Introduction to Aspen Dynamics

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Introduc tion to t o Aspen Dynamics Dynamics ES102.111.03

© 2002 AspenTech. All Rights Reserved.

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Ag A g en end d a Day 1 • Cours Course e introduction introduction Aspen Aspen Dynamics Dynamics demonstratio demonstration n • Addin Adding g dynamic dynamic data in Aspen Aspen Plus Plus • Runnin Running g simulations simulations in Aspen Aspen Dynamics Dynamics • Backgroun Background d information information on resolution resolution method method used by Aspen Dynamics • Com Compon ponent ents s and Stre Streams ams • Dis Distil tillat lation ion with with RADFRA RADFRAC C

© 2002 AspenTech. All Rights Rights Reserved.

Ag A g en end d a Day 2 • Hea Heatt Exchan Exchanger ger mode models ls • Re Reac acto torr mode models ls • Ta Task sk la lang ngua uage ge • Pre Pressu ssure re cha change ngers rs • Pres Pressure sure drive driven n simulat simulations ions • Re Reve vers rse e flo flow w • Phy Physic sical al prope properti rties es


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Ag A g en end d a Day 3 • Pro Proces cess s Contro Controll Models Models – Application 1: control of a distillation distillation column column – Application 2: 2: control of a compressor compressor

• Pre Pressu ssure re rel relief ief • Scri ript pts s • Troub Troubleshoo leshooting ting (Hint (Hints s and Tips)


Optional Lesson Lesson s • More informat information ion about about Aspen Dynamic Dynamics s models • Mod Model el cust customi omizat zation ion • Kin Kineti etic c model model estimat estimation ion


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Introduction Introduction to Aspen Dynamics


Introduction t o As pen Dynamics Dynamics • Aspen Aspen Dynamics Dynamics is a tool in the Aspen Engineeri Engineering ng Suite for dynamic simulation of flowsheets • You build build and and converg converge e the stea steady dy state state flows flowsheet heet in Aspen Plus® • You export export from from Aspen Aspen Plus a simulation simulation for for Aspen Aspen Dynamics – Starts from the same steady state, same properties, same

components, etc.

• This course course is is for Aspen Aspen Dynamic Dynamics s 11.1 – Significant differences are flagged with


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Overview Ove rview of Aspen Dynamics Build steady state flowsh flo wsheet eet in in A Asp sp en Pl us Prepare flows Prepare flowsheet heet for dynamic simulation Add Dynamic data Export simulation Simulation in Asp A sp en Dyn Dy n ami cs Change control system, apply disturbances... © 2002 AspenTech. All Rights Rights Reserved.

FAQ: What What is th e dif ference between between Asp en Custom Modeler and Aspen Dynamics? • Thes These e products products are for two differen differentt types of situation situations: s: – Aspen Dynamics: Dynamics:

Running "off the shelf" models based on Aspen Plus simulation flowsheet – Aspen Custom Modeler:

Create and run your own "custom" models

• You can use use the Custom Custom Modeling Modeling feature feature simply simply by activating the "Custom Modeling" option in Aspen Dynamics (if you have both licenses)


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As A s p en Cu Cus s t o m Mo Mod d el eler er an and d Dy Dyn n am amii c s Feat u r e

A CM

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A CM+A D

Run GUI and calculations

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Create new models m odels

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Use the Dynamics library Call Properties Plus

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A Si Sim m p l e Exam Ex amp p l e: Qu Quii c k To Tou ur of As A s p en Dyn Dy n am amii c s Introduction to Aspen Dynamics


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Example: Exa mple: Appl ying A spen Dynamics Dynamics • What happens happens if operati operating ng conditions conditions change change? ? VAP

FEED

FLASH

Flowrate 100 kmol/hr Flowrate kmol/hr Temperature 50 C LIQ Pressure 2 Bar Vapor fraction 0.5 Mole-Fractions: Pressure drop 0.0 bar Water 0.5 Vertical Vessel Methanol 0.5 Length 3.0 m Diameter 2.0 m Constant duty heat transfer Initial liquid fillage fillage fraction 0.5 © 2002 AspenTech. All Rights Rights Reserved.

Simple Example 1: Create the simulation flowsheet in Aspen Aspen Plus – Properties, components, streams, blocks, ... – Develop the flowsheet

2: Enter the dynamic information in Aspen Plus 3: Export the simulation to Aspen Dynamics 4: We have a dynamic model for our flowsheet – Apply disturbances disturbances – Change control system – etc...


files

Dynamic Dyna mic Data in As pen Plus Introduction to Aspen Dynamics


Lesson Objectives • Describe Describe the data data required required to create create a dynamic dynamic simulation simula tion input from from an Aspen Plus flowsh flowsheet eet • Compl Complete ete Worksh Workshop op 102-dyn 102-dynamic-d amic-data ata


Topics • Acc Accessi essing ng the the dynamic dynamic data data form forms s in Aspen Aspen Plus Plus • Adding the the data required required for the the dynamic simulatio simulation n in Aspen Plus • Creat Creating ing the Aspen Aspen Dynamics Dynamics simulatio simulation n files


Ac A c c es ess s i n g t h e Dyn Dy n am amii c Dat Data a For Fo r m s (1) • To view Dynamic Dynamic Toolba Toolbarr make sure sure Dynamic Dynamic check box box is selected from Toolbars dialog window under View menu


Ac A c c es ess s i n g t h e Dyn Dy n am amii c Dat Data a For Fo r m s (2) • On the Dyna Dynamic mic Tool Toolbar bar,, press press dyn dynami amic c button button to access dynamic data forms

• Lets you specify specify the data data for the dynamic dynamic simulation simulation file file to be exported to Aspen Dynamics – It does not affect the steady state results

• Tip Tip:: Enter Enter the the data data as you you build build your your flo flowsh wsheet eet – Do not assume that default values apply to your case!


Ad A d d i n g Dyn am amii c Dat Data a • Data is requir required ed to calculat calculate e the followi following: ng: – Vessel geometry (required for vessel volume) – Vesse Vessell initial initial fill fillage age (used for starting starting liquid liquid holdup) holdup) – Process heat-transfer method – Equipment heat transfer options • •

Equipment heat capacity Environmental heat transfer


Vessel Ve ssel Geometry Dynamic Da Data ta • Ve Vess ssel el ty type pe – Instantaneous •

Default vessel vessel type for most vessels - require requires s no input for vessel geometry geometry

– Vertical – Horizontal

• Ve Vess ssel el ge geom omet etry ry – Head Type Elliptical • Hemispherical • Flat •

– Length – Diameter


Vessel Geometry: Cylinders FLAT

L A C I T R E V

Length

HEMISPHERICAL

ELLIPTICAL

Level

L

L Level

Level

Diameter D

L A T N O Z I R O H

D

D

D

Diameter Level

Level Level

Length © 2002 AspenTech. All Rights Rights Reserved.

L

L

Vessel Ve ssel Initi al Cond Cond it ition ion Sheet • Specify the the fraction fraction of the the total total vessel volume volume that that is occupied by the liquid phase at time tim e 0 (initial condition)

vapor

liquid

Liquid Volume Fraction © 2002 AspenTech. All Rights Rights Reserved.

Process Heat Heat Transfer Opti on • Co Const nstan antt Dut Duty y – Default (requires no further data addition)

• Const Constant ant Medium Temp Temperatu erature re – Heat duty is dependent on the temperature difference between

process fluid and the heating/cooling medium – Defaults to constant duty option when steady state duty, Q is

zero

• LMTD (log (log mean mean temperatur temperature e difference) difference) – Heat duty is dependent on the log mean temperature t emperature difference

between the process fluid and the heating/cooling medium


Process Heat Heat Transfer Transf er Optio n Sheet Sheet


Constant Heat Duty Option • Dut Duty y is a “fixed” “fixed” var variab iable le in the the dynamic dynamic simul simulati ation on – Set to the steady state Aspen Plus simulation results value

• Duty can be be manipulated manipulated in the the dynamic dynamic simulation simulation – Manipulate directly by manually changing the value – Manipulate with a PID controller

• Exampl Example e for Constant Constant Heat Heat Duty option option application application – A fired heater

• Duty can can be supplied supplied by by an inlet inlet heat strea stream m


Constant Temperature Option • Specify T_med T_medium ium value value on dynamic dynamic input input form form • Vary value value of T_medium T_medium in the the dynamic dynamic simulation simulation directly or with a controller • Equ Equati ation on is:

Q = UA . (T_ (T_pro proces cess s – T_m T_medi edium) um)

Where: Q

= Heat duty

UA

= Product of the overall heat transfer coefficient and the heat transfer area

T_pr T_ pro oce ces ss

= Te Tem mpe pera ratu turre of th the e pro roce cess ss fl flui uid d

T_me T_ med diu ium m

= He Heat atin ing/ g/c coo ooli lin ng me medi diu um tem tempe pera ratu ture re


Log Mean Tempe mpera rature ture Diffe Differe rence nce Option (1) [1] Q = UA . LMTD [2]] Q = Fm [2 Fmme med d . Cpm Cpmed ed . (Tm (Tmed ed_O _Out ut – Tm Tmed ed_I _In) n) Var i ab l e

Des c r i p t i o n

LMTD

Log mean temperature difference

Fmmed

Mass flow rate of the heating/cooling medium

Tmed_In

Inlet te tem mperature of heating/cooling medium

Tmed Tm ed_O _Out ut

Outl Ou tlet et te temp mper erat atur ure e of of the the he heat atin ing/ g/co cool olin ing g med mediu ium m

Cpmed

Specific heat capacity of the heating/cooling medium

UA

Product of the OHTC and the heat transfer


Log Mean Tempe mpera rature ture Diffe Differe rence nce Option (2) • When you expor exportt the simulation simulation to to Aspen Dynami Dynamics: cs: – Tmed_out is calculated calculated from the specified temperature

approach – Fmmed is calculate calculated d from the heat duty – LMTD and UA are calculated

• In Aspen Dynam Dynamics ics simula simulation: tion: – Fmmed and UA are are specified (fixed) to the values found above – When process temperature changes, Q will vary – Fmmed can be manipulated manipulated by the user user or a temperature

controller


Comparison o f t he Heat Heat Transfer Transfer Options • Example 0 1 1

) e 5 r 0 u t 1 a r e 0 ) p ) 0 y m n 1 t u e i o D T t p 5 t n m o 9 u a i t d D s T 0 n e M o M L 9 C t ( ( n T a T t 5 8 s n o C 0 ( 8 T

Constant duty heats up Results

0 0 1

the vapor after all the liquid has been vaporized

r h / 5 l o 7 m k e t a r w 0 o 5 l F d e e F

Feed flow closed LMTD (example : T = 90 C)

Constant medium temperature (ex: T = 80 C)

5 2

5 7 0 7

0


0.25

0.5

0.75

1 Time Hours

1.25

1.5

1.75

2

Equip ment Heat Heat Transfer • Equipment Equipment heat capacity capacity can can be important important when there there are large changes in the equipment temperature possible scenarios include startup, shutdown and pressure relief – Data required • •

Equipment mass Equipment heat capacity

• Enviro Environment nmental al heat trans transfer fer – Environmental heat transfer is important when the process is

sensitive to changes in the global ambient temperature

• Wall heat heat transfer transfer (new in 11.1) 11.1)


Equip ment He Heat at Transfer Shee Sheett


Setup Specifications Global Sheet • To specify specify Ambien Ambientt tempera temperature ture


Ad A d v i c e When Wh en Pr Prep epar arii n g a Dyn Dy n am amii c Si Sim m u l at atii o n • Brea Break k do down wn the the flow flowsh shee eett in into to sm smal alle lerr secti section ons s to work work out the details of the dynamic simulation before you attempt attem pt to the expor exportt a comple complex x flowshee flowsheett • Rev Review iew caref carefully ully your your flow flowshe sheet et blo block ck by block block – Check the default settings in the Dynamic for ms – Check for missing blocks (i.e., storage tanks to be modeled

with MIXER, FLASH2, FLASH3) – Check for missing streams (i.e., bypass streams, N2 streams, etc.) – Remove unused components – Selection of Valid Phases in blocks and feed streams


Create Crea te the Aspen As pen Dynamics Files • Export – Creates and saves the Aspen Dynamics problem file •

runid.dynf

– Creates and saves the Aspen Plus Properties Definition File

(APPDF) required for the properties calculations •

runiddyn.appdf

• Send To To – Exports then automatically starts Aspen Dynamics and loads

the exported problem files • •

runid#.dynf runiddyn#.appdf


Types Type s of Dyna Dynamic mic Simulations • Fl Flow ow dr driv iven en – Feed flowrate flowrate and pressures pressures are specified specified – Flowr Flowrate ate is not controlled by pressure pressure differences – Useful for a first approach of the dynamic behavior of the process – Good for liquid processes (usually good flow controllability)

• Pr Pres essu sure re dr driv iven en – Feed and product pressures are specified – Flowr Flowrate ate result results s from pressure difference difference – A bit more complex to specify (because you need to balance the

pressures in Aspen Plus with valves, pumps, ...) but more rigorous

• Difference Differences s will be discussed discussed in detail detail in "Pressure "Pressure driven driven simulations" lesson


Problems Durin Durin g Export • Some models models and option options s are not support supported ed by Aspen Aspen Dynamics • These are are detected detected when entering entering the dynamic dynamic data or when exporting the dynamic simulation


Message Me ssages s While Export ing the Simulation • Always analyze analyze the the messages messages while while exporting exporting the simulation as they are really important • Wa Warn rnin ing: g: something you should really check! – Examples: • •

Zero flow in a stream: no results to initialize composition Flash vessel full of liquid: will be at bubble pressure in dynamic simulation (can cause flows to change)

• (Fatal) (Fatal) Error: Error: The simulation simulation cannot cannot be exported or used used without corrective action – Pressure checker


Types of Messages Messages During Durin g Expor t (1) (1) • FA FATA TAL L ERR ERROR OR:: – Use of any Aspen Plus feature, which is not supported in Aspen

Dynamics – Any results, which are inconsistent with a dynamic simulation, e.g., problems proble ms with RadFrac pressu pressure re profile.

• ERROR: – A block that is not supported

Note: If a flowshe Note: flowsheet et includ includes es an unsupported block, block, it will still be exported but a message will be output about the unsupported block

• WA WAR RNING – Anything which could cause a problem in the d ynamic simulation.

