Gasification of wood particles in a co-current packed bed: Experiments and model analysis

•Estimation of flame front movement, bed movement in down draft gasification system.•Experimental and model analysis on propagation rate under gasification conditions.•Gas composition is estimated by using the model and compared with experimental results.•Flame propagation rate movement is an important parameter to decide the operating range.•Propagation movement is strongly dependent on surface area/volume ratio of the fuel samples.

This study focuses on addressing the propagation front movement in a co-current downdraft gasification system. A detailed single particle modeling analysis extended to the packed bed reactor is used to compare with the experimental measurement as well those available in the literature. This model for biomass gasification systems considered pyrolysis process, gas phase volatile combustion, and heterogeneous char reactions along with gas phase reactions in the packed bed. The pyrolysis kinetics has a critical influence on the gasification process. The propagation front has been shown to increase with air mass flux, attains a peak and then decreases with further increase in air mass flux and finally approaches negative propagation rate. This indicates that front is receding, or no upward movement, rather it is moving downward towards the char bed. The propagation rate correlates with mass flux as ṁ''0.883 during the increasing regimes of the front movement. The study clearly identifies that bed movement is an important parameter for consideration in a co-current configuration towards establishing the effective bed movement. The study also highlights the importance of surface area to volume ratio of the particles in the packed bed and its influence on the volatile generation. Finally, the gas composition for air gasification under various air mass fluxes is compared with the experimental results.