97448371-Aspen-Plus-Nice-Tutorial.pps

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©2000 AspenTech. All Rights Reserved.

Introduction to Flowsheet Simulation

Objective:

Introduce general flowsheet simulation conceptsand Aspen Plus features



©2000 AspenTech. All Rights Reserved. Introduction to Aspen Plus

Flowsheet Simulation

• What is flowsheet simulation?

Use of a computer program to quantitatively model thecharacteristic equations of a chemical process

• Uses underlying physical relationships – Mass and energy balance

– Equilibrium relationships

– Rate correlations (reaction and mass/heat transfer)

• Predicts

– Stream flowrates, compositions, and properties

– Operating conditions

– Equipment sizes




Advantages of Simulation

• Reduces plant design time

– Allows designer to quickly test various plant configurations

• Helps improve current process

– Answers “what if” questions

– Determines optimal process conditions within given constraints

– Assists in locating the constraining parts of a process(debottlenecking)




• What is the composition of stream PRODUCT?

• To solve this problem, we need: – Material balances

– Energy balances

REACTOR

FEED

RECYCLE

REAC-OUT

COOL

COOL-OUT SEP

PRODUCT

General Simulation Problem




Approaches to Flowsheet Simulation

• Sequential Modular

– Aspen Plus is a sequential modular simulation program.

– Each unit operation block is solved in a certain sequence.

• Equation Oriented

– Aspen Custom Modeler (formerly SPEEDUP) is an equation orientedsimulation program.

– All equations are solved simultaneously.

• Combination

– Aspen Dynamics (formerly DynaPLUS) uses the Aspen Plussequential modular approach to initialize the steady state simulationand the Aspen Custom Modeler (formerly SPEEDUP) equationoriented approach to solve the dynamic simulation.




Good Flowsheeting Practice

• Build large flowsheets a few blocks at a time.

– This facilitates troubleshooting if errors occur.

• Ensure flowsheet inputs are reasonable.

• Check that results are consistent and realistic.


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Important Features of Aspen Plus

• Rigorous Electrolyte Simulation

• Solids Handling

• Petroleum Handling

• Data Regression

• Data Fit

• Optimization

• User Routines


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Aspen Plus References:

User Guide, Chapter 1, The User Interface

User Guide, Chapter 2, Creating a Simulation Model

User Guide, Chapter 4, Defining the Flowsheet

The User Interface

Objective:

Become comfortable and familiar with the AspenPlus graphical user interface



Run ID

Tool Bar

Title Bar

Menu Bar

Select Mode

button Model

Library

Model Menu Tabs Process

Flowsheet Window

Next Button

Status Area

The User Interface

Reference: Aspen Plus User Guide, Chapter 1, The User Interface



RStoicModel

Heater Model

Flash2Model

Filename: CUMENE.BKP

REACTOR

FEED

RECYCLE

REAC-OUT

COOL

COOL-OUT SEP

PRODUCT

Cumene Flowsheet Definition



Using the Mouse

• Left button click - Select object/field

• Right button click - Bring up menu for selectedobject/field, or inlet/outlet

- Cancel placement of streams or blocks on the flowsheet

• Double left click - Open Data Browser object sheet

Reference: Aspen Plus User Guide, Chapter 1, The User Interface



Graphic Flowsheet Operations

• To place a block on the flowsheet:

1. Click on a model category tab in the Model Library.

2. Select a unit operation model. Click the drop-down arrow toselect an icon for the model.

3. Click on the model and then click on the flowsheet to placethe block. You can also click on the model icon and drag itonto the flowsheet.

4. Click the right mouse button to stop placing blocks.



Graphic Flowsheet Operations (Continued)

• To place a stream on the flowsheet:

1. Click on the STREAMS icon in the Model Library.

2. If you want to select a different stream type (Material, Heat or Work), click the down arrow next to the icon and choose a

different type.

3. Click a highlighted port to make the connection.

4. Repeat step 3 to connect the other end of the stream.

5. To place one end of the stream as either a process flowsheet

feed or product, click a blank part of the Process Flowsheetwindow.

6. Click the right mouse button to stop creating streams.



Automatic Naming of Streams and Blocks

• Stream and block names can be automatically assignedby Aspen Plus or entered by the user when the object iscreated.

• Stream and block names can be displayed or hidden.

• To modify the naming options:

– Select Options from the Tools menu.

– Click the Flowsheet tab.

– Check or uncheck the naming options desired.



When finished, save in backupformat (Run-ID.BKP).filename: BENZENE.BKP

FL1

Heater Model

Flash2

Model

Flash2

Model

COOL

FEED COOL

VAP1

LIQ1FL2

VAP2

LIQ2

Benzene Flowsheet Definition Workshop

• Objective - Create a graphical flowsheet

– Start with the General with English Units Template.

– Choose the appropriate icons for the blocks.

– Rename the blocks and streams.


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User Guide, Chapter 3, Using Aspen Plus Help

User Guide, Chapter 5, Global Information for Calculations

User Guide, Chapter 6, Specifying Components

User Guide, Chapter 7, Physical Property Methods

User Guide, Chapter 9, Specifying Streams

User Guide, Chapter 10, Unit Operation Models

User Guide, Chapter 11, Running Your Simulation

Basic Input

Objective:

Introduce the basic input required to run an AspenPlus simulation



The User Interface

• Menus

– Used to specify program options and commands

• Toolbar

– Allows direct access to certain popular functions

– Can be moved

– Can be hidden or revealed using the Toolbars dialog box fromthe View menu

• Data Browser

– Can be moved, resized, minimized, maximized or closed

– Used to navigate the folders, forms, and sheets



The User Interface (Continued)

• Folders

– Refers to the root items in the Data Browser

– Contain forms

• Forms – Used to enter data and view results for the simulation

– Can be comprised of a number of sheets

– Are located in folders

• Sheets

– Make up forms

– Are selected using tabs at the top of each sheet




• Object Manager

– Allows manipulation of discrete objects of information

– Can be created, edited, renamed, deleted, hidden, andrevealed

• Next Button

– Checks if the current form is complete and skips to the next

form which requires input

The User Interface (Continued)




The Data Browser

Menu tree

Previous sheet

Next sheet

Status area

Parent button Units

Go back Go forward

Comments

Next

Description area

Status




Help

• Help Topics

– Contents - Used to browse through the documentation. TheUser Guides and Reference Manuals are all included in thehelp.

• All of the information in the User Guides is found under the “Using Aspen Plus” book.

– Index - Used to search for help on a topic using the indexentries

– Find - Used to search for a help on a topic that includes any

word or words

• “What’s This?” Help

– Select “What’s This?” from the Help menu and then click onany area to get help for that item.




Functionality of Forms

• When you select a field on a form (click left mousebutton in the field), the prompt area at the bottom of thewindow gives you information about that field.

• Click the drop-down arrow in a field to bring up a list of possible input values for that field.

– Typing a letter will bring up the next selection on the list thatbegins with that letter.

• The Tab key will take you to the next field on a form.




Basic Input

• The minimum required inputs (in addition to the graphical flowsheet)to run a simulation are:

– Setup

– Components

– Properties – Streams

– Blocks

• Data can be entered on input forms in the above order by clickingthe Next button.

• These inputs are all found in folders within the Data Browser.

• These input folders can be located quickly using the Data menu or the Data Browser buttons on the toolbar.




Status Indicators

Input for the form is incomplete

Input for the form is complete

No input for the form has been entered. It is optional.

Results for the form exist.

Results for the form exist, but there were calculation

errors.

Results for the form exist, but there were calculation

warnings.

Results for the form exist, but input has changed since

the results were generated.

Symbol Status




Cumene Production Conditions

Q = 0 Btu/hr

Pdrop = 0 psi

C6H6 + C3H6 = C9H12

Benzene Propylene Cumene (Isopropylbenzene)90% Conversion of Propylene

T = 130 F

Pdrop = 0.1 psi

P = 1 atmQ = 0 Btu/hr

Benzene: 40 lbmol/hr

Propylene: 40 lbmol/hr

T = 220 FP = 36 psia

Use the RK-SOAVE Property MethodFilename: CUMENE.BKP

REACTOR

FEED

RECYCLE

REAC-OUT

COOL

COOL-OUT SEP

PRODUCT




Setup

• Most of the commonly used Setup information is enteredon the Setup Specifications Global sheet:

– Flowsheet title to be used on reports

– Run type

– Input and output units

– Valid phases (e.g. vapor-liquid or vapor-liquid-liquid)

– Ambient pressure

• Stream report options are located on the Setup Report Options Stream sheet.




Setup Specifications Form




Stream Report Options

• Stream report options are located on the Setup Report Options Stream sheet.




Setup Run Types

Run Type

Flowsheet Standard Aspen Plus flowsheet run including sensitivity studies and optimization.

Flowsheet runs can contain property estimation, assay data analysis, and/or property analysiscalculations.

Assay Data Analysis

A standalone Assay Data Analysis and pseudocomponent generation run

Use Assay Data Analysis to analyze assay data when you do not want to perform a flowsheetsimulation in the same run.

Data

Regression

A standalone Data Regression run

Use Data Regression to fit physical property model parameters required by ASPEN PLUS tomeasured pure component, VLE, LLE, and other mixture data. Data Regression can containproperty estimation and property analysis calculations. ASPEN PLUS cannot perform dataregression in a Flowsheet run.

PROPERTIESPLUS

PROPERTIES PLUS setup run

Use PROPERTIES PLUS to prepare a property package for use with Aspen Custom Modeler (formerly SPEEDUP) or Aspen Pinch (formerly ADVENT), with third-party commercialengineering programs, or with your company's in-house programs. You must be licensed to usePROPERTIES PLUS.

Property Analysis

A standalone Property Analysis runUse Property Analysis to generate property tables, PT-envelopes, residue curve maps, and other property reports when you do not want to perform a flowsheet simulation in the same run.Property Analysis can contain property estimation and assay data analysis calculations.

PropertyEstimation

Standalone Property Constant Estimation run

Use Property Estimation to estimate property parameters when you do not want to perform aflowsheet simulation in the same run.




Setup Units

• Units in Aspen Plus can be defined at 3 different levels:

1. Global Level (“Input Data” & “Output Results” fields on theSetup Specifications Global sheet)

2. Object level (“Units” field in the top of any input form of an

object such as a block or stream3. Field Level

• Users can create their own units sets using the SetupUnits Sets Object Manager. Units can be copied from an

existing set and then modified.




Components

• Use the Components Specifications form to specify allthe components required for the simulation.

• If available, physical property parameters for each

component are retrieved from databanks.• Pure component databanks contain parameters such as

molecular weight, critical properties, etc. The databanksearch order is specified on the Databanks sheet.

• The Find button can be used to search for components.

• The Electrolyte Wizard can be used to set up anelectrolyte simulation.




Components Specifications Form




Entering Components

• The Component ID is used to identify the component in simulationinputs and results.

• Each Component ID can be associated with a databank componentas either:

– Formula: Chemical formula of component (e.g., C6H6)(Note that a suffix is added to formulas when there are isomers, e.g.C2H6O-2)

– Component Name: Full name of component (e.g., BENZENE)

• Databank components can be searched for using the Find button.

– Search using component name, formula, component class, molecular weight, boiling point, or CAS number.

– All components containing specified items will be listed.




Find

• Find performs an AND search when more than onecriterion is specified.




• Parameters missing from the first selected databank will besearched for in subsequent selected databanks.

Databank Contents Use

PURE10 Data from the Design Institute for Physical Property Data (DIPPR) and AspenTech

Primary component databank in

Aspen Plus

AQUEOUS Pure component parameters for ionic and molecular species in aqueous solution Simulations containing electrolytes

SOLIDS Pure component parameters for strong

electrolytes, salts, and other solids

Simulations containing

electrolytes and solids

INORGANIC Thermochemical properties for inorganic

components in vapor, liquid and solid states

Solids, electrolytes, and

metallurgy applications


delivered with Aspen Plus 9.3

For upward compatibility


delivered with Aspen Plus 8.5-6

For upward compatibility

ASPENPCD Databank delivered with Aspen Plus 8.5-6 For upward compatibility

Pure Component Databanks




Properties

• Use the Properties Specifications form to specify thephysical property methods to be used in the simulation.

• Property methods are a collection of models and

methods used to describe pure component and mixturebehavior.

• Choosing the right physical properties is critical for obtaining reliable simulation results.

• Selecting a Process Type will narrow the number of methods available.




Properties Specifications Form




Streams

• Use Stream Input forms to specify the feed streamconditions and composition.

• To specify stream conditions enter two of the following:

– Temperature – Pressure

– Vapor Fraction

• To specify stream composition enter either:

– Total stream flow and component fractions

– Individual component flows

• Specifications for streams that are not feeds to theflowsheet are used as estimates.




Blocks

• Each Block Input or Block Setup form specifies operatingconditions and equipment specifications for the unitoperation model.

• Some unit operation models require additionalspecification forms

• All unit operation models have optional information forms(e.g. BlockOptions form).




Block Form




Starting the Run

• Select Control Panel from the View menu or press theNext button to be prompted.

– The simulation can be executed when all required forms arecomplete.

– The Next button will take you to any incomplete forms.




Run Start or continue calculations

Step Step through the flowsheet oneblock at a time

Stop Pause simulation calculations

Reinitialize Purge simulation results

Results Check simulation results

Control Panel

• The Control Panel consists of:

– A message window showing the progress of the simulation bydisplaying the most recent messages from the calculations

– A status area showing the hierarchy and order of simulation

blocks and convergence loops executed – A toolbar which you can use to control the simulation




Reviewing Results

• History file or Control Panel Messages

– Contains any generated errors or warnings

– Select History or Control Panel on the View menu to displaythe History file or the Control Panel

• Stream Results

– Contains stream conditions and compositions

• For all streams ( /Data/Results Summary/Streams)

• For individual streams (bring up the stream folder in the Data Browser

and select the Results form)

• Block Results

– Contains calculated block operating conditions (bring up theblock folder in the Data Browser and select the Results form)




Benzene Flowsheet Conditions Workshop

• Objective: Add the process and feed stream conditions to aflowsheet.

– Starting with the flowsheet created in the Benzene FlowsheetDefinition Workshop (saved as BENZENE.BKP), add the process andfeed stream conditions as shown on the next page.

• Questions:

1. What is the heat duty of the block “COOL”? _________

2. What is the temperature in the second flash block “FL2”? _________

Note: Answers for all of the workshops are located in the very back of the course notes in Appendix C.




