The four types of coal are peat, lignite, bituminous, and anthracite. Peat is often not listed as a type of coal since the use of it as an energy source is limited today. However, it's still a type of coal and can be used as an energy source
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 60–70 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 colour and has a carbon content around 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.
The carbon content of lignite ranges from 65-70% and represents the youngest rank of fuel—with approximate ages of around 60 million years. Lignite is the first "stage" of coal that forms after sediment piles on top of layers of peat, which gets heated and compressed.
Before mining begins, a rotary drill is used to define the lignite field, the depth and thickness of lignite seams, and the amount and type of material (or "overburden") overlying the lignite. The lignite deposits are then selected as potential places for mining to take place.
The state of Rajasthan is endowed with large lignite deposits in the country after Tamilnadu & Gujarat. In the three districts of the state viz. Bikaner, Nagaur and Barmer, geological reserves of more than one billion tonnes have been confirmed so far by exploratory drilling. Beside, deep seated reserves of lignite suitable for underground lignite gasification also exists in the state. The state is also having lignite blocks suitable for development of Coal Bed Methane projects.
RSMML is a State Government Enterprise involved with the work of development of Lignite deposit for mercantile sale in cement, textile, brick kiln etc industries and for the ultimate end use of power generation by open cast mining or underground lignite gasification.
RSMML at present is operating two lignite mines one at Giral in district Barmer and another at Kasnau-Matasukh in district Nagaur.
Giral mine is situated near village Giral, 43 Km from Barmer district in western Rajasthan. Giral mines, the first modern OPENCAST Lignite mine in Rajasthan (after closure of Palana underground mine in 1967) was started by the erstwhile RSMDC in the year 1994. The commercial production of Lignite from this mine, with envisaged capacity of 300,000 MT per year, was started in May 1995. At Giral mines, the production and the allied mining activities are being executed in highly scientific and technically sound manner so as to achieve excellence in all spheres with particular emphasis on bringing a great degree of consumer satisfaction.
NLC India Limited (formerly Neyveli Lignite Corporation 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.
79% of all lignite coal is used in these boilers to generate electricity, and 13.5% is used to generate synthetic natural gas. A small 7.5% is used to produce various fertilizer products. Virtually none is used as a home heating fuel due to its poor burn quality.
In 2018, production of lignite coal for India was 49,983 thousand short tons. Production of lignite coal of India increased from 27,076 thousand short tons in 1999 to 49,983 thousand short tons in 2018 growing at an average annual rate of 3.37%.
Hope my blog on lignite mining in India shall be found useful and value adding by readers.
Shyamal Kumar Bag
Merchentus India Exim International LLP