Aspen Manual (Version10)

8/13/2019 Aspen Manual (Version10)

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COP YRI G H T 19811998 Aspen Techn ology, In c.ALL RIG HTS RE SE RVED

The flowsheet graphics and plot components of Aspen Plus were developed by MY-Tech, Inc.

ADVENT ,Aspen Custom Modeler,Aspen Dyn a mics,Aspen P lus , AspenTech , BioP rocessSimula tor (B P S), D y na P L U S, ModelManager, P lant elligence, the P lan telligence logo,POLYMERS PLU S , PROPERTIES PLU S , S P E E D U P , an d the a spen leaf logoa re either registeredtr a dema rks, or tra dema rks of Aspen Technology, In c., in the U nited S ta tes a nd/or oth er count ries.

BATCHFRACa nd R ATE FR ACa re tra demarks of Koch E ngineering Company, In c.

Activat or is a tra demark of Softw ar e Security, Inc.

Rainbow SentinelSuperProis a t ra dema rk of Rainbow Technologies, Inc.

la n License Mana ger is a tr a demark of lan C omputer G roup, Inc., Mounta in View , Ca lifornia , US A.

Microsoft Windows, Windows NT, an d Windows 95 are either r egistered tr a dema rks or tr a dema rks ofMicrosoft C orpora tion in the U nited S ta tes a nd/or other countries.

All other bra nd a nd product na mes ar e tra demarks or registered tr adema rks of their respectivecompanies.

The License Man a ger portion of this product is ba sed on:

la n License Mana ger 1989-1997 la n C omputer G roup, Inc.All right s reserved

U se of Aspen P lus a nd This Ma nua l

This manual is intended as a guide to using Aspen Plus process modeling software. This documentation containsAspenTech proprieta ry a nd confidentia l informa tion a nd ma y not be disclosed, used, or copied wit hout t he priorconsent of AspenTech or a s set fort h in t he a pplica ble license ag reement. U sers a re solely r esponsible for theproper use of Aspen Plus and the application of the results obtained.

Although AspenTech ha s tested t he softw ar e an d reviewed the documenta tion, the sole wa rra nty for Aspen P lusmay be found in the applicable license agreement between AspenTech and the user. ASPENTECH MAKES NOWARRANTY OR REPRESENTATION, EITHER EXPRESS OR IMPLIED, WITH RESPECT TO THIS

DOCUMENTATION, ITS QUALITY, PERFORMANCE, MERCHANTABILITY, OR FITNESS FOR A

PARTICULAR PURPOSE.


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Aspen P lus G et t ing S t a rt ed iiVersion 10

Contents

About Get t i n g S ta r t ed Bu i l d i n g and Ru nn i n g a P ro cess Model

Why U se P rocess Sim ulat ion? .....................................................................vii

Wha t is a n Aspen P lus P rocess Sim ula tion Model? ..................................viii

Sessions in th is B ook..................................................................................... ix

For More I nforma tion ................................................................................... ix

Technical Support .......................................................................................... x

1 Aspen Plus Basics

St a rt ing Aspen P lus.....................................................................................1-2

The Aspen P lus Ma in Window ...................................................................1-2Opening a File .............................................................................................1-3

Selecting Flows heet Objects ................. .................. .................. .................. .1-6

U sing a Sh ortcut Menu ...............................................................................1-7

Opening Input Forms ..................................................................................1-8

U sing Help ...................................................................................................1-9

Ent ering Da ta on a Form...........................................................................1-11

Expert Guidancethe Next Function.......................................................1-12

Runn ing the Simu lat ion ...........................................................................1-16

Exa mining S tr eam a nd B lock Results .....................................................1-17

Modifying and Rerunning Your Model......................................................1-19

Exiting Aspen Plus.....................................................................................1-20

2 Building and Running a Process Simulation Model

B uilding the P rocess Model ........................................................................2-2

Defining th e Pr oblem: Methylcyclohexa ne Recovery C olumn .................2-2

St a rt ing Aspen P lus ....................................................................................2-3

Cr eat ing a New Simu lat ion ........................................................................2-3

The Aspen P lus Ma in Window ...................................................................2-4

Defining the Flowsh eet ...............................................................................2-5

Adding Da ta to t he P rocess Model ...........................................................2-11

Specifying Title, Str eam P ropert ies, and U nits ......................................2-13

En tering Components ...............................................................................2-14

Selecting Thermodyn a mic Methods .........................................................2-16En tering S tr eam D a ta ..............................................................................2-18

En tering U nit Opera tion B lock Da ta .......................................................2-20

Runn ing the Simu lat ion ...........................................................................2-25

Exa mining Sim ulat ion Results.................................................................2-26

Exa mining B lock Results ..........................................................................2-26

Exa mining St rea m Results .......................................................................2-29

Ch an ging Input Specifica tions .................................................................2-30

Rerunn ing th e Sim ulat ion ........................................................................2-31


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iv Aspen P lus G et t ing S t a rt edVersion 10

Cr eat ing Report s .......................................................................................2-32

E xitin g Aspen P lus .................. .................. .................. .................. ............2-33

3 Performing a Sensitivity Analysis

St a rt ing Aspen P lus ....................................................................................3-2Opening an Existing Simulat ion .................................................................3-2

Saving a Simulation under a New Name...................................................3-3

Defining the Sensitivity Ana lysis ................................................................3-4

Entering Sensitivity Specifications..............................................................3-4

Defining Sa mpled Varia bles.................................................................3-5

Defining Ma nipulat ed Varia bles..........................................................3-9

Defining Ta bula ted Varia bles ............................................................3-11

Running the Simulation.............................................................................3-14

Displa ying Sensit ivity Ana lysis R esults ..................................................3-15

P lotting Sensitivity Results .......................................................................3-16


4 Meeting Process Design Specifications

Sta rting Aspen P lus .....................................................................................4-2

Opening a n Exist ing Sim ula tion ................................................................4-2

Sa ving a S imulation U nder a New Nam e ...................................................4-3

Defining the Design Specification................................................................4-4

Entering Design Specifications....................................................................4-4

Running the Simulation...............................................................................4-9

Examining Design Specification Results...................................................4-10


5 Creating a Process Flow Diagram


Opening an Existing Simulat ion .................................................................5-2

Sw itching to P FD Mode ...............................................................................5-3

Adding Eq uipment Icons an d Str eams ........................................................5-4

Displaying Str eam Da ta ...............................................................................5-8

Adding a St rea m Ta ble .............................................................................5-11

Adding Text .................. .................. ................... .................. .................. .....5-13

P rinting a P rocess Flow Dia gra m ..............................................................5-15

Leavin g P FD Mode....................................................................................5-16


6 Estimating Physical Properties for a Non-Databank Component

Thiazole P hysical P roperty Da ta .................................................................6-2


Creating a Property Estimation Simulation..............................................6-3

Entering Components Information..............................................................6-4

Specifying P roperties to Est imat e ...............................................................6-5

Entering Molecular Structure......................................................................6-7

Ent ering P roperty Da ta ...............................................................................6-9


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Aspen P lus G et t ing S t a rt ed vVersion 10

Running a P roperty C onstant E stima tion (P CE S) ...................................6-14

Exa mining Pr operty Consta nt Est imat ion Results ..................................6-14

Crea ting a P roperty B ackup F ile...............................................................6-15


7 Analyzing Properties


Ent ering Components an d P roperties .........................................................7-2

G enerating a Txy Dia gra m ..........................................................................7-5

A Connecting to the Aspen Plus Simulation Engine


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vi Aspen P lus G et t ing S t a rt edVersion 10


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Aspen P lus Get t ing S tart edVersion 10 vi

About Getting Star tedBui lding and Running a

Process ModelAspen Plus m a kes it easy t o build an d run a process simula tion model byproviding you w ith a comprehensive syst em of online prompts, hypertext h elp,an d expert system guida nce at every st ep. In ma ny cases, you w ill be able todevelop an Aspen P lus process simula tion model with out referring t o print edmanuals .

