U.S. patent application number 14/266972 was filed with the patent office on 2014-11-06 for apparatus and method for minimizing smoke formation in a flaring stack.
This patent application is currently assigned to UOP LLC. The applicant listed for this patent is UOP LLC. Invention is credited to Jay D. Jennings, Richard R. Martin, Donnie Dee McClain.
Application Number | 20140329189 14/266972 |
Document ID | / |
Family ID | 51841577 |
Filed Date | 2014-11-06 |
United States Patent
Application |
20140329189 |
Kind Code |
A1 |
McClain; Donnie Dee ; et
al. |
November 6, 2014 |
APPARATUS AND METHOD FOR MINIMIZING SMOKE FORMATION IN A FLARING
STACK
Abstract
An apparatus and method for minimizing smoke formation in the
operation of a flaring stack. The apparatus includes a generally
annular gas deflector having an outer surface for deflecting the
waste gas therealong. A plurality of lobes extend radially from the
deflector to provide improved mixing between the waste gas, steam,
and combustion air during combustion to reduce smoke formation.
Inventors: |
McClain; Donnie Dee; (Round
Rock, TX) ; Martin; Richard R.; (Tulsa, OK) ;
Jennings; Jay D.; (Broken Arrow, OK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UOP LLC |
Des Plaines |
IL |
US |
|
|
Assignee: |
UOP LLC
Des Plaines
IL
|
Family ID: |
51841577 |
Appl. No.: |
14/266972 |
Filed: |
May 1, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61819173 |
May 3, 2013 |
|
|
|
Current U.S.
Class: |
431/202 ;
110/161 |
Current CPC
Class: |
F23J 2213/50 20130101;
F23G 7/085 20130101; F23J 13/08 20130101 |
Class at
Publication: |
431/202 ;
110/161 |
International
Class: |
F23G 7/08 20060101
F23G007/08 |
Claims
1. An apparatus for minimizing the formation of smoke in the
operation of a flaring stack, the apparatus comprising: a support
arm having a generally hollow waste gas passageway for connection
to a waste gas source; a generally annular gas deflector having an
outer surface for deflecting waste gas; a waste gas outlet between
the gas deflector and the support arm; a steam distributor for
distributing steam; an outlet of the steam distributor configured
to direct steam along the outer surface of the gas deflector; and a
plurality of lobes extending generally radially from the gas
deflector outer surface for providing improved mixing between the
steam, waste gas, and combustion air during combustion.
2. The apparatus of claim 1, wherein the gas deflector includes a
tulip-shaped Coanda bowl.
3. The apparatus of claim 1, wherein the lobes include
circumferentially spaced generally vertical ribs extending radially
from the outer surface of the gas deflector.
4. The apparatus of claim 3, wherein the steam distributor includes
an annular outlet positioned about the annular gas deflector for
directing steam therealong.
5. The apparatus of claim 4, wherein the steam distributor annular
outlet includes a plurality of circumferentially spaced openings
positioned about the annular gas deflector.
6. The apparatus of claim 5, wherein the openings are generally
aligned with the ribs.
7. The apparatus of claim 5, wherein the openings are generally
aligned with channels formed between the ribs.
8. The apparatus of claim 4, wherein the waste gas outlet includes
a generally annular outlet positioned radially outwardly of the
steam distributor.
9. The apparatus of claim 3, wherein a ratio of a perimeter of a
ribbed portion of the bowl to an outer diameter of the ribbed
portion is between about 6.5 and about 20.
10. The apparatus of claim 3, wherein the ribs are tapered radially
with respect to the outer surface from a generally lower rib
portion flush with the outer surface to a raised rib portion above
the outer surface.
11. The apparatus of claim 3, wherein the ribs include inclined
sidewalls extending from channels between the ribs to upper raised
rib portions.
