关键词: 膜, 沼气, 碳捕集, 天然气, 工艺设计

Abstract: In view of the shortage of natural gas, high carbon neutrality pressure and lowvalue utilization of biogas in China, a carbon capture process for highvalue and diversified utilization of biogas coupled with membranes and compression condensation was developed to achieve nearzero emission and highvalue comprehensive recycling of lowvalue biogas. Using Aspen HYSYS to design and optimize the 1 000 Nm3/h biogas purification process, highgrade gas was produced through the membrane separation unit of the gas system, and the CO2 system used the highquality CO2rich feed gas provided by the gas system to produce liquid CO2 product and lowgrade gas. The optimization process mainly examined the impact of operating pressure on factors such as recovery rate, product value, operating cost and equipment investment, as well as the impact of feed gas flow fluctuations on recovery rate, product and economy. The results showed that under the condition of 1.8~3.8 MPa, highgrade gas with a calorific value of 31.4 MJ/Nm3, lowgrade gas with a calorific value of 17.9 MJ/Nm3 and liquid CO2 with a CO2 concentration of 95 vol% could be produced at the same time. The annual optimal economic benefit was about 2.61×106 CNY, and the annual emission reduction was about 9 755 tons of CO2 equivalent greenhouse gas. Compared with the calorific value of lowgrade gas and the concentration of liquid CO2 product, the calorific value of highgrade gas was greatly affected by flow fluctuations.

Key words: membranes, biogas, carbon capture, natural gas, process design