PLANTWIDE CONTROL STRUCTURE DESIGN OF METHANOL PROCESS

Abstract

This study presented the plantwide control structure design and the performance evaluation results of the methanol process with three gas recycled streams to produce high purity methanol from the synthesis gas. Wongsri’s plantwide control structure design procedure (2012) is applied to design the plantwide control structure in order to satisfy the control objectives. The Wongsri’s design procedure is explicit and systematic. It comprises of five stages with eight steps, emphasizing the establishment of a fixture plant by designing control loops, using the material quantifiers and their handlers, to regulate material component flows. The other plant level loops are designed using material and heat disturbance management for quality control. The changes of synthesis gas feed flow and synthesis gas composition are made to test the ability of the plantwide control structure proposed. The new design structures are compared with Luyben’s structure (2010). Dynamic performance results show that the new control structure gives better performance than that of Luyben as a result of creating fixture plant and disturbance management supporting to reduce the disturbance propagation throughout an entire plant.