Introduction to Coal
Developed by:
2008-2009 TESSE Graduate Student Fellows
Penn State University
What is coal?
http://cleantechnica.com
The 3 P’s of coal formation:
Plants
Preservation
Pressure (& temperature)
1. PLANTS
Large amounts of plant material accumulate over
thousands of years, usually in a swamp. (Peat)
www.fieldmuseum.org
Smithsonian National
Natural History Museum’s
recreation of coal swamp
300 million years ago
Modern-day swamp of the
Mississippi River Delta
http://confluence.org/us/la/n30w090v3/pic8.jpg
2. PRESERVATION
Dead plant material is very fragile and decays
easily in the presence of oxygen.
Swamp waters are ideal for preservation
stagnant and low in oxygen
Organisms that might eat the plants can not live in
those conditions
Rivers overflow into swamps
Bury plant material in sand and mud
Sea level rises and floods the swamps
Covers plant material with marine mud
Plants & Preservation
 It takes about 10 ft. of dead plant material to
produce 1 ft. of coal.
 The conditions of the water and plants must be
just right for enough organic material to
accumulate
West Virginia Geological & Economic Survey
3. PRESSURE & temperature
Coalification: How peat becomes coal
 Dead plant material is compressed from above by thick,
heavy layers of sediment, slowly turning the deposits to
solid rock
 As it is buried deeper below the earth’s surface, pressure
and temperature increase, removing moisture and gases,
and changing the proportions of the 3 main elements:
CARBON, OXYGEN, and HYDROGEN
Changes are gradual and occur over millions of
years
Coal Classification
Kentucky Geological Survey (2006)
http://www.uky.edu/KGS/coal/coalkinds.htm
 Coal is classified into 4 main ranks based on
chemical composition and which stage of development
it is in.
Peat (precursor to coal)  Lignite  Sub-bituminous
Coal’s Components
Coal in Pennsylvania ( 2002)
Carbon, Hydrogen, & Oxygen content are
important for determining rank
 Coal also contains varying amounts of Nitrogen, Sulfur, and
mineral particles of clay, quartz and calcite (ash)
Distinguishing among ranks of coal
18000
16000
14000
Calorific Value (btu)
12000
10000
Data
compiled
from:
Penn State
Coal
Database
and
Argonne
Premium
Coal
Sample
Program
8000
6000
Anthracite
Bituminous
4000
2000
0
60
65
70
75
80
85
90
95
100
%C, dmmf
How do %C and heating value change with rank?
How does oxygen and hydrogen
content vary with rank?
35
25
%O, dmmf
20
B
A
%H, dmmf
30
15
10
5
0
60 65 70 75 80 85 90 95 100
%C, dmmf
8
7
6
5
4
3
2
1
0
A
B
60
65
Data compiled from:
Penn State Coal Database and
Argonne Premium Coal Sample Program
70
75 80 85
%C, dmmf
90
95 100
Description & Ranks of Coal
Peat
Lignite
Subbituminous
Bituminous
Anthracite
<55% Carbon
55-61.5% Carbon
61.5-64% Carbon
64-86% Carbon
>86% Carbon
4500 BTU/lb
7000 BTU/lb
9,300 BTU/lb
11,250 to
14,350 BTU/lb
13,600 BTU/lb
A brownish-black coal
with generally high
moisture and ash
content and the lowest
carbon content and
energy value.
A dull black coal. It
has a littler higher
energy value than
lignite when it burns.
A soft, intermediate grade
of coal with carbon content
and moisture between that
of lignite and anthracite. It
is the most common and
widely used coal in the
United States.
The hardest type of
coal, consisting of
nearly pure carbon. It
has the highest heating
value and the lowest
moisture and ash
content.
Lowest Rank
Low-Middle Rank
High-Middle Rank
Highest Rank
A brownish-black
organic matter that
looks very much like
decayed wood. It is
commonly used for
peat moss or garden
mulch.
Peat is not coal.
Pre-Cursor to Coal
No Rank
Adapted from American Coal Foundation (2010) and Coal in Pennsylvania (2002)
What are the distinguishing characteristics or properties of coal?
Which rank(s) of coal would be best for energy production?
Which rank(s) of coal has the most stored energy?
What tests could we perform
to identify the different ranks
of coal in hand sample?
More than a black rock!
1 mm
Coal Through a Microscope (2010)
http://geology.com/articles/coalthrough-a-microscope.shtml
Now, you will identify and compare
different types of coal.
 You will examine four unidentified types of coal( #1 – 4)
Document your visual observations about each sample
Document your observations about the burning
behavior of each sample
Identify each sample based on your observations
 Consult the Descriptions and Ranks of Coal and Peat
sheet