
Load the file METH-ETH.SEP from disk. Use the cursor control keys to
go the Input menu. Press C to bring up the list of Selected
components:
ChemSep 2.00
File Input Results Options Quit
C:METH-ETH.SEP 19 iterations
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ÚÄ< Components >Ä¿
³ Components ³ ³ Methanol ³
³ÚÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ³ ³ Ethanol ³
³³ Select ³ ³ ³ Water ³
³³ Delete ³ ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
³³ Substitute ³ ³
À³ Reorder ³ÄÙ
³ Save set ³
³ Load set ³
³ÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
F1:Help F2:Last help F3:Load F4:Save F5:Units F6:Options F9:Info F10:Main menu
The box in the upper right hand corner lists the components that have
already been selected. Adding (or removing) components from the list
in the top right is fully described in the Components section of this
User's Guide. We used Select by Name to load the three components in
this problem. Remember to use the Escape key if you think you find
yourself stuck somewhere in the interface. Now accept the Return
option in the Components menu. This will send you back one menu level
and place the cursor on the next item in that menu. Press Enter to
bring up the Operation menu:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Flash ³
³ Column ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
The cursor should be on Column. Press Enter (or press C) to bring up
the Operation spreadsheet:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Operation Complex Column ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Condenser Total (Liquid product) ³
³ Reboiler None (Liquid product) ³
³ Stages 76 ³
³ Feed stages 12,24,76 ³
³ Sidestream stages 71 ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
The Operation spreadsheet summarizes the column configuration. Here,
we have specified a Complex Column since there are multiple feeds, a
sidestream and the column has no reboiler. Note the three Feed stages
are listed in the appropriate field and the Sidestream from stage 71.
Compare the information in this window to that listed in the summary
specification given above. Move the cursor to the Return field and
press Enter. This action will return you to the Input menu with the
cursor located on the Properties option. Press Enter to display the
following menu:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Equilibrium models ³
³ Enthalpy ³
³ Load data ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Locate the cursor on the Equilibrium Models option (it should be
there) and press Enter (or press E) to obtain the K-models menu:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ K model ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Raoult's law ³
³ EOS ³
³ Gamma-Phi ³
³ DECHEMA ³
³ Chao-Seader ³
³ Polynomial ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
For nonideal systems like the methanol-ethanol-water mixture, the most
appropriate K-value models are Gamma-Phi or DECHEMA. In this case we
selected the DECHEMA model. Locate the cursor on DECHEMA and press
Enter to bring up the Activity Coefficient menu
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Activity coefficient ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Ideal ³
³ Regular ³
³ Wilson ³
³ NRTL ³
³ UNIQUAC ³
³ UNIFAC ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Each of the items in this menu is a method for estimating activity
coefficients for multicomponent liquid mixtures. The Ideal and Regular
Solution models should not be used for this system. Three of these
models (Wilson, NRTL and UNIQUAC) require interaction parameters so
you must have them available before you continue (they are listed in
the summary above). In this case we had UNIQUAC parameters available.
Press U to select the UNIQUAC model. This brings up the UNIQUAC menu:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ UNIQUAC model ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Original ³
³ Q' ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
There are several versions of the UNIQUAC model that are used. Two of
the most commonly used forms are listed here. q and q' are parameters
in the UNIQUAC model. These parameters are available in ChemSep's
databanks so you won't have to find their values. However, we do need
to know which of these two options to select. The book by Prausnitz et
al. cited above from which we obtained our interaction parameters uses
the q' form of UNIQUAC. Therefore, we select the q' option. Selection
of the UNIQUAC model brings up the Vapour Pressure menu:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Vapour pressure ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Antoine ³
³ Extended Antoine ³
³ DIPPR ³
³ Lee Kesler ³
³ Riedel ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
We selected the Antoine option for this example since the parameters
for this model are in ChemSep's databanks. Strictly speaking, however,
we should have selected the Extended Antoine equation since that is
the model used by Prausnitz et al. We would then have to enter all the
parameters for that equation and, being somewhat lazy as well as in a
hurry to write this document, we elected not to do this. The results
we obtain do not differ qualitatively from the results obtained with a
completely consistent thermodynamic model and set of parameters so our
present purpose (of demonstrating ChemSep) is well enough served by
our choices. Press A to accept the Antoine option. This should bring
you back to the Properties menu with the cursor on Enthalpy. Press
Enter to see the list of enthalpy models:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Enthalpy ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ None ³
³ Ideal ³
³ Excess ³
³ Polynomial ³
³ User defined ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
We selected Excess. Refer to the discussion of Enthalpy model
selection in the depropanizer example for our reasons for this choice.
