Lignite, often referred to as brown coal, or Rosebud coal by Northern Pacific Railroad, is a soft brown fuel with characteristics that put it somewhere between coal and peat. It is considered the lowest rank of coal, and is found in the United States, Canada, Greece, and Germany where it is used almost exclusively as a fuel for for steam-electric power generation. Up to 50% of Greece's electricity comes from lignite power plants, and 25% of Germany's electricity.
Lignite is brownish-black in color and has a carbon content of around 60%, a high inherent moisture content sometimes as high as 66%, and an ash content ranging from 6% to 19% compared with 6% to 12% for bituminous coal.[1]
The heat content of lignite ranges from 10 to 20 MJ/kg (9 to 17 million Btu per short ton) on a moist, mineral-matter-free basis. The heat content of lignite consumed in the United States averages 13 million Btu/ton (15 MJ/kg), on the as-received basis (i.e., containing both inherent moisture and mineral matter). When reacted with quaternary amine, amine treated lignite (ATL) forms. ATL is used in drilling mud to reduce fluid loss.
Lignite has a high content of volatile matter which makes it easier to convert into gas and liquid petroleum products than higher ranking coals. However, its high moisture content and susceptibility to spontaneous combustion can cause problems in transportation and storage.
Because of its low energy density, brown coal is inefficient to transport and is not traded extensively on the world market compared with higher coal grades. It is often burned in power stations constructed very close to any mines, such as in Australia's Latrobe Valley and Luminant's Monticello plant in Texas. Carbon dioxide emissions from brown coal fired plants are generally much higher than for comparable black coal plants, with the world's worst carbon dioxide polluting being the brown coal fueled Hazelwood Power Station, Victoria[2]. The continued operation of brown coal plants, particularly in combination with strip mining and in the absence of emissions-avoiding technology like carbon sequestration, is politically contentious.[3][4]
Types
Lignite can be separated into two types. The first is xyloid lignite or fossil wood and the second form is the compact lignite or perfect lignite.
Although xyloid lignite may sometimes have the tenacity and the appearance of ordinary wood it can be seen that the combustible woody tissue has experienced a great modification. It is reducible to a fine powder by trituration and if submitted to the action of a weak solution of potash it yields a considerable quantity of ulmic acid.[5]
Production
Lignite mined in millions of metric tons
| Country |
1970 |
1980 |
1990 |
2000 |
2001 |
 Germany |
369,300 |
388,000 |
356,500 |
167,700 |
175,400 |
 Russia |
127,000 |
141,000 |
137,300 |
86,400 |
83,200 |
 United States |
5,400 |
42,300 |
82,600 |
83,500 |
80,500 |
 Australia |
24,200 |
32,900 |
46,000 |
65,000 |
67,800 |
 Greece |
8,100 |
23,200 |
51,700 |
63,300 |
67,000 |
 Poland |
32,800 |
36,900 |
67,600 |
61,300 |
59,500 |
 Turkey |
4,400 |
15,000 |
43,800 |
63,000 |
57,200 |
 Czech Republic |
67,000 |
87,000 |
71,000 |
50,100 |
50,700 |
 People's Republic of China |
13,000 |
22,000 |
38,000 |
40,000 |
47,000 |
 SFR Yugoslavia |
26,000 |
43,000 |
60,000 |
- |
- |
 FR Yugoslavia |
- |
- |
- |
35,500 |
35,500 |
 Romania |
14,100 |
27,100 |
33,500 |
17,900 |
29,800 |
 North Korea |
5,700 |
10,000 |
10,000 |
26,000 |
26,500 |
| Total |
804,000 |
1,028,000 |
1,214,000 |
877,400 |
894,800 |
See also
References
External links
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