Optimal Retrofit of a Post Combustion CO2 Capture Process Using Reduced Superstructure and Rate-Based Models

We propose a superstructure-based methodology for optimal retrofit of a CO₂ capture pilot plant using rigorous rate-based model for the reactive distillation. The optimal retrofit for existing plants is particular challenging because rigorous process models used for describing the currently operating process often result very complex optimization problems.¹ Herein, we preselect process alternatives implemented in the superstructure based on thermodynamic analysis. Thermodynamic analysis identifies unit operations that have high energy saving potential and process alternatives improving these unit processes are considered in the superstructure. Consequently, the problem size of the superstructure can be substantially reduced and optimization can be performed using commercially available process simulators and optimization solvers. The optimum process configuration and operating conditions are obtained stochastically using a genetic algorithm. Near global optimum solution is obtained by solving the problem multiple times with different crossover fraction. Results indicate that the optimum retrofit process includes three stages solvent recirculation, lean vapor recompression, and mechanical vapor recompression. Thermal energy and total energy consumption in the optimal retrofit process are reduced about 59% and 27%, respectively.