褐煤直接热解特性及动力学行为的热分析研究

Thermal analysis on in-situ pyrolysis and kinetics characteristics of lignite

提出了一种不经预干燥的褐煤直接热解工艺,将褐煤的干燥与热解气化集成于同一个反应器中,利用自身干燥产生的水蒸气作为气化剂,提高其转化效率。采用热质量分析仪测定了海拉尔褐煤的热解特性,分析了其直接热解的可行性;考察了升温速率和含水率对直接热解行为的影响;通过动力学参数对直接热解行为进行定量分析。结果表明：海拉尔褐煤的直接热解可分为初始干燥阶段、干燥-热解阶段（活化能小于5 kJ/mol）、主要热解阶段（活化能为10~24 kJ/mol）和缩聚反应阶段（活化能为65~85 kJ/mol）;提高升温速率促进了水分和挥发分的协同反应、挥发分析出和缩聚反应降低了活化能,固定碳剩余质量分数由23.34%减小至19.66%;在升温速率100℃/min条件下,随着试样含水率的增加,水分与固体的反应加强,活化能降低,热解固体干基产率由61.62%降低至59.23%,说明褐煤中水分对其热解有促进作用。

An in-situ pyrolysis technique by integrated drying and pyrolysis in one reactor for lignite with high moisture content was proposed. The in-situ steam evaporated from the lignite was utilized as a gasification agent to improve the conversion efficiency. In-situ pyrolysis characteristic of Hailer lignite was investigated by a thermogravimetric analyzer. The feasibility of in-situ pyrolysis,the effects of moisture content and heating rate were discussed,and quantitative analysis was carried out according to kinetics parameters. Results demonstrated that there were 4 sections in the direct pyrolysis,called the initial drying,drying-pyrolysis（ activation energy 5 kJ / mol）,main pyrolysis（ activation energy between 10-24 kJ / mol）,and polycondensation stage（ activation energy between 65-85 kJ / mol）. The fast-heating condition postponed the desorption of water,which favored the copyrolysis among the in-situ moisture, volatiles and char. The fixed carbon yield reduced from 23. 34% to 19. 66%. The increase of moisture content reduced the activation energy,while interaction between the water and the solid was strengthened. The yield of solid（ on a dry basis） decreased from 61. 62% to 59. 23%,thus it proved that the moisture in the lignite promoted the pyrolysis reaction.