A hybrid method combining membrane separation and chemical absorption for flexible CH4 refinement and CO2 separation in natural gas

CO2 removal is imperative in the sweetening of natural gas. In this work, a hybrid method combining membrane separation and chemical absorption is proposed and applied to test its performances in CH4 refinement and CO2 separation from natural gas. Specifically, the permeate stream from the membrane separation part was fed into the chemical absorption column. The retentate stream and the chemically scrubbed permeate stream were mixed to produce the final sweetened CH4. Parametric analysis indicates that the enriched CH4 volume fraction increases with the growth of feed pressure, but it decreases as the gas flow rate increases. The CO2 removal efficiency gets enhanced with the increment of feed pressure, gas temperature and monoethanolamine (MEA) concentration. Under an optimized condition with a feed pressure of 0.9 MPa, a gas flow rate of 40 L/min, a gas temperature of 45°C, a MEA concentration of 15%, and a MEA flow rate of 20 L/h, the high CH4 volume fraction of 96.8%, 100% CH4 recovery efficiency, and 80.4% CO2 removal efficiency can be simultaneously achieved using the hybrid method. Compared with the membrane separation method, the hybrid method has higher CH4 recovery efficiency and higher CH4 volume fraction, which can meet the requirements of carbon capture utilization and storage (CCUS). Compared with the chemical absorption, the hybrid method consumes less MEA since a part of CO2 can be separated by membrane separation. Therefore, the hybrid method is a promising technique for flexible CH4 refinement and CO2 separation in natural gas. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd.