【作者】 刘海明；

【导师】 郑楚光； 张军营；

【作者基本信息】 华中科技大学 ， 热能工程， 2004， 硕士

【摘要】 随着社会发展和人民生活水平的日益提高,环境问题越来越引起人们的重视。这其中大气污染是一个较为突出的问题。大气污染物又分为颗粒污染物和气态污染物,而气态污染物主要由SO2和NOX构成。如何有效的将SO2和NOX脱除已成为当今研究的热点问题。到目前为止,人们对煤转化过程中含氮化合物的释放规律,特别是对煤热解气化过程中HCN和NH3的生成及转化机理缺乏了解,因此,深入研究NOX前驱物的生成机理以及与煤中有机氮定量关系有着十分重要的理论意义和应用价值。本文以量子化学理论以及有机反应理论为基础,将做为化学前沿的量子化学计算应用于热能领域中NOX前驱物生成机理的研究,希望对进一步探索NOX前驱体形成的机理提供理论帮助。 在前人研究结果的基础上,首先对煤中吡啶型氮和吡咯型氮进行了合理简化。吡咯型氮和吡啶型氮在释放过程中将分别产生两类吡咯自由基和三类吡啶自由基。使用Gaussian98软件,采用密度泛函方法,对两类吡咯自由基和三类吡啶自由基进行了计算,以键的Mulliken重叠布居数为判据,研究了它们的热解过程。煤中吡啶型氮和吡咯型氮,C-N键强度较弱,在热解时会优先发生断裂,是热解的引发键;吡啶型氮最终是以HCN的形式释放出;BGA型吡咯自由基最终的热解产物为乙炔和NH3, BGB型吡咯自由基最终的热解产物为丙稀和HCN。由于吡咯型氮环所处的位置不同而产生了这两类吡咯型自由基,因此吡咯型氮以何种形式释放出还取决于周围环境的不同。通过计算建立了吡啶型氮和吡咯型氮的热解机理模型。计算了三类吡啶型氮、两类吡咯型氮环裂活化能。吡咯自由基环裂的活化能低于吡啶自由基的活化能,吡啶型氮要比吡咯型氮稳定。有一部分吡咯型氮会向吡啶型氮转化。对大同、抚顺、内蒙霍林河三种煤样进行热解实验,通过实验发现:随温度的升高,煤中的含氮官能团的分解加剧,HCN和NH3的量随之增加;在达到一定温度时,煤中的含氮官能团热解完毕或转化为稳定的构型,温度再升高将没有更多的<WP=4>HCN释放出,在高温下HCN将发生二次反应生成NH3,此后HCN的量将随温度的升高而降低,随着HCN向NH3转化的完成,NH3的量将趋于一个稳定值。更多还原

【Abstract】 With the development of our society and the improvement of living level, the issue of environment attractes more and more people’attention. Air pollution is the most serious environment problem. SO2 and NOX are the main composition in the air pollution, and how to remove them has become a focus in recent years. Because the limite of analysis method, at present there still has some unknown about the mechanism of nitrogen release, especially the form mechanism of HCN and NH3. It is significant to build the relationship of NOX procursors and organic nitrogen in coal.Based on Quantum Chemistry theory and Organic Chemistry theory, formation mechanism of NOX procursors during coal combustion was studied in this paper by Quantum Chemistry Calculation.The model of pyridinic nitrogen and pyrrolic nitrogen was predigested rationally based on former researches at first. Pyrrolic nitrogen may release two types of pyrrolic free radicals and pyridinic nitrogen may release three types of pyridinic free radicals. The pyrolysis mechanisms of two types of pyrrolic free radicals and three types of pyridinic free radicals have been investigated using Density Functional Theory (DFT) UB3LYP/6-31G(d) by Gaussian 98 in this paper. Comparing the Bond Mulliken Population, we found C-N bond was the initial bond for pyrolysis. Pyridinic nitrogen was released in the form of HCN. BGA Pyrrolic free radical release C2H2 and NH3, but BGB Pyrrolic free radical release propene and HCN.Then the release modeles of pyridinic nitrogen and pyrrolic nitrogen were built. Activation energy of two types of two types of pyrrolic free radicals and three types of pyridinic free radicals was calculated. The active energy of pyrrolic free radicals is smaller than the pyridinic free radicals’s , so pyridinic free radicals is more stable than pyrrolic free radicals. Pyrrolic free radicals can convert to pyridinic free radicals during <WP=6>pyrolysis.Pyrolysis experiences were carried out using Datong、Fushun and Neimeng coal. When heating temperature growing, nitrogen groupes in coal decompose deeply and the quantity of HCN and NH3 grows. At certain temperature the quantity reach peak. After that, when temperature growing, HCN will begin to convert to NH3 and the quantity of HCN reduce, but the quantity of NH3 is stable.更多还原