Ironmaking

Ironmaking in the United States did not expand rapidly until after the Revolutionary War. Then, as the colonists moved westward, the need for iron prompted the estabUshment of ironworks near the new settiements. A blast furnace built by Jacob Anschut2 in 1796 was the beginning of the iron and steel center in Pittsburgh, Pennsylvania. 

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

Ironmaking refers to those processes which reduce iron oxides to iron. By the nature of the processes, the iron produced usually contains carbon and/or other impurities which are removed in downstream processing. There are three principal categories of ironmaking processes, in order of commercial importance blast furnace, direct reduction, and direct smelting. 

Blast Furnace. The blast furnace is the predominant method for making iron. Estabhshed for centuries as the premier ironmaking process, blast furnace ironmaking both enabled and profited from the Industrial Revolution. Although the fundamental principles of operation are unchanged, the blast furnace has evolved into a highly efficient and productive process. 

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). ... 

Perhaps the biggest environmental challenge for ironmaking processes into the twenty-first century involves responding to the concerns about global warming. Ironmaking processes require the use of carbon-based reductants, and ultimately result in the emission of carbon dioxide. 

J. J. Poveromo, "AISI Survey of Blast Eumace Pellet Properties," in Proceedings, 52nd Ironmaking Conference, AIME-ISS, Dallas, Tex., 1993. 

The most important indusuial reaction of this kind occurs in die ironmaking blast furnace in which iron oxide ore is reduced by carbon in the form of coke. The mixture is heated by the combustion of part of the coke input in air to produce temperatures as high as 2000 K. The reduction reaction is caiTied out via the gas phase by the reaction... 

The lead blast furnace operates at a lower temperature than the iron blast furnace, die temperature at the tuyeres being around 1600K as opposed to 1900K in the ironmaking furnace (see p. 333) and this produces a gas in which die incoming air is not completely reduced to CO and N2, as much as one per cent oxygen being found in the hearth gas. 

Of these terms tlrose involving iron and calcium can be compared as an exatrrple of the exchatrge under ironmaking conditions. Experimental values for tire conesponding equilibria between gas and slag yield values of the sulphide capacities... 

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