If you a re new to Aspen P lus, you should do all of these Gett in g Star tedsessions.To familia rize yourself wit h Aspen P lus ba sics, first do the brief ha nds-on session

in C ha pter 1. Then do th e six other sessions in t his book to lear n st ep-by-stephow t o use the full pow er a nd scope of Aspen P lus. Ea ch session requ ires only 20to 30 minut es.

This guide ass umes only tha t you ha ve an inst a lled copy of the softw a re. If youha ve not inst a lled th e softw ar e, please see the a ppropriat e insta llat ion guide.

Why Use Process Simulation?

P rocess simula tion a llow s you to predict the beha vior of a process by using ba sicengineering relat ionships, such a s ma ss a nd energy bala nces, and pha se andchemical equilibrium. G iven r eliable th ermodyna mic data , realistic operat ingconditions, and rigorous equipment models, you can simulate actual plantbehavior. P rocess simulation enables you to run ma ny cases, conduct " wh at if"an a lyses, and perform sensitivity st udies a nd optimizat ion runs. With simulation,you can design better pla nts an d increase profita bility in existing plants.


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Aspen Plus Gett ing StartedVersion 10viii

P rocess simula tion is useful t hroughout t he entir e lifecycle of a process, fromresear ch an d development t hrough process design to production.

What is an Aspen Plus Process Simulation

Model?

A process consist s of components being mixed, separa ted, h eat ed, cooled, a ndconvert ed by unit opera tions. These component s a re tr a nsferred from unit to unitthrough process strea ms.

You can tr a nsla te a process into an Aspen P lus process simulat ion model by

doing the follow ing st eps:

1. Defin e th e process flow sheet configu ra tion. To do th is step, you:

Define the unit opera tions in th e process Define the process stream s tha t f low betw een t hese unit operat ions Select un it opera tion models from th e Aspen P lus model libra ry t o

describe each un it operat ion

2. Specify the chemica l components in th e process. You can ta ke thesecomponents from the Aspen Plus da ta ba nks, or you can define them.

3. Ch oose a ppropriat e therm odyna mic models from those a va ilable in AspenP lus, to represent t he physical properties of the component s a nd mixt ures inthe process.

4. Specify the component flow ra tes an d the thermodyna mic conditions (forexample, tempera tur e and pressur e) of feed str eam s to the process.

5. Specify the operat ing conditions for the unit opera tions in the flowsheet.

When you ha ve specified this informa tion, you ha ve defined a n Aspen P lusprocess simula tion m odel of your process. You ca n us e th e Aspen P lus processsimula tion model to predict process beha vior.

With Aspen P lus you can int era ctively cha nge specifica tions, such a s flowsheetconfigura tion, operat ing conditions, a nd feed compositions, to run new cases a ndanalyze alternatives.

In addition to process simulation, Aspen Plus allows you to perform a wide rangeof other t a sks such a s est ima ting a nd regressing physical propert ies, genera t ingcustom graphical a nd ta bular output results, data -fit t ing plan t da ta tosimula tion models, costing y our plant , optimizing your process, and interfa cingresults to spreadsheets.


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Aspen P lus Get t ing S tart edVersion 10 ix

Sessions in this Book

The ha nds-on sessions in th is book a re described in t he following t a ble:

Follow the steps in Chapter To learn how to

1 Aspen Plus Basics Start Aspen Plus, use the Aspen Plus user interface, exit Aspen Plus

2 Building and Running a Process Simulation

Model

Build and run a typical Aspen Plus process simulation model.

3 Performing a Sensitivity Analysis Use Aspen Plus to study the sensitivity of process performance to changes

in process feeds and operating variables.

4 Meeting Process Design Specifications Use Aspen Plus to make your process model meet a design specification

by manipulating a process feed or operating variable.

5 Creating a Process Flow Diagram Add stream tables, graphics, and text to your graphical simulationflowsheet.

6 Estimating Physical Properties for a Non-

Databank Component

Use Aspen Plus to enter and estimate missing physical properties required

for simulation.

7 Analyzing Properties Use Aspen Plus to generate tables and plots of physical properties,

computed over a range of values.

For More Information

On l i n e H el p ASP EN P LU S ha s a complete system of online help andcont ext-sensitive prompts . The h elp syst em conta ins both context-sensitive h elpa nd reference informa tion. For more informa tion about using ASP EN P LU S help,see the ASPEN PLUS U ser Guide, Cha pter 3.

ASPEN PLU S Get t i n g S ta r t ed Bu i l d i n g and Ru nn i n g a P rocess Model This tu toria l includes severa l ha nds-on sessions to fa miliar ize you w ithASP EN P LU S. The guide ta kes you step-by-step to learn the full pow er a nd scope

of ASP EN P LUS .

ASPEN PLU S User Gu i d e The three-volume ASPEN PLUS U ser Guideprovides step-by-step procedures for developing a nd using a n ASP EN P LU Sprocess simu lat ion model. The guide is ta sk-orient ed t o help you a ccomplish t heengineering w ork you need t o do, using t he pow erful capabilities ofASP EN PLUS.


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ASPEN P LU S r ef er ence ma nu a l ser i e s ASP EN P LUS reference manua lsprovide deta iled technical r eference informa tion. These ma nua ls includebackground informat ion a bout the unit operat ion m odels a nd t he physica lpropert ies methods and models a vailable in ASP EN P LU S, ta bles of

ASP EN P LU S da ta bank para meters, group contribution method functiona lgroups, an d a w ide ra nge of oth er reference informa tion. The set comprises:

Uni t Operat ion Models

Physi cal Proper ty M ethods and M odels

Physical Pr oper ty Data

User M odels

System M anagement

Summ ary Fil e Toolk it

ASPEN PL US app l i c a t i o n exam p le s A suite of sample online ASP EN P LU Ssimulations illustrating specific processes is delivered with ASPEN PLUS.

ASPEN PLU S I n s t a l l a t i o n Gu i d es These guides provide instructions onpla t form an d netw ork insta llat ion of ASP EN P LU S. The set comprises:

ASPEN PL US In stal lat i on Guidefor Windows ASPEN PLU S Instal l at ion Gui de for OpenVMS ASPEN PLU S Instal l at ion Gui de for U NIX

The ASPEN PLUS manuals are delivered in Adobe portable document format(P DF ) on the ASP EN P LU S D ocumenta t ion CD. You can a lso order printedmanuals from AspenTech.

Technical SupportWor ld Wid e Web For a dditiona l informa tion a bout AspenTech products a ndservices, check th e AspenTech World Wide Web home pa ge on th e Int ernet a t:

http://www.aspentech.com/

Techn ica l r esou r ces To obta in in-depth t echnical su pport informa tion on th eInt ernet, visit th e Technical S upport h omepa ge. Register at :

http://www.aspentech.com/ts/

Approxima tely th ree days a fter registerin g, you will receive a confirma tion e-ma iland you will then be able to access this information.

The most current H otline conta ct informa tion is listed. Other informa tionincludes:

Frequently a sked questions P roduct tra ining courses Technical tips


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Aspen P lus Get t ing S tart edVersion 10 xi

AspenTechHo t l i n e If y ou need help from a n AspenTech C ustomer Supportengineer, conta ct our Hotline for an y of the following loca tions:

If you are located in: Phone Number Fax Number E-Mail Address

North America & theCaribbean

+1-617/949-1021

+1-888/996-7001

(toll free)

+1-617/949-1724 [email protected]

South America

(Argentina office)

(Brazil office)

+54-1/326-9835

+55-11/5506-0756

+54-1/394-8621

+55-11/5506-0567

[email protected]

[email protected]

Europe, Gulf Region, & Africa

(Brussels office)

(UK office)

+32-2/724-0100

+44-1223/312220

+32-2/705-4034

+44-1223/366980

[email protected]

[email protected]

Japan +81-3/3262-1743 +81-3/3262-1744 [email protected]

Asia & Australia +85-2/2838-6077 +85-2/2833-5642 [email protected]


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Aspen P lus G et t ing S t a rt ed 1-

Version 10

Chapter 1

1 Aspen P lus B asics

The best w a y t o lea rn bas ic Aspen P lus concepts is by using Aspen P lus. Thissession leads you through an example Aspen Plus simulation to explain how to

open a f i le, enter data , run a simulat ion, and examine resultsAllow a bout 20 minut es for t his session.


