EP1906089A2 - Brûleur de torche à pré-mélange partiel et procédés - Google Patents

Brûleur de torche à pré-mélange partiel et procédés Download PDF

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Publication number
EP1906089A2
EP1906089A2 EP07253574A EP07253574A EP1906089A2 EP 1906089 A2 EP1906089 A2 EP 1906089A2 EP 07253574 A EP07253574 A EP 07253574A EP 07253574 A EP07253574 A EP 07253574A EP 1906089 A2 EP1906089 A2 EP 1906089A2
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EP
European Patent Office
Prior art keywords
fuel
air
mix
mix chamber
burner
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP07253574A
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German (de)
English (en)
Inventor
Roger L. Poe
James Wilkins
Jeff W. White
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
John Zink Co LLC
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John Zink Co LLC
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Filing date
Publication date
Application filed by John Zink Co LLC filed Critical John Zink Co LLC
Publication of EP1906089A2 publication Critical patent/EP1906089A2/fr
Withdrawn legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G7/00—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals
    • F23G7/06—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of waste gases or noxious gases, e.g. exhaust gases
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G7/00—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals
    • F23G7/06—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of waste gases or noxious gases, e.g. exhaust gases
    • F23G7/08—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of waste gases or noxious gases, e.g. exhaust gases using flares, e.g. in stacks
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
    • F23D14/02—Premix gas burners, i.e. in which gaseous fuel is mixed with combustion air upstream of the combustion zone

Definitions

  • the present invention relates to flare apparatus and methods of flaring flammable waste gases and diverted fuel stock.
  • the invention relates to ground flare burners, ground flares and associated methods.
  • Flare apparatus and methods are utilized to burn and dispose flammable waste gases and diverted fuel stock in a variety of applications.
  • flares are typically located at production facilities, refineries, processing plants and the like for disposing of flammable waste gases that are dumped and/or fuel stock streams that are diverted during venting, shut-downs, upsets or emergencies.
  • the flaring of flammable waste gases and diverted fuel stock (hereinafter referred to as "fuel") without producing smoke is usually desirable or even mandatory.
  • Smokeless flaring is accomplished by assuring that non-oxidized soot does not form in a sufficient quantity to leave the flame. This is accomplished by assuring that a sufficient amount of oxygen is mixed with the fuel to prevent a situation in which the mixture becomes too fuel rich to be effective.
  • the length of the flame envelope created by the flare is also important.
  • types of flares in which a relatively short flame envelope is desirable include aesthetic flares such as pit-type enclosed flares, ground flares and high pressure flares on floating production facilities. In such flares, it is often necessary to prevent the flames from being visible to the surrounding community. On the other hand, such flares need to have the capacity to combust a large volume of fuel at any given time. The length of the flame envelope tends to increase as the volume of fuel being flared increases.
  • Ground flares also referred to as multi-point flares
  • the amount of fuel to be flared at a given time can vary from a relatively small volume to a very high volume (for example, 1,000,000 pounds per hour or higher).
  • a control system that is responsive to the pressure and volume of fuel to be flared. In this way, sufficient pressure is available to each burner in operation to assure that an appropriate amount of air is entrained and that sufficient mixing of the air and fuel occurs to ensure smokeless combustion in the range of application.
  • a ground flare system is typically spread out over a large area, for example, three acres, and surrounded by a large fence or other enclosure.
  • the enclosure functions to exclude personnel and animals from the flame area and minimize radiation, visibility and noise to the surrounding area.
  • the enclosure is typically made of metal or some other heat refracting material and is from 20 to 60 feet high. As a result, the enclosure can be costly to erect and maintain.
  • the spacing of the burners and flow rate of fuel in a ground flare system is also important.
  • the burners need to be close enough to one another for cross-lighting to occur and packed close enough in general to reduce the overall size of the system and the surrounding enclosure.
  • a minimal number of ignition pilots are desirable.
  • Typical units include a single pilot at the end of each row of burners.
  • the burners must not be so close to one another as to restrict air flow and hinder smokeless burning or cause the flames to coalesce into a ball of fire that exceeds the height of the enclosure.
  • the flow rate of the fuel must be controlled so that the height of the individual flames does not exceed the height of the enclosure.
  • One type of ground flare burner utilized heretofore includes a plurality of diffusion jets to distribute the fuel and draw in the air required for combustion.
  • the jets are injected into the atmosphere at a sufficient velocity to draw combustion air into the jets.
  • air from the surrounding environment is laterally entrained from above the discharge point of the fuel.
  • the buoyancy effect of the hot gases then contributes to the overall mixing regimen of the fuel and air which allows combustion of the remaining fuel to be completed.
  • the overall flame envelope created by utilizing only diffusion jets to distribute the fuel and laterally entrain the air required for combustion includes a dense, central core of fuel. This central core of fuel remains intact until the outer portions of the flame envelope begin to burn off. As the outer portions of the flame envelope combust, air can then enter the inner confines of the flame envelope to complete the oxidation process.
  • the dense core of fuel formed at the center of the flame envelope makes it difficult to increase the flow rate of the fuel to support a larger capacity without causing the length of the flame envelope to increase and/or smoke to occur.
  • An increase in the length of the flame envelope often requires the enclosure surrounding the ground flare to be higher which can significantly increase the cost of the enclosure.
  • a flare burner is provided which is useful in association with ground flares, high pressure flares and other types of flares.
  • the inventive flare burner overcomes the problems associated with the ground flare burners utilized heretofore.
  • the invention also provides a ground flare apparatus and a method of burning fuel in a flare burner.
  • a flare burner is provided that is capable of combusting a high volume of fuel with a relatively short flame envelope.
  • the decrease in the length of the flame envelope leads to many advantages. For example, the height of the surrounding enclosure of a ground flare can be decreased or the volume of the fuel that can be flared with an existing enclosure height can be increased.
  • the pre-mix chamber includes a top, a bottom and a sidewall connecting the top to the bottom.
  • the sidewall includes an interior surface and an exterior surface.
  • An air inlet is disposed in one of the bottom and the sidewall, and an air/fuel outlet is disposed in the top.
  • the main fuel outlet is located in a position with respect to the top of the pre-mix chamber such that fuel can be injected from the main fuel outlet around the perimeter of the air/fuel outlet of the pre-mix chamber.
  • the main fuel outlet is spaced outwardly from the pre-mix chamber to provide a space between the exterior surface of the sidewall of the pre-mix chamber and the main fuel outlet. As discussed further below, this space allows fresh air to be entrained from below the burner to a point adjacent to the fuel ports disposed on an inner portion of the main fuel outlet.
  • the enhanced mixing created by such entrainment can be important in certain applications, such as when heavy hydrocarbons or unsaturated fuels are being flared.
  • the fuel feed conduit conducts fuel to the supplemental fuel gas inlet and the main fuel gas outlet.
  • the fuel can be supplied to the supplemental fuel inlet and the main fuel outlet at the same pressure or different pressures depending on the application.
  • the inventive flare burner can further comprise a fuel membrane disposed around the outside perimeter of the pre-mix chamber.
  • the fuel membrane includes a fuel inlet and is in fluid communication with the main fuel outlet.
  • the fuel membrane is also in fluid communication with the supplemental fuel inlet.
  • the fuel membrane can be spaced outwardly from the exterior surface of the sidewall of the pre-mix chamber.
  • the pre-mix chamber and fuel membrane can be formed in a variety of shapes and sizes. In one embodiment, the pre-mix chamber and fuel membrane have a round cross-section. In another embodiment, the pre-mix chamber and fuel membrane have a rectangular cross-section.
  • the interior surface of the pre-mix chamber can include a section that is a Coanda surface.
  • the supplemental fuel inlet is located in a position with respect to the pre-mix chamber such that fuel can be injected from the supplemental fuel inlet onto the Coanda surface.
  • the fuel tends to adhere to and follow the path of the Coanda surface and form into a relatively thin film which causes more air to be entrained into the pre-mix chamber and better mixing of the air with the fuel to occur in the pre-mix chamber.
  • the pre-mix chamber can have a length to inside hydraulic diameter ratio in the range of from about 0.25:1 to about 4:1.
  • a unit with a pre-mix chamber having a length to inside hydraulic diameter ratio greater than 4:1 would function with an added benefit but would generally be cost prohibitive.
  • the pre-mix chamber has a length to inside hydraulic diameter ratio in the range of from about 1:1 to about 3:1.
  • the pre-mix chamber has a length to inside hydraulic diameter ratio of about 1:1 or less.
  • a relatively short length of the pre-mix chamber can be advantageous in ground flare and other flare applications in which the length (or height) of the burner is important, or in applications in which highly reactive fuels might lead to internal burning.
  • the fuel is injected from the supplemental fuel inlet under conditions (for example, a plurality of small jets; high pressure) that allow a uniform mixture of air and fuel to be achieved even when the pre-mix chamber has a very low length to inside hydraulic diameter ratio.
  • conditions for example, a plurality of small jets; high pressure
  • the inventive ground flare comprises a plurality of flare burners, a fence or other enclosure extending around the flare burners and a fuel supply line for supplying fuel to the flare burners. At least one of the flare burners is the inventive flare burner described above.
  • the invention also includes a method of flaring fuel with a flare burner wherein the fuel to be flared is injected through a fuel outlet of the burner into a combustion zone and ignited to create a flame envelope and combust the fuel.
  • a portion of the fuel is introduced into a pre-mix zone of the flare burner in a manner that entrains air into the pre-mix zone and creates a mixture of air and fuel within the pre-mix zone.
  • the mixture of air and fuel is injected from the pre-mix zone into a central portion of the flame envelope.
  • the amount of air entrained into the pre-mix zone and injected into the central portion of the flame envelope is preferably at least about 15% of the stoichiometric amount of air required to support combustion of the fuel introduced into the pre-mix zone.
  • injection of a "fuel-rich" mixture of fuel and air i.e., a mixture having less than 100% of the stoichiometric amount of air required to support combustion of the fuel introduced into the pre-mix zone
  • injection of a "fuel-rich" mixture of fuel and air i.e., a mixture having less than 100% of the stoichiometric amount of air required to support combustion of the fuel introduced into the pre-mix zone
  • the amount of fuel introduced into the pre-mix zone is preferably in the range of from about 5% to about 50% of the total amount of fuel to be flared by the flare burner. Due to the injection of a pre-mixed fuel stream into a central portion of the flame envelope in accordance with the inventive method, the flame envelope includes combustion at its center as well as its outer surface. The resulting toroidal flame creates additional mixing and turbulence which results in more uniform and faster combustion of the flame envelope. As a result, the height of the flame envelope can be decreased or the volume of fuel that can be flared with a given flame envelope can be increased. Other advantages are achieved by the inventive flare burner and method as well.
  • FIG. 1 is a front elevation view of a prior art ground flare burner.
  • FIG. 2 is a top view of the flare burner shown by FIG. 1.
  • FIG. 3 is a general depiction of the flame envelope created by the prior art flare burner shown by FIGS. 1 and 2.
  • FIG. 4 is a perspective view of a first embodiment of the inventive ground flare burner.
  • FIG. 5 is a sectional view taken along the line 5-5 of FIG. 4.
  • FIG. 6 is a top view of the burner shown by FIGS. 4 and 5.
  • FIG. 7 is a sectional view taken along the line 7-7 of FIG. 6 and showing optional risers or tip extensions.
  • FIG. 8 illustrates an alternative embodiment of an annular fuel injector body that can be utilized in association with the first, second and fourth embodiments of the inventive flare burner.
  • FIG. 9 is a perspective view of a second embodiment of the inventive flare burner.
  • FIG. 10 is a sectional view taken along lines 10-10 of FIG. 11.
  • FIG. 10A illustrates an alternative embodiment of the annular distribution manifold used in association with the second embodiment.
  • FIG. 11 is a top view of the flare burner shown by FIGS. 9 and 10.
