Petroleum coke is a solid material with a honeycomb appearance that contains high carbon content. It is the result of destructive distillation (thermal cracking) of petroleum residua and can also contain hydrogen and sulfur, as well as other metal contaminants. It is insoluble in organic solvents and insoluble in carbon disulfide, but it is soluble in hot water.
Its high carbon content makes petroleum coke a good fuel for power generation. Its calorific value is very close to that of coal. This is why it is used in many thermal power plants as a substitute for coal. It is also being increasingly used in the steel industry to increase the carbon content of molten steel during the steelmaking process.
The price of petroleum coke fluctuates, depending on the state of the energy market and crude oil prices. This can influence the fuel selection decision for power generation companies.
Unlike most other fossil fuels, petroleum coke has a low moisture content and can be burned with minimal ash residue or slag formation. These characteristics make it an excellent alternative to traditional coal for cyclone-type boilers, which require a large amount of ash to form the slag layer that protects the turbine from erosion and deposits carbon dioxide into the atmosphere.
In addition, a substantial portion of the contaminant content of coal is reduced by cofiring with petroleum coke in steam-generating units. This is especially true for sulphur and vanadium, which are the primary contaminant sources in coal. This is due to the fact that petroleum coke carries much less sulfur and vanadium than most coals.
Cofiring testing at the Bailly Generating Station (BGS) showed that combining petroleum coke with both low-sulfur and high-sulfur coal produces very clean coal fuel mixtures. Moreover, cofiring with low-sulfur coal reduces emissions of CO, hydrocarbons and SO3. It also decreases the concentrations of trace metals in feedstocks such as arsenic, cadmium, chromium, lead and mercury. In addition, it significantly improves furnace performance.
BGS cofiring tests with petroleum coke and urban wood waste also demonstrated that the combination is a very efficient source of heat. This is largely because cofiring with petroleum coke increases the combustion efficiency of both coal and wood. In addition, it substantially lowers the concentration of trace metals in the cofiring mix.
There are several different types of petcoke available in the market, which are distinguished by their physical properties, such as density, porosity and resistivity. The physical parameters can be assessed by various methods such as drainage method, gas adsorption method and X-ray diffraction technique. The characterization of petroleum coke can be completed by physical tests and expert judgment. The acicular structure and high conductivity of graphite fossil petcoke are particularly valuable for electric steel furnaces. This type of petcoke has the capacity to carry a lot of current in the electric arc furnace and produce high temperatures for melting scrap steel, raw materials and slag. It is also very effective in improving the quality of metallurgical products, such as cast iron and steel alloys.
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