Carbon-material-containing iron oxide briquette composition, method for producing the same, and method for producing direct reduced iron using the same

Abstract

Disclosed is a carbon-material-containing iron oxide briquette composition that, when obtaining direct reduced iron by heating in a moving hearth reduction furnace, does not turn into powder in the furnace leading to an accumulation of powder, and reliably prevents the obtained direct reduced iron from turning into powder during conveyance, decreasing yield. Further disclosed are a method for producing same, and a method for producing direct reduced iron using same. The carbon-material-containing iron oxide briquette composition is characterized by: the solidus temperature that is of an Al2O3-CaO—SiO2 ternary system slag in said briquette composition and that is determined by the amount of contained Al2O3, CaO, and SiO2 being no greater than 1300 DEG C.; and having an amount of combined carbon material such that the carbon remaining in the direct reduced iron produced by heat treating said briquette composition in the aforementioned moving hearth reduction furnace at a temperature above the aforementioned solidus temperature and below the liquidus temperature of the aforementioned ternary system slag being no more than 6 mass %.

1 : A carbon-material-containing iron oxide briquette composition, comprising a blended carbon material,
 wherein a solidus temperature of an Al 2 O 3 —CaO—SiO 2  ternary slag that is determined from a content of Al 2 O 3 , CaO, and SiO 2  in the briquette composition is 1,300° C. or lower, and   wherein residual carbon in direct reduced iron produced by heat-treating the briquette composition in a moving hearth reduction furnace at a temperature higher than the solidus temperature and lower than a liquidus temperature of the ternary slag is 6% by mass or less.   
     
     
         2 : A method for producing a carbon-material-containing iron oxide briquette composition, the method comprising
 adjusting a blending ratio of an iron oxide-containing material, a carbon material, and an auxiliary material to have a solidus temperature of an Al 2 O 3 —CaO—SiO 2  ternary slag that is determined from a content of Al 2 O 3 , CaO, and SiO 2  in the briquette composition at 1,300° C. or lower and to obtain 6% by mass or less of residual carbon in direct reduced iron by produced by heat-treating the briquette composition in a moving hearth reduction furnace at a temperature higher than the solidus temperature and lower than a liquidus temperature of the ternary slag at.   
     
     
         3 : The method for producing the carbon-material-containing iron oxide briquette composition according to  claim 2 , wherein the auxiliary material used is at least one of a calcium oxide-containing substance and a silicon dioxide-containing substance. 
     
     
         4 : A method for producing direct reduced iron, the method comprising
 heat-treating the carbon-material containing iron oxide briquette composition according to  claim 1 ,   adjusting the heat treatment temperature in a range of from higher than the solidus temperature and lower than the liquidus temperature,   wherein a carbon use efficiency η c  defined by the following equation ranges from 0.08 to 0.12:
   η c =NCO 2 /(NCO+NCO 2 ),  Equation
 
   wherein NCO and NCO 2  are a total molar quantity of CO and a total molar quantity of CO 2 , respectively, and   wherein the NCO and the NCO 2  are generated from the carbon-material-containing iron oxide briquette composition during the heat treatment.   
     
     
         5 : A carbon-material-containing iron oxide briquette composition, comprising a pre-melt slag, wherein a pre-melt slag solidus temperature T S·P  of an Al 2 O 3 —CaO—SiO 2  ternary slag that is determined from a content of Al 2 O 3 , CaO, and SiO 2  in the briquette composition is 1,300° C. or lower. 
     
     
         6 : The carbon-material-containing iron oxide briquette composition according to  claim 5 , wherein the pre-melt slag solidus temperature T S·P  is 1,200° C. or lower. 
     
     
         7 : The carbon-material-containing iron oxide briquette composition according to  claim 5 , wherein the pre-melt slag is at least one of a blast furnace slag and a steelmaking slag. 
     
     
         8 : The carbon-material-containing iron oxide briquette composition according to  claim 6 , wherein the pre-melt slag is at least one of a blast furnace slag and a steelmaking slag. 
     
     
         9 : A method for producing the carbon-material-containing iron oxide briquette composition according to  claim 5 , comprising:
 adjusting a blending ratio of the pre-melt slag,   wherein a total-slag solidus temperature T S·S  of the Al 2 O 3 —CaO—SiO 2  ternary slag that is determined from a content of Al 2 O 3 , CaO, and SiO 2  in the briquette composition is 1,300° C. or lower,   wherein direct reduced iron is produced by heat-treating the briquette composition in a moving hearth reduction furnace at a heat treatment temperature higher than a total-slag solidus temperature T S·S  and lower than a total-slag liquidus temperature T L·S  of the Al 2 O 3 —CaO—SiO 2  ternary slag that is determined from the content of Al 2 O 3 , CaO, and SiO 2  in the briquette composition,   wherein a melt ratio of the Al2O3-CaO—SiO2 ternary slag in the direct reduced iron is in a range of from 1% to 20%, and   wherein the melt ratio of the Al 2 O 3 —CaO—SiO 2  ternary slag in the direct reduced iron is defined as a mass ratio of a portion of the Al 2 O 3 —CaO—SiO 2  ternary slag in the direct reduced iron to the direct reduced iron, the portion being converted into a liquid phase at the heat treatment temperature.   
     