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1-2 Aspen P lus G et t ing S t a r t edVersion 10

Aspen Plus

Basics

Starting Aspen Plus

To sta rt Aspen P lus:

From your Windows desktop, click Start and then select Programs.

Click AspenTech, select Aspen Plus 10.0-1, and click Aspen Plus User Interface.

The Aspen Plus Startup dialog box appears. You can use this dialog box to open anexisting simulation or to create a new simulation using a template or a blanksimulation.

Select the Blank Simulation option and click OK to start the new Aspen Plus

simulation.

Note If t he Connect to Eng ine dialog box appear s, see Appendix A.

Aspen Plus starts a new simulation with the default name, Simulation 1.

Tip You can creat e a sh ortcut icon for your Windows deskt op tha t youdouble-click to start Aspen Plus. To create this icon, use WindowsExplorer to naviga te to th e xeq folder of your Aspen P lus U serInt erface insta llat ion. Next , select t he a pwn.exe progra m a nddra g it onto your Windows deskt op.

The Aspen Plus Main Window

The Aspen P lus ma in w indow (shown in Figur e 1.1) is displayed w hen you sta rtAspen Plus. In the w orkspace of this w indow you creat e and display yoursimula tion flow sheet. The workspa ce rema ins blan k until you enter problemspecifications.

Aspen P lus displays context-dependent definitions and informa tion in the promptar ea of the ma in w indow . Whenever you need informa tion about the currentlyhighlight ed field or item, refer t o the prompt for guida nce.


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Figure 1.1 Aspen Plus Main Window

Opening a File

You can open a file for a n Aspen P lus simula tion by either:

Double-clicking t he file from Windows E xplorer Selecting t he Open comma nd from th e File menu in Aspen P lus

In this s ection you w ill use the Open comma nd on th e File menu to open a

par tia lly completed Aspen P lus simula tion stored in a ba ckup file.

To display the File menu, click File on the menu bar.

Menu bar

Prompt

area

Flowsheet

work space

Model Library

Toolbar

Status indicat

Scroll bars

Next buttonHelp button

Select Mode

button


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Aspen Plus

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Aspen Plus displays the File menu:

From the File menu select Open.

The Open dialog box appears. Your default working directory is displayed in the LookIn box. You can navigate to the folder containing a file by using the Look In box or the

Look In Favorites button .

Click the Look in Favorites button.


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A list of folders is displayed in the Open dialog box:

B y default , t he Fa vorites list conta ins five folders tha t ar e provided w ith AspenP lus. The files in th ese folders a re designed to ass ist you in creat ing suita blesimula tion models in Aspen P lus.

Tip You can a dd folders to the Fa vorites list by na vigat ing t o the

a ppropriat e folder a nd clicking th e Add to Fa vorites butt on.

Double-click the Examples folder.

From the files list, select flash.bkp and click Open.

Click Yes when Aspen Plus prompts "Do you want to close current run before openingnew run?"

Click No when Aspen Plus prompts "Save changes to Simulation 1?"

While Aspen P lus opens th e simula tion model, the mouse pointer shows the bus ysymbol, to indica te th a t Aspen Plus is finishing a n opera tion. When th e operat ionis complete, the mouse pointer r eturn s to the Select a rrow sha pe.


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Aspen Plus

Basics

Selecting Flowsheet Objects

In t he ma in w indow w orkspace, Aspen P lus displays the gra phica l flow sheet forthe opened Fla sh simula tion:

The gra phica l simula tion flow sheet show s th e feeds, products, unit operat ionblocks, an d process strea ms. The Fla sh simula tion ha s one feed stream (str eam1), tw o product st rea ms (strea ms 2 a nd 3), a nd one unit opera tion block (B 1).

In t his section, you will select t he feed str eam (str eam 1) on the simula tionflow sheet a nd enter specifica tions.


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To select stream 1, place the mouse pointer over stream 1 in the graphical simulationflowsheet and click.

Stream 1 is selected and highlighted, as shown in the following figure:

Using a Shortcut Menu

A shortcut m enu of comma nds is a va ilable for the flowsheet objects. To display theshortcut m enu for st ream 1:

Place the mouse pointer over stream 1 and click with the right mouse button.


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The stream shortcut menu appears, listing the commands that you can execute forstream 1:

Use the Up and Down arrow keys to highlight the commands in the shortcut menu.The prompts at the bottom of the main window change as you highlight each

command.

Opening Input Forms

To open the input forms for a st rea m, you can do a ny of the follow ing:

Select St reams from the Da ta menu.

Click the St reams button on the ma in w indow toolbar. Select Input on t he shortcut menu for t he strea m.

To open the input forms for stream 1, select Input on the shortcut menu.

Tip Alterna tively, to open a str eam or block input form q uickly,double-click t he object from t he gra phica l simula tion flowsh eet inthe P rocess Flowsh eet w indow.


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The input forms for stream 1 (Material) appear in a Data Browser window, which isdisplayed on top of the Aspen Plus main window:

The Da ta B rowser is a sheet a nd form viewer w ith a hierarchical menu t ree view(on the left side of the w indow) of the a va ilable simulat ion input, results , an dobjects t ha t h a ve been defined.

Using HelpWhen you view a form or a dia log box, you can get cont ext-sensitive help in a ny ofthe following w ay s:

Click the box you wa nt informa tion on an d the Help button on the ma inwindow toolbar

From H elp on the ma in w indow menu ba r, select What s This? from t he Helpmenu

P ress th e Help key (F1)

Click the Help button on the main window toolbar, then click the Specifications tabin the Data Browser.

Aspen Plus displays a Help window that explains how to use the current sheet, theStream Input Specifications Sheet:

Data Browser

menu tree


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Aspen Plus

Basics

In Help, green underlined words identify topics with additional or related help.In t his exam ple there is a l ink to help on the Strea m Input F orm at the end ofth e Help t opic.

Scroll to the end of this Help topic and click the underlined text Input Form Help.

Help on this topic appears.

When you finish reading the help, close the Help window by clicking the Close button

on the upper right corner of the Help window.

You can a lso get help on a ny t opic a t a ny t ime by using the H elp menu. Forexample:

Click Help on the main window menu bar.

Use the arrow keys to move through the menu, and read the prompts at the bottom ofthe screen to see a description of each item .

To learn more about the Aspen Plus online help system, select Help Topics.


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Aspen P lus G et t ing S t a rt ed 1-1

Version 10

Chapter 1

From the Contents tab, double-click Using Aspen Plus Help and select a help topic todisplay.

When you are finished, close the Help window by clicking the Close button.

Entering Data on a Form

You use the Da ta B rowser to enter dat a on forms. In this section, you w ill entermissing tempera ture, pressure, and component flow da ta for str eam 1.

To move from box to box on a form, us e th e Ta b key or t he mouse.

Click the open Data Browser window to make it active. This returns you to the StreamsInput Specifications sheet.

Tip Alternatively, you can select streams 1 (Material) - Data Browserfrom the Window menu in the ma in window t o make the Da taB rowser window act ive.

Enter the following specifications:

Temperature 180F Pressure 20 psi

Methanol component flow 50 lbmol/hr

Water component flow 50 lbmol/hr

Since the default units are appropriate for this simulation, you will need to enter onlythe values.

Note If you make a mista ke while typing, use the Ba ckspace key toerase t he previous cha ra cters.


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The completed St rea ms I nput S pecifica tions sheet is sh own in the follow ingfigure:

When you enter va lues in boxes or cha nge defau lt options on In put forms, t hespecifications you enter and the defaults you modify are shown in black text, and

a check ma rk w ill a ppea r next to th e sheet na me. On th e Specifica tions sheet,the t emperat ure, pressure, and component flow specifica tions a re black,indicat ing user input .

Expert Guidancethe Next Function

The Aspen P lus expert sy stem, know n a s th e Next function, guides you through a llth e steps for entering specifica tions for your simu lat ion model. The Next function:

G uides you through t he required and optional input for a simulat ion bydisplaying the a ppropriat e forms

Displays messa ges informing you w ha t y ou need to do next En sures t ha t y ou do not ent er incomplete or inconsistent specifica tions even

w hen you cha nge options a nd specifica tions you have alr eady ent ered

To use the Next function to complete the simulation model, click the Next buttonon the Data Browser window toolbar. (When the Data Browser window is not open,you can also click the Next button on the main window toolbar.)


