US3914093A

US3914093A - Combustion apparatus

Info

Publication number: US3914093A
Application number: US431903A
Authority: US
Inventors: Albert Edward Proctor
Original assignee: Flaregas Engineering Ltd
Current assignee: Airoil Flaregas Ltd
Priority date: 1973-01-18
Filing date: 1974-01-09
Publication date: 1975-10-21
Anticipated expiration: 1992-10-21
Also published as: GB1453440A; ES422652A1; JPS49110167A; CA995064A; IT1006777B; FR2324988B1; JPS5641884B2; FR2324988A1; DE2401403A1

Abstract

Combustion apparatus usable in a ground flare and employing discharge means, such as a nozzle, for emitting a combustible waste gas into the inlet of an air inducing device. The air inducing device is fed with an inducing medium, preferably steam, which causes air to be induced into the inlet to mix with the waste gas. The air inducing device then preferably emits a mixture of air, gas and steam for combustion. To ensure that the combustion process is substantially smokeless, control is effected by varying the distance between the outlet of the discharge means and the inlet of the air inducing device.

Description

0 United States Patent 11 1 1111 3,914,093 Proctor 51 Oct. 21, 1975 [5 COMBUSTION APPARATUS 2,121,802 6/1938 Kleist et al 239/428 2,713,510 7/1955 Coanda 239/428 [75] gggzgg Bumham 3,807,940 4/1974 Juricek 431/202 [73] Assignee: Flaregas Engineering Limited, West Primary Examiner-Carroll B. Dority, Jr.

Drayton, England Attorney, Agent, or Firm-Thompson, Birch, Gauthier [221 Filed: Jan. 9, 1974 Samuels [21] Appl. No.: 431,903 [57] ABSTRACT [30] Foreign Application priority Data Combustion apparatus usable in a ground flare and employing discharge means, such as a nozzle, for emit- 1973 Umted Kmgdom "2626/73 ting a combustible waste gas into the inlet of an air inducing device. The air inducing device is fed with an [52] X 8 inducing medium, preferably steam, which causes air [51] Int Cl 2 F23}; 1/08. F531) 13/40 to be induced into the inlet to mix with the waste gas. [58] Fieid 431/205 354 4 89 The air inducing device then preferably emits a mix- 239,428 417 4l7/l83 1 ture of air, gas and steam for combustion. To ensure that the combustion process is substantially smokeless, control is effected by varying the distance between the [56] References Cited outlet of the discharge means and the inlet of the air UNITED STATES PATENTS inducing device 1,711,982 51929 A t l ..431354 1,807,178 511931 2391428 13 Clams 5 Drawmg I U.S. Patent Oct. 21, 1975 Sheet 1 of2 3,914,093

F/az I US. Patent Oct. 21, 1975 Sheet20f2 3,914,093

VALVE POSITION L SIGNAL COMBUSTION APPARATUS BACKGROUND OF THE INVENTION The present invention relates to apparatus for mixing air with waste gas subsequently disposed of by combustion. The apparatus is particularly, but not solely, intended for use with ground flares.

SUMMARY OF THE INVENTION According to the invention there is provided apparatus for mixing air with waste gas for combustion; said apparatus comprising means for discharging waste gas, an air inducing device with an inlet for receiving the discharged waste gas and air induced into the device and means for varying the distance between the inlet of the air inducing device and the dishcarge means.

The air inducing device preferably operates on the Coanda effect and preferably uses steam as an inducing medium so that the device discharges a mixture of air, waste gas and steam into a combustion zone. The air and steam are intended to ensure that the waste gas burns substantially smokelessly.

The discharge means can be a simple nozzle and it has been found that by the provision for the adjustment of the distance between the air inducing device and the nozzle, the apparatus can be effectively controlled to cope with variations in gas pressure, in gas flow rate and in the molecular weight of the gas to ensure substantially smokeless combustion under various conditions. The apparatus can employ air inducing devices and nozzles of various sizes. In practice, variation of the aforesaid distance causes the suction pressure at the inlet of the air inducing device to vary with the result that a greater or smaller quantity of air enters the device per unit time. It has been found that the apparatus will perform satisfactorily over a wide range of variation in the pressure of the inducing medium provided this pressure exceeds a minimum threshold value.

