Chemical reactivity of Canadian coal-derived chars

The reactivities of eight Canadian coal-derived chars of four different ranks were measured thermogra-vimetrically at 500°C. It has been found that char reactivity decreases with increase in the carbon content (or rank) of the parent coal. Chars containing more calcium and magnesium oxides have higher reactivities. The experimental results of mass conversion are well represented by the shrinking core model in which the initial stage of the reaction is kinetically controlled by chemical reaction and the later stage by gas diffusion through the ash.