Effect of pyrolysis time on the gasification reactivity of char with CO2 at elevated temperatures

Gasification of a char has so far been mainly studied at low temperatures and low heating rates with a TGA (thermogravimetric analyzer). Studies on gasification of a char in CO2 at elevated temperatures and high heating rates are necessary to develop IGCC technology. With a unique fluidized bed. the effect of pyrolysis time on char reactivity was investigated. It was found that a longer pyrolysis time led to lower reactivity of a char, while this effect leveled off as pyrolysis time increased. The pyrolysis time also had an influence on the temperature dependence of gasification reactivity. Initial char gasification rate decreased as pyrolysis time increased. The pyrolysis time had effect on the entire process of char gasification. The effect of pyrolysis time was more remarkable for a coal with high volatile matter content among the three coals tested. The gasification rate of a char was very different from that of a raw coal (gasification without pyrolysis in advance), which suggested an influence of pyrolysis time and atmosphere on char reactivity. Accordingly, those results obtained from a TGA are necessary to be corrected when applied to a practical entrained flow gasifier. (C) 2004 Elsevier Ltd. All rights reserved.