Process Synthesis and Optimization of Heat Pump Assisted Distillation for Ethylene-Ethane Separation

Ethylene is a platform chemical, and its production process includes energy intensive ethylene-ethane separation via cryogenic distillation. As potential avenues for energy reduction, in this study we have explored four distillation process configurations based on the concepts of mechanical vapor recompression (MVR) of the top product and throttling of the bottom product i.e., bottom flashing (BF). Each of these configurations is optimized in MATLAB using the genetic algorithm to minimize the total annualized cost (TAC) of separation. Our results show that both MVR and BF reduce energy as well as cost of separation compared to the conventional distillation configuration. However, BF outperforms MVR, and together with a prethrottling cooler it provides the minimum TAC configuration for ethylene-ethane separation. The proposed heat pump assisted distillation configuration has the potential to reduce the total energy requirement by 57% and the separation cost by 44% over the conventional distillation process.