  • FIG. 12 is a sectional view taken along lines 12-12 of FIG. 10.
  • FIG. 13 is a perspective view of a third embodiment of the inventive flare burner.
  • FIG. 14 is a sectional view taken along lines 14-14 of FIG. 13.
  • FIG. 15 is a top view of the flare burner shown by FIGS. 13 and 14.
  • FIG. 16 is a sectional view taken along lines 16-16 of FIG. 13 and showing optional risers or tip extensions.
  • FIG. 17 is a sectional view taken along lines 17-17 of FIG. 15.
  • FIG. 17A illustrates an alternative embodiment of the tubular distribution manifolds used in association with the third embodiment.
  • FIG. 18 is a sectional view taken along lines 18-18 of FIG. 14.
  • FIG. 19 is a perspective view of a fourth embodiment of the inventive flare burner.
  • FIG. 20 is a sectional view taken along lines 20-20 of FIG. 19.
  • FIG. 21 is a sectional view taken along lines 21-21 of FIG. 22 and showing an optional component of the burner.
  • FIG. 22 is a top view of the burner shown by FIGS. 19-21.
  • FIG. 23 illustrates an alternative embodiment of the supplemental fuel inlet of the burner shown by FIGS. 19-22.
  • FIG. 24 is a general depiction of the flame envelope created by each embodiment of the inventive flare burner.
  • FIG. 25 is a perspective view illustrating a modification that can be made to each embodiment of the inventive flare burner.
  • FIG. 26 is a sectional view taken along lines 26-26 of FIG. 25.
  • FIG. 27 is a top view of the burner shown by FIGS. 25 and 26.
  • FIG. 28 is a general depiction of the flame envelope created by each embodiment of the inventive flare burner as modified in the manner illustrated by FIGS. 25-27.
  • FIG. 29 is a schematic illustration of one embodiment of the inventive the ground flare.
  • the prior art burner 10 includes a burner casting 12 attached to a fuel riser 14.
  • the burner casting 12 includes a central portion 15 and a plurality of fuel outlet arms 16 concentrically arranged around the central portion and the top of the riser 14.
  • Each fuel outlet arm 16 includes one or more fuel ports 18.
  • Fuel is provided directly to the fuel ports 18, that is, the fuel is not first pre-mixed with air.
  • the fuel jets created by the ports 18 are diffusion fuel jets.
  • FIG. 3 generally depicts a flame envelope 20 created by the burner 10.
  • the fuel (generally depicted by black arrows) is injected into the combustion zone 22 through the ports 18 at a high velocity which draws air into the jets. Air from the surrounding environment is laterally entrained from above the discharge point of the fuel. As the velocity of the stream is diminished, the buoyancy effect of the hot gases then contributes to the overall mixing regimen of the fuel which allows combustion to be completed.
  • the overall flame envelope 20 has a length 23 and includes a dense, central core of fuel 24. The central core of fuel 24 remains un-oxidized until the outer portions 26 of the flame 22 begin to burn off.
  • the central portion of the flame envelope may include some air pockets 28, the amount of air in the air pockets is not sufficient to support homogenous combustion of the central core of fuel 24.
  • the dense, central core of fuel 24 generally remains intact until sufficient attrition of the outer portions 26 of the fuel occurs to allow sufficient amounts of air to enter the inner confines of the flame envelope and allow completion of the oxidation process.
  • the dense core of fuel 24 in the center of the flame envelope 20 makes it difficult to increase the flow rate of the fuel to support a larger flame without causing the length of the flame to increase and/or smoke to occur.
  • the flare burner 30 comprises a pre-mix zone 31 including a pre-mix chamber 32, and a supplemental fuel inlet 34 for injecting fuel into the pre-mix zone, a main fuel outlet 36 and a fuel feed conduit 38.
  • fuel means the waste gas, diverted fuel stock and/or other gas or liquid to be flared by the inventive flare burner, flare apparatus (for example, the inventive ground flare apparatus) and method. Liquids can form, for example, when the partial pressure of heavy unsaturated or saturated fuels is at or below saturated conditions.
  • a pilot 40 may be associated with the burner 30 (as well as the burners 130, 230 and 330 described below) to initially ignite the fuel and air mixture that is discharged by the burner.
  • the top 42 and bottom 44 are open thereby forming the air inlet 48 and air/fuel outlet 50.
  • the air inlet 48 and air/fuel outlet 50 each also have a round cross-section.
  • a lower portion 52 of the pre-mix chamber 32 is flared outwardly to impart a bell (well-rounded) shape to the lower section to enhance the rate of flow of the incoming fuel and air.
  • the lower portion 52 of the pre-mix chamber 32 is not flared outwardly, i.e., the entire pre-mix chamber has a uniform cylindrical shape. As best shown by FIG.
  • the pre-mix zone 31 includes a pre-mix space 31 (a) below the pre-mix-chamber 32 (between the supplemental fuel inlet 34 and the bottom 44 and air inlet 48 of the pre-mix chamber), the interior 31 (b) of the pre-mix chamber, and a pre-mix space 31(c) immediately above the top 42 and air/fuel outlet 50 of the pre-mix chamber.
  • the primary mixing of the pre-mix air and fuel occurs in the interior 31(b) of the pre-mix chamber 32 and in the pre-mix space 31(c).
  • the pre-mix chamber 32 has a length (or height) to inside hydraulic diameter ratio in the range of from about 0.25:1 to about 4:1, preferably about 1:1 to about 3:1.
  • the exact ratio of the length (or height) to inside hydraulic diameter of the pre-mix chamber 32 will depend in part on the type of fuel to be flared and the pressure available for entrainment and mixing. Generally, a longer pre-mix chamber can result in better mixing of fuel and air therein; however, this advantage is balanced against cost and other considerations.
  • the length (or height) to inside hydraulic diameter ratio of the pre-mix chamber 32 is approximately 1.5:1.
  • inside hydraulic diameter means four (4) times the area within the pre-mix chamber divided by the perimeter of the interior surface of the sidewall of the pre-mix chamber.
  • the supplemental fuel inlet 34 is located in a position with respect to the pre-mix zone 31 such that the injection of fuel from the supplemental fuel inlet into the pre-mix zone entrains air into the pre-mix space 31 (a) and through the air inlet 48 into the pre-mix chamber 32 whereby a mixture, preferably a substantially homogenous mixture, of fuel and air is formed in the pre-mix zone and caused to exit the air/fuel outlet 50 in the top 42 of the pre-mix chamber.
  • the fuel and air continue to mix in the pre-mix space 31 (c). Combustion of the mixture of fuel and air does not typically occur until the mixture exits the air/fuel outlet 50, generally a detached distance from the air/fuel outlet.
  • the supplemental fuel inlet 34 comprises a central fuel injector 54 having one or more fuel ports 58 therein.
  • An annular fuel membrane 60 is disposed around the outside perimeter of the pre-mix chamber 32.
  • the fuel membrane 60 is connected to the fuel feed conduit 38 and in fluid communication with the main fuel outlet 36.
  • the fuel membrane 60 comprises an open top 62, a bottom 64, and an external sidewall 66 and internal sidewall 67 connecting the top to the bottom.
  • the internal sidewall 67 of the membrane 60 is also the sidewall 46 of the pre-mix chamber 32.
  • An annular seal 68 is attached to the bottom 64 of the fuel membrane 60 and extends around the sidewall 46 of the pre-mix chamber 32 to ensure the integrity of the membrane.
  • the fuel membrane 60 can be spaced outwardly from the sidewall 46 of the pre-mix chamber 32 in order to provide an annular space between the exterior surface of the sidewall 46 and the main fuel outlet 36.
  • the annular space allows air to be entrained from below the burner to a point adjacent to the fuel ports 74 disposed on an inner portion of the main fuel outlet 36.
  • the internal sidewall 67 of the membrane 60 is separate from the sidewall 46 of the pre-mix chamber 32.
  • the main fuel outlet 36 is located in a position with respect to the top 42 of the pre-mix chamber such that fuel can be injected from the main fuel outlet 36 around the perimeter 69 of the air/fuel outlet 50 of the pre-mix chamber.
  • the main fuel outlet 36 comprises a flat, annular fuel injector body 70 having a plurality of fuel ports 74 therein.
  • the fuel jets created by the ports 74 are diffusion fuel jets.
  • the annular fuel injector body 70 is attached to the open top 62 of the annular membrane 60 such that the fuel ports 74 are disposed around the perimeter 69 of the air/fuel outlet 50 of the pre-mix chamber.
  • the inside and outside diameters of the annular membrane 60 and annular fuel injector body 70 are approximately the same.
  • Fuel can be annularly injected from the main fuel outlet 36 (i.e., the annular fuel injector body 70) around the perimeter 69 of the air/fuel outlet 50.
  • the ports 74 can be sized and spaced to control the manner (e.g., direction and velocity) in which the fuel is injected from the ports. This feature in conjunction with the flow of fuel and air through the air/fuel outlet 50 allows the shape and length of the overall flame envelope to be controlled.
  • the diffusion fuel ports 74 can be spaced from the fuel injector body 70 by a plurality of corresponding short gas risers or tip extensions 76. Spacing the ports 74 from the fuel injector body 70 with the risers 76 can result in better lateral entrainment of air in some applications.
  • the risers also allow the configurations of the ports and resulting fuel flow properties to be mechanically changed if necessary.
  • FIG. 8 An alternative embodiment of the annular fuel injector body 70 is shown by FIG. 8.
  • a plurality of fuel ports 74 is strategically spaced around the outside, inside and middle of the fuel injector body 70. Spacing of the fuel ports 74 around the fuel injector body 70 in this manner allows entrainment corridors between the jets to be utilized for better mixing and entrainment.
  • the injector body 70 can include various iterations of the ports 74. The particular port configuration utilized will depend on various factors including the type of fuel to be flared (including the molecular weight, heating value, stoichiometry and temperature of the stream) and available pressure in connection therewith.
  • the fuel feed conduit 38 is in fluid communication with the supplemental fuel inlet 34 and the main fuel outlet 36 for conducting fuel thereto.
  • the fuel feed conduit 38 includes a main branch 80 having a first end 82 and a second end 84.
  • the first end 82 includes a flange 86 for connecting the first end to a source of the fuel (as understood by those skilled in the art, these types of connections are more typically made by welding the pipe sections directly together or with some other mechanical connection that does not require gaskets; e.g., the gaskets between corresponding flanges generally cannot withstand the radiant heat in the surrounding environment).
  • the second end 84 is connected to a corresponding inlet 88 in the external sidewall 66 of the fuel membrane 60.
  • the fuel feed conduit 38 also includes a supplemental branch 90 which connects the fuel feed conduit to the supplemental fuel inlet 34.
  • the supplemental branch 90 includes a first end 92 and a second end 94. The first end 92 is connected to the main branch 90 of the feed conduit 38.
  • a coupling 96 connects the second end 94 to the supplemental fuel inlet 34.
  • separate fuel feed conduits or risers can conduct fuel to the supplemental fuel inlet 34 and main fuel outlet 36 (as opposed to the single integrated conduit or riser 38). The separate conduits or risers will typically run from a common fuel header.
  • a portion of the fuel to be flared (generally depicted by black arrows) is conducted through the main branch 80 of the fuel feed conduit 38 to the fuel membrane 60 and to the main fuel outlet 36.
  • a portion of the fuel to be flared is also conducted from through the supplemental branch 90 of the fuel feed conduit 38 to the supplemental fuel inlet 34.
  • the injection of fuel from the supplemental fuel inlet 34 into the pre-mix zone 31 and pre-mix chamber 32 entrains air into the pre-mix space 31 (a) and through the air inlet 48 into the interior 31(b) of the pre-mix chamber whereby a mixture (preferably a substantially homogenous mixture) of fuel and air is formed in the pre-mix zone and caused to exit the air/fuel outlet 50.
