Lignite, often referred to as brown coal,is a soft, brown, combustible, sedimentary rock formed from naturally compressed peat. It is considered the lowest rank of coal due to its relatively low heat content. It has a carbon content around 20-35% percent. It is mined all around the world, is used almost exclusively as a fuel for steam-electric power generation, and is the coal which is most harmful to health.
Lignite is brownish-black in color and has a carbon content from as low as 20-25 percent up to 60–70 percent, a high inherent moisture content sometimes as high as 75 percent,and an ash content ranging from 6–19 percent compared with 6–12 percent for bituminous coal.
The energy content of lignite ranges from 10 to 20 MJ/kg (9–17 million BTU per short ton) on a moist, mineral-matter-free basis. The energy content of lignite consumed in the United States averages 15 MJ/kg (13 million BTU/ton), on the as-received basis (i.e., containing both inherent moisture and mineral matter). The energy content of lignite consumed in Victoria, Australia, averages 8.4 MJ/kg (7.3 million BTU/ton).
Lignite has a high content of volatile matter which makes it easier to convert into gas and liquid petroleum products than higher-ranking coals. Unfortunately, its high moisture content and susceptibility to spontaneous combustion can cause problems in transportation and storage. It is now known that efficient processes which remove latent moisture locked within the structure of brown coal will relegate the risk of spontaneous combustion to the same level as black coal, transform the calorific value of brown coal to a black coal equivalent fuel, and significantly reduce the emissions profile of 'densified' brown coal to a level similar to or better than most black coals.However, removing the moisture increases the cost of the final lignite fuel.
Because of its low energy density and typically high moisture content, 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 near the mines, such as in Australia's Latrobe Valley and Luminant's Monticello plant in Texas. Primarily because of latent high moisture content and low energy density of brown coal, carbon dioxide emissions from traditional brown-coal-fired plants are generally much higher per megawatt generated than for comparable black-coal plants, with the world's highest-emitting plant being Hazelwood Power Stationuntil its closure in March 2017. The operation of traditional brown-coal plants, particularly in combination with strip mining, is politically contentious due to environmental concerns.
In 2014, about 12 percent of Germany's energy and, specifically, 27 percent of Germany's electricity came from lignite power plants,while in 2014 in Greece, lignite provided about 50 percent of its power needs.
An environmentally beneficial use of lignite can be found in its use in cultivation and distribution of biological control microbes that suppress plant disease causing microbes. The carbon enriches the organic matter in the soil while the biological control microbes provide an alternative to chemical pesticides.
Reaction with quaternary amine forms a product called amine-treated lignite (ATL), which is used in drilling mud to reduce fluid loss during drilling.
Lignite begins as an accumulation of partially decayed plant material, or peat. Burial by other sediments results in increasing temperature, depending on the local geothermal gradient and tectonic setting, and increasing pressure. This causes compaction of the material and loss of some of the water and volatile matter (primarily methane and carbon dioxide). This process, called coalification, concentrates the carbon content, and thus the heat content, of the material. Deeper burial and the passage of time result in further expulsion of moisture and volatile matter, eventually transforming the material into higher-rank coals such as bituminous and anthracite coal.
Lignite deposits are typically younger than higher-ranked coals, with the majority of them having formed during the Tertiary period.
Germany has the biggest deposits,followed by China, Russia and United States.
The Latrobe Valley in Victoria, Australia, contains estimated reserves of some 65 billion tonnes of brown coal.The deposit is equivalent to 25 percent of known world reserves. The coal seams are up to 100 metres thick, with multiple coal seams often giving virtually continuous brown coal thickness of up to 230 metres. Seams are covered by very little overburden (10 to 20 metres).
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 humic acid.Leonardite is an oxidized form of lignite, which also contains high levels of humic acid.
Jet is a hardened, gem-like form of lignite used in various types of jewelry.
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|Source: World Coal Association · U.S. Energy Information Administration · BGR bund.de Energiestudie 2016 ·1970 data from World Coal (1987) |
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Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements; chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when dead plant matter decays into peat and is converted into coal by the heat and pressure of deep burial over millions of years. Vast deposits of coal originate in former wetlands—called coal forests—that covered much of the Earth's tropical land areas during the late Carboniferous (Pennsylvanian) and Permian times.
Bituminous coal or black coal is a relatively soft coal containing a tarlike substance called bitumen or asphalt. It is of higher quality than lignite coal but of poorer quality than anthracite. Formation is usually the result of high pressure being exerted on lignite. Its coloration can be black or sometimes dark brown; often there are well-defined bands of bright and dull material within the seams. These distinctive sequences, which are classified according to either "dull, bright-banded" or "bright, dull-banded", is how bituminous coals are stratigraphically identified.