This includes things like negative or zero pressure drops etc. in valves


Types of Messages Messages During Durin g Expor t (2) (2) • IN INFO FORM RMAT ATIO ION: N: – Information about the dynamic simulation. Often used to output

information before fatal error message

• Note that that problems problems are detected detected only only when you try try to export the simulation (using File/Export or File/Send to) • For press pressure ure drive driven n simulatio simulations ns – Pressure checker tool checker tool can be used to detect specific pressure

driven problems that need to be addressed, without trying to export the file – This will be reviewed later in the course (Day 2)


Objects Obje cts Exported • The followi following ng objects objects are are exporte exported: d: – Components – Properties – Streams and blocks (supported models only)

• The follow following ing are are not not exporte exported: d: – Specifications (Design-Specs, Balance blocks, ...) – Calculator blocks – However, the dynamic dynamic simulation starts from the results of

these blocks


As A s p en Dy Dyn n am amii c s RA RATING TING Sim Si m u l at atii o n • In Aspen Aspen Plus, you have have many option options s for the the specification of blocks, for design or rating simulations • Example Example to illustrate illustrate the differen difference ce in specification specifications s between Aspen Plus and Aspen Dynamics – Aspen Plus: A Flash2 block with with temperature and pressure

specification, or vapor fraction and pressure, or... – In Aspen Dynamics: the heat duty is "fixed" to the Aspen Plus

calculated duty, so the temperature will vary – In Aspen Dynamics: the pressure is controlled (no longer fixed)


Stream Stre am Specification s • Fee Feed d stream stream specifica specificatio tions ns – Same specifications as in Aspen Plus for the temperature,

pressure or vapor fraction – Same specifications as in Aspen Plus for the composition and

flowrate flowr ate speci specificati fication on – For Flow driven simulations: • •

Flowrate and pressure of feed streams are fixed Pressure of product streams are calculated

– For Pressure driven simulations: • •

Pressure of feed and product streams are fixed Flows are calculated from pressure difference and resistance to flow (i.e., valves, ...)


Default De fault Control Syste System m • When the flowsh flowsheet eet is exporte exported, d, level, level, pressu pressure re and, and, in some cases, temperature controllers are automatically added to the vessels – Flow driven simulation: manipulate the flowrates – Pressure driven simulation: manipulate the valve position

• These controlle controllers rs are added added automatically automatically because because otherwise other wise the flowsheet flowsheet would be unstable unstable • You should should check that that the defaul defaultt settings settings for the the controllers are suitable for your application and modify them if needed © 2002 AspenTech. All Rights Rights Reserved.

Workshop 102-dynamic-data Introduction to Aspen Dynamics


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Running Simula Simulations tions in As A s p en Dyn Dy n am amii c s Introduction to Aspen Dynamics


Lesson Ove Overview rview • Review the the basic concept concepts s in running running the simulati simulation on • Explain how to run and and pause pause the simulati simulation on • Show how to display display the result results s • Compl Complete ete Worksho Workshop p 103-dyna 103-dynamic-ru mic-run n


Starti Sta rti ng As pen Dynamics Dynamics • Dou Double ble-cli -click ck on the the file file (ext (extens ension ion dyn dynf) f) – You usually usually start Aspen Aspen Dynamics with a file

• Can be started started from Aspen Aspen Plus when when exporting exporting the file file • It is a good idea to keep keep a copy of of the simulatio simulation n that you you have exported from Aspen Plus • Note: Aspen Dynamics Dynamics simula simulation tion consists consists of: of: .dynf: dynamic file DYN.appdf: physical properties .bkp: Aspen Plus simulation file


As A s p en Dy Dyn n am amii c s Gr Grap aph h i c al In Intt er erff ac ace e

A t abl e

A p lo t

Flowshe Fl owsheet et window Simulation Explorer Simulation messages window


Simulation Explorer • Display the content content of the the simulation simulation – Flowsheet: blocks and streams on the

flowsheet – Custom Modeling: (only (only if licensed) licensed)

customized models – Dynamics Dynamics:: library of models – Syste System m Library Library:: library of fundamental

types – ComponentList ComponentList:: components and physical

properties – Diagnostics Diagnostics:: information on resolution


Run Mode • Sel Select ects s the type type of simul simulati ation on • Aspen Dynamics Dynamics is is typically typically used with with "Dynamic" "Dynamic" and and "Initialization" run modes • Init Initiali ializat zation ion run run:: – Solves the system's equations at time zero to find the values of

the free variables

• Dy Dyna nami mic c run: run: – First it does an initialization run at time 0 – Then integrate step by step the system's equations – Report results at each communication interval


Run Cont Cont rols To start the simulation: click on the Run button To pause the simulation: click on the Pause button Continue the simulation: click on Run button again To go back to time 0: click on Restart button To go back to a previous step: click on Rewind button To interrupt the simulation: Run menu, Interrupt Stops before the completion of the communication interval

To run step-by-step © 2002 AspenTech. All Rights Rights Reserved.

Menu Me nu Run, Run Opt Option ion s • Select Selection ion of the communic communication ation inter interval val

Communication interval

Time units for display (plots) New


Menu Me nu Run, Solver Optio ns • Selects Selects the parameters parameters for for the numerical numerical resolutio resolution n methods • This will will be reviewe reviewed d later in the course course • Important Important settin settings gs on Integ Integrator rator sheet: – Initial Integration Step – Minimum Integration Step – Default values are appropriate

for the other settings


Simul ation Me Messages ssages (View, Messages) Messages) • Shows message messages s while running running the simulatio simulation n – Task execution – Vessels being full of liquid, or empty – etc.

• Can be be selected selected from from the the View View menu menu


Display Displ ay the Variabl Variables es • Pre Predef defined ined tab tables les – Results: to display key results – Manipulate: to display key variables that can be manipulated (if

they are "fixed") – Many other tables (specific to models) – AllVariables: to show all variables variables

• Pr Pred edef efine ined d plots plots • You can creat create e your own tables tables and and plots plots


Example of a Table Table • Str Stream eam "Mani "Manipul pulate ate"" table table

Var i abl abl e uni uni t s Var i abl e name Cur r ent ent val ue


Var Var i abl e speci f i cat i on mode

Specifications and Values of Variables Fixed:: • Fixed

You give the value of the variable for the calculations

• Free Free::

Value is calculated by Aspen Dynamics (i.e., it is a result)

• Initial Initial::

You give the value of the variable at time 0 (i.e. it is the starting point for the simulation)

• Original Original values are are from from the Aspen Aspen Plus simulatio simulation, n, exported file • You can save save new startin starting g points in "Kept Results Results"" sections or in "Snapshots" © 2002 AspenTech. All Rights Rights Reserved.

Units o f Measurement Measurement • Select from from Tools Tools menu, menu, Units of of Measuremen Measurementt • Can be changed changed on on tables for for individual individual variables variables • Predefined Predefined units units of measuremen measurementt sets consistent consistent with Aspen Plus simulation – Advanced users can create their own sets if required

• Aspen Dynamics Dynamics does does its internal internal calculations calculations with with the "Metric" unit set – Example: convergence messages


You can Create Create Your ow n Plots Plot s and Tables • Dr Drag ag an and d Dro Drop p • User-create User-created d plots plots and tables definitions are stored in the "Flowsheet"

profile table plot history table

profile plot

table


Steps to Crea Create te a Plot 1. Cli Click ck on the Plot Plot butt button on and and give give it a nam name e 2. Ope Open n a table table that that disp display lays s the var variab iable le 3. Cli Click ck on on the the name name of the var variab iable le 4. Hold down down the the left mouse butto button n to drag it and drop it on the Plot form 5. Do a right right mous mouse e click click on the the Plot Plot to chang change e its properties (i.e., to remove variables, display grid, ...) 6. The Plo Plott is is defi defined ned in the Flo Flowsh wsheet eet fol folder der


Interactin Intera ctin g with t he Simul Simul ation • You can change change the the value of fixed fixed variables variables while while the dynamic simulation is running – Example: Manipulate table

• You can change change the the settings settings of the contro controllers llers – FacePlate form

CompactFacePlate

New

– Configure form

• Task languag language e will be presen presented ted on Day Day 2 © 2002 AspenTech. All Rights Rights Reserved.

Simulation Simul ation Files (Graphical (Graphical Interf ace Side) process.bkp

• Asp Aspen en Plus Plus simula simulatio tion n file

process.dynf

• Asp Aspen en Dynamic Dynamics s simulati simulation on file – Can include "kept results" to save starting point

• Phy Physica sicall proper propertie ties s file – This file can be recreated from the bkp file

• It is importa important nt that that you keep keep these these files! files!


processDYN.appdf

Simulation Simul ation Files (Client (Client and Server Server Sides) • Graph Graphical ical User User Interface Interface (client (client)) side: process . bkp bkp

process . dynf dynf

pr ocess DYN. YN. appdf

• Simula Simulation tion server "Wor "Working king Folder" Folder" snapshot.snp

– Snapshot and results (binary files) – Plot data

snplnnnn.snp

PlotData.cpd

– Physical properties files SAI.rep

SAI.his


Usage Suggestions • Make Make a back backup up copy copy of the the dyn dynff file bef before ore ope openin ning g it in Aspen Dynamics • Creat Create e "Kept results" results" to save save important important starting starting points points • Clean up the the Working Folder Folder to avoid avoid running running out of disk space • When working working on long long projects, projects, it is a good good idea to create creat e an archive archive file every every day with with the the bkp, the the dynf and the appdf file (consist (consistent ent set) set) so that that you can can easily easily track back if needed


Work orksho shop p 103 03-dynamic-run -dynamic-run Introduction to Aspen Dynamics


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As A s p en Dyn Dy n am amii c s Res Reso olution Introduction to Aspen Dynamics


Lesson Objectives • Explain how how Aspen Dynam Dynamics ics is solving solving the simulatio simulation n – Equation oriented: specifications – Dynamic system: initial conditions – Illu Illustrate strate this this with an example, example, using using flow flowsheet sheet constr constraints aints

(adding one equation) and changing specifications

• Demonstrat Demonstrate e the equation equation oriented oriented approach approach using Aspen Plus


Calcul Ca lcul ations Done by As pen Dynamics Dynamics • Basi Basis s of of the the mod models els – Dynamic Material and Energy balances – Thermodynamic equilibrium – Geometry constraints (to relate volume and level) – etc.

• Implem Implementat entation: ion: algebraic algebraic and different differential ial equations equations – Models in the Dynamics library – Written in Aspen Custom Modeler Language

• Run is possible possible only only if the simulatio simulation n has the correct correct number of specifications ("no degree of freedom")


As A s p en Dyn am amii c s Mo Mod d el els s Eq Equ u at atii o n s • Expand Dynamics Dynamics librar library y from Simulatio Simulation n Explorer Explorer – Double-click on the "equation" icon to see the model's code


Specifications • Every variable variable has a "Spec" "Spec" property property,, which selects selects its specification mode • Va Vali lid d valu values es:: Spec Fixed Fixed

Des cript ion The The variab variable le value value is specifie specified d by the user user (A (A variab variable le whose value is not being solved for)

Initi Initial al

A varia variabl ble e whose whose valu value e is know known n at tim time e zer zero o for an an initialization or dynamic run

RateInitial RateInitial Free Free

A state variabl variable e whose whose time time derivative derivative is known known at time time zero for an i nitialization nitialization or dynamic dynamic run A variab variablle whose whose val value ue is bein being g sol solved ved for (defa (defau ult) lt)


Initialization Initializa tion Run • Solve the system's system's equat equations ions at at time 0 – Known • •

Fixed variables Initial variables

– Unknown • •

Free variables Derivative of state variables

• The value value of variable variable time derivative derivative gives gives an idea of the the direction of change and how fast the system will move in the dynamic run


Dynamic Run • Numer Numerical ical integrat integration ion proceeds proceeds step step by step step – Time step is automatically adjusted to maintain integration

accuracy • •

Increase step size when nothing happens Cut step size when fast events are taking place

– Settings in Run/Solver Options – Aspen Dynamics can use VSIE or ImpEuler only

• Result Results s are available available at every every communication communication interval interval – Tables, plots, etc. – Settings in Run/Run Options


Variable’s Values from Aspen Plus Results • The results results from from Aspen Plus Plus are used used to specify specify the initial values of variables – Fixed variables:

Feed streams, characteristics of the equipments, controller settings, ...

– Initial variables:

Content of the vessels (holdup of mass and energy), ...

– Free variables:

Given values close to the solution to ensure convergence


Note • Fixed variables variables can be be manipulated manipulated during during a dynamic dynamic run – Manipulate the value in tables – Define and activate tasks to implement ramps FIXED

FIXED

time

time Ramp

Change in a table or with a task © 2002 AspenTech. All Rights Rights Reserved.

Initial Conditions • Initial Initial cond conditi itions ons:: the starting point for the dynamic simulation • So don't confus confuse e INITIAL INITIAL and FIXED FIXED as they they are different things!

INITIAL

FIXED

time © 2002 AspenTech. All Rights Rights Reserved.

0

time

System Syste m Specificatio n • Simulations Simulations exported exported from from Aspen Plus Plus are correctly correctly specified – Consequence: you need to free a variable to fix another

• St Stat atus us indic indicat atio ion n Incomplete Under-specified Complete Over-specified Initial state under-specified Initial state over-specified Singular


View Status Status Wind ow • Doubl Double-click e-click on Status Status check check button for for the full message message


Variabl Va riable e Find • Very useful useful to to find variabl variables es in the the simulation simulation • Can be used used to create create tables tables and plots plots (drag (drag and drop) drop)


Snapsho Sna psho t and Results • To rest restart art a simula simulatio tion n – To time 0 for dynamic simulation (snapshot 'Dynamic

Initialization')

• To rewin rewind d the simu simulat lation ion – To any timed snapshot

• To keep, keep, export, export, import import and and copy copy results results

Snapshot Management © 2002 AspenTech. All Rights Rights Reserved.

