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==Overall flare system in industrial plants==
[[File:FlareStack System.png|right|thumbnail|400px|Schematic flow diagram of an overall vertical, elevated flare stack system in an industrial plant.|class=skin-invert-image]]
When industrial plant equipment items are overpressured, the [[pressure relief valve]] is an essential safety device that automatically releases gases and sometimes liquids. Those pressure relief valves are required by industrial design codes and standards as well as by law.
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The adjacent flow diagram depicts the typical components of an overall industrial flare stack system:<ref name=EPA-VOC/><ref name=Coker/><ref name=Mannan/>
* A knockout drum to remove any oil or water from the relieved gases. There may be several knock out drums: high
* A water seal drum to prevent any flashback of the [[flame]] from the top of the flare stack.
* An alternative gas recovery system for use during partial plant startups and shutdowns as well as other times when required. The recovered gas is routed into the fuel gas system of the overall industrial plant.
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==Crude oil production flares==
{{Main article|Routine flaring}}
[[File:North Dakota Flaring of Gas.JPG|thumb|
When [[crude oil]] is extracted and produced from [[oil well]]s, [[Natural gas|raw natural gas]] associated with the oil is brought to the surface as well. Especially in areas of the world lacking [[Pipeline transport|pipelines]] and other gas transportation infrastructure, vast amounts of such [[Associated petroleum gas|associated gas]] are commonly flared as waste or unusable gas. The flaring of associated gas may occur at the top of a vertical flare stack, or it may occur in a ground-level flare in an earthen pit
Advances in satellite monitoring, along with voluntary reporting, have revealed that about 150 × 10<sup>9</sup> cubic meters (5.3 × 10<sup>12</sup> cubic feet) of associated gas have been flared globally each year since at least the mid
Additionally, the waste is a significant source of [[carbon dioxide]] (CO<sub>2</sub>) and other [[greenhouse gas emissions]].
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Gas flares on biogas collection systems are used if the gas production rates are not sufficient to warrant use in any industrial process. However, on a plant where the gas production rate is sufficient for direct use in an industrial process that could be classified as part of the [[circular economy]], and that may include the [[Landfill gas utilization|generation of electricity]], the production of [[natural gas]] quality biogas for vehicle fuel<ref>{{Cite web|url=https://afdc.energy.gov/fuels/|title=Alternative Fuels Data Center: Alternative Fuels and Advanced Vehicles|website=afdc.energy.gov|access-date=2019-03-29}}</ref> or for heating in buildings, drying refuse-derived fuel or [[leachate]] treatment, gas flares are used as a back-up system during down-time for maintenance or breakdown of generation equipment. In this latter case, generation of biogas cannot normally be interrupted, and a gas flare is employed to maintain the internal pressure on the biological process.<ref>{{Cite web|url=https://www.gov.uk/government/publications/management-of-landfill-gas-lftgn-03|title=Management of landfill gas: LFTGN 03|website=GOV.UK|language=en|access-date=2019-03-29}}</ref>
There are two types of gas flare used for controlling biogas, open or enclosed. Open flares burn at a lower temperature, less than 1000 °C and are generally cheaper than enclosed flares that burn at a higher [[combustion]] temperature and are usually supplied to conform to a specific [[residence time]] of 0.3s within the chimney to ensure complete destruction of the toxic elements contained within the biogas.
==Environmental impacts==
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[[File:First gas from the Oselvar module on the Ula platform on April 14th, 2012.jpg|right|thumbnail|185px|Flaring gases from an oil platform in the [[North Sea oil|North Sea.]]]]
[[File:Flare, Bayport Industrial District, Harris County, Texas.jpg|200px|thumb|Flare, Bayport Industrial District, Harris County, Texas]]
The natural gas that is not combusted by a flare is vented into the atmosphere as methane. [[Methane]]'s estimated [[global warming potential]] is 28-36 times greater than that of CO<sub>2</sub> over the course of a century, and 84-87 times greater over two decades.<ref>{{Cite web |last=US EPA |first=OAR |date=2016-01-12 |title=Understanding Global Warming Potentials |url=https://www.epa.gov/ghgemissions/understanding-global-warming-potentials |access-date=2022-03-16 |website=www.epa.gov |language=en}}</ref> Natural gas flaring produces CO2 and many other compounds, depending on the chemical composition of the natural gas and on how well the natural gas burns in the flare. Therefore, to the extent that gas flares convert methane to CO<sub>2</sub> before it is released into the atmosphere, they reduce the amount of global warming that would otherwise occur.<ref>{{cite web |title=Natural gas - Gas flaring and gas venting - Eniscuola |url=http://www.eniscuola.net/en/argomento/natural-gas1/environment-and-territory1/gas-flaring-and-gas-venting/ |website=Eniscuola Energy and Environment |access-date=23 June 2018}}</ref><ref>{{cite web | url=https://www.eia.gov/energyexplained/natural-gas/natural-gas-and-the-environment.php | title=Natural gas and the environment - U.S. Energy Information Administration (EIA) }}</ref>
Flaring emissions contributed to 270 Mt ([[megatonnes]]) of CO<sub>2</sub> in 2017 and reducing flaring emissions is thought to be an important component in curbing global warming.<ref name="iea.org">{{Cite web|url=https://www.iea.org/reports/tracking-fuel-supply-2019/flaring-emissions|title=Flaring emissions – Tracking Fuel Supply – Analysis|website=IEA|language=en-GB|access-date=2020-02-12}}</ref> An increasing number of governments and industries have pledged to eliminate or reduce flaring.<ref name="iea.org" /> The [https://www.globalmethanepledge.org Global Methane Pledge] signed at [[COP26]], in which 111 nations committed to reducing methane emissions by at least 30 percent from 2020 levels by 2030, is also playing a role in raising the global focus on methane.
