ANALYSIS OF 2-STEP REACTION OBSERVED IN AIR GASIFICATION OF COAL THROUGH A TEMPERATURE-PROGRAMMED REACTION TECHNIQUE

Recently the authors presented a temperature-programmed reaction (TPR) technique to analyze the gasification of coal chars. This technique is suitable to find a slight difference in the reactivity. By use of this technique they found that some reactive coal chars were gasified in two steps in air. The two-step gasification means that two parallel reactions of different rate parameters are occurring. This phenomenon was associated with heterogeneity in the char, demonstrated by the strong influence of the mineral matter, but the source of the heterogeneity could not be clarified. In this work we performed systematic experiments to find the source of the heterogeneity. Through these experiments it was found that cations such as Ca and Mg produce less reactive carbon during the gasification, which is the source of the two-step gasification observed for some reactive chars.