HK1109198B - Flare apparatus - Google Patents

Description

Torch device

Technical Field

The present invention relates to an improved flare apparatus and more particularly to an efficient steam assisted flare apparatus.

Background

Flare apparatus for burning and disposing of combustible gases are well known. Flare apparatus are typically installed on flare stacks and disposed in production plants, refineries, petroleum processing plants, and the like to process flammable waste gases or other flammable gas streams that are diverted for any reason including, but not limited to, ventilation, shut-down, tipping, and/or emergency situations. In the event of an emergency situation at the plant, such as a fire or power failure, flare apparatus are of paramount importance, and properly operating flare systems are plumbing components that protect the plant from damage in any of the above situations or other situations.

It is generally desirable that combustible gases burn without generating smoke and generally such smokeless or substantially smokeless combustion is mandatory. One way to achieve smokeless combustion is by providing the combustion air with a steam injection pump, sometimes referred to as an injector (injector). The combustion air ensures complete oxidation of the combustible gases to prevent the generation of smoke. Thus, steam is typically used as a motive force to move air within the flare apparatus. When a sufficient amount of combustion air is provided, the supplied air can be mixed well with the combustible gas, and the steam/air mixture and the combustible gas can be burned smokeless. In a typical flare apparatus, only a portion of the required combustion air is provided through the use of a motive force such as a blower, a jet pump using steam, compressed air, or other gas. Most of the required combustion air is obtained from the ambient atmosphere along the length of the flame.

One known type of flare apparatus utilizing steam includes a generally cylindrical gas tube into which a combustible gas is delivered. The lower steam is conveyed through a plurality of steam tubes at the inlet and is forced through bends in the steam tubes, which results in a pressure drop. At the bend, the steam tubes change direction so that they are parallel to the outer cylinder. The central steam is injected into the center of the gas tube so that the combustible gas and steam pass upwardly through the outer tube and mix with the steam exiting the lower steam tube. At the upper end or outlet of the gas tube, a steam injector directs steam radially inward to control the circumference of the mixture exiting the gas tube, and the steam/air and gas mixture is ignited. A central steam is provided to ensure that combustion does not occur inside the gas tubes. Internal combustion is typically seen at low gas flow rates, e.g. purge rates, and is exacerbated by cross-winds, a capping effect caused by overhead steam, if the purge gas has a lower molecular weight than air. The purge rate is typically the minimum gas flow rate that is continuously flowing onto the torch to prevent an explosion in the torch chimney.

Another type of steam assisted flare uses only central and upper steam injectors and works in a similar manner. The steam-utilizing flare described herein can achieve smokeless combustion. However, such flare apparatus can generate excessive noise. Noise from the lower steam can be muffled, while noise from the upper steam is difficult or impractical to muffle due to its proximity to the flare flame. The silencer for the lower steam not only increases the cost, but also increases the wind load of the flare stack, resulting in increased cost of the flare stack. Because of the high cost of steam, piping associated with the delivery of steam, and flare stack structures, it is desirable to achieve smokeless combustion with less steam. Accordingly, there is a need for an improved flare apparatus and method for smokeless combustion of combustible gases using air, thereby reducing noise and increasing efficiency, whereby more fuel can be combusted with less added steam.

Disclosure of Invention

The flare apparatus according to the present invention includes a plurality of flare tip units. Each flare tip unit has an outer member with first and second ends and an inner member defining an inlet and an outlet. At least a portion of the inner member is disposed within the outer member and is preferably coaxially or concentrically disposed within the outer member. An annular gas passage is defined between the inner and outer members of each flare tip unit. The upper end of the outer member defines an exit aperture and the upper end of the inner member defines an inner member outlet. The air flows through the inner member and exits the inner member outlet into the outer member.

The combustible gas flows through the annular gas passage and exits the annular gas passage into the outer member above the inner member outlet, where the combustible gas mixes with at least air in the outer member. The space between the inner member outlet and the exit opening may be referred to as a premixing zone, as the gas and at least air will mix therein before exiting from the exit opening for combustion in the atmosphere.

While mechanical devices such as fans or blowers may be utilized to move air through the internals, it is preferred to utilize steam as the motive force for the air. Likewise, compressed air, nitrogen, carbon dioxide, fuel gas, or other gases may be used as power in a manner similar to steam. In a preferred embodiment of the invention, steam is injected into the inlet of the inner member at a velocity sufficient to draw air into the inner member such that the steam and air mixture flows through the inner member outlet into the premixing zone. Preferably, the length of the premixing zone is greater than the width of the annular gas passage and preferably at least four times the width of the annular gas passage. The premixing zone provides a space for mixing of the gas with air and steam and also includes perimeter control.