12. An apparatus for minimizing the formation of smoke in the
operation of a flaring stack, the apparatus comprising: a support
arm having a generally hollow waste gas passageway for connection
to a waste gas source; a generally annular gas deflector having an
outer surface for deflecting waste gas; a waste gas outlet between
the gas deflector and the support arm; a steam distributor for
distributing steam; a plurality of circumferentially spaced
generally vertical ribs extending radially from the gas deflector
outer surface for providing improved mixing between the steam,
waste gas, and combustion air during combustion; and a generally
annular outlet of the steam distributor configured to direct steam
along the outer surface of the gas deflector.
13. The apparatus of claim 12, wherein the support arm includes a
steam passageway positioned within the waste gas passageway.
14. The apparatus of claim 12, wherein the steam distributor
includes a steam chamber and the steam chamber outlet includes
plurality of upper openings.
15. The apparatus of claim 14, wherein the steam chamber includes
an inverted generally hollow frustoconical member with the upper
openings about an upper portion thereof
16. The apparatus of claim 14, wherein the steam chamber upper
openings include a notched upper rim adjacent to a bottom portion
of the steam distributor.
17. The apparatus of claim 14, wherein the steam chamber upper
openings include a plurality of apertures about the upper portion
of the steam chamber.
18. The apparatus of claim 14, wherein the upper openings are
generally aligned with the ribs.
19. The apparatus of claim 14, wherein the upper openings are
generally aligned with channels between the ribs.
20. The apparatus of claim 12, wherein the waste gas outlet is
generally annular and positioned radially outwardly of the steam
distributor outlet to provide steam along the outer surface of the
gas deflector.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/819,173 filed May 3, 2013.
FIELD OF THE INVENTION
[0002] The subject application relates to an apparatus for
minimizing smoke formation in a flaring stack.
BACKGROUND OF THE INVENTION
[0003] Flare apparatus have traditionally been utilized for burning
and exhausting combustible gases. Flare apparatus are commonly
mounted on flare stacks and located at production, refining, and
processing plants for disposing of flammable waste gases or other
flammable gas streams, which are diverted for any reason, including
but not limited to venting, shut-downs, upsets, and/or emergencies.
Primarily, flare stacks are used for venting unwanted waste gas
streams from a facility.
[0004] It is generally desirable that flammable gas be burned
without producing smoke, and reduction in smoke production during
burning may be mandated by regulatory requirements.
[0005] One method that has been adopted for reducing smoke
formation during burning includes mixing the waste gas stream to be
burned with ambient air to maximize oxidation of the flammable
waste gas to prevent the production of smoke. Another method that
has been used includes supplying steam to the combustion zone, such
as, for example, by an eductor to increase oxidation to restrict
smoke formation. In some applications, ambient air and steam
introduction are used together to further reduce smoke
formation.
[0006] When sufficient ambient air and/or steam is available to
contact the combustible waste gas, the mixture may be smokelessly
burned. In typical flare apparatus, only a portion of the desired
amount of air and/or steam is present for mixing with the waste
gas.
[0007] A wide variety of apparatus and processes have been proposed
to increase the smokeless burning of combustible gas from a flare.
For example, U.S. Pat. No. 3,833,337 to Desty et al. and U.S. Pat.
No. 8,337,197 to Poe et al. propose the use of a tulip shaped
Coanda tip. Coanda tips have been used in flares with high flow
rates and pressures to cause the adherence of the waste gas to the
surface. The negative pressure and viscous forces caused by the
Coanda effect cause the fluid to be drawn against the surface in a
relatively thin film, which allows proximate fluid (e.g. ambient
air) to be mixed efficiently with the fluid stream. Poe describes
that to achieve a Coanda effect, the surface of the Coanda surface
should be substantially smooth.
[0008] While current apparatus and methods have improved the
smokeless combustion of waste gas streams, it is desirable to
further reduce the amount of smoke formation based on regulatory
and environmental considerations.
SUMMARY OF THE INVENTION
[0009] By one aspect, an apparatus is provided minimizing the
formation of smoke in the operation of a flaring stack. The
apparatus includes a support arm having a generally hollow waste
gas passageway for connection to a waste gas source. The apparatus
further includes a generally annular gas deflector having an outer
surface for deflecting waste gas and steam therealong. A waste gas
outlet is provided between the gas deflector and the support arm.
