CO₂removal from biogas by using membrane absorption technology

In order to integrate the unique advantages of chemical absorption technology and membrane separation technology used to capture CO2 from biogas, membrane CO2 absorption technology was put forward in this study. Based on the CH4 volume fraction in the treated gas, CO2 mass transfer rate of absorption and energy consumption factor, CO2 removal performances from the simulated biogas by monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA) were experimented by using hydrophobic polypropylene hollow fiber membrane contactor as CO2 absorber. Results showed that CO2 can be successfully captured from biogas by using membrane CO2 absorption technology. And when MEA was selected to act as CO2 absorbent and biogas flow rate was 120 L/h, CH4 volume fraction can be increased from 60% to up to 97.8%. But CO2 mass transfer rate of absorption can reach the maximum, approximate 18.03 mol/(m2·h) by adopting 300 L/h biogas flow rate. In addition, CO2 removal performance of these three absorbents can be ranked as: MEA>DEA>TEA. The operating conditions were also optimized on the basis of the calculation of regeneration energy consumption factor, where 0.175-0.2 mol/mol lean CO2 loading should be recommended for MEA, and 16.7 L/L gas-liquid ratio may be suitable for DEA. Finally, an economic analysis of CO2 removal from biogas by using membrane absorption process was also put forward in this study. The results showed that the cost of CO2 captured is relatively lower, and when the biogas production increases from 1 000 to 12 000 m3/d, CO2 removal cost can be reduced by about 78.6% to 0.5 Yuan/m3 of biogas. The results can provide references for selection of biogas upgrading technology with high efficiency.