Additional noxious fumes emitted by flaring may include, [[aromatic hydrocarbons]] ([[benzene]], [[toluene]], [[xylenes]]) and [[benzo(a)pyrene]], which are known to be carcinogenic. A 2013 study found that gas flares contributed over 40% of the [[black carbon]] deposited in the Arctic.<ref>{{Citation |author=Stohl, A. |author2=Klimont, Z. |author3=Eckhardt, S. |author4=Kupiainen, K. |author5=Chevchenko, V.P. |author6=Kopeikin, V.M. |author7=Novigatsky, A.N. |title=Black carbon in the Arctic: the underestimated role of gas flaring and residential combustion emissions |journal=Atmos. Chem. Phys. |volume=13 |issue=17 |pages=8833–8855 |year=2013 |doi=10.5194/acp-13-8833-2013 |bibcode=2013ACP....13.8833S |doi-access=free |hdl=11250/2383886 |hdl-access=free }}</ref><ref>{{Cite web |url=https://arctic-council.org/images/PDF_attachments/COP24_2018/2018-11-10-COP24-Stanley-flaring-World-Bank-BC.pdf |title=Gas flaring: An industry practice faces increasing global attention |author=Michael Stanley |publisher=World Bank |date=2018-12-10 |access-date=2020-01-20}}</ref>
Flaring can affect wildlife by attracting birds and insects to the flame. Approximately 7,500 migrating songbirds were attracted to and killed by the flare at the [[liquefied natural gas]] terminal in Saint John, New Brunswick, Canada on September 13, 2013.<ref>[http://www.cbc.ca/news/canada/new-brunswick/7-500-songbirds-killed-at-canaport-gas-plant-in-saint-john-1.1857615 7,500 songbirds killed at Canaport gas plant in Saint John] (online CBC News, September 17, 2013).</ref> Similar incidents have occurred at flares on offshore oil and gas installations.<ref>[http://play.psych.mun.ca/~mont/pubs/seabirds.pdf Seabirds at Risk around Offshore Oil Platforms in the North-west Atlantic], Marine Pollution Bulletin, Vol. 42, No. 12, pp. 1,285–1,290, 2001.</ref> Moths are known to be attracted to lights. A brochure published by the Secretariat of the [[Convention on Biological Diversity]] describing the Global Taxonomy Initiative describes a situation where "a taxonomist working in a tropical forest noticed that a gas flare at an oil refinery was attracting and killing hundreds of these [hawk or sphinx] moths. Over the course of the months and years that the refinery was running a vast number of moths must have been killed, suggesting that plants could not be pollinated over a large area of forest".<ref>[http://www.cbd.int/doc/publications/gti-brochure-en.pdf The Global Taxonomy Initiative - The Response to a Problem] (scroll down to the section entitled "Pollinating moths")</ref>
=== Adverse health effects ===
Flares release several different chemicals including: [[benzene]], [[particulates]], [[
A 2021 study found that a 1% increase in flared natural gas increases the respiratory-related hospitalization rate by 0.73%.<ref>{{Cite journal |last1=Blundell |first1=Wesley |last2=Kokoza |first2=Anatolii |date=2022-04-01 |title=Natural gas flaring, respiratory health, and distributional effects |url=https://www.sciencedirect.com/science/article/pii/S0047272722000032 |journal=Journal of Public Economics |language=en |volume=208 |pages=104601 |doi=10.1016/j.jpubeco.2022.104601 |issn=0047-2727 |s2cid=232350369}}</ref>
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==Media==
{{externalimage|
{{commons|Gas flare|Gas flare}}
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