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Aspen Plus displays the next sheet on which input data is required for the simulationmodel, the Flash2 Input Specifications sheet for Block B1:

The input data for Block B1 on the Specifications tab is incomplete as indicated by the

symbol on the Specifications tab.

Click the Next button again.

Aspen Plus displays a Completion Status window that indicates additional data are

required:


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Close the Completion Status window.

Move to the first flash specification box and click the Down arrow to display the list offlash specification types.

Select Heat Duty from the list.

In the Heat Duty value box , enter 0. Press Enter.

To specify the flash conditions of 1 atmosphere, move the pointer to the Pressurevalue box, and type 1. Press Enter.

To change the input units from psi to atm, move to the Pressure Units box, whichcurrently displays units of psi.

Click the arrow on the pressure units box to display the available options.

The units list for pressure appears:


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Select atm from the list.

The input data on the Specifications tab is now complete, as indicated by the checkmark on the Specifications tab:

The input for B lock B1 is complete a s indicat ed by th e check ma rk on th e B 1folder in the menu tree view on the left side of the Da ta B rowser w indow .

The input specifica tions for the simu lat ion ar e complete a s indicat ed by th emessage in the sta tus bar a t the bottom of the main w indow.

Close the Data Browser window by clicking the Close button .


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While Aspen P lus performs calculations for t he simula tion, the m ouse pointer ha sa stop sign sha pe. The block being executed is a lso highlighted in t he simula tionflow sheet in the P rocess Flowsheet w indow. When th e ca lcula tions a re complete,the mouse pointer returns to the Select arrow sha pe. In the sta tus bar a t th e

bott om of the ma in w indow , the prompt message " Simula t ion run completed"appears on the left a nd on the right , the sta tus messa ge "Results Available"appears in blue.

Note If th e calcula t ions are completed w ith errors or w ar nings, thesta tus message indicat es "Results Available with E rrors" a nd"Results Available with Warnings," respectively.

Examining Stream and Block ResultsIn t his section you w ill view th e results for t he flash overhea d va por st ream(str eam 2) a nd t he summ a ry result s for the Fla sh block (B lock B 1).

To display the flash overhead vapor (stream 2) results, click stream 2 in the graphicalflowsheet to select the stream.

With stream 2 selected, right-click on the stream to display the shortcut menu for thestream.

Select Results from the menu.


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Aspen Plus displays the thermodynamic state and composition flows of the vaporstream, stream 2, on the Streams 2 (Material) Results Sheet in a Data Browserwindow:

Use the vertical scrollbar to the right of the results to scroll down the stream results.

To display the results for the Flash Block B1, double-click Blocks on the Data Browsermenu tree and then double-click B1.


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Aspen Plus displays the results forms for Block B1 in a Data Browser window. TheBlock B1 (Flash2) Results Summary sheet displays the overall results for the block.You can see the calculated flash outlet temperature and overall vapor fraction:

Click the Next Form button on the toolbar of the Data Browser window to browsethrough the results.

Close the Data Browser window by clicking .

Modifying and Rerunning Your Model

To simula te cha nging the composition of t he feed st rea m t o 60 lbmol/hr meth a nola nd 40 lbmol/hr w a ter:

Click stream 1 in the graphical simulation flowsheet to select it.

Right-click to display the stream shortcut menu.

Select Input from the menu.


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The input form for stream 1 appears.

Move to the Value boxes in the Composition group box and enter a component flow of60for METHANOL and 40for WATER.

Close the Data Browser window.

To run the simulation, select Run from the Run menu.

When the run is completed, select and display results for the outlet streams and theflash block to examine the new process results. (See Examining Stream and BlockResults, this chapter, to review how to do this.)

Exiting Aspen Plus

To exit Aspen P lus:

Click File on the main window menu bar to display the File menu.

Select Exit.

Aspen Plus displays a dialog box asking if you want to save your simulation.

Select No to exit without saving the simulation.

Congra tula tions! You have successfully completed a n Aspen P lus simulat ion.


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Chapter 2

2 B uilding and Running aP rocess S imulation Model

In this s ession you w ill crea te a n Aspen P lus process model for amethylcyclohexane (MCH) recovery column.

This session is divided into three sections:

B uilding the P rocess Model Adding Da ta to the P rocess Model Running the Simula t ion

Allow a bout 50 minutes t o complete t he entir e session.


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Building the Process Model

In t his section, you w ill build the process model by performing t hese ta sks: Define the problem t o be simula ted St ar t Aspen P lus Create a new simulat ion Define the flow sheet using the gra phical interface

Defining the Problem: Methylcyclohexane

Recovery ColumnThe process flow dia gra m, opera ting condit ions, a nd problem definition a re shownin F igure 2.1.

Figure 2.1 Problem Definition: MCH Recovery Column

MCH a nd toluene form a close-boiling syst em tha t is difficult t o separa te bysimple binary distilla tion. In t he recovery column in Figur e 2.1, phenol is used toextra ct toluene, allowing r elat ively pure methylcyclohexa ne to be recovered inthe overhead.


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In t his session, you w ill eva lua te th e performa nce of an existing column forrecovering MCH from a feed strea m w ith a lower concentra t ion tha n t he originaldesign conditions. You ca n increase t he phenol solvent ra te t o improve MCHrecovery. H owever, you need to simulat e the column t o determine the product

purity, column flow, a nd composition profiles, an d t he condenser a nd r eboilerduties, for a given solvent rate.

Starting Aspen Plus


Start Aspen Plus from the Windows Start menu or by double-clicking the Aspen Plusicon on your desktop.

For more deta iled informa tion, see St ar t ing Aspen P lus in Cha pter 1.

The Aspen P lus St a rt up dialog box appears.

Creating a New Simulation

Aspen P lus provides built-in templa tes for a pplications such a s chemica ls,petroleum, electrolytes, specialty chemicals, pharmaceuticals, and metallurgy.

On the Aspen Plus Startup dialog box, select the Template option. Click OK tocontinue.

The New dialog box appears.

U se the New dia log box to specify the t emplat e and Run Type for t he newsimula tion. Use t he Run Type option to select t he type of ca lcula tions you wa nt t operform. For exam ple, you ca n perform flowsh eet simula tion, dat a r egression,

an d property est imat ion calculat ions.

On the New dialog box, click any item in the list of templates.

A brief description of the selected template appears in the Preview box on the rightside of the dialog box.

Select the General with English Units template for this session.


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The defa ult R un Type, Flowsheet, is a ppropriat e for t his session.

Click OK to start the new Aspen Plus simulation.

Note If t he Connect t o Engine dia log box a ppea rs, see Appendix A.

Aspen Plus starts a new simulation with the default name, Simulation 1.

The Aspen Plus Main Window

The Aspen P lus ma in w indow is display ed wh en you sta rt Aspen P lus. Because you

have not entered any problem specifications yet, the workspace is blank:

For more informa tion a bout th e ma in w indow, refer t o the section, The AspenP lus Main Window, in C ha pter 1.

Click the Next button on the Aspen Plus main window toolbar.


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The list of available distillation columns is displayed. Move the mouse over any modelin the Model Library and read the description in the lower left of the window.

Move the mouse over the RadFrac block and read the prompt.

The prompt for RadFrac suggests this is the right model for this problem.

Click RadFrac, then press the Help key (F1).

The help information confirms that RadFrac is suitable for extractive distillation.

Close the Help window.

The Ra dFr a c model ca n be represent ed on th e flow sheet by a number of pictoria licons. You can s elect the defa ult displa yed in t he Model Libra ry or select a

different icon fr om the icon list:

To choose a different icon for RadFrac, click the down arrow to the right of RadFrac inthe Model Library.

The available icons for RadFrac are displayed:


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The inserted RadFrac block is shown below:

Next, place th e strea ms for the Ra dFr a c column by doing the follow ing:

Click the Material Stream icon on the left side of the Model Library.

