Recovery method of heavy metals from exhaust gas generated during melting of incineration ash and fly ash

摘要

PROBLEM TO BE SOLVED: To recover heavy metals inexpensively and easily recyclably from fly ash in exhaust gas generated when bottom ash and fly ash are melted. SOLUTION: An exhaust gas contg. fly ash generated when bottom ash and fly ash are melted is introduced into a wet scrubber and the fly ash and evaporated heavy metals caught by cleaning in the wet scrubber 2 are inexpensively dissolved with a post-cleaning drain water contg. hydrochloric acid generated by cleaning. NaHS or Na2 S and NaOH are added to this drain water to adjust pH to lower than 0.4 and the heavy metals contg. a large amount of Cu component are separated in the primary precipitation tank 3 and they are filtered. Then, the filtered water is sent into the secondary precipitation tank 5 and pH is adjusted to at least 0.4 and heavy metals contg. a large amount of (Pb+Zn) components are separated and filtered to obtain the primary recovered matter contg. a large amount of easily recyclable Cu component and the secondary recovered matter contg. a large amount of the (Pb+Zn) components.