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					          Coal
Energy Issues and Technology
     Coal
   How, What, When?
   Types
   Reserves (Where?)
   Mining
   Consumption
   Environmental Consequences
   The future
   …
     Coal: What is it?
   Carbon!
   Valuable as an fuel, because carbon readily
    reacts with oxygen and releases energy
    (and CO2)
   Molecules also contain hydrogen, oxygen,
    sulfur, and nitrogen
   No single “coal molecule”, but all are large,
    complex hydrocarbons
Coal: What is it?
     Coal: What is it?
   Formed from the remains of vegetation that
    grew million of years ago
   As plants and trees died, their remains sank
    to the bottom of a swampy areas
   A soggy, dense material formed in low
    oxygen conditions, called peat
     Coal: What is it?
   Over time, sand and silt accumulated above
    the peat
   Pressure and temperature changed sand
    into sandstone, and chemically converted
    peat into coal
   Differences in composition, pressure,
    temperature, and time results in different
    grades of coal
Coal: What is it?
     Coal: When?
   Coal has always been forming and is still
    forming now
   Two periods when conditions were
    particularly good for US coal formation
    – ~ 300 million years ago (Carboniferous period):
      Eastern coal
    – ~ 150 million years ago (Cretaceous and
      Jurassic periods): Western coal
     Coal: Necessary Conditions
   Rapid growth of plants
   Certain types of plants
   High Water Table
   Land Subsidence
   Burial of Sediments
   Uplift
     Coal: Necessary Conditions
   Rapid growth of plants
    – Best conditions are a warm climate with little
      temperature fluctuations (Everglades)
    – One meter of low grade coal takes 6,000 –
      9,000 years of organic sedimentation
     Coal: Necessary Conditions
   Types of plants
    – Grasses contribute little mass
    – “Trees” are best
        Carboniferous (300 MYA) trees like modern ferns:
         Eastern coal seams a few meters thick
        Cretaceous and Jurassic (150 MYA) trees like
         modern coniferous trees: Western coal seams 100s
         of meters thick
     Coal: Necessary Conditions
   High Water Table
    – A swamp that never dries out: Peat must be
      continuously covered to prevent oxygen from
      causing organic material to decay
    – Slow moving water better (swamp): Fast
      moving water is constantly replenishing
      dissolved oxygen (bad!)
     Coal: Necessary Conditions
   Land Subsidence
    – The land must continuously and gradually
      subside to maintain proper water depths
       Too shallow: peat decays in oxygen
       Too deep: inadequate organic mass (few plants)
     Coal: Necessary Conditions
   Burial of Sediment
    – Peat must eventually be buried to seal off
      oxygen and ensure adequate depth, pressure
      and temperature
     Coal: Necessary Conditions
   Uplift
    – A rising landform must lift coal near the
      surface, or it’s too expensive to mine
Coal: Types




   Volatiles: “coal tar” organics
     Coal: Types
   Lignite: brown coal
    – 25% - 35% carbon content
    – Energy Content: 5,000 – 7,000 Btu/lb
    – Peat compressed to 20% of original thickness
    – Relatively young and formed under moderate
      temperatures and pressures
    – Found in the US in Texas and North Dakota
     Coal: Types
   Subbituminous and Bituminous: soft coal
    – Subbituminous
        35% - 45% carbon content
        Energy content 8,000 – 10,000 Btu/lb

        Accounts for 40% of US coal (Western)

    – Bituminous
        45% - 86% carbon content
        Energy content 11,000 – 15,000 Btu/lb

        Accounts for 50% of US coal (Appalachian)

