Qiao Ling, Mu Xiaogang, Deng Cunbao, Wang Xuefeng, Wang Yansheng
College of Safety and Emergency Management Engineering, Taiyuan University of Technology, Taiyuan, Shanxi 030024, China.
ACS Omega. 2023 Apr 7;8(15):13680-13689. doi: 10.1021/acsomega.2c07741. eCollection 2023 Apr 18.
In order to study the effect of inherent metals in coal on spontaneous combustion, Hongmiao lignite and Hongqingliang long-flame coal were demineralized by hydrochloric acid, the raw coal and demineralized coal were characterized by Fourier transform infrared spectrometry, X-ray diffraction, and synchronous thermal analysis experiments, and the corresponding ash content was detected by inductively coupled plasma mass spectrometry. The results show that the effect of demineralization on the volatile matter of low-rank coal is small, and the change of crystallite structure is not significant. The removed parts are mainly water-soluble salts and soluble minerals, such as carbonates and metal ions, that are not tightly bound to the organic matter of coal structure. The removed metal elements are mainly alkali metals Na and K, alkaline earth metals Ca, Mg, Sr, and Ba, and transition metals Fe, Mn, Ti, and so forth. The temperatures corresponding to the end of weight loss, ignition, and maximum weight loss rates were elevated on the thermogravimetric curves of the demineralized coal samples. The heat absorbed by evaporation of water in coal and the heat released by oxidation and combustion of coal are decreased to different degrees, indicating that the spontaneous combustion tendency of coal after demineralization is reduced, and alkali metal, alkaline earth metals, and transition metals in coal have a catalytic effect on spontaneous combustion of coal. After adding the metal chelating agent ethylenediaminetetraacetic acid (EDTA), the apparent activation energy decreased by 33.08 and 2.42%, respectively. EDTA and the alkali metal, alkaline earth metal, or transition-metal ions formed a stable chelate in coal. The catalytic activity of metals is weakened or even lost, thereby inhibiting spontaneous combustion of coal, and verifying the catalytic effect of internal metals in coal on the spontaneous combustion of coal.
为研究煤中固有金属对自燃的影响，采用盐酸对红庙褐煤和红庆梁长焰煤进行脱矿处理，通过傅里叶变换红外光谱、X射线衍射和同步热分析实验对原煤和脱矿煤进行表征，并用电感耦合等离子体质谱检测相应的灰分含量。结果表明，脱矿对低阶煤挥发分的影响较小，微晶结构变化不显著。去除的部分主要是水溶性盐和可溶性矿物，如碳酸盐和金属离子，它们与煤结构中的有机质结合不紧密。去除的金属元素主要有碱金属Na和K、碱土金属Ca、Mg、Sr和Ba以及过渡金属Fe、Mn、Ti等。脱矿煤样热重曲线上失重结束、着火和最大失重速率对应的温度升高。煤中水分蒸发吸收的热量以及煤氧化燃烧释放的热量均有不同程度降低，表明脱矿后煤的自燃倾向降低，煤中的碱金属及碱土金属、过渡金属对煤的自燃有催化作用。添加金属螯合剂乙二胺四乙酸（EDTA）后，表观活化能分别降低了33.08%和2.42%。EDTA与煤中的碱金属、碱土金属或过渡金属离子形成稳定的螯合物，金属的催化活性减弱甚至丧失，从而抑制了煤的自燃，验证了煤中内在金属对煤自燃的催化作用。
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