烟煤中有机硫对其低温氧化特性的影响

Effect of Organic Sulfur in Bituminous Coal on its Low Temperature Oxidation Characteristics

为考察高硫烟煤低温氧化过程中有机硫对煤氧化特性的影响,采用煤低温氧化实验系统及热重分析测试对变质程度相同、有机硫含量不同的煤自燃倾向性进行研究,并采用傅里叶红外光谱(FT-IR)分析烟煤在低温氧化过程中的有机硫官能团的变化。结果表明:煤的低温氧化进程不仅与有机硫含量相关,还与煤中有机硫的类型相关,有机硫含量低、硫醇(醚)等活性有机硫基团占比小的煤样,产生的CO、CO_(2)、CH_(4)等气体体积分数越低,释出速度越缓慢;有机硫含量越低的煤样,进入氧化增重阶段的起始温度越向高温区偏移,煤氧化自燃倾向越小;低温氧化反应中,低温下硫醇的反应活性大于噻吩;硫醇与氧气反应经历二硫醚最终生成(亚)砜,噻吩与氧气反应直接生成(亚)砜;推测低价态硫通过提供巯基自由基(·SH)、硫自由基(C-S·)以与活性氧原子结合的方式向高价态硫变迁,部分有机硫以稳定的芳香族硫的形式或硫氧化物存在于固态氧化产物中,小部分硫以SO_(2)和H_(2)S气体的形式逸出。

To study the influence of organic sulfur on the oxidation characteristics of coal during the low-temperature oxidation of high-sulfur bituminous coal,the spontaneous combustion tendency of coals with the same degree of metamorphism and different organic sulfur contents was investigated using the coal low-temperature oxidation experiment and thermogravimetric analysis,and the changes of organic sulfur functional groups of bituminous coal during the low-temperature oxidation were analyzed by Fourier transform infrared spectrum(FT-IR).The results showed that the low-temperature oxidation process of coal was not only related to the organic sulfur content but also to the type of organic sulfur in the coal.The lower the volume fraction of gases such as CO,CO_(2),and CH_(4)produced and the slower the release rate of samples with low organic sulfur content and small proportion of active organic sulfur groups such as mercaptan(thioether).The lower the organic sulfur content,the more the initial temperature of the oxidation weight gain stage shifts toward the high-temperature region,and the less the spontaneous combustion tendency of coal oxidation.The reactivity of thiols at low-temperatures is greater than that of thiophenes in the low temperature oxidation reactions.While thiol reacts with oxygen to generate(sulfoxide)sulfone through dithioether,thiophene reacts with oxygen to directly generate(sulfoxide)sulfone.It is presumed that the low-valent sulfur transitions to the high-valent sulfur by providing sulfhydryl radicals(·SH),and sulfur radicals(C-S·)in combination with active oxygen atoms.Part of the organic sulfur exists as stable aromatic sulfur or sulfur oxides in solid oxidation products,and a small fraction of sulfur escapes as SO_(2)and H_(2)S gases.