Feed

T = 1000 F

P = 550 psia

Hydrogen: 405 lbmol/hr

Methane: 95 lbmol/hr

Benzene: 95 lbmol/hr

Toluene: 5 lbmol/hr

T = 200 F

Pdrop = 0

T = 100 F

P = 500 psia

P = 1 atm

Q = 0

Use the PENG-ROB Property Method When finished, save asfilename: BENZENE.BKP

FL1

COOL

FEED COOL

VAP1

LIQ1FL2

VAP2

LIQ2

Benzene Flowsheet Conditions Workshop




Unit Operation Models

Objective:

Review major types of unit operation models


User Guide, Chapter 10, Unit Operation Models

Unit Operation Models Reference Manual




Unit Operation Model Types

• Mixers/Splitters

• Separators

• Heat Exchangers

• Columns

• Reactors

• Pressure Changers

• Manipulators

• Solids

• User Models

Reference: The use of specific models is best described by on-line help and thedocumentation. Aspen Plus Unit Operation Models Reference Manual




Model Description Purpose Use

Mixer Stream mixer Combine multiplestreams into onestream

Mixing tees, stream mixingoperations, adding heatstreams, adding work streams

FSplit Stream splitter Split stream flows Stream splitters, bleed valves

SSplit Substream splitter Split substream flows Solid stream splitters, bleedvalves

Mixers/Splitters




Model Description Purpose UseFlash2 Two-outlet flash Determine thermal

and phase conditions

Flashes, evaporators, knockout

drums, single stage separators,

free water separations

Flash3 Three-outlet

flash

Determine thermal


Decanters, single stage separators

with two liquid phases

Decanter Liquid-liquid

decanter

Determine thermal


Decanters, single stage separators

with two liquid phases and no vapor

phase

Sep Multi-outlet

component

separator

Separate inlet stream

components into any

number of outletstreams

Component separation operations

such as distillation and absorption,

when the details of the separation areunknown or unimportant

Sep2 Two-outlet

component

separator

Separate inlet stream

components into two

outlet streams

Component separation operations

such as distillation and absorption,

when the details of the separation are

unknown or unimportant

Separators




Heat Exchangers

* Requires separate license


Heater Heater or cooler Determines thermal and

phase conditions

Heaters, coolers, valves. Pumps and

compressors when work-related results are not

needed.

HeatX Two-stream heat

exchanger

Exchange heat between two

streams

Two-stream heat exchangers. Rating shell and

tube heat exchangers when geometry is known.

MHeatX Multistream heat

exchanger

Exchange heat between any

number of streams

Multiple hot and cold stream heat exchangers.

Two-stream heat exchangers. LNGexchangers.

Hetran* Interface to B-JAC

Hetran program

Design and simulate shell and

tube heat exchangers

Shell and tube heat exchangers with a wide

variety of configurations.

Aerotran* Interface to B-JAC

Aerotran program

Design and simulate air-

cooled heat exchangers

Air-cooled heat exchangers with a wide variety

of configurations. Model economizers and the

convection section of fired heaters.

HXFlux Heat transfercalculation model

Models convective heattransfer between a heat sink

and a heat source.

Determines the log-mean temperaturedifference, using either the rigorous or the

approximate method.

HTRIIST* Interface to the IST

heat exchanger

program from HTRI.

Design and simulate shell and

tube heat exchangers

Shell and tube heat exchangers with a wide

variety of configurations, including kettle

boilers.




Columns - Shortcut


DSTWU Shortcut distillationdesign

Determine minimum RR,minimum stages, and either actual RR or actual stagesby Winn-Underwood-Gilliland method.

Columns with one feed andtwo product streams

Distl Shortcut distillationrating

Determine separationbased on RR, stages, andD:F ratio using Edmister method.

Columns with one feed andtwo product streams

SCFrac Shortcut distillationfor petroleum

fractionation

Determine productcomposition and flow,

stages per section, dutyusing fractionation indices.

Complex columns, such ascrude units and vacuum

towers




Columns - Rigorous

Model Description Purpose UseRadFrac Rigorous

fractionationRigorous rating and design for singlecolumns

Distillation, absorbers, strippers,extractive and azeotropic distillation,

reactive distillation

MultiFrac Rigorous

fractionation for complex columns

Rigorous rating and design for

multiple columns of any complexity

Heat integrated columns, air separators,

absorber/stripper combinations, ethyleneprimary fractionator/quench tower

combinations, petroleum refiningPetroFrac Petroleum refining

fractionation

Rigorous rating and design for

petroleum refining applications

Preflash tower, atmospheric crude unit,

vacuum unit, catalytic cracker or coker fractionator, vacuum lube fractionator,

ethylene fractionator and quench towers

BatchFrac*+ Rigorous batch

distillation

Rigorous rating calculations for

single batch columns

Ordinary azeotropic batch distillation,

3-phase, and reactive batch distillation

RateFrac* Rate-based

distillation

Rigorous rating and design for single

and multiple columns. Based onnonequilibrium calculations

Distillation columns, absorbers, strippers,

reactive systems, heat integrated units,petroleum applications

Extract Liquid-liquid

extraction

Rigorous rating for liquid-liquid

extraction columns

Liquid-liquid extraction

* Requires separate license

+ Input language only in Version 10.0




Model Description Purpose UseRStoic Stoichiometric

reactor

Stoichiometric reactor with

specified reaction extent or conversion

Reactors where the kinetics are unknown or

unimportant but stoichiometry and extent areknown

RYield Yield reactor Reactor with specified yield Reactors where the stoichiometry and kineticsare unknown or unimportant but yield

distribution is known

REquil Equilibrium reactor Chemical and phaseequilibrium by

stoichiometric calculations

Single- and two-phase chemical equilibriumand simultaneous phase equilibrium

RGibbs Equilibrium reactor Chemical and phaseequilibrium by Gibbs

energy minimization

Chemical and/or simultaneous phase andchemical equilibrium. Includes solid phase

equilibrium.

RCSTR Continuous stirred

tank reactor

Continuous stirred tank

reactor

One, two, or three-phase stirred tank reactors

with kinetics reactions in the vapor or liquid

RPlug Plug flow reactor Plug flow reactor One, two, or three-phase plug flow reactors withkinetic reactions in any phase. Plug flowreactions with external coolant.

RBatch Batch reactor Batch or semi-batchreactor

Batch and semi-batch reactors where thereaction kinetics are known

Reactors




Pressure Changers

Model Description Purpose UsePump Pump or

hydraulicturbine

Change stream pressure whenthe pressure, power requirementor performance curve is known

Pumps and hydraulic turbines

Compr Compressor or turbine

Change stream pressure whenthe pressure, power requirementor performance curve is known

Polytropic compressors, polytropicpositive displacementcompressors, isentropiccompressors, isentropic turbines.

MCompr Multi-stagecompressor or turbine

Change stream pressure acrossmultiple stages with intercoolers.

Allows for liquid knockoutstreams from intercoolers

Multistage polytropic compressors,polytropic positive compressors,isentropic compressors, isentropicturbines.

Valve Control valve Determine pressure drop or

valve coefficient (CV)

Multi-phase, adiabatic flow in ball,

globe and butterfly valves

Pipe Single-segmentpipe

Determine pressure drop andheat transfer in single-segmentpipe or annular space

Multi-phase, one dimensional,steady-state and fully developedpipeline flow with fittings

Pipeline Multi-segmentpipe

Determine pressure drop andheat transfer in multi-segmentpipe or annular space

Multi-phase, one dimensional,steady-state and fully developedpipeline flow




Manipulators


Mult Stream multiplier Multiply stream flows bya user supplied factor

Multiply streams for scale-up orscale-down

Dupl Streamduplicator

Copy a stream to anynumber of outlets

Duplicate streams to look atdifferent scenarios in the same

flowsheet

ClChng Stream classchanger

Change stream class Link sections or blocks that usedifferent stream classes

Selector Stream selector Switch between differentinlet streams.

Test different flowsheet senarios




Model Description UsesCrystallizer Continuous Crystallizer Mixed suspension, mixed product removal (MSMPR)

crystallizeer used for the production of a single solid product

Crusher Crushers Gyratory/jaw crusher, cage mill breaker, and single or multiple roll crushers

Screen Screens Solids-solids separation using screens

FabFl Fabric filters Gas-solids separation using fabric filters

Cyclone Cyclones Gas-solids separation using cyclones

VScrub Venturi scrubbers Gas-solids separation using venturi scrubbers

ESP Dry electrostatic precipitators Gas-solids separation using dry electrostatic precipitators

HyCyc Hydrocyclones Liquid-solids separation using hydrocyclones

CFuge Centrifuge filters Liquid-solids separation using centrifuge filters

Filter Rotary vacuum filters Liquid-solids separation using continuous rotary vacuumfilters

SWash Single-stage solids washer Single-stage solids washer

CCD Counter-current decanter Multistage washer or a counter-current decanter

Solids




User Models

• Proprietary models or 3-rd party software can beincluded in an Aspen Plus flowsheet using a User2 unitoperation block.

• Excel Workbooks or Fortran code can be used to definethe User2 unit operation model.

• User-defined names can be associated with variables.

• Variables can be dimensioned based on other input

specifications (for example, number of components).

• Aspen Plus helper functions eliminate the need to knowthe internal data structure to retrieve variables.





Unit Operation Models Reference Manual , Chapter 4, Columns

RadFrac

Objective:Discuss the minimum input required for theRadFrac fractionation model, and the use of design specifications and stage efficiencies




RadFrac: Rigorous Multistage Separation

• Vapor-Liquid or Vapor-Liquid-Liquid phase simulation of:

– Ordinary distillation

– Absorption, reboiled absorption

– Stripping, reboiled stripping

– Azeotropic distillation – Reactive distillation

• Configuration options:

– Any number of feeds

– Any number of side draws – Total liquid draw off and pumparounds

– Any number of heaters

– Any number of decanters




RadFrac Flowsheet Connectivity

Vapor Distillate

Top-Stage or 1Condenser Heat Duty Heat (optional)

Liquid Distillate

Water Distillate (optional)Feeds

Reflux

Products (optional)Heat (optional)

Pumparound

DecantersHeat (optional)

ProductHeat (optional)

Return

Boil-up

Bottom Stage or NstageReboiler Heat Duty Heat (optional)

Bottoms




RadFrac Setup Configuration Sheet

• Specify:

– Number of stages

– Condenser and reboiler configuration

– Two column operatingspecifications

– Valid phases

– Convergence




RadFrac Setup Streams Sheet

• Specify:

– Feed stage location

– Feed stream convention(see Help)

ABOVE-STAGE:Vapor from feed goes tostage above feed stage

– Liquid goes to feed stage

ON-STAGE:

Vapor & Liquid from feedgo to specified feed stage




Feed Convention

On-stage

n

Above-stage(default)

n-1

n

Vapor

Feed

n-1

Liquid

Feed




RadFrac Setup Pressure Sheet

• Specify one of:

– Column pressure profile

– Top/Bottom pressure

– Section pressure drop




Kettle Reboiler

T = 65 C

P = 1 bar

Water: 100 kmol/hr

Methanol: 100 kmol/hr

9 StagesReflux Ratio = 1

Distillate to feed ratio = 0.5

Column pressure = 1 bar

Feed stage = 6

RadFrac specifications

Filename: RAD-EX.BKP

Methanol-Water RadFrac Column

Use the NRTL-RK Property Method

COLUMNFEED

OVHD

BTMS

Total Condenser




RadFrac Options

• To set up an absorber with no condenser or reboiler, setcondenser and reboiler to none on the RadFrac SetupConfiguration sheet.

• Either Vaporization or Murphree efficiencies on either astage or component basis can be specified on theRadFrac Efficiencies form.

• Tray and packed column design and rating is possible.

• A Second liquid phase may be modeled if the user selects Vapor-liquid-liquid as Valid phases.

• Reboiler and condenser heat curves can be generated.




Plot Wizard

• Use Plot Wizard (on the Plot menu) to quickly generate plots of results of a simulation. You can use Plot Wizard for displayingresults for the following operations:

– Physical property analysis

– Data regression analysis

– Profiles for all separation models RadFrac, MultiFrac, PetroFrac andRateFrac

• Click the object of interest in the Data Browser to generate plots for that particular object.

• The wizard guides you in the basic operations for generating a plot.

• Click on the Next button to continue. Click on the Finish button togenerate a plot with default settings.




Block COLUMN: Vapor Composition Prof iles

Stage

1 2 3 4 5 6 7 8 9

Y

( m o l e f r a c )

0 . 2

5

0 . 5

0 . 7

5

1WATER

METHANOL

Plot Wizard Demonstration

• Use the plot wizard on the column to create a plot of thevapor phase compositions throughout the column.




RadFrac DesignSpecs and Vary

• Design specifications can be specified and executed inside theRadFrac block using the DesignSpecs and Vary forms.

• One or more RadFrac inputs can be manipulated to achievespecifications on one or more RadFrac performance parameters.

• The number of specs should, in general, be equal to the number of varies.

• The DesignSpecs and Varys in a RadFrac are solved in a “Middleloop.” If you get an error message saying that the middle loop wasnot converged, check the DesignSpecs and Varys you have

entered.




RadFrac Convergence Problems

• If a RadFrac column fails to converge, doing one or moreof the following could help:

1. Check that physical property issues (choice of Property

Method, parameter availability, etc.) are properly addressed.

2. Ensure that column operating conditions are feasible.

3. If the column err/tol is decreasing fairly consistently, increasethe maximum iterations on the RadFrac Convergence Basic sheet.




RadFrac Convergence Problems (Continued)

4. Provide temperature estimates for some stages in thecolumn using the RadFrac Estimates Temperature sheet (useful for absorbers).

5. Provide composition estimates for some stages in thecolumn using the RadFrac Estimates Liquid Composition and Vapor Composition sheet (useful for highly non-ideal systems).

6. Experiment with different convergence methods on the

RadFrac Setup Configuration sheet.

Note: When a column does not converge, it is usuallybeneficial to Reinitialize after making changes.




