Method for recovering metallic elements, especially metallic chromium, from slag containing metal oxides in an electric-arc furnace

Abstract

The invention relates to a method for recovering metallic elements, especially metallic chromium, from slag containing oxides, especially chromium oxides, in an electric-arc furnace. According to said method, the slag is not reduced in a separate step after melting, but the following steps are carried out: a charge is introduced into tile electric-arc furnace, and melted, forming a molten metal and slag; said molten metal is tapped off, leaving the unreduced slag in the furnace vessel; a further charge of scrap metal including reducing agents for tile slag is added; the slag is reduced during the melting of said charge; and the slag and the molten metal are then lapped off. The inventive method can also be used in ladle metallurgy or converter metallurgy.

1 . Method for recovering metallic elements, especially metallic chromium, from slags that contain oxides, especially chromium oxides, in an electric arc furnace, with the following steps: 
 (a) introduction of a charge into the arc furnace;    (b) meltdown of the charge to produce a metal melt and slag;    (c) tapping of the melt while leaving the unreduced slag in the furnace vessel;    (d) introduction of another charge that contains scrap and reducing agents for the slag, such as carbon and/or silicon and/or aluminum;    (e) meltdown and direct reduction of the slag, especially direct reduction of chromium oxide, by the reducing agents in the charge during the melting process;    (g) tapping of the melt and the reduced slag.    
     
     
         2 . Method in accordance with  claim 1 , comprising 
 the melting down of a buildup melt at the beginning of a melting campaign;    a partial tapping of the melt in step (c) while leaving metal bottoms in the furnace vessel;    the charging of another charge onto the remaining metal bottoms and the slag;    a partial tapping of the metal melt after the meltdown of the charge and the reduction of the slag; and    repetition of the steps of charging, melting, and slag reduction for each melt of the campaign or termination by total tapping of a separation melt together with the metal bottoms.    
     
     
         3 . Method in accordance with  claim 1 , wherein the reducing agents carbon and/or silicon and/or aluminum are charged in the form of alloying materials with a high carbon and silicon content.  
     
     
         4 . Method in accordance with  claim 1 , wherein residual dusts are charged as reducing agents for the slag, especially a chromium-containing slag.  
     
     
         5 . Method in accordance with  claim 1 , wherein thorough mixing is carried out by means of inert gases, which are introduced through bottom nozzles and/or side nozzles in the arc furnace and/or through a top lance.  
     
     
         6 . Method for recovering metallic elements, especially metallic chromium, from slags that contain oxides, especially chromium oxides, in ladle metallurgy or converter metallurgy, with the following steps: 
 (a) introduction of a first metal melt with slag into a ladle or a converter;    (b) after the treatment of the melt, especially with oxygen, tapping of the melt while leaving the unreduced slag in the ladle or converter;    (c) introduction of another melt together with reducing agents for the slag, such as carbon and/or silicon and/or aluminum;    (d) thorough mixing of the melt with the slag, resulting in direct reduction of the slag, especially chromium oxide, by the reducing agents;    (g) tapping of the melt and the reduced slag.    
     
     
         7 . Method in accordance with  claim 6 , comprising 
 a partial tapping of the melt in step (b) while leaving metal bottoms in the ladle;    the charging of another melt onto the remaining metal bottoms and the slag;    a partial tapping of the metal melt in step (g) after reduction of the slag;    repetition of the steps of charging and of slag reduction for each melt of the campaign or termination by total tapping of a separation melt together with the metal bottoms.