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Coal
• Coal is a rock that has so much carbon in
it that the rock burns.
• Coal is old. It is millions of years old. It
forms from the same processes that form
all sedimentary rocks.
• Charcoal is different from coal. Charcoal
is made by partially burning wood. It is
made now, by people.
Coal is found in many places in the
United States
Kinds of Coal
Peat: not coal yet,
but burnable
Bituminous coal
Lignite Coal
Anthracite Coal
Peat
• Peat is an accumulation of partially
decayed vegetation matter.
• Peat forms when plant material, usually in
marshy areas, is inhibited from decaying
fully by wet and acidic conditions.
• Under the right conditions, peat is the
earliest stage in the formation of coal.
Lignite Coal
• Lignite, often referred to as brown coal, is
the lowest rank of coal and used almost
exclusively as fuel for steam-electric
power generation.
• Lignite contains more moisture than higher
ranked coal and when dried, it crumbles
easily.
Bituminous Coal
• Bituminous coal is a relatively hard coal
containing a tar-like substance called
bitumen. It is of higher quality and rank
than lignite.
• It is usually black, sometimes dark brown,
often with well-defined bands of bright and
dull material associated with sedimentary
rocks.
Anthracite Coal
• Anthracite is the highest rank of all coals. It is a
high carbon, low sulfur and high BTU coal.
Anthracite is a "smokeless" fuel unlike some of
the lower grades of coal. It burns cleaner, hotter
and longer than any other coal.
• Anthracite coal is a metamorphic rock and is
considered to be a transition stage between
ordinary bituminous coal and graphite.
Coals’ energy comes from the sun
• Plants in the biosphere store solar energy
through photosynthesis by converting it
into chemical energy in the form of organic
(carbon-based) molecules.
• Energy that enters the biosphere nearly
equals that lost by oxidation.
• A small percent is stored in the form of
fossil fuels in sedimentary rocks
Formation of Coal
Steps to form coal
• Thick layers of nearly pure plant material are
deposited.
• During compaction by overlying sediment, water
and gases are squeezed out.
• The percent of carbon increases as the coal is
compacted more, and the rank increases.
• The greater the carbon content, the greater the
energy stored in the coal
• Coal also contains sulfur compounds and ash,
the unburnable part, composed of sand, silt and
clay.
The greater the time, heat and pressure of
burial, the higher the rank of coal