Experimental optimization of an innovative biogas upgrading process adapted to the agricultural context

The development of the large European biomethane potential is facing the challenge of the biogas upgrading technologies adaptation to the agricultural context (small and medium size anaerobic digestion units, rural environment). Membrane contactors are an opportunity to adapt the robust Water Scrubbing (WS) process and to decrease the high specific investment costs reported for available technologies. Microporous polypropylene (PP) hollow fiber membrane contactors were combined in an absorption/desorption closed-loop using water as the absorbent. A Design of Experiments methodology highlighted the gas and liquid flowrates, the inlet biogas composition and the absorption gas pressure to be the most significant parameters impacting biomethane quality with a low level of interactions. From the subsequent optimization, gas-grid quality biomethane (......4......=97.6%) was produced with a moderate recovery rate (......4=83.7%). The limited mass transfer efficiency may be compensated by a larger membrane area. Alternatively, the addition of a methane recycling loop, similarly to the conventional WS process, significantly improved the methane recovery rate (......4......=95.9% / ......4=93.5%). These experimental results were confirmed by on-site upgrading of raw farm biogas.
Proceedings of the 25th European Biomass Conference and Exhibition, 12-15 June 2017, Stockholm, Sweden, pp. 1116-1125