With the cursor on Excess press Enter (or press E) to accept the
enthalpy model and return to the properties menu. Now go to the Load
data option (the cursor should be there) and press Enter. This brings
up a menu that lists the models for which you must enter parameters.
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Load data for: ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Activity coefficient ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
In this case there is only one type of model in this list, the
Activity coefficient. Press Enter to bring up a spreadsheet where you
can enter the necessary data:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Activity coefficient: UNIQUAC (K) ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Component i Component j Aij Aji ³
³ Methanol Ethanol 660.190 -292.390 ³
³ Methanol Water -50.8200 148.270 ³
³ Ethanol Water -64.5600 380.680 ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Reset Library Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Notice that this window identifies the model selected earlier
(UNIQUAC). The Units of the parameters are shown between () after the
model name. (K) means the parameters have the units of Kelvin. The
numerical values of the parameters are shown in the appropriate
spreadsheet fields. Check that these parameters correspond to those
given in the problem summary above. Use the cursor control keys to go
to the Return field and press Enter. This will bring us to the
Specifications menu:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Analysis ³
³ Pressures ³
³ Heaters/Coolers ³
³ Efficiencies ³
³ Feeds ³
³ Condenser ³
³ Sidestreams ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
You should compare this menu with the corresponding one for the
depropanizer. Since this column has no reboiler, the Reboiler menu
item does not appear. Instead we have a new item, Sidestreams. Use the
cursor control keys and F1 (Help) to explore each of these items. The
Analysis window looks like this:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ CHEMSEP requires the following to be specified: ³
³ - The number of stages (1) ³
³ - The location of all feeds (2) ³
³ - The location of all sidestreams (1) ³
³ - For each feed stream you must specify ³
³ the component flows (3) and ³
³ two of the temperature, pressure and vapor fraction (2) ³
³ - The pressure in each stage (75) ³
³ - The heat duty on each stage except reboilers and condensers (75), ³
³ the heat duty will be assumed to be zero unless specified differently ³
³ - The pressure in the condenser (1) ³
³ - For the condenser you must select one variable to specify (1) ³
³ ³
³ Therefore, the total number of degrees of freedom is 172. ³
³ ³
³ Press
Press F1 to find out how the number of degrees of freedom has been
calculated. The Pressure spreadsheet looks like this:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Pressures (atm) ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Condenser pressure 1.00000 ³
³ Column pressure Constant pressure ³
³ Top pressure 1.00000 ³
³ Pressure Drop ³
³ Bottom pressure ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
The second line in this window indicates the method of calculating the
pressure profile in the column. Locate the cursor on line two and
press Enter to bring up a list of options. The choice you make here
determines how many fields in the Pressure spreadsheet need to be
filled in. The Heaters/Coolers and Efficiencies spreadsheets look
exactly the same as they do in the Depropanizer case study and we will
not reproduce the screen images here. The Feed spreadsheet looks like
this.
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Feed 1 2 3 ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Feed stage 12 24 76 ³
³ State: P & V P & V P & V ³
³ Pressure (atm) 1.00000 1.00000 1.00000 ³
³ Vapour fraction (Ä) 0.00000 0.00000 1.00000 ³
³ Temperature (K) ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Flowrates (mol/h) ³
³ Methanol 0.00000 16.0000 0.00000 ³
³ Ethanol 0.00000 16.0000 0.00000 ³
³ Water 3220.00 68.0000 650.002 ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Total flowrate 3220.00 100.000 650.002 ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Insert Delete Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Use the cursor control keys and Enter to explore this spreadsheet.
Notice that fields for all three feeds are available in this
spreadsheet. Feed number 1 is the water (solvent) feed to stage 12.
