Aspen Plus (Nice Tutorial)

Introduction to Flowsheet Simulation Objective: Introduce general flowsheet simulation concepts and Aspen Plus features

©2000 AspenTech. All Rights Reserved.

Flowsheet Simulation • What is flowsheet simulation? Use of a computer program to quantitatively model the characteristic 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


Introduction to Aspen Plus

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)



General Simulation Problem • What is the composition of stream PRODUCT? RECYCLE REACTOR COOL FEED REAC-OUT

• To solve this problem, we need:

COOL-OUT

SEP

PRODUCT

– Material balances

– Energy balances



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 oriented

simulation program. – All equations are solved simultaneously.

• Combination – Aspen Dynamics (formerly DynaPLUS) uses the Aspen Plus

sequential modular approach to initialize the steady state simulation and the Aspen Custom Modeler (formerly SPEEDUP) equation oriented 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.



Important Features of Aspen Plus • Rigorous Electrolyte Simulation • Solids Handling

• Petroleum Handling • Data Regression

• Data Fit • Optimization • User Routines



The User Interface Objective: Become comfortable and familiar with the Aspen Plus graphical user interface

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 ©2000 AspenTech. All Rights Reserved.

The User Interface Run ID

Title Bar Menu Bar Next Button Tool Bar

Select Mode button

Model Library

Model Menu Tabs

Status Area Process Flowsheet Window

Reference: Aspen Plus User Guide, Chapter 1, The User Interface ©2000 AspenTech. All Rights Reserved.


Cumene Flowsheet Definition RECYCLE REACTOR COOL FEED REAC-OUT

RStoic Model

COOL-OUT

Heater Model

SEP

Flash2 Model PRODUCT

Filename: CUMENE.BKP



Using the Mouse • Left button click

-

Select object/field

• Right button click

-

Bring up menu for selected object/field, or inlet/outlet

-

Cancel placement of streams or blocks on the flowsheet

-

Open Data Browser object sheet

• Double left click

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 to select an icon for the model. 3. Click on the model and then click on the flowsheet to place the block. You can also click on the model icon and drag it onto 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 Flowsheet window. 6. Click the right mouse button to stop creating streams.



Graphic Flowsheet Operations (Continued) • To display an Input form for a Block or a Stream in the Data Browser: 1.

Double click the left mouse button on the object of interest.

• To Rename, Delete, Change the icon, provide input or view results for a block or stream: 1. 2. 3.

Select object (Block or Stream) by clicking on it with the left mouse button. Click the right mouse button while the pointer is over the selected object icon to bring up the menu for that object. Choose appropriate menu item.

Reference: Aspen Plus User Guide, Chapter 4, Defining the Flowsheet ©2000 AspenTech. All Rights Reserved.


Automatic Naming of Streams and Blocks • Stream and block names can be automatically assigned by Aspen Plus or entered by the user when the object is created. • 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.



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.

VAP1

COOL

VAP2 FL1

FEED

COOL

Flash2 Model

Heater Model

FL2 LIQ1

Flash2 Model

When finished, save in backup format (Run-ID.BKP). filename: BENZENE.BKP LIQ2 ©2000 AspenTech. All Rights Reserved.


Basic Input Objective: Introduce the basic input required to run an Aspen Plus simulation

Aspen Plus References: 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 ©2000 AspenTech. All Rights Reserved.

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 from

the 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



The User Interface (Continued) • Object Manager – Allows manipulation of discrete objects of information – Can be created, edited, renamed, deleted, hidden, and

revealed

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

form which requires input



The Data Browser Go back

Go forward

Next sheet Comments

Parent button

Units

Previous sheet

Status

Next

Menu tree

Status area

Description area ©2000 AspenTech. All Rights Reserved.


Help • Help Topics – Contents - Used to browse through the documentation. The

User Guides and Reference Manuals are all included in the help. •

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 index

entries – 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 on

any area to get help for that item. ©2000 AspenTech. All Rights Reserved.


Functionality of Forms • When you select a field on a form (click left mouse button in the field), the prompt area at the bottom of the window 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 that

begins 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 clicking the 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. ©2000 AspenTech. All Rights Reserved.


Status Indicators Symbol

Status 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.



Cumene Production Conditions RECYCLE

REACTOR COOL FEED

T = 220 F P = 36 psia Benzene: 40 lbmol/hr Propylene: 40 lbmol/hr

REAC-OUT

Q = 0 Btu/hr Pdrop = 0 psi

COOL-OUT


P = 1 atm Q = 0 Btu/hr

T = 130 F Pdrop = 0.1 psi

C6H6 + C3H6 = C9H12 Benzene Propylene Cumene (Isopropylbenzene) 90% Conversion of Propylene

Use the RK-SOAVE Property Method

SEP

PRODUCT

Filename: CUMENE.BKP


Setup • Most of the commonly used Setup information is entered on 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 analysis calculations.

Assay Data Analysis

A standalone Assay Data Analysis and pseudocomponent generation run

Data Regression

A standalone Data Regression run

PROPERTIES PLUS

PROPERTIES PLUS setup run

Property Analysis

Property Estimation


Use Assay Data Analysis to analyze assay data when you do not want to perform a flowsheet simulation in the same run. Use Data Regression to fit physical property model parameters required by ASPEN PLUS to measured pure component, VLE, LLE, and other mixture data. Data Regression can contain property estimation and property analysis calculations. ASPEN PLUS cannot perform data regression in a Flowsheet 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 commercial engineering programs, or with your company's in-house programs. You must be licensed to use PROPERTIES PLUS. A standalone Property Analysis run Use 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. Standalone Property Constant Estimation run Use Property Estimation to estimate property parameters when you do not want to perform a flowsheet 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 the Setup Specifications Global sheet) 2. Object level (“Units” field in the top of any input form of an object such as a block or stream 3. Field Level

• Users can create their own units sets using the Setup Units Sets Object Manager. Units can be copied from an existing set and then modified.



Components • Use the Components Specifications form to specify all the 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 databank search 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 an electrolyte simulation. ©2000 AspenTech. All Rights Reserved.


Components Specifications Form



Entering Components • The Component ID is used to identify the component in simulation inputs and results. • Each Component ID can be associated with a databank component as 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 one criterion is specified. ©2000 AspenTech. All Rights Reserved.


Pure Component Databanks • Parameters missing from the first selected databank will be searched 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

PURE93

Data from the Design Institute for Physical Property Data (DIPPR) and AspenTech delivered with Aspen Plus 9.3

For upward compatibility

PURE856

Data from the Design Institute for Physical Property Data (DIPPR) and AspenTech delivered with Aspen Plus 8.5-6


ASPENPCD

Databank delivered with Aspen Plus 8.5-6




Properties • Use the Properties Specifications form to specify the physical property methods to be used in the simulation. • Property methods are a collection of models and methods used to describe pure component and mixture behavior. • 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 stream conditions 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 the flowsheet are used as estimates. ©2000 AspenTech. All Rights Reserved.


Streams Input Form



Blocks • Each Block Input or Block Setup form specifies operating conditions and equipment specifications for the unit operation model. • Some unit operation models require additional specification 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 the Next button to be prompted. – The simulation can be executed when all required forms are

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



Control Panel • The Control Panel consists of: – A message window showing the progress of the simulation by

displaying 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


Run

Start or continue calculations

Step

Step through the flowsheet one block at a time

Stop

Pause simulation calculations

Reinitialize

Purge simulation results

Results

Check simulation results Introduction to Aspen Plus

Reviewing Results • History file or Control Panel Messages – Contains any generated errors or warnings – Select History or Control Panel on the View menu to display

the 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 the

block folder in the Data Browser and select the Results form) ©2000 AspenTech. All Rights Reserved.


Benzene Flowsheet Conditions Workshop • Objective: Add the process and feed stream conditions to a flowsheet. – Starting with the flowsheet created in the Benzene Flowsheet

Definition Workshop (saved as BENZENE.BKP), add the process and feed 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.



Benzene Flowsheet Conditions Workshop VAP1

COOL FL1 FEED

Feed

T = 1000 F P = 550 psia

COOL

T = 100 F P = 500 psia

T = 200 F Pdrop = 0

VAP2

FL2 LIQ1

P = 1 atm Q=0

Hydrogen: 405 lbmol/hr

Methane: 95 lbmol/hr Benzene: 95 lbmol/hr Toluene: 5 lbmol/hr

Use the PENG-ROB Property Method


LIQ2

When finished, save as filename: BENZENE.BKP Introduction to Aspen Plus

Unit Operation Models Objective: Review major types of unit operation models

Aspen Plus References: User Guide, Chapter 10, Unit Operation Models Unit Operation Models Reference Manual ©2000 AspenTech. All Rights Reserved.

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 the documentation. Aspen Plus Unit Operation Models Reference Manual



Mixers/Splitters Model

Description

Purpose

Use

Mixer

Stream mixer

Combine multiple streams into one stream

Mixing tees, stream mixing operations, adding heat streams, adding work streams

FSplit

Stream splitter

Split stream flows

Stream splitters, bleed valves

SSplit

Substream splitter

Split substream flows

Solid stream splitters, bleed valves



Separators Model

Description Purpose

Use

Flash2

Two-outlet flash Determine thermal and phase conditions

Flashes, evaporators, knockout drums, single stage separators, free water separations

Flash3

Three-outlet flash

Determine thermal and phase conditions

Decanters, single stage separators with two liquid phases

Decanter

Liquid-liquid decanter

Determine thermal and phase conditions

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 outlet streams

Component separation operations such as distillation and absorption, when the details of the separation are unknown 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



Heat Exchangers Model

Description

Purpose

Use

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. LNG exchangers.

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 aircooled heat exchangers

Air-cooled heat exchangers with a wide variety of configurations. Model economizers and the convection section of fired heaters.

HXFlux

Heat transfer calculation model

Models convective heat transfer between a heat sink and a heat source.

Determines the log-mean temperature difference, 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.

*

Requires separate license



Columns - Shortcut Model

Description

DSTWU

Shortcut distillation Determine minimum RR, Columns with one feed and design minimum stages, and either two product streams actual RR or actual stages by Winn-UnderwoodGilliland method.

Distl

Shortcut distillation Determine separation rating based on RR, stages, and D:F ratio using Edmister method.

Columns with one feed and two product streams

SCFrac

Shortcut distillation Determine product for petroleum composition and flow, fractionation stages per section, duty using fractionation indices.

Complex columns, such as crude units and vacuum towers


Purpose

Use


Columns - Rigorous Model

Description Purpose

Use

RadFrac

Rigorous fractionation

Rigorous rating and design for single Distillation, absorbers, strippers, columns extractive and azeotropic distillation, reactive distillation

MultiFrac

Rigorous fractionation for complex columns

Rigorous rating and design for multiple columns of any complexity

PetroFrac

Petroleum refining Rigorous rating and design for fractionation 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 Distillation columns, absorbers, strippers, and multiple columns. Based on reactive systems, heat integrated units, nonequilibrium calculations petroleum applications

Extract

Liquid-liquid extraction

Rigorous rating for liquid-liquid extraction columns

Heat integrated columns, air separators, absorber/stripper combinations, ethylene primary fractionator/quench tower combinations, petroleum refining

Liquid-liquid extraction

*

Requires separate license + Input language only in Version 10.0 ©2000 AspenTech. All Rights Reserved.


Reactors Model

Description

Purpose

Use

RStoic

Stoichiometric reactor

Stoichiometric reactor with specified reaction extent or conversion

Reactors where the kinetics are unknown or unimportant but stoichiometry and extent are known

RYield

Yield reactor

Reactor with specified yield Reactors where the stoichiometry and kinetics are unknown or unimportant but yield distribution is known

REquil

Equilibrium reactor

Chemical and phase equilibrium by stoichiometric calculations

Single- and two-phase chemical equilibrium and simultaneous phase equilibrium

RGibbs

Equilibrium reactor

Chemical and phase equilibrium by Gibbs energy minimization

Chemical and/or simultaneous phase and chemical 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 with kinetic reactions in any phase. Plug flow reactions with external coolant.

RBatch

Batch reactor

Batch or semi-batch reactor

Batch and semi-batch reactors where the reaction kinetics are known



Pressure Changers Model Description Purpose

Use

Pump

Pump or hydraulic turbine

Change stream pressure when the pressure, power requirement or performance curve is known

Pumps and hydraulic turbines

Compr

Compressor or turbine

Change stream pressure when the pressure, power requirement or performance curve is known

Polytropic compressors, polytropic positive displacement compressors, isentropic compressors, isentropic turbines.

MCompr

Multi-stage compressor or turbine

Change stream pressure across multiple stages with intercoolers. Allows for liquid knockout streams from intercoolers

Multistage polytropic compressors, polytropic positive compressors, isentropic compressors, isentropic turbines.

