Dry reforming of multiple biogas types for syngas production simulated using Aspen Plus: The use of partial oxidation and hydrogen combustion to achieve thermo-neutrality

The study compares the syngas production capabilities of landfill (LF), corn cob (CC), whole stillage (WS), and combined cob and stillage (CS) biogas from the dry reforming of methane (DRM) in terms of H2 and CO yield. A syngas H2/CO ratio of 1.6-1.7 was desired for downstream application to Fischer-Tropsch Synthesis. Three cases were simulated and investigated in the study using the Aspen Plus simulation software: Case 1 (DRM Alone), Case 2 (DRM and partial oxidation, POX), and Case 3 (DRM and hydrogen oxidation, HOX). The optimal operating temperature and pressure for DRM were observed as 950 °C and 1 atm. CS biogas generated the most favourable syngas in terms of H2/CO ratio and by-product content. Addressing the extreme endothermicity of DRM on its own by counterbalancing it with exothermic processes such as POX and HOX to achieve thermo-neutrality was explored. Case 2 thermo-neutrality was achieved by supplying sufficient O2 to the DRM-POX system, however syngas were diluted with combustion products from CH4 oxidation. Dilution was mitigated using CS biogas and varying inlet O2/CO2 ratio to control syngas H2/CO ratio within the desired range. However, thermo-neutrality was not achieved under these conditions and the other biogas types did not achieve the desired range. Case 3 thermo-neutrality was achieved for LF and CC biogas through external supply of H2 to the DRM-HOX system. Excess H2 was present in WS and CS biogas feeds to exceed thermo-neutrality into exothermicity and thereby qualifying them as excellent candidates for DRM-HOX.