Waste heat recovery from the stripped gas in carbon capture process by membrane technology: Hydrophobic and hydrophilic organic membrane cases

In this study, hydrophobic polytetrafluoroethylene (PTFE) and hydrophilic polyetheretherketone (PEEK) membranes were used as heat exchangers in rich‐split CO2 capture process to recover the waste heat from the stripped gas (i.e., mixture of water vapor and CO2). Technical feasibilities of these two membrane exchangers were assessed by heat recovery and energy intensity in the monoethanolamine (MEA)‐based carbon capture process. The heat recovery of these two membrane exchangers with different pore sizes were then systematically compared under various operating parameters. The underlying mass and heat transfer mechanisms of two membranes were also investigated and compared to figure out the suitable candidate for heat recovery. Additionally, the potential risks of using these membrane exchangers were identified and investigated. Results showed that the PTFE membrane displays a better heat recovery performance than the PEEK membrane with the same pore size. The heat recovery of both PTFE and PEEK membranes first increases to a plateau and then drops slightly with the increased CO2‐rich solvent flow rate. The heat recovery of PTFE and PEEK membranes decreases with the increased flow rate and water vapor fraction of the inlet stripped gas, MEA temperature, and MEA concentration. Furthermore, the larger pore size results in higher heat recovery for both PTFE and PEEK membranes. PTFE membranes displayed lower MEA transfer flux than PTFE membranes at any rich MEA flow rate as the enhanced MEA transfer from the cold solution to the other side via PEEK membrane pores filled with liquid water. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.