Si/Al基质作用下NaCl高温氯化PbO的机制

High temperature chlorination of PbO by NaCl and Si/Al matrix

垃圾焚烧过程中,在灰中Si/Al基质的作用,NaCl可以将不易挥发的PbO转化为易挥发的PbCl_2,从而显著增加烟气中的Pb排放。使用管式炉加热NaCl/Si/Al基质/PbO反应物体系,通过分析升温过程Cl和Pb的释放过程,从间接氯化和直接氯化角度,探索了高温氯化规律与机制。试验发现,间接氯化时氧气中有水蒸气比无水蒸气更有利于反应,Al_2O_3比SiO_2更有利于反应,初始氯化温度通常为700~800℃,NaCl以气态形式参与反应;通过SiO_2直接氯化时,约500℃时PbO与SiO_2反应生成硅酸盐,然后与NaCl蒸气反应,初始氯化温度约650℃;通过Al_2O_3直接氯化时,700~800℃时PbO与Al_2O_3反应生成铝酸盐,然后与NaCl蒸气反应;向SiO_2中添加Al_2O_3会阻碍PbO与SiO_2的反应,氯释放特征由SiO_2基质型向Al_2O_3基质型转变,初始氯化温度升高至700~800℃。

During waste incineration,PbO(difficult to volatilize)can be chlorinated to PbCl2(easy to volatilize)by the interaction of NaCl and Si/Al in ash at high temperature.The mechanisms of this transformation were investigated by analyzing the release of chlorine and lead in the view of indirect and direct chlorination during the tube furnace incineration at rising temperature.During the indirect chlorination initialized at 700-800℃,oxygen containing water vapor was found more favorable to reaction than oxygen without water vapor,while Al2O3 was more favorable than SiO2.NaCl was found as vapor to participate indirect chlorination.During the direct chlorination through SiO2,PbO reacted with SiO2 first to form silicate at about 500℃,and then reacted with NaCl vapor produced initially at about 650℃.During the direct chlorination through Al2O3,PbO reacted with Al2O3 first to form aluminate at 700-800℃,and then reacted with NaCl.When Al2O3 was mixed with SiO2,the direct chlorination properties turned from SiO2 matrix type to Al2O3 matrix type,and the initial chlorination temperature increased from about 650℃to 700-800℃.