Hybrid membrane cryogenic process for post-combustion CO2 capture

Reducing the energy requirement for the capture step is a major challenge in Carbon Capture and Storage (CCS) technology. Different capture processes have been investigated in the literature, such as absorption, adsorption, chemical looping and membrane separation. In this paper, the potential for a hybrid process combining membrane and cryogenic separation to achieve efficient post-combustion carbon capture has been investigated through a simulation study. The hybrid process combines a first step CO2 pre-concentration with a membrane unit and a second step CO2 cryogenic condensation. The influence of three CO2 feed contents (5, 15 and 30%), 3 different compression strategies and two membrane selectivities (α CO2/N2=50 and 100) on the separation performances have been investigated for a required CO2 purity of 0.9 and a capture ratio larger than 85%. It is shown that the use the use of feed compression with Energy Recovery System (ERS) membrane module offers the best performances when energy requirement and membrane surface area taken into account. More specifically for a CO2 feed concentration ranging between 15 and 30%, the hybrid process shows a reduced energy requirement compared to the reference technology, chemical absorption in MonoEthanolAmine (MEA). In this CO2 concentration range, a minimum energy requirement lower than 3 GJth/ton CO2 is obtained (including compression of CO2 to 110 bar), with a CO2 recovery ratio above 85% and CO2 purity above 89%.