Volatility of heavy metals during incineration of tannery sludge in the presence of chlorides and phosphoric acid
Volatility of heavy metals during incineration of tannery sludge in the presence of chlorides and phosphoric acid
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DOI：
10.1177/0734242x08092024
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发表时间：
2008-08
影响因子：
3.9
通讯作者：
P. Tang;Y.C. Zhao;D. Chen;F. Xia
中科院分区：
文献类型：
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作者：
P. Tang;Y.C. Zhao;D. Chen;F. Xia
了解重金属在燃烧过程中的行为是选择废物处置替代品的最重要因素。因此，本文对高浓度重金属(铅、锌、铜、铬)在制革污泥中的蒸发行为进行了实验研究。在污泥中加入不同的氯化合物(如PVC、FeCl3、CaCl2和氯化钠)，并用磷酸进行预处理，以评价其对制革污泥中重金属挥发性的增强和减弱能力。实验结果表明，蒸发率随氯泥比和温度的增加而增大，投加氯化物对重金属蒸发率的促进和提高作用与氯自由基释放量有关。在800℃时，铅和锌的挥发率增加了15-20%，而铜和铬的挥发率仅增加了约3%和10%。然而，尽管氯/污泥的比例很高，但重金属在燃烧过程中并不会完全释放出来。另外，制革污泥中含有的重金属也可以通过磷酸处理得到有效的固定化。当85%磷酸占制革污泥干基的10%时，磷酸盐处理污泥的挥发率最低，约为3~15%，底灰中生成Ca18Cu3(PO4)14、Ca9Cr(PO4)7、Ca19Zn2(PO4)14和PbMgP2O7。
Knowledge of the behaviour of heavy metals in the combustion process is a most important factor in selecting disposal alternatives for waste materials. Accordingly, in this work, the vaporization behaviour of highly concentrated heavy metals (Pb, Zn, Cu and Cr) in tannery sludge were investigated experimentally. The sludge was spiked with various chlorine compounds (i.e. PVC, FeCl3, CaCl2 and NaCl) and pre-treated with phosphoric acid in order to evaluate the capacity of enhancement and weakening of the volatility of the heavy metals contained in tannery sludge. The experimental results show that the vaporization percentages increased with increasing ratio of Cl/sludge and temperature, and the accelerating and increasing effect of the addition of chlorides on the vaporization percentage of heavy metals was dependent on the release capacity of chlorine radicals. The vaporization percentages of lead and zinc increased by 15—20%, whereas those of copper and chromium increased by only about 3 and 10% at 800 °C. However, heavy metals were not expected to be completely released in the combustion process in spite of the high ratio of Cl/sludge. Alternately, heavy metals contained in tannery sludge can be immobilized effectively by pre-treatment with phosphoric acid. When the 85% phosphoric acid accounted for 10% of dry basis of tannery sludge, the phosphate-treated sludge showed the lowest vaporization percentage of about 3—15% with formation of Ca18Cu3(PO4)14, Ca9Cr(PO 4)7, Ca19Zn2(PO4) 14 and PbMgP2O7 in the bottom ash.