The apparatus further includes a steam distributor for distributing
steam with an outlet configured to direct the steam along the outer
surface of the gas deflector. The gas deflector includes a
plurality of lobes extending generally radially from the gas
deflector outer surface for providing improved mixing between the
steam, waste gas, and combustion air during combustion.
[0010] By another aspect, a method is provided for combusting a
waste gas to reduce the formation of smoke. The method includes
passing steam along an outer surface of a generally annular gas
deflector including a plurality of lobes extending radially
outwardly therefrom. The method includes passing the waste gas
along the outer surface of the gas deflector, including over the
plurality of lobes. The method further includes drawing ambient air
toward the outer surface for mixing with the waste gas and steam
and igniting the waste gas mixture.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a perspective view of an apparatus including a
plurality of support arms and a plurality of corresponding gas
deflectors in accordance with various embodiments;
[0012] FIG. 2 is a perspective view of a support arm of the
apparatus with a gas deflector in accordance with various
embodiments;
[0013] FIG. 3 is a cross-sectional view of the support arm of FIG.
2 with the gas deflector supported thereon in a lowered
position;
[0014] FIG. 4 is a top view of the gas deflector of FIG. 2;
[0015] FIG. 5 is a side cross sectional view of the gas deflector
of FIG. 4 taken along line A-A;
[0016] FIG. 6 is a side cross sectional view of the gas deflector
of FIG. 5 taken along line B-B;
[0017] FIG. 7 is a perspective view of a support arm of the
apparatus with a gas deflector in accordance with another
approach;
[0018] FIG. 8 is a perspective view of a steam chamber in
accordance with various embodiments;
[0019] FIG. 9 is a perspective view of a steam chamber in
accordance with other embodiments; and
[0020] FIG. 10 is a perspective view of a steam chamber in
accordance with other embodiments.
[0021] Skilled artisans will appreciate that elements in the
figures are illustrated for simplicity and clarity and have not
necessarily been drawn to scale. For example, the dimensions and/or
relative positioning of some of the elements in the figures may be
exaggerated relative to other elements to help to improve
understanding of various embodiments of the present invention.
Also, common but well-understood elements that are useful or
necessary in a commercially feasible embodiment are often not
depicted in order to facilitate a less obstructed view of these
various embodiments of the present invention. It will further be
appreciated that certain actions and/or steps may be described in a
particular order of occurrence while those skilled in the art will
understand that such specificity with respect to sequence is not
actually required. It will also be understood that the terms and
expressions used herein have the ordinary technical meaning as is
accorded to such terms and expressions by persons skilled in the
technical field as set forth above except where different specific
meanings have otherwise been set forth herein.
DETAILED DESCRIPTION
[0022] The apparatus and method presented herein, in accordance
with various aspects, relates to reducing smoke formation during
combustion of a waste gas in a flare stack. The apparatus may be
used with a flare stack, for example, at a refinery or production
facility for flaring waste gas or other gas streams to the
atmosphere. As used herein, the term "waste gas" refers to any
combustible gas stream that is combusted by the flare stack,
including, but not limited to undesired gas streams, product
streams combusted during shutdown or emergency situations, and
other streams.
[0023] Referring now to FIGS. 1 and 2, an apparatus 2 for the
combustion of a waste gas stream in accordance with various aspects
is provided. The apparatus 2 includes a gas deflector 4 for
deflecting fluid along a surface 6 thereof. The apparatus also
includes a steam distributor 7 for distributing steam along the
surface of the gas deflector. The apparatus 2 may also include a
support arm 8 for supporting the gas deflector 4 thereon. One or
both of the waste gas and the steam may be passed through the
support arm 8 to the gas deflector 4. In this regard, the support
arm 8 may have a waste gas passageway 10 and/or a steam passageway
11 formed therein, as illustrated in FIG. 3 for facilitating the
flow of the waste gas and the steam therethrough. A waste gas
outlet 12 is provided for introducing the waste gas from the waste
gas passageway 10 to the gas deflector 4. A steam outlet 13 is
provided for dispersing the steam from the steam passageway 11 to
the gas deflector 4. As illustrated in FIG. 3 and described further
below, the outlets 12 and 13 may include annular openings 14 and 15
respectively between the support arm 8 and the gas deflector 4 so
that the waste gas flows through the opening 14 and along the gas
deflector outer surface 6. By one aspect, the steam outlet 13 may
be positioned radially inwardly of the waste gas outlet 12.
