Note: Descriptions are shown in the official language in which they were submitted.
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LINEAR COANDA FLARE METHODS AND APPARATUS
BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
(0001] The present invention relates to linear Coanda flare apparatus and
methods of
burning waste flammable gas in the apparatus.
2. DESCRIPTION OF THE PRIOR ART
[0002] High pressure Coanda flares have been utilized in the oil and gas and
petro-
chemical industries for many years. The flares include a Coanda body having a
surface
shape similar to a pot that has an enlarged round bottom and a smaller
circular top. The
Coanda bodies utilized heretofore have been formed from castings or forgings.
[0003) The prior art Coanda flares include a Coanda body attached to the top
of a
vertical pipe whereby a circular slot is formed between the top of the pipe
and the bottom of
the Coanda body. Pressurized waste flammable gas exits the slot at a velocity
that creates
low pressure regions at the boundaries of the gas stream. The space between
the Coanda
body and the gas stream is quickly evacuated by the low pressure which forces
the waste
gas to attach to the Coanda surface and follow its form until it has turned
through
approximately 90°.
[0004] The normal operating range is at sonic velocity and many small eddies
are
formed whereby at any point in the gas stream, the velocity is greater than
the linear
velocity of the overall stream. In addition, the linear velocity is greater
than a conventional
jet at the same distance from the gas exit. This increases the low pressure
region at the film
boundary thereby increasing air entrainment efficiency. As the gas and air
reach the
maximum diameter of the Coanda body surface, the inherent turbulence provides
effective
mixing of the gas and air thereby producing a very stable and efficient flare
device.
(OOOSj When the fuel pressure at the Coanda slot is about 11 psig, the fuel
velocity at
the slot becomes sonic. The relationship between gas flow rate and Coanda slot
exit
pressure becomes linear once sonic exit velocity is achieved and the only way
to increase
capacity is to increase either the gas pressure or the Coanda slot area. As a
result, in order
to achieve higher capacities, larger diameter flares with larger Coanda
bodies, slots and
surfaces are required which become very heavy and costly.
(0006] In some cases, the waste flammable gas pressure in a Coanda flare is
limited by
the process involved and by the geometry of the flare. Once a certain pressure
is attained,
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the mass flow achieves a critical level whereby there is such momentum in the
gas film
passing over the Coanda surface that the flame detaches from the Coanda
surface and the
Coanda effect is lost.
(0007] Thus, there is a need for improved high pressure flares which utilize
the Coanda
effect, that do not have the disadvantages mentioned above and instead have
the advantages
of a robust long life design, low radiation, low weight, high smokeless
turndown, wide
operating range, low purge rate requirement and a stable flame in all
conditions.
SUMMARY OF THE INVENTION
[0008] The present invention provides a linear Coanda flare apparatus for
burning
pressurized waste flammable gas which overcomes the deficiencies of the prior
art and
meets the needs described above. A linear Coanda flare apparatus for burning
pressurized
waste flammable gas of this invention comprises the following elements. An
elongated
closed end pipe is connected to a waste flammable gas supply pipe. The
elongated closed
end pipe has an elongated linear opening therein, and an elongated flammable
gas
distributor trough is positioned adjacent to the elongated linear opening. The
sides of the
distributor trough are positioned adjacent to the outer curved surfaces of the
closed end pipe
thereby forming slots that discharge pressurized waste flammable gas over the
outer curved
surfaces of the closed end pipe.
[0009] A method of burning waste flammable gas of this invention comprises the
following steps. The waste flammable gas is conducted to a linear Coanda flare
apparatus
comprising a waste flammable gas supply pipe connected to an elongated closed
end pipe
having an elongated linear opening therein. The waste flammable gas is
discharged through
the elongated linear opening into an elongated flammable gas distributor
trough positioned
adjacent to the elongated linear opening. The elongated sides of the
distributor trough are
positioned adjacent to the outer curved surfaces of the closed end pipe
thereby forming
elongated discharge slots. The waste flammable gas is discharged through the
elongated
discharge slots over the curved surfaces of the closed end pipe. The waste
flammable gas is
ignited by a pilot light positioned adjacent to the closed end pipe.
