Method for producing metallic iron

Abstract

An object of the present invention is to provide a method for producing metallic iron, in which after a mixture including a carbonaceous reducing agent and iron oxide is fed onto a hearth of a moving hearth reducing-melting furnace and is then heated so that the iron oxide is reduced and melted, metallic iron to be obtained is cooled and is then discharged outside the furnace for recovery. In the method described above, even when powdered metallic iron is squeezed into the surface of the hearth, or the hearth is damaged by slag infiltration and corrosion, the removal and repair can be easily performed, the operation rate and maintenability of the hearth can be improved, and hence a long continuous operation can be suitably performed. According to the present invention, metallic iron is produced by the steps of, prior to the feed of raw agglomerates, bedding a granular hearth material on the moving hearth for forming a layered renewable hearth, which can be renewed; removing part or the entirety of the renewable hearth, which was degraded during operation, and then newly feeding the hearth material for forming a new renewable hearth; leveling the surface of the newly formed hearth; and subsequently feeding the mixture.

1 . A method for producing metallic iron, in which after a mixture including a carbonaceous reducing agent and iron oxide is fed onto a moving hearth of a moving hearth reducing-melting furnace and is then heated so that the iron oxide is reduced and melted, metallic iron to be obtained is cooled and is then discharged outside the furnace for recovery, the method comprising: prior to the feed of the mixture, bedding a granular hearth material on the moving hearth for forming a layered renewable hearth which is renewable; removing part or the entirety of the renewable hearth, which is degraded during operation, and then newly feeding the hearth material for newly forming a renewable hearth; leveling the surface of the newly formed hearth; and subsequently feeding the mixture for producing the metallic iron.  
   
   
       2 . The method according to  claim 1 , wherein the degradation comprises solidification of the renewable hearth.  
   
   
       3 . A method for producing metallic iron, in which after a mixture including a carbonaceous reducing agent and iron oxide is fed onto a hearth of a moving hearth reducing-melting furnace and is then heated so that the iron oxide is reduced and melted, metallic iron to be obtained is cooled and is then discharged outside the furnace for recovery, the method comprising: prior to the feed of the mixture, bedding a hearth material on the hearth for forming a layered renewable hearth which is renewable; feeding the hearth material on the surface of the renewable hearth which is degraded during operation so as to form a new surface of the hearth; leveling the new surface of the hearth; and subsequently feeding the mixture for producing the metallic iron.  
   
   
       4 . The method according to  claim 3 , wherein the hearth material is fed so as to fill a recess formed on the surface of the degraded renewable hearth.  
   
   
       5 . The method according to  claim 3 , wherein the leveling comprises moving the fed hearth material in the direction intersecting the moving direction of the moving hearth.  
   
   
       6 . The method according to  claim 5 , wherein metallic iron and/or slag remaining after discharge is discharged in the moving direction concomitant with the moving.  
   
   
       7 . The method according to  claim 3 , wherein the thickness of the renewable hearth is adjusted.  
   
   
       8 . The method according to  claim 3 , wherein, after the renewable hearth is leveled, the hearth material is further fed so as to complete the renewal prior to the feed of the mixture.  
   
   
       9 . The method according to  claim 3 , wherein the hearth material comprises a carbonaceous material.  
   
   
       10 . The method according to  claim 3 , wherein the hearth material comprises a high melting point material having corrosion resistance against produced slag.  
   
   
       11 . The method according to  claim 10 , wherein the high melting point material comprises an oxide containing alumina and/or magnesia or silicon carbide.  
   
   
       12 . The method according to  claim 10 , wherein the hearth material further comprises a carbonaceous material.  
   
   
       13 . The method according to  claim 9 , wherein the hearth material further comprises a material which is to be used as a CaO source or an MgO source.  
   
   
       14 . The method according to  claim 9 , wherein the hearth material further comprises a sintering promoter.  
   
   
       15 . The method according to  claim 3 , wherein the cooling is performed by supplying a coolant or the hearth material.  
   
   
       16 . The method according to  claim 1 , wherein, when the degraded renewable hearth is removed, the renewable hearth is softened and is then removed:  
   
   
       17 . The method according to  claim 3 , wherein, before the feed of the mixture, an atmosphere-adjusting agent containing a powdered carbonaceous material is bedded on the renewable hearth, which has been renewed, so as to form a layered structure, and subsequently the mixture is fed.  
   
   
       18 . The method according to  claim 17 , wherein the atmosphere-adjusting agent comprises a material which is to be used as a CaO source or an MgO source.  
   
   
       19 . The method according to  claim 17 , wherein the hearth material is blended in the atmosphere-adjusting agent.  
   
   
       20 . The method according to  claim 17 , wherein THE atmosphere-adjusting agent is fed in twice or more.  
   
   
       21 . The method according to  claim 3 , wherein a layer containing a powdered carbonaceous material is present between the moving hearth and the renewable hearth or in each of a plurality of layers formed of the renewable hearths.  
   
   
       22 . The method according to  claim 3 , wherein the hearth material is compacted when the surface of the hearth is leveled.