Experimental research on bimetallic ion crosslinked gel to inhibit the spontaneous combustion of coal

To address the environmentally friendly issue of fire prevention and extinguishing materials in coal mines, a new type of mine fire prevention and extinguishing gel was prepared using sodium carboxymethyl cellulose (CMC) as the matrix, ferro aluminum citrate (Fe-AlCit) as the cross-linking agent, and gluconic acid-delta-lactone (GDL) as the pH modifier. The preferred ratio was 2.5 % CMC + 4 % Fe-AlCit + 2 % GDL of No. 23 gel material by gelation time, thermal stability, strength, and permeability performance tests. The results show that the gelation time of No. 23 gel was 10 min, and its complete water loss time was 1.97 times that of water at a high temperature of 180 degrees C. The gel for sealing the surface of the coal body still maintained good stability after two weeks. Furthermore, A metal coordination bond favorable to the stability of gel is formed by the carboxylate ion in CMC and the double high-valent metal ions Fe3+ and Al3+ ionized by Fe-AlCit. No. 23 gel exhibits excellent fire prevention and extinguishing properties. The temperature-programmed test showed that the CO and C2H4 gas inhibition rate of the coal sample treated with No. 23 gel reached 33.42 % and 56.86 % at 220 celcius, and the activation energy growth rate reached 26.5 % and 21.1 % in the first and second stages, respectively. The fire extinguishing test indicated that No. 23 gel can significantly reduce the temperature of the coal sample and extinguish the coal fire quickly. The study is useful to develop efficient and environmentally friendly coal mine fire prevention and extinguishing materials.