Removal of CO2 and H2S from biogas and enhanced compressed bio-methane gas production from swine manure and elephant grass

Abstract

Anaerobic co-digestion of concentrated swine manure with elephant grass silage was used, and this study carried out in full-scale three continuously stirred tank reactors was operated at mesophilic temperature. The Biogas impurity removal procedure was enhanced by using a molecular sieve and activated carbon. Two molecular sieve tanks are used to absorb water from the biogas. An activated carbon tank (2 meters) was used to eliminate H₂S to < 1 ppm before entering the gas tank. In the form of compressed bio-methane gas (CBG), production was 14,400 m³/day (CH₄ 60-70%), and the amount of CBG was 9,600 m³/day 6.8 tons/day. The raw biogas containing CH₄, CO₂, and O₂ are 68.8%, 29.7% and 0% with H₂S 768 ppm. After the enhancement process, CBG having CH₄, CO₂, O₂ are 89.35%, 10.05 0% and 0.02% with < 0.01 ppm H₂S. Therefore, after the purification process amount of CO₂, H₂S gas was considerably reduced and CH₄ was improved by up to 90% by volume, and then the CBG was compressed to 250 bar tanks to the fuel for cars. Therefore, these results clearly demonstrate that the activated carbon method is feasible to process for the removal of CO₂ and H₂S from biogas in a large-scale plant.