Modified Dry Water for Fire Control in Spontaneous Coal Combustion: Preparation and Anti-Reignition Performance

Spontaneous coal fire seriously affects the normal production of mines. In order to further improve the ability of preventing and controlling coal fire disasters, it is necessary to explore new materials for fast and efficient management of coal fire disasters in the context of carbon peak. This study employed a mechanical stirring method to prepare pure dry water (DW) material, with process parameters determined using the controlled variable method. To enhance the fire suppression capability of DW formed from pure distilled water, modifications were made using high-acyl gellan gum, potassium chloride, magnesium hydroxide, and ammonium dihydrogen phosphate. The physical properties of these four modified DW materials were systematically examined. Experimental results indicated that hydrophobic fumed silica and deionized water at a solid–liquid ratio of 1:12, a dispersion disc speed of 3500 r/min, a dispersion time of 3 minutes (min), and a distance of 1.5 cm between the dispersion disc and the container bottom yielded DW powder particles with favorable dispersibility and high uniformity. Under these process conditions, the flowability of the four modified DW materials, ranked from strongest to weakest, was as follows: potassium chloride DW (K-DW) > high-acyl gellan gum DW (G-DW) > ammonium dihydrogen phosphate DW (NH₄-DW) > magnesium hydroxide DW (Mg-DW). Compared to pure DW, the water loss time was extended by 6 h for G-DW and 3 h for K-DW, while Mg-DW and NH₄-DW exhibited only a 1-h extension in water loss time along with solid particle caking, indicating inferior overall performance. During the cooling phase, G-DW demonstrated the most remarkable cooling performance, with a cooling rate 1.67 times that of DW, 1.14 times that of K-DW, 1.11 times that of NH₄-DW, 1.08 times that of water mist, and 1.71 times that of gel foam. Compared to other fire-extinguishing materials, K-DW and G-DW exhibited heating rate of 0.12°C/s and 0.09°C/s, respectively, during the temperature rebound phase, indicating a significantly less pronounced reheating effect. At 25 min after the application of K-DW and G-DW, the central temperature of the coal body fluctuated around 75°C and 65°C, demonstrating remarkable cooling performance and effective suppression of coal spontaneous combustion hazards. Four modified dry water materials were prepared using the mechanical stirring method (K-DW、G-DW、NH₄-DW、Mg-DW).The flowability of the four modified dry water materials, from strongest to weakest, is as follows: K-DW > G-DW > NH₄-DW > Mg-DW.Compared with pure dry water, the water loss time of G-DW and K-DW was extended by 6 h and 3 h, respectively.G-DW fire extinguishing agent can effectively address the hazards and disasters caused by coal spontaneous combustion. Four modified dry water materials were prepared using the mechanical stirring method (K-DW、G-DW、NH₄-DW、Mg-DW). The flowability of the four modified dry water materials, from strongest to weakest, is as follows: K-DW > G-DW > NH₄-DW > Mg-DW. Compared with pure dry water, the water loss time of G-DW and K-DW was extended by 6 h and 3 h, respectively. G-DW fire extinguishing agent can effectively address the hazards and disasters caused by coal spontaneous combustion.