Steam gasification of Indonesian subbituminous coal with calcium carbonate as a catalyst raw material

• Char conversion increased significantly by loading CaCO3 in the steam gasification.
• Gasification temperature lowered by about 100 °C by loading 1.7% of CaCO3.
• Ca catalyst in coals with a small amount of Ca exists in the ion-exchanged form.

The effect of Ca catalysts prepared from CaCO3 on the steam gasification of Indonesian subbituminous coal at 700–800 °C is examined. The char obtained by pyrolyzing the coal with 0.59 wt.% of Ca (dry basis) showed conversions in steam gasification at 750 and 800 °C of around 70 and 90 wt.% (dry ash and catalyst free basis), which were 2 and 1.5 times larger than those of the coal without the Ca catalyst, respectively. The activity of this Ca catalyst was as high as that prepared using an aqueous solution of Ca(OH)2. The TPD and XRD measurements demonstrated that the Ca catalyst from CaCO3 was initially present in the ion-exchanged form, and as a finely dispersed calcium species after pyrolysis. These results confirm that CaCO3 is effective as a catalyst raw material in the steam gasification of subbituminous coal, even at low catalyst loadings.