The Production of Iron

Iron is produced by the reduction of iron ore (oxides of iron), by coke in blast furnaces. Limestone is used as a fluxing agent. It dissociates into quicklime in the blast furnace, and helps to remove impurities in the iron ore (mainly silica and alumina) by reacting with them to form a molten slag. The slag also assists in the removal of other impurities. Traditionally, all of the limestone was charged with the other raw materials into the blast furnace. In current practice, limestone is also used as a component of the feed to sinter strands, which are used to agglomerate finely divided iron ore before it is fed into the blast furnace. 

The blast furnace requires the feed materials, including the iron ore, to be in a granular form. All of the materials must, therefore, have adequate strength to resist degradation during transport, storage and handling. 

The proportion of fines and concentrate used varies with the quality of ore and with local economic factors. On average, in Europe, the sinter process is used to 

The pellets are then fed onto the sinter strand and are heated by burning blast furnace gas. This ignites the coke and raises the temperature of the solids to about 1280 °C. The limestone is calcined and reacts with silica and alumina in the ore to produce a molten calcium silicate-aluminate-ferrite system, which bonds the iron ore particles and produces strong pellets. 

Some producers add 1 to 2 % of quicklime to the raw mix, to improve agglomeration and produce stronger green pellets. This increases the output of the sinter strand and reduces heat usage (see section 27.2). 

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Production. Three commercial processes are used for the production of iron yellows the Penniman-Zoph process, the precipitation process, and the Faux process. 

This law was first stated, in a more complex form, in 1884 by Henri Le CMtelier (1850-1936), a French chemist who had studied a variety of industrial equilibria, including those involved in the production of iron in the blast furnace. The statement is commonly referred to as Le Ch telier s principle. 

A reaction involved in the production of iron from iron ore is... 

Basically, the oxidation of iron pyrite, FeS2, results in the production of iron(III) sulfate and sulfuric acid, H2SO4. However, two overall reaction stoichiometries are possible and each will yield a different acid generation capacity (e.g., Langmuir, 1997 Baird, 1995) ... 

Iron has been the dominant structural material of modem times, and despite the growth in importance of aluminum and plastics, iron still ranks first in total use. Worldwide production of steel (iron strengthened by additives) is on the order of 700 million tons per year. The most important iron ores are two oxides, hematite (Fc2 O3) and magnetite (Fc3 O4). The production of iron from its ores involves several chemical processes that take place in a blast furnace. As shown in Figure 20-22. this is an enormous chemical reactor where heating, reduction, and purification all occur together. 

Two different methods were used to produce Iron oxide (Fe203) particles on Grafoll. One method was a simple Impregnation-calcination based on the method of Bartholomew and Boudart (20). The exact method used 1s described elsewhere (27). The second method used was a two step process. First, metallic iron particles were produced on the Grafoll surface via the thermal decomposition of Iron pentacarbonyl. This process Is also described in detail elsewhere (25). Next, the particles were exposed to air at room atmosphere and thus partially oxidized to 2 3 Following the production of Iron oxide particles (by... 

Coke byproduct wastes. Coke, used in the production of iron, is made by heating coal in high-temperature ovens. Throughout the production process many byproducts are created. The refinement of these coke byproducts generates several listed and characteristic wastestreams. However, to promote recycling of these wastes, U.S. EPA provided an exclusion from the definition of solid waste for certain coke byproduct wastes that are recycled into new products. 

Perhaps the most important use of carbon is as a reducing agent because it is the least expensive reducing agent used on a large scale. Two of major uses of carbon as a reducing agent are the production of iron,... 

Another important deviation from constancy in the abundance ratio of elements supposed to be primary is displayed by the ratios Fe/O and [Tc/a-elements in stars, which increase systematically with [Fe/H] (Figs. 8.5,8.6). This is usually attributed to the existence of a substantial contribution to the production of iron found in the younger, more metal-rich stars (like the Sun) by SN la, which take times of the order of a Gyr to complete their evolution and therefore cannot be treated... 

Manganese carbonate (MnCO ) is used in the production of iron ore and as a chemical reagent. 

Various forms of carbon, semigraphite, and graphite materials have found wide application in the metals industry, particulady in connection with the production of iron, aluminum, and ferroalloys. Carbon has been used as a refractory material since 1850, though full commercial acceptance and subsequent rapid increase in use has occurred only since 1945. 

The iron sulfate is used in water purification, and as a raw material for the production of iron oxide pigments. Alternatively, it can be dehydrated and thermally decomposed to give iron(III) oxide and sulfur dioxide. 

Table 23. Reaction equations for the production of iron oxide pigments...

Most phosphorus and sulfur impurities are removed in a basic oxygen furnace, but the purified metal still contains about 3 percent carbon. For the production of iron, this carbon is desirable. Iron atoms are relatively large, and when they pack together, small voids are created between atoms, as shown in... 

Suppose we deal with a process in which iron, Fe, has to be used as a reactant, for example, in a reduction reaction. The standard chemical exergy of Fe is 376.4 kj/mol. If we wish to carry out a thermodynamic or exergy analysis of this process, this value is not appropriate. After all, to put the exergy cost of the product, for which Fe was needed as a reactant, in proper perspective, we need to consider all the exergetic costs incurred in order to produce this product all the way from the original natural resources— iron ore and fossil fuel in this example. The production of iron from, for example, the iron ore hematite and coal has a thermodynamic efficiency of about 30% [1], and therefore it is not 376.4 kj/mol Fe that we need to consider... 

During the first six hours of extraction, more iron is removed from the altered granite than from the fresh granite. The extra iron from the altered granite is believed to be that associated with the production of iron oxyhydroxides during the 101-d exposure of the granite to GGW. 

Several operations for the production of iron and steel, including sinter production, coke production, and electric arc furnaces, have been identified as potential emission sources of PCDD/Fs. China is the largest producer of steel in the world. According to 2005 statistical data, the iron and steel production of China was 349 million tons. It is reasonable to assume that the iron and steel industry could be a major source of PCDD/ F emission to air in China, but data are not available for an assessment of the emissions from this source. 

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