Method for producing metallic iron

Abstract

Disclosed is a technique for preventing the adhesive of metallic iron and/or wustite (which is a material produced by the heat reduction of iron oxide contained in a powder derived from an agglomerate that comprises, as a raw material, a mixture containing a iron-oxide-containing substance and a carbonaceous reducing material) on a heath of a movable furnace heath type heating furnace without largely changing the design of a facility for the production, in the production of metallic iron by placing the agglomerate on the heath and heating the agglomerate in the heating furnace to reduce iron oxide contained in the agglomerate. A heath-forming material for preventing the cohesive of metallic iron and/or wustite (which is a material produced by the heat reduction of iron oxide contained in the powder derived from the agglomerate) on the heath is charged into the furnace together with the agglomerate.

1 . A method for producing metallic iron, the method comprising:
 placing on a hearth of a movable hearth furnace an agglomerate comprising a raw material mixture comprising a carbonaceous reducing material and a substance comprising iron oxide, and   heating the agglomerate to reduce iron oxide in the agglomerate,   wherein a hearth-forming material that prevents metallic iron, wustite, or both, from sticking to the hearth is charged into the furnace together with the agglomerate, and   wherein the metallic iron, wustite, or both, are produced by heat reduction of iron oxide in a powder derived from the agglomerate.   
     
     
         2 . The method of  claim 1 , wherein, when a carbon content of the agglomerate is 122 mass % or more of a carbon content required to reduce the iron oxide in the agglomerate, the hearth-forming material has a composition such that CaO, SiO 2 , and Al 2 O 3  contents of a total composition of the powder derived from the agglomerate and the hearth-forming material satisfy formulae (1) and (2):
   [CaO]/[SiO 2 ]=0.25 to 1.20   (1)
     [Al 2 O 3 ]/[SiO 2 ]=0.2 to 0.7   (2)
   wherein each [ ] in the formulae (1) and (2) denotes the content (% by mass) in mass % for the component specified in the square brackets.   
     
     
         3 . The method of  claim 1 , wherein
 when a carbon content of the agglomerate is less than 122 mass % of a carbon content required to reduce the iron oxide in the agglomerate,   the hearth-forming material has a composition such that   a total carbon content of a total composition of the powder derived from the agglomerate and the hearth-forming material is 122% or more of the carbon content required to reduce the iron oxide in the agglomerate, and   CaO, SiO 2 , and Al 2 O 3  contents of the total composition of the powder derived from the agglomerate and the hearth-forming material satisfy formulae (3) and (4):
   [CaO]/[SiO 2 ]=0.25 to 1.20   (3)
 
   [Al 2 O 3 ]/[SiO 2 ]=0.2 to 0.7   (4)
 
   wherein each [ ] in the formulae (3) and (4) denotes the content (% by mass) in mass % for the component specified in the square brackets.   
     
     
         4 . The method of  claim 1 , wherein
 when a carbon content of the agglomerate is less than 122 mass % of a carbon content required to reduce the iron oxide in the agglomerate,   the hearth-forming material has a composition such that   a total carbon content of a total composition of the powder derived from the agglomerate and the hearth-forming material remains less than 122% of the carbon content required to reduce the iron oxide in the agglomerate, and   CaO, SiO 2 , Al 2 O 3 , and MgO contents of the total composition of the powder derived from the agglomerate and the hearth-forming material satisfy at least one formula selected from the group consisting of formulae (5) to (9):
   [CaO]/[SiO 2 ]<0.25   (5)
 
   [CaO]/[SiO 2 ]>1.20   (6)
 
   [Al 2 O 3 ]/[SiO 2 ]<0.2   (7)
 
   [Al 2 O 3 ]/[SiO 2 ]>0.7   (8)
 
   [MgO]/[SiO 2 ]>0.4   (9)
 
   wherein each [ ] in the formulae (5) to (9) denotes the content (% by mass) in mass % for the component specified in the square brackets.   
     
     
         5 . The production method according to of  claim 2 , wherein the hearth-forming material has a composition such that a total CaO, SiO 2 , and Al 2 O 3  content is 3.0% to 7.0% by mass of the total composition of the powder derived from the agglomerate and the hearth-forming material. 
     
     
         6 . The method of  claim 4 , wherein the hearth-forming material has a composition such that a total CaO, SiO 2 , and Al 2 O 3  content is more than 7.0% by mass of the total composition of the powder derived from the agglomerate and the hearth-forming material. 
     
     
         7 . The production method according to  claim 1 , wherein at least 50% by mass of the hearth-forming material has a particle diameter of 0.5 to 2 mm. 
     
     
         8 . The method of  claim 1 , wherein the agglomerate has a particle size of 5 to 50 mm. 
     
     
         9 . The method of  claim 1 , wherein the agglomerate is heated in the movable hearth furnace at a temperature of 1200° C. to 1400° C. 
     
     
         10 . The method of  claim 2 , wherein [CaO]/[SiO 2 ] is 0.3 to 1.1. 
     
     
         11 . The method of  claim 2 , wherein [Al 2 O 3 ]/[SiO 2 ] is 0.2 to 0.6. 
     
     
         12 . The method of  claim 2 , wherein [Al 2 O 3 ]/[SiO 2 ] is 0.2 to 0.4. 
     
     
         13 . The method of  claim 3 , wherein [CaO]/[SiO 2 ] is 0.3 to 1.1. 
     
     
         14 . The method of  claim 3 , wherein [Al 2 O 3 ]/[SiO 2 ] is 0.2 to 0.6. 
     
     
         15 . The method of  claim 3 , wherein [Al 2 O 3 ]/[SiO 2 ] is 0.2 to 0.4. 
     
     
         16 . The method of  claim 5 , wherein the total CaO, SiO 2 , and Al 2 O 3  content is 4.5% to 6.5% by mass of the total composition of the powder derived from the agglomerate and the hearth-forming material. 
     
     
         17 . The method of  claim 5 , wherein the total CaO, SiO 2 , and Al 2 O 3  content is 5.0% to 6.5% by mass of the total composition of the powder derived from the agglomerate and the hearth-forming material. 
     
     
         18 . The method of  claim 6 , wherein the total CaO, SiO 2 , and Al 2 O 3  content is more than 7.5% by mass of the total composition of the powder derived from the agglomerate and the hearth-forming material. 
     
     
         19 . The method of  claim 6 , wherein the total CaO, SiO 2 , and Al 2 O 3  content is more than 8% by mass of the total composition of the powder derived from the agglomerate and the hearth-forming material. 
     
     
         20 . The method of  claim 6 , wherein the total CaO, SiO 2 , and Al 2 O 3  content is more than 7.0% and less than 10% by mass of the total composition of the powder derived from the agglomerate and the hearth-forming material.