Valve

Control valve

Determine pressure drop or valve coefficient (CV)

Multi-phase, adiabatic flow in ball, globe and butterfly valves

Pipe

Single-segment Determine pressure drop and pipe heat transfer in single-segment pipe or annular space

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

Pipeline

Multi-segment pipe

Multi-phase, one dimensional, steady-state and fully developed pipeline flow


Determine pressure drop and heat transfer in multi-segment pipe or annular space


Manipulators Model

Description

Purpose

Use

Mult

Stream multiplier

Multiply stream flows by a user supplied factor

Multiply streams for scale-up or scale-down

Dupl

Stream duplicator

Copy a stream to any number of outlets

Duplicate streams to look at different scenarios in the same flowsheet

ClChng

Stream class changer

Change stream class

Link sections or blocks that use different stream classes

Selector

Stream selector

Switch between different inlet streams.

Test different flowsheet senarios



Solids Model

Description

Uses

Crystallizer

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 vacuum filters

SWash

Single-stage solids washer

Single-stage solids washer

CCD

Counter-current decanter

Multistage washer or a counter-current decanter



User Models • Proprietary models or 3-rd party software can be included in an Aspen Plus flowsheet using a User2 unit operation block. • Excel Workbooks or Fortran code can be used to define the 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 know the internal data structure to retrieve variables. ©2000 AspenTech. All Rights Reserved.


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

Aspen Plus References: Unit Operation Models Reference Manual, Chapter 4, Columns ©2000 AspenTech. All Rights Reserved.

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 Condenser Heat Duty

1

Heat (optional) Liquid Distillate Water Distillate (optional)

Feeds Reflux Products (optional)

Heat (optional) Pumparound

Decanters

Heat (optional) Heat (optional)

Bottom Stage or Reboiler Heat Duty

Boil-up Nstage

Product Return

Heat (optional)

Bottoms



RadFrac Setup Configuration Sheet • Specify: – Number of stages – Condenser and reboiler

configuration – Two column operating specifications – Valid phases – Convergence



RadFrac Setup Streams Sheet • Specify: – Feed stage location – Feed stream convention

(see Help) ABOVE-STAGE: Vapor from feed goes to stage above feed stage – Liquid goes to feed stage

ON-STAGE: Vapor & Liquid from feed go to specified feed stage



Feed Convention Above-stage (default) n-1

On-stage

n-1

Vapor

Feed

Liquid

n

Feed

n



RadFrac Setup Pressure Sheet • Specify one of: – Column pressure profile – Top/Bottom pressure – Section pressure drop



Methanol-Water RadFrac Column OVHD

FEED

RadFrac specifications Total Condenser

COLUMN

Kettle Reboiler

T = 65 C P = 1 bar

BTMS Water: 100 kmol/hr Methanol: 100 kmol/hr

9 Stages Reflux Ratio = 1 Distillate to feed ratio = 0.5 Column pressure = 1 bar Feed stage = 6

Use the NRTL-RK Property Method Filename: RAD-EX.BKP



RadFrac Options • To set up an absorber with no condenser or reboiler, set condenser and reboiler to none on the RadFrac Setup Configuration sheet. • Either Vaporization or Murphree efficiencies on either a stage or component basis can be specified on the RadFrac 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. ©2000 AspenTech. All Rights Reserved.


Plot Wizard • Use Plot Wizard (on the Plot menu) to quickly generate plots of results of a simulation. You can use Plot Wizard for displaying results for the following operations: – Physical property analysis – Data regression analysis – Profiles for all separation models RadFrac, MultiFrac, PetroFrac and

RateFrac

• 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 to generate a plot with default settings.



Plot Wizard Demonstration

1

• Use the plot wizard on the column to create a plot of the vapor phase compositions throughout the column. Block COLUMN: Vapor Composition Prof iles WATER

Y (mole frac) 0.25 0.5 0.75

METHANOL

1 ©2000 AspenTech. All Rights Reserved.

2

3

4

5 Stage

6

7

8

9 Introduction to Aspen Plus

RadFrac DesignSpecs and Vary • Design specifications can be specified and executed inside the RadFrac block using the DesignSpecs and Vary forms. • One or more RadFrac inputs can be manipulated to achieve specifications 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 “Middle loop.” If you get an error message saying that the middle loop was not converged, check the DesignSpecs and Varys you have entered.



RadFrac Convergence Problems • If a RadFrac column fails to converge, doing one or more of 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, increase the maximum iterations on the RadFrac Convergence Basic sheet.



RadFrac Convergence Problems (Continued) 4. Provide temperature estimates for some stages in the column using the RadFrac Estimates Temperature sheet (useful for absorbers). 5. Provide composition estimates for some stages in the column 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 usually beneficial to Reinitialize after making changes. ©2000 AspenTech. All Rights Reserved.


RadFrac Workshop Part A • Perform a rating calculation of a Methanol tower using the following data: •

DIST

FEED

COLUMN

Feed: 63.2 wt% Water 36.8 wt% Methanol Total flow = 120,000 lb/hr Pressure 18 psia Saturated liquid Use the NRTL-RK Property Method ©2000 AspenTech. All Rights Reserved.

Column specification: 38 trays (40 stages) Feed tray = 23 (stage 24) Total condenser Top stage pressure = 16.1 psia Pressure drop per stage = 0.1 psi Distillate flowrate = 1245 lbmol/hr Molar reflux ratio = 1.3

BTMS

Filename: RADFRAC.BKP Introduction to Aspen Plus

RadFrac Workshop (Continued) Part B • Set up design specifications within the column so the following two objectives 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 (8001700 lbmol/hr) and the reflux ratio (0.8-2). Make sure stream compositions are reported as mass fractions before running the problem. Note the condenser and reboiler duties: Condenser Duty :_________ Reboiler Duty :_________



RadFrac Workshop (Continued) Part C • Perform the same design calculation after specifying a 65% Murphree efficiency for each tray. Assume the condenser and reboiler have stage efficiencies of 90%. • How do these efficiencies affect the condenser and reboiler duties of the column? Part D • Perform a tray sizing calculation for the entire column, given that Bubble Cap trays are used. (When finished, save as filename: RADFRAC.BKP) ©2000 AspenTech. All Rights Reserved.


Reactor Models Objective: Introduce the various classes of reactor models available, and examine in some detail at least one reactor from each class

Aspen Plus References Unit Operation Models Reference Manual, Chapter 5, Reactors ©2000 AspenTech. All Rights Reserved.

Reactor Overview Reactors

Balance Based RYield RStoic


Equilibrium Based REquil RGibbs

Kinetics Based RCSTR RPlug RBatch


Balanced Based Reactors • RYield – Requires a mass balance only, not an atom balance – Is used to simulate reactors in which inlets to the reactor are

not completely known but outlets are known (e.g. to simulate a furnace) RYield

1000 lb/hr Coal

70 lb/hr H2O 20 lb/hr CO2 60 lb/hr CO 250 lb/hr tar 600 lb/hr char

IN

OUT



Balanced Based Reactors (Continued) • RStoic – Requires both an atom and a mass balance – Used in situations where both the equilibrium data and the

kinetics are either unknown or unimportant – Can specify or calculate heat of reaction at a reference temperature and pressure RStoic

C, O2 IN

2 CO + O2 --> 2 CO2 C + O2 --> CO2 2 C + O2 --> 2 CO C, O2, CO, CO2 OUT



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 by

solving reaction equilibrium equations – Cannot do a 3-phase flash – Useful when there are many components, a few known

reactions, and when relatively few components take part in the reactions



Equilibrium Based Reactors (Continued) • RGibbs – Unknown Reactions - This feature is quite useful when

reactions occurring are not known or are high in number due to many components participating in the reactions. – Gibbs Energy Minimization - A Gibbs free energy minimization is done to determine the product composition at which the Gibbs free energy of the products is at a minimum. – Solid Equilibrium - RGibbs is the only Aspen Plus block that

will 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 be specified. • 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 the reactor, 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 rate  k *  [concentrationi ]exponent i i

 Activation Energy  1 1   T  k  (Pre  exponentia l Factor)   exp       R  T0   T T0    n

 C  2 D 2 A  3B   k 2 k1

Example:

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

coefficients:

A: -2

B: -3

C: 1

D: 2

exponents:

A: 2

B: 0

C: 0

D: 0

Reverse reaction: (Assuming the reaction is 1st order in C and D) coefficients: C: -1 D: -2 A: 2 B: 3 exponents: C: 1 D: 1 A: 0 B: 0 ©2000 AspenTech. All Rights Reserved.


Heats of Reaction • Heats of reaction need not be provided for reactions. • Heats of reaction are typically calculated as the difference between inlet and outlet enthalpies for the reactor (see Appendix A). • If you have a heat of reaction value that does not match the value calculated by Aspen Plus, you can adjust the heats of formation (DHFORM) of one or more components to make the heats of reaction match. • Heats of reaction can also be calculated or specified at a reference temperature and pressure in an RStoic reactor. ©2000 AspenTech. All Rights Reserved.


Reactor Workshop • Objective - Compare the use of different reactor types to model one 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 Valid phases. ©2000 AspenTech. All Rights Reserved.


Reactor Workshop (Continued) Use the NRTL-RK property method

P-STOIC RSTOIC

F-STOIC

FEED Feed: Temp = 70 C DUPL Pres = 1 atm Water: 8.892 kmol/hr Ethanol: 186.59 kmol/hr Acetic Acid: 192.6 kmol/hr

70 % conversion of ethanol

F-GIBBS

P-GIBBS

RGIBBS

F-PLUG

P-PLUG RPLUG

F-CSTR

P-CSTR

When finished, save as filename: REACTORS.BKP RCSTR ©2000 AspenTech. All Rights Reserved.

Length = 2 meters Diameter = 0.3 meters

Volume = 0.14 Cu. M. Introduction to Aspen Plus

Cyclohexane Production Workshop • Objective - Create a flowsheet to model a cyclohexane production process • Cyclohexane can be produced by the hydrogenation of benzene in the following reaction: C6H6 Benzene

+

3 H2 = Hydrogen

C6H12 Cyclohexane

• The benzene and hydrogen feeds are combined with recycle hydrogen and cyclohexane before entering a fixed bed catalytic reactor. Assume a benzene 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 as recycle hydrogen. • The liquid product stream from the separator is fed to a distillation column to further remove any dissolved light gases and to stabilize the end product. A portion of the cyclohexane product is recycled to the reactor to aid in temperature control. ©2000 AspenTech. All Rights Reserved.


Cyclohexane Production Workshop C6H6 + 3 H2 = C6H12 Benzene Hydrogen Cyclohexane Total flow = 330 kmol/hr

92% flow to stream H2RCY

T = 50 C P = 25 bar Molefrac H2 = 0.975 N2 = 0.005 CH4 = 0.02

H2IN

PURGE

VFLOW

H2RCY

VAP FEED-MIX

REACT

RXIN

BZIN

T = 150C P = 23 bar

T = 40 C P = 1 bar Benzene flow = 100 kmol/hr

HP-SEP RXOUT T = 200 C Pdrop = 1 bar Benzene conv = 0.998

LTENDS

T = 50 C Pdrop = 0.5 bar

Theoretical Stages = 12 Reflux ratio = 1.2 Bottoms rate = 99 kmol/hr Partial Condenser with vapor distillate only Column Pressure = 15 bar Feed stage = 8

LIQ

CHRCY

COLFD LFLOW 30% flow to stream CHRCY

Use the RK-SOAVE property method When finished, save as filename: CYCLOHEX.BKP ©2000 AspenTech. All Rights Reserved.

PRODUCT COLUMN Specify cyclohexane mole recovery in PRODUCT stream equal to 0.9999 by varying Bottoms rate from 97 to 101 kmol/hr Introduction to Aspen Plus

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

Aspen Plus References: User Guide, Chapter 7, Physical Property Methods User Guide, Chapter 8, Physical Property Parameters and Data User Guide, Chapter 29, Analyzing Properties ©2000 AspenTech. All Rights Reserved.

Case Study - Acetone Recovery • Correct choice of physical property models and accurate physical property parameters are essential for obtaining accurate simulation results. OVHD

COLUMN

FEED

5000 lbmol/hr 10 mole % acetone 90 mole % water

BTMS

Specification: 99.5 mole % acetone recovery

Predicted number of stages required Approximate cost in dollars ©2000 AspenTech. All Rights Reserved.

Ideal

Equation of

Activity Coefficient

Approach

State Approach

Model Approach

11

7

42

520, 000

390, 000

880, 000 Introduction to Aspen Plus

How to Establish Physical Properties Choose a Property Method

Check Parameters/Obtain Additional Parameters

Confirm Results

Create the Flowsheet



Property Methods • A Property Method is a collection of models and methods used to calculate physical properties. • Property Methods containing commonly used thermodynamic models are provided in Aspen Plus. • Users can modify existing Property Methods or create new ones.



Physical Property Models • Approaches to representing physical properties of components Physical Property Models

Ideal

Equation of State

Activity

Special

(EOS)

Coefficient

Models

Models

Models

• Choice of model types depends on degree of non-ideal behavior and operating conditions. ©2000 AspenTech. All Rights Reserved.


