aspen plus 2

8/14/2019 Aspen Plus 2

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DEPARTMENT OF CHEMICAL & BIOIMOLECULAR ENGINEERINGNORTH CAROLINA STATE UNIVERSITY

Running an ASPEN PLUS Simulation

Broad Outline CommentsASPEN Plus is designed for the simulation of steady-state processes. It is especially useful forthe simulation of steady-state processes that are computationally laborious to analyze by handcalculations, such as processes involving recycle streams, non-ideal phase or chemical equilibria,adiabatic operations. It is ideally suited to provide answers on What I f -type of questions on

process design and optimization.

There are two ways of running an ASPEN simulation: an old fashion way of using an input filewhich has to be created, or a new way of using the graphical user interface (GUI) based on anexpert system technology (or artificial intelligence). This set of tutorial notes covers bothmethods, but to save your time, I recommend that you start directly with the GUI method and

come back to the input-file method when you have the time to learn more of what goes on behindthe GUI method. Tutorial notes on the GUI method begin on page 29.

All ASPEN simulations have to be run through a server on the Virtual Computing Lab (VCL). Areservation can be made to get access to the VCL server by logging onto the VCL website(http://vcl.ncsu.edu/ ) and making the request.

I. Introduction ASPEN simulation is performed by the ASPEN Simulation Engine interpreting an input file thatcontains a set of instructions defining and specifying the process flow scheme to be simulated.The input file can have any arbitrary name, file-id , but it must have the identifying .inp extensionsuch that its filename is file-id inp . It may be composed manually using a text editor or it may

be generated automatically using the ASPEN Graphical User Interface or GUI . The ASPENSimulation Engine , GUI , and Documentation can be found as three separate links on the

Novell Application Launcher after you log onto a Windows XP or Vista workstation.

Experienced ASPEN users typically utilize the ASPEN GUI , which offers the convenience andadvantages of the expert systems technology, including the avoidance of the need to compose theinput file directly. For the beginners, it is necessary to learn the skill of reading, interpreting andcomposing an ASPEN input file, a skill that is essential to understanding ASPEN programswritten by others as well as making one s own programs more easily understood by others. For

this reason and for the fact that the structure and rules of ASPEN are best understood through theconstruction of the input files, we will spend some time learning a manual construction of theinput file.

______________________________________________________________________________P. K. Lim, Department of Chemical & Biomolecular Engineering, North Carolina State

University, June 5, 2005 and revised on August 20, 2009.
http://vcl.ncsu.edu/http://vcl.ncsu.edu/http://vcl.ncsu.edu/http://vcl.ncsu.edu/


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II. Manual Construction of an ASPEN Input File (A) Text Editor to Use The ASPEN input file may be composed using either the built-in text editor of the SimulationEngine or an external text editor such as NAGf90 Plato or Notepad . In either case, the input

file that is to be submitted to the Simulation Engine must be created and saved in the K drive ,not in the default Temp directory of the C drive on the workstation you log on . To access the Kdrive , double click the My Computer icon on the desktop and look in one of the four networkdrive icons by moving the cursor over them to display the hidden drive letters. The identifyingtext on the K drive should read something like name on Pc id -afs (K:) where name is your nameand id is the id of the EOS computer, e.g., lim on Pc02003rd-afs (K:).

The Plato Editor can be selected and launched from the Novell Application Launcher menuwhile Notepad can be accessed by clicking Start and then going to Programs and thenAccessories . If the input file is created using the built-in text editor of the Simulation Engine , itwill be saved in a binary mode and can be accessed subsequently only by the built-in text editor

for any editing and modification. On the other hand, if the input file is created using an externaltext editor, it can be opened and modified by another text editor, including the built-in editor ofthe Simulation Engine ; however, it must be saved as an input file with the characteristic .inp extension--as opposed to a default Plato file in the case of the Plato Editor or a default text ( .txt )file in the case of Notepad . To override the default Save setting of Plato Editor or Notepad ,click the Save As option on the File pulldown menu to invoke the dialog window that has twodialog boxes. In the File name dialog box, type the file name and .inp extension. In theSave as type dialog box that is directly below, click the selection down-arrow to change thedefault setting from either All Plato Files (*.for*; .....) in the case of the Plato Editor or TextDocuments (*.txt*) in the case of Notepad to All Files option in both cases. Then click theSave button.

Avoid using WordPad , Word or WordPerfect as an editor to create the input file as theirformats are not compatible with the format expected by ASPEN. Although a format conversionis possible, its success is by no means assured and it is prudent to avoid the potential difficulty.

(B) Structure of the Input File and Basic Rules Governing its Construction An ASPEN input file has the generic structure shown in Table 1. It is composed of keywords arranged to give ASPEN paragraphs and sentences. Selected ASPEN keywords that are inroutine use are defined and explained in Section II-C . For now it should be noted that anASPEN paragraph can consist of a single statement or multiple statements, but in either case the

first statement must be headed by a pri mary keyword (e.g., In-Units , Properties , Components ,Flowsheet , Block , and Stream ) that has to start in column one . Any other statements in the

paragraph will start with secondary keywords (e.g., Param, Stoic, Conv, Define ) and tertiarykeywords (e.g., Temp, Pres , Mole-Flow, Mole-Frac ). A tertiary keyword is designed for dataentry and should be followed by an equal sign and data entry. A secondary keyword must beindented to the right of the primary keyword by at one least space and a tertiary keyword must,in turn, be indented to the right of the secondary keyword by at least one space . Thus, an


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ASPEN paragraph consisting of multiple statements may easily be recognized by the hierarchalorder of indentation of the succeeding statements within the paragraph. The ASPEN paragraphsmay be arranged in any order but it is a good practice to arrange them in a logical order that iseasy to follow.

The statements headed by the pri mary keywords In-Units , Properties , Components ,Flowsheet , Block , and Stream are mandatory in every ASPEN input file. The statementsTable 1. The generic structure of an ASPEN input file.

Title . . . . . . . . . . . . . . (Optional)

Description . . . . . . . . (Optional)

Properties Sysop __ (Ex. Sysop0 or Ideal, Sysop3, etc.)

In-Units ___ (Ex. In-Units SI or In-Units ENG or In-Units MET)

Out-Units ___ (Optional, used when the output units are to differ from the input units)

Components componentid-1 alias-1 / . . . . . . / componentid-k alias-k

Flowsheet Block blockid-1 In = streamid-1 streamid-2 Out = streamid-3 streamid-4 Block blockid-2 In = streamid-i streamid-j Out = streamid-m streamid-n . . . . . . . . . . . . . . . . . . . . (Each block must have at least one In stream & one Out stream.)

Block blockid-1 aspen_model_1 Param . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . .

Block blockid0-2 aspen_model_2 Param . . . . . . . . . . . .

Stream streamid-1 . . . . . . . . . . . .. . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . .

Stream streamid-k . . . . . . . . . . . .. . . . . . . . . . . .

Design-Spec ____ (Required whenever input information expected byDefine . . . . . . . . . . . . ASPEN is part of the results to be determined by the


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F optional Fortran statement(s) simulation--see later)Spec result to target Tol-Spec . . . . .Vary . . . . . . . . . . . .Limits l-limit u_limit

headed by Titles and Description are optional, but it is a good practice to include them asexplanation and reminder. The Out-Units statement is seldom used. A Design-Spec paragraphis needed whenever an answer being sought in the simulation is an input data that ASPENexpects to compile--typically on an input stream or a block--before the start of the simulation.Thus, a Design-Spec paragraph is needed whenever a trial-and-error approach is called for indetermining an unknown input data on either a feed stream or a block.

Every input file must contain the same numbers of Block and Stream paragraphs as the numbersof unit operations and input (or feed) streams. Note that the Stream paragraph is intended

ONLY for the specification of an input or feed stream that does NOT originate from any unitblock in the process scheme; it should NEVER be used to specify any product stream thatoriginates from a unit block in the process scheme. I n A SPEN, AL L product streams are fixedautomaticall y by the specif ication s on th e un it blocks fr om whi ch they emerge . Thus,specification of a product stream can only be achieved indirectly through the use of a Block

paragraph that specifies the parent block of the product stream.

A data entry in a sentence may be a number or a character string (as for example in a unit). Thefirst character of a string must be alphanumeric. A character string must be enclosed in quotationmarks if it contains a blank space or any of the special characters, ; / ( ) [ ] = & . Anythingthat follows a semicolon (;) is treated as a comment that will be displayed but not executed .

The maximum length of an input line is 80 characters. To continue a sentence on more than oneline, an ampersand (&) is placed at the end of the line to be continued and the continuation linemust have a blank in column one. If the sentence to be continued onto the next line is a part ofstatements within quotations (as in a Description paragraph), the ampersand is not needed.

Units can be specified along with the numerical entries that precede them, provided that they areenclosed within triangle brackets (< >). This option can sometimes be convenient and useful.For example, if one has chosen MET or Metric as the default global units set, one can stillspecify an input temperature in oC--thereby overriding K, the default unit--by appending after the numerical entry. One can also override specific units of the chosen global units set byincluding exceptions in the In-Units and Out-Units statements, e.g.,

In-Units Metric Temp = C Mole-Flow = mol/s (overriding the default units, K andkmol/hr)

Out-Units Duty = kW (overriding the default unit, cal/s, of the Metric In-Units )


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(C) Brief Descriptions and Comments on Selected Keywords

Title is an optional primary keyword that can be used to specify a program title of up to 64characters enclosed in quotation marks, e.g.,

Title Simulation Example 1'

Description is an optional primary keyword that can be used to specify a program description ofany length enclosed within double quotation marks, e.g.,

Description Learning ASPEN Simulation by Submitting an Input File to the SimulationEngine.