In a preferred embodiment, the flare apparatus of the present invention comprises a plurality of flare tip units, wherein the annular gas channel in each of the plurality of flare tip units receives gas from a single combustible gas supply. The single combustible gas supply may, for example, be a plenum chamber to which each flare tip unit is connected. Combustible gas may be passed from the plenum into the annular gas passage of each flare tip unit, and the combustible gas and air/steam mixture will flow through the exit opening of each flare tip unit into the atmosphere. Each flare tip unit of the plurality of units preferably has a steam injector associated therewith to power the air through the internal components of the flare tip unit. Preferably, steam is supplied from a single source like each steam injector. The combustible gas may be delivered to the plenum through a gas pipe connected in a flare stack.

Drawings

FIG. 1 is a perspective view of a flare apparatus of the present invention.

Fig. 2 is a cross-sectional view taken along line 2-2 of fig. 1.

FIG. 3 is a cross-sectional view similar to FIG. 2 of another embodiment of the invention having a generally cylindrical plenum.

Fig. 4 is a cross-sectional view of an embodiment of the present invention that uses a draft tube as the gas supply.

Fig. 5 is a view from line 5-5 in fig. 4.

FIGS. 6 and 7 are alternative embodiments of flare tip units.

FIGS. 8-14 are alternative embodiments of the flare tip unit and in particular embodiments having different configurations of external members.

FIG. 15 shows an embodiment of a single flare tip unit.

FIGS. 16 and 17 are illustrations of a flare apparatus in the prior art.

Detailed Description

Referring now to the drawings, there is shown a flare apparatus which may be referred to as a flare tip 10. The flare apparatus 10 is adapted for use at the top of a flare stack, which is known in the art to deliver combustible gas from a combustible gas source to the flare apparatus 10. The combustible gas may be from a refinery, petroleum processing plant, chemical plant, production site, LNG production plant, or other source. The gas may include, for example, propane, propylene, natural gas, hydrogen, carbon monoxide, ethylene, or other gases. The flare apparatus 10 includes a plurality of flare tip units or flare structures 15 for receiving combustible gas from a single gas supply source 20, which in FIG. 1 is a plenum 20. A gas pipe 25 connectable to a flare stack (not shown) delivers combustible gas from a combustible gas source to the plenum 20.

The flare apparatus 10 may include a plurality of steam injectors 30, the steam injectors 30 for providing power to move air through each flare tip unit 15. Thus, each flare tip unit 15 may have a steam injector 30 associated therewith. Preferably, steam is provided to each steam injector 30 from a single steam source (not shown). The steam source may be connected to the steam injector and controlled using any means known in the art. In operation, a combustible gas is delivered through the gas tube 25 into the plenum 20. The air/steam and combustible gas mixture exits each flare tip unit 15 and is ignited for efficient combustion in the atmosphere. The flare apparatus 10 of the present invention is more efficient than the flare tip of the prior art in that less steam is required. The plant 10 will also operate at a lower noise level than other flare apparatus utilizing steam. These and other advantages will be described in more detail below.

Referring now to FIG. 2, each flare tip unit 15 includes an inner tubular member 32 and an outer tubular member 34. The inner member 32 is preferably a generally cylindrical inner member having a longitudinal central axis 36. The inner member 32 has a first or lower end 38 and a second or upper end 40. An inlet shroud 42 may be defined at the first end 38. The inlet cowling directs steam to the inlet 44. The steam injector 30 may be a star injector, wherein the star arms have apertures through which steam is injected. The steam may be directed into the surface of the inlet hood and may be similar to an internal Coanda (Coanda) nozzle. An inner member inlet 44 is defined at the lower end 38, while the upper end 40 defines an inner member outlet 46. In the preferred embodiment, at least air, and preferably a steam/air mixture, will flow through the inner member 32 and enter the outer member 34 through the inner member outlet 46. The inner member 32 has an outer surface 48 and an inner surface 50, the inner surface 50 defining a passageway 52 for air or air/steam to pass therethrough. The inner member 32 is preferably a straight cylinder from the inlet 44 to the outlet 46 without bends, bumps, depressions or other interruptions so that the flow of air or steam and air therethrough is not interrupted.