    – In order to form, must be heated to between
      100°C and 200°C
     Coal: Types
   Anthracite: hard coal
    – 86% - 97% carbon content
    – Energy content 14,000 Btu/lb
    – Compressed to 5% of original thickness
    – Contains less than 10% water and other
      volatiles
    – Found in NE PA
Coal: Reserves
Coal: Reserves
     Coal: Types
   Coals also vary in composition
    – Western coal contains trapped sediment from
      volcanic ashfalls
    – Coal contains elements adsorbed by carbon
      from groundwater
          Carbon is a good filter!
    – Appalachian coal (particularly from northern
      WV) has a higher sulfur content compared to
      Western coal
     Coal: Reserves
   Reserves…
    – Proven reserves: well documented and
      economically recoverable at today's prices with
      current technology
    – Indicated or inferred reserves: sketchier -
      not as well documented, or not economically
      recoverable with current technology
    – US proven reserves: 270 billion short tons
    – US inferred reserves: 500 billion short tons
    – 1 short ton = 2,000 lbs
     Coal: Reserves
   World Proven Reserves (2006)
    – US:           271 billion short tons (27%)
    – Russia:       173 (17%)
    – China:        126 (12%)
    – India         102 (10%)
    – Australia     87 (9%)
    – World         1,000
     US Reserves
   How long will 271 billion tons last?
   At 1.1 billion tons/year (current US consumption)?
        250 yrs
   At 2% consumption growth? 90 yrs
   At 4% consumption growth? 60 yrs
     Coal: Production
   World Coal Mining Production (2006)
    – China:     2,578 million short tons (38%)
    – US:        1,114 (17%)
    – India:     543 (8%)
    – Germany:   272 (4%)
    – Russia:    264 (4%)
    – World:     6,719
     Coal: Production
   World Coal Production Growth
    – 2000:   5,098   million short tons
    – 2001:   5,191   (2% growth)
    – 2002:   5,272   (2% growth)
    – 2003:   5,706   (8% growth)
    – 2004:   6,150   (8% growth)
    – 2005:   6,483   (5% growth)
    – 2006:   6,719   (4% growth)
     Coal: Reserves
   US Coal Mining Production (by state, 2006):
     Coal: Reserves
   US Coal Mining Production (by state, 2006):
    – Wyoming         447 million short tons
     Coal: Reserves
   US Coal Mining Production (by state, 2006):
    – Wyoming         447 million short tons
    – West Virginia   152
     Coal: Reserves
   US Coal Mining Production (by state, 2006):
    – Wyoming         447 million short tons
    – West Virginia   152
    – Kentucky        121
     Coal: Reserves
   US Coal Mining Production (by state, 2006):
    – Wyoming         447 million short tons
    – West Virginia   152
    – Kentucky        121
    – Pennsylvania    66
     Coal: Reserves
   US Coal Mining Production (by state, 2006):
    – Wyoming         442 million short tons (38%)
    – West Virginia   152 (13%)
    – Kentucky        121 (10%)
    – Pennsylvania    66 (6%)
    – Texas           46 (4%)
    – US Total        1,163 million tons
     Coal: Wyoming
   442 million tons per year
    1 million tons per day

   1 “unit train”: 1 mile long, 100 cars, each
    carrying 100 tons  10,000 tons per mile

   Exporting coal from Wyoming requires
    1,000,000 tons/(10,000 tons/mile) = 100
    miles of train daily
Coal: Transporation
Coal: US Production
Price of Coal
Coal: spot price vs. region
     Coal: Power Plant
   A typical 1,000 MW power plant will
    consume 9,000 tons (90 railroad cars) of
    coal every day
Coal
   Mining
   Consumption
   Environmental Consequences – S, CO2
   The future – coal gas, …
Coal Mining
   Types of mines:
    – Underground, or “deep” mines
    – Surface mines
Mines
   Number of mines
    – East:       surface: 663   uground: 530
    – Interior:   surface: 68    uground: 32
    – West:       surface: 40    uground: 24
   Coal production (million short tons)
    – East:       surface: 138   uground: 251
    – Interior:   surface: 34    uground: 56
    – West:       surface: 515   uground: 59
Surface vs. Underground
• Production in
  # short tons/miner hr
• Production vs. mine type
Surface vs. Underground
Productivity
Underground Mining
   Drift
    – When side of seam
      is accessible
   Slope
    – When side of seam is
      not accessible
   Shaft
    – Deep seams
Underground Mining
   Old way: explosives and shovels
   New way!
Underground Mining
   New way!
Underground Mining
   Coal pillars must be left in place to
    support roof
   Roof bolts are also installed
   Pillars removed as mining process retreats
   Temporary supports installed
   Mine sealed
   Subsidence a problem
Underground Mining
   Dangerous!
    – 390 coal miner deaths since 1996 (35/year
      average)
    – Since 1996
       9 miner deaths in WY
       129 in WV

       114 in KY

    – 1925: 686 coal miners died in WV alone
      (worst year)
    – 2005: 3 miner fatalities in WV (safest year)
    – Aug., 2007: 6 miners and 3 rescuers die
         Crandell Canyon Mine, Huntington, UT
Mining Safety

     http://www.msha.gov/stats/charts/coalbyst
      ate.asp
Mining Safety

   China has a very poor mine safety record
    – US: 0.04 fatalities per million tons
    – China: 2.72 (almost 70 times greater)
   Why?
    – Lack of regulations and oversight
    – Lots of underground mining for preferred higher
      quality (deeper) coal
    – Low productivity (lots of workers)
        US: 13,300 tons per worker per year
        China: 600 (22  lower)
Surface Mining
   Area/Strip: Flat terrain, shallow overburden
   “Highwall”
    – Contour: Follows coal seam along hillside
    – Auger: Large drills
   Open pit: Thick seams; Can reach several
    hundred feet deep
   Mountain Top Removal
Area
   Overburden is blasted and removed by
    dragline
   Shovel loads coal into dump trucks
   Strips 100 ft – 200 ft wide are mined
Area