Properties is a mandatory primary keyword that is used to specify the thermodynamic basis fordetermining the thermochemical properties of substances involved in the simulation, e.g.,

Properties Sysop0 (or, equivalently, Properties Ideal)

which instructs ASPEN to assume the simplest thermodynamic model--namely, an idealcomponent or mixture model (e.g., ideal gas law for vapor, etc)--for evaluating thermochemical

properties of substances. More sophisticated and realistic models are available and they aredescribed in APLUS 111 Physical Property Methods and Models.pdf . These models can be

better understood after taking the two-course sequence of thermodynamics covered by CHE 315and 316. The provision for using different thermodynamic models in phase and chemicalequilibrium analyses is a major strength and advantage of ASPEN as the calculations involvedwith these models are often complex and laborious. Consult APLUS 111 Physical Property

Methods and Models . pdf for details of the various thermodynamic models and theirrecommended use.

In-Units is a mandatory primary keyword used to specify the global set of default units whichASPEN will associate with all numeral input, except when specifically stated otherwise. Threemajor options are available for the In-Units specification: SI (Systeme Internationale), ENG(English or American engineering), and MET (metric). Details of these three units sets are

provided in Table 2 on the next page. An example of its construction is as follows:

In-Units Met temp = C moleflow = mol/s

where the metric units set is specified as the global units set for all input data with the exceptionsof temperature and mole-flow that will be in oC and mol/s (instead of the default K and kmol/h).Note : Any time a unit containing a slash (/) is specified, it must be enclosed in quotation marks,e.g., mol/s and kcal/h . Out-Units is an optional primary keyword used to specify the globalset of default units which ASPEN will associate with all numeral output. By default, the outputunits are presumed to be the same as the input units. An Out-Units statement can be used to


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override the default established by the In-Units set, e.g.,

Out-Units duty = kcal/h

instructs ASPEN to display all simulation results on heat duty in kcal/h instead of cal/s that

would otherwise be assumed by default in the case of In-Units Met specification.

Components is a mandatory keyword that is used to specify the names of all substances that will be involved in the simulation. The Components paragraph has the following standard structure

Table 2. Details of the SI, ENG and MET units sets.

MeasurementParameter

Unit SetSI ENG MET Other

Mass kg lb m kg g, tonLength m ft m cm, in

Volume m3 ft

3 L in

3, gal, barrel

Time s h h day, min

Temperature K oF K oC, oRPressure N/m psi atm bar, torr

Force N lb f dyneHeat J Btu cal kJ, kcalWork J HP-h kW-h ft-lb f , kJ, kcal, L.atm

Mass-Flow kg/s lb m/h kg/h ton/dayMole-Flow kmol/s lb

m-mol/h kmol/h g-mol/s, m 3(stp)/h

StdVol-Flow m (stp)/s ft (stp)/h L(stp)/hEnthalpy-Flow W Btu/h cal/s kcal/h, kJ/hDuty or Power W Btu/h cal/s kcal/h, kJ/h

Components component id -1 alias-1 /component id -2 alias-2 /component id -3 alias-3(e.g., Components EtOH Ethanol /DEE C4H10O-5 /H2O H2O)

where component id -k (k = 1, 2, 3, etc) is the name specified by the ASPEN user to denotesubstance k and alias-k is either the chemical name or formula by which substance k is registered

in ASPEN s data banks. The specified name, component id -k, can be arbitrary but alias-k mustcorrespond exactly to the registered chemical alias or formula of substance k in ASPEN s data

banks. Consult Physical PropData . pdf for the lists of registered aliases and formulae ofsubstances in ASPEN s data banks, along with their physical and chemical properties.

By default, ASPEN will use the specified name, component id -k, to refer to substance k in both


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simulation and output results. If, for whatever reason, the output name for substance k is shoulddiffer from its input name, one will modify the Components paragraph as follows:

Components component id -1 alias-1 component id -1 /... /component id -3 alias-3 component id -3(e.g., Components EtOH Ethanol Ethanol /DEE C4H10O-5 Ether /H2O H2O H2O)

where the third entry for each substance k, component id -k, is the output name for substance k.Input files generated by the User Interface generally have the 3-entry format for eachcomponent, with the first and third entries being the same by default.

Flowsheet is a mandatory keyword that is used to specify the unit operations of the process flowscheme and their linkage to one another through material and, sometime, energy (heat or work)streams. The Flowsheet paragraph has the following standard structure

Flowsheet

Block block id-1 In = stream id-1 stream id-2 Out = stream id-3 stream id-4 Block block id-2 In = stream id-i stream id-j Out = stream id-m stream id-n . . . . . . . . . . . . . . . . . . . .

(e.g., Flowsheet Block B1 In = S1 Out = S2Block B2 In = S2 Out = S3Block B3 In = S3 Out = S4Block B4 In = S4 Out = S5 S6 )

where block id-k and stream id-k (k = 1, 2, .., i, j, etc) are arbitrary names assigned by the ASPENuser to block k and stream k, respectively. Each block must have at least one In stream and oneOut stream, although it does not need to have more than one of each. Unless otherwisespecified, all streams in the flowsheet are presumed to be material streams. Specification of anenergy stream--such as a heat or work stream--to or from a block is optional in ASPEN. If anenergy stream is involved with a unit block--such as Heater or Pump--and it is not explicitlyspecified, ASPEN will introduce the energy stream later when it presents the simulation resultson the block. If an energy stream is explicitly specified in the flowsheet, it must be specificallydistinguished from the material streams (see below). Blocks can be connected either in series orin parallel by material or energy streams.

Block is a mandatory keyword used to specify a unit operation. A Block paragraph has a general

structure as follows:

Block block id-k aspen_model_k Param . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . .

(e.g., Block B2 HeaterParam Temp = 250 Pres = 5 )


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where block id-k is the arbitrary name assigned to unit operation, aspen_model_k is the precisename of the ASPEN model used to simulate the unit operation, and Param is the secondarykeyword used to specify the parametric conditions of the unit operation. The Param statementmust always be present in every Block paragraph. Consult UnitOpModels . pdf for the

descriptions and specification options and requirements of the various ASPEN unit models. Adegrees-of-freedom analysis may sometimes be needed to fix the correct number of parametricspecifications. In any case, the number of Block paragraphs in an input file must correspondexactly to the same number of blocks specified in the Flowsheet paragraph.

The keywords that may be used in any suitable combinations in the Param statement of a Block paragraph are Temp, Pres, Vfrac, NPhase (number of phases), and Phase (V for vapor, L forliquid, Phase=V by default). Vfrac is used to specify the relative proportion of saturated vapor ina wet mixture of saturated liquid and saturated vapor; it is defined the same way as quality whichis often used to specify a wet mixture. Thus, Vfrac = 0 refers to a saturated liquid, Vfrac = 1.0 asaturated vapor, and Vfrac = 0.90 a wet mixture with 90% saturated vapor. Vfrac should never be

used in connection with a superheated vapor or a subcooled liquid.

The keywords NPhase and Phase should not be used unless one is absolutely certain of thenumber and identity of the phase(s) present. Normally, ASPEN will start with a defaultassumption of NPhase = 2 when analysing a block or a stream; it will perform a phaseequilibrium analysis to determine the correct number and identity of the phase(s) present. If onespecifies Nphase = 1 and Phase = L, for example, ASPEN will bypass the phase equilibriumanalysis and this could result in a wrong answer if it turns out that more than one phase is presentor the correct phase is not liquid.

Depending on the specific ASPEN unit models, a Block paragraph may contain other statements

in addition to the Param statement, as exemplified by the ASPEN model for stoichiometricreactor, RStoic.

Block B3 RstoicParam Temp = 250 Pres = 5Stoic 1 Mixed EtOH -2 / DEE 1 / H2O 1Conv 1 Mixed EtOH 0.85

Stream is a mandatory primary keyword used to specify any input (or feed) stream that does notoriginate from any block in the flowsheet. A Stream paragraph has a typical structure as follows

Stream stream id-k . . . . . . . . . . . .. . . . . . . . . . . .

(e.g., Stream S1 Temp = 25 Pres = 1 Mole-Flow = 0.36Mole-Frac EtOH 1.0 / H2O 0 / DEE 0 )

where stream id-k is the arbitrary name assigned to the input stream k. Every flowsheet must


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have at least one input stream and it can have multiple input streams. The input file must,accordingly, have the same number of Stream paragraphs as the total number of input streams.

For every input stream, the flowrate, composition and thermodynamic conditions must bespecified. The keywords that may be used in any suitable combinations in the first line of aStream paragraph are Temp, Pres, Vfrac, Mole-Flow, Mass-Flow, Stdvol-Flow, NPhase, andPhase. The same comments mentioned above on NPhase and Phase in connection with a Block

paragraph also apply to a Stream paragraph.

The keywords that may be used in the second line are Mole-Frac, Mass-Frac, and Stdvol-Frac.The flowrate and composition of a stream may be set by specifying the total flowrate in the firstline of a Stream paragraph and specifying the composition in the second line, as in the examplegiven above. Alternately, they can be set by specifying the individual flowrates of thecomponents in the second line, as in the example below

Stream S1 Temp = 25 Pres = 1

Mole-Flow EtOH 0.36 / H2O 0 / DEE 0If an energy stream is to be explicitly specified in a process scheme, it must be distinguishedfrom material streams by a declarative statement such as

Def-Streams Heat S- id

if stream S- id is a heat stream or

Def-Streams Work S- id

if stream S- id is a work stream.

(D) The Use of Design-Spec, its Construction and Input Requirements ASPEN is structured such that before it carries out the computations that are at the heart of thesimulation, it performs a check on the input file to ensure that the input information is completeand that there is no structural, typographical or logical error. As part of the check it performs adegrees-of-freedom analysis to make sure that each of the input streams and blocks is not over-or under-specified. In particular, on each input stream, it looks for the flowrate, composition andthermodynamic conditions. Likewise, on each block, it looks for the operating conditions. If anyof the input data that it expects is missing, ASPEN will issue an error message and will not

proceed with any computation.

