Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02680709 2009-09-25
BURNER APPARATUS AND METHODS
BACKGROUND OF THE INVENTION
[0001] Burner assemblies are used in many applications. For example, process
burner
assemblies are used in connection with industrial furnaces in petroleum
refineries, chemical
plants and similar facilities. The specific type and configuration of burner
assemblies used
will vary depending on the specific application, the type of furnace, the
applicable
emissions regulations and other factors known to those skilled in the art.
[0002] A typical process burner includes a burner tile having a burner throat
extending
therethrough. The burner tile extends into the furnace. Combustion air is
conducted
through the burner throat to create a combustion zone in the furnace adjacent
to the outlet of
the burner throat. Fuel is injected into the burner throat, admixed with the
combustion air
and burned in the combustion zone.
[0003] Many government authorities have adopted regulations relating to the
amount of
nitrogen oxides (commonly designated as "NOx" and primarily including NO and
NO2) and
other potentially polluting compounds that can be emitted into the atmosphere
from process
furnaces and other combustion equipment. The United States, for example, has
stringent
regulations relating to nitrogen oxides emissions. These regulations have led
to the
development of burner apparatus and corresponding methods of operation that
result in
significantly lower nitrogen oxide emissions.
[0004] In one approach, the fuel admixed with combustion air in the burner
throat
(commonly referred to as primary fuel) is burned in a first combustion zone.
Additional
fuel (often referred to as secondary or staged fuel) is burned in a second
combustion zone.
In such a burner assembly, the secondary or staged fuel becomes dilute with
furnace flue
gas thereby lowering the combustion temperature of the gases. The flue gas
functions as a
heat sink in that it absorbs heat from the flame. The flue gas can come from
the furnace
stack (external flue gas) or from the furnace itself (internal flue gas).
Lowering the
combustion temperature of the gases lowers the formation of nitrogen oxides in
the
produced flue gases. Secondarily, flue gas admixed with the combustion
reactants reduces
the species concentration of oxygen necessary for nitrogen oxide formation,
thereby
contributing to further nitrogen oxide reduction.
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[0005] It has been thought heretofore that it is necessary to admix primary
fuel with
combustion air in the throat of the burner, even in staged combustion burner
assemblies.
The primary fuel in the throat of the burner helps assure that the mixture of
fuel and
combustion air is ignited in the combustion zone and helps stabilize the
burner.
Unfortunately, in some applications, the admixture of primary fuel with
combustion air in
the throat of the burner can generate temperatures therein that are high
enough to allow
nitrogen oxides to form. Of secondary importance, the combustion air in the
burner throat
includes a substantially higher concentration of oxygen than the concentration
of oxygen in
flue gas. Combining a relatively high concentration of oxygen in the burner
throat with
higher temperatures caused by introducing primary fuel to the burner throat
can cause a
significant amount of nitrogen oxides to form. This diminishes the
significance of the other
steps taken to reduce the formation of nitrogen oxides.
SUMMARY OF THE INVENTION
[0006] The invention provides a burner assembly for a furnace. The invention
also
provides a method of using a burner assembly that includes a burner tile and a
burner throat
extending therethrough to combust fuel gas in a furnace space in order to
generate heat.
[0007] In a first aspect, the inventive burner assembly comprises a burner
tile for
association with the furnace, a burner pilot assembly and a fuel injection
assembly.
[0008] The burner tile of the first aspect of the burner assembly includes an
exterior
surface to be positioned within the furnace, and a burner throat disposed
through the burner
tile. The burner throat has an inlet and an outlet. The inlet of the burner
throat is adapted to
receive combustion air from outside the burner throat. The outlet of the
burner throat is
positioned adjacent to the exterior surface of the burner tile, and is
positioned to introduce
combustion air into a combustion zone located within the furnace and adjacent
to the
exterior surface of the burner tile.
[0009] The burner pilot assembly of the first aspect of the burner assembly is
for
generating a pilot flame within the burner throat. The burner pilot assembly
includes a pilot
fuel tip and a pilot fuel riser. The pilot fuel riser has an inlet adapted to
be fluidly connected
to a source of fuel, and an outlet fluidly connected to the pilot fuel tip.
The pilot fuel tip is
disposed within the burner throat.
[0010] The fuel injection assembly of the first aspect of the burner assembly
is adapted
to inject essentially all of the fuel needed for operation of the burner
assembly into the
furnace from one or more fuel tips located outside the burner throat. The fuel
injection
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assembly includes a main fuel tip and a main fuel riser for injecting main
fuel into an
ignition zone located within the furnace and adjacent to the exterior surface
of the burner
tile. The main fuel riser has an inlet adapted to be fluidly connected to a
source of fuel, and
an outlet fluidly connected to the fuel tip. The fuel tip is at least
partially disposed within
the furnace and positioned adjacent to the exterior surface of the burner
tile.
[0011] In a second aspect, the inventive burner assembly includes a burner
tile for
association with the furnace, an ignition passageway, a burner pilot assembly
and a fuel
injection assembly.