Tip To select a Hea t or Work strea m, click th e dow n a rrow next t o theMat erial St ream icon and choose Heat or Work stream.

Move the cursor to the Process Flowsheet window.

For each block in the Process Flowsheet window, all ports that are compatible with thestream type you selected are highlighted.


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P orts tha t must ha ve at least one stream connected are shown in red. Optiona lport s a re show n in blue. If you position th e mouse point er over a port for a fewseconds, the arrow is highlighted and a description of the port appears.

Four required ports, shown with red arrows, appear on the RadFrac block B1. Movethe mouse over the red arrows; the port labels indicate the types of port that arerequired to be connected to at least one stream.

To connect the feed streams:

Point to the RadFrac Feed (Required; one or more) port on the RadFrac icon in theprocess flowsheet window. Click once to select it.

Move the mouse pointer to a blank part of the process flowsheet window where youwant the feed stream to originate in your graphical flowsheet and click once.

A feed stream connecting the selected inlet port is created. Aspen Plus automaticallyassigns the ID 1 to this stream.

Similarly, connect a second feed stream to the same feed port on the RadFrac icon.


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To connect t he overhea d liquid dist illat e product s trea m:

Move the mouse pointer through the ports until the port labeled Liquid Distillate(Required if Distillate Vapor Fraction < 1(Setup Condenser sheet)) appears. Click the

left mouse button once to select it.

Move the mouse pointer to a blank part of the process flowsheet window where youwant the product stream to terminate in your graphical flowsheet, and click.

Product stream 3 is created, connected to the selected outlet port.

To connect the bottoms product st rea m:

Move the mouse pointer through the ports until the port labeled Bottoms (Required)appears. Click once to select it.

Move the mouse pointer to a blank part of the Process Flowsheet window and clickonce to create Stream 4.

When you have finished placing streams, click the Select Mode button in theupper left corner of the Model Library.

Tip To cancel connecting the stream at any time, press ESC.To delete a str eam , select t he strea m in th e gra phica l flow sheeta nd press the D elete key.

Your gra phica l simulat ion flow sheet is now complete. The sta tus indicat or in thebott om right of the main w indow say s " Required Input Incomplete" indicat ingtha t further input specifica t ions ar e required for t he simulat ion.


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Chapter 2

Adding Data to the Process Model

Now tha t you have defined your flowsh eet gra phica lly, use the Da ta B rowser inputforms t o enter t he remaining required informa tion for t his run.

You can rely on the Aspen Plus Next fun ction t o displa y t he required input forms.As a n a lternat ive, you can display the input forms by:

Selecting t he appropriate forms from t he Da ta menu

Clicking the a ppropriat e button on the Da ta B rowser toolbarin the main w indow

Selecting a n object in t he gra phica l flow sheet a nd clicking In put on theshortcut menu

Double-clicking a n object in t he gr a phica l flowsheet

(For more informa tion on opening In put forms, see Ch a pter 1.)


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Specifying Title, Stream Properties, and

Units

The Set up Specifica tions form display s some of the defa ults Aspen P lus uses for theother simulation forms. (Global defaults a ppear on all subsequent forms, but y oucan override them.) You w ill use th e Global sh eet to give your simula tion a t itle.You can also review the other global options that were set when you selectedG eneral w ith E nglish Un its a s th e Applica tion Type.

Use either the mouse, or the Tab key to move from box to box on the form and readthe prompts at the bottom of the main window.

When you are finished reading about the boxes on this form, click the Title box.

In the Title box, enter Methylcyclohexane Recovery Processand then press Enter.

The va lues for t he rema ining boxes on this sheet est a blish globa l default s foryour simulat ion input . For this session you w ill use English units a nd t he otherdefault s, so you do not need to specify a nyt hing else on th is sheet.

In the menu tree of the Data Browser window, click the Report Options form in theSetup folder to review the report options specified in the selected Template.

Aspen Plus always calculates temperature, pressure, vapor fraction, molecularweight a nd tota l f low, enthalpy, entropy, and density for the simulat ion stream s.B eca use you selected th e Genera l wit h En glish U nits Applica tion Type when youcreated t his run , Aspen P lus will also calculate component mole flow by default .

Click the Stream tab to view the Stream sheet.

On the S trea m sheet , you can specify wh ich a ddit iona l propert ies you wa ntAspen P lus to ca lcula te a nd report. The component flow a nd fra ction ba ses a ndadditional properties requested on this form will be included in the Stream-

Summary reports.

To specify that you would like to have Aspen Plus calculate mole fractions, click theFraction Basis Mole checkbox.

You can a lso request tha t Aspen P lus calculate a nd report addit ional st reamproperties. A number of sets of a dditiona l properties a re built in to Aspen P lus foreach applica t ion type, as P roperty S ets.


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For meth ylcyclohexa ne, use th e abbrevia tion MCH for the component I D:

Move to the next blank Component ID box for MCH. Type MCH and press Enter.

Because you have used an abbreviation, MCH, to represent methylcyclohexane,you must a lso enter a da ta bank formula or dat aba nk name to retrieve theappropriat e component dat a from t he Aspen P lus data bank.

Click the blank Component Name box. Type the partial name METHYLCYC andpress Enter.

The Fin d dia log box appear s, listing a ll the components in t he Aspen P lusdat aba nk tha t ha ve a na me containing the let t ers you typed, METHYLCYC:

U se th e Find dia log box to choose the component you need.

Tip To view the complete component n a me, click an d slide t he righ tedge of the component n a me column la bel to the right .


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Using the mouse, or the Up and Down arrow keys, look through the list until you findMETHYLCYCLOHE... The corresponding Formula, Databank, Molecular Weight,Boiling Point, CAS Number, and Component Class are displayed in the searched list.

Select the component METHYLCYCLOHEXANE from the list and click Add to add it tothe component list.

Note You can contin ue a dding components from th is dia log box or closeit .

Tip If you need to sea rch for components ba sed on molecular w eightra nge, boiling point r a nge, or C AS n umbers, you should use theAdva nced sheet in t he Find d ialog box.

Click Close to return to the Components Specifications Selection sheet.

You ha ve now specified the t hree components req uired for th is processsimula tion m odel, Toluene, P henol, and Methylcyclohexa ne.

Click the Next button on the Data Browser window toolbar.

The Aspen P lus expert syst em displays t he next requir ed sheet, the P ropert iesSpecifica tions G loba l sheet.

Selecting Thermodynamic Methods

Use t he P roperties Specificat ions G lobal sheet to select t he thermodynamicmethods used to calculate properties such as K-values, enthalpy, and density.Property methods in Aspen Plus are arranged according to Process Types and inlogical groupings ca lled Ba se Method.

For this simulation, use the UNIFAC activity coefficient model to estimate

liquid-pha se nonideality.To find t he appropriat e type of bas e method for t his simula tion:

Click the arrow to the right of the Base Method box to display the availablethermodynamic property methods in Aspen Plus.


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You can get basic informa tion about a base method by using t he mouse or t hear row keys to move to the base method an d reading t he prompt. For moreinforma tion about a base method, you can move to the base method name a nduse Help.

To select th e U NIF AC property meth od:

Move the highlight down the list to the UNIFAC property method. The information inthe prompt indicates this is the appropriate property method for this simulation.

Select UNIFAC by clicking it.


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The Requ ired P ropert ies Input Complete dialog box appear s. This dia log boxallows you t o select addit ional input forms for physical property para meters a ndestimation.

How ever, the propert y specifica tions for th is problem a re complete, so you cancontin ue to the next required input.

Click OK to close the dialog box.

Entering Stream Data

The St ream Input S pecifica tions sheet for St ream 1 appear s, as indicat ed in theDa ta B rowser window title bar. St ream 1 will be the MCH-toluene feed stream.

Enter the following state variable and component flow specifications for the MCH-toluene feed stream:

Temperature 220 FPressure 20 psiToluene flow value 200 lbmol/hrMCH flow value 200 lbmol/hr


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Because the default units are correct for this simulation, you will need to only enter thevalues. (Refer to Entering Data on Forms in Chapter 1 for more information.)

