Flare stack: Difference between revisions
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{{Image|Gas Flare.jpg|right|200px|A gas flare as used in the petroleum industry.}} | {{Image|Gas Flare.jpg|right|200px|A gas flare as used in the petroleum industry.}} | ||
A '''flare stack''' or '''gas flare''' is a tall vertical vent pipe used in [[Petroleum refining processes|petroleum refineries]], [[ | A '''flare stack''' or '''gas flare''' is a tall vertical vent pipe used in [[Petroleum refining processes|petroleum refineries]], [[petrochemical plant]]s, [[chemical plant]]s and [[Natural gas processing|natural gas processing plants]] for burning off flammable [[gas]] released by pressure [[relief valve]]s during unplanned over-pressuring of plant equipment.<ref>{{cite book|author=John J McKetta, Editor|title=Encyclopedia of Chemical Processing and Design|publisher=Marcel Dekker|year=1985|pages=144|id=ISBN 0-8247-2491-7}}</ref><ref name=Beychok>{{cite book|author=Milton R. Beychok|title=[[Fundamentals of Stack Gas Dispersion]]|edition=Fourth edition|publisher=self-published |year=2005|id=ISBN 0-9644588-0-2}} See Chapter 11, ''Flare Stack Plume Rise''.</ref><ref>[http://aiche.confex.com/aiche/s06/techprogram/P40539.HTM A Proposed Comprehensive Model for Elevated Flare Flames and Plumes], David Shore, Flaregas Corporation, [[AIChE]] 40th Loss Prevention Symposium, April 2006.</ref> | ||
When crude oil is extracted and produced from oil wells, natural gas associated with the oil is produced to | |||
the surface as well. In areas of the world lacking pipelines and other infrastructure, this associated | |||
gas is usually flared as waste or unusable gas. | |||
==The purpose of industrial plant flare stacks== | |||
In industrial plants such as petroleum refineries, petrochemical or other chemical plants, and natural gas processing plants, the main purpose of a flare stack is that of safety by protecting [[pressure vessels]] or [[Piping (engineering)|pipes]] from over-pressuring due to unplanned upsets. | |||
Whenever plant equipment items are over-pressured, | Whenever any plant equipment items are over-pressured, [[pressure relief valves]] (in most cases, required by law) automatically release gas and sometimes liquids as well. The released gases and/or liquids are routed to a flare stack and burned as the they exit the flare stack. | ||
==How industrial plant flare stacks work== | |||
Whenever plant equipment items are over-pressured, the [[pressure relief valve]]s provided as essential safety devices on the equipment automatically release gases and sometimes liquids as well. Those pressure relief valves are required by industrial design codes and standards as well as by law. | |||
==Environmental impacts== | The released gases and liquids are routed through large [[Piping (engineering)|piping]] systems called ''flare headers'' to a flare stack. The released gases are [[Combustion|burned]] as they exit the flare stacks. The size and brightness of the resulting flame depends upon the flammable material's flow rate in terms of [[Joule|joules]] per hour (or [[U.S. customary units|btu]] per hour).<ref name=Beychok/> | ||
Most flares have a [[Vapor-liquid separator|vapor-liquid separator]] upstream of the flare to remove any large amounts of liquid that may accompany the relieved gases. | |||
Steam is very often injected into the flame to reduce the formation of black smoke. In order to keep the flare system functional, a small amount of gas is continuously burned, like a pilot light, so that the system is always ready for its primary purpose as an over-pressure safety system. | |||
==Environmental impacts of flaring associated gas from oil drilling sites == | |||
The flaring and venting of [[associated gas]] from oil drilling sites is a significant source of [[carbon dioxide]] (CO<sub>2</sub>) emissions. The amount of such emissions has declined from a peak of about 110×10<sup>6</sup> metric tons in the 1970s to 40×10<sup>6</sup> metric tons in 2005, a decrease of about 64 percent.<ref name=Lulea>[http://www.ltu.se/polopoly_fs/1.5035!gas%20flaring%20report%20-%20final.pdf Gas Flaring Emission Contributes to Global Warming] Lulea University of Technology (Sweden) and Institut National des Sciences Appliquées de Lyon (France)</ref> | The flaring and venting of [[associated gas]] from oil drilling sites is a significant source of [[carbon dioxide]] (CO<sub>2</sub>) emissions. The amount of such emissions has declined from a peak of about 110×10<sup>6</sup> metric tons in the 1970s to 40×10<sup>6</sup> metric tons in 2005, a decrease of about 64 percent.<ref name=Lulea>[http://www.ltu.se/polopoly_fs/1.5035!gas%20flaring%20report%20-%20final.pdf Gas Flaring Emission Contributes to Global Warming] Lulea University of Technology (Sweden) and Institut National des Sciences Appliquées de Lyon (France)</ref> | ||
Revision as of 13:44, 22 February 2012
A flare stack or gas flare is a tall vertical vent pipe used in petroleum refineries, petrochemical plants, chemical plants and natural gas processing plants for burning off flammable gas released by pressure relief valves during unplanned over-pressuring of plant equipment.[1][2][3]
When crude oil is extracted and produced from oil wells, natural gas associated with the oil is produced to the surface as well. In areas of the world lacking pipelines and other infrastructure, this associated gas is usually flared as waste or unusable gas.