Ideal vs. Non-Ideal Behavior • What do we mean by ideal behavior?

y

– Ideal Gas law and Raoult’s law

x

• Which systems behave as ideal? – Non-polar components of similar size and shape

• What controls degree of non-ideality? – Molecular interactions

e.g. Polarity, size and shape of the molecules

• How can we study the degree of non-ideality of a system? – Property plots (e.g. TXY & XY)

y

y x


x Introduction to Aspen Plus

Comparison of EOS and Activity Models

EOS Models

Activity Coefficient Models

Limited in ability to represent non-ideal liquids

Can represent highly non-ideal liquids

Fewer binary parameters required

Many binary parameters required

Parameters extrapolate reasonably with temperature

Binary parameters are highly temperature dependent

Consistent in critical region

Inconsistent in critical region



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 activity coefficient models. • It is used to determine the amount of a supercritical component 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 on Properties Specifications Global sheet in the Henry Components field.



Choosing a Property Method - Review Do you have any polar components in your system? N Y Use EOS Model

Y

Are the operating conditions near the critical region of the mixture? N Do you have light gases or supercritical components in your system? Y

References: Aspen Plus User Guide, Chapter 7, Physical Property Methods, gives similar, more detailed guidelines for choosing a property Method. ©2000 AspenTech. All Rights Reserved.

Use activity coefficient model with Henry’s Law

N

Use activity coefficient model Introduction to Aspen Plus

Choosing a Property Method - Example System

Model Type

Property Method

Propane, Ethane, Butane

EOS

RK-SOAVE, PENG-ROB

Benzene, Water


NRTL-RK, UNIQUAC

Acetone, Water


NRTL-RK, WILSON

• Choose an appropriate Property Method for the following systems of components at ambient conditions. System

Property Method

Ethanol, Water Benzene, Toluene Acetone, Water, Carbon Dioxide Water, Cyclohexane Ethane and Propanol ©2000 AspenTech. All Rights Reserved.




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 selecting Retrieve 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 input forms in the Graphical User Interface. • Parameter forms that include data from the databanks must be viewed 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 on the parameter input forms. • Select Retrieve Parameter Results from the Tools menu to retrieve all parameters for the components and property methods defined in the simulation. • All results that are currently loaded will be lost. They can be regenerated by running the simulation again. • The parameters are viewed on the Properties Parameters Results forms.



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. PHYSICAL PROPERTIES SECTION PROPERTY PARAMETERS ------------------PARAMETERS ACTUALLY USED IN THE SIMULATION

PURE COMPONENT PARAMETERS ------------------------COMPONENT ID: BENZENE FORMULA: C6H6

NAME: C6H6

SCALAR PARAMETERS ----------------PARAM NAME


SET DESCRIPTIONS NO.

VALUE

UNITS

28.500

SOURCE

API

1

STANDARD API GRAVITY

CHARGE

1

IONIC CHARGE

0.00000E+00

AQUEOUS

CHI

1

STIEL POLAR FACTOR

0.00000E+00

DEFAULT

DCPLS

1

DIFFERENCE BETWEEN LIQUID AND SOLID CP AT TRIPLE POINT

0.31942

DGFORM

1

IDEAL GAS GIBBS ENERGY OF FORMATION

30.954

PURE10

CAL/MOL-K

PURE10

KCAL/MOL

PURE10


Reporting Physical Property Parameters • Follow this procedure to obtain a report file containing values of ALL pure component and binary parameters for 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, and sources of data.

2. After running the simulation, export a report (*.rep) file (Select Export from the File menu). 3. Edit the .rep file using any text editor. (From the Graphical User Interface, you can choose Report from the View menu.) The parameters are listed under the heading PARAMETER VALUES in the physical properties section of the report file. ©2000 AspenTech. All Rights Reserved.




Confirm Results




Property Analysis • Used to generate simple property diagrams to validate physical property models 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 result form 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. ©2000 AspenTech. All Rights Reserved.


Property Analysis - Common Plots Ideal XY Plot:

XY Plot Showing Azeotrope:

y-x diagram for METHANOL / PROPANOL

y-x diagram for ETHANOL / TOLUENE

(PRES = 14.7 PSI)

0

(PRES = 14.7 PSI)

0.2 0.4 0.6 0.8 1 LIQUID MOLEFRAC METHANOL

0

0.2 0.4 0.6 0.8 1 LIQUID MOLEFRAC ETHANOL

XY Plot Showing 2 liquid phases: y-x diagram for TOLUENE / WATER

(PRES = 14.7 PSI)


0

0.2 0.4 0.6 0.8 1 LIQUID MOLEFRAC TOLUENE




Confirm Results

Create the Flowsheet ©2000 AspenTech. All Rights Reserved.


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 needed can 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 property data using – Physical Property Analysis ©2000 AspenTech. All Rights Reserved.


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 an application. • 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.)



Properties included in Prop-Sets • Properties commonly included in property sets include: – – – –

VFRAC BETA CPMX MUMX

-

Molar vapor fraction of a stream Fraction of liquid in a second liquid phase Constant pressure heat capacity for a mixture 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 a complete list of properties that can be included in a property set.



Specifying Property Sets • 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, where applicable. • Users can define new properties on the Properties Advanced UserProperties form by providing a Fortran subroutine. ©2000 AspenTech. All Rights Reserved.


Predefined Property Sets • Some simulation Templates contain predefined property sets. • The following table lists predefined property sets and the types of properties they contain for the General Template:


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 Introduction to Aspen Plus

Stream Results Options

• On the Setup Report Options Stream sheet, use: – Flow Basis and Fraction Basis check-boxes to specify how

stream composition is reported – Property Sets button to specify names of property sets

containing additional properties to be reported for each stream ©2000 AspenTech. All Rights Reserved.


Definition of Terms • Property Method - Set of property models and methods used to calculate the properties required for a simulation • Property - Calculated physical property value such as mixture enthalpy • Property Model - Equation or equations used to calculate a physical property • Property Parameter - Constant used in a property model • Property Set (Prop-Set) - A method of accessing properties so that they can be used or tabulated elsewhere ©2000 AspenTech. All Rights Reserved.


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 Excel functions 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 pure components. ©2000 AspenTech. All Rights Reserved.


Physical Properties Workshop • Objective: Simulate a two-liquid phase settling tank and investigate 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 tank also contains some carbon-dioxide and nitrogen. The tank and feed are at ambient temperature and pressure (70o F, 1atm), and have the following flow rates of the various components: Water

515 lb/hr

Oil CO2

4322 lb/hr 751 lb/hr

N2

43 lb/hr

• Use the compound n-decane to represent the oil. It is known that water and oil form two liquid phases under the conditions in the tank. ©2000 AspenTech. All Rights Reserved.


Physical Properties Workshop (Continued) 1. Choose an appropriate Property Method to represent this system. Check to see that the required binary physical property parameters are available. 2. Retrieve the physical property parameters used in the simulation and determine the critical temperature for carbon dioxide and water. TC(carbon dioxide) = _______; TC(water) = _______ 3. Using the property analysis feature, verify that the chosen physical property 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 to represent the tank. 5. Modify the stream report to include the constant pressure heat capacity (CPMX) for each phase (Vapor, 1st Liquid and 2nd Liquid), and the fraction of liquid in a second liquid phase (BETA), for all streams. ©2000 AspenTech. All Rights Reserved.


Physical Properties Workshop (Continued) This Portion is Optional • Objective: Generate a table of compositions for each liquid phase (1st Liquid and 2nd Liquid) at different temperatures for a mixture of water and oil. Tabulate the vapor pressure of the components in the same table. • In addition to the interactive Analysis commands under the Tools menu, you also can create a Property Analysis manually, using forms. • Manually generated Generic Property Analysis is similar to the interactive Analysis commands, however it is more flexible regarding input and reporting.

Detailed instructions are on the following slide. ©2000 AspenTech. All Rights Reserved.


Physical Properties Workshop (Continued) • 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. b. c. d.

Mole fraction of water and oil in the 1st and 2nd liquid phases (MOLEFRAC) Mole flow of water and oil in the 1st and 2nd liquid phases (MOLEFLOW) Beta - the fraction of the 1st liquid to the total liquid (BETA) Pure component vapor pressures of water and oil (PL)



Accessing Variables Objective: Become familiar with referencing flowsheet variables

Aspen Plus References: 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 ©2000 AspenTech. All Rights Reserved.

Why Access Variables?

OVHD

FEED

COLUMN

BTMS

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

• To perform this analysis, references must be made to 2 flowsheet quantities, 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 ©2000 AspenTech. All Rights Reserved.


Accessing Variables • An accessed variable is a reference to a particular flowsheet quantity, e.g. temperature of a stream or duty of a block. • Accessed variables can be input, results, or both. • Flowsheet result variables (calculated quantities) should not be overwritten or varied. • The concept of accessing variables is used in sensitivity analyses, design specifications, calculator blocks, optimization, etc.



Variable Categories Variable Category

Type of Variable

Blocks

Block variables and vectors

Streams

Stream variables and vectors. Both non-component variables and component dependent flow and composition variables can be accessed.

Model Utility

Parameters, balance block and pressure relief variables

Property

Property parameters

Reactions

Reactions and chemistry variables

Costing

Costing variables



Variable Definition Dialog Box • When completing a Define sheet, such as on a Calculator, Design specification or Sensitivity form, specify the variables on the Variable Definition dialog box.

• You cannot modify the variables on the Define sheet itself. • On the Variable Definition dialog box, select the variable category and Aspen Plus will display the other fields necessary to complete the variable definition. • If you are editing an existing variable and want to change the variable name, click the right mouse button on the Variable Name field. On the popup menu, click Rename.



Notes 1. If the Mass-Frac, Mole-Frac or StdVol-Frac of a component in a stream is accessed, it should not be modified. To modify the composition of a stream, access and modify the Mass-Flow, MoleFlow 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 is calculated during simulation, it should be read using the variable QCALC. 3. PRES is the specified pressure or pressure drop, and PDROP is pressure 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

Aspen Plus References: User Guide, Chapter 20, Sensitivity Related Topics: User Guide, Chapter 18, Accessing Flowsheet Variables User Guide, Chapter 19, Calculator Blocks and In-Line Fortran ©2000 AspenTech. All Rights Reserved.

Sensitivity Analysis • Allows user to study the effect of changes in input variables on process outputs. • Results can be viewed by looking at the Results form in the folder for the Sensitivity block. • Results may be graphed to easily visualize relationships between different variables. • Changes made to a flowsheet input quantity in a sensitivity block do not affect the simulation. The sensitivity study is run independently of the base-case simulation. • Located under /Data/Model Analysis Tools/Sensitivity ©2000 AspenTech. All Rights Reserved.


Sensitivity Analysis Example RECYCLE REACTOR COOL FEED REAC-OUT

COOL-OUT

SEP

Filename: CUMENE-S.BKP PRODUCT

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

» Cooler outlet temperature • What is the manipulated (varied) variable?

» Purity (mole fraction) of cumene in product stream • What is the measured (sampled) variable? ©2000 AspenTech. All Rights Reserved.


Sensitivity Analysis Results

CUMENE PRODUCT PURITY 0.85 0.9 0.95 1

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

50


Sensitivity S-1 Results Summary

75 100 125 150 175 200 225 250 275 300 325 350 VARY 1 COOL PARAM TEMP F


Uses of Sensitivity Analysis • Studying the effect of changes in input variables on process (model) outputs • Graphically representing the effects of input variables • Verifying that a solution to a design specification is feasible

• Rudimentary optimization • Studying time varying variables using a quasi-steadystate approach



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 as

equidistant 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 containing

variables defined in step 1 (Sensitivity Input Tabulate sheet). ©2000 AspenTech. All Rights Reserved.


Plotting 1. Select the column containing the X-axis variable and then select X-Axis Variable from the Plot menu. 2. Select the column containing the Y-axis variable and then select Y-Axis Variable from the Plot menu. 3. (Optional) Select the column containing the parametric variable and then select Parametric Variable from the Plot menu. 4. Select Display Plot from the Plot menu. Note: To select a column, click on the heading of the column with the left mouse button. ©2000 AspenTech. All Rights Reserved.


Notes 1. Only quantities that have been input to the flowsheet should 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 • Objective: Use a sensitivity analysis to study the effect of the recycle flowrate on the reactor duty in the cyclohexane flowsheet • Part A – Using the cyclohexane production flowsheet Workshop (saved as

CYCLOHEX.BKP), plot the variation of reactor duty (block REACT) as the recycle 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 and construct a parametric plot showing the dependence of reactor duty on the fraction split off as recycle and conversion of benzene.

Note: Both of these studies (parts A and B) should be set up within the same sensitivity analysis block. • When finished, save as filename: SENS.BKP.



