Process for producing sponge iron and reduced iron powder sponge iron and charging apparatus

Abstract

A method for manufacturing sponge iron and an apparatus for charging in the method are disclosed. Iron oxide powder and reducing-agent powder are charged such that alternating layers of the iron oxide powder and the reducing-agent powder are formed and such that each of the layers is in the form of a helix, and then a reduction treatment is performed. The method has not only high reaction efficiency of a gas, high quality, and high productivity, but also the advantage for a production adjustment because the amount of charge can be adjusted without the limitation of a reduction time. The molar ratio of the carbon content in the reducing agent to the oxygen content in the iron oxide in the reaction container is preferably 1.1 or more.

1 . A method for manufacturing sponge iron, comprising: 
 a charging step of charging iron oxide powder and reducing-agent powder into a reaction container; and    a reducing step of reducing the iron oxide powder in the reaction container to produce a mass of sponge iron by heating from the outside of the reaction container, wherein, in the charging step, the iron oxide powder and the reducing-agent powder are charged such that alternating layers of the iron oxide powder and the reducing-agent powder are formed and such that each of the layers is in the form of a helix.    
     
     
         2 . The method for manufacturing sponge iron according to  claim 1 , wherein, in the charging step, the iron oxide powder and the reducing-agent powder are charged such that layers composed of the reducing-agent powder are disposed on an inner side-surface of the reaction container (referred to as “peripheral portion”) and disposed at a central portion along the vertical central axis and such that the alternating layers that are in the form of helices are disposed at a portion (referred to as “intermediate portion”) other than the portion of the layers disposed on the inner side-surface and at the central portion.  
     
     
         3 . The method for manufacturing sponge iron according to  claim 1 , wherein the iron oxide powder comprises at least one selected from the group consisting of an iron ore, mill scale, and iron oxide powder recovered from a waste pickling solution.  
     
     
         4 . The method for manufacturing sponge iron according to  claim 1 , wherein the reducing-agent powder comprises at least one selected from the group consisting of coke, char, and coal.  
     
     
         5 . The method for manufacturing sponge iron according to  claim 1 , wherein a source of a carbon dioxide gas is added to the reducing-agent powder.  
     
     
         6 . The method for manufacturing sponge iron according to  claim 1 , wherein the heating temperature is 1000° C. to 1300° C. in the reducing step.  
     
     
         7 . The method for manufacturing sponge iron according to  claim 1 , wherein, in the charging step, the thicknesses of the layers of the iron oxide powder and the reducing-agent powder are variable when forming the layers that are in the form of helices.  
     
     
         8 . The method for manufacturing sponge iron according to  claim 1 , wherein, in the charging step, the amounts of iron oxide powder and reducing-agent powder in the reaction container are controlled such that the molar ratio of the carbon content in the reducing-agent powder to the oxygen content in the iron oxide powder is at least 1.1.  
     
     
         9 . The method for manufacturing sponge iron according to  claim 2 , wherein, in the charging step, the amounts of iron oxide powder and reducing-agent powder in the reaction container are controlled such that the molar ratio of the carbon content in the reducing-agent powder to the oxygen content in the iron oxide powder is at least 1.1.  
     
     
         10 . The method for manufacturing sponge iron according to  claim 9 , wherein, in the charging step, the amounts of iron oxide powder and reducing-agent powder in the intermediate portion are controlled such that the molar ratio of the carbon content in the reducing-agent powder to the oxygen content in the iron oxide powder is at least 0.5.  
     
     
         11 . A method for manufacturing reduced iron powder, comprising the steps of: pulverizing sponge iron manufactured by the method according to  claim 1;  reducing the resulting pulverized iron; and repulverizing the resulting reduced iron.  
     
     
         12 . Sponge iron having a helical shape.  
     
     
         13 . The sponge iron according to  claim 12 , wherein the sponge iron has a metallic iron content of at least 97 percent by mass.  
     
     
         14 . An apparatus for charging materials used to manufacture sponge iron into a container, the materials being iron oxide powder and reducing-agent powder, the apparatus comprising: 
 a charger capable of rotating and vertically moving in the container when the charger is disposed in the container;    an outlet for the iron oxide powder and an-outlet for the reducing-agent powder, these outlets being provided at the bottom of the charger and capable of rotating together with the charger.    
     
     
         15 . The apparatus for charging materials used to manufacture sponge iron into a container according to  claim 14 , wherein the opening areas of the outlet for the iron oxide powder and the outlet for the reducing-agent powder can be variable.  
     
     
         16 . The apparatus for charging materials used to manufacture sponge iron into a container according to  claim 14 , wherein the charger comprises: 
 a cylindrical main body having a diameter of up to 85% of the inside diameter of the container; and    a lower end composed of part of a cylinder, the horizontal section of the cylinder being a circle having a diameter of 90% to 95% of the inside diameter of the container, wherein the horizontal section of the lower end has the shape of a sector including the center of the circle and part of the circumference of the circle, or has a shape including the sector.