煤炭作为我国主要的能源，在社会经济发展中具有非常重要的地位，但煤炭在开采过程中，煤燃烧灾害频发，常造成人员伤亡、经济损失、生态破坏等重大问题，严重影响国民经济发展。基于此,众多抑制煤燃烧的手段应运而生，其中，复合抑制剂有着较单一抑制剂更多的优点，是国内外研究抑制煤燃烧的热点方向。本文选取三种变质程度不同的褐煤、气煤和无烟煤作为研究对象，以不同配比的Mg(OH)₂-NH₄H₂PO₄复合粉体作为抑制剂，主要开展以下研究：

系统研究了样品的微观表征，发现褐煤的孔隙与裂隙比较明显，最容易与氧分子接触并充分燃烧。通过TG-DSC实验，分析对比了褐煤、气煤和无烟煤的氧化行为，其特征温度点和氧化过程阶段被划分，并基于Coats-Redfern方法，分别计算了褐煤、气煤和无烟煤在150-300 ℃阶段和300-500 ℃阶段的活化能，其中在150-300 ℃阶段的活化能依次为31.58、63.39和75.92 kJ/mol；在300-500 ℃阶段的活化能依次为23.13、27.18和30.19 kJ/mol，可见褐煤的活化能最低，因此褐煤最容易燃烧。同时，分析了添加6种抑制剂的煤粉氧化过程和氧化动力学参数，得到Mg(OH)₂-NH₄H₂PO₄复合粉体对煤燃烧过程有明显抑制作用，主要表现为：随着Mg(OH)₂-NH₄H₂PO₄复合粉体中Mg(OH)₂的增加，三种煤的表观活化能均呈先增大后减小的趋势，在Mg(OH)₂-NH₄H₂PO₄复合粉体配比为1:4时达到了最大，说明1:4是Mg(OH)₂-NH₄H₂PO₄复合粉体的最佳抑制配比。

通过傅里叶红外变换光谱实验，对原煤样和添加了最佳配比抑制剂煤样的官能团分布特征进行了微观抑制特性研究。发现添加Mg(OH)₂-NH₄H₂PO₄复合粉体会降低煤中的羟基、甲基以及亚甲基等活性基团，增加较为稳定的醚键官能团。煤氧化前期，由于NH₄H₂PO₄的主要热分解吸热抑制了煤中羟基的产生，且P₂O₅能够覆盖在煤粉颗粒表面，使得热源向煤粉颗粒的热辐射或热传递受阻；煤氧化后期，由于Mg(OH)₂反应吸收了热量分解，生成的MgO和H₂O使得醚键无法继续被氧化，起到抑制作用，并且MgO为多孔层的氧化膜，具有吸附烟气的作用。另外，在煤粉中加入Mg(OH)₂-NH₄H₂PO₄复合粉体，会扰乱煤粉颗粒的均匀分布，使得单位体积内煤粉的质量浓度降低，加之抑制剂研磨较小，受热面积增大，分解速度加快，最终致使反应终止。由于低变质程度的褐煤反应活性最低，且含有最多的活性基团，Mg(OH)₂-NH₄H₂PO₄(1:4)复合粉体对褐煤的抑制效果最好，气煤次之，最后是无烟煤。

本研究揭示了Mg(OH)₂-NH₄H₂PO₄复合粉体对三种不同变质程度煤燃烧的影响，将为预防矿井火灾提供基础数据。

As the main energy source in China, coal plays a crucial role in the country's socio-economic development. However, during the process of coal mining and combustion, frequent coal combustion disasters often result in significant problems such as casualties, economic losses, and ecological damage, seriously affecting national economic development. In light of this, numerous methods to inhibit coal combustion have emerged, among which compound inhibitors have more advantages than single inhibitors and have become a hot research direction both domestically and internationally. In this article, three types of coal with different degrees of metamorphism, namely lignite coal, gas coal, and anthracite, were selected as research objects， and using Mg(OH)₂-NH₄H₂PO₄ compound powders with different ratios as inhibitors. The main research was as follows:

Microscopic characterization of the samples was systematically studied, and it was found that the pores and cracks of lignite coal were more obvious, making it easier for oxygen molecules to come into contact and fully combust. By conducting TG-DSC experiments, the oxidation behaviors of lignite coal, gas coal, and anthracite were analyzed and compared. Their characteristic temperature points and oxidation process stages were identified, and based on the Coats-Redfern method, the activation energies of the three types of coal were calculated in the temperature ranges of 150-300 ℃ and 300-500 ℃, respectively. The activation energies of lignite coal in the temperature ranges of 150-300 ℃ and 300-500 ℃ were 31.58, 63.39, 75.92 kJ/mol, and 23.13, 27.18, 30.19 kJ/mol, respectively. It can be seen that the activation energy of lignite coal was the lowest, indicating that it was the easiest to combust. Furthermore, the oxidation process and kinetic parameters of coal powder with six inhibitors were analyzed. It was found that the Mg(OH)₂-NH₄H₂PO₄ compound powder has a significant inhibitory effect on the coal combustion process. Specifically, with the increase of Mg(OH)₂ content in the compound powder, the apparent activation energies of the three types of coal first increased and then decreased. The maximum inhibition effect was achieved at a ratio of 1:4, indicating that this is the optimal ratio for the Mg(OH)₂-NH₄H₂PO₄ compound powder.

Microscopic inhibition characteristics of the functional group distribution of raw coal samples and coal samples with the optimal ratio of inhibitor were studied through Fourier transform infrared spectroscopy experiments. It was found that adding Mg(OH)₂-NH₄H₂PO₄ compound powder can decrease the active groups such as hydroxyl, methyl, and methylene in coal, and increase relatively stable ether functional groups. In the early stage of coal oxidation, the main exothermic decomposition of NH₄H₂PO₄ suppressed the production of hydroxyl groups in coal, and P₂O₅ can cover the surface of coal particles, obstructing thermal radiation or heat transfer to coal particles. In the later stage of coal oxidation, the exothermic reaction of Mg(OH)₂ absorbed heat and generates MgO and H₂O, which prevented further oxidation of ether bonds, and MgO formed a porous oxide film with adsorption of smoke gas. Additionally, adding Mg(OH)₂-NH₄H₂PO₄ compound powder to coal powder disturbed the even distribution of coal particles, resulting in a decrease in the mass concentration of coal powder per unit volume. Furthermore, due to the smaller size of the inhibitor particles, the heat transfer area increased, and the decomposition rate accelerated, ultimately leading to the termination of the reaction. Due to the low reactivity and the highest content of active groups in low-grade metamorphic lignite coal, the Mg(OH)₂-NH₄H₂PO₄(1:4) compound powder had the best inhibitory effect on lignite coal, followed by gas coal and then anthracite.

This study revealed the influence of Mg(OH)₂-NH₄H₂PO₄ compound powder on the combustion of three different degrees of metamorphic coal, and would provide fundamental data for preventing mine fires.

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