Cyclohexane Production Workshop C6H6 + 3 H2 = C6H12 Benzene Hydrogen Cyclohexane PURGE Total flow = 330 kmol/hr



H2IN

VFLOW

H2RCY

VAP FEED-MIX

REACT

RXIN

BZIN T = 40 C P = 1 bar Benzene flow = 100 kmol/hr

T = 150C P = 23 bar

HP-SEP

T = 200 C Pdrop = 1 bar Benzene conv = 0.998

LTENDS


RXOUT


LIQ

CHRCY

COLFD LFLOW 30% flow to stream CHRCY

Use the RK-SOAVE property method

PRODUCT COLUMN Specify cyclohexane mole recovery of 0.9999 by varying Bottoms rate from 97 to 101 kmol/hr



Design Specifications Objective: Introduce the use of design specifications to meet process design requirements

Aspen Plus References User Guide, Chapter 21, Design Specifications Related Topics User Guide, Chapter 18, Accessing Flowsheet Variables User Guide, Chapter 19, Calculator Blocks and In-Line Fortran User Guide, Chapter 17, Convergence


Design Specifications • Similar to a feedback controller • Allows user to set the value of a calculated flowsheet quantity to a particular value • Objective is achieved by manipulating a specified input variable

• No results associated directly with a design specification • Located under /Data/Flowsheeting Options/Design Specs



Design Specification Example RECYCLE REACTOR COOL FEED REAC-OUT

COOL-OUT

SEP

Filename: CUMENE-D.BKP PRODUCT

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

» Cooler outlet temperature •

What is the manipulated (varied) variable?

» Mole fraction of cumene in stream PRODUCT •

What is the measured (sampled) variable?

» Mole fraction of cumene in stream PRODUCT = 0.98 •

What is the specification (target) to be achieved?



Steps for Using Design Specifications 1. Identify measured (sampled) variables – These are flowsheet quantities, usually calculated quantities, to be

included in the objective function (Design Spec Define sheet).

2. Specify objective function (Spec) and goal (Target) – This is the equation that the specification attempts to satisfy

(Design Spec Spec sheet). The units of the variable used in the objective function are the units for that type of variable as specified by the Units Set declared for the design specification.

3. Set tolerance for objective function – The specification is said to be converged if the objective function

equation is satisfied to within this tolerance (Design Spec Spec sheet).



Steps for Using Design Specifications (Continued) 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 (Design Spec Vary sheet). The units of the limits for the varied variable are the units for that type of variable as specified by the Units Set declared for the design specification.



Notes 1. Only quantities that have been input to the flowsheet should be manipulated. 2. The calculations performed by a design specification are iterative. Providing a good estimate for the manipulated variable will help the design specification converge in fewer iterations. This is especially important for large flowsheets with several interrelated design specifications. 3. The results of a design specification can be found under Data/Convergence/Convergence, by opening the appropriate solver block, and choosing the Results form. Alternatively, the final values of the manipulated and/or sampled variables can be viewed directly on the appropriate Stream/Block results forms.



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 indeed affect the value of the sampled variables. d. Try providing a better starting estimate for the value of the manipulated variable.



Notes (Continued) e. Try narrowing the bounds of the manipulated variable or loosening the tolerance on the objective function to help convergence. f. Make sure that the objective function does not have a flat region within the range of the manipulated variable. g. Try changing the characteristics of the convergence block associated with the design-spec (step size, number of iterations, algorithm, etc.)



Design Specification Workshop • Objective: Use a design specification in the cyclohexane flowsheet to fix the heat load on the reactor by varying the recycle flowrate.

• The cyclohexane production flowsheet workshop (saved as CYCLOHEX.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 recycle necessary to keep the cooling load on the reactor to this amount. Note: The heat convention used in Aspen Plus is that heat input to a block is positive, and heat removed from a block is negative. • When finished, save as filename: DES-SPEC.BKP



Cyclohexane Production Workshop C6H6 + 3 H2 = C6H12 Benzene Hydrogen Cyclohexane PURGE Total flow = 330 kmol/hr



H2IN

VFLOW

H2RCY

VAP FEED-MIX

REACT

RXIN

HP-SEP LTENDS

BZIN

T = 40 C P = 1 bar Benzene flow = 100 kmol/hr

T = 150C P = 23 bar


RXOUT T = 200 C Pdrop = 1 bar Benzene conv = 0.998


LIQ

CHRCY

COLFD LFLOW

30% flow to stream CHRCY

Use the RK-SOAVE property method

PRODUCT COLUMN Specify cyclohexane mole recovery of 0.9999 by varying Bottoms rate from 97 to 101 kmol/hr



Calculator Blocks Objective: Introduce usage of Excel and Fortran Calculator blocks

Aspen Plus References: User Guide, Chapter 19, Calculator Blocks and In-Line Fortran Related Topics: User Guide, Chapter 20, Sensitivity User Guide, Chapter 21, Design Specifications User Guide, Chapter 18, Accessing Flowsheet Variables User Guide, Chapter 22, Optimization


Calculator Blocks • Allows user to write equations in an Excel spreadsheet or in Fortran to be executed by Aspen Plus • Results of the execution of a Calculator block must be viewed by directly examining the values of the variables modified by the Calculator block. • Increasing the diagnostics for the Calculator block will print the value of all input and result variables in the Control Panel. • Located under /Data/Flowsheeting Options/Calculator



Calculator Block Example • Use of a Calculator block to set the pressure drop across a Heater block. RECYCLE REACTOR COOL FEED REAC-OUT

V

COOL-OUT

DELTA-P

Calculator Block DELTA-P = -10-9 * V2

SEP

PRODUCT

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

• Pressure drop across heater is proportional to square of volumetric flow into heater. ©2000 AspenTech. All Rights Reserved.


Calculator Block Example (Continued) • Which flowsheet variables must be accessed? » Volumetric flow of stream REAC-OUT This can be accessed in two different ways: 1. Mass flow and mass density of stream REAC-OUT 2. A prop-set containing volumetric flow of a mixture

» Pressure drop across block COOL • When should the Calculator block be executed? » Before block COOL • Which variables are imported and which are exported? » Volumetric flow is imported » Pressure drop is exported ©2000 AspenTech. All Rights Reserved.


Excel Aspen Plus toolbar in Excel Connect Current Cell to a Defined Variable

Import Variables

=FLOW/DENS

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



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 execution sequence (Calculator Input Sequence sheet) – Specify directly, or – Specify with import and export variables ©2000 AspenTech. All Rights Reserved.


Uses of Calculator Blocks • Feed-forward control (setting flowsheet inputs based on upstream calculated values) • Calling external subroutines • Input / output to and from external files • Writing to an external file, or the Control Panel, History File, or Report File • Custom reports



Increasing Diagnostics Increase Calculator defined variables Diagnostics message level in Control Panel or History file to 8.

Calculator Block F-1

In the Control Panel or History File

VALUES OF ACCESSED VARIABLES VARIABLE VALUE ======== ===== DP -2.032782930000 FLOW 5428.501858128 DENS 0.1204020367004 RETURNED VALUES OF VARIABLES VARIABLE VALUE ======== ===== DP -2.032790410000



Excel • Excel workbook is embedded into simulation for each Calculator block. • When saving as a backup (.bkp file), a .apmbd file is created. This file needs to be in the working directory. • Full functionality of Excel is available including VBA and Macros. • 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 (Continued) • Variables can be defined in Aspen Plus on the Define sheet or in Excel using the Aspen Plus toolbar. (It is generally faster to add variables inside Aspen Plus.) • No Fortran compiler is needed.



Excel Aspen Plus Toolbar • Connect Cell Combo Box – Use this Combo Box to attach the current cell on the Excel spreadsheet to

a Defined Variable. If the Defined Variable chosen is already connected to 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 an

existing 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 Defined Variable.

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

Variable. Clicking on this button does not delete the Defined Variable. ©2000 AspenTech. All Rights Reserved.


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 have changed the list of Defined Variables by making changes on the Calculator Define sheet.

• Changed Button – Click the Changed Button to set the "Input Changed" flag of this

Calculator block. This will cause the Calculator to be re-executed the next time you run the simulation. You should click this button if, after the calculator block is executed, you make changes to the Excel spreadsheet without making any changes on the Calculator block forms. ©2000 AspenTech. All Rights Reserved.


Windows Interoperability Objective: Introduce the use of windows interoperability to transfer data easily to and from other Windows programs.

Aspen Plus References User Guide, Chapter 37, Working with Other Windows Programs User Guide, Chapter 38, Using the Aspen Plus ActiveX Automation Server


Windows Interoperability • Copying and pasting simulation data into spreadsheets or reports • Copying and pasting flowsheet graphics and plots into reports • Creating active links between Aspen Plus and other Windows applications • OLE - Object Linking and Embedding • ActiveX automation



Windows Interoperability - Examples • Copy simulation results such as column profiles and stream results into – Spreadsheet for further analysis

– Word processor for reports and documentation – Design program – Database for case storage and management

• Copy flowsheet graphics and plots into – Word processor for reports – Slide making program for presentations

• Copy tabular data from spreadsheets into Aspen Plus for Data Regression, Data-Fit, etc. • Copy plots or tables into the Process Flowsheet Window. ©2000 AspenTech. All Rights Reserved.


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 automatically propagate results of engineering changes. – The benefits to the engineer are quick and error-free data transfer and consistent engineering results throughout the engineering work process.



Steps for Using Copy and Paste 1. Select – Select the data fields or the graphical objects. •

Multiple fields of data or objects can be selected by holding down the CTRL key while clicking the mouse on the fields. • Columns of data can be selected by clicking the column heading, or an entire grid can be selected by clicking on the top left cell.

2. Copy – Choose Copy from the Edit menu or type CTRL-C.

3. Paste – Click the mouse in the input field where you want the

information and choose Paste from the Edit menu or click CTRL-V. ©2000 AspenTech. All Rights Reserved.


OLE - Object Linking and Embedding • What is OLE? – Applications can be used within applications.

• Uses of OLE – Aspen Plus as the OLE server: Aspen Plus flowsheet graphics

can be embedded into a report document, or stream data into a CAD drawing. The simulation model is actually contained in the document, and could be delivered directly with that document. – Aspen Plus as the OLE container: Other windows applications

can be embedded within the Aspen Plus simulation.



OLE (Continued) • Examples of OLE – OLE server: If the recipient of an engineering report, for

example, wanted to review the model assumptions, he could access and run the embedded Aspen Plus model directly from the report document. – OLE container: For example, Excel spreadsheets and plots

could be used to enhance Aspen Plus flowsheet graphics.



Embedding Objects in the Flowsheet • You can embed other applications as objects into the Process 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 by double clicking on the object to edit it inside Aspen Plus. • You can also move, resize or attach the object to a block or stream in the flowsheet.



Copy and Paste Workshop 1 Objectives: Use copy and paste to copy and paste the stage temperatures into a spreadsheet.

Use the Cyclohexane flowsheet workshop (saved as CYCLOHEX.BKP) Copy the temperature profile from COLUMN into a spreadsheet. Generate a plot of the temperature using the plot wizard and copy and paste the plot into the spreadsheet. Save the spreadsheet as CYCLOHEX-result.xls ©2000 AspenTech. All Rights Reserved.

Copy and Paste Workshop 2 • Objective: Use copy and paste to copy the stream results to a stream input form. • Use the Cyclohexane flowsheet workshop (saved as CYCLOHEX.BKP) • Copy the stream results from stream RXIN into the input form. – Copy the compositions, the temperature and the pressure

separately.

Note: Reinitialize before running the simulation in order to see how many iterations are needed before and after the estimate is added. ©2000 AspenTech. All Rights Reserved.


Creating Active Links • When copying and pasting information, you can create active links between input or results fields in Aspen Plus and other applications such as Word and Excel. • The links update these applications as the process model is modified to automatically propagate results of engineering changes.



Steps for Creating Active Links 1. Open both applications. 2. Select the data (or object) that you want to paste and link. 3. Choose Copy from the Edit menu. 4. In the location where you want to paste the link, choose Paste Special from the Edit menu. 5. In the Paste Special dialog box, click the Paste Link radio button.



Paste Link Demonstration • Objective: Create an active link from Aspen Plus Results into a spreadsheet. • Start with the cumene flowsheet demonstration. • Open a spreadsheet and create a cell with the temperature for the cooler in it. • Copy and paste the link into the Aspen Plus flowsheet.

• Copy and paste a link with the flow and composition of cumene in the product stream into the spreadsheet. • Change the temperature in the spreadsheet and then rerun the flowsheet. Notice the changes.



Paste Link Workshop • Objective: Create an active link from Aspen Plus results into a spreadsheet • Use the Cyclohexane flowsheet workshop (saved as CYCLOHEX.BKP) • Copy the Condenser and Reboiler duty results from the RadFrac COLUMN Summary sheet. Use Copy with Format and copy the value, the label and the units. • Paste the results into the CYCLOHEX-results.xls spreadsheet as a link. Use Paste Special and choose Link. • Change the Reflux ratio in the column to 2 and rerun the flowsheet. Check the spreadsheet to see that the results have changed there also. Notice that the temperature profile results have not changed since they were not pasted as a link. ©2000 AspenTech. All Rights Reserved.


Saving Files with Active Links • Be sure to save both the link source file and the link container file. • If you save the link source with a different name, you must save the link container after saving the link source. • If you have active links in both directions between the two applications and you change the name of both files, you must do three Save operations: – Save the first application with a new name. – Save the second application with a new name.

– Save the first application again.



Running Files with Active Links • When you open the link source file, there is nothing special that you need to do. • When you open the link container file, you will usually see 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 Data Browser is active. ©2000 AspenTech. All Rights Reserved.


Heat Exchangers Objective: Introduce the unit operation models used for heat exchangers and heaters.