  • the fuel and air continue to mix for a short distance above the air/fuel outlet 50.
  • the remaining fuel to be flared is annularly injected from the main fuel outlet 36 around the perimeter 69 of the air/fuel outlet 50 of the pre-mix chamber and hence around the air/fuel mixture exiting the air/fuel outlet of the pre-mix chamber.
  • the burner is preferably designed and operated in a manner such that the amount of air entrained into the pre-mix zone 31 including the pre-mix chamber 32 is in excess of the stoichiometric amount of air required to combust the fuel injected into the pre-mix zone. The excess air is imparted to the center of the flame envelope for combustion of fuel therein. As explained further below, however, in some applications the burner is designed and operated in a manner such that the amount of air entrained into the pre-mix zone 31 including the pre-mix chamber 32 is equal to or less than the stoichiometric amount of air required to combust the fuel injected into the pre-mix zone (although it is still flammable).
  • a "fuel-rich" mixture of fuel and air i.e., a mixture having less than the stoichiometric amount of air required to support combustion of the fuel introduced into the pre-mix zone
  • a "fuel-rich" mixture of fuel and air i.e., a mixture having less than the stoichiometric amount of air required to support combustion of the fuel introduced into the pre-mix zone
  • FIG. 24 generally depicts the flame envelope 100 created by the flare burner 30 (as well as the burners 130, 230 and 330 described below). As shown, excess air is injected from the pre-mix chamber 32 into a center portion 102 of the flame envelope 100. The excess air, depicted by air pockets 103 in FIG. 24 mixes with fuel in the center portion 102 of the flame envelope 100 to form, in effect, two initial zones of flammability, zone 104(a) and 104(b). The fuel in the center portion 102 of the flame would otherwise not encounter oxidizer (air) until the outer portions 105 of the flame envelope begin to combust, allowing the next layers of fuel access to the air.
  • oxidizer air
  • the flame envelope 100 has a length 106 that is substantially less for the same amount of fuel than the length 23 of the prior art flame envelope 20 shown by FIG. 3.
  • the flare burner 130 comprises a pre-mix zone 131 including a pre-mix chamber 132, and a supplemental fuel inlet 134 for injecting fuel into the pre-mix zone, a main fuel outlet 136 and a fuel feed conduit 138.
  • a pilot (as shown by FIG. 4) may be associated with the burner 130 to initially ignite the fuel and air mixture that is discharged by the burner.
  • the pre-mix chamber 132 of the flare burner 130 provides the predominant portion of the pre-mix zone 131.
  • a mixture (preferably a substantially homogenous mixture) of fuel and air can be formed in the pre-mix zone 131 including the pre-mix chamber 132.
  • the mixture formed in the pre-mix zone 131 can be either fuel-rich or fuel-lean.
  • the pre-mix chamber 132 includes a round cross-section and has a cylindrical shape. It includes a top 142, a bottom 144, a sidewall 146 connecting the top to the bottom, an air inlet 148 disposed in the bottom 144 and an air/fuel outlet 150 disposed in the top.
  • the top 142 and bottom 144 are open thereby forming the air inlet 148 and air/fuel outlet 150.
  • the air inlet 148 and air/fuel outlet 150 each also have a round cross-section.
  • the pre-mix zone 131 includes a pre-mix space 131(a) below the pre-mix-chamber 132 (between the supplemental fuel inlet 134 and the bottom 144 and air inlet 148 of the pre-mix chamber), the interior 131 (b) of the pre-mix chamber, and a pre-mix space 131(c) immediately above the top 142 and air/fuel outlet 150 of the pre-mix chamber.
  • the primary mixing of the air and fuel occurs in the interior 131 (b) of the pre-mix chamber 132 and in the pre-mix space 131 (c).
  • the sidewall 146 of the pre-mix chamber 132 includes an interior surface 154 and an exterior surface 156.
  • a lower section 158 of the sidewall 146 is flared outwardly in a curvilinear manner to impart an annular Coanda surface 160 to the interior surface 154 of the sidewall.
  • the pre-mix chamber 132 has a length (or height) to inside hydraulic diameter ratio in the range of from about 0.25:1 to 4:1, preferably about 1:1 to about 3:1.
  • the exact ratio of the length (or height) to inside hydraulic diameter of the pre-mix chamber 132 will depend in part on the type of fuel to be flared and the pressure available for entrainment and mixing. Generally, a longer pre-mix chamber can result in better mixing of fuel and air therein; however, this advantage is balanced against cost and other considerations.
  • the length (or height) to inside hydraulic diameter ratio of the pre-mix chamber 132 is approximately 1.5:1.
  • the supplemental fuel inlet 134 is located in a position with respect to the pre-mix zone 131 such that the injection of fuel from the supplemental fuel inlet into the pre-mix zone entrains air into the pre-mix space 131 (a) and through the air inlet 148 into the pre-mix chamber whereby a mixture, preferably a substantially homogenous mixture, of fuel and air is formed in the pre-mix zone and caused to exit the air/fuel outlet 150 in the top 142 of the pre-mix chamber.
  • the fuel and air continue to mix in the pre-mix space 131(c). Combustion of the mixture of fuel and air does not typically occur until the mixture exits the air/fuel outlet 150, generally a detached distance from the air/fuel outlet.
  • the supplemental fuel gas inlet 134 comprises an annular distribution manifold 164 having a plurality of fuel ports 166 therein.
  • the fuel ports 166 are substantially round apertures.
  • the annular distribution manifold 164 is located in a position with respect to the pre-mix chamber 132 such that fuel can be annularly injected from the manifold 164 onto the annular Coanda surface 160.
  • FIG. 10A illustrates an alternative embodiment of the annular distribution manifold 164.
  • the fuel ports 166 are elongated apertures or slots.
  • the slotted shape of the fuel ports 166 causes the fuel to be injected onto the annular Coanda surface 160 in a sheeted pattern which serves to enhance the entrainment and mixing effect created by the Coanda surface and allows the fuel to be injected from the manifold 164 at a higher rate.
  • the slots 166 can be connected to form continuous elongated apertures or slots in the distribution manifold 164.
  • An annular fuel membrane 170 is disposed around the outside perimeter of the pre-mix chamber 132.
  • the fuel membrane 170 is connected to the fuel feed conduit 138 and in fluid communication with both the main fuel outlet 136 and the supplemental fuel inlet 134.
  • the fuel membrane 170 comprises an open top 172, a bottom 174, and an external sidewall 176 and internal sidewall 177 connecting the top to the bottom.
  • the internal sidewall 177 is also the sidewall 146 of the pre-mix chamber.
  • An annular seal 178 is attached to the bottom 174 of the fuel membrane 170 and extends around the sidewall 146 of the pre-mix chamber 132 to ensure the integrity of the membrane.
  • FIGS. 9-12 An annular seal 178 is attached to the bottom 174 of the fuel membrane 170 and extends around the sidewall 146 of the pre-mix chamber 132 to ensure the integrity of the membrane.
  • the fuel membrane 170 can be spaced outwardly from the sidewall 146 of the pre-mix chamber 132 in order to provide an annular space between the exterior surface of the sidewall 146 and the main fuel outlet 136.
  • the annular space allows air to be entrained from below the burner to a point adjacent to the fuel ports 192 disposed on an inner portion of the main fuel outlet 136.
  • the internal sidewall 177 of the membrane 170 is separate from the sidewall 146 of the pre-mix chamber 132.
  • Supplemental fuel feed conduits 180(a), 180(b), 180(c) and 180(d) extend from the annular fuel membrane 170 to the supplemental fuel inlet 134 (i.e., to the annular distribution manifold 164) to deliver fuel from the fuel membrane 170 to the inlet 134 (i.e., the manifold 164).
  • Each of the supplemental fuel feed conduits 180(a), 180(b), 180(c) and 180(d) includes a first end 182 attached to the membrane 170 and a second end 184 attached to the inlet 134 (i.e., the manifold 164).
  • the main fuel outlet 136 is located in a position with respect to the top 142 of the pre-mix chamber 132 such that fuel can be injected from the main fuel outlet around the perimeter 186 of the air/fuel outlet 150 of the pre-mix chamber.
  • the main fuel outlet 136 comprises a flat, annular fuel injector body 188 having a plurality of fuel ports 192 therein.
  • the fuel jets created by the ports 192 are diffusion fuel jets.
  • the annular fuel injector body 188 is attached to the open top 172 of the annular membrane 170 such that the fuel ports 192 are disposed around the perimeter 186 of the air/fuel outlet 150 of the pre-mix chamber 132.
  • the inside and outside diameters of the annular membrane 170 and annular fuel injector body 188 are approximately the same.
  • Fuel can be annularly injected from the main fuel outlet 136 (i.e., the annular fuel injector body 188) around the perimeter 186 of the air/fuel outlet 150.
  • the ports 192 can be sized and spaced to control the manner (e.g., direction and velocity) in which the fuel is injected from the ports. This feature in conjunction with the flow of fuel and air through the air/fuel outlet 150 allows the shape and length of the overall flame envelope to be controlled.
  • the diffusion fuel ports 192 can be spaced from the fuel injector body 188 by a plurality of corresponding short gas risers or tip extensions 196. Spacing the ports 192 from the fuel injector body 188 with the risers 196 can result in better lateral entrainment of air in some applications.
  • the risers also allow the configurations of the ports and resulting fuel flow properties to be mechanically changed if necessary.
  • the alternative embodiment of the fuel injector body 70 shown by FIG. 8 may also be used in lieu of the annular fuel injector body 188.
  • the injector body 188 can include various iterations of the ports 192. The particular port configuration utilized will depend on various factors including the type of fuel to be flared (including the molecular weight, heating value, stoichiometry and temperature of the stream) and available pressure in connection therewith.
  • the fuel feed conduit 138 is in fluid communication with the supplemental fuel inlet 134 and the main fuel outlet 136 for conducting fuel thereto.
  • the fuel feed conduit 138 has a first end 200 and a second end 202.
  • the first end 200 includes a flange 204 for connecting the first end to a source of the fuel (again, these types of connections are more typically made by welding).
  • the second end 202 is connected to a corresponding inlet 206 in the external sidewall 176 of the annular gas membrane 170.
  • separate fuel feed conduits or risers can conduct fuel to the supplemental fuel inlet 134 and main fuel outlet 136 (as opposed to the single integrated conduit or riser 138). The separate conduits or risers will typically run from a common fuel header.
  • Fuel to be flared (generally depicted by black arrows) is conducted through the fuel feed conduit 138 to the annular gas membrane 170. A portion of the fuel is conducted by the fuel membrane 170 to the main fuel outlet 136 (i.e., the annular injector body 188). The remaining portion of the fuel is conducted by the membrane 170 through the fuel feed conduits 180(a), 180(b), 180(c) and 180(d) to the supplemental fuel inlet 134 (i.e., the annular distribution manifold 164).
  • Fuel is injected from the fuel ports 166 of the annular distribution manifold 164 through the pre-mix space 131 (a) onto the annular Coanda surface 160 on the interior surface 154 of the pre-mix chamber 132.
  • the injection of fuel from the gas ports 166 into the pre-mix zone 131 and pre-mix chamber 132 entrains air into the pre-mix space 131 (a) and through the air inlet 148 into the interior 131(b) of the pre-mix chamber whereby a mixture (preferably a substantially homogenous mixture) of fuel and air is formed in the pre-mix zone and caused to exit the air/fuel outlet 150.
  • the fuel and air continue to mix for a short distance above the air/fuel outlet 150.
  • Injection of the fuel from the fuel ports 166 onto the Coanda surface 160 causes the fuel to adhere to and follow the path of the Coanda surface and form into a relatively thin film which results in a more efficient entrainment of the air and mixing of the air with the fuel.
