The reactivities of chars were investigated for gasification with steam and carbon dioxide by thermogravimetry in the temperature range of 1100 to 1400℃ and at atmospheric pressure

and the results were compared to those of the previous work at temperatures below 1000℃

where the gasification velocity was chemically controlled. The parent coals of the six char samples differed in rank from brown coal to anthracite and from non-caking coal to strongly caking coal. The rate equation

f=1- exp( -aθb)

designated as the modified volume reaction model

was applied to evaluating gasification reactivities using an average rate constant k.