[0012] _ The burner tile of the second aspect of the burner assembly includes
an exterior
surface to be positioned within the furnace and a burner throat disposed
through the burner
tile. The burner throat has an inlet and an outlet. The inlet of the burner
throat is adapted to
receive combustion air from outside the burner throat. The outlet of the
burner throat is
positioned adjacent to the exterior surface of the burner tile, and positioned
to introduce
combustion air into a combustion zone located within the furnace and adjacent
to the
exterior surface of the burner tile.
[0013] The ignition passageway of the second aspect of the burner assembly
extends
through the burner tile between the burner throat and the exterior surface of
the burner tile,
and has an inlet and an outlet. The inlet of the ignition passageway is
positioned adjacent to
the burner throat, and the outlet of the ignition passageway is positioned
adjacent to the
exterior surface of the burner tile.
[0014] The burner pilot assembly of the second aspect of the burner assembly
is for
generating a pilot flame within the burner throat. The burner pilot assembly
includes a pilot
fuel tip and a pilot fuel riser. The pilot fuel riser has an inlet adapted to
be fluidly connected
to a source of fuel, and an outlet fluidly connected to the pilot fuel tip.
The pilot fuel tip is
disposed within the burner throat.
[0015] The fuel injection assembly of the second aspect of the burner assembly
is
adapted to inject fuel into the furnace from one or more fuel tips located
outside of the
burner throat. The fuel injection assembly includes a main fuel tip and a main
fuel riser for
injecting main fuel into an ignition zone located within the furnace and
adjacent to the
exterior surface of the burner tile. The main fuel riser has an inlet adapted
to be fluidly
connected to a source of fuel, and an outlet fluidly connected to the main
fuel tip. The main
fuel tip is at least partially disposed within the furnace and positioned
adjacent to the
exterior surface of the burner tile.
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[00161 The ignition passageway of the second aspect of the burner assembly
receives at
least a portion of the pilot flame generated by the burner pilot assembly, and
conducts the
flame, or portion thereof, to the ignition zone such that the flame or portion
thereof can
contact and ignite the main fuel injected by the main fuel tip into the
ignition zone.
[0017] In a first aspect, the inventive method is carried out without admixing
a
significant amount of fuel with combustion air in the burner throat. The
method comprises
the following steps:
(a) conducting combustion air through the burner throat into a combustion
zone located within the furnace, and adjacent to the exterior surface of
the burner tile;
(b) generating a pilot flame in the burner throat with pilot fuel provided by
a
burner pilot assembly;
(c) injecting essentially all of the fuel needed for operation of the burner
assembly into the furnace from one or more fuel tips located outside of
the burner throat, the one or more fuel tips including a main fuel tip for
injecting main fuel into an ignition zone located within the furnace, and
adjacent to the exterior surface of the burner tile;
(d) igniting main fuel in the ignition zone; and
(e) admixing ignited main fuel with combustion air conducted through the
burner throat in the combustion zone.
[0018] In a second aspect, the inventive method comprises the following steps:
(a) conducting combustion air through the burner throat into a combustion
zone located within the furnace, and adjacent to the exterior surface of
the burner tile;
(b) generating a pilot flame in the burner throat with pilot fuel provided by
a
burner pilot assembly;
(c) injecting fuel into the furnace from one or more fuel tips located outside
of the burner throat, the one or more fuel tips including a main fuel tip
for injecting main fuel into an ignition zone located within the furnace
and adjacent to the exterior surface of the burner tile;
(d) conducting at least a portion of the pilot flame from the burner throat to
the ignition zone and using said pilot flame, or portion thereof, to ignite
main fuel in the ignition zone; and
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(e) admixing ignited main fuel with combustion air conducted through the
burner throat into the combustion zone.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a front perspective view of the inventive burner assembly.
[0020] FIG. 2 is a section view of the inventive burner assembly taken along
line 2-2 in
FIG. 1. FIG. 2 also illustrates the flow of combustion air and the flame
generated by the
burner pilot assembly the inventive burner assembly.
[0021] FIG. 3 is a front view of the inventive burner assembly and further
illustrates the
deflection of a flame across the exterior of the burner tile.
[0022] FIG. 4 is an enlarged detail view of the burner tile exterior shown by
FIG. 3.
[0023] FIG. 5 is a partial top view of the inventive burner assembly.
[0024] FIG. 6 is an enlarged front perspective view of a turning member and
stabilizing
member of the inventive burner assembly.
[0025] FIG. 7 is a section view taken along line 7-7 in FIG. 6.
[0026] FIG. 8 is a section view of an alternative configuration of the
inventive burner
assembly.
[0027] FIG. 9 is a section view of another configuration of the inventive
burner
assembly.
[0028] FIG. 10 is a section view of yet another configuration of the inventive
burner
assembly.
[0029] FIG. I I A is a front view of the burner tile exterior and illustrates
an alternative
embodiment of the inventive burner assembly.
[0030] FIG. 11 B is a partial top view of the embodiment shown by FIG. 11 A.
[00311 FIG. 1 1 C is a section view taken along line 11 C-11 C of FIG. 11 A.
