Process for Producing Molten Iron and Apparatus Therefor

Abstract

A bedding carbonaceous material is charged onto a hearth of a rotary hearth furnace, carbonaceous-material containing pellets containing powdery iron ore and powdery coal are placed on the bedding carbonaceous material, and the hearth is caused to pass inside the rotary hearth furnace to heat and reduce the carbonaceous-material containing pellets to solid reduced iron and to heat and dry the bedding carbonaceous material by distillation into char. Subsequently, the solid reduced iron and the char are charged into an iron-melting furnace without being substantially cooled, and an oxygen gas is blown into the iron-melting furnace to melt the solid reduced iron, thereby obtaining molten iron. At least a part of an exhaust gas from the iron-melting furnace is used as a fuel gas for the rotary hearth furnace after being cooled and having dust removed.

1 : A molten iron producing method for producing molten iron using a molten iron production process constructed by combining a moving hearth type reducing furnace and an iron-melting furnace, comprising the steps (1) to (4): 
 (1) reducing furnace charging step of charging a bedding carbonaceous material onto a hearth of the moving hearth type reducing furnace and placing carbonaceous-material composite agglomerates containing a powdery iron oxide source and a powdery carbonaceous reducing agent on the bedding carbonaceous material;    (2) reduction step of moving the hearth inside the moving hearth type reducing furnace, thereby heating and reducing the carbonaceous-material composite agglomerates to solid reduced iron and heating and drying the bedding carbonaceous material by distillation into char;    (3) melting furnace charging step of charging the solid reduced iron and the char into the iron-melting furnace without being substantially cooled; and    (4) melting step of blowing an oxygen-containing gas into the iron-melting furnace to melt the solid reduced iron into the molten iron.    
     
     
         2 : A molten iron producing method according to  claim 1 , wherein the carbonaceous-material composite agglomerates are heated and reduced to the solid reduced iron having a metallization degree of 92% or higher in the step (2).  
     
     
         3 : A molten iron producing method according to  claim 1 , wherein the following step (5) is provided after the step (4): 
 (5) exhaust gas circulating step of using at least a part of an exhaust gas from the iron-melting furnace as a fuel gas for the moving hearth type reducing furnace.    
     
     
         4 : A molten iron producing method according to  claim 1 , wherein the carbon content of the solid reduced iron is 10 mass % or lower in the step (2).  
     
     
         5 : A molten iron producing method according to  claim 1 , wherein the melting is performed on the condition of a secondary combustion ratio of 40% or lower in the step (4).  
     
     
         6 : A molten iron producing method according to  claim 1 , wherein the thickness of the bedding carbonaceous material charged onto the hearth is 1 to 10 mm.  
     
     
         7 : A molten iron producing method according to  claim 1 , wherein the average particle diameter of the bedding carbonaceous material is 1 to 5 mm.  
     
     
         8 : A molten iron producing method according to  claim 1 , wherein the Giesler's maximum fluidity MF of the bedding carbonaceous material satisfies a relationship of log MF equal or lower than 2.  
     
     
         9 : A molten iron producing method according to  claim 1 , wherein the volatile content of the bedding carbonaceous material is 10 mass % or higher by dry weight.  
     
     
         10 : A molten iron producing method according to  claim 1 , wherein the volatile content of the bedding carbonaceous material is 50 mass % or lower by dry weight.  
     
     
         11 : A molten iron producing method according to  claim 1 , wherein another carbonaceous material is additionally charged into the iron-melting furnace in the step (3).  
     
     
         12 : A molten iron producing method according to  claim 1 , wherein the average volatile matter content of all the carbonaceous materials charged into the iron-melting furnace is 15 mass % or lower by dry weight with the carbon contained in the solid reduced iron excluded.  
     
     
         13 : A molten iron producing method according to  claim 1 , wherein the following step (6) is provided between the steps (2) and (3): 
 (6) hot-molding step of molding the solid reduced iron and the char without being substantially cooled.    
     
     
         14 : A molten iron producing method according to  claim 1 , wherein the temperatures of the solid reduced iron and the char are 500° C. to 1100° C. in the step (3).  
     
     
         15 : A molten iron producing method according to  claim 1 , wherein the following steps (7) to (9) are provided instead of the step (3): 
 (7) hot-classifying step of classifying the solid reduced iron and the char into coarse particles and fine particles without being substantially cooled after taking the solid reduced iron and the char together from the moving hearth type reducing furnace,    (8) coarse particle charging step of gravitationally charging the coarse particles into the iron-melting furnace, and    (9) fine particles injection step of charging the fine particles into the iron-melting furnace by injection.    
     
     
         16 : A molten iron producing method according to  claim 15 , wherein the temperature of the coarse particles is 500° C. to 100° C. in the step (8).  
     
     
         17 : A molten iron producing method according to  claim 1 , wherein the solid reduced iron and the char are charged into the iron-melting furnace from above without being substantially cooled in the step (3).  
     
     
         18 : A molten iron producing method according to  claim 17 , wherein the char is charged into the iron-melting furnace together with the solid reduced iron and/or auxiliary raw material and other charged materials in the step (3).  
     
     
         19 : A molten iron producing method according to  claim 17 , wherein the char and the solid reduced iron are discharged from the moving hearth type reducing furnace, stored in a container, conveyed from the container to a hopper disposed above the iron-melting furnace and consequently charged into the iron-melting furnace without being substantially cooled by being intermittently dispensed from the hopper in the step (3).  
     
