超细煤粉热解及燃烧过程中间体生成机理耦合反应过程调控

Nitrogen oxide (NOX) emission from superfine pulverized coal combustion is known to be a complicated physical and chemical reaction process, which has been attracted considerable attention. In order to reduce NOX emission, it is meaningful to explore the formation mechanism and reaction path of nitrogen-containing intermediates during pyrolysis and combustion. Firstly, part parameters, such as pore structures, crystal unit cell parameter and mineral distribution, should be characterized by several line stations in Shanghai Synchrotron Radiation Facility for perfecting the macromolecular structure model of pulverized coal with superfine functional groups. Secondly, Hefei tunable synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) will be applied to quantitatively characterize the types and contents of nitrogen-containing transient intermediates and active free radicals under different conditions. Furthermore, based on the macromolecular model of superfine pulverized coal, the formation of transient intermediate and active free radical is simulated by quantum chemical calculation, and the reaction path and the related transition states can be obtained. Meantime, the heterogeneous reduction mechanism between intermediates and free radicals and coal char is also proposed under different conditions. The control strategies of intermediates and active free radicals are put forward for the purpose of pollutant emission reduction, and the effects of these control strategies will be verified by two- stage high temperature experiment system.

超细煤粉燃烧过程氮氧化物排放是一个复杂的物理化学耦合反应过程，研究其热解及燃烧过程相应含氮中间体的生成机理及反应路径对于控制污染物的排放有重要的指导意义。本研究旨在通过上海光源相关线站精细化表征超细煤粉孔隙、晶胞结构、矿物质分布等相关参数，完善前期构建的具有超细特征官能团的煤粉大分子结构模型；其次，利用合肥同步辐射光电离质谱耦合分子束取样技术线站，定量表征不同外部条件下含氮瞬态中间体以及活泼自由基的含量及种类；再者通过量子力学计算软件，以完善后的具有超细特征的煤粉结构大分子模型为反应物，模拟瞬态中间体及活泼自由基生成过程，寻找其反应路径和相关过渡态等各项参数；而后，再次以瞬态中间体及自由基为反应产物，以煤焦作为反应载体，研究不同参变量条件下其异相还原反应机理，以降低污染物排放为目的，提出相应的中间体及活性自由基调控策略并通过两段式高温试验台对调控策略效果进行验证。

研究超细煤粉热解及燃烧过程中间体及活泼自由基生成机理以及转化路径，可以更加明晰煤粉受热转化分子机理，对于控制污染物的排放有重要的指导意义。本项目首先通过上海光源相关线站精细化表征超细煤粉孔隙、晶胞结构、矿物质分布等相关参数，研究发现随煤粉粒径的减小，孔隙、中孔及微孔的比表面积和孔体积、重金属矿物质含量、矿物质的解离程度、不稳定含氮官能团、芳构化程度等相关参数均发生相应变化，揭示了粉碎过程中煤粉物理特性变化与化学特性变化的内在关联耦合机制。采用多种不同尺度的热转化装置研究了超细煤粉在受热转化过程中理化特性的变化，揭示了气相产物中CH4、NH3，HCN，CO和轻质烃的释放规律，并验证了均相还原和异相还原反应之间存在一定的协同促进机制，为后续模型的改进和机理的研究奠定了基础。.利用量子化学模拟仿真手段，深入研究超细煤粉热解及燃烧中间过程反应机理及路径。根据实验得出的结果，在传统zigzag模型的基础上建立了更符合实际的含Fe煤焦模型，解决了煤焦气化反应中模拟理论活化能大于实验结果这一问题。借助改进的煤焦模型，研究模拟了HCN与NO的反应过程，证明了HCN及其氧化对NO异相还原的促进作用，充分探讨了不同吸附机理对后续氮迁移路径的影响。根据多相催化机理，模拟研究了NH3对NO异相还原反应的影响，证明了Eley-Rideal机理在NO还原反应中的主导地位以及O2的作用，为中间体生成过程调控策略提供了理论依据。本项目深化和丰富了超细煤粉热解及燃烧反应机理，为降低污染物排放、实现高效清洁利用奠定基础。