Aspen Plus References: Unit Operation Models Reference Manual, Chapter 3, Heat Exchangers


Heat Exchanger Blocks • Heater - Heater or cooler • HeatX - Two stream heat exchanger

• MHeatX - Multi-stream heat exchanger • Hetran - Interface to B-JAC Hetran block

• Aerotran - Interface to B-JAC Aerotran block



Working with the Heater Model • The Heater block mixes multiple inlet streams to produce a single outlet stream at a specified thermodynamic state. • 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 thermodynamic conditions of a stream. ©2000 AspenTech. All Rights Reserved.


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 a Heater. • One outlet heat stream can be specified for the net heat load from a Heater. • The net heat load is the sum of the inlet heat streams minus the actual (calculated) heat duty. • If you give only one specification (temperature or pressure), Heater uses the sum of the inlet heat streams as a duty specification. • If you give two specifications, Heater uses the heat streams only to calculate the net heat duty. ©2000 AspenTech. All Rights Reserved.


Working with the HeatX Model • HeatX can perform simplified or rigorous rating calculations. • Simplified rating calculations (heat and material balance calculations) can be performed if exchanger geometry is unknown or unimportant. • For rigorous heat transfer and pressure drop calculations, the heat exchanger geometry must be specified.



Working with the HeatX Model (Continued) • HeatX can model shell-and-tube exchanger types: – Counter-current and co-current – Segmental baffle TEMA E, F, G, H, J and X shells – Rod baffle TEMA E and F shells – Bare and low-finned tubes

• HeatX performs: – Full zone analysis – Heat transfer and pressure drop calculations – Sensible heat, nucleate boiling, condensation

film coefficient calculations – Built-in or user specified correlations



Working with the HeatX Model (Continued) • HeatX cannot: – Perform design calculations – Perform mechanical vibration analysis – Estimate fouling factors



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



Working with the MHeatX Model • MHeatX can be used to represent heat transfer between multiple hot and cold streams. • Detailed, rigorous internal zone analysis can be performed to determine pinch points. • MHeatX uses multiple Heater blocks and heat streams to enhance flowsheet convergence. • Two-stream heat exchangers can also be modeled using MHeatX.



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 Hetran program for designing and simulating shell and tube heat exchangers. • The Aerotran block is the interface to the B-JAC Aerotran program for designing and simulating air-cooled heat exchangers.

• Information related to the heat exchanger configuration and geometry is entered through the Hetran or Aerotran standalone program interface.



Working with HTRI-IST • The HTRIIST block called HTRI IST as a subroutine for licensed IST users only. • Aspen Plus properties are used. • Users can create a new IST model or access an existing model.

• Key IST results are retrieved and reported inside Aspen Plus.



Heat Curves • All of the heat exchanger models are able to calculate Heat Curves (Hcurves). • Tables can be generated for various independent variables (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



Heat Curve Plot



HeatX Workshop • Objective: Compare the simulation of a heat exchanger that uses water to cool a hydrocarbon mixture using three methods: a shortcut HeatX, a rigorous HeatX and two Heaters connected with a Heat stream. • Hydrocarbon stream – Temperature: 200 C – Pressure: 4 bar – Flowrate: 10000 kg/hr – Composition: 50 wt% benzene, 20% styrene,

20% ethylbenzene and 10% water

• Cooling water – Temperature: 20 C

– Pressure: 10 bar – Flow rate: 60000 kg/hr – Composition: 100% water ©2000 AspenTech. All Rights Reserved.


HeatX Workshop (Continued) When finished, save as filename: HEATX.BKP HEATER-1 HCLD-IN

HCLD-OUT

SHOT-OUT

RHOT-OUT

SHEATX SCLD-IN

SCLD-OUT

RHEATX RCLD-IN

RCLD-OUT

Q-TRANS

HEATER-2 HHOT-IN

HHOT-OUT

SHOT-IN

RHOT-IN

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. ©2000 AspenTech. All Rights Reserved.


HeatX Workshop (Continued) • Shortcut HeatX simulation: – Hydrocarbon stream exit has a vapor fraction of 0 – No pressure drop in either stream

• Two Heaters simulation: – Use the same specifications as the shortcut HeatX simulation

• Rigorous HeatX simulation: – Hydrocarbons in shell leave with a vapor fraction of 0 – Shell diameter 1 m, 1 tube pass – 300 bare tubes, 3 m length, pitch 31 mm, 21 mm ID, 25 mm OD – All nozzles 100 mm

– 5 baffles, 15% cut – Create heat curves containing all info required for thermal design. – Change the heat exchanger specification to Geometry and re-run. ©2000 AspenTech. All Rights Reserved.


Pressure Changers Objective: Introduce the unit operation models used to change pressure: pumps, compressors, and models for calculating pressure change through pipes and valves.

Aspen Plus References: Unit Operation Models Reference Manual, Chapter 6, Pressure Changers ©2000 AspenTech. All Rights Reserved.

Pressure Changer Blocks • Pump - Pump or hydraulic turbine • Compr - Compressor or turbine

• MCompr - Multi-stage compressor or turbine • Valve - Control valve

• Pipe - Single-segment pipe • Pipeline - Multi-segment pipe



Working with the Pump Model • The Pump block can be used to simulate: – Pumps – Hydraulic turbines

• Power requirement is calculated or input. • A Heater model can be used for pressure change calculations only. • Pump is designed to handle a single liquid phase. • Vapor-liquid or vapor-liquid-liquid calculations can be specified to check outlet stream phases.



Pump Performance Curves • Rating can be done by specifying scalar parameters or a pump performance curve. • Specify: – Dimensional curves •

Head versus flow • Power versus flow – Dimensionless curves: •

Head coefficient versus flow coefficient



Working with the Compr Model • 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 phase calculations.



Working with the MCompr Model • The MCompr block can be used to simulate: – Multi-stage polytropic centrifugal compressor – Multi-stage polytropic positive displacement compressor – Multi-stage isentropic compressor – Multi-stage isentropic turbine

• MCompr can have an intercooler between each stage, and an aftercooler after the last stage. – You can perform one-, two-, or three- phase flash calculations

in the intercoolers. – Each cooler can have a liquid knockout stream, except the

cooler after the last stage. – Intercooler specifications apply to all subsequent coolers. ©2000 AspenTech. All Rights Reserved.


Compressor Performance Curves • Rating can be done by specifying a compressor performance curve. • Specify: – Dimensional curves •

Head versus flow • Power versus flow – Dimensionless curves: •

Head coefficient versus flow coefficient

• Compr cannot handle performance curves for a turbine.



Work Streams • Any number of inlet work streams can be specified for pumps and compressors. • One outlet work stream can be specified for the net work load from pumps or compressors. • The net work load is the sum of the inlet work streams minus the actual (calculated) work.



Working with the Valve Model • The Valve block can be used to simulate: – Control valves – Pressure drop

• The pressure drop across a valve is related to the valve flow coefficient. • Flow is assumed to be adiabatic. • Valve can perform single or multiple phase calculations.



Working with the Valve Model (Continued) • The effect of head loss from pipe fittings can be included. • There are three types of calculations: – Adiabatic flash for specified outlet pressure (pressure changer) – Calculate valve flow coefficient for specified outlet pressure

(design) – Calculate outlet pressure for specified valve (rating)

• Valve can check for choked flow. • Cavitation index can be calculated.



Working with the Pipe Model • 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 pressure and updates the state variables of the inlet stream. • Entrance effects are not modeled.



Pressure Changers Block Example • Add a Compressor and a Valve to the cumene flowsheet. COMPR RECYCLE VALVE RECYCLE2 RECYCLE3

Outlet Pressure = 3 psig

Polytropic compressor model using GPSA method Discharge pressure = 5 psig

FEED REAC-OUT REACTOR

COOL-OUT

SEP

COOL

PRODUCT

Filename: CUMENE-P.BKP



Pressure Changers Workshop • Objective: Add pressure changer unit operations to the Cyclohexane flowsheet. • Start with the Cyclohexane Workshop flowsheet (CYCLOHEX.BKP)



Pressure Changers Workshop (Continued) Isentropic 4 bar pressure change COMP

H2IN

PURGE VFLOW

VAP

H2RCY2 FEED-MIX

PURGE2

20 bar outlet pressure Globe valve V810 equal percent flow 1.5-in size

REACT

RXIN

FEEDPUMP BZIN

H2RCY

VALVE

HP-SEP RXOUT

BZIN2 CHRCY3

Pump efficiency = 0.6 Driver efficiency = 0.9

LTENDS LIQ

PIPE

PUMP CHRCY2

Performance Curve Head Flow [m] [cum/hr] 40 20 250 10 300 5 400 3 ©2000 AspenTech. All Rights Reserved.

Carbon Steel Schedule 40 1-in diameter 25-m length

CHRCY

COLFD

LFLOW

26 bar outlet pressure

PRODUCT COLUMN

When finished, save as filename: PRESCHNG.BKP Introduction to Aspen Plus

Flowsheet Convergence Objective: Introduce the idea of convergence blocks, tear streams and flowsheet sequences

Aspen Plus References User Guide, Chapter 17, Convergence ©2000 AspenTech. All Rights Reserved.

Convergence Blocks • Every design specification and tear stream has an associated convergence block. • Convergence blocks determine how guesses for a tear stream or design specification manipulated variable are updated from iteration to iteration. • Aspen Plus-defined convergence block names begin with the character “$.” – User defined convergence block names must not begin with the

character “$.”

• To determine the convergence blocks defined by Aspen Plus, look under the “Flowsheet Analysis” section in the Control Panel messages. • User convergence blocks can be specified under /Data/Convergence/Convergence... ©2000 AspenTech. All Rights Reserved.


Convergence Block Types • Different types of convergence blocks are used for different purposes: – To converge tear streams: • • • •

WEGSTEIN DIRECT BROYDEN NEWTON

– To converge design specifications: • • •

SECANT BROYDEN NEWTON

– To converge design specifications and tear streams: • •

BROYDEN NEWTON

– For optimization: •

•

SQP COMPLEX

• Global convergence options can be specified on the Convergence ConvOptions Defaults form. ©2000 AspenTech. All Rights Reserved.


Flowsheet Sequence • To determine the flowsheet sequence calculated by Aspen Plus, look under the “COMPUTATION ORDER FOR THE FLOWSHEET” section in the Control Panel, or on the left-hand pane of the Control Panel window. • User-determined sequences can be specified on the Convergence Sequence form.

• User-specified sequences can be either full or partial.



Tear Streams • Which are the recycle streams? • Which are the possible tear streams? S7

S1

B1 MIXER

S2

B2 MIXER

S3

B3 FSPLIT

S4

B4

S5

FSPLIT

S6

• A tear stream is one for which Aspen Plus makes an initial guess, and iteratively updates the guess until two consecutive guesses are within a specified tolerance. • Tear streams are related to, but not the same as recycle streams. ©2000 AspenTech. All Rights Reserved.


Tear Streams (Continued) • To determine the tear streams chosen by Aspen Plus, look under the “Flowsheet Analysis” section in the Control Panel. • User-determined tear streams can be specified on the Convergence Tear form. • Providing estimates for tear streams can facilitate or speed up flowsheet convergence (highly recommended, otherwise the default is zero). • If you enter information for a stream that is in a “loop,” Aspen Plus will automatically try to choose that stream to be a tear stream. ©2000 AspenTech. All Rights Reserved.


Reconciling Streams • Simulation results for a stream can be copied onto the its input form. • Select a stream on the flowsheet, click the right mouse button and select “Reconcile” from the list to copy stream results to the input form. – Two state variables must be selected for the stream flash

calculation. – Component flows, or component fractions and total flow can be

copied. – Mole, mass, or standard liquid volume basis can be selected.



Convergence Workshop • Objective – Converge this flowsheet. – Start with the file CONVERGE.BKP. 100 lbmol/hr

T=70 F P=35 psia 50 lbmol/hr Ethylene Glycol

T=165 F P=15 psia FEED XH20 = 0.4 XMethanol = 0.3 XEthanol = 0.3

COLUMN

GLYCOL DIST

PREHEATR BOT-COOL VAPOR

Area = 65 sqft

PREFLASH FEED-HT

Theoretical Stages = 10 Reflux Ratio = 5 Distillate to Feed Ratio = 0.2 Column Pressure = 1 atm Feed Stage = 5 Total Condenser

DP=0 Q=0 LIQ

BOT

Use NRTL-RK Property Method ©2000 AspenTech. All Rights Reserved.

When finished, save as filename: CONV-R.BKP Introduction to Aspen Plus

Convergence Workshop (Continued) • Hints for Convergence Workshop – Questions to ask yourself: • • • • •

What messages are displayed in the control panel? Why do some of the blocks show zero flow? What is the Aspen Plus-generated execution sequence for the flowsheet? Which stream does Aspen Plus choose as a tear stream? What are other possible tear streams?

– Recommendation •

Give initial estimates for a tear stream. • Of the three possible tear streams you could choose, which do you know the most about? (Note: If you enter information for a stream that is in a “loop,” Aspen Plus will automatically choose that stream to be a tear stream and set up a convergence block for it.)