(0010] The features and advantages of the present invention will be readily
apparent to
those skilled in the art upon a reading of the description of preferred
embodiments which
follows when taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a side, partly sectional view of a prior art Coanda flare.
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[0012) FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1.
[0013] FIG. 3 is a side view of one form of the linear Goanda flare apparatus
of the
present invention.
[0014] FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 3.
[0015] FIG. 5 is a side cutaway view of another form of the linear Coanda
flare
apparatus of the present invention.
[0016] FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 5
illustrating a
spring assembly attached to the bottom of the distributor trough and attached
to the closed
end pipe.
[0017] FIG. 7 is a cross-sectional view similar to FIG. 6, but illustrating a
spring
assembly attached inside the flare apparatus and attached to the distributor
trough.
[0018] FIG. 8 is another cross-sectional view similar to FIG. 6, but
illustrating the
spring assembly attached to the top of the closed end pipe and attached to the
distributor
trough.
[0019] FIG. 9 is a cross-sectional view of a linear Coanda flare apparatus
similar to
FIG. 4, but illustrating the elongated closed end pipe and the distributor
trough positioned at
an angle.
[0020] FIG. 10 is a side view of a linear Coanda flare apparatus similar to
FIG. 5, but
illustrating the closed end pipe and distributor trough positioned at an
angle.
[0021] FIG. 1I is a cross-sectional view of two linear Coanda flare
apparatuses
positioned close together having elongated closed end pipes formed in tear
drop cross-
sectional shapes.
[0022] FIG. 12 is a side view of a linear Coanda flare apparatus of the
present invention
including means for injecting water into the gas stream flowing through the
elongated
closed end pipe.
[0023] FIG. 13 is a side view of a linear Coanda flare apparatus of the
present invention
including means for injecting water into the flame produced by the flare
apparatus.
(0024] FIG. 14 is a perspective view of a linear Coanda flare apparatus of
this invention
comprised of a single closed end pipe and distributor connected to a waste
flammable gas
supply pipe.
[0025] FIG. 15 is a perspective view similar to FIG. 14 but including two
closed end
pipes and distributors attached to a waste flammable gas supply pipe.
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(0026] FIG. 16 is a perspective view of four elongated closed end pipes and
distributors
connected to a waste flammable gas supply pipe.
[0027] FIG. 17 is a perspective view of six closed end pipes and distributors
connected
to a waste flammable gas supply pipe.
[0028] FIG. 18 is a perspective view of an alternate arrangement of four
closed end
pipes and distributors connected to a waste flammable gas supply pipe.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0029] Referring now to the drawings, and particularly to FIGS. 1 and 2, a
prior art
Coanda flare 10 is illustrated having an upstanding waste flammable gas supply
pipe I2 and
a Coanda body 14 attached to the top of the supply pipe 12. A circular slot 16
is provided
between the top of the pipe 12 and the bottom of the Coanda body 14 through
which
pressurized waste flammable gas flows at high velocity. The gas follows the
Coanda
surface until it has turned through approximately 90° thereby producing
a very stable and
efficient flare device. However, in order to achieve higher capacities, larger
diameter waste
flammable gas supply pipes, larger Coanda slots and larger Coanda bodies are
required
which are heavy and costly.
[0030] Referring now to FIGS. 3 and 4, one form of the linear Coanda flare
apparatus of
the present invention is illustrated and designated by the numeral 18. The
linear Coanda
flare apparatus 18 comprises an elongated closed end pipe 20 connected to a
waste
flammable gas supply pipe 22. The top open end of the supply pipe 22 is
positioned within
the closed end pipe 20, as is shown best in FIG. 4. Elongated linear openings
24 are
provided in the bottom of the closed end pipe 20 extending on both sides of
the supply pipe
22.
