Comparing the performance of a 13X zeolite and an impregnated activated carbon for H2S removal from biogas to fuel an SOFC: Influence of water

Due to a strict H2S tolerance limit, an advanced H2S removal treatment (primary and polishing) is required to fuel a solid oxide fuel cell. With a focus on the polishing treatment, adsorption tests were performed to compare the efficiency of two commercial adsorbents: a 13X zeolite (Z) and a coal-based impregnated activated carbon (IAC). The experiments conducted at lab-scale on a synthetic polluted gas highlighted the impact of the gas humidity. The presence of humidity in the gas dramatically degraded the performance of Z but significantly improved that of IAC. This could be due to differences in adsorbent affinity for water. In appropriate humidity conditions, the efficiency of IAC proved to be better than that of Z. Recommendations made from lab-scale experiments were taken into account for on-site tests with landfill gas. The H2S adsorption capacity of Z was 142mgH2S/gZ. An excellent removal of H2S by IAC was demonstrated. The complex biogas matrix seemed to enhance IAC efficiency, as the quantity of H2S adsorbed was 785mgH2S/gIAC without reaching saturation of the adsorbent.