Patent ID: 6361753
Filing Date: 2002-03-26
Classification: C22B,Y02P

Abstract:
A method for converting zinc chloride in a mixed metal solution of soluble base metals leached from electric arc flue dust to a zinc oxide precipitate, comprising the steps of:(a) adding Ca(OH)2 to the mixed metal solution in at least about 90% of the theoretical stoichiometric amount of Ca(OH)2 necessary to convert ZnCl2 in the solution to zinc oxide at a reaction temperature of at least about 150Â° C. and at an elevated pressure of at least about 20 psi higher than the vapor pressure of the solution at the reaction temperature to produce a zinc-rich precipitate; and (b) filtering the zinc-rich precipitate from the solution to leave a calcium chloride solution suitable for recycling to a reactor for treating EAFD and to yield zinc oxide solid that has less than 1.0 wt % Cl.