Method for manufacturing iron nuggets

Abstract

Provided is a method for manufacturing iron nuggets by which reduced iron obtained by heating and reducing agglomerates, or iron nuggets obtained by melting and aggregating the reduced iron can be prevented from reoxidation inside a movable hearth heating furnace and quality of the reduced iron can be improved. The method involves charging and heating agglomerates including iron oxide and a carbonaceous reducing agent on a hearth of a movable hearth heating furnace, reducing and melting the iron oxide in the agglomerates, and then discharging obtained iron nuggets to the outside of the furnace and recovering the iron nuggets. The agglomerates have a coating layer, including a fluid carbonaceous material, on the surface.

1 . A method for manufacturing iron nuggets by charging and heating agglomerates including iron oxide and a carbonaceous reducing agent on a hearth of a movable hearth heating furnace, reducing and melting the iron oxide in the agglomerates, and then discharging obtained iron nuggets to the outside of the furnace and recovering the iron nuggets, wherein
 the agglomerates have a coating layer, including a fluid carbonaceous material, on the surface.   
     
     
         2 . The method according to  claim 1 , wherein the fluid carbonaceous material is at least one selected from the group consisting of bituminous coal, subbituminous coal, and lignite. 
     
     
         3 . The method according to  claim 1 , wherein an average thickness of the coating layer is greater than 0.30 mm. 
     
     
         4 . The method according to  claim 1 , wherein
 the agglomerates are obtained by   agglomerating a mixture including the iron oxide and the carbonaceous reducing agent in a first pelletizer to form core portions, and then   forming the coating layer including the fluid fluid carbonaceous material on the surface of the obtained core portions in a second pelletizer.   
     
     
         5 . The method according to  claim 1 , wherein
 a top portion of the coating layer is not lower than a top portion of the iron nuggets while the agglomerates are heated.   
     
     
         6 . The method according to  claim 1 , wherein
 the coating layer becomes a shell-shaped coke while the agglomerates are heated.   
     
     
         7 . The method according to  claim 1 , wherein
 the agglomerates are charged to form a single layer on the furnace hearth.   
     
     
         8 . The method according to  claim 1 , wherein
 the carbonaceous reducing agent is placed on the furnace hearth before the agglomerates are charged on the furnace hearth.   
     
     
         9 . The method according to  claim 1 , wherein
 a C amount in the iron nuggets is 2.5 mass % or more.   
     
     
         10 . The method according to  claim 1 , wherein
 an S amount in the iron nuggets is 0.120 mass % or less.