There are many engineering problems in which the results of interest are on the input parametersof feed streams and blocks. For this broad class problems, ASPEN will run into difficulty if notfor the remedy provided by the Design-Spec option. A simple heat exchange problem between

______________________________________________________________________________This section may be skipped until after some experience has been gained running some basic


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ASPEN simulations.

two water streams will illustrate this point. Let s suppose that a hot water stream S H with aknown mass flowrate m H and a known temperature T H-1 is to be cooled to a specified temperatureTH-2 by a steady-state heat exchange with a cooling water stream S C. Let s suppose further that

the cooling water stream has a known temperature T C-1 and that it is desired to determine its massflowrate (m C = ?) such that its temperature after the heat exchange is some targeted value T C-2,

Solution to the above heat exchange problem is rather trivial by a hand calculation. An energy balance between the two streams gives m HC p(TH-2 TH-1) = H H = H C = m CC p(TC-2 TC-1) ormC = m H(TH-1 TH-2)/(T C-2 TC-1). On ASPEN, however, the heat exchange problem presents adifficulty because the mass flowrate of the cooling stream, which is an input data normallyexpected by ASPEN, is an unknown to be determined in the simulation. For all itscomputational prowess, ASPEN is still not yet clever enough to figure out that a specification ona product stream--or, equivalently, an extra block specification--can be traded as an input datafor the missing stream or block parameter.

The Design-Spec option provides ASPEN with a way out of this difficulty. It allows ASPEN toiteratively assume different values for the unknown parameter (of the input stream or block)until a convergence criterion is met. Thus, by systematically adjusting an assumed value for themissing input parameter, the Design-Spec option satisfies ASPEN s insistence for a completesetof input data while allowing the simulation to converge on the desired results. The variousstatements of a Design-Spec paragraph are intended to meet this goal.

A Design-Spec paragraph has the following standard structure:

Design-Spec paragraphid Define . . . . . . . . . . . .

F optional Fortran statement(s)Spec c_result to target Tol-Spec . . . . .Vary . . . . . . . . . . . .Limits l_limit u_limit

where Design-Spec is a primary keyword (starting at column one), Define , Spec , Tol-Spec ,Vary , and Limits are secondary keywords, paragraphid is a name given to the Design-Spec

paragraph (to distinguish it from possibly other Design-Spec paragraphs in the same input file),c_result is the result of the current iteration which is to be compared with the target valuespecified in target , l_limit and u_limit are the lower and upper limits for the input parameter

being varied, and Fortran statement(s) is optional (see later)

There may be more than one Define statement in a Design-Spec paragraph but only one of eachof the other statements should be present. The Define statement allows one to access a


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parameter value or result for the purpose of comparison before the end of a simulation run. Normally, ASPEN does not provide any results until the end of a simulation run. However, forthe trial-and-error process to converge on the desired results, access to the simulation results ateach iteration is necessary to guide the trial-and-error process for the next iteration. The Define statement makes that possible. It has the following standard format:

Define var-name var-type keyword = id variable = parameter

where var-name is a name chosen to represent the sampled variable whose value or result is ofinterest, var-type specifies the sampled variable s classification type (see below), keyword = id iseither stream = id or block = id Sentence = Param , id is the name of the stream or block, and

parameter is the parameter of the stream or block. var-type can be any of the following: Block-Var (block variable), Stream-Var (stream variable), basis -Flow, basis -Frac (where basis = Moleor Mass or Stdvol).

Some examples of Define statements are given below:

Define TS6 Stream-Var Stream = S6 Variable = Temp

Define PB2 Block-Var Block = B2 Sentence = Param Variable = Pres

Define QB2 Block-Var Block = B2 Sentence = Param Variable = Qcalc

The Spec and Tol-Spec statements specify the convergence criterion of the trial-and-error process. Spec sets the desired target value, target , for the result of the current iteration, c_result .The latter could be the value of a variable sampled by a preceding Define statement or it could bea result computed in a Fortran expression using the sampled variable. Tol-Spec sets theconvergence tolerance (i.e., the acceptable deviations from the target value).

An example of Spec and Tol-Spec statements is given below:

Spec TS6 350Tol-Spec 0.05

The Vary statement specifies the input parameter to be varied in the trial-and-error process toconverge to the desired target results. It has a similar format to the Define statement, viz.

Vary var-type keyword = id variable = parameter

where the entries after Vary are similarly defined as above.

Some examples of Vary statements are given below:

Vary Stream-Var Stream = S1 Variable = Mole-Flow


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IV. Input Files for the Illustrative Examples (A) Input Files for the Simulation Defined by the First Problem Statement First, a block diagram is sketched for the process scheme defined by the problem statement, asone has learned to do in CHE 205 when solving a material-&-energy-balance problem. Thestreams and unit blocks are labeled and the input information on the streams and blocks are filledin on the flowsheet as follows:

S5 (V)|

-------------- ------------------ ----------------- ------------------S1 Pump B1 S2 Vaporizer S3 Reactor B3 S4 Flash Unit

------ -------| 5 atm out |--- ---| B2 |--- ---| 250 oC, 5 atm |--- ---| B4 |EtOH = 0.75 250 oC, 5 atm EtOH = 0.85 76 oC, 1 atm

25oC, 1 atm -------------- ------------------ ------------------ -----------------0.36 kmol/h 2C 2H5OH |

C2H5OC 2H5 + H 2O S6 (L)

Next, following the guidelines provided in Section II, one can construct the input file shown inTable 3A. For a later comparison, one can also come up with the corresponding input file,shown in Table 3B, that is generated by the use of the GUI for the same process scheme. Thetwo input files show some slight differences, but they both work on the Simulation Engine andyield essentially the same simulation results.Table 3A. An ASPEN input file for the process flow scheme described in Section III-A.

Title "ASPEN Simulation 1"

Description "Learning to Run ASPEN Simulation Using the InputFile Method"

Properties Sysop0

In-Units Met

Components EtOH Ethanol /DEE Diethyl-ether /H2O H2O

FlowsheetBlock B1 In = S1 Out = S2Block B2 In = S2 Out = S3Block B3 In = S3 Out = S4Block B4 In = S4 Out = S5 S6

Block B1 PumpParam Pres = 5 Eff = 0.75 Deff = 1.0

Block B2 HeaterParam Temp = 250 Pres = 5

Block B3 RStoic


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Param Temp = 250 Pres = 5Stoic 1 Mixed EtOH -2.0 / DEE 1.0 / H2O 1.0Conv 1 Mixed EtOH 0.85

Block B4 Flash2Param Temp = 76 Pres = 1

Stream S1 Temp = 25 Pres = 1 Mole-Flow = 0.36Mole-Frac EtOH 1.0 / DEE 0 / H2O 0

The entries for the primary keywords Title , Description , Properties and Flowsheet in Table 3Aare self-explanatory. In the Components statement, the entries EtOH and Ethanol are,respectively, the component name chosen for ethanol and the chemical alias registered forethanol in ASPEN s data banks. Alternatively, one can use the registered formula of ethanol,C2H6O-2, in place of the registered name of ethanol. (ASPEN uses hyphenated numbers todistinguish between different isomers with a common chemical formula, here, C2H6O-1 for

dimethylether and C2H6O-2 for ethanol.) Likewise, the entries DEE and Diethyl-ether are,respectively, the component name and registered name of diethylether. One can also use theregistered formula of diethylether, C4H10O-5, in place of its registered name. The entries forH2O and H2O (or Water ) require no explanation. Note that the registered name fordiethylether should appear exactly as it is. If diethylether had been used instead, for example,ASPEN would have given out an undefined component error message. To ensure the correctTable 3B. An ASPEN input file created by the ASPEN GUI method for the process flow schemedescribed in Section III-A.

;Input Summary created by Aspen Plus Rel.11.1 at 17:36:17 Sat;Oct 11, 2003. Directory K:\ Filename D:\aspenex1.inp

TITLE ASPEN Simulation 2

DESCRIPTION 'Learning to Run ASPEN Simulation Using the GUIMethod'

IN-UNITS MET

DEF-STREAMS CONVEN ALL

DATABANKS PURE11 / AQUEOUS / SOLIDS / INORGANIC / NOASPENPCD

PROP-SOURCES PURE11 / AQUEOUS / SOLIDS / INORGANIC

COMPONENTSETOH C2H6O-2 / DEE C4H10O-5 / H2O H2O

FLOWSHEETBLOCK B1 IN=S1 OUT=S2


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BLOCK B2 IN=S2 OUT=S3

BLOCK B3 IN=S3 OUT=S4BLOCK B4 IN=S4 OUT=S5 S6

PROPERTIES IDEAL

STREAM S1SUBSTREAM MIXED TEMP=25. PRES=1. MOLE-FLOW=0.36MASS-FRAC ETOH 1. / DEE 0. / H2O 0.

BLOCK B2 HEATERPARAM TEMP=250. PRES=5.

BLOCK B4 FLASH2PARAM TEMP=76. PRES=1.

BLOCK B3 RSTOIC

PARAM TEMP=250. PRES=5.STOIC 1 MIXED ETOH -2. / DEE 1. / H2O 1.CONV 1 MIXED ETOH 0.85

BLOCK B1 PUMPPARAM PRES=5. EFF=0.75 DEFF=1.

EO-CONV-OPTIchemical aliases or formulae are used in the Components statement, one should consult APLUS

III Physical Property Data.pdf .

The input file contains four Block paragraphs and one Stream paragraph, precisely the numbersof paragraphs needed to specify the four unit blocks--pump, vaporizer, stoichometric reactor, andflash separator--and one input stream. Only one Stream paragraph is needed as there is only oneinput or feed stream--namely S1--that does not originate from any block in the flowsheet. Allother streams, S2 through S6, are product streams that come from some blocks.

The specification of a material stream requires that its flowrate, composition and thermodynamicconditions be specified. This means a total of (2 + N) independent specifications, where N is thetotal number of independent components in the system. Thus, for S1 which can potentiallycontain up to three components--the total number defined in the flowsheet--a total of fiveindependent specifications are needed to pin it down. The five specifications may consist of

temperature, pressure, total flow rate, and two mole- or mass-fraction values or they may bemade up of temperature, pressure, and three component flow rates. The Stream paragraph for S1meets the specification requirements.

