Abstract:
A method for producing pig iron by direct processing of ferrotitania sands, by the steps of:
       (a) mixing carbonaceous reductant, a fluxing agent, and a binder with titanium-containing materials selected from iron sands, metallic oxides, and/or iron ore concentrates, to form a mixture;   (b) forming agglomerates from the mixture   (c) introducing the agglomerates to a melting furnace;   (d) melting the agglomerates at a temperature of from 1500 to 1760 C and forming hot metal with a slag thereon;   (e) removing the slag;   (f) tapping the hot metal; and   (g) recovering the titanium and vanadium values.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority of the following applications:
     PCT Application PCT/US2008/010122 filed: 12 Aug. 2008, U.S. Provisional Patent Application Ser. No. 60/967,347, filed 4 Sep. 2007;   PCT Application PCT\US 2008\010124, filed: 12 Aug. 2008, U.S. Provisional Patent Application Ser. No. 60/997,616, filed: 4 Oct. 2007   PCT Application PCT\US 2008\010123, filed 12 Aug. 2008, and U.S. Provisional Patent Application Ser. No. 61/126,915, filed 8 May 2008.   

    
    
     FIELD OF THE INVENTION 
     The present invention relates to a method and apparatus for direct processing of ferrotitania ores and ferrotitania sands to produce pig iron employing the concept of combined cycle power generation using a gas combustion turbine. 
     SUMMARY OF THE INVENTION 
     Ferrotitania sands include vanadium compounds, whereas other ferrotitania ores may contain only a trace or no vanadium values. Iron sands, ferrotitania ores, ferrotitania sands and/or beach sands are cold briquetted to form compact agglomerates containing a carbonaceous material such as coal, petcoke, char, etc., iron oxide (either already contained in the ore or added separately as iron ore fines, mill scale, metalized iron fines, etc., to the mix), fluxes such as lime, silica, spar, etc., and binder. An excess amount of carbon is present in the agglomerate not only to react with the titania or manganese compounds but also to reduce the iron oxide, manganese oxide, etc., so that the melter atmosphere is predominantly CO with some liberated H 2  from the volatilization of the carbonaceous material such as coal. Sulfur in the system is free to combine with flux additions (CaO, MgO, CaF 2 , etc.) to form a sulfur-containing liquid slag. 
     OBJECTS OF THE INVENTION 
     The principal object of the present invention is to provide a method of producing pig iron from ferrotitania ores and/or ferrotitania sands. 
     Another object of the invention is to provide a method of recovering vanadium oxide and titanium oxides from ferro-titania ores and/or sands. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other objects will become more readily apparent by referring to the following detailed description and the appended drawings in which: 
         FIG. 1  is a schematic flowsheet of the process, wherein the reference numerals refer to the items as indicated below. 
         FIG. 2  is a schematic flowsheet for treating hot metal to form vanadium and titanium oxides. 
         FIG. 3  is a schematic depiction of a slag treatment to recover vanadium and titanium oxides. 
         FIG. 4  is a schematic flowsheet showing an alternative to the invented process in which feed materials are preheated with or without agglomeration in a heater such as a rotary kiln, then fed to the melting furnace. 
     
    
    
     REFERENCE NUMERALS REFER TO 
     
         
           10 —iron sands, or ore concentrates—100% of which pass 10 mesh, Tyler Standard (1.70 mm), preferably 100% passing 100 mesh Tyler Standard (150 microns) 
           12 —metallic iron fines, and iron oxide fines—100% minus 25 mm 
           14 —prepared reductant, such as coal, petroleum coke, char, etc., 100% passing 25 mm, preferably 100% passing 100 mesh Tyler Standard (150 microns) 
           16 —fluxing agents—CaO, MgO, CaF 2 , SiO 2 , Al 2 O 3 —100% minus 25 mm 
           18 —binder such as cellulose, bentonite, molasses, starch—either organic or inorganic 
           20 —recycled fines 
           22 —mixer 
           24 —briquetter/agglomerator (size 8 to 100 cc) 
           26 —water addition (preferably spray) 
           28 —pelletizer—drum or disc type 
           30 —screens—dry or roller type 
           32 —greenball dryer (dries pellets to 1% moisture or less) 
           34 —agglomerate (briquette) curing/storage hoppers 
           36 —feed loss in weight system 
           37 —pressure seal 
           38 —electric furnace or melter &gt;1500 C 
           40 —ladles A and B for liquid iron 
           42 —slag addition for desulfurization 
           44 —pig iron caster 
           45 —pig iron 
           46 —slag ladle (C) 
           48 —slag disposal/quench bunker 
           50 —recycle slag 
           52 —offgas cooling scrubber/bag filter 
           54 —compressor 
           56 —stack with combustion to convert CO &amp; H 2  to CO 2  &amp; H 2 O 
           58 —high pressure compressor (100-350 psig) 
           60 —optional gas stream, sulfur removal system, such as Selexol 
           62 —high pressure gas accumulator tank 
           64 —gas turbine (exit gas temp 600-700 C) 
           66 —generator 
           68 —waste heat boiler exchanger 
           70 —high pressure steam turbine 
           72 —generator 
           74 —boiler closed circuit water conduit 
           76 —pump 
           78 —optional chiller upstream of gas sulfur removal system 
           80 —optional supplemental fuel gas addition. 
           84 —heater, preferably direct or indirect heated rotary kiln type 
       
