水泥窑协同处置生活垃圾焚烧飞灰过程中Pb和Zn的迁移转化特性

Migration and transformation of Pb and Zn during co-processing of municipal solid waste incineration fly ash by cement kiln

对某水泥窑协同处置生活垃圾焚烧飞灰系统进行采样分析,研究飞灰中的Pb、Zn在水洗脱氯预处理及水泥窑协同处置过程中的迁移转化特性。结果表明,水洗预处理过程中,飞灰中0.15%Pb和0.015%Zn进入结晶盐,94.05%的Pb和93.17%的Zn留存在水洗灰中,且赋存形态基本不变。水泥窑协同处置飞灰过程中,进入窑内的Pb和Zn少部分在窑内和预热器系统形成内循环,93.84%Pb和81.38%的Zn进入水泥熟料,0.0027%的Pb进入窑尾烟气,0.0014%的Pb和0.0011%的Zn进入窑灰。热力学平衡计算表明,水泥熟料中Pb的主要存在形态是PbO、PbSiO_(3),Zn的主要存在形态是ZnO、ZnFe_(2)O_(4)、ZnAl_(2)O_(4)。窑尾烟气排放指标和水泥熟料性能指标均满足相关规范要求,这说明Pb和Zn在水泥窑中实现了良好的固化,环境风险可接受。本研究结果可为水泥窑协同处置飞灰工艺系统设计优化提供参考。

This work investigated the Pb and Zn migration and transformation of municipal solid waste incineration(MSWI)fly ash during the combination of dechlorination by water washing with cement kiln incineration.The samples from the combination of dechlorination by water washing with cement kiln incineration was analyzed according to HJ 781-2016 and HJ 657-2013.Results showed that 0.15%Pb and 0.015%Zn entered crystalline salt and 94.05%Pb and 93.17%Zn remained in the washed fly ash without changing their state after water washing.Combining water washing with cement kiln incineration,a small part of Pb and Zn entered the kiln formed an internal circulation in the kiln and preheater system.93.84%Pb and 81.38%Zn entered cement clinker.0.0027%Pb released in the flue gas,and 0.0014%Pb and 0.0011%Zn remained into the kiln dust.Pb mainly existed in the forms of PbO and PbSiO_(3),and Zn mainly existed in the forms of ZnO,ZnFe_(2)O_(4)and ZnAl_(2)O_(4)according to thermodynamic equilibrium calculation.The flue gas emission Index and the performance Index of cement clinker could fulfill the requirements of relevant technical specifications and standards,indicating that Pb and Zn could be well fixed in clinker by cement kiln incineration and the environmental risk could be well controlled.This work could provide some referential values for the optimization design of co-processing of fly ash by cement kiln.