You ha ve now finished entering da ta for St ream 1, as indicated by the InputComplete message in the Dat a B rowser sta tus bar , a t th e lower left of the

window.

Click Next on the Data Browser window toolbar to guide you to the next form.

The St ream Specificat ions form for S trea m 2 a ppears, a s indicat ed in the Da taB rowser w indow t it le bar. S trea m 2 will be the phenol feed stream.

Enter the following stream specifications for the phenol solvent stream:

Temperature 220 FPressure 20 PSIPhenol flow value 1200 lbmol/hr

The feed str eam specifica tions for t he model a re now complete.

Click Next on the Data Browser window toolbar.

The RadFrac Setup form for block B1 appears.


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Entering Unit Operation Block DataOn the R adF ra c Setup Configura t ion sheet , you enter the n umber of theoreticalsta ges, the valid phases in t he column, the dist il late va por fra ct ion, and otheropera ting specifica tions for t he column.

Use the TAB key to move through the boxes on the form, and read the descriptiveprompts for each box.

The red Incomplete sta tus indicator next to th e Configura tion ta b tells youtha t t he sheet is not yet complete a nd you must enter some addit ionalspecifications.

To learn what specifications this sheet requires, click the Next button on the DataBrowser window title bar.

The Aspen P lus expert syst em displays a Completion S ta tus w indow, sta t ing t ha tyou need to enter Number of sta ges, Condenser type, and t w o out of a list ofspecifica tions, in order t o complete t his sh eet:


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Close the Completion Status window.

Now enter the operating specifications for the column:

Number of stages 22

Click the Condenser list box and select Total

Distillate Rate 200lbmol/hr

Reflux ratio 8

The defa ult of Va por-Liquid for Valid pha ses is correct for th is problem becaus ew e expect only a va por pha se and one liquid phase.

The blue check ma rk next t o the Configura tion ta b indica tes t he sheet iscomplete.


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The Ra dFr a c column model requires more tha n one sheet t o enter t he necessa ryinforma tion. The expert sy stem displa ys t he St rea ms sh eet, on w hich you specifyfeed a nd product st a ge locations.

In t he Ra dFr a c model, sta ge 1 is the top sta ge (condenser) a nd st a ge N (w here Nis th e number of sta ges) is the bott om sta ge (reboiler). For th e process t ha t y oua re simula ting (shown in Figur e 2.1), the MC H-toluene feed (str eam 1) enters

a bove sta ge 14, a nd th e phenol solvent st rea m (str eam 2) enters a bove sta ge 7.

For stream 1, enter a feed stage location of 14.

For stream 2, enter a feed stage location of 7and press Enter.

The St rea ms sh eet is now complete:


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Click the Next button to view the next required input sheet.

On the next req uired sheet, the P ressure sheet, you will enter th e columnpressure profile. You ma y ent er a sta ge-by-sta ge profile, or specify a top-sta gepressure a nd a pressure drop for t he rest of the column. For t he MCH recoverycolumn in this exa mple, use a condenser pressur e of 16 psia, a nd a reboilerpressure of 20.2 psia. I n t he simula tion, Aspen P lus will interpolat e the pressureof the intermediat e sta ges.

Click the arrow to the right of the View box to display a list of available views, andselect Pressure profile.

In the Stage box, enter 1to indicate the top stage (condenser). Enter 16psi for thepressure of this stage.

In the next Stage box enter 22to indicate the bottom stage (reboiler). Enter 20.2psifor the pressure and press Enter.

The P ressure sh eet is now complete.


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The Input Complete message in the Da ta B rowser sta tus ba r in the low er left ofthe w indow, indicat es tha t you ha ve completed th e required specifica tions for th ecolumn model.

All the requ ired forms for the flowsheet a re now complete. You ca n st ill ent erspecifica tions on optiona l input forms. You ca n a lso go back to a ny of th e requiredforms a nd ma ke cha nges.

To see what optional input forms are available, use the scroll bar on the left side of theData Browser window to view all the folders.

The blue check ma rks on the Setup, Components, P ropert ies, Strea ms, a ndB locks folders indicate th a t t hese required forms a re complete.

The rema ining input folders Rea ctions, C onvergence, Flowsheeting Opt ions, a ndModel Analysis Tools are optional

For this example, there is no additional input.


The Required I nput C omplete dia log box confirms t ha t a ll required specifica tions

a re complete, an d prompts you to run t he simulat ion:


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Running the Simulation

To run th e simula tion:

Click OK on the Required Input Complete dialog box.

Aspen Plus displays the Control Panel.

The Control Panel allows you to monitor and interact with the Aspen Plussimula tion ca lcula tions. For more informa tion on how t o control the simula tionthrough th e Control Pa nel, you can either see the Aspen Pl usUser Gui de,Volume 1, Cha pter 11, or see th e topic Contr ol Panel:aboutin t he on-line H elp.

The simula tion calculat ions occur in t hree sequent ial st eps:

P rocessing input specifica tions Calculations begin Generat ing results

As Aspen P lus executes t he simula tion, sta tus m essa ges appear in t he ControlP an el. When th e simulat ion ha s completed, the m essage Resul ts Avai labl eappears in the stat us bar a t the bott om of the ma in window.


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Examining Simulation Results

When the Resul ts Avai l ablemessage appea rs in the stat us area , you can exam inethe results of your flowsh eet simula tion run.

If the Control Panel window obscures your view of the graphical simulation flowsheet,

close the window by clicking .

Examining Block Results

To display th e results for block B1:

Click Block B1 in the simulation flowsheet.

The Block icon is surrounded by square bullets, indicating it is selected.

Continue to point to the column and click (or press and hold) the right mouse button.

The B lock menu a ppea rs, show ing a ll the comma nds t ha t a pply to a block.

Select Results from the menu.

The RadFrac ResultsSummary form appears in a Data Browser window.

For this r un, results a re report ed on several forms, a s indicated by t he check

ma rk next to the form names in the menu tree. The Summ ar y sheet reports asumm a ry of column results, such as condenser a nd reboiler duties:


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To examine the RadFrac profile results, click the Next Form button on the DataBrowser window toolbar.

-or-

Click the Profiles form in the menu tree on the left side of the Data Browser window.

The displayed P rofiles TP FQ sheet r eport s tempera tur e, pressure, enth a lpies,a nd flow profiles for th e Rad Fra c column:


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Use the scroll bars at the bottom of the window and to the right to view up and down,and left and right, through the displayed profiles. You can also resize the window toexpand the view.

By default, the Summary view of the TPFQ profile results is shown. You can use theView box to select a different view of the TPFQ profile results.

Click the arrow on the right of the View box to display a list of available views, andselect Stage Flows.

You can use the Basis box to specify the flow basis for the displayed results.

Click the arrow on the right of the Basis box to display a list of available flow bases.

To display the RadFrac Composition results, click the RadFrac Profiles Compositionstab.

On t he Composition sh eet, w hen t he Liqu id View is selected, liquid composition(a s mole fra ction) profiles are show n for the Ra dFr a c column:

Check the purity of the methylcyclohexane overhead product (about 97%) byexamining the composition at the top of the column (stage 1).


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To display the results for Str eams 1 and 4 on the sa me form a s the results forStream 3:

Move to the blank box next to 3 (in the next column).

Click the list box and select 4 from the dropdown list to display results for stream 4.

To display results for stream 1, repeat the preceding step and select 1 in the nextcolumn of the table.

The Mat erial sheet displa ys result s for St rea ms 3, 4, an d 1:

From th e component f low ra tes reported in t he strea m results, you ca n determinetha t the meth ylcyclohexan e recovery overhea d is 97%.

Changing Input Specifications

In this section, you want to see the effect of increasing the solvent flow rate on thepurity a nd r ecovery of met hylcyclohexan e. To increa se th e phenol solvent str eamflow ra te f rom 1200 lbmol/hr to 1800 lbmol/hr :

Close the Stream Results form by clicking the in the top right corner of the DataBrowser window.


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Select Stream 2 on the graphical simulation flowsheet.

From the Stream shortcut menu, select Input to display the Stream InputSpecifications sheet.

Use the Tab key to move to the PHENOL flow value box, or click in the box.