Anthracite, often referred to as hard coal, is a hard, compact variety of coal that has a submetallic luster. It has the highest carbon content, the fewest impurities, and the highest energy density of all types of coal and is the highest ranking of coals.
Coal mining is the process of extracting coal from the ground. Coal is valued for its energy content and since the 1880s, has been widely used to generate electricity. Steel and cement industries use coal as a fuel for extraction of iron from iron ore and for cement production. In the United Kingdom and South Africa, a coal mine and its structures are a colliery, a coal mine is a 'pit', and the above-ground structures are a 'pit head'. In Australia, "colliery" generally refers to an underground coal mine. In the United States, "colliery" has been used to describe a coal mine operation, but this usage is less common.
NLC India Limited (NLC) is a 'Navratna' government of India company in the fossil fuel mining sector in India and thermal power generation. It annually produces about 30 million tonne lignite from opencast mines at Neyveli in the state of Tamil Nadu in southern India and at Barsingsar in Bikaner district of Rajasthan state. The lignite is used at pithead thermal power stations of 3640 MW installed capacity to produce electricity. Its joint venture has a 1000 MW thermal power station using coal. Lately, it has diversified into renewable energy production and installed 1404 MW solar power plant to produce electricity from photovoltaic (PV) cells and 51 MW electricity from windmills.
Sub-bituminous coal is a type of coal whose properties range from those of lignite to those of bituminous coal and are used primarily as fuel for steam-electric power generation.
The Hazelwood Power Station is a decommissioned brown coal-fuelled thermal power station located in the Latrobe Valley of Victoria, Australia. Built between 1964 and 1971, the 1,600 megawatt capacity power station was made up of eight 200MW units, and supplied up to 25% of Victoria's base load electricity and more than 5% of Australia's total electricity demand. It was a 'subcritical' pulverized coal-fired boiler. The station was listed as the least carbon efficient power station in the OECD in a 2005 report by WWF Australia, making it one of the most polluting power stations in the world. At 1.56 tonnes of CO2 for each megawatt hour of electricity, it was 50% more polluting than the average black coal power station in New South Wales or Queensland. Hazelwood emitted 14% of Victoria's annual greenhouse gas emissions and 3% of Australia's greenhouse gas emissions.
The Yallourn Power Station is a complex of six brown coal–fuelled thermal power stations built progressively from the 1920s to the 1960s. Located in the Latrobe Valley of Victoria, Australia, the complex was situated beside the Latrobe River, with the company town of Yallourn located to the south west. Today only the 1,450 megawatts (1,940,000 hp) Yallourn W plant remains, the second largest power station in Victoria which supplies 22% of the state's electricity and 8% of the National Electricity Market needs. The adjacent open cut brown coal mine is the largest open cut coal mine in Australia, with reserves sufficient to meet the projected needs of the power station to 2032.
Coal analysis techniques are specific analytical methods designed to measure the particular physical and chemical properties of coals. These methods are used primarily to determine the suitability of coal for coking, power generation or for iron ore smelting in the manufacture of steel.
Potassium humate is the potassium salt of humic acid. It is manufactured commercially by alkaline extraction of brown coal (lignite) Leonardite to be used mainly as a soil conditioner. The extraction is performed in water with the addition of potassium hydroxide (KOH), sequestering agents and hydrotropic surfactants. Heat is used to increase the solubility of humic acids and hence more potassium humate can be extracted. The resulting liquid is dried to produce the amorphous crystalline like product which can then be added as a granule to fertiliser. The potassium humate granules by way of chemical extraction lose their hydrophobic properties and are now soluble. Depending on the source material product quality varies. High quality oxidised lignite, usually referred to as leonardite, is the best source material for extraction of large quantities of potassium humate. The less oxidised the coal the less potassium humate extracted. Sources low in ash produce the best quality. Less oxidised brown coal contains a higher proportion of the insoluble humin fraction and along with peat which is lower in humic acid content and usually high in ash content requires separation by filtration or centrifugation to remove ash, humin. Peat is also high in non humified organic matter that needs to be reduced to produce a high quality product. The benefit of peat is that it is usually 2-3 times higher in fulvic acid content, which are the low molecular weight fractions of humic acid that are high in oxygen containing functional groups and soluble at a low pH of <1. Fulvic acids have a higher cation exchange capacity and therefore have a higher chemical interaction with fertilisers and are able to form soluble chelates of trace metals.
The Energy Brix Power Station was a brown coal–fired thermal power station located at Morwell, in Victoria, Australia. The power station was used to supply electricity for the retail market, as well as the production of briquettes in the adjacent Energy Brix briquette works. It was shut down in August 2014 and is currently the earliest surviving large-scale power station designed to provide electricity to the state electricity network.