An adiabatic pump requires only one specification--that of outlet pressure--if it is reversible, i.e.,if its efficiency, eff, is 1. For an actual pump, both the outlet pressure and efficiency need to bespecified. The driver efficiency, deff, is often assumed 1; otherwise, an additional specification


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is needed. The Block paragraph for B1 (Pump) meets the specification requirements.

A heater (or cooler) requires two specifications that can be met by any combination oftemperature, pressure, vapor fraction, degree of subcool or superheat, and duty. Likewise, a flashseparator requires two specifications that can also be met by any combination of two of the above

parameters. The Block paragraphs for B2 (Vaporizer) and B4 (flash separator) both meet thespecification requirements.

A stoichiometric reactor requires specifications of temperature and pressure (or duty in place oftemperature), and stoichiometry and conversion for every reaction involved. An extent ofreaction may be specified in place of the conversion of the key component for every reaction.The Block paragraph for B3 (Reactor) meets the specification requirements. The input file isnow complete and ready to be submitted to the Simulation Engine . Proceed to Section V .

(B) Input Files for the Simulation Defined by the Second Problem Statement An manually-constructed input file for the simulation defined by the second problem statement is

shown in Table 4. It shares similarities with the input file listed in Table 3A on common aspectsof the process scheme, but it shows two differences. The first and most obvious difference is the presence of a Design-Spec paragraph, DS1, which is needed because an input parameterexpected of the flash separator (block B4) is an unknown to be determined. The input parameterthat is expected along with the specified pressure is one of the following: temperature, Vfrac,duty. The second difference, which is somewhat subtle, is a switch from the use of temperatureto Vfrac as an input block parameter for the flash separator.

Table 4. An ASPEN input file for the process flow scheme described in Section III-B.

Title "ASPEN Simulation 2"

Description "Using the Input File Method to Run an ASPENSimulation With a Design Specification"

Properties Sysop0

In-Units Met

Components EtOH Ethanol /DEE Diethyl-ether /H2O H2O

FlowsheetBlock B1 In = S1 Out = S2

Block B2 In = S2 Out = S3Block B3 In = S3 Out = S4Block B4 In = S4 Out = S5 S6

Block B1 PumpParam Pres = 5 Eff = 0.75 Deff = 1.0


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Block B2 HeaterParam Temp = 250 Pres = 5

Block B3 RStoicParam Temp = 250 Pres = 5Stoic 1 Mixed EtOH -2 / DEE 1 / H2O 1

Conv 1 Mixed EtOH 0.85

Block B4 Flash2Param Vfrac = 0.5 Pres = 1

Stream S1 Temp = 25 Pres = 1 Mole-Flow = 0.36Mole-Frac EtOH 1.0 / DEE 0 / H2O 0

Design-Spec DS1Define DEES5 Mole-Flow Stream=S5 Component=DEEDefine DEES4 Mole-Flow Stream=S4 Component=DEE

F R = DEES5/DEES4

Spec R to 0.95Tol-Spec 0.005Vary Block-Var Block=B4 Sentence=Param Variable=VfracLimits 0 1.0

In flash operation--as well as in any unit operation involving a vapor-liquid equilibria--Vfrac isnot only an equivalent but, generally, preferable substitute for temperature or pressure, dependingon whether one or the other is specified. The reason for this is that vapor-liquid equilibrium--orthe co-existence of vapor and liquid phases--is confined to a very narrow range of temperature or

pressure, depending on whether pressure or temperature is specified. Thus, unless one is guided

by prior experience or is lucky, one is likely to miss the vapor-liquid co-existence window if one picks a temperature at a fixed pressure or a pressure at a fixed temperature. On the other hand,the use of Vfrac in conjunction with either a fixed pressure or a fixed temperature will alwaysensure a co-existence of the vapor and liquid phases, as well as the correct range of co-existencetemperature or pressure.

The 0.5 value specified for Vfrac in the Param statement of the Block B4 paragraph is arbitraryto get the simulation started. One could have specified any other value between 0 and 1.0, andessentially the same simulation results would be obtained.

The Design-Spec DS1 paragraph conforms to the format discussed in Section II-D . Note the useof a Fortran mathematical statement in the paragraph to perform a running calculation of the

parameter, fractional recovery of diethylether in the overhead product stream, that is to becompared to the specified goal. Verify that the input file works by test-running it yourself on theSimulation Engine .

V. Submitting the Input File to the Simulation Engine The input file may be submitted to the ASPEN simulation engine either directly by means of


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MSDOS commands or indirectly through the use of the ASPEN GUI. The use of MSDOScommands, unfortunately, is made difficult by the ever-changing syntax on each new release ofASPEN. By comparison, the GUI provides a simpler and more convenient way to link up theinput file with the simulation engine and it will be described here.

Double click ASPEN GUI on the Novell Application Launcher. An ASPEN Plus Startupwindow will appear over a main window that is not yet activated (see Section VII). A dialog boxwill appear asking one to select one of two options: Create a New Simulation by either BlankSimulation or Template , or Open an Existing Simulation (by picking an ASPEN file with an .inp or .apw extension). Select the Open an Existing Simulation option, but instead of opening any.apw file, click the More Files option (at the top of the list) in the dialog box. In the pop-updialog box that appears, direct ASPEN to the directory where the input file that is to be submittedto the simulation engine is stored (by over-riding the default C:\Temp directory). Double clickthe input file and GUI will submit it to the simulation engine.

Upon receiving the input file, the simulation engine will first process it to ensure that the input

information is complete and that there is no structural, typographical or logical error. If that isnot the case, the simulation will stop and error message(s) will appear in the background. Inmost cases, it should be obvious from the error message(s) what needs to be fixed. In some othercases, a careful study may be needed to correct the less obvious error(s). In still other cases, youmay have to consult others to fix the problem(s). In debugging, it is often useful to rememberthat the computer is a mechanical robot--even a very clever robot--that can only literally interpretwhat is specified in the input file according to the ASPEN rules. Thus, a robotic anddispassionate interpretation--as opposed to a human, wishful interpretation--of the inputstatements is more likely to pin-point and resolve the error(s).

The simulation engine will proceed with computation if no error is found in the processing phase.Any error that comes up in the computation phase will most likely revolve around a convergence

problem that can be caused by faulty logics, an unrealistic or internally inconsistent specification,an incorrect specification of parameter range to look for the solution, a wrong approach, or afaulty convergence scheme. The error message(s) will again appear in the background.Debugging may require a bit more thought than correcting a processing error, but with some

patience and a dispassionate analysis, it can usually be done. If you are unable to resolve the problem(s) after making some attempts on your own, you should consult a TA or the instructor.Be sure to bring the error message(s) and your input file with you.

The processing and computation phases are indicated by running messages that flash across thecomputer screen. If the computation is completed without error, a message will accompany thesimulation results stating that the simulation is completed normally, i.e., without error, and thesimulation results will be placed in a report file ( file_name .rep) in the Temp directory of the Cdrive . The latter has to be specifically requested by clicking the Export option under the File

pulldown menu in the GUI window (see Section VII).

Simulation results are sometimes reported even when there are errors in the program. In such a


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case, the simulation results should be treated with reservation and effort should be made toresolve the problems that give rise to the error or warning messages.

VI. Reading the Output/Report File and the Simulation ResultsThe report file can be opened and edited using the same text editor-- Notepad Editor--which youhave used to create the input file. A double click on the file will automatically load the file onNotepad . For editing the report file, you can use WordPad , which offers more features and agreater format control than Notepad . Abbreviated versions of the report files for the twosimulations described in Sections III-A and III-B (or IV-A and IV-B ) are shown in Tables 5 and6. They have been edited from the original report files to delete non-essential pages--such asASPEN logo and license information, run control information, convergence iterations, table ofcontents--that can consume much print quota. Table 5 shows the essential elements of a reportfile that should be turned in for every ASPEN assignment not involving a Design-Spec feature.Table 6 shows the corresponding version for a simulation involving a Design-Spec feature.

It is seen that the report file presents results on every block or unit operation, including anyDesign-Specification block, as well as specifications on every the product stream. It also

presents a summary table for all streams at the end, along with the computation status and theconvergence status of any Design-Specification block. The results are self-explanatory.

Table 5. An abbreviated report file for the simulation described in Section III-A and IV-A.

TITLE ASPEN Simulation 1-----DESCRIPTION LEARNING TO RUN ASPEN SIMULATION USING THE INPUT FILE----------- METHOD.

FLOWSHEET SECTIONFLOWSHEET CONNECTIVITY BY STREAMS---------------------------------

STREAM SOURCE DEST STREAM SOURCE DESTS1 ---- B1 S2 B1 B2S3 B2 B3 S4 B3 B4S5 B4 ---- S6 B4 ----

FLOWSHEET CONNECTIVITY BY BLOCKS--------------------------------

BLOCK INLETS OUTLETSB1 S1 S2B2 S2 S3B3 S3 S4B4 S4 S5 S6

COMPUTATIONAL SEQUENCE SEQUENCE USED WAS: B1 B2 B3 B4----------------------

OVERALL FLOWSHEET BALANCE-------------------------

*** MASS AND ENERGY BALANCE ***IN OUT GENERATION RELATIVE DIFF.

CONVENTIONAL COMPONENTS


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(KMOL/HR)ETOH 0.360000 0.540000E-01 -0.306000 -0.238940E-09DEE 0.000000E+00 0.153000 0.153000 0.170908E-07H2O 0.000000E+00 0.153000 0.153000 -0.165286E-07

TOTAL BALANCEMOLE(KMOL/HR) 0.360000 0.360000 0.000000 0.000000E+00MASS(KG/HR ) 16.5849 16.5849 0.870085E-08ENTHALPY(CAL/S) -6627.77 -6113.24 -0.776328E-01