Change the PHENOL flow rate from 1200 to 1800 lbmol/hr by entering 1800.

Rerunning the Simulation

To rerun the model wit h th e cha nged input:

Click the Next button on the main window toolbar.

The Required In put C omplete dialog box appear s telling you tha t you input iscomplete and a sking if you wa nt t o run the simulat ion with t he newspecifications.

Select OK to run the simulation.

The Control Panel appears again, and the column calculations are completedusing the new phenol f low ra te.

Displa y th e block an d str eam results for the new conditions, as previouslydescribed. You w ill observe tha t increa sing t he solvent flow ra te from 1200 to1800 lbmol/hr increases t he MC H purity in t he overhead product to 98.4%an dth e MC H recovery t o 98.4%.

To choose th e optima l conditions, it w ould be helpful to genera te a sensitivityta ble of MCH recovery a nd purity versus phenol flow ra te. This exam ple is inCha pter 3.


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Creating Reports

To genera te a report of the simula tion specifica tions, ca lcula tions, an d results :

From the File menu in the main window, select Export.

On the Export dialog box, select Report File (*.rep) in the Save As Type box.

Type the filename mchin the File name box.

Click Save to generate the report file, mch.rep.

You ca n open this file w ith a text editor or you ca n print th e file. B y default , thereport file mch.rep is sa ved in your working directory (displayed in t he Sa ve Inbox). You can select a nother directory by na vigat ing to it using t he Sa ve In box.

Tip You can a lso exam ine the report by selecting R eport from theView menu on the ma in w indow. The Report dia log box a llow s


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you to select wh ich section of the report you wa nt d isplayed in atext editor (selecting t he simulat ion will display the entir ereport).

Exiting Aspen Plus

When you ar e finished working w ith t his model, you ca n exit Aspen P lus a s follows

From the File menu, select Exit.

When the dialog box appears, select YES to save the simulation.

In the Save As dialog box, enter the Run ID mchin the File name box.

Aspen Plus saves the simulation as the Aspen Plus Document file, mch.apw, in yourdefault working directory (displayed in the Save In box). This saved simulation will beused as the starting point for the exercises in Chapters 3 and 4.

Congrat ulat ions! You ha ve just built a nd run a complete simulat ion m odel usingAspen P lus.


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3 P erforming a Sensit ivityAnalysis

One of the benefits of using a process simula tion model is th a t you can q uicklystud y t he sensitivity of process performa nce to cha nges in process opera tingvariables. With Aspen Plus, you can allow simulation inputs to vary, and canta bulat e the effect on a set of results of your choice.

In t his session, you w ill learn how to perform sensit ivity a na lysis withAspen P lus.

Allow a bout 20 minut es for t his session.

This session a ssumes t ha t y ou have successfully completed themethy lcyclohexan e (MCH ) recovery column simula tion in Cha pter 2, and t ha tyou have sa ved the simula tion as t he Aspen P lus document file, mch.apw . If youha ve not creat ed the Cha pter 2 exam ple, you can open a backup file from th eAspen Plus E xa mples folder as described in Opening an E xisting S imula tion, thischapter.


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Starting Aspen Plus


Start Aspen Plus from the Windows Start menu or by double-clicking the Aspen Plusicon on your desktop.

For more deta ils, see Sta rt ing Aspen P lus in Cha pter 1.

The Aspen P lus St a rt up dialog box appears.

Opening an Existing Simulation

If you sa ved the met hylcyclohexa ne (MCH ) recovery column s imula tion creat ed inCha pter 2:

Select the option Open an Existing Simulation on the Aspen Plus Startup dialog box.

If your sa ved file mch.a pw is display ed in the list box:

Select mch.apw in the list and click OK.

If your sa ved file mch.a pw is not display ed in the list box:

Double-click on More Files in the list box.

In the Open dialog box that appears, use the Look In box to navigate to the directorythat contains your saved file mch.apw.

Select mch.apw in the list of files and click Open.


Aspen Plus displays the graphical flowsheet for the MCH column simulation.

If you did not creat e the MCH simulat ion in Cha pter 2, you can open t he backupfile mch.bkp in th e Exa mples folder.


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From the Aspen Plus Startup dialog box, select the option Open an Existing Simulationand then click OK.

The Open dialog box appears.

Using the Look In box and the list of files and folders displayed, navigate to theExamples folders in the Aspen Plus user interface installation directory (e:\ProgramFiles\AspenTech\Apui100\Examples by default).

Double-click the Examples folder.

Select mch.bkp and click OK.


Aspen Plus displays the graphical flowsheet for the MCH column simulation.

Saving a Simulation under a New Name

B efore you creat e a sensitivity simulat ion sta rting from the MCH columnsimulation, creat e and save a copy of the MCH simulation file with a new filena me, MCHS ENS . Then you ca n modify this new file.

From the File menu, click Save As.

In the Save As dialog box, choose the directory where you want to save the simulation

In the Filename box, enter the new filename mchsens.

From the Save as Type list, select Aspen Plus Documents (*.apw).

Click Save to save the simulation and continue.

Aspen P lus creat es a new simulat ion model, MCHS ENS , w hich is a copy of thebase case simulat ion, MCH.


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Defining the Sensitivity Analysis

In t he base case MCH simula tion in Cha pter 2, you simulat ed the MCH recoverycolumn performa nce at tw o values for th e phenol solvent flow ra te (1200 an d 1800lbmol/hr). In t he sensitivity a na lysis, you w ill w a nt t o ta bulat e methylcyclohexan e(MCH ) distilla te product purit y (mole fra ction), as w ell a s condenser dut y a ndreboiler duty , for severa l different flow ra tes of phenol.

Entering Sensitivity Specifications

To ent er sensitivit y specifica tions, use Sensit ivity forms, w hich you access from th eData menu:

To display the Data menu, click Data on the main window menu bar.

Drag the mouse through the Data menu and read the prompts at the bottom of thewindow for each type of form.

Select Model Analysis Tools and then select Sensitivity from the submenu.

Aspen Plus displays the Sensitivity Object Manager from which you can create newSensitivity blocks, as well as edit input, display results, or perform other operations onexisting Sensitivity blocks.

On the Sensitivity Object Manager, click New.

The Create New ID dialog box appears, displaying an automatically generatedSensitivity ID, S-1. You can accept the default ID or replace it with an ID of yourchoice.

In the Create New ID dialog box, click OK to accept the default ID and continue.


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The Sensitivity Input Define sheet for S-1 appears:

Ea ch sensit ivity a na lysis generat es a t able. You w ill define the results you wa ntto look at , the inputs you wa nt t o var y, and h ow Aspen P lus tabulat es the results.

Defining Sampled Variables

On the In put Define sheet , you select the simulat ion var iables you w a nt t osam ple for th e sensit ivity ana lysis and give each var iable a unique na me. In thisexample you will define the MCH distilla te product purity , the condenser dut y,an d the reboiler duty as sa mpled var iables.

To select the MCH distillate product purity as a sampled variable:

Click the New button.

The Create New Variable dialog box appears.

Type XMCHin the Variable Name field and click OK to continue.

The Variable Definition dialog box appears. MCH distillate product purity is the molefraction of component MCH in the distillate product, stream 3. This sampled variablebelongs to the Streams category and is of type Mole fraction.

Under Category, click the Streams button to select the variable category.


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In the Reference frame, click the arrow to the right of the Type box to display a list offlowsheet variable types that can be accessed for streams.

Move through the list using the arrow keys, and look at the descriptive prompts.

Select the Type Mole-Frac, since the variable is a component mole fraction.

Aspen Plus displays the other fields necessary to complete the variable definition. Inthis case, the Stream list box appears.

Select stream 3, the liquid distillate stream from the dropdown list in the Stream listbox.

The Substream and Component list boxes appear. In this example, you do not need tomodify the default choice of MIXED in the Substream list box.

Click the Component list box to display a list of valid components. Select MCH.

The blue check mark next to XMCH in the Variable Name list box indicates that thedefinition of variable XMCH is complete.

Click the Close button to close the Variable Definition dialog box and return to theDefine sheet.


