Information AboutShale Oil |
| CATEGORIES ABOUT OIL SHALE EXTRACTION | |
| oil shale | |
| petroleum | |
| chemical engineering | |
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There are hundreds of patents for oil shale retorting technologies. However, only a few dozen have been tested in a pilot plant (1 to 10 t/h) and less than ten technologies have been tested at a demonstration scale (40 to 400 t/h). Only five technologies are currently in commercial use, which are Kiviter, Galoter, Fushun, Petrosix , and Alberta Taciuk. Almost all of the commercial retorts currently in use or in developing are the internal heating retorts.1 At present shale oil extraction is being undertaken in Estonia, Brazil and China, while some other countries as Australia, USA, Canada and Jordan have planned to start or restart shale oil production.23 CLASSIFICATION OF TECHNOLOGIES There are several classifications of extraction technologies. The main classification divides technologies into two primary methods basing on the location of extraction. The first method is to mine the oil shale and then process the shale rock to extract the oil, known as ''ex-situ'' or above-ground retorting. The second method converts the kerogen while it is still in the formation and then extracts normally via a well, known as ''in-situ''. Both primary methods could be subdivided into classes by the method that is used to heat the shale to retorting temperature. The classes are internal combustion, hot recycled solids, conduction through a wall, externally generated hot gas, reactive fluids, and volumetric heating.4 Based on the size of used shale fraction the ''ex-situ'' technologies could be divided to lump shale using technologies and particulate shale using technologies. In general, the lump shale is used in internal hot gas carrier technologies, while the particulate oil shale (less than ) is used in internal hot solid carrier technologies. The ''in-situ'' technologies are usually classified as ''true in-situ'' processes (TIS) and ''modified in-situ'' processes (MIS). While ''true in-situ'' processes do not involve mining the shale, the ''modified in-situ'' involves prior to heating mining beneath the target oil shale deposit, and drilling and fracturing the target deposit above the mined area to create void space of 20-25 % to improve the flow of gases and liquid fluids through the rock formation, and by that increasing the volumes and quality of the oil produced. EX-SITU TECHNOLOGIES In case of the ''ex-situ'' method, the oil shale is/can be mined either by traditional underground mining or surface mining from the ground and then transported to a processing facility. At the facility, the shale is usually heated to – . At this temperature, the kerogen in the shale decomposes to gas, oil vapour and char, a process known as retorting. The gas and oil vapours are separated from the spent shale and cooled causing the oil to condense. The oil may be sold as a fuel oil or upgraded to meet refinery feed specifications by adding hydrogen and removing impurities such as sulphur and nitrogen. The non-condensible retort gas and char on the spent shale may be burned and the heat may be recovered for heating the raw shale or generating electricity. Combustion exhaust gases and water condensed with the oil need to be treated prior to emission to the environment. Usually the spent shale is cooled and moistened with water before disposal back to the mine, settling ponds or tailing piles. Internal combustion technologies Internal combustion or directly heated technologies uses heat, which is transferred by flowing gases generated by combustion within the retort. Common characteristics of these technologies are the feed shale consists of lumps ( - ) and the retort vapours are diluted with the combustion exhaust. The main technologies are Kiviter, Union A, Paraho Direct, Superior Direct, and Fushun processes. The Kiviter processing takes place in gravitational shaft retorts and it's possible only using large-particle feed. The process gas combustion products are used as the heat carrier. In the case of ''kukersite'' the yield of crude oil accounts 14-17 % of shale and the oil consists only small amount of low-boiling fractions. Main problems of Kiviter process are related with environmental concerns like extensive use and pollution of water in the process, as also solid residue continues to leach toxic substances.56 The Kiviter process is used by Estonian company VKG Oil, a subsidiary of Viru Keemia Grupp .7 The company operates several retorts, the largest processing 40 t/h of oil shale. Like the Kiviter, the Fushun-type retort processes oil shale lumps in a vertical shaft kiln. The Fushun Mining Group in Liaoning Province , China operates the largest shale oil plant in the world employing 80 Fushun-type retorts.8 The Paraho Direct is an American version of the lump-processing vertical shaft kiln. This technology is used by Shale Technologies LLC in a pilot plant facility in Rifle, Colorado.9 Hot recycled solids technologies Hot recycled solids technologies use heat, which is transferred by mixing hot solid particles with the oil shale. These technologies usually process oil shale fines (less than 10 mm). The heat carrier (usually shale ash) is heated by combustion in a separate chamber or vessel, thus the retort vapours are not diluted with combustion exhaust. The main technologies are Alberta Taciuk Process, Galoter, TOSCO II, Lurgi-Ruhrgas , Chevron STB, LLNL HRS, and Shell Spher processes. In the Galoter process, retorting takes place in a rotary kiln-type retort and it's possible to use also shale fines. The spent shale is burned in a spouted bed and solid shale ash is used as the heat carrier. In the case of ''kukersite'' the yield of crude oil accounts roughly 12 % of shale and the oil consists 15-20 % of low-boiling fractions. The Galoter process is more environmental-friendly than the Kiviter process, as the water use and pollution is smaller. However, the burning residue causes some environmental problems because of organic carbon and calcium sulphide consistent. The Galoter process is used for oil production by Eesti Energia , Estonian energy company. The company has 2 retorts both processing 125 tonne/hour of oil shale and plans to build two more. |
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