Iron ore briquetting

Abstract

A method of producing an iron ore briquette that is suitable for use as a blastfurnace or other direct reduction furnace feedstock which includes the steps of: (1) mixing ore and a flux to form an ore/flux mixture (2) pressing the ore/flux mixture into a green briquette using a low roll pressure; and (3) indurating the green briquette to form a fired briquette.

1 . A method of producing an iron ore briquette that is suitable for use as a blast furnace or other direct reduction furnace feedstock which includes the steps of: 
 (a) mixing ore and a flux to form an ore/flux mixture;    (b) pressing the ore/flux mixture into a green briquette using a low roll pressure; and    (c) indurating the green briquette to form a fired briquette.    
     
     
         2 . The method defined in  claim 1  wherein the low roll pressure is generated by a roll pressure force that is sufficient to produce briquettes having a green compressive strength of at least 2 kgf.  
     
     
         3 . The method defined in  claim 2  wherein the green compressive strength is at least 4 kgf.  
     
     
         4 . The method defined in  claim 2  wherein the green compressive strength is at least 5 kgf.  
     
     
         5 . The method defined in  claim 2  wherein the green compressive strength is 5-30 kgf.  
     
     
         6 . The method defined in  claim 2  wherein the green compressive strength is 15-30 kgf.  
     
     
         7 . The method defined in  claim 1  wherein the low roll pressure is generated by a roll pressing force of 10-140 kN/cm on the mixture of ore/flux.  
     
     
         8 . The method defined in  claim 7  wherein the roll pressing force is 10-60 kN/cm.  
     
     
         9 . The method defined in  claim 7  wherein the roll pressing force is 10-40 kN/cm.  
     
     
         10 . The method defined in  claim 1  wherein step (a) includes mixing ore having a predetermined particle size distribution of ore particles and flux particles.  
     
     
         11 . The method defined in  claim 10  wherein the predetermined particle size distribution of ore particles that is mixed with flux in step (a) can be produced without grinding ore.  
     
     
         12 . The method defined in  claim 10  includes crushing and screening ore to form the predetermined particle size distribution that is mixed with flux in step (a).  
     
     
         13 . The method defined in  claim 10  wherein the top size of the predetermined particle size distribution of ore that is mixed with flux in step (a) is 4.0 mm or less.  
     
     
         14 . The method defined in  claim 13  wherein the top size is 3.5 mm or less.  
     
     
         15 . The method defined in  claim 13  wherein the top size is 3.0 mm or less.  
     
     
         16 . The method defined in  claim 13  wherein the top size is 2.5 mm or less.  
     
     
         17 . The method defined in  claim 13  wherein the top size is 1.5 mm or less.  
     
     
         18 . The method defined in  claim 10  wherein the predetermined particle size distribution of ore that is mixed with flux in step (a) includes less than 50% passing a 45 μm screen.  
     
     
         19 . The method defined in  claim 18  wherein the particle size distribution includes less than 30% passing the 45 μm screen.  
     
     
         20 . The method defined in  claim 18  wherein the particle size distribution includes less than 10% passing the 45 μm screen.  
     
     
         21 . The method defined in  claim 1  wherein the ore is a hydrated iron ore.  
     
     
         22 . The method defined in  claim 21  wherein the hydrated ore is a goethite-containing ore.  
     
     
         23 . The method defined in  claim 1  wherein the flux has a particle size distribution that is predominantly less than 100 μm.  
     
     
         24 . The method defined in  claim 23  wherein the particle size distribution of the flux includes more than 95% passing a 250 μm screen.  
     
     
         25 . The method defined in  claim 1  wherein the ore/flux mixture produced in step (a) is selected so that the basicity of the fired briquette is greater than 0.2.  
     
     
         26 . The method defined in  claim 25  wherein preferably the basicity is greater than 0.6.  
     
     
         27 . The method defined in  claim 1  wherein there is no binder in the ore/flux mixture.  
     
     
         28 . The method defined in  claim 1  wherein the method includes adjusting the water content of the ore prior to or during mixing step (a) to optimise briquette quality and product yield.  
     
     
         29 . The method defined in  claim 28  wherein the step of adjusting the water content of the ore includes adjusting the water content so that the moisture content of the ore/flux mixture is 2-12% by weight of the total weight of the ore/flux mixture.  
     
     
         30 . The method defined in  claim 28  wherein the step of adjusting the water content of the ore includes adjusting the water content so that the moisture content of the ore/flux mixture is 2-5% by weight of the total weight of the ore/flux mixture for ores that are dense hematite ores.  
     
     
         31 . The method defined in  claim 28  wherein the step of adjusting the water content of the ore includes adjusting the water content so that the moisture content of the ore/flux mixture is 4-8% by weight of the total weight of the ore/flux mixture for ores containing up to 50% geothite.  
     
     
         32 . The method defined in  claim 28  wherein the step of adjusting the water content of the ore includes adjusting the water content so that the moisture content of the ore/flux mixture is 6-12% by weight of the total weight of the ore/flux mixture for ores that are predominantly, ie contain more than 50%, goethite ores.  
     
     
         33 . The method defined in  claim 1  wherein pressing step (c) produces briquettes that are 10 cc or less in volume.  
     
     
         34 . The method defined in  claim 33  wherein pressing step (c) produces briquettes that are 8.5 cc or less in volume.  
     
     
         35 . The method defined in  claim 33  wherein pressing step (b) produces briquettes that are 6.5 cc or less in volume.  
     
     
         36 . The method defined in  claim 1  wherein indurating step (c) includes heating the briquette to a firing temperature with 40 minutes.  
     
     
         37 . The method defined in  claim 36  wherein indurating step (d) includes heating the briquette to a firing temperature within 35 minutes.  
     
     
         38 . The method defined in  claim 36  wherein indurating step (d) includes heating the briquette to the firing temperature within 30 minutes.  
     
     
         39 . The method defined in  claim 36  wherein step (c) includes heating the briquette to the firing temperature within 20 minutes.  
     
     
         40 . The method defined in  claim 36  wherein step (c) includes heating the briquette to the firing temperature within 15 minutes.  
     
     
         41 . The method defined in  claim 36  wherein the firing temperature is at least 1200° C.  
     
     
         42 . The method defined in  claim 41  wherein the firing temperature is at least 1260° C.  
     
     
         43 . The method defined in  claim 41  wherein the firing temperature is at least 1320° C.  
     
     
         44 . The method defined in  claim 41  wherein the firing temperature is at least 1350° C.  
     
     
         45 . The method defined in  claim 41  wherein the firing temperature is at least 1380° C.  
     
     
         46 . The method defined in  claim 1  wherein the fired briquette has a crush strength of at least 200 kgf.  
     
     
         47 . The method defined in  claim 46  wherein the fired briquette has a crush strength of at least 250 kgf.