Kinetics of metal oxide-catalyzed CO2 gasification of coal in a fluidized-bed reactor for solar thermochemical process

Metal oxide-catalyzed CO2 gasification of coal was examined in a small-scal e fluidized-bed reactor at 1073-1223 K and at atmospheric pressure, for the purpose of converting solar high-temperature heat to chemical fuels. The m etal oxide powder of In2O3, ZnO, or Fe2O3 in the grain sizes of 4-9 mum was simply mixed with the ground bituminous coal (grain size < 300 mum) and th e catalytic effects of the metal oxide on the Boudouard reaction (C-CO2 rea ction) in the coal gasification were kinetically studied. The initial coal gasification rate followed the homogeneous or shrinking core model. Gasific ation activity followed the order of In2O3 > ZnO > Fe2O3 at high temperatur es above 1123 K while the order changed to In2O3 > Fe2O3 > ZnO at lower tem peratures. The comparison on the Arrhenius parameters for the catalytic and noncatalytic gasification suggests that the gas species of In2O(g) and Zn( g) are the intermediates to react with CO2 in the cases of the In2O3- and Z nO-catalyzed gasifications, respectively. High-temperature separation of us ed ZnO catalyst from the remaining coal ash by Zn evaporation was demonstra ted at 1423 K.