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Delayed coking is an industrial process used to extract fuel from coal and other natural resources. Delayed coking is a variation on the process of traditional coking, in which coal is converted into coke. Delayed coking typically uses lower temperatures and a longer period of time than traditional coking and produces both the solid coke as well as a liquid or gaseous material.
To understand how this process works, it's helpful to know a bit about the traditional coking process. During coking, coal is heated and dried at extremely high temperatures, which removes water as well as tar and gaseous materials. The resulting product is a very hard, dense material known as “coke.” Coke is widely used as a fuel source for industrial furnaces and burners.
With delayed coking, the coal is heated using a much more complex system, which often consists of multiple furnaces or drums. The coal is generally heated at lower temperatures for shorter periods of time, which removes water and other by-products much more slowly than with traditional coking. The heating process is repeated many times for a simple batch of coal, with pressure and temperature levels precisely controlled at each stage.
The delayed coking process allows manufacturers to develop two separate fuel sources. The dried coal, or coke, is a solid fuel, and is used for many industrial fueling purposes. It may take one of three different forms depending on the temperatures and pressure applied during delayed coking. Shot coke is the most common, and consist of balls of fuel with a tar-like consistency. Sponge coke has a softer, spongy texture while needle coke is the most valuable and rarest of the three types.
Delayed coking also produces a variety of liquid or gaseous fuel materials, including liquid propane, diesel fuel, heating oil, or propane gas. As the coal is dried in the coking machine, the water and other impurities rise out of the machine in the form of steam. These materials pass into a separate device called a fractionator, where they are converted into these different fuel products.
Both coking and delayed coking are performed in industrial facilities throughout the world. They are primarily found in oil refineries, but can also be used in many other manufacturing applications. Some companies perform delayed coking as a way to produce fuel for internal use, while others use the coking process to create fuels to sell outside of the company.
The delayed coking process offers a number of advantages over traditional coking processes. It allows for a much higher level of control over temperature and other settings, which means more refined production and less waste. Because most of the by-products of delayed coking are in the form of usable fuels, this process is highly efficient and can be considered a form of recycling. Delayed coking also results in the production of valuable fuel products, which can be sold for substantial sums depending on the market and the quality of the product.