CO2-gasification kinetics of biomass char with a red mud oxygen carrier for chemical looping combustion

Abstract

Experiments and modelling of CO2-gasification of rice husk char which was derived from its pellet pyrolysis, were performed in a bed of red mud oxygen-carrier with respect to chemical looping combustion. Effects of oxygen carrier, temperature, CO2 concentration were evaluated and modeled. An experimentally-fitted function was used for expressing the char characteristics evolution. The red mud remarkably enhanced char gasification due to the fast consumption of CO. Thus, a simplified Langmuir-Hinshelwood equation by neglecting the influence of CO was applied for evaluating the intrinsic kinetics. A model coupling the kinetics of char gasification and mass transfers throughout and surrounding the whole char were established. A good agreement between modelling and experimental results was obtained. With the reaction progressing, the dynamic of concentration gradients suggested the mass transfer resistance within the char particle. The gradients increased until the carbon conversion was about 0.3, which was corresponding to the pore structure change.