    
     DETAILED DESCRIPTION 
     As shown in  FIG. 1 , feed materials are introduced to mixer  22 , the input materials consisting of: iron sands, metallic oxides, and/or beach sands  10 , 100% of which pass 10 mesh, Tyler Standard (1.70 mm), preferably 100% passing 100 mesh (150 microns); prepared reductant  14 , such as coal, petroleum coke, char, or other carbonaceous material, 100% passing 25 mm, preferably 100% passing 100 mesh Tyler Standard (150 microns); slag formers or fluxing agents  16 , such as MgO, CaO, Al 2 O 3 , CaF 2  (fluorspar), SiO 2 , or combinations thereof, 100% of which are minus 25 mm; an organic or inorganic binder  18 , such as cellulose, bentonite, molasses, or starch; recycled fines  20 , and water  26  as needed. Optionally, metallic iron fines, and/or iron oxide fines  12 , 100% of which are minus 25 mm, may be added to the feed materials. 
     The feed materials are mixed in mixer  22 , then formed into agglomerates in briquetter/agglomerator  24 , or in pelletizer  28  such as a drum or disc type pelletizer, the resulting agglomerates being in the form of uniformly sized briquettes or pellets, preferably from about 8 cc to 100 cc in size. The agglomerates are screened by sizer  30 , which may be a dry screen or a roller type screen, the undersized material being returned to the agglomerator  24  or to the mixer  22 . 
     Alternatively, material D 1  exiting mixer  22  can be fed to a heater  84  for the purpose of preheating the mixture to about 500 to 1200 C, devolatizing the reductant, and producing a preheated charge to electric furnace melter  38 . Pre-reduction of the iron oxide will occur to levels ranging from about 0 to 90%. Agglomerated material D 2  can also be preheated, if desired, prior to feeding the material to the melter through the pressure seal  37 . The heater  84  can be an indirectly heated rotary kiln, or a direct fired kiln, as shown, with off-gases being recycled. The heater  84  can be refractory lined, or it can be unlined, as desired. 
     Screened pellets from pelletizer  28  are dried in a greenball dryer  32  to 1% or less moisture content. The agglomerates are cured and/or stored in hoppers  34 , then fed into an electric melting furnace  38  through a pressure-sealed feed system  37 . Feed to the melter is through a pressure-sealed system, a conventional feed leg as is used with a shaft furnace, or through lock valves. Melter off-gas is treated, cooled and scrubbed in cooler-scrubber  52 . Stack  56  includes combustion means for converting carbon monoxide and hydrogen to carbon dioxide and water vapor. The melter  38  operates normally under a slight positive pressure. Tapping is done on an intermittent basis. 
     Optionally one or more additional feed materials may be introduced through a pressure seal directly to the melter  38 , such additional materials being selected from a group including metallic iron fines and iron oxide fines  12 , 100% of which are minus 25 mm; prepared reductant  14 , such as coal, petroleum coke, or other carbonaceous material, 100% of which are minus 25 mm, preferably 50% of which pass 10 mesh; slag formers or fluxing agents  16 , such as MgO, CaO, Al 2 O 3 , CaF 2  (fluorspar) and SiO 2 , 100% of which are minus 25 mm; and recycled slag  50 . 
     Liquid iron is removed from the melter into ladles  40  and may be cast into pig iron  45  at pig caster  44 , as shown. Additional fluxing agents  16  may be added to the hot metal as it is discharged into ladles  40  (A and B). A desulfurizing slag addition  42  is introduced into the hot metal ladle shown as B, the addition being CaO, MgO, Ca/Mg wire, or a mixture thereof. 
     In the event that vanadium or titanium reports to the hot metal, the hot metal in ladle  40 A is treated as shown in  FIG. 2  by oxidation to make V 2 O 5  and TiO 2 . 
     The hot metal from ladle  40  B is cast into pigs  45  in pig caster  44  as shown in  FIG. 1 . 
     The slag from the furnace  38  is drawn off into ladle C is treated as shown in  FIG. 3  by quenching and grinding and electrostatic separation to recover V 2 O 5  and TiO 2 . The slag  50  from the ladle  46  C may be recycled to the melter  38 , if desired. 
     The slag may include MnO, Cr 2 O 5 , V 2 O 5 , and TiO 2 , which may be recovered by quenching and grinding the tapped slag, then separating the MnO, Cr 2 O 5 , V 2 O 5 , and TiO 2 , by high intensity electrostatic separation and producing a concentrate that can be recycled to the melting furnace. Selective solvent extraction may be utilized to aid in separating the MnO, Cr 2 O 5 , V 2 O 5 , and TiO 2 . 
     The operating parameters of the invented process are as follows: 
     
