Note: Descriptions are shown in the official language in which they were submitted.
CA 02892292 2015-05-22
WO 2014/105067 PCT/US2012/072181
EXHAUST FLOW MODIFIER, DUCT INTERSECTION
INCORPORATING THE SAME, AND METHODS THEREFOR
TECHNICAL FIELD
[0001] The present
technology is generally directed to devices and methods for
modifying fluid flow within a duct. More specifically, some embodiments are
directed
to flow modifiers and transition portions for improving the exhaust flow from
a coke
oven through a duct intersection.
BACKGROUND
[0002] Coke is a
solid carbonaceous fuel that is derived from coal. Because of
its relatively few impurities, coke is a favored energy source in a variety of
useful
applications. For example, coke is often used to smelt iron ores during the
steelmaking process. As a further example, coke may also be used to heat
commercial buildings or power industrial boilers.
[0003] In a
typical coke making process, an amount of coal is baked in a coke
oven at temperatures that typically exceed 2000 degrees Fahrenheit. The baking
process transforms the relatively impure coal into coke, which contains
relatively few
impurities. At the end of the baking process, the coke typically emerges from
the
coke oven as a substantially intact piece. The coke typically is removed from
the
coke oven, loaded into one or more train cars (e.g., a hot car, a quench car,
or a
combined hot car/quench car), and transported to a quench tower in order to
cool or
"quench" the coke before it is made available for distribution for use as a
fuel source.
[0004] The hot
exhaust (i.e. flue gas) is extracted from the coke ovens through
a network of ducts, intersections, and transitions. The intersections in the
flue gas
flow path of a coke plant can lead to significant pressure drop losses, poor
flow
zones (e.g. dead, stagnant, recirculation, separation, etc.), and poor mixing
of air
and volatile matter. The high pressure drop losses lead to higher required
draft
which can lead to leaks and a more difficult to control system. In addition,
poor
mixing and resulting localized hot spots can lead to earlier structural
degradation
due to accelerated localized erosion and thermal wear. Erosion
includes
1
CA 02892292 2015-05-22
WO 2014/105067
PCT/US2012/072181
deterioration due to high velocity flow eating away at material. Hot spots can
lead to
thermal degradation of material, which can eventually cause thermal/structural
failure. This localized erosion and/or hot spots can, in turn, lead to
failures at duct
intersections. For example, the intersection of a coke plant's vent stack and
crossover duct is susceptible to poor mixing/flow distribution that can lead
to hot
spots resulting in tunnel failures.
[0005] Traditional duct intersection designs also result in significant
pressure
drop losses which may limit the number of coke ovens connected together in a
single battery. There are limitations on how much draft a coke plant draft fan
can
pull. Pressure drops in duct intersections take away from the amount of draft
available to exhaust flue gases from the coke oven battery.
[0006] These and other related problems with traditional duct intersection
design result in additional capital expenses. Therefore, a need exists to
provide
improved duct intersection/transitions that can improve mixing, flow
distribution,
minimize poor flow zones (e.g. dead, stagnant, recirculation, separation,
etc.), and
reduce pressure drop losses at the intersection thereby leading to improved
coke
plant operation as well as potentially lower costs to design, build, and
operate a coke
plant.
SUMMARY
[0007] Provided herein are contoured duct liners, turning vanes, transition
portions, duct intersections, and methods of improving gas flow in an exhaust
system. In an exemplary embodiment, a duct intersection comprises a first duct
portion and a second duct portion extending laterally from a side of the first
duct
portion. The second duct portion may tee into the first duct portion. The
second
duct portion may extend laterally from the side of the first duct portion at
an angle of
less than 90 degrees.
[0008] At least one flow modifier is mounted inside one of the first and
second
duct portions. In one aspect of the technology described herein, the flow
modifier is
a contoured duct liner. In another aspect of the present technology, the flow
modifier includes at least one turning vane.
