Fossil Fuels

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Fossil Fuels Coal
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Coal
Coal currently provides 20 of the total U.S.
energy needs Now that oil and gas are dwindling,
many energy producers and users are looking again
at the potential of coal
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Formation of Coal Deposits
Unlike petroleum, coal is not formed from marine
organisms, but from the remains of land plants A
swampy setting, in which plant growth is lush and
where there is water to cover fallen trees, dead
leaves and other plant debris, is ideal for the
initial stages to create coal
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Formation of Coal Deposits
The formation of coal from dead plant matter
requires burial, pressure, heat and time The
process works best under anaerobic conditions (no
oxygen) since the reaction with oxygen during
decay destroys the organic matter It is the
carbon content of the coal that supplies most of
its heating value The greater the carbon to
oxygen ratio the harder the coal, the more
reduced the state of the carbons and the more
potential energy it contains
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Formation of Coal Deposits
The products of coalification are divided into
four major categories based on the carbon content
of the material Peat Lignite Bi
tuminous Anthracite
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Peat
Peat is the first stage in the formation of coal
Peat is an accumulation of partially decayed
vegetation matter Peat forms in wetlands or
peatlands, variously called bogs, moors, muskegs,
pocosins, mires, and tropical swamp forests It
contains a large amount of water and must be
dried before use Historically, it has been used
as a source of heat and burns with a long flame
and considerable smoke
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Peat
Peat deposits are found in many places around the
world, notably in Russia, Ireland, Finland,
Scotland, Poland, northern Germany, the
Netherlands and Scandinavia, and in North
America,
Approximately 60 of the world's wetlands are
peat
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Peat
Peat is still mined as a fuel in Ireland and
England
The peat is stacked to slowly dry out
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Lignite
Lignite is the second step in the formation of
coal and is formed when peat is subjected to
increased vertical pressure from accumulating
sediments Lignite, often referred to as brown
coal, is the lowest rank of coal and used almost
exclusively as fuel for steam-electric power
generation It is brownish-black and has a high
inherent moisture content, sometimes as high as
66 percent, and very high ash content compared to
bituminous coal
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Lignite
Because of its low energy density, brown coal is
inefficient to transport and is not traded
extensively on the world market compared to
higher coal grades It is often burned in power
stations constructed very close to the mines
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Jet (Lignite)
Jet is a form of decayed wood found in lignite
that was once valued for jewelry as far back as
10,000 B.C.
Hallstatt culture bracelets made from jet and
bronze, unearthed in Germany
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Bituminous
Bituminous Coal is the third stage of coal
formation Additional pressure over time has made
it compact and virtually all traces of plant life
have disappeared It is of higher quality than
lignite coal but of poorer quality than
anthracite coal It is greatly used in industry
as a source of heat energy
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Bituminous
Bituminous coal is usually black, sometimes dark
brown, often with well-defined bands of bright
and dull material It is a relatively hard coal
containing a tar-like substance called bitumen
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Bituminous
Bituminous coal is a complex molecular mix of
60-80 carbon, plus oxygen, hydrogen and
nitrogen, plus some occasional impurities like
sulfur
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Coking Coal
When used for many industrial processes,
bituminous coal must first be "coked" to remove
volatile components Coking is achieved by heating
the coal in the absence of oxygen, which drives
off volatile hydrocarbons such as propane,
benzene and other aromatic hydrocarbons, and some
sulfur gases and a considerable amount of the
contained water of the bituminous coal Coking
coal is used in the manufacture of steel, where
carbon must be as volatile-free and ash-free as
possible
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Anthracite
Anthracite is formed during the forth stage of
coal formation It is the most valuable and
highest grade of coal, and has a carbon content
of 92-98
Physically, anthracite differs from bituminous
coal by its greater hardness and higher
density Plus, it burns far more efficiently with
less smoke
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Fuel Efficiency
As the coals becomes harder, their carbon content
increases, and so does the amount of heat
released Anthracite produces twice the energy
(BTUs) of lignite
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U.S. Coal Reserves
The U.S. possesses 25 of all the known coal in
the world
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U.S. Coal Reserves
U.S. coal reserves represent about 50 times the
energy remaining in known oil reserves and 40
times the energy in known natural gas reserves
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U.S. Coal Reserves
The U.S. has consumed half of our oil reserves,
but only a few percent of our coal reserves Our
coal reserves could meet current U.S. energy
needs for 200 years (compared to 50 years for oil)
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World Coal Reserves
