Process simulation, optimization and assessment of post-combustion carbon dioxide capture with piperazine-activated blended absorbents

Abstract

High efficiency, large capacity, and low energy consumption have become an important challenge in performances of post-combustion carbon dioxide (CO2) capture and regeneration. Blended absorbents have shown great potential but their process simulation, modeling, and optimization have not been known definitively. This work developed the blended aqueous absorbents based on piperazine (PZ) activators: PZ-activated methyldiethanolamine (MDEA), potassium carbonate solution (K2CO3), and aqueous ammonia (NH3.H2O) to improve their techno-economic performances. The whole process simulation was conducted using a validated rate-based model under given a CO2 capture efficiency of 85%. In this process, the key factors including the molar concentration of the absorbent, PZ molar ratio, CO2 load of lean liquid, lean-liquid temperature, flue-gas temperature, and rich-liquid temperature, were employed for the design of experiment using response surface methodology. A series of nonlinear regression equations were developed using the flow rate of absorbents, the reboiler heat duty (in the units of gigajoules per ton of CO2), and the cooling-water flow rate as the multi-objective function. Subsequently, the optimal Pareto solution set and compromise solutions were determined using the multi-objective genetic algorithm and finally, their performances were assessed using the fuzzy close-degree algorithm. It was found that the optimal operating parameters can be determined effectively according to the proposed approach. For each PZ-activated blended absorbents, the trade-off effect exists between absorbent flow rate, reboiler heat duty, and cooling water consumption. The absorbents having optimal techno-economic performance were recommended to be PZ-activated MDEA, followed by PZ-activated K2CO3 and PZ-activated NH3.H2O when considering the regeneration energy consumption. The results may provide a positive reference for process design and optimization of the industrial post-combustion CO2 capture system.