The outer member 34 is preferably coaxial with the inner member 32 and shares a longitudinal central axis 36. The outer member 34 has a first or lower end 54 and a second or upper end 56. An exit aperture 58 is defined at the upper end 56. The outer member 34 has an outer surface 60 and an inner surface 62. An annular passageway, which may be referred to as an annular gas passage 64, is defined by and between the inner and outer members 32, 34. A gas inlet 66 is defined at the lower end 54 of the outer member 34 and a gas outlet 68 is defined at the upper end 40 of the inner member 32 in the illustrated embodiment. As can be readily seen from the drawings, the inner member outlet 46 is positioned below and spaced from the exit opening 58. The distance between the outlet 46 and the exit opening 58 may be referred to as a premixing zone 70. The combustible gas exiting the annular gas passage 64 through the gas outlet 68 will enter the premixing region 70 and will mix with at least the air and, in the illustrated embodiment, the air and steam mixture flowing through the inner member outlet 46. The combustible gas will mix with the air/steam mixture in the premixing zone 70 and the gas/steam/air mixture will flow through the exit apertures 58 and be ignited for combustion in the atmosphere. Thus, the length of the premixing zone is such that the air/steam flow in the inner barrel will expand and mix with the combustible gas. The length 72 of the pre-mixing region 70 is preferably greater than the width 74 of the annular gas passage 64, more preferably at least four times greater than the width 74 of the annular gas passage 64, and more preferably four to five times greater than the width 74 of the annular gas passage 64. The portion of the outer member 34 that extends above the inner member 32 to define the premixing area 70 may also be referred to as a perimeter control portion because, in addition to allowing air and combustible gases to mix before combustion occurs, this portion of the outer member may also prevent ambient wind from sweeping unburned combustible gases or causing smoke to appear in the atmosphere.

In a preferred embodiment, the outer member 34 includes a cylindrical portion 78 extending from the lower end 54 of the outer member to an upper end 80 of the cylindrical portion 78. The cylindrical portion 78 may be referred to as a first cylindrical portion 78. A radially inwardly directed cone, which may be referred to as a converging cone 82, extends upwardly from the upper end 80 and has an upper end 84. The converging cone 82 will preferably improve the mixing between the gas and at least air. A second cylindrical portion 86 extends upwardly from the converging cone 82. The second cylindrical portion 86 will further enhance the mixing between the gas and at least air and allow for a more uniform velocity profile. The second cylindrical portion 86 has an upper end 88. A radially outwardly directed cone, which may be referred to as a diffuser cone 90, extends upwardly from the upper end 88. Preferably, the diverging cone 90 diverges radially outward from the second cylindrical portion 86 at an angle of about 45 degrees. A flame stabilizing ring 92, which is preferably a generally horizontal flame stabilizing ring, extends radially inward from the upper end 91 of the diffuser cone 90. The flame stabilizing ring 92 may have a plurality of openings 99, the openings 99 allowing the combustible mixture to pass therethrough and form a stable flame on the flame stabilizing ring 92. Fig. 1 shows eight openings 97. However, it is preferred to have more openings with closer spacing than shown in FIG. 1. The flame stabilizing ring 92 preferably does not impede or restrict the flow of the air/steam and combustible gas mixture so that it does not cause the combustible gas to flow back or down the internals in the event that auxiliary media or motive gas (i.e., steam, compressed air, gas, or any other gas) or blower air is lost therein. The inner diameter of the flame stabilizing ring 92, including the exit openings 58, is preferably equal to or at least slightly less than the inner diameter of the second cylindrical portion 86. Preferably, the inner diameter of the flame stabilizing ring 92 is such that the exit apertures 58 have a cross-sectional area that is no less than the cross-sectional area of the annular gas outlet 68, and more preferably 20% greater than the area of the gas outlet 68.

In the embodiment of fig. 2, the plenum chamber 20 includes a generally curved upper plate 93 and a curved lower plate 94, the upper and lower plates 93, 94 forming a generally oval shape in cross-section and defining a plenum chamber interior 95. The outer member 34 extends into the plenum interior 95 such that the lower end 54 and the gas inlet 66 are disposed therein. The outer member 34 may have an inlet cover 97. Alternatively, the outer member 34 may terminate at the lower end 54 at a curved upper plate 93, such that the gas inlet 66 may be defined at the curved upper plate 93. The inner member 34 extends completely through the plenum 20 such that the first and second ends 38 and 40, respectively, are disposed outside of the plenum 20. Thus, a single combustible gas supply, i.e., plenum 20, provides combustible gas to the plurality of flare tip units 15 and more specifically delivers gas from a source of combustible gas (not shown) that enters the plenum 20 through the gas tube 25 to the annular gas passage 64 of each flare tip unit 15.