[0032] FIG. 12A is a front view of the burner tile exterior and illustrates
another
alternative embodiment of the inventive burner assembly.
[0033] FIG. 12B is a partial top view of the embodiment of the inventive
burner
assembly shown by FIG. 12A.
[0034] FIG. 12C is a section view taken along line I1 C-I1 C of FIG. 12A.
[0035] FIG. 13A is a front view of the burner tile exterior and illustrates
yet another
alternative embodiment of the inventive burner assembly.
[0036] FIG. 13B is partial top view of the embodiment of the inventive burner
assembly
shown by FIG. 13 A.
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[0037] FIG. 13C is a section view taken along line 1I C-I1 C of FIG. 13A.
DETAILED DESCRIPTION
[0038] Referring to the drawings, the inventive burner assembly is illustrated
and
generally designated by the numeral 10. As shown by the drawings and
understood by
those skilled in the art, the burner assembly 10 and components thereof are
designed to be
associated with a furnace 12 (the overall furnace is not shown) and can be
used to generate
heat in a petroleum refinery, chemical plant or other applications. The burner
assembly 10
is attached to a wall 14 of the furnace 12 (for example, a side wall, bottom
wall (or floor) or
top wall (or ceiling)) and extends into a furnace space 16 of the furnace. The
burner
assembly 10 can also freely stand in the furnace 12, for example on the floor
of the furnace.
The furnace wall 14 includes an internal layer of insulating material 14(a)
attached thereto.
[0039] The burner assembly 10 shown by FIGS. 1 and 2 is attached to and
horizontally
associated with a side wall 14 of a furnace and fired upwardly (up-fired) with
respect
thereto. As discussed further below, the burner assembly 10 can be configured
and
associated with the furnace 12 in other ways as well. The burner assembly 10
discharges a
mixture of fuel gas and air into furnace space 16 where the mixture is burned
in the
presence of flue gas while producing a relatively low content of nitrogen
oxides (NOx) and
carbon products. Typically, multiple burner assemblies 10 are installed in a
single furnace
12.
[0040] The burner assembly 10 comprises a burner tile 18 for association with
the
furnace 12, a burner pilot assembly 20 and a fuel injection assembly 22. As
understood by
those skilled in the art, the burner assembly 10 can be a natural draft burner
(i.e., the air
required for combustion is naturally drafted into burner tile 18), a forced
draft burner (for
example, a blower is used to blow the combustion air into burner tile 18), a
balanced draft
burner (for example, blowers are used to blow air both in and out of the
burner to achieve an
appropriate balance of combustion air) or variations thereof.
[0041] The burner tile 18 includes a base 24, and an exterior surface 26 to be
positioned
within the furnace 12 (to extend within the furnace space 16). The exterior
surface 26
includes a top section 28, a bottom section 30, and a sidewall section 32
connecting the top
section to the bottom section. The base 24 of the burner tile 18 is attached
to the furnace
wall 14. The bottom section 30 is slightly tapered from the base 24 to the
sidewall section
32. The sidewall section 32 includes a front face 34 and side faces 36. The
front face 34
includes a lower front face 34(a) and a sloped front face 34(b). The sloped
front face 34(b)
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tapers inwardly from the lower front face 34(a) to the top section 28 of the
exterior surface
26 of the burner tile 18.
[00421 As illustrated in the drawings, the burner assembly 10 is a natural
draft burner
(i.e., the air required for combustion is naturally drafted into burner tile
18). A plenum 38 is
attached to the back of the furnace wall 14 and to the base 24 of the burner
tile 18 to provide
combustion air (illustrated in the drawings by arrows 40) from outside the
furnace 12 to the
burner assembly 10. The plenum 38 includes an air inlet 42. A damper assembly
44 is
attached to the air inlet 42 for regulating the amount of air that is
introduced into the plenum
38 and burner assembly 10. An air opening 46 extends through the furnace wall
14 to allow
air to be conducted from the plenum 38 to the burner tile 18.
[00431 A burner throat 48 is disposed through the burner tile 18. The burner
throat 48
includes a throat wall 50 that defines and surrounds burner throat. The burner
throat 48 has
an inlet 52 and an outlet 54. The inlet 52 is adapted to receive combustion
air (designated
by arrows 40) from outside of the burner throat 48 (specifically, the plenum
38). The inlet
52 of the burner throat 48 is aligned over the air opening 46 extending
through the furnace
wall 14, thereby providing fluid communication between the burner throat 48
and the
plenum 38. The outlet 54 of the burner throat 48 is positioned adjacent to the
exterior
surface 26 of the burner tile, and is positioned to introduce combustion air
(designated by
the arrows 40) into a combustion zone 58 located within the furnace 12 and
adjacent to the
exterior surface of the burner tile 18. Combustion air is discharged into the
combustion
zone 58 in the furnace 12 through the outlet 54 of the burner throat 48.
[0044] The wall 50 of the burner throat 48 extends inwardly adjacent to the
outlet 54 of
the burner throat 48 to form a throat ledge 60. The throat ledge 60 functions
to stabilize the
flame.
