Coke (fuel)
Coke is a grey, hard, and
The unqualified term "coke" usually refers to the product derived from low-ash and low-sulphur 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]
History
China
Many historical sources dating to the 4th century describe the production of coke in
China is the largest producer and exporter of coke today.[5] China produces 60% of the world's coke. Concerns about air pollution have motivated technological changes in the coke industry by elimination of outdated coking technologies that are not energy-efficient.[6]
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".[7] 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 of smoke.[8]
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 sulphurous fumes would impart a foul taste to the beer.[9] 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.[8]
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.[10]
In 1768, John Wilkinson built a more practical oven for converting coal into coke.[11] 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.[12]
In 1802, a battery of beehive ovens was set up near
In the first years of steam locomotives, coke was the normal fuel. This resulted from an early piece of environmental legislation; any proposed locomotive had to "consume its own smoke".[13] 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. The smoke plume produced by a travelling locomotive seems now to be a mark of a steam railway, and so preserved for posterity.
So-called "gas works" produced coke by heating coal in enclosed chambers. The flammable gas that was given off was stored in
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
Between 1870 and 1905, the number of beehive ovens in the US increased from approximately 200 to nearly 31,000, which produced nearly 18,000,000 tons of coke in the Pittsburgh area alone.[17] 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.[18]
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.
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Coal coking ovens at Cokedale, Colorado, supplied steel mills in Pueblo, CO
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The 200 Cherry Valley Coke Ovens built around 1866
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).[20] This process vaporises or decomposes organic substances in the coal, driving off water and other volatile and liquid products such as coal gas and coal tar. Coke is the non-volatile residue of the decomposition, the cemented-together carbon and mineral residue of the original coal particles in the form of a hard and somewhat glassy solid.[citation needed]
Additional byproducts of the coking are
Sources
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. If the range of coal types is too great, the resulting coke is of widely varying strength and ash content, and is usually unsaleable, although in some cases it may be sold as an ordinary heating fuel. As coke has already lost its volatile matter, it cannot be coked again.
Coking coal is different from thermal coal, but arises from the same basic coal-forming process. Coking coal has different
- 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%)[23]
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 coal, 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.[12] 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 about 4 meters (13 ft) wide and 2.5 meters (8 ft) high. The roof has a hole for charging the coal or other kindling from the top. A 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.[24]
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. The heat required for the process 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 is discharged manually through the side door. When the oven is used on a continuous basis, 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 that were not driven off as gases accumulated in the oven as slag – effectively a conglomeration of the removed impurities. Since this slag was not the desired product, it was initially just discarded. Later, however, coke oven slag was found to be useful, and has since been used as an ingredient in brick-making, mixed cement, granule-covered shingles, and even as a fertilizer.[25]
Occupational safety
People can be exposed to coke oven emissions in the workplace by inhalation, skin contact, or eye contact. For the United States, 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 US 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.[26]
Uses
Coke can be used as a fuel and as a reducing agent in smelting iron ore in a blast furnace.[27] The carbon monoxide produced by combustion of coke reduces iron oxide (hematite) to produce iron:[28]
- .
Coke is commonly used as fuel for blacksmithing.
Coke was used in Australia in the 1960s and early 1970s for house heating,[citation needed] and was incentivized for home use in the UK (so as to displace coal) after the 1956 Clean Air Act, which was passed in response to the Great Smog of London in 1952.
Since
Highland Park distillery in Orkney roasts malted barley for use in their Scotch whisky in kilns burning a mixture of coke and peat.[29]
Coke may be used to make synthesis gas, a mixture of carbon monoxide and hydrogen.
- Hydrocarbonate (gas) is identical, although it emerged in the late eighteenth century as an inhalation therapeutic developed by Thomas Beddoes and James Watt categorized under factitious airs
- Producer gas; wood gas; generator gas; synthetic gas: a mixture of carbon monoxide, hydrogen, and nitrogen, made by passing air over red-hot coke (or any carbon-based char)
- Coke oven gas generated from coke ovens is similar to Syngas with 60% hydrogen by volume.[30] The hydrogen can be extracted from the coke oven gas economically for various uses (including steel production).[31]
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.
