2005 Volume 31 Issue 4 Pages 278-284
To obtain fundamental data for developing an efficient recovery process of heavy metals from various molten fly ashes, chlorination behavior of lead and zinc was investigated for the three types of ash produced from electric resistance, gasification melting and coke bed melting furnaces. Ash samples were heated at terminal temperatures ranging from 873 to 1073 K in a nitrogen stream with a fixed bed reactor. Polyvinyl chloride and carbon derived from phenolphthalein were used as chlorination accelerating agents.
The addition of polyvinyl chloride was effective for the release of lead, which was identified as the oxide in every sample. Several zinc compounds such as the oxide, sulfide, carbonate, silicate and aluminosilicate were observed depending on the ash. Zinc originating from oxide and aluminosilicate was volatilized at 1073 K by the addition of polyvinyl chloride, while zinc sulfide and zinc silicate did not react with it. All forms of zinc were released effectively from the three sample ashes by the addition of carbon, and more than 90% of zinc was released at 1073 K.