富氧燃烧环境下CO对煤焦异相还原NO的量子化学研究

Quantum chemistry research on NO heterogeneous reduction by char with the participation of CO under oxy-fuel combustion atmosphere

为掌握煤焦对NO异相还原反应规律,揭示氧燃烧方式下NOx排放量少的微观机理基于密度泛函理论和过渡态原理,使用DMOL3模块在分子水平上研究了在富氧燃烧条件下CO参与煤焦还原NO的反应过程,并从能量和热力学角度分析CO对煤焦还原NO是否具有促进作用。对每一步基元反应寻找了过渡态,计算得到了每一步反应的焓变和活化能。对每个反应从吉布斯自由能角度分析和能量对比发现,zigzag型煤焦模型相对于armchair型煤焦模型具有更强的吸附能力,CO参与zigzag型煤焦异相还原NO过程为所设计4条反应路径中最容易发生的反应,CO对于zigzag型煤焦还原NO具有促进作用,而对armchair型煤焦则没有促进作用。

In order to master the rules of heterogeneous reduction between NO and char edge models,and to reveal the microcosmic mechanisms of less NOxemissions under the oxy-fuel combustion atmosphere. A molecular modeling study based on transition state theory and density functional theory was performed to investigate the elemental reactions of NO heterogeneous reduction by char with the participation of CO under the Oxy-fuel combustion atmosphere. The effect of CO in NO heterogeneous reduction by char was studied from the point of energy and thermodynamics. The transition states of every elementary reaction were found. The enthalpy and activation energy of every step were also calculated.The results show that the zigzag configuration char has stronger adsorption ability comparing to the armchair configuration char. Moreover the process of the reaction of NO heterogeneous reduction by zigzag configuration char with the participation of CO needs least energy to react in the four pathways designed in the paper by the contrast of energy and the Gibbs free energy. It concludes that CO promotes the NO heterogeneous reduction by zigzag configuration char and does not promote the NO heterogeneous reduction by armchair configuration char.