On the relevance of gas distribution on the performance of a biomass catalytic fluidized bed gasifier

The paper analyzes the effect of a progressive shift from bubbling to spouted gas-solid fluidization on catalytic as well as non-catalytic biomass gasification. A central vertical jet has been added to a conical shape gas distributor as a strategy to decrease the segregation phenomena occurring in the bed to biomass particles and their emitted volatiles. Commercial spruce wood pellets have been continuously fed to a 140 mm ID fluidized bed gasifier. Four different values of the air flow rate in the central jet, corresponding to 10, 20, 50, 80% of the total air flow rate, have been tested. Experimental results indicated that operating the bed under spouted bed regime does not result in an increase of conversion to H2 and CO. Further, it dramatically enhances elutriation rate of carbon fines and attrition of catalytic particles. On the contrary, under spouted operating conditions, there is a favourable and significant decrease of tar concentration in final producer gas whatever bed material is used, i.e., catalyst or simply sand particles.