Waste to wheels: Performance comparison between pressure swing adsorption and amine-absorption technologies for upgrading biogas containing hydrogen sulfide to fuel grade standards

Amine-absorption and pressure swing adsorption (PSA) technologies have been regarded as attractive methods to upgrade biogas by separating acid gases such as CO2 and H2S from its main component, CH4. This paper com-pares the separation performance and energy consumption by pressure swing adsorption and amine-absorption processes in upgrading biogas containing 39.9% CO2, 0.1% H2S, and 60% CH4. PSA and amine-absorption processes were emulated using Aspen Adsorption and Aspen Hysys platforms and validated from experimental data. The results reveal that amine-absorption technology was favorable in terms of purity and recovery of products in both streams. The optimum points of the process with desirability of 99.9% were at 0.1% H2S content, 30% CO2 content, 1% piperazine concentration, and 50% MDEA concentration with biomethane purity (99.64%) and recovery (94.84%) in the product stream, and acid gases purity (94.84%) and recovery (99.97%) in the waste stream. In term of energy consumption, however, the pressure swing adsorption process recorded a lower energy requirement of 0.178 kW/molCH4 at comparable biomethane purity of 96.2% and lower methane recovery of 80% with subsequently lower acid gases purity (85.5%) and recovery (86.7%).