Rewin Re win d and Restart • Rewind Rewind lets you select select the the snapshot snapshot to which which you want want to go • Restart Restart is is a short cut to to Rewind: Rewind: retur returns ns the the dynami dynamic c simulation to its solved initial state – Uses the 'Dynamic Initialization' snapshot

Restart

Run

Step

Rewind

Pause


How to Enable Rewind Rewind? ? • Go to Snapshot Snapshot management management tool, tool, select select "Take regular regular snapshots"


Snapshott Management Snapsho Management Tool • Sn Snap apsh shot ots s can can be: be: – Used for rewind and copy – Marked as "kept" so that the data will be saved in acmf

• Resu sullts – "Old" snapshots Snapshots

Results


Export, Import, Keep • Export: Export : Export the snapshot or result to a text file (asnp) (*) • Import Import:: Import a file into a result (*) • Keep: Keep : Mark the snapshot or result to be saved in the dynf dy nf fi file le • Settings Settings:: Access options controlling snapshot handling • Compress: Removes deleted snapshots snapshots from from .snp files Compress : Removes in working working direc directory tory (*) ( *)

New


Demons De mons tration 10 104 4-re -resol soluti ution on Introduction to Aspen Dynamics


files

Comp omponents onents and Streams Streams Introduction to Aspen Dynamics


Lesson Objectives • Review import important ant informat information ion on streams streams and components • Compl Complete ete Works Workshop hop 105-s 105-stream treams s


As A s p en Dy Dyn n am amii c s L i b r ar ary y o f Mo Mod d el els s • Review strea stream m and and compo components nents • Show how how to create create a controlle controllerr on the flowshee flowsheett


Simulation Explorer • Flows Flowsheet: heet: Shows Shows the the streams streams and and blocks • Dyn Dynami amics cs library library:: Models Models – Specific details will be reviewed later – Stream types: •

ControlSignal: to connect controllers

• ComponentL ComponentList: ist: Components Components and physical physical propertie properties s referring to Aspen Plus physical properties


Components • Asp Aspen en Dynam Dynamics ics suppo supports rts:: – Conventional components – Pseudocomponents, assays and blends

• Simula Simulation tion with electr electrolytes olytes:: – Apparent component approach only – Solid components if defined in salt reactions in the chemistry

• Polyme Polymers: rs: See docum documentat entation ion • Usage tip: tip: Remove Remove unused unused components components from from Aspen Aspen Plus before exporting the simulation to Aspen Dynamics © 2002 AspenTech. All Rights Rights Reserved.

Stream Types • Strea Stream m types types to match match Aspen Aspen Plus stream streams s – MaterialStream: Only CONVEN stream class is supported – WorkStream – HeatStream

• Strea Stream m type to connect connect controller controllers s to the other other objects – ControlSignal

• Pseudo strea streams ms are are not suppo supported rted


Stream Stre am Specification s • Feed streams streams are specifie specified d following following the values values entered entered in Aspen Plus • Can be modified modified using using the Stream Stream Configu Configure re form

New

Note: In versions before 11, Configure is simply a table © 2002 AspenTech. All Rights Rights Reserved.

ConfigureSensor • Access to switch switch for calculat calculation ion of additional additional stream stream properties – Phase fractions – Phase compositions – Phase densities – Volumetric flow rate – pH – Petroleum properties

• Calcul Calculated ated properti properties es are displayed displayed in Results Results form


Configure onfigureS Sensor Form

Check Sensor On


Petroleum Properties • Prope Properties rties calculat calculated ed using the the Stream Stream Sensor – ASTM D86 and D1160 temperature – Cet Cetane ane num number ber – Reid Vapor Pressure (same as RVP-ASTM in Aspen Plus) Plus) – Specific gravity (60/60F) – Watson UOP K-Factor

• Free water water is not supporte supported: d: Use liquid-liqu liquid-liquid-vap id-vapor or instead


Worksho Works hop p 105105-st strea reams ms

files

Introduction to Aspen Dynamics


Operati Opera tion on of the PID Fa Faceplate ceplate • A description description of the PID PID faceplate faceplate operation operation follows follows Manua nuall mod mode e swi switch tch

Au to mo de s wi tc h


Casca scade de mode swi switch tch

Confi onfigur gure e for form m

Plot forms

PID PI D Init Init ialize Values Values But ton • PID Initialize Values Button • Uses the current current values values of the measured measured variabl variable e and manipulate manipulated d variable to initialize controller parameters – The value for the operator set point changes to the value of the

measured variable – The value for bias changes to the value of the manipulated variable – Proce Process ss variab variable le and output output ranges changed to 0 and 2 times the

value •

Exception: For valve position, the range is specified to 0 and 100%

• Typica Typically, lly, you use use this only only once, once, when you you create the the PID block block


Distillation Distil lation wi th RADFR RADFRAC Introduction to Aspen Dynamics


Lesson Objectives • Overvi Overview ew of of RADFR RADFRAC AC capabili capabilities ties • Dyn Dynami amic c forms forms in Aspe Aspen n Plus Plus • Model and and specification specifications s of exported exported simulation simulation to: to: – Show how Aspen Plus data and results are used – Review some specific details of Aspen Dynamics assumptions

• Pr Pres essu sure re prof profile ile • Control • Compl Complete ete Works Workshop hop 106-r 106-radfra adfrac c


RADFRAC Capabilities • Dynamic Dynamic RadFrac RadFrac may be be used used in the the same appl applicati ications ons as as the steady-state model • In dynamic dynamic mode, mode, RadFrac RadFrac mode models ls the pressu pressure re drop drop across across each stage due to the head of liquid and vapor flow resistance • Stage hydr hydraulic aulics s are are also also modeled modeled • React Reactive ive distillati distillation: on: only React-D React-Dist ist reaction reaction type type – Equilibrium reactions are not supported

• Un Unsu supp ppor orte ted d – User-KLL, polynomial KLL – VL1/LL prop-sections – Different VL1 and VL2 efficiencies – Thermo Thermosyphon syphon reboilers reboilers with above-stage above-stage return convention © 2002 AspenTech. All Rights Rights Reserved.

RADF RAD FRAC Dyna Dynamic mic Forms in Asp en Plus Plus • Conde Condenser: nser: Heat Heat transfer transfer option option for the condenser condenser duty duty • Reb Reboile oiler: r: Heat Heat transfe transferr option option for the the reb reboil oiler er • Reflu Reflux x drum: Size Size and initial conditio condition n for the reflux reflux drum • Sump: Size Size and initial initial condition condition for for the column column sump sump • Decant Decanter: er: Size and and initial condition conditions s for the decanters decanters • Hydraulics: Hydraulics: Selection Selection of the pressur pressure e drop and holdup holdup calculation for the stages • Dynam Dynamic ic equipmen equipmentt HT: HT: Pption to model model therm thermal al inertia inertia


Simple Disti Disti llation Condenser(1)

Reflux.FmR

Stage(2) Stage(1): Stage(1): Reflux Reflux drum

Stage( Stage(nstage) nstage):: Sump and reboiler © 2002 AspenTech. All Rights Rights Reserved.

Overhead Overhea d System • Con Conden denser ser:: Con Conden denser ser(1) (1) – Assumes instantaneous operation

• Ref Reflux lux drum drum:: Stage( Stage(1) 1) – Both liquid and and vapor holdup are modeled – There is no hydraulic equation for reflux flow – Liquid reflux mass flow rate is fixed •

Variable name: Reflux.FmR


Bottoms System • Reb Reboile oiler: r: Stage(n Stage(nsta stage) ge) – For thermosy thermosyphon phon optio option: n: •

Relation between duty and flowrate - Re Rebo boil iler er re reci circu rcula lati tion on mo mole le fl flow owra rate te FR - Re Rebo boil iler er du duty ty QR

QR = K_thermo*FR^3 where : K_thermo constant from steady state results


Stage • Mat Materi erial al and ener energy gy balan balance ce – Include liquid and vapor holdup, reactions, feed above and on-

stage, heat heat duty, feed, feed, sided sidedraw, raw, etc.

• Liq Liquiduid-vap vapor or equilibr equilibrium ium • Hy Hydr drau auli lics cs – Rela Relation tion with with liquid and vapor vapor flowr flowrates ates to give liquid liquid holdup – Rela Relation tion with with liquid liquid level and and vapor flow flowrate rate to pressure pressure drop – More details in online help "RADFRAC Hydraulics and

pressure drop equations"


Options for Hydraulics • Simpl e Trays Trays::

Uses simple corre correlation lation for trays

• Simple Packing: correlation lations s for packin packing g Packing : Uses simple corre • Rigorous Rigorous::

Uses the same correlations as Tray Rating or Packin Packing g Rating

• Model Model include includes s weeping weeping for for trays trays if vapor vapor flo flowra wrate te becomes too low


Simple Simpl e Stage Hydrauli cs

Ql_out =

K1 *L_weir*Ht_Crest 2/3

Vl = Stage StageAr Area* ea*Le Leve vell P

V = Vl + Vv P_diff =

*Fv_inp^ 2 K2 *Fv_inp^

+

K3 *Level

P_diff Ht_Crest

Level

Ht_Weir

P'

Fv_ v_inp inp =

Stage(i+1).vapout.F © 2002 AspenTech. All Rights Rights Reserved.

Note: Simple tray model accounts accounts for liquid in in downc downcomer omer as if level level was was same as on stage (stagearea*level)

Simple Tray Hydraulics • Requi Required red inpu inputt from from Aspe Aspen n Plus Plus – Diameter – Tray spacing – Ratio of weir length to column diameter (Lw/D)

New

– The % active area •

•

Adjust these to model a wide wide range of tray configurations, configurations, including multip mul tipass ass tra trays ys The value of the constants K1, K2 and K3 are calculated from flowrate and pressure profile specified or calculated calculated in Aspen Plus

Note:: You need to define a realistic pressure profile in Aspen Plus Note


Usage Usa ge Not Note e in Aspen Asp en Plus Plus Hydrauli cs Sheet Sheet • May need to to scroll to to the right right to make Lw/D and and %Active area visible


Simple Packin Packin g Hydraulics • Same principl principle e as for simple tray option option – Liquid holdup proportional to liquid velocity – Pressure drop proportional to square of vapor flowrate

• Req Requir uired ed specifi specificat cations ions – Diameter – HETP – Initial liquid volume fraction

• See online online help help for for more more informatio information n


Rigorou Rigor ous s Tray and and Pack Rating Rating Optio n (1) (1) • Usage note: note: To complete complete the form form you need to to select on tray rating or pack rating section the option "Update Pressure Profile" Why does it say "incomplete"?


Rigorou Rigor ous s Tray and and Pack Rating Rating Optio n (2) (2) • Check "Updat "Update e section section pressure pressure profile" profile"


Control • Exampl Example e showing default default controlle controllers rs for a simple simple column PC Drum pressure

Condenser duty

LC Drum level

Distillate Disti llate flowra flowrate te Reflux is fixed

Reboiler Reboi ler duty is fixed fixed

LC Sump level Bottom Bot tom flo flowra wrate te © 2002 AspenTech. All Rights Rights Reserved.

Condenser and Reflu Reflu x Drum • Dru Drum m leve levell cont control rol – Manip Manipulat ulate e liquid liquid disti distillate llate mass flowr flowrate ate – Reflu Reflux x mass mass flowr flowrate ate is fixed fixed (Reflu (Reflux.FmR x.FmR)) – If no liquid distillate stream, then level is controlled by

manipulati manip ulating ng reflux mass flowra flowrate te

• Special Special case for decanter decanter in condenser condenser:: additional additional level controller to control interface position • Top stage stage press pressure ure contr control ol – Manipulate vapor distillate stream (if there is a vapor distillate

stream) – Manipulate condenser duty (if there is a condenser) © 2002 AspenTech. All Rights Rights Reserved.

RadF adFra rac c Reboile eboilerr Control • Bottom stream stream manipulat manipulated ed to control control the level in the sump • Reboiler duty – Fixed if using Constant Duty option – Calculated from medium temperature (with constant medium

temperature option) or medium flowrate (with LMTD option)


RadFra Ra dFrac c Deca ecanter nter • Assu Assumes mes no no vapor vapor in sys system tem • Flow rate rate of the the first liquid liquid phase phase is manipulate manipulated d to control the total liquid level • Flow rate rate of second second liquid phase phase is manipula manipulated ted to control the interface level


Connectivit y fo r th e Deca Decanter nter VapOut

Li qI n Decanter(n)

Stage(n)

VapI n

Li qOut

Li qDr aw

LC Li qI n

flow = 0

Stage(n+1)

LC Li q1Dr aw( i >1) >1) Li q1Dr aw( 1) Li q2Dr aw( i >1) FmR

Stage(n+2)

FmR

Li q2Dr aw( 1)

If there is only one stream connected to the decanter, then it is connected to LiqDraw, LiqDraw, which which is the sum of Liq1Draw(1) and Liq2Draw(1).


RadFrac Ra dFrac Pumparound Pumparou nd • Assume Assumes s instant instantaneou aneous s opera operation tion • Const Constant ant duty duty option option for heat heat transfer transfer


Stage Sta ge Side Sidedraw draw Stre Streams ams • Flow-driven Flow-driven simulatio simulation: n: Flow rate is fixed at steady-st steady-state ate value • Pressure-d Pressure-driven riven simulation simulation:: Flow rate rate results from from pressure-flow relation in product line


Workshop Works hop 10 1066-radfr radfrac ac

files



Workshop Summary Step 1: Open file in As pen Plu s

Step 2: Enter dynamic data

Step 3: Try dynamic simulation


Step 4: Change control system and test

files

Heat He at Exchangers Exc hangers Introduction to Aspen Dynamics


Heat He at Exch angers • Heater – Instantaneous only

• HeatX – Instantaneous or Dynamic

• MHeatX – Instantaneous or Dynamic


HeatX He atX Hea eatt Exchangers • Dynamic model consists of two perfectly mixed tanks for each side and heat exchange based on LMTD dp hot hot hot out

hot i n Q = U*A*LMTD

col d ou out

c ol ol d i n dp c ol d

– You need to adjust the volumes to fit plant data


MHeatX • Dy Dyna nami mic c model model simi simila larr to He Heat atX X – Dynamic characteristics are modeled using volume holdups on

each side of exchanger • •

MHeatX Total volume (one for each stream) is split in two, inlet and outlet All the pressure drop is assumed to occur occur between the inlet and outlet volumes

• Product Product of exchanger exchanger area area and the overall overall heat transfe transferr coefficient (UA) for each zone is automatically “Fixed” at the steady-state value


Heat He at Exchangers Exch angers • The pressur pressure e drop drop is relat related ed to the volume volumetric tric flow rate by: ΔP

= K * Rho * Fv Fv 2

Where: K

=

Constant determined by fitting to steadystate conditions

P

=

Pressure drop

Rho

=

Mass density at outlet conditions

Fv

=

Volumetric flow rate (inlet or outlet)

Δ


HeatX vs. Two He Heate aterr Blocks Approach • Heat stream stream Q should should be dependent dependent on temperat temperature ure difference implemente emented d using using flows flowsheet heet constr constraints aints – Can be impl •

Streams("Q").Q = UA*(Blocks("HOT-SIDE").T - Blocks("CLD-SIDE").T);


Reactors Introduction to Aspen Dynamics


Reactors • RSt RStoic, oic, RYi RYield eld,, RGi RGibbs bbs:: Pse Pseudo udo-dy -dynam namic ic mod models els • RCSTR • RPlug


RSto toic ic / RYie ield ld / RGib ibbs bs Instantaneous

• Sim Simple ple flo flow w mode models ls – Instantaneous

CSTR PFR

– Stirred tank geometry – Plug flow geometry

time

• Reacti Reactions ons equations equations are applied applied at outlet outlet conditions conditions • RGIBBS: RGIBBS: advanced advanced specification specifications s can not be accessed accessed in Aspen Dynamics Example: le: Avoid Avoid using using flowrate flowrate - use flow flow ratio instead instead – Examp


RCSTR • Pe Perf rfec ectl tly y mixe mixed d reac reacto tor r • Onl Only y kineti kinetic c reacti reactions ons are are suppo supporte rted d – You need to convert equilibrium reactions into two kinetic reactions

(forward and reverse)

• Ha Hand ndli ling ng of of outl outlet et stre stream ams s model enables the outlet flow of each phase to – Aspen Dynamics model be manipulated independently – If you have multiple phases but a single outlet stream, the vapor and liquid phases are mixed at the outlet of the reactor to match Aspen Plus configuration (see next slide)

• It is possibl possible e to reconnec reconnectt the liquid liquid and and the vapor vapor streams streams in Aspen Dynamics if required


RCST RC STR R Connecti vit y • Multiple Multiple outlet outlet streams streams supported supported in both Aspen Aspen Plus and Aspen Aspen Dynamics 11.1 Feed

Vapor

f l ow

PC

mi xer Product

LC

New

f l ow si ngl e out l et st ream ream str ucture Liquid

mul t i pl e out l et s str ucture

( ver ver si on 10 10. 2)

• Right side side structure structure shows what what Aspen Dynamics Dynamics model model does does for single outlet multiple phases reactors – Prefer to use separate outlet streams in Aspen Plus! © 2002 AspenTech. All Rights Rights Reserved.

