Petroleum Coke, a black solid material produced from the refining of crude oil, has many uses in steel manufacturing. It can be used as a fuel, to make graphite electrodes for electric steel furnaces or in the production of titanium dioxide. Its energy content is much higher than coal and has a lower ash content, making it a better alternative to coal in iron and steel production. In addition to its energy and carbon content, petcoke has a low sulfur content and does not produce harmful particulates. It is available in a variety of grades and forms, including fuel-grade coke, calcined petroleum coke (CPC), needle coke, and sponge coke.
Using petroleum coke as a fuel in the production of steel reduces emissions from the plant and cuts costs. The coke burns at a lower temperature than coal, making it more efficient and safer to handle. It also has a higher calorific value and less ash, meaning that it can provide more heat with the same amount of fuel. This lowers the cost on a ton-by-ton basis for clinker and saves energy in the production of cement.
The high carbon monoxide levels of petcoke allow for higher process gas temperatures during reduction which increases productivity and improves the quality of the reduced iron. Indirectly, the higher carbon content of the petcoke increases the level of carburization in the reduced iron which enhances the quality and stability of the product.
A high carbon content also helps to minimize clustering during the direct reduction of the metals. This is due to the fact that the high carbon monoxide levels reduce the reactivity of the reduction gases which prevents sintering and clustering of the reduced metallic iron particles.
Steel mills focused on protecting the environment use calcined petroleum coke-made graphite electrodes to ensure long, high current conductivity and low maintenance. Graphite electrodes made from calcined coke are the only ones that can meet these demands.
In addition, a low sulphur content in the coke helps to eliminate slag formation during the ironmaking process. Without a low sulphur content, the coke would need to be mixed with a high volume of limestone which can lead to costly waste management and environmental issues.
For these reasons, steel manufacturers prefer to use petcoke in their ironmaking processes, especially in the coking process. The sulphur content in the petcoke is typically controlled below a maximum of 2.5 percent, which allows for a more efficient smelting operation. This is especially true in a COREX system where the slag is disposed of as liquid slag external to the reduction furnace rather than being returned to the blast furnace for re-melting. This enables the use of less raw coking coal which reduces overall sulphur emissions. This is especially beneficial to plants with strict environmental requirements.
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