Removal of high concentration CO2 from natural gas using high pressure membrane contactors

Abstract

The feasibility of removing high concentration CO2 from natural gas using membrane contactors at elevated pressures was preliminarily investigated in this study. CO2-CH4 gas mixture and activated methyldiethanolamine (aMDEA) solution were used as simulated natural gas and absorbent, respectively. The stability of poly(vinylidene fluoride) (PVDF) hollow fiber membranes in aMDEA solution at room temperature was first investigated through Fourier transform infrared spectroscopy (FTIR) and contact angle (CA) analyses. The effect of operation pressure, membrane area and feed gas flow rate on CO2 removal performance as well as CH4 loss was studied. The results indicated that the CO2 removal efficiency was significantly improved with increasing operation pressure. For 70% CO2 in feed, the removal efficiency of CO2 increased from 33.3% at 1bar to 91.3% at 60bar under the experimental conditions. Meanwhile, the overall mass transfer coefficient (KOG) gradually decreased due to the decrease of CO2 diffusion coefficient. The CO2 outlet concentration, CO2 flux and CH4 loss were also affected by membrane area and feed gas flow rate. This study provides a reference for the understanding of removal of high concentration CO2 from natural gas using membrane contactors at elevated pressures.