Iron and Steel Production and Recycling (Produksi dan Pengolahan Besi dan Baja)

Production

     The major ray materials for the commercial production of Fe are haematite (Fe2O3), magnetite (Fe3O4)  and siderite (FeCO3). The extraction of iron is carried out on an enormous scale to meet the consumer demands for both iron and steel. In 2001, China, Japan, the US and Russia led the world in the production of steel : You can check at http://worldsteel.org/statistics/top-producers.html

Note : Production of Molten Steel

Source : http://www.eef.org.uk

     The industrial manufacturing process for iron and steel can be summarized as follows. Iron ore is mixed with limestone (CaCO3) and coke in a blast furnace in which temperatures vary from 750 to 2250 K. Carbon is converted to CO in the highest temperature zone, but both C and CO may reduce the iron ore :

2C + O2 --> 2CO

Fe2O3 + 3C --> 2Fe + 3CO

Fe2O3 + 3CO --> 2Fe + 3CO2

     The function of the limestone is ti remove impurities and the product of these reactions is slag, which contains, for example, calcium silicate. Molten Fe from the furnace is collected and cooled in salt-moulds as pig iron, which contains 2-4% C plus small amounts of P, Si, S and Mn. After remelting and moulding, the product is cast iron, this is brittle and its exact nature depends upon the relative amounts of secondary elements. A high Si content results in the C being in the form of graphite, and the cast iron so formed is called grey cast iron. On the other hand, white cast iron  forms when the Si content is low and carbon is present within the iron carbon phase cementite, Fe3C.

     The pudding process is used to convert cast iron to wroght iron; oxidation of C, S and other impurities leaves wrought iron with <0.2% C content. Unlike cast iron, wrought iron is tough and malleable and is readily worked; its applications, in wrought iron railings and window and door grills, are widespread.

     Iron can be converted into steel by the Bessemer, Siemens electric arc and basic oxygen processes. the Bessemer process was the first to be patented, but the Siemens electric arc and basic oxygen process used in modern steel production. In the basic oxygen process, O2 oxidizes the carbon in pig iron, reducing its content to the levels required for commercial steel. In the US, the basic oxygen process uses >25% recycled steel and and produces steel suitable for, for example, vehicle bodies. The electric arc process is used to produce steel for large steel structures (e.g bridge girders) and almost 100% of such steel is recycled. 

Recycling

     Considering the period over which steel has been commercially produced, steel recycling has become important only relatively recently. In the US, the Steel Recycling Institute encourages steel-can recycling, a process that has grown from 15% of cans being reclaimed in 1988, to nearly 60% in 2000; this corresponded to 18 billion cans in 2000. Recycled steel can originate from steel cans, household appliances, vehicles and construction materials.   

Source : 

Housecroft, E. Catherine and Alan G. Sharpe. 2005. Inorganic Chemistry 2nd edition. Edinburg. Ashford Colour Press Ltd., Gosport