Properties
Before bituminous coal is used as coking coal, it must meet a set of criteria determined by particular
The bulk
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.
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.
Due to a lack of oil or high-quality coals in East Germany, scientists developed a process to turn low-quality lignite into coke called high temperature lignite coke.
See also
- Charcoal, made from wood rather than coal
- History of manufactured gas
- List of CO2 emitted per million Btu of energy from various fuels
- Petroleum coke
- Pyrolysis
- Sydney Tar Ponds, environmental damage caused by coke oven
- Tar
References
- ^ 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
- ^ McNeil, William H. The Pursuit of Power. University of Chicago Press, 1982, pp. 26, 33, and 45.
- ISBN 978-0521435192.
- hdl:2027.42/99106. Retrieved 22 December 2020.
- ^ "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.
- ^ a b Peckham, Stephen (1880). Special Reports on Petroleum, Coke, and Building Stones. United States Census Office. 10th census. p. 53.
- ISBN 978-0-7656-2413-0.
- ^ 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 10 February 2015.
- ISBN 978-3-527-30289-5.
- ^ JSTOR 621295.
- 8 & 9 Vict.c. 20) section 114
- ^ DiCiccio, Carmen. Coal and Coke in Pennsylvania. Harrisburg, PA: Pennsylvania Historical and Museum Commission.
- ^ A subsidiary of the Buffalo, Rochester and Pittsburgh Railway.
- ^ "National Register Information System". National Register of Historic Places. National Park Service. 9 July 2010.
- ^ Eavenson, Howard N. (1942). The First Century and a Quarter of American Coal Industry. Pittsburgh, PA: Waverly Press.
- ^ Warren, Kenneth (2001). Wealth, Waste, and Alienation: Growth and Decline in the Connellsville Coke Industry. Pittsburgh, PA: University of Pittsburgh.
- ^ a b Martin, Scott C. Killing Time: Leisure and Culture in Southwestern Pennsylvania, 1800–1850. Pittsburgh, PA: University of Pittsburgh Press.
- ^ "Coal and Steel". World Coal Association. 28 April 2015. Archived from the original on 14 March 2012.
- S2CID 98805474.
- ^ "Cokemaking: The SunCoke Way". YouTube. Archived from the original on 3 June 2016.
- ^ "Coal Grades". Ministry of Coal. Archived from the original on 1 February 2016.
- ^ "Manufacture of Coke at Salem No. 1 Mine Coke Works". Pathoftheoldminer. Archived from the original on 3 July 2013. Retrieved 14 May 2013.
- ^ "Coke Ovens". The Friends of the Cumberland Trail. Archived from the original on 25 June 2012.
- ^ "CDC – NIOSH Pocket Guide to Chemical Hazards – Coke oven emissions". www.cdc.gov. Archived from the original on 23 November 2015. Retrieved 27 November 2015.
- ^ Chisholm, Hugh, ed. (1911). . Encyclopædia Britannica. Vol. 6 (11th ed.). Cambridge University Press. p. 657.
- ^ "Science Aid: Blast Furnace". Retrieved 13 October 2021.
- The Scotch Malt Whisky Society: Highland Park: Where the peat still reeks in the old way "The Scotch Malt Whisky Society - USA". Archivedfrom the original on 16 July 2011. Retrieved 22 February 2011.
- ^ "Different Gases from Steel Production Processes". Retrieved 5 July 2020.
- ^ "Steel making today and tomorrow". Retrieved 30 June 2019.
- ^ "Cutting-Edge Solutions For Coking Wastewater Reuse To Meet The Standard Of Circulation Cooling Systems". www.wateronline.com. Archived from the original on 15 August 2016. Retrieved 16 January 2016.
- PMID 24520694.
- S2CID 98288378.
- .
- PMID 19062164.
- ISBN 978-3527306732.