[0031] An elongated flammable gas distributor trough 26 is attached to the
bottom of
the elongated closed end pipe 20 adjacent to the linear opening 24. The
elongated sides of
the distributor trough 26 are positioned adjacent to the outer curved surfaces
of the closed
end pipe 20 thereby forming slats 27 that discharge pressurized waste
flammable gas from
inside the closed end pipe 20 over the outer curved surfaces of the closed end
pipe 20. The
pressurized waste flammable gas attaches to the pipe surface and follows its
form until it
has turned through approximately 90°. The gas is ignited by a pilot
light 28 positioned
adjacent to the closed end pipe.
[0032] The linear Coanda flare apparatus 18 described above has the following
advantages. The closed end pipe 20 and waste flammable gas supply pipe 22 are
formed of
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light weight steel and no special high cost castings or forgings are required
thereby reducing
costs and weight. The capacity of the linear Coanda flare apparatus 18 can be
increased
simply by extending the lengths of the closed end pipe 20, the linear openings
24 and the
distributor trough 26.
[0033] The performance of the linear Coanda flare apparatus of this invention
is
enhanced by maintaining narrow slots between the sides of the distributor
trough 26 and the
closed end pipe 20 which improve air entrainment, mixing and maximum operating
pressure. The waste flammable gas fed through the supply pipe 22 flows through
the closed
end pipe 20 thereby providing cooling to the flare apparatus 18. The path of
the waste
flammable gas restricts the ability of air to enter the flare apparatus 18
thereby mitigating
the risk of internal burning and reducing purge gas requirements. The waste
flammable gas
supply pipe 22 can be arranged centrally as shown in the drawings or at either
end of the
elongated closed end pipe 20 or at any location in between. The elongated
flammable gas
distributor trough 26 which forms the fuel exit slots 27 can be of various
shapes including,
but not limited to, a flat bottom trough with outwardly slanted sides, a semi-
circular trough,
a partial circular trough, a V-shaped trough and the like. The gas distributor
trough can be
arranged to be fixed in one position or it can be spring loaded to form
variable fuel exit slots
which open without increasing pressure to a set maximum as will be described
further
herein below.
(0034] The linear Coanda flare apparatus 18 can be arranged to fire at an
angle by
rotating the closed end pipe containing the elongated linear openings 24 and
the elongated
flammable gas distributor trough 26. In many cases, radiation and noise must
be reduced in
sensitive areas adjacent to flares or due to space requirements. That is, the
flares must be
moved or angled to a particular direction. Refernng to FIGS. 4, 5, 9 and 10,
this can be
accomplished in a horizontal flare 18 or 30 of this invention by simply
rotating the
elongated closed end pipes 20 or 32 and distributor troughs 26 or 38 to an
angle whereby
the flame is directed awav from the sensitive area as shown in FIG. 9. When
required. the
elongated closed end pipe 32 can also be moved upright as shown in FIG. 10.
[0035] Referring now to FIGS. 5-8, an alternate arrangement of the linear
Coanda flare
apparatus of this invention is illustrated and generally designated by the
numeral 30. The
linear Coanda flare apparatus 30 comprises a closed end pipe 32 having an
elongated linear
opening or a series of linear openings 34 in the bottom thereof. A waste
flammable gas
supply pipe 36 is connected to one end of the closed end pipe 32 by welding or
other means.
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An elongated waste flammable gas distributor trough 38 is provided adjacent to
the
elongated linear opening or openings 34 at the bottom of the closed end pipe
32. The
distributor trough 38 is held in position below the linear opening or openings
34 by spring
assemblies 40 attached to the bottom of the flammable gas distributor trough
38 and to the
closed end pipe 32 by elongated bolts or rods 42. In addition, spring loaded
seal plate
assemblies 45 are attached to the elongated closed end pipe 32 which exert
pressure on the
ends of the distributor trough 38 to prevent waste flammable gas from escaping
through the
ends of the distributor trough 38. A pilot light 41 is provided to ignite the
discharged waste
flammable gas.
