Experimental study and characterisation of a novel two stage bubbling fluidised bed gasification process utilising municipal waste wood

Abstract

Biomass gasification has increased due to its ability to provide high-temperature heat, making it promising for the decarbonisation of industrial processes. The economic and technical challenges of large-scale operations need to be addressed by focusing on small-sized gasifiers, while the use of low-grade biomass, is essential to increase the flexibility and sustainability of the plant. However, the utilisation of low-grade biomass is hindered by challenges stemming from variations in the particle distribution and shape, which significantly impact the fluidisation process and overall. In this research, the gasification of shredded municipal waste wood in a pilot-scale bubbling fluidised bed reactor was demonstrated, and the fluid-dynamics and gas production were assessed. The gasification process was yielding a gas with a lower heating value between 3.5 MJNm⁻³ and 3.9 MJNm⁻³ and a cold gas efficiency (CGE) of 46.4 %–48.6 %. Notably, these CGE values are consistent with pilot-scale setups, where CGE values above 50 % are typically not achievable because of poor insulation standards. The reactor's conical shape facilitated dynamic fluid regime transitions, ensuring efficient gas-solid interactions. This design allowed optimisation of fluidisation by accommodating particles of varying sizes throughout the reactor's height, thereby promoting efficient gasification suitable for industrial applications with diverse biomass feedstocks.