   250 ton
Contour
   Can access ends of seams
Contour
Auger




Often done after
contour mining
Open Pit




For very thick seams
Mountain Top Removal




             Kayford Mountain, WV
Kayford Mountain, WV
Mountain Top Removal
Mountain Top Removal




                   Blair, WV
Slurry
   Slurry
    – toxic sludge: a mix of water, coal dust, clay
      and toxic chemicals such as arsenic, mercury,
      lead, copper, and chromium
    – Result of washing coal
   800 slurry ponds are in the US
    – 200 built on top of abandoned surface mines
Slurry
   Map of WV slurry ponds
  Slurry




8 billion gallon Brushy Fork slurry impoundment in Whitesville, WV
Will eventually include a 954 ft dam (tallest in US)
Slurry
   In 2000, a coal impoundment near Inez,
    KY broke and spilled
    306 million gallons of
    slurry
    – 70 miles of streams
      destroyed
    – 20 times the amount of
      oil spilled by the Exxon
      Valdez in 1989
Slurry
   December, 2008
    – 2.6 million cubic yards of coal ash spills into
      Emory River in east TN
    – Impoundment pond at Kingston coal plant
    – 500 million gallons of sludge
    – 48 times the Valdez spill
    – http://www.treehugger.com/files/2008/12/ten
      nessee-coal-ash-slurry-spill-48-times-bigger-
      than-exxon-valdez-spill.php
Slurry
   Slurry Injection: Injecting slurry into
    abandoned underground wells
   WV’s Department of Environmental
    Protection has permitted 400 injections
    since 2000
    – Many illegal injections are likely
Power Plants
   US currently has around 1,600 coal-fired
    units
   NC has 14 power plants (all with multiple
    units), several dating from the 40’s
   Duke Energy
    – Gaston, Stokes, Rowan, Rutherford/Cleveland,
      Rockingham, Catawba Counties
   Progress Energy
    – Buncombe, Moncure, Goldsboro, Roxboro (one of
      largest in US at 2,462 MW), Wilmington, Lumberton
NC Power Plants




  http://www.bredl.org/air/nc_coal-fired_map.htm
NC Power Plants




 Marshall Steam Station, Catawba County
 Burns 18,000 tons (180 hopper cars) of coal per day
NC Power Plants




   Roxboro Steam Station, Person Co
   800 ft tall stacks
Power Plants
 Duke Energy applied to NC Utilities
  Commission for 1,600 MW of coal-
  fired plants at Cliffside, west of
  Charlotte
 Feb 2007: NCUC granted permit for
  800 MW, citing energy conservation is
  more effective; appealed
 Jan 2008 – Final (?) NCUC approval
  of 800 MW generation
    Surface Mine Regulations
   Surface mining and reclamation unregulated pre-1977
   1977: SMCRA (Surface Mining Control and
    Reclamation Act)
    – Establishes Office of Surface Mining
    – Illegal to abandon mines, and established a fund, with coal
      tax money, for abandoned mine cleanup
    – Surface mines must be returned to “approximate original
      contours”, but a waiver from this rule may be granted with a
      “post-mining land use plan”
    – Restore land to “a condition capable of supporting the uses
      which it was capable of supporting prior to any mining”, or
      to a condition that supports “higher and better uses.”
    – Lays out process of public participation
Surface Mine Regulations
   MTR has been fought by legal filings claiming
    mines violate the EPA’s Clean Water Act
   How the CWA works
    – Designated uses (DUs) of a waterbody are determined.
    – Water quality criteria (WQC) in a waterbody necessary
      to support the Dus are determined. These can be
      expressed as concentrations of pollutants, temperature,
      pH, turbidity units, toxicity units, or other quantitative
      measures.
    – Antidegradation policies are set that should be followed
      when addressing proposed activities that could reduce
      the amount of water that exceeds the criteria
      necessary to meet the designated uses.
Surface Mine Regulations
   March, 2007: U.S. District Judge Robert Chambers
    (Huntington, WV) ruled that MTR permits must
    give full consideration to the environmental
    effects of mountaintop removal
    – In effect halted 4 MTR mines
   Feb 17, 2009: Fourth Circuit Court of Appeals
    (Richmond, VA) overturned District Court’s
    findings
    – Procedural ruling – cited the Courts should defer to
      Army Corp of Engineers assessment that the mining
      operations in question would cause no environmental
      degradation
    – Environmental groups fear that 90 additional mountain
      tops will be blasted as a result
Surface Mine Regulations
   1983: “ Buffer zone rule” amended to SMACRA:
    prohibits coal mining activities from disturbing
    areas within 100 feet of streams
    – Allowed if activity “will not cause or contribute to the
      violation of State or Federal water quality standards”
   December, 2008: Bush administration amended
    (repealed) the “buffer zone rule”
    – Added language: ”The findings … do not apply to the
      construction of excess spoil fills in perennial or
      intermittent streams.”
    – Result: Valley fill not subject to the CWA
Environmental Consequences
   Sulfur
   Carbon
   Surface
    – Spills
Sulfur
   Sulfur found in some Eastern coal (Northern
    WV, Western KY)
   Sulfur in emission reacts with atmospheric
    oxygen to form sulfuric acid (acid rain)
   Causes respiratory illness, acidifies streams,
    damages buildings
   Acid mine drainage: acidification of
    groundwater runoff
Sulfur
   Clean Air Act Amendments (1990) placed
    limits on sulfur emissions through EPA’s
    Acid Rain Program
    – Cap and Trade System
    – Utilities must purchase permits to emit SO2
    – Permits are bought and sold on open market
        Provides economic incentive to clean up exhaust
        Permits initially fixed, then decreased in number

