Experimental study and modelling of the kinetic of biomass char gasification in a fluidized bed reactor

This work presents experimental data on the kinetic of steam gasification of biomass char in a fluidized bed reactor at atmospheric pressure. The char was obtained from fast pyrolysis of cylindrical beech stick in an annex batch fluidized bed reactor at 650 °C. The experiments were performed for temperatures in the range of 700-850 °C and steam partial pressures between 0.1 and 0.7 bars. The results showed that the char steam gasification is done in two steps. First, a thermal degradation of char takes place just after its introduction in the fluidized bed. This step leads to a partial conversion of the reactive solid and a formation of volatile products. Then, the new carbonaceous residue reacts with steam to produce syngas. The effect of hydrogen partial pressure up to 0.25 bars on the kinetic of char gasification was also investigated. The results revealed that the presence of H2 inhibits the reaction of steam gasification. Besides, interactions also occur between char and H2 which lead to the formation of CH4 in the product gas. Moreover, as the hydrogen partial pressure increases, the methane production also increases. Finally, a modelling kinetic study including the inhibiting effect of H2 showed that experimental data can be well-represented by the Shrinking Core Model with an activation energy and a reaction order with respect to steam equal to 123 kJ/mol and 0.62, respectively.