燃煤烟气中汞与溴化氢的反应机理研究

Research on Reaction Mechanism of Mercury and HBr in Coal Combustion Flue Gas

应用量子化学密度泛函理论方法,分别采用不同的基组计算汞-溴体系中的分子几何构型、振动频率和反应焓变,并与NIST数据库及相关文献数据进行了比较,最后得出采用B3PW91/Stevens组合计算得到的结果与实验值最为符合。在此基础上,研究了煤燃烧过程中汞与溴化氢的反应机理,优化得到反应过程中各驻点(反应物、过渡态和产物)的几何构型,计算了活化能并校正了零点能。利用经典过渡态理论,计算了反应的指前因子A及不同温度下的反应速率常数。计算得到的相关参数为深入研究煤燃烧过程中汞的排放控制及动力学模型提供了可靠的参考依据。

The geometry optimizations of molecular, vibration frequencies and reaction enthalpies for mercury/ bromine system were calculated by quantum chemistry density functional theory methods on different basis sets. The calculating results were compared with the NIST data and related literature data. The results show that B3PW91/Stevens is the most consistent with experimental values. Also, the reaction mechanisms of mercury and HBr in coal combustion flue gas were investigated. All geometries of the stationary points in the reaction process（reactant, transition state and product）were optimized. The activation energy was calculated and all energies corresponding to the optimized structures were corrected for zero-point energy. The pre-exponential factor and reaction rate constant at different temperatures were calculated with the classical transition state theory. The obtained kinetics parameters provide a base for investigating kinetic mechanism of mercury in coal combustion flue gas and its emission control.