PHYSICAL PROPERTIES SECTIONCOMPONENTS----------

ID TYPE FORMULA NAME OR ALIAS REPORT NAMEETOH C C2H6O-2 C2H6O-2 ETOHDEE C C4H10O-5 C4H10O-5 DEEH2O C H2O H2O H2O

U-O-S BLOCK SECTIONBLOCK: B1 MODEL: PUMP----------------------------

INLET STREAM: S1OUTLET STREAM: S2

PROPERTY OPTION SET: IDEAL IDEAL LIQUID / IDEAL GAS

*** MASS AND ENERGY BALANCE ***IN OUT RELATIVE DIFF.

TOTAL BALANCEMOLE(KMOL/HR) 0.360000 0.360000 0.000000E+00MASS(KG/HR ) 16.5849 16.5849 0.000000E+00ENTHALPY(CAL/S) -6627.77 -6627.00 -0.116719E-03

*** INPUT DATA ***OUTLET PRESSURE ATM 5.00000PUMP EFFICIENCY 0.75000DRIVER EFFICIENCY 1.00000

FLASH SPECIFICATIONS:LIQUID PHASE CALCULATIONNO FLASH PERFORMEDMAXIMUM NUMBER OF ITERATIONS 30TOLERANCE 0.00010

*** RESULTS ***VOLUMETRIC FLOW RATE L/MIN 0.35961PRESSURE CHANGE ATM 4.00000NPSH AVAILABLE M-KGF/KG 12.3907FLUID POWER KW 0.0024291BRAKE POWER KW 0.0032389ELECTRICITY KW 0.0032389PUMP EFFICIENCY USED 0.75000NET WORK REQUIRED KW 0.0032389

HEAD DEVELOPED M-KGF/KG 53.7680

BLOCK: B2 MODEL: HEATER------------------------------

INLET STREAM: S2OUTLET STREAM: S3PROPERTY OPTION SET: IDEAL IDEAL LIQUID / IDEAL GAS


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TOTAL BALANCEMOLE(KMOL/HR) 0.360000 0.360000 0.000000E+00MASS(KG/HR ) 16.5849 16.5849 0.000000E+00ENTHALPY(CAL/S) -6627.00 -5166.61 -0.220370

*** INPUT DATA ***TWO PHASE TP FLASHSPECIFIED TEMPERATURE K 523.150SPECIFIED PRESSURE ATM 5.00000MAXIMUM NO. ITERATIONS 30CONVERGENCE TOLERANCE 0.00010

*** RESULTS ***OUTLET TEMPERATURE K 523.15OUTLET PRESSURE ATM 5.0000HEAT DUTY CAL/SEC 1460.4OUTLET VAPOR FRACTION 1.0000PRESSURE-DROP CORRELATION PARAMETER 0.0000

V-L PHASE EQUILIBRIUM :COMP F(I) X(I) Y(I) K(I)ETOH 1.0000 1.0000 1.0000 13.926

BLOCK: B3 MODEL: RSTOIC------------------------------

INLET STREAM: S3OUTLET STREAM: S4PROPERTY OPTION SET: IDEAL IDEAL LIQUID / IDEAL GAS


TOTAL BALANCEMOLE(KMOL/HR) 0.360000 0.360000 0.000000E+00 0.000000E+00MASS(KG/HR ) 16.5849 16.5849 0.000000E+00ENTHALPY(CAL/S) -5166.61 -5376.30 0.390032E-01

*** INPUT DATA ***STOICHIOMETRY MATRIX:

REACTION #1: SUBSTREAM MIXED: ETOH -2.00 DEE 1.00 H2O 1.00

REACTION CONVERSION SPECS: NUMBER= 1REACTION #1: SUBSTREAM:MIXED KEY COMP:ETOH CONV FRAC: 0.8500

TWO PHASE TP FLASHSPECIFIED TEMPERATURE K 523.150SPECIFIED PRESSURE ATM 5.00000MAXIMUM NO. ITERATIONS 30CONVERGENCE TOLERANCE 0.00010

SIMULTANEOUS REACTIONSGENERATE COMBUSTION REACTIONS FOR FEED SPECIES NO

*** RESULTS ***OUTLET TEMPERATURE K 523.15OUTLET PRESSURE ATM 5.0000HEAT DUTY CAL/SEC -209.69VAPOR FRACTION 1.0000


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REACTION EXTENTS:REACTION NUMBER: 1 REACTION EXTENT, KMOL/HR: 0.15300

V-L PHASE EQUILIBRIUM :COMP F(I) X(I) Y(I) K(I)ETOH 0.15000 0.11643 0.15000 13.926DEE 0.42500 0.29759 0.42500 15.437H2O 0.42500 0.58598 0.42500 7.8399

BLOCK: B4 MODEL: FLASH2------------------------------

INLET STREAM: S4OUTLET VAPOR STREAM: S5OUTLET LIQUID STREAM: S6PROPERTY OPTION SET: IDEAL IDEAL LIQUID / IDEAL GAS


TOTAL BALANCEMOLE(KMOL/HR) 0.360000 0.360000 0.000000E+00MASS(KG/HR ) 16.5849 16.5849 0.870085E-08

ENTHALPY(CAL/S) -5376.30 -6113.24 0.120548


*** RESULTS ***OUTLET TEMPERATURE K 349.15OUTLET PRESSURE ATM 1.0000HEAT DUTY CAL/SEC -736.94VAPOR FRACTION 0.61687

V-L PHASE EQUILIBRIUM :COMP F(I) X(I) Y(I) K(I)ETOH 0.15000 0.15857 0.14468 0.91242DEE 0.42500 0.16457 0.58675 3.5653H2O 0.42500 0.67686 0.26857 0.39679


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STREAM SECTIONS1 S2 S3 S4 S5 S6-----------------STREAM ID S1 S2 S3 S4 S5 S6FROM : ---- B1 B2 B3 B4 B4TO : B1 B2 B3 B4 ---- ----

SUBSTREAM: MIXEDPHASE: LIQUID LIQUID VAPOR VAPOR VAPOR LIQUIDCOMPONENTS: KMOL/HR

ETOH 0.3600 0.3600 0.3600 5.4000-02 3.2130-02 2.1870-02DEE 0.0 0.0 0.0 0.1530 0.1303 2.2699-02H2O 0.0 0.0 0.0 0.1530 5.9643-02 9.3357-02

TOTAL FLOW:KMOL/HR 0.3600 0.3600 0.3600 0.3600 0.2221 0.1379KG/HR 16.5849 16.5849 16.5849 16.5849 12.2130 4.3719L/MIN 0.3596 0.3597 51.5132 51.5132 106.0400 9.3798-02

STATE VARIABLES:TEMP K 298.1500 298.4056 523.1500 523.1500 349.1500 349.1500PRES ATM 1.0000 5.0000 5.0000 5.0000 1.0000 1.0000VFRAC 0.0 0.0 1.0000 1.0000 1.0000 0.0LFRAC 1.0000 1.0000 0.0 0.0 0.0 1.0000

SFRAC 0.0 0.0 0.0 0.0 0.0 0.0ENTHALPY:

CAL/MOL -6.628+04 -6.627+04 -5.167+04 -5.376+04 -5.784+04 -6.643+04CAL/GM -1438.661 -1438.493 -1121.492 -1167.009 -1051.800 -2095.680CAL/SEC -6627.773 -6627.000 -5166.607 -5376.300 -3568.223 -2545.018

ENTROPY:CAL/MOL-K -82.7724 -82.7466 -46.0413 -46.2268 -66.3961 -54.5533CAL/GM-K -1.7967 -1.7961 -0.9994 -1.0034 -1.2073 -1.7211

DENSITY:MOL/CC 1.6685-02 1.6679-02 1.1648-04 1.1648-04 3.4904-05 2.4508-02GM/CC 0.7687 0.7684 5.3659-03 5.3659-03 1.9196-03 0.7768

AVG MW 46.0690 46.0690 46.0690 46.0690 54.9950 31.6974

PROBLEM STATUS SECTIONBLOCK STATUS------------******************************************************************** ** Calculations were completed normally ** ** All Unit Operation blocks were completed normally ** ** All streams were flashed normally ** ********************************************************************


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Table 6. An abbreviated report file for the simulation described in Section III-B and IV-B.

ASPEN SIMULATION 2

DESCRIPTION USING THE INPUT FILE METHOD TO RUN AN ASPEN SIMULATION----------- WITH A DESIGN SPECIFICATION.

FLOWSHEET SECTIONFLOWSHEET CONNECTIVITY BY STREAMS---------------------------------

STREAM SOURCE DEST STREAM SOURCE DESTS1 ---- B1 S2 B1 B2S3 B2 B3 S4 B3 B4S5 B4 ---- S6 B4 ----

FLOWSHEET CONNECTIVITY BY BLOCKS--------------------------------

BLOCK INLETS OUTLETSB1 S1 S2B2 S2 S3B3 S3 S4

B4 S4 S5 S6CONVERGENCE STATUS SUMMARY--------------------------

DESIGN-SPEC SUMMARY===================DESIGN CONVSPEC ERROR TOLERANCE ERR/TOL VARIABLE STAT BLOCK------ ----- --------- ------- -------- ---- -----DS1 -0.1418E-02 0.500E-02 -0.28352 0.82085 # $OLVER01

# = CONVERGED * = NOT CONVERGEDLB = AT LOWER BOUNDS UB = AT UPPER BOUNDS

DESIGN-SPEC: DS1-----------------

SAMPLED VARIABLES:DEES5 : DEE MOLEFLOW IN STREAM S5 SUBSTREAM MIXEDDEES4 : DEE MOLEFLOW IN STREAM S4 SUBSTREAM MIXED

FORTRAN STATEMENT: R = DEES5/DEES4

SPECIFICATION: MAKE R APPROACH 0.95000 WITHIN 0.0050000

MANIPULATED VARIABLE:VARY : SENTENCE=PARAM VARIABLE=VFRAC IN UOS BLOCK B4LOWER LIMIT = 0.0 UPPER LIMIT = 1.000 FINAL VALUE = 0.82085

VALUES OF ACCESSED FORTRAN VARIABLES:

VARIABLE VALUE AT START OF LOOP FINAL VALUE UNITS-------- ---------------------- ----------- -----DEES5 0.116976 0.145133 KMOL/HRDEES4 0.153000 0.153000 KMOL/HR

