Устройство безопасности для сжигания горючего газа

Safety device for burning off flammable gas

A gas flare, alternatively known as a flare stack, flare boom, ground flare, or flare pit, is a gas combustion device used in places such as petroleum refineries, chemical plants and natural gas processing plants, oil or gas extraction sites having oil wells, gas wells, offshore oil and gas rigs and landfills. In industrial plants, flare stacks are primarily used for burning off flammable gas released by safety valves during unplanned overpressuring of plant equipment. During plant or partial plant startups and shutdowns, they are also often used for the planned combustion of gases over relatively short periods. At oil and gas extraction sites, gas flares are similarly used for a variety of startup, maintenance, testing, safety, and emergency purposes. In a practice known as production flaring, they may also be used to dispose of large amounts of unwanted associated petroleum gas, possibly throughout the life of an oil well.

An important source of anthropogenic methane comes from the treatment and storage of organic waste material including waste water, animal waste and landfill. Gas flares are used in any process that results in the generation and collection of biogas. As a result, gas flares are a standard component of an installation for controlling the production of biogas. They are installed on landfill sites, waste water treatment plant and anaerobic digestion plant that use agriculturally or domestically produced organic waste to produce methane for use as a fuel or for heating. 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 generation of electricity, the production of natural gas quality biogas for vehicle fuel 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. 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. Flare specification usually demands that enclosed flares must operate at >1000 °C and <1200 °C; this in order to ensure a 98% destruction efficient and avoid the formation of NOx.

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 CO2 over the course of a century, and 84 87 times greater over two decades. Therefore, to the extent that gas flares convert methane to CO2 before it is released into the atmosphere, they reduce the amount of global warming that would otherwise occur. Flaring emissions contributed to 270 Mt (megatonnes) of CO2 in 2017 and reducing flaring emissions is thought to be an important component in curbing global warming. An increasing number of governments and industries have pledged to eliminate or reduce flaring. 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. Similar incidents have occurred at flares on offshore oil and gas installations. 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".

Flares release several different chemicals including: benzene, particulates, nitrogen oxides, heavy metals, black carbon, and carbon monoxide. Several of these pollutants correlate with preterm birth and reduced newborn birth weight. According to one study from 2020, pregnant women living near flaring natural gas and oil wells have reportedly experienced a 50% greater premature birth rate. Flares may emit methane and other volatile organic compounds as well as sulfur dioxide and other sulfur compounds, which are known to exacerbate asthma and other respiratory disease. A 2021 study found that a 1% increase in flared natural gas increases the respiratory related hospitalization rate by 0.73%.