# Coke (fuel)

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Coke is a grey, hard, and porous fuel with a high carbon content and few impurities, made by heating coal or oil in the absence of air — a destructive distillation process. It is an important industrial product, used mainly in iron ore smelting, but also as a fuel in stoves and forges when air pollution is a concern.

Carbon is a chemical element with symbol C and atomic number 6. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Three isotopes occur naturally, 12C and 13C being stable, while 14C is a radionuclide, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity.

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 if dead plant matter decays into peat and over millions of years the heat and pressure of deep burial converts the peat into coal. Vast deposits of coal originates in former wetlands—called coal forests—that covered much of the Earth's tropical land areas during the late Carboniferous (Pennsylvanian) and Permian times.

Petroleum is a naturally occurring, yellowish-black liquid found in geological formations beneath the Earth's surface. It is commonly refined into various types of fuels. Components of petroleum are separated using a technique called fractional distillation, i.e. separation of a liquid mixture into fractions differing in boiling point by means of distillation, typically using a fractionating column.

## Contents

The unqualified term "coke" usually refers to the product derived from low-ash and low-sulfur bituminous coal by a process called coking. A similar product called petroleum coke, or pet coke, is obtained from crude oil in oil refineries. Coke may also be formed naturally by geologic processes. [1]

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.

Coking is the deposition of carbon-rich solids. In heterogeneous catalysis, the process is undesirable because the clinker blocks the catalytic sites. Coking is characteristic of high temperature reactions involving hydrocarbons feedstocks. Typically coking is reversed by combustion, provided that the catalyst will tolerate such.

Petroleum coke, abbreviated coke or petcoke, is a final carbon-rich solid material that derives from oil refining, and is one type of the group of fuels referred to as cokes. Petcoke is the coke that, in particular, derives from a final cracking process—a thermo-based chemical engineering process that splits long chain hydrocarbons of petroleum into shorter chains—that takes place in units termed coker units. Stated succinctly, coke is the "carbonization product of high-boiling hydrocarbon fractions obtained in petroleum processing ." Petcoke is also produced in the production of synthetic crude oil (syncrude) from bitumen extracted from Canada’s oil sands and from Venezuela's Orinoco oil sands.

## History

### China

Historical sources dating to the 4th century describe the production of coke in ancient China. [2] The Chinese first used coke for heating and cooking no later than the ninth century.[ citation needed ] By the first decades of the eleventh century, Chinese ironworkers in the Yellow River valley began to fuel their furnaces with coke, solving their fuel problem in that tree-sparse region. [3]

China, officially the People's Republic of China (PRC), is a country in East Asia and the world's most populous country, with a population of around 1.404 billion. Covering approximately 9,600,000 square kilometers (3,700,000 sq mi), it is the third- or fourth-largest country by total area. Governed by the Communist Party of China, the state exercises jurisdiction over 22 provinces, five autonomous regions, four direct-controlled municipalities, and the special administrative regions of Hong Kong and Macau.

The Yellow River or Huang He is the second longest river in China, after the Yangtze River, and the sixth longest river system in the world at the estimated length of 5,464 km (3,395 mi). Originating in the Bayan Har Mountains in Qinghai province of Western China, it flows through nine provinces, and it empties into the Bohai Sea near the city of Dongying in Shandong province. The Yellow River basin has an east–west extent of about 1,900 kilometers (1,180 mi) and a north–south extent of about 1,100 km (680 mi). Its total drainage area is about 752,546 square kilometers (290,560 sq mi).

### Britain

In 1589, a patent was granted to Thomas Proctor and William Peterson for making iron and steel and melting lead with "earth-coal, sea-coal, turf, and peat". The patent contains a distinct allusion to the preparation of coal by "cooking". In 1590, a patent was granted to the Dean of York to "purify pit-coal and free it from its offensive smell". [4] In 1620, a patent was granted to a company composed of William St. John and other knights, mentioning the use of coke in smelting ores and manufacturing metals. In 1627, a patent was granted to Sir John Hacket and Octavius de Strada for a method of rendering sea-coal and pit-coal as useful as charcoal for burning in houses, without offense by smell or smoke. [5]

The Dean of York is the member of the clergy who is responsible for the running of the York Minster cathedral. As well as being the head of the cathedral church of the diocese and the metropolitical church of the province, the Dean of York holds preeminence as the Vicar of the Northern Province.

