Preparation and characterization of DOPO-MMT co-stabilized gel foam for inhibiting coal spontaneous combustion

To improve the inhibitory effect of gel foam on coal spontaneous combustion, this paper proposes a DOPO-MMT co-stabilized gel foam (D-M/CSGF) mining extinguishing material composed of a foaming system, stabilizing system, gel system, and DOPO-MMT based on the assembly effect of hydrophobic nanoparticles (DOPO-MMT) and hydrophilic macromolecules. The optimal ratio of D-M/CSGF is determined through single-factor experiments and orthogonal experiments. The microstructure of D-M/CSGF is characterized using stereomicroscopy, and the foaming properties, foam stability, and water retention of the gel foam are investigated. The inhibitory effects of DOPO-MMT co-stabilized gel foam (D-M/CSGF), ordinary gel foam (GF), and water-based foam (OF) on coal spontaneous combustion are compared through temperature-programmed experiments and infrared spectroscopy. The results show that when the mass fractions of the foaming system, foam stabilization system, gel system, and nanoparticles are 0.9 wt%, 0.3 wt%, 1.7 wt%, and 0.5 wt%, respectively, D-M/CSGF exhibits better foam properties, with small bubble size, long retention time, and uniform distribution, and a half-life of over 12 h. At 100 degrees C, OF, GF and D-M/CSGF reach 90 % moisture loss after 5 h, 8 h, and 10 h, respectively. Comparing with OF and GF, the water retention time of D-M/CSGF increases by 50 % and 20 %, respectively. The CO inhibition rate of D-M/CSGF at 150 degrees C is 93.7 %, the oxygen consumption rate is reduced by 46.64 % at 100 degrees C, and the inhibition rate is 87.6 %, which can effectively slow down the low temperature oxidation process of coal. Meanwhile, the content of active functional groups such as-OH and aliphatic hydrocarbons in the coal molecules is reduced by 40.92 % and 64.13 %, respectively, comparing with the original coal, which effectively reduces the oxidative activity of coal molecules. This study provides a D-M/CSGF with good foam properties and inhibitory effects, which can effectively isolate oxygen, reduce temperature, and heat radiation during the inhibition process, achieve efficient inhibition of coal spontaneous combustion, and have excellent fire extinguishing performance.