褐煤半焦燃烧特性的热重试验研究

Thermogravimetric study on combustion characteristics of lignite semicoke

选用管式炉对褐煤进行500～650℃的加热处理,运用热分析法研究制得半焦的燃烧特性,考察热解温度和停留时间对半焦的产率、组成、发热量和燃烧性能的影响,同时,利用热重试验并采用Coats-Redfern积分法对样品的燃烧动力学特性进行了研究.结果表明:停留时间对半焦的产率、组成、发热量和燃烧性能的影响并不明显,而热解温度对半焦性能的影响较大;热解后,半焦的煤阶有所提高,随着热解温度的升高,半焦挥发分含量降低,固定碳和灰分含量增加,C/O升高,发热量增加,半焦产率降低,着火及燃烧性能变差,半焦更趋向于高阶煤特征;褐煤半焦的燃烧反应可用反应级数(n=7/6)模型来描述,半焦的活化能随着热解最终温度和停留时间的增加而升高,反应活性随之降低,活化能在78.1～116.4 kJ/mol范围内变化.

The lignite was pyrolyzed in a tube furnace at medium-low temperature between 500℃and 650℃,then the combustion characteristics of the lignite semicoke was analyzed by thermal analysis method.The effects of pyrolysis temperature and holding time on yield,composition and calorific value of the semicoke were investigated.Moreover,the combustion dynamics of the coal samples was studied by the Coats-Redfern integration method,on the basis of the thermogravimetric experiment.The results show that the holding time has no obvious influence on yield,composition,calorific value and combustion characteristics of the lignite semicoke,while the pyrolysis temperature has a great one.After paralysis,the coal rank of the semicoke increased.With an increase in pyrolysis temperature,the C/O ratio,fixed carbon content,ash content and calorific value of semicoke increase,while the yield and volatile content of the semicoke decrease.High temperature makes the combustion characteristics of semicoke be worse and the coal rank tend to be higher.The results indicate that the reaction order model(n=7/6)can be adopted to describe the lignite semicoke combustion.With the increase of pyrolysis temperature and holding time,the reaction reactivity of semicoke decreases while activation energy increases,the activation energy changes within the range from 78.1kJ/mol to 116.4kJ/mol.