In 1603, Hugh Plat suggested that coal might be charred in a manner analogous to the way charcoal is produced from wood. This process was not employed until 1642, when coke was used for roasting malt in Derbyshire; previously, brewers had used wood, as uncoked coal cannot be used in brewing because its sulfurous fumes would impart a foul taste to the beer. [6] It was considered an improvement in quality, and brought about an "alteration which all England admired"—the coke process allowed for a lighter roast of the malt, leading to the creation of what by the end of the 17th century was called pale ale. [5]

Sir Hugh Plat (1552–1608) was an English writer on agriculture and inventor, known from his works The Jewell House of Art and Nature (1594) and his major work on gardening Floraes Paradise (1608).

Charcoal is the lightweight black carbon and ash residue hydrocarbon produced by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by slow pyrolysis — the heating of wood or other substances in the absence of oxygen. This process is called charcoal burning. The finished charcoal consists largely of carbon.

Malt is germinated cereal grain that have been dried in a process known as "malting". The grains are made to germinate by soaking in water and are then halted from germinating further by drying with hot air. Malting grains develop the enzymes required for modifying the grain's starches into various types of sugar, including monosaccharide glucose, disaccharide maltose, trisaccharide maltotriose, and higher sugars called maltodextrines. It also develops other enzymes, such as proteases, which break down the proteins in the grain into forms that can be used by yeast. Depending on when the malting process is stopped, one gets a preferred starch to enzyme ratio and partly converted starch into fermentable sugars. Malt also contains small amounts of other sugars, such as sucrose and fructose, which are not products of starch modification but were already in the grain. Further conversion to fermentable sugars is achieved during the mashing process.

In 1709, Abraham Darby I established a coke-fired blast furnace to produce cast iron. Coke's superior crushing strength allowed blast furnaces to become taller and larger. The ensuing availability of inexpensive iron was one of the factors leading to the Industrial Revolution. Before this time, iron-making used large quantities of charcoal, produced by burning wood. As the coppicing of forests became unable to meet the demand, the substitution of coke for charcoal became common in Great Britain, and coke was manufactured by burning coal in heaps on the ground so that only the outer layer burned, leaving the interior of the pile in a carbonized state. In the late 18th century, brick beehive ovens were developed, which allowed more control over the burning process. [7]

Abraham Darby, in his later life called Abraham Darby the Elder, now sometimes known for convenience as Abraham Darby I was the first and best known of several men of that name. Born into an English Quaker family that played an important role in the Industrial Revolution, Darby developed a method of producing pig iron in a blast furnace fuelled by coke rather than charcoal. This was a major step forward in the production of iron as a raw material for the Industrial Revolution.

A blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally pig iron, but also others such as lead or copper. Blast refers to the combustion air being "forced" or supplied above atmospheric pressure.

Cast iron is a group of iron-carbon alloys with a carbon content greater than 2%. Its usefulness derives from its relatively low melting temperature. The alloy constituents affect its colour when fractured: white cast iron has carbide impurities which allow cracks to pass straight through, grey cast iron has graphite flakes which deflect a passing crack and initiate countless new cracks as the material breaks, and ductile cast iron has spherical graphite "nodules" which stop the crack from further progressing.

In 1768, John Wilkinson built a more practical oven for converting coal into coke. [8] Wilkinson improved the process by building the coal heaps around a low central chimney built of loose bricks and with openings for the combustion gases to enter, resulting in a higher yield of better coke. With greater skill in the firing, covering and quenching of the heaps, yields were increased from about 33% to 65% by the middle of the 19th century. The Scottish iron industry expanded rapidly in the second quarter of the 19th century, through the adoption of the hot-blast process in its coalfields. [9]

In 1802, a battery of beehives was set up near Sheffield, to coke the Silkstone seam for use in crucible steel melting. By 1870, there were 14,000 beehive ovens in operation on the West Durham coalfields, capable of producing 4,000,000 long tons (4,480,000 short tons; 4,060,000 t) of coke. As a measure of the extent of the expansion of coke making, it has been estimated that the requirements of the iron industry were about 1,000,000 long tons (1,120,000 short tons; 1,020,000 t) a year in the early 1850s, whereas by 1880 the figure had risen to 7,000,000 long tons (7,800,000 short tons; 7,100,000 t), of which about 5,000,000 long tons (5,600,000 short tons; 5,100,000 t) were produced in Durham county, 1,000,000 long tons (1,120,000 short tons; 1,020,000 t) in the South Wales coalfield, and 1,000,000 long tons (1,120,000 short tons; 1,020,000 t) in Yorkshire and Derbyshire. [9]

