Calcium-promoted catalytic activity of potassium carbonate for steam gasification of coal char: Effect of hydrothermal pretreatment

Hydrothermal pretreatment of coal with the addition of Ca(OH)2 was found more effective for promoting the K2CO3-catalyzed char gasification than the physical addition way for both JY anthracite coal and HB bituminous coal used. The effect of hydrothermal pretreatment was more remarkable for JY coal which suffers significant catalyst deactivation due to its high mineral content. For this type of coal, employing more severe hydrothermal pretreatment conditions was proven to significantly enhance the gasification rate. It was observed that kaolinite and quartz in coal hydrothermally reacted with calcium forming hydrated calcium aluminosilicates, which, unlike the original minerals, was inactive for the deactivation reactions of potassium. Consequently, the hydrothermal pretreatment allowed more potassium to persist as a water-soluble entity during the gasification. This was a main mechanism underlying the promoted catalytic gasification by the hydrothermal treatment.