Feed number 2 is the methanol-ethanol feed to stage 24. Both these
feeds are specified as saturated liquids. Hence the pressure and
vapour fraction of these feeds has been specified, with the vapour
fraction set to zero. Feed number 3 is the live steam injected into
the foot of the column. The vapour fraction of this feed is 1 since
this feed is, at it must be, a vapour. With the cursor on Condenser
press Enter to see the Top product/condenser specification
spreadsheet:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Top product / condenser Reflux ratio ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Reflux ratio (Ä) 32.000 ³
³ Heat duty of condenser (J/s) ³
³ Temperature of condensate ( C) ³
³ Distillate flow rate (mol/s) ³
³ Reflux flow rate (mol/s) ³
³ Component flow (mol/s) ³
³ Mole fraction of a component (Ä) ³
³ Component recovery (Ä) ³
³ Fraction of combined feeds recovered (Ä) ³
³ Split between two components (Ä) ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
The Sidestreams spreadsheet looks like this:
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Sidestream 1 ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Stage 71 ³
³ Phase Liquid ³
³ Specification Total flow ³
³ Flow (mol/h) 224.000 ³
³ Flow ratio ³
³ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄij
³ Insert Delete Return ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
This spreadsheet identifies the stage from which the sidestream is
withdrawn, the phase of the sidestream, whether the total flow or flow
ratio is specified, and the numerical value of the specification (a
flow in this case). Place the cursor on the Return field and press
Enter to return to the Input menu. The cursor will be located on the
Solve item and that is the only thing left for us to do. Press Enter
to initiate the solution procedure. After the program loads the screen
will look something like this:
ChemSep 2.00
File Input Results Options Quit
C:METH-ETH.SEP 19 iterations
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Components ³
³ Operation ³
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ ³
³ ³
³ ChemSep / Column Version 2.0A ³
³ Copyright(c) H.Kooijman, A.Haket,R.Taylor, 1989-91 ³
³ ³
³ Checking data file C:\CS2\METH-ETH.SEP ³
³ Reading column configuration ³
³ Reading pure component property libraries ³
³ Reading thermodynamic property options and data ³
³ ³
³ ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
F1:Help F2:Last help F3:Load F4:Save F5:Units F6:Options F9:Info F10:Main menu
Later on, when the simulation program is doing calculations (rather
than reading the input files and databanks) the screen should look
something like this:
ChemSep 2.00
File Input Results Options Quit
C:METH-ETH.SEP 19 iterations
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Components ³
³ Operation ³
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ ³
³ ³
³ 0 8.5437E+01 ³
³ 1 7.4710E+03 ³
³ 2 7.9108E+03 ³
³ 3 1.0654E+04 ³
³ 4 2.2384E+04 ³
³ 5 1.4985E+04 ³
³ 6 1.8913E+04 ³
³ ³
³ ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
F1:Help F2:Last help F3:Load F4:Save F5:Units F6:Options F9:Info F10:Main menu
Notice that in this example the Sum of Squares (the number in
E-format) in the window above is increasing for several iterations.
Then it goes down and back up before converging after 19 iterations.
This particular problem is quite a bit more difficult for ChemSep to
solve than is the depropanizer. Several years ago we used this problem
to test several commercially available simulation programs. It was
