Specialized metallurgical processes – compositions for use therei – Processes – Electrothermic processes
Patent
1995-01-23
1998-01-20
Andrews, Melvyn
Specialized metallurgical processes, compositions for use therei
Processes
Electrothermic processes
75724, 75725, 75726, 75961, 204106, 204114, 423554, C21B 1110
Patent
active
057097305
ABSTRACT:
Electric arc furnace production of recycled steel is plagued by the formation of an iron-depleted, metal-rich electric arc flue dust (EAFD). In the present invention, we recover at least about 85 wt. % of the base metals in the EAFD (i.e., lead, cadmium, copper, and zinc) as high quality metals products without producing any solid, liquid, of gaseous wastes. We use a recyclable calcium chloride/hydrochloric acid leach mill solution to extract the base metals form the EAFD in a reactor under a controlled pH of about 2.6 at an elevated temperature and pressure in an oxygen environment wherein the solids content in the reaction slurry is about 15-30 wt. %. In this way, we place the base metals in solution while leaving the iron as a solid hematite iron complex. When separated from the metal-rich solution, the solid hematite iron complex is recycled to the electric arc furnace. The base metals are precipitated and recovered. The calcium chloride/hydrochloric acid leach mill solution is regenerated through the addition of sulfuric acid to precipitate gypsum. Sodium, potassium, and magnesium in the EAFD remains insoluble or becomes insoluble in the reactor and is recycled in the solid hematite iron complex.
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Andrews Melvyn
Hammar John C.
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