Comparative Air Gasification of Agricultural Residues in an Indigenously Designed Fluidised Bed Gasifier

This study evaluates the performance and operational feasibility of a low-cost, indigenously developed pilot-scale fluidised bed gasifier operated under fixed conditions using multiple biomass feedstocks. The adaptability of the reactor for multi-biomass gasification was assessed using sawdust (SD), wheat straw (WS), rice husk (RH), corn stalk (CS), and spent tea waste (STW). Gasification experiments were carried out in an externally heated fluidised bed reactor using air as the gasifying agent. The reactor was equipped with custom-designed lateral nozzles to ensure uniform air distribution and to minimise particle clogging during prolonged operation. All experiments were conducted at a constant fuel feed rate of 20 kgh-1, operating temperatures between 750 and 950 °C, and equivalence ratios of 0.20, 0.25, and 0.30. Reactor performance was evaluated based on syngas composition (CO, H2, CH4), syngas yield, lower heating value (LHV), carbon conversion efficiency (CCE), and cold gas efficiency (CGE). The results showed that at an ER of 0.2, SD produced the highest CO (27.56%) concentration, LHV of 6.57 MJNm-3, and maximum CGE of 76%. STW yielded the highest H2 (21.45%) and CH4 (3.39%) contents and syngas yield (2.31 Nm3kg-1) at an ER of 0.3, while CS exhibited the maximum CCE of 82% at an ER of 0.25. CGE values above 60% were obtained for all feedstocks. These findings demonstrate stable reactor operation, effective nozzle performance, and strong adaptability to diverse biomass types. The developed system shows potential for decentralised energy generation and sustainable utilisation of locally available biomass resources.