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Process and technologies

Mining

Mining methods
Oil shale is a rock can can be mined, then converted into oil or electricity. Oil shale can be mined using either underground or open-cast mining methods.

Opencast mining
In places where the oil shale stratum is not very deep below the surface, oil shale is mined in quarries.

Underground mining
If the oil shale stratum lies deeper below the surface, extraction must take place in an underground mine. This requires that mining chambers be dug and supported, and transport systems built to transport the mined rock to the surface.

 

Production of electricity

Technology
Oil shale can be used for power generation with direct combustion. In Circulating Fluidised Bed (CFB) boilers, the finely ground oil shale is burned in a stream of air directed into the combustion chamber from below, creating a so-called fluidised bed. The combustion heat is used to produce steam from water. Steam is directed into a turbine where the kinetic energy of the steam rotates a turbine generator that produces the electrical energy.

Advantages of the circulating fluidised bed
Oil shale power can also be produced by burning pulverized oil shale, but the newer circulating fluidised bed technology has several advantages compared with older technologies:

  • Lower combustion temperatures of 850˚C-900˚C.
  • The heating surfaces of fluidised bed boilers do not corrode like they do in the higher temperatures of pulverised oil shale boilers.
  • Low-abrasion dust particles prevent the erosion of the heating surfaces.
  • The wastes that collect on the heating surfaces are easily removable large sediments, allowing the use of simpler cleaning methods.
  • The low temperature in the combustion chamber and the circulating ash effectively bind sulphur.
  • Air emissions are in conformance with strict EU regulations.
 

Industrial scale production

Ways to produce oil
Oil shale can also be used to produce oil. There are two possible ways to produce oil out of oil shale, and only one of those — using traditional mining and refining techniques — is commercially proven. The other possible way, called "in-situ" production, is still only in the experimental stage at this point.

Retorting
After the oil shale has been excavated it will then undergo retorting - the mined rock is exposed to the process of pyrolysis whereby extreme heat is applied to the rock in the absence of oxygen resulting in a chemical change. Once the chemical change takes place, the kerogen trapped within the rock begins to liquefy and separate from the rock. The oil-like substance can then be further refined into synthetic crude oil.

Efficiency
Due to the efficiency of advanced oil shale technology, 100% of the organic matter in the mined oil shale is utilised, while the excess heat and gas produced is used to generate electricity, making oil shale plants net producers of electricity.