Reducing the spontaneous combustion and analysis of the oxidation reaction kinetics of brown coal upgraded by oxidation treatment

Abstract

To optimize the use of brown coal, methods for minimizing the spontaneous combustion of upgraded brown coal were investigated. Previous studies have shown that the controlled oxidation at 200–240 °C of Loy Yang coal from Australia, a typical brown coal, stabilized the functional groups of the coal which significantly reduced its ignition potential to the level of bituminous coal. However, the influence of the oxidation conditions on further reducing the spontaneous combustion potential of the upgraded coal was not thoroughly assessed. In this study, the exothermic reaction rate during the oxidation of upgraded Loy Yang coal was carefully examined. Its weight change and heat generation rates were measured during oxidation at temperatures between 140 °C and 300 °C, with O₂ concentrations of 1‒15 vol%, using thermogravimetry-differential scanning calorimetry. The exothermic reaction was identified as an apparent first-order reaction in the temperature range of 140–240 °C, and the heat generation rate was described by an Arrhenius-type equation. The activation energy was found to be approximately 60 kJ/mol, with the O₂ concentration affecting the frequency factor. Based on these results, a new equation was proposed to predict the oxidation conditions of the upgraded brown coal.