interesting (but not altogether surprising) to find that some of them
could not find a converged solution and one that did find it took a
very long time indeed. When the calculations are complete, the program
will inform you of this fact, the interface reloads the input data
together with the results and jumps to the Results menu. Review the
profiles in order to explain to yourself exactly what this column is
doing. Below we have reproduced a selection of Tables and Graphs.
Mass and Energy Balances
Stream / Apparatus Mass (mol/h) Energy (J/s)
Feed 1 3220.0 -34211
Feed 2 100.00 -1045.8
Feed 3 650.00 460.59
Top -20.727 204.85
Bottom -3725.3 39593
Side draw 1 -224.00 2387.0
Condenser Duty -7388.2
ÄÄÄÄÄÄÄÄÄÄÄ + ÄÄÄÄÄÄÄÄÄÄÄ +
Balance -0.0065484 0.053223
Component discrepancies (mol/h)
Methanol 1.0212E-05
Ethanol 7.2669E-06
Water -0.0047597
Flow, Temperature and Pressure Profiles
Stage Temperature Pressure Flow rates (mol/h)
(K) (kPa) Liquid Vapour Feed
Product
1 349.77 101.32 663.25 20.727 L 20.727
2 350.37 101.32 661.57 683.98
3 350.75 101.32 660.35 682.30
4 351.00 101.32 659.37 681.08
5 351.17 101.32 658.46 680.09
6 351.30 101.32 657.50 679.19
7 351.42 101.32 656.33 678.23
8 351.58 101.32 654.70 677.06
9 351.87 101.32 652.02 675.42
10 352.54 101.32 646.19 672.75
11 354.98 101.32 630.54 666.91
12 364.43 101.32 3813.4 651.27 3220.0
13 364.49 101.32 3813.9 614.09
14 364.56 101.32 3814.6 614.65
15 364.64 101.32 3815.3 615.30
16 364.72 101.32 3816.1 616.02
17 364.79 101.32 3817.0 616.83
18 364.86 101.32 3817.9 617.70
19 364.89 101.32 3818.8 618.60
20 364.89 101.32 3819.6 619.49
21 364.81 101.32 3820.3 620.33
22 364.62 101.32 3820.9 621.05
23 364.24 101.32 3821.2 621.59
24 363.55 101.32 3919.2 621.90 100.00
25 363.63 101.32 3920.1 619.93
26 363.73 101.32 3921.1 620.84
27 363.83 101.32 3922.2 621.85
28 363.95 101.32 3923.4 622.95
29 364.08 101.32 3924.6 624.13
30 364.21 101.32 3925.9 625.37
31 364.34 101.32 3927.2 626.63
32 364.47 101.32 3928.4 627.89
33 364.60 101.32 3929.5 629.12
34 364.71 101.32 3930.6 630.28
35 364.82 101.32 3931.6 631.36
36 364.92 101.32 3932.5 632.34
37 365.00 101.32 3933.2 633.20
38 365.07 101.32 3933.9 633.95
39 365.13 101.32 3934.4 634.60
40 365.18 101.32 3934.9 635.14
41 365.23 101.32 3935.2 635.59
42 365.26 101.32 3935.6 635.97
43 365.29 101.32 3935.8 636.27
44 365.31 101.32 3936.0 636.52
45 365.33 101.32 3936.1 636.72
46 365.34 101.32 3936.3 636.88
47 365.36 101.32 3936.4 637.01
48 365.36 101.32 3936.5 637.11
49 365.37 101.32 3936.5 637.19
50 365.38 101.32 3936.6 637.25
51 365.38 101.32 3936.6 637.31
52 365.39 101.32 3936.6 637.35
53 365.39 101.32 3936.7 637.38
54 365.39 101.32 3936.7 637.41
55 365.40 101.32 3936.7 637.43
56 365.40 101.32 3936.7 637.44
57 365.41 101.32 3936.7 637.46
58 365.41 101.32 3936.7 637.47
59 365.42 101.32 3936.7 637.48
60 365.44 101.32 3936.8 637.48
61 365.46 101.32 3936.8 637.50
62 365.49 101.32 3936.8 637.51
63 365.55 101.32 3936.8 637.52
64 365.62 101.32 3936.9 637.54
65 365.74 101.32 3936.9 637.57
66 365.92 101.32 3937.0 637.62
67 366.18 101.32 3937.1 637.71
68 366.55 101.32 3937.4 637.86
69 367.06 101.32 3937.9 638.14
70 367.74 101.32 3938.7 638.64
71 368.59 101.32 3716.0 639.46 L 224.00
72 369.57 101.32 3717.8 640.76
73 370.54 101.32 3719.8 642.48
74 371.42 101.32 3721.8 644.49
75 372.15 101.32 3723.7 646.55
76 372.73 101.32 3725.3 648.44 650.00 L 3725.3
Profile for Ethanol
Stage Liquid (Ä) Vapour (Ä) K (Ä)
1 0.77194 0.72809 0.94319
2 0.79762 0.77194 0.96780
3 0.80944 0.79684 0.98444
4 0.81116 0.80829 0.99646
5 0.80486 0.80997 1.0064
6 0.79096 0.80385 1.0163
