Petroleum coke is a manufactured carbon product produced at a limited number of oil refineries. Petroleum coke results from the thermal processing of residual oil, which has been cracked or otherwise processed to remove low boiling fractions. Coke is made by heat-treating the residual oil (more accurately described as tar) to a temperature high enough to result in its polymerization to form a non-melting solid carbon. The process is performed to maximize the yield of lower molecular weight compounds derived from crude oil feedstocks.
Coke, as it is removed from the coking process, is referred to as “green coke”. Green petroleum coke contains approximately 15-20% residual hydrocarbon materials. These hydrocarbons are those compounds that do not polymerize in the coking process and cannot be removed from the coke substrate due to process limitations. Calcined petroleum coke (CPC) is manufactured by heating green coke to approximately 1300-1400 C in a rotary kiln. This effects the removal of virtually all residual hydrocarbons and moisture. The final calcined product contains only a trace of volatile matter, and from 0.3 to 6% sulfur depending on the petroleum base used to make the coke.
Calcined, and green petroleum cokes are inherently low in ash constituents. The fixed carbon content of most calcined petroleum coke products ranges from approximately 97 to 99.5%. Petroleum coke is used in applications where high quality non-graphitic carbons are required. Some applications for petroleum coke include foundry products, wear moderators for PTFE compounds, rubber compounds, reducing reagents, ceramic packing media, oxygen exclusion from molten metals, manufactured carbon shapes, alloys, cathodic backfill, drilling additives, Case hardening, seals, mechanical carbons, and flooring.