Pressure Swing Adsorption Configurations for Simultaneous Production of High-Purity Biomethane and Carbon Dioxide from Biogas

Stringent legislation in a few countries created the technological need to develop small and medium plants for biogas upgrading with low methane slip. Pressure swing adsorption (PSA) has the potential to reach those targets. In this work, we have simulated several single-stage and dual-stage PSA configurations aiming to produce biomethane with purity over 97.3% while keeping the CO2 purity over 99%. Limiting the amount of biomethane in the column before the blowdown step is the most important parameter, and it can be accomplished by increasing the number of pressure equalizations or by using a rinse step. Accordingly, five single-stage PSA cycles and three dual-stage PSA cycles with different bed configurations were developed and simulated. Of all the simulated cycles, the single-stage PSA with five columns and the dual-stage PSA with four columns in the first stage and 2 columns in the second stage have rendered better performance by reaching a biomethane purity of 97.3% and a CO2 purity >99.0%. The single-stage five-column PSA could achieve this with an energy consumption of 937 kJ/kgbiomethane, while the dual-stage PSA required 1276.5 kJ/kgbiomethane. In addition, a sensitivity analysis is carried out by studying the effect of three process parameters (adsorption time, feed flow rate, and feed gas composition) on the PSA process performance of the single-stage 5-column configuration.