The high thermal and electrical conductivity of graphitized fossil oil coke makes it an essential ingredient in making a wide range of products, including pencils, lubricants, casting cores, foundry facings, polishes, and brushes for electric motors. Graphitized petroleum coke is also used in many advanced materials, including battery electrodes and nuclear reactor cores. The production of these critical industrial materials depends on a number of factors, such as the temperature and pressure used during the coking process. The quality of the final product depends on how well these conditions are managed, and this has a direct impact on its price.
Graphitized fossil oil coke is produced by treating coal in an oxygen-free atmosphere with extreme heat to create a material with the same chemical composition as natural graphite, but with significantly improved physical properties. The material can be spherical or flaky and is usually dark brown in color. The improvement in physical properties includes increased electrical conductivity and thermal conductivity, as well as a reduced coefficient of friction.
There are several grades of petroleum coke, which differ in their carbon content and density. The lowest-grade vacuum residue coke is known as fuel coke and is used for electricity generation and as a feedstock for cement kilns. Anode coke, which is used in the aluminum industry, is produced from higher-quality vacuum residues and is characterized by its sponge or honeycomb morphology. Needle coke, which is the highest-grade coke, is a highly crystalline form of petroleum coke and is used for high-grade graphite electrodes in electric arc furnaces.
The coke quality of these different grades is determined by the quality of the raw pet coke used as a starting material and by the coking conditions, such as temperature and pressure. The calcination of petroleum coke results in the removal of volatile components and increases the carbon content and density. This process is carried out in a rotary kiln with temperatures of around 1,200°C.
This process produces a coal byproduct called petroleum coke, or “petcoke,” which has low sulfur, nitrogen, and ash content. It can be used as a fuel for power generation and is a source of anode material for aluminum electrolytic cells. To ensure the high quality of anode material, a specific specification of pet coke is required, such as low impurity content and uniform particle size.
The characterization of petroleum coke is performed by proximate analysis, X-ray fluorescence analysis (XRF), coke reactivity index and strength after reaction with CO2, Brunauer-Emmett-Teller (BET) surface area, Barrett-Joyner-Halenda (BJH) pore size and volume distribution analysis, optical and scanning microscopy, and Raman spectroscopy. These results show that the ECE process does a good job of isolating primarily sp2 structures from less crystalline precursors. The ID/IG ratio of CK-2a and CK-3a is comparable to the parent coke, but the CK-2d isotope has a lower IG ratio than both of these. This may indicate that the reactivity of carbon in the coke is enhanced by the addition of additives to the ECE system.
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