Corex Process

Last updated November 03, 2022

The Corex Process is a smelting reduction process created by Primetals as a more environmentally friendly alternative to the blast furnace. Presently, the majority of steel production is through the blast furnace which has to rely on coking coal. That is coal which has been cooked in order to remove impurities so that it is superior to coal.^[1] The blast furnace requires a sinter plant in order to prepare the iron ore for reduction.^[2] Unlike the blast furnace, smelting reduction processes are typical smaller and use coal and oxygen directly to reduce iron ore into a usable product. Smelting reduction processes come in two basic varieties, two-stage or single-stage. In a single-stage system the iron ore is both reduced and melted in the same container. In a two-stage process, like Corex, the ore is reduced in one shaft and melted and purified in another.^[3] Plants using the Corex process have been put use in areas such as South Africa, India, and China.^[4] First COREX process was installed in 1988 at South Africa.

Process

The Corex process consists of two main parts: a Reduction Shaft and a Melter-Gasifier.^[4] The main reagents for the Corex process are iron ore, noncoking coal, and oxygen.^[5] Unlike a blast furnace, the Corex process does not use a hot blast of nitrogen, thereby greatly reducing NOx gas emissions, but instead uses oxygen. In addition, the Corex process can use iron oxides containing up to 80% lump ore and uses non-coking coal directly as a reducing agent.

In the reduction shaft the iron ore, along with limestone and dolomite additives, is added and then reduced by reduction gas into 95% direct reduced iron, DRI.^[6] The DRI is then redirected via six discharge screws into the melter-gasifier. The melter-gasifier has three main sections, the gaseous free board zone, the char bed, and the hearth zone, and it has an effect on several stages in the process. First it serves to create the reduction gas by gasifying the coal with oxygen and then cooling it. After being reduced, the DRI is redirected to the char bed where the iron and slag are melted and then directed to the hearth zone.^[6] The heat inside the metal gasifier keeps the amount of phenols small, keeping them out of the atmosphere. Meanwhile, carbon monoxide and hydrogen gas from the original gasification of the coal exit the gasifier while other byproducts are captured in the metallic slag. The rest of the hot gas is then cooled and sent into the reduction shaft resulting in the Corex export gas which is used to control pressure in the plant. Many of the gases resulting from this process can then be recycled or used to produce electricity.^[5] Dust particles also appear in these gases and the melter-gasifier recycles them with four dust burners.^[6]

Advantages

There are many advantages to the Corex Process, for example carbon dioxide emissions are up to 20% lower than with the conventional blast furnace, and the Corex process produces far less SO2 and dust than the blast furnace.^[4] In addition Corex plants do not release as many phenols or sulfides limiting water contamination.^[4]

Disadvantages

There are drawbacks. For example, at the JSW Steel plant in India it was found that to be viable the Corex process still needed about 15% coke. Furthermore, it has also been found that Corex plants require large amounts of oxygen which can be expensive. Also the export gas can make the process highly inefficient. However, this particular problem can be mitigated by using the export gas in electricity production.^[3]

Related Research Articles

Smelting is a process of applying heat to ore, to extract a base metal. It is a form of extractive metallurgy. It is used to extract many metals from their ores, including silver, iron, copper, and other base metals. Smelting uses heat and a chemical reducing agent to decompose the ore, driving off other elements as gases or slag and leaving the metal base behind. The reducing agent is commonly a fossil fuel source of carbon, such as coke—or, in earlier times, charcoal. The oxygen in the ore binds to carbon at high temperatures due to the lower potential energy of the bonds in carbon dioxide. Smelting most prominently takes place in a blast furnace to produce pig iron, which is converted into steel.

Coke is a grey, hard, and porous coal-based fuel with a high carbon content and few impurities, made by heating coal or oil in the absence of air—a destructive distillation process. It is an important industrial product, used mainly in iron ore smelting, but also as a fuel in stoves and forges when air pollution is a concern.

Steelmaking is the process of producing steel from iron ore and/or scrap. In steelmaking, impurities such as nitrogen, silicon, phosphorus, sulfur and excess carbon are removed from the sourced iron, and alloying elements such as manganese, nickel, chromium, carbon and vanadium are added to produce different grades of steel. Limiting dissolved gases such as nitrogen and oxygen and entrained impurities in the steel is also important to ensure the quality of the products cast from the liquid steel.

<span class="mw-page-title-main">Slag</span> By-product of smelting ores and used metals

Slag is a by-product of smelting (pyrometallurgical) ores and used metals. Broadly, it can be classified as ferrous, ferroalloy or non-ferrous/base metals. Within these general categories, slags can be further categorized by their precursor and processing conditions.

A blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally pig iron, but also others such as lead or copper. Blast refers to the combustion air being "forced" or supplied above atmospheric pressure.

