Detailed CFD simulation and experimental validation of oxy-steam fluidized bed gasification for biomass, coal, and plastic feedstocks

Gasification of solid waste in fluidized bed reactors involves complex multi-physics processes requiring advanced modeling. While extensive CFD studies exist for biomass and coal gasification, research on plastic waste gasification remains limited. Many models oversimplify the chemistry, excluding critical reactions like tar cracking, which significantly impact syngas quality. This study develops an Eulerian-Eulerian CFD model integrated with a comprehensive reaction mechanism involving 14 reactions: one devolatilization, six oxidation, five reduction, and two tar-cracking reactions. The model simulates oxy-steam gasification of biomass, coal, and plastic waste and is validated against experimental syngas composition data. The model shows a maximum root mean square error of 2.24% for CO in coal gasification and a minimum of 0.01% for CH4 in biomass gasification. Geometrical optimization was also studied. Results indicate that in-bed feedstock injection improves gas–solid mixing and enhances gasification performance over on-bed injections. Additionally, increasing the freeboard height to 1.2 times that of the base case results in the highest hydrogen content in syngas.