(0036] In operation of the linear Coanda flare apparatus 30, waste flammable
gas enters
the apparatus 30 by way of the waste flammable gas supply pipe 36 and flows
into the
elongated closed end pipe 32. From the closed end pipe 32, the gas passes
through the slot
or slots 34 into the elongated flammable gas distributor trough 38. From the
distributor
trough 38, the gas flows through the side slots 43 formed between the sides of
distributor
trough 38 and the closed end pipe 32 and then adjacent to the curved surfaces
of the closed
end pipe 32 where it entrains and mixes with ambient air in proportions to
create a
smokeless and low radiation flame.
[0037] As the gas flows through the elongated flammable gas distributor trough
38, it
applies or reduces pressure on the distributor trough 38 which in turn applies
or reduces
load on the spring assemblies 40 thereby compressing or decompressing the
springs in the
spring assemblies 40 and moving the distributor trough 38 away from or closer
to the closed
end pipe 32. The movement away from or closer to the closed end pipe 32
increases or
decreases the widths of the gas exit slots 43 between the closed end pipe 32
and the
distributor trough 38 thereby allowing greater or lesser gas flow onto the
surface of the
closed end pipe 32.
[0038] The variation in the width of the slots 43 not only regulates gas flow
and
pressure. it also serves to continuously maintain a high velocitv at the gas
slots which in
turn restricts the amount of air that can ingress into the distributor trough
by high wind
pressure. A narrow slot at low gas flows and pressure causes even distribution
of gas along
the slot thereby ensuring localized burning and preventing hot spots.
(0039] Referring now to FIG. 6, an enlarged side view of the closed end pipe
32, the
distributor trough 38 and the spring assembly 40 is shown. The spring assembly
40
includes an elongated threaded rod 42 that is attached to and passes through
and below the
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closed end pipe 32 and the distributor trough 38. A spring 47 is disposed
between the
bottom of the distributor trough 38 and a moveable circular plate 44 held in
position by a
nut 46 threaded on the rod 42. The nut 46 can be moved up or down to adjust
the
compression of the spring 47. A second circular plate 48 is disposed on the
rod 42 and a
second nut 50 is disposed on the threaded rod 42 below the plate 48. The
second nut 50 is
utilized to adjust the distance between the bottom of the closed end pipe 32
and the sides of
the distributor trough 38, i.e., the slots 43.
[0040] FIG. 7 illustrates an alternate arrangement wherein the spring assembly
52 is
mounted within the closed end pipe 32 and is used to adjust the position of
the distributor
trough 3 8.
[0041] FIG. 8 illustrates another spring assembly arrangement wherein a spring
assembly 54 is mounted on top of the closed end pipe 32 and is used to adjust
the spring
tension and location of the distributor trough 38.
[0042] While all of the spring assembly arrangements illustrated in FIGS. 6, 7
and 8 can
be utilized, the spring arrangement illustrated in FIG. 7 is generally
preferred for the reason
that the spring assembly located within the closed end pipe is cooled by the
flow of the cool
flammable gas flowing through the pipe and is out of the flame zone at all
times. As will be
understood by those skilled in the art, a variety of spring assembly
arrangements can be
utilized other than those described above.
[0043] In many refinery and other industrial plants, flare systems are
required that must
handle large ranges of gas compositions and capacities which require multiple
staged flares
and systems. The multiple flares and systems require costly piping and valves
that switch
on and off the multiple flares to insure maximum performance over the
operating range of
the flares.
