Patent ID: 7435281

Claim:
A pyromettallurgic process for the treatment of post-steelwork residues of a Waelz process in the form of melted slag, comprising the steps of: providing: an EAF arc electric furnace (A): a rotating furnace (B) of a Waelz process fed by EAF powders for a recovery treatment; a pyrometallurgic treatment section (D) in the form of an electric furnace ( 1 ), suitable for the introduction of residues; a hydrometallurgic section (C) for the treatment of the powders collected from said rotating furnace (B) and said pyrometallurgic treatment section (D); preparing the residues from the Waelz process together with other post-steelworks residues, in a hopper and optionally adding additives and reaction elements; starting the pyrometallurgic treatment in pyrometallurgic treatment section (D) with a metal bath ( 6 ) or liquid foot and an overlying layer of slag ( 7 ), both remaining from the previous casting, already present in the electric furnace; introducing the residues from the Waelz process together with other post-steelworks residues, together with suitable additives including at least one carbon and chemical reagents, into the furnace ( 1 ) of said pyrometallurgic treatment section (D), in an homogeneous distribution effected on the surface of the slag ( 7 ); introducing directly into the slag ( 7 ), by means of lances ( 4 ), additive, flushing and reaction elements to correct the composition of the slag ( 7 ); reacting the residues with the slag ( 7 ) to obtain: a) separation of the liquid metallic phases which are added to the metal bath ( 6 ) to form a sellable liquid metal; b) separation of the metallic volatile elements in vapour phase which, when transferred to the free zone of the furnace ( 1 ), possibly with the help of post-combustion, recombine with oxygen for the formation of oxide powder; c) separation of the stable ceramic and/or silicate phases which form the inert phase of the slag ( 7 ); d) (separation and neutralization of other elements risky for the environment that are present in the residues to provides inert slag ( 7 ); and supplying energy by means of an electrode column ( 5 ) to the reaction bed or slag ( 7 ) to sustain the reactions set forth above; extracting the metallic bath ( 6 ) and inert slag ( 7 ); extracting the powders leaving the pyrometallurgic treatment section (D), collecting and sending the powders to the hydrometallurgic treatment section (C) together with the powder coming from the rotating furnace (B); and obtaining zinc and lead from hydrometallurgic treatment section (C).