Industrial processes are procedures involving chemical, physical, electrical or mechanical steps to aid in the manufacturing of an item or items, usually carried out on a very large scale. Industrial processes are the key components of heavy industry.

<span class="mw-page-title-main">Steel mill</span> Plant for steelmaking

A steel mill or steelworks is an industrial plant for the manufacture of steel. It may be an integrated steel works carrying out all steps of steelmaking from smelting iron ore to rolled product, but may also be a plant where steel semi-finished casting products are made from molten pig iron or from scrap.

New Zealand Steel Limited is the owner of the Glenbrook Steel Mill, the steel mill located 40 kilometres south of Auckland, in Glenbrook, New Zealand. The mill was constructed in 1968 and began producing steel products in 1969. Currently, the mill produces 650 000 tonnes of steel a year which is either domesticity used or exported. Over 90% of New Zealand's steel requirements are produced at Glenbrook while the remaining volume is produced by Pacific Steel, a steel recycling facility in Otahuhu, Auckland. The mill is served by the Mission Bush Branch railway line, which was formerly a branch line to Waiuku. Coal and lime trains arrive daily. Steel products are also transported daily. The mill employs 1,150 full-time staff and 200 semi-permanent contractors.

An electric arc furnace (EAF) is a furnace that heats material by means of an electric arc.

A bloomery is a type of metallurgical furnace once used widely for smelting iron from its oxides. The bloomery was the earliest form of smelter capable of smelting iron. Bloomeries produce a porous mass of iron and slag called a bloom. The mix of slag and iron in the bloom, termed sponge iron, is usually consolidated and further forged into wrought iron. Blast furnaces, which produce pig iron, have largely superseded bloomeries.

Pyrometallurgy is a branch of extractive metallurgy. It consists of the thermal treatment of minerals and metallurgical ores and concentrates to bring about physical and chemical transformations in the materials to enable recovery of valuable metals. Pyrometallurgical treatment may produce products able to be sold such as pure metals, or intermediate compounds or alloys, suitable as feed for further processing. Examples of elements extracted by pyrometallurgical processes include the oxides of less reactive elements like iron, copper, zinc, chromium, tin, and manganese.

Direct reduced iron (DRI), also called sponge iron, is produced from the direct reduction of iron ore into iron by a reducing gas or elemental carbon produced from natural gas or coal. Many ores are suitable for direct reduction.

<span class="mw-page-title-main">Saldanha Steel</span>

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References

↑ Ricketts, John. "How A Blast Furnace Works". Steel Works. Archived from the original on December 9, 2014. Retrieved November 3, 2013.
↑ "Sintering plant". Salzgitter Flachstahl. Archived from the original on 2013-11-13. Retrieved 2013-11-13.
1 2 Agrawal, Mathur, B,A. "Dr" (PDF). R & D Centre for Iron & Steel Steel Authority of India Ltd. Ranchi, India. Retrieved October 27, 2013.
1 2 3 4 SIEMENS VAI. "SIMETAL Corex technology" (PDF). SIEMENS VAI. Archived from the original (PDF) on June 26, 2013. Retrieved October 16, 2013.
1 2 Industrial Efficiency Technology Database. "Corex Process". ndustrial Efficiency Technology Database. Archived from the original on August 6, 2018. Retrieved October 16, 2013.
1 2 3 Gupta, S. "Corex Process - One of the dynamic routes for gel making with special reference to the success of JVSL". jpcindiansteel. Archived from the original on October 6, 2013. Retrieved October 16, 2013.

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[How_A_Blast_Furnace_Works-1] Ricketts, John. "How A Blast Furnace Works". Steel Works. Archived from the original on December 9, 2014. Retrieved November 3, 2013.

[Sintering_plant-2] "Sintering plant". Salzgitter Flachstahl. Archived from the original on 2013-11-13. Retrieved 2013-11-13.

[New_Iron_Making_Process:_Relevence_to_India-3] 1 2 Agrawal, Mathur, B,A. "Dr" (PDF). R & D Centre for Iron & Steel Steel Authority of India Ltd. Ranchi, India. Retrieved October 27, 2013.

[SIMETAL_Corex_technology-4] 1 2 3 4 SIEMENS VAI. "SIMETAL Corex technology" (PDF). SIEMENS VAI. Archived from the original (PDF) on June 26, 2013. Retrieved October 16, 2013.

[IETD-5] 1 2 Industrial Efficiency Technology Database. "Corex Process". ndustrial Efficiency Technology Database. Archived from the original on August 6, 2018. Retrieved October 16, 2013.

[Gupta-6] 1 2 3 Gupta, S. "Corex Process - One of the dynamic routes for gel making with special reference to the success of JVSL". jpcindiansteel. Archived from the original on October 6, 2013. Retrieved October 16, 2013.

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