[0024] The waste gas deflector includes a plurality of lobes 16
that extend radially therefrom. In this regard, as steam and waste
gas flow along the outer surface of the gas deflector 4, the steam
and gas flow over and between the lobes 16. It has been identified
that including radially extending lobes 16 on the gas deflector 4
improves mixing of the waste gas stream and the steam, and also
combustion air where present during operation of the flare stack
resulting in a reduction in the amount of smoke that is produced
during combustion. It has further been identified that including
radially extending lobes 16 as described herein provides a lower
flame temperature and reduced emissions of unwanted by-products
into the atmosphere, such as NO.sub.X. By one aspect, the lobes 16
include a plurality of generally vertically oriented ribs 18 spaced
circumferentially about the gas deflector 4 such that the steam and
gas flow along the ribs and through channels 20 formed between
adjacent ribs 18.
[0025] According to various aspects, the support arm 8 is provided
for supporting the gas deflector 4 thereon. The support arm 8 may
also include a gas passageway 10 for passing the waste gas to be
combusted from a gas source to the gas deflector 4. The support arm
may also include a steam passageway 11 for passing steam from a
steam source to the gas deflector. In one approach, as illustrated
in FIG. 1, the apparatus 2 may include a plurality of support arms
8 supporting a plurality of gas deflectors 4. In this manner, the
size of each gas deflector 4 may be decreased as opposed to having
a single large gas deflector. This may improve the ability for
smoke free combustion by increasing the amount of combustion air
available for mixing with the gas at each of the plurality of gas
deflectors 4 as opposed to a single larger gas deflector.
[0026] The support arm 8 may extend from a central plenum 22 as
illustrated in FIG. 1. As shown, one support arm 8 extends upwardly
from the top of the plenum 22 while additional support arms 8
extend at inclined angles from side portions 24 of the plenum 22
and extend generally vertically at bent portions 26 thereof In one
example, the vertical portions 28 of the support arms 8 extend
vertically at an angle of less than about 5 degrees from the
vertical, less than about 3 degrees from the vertical axis in
another example, and at less than about 1 degree from the vertical
in yet another example.
[0027] The support arm 8 may include the gas passageway 10 as
illustrated in FIG. 3 for passing the waste gas through the support
arm 8 toward the gas deflector 4. In one approach, as shown in FIG.
3, the gas passageway 10 may include a hollow passageway through
the support arm 8. In this regard, the support arm 8 may be formed
by a generally hollow tube providing the passageway 10. The tube
may be cylindrical as illustrated in FIG. 3 or other suitable
configurations.
[0028] The support arm 8 may also include the steam passageway as
illustrated in FIG. 3 for passing the steam through the support arm
8 toward the gas deflector 4. In one approach, as shown in FIG. 3,
the steam passageway 11 includes a tube or pipe 13 positioned
within the gas distributor. The tube 13 may run through a generally
central portion of the support arm 8 to form a generally annular
gas passageway 12 thereabout. The steam distributor 7 may include a
steam distribution system 29, including steam conduits external of
the support arm 8 and plenum 22 for passing the steam into the
support arm 8.
[0029] As mentioned previously, the apparatus 2 according to
various aspects includes a gas deflector 4. In one preferred form,
the gas deflector 4 includes a gas deflector bowl 36 having a
Coanda surface 38 as illustrated in the figures. The Coanda bowl 36
may have a tulip-shaped configuration as illustrated in FIG. 3
having a generally horizontal lower portion 40, a vertical or
inclined upper portion 42, and a convex portion 44 connecting the
lower portion 40 to the upper portion 42. The remainder of the
description will be made with reference with use of the Coanda bowl
36 as the gas deflector. Coanda bowls are generally known and
understood by those of skill in the art, and are known to produce a
"Coanda effect", wherein gases flowing along the outer surface
thereof tend to follow the surface forming a thin film and drawing
in surrounding gas or air. In one approach, the Coanda bowl has a
generally round cross-section taken along a plane orthogonal to a
longitudinal axis 46 of the bowl, although the bowl 36 may also
include other suitable cross-sectional configurations, for example
oval or polygonal.