  • the fuel to be flared is injected from the main fuel outlet 136 (the annular injector body 188) around the perimeter 186 of the air/fuel outlet 150 of the pre-mix chamber 132 and hence around the air/fuel mixture exiting the air/fuel outlet 150 of the pre-mix chamber.
  • the flare burner 130 is preferably designed and operated in a manner such that the amount of air entrained into the pre-mix zone 131 including the pre-mix chamber 132 is in excess of the stoichiometric amount of air required to combust the fuel injected into the pre-mix zone. The excess air is imparted to the center of the flame envelope for combustion of fuel therein. As explained further below, however, in some applications the burner is designed and operated in a manner such that the amount of air entrained into the pre-mix zone 131 including the pre-mix chamber 132 is equal to or less than the stoichiometric amount of air required to combust the fuel injected into the pre-mix zone.
  • a "fuel-rich" mixture of fuel and air i.e., a mixture having less than the stoichiometric amount of air required to support combustion of the fuel introduced into the pre-mix zone
  • a "fuel-rich" mixture of fuel and air i.e., a mixture having less than the stoichiometric amount of air required to support combustion of the fuel introduced into the pre-mix zone
  • the flare burner 130 achieves the same advantages that are achieved by the flare burner 30.
  • the flame envelope 100 generally depicted by FIG. 24 is also created by the flare burner 130.
  • the flare burner 230 comprises a pre-mix zone 231 including a pre-mix chamber 232, and a supplemental fuel inlet 234 for injecting fuel into the pre-mix zone, a main fuel outlet 236 and a fuel feed conduit 238.
  • a pilot (as shown by FIG. 4) may be associated with the burner 130 to initially ignite the fuel and air mixture that is discharged by the burner.
  • the pre-mix chamber 232 of the flare burner 230 provides the predominant portion of the pre-mix zone 231.
  • a mixture preferably a substantially homogenous mixture
  • fuel and air can be formed in the pre-mix zone 231 including the pre-mix chamber 232.
  • the mixture formed in the pre-mix zone 231 can be either fuel-rich or fuel-lean.
  • the pre-mix chamber 232 includes a rectangular cross-section and has a rectangular shape. It includes a top 242, a bottom 244, a sidewall 246 connecting the top to the bottom, an air inlet 248 disposed in the bottom 244 and an air/fuel outlet 250 disposed in the top.
  • the top 242 and bottom 244 are open thereby forming the air inlet 248 and air/fuel outlet 250.
  • the air inlet 248 and air/fuel outlet 250 each also have a rectangular cross-section.
  • the pre-mix zone 231 includes a pre-mix space 231(a) below the pre-mix-chamber 232 (between the supplemental fuel inlet 234 and the bottom 244 and air inlet 248 of the pre-mix chamber), the interior 231 (b) of the pre-mix chamber, and a pre-mix space 231 (c) immediately above the top 242 and air/fuel outlet 250 of the pre-mix chamber.
  • the primary mixing of the air and fuel occurs in the interior 31 (b) of the pre-mix chamber 232 and in the pre-mix space 231 (c).
  • the sidewall 246 of the pre-mix chamber 232 includes four sides 246(a), 246(b), 246(c) and 246(d). Each of the sides 246(a), 246(b), 246(c) and 246(d) includes an interior surface 254 and an exterior surface 256. A lower portion 258 of each of the sides 246(a), 246(b), 246(c) and 246(d) is flared outwardly in a curvilinear manner to impart an annular Coanda surface 260 to the interior surface 254 of the side.
  • the pre-mix chamber 232 has a length (or height) to inside hydraulic diameter ratio in the range of from about 0.25:1 to 4:1, preferably about 1.1 to about 3:1.
  • the exact ratio of the length (or height) to inside hydraulic diameter of the pre-mix chamber 232 will depend in part on the type of fuel to be flared and the pressure available for entrainment and mixing. Generally, a longer pre-mix chamber can result in better mixing of fuel and air therein; however, this advantage is balanced against cost and other considerations. In a preferred embodiment, the length (or height) to inside hydraulic diameter ratio of the pre-mix chamber 232 is approximately 1.5:1.
  • the supplemental fuel inlet 234 is located in a position with respect to the pre-mix zone 231 such that the injection of fuel from the supplemental fuel inlet into the pre-mix zone entrains air into the pre-mix space 231 (a) and through the air inlet 248 into the pre-mix chamber 232 whereby a mixture, preferably a substantially homogenous mixture, of fuel gas and air is formed in the pre-mix zone and caused to exit the air/fuel outlet 250 in the top 242 of the pre-mix chamber. Combustion of the mixture of fuel and air does not typically occur until the mixture exits the air/fuel outlet 250, generally a detached distance from the air/fuel outlet.
  • the distance from the air/fuel outlet 250 at which combustion occurs varies due to the amount of air in the mixture and the velocity at which the mixture is discharged from the air/fuel outlet. In some cases, due to short de-stage timing sequences, combustion can occur in the pre-mix zone (for example, in short duration, very low pressure scenarios).
  • the supplemental fuel inlet 234 comprises two tubular distribution manifolds 264(a) and 264(b), each having a plurality of fuel ports 266 therein.
  • the fuel ports 266 are substantially round apertures.
  • the distribution manifold 264(a) is located in a position with respect to the pre-mix chamber 232 such that fuel can be injected from the manifold 264(a) onto the Coanda surface 260 on the interior surface 254 of the side 246(a).
  • the distribution manifold 264(b) is located in a position with respect to the pre-mix chamber 232 such that fuel can be injected from the manifold 264(b) onto the Coanda surface 260 on the interior surface 254 of the opposing side 246(c).
  • fuel ports and jets can be utilized to inject the fuel onto the Coanda surfaces in this embodiment.
  • the number and spacing of fuel ports can vary depending on the desired thickness of the film to be created on the Coanda surfaces.
  • a rectangular fuel membrane 270 is disposed around the outside perimeter of the pre-mix chamber 232.
  • the fuel membrane 270 is connected to the fuel feed conduit 238 and in fluid communication with both the main fuel outlet 236 and the supplemental fuel inlet 234.
  • the membrane 270 comprises an open top 272, a bottom 274, and an external sidewall 276 and internal sidewall 277 connecting the top to the bottom.
  • the internal sidewall 277 is also the sidewall 246 of the pre-mix chamber.
  • a matching seal mechanism 278 is attached to the bottom 274 of the fuel membrane 270 and extends around the sidewall 246 of the pre-mix chamber 232 to ensure the integrity of the membrane.
  • FIGS. 1 an alternate embodiment, as exemplified by FIGS.
  • the fuel membrane 270 can be spaced outwardly from the exterior surfaces 256 of the sides 246(a), 246(b), 246(c) and 246(d) of the sidewall 246 of the pre-mix chamber 232 in order to provide a space between the exterior surface of the sidewall 246 and the main fuel outlet 236.
  • the space allows air to be entrained from below the burner to a point adjacent to the fuel ports 292 disposed on an inner portion of the main fuel outlet 236.
  • the internal sidewall 277 of the membrane 270 is separate from the sidewall 246 of the pre-mix chamber 232.
  • Supplemental fuel feed conduits 280(a), 280(b), 280(c) and 280(d) extend from the fuel membrane 270 to the supplemental fuel inlet 234, that is to the tubular distribution manifolds 264(a) and 264(b), to deliver fuel from the fuel membrane thereto.
  • Each of the supplemental fuel feed conduits 280(a), 280(b), 280(c) and 280(d) includes a first end 282 attached to the fuel membrane 270 and a second end 284.
  • the second ends 284 of the conduits 280(a) and 280(d) are attached to opposing ends of the tubular distribution manifold 264(a).
  • the second ends 284 of the conduits 280(b) and 280(c) are attached to opposing ends of the tubular distribution manifold 264(b).
  • the main fuel outlet 236 is located in a position with respect to the top 242 of the pre-mix chamber 232 such that fuel can be injected from the main fuel outlet around the perimeter 286 of the air/fuel outlet 250 of the pre-mix chamber.
  • the main fuel outlet 236 comprises a flat, rectangular fuel injector body 288 having a plurality of diffusion fuel ports 292 therein.
  • the fuel jets created by the ports 292 are diffusion fuel jets.
  • the fuel injector body 288 is attached to the open top 272 of the fuel membrane 270 such that the diffusion fuel ports 292 are disposed around the perimeter 286 of the air/fuel outlet 250 of the pre-mix chamber 232.
  • the inside and outside diameters of the membrane 270 and fuel injector body 288 are approximately the same.
  • Fuel can be injected from the main fuel outlet 236 (i.e., the fuel injector body 288) around the perimeter 286 of the air/fuel outlet 250.
  • the ports 292 can be sized and spaced to control the manner (e.g., direction and velocity) in which the fuel is injected from the ports. This feature in conjunction with the flow of fuel and air through the air/fuel outlet 250 allows the shape and length of the overall flame envelope to be controlled.
  • the diffusion fuel ports 292 can be spaced from the fuel injector body 288 by a plurality of corresponding short gas risers or tip extensions 296. Spacing the ports 292 from the fuel injector body 288 with the risers 296 can result in better lateral entrainment of air in some applications.
  • the risers also allow the configurations of the ports and resulting fuel flow properties to be mechanically changed if necessary.
  • the injector body 288 can include various iterations of the ports 292. The particular port configuration utilized will depend on various factors including the type of fuel to be flared (including the molecular weight, heating value, stoichiometry and temperature of the stream) and available pressure in connection therewith.
  • the fuel feed conduit 238 is in fluid communication with the supplemental fuel inlet 234 and the main fuel outlet 236 for conducting fuel gas thereto.
  • the fuel feed conduit 238 has a first end 300 and a second end 302.
  • the first end 300 includes a flange 304 for connecting the first end to a source of the fuel gas (again, these types of connections are more typically made by welding).
  • the second end 302 is connected to a corresponding inlet 306 in the external sidewall 276 of the annular fuel membrane 270.
  • separate fuel feed conduits or risers can conduct fuel to the supplemental fuel inlet 234 and main fuel outlet 236 (as opposed to the single integrated conduit or riser 238).
  • the separate conduits or risers will typically run from a common fuel header.
  • fuel to be flared (generally depicted by black arrows) is conducted through the fuel feed conduit 238 to the fuel membrane 270.
  • a portion of the fuel is conducted by the fuel membrane 270 to the main fuel outlet 236 (and the fuel injector body 288).
  • the remaining portion of the fuel is conducted by the membrane 270 through the fuel feed conduits 280(a), 280(b), 280(c) and 280(d) to the supplemental fuel inlet 234 (and the tubular distribution manifolds 264(a) and 264(b) thereof).
  • Fuel is injected from the fuel ports 266 of the distribution manifolds 264(a) and 264(b) onto the Coanda surface 260 on the interior surface 254 of the sides 246(a) and 246(c) of the pre-mix chamber 232.
  • the injection of fuel from the fuel ports 266 into the pre-mix zone 231 and pre-mix chamber 232 entrains air into the pre-mix space 231 (a) and through the air inlet 248 into the interior 231 (b) of the pre-mix chamber whereby a mixture (preferably a substantially homogenous mixture) of fuel and air is formed in the pre-mix zone and caused to exit the air/fuel outlet 250.
  • the fuel and air continue to mix for a short distance above the air/fuel outlet 250.
  • Injection of the fuel from the fuel ports 266 onto the Coanda surface 260 on the interior surface 254 of the sides 246(a) and 246(c) causes the fuel to adhere to and follow the path of the Coanda surface and form into a relatively thin film thereon which results in a more efficient entrainment of the air and mixing of the air with the fuel.
  • the fuel to be flared is injected from the main fuel outlet 236 (and the annular fuel injector body 288) around the perimeter 286 of the air/fuel outlet 250 of the pre-mix chamber 232 and hence around the air/fuel mixture exiting the air/fuel outlet of the pre-mix chamber.
