Influence of pre-injection of retardant fluid on the microscopic physicochemical structure of coal during the spontaneous combustion process

Pre-injection of blocking fluid is a preventive technology for the source of coal spontaneous combustion, which can effectively solve the fire problem caused by the natural oxidation of coal. This article combines low-temperature nitrogen adsorption, scanning electron microscopy, and infrared spectroscopy experiments to study the changes in pore and fracture structure, fractal characteristics, and functional group content of coal before and after treatment with blocking solution. The results showed that during the process of coal oxidation and heating, the specific surface area, large pore volume, and number of surface pore cracks of the blocked coal sample all decreased. At 200 °C, the fractal dimension of the blocked coal sample decreased the most significantly, by 2.54 %. At the same time, the proportion of fatty hydrocarbons and OH peak areas in the coal sample increases while the proportion of CO and OH peak areas decreases, reducing the risk of coal spontaneous combustion. In the early stage (25 °C ∼ 200 °C), the inhibitory effect of the inhibitor solution is significant. As the temperature further increases (200 °C ∼ 300 °C), the inhibitory effect of the inhibitor decreases significantly. This study is of great significance for improving the application technology of inhibitors.