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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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