  • a "fuel-rich" mixture of fuel and air i.e., a mixture having less than the stoichiometric amount of air required to support combustion of the fuel introduced into the pre-mix zone
  • a "fuel-rich" mixture of fuel and air i.e., a mixture having less than the stoichiometric amount of air required to support combustion of the fuel introduced into the pre-mix zone
  • the polygonal (rectangular in the embodiment illustrated) shape of the flare burner 230 may allow more flexibility in spacing the flare burners in a ground flare application. Also, such a shape may allow more flexibility in how the fuel is directed from the diffusion gas ports 292 due to the fact that the geometry can be rotated to change the interaction zones.
  • the flare burner 330 comprises a pre-mix zone 331 including a pre-mix chamber zone 332, and a supplemental fuel inlet 334 for injecting fuel into the pre-mix zone, a main fuel outlet 336 and a fuel feed conduit 338.
  • a pilot 40 (as shown by FIG. 4) may be associated with the burner 330 to initially ignite the fuel and air mixture that is discharged by the burner.
  • a mixture (preferably a substantially homogenous mixture) of fuel and air can be formed in the pre-mix zone 331 including the pre-mix chamber 332.
  • the mixture formed in the pre-mix zone 331 can be either fuel-rich or fuel-lean.
  • the pre-mix chamber 332 includes a round cross-section and has a cylindrical shape.
  • the pre-mix chamber includes a top 342, a bottom 344, a sidewall 346 connecting the top to the bottom, an air inlet 348 disposed in the bottom 344 and an air/fuel outlet 350 disposed in the top 342.
  • the sidewall 346 includes an interior surface 347 and an exterior surface 349.
  • the top 342 and bottom 344 are open thereby forming the air inlet 348 and air/fuel outlet 350.
  • the air inlet 348 and air/fuel outlet 350 each also have a round cross-section.
  • the pre-mix chamber 332 has a length (or height) to inside hydraulic diameter ratio in the range of from about 0.25:1 to about 4:1.
  • the pre-mix chamber 332 has a length (or height) to inside hydraulic diameter ratio of about 1:1 or less.
  • the pre-mix chamber 332 has a length (or height) to inside hydraulic diameter ratio in the range of from about 0.25:1 to about 1:1.
  • a longer pre-mix chamber generally allows better mixing of the fuel and air in the pre-mix chamber to occur.
  • the pre-mix zone 331 in this particular embodiment (which does not include the extension cylinder 400 discussed below) includes a significant pre-mix space 331 (a) below the pre-mix-chamber 332 (between the supplemental fuel injector 334 and the bottom 344 and air inlet 348 of the pre-mix chamber), the interior 331 (b) of the pre-mix chamber, and a pre-mix space 331(c) immediately above the top 342 and air/fuel outlet 350 of the pre-mix chamber.
  • mixing of the air and fuel occurs in all three sections of the pre-mix zone 331.
  • the supplemental fuel inlet 334 is located in a position with respect to the pre-mix zone 331 such that the injection of fuel from the supplemental fuel inlet into the pre-mix zone entrains air into the pre-mix space 331 (a) and through the air inlet 348 into the pre-mix chamber 332 whereby a mixture, preferably a substantially homogenous mixture, of fuel gas and air is formed in the pre-mix zone and caused to exit the air/fuel outlet 350 in the top 342 of the pre-mix chamber. Combustion of the mixture of fuel and air does not typically occur until the mixture exits the air/fuel outlet 350, generally a detached distance away from the air/fuel outlet.
  • the distance from the air/fuel outlet 350 at which combustion occurs varies due to the amount of air in the mixture and the velocity at which the mixture is discharged from the air/fuel outlet. In some cases, due to short de-stage timing sequences, combustion can occur in the pre-mix zone (for example, in short duration, very low pressure scenarios).
  • the supplemental fuel inlet 334 comprises a burner casting 352 having a bull nose 353 and a plurality of fuel outlet arms 354 concentrically arranged around the bull nose and centered below the air inlet 348 of the pre-mix chamber 332.
  • the supplemental fuel inlet 334 is concentric with the air inlet 348 and pre-mix chamber 332.
  • the supplemental fuel inlet 334 is spaced below the air inlet 348 of the pre-mix chamber 332.
  • the supplemental fuel inlet 334 can be in the range of from zero to two inches below the air inlet 348; preferably it is approximately one inch below the air inlet. The exact distance can vary depending on the type of fuel being flared, the particular application, the permitted length of the flame envelope and other factors.
  • Each fuel outlet arm 354 and the bull nose 353 include a plurality of fuel ports 356.
  • the ports 356 are linearly arranged along the longitudinal axis of each fuel outlet arm 354.
  • An alternative embodiment of the supplemental fuel inlet 334 is shown by FIG. 23.
  • each gas outlet arm 354 includes two rows of diffusion fuel ports 356, each port in each row being aligned such that it is not directly across from a port in the adjacent row.
  • the supplemental fuel inlet 334, including the fuel outlet arms 354 is intentionally small to allow as much interaction between the discharged fuel and entrained air as possible. The "bluff body" effect created by the size and shape of the inlet 334 is minimized, leaving a clean approach of the air to the discharged fuel.
  • An annular fuel membrane 360 is disposed around the outside perimeter of the pre-mix chamber 332.
  • the fuel membrane 360 is connected to the fuel feed conduit 338 and in fluid communication with the main fuel outlet 336.
  • the membrane 360 comprises an open top 362, a bottom 364, and an external sidewall 366 and internal sidewall 367 connecting the top to the bottom.
  • the external sidewall 366 is spaced approximately three inches from the internal sidewall 367 (this distance depends on the nature of the fuel and the overall configuration of the burner).
  • the internal sidewall 367 of the membrane 360 is also the exterior surface 349 of the sidewall 346 of the pre-mix chamber 332.
  • the fuel membrane 360 can be spaced outwardly from the exterior surface 349 of the sidewall 346 of the pre-mix chamber 332 in order to provide an annular space between the exterior surface 349 of the sidewall 246 and the main fuel outlet 336.
  • the space allows air to be entrained from below the burner to a point adjacent to the fuel ports 374 disposed on an inner portion of the main fuel outlet 336.
  • the internal sidewall 367 of the membrane 360 is separate from the sidewall 346 of the pre-mix chamber 332.
  • the main fuel outlet 336 is located in a position with respect to the top 342 of the pre-mix chamber such that fuel can be injected from the main fuel outlet 336 around the perimeter 368 of the air/fuel outlet 350 of the pre-mix chamber.
  • the main fuel outlet 336 comprises a flat, annular fuel injector body 370 having a plurality of fuel ports 374 therein.
  • the fuel jets created by the ports 374 are diffusion fuel jets.
  • the ports 374 are preferably spaced at six degree increments, although the spacing can vary depending on the particular application.
  • the annular fuel injector body 370 is attached to the open top 362 of the annular membrane 360 such that the fuel ports 374 are disposed around the perimeter 368 of the air/fuel outlet 350 of the pre-mix chamber.
  • the inside and outside diameters of the annular membrane 360 and fuel injector body 370 are approximately the same.
  • Fuel can be annularly injected from the main fuel outlet 336 (i.e., the fuel injector body 370) around the perimeter 368 of the air/fuel outlet 350.
  • the ports 374 can be sized and spaced to control the manner (e.g., direction and velocity) in which the fuel is injected from the ports. This feature in conjunction with the flow of fuel and air through the air/fuel outlet 350 allows the shape and length of the overall flame envelope to be controlled.
  • the diffusion fuel ports 374 can be spaced from the fuel injector body 370 by a plurality of corresponding short gas risers or tip extensions 376. Spacing the ports 374 from the fuel injector body 370 with the risers 376 can result in better lateral entrainment of air in some applications.
  • the risers also allow the configurations of the ports and resulting fuel flow properties to be mechanically changed if necessary.
  • the fuel injector body 370 can include various iterations of the ports 374. The particular port configuration utilized will depend on various factors including the type of fuel to be flared (including the molecular weight, heating value, stoichiometry and temperature of the stream) and available pressure in connection therewith.
  • the fuel feed conduit 338 is in fluid communication with the supplemental fuel inlet 334 and the main fuel outlet 336 for conducting fuel thereto.
  • the fuel feed conduit 338 includes a main branch 380 having a first end 382 and a second end 384.
  • the first end 382 includes a flange 386 for connecting the first end to a source of the fuel (again, these types of connections are more typically made by welding).
  • the second end 384 is connected to a corresponding inlet 388 in the external sidewall 366 of the fuel membrane 360.
  • the fuel feed conduit 338 also includes a supplemental branch 390 which connects the fuel feed conduit to the supplemental fuel inlet 334.
  • the supplemental branch 390 includes a first end 392 and a second end 394.
  • the first end 392 is connected to the main branch 390 of the feed conduit 338.
  • the second end 394 is connected to the supplemental fuel inlet 334 (specifically the casting 352).
  • separate fuel feed conduits or risers can conduct fuel to the supplemental fuel inlet 334 and main fuel outlet 336 (as opposed to the single integrated conduit or riser 338).
  • the separate conduits or risers will typically run from a common fuel header.
  • the top 342 and air/fuel outlet 350 of the pre-mix chamber 332 are spaced above the main fuel outlet 336.
  • the top 342 and air/fuel outlet 350 of the pre-mix chamber 332 are in the range of from about 0.5 inches to about 10 inches, preferably in the range of from about 6 inches to about 8 inches, above the main fuel outlet 336. The exact distance can vary depending on the type of fuel being flared, the particular application, the permitted height of the flame envelope and other factors.
  • the bottom 344 of the pre-mix chamber 332 is approximately flush with or about one inch above the supplemental fuel inlet 334. As shown by FIG.
  • the pre-mix zone 331 in this particular embodiment (which includes the extension cylinder 400) includes a pre-mix space 331(a) below the pre-mix-chamber 332 (between the supplemental fuel injector 334 and the bottom 344 and air inlet 348 of the pre-mix chamber), the interior 331 (b) of the pre-mix chamber, and a pre-mix space 331(c) immediately above the top 342 and air/fuel outlet 350 of the pre-mix chamber.
  • the predominant mixing of the air and fuel occurs in the pre-mix chamber 332 (in the pre-mix zone 331 (b)).
  • the top section 402 of the pre-mix chamber extension cylinder 400 serves both as a wind shield as well as a physical barrier to delay ignition. Specifically, the top section 402 offsets the detrimental cross flow air effects which can force the flame inside the diameter of the pre-mix chamber and interfere with the smokeless capacity of the flare burner. The top section 402 also functions to isolate the pre-mix fuel stream from the diffusion flame ignition. Similarly, the bottom section 404 of the cylinder 400 serves as a bottom wind shield and helps prevent the flame from being pulled back and causing premature ignition. Again, the increased length of the pre-mix chamber 332 created by the extension cylinder 400 enhances mixing of the fuel and air in the pre-mix chamber.
  • the extension cylinder is not necessary in all applications; e.g., it may not be necessary when cross-flow effects are not an issue or when low molecular weight fuels are being flared.
  • the inclusion or non-inclusion of the shield will depend on the molecular weight and heating value of the fuel to be flared, whether the fuel contains saturated or unsaturated hydrocarbons, the involved temperature and pressure and other factors.
  • the internal sidewall 367 of the membrane 360 is attached to the mid-section 406 of the extension cylinder 400.
  • the fuel membrane 360 can be spaced outwardly from the extension cylinder 400 (and hence the exterior surface of the pre-mix chamber 332) in order to provide a space between the exterior surface of the extension cylinder and the main fuel outlet 336. The space allows air to be entrained from below the burner to a point adjacent to the fuel ports 374 disposed on an inner portion of the main fuel outlet 336.
  • a portion of the fuel to be flared (generally depicted by black arrows) is conducted through the main branch 380 of the fuel feed conduit 338 to the fuel membrane 360 and to the main fuel outlet 336.