[0045] The burner pilot assembly 20 is utilized to generate a pilot flame 62
within the
burner throat 48. The burner pilot assembly 20 includes a pilot fuel riser 64
and a pilot fuel
tip 66. The pilot fuel riser 64 has an inlet 68 adapted to be connected to a
source of fuel 70,
and an outlet 72 fluidly connected to the pilot fuel tip 66. The pilot riser
extends through
the air opening 46 in the furnace wall 14 into the burner throat 48. The pilot
tip 66 is
disposed within the burner throat 48. Preferably, the burner pilot assembly 20
pre-mixes the
fuel with oxygen in the burner pilot assembly prior to generating the flame
62. This can be
accomplished, for example, by using a mixer jet at the inlet of the pilot
riser. The motive
force of the fuel in the mixer jet draws in and admixes air (including oxygen)
with the fuel.
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[00461 The fuel injection assembly 22 is preferably adapted to inject
essentially all of
the fuel needed for operation of the burner assembly 10 into furnace 12 from
one or more
fuel tips 74 located outside of the burner throat. As used herein and in the
appended claims,
"essentially all" of the fuel needed for operation of the burner assembly 10
means all of the
fuel needed to operate the burner except for fuel used in operating the burner
pilot assembly
20. The fuel injection assembly 22 includes main fuel risers 76 and main fuel
tips 78 for
injecting main fuel into ignition zones 80 located within the furnace 12 and
adjacent to the
exterior surface 26 of the burner tile 18. The main fuel risers 76 have inlets
82 adapted to
be fluidly connected to a source of fuel 84, and outlets 86 fluidly connected
to the main fuel
tips 78. Preferably, the portions of the main fuel risers 76 that would
otherwise extend into
the furnace 14 are disposed through the burner tile 18. The main fuel tips 78
are at least
partially disposed within the furnace 12 and positioned adjacent to the lower
front face
34(a)of the front face 34 of the sidewall section 32 of the burner tile 18.
The main fuel tips
78 are positioned to inject main fuel along the front face 34 into the
ignition zones 80. The
ignition zones 80 are positioned adjacent to the sloped front face 34(b) of
the front face 34.
A plurality of main fuel risers 76 and main fuel tips 78 and a plurality of
ignition zones 80
can be used. FIGS. 1 and 3-5 all depict two main fuel risers 76 and two
corresponding main
fuel tips 78, each injecting main fuel toward a separate ignition zone 80.
[00471 The fuel injection assembly 22 also includes a supplemental fuel
injection
assembly 90. The supplemental fuel injection assembly 90 is positioned to
inject
supplemental fuel into the combustion zone 58. The supplemental fuel injection
assembly
90 includes supplemental fuel risers 92 and supplemental fuel tips 94. The
supplemental
fuel risers 92 have inlets 98 that are adapted to be fluidly connected to a
source of fuel 100,
and outlets 102 that are fluidly connected to the supplemental fuel tips 94.
The
supplemental fuel risers 92 are partially disposed through the burner tile 18
and extend into
troughs 104 that are disposed in the burner tile 18. Each trough 104 includes
a trough wall
106 and a trough outlet 108. The supplemental fuel risers 92 extend through
the walls 106
of the troughs 104. The supplemental fuel tips 94 are positioned within the
troughs 104 and
positioned to inject supplemental fuel into the combustion zone 58 through the
outlets 108
of the troughs. A plurality of supplemental fuel risers 92, supplemental fuel
tips 94 and
corresponding troughs 104 can be utilized. As depicted, the fuel injection
assembly 22
includes two supplemental fuel risers 92, two supplemental fuel tips 94 and
two
corresponding troughs 104.
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[00481 The burner assembly 10 further comprises ignition passageways 114 for
receiving at least a portion of the flame 62 generated by the burner pilot
assembly 20. The
ignition passageways 114 conduct the flame 62 or portion thereof to the
ignition zones 80
whereby the flame 62 or portion thereof can ignite main fuel injected by the
main fuel tips
78 into the ignition zones. The ignition passageways 114 extend through the
burner tile 18
between the burner throat 48 and the exterior surface 26 of the burner tile
18, specifically
the sloped front face 34(b) of the front face 34 of the sidewall section 32 of
the exterior
surface 26 of the burner tile 18. The ignition passageways 114 include inlets
116 positioned
adjacent to the burner throat 48, and outlets 118 positioned adjacent to the
sloped front face
34(b).
[00491 As illustrated, each ignition passageway 114 receives a portion 62(a)
of the
flame 62 and conducts the flame portion 62(a) to an ignition zone 80. The
flame portions
62(a) contact and ignite main fuel injected by the main fuel tips 78 into the
ignition zones
80. A plurality of ignition passageways 114 may be used. As illustrated, the
burner
assembly includes two ignition passageways 114.
