CO₂ removal from biogas with supported amine sorbents: First technical evaluation based on experimental data

Biogas from fermentation of manure and organic residues produces a gas stream that can be fed into the natural gas grid, provided impurities (CO₂, H₂S and H₂O) are removed according to specifications prior to grid injection. Compared to conventional technologies, supported amine sorbents (SAS) seem attractive for their high working capacity and fast uptake rate. In this study a technical evaluation for the conceptual design of a system for CO₂ capture from biogas with SAS is carried out and the performance is compared with liquid amine scrubbing. As the basis of this study, 1000 Nm³/h of raw biogas with 45%-v of CO₂ is to be upgraded to gas product containing max. 10%-v of CO₂, according to low calorific gas specifications. For the selected SAS (Lewatit VP OC 1065 and PEI/SiO₂) capacity measurements were carried out and results were correlated by Toth sorption isotherms. The heat of adsorption was calculated from the isotherms using the Clausius-Clapeyron equation and validated by measurements at different temperatures using calorimetry. Using the isotherms, a process analysis study with Aspen Plus software was carried out to obtain the best operating conditions for temperature swing between adsorption and desorption conditions, and subsequently the contactor size was determined. System integration studies show that the heat released during the adsorption can be integrated with the heat required in the digester (∼60 °C), resulting in a primary energy use of 20–22% for SAS, while for conventional amine scrubbing this is 38%. This study shows that SAS is an attractive technology option for CO₂ removal from biogas.