Calcium-promoted catalytic activity of potassium carbonate for steam gasification of coal char: Transformations of sulfur

► A high-sulfur bituminous coal char was gasified with K2CO3 by pre-addition of Ca(OH)2 to coal. ► Sulfur XANES was used to determine sulfur transformations associated with coal pyrolysis and gasification. ► The calcium additive facilitated the decomposition of both inorganic and organic sulfur during coal pyrolysis. ► The calcium additive allowed more sulfur to be retained in the ash as K2SO4 after gasification.