Plantwide control design of vinyl acetate monomer plant

Abstract

This research applied plantwide control strategies for designing control structures of a Vinyl Acetate monomer plant to achieve the objective of this process and can operate within constraint of safety, environment, and operation. Three alternative plantwide control structures are designed, tested and compared the performance with Luyben’s structure (CS1). For the result, the most effective control structure is designed control structure I (CS2). It uses the fresh acetic feed to manipulate the total acetic feed in vaporizer and control the water composition in overhead column. This structure resulted is faster dynamic response than CS1 and gives the effective water composition control without using cascade control as CS1. In the azeotrope column is high boilup ratio so the designed control structure II (CS3) is designed that modifying from CS2 in column temperature loop. This scheme measure the tray temperature and adjust the bottom flowrate to control the vinyl acetate composition and the level is controlled by changing the reboiler heat input. The last structure (CS4) might be used when the reactant comes from upstream unit. The production rate is set by changing the fresh ethylene feed. All of control structures can operate within constraint and achieve the objectives and a good control structure should be quickly response to disturbance and adjust itself to steady state while minimizing the deviation of the product quality. Thus, the designed control structure I is the most effective control structure.