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Chapter 10 Shale Oil.pptx

  1. CHAPTER 10 – Shale Oil Introduction Shales are geologic formations composed of thinly layered sedimentary rocks, and these are widely dispersed on the Earth. It has partially decomposed and metamorphosed over the ages until it now exists as a mixture of organic substances locked within the shale. The organic material contained in shale is called kerogen. The shale itself contains no oil as it is known today. However, if the shale is pretreated and fractionated at elevated temperatures, the kerogen decomposes and part of it is discharged as an oily vapor, which can be condensed into a viscous liquid referred to as shale oil. Unlike typical crude oil, this shale oil contains large amounts of compounds of nitrogen and large amounts of sulfur. These must be removed before a product like crude oil results.
  2. Early History Introduction Oil shale has been used since ancient times. It was first used for industrial purposes in the early seventh century. The world’s first commercial use of shale oil was based on mining operations in the Lothian region of Scotland in the middle of the nineteenth century, after the scientist James “Paraffin” Young devised a process of removing the oil by roasting the rock in ovens and draining away the fluid that it gave off. Following the 1973 oil crisis, the oil shale industry was resurrected in several countries, including the United States. However, in the 1980s, when oil prices fell, the industry again declined. The industry grew in full force at the start of the twenty-first century.
  3. Availability/Distribution and Characterization United States has a considerable fraction of the world’s oil shale deposits (approximately 73 percent according to an earlier 1974 World Energy Conference). Huge amounts of oil are also found along the Athabasca River in Alberta, Canada, where the tar sand deposits are near enough to the surface to be removed by a method like strip mining. The oil produced per ton is directly proportional to the amount of kerogen per unit of mass. The mass of oil is typically two-thirds of the mass of kerogen; however, it varies from 10 to 80 percent for various formations throughout the world. Oil shale must be hydrogenated to form a high-quality Syncrude oil for Refinery input.
  4. Availability/Distribution and Characterization Oil can also be extracted from bituminous tar sands that contain elevated quantities of hydrocarbons. The “Alberta Sands” of Canada, for example, average 83 percent sand, 13 percent bituminous matter, and 4 percent water. The heavy oils from shale are characterized by an unfavorable hydrogen/carbon ratio. These issues are typically corrected when hydrogen is added during the refining operation. Shale gas is also widely distributed throughout the U.S. Recent advances in hydrofracturing techniques have allowed for the development of these here-to- fore untapped resources. Shale gas resources are also being developed abroad as well.
  5. Extraction Oil shale is mined either by (1) traditional underground mining or (2) surface mining techniques. The two methods of surface mining are: (1) open pit mining and (2) strip mining. A method of subsurface mining is the room-and-pillar method, where the shale is extracted across a horizontal plane while leaving pillars of untouched material to support the roof. The main recovery technique involves first removing as much as 150 feet of overburden to allow huge mechanical diggers to start scooping out the shale.
  6. Extraction The operation is complex and expensive since huge digging machines are required to handle more than 6,000 tons of material an hour. Another type of oil that can be recovered by mining rather than drilling is found in grayish rocks known as shales. The oil is chemically combined with the shales. Very high temperatures are again required to force the rock to decompose so that it will discharge its oil content. However, this is a costly operation.
  7. Processing The four earlier commercially acceptable aboveground retorting processes required crushing shale and heating it to an elevated temperature to decompose the organic material. Each differs in the manner of heating. These methods yield shale oil and gas. In the Tosco process, the mined shale is crushed and fed to a preheat tower where it is heated by hot gas. This material is then fed into a rotary drum, where it mixes with marble-sized ceramic balls that have been preheated. The hot ceramic balls pulverize and heat the shale until oil and gas boil off. The spent shale is removed in the bottoms. The vapors can be sent to a distillation column
  8. Processing Finally, power plants can directly use oil shale as a fuel to employ two types of combustion methods. The traditional method is pulverized combustion, which is used in the older units in Estonia. The more advanced method is fluidized bed combustion, which is used in Germany and Israel. The two main fluidized bed technologies are the bubbling fluidized bed and circulated fluidized bed units.
  9. Environmental Issues Environmental concerns with oil shale are broad and encompass not only the industrial complex, but also the effect on the surrounding socioeconomic area and region. There is a considerable amount of air pollution, including the release of particulate, SO2, NOX, CO, and hydrocarbons from any of the processes discussed in the previous section. Blasting, mining, crushing, and transporting the oil shale all contribute to air quality particulate levels, and the transportation and storage of spent shale contributes even more. Air pollution will still be a major obstacle to oil shale development. It is estimated that slightly more than three barrels of water will be required for every barrel of oil produced from shale oil.
  10. Environmental Issues Water obtained from the oil shale itself is also contaminated with organics such as phenols and carboxylic acids. Summarizing, oil shale processes involve a number of environmental impacts; they are more pronounced in surface mining than in underground mining. They include acid drainage induced by the sudden rapid exposure and subsequent oxidation of formerly buried materials; the introduction of both organics and metals into surface water and groundwater; and increased erosion, sulfur emissions, particulate matter, and other forms of air pollution. The processes can also damage the biological and recreational value of land and the ecosystem in the area. The extensive use of water in arid regions is an extremely sensitive environmental issue.
  11. Future Prospects and Concerns In the future, it may be possible to produce oil from shale without costly excavation and processing. Some pyrolysis processes have been recommended and are currently under study. One of the processes involves combining a fluidized bed and a circulated fluidized bed for the purpose of burning the by-products of pyrolysis. Perhaps the most promising process is a pressurized fluid bed combustion process; however, this process is in the developmental stage.