Separation and Recovery of Heavy Metals in Incinerator Fly Ash by Chloride Volatilization

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The concentrated heavy metals in the fly ash from municipal solid wasete incinerators were recovered and separated from that by chloride volatilization. The volatility of heavy metals was improved by forming chloride complex using NH_4Cl. Two types of fly ash in this experiment were sampled from electrostatic precipitator with or without lime injection for acid gas, The volatilization of heavy metals in fly ash was tested in N_2 or air atmosphere using both batch type and continuous type electric furnaces. The behavior of heavy metals in this experiment can be characterized as follows :1) According to the results of metal volatilization for both types of fly ash, the remaining ratios of metals in treated fly ash were 5% for Cd, 10% for Pb, and 20% for Zn at the temperature of 900ﾟC using a batch type electric furmace.2) The volatilization of Cu was facilitated more easily in air than in N_23) Heavy metal volatilization was not so much in a contimuous type furnance, but most of heavy metals remaining in ash became soluble in water.4) The vaporized part was treated by Na_2S to precipitate heavy metals, and the precipitate contained high concentration of Pb at 28.3%5) The validity of chloride volatilization in this experiments was confirmed by thermochemical data.