二次氧化煤自燃过程关键官能团的转变规律
Transformation law of key functional groups in the process of coal secondary oxidation
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摘要: 为掌握二次氧化过程中关键官能团转变对煤自燃的影响，分别采集新疆艾维尔沟气肥煤和 新疆硫磺沟长焰煤，在不同预氧化温度(100，200，300，400 和 500 °C)下对 2 种煤样进行处理，氧化 时间为 40 min，并以原煤作为对照组，开展二次氧化煤样热重和原位漫反射红外光谱试验研究。 通 过热重实验分析煤样热失重过程(30~800 °C)，基于质量变化速率为 0 的 3 个特征温度(T2，T5， T7)，将煤样氧化过程划分为 3 个阶段。 通过原位漫反射红外光谱仪分析了煤样升温过程中(30~ 300 °C)关键官能团的变化情况。 结果表明:在煤氧反应中羟基的主要反应温度范围是 Tc ~T1(Tc 为常温，T1为临界温度)，氧化反应后期羟基含量基本不变。 其中羟基含量增加量最大的煤样分别 为 L500( 预氧化温度为 500 °C 的硫磺沟煤样) 和 A400( 预氧化温度为 400 °C 的艾维尔沟煤样) 。 脂肪 烃、芳香烃和含氧官能团主要反应阶段为 T2 ~ Tz( T2 为干裂温度，Tz 为终止温度) ，当温度小于 T2 时， 这几种官能团参与反应程度较小。 经过不同的预氧化温度处理后，煤样关键官能团含量变化差异 明显。 过高的预氧化温度会使煤中脂肪烃、芳香烃和含氧官能团含量减少。 对比不同预氧化温度 下煤样的官能团变化，发现预氧化温度为 200 °C 时，煤分子中芳香烃、含氧官能团和脂肪烃都达到峰值。Abstract: To grasp the influence of changes in the content of key functional groups on the coal spontaneous combus⁃ tion during the secondary oxidation process，the samples of gas fat coal and long flame coal were collected from Ewirgol and Liuhuanggou in Xinjiang，China. The two coal samples were treated at different pre⁃oxidation temperatures(100， 200，300，400 and 500 °C)，and the oxidation time was 40 min. The secondary oxidized coal samples were conducted by the experimental tests from the thermogravimetric and in⁃situ diffuse reflectance infrared spectroscopy. The raw coal used as a control group. Thermal gravimetric experiment was used to analyze the mass change characteristics of the coal during the thermal mass loss process(30-800 °C). Based on the three characteristic temperature points(T2， T5，T7) where the rate of mass change was 0，the coal sample oxidation process was divided into three stages. The changes of key functional groups during the heating process coal samples were analyzed by in⁃situ infrared spectrometer. The results show that the main reaction temperature range of hydroxyl is Tc-T1(Tc is room temperature，and T1 is critical temperature)，and there is almost no change in the late stage of the reaction in the coal⁃oxygen reaction. Among the different pre⁃oxidized coal samples of two coal samples with the largest increase in hydroxyl content is L500 and A400(L500 is the Liuhuanggou coal sample with the pre⁃oxidation at 500 °C，and A400 is the Ewirgol coal sample with the pre⁃oxidation at 400 °C). The main reaction stage of aliphatic hydrocarbons，aromatic hydrocarbons and oxy⁃ gen⁃containing functional groups is T2-Tz(T2 is the cracking temperature，and Tz is final temperature). When the tem⁃ perature is lower than T2 ，these functional groups are less involved in the reaction. The content of key functional groups of coal samples changes significantly after being treated at different pre⁃oxidation temperatures. Excessive high pre⁃oxi⁃ dation temperature will reduce the content of aliphatic hydrocarbons，aromatic hydrocarbons and oxygen⁃containing functional groups in coal. When the pre⁃oxidation temperature is 200 °C，comparing the changes in functional groups of coal samples with different pre⁃oxidation temperatures，the aromatic hydrocarbons，oxygen⁃containing functional groups and aliphatic hydrocarbons which from coal molecules all reach their peaks.
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