Structural and Operating Optimization of the Methanol Process Using a Metaheuristic Techniqued

This paper presents a systematic approach for the synthesis, selection, design, and optimization of methanol plants. A metaheuristic optimization approach is proposed to reconcile the economic and environmental objectives of the process while incorporating simulation tools for the reliable modeling of the generated alternatives. In addition to shale/natural gas as the primary feedstock, CO2 utilization is considered. Nine different configurations were synthesized, analyzed, and optimized. The optimization variables included the structural configurations as well as design and operating variables such as flowrates, temperatures, and pressures. The model is a multiobjective problem involving economic and environmental objectives. The economic objective function consists of maximizing the net profit. The environmental objective function is aimed at minimizing the total annual CO2, emissions. To perform the optimization of this problem, process data were obtained from the chemical process simulation software Aspen HYSYS. The used stochastic optimization algorithm was an improved multiobjective differential evolution. A client-server interface based on Component Object Module technology using Excel-Visual Basic for Applications scripts was developed to call the Aspen HYSYS simulator repetitively for various sets of input variables. The results offer attractive options for both the economic and the environmental objectives.