[0030] By one aspect, the Coanda bowl 36 includes a plurality of
lobes 16 extending radially outwardly from its outer surface 38. As
illustrated in the figures, the lobes 16 may include a plurality of
generally vertical ribs 18 spaced circumferentially about the bowl
outer surface 38. In one approach, the ribs extend radially
outwardly from the Coanda bowl outer surface 38 (or floors 20 of
the channels). As used herein, the phrase "total outer surface"
refers to the outer surface formed along all outer surface of the
gas deflector, including by one example along the outer surfaces of
the Coanda bowl 36, ribs 18, and channels 20, such that the "total
outer surface" of a ribbed portion of the Coanda bowl 36 has a
larger surface area than the outer surface of a corresponding
Coanda bowl without ribs.
[0031] According to one approach, the ribs 18 extend generally
vertically along the Coanda bowl outer surface 38. It should be
understood that as described herein, the ribs 18 extend generally
vertically as viewed head-on and that where the upper portion 42 of
the bowl 36 is inclined as illustrated in FIG. 5, the vertically
extending ribs may similarly be inclined toward the longitudinal
axis 46 of the bowl 36 when viewed from profile (i.e. 90 degrees
from head-on as shown by the side-cross section of FIG. 5). With
this in mind, by one approach, the ribs have a generally vertical
axis 48 when viewed head-on as shown in FIG. 2 that is less than
about 5 degrees from vertical in one example, less than about 2
degrees in another example, and less than about 1 degree from
vertical in yet another example.
[0032] The ribs are circumferentially spaced so that a plurality of
corresponding channels 20 are formed between adjacent ribs 18 as
illustrated in FIG. 2. The channels 20 extend generally vertically
between the ribs 18 and can have a variety of different shapes and
configurations. The channels 20 include a channel floor 50 at a
base thereof The channel floor 50 may be flush with the Coanda bowl
outer surface 36, or may be raised or indented relative
thereto.
[0033] The ribs 18 may have a generally constant radial profile
(i.e. distance the ribs extend from the bowl outer surface 36
and/or channel floor 50). Alternatively, the ribs 18 may have a
varying radial profile as illustrated in FIG. 5. By one approach,
as seen in FIGS. 2 and 5, the ribs 18 are tapered from a lower rib
portion 52 to raised rib portion 54. In this regard, the tapered
lower portion 52 may be slightly elevated with respect to, or flush
with, the bowl surface 36 to provide a smooth transition surface
over which steam and gas traveling upwardly therealong can flow.
The ribs 18 may also include a tapered upper rib portion 56 to
provide for smooth flow of the steam, waste gas and combustion air
mixture as it exits the Coanda surface. It should be understood
that the radially extending ribs may be radially extending relative
to an outer surface of a Coanda bowl and/or relative to
channels.
[0034] In this regard, the ribs may be formed, for example by
providing ribs along the outer surface of a Coanda bowl, or by
forming channels or indentations in a Coanda bowl so that the ribs
are formed above the channels.
[0035] The ribs may have a constant circumferential width or a
varying width about the perimeter of the Coanda bowl 36 as
illustrated in FIG. 2. Similarly, the channels 20 may have a
constant or varying circumferential width. Typically, where the
Coanda bowl includes an inwardly tapered upper portion 42 as
illustrated, at least one of the ribs and channels will have a
varying width to account for the upwardly decreasing
circumference.
[0036] By one aspect, the ribs 18 may have inclined sidewalls 58
extending between rib top portions 60 and the channel floors 50 as
best seen with reference to FIGS. 3 and 5. The inclined sidewalls
58 can be generally flat, or may be curved or formed in other
manners. The inclined side walls 58 provide a smooth surface over
which the steam and gas can flow by reducing the amount of sharp
angles between the ribs and the channels.
