ENERGY CONVERSION

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• ENERGY CONVERSION
• ES 832a
• Eric Savory
• www.eng.uwo.ca/people/esavory/es832.htm
• Lecture 4 Fuels
• Department of Mechanical and Material Engineering
• University of Western Ontario

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Aim To examine the different fuel sources These
include Fossil fuels - Coal - Fuel oil -
Natural gas - Bitumen Synthetic fuel
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Fossil fuels

• Four main types Coal, fuel oil, natural gas and
  bitumen
• Fossil Fuels are hydrocarbons, formed from the
  remains of dead plants and animals. Fossil fuel
  is a general term for buried combustible
  geological deposits of organic materials, formed
  from decayed plants and animals that have been
  converted to crude oil, coal, natural gas or
  heavy oils by exposure to heat and pressure in
  the earth's crust over hundreds of millions of
  years.
• The chemical compound is Cx(H20)y, which is
  produced by plants through photosynthesis where
  solar energy is converted to chemical energy.
• Most of the fossil fuels were produced in the
  Carboniferous Period of the Paleozoic Era 299 -
  359 million years ago.
• The fuel formulation is CnH2n2.

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Fossil fuels

• Coal - it is composed primarily of carbon along
  with assorted other elements, including sulphur.
• Fuel oil - it is made of long hydrocarbon chains,
  particularly alkanes, cycloalkanes and aromatics.
  
• Natural gas - consisting primarily of methane
  (CH4) but including significant quantities of
  ethane (C2H6), propane (C3H8), butane (C4H10),
  carbon dioxide, nitrogen, helium and hydrogen
  sulphide. It is found in oil fields, natural gas
  fields and in coal beds.

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Fossil fuels
Bitumen it is a mixture of organic liquids that
are highly viscous, black, sticky, entirely
soluble in carbon disulphide (CS2), and composed
primarily of highly condensed polycyclic aromatic
hydrocarbons (PAHs). Bitumen is primarily used
for paving roads. Its other uses are for general
waterproofing products, including the its use in
the production of roofing felt. Oil shale - is a
general term applied to a group of rocks rich
enough in organic material (called kerogen) to
yield petroleum upon distillation.
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Coal

• Coal is formed from plant remains that have been
  compacted, hardened, chemically altered, and
  metamorphosed by heat and pressure over
  geological time.
• Coal was formed in swamp ecosystems which
  persisted in lowland sedimentary basins. These
  swamp environments were formed during slow
  subsidence of passive continental margins, and
  most seem to have formed adjacent to estuarine
  and marine sediments.
• When plants die in these peat swamp environments,
  their biomass is deposited in anaerobic aquatic
  environments where low oxygen levels prevent
  their complete decay by bacteria and oxidation.

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Burial by sedimentary loading on top of the peat
swamp converts organic matter to coal by -
Compaction, due to loading of the sediments on
the coal which flattens the organic matter -
Removal of water held within the peat in between
the plant fragments - Ongoing compaction ?
removal of water from the inter-cellular
structure of fossilized plants - Heat and
compaction ? removal of water - Methanogenesis
similar to treating wood in a pressure cooker,
methane is produced, which removes hydrogen and
some carbon, and some further oxygen (as water)
- Dehydrogenation, which removes hydroxyl groups
(OH) from the cellulose and other plant
molecules, resulting in the production of
hydrogen-reduced coals Generally, to form a coal
seam 1m thick, some 10 - 30m of peat is required.
Peat has a moisture content of up to 90.
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Coal formation
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Coal mining

• The most economical method of coal extraction
  from coal seams depends on the depth and quality
  of the seams, and also the geology and
  environmental factors of the area being mined.
• Surface and mountain top mining
• If the coal seams are near the surface, the coal
  is extracted by strip mining. Strip mining
  exposes the coal by the advancement of an open
  pit or strip.
• Mountain top removal is a form of surface mining
  that takes place at the topmost portion of a
  mountain. Utilized for the past 30 years,
  mountain top mining involves removing the highest
  part of the mountain for the maximum recovery of
  coal.
• Underground mining
• Most coal seams are too deep underground for open
  cast mining and thus this type of mining is
  called underground mining. In deep mining, the
  room and pillar method progresses along the
  Mammoth coal vein seam, while pillars and timber
  are left standing to support the coal mine roof.

