Rate retardation phenomenon during gasification of Wandoan coal char

During the course of coal gasification, the rate per unit weight of remaining char often decreases as the coal conversion increases. The present study has tried to elucidate the reason why this rate retardation occurs. Possible reasons can be roughly divided into two categories; one due to the change of the mineral matter in char, and one related to the variation of carbon structure. Char samples at different conversion levels were prepared from raw and demineralized Wandoan coal. Their reactivities and other properties were examined, and their relationship was considered. The principal reason for the rate retardation in the present case was attributed to the loss of catalytic activity of mineral matter as the conversion increases.