Use of coupled TG-FTIR and Py-GC/MS to study combustion characteristics of conveyor belts in coal mines

This article lays the groundwork for the prevention and control of coal mine roadway fires, as well as the construction of a mine transportation belt fire early warning system. Through thermogravimetric analysis-Fourier transform infrared spectroscopy, the thermogravimetric changes of coal mine conveyor belts at four heating rates were tested, and seven characteristic temperature points were obtained. The gaseous products released during the belt combustion process were analyzed using pyrolysis–gas chromatography–mass spectrometry, and the combustion reaction process and belt combustion characteristics were investigated. According to the findings, the primary components of the gaseous products emitted during belt combustion were salts, amides, aliphatic hydrocarbons, phthalates, and aromatic hydrocarbons, and these components varied significantly as temperature increased. The belt combustion process was broken down into three phases. In the first stage, dioctyl phthalate molecules escaped, and during this process, carbon–oxygen (C–O) and carbon–carbon (C–C) bonds were broken to generate phthalates, fatty acids, and methane (CH4). In the second stage, conjugated dienes and substituted alkenes generated aromatic hydrocarbons through the Diels–Alder reaction, and the C–O and C–C bonds of the plasticizer (dioctyl phthalate) were continuously cleaved and decarboxylated to generate phthalates, amides, fatty acids, ketones, CO, and H2O (g), whereas CO2 volatilization and fatty acid decarboxylation caused aliphatic hydrocarbons and CO2 to be generated. In the third stage, the phthalates and polyvinyl chloride volatiles generated in the previous stage underwent a reduction–oxidation reaction and were decomposed into aliphatic hydrocarbons, aldehydes, aromatic hydrocarbons, amides, small organic molecules (e.g., benzene, indene, and fluorene), and metal substances that were non-decomposable.