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Petroleum (oil, gas)

• Petroleum forms from the remains of plants and
  animals that lived in the ocean 10-160 million
  years ago.
• When organisms died and sank to the bottom, they
  were covered in mud, sand, and other mineral
  deposits. This rapid burial prevented immediate
  decay, which would normally occur if the
  organisms remained exposed on the sea floor.
• The lack of oxygen in the sedimentary layers
  caused organisms to slowly decay into carbon-rich
  compounds. These compounds mixed with surrounding
  sediments and formed source rock, which is a type
  of fine-grained shale.
• As more layers were deposited on top of one
  another, pressure and heat acting on the source
  rock compressed the organic material into crude
  oil.

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Petroleum finding oil

• Discovering the location of oil within the earth
  is difficult because of the presence of cap rock,
  which can be miles thick in some locations. Oil
  geologists study surface rocks and the terrain to
  determine if any oil is present underground, but
  the best evidence comes from various satellite
  imaging techniques.
• Oil flows may disrupt the earth's gravitational
  or magnetic field and so gravity meters and
  magnetometers can detect some oil sources.
• The most reliable method for finding oil is
  through the use of shock waves in a process
  called seismology. In a seismological survey a
  shock wave is aimed at the surface of the water
  or land and the length of time it takes for the
  waves to reflect back to the sensor is recorded.
  The speed of the shock wave depends on the type
  of rock it travels through, and by comparing the
  travel times to known densities of rock,
  seismologists can determine what rocks are
  underground and predict if they might contain
  oil.

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Petroleum production

• The most common method of obtaining petroleum is
  extracting it from oil wells found in oil fields.
  
• Primary recovery methods are used to extract oil
  that is brought to the surface by underground
  pressure and can generally recover about 20 of
  the oil present.
• After the oil pressure has depleted to the point
  that the oil is no longer brought to the surface,
  secondary recovery methods draw another 5 to 10
  of the oil in the well to the surface.
• Finally, when secondary oil recovery methods are
  no longer viable, tertiary recovery methods
  reduce the viscosity of the oil in order to bring
  more to the surface.

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Crude oilrefinement fractional distillation
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Oil shale fine grained sedimentary rock
containing kerogen

• The kerogen in oil shale can be converted to oil
  by the chemical process of pyrolysis, during
  which the oil shale is heated to 445 - 500C in
  the absence of air (pyrolysis) and the kerogen
  is converted to oil and separated out, a process
  called "retorting".
• Oil shale has been burnt directly as a low-grade
  fuel.
• It was estimated that in earths crust there are
  6.5x1015 Tons of oil shale, about 1,000 times
  more than coal.
• The US Energy Information Administration
  estimates the world supply of oil shale at 2.6
  trillion barrels of recoverable oil, 1.0-1.2
  trillion barrels of which are in the US. However,
  attempts to develop these reserves have been
  going on for over 100 years with limited success.
• The caloric value of oil shale is 100 times
  smaller than coal.

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Crude oil production from oil shale
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Energy overview
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Crude oil and natural gas field counts,
cumulative production, proven reserves, and
ultimate recovery
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US Coal Demonstrated Reserve Base (as at 1
January 2005)
Energy Information Administration / Annual Energy
Review 2005
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US Uranium Reserves and Resources
Energy Information Administration / Annual Energy
Review 2005
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World Primary Energy Production by Region and
Country
Energy Information Administration/ Annual Energy
Review 2005
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World Crude Oil and Natural Gas Reserves (as at 1
Jan 2005)
DOE-EIA /Annual Energy Review 2005
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World Crude Oil Production
DOE-EIA / Annual Energy Review 2005
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World Natural Gas Plant Liquid Production
DOE-EIA / Annual Energy Review 2005
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Retail Motor Gasoline Prices in Selected
Countries, 2005
DOE-EIA/ Annual Energy Review 2005
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World Petroleum Consumption
DOE-EIA / Annual Energy Review 2005
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World Dry Natural Gas Consumption
DOE-EIA / Annual Energy Review 2005
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• Synthetic Fuels