  • a portion of the fuel to be flared is also conducted from through the supplemental branch 390 of the fuel feed conduit 338 to the supplemental fuel inlet 334.
  • the fuel and air continue to mix for a short distance above the air/fuel outlet 350.
  • the remaining fuel to be flared is injected from the main fuel outlet 336 around the perimeter 368 of the air/fuel outlet 350 of the pre-mix chamber and hence around the air/fuel mixture exiting the air/fuel outlet of the pre-mix chamber.
  • the flare burner 330 is preferably designed and operated in a manner such that the amount of air entrained into the pre-mix zone 331 including the pre-mix chamber 332 is in excess of the stoichiometric amount of air required to combust the fuel injected into the pre-mix zone. The excess air is imparted to the center of the flame envelope for combustion of fuel therein.
  • the burner 330 is designed and operated in a manner such that the amount of air entrained into the pre-mix zone 331 including the pre-mix chamber 332 is equal to or less than the stoichiometric amount of air required to combust the fuel injected into the pre-mix zone.
  • the injection of a "fuel-rich" mixture of fuel and air i.e., a mixture having less than the stoichiometric amount of air required to support combustion of the fuel introduced into the pre-mix zone
  • a "fuel-rich" mixture of fuel and air i.e., a mixture having less than the stoichiometric amount of air required to support combustion of the fuel introduced into the pre-mix zone
  • the flare burner 330 achieves the same advantages that are achieved by the flare burners 30, 130 and 230.
  • the flame envelope 100 generally depicted by FIG. 24 is also created by the flare burner 330.
  • FIGS. 25-28 a modification that can be made to the fourth embodiment of the inventive flare burner described above (the embodiment shown by FIGS. 19-23) is illustrated. The same modification can be made to the first, second and third embodiments of the inventive flare burner described above as well.
  • the flare burner 330 includes the pre-mix chamber extension cylinder 400.
  • the extension cylinder 400 (and hence the pre-mix chamber 332) is spaced inwardly from the fuel membrane to provide an air pathway between the extension cylinder and fuel membrane to allow air to effectively reach the fuel ports 374 disposed on the inner portion of the main fuel outlet 336.
  • the diameter of the extension cylinder 400 (and hence the pre-mix chamber 332) is significantly smaller than the inside diameter of the fuel membrane 360.
  • the pre-mix chamber has a length (or height) to inside hydraulic diameter ratio in the range of from about 0.5:1 to about 4:1, more preferably in the range of from about 1:1 to about 3:1. Most preferably, the pre-mix chamber has a length (or height) to inside hydraulic diameter ratio in the range of from about 1.5:1.
  • annular space 430 exists between the internal sidewall 367 of the fuel membrane 360 and the exterior surface of the extension cylinder 400 (which is also the exterior surface 349 of the sidewall 346 of the pre-mix chamber 332).
  • a plurality of thin, rectangular gusset plates 432 are utilized to center and hold the extension cylinder 400 (and hence the pre-mix chamber 332) within the fuel membrane 360. As illustrated, four plates 432 are disposed 90° apart within the annular space 430. One end of each plate 432 is attached to the internal sidewall 367 of the fuel membrane 360. The other end of each of the plates 432 is attached to the exterior surface of the extension cylinder 400 (which is also the exterior surface 349 of the sidewall 346 of the pre-mix chamber 332).
  • the burner 330 illustrated by FIGS. 25-28 is the same in all respects as the embodiment illustrated by FIGS. 19-23 and described above.
  • the main fuel outlet 336 is still located in a position with respect to the top 342 of the pre-mix chamber such that fuel can be injected from the main fuel outlet 336 around the perimeter 368 of the air/fuel outlet 350 of the pre-mix chamber.
  • the annular space 430 merely provides an air pathway between the extension cylinder and fuel membrane to allow fresh oxidizer to effectively reach the fuel ports 374 disposed on the inner portion of the main fuel outlet 336.
  • the operation of the burner 330 remains the same, except fresh air is entrained from below the burner by the motive force of the inner row of fuel ports 374 through the annular space 430.
  • the entrained air is in close proximity to the fuel being discharged by the inner row of fuel ports 374 on the main fuel outlet 336 and mixes therewith.
  • the enhanced mixing regimen provided by the annular space 430 is useful when relatively heavy and unsaturated fuel stocks, which tend to smoke more readily, are flared. It optimizes the burner for soot free combustion.
  • the same modification can also be made to the other three embodiments of the inventive flare burner described above.
  • the cross-sectional diameter of the pre-mix chamber 32 is reduced and the pre-mix chamber 32 is spaced inwardly from the fuel membrane 60.
  • Either the internal sidewall 67 of the annular fuel membrane 60 or the sidewall 46 of the pre-mix chamber 32 is added (as shown, the internal sidewall of the membrane and the sidewall of the pre-mix chamber are the same).
  • the annular seal 68 is eliminated. Spacing the pre-mix chamber 32 inwardly from the fuel membrane 60 provides an air space between the pre-mix chamber and fuel membrane.
  • Fresh air can then be entrained from below the burner to a point in close proximity to the fuel that is discharged from the fuel ports 74 on the inner portion of the main fuel outlet 36.
  • the pre-mix chamber 32 can be centered within and attached to the fuel membrane 60 with a plurality of gussets as shown by FIGS. 25-28.
  • FIG. 28 generally depicts the flame envelope 100 created by the modified flare burner 330 illustrated by FIGS. 25-27 (as well as the burners 130, 230 and 330 if modified in the same manner).
  • excess air is injected from the pre-mix chamber 332 into a center portion 102 of the flame envelope 100.
  • the excess air depicted by air pockets 103 in FIG. 28 mixes with fuel in the center portion 102 of the flame envelope 100 to form, in effect, two initial zones of flammability, zone 104(a) and 104(b).
  • Air is also entrained from below the burner 330 through the annular space 430 to a point in close proximity to the fuel being discharged by the inner row of fuel ports 374 on the main fuel outlet 336.
  • the flame envelope 100 has a length 106 that is substantially less for the same amount of fuel than the length 23 of the prior art flame envelope 20 shown by FIG. 3.
  • the partial pre-mix approach of the present invention allows two flame zones to be initiated within the same flame envelope as the fuel is flared.
  • the outer flame zone is typical to what would normally be observed with a burner of the type utilized heretofore, i.e., a type utilizing only diffusion mixing.
  • the outer layers of gas are shredded away to expose consecutive layers of gas for repeated diffusion and subsequent combustion.
  • the second flame zone is created by the pre-mix zone of the burner which delivers a combustible mixture to the inside of the main flame envelope.
  • This combusting flow field serves to create an appreciable turbulent regime at the core of the flame which is atypical of a normal diffusion flame. As the pre-mix zone becomes more fuel lean, the flame will become shorter due to the additional oxidizer delivered to the core of the flame.
  • the excess air is utilized by the remaining flame cloud and functions to shorten the flame (or allow the mass flow to be increased) while also serving further as a quench mechanism to diminish emissions such as nitrous oxides and carbon monoxide.
  • the excess air also reduces the formation of soot and results in the combustion of any unburned hydrocarbons.
  • Each of the flare burners 30, 130, 230 and 330 is preferably designed and operated such that the amount of air entrained into the pre-mix zone and injected into the central portion of the flame envelope is in the range of from about 15% to about 300% of the stoichiometric amount of air required to support combustion of the fuel introduced into the pre-mix zone.
  • both a fuel-rich approach (the injection of a mixture of fuel and air having less than 100% of the stoichiometric amount of air required to support combustion of the fuel introduced into the pre-mix zone into the central portion of the flame envelope) and a fuel-lean approach (the injection of a mixture of fuel and air having more than 100% of the stoichiometric amount of air required to support combustion of the fuel introduced into the pre-mix zone into the central portion of the flame envelope) can be utilized.
  • Each approach has its own advantages as compared to the typical diffusion/free jet driven combustion regimen utilized heretofore. The particular approach utilized will depend upon the particular application including the type of fuel to be flared and the available pressure. The approach can be modified by typical porting and fuel delivery mechanisms.
  • the pre-mix stream delivered to the center of the flame envelope it is important for the pre-mix stream delivered to the center of the flame envelope to remain within the range of combustibility. If not, the augmented mixing and combustion in the center of the flame envelope may not occur.
  • the enhanced mixing is benefited by a pre-mixed flame which initiates at the core of the flame and expands at an appreciable velocity to create significant turbulence at the core of the flame.
  • a "lean" mixture of fuel and air i.e., a mixture having more than 100% of the stoichiometric amount of air required to support combustion of the fuel introduced into the pre-mix zone
  • the amount of air entrained into the pre-mix zone and injected into the central portion of the flame envelope is in the range of from about 125% to about 300% of the stoichiometric amount of air required to support combustion of the fuel introduced into the pre-mix zone.
  • the amount of air entrained into the pre-mix zone is in the range of from about 150% to about 300%, more preferably from about 175% to about 300%, of the stoichiometric amount of air required to support combustion of the fuel injected into the pre-mix zone.
  • the amount of excess air entrained into the pre-mix zone increases (that is, as the amount of air entrained into the pre-mix zone in excess of the stoichiometric amount of air required to support combustion of the fuel introduced into the pre-mix zone increases), the benefit with respect to flame length and emissions also increases.
  • an amount of air entrained into the pre-mix zone greater than 300% of the stoichiometric amount of air required to support combustion of the fuel injected into the pre-mix zone would be advantageous, it would require an extraneous source of air entrainment (such as steam injection) and possibly other modifications, and may therefore be cost prohibitive.
  • the amount of air entrained into the pre-mix zones of each of the burners 30, 130, 230 and 330 is highly dependent on the pressure and mass flow of the fuel injected from the supplemental fuel inlet, the type of fuel being flared, the structure of the supplemental fuel inlet including the number and size of the ports therein, the placement of the supplemental fuel inlet with respect to the air inlet into the pre-mix chamber and the size of the air inlet.
  • the ultimate goal is to achieve a highly dilute, preferably inflammable mixture of fuel and air. An inflammable, lean mixture will quickly assimilate the fuel required to become again combustible once inside the core of the flame envelope.
  • the air and gas will then create a large flame zone on the inside of the flame envelope which will significantly increase the rate at which the fuel is oxidized while also creating significant turbulence to augment the diffusion mixing on the external surface of the flame zone as well.
  • the additional mass transported to the center of the flame envelope also serves as a quench mechanism to lower the production of emissions such as nitrous oxides and carbon monoxide.
  • the added rate at which combustion occurs while maintaining two flame fronts also serves to lower the production of carbon monoxide and soot, and further reduces the release of unburned hydrocarbons.
  • the fuel is injected into the pre-mix zone with sufficient momentum to entrain air radially and from below the burner into the jet(s) of fuel and pre-mix zone.
  • the burner can entrain air from up to 2 feet below the supplemental fuel inlet.
  • the amount of fuel introduced into the pre-mix zone of each of the burners 30, 130, 230 and 330 is in the range of from about 5% to about 50%, more preferably in the range of from about 10% to about 30%, of the total amount of fuel to be flared by the flare burner.
  • the amount of fuel introduced into the pre-mix chamber is in the range of from about 10% to about 25% of the total amount of fuel to be flared by the flare burner.
  • the amount of fuel introduced into the pre-mix zone can be controlled by manipulating the diameter of the fuel ports and the pressure of the fuel.
  • a proper balance between the percentage of fuel injected into the pre-mix zone and the amount of air that can be entrained into the pre-mix zone must be achieved.
  • a lesser amount of air could create a very reactive (combustible) mixture that could make the burner prone to either burn-back or flashback at maximum rates, eventually causing damage to the burner.
  • a sufficiently dilute stream of air and fuel will assure that the mixture of air and fuel is not ignited until the mixture exits the air/fuel outlet and reaches the center of the flame envelope.
