Production of pig iron

Abstract

A method for producing pig iron by direct processing of iron-containing materials such as iron-containing sands, in which the iron-containing materials and carbonaceous reductant are mixed with a fluxing agent to form a mixture; briquettes or agglomerates are formed from the mixture; at least a portion of the agglomerates are preheated to a temperature of 750 to 1200° C. and are pre-reduced, then the preheated, pre-reduced agglomerates are introduced into the melting furnace; the agglomerates are melted at a temperature of from 1300 to 1760° C. and form hot metal with a slag thereon; the slag is removed and the hot metal is tapped as pig iron, and the off-gas from the smelter is used to operate a preheater for the agglomerates.

What is claimed is: 
     
         1 . A process for producing pig iron by direct processing of iron-containing materials, comprising the steps of:
 a. mixing iron-containing materials, carbonaceous reductant, and a fluxing agent to form a mixture;   b. forming agglomerates from said mixture;   c. introducing a portion of said agglomerates to an electric melting furnace as cold charge;   d. preheating and pre-reducing at least a portion of said agglomerates to a temperature of 750 to 1200° C., and introducing said preheated agglomerated to the melting furnace;   e. melting the agglomerates at a temperature of from 1300 to 1760° C. and forming hot metal with a slag thereon;   f. removing the slag;   g. tapping the hot metal as pig iron, and   h. recovering the heating value from the off-gas from the smelter.   
     
     
         2 . A process according to  claim 1 , further comprising screening the iron-containing materials to pass 80 mesh Tyler Standard. 
     
     
         3 . A process according to  claim 1  wherein said iron-bearing materials are iron sands. 
     
     
         4 . A process according to  claim 1 , further comprising introducing a binder into said mixture. 
     
     
         5 . A process according to  claim 1 , further comprising preventing substantially all air ingress to the melting furnace by providing a pressure seal. 
     
     
         6 . A process according to  claim 1 , further comprising forming hot off-gases in the melting furnace, cleaning and cooling the off-gases, and utilizing the cleaned off-gases as the fuel gas to preheat the preheated portion of the agglomerates. 
     
     
         7 . A process according to  claim 3 , wherein:
 100% of the iron-containing sands pass 10 mesh Tyler Standard (1.70 mm);   100% of the carbonaceous reductant is minus 25 mm; and   100% of the fluxing agent is minus 25 mm.   
     
     
         8 . A process according to  claim 1  wherein the carbonaceous reductant is selected from the group consisting of coal, coke, petroleum coke, and char. 
     
     
         9 . A process according to  claim 1 , wherein the fluxing agent is selected from the group consisting of CaO, MgO, CaF 2 , Al 2 O 3 , SiO 2 , and mixtures thereof. 
     
     
         10 . A process according to  claim 4 , wherein the binder is selected from the group consisting of cellulose, bentonite, molasses, starch or mixtures thereof. 
     
     
         11 . A process according to  claim 1 , further comprising maintaining a reducing atmosphere within said melting furnace. 
     
     
         12 . A process according to  claim 1 , further comprising recovering hot off gases from the preheater and passing them through a waste heat boiler to form steam, and utilizing the steam to drive a steam turbine and/or a generator to produce electricity. 
     
     
         13 . A process according to  claim 1 , wherein the preheater is a rotary hearth furnace. 
     
     
         14 . A process according to  claim 1  wherein the preheater is a tunnel furnace. 
     
     
         15 . A process according to  claim 1 , wherein the iron-containing sands contains titanium values which report to the slag, further comprising recovering the titanium values from the slag. 
     
     
         16 . A method for producing pig iron by direct processing of iron-containing sands, comprising the steps of:
 a. mixing iron-containing sands, carbonaceous reductant, and a fluxing agent to form a mixture;   b. forming agglomerates from said mixture;   c. preheating and pre-reducing at least a portion of said agglomerates to a temperature of 750 to 1200° C., and introducing said preheated agglomerated to a smelting furnace;   d. melting the agglomerates at a temperature of from 1300 to 1760° C. and forming hot metal with a slag thereon;   e. removing the slag; and   f. tapping the hot metal as pig iron.   
     
     
         17 . A method according to  claim 16 , further comprising forming an off-gas in the smelting furnace, removing the off-gas and recovering the heating value from the off-gas from the smelting furnace. 
     
     
         18 . A method according to  claim 16 , further comprising screening the sands to pass 80 mesh Tyler Standard. 
     
     
         19 . A method according to  claim 16 , further comprising introducing a binder into said mixture. 
     
     
         20 . A method according to  claim 16 , further comprising preventing substantially all air ingress to the melting furnace by providing a pressure seal. 
     
     
         21 . A method according to  claim 16 , further comprising forming and removing off-gases in the melting furnace, cleaning and cooling the removed off-gases, and utilizing the cleaned off-gases to preheat the preheated portion of the briquette charge. 
     
     
         22 . A method according to  claim 16 , further comprising introducing a portion of said agglomerates to the melting furnace as cold charge. 
     
     
         23 . A method according to  claim 16  wherein fuel for preheating said agglomerates is selected from the group consisting of natural gas, cleaned and cooled off-gas from the melting furnace, or a combination thereof. 
     
     
         24 . A method according to  claim 16 , wherein:
 100% of the iron-containing sands pass 10 mesh Tyler Standard (1.70 mm);   100% of the carbonaceous reductant is minus 25 mm; and   100% of the fluxing agent is minus 25 mm.   
     
     
         25 . A method according to  claim 16  wherein the carbonaceous reductant is selected from the group consisting of coal, coke, petroleum coke, and char. 
     
     
         26 . A method according to  claim 16 , wherein the fluxing agent is selected from the group consisting of CaO, MgO, CaF 2 , SiO 2 , Al 2 O 3 , and mixtures thereof. 
     
     
         27 . A method according to  claim 19 , wherein the binder is selected from the group consisting of cellulose, bentonite, molasses, starch or mixtures thereof. 
     
     
         28 . A method according to  claim 16 , further comprising maintaining a reducing atmosphere within said melting furnace. 
     
     
         29 . A method according to  claim 16 , further comprising recovering hot off gases from the preheater and passing them through a waste heat boiler to form steam, and utilizing the steam to drive a steam turbine and/or a generator to produce electricity. 
     
     
         30 . A method according to  claim 16 , wherein the preheater is a rotary hearth furnace. 
     
     
         31 . A method according to  claim 16  wherein the preheater is a tunnel furnace. 
     
     
         32 . A method according to  claim 16 , wherein the iron-containing sands contains titanium values which report to the slag, further comprising recovering the titanium values from the slag. 
     
     
         33 . A method according to  claim 21 , wherein the removed off-gases from the melting furnace are cooled to a temperature of from about 25° C. to about 1,200° C. 
     
     
         34 . A method according to  claim 16 , further comprising recovering TiO 2  from the slag by converting the titanium values to a salt by a medium temperature roast, dissolving the oxide in a solvent, then precipitating TiO 2  as a solid by solvent extraction.