Enhancement of Chloride Volatilization of Zn, Pb and Cu from Molten Fly Ash under Reduced Pressure

Mizuno Shigeo, Nakayama Katsuya, Kawachi Takahiro, Kojima Yoshihiro, Watanabe Fujio, Matsuda Hitoki, Takada Mitsuru

doi:10.1252/kakoronbunshu.32.99

Experimental study on enhancement of chloride volatilization of Zn, Pb and Cu from molten fly ash less than 75 µm in particle size soaked with hydrochloric acid was conducted in the temperature range 873–1123 K, holding time of 1–120 min and reduced pressure lower than 101.3 kPa to 1.3 kPa.<br>As a result, it was found that the volatilization ratio of ZnCl₂, PbCl₂ and CuCl in 1.3 kPa were 1.5–3.0 times higher than those obtained in 101.3 kPa. The volatilization ratio of these heavy metal chlorides rapidly increased with the heating temperature, under reduced pressure. At a higher heating temperature of 1123 K, almost 100% of ZnCl₂ and PbCl₂ were volatilized within 1 min, in the reduced pressure of 1.3 kPa.<br>The volatilization of the heavy metal chlorides at a constant temperature increased with a decrease in the pressure. In particular, the volatilization of ZnCl₂ and CuCl was significant when the pressure was reduced below saturated vapor pressure of ZnCl₂ and CuCl. However the volatilization of PbCl₂ was increased over saturated vapor pressure of PbCl₂. It was found that KPb₂Cl₅ was formed in the residue during heating under reduced pressure.

Enhancement of Chloride Volatilization of Zn, Pb and Cu from Molten Fly Ash under Reduced Pressure

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