CONVERGENCE BLOCK: $OLVER01----------------------------

SPECS: DS1MAXIT= 30 STEP-SIZE= 1.0000 % OF RANGE


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MAX-STEP= 100. % OF RANGEXTOL= 1.000000E-08

THE NEW ALGORITHM WAS USED WITH BRACKETING=NOMETHOD: SECANT STATUS: CONVERGEDTOTAL NUMBER OF ITERATIONS: 5

*** FINAL VALUES ***VARIABLE VALUE PREV VALUE ERR/TOLBLOCK-VAR 0.8209 0.8846 -0.2835

COMPUTATIONAL SEQUENCE SEQUENCE USED WAS: B1 B2 B3---------------------- $OLVER01 B4

(RETURN $OLVER01)OVERALL FLOWSHEET BALANCE-------------------------


CONVENTIONAL COMPONENTS(KMOL/HR )

ETOH 0.3600 0.5400E-01 -0.306000 0.994434E-11DEE 0.0000E+00 0.153000 0.153000 0.626456E-09H2O 0.0000E+00 0.153000 0.153000 -0.649854E-09

TOTAL BALANCEMOLE(KMOL/HR) 0.360000 0.360000 0.0000E+00 -0.154198E-15MASS(KG/HR ) 16.5849 16.5849 0.330314E-09ENTHALPY(CAL/S) -6644.48 -5926.00 -0.108131

PHYSICAL PROPERTIES SECTIONCOMPONENTS----------

ID TYPE FORMULA NAME OR ALIAS REPORT NAMEETOH C C2H6O-2 C2H6O-2 ETOHDEE C C4H10O-5 C4H10O-5 DEEH2O C H2O H2O H2O

U-O-S BLOCK SECTIONBLOCK: B1 MODEL: PUMP----------------------------

INLET STREAM: S1OUTLET STREAM: S2PROPERTY OPTION SET: SYSOP0 IDEAL LIQUID / IDEAL GAS


TOTAL BALANCEMOLE(KMOL/HR) 0.36000 0.36000 0.000000E+00MASS(KG/HR ) 16.5849 16.5849 0.000000E+00ENTHALPY(CAL/S) -6644.48 -6643.72 -0.114243E-03

*** INPUT DATA ***OUTLET PRESSURE ATM 5.00000

PUMP EFFICIENCY 0.75000DRIVER EFFICIENCY 1.00000

FLASH SPECIFICATIONS:LIQUID PHASE CALCULATIONNO FLASH PERFORMEDMAXIMUM NUMBER OF ITERATIONS 30TOLERANCE 0.00010


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*** RESULTS ***VOLUMETRIC FLOW RATE L/MIN 0.35286PRESSURE CHANGE ATM 4.00000NPSH AVAILABLE M-KGF/KG 12.2125FLUID POWER KW 0.0023836BRAKE POWER KW 0.0031781ELECTRICITY KW 0.0031781PUMP EFFICIENCY USED 0.75000NET WORK REQUIRED KW 0.0031781HEAD DEVELOPED M-KGF/KG 52.7597

BLOCK: B2 MODEL: HEATER------------------------------



TOTAL BALANCEMOLE(KMOL/HR) 0.36000 0.36000 0.000000E+00MASS(KG/HR ) 16.5849 16.5849 0.000000E+00

ENTHALPY(CAL/S) -6643.72 -5168.53 -0.222043


*** RESULTS ***OUTLET TEMPERATURE K 523.15OUTLET PRESSURE ATM 5.0000HEAT DUTY CAL/SEC 1475.2OUTLET VAPOR FRACTION 1.0000PRESSURE-DROP CORRELATION PARAMETER 0.0000

V-L PHASE EQUILIBRIUM :COMP F(I) X(I) Y(I) K(I)ETOH 1.0000 1.0000 1.0000 14.187

BLOCK: B3 MODEL: RSTOIC------------------------------



TOTAL BALANCE

MOLE(KMOL/HR) 0.36000 0.36000 0.0000E+00 0.000000E+00MASS(KG/HR ) 16.5849 16.5849 0.000000E+00ENTHALPY(CAL/S) -5168.53 -5393.48 0.417083E-01

*** INPUT DATA ***STOICHIOMETRY MATRIX:

REACTION #1: SUBSTREAM MIXED: ETOH -2.00 DEE 1.00 H2O 1.00

REACTION CONVERSION SPECS: NUMBER= 1


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STREAM SECTIONS1 S2 S3 S4 S5 S6-----------------STREAM ID S1 S2 S3 S4 S5 S6FROM : ---- B1 B2 B3 B4 B4TO : B1 B2 B3 B4 ---- ----

SUBSTREAM: MIXEDPHASE: LIQUID LIQUID VAPOR VAPOR VAPOR LIQUIDCOMPONENTS: KMOL/HR

ETOH 0.3600 0.3600 0.3600 5.4000-02 4.5056-02 8.9441-03DEE 0.0 0.0 0.0 0.1530 0.1451 7.8669-03H2O 0.0 0.0 0.0 0.1530 0.1053 4.7683-02

TOTAL FLOW:KMOL/HR 0.3600 0.3600 0.3600 0.3600 0.2955 6.4494-02KG/HR 16.5849 16.5849 16.5849 16.5849 14.7307 1.8542L/MIN 0.3529 0.3530 51.5132 51.5132 143.0289 3.8821-02

STATE VARIABLES:TEMP K 298.1500 298.3732 523.1500 523.1500 353.9138 353.9138PRES ATM 1.0000 5.0000 5.0000 5.0000 1.0000 1.0000VFRAC 0.0 0.0 1.0000 1.0000 1.0000 0.0LFRAC 1.0000 1.0000 0.0 0.0 0.0 1.0000

SFRAC 0.0 0.0 0.0 0.0 0.0 0.0ENTHALPY:

CAL/MOL -6.645+04 -6.644+04 -5.169+04 -5.394+04 -5.768+04 -6.651+04CAL/GM -1442.287 -1442.122 -1121.909 -1170.738 -1157.040 -2313.489CAL/SEC -6644.478 -6643.719 -5168.525 -5393.478 -4734.442 -1191.560

ENTROPY:CAL/MOL-K -82.7906 -82.7656 -45.6490 -46.4569 -57.7166 -49.9850CAL/GM-K -1.7971 -1.7966 -0.9909 -1.0084 -1.1578 -1.7386

DENSITY:MOL/CC 1.7004-02 1.6998-02 1.1648-04 1.1648-04 3.4434-05 2.7689-02GM/CC 0.7833 0.7831 5.3659-03 5.3659-03 1.7165-03 0.7960

AVG MW 46.0690 46.0690 46.0690 46.0690 49.8489 28.7498

PROBLEM STATUS SECTIONBLOCK STATUS------------******************************************************************* ** Calculations were completed normally ** ** All Unit Operation blocks were completed normally ** ** All streams were flashed normally ** ** All Convergence blocks were completed normally ** *******************************************************************


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VII. Use of Graphical User Interface (GUI) to Run ASPEN Plus Simulations (A) Advantages of the GUI Method While the input-file method is useful for the beginners to quickly learn the language, structure,and computation approach of the ASPEN simulation package, it is seldom used in routinesimulations because it is less convenient than the alternate approach, namely, the use of ASPENGraphical User Interface or GUI that avoids the need to compose the input file explicitly whileat the same time permits the use of an expert guidance system. An effective use of ASPEN GUI ,however, requires a knowledge of the structure and ground rules of ASPEN which is best learned

by the input-file method. Interpretation of simulation results and debugging of program errors becomes much easier with the knowledge gained from the input-file method.

With ASPEN GUI , the input file is created by the computer based on the process scheme that theASPEN user constructs on the computer screen. As with the input-file method, the processscheme is defined by a flowsheet which consists of unit blocks linked by material streams andheat and/or work streams. Each unit block simulates a process or unit operation. Constructingthe process scheme on screen is analogous to sketching a flowsheet on paper when one works on

an energy-&-material-balance problem in CHE 205. Seeing the process scheme on screen provides for an easy check for any missing link, either a block or stream.

Perhaps the single most important advantage of ASPEN PLUS over the input-file method is the built-in guidance of the expert system technology that eliminates the problem of over- or under-specification, which is frequently encountered in the input-file method. The parametricspecification of a unit block or stream is achieved by completing a dialog box or form. Theexpert system technology anticipates all possible combinations of input parameters that willuniquely specify a process scheme; it automatically performs a degree-of-freedom analysis toarrive at precisely the correct number of input specifications. Except for the simplest processschemes, a degree-of-freedom analysis is often complicated and tedious to perform by hand, as

would be required in order to determine a priori the right number of input specifications by theinput-file method.

The built-in guidance of the expert system technology allows one to invoke the Next command--which is available on every electronic form as well as on the window menu bar and toolbar--tocomplete the next logical input specification or perform the logical step. The Next commandappears as a light blue button with the symbol N in it. One can rely almost exclusively on theNext command to complete all required input specifications; however, in the tutorial to follow,you are strongly urged to avoid using the Next command but rather follow exactly the stepsoutlined below so as not to be side-tracked from the key points being made. After completingthe prescribed steps once or twice, you can return and use the Next command to enter the inputinformation in a different sequence.

(B) Step-by-Step GUI Instructions for Running an ASPEN Plus Simulation The use of ASPEN GUI will be illustrated by re-working the problems described in Sections III-A and III-B .


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(1) ASPEN GUI Simulation for the First Problem Statement Double click ASPEN GUI on the Nowell Application Launcher. An Aspen Plus Startup window as shown in Figure 1 on the next page will appear over a main window that is not yetactivated. One will be asked to select one of two options: Create a New Simulation by either

Blank Simulation or Template , or Open an Existing Simulation (by picking a .bkp or .apw or

.inp file).

Figure 1. An Aspen Plus Startup window.

Select the Blank Simulation option and click the OK button. A Connect to Engine dialog boxwill appear with a default entry of local PC for Server type. Click the OK button withoutmaking any changes. A Connecting to local server message will appear briefly that will bereplaced by a dialog box declaring Connection Established . Click the OK button on the dialog

box.