2
CA 02892292 2015-05-22
WO 2014/105067
PCT/US2012/072181
[0009] In an embodiment, the contoured duct liner comprises a first
contoured
wall mated to an inside surface of the duct and a second contoured wall mated
to
the first contoured wall. In one aspect of the present technology, the
contoured duct
liner may be mounted inside the first duct portion. In another aspect of the
present
technology, the contoured duct liner is mounted inside the second duct
portion. The
second contoured wall may comprise a refractory material.
[0010] In another embodiment, the contoured duct liner comprises a first
wall
contoured to mate with an inside surface of a duct intersection and a second
wall
attached to the first wall. The second wall is contoured to modify the
direction of gas
flow within the duct intersection. In one aspect of the present technology,
the
second wall includes at least one convex surface.
[0011] In yet another embodiment, the duct intersection comprises a first
duct
portion and a second duct portion extending laterally from a side of the first
duct
portion. A transition portion extends between the first and second duct
portions,
wherein the transition portion has a length extending along a side of the
first duct
portion and a depth extending away from the side of the first duct portion. In
an
embodiment, the length is a function of the diameter of the second duct
portion. In
another embodiment, the length is greater than a diameter of the second duct
portion. In a still further embodiment, the length is twice the depth.
[0012] Also provided herein is a coking facility exhaust system. In an
embodiment the exhaust system comprises an emergency stack and a crossover
duct extending laterally from a side of the emergency stack. The system also
includes a contoured duct liner including a first wall mated to an inside
surface of the
emergency stack and a second wall attached to the first wall. The second wall
is
contoured to modify the direction of gas flow proximate an intersection of the
emergency stack and crossover duct. The exhaust system may further comprise a
second contoured duct liner mated to an inside surface of the crossover duct.
[0013] Also contemplated herein are methods for improving gas flow in an
exhaust system. In one embodiment the method may include determining a
location
of a poor flow zone (e.g. dead, stagnant, recirculation, separation, etc.)
within the
duct intersection and mounting a flow modifier in the duct intersection at the
determined location. In one aspect of the disclosed technology, the location
is
3
CA 02892292 2015-05-22
WO 2014/105067
PCT/US2012/072181
determined with a computer aided design system, such as a computational fluid
dynamics (CFD) system. In other aspects of the disclosed technology, the
location
is determined by measuring conditions at the duct intersection, such as
temperature,
pressure, and/or velocity.
[0014] In another embodiment, a method of improving gas flow in an exhaust
system including at least one duct intersection comprises determining a
location of a
poor flow zone within the duct intersection and injecting a fluid into the
duct
intersection at the determined location.
[0015] These and other aspects of the disclosed technology will be apparent
after consideration of the Detailed Description and Figures herein. It is to
be
understood, however, that the scope of the invention shall be determined by
the
claims as issued and not by whether given subject matter addresses any or all
issues noted in the background or includes any features or aspects recited in
this
summary.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Non-limiting and non-exhaustive embodiments of the devices, systems,
and methods, including the preferred embodiment, are described with reference
to
the following figures, wherein like reference numerals refer to like parts
throughout
the various view unless otherwise specified.
[0017] FIG. 1 is a schematic representation of a coke plant;
[0018] FIG. 2 is a schematic representation of a representative coke oven
and
associated exhaust system;
[0019] FIG. 3 is a side view in cross-section of an emergency stack and
cross-
over duct intersection indicating various flow anomalies near the
intersection;
[0020] FIG. 4 is a side view in cross-section of a duct intersection
according to
an exemplary embodiment;
[0021] FIG. 5 is a perspective view of a fan manifold that extends between
the
duct fan and main stack of a coke plant;
4
CA 02892292 2015-05-22
WO 2014/105067
PCT/US2012/072181
[0022] FIG. 6 is a side view in cross-section of a traditional fan manifold
indicating the velocity of gases traveling through the manifold and main
stack;
[0023] FIG. 7 is a side view in cross-section of a modified fan manifold
indicating the velocity of gases traveling through the manifold and main
stack;
[0024] FIG. 8 is a side view in cross-section of a turning vane assembly
according to an exemplary embodiment;
[0025] FIG. 9 is a perspective view of the turning vane assembly shown in
FIG.