Filename: RADFRAC.BKPUse the NRTL-RK Property Method

COLUMNFEED

DIST

BTMS

Feed:63.2 wt% Water 36.8 wt% MethanolTotal flow = 120,000 lb/hr Pressure 18 psiaSaturated liquid

Column specification:38 trays (40 stages)Feed tray = 23 (stage 24)Total condenser Top stage pressure = 16.1 psiaPressure drop per stage = 0.1 psiDistillate flowrate = 1245 lbmol/hr

Molar reflux ratio = 1.3

RadFrac Workshop

Part A

• Perform a rating calculation of a Methanol tower usingthe following data:

•




RadFrac Workshop (Continued)

Part B

• Set up design specifications within the column so the following twoobjectives are met:

– 99.95 wt% methanol in the distillate

– 99.90 wt% water in the bottoms

• To achieve these specifications, you can vary the distillate rate (800-1700 lbmol/hr) and the reflux ratio (0.8-2). Make sure streamcompositions are reported as mass fractions before running theproblem. Note the condenser and reboiler duties:

Condenser Duty :_________

Reboiler Duty :_________




Reactor Models

Objective:Introduce the various classes of reactor models

available, and examine in some detail at least onereactor from each class

Aspen Plus References

Unit Operation Models Reference Manual , Chapter 5, Reactors




Reactor Overview

Reactors

Balance BasedRYieldRStoic

Equilibrium BasedREquilRGibbs

Kinetics BasedRCSTRRPlug

RBatch




70 lb/hr H2O20 lb/hr CO2 60 lb/hr CO250 lb/hr tar

600 lb/hr char

1000 lb/hr Coal

IN

OUT

RYield

Balanced Based Reactors

• RYield

– Requires a mass balance only, not an atom balance

– Is used to simulate reactors in which inlets to the reactor arenot completely known but outlets are known (e.g. to simulate a

furnace)




2 CO + O2 --> 2 CO2C + O2 --> CO2

2 C + O2--

> 2 CO

C, O2

IN

OUT

RStoic

C, O2, CO, CO2

Balanced Based Reactors (Continued)

• RStoic

– Requires both an atom and a mass balance

– Used in situations where both the equilibrium data and thekinetics are either unknown or unimportant

– Can specify or calculate heat of reaction at a referencetemperature and pressure




Equilibrium Based Reactors

• GENERAL

– Do not take reaction kinetics into account

– Solve similar problems, but problem specifications are different

– Individual reactions can be at a restricted equilibrium

• REquil

– Computes combined chemical and phase equilibrium bysolving reaction equilibrium equations

– Cannot do a 3-phase flash

– Useful when there are many components, a few knownreactions, and when relatively few components take part in thereactions




Equilibrium Based Reactors (Continued)

• RGibbs

– Unknown Reactions - This feature is quite useful whenreactions occurring are not known or are high in number due tomany components participating in the reactions.

– Gibbs Energy Minimization - A Gibbs free energyminimization is done to determine the product composition atwhich the Gibbs free energy of the products is at a minimum.

– Solid Equilibrium - RGibbs is the only Aspen Plus block thatwill deal with solid-liquid-gas phase equilibrium.




Kinetic Reactors

• Kinetic reactors are RCSTR, RPlug and RBatch.

• Reaction kinetics are taken into account, and hence must bespecified.

• Kinetics can be specified using one of the built-in models, or with a

user subroutine. The current built-in models are – Power Law

– Langmuir-Hinshelwood-Hougen-Watson (LHHW)

• A catalyst for a reaction can have a reaction coefficient of zero.

• Reactions are specified using a Reaction ID.




Using a Reaction ID

• Reaction IDs are setup as objects, separate from thereactor, and then referenced within the reactor(s).

• A single Reaction ID can be referenced in any number of kinetic reactors (RCSTR, RPlug and RBatch.)

• To set up a Reaction ID, go to the Reactions Reactions Object Manager




Power-law Rate Expression

0

n

0

11EnergyActivationexp Factor)lexponentiaPre(

T T RT

T k

rate k concentrationi

i * [ ]

exponenti

Example: 2 3 21

2

A B C Dk

k

Forward reaction: (Assuming the reaction is 2nd order in A)

coefficients: A: B: C: D:

exponents: A: B: C: D:

-2 -3 1 2

2 0 0 0

Reverse reaction: (Assuming the reaction is 1st order in C and D)

coefficients: C: D: A: B:

exponents: C: D: A: B:-1 -2 2 3

1 1 0 0




Heats of Reaction

• Heats of reaction need not be provided for reactions.

• Heats of reaction are typically calculated as thedifference between inlet and outlet enthalpies for thereactor (see Appendix A).

• If you have a heat of reaction value that does not matchthe value calculated by Aspen Plus, you can adjust theheats of formation (DHFORM) of one or morecomponents to make the heats of reaction match.

• Heats of reaction can also be calculated or specified at areference temperature and pressure in an RStoicreactor.




Reactor Workshop

• Objective - Compare the use of different reactor types to modelone reaction.

• Reactor Conditions:Temperature = 70 C

Pressure = 1 atm

• Stoichiometry:Ethanol + Acetic Acid <--> Ethyl Acetate + Water

• Kinetic Parameters: – Forward Reaction: Pre-exp. Factor = 1.9 x 108, Act. Energy = 5.95 x 107 J/kmol – Reverse Reaction: Pre-exp. Factor = 5.0 x 107, Act. Energy = 5.95 x 107 J/kmol – Reactions are first order with respect to each of the reactants in the reaction (second

order overall). – Reactions occur in the liquid phase. – Composition basis is Molarity.

Hint: Check that each reactor is considering both Vapor and Liquid as Validphases.




Temp = 70 CPres = 1 atm

Feed:

Water: 8.892 kmol/hr Ethanol: 186.59 kmol/hr Acetic Acid: 192.6 kmol/hr

Length = 2 meters

Diameter = 0.3 meters

Volume = 0.14 Cu. M.

70 % conversion of ethanol

When finished, save asfilename: REACTORS.BKP

Use the NRTL-RKproperty method

RSTOICF-STOIC

P-STOIC

RGIBBS

F-GIBBS P-GIBBS

RPLUG

F-PLUG P-PLUG

DUPL

FEED

F-CSTR

RCSTR

P-CSTR

Reactor Workshop (Continued)




Cyclohexane Production Workshop

• Objective - Create a flowsheet to model a cyclohexane productionprocess

• Cyclohexane can be produced by the hydrogenation of benzene in thefollowing reaction:

C6H6 + 3 H2 = C6H12Benzene Hydrogen Cyclohexane

• The benzene and hydrogen feeds are combined with recycle hydrogen andcyclohexane before entering a fixed bed catalytic reactor. Assume abenzene conversion of 99.8%.

• The reactor effluent is cooled and the light gases separated from the

product stream. Part of the light gas stream is fed back to the reactor asrecycle hydrogen.

• The liquid product stream from the separator is fed to a distillation column tofurther remove any dissolved light gases and to stabilize the end product. Aportion of the cyclohexane product is recycled to the reactor to aid intemperature control.




C6H6 + 3 H2 = C6H12

Benzene Hydrogen Cyclohexane

Use the RK-SOAVE property method

When finished, save asfilename: CYCLOHEX.BKP

Bottoms rate = 99 kmol/hr

P = 25 bar T = 50 C

Molefrac H2 = 0.975N2 = 0.005CH4 = 0.02

Total flow = 330 kmol/hr

T = 40 C

P = 1 bar

Benzene flow = 100 kmol/hr

T = 150C

P = 23 bar T = 200 CPdrop = 1 bar

Benzene conv =0.998

T = 50 C

Pdrop = 0.5 bar

92% flow to stream H2RCY

30% flow to stream CHRCY

Specify cyclohexane molerecovery in PRODUCT streamequal to 0.9999 by varyingBottoms rate from 97 to 101 kmol/hr

Theoretical Stages = 12Reflux ratio = 1.2

Partial Condenser with

vapor distillate onlyColumn Pressure = 15 bar Feed stage = 8

REACTFEED-MIX

H2IN

BZIN

H2RCY

CHRCY

RXIN

RXOUT

HP-SEP

VAP

COLUMN

COLFD

LTENDS

PRODUCT

VFLOW

PURGE

LFLOW

LIQ





Physical Properties

Objectives:

Introduce the ideas of property methods and physical property parameters

Identify issues involved in the choice of a property method

Cover the use of Property Analysis for reporting physical properties


User Guide, Chapter 7, Physical Property Methods

User Guide, Chapter 8, Physical Property Parameters and Data

User Guide, Chapter 29, Analyzing Properties




• Correct choice of physical property models and accurate physicalproperty parameters are essential for obtaining accurate simulationresults.

FEED

OVHD

BTMS

COLUMN

5000 lbmol/hr

10 mole % acetone

90 mole % water

Specification: 99.5 mole % acetone recovery

Case Study - Acetone Recovery

Ideal

Approach

Equation of

State Approach

Activity Coefficient

Model Approach

Predicted number of

stages required

Approximate cost in dollars

11

520, 000

7

390, 000

42

880, 000




How to Establish Physical Properties

Choose a Property Method

Check Parameters/ObtainAdditional Parameters

Confirm Results

Create the Flowsheet




Property Methods

• A Property Method is a collection of models and methodsused to calculate physical properties.

• Property Methods containing commonly usedthermodynamic models are provided in Aspen Plus.

• Users can modify existing Property Methods or createnew ones.




x

y

x

y

x

y

Ideal vs. Non-Ideal Behavior

• What do we mean by ideal behavior? – Ideal Gas law and Raoult’s law

• Which systems behave as ideal?

– Non-polar components of similar size and shape

• What controls degree of non-ideality?

– Molecular interactionse.g. Polarity, size and shape of the molecules

• How can we study the degree of non-ideality of asystem?

– Property plots (e.g. TXY & XY)




EOS Models Activity Coefficient Models

Limited in ability to representnon-ideal liquids

Can represent highly non-ideal liquids

Fewer binary parametersrequired

Many binary parameters required

Parameters extrapolatereasonably with temperature

Binary parameters are highlytemperature dependent

Consistent in critical region Inconsistent in critical region

Comparison of EOS and Activity Models




Common Property Methods

• Equation of State Property Methods – PENG-ROB

– RK-SOAVE

• Activity Coefficient Property Methods

– NRTL

– UNIFAC

– UNIQUAC

– WILSON




Henry's Law

• Henry's Law is only used with ideal and activitycoefficient models.

• It is used to determine the amount of a supercriticalcomponent or light gas in the liquid phase.

• Any supercritical components or light gases (CO2, N2,etc.) should be declared as Henry's components(Components Henry Comps Selection sheet).

• The Henry's components list ID should be entered onProperties Specifications Global sheet in the Henry Components field.




Do you have any polar components in your system?

Are the operating conditions

near the critical region of the

mixture?

Use activity

coefficient model

with Henry’s Law

Use activity

coefficient

model

Use EOS Model

N

N

NY

Y

Y

References:

Aspen Plus User Guide, Chapter 7, Physical Property Methods,

gives similar, more detailed guidelines for choosing a

property Method.

Choosing a Property Method - Review

Do you have light gases or

supercritical components

in your system?




System Model Type Property Method

Propane, Ethane, Butane EOS RK-SOAVE, PENG-ROB

Benzene, Water Activity Coefficient NRTL-RK, UNIQUAC

Acetone, Water Activity Coefficient NRTL-RK, WILSON

System Property Method

Ethanol, Water

Benzene, Toluene

Acetone, Water, Carbon Dioxide

Water, Cyclohexane

Ethane and Propanol

Choosing a Property Method - Example

• Choose an appropriate Property Method for the followingsystems of components at ambient conditions.






Check Parameters/Obtain

Additional Parameters

Confirm Results





Pure Component Parameters

• Represent attributes of a single component

• Input in the Properties Parameters Pure Component folder.

• Stored in databanks such as PURE10, ASPENPCD, SOLIDS, etc.(The selected databanks are listed on the Components

Specifications Databanks sheet.)

• Parameters retrieved into the Graphical User Interface by selectingRetrieve Parameter Results from the tools menu.

• Examples

– Scalar: MW for molecular weight

– Temperature-Dependent: PLXANT for parameters in the extended Antoine vapor pressure model




Binary Parameters

• Used to describe interactions between two components

• Input in the Properties Parameters Binary Interaction folder

• Stored in binary databanks such as VLE-IG, LLE-ASPEN

• Parameter values from the databanks can be viewed on the inputforms in the Graphical User Interface.

• Parameter forms that include data from the databanks must beviewed before the flowsheet is complete.

• Examples

– Scalar: RKTKIJ for the Rackett model

– Temperature-Dependent: NRTL for parameters in the NRTL model




Displaying Property Parameters

• Aspen Plus does not display all databank parameters onthe parameter input forms.

• Select Retrieve Parameter Results from the Tools menuto retrieve all parameters for the components and

property methods defined in the simulation.

• All results that are currently loaded will be lost. They canbe regenerated by running the simulation again.

• The parameters are viewed on the PropertiesParameters Results forms.




PHYSICAL PROPERTIES SECTION

PROPERTY PARAMETERS-------------------

PARAMETERS ACTUALLY USED IN THE SIMULATION

PURE COMPONENT PARAMETERS-------------------------

COMPONENT ID: BENZENEFORMULA: C6H6 NAME: C6H6

SCALAR PARAMETERS-----------------

PARAM SET DESCRIPTIONS VALUE UNITS SOURCE

NAME NO.

API 1 STANDARD API GRAVITY 28.500 PURE10

CHARGE 1 IONIC CHARGE 0.00000E+00 AQUEOUS

CHI 1 STIEL POLAR FACTOR 0.00000E+00 DEFAULT

DCPLS 1 DIFFERENCE BETWEEN LIQUID AND 0.31942 CAL/MOL-K PURE10SOLID CP AT TRIPLE POINT

DGFORM 1 IDEAL GAS GIBBS ENERGY 30.954 KCAL/MOL PURE10OF FORMATION

Reporting Parameters

• To get a Report of the retrieved parameters in a text file. – Select Retrieve Parameter Results from the Tools menu,

– Select Report from the View menu.

– Select display report for Simulation and click Ok.




Reporting Physical Property Parameters

• Follow this procedure to obtain a report file containingvalues of ALL pure component and binary parametersfor ALL components used in a simulation:

1. On the Setup Report Options Property sheet,select All physical property parameters used (in SI units) or select Property parameters’ descriptions, equations, andsources of data.

2. After running the simulation, export a report (*.rep) file (SelectExport from the File menu).

3. Edit the .rep file using any text editor. (From the GraphicalUser Interface, you can choose Report from the View menu.)The parameters are listed under the heading PARAMETERVALUES in the physical properties section of the report file.






Check Parameters/Obtain

Additional Parameters

Confirm Results





Property Analysis

• Used to generate simple property diagrams to validate physical propertymodels and data

• Diagram Types:

– Pure component, e.g. Vapor pressure vs. temperature

– Binary, e.g. TXY, PXY

– Ternary residue maps

• Select Analysis from the Tools menu to start Analysis.

• Additional binary plots are available under the Plot Wizard button on resultform containing raw data.

• When using a binary analysis to check for liquid-liquid phase separation,remember to choose Vapor-Liquid-Liquid as Valid phases.

• Property analysis input and results can be saved as a form for later reference and use.




