Solid residue from the shale oil extraction process
"Semi-coke" redirects here. For a fuel made from coal, see
Coke (fuel). For a solid residue derived from distillation of crude oil, see
Petroleum coke.
Spent shale or spent oil shale (also known as retorted shale) is a solid residue from the
shale oil extraction process of producing synthetic
shale oil from
oil shale. It consists of
inorganic compounds (
minerals) and remaining
organic matter known as
char—a
carbonaceous residue formed from
kerogen. Depending on the extraction process and the amount of remaining organic matter, spent shale may be classified as oil shale coke, semi-coke or coke-ash residue, known also as oil shale ash.[1][2] According to the European Union waste list all these types of spent shale are classified as hazardous waste.[2]
Oil shale coke is created by chamber ovens which were used for
oil shale gas production.[1] Vertical retorts create mainly semi-coke. Most solid heat carrier processes create coke-ash residue as the semi-coke created during the process is combusted for the process's energy needs.[3]