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You ha ve specified the first sa mpled varia ble, XMCH :

To select t he condenser dut y a s a sa mpled varia ble:

Click the New button.

In the Create New Variable dialog box, enter QCONDin the Variable Name box. ClickOK to continue.

Since condenser duty is a scala r result for the Ra dFra c block B 1, this sam pledva ria ble belongs t o the B locks category a nd is of type Block-Var.

Click the Blocks option under Category.

Click the Type list box to display the flowsheet variable types that can be accessed forblocks.

Select Block-Var for Type.

In the Blocks list box that appears, select block B1.

Click the Variable list box to display the list of variables. Move through the list and lookat the descriptive prompts.

Select COND-DUTY for Variable since it represents the result of interest.


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Aspen Plus automatically fills the Sentence box based on your choice of variable.

The definition of the va ria ble QCOND is now complete.

You ha ve creat ed tw o new sam pled va riables (XMCH a nd QCOND) using the

New butt on on t he Define sheet . To illustra te a nother wa y t o creat e sam pledvariables, you will now use the Variable Name list box in the Variable Definitiondia log box to define th e column reboiler duty a s a sa mpled varia ble.

Click the Variable Name box and select New.

Tip You can a lso right-click on th e Varia ble Nam e box a nd selectCr eat e from th e popup menu.

The New item dialog box appears.

In the Create a New Item box enter QREB, the name of the new variable that you wantto define. Click OK to continue.

You are returned to the Variable Definition dialog box with QREB displayed in theVariable Name box.

Reboiler duty is a lso a B lock varia ble of type B lock-Var.

Click the Blocks option button under Category.

Select Block-Var in the Type list box.


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Select B1 for Block and REB-DUTY for Variable.

The definition of varia ble QREB is now complete.

Click Close to close the Variable Definition dialog box and to return to the Definesheet.

You ha ve ident ified th e three process va ria bles to sample for th e sensitivityan alysis and given each a unique name.

Click the Next button.

The expert system displays the next required sheet, the Vary sheet.

Defining Manipulated Variables

On the In put Vary sheet , you define the simulat ion va riable to be manipula tedfor the sensitivity analysis, identify the variable values to be used, and specifythe labels for t he varia ble to be used in the t abula ted results. In th is exam ple,you will ma nipulat e the molar flow ra te of th e phenol feed strea m (str eam 2).

Click the Variable Number list box, select to create a new manipulatedvariable.

Aspen Plus creates the manipulated variable and displays the ID 1 in the VariableNumber list box.

Click the Type box to display a list of valid variable types.

Select Stream-Var for the Type.

Aspen Plus displays the remaining fields necessary to uniquely identify the flowsheetvariable.

Select 2 for the Stream.

Select MOLE-FLOW for the Variable.


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For t his session, you w ill var y t he flow ra te betw een 1200 a nd 2000 lbmol/hr a tincr emen ts of 100 lbmol/hr :

Click the Overall Range option button.

Move to the Lower box and enter 1200for the bottom of the range.

On the Upper box, enter 2000for the top of the range.

On the Incr field, enter 100for the increment size.

For th is session, you will specify P HE NOL F LOWRATE a s th e label for th emanipulated variable.

Enter the label PHENOLfor Line1 and FLOWRATEfor Line2 of the Report labels.

You ha ve specified th e informa tion for th e man ipulat ed process va ria ble:

Click the Next button.

The Tabulate sheet appears.


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Defining Tabulated Variables

On the Tabulate sheet, you specify the variables to be tabulated by the sensitivitya na lysis, an d supply optional hea dings for the ta ble columns. You ca n choose

from a mong the varia bles tha t y ou defined on th e Sensit ivity I nput Define sheet .You can also ta bulate a ny a lgebraic combina tions of those varia bles.

To ta bulat e MCH distilla te composition:

In the Column Number box, enter 1, indicating that this is the first tabulated variable.

A second row opens up in the table to define a second tabulated variable.

On the Tabulate variable or expression box, in the first row enter XMCH.

To specify column la bels for t he ta bulat ed MCH distilla te composition:

Click the Table Format button, the Table Format dialog box appears.

Enter the label MCHPURITY IN DISTon the column label field in the first column, asshown:


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Click Close to close the Table Format dialog box.

To ta bulat e the column condenser dut y a nd reboiler dut y:

On the Column Number box in the second row, enter 2.

Enter QCONDfor the Tabulate variable or expression field.

On the next Column Number field, enter 3.

Enter QREBfor the Tabulate variable or expression field.

You ha ve now defined the thr ee variables to be tabula ted in your Sensit ivityanalysis .


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To specify t he column labels for condenser dut y a nd r eboiler duty :

Click the Table Format button.

Enter the label CONDENS DUTYin the column label boxes under Column Number 2.

Enter the label REBOILER DUTYin the Column label boxes under Column Number 3


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Close the Table Format dialog box.

The I nput St a tus for Sensit ivity block S -1 (the blue check ma rk on folder S -1 inthe left pa ne of Da ta B rowser w indow ) shows tha t a ll required input is complete.

Running the Simulation Click the Next button.

The Required Input Complete dialog box appears.

Click OK to run the simulation.

Aspen Plus displays the Control Panel. As the simulation executes, status messagesappear in the Control Panel.

When the Simulation Run Completed andResults Availablemessages appear in thestatus bar at the bottom of the the main window, close the Control Panel window.

You can now exa mine the results of your simulat ion.


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Displaying Sensitivity Analysis Results

The Sensit ivity Analys is Results consist of a t a ble of the va lues you requested onthe In put Ta bulate sheet, shown a s a function of the ma nipulat ed varia ble definedon the Input Vary sheet.

To view t he Sensit ivity result s:

On the menu tree of the Data Browser window, click Results under Sensitivity block,S-1.

The Summary sheet appears.

Note The above results w ere obta ined by using t he Aspen P lusdocument file, mch.apw , as described in Opening an E xistingRun, t his chapt er. If you used the Aspen P lus backup file,mch.bkp, from the Exa mples folder, your result s ma y be slight lydifferent (the 3rd significant digit). These differences occur because

th e sta rt ing point for the calculations a re different. When you usea n .a pw file, Aspen P lus sta rts calculat ing from th e previousresults. When you use a .bkp file, Aspen P lus reinitia lizes beforesta rt ing calculat ions.


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Plotting Sensitivity Results

In a ddition to display ing the sensitivity r esults in t abula r form, you can plot t heresults.

To genera te a plot of MCH dist illat e purity versus phenol flow r a te:

Click the column label you want to plot on the X-Axis. In this case, click the VARY 1column label.

From the Plot menu, select X-Axis Variable.

Click the column label on the MCH PURITY IN DIST column.

From the Plot menu, select Y-Axis Variable.

To crea te t he plot:

Select Display Plot from the Plot menu.

The plot of MCH distillate purity versus phenol flow rate appears in a Plot window:


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You can use the Ma ximize button in the P lot w indow t it le bar to obta in ama ximized full-screen plot. You can a lso customize t he plot by using t he P lotpopup menu (displayed by r ight-clicking in the plot w indow).

Exiting Aspen Plus

When you finish exa mining the plot, exit Aspen P lus:

From the File menu, select Exit.

In the dialog box that appears select Yes to save the simulation.


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4 Meeting P rocess DesignSpecifications

In Cha pter 3, you used Aspen P lus to tabula te th e sensit ivity of MCH dist il la tepurity a nd column dut ies to cha nges in phenol solvent flow ra te. You can a lso useAspen Plus to meet a specific process design target (or design specification) byma nipulat ing any simulat ion input var iable.

In t his session, you w ill lear n how t o use Aspen P lus to ma ke your process modelmeet a process design specifica tion.

Allow a bout 20 minut es for t his session.

This session a ssumes t ha t y ou have successfully completed themethy lcyclohexan e (MCH ) recovery column simula tion in Cha pter 2, and t ha tyou have sa ved the simula tion as t he Aspen P lus document file, mch.apw . If youha ve not creat ed the Cha pter 2 exam ple, you can open a backup file from th eAspen Plus E xa mples folder as described in Opening an E xisting S imula tion, thischapter.


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From the Aspen Plus Startup dialog box, select the