A H2S reactive adsorption process for the purification of biogas prior to its use as a bioenergy vector

This work studies, at lab scale, a reactive adsorption technology for the removal of the H2S from biogas produced in landfills or anaerobic digesters. The main phenomenon is an irreversible chemical reaction between the solid and gas phase. The study produces data on the efficiency of the process as function of a number of variables including: the nature and properties of the adsorbent; the biogas flow rate and the contact time of the gas with the adsorbent; the geometry of the adsorption columns and the linear velocity of the flow; the concentration of the contaminant (H2S) and humidity in the biogas. The work reported in this paper focuses on a promising adsorbent available commercially and includes the “breakthrough” curves and the compilation of a phenomenological model for the process. These first results show that the rates of the external diffusion, internal diffusion and surface reaction steps are relatively close and that the limiting step of the process changes with experimental conditions. Globally, the phenomenological model predicts that the rate of the process is near first order with respect to the H2S concentration and zero order with respect to the solid reactant (adsorbent). The reported data constitute the basis for the scale-up of the unit at a commercial level.