The Aspen Plus main window that was in a deactivated mode in the background is now activatedand it looks like Figure 2 shown on the next page. The window shows a blank flowsheet work

space in the center which is flanged on the right and the bottom by vertical and horizontalscroll bars, respectively. Above the work space and on the very top is the title bar with a defaultfilename Simulation 1 that may be changed by clicking the File pulldown menu on the menu barand choosing the Save option (see Table 7). The title bar has the provisions for minimizing, re-sizing and closing the main window. Immediately below the title bar is the menu bar and belowthat, the toolbar. Note the presence of the Next command button ( N ) in the middle of thetoolbar. Further below is the drawing toolbar which is immediately above the work space. The


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various options on the menu bar and toolbar are described in Tables 7 and 8. For the type ofsimulations we will perform, the default settings on the drawing toolbar are generally satisfactoryand there is no special need for the options in the drawing toolbar. We will defer learning aboutthe drawing toolbar features until there is a need for them.

Figure 2. An Aspen Plus window in an activated mode that is ready to receive input data.

Immediately below the horizontal scroll bar underneath the work space are the ASPEN Model Library menu that extends from the right to almost all the way to the left, a select mode button,and options for material streams, heat and work streams. Below that are the prompt area on theleft and status indicator on the right. The Model Library menu is described in Table 9. Usefulguidance and hint can often be found in the prompt area about the next logical step to take incompleting input information on the flowsheet. The status indicator should now read

Flowsheet Not Complete in red.

Go to the Model Library menu below the work space and click Pressur e Chan gers . A dialogwindow should appear showing a list of icons with the names Pump , Compr , Mcompr , Valve ,

Pipe and Pipeline . Click Pump and drag it into the work space and release the mouse button. Asquare box should appear in the work space with the label B1 PUMP . The word PUMP inthe square box may be too small to read easily. It, along with the square box, can be magnified

by going to the View pulldown menu and select successively Zoom and Zoom In . Notice that the


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square box and the characters within it are magnified. A second click on Zoom In will magnifythe square further. Conversely, a click on Zoom Out on the View pulldown menu will reduce thesquare box.

An automatic labeling of the block as it is being introduced into the flowsheet gives it the blockidB1". To stop the automatic naming of blocks (or streams, see later), select Options from theTools pulldown menu and click the Flowsheet tab and deselect the Automatically assign blockname with the prefix B option (or, in the case of streams, Automatically assign stream namewith the prefix __ option). Note that the prefix B in the dialog box in the above option may

be changed to some other letter if an automatic block labeling is desired with a different prefix.Likewise, if an automatic stream labeling is desired with a prefix S, for example, the letter S may be entered into the empty dialog box in the case of Automatically assign stream name withthe prefix __ option. In this tutorial, the automatic block labeling with prefix B will be kept andthe automatic stream labeling will be given the prefix S in place of no prefix such that the streamnames will appear as S1, S2, , as opposed to simply 1, 2,.. .

Go to the Stream menu on the left corner of the flowsheet window and click Material Stream and drag it into the work space to connect with the connecting port on the left side of the B1 block. Notice that as soon as a stream is dragged into the work space, the pointer shape changesto + that signifies an insert mode and at the same time the connecting ports on all the blocks lightup in red and blue. The red connecting ports are the ones normally used. The blue connecting

ports are meant for aqueous product streams when the free water option is picked in asimulation. To connect a stream to a connecting port, simply drag it from the Stream menu intothe work space and contact the pointer with the red connecting port. Note that as soon as thecontact is made, the red marking transforms into light green and the pointer changes its shape to

| that signifies a connect mode. (The other pointer shapes and the operation modes theyrepresent are described in Chapter 4, Defining the Flowsheet, in APLUS 111 User Guide.pdf ).Release the mouse button and drag the pointer the desired distance to the left of the B1 block (todefine the length of line representing the stream on the flowsheet) and click the mouse button toremove the stream from an active input mode. Notice that the label S1" appears automaticallyon the stream. The pointer shape should return to its normal select mode indicated by a pointingarrow. If not, right click the mouse to de-select whichever other mode that the mouse may be in.

Repeat the process to introduce stream S2, but this time the stream is connected to two ports,first, the product port on the right side of the B1 block and, second, the inlet port on the left sideof the B2 block. To straighten out the connection between the blocks and to align the blocks sothat the flowsheet will appear neater, click S2 and then right click to invoke a shortcut menu that

provides the following options:

InputResultsReconcileAnalysisChange Stream Class..


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Delete StreamRename StreamReconnect SourceReconnect DestinationRotate IconAlign Blocks

Select the Align Blocks option and notice that S2 is straightened out and B1 and B2 arealigned. By means of this right-click shortcut menu on a selected stream, one can rename thestream ( Rename Stream ), delete the stream ( Delete Stream ), connect the stream as a productstream from a block ( Reconnect Source ), connect the stream as an input stream to a block( Reconnect Destination ), specify input data on the stream ( Input ), review simulation results onthe stream ( Results ), or change the classification of the stream ( Change Stream Class ..).

Similarly, if one selects a block say, B2, and then click the right mouse button, a shortcut menuthe following options will be invoked:

InputResultsStream ResultsChange SectionAdd to Model LibraryDelete BlockRename BlockRotate IconResize IconExchange Icon

HideUnplace IconCenter View

Thus, by means of the right-click shortcut menu on a selected block, one can rename the block( Rename Block ), delete the block ( Delete Block ), specify input data on the block ( Input ), reviewsimulation results on the block ( Results ) and on the product stream(s) of the block (StreamResults), and change the icon or icon size of the block ( Resize Icon , Exchange Icon ).

Returning to the flowsheet, one can repeat similar steps like those taken in connection withstream S2 to introduce stream S3 to connect blocks B2 and B3, stream S4 to connect blocks B3and B4, and streams S5 and S6 as the overhead and bottom product streams of block B4. The

precise number of streams to be connected to a block is indicated by the number of redconnecting ports on the block: 2 each in the case of Pump , Heater , RStoic and 3 in the case of

Flash2 . Addition of stream to the work space should continue until there is no outstandingconnecting port (in red) on the flowsheet.

The flowsheet connection is now completed and the ASPEN Plus window should look like Fig.


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3. This is a good time to save the .apw file that is created by the ASPEN GUI with the inputdata given to it so far. It is a good practice to save often to avoid the possibility of losing yourwork in the event of your workstation locking up or crashing. Select Save on the File pulldownmenu. A Save As dialog window will appear with the default name and file type, Simu1 and.apw , and the default directory specified as C:\Temp . One could accept the default file name

but we choose to change it to AspenEx1 and then click the Save button.

Fig. 3. Completed flowsheet connection with labeled blocks and streams for the process scheme.

Input specifications should next be made on the feed stream(s)--only one in this example--and blocks. For input specifications, the provisions on the Data pulldown menu are most helpful andshould be used routinely. Select Setup on the Data pulldown menu. After a 10-20-s wait, a Data

Browser dialog window will appear with a Global Specifications as the data entry section on theright. Look for the Title dialog box and key in Repeating Simulation 1 Using ASPEN GUI orsome other similarly descriptive title. In the Input data dialog box under the Units of measurement section, use the selection arrow to change the default units set from ENG (American engineering) to MET (metric). Note that the entry in the Output results dialog boxchanges automatically from ENG to MET . Skip the dialog boxes in Global settings section.Click the Description tab (next to the Global tab) on the same data entry section. In the


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Description dialog box that appears, key in Learning to use ASPEN GUI to re-run AspenEx1that was previously carried out using the Input-File method or some similar message. Skip the

Accounting and Diagnostics tabs.

Note that in addition to the data entry section which has already been mentioned, the DataBrowser window also shows on the left an input summary table on the completion status of thevarious input parameters. It should now show check marks ( ) against Setup , Specifications ,Simulation Options , Stream Class. , Units Sets and Report Options signifying completion of inputspecifications on these items. On the other hand, the following items each has a symbol of a halfempty bottle associated with them: Components , Properties , Streams , Blocks . The symbolsignifies that the input specification on each of these items is still incomplete.

Click the Components option (with a symbol of a half empty bottle) in the input summary tableand then click the Specifications option that appears below it (also with a symbol of a half empty

bottle). A Components Selection dialog window should appear on the right. The same dialogwindow may also be invoked by selecting Components on the Data pulldown menu. Change the

default units set from ENG to MET in the dialog box on top. In the first set of dialog boxes forComponent ID and Component name , key in ETOH and ETHANOL , respectively, for the ID andregistered name of ethanol. Note that the entries conventional and C2H6O-2 appearautomatically in the first set of dialog boxes for Type and Formula , respectively. One could havekeyed in C2H6O-2 as the registered formula of ethanol in place of its registered name.

In the second row of dialog boxes that appear below the first for the ethanol entries, enter DEE and DIETHYL-ETHER , respectively, for the Component ID and Component name of diethyletherand notice the automatic entries of conventional and C4H10O-5 under the Type and Formula columns. In the third row of dialog boxes, enter H2O for Component ID of water and notice theautomatic entries of conventional , H2O and H2O under the Type , Component name and Formula

columns.

If one knows neither the registered name (or alias) nor the registered formula of a substance inASPEN s databanks, one can click the Find button below the entry table to get help. Forexample, if the registered name and formula of diethylether are unknown, a click the Find buttonwill bring up a Find Name or Formula window with a dialog box for Compound name or

formula . The entry of C4H10O will bring up a table of isomers sharing the same chemicalformula, along with their registered names (or aliases) and formulae in ASPEN s databanks.One can pick DIETHYL-ETHER and C4H10O-5 from the table.

The Components Selection is now completed. Skip the Petroleum , Nonconventional and Databanks tabs to the right of the Selection tab. Note the appearance of the check mark againstthe Components and Specifications options in the input summary table on the left.

