Petroleum coke has many uses and is one of the most important by-products in commercial production. It's hard, brittle granular and coarse material, which contains a lot of carbon. There is little or no residual hydrocarbons in the material. The availability of calcined coke and its relatively low level of impurities make it a good material to be used as an anode during the Hall-Heroult process for aluminum smelting.
It is found in the oil refinery's delayed coking units. The units convert heavy crude oil into diesel or gasoline. Refineries which have heavy crude mixtures produce more delayed coal than refineries who have lighter blends. The liquid fractions that are produced from the delayed reactors go into coke drums to be carbonized. The resulting green petroleum coke (GPC) is typically sold as fuel for power generation and cement production or used to calcine into CPC.
Most calcining plants today utilize a combination of rotary and shaft kilns for the production of CPC. This allows for blending of GPC from different sources to match the required bulk density and porosity profile. The increasing sulfur levels of GPC in conjunction with tightening SO2 emission limits is a major driving force behind the blending requirement. We expect this trend to continue and that smelters will need to be equipped with SO2 scrubbing technologies.
Waste heat energy recovery is available on many rotary ovens. They capture the heat of hot flue gases exiting the kiln in an opposite direction to the coke beds and then pass it to a heat-exchanger, producing steam. This steam can be used for process heat in the smelter or can be combined with a turbine to generate electricity.
Heat is wastefully lost during the calcination. It is because of the huge temperature difference between the petroleum coke calcinated and the hot gas. This heat could be recovered, and is a potential major energy source for an aluminium smelter.
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