Clean Coal

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Clean Coal

• Oxymoron or Key to Energy Independence?
• Michelle Chesebro
• mjchesebro_at_sbcglobal.net

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Current Coal Usage

• 50 of the energy in the U.S. is generated from
  coal
• More than 500 coal-fired power plants in U.S.
  with average age of 35 years
• U.S. supplies of coal projected to last from 164
  -250 years

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Economics and Security of Supply

• Coal is plentiful and cheap
• Coal is found in abundance in countries with
  stable governments
• United States, India, China
• MIT concluded that coal will continue to be used
  to meet the worlds energy needs in significant
  quantities.

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Greenhouse Gases

• Among fossil fuels, coal is the most
  carbon-intensive so electricity generated by coal
  produces high CO2 emissions
• U.S. coal-burning power plants contribute 1.5
  billion tons per year of CO2
• Globally, coal is responsible for 40 of CO2
  emissions

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Chinas Contribution to Greenhouse Gases from CO2

• International Energy Agency now predicts China
  will surpass the U.S. in CO2 emissions by 2009,
  10 years earlier than previous projections
• China uses more coal than the U.S., the E.U. and
  Japan combined
• China is bringing new coal-fired power plants
  online almost every week

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Proposed Solution

• Carbon Capture Sequestration (CCS) can reduce
  CO2 emissions significantly while using coal to
  meet energy needs
• Components

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Initial Step Coal Gasification

• Coal put in gasifier with oxygen and steam where
  heat and pressure are used to form a synthetic
  gas, known as syngas
• CO2 can then be captured
• Before combustion (IGCC)
• After combustion (Pulverized Coal plants)

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Product Syngas

• Composition Carbon Monoxide and Hydrogen
• Potential Uses
• Power Generation (IGCC)
• Fertilizers Methanol
• Natural Gas
• Gasoline Diesel Fuels (Fischer-Tropsch)

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Post-Combustion Capture

• Used in conventional pulverized coal-fired power
  (PC) plants that produce flue gases
• CO2 separated out from flue gas
• 80-95 captured (but low concentrations to begin
  with in flue gas)

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Post-Combustion Process

• Flue gas is passed through an absorber where a
  solvent removes most of the CO2
• CO2-containing solvent goes to stripper and is
  heated to release the CO2
• New process being used by American Electric
  Power chilled ammonia used as solvent can
  process larger amounts of CO2, but requires less
  energy

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Post Combustion
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Pre-Combustion Capture

• Integrated Gasification Combined-Cycle (IGCC)
  technology
• Used in new power plants and well suited for high
  grade bituminous coal
• 90 of CO2 removed

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IGCC Process

• Coal gasification to produce syngas
• Syngas cooled and cleaned to remove particulates
  and other emissions
• Electricity generation
• Syngas then combusted with air or oxygen to drive
  gas turbine
• Exhaust gases are heat exchanged with water/steam
  to drive steam turbine
• By introducing steam between cooler and gas
  clean-up, CO converted to CO2 which can be
  captured and stored before combustion

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IGCC Process

1. Coal burned to produce syngas
2. Syngas burned in combustor
3. Hot gas drives gas turbines
4. Cooling gas heats water
5. Steam drives steam turbines

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Competing Technologies

• Because of the differences in coal type, a wide
  range of technologies will need to be deployed.
  We should not jump on the IGCC bandwagon too
  quickly for research development , but
  continue to fund a variety of options
• Clear preference for IGCC or SCPC (Super Critical
  Pulverized Coal) cannot be justified at this time

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Comparison of IGCC and SCPC

• Reasons to prefer IGCC
• Potential tightening of air quality standards for
  other pollutants reduced by IGCC, such as SO2,
  NOx and mercury
• Likelihood of a future carbon charge
• Possible federal or state financial assistance
  for IGCC
• Reasons to prefer SCPC
• Near-term opportunity for higher efficiency
• Capability to use lower cost coals
• Ability to cycle the power plant more readily in
  response to grid conditions
• Confidence in reaching capacity factor/efficiency
  performance goals

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Retrofitting Costs

• Major technical modifications required regardless
  of which technology is used
• Based on todays engineering estimates, cost of
  retrofitting for IGCC appears to be cheaper than
  retrofitting for SCPC
• Variables
• Timing and size of carbon charge
• Difference in retrofit cost
• Very possible that old plants will just have to
  be bulldozed because retrofitting will prove to
  be cost-prohibitive

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Another Option UCG

• Underground Coal Gasification
• Addresses other environmental concerns associated
  with coal mining