Property Analysis - Common Plots

y-x diagram for METHANOL / PROPANOL

LIQUID MOLEFRAC METHANOL

0 0.2 0.4 0.6 0.8 1

(PRES = 14.7 PSI)

y-x diagram for ETHANOL / TOLUENE

LIQUID MOLEFRAC ETHANOL

0 0.2 0.4 0.6 0.8 1

(PRES = 14.7 PSI)

y-x diagram for TOLUENE / WATER

LIQUID MOLEFRAC TOLUENE0 0.2 0.4 0.6 0.8 1

(PRES = 14.7 PSI)

XY Plot Showing 2 liquid phases:

Ideal XY Plot: XY Plot Showing Azeotrope:




Establishing Physical Properties - Review

1. Choose Property Method - Select a Property Method based on – Components present in simulation

– Operating conditions in simulation

– Available data or parameters for the components

2. Check Parameters - Determine parameters available in Aspen Plus

databanks

3. Obtain Additional Parameters (if necessary) - Parameters that are neededcan be obtained from

– Literature searches (DETHERM, etc.)

– Regression of experimental data (Data Regression)

– Property Constant Estimation (Property Estimation)

4. Confirm Results - Verify choice of Property Method and physical propertydata using

– Physical Property Analysis

S




Property Sets

• A property set (Prop-Set) is a way of accessing a collection, or set,of properties as an object with a user-given name. Only the name of the property set is referenced when using the properties in anapplication.

• Use property sets to report thermodynamic, transport, and other

property values.

• Current property set applications include:

– Design specifications, Fortran blocks, sensitivity

– Stream reports

– Physical property tables (Property Analysis)

– Tray properties (RadFrac, MultiFrac, etc.)

– Heating/cooling curves (Flash2, MHeatX, etc.)

P ti i l d d i P S t




Properties included in Prop-Sets

• Properties commonly included in property sets include: – VFRAC - Molar vapor fraction of a stream – BETA - Fraction of liquid in a second liquid phase – CPMX - Constant pressure heat capacity for a mixture – MUMX - Viscosity for a mixture

• Available properties include: – Thermodynamic properties of components in a mixture

– Pure component thermodynamic properties

– Transport properties

– Electrolyte properties

– Petroleum-related properties

Reference: Aspen Plus Physical Property Data Reference Manual , Chapter 4, Property Sets, has acomplete list of properties that can be included in a property set.

S if i P t S t




• Use the Properties Prop-Sets form to specify properties in a property set.

• The Search button can be used to search for a property.

• All specified qualifiers apply to each property specified, whereapplicable.

• Users can define new properties on the Properties Advanced User-Properties form by providing a Fortran subroutine.

Specifying Property Sets

P d fi d P t S t




Predefined Property Set Types of Properties

HXDESIGN Heat exchanger design

THERMAL Mixture thermal (HMX, CPMX,KMX)

TXPORT Transport

VLE Vapor-liquid equilibrium(PHIMX, GAMMA, PL)

VLLE Vapor-liquid-liquid equilibrium

Predefined Property Sets

• Some simulation Templates contain predefined propertysets.

• The following table lists predefined property sets and thetypes of properties they contain for the General

Template:

St R lt O ti




Stream Results Options

• On the Setup Report Options Stream sheet, use:

– Flow Basis and Fraction Basis check-boxes to specify howstream composition is reported

– Property Sets button to specify names of property setscontaining additional properties to be reported for each stream

D fi iti f T




Definition of Terms

• Property Method - Set of property models and methodsused to calculate the properties required for a simulation

• Property - Calculated physical property value such asmixture enthalpy

• Property Model - Equation or equations used tocalculate a physical property

• Property Parameter - Constant used in a property

model

• Property Set (Prop-Set) - A method of accessingproperties so that they can be used or tabulatedelsewhere

A P ti




Aspen Properties

• Aspen Properties is now a stand-alone product.

• In addition to the standard property features available in Aspen Plus, Aspen Properties includes:

– Excel Interface

– Web Interface

• Excel Interface is an Excel Add-In that has Excelfunctions to do property calculations such as:

– Flash at a given set of conditions – Calculate a property such as density or viscosity

• Web Interface is currently only available for purecomponents.

Ph i l P ti W k h




Physical Properties Workshop

• Objective: Simulate a two-liquid phase settling tank andinvestigate the physical properties of the system.

• A refinery has a settling tank that they use to decant off the water from a mixture of water and a heavy oil. The inlet stream to the tankalso contains some carbon-dioxide and nitrogen. The tank and feed

are at ambient temperature and pressure (70o F, 1atm), and havethe following flow rates of the various components:

Water 515 lb/hr

Oil 4322 lb/hr

CO2 751 lb/hr

N2 43 lb/hr

• Use the compound n-decane to represent the oil. It is known thatwater and oil form two liquid phases under the conditions in the tank.

Ph sical Properties Workshop (Contin ed)




Physical Properties Workshop (Continued)

1. Choose an appropriate Property Method to represent this system.Check to see that the required binary physical property parametersare available.

2. Retrieve the physical property parameters used in the simulation anddetermine the critical temperature for carbon dioxide and water.TC(carbon dioxide) = _______; TC(water) = _______

3. Using the property analysis feature, verify that the chosen physicalproperty model and the available parameters predict the formation of 2 liquid phases.

4. Set up a simulation to model the settling tank. Use a Flash3 block torepresent the tank.

5. Modify the stream report to include the constant pressure heatcapacity (CPMX) for each phase (Vapor, 1st Liquid and 2nd Liquid),and the fraction of liquid in a second liquid phase (BETA), for allstreams.






This Portion is Optional

• Objective: Generate a table of compositions for each liquidphase (1st Liquid and 2nd Liquid) at different temperatures for a mixture of water and oil. Tabulate the vapor pressure of thecomponents in the same table.

• In addition to the interactive Analysis commands under the Toolsmenu, you also can create a Property Analysis manually, usingforms.

• Manually generated Generic Property Analysis is similar to the

interactive Analysis commands, however it is more flexible regardinginput and reporting.

Detailed instructions are on the following slide.






• Problem Specifications:1. Create a Generic type property analysis from the Properties/Analysis

Object manager.

2. Generate points along a flash curve.

3. Define component flows of 50 mole water and 50 mole oil.

4. Set Valid phases to Vapor-liquid-liquid.

5. Click on the Range/List button, and vary temperature from 50 to 400 F.

6. Use a vapor fraction of zero.

7. Tabulate a new property set that includes:

a. Mole fraction of water and oil in the 1st and 2nd liquid phases (MOLEFRAC)b. Mole flow of water and oil in the 1st and 2nd liquid phases (MOLEFLOW)

c. Beta - the fraction of the 1st liquid to the total liquid (BETA)

d. Pure component vapor pressures of water and oil (PL)




Accessing Variables

Objective:Become familiar with referencing flowsheet

variables


User Guide, Chapter 18, Accessing Flowsheet Variables

Related Topics:

User Guide, Chapter 20, Sensitivity

User Guide, Chapter 21, Design Specifications

User Guide, Chapter 19, Calculator Blocks and In-Line Fortran

User Guide, Chapter 22, Optimization

User Guide, Chapter 23, Fitting a Simulation Model to Data

Why Access Variables?




COLUMNFEED

OVHD

BTMS

Why Access Variables?

• What is the effect of the reflux ratio of the column on the purity (molefraction of component B) of the distillate?

• To perform this analysis, references must be made to 2 flowsheetquantities, i.e. 2 flowsheet variables must be accessed:

1. The reflux ratio of the column

2. The mole fraction of component B in the stream OVHD

Accessing Variables




Accessing Variables

• An accessed variable is a reference to a particular flowsheet quantity, e.g. temperature of a stream or dutyof a block.

• Accessed variables can be input, results, or both.

• Flowsheet result variables (calculated quantities) shouldnot be overwritten or varied.

• The concept of accessing variables is used in sensitivity

analyses, design specifications, calculator blocks,optimization, etc.

Variable Categories




Variable Categories

Variable Category Type of VariableBlocks Block variables and vectors

Streams Stream variables and vectors.

Both non-component variables andcomponent dependent flow and compositionvariables can be accessed.

Model Utility Parameters, balance block and pressurerelief variables

Property Property parameters

Reactions Reactions and chemistry variables

Costing Costing variables

Variable Definition Dialog Box




Variable Definition Dialog Box

• When completing a Define sheet, such as on a Calculator, Designspecification or Sensitivity form, specify the variables on the VariableDefinition dialog box.

• You cannot modify the variables on the Define sheet itself.

• On the Variable Definition dialog box, select the variable categoryand Aspen Plus will display the other fields necessary to completethe variable definition.

• If you are editing an existing variable and want to change thevariable name, click the right mouse button on the Variable Name

field. On the popup menu, click Rename.

Notes




Notes

1. If the Mass-Frac, Mole-Frac or StdVol-Frac of a component in astream is accessed, it should not be modified. To modify thecomposition of a stream, access and modify the Mass-Flow, Mole-Flow or StdVol-Flow of the desired component.

2. If duty is specified for a block, that duty can be read and written

using the variable DUTY for that block. If the duty for a block iscalculated during simulation, it should be read using the variableQCALC.

3. PRES is the specified pressure or pressure drop, and PDROP ispressure drop used in calculating pressure profile in heating or

cooling curves.

4. Only streams that are feeds to the flowsheet should be varied or modified directly.




Sensitivity Analysis

Objective:Introduce the use of sensitivity analysis to study

relationships between process variables


User Guide, Chapter 20, Sensitivity

Related Topics:


User Guide, Chapter 19, Calculator Blocks and In-Line Fortran



Sensitivity Analysis Example




• What is the effect of cooler outlet temperature on the purity of theproduct stream?

• What is the manipulated (varied) variable?

• What is the measured (sampled) variable?

Filename: CUMENE-S.BKP

» Cooler outlet temperature

» Purity (mole fraction) of cumene in product stream

REACTOR

FEED

RECYCLE

REAC-OUT

COOL

COOL-OUT SEP

PRODUCT

Sensitivity Analysis Example

Sensitivity Analysis Results




Sensitivity S-1 Results Summary

VARY 1 COOL PARAM TEMP F

50 75 100 125 150 175 200 225 250 275 300 325 350

C

U M E N E P R O D U C T P U R I T Y

0 . 8 5

0 . 9

0 . 9 5

1

Sensitivity Analysis Results

• What is happening below 75 F and above 300 F?



Steps for Using Sensitivity Analysis




Steps for Using Sensitivity Analysis

1. Specify measured (sampled) variable(s) – These are quantities calculated during the simulation to be used in

step 4 (Sensitivity Input Define sheet).

2. Specify manipulated (varied) variable(s)

– These are the flowsheet variables to be varied (Sensitivity Input Vary sheet).

3. Specify range(s) for manipulated (varied) variable(s)

– Variation for manipulated variable can be specified either asequidistant points within an interval or as a list of values for the

variable (Sensitivity Input Vary sheet).

4. Specify quantities to calculate and tabulate

– Tabulated quantities can be any valid Fortran expression containingvariables defined in step 1 (Sensitivity Input Tabulate sheet).

Plotting




Plotting

1. Select the column containing the X-axis variable andthen select X-Axis Variable from the Plot menu.

2. Select the column containing the Y-axis variable andthen select Y-Axis Variable from the Plot menu.

3. (Optional) Select the column containing the parametricvariable and then select Parametric Variable from thePlot menu.

4. Select Display Plot from the Plot menu.

Note: To select a column, click on the heading of thecolumn with the left mouse button.

Notes




Notes

1. Only quantities that have been input to the flowsheetshould be varied or manipulated.

2. Multiple inputs can be varied.

3. The simulation is run for every combination of manipulated (varied) variables.

Sensitivity Analysis Workshop




Sensitivity Analysis Workshop

• Objective: Use a sensitivity analysis to study the effect of the recycleflowrate on the reactor duty in the cyclohexane flowsheet

• Part A

– Using the cyclohexane production flowsheet Workshop (saved asCYCLOHEX.BKP), plot the variation of reactor duty (block REACT) as therecycle split fraction in LFLOW is varied from 0.1 to 0.4.

• Optional Part B

– In addition to the fraction split off as recycle (Part A), vary the conversion of benzene in the reactor from 0.9 to 1.0. Tabulate the reactor duty andconstruct a parametric plot showing the dependence of reactor duty on thefraction split off as recycle and conversion of benzene.

Note: Both of these studies (parts A and B) should be set up within the samesensitivity analysis block.

• When finished, save as filename: SENS.BKP.





Cyclohexane Production Workshop C6H6 + 3 H2 = C6H12




P = 25 bar T = 50 C

Molefrac H2 = 0.975N2 = 0.005CH4 = 0.02


T = 40 C

P = 1 bar

Benzene flow = 100 kmol/hr

T = 150C


Benzene conv =0.998

T = 50 C

Pdrop = 0.5 bar



Specify cyclohexane molerecovery of 0.9999 by varyingBottoms rate from 97 to 101 kmol/hr


Partial Condenser with

vapor distillate onlyColumn Pressure = 15 bar Feed stage = 8

REACTFEED-MIX

H2IN

BZIN

H2RCY

CHRCY

RXIN

RXOUT

HP-SEP

VAP

COLUMN

COLFD

LTENDS

PRODUCT

VFLOW

PURGE

LFLOW

LIQ



Design Specifications




Design Specifications

• Similar to a feedback controller

• Allows user to set the value of a calculated flowsheetquantity to a particular value

• Objective is achieved by manipulating a specified inputvariable

• No results associated directly with a design specification

• Located under /Data/Flowsheeting Options/DesignSpecs

Design Specification Example




• What should the cooler outlet temperature be to achieve a cumeneproduct purity of 98 mole percent?

• What is the manipulated (varied) variable?

• What is the measured (sampled) variable?

• What is the specification (target) to be achieved?

Filename: CUMENE-D.BKP

» Cooler outlet temperature

» Mole fraction of cumene in stream PRODUCT

» Mole fraction of cumene in stream PRODUCT = 0.98

REACTOR

FEED

RECYCLE

REAC-OUT

COOL

COOL-OUT SEP

PRODUCT

Design Specification Example



Steps for Using Design Specifications (Continued)




p g g p ( )

4. Specify manipulated (varied) variable – This is the variable whose value the specification changes in

order to satisfy the objective function equation (Design Spec Vary sheet).

5. Specify range of manipulated (varied) variable – These are the lower and upper bounds of the interval within

which Aspen Plus will vary the manipulated variable (DesignSpec Vary sheet). The units of the limits for the variedvariable are the units for that type of variable as specified by

the Units Set declared for the design specification.



Notes (Continued)




( )

4. If a design-spec does not converge:a. Check to see that the manipulated variable is not at its lower

or upper bound.

b. Verify that a solution exists within the bounds specified for the manipulated variable, perhaps by performing a

sensitivity analysis.

c. Check to ensure that the manipulated variable does indeedaffect the value of the sampled variables.

d. Try providing a better starting estimate for the value of the

manipulated variable.



Design Specification Workshop




g p p

• Objective: Use a design specification in the cyclohexaneflowsheet to fix the heat load on the reactor by varying therecycle flowrate.