7 0.76814 0.79038 1.0289
8 0.73222 0.76826 1.0492
9 0.67265 0.73344 1.0904
10 0.55846 0.67571 1.2099
11 0.27855 0.56509 2.0287
12 0.042128 0.29426 6.9847
13 0.040948 0.28766 7.0251
14 0.039618 0.28012 7.0705
15 0.038147 0.27162 7.1202
16 0.036562 0.26223 7.1723
17 0.034904 0.25214 7.2237
18 0.033234 0.24159 7.2693
19 0.031632 0.23098 7.3021
20 0.030201 0.22082 7.3117
21 0.029072 0.21175 7.2836
22 0.028430 0.20460 7.1966
23 0.028577 0.20049 7.0160
24 0.030143 0.20131 6.6786
25 0.028298 0.19056 6.7341
26 0.026290 0.17868 6.7965
27 0.024146 0.16577 6.8654
28 0.021906 0.15202 6.9400
29 0.019619 0.13770 7.0190
30 0.017340 0.12312 7.1005
31 0.015125 0.10864 7.1826
32 0.013024 0.094597 7.2631
33 0.011080 0.081327 7.3401
34 0.0093202 0.069079 7.4117
35 0.0077604 0.058024 7.4769
36 0.0064037 0.048251 7.5349
37 0.0052428 0.039769 7.5855
38 0.0042637 0.032527 7.6290
39 0.0034478 0.026430 7.6657
40 0.0027750 0.021358 7.6963
41 0.0022249 0.017180 7.7216
42 0.0017781 0.013767 7.7422
43 0.0014174 0.010998 7.7591
44 0.0011275 0.0087640 7.7726
45 0.00089544 0.0069697 7.7836
46 0.00071015 0.0055338 7.7923
47 0.00056260 0.0043879 7.7993
48 0.00044531 0.0034756 7.8050
49 0.00035222 0.0027507 7.8094
50 0.00027843 0.0021754 7.8130
51 0.00021999 0.0017194 7.8160
52 0.00017374 0.0013584 7.8184
53 0.00013716 0.0010727 7.8205
54 0.00010825 0.00084674 7.8224
55 8.5390E-05 0.00066812 7.8243
56 6.7330E-05 0.00052695 7.8264
57 5.3061E-05 0.00041541 7.8290
58 4.1785E-05 0.00032728 7.8325
59 3.2874E-05 0.00025764 7.8375
60 2.5827E-05 0.00020261 7.8448
61 2.0252E-05 0.00015909 7.8558
62 1.5835E-05 0.00012466 7.8725
63 1.2330E-05 9.7381E-05 7.8980
64 9.5429E-06 7.5738E-05 7.9366
65 7.3202E-06 5.8525E-05 7.9949
66 5.5425E-06 4.4798E-05 8.0825
67 4.1181E-06 3.3818E-05 8.2120
68 2.9785E-06 2.5018E-05 8.3997
69 2.0750E-06 1.7978E-05 8.6639
70 1.3741E-06 1.2395E-05 9.0204
71 8.5116E-07 8.0647E-06 9.4749
72 4.8289E-07 4.8355E-06 10.014
73 2.5496E-07 2.6939E-06 10.566
74 1.2375E-07 1.3714E-06 11.082
75 5.3149E-08 6.1255E-07 11.525
76 1.7320E-08 2.0571E-07 11.877
Stream Summary Table
Stream Feed 1 Feed 2 Feed 3 Top
Stage 12 24 76 1
Pressure (kPa) 101.32 101.32 101.32 101.32
Vapour fraction (Ä) 0.00000 0.00000 1.0000 0.00000
Temperature (K) 373.15 351.98 373.15 349.77
Enthalpy (J/mol) -38248 -37650 2550.9 -35581
Mole flows (mol/h)
Methanol 0.00000 16.000 0.00000 2.2311
Ethanol 0.00000 16.000 0.00000 16.000
Water 3220.0 68.000 650.00 2.4959
Total molar flow 3220.0 100.00 650.00 20.727
Mole fractions (Ä)
Methanol 0.00000 0.16000 0.00000 0.10764
Ethanol 0.00000 0.16000 0.00000 0.77194
Water 1.0000 0.68000 1.0000 0.12042
Mass flows (kg/h)
Methanol 0.00000 0.51268 0.00000 0.071488
Ethanol 0.00000 0.73710 0.00000 0.73709
Water 58.009 1.2250 11.710 0.044964
Total mass flow 58.009 2.4748 11.710 0.85354
Mass fractions (Ä)
Methanol 0.00000 0.20716 0.00000 0.083754
Ethanol 0.00000 0.29784 0.00000 0.86357
Water 1.0000 0.49500 1.0000 0.052679
Stream Bottom Side draw
Stage 76 71
Pressure (kPa) 101.32 101.32
Vapour fraction (Ä) 0.00000 0.00000
Temperature (K) 372.73 368.59
Enthalpy (J/mol) -38261 -38362
Mole flows (mol/h)
Methanol 7.9444 5.8246
Ethanol 6.4523E-05 0.00019066
Water 3717.3 218.18
Total molar flow 3725.3 224.00
Mole fractions (Ä)
Methanol 0.0021326 0.026003
Ethanol 1.7320E-08 8.5116E-07
Water 0.99787 0.97400
Mass flows (kg/h)
Methanol 0.25456 0.18663
Ethanol 2.9725E-06 8.7835E-06
Water 66.969 3.9305
Total mass flow 67.223 4.1171
Mass fractions (Ä)
Methanol 0.0037867 0.045330
Ethanol 4.4218E-08 2.1334E-06
Water 0.99621 0.95467
ChemSep User's Guide