[0037] Without intending to be bound by theory, it is believed that
the addition of ribs 18 to the Coanda bowl 36 increases the total
surface area of the Coanda bowl 36 to improve mixing of the steam
and waste gas, and also combustion air when it is present, without
providing a corresponding increase in outer diameter of the bowl.
In this manner, the Coanda bowl 36 can advantageously be kept
relatively small while providing sufficient surface area for mixing
of the steam, gas and combustion air reducing smoke formation.
[0038] To this end, by one aspect, the ribbed Coanda bowl has a
relatively high ratio of a perimeter (as shown in FIG. 4) to an
outer radius 62. As used herein, outer radius refers to the
distance between the bowl longitudinal axis 46 and the rib top
portions 60. For example, a traditional un-ribbed Coanda bowl has a
ratio of perimeter (circumference) to outer radius of 2 .pi.r/r=2
.pi.. In one example, the ratio of the perimeter to the outer
radius of the ribbed bowl described herein is greater than 2 .pi..
In another example, the ratio of perimeter to outer radius is
between about 6.5 and about 20, between about 7.5 and about 16 in
another example, and between about 8.5 and about 12 in yet another
example.
[0039] According to one aspect ribs 18 may be formed along the
entire outer surface 38 of the Coanda bowl 36. In this regard, the
surface area of the entire bowl 36 is increased such that mixing
between the steam, waste gas and the combustion air is improved
along the total outer surface as described above.
[0040] According to another aspect, the ribs 18 may extend along
one or more portions of the Coanda bowl 36, but less than the full
outer surface 38 thereof, such that a portion of the gas deflector
is unribbed and provides a relatively smooth surface for gas flow.
For example, as illustrated in FIG. 2, the lower portion 40 and/or
the intermediate portion 44 of the Coanda bowl 36 may be unribbed,
while an upper portion 42 includes ribs. In this regard, gas may
better flow along the lower portion 40 of the Coanda bowl 36, along
the convex intermediate portion 44, and to the ribbed upper portion
42 before flowing over and between the ribs 18. In one example,
between about a bottom 5 to 50 percent of the Coanda bowl is
unribbed with an upper portion including ribs. In another example
between about a bottom 10 to 40 percent of the Coanda bowl is
unribbed with an upper portion including ribs. In another example,
as illustrated in FIG. 7 a bottom portion may include ribs with at
least an intermediate portion and/or a top portion being
unribbed.
[0041] As illustrated in FIGS. 2 and 7, different numbers and sizes
of ribs 18 may be included on the Coanda bowl to maximize the
steam/waste gas/combustion air mixing. For example, it may be
beneficial to select the number of ribs extending circumferentially
about the Coanda bowl 36 to provide increased surface area and the
associated improvement in steam/gas mixing, while still ensuring
that the steam and gas will flow smoothly over the total surface
area during operation. FIG. 2 illustrates an example of a Coanda
bowl 36 that includes a smaller number of relatively wider ribs 18
while FIG. 7 illustrates another example where a larger number of
narrower ribs 18 are used. With this in mind, in one example a
ratio of a combined circumferential width of the one or more ribs
18 to a combined circumferential width of a plurality of channels
12 between the ribs 18 is between about 0.5 and about 5 and between
about 1 and about 3 in another example. In another example, a ratio
of a rib radial height above the channel floor to the outer radius
of the bowl is between about 0.01 and about 0.2 in one example and
between about 0.03 and about 0.2 in another example.
[0042] As mentioned previously, by one aspect, a steam outlet 13 is
provided for introducing the steam toward the outer surface of the
Coanda bowl. With reference to FIGS. 2 and 3, the steam outlet may
include a generally annular opening 15 of the steam passageway
extending about the longitudinal axis of the Coanda bowl 36 for
distributing the steam along the surface thereof The annular
opening 15 may be formed of a single opening, or a plurality of
smaller openings as illustrated in FIGS. 2 and 3. By one approach,
the steam outlet 13 includes a steam disperser 70 as illustrated in
FIG. 3. The steam disperser may be formed in a variety of different
configurations. As illustrated, the steam disperser 70 includes an
inverted frusto-conical chamber 72 having a narrower bottom portion
74 and a broader top portion 76. One or more chamber openings 78
are formed about the perimeter of the top portion 76 to provide the
annular opening 15 for dispersing the steam. In this manner, steam
may be dispersed from the generally central steam passageway 11
along the surface of the Coanda bowl 36.
