GB1604441A - Flares - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO FLARES (71) We, AIROIL FLAREGAS LIMITED, a British Company, of Horton Road, West Drayton, Middlesex UB7 8BG, whose registered office is at Vale Road, Tonbridge, Kent, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to flares and particularly, but not solely, to elevated flares, i.e., flarestacks.

In order to promote, as far as possible, smokeless combustion and to reduce noise it is known to inject an air and steam mixture into a dump gas either prior to its discharge from the outlet of a flare of flare stack tip for combustion or after such discharge.

The present invention provides a flare or flare stack tip which has a plurality of nozzle devices mounted and arranged so as to cause the discharge of air, or a gaseous mixture including air, into dump gas subsequent to its discharge from its outlet, during operation, wherein the nozzle devices are designed to operate in the manner known as the Coanda effect.

The invention also provides a method of disposing of dump gas involving the introduction of air, or a gaseous mixture including air, into the dump gas subsequent to its discharge from a flare or flare tip outlet by utilizing nozzle devices operating in the manner known as the Coanda effect as aforesaid.

The nozzle devices used in performing the invention preferably use steam to induce or inspirate air and hence discharge an air/steam mixture into the dump gas. However, the devices can operate with some other high pressure fluid as an inducing medium.

The devices used in performing the invention preferably each have a Coanda slot or aperture which acts to pass fluid inducing medium, e.g., steam, over an external deflector surface of a Coanda body to thereby inspirate air which mixes with the inducing medium.

The invention also provides an arrangement composed of a plurality of devices disposed about a flare or flare stack outlet, each of the devices having a Coanda body and being fed, during operation, with an inducing medium, preferably steam, wherein each of the devices is designed to direct the inducing medium over an external surface of its Coanda body to thereby aspirate ambient air which is discharged with the inducing medium along a path which intersects the axis of the flare or flare stack outlet.

The invention may be understood more readily and various other features of the invention may become apparent from consideration of the following description.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein: Figure 1 is a schematic elevation of a flare stack tip assembly and arrangement constructed in accordance with the invention, and Figure 2 is a schematic elevation of one of the nozzle devices employed in the assembly of Figure 1.

As shown in Figure 1, a flare stack tip 10, i.e., the upper section of an elevated flare, has a flame retention head 11 and one or more pilot burners 12 all know per se.

In accordance with the invention, the outlet 13 of the tip 10 is surrounded by a plurality of nozzle devices 14 only two of which are illustrated in Figure 1. A manifold 15 spaced below the outlet 13 and coaxially surrounding the top 10 communicated via feed conduits 16 with the individual nozzle devices 14. The manifold 15 and the conduits 16 serve to feed a high pressure inducing medium to the devices 14, as described in more detail hereinafter, and also serve to mount the devices 14 in relation to the outlet 13. Thus, the devices are mounted preferably in a symmetrical manner, so that their axes K-which define the discharge path of their fluid outlets-intersect the axis T of the tip 10 at a region spaced above the outlet 13 to thereby interrupt the flow of gases out of the tip 10 during use.In this embodiment of the invention, steam is supplied under pressure to the manifold 15 and thence via the conduits 16 to the devices 14.

Referring now to Figure 2, each device has a shaped body 17 resembling a tulip. The body 17 which at least partly forms a Coanda body, is mounted above a mounting head 18 at the terminal end of the associated conduit 16. A narrow Coanda slot 19 is formed between the lower end of the body 17 and the mounting head 18. The body 17 is hollow and an internal pipe 20, which effectively forms a continuation of the conduit 16, is located within the body 17.The lower curvilinear exterior surface 21 of the body 17 forms a Coanda deflector surface which merges with an upper frusto-conical surface 22 of the body 17. During operation, steam applied to each nozzle device 14 via its associated conduit 16 is split into two paths: one passing through the slot 19 and over the surface 21 and the other passing through the pipe 20 and discharging from the device 14 as represented by arrow S in Figure 2. The steam emerging through the slot 19 tends to adhere to the surface 21 as represented by arrows C in Figure 2. In accordance with the known Coanda effect, a low pressure region is formed in the vicinity of the surface 21 and the slot 19 and surrounding air is inspirated to join the steam flowing over the surface 21 as indicated by arrows A in Figure 2.The resultant air and steam mixture tends to break away from the surface 22 and follows a path generally parallel to the axis of the body 17 as represented by arrows M in Figure 2.

This mixture M is thus injected, with the steam (S) emitted from the pipe 20 generally axially of the body 17 and the device 14 into the dump gas discharged from the tip 20. In an alternative embodiment, the position of the slot 19 in relation to the surface 21 is modified by extending the mounting head 18 in the general direction of the surface 22.

