Experimental research on the influence of pyrite on natural oxidation of coal

Pyrite is an important factor that promotes spontaneous combustion of coal.While the heat released by the oxidation reaction promotes the heating of the coal, the oxidation products formed by pyrite are also continuously maintained in the coal.This paper focuses on the influence of the main oxidation products of pyrite on the natural oxidation of coal.Four types of natural oxidation products of pyrite are added to coal to carry out temperature-programming experiments.By analyzing the characteristic temperature and heat release on the TG-DSC curve, the influence of different oxidation products on the natural oxidation of coal can be judged.Experiments show that different concentrations of Fe³⁺ and Fe²⁺ reduce the temperature of the three characteristic points of coal, and as the concentration increases, the temperature of the three characteristic points decreases, which promotes the heat release of coal.The characteristic temperature points on the TG curve cannot be clearly seen due to the minerals in the H⁺ oxidized coal.Fe(OH)₃ has an inhibitory effect on low-temperature oxidation of coal.Through the FTIR test of coal samples at different characteristic temperatures, the mechanism of pyrite oxidation products promoting the natural oxidation of coal is analyzed.Both Fe³⁺ and Fe²⁺ accelerate the oxidation of active structural oxygen-containing functional groups (C=O, —CO—O—, —OH) and aliphatic hydrocarbons (—CH₃, —CH₂—) in coal.H⁺ can promote the oxidation of —OH and —CH₂— to a certain extent.Fe(OH)₃ has little effect on the active groups in coal, and has a physical inhibitory effect on the natural oxidation of coal.