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Other Technologies

• Oxygen fired pulverized coal combustion (more
  promising for lower quality coals)
• Burning coal in oxygen-rich atmosphere to produce
  a pure stream of CO2
• Chemical looping combustion
• Continually looping two stage reaction process
  that provides two waste streams from coal
  combustion
• The first contains carbon dioxide and water, and
  the CO2 can be compressed for storage

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Transport of Captured CO2

• Compressed to supercritical fluid
• Dense as liquid
• Gas-like viscosity
• Transported through pipelines
• Or further cooled and transported in marine
  tankers like LNG

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Sequestration
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Storage of Captured CO2

• Deep geologic formations such as saline aquifers
• Depleted oil and natural gas fields
• Ocean
• Dissolving CO2 deeper than ½ mile
• Depositing liquefied CO2 on sea floor 2 miles down

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Carbon Options

1. CO2 pumped into disused coal fields displaces
   methane which can be used as fuel
2. CO2 can be pumped into and stored safely in
   saline aquifers
3. CO2 pumped into oil fields helps maintain
   pressure, making extraction easier

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Storage Concerns

• Leakage presents an immediate hazard to humans
  and ecosystems (CO2 is an asphyxiant)
• Possibilities
• Blow-out at injection well
• Slow leak through faulty well or ground fractures
• Even slow leaks negate the benefit of burying the
  CO2 in the first place

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Regulatory Framework for Storage

• Must include
• Site selection
• Injection and surveillance
• Eventual transfer of liability to the government
• The goal of energy independence cannot be allowed
  to trump global warming concerns. Even if a
  regulatory framework is developed for the U.S.,
  who will be the global carbon police?

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Status of CCS Projects

• Current IGCC Projects used primarily for
  enhanced oil gas recovery, not CO2 storage
• Sleipner in Norway
• Weyburn in Canada
• In Salah in Algeria
• Need large-scale demonstration before this can be
  considered a viable proposal
• Large-scale electricity generation proposed
  projects
• FutureGen in the U.S.
• ZeroGen in Australia
• A number of proposals in Europe and Canada

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Price of Coal

• Coal is plentiful and currently cheap because the
  health and environmental costs are borne by the
  public, not the industry
• But price will increase
• Charge for CO2 emissions to account for health
  and environmental costs
• Deploying carbon capture and storage will
  increase price of coal-fired power by at least
  50, with some estimating twice that amount

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Grandfathering Loophole

• Utilities may be tempted to invest in new power
  plants without capture in the hope that these
  plants will be grandfathered in
• Expectation of free CO2 allowances under future
  carbon emissions regulations
• Benefit when electricity prices increase as a
  result of a carbon control regime
• Congress needs to close the loophole

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Coal to Liquid

• The bigger hurdle for energy independence is
  finding a replacement for gasoline. Other
  countries have used a process for turning coal
  into gasoline (Nazi Germany and the apartheid
  government of South Africa).
• Coal ? Gasifier ? Syngas
• Fischer-Tropsch Process
• Syngas ? Reactor ? Hydrocarbons
• Hydrocarbons cooled liquid fuel
• Concern Coal to Liquid (CTL) development has no
  near-term plan to capture any of the CO2 it
  produces. Until it does, using the label clean
  coal is inaccurate.

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Liquid Fuel from Coal

• Second approach direct coal liquefaction ? coal
  is pulverized and mixed with oil and hydrogen in
  a pressurized environment

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CTL

• CTL with carbon capture
• Will be incredibly expensive and will require
  government subsidies
• If 85 of the CO2 is captured, the liquid fuel
  that is produced will have the same emissions as
  a gallon of regular diesel
• CTL without carbon capture
• May be economically viable without government
  subsidies
• Will be a disaster in terms of global warming

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Concerns

• Technological issues for both capture and
  sequestration are not trivial and we are still at
  least five to ten years away
• Any sequestration method still has the potential
  for leaks
• Impact to human health high concentrations of
  CO2 causes loss of consciousness
• CO2 makes water in aquifers acidic enough to
  dissolve certain types of rocks releasing toxins
  that seep into drinking water
• Any leak at all reduces the benefits of carbon
  capture technology, because there is no way to
  recapture the leaked CO2 and store it again

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Big Picture

• Federal funding should continue so that we can
  learn more about the costs and risks of burying
  CO2
• However, coal is the fuel of the past, not the
  future. (Jeff Goodell) Clean coal technology is
  not a long-term solution to Americas (or the
  worlds) energy problems.