K2CO3 catalyzed steam gasification of ash-free coal. Studying the effect of temperature on carbon conversion and gas production rate using a drop-down reactor

Steam gasification experiments of ash-free coal with and without potassium carbonate were performed in a newly designed drop-down reactor. The temperature dependency on the carbon conversion and gas production rates was investigated in a range of 600-800 degrees C and 2.5 bar. The gasification rate at 700 degrees C was approximately 20 times faster in the presence of the potassium catalysts. The gasification temperature could be lowered by similar to 125 degrees C. For example, at 625 degrees C the catalyzed gasification rate was essentially the same as for uncatalyzed rate at 750 degrees C. In addition, the catalyst reduced the apparent activation energy from 268 to 161 kJ mol(-1). The water-gas-shift reaction was in equilibrium for both the uncatalyzed and catalyzed gasification of the ash-free coal samples. At low temperatures, a considerable amount of methane was formed through direct hydrogenation of the carbon substrate. Methane formation was decoupled from the COx production. (C) 2014 Elsevier Ltd. All rights reserved.