In a practical construction some 1/3rd. of the quantity of steam supplied to each conduit 16 would be directed through the associated body 17 and discharged from the pipe 20 and the remaining 2/3rds., would be split off and directed over the surface 21.

As represented in Figure 1, the nozzle devices 14 can be arranged in two or more concentric rings around the tip 10 although with a small diameter flarestack a single ring can be sufficient. The primary purpose of the nozzle devices 14 is to inject air into the dump gas emitted by the tip 10 for combustion, although it is preferred to inject a mixture of air and steam into the dump gas.

The presence of steam is beneficial, but not essential, and other high pressure gases can also be used in the mixture as a substitute for steam. The choice between such gases and steam largely depends on the availability of such products on the site of the flare system.

It is envisaged that where the stack diameter is relatively small, say 6 inches, some six nozzle devices 14 would be provided.

On larger stacks additional devices 14 would be provided so that, for example, thirty devices 14 would be provided on a 24 inch diameter stack and forty devices 14 provided on a 30 inch diameter stack. For convenience, and as already mentioned, the devices can be arranged in a number of concentric rings and one or more additional manifolds 15 can be used where a large number of devices are employed.

It is envisaged that each nozzle device 14 would consume something in the order of 500 lbs. per hour of steam at 50 p.s.i., and would have an air entrainment ration, depending on conditions, somewhere in the region of 10 or 20 to 1.

It is known to use devices operating on the Coanda principle to inject an air/steam mixture into the dump gas prior to its emergence from the tip outlet for combustion. The main advantage of the arrangement in accordance with the present invention over this known arrangement is that there is a better control aspect which inhibits the tendency of the flame to burn back inside the flare stack. Although the arrangement as described is intended to inject or introduce an air/steam mixture solely into the dump gas emerging from the tip outlet it is also possible to utilize means which introduces additional steam within the flare stack to contact the dump gas prior to its emergence from the flare stack to further reduce the tendency of the flame to burn back inside the flare stack.

The advantage of the present invention over arrangement which employ a plurality of non-Coanda nozzles designed to inject an air/steam mixture into the dump gas as it emerges from the tip outlet are two fold:- There is generally a much better aspiration ratio and the fluid flow over the external surfaces (21, 22) of the devices 14 tends to render the devices 14 self cooling if the flame should be directed, e.g., by wind onto the devices 14.

WHAT WE CLAIM IS: 1. A flare or flare stack tip which has a plurality of nozzle devices, which operate in the manner known as the Coanda effect, mounted and arranged so as to cause the discharge of air, or a gaseous mixture including air, into dump gas subsequent to discharge from its outlet.

2. A flare or flare stack tip according to claim 1, wherein the nozzle devices utilize steam to induce or inspirate air.

3. A flare of flare stack tip according to claim 2, wherein the nozzle devices discharge an air/steam mixture into the dump gas.

4. A flare or flare stack tip according to claim 1, wherein the nozzle devices utilize a high pressure fluid to induce or inspirate air.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (16)

