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Economic Plantwide Control using Commercial Process Simulation Software. Adriana Reyes Lúa. Supervisor: Sigurd Skogestad Co-supervisor: Vladimiros Minasidis. TKP4550 Specialization Project. Fall 2013. Name, title of the presentation. Plantwide Control.
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Economic Plantwide Control using Commercial Process Simulation Software Adriana Reyes Lúa Supervisor: Sigurd Skogestad Co-supervisor: Vladimiros Minasidis TKP4550 Specialization Project Fall 2013 Name, title of the presentation
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
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.
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? • Intuitive • Widely used • Pre-loaded information • Design mode vs. operation mode. • Poor numerical properties. • Not standardized.
Objective To explore the use of commercial process simulators to generate process models suitable for an automated economic plantwide control procedure.
Methanol Plant • Reactor, a separator, and a recycle stream with purge Scheme of a methanol plant (Løvik,2001)
Methanol Plant 4 steady state degrees of freedom
”Operation Mode” Simulation Reactor • Kinetics • Sizing • Ergun Δp
”Operation Mode” Simulation Circulation compressor • Actual gas flow is limited by compressor curve.
”Operation Mode” Simulation Heat Exchangers From recirculation From Reactor To Separator • UA is fixed. • Inlet temperatures are given. To Reactor Find Tc,out!
Plantwide Procedure: Step 1 • OK! Define operational objectives (economics) and constraints.
Step 2 Optimizing the Simulation Hard constraints as inputs
Optimizing the Simulation COM Matlab UniSim • NLP Solver • fmincon • NLP Model
Plantwide Procedure: Step 2 • OK! • Identify steady state degrees of freedom. • Identify important disturbances • Determine steady state operation conditions.
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.