Click the Properties option (with a symbol of a half empty bottle) in the input summary table andthen click the Specifications option that appears below it (also with a symbol of a half empty

bottle). A Global Properties Specification dialog window should appear. The same dialog


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window may also be invoked by selecting Properties on the Data pulldown menu. Click theselection arrow in the Property method dialog box and scroll down to pick IDEAL from the listthat appears. This setting corresponds to Sysop0 or ideal components or mixture assumption.Skip the other dialog boxes. Note the appearance of the check mark against the Properties ,Specifications , Properties Methods , and Molecular Structure options in the input summary table.

Select Save on the File pulldown menu to save the work.

Click the Streams option (again, with a symbol of a half empty bottle) in the input summary tableand then click the S1 option that appears below it (also with a symbol of a half empty bottle).You may have to use the vertical scroll bar on the input summary table to bring the Streams andS1 options in view. A Stream S1 Specifications dialog window should appear. The same dialogwindow may also be invoked by selecting Streams on the Data pulldown menu. Accept thedefault entries of Temperature and Pressure in the State variables section and Mixed in theSubstream name dialog box near the top. Key in 25 in the temperature-value dialog box and usethe selection arrow in the temperature-unit dialog box to change K to C. Key in 1 and 0.36 ,respectively, in the dialog boxes for the pressure value and total flow value, and accept the

default units for Pressure and Total flow . In the Composition section, accept the default settingof Mole-Flow in the top dialog box and key in 0.36 , 0, 0, respectively, as the component-flowvalues of ETOH , DEE and H2O under the Value column. Alternatively, one could change thedefault entry of Mole-Flow to Mole-Frac and then key in 1, 0, 0, respectively, as the molefraction values of ETOH , DEE and H2O under the Value column. Skip the Flash Options tab tothe right of the Specifications tab. Note the appearance of the check mark against the Streams ,S1, and Input options in the input summary table, as well as the notable absence of the half-filled

bottle symbol against any of the streams S2 through S6. The latter is to be expected becausestreams S2 through S6 are all product streams that should not be specified by Streams input

provisions.

Click the Blocks option in the input summary table and then click the B1 option that appears below it. A Block B1 Specifications dialog window should appear for the pump. The samedialog window may also be invoked by selecting Blocks on the Data pulldown menu. In the

Pump outlet specification section, select the Discharge pressure option and key in the dialog boxto its right the value of 5. In the Efficiencies section below, key in 0.75 and 1, respectively, in the

Pump and Driver dialog boxes. Note the appearance of the check mark against B1 and all theoptions beneath it in the input summary table. Note however that the half-filled bottle symbolremains with the Blocks option since the input specifications are still to be completed on B2, B3and B4.

Click the B2 option in the input summary table to invoke the Block B2 Specifications dialogwindow for the heater. The same dialog window may also be invoked by selecting Blocks on theData pulldown menu. Accept the default entries of Temperature and Pressure and key in 250 and 5 as their respective values in their dialog boxes, after changing the temperature unit from K to C . Skip the Flash Options tab to the right of the Specifications tab and note the appearance ofthe check mark against B2 and all the options beneath it.


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Click the B3 option in the input summary table to invoke the Block B3 Specifications dialogwindow for the stoichiometric reactor. The same dialog window may also be invoked byselecting Blocks on the Data pulldown menu. Accept the default entries of Temperature and

Pressure and key in 250 and 5 as their respective values in their dialog boxes, after changing thetemperature unit from K to C . Click the Reactions tab to the right of the Specifications tab to callup the Reactions specifications window, which appears to accept data entries in its table butactually does not. Click the New.. button below the table to call up the Edit Stoichiometry dialogform. Accept the default value of 1 in the Reaction No. dialog box on the Edit Stoichiometry form. Under the Reactants column, key in ETOH and -2, respectively, in the Component andCoefficient dialog boxes. In the Products column, key in DEE and 1, respectively, in theComponent and Coefficient dialog boxes in the first row and H2O and 1, respectively, in thesame dialog boxes in the second row. The row order for the DEE and H2O entries may beswitched. In the Products generation section, accept the default selection of Fractionalconversion , and in the ___ of component ___ string that appears to its right, key in 0.85 and

ETOH in the two dialog boxes. The stoichiometry and conversion specifications are nowcompleted. Click either the N or CLOSE button below the data entry table and one is returned

to the Reactions specifications window mentioned earlier. This time, however, the windowshows completed information in the table on Reaction 1 and the activation of the Edit and Delete buttons that were previously deactivated. These two buttons are located to the right of the New button, which remains activated in case additional input is needed to specify multiple reactions.The Edit and Delete buttons provide options for editing or deleting any of reaction(s) listed in thetable. Note the appearance of the check mark against B3 and all options beneath it.

Click the B4 option in the input summary table to invoke the Block B4 Specifications dialogwindow for the flash separator. The same dialog window may also be invoked by selecting

Blocks on the Data pulldown menu. Accept the default entries of Temperature and Pressure andkey in 76 and 1 as their respective values in their dialog boxes, after changing the temperature

unit from K to C . Skip the Flash Options and Entrainment tabs to the right of the Specifications tab. The input specification on B4 is now completed, as evident by the appearance of the checkmark against B4 and all the options beneath it. The absence of any option in the inputsummary table with any outstanding symbol of a half-filled bottle suggests that the inputspecification for the overall flowsheet may be complete. This is confirmed when the Nextcommand button ( N ) near the upper right corner of the B4 Specifications dialog window (or onthe Toolbar) is clicked. A dialog notification window appears with the headline Required Input(is) Complete (is being added) and the following message:

All required input is complete. You can run the simulation now, or

you can enter more input. To enter more input, select Cancel, then select the options you want from the Data pulldown menu.

Run the simulation now?

OK button Cancel button


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The option for entering more input is needed anytime a Flowsheeting Option --such as Design Spec--or a Model Analysis Tools option--such as Sensitivity , Optimization or Case Study --(allunder the Data pulldown menu) is invoked. Since none of these options is involved in this case,click the OK button to instruct ASPEN to proceed with the simulation.

A Control Panel window appears and the following messages appear in succession:

buttons on the Data Browser toolbar that is locatedimmediately above the Summary Results table to review the simulation results on the blocks andstreams. Use the >> button to scroll forward and the


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printed using Notepad , WordPad or Plato .

(2) ASPEN GUI Simulation for the Second Problem Statement The ASPEN GUI file generated in the preceding section, Simu1 .apw, may be used as a templatefor this problem. Re-open Simu1 .apw using ASPEN GUI and save the file under a different

name, say Aspenex2 .apw.

Select Blocks on the Data pulldown menu and on the Data Browser window that appears, select B4 in the input summary table to invoke the B4 Specifications dialog window. In the top dialog box for a parametric entry, de-select Temperature and select Vfrac instead since, as noted previously in Section IV-B , Vfrac is a much more convenient parameter to use than eithertemperature or pressure in equilibrium phase analysis. Note that when Temperature is de-selected, the entry of 76 C previously associated with it also disappears. Key in an arbitrary trialvalue of 0.5 in the Vfrac dialog box, since neither Vfrac nor Temperature is known at the start ofthe simulation. Click the N button near the top right corner of the B4 Specifications window.The Required Input (is) Complete notification window appears, but this time click the Cancel

button instead of the OK button because a Design-Spec option is yet to be completed. Select Flowsheeting Options and then Design Spec on the Data pulldown menu. On the Design Spec Object manager window that appears, click the New . . button (instead of trying to enter any dataon the Object manager table). On the Create new ID window that appears, accept the defaultentry of DS-1 (as the name of the Design Spec block) in the Enter ID dialog box by clicking theOK button. A Data Browser dialog window appears for the DS-1 block with the followingoptions listed as tabs directly below the window s toolbar: Define , Spec, Vary , Fortran ,

Declarations . On the Define window activated by the default selection of the Define option,click the New . . button (again instead of trying to enter any data in the table above the New . .

button). A dialog window appears with the heading, Create new variable , and an Enter variablename dialog box. Key in the selected name DEES4 in the dialog box and click the OK button

below it. A Variable Definition window appears asking for the specifications of the variable sCategory and Reference . In the Category section on the left, change the selection from default

All to Streams . In the Reference section on the right, use the selection arrow in the Type dialog box to select Mole-Flow . A Stream dialog box appears automatically below the Type dialog boxas soon as the selection of Mole-Flow is made in the Type dialog box; key in or select S4 in theStreams dialog box. A Substream dialog box with the entry of Mixed appears, along with aComponents dialog box. Key in or select DEE in the Components dialog box and then click the

N button below it.

The Define window previously mentioned re-appears, but this time it lists DEES4 as a Fortran

variable with the definition: Mole-Flow Stream=S4 Substream=Mixed Component=DEE . The previously deactivated Edit and Delete buttons to the right of the New. . button are now activatedso that they can be used to edit or delete any of the defined components listed in the Define table.Click the New . . button again to make a second Define statement. DEES5 may be defined in thesame manner as DEES4, with the substitution of stream S4 to S5. The input for the Define segment of the Design Spec block is now completed.


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Click the Fortran tab two spots to the right of the Define tab in the Data Browser window forthe DS-1 block. In the Fortran window that appears, key in the following mathematicalexpression, R = DEES5/DEES4 , in the dialog box for Enter executable Fortran statement ,making sure that th e expression starts in column 7 or l ater . If the expression starts in a columnearlier than column 7, it will not be recognized as a valid Fortran statement and will be ignored

(as will be indicated by the association of a half-filled bottle symbol with the Fortran tab).

Click the Spec tab immediately to the right of the Define tab in the Data Browser window forthe DS-1 block. In the Design Specification expressions window that appears, key in R, 0.95 and 0.001 , respectively, in the Spec, Target and Tolerance dialog boxes. Save the work by selectingSave on the File pulldown menu.

Click the Vary tab immediately to the right of the Spec tab in the Data Browser window for the DS-1 block. In the Vary window that appears, select Block-Var in the Type dialog box under the Manipulated variable section on the left, and then select in a follow-up sequence the followingentries, B4, Vfrac and Param , in the Block name , Variable and Sentence dialog boxes that appear

successively below the Type dialog box as each preceding entry is selected. The Param entryappears automatical