Thermal Decomposition Model and Its Reaction Kinetic Parameters for Coal Smoldering with the Use of TG Tests in Oxygen-depleted Air

Abstract

ABSTRACT Smoldering of coal is a considerable source of danger in coal mines because it can lead to a gas explosion, which can cause heavy casualties. This work investigated the apparent smoldering reaction model of coal and its kinetic parameters, which are needed to study smoldering fire in a closed fire area of a coal mine. A series of thermogravimetric tests at different oxygen concentrations were performed, and the change in the pyrolysis and oxidation reaction with the oxygen concentration was analyzed. It is concluded that the apparent reaction model of smoldering coal should include a three-step pyrolysis reaction (i.e., drying, depolymerization, and polycondensation) and a five-step oxidation reaction (i.e., oxidation of coal, semi-coke, and three types of char). A genetic algorithm is used to identify the optimal kinetic parameters of the smoldering reaction. It is determined that in atmospheres with different oxygen concentrations, coal has different kinetic parameters. When studying smoldering fire in a closed fire area of a coal mine, it is suggested to adopt the kinetic parameters of the smoldering reaction in a 1% oxygen concentration atmosphere.