Rplug (1 (1)) • Plug flow is discretiz discretized ed with a series series of of reactor reactor eleme elements nts • Supports Supports liquid liquid,, vapor, vapor, liquidliquid-vapor vapor and liquidliquid-liquidliquidvapor vap or pha phase se options options • Only kinetic kinetic reactio reactions ns are are supported supported – You need to convert equilibrium reactions into two kinetic

reactions (forward and reverse)

• Heat transfer transfer effect effect between between catalyst catalyst and and process process fluid is modeled


Rplug (2 (2)) • The pressur pressure e drop drop is relat related ed to the volume volumetric tric flow rate by: 2

ΔP

= K * Rho * Vel

=

Constant determined by fitting to Con steady-state conditions

P

=

Pressure drop

Rho

=

Mass density

Vel

=

Fluid Velocity

Where: K Δ

– Coolant pressure drop is fixed


RPlug Cooling Options Options

Co o l i n g Ty p e TCO COOL OL_S _SP PEC ADIABATIC CO-COOL COUNTER-COOL

Des c r i p t i o n Reacto Reac torr wit with h con const stan antt coo cooli ling ng te tem mpe perrat atur ure e Adiabatic reactor Reactor with co-current external coolant Reactor with counter-current external coolant

Note: T_SPEC option is not supported (Use high flow rate coolant for constant reactor temperature) © 2002 AspenTech. All Rights Rights Reserved.

RPlug RP lug Ca Catalyst talyst Heat Heat Transfer Transfer Opti Opti ons If y o u c h o o s e

Sp ec i f y

Des c r i p t i o n

No heat transfer (default)

No additi additional onal input

No catalyst present, or the effect of heat transfer transfer between between catalyst and process fluid on the reactor dynamics is neglected.

Heat transfer at equal temperatures

Voidag Vo idage e fraction of cata catalyst lyst

There is very fast heat transfer between the catalyst and the process fluid, and they are assumed to be always at the same temperature

Heat capacity of catalyst Mass density of catalyst

Heat transfer at different temperatures

Voidag Vo idage e fraction Heat capacity of catalyst Mass density of catalyst

This is the most rigorous option. Heat transfer between the catalyst and process fluid is determined by their temperature differential, contact area, and overall heat transfer coefficient

Specific surface area of catalyst Overall heat transfer coefficient © 2002 AspenTech. All Rights Rights Reserved.

RPlug in Dyna Dynamic mic Simulations Simulations • Aspen Dynamics Dynamics uses uses a one-dimensiona one-dimensional, l, first order order finite difference scheme to solve the partial differential equations equati ons for the RPlug react reactor. or. The The finite finite size of of each element may cause a certain amount of error • Reduce the the error error by increasing increasing the number number of finite finite difference elements from the default value of 10 – RPlug Block-Options sheet in Aspen Plus Plus

• A general general rule is to to use 5 points points for every every 10 deg deg Celsius Celsius change in temperature or 10% change in composition


Work orkshop shop 20 201 1-rpl rplug ug Introduction to Aspen Dynamics


files

Task Ta sk Language L anguage Introduction to Aspen Dynamics


Lesson Objectives • Descr Describe ibe the function functionality ality and and uses of tasks, tasks, including including how to: to: – Create tasks – Activate tasks

• Dis Discus cuss s the follo followin wing g topics: topics: – What is a task? – Types of tasks – Uses and examples of tasks – Creating a task – Activating a task

• Com Comple plete te Worksho Workshop p 202-tas 202-tasks ks


What is a Task? Task? • A Task is a set of statements statements (instru (instructions ctions)) that defines defines a sequence of discrete actions – Disturbances in feed conditions – Changes to controller set points

• Tasks can trigger trigger an event event or action action when a predefin predefined ed condition becomes true – Rudimentary control e.g., close/open a valve when the fluid

level falls/rises above/below a value

• Task stateme statements nts are are executed executed in sequenc sequence e


Types of Tasks • Eve Eventnt-Dri Driven ven Tas Tasks ks – Requires a conditional expression to determine when the task

begins – Events can be: • •

Explicit - will happen (usually time-specific time-specific events) Implicit - may or may not happen depending on other events or conditions

• Ca Call llab able le Ta Tasks sks – Called by other tasks, including other callable tasks – Is not triggered by an event – Can pass parameters to the called task – Can call tasks in Parallel


Task Ta sk Ma Manager nager • Ove Overa rall ll pict pictur ure e Graphical User Interface

Create/remove tasks Activate/deactivate tasks

Tasks

Limit time step Query variable Change variable value

task

status

action

t k1

ac t i ve

wai t

t k2

ac t i ve

done

...

Simulation server

Task manager


Where to Define Tasks? • Def Define ine tas tasks ks in the Flo Flowsh wsheet eet fol folder der • Event-driven Event-driven tasks tasks need need to be "activate "activated" d" to be considered by the task manager during the dynamic simulation – Select the task, then RMB, Activate

Inactive

Active

Event Driven Tasks © 2002 AspenTech. All Rights Rights Reserved.

Callable Task

Incorrect task

Creating Cre ating and Ac tivating Ta Tasks sks

Ac t i ve Task Tas k with checkmark

Ad d Task Ico n in Flowshe Flowshee et folde folder r


Task Language • Task statement statements s are written written in Aspen Custom Custom Modeler Modeler language – It is not case sensitive – You need to end statements with a semi colon (;)

• Syntax to access access a variab variable le within within a: – Block: Blocks("block name"). •

Example: Blocks("C130").Level

– Stream: Streams("stream name"). •

Example: Streams("FEED").FmR


Event-Driv Event-D riv en Ta Task sk • Syntax: TASK TASK TaskNam TaskName RUNS WHEN Condi ondi t i on TaskSt at ement s ; END END TASK TASK TaskNam TaskName RUNS ONCE WHEN Condi ondi t i on TaskSt at ement s ; END END

• Co Cond ndit itio ion: n: – time == value – expression1 >, <, ==, <>, >=, <= expression2


Task Event • Event-driven Event-driven task task status status is checked at communic communication ation intervals • Task execute executed d whenever whenever the conditio condition n becomes true (i.e., changes from false to true) level

lev_alarm time t ask xmp r uns when bl ocks( cks( "M") . l evel > l ev_al _al ar m © 2002 AspenTech. All Rights Rights Reserved.

Tasks • "O "ONC NCE" E" qual qualif ifie ier r p

p_burst time t ask bu bur st i ng r uns once once when st r ea eam ms( " V" ) . p > p_bur _bur st


Task Ta sk Stateme Statements nts • Varia Variable ble assignment assignment (variab (variable le must be fixed!) – Direct – Ramping functions (RAMP and SRAMP)

TASK TASK Task4 RUNS WHEN TI ME == 4. 0 / / Fl ow cha changes t o 5. 0 l i near l y / / over ver a per i od of 2 t i me uni t s RAMP ( st r ea eam ms( " A" ) . FmR, 5. 0, 2. 0) ; / / Te Tem mper per at ur e chang changes es wi t h an S- shaped shaped cur ve / / t o 15. 0 over a per i od of 3 t i me uni t s SRAMP ( st r eams( " B") . T, 15. 0, 3. 0, di scr et e) ; bl ocks( " HTX" ) . QR : 0; END END


Task Statements are Execut Task Executed ed in Sequenti al Order (I(Illustr llustr ate ates s p revious exa example) mple)

second ramp (sramp)

step change (assignment)

first ramp

15

(continuous)

4

5

6

9

time


Ramp Ra mp Statements sy nt ntax ax – Linear ramp discrete

RAMP ( var i abl e, f i nal val ue, dur at i on, di s cr cr et e) ; – Linear ramp continuous

RAMP ( var i abl e, f i nal val ue, dur at i on, con cont i nuous) ; – Sine ramp discrete

SRAMP ( var i abl e, f i nal val ue, dur at i on, di scr scr et e) ; – Sine ramp continuous

SRAMP ( var i abl e, f i nal val ue, dur at i on, con cont i nuous) ;


0

Task Ta sk Stateme Statements nts • Cr Crea eate te a snap snapsh shot ot TASK TASK Task2 RUNS WHEN Ti me == 10. 0 CREATE EATE SNA SNAPSHO PSHOT " TaskTask - Cr eat ed Snaps Snaps hot #1" ; END END

• Pr Print int a mes messa sage ge • Pau Pause se the the simu simulat lation ion TASK TASK Test 3 RUNS WHEN Ti me == 1. 0 PRI PRI NT " St ar t Task Test 3" ; RAMP ( st r eams( " D" ) . FR FR,, 2. 5, 5. 0) ; PRI PRI NT " Task Test 3 Fi ni shed shed" ; PAUSE; END END © 2002 AspenTech. All Rights Rights Reserved.

Task Ta sk Execut Exec utio io n: WAIT FO FOR R and and WAIT • WAIT FOR: FOR: To hold the task task execution execution until until condition condition is satisfied: WAI T FOR FOR condi condi t i on; on;

• WAIT: To To hold task task execution execution for a given period period WAI T du dur at i on; on; / / wai t f or 2 hour s f r om now WAI T 2. 0; // start feed st r eams( " S34" ) . FR : 400; / / wai t l evel t o r each desi r ed val ue WAI T FOR bl ocks( " V" ) . l evel vel > 1. 0; / / st op t he f eed st r eams( " S34" ) . FR : 0; © 2002 AspenTech. All Rights Rights Reserved.

Task Ta sk Executio n: RE REST START ART • RESTART RESTART makes makes the task execution execution jump jump up to the first first line x

4 5 . 3

RESTA ESTART AFTER AFTER dur dur at i on;

3 5 . 2 y . x . 1 1 B B 2

RESTAR ESTART WHEN c ondi t i on;

5 . 1 1 5 . 0

0

1

2

3

4

5 6 Time Hours

7

8

9

Task r es r uns when t i me == 1 / / st ep cha change o off f l ow st r eams( "F") . FR : 4; / / wai t 2 uni t s of of t i me wai t 2; st r eams( "F") . FR : 0; r est art when bl bl ocks(" B1") . l evel vel < 1; End © 2002 AspenTech. All Rights Rights Reserved.

Conditio nals in Tasks Tasks

TASK TASK Condi ondi t i on RUNS WHEN Bl ocks ( " D101" 101")) . Level < 0. 01 I F St r ea eam ms( " S10 S101" ) . FmR <= 0. 1 THEN St r eams( " S101" ) . FmR : 10. 0; ELSE St r eams( " S101" ) . FmR : 1. 0; END ENDI F END END


10 10

Callllable Ca able Task • Syntax TASK TASK TaskNam TaskName ( Par amet er Li s t ) TaskSt at ement s END END

• Call CALL TaskNa skName ( Par Par amet er Li st ) ;


Callable Task: Example TASK TASK Mai nTas nTas k RUNS WHEN TI ME == 1. 0 St r eams( " FEE FEED" ) . FR FR:: 4; CALL SubT SubTaskA askA;; CALL SubT SubTaskB askB;; End End TASK TASK SubTa SubTas s kA / / cha change val ve posi t i on RAMP( Bl ocks( ocks( " FV1 FV101" ) . pos, 10, 3. 0) ; END END TASK TASK SubTa SubTas s kB / / cha change f eed mol e f r act i on of wat er SRAMP( St r ea eam ms( " FEED FEED" ) . ZR( " H2O" ) , 0. 5, 2. 2. 0) ; END END


Task Execution: PARALLEL • PA PAR RAL ALLE LEL L – Each action is executed until it completes – The parallel section completes when all actions in it are

complete TASK TASK Task1 RUNS WHEN TI ME == 1. 25 PARALLEL CALL SubTaskA; CALL SubTaskB; ENDPARALLEL; st r eams( "F4") "F4") . FmR : 0. 0; END END


Task Ta sk Notes (1) • Values must be expres expressed sed in metric metric units • Snapshots Snapshots taken taken when a ramp ramp is running running will will be flagged flagged as "Modified" • Only fixed fixed variables variables can be ramped ramped or or changed changed with assignments in tasks


Task Ta sk Notes (2) • Task conditions conditions are are checked at at communication communication interva intervall – Don't make it too long!

Task action

Event WAIT FOR x > 3

x Communication interval © 2002 AspenTech. All Rights Rights Reserved.

Conflicting Tasks • Ta Task sk Ra Ramp mpFl Flow ow wi will ll ov over erri ride de ta task sk St Step epfl flow ow TASK TASK RampFl ow RUNS WHEN TI ME == 1. 0 Ramp( St r ea eam ms( " FEE FEED" ) . FmR, 4. 0, 2. 0) ; END END TASK TASK St epFl ow RUNS WHEN TI ME == 2. 0 St r ea eam ms( " FE FEE ED" ) . FmR: 0. 5; END END Which value do you

FmR

really want?

1 © 2002 AspenTech. All Rights Rights Reserved.

