Membrane separation technology for CO2 capture in pre-combustion has the advantages of easy operation, minimal land use and no pollution and is considered a reliable alternative to traditional technology. However, previous studies only focused on the H2-selective membrane (HM) or CO2-selective membrane (CM), paying little attention to the combination of different membranes. Therefore, it is hopeful to find the optimal process by considering the potential combination of H2-selective and CO2-selective membranes. For the CO2 capture process in pre-combustion, this paper presents an optimization model based on the superstructure method to determine the best membrane process. In the superstructure model, both CO2-selective and H2-selective commercial membranes are considered. In addition, the changes in optimal membrane performance and capture cost are studied when the selectivity and permeability of membrane change synchronously based on the Robeson upper bound. The results show that when the CO2 purity is 96% and the CO2 recovery rate is 90%, the combination of different membrane types achieves better results. The optimal process is the two-stage membrane process with recycling, using the combination of CM and HM in all situations, which has obvious economic advantages compared with the Selexol process. Under the condition of 96% CO2 purity and 90% CO2 recovery, the CO2 capture cost can be reduced to 11.75$/t CO2 by optimizing the process structure, operating parameters, and performance of membranes.
Keywords: IGCC power plant; membrane separation; pre-combustion CO2 capture; superstructure.