Method for producing granular iron

Abstract

A method for producing granular iron comprising: charging agglomerates formed from a raw material mixture containing an iron oxide-containing substance and a carbonaceous reducing agent onto a carbonaceous material spread on a hearth of a furnace; and heating the agglomerates to thereby reduce and melt iron oxides in the agglomerates, wherein the temperature of the agglomerates in the furnace is set in a range between 1200° C. and 1500° C.; the oxygen partial pressure in atmospheric gas under which the agglomerates are heated is set to 2.0×10 −13 atm or more at standard state; and the linear speed of the atmospheric gas in the furnace is set to 4.5 cm/second or more.

1 . A method for producing granular iron, comprising:
 charging an agglomerate formed from a raw material mixture comprising an iron oxide comprising substance and a carbonaceous reducing agent onto a carbonaceous material spread on a hearth of a furnace; and   heating the agglomerate to thereby reduce and melt at least one iron oxide in the agglomerate, wherein   a temperature of the agglomerate in the furnace is in a range between 1200° C. and 1500° C.,   an oxygen partial pressure in atmospheric gas under which the agglomerate is heated is to 2.0×10 −13  atm or more at standard state, and   a linear speed of the atmospheric gas in the furnace is 4.5 cm/second or more.   
     
     
         2 . The method of  claim 1 , wherein a composition of the raw material mixture is adjusted so that a percentage of an amount of fixed carbon comprised in the carbonaceous reducing agent is in a range between 98 mass % and 102 mass % with respect to an amount of fixed carbon needed to reduce the at least one iron oxide. 
     
     
         3 . The method of  claim 1 , wherein a composition of the raw material mixture is adjusted so that a basicity of slag subgenerated in reducing the at least one iron oxide is in a range between 1.0 and 1.6. 
     
     
         4 . The method of  claim 1 , wherein a percentage of an amount of fixed carbon comprised in the carbonaceous reducing agent is in a range between 98 mass % and 100 mass % with respect to an amount of fixed carbon needed to reduce the at least one iron oxide. 
     
     
         5 . The method of  claim 1 , wherein the linear speed of the atmospheric gas is 5.4 cm/second or less (including 0 cm/second) until the at least one iron oxide begins to melt, and
 the linear speed of the atmospheric gas is 4.5 cm/second or more after the at least one iron oxide begins to melt.   
     
     
         6 . The method of  claim 1 , wherein a percentage of an amount of fixed carbon comprised in the carbonaceous material which is spread on the hearth is in a range between 2 mass % and 5 mass % with respect to an amount of fixed carbon needed to reduce the at least one iron oxide, and
 a maximum particle size of the carbonaceous material is 2 mm or less.   
     
     
         7 . The method of  claim 1 , wherein the agglomerate size (maximum diameter) is 50 mm or smaller. 
     
     
         8 . The method of  claim 1 , wherein the agglomerate size (maximum diameter) is 5 mm or larger. 
     
     
         9 . The method of  claim 7 , wherein the agglomerate size (maximum diameter) is 5 mm or larger. 
     
     
         10 . The method of  claim 1 , wherein the temperature of the agglomerate in the furnace is in a range between 1250° C. and 1500° C. 
     
     
         11 . The method of  claim 1 , wherein the temperature of the agglomerate in the furnace is in a range between 1200° C. and 1450° C. 
     
     
         12 . The method of  claim 1 , wherein the temperature of the agglomerate in the furnace is in a range between 1250° C. and 1450° C. 
     
     
         13 . The method of  claim 1 , wherein the oxygen partial pressure of the atmospheric gas under which the agglomerate is heated is 2.8×10 −13  atm or more at standard state. 
     
     
         14 . The method of  claim 1 , wherein the oxygen partial pressure of the atmospheric gas under which the agglomerate is heated is 4.8×10 −13  atm or less at standard state. 
     
     
         15 . The method of  claim 1 , wherein the oxygen partial pressure of the atmospheric gas under which the agglomerate is heated is 4.0×10 −13  atm or less at standard state. 
     
     
         16 . The method of  claim 13 , wherein the oxygen partial pressure of the atmospheric gas under which the agglomerate is heated is 4.8×10 −13  atm or less at standard state. 
     
     
         17 . The method of  claim 13 , wherein the oxygen partial pressure of the atmospheric gas under which the agglomerate is heated is 4.0×10 −13  atm or less at standard state. 
     
     
         18 . The method of  claim 1 , wherein the linear speed of the atmospheric gas in the furnace is 5 cm/second or more. 
     
     
         19 . The method of  claim 1 , wherein the linear speed of the atmospheric gas in the furnace is 13.5 cm/second or less. 
     
     
         20 . The method of  claim 1 , wherein the linear speed of the atmospheric gas in the furnace is 9 cm/second or less.