Oxidation Characteristics and Corresponding Reaction Mechanism of Coal During the Spontaneous Combustion Latency

The study of the formation of CO and CO2 is an important means of investigating the mechanism of low-temperature coal oxidation. However, the small changes in the gas produced by oxidation during the spontaneous combustion latency cannot be accurately measured by traditional flow reactors. A set of coal low-temperature closed oxidation multi-component gas online monitoring system was designed. Small changes in the volume fractions of O2, CO and CO2 can be automatically monitored in real time. Experiments on the isothermal oxidation of coal were conducted during the spontaneous combustion latency under different conditions (different temperatures, different initial oxygen volume fractions and different oxidation times). The oxidation experiment results were corrected by Henry model. According to the retardation time of gas production and the changes in Graham’s ratio, CO and CO2 are produced from different reaction sequences during the spontaneous combustion latency. The active substances in coal react with O2 to produce unstable carbon-oxygen complexes, and CO2 is mainly derived from the decomposition of the intermediates. CO is derived from the H-capture reaction of stable solid oxygenated complexes. The research results will help to further understand the mechanism of spontaneous combustion of coal.