No-mixing-loss design of a multistage membrane carbon capture process for off-gas in thermal power plants

Abstract

Carbon capture and storage (CCS) is a promising method for limiting the effects of global warming. A multistage membrane process is needed to capture and recover high-purity CO2 from off-gas with low CO2 concentrations in thermal power plants. In this study, a simple design method based on the “no-mixing-loss” concept was suggested. The performance of the process could be improved by avoiding mixing loss and the optimization process was simplified using a reduced number of optimization parameters. The feed and permeate pressure, and the design criteria of CO2 concentration at the retentate side in each section were considered as decision variables for optimizing the process with a target purity of 95% and a target recovery of 90%. Three-, five-, and seven-stage processes were designed and evaluated in terms of energy consumption and capture cost. In addition, a well-designed inner cooling system in the pressure units enhanced compressor efficiency and contributed to the reduction in energy consumption and costs.