Multi-stage adsorptive purification process for improving desulfurization performance of biogas

Abstract

In this study, an experimental investigation was performed to suggest and demonstrate a multi-stage adsorption process that can simultaneously and more effectively remove major impurities (e.g., H2S, COS, CS2, and siloxanes D4 and D5) from methane- and carbon dioxide-rich biogas. Commercially available adsorbents, including iron oxide (IO), iron oxide hydroxides (IH and IHS), activated carbon (AC), impregnated activated carbon (IAC), silica gels (A2 and NS10), and zeolites (5A and 13X) were used as the candidate adsorbents. Five candidate adsorbents were first selected by dynamic adsorption analysis of each individual adsorbent for binary gas mixtures containing a trace impurity gas in a nitrogen balance; subsequently, three adsorbents were selected as the most promising candidates for the multi-stage adsorption process via dynamic breakthrough measurements using a simulated biogas mixture. Furthermore, using dynamic breakthrough tests on a series of configurations based on a tandem arrangement of the three adsorbents using the simulated biogas mixture, it was demonstrated that the optimal packing configuration for the multi-stage adsorptive purification process, in which the maximum increase in breakthrough time was achieved, consisted of AC, A2, and IHS along the gas-flow direction.