Coal is mined in every state of Australia. The largest black coal resources occur mainly in Queensland and New South Wales. About 70% of coal mined in Australia is exported, mostly to eastern Asia, and of the balance most is used in electricity generation. Coal production in Australia increased 13.6% between 2005 and 2010 and 5.3% between 2009 and 2010. In 2016, Australia was the biggest net exporter of coal, with 32% of global exports, and was the fourth-highest producer with 6.9% of global production. 77% of production was exported.
Energy in Victoria, Australia is generated using a number of fuels or technologies, including coal, natural gas and renewable energy sources. Brown coal is the main primary energy source for the generation of electricity in the state, accounting for about 85% of electricity generation in 2008. Brown coal is also one of the largest contributors to Australia's total domestic greenhouse gas emissions and a source of controversy for the country. Australia is one of the highest polluters of greenhouse gas per capita in the world.
Refined coal is the product of the application of a coal-upgrading technology that removes moisture and certain pollutants from lower-rank coals such as sub-bituminous and lignite (brown) coals and raising their calorific values. Coal refining or upgrading technologies are typically pre-combustion treatments and/or processes that alter the characteristics of a coal before it is burned. The goals of pre-combustion coal-upgrading technologies are to increase efficiency and reduce emissions when coal is burned. Depending on the situation, pre-combustion technology can be used in place of or as a supplement to post-combustion technologies to control emissions from coal-fueled boilers. A primary benefit of refined coal is the capacity to reduce the net volume of carbon emissions that is currently emitted from power generators and would reduce the amount of emissions that is proposed to be managed via emerging carbon sequestration methodologies. Refined coal technologies have primarily been developed in the United States, several similar technologies have been researched, developed and tested in Victoria, Australia, including the Densified coal technology developed to alter the chemical bonds of brown coal to create a product that is cleaner, stable, exportable and of sufficiently high calorific value to be a black coal equivalent.
Leonardite is a soft waxy, black or brown, shiny, vitreous mineraloid that is easily soluble in alkaline solutions. It is an oxidation product of lignite, associated with near-surface mining. It is a rich source of humic acid and is used as a soil conditioner, as a stabilizer for ion-exchange resins in water treatment, in the remediation of polluted environments and as a drilling additive. It was named after A. G. Leonard, first director of the North Dakota Geological Survey, in recognition of his work on these deposits.
The Kemper Project, also called the Kemper County energy facility or Plant Ratcliffe, is a natural gas-fired electrical generating station currently under construction in Kemper County, Mississippi. Mississippi Power, a subsidiary of Southern Company, began construction of the plant in 2010. The initial, coal-fired project was central to President Obama's Climate Plan, as it was to be based on "clean coal" and was being considered for more support from the Congress and the incoming Trump Administration in late 2016. If it had become operational with coal, the Kemper Project would have been a first-of-its-kind electricity plant to employ gasification and carbon capture technologies at this scale.
Maddingley Mine near Bacchus Marsh Railway Station, Victoria, Australia contains a concentration of a particular brown coal (lignite) formation called Leonardite. A relatively high altitude formation, Maddingley brown coal is distinguished as having 60 per cent moisture content and a rich fulvic acid and humic acid content. A declared strategic State mining reserve, the estimated 400 million tonne deposit at Maddingley is the largest of three known deposits of high value Leonardite in the world, the others occurring in Mexico and Germany.
Densified coal is the product of the Coldry Process coal upgrading technology that removes moisture from low-rank coals such as sub-bituminous and lignite/brown coal. The densification process raises the calorific value of low-rank coal to equal or exceed that of many export-grade black coals. Densified coal resulting from the Coldry Process is regarded as a black coal equivalent or replacement for black coal.
Black coal equivalent (BCE) is an export coal product derived from the Coldry Process, a patented coal upgrading technology operated by Environmental Clean Technologies Limited, in Victoria, Australia. The Coldry Process is applied to brown coal (lignite) with a typical moisture content of 60 per cent by weight and transforms the coal into a densified coal product of equal or better calorific value to typical export quality black coal, with less ash and sulfur content. Black coal equivalent derived from brown coal is ostensibly a 'cleaner' burning coal fuel than most black coals.
Coal in Europe describes the use of coal as an energy fuel in Europe. Coal includes hard coal, black coal, and brown coal.
Germany has been the largest lignite producer in the world since the beginning of industrial lignite mining. It still is, followed by China, Russia, and the United States. The softer and moister lignite (also called brown or soft coal) has a lower calorific value than hard coal and can only be mined in opencast operations. When burned, it is more CO2 intensive than hard coal.
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