Two Types of Two-Step Reaction Observed During Air Gasification of Coal Chars

Chars prepared from 22 kinds of coals and demineralized coals are gasified in an air atmosphere using a temperature-programmed reaction (TPR) technique in which the chars were heated at a constant rate. It was found that 8 kinds of coal chars were gasified in two steps. This phenomenon was called two-step reaction here. There found to be exist at least two types of two-step reaction. Based on the measure-ment of the heat of reaction and the activation energy, the second step reaction observed for the chars prepared from several low rank coals was found to be due to the gasifica-tion of a less reactive carbon produced by the catalytic effect of Ca and/or Mg during the first step reaction, as has been reported in our recent works. On the other hand, the two-step reaction observed for two high rank coal chars was found to derive from the gasification of different maceral groups. It was clarified that the first step is mainly the gasification of vitrinite, and that the second step is mainly the gasification of inertinite.