  • the mixture then assimilates sufficient additional fuel to reach a combustible mixture at which time the fuel ignites inside the main flame envelope.
  • This flow regimen creates a flame within a flame or a toroidal flame geometry combusting with two individual flame fronts.
  • the additional turbulence created by the gas expanding at the center of the flame during combustion then serves to increase the mixing regimen for the remaining fuel by fracturing the dense fuel core and pushing it to the outer flame boundary. This approach reduces the flame's height and ability to smoke, while also increasing the overall combustion efficiency due to increased mixing.
  • the overall cross-sectional size of the burners is comparatively small. It would be size prohibitive to design and build a burner capable of supplying 100% of the air needed for combustion in a total pre-mix approach.
  • the venturi or mixer portion of such a burner would necessarily be appreciably large and lack the ability to accommodate low fuel pressures.
  • the set up is capable of providing sufficient air and fuel to create a pre-mixed air and fuel stream with an appreciable amount of entrained excess air.
  • a significant increase in the overall flow of fuel may be realized with an equivalent flame height and diameter.
  • the inventive burners can easily accommodate a fuel flow rate that can be designed to deliver fuel in excess of 1.4 times the rate typically achievable by the diffusion jet-type burners utilized heretofore. In most cases, this can also be accomplished while maintaining roughly the same flame length and diameter.
  • the ignition spacing and turn down capabilities can be conserved while the fuel flow rates are increased.
  • the radiant fraction of the flame may also be somewhat decreased with the tempering of the flame, reducing the overall flame temperature. In some cases, this allows the burners to maintain or only minimally increase the distance between the burners and the fencing even though the fuel flow rate has been increased.
  • the excess air delivered to the center of the flame serves not only to impart air to the center of the flame but also to decrease the timed rate in which the resulting fuel cloud is oxidized upon exiting the tip of the burner. This results in a cleaner, smoke-free flame that is proportionally shorter for a given heat release.
  • the dilution and subsequent quench effect to the flame also serves to decrease nitrous oxide and carbon monoxide emissions.
  • the flow of fuel and air through the pre-mix chamber also aids in cooling the burner assembly.
  • supplemental fuel inlet Various configurations of the supplemental fuel inlet have been described. Additional configurations are also possible, including multi-point injector bodies or headers drilled to maximize air entrainment and mixing in view of available fuel pressures.
  • the lower section of each of the embodiments described above can include a Coanda surface or can be a straight section. If Coanda surfaces are utilized, the ports in the supplemental fuel inlet can be round orifices (jets) or slots.
  • the fuel can be injected from the supplemental fuel inlet at a relatively high velocity to rapidly achieve a mixture of fuel and air that can be injected into the center of the flame envelope.
  • the dimensions of the various components of the inventive flare burner including the dimensions of the pre-mix chamber and fuel membrane can vary.
  • a myriad of port configurations can be used in association with the main fuel outlet and the supplemental fuel inlet.
  • the particular dimensions and configurations utilized will depend on the type of fuel and the molecular weight, temperature, heating value and reactivity thereof, operational parameters (for example, the available pressure) and other factors.
  • a tertiary inerting fluid can be injected into the pre-mix zone of the inventive flare burner (any of the embodiments of the flare burner) to enhance the entrainment of air into the pre-mix zone.
  • tertiary inerting fluids that can be used include steam, air and nitrogen. Steam is preferred.
  • FIG. 1 illustrate round and rectangular (polygonal) embodiments of the inventive flare burner.
  • Each embodiment of the inventive flare burner can be formed in other geometries as well.
  • elliptical, triangular, square, pentagonal, octagonal and other polygonal shapes can be employed. These other geometric shapes may prove beneficial from a cost or fabrication standpoint.
  • the optimum approach is to create a dilute excess air stream which can then be delivered from the pre-mix chamber to the center of the main body of the flame.
  • a fuel rich stream still offers benefits over the diffusion only type burners utilized heretofore due to the enhanced mixing created by the inventive burner.
  • the ground flare 420 comprises a plurality of flare burners 422, an enclosure 424 extending around the flare burners and a fuel supply line 426 for supplying fuel to the flare burners.
  • the flare burners are arranged in rows 430(a) - (f) and rows 432(a) - (e). Rows 430(a) - (f) form a first stage 434 of the flare burners 422, whereas the rows 432(a) - (e) form a second stage 436 of the flare burners.
  • At least one of the flare burners 422 is one of the embodiments of the inventive flare burner described above.
  • each of the flare burners 422 in the second stage 436 of flare burners 422 (the burners utilized when a relatively high volume of fuel needs to be flared) is one of the embodiments of the inventive flare burner described above.
  • each of the flare burners 422 in both the first stage 434 of burners and the second stage 436 of burners is one of the embodiments of the inventive flare burner described above.
  • the fuel supply line 426 comprises a main line 440 which terminates in a distribution manifold 442.
  • a first stage supply line 444 and a second stage supply line 446 are attached and in fluid communication with the distribution manifold 442.
  • Individual first stage supply lines 450(a) - (f) run from the first stage fuel supply line 444 to corresponding burner rows 430(a) - (f).
  • individual second stage supply lines 452(a) - (e) run from the second stage fuel supply line 446 to corresponding burner rows 432(a) - (e).
  • the first end 382 of the main branch 380 of the fuel feed conduit 338 of the inventive flare burner 330 is attached to one of the individual supply lines 450(a) - (f) or 452(a) - (e).
  • the fuel feed conduit of such burner is attached as appropriate to one of the individual supply lines 450(a) - (f) or 452(a) - (e).
  • a series of pilots 460(a) - (f) are in fluid communication with the first stage supply line 444 and positioned with the appropriate burner and fuel separation prior to ignition. Pilots are typically located adjacent to the first flare burner 422 in corresponding rows 430(a) - (f). Similarly, a series of pilots 462(a) - (e) are in fluid communication with the second stage supply line 446 and positioned adjacent to the first flare burner 422 in corresponding rows 432(a) - (e).
  • the enclosure 424 surrounds the flare burners 422 and comprises a plurality of posts 470 and fence sections 472 connected between the posts.
  • the enclosure or fence is in the range of from about 30 feet to about 60 feet high.
  • the enclosure 424 is designed such that air can be pulled into the ground flare through and under the enclosure.
  • fuel to be flared is conducted through the main line 440 to the distribution manifold 442.
  • a valve control system (not shown) functions to distribute the fuel to either the first stage fuel supply line 444 or both the first stage fuel supply line 444 and the second stage fuel supply line 446. If a relatively low volume of fuel is conducted to the distribution manifold 442, the valve system directs the fuel only to the first stage fuel supply line 444. If the volume of fuel gas conducted to the distribution manifold 442 is relatively high, the fuel is conducted to both the first stage fuel supply line 444 and the second stage fuel supply line 446. Additional staging can also be incorporated to cycle in and out as needed.
  • Fuel is conducted from one or both of the fuel supply lines 444 and 446, depending on the volume of the fuel, to the corresponding individual supply lines 450(a)-(f) and/or 452(a) - (e).
  • the fuel is conducted from the individual supply lines 450(a) - (f) and/or 452(a) - (e) to the flare burners 422 in the corresponding rows 430(a) - (f) and 432(a) - (e).
  • the pilots 460(a) - (f) and 460(a) - (e) ignite the fuel discharged from the corresponding first burner 422 in each of the row.
  • the ignited fuel from the first burner 422 in each row then ignites the fuel being discharged from the adjacent burner which in turn ignites the fuel being discharged from the next burner in the row and so on until the fuel being discharged from each of the burners in the row has been ignited.
  • the air required for combustion is pulled through and/or under the walls of the enclosure 424. It is not necessary to separately supply air to the burners 422 or ground flare.
  • the inventive ground flare can be used to combust from a relatively small volume of fuel (for example, 3,000 pounds per hour or less) to a very large volume of fuel gas (for example, 10,000 to 15,000 pounds per hour and up depending on the molecular weight of the fuel to be flared, pressure availability, temperature and other factors). Even at a very high flow rate (for example, 10,000 pounds per hour), the flame envelope created by the inventive ground flare burner can be contained in a typical ground flare enclosure. Due to the structure of the inventive flare burner, a higher volume of fuel can be flared with smaller ports and higher pressures without significantly increasing the height of the flame envelopes created by the ground flare. Alternatively, the flame heights can be decreased allowing the enclosure 424 to be reduced in height. The inventive burners pump air from below the burners which allows the burners to be placed closer to the ground, again resulting in a reduction in the required height of the enclosure 424. A smaller portion of land may be required due to a smaller number of burners and related components.
  • existing ground flares can be retrofitted with the inventive flare burner 422 to allow more fuel to be flared without causing the height of the flame envelope to significantly exceed the height of the enclosure surrounding the ground flare.
  • the smokeless rate for a given flare tip may be significantly larger in range.
  • more gas can be delivered per an individual header. This can result in fewer headers coupled with fewer control mechanisms such as gas control valves, shut-off valves, regulators and physical piping. Increased capacity with fewer headers also allows for a smaller enclosure 434.
  • the inventive ground flare can be used to flare various types of fuel gas.
  • fuel gas examples include saturated and unsaturated hydrocarbons such as propane and propylene and mixtures thereof, alone or with hydrogen, water vapor and/or inert gases such as nitrogen, carbon monoxide, argon, etc.
  • inventive ground flare is intended to illustrate the ground flare and particularly how the inventive flare burner is used in association therewith.
  • ground flare installations can vary widely in terms of how they are configured, the number and types of burners, headers, flow systems, control valves and related components, the type and height of the enclosure surrounding the installation and in many other ways.
  • the inventive ground flare encompasses any ground flare installation in which the inventive flare burner is utilized.
  • fuel is burned in one of the inventive flare burners 30, 130, 230, or 330.
  • the fuel is injected through a fuel injector body (i.e., the main fuel outlet 36, 136, 236 or 336) into the combustion zone 101 and ignited to create a flame envelope 100 and combust the fuel.
  • a portion of the fuel to be burned is introduced into the pre-mix zone including the pre-mix chamber of the burner (i.e., the pre-mix chamber 32, 132, 232 or 332) in a manner that entrains air into the pre-mix zone and creates a mixture (preferably a substantially homogenous mixture) of air and fuel within the pre-mix zone.
  • the mixture of air and fuel is then injected from the pre-mix chamber into a central portion 104 of the flame envelope.
  • the amount of air entrained into the pre-mix zone and injected into the central portion of the flame envelope can range from a fuel rich but combustible mixture to a mixture having entrained air in excess of the stoichiometric amount required for combustion.
  • This pre-mixed fuel and air stream injected into the center of the flame envelope initiates a second flame zone, creating a toroidal shaped flame envelope.
  • the overall result is faster and more uniform combustion of the overall flame envelope thereby achieving the advantages discussed above in connection with the inventive flare burner.
  • the amount of air entrained into the pre-mix zone and injected into the central portion of the flame envelope is preferably at least about 15% of the stoichiometric amount of air required to support combustion of the fuel introduced into the pre-mix zone.
  • injection of a "fuel-rich" mixture of fuel and air i.e., a mixture having less than 100% of the stoichiometric amount of air required to support combustion of the fuel introduced into the pre-mix zone
  • injection of a "fuel-rich" mixture of fuel and air i.e., a mixture having less than 100% of the stoichiometric amount of air required to support combustion of the fuel introduced into the pre-mix zone
  • a "lean" mixture of fuel and air i.e., a mixture having more than 100% of the stoichiometric amount of air required to support combustion of the fuel introduced into the pre-mix zone
  • the amount of air entrained into the pre-mix zone and injected into the central portion of the flame envelope is in the range of from about 125% to about 300% of the stoichiometric amount of air required to support combustion of the fuel introduced into the pre-mix zone.