     
         10 : A method for producing the carbon-material-containing iron oxide briquette composition according to  claim 6 , comprising adjusting a blending ratio of the pre-melt slag,
 wherein a total-slag solidus temperature T S·S  of the Al 2 O 3 —CaO—SiO 2  ternary slag that is determined from the content of Al 2 O 3 , CaO, and SiO 2  in the briquette composition is 1,200° C. or lower,   wherein direct reduced iron is produced by heat-treating the briquette composition in a moving hearth reduction furnace at a heat treatment temperature higher than a total-slag solidus temperature T S·S  and lower than a total-slag liquidus temperature T L·S  of the Al 2 O 3 —CaO—SiO 2  ternary slag that is determined from the content of Al 2 O 3 , CaO, and SiO 2  in the briquette composition   wherein a melting ratio of the Al 2 O 3 —CaO—Si 2 O in ternary slag in the direct reduced iron is in a range of from 1% to 20%, and   wherein the melt ratio of the Al 2 O 3 —CaO—SiO 2  ternary slag in the direct reduced iron is defined as the mass ratio of a portion of the Al 2 O 3 —CaO—SiO 2  ternary slag in the direct reduced iron to the direct reduced iron, the portion being converted into a liquid phase at the heat treatment temperature.   
     
     
         11 : A method for producing direct reduced iron, comprising heat-treating the carbon-material-containing iron oxide briquette composition according to  claim 5 , adjusting the heat treatment temperature in a range of from higher than a total-slag solidus temperature T S·S  to lower than a total-slag liquidus temperature T L·S ,
 wherein a carbon use efficiency η c  defined by the following equation ranges from 0.08 to 0.12 to obtain direct reduced iron with a carbon content of 6% by mass or less:
   η c =NCO 2 /(NCO+NCO 2 ),  Equation
 
   wherein NCO and NCO 2  are a total molar quantity of CO and a total molar quantity of CO 2 , respectively, and   wherein the NCO and NCO 2  are generated from the carbon-material-containing iron oxide briquette composition during the heat treatment.   
     
     
         12 : A method for producing direct reduced iron, comprising heat-treating the carbon-material-containing iron oxide briquette composition according to  claim 9  in a moving hearth reduction furnace, adjusting the heat treatment temperature in a range of from higher than a total-slag solidus temperature T S·S  to lower than a total-slag liquidus temperature T L·S ,
 wherein a carbon use efficiency η c  defined by the following equation ranges from 0.08 to 0.12 to obtain direct reduced iron with a carbon content of 6% by mass or less:
   η c =NCO 2 /(NCO+NCO 2 ),  Equation
 
 
 wherein NCO and NCO 2  are a total molar quantity of CO and a total molar quantity of CO 2 , respectively, and 
 wherein the NCO and NCO 2  are generated from the carbon-material-containing iron oxide briquette composition during the heat treatment. 
 
     
     
         13 : A method for producing direct reduced iron, comprising heat-treating the carbon-material-containing iron oxide briquette composition according to  claim 10  in a moving hearth reduction furnace, adjusting the heat treatment temperature in a range of from higher than a total-slag solidus temperature T S·S  to lower than a total-slag liquidus temperature T L·S ,
 wherein a carbon use efficiency η c  defined by the following equation ranges from 0.08 to 0.12 to obtain direct reduced iron with a carbon content of 6% by mass or less:
   η c =NCO 2 /(NCO+NCO 2 ),  Equation
 
 
 wherein NCO and NCO 2  are a total molar quantity of CO and the total molar quantity of CO 2 , respectively, and 
 wherein the NCO and the NCO 2  are generated from the carbon-material-containing iron oxide briquette composition during the heat treatment. 
 
     
     
         14 : A direct reduced iron obtained by the method according to  claim 11 . 
     
     
         15 : A direct reduced iron obtained by the method according to  claim 12 . 
     
     
         16 : A direct reduced iron obtained by the method according to  claim 13 . 
     
     
         17 : A direct reduced iron obtained by the method according to  claim 4 .