    – Hugely successful program
          Market based approach is an “easy” sell to business
Sulfur Removal
   Pre Combustion
    – At the mine: crushing and washing (removes
      90%)
    – Chemical and biological cleaning is being tried
   Combustion
    – Example: Fluidized-bed combustion: coal
      pulverized and mixed with limestone, then
      burned while suspended by jets of air;
      limestone absorbs sulfur (removes 90%)
   Post combustion
    – “scrubbers”: flue gas mixed with limestone
      (removes 95%)
Carbon
   Environmentalists seem most concerned
    about global warming
   CO2 is a known Greenhouse Gas
    – When light waves reflect, their wavelength
      increases
    – CO2 is more transparent to short wavelengths,
      or in other words, more opaque to long
      wavelengths
    – Reflected light is selectively captured
Carbon
Carbon
   Burning coal releases ~ 2 lb CO2 per 1
    kWhr generated
   Around 1 lb coal required to generate 1
    kWhr
   Around 2 lbs CO2 released per 1 lb coal
   Global annual coal consumption: 5.5 billion
    tons
   Global annual CO2 emissions: 11 billion tons
Carbon
   Global average temperature linked to
    atmospheric CO2 concentration:
    – Pre 1800: 280 ppM (parts per million)
    – 1970: 325 ppM
    – 1990: 350 ppM
    – 2005: 375 ppM
    – Concentrations of 450 ppM  “warming light”
    – Concentrations of 550 ppM  significant, long
      term consequences
Carbon
   Carbon CANNOT be “cleaned” out of coal,
    but can be removed pre combustion
    (changes coal to a different fuel)
   Improved efficiency reduces CO2/kWh
   Reduced consumption reduces CO2 emissions
Carbon
   How to reduce consumption?
   Feb 24, 2009 (last night!): Obama’s Address
    to Joint Session of Congress
    – Mainly a Stimulus Package Sales Pitch
    – Called for a “Carbon Tax” within 4 years
    – Probably in the range of $1/ton - $10/ton of C02
    – Possibly market driven
    – $10/ton will add around 1¢/kWh to coal
      generated electricity
    – Sweden’s carbon tax is $150/ton
The Future
   Carbon capture and sequestration
    – Natural sequestration: forests, oceans, soil
          Terrestrial carbon uptake offsets around 1/3 of
           manmade carbon emissions
    – Capture is feasible at point-source emitters, like
      power plants (not cars)
    – Sequestration: storing it somewhere…
        Deep oceans (greatest potential, but not currently
         part of DOE’s research)
        Underground (has been done for years in played out
         oil and gas wells)
        Minerals (chemical reactions)
The Future
   Carbon capture and “recycling”
    – Small scale flue gas algae farm in operation at
      MIT
    – Flue gas provides algae with CO2 and heat
    – CO2 emissions cut 40%
    – Algae harvested and pressed to make biofuel
    – Greenfuels Technologies
The Future
   Combined-Cycle Coal Gasification
    1. Coal is gasified with high temperature steam
       and air (oxygen) – requires energy!!
    2. Gaseous pollutants (sulfur, etc. and including
       some CO2) removed pre-combustion
    3. Gas burned, and hot exhaust sent to gas
       turbine to generate electricity
    4. Residual heat in exhaust is used to make
       steam, which is sent to a steam turbine
    5. Efficiencies of over 50% possible
   Underground gasification is possible
The Future
   What a future “net-zero carbon” coal-fired
    power plant might look like…
    – Coal is gasified and burned in combined cycle
      power plant
    – During the day, flue gas is fed to algae for
      production of biofuel
    – Remainder of flue gas CO2 is captured and
      sequestered
    – Utility earns “carbon credits” for remaining
      carbon by planting trees
The Future
   Clean coal??
    – Typically refers to high efficiency power plants,
      perhaps using gasification

				
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