Iron ore, 1.27

The process of extraction requires first smelting (to obtain the crude metal) and then refining. In smelting, iron ore (usually an oxide) is mixed with coke and limestone and heated, and hot air (often enriched with oxygen) is blown in from beneath (in a blast furnace). At the lower, hotter part of the furnace, carbon monoxide is produced and this is the essential reducing agent. The reduction reactions occurring may be represented for simplicity as ... 

Vanadium is found in about 65 different minerals among which are carnotite, roscoelite, vanadinite, and patronite, important sources of the metal. Vanadium is also found in phosphate rock and certain iron ores, and is present in some crude oils in the form of organic complexes. It is also found in small percentages in meteorites. 

It occurs in the minerals rutile, ilmenite, and sphene, and is present in titanates and in many iron ores. Titanium is present in the ash of coal, in plants, and in the human body. 

Gobalt occurs in the minerals cobaltite, smaltite, and erythrite, and is often associated with nickel, silver, lead, copper, and iron ores, from which it is most frequently obtained as a by-product. It is also present in meteorites. 

A2.6540-g sample of an iron ore known to contain 53.51% w/w Fe is dissolved in a small portion of concentrated HCl and diluted to volume in a 250-mL volumetric flask. A spectrophotometric method is used to determine the concentration of Fe in this solution, yielding results of 5840, 5770, 5650, and 5660 ppm. Determine whether there is a significant difference between the experimental mean and the expected value at a = 0.05. 

A sample of an impure iron ore is believed to be approximately 55% w/w Fe. The amount of Fe in the sample is to be determined gravimetrically by isolating it as Fe203. How many grams of sample should be taken to ensure that approximately 1 g of Fe203 will be isolated ... 

Acrylamide copolymers are effective iron ore pellet binders (118). When the ore slurry in water has a pH above 8, anionic polymers are effective. If the ore is acid washed to remove manganese, then a cationic polymer is effective. 

The basic flow sheet for the flotation-concentration of nonsulfide minerals is essentially the same as that for treating sulfides but the family of reagents used is different. The reagents utilized for nonsulfide mineral concentrations by flotation are usually fatty acids or their salts (RCOOH, RCOOM), sulfonates (RSO M), sulfates (RSO M), where M is usually Na or K, and R represents a linear, branched, or cycHc hydrocarbon chain and amines [R2N(R)3]A where R and R are hydrocarbon chains and A is an anion such as Cl or Br . Collectors for most nonsulfides can be selected on the basis of their isoelectric points. Thus at pH > pH p cationic surfactants are suitable collectors whereas at lower pH values anion-type collectors are selected as illustrated in Figure 10 (28). Figure 13 shows an iron ore flotation flow sheet as a representative of high volume oxide flotation practice. 

Fig. 13. Experimental iron ore flotation flow sheet (28) (-), forward flow (-----), return flow. Courtesy of USBM. Note the combination of flotation...

Pure iron is a silvery white, relatively soft metal and is rarely used commercially. Typical properties are Hsted in Table 1. Electrolytic (99.9% pure) iron is used for magnetic cores (2) (see Magnetic materials, bulk). Native metallic iron is rarely found in nature because iron which commonly exhibits valences of +2 and +3 combines readily with oxygen and sulfur. Iron oxides are the most prevalent form of iron (see Iron compounds). Generally, these iron oxides (iron ores) are reduced to iron and melted in a blast furnace. The hot metal (pig iron) from the blast furnace is refined in steelmaking furnaces to make steel... 

In the United States, the first ironworks was built at Jamestown, Virginia, in 1619. The Hammersmith furnace in Saugus, Massachusetts, built in 1645, operated until 1675. This early American ironworks has been restored and is called the Saugus Iron Works. Iron blast furnaces appeared in many locahties where there were deposits of iron ore. Small bodies of iron ore in New Jersey, Connecticut, Massachusetts, Pennsylvania, and New York formed the basis of many small colonial furnaces. 

Sources. Iron ore deposits were formed by many different processes, eg, weathering, sedimentation, hydrothermal, and chemical. Iron ores occur in igneous, metamorphic, and sedimentary deposits. Normally, as-mined iron ore contains 25 to 68% iron. 

The Utah deposit is located in southwestern Utah near Cedar City. The iron ore deposits are of contact metamorphic origin. The cmde ore contains 35 to 65% iron, primarily in the form of magnetite and goethite. Mining is done by the open pit method. The cmde ore is cmshed, screened at —75 mm (—200 mesh size) and shipped as lump ore containing 54% iron. The ore is rescreened at the steel mill to produce lump ore (10—64 mm) for the blast furnace and sinter feed (0—10 mm) for the sinter plant. 

Other countries that have large iron ore deposits include Brazil (Carajas and Quaddlatero Ferrifero deposits), AustraUa (Pilbara deposits), Ukraine (Krivi Rog deposit), Russia (Kursk deposit), Venezuela (Cerro BoHvar deposit), India (Bihar-Orissa, Hospet, Kudremukh, and Goa deposits). South Africa (Sishen and Thabazimbi deposits), and Sweden (Kimna, Svappavaara, and Malmberget deposits). A Hst of world iron ore production and reserves in 1992 by country is shown in Table 3. 

Annual world iron ore production has hovered around 9 to 9.75 x 10 t since the mid-1980s. International trade of iron ore peaked in 1980 at 4.24 X 10 t otherwise it has remained fairly steady in the range of3.6to4x 10 t/yr per year since the mid-1980s. The main exporting countries are Brazil, AustraUa, India, Canada, South Africa, Russia, Ukraine, and Venezuela. 

Iron ores of different characteristics and compositions can be blended to a more uniform composition. This can be accompHshed during handling operations involved in transporting ore to its point of use, or through special blending faciUties, such as stacking and reclaiming. 

Low intensity magnetic separators are used to upgrade iron ores containing magnetite. Dry separators are used for coarse (up to 100 mm in size) ore and wet separators are used for fine (—9.5 mm) ores. 

High intensity magnetic separators are used to upgrade iron ores containing hematite or ilmenite. Dry separators require ore that is finely sized and bone dry. They are dusty, expensive, and have a low capacity. Wet separators have larger capacity, are less dusty and can handle ore sizes up to 1 mm. 

Agglomeration. Iron ore concentrates are often too fine to be used directly in ironmaking processes therefore they must be agglomerated. 

The agglomerating methods typically used in the iron ore industry are pelletizing, sintering and, to a limited extent, briquetting and nodulizing (see Size enlargel nt). 

Direct Reduction. Direct reduction processes are distinguished from other ironmaking processes in that iron oxide is converted to metallic iron without melting. Because this product, called direct reduced iron (DRI), is soHd, it is most suitable for melting in an electric arc furnace (EAF) as a substitute for scrap (see Furnaces, electric). The briquetted form of DRI, hot briquetted iron (HBI) is used when the product is to be transported. Briquetting increases density and chemical stabiUty. The predominant direct reduction processes (MIDREX and HyL III) are based on natural gas as a fuel and reductant source. They are economically attractive in regions where natural gas is cheap and abundant, especially if iron ore is available nearby (see Iron BY DIRECT reduction). ... 

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