The combustible gas exits the annular gas passage 64 through the gas outlet 68 and enters the premixing area 70. The combustible gas mixes with at least the air moving through the inner member 32. Preferably, air moves through each inner member along with steam injected into inner member 32 with steam injector 30. As described herein, steam is preferably provided to each injector 30 from a single steam source and injected at a velocity such that air is drawn into the inner member 32 through the inlet 44 along with the steam. The steam injector 30 may include a star injector or other known injector, or the steam injector and inlet hood 42 may function similar to an internal coanda nozzle. The air/steam mixture will flow through the inner member outlet 46 into the premixing zone 70 and mix therein with the combustible gas. The combustible air/steam mixture will flow through exit openings 58 where it will ignite and combust in the atmosphere.

Other plenum configurations may also be used and the description herein is not intended to be limiting. For example, the flare apparatus 10a shown in FIG. 3 has a plenum 96, the plenum 96 comprising a generally cylindrical drum having a lower plate 98, an upper plate 100, and a sidewall 102 connecting the upper and lower plates 98 and 100. Like elements in the flare tip unit are numbered similarly to the flare tip unit in FIG. 2, but include the subscript "a". The plenum 96 defines a plenum interior 104, with a combustible gas provided in the plenum interior 104, as described with respect to the embodiment shown in fig. 2. In the embodiment shown in fig. 3, a molecular seal or tubular seal 106 is included. The molecular seal 106 has a lower end 108, the lower end 108 being connected to the lower plate 98 and extending upwardly therefrom to an upper end 110. The upper end 110 is disposed at a higher elevation than the lower end 54a of the outer member 34a and surrounds the lower end 54a, which defines a seal annulus 112 between the molecular seal 106 and the outer member 34 a. Thus, in the embodiment shown in FIG. 3, the lower end 54a of the outer member 34a is disposed within the plenum interior 104. The combustible gas must pass into the plenum 96 and around the upper end 110 of the molecular seal 106, around the lower end 54a of the outer member 34a and up into the annular gas passage 64 a. The molecular seal 106 is optional but may be used to reduce the likelihood of any internal combustion or purge gas requirements. The molecular seal 106 will prevent air from moving into the plenum 96 and from burning in the plenum. If the air is heavier than the combustible gas, the air will be at the bottom of the molecular seal 106. If the air is lighter than the combustible gas, it will be pushed out by the combustible gas.

FIG. 4 shows a flare apparatus 10b of the present invention in which the gas supply includes a riser 114 that receives gas from the gas tube 25. The risers 114 will distribute the gas through the tubular spokes 116, each of which tubular spokes 116 in turn will deliver the combustible gas to the flare tip unit as described herein. The heavy flare tip unit of FIG. 4 is numbered similarly to FIG. 2 and includes the subscript "b".

The flare apparatus of the present invention provides a number of advantages over prior art flare apparatus, one configuration of which is shown schematically in FIGS. 16 and 17. The prior art flare end 116 has an outer cylinder 118 into which the combustible gas is delivered. Steam is injected into the outer cylinder 118 through the central steam injector 120. The plurality of lower steam injectors 122 direct steam into a plurality of lower steam tubes 124. The combustible gas moves in the outer cylinder 118 between the lower steam pipes 124. The upper steam is injected through the upper steam injector 126. The upper steam is necessary to maintain circumferential control and provide an efficient air/steam and combustible gas mixture above the outer cylinder 118 for smokeless combustion.

The flare tip 116 requires more steam than the flare apparatus of the present invention because the steam from the injector 122 must bend and turn rather than follow a straight path defined by the inner member 32 of the present invention. In addition, because of the required central and upper steam and sometimes lower steam injectors, the noise generated by the prior art arrangement is much greater and a silencer is required for the lower portion. Silencing the upper steam is difficult or impractical because flames can damage these silencers. Each flare tip unit of the present invention requires only one injection location and only one steam source for steam, whereas in prior art configurations, the upper, lower or central steam injectors typically required separate steam sources. Although sometimes the central, lower and upper steam may be connected to common steam pipes, doing so reduces operational flexibility and may create problems.

For example, connecting the core steam to the lower or upper steam may make it impossible to disconnect the core steam without disconnecting other steam sources that share common steam pipes. Under some adverse conditions, it may be desirable to disconnect the core steam and keep another steam source running. These undesirable conditions include, but are not limited to: 1) cold or arctic climates, 2) acid gases, 3) gases that react with water to form polymers. Under one or more of the above-mentioned adverse conditions, turning off the core steam typically requires a substantial increase in purge gas velocity to prevent internal combustion from rapidly damaging the flare tip. The increased purge gas rate generally presents high costs to the end user. The present invention does not require a central steam or high purge rate to prevent internal combustion. Tests have shown that when a minimum amount of power (e.g., steam or blower) is available, no internal combustion occurs in the annular gas passage 64 or plenum 20 or tube 25. In the event of a total steam failure in the present invention, internal combustion can be prevented or at least limited by the following measures: 1) directing another motive gas, such as compressed air or nitrogen, to the steam line; 2) the purification speed is considerably increased, either of which can be automated.

