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 H-2 and CO yield. A syngas H-2/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 degrees C and 1 atm. CS biogas generated the most favourable syngas in terms of H-2/CO ratio and byproduct 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 O-2 to the DRM-PDX system, however syngas were diluted with combustion products from CH4 oxidation. Dilution was mitigated using CS biogas and varying inlet O-2/CO2 ratio to control syngas H-2/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 H-2 to the DRM-HOX system. Excess H-2 was present in WS and CS biogas feeds to exceed thermoneutrality into exothermicity and thereby qualifying them as excellent candidates for DRM-HOX. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.