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The Union process was an above ground shale oil extraction technology for production of shale oil, a type of
synthetic crude Synthetic crude is the output from a bitumen/extra heavy oil upgrader facility used in connection with oil sand production. It may also refer to shale oil, an output from an oil shale pyrolysis. The properties of the synthetic crude depend on the ...
oil. The process used a vertical retort where heating causes decomposition of oil shale into shale oil, oil shale gas and spent residue. The particularity of this process is that oil shale in the retort moves from the bottom upward to the top, countercurrent to the descending hot gases, by a mechanism known as a rock pump. The process technology was invented by the American oil company Unocal Corporation in late 1940s and was developed through several decades. The largest oil shale retort ever built was the Union B type retort.


History

Union Oil Company of California (Unocal) started its oil shale activities in 1920s. In 1921, it acquired an oil shale tract in the
Parachute Creek Parachute Creek is a U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map accessed March 18, 2011 tributary of the Colorado River in Garfield County, Colorado. The confluence with the Colorado is just ...
area of Colorado, southern Piceance Basin. The development of the Union process began in the late 1940s, when the Union A retort was designed. This technology was tested between 1954 and 1958 at the company-owned tract in the Parachute Creek. During these tests, up to 1,200 tonne per day of oil shale was processed, resulting of shale oil, which was refined at a Colorado refinery. More than of gasoline and fuels were produced. This production was finally shut down in 1961 due to cost. In 1974, the Union B process, evolved from the Union A process, was developed. In 1976, Union announced its plans to build a Union B demonstration plant. Construction started in 1981 at Long Ridge in Garfield County, Colorado, and the plant was started its operations in 1986. It was closed in 1991 after production of shale oil.


Process

The Union process can be operated in two different combustion modes, which are direct and indirect. The Union A (direct) process is similar to the gas combustion retort technology, classified as an internal combustion method, while the Union B (indirect) process is classified as an externally generated hot gas method. The Union retort is a vertical shaft retort. The main difference to other vertical shaft retorts such as Kiviter, Petrosix, Paraho and Fushun is that crushed oil shale is fed through the bottom of the retort rather than the top. Lumps of oil shale in size of are moved upwards through the retort by a solids pump (known as a "rock pump"). Hot gases, generated by internal combustion or circulated through the top of the retort, decompose the oil shale while descending. The pyrolysis occurs at the temperature of to . Condensed shale oil and gases are removed from the retort at the bottom. Part of the gases is recirculated for pyrolysis and fueling combustion, while other part could be used as product gas. The
spent shale 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 kno ...
is removed from the top of the retort. After cooling with a water, it is conveyed to the waste disposal.


Advantages

The Union retort design has several advantages. The reducing atmosphere in the retort allows the removal of sulfur and nitrogen compounds through the formation of
hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...
and ammonia. Oil vapors are cooled by the raw oil, thus minimizing polymer formation among the hydrocarbon fractions.


See also

* Alberta Taciuk Process *
Galoter process The Galoter process (also known as TSK, UTT, or SHC; its newest modifications are called Enefit and Petroter) is a shale oil extraction technology for a production of shale oil, a type of synthetic crude oil. In this process, the oil shale is d ...
* Fushun process *
Kiviter process The Kiviter process is an above ground retorting technology for shale oil extraction. History The Kiviter process is based on the earlier vertical retort technology (Pintsch's generator). This technology underwent a long process of development. ...
* Lurgi-Ruhrgas process *
Paraho process The Paraho process is an above ground retorting technology for shale oil extraction. The name "Paraho" is delivered from the words "''para homem''", which means in Portuguese "for mankind". History The Paraho process was invented by John B. Jones, ...
*
Petrosix Petrosix is the world's largest surface oil shale pyrolysis retort with an diameter vertical shaft kiln, operational since 1992. It is located in São Mateus do Sul, Brazil, and it is owned and operated by the Brazil energy company Petrobras. Pet ...
*
TOSCO II process The TOSCO II process is an above ground retorting technology for shale oil extraction, which uses fine particles of oil shale that are heated in a rotating kiln. The particularity of this process is that it use hot ceramic balls for the heat tran ...
*
Superior multimineral process The Superior multimineral process (also known as the McDowell–Wellman process or circular grate process) is an above ground shale oil extraction technology designed for production of shale oil, a type of synthetic crude oil. The process heats oil ...


References

{{Reflist, 2 Oil shale technology