[00501 The burner assembly 10 further comprises flame diverters 124 for
causing at
least a portion of the flame 62 generated by the burner pilot assembly 20 to
be diverted into
the ignition passageways 114. As illustrated, the flame diverters 124 are
adapted to cause a
portion of the flame 62 generated by the burner pilot assembly 20, flame
portion 62(a), to be
diverted into the ignition passageways 114, and a portion of the flame 62
generated by said
burner pilot assembly, flame portion 62(b), to be conducted through the outlet
54 of the
burner throat 48 into the combustion zone 58. The relative amounts of the
flame 62 forming
the flame portions 62(a) and 62(b) can be adjusted as necessary. For example,
the amount
of the flame 62 diverted into flame portions 62(a) needs to be sufficient to
allow the flame
portions 62(a) to reach the ignition zones 80 and ignite main gas therein.
[00511 In the embodiment of the burner assembly 10 shown by FIGS. 1-7, the
flame
diverters 124 are impingement blocks 126 that are attached to the wall 50 of
the burner
throat 48 adjacent to the ignition passageway inlets 116. The impingement
blocks 126 split
the flame 62 into flame portions 62(a) and 62(b). They can also be configured
to divert the
entire pilot flame 62 into the ignition passageways 114.
[00521 As best shown by FIGS. 4-7, the flame portions 62(a) that are conducted
through
the ignition passageways 114 are also manipulated on the outside of the burner
tile. In this
respect, the burner assembly 10 includes turning members 140, the turning
members 140
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being located adjacent to the exterior surface 26 of the burner tile 18 and
positioned to
redirect the flame portions 62(a) from the outlets 118 of the ignition
passageways across the
exterior surface of the burner tile. In one embodiment, the turning members
140 are turning
blocks 142 that are positioned on the sloped front face 34(b) of the front
face 34 of the
sidewall section 32 of the exterior surface 26 over the ignition passageway
outlets 118. The
flame portions 62(a) conducted through the ignition passageway outlets 118
impinge on the
turning blocks 142 and are redirected through channels 144 that are disposed
in the front
sloped front face 34(b) across the sloped front face 34(b).
[0053] Stabilizing members 150 are positioned on the exterior surface 26 of
the burner
tile 18 to receive the flame portions 62(a) (or a portion thereof) and
facilitate contact of the
received flame with main fuel injected by the main fuel tips 78. Specifically,
each
stabilizing member 150 is attached to a corresponding turning block 142 and
extends
substantially perpendicularly therefrom below the corresponding channel 144
and along the
sloped front face 34(b). The stabilizing members 150 act as bluff bodies in
that they receive
both the flames (or a portion thereof) from the turning blocks 142 and main
fuel that is
discharged from the main fuel tips 78. Main fuel discharged from the main fuel
tips 78 is
caused to slow down or impinge on the stabilizing members 150 where it is
ignited by the
flames.
[0054] A plurality of turning blocks 142, channels 144 and stabilizing members
150 can
be utilized. As illustrated, a turning block 142, channel 144 and stabilizing
member 150 are
used in association with each of the two ignition passageways 114.
[0055] Referring now to FIGS. 8-10, additional configurations of the burner
assembly
10 are illustrated. As mentioned above, the burner assembly 10 can be
configured and
associated with the furnace 12 in various ways. For example, the burner
assembly 10 can
be associated with the furnace 12 horizontally or vertically and can be fired
upwardly (up-
fired) or fired downwardly (down-fired). The burner assembly 10 can be
associated with
the furnace 12 at any orientation.
[00561 As shown by FIGS. 1 and 2, the burner assembly 10 is designed and
configured
to be horizontally mounted on a wall 14 of the furnace 12 and vertically fired
adjacent to a
side wall of the furnace. FIG. 8 illustrates a design and configuration of the
burner
assembly 10 that is adapted to be vertically mounted on a wall 14 of the
furnace 12 and
vertically fired adjacent to a side wall of the furnace. The inventive burner
assembly shown
by FIG. 8 is fired along the side wall of the furnace. For example, unlike the
burner throat
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48 illustrated by FIGS. I and 2, the burner throat 48 in the configuration
shown by FIG. 8 is
not "L" shaped but is straight.
[00571 FIG. 9 illustrates a design and configuration of the burner assembly 10
that is
adapted to be vertically mounted on the floor 14 of the furnace and vertically
fired into the
interior 160 of the furnace. The inventive burner assembly shown by FIG. 9 can
be attached
or free standing in a middle area 162 of the interior 160 of the furnace. This
configuration
includes multiple main fuel tips and risers, ignition passageways and
corresponding
components. It does not include the troughs 104 and corresponding components
for
supplemental fuel injection.
100581 FIG. 10 illustrates a design and configuration of the burner assembly
10 that is
similar to the inventive burner assembly shown by FIG. 9, except in this
configuration the
inventive burner assembly is adapted to be vertically mounted from the ceiling
14 of the
furnace 12 and vertically down fired into a middle area 162 of the interior
160 of the
furnace.
[00591 Referring now to FIGS. I I A- I 1 C, an alternative embodiment of the
inventive
burner assembly 10 is illustrated. In this embodiment, the ignition
passageways 114 include
Coanda surfaces 170 adjacent to the inlets 116 for causing at least a portion
of the flame 62
generated by the burner pilot assembly 20 to be diverted into the ignition
passageways 114.
