低瓦斯气氛下煤氧化热效应和关键基团演变特性

Thermal effect of coal oxidation and evolution properties of key functional groups of coal oxidation at low gas atmospheres

为了研究瓦斯气氛下煤氧化特性,利用C80微量热仪和X射线电子能谱仪研究了不同瓦斯气氛下煤的放热特性和主要官能团变化规律.采用灰色关联分析与量子化学相结合的方法,确定了对煤低温氧化放热贡献最大的官能团及其反应特征,认为煤分子间脂肪烃的断裂和羰基向羧基的转化过程是煤低温氧化放热的主要来源,而瓦斯的存在对该过程具有抑制作用;低浓度瓦斯能够降低煤样的低温氧化进程,从而在一定程度上抑制煤自燃的发展.研究结果表明:随着瓦斯体积分数的升高,煤的吸热量降幅小于10 J,而放热量的降幅则接近300 J.相较于空气气氛,当瓦斯体积分数为2%时,氧化后煤中C—C&C—H和COO—分别下降2.01%和0.28%,而C—O—和C=0分别增加0.2%和2.09%;当瓦斯体积分数为4%时,C—C&C—H和COO—分别下降3.52%和0.3%,而C—O—和C=0分别增加0.78%和3.04%.

In order to study the spontaneous combustion characteristics of coal in methane atmospheres,a C80 microcalorimeter and an X-ray electron spectrometer were used to explore the heat release characteristics and the change rule of main functional groups of coal in different CH4 atmosphere.Based on the grey correlation analysis and quantum chemistry,the functional groups that contribute the most to the exothermic process of coal oxidation at low temperatures and their reaction characteristics were determined.It is considered that the main source of the exothermic process of coal oxidation at low temperatures is the fracture of aliphatic hydrocarbon between coal molecules and the conversion of the carbonyl group to the carboxyl group,and the existence of gas can inhibit this process.The lower concentration gas can retard the low-temperature oxidation process of coal samples,thus inhibiting the development of coal spontaneous combustion to a certain extent.The results show that with the increase of gas concentration,the decrease of heat absorption of coal is less than 10 J,while the decrease of heat release is close to 300 J.Compared with air atmosphere,at 2%gas volume fraction,C—C&C—H and COO—in oxidized coal decrease by 2.01%and 0.28%,respectively,while C=0 increase by 0.2%and 2.09%,respectively.At 4%gas volume fraction,C—C&C—H and COO—decrease by 3.52%and 0.3%,respectively,while C—O—and C=0 increase by 0.78%and 3.04%,respectively.