Instead of moving the air inducing device and/or the discharge means, e.g., the nozzle, bodily the discharge means can take the form of a nozzle having a slidably movable insert which provides the outlet therefrom.

The distance variation means can take a variety of forms, discussed hereinafter, operated manually or automatically. A control/system can be provided so that variation in the aforesaid distance is made automati cally dependent on one or more of the parameters associated with the waste gas such as its pressure.

In a preferred form the air inducing device has a body with a bore of aerofoil section extending between the inlet and outlet of the device. An internal Coanda annulus is provided over which the inducing medium is caused to flow to induce air to enter the inlet with the gas.

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

BRIEF DESCRIPTION OF DRAWINGS Embodiments of the invention will now be described by way of examples only, with reference to the accompanying drawings, wherein:

FIG. 1 is a diagrammatic view of an apparatus to which the invention relates;

FIG. 2 is a longitudinal sectional view of the air inducing device. used in the apparatus depicted in FIG. 1;

FIG. 3 is a diagrammatic view of an apparatus made in accordance with the invention;

FIG. 4 is a diagrammatic part-sectional view of a further form of. apparatus made in accordance with the invention; and

FIG. 5 is a schematic representation of a control system for use with apparatus made in accordance with the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring initially to FIG. 1, the apparatus is composed of an air inducing device generally designated 10 and a nozzle unit generally designated 15. The device 10 has an inlet 11 for receiving an inducing medium, usually steam, from a flexible pipe. The effect of the steam is to cause surrounding air to be induced into the main inlet 14 of the device 10. The movement of the air is represented by arrows A. The nozzle unit 15 has a nozzle proper 12 which discharges waste gas denoted G, from its upper end 17 into the inlet 14 of the device 10. The units 15 preferably incorporates a non-return valve 13 for the waste gas. The mixture of waste gas and air entering the inlet 14 mixes with the steam in the device 10 so that the latter discharges from its outlet 16 a mixture of waste gas, air and steam designated K. This mixture K is subsequently combusted in known manner such as in a ground flare and the presence of the air and steam is designed to effect clean combustion, i.e., without smoke. In accordance with the invention it has been found that the operation of the apparatus can be optimized by adjusting the position between the upper end 17 of the nozzle 12 and the inlet 14 of the device 10 as represented by arrows X-X. Depending on the various parameters involved the optimal distance between the end 17 of the nozzle 12 and the inlet 14 can take a whole range of values even including negative values where the end 17 is disposed within the inlet 14.

The nozzle 12 may be in the form of a simple pipe connected to a supply of the waste gas. A preferred form of inducing device is shown in FIG. 2, where like reference numerals denote like parts to FIG. 1. The device 10 has a body 20 with a central bore 21 of aerofoil section communicating with the inlet 14. The device 10 has a central Coanda annulus denoted 22. Steam introduced into a chamber 23 via the inlet 11 is caused to flow over the annulus 22 and thereby to induce air to enter the inlet 14. The mixture of air, waste gas and steam flows through the bore 21 to the outlet 16. The induction of air in this manner is known as the Coanda effect.

For a device with a six inch diameter inlet operated with a constant steam pressure of 50 p.s.i., it has been found that a change in the distance between the end 17 of the nozzle 12 and the inlet 14 of the device 10 over the range 1 to +3 inches, i.e., from an insertion of the nozzle 12 in the inlet 14 of one inch to a gap of three inches gave a variation in suction at the inlet 14 of from about 1 to 7 inches water gauge.

There are various ways in which the distance between the outlet 17 of the nozzle 12 and the inlet 14 of the device 10 can be adjusted and FIG: 3 depicts one form of adjusting mechanism where like reference numerals denote like parts to FIG. 1. As shown in FIG. 3, the nozzle 12 supports a cross-piece 30 connected to two guide rods 31. The device 10 is carried by a further cross-piece 32 which has bores or apertures therein slidably receiving the rods 31. Clamping members 33 enable the crosspiece 32 to be clamped to the rods 31 at any desired position. To re-adjust the distance between the end 17 of the nozzle 12 and the inlet of the device 10, the members 33 are loosened and the crosspiece 32 moved along the rods 31 to the new position whereat the members 33 are re-tightened.