8;
[0026] FIG. 10 is a side view in cross-section of a fan manifold according
to an
exemplary embodiment indicating the velocity of gases traveling through the
manifold and main stack;
[0027] FIG. 11A is a front view schematic representation of a duct
intersection
according to an exemplary embodiment;
[0028] FIG. 11B is a side view schematic representation of the duct
intersection
shown in FIG. 11A;
[0029] FIG. 12A is a front view schematic representation of a duct
intersection
according to an exemplary embodiment;
[0030] FIG. 12B is a side view schematic representation of the duct
intersection
shown in FIG. 12A;
[0031] FIG. 13 is a side view of a duct intersection according to another
exemplary embodiment;
[0032] FIG. 14 is a schematic representation of a fluid injection system
for use
at a duct intersection;
[0033] FIG. 15A is a perspective view of an intermediate HRSG tie in with
transition pieces at the tie-in joints;
[0034] FIG. 15B is a side view of an intermediate HRSG tie in with
transition
pieces at the tie-in joints;
[0035] FIG. 15C is a perspective view of an intermediate HRSG tie in with
transition pieces at the tie-in joints; and
CA 02892292 2015-05-22
WO 2014/105067
PCT/US2012/072181
[0036] FIG. 15D is a top view of an intermediate HRSG tie in with
transition
pieces at the tie-in joints.
DETAILED DESCRIPTION
[0037] Provided herein is a contoured duct liner, a duct intersection, and
methods of improving gas flow in an exhaust system. The described embodiments
may be implemented as original designs or as retrofits to existing facilities.
The
disclosed designs have been found to improve flow, thermal conditions, and
structural integrity at intersections or tie-ins in a coke oven or similar
system. By
optimizing the external and/or internal shape of intersections, the mixing can
be
improved, areas of relatively undesirable conditions can be minimized, and
pressure
drop losses at the intersection can be minimized. Reducing pressure losses at
the
intersections can help lower draft set point(s), which can lead to improved
operation
as well as potentially lower cost designs and maintenance. Furthermore, it can
be
advantageous to minimize the draft set point of the overall system to minimize
infiltration of any unwanted outside air into the system.
[0038] Specific details of several embodiments of the technology are
described
below with reference to FIGS. 1-14. Other details describing well-known
structures
and systems often associated with coke making and/or duct design have not been
set forth in the following disclosure to avoid unnecessarily obscuring the
description
of the various embodiments of the technology. Many of the details, dimensions,
angles, and other features shown in the figures are merely illustrative of
particular
embodiments of the technology. Accordingly, other embodiments can have other
details, dimensions, angles, and features without departing from the spirit or
scope
of the present technology. A person of ordinary skill in the art, therefore,
will
accordingly understand that the technology may have other embodiments with
additional elements, or the technology may have other embodiments without
several
of the features shown and described below with reference to FIGS. 1-14.
[0039] FIG. 1 illustrates a representative coke plant 5 where coal 1 is fed
into a
battery of coke ovens 10 where the coal is heated to form coke. Exhaust gases
(i.e.
flue gases) from the coke ovens are collected in a common tunnel 12 which
intersects emergency stack 14. Cross-over duct 16 is also connected to common
tunnel 12 via the emergency stack 14. Hot flue gases flow through the cross-
over
6
CA 02892292 2015-05-22
WO 2014/105067
PCT/US2012/072181
duct 16 into a co-generation plant 18 which includes a heat recovery steam
generator (HRSG) 20 which in turn feeds steam turbine 22. The flue gases
continue
on to a sulfur treatment facility 24 and finally the treated exhaust gases are
expelled
through main stack 28 via duct fans 26, which provide negative pressure on the
entire system in addition to the draft created by gases rising through the
main stack
28.