  • the amount of fuel introduced into the pre-mix zone and pre-mix chamber is in the range of from about 5% to about 50%, more preferably from about 10% to about 30%, most preferably from about 10% to about 25%, of the total amount of fuel to be flared by the flare burner.
  • the first embodiment of the inventive flare burner, flare burner 30, was compared to a prior art high capacity diffusion-type ground flare burner, namely the burner illustrated in FIGS. 1 and 2. Two of the inventive flare burners were tested, one approximately 30 inches in length and the other approximately 16 inches in length. The inventive flare burners were ported to match the three square inches of flow area contained in the prior art flare burner.
  • the inventive flare burners were first tested singularly. Tests were carried out using propane and propylene. Approximately 20% of the fuel was injected into the pre-mix chamber of each of the inventive flare burners. The remaining fuel was then injected around the perimeter of the air/fuel mixture discharged from the pre-mix chamber. It was determined that with both types of fuels, each of the inventive flare burners were able to support a significant flow of fuel while developing a smokeless flame.
  • the flame envelope from each burner was found to be very stable, capable of significant turndown ratios, and also very symmetrical throughout the range of heat releases fired. The flame envelopes from each burner were observed as being very short in length and having a small diameter.
  • the inventive flare burner having a length of approximately 30 inches was then compared to the prior art burner.
  • the two flare burners were tested side by side.
  • the burners were attached to the same header to insure that the same volume of fuel was supplied to each burner.
  • the inventive flare burner produced a shorter flame envelope in most of the test points observed.
  • the inventive flare burner remained lit at lower pressures during turn down, indicating a somewhat expanded range of operability.
  • the flame envelope generated by the inventive flare burner was shorter in overall length as compared to the prior art high capacity diffusion-type ground flare burner.
  • the vertical cross-section (width) of the flame envelope created by the prior art flare burner was larger than the flame envelope created by the inventive flare burner. No burn-back was observed with the inventive flare burner until the pressure was notably under 1 psig. Radiation from the flame envelope generated by the inventive flare burner appeared to be equivalent to or slightly less than the radiation generated by the flame envelope produced by the prior art flare burner.
  • the prior art flare burner smoked at approximately the same rate as the inventive flare burner. Trailing smoke typically could be noted from both burners at about the same flow rate and pressure. However, the inventive flare burner appeared to maintain a less dense trail of smoke at lower pressures than the diffusion type burner tip during initial testing. The prior art burner transitioned to heavier smoke production as pressure was reduced.
  • the third embodiment of the inventive flare burner, flare burner 230 was also tested and compared to the prior art flare burner discussed above.
  • the performance of this embodiment of the inventive flare burner appeared to be at least equivalent to the prior art burner.
  • the inventive burner produced more smoke at low pressure than the first embodiment of the inventive flare burner described in Example I.
  • the range of smokeless operation was comparative to the smokeless performance of the prior art flare burner.
  • a weld used in assembling the test unit of the inventive flare burner described in this example was faulty and ultimately failed (only after appreciable testing was carried out).
  • the weld in question was utilized only for the test unit (which was made out of carbon steel); the failure of the weld was not due to a design issue and has no relevance to the operation or performance of the actual burner. In any event, the tests showed that the flare burner 230 is very capable of handling large fuel flows with minor smoke issues.

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9816705B2 (en) 2014-11-18 2017-11-14 Honeywell International Inc. Flare burner for a combustible gas
US10598375B2 (en) 2016-11-01 2020-03-24 Honeywell International Inc. Asymmetrical and offset flare tip for flare burners

Families Citing this family (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5260211B2 (ja) * 2007-10-01 2013-08-14 株式会社神戸製鋼所 燃焼装置およびそれを備えたグランドフレアー
US7811081B2 (en) * 2008-04-18 2010-10-12 Moneyhun Equipment Sales & Service Off-gas flare
US20100291492A1 (en) * 2009-05-12 2010-11-18 John Zink Company, Llc Air flare apparatus and method
US8629313B2 (en) 2010-07-15 2014-01-14 John Zink Company, Llc Hybrid flare apparatus and method
CN102680454B (zh) * 2011-09-20 2014-06-18 深圳市爱诺实业有限公司 二阶微分火焰发射光谱仪
CA2808707C (fr) 2012-11-23 2014-02-11 Charles Tremblay Systeme de torche et methode de destruction de gaz inflammable dans un flux de gaz uses
US20150104752A1 (en) * 2013-10-15 2015-04-16 Jlcc, Inc. Smokeless flare burner
US20150323177A1 (en) * 2014-05-06 2015-11-12 Steffes Corporation Air-assist flare
US9416966B2 (en) 2014-07-25 2016-08-16 Flame Commander Corp. Venturi nozzle for a gas combustor
KR101724904B1 (ko) * 2015-09-16 2017-04-07 현대자동차주식회사 연료전지 시스템용 수소 공급 조절 장치
CN105135451A (zh) * 2015-10-13 2015-12-09 中国石油化工股份有限公司 带取热盘管的地面火炬
CN107152679A (zh) * 2016-03-03 2017-09-12 中国海洋石油总公司 燃气喷头和燃烧器
CN107013912B (zh) * 2017-05-31 2023-09-19 深圳智慧能源技术有限公司 自冷却引射式燃烧装置
CN107300172A (zh) * 2017-08-17 2017-10-27 上海钜荷热力技术有限公司 一种具有多点点火及检测系统的全预混表面燃烧器
CN109798518B (zh) * 2019-03-29 2024-03-15 烟台龙源电力技术股份有限公司 低氮燃烧器和燃烧系统
NZ787609A (en) 2019-11-04 2022-12-23 Randall J Thiessen Burner tube
US11781763B2 (en) * 2020-01-13 2023-10-10 Johnson Controls Tyco IP Holdings LLP Air flow amplifier for HVAC system
US11796172B2 (en) * 2020-01-30 2023-10-24 All American Services, LLC Portable flaring apparatus
CN114321903A (zh) * 2020-10-12 2022-04-12 北京动力机械研究所 一种燃烧器及方法
CN112283701B (zh) * 2020-12-29 2021-04-06 烟台工程职业技术学院(烟台市技师学院) 一种预混式混合燃料燃烧器
CN117387084B (zh) * 2023-12-11 2024-03-08 西安紫光环保科技有限公司 一种地面火炬燃烧器
CN117883929B (zh) * 2024-03-15 2024-05-28 新疆天利石化股份有限公司 一种碳五加工产业链排放尾气处理与回收装置及工艺

Family Cites Families (39)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3302596A (en) * 1966-01-21 1967-02-07 Little Inc A Combustion device
US3703349A (en) * 1971-05-17 1972-11-21 Combustion Unltd Inc Ground flare
US3749546A (en) * 1971-09-20 1973-07-31 Zink Co John Smokeless flare pit burner and method
GB1453440A (en) * 1973-01-18 1976-10-20 Flaregas Eng Ltd Apparatus for use in the disposal of waste gas
US3822983A (en) * 1973-04-23 1974-07-09 Proctor A & Montecatini Edison Ground flares
US3982881A (en) * 1975-02-03 1976-09-28 John Zink Company Invisible flare burner
US3954385A (en) * 1975-02-24 1976-05-04 John Zink Company Air powered smokeless flare
GB1551915A (en) * 1975-11-12 1979-09-05 British Petroleum Co Burner element
US3994663A (en) * 1975-11-28 1976-11-30 John Zink Company Method and apparatus to prevent air flow inversion in flare stacks
US4065248A (en) * 1976-01-08 1977-12-27 National Airoil Burner Co., Inc. Ground flare
US4039276A (en) * 1976-03-11 1977-08-02 John Zink Company Noise and smoke retardant flare
US4035171A (en) * 1976-04-26 1977-07-12 John Zink Company Gas liquid separator for flare systems
US4036580A (en) * 1976-06-04 1977-07-19 John Zink Company Turbine-driven air-powered flare
US4105394A (en) * 1976-10-18 1978-08-08 John Zink Company Dual pressure flare
US4140471A (en) * 1977-05-09 1979-02-20 National Airoil Burner Company, Inc. Ground flare stack
US4154570A (en) * 1977-09-12 1979-05-15 John Zink Company Gaseous molecular seal for flare stack
JPS5826497B2 (ja) * 1977-10-04 1983-06-03 日立造船株式会社 グランドフレアの廃ガス導入制御装置
GB2005821B (en) * 1977-10-07 1982-01-20 Hitachi Shipbuilding Eng Co Apparatus for disposing of waste gas by burning
US4227872A (en) * 1978-05-30 1980-10-14 John Zink Company Apparatus for supplying alternate gases to steam injection means on a flare stack
US4265611A (en) * 1979-03-15 1981-05-05 John Zink Company Control system for purge gas to flare
US4457696A (en) * 1980-09-24 1984-07-03 John Zink Company Large capacity air-powered smokeless flare
JPS6053810B2 (ja) * 1981-01-10 1985-11-27 日揮株式会社 グラウンドフレア−スタツク
US4493638A (en) * 1981-02-18 1985-01-15 The British Petroleum Company, P.L.C. Post-aerated burner for ground flare, and ground flare incorporating same
US4419071A (en) * 1981-08-03 1983-12-06 John Zink Company Portable high-flow rate flare for smokeless burning of viscous liquid fuels
US4824361A (en) * 1982-04-05 1989-04-25 Mcgill Incorporated Smoke suppressant apparatus for flare gas combustion
US4652232A (en) * 1983-05-16 1987-03-24 John Zink Co. Apparatus and method to add kinetic energy to a low pressure waste gas flare burner
US4565522A (en) * 1984-08-29 1986-01-21 John Zink Company Shielded flare gas burner
US4579521A (en) * 1984-08-29 1986-04-01 John Zink Company Flare gas burner
US4573906A (en) * 1984-08-29 1986-03-04 John Zink Company Shielded smoke suppressing flare gas burner
US4637793A (en) * 1984-08-29 1987-01-20 John Zink Company Flare gas burner
US4952137A (en) * 1986-09-08 1990-08-28 John Zink Company Flare gas burner
US5195884A (en) * 1992-03-27 1993-03-23 John Zink Company, A Division Of Koch Engineering Company, Inc. Low NOx formation burner apparatus and methods
US5810575A (en) * 1997-03-05 1998-09-22 Schwartz; Robert E. Flare apparatus and methods
US6146131A (en) * 1999-06-25 2000-11-14 Rana Development, Inc. Enclosed ground-flare incinerator
US6012917A (en) * 1999-06-25 2000-01-11 Rana Development, Inc. Enclosed ground-flare incinerator
US6565361B2 (en) * 2001-06-25 2003-05-20 John Zink Company, Llc Methods and apparatus for burning fuel with low NOx formation
US6702572B2 (en) * 2001-08-20 2004-03-09 John Zink Company, Llc Ultra-stable flare pilot and methods
US20060105276A1 (en) * 2004-11-16 2006-05-18 James Wilkins Linear Coanda flare methods and apparatus
US7967600B2 (en) * 2006-03-27 2011-06-28 John Zink Company, Llc Flare apparatus

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9816705B2 (en) 2014-11-18 2017-11-14 Honeywell International Inc. Flare burner for a combustible gas
US10598375B2 (en) 2016-11-01 2020-03-24 Honeywell International Inc. Asymmetrical and offset flare tip for flare burners
US11105508B2 (en) 2016-11-01 2021-08-31 Honeywell International Inc. Asymmetrical and offset flare tip for flare burners

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KR20080029901A (ko) 2008-04-03
US20080081304A1 (en) 2008-04-03
MX2007011586A (es) 2008-10-28
BRPI0703675A (pt) 2008-06-03
CA2600248A1 (fr) 2008-03-29
CN101153711A (zh) 2008-04-02
TW200819678A (en) 2008-05-01
AU2007204081A1 (en) 2008-04-17
AR062920A1 (es) 2008-12-17

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