Anthracite
Anthracite is a compact and hard variety of coal distinguished by its shiny, submetallic luster and high carbon content, typically up to 95%. Known for its superior energy density, anthracite has the potential to produce more heat than any other coal type, making it a favored choice for home heating systems. This coal type is notable for its minimal impurities and clean-burning properties, resulting in almost no smoke or particulate emissions when combusted. It burns at high temperatures, producing a blue flame and generating between 13,000 to 15,000 BTU per pound.
Despite its advantages, anthracite is the rarest form of coal, primarily mined in limited regions, with the largest deposits located in northeastern Pennsylvania, and significant production also occurring in China, Russia, and Ukraine. Historically, anthracite mining flourished in Pennsylvania during the 19th and early 20th centuries but has since diminished, with some operations still ongoing. The unique characteristics and scarcity of anthracite contribute to its high value in various heating applications, though it is less common in industrial coal-fired power plants due to its slow-burning nature.
On this Page
Subject Terms
Anthracite
Anthracite is a particularly hard, compact form of coal that is easily identified by its submetallic luster. Anthracite has the highest carbon content and greatest energy density of any coal variety. It also has the fewest impurities. As compared to other types of coal, anthracite spends the longest amount of time underground and is subjected to more pressure and heat. All of this means that anthracite holds greater potential to produce heat energy than any other form of coal, which makes it an ideal fuel for home heating. Since it produces almost no smoke or particulate emissions when burn, anthracite is also the cleanest and most environmentally friendly form of coal. At the same time, however, anthracite is also the scarcest coal variety. It is mined in only a few countries worldwide, with China being the world’s largest modern producer. In the United States, anthracite coal was primarily mined in a small section of northeastern Pennsylvania.
Background
Anthracite is one of several common types of coal. Coal is an organic sedimentary rock that is formed over a long time due to the accumulation and preservation of plant material, usually in a swamp environment. A plant that dies and falls into oxygen-deficient swamp water will decay at a slower-than-normal rate because of the lack of oxygen. A coal seam can only be formed when the rate of plant debris accumulation is greater than the rate of decay. When a sufficiently thick layer of plant debris forms, it must also be buried by sediments like mud or sand. The weight of these sediments compacts the plant debris and therefore plays a critical role in its transformation into coal. The formation of coal also requires a precise water depth that is maintained for a long period. When conditions are just right, a mass of accumulated plant debris will eventually begin to carbonize into an organic sediment called peat and ultimately form a coal seam.
There are several common forms of coal, ranked according to their specific composition and properties. The rank progression of the different types of coal also reflects each variety’s particular level of organic metamorphism. The lowest ranked form of coal is lignite. Lignite is a peat that has just been transformed into coal. Brownish-black in color, lignite contains less carbon than any other form of coal. It can also contain recognizable plant structures and is typically moist and crumbly when compared to other coal varieties. Lignite is primarily used in electricity generation. Subbituminous coal, the third-ranked form of coal, is lignite that has undergone a greater degree of organic metamorphism. As a result, it has a higher carbon content and is darker in color. Like lignite, subbituminous coal is mainly used for electricity generation. The second-ranked form of coal is bituminous coal. Bituminous coal, which is exposed to even greater levels of organic metamorphism, is the most abundant type of coal. It has a higher carbon content than ligate or subbituminous coal and may also include a greater amount of volatile content. Often referred to as “soft coal,” bituminous coal is known for its shiny luster and layered texture and is mostly used for industrial purposes. The highest-ranked form of coal is anthracite.
Overview
Lustrous and smooth anthracite is the highest-quality coal variety. Because it is exposed to more organic metamorphism than any other type of coal, anthracite is particularly hard and brittle. In fact, anthracite is often considered to be a true metamorphic rock. Anthracite also contains a high percentage of fixed carbon, usually up to 95 percent, and very little sulfur or nitrogen. This makes it the cleanest-burning form of coal.
Perhaps most importantly, anthracite coal is especially valued because it possesses greater potential to produce heat energy than any other type of coal. Exhibiting a hot blue flame when burned, anthracite produces more heat and less smoke than other coal varieties. It also burns longer than wood. Anthracite typically burns at 900°F or higher and produces anywhere from 13,000 to 15,000 BTU per pound. For this reason, anthracite is commonly used as fuel in hand-fired furnaces, including those that are a part of residential heating systems. However, because it is dense, slow-burning, and difficult to ignite, anthracite is not typically used at coal-fired power plants.
Anthracite is considered a free-burning material because it does not coke, or expand and fuse when heated. It is usually burned in either underfeed stoker boilers or single-retort side-dump stoker boilers equipped with stationary grates. Regardless of what type of boiler or furnace is used, anthracite produces particulate matter in the form of fine soot and ash when burned. The amount of particulate matter produced can be reduced through attention to furnace configuration and boiler load, as well as the use of things like fabric filters, scrubbers, and electrostatic precipitators. The mining of anthracite also leads to the accumulation of a waste product called culm. Culm is an inferior form of coal that is rejected from anthracite mines. While culm can be burned and is sometimes used in fluidized bed combustion boilers, it is often simply discarded.
In addition to its attractive properties, much of anthracite’s value is tied to its relative scarcity. Anthracite is the least-common type of coal in the United States, accounting for only a small fraction of the nation’s existing coal resources. The largest deposit of anthracite in the United States is found in northeastern Pennsylvania, specifically in a 480-square-mile region located in Lackawanna, Luzerne, and Schuylkill counties. This deposit was heavily mined in the nineteenth and early twentieth centuries before the mining industry there began to die out in the 1950s. Some surface mining operations continue to extract anthracite in Pennsylvania. Anthracite is also produced in a number of other countries, including China, Russia, and Ukraine. Regardless, Pennsylvania’s anthracite is considered to be the highest quality available anywhere in the world.
Bibliography
“About the Anthracite Coal Mining Region of Northeastern Pennsylvania.” Penn State Universities Libraries, 2020, guides.libraries.psu.edu/anthracite. Accessed 8 Jan. 2020.
Brady, Jeff. “For the Few Who Heat Homes with Coal, It’s Still King.” NPR, 3 Mar. 2019, www.npr.org/2019/03/03/699325560/for-the-few-who-heat-homes-with-coal-its-still-king. Accessed 8 Jan. 2020.
“It’s Not Just Coal—It’s Anthracite.” Blaschak Coal Corporation, 2020, www.blaschakcoal.com/its-not-just-coal-its-anthracite. Accessed 8 Jan. 2020.
Kay, Amanda. “Coal 101: What Is Anthracite?” Investing News, 18 June 2018, investingnews.com/daily/resource-investing/industrial-metals-investing/coal-investing/coal-101-what-is-anthracite. Accessed 8 Jan. 2020.
King, Hobart M. “Coal: What Is Coal and How Does It Form?” Geology.com, 2020, geology.com/rocks/coal.shtml. Accessed 8 Jan. 2020.
Lyons Sunshine, Wendy. “All About Anthracite Coal.” The Balance, 1 Aug. 2019, www.thebalance.com/what-is-anthracite-coal-1182544. Accessed 8 Jan. 2020.
“Real Facts About Anthracite Coal.” Leisure Line Stove Company, 2020, leisurelinestove.com/anthracitecoal. Accessed 8 Jan. 2020.
“What Are the Different Types of Coal?” American Geosciences Institute, 2020, www.americangeosciences.org/critical-issues/faq/what-are-the-different-types-of-coal. Accessed 8 Jan. 2020.