Effect of Bio-Based Organic‒Inorganic Hybrid Hydrogels on Fire Prevention of Spontaneous Combustion of Coals

To solve the fire accidents caused by coal combustion, this work prepared four hybrid hydrogel materials using bio-based polymers, flame retardants, and inorganic materials.Compared to pure water and 3.5 wt% MgCl 2 solution, the as-prepared hydrogel presents good fire prevention performance.In addition, it is found that CO and CO 2 are not produced by coal when the pyrolysis temperature is lower than 200°C.During low-temperature pyrolysis, CO is more likely to be produced than CO 2 , indicating inadequate pyrolysis behavior.At the same time, the addition of fire-preventing hydrogel can not only decrease the maximum CO 2 concentration before the critical temperature but also prolong the corresponding time.In addition, based on the cone calorimeter test, the inhibition effects of pure water, magnesium chloride solution, and four hybrid hydrogels on heat release behavior are evaluated.It is demonstrated that different dosages of different hydrogels affected the fire prevention effect.Phosphorous-modified cellulose/silica and carrageenan/DMMP/vermiculite composite hydrogels have the weakest fire prevention effect at 20 g, which is weaker than that of water.However, the fire prevention effect of carrageenan/ DMMP/vermiculite composite hydrogels exceeded that of water at 40 and 60 g.Additionally, the fire prevention effect of the sodium alginate/sepiolite/ammonium polyphosphate composite hydrogel is most significant in common tests, attributed to the intumescent flame retardant system.