胜利褐煤低温氧化过程中微结构的转化特性研究

选用内蒙古的胜利褐煤作为研究对象,通过固定床反应装置对褐煤进行不同温度(200-300℃)下的低温氧化,利用FT-IR、Raman和XPS等方法对氧化处理后煤样的结构进行了表征,考察了不同温度下低温氧化对褐煤微结构和质量变化的影响,并利用热重分析仪研究了氧化后煤样的燃烧反应性能。结果表明,温度对低温氧化过程中胜利褐煤的质量变化率影响较大,低于220℃时,褐煤的质量变化率很小,高于220℃时,质量变化率有明显的改变。特别在220-230℃,煤样的质量变化率由5. 80%(220℃)突变为42. 55%(230℃)。FT-IR/Raman/XPS表征结果显示,220℃氧化后的煤样中有明显的苯醌类结构形成,此结构的形成使苯环骨架C=C的伸缩振动吸收峰发生红移,且Raman谱图中D峰位置偏移,D峰和G峰两峰间距增大。氧化温度低于220℃的煤样表面C-O-和C=O的含量均增加,推测煤样在220-230℃质量变化率的突变主要与苯醌类结构的氧化分解有关。

Study on the transformation characteristics of microstructure in Shengli lignite during low-temperature oxidation

A Shengli lignite from Inner Mongolia was selected as the research object, with which the low-temperature oxidation experiments were carried out at different temperatures (200-300℃) in a fixed bed reactor. The structure of coal samples after oxidation treatment was characterized by FT-IR, Raman and XPS. The effects of low-temperature oxidation at different temperatures on the microstructure and mass change of lignite were investigated and the combustion performance was determined by TGA. The results show that the temperature has a significant influence on mass change rate of Shengli lignite during low-temperature oxidation. The mass change rate of lignite is very limited when temperature is below 220℃ and it changes obviously when the temperature is higher than 220℃. Especially at 220-230℃, the mass change rate of coal samples is changed from 5.80% (220℃) to 42.55% (230℃). The FT-IR/Raman/XPS characterization results show that the analogous benzoquinone structure forms after oxidized at 220℃, and these lead to the stretching vibration absorption peak of the aromatic C=C shift to lower wavenumber. In Raman spectra, the position of the D peak shifts, and the distance between the peaks of D and G increases. The content of C-O-and C=O on the surface of coal samples increases at oxidation temperature lower than 220℃. It is speculated that the jump of mass change rate of coal samples at 220-230℃ is mainly related to the oxidative decomposition of analogous benzoquinone structure.