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Effects of cyclic freezing and thawing of coals at their behavior at low- and high-temperature oxidation

机译：煤晶冻结和煤的影响在低温氧化下的行为

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Effects of cyclic freezing and thawing (FTC) on coals properties, such as technological, structural and sorption, has recently attracted wide interest. This article is dedicated to studying of FTC on behavior of coals of different types at low- and high-temperature oxidation. Scanning electron microscopy revealed that coals particles morphology after FTC alters similarly for coals of different types. These changes relate to formation of partially oxidized coal matter films. Thermogravimetric studies allowed to observe that, after FTC, the combustion interval for bituminous coals was widened by additional high-temperature stage (750-900 degrees C). The rate of combustion and its activation energy were decreased significantly. As for lignite, FTC does not lead to any pronounced alterations of the combustion pattern. Isothermal calorimetry (at 40 degrees C) allowed revealing that FTC at the lignite led to increase of heat generation during low-temperature oxidation. But no significant changes were observed for bituminous coals. The obtained results on changes of coals structure and properties after FTC are similar to given in the literature regarding the behavior of coals after mild oxidation. This allows to presume that FTC of the studied coals led to their mild oxidation. The interrelation was found between the rate of deactivation of the active sites of the first type and the combustion rate constant. It was shown that this relation determines the decrease of the combustion rate and its activation energy for coals after FTC. Active sites of the second type presumably determine the intensity of the processes of coals low temperature oxidation.
机译：循环冷冻和解冻（FTC）对煤层的影响，例如技术，结构和吸附，最近吸引了广泛的兴趣。本文致力于在低温和高温氧化下研究不同类型煤的行为的FTC。扫描电子显微镜显示，FTC后的煤颗粒形态类似于不同类型的煤。这些变化涉及部分氧化煤物膜的形成。热升级研究允许观察到，在FTC之后，通过额外的高温阶段（750-900℃）来加宽沥青煤的燃烧间隔。燃烧速率及其活化能量显着下降。至于褐煤，FTC不会导致任何明显的燃烧模式改变。等温热量测定法（40摄氏度）允许揭示褐煤处的FTC导致低温氧化期间发热的增加。但对于沥青煤没有观察到显着的变化。在FTC后，在FTC后的煤结构和性能变化的结果与在轻度氧化后的煤的行为中的文献中相似。这允许预设所研究的煤的FTC导致它们温和的氧化。在第一类型的活性位点和燃烧速率常数的停用速率之间发现相互关联。结果表明，该关系决定了FTC后煤的燃烧速率及其活化能量的降低。第二种类型的活性位点可能会确定煤的低温氧化方法的强度。

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