• The cyclohexane production flowsheet workshop (saved asCYCLOHEX.BKP) is a model of an existing plant. The cooling

system around the reactor can handle a maximum operating load of 4.7 MMkcal/hr. Determine the amount of cyclohexane recyclenecessary to keep the cooling load on the reactor to this amount.

Note: The heat convention used in Aspen Plus is that heat input to ablock is positive, and heat removed from a block is negative.

• When finished, save as filename: DES-SPEC.BKP





y pC6H6 + 3 H2 = C6H12




P = 25 bar T = 50 C

Molefrac H2 = 0.975N2 = 0.005CH4 = 0.02


T = 40 C

P = 1 bar Benzene flow = 100 kmol/hr

T = 150C


Benzene conv =0.998

T = 50 C

Pdrop = 0.5 bar



Specify cyclohexane molerecovery of 0.9999 by varyingBottoms rate from 97 to 101 kmol/hr


Partial Condenser withvapor distillate onlyColumn Pressure = 15 bar Feed stage = 8

REACTFEED-MIXH2IN

BZIN

H2RCY

CHRCY

RXIN

RXOUT

HP-SEP

VAP

COLUMN

COLFD

LTENDS

PRODUCT

VFLOW

PURGE

LFLOW

LIQ



Calculator Blocks




• Allows user to write equations in an Excel spreadsheetor in Fortran to be executed by Aspen Plus

• Results of the execution of a Calculator block must beviewed by directly examining the values of the variables

modified by the Calculator block.

• Increasing the diagnostics for the Calculator block willprint the value of all input and result variables in theControl Panel.

• Located under /Data/Flowsheeting Options/Calculator

Calculator Block Example




• Use of a Calculator block to set the pressure drop acrossa Heater block.

• Pressure drop across heater is proportional to square of volumetric flow into heater.

Calculator BlockDELTA-P = -10-9 * V2

V

Filename: CUMENE-F.BKPor CUMENE-EXCEL.BKP

DELTA-P

REACTOR

FEED

RECYCLE

REAC-OUT

COOL

COOL-OUTSEP

PRODUCT

Calculator Block Example (Continued)




• Which flowsheet variables must be accessed?

• When should the Calculator block be executed?

• Which variables are imported and which are exported?

» Volumetric flow of stream REAC-OUT

This can be accessed in two different ways: 1. Mass flow and mass density of stream REAC-OUT2. A prop-set containing volumetric flow of a mixture

» Pressure drop across block COOL

» Before block COOL

» Volumetric flow is imported

» Pressure drop is exported

Excel




Import Variables

Export Variable

=(-10^-9)*B6^2

=FLOW/DENS

Connect Current Cell

to a Defined Variable

Aspen Plus toolbar in Excel

Steps for Using Calculator Blocks




1. Access flowsheet variables to be used within Calculator – All flowsheet quantities that must be either read from or written

to, must be identified (Calculator Input Define sheet).

2. Write Fortran or Excel

– Fortran includes both non-executable (COMMON,EQUIVALENCE, etc) Fortran (click on the Fortran Declarations button) and executable Fortran (Calculator Input Calculate sheet) to achieve desired result.

3. Specify location of Calculator block in executionsequence (Calculator Input Sequence sheet)

– Specify directly, or

– Specify with import and export variables



Excel




• Excel workbook is embedded into simulation for eachCalculator block.

• When saving as a backup (.bkp file), a .apmbd file iscreated. This file needs to be in the working directory.

• Full functionality of Excel is available including VBA andMacros.

• Cells that contain Import variables have a green border.

Cells that contain Export variables have a blue border.Cells that contain Tear variables have an orange border.



Excel Aspen Plus Toolbar




• Connect Cell Combo Box

– Use this Combo Box to attach the current cell on the Excel spreadsheet toa Defined Variable. If the Defined Variable chosen is already connectedto another cell, the link between that cell and the Defined Variable is

broken.• Define Button

– Click the Define Button to create a new Defined Variable or to edit anexisting one. If this cell is already connected to a Defined Variable,clicking on this button will allow you to edit it. If this cell is not connected

to a Defined Variable, clicking on this button will create a new DefinedVariable.

• Unlink Button

– Click the Unlink Button to remove the link between a cell and a DefinedVariable. Clicking on this button does not delete the Defined Variable.

Excel Aspen Plus Toolbar (Continued)




• Delete Button – Click the Delete Button to remove the link between a cell and a

Defined variable and delete the Defined Variable.

• Refresh Button

– Click the Refresh Button to refresh the list of Defined Variables in the

Connect Cell Combo Box. You should click this button if you havechanged the list of Defined Variables by making changes on theCalculator Define sheet.

• Changed Button

–Click the Changed Button to set the "Input Changed" flag of thisCalculator block. This will cause the Calculator to be re-executed thenext time you run the simulation. You should click this button if, after the calculator block is executed, you make changes to the Excelspreadsheet without making any changes on the Calculator blockforms.



Benefits of Windows Interoperability




• Benefits of Copy/Paste/Paste Link – Live data links can be established that update these

applications as the process model is changed to automaticallypropagate results of engineering changes.

– The benefits to the engineer are quick and error-free data

transfer and consistent engineering results throughout theengineering work process.



Embedding Objects in the Flowsheet




• You can embed other applications as objects into theProcess Flowsheet window.

• You can do this in two ways:

– Using Copy and Paste

– Using the Insert dialog box

• You can edit the object embedded in the flowsheet bydouble clicking on the object to edit it inside Aspen Plus.

• You can also move, resize or attach the object to a blockor stream in the flowsheet.



Copy and Paste Workshop 2




• Objective: Use copy and paste to copy the streamresults to a stream input form.

• Use the Cyclohexane flowsheet workshop (saved asCYCLOHEX.BKP)

• Copy the stream results from stream RXIN into the inputform.

– Copy the compositions, the temperature and the pressureseparately.

Note: Reinitialize before running the simulation in order tosee how many iterations are needed before andafter the estimate is added.



Paste Link Demonstration




• Objective: Create an active link from Aspen Plus Results into aspreadsheet.

• Start with the cumene flowsheet demonstration.

• Open a spreadsheet and create a cell with the temperature for thecooler in it.

• Copy and paste the link into the Aspen Plus flowsheet.

• Copy and paste a link with the flow and composition of cumene inthe product stream into the spreadsheet.

• Change the temperature in the spreadsheet and then rerun theflowsheet. Notice the changes.



Running Files with Active Links




Introduction to Aspen Plus

• When you open the link source file, there is nothingspecial that you need to do.

• When you open the link container file, you will usuallysee a dialog box asking you if you want to re-establish

the links. You can select Yes or No.

• To make a link source application visible:

– Select Links, from the Edit menu in Aspen Plus.

– In the Links dialog box, select the source file and click Open

Source.

Note: The Process Flowsheet must be the active window.Links is not an option on the Edit menu if the DataBrowser is active.




Heat Exchangers

Objective:Introduce the unit operation models used for heat

exchangers and heaters.


Unit Operation Models Reference Manual , Chapter 3, Heat Exchangers



Working with the Heater Model




• The Heater block mixes multiple inlet streams to producea single outlet stream at a specified thermodynamicstate.

• Heater can be used to represent:

– Heaters – Coolers

– Valves

– Pumps (when work-related results are not needed)

– Compressors (when work-related results are not needed)

• Heater can also be used to set the thermodynamicconditions of a stream.

Heater Input Specifications




• Allowed combinations: – Pressure (or Pressure drop) and one of:

• Outlet temperature

• Heat duty or inlet heat stream

• Vapor fraction

• Temperature change• Degrees of subcooling or superheating

– Outlet Temperature or Temperature change and one of:

• Pressure

• Heat Duty

• Vapor fraction

Heater Input Specifications (Continued)




• For single phase use Pressure (drop) and one of: – Outlet temperature

– Heat duty or inlet heat stream

– Temperature change

• Vapor fraction of 1 means dew point condition,0 means bubble point

Heat Streams




• Any number of inlet heat streams can be specified for aHeater.

• One outlet heat stream can be specified for the net heatload from a Heater.

• The net heat load is the sum of the inlet heat streamsminus the actual (calculated) heat duty.

• If you give only one specification (temperature or

pressure), Heater uses the sum of the inlet heat streamsas a duty specification.

• If you give two specifications, Heater uses the heatstreams only to calculate the net heat duty.



HeatX Input Specifications




• Select one of the following specifications: – Heat transfer area or Geometry

– Exchanger duty

– For hot or cold outlet stream:

• Temperature

• Temperature change

• Temperature approach

• Degrees of superheating / subcooling

• Vapor fraction



HeatX versus Heater




• Consider the following: – Use HeatX when both sides are important.

– Use Heater when one side (e.g. the utility) is not important.

– Use two Heaters (coupled by heat stream, Calculator block or design spec) or an MHeatX to avoid flowsheet complexity

created by HeatX.

Two Heaters versus One HeatX




Working with Hetran and Aerotran




• The Hetran block is the interface to the B-JAC Hetranprogram for designing and simulating shell and tube heatexchangers.

• The Aerotran block is the interface to the B-JAC Aerotran

program for designing and simulating air-cooled heatexchangers.

• Information related to the heat exchanger configurationand geometry is entered through the Hetran or Aerotran

standalone program interface.



Heat Curves




• All of the heat exchanger models are able to calculateHeat Curves (Hcurves).

• Tables can be generated for various independentvariables (typically duty or temperature) for any property

that Aspen Plus can generate.• These tables can be printed, plotted, or exported for use

with other heat exchanger design software.

Heat Curves Tabular Results



When finished, save as filename: HEATX.BKP

HeatX Workshop (Continued)




RHEATX

RHOT-IN

RCLD-IN RCLD-OUT

RHOT-OUT

SHEATX

SHOT-IN

SCLD-IN SCLD-OUT

SHOT-OUT

HEATER-1

HCLD-IN

Q-TRANS

HCLD-OUT

HEATER-2

HHOT-IN HHOT-OUT

Start with the General with Metric Units Template.

Use the NRTL-RK Property Method for the hydrocarbon streams.

Specify that the valid phases for the hydrocarbon stream is Vapor-Liquid-Liquid.

Specify that the Steam Tables are used to calculate the properties for the cooling water streams on the Block BlockOptions Properties sheet.

When finished, save as filename: HEATX.BKP



Working with the Compr Model

Th C bl k b d t i l t




• The Compr block can be used to simulate:

– Polytropic centrifugal compressor

– Polytropic positive displacement compressor

– Isentropic compressor

– Isentropic turbine

• MCompr is used for multi-stage compressors.

• Power requirement is calculated or input.

• A Heater model can be used for pressure change calculations only.

• Compr is designed to handle both single and multiple phasecalculations.



Work Streams

Any number of inlet work streams can be specified for




• Any number of inlet work streams can be specified for pumps and compressors.

• One outlet work stream can be specified for the net workload from pumps or compressors.

• The net work load is the sum of the inlet work streamsminus the actual (calculated) work.



Working with the Pipe Model

• The Pipe block calculates the pressure drop and heat transfer in a




• The Pipe block calculates the pressure drop and heat transfer in a

single pipe segment.

• The Pipeline block can be used for a multiple-segment pipe.

• Pipe can perform single or multiple phase calculations.

• If the inlet pressure is known, Pipe calculates the outlet pressure.

• If the outlet pressure is known, Pipe calculates the inlet pressureand updates the state variables of the inlet stream.

• Entrance effects are not modeled.



Pressure Changers Workshop

• Objective: Add pressure changer unit operations to




• Objective: Add pressure changer unit operations tothe Cyclohexane flowsheet.

• Start with the Cyclohexane Workshop flowsheet(CYCLOHEX.BKP)

VALVE Isentropic4 bar pressure change

Pressure Changers Workshop (Continued)




FEED-MIX

H2IN

CHRCY3

H2RCY2

BZIN2

RXIN

REACT

RXOUT

HP-SEP

LIQ

VAP

COLUMN

COLFD

LTENDS

PRODUCT

VFLOW H2RCY

PURGE

LFLOW

CHRCY

PUMP

CHRCY2

PIPE

COMP

FEEDPUMP

BZIN

PURGE2

When finished, save asfilename: PRESCHNG.BKP

Pump efficiency = 0.6Driver efficiency = 0.9

Performance Curve

Head Flow[m] [cum/hr]40 20250 10300 5400 3

Carbon SteelSchedule 401-in diameter 25-m length

26 bar outlet pressure

20 bar outlet pressureGlobe valveV810 equal percent flow1.5-in size

4 bar pressure change



• Objective

Convergence Workshop




– Converge this flowsheet.

– Start with the file CONVERGE.BKP.

LIQ

VAPOR

FEED-HT

FEED

BOT

DIST

BOT-COOL

GLYCOL

COLUMN

PREHEATR

PREFLASH

T=165 FP=15 psia

100 lbmol/hr

XH20 = 0.4XMethanol = 0.3XEthanol = 0.3

Area = 65 sqft

DP=0Q=0

Theoretical Stages = 10Reflux Ratio = 5Distillate to Feed Ratio = 0.2

Feed Stage = 5Column Pressure = 1 atm

Total Condenser

Use NRTL-RK Property Method

T=70 FP=35 psia50 lbmol/hr Ethylene Glycol

When finished, save asfilename: CONV-R.BKP



Full-Scale Plant Modeling Workshop

• Objective: Practice and apply many of the




Objective: Practice and apply many of thetechniques used in this course and learn how to bestapproach modeling projects

Full-Scale Plant Modeling Workshop

• Objective: Model a methanol plant.




Objective: Model a methanol plant.

• The process being modeled is a methanol plant. Thebasic feed streams to the plant are Natural Gas, CarbonDioxide (assumed to be taken from a nearby AmmoniaPlant) and Water. The aim is to achieve the methanolproduction rate of approximately 62,000 kg/hr, at a purityof at least 99.95 % wt.

• This is a large flowsheet that would take an experienced

engineer more than an afternoon to complete. Startbuilding the flowsheet and think about how you wouldwork to complete the project.



Part 1: Front-End Section (Continued)

• Carbon Dioxide Stream – CO2 • Circulation Water - H2OCIRC




– Temperature = 43 C – Pressure = 1.4 bar

– Flow = 24823 kg/hr

– Mole Fraction

• CO2 - 0.9253

• H2 - 0.0094

• H2O - 0.0606• CH4 - 0.0019

• N2 - 0.0028

• Natural Gas Stream - NATGAS

– Temperature = 26 C

– Pressure = 21.7 bar

– Flow = 29952 kg/hr – Mole Fraction

• CO2 - 0.0059

• CH4 - 0.9539

• N2 - 0.0008

• C2H6 - 0.0391

• C3H8 - 0.0003

– Pure water stream – Flow = 410000 kg/hr


– Pressure = 26 bar

• Makeup Steam - MKUPST

– Stream of pure steam


– Pressure = 26 bar

– Vapor Fraction = 1

– Adjust the makeup steam flow toachieve a desired steam to methanemolar ratio of 2.8 in the Reformer feedREFFEED.



