Petroleum coke (also called petcoke, a derivative of petroleum) is a solid carbonaceous byproduct of oil refining. It is created by thermally cracking crude oil residues in oil refinery delayed coker units. Coke is an insoluble, grey-black material with a honeycomb pattern and a high carbon content. It has low melting points and is brittle.
It is usually used as a fuel for power generation or for reducing sulfur and heavy metals in cement kilns. Because of its relatively higher sulphur, however, it has been uneconomical to use as a carbon electrode bar or in metallurgical applications. There are also environmental issues associated with its use as an alternative to coke (Speight 2014).
Therefore, the major use of petroleum coke is to generate electricity by gasification of it. The combustion of coal and coke, known as the "coal/petcoke" process, can be carried out either by using only the coke or a combination. This produces electricity that is high in heat capacity and can be used for industrial steam, compressors, pumps, or cogeneration.
Gas from fractionation can be used as a fuel for heating, steam tracking and partial pressurization. The gas can be used to make graphite electrodes or as a substitute for natural gas in synthesis gas reactors. It can also produce metallurgical coal for the steel industry.
Oil coke is calcined in order to remove volatiles. This makes it more useful as a source of electricity and lowers its moisture to a level that can be mixed with other fuels. Calcined petroleum coal, or CPC, is a fuel with a high calorific content that can be used to generate electricity. Alternatively, it can be re-gasified as a substitute for natural gas in the IGCC process.
IGCC systems are designed to gasify fossil fuels and biomass such as coal or petroleum coke in order to generate electricity. These systems have many advantages over conventional cyclone and pulverized coal boilers. These systems are capable of cofiring petroleum coke along with pulverized coal, and can reduce the sulfur dioxide level in their overall emissions. They can also burn petroleum coke that has a higher ash content. This is not possible with PC or cyclone boilers. This flexibility makes them very attractive for cofiring petroleum coke.
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