Calcium-containing incineration fly ash and molten fly ash treatment method

摘要

PROBLEM TO BE SOLVED: To provide a treating method of fly ash capable of simply separating heavy metals such as lead and zinc in a stable form from incineration fly ash or molten fly ash containing calcium. SOLUTION: The treating method of the fly ash comprises of a 1st process of adding a dil. hydrochloric acid into the fly ash containing the heavy metals, salts and unreacted slaked lime to make into sludge, eluting the most part of the salts containing calcium chloride and zinc, and then solid-liquid separating and a 2nd process of adding an ammonium chloride aq. solution to the resultant residue to make into sludge again, solubilizing the unreacted slaked lime, and then solid-liquid separating to obtain a residue containing the heavy metal consisting essentially of lead. And further a 3rd process of making the residue obtained in the 2nd process into sludge in an aq. solution, adding sulfuric acid to make it acidic to elute the metals except lead and solid-liquid separating to obtain residue containing lead is provided and next, the liquid phases obtained in each process are mixed and after made it alkaline with an alkali agent, the hydroxides and the sulfides of the heavy metals consisting essentially of zinc are precipitated by adding a sulfidizing agent.