Pressure swing adsorption (PSA) processes have been used extensively for gas separation, especially in the separation of hydrogen from CO2, and in air purification. The objective of this paper is to examine the economic feasibility of pressure swing adsorption (PSA) for recovering CO2 from postcombustion power plant flue gas. The analysis considers both high-pressure feed and vacuum desorption using commercial adsorbent 13X, which has a working capacity of 2.2 mol/kg and CO2/N2 selectivity of 54. The results show that using vacuum desorption reduces the capture cost from US$57 to US$51 per ton of CO2 avoided and is comparable in cost to CO2 capture using conventional MEA absorption of US$49 per ton of CO2 avoided. In this paper, a sensitivity analysis is also presented showing the effect on the capture cost with changes in process cycle; feed pressure and evacuation pressure; improvements the adsorbent characteristics; and selectivity and working capacity. The results show that a hypothetical adsorbent with a working capacity of 4.3 mol/kg and a CO2/N2 selectivity of 150 can reduce the capture cost to US$30 per ton of CO2 avoided.

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Studies of CO 2 capture using membrane technology from coal-fired power-plant flue gas typically assume compression of the feed to achieve a driving force across the membrane. The high CO 2 capture cost of these systems reflects the need to compress the low-pressure feed gas (1 bar) and the low CO 2 purity of the product stream. This article investigates how costs for CO 2 capture using membranes can be reduced by operating under vacuum conditions. The flue gas is pressurized to 1.5 bar, whereas the permeate stream is at 0.08 bar. Under these operating conditions, the capture cost is U.S. $54/tonne CO 2 avoided compared to U.S. $82/ tonne CO 2 avoided using membrane processes with a pressurized feed. This is a reduction of 35%. The article also investigates the effect on the capture cost of improvements in CO 2 permeability and selectivity. The results show that the capture cost can be reduced to less than U.S. $25/tonne CO 2 avoided when the CO 2 permeability is 300 barrer, CO 2 /N 2 selectivity is 250, and the membrane cost is U.S. $10/m 2 .