How to Write You Own User Kinetics Fortran Routine 06 UserKinetics

Reactor Modeling with Aspen Plus

User Kinetics

User Kinetics Objective: How to write you own User Kinetics Fortran routine

Aspen Plus Refere References: nces: User Models Reference Manual , Manual , Chapter 11. User Kinetics Subroutines ©2002 AspenTech. All Rights Reserved.

User Kinetic Subroutines • When your your reaction reaction kinetic kinetic does not not fit the the standard standard Aspen Plus expressions. The following models allow you to supply a kinetic subroutine to calculate the reaction rates

Model Na Name

Reaction Type

RPlug

USER

RCSTR

USER

RBatch

USER

Pres Relief

USER

RadFrac

REAC-DIST or USER

RateFrac

REAC-DIST or USER

BatchFrac

REAC-DIST

©2002 AspenTech. All Rights Reserved.


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Aspen Technology, Inc.


User Kinetics

The Goal of the Kinetics Routine • For reactor models – Calculate rate of generation for each component in each

substream – Make sure rates are in mass balance

• For stage separation models – Calculate the rate of generation for each component on a

given stage – Make sure rates are in mass balance


User Kinetic: Subroutine • All units are in SI • Have access to – Aspen Plus physical property system through the physical

property monitors – Pure component physical property parameters – Parameters specific to a reactor



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User Kinetics

User Kinetic Reactions • Fortran subroutine – Name maximum 6 characters in length – Uses real variables in double precision

• On the Reactions Reactions sheets specify: – Reaction stoichiometry – Subroutine name – Input variables through the INT and REAL vectors


Reaction Rates (1) • Units of reaction rates are different in different blocks:

• For RBatch and RCSTR – Conventional components:

(kgmole/m3-s)(m3) = kgmole/s

Note: Rates per unit volume are multiplied by the volume occupied by the reacting phase



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User Kinetics

Reaction Rates (2) • For RPLUG – Conventional components:

(kgmole/m3-s)(m2) = kgmole/m-s

Note: Rates per unit volume are multiplied by the crosssectional area covered by the reacting phase


Points to Remember about Reaction Rates • We recommend that when calculating the final rates, use the reaction volume variables, RPROPS_VLIQ and RPROPS_VVAP from common RXN_RPROPS. This guarantees: – That RCSTR behaves the same way with or without the user

kinetics subroutine. (in terms of the behavior of the parameters VOL and REAC-VOL) – That the same subroutine can be used for all types of reactor

blocks



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User Kinetics

User Kinetics: Physical Properties (1) • Use the ASPEN PLUS monitor routines to access the Aspen Plus physical property system • Monitors are available to calculate the following pure component and mixture thermodynamic properties for either vapor, liquid or solid – Fugacity coefficients – Enthalpies – Entropies – Free energies – Molar volumes – K-values – Ideal gas properties


User Kinetics: Physical Properties (2) • Vapor, Liquid and Solids transport properties are also available

• See the User Models Reference Manual Chapter 3 for more details



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User Kinetics

Passing Parameters • User constants and variables are available to kinetics routine in the real and integer vectors • They can be defined in two places – Reactions Reactions Subroutine sheet • •

Global variables Vector names in subroutine REALR and INTR

– The User Subroutine Kinetics sheet, for the RCSTR, RBatch

and RPlug reactors • •

Local to that reactor Vector names in subroutine REAL and INT


Useful Argument List Parameters • SOUT - Vector containing information about the reactor contents at the time of calling the Fortran routine – Total and component flow rates – Temperature and Pressure – Total mass enthalpy and entropy – Vapor and liquid molar fractions – Mass density – Molecular weight

• Detailed list of contents and units in this array see User Models reference manual, Appendix C



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User Kinetics

SOUT: Stream Vector Array Index

Description

1,……,NCC

Component mole flows (kmol/s)

NCC+1

Total mole flow (kmol/s)

NCC+2

Temperature (K)

NCC+3

Pressure (N/m )

NCC+4

Mass enthalpy (J/kg)

NCC+5

Molar Vapor Fraction

NCC+6

Molar Liquid Fraction

NCC+7

Mass entropy (J/kg-K)

NCC+8

Mass Density (kg/m )

NCC+9

Molecular weight (kg/kmol)

2

3


Useful Argument List Parameters • Arrays, Y, X, X1 and X2. Vapor, liquid, liquid1 and liquid2 mole fraction arrays – Mole fraction arrays are packed vectors of length NCOMP – Contain only components with non zero fractions – IDX vector defines the order of components with respect to the

Components Specifications Selection sheet Example.

