我国煤炭资源丰富，总储量高居世界前三，煤炭的生产对实现我国经济快速发展具有重要作用。但在生产煤炭的过程中，瓦斯事故时有发生，严重阻碍煤矿安全生产。目前国内外研究学者在瓦斯抑爆技术上做了大量研究，其中干水粉体作为一种新型抑爆材料，拥有粉体类抑制剂和细水雾抑制剂的双重抑制效果，具有很广阔的市场前景。

本文主要对干水粉体的制备方法、瓦斯抑爆性能及抑爆机理进行了研究。首先，研究了质量配比、搅拌转速以及搅拌时间对普通干水粉体制备的影响，得到了其制备时的最佳质量配比为9:100，最佳搅拌转速为5000 rpm，最佳搅拌时间为240 s。此外，对普通干水粉体进行了改性研究，分别制备出4种不同浓度尿素改性干水粉体和3种海藻酸钙凝胶型改性干水粉体。对制备出的干水粉体进行性能表征测试，发现在普通干水粉体中添加凝胶剂和改性剂以后，干水粉体的松密度、保湿性和流动性均有明显改善，稳定性增强，粒径分布更加均匀。

其次，采用瞬态爆炸火焰传播实验系统开展瓦斯抑爆实验。得出在10%瓦斯浓度下，添加0.13-0.26 g/L的普通干水粉体时，会对瓦斯爆炸呈现出促进效果；添加0.39-1.04 g/L的普通干水粉体时，呈现出抑制效果，且在此浓度范围内，瓦斯抑爆效果随粉体浓度的增加而逐渐增强。此外，当尿素溶液浓度为0%、5%、10%、15%和20%时，制备出的改性干水粉体瓦斯抑爆效果呈现出先上升后下降的趋势。10%尿素溶液浓度在上述5种溶液浓度中具有最佳的抑制效果。添加6种不同的粉体去抑制6%、8%、10%、12%浓度瓦斯爆炸时，抑爆效果从弱到强排序依次为：SiO₂粉体＜普通干水粉体＜海藻酸钙-普通干水粉体＜10%尿素改性干水粉体＜海藻酸钙-磷酸二氢铵干水粉体＜海藻酸钙-尿素改性干水粉体。其中，海藻酸钙-尿素改性干水粉体可使得瓦斯爆炸火焰传播到管道的时间最大延长40 ms，最大火焰传播速度降低幅度最大达到42.46%，火焰温度峰值最大下降幅度可到达58.99%，最大泄爆压力达到15.71%。

再次，使用20 L球形爆炸实验系统测试了海藻酸钙-尿素改性干水粉体在6%、8%、10%、12%瓦斯浓度下的最佳用量，得出最佳用量分别为0.125、0.3、0.5、0.225 g/L，总体呈现出先上升后下降的趋势。当添加海藻酸钙-尿素改性干水粉体过少时，不能在瓦斯爆炸反应初始阶段对反应进程形成有效阻碍；而添加过量的海藻酸钙-尿素改性干水粉体，又会导致粉体在受限空间内出现团聚现象，并且增大了其体积负荷，使得粉体自身的热解效率降低。这两种情况均会使得海藻酸钙-尿素改性干水粉体的瓦斯抑制效果变差。

最后，分析了海藻酸钙-尿素改性干水粉体的瓦斯抑爆机理，得出其在抑制瓦斯爆炸时，可使得瓦斯爆炸体系中的CHOꞏ、OHꞏ和CNꞏ等关键自由基含量明显降低，并且生成大量HNOꞏ和NOꞏ可继续消耗瓦斯爆炸体系中的自由基。通过将上述结论与干水粉体的TG-DSC热过程分析相结合得到海藻酸钙-尿素改性干水粉体的瓦斯抑爆机理，主要包含以下四个方面：① 隔绝瓦斯爆炸反应，降低氧浓度；② 水分子蒸发吸热，降低火焰温度；③ 水蒸气稀释可燃气体，惰化反应；④ 各自由基发生链式反应，降低关键自由基浓度。

China possesses considerable coal resources, with the total reserves ranking top three in the world. Coal production plays an important role in realizing the rapid development of China's economy. But in the process of coal production, gas accidents happen from time to time, which seriously hinders coal mine safety production. At present, researchers at home and abroad have done a lot of research on gas explosion suppression technology. As a new type of explosion suppression material, dry water powder has the double inhibition effect of powder inhibitor and fine water mist inhibitor and has a very broad market prospect.

