Thesis (M.E ng.)--Chulalongkorn University, 2011

The most important task in a chemical process is controlling the process to achieve the setpoint in such a way of minimizing energy loss and waste generation. In general, the chemical plant is composed of material recycle and energy integration. These affect the control system in more complexity. Plantwide control structure was adapted for developing control loops in the plant since its approach is holistic which could provide a better control system In this work, plantwide control procedure of Wongsri (2009) is proposed and applied to the styrene process. The styrene process consists of multiple operating units. This plant is one of the top ten bulk petrochemicals in the world. Therefore, we designed four plantwide control structures (CS1 to CS4) and simulated styrene process at steady state and dynamic via HYSYS. Moreover, all designed control structures are evaluated the dynamics performance and compared with the base case control structure designed by Luyben (2011). The result shows that the designed control structure I (CS1) can handle disturbances and maintain product quality better than other control structures as compared with Integral absolute error (IAE) In addition, the energy used in all designed control structures are less than the base case control structure.