[0043] As illustrated in FIG. 8, by one approach, the chamber 72
includes upper apertures 80 formed through the top portion 76 of
the chamber forming the chamber openings 78. By one aspect, as
illustrated in FIGS. 9-10, the chamber 72 includes a notched upper
rim portion 82. In this regard, with the chamber 72 in position
below the Coanda bowl 36, the openings are formed between the
Coanda bowl outer surface 38 and indentations 84 formed in the
notched upper rim portion Various configurations are possible for
the notched upper rim portion 82. In one example, as illustrated in
FIG. 9 the notched upper rim portion includes serrations 86
providing a saw tooth appearance with triangular openings formed
between the Coanda bowl 36 and the serrations 86. By another
approach, the notched upper rim portion may be formed of
alternating crenels 88 and merlons 90 as illustrated in FIG. 10 to
form openings between the crenels and the Coanda bowl 36.
[0044] By one aspect, the openings 78 may be aligned with the ribs
18 to provide for increased flow of steam over the ribs 18. By
another approach, the openings 78 may be aligned with the channels
20. By yet another approach, openings may be aligned with both the
ribs and the channels or may be offset relative to one or both.
[0045] As mentioned, by one aspect, the gas outlet 12 is provided
for introducing the waste gas toward the outer surface of the
Coanda bowl. As illustrated in FIGS. 2-3, the gas outlet 12 may
include a generally annular opening 14 of the waste gas passageway
10 formed about the outer surface 38 so that the waste gas can flow
through the opening and along the outer surface. The annular
opening 14 may include a relatively round shape, or another shape,
such as an oval or polygon. By one approach, the annular opening
includes a single annular opening, but may also include a plurality
of openings formed about the Coanda bowl 36. The annular opening 14
may be formed by a gap between the support arm upper seating
portion 30 and the Coanda bowl lower portion 40, such that waste
gas flowing through the gas passageway 10 exits through the opening
14 and flows along the outer surface 38.
[0046] According to one aspect, the gas outlet 12 is provided
radially outwardly of the steam outlet 13 as illustrated in FIGS. 2
and 3. In this manner, steam is directed along outer surface 38 and
the waste gas is directed toward the outer surface 38 and the steam
flowing thereover. Not to be bound by theory, it is believed that
by forming the gas outlet radially outwardly of the steam outlet
13, a thin layer of steam is formed over the outer surface 38 of at
least a portion of the Coanda bowl 36. The waste gas is directed
toward the steam and forms a layer of waste gas flowing along the
layer of steam. Combustion air may then be available radially
outwardly of the waste gas layer. In this manner, as the steam and
gas stream flow over the ribbed surface of the Coanda bowl, 36
improved mixing may occur as the waste gas layer is contacted by
the steam on one side and the combustion air on the other side,
resulting in reduced smoke formation during combustion.
[0047] According to various aspects, during operation, the steam
flows through the steam passageway 11 and through the annular
opening 15 along the Coanda bowl outer surface 38. The waste gas to
be combusted flows through the gas passageway 10 and through the
annular opening 14. As the steam and waste gas flow along the outer
surface 38, they mix together and may further mix with combustion
air (for example surrounding ambient air) that is drawn toward the
waste gas and steam and mixed therewith. The steam and waste gas
pass over the ribs 18 and through the channels 20 therebetween. The
mixture is ignited and combusted with reduced smoke formation.
[0048] The above description and examples are intended to be
illustrative of the invention without limiting its scope. While
there have been illustrated and described particular embodiments of
the present invention, it will be appreciated that numerous changes
and modifications will occur to those skilled in the art, and it is
intended in the appended claims to cover all those changes and
modifications which fall within the true spirit and scope of the
present invention.
* * * * *