Calcined Petroleum Coke (CPC)
Anode grade calcined petcoke is the principal raw material used in manufacturing carbon anodes for use in aluminum smelting. The anodes act as conductors of electricity and as a source of carbon in the electrolytic cell that reduces alumina into aluminum metal. Carbon anode manufacturers, predominantly captive operations of aluminum smelting companies, purchase anode grade calcined petcoke, mix it with pitch binders, press the mixture into blocks, and then bake the mixture to form a finished, hardened carbon anode.
The coking processes described in the GPC section produce “green coke,” which then requires additional thermal processing to remove any residual hydrocarbons (volatile matter) to increase the percentage of elemental carbon. Thermal processing lowers the potential toxicity of the coke.
Depending on the coking operation temperatures, length of coking-time, and quality of the crude oil feedstock, one of several grades of petcoke can be produced:
- sponge coke, the most common type of regular-grade petcoke, used as a solid fuel
- needle coke, a premium-grade coke made from special petroleum feedstock, used in the manufacture of high-quality graphite electrodes for the steel industry
- shot coke, produced from heavy petroleum feedstock, used as fuel, but less desirable than sponge coke
- purge coke, produced by flexi-coking, used as a fuel in coke-burning boilers
- catalyst coke, carbon deposited on catalysts, used in various refining processes and burned off and used as a fuel in the refining process; not recoverable in a concentrated form