Another disadvantage of the prior art arrangement is that it is difficult to coordinate the separate control of the lower and upper steam. The upper steam is typically injected vertically and inwardly. The upper steam from the different steam nozzles may collide at the center above the flare tip, resulting in a localized high pressure region. This high pressure region can drive the combustible mixture into the flare tip, causing internal combustion, and down in the lower steam tube, which can cause the entire flare tip to be engulfed in the flame. This is commonly referred to as the capping effect of the upper vapor. If the lower steam velocity is insufficient to overcome the capping effect, the combustible mixture will move downward and rearward and exit at the entrance of the lower steam tube, and the torch end will be engulfed into the flame, resulting in rapid tip damage. Therefore, it is necessary to maintain a sufficient lower steam flow velocity with respect to the upper steam. The present invention requires only a single steam source, thus eliminating the need to coordinate upper and lower steam control.

The flare apparatus in FIGS. 1 and 2 includes a plenum 20 and six flare tip units 15. The draft tube embodiment of FIG. 4 has four flare tip units. More or fewer flare tip units may be used in the flare apparatus of the present invention, and a single flare tip unit may be used as a flare apparatus if desired. For example, FIG. 15 shows a single flare tip unit 130. The flare tip unit 130 is similar to each flare tip unit 15 and thus has an inner member 132 and an outer member 134 that define an annular gas passage 136. The outer member 134 defines an exit aperture 138. The inner member 132 is generally identical to the inner member 32 described previously and preferably receives steam from the steam injector 140, or may simply receive air from a fan or other known structure that moves air through the inner member 132, if desired. It should be understood that the inner member 132 may alternatively comprise an inlet cover. In a preferred embodiment, the steam will be injected at a velocity sufficient to entrain air and move it up through the outlet 142 at the upper end of the inner member 132 and into the premixing zone 144. The outer member 134 has a closed lower end 145, and a combustible gas inlet or intake 146 is defined by one side of the outer member 134. Alternatively, the outer member 134 is substantially identical to the outer member 34 described previously herein. The combustible gas is provided from a flare stack, as is known in the art. Operation of the single flare tip unit 130 is as described with respect to the flare tip unit 15, wherein the steam/air and combustible fuel mixture mixed in the premixing region 144 exits through the exit openings 138 and burns in the atmosphere, preferably in a smokeless manner.

The outer member of the flare tip unit of the flare apparatus described herein may include a variety of different configurations. The upper portions of some exemplary configurations are shown in fig. 8-14. Fig. 8 shows an outer member 150 having a converging cone 152 extending upwardly from a generally cylindrical portion 154 of the outer member 150. The taper angle 155 is between 0 ° and 75 ° and is preferably substantially 17 °. The exit aperture 156 defined by the converging cone 152 preferably has an area no less than the area of the neck 158 of the annular fuel passage, and more preferably has an area 20% greater than the neck 158 of the annular fuel passage, and the annular fuel passage is substantially an annular gas outlet. If desired, the upper end of the inner member of the flare tip unit may be fitted with a converging cone 160 or a diverging cone 162, as shown in FIGS. 9 and 10.

The flare tip unit in FIG. 11 has first and second converging cones 164 and 166 extending upwardly from a cylindrical portion 167 of the outer member of the flare tip unit, wherein the cone angle 168 of the first converging cone 164 is less than the cone angle 170 of the second converging cone 166. In fig. 12, the generally cylindrical portion 171 of the outer member may have first and second converging tapers 172 and 174, respectively, with a first taper angle 176 being greater than a second taper angle 178. The doubly curved shape 180 extends upwardly from a cylindrical portion 182 of the outer member of the flare tip unit, as shown in FIG. 13. In FIG. 14, the simplest configuration of the flare tip unit is shown, having only straight cylindrical inner and outer members 184 and 186. It should be understood that the flare tip unit shown in FIGS. 8-14 will operate as the flare tip unit 15 described herein. The fig. 8-14 additions are merely illustrative of the different configurations possible. In all cases, the inner member is preferably a straight cylinder from inlet to outlet with an optional inlet hood to direct the steam.