Part 1: Front-End Section Check

Reformer Product

Temperature C 860




Pressure bar 18Vapor Frac 1

Mole Flow kmol/hr 10266.6541

Mass Flow kg/hr 139696.964

Volume Flow cum/hr 53937.9538

Enthalpy MMkcal/hr -213.933793

Mole Flow kmol/hr

CO 1381.68394

CO2 751.335833H2 4882.77068

WATER 2989.25863

METHANOL 0.000686384

METHANE 258.513276

NITROGEN 3.08402321

BUTANOL 0

DME (DIMETHYLETHER) 2.06E-10

ACETONE 2.18E-08

OXYGEN 1.80E-15

ETHANE 0.007007476

PROPANE 6.74097E-07

SYNCOMP

To Methanol Loop

Part 2: Heat Recovery Section




COOL4

FL3

FL1

FL2

COOL1

COOL3COOL2

BOILER

To TOPPINGTo REFINING

From Reformer

Part 2: Heat Recovery Section (Continued)

• This section consists of a series of heat exchangers and flash vessels used to recover theavailable energy and water in the Reformed Gas stream.




FL1

Pressure Drop = 0 bar

Heat Duty = 0 MMkcal/hr

FL2

Exit Pressure = 17.7 bar


FL3



SYNCOM

Two Stage Polytropic compressor

Discharge Pressure = 82.5 bar

Intercooler Exit Temperature = 40 C

available energy and water in the Reformed Gas stream.

BOILER

Exit temperature = 166 C

Exit Pressure = 18 bar

COOL1


Exit Pressure = 18 bar

COOL2



COOL3


Pressure Drop = 0.1 bar

COOL4





MEOHRXR

To Furnace

Part 3: Methanol Synthesis Section




SPLIT1

MIX2

E121

From SYNCOMP

E122

CIRC

E124E223

FL4

SPLIT2

To FL5



To Furnace

From FL4

Part 4: Distillation Section




FL5

M4

MKWATER

TOPPING

REFINING

From COOL2From COOL1



Part 4: Distillation Section (Continued)

• Refining Column - REFINING

– Number of Stages = 95 (including condenser and reboiler)




– Condenser Type = Total

– Distillate Rate = 1 kg/hr

– Feed stage = 60

– Liquid Product sidedraw from Stage 4 @ 62000 kg/hr (Stream name – PRODUCT)

– Liquid Product sidedraw from Stage 83 @ 550 kg/hr (Stream name – FUSELOIL)

– Reflux rate = 188765 kg/hr

– Pressure profile: stage 1= 1.5bar and stage 95=2bar – Reboiler heat duty is provided via a conventional reboiler supplemented by a heat stream from a

heater block to stage 95

– Boil-up Ratio is approximately 4.8

– Valve trays

– To meet environmental regulations, the bottoms stream must contain no more than 100ppm by weightof methanol as this stream is to be dumped to a nearby river.

• FL5

– Exit Pressure 5 bar

– Heat Duty 0 MMkcal/hr

• M4

– For water addition to the crude methanol



Part 5: Furnace Section (Continued)

• Air to Furnace - AIR





– Pressure = 1 atm

– Flow = 281946 kg/hr

– Adjust the air flow to achieve 2%(vol.) of oxygen in the

FLUEGAS stream.

• Fuel to Furnace - FUEL


– Conditions and composition are the same as for the natural gasstream




Maintaining Aspen Plus Simulations

Objective:

Introduce how to store simulations and retrievethem from your computer environment


User Guide, Chapter 15, Managing Your Files



How to Create a Personal Template

• Any flowsheet (complete or incomplete) can be saved as

t l t fil




a template file.

• In order to have a personal template appear on thePersonal sheet of the New dialog box, put the templatefile into the Aspen Plus GUI\Templates\Personal folder.

• The text on the Setup Specifications Description sheetwill appear in the Preview window when the template fileis selected in the New dialog box.



Maintaining Your Hard Disk

• Keep plenty of free space on disk used for:




– Your Aspen working directory

– Windows swap files

• Delete unneeded files:

– Old .appdf, .his, etc. – Aspen document files (*.apw) that aren’t active

– Aspen temporary files (_4404ydj.appdf, for example)

• Defragment regularly (once a week), even if Windows

says you don’t need to -- make the free spacecontiguous.

C t i i th L k f Y




Customizing the Look of Your Flowsheet

Objective:

Introduce several ways of annotating your flowsheetto create informative Process Flow Diagrams


User Guide, Chapter 14, Annotating Process Flowsheets

Related Topics:

User Guide, Chapter 37, Working with Other Windows Programs



Viewing

• Use the View menu to select the elements that you wish

t i




to view:

– PFD Mode

– Global Data

– Annotation

– OLE Objects

• All of the elements can be turned on and off independently.



Heat and Material Balance Table

Stream ID COOL-OUT FEED PRODUCT REAC-OUT RECYCLE

Temperature F 130 0 220 0 130 1 854 7 130 1

Example of a Stream Table




Temperature F 130.0 220.0 130.1 854.7 130.1Pressure PSI 14.60 36.00 14.70 14.70 14.70

Vapor Frac 0.054 1.000 0.000 1.000 1.000

Mole Flow LBMOL/HR 44.342 80.000 41.983 44.342 2.359

Mass Flow LB/HR 4914.202 4807.771 4807.772 4914.202 106.431

Volume Flow CUFT/HR 1110.521 15648.095 93.470 42338.408 1003.782

Enthalpy MMBTU/HR -0.490 1.980 -0.513 2.003 0.023

Mole Flow LBMOL/HR

BENZENE 2.033 40.000 1.983 2.033 0.050

PROPYLEN 4.224 40.000 1.983 4.224 2.241

CUMENE 38.085 38.017 38.085 0.069

Mole Frac

BENZENE 0.046 0.500 0.047 0.046 0.021

PROPYLEN 0.095 0.500 0.047 0.095 0.950

CUMENE 0.859 0.906 0 .859 0 .029



Using PFD Mode

• In this mode, you can add or delete unit operation icons

to the flowsheet for graphical purposes only




to the flowsheet for graphical purposes only.

• Using PFD mode means that you can change flowsheetconnectivity to match that of your plant.

• PFD-style drawing is completely separate from thegraphical simulation flowsheet. You must return tosimulation mode if you want to make a change to theactual simulation flowsheet.

• PFD Mode is indicated by the Aqua border around theflowsheet.

Examples of When to Use PFD Mode

• In the simulation flowsheet, it may be necessary to use

more than one unit operation block to model a single




more than one unit operation block to model a singlepiece of equipment in a plant.

– For example, a reactor with a liquid product and a vent mayneed to be modeled using an RStoic reactor and a Flash2block. In the report, only one unit operation icon is needed torepresent the unit in the plant.

• On the other hand, some pieces of equipment may notneed to be explicitly modeled in the simulation flowsheet.

– For example, pumps are frequently not modeled in thesimulation flowsheet; the pressure change can be neglected or included in another unit operation block.

Annotation Workshop

• Objective: Use annotation to create a process flow diagram for

the cyclohexane flowsheet




the cyclohexane flowsheet

• Part A

– Using the cyclohexane production Workshop (saved asCYCLOHEX.BKP), display all stream and block global data.

• Part B – Add a title to the flowsheet diagram.

• Part C

– Add a stream table to the flowsheet diagram.

• Part D

– Using PFD Mode, add a pump for the BZIN stream for graphicalpurposes only.




Estimation of Physical Properties

Objective:

Provide an overview of estimating physicalproperty parameters in Aspen Plus


User Guide, Chapter 30, Estimating Property Parameters

Physical Property Methods and Models Reference Manual ,

Chapter 8, Property Parameter Estimation

What is Property Estimation?

• Property Estimation is a system to estimate parameters

required by physical property models It can be used to




required by physical property models. It can be used toestimate:

– Pure component physical property constants

– Parameters for temperature-dependent models

– Binary interaction parameters for Wilson, NRTL and UNIQUAC

– Group parameters for UNIFAC

• Estimations are based on group-contribution methodsand corresponding-states correlations.

• Experimental data can be incorporated into estimation.

Using Property Estimation

• Property Estimation can be used in two ways:

On a stand alone basis: Property Estimation Run Type




– On a stand-alone basis: Property Estimation Run Type

– Within another Run Type: Flowsheet, Property Analysis, DataRegression, PROPERTIES PLUS or Assay Data Analysis

• You can use Property Estimation to estimate propertiesfor both databank and non-databank components.

• Property Estimation information is accessed in theProperties Estimation folder.

Estimation Methods and Requirements

• User Guide, Chapter 30, Estimating Property

Parameters has a complete list of properties that can be




Parameters, has a complete list of properties that can beestimated, as well as the available estimation methodsand their respective requirements.

• This same information is also available under the on-line

help in the estimation forms.



Defining Molecular Structure

• Molecular structure is required for all group-contribution

methods used in Property Estimation You can:




methods used in Property Estimation. You can: – Define molecular structure in the general format and allow

Aspen Plus to determine functional groups,

or

– Define molecular structure in terms of functional groups for particular methods

• Reference: For a list of available group-contribution

method functional groups, see Aspen Plus PhysicalProperty Data Reference Manual, Chapter 3, GroupContribution Method Functional Groups.

Steps For Defining General Structure

1. Sketch the structure of the molecule on paper.

2 Assign a number to each atom omitting hydrogen (The numbers




2. Assign a number to each atom, omitting hydrogen. (The numbersmust be consecutive starting with 1.)

3. Go to the Properties Molecular Structure Object Manager, choosethe component, and select Edit.

4. On the Molecular Structure General sheet, define the molecule byits connectivity. Describe two atoms at a time:

– Specify the types of atoms (C, O, S, …)

– Specify the type of bond that connects the two atoms (single,double, …)

Note: If the molecule is a non-databank component, on theComponents Specifications form, enter a Component ID, butdo not enter a Component name or Formula.

Example of Defining Molecular Structure

• Example of defining molecular structure for isobutyl

alcohol using the general method




C2

C1

C4

C3

O5

alcohol using the general method – Sketch the structure of the molecule, and assign a number to

each atom, omitting hydrogen.

Example of Defining Molecular Structure

• Go to the Properties Molecular Structure Object Manager, choose

the component, and select Edit.




the component, and select Edit.

• On Properties Molecular Structure General sheet, describe moleculeby its connectivity, two atoms at a time.

Atom Types

Current available atom types:

Atom Type Description Atom Type Description




Atom Type Description Atom Type DescriptionC Carbon P Phosphorous

O Oxygen Zn Zinc

N Nitrogen Ga Gallium

S Sulfur Ge GermaniumB Boron As Arsenic

Si Silicon Cd Cadmium

F Fluorine Sn Tin

CL Chlorine Sb AntimonyBr Bromine Hg Mercury

I Iodine Pb Lead

Al Aluminum Bi Bismuth

Bond Types

• Current available bond types:

– Single bond




Single bond

– Double bond

– Triple bond

– Benzene ring

–Saturated 5-membered ring

– Saturated 6-membered ring

– Saturated 7-membered ring

– Saturated hydrocarbon chain

Note: You must assign consecutive atom numbers to Benzene ring,Saturated 5-membered ring, Saturated 6-membered ring,Saturated 7-membered ring, and Saturated hydrocarbon chainbonds.

Steps For Using Property Estimation

1. Define molecular structure on the Properties Molecular

Structure form




Structure form.

2. Enter any experimental data using Parameters or Dataforms.

– Experimental data such as normal boiling point (TB) is veryimportant for many estimation methods. It should beentered whenever possible.

3. Activate Property Estimation and choose propertyestimation options on the Properties Estimation Input

form.

Example of Entering Additional Data

• Enter following data for isobutyl alcohol into the

simulation to improve the estimated values




simulation to improve the estimated values. – Normal boiling point (TB) = 107.6 C

– Critical temperature (TC) = 274.6 C

– Critical pressure (PC) = 43 bar

Example of Entering Additional Data

• Go to the Properties Parameters Pure Component Object Manager

and create a new Scalar parameter form.




p

• Enter the parameters, the components, and the values.

Steps For Using Property Estimation

1. Define molecular structure on the Properties Molecular

Structure form.




Structure form.

2. Enter any experimental data using Parameters or Dataforms.

– Experimental data such as normal boiling point (TB) is veryimportant for many estimation methods. It should beentered whenever possible.

3. Activate Property Estimation and choose propertyestimation options on the Properties Estimation

Input form.

Activating Property Estimation

• To turn on Property Estimation, go to the Properties

Estimation Input Setup sheet, and select one of the




Estimation Input Setup sheet, and select one of thefollowing:

– Estimate all missing parameters

• Estimates all missing required parameters and any parameters youmay request in the optional Pure Component, T-Dependent, Binary,and UNIFAC-Group sheets

– Estimate only the selected parameters

• Estimates on the parameter types you select on this sheet (and thenspecify on the appropriate additional sheets)

Property Estimation Notes

• You can save your property data specifications,

structures, and estimates as backup files, and import




structures, and estimates as backup files, and importthem into other simulations (Flowsheet, DataRegression, Property Analysis, or Assay Data AnalysisRun-Types.)

• You can change the Run type on the SetupSpecifications Global sheet to continue the simulation inthe same file.

• If you want to change the Run type back to Property

Estimation from another Run type, no flowsheetinformation is lost even though it may not be visible inthe Property Estimation mode.

Property Estimation Workshop

• Objective: Estimate the properties of a dimer,

ethycellosolve.




When finished, save asfilename: PCES.BKP

ethycellosolve.

• Ethylcellosolve is not in any of the Aspen Plusdatabanks.

• Use a Run Type of Property Estimation, and estimate theproperties for the new component.

• The formula for the component is shown below, alongwith the normal boiling point obtained from literature.

Formula: CH3 - CH2 - O - CH2 - CH2 - O - CH2 - CH2 - OH TB = 195 C

Property Estimation Workshop (Continued)

1. Use a Run Type of Property Estimation and enter the

structure and data for the Dimer.




s uc u e a d da a o e e

2. Run the estimation, and examine the results.

– Note that the results of the estimation are automaticallywritten to parameters forms, for use in other simulations.