       
         
               
               
               
             
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Normal Range 
                 Maximum 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Iron Beach Sands 
                 1500-1600 C. 
                 1700-1760 C. 
               
               
                   
                 Ferro-Titania 
               
               
                   
                 Melter Temp. 
               
               
                   
                 Melter Off-Gas 
                 500-1500 C. 
                 1200-1650 C. 
               
               
                   
                 Melter Off-Gas 
                 0-0.2″ H 2 O gauge 
                 &lt;15″ H 2 O gauge 
               
               
                   
                 Pressure 
               
               
                   
                 Gas Accumulator 
                 100-350 psig 
               
               
                   
                 Off-Gas Pressure 
               
               
                   
                 Gas Turbine 
                 750-900 C. 
                 &lt;1000 C. 
               
               
                   
                 Combined Product 
               
               
                   
                 Exit Temp. 
               
               
                   
                   
               
             
          
         
       
     
     Offgas exiting the furnace  38  is cleaned in cooler-scrubber  52 , is compressed in compressor  54 , and may be used as combustion fuel in gas turbine  64 . Gas turbine  64  drives generator  66  to produce electricity, and sensible heat contained in offgas exiting the gas turbine is recovered in a waste heat recovery boiler system  68 . The waste heat boiler system steam cycle could be a “Kalina” cycle based on using 70% ammonia and 30% water for better range processing and heat recovery efficiency at lower gas temperatures. Ammonia/water boiling occurs over a range of temperatures rather that at a specific temperature and pressure. Steam produced by the waste heat boiler system  68  is then used to drive a steam turbine  70  and generator  72  to produce additional electricity. One of the principal objectives of the invention is to produce all the required electricity to accommodate the process and operate the plant so as to be electricity self sufficient. In the event that insufficient fuel is produced by the melter in the form of off-gas, additional fuel gas  80 , such as natural gas, supplements the fuel gas feed to gas accumulator tank  62  and turbine  64 . 
     Gas from the compressor  54  can be treated for sulfur removal in an optional sulfur removal system  60 , which may require an optional chiller  78  upstream of the sulfur gas removal system. 
     The agglomerate curing or storage hoppers  34  can be preheaters, such as a shaft or vessel preheater, as desired. When used as preheaters, off-gas from the electric furnace or melter  38  can be utilized as shown in  FIG. 1 . The off-gas is returned to the gas handling system at cooler-scrubber  52 . 
     SUMMARY OF THE ACHIEVEMENT OF THE OBJECTS OF THE INVENTION 
     From the foregoing, it is readily apparent that I have invented an improved method of producing pig iron from ferrotitania sands, as well as a method of recovering vanadium oxide and titanium oxides from ferro-titania sands. 
     It is to be understood that the foregoing description and specific embodiments are merely illustrative of the best mode of the invention and the principles thereof, and that various modifications and additions may be made to the apparatus by those skilled in the art, without departing from the spirit and scope of this invention.