In this paper, the preparation method of dry water powder, gas explosion suppression performance, and explosion suppression mechanism was studied. Firstly, the effects of mass ratio, stirring speed, and stirring time on the preparation of an ordinary dry water powder system were studied. The best mass ratio of the preparation was 9:100, the best stirring speed was 5000 rpm, and the best stirring time was 240 s. In addition, the modification of ordinary dry water powder was studied, and four kinds of urea-modified dry water powder and three kinds of calcium alginate gel modified dry water powder were prepared. It was found that the bulk density, moisture retention, and fluidity of the dry water powder were significantly improved, the stability was enhanced, and the particle size distribution was more uniform after adding gel agent and modifier to the ordinary dry water powder.

Second, the gas explosion suppression experiments were carried out using the transient explosion flame propagation experimental system. It is obtained that at 10% gas concentration, when adding 0.13-0.26 g/L of ordinary dry water powder, it will show the promotion effect on gas explosion; when adding 0.26-1.04 g/L of ordinary dry water powder, it shows the inhibition effect, and in this concentration range, the gas explosion suppression effect is gradually enhanced with the increase of powder concentration. In addition, when the concentration of urea solution was 0%, 5%, 10%, 15%, and 20%, the gas inhibition effect of the prepared modified dry water powder showed a trend of increasing and then decreasing. 10% urea solution concentration had the best inhibition effect among the five above solutions. Add six different powders to inhibit 6%, 8%, 10%, 12% concentration of gas explosion, the inhibition effect from weak to strong in order: SiO₂ powder < ordinary dry water powder < calcium alginate - ordinary dry water powder < 10% urea modified dry water powder < calcium alginate-ammonium phosphate dry water powder < calcium alginate-urea modified dry water powder. Among them, calcium alginate-urea-modified dry water powder can make the gas explosion flame propagation to the pipe of the maximum extension of 40 ms, the maximum flame propagation speed reduction of 42.46%. The maximum flame temperature peak drop can reach 58.99%, and the maximum detonation pressure of 15.71%.

Again, using a 20 L spherical explosion experimental system tested the optimal amount of calcium alginate-urea modified dry water powder in 6%, 8%, 10%, and 12% gas concentration of the best amount of explosion suppression, resulting in the best amount of 0.125, 0.3, 0.5, 0.225 g / L, the overall trend of rising and then falling. When too little calcium alginate-urea modified dry water powder is added, it cannot form a practical obstacle to the reaction process at the initial stage of gas explosion reaction; while adding too much calcium alginate-urea modified dry water powder will lead to accumulation of the powder in the restricted space and increase its volume load, making the powder itself less efficient in pyrolysis. These conditions make the gas inhibition of calcium alginate-urea modified dry water powder less effective.

Finally, the gas suppression mechanism of calcium alginate-urea modified dry water powder was analyzed. It was concluded that it could reduce the content of vital free radicals such as CHOꞏ, OHꞏ, and CNꞏ in the gas explosion system when suppressing gas explosion and generate a large amount of HNOꞏ and NOꞏ to continue to consume the free radicals in the gas explosion system. By combining the above conclusions with the TG-DSC thermal process analysis of dry water powder to obtain the mechanism of explosion suppression of calcium, alginate-urea modified dry water powder contains the following four aspects: ① isolation of gas explosion reaction, reduction the oxygen concentration; ② evaporation of water molecules to absorb heat, reduce the flame temperature; ③ water vapor dilution of combustible gases, inert reaction; ④ chain reaction, reduce the concentration of critical radicals.

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