Preparation and properties of coal slime-based biomass composite gel——Coal mine fire prevention and control

To improve coal spontaneous combustion (CSC) prevention while promoting the high-value utilization of coal slime (SM), a novel SM-based biomass composite gel (SA/H/X/SM) was developed. The formulation was optimized using an orthogonal experimental design, and its rheological behavior, thermal stability, sealing performance, and CSC inhibition mechanism were systematically investigated by rheological measurements, thermogravimetric analysis (TGA), air-leakage tests, temperature-programmed oxidation, and molecular dynamics (MD) simulations. The results show that sodium alginate (SA) and calcium lactate (CL) formed a three-dimensional gel network through ionic crosslinking, while hydroxypropyl methylcellulose (HPMC) and xanthan gum (XG) further reinforced the structure via hydrogen bonding and chain entanglement. SM particles contributed to network integrity through particle filling and interfacial interactions, improving the thermal stability and mechanical performance of the gel. SA/H/X/SM exhibited typical yield-pseudoplastic behavior and achieved an average air-leakage sealing efficiency exceeding 48.5% under different pressure and flow conditions, demonstrating excellent transportability and sealing performance. The composite gel effectively inhibited coal oxidation by delaying CO and C 2 H 4 release and increasing the apparent activation energy by 4.97% and 29.78% during the low-temperature and accelerated oxidation stages, respectively. MD simulations further revealed that abundant hydrophilic functional groups promoted the adsorption and diffusion of water molecules on the coal surface, thereby enhancing coal wetting. Consequently, SA/H/X/SM efficiently inhibited CSC through the synergistic effects of oxygen isolation and sealing, wetting and cooling, and high-temperature carbonization for thermal dissipation. These findings provide a sustainable and scalable strategy for CSC prevention and valorization of SM in underground fire control applications.