As a result, the flame diverters 124 are not necessarily needed. The flame 62
emitted from
the pilot tip 66 or a portion thereof (depending on the velocity of the flame,
the curvature of
the Coanda surfaces and other factors known to those skilled in the art)
adheres to and
follows the path of the Coanda surfaces 170 into the ignition passageways 114.
The Coanda
surfaces 170 can be utilized in association with flame diverters 124 if
desired.
[00601 As illustrated by FIGS. 1 1A-IIC, the ignition passageways 114 can also
include
Coanda surfaces 174 adjacent to the outlets 118 of the ignition passageways
114 for causing
at least a portion of the flame portions 62(a) conducted through the outlets
118 to be
redirected across the sloped front face 34(b) of the front face 34 of the
sidewall section 32
of the exterior surface 26 of the burner tile 18. As a result, the turning
members 140 are not
necessarily needed. The flame portions 62(a) conducted through the outlets 118
of the
ignition passageways 114 adhere to and follow the paths of the Coanda surfaces
174 such
that they are received by the stabilizing member 150. In this embodiment, the
stabilizing
member 150 is a ledge 178 positioned below the outlets 118. Turning members
140 can
still be utilized if desired.
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[00611 Referring now to FIGS. 12A-12C, another alternative embodiment of the
inventive burner assembly 10 is illustrated. In this embodiment, the flame
diverters 124 are
fluid injection assemblies 180 associated with the ignition passageways 114
for injecting
fluid into the ignition passageways toward the ignition zones 80 to create
pressures in the
injection passageways 114 that are lower than the pressure in the burner
throat 48. The
relatively low pressures in the injection passageways draw the pilot flame 62
or a portion
thereof (flame portions 62a) into the injection passageways 114. The fluid
injection
assemblies 180 are adapted to be fluidly connected to a source of fuel 182
whereby the fluid
injection assemblies can inject fuel into the ignition passageways 114. As
best shown by
FIG. 12C, fuel eductor passageways 190 are formed in the burner tile 18. Each
fluid
eductor passageways 190 extends from a main fuel riser 76 to the corresponding
ignition
passageway 114. An inlet 192 of each fuel eductor passageway 190 is fluidly
connected to
and receives main fuel from the corresponding main fuel riser 76. An outlet
194 of each
fuel eductor passageway 190 is fluidly connected to the corresponding ignition
passageway
114. In this way, fuel can be directly injected from the main fuel risers 76
into the ignition
passageways 114 to educt the pilot flame 62 or a portion thereof into the
ignition
passageways. The main fuel in the fuel eductor passageways 190 is either
ignited by the
flame 62 and burned in the passageways or ignited and burned in the ignition
zones.
[0062] Referring now to FIGS. 13A-13C, another alternative embodiment of the
inventive burner assembly 10 is illustrated. In this embodiment, the ignition
passageways
114 are disposed through the burner tile 18 at angles diverging radially
outward from the
burner throat 48. In this embodiment, the passageways 114 diverge radially
outwardly at
much greater angles from the burner throat 48 (as compared to the angles at
which the
passageways 114 diverge radially outwardly from the burner throat 48 as shown
in FIG. 5).
This places the flames emitted from the passageways 114 in closer proximity to
the main
fuel tips 78 and helps direct the flames across the sloped front face 34(b).
Due to the
location of the outlets 118 and the angle of injection of the flame therefrom,
the turning
members 140 are not necessarily needed. The flame portions 62(a) conducted
through the
outlets 118 of the ignition passageways 114 are received by stabilizing
members 196. The
stabilizing members 196 are ledges 198 positioned below the outlets 118.
Turning members
140 can still be utilized if desired.
CA 02680709 2009-09-25
13
[0063] The sloped front face 34(b) can be steeply sloped or gently sloped. One
determining factor includes the pressure used to inject main fuel from main
fuel tips 78 onto
the sloped front face 34(b).
Operation of the Inventive Burner Assembly
[0064] A variety of different types of fuels can be burned by the inventive
burner
assembly 10, including natural gas, methane, hydrogen, propane, propylene,
ethane,
ethylene, butane, butane, butylene, other typical refinery-type fuels and
mixtures thereof.
Preferably the fuel is in gaseous form, although with a fuel atomizer and
other equipment as
known in the art liquid fuel can be used.
[0065] The inventive burner assembly 10 can be used to combust fuel in the
furnace
space 16 in order to generate heat without admixing a significant amount of
fuel with
combustion air in the burner throat 48. As used herein and in the appended
claims, "without
admixing a significant amount of fuel with combustion air in the burner throat
48" means
without adding fuel (e.g., primary fuel) to the burner throat except for fuel
added to the
burner throat in connection with generating the pilot flame 62 therein.
[0066] The inventive burner assembly 10 is attached to the furnace wall 14
such that the
exterior surface of the burner tile 18 extends into the furnace space 16. The
burner
assembly 10 can also freely stand in the interior of the furnace 12. As
explained above,
combustion air (illustrated in the drawings by arrows 40) is provided to the
burner throat
inlet 52 from plenum 38 through the air opening 46.