Convergence Workshop (Continued) • Questions to ask yourself: – Does the flowsheet converge after entering initial estimates for the tear

stream? – If not, why not? (see control panel) – How is the err/tol value behaving, and what is its value at the end of the run? – Does it appear that increasing the number of convergence iterations will help? – What else can be tried to improve this convergence?

• Recommendation – Try a different convergence algorithm (e.g. Direct, Broyden, or Newton).

Note: You can either manually create a convergence block to converge the tear stream of your choice, or you can change the default convergence method for all tear streams on the Convergence Conv Options Defaults Default Methods sheet.



Full-Scale Plant Modeling Workshop • Objective: Practice and apply many of the techniques used in this course and learn how to best approach modeling projects



Full-Scale Plant Modeling Workshop • Objective: Model a methanol plant. • The process being modeled is a methanol plant. The basic feed streams to the plant are Natural Gas, Carbon Dioxide (assumed to be taken from a nearby Ammonia Plant) and Water. The aim is to achieve the methanol production rate of approximately 62,000 kg/hr, at a purity of at least 99.95 % wt. • This is a large flowsheet that would take an experienced engineer more than an afternoon to complete. Start building the flowsheet and think about how you would work to complete the project. ©2000 AspenTech. All Rights Reserved.


General Guidelines • Build the flowsheet one section at a time. • Simplify whenever possible. Complexity can always be added later. • Investigate the physical properties. – Use Analysis.

– Check if binary parameters are available. – Check for two liquid phases. – Use an appropriate equation of state for the portions of the

flowsheet involving gases and use an activity coefficient model for the sections where non-ideal liquids may be present.



Full-Scale Plant Modeling Workshop Air

FURNACE

Fuel

MEOHRXR

SYNCOMP

SPLIT1

COOL4

E121

SPLIT2

FL3 COOL2 COOL3

MKUPST

M2 FEEDHTR

FL2

MIX2

COOL1

CIRC E122 FL4

BOILER FL1 H2OCIRC

REFORMER

CO2 CO2COMP M1

E223

E124

SATURATE

NATGAS

TOPPING

CH4COMP

FL5

M4

REFINING MKWATER



Part 1: Front-End Section

MKUPST

M2

From Furnace

FEEDHTR To BOILER

REFORMER

H2OCIRC CO2COMP CO2

NATGAS


M1

SATURATE

CH4COMP


Part 1: Front-End Section (Continued) • Carbon Dioxide Stream – CO2 – Temperature

• Circulation Water - H2OCIRC – Pure water stream

= 43 C

– Pressure = 1.4 bar

– Flow = 410000 kg/hr

– Flow = 24823 kg/hr

– Temperature

– Mole Fraction

– Pressure = 26 bar

• • • • •

CO2 H2 H2O CH4 N2 -

0.0094 0.0028

= 195 C

0.9253 0.0606 0.0019

• Makeup Steam - MKUPST – Stream of pure steam

• Natural Gas Stream - NATGAS


– Temperature = 26 C

– Pressure = 26 bar

– Pressure = 21.7 bar

– Vapor Fraction = 1


– Adjust the makeup steam flow to

– Mole Fraction • • • • •

CO2 CH4 N2 C2H6 C3H8


-

0.0059 0.9539 0.0008 0.0391 0.0003

achieve a desired steam to methane molar ratio of 2.8 in the Reformer feed REFFEED.


Part 1: Front-End Section (Continued) • Carbon Dioxide Compressor - CO2COMP –

Discharge Pressure = 27.5 bar – Compressor Type = 2 stage

• Natural Gas Compressor - CH4COMP –

Discharge Pressure = 27.5 bar

–

Compressor Type = single stage

• Reformer Process Side Feed Stream Pre-Heater - FEEDHTR –

Exit Temperature = 560 C – Pressure drop = 0

• Saturation Column - SATURATE –

1.5 inch metal pall ring packing. – Estimated HETP = 10 x 1.5 inches = 381 mm –

Height of Packing = 15 meters – No condenser and no reboiler.

• Reformer Reactor - REFORMER –

Consists of two parts: the Furnace portion and the Steam Reforming portion – Exit Temperature of the Steam Reforming portion = 860 C –

Pressure = 18 bar



Part 1: Front-End Section Check Temperature C Pressure bar Vapor Frac Mole Flow kmol/hr Mass Flow kg/hr Volume Flow cum/hr Enthalpy MMkcal/hr Mole Flow kmol/hr CO CO2 H2 WATER METHANOL METHANE NITROGEN BUTANOL DME (DIMETHYLETHER) ACETONE OXYGEN ETHANE PROPANE


Reformer Product 860 18 1 10266.6541 139696.964 53937.9538 -213.933793 1381.68394 751.335833 4882.77068 2989.25863 0.000686384 258.513276 3.08402321 0 2.06E-10 2.18E-08 1.80E-15 0.007007476 6.74097E-07


Part 2: Heat Recovery Section SYNCOMP To Methanol Loop

COOL4 FL3

COOL2

COOL3

FL2

COOL1 From Reformer BOILER

FL1

To REFINING


To TOPPING


Part 2: Heat Recovery Section (Continued) • This section consists of a series of heat exchangers and flash vessels used to recover the available energy and water in the Reformed Gas stream. BOILER Exit temperature = 166 C

Exit Pressure = 18 bar

COOL1 Exit temperature = 136 C Exit Pressure = 18 bar

FL1 Pressure Drop = 0 bar Heat Duty = 0 MMkcal/hr

FL2 Exit Pressure = 17.7 bar Heat Duty = 0 MMkcal/hr

COOL2 Exit temperature = 104 C Exit Pressure = 17.9 bar

COOL3 Exit temperature = 85 C Pressure Drop = 0.1 bar

COOL4 Exit temperature = 40 C Exit Pressure = 17.6 bar ©2000 AspenTech. All Rights Reserved.

FL3 Exit Pressure = 17.4 bar Heat Duty = 0 MMkcal/hr

SYNCOM Two Stage Polytropic compressor Discharge Pressure = 82.5 bar Intercooler Exit Temperature = 40 C Introduction to Aspen Plus

Part 2: Heat Recovery Section Check

Temperature C Pressure bar Vapor Frac Mole Flow kmol/hr


To Methanol Loop 40.0 82.50 0.997465769 7302.28917


Part 3: Methanol Synthesis Section MEOHRXR To Furnace

SPLIT1 From SYNCOMP E121 SPLIT2 MIX2

CIRC E122

FL4 E223

E124 To FL5



Part 3: Methanol Synthesis Section (Continued) •

Methanol Reactor - MEOHRXR – – – –

Tube cooled reactor Exit Temperature from the tubes = 240 C No pressure drop across the reactor Reactions • • • • •

•

–

–

E124 – –

Exit Temperature - 45 C Exit Pressure - 75.6 bar


–

Exit Pressure = 75.6 bar

–

Heat Duty = 0 MMkcal/hr

CIRC – Single stage compressor – Discharge Pressure = 83 bar – Discharge Temperature = 55 C

•

SPLIT1 – Split Fraction = 0.8 to stream to E121

•

SPLIT2 – Stream PURGE = 9000 kg/hr – Stream RECYCLE = 326800 kg/hr

Cold Side Exit Temperature - 120 C

Exit Temperature - 60 C Exit Pressure - 77.3 bar

FL4

•

E223 –

•

•

Exit Temperature - 150 C Exit Pressure - 81 bar

E122 –

•

(Equilibrium) (+15 C Temperature Approach) (Molar extent 0.2kmol/hr) (Molar extent 0.8kmol/hr) (Molar extent 0.3kmol/hr)

E121 –

•

CO + H2O <-> CO2 + H2 CO2 + 3H2 <-> CH3OH + H2O 2CH3OH <-> DIMETHYLETHER + H2O 4CO + 8H2 <-> N-BUTANOL + 3H2O 3CO + 5H2 <-> ACETONE + 2H2O


Part 3: Methanol Synthesis Section Check Temperature C Pressure bar Vapor Frac Mole Flow kmol/hr


To FL5 45.0 75.60 0.000 2673.354

Temperature C Pressure bar Vapor Frac Mole Flow kmol/hr Mass Flow kg/hr Volume Flow cum/hr Enthalpy MMkcal/hr Mole Flow kmol/hr CO CO2 H2 WATER METHANOL METHANE NITROGEN BUTANOL DME ACETONE OXYGEN ETHANE PROPANE

MEOHRXR Product 249.7 83.00 1.000 29091.739 413083.791 15637.807 -559.129 799.563 3137.144 13379.353 644.301 2140.046 8896.430 91.428 0.845 1.864 0.588 0.000 0.177 0.000


Part 4: Distillation Section

To Furnace

From FL4

From COOL1

FL5

From COOL2

TOPPING REFINING

M4

MKWATER



Part 4: Distillation Section (Continued) •

Makeup Steam - MKWATER – – – – –

•

Stream of pure water Flow = 10000 kg/hr Pressure = 5 bar Temperature = 40 C Adjust the make-up water flow (stream MKWATER) to the CRUDE stream to achieve a stream composition of 23 wt.% of water in the stream feeding the Topping column (stream TOPFEED) to achieve 100 ppm methanol in the Refining column BTMS stream.

Topping Column - TOPPING – – – – – – – – – – – – –

Number of Stages = 51 (including condenser and reboiler) Condenser Type = Partial Vapor/Liquid Feed stage = 14 Distillate has both liquid and vapor streams Distillate rate = 1400 kg/hr Pressure profile: stage 1 = 1.5 bar and stage 51 = 1.8 bar Distillate vapor fraction = 99 mol% Stage 2 heat duty = -7 Mmkcal/hr Stage 51 heat duty Specified by the heat stream Reboiler heat duty is provided via a heat stream from block COOL2 Boil-up Ratio is approximately 0.52 Valve trays The column has two condensers. To represent the liquid flow connections a pumparound can be used between stage 1 and 3.



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 weight of 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 4: Distillation Section Check Temperature C Pressure bar Vapor Frac Mole Flow kmol/hr Mass Flow kg/hr Volume Flow cum/hr Enthalpy MMkcal/hr Mole Flow kmol/hr CO CO2 H2 WATER METHANOL METHANE NITROGEN BUTANOL DME ACETONE OXYGEN ETHANE PROPANE


TOPFEED LTENDS SECPURGE REFINE PRODUCT BTMS LIQPURGE FUSELOIL 43.8 33.1 33.1 85.8 75.1 120.1 74.8 90.4 5.00 1.50 1.50 1.80 1.52 2.00 1.50 1.95 0.001 1.000 0.000 0.000 0.000 0.000 0.000 0.000 3029.767 33.807 0.341 2995.618 1928.736 1047.117 0.031 19.733 82623.475 1388.896 11.104 81223.475 61800.974 18871.500 1.000 550.000 111.175 573.782 0.014 107.201 83.975 21.058 0.001 0.722 -186.388 -2.802 -0.020 -178.587 -107.391 -69.633 -0.002 -1.199 0.004 26.537 0.014 1054.851 1945.891 1.267 0.003 0.798 0.116 0.285 0.000 0.000 0.000

0.004 26.535 0.014 0.000 5.591 1.267 0.003 0.000 0.116 0.276 0.000 0.000 0.000

0.000 0.002 0.000 0.000 0.334 0.000 0.000 0.000 0.000 0.005 0.000 0.000 0.000

0.000 0.000 0.000 1054.851 1939.966 0.000 0.000 0.798 0.000 0.004 0.000 0.000 0.000

0.000 0.000 0.000 0.000 1928.733 0.000 0.000 0.000 0.000 0.004 0.000 0.000 0.000

0.000 0.000 0.000 1046.942 0.059 0.000 0.000 0.117 0.000 0.000 0.000 0.000 0.000

0.000 0.000 0.000 0.000 0.031 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

0.000 0.000 0.000 7.910 11.143 0.000 0.000 0.681 0.000 0.000 0.000 0.000 0.000


Part 5: Furnace Section

To REFORMER

From FL5 Air

From SPLIT2 FURNACE

Fuel



Part 5: Furnace Section (Continued) • Air to Furnace - AIR – Temperature = 366 C – 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 – Flow = 9436 kg/hr – Conditions and composition are the same as for the natural gas

stream



Maintaining Aspen Plus Simulations Objective: Introduce how to store simulations and retrieve them from your computer environment

Aspen Plus References: User Guide, Chapter 15, Managing Your Files ©2000 AspenTech. All Rights Reserved.

File Formats in Aspen Plus File Type Extension

Format Description

Document

*.apw

Binary

File containing simulation input and results and intermediate convergence information

Backup

*.bkp

ASCII

Archive file containing simulation input and results

Template

*.apt

ASCII

Template containing default inputs

Input

*.inp

Text

Simulation input

Run Message *.cpm

Text

Calculation history shown in the Control Panel

History

*.his

Text

Detailed calculation history and diagnostic messages

Summary

*.sum

ASCII

Simulation results

Problem Definition

*.appdf

Binary

File containing arrays and intermediate convergence information used in the simulation calculations

Report

*.rep

Text

Simulation report



File Type Characteristics • Binary files – Operating system and version specific – Not readable, not printable

• ASCII files – Transferable between operating systems – Upwardly compatible – Contain no control characters, “readable” – Not intended to be printed

• Text files – Transferable between operating systems

– Upwardly compatible – Readable, can be edited – Intended to be printed ©2000 AspenTech. All Rights Reserved.


