TREATMENT METHOD FOR DUST IN CEMENT KILN EXTRACTION GAS

PROBLEM TO BE SOLVED: To treat selenium and heavy metal of dust in cement kiln extraction gas to ≤0.1 mg/L being the effluent standard value or below. SOLUTION: A treatment method for the dust in cement kiln extraction gas comprises the following respective steps: (1) a first step of carrying out solid/liquid separation after water is added to the dust in cement kiln extraction gas to make slurry; (2) a second step of adding a ferric salt compound to a liquid phase (hereinafter referred to raw water) after the solid/liquid separation obtained in the first step, further adding an aluminum salt compound thereto, thereafter adjusting pH to 4 to 8, adding a polymer coagulant and carrying out solid/liquid-separation; (3) a third step of adding a ferrous salt compound to the liquid phase after the solid/liquid separation obtained in the second step in an amount of 150 to 300 times moles relative to hexavalent selenium in the raw water, adjusting pH to 8 to 12, thereafter adding a polymer coagulant and carrying out solid/liquid separation; and (4) a fourth step of adding the ferric salt compound to the liquid phase after the solid/liquid separation obtained in the third step, adjusting pH to 8 to 12, thereafter adding the polymer coagulant and carrying out solid/liquid separation. COPYRIGHT: (C)2009,JPO&INPIT