[0067] Combustion air is conducted from the plenum 38 into the burner throat
48 and
through the outlet 54 of the burner throat into the combustion zone 58. The
combustion
zone 58 is located within the furnace 12 and adjacent to exterior surface 26
of burner tile 18.
A pilot flame 62 is generated within burner throat 48 with pilot fuel provided
by the burner
pilot assembly 20. Prior to generating the pilot flame, oxygen is pre-mixed
with the pilot
fuel in the burner pilot assembly 20.
[0068] Essentially all of the fuel needed for operation of burner assembly 10
is injected
into the furnace 12 from fuel tips 74 located outside of burner throat 48. As
stated above, as
used herein and in the appended claims, "essentially all" of the fuel needed
for operation of
the burner assembly 10 means all of the fuel needed to operate the burner
except for fuel
used in operating the burner pilot assembly 20. The fuel tips 74 include main
fuel tips 78.
Main fuel tips 78 inject main fuel into the ignition zones 80 located within
the furnace 12
and adjacent to the exterior surface 26 of burner tile 18. Main fuel is
ignited in ignition
CA 02680709 2009-09-25
14
zones 80. The ignited main fuel is then admixed with combustion air in the
combustion
zone 58. The primary combustion of the fuel for generating heat in the furnace
occurs in
the combustion zone 58.
[0069] In one embodiment, at least a portion of the pilot flame 62 generated
in the
burner throat 48 is used to ignite main fuel in the ignition zones 80. The
pilot flame 62 or
portion thereof is conducted into the ignition zones 80 through ignition
passageways 114
extending through the burner tile 18 between the burner throat 48 and the
exterior surface
26 of the burner tile whereby the pilot flame or portion thereof can contact
and ignite fuel in
the ignition zones 80.
[0070] The pilot flame 62 or portion thereof is diverted into the ignition
passageways
114. Preferably, first portions 62(a) of the pilot flame are diverted into the
ignition
passageways 114 and a second portion 62(b) of the pilot flame is allowed to be
conducted
through the burner throat 48 into the combustion zone 58. In one embodiment,
the pilot
flame or portions thereof are diverted into the ignition passageways by
impinging the pilot
flame or portions thereof on the flame diverters 124 located in the burner
throat. In another
embodiment, the ignition passageways 114 include Coanda surfaces, and the
pilot flame
62or portions thereof are diverted into the ignition passageways by directing
the pilot flame
or portions thereof on the Coanda surfaces. In yet another embodiment, the
pilot flame 62
or portions thereof are diverted into the ignition passageways 1 l4 by causing
the pressures
in the ignition passageways to be lower than the pressure in the burner throat
48. The
pressures in the ignition passageways 114 are preferably caused to be lower
than the
pressure in the burner throat 48 by injecting an eductor fluid into the
ignition passageways
toward the ignition zones 80. Preferably, the eductor fluid is fuel.
[0071] The fuel tips 74 also include supplemental fuel tips 94 for injecting
supplemental
fuel into the combustion zone 58. Supplemental fuel is injected from the
supplemental fuel
tips 94 into the troughs 104 and into the combustion zone 58. As the
supplemental fuel
burns, it controls the flame in the combustion zone 58 by drawing the flame
closer to the
side wall 14 of the furnace 12. Use of the term "supplemental" herein should
not be
construed to mean that less fuel is conducted through the supplemental fuel
tips 94 than
through the main fuel tips 78. The volume of supplemental fuel discharged into
the
combustion zone 58 by the supplemental fuel tips 94 may exceed the volume of
the main
fuel discharged by the main fuel tips 78 in some applications.
CA 02680709 2009-09-25
[00721 In order to further illustrate the invention, the following example and
test data
are provided.
[00731 The inventive burner assembly 10 was tested for performance. The burner
assembly 10 that was tested was generally configured like the burner assembly
10 shown in
FIGS. 1-7.
[00741 The furnace 12 was cold when each test was started. The test data shown
below
was derived following a light-off procedure. The light-off procedure included
the steps of
opening the furnace damper, warming up the furnace with a heat release of
about 0.75
MMBtu/hr for about 10 minutes at 12% 02, and then increasing the. heat release
to about
1.25 MMBtu/hr for about 30 minutes at 9% 02.
[00751 During startup, main fuel was injected onto the sloped front face 34(b)
and
impinged on flame stabilizing members 150. A portion of the pilot flame 62
(pre-mixed
with oxygen) was diverted through ignition passageways 114 by flame diverter
124. The
diverted flame was discharged from the ignition passageway 114 and was
redirected onto
the flame stabilizing members 150 by turning blocks 142. The diverted flame
and main fuel
injected from the main fuel tips 78 made contact in the ignition zones 80, and
main fuel was
ignited therein. The ignited main fuel continued to flow upwardly over the
sloped front face
34(b) into the combustion zone 58. A portion of the flame 62 exited the outlet
54 of the
burner throat 48 thereby providing an additional source of ignition and
stabilizing the
burner. In the combustion zone 58, supplemental fuel, combustion air from the
burner
throat 48 and the ignited main fuel further combusted in a manner in which a
relatively low
level of nitrogen oxides were produced.
