Thesis (M.Eng.)--Chulalongkorn University, 2013

Plantwide control structure design is to design a control system for an entire plant. It becomes crucial when plant in considered consisting of many interconnected unit operations with material and energy recycles. The methodologies for plantwide control design have been developed in four styles. They are mathematical, optimization, heuristic and mixed approaches. Wongsri’s Design Procedure, heuristic in nature, is illustrated in this paper. 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. Another important feature is the use of dynamic performance measures to select an appropriate structure for a control distillation column. This method is applied to the styrene monomer plant based on the optimum design process from Luyben (William L. Luyben, Design and Control of the Styrene Process, Ind. Eng. Chem., Vol. 50, No. 3, 2011). The performance of new design structure is compared with two base case control structures selected (S. Vasudevan and G. P. Rangaiah, Integrated Framework Incorporating Optimization for Plant-Wide Control of Industrial Processes, I&EC Research, Vol. 50, 2011 and S. Vasudevan, et. al., Application and evaluation of three methodologies for plantwide control of the styrene monomer plant, Ind. Eng. Chem. Vol. 48, No. 24, 2009). The new control structure performance is comparable with the base cases. The Wongsri design procedure is detailed, instructive, clearcut, and readily to be applied even for a novice designer.