Instead of an essentially manual form of adjusting mechanism an automatic mechanism is also envisaged. For example a piston and cylinder unit may be coupled between the device and the nozzle unit 15. This piston and cylinder unit could be double-acting although it is preferred to use a single acting unit and to bias the piston of this unit with a spring which acts against the fluid pressure and tends to restore the piston to a set position. A pressure operated unit incorporating a flexible diaphragm which is moved by fluid pressure against the force of a spring can also be used in a similar manner to the piston and cylinder unit.

However, it is not necessary for the nozzle unit and/or the device 10 to move bodily and FIG. 4 depicts an alternative form of apparatus where the nozzle 12 has a displaceable insert. In FIG. 4 like reference numerals are again used to denote features described earlier. As shown in FIG. 4 the nozzle 12, or the main body of the nozzle unit 15, is rigidly affixed to the device 10 by means of a bracket 41. An insert 42 is provided at the end of the body 40. The insert 42 fits within the body 40 and is capable of sliding longitudinally thereof. The insert 42 has a groove 43 accommodating an O- ring 44 made for example of nitrile which provides sealing between the outer surface of the portion of the insert 42 which locates in the body 40 and the inner surface of the body 40. The upper end 17 of the nozzle 12 is thus constituted by the upper end of the insert 42 and by sliding the insert 42 into or out from the body the distance XX can be varied as before. The insert 42 is depicted as having a flange 45 which engages on the upper end of the body 40 when the insert 42 is fully retracted into the body 40. The movement of the insert 42 can be accomplished by forces acting on this flange 45. In practice, the means for moving the insert 42 can be in the form of a cam connected via a mechanical linkage to an actuator or a system of cables, a pneumatic or hydraulic piston and cylinder unit or an electro-magnetic device.

In certain applications, such as in ground flares, where several apparatuses of the aforementioned kind are employed it may be desirable to synchronize the adjustment of the relative position of the device 10 and unit 15 of each apparatus. Where piston and cylinder units are provided to effect the adjustment then it is quite easy to feed the pressure fluid to all the units in common or to use one unit to adjust several apparatuses by means of the cables or cam linkage just mentioned.

In a plant installation it may also be desired to employ an automatic adjustment which forms part of a servo-control sequence and is dependent on some parameter change. For example it is possible to adjust the distance between the end 17 of the nozzle 12 and the inlet 14 of the device 10 in dependence on any change in the pressure or flow rate of the waste gas. FIG. 5 depicts one example of an automatic control system.

As shown in FIG. 5, a plurality of nozzle units 15, here represented as two simple nozzles 12, are installed in a ground flare and are fed with waste gas from a manifold which may be disposed below ground.

Each nozzle 12 directs waste gas into an associated air inducing device 10 and as described hereinbefore the devices 10 each discharge a mixture of waste gas air and steam, denoted K, into a combustion zone. The devices 10 are movable to vary the distance between their inlets and the outlets of their associated units 15 as represented by the arrows X-X. In this example the devices 10 move in unison and are supported by a common support member 51, which can be guided by means not shown and which can be moved by a cam 52 to effect a change in the aforesaid distance. This cam 52 is connected via a linkage 53 to the piston rod 67 of a unit 54. This unit 54 employs a flexible diaphragm 65 which can be moved against the force of a spring 66 by pressure fluid to extend the piston rod 67 and hence actuate the cam 52. The pressure fluid fed to the unit 54 is derived by means of a control system which is sensitive to variation in the pressure of the waste gas. As shown, the pressure of the waste gas in the manifold 50 is converted in a unit 55 to a proportional analogue electrical current which is fed to a control unti 56. This control unit 56 has provision for a manual overide facility which enables an operator to effect manual control of the system. The unit 56 may employ an amplifier and the manual control may effect variation in the gain of this amplifier.

The units 56 also has a meter, or some other visual indicator, which enables an operator to determine the operational properties of the control system.

