PURPOSE: To inexpensively fix (or insolubilize) hexavalent chromium by a method wherein water and ferrous chloride and/or ferrous sulfate are added to the dust separated by the dust collector in incineration ash melting treatment equipment to be kneaded therewith.
CONSTITUTION: In incineration ash melting treatment equipment melting incineration ash of industrial waste by arc discharge, incineration ash is melted in a melting furnace 2 to form molten slag and generated exhaust gas is cooled by a cooler 3 and the dust in the exhaust gas is separated by a dust collector 4. Since the separated dust is rich in scattering properties and contains a harmful heavy metal such as hexavalent chromium, when this dust is treated, water and ferrous chloride and/or ferrous sulfate are added to and kneaded with the dust. Or, water, a chelating agent and ferrous chloride and/or ferrous sulfate are added to and mixed with the dust. At this time, with respect to 1 pts.wt. of dust, water is set to 0.22-0.30 pts.wt., the chelating agent is set to 0.01 pts.wt. or more and ferrous chloride and/or ferrous sulfate is set to 0.002 pts.wt. or more.
HAMA TOSHIO
SANO NORIO
DAIDO STEEL CO LTD