【作者】 蔡俊青；

【导师】 王一平；

【作者基本信息】 天津大学 ， 环境化工， 2008， 博士

【摘要】 在研究甲烷气氛下煤热解特性及甲烷在溶剂中溶解特性的基础上,采用长径比较大的管式反应器,对煤的高温快速液化性能进行研究,考察相关参数对液化反应的影响,并对煤快速液化机理进行初步探讨。以龙口褐煤为原料,在甲烷气氛下分别进行25、40、55及70℃.min^-1四个加热速率下的热重分析,发现在热解反应过程中甲烷和煤之间具有协同效应。根据热重数据,关联了系列不同挥发度下煤的活化能与指前因子等动力学参数。活化能和指前因子随挥发度的变化而变化,指前因子的对数与活化能之间有很好的直线关系,显示出良好的补偿效应,说明龙口褐煤热解反应由许多具有不同的动力学参数的平行反应组成。用活化能分布模型计算了活化能和指前因子的分布函数,该模型能较好的表达褐煤在甲烷气氛下的热解特性。自建了气体高压溶解度的实验装置,测定了甲烷在溶剂中的溶解度,并选择Peng-Robinson状态方程和两种不同混合规则及基团贡献法对气液平衡数据进行了拟合计算,计算结果表明Peng-Robinson状态方程和基团贡献法都能对实验物系较好拟合。在甲烷气氛下对煤的快速液化性能进行了研究,反应温度为400℃～800℃,停留时间为4s～12s,反应压力为10～15MPa。反应产物分别用正己烷、苯和四氢呋喃萃取,通过转化率及产物收率的分析,未加催化剂的情况下,反应温度为750℃,停留时间为9s时,煤液化达到最佳效果,煤总转化率为25.44%,油气收率达到21.97%,说明甲烷气氛下煤的高温快速液化是可行的。应用扫描电镜、红外光谱、热重分析仪、X射线衍射仪和元素分析等分析手段对原煤、液化残渣及液体产物的结构变化进行了表征,分别从宏观和微观探讨了煤在本工艺中液化反应的历程,考察了煤中有机元素和官能团在反应前后的变化以及液化反应对煤结构变化的影响,同时为工艺的改进和反应机理的探讨提供了一定的理论数据。更多还原

【Abstract】 On the basis of kinetic analysis of coal pyrosis in methane atmosphere and gas-liquid equilibrium analysis of methane-solvent, rapid liquefaction of Longkou lignite coal was studied in a novel laboratory scale tubular reactor. The effect of several parameters on the liquefaction reaction has been investigated, moreover, the mechanism of rapid liquefaction has also been preliminarily studied.Thermogravimetric analysis (TGA) was carried out for Longkou lignitic coal with four different heating rates of 25, 40, 55 and 70 oC.min-1. The experimental results indicated a synergistic effect during methane and coal. The kinetic parameters, activation energies (E) and pre-exponential factors (k0), of thermal pyrolysis for coal at different conversion levels were correlated from the thermogavimetric data. The conversion dependent E and k0 values were obtained. The compensation effect was clearly observed from the straight line of the plot of ln(k0) versus E. It indicated that many parallel reactions with different rate parameters occur simultaneously during the pyrolysis of coal. The distribution functions, f(E) and k0(E), were then established satisfactorily by the distributed activation energy model (DAEM).A set of experiment apparatus for determining gas solubility in liquids at high pressures was designed and established. Its reliability was confirmed with literature data. The solubility of methane in the solvent at high pressures was measured exactly and then the Peng-Robison EOS coupled with two kinds of mixing rules was adopted to calculate the GLE data under high pressure by correlation. The calculated results showed that the data of the system were well described by the Peng-Robison EOS.Liquefaction experiments were performed at a temperature ranging from 400 to 800 0C, a residence time ranging from 4.5 to 11.2 seconds and 10-15 MPa (without catalyst). Reactions were also carried out under nitrogen gas atmosphere at the same reaction conditions. The results indicated that there were synergism effects between coal and methane at the temperature over 6000C, and the temperature and residence time were the main factors influencing the coal conversion and products distribution. The oil yield reached a maximum of 21.97 (wt.% daf) at 750 0C during 9.0 seconds. The results indicated that the liquefaction process was reasonable and rapid liquefaction was feasible.Raw coal and liquefaction residue were characterized by scanning electron microscope (SEM), Fourier transformation infrared microspectroscopy (FTIR), Temperature-Programmed Thermogravimetry instrument, X-Ray Diffractometer (XRD) and Elemental Analyzer. These results have provided a scientific basis for improvement of the novel technology.更多还原