瓦斯对煤低温氧化过程微观结构及热反应性的影响研究

Effect of gas on microstructure and thermal reactivity of coal during low temperature oxidation

为研究瓦斯气氛下煤低温氧化过程中微观理化特性及宏观煤氧复合热效应,选择不同变质煤及二次氧化煤样作为研究对象,利用傅里叶红外光谱仪和C80微量量热仪,研究在不同瓦斯气氛下煤低温氧化过程物理化学结构特性、动力学参数、热效应等变化特征。通过分析不同瓦斯气氛下煤自燃氧化过程中微观结构以及宏观放热特性,明确瓦斯对煤氧化特性的最终影响。结果表明:瓦斯通过抑制煤低温氧化过程中关键活性基团相对含量,延缓煤低温氧化进程,4%瓦斯具有最为明显的抑制效果,其对4种活性基团的抑制程度为:含氧官能团(66.5%)>芳香烃(47.0%)>脂肪烃(29.7%)>羟基(24.7%)。在快速放热阶段,由于煤对瓦斯分子的吸附能力较大,瓦斯气体占据煤分子中的吸附位点,阻碍了煤氧复合反应进程,导致放热效应受到瓦斯抑制;同时瓦斯含量显著影响煤氧复合进程活化能的大小。对于较高变质程度的不黏煤、瘦煤和无烟煤,瓦斯对其低温氧化反应的抑制作用较为显著;对较低变质程度的长焰煤影响较小。对于二次氧化煤样,瓦斯对于煤样的抑制作用随着瓦斯含量的增加而增强,而瓦斯对一次氧化煤样的影响随变质程度降低而减弱,且瓦斯含量2%时的抑制程度强于4%。研究结果对防治瓦斯与煤自燃耦合致灾事故的理论研究有重要意义。

In order to investigate the microscopic physicochemical properties and macroscopic coal-oxygen complex thermal effects in the low-temperature oxidation of coal under gas atmosphere, different metamorphic coal and secondary oxidized coal samples as research objects were selected in this paper. Fourier infrared spectrometer and C80 microcalorimeter were employed to study the changes of physicochemical structural properties, kinetic parameters and thermal effects in the low-temperature oxidation of coal under different gas atmospheres. By analysing the microstructure and macroscopic exothermic characteristics of different gas content during coal spontaneous oxidation, the ultimate influence of gas on the oxidation characteristics of coal was clarified. The results show that gas delays the low-temperature oxidation process of coal by inhibiting the relative content of key active groups in the low-temperature oxidation process of coal. 4%gas has the most obvious inhibitory effect. The degree of inhibition on the four active groups is: oxygen-containing functional groups(66.5%) > Aromatic hydrocarbons(47.0%) > Aliphatic hydrocarbons(29.7%) > Hydroxyl(24.7%). In the rapid exothermic stage, due to the large adsorption capacity of coal to gas molecules, gas occupies the adsorption sites in coal molecules, which hinders the process of coal-oxygen recombination reaction, resulting in the exothermic effect being suppressed by gas;at the same time, gas content significantly affects coal oxygen. The amount of activation energy required for the recombination process. For high metamorphic non-stick coal, lean coal and anthracite, gas has a more significant inhibitory effect on its low temperature oxidation reaction;it has less effect on low metamorphic long flame coal. For secondary oxidized coal samples, the inhibitory effect of gas on coal samples increases with the increase of gas content, while the effect of gas on primary oxidized coal samples decreases as the degree of metamorphism decreases, and the degree of inhibition when the gas content is 2% is stronger than 4%. The results of the work have great significance to the theoretical study of the prevention and control of the coupling of gas and coal spontaneous combustion causing accidents.