How to Store a Simulation Three ways to store simulations: Document

Backup

Input

(*.apw)

(*.bkp)

(*.inp)

Simulation definition

Yes

Yes

Yes

Convergence info

Yes

No

No

Results

Yes

Yes

No

Flowsheet Graphics

Yes

Yes

Yes/No

User readable

No

No

Yes

Open/save speed

High

Low

Lowest

Space requirements

High

Low

Lowest



Template Files • Template files are used to set your personal preferences: – Units of measurement – Property sets for stream reports – Composition basis – Stream report format – Global flow basis for input specifications – Setting Free-Water option – Selection for Stream-Class – Property Method – (Required) Component list – Other application-specific defaults



How to Create a Personal Template • Any flowsheet (complete or incomplete) can be saved as a template file. • In order to have a personal template appear on the Personal sheet of the New dialog box, put the template file into the Aspen Plus GUI\Templates\Personal folder. • The text on the Setup Specifications Description sheet will appear in the Preview window when the template file is selected in the New dialog box.



Maintaining Your Computer • Aspen Plus 10 runs best on a healthy computer. • Minimum RAM GUI only Win 95 and 32 MB Win 98 Windows NT 64 MB

GUI and Engine 64 MB 96 MB

• Having more is better -- if near minimum, avoid running too many other programs along with Aspen Plus.

• Active links increase needed RAM. ©2000 AspenTech. All Rights Reserved.


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 space contiguous.



Customizing the Look of Your Flowsheet Objective: Introduce several ways of annotating your flowsheet to create informative Process Flow Diagrams

Aspen Plus References: User Guide, Chapter 14, Annotating Process Flowsheets Related Topics: User Guide, Chapter 37, Working with Other Windows Programs ©2000 AspenTech. All Rights Reserved.

Customizing the Process Flow Diagram • Add annotations – Text – Graphics – Tables

• Add OLE objects – Add a titlebox – Add plots or diagrams

• Display global data – Stream flowrate, pressure and

temperature – Heat stream duty – Work stream power – Block duty and power

• Use PFD mode – Change flowsheet connectivity



Viewing • Use the View menu to select the elements that you wish to view: – PFD Mode – Global Data – Annotation – OLE Objects

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



Adding Annotation • Use the Draw Toolbar to add text and graphics. (Select Toolbar… from the View menu to select the Draw Toolbar if it is not visible.) • To create a stream table, click on the Stream Table button on the Results Summary Streams Material sheet. • Annotation objects can be attached to flowsheet elements such as streams or blocks.



Example of a Stream Table 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

Pressure

PSI

14.60

36.00

14.70

14.70

14.70

0.054

1.000

0.000

1.000

1.000

44.342

80.000

41.983

44.342

2.359

Vapor Frac Mole Flow

LBMOL/HR

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

38.017

38.085

0.069

CUMENE

38.085

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


Adding Global Data • On the Results View sheet when selecting Options from the Tools menu, choose the block and stream results that you want displayed as Global Data.

• Check Global Data on the View menu to display the data on the flowsheet. 130 15

Temperature (F)

106

Pressure (psi) Flow Rate (lb/hr) Q

RECYCLE

Duty (Btu/hr)

220 36 4808

REACTOR

855

130

15

15

4914

4914

COOL

FEED REAC-OUT Q=0

COOL-OUT

130 SEP

15 4808

Q=-2492499 Q=0 PRODUCT



Using PFD Mode • In this mode, you can add or delete unit operation icons to the flowsheet for graphical purposes only. • Using PFD mode means that you can change flowsheet connectivity to match that of your plant. • PFD-style drawing is completely separate from the graphical simulation flowsheet. You must return to simulation mode if you want to make a change to the actual simulation flowsheet. • PFD Mode is indicated by the Aqua border around the flowsheet.



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 piece of equipment in a plant. – For example, a reactor with a liquid product and a vent may

need to be modeled using an RStoic reactor and a Flash2 block. In the report, only one unit operation icon is needed to represent the unit in the plant.

• On the other hand, some pieces of equipment may not need to be explicitly modeled in the simulation flowsheet. – For example, pumps are frequently not modeled in the

simulation 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 • Part A – Using the cyclohexane production Workshop (saved as

CYCLOHEX.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 graphical

purposes only. ©2000 AspenTech. All Rights Reserved.


Estimation of Physical Properties Objective: Provide an overview of estimating physical property parameters in Aspen Plus

Aspen Plus References: 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 estimate: – 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 methods and 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 – Within another Run Type: Flowsheet, Property Analysis, Data

Regression, PROPERTIES PLUS or Assay Data Analysis

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

• Property Estimation information is accessed in the Properties Estimation folder.



Estimation Methods and Requirements • User Guide, Chapter 30, Estimating Property Parameters, has a complete list of properties that can be estimated, as well as the available estimation methods and their respective requirements. • This same information is also available under the on-line help in the estimation forms.



Steps For Using Property Estimation 1. Define molecular structure on the Properties Molecular Structure form. 2. Enter any experimental data using Parameters or Data forms. – Experimental data such as normal boiling point (TB) is very

important for many estimation methods. It should be entered whenever possible.

3. Activate Property Estimation and choose property estimation options on the Properties Estimation Input form.



Defining Molecular Structure • Molecular structure is required for all group-contribution 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 Physical Property Data Reference Manual, Chapter 3, Group Contribution Method Functional Groups. ©2000 AspenTech. All Rights Reserved.


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 must be consecutive starting with 1.) 3. Go to the Properties Molecular Structure Object Manager, choose the component, and select Edit. 4. On the Molecular Structure General sheet, define the molecule by its 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 the Components Specifications form, enter a Component ID, but do not enter a Component name or Formula. ©2000 AspenTech. All Rights Reserved.


Example of Defining Molecular Structure • Example of defining molecular structure for isobutyl alcohol using the general method – Sketch the structure of the molecule, and assign a number to

each atom, omitting hydrogen.

C1 C2

C4

O5

C3 ©2000 AspenTech. All Rights Reserved.


Example of Defining Molecular Structure • Go to the Properties Molecular Structure Object Manager, choose the component, and select Edit. • On Properties Molecular Structure General sheet, describe molecule by its connectivity, two atoms at a time.



Atom Types Current available atom types: Atom Type

Description

Atom Type

Description

C

Carbon

P

Phosphorous

O

Oxygen

Zn

Zinc

N

Nitrogen

Ga

Gallium

S

Sulfur

Ge

Germanium

B

Boron

As

Arsenic

Si

Silicon

Cd

Cadmium

F

Fluorine

Sn

Tin

CL

Chlorine

Sb

Antimony

Br

Bromine

Hg

Mercury

I

Iodine

Pb

Lead

Al

Aluminum

Bi

Bismuth



Bond Types • Current available bond types: – 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 chain bonds. ©2000 AspenTech. All Rights Reserved.


Steps For Using Property Estimation

 1.

Define molecular structure on the Properties Molecular Structure form.

2. Enter any experimental data using Parameters or Data forms. – Experimental data such as normal boiling point (TB) is very





Example of Entering Additional Data • Enter following data for isobutyl alcohol into the 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. • Enter the parameters, the components, and the values.



Steps For Using Property Estimation

1. 2.

Define molecular structure on the Properties Molecular Structure form. Enter any experimental data using Parameters or Data forms. – Experimental data such as normal boiling point (TB) is very





Activating Property Estimation • To turn on Property Estimation, go to the Properties Estimation Input Setup sheet, and select one of the following: – Estimate all missing parameters •

Estimates all missing required parameters and any parameters you may 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 then specify on the appropriate additional sheets)



Property Estimation Notes • You can save your property data specifications, structures, and estimates as backup files, and import them into other simulations (Flowsheet, Data Regression, Property Analysis, or Assay Data Analysis Run-Types.) • You can change the Run type on the Setup Specifications Global sheet to continue the simulation in the same file. • If you want to change the Run type back to Property Estimation from another Run type, no flowsheet information is lost even though it may not be visible in the Property Estimation mode. ©2000 AspenTech. All Rights Reserved.


Property Estimation Workshop • Objective: Estimate the properties of a dimer, ethycellosolve. • Ethylcellosolve is not in any of the Aspen Plus databanks. • Use a Run Type of Property Estimation, and estimate the properties for the new component. • The formula for the component is shown below, along with the normal boiling point obtained from literature. Formula: CH3 - CH2 - O - CH2 - CH2 - O - CH2 - CH2 - OH TB = 195 C When finished, save as filename: PCES.BKP



Property Estimation Workshop (Continued) 1. Use a Run Type of Property Estimation and enter the structure and data for the Dimer. 2. Run the estimation, and examine the results. – Note that the results of the estimation are automatically

written 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, and choose Do not estimate any parameters. 5. Optionally, add a flowsheet and use this component.



Electrolytes Objective: Introduce the electrolyte capabilities in Aspen Plus

Aspen Plus References: User Guide, Chapter 6, Specifying Components Physical Property Methods and Models Reference Manual, Chapter 5, Electrolyte Simulation


Electrolytes Examples • Solutions with acids, bases or salts • 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 • Liquid phase reactions are always at chemical equilibrium • Presence of ions in the liquid phase requires non-ideal solution 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) ©2000 AspenTech. All Rights Reserved.


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 before

considering solution chemistry – Ions and precipitated salts cannot be apparent components – Specifications must be made in terms of apparent components

and 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+ + ClNaCl(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 ©2000 AspenTech. All Rights Reserved.


Electrolyte Wizard (Continued) • Generated chemistry can be modified. Simplifying the Chemistry can make the simulation more robust and decrease execution time. Note: It is the user’s responsibility to ensure that the Chemistry 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: • Kinetic reactors: • Shortcut distillation: • Rigorous distillation:


RGibbs and REquil RPlug, RCSTR, and RBatch Distl, DSTWU and SCFrac MultiFrac and PetroFrac


Limitations of Electrolytes (Continued) • Restrictions using the Apparent component approach: – Chemistry may not contain any volatile species on the right

side of the reactions. – Chemistry for liquid-liquid equilibrium may not contain

dissociation 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 streams containing aqueous electrolytes. Use the Electrolyte Wizard to generate the Chemistry. Temp = 25 C Pres = 1 bar 10 kmol/hr H2O

Filename: ELEC1.BKP

1 kmol/hr HCl HCL

VAPOR

MIX NAOH

Temp = 25 C Pres = 1 bar 10 kmol/hr H2O

1.1 kmol/hr NaOH ©2000 AspenTech. All Rights Reserved.

MIXED

MIXER

FLASH

FLASH2

Isobaric Molar vapor fraction = 0.75

P-drop = 0 Adiabatic LIQUID Introduction to Aspen Plus

Steps for Using Electrolytes 1. Specify the possible apparent components on the Components Specifications Selection sheet. 2. Click on the Elec Wizard button to generate components and reactions for electrolyte systems. There are 4 steps: 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. ©2000 AspenTech. All Rights Reserved.


Steps for Using Electrolytes (Continued)



Steps for Using Electrolytes (Continued) Step 1: Define base components and select reaction generation options.



Steps for Using Electrolytes (Continued) Step 2: Remove any undesired species or reactions from the generated list.



Steps for Using Electrolytes (Continued) Step 3: Select simulation approach for electrolyte calculations.



Steps for Using Electrolytes (Continued) 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 acid waste water stream using lime (Calcium Hydroxide). Use the Electrolyte Wizard to generate the Chemistry. Use the true component approach. Temperature = 25C Pressure = 1 bar Flowrate = 10 kmol/hr 5 mole% sulfuric acid solution

Note: Remove from the chemistry: CaSO4(s) CaSO4•1:2W:A(s)

WASTEWAT B1 LIME

Temperature = 25C Temperature = 25C P-drop = 0 Pressure = 1 bar Flowrate = 10 kmol/hr 5 mole% lime (calcium hydroxide) solution ©2000 AspenTech. All Rights Reserved.

LIQUID

When finished, save as filename: ELEC.BKP Introduction to Aspen Plus

Electrolyte Workshop (Continued) 1. Open a new Electrolytes with Metric units flowsheet. 2. Draw the flowsheet.

3. Enter the necessary components and generate the electrolytes using the Electrolytes Wizard. Select the true approach and remove the solid salts not needed from 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 the Electrolyte Wizard to generate the Chemistry. Use the apparent component approach. VAPOR Saturated vapor

Above stage 3 P = 15 psia 10,000 lbs/hr SOURWAT

Mass fractions: H2O 0.997 NH3 0.001 H2S 0.001 CO2 0.001

B1

Theoretical trays: 9 (does not include condenser) Partial condenser Reflux Ratio (Molar): 25 No reboiler

STEAM

On stage 10 P = 15 psia Vapor frac = 1 2,000 lbs/hr ©2000 AspenTech. All Rights Reserved.

BOTTOMS Introduction to Aspen Plus

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 the electrolytes using the Electrolytes Wizard. Select the apparent approach and remove all solid salts used in the generated reactions. Questions: Why aren’t the ionic species’ compositions displayed 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 tabulate the ammonia concentration in the bottoms stream. The target is 50 ppm. b) Vary the column reflux ratio from 10-50 and observe the condenser temperature. The target is 190 F.

