Coal%20vs%20Diamonds

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Coal vs Diamonds

• Diamonds need high temperature and pressure,
  which is found at large depths in the Earth,
  usually between 140-190 km deep.
• Coal mines reach depths of 2000 ft (0.6 km)
• Dont form from coal, dating of diamonds shows
  them to be older than the oldest known plants
  that existed on the planet and it is unlikely to
  find coal that deep.
• Confusion stems from both being high in carbon
  content

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US Coal resources
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World distribution of coal
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World coal production
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Problems with coal

• Like oil and natural gas it will not last forever
• Best estimates are 100-200 years
• Be skeptical of large estimates, based on new
  discoveries, new technologies
• It is not a clean fuel source, lots of
  environmental impact from using coal
• Environmental effects of surface (strip) mining
• CO2 (carbon dioxide) emissions impact environment
  (green house effect)
• SO2 (sulfur dioxide) emissions pose health risks
• Mining risks (mine accidents, black lung disease)
• Is it really cheap?
• From an NRC report on the hidden costs of energy
  production
• In 2005 the total annual external damages from
  sulfur dioxide, nitrogen oxides, and particulate
  matter created by burning coal at 406 coal-fired
  power plants, which produce 95 percent of the
  nation's coal-generated electricity, were about
  62 billion
• This is twice as high as the cost of the coal
  itself

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Coal Liquefaction

• Process of producing synthetic fuel from coal
• Direct and indirect process to achieve this
• Direct
• Carbonization- produces coal tar, oil, water
  vapor, synthetic gas and char (a solid residue).
  Produces fluids that are of low quality for fuel.
• Hydrogenation add H2 to coal mixed with solvents
  and catalysts. No proven commercial value to the
  process
• Indirect Fischer-Tropsch process (Coal
  gasification)
• Coal is gasified into syngas, which is converted
  to gasoline ad diesel.
• Produces more CO2 than the crude oil
  refinement-needs carbon sequestering
  technologies.

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Coal gasification

• Process of producing coal gas, which can be
  converted into gasoline and diesel fuel and
  Hydrogen.
• Coal is heated and blown with oxygen and steam.
  Produces syngas, which can then be turned into
  gasoline as described on the previous slide.
• Or syngas is fed into another reaction which
  produces H
• Produces by-products which are environmentally
  damaging and need mitigation techniques

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Shale oil and tar sandsNonconventional fossil
fuels

• Shale oil largest deposit is found in the Green
  River Formation
• 50 million years ago, this area was covered by 2
  large tropical lakes. Organic material at the
  bottom of the lakes combined with sediment and
  formed a carbon containing mudstone, called
  marlstone.

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Green River Formation
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Recovery methods

• Getting the oil is not easy, nor is it cheap,
  thus as long as there is abundant, cheaper coal,
  this resources will remain untapped
• Same amount of coal produces much more energy
• Traditional removal process require heating (a
  process called retorting) of the shale to remove
  the hydrocarbons which expands the remaining
  shale by 35. Need a deposit site to handle the
  waste
• This process also requires lots of water, Green
  River formation is in a very dry part of the
  country.
• In situ (on site) recovery methods are being
  developed to overcome these difficulties

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Recovery methods
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Recovery methods
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Recovery methods
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Tar Sands

• Deposits of sand mixed with a thick hydrocarbon
  substance called bitumen
• Bitumen is so thick (viscous) that it does not
  flow. So sands must be transported to a
  processing plant.

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Locations

• Primarily in Canada
• Tar sands form where petroleum migrates upward
  into deposits of sand or consolidated sandstone.
  When the petroleum is exposed to water and
  bacteria present in the sandstone, the
  hydrocarbons often degrade over time into
  heavier, asphaltlike bitumen.

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Tar sands processing

• Tar sand is placed in rotating
  drums along with water and
  caustic soda that separates the
  water, soda and bitumen.
• Bitumen is placed in a centrifuge and cracked
  into naptha, kerosene and heavy fuel oil
• Similar energy density to shale oil, much less
  than coal

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In situ processing

• Two parallel horizontal oil wells are drilled in
  the formation. The upper well injects steam and
  the lower one collects the water that results
  from the condensation of the injected steam and
  the crude oil or bitumen.
• The injected steam heats the bitumen and lowers
  its viscosity, which allows it to flow down into
  the lower wellbore.
• The water and bitumen is recovered to the
  surface by several methods including a natural
  steam lift or by pumps that work well for moving
  high-viscosity fluids with suspended solids.

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Fossil fuels-going the way of the dinosaur?

• Total resource vs proved reserve
• Total resource is the amount of a resource that
  is known to exist
• Proven resource is the amount that is recoverable
  under current economic and technical conditions
• They are not equal!
• Barriers to untapped resources
• Restrictions on offshore oil drilling
• Strip mining of coal-environmentally a bad idea
• Tar sands mining has been referred to as the
  most destructive project on Earth
• No mater how you look at it, fossil fuels follow
  a Hubbert type curve, they will run out! It is a
  question of when, not if.

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Heat Engines

• How do we get the heat energy of the fuel and
  turn it into mechanical energy?
• Simply put we combine the carbon and hydrogen in
  the fuel with oxygen.
• 2 reactions that occur are
• C O2 ? CO2 heat energy
• H2 O ? H2O heat energy
• This process is just the reverse of
  photosynthesis.