2

3

time

Tip: How t o Find t he Name Name of Va Variabl riabl es? • Var Variab iables les in cond conditi itions ons:: – Check in Results tables – Check AllVariables, with Description

• Variab Variables les in in assignmen assignments ts (actions (actions): ): – Check in Manipulate tables – Make sure the variable is Fixed

• The name name to to use in in the task task is: is: – Blocks("name").variable or Streams("name").variable – Tip: Look at the title title of the the table table from which which you you found found the

variable


Usefu Use full Task Task Statements wi th PID Contr Control oller ler • To switch switch a PID control controller ler to automatic automatic mode mode Bl oc ks ks ( " PC1" ) . Aut oMan : 0; / / aut o

• To cha change nge the set setpoi point nt of a PID PID Bl oc ks ks ( " PC P C1" ) . SPo : 0. 123; / / s et et poi nt

• To switch switch a PID PID controller controller to manual manual mode mode Bl oc ks ks ( " L C1" ) . Aut oMan : 1;

/ / manual

• To change change the manip manipulate ulated d variable variable of a PID Bl ocks( cks( "LC1 "LC1") . OPman : 3. 21; / / manual


Rampin Ra mpin g Va Variables riables fro m Tables Tables (Continuo us) New

• You can ramp a fixed variab variable le from from tables tables – Ramped variables are displayed in red


Workshop 202-tasks Introduction to Aspen Dynamics


files

Pressure Pressur e Changers Changers Introduction to Aspen Dynamics


Pressure Changers • Valve • Pipe • Pump • Co Comp mprr an and d MCo MCom mpr


Valve • "S "Sim impl ple" e" val valve ve – Valve coefficient not specified in Aspen Plus • •

Default position: 50% Valve coefficient calculated from specified pressure drop

• "Ri "Rigor gorous ous"" val valve ve – Valve coefficient (table or characteristic) specified in Aspen

Plus

• Opt Option ions s to check check chok choking ing and and cav cavita itatio tion n • If required, required, valves valves can be resized resized in Aspen Aspen Dynamics Dynamics (i.e., evaluate a new value for the valve coefficient) © 2002 AspenTech. All Rights Rights Reserved.

Pipe • Sup Suppor ported ted Solut Solution ion Metho Methods ds – Integrate – Con Consta stant nt dP/d dP/dL L •

Outlet flow rate always equal to inlet flow rate

• Tur Turbul bulent ent flow flow is is assume assumed d • Can calcula calculate te sub-criti sub-critical cal and and critical critical flow flow • Conti Continuou nuous s mome momentum ntum bala balance nce • Gener Generalize alized d fittings fittings are allow allowed ed • Multiple Multiple liquid liquid phases phases are treated treated as a single homogen homogenous ous liquid liquid phase except for flash calculations


Pipe for Dynamic Dynamic Simul ations • Aspen Aspen Dynamics Dynamics uses a one-dimens one-dimensional, ional, first first order finite difference scheme to solve the partial differential equations for the Pipe model – The finite size of each element may cause a certain amount of

error – Reduce the error by increasing the number of elements from

the default value of 10 •

Pipe, Advanced, Methods sheet in Aspen Plus


Pump • Use Pump Pump performance performance curve curve entered entered in Aspen Aspen Plus Plus – If no curve entered, it creates one Head curve

1.4 1.2 d a e h 1 l a 0.8 n i m0.6 o n / 0.4 d a e 0.2 H 0 0

0. 2

0. 4

0. 6

0. 8

1

1. 2

1.4

1. 6

Flow / nominal flow

– Need to to change change Extra Extrapolat polateFanL eFanL to "Yes" "Yes" to have have

ActShaftSpeed ActShaftSpee d to have proper effect

• Change Change Us UseCu eCurv rves es to "Fals "False" e" in Conf Configu igure re form form if you you do not wish to use performance curves © 2002 AspenTech. All Rights Rights Reserved.

Compressor and Turbi Turbi ne • COM COMPR PR and MCO MCOMP MPR R • Most types types of performa performance nce curve curve are support supported ed – Types GPSA polytropic and isentropic isentropic with "GPSA basis =

average" are not supported

• Com Compre presso ssorr ine inerti rtia a can be tak taken en int into o acco account unt


Note About Performance Curves • Curve Curve data should should cover cover the full range range of operating operating conditions expected during the dynamic simulation • Tabula Tabularr data: data: A cub cubic ic spl spline ine fit is is used used to int interp erpola olate te between betwe en the data points points.. The cubic splin spline e fit is most accurate when the: – Data points are evenly spread – Curve is smooth (gradually changing gradient with no

deviations)

• Polynomial Polynomial coeffici coefficients: ents: Check Check that the the shape of the curve is realistic over the full range of operating conditions expected during the dynamic simulation


Example • Make sure you have have enough enough points 20

Splin Sp line e fi fitt

18 16 14 12 p R10

8 6 4 2 0 42000


43000

44000

45000

46000 47000 Fv (ft3/min)

48000

49000

50000

51000

Pressu Pre ssure re Driv Driven en Simu Simulations lations Introduction to Aspen Dynamics


Lesson Objectives • Disc Discuss uss the the followi following ng topics: topics: – What is a Flow Driven Simulation? – What is a Pressure Driven simulation? – Configuring a Pressure Driven Simulation •

Use of the Pressure Checker

• Compl Complete ete Workshop Workshop 204-p 204-pressur ressure-dri e-driven ven


Whatt i s a Flow Driven Simulation? Wha • What is a Flow Driven Simula Simulation? tion? – Outlet flow rate from a block is specified or determined from the

material balance – Outlet flow rates are unaffected by downstream pressures – Assumes perfect flow and pressure control

• Usuall Usually y a good appro approach ach for liquid system systems s


What is a Pre Pressu ssu re Driv Driv en Simu Simu latio n? • Downs Downstream tream pressu pressures res influence influence flowrat flowrates es • Flowrates Flowrates are deter determined mined by pressur pressure/flow e/flow relat relationship ionship between upstream and downstream blocks – Line or system resistance forces a pressure drop between units

Note: Note: Pressure/flow relationship blocks are not necessary in streams connected to unit operations modeled with a pressure/flow equation such as Heater, HeatX, MHeatX, RPlug, etc.


Pressure Driven • Example – When flow increases, pressure drop of the system increases – When flow increases, head (pressure increase) of the pump

decreases pressures

5 1

Syst emcurve

r r a a 0 b b 1 1 1 p p . . p o r m p p 5

0

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Flowrate

1

Pump cur ve


Pressur Pre ssur e Driven Driven in Aspen Dynamics • Pressu Pressure re setting: setting: Where Where we have have a gas/vapor gas/vapor holdup holdup – Pressure = gas holdup = initial condition

• Pressure Pressure driven driven node: Where Where the flow depend depends s on the pressure difference – Flow = function of pressure difference

• Pre Pressur ssure e "neutr "neutrali ality" ty" – Pressure of all feed streams to a block must be equal

• Fi Fixe xed d pre pressu ssure re – Feed streams, product streams, liquid-only blocks


Pressure Driven • Pressu Pressure re specif specificatio ication n (fixed) (fixed) • Pressu Pressure re equali equality ty (neutr (neutral al node) node) V-2 8

11

F-1

V-1 1

V-3

M-1

9

2

7

E-1 3

F-2 4 V-4 5

6


Steps to Prepare a Pressure Driven Simul ation • Rem Remove ove unsupp unsupport orted ed models models • Defin Define e a valid valid pressure pressure/flow /flow netwo network rk – Add blocks for pressure/flow relationships •

Units that determine pressure must not be connected directly together

– Ensure block pressures are balanced and consistent • •

Equal upstream and downstream block pressures Inlet pressures greater than outlet pressure

• "Pressure "Pressure Checker" Checker" tool tool will assist you you in completing completing these tasks • Ex Expo port rt/S /Sen end d To To “P “P Dri Drive ven n Dy Dyn n Si Simu mula lati tion on”” fi file le © 2002 AspenTech. All Rights Rights Reserved.

The Pressure Checker • Ch Chec ecks ks fl flow owsh shee eett fo forr co consi nsist sten ency cy – Consistency of interconnecting blocks – Consistency of pressures

• Advi Advises ses on on requi required red chan changes ges to to flo flowsh wsheet eet • Warns of potenti potential al problems problems in dynamic dynamic simulatio simulations ns This is the "Pressure Checker" button


Unsuppor ted Models Models i n Pressure Driven Driven Mode • Models not not supported supported in Pressu Pressure re Driven Driven Mode – Sep / Sep2 – Extract – Dupl – Distl

• Models not not supported supported in Instant Instantaneou aneous s mode of operation – Flash2 / Flash3


Which Simu latio n Mode to Use? (1) (1) • It depe depends nds on on your your model modeling ing obj object ective ives s – If pressure is important for you, then pressure driven mode

may be required

• It depends depends on on the type of process process – Gas phase will typically require pressure driven mode •

Examples: Steam network, gas net work, pressure relief (especially multiple relief in same piping), compressor system

– Liquid phase will typically not require pressure driven mode • •

Example: Liquid-liquid decanter Counter example: Gravity driven system will require pressure driven, especially if lines are undersized (poor flow controllability)


Which Simu latio n Mode to Use? (2) (2) • Con Conside siderr the contro controll system system – If you know you already have a good pressure and good flow

control, then flow driven simulation may be suitable

• Consid Consider er the effect effect of pressur pressure e on propertie properties s – Effect is large on gas phase (density, kinetics) – Effect is low on liquid phase (actually, liquid compressibility is

not calculated by most density models)

• Note that that some blocks blocks are internally internally pressure pressure driven driven – RADFRAC, PIPE, RPLUG


Problems to Consid er • Pr Pres essu sure re at fl flow owshe sheet et bo boun unda dari ries es – Is the assumption that the pressure is fixed a good

approximation? • •

Vent to atmosphere: yes Feed to another process?

• Include Include more blocks blocks upstream upstream and downstr downstream eam if you need to have their press pressure-f ure-flow low characteristi characteristics cs


Typical Modifications • Use a valve valve on the outlet outlet to get get at least least some resistan resistance ce to the flow (i.e., outlet of a compressor) • Use a block with with vapor holdup holdup to avoid "stiffn "stiffness" ess" of the the system (liquid-only systems...) • Inc Includ lude e volum volume e of pip pipes es – Prefer using Mixer blocks instead of Pipe model


Typical Problems with Pressure Checker • Mes Messag sages es durin during g export export – Warning for pressure difference around a pressure neutral

node: This will cause a kick in flows at initialization and the exported simulation will not be at steady state – Flash2/Flash3 with sub-cooled liquid: Exports at bubble

pressure, which causes all sort of trouble

• Typica Typically lly you need need to address address these these warnings warnings – Use design-specs or calculator blocks to ensure pressure

equality – Add padding gas (N2) where appropriate – Model customization (for compressed liquid)


Valve Va lve Model Model in As Aspen pen Plus (Operatio (Operatio n) • Cal Calcul culatio ation n Typ Type: e: – "Adiabatic..." becomes a "Simple" valve in Aspen Dynamics – "Calculate..." becomes a "Rigorous" valve in Aspen Dynamics


Valve Va lve Model in Asp en Plus (Parameters) (Parameters) • Typica Typically lly you will use the the Valve Character Characteristics istics option option Tabulated characteristics

Standard characteristics


Valve Va lve Model Model in Aspen Plus (O (Optio ptio ns) • Cal Calcul culatio ation n opti options ons – Choked flow checking – Cavitation

• These options options can can be modified modified in Aspen Aspen Dynamics Dynamics


Workshop 204-pressure-driven Introduction to Aspen Dynamics


Workshop: 204-pressure-driven • Config Configure ure a simulati simulation on to be be pressure pressure driven driven – Adding valves where required required – Using design specs for pressure balance D101VAPV

D101V C2PRODV C2OUT VAPFEED

C2PRODV

C2PROD

T101 HCFEED

FLASHFD

D101

E101

C3PRODV C3PRODP LIQFEED

C2IN

C3PROD

D101LIQV D101L

– Hydraulic option and valve resize in Aspen Dynamics


files

Reverse Flow Introduction to Aspen Dynamics


Lesson Objectives • Discu Discuss ss the follow following ing topic topics: s: – Reverse flow overview – Creating a Reverse Flow Simulation – Modeling Features – Recommendat Recommendations ions and Red Flags

• Compl Complete ete Worksh Workshop op 205-reve 205-reverse rse flow flow


Reversi Re versible ble Flow Overvi ew • Allows Allows flow to reverse reverse direction direction when the pressu pressure re gradient reverses • May be require required d for applicati applications ons such such as: – Steam systems – Fuel gas networks – Some pressure relief applications

• For use use in pressure pressure driven driven simulat simulation ion only


Creati Crea ting ng a Reve Reverse rse Flow Simul Simulation ation (1 (1)) • Creat Create e simulati simulation on in Aspe Aspen n Plus Plus • Expo Export rt as Pressure Pressure Driven Driven Dynamic Dynamic Simulatio Simulation n • Pe Perf rfor orm m Initia Initializ lizat atio ion n ru run n • Ena Enable ble rev revers erse e flow flow • Per Perfor form m Initiali Initializat zation ion run • Config Configure ure product product streams streams and blocks blocks as required required • Per Perfor form m Initializ Initializati ation on run (save (save snaps snapshot hot))


New

Creati Crea ting ng a Reve Reverse rse Flow Simul Simulation ation (2 (2)) • Enabl Enable e reverse reverse flow in Global Global table table – Chan Change ge GlobalRFlo GlobalRFlow w to "True" – Wait for simulation update to be complete

Switch to enable/disable Default is disabled © 2002 AspenTech. All Rights Rights Reserved.