[0076] The following test data was generated.
Test Data
Data Set 1 (light off):
Fuel 100% TNG*
Fuel Flow Rate 793.0 scfh
Fuel Temperature 94 F
Combustion Air Temperature 76 F
Stack Temperature 648 F
Furnace Temperature 799 F
Lower Furnace Temperature 278 F
Furnace Draft 0.24 in. H2O
dP Burner 0.21 in. H2O
Fuel Pressure 2.6 psig
CA 02680709 2009-09-25
16
Pre-Mixed Gas For Pilot
Burner Heat Release 0.72 MMBtulhr
Burner Flow Rate 793 sefll
Burner Lower Heating Value 913.00 Btu/scf
NOx Emissions 9.72 ppmvd
CO Emissions 307.94 ppmvd
02 (Dry) 14.34%vd
* Tulsa Natural Gas
Data Set 2 (rapid warm up):
Fuel 100% TNG*
Fuel Flow Rate 1102.0 scfll
Fuel Temperature 94 F
Combustion Air Temperature 77 F
Stack Temperature 796 F
Furnace Temperature 960 F
Lower Furnace Temperature 394 F
Furnace Draft 0.25 in. H2O
dP Burner 0.23 in. H2O
Fuel Pressure 4.8 psig
Pre-Mixed Gas For Pilot
Burner Heat Release 1.01 MMBtu/hr
Burner Flow Rate 1102 scfh
Burner Lower Heating Value 913.00 Btu/scf
NOx Emissions 9.99 ppmvd
CO Emissions 653.77 ppmvd**
02 (Dry) 12.23%vd
* Tulsa Natural Gas
**this value can be substantially decreased with a slower warm- up rate
Data Set 3 (normal operation, TNG*):
Fuel 100% TNG*
Fuel Flow Rate 1806.0 scfh
Fuel Temperature 99 F
Combustion Air Temperature 83 F
Stack Temperature 1417 F
Furnace Temperature 1573 F
Lower Furnace Temperature 1249 F
Furnace Draft 0.22 in. H2O
dP Burner 0.15 in. H2O
Fuel Pressure 12.1 psig
CA 02680709 2009-09-25
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Pre-Mixed Gas For Pilot
Burner Heat Release 1.65 MMBtu/hr
Burner Flow Rate 1806 scfh
Burner Lower Heating Value 913.00 Btu/scf
NOx Emissions 10.92 ppmvd
CO Emissions 0.0 ppmvd
02 (Dry) 4.01 %vd
* Tulsa Natural Gas
Data Set 4 (normal operation, high hydrogen fuel):
Fuel 47.70% TNG*
20.79% Propane
31.51%H2
Fuel Flow Rate 811.0 scfh TNG
353 scth Propane
536 scth H2
Fuel Temperature 106 F
Combustion Air Temperature 82 F
Stack Temperature 1448 F
Furnace Temperature 1591 F
Lower Furnace Temperature 1283 F
Furnace Draft 0.24 in. H2O
dP Burner 0.17 in. H2O
Fuel Pressure 12.1 psig
Pre-Mixed Gas For Pilot
Burner Heat Release 1.71 MMBtu/hr
Burner Flow Rate 1701 scth
Burner Lower Heating Value 1003.00 Btu/scf
NO, Emissions 20.27 ppmvd
CO Emissions 0.0 ppmvd
02 (Dry) 3.88%vd
* Tulsa Natural Gas
Data Set 5 (normal operation, high hydrogen fuel with air pre-heat):
Fuel 48,01% TNG*
20.47% Propane
31.53% H2
Fuel Flow Rate 818.0 seth TNG
350 scth Propane
537 scfh H2
Fuel Temperature 120 F
Combustion Air Temperature 554 F
Stack Temperature 1525 F
CA 02680709 2009-09-25
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Furnace Temperature 1674 F
Lower Furnace Temperature 1361 F
Furnace Draft 0.28 in. H2O
dP Burner 0.24 in. H2O
Fuel Pressure 14.0 psig
Pre-Mixed Gas For Pilot
Burner Heat Release 1.70 MMBtu/hr
Burner Flow Rate 1704 scfh
Burner Lower Heating Value 998.39.00 Btu/scf
NOS Emissions 26.06 ppmvd
CO Emissions 0.0 ppmvd
02 (Dry) 2.97%vd
* Tulsa Natural Gas
[00771 Thus, the inventive burner assembly 10 performed very well. Essentially
no
carbon monoxide emissions were observed during normal operation of the burner
assembly.
Nitrogen oxide emissions were very low.
[00781 Other embodiments of the current invention will be apparent to those
skilled in
the art from a consideration of this specification or practice of the
invention disclosed
herein. Thus, the foregoing specification is considered merely exemplary of
the current
invention with the true scope thereof being defined by the following claims.
[00791 Thus, the present invention is well adapted to carry out the objects
and attain the
ends and advantages mentioned and alluded to as well as those which are
inherent therein.
What is claimed is:
