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典型陕北长焰煤热解行为及其动力学实验研究

     

摘要

Thermo-gravimetric analysis (TGA ) is applied to the study of the pyrolysis process and kinetic parameters of the typical Shanbei long flame coals (FLCs) .The overall reaction model and distribution activation energy model (DAEM ) are applied to analyzing the coal pyrolysis dynamics . TGA results show that the pyrolysis of typical Shanbei FLCs can be divided into three stages .The peak temperatures corresponding to maximum weight-loss peaks of active pyrolysis stage and second degassing stage are increased by increasing the heating rate ,whereas the conversion rate is decreased . Kinetic analysis shows that the overall reaction model can only get the average values of activation energy and pre-exponential factor in some temperature and the calculated results of it are lower than those of DAEM ,due to its assumption .Using DAEM ,the calculated activation energy of the Shanbei LFCs pyrolysis ranges from 32 to 446 kJ・mol-1 ,and the three samples exhibit different distribution trends .DAEM can describe the whole pyrolysis process of Huangtumiao (HTM ) coal ,the calculated activation energy varies from 181 to 425 kJ ・ mol-1 , two peaks are found in the region , the corresponding activation energies are 419 kJ ・ mol-1 and 425 kJ ・ mol-1 . However ,DAEM can describe the pyrolysis process of Fugu (FG ) and Zhangming Gou (ZMG ) coal in 10%-55% weight-loss rate ,and the calculated activation energy and the frequency factor are increased with conversion rate increasing .Therefore ,DAEM ,which can describe the nonisothermal pyrolysis process from low-temperature to high-temperature , can accurately reflect the continuous , complex and different pyrolysis process of coal .%  利用热重分析(TGA)技术研究了升温速率对典型陕北长焰煤热解行为的影响,并用总包反应模型和分布活化能模型(DAEM )对其进行了动力学分析,比较了两种模型对3种典型陕北长焰煤热解的适应性.TGA结果表明典型陕北长焰煤热解分为3个阶段,增加升温速率使活泼热分解阶段和二次脱气阶段最大失重峰对应的热解温度向高温区移动,热解转化率降低.动力学分析表明:总包反应模型由于其假设只能得到某一温度范围内活化能和指前因子的平均值,且数值较低.DAEM可得到热解活化能的分布区间32~446 kJ・mol-1,3种长焰煤热解表现出不同的活化能分布趋势.DAEM可较好描述黄土庙(HTM )煤样热解的全过程,活化能主要分布于181~425 kJ・mol-1,出现两个峰值,对应的活化能分别为419 kJ・mol-1和425 kJ・mol-1.DAEM 可描述府谷(FG)和张明沟(ZMG)煤样失重率在10%~55%的热解行为,活化能和频率因子随转化率的增加而升高.DAEM 能描述非等温热解从低温到高温的过程,真实反映不同煤样热解过程的差异性、复杂性、连续性.

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