Petroleum coke is a dark brown, solid fuel that has the appearance and physical properties of coal. It is produced as a byproduct of oil refinery operations and it is the predominant solid fuel used in power plants and cement kilns. However, because of its high sulfur content it poses problems in cement kilns and the ash chemistry makes it less than ideal as a boiler fuel. In addition, it contains high concentrations of vanadium and nickel.
Steel makers often use petroleum coke because of its carbon content and it is also an excellent raw material for making graphite electrodes. It increases the conductivity of electric arc furnace (EAF) electrodes which in turn improves the quality and strength of final steel products.
The petroleum coke has to be processed in order to remove sulfur and other impurities before it can be used for steel making. The process known as “coking” is a series of chemical reactions that transform the coke into metallurgical coke or “metal” coke. The coke is then combined with limestone and clay in order to create a slag that can be used for the production of steel. During this process, the coke is heated to temperatures of about 1,200°C in order to avoid the formation of volatile components.
A new solution is now available for utilizing petroleum coke as an energy source in the steel manufacturing process. The invention is based on the fact that petroleum coke can be used as a replacement for iron ore in the steelmaking process. This is done by introducing the coke into the melter gasifier unit of a steelmaking plant and burning it with oxygen and iron ore that has been reduced in the reduction furnace. The combusting of the coke generates a liquid iron rich in heavy metals and an oxide slag that can be used to make steel.
To obtain a metallurgical coke with a low sulphur content, the industry typically burns a mixture of 5% to 40% of the petroleum coke with coal in the coking oven. This reduces the sulphur to below the limit for steelmaking, thus making the resulting coke more valuable. Sulfur is the enemy of steelmakers because it decreases the quality of steel products. Therefore, it is very important that the sulphur content of the coke is as low as possible.
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