Method of recovering valuable metal from slag

Abstract

A method of recovering a valuable metal from slag is disclosed. The method includes the steps of: applying a magnetic field whose magnitude is increased in a stepwise fashion to crushed slag to separate a magnetic material from the crushed slag; and introducing a reductant into the separated magnetic material to recover a valuable metal therefrom. The method is advantageous and cost effective because the recovery rate of iron (Fe) from slag exceeds 50% by using a magnetic field, thus reducing the amount of slag to be wasted.

1 . A method of recovering a metal from slag, the method comprising:
 providing slag particles;   applying a first magnetic field to the slag particles to separate slag particles containing a metal from the slag particles;   subsequent to the application of the first magnetic field, applying a second magnetic field which has a magnitude substantially greater than that of the first magnetic field to the slag particles to separate slag particles containing at least an oxide of the metal; and   processing the slag particles containing the metal and the slag particles containing the at least an oxide of the metal to recover the metal.   
     
     
         2 . The method of  claim 1 , wherein the metal comprises iron and the at least an oxide of the metal comprises at least one selected from the group consisting of FeO, Fe 2 O 3 , and Fe 3 O 4 . 
     
     
         3 . The method of  claim 1 , wherein the metal is iron and the oxide of the metal is FeO, wherein the method further comprises:
 subsequent to the application of the second magnetic field, applying a third magnetic field which has a magnitude substantially greater than that of the second magnetic field to the slag particles to separate slag particles containing at least one of Fe 2 O 3  and Fe 3 O 4 .   
     
     
         4 . The method of  claim 1 , wherein the magnitude of each of the first and second magnetic fields ranges 100 G to 1000 G. 
     
     
         5 . The method of  claim 1 , wherein the magnitude of each of the first and second magnetic fields ranges 100 G to 340 G. 
     
     
         6 . The method of  claim 1 , wherein processing comprising:
 melting the separated slag particles containing the at least an oxide of the metal; and   exposing the melted slag to a reductant.   
     
     
         7 . The method of  claim 6 , wherein the reductant comprises at least one selected from carbon (C), aluminum (Al), silicon (Si), sodium (Na), calcium (Ca), magnesium (Mg), and carbon monoxide (CO) gas. 
     
     
         8 . The method of  claim 1 , wherein providing slag particles comprising:
 prior to the application of the first magnetic field, exposing molten slag to a reductant to separate the metal from the molten slag;   subsequent to exposing, cooling the molten slag into solidified slag; and   breaking the solidified slag into the slag particles.   
     
     
         9 . The method of  claim 8 , wherein cooling comprises supplying a gas mixture comprising steam to the molten slag. 
     
     
         10 . The method of  claim 8 , wherein the solidified slag has a porous structure. 
     
     
         11 . The method of  claim 8 , wherein the molten slag is cooled at a cooling rate of 5 to 50° C./sec.