溴水脱硫对煤自燃特征温度及活性基团的影响

Influence of Bromine Water Desulfurization on Characteristic Temperature and Active Groups of Coal

以山西柳湾和两渡的炼焦精煤为研究对象,利用热重分析(TG-DTG)、X射线光电子能谱(XPS)和红外光谱(FTIR)等测试技术,研究了室温环境下溴水脱硫对煤自燃特征温度与煤活性基团的影响。结果表明:随着脱硫次数增加,煤进入氧化增重阶段的起始温度向高温区偏移,煤进入快速燃烧阶段与达到最大失重速率的温度点均向低温区偏移,即煤的氧化自燃进程加快。煤的发热量呈下降趋势,但最多仅降低原煤发热量的3.4%。煤表面C元素、N元素和S元素含量随着脱硫次数的增加而规律性地减少,而O元素含量呈增加趋势,煤中硫醇、硫醚、噻吩、芳碳、碳氢键碳与质子化吡啶等官能团相对含量逐渐降低,砜、亚砜、羧基、羰基、吡啶、吡咯与氮氧化物等含氧官能团相对含量逐渐增加,说明脱硫后煤中各元素以更高的价态存在,溴水脱硫是一个氧化过程。IR光谱显示芳香族官能团和脂肪烃官能团中的C—H键伸缩振动锋均变弱,含氧官能团中的C=O双键和酚羟基中的C—O—H键伸缩振动峰均变强,说明煤中C—H键含量减少,C=O双键和C—O—H键含量增大,这与TG-DTG和XPS的分析结果相一致,说明脱硫后煤中的C元素、S元素和N等元素被氧化,煤的氧化程度变高。

Taking the cooking coal of Liuwan and Liangdu in Shanxi as the research object,the effects of bromine water desulfurization process on the characteristic temperature of the spontaneous combustion and the active groups of coal at the room temperature were studied by thermogravimetry analysis(TG-DTG),X-ray photoelectron spectroscopy(XPS)and infrared spectroscopy(FTIR).The results show that with the increasing time of the desulfurization,the initial temperature of coal enters the oxidation and weight gain stage shifts toward the high temperature region,and the temperature at which coal enters the rapid combustion stage as well as the temperature at which the maximum weight loss rate is reached shifts toward the low temperature region.That is,the oxidation and spontaneous combustion process of coal is accelerated.The calorific value of coal decreases slightly by 3.4%of the calorific value of raw coal at most.The elemental content of C,N and S on the coal surface decreases regularly with the increasing time of the desulfurization,the elemental content of O intends to increase,the relative content of the functional groups such as mercapan,thioether,thiophene,aromatic carbon,hydrocarbon bonded carbon and protonated pyridine in coal decrease gradually,and the relative contents of the oxygen-containing functional groups such as sulfone,sulfoxide,carboxyl,carbonyl,pyridine,pyrrole and nitrogen oxide increase gradually.It shows that the elements in the coal existed in higher valence state after the desulfurization and bromine water desulfurization is an oxidation process.The IR spectra results show that stretching vibration fronts of the C—H bond in the aromatic functional groups and aliphatic hydrocarbon functional groups become weaker,and stretching vibration peaks of the C=O double bonds in the oxygenated functional groups and the C—O—H bond in the phenolic hydroxyl groups become stronger.It shows that content of the C—H bond in coal decreases and content of the C=O double bonds and C—O—H bond increases.These results are consistent with the analysis results of TG-DTG and XPS,indicating that the C,S and N elements in the coal are oxidized and the coal is oxidized to a higher degree after the desulfurization.