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 °C and 2.5 bar. The gasification rate at 700 °C was approximately 20 times faster in the presence of the potassium catalysts. The gasification temperature could be lowered by ∼125 °C. For example, at 625 °C the catalyzed gasification rate was essentially the same as for uncatalyzed rate at 750 °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.