As described herein, the preferred embodiment of the flare tip unit includes a flare tip unit 15, the flare tip unit 15 having an outer member 34 and an inner member 32, wherein the inner member 32 is substantially straight from an inlet 44 to an outlet 46 thereof. If desired, a flare tip unit of the type wherein the inner member has a curvature as shown in FIGS. 6 and 7 may be utilized. Shown therein are flare tip units 200 and 200a, respectively. Flare tip unit 200a is similar to flare tip 200, so the same reference numbers with subscript "a" will be used for common parts. The flare tip unit 200a is augmented with an additional steam injection location and therefore the main description will be made with respect to the flare tip unit 200.

Flare tip unit 200 has an inner member 202 and an outer member 204. The inner member 202 defines a passageway 203 and receives air, and preferably air moved by steam from a steam injector 206. Steam and air enter the inlet 208 of the inner member 202. Steam and air flow through the outlet 210 of the inner member 202. The inner member 202 flows past one side of the outer member 204 and has a bend 211 therein from an inlet portion 212 to a generally vertical portion 214. The gas flow passes to the outer member 204 and upwardly through an annular gas passage 216 defined between the vertical portion 214 of the inner member 202 and the outer member 204. The vertical portion 214 is coaxial with the outer member 204 and shares a longitudinal central axis 215. A premixing area 218 is defined between the outlet 210 of the outer member 214 and an exit aperture 220. The flare tip unit 200a is identical except that steam is injected into the inner member from a donut shaped plenum 222 for delivery into the inner member 202, wherein the plenum 222 has a plurality of apertures 223.

Flare apparatus, whether used as a single flare tip unit or as multiple flare tip units with a single combustible gas supply, reduces the amount of steam required to achieve smokeless combustion. For example, for a single flare tip unit comprising two straight barrels similar to that shown in FIG. 14, the steam consumption rate required to achieve smokeless combustion of 13,000 pounds of propylene per hour is 3,200 pounds per hour. The inner member is an 8 inch diameter tubular member and the outer member is a 12 inch diameter tubular member. For a similar sized prior art device similar to that shown in fig. 16 and 17, but using only the center and upper steam injectors, 6,000 pounds per hour of steam are required to achieve smokeless combustion of 16,000 pounds per hour of propylene. Thus, steam consumption can be reduced by 34%. The single unit described herein is mathematically scaled up by a factor of 2 to a 16 inch diameter inner member and a 24 inch diameter outer member, and the premixing area is modified to that of FIG. 15. 13,000 pounds of steam per hour are required for smokeless combustion of 39,000 pounds of propylene per hour. For a flare apparatus of similar size to that shown in fig. 16 and 17, 16,000 pounds of steam per hour was required to achieve a smokeless combustion of 34,500 pounds of propylene per hour, which reduced the steam for propylene by 28%. When multiple flare tip units are connected by a plenum, the increased efficiency is similar to a single flare tip unit and in many cases is higher because the space between the multiple flare tip units 15 allows air from the atmosphere to be entrained into the individual flames from each flare tip unit. Each individual flare tip unit has a flame located thereon, and at some point all of the flames will merge to form a generally cylindrical flame having a hollow interior. Air may be entrained into the combined flame from the hollow interior. Eventually as the height of the flame increases, a single flame will appear. Because of the additional entrainment into the flame from the atmosphere, the present invention is more efficient in terms of smokeless performance than prior art arrangements, which include a single flame because it leaves the flare tip and therefore entrains less air from the atmosphere than the present invention.

It will thus be seen that this invention is one well adapted to attain the ends and objects set forth above, as well as those inherent therein. Although certain preferred embodiments of the invention have been described for purposes of this disclosure, numerous changes in the construction and arrangement of parts and the performance of steps may be made by those skilled in the art, and are encompassed within the scope and spirit of the invention as defined by the appended claims.

Claims (36)

1. A flare apparatus for burning a combustible gas, comprising:

a plurality of torch structures, each torch structure comprising:

an outer member having first and second ends, the second end defining an exit aperture; and

an inner member having an inlet and an outlet, at least a portion of the inner member being disposed in the outer member to define an annular gas passage therebetween, the inner member outlet being disposed below the exit aperture of the outer member, the flare structures being spaced apart such that each flare structure has a respective flame above the exit aperture;

a plenum for receiving a combustible gas, wherein all of the combustible gas contained therein passes from the plenum to an annular gas passage in a flare structure, the inner member extending completely through the plenum from an exterior of the plenum and into the outer member, the inner member comprising a generally straight cylinder from an inner member inlet to an inner member outlet, the inner member inlet being positioned exterior to the plenum; and

a steam injector that injects steam into the inner member inlet at a velocity sufficient to draw air into the inner member of each flare structure and move the air through the inner member, wherein the air/steam mixture exits the inner member outlet into the outer member and the air/steam mixture mixes with combustible gas in the outer member and the mixture of combustible gas and air/steam flows through the exit aperture for combustion.

