In the aluminum industry, calcined coke is a crucial ingredient in the production of carbon anodes. It is also used in the steel industry, as well as for electricity generation. As the world becomes increasingly urbanized, construction expenditure is rising, which puts additional pressure on the global supply of calcined petcoke. This article provides a review of the history and use of calcined coke, as well as its current status and implications.
The aluminum industry accounts for a significant percentage of the worldwide calcined petcoke market. Aluminum smelting facilities are currently expanding, and this will put further pressure on the coke supply. However, calcining technologies and blending strategies have increased to accommodate a growing demand.
Cokes are available in a variety of qualities and are sold to a variety of end users. The highest quality cokes are traditionally used in the aluminum industry. These are also more expensive. Traditionally, smelters have relied on simple weigh belt systems to blend cokes. Some smelters are now utilizing more sophisticated blending practices, and more are expected to follow suit.
Calcined coke can be produced in both rotary and shaft kilns. Rotary kilns are more common in the Western world. They are sloped and turn slowly to move the coke through the kiln. Shaft CPC, on the other hand, has more coarse-grained and variable porosity profiles. Depending on the calcining technology, residual volatile matter can be anywhere from 9 to 14 percent.
During the process, volatile hydrocarbons are removed from the coke by heating it. Typically, the calcining process requires an average of 0.1 wt% of hydrogen. While there are many different ways to produce calcined coke, the most common method is by removing the volatiles using a rotary kiln.
Most rotary kilns are integrated with waste heat energy recovery systems. A waste heat recovery boiler generates steam from the exhaust gas from the kiln. Using this boiler, waste heat from the VM can be recovered and reused, allowing for a more efficient process. Waste heat energy recovery systems can also be used to produce power with a steam turbine generator.
Many smelters are using more sophisticated blending approaches to maximize anode density. In addition, more smelters are blending CPC from multiple suppliers. This can help improve the quality of the anode and minimize problems with fraction preparation. If a smelter blends cokes at a consistent ratio, this can also help improve the anode quality.
Another type of calcining process is the delayed coking process, which was developed in 1929. This is also a rotary kiln process, but it has a shorter cycle time. When the coke exits the kiln, it is chilled through direct quenching with water in a rotary cooler. Several rotary kilns are built with waste heat energy recovery systems to recover the heat from fine coke particles.
Because of its high density, calcined coke is favored in the aluminum industry. Smelters often blend cokes to achieve higher VBDs. Higher VBDs enable the anode to last longer.
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