4. Create design specifications a) After hiding the sensitivity blocks, solve the column with two design specifications. Use the targets and variables from part 3.

Save as: SOURWAT.BKP ©2000 AspenTech. All Rights Reserved.


Solids Handling Objective: Provide an overview of the solid handling capabilities

Aspen Plus References: User Guide, Chapter 6, Specifying Components Physical Property Methods and Models Reference Manual, Chapter 3, Property Model Descriptions ©2000 AspenTech. All Rights Reserved.

Classes of Components • Conventional Components – Vapor and liquid components – Solid salts in solution chemistry

• Conventional Inert Solids (CI Solids) – Solids that are inert to phase equilibrium and salt

precipitation/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 appropriate component type in the Type column. –

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 conventional components 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 Solid components is possible. • Components are heterogeneous substances and do not have 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 identifiable constituents • 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 are calculated by the physical property system using component attributes. ©2000 AspenTech. All Rights Reserved.


Component Attribute Descriptions Attribute Type

Elements

Description

PROXANAL

1. Moisture 2. Fixed Carbon 3. Volatile Matter 4. Ash

Proximate analysis, weight %dry basis

ULTANAL

1. Ash 2. Carbon 3. Hydrogen 4. Nitrogen 5. Chlorine 6. Sulfur 7. Oxygen

Ultimate analysis, weight % dry basis

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, weight or volume %



Solid Properties • For conventional components and conventional solids – Enthalpy, entropy, free energy and molar volume are

computed. – Property models in the Property Method specified on the

Properties 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 selected

temperature ranges – List INORGANIC databank before SOLIDS

• Conventional Equations – Combines heat of formation and free energies of formation with

heat capacity models – Aspen Plus and DIPPR model parameters – List SOLIDS databank before INORGANIC ©2000 AspenTech. All Rights Reserved.


Solids Properties - Conventional Solids • Solid Heat Capacity – Heat capacity polynomial model C C C CpoS  C1  C2T  C3T 2  4  52  63 T T T – Used to calculate enthalpy, entropy and free energy – Parameter name: CPSP01

• Solid Molar Volume – Volume polynomial model V S  C1  C2T  C3T 2  C4T 3  C5T 4

– Used to calculate density – Parameter name: VSPOLY ©2000 AspenTech. All Rights Reserved.


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 – Uses a mass fraction weighted average – 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

attributes

• 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

MIXCISLD

Conventional components and inert solids

MIXNCPSD

Conventional components and nonconventional solids with particle size distribution

MIXCIPSD

Conventional components and inert solids with particle size distribution

MIXCINC

Conventional components and inert solids and nonconventional solids

MIXCINCPSD

Conventional components and nonconventional solids 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

streams (exceptions: Mixer and ClChng). – Attributes (components or substream) not recognized are passed 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 the

sub-streams of a stream.



Solids Workshop 1 (Continued) Temp = 190 F Pres = 14.7 psia Flow = 1 lbmol/hr 0.79 mole% N2 0.21 mole% O2

AIR-OUT

Design specification: Vary the air flow rate from 1 to 10 lbmol/hr to achieve 99.9 wt.% SiO2 [SiO2/(SiO2+Mixed)]

AIR DRYER WET

Temp = 70 F Pres = 14.7 psia

FLASH2

DRY

Pressure Drop = 0 Adiabatic

995 lb/hr SiO2 5 lb/hr H2O Use the SOLIDS Property Method ©2000 AspenTech. All Rights Reserved.

When finished, save as filename: SOLIDWK1.BKP Introduction to Aspen Plus

Solids Workshop 2 • Objective: Use the solids unit operations to model the particulate 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 to interfere 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 a balance between the technical performance and the cost associated with using a particular unit. • In this workshop, various options for removing particulates from the syngas obtained by coal gasification are compared. ©2000 AspenTech. All Rights Reserved.


Solids Workshop 2 (Continued) 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 H2 0.05 H2S 0.02 O2 0.03 CH4 0.01 H2O 0.05 N2 0.35 SO2 0.10

G-CYC

F-CYC

Temp = 40 C S-CYC Pres = 1 bar Water Flowrate = 700 kg/hr

G-SCRUB

FEED

F-SCRUB

DUPL

Particle size distribution (PSD) Size limit wt. % [mu] 0- 44 30 44- 63 10 63-90 20 90-130 15 130-200 10

S-SCRUB

V-SCRUB

G-ESP Design Mode Separation Efficiency = 0.9 Dielectric constant = 1.5

F-BF

ESP

S-ESP G-BF

15

When finished, save as ©2000 AspenTech. All Rights Reserved.

Design Mode Separation Efficiency = 0.9

LIQ

F-ESP

200-280

Design Mode High Efficiency Separation Efficiency = 0.9

CYC

filename: SOLIDWK2.BKP

Design Mode Max. Pres. Drop = 0.048 bar

FABFILT

S-BF Introduction to Aspen Plus

Solids Workshop 2 (Continued) • Coal ash is mainly clay and heavy metal oxides and can be considered a non-conventional component. • HCOALGEN and DCOALIGT can be used to calculate the enthalpy and material density of ash using the ultimate, proximate, and sulfur analyses (ULTANAL, PROXANAL, SULFANAL). These are specified on the Properties Advanced NC-Props form. • Component attributes (ULTANAL, PROXANAL, SULFANAL) are specified on the Stream Input form. For ash, zero all non-ash attributes. • 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

Aspen Plus References: User Guide, Chapter 22, Optimization Related Topics: User Guide, Chapter 17, Convergence User Guide, Chapter 18, Accessing Flowsheet Variables ©2000 AspenTech. All Rights Reserved.

Optimization • Used to maximize/minimize an objective function • Objective function is expressed in terms of flowsheet variables and In-Line Fortran. • Optimization can have zero or more constraints. • Constraints can be equalities or inequalities. • Optimization is located under /Data/Model Analysis Tools/Optimization • Constraint specification is under /Data/Model Analysis Tools/Constraint ©2000 AspenTech. All Rights Reserved.


Optimization Example REACTOR

A, B FEED

Desired Product C By-product D Waste Product E

$ 1.30 / lb $ 0.11 / lb $ - 0.20 /lb

A + B --> C + D + E

A, B, C, D, E PRODUCT

• For an existing reactor, find the reactor temperature and inlet amount of reactant A that maximizes the profit from this reactor. The reactor can only handle a maximum cooling 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? – 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 the

objective 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 objective function (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 manipulated 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 and minima in the objective function. It is theoretically possible to obtain a different maximum/minimum in the objective function, in some cases, by starting at a different point in the solution space. ©2000 AspenTech. All Rights Reserved.


Notes (Continued) 4. Equality constraints within an optimization are similar to design specifications. 5. If an optimization does not converge, run sensitivity studies with the same manipulated variables as the optimization, to ensure that the objective function is not discontinuous with respect to any of the manipulated variables. 6. Optimization blocks also have convergence blocks associated with them. Any general techniques used with convergence blocks can be used if the optimization does not converge. ©2000 AspenTech. All Rights Reserved.


Optimization Workshop • Objective: Optimize steam usage for a process. • The flowsheet shown below is part of a Dichloro-Methane solvent recovery system. The two flashes, TOWER1 and TOWER2, are run adiabatically at 19.7 and 18.7 psia respectively. The stream FEED contains 1400 lb/hr of Dichloro-Methane and 98600 lb/hr of water at 100oF and 24 psia. Set up the simulation as shown below, and minimize the total usage of steam in streams STEAM1 and STEAM2, both of which contain saturated steam at 200 psia. The maximum allowable concentration of Dichloro-Methane in the stream EFFLUENT from TOWER2 is 150 ppm (mass) to within a tolerance of a tenth of a ppm. Use the NRTL Property Method. Use bounds 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 and mass fraction units before running. Refer to the Notes slides for some hints on the previous page if there are problems converging the optimization. ©2000 AspenTech. All Rights Reserved.


Optimization Workshop (Continued) TOP1 STEAM1

TOWER1

FEED

TOP2

BOT1

TOWER2

STEAM2 EFFLUENT When finished, save as filename: OPT.BKP



RadFrac Convergence Objective: Introduce the convergence algorithms and initialization strategies available in RadFrac

Aspen Plus References: Unit Operation Models Reference Manual, Chapter 4, Columns ©2000 AspenTech. All Rights Reserved.

RadFrac Convergence Methods • RadFrac provides a variety of convergence methods for solving separation problems. Each convergence method represents a convergence algorithm and an initialization method. The following convergence methods are available: – Standard (default) – Petroleum / Wide-Boiling – Strongly non-ideal liquid – Azeotropic – Cryogenic

– Custom



Convergence Methods (Continued) Method

Algorithm

Initialization

Standard

Standard

Standard

Petroleum / Wide-boiling

Sum-Rates

Standard

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-rates

algorithm – 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-rates

algorithm – 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 physical

property models – 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. On the RadFrac Setup Configuration sheet, select VaporLiquid-Liquid in the Valid Phases field. • Vapor-Liquid-Liquid calculations: – Handle column calculations involving two liquid phases

rigorously – 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. – Use the Custom method and change Absorber to Yes on the

RadFrac Convergence Algorithm sheet, if the column is an absorber or a stripper. – Use the Strongly non-ideal liquid method if the mixture is highly non-ideal. – Use the Azeotropic method for azeotropic distillation problems with multiple solutions possible. The Azeotropic algorithm is also 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 field

of the RadFrac Setup Configuration sheet and use the Standard convergence method. – If the Standard method fails, try the Custom method with the Nonideal 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

average vapor and liquid compositions – Assumes a constant composition profile – Estimates temperature profiles based on bubble and dew point

temperatures of composite feed



Specialized Initialization Methods • Four specialized Initialization methods are available. Use: Crude Chemical

For: Wide boiling systems with multi-draw columns Narrow boiling chemical systems

Azeotropic Cryogenic

Azeotropic distillation columns 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 convergence

problems – Liquid and/or vapor flow estimates for the separation of wide

boiling 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 point system:



RadFrac Convergence Workshop • Objective: Apply the convergence hints explained in this section. • HCl column in a VCM production plant • 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 ©2000 AspenTech. All Rights Reserved.


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



RadFrac Convergence Workshop (Continued) • 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. – Question: How should these specifications be implemented?

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



RadFrac Convergence Workshop (Continued) Use the PENG-ROB Property method flow : HCl in feed

130000 kg/h 50 C, 18 bar, HCl 19.5%wt VCM 33.5%wt EDC 47.0%wt

max 10 ppm VCM 17.88 bar mass reflux ratio:0.7

feed on stage 17 18.24 bar

max 5 ppm HCl

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



Vinyl Chloride Monomer (VCM) Workshop • Objective: Set up a flowsheet of a VCM process using the tools learned in the course. • Vinyl chloride monomer (VCM) is produced through a high pressure, noncatalytic process involving the pyrolysis of 1,2-dichloroethane (EDC) according to the following reaction: 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. EDC conversion in the reactor is maintained at 55%. The hot gases from the reactor are subcooled by 10 degrees before fractionation. • Two distillation columns are used for the purification of the VCM product. In the first column, anhydrous HCl is removed overhead and sent to the oxy chlorination unit. In the second column, VCM product is removed overhead and the bottoms stream containing unreacted EDC is recycled back to the furnace. 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. Use the RK-SOAVE Property Method. ©2000 AspenTech. All Rights Reserved.


VCM Workshop (Continued) CH2Cl-CH2Cl

HCl + CHCl=CH2

EDC 1000 kmol/hr EDC 20C 30 bar

FEED

HCl

RStoic Model

VCM

RadFrac Model Heater Model

REACTOUT

COOLOUT

RadFrac Model

HCLOUT COL1

VCMOUT CRACK RECYCIN

Pump Model

500 C 30 bar EDC Conv. = 55%

QUENCH

10 deg C subcooling 0.5 bar pressure drop

VCMIN

15 stages

Reflux ratio = 1.082 Distillate to feed ratio = 0.354 Feed enters above stage 8 Column pressure = 25 bar

PUMP

30 bar outlet pressure

COL2

10 stages Reflux ratio = 0.969 Distillate to feed ratio = 0.550 Feed enters above stage 7 Column pressure = 8 bar

RECYCLE

Use RK-SOAVE property method ©2000 AspenTech. All Rights Reserved.

When finished, save as filename: VCM.BKP Introduction to Aspen Plus

VCM Workshop (Continued) Part A:

• With the help of the process flow diagram on the previous page, set up a flowsheet to simulate the VCM process. What are the values of the following quantities? 1. Furnace heat duty ________

2. Quench cooling duty ________ 3. Quench outlet temperature ________ 4. Condenser and Reboiler duties for COL2

________________

5. Concentration of VCM in the product stream ________

Part B: • The conversion of EDC to VCM in the furnace varies between 50% and 55%. Use the sensitivity analysis capability to generate plots of the furnace heat duty and quench cooling duty as a function of EDC conversion. ©2000 AspenTech. All Rights Reserved.


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