Creati Crea ting ng a Reve Reverse rse Flow Simul Simulation ation (3 (3)) • Configure Configure form form for produc productt streams streams show condi conditions tions that will apply if stream flow reverses


Modeling Feature atures s (1) • Models suppo supporting rting rever reverse se flow flow – Pipe, Valve – Flash2, Flash3, Decanter – Heater, HeatX – FSplit, Mixer, Mult – BurstingDisk, Expansion, Orifice, PSV, TValve – RCSTR

• Models behav behavior ior based on symmet symmetry ry were applic applicable able should give the same results in each direction


Modeling Feature atures s (2) • Valve – CheckValve option to prevent prevent reverse flow

• Flash Flash2, 2, Flash3, Flash3, Decante Decanterr and RCSTR RCSTR – Choose which phase flows out through feed if it reverses with

parameter RFlowPhase in Configure Configure form form

• Bu Burs rsti ting ngDi Disk sk – Specify reverse bursting pressure

• Detail Details s for each model in online online help help


Modeling Feature atures s (3) • If you need need to mix reverse reverse flow flow and non-rever non-reverse se flow models in the same simulation: – Non-supported models must be isolated by Valves with

CheckValve=True. Failure to do so will result in underspecification – Solution speed and robustness may be affected


Modeling Fe Features atures (4 (4)) • Rever Reverse se flow variab variables les in blocks/ blocks/stre streams ams – Trev, hrev, hrev, zrev zrev - analo analogous gous to forward forward flow condit conditions ions – Passed through streams and blocks but you only see their

effect if flow reverses

• For feed feed streams, streams, T on the the Results Results form form is ALWAY ALWAYS S the forward temperature, regardless of actual flow direction In_F.Trev on AllVariabl AllVariables es form to see actual actual temperatur temperature e – Use In_F.Trev in all cases

• Negat Negative ive flows/press flows/pressure ure drops indicate indicate reverse reverse flow


Recom Re com mendati mendations ons and Red Red Flags (1) • Rever Reverse se flow only supporte supported d in pressure pressure driven mode mode – If you disable pressure driven either globally or locally for a

block, the reverse flow functionality is disabled and you may encounter specification problems

• Avoid discontinu discontinuities ities where possible possible (use tasks/ra tasks/ramps) mps) • For convergen convergence ce problems problems with physical physical properties properties caused by reverse flow, procedure based physical property sub-models are typically more robust (but slower) – To use, change change GlobalFlashB GlobalFlashBasis asis param parameter eter on Globals Globals tabl table e


Recom Re com mendati mendations ons and Red Red Flags (2) • VSIE Integ Integrato ratorr may may “blur” “blur” point of flow flow revers reversal al – Goto Run\Solver Options, Options, and uncheck Use Interpolation on

Integrator tab

• By default, default, Aspen Aspen Dynamics Dynamics allows 10 divergent divergent steps steps when solving non-linear blocks before convergence failure is assumed Options, and increase Max. Max. Divergent steps – Goto Run\Solver Options, on Non Linear Solver tab for difficult problems


Workshop Works hop 20 2055-reversereverse-fl flow ow Introduction to Aspen Dynamics


files

Physica Physic al Propertie Properti es Introduction to Aspen Dynamics


Physical Properties Calcul Calcul ations • Aspen Aspen Dynamics Dynamics uses the the same physical physical property property calculation routines as Aspen Plus • Use local local models to to improve improve speed of calcula calculation tion • Selection Selection of how physical physical properties properties and equilibri equilibrium um are calculated can be changed if required – At global level (in Globals table) – On a block block or stream stream basis basis (in AllVaria AllVariable ble tabl tables) es)


Selection Se lection of Physical Property Calcul Calcul ations

Global table


Physical Properties Calcul Calcul ations • "Lo "Local cal"" prope property rty mod mode e – Properties are modeled on simple functions of temperature and

pressure – Faster to evaluate than full physical properties calculations – Accuracy is comparable comparable to using full full physical properties properties – Local property parameters are updated at every integration step for accuracy

• "Ri "Rigor gorous ous"" propert property y mode – Calls the property routines every time – Slower, but may be required for strongly non-ideal systems

• Selec Selected ted by param parameter eter Globa GlobalProp lPropMode Mode or Prop PropMode Mode © 2002 AspenTech. All Rights Rights Reserved.

Example Exa mple of Loc al Property Property fo r Liq uid Enthalpy nc

h L =

∑ x ( A + B T ) i

i

i

i=1

Where: = Liquid molar enthalpy = Mole fraction of component i xi Ai Bi = Local property property paramete parameters rs for component component i T = Te Temp mper erat atur ure e nc = Num Number ber of of compone components nts hL


FlashMode: 2 and 3 Phase Phase Flash Calcu Calcu latio lation n • Selec Selects ts the the flash flash calcu calculation lation "Equation"

Equation based LV and LLV equilibrium

"Procedure"

More robust (uses Flash algorithm to solve New equilibrium at given temperature and pressure)

"ProcedurePH“ More robust (uses Flash algorithm to solve equilibrium at given enthalpy and pressure) Eq u a ti o n

Pr o c e d u r e Local properties for single Local properties, equation- phase, Rigorous properties Local based flash (LV, LLV) for LV and LLV, procedure based flash Rigorous Rigorous properties, properties, Rigorous properties and Rigorous equation-based flash procedure based flash


Guidelines for the Selection Selection • Firs Firstt try to run the the simulation simulation with with default setting settings! s! • Tightening Tightening the flash, flash, tear and block block toler tolerances ances in Aspen Aspen Plus can help resolve some initialization problems • In case case of conv converg ergenc ence e difficu difficulti lties es or "nois "noise,“ e,“ try othe otherr combinations – Change PropMode PropMode to Rigorous for electrolytes electrolytes and strongly strongly

non-ideal systems Change ge FlashMode FlashMode Proce Procedure dure or ProcedurePH ProcedurePH for difficul difficultt – Chan cases • •

For example, if in critical region of the mixture With reverse flow


Good Practice Practic e Adv ice #1 • Selec Selectt appropriate appropriate valid valid phases phases in Aspen Aspen Plus – Liquid only if there is only a liquid phase – Vapor only if there is only a vapor phase

• Reason: Reason: The calculatio calculations ns of the properties properties of the missing missing phase can cause problems • Addit Additional ional benefit: benefit: Your Your simulation simulation will will run faster faster


Good Practice Practic e Adv ice #2 • Remove Remove components components that that are not requir required ed for the dynamic simulation – This is easier done in Aspen Plus

• Reason: Reason: The calculat calculation ion of the properti properties es of these these components (with mole fraction of 0) can lead to problems • Additional Additional benefit: benefit: Your simulatio simulation n size will decrease, decrease, hence it will run faster


ComponentLists in Aspen Aspen Dyna ynamics mics • List of compone components nts and physica physicall property property method method

Can be used to remove components © 2002 AspenTech. All Rights Rights Reserved.

Note on Liq uid-Liqu id Calcul Calcul ations • Phase Phase labeling labeling (i.e., Phase Phase 1 and Phase Phase 2) is based based on density • Free water is not not support supported ed – Use liquid-liquid-vapor calculation instead

• Rigorous Rigorous properties properties may may fail for liquid-liquid liquid-liquid calculat calculation ion because this mode does not check for phase stability – Use Procedure flash or leave to Local properties


Demons De mons tration 20 206 6-physic -physica al-properties files



Process Control Introduction to Aspen Dynamics


Lesson Objectives • Learn about about the Aspen Dynamic Dynamics s process process control control models • Beco Become me familiar familiar with with the PID PID controller controller • Compl Complete ete Works Workshop hop 301-c 301-contro ontroll


Process Contr Contr ol • Compr Comprehens ehensive ive Control Control Model Model Librar Library y • AutoAuto-gener generated ated PID Contr Controller ollers s – Pressure – Level – Temperature in RCSTR


Process Contr Contr ol Models Mo d el

Des c r i p t i o n

Compar Comp arat ator or Dead_time Discretize DMCplus FeedForward HiLoSelect IAE ISE Lag_1 Lead_lag Multiply Noise PID PRBS Ratio Scale SplitRange Sum Tra rans nsfo form rm Valve_dyn

Calc Ca lcul ulat ates es the the dif difffer eren ence ce be betw twee een n two two inpu inputt sig signa nalls Delays a signal by a specified time Discretizes a signal Interface to to DMCplus online co control (r (requires lilicense) Feedforward controller Selects th the hi higher or or lo lower of of tw two in inpu putt si sign gna als Calculates the integral of the absolute value Calculates the integral of the squared error Models a first order lag between the input and output Models a lead-lag element Calculates the product of two input signals Gaussian white noise signal A t h r ee m o d e p r o p o r t i o n al i n t eg r al d er i v at i v e c o n t r o l l er Generates a pseudo-random binary signal Calculates the ratio of two input signals Scales an input signal Models a split range controller Calculates the sum of two input signals Perf Pe rfor orm ms a lo loge ge,, sq squa uare re,, squ quar are e ro root ot,, or po pow wer tr tran ans sfo form rm Models the dy dynamics of a va valve ac actuator


PID Control Block – Prede redefined fined Forms • Al AllV lVar aria iabl bles es • Co Con nfi figu gure re • Fac Facepl eplate ate an and d Com Compa pactFa ctFaceP cePlat late e – Set point – Process variable – Controller output – Mode

• Results • Re Resu sult ltsP sPlo lott an and d Re Resu sult ltsP sPlo lotP tPer erce cent nt – Set point – Process variable – Controller output © 2002 AspenTech. All Rights Rights Reserved.

PID PI D Controll er Face acePla Plate te

Manual mode switch A ut o Aut mode switch


Cascade mode switch

Percent toggl es display b/w b/w process unit s and % Configure form Plot form

PID PI D Block Configur e Form: Form: Tuning and Ranges Ranges


PID PI D Bloc k Confi Confi gure Form Form – Tuni ng (1) (1) • Ope Operat rator or set poi point nt – Used when controller is in auto mode

• Bias – Constant term added to the controller output – Typically set to value of manipulated variable when process is

in steady state

• Gain – Dimensionless units

[gain with units ] © 2002 AspenTech. All Rights Rights Reserved.

=

[gain]

[rangeOP] [range PV ]

PID PI D Bloc k Confi Confi gure Form Form – Tuni ng (2) (2) • Int Integr egral al Time Time (reset (reset time) time) – Units of time/repeat – Set to a large value for no integral action

• Deriv Derivative ative Time (rat (rate e time) time) – Units of time – Set to 0 for no derivative action


PID PI D Contr Contr oller Ac tion • Ho How w to to sele select ct? ? – When the measured variable increases increases,, the manipulated

variable should be increased increased:: select "Direct " Direct"" – When the measured variable increases increases,, the manipulated

decreased:: select "Reverse variable should be decreased " Reverse"" REVERSE

DIRECT

LC

f l ow

LC flow


PID Block Block Configure Configure Form – Filte iltering ring • Vario Various us options options for filter filtering ing – See online help for details


PID PI D Block Configure Form Form – Other • Con Contro troll alg algori orithm thm – Ideal (default) – Series (interacting or analog algorithm) – Parallel (ideal parallel or

non-interacting algorithm)

• Bu Bump mple less ss tr tran ansf sfer er • Ant Anti-r i-rese esett win windup dup • De Dead adba band nd


PID PI D Initialize Va Values lues Button • Uses the the current current values values of the measured measured variabl variable e and manipulated variable to initialize controller parameters – The value for the operator set point changes to the value of

the measured variable – The value for bias changes to the value of the manipulated

variable – Proce Process ss varia variable ble and output output ranges changed to 0 and 2 times

the value •

Exception: For valve position, the range is specified to 0 and 100%

• Typically, Typically, you you use this only only once, once, when you you create create the PID block


PID PI D Gain Gain and Integral A cti on • You may observ observe e a disturbance disturbance when when you change change the gain, due to the way integral action is implemented 4 0 . 8 7 2 0 . 8 7 8 7 C e l b C 8 a t 9 i . r i n 7 a o 7 V P s t s e 6 e S c 9 . o 7 r P 7 4 9 . 7 7 2 9 . 7 7 9 . 7 7

5 4 . 0 1 1 4 . 0 1 1 5 3 . 0 1 1 3 C . t 0 u 1 p 1 t u 5 O 2 . r 0 e l 1 l 1 o r t 2 n . o 0 1 C 1 5 1 . 0 1 1 1 . 0 1 1 5 0 . 0 1 1

0.1

0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19

set poi nt chan change ge © 2002 AspenTech. All Rights Rights Reserved.

0.2 0.21 0.22 0.23 0.24 0.25 0.26 0.27 0.28 0.29 Time Hours

0.3

0.31

gai n cha changed - di st ur bance ance!!

Au A u t o -Gen -Gener erat ated ed Co Con n t r o l l er ers s • PID controller controllers s are automatica automatically lly added during during the export export from Aspen Plus – Pressure – Level – Temperature in RCSTR

• More detail detail can can be found found in the online online help help


Au A u t o -Gen -Gener erat ated ed Co Con n t r o l l er ers s (Fl (Flo o w d r i v en m o d e)

Co n t r o l l er ad d ed

Wh en

Meas u r ed v ar i ab l e

Man i p u l at ed v ar i ab l e

Pressure

Vapor holdup is modeled

Pressure in vessel

Vapor outlet mole flow rate

Level

Liquid holdup is modeled

Liquid level

Liquid outlet mass flow rate

Temperature CSTR block


Temperature

Duty

Au A u t o -Gen -Gener erat ated ed Co Con n t r o l l er ers s (p d r i v en m o d e) • During the the export, export, it checks for for valve connecte connected d on liquid and vapor outlets – If a valve block is present, the controller will manipulate the

valve position • •

Pressure control with vapor outlet Liquid level with liquid outlet

– If no valve block is present, the controller controller is still created so that

you can select another appropriate variable to manipulate in Aspen Dynamics Dynamics


Control Syste System m • The purpos purpose e of the the controlle controllers rs crea created ted automati automatically cally is to make sure the simulation will remain at steady state in Aspen Dynamics – It usually provides a good starting point for the control strategy,

which you can modify in Aspen Dynamics

• You can invoke invoke the the script script "RemoveCon "RemoveControl" trol" from from Dynamics library, Scripts to remove all these controllers if you prefer to define your system from scratch


Work orksho shop p 301 301-contro -controll

files



Workshop 301: 301: Control of a Disti Disti llation Colum n C4/C5 C4/ C5 split ter • Purpose: separate separate C3, iC4, nC4 in distillate and iC5, nC5 in residue • Contr Control ol tempera temperature ture on stage 18 – Dead_Time and PID models – Tuning the controller using Ziegler Nichols method

• Contr Control ol of composi composition tion (iC5 (iC5 + nC5) nC5) in distilla distillate te – Compos Composition ition analyzer analyzer with Sum, Dead_Time Dead_Time and Discretiz Discretize e model,

PID for control

• Overri Override de contro controll for pres pressure sure drop – Compare model for pressure drop calculation – HiLoSelector to override the temperature controller action

• Optio Option: n: pressure pressure compensati compensation on for temperature temperature control control – Using Flowshee Flowsheett constr constraints aints © 2002 AspenTech. All Rights Rights Reserved.

