CATALYSIS OF CHAR OXIDATION BY CALCIUM MINERALS - EFFECTS OF CALCIUM COMPOUND CHEMISTRY ON INTRINSIC REACTIVITY OF DOPED SPHEROCARB AND ZAPCHARS

Catalysis by CaO, CaCO3, and CaSO4 of the oxidation of a well-defined, high-purity synthetic char, Spherocarb, was investigated at low react ion temperatures using thermogravimetric analysis. results indicate si gnificant catalytic effects-up to a 160-fold increase for CaCO3 cataly sis, 290-fold increase for CaSO4, and up to 2700 times for CaO. Oxidat ion rates were likewise measured for fresh, demineralized, and Ca-load ed chars prepared from Beulah-Zap lignite coal in a flat flame burner at 1473 K. The oxidation rates of CaO-catalyzed Spherocarb and Zap cha r are the same within experimental error, suggesting that the high rea ctivity of the Zap char is due in large part to catalysis by CaO. It w as also found that chlorine added to Ca-loaded char had a negligible e ffect on its low-temperature reactivity.