Iron metal, refining

The iron formed in a blast furnace, called pig iron, contains impurities that make the metal brittle. These include phosphorus and silicon from silicate and phosphate minerals that contaminated the original ore, as well as carbon and sulfur from the coke. This iron is refined in a converter furnace. Here, a stream of O2 gas blows through molten impure iron. Oxygen reacts with the nonmetal impurities, converting them to oxides. As in the blast furnace, CaO is added to convert Si02 into liquid calcium silicate, in which the other oxides dissolve. The molten iron is analyzed at intervals until its impurities have been reduced to satisfactory levels. Then the liquid metal, now in the form called steel, is poured from the converter and allowed to solidify. 

Some chemical processes use energy directly to drive the transformation. For example, the conversion of iron ore, iron oxide, to iron metal requires chemical energy to remove the oxygen atoms. In early times the iron ore was heated with charcoal in more recent times it is heated with refined coal (coke), but in both cases the result is conversion of coal or wood into carbon monoxide, which is toxic but can be burned to carbon dioxide to generate needed heat. There is now interest in devising processes that do not use carbon in this way, but use electrical energy to avoid the production of carbon oxides. 

In this process, molten iron is refined to steel by mp-hlowing oxygen at high pressure onto the surface of the metal through a waier-eooled lance contained in a tilling furnace. The oxidation of carhon. silicon, manganese. 

Iron has more uses and applications than any other metal. With world production of new iron reaching approximately 500 million tons a year, more than 90% of all metal refined is iron. Iron s uses are too numerous to list. From cars to buildings, to ships and... 

Wrought or 6ar iron is a fibrous, tough metal, freed in part from the impurities of cast iron by refining and puddling. 

Coalbrookdale in Shropshire, England, around the year 1773 and is said to have been a factor in initiating the Industrial Revolution. The blast furnace method is still one of the primary methods by which iron metal is refined from iron ores. 

The solid residues from the filter and from various other plant sources contain some cadmium as well as iron, nickel, and cobalt. Since they may not be discarded as waste, they are processed further by a sequence of selective dissolution steps, electrolysis, and differential precipitation to recover metallic cadmium and separate solutions of cadmium sulfate, nickel sulfate, and cobalt sulfate that are sold to metal refiners for recycling. Depending on their compositions, the rinse and neutralizing liquors may be discarded as waste or reprocessed to recover their metal values and to reduce the plant emissions to acceptable levels. 

Iron metal can be refined from the mineral hematite (Fe203). One way of converting the mineral to iron is to react it with carbon monoxide, as shown below ... 

Proton-induced X-ray emission (PIXE) technique has been used to determine the distribution of minor and trace elements in magmatic Ni-Cu ores, volcanogenic massive sulphide Cu-Pb-Zn-(Ag-Au) ores and lode Au-(Ag) deposits. Minor elements of importance include possible by-products or co-products of metal refining, as well as deleterious impurities in mill-feed, e.g., Cd, In, Sn, As, Se, Te, Tl, and Hg. Weathering products of primary sulphide mineralization, including tropical laterites and other oxidized assemblages, were analyzed by Wilson et al. (2002) and found to contain a wide range of minor elements which reflect the bedrock style of mineralization. The iron... 

Iron, a reddish brown metal, is the friendliest of the metals. It readily combines with many other elements to form a huge variety of products known for their strength, since primitive times, to make hand tools, cups, and plows to name just a few. Iron is the fourth most plentiful element in the Earth s crust making up about 5% of the elements present. Currently, more than 90% of all metal refined in the world is iron. 

The high-grade matte from the converter process or the flash melting process contains sulfur and some amounts of copper, cobalt and iron and, in addition, traces of noble metals. Refined nickel is produced by a variety of methods and is delivered as nickel cathodes or nickel powder. The latter are produced partly by carbonyl processes, partly by hydrogen reduction in conjunction with pressure leaching processes. In the latter, matte is leached under pressure with acid or ammonia, and nickel is recovered as a powder by reduction with hydrogen under pressure. 

The main route from iron ore to steel is via blast furnaces to produce molten iron (pig iron) from iron ore, coke and air. The coke is produced in coking plants from hard coal. Once the iron is refined in the blast furnace, the hot metal is transferred to the basic oxygen furnace, where pure oxygen is blown into the liquid pig iron through a water-cooled lance. The carbon content is reduced by oxidation to CO... 

Aluminium is obtained on a large scale by the electrolysis of the oxide, dissolved in fused cryolite The oxide, occurring naturally as bauxite, AI2O3.2H2O, usually contains silica and iron(III) oxide as impurities. These must be removed first, since aluminium, once prepared, cannot be freed of other metals (which will be deposited on electrolysis) by refining it. The crude oxide is dissolved under pressure in caustic soda solution the aluminium oxide and silica dissolve and the ironflll) oxide is left ... 

Before this treatment, the cassiterite content of the ore is increased by removing impurities such as clay, by washing and by roasting which drives off oxides of arsenic and sulphur. The crude tin obtained is often contaminated with iron and other metals. It is, therefore, remelted on an inclined hearth the easily fusible tin melts away, leaving behind the less fusible impurities. The molten tin is finally stirred to bring it into intimate contact with air. Any remaining metal impurities are thereby oxidised to form a scum tin dross ) on the surface and this can be skimmed off Very pure tin can be obtained by zone refining. 

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 ... 

Open-Arc Furnaces. Most of the open-arc furnaces are used in melting and refining operations for steel and iron (Fig. 1). Although most furnaces have three electrodes and operate utilizing three-phase a-c power to be compatible with power transmission systems, d-c furnaces are becoming more common. Open-arc furnaces are also used in melting operations for nonferrous metals (particularly copper), slag, refractories, and other less volatile materials. 

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... 

HBI is an effective trim coolant for molten steel in ladle metallurgy faciUties, ladle refiners, ladle furnaces, and vacuum degassers. It provides cold iron units in an ideal size and density for penetrating the ladle slag and cooling the metal. 

Lead and its alloys are generally melted, handled, and refined in cast-iron, cast-steel, welded-steel, or spun-steel melting ketdes without fear of contamination by iron (qv). Normal melting procedures require no dux cover for lead. Special reactive metal alloys require special alloying elements, duxes, or covers to prevent dross formation and loss of the alloying elements. 

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