水泥窑共处置危险废物过程中重金属的分配

Distribution of heavy metals during co-processing hazardous wastes in new dry cement kilns

以废弃农药、污染土壤和废白土为研究对象,在3个新型干法水泥厂开展了水泥窑共处置的工程试验,分析了共处置对13种重金属在不同相分配情况的影响.结果表明,重金属的分配不受危险废物投加的影响,不挥发和半挥发重金属在烟气中的分配率远低于在熟料中的分配率;尾气中Hg及部分重金属的排放浓度很小甚至低于检测限;As在烟气中分配率较高,与该金属在窑内的存在形态以及As的某些化合物具有挥发性等因素有关;为控制尾气中重金属含量满足相关标准的排放限值,根据本研究和相关研究数据预测了重金属允许的最大投加量和废物中允许的重金属最大含量.

Distributions of 13 heavy metals in different phases produced by co-processing obsolete pesticides, contaminated soil and spent bleaching clay were studied on three new dry cement kilns respectively. Through analysis of the distribution ratios of heavy netals in stack emissions and cement clinkers, both ratios were steady no matter whether the hazardous waste was fed to the kiln or not. Moreover, the distribution ratios of non-volatile and semi-volatile heavy metals in stack emissions were far less than that in clinkers. The concentrations of Hg and several heavy metals in stack emissions were low or below the detection limit. In particular, the distribution ratio of As in stack emissions was high. Some As compounds would be volatile due to their chemical form in cement kilns. In order to control heavy metals concentration in stack emissions to comply with emission limitations of correlated standards, both maximum allowable feeding rates and concentrations of heavy metals during co-processing waste were determined at last.