Biochar and Ni-biochar based catalysts: A sustainable catalyst for treatment of tar obtained from co-gasification of coal and biomass in a fluidised bed gasifier

Tars are produced during biomass gasification or co-gasification of biomass and coal. It could lead to operational difficulties such as blockages of valves, filters, condensers and feed line of gasifiers. Secondly, the presence of tar in the produced gas affects the quality and the performance of end user equipment. Catalysts are employed to crack tars to minimise their production, hence; resulting to a reduction in the cost of gas cleaning and an enhancement of the product gas quality and yield. In this study, 3 biochar based (corn cob (CC-BC), sugarcane bagasse (SCB-BC), & pine sawdust (PSD-BC) and 3 Ni-biochar based catalysts (Ni-CC-BC), Ni-SCB-BC, & Ni-PSD-BC were used to carry out the tar treatment. The Ni-biochar based catalysts were synthesised via wet incipient impregnation method, and using Ni-to-Biochar ratio of 10:15. The tars that were treated were produced from Coal + CC, Coal + SCB, & Coal + PSD, and were referred to as CCC-T, CSCB-T, & CPSD-T, respectively. Averagely, the percentage amount of tar conversion (PTC) obtained from the optimum catalysts: PSD-BC and Ni-PSD-BC were around 89.76 and 96.73 %, respectively. An evaluation of the catalyst activity using conversion times of 10, 15, and 20 min at 900 ^OC revealed that the Ni-biochar catalysts were more efficient in tar cracking than that of biochar by 7.87, 3.87, & 3.79 % respectively. In terms of sustainability and cost effectiveness, biochar based catalyst may be considered more attractive. A comprehensive tar treatment model was developed, and could be instrumental for estimating the PTC for feedstock (precursors) similar to the ones studied.