In the first years of steam railway locomotives, coke was the normal fuel. This resulted from an early piece of environmental legislation; any proposed locomotive had to "consume its own smoke". [10] This was not technically possible to achieve until the firebox arch came into use, but burning coke, with its low smoke emissions, was considered to meet the requirement. This rule was quietly dropped, and cheaper coal became the normal fuel, as railways gained acceptance among the public.

### United States

In the US, the first use of coke in an iron furnace occurred around 1817 at Isaac Meason's Plumsock puddling furnace and rolling mill in Fayette County, Pennsylvania. [11] In the late 19th century, the coalfields of western Pennsylvania provided a rich source of raw material for coking. In 1885, the Rochester and Pittsburgh Coal and Iron Company [12] constructed the world's longest string of coke ovens in Walston, Pennsylvania, with 475 ovens over a length of 2 km (1.25 miles). Their output reached 22,000 tons per month. The Minersville Coke Ovens in Huntingdon County, Pennsylvania, were listed on the National Register of Historic Places in 1991. [13]

Between 1870 and 1905, the number of beehive ovens in the US skyrocketed from about 200 to almost 31,000, which produced nearly 18,000,000 tons of coke in the Pittsburgh area alone. [14] One observer boasted that if loaded into a train, “the year's production would make up a train so long that the engine in front of it would go to San Francisco and come back to Connellsville before the caboose had gotten started out of the Connellsville yards!” The number of beehive ovens in Pittsburgh peaked in 1910 at almost 48,000. [15]

Although it made a top-quality fuel, coking poisoned the surrounding landscape. After 1900, the serious environmental damage of beehive coking attracted national notice, although the damage had plagued the district for decades. “The smoke and gas from some ovens destroy all vegetation around the small mining communities,” noted W. J. Lauck of the U.S. Immigration Commission in 1911. [16] Passing through the region on train, University of Wisconsin president Charles van Hise saw “long rows of beehive ovens from which flame is bursting and dense clouds of smoke issuing, making the sky dark. By night the scene is rendered indescribably vivid by these numerous burning pits. The beehive ovens make the entire region of coke manufacture one of dulled sky: cheerless and unhealthful." [16]

## Production

### Industrial coke furnaces

The industrial production of coke from coal is called coking. The coal is baked in an airless kiln, a "coke furnace" or "coking oven" at temperatures as high as 2,000 °C (3,600 °F) but usually around 1,000–1,100 °C (1,800–2,000 °F). [17] This process vaporizes or decomposes organic substances in the coal, driving off volatile products, including water, in the form of coal-gas and coal-tar. The non-volatile residue of the decomposition is mostly carbon, in the form of a hard somewhat glassy solid that cements together the original coal particles and minerals.

Some facilities have "by-product" coking ovens in which the volatile decomposition products are collected, purified and separated for use in other industries, as fuel or chemical feedstocks. Otherwise the volatile byproducts are burned to heat the coking ovens. This is an older method, but is still being used for new construction. [18]

Bituminous coal must meet a set of criteria for use as coking coal, determined by particular coal assay techniques. These include moisture content, ash content, sulfur content, volatile content, tar, and plasticity. This blending is targeted at producing a coke of appropriate strength (generally measured by coke strength after reaction), while losing an appropriate amount of mass. Other blending considerations include ensuring the coke doesn't swell too much during production and destroy the coke oven through excessive wall pressures.

The greater the volatile matter in coal, the more by-product can be produced. It is generally considered that levels of 26–29% of volatile matter in the coal blend are good for coking purposes. Thus different types of coal are proportionally blended to reach acceptable levels of volatility before the coking process begins.