3. Change the Run Type back to Flowsheet.

4. Go to the Properties Estimation Input Setup sheet, andchoose Do not estimate any parameters.

5. Optionally, add a flowsheet and use this component.

Electrolytes




Electrolytes

Objective:

Introduce the electrolyte capabilities in Aspen Plus



Physical Property Methods and Models Reference Manual , Chapter 5, Electrolyte Simulation

Electrolytes Examples

• Solutions with acids, bases or salts

• Sour water solutions




• Sour water solutions

• Aqueous amines or hot carbonate for gas sweetening

Characteristics of an Electrolyte System

• Some molecular species dissociate partially or

completely into ions in a liquid solvent




p y q

• Liquid phase reactions are always at chemicalequilibrium

• Presence of ions in the liquid phase requires non-idealsolution thermodynamics

• Possible salt precipitation

Types of Components

• Solvents - Standard molecular species

– Water




– Methanol

– Acetic Acid

• Soluble Gases - Henry’s Law components – Nitrogen

– Oxygen

– Carbon Dioxide

Types of Components (Continued)

• Ions - Species with a charge

– H3O+




– OH-

– Na+

– Cl-

– Fe(CN)63-

• Salts - Each precipitated salt is a new pure component.

– NaCl(s)

– CaCO3(s) – CaSO4•2H2O (gypsum)

– Na2CO3•NaHCO3 •2H2O (trona)

Apparent and True Components

• True component approach

– Result reported in terms of the ions, salts and molecular




species present after considering solution chemistry

• Apparent component approach

– Results reported in terms of base components present beforeconsidering solution chemistry

– Ions and precipitated salts cannot be apparent components

– Specifications must be made in terms of apparent componentsand not in terms of ions or solid salts

• Results are equivalent.

Apparent and True Components Example

• NaCl in water

– Solution chemistry




• NaCl --> Na+ + Cl-

• Na+ + Cl- <--> NaCl(s)

– Apparent components

• H2O, NaCl

– True components:

• H2O, Na+, Cl-, NaCl(s)

Electrolyte Wizard

• Generates new components (ions and solid salts)

• Revises the Pure component databank search order so that the first




databank searched is now ASPENPCD.

• Generates reactions among components

• Sets the Property method to ELECNRTL

• Creates a Henry’s Component list

• Retrieves parameters for

– Reaction equilibrium constant values

– Salt solubility parameters – ELECNRTL interaction parameters

– Henry’s constant correlation parameters

Electrolyte Wizard (Continued)

• Generated chemistry can be modified. Simplifying the

Chemistry can make the simulation more robust anddecrease execution time




ydecrease execution time.

Note: It is the user’s responsibility to ensure that theChemistry is representative of the actual chemical

system.

Simplifying the Chemistry

• Typical modifications include:

– Adding to the list of Henry’s components




– Eliminating irrelevant salt precipitation reactions

– Eliminating irrelevant species

– Adding species and/or reactions that are not in the electrolytes

expert system database – Eliminating irrelevant equilibrium reactions

Limitations of Electrolytes

• Restrictions using the True component approach:

– Liquid-liquid equilibrium cannot be calculated.




– The following models may not be used:

• Equilibrium reactors: RGibbs and REquil

• Kinetic reactors: RPlug, RCSTR, and RBatch

• Shortcut distillation: Distl, DSTWU and SCFrac

• Rigorous distillation: MultiFrac and PetroFrac

Limitations of Electrolytes (Continued)

• Restrictions using the Apparent component approach:

– Chemistry may not contain any volatile species on the rightid f th ti




side of the reactions.

– Chemistry for liquid-liquid equilibrium may not containdissociation reactions.

– Input specification cannot be in terms of ions or solid salts.

Electrolyte Demonstration

• Objective: Create a flowsheet using electrolytes.

• Create a simple flowsheet to mix and flash two feed streamscontaining aqueous electrolytes Use the Electrolyte Wizard to




FLASH2

FLASH

MIXED

VAPOR

LIQUID

MIXER

MIX

NAOH

HCL

Temp = 25 C

Pres = 1 bar

10 kmol/hr H2O

1 kmol/hr HCl

P-drop = 0

Adiabatic

IsobaricMolar vapor fraction = 0.75

Filename: ELEC1.BKP

Temp = 25 C

Pres = 1 bar

10 kmol/hr H2O

1.1 kmol/hr NaOH

containing aqueous electrolytes. Use the Electrolyte Wizard togenerate the Chemistry.

Steps for Using Electrolytes

1. Specify the possible apparent components on the

Components Specifications Selection sheet.




2. Click on the Elec Wizard button to generatecomponents and reactions for electrolyte systems.There are 4 steps:

Step 1: Define base components and select reactiongeneration options.

Step 2: Remove any undesired species or reactions from thegenerated list.

Step 3: Select simulation approach for electrolytecalculations.

Step 4: Review physical properties specifications and modifythe generated Henry components list and reactions.

Steps for Using Electrolytes (Continued)





Step 1: Define base components and select reaction

generation options.





Step 2: Remove any undesired species or reactions from

the generated list.





Step 3: Select simulation approach for electrolyte

calculations.





Step 4: Review physical properties specifications and modify the

generated Henry components list and reactions.




Electrolyte Workshop

• Objective: Create a flowsheet using electrolytes.

• Create a simple flowsheet to model the treatment of a sulfuric acidwaste water stream using lime (Calcium Hydroxide) Use the




B1

WASTEWAT

LIME LIQUID

Temperature = 25CPressure = 1 bar

Flowrate = 10 kmol/hr 5 mole% lime (calcium hydroxide) solution

Temperature = 25CPressure = 1 bar

Flowrate = 10 kmol/hr 5 mole% sulfuric acid solution

Temperature = 25CP-drop = 0

Note: Remove from the chemistry:CaSO4(s)

CaSO4•1:2W:A(s)

When finished, save asfilename: ELEC.BKP

waste water stream using lime (Calcium Hydroxide). Use theElectrolyte Wizard to generate the Chemistry. Use the truecomponent approach.

Electrolyte Workshop (Continued)

1. Open a new Electrolytes with Metric units flowsheet.

2. Draw the flowsheet.




3. Enter the necessary components and generate theelectrolytes using the Electrolytes Wizard. Select the

true approach and remove the solid salts not neededfrom the generated reactions.

Sour Water Stripper Workshop

• Objective: Model a sour water stripper using electrolytes.

• Create a simple flowsheet to model a sour water stripper. Use theElectrolyte Wizard to generate the Chemistry. Use the apparent component




On stage 10

P = 15 psia

Vapor frac = 1

2,000 lbs/hr

Above stage 3

P = 15 psia

10,000 lbs/hr

Mass fractions:

H2O 0.997

NH3 0.001

H2S 0.001

CO2 0.001

Saturated vapor

Theoretical trays: 9

(does not include condenser)

Partial condenser

Reflux Ratio (Molar): 25

No reboiler

B1

SOURWAT

STEAM

BOTTOMS

VAPOR

y g y pp papproach.

Sour Water Stripper Workshop (Continued)

1. Open a new Electrolytes with English units flowsheet.

2. Draw the flowsheet.




3. Enter the necessary components and generate theelectrolytes using the Electrolytes Wizard. Select the

apparent approach and remove all solid salts used inthe generated reactions.

Questions: Why aren’t the ionic species’ compositionsdisplayed on the results forms? How can they be

added?

Sour Water Stripper Workshop (Continued)

3. Add a sensitivity analysis

a) Vary the steam flow rate from 1000-3000 lb/hr and tabulatethe ammonia concentration in the bottoms stream The




Save as: SOURWAT.BKP

the ammonia concentration in the bottoms stream. Thetarget is 50 ppm.

b) Vary the column reflux ratio from 10-50 and observe thecondenser temperature. The target is 190 F.

4. Create design specifications

a) After hiding the sensitivity blocks, solve the column with twodesign specifications. Use the targets and variables frompart 3.

Solids Handling




g

Objective:

Provide an overview of the solid handlingcapabilities



Physical Property Methods and Models Reference Manual , Chapter 3, Property Model Descriptions

Classes of Components

• Conventional Components

– Vapor and liquid components

S lid lt i l ti h i t




– Solid salts in solution chemistry

• Conventional Inert Solids (CI Solids)

– Solids that are inert to phase equilibrium and saltprecipitation/solubility

• Nonconventional Solids (NC Solids)

– Heterogeneous substances inert to phase, salt, and chemical

equilibrium that cannot be represented with a molecular structure

Specifying Component Type

• When specifying components on the Components

Specifications Selection sheet, choose the appropriatecomponent type in the Type column.




p yp yp

– Conventional - Conventional Components

– Solid - Conventional Inert Solids

– Nonconventional - Nonconventional Solids

Conventional Components

• Components participate in vapor and liquid equilibrium

along with salt and chemical equilibrium.




• Components have a molecular weight.

– e.g. water, nitrogen, oxygen, sodium chloride, sodium ions,chloride ions

– Located in the MIXED substream

Conventional Inert Solids (CI Solids)

• Components are inert to phase equilibrium and salt

precipitation/solubility.




• Chemical equilibrium and reaction with conventionalcomponents is possible.

• Components have a molecular weight. – e.g. carbon, sulfur

– Located in the CISOLID substream

Nonconventional Solids (NC Solids)

• Components are inert to phase, salt or chemical

equilibrium.




• Chemical reaction with conventional and CI Solidcomponents is possible.

• Components are heterogeneous substances and do nothave a molecular weight.

– e.g. coal, char, ash, wood pulp

– Located in the NC Solid substream

Component Attributes

• Component attributes typically represent the composition

of a component in terms of some set of identifiableconstituents




• Component attributes can be

– Assigned by the user

– Initialized in streams

– Modified in unit operation models

• Component attributes are carried in the material stream.

• Properties of nonconventional components arecalculated by the physical property system usingcomponent attributes.

Component Attribute Descriptions

Attribute Type Elements Description

PROXANAL 1. Moisture

2. Fixed Carbon3. Volatile Matter

Proximate analysis, weight %dry

basis




4. Ash

ULTANAL 1. Ash

2. Carbon

3. Hydrogen

4. Nitrogen5. Chlorine

6. Sulfur

7. Oxygen

Ultimate analysis, weight % drybasis

SULFANAL 1. Pyritic

2. Sulfate

3. Organic

Forms of sulfur analysis, weight %of original coal, dry basis

GENANAL 1. Constituent 1

2. Constituent 2

:

20. Constituent 20

General constituent analysis, weightor volume %

Solid Properties

• For conventional components and conventional solids

– Enthalpy, entropy, free energy and molar volume arecomputed.




p

– Property models in the Property Method specified on theProperties Specification Global sheet are used.

• For nonconventional solids – Enthalpy and mass density are computed.

– Property models are specified on the Properties Advanced NC-Props form.

Solids Properties - Conventional Solids

For Enthalpy, Free Energy, Entropy and Heat Capacity

• Barin Equations




– Single parameter set for all properties

– Multiple parameter sets may be available for selectedtemperature ranges

– List INORGANIC databank before SOLIDS

• Conventional Equations

– Combines heat of formation and free energies of formation withheat capacity models

– Aspen Plus and DIPPR model parameters

– List SOLIDS databank before INORGANIC

• Solid Heat Capacity

– Heat capacity polynomial modelC C C T C T

C C C oS 2 4 5 6

Solids Properties - Conventional Solids




– Used to calculate enthalpy, entropy and free energy

– Parameter name: CPSP01

• Solid Molar Volume

– Volume polynomial model

– Used to calculate density

– Parameter name: VSPOLY

C C C T C T T T T p 1 2 3 2 3

V C C T C T C T C T S 1 2 32

43

54

Solids Properties - Nonconventional Solids

• Enthalpy

– General heat capacity polynomial model: ENTHGEN

– Uses a mass fraction weighted average





– Based on the GENANAL attribute

– Parameter name: HCGEN

• Density

– General density polynomial model: DNSTYGEN


– Based on the GENANAL attribute

– Parameter name: DENGEN

Solids Properties - Special Models for Coal

• Enthalpy

– Coal enthalpy model: HCOALGEN

– Based on the ULTANAL PROXANAL and SULFANAL




– Based on the ULTANAL, PROXANAL and SULFANALattributes

• Density

– Coal density model: DCOALIGT

– Based on the ULTANAL and SULFANAL attributes

Built-in Material Stream Classes

Stream Class Description

CONVEN* Conventional components only

MIXNC Conventional and nonconventional solids




C Co e t o a a d o co e t o a so ds

MIXCISLD Conventional components and inert solids

MIXNCPSD Conventional components and nonconventionalsolids with particle size distribution

MIXCIPSD Conventional components and inert solids withparticle size distribution

MIXCINC Conventional components and inert solids andnonconventional solids

MIXCINCPSD Conventional components and nonconventionalsolids with particle size distribution

* system default

Unit Operation Models

• General Principles

– Material streams of any class are accepted.

– The same stream class should be used for inlet and outlet




The same stream class should be used for inlet and outletstreams (exceptions: Mixer and ClChng).

– Attributes (components or substream) not recognized arepassed unaltered through the block.

– Some models allow specifications for each substream present(examples: Sep, RStoic).

– In vapor-liquid separation, solids leave with the liquid.

– Unless otherwise specified, outlet solid substreams are in

thermal equilibrium with the MIXED substream.

Solids Workshop 1

• Objective: Model a conventional solids dryer.

• Dry SiO2 from a water content of 0.5% to 0.1% using air.




• Notes

– Change the Stream class type to: MIXCISLD.

– Put the SiO2 in the CISOLID substream.

– The pressure and temperature has to be the same in all thesub-streams of a stream.

AIR-OUT

Temp = 190 F

Pres = 14.7 psia

Flow = 1 lbmol/hr

0.79 mole% N2

Solids Workshop 1 (Continued)




When finished, save as

filename: SOLIDWK1.BKP

Temp = 70 F

Pres = 14.7 psia

995 lb/hr SiO2 5 lb/hr H2O

FLASH2

DRYER

AIR

WET

DRY

Pressure Drop = 0

Adiabatic

2

0.21 mole% O2

Design specification:

Vary the air flow rate

from 1 to 10 lbmol/hr toachieve 99.9 wt.% SiO2

[SiO2/(SiO2+Mixed)]

Use the SOLIDS Property Method

Solids Workshop 2

• Objective: Use the solids unit operations to model theparticulate removal from a feed of gasifier off gases.

• The processing of gases containing small quantities of particulate




materials is rendered difficult by the tendency of the particulates tointerfere with most operations (e.g., surface erosion, fouling,plugging of orifices and packing). It is therefore necessary to

remove most of the particulate materials from the gaseous stream.Various options are available for this purpose (Cyclone, Bag-filter,Venturi-scrubber, and an Electrostatic precipitator) and their particulate separation efficiency can be changed by varying their design and operating conditions. The final choice of equipment is abalance between the technical performance and the cost associated

with using a particular unit.

• In this workshop, various options for removing particulates from thesyngas obtained by coal gasification are compared.

