However, not all coal used is the same; it comes in different quantity levels of carbon—which dictates the quality of the coal. Higher quality coal produces less smoke , burns longer, and provides more energy than lower quality coal. The table below includes the carbon contents, and energy densities of coal.
In addition, it states the moisture content before drying, and the amount of volatile content, after it's dried. The following is an overview of the different grades of coal, ordered from lowest to highest quality. Please see their main pages to learn more about each type. Peat is a soft, crumbly, dark brown substance that is formed from generations of dead and partially decaying organic matter.
Peat is the first step in the formation of coal , and slowly becomes lignite after pressure and temperature increase as sediment is piled on top of the partially decaying organic matter. In order to be turned into coal, the peat must be buried from km deep by sediment. Lignite or brown coal is brown in colour and the lowest quality of coal. Sub-bituminous coal or black lignite is a grey-black or dark brown coal. It ranges from hard to soft as it represents an intermediate stage between low quality lignite and higher quality bituminous coal.
Anthracite is a dark black form of coal and the highest quality coal. In addition, anthracite is usually the oldest type of coal, having formed from biomass that was buried million years ago.
Its clean burning properties allows anthracite to burn longer than wood, making it appealing to use in home heating stoves. It is more expensive than other coals, and is rarely used in power plants. Instead, anthracite is mainly used in stoves and furnaces. Anthracite is also used in water- filtration systems. It has tinier pores than sand, so more harmful particles are trapped. This makes water safer for drinking, sanitation , and industry.
Anthracite can typically be found in geographical areas that have undergone particularly stressful geologic activity. For example, the coal reserves on the Allegheny Plateau in Kentucky and West Virginia stretch to the base of the Appalachian Mountains.
Here, the process of orogeny , or mountain formation, contributed to temperatures and pressures high enough to create anthracite. China dominates the mining of anthracite, accounting for almost three-quarters of anthracite coal production.
Graphite Graphite is an allotrope of carbon, meaning it is a substance made up only of carbon atoms. Diamond is another allotrope of carbon. Graphite is the final stage of the carbonization process. Graphite conducts electricity well, and is commonly used in lithium ion batteries. It can be used in products such as fire-resistant doors, and missile parts such as nose cones. Coal Mining Coal can be extracted from the earth either by surface mining or underground mining.
Once coal has been extracted, it can be used directly for heating and industrial processes or to fuel power plants for electricity. Surface Mining If coal is less than 61 meters feet underground, it can be extracted through surface mining. In surface mining, workers simply remove any overlying sediment, vegetation, and rock, called overburden. Economically, surface mining is a cheaper option for extracting coal than underground mining. About two and a half times as much coal can be extracted per worker, per hour, than is possible with underground mining.
The environmental impacts of surface mining are dramatic. The landscape is literally torn apart, destroying habitats and entire ecosystem s. Surface mining can also cause landslide s and subsidence when the ground begins to sink or cave in. Toxic substances leach ing into the air, aquifer s, and water table s may endanger the health of local residents.
In the United States, the Surface Mining Control and Reclamation Act of regulates the process of coal mining, and is an effort to limit the harmful effects on the environment. The act provides funds to help fix these problems and clean up abandoned mining sites. The three main types of surface coal mining are strip mining, open-pit mining, and mountaintop removal MTR mining.
Surface Mining: Strip Mining Strip mining is used where coal seams are located very near the surface and can be removed in massive layers, or strips. Overburden is usually removed with explosives and towed away with some of the largest vehicles ever made. Dump trucks used at strip mines often weigh more than tons and have more than 3, horsepower.
Strip mining can be used in both flat and hilly landscapes. Strip mining in a mountainous area is called contour mining. Contour mining follows the ridges, or contours, around a hill. A pit, sometimes called a borrow, is dug in an area. This pit becomes the open-pit mine , sometimes called a quarry. Open-pit mines can expand to huge dimensions, until the coal deposit has been mined or the cost of transporting the overburden is greater than the investment in the mine.
Open-pit mining is usually restricted to flat landscapes. After the mine has been exhausted, the pit is sometimes converted into a landfill. After the summit is cleared of vegetation, explosives are used to expose the coal seam.
After the coal is extracted, the summit is sculpted with overburden from the next mountaintop to be mined. By law, valuable topsoil is supposed to be saved and replaced after mining is done. Barren land can be replanted with trees and other vegetation. Mountaintop removal began in the s as a cheap alternative to underground mining. It is now used for extracting coal mainly in the Appalachian Mountains of the U. MTR is probaby the most controversial coal mining technique.