If NCOMP=2 and IDX(1,3) Then Y(2) is the vapor mole fraction of the third component on the Components Specifications Selection sheet



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User Kinetics

Component Mole Fractions Size = NC Size = NCOMP X 0.3 0.3 0.4

IDX 1 2 4

Order Components.Main 1 Water 2 Ethanol 3 Methanol 4 Benzene 5 Nitrogen

Stream Liquid Mole Fractions 0.3 0.3 0 0.4 0


Accessing Universal Constants • All physical property parameters used in the simulation are available to a user routine • Stored in a labeled common call the DMS_PLEX • Each parameter occupies a continuous area within the PLEX • To access a parameter you will need to know: – The name of the parameter – The offset of the parameter in the PLEX – The structure of that area



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User Kinetics

User Kinetics: Universal Constants (1) • You can access the following universal constants: Name

Definition

MW

Molecular weight(kg/kgmole)

TC

Critical Temperature (K)

PC

Critical Pressure (N/m )

VC

Critical volume (m /kgmole)

OMEGA

Pitzer acentric factor

DHFOR M

Standard heat of formation of ideal gas at 298.15 K (J/kgmole)

DGFORM

Standard energy of formation of ideal gas at 298.15 K (J/kgmole)

TB

Normal boiling poi nt (K)

VB

Liquid molar volume at TB (m /kgmole)

TFP

Normal freezing point (K)

DEL TA

Solubility parameter at 298.15 K (J/m )

2

3

3

3 1/2


User Kinetics: Universal Constants (2) Name

Definition

MUP

Dipole moment (J*m )

RGYR

Radius of gyration (m)

CHI

Stiel polar factor

CHARGE

Ionic charge number

3 1/2



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User Kinetics

Practical Steps Required to Get a Value (1) • Include the labeled common DMS_PLEX in the model • Find the parameters name – See page 6-13 of “User Model” Reference Manual for a list of

common parameters

• Determine the offset of the parameter – Use the functions DMS_IFCMNC or DMS_IFCMN

LMW = DMS_IFCMNC(‘MW’) – This line must appear before any executable code – The MW values start from B(LMW + 1) and will be in the same order as components on Components Specifications sheet


Practical Steps Required to Get a Value (2) • Use statement functions to find the offset of any component: XMW(I) = LMW + I – Define XMW as an integer

INTEGER XMW • Use the parameter in your equation SUM=0 DO 10 I=1,NC SUM=SUM+B(XMW(I)) 10

CONTINUE



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User Kinetics

Reactor Specific Parameters (1) • Different parameters are available for each reactor unit operation • RPlug COMMON Block

Description

RPLG_RPLUGI

Integer configuration parameters, Number of reactor tubes

RPLG_RPLUGR Reactor length Reactor diameter


Reactor Specific Parameters (2) • RBatch COMMON Block

Description

RBTC_RBATI

Reactor Type

RBTC_VOLRB

Reactor volume (m )

3



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User Kinetics

Reactor Specific Parameters (3) • RCSTR COMMON Block

Description

RCST_RCSTRI

Reactor Type

RXN_RCSTRR

Reactor volume (m ), Reactor volume fraction

3


Reactor Specific Parameters (4) • General properties COMMON Block

Description

RXN_RPROPS

Reactor temperature, pressure, molar vapor fraction, BETA, Volume of vapor, liquid or liquid and solid



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User Kinetics

Using a Fortran Routine • You must compile on the Aspen Plus server with the command aspcomp

• Place the compiled object files in the run directory

• Alternatively – Write a Dynamic Linking Options (DLOPT) file which specifies

the objects to use


Fortran Compiler • To develop user kinetics routines on the PC you require a Digital Visual Fortran 5.0 compiler • End users do not required a compiler, distribute file as as shared library – Create shared libraries with the command: asplink



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User Kinetics

User Kinetic References • See User Models Reference Manual for more detailed information

• Templates are provided for many user subroutines. By default they are located in the Program Files\AspenTech\ap100\user directory


User Kinetics: Workshop 7 (1) Objective: To model a Power Law expression using a User Kinetics routine CSTR-PL

DUPL FEED

FEEDPL

PRODUCT

FEEDUK CSTR-UK

PRODUK

Filename: WK7-USERKIN.BKP



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User Kinetics

User Kinetics: Workshop 7 (2) • Setup two RCSTR reactors – Use the standard Power Law expression – Use a User kinetic routine of the Power Law expression

• Reaction Acetone + Allyl Alcohol

→

N-Propyl Propionate

r = K*EXP(-E/RT)*C ACB0. 5

Where C A

=

Concentration of Allyl-Alcohol, in kmol/m 3

CB

=

Concentration of Acetone, in kmol/m 3


User Kinetics: Workshop 7 (3) • Reaction Kinetics Pre-Exponential Factor= 52860000 m3**0.5/kmol**0.5-Sec Activation Energy = 62E6 J/kmol • Reactor Conditions Temperature = Pressure = Volume =

25 C 1 Atm 300 Liters

• Feed Conditions Acetone Allyl Alcohol Temperature Pressure

= = = =

75 kg/hr 50 kg/hr 25 C 1 Atm



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User Kinetics

User Kinetics: Workshop 7 (4) • Property Method : NRTL-RK • A template has been supplied for the User kinetic routine, USRKIN.F • Calculate the rate of reaction for all the components from the information given • Save file as WK7-USERKIN.BKP



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How to Write You Own User Kinetics Fortran Routine 06 UserKinetics

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