Coking coal is different from thermal coal, but it differs not by the coal forming process. Coking coal has different macerals from thermal coal. Based on the ash percentage coking coal can be divided into various grades. These grades are:

• Steel Grade I (Ash content not exceeding 15%)
• Steel Grade II (Exceeding 15% but not exceeding 18%)
• Washery Grade I (Exceeding 18% but not exceeding 21%)
• Washery Grade II (Exceeding 21% but not exceeding 24%)
• Washery Grade III (Exceeding 24% but not exceeding 28%)
• Washery Grade IV (Exceeding 28% but not exceeding 35%) [19]

The different macerals are related to source of material that compose the coal. However, the coke is of wildly varying strength and ash content and is generally considered unsellable except in some cases as a thermal product. As it has lost its volatile matter, it has lost the ability to be coked again.

### The "hearth" process

The "hearth" process of coke-making, using lump coal, was akin to that of charcoal-burning; instead of a heap of prepared wood, covered with twigs, leaves and earth, there was a heap of coals, covered with coke dust. The hearth process continued to be used in many areas during the first half of the 19th century, but two events greatly lessened its importance. These were the invention of the hot blast in iron-smelting and the introduction of the beehive coke oven. The use of a blast of hot air, instead of cold air, in the smelting furnace was first introduced by Neilson in Scotland in 1828. [9] The hearth process of making coke from coal is a very lengthy process.[ citation needed ]

### Beehive coke oven

A fire brick chamber shaped like a dome is used, commonly known as a beehive oven. It is typically 4 meters (13.1 ft) wide and 2.5 meters (8.2 ft) high. The roof has a hole for charging the coal or other kindling from the top. The discharging hole is provided in the circumference of the lower part of the wall. In a coke oven battery, a number of ovens are built in a row with common walls between neighboring ovens. A battery consisted of a great many ovens, sometimes hundreds, in a row. [20]

Coal is introduced from the top to produce an even layer of about 60 to 90 centimeters (24 to 35 in) deep. Air is supplied initially to ignite the coal. Carbonization starts and produces volatile matter, which burns inside the partially closed side door. Carbonization proceeds from top to bottom and is completed in two to three days. Heat is supplied by the burning volatile matter so no by-products are recovered. The exhaust gases are allowed to escape to the atmosphere. The hot coke is quenched with water and discharged, manually through the side door. The walls and roof retain enough heat to initiate carbonization of the next charge.

When coal was burned in a coke oven, the impurities of the coal not already driven off as gases accumulated to form slag, which was effectively a conglomeration of the removed impurities. Since it was not the desired coke product, slag was initially nothing more than an unwanted by-product and was discarded. Later, however, it was found to have many beneficial uses and has since been used as an ingredient in brick-making, mixed cement, granule-covered shingles, and even as a fertilizer. [21]

### Occupational safety

People can be exposed to coke oven emissions in the workplace by inhalation, skin contact, or eye contact. The Occupational Safety and Health Administration (OSHA) has set the legal limit for coke oven emissions exposure in the workplace as 0.150 mg/m3 benzene-soluble fraction over an eight-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set a Recommended exposure limit (REL) of 0.2 mg/m3 benzene-soluble fraction over an eight-hour workday. [22]

## Uses

Coke is used as a fuel and as a reducing agent in smelting iron ore in a blast furnace. [23] The carbon monoxide produced by its combustion reduces iron oxide (hematite) in the production of the iron product. ( ${\displaystyle {\ce {2Fe2O3 + 3C -> 4Fe + 3CO2}}}$)

Coke is commonly used as fuel for blacksmithing.

Coke was used in Australia in the 1960s and early 1970s for house heating.[ citation needed ]

Since smoke-producing constituents are driven off during the coking of coal, coke forms a desirable fuel for stoves and furnaces in which conditions are not suitable for the complete burning of bituminous coal itself. Coke may be combusted producing little or no smoke, while bituminous coal would produce much smoke. Coke was widely used as a substitute for coal in domestic heating following the creation of smokeless zones in the United Kingdom.

Highland Park distillery in Orkney roasts malted barley for use in their Scotch whisky in kilns burning a mixture of coke and peat. [24]

Coke may be used to make synthesis gas, a mixture of carbon monoxide and hydrogen.

## Phenolic byproducts

Wastewater from coking is highly toxic and carcinogenic. It contains phenolic, aromatic, heterocyclic, and polycyclic organics, and inorganics including cyanides, sulfides, ammonium and ammonia. [25] Various methods for its treatment have been studied in recent years. [26] [27] [28] The white rot fungus Phanerochaete chrysosporium can remove up to 80% of phenols from coking waste water. [29]

## Properties

The bulk specific gravity of coke is typically around 0.77. It is highly porous.

