Preparation and properties of nano-composite gel foam for preventing spontaneous combustion of residual coal in mined-out areas

Existing technologies for the prevention of spontaneous combustion of coal, such as grouting, inert gases, inhibitors, gels, and foams, have significant drawbacks, including high pollution, poor fluidity, and high-temperature failure. To explore an environmentally friendly, efficient, and highly stable composite gel foam for inhibiting coal self-ignition, SiO₂ and tert-butylhydroquinone were incorporated into the gel foam. The coverage ability of the nano-composite gel foam was assessed using scanning electron microscopy. Physical properties of the gel, namely viscosity, fluidity, and thermal stability, were investigated. Through an in situ infrared spectroscopy simulation, we analysed the changes in the active functional groups between the raw coal and treated coal samples. Additionally, the effectiveness of the nano-composite gel foam in preventing coal self-ignition was verified using a custom-built experimental platform. The results demonstrated that the nano-composite gel foam rendered the active functional groups inert and effectively suppressed the generation of gases, such as CO and C₂H₄, while also covering the surface of the residual coal, thereby blocking direct contact with oxygen. The results of this study provide the basis for further development of new technologies to prevent spontaneous combustion in goaf areas.