Hybrid membrane-cryogenic CO2 capture technologies: A mini-review
S. Sreenath, Ashish Alex Sam
Abstract
The use of membranes to capture CO 2 is a proven carbon capture technique. Gas separation membranes enhance the mole fraction of CO 2 in the feed gas. The membrane separation technique is low-cost because of its compact size, excellent energy efficiency, minimum environmental effect, simplicity of scale-up, fewer moving parts, moderate energy consumption, and ease of handling. Hybrid membrane cryogenic (HMC) and low-temperature membrane cryogenic (LTMC) are hybrid capture systems that combine the advantages of membrane and cryogenic techniques. In the HMC process, the flue gas is first pre-treated by the membrane process for CO 2 enrichment and the cryogenic process to capture the CO 2 . In the LTMC process, low-temperature membrane units increase flue gas CO 2 concentration to 50%–75%, and a cryogenic process liquefies the rich CO 2 stream. Permeability and selectivity are the crucial parameters of the membrane which determine the CO 2 purity and recovery of capture. Most polymeric membranes have a trade-off of CO 2 /N 2 selectivity (α CO2/N2 ) and CO 2 permeability (P CO2 ). The operating temperatures also impact membrane performance. An anti-trade-off effect was observed upon cooling down by increasing P CO2 and α CO2/N2 . With increased P CO2 and α CO2/N2 , sub-ambient temperature-based membrane cryogenic CO 2 capture techniques will lower power consumption and energy cost for CO 2 capture (CC). This review analyses the costs and energy requirements of various HMC and LTMC configurations for CO 2 capture. The study also examines the features of the different membranes used and the effect of operating and membrane parameters on the process performance.