[0044] The linear Coanda flare apparatus of the present invention can include
multiple
or elongated pipes connected to a waste flammable gas supply pipe. The
multiple or
elongated pines can have multirle linear openings therein and multiple gas
distributor
troughs having spring assemblies set to operate at different pressures. As the
gas pressure
increases, the various gas distributor troughs open in sequence. This ensures
that each part
of the flare apparatus operates above its critical pressure at all flow rates
thereby ensuring
optimum performance at all times.
[0045] As illustrated in the drawings, the linear Coanda flare apparatus of
this invention
utilizes ordinary cylindrical pipe as the elongated closed end pipe having
elongated linear
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openings therein. The pressurized waste flammable gas discharged through the
slots formed
by the cylindrical pipe and the sides of the distributor trough flows over the
outer curved
surfaces of the closed end pipe and follows the curved surfaces until it has
turned through
approximately 90 degrees, i.e., the curved surfaces of the closed end pipe
bring about the
"Coanda effect." The cylindrical pipe is inexpensive as compared to the Coanda
bodies
used heretofore and the pipe can be utilized in any desired flare length or
position.
[0046] Referring now to FIG. 11, in certain applications such as when two or
more
linear Coanda flare apparatus are located very close together, aerodynamic
shaped closed
end pipes 56 can be utilized to provide better air distribution and flare
performance. When
required, other shapes of closed end pipes can also be used. However, the use
of cylindrical
closed end pipes is preferred.
[0047] The introduction of water into the waste gas stream or into the flame
produced
by a flare apparatus of this invention is some times required to reduce noise
and/or
radiation. As shown in FIG. 12, the water can be introduced into the closed
end pipe to
reduce noise, and as shown in FIG. 13, the water can be introduced into the
flame above the
closed end pipe to reduce radiation.
[0048] Refernng now to FIGS. 14-18, various arrangements of the linear Coanda
flare
apparatus of this invention connected to waste gas supply pipes are
illustrated. As shown,
up to six or more closed end pipes 32 can be connected to a single waste
flammable gas
supply pipe.
[0049] In ground flare applications, the linear Coanda flare apparatus of this
invention is
ideal in that it can be as long as 40 to 50 feet in one continuous run of a
relatively small
diameter with the fuel being fed from one end instead of from the bottom.
[0050] Regardless of the particular application in which the linear Coanda
flare
apparatus of this invention is utilized, the flare apparatus will produce a
very large heat
release from a relatively small flare tip.
[0051] A preferred linear Coanda flare apparatus of this invention for burning
pressurized waste flammable gas comprises: an elongated closed end pipe
connected to a
waste flammable gas supply pipe, the elongated closed end pipe having an
elongated linear
opening therein; and an elongated flammable gas distributor trough positioned
adjacent to
the elongated linear opening in the closed end pipe with the sides of the
distributor trough
positioned adjacent to the outer curved surfaces of the closed end pipe
thereby forming slots
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that discharge pressurized waste flammable gas from inside the closed end pipe
over the
outer curved surfaces of the closed end pipe.
[0052] A preferred method of burning waste flammable gas of this invention
comprises
the steps of: (a) conducting the waste flammable gas to a Coanda flare
apparatus
comprising a waste flammable gas supply pipe connected to an elongated closed
end pipe
having an elongated linear opening therein; (b) discharging the waste
flammable gas
through the elongated linear opening into an elongated flammable gas
distributor trough
positioned adjacent to the elongated linear opening, the elongated sides of
the distributor
trough being positioned adjacent to the outer curved surfaces of the closed
end pipe thereby
forming elongated discharge slots; (c) discharging the waste flammable gas
through the
elongated discharge slots over the curved surfaces of the closed end pipe; and
(d) igniting
the waste flammable gas.
[00S3] Thus, the present invention is well adapted to carry out the objects
and attain the
ends and advantages mentioned as well as those inherent therein. While
presently preferred
embodiments of the invention have been described for purposes of this
disclosure,
numerous changes in the arrangement and construction of parts will suggest
themselves to
those skilled in the art, which changes are encompassed within the spirit of
this invention as
defined by the appended claims.