The purpose of industrial plant flare stacks
In industrial plants such as petroleum refineries, petrochemical or other chemical plants, and natural gas processing plants, the main purpose of a flare stack is that of safety by protecting pressure vessels or pipes from over-pressuring due to unplanned upsets.
Whenever any plant equipment items are over-pressured, pressure relief valves (in most cases, required by law) automatically release gas and sometimes liquids as well. The released gases and/or liquids are routed to a flare stack and burned as the they exit the flare stack.
How industrial plant flare stacks work
Whenever plant equipment items are over-pressured, the pressure relief valves provided as essential safety devices on the equipment automatically release gases and sometimes liquids as well. Those pressure relief valves are required by industrial design codes and standards as well as by law.
The released gases and liquids are routed through large piping systems called flare headers to a flare stack. The released gases are burned as they exit the flare stacks. The size and brightness of the resulting flame depends upon the flammable material's flow rate in terms of joules per hour (or btu per hour).[2]
Most flares have a vapor-liquid separator upstream of the flare to remove any large amounts of liquid that may accompany the relieved gases.
Steam is very often injected into the flame to reduce the formation of black smoke. In order to keep the flare system functional, a small amount of gas is continuously burned, like a pilot light, so that the system is always ready for its primary purpose as an over-pressure safety system.
Environmental impacts of flaring associated gas from oil drilling sites
The flaring and venting of associated gas from oil drilling sites is a significant source of carbon dioxide (CO2) emissions. The amount of such emissions has declined from a peak of about 110×106 metric tons in the 1970s to 40×106 metric tons in 2005, a decrease of about 64 percent.[4]
The World Bank estimates that 150 billion cubic meters of raw natural gas are flared.[5] This flaring is highly concentrated: 10 countries account for 75% of emissions, and twenty for 90%.[4] The largest flaring operations occur in the Niger Delta region of Nigeria. The leading contributors to gas flaring are (in declining order): Nigeria, Russia, Iran, Iraq, Angola, Qatar, Algeria, Venezuela, Equatorial Guinea and Indonesia.[4]
References
- ↑ John J McKetta, Editor (1985). Encyclopedia of Chemical Processing and Design. Marcel Dekker, 144. ISBN 0-8247-2491-7.
- ↑ 2.0 2.1 Milton R. Beychok (2005). Fundamentals of Stack Gas Dispersion, Fourth edition. self-published. ISBN 0-9644588-0-2. See Chapter 11, Flare Stack Plume Rise.
- ↑ A Proposed Comprehensive Model for Elevated Flare Flames and Plumes, David Shore, Flaregas Corporation, AIChE 40th Loss Prevention Symposium, April 2006.
- ↑ 4.0 4.1 4.2 Gas Flaring Emission Contributes to Global Warming Lulea University of Technology (Sweden) and Institut National des Sciences Appliquées de Lyon (France)
- ↑ The World Bank