Environmental Engineering Reference
In-Depth Information
TABLE 2.3
Composition and Characteristics of Coal, Percent by Weight a
Pittsburgh
Illinois
North
Pennsylvania
Seam
No. 6
Montana
Dakota
Anthracite
Bituminous
Bituminous
Subbituminous
Lignite
Moisture
4.5
2.0
13.2
10.5
33.7
Volatile matter
1.7
30.5
36.0
34.7
26.6
Fixed carbon
84.1
58.2
41.8
43.6
32.5
Sulfur
0.7
2.2
3.4
1.2
0.9
Ash
0.7
9.3
9.0
11.2
7.2
HHV, Btu/lb
12,750
13,620
11,080
10,550
7,070
a Percentages may not add up to 100 % because of other elements present in coal.
value; hardness; porosity; and so on. Table 2.3 lists the characteristics and composition of several
U.S. coals. The variability from coal to coal is clearly evident. For example, the carbon content
varies from 62.9% for North Dakota lignite (a relatively young coal) to 93.9% for Pennsylvania
anthracite (a relatively old coal). The sulfur content varies from 0.7% to 3.4% by weight, and the
higher heating value (HHV) varies from 7070 Btu/lb (16,430 kJ/kg) for North Dakota lignite to
13,620 Btu/lb (31,650 kJ/kg) for Pittsburgh seam bituminous. 4
Because of the widely varying characteristics of coals, it is difficult to estimate the precise
energy reserves residing in the world's coal deposits. The world total coal reserves are estimated at
1.037E(12) metric tons. 5 About one-half is bituminous and anthracite coal, whereas the other half is
subbituminous and lignite coal. Assuming that the average HHV of bituminous and anthracite coal is
12,500 Btu/lb (29,050 kJ/kg), and that of subbituminous and lignite is 8200 Btu/lb (19,055 kJ/kg),
the world's coal reserves have a total heating value of about 24,000 Q. The 1995 world coal
consumption amounted to a little more than 93 Q/y. If the present consumption level were to
continue into the distant future, the world coal reserves would last about 250-300 years. However,
if coal consumption keeps increasing at a rate of 0.8%/y (see Section 2.3), the lifetime of the world's
coal reserves would be only about 140 years.
The countries where the world's major coal reserves are found are (in percent of the total)
United States (26), former Soviet Union countries (25), China (12), Australia (10), Germany (7),
South Africa (7), Poland (4), and other countries (9) (see Figure 2.13).
In addition to the above reserves, coal may be found in yet unproven reservoirs. Unproven
reservoirs are called resources . 6 Some estimates place the coal resources at about 140,000 Q. 7 The
4 The higher heating value (HHV) includes the latent heat of condensation of the moisture content of the coal
and the water vapor formed in combustion, whereas the lower heating value (LHV) excludes it.
5 Energy Information Agency, 1997. International Energy Outlook, DOE/EIA-0484(97).
6 Reserves of a given fossil fuel are those quantities that geological and engineering information indicate
with reasonable certainty to be extractable under existing economic and operating conditions. Resources are
those quantities that from geological and engineering information may exist, but their extraction will require
different economic and operating conditions.
7 Anonymous, 1978. World Energy Conference . Guildford: IPC Science and Technology Press.
 
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