Calcium-promoted catalytic activity of potassium carbonate for steam gasification of coal char: Influences of calcium species

Experiments were carried out to investigate the K2CO3-catalyzed gasification performances for varying chars prepared from four coals with prior addition of calcium additive and without calcium additive. Three calcium species, Ca(OH)2, Ca(Ac)2 or Ca(CH3COO)2, and CaCO3, were used in the study. Experiments were also conducted in an attempt to achieve the understanding of the effect of calcium additive on the potassium deactivation, as well as the interactive effect between potassium, calcium and char. It was found that each calcium additive acted as a deterrent to the potassium deactivation and thus promoted the catalytic gasification, and the magnitudes of promotion varied depending on coal and calcium species. Ca(OH)2 and Ca(Ac)2 were more effective to inhibit the potassium deactivation than CaCO3. Furthermore, potassium together with calcium showed a mineral-unrelated synergy towards the char gasification. A bimetallic carbonate, K2Ca(CO3)2, which formed even when the chars prepared from coal with either Ca(OH)2 or Ca(Ac)2 was subsequently mixed with K2CO3, was likely to contribute to the synergistic effect.