Methane recovery in a combined amine absorption and gas steam boiler as a self-provided system for biogas upgrading

Biogas, which primarily consists of methane (CH4) and carbon dioxide (CO2), is a renewable energy carrier, and can be upgraded to a natural gas substitute after removing trace impurities and CO2. Among the various CO2 separation technologies, amine absorption is generally considered to be energy intensive as regenerating the rich solution need additional heat to strip CO2. However, it could hardly be found the related data concerning energy consumption of biogas upgrading projects adopting amine absorption. In this work, a pilot biogas upgrading project with combined amine absorption unit and gas steam boiler was established with treatment capacity of 300 Nm3/h feed biogas. The major energy for operating this biogas upgrading project was self-provided through combustion a fraction of the biogas to generate steam for regenerating rich absorbent. Operation results showed that, besides much higher CO2 removal efficiency (>99.5%), CH4 recovery of this project attained around 89.0%, which was higher than that of several biogas upgrading projects using one-stage PSA or two-stage membrane permeation technologies. Based on the results of this work, it proves that amine absorption is a highly effective technique for CO2 removal in biogas upgrading projects, and its energy consumption is not higher than other technologies.