lignite n : intermediate between peat and bituminous coal [syn: brown coal, wood coal]

English

Pronunciation

lig·nite

Noun

1. A low-grade, brownish-black coal

Translations

Lignite, often referred to as brown coal, or Rosebud coal by Northern Pacific Railroad, 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%, and very high ash (50%) content compared with bituminous coal. It is also a heterogeneous mixture of compounds for which no single structural formula will suffice.

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.

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. 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.

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 the 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.

Production

Lignite mined in millions of metric tons:

See also

• Coal
• Bituminous coal
• Energy value of coal
• Coal assay
• Karrick process
• Fischer-Tropsch process
• Bergius process

External links

• Geographyinaction - an Irish case study
• Photograph of lignite
• Environmental Clean Technologies - What is brown coal?
• Why Brown Coal Should Stay in the Ground

References