Experimental preparation and mechanism analysis of a neotype composite gel for coal spontaneous combustion prevention and coal-fire extinguishment

Abstract

Spontaneous coal combustion (SCC) seriously threatens the safety production of coal mines. A neoteric irreversibly thermo-sensitive composite gel based on konjac glucomannan (KGM) and expandable graphite (EG) was elaborately synthesized for preventing SCC disasters and coal fires. Firstly, the primary properties such as the gelation time, the water retention rate, the rheological law, the microstructure characteristics, and the thermal decomposition properties concerning the composite gel were explored systematically. The results demonstrated that composite gel is non-Newton fluids with excellent self-repairing capability, and the gel exhibited controllable gelation properties, favorable seepage capacity, and strong water retention characteristics. Besides, SEM observations and thermogravimetry analysis suggested that the interspersed network structures of KGM embedded by EG exhibits higher denseness, greater physical strength, superior structural stability, and more remarkable thermal stability, and EG was closely adhered to the KGM hydrogel network but distributed inhomogeneously. Furthermore, the high-temperature pyrolysis tests showed that the decomposition rate accelerated to 0.234 %/°C and 0.225 %/°C at the temperature of 266.5 °C and 275.1 °C, respectively. Meanwhile, both the low-temperature oxidation experiments and fire-extinguishing experiments showed a favorable inhibition effect of the composite KGM@EG gel, indicating that KGM@EG gel is applicable to inhibit the high-temperature pyrolysis rate of coal, and could effectively inhibit the heat buildup, O2 consumption, and CO formation over the oxidation and combustion process of coal, which would lower the possibility of SCC and coal fires. Therefore, KGM@EG composite gel can play an efficient SCC-preventing and fire-extinguishing role in the safety production of coal mines. Finally, the underlying mechanism for SCC preventing and fire-extinguishing concerning the thermo-sensitive gel was revealed and proposed.