DDPM modelling of kinetic parameter sensitivity and bed size effects in biomass fluidised bed gasification

Fluidized bed gasification is a promising technique due to its beneficial mass and heat transfer characteristics. The present study investigates this technique for biomass gasification using a Dense Discrete Phase Model (DDPM). The DDPM combines a Eulerian treatment for the fluid phase and a Discrete Element Method (DEM) for tracking solid particles grouped into parcels. Biomass undergoes a series of complex chemical reactions, and the kinetic rate parameters reported in the literature often vary significantly, even for similar gasification conditions. This study, therefore, focuses on developing a detailed understanding of the sensitivity of these kinetic parameters. The results demonstrate that reaction kinetics, particularly the rate of the water–gas shift reaction, have a major impact on product yields. Furthermore, the study examines the influence of inert sand bed sizes (300 mm, 150 mm, and 75 mm) on fluidisation and product yields. The difference in yields between the 300 mm and 150 mm beds is minimal at about 3 %. In contrast, the 75 mm bed shows significant variations, ranging from 5 to 12 %. Variations in grain ratios (4, 3, 2 and 1) for a fixed number of parcels are also explored, indicating their effect on the fluidisation zone and gasification process. Product yields between grain ratios of 4 and 3 differ by 3–8 %, while reducing the grain ratio to 1 increases the variation to 8–20 %. Overall, the findings provide valuable insights into the hydrodynamics of fluidised bed and the associated gasification mechanisms. • DDPM modelling of fluidised bed gasification. • Sensitivity of gasification kinetics. • WGS reaction is more sensitive to the gasification process. • Reduction in bed size significantly influences the gasification performance. • Lower grain ratio impacts both fluidisation behaviour and gasification process.