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Introduction

• Synthetic fuel or synfuel is any liquid fuel
  obtained from coal, natural gas, or biomass. It
  can sometimes refer to fuels derived from other
  solids such as oil shale, tar sand, waste
  plastics, or from the fermentation of biomatter.
  It can also refer to gaseous fuels produced in a
  similar way.
• The process of producing synfuels is often
  referred to as Coal-To-Liquids (CTL),
  Gas-To-Liquids (GTL) or Biomass-To-Liquids (BTL),
  depending on the initial feedstock.

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Motivation

• Synthetic fuels require a relatively high price
  of crude oil in order to be competitive with
  petroleum-based fuels without subsidies. However,
  they offer the potential to supplement or replace
  petroleum-based fuels if oil prices continue to
  rise. Several factors make synthetic fuels
  attractive relative to competing technologies
  such as biofuels, ethanol / methanol or hydrogen
• The raw material (coal) is available in
  quantities sufficient to meet current demand for
  centuries
• It can produce gasoline, diesel or kerosene
  directly without the need for additional steps
  such as reforming or cracking
• There is no need to convert vehicle engines to
  use a different fuel
• There is no need to build a new distribution
  network

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Substitute Natural Gas (SNG)

• Infrastructure of gas supply near coal mining.
• The obtained gas is often Methane CH4 which has
  a caloric value of 1,000 Btu/scf.
• Gasification is a process that converts
  carbonaceous materials, such as coal, petroleum,
  or biomass, into carbon monoxide and hydrogen.
• Produces High Btu Gas (1,000) Low Btu Gas
  (500).
• The gas tends to be cheaper than coal.
• The gas production technology is simple.

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Gasification processes using coal

• 1. COAL H2 ? CH4 C (heat)
• 2. COAL 2H2 ? CH4 (heat)
• 3. COAL H2O ? CO H2 (-heat)
• 4. 4C O2 ? CO2 heat
• 5. 2C O2 ? 2CO2 heat

H20
O2 (AIR)
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Upgrading

• CH4, CO, H2 Raw Gas (500 Btu/scf)
• CO2, H2S, NH3 Residual
• 1. CO H2O ? CO2 H2
• 2. CO2 H2, H2S Acid gases removal
• 3. CO 3H2 ? CH4 H2O Catalytic methanation
• Pipe line gas 1000 Btu/scf

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Technological parameters

• Type of coal being used
• Preparation
• Feeding technique to the reactor
• Reactor type
• Fixed bed
• Fluidized bed
• Entrained flow
• Heat supply - external / internal
• Temperature and pressure

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Fischer-Tropsch process

• Oil gasification is a catalyzed chemical reaction
  in which carbon monoxide and hydrogen are
  converted into liquid hydrocarbons of various
  forms. Typical catalysts used are based on iron
  and cobalt. The principal purpose of this process
  is to produce a synthetic petroleum substitute
  for use as synthetic lubrication oil or as
  synthetic fuel.

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• In-direct method
• Following the gasification process, by using H2
  and CO, these reactions can occur
• (2m1)H2 mCO ? CmH2m2 mH2O
• (n1)H2 2mCO ? CmH2m2 nCO2
• CmH2m2 is fuel ? C8H18
• Direct method
• Coal dissolving and by adding H2 (at temp. of
  5000C)
• nC (n1)H2 ? CnH2n2

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Contamination

• CO unburned fuel
• Hydrocarbons unburned fuel
• NOx, N2OS, NO2 reaction at high temp.
• SO2 after oxidation, once in contact with water
  turns to H2SO4
• More information on these processes can be found
  at SASOL Technology
• www.sasol.com