2. The flare apparatus of claim 1, wherein the first end of each of the outer members defines a gas inlet for delivering a combustible gas into the annular gas passage.

3. The flare apparatus of claim 1, wherein the outer member of each flare structure comprises a straight barrel from a gas inlet to an exit aperture.

4. The flare apparatus of claim 1, wherein the outer member of each flare structure comprises:

a first cylindrical portion having first and second ends, the first end of the first cylindrical portion comprising the first end of the outer member; and

a converging cone extending upwardly from the second end of the first cylindrical portion.

5. The flare apparatus of claim 4, wherein at least a portion of the converging cone extends above the outlet of the inner member.

6. The flare apparatus of claim 5, wherein the outer member further comprises a second cylindrical portion extending upwardly from the converging cone.

7. The flare apparatus of claim 6, wherein the outer member further comprises a diffuser cone extending upwardly from the second cylindrical portion, and a generally horizontal ring extending radially inwardly from an upper end of the diffuser cone, wherein the horizontal ring defines the exit aperture.

8. The flare apparatus of claim 1, further comprising a molecular seal surrounding the inlet of the outer member of each flare unit.

9. The flare apparatus of claim 8, wherein the molecular seal comprises a tubular seal connected at a first end thereof to a plenum and extending upwardly therefrom to a second end thereof, wherein the molecular seal and the outer member of each of the plurality of flare structures define a sealed annulus through which the combustible gas must pass before entering the annular gas channel.

10. A flare apparatus for burning a combustible gas, comprising:

a plurality of flare tip units spaced apart such that each flare tip unit will have a respective flame thereon while combusting a combustible gas, each flare tip unit comprising:

a single outer member having first and second ends, a portion of the outer member defining a converging cone; and

a single inner member having an inlet and an outlet, wherein at least a portion of the inner member is disposed in the outer member to define an annular gas passage, and at least a portion of the converging cone extends above the inner member outlet; and

a plenum connected to a source of combustible gas for conveying the combustible gas to the annular gas channel of each flare tip unit, wherein each flare tip unit is connected to the plenum such that all of the combustible gas received by the plenum from the source of combustible gas is directed from the plenum to the annular gas channel and each annular gas channel receives a portion of the combustible gas, the combustible gas exiting the annular gas channel in each flare tip unit being directed radially inward through a converging cone and mixed in the outer member with at least the air flowing through the outlet of each inner member, and wherein the mixture of at least the air and the combustible gas flows through an exit aperture defined at the second end of the outer member.

11. The flare apparatus of claim 10, wherein the first end of each outer member defines a gas inlet for an annular gas passage.

12. The flare apparatus of claim 10, wherein the plenum defines a plenum interior into which the combustible gas is communicated from the source of combustible gas, wherein the first end of each outer member is positioned within the plenum interior and extends from the plenum interior to the plenum exterior, and wherein the inner members pass entirely through the plenum such that the inner member inlet and outlet of each flare tip unit are positioned outside of the plenum.

13. The flare apparatus of claim 12, wherein the plenum comprises:

a substantially flat upper plate;

a cylindrical sidewall connected to and extending downwardly from the upper plate; and

a flat lower plate connected to the cylindrical sidewall, the lower plate having an opening for receiving a combustible gas, wherein the upper and lower plates and the sidewall define a plenum interior.

14. The flare apparatus of claim 10, wherein the plenum comprises a curved upper plate connected to a curved lower plate to define a plenum interior.

15. The flare apparatus of claim 14, wherein the curved upper and lower plates are connected by a sidewall.

16. The flare apparatus of claim 10, wherein the combustible gas supply comprises:

a riser for receiving a combustible gas from a source of combustible gas; and

a plurality of spokes extending from the riser, each spoke conveying gas from the riser into one of the plurality of flare tip units.

17. The flare apparatus of claim 10, further comprising a steam injector for injecting steam into each inner member, wherein the steam draws air into the inner member such that an air/steam mixture flows through the inner member outlet and mixes with the combustible gas in the outer member, and wherein the mixture of air/steam and combustible gas flows through the exit aperture of each flare tip unit and is ignited to produce a respective flame thereabove.

18. The flare apparatus of claim 10, wherein each outer member comprises:

a first cylindrical portion, the converging cone extending upwardly from the first cylindrical portion.