Workshop 30 301: 1: Temperature Temperature Contr Contr ol Loop

C-101 DIST FEED

Dead_ Ti me PI D

BOTM


Compressor Control Introduction to Aspen Dynamics


Lesson Objectives • Revie Review w some issues issues with compress compressor or system system modeling modeling • Compl Complete ete Works Workshop hop 302-co 302-compres mpressor sor


Compressor Control • Sim Simple ple anti-s anti-surg urge e control control – PID block – Illustrate the Lag_1 block for dynamic response of valve

• Speed – Performance curve – Instantaneous vs. dynamic compressor

• Fl Flow owsh shee eett co cons nsid ider erat atio ion n – Use of simple phase option (vapor only vs. vapor-liquid) – Addition of blocks blocks for dynamic simulation simulation (volume (volume of pipes)


Work orksho shop p 30 302 2-compressor files



Press Pre ssur ure e Re Reli lief ef Capa Capabi bili liti ties es (Optional) Introduction to Aspen Dynamics


Pressure Reli Relief ef Capabil Capabil it ities ies • The followi following ng models models are are available available:: Mo d el

Des c r i p t i o n

BurstingDisk

Bursting disk

DeltaP

User pressure drop – si simple representation of flow resistance

Expansion

Pipe expansion/contraction

Orifice

Orifice

PSV

Pressure safety valve

Tvalve

Conventional valve using the same methods as in PSV


Flow Calculatio Calculatio n Mode Models ls • Calcu Calculates lates sub-cr sub-critical itical and and critical critical flow flow • Models single single-phas -phase e or two-pha two-phase se flow flow • Flow Equat Equations ions taken from from:: – Modified omega method (Schmidt /Westphal, 1997) – Frozen or partially frozen flow (Henry-Fauske, 1992) – German standard AD-A2 (Diener/Friedel, 1997) – Ideal nozzle (HEM), (DIERS,1992) – Ideal nozzle (HEM), (Simpson, as per Aspen Plus) – Vapor phase compressible compressible flow (as in API 520) 520) – Simple single-phase relationship (incompressible flow)


PSV • Conve Conventiona ntionall or Balan Balanced ced type • Vario Various us valve valve characteris characteristics tics can can be defined defined • Hyst Hysteres eresis is (diffe (different rent open and close pres pressure sures) s)


PSV PS V Conf Conf igu re Hyst Hyst eresis • Va Valv lve e sett settin ings gs full lift pressure,

full lift pressure,

closing

opening

reset

primary lift

valve position

valve position

reset pressure

set pressure


Relief Re lief Outlet Out let Port • Vap Vapor or pha phase se rel relief ief – Flash2 – Flash3 – Mixer – RadFrac

• Singl Single e and two phas phases es relief relief – RCSTR


RCSTR • Allow Allows s venting venting from from top or bottom bottom of of vessel vessel • Models liquid liquid swelling swelling during during relief relief to predict predict quality in the vent line • Dis Diseng engage agemen mentt model models s – Homogeneous – Zero vapor-liquid disengagement – All vapor/All liquid – Total vapor-liquid disengagement – DIERS bubbly/churn-turbulent model – User specified constant vapor fraction


Ad A d d i t i o n al Feat Featu u r es o f RCSTR • Models thermal thermal inertia inertia of vessel vessel and/or solid solid catalyst catalyst • Cat Cataly alyst st deact deactiva ivatio tion n

Switch for Pressure Relief Calculations


Pipe • Calcu Calculates lates sub-cr sub-critical itical and and critical critical flow flow • Handle Handles s single-ph single-phase ase or two-p two-phase hase flow flow – Friction models (Beggs-Brill, Darcy, Lockhart-Martinell Lockhart-Martinelli) i) – Holdup models (Beggs-Brill, Darcy, Rouhani)

• Models slip slip between between vapor vapor and liquid phases phases when when modeling multi-phase flow • Dynamic Dynamic momentum momentum balance balance predicts predicts velocities velocities and detects state of critical flow at end of pipe • Includ Includes es continuous continuous phase phase changes changes along along the length length


Creati Crea ting ng a Pressure Relief Relief Simu latio n • Conv Converge erge the pressure pressure driven driven simulatio simulation n in Aspen Plus • Export Export the simulation simulation as a pressure pressure driven driven dynamic dynamic simulation • Load the problem problem in Aspen Aspen Dynamics Dynamics and and remove remove any unwanted control loops • Add the required required relief relief blocks to the relevant relevant block’s block’s relief port • Use the relevan relevantt block Configur Configure e form to switch switch to “Perform pressure relief vapor/liquid disengagement calculations” © 2002 AspenTech. All Rights Rights Reserved.

Creatio Crea tio n of a PSV PSV Blo ck • Chang Change e the run run mode mode to Initializ Initialization ation • Do a run run and creat create e a kept kept result result • To create create a Pressure Pressure Safety Safety Valve Valve block block – Drag and drop PSV from Dynamics library, Pressure Relief – Connect the input input and output streams streams using the MaterialStream

type – Check the pressure for the output stream •

Defaults to 1 bar


Settin Se ttin g u p t he PSV PSV • First First speci specify fy the the options options for for the the hys hyster teresi esis s to make make sure sure that the valve will be closed • Click on the the "Initial "Initialize" ize" butto button n • Then you you can change change the other other settings settings (flow method method,, diameter, etc.) – Click on "Initialize" after each change

• The purpose purpose of the the "Initializ "Initialize" e" button button is to: – Run the simulation in a specific way first to solve the complex

equations of the PSV – Give good preset values to the variables


Worksho Works hop p 303303-pr pressur essuree-relief relief Introduction to Aspen Dynamics


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Scripts Introduction to Aspen Dynamics


Lesson Objectives • Introd Introduce uce Micr Microso osoft® ft® Visu Visual al Basic® Basic® Scr Script ipting ing Edit Edition ion (VBScript) and its applications • Disc Discuss uss the the followi following ng topics: topics: – What is a Script? – Uses of Scripts – Creating a Script – Invoking a Script – Examples of Scripts

• Compl Complete ete Works Workshop hop 304-s 304-scripts cripts


Whatt is a Scrip Wha Scrip t? • A Script is a set of instruct instructions ions written written in Microsoft Microsoft Visual Visual Basic Script Scripting ing Edition (VBScript) (VBScript) – Method to automate simulation setup and control – Uses automation methods and properties to control the

simulation

• Us Use e VBSc VBScrip riptt from from – Scripts that use Microsoft Visual Basic Scripting – External Microsoft Visual Basic applications • •

Microsoft Visual Basic Microsoft Micro soft Visua Visuall Basic for Applications Applications (VBA) (VBA) as supplied supplied with Microsoft Microsoft Office applications, such as Microsoft Microsoft Excel and Microsoft Word


Uses Use s of Scrip Scripts ts (1) • Aut Automa omate te and rec record ord flo flowsh wshee eett act action ions s • Contr Control ol sequen sequences ces of of simulati simulation on runs runs • Def Define ine varia variable ble prope properti rties es • Aut Automa omate te flo flowsh wshee eett pro proble blem m spe specif cifica icatio tion n • Con Constr struct uct or mod modify ify flo flowsh wsheet eet con connec nectiv tivity ity • Ma Mani nipu pula late te tas tasks ks • Automa Automate te simul simulation ation initi initializa alization tion • Acc Access ess com compon ponent ent lis lists ts


Uses Use s of Scrip Scripts ts (2) • Defin Define e custom custom Units of Measure Measure (UOM) (UOM) sets sets • Store and and apply differe different nt sets of specifi specification cations s • Call extern external al windows windows applica applications tions • Cal Calll scripts scripts with within in script scripts s • Call Scripts Scripts from other applic applications ations – Excel macro – Visual Basic


Uses Use s of Scrip Scripts ts (3) • Use “FO “FOR R LOO LOOPS” PS” spe specifi cificat cation ions s • Print message messages s in Simulatio Simulation n Messages Messages window window • Inp InputB utBox ox to requ request est dat data a from from use user r


Creati Crea ting ng a Scri Scri pt (1 (1)) • AutoAuto-genera generate te scrip scripts ts from: – Status window – Variable Find tool

• Add scr script ipts s manu manuall ally y – Simulation Explorer


Creati Crea ting ng a Scri Scri pt (2 (2)) • Syntax for variable variable name assign assignments ments – BlockName.VariableN BlockName.VariableName.Property ame.Property = ##### – StreamName.VariableName.Prop StreamName.VariableName.Property erty = #####

• Example Example of Script Script statements, statements, assigning assigning values values to properties – Blocks(“B1”).Temp.Value= 550.0 – Blocks(“B1”).Temp.spec = “Fixed” – Blocks(“B1”).X(“CO2”).Value = 0.03 – Blocks(“B1”).X(“CO2”).Upper = 0.1


Creatin Crea tin g a Scri Scri pt With Variable Find Find • Script with curren currentt values values and specifica specification tion

2.Enter the script name

3. Edit the Script 1. Select the variables to put on the script © 2002 AspenTech. All Rights Rights Reserved.

Creati Crea ting ng a Scri Scri pt (3 (3)) Add A dd Scr ip t i co n i n Flowshe lowshee et folde folder r


Invoking a Scrip Scrip t


Example – Controlling a Simulation Simulation • Contr Controlling olling a simulation simulation with with automatio automation n B2. V. val ue = 15 ' set s t he r un mod ode e Appl i cat i on. Si mul at i on. RunMod ode e = " Dyn ynam ami c" ' se sett s t he end t i me Appl i ca catt i on. Si mul at i on. EndTi me = 13 ' s t ar a r t s t he s i mul at i on Appl i ca catt i on. Si mul at i on. Run( t r ue)


Example Exa mple – Writ ing Message Messages s • Write to the Simula Simulation tion Messages Messages Window Appl i ca catt i on. Msg Appl i cat cat i on. Msg Appl i ca catt i on. Msg Appl i Appl i cat i on. Msg

"Hel l o Wor l d" "He Appl i ca catt i on. Si mul at i on. RunMode " Run Mode i s " & _ catt i on. Si mul at i on. RunMode ca " Run compl et e at t i me " & Ti me


Example – Automation Methods Methods (1) • Creat Creating ing an instan instance ce of an applica application tion object object Di m ADApp as Obj ect ‘ cr eat e an i nst ance of an appl i ca catt i on obj ect Set ADApp = Cr eat eObj ect ( ”A ”AD D Appl i ca catt i on”) ‘ make t he obj ect vi si bl e ADApp. Vi si bl e = Tr ue


Example – Automation Methods Methods (2) • Accessi Accessing ng an applica application tion objec objectt Di m ADDocu ocum men entt as Obj Obj ect ‘ Ope pen n an ex exii st i ng si mul at i on docu ocum men entt Set ADDocu ocum men entt = ADApp. Open enD Docu ocum men entt ( ”C ”C:: \ Fl ash ash.. dyn ynff " )

Di m ADSi mul at i on as Ob Obj ect ‘ Ask t he ap appl i ca catt i on f or acce ccess ss t o the si mul at i on Set ADSi mul at i on = ADApp. Si mul at i on


Example – Automation Methods Methods (3) • Using a simulatio simulation n variable variable to run the the simulation simulation ‘ Chan hange ge t he r un mode t o dynam dynami c ADSi mul at i on on.. Run unM Mod ode e = “D “Dyna ynam mi c” ‘ Run t he si mul at i on and wai t f or i t t o co com mpl et e ADSi mul at i on on.. Run ( Tr ue)

• It is not necessar necessary y to explicitly explicitly create create a new variab variable le for the simulation ‘ Chan hange ge t he r un mode t o dynam dynami c ADApp pp.. Si mul at i on on.. Run unM Mod ode e = “ Dyna ynam mi c” ‘ Run t he si mul at i on and wai t f or i t t o co com mpl et e ADApp. Si mul at i on on.. Run ( Tr ue)


Example – Automation Methods Methods (4) • Checki Checking ng the the Simulatio Simulation n for Succes Success s I f ADSi mul at i on. Succ cce essf ul Then MsgB sgBox ox “Si mul at i on Compl et e” El s e Msg sgB Box “S “Sii mul at i on Fa Fai l ed” End I f


Example – Automation Methods Methods (5) • Saving change changes s and quitting quitting the Applicati Application on ‘ Save t he changes changes and s hu hutt down t he As As pen Dynami cs ‘ appl i c at i on ADAp App. p. SaveD SaveDoc ocum ument ( ) ADApp pp.. Qui t


Scripts References • More informa information tion and example examples s on Scripts Scripts and automation methods and properties can be found in online help – Under Aspen Custom Modeler, Automation Reference


Work orksho shop p 304 304-scr script ipts s Introduction to Aspen Dynamics


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Hint ints s and and Tips Using Aspen A spen Dynamics Dynamics Introduction to Aspen Dynamics


Hints and Tips Using Asp en Dynamics Dynamics • First, First, always investi investigate gate the proble problem m from the the engineering point of view • Di Diag agno nost stic ic tool tools s • So Solv lver er set setti ting ngs s • Fi File le mana manage geme ment nt


Look ing at a Problem • It may may be be usefu usefull to stu study dy a lar large ge flow flowshe sheet et in smalle smallerr sections • Create Create tables tables and plots plots to help you you investigate investigate the the behavior of a simulation • Create Create tasks to help help you repeat repeating ing actions actions in a consistent way • Try changin changing g only one thing thing at at a time time • Use "kept "kept results" results" to store store your your starting starting points points


Problems with Init ializ ialization ation • Chang Change e the run mode mode to to initializati initialization on • Run the sim simula ulatio tion n • In case case of prob problem lems: s: – Tighten tolerances (Flash calculations, design-specs, which are

used to ensure pressure balance, tear streams) – Increase number of segments in RPLUG or PIPE – Consider simplifying phase option and removing components where applicable – Try rigorous properties – Try to avoid blocks blocks with with zero flowr flowrate ate – Review any warning message displayed during export © 2002 AspenTech. All Rights Rights Reserved.

