Effect of unburned carbon on lead, zinc, and copper recovery from molten fly ash by chloride-induced volatilization |
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Authors: | Katsuya Nakayama Kuchar Dalibor Keisuke Sakai Mitsuhiro Kubota Hitoki Matsuda |
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Institution: | (1) Engineering Division, Sinto Ecotec Company, Koda, Aichi, Japan;(2) Department of Energy Engineering and Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan |
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Abstract: | The present work focuses on investigation of the effective recovery of heavy metals from molten fly ash by applying chloride-induced
volatilization. In particular, the effect of unburned carbon on the chloride-induced volatilization of lead, zinc, and copper
from model and real molten fly ashes was investigated in the temperature range 873–1173 K under a N2 atmosphere. As a result, almost 100% of lead and a significant proportion of zinc were volatilized from the real molten fly
ash samples at 1173 K. In contrast, for the model fly ash, volatilization ratios of lead and zinc at 1173 K were only 85%
and 25%, respectively. Further, the results of X-ray diffraction analysis suggested that PbO in molten fly ash was converted
either to Pb2OCl2 or Pb by respective chlorination and reduction reactions. Meanwhile ZnO and CuO in the molten fly ash were reduced to Zn
and Cu by reaction with unburned carbon. Subsequently, Pb, Zn, and Pb2OCl2 were volatilized, but Cu remained in the solid residue. Finally, the volatilization ratio of zinc increased with the addition
of carbon, and more than 98% of zinc was volatilized at 1173 K from a fly ash with a carbon content of 20%. |
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Keywords: | Unburned carbon Reduction Heavy metal Volatilization Molten fly ash |
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