Abstract: During oily sludge pyrolysis, the heavy metals contained in oily sludge may migrate to pyrolysis gas, pyrolysis liquid, or remain in the pyrolysis residue. In order to explore the migration and transformation behavior of heavy metals during oily sludge pyrolysis, the effects of pyrolysis temperature and residence time on the distribution of heavy metals in the solid-gas-liquid phase products and their morphological distribution in the pyrolysis residue were mainly investigated. In addition, the leaching characteristics of heavy metals in the pyrolysis residue were analyzed, and their ecological risks were assessed. The modified BCR three-stage sequential extraction procedure and risk assessment index method were adopted to conduct morphological analysis and risk assessment on heavy metals in the pyrolysis residue. Later, the pyrolysis residue was analyzed by means of elemental analysis, X-ray fluorescence spectroscopy, and Fourier infrared spectroscopy, and the influence mechanism of various factors on the migration and transformation of heavy metals was discussed. The results indicate that:(1)During oily sludge pyrolysis, heavy metals are mainly distributed in the pyrolysis residue, and less than 3 % of heavy metals are distributed in the pyrolysis liquid and pyrolysis gas. (2)Low temperature has little effect on the migration of heavy metals, and the migration rates of Cr, Cu and Pb rise sharply at 700 ℃. (3)Pyrolysis enhances the stability of Cr, Cu and Pb, but is not conducive to the immobilization of Ni and Zn. (4)Pyrolysis reduces the leaching concentrations of Cr, Ni and Pb, but activates the leaching activity of Zn, which results in an increased risk for Zn from low to medium level and the immobilization effect of heavy metals is closely related to the content of inorganic minerals.

Key words: oily sludge, pyrolysis, heavy metals, leaching characteristics, morphological distribution

摘要： 油泥中含有重金属,在油泥热解过程中,其含有的重金属或迁移到热解气、热解液中,或残留在热解残渣中。为研究含油污泥热解过程中重金属的迁移转化行为,考察了热解温度、停留时间对重金属在固、气、液三相产物中的分配及热解残渣中重金属形态分布的影响。此外,分析了热解残渣中重金属的浸出特性,对其生态风险进行评估。采用改进的3级连续提取BCR法和风险评价指数法对热解残渣中的重金属进行形态分析和风险评估,借助元素分析、X射线荧光光谱、傅里叶红外光谱等表征手段对热解残渣进行分析,将各因素对重金属迁移转化的影响机制进行了研究。研究结果表明:①在含油污泥热解过程中,重金属主要分布在热解残渣中,仅有不足3%的重金属分布在热解液和热解气中。②低温对重金属迁移行为的影响较小,但在700℃时,Cr、Cu和Pb向热解液中的迁移率急剧增加。③热解增加了Cr、Cu和Pb的稳定性,但不利于Ni和Zn的固定。④热解降低了Cr、Ni和Pb的浸出浓度,但激活了Zn的浸出活性,致使Zn从低风险升高至中风险,重金属的固定效果与无机矿物的含量密切相关。

关键词: 含油污泥, 热解, 重金属, 浸出特性, 形态分布