Control Syste System m • Always do an initializa initialization tion run before before changing changing control control structure – Otherwise you may get "default" values in new controllers with

the "initialize" button

• Check for for control control system not operating operating prope properly rly – Add controllers where required – Double check their settings – Suspect saturated controllers – Suspect controllers with high gain, short integral time


Tasks • Values in task task must be in Metrics Metrics units • You can only only change change the value value of fixed variab variables les • Consid Consider er trying contin continuous uous ramps – RAMP (variable, final value, duration, continuous);

• Conve Convergenc rgence e failure failure after after a step step change change – Try making the initial step smaller – Create plots to investigate what is happening


Diagnost Dia gnost ic Tools • Gro Group up dec decomp omposit osition ion – May give a hint on the location of the problem

• Sol Solver ver repo reporti rting ng level level • So Solve lverr opt optio ions ns – High residual option

Notes:: Notes – If you observe numerical noise, consider switching physical

properties to rigorous mode – It may be useful to look at the model equations (in Dynamics library)


Group Decomposition • Displays Displays how the system system is decompo decomposed sed for the the resolution – A red cross on a group indicates the non-converged group,

which may give an indication of where the problem is located – Details of equations and variables are displayed


Simulation Simul ation Me Messages ssages (1) (1) • Solver repor reporting ting level: level: Use Mediu Medium m and High High • Messag Message: e: "Integratin "Integrating g from ..." = communicati communication on interval interval • Mes Messag sage: e: "Step "Step nnn nnn... ..."" = integra integratio tion n step


Simulation Simul ation Me Messages ssages (2) (2) • Time: Value Value of time time at which which it is trying trying to solve solve • Step size: size: Controlled Controlled by the integrat integrator or for accuracy accuracy – Small step size means fast phenomenon taking place, or in

other words, far from steady state

• Step factor: factor: Amount Amount by by which the the step size is is increased increased – Value lower than 1 means that integrator is detecting faster

changes

• Accept Accepted/Rej ed/Rejected: ected: Succes Success s flag – When a step is rejected, the step size is cut


Run, Solv Solv er Opt Option ion s: Convergence Conv ergence Parame Parameters ters • Int Integr egrati ation on paramet parameters ers – Aspen Dynamics works only with VSIE VSIE and Implicit Euler – Minimum integration step – Initial integration step – Maximum integration step •

Make them smaller based on the expected process time constants

• Reporting Reporting the highest highest residual residual can give give some indication indication of the problem – Selected on Non-Linear Solver tab – Bounds may prevent convergence


Non-Linear Solv er Tab Tab • Di Diag agno nost stic ics s


File Management • Keep the bkp! • Dyn Dynami amic c sim simula ulatio tion: n: – dy dynf nf fi file le – appdf file (physical (physical properties properties)) – Snapshots: use kept results

• Wo Work rkin ing g folde folder: r: – Keep it tidy •

c:\program files\aspentech\working folders\Aspen Dynamics...


Snapshott Management Snapsho Management Tool • Cop Copy y Values Values to copy copy fro from m a prev previou ious s run run • Keep/Don't Keep/Don't keep contr controls ols if the result results s are store stored d in dynf file or not


Create Cre ate Snapshot Snapshot to Store Startin Startin g Point • Snapsh Snapshot ot managem management ent tool, Creat Create e


Workshop Works hop 30 3055-us usage age Introduction to Aspen Dynamics


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Handl Ha ndling ing Extr eme Condi Conditio tions ns (Reference Only) Introduction to Aspen Dynamics


Features Fe atures of Aspen Dynamics Mode Models ls • Handli Handling ng of extr extreme eme temper temperature ature – Typical problem with constant duty heat transfer option

• Handli Handling ng of empty and full full vesse vessels ls


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Process Heat Heat Transfer Opti on • Co Cons nsta tant nt Du Duty ty – Consider this like a fired heater: the duty is given to the block

regardless of the process stream flowrate – If that flow becomes too low, the temperature trips – Note: the same problem happens with cooling duty

• Aspen Aspen Dynamic Dynamic models have have a protection protection feature feature for "extreme" temperatures to prevent convergence failure – However, in practice the physical property calculations usually

fail before

• Moral Moral:: Better avoid avoid constan constantt duty when when you can!


Handl Ha ndl ing of Temperatu Temperature re Extr Extr eme emes s • Exam Example ple for a cooling cooling duty duty (Q is negative) negative) 0 Heat duty Q

Normal: Q = QR QR

QR Temperature T_min

T_min + delta_T

T_max as gl obal r eal par amet er ; T_mi n as gl obal r eal par amet er ; del t a_t as gl obal r eal param aramet er ; c al l ( Q) = © 2002 AspenTech. All Rights Rights Reserved.

pqs pec

/ / Max. Temp. l i mi t ( 1995 / / Mi n. Temp. l i mi t ( -214 / / Temp. di f f . ( 5 C)

(Q QR R, T, T_ mi n, T_ max, del t a a_ _ T) ;

C !) C !)

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Handli Ha ndli ng of Empty and Full Ve Vessels ssels • Flow driven driven simul simulations ations allow change change of flowrat flowrate e direc directly tly by user or with controller. You can: – “Remove” liquid from empty vessel vessel flow – “Add” liqu liquid id to full vessel vessel where inlet inlet flowrate flowrate is greater greater than

outlet flowrate

• Concept Concept of “req “required” uired” liquid outlet flow rate rate is intro introduced duced in the material balance for the vessel empty case • “Overflow “Overflow”” liquid flow is introdu introduced ced in the the material material balance for vessel full case


Handli Ha ndli ng of Empty Vessels Vessels Fl_outR Normally: Fl_out = Fl_outR Liquid Flow Rate Fl_out

Flow stops as in reality 0

Liquid Volume V_min V_low

Fl_outR Fl_out V_low V_Min © 2002 AspenTech. All Rights Rights Reserved.

Required liquid outlet flowrate Actual liquid flowrate 0.5% of the vessel volume Zero volume

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ng xtreme on t ons

Handl Ha ndl ing Full Vessel Fmax Liquid Overflow Rate (Fl_over)

Loss of material! vapor

0

Fl_over Fmax V_high V_Max

Liquid Volume

V_high

V_Max

Liquid overflow rate Maximum allowable liquid flow 99.5% of the vessel volume Vessel volume

liquid overflow

liquid


Warnin Wa rnin g in Simulation Me Message ssages s • Warning Warning in Simulation Simulation Messag Messages es when vessel vessel is full full or flow specification cannot be met pCha pChaii r X- W- Li qui qui d vol ume or pr ess ur e of appr oachi oac hi ng maxi mum of #### Mat er i al i s bei bei ng vent ed, vent f l ow = #### kmol / hr

####

• Liquid overflo overflow w and vent vent stream are are not modeled, modeled, i.e., i.e., they are lost in the overall material balance – "Overflow stream goes on the plant floor..."


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Sele Se lection ction of Limits

Global table


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Modell Customi Mode Cust omiz zation (Optional) Introduction to Aspen Dynamics


Lesson Objectives • Disc Discuss uss the the followi following ng topics: topics: – A primer on ACM language (survival kit) – The main steps in customizing a model •

Introduction to Aspen Custom Modeler (ACM) course covers all the

details of the language, hence this will not be repeated here

• Demon Demonstrate strate Heate Heaterr Customi Customization zation


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Overview of Modelin g Langu age in 5 Minu Minu tes • ACM lan langua guage ge is not not CaS CaSe e Sens SensiTI iTIVE VE • Mark the the end of each each statemen statementt with with

;

• Co Comm mmen ents ts : – // comment to the end of the line – /* multi lines

comments */

• $Variab $Variable le : time time derivative derivative of the variable variable


Simple Customization Customization s • Pr Pro obl ble em: – Design specifications and FORTRAN blocks are not translated

in Aspen Dynamics

• So Solu luti tion on:: – Use the flo flows wshee heett con constr strain aints ts

• Re Requ quir ires es – Minimal knowledge of Aspen Custom Modeler language


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Example Exa mple of a Simpl Simpl e Custo Custo miza mization tion • Heat transfer transfer function function of of temperature temperature differe difference nce • Furna Furnace: ce: modele modeled d using using RGIBB RGIBBS S • Steam/ Steam/heatin heating: g: modeled modeled using using a HEATER HEATER • Aspen Plus: FORT FORTRAN RAN : Q = UA*DT UA*DT • Aspen Dynam Dynamics: ics: FLOWSH FLOWSHEET EET constra constraint int


Other Examples • Averag Average e of tray tray temperatur temperatures es in RADFRAC RADFRAC • Pressur Pressure e correction correction of a temperatur temperature e controller controller • Calculation Calculation of reporting reporting quantitie quantities s (i.e., efficiency efficiency of the the plant, composition in customary units, etc...)


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Custom Modeling in A spen Dynamics Dynamics Asp A sp en Dyn Dy n ami cs As p en Cu st om Mod eler

A s p en As Plus

Export

Browse Models and Modify Flowsheet

Transfer Models

Create and Edit Custom Models

As A s p en Pr Pro o p er ertt i es Sy Sys s t em © 2002 AspenTech. All Rights Reserved.

As A s p en Cu Cus s t o m Mo Mod d el eler er an and d Dy Dyn n am amii c s Feat u r e

A CM

AD

A CM+A D

Run GUI and calculations







Create new models m odels



Use the Dynamics library Call Properties Plus


yes

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yes

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Steps Ste ps i n Custom izing a Model • Enable "Cust "Custom om Modeling" Modeling" (Tools, Settin Settings) gs) • Copy the the model from from the library library to "Custom "Custom Modeling" Modeling" • Sa Save ve th the e fil file e • Reload • Apply your your modificatio modifications ns to the the copied copied model model


Overview of ACM Types Types Flowsheet

block submodels

Model Types Model Types Models

stream stream

Stream Types Stream Strea m Types

block port Port Types

... is declared by ... name AS type;

Port Types

variable or

parameter

Parameter Para meter Types Variable Types


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Basic Elements o f a Model Model MODEL

Model odel Name

/ / va varr i abl e and par amet er decl ar at i ons Var i abl abl eNam eName

AS

Par amet er Name

Var i abl abl eTypeN eTypeNam ame;

AS

Par amet er TypeName;

/ / por t decl ar at i ons Por t Name1

AS INPUT

Por t TypeNam TypeName;

Por t Name2

AS OUTPUT

Por t TypeNam TypeName;

/ / Assi gnment s Var i abl eName. pr oper t y : expr xpr essi on; / / Equat i ons Equa Equatt i onN onName: exp expr essi on1 on1 = expr expr essi on2; on2; END © 2002 AspenTech. All Rights Reserved.

Documentation • Aspen Dynami Dynamics cs physical physical property property submodel submodels s – See online documentation for list of available models

• Con Convers version ion para paramet meters ers – See online documentatio documentation n

• See models models comments comments for additio additional nal informatio information n


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Typical Applications for Customization • Cha Change nges s for for usabi usability lity – Exam Example ple to to create create new new varia variables bles as input/ input/outpu outputt for contr control ol or

reporting purposes

• Cha Change nges s of equ equati ations ons – Geometry, reactions, other correlations, etc...

• Exampl Example: e: heater heater with with calculated calculated heating heating curve – Illu Illustrat strate e the submo submodels dels – Illustrate the use of a script to preset the submodels


Demonstr emonstra atio tion n 306 06--cus custom tomiza izatio tionnheater Introduction to Aspen Dynamics


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Kinetics Estimation Estimation with wit h As A s p en Dy Dyn n am amii c s (Op (Optt i o n al al)) Introduction to Aspen Dynamics


Lesson Objectives • Aspe Aspen n Dynamics Dynamics estimati estimation on capabilitie capabilities s • Ki Kine neti tics csEs Estt mo mode dell • Compl Complete ete Workshop Workshop 307-kineti 307-kinetic-es c-estimati timation on


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Estimating Re Reaction action Kinetic Pa Parame rameters ters • Ki Kine neti ticE cEst st mo mode dell provi provide des s – Power Law and LHHW •

Customized reactions possible with Aspen Custom Modeler license

– Rigorous or "bulk" physical properties

• Esti Estimatio mation n of fixed variables variables using using Estimation Estimation run mode – Weighted least square estimation – Maximum likelihood


How to Use the Kinetic Estim ation? • Prep Prepare are physical physical proper properties ties in Aspen Aspen Plus Plus – Use Run Type "PROPERTIES PLUS"

• Creat Create e a blank simulat simulation ion in Aspen Aspen Dynamics Dynamics • Cha Change nge solv solver er optio options: ns: – General: to use Tearing – Integrator: VSIE or Gear

• Cre Create ate a com compon ponent entlis listt wit with h the req requir uired ed compo componen nents ts • Drag Drag and drop drop the the Kin Kineti eticE cEst st mod model el from from React Reactors ors fol folder der in Dynamics library


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Configur ation of t he Rea Reacto cto r • Use the the Confi Configur gure e form: form: – Specification – Reaction – Estimated Variables – Measured Variables – Dosing – Experiments


Specification Sheet • Properties Properties Compo ComponentLi nentList: st: selec selection tion of the the compone components nts (both reactor and doses) • Solv Solvent ent relevant relevant for some some compositi composition on basis • Pr Prop oper erty ty mod mode: e: – Rigorous: using Physical properties from Aspen Plus – Bulk: constant properties given by the user – Local: similar to Rigorous (prefer to use rigorous)


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Reactions • Spec Specificat ification ion of the reacti reactions: ons: – Power Law – Langmuir-Hinshel Langmuir-Hinshelwood-Hougen-Watson wood-Hougen-Watson (LHHW) – Custom Reaction


Estimated Estim ated and Measur Measur ed Variabl Variables es • To select select the variables variables for for the estimatio estimation n and the experiments


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Dose • Each dose dose corresponds corresponds to a feed stream stream for which which you can specify the conditions (flowrate) • Flowr Flowrate ate will be specifi specified ed in the Exper Experiment iment infor information mation


Experiments • Ex Exper perime iments nts def define ine:: – Values vs. time of the measured variables •

Typical example: Q = heat duty

– Starting conditions (initial variables) •

Typical example: initial holdup in the reactor

– Run conditions (fixed variables) • •

Variables can be ramped, i.e., changed as a function of time Typical example: flowrate for the dose

• You can can copy and and paste paste the data data from Excel Excel


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Running th e Estimation • Chang Change e the run mode mode to to Estimati Estimation on • Run the sim simula ulatio tion n • Iterations Iterations and and results results can be seen in the the Simulation Simulation Messages window • Resul Results ts can also also be displayed displayed in Tools, Tools, Estimati Estimation on • Ex Exper perime iment nt dat data a will will be sav saved ed in the the dyn dynff file


Note • Pay attent attention ion to the the heat heat of reactio reaction n – Defined via DHFORM parameter in Aspen Plus

• Give good good initial estimates estimates for the the regressed regressed parameter parameters s • Do not try try to regress regress too too many param parameters eters


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Workshop Worksho p 307 07-kinetic-e -kinetic-esti stimation mation Introduction to Aspen Dynamics


Workshop Summary • Hydrolysis of acetic anhydride 5 2 . 0

dose

Estimation: Fixed Variable - KineticEstimation

2

. r 0 h / g 5 k 1 ) . 1 ( 0 n i _ 1 . 0 m F . 1 R 5 0 . 0

R1 0

500 10001500200025 10001500200025003000350 00300035004000450 040004500500055006 0500055006000650 0006500 0 Time: Seconds

4 . 5 2

Estimation: Fixed Variable - KineticEstimation

Estimation: Measured Variable - KineticEstimation 0 3

Observed

5 2

Predicted

0 2

C 2 . T . 5 1 2 R

W Q . 5 1 1 R 0 1

5

5500

6000

6500

7000

7500

8000

Time: Seconds


8500

9000

9500

5500

6000

6 500

7 000

7500

8000

Time: Seconds

8500

9 000

9 500

files

spen

ynam cs

ntro uct on to

spen

ynam cs


The End . . . Cong Cong ratul ratulation ation s!

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spen

ynam cs

Introduction to Aspen Dynamics

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