(147ag) Analysis and Optimal Design of Membrane Processes for Flue Gas CO2 Capture

Membrane separation technology is a potential low-cost flue gas CO₂ capture technology to cope with increasing CO₂ content in the atmosphere. This paper analyzes the effects of membrane separation performance, driving force generation strategies and water vapor on the operating energy consumption and CO₂ capture cost through process simulation, and then membrane processes are optimized and designed under a wide range of separation requirements. The energy consumption of feed compression combined with permeate vacuum is the lowest when the stage cut is larger than 33.8% when the pressure ratio of the membrane is 5, but from the perspective of CO₂ capture cost, the vacuum operation is suitable for membranes with high CO₂ permeance and moderate selectivity, such as the CO₂ permeance above 4000 GPU and the CO₂/N₂ selectivity below 100, to reduce the investment cost of membrane-related equipment. Since only improving the CO₂/N₂ selectivity results in an enlarged membrane area and consequently limits the reduction of CO₂ capture cost, the development trend of CO₂ permeance with increasing CO₂/N₂ selectivity is proposed to restrain the expansion of membrane area. The water vapor in flue gas can improve the mass transport driving force of CO₂ and reduce the membrane area and the capture cost. For water-facilitated membranes, it is recommended to use segmented humidification to replenish the water vapor content of the residue side, especially for the membrane process with a high stage cut, such as the first stage of a two-stage membrane process. Finally, the optimal membrane process and operating pressure under different separation targets, specifically 50–95% dry basis CO₂ purity and 50–90% CO₂ recovery rate, are obtained by the techno-economic analyses.

Research Interests: gas separation membrane, process simulation, transport mechanism.