Gproms Guide
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Transcript of Gproms Guide
Yoshiaki [email protected]
Department of Chemical EngineeringCarnegie Mellon University
Pittsburgh, PA, 15213
PSE Seminar
February 3, 2006
Dynamic Simulation and Optimization using gPROMS
What is gPROMS?
• Stands for “general PROcess Modeling System”
• Initially developed at Imperial College, and currently sold by Process Systems Enterprise Ltd.
• Equation based process simulation/optimization software
• Windows 2000/XP and Linux are supported
• Interfaces to MATLAB, Simulink, Excel, CFD software etc.
Larry Biegler’s group currently has two licenses (two simultaneous users)
- used for simulation/optimization of adsorption processes
User Interface of gPROMS
gRMS(gPROMS Result Management System)
gPROMS Model Builder
Communicate using TCP/IP
Dynamic simulation of Differential Algebraic Equation (DAE) systems using gPROMS
• gPROMS assumes problems are dynamic by default
• Integrator: BDF and implicit Runge-Kutta
• Checks index of given DAE system (warns and stops if it is high-index)
Dynamic simulation example 1: Tank with orificeProcess Equation (DAE)
H(t) h(t)
Fin(t)
Fout(t)
h(t): Hold upH(t): Height Fin(t): Inlet flow rateFout(t): Outlet flow rate
: Orifice constant: Density
A : Cross sectional area
Parameters (constants)Variables
4 variables, 3 equations :
Need to “assign” one variable to make degree of freedom to be zero
Model Implementation
: density
: cross sectional area
A :orifice constant
h(t): Hold upFin(t): Inlet flow rate, Fout(t): Outlet flow rate
H(t): Height
Model
Model Specification
Parameter values
Call “Unit” (Tank model)
Assign variable (Make DOF be zero)
Initial condition
Integration
Process
Option
Sequence
20
Fin(t):
1800 t 1800 t
20
Fin(t):
900
10
Model of cooled reactor
Dynamic simulation example 2: Tubular reactor with cooling jacket
z
r
Reactor model
Jacket model
Handling PDAEs
Model
Domain of zDomain of r
Discretization
BFDM: Backward Finite Difference Method
OCFEM: Orthogonal Collocation on Finite Elements Method
Process
1st order, 50 elements2nd order, 5 elements
Discretize in all domains except time
Dynamic Optimization Example: Batch Reactor
Ni(t), T(t)
Fcw(t): Control variable
A+B C+D
Implementation
tf=1000 (fixed)
Parameterization of time domain
Profile of control variable Fcw(t)(Piecewise constant)
(Initial value : Lower bound : Upper bound)
Fcw(t):
10000
Constraints and objective function
Solvers: CVP_SS and CVP_MS
• Single shooting
• NLP problem is handled by the default solver SRQPD (SQP based), or an external CAPE-OPEN compliant solver.
• Handles integer variables (default: Outer Approximation)
• Multiple shooting
• NLP problem is handled by HQP (SQP based)
CVP_SS
CVP_MS
tf0
0 tf
How gPROMS get Jacobians?
• Jacobian is obtained from sensitivity equations (automatically generated and integrated), or from finite difference approximation.
• Exact first derivative can be obtained.
Conclusion (and some personal opinion)
• Easy model implementation
• Good user interface for simulation
• Useful for simulation of complex dynamic systems
References:
gPROMS Introductory User Guide Release 2.3, Process Systems Enterprise Ltd., 2004, London
gPROMS Advanced User Guide Release 2.3, Process System Enterprise Ltd., 2004, London
Process System Enterprise Homepage: http://www.psenterprise.com/