Post-combustion CO2 capture with membrane process: Practical membrane performance and appropriate pressure

Membrane separation process is one of the most promising methods for post-combustion CO2 capture from coal-fired power plant. In this paper, a multicomponent gas separation process using spiral-wound membrane modules is explored to optimize its membrane area and energy consumption. Firstly, the parametric analysis is conducted for the single-stage membrane process to study the impact of the feed gas CO2 concentration, feed pressure and selectivity on the permeate gas flow rate, permeate gas CO2 concentration and membrane area. Secondly, a feasible procedure that maintains product purity and recovery is applied to discuss the impact of the membrane selectivity, permeance and the feed pressure on the two-stage membrane process. Based on the analysis and conclusions in the single-stage membrane process, the trade-off between membrane area and energy consumption has been analyzed in detail. By varying the selectivity and the feed pressure, the impact of these two parameters on the membrane area and energy consumption is discussed, finding that the combination of low selectivity in the first stage and high selectivity in the second stage has much smaller membrane area and slightly higher energy consumption than that of high selectivity in both stages. Moderate feed pressure, varying from 0.55 MPa to 0.65 MPa, is found to provide relatively low CO2 capture energy consumption. Techno-economic analysis is conducted to further validate the above strategy. To minimize the CO2 capture cost, high CO2 permeance and moderate selectivity is desirable for the first stage, while high selectivity and moderate CO2 permeance should be maintained for the second stage. The membrane developed for the flue gas CO2 capture do not have to simultaneously enhance the CO2/N2 selectivity and CO2 permeance. Even considering the uncertainties related to economic parameters, the optimum feed pressure that provides the minimum CO2 capture cost only varies from 0.69 MPa to 0.83 MPa.