The catalytic effects of alkali metal carbonates on the rate of steam gasification of Australian lignite char having mean particle diameter 0.3 mm have been investigated under the atmospheric pressure in a 5.5 cm I.D. × 100 cm height thermobalance. Fresh and the char impregnated with catalysts ($K_2CO_3&, Na_2CO_3,Li_2CO_3$ and mixed$(Na,K)_2CO_3$) were used for steam gasification reaction.
The effects of $K_2CO_3$ loading (1-5 wt%) and the reaction temperature ( 700-800℃) on the rate of gasification have been examined.
The reaction orders with respect to carbon was found to be 2/3 in case of no-catalytic and $Li_2CO_3$ catalytic reaction, and zero in case of $K_2CO_3$ catalytic reaction. In the case of $Na_2CO_3$ and mixed $(Na,K)_2CO_3$ catalytic reactions, the reaction orders were found to be zero order. However, the rate constants of the reactions were not described as an unique value.
Under the same conditions of 3 wt% catalyst loading, the catalytic activities were found to be ranked as $Na_2CO_3$ ＞ mixed $(Na,K)_2CO_3$ ＞ $K_2CO_3$ ＞ $Li_2CO_3$.
The gasification rate increased linearly with the amount of $K_2CO_3$ loading. Activation energy and frequency factors of the catalytic reactions were found to be smaller than those of nocatalytic reactions.
