Petroleum coke is a carbon-rich byproduct of oil refining that has numerous industrial applications including metallurgical coking, power generation and fuel for rotary kilns. While it is often regarded as a “dirty coal,” it is a valuable resource with several benefits for steel production.
A key part of the crude oil refining process is cracking, a heat-based chemical engineering process that breaks large petroleum hydrocarbon molecules into smaller ones. Modern refineries employ a variety of cracking techniques to produce different fuels, bitumens, and coke byproducts. The final byproduct of the cracking process is a dense, honeycomb-shaped material called petroleum coke.
Coke is insoluble and has a low energy content, but it is also carbon-rich with a high fixed carbon content of up to 85%. It can be found in two forms: uncalcined (raw) petcoke and calcined (“cooked”) petcoke. Uncalcined petcoke is usually very porous with a wide range of pore size characteristics, while calcined petcoke has a much narrower pore structure and is harder. The type of pore structure and the fixed carbon content of the petcoke determine its suitability for various industrial applications.
As the global energy industry continues to move towards more sustainable practices, the role of petroleum coke in a wide variety of industrial processes must evolve to align with sustainability goals. The future of this critical byproduct will depend on the ability to increase combustion efficiency and adsorption performance and develop new carbon capture and storage technologies that allow it to be used alongside cleaner fuels.
In addition to the benefits discussed above, coking petroleum coke produces a high-quality, solid carbon fuel called metallurgical coke that is used in the steelmaking process. Coke is added to coal in coking ovens at a ratio of 5% to 40% (weight basis) to reduce its reactivity and improve its quality, which ultimately allows for a higher carbon yield in the resulting steel.
Testing petroleum coke ensures it is safe to use and meets industry standards. Its volatile matter content must be low enough to protect industrial equipment and the environment, its sulfur contents need to be minimized, and its metal concentrations must be limited for optimal performance. Testing also determines its pore structure and porosity characteristics, which affects the adsorption properties of the coke in chemical reactions.
The best way to test petroleum coke is by performing a physical analysis. This can be done with a petcoke grinder or by using a vibrating screen. The results of the physical and chemical tests provide valuable information about the petcoke’s quality, suitability, and utility. Specifically, by determining the metal, sulfur and carbon content of a sample, the specific type of petroleum coke can be accurately identified. For example, a high-quality graphite fossil oil coke has a high carbon content and low sulfur and impurity content, while an ordinary delayed oil coke has a higher sulfur content and lower carbon content.
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