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2/13/2019
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Coal
Outline
• ‘Refining’ coal
• Uses of coal
• Production of coal
• US trends
• Coal reserves
• Byproducts / concerns of coal use
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Refining coal
Coal refining is relatively straightforward process:
• Crushing to obtain desired size classes
• Cleaning to remove waste rock (mostly clay)
• Centrifuging / washing with water & chemical surfactants
• Drying
Cleaning process generates
large volumes of ‘blackwater’
(coal slurry)
1. Energy generation (‘Thermal’ / ‘steam’ coal) Uses of coal
2. Steel production (‘Coking’ coal)
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3. Production of FUELS: Gasification and LiquefactionUses of coal
4. Cement production
Drake cement plant (Arizona)
5. Aluminum production
Alcan Gove alumina refinery (Australia)
Outline
• ‘Refining’ coal
• Uses of coal
• Production of coal
• US trends
• Coal reserves
• Byproducts / concerns of coal use
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Coal production
EIA data
Globally, production ~ consumption;
Individual countries are importers or
exporters (or both)
Australia?
Global average annual coal
consumption per capita?
Energy Information
Administration (EIA, 2018)
Coa
l R
an
k
Coal ‘flow’ in the US
Electricity
(665 Mt)
Production
(774 Mt)
Consumption
(717 Mt)
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Trend in US production
Without the ‘fracking boom,’ would the Obama
administration have been this successful in
curtailing US production?
EIA data
US: Production trends by RANK
What is the significance of 1970?
EIA data
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US: Production trends by type of mining
EIA data
US: Production trends by region
Low sulfur ‘western’ coalEIA data
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Outline
• ‘Refining’ coal
• Uses of coal
• Production of coal
Imports / exports
• Coal energy flow
United States vs. China
• Coal reserves
• Byproducts / concerns of coal use
Coal reserves in context
Note: This is conventional oil
Note UNITS: ‘btoe’
2015 global reserves ~ 1000 Gt coal
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Using 2016 consumption rate (~7 Gt/a), about how
long until we ‘run out’ of coal globally?
The fossil-fuel reservoir
~4000 GtC total
~85% Coal
~5% Petroleum
~3% Gas
Gut check: Resources vs. reserves
Given the data at left, estimate
the size of the coal resource
in gigatons (Gt)
In 2015, estimates of proved
global coal reserves were
about 1000 gigatons (Gt)
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Outline
• ‘Refining’ coal
• Uses of coal
• Production of coal
Imports / exports
• Coal energy flow
United States vs. China
• Coal reserves
• Byproducts / concerns of coal use
What’s in coal?
Representative structure of bituminous coal
www.wou.edu
BituminousC137H97O9NS
C240H90O4NS Anthracite
Amount of sulfur (S) controlled
by salinity of ‘swamp water’
(fresh vs. brackish)
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Byproducts of coal production / consumption
‘Front End’ (production):
• ‘Blackwater’ (coal slurry)
• Acid mine drainage
• Coal-seam fires
‘Back End’ (consumption / combustion):
• Carbon dioxide (CO2)
• Sulfur dioxide (SO2)
• NOx (NO and NO2)
• Particulate matter (‘fly ash’)
Acid mine drainage (runoff)
Sulfur present in all coal (0.2 – 7% S)
Mining exposes sulfide minerals to air
and water producing:
Ferrous sulfate (SO4)
Sulfuric acid (‘acid mine drainage’)
Harmful to rivers & streams
Stringent regulations controlling the
discharge of water from mines and the
handling and dumping of mining debris
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Blair Athol Coal Mine, Australia
Coal seam fires
• 5000 km coal belt
• Hundreds of active fires
• Consume 20 Million tons
of coal per year
• Burn for decades -
centuries
Coal-seam fires in China
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Uncontrolled “in-seam” coal fires in the United States
Centralia, PA.
• Ignited 1962; spread underground.
• Health risks (CO poisoning)
• Spontaneous opening of sinkholes.
• Damage to infrastructure
• Covers ~ 400 acres
• City largely abandoned by early 1980s
• Buy-out program (cost ~$42 million)
• Sufficient fuel to support continued
combustion for another 250 years!
Byproducts of coal production / consumption
‘Front End’ (production):
• ‘Blackwater’ (coal slurry)
• Acid mine drainage
• Coal-seam fires
‘Back End’ (consumption / combustion):
• Carbon dioxide (CO2)
• Sulfur dioxide (SO2)
• NOx (NO and NO2)
• Particulate matter (‘fly ash’)
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Coal (anthracite) 227
Coal (bituminous) 205
Coal (lignite) 215
Coal (subbituminous) 213
Diesel fuel & heating oil 161
Gasoline 156
Propane 139
Natural gas 117
Cage match: Pounds CO2 emitted per million Btu of energy
Fair / unfair?
Combustion byproduct: SO2 + NOx + particulates
Sulfur Dioxide (SO2) and NOx (NO
& NO2) are major contributors to the
formation of acid rain
The primary source for sulfur
dioxide is coal-fired power stations
SO2 + NOx + particulates + sunlight
= smog
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Combustion byproduct: SO2
Mitigate SO2 emissions with exhaust ‘scrubbers’
Basic solid:
Limestone /
lime
Oxidize further
to get gypsum
(CaSO4·2H2O)
SO2 scrubbers are effective
What’s behind
the panel?
Who is hiding
behind the
panel?
Teragrams?
EPA data
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Combustion byproduct: Particulates (fly ash)
Fly ash
• Fine particles that rise with the flue gas (contrast w/ ‘bottom’ ash)
• Mostly amorphous glass that solidified (quenched) in the flue
• Spherical particles of size 100 – 102 microns
• Some ‘refractory’ minerals
Contributes to smog formation
Combustion byproduct: Particulates (fly ash)
Mitigate particulate emission
with electrostatic precipitators
What is the fate of the collected
fly ash?
Combine fly ash with standard
Portland cement and use in
concrete
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