A relationship between the kinetic parameters of char combustion and the coal's properties

It is suggested that the activation energy, E, for the combustion of a char is independent of the coal's properties and only varies with the temperature of the char particle; also, the frequency factor of char oxidation, k(o,ch) depends on the coal's properties during its burning in air. We have taken E = 180 kJ/mol as a constant in the oxidation of any coal char burning in air. Based on experiments for different coals, a relationship between k(o,ch) and the coal's properties, applicable to any coal char burning in air, is derived. The relationship is different from those proposed previously, i.e., with both E and k(o,ch) varying disorderly with a coal's properties. Now, k(o,ch) can easily be predicted from the proximate analysis of the coal. Furthermore, it can be demonstrated that k(o,ch) is also related to the burning regime; a quantitative relationship is presented. (C) 1997 by The Combustion Institute.