**WARNING** start of CLMS field may overlap end of DESC **. conduits 16 to the devices 14. Referring now to Figure 2, each device has a shaped body 17 resembling a tulip. The body 17 which at least partly forms a Coanda body, is mounted above a mounting head 18 at the terminal end of the associated conduit 16. A narrow Coanda slot 19 is formed between the lower end of the body 17 and the mounting head 18. The body 17 is hollow and an internal pipe 20, which effectively forms a continuation of the conduit 16, is located within the body 17.The lower curvilinear exterior surface 21 of the body 17 forms a Coanda deflector surface which merges with an upper frusto-conical surface 22 of the body 17. During operation, steam applied to each nozzle device 14 via its associated conduit 16 is split into two paths: one passing through the slot 19 and over the surface 21 and the other passing through the pipe 20 and discharging from the device 14 as represented by arrow S in Figure 2. The steam emerging through the slot 19 tends to adhere to the surface 21 as represented by arrows C in Figure 2. In accordance with the known Coanda effect, a low pressure region is formed in the vicinity of the surface 21 and the slot 19 and surrounding air is inspirated to join the steam flowing over the surface 21 as indicated by arrows A in Figure 2.The resultant air and steam mixture tends to break away from the surface 22 and follows a path generally parallel to the axis of the body 17 as represented by arrows M in Figure 2. This mixture M is thus injected, with the steam (S) emitted from the pipe 20 generally axially of the body 17 and the device 14 into the dump gas discharged from the tip 20. In an alternative embodiment, the position of the slot 19 in relation to the surface 21 is modified by extending the mounting head 18 in the general direction of the surface 22. In a practical construction some 1/3rd. of the quantity of steam supplied to each conduit 16 would be directed through the associated body 17 and discharged from the pipe 20 and the remaining 2/3rds., would be split off and directed over the surface 21. As represented in Figure 1, the nozzle devices 14 can be arranged in two or more concentric rings around the tip 10 although with a small diameter flarestack a single ring can be sufficient. The primary purpose of the nozzle devices 14 is to inject air into the dump gas emitted by the tip 10 for combustion, although it is preferred to inject a mixture of air and steam into the dump gas. The presence of steam is beneficial, but not essential, and other high pressure gases can also be used in the mixture as a substitute for steam. The choice between such gases and steam largely depends on the availability of such products on the site of the flare system. It is envisaged that where the stack diameter is relatively small, say 6 inches, some six nozzle devices 14 would be provided. On larger stacks additional devices 14 would be provided so that, for example, thirty devices 14 would be provided on a 24 inch diameter stack and forty devices 14 provided on a 30 inch diameter stack. For convenience, and as already mentioned, the devices can be arranged in a number of concentric rings and one or more additional manifolds 15 can be used where a large number of devices are employed. It is envisaged that each nozzle device 14 would consume something in the order of 500 lbs. per hour of steam at 50 p.s.i., and would have an air entrainment ration, depending on conditions, somewhere in the region of 10 or 20 to 1. It is known to use devices operating on the Coanda principle to inject an air/steam mixture into the dump gas prior to its emergence from the tip outlet for combustion. The main advantage of the arrangement in accordance with the present invention over this known arrangement is that there is a better control aspect which inhibits the tendency of the flame to burn back inside the flare stack. Although the arrangement as described is intended to inject or introduce an air/steam mixture solely into the dump gas emerging from the tip outlet it is also possible to utilize means which introduces additional steam within the flare stack to contact the dump gas prior to its emergence from the flare stack to further reduce the tendency of the flame to burn back inside the flare stack. The advantage of the present invention over arrangement which employ a plurality of non-Coanda nozzles designed to inject an air/steam mixture into the dump gas as it emerges from the tip outlet are two fold:- There is generally a much better aspiration ratio and the fluid flow over the external surfaces (21, 22) of the devices 14 tends to render the devices 14 self cooling if the flame should be directed, e.g., by wind onto the devices 14. WHAT WE CLAIM IS:

1. A flare or flare stack tip which has a plurality of nozzle devices, which operate in the manner known as the Coanda effect, mounted and arranged so as to cause the discharge of air, or a gaseous mixture including air, into dump gas subsequent to discharge from its outlet.

2. A flare or flare stack tip according to claim 1, wherein the nozzle devices utilize steam to induce or inspirate air.

3. A flare of flare stack tip according to claim 2, wherein the nozzle devices discharge an air/steam mixture into the dump gas.

4. A flare or flare stack tip according to claim 1, wherein the nozzle devices utilize a high pressure fluid to induce or inspirate air.

5. A flare or flare stack tip according to

claim 1, wherein each nozzle device has a Coanda slot or aperture which acts to pass fluid inducing medium supplied to the device over an external deflector surface of a Coanda body to thereby inspirate air to mix with the inducing medium.

6. A flare or flare stack tip according to claim 5, wherein the nozzle devices are connected to one or more manifolds surrounding the tip or flare which feed the inducing medium to the nozzle devices.

7. A flare or flare stack tip according to any one of claims 1 to 6, wherein the nozzle devices are arranged so that their axes, defining their discharge paths, intersect the axis of the outlet at a region spaced above said outlet.

8. A flare or flare stack tip according to any one of the preceding claims, wherein the nozzle devices are arranged in symmetrical manner in two or more concentric rings in relation to the outlet.

9. A flare or flare stack tip according to any one of the preceding claims wherein each nozzle device is constructed and/or operates substantially in accordance with Figure 2 of the accompanying drawings.

10. An arrangement composed of a plurality of devices disposed about a flare or flare stack outlet, each of said devices having a Coanda body and being fed, during operation, with an inducing medium, wherein each of the devices is designed to direct the inducing medium over an external surface of its Coanda body to thereby aspirate ambient air which is discharged with the inducing medium along a path which intersects the axis of the flare or flare stack outlet.

11. A flare or flare stack tip arrangement according to any one of the preceding claims and further comprising means for introducing steam into the dump gas prior to its discharge from the outlet.

12. A flare or flare stack tip arrangement substantially as described with reference to, and as illustrated in, the accompanying drawings.

13. A method of disposing of dump gas involving the introduction of air, or a gaseous mixture including air, into the dump gas subsequent to its discharge from a flare or flare tip outlet by utilizing nozzle devices operating in the manner known as the Coanda effect.

14. A method according to Claim 12, wherein the nozzle devices discharge a mixture of air and steam into the dump gas.

15. A method according to claim 13 or 14 and further comprising introducing steam into the dump gas prior to its discharge from the outlet.

16. A method of disposing of dump gas substantially as described hereinbefore with reference to the accompanying drawings.