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Economic Plantwide Control usingCommercial Process Simulation Software
Name, title of the presentation
Adriana Reyes Lúa Supervisor: Sigurd SkogestadCo-supervisor: Vladimiros Minasidis
TKP4550 Specialization Project Fall 2013
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Plantwide Control
• “Control structure design for complete chemical plants”.
• Systematic procedure for the design of an economic plantwide control, based on steady state plant economics.
– Top down
– Bottom up
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Plantwide Control
1. Top-down
Step 1: Define operational objectives (economics) and constraints.
Step 2: Identify steady state degrees of freedom and determine steady state operation conditions.
Step 3: Identify candidate measurements y and select CV1 =Hy .
Step 4: Select the location of the throughput manipulator.
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Plantwide Control: The Challenge• To be accepted and used in industry, the procedure:
• must result in processes with near optimal operation • should not employ complex control technology.
• Proposed solution:• Develop an automated procedure. • Use of commercial process simulators?
Design mode vs. operation mode. Poor numerical properties. Not standardized.
Intuitive Widely used Pre-loaded information
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Objective
To explore the use of commercial process simulators to generate process models suitable for an
automated economic plantwide control procedure.
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Methanol Plant
• Reactor, a separator, and a recycle stream with purge
Scheme of a methanol plant (Løvik,2001)
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Methanol Plant
4 steady state degrees of freedom
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Methanol Plant Simulation
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”Operation Mode” Simulation
Reactor
Kinetics Sizing Ergun Δp
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”Operation Mode” Simulation
Circulationcompressor
Actual gas flow is limited by compressor curve.
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”Operation Mode” Simulation
Heat Exchangers
UA is fixed. Inlet temperatures
are given.
From recirculation
To Separator
To Reactor
From Reactor
Find Tc,out!
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Optimization Problem
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Plantwide Procedure: Step 1
Define operational objectives (economics) and constraints.
OK!
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Optimizing the Simulation
Hard constraints as inputs
Step 2
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Optimizing the Simulation
Matlab UniSim
• NLP Solver• fmincon • NLP Model
COM
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Plantwide Procedure: Step 2
Identify steady state degrees of freedom.
Identify important disturbances
Determine steady state operation conditions.
OK!
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Conclusion
• The use of commercial process simulators to generate process models suitable for an automated economic plantwide control procedure was explored.
• NLP model independent of NLP solver.
• The model for the methanol plant in ”operation mode” was generated.
• Recommendations for set-up of heat exchangers and compressors were given.
• Steps 1 and 2 of plantwide control procedure achieved.
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Thank you for your attention!