The most important properties of coke are ash and sulfur content, which are dependent on the coal used for production. Coke with less ash and sulfur content is highly priced on the market. Other important characteristics are the M10, M25, and M40 test crush indexes, which convey the strength of coke during transportation into the blast furnaces; depending on blast furnaces size, finely crushed coke pieces must not be allowed into the blast furnaces because they would impede the flow of gas through the charge of iron and coke. A related characteristic is the Coke Strength After Reaction (CSR) index; it represents coke's ability to withstand the violent conditions inside the blast furnace before turning into fine particles.

The water content in coke is practically zero at the end of the coking process, but it is often water quenched so that it can be transported to the blast furnaces. The porous structure of coke absorbs some water, usually 3–6% of its mass. In more modern coke plants an advanced method of coke cooling uses air quenching.

Bituminous coal must meet a set of criteria for use as coking coal, determined by particular coal assay techniques. See Section "Production".

## Other processes

The solid residue remaining from refinement of petroleum by the "cracking" process is also a form of coke. Petroleum coke has many uses besides being a fuel, such as the manufacture of dry cells and of electrolytic and welding electrodes.

Gas works manufacturing syngas also produce coke as an end product, called gas house coke.

Fluid coking is a process which converts heavy residual crude into lighter products such as naphtha, kerosene, heating oil, and hydrocarbon gases. The "fluid" term refers to the fact that solid coke particles behave as a fluid solid in the continuous fluid coking process versus the older batch delayed-coking process where a solid mass of coke builds up in the coke drum over time.

## Related Research Articles

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.

Steelmaking is the process for producing steel from iron ore and scrap. In steelmaking, impurities such as nitrogen, silicon, phosphorus, sulfur and excess carbon are removed from the sourced iron, and alloying elements such as manganese, nickel, chromium and vanadium are added to produce different grades of steel. Limiting dissolved gases such as nitrogen and oxygen, and entrained impurities in the steel is also important to ensure the quality of the products cast from the liquid steel.

Coal gas is a flammable gaseous fuel made from coal and supplied to the user via a piped distribution system. It is produced when coal is heated strongly in the absence of air. Town gas is a more general term referring to manufactured gaseous fuels produced for sale to consumers and municipalities.

Anthracite iron or Anthracite 'Pig Iron' is the substance created by the smelting together of anthracite coal and iron ore, that is using Anthracite coal instead of charcoal to smelt iron ores — and was an important historic advance in the late-1830s enabling great acceleration the industrial revolution in Europe and North America.

A reverberatory furnace is a metallurgical or process furnace that isolates the material being processed from contact with the fuel, but not from contact with combustion gases. The term reverberation is used here in a generic sense of rebounding or reflecting, not in the acoustic sense of echoing.

A fossil fuel power station is a thermal power station which burns a fossil fuel such as coal, natural gas, or petroleum to produce electricity. Central station fossil fuel power plants are designed on a large scale for continuous operation. In many countries, such plants provide most of the electrical energy used. Fossil fuel power stations have machinery to convert the heat energy of combustion into mechanical energy, which then operates an electrical generator. The prime mover may be a steam turbine, a gas turbine or, in small plants, a reciprocating internal combustion engine. All plants use the energy extracted from expanding gas, either steam or combustion gases. Although different energy conversion methods exist, all thermal power station conversion methods have efficiency limited by the Carnot efficiency and therefore produce waste heat.

Puddling was one step in one of the most important processes of making the first appreciable volumes of high-grade bar iron during the Industrial Revolution. In the original puddling technique, molten iron in a reverberatory furnace was stirred with rods, which were consumed in the process. It was one of the first processes for making bar iron without charcoal in Europe, although much earlier coal-based processes had existed in China. Eventually, the furnace would be used to make small quantities of specialty steels.