Temp = 650 C

Pres = 1 bar

Gas Flowrate = 1000 kmol/hr

Ash Flowrate = 200 kg/hr

Composition (mole-frac)CO 0.19

CO2 0.20

CYC

F CYC

G-CYC

S-CYCTemp = 40 C

Pres = 1 bar

Water Flowrate = 700 kg/hr

Design Mode

High Efficiency

Separation Efficiency = 0.9

D i M d






filename: SOLIDWK2.BKP

H2 0.05

H2S 0.02

O2 0.03

CH4 0.01

H2O 0.05

N2 0.35

SO2 0.10

Particle size distribution (PSD)

Size limit wt. %

[mu]

0- 44 30

44- 63 10

63-90 20

90-130 15130-200 10

200-280 15

DUPL

FAB-

FILT

ESP

V-SCRUB

FEED

F-CYC

F-SCRUB

F-ESP

F-BF

S-BF

G-SCRUB

S-SCRUB

LIQ

G-ESP

S-ESP

G-BF

Water Flowrate 700 kg/hr

Design Mode

Max. Pres. Drop = 0.048 bar

Design Mode


Dielectric constant = 1.5

Design Mode



• Coal ash is mainly clay and heavy metal oxides and can beconsidered a non-conventional component.

• HCOALGEN and DCOALIGT can be used to calculate the enthalpyf f




and material density of ash using the ultimate, proximate, and sulfur analyses (ULTANAL, PROXANAL, SULFANAL). These arespecified on the Properties Advanced NC-Props form.

• Component attributes (ULTANAL, PROXANAL, SULFANAL) arespecified on the Stream Input form. For ash, zero all non-ashattributes.

• The PSD limits can be changed on the Setup Substreams PSD form.

• Use the IDEAL Property Method.

Optimization




Objective:

Introduce the optimization capability in Aspen Plus


User Guide, Chapter 22, Optimization

Related Topics:

User Guide, Chapter 17, Convergence


Optimization

• Used to maximize/minimize an objective function

• Objective function is expressed in terms of flowsheetvariables and In-Line Fortran




variables and In-Line Fortran.

• Optimization can have zero or more constraints.

• Constraints can be equalities or inequalities.

• Optimization is located under /Data/Model AnalysisTools/Optimization

• Constraint specification is under /Data/Model AnalysisTools/Constraint

FEED

REACTORA, B

A + B --> C + D + E

Optimization Example




Desired Product C $ 1.30 / lbBy-product D $ 0.11 / lbWaste Product E $ - 0.20 /lb PRODUCT

A, B, C, D, E

• For an existing reactor, find the reactor temperature andinlet amount of reactant A that maximizes the profit fromthis reactor. The reactor can only handle a maximumcooling load of Q.

Optimization Example (Continued)

• What are the measured (sampled) variables?

– Outlet flowrates of components C, D, E

• What is the objective function to be maximized?




• What is the objective function to be maximized?

– Maximize 1.30*(lb/hr C) + 0.11*(lb/hr D) - 0.20*(lb/hr E)

• What is the constraint? – The calculated duty of the reactor can not exceed Q.

• What are the manipulated (varied) variables?

– Reactor temperature

– Inlet amount of reactant A

Steps for Using Optimization

1. Identify measured (sampled) variables.

– These are the flowsheet variables used to calculate theobjective function (Optimization Define sheet).




2. Specify objective function (expression).

– This is the Fortran expression that will be maximized or

minimized (Optimization Objective & Constraints sheet).

3. Specify maximization or minimization of objectivefunction (Optimization Objective & Constraints sheet).

Steps for Using Optimization (Continued)

4. Specify constraints (optional).

– These are the constraints used during the optimization(Optimization Objective & Constraints sheet).




5. Specify manipulated (varied) variables.

– These are the variables that the optimization block will

change to maximize/minimize the objective function(Optimization Vary sheet).

6. Specify bounds for manipulated (varied) variables.

– These are the lower and upper bounds within which to vary

the manipulated variable (Optimization Vary sheet).

Notes

1. The convergence of the optimization can be sensitive

to the initial values of the manipulated variables.

2 It is best if the objective the constraints and the




2. It is best if the objective, the constraints, and themanipulated variables are in the range of 1 to 100.This can be accomplished by simply multiplying or

dividing the function.

3. The optimization algorithm only finds local maxima andminima in the objective function. It is theoreticallypossible to obtain a different maximum/minimum in the

objective function, in some cases, by starting at adifferent point in the solution space.

Notes (Continued)

4. Equality constraints within an optimization are similar to

design specifications.

5 If an optimization does not converge run sensitivity




5. If an optimization does not converge, run sensitivitystudies with the same manipulated variables as theoptimization, to ensure that the objective function is not

discontinuous with respect to any of the manipulatedvariables.

6. Optimization blocks also have convergence blocksassociated with them. Any general techniques used

with convergence blocks can be used if the optimizationdoes not converge.

Optimization Workshop

• Objective: Optimize steam usage for a process.

• The flowsheet shown below is part of a Dichloro-Methane solventrecovery system. The two flashes, TOWER1 and TOWER2, are runadiabatically at 19 7 and 18 7 psia respectively The stream FEED




adiabatically at 19.7 and 18.7 psia respectively. The stream FEEDcontains 1400 lb/hr of Dichloro-Methane and 98600 lb/hr of water at100oF and 24 psia. Set up the simulation as shown below, and

minimize the total usage of steam in streams STEAM1 andSTEAM2, both of which contain saturated steam at 200 psia. Themaximum allowable concentration of Dichloro-Methane in thestream EFFLUENT from TOWER2 is 150 ppm (mass) to within atolerance of a tenth of a ppm. Use the NRTL Property Method. Usebounds of 1000 lb/hr to 20,000 lb/hr for the flowrate of the two steam

streams. Make sure stream flows are reported in mass flow andmass fraction units before running. Refer to the Notes slides for some hints on the previous page if there are problems convergingthe optimization.

STEAM1

TOP1

TOWER1

Optimization Workshop (Continued)





filename: OPT.BKP

FEED

BOT1

TOP2

EFFLUENT

STEAM2

TOWER2

RadFrac Convergence




Objective:

Introduce the convergence algorithms andinitialization strategies available in RadFrac


Unit Operation Models Reference Manual , Chapter 4, Columns

RadFrac Convergence Methods

• RadFrac provides a variety of convergence methods for

solving separation problems. Each convergence methodrepresents a convergence algorithm and an initializationmethod The following convergence methods are




method. The following convergence methods areavailable:

– Standard (default)

– Petroleum / Wide-Boiling

– Strongly non-ideal liquid

– Azeotropic

– Cryogenic

– Custom

Method Algorithm Initialization

Standard Standard StandardPetroleum / Wide-boiling Sum-Rates Standard

Convergence Methods (Continued)




Strongly non-ideal liquid Nonideal Standard

Azeotropic Newton Azeotropic

Cryogenic Standard Cryogenic

Custom select any select any

RadFrac Convergence Algorithms

• RadFrac provides four convergence algorithms:

– Standard (with Absorber=Yes or No) – Sum-Rates




– Nonideal

– Newton

Standard Algorithm

• The Standard (default, Absorber=No) algorithm:

– Uses the original inside-out formulation – Is effective and fast for most problems




– Solves design specifications in a middle loop

– May have difficulties with extremely wide-boiling or highly non-

ideal mixtures

Standard Algorithm (Continued)

• The Standard algorithm with Absorber=Yes:

– Uses a modified formulation similar to the classical sum-ratesalgorithm

A li t b b d t i l




– Applies to absorbers and strippers only

– Has fast convergence

– Solves design specifications in a middle loop – May have difficulties with highly non-ideal mixtures

Sum-Rates Algorithm

• The Sum-Rates algorithm:

– Uses a modified formulation similar to the classical sum-ratesalgorithm

S l d i ifi ti i lt l ith th l




– Solves design specifications simultaneously with the column-describing equations

– Is effective and fast for wide boiling mixtures and problems with

many design specifications

– May have difficulties with highly non-ideal mixtures

Nonideal Algorithm

• The Nonideal algorithm:

– Includes a composition dependency in the local physicalproperty models

Uses the continuation convergence method




– Uses the continuation convergence method

– Solves design specifications in a middle loop

– Is effective for non-ideal problems

Newton Algorithm

• The Newton algorithm:

– Is a classic implementation of the Newton method – Solves all column-describing equations simultaneously




– Uses the dogleg strategy of Powell to stabilize convergence

– Can solve design specifications simultaneously or in an outer

loop – Handles non-ideality well, with excellent convergence in the

vicinity of the solution

– Is recommended for azeotropic distillation columns

Vapor-Liquid-Liquid Calculations

• You can use the Standard, Newton and Nonideal

algorithms for 3-phase Vapor-Liquid-Liquid systems. Onthe RadFrac Setup Configuration sheet, select Vapor-Liquid-Liquid in the Valid Phases field.




Liquid Liquid in the Valid Phases field.

• Vapor-Liquid-Liquid calculations:

– Handle column calculations involving two liquid phasesrigorously

– Handle decanters

– Solve design specifications using:

• Either the simultaneous (default) loop or the middle loop approach for the Newton algorithm

• The middle loop approach for all other algorithms

Convergence Method Selection

• For Vapor-Liquid systems, start with the Standard

convergence method. If the Standard method fails: – Use the Petroleum / Wide Boiling method if the mixture is very

wide-boiling




wide-boiling.

– Use the Custom method and change Absorber to Yes on theRadFrac Convergence Algorithm sheet, if the column is an

absorber or a stripper.

– Use the Strongly non-ideal liquid method if the mixture is highlynon-ideal.

– Use the Azeotropic method for azeotropic distillation problemswith multiple solutions possible. The Azeotropic algorithm isalso another alternative for highly non-ideal systems.

Convergence Method Selection (Continued)

• For Vapor-Liquid-Liquid systems:

– Start by selecting Vapor-Liquid-Liquid in the Valid Phases fieldof the RadFrac Setup Configuration sheet and use theStandard convergence method.




Standard convergence method.

– If the Standard method fails, try the Custom method with theNonideal or the Newton algorithm.

RadFrac Initialization Method

• Standard is the default Initialization method for RadFrac.

• This method:

– Performs flash calculations on composite feed to obtain




paverage vapor and liquid compositions

– Assumes a constant composition profile

– Estimates temperature profiles based on bubble and dew pointtemperatures of composite feed

Specialized Initialization Methods

• Four specialized Initialization methods are available.

Use: For:Crude Wide boiling systems with

multi draw columns




multi-draw columns

Chemical Narrow boiling chemical systems

Azeotropic Azeotropic distillation columnsCryogenic Cryogenic applications

Estimates

• RadFrac does not usually require estimates for

temperature, flow and composition profiles.• RadFrac may require:




– Temperature estimates as a first trial in case of convergenceproblems

– Liquid and/or vapor flow estimates for the separation of wideboiling mixtures.

– Composition estimates for highly non-ideal, extremely wide-boiling (for example, hydrogen-rich), azeotropic distillation or vapor-liquid-liquid systems.

Composition Estimates

• The following example illustrates the need for

composition estimates in an extremely wide-boiling pointsystem:




RadFrac Convergence Workshop

• Objective: Apply the convergence hints explained in thissection.

• HCl column in a VCM production plant

F d




• Feed

– 130000 kg/hr at 50C, 18 bar

– 19.5%wt HCl, 33.5%wt VCM, 47%wt EDC – (VCM : vinyl-chloride, EDC : 1,2-dichloroethane)

• Column

– 33 theoretical stages

– partial condenser (vapor distillate) – kettle reboiler

– pressure : top 17.88 bar, bottom 18.24 bar

– feed on stage 17

RadFrac Convergence Workshop (Continued)

• First Step:

– Specify the column.• Set the distillate flow rate to be equal to the mass flow rate of HCl in the

feed.




• Specify that the mass reflux ratio is 0.7.

• Use Peng-Robinson equation of state (PENG-ROB).

– Question: How should these specifications be implemented?

• Note: Look at the results.

– Temperature profile

– Composition profile


• Second step:

– VCM in distillate and HCl in bottom are much too high! – Allow only 5 ppm of HCl in the residue and 10 ppm VCM in the

distillate




distillate.

– Question: How should these specifications be implemented?

• Note: You may have some convergence difficulties. – Apply the guidelines presented in this section

130000 kg/h

50 C, 18 bar,

flow : HCl in feed

max 10 ppm VCM

17 88 b

Use the PENG-ROB Property method





feed on stage 17

, ,

HCl 19.5%wt

VCM 33.5%wt

EDC 47.0%wtmass reflux ratio:0.7

max 5 ppm HCl

17.88 bar

18.24 bar

When finished, save as filename: VCMHCL1.BKP (step 1) and VCMHCL2.BKP (step 2)

• Objective: Set up a flowsheet of a VCM process using the toolslearned in the course.

• Vinyl chloride monomer (VCM) is produced through a high pressure, non-catalytic process involving the pyrolysis of 1,2-dichloroethane (EDC)according to the following reaction:

Vinyl Chloride Monomer (VCM) Workshop




CH2Cl-CH2Cl HCl + CHCl=CH2

• The cracking of EDC occurs at 500 C and 30 bar in a direct fired furnace.1000 kmol/hr of pure EDC feed enters the reactor at 20 C and 30 bar. EDCconversion in the reactor is maintained at 55%. The hot gases from thereactor are subcooled by 10 degrees before fractionation.

• Two distillation columns are used for the purification of the VCM product. Inthe first column, anhydrous HCl is removed overhead and sent to the oxy

chlorination unit. In the second column, VCM product is removed overheadand the bottoms stream containing unreacted EDC is recycled back to thefurnace. Overheads from both columns are removed as saturated liquids.The HCL column is run at 25 bar and the VCM column is run at 8 bar. Usethe RK-SOAVE Property Method.

1000 kmol/hr EDC20C30 bar

FEED

HCLOUT

RStoic ModelHeater Model

RadFrac Model

RadFrac Model

CH2Cl-CH2Cl HCl + CHCl=CH2

EDC HCl VCM

VCM Workshop (Continued)




CRACK

RECYCIN

REACTOUT

PUMP

RECYCLE

QUENCH

COOLOUT COL1

VCMIN COL2

VCMOUT

Pump Model

30 bar outlet pressure

500 C

30 bar EDC Conv. = 55%

10 deg C subcooling0.5 bar pressure drop

10 stagesReflux ratio = 0.969

Distillate to feed ratio = 0.550Feed enters above stage 7Column pressure = 8 bar

15 stages

Reflux ratio = 1.082Distillate to feed ratio = 0.354

Feed enters above stage 8Column pressure = 25 bar

When finished, save asfilename: VCM.BKPUse RK-SOAVE property method

VCM Workshop (Continued)

Part A:

• With the help of the process flow diagram on the previous page, setup a flowsheet to simulate the VCM process. What are the values of the following quantities?



1. Furnace heat duty ________

2. Quench cooling duty ________

97448371-Aspen-Plus-Nice-Tutorial.pps

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