The unit 56 feeds a further convertor unit 57 which receives pneumatic pressure from a source S via a pressure reducing unit 58. The electrical current input to the unit 57 is converted to a corresponding output pressure which is fed via a booster unit 59 to the unit 54. When the unit 56 is set to automatic control any variation in the pressure of the waste gas will cause the devices 10 to be moved to compensate the maintain the optimum level of clean combustion.

I claim:

1. In an apparatus for mixing air with waste gas for combustion, said apparatus having means for discharging waste gas and having a separate air inducing device which operates in the manner known as Coanda Effect, said air inducing device being axially spaced from said discharge means, said air inducing device having a main inlet for receiving the waste gas emitted by said discharging means together with air induced into said device; the improvement comprising means for varying the distance between the main inlet of the air inducing device and the discharging means whereby to control mixing and combustion.

2. Apparatus according to claim 1, wherein an inducing medium is fed to the device to induce air into said main inlet.

3. Apparatus according to claim 2, wherein steam is used as an inducing medium and the device has an outlet which, in operation, discharges a mixture of waste gas, air and steam into a combustion zone.

4. Apparatus according to claim 3, wherein the air inducing device has a bore of aerofoil section extending between its outlet and inset and an internal Coanda annulus over which the inducing medium is made to flow to induce said air into the inlet.

5. Apparatus according to claim 1, wherein the discharging means is a nozzle.

6. Apparatus according to claim 1 wherein the distance-varying means is manually operable.

7. Apparatus according to claim 1 wherein the distance-varying means is operated automatically by a control system.

8. Apparatus according to claim 7, wherein the control system is adapted to operate the distance-varying means in accordance with changes in the pressure of the waste gas.

9. Apparatus according to claim 5, wherein the nozzle is provided with an insert which is displaceable longitudinally of the nozzle to effect said distance variation.

10. Apparatus according to claim 1 wherein the distance-varying means at least includes a piston and cylinder unit.

11. In an apparatus for mixing air with waste gas for combustion, said apparatus having means for discharging waste gas and having a separate air inducing device which operates in the manner known as the Coanda Effect, said air inducing device having a main inlet for receiving the waste gas emitted by said discharging means together with air induced into said device, the improvement therein comprising: means for varying the distance between said main inlet and said discharging means to control mixing and combustion, and a control system for automatically operating said distance varying means, said control system operating in accordance with changes in the pressure of the waste gas.

12. In an apparatus for mixing air with waste gas for combustion, said apparatus having means for discharging waste gas and having a separate air inducing device which operates in the manner known as the Coanda Effect, said air inducing device having a main inlet for receiving the waste gas emitted by said discharging means together with air induced into said device, the improvement therein comprising: means for varying the distance between said main inlet and said discharging means to control mixing and combustion, said discharging means including a nozzle, said nozzle having a longitudinally displaceable insert to effect said distance variation.

13. In an apparatus for mixing air with waste gas for combustion, said apparatus having means for discharging waste gas and having a separate air inducing device which operates in the manner known as the Coanda Effect, said air inducing device having a main inlet for receiving the waste gas emitted by said discharging means together with air induced into said device, the improvement therein comprising: means for varying the distance between said main inlet and said discharging means to control mixing and combustion, said distance varying means including a piston and cylinder unit.

Claims

1. IN AN APPARATUS FOR MIXING AIR WITH WASTE GAS FOR COMBUSTION, SAID APPARATUS HAVING MEANS FOR DISCHARGING WASTE GAS AND HAVING A SEPERATE AIR INCLUDING DEVICE WHICH OPERATES IN THE MANNER KNOWN AS COANDA EFFECT, SAID AIR INDUCING DEVICE BEING AXIALLY SPACED FROM SAID DISCHARGE MEANS, SAID AIR INDUCING DEVICE HAVING A MAIN INLET FOR RECEIVING THE WASTE GAS EMITTED BY SAID DISCHARGE MEANS TOGETHER WITH AIR INDUCED INTO SAID DEVICE, THE IMPROVEMENT COMPRISING MEANS FOR VARYING THE DISTANCE BETWEEN THE MAIN INLET OF THE AIR INDUCING

5. Apparatus according to claim 1, wherein the discharging means is a nozzle.