46 of the U.S. reserves are bituminous and
anthracite The remaining 54 is lignite
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Coal Gasification
One of the most advanced - and cleanest - coal
power plants in the world is Tampa Electric's
Polk Power Station in Florida It uses a coal
gasification process that turns coal into a gas
that can be cleaned of almost all pollutants
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Coal Gasification
The coal is heated inside a large oven and
blasted with steam The coal is converted into
carbon monoxide and hydrogen gas Hydrogen gas
burns very easily
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Coal Gasification
This 2544-ton-per-day coal gasification
demonstration pilot plant in Pennsylvania, will
have energy conversion efficiencies 20 to 35
higher than those of conventional pulverized-coal
steam power plants
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Coal Liquefaction
Coal can also be converted into liquid fuels like
gasoline or diesel by several different
processes This is an attractive technology
because it is well developed and thus could be
implemented fairly rapidly and there are
relatively large quantities of coal reserves
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Coal Liquefaction
Estimates of the cost of producing liquid fuels
from coal suggest that domestic U.S. production
of fuel from coal becomes cost-competitive with
oil priced at around 35 US per barrel (currently
134 per barrel)
A coal liquefaction test plant in Japan
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Coal Environment
A major problem with coal is the pollution
associated with its mining and use Coal is a
major source of the greenhouse gas, carbon
dioxide In fact, coal releases more carbon
dioxide per unit energy burned than natural gas
or oil
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Coal Sulfur
The pollutant of special concern with coal is
sulfur The sulfur content of coal can be as high
as 3, with some in the form of the iron sulfate
mineral pyrite (FeS2) and some bound in the
remaining organic matter When a coal containing
sulfur is burned, sulfur gases, notably sulfur
dioxide (SO2), are emitted These gases are
poisonous and are extremely irritating to both
eyes and lungs
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Acid Rain
These sulfur gases also react with water in the
atmosphere to produce sulfuric acid, which is a
very strong acid This acid falls to earth as acid
rain
These trees near coal-fired power plants have
been killed by acid rain
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A Hard Rains A-gonna Fall
Acidity in rain is measured by collecting samples
of rain and measuring its pH The areas of
greatest acidity (lowest pH values) are located
in the Northeastern U.S.
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A Hard Rains A-gonna Fall
This pattern of high acidity is caused by the
large number of cities, the dense population, and
the concentration of power and industrial plants
in the Northeast
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A Hard Rains A-gonna Fall
Acid rain can acidify soil, stunting plant
growth It can kill fish and other aquatic life,
dissolve rocks, destroy the surface of building
facades and monuments
Most coal-burning power plants have scrubbers in
the smoke stacks that remove most, but not all of
the sulfur gas emissions Low sulfur coal, less
than 1, is the coal of choice
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Ash
Coal also produces a tremendous amount of solid
waste The ash residue left after coal is burned
is typically 5-20 of the original volume
It is primarily composed primarily of
non-combustible silicate minerals, but also
contains toxic metals
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Ash
If released with emission gases, the ash fouls
the air When dumped onto the surface, the
fine-grained ash weathers very rapidly, releasing
toxic metals, such as selenium, creating a
serious water-pollution threat
The average coal-fired power plant produces one
million tons of ash per year, which is usually
buried
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Coal Mining Hazards
Underground coal mining is notoriously dangerous
The decrease in coal mining fatalities is due to
more surface mining and less underground
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More Surface Mining
In 1950, only 20 of U.S. coal was obtained by
surface strip mining By 2000, over 65 of U.S.
coal was from surface strip mining
This is partly due to increased mining of
near-surface coal seams out west
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More Surface Mining
50 of U.S. coal reserves are in the western
U.S., of which about 40 can be surfaced mined
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Coal-bed Methane
During the formation of coal deposits, quantities
of methane-rich gas are also formed Historically,
methane has been considered as a hazardous
nuisance In fact, currently it is usually burned
off rather than recovered
It is estimated that 100 trillion cubic feet of
methane can be economically recovered from
existing U.S. coal beds
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Coal-bed Methane
U.S. coal deposits are already mapped, so there
would be no exploration cost Waste water is a
potential pollution problem Coal-bed methane is
already being produced in Utah
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Coal On Fire
An underground coal mine has been on fire in
Centralia, Pennsylvania for 45 years It was
started by a fire in an adjacent dump Over 1000
residents have been located, at a cost of over
40 million
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Coal On Fire
The Centralia fire closed highway 61
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Coal On Fire
Uncontrolled coal mine fires in China have cost
over 100 million and are a major source of CO2
greenhouse emissions