19. The flare apparatus of claim 18, wherein each outer member further comprises:

a second cylindrical portion extending upwardly from the converging cone;

a diffusion cone extending upwardly from the second cylindrical portion; and

extending inwardly from the diffuser cone and defining a flame stabilizing annulus exiting the aperture.

20. The flare apparatus of claim 10, further comprising a steam injector associated with each inner member to inject steam into the inner member of each flare tip unit at a velocity sufficient to draw air into the inner member and move the air therethrough.

21. The flare apparatus of claim 20, wherein each flare tip unit defines a premixing region between the inner member outlet and the exit opening in which an air/steam mixture exiting the inner member outlet mixes with the combustible gas exiting the annular gas passage before the gas/air/steam mixture flows through the exit opening.

22. The flare apparatus of claim 21, wherein a portion of the outer member extending over the inner member of each flare tip unit comprises a perimeter control portion.

23. The flare apparatus of claim 20, wherein the steam injector receives steam from a single steam source.

24. A flare apparatus, comprising:

a plurality of steam assisted flare structures for combusting a combustible gas, each flare structure being spaced apart from all other flare structures, each flare structure comprising:

a single outer member including a first cylindrical portion and a converging cone extending upwardly from the first cylindrical portion, the single outer member having a first end and a second end, the second end defining an exit aperture;

a single inner member having an inner member inlet and an inner member outlet coaxially disposed in the outer member and defining a passage for passage of air and steam;

an annular gas passage defined therebetween by the outer member and the inner member; and

a steam injector for injecting steam into the single inner member, wherein the air/steam mixture flows through the inner member outlet into the premixing zone in the outer member, and wherein the combustible gas delivered into the annular gas passage exits the annular gas passage into the premixing zone and mixes with the air/steam mixture such that the combustible gas and the air/steam mixture exit through the exit apertures; and

a plenum chamber, wherein the plenum chamber receives combustible gas from a combustible gas source and communicates all of the combustible gas received therein into an annular gas passage in the plurality of torch structures, the inner member inlet being located outside of the plenum chamber.

25. The flare apparatus of claim 24, wherein a single steam source provides steam to each of the plurality of steam injectors in the plurality of flare structures.

26. The flare apparatus of claim 24, wherein the first end of each outer member defines a gas inlet to the annular gas passage in each of the plurality of flare structures.

27. The flare apparatus of claim 24, wherein the inner member is a straight cylinder from an inlet to an outlet thereof.

28. The flare apparatus of claim 24, wherein a distance from the inner member outlet to the exit opening is greater than a width of the annular gas passage.

29. The flare apparatus of claim 28, wherein the distance from the inner member outlet to the exit opening is at least four times the width of the annular gas passage.

30. The flare apparatus of claim 24, further comprising:

a second cylindrical portion extending upwardly from the converging cone;

a diffuser cone extending upwardly from the second cylindrical portion; and

a flame stabilizing ring connected to and extending radially inward from an upper end of the diffuser cone.

31. A method for combusting a combustible gas, comprising:

(a) providing a combustible gas to a plurality of flare tip units, each flare tip unit comprising coaxial inner and outer tubular members;

(b) delivering a combustible gas into an annulus between coaxial inner and outer tubular members of each flare tip unit;

(c) moving at least air into the inner member inlet and through the inner member outlet into the premixing zone within the outer member of each flare tip unit;

(d) passing a combustible gas through the annulus into the premixing zone of each flare tip unit;

(e) directing the combustible gas radially inwardly through a converging cone defined by a portion of the outer tubular member toward at least the air moving through the inner member outlet;

(f) discharging at least air and combustible gas through the exit aperture of the outer member;

(g) spacing the flare tip units apart for a flame above each flare tip unit resulting from igniting a combustible mixture of at least air and a combustible gas; and

(h) at least the air and combustible gas above each flare tip unit is ignited.

32. The method of claim 31, wherein the moving step comprises injecting steam into the inner member at a velocity sufficient to entrain and move air into the inner member and through the inner member outlet.

33. The method of claim 32, comprising: the air/steam mixture from the internals is mixed with the combustible gas in the premixing zone to form a combustible mixture of steam, air and gas, and the combustible mixture flowing through the exit openings is ignited.

34. The method of claim 31, wherein step (b) comprises delivering combustible gas from a single gas supply to the annulus of each flare tip unit.

35. The method of claim 31, comprising providing steam from a single steam source to the steam injector of each flare tip unit.

36. The method of claim 31, wherein the length of the premixing zone is at least four times the width of the annulus.