Blast furnace gas (BFG) is a by-product of blast furnaces that is generated when the iron ore is reduced with coke to metallic iron. It has a very low heating value, about 93 BTU/cubic foot (3.5 MJ/m3), because it consists of about 60 percent nitrogen and 18-20% carbon dioxide, which are not flammable. The rest is mostly carbon monoxide, which has a fairly low heating value already and some (2-4%) hydrogen. It is commonly used as a fuel within the steel works, but it can be used in boilers and power plants equipped to burn it. It may be combined with natural gas or coke oven gas before combustion or a flame support with richer gas or oil is provided to sustain combustion. Particulate matter is removed so that it can be burned more cleanly. Blast furnace gas is sometimes flared without generating heat or electricity.

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.

Hot blast refers to the preheating of air blown into a blast furnace or other metallurgical process. As this considerably reduced the fuel consumed, hot blast was one of the most important technologies developed during the Industrial Revolution. Hot blast also allowed higher furnace temperatures, which increased the capacity of furnaces.

A beehive oven is a type of oven in use since the Middle Ages in Europe. It gets its name from its domed shape, which resembles that of an old-fashioned beehive.

A delayed coker is a type of coker whose process consists of heating a residual oil feed to its thermal cracking temperature in a furnace with multiple parallel passes. This cracks the heavy, long chain hydrocarbon molecules of the residual oil into coker gas oil and petroleum coke.

According to the United States Energy Information Administration (EIA), Pakistan may have over 9 billion barrels (1.4×109 cubic metres) of petroleum oil and 105 trillion cubic feet (3.0 trillion cubic metres) in natural gas (including shale gas) reserves.

The Pittsburgh Coal Seam is the thickest and most extensive coal bed in the Appalachian Basin; hence, it is the most economically important coal bed in the eastern United States. The Upper Pennsylvanian Pittsburgh coal bed of the Monongahela Group is extensive and continuous, extending over 11,000 mi2 through 53 counties. It extends from Allegany County, Maryland to Belmont County, Ohio and from Allegheny County, Pennsylvania southwest to Putnam County, West Virginia.

The Dunlap coke ovens are the remnants of a coke production facility near Dunlap, in the U.S. state of Tennessee. Built in the early 1900s, the facility consists of five batteries of 268 beehive ovens, which operated under various companies until the early 1920s. The ovens are now listed on the National Register of Historic Places, and are maintained by the Sequatchie Valley Historical Society as part of Dunlap Coke Ovens Park.

Visakhapatnam Steel Plant, popularly known as Vizag Steel, is an integrated steel producer in Visakhapatnam, India built using German and Soviet technology. The company has grown from a loss-making industry to 3-billion-dollar turnover company registering a growth of 203.6% in just four years. Vizag Steel Plant was conferred Navratna status on 17 November 2010. Founded in 1971, the company focuses on producing value-added steel, with 214,000 tonnes produced in August 2010, out of 252,000 tonnes total of salable steel produced.

The Cherry Valley Coke Ovens consisted of 200 coke ovens built by the Leetonia Iron and Coal Company around 1866, near Leetonia, Ohio, United States. The function of the "beehive" coke ovens was to purify coal and turn it into coke. The coke was burned in furnaces that produced iron and steel.

