Influence of low-temperature oxidation on structure of coke making coal

Abstract

Self-exothermic reaction of coal is initiated by the reaction of coal in a pile with oxygen in the air to be oxidized. Then, the heat generated by the oxidation promotes further oxidation, resulting in ignition. In order to prevent this phenomenon, it is necessary to understand the initial stage of oxidation of coal in the condition of heat-accumulation. Conventionally, there are very few researches to understand the early stage of coal oxidation. In this study, we aimed at to elucidate the earlier oxidation stage of coals by employing low temperature oxidation of a mass of coals and several instrumental analysis techniques. The oxidation we used were heating 50 g of coal charged in a stainless steel closed container at 80°C for 24 h by flowing hot air to simulate the self-exothermic reaction condition. XRD and Raman spectroscopic measurements showed that the carbon skeleton structure of coal did not change by the oxidation treatment, while FTIR, 1H NMR and 13C NMR measurements showed a decrease in aliphatic side chains and an increase in hydroxyl groups in coal. The information obtained here will help to understand the whole process of self-exothermic reaction of coal to prevent burning.