Mineral reaction and morphology change during gasification of coal in CO2 at elevated temperatures

Studies of the gasification of char in CO₂ at elevated temperatures are necessary for the development of IGCC technology. Experiments at high heating rates and elevated temperatures revealed that the temperature dependence of gasification reactivity was very different for low compared with high temperature ranges. To elucidate these mechanisms, the reaction of mineral matter and the change in morphology during gasification of a char at elevated temperatures were examined by char characterisation. CO₂ gasification experiments showed a large difference in gasification rate for chars prepared at higher temperatures compared to those prepared at lower temperatures. Changes in char particle morphology and mineral matter during gasification are also quite different. At higher carbonisation temperatures, mineral reactions during pyrolysis, which occurs in addition to ash fusion, appear to be one of the factors accounting for these differences. Certainly, a change of mechanism is involved. Graphite enrichment may also contribute to the decrease in char reactivity.