Energy -II

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Energy -II
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Assuming no action is taken to reduce these
emissions, the U.S. will emit approximately 8,000
million metric tons (8,800 million tons) of CO2
by 2030, increasing 2005 emission levels by more
than 33 percent 86 of the emission will be for
power generation
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Clean Coal

• Scrubbers and electrostatic precipitaors
• Low Nox burners
• Crushing and washing coal
• Fluidized bed
• Capture and sequester CO2

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Reducing emissions

• Soot Electrostatic precipitators, along with
  baghouses (which work like large industrial-scale
  vacuum cleaners to capture ash and dust particles
  in felt or woven fabric bags), have been able to
  reduce the release of soot-forming particulate
  matter by 99 percent or more. Today, all coal
  burning power plants employ one, or in some
  cases, both of these devices
• SO2 Scrubbers can reduce sulfur emissions by 90
  percent or more. They are essentially large
  towers in which aqueous mixtures of lime or
  limestone sorbents are sprayed through the flue
  gases exiting a coal boiler. The lime/limestone
  absorbs the sulfur from the flue gas.
• NOx Exhaust gases, prior to going up the
  smokestack, pass through the system where
  anhydrous ammonia reacts with the NOx and
  converts it to harmless nitrogen and water.
• Mercury activated carbon a powdery substance
  commonly used to remove odors and contaminants in
  drinking water systems has also been shown to
  be effective in absorbing mercury from the flue
  gases of coal plants
• Fluidized-bed combustors

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Fluidized bed combustion

• Blowing pulverized particles of coal into a
  super-hot (approx. 3,000 degrees F) combustion
  chamber fluidized-bed combustors suspend larger
  chunks of coal (about the size of your
  fingernail) on upward-blowing jets of air. 
• The bed material consists of a coal-water fuel
  paste, coal ash, and a dolomite or limestone
  sorbent.
• Dolomite or limestone in the bed reacts with
  sulfur to form calcium sulfate, a dry, granular
  bed-ash material, which is easily disposed of or
  is usable as a by-product.
• A low bed-temperature of about 1,600F limits NOx
  formation.
•  effective in reducing SO2 and Nox by more than
  90
• eliminate the need for a post-combustion
  scrubber, and they can burn almost any grade of
  coal.

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• More than 170 fluidized-bed combustion units now
  operate in the United States.
• From 1980 to 2003,
• the amount of coal used to generate electricity
  in the United States increased by 75 percent
• sulfur dioxide, nitrogen oxide and mercury
  emissions declined by 40 percent

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CO2 sequestration

• Carbon sequestration encompasses the processes of
  capture and storage of CO2 that would otherwise
  reside in the atmosphere for long periods of
  time.
• Geologic sequestration
• Terrestrial sequestration

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Geologic sequestration

• is defined as the placement of CO2 into an
  underground repository in such a way that it will
  remain permanently stored.
• (1) mature oil and natural gas reservoirs,
• (2) deep unmineable coal seams,
• (3) deep saline formations,
• (4) oil- and gas-rich organic shales, and
• (5) basalt formations.

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Deep unmineable coalseams
Deep Saline Formations
Mature oil and natural gas fields
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• Terrestrial sequestration involves the net
  removal of CO2 from the atmosphere by plants and
  microorganisms and its storage in vegetative
  biomass and in soils.
• Also provides ancillary benefits such as habitat
  and water quality improvements
• increasing carbon uptake through reforestation
  and amendment of minelands and other damaged
  soils.
• through various land management techniques
  including no-till farming and wetland
  restoration.

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The Coal Plant of the Future

• Coal gasification (Synthetic Natural Gas SNG)
•  reacting coal with steam and oxygen under high
  pressures produces a gas
• can be cleaned of more than 99 of its sulfur and
  nitrogen and remove Mercury and other potential
  pollutants
• the coal gas can be cleaned to purity levels
  approaching, or, surpassing those of natural gas.
   
• Integrated gasification combined-cycle like
  natural gas, cleaned, the coal gases are burned
  in a gas turbine-generator to produce
  electricity. 
• Exhaust gases exiting the turbine are hot enough
  to boil water, creating steam that drives a steam
  turbine-generator, producing a second source of
  electricity.
• Integrated gasification combined-cycle power
  plants are one of the cleanest and most efficient
  coal-fueled power stations.
• eliminate virtually all of coal's pollutants,
• generate considerably more power from a given
  quantity of coal. 60 against 33-35 of today's
  power plants
• Higher coal-to-electricity efficiencies mean that
  less coal is used to generate power hence less
  carbon dioxide is emitted.

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SNG problems

• Require 50 more coal
• Produces 50 more CO2
• Costlier

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Natural Gas

• US proven reserve 164 trillion cubic feet
• Supplies 25 of all energy consumed in US
• Consumption 22 trillion cubic feet /year
• World reserve lt5000 trillion cubic feet
• Former USSR and Iran account for more than 60 of
  world reserve
• Cleanest Fossil Fuel Emits 30 less CO2 than oil
  and 43 less than coal, mostly free of sulfur and
  NO.

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Enhanced Recovery

• Any dramatic rise in reserves unlikely
• Typically about 2/3rd of all oil deposits are
  left in the ground because of difficulty of
  recovery
• Methods used for Enhanced recovery include
• Water and CO2 under high pressure and explosives
  to increase permeability
• Hot water and detergents to decrease viscosity
• Can increase yield by an additional 40
• Can be used for old and new fields
• Increases risks of pollution and ground
  subsidence
• Adds to the cost

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Alternate Gas sources

• Geopressurized gas At very great depths oil
  breaks down to natural gases which dissolves in
  pore waters and can be recovered by drilling.
  Est. Reserve 150 to 2000 trillion cu. ft
• Gas Hydrates In arctic regions and in marine
  sediments crystalline solids of gas and water
  called hydrates occur in commercial quantities.
  Estimated reserve 10,000 trillion cubic feet (2
  X Fossil Fuel reserve)
• Potential greenhouse effect of methane
• Enhanced recovery by fracturing of tight
  sandstones and gas bearing shale in the
  Appalachians

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Oil shale

• Sedimentary rocks containing kerogen a waxy
  substance formed from the remains of plant, algae
  and bacteria.
• Oil Shale has to be powdered and distilled to
  recover oil
• US reserve2 to 5 trillion barrels 2/3rd of
  World supply.
• Enough oil to supply USA for 110 years
• Found in Green River Formation of CO,WY and UT
• World supply 240X crude oil
• 1 ton of oil 3 tons of rock and 3 barrels of
  water,
• Problem of water, waste disposal and land
  reclamation

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Retorting is the process by which oil is
recovered from oil shale by application of heat
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Tar Sand

• Sedimentary rocks containing semi-solid tar-like
  petroleum (Bitumen)
• Either early stage of oil formation or residues
  after lighter fraction has migrated away
• Too thick to be pumped out
• Athabasca Tar Sands of Canada may contain 280-300
  billion barrels of recoverable oil (total reserve
  may be more than 2000 billion barrels). Canada
  hopes to meet 1/3rd of their oil needs from the
  tar sands.
• 15 of worlds oil supply, second only to Saudi
  Arabia. Venezuela other major country with huge
  tar sand deposit
• Uses natural gas and water, produces 80 kg of
  greenhouse gas each barrel of oil, destroys
  boreal forests, bogs, rivers
• Same processing and disposal problem as oil shale
• 1 barrel of oil uses up 0.7 barrels of energy

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Athabasca tar sand
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