Pressure Swing\nAdsorption Configurations for Simultaneous\nProduction of High-Purity Biomethane and Carbon Dioxide from Biogas

Stringent legislation in a few countries created the\ntechnological\nneed to develop small and medium plants for biogas upgrading with\nlow methane slip. Pressure swing adsorption (PSA) has the potential\nto reach those targets. In this work, we have simulated several single-stage\nand dual-stage PSA configurations aiming to produce biomethane with\npurity over 97.3% while keeping the CO<sub>2</sub> purity over 99%.\nLimiting the amount of biomethane in the column before the blowdown\nstep is the most important parameter, and it can be accomplished by\nincreasing the number of pressure equalizations or by using a rinse\nstep. Accordingly, five single-stage PSA cycles and three dual-stage\nPSA cycles with different bed configurations were developed and simulated.\nOf all the simulated cycles, the single-stage PSA with five columns\nand the dual-stage PSA with four columns in the first stage and 2\ncolumns in the second stage have rendered better performance by reaching\na biomethane purity of 97.3% and a CO<sub>2</sub> purity >99.0%.\nThe\nsingle-stage five-column PSA could achieve this with an energy consumption\nof 937 kJ/kg<sub>biomethane</sub>, while the dual-stage PSA required\n1276.5 kJ/kg<sub>biomethane</sub>. In addition, a sensitivity analysis\nis carried out by studying the effect of three process parameters\n(adsorption time, feed flow rate, and feed gas composition) on the\nPSA process performance of the single-stage 5-column configuration.