     
         20 : A molten iron producing method according to  claim 17 , wherein the char and the solid reduced iron are discharged from the moving hearth type reducing furnace, temporarily stored in a hopper disposed above the iron-melting furnace and consequently charged into the iron-melting furnace without being substantially cooled by being intermittently dispensed from the hopper in the step (3).  
     
     
         21 : A molten iron producing method according to  claim 17 , wherein a rate of blowing the oxygen-containing gas into the iron-melting furnace is reduced at the time of charging the char in the step (3).  
     
     
         22 : A molten iron producing method according to  claim 21 , wherein the rate of blowing the oxygen-containing gas into the iron-melting furnace at the time of charging the char is 80% or less of the one when the char is not charged.  
     
     
         23 : A molten iron producing method according to  claim 21 , wherein a plurality of lances are provided to blow the oxygen-containing gas, and the blowing rate from some of the lances is reduced or the blowing therefrom is stopped.  
     
     
         24 : A molten iron producing apparatus constructed by combining a moving hearth type reducing furnace and an iron-melting furnace, comprising the following means (1) to (5): 
 (1) bedding carbonaceous material charging means for charging a bedding carbonaceous material onto a hearth of the moving hearth type reducing furnace;    (2) raw material charging means for placing carbonaceous-material composite agglomerates containing a powdery iron oxide source and a powdery carbonaceous reducing agent on the bedding carbonaceous material;    (3) heating means for heating and reducing the carbonaceous-material composite agglomerates to solid reduced iron and heating and drying the bedding carbonaceous material by distillation into char while the hearth is moved inside the moving hearth type reducing furnace;    (4) melting furnace charging means for charging the solid reduced iron and the char into the iron-melting furnace from above without being substantially cooled, at least the char being intermittently charged; and    (5) oxygen blowing means for blowing an oxygen-containing gas into the iron-melting furnace to melt the solid reduced iron into the molten iron.    
     
     
         25 : A molten iron producing apparatus constructed by combining a moving hearth type reducing furnace and an iron-melting furnace, comprising the following means (1) to (6): 
 (1) bedding carbonaceous material charging means for charging a bedding carbonaceous material onto a hearth of the moving hearth type reducing furnace;    (2) raw material charging means for placing carbonaceous-material composite agglomerates containing a powdery iron oxide source and a powdery carbonaceous reducing agent on the bedding carbonaceous material;    (3) heating means for heating and reducing the carbonaceous-material composite agglomerates into solid reduced iron and heating and drying the bedding carbonaceous material by distillation while the heat is moved inside the moving hearth type reducing furnace;    (4) reduced iron containing means for containing the solid reduced iron and the char discharged from the moving hearth type reducing furnace without being substantially cooled;    (5) reduced iron storing means disposed above the iron-melting furnace for temporarily storing the solid reduced iron and the char conveyed from the reduced iron containing means and including intermittent dispensing means for intermittently dispensing and charging the solid reduced iron and the char into the iron-melting furnace without being substantially cooled; and    (6) oxygen blowing means for blowing an oxygen-containing gas into the iron-melting furnace to melt the solid reduced iron into the molten iron.    
     
     
         26 : A molten iron producing apparatus constructed by combining a moving hearth type reducing furnace and an iron-melting furnace, comprising the following means (1) to (5): 
 (1) bedding carbonaceous material charging means for charging a bedding carbonaceous material onto a hearth of the moving hearth type reducing furnace;    (2) raw material charging means for placing carbonaceous-material composite agglomerates containing a powdery iron oxide source and a powdery carbonaceous reducing agent on the bedding carbonaceous material;    (3) heating means for heating and reducing the carbonaceous-material composite agglomerates into solid reduced iron and heating and drying the bedding carbonaceous material by distillation while the heat is moved inside the moving hearth type reducing furnace;    (4) reduced iron storing means for temporarily storing the solid reduced iron and the char discharged from the moving hearth type reducing furnace, the reduced iron storing means including intermittent dispensing means for intermittently dispensing and charging the solid reduced iron and the char into the iron-melting furnace without being substantially cooled; and    (5) oxygen blowing means for blowing an oxygen-containing gas into the iron-melting furnace to melt the solid reduced iron into the molten iron.    
     
     
         27 : A molten iron producing apparatus according to  claim 24 , wherein a baffle plate for suppressing the scattering of the char into an exhaust gas is provided between a charging portion for the char and a discharging portion for discharging the exhaust gas from the iron-melting furnace at a ceiling portion of the iron-melting furnace.  
     
     
         28 : A molten iron producing apparatus according to  claim 24 , wherein guiding means for guiding the char to the outer surface of molten metal in the iron-melting furnace is provided at the charging portion for the char.  
     
     
         29 : A molten iron producing apparatus according to  claim 25 , wherein a baffle plate for suppressing the scattering of the char into an exhaust gas is provided between a charging portion for the char and a discharging portion for discharging the exhaust gas from the iron-melting furnace at a ceiling portion of the iron-melting furnace.  
     
     
         30 : A molten iron producing apparatus according to  claim 26 , wherein a baffle plate for suppressing the scattering of the char into an exhaust gas is provided between a charging portion for the char and a discharging portion for discharging the exhaust gas from the iron-melting furnace at a ceiling portion of the iron-melting furnace.  
     
     
         31 : A molten iron producing apparatus according to  claim 25 , wherein guiding means for guiding the char to the outer surface of molten metal in the iron-melting furnace is provided at the charging portion for the char.  
     
     
         32 : A molten iron producing apparatus according to  claim 26 , wherein guiding means for guiding the char to the outer surface of molten metal in the iron-melting furnace is provided at the charging portion for the char.