Influence of Heating Rate during Pyrolysis on Gasification Reactivity of Coal Chars at High Temperatures.

Reactivity of coal chars to carbon dioxide at high temperatures of 1273-1873K was investigated using a fluidized bed reactor (FBR). Coal samples were pyrolyzed in nitrogen flow under rapid and slow heating condition, and then in-situ measurement of gasification rates of the prepared chars was carried out. It was found that the heating rate during the pyrolysis affected the reactivity of coal char significantly, namely, more rapid heating led the higher reactivity of chars. Especially for coals with high volatile content, the reactivity of coal chars prepared under the rapid heating was several times as large as that under the slow heating. The results of nitrogen adsorption measurements indicate that porosity and surface area of mesopores were proportional to the reactivity of chars. The high gasification reactivity of rapid heating chars can be explained by their high surface area in mesopore range.