Simplified and cost-effective pressure swing adsorption system for simultaneous production of bio-methane & biogenic CO2 from biogas

Abstract

This study presents a new pressure swing adsorption (PSA) configuration using two columns integrated with a tail gas balloon that enables simultaneous production of two high purity products. Two of the four cycle developed were able produce two products, i.e. bio-methane with purity > 97.0 and biogenic CO2 with purity > 99.5 mol%, simultaneously. The energy efficiency of the best cycle is found to be 823 kJ/kgbiomethane which is slightly better than other reported PSA systems. Most importantly, the system productivity (7.975 mol.kg−1.h−1) is much higher than other PSA configurations that have low methane slip in the CO2-rich stream. A cost estimation (CAPEX and OPEX) determined CAPEX of 1.66 million USD for a PSA system processing 500 Nm3/h of biogas. Use of polymeric balloons contribute in cost reductions by 8.3 %. The production cost of bio-methane is estimated to be 0.595 USD/Nm3 with further available reduction upon valorization of biogenic CO2. This study demonstrates that a system analysis can significantly contribute in improving the overall separation performance of biogas upgrading. The economic analysis helped us in determining that the compressor constitutes 60 % of the CAPEX and cost reductions in this area are very important to improve upgrading plants.