The environmental consequences are radical and severe. Waterways are cut off or contaminated by valley fill. Habitats are destroyed. Toxic byproduct s of the mining and explosive processes can drain into local waterways and pollute the air.
Miners travel by elevator down a mine shaft to reach the depths of the mine, and operate heavy machinery that extracts the coal and moves it above ground. The immediate environmental impact of underground mining appears less dramatic than surface mining. There is little overburden, but underground mining operations leave significant tailings.
Tailings are the often-toxic residue left over from the process of separating coal from gangue , or economically unimportant minerals. Toxic coal tailings can pollute local water supplies. To miners, the dangers of underground mining are serious. Underground explosions, suffocation from lack of oxygen, or exposure to toxic gases are very real threats.
To prevent the buildup of gases, methane must be constantly ventilated out of underground mines to keep miners safe. There are three major types of underground coal mining: longwall mining, room-and-pillar mining, and retreat mining. Underground Mining: Longwall Mining During longwall mining , miners slice off enormous panels of coal that are about 1 meter 3 feet thick, kilometers The panels are moved by conveyor belt back to the surface.
The roof of the mine is maintained by hydraulic supports known as chock s. As the mine advances, the chocks also advance. The area behind the chocks collapses. Longwall mining is one of the oldest methods of mining coal.
Before the widespread use of conveyor belts, ponies would descend to the deep, narrow channels and haul the coal back to the surface. Today, almost a third of American coal mines use longwall mining. Columns pillars of coal support the ceiling and overburden. The rooms are about 9 meters 30 feet wide, and the support pillars can be 30 meters feet wide.
There are two types of room-and-pillar mining: conventional and continuous. In conventional mining, explosives and cutting tools are used.
In continuous mining, a sophisticated machine called a continuous miner extracts the coal. In developing countries, room-and-pillar coal mines use the conventional method. Underground Mining: Retreat Mining Retreat mining is a variation of room-and-pillar.
When all available coal has been extracted from a room, miners abandon the room, carefully destroy the pillars, and let the ceiling cave in. Remains of the giant pillars supply even more coal. Retreat mining may be the most dangerous method of mining.
A great amount of stress is put on the remaining pillars, and if they are not pulled out in a precise order, they can collapse and trap miners underground. How We Use Coal People all over the world have been using coal to heat their homes and cook their food for thousands of years.
Coal was used in the Roman Empire to heat public baths. In the Aztec Empire, the lustrous rock was used for ornaments as well as fuel. The Industrial Revolution was powered by coal. It was a cheaper alternative than wood fuel, and produced more energy when burned. Coal provided the steam and power needed to mass-produce items, generate electricity, and fuel steamships and trains that were necessary to transport items for trade.
Today, coal continues to be used directly heating and indirectly producing electricity. Coal is also essential to the steel industry. Fuel Around the world, coal is primarily used to produce heat.
Coal can be burned by individual households or in enormous industrial furnace s. It produces heat for comfort and stability, as well as heating water for sanitation and health. Electricity Coal-fired power plants are one of the most popular ways to produce and distribute electricity. In coal-fired power plant s, coal is combusted and heats water in enormous boilers. The boiling water creates steam, which turns a turbine and activates a generator to produce electricity.
Poland, China, Australia, and Kazakhstan are other nations that rely on coal for electricity. Coke Coal plays a vital role in the steel industry. In order to produce steel, iron ore must be heated to separate the iron from other minerals in the rock. In the past, coal itself was used to heat and separate the ore.
However, coal releases impurities such as sulfur when it is heated, which can make the resulting metal weak. As early as the 9th century, chemists and engineer s discovered a way to remove these impurities from coal before it was burned. This drives off impurities such as coal gas, carbon monoxide, methane, tars, and oil. The resulting material—coal with few impurities and high carbon content—is coke. The method is called coking.
The hot air ignites the coke, and the coke melts the iron and separates out the impurities. The resulting material is steel. Coke provides heat and chemical properties that gives steel the strength and flexibility needed to build bridges, skyscrapers, airports, and cars.
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Safe Deliveries Our delivery team have specific instructions on how to deliver your order. Home blog The different types of coal. The different types of coal. Have a read and see if you can figure them all out How is coal made? How many types of coal are there? There are six main types of coal that are regularly used by humans: Peat Peat is formed from decaying vegetation, and is considered to be the precursor of coal.
Lignite Lignite is formed from compressed peat, and is often referred to as brown coal. Steam Coal Steam coal is the stepping stone between bituminous coal and anthracite.
Anthracite Anthracite is the highest rank of ignitable coal. Graphite The technically highest ranking coal, graphite is difficult to ignite, and is rarely used as a fuel.
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