## References

1. B. Kwiecińska and H. I. Petersen (2004): "Graphite, semi-graphite, natural coke, and natural char classification — ICCP system". International Journal of Coal Geology, volume 57, issue 2, pages 99-116. doi : 10.1016/j.coal.2003.09.003
2. The Coming of the Ages of Steel. Brill Archive. 1961. p. 55. GGKEY:DN6SZTCNQ3G. Archived from the original on 1 May 2013. Retrieved 17 January 2013. Historic sources mention the use of coke in the fourth century AD
3. McNeil, William H. The Pursuit of Power. University of Chicago Press, 1982, pp. 26, 33, and 45.
4. "CCHC—Your Portal to the Past". Coal and Coke Heritage Center. Penn State Fayette, The Eberly Campus. Archived from the original on 23 May 2013. Retrieved 19 March 2013.
5. Peckham, Stephen (1880). Special Reports on Petroleum, Coke, and Building Stones. United States Census Office. 10th census. p. 53.
6. Nersesian, Roy L (2010). "Coal and the Industrial Revolution". Energy for the 21st century (2 ed.). Armonk, NY: Sharpe. p. 98. ISBN   978-0-7656-2413-0.
7. Cooper, Eileen Mountjoy. "History of Coke". Special Collections & Archives: Coal Dust, the Early Mining Industry of Indiana County. Indiana University of Pennsylvania. Archived from the original on 2015-02-10.
8. Wittcoff, M.M. Green ; H.A. (2003). Organic chemistry principles and industrial practice (1. ed., 1. reprint. ed.). Weinheim: Wiley-VCH. ISBN   978-3-527-30289-5.
9. Beaver, S. H. (1951). "Coke Manufacture in Great Britain: A Study in Industrial Geography". Transactions and Papers (Institute of British Geographers). The Royal Geographical Society (with the Institute of British Geographers (17): 133–48. doi:10.2307/621295. JSTOR   621295.
10. 8 & 9 Vict. cap. 20 (Railway Clauses Consolidation Act, 1845) section 114
11. DiCiccio, Carmen. Coal and Coke in Pennsylvania. Harrisburg, PA: Pennsylvania Historical and Museum Commission.
12. A subsidiary of the Buffalo, Rochester and Pittsburgh Railway.
13. National Park Service (2010-07-09). "National Register Information System". National Register of Historic Places . National Park Service.
14. Eavenson, Howard N. (1942). The First Century and a Quarter of American Coal Industry. Pittsburgh, PA: Waverly Press.
15. Warren, Kenneth (2001). Wealth, Waste, and Alienation: Growth and Decline in the Connellsville Coke Industry. Pittsburgh, PA: University of Pittsburgh.
16. Martin, Scott C. Killing Time: Leisure and Culture in Southwestern Pennsylvania, 1800–1850. Pittsburgh, PA: University of Pittsburgh Press.
17. "Coal and Steel". World Coal Association. 2015-04-28. Archived from the original on 2012-03-14.
18. "Cokemaking: The SunCoke Way". Archived from the original on 2016-06-03.
19. "Coal Grades" Archived 1 February 2016 at the Wayback Machine ,"Ministry of Coal"
20. "Manufacture of Coke at Salem No. 1 Mine Coke Works". Pathoftheoldminer. Archived from the original on 2013-07-03.
21. "Coke Ovens". The Friends of the Cumberland Trail. Archived from the original on 2012-06-25.
22. "CDC – NIOSH Pocket Guide to Chemical Hazards – Coke oven emissions". www.cdc.gov. Archived from the original on 2015-11-23. Retrieved 2015-11-27.
23.  Chisholm, Hugh, ed. (1911). . Encyclopædia Britannica . 6 (11th ed.). Cambridge University Press. p. 657.
24. The Scotch Malt Whisky Society: Highland Park: Where the peat still reeks in the old way "The Scotch Malt Whisky Society - USA". Archived from the original on 2011-07-16. Retrieved 2011-02-22.
25. "Cutting-Edge Solutions For Coking Wastewater Reuse To Meet The Standard Of Circulation Cooling Systems". www.wateronline.com. Archived from the original on 2016-08-15. Retrieved 2016-01-16.
26. Jin, Xuewen; Li, Enchao; Lu, Shuguang; Qiu, Zhaofu; Sui, Qian (2013-08-01). "Coking wastewater treatment for industrial reuse purpose: Combining biological processes with ultrafiltration, nanofiltration and reverse osmosis". Journal of Environmental Sciences. 25 (8): 1565–74. doi:10.1016/S1001-0742(12)60212-5.
27. Güçlü, Dünyamin; Şirin, Nazan; Şahinkaya, Serkan; Sevimli, Mehmet Faik (2013-07-01). "Advanced treatment of coking wastewater by conventional and modified fenton processes". Environmental Progress & Sustainable Energy. 32 (2): 176–80. doi:10.1002/ep.10626. ISSN   1944-7450.
28. Wei, Qing; Qiao, Shufeng; Sun, Baochang; Zou, Haikui; Chen, Jianfeng; Shao, Lei (2015-10-29). "Study on the treatment of simulated coking wastewater by O3 and O3/Fenton processes in a rotating packed bed". RSC Advances. 5 (113): 93386–93393. doi:10.1039/C5RA14198B.
29. Lu, Y; Yan, L; Wang, Y; Zhou, S; Fu, J; Zhang, J (2009). "Biodegradation of phenolic compounds from coking wastewater by immobilized white rot fungus Phanerochaete chrysosporium". Journal of Hazardous Materials. 165 (1–3): 1091–97. doi:10.1016/j.jhazmat.2008.10.091. PMID   19062164.