[0040] With further reference to FIG. 2, it can be appreciated that coke
ovens
are connected to the common tunnel 12 via uptakes 15. Common tunnel 12
extends horizontally along the top of the coke ovens 10. An emergency stack 14
extends vertically from common tunnel 12 as shown. Cross-over duct 16
intersects
emergency stack 14 at a duct intersection 30. In normal operation, the
emergency
stack 14 is closed whereby exhaust gases travel through the cross-over duct 16
to
the co-generation plant 18 (see FIG. 1). In the event of a problem with the co-
generation plant 18, or other downstream equipment, the emergency stack 14 may
be opened to allow exhaust gases to exit the system directly. While the
figures
show the common tunnel 12 and cross-over duct 16 intersecting the emergency
stack 14 at different elevations, the common tunnel 12 and cross-over duct 16
may
intersect the emergency stack 14 at the same elevation. Furthermore, the
technology disclosed herein may be applied to the intersections whether they
are at
the same elevation or different elevations.
[0041] FIG. 3 illustrates various flow anomalies present in traditional
duct
intersections, such as duct intersection 30. Flow anomaly 32 is a point of
localized
combustion that is due to poor flow/distribution. An additional area of poor
flow/mixing distribution 36 is located in the emergency stack 14 across from
the
cross-over duct 16. A poor flow zone 34 (e.g. dead, stagnant, recirculation,
separation, etc.) is located in cross-over duct 16. These poor flow zone areas
contain separated flows which can dissipate useful flow energy. These
potential poor
flow spaces can also contain unwanted, unsteady vortical flow, sometimes
enhanced by buoyancy or chemical reactions, which can contribute to unwanted,
poor acoustics, forced harmonics, potential flow instabilities, and incorrect
instrument readings. Incorrect instrument readings may occur if measurements
are
made in a poor flow zone that has conditions not representative of flow in the
duct.
7
CA 02892292 2015-05-22
WO 2014/105067
PCT/US2012/072181
Because of the nature of the poor flow zones, these areas can also cause
particle
drop out and promote particle accumulation.
[0042] FIG. 4 illustrates an improved duct intersection 130 according to an
exemplary embodiment. Duct intersection 130 includes a first duct portion in
the
form of emergency stack 114 and a second duct portion in the form of cross-
over
duct 116 that extends laterally from a side of the emergency stack 114. In
this
embodiment, duct intersection 130 includes a plurality of flow modifiers (40,
42, 44)
to improve exhaust flow. For example, flow modifier 40 is in the form of a
contoured
duct liner that is positioned at the intersection 130 of emergency stack 114
and
cross-over duct 116. Flow modifier 40 occupies the area where traditional
designs
have poor flow and mixing such as flow anomaly 32 in FIG. 3. Flow modifier 42
is
disposed in cross-over duct 116 to occupy the poor flow zone 34 shown in FIG.
3.
Flow modifier 44 is disposed in the emergency stack 114 opposite the cross-
over
duct 116 and, in this case, occupies the poor mixing distribution region 36
shown in
FIG. 3. With the addition of flow modifiers 40, 42, and 44 the flow F within
intersection 130 is improved (see FIG. 4).
[0043] The duct liners reshape the internal contours of the duct,
inherently
changing the nature and direction of the flow path among other effects. The
duct
liners can be used to smooth or improve flow entrance or provide better
transition
from one path to another especially when there are limitations to do so with
the duct
shape. The contoured duct liners can be used to alleviate wall shear
stress/erosion
stemming from high velocities and particle accumulation from settling and/or
particle
impaction, which could result in slow or poor flow zones. The contoured duct
liners
also provide better duct transitions, or paths, for better flow transition and
movement, mitigation of stress and thermal concentrations, and mitigation of
flow
separation, etc.
[0044] With continued reference to FIG. 4 it can be appreciated that, in
this
embodiment, the contoured duct liners 40, 42, and 44 are each comprised of a
first
contoured wall mated to an inside surface of the duct intersection and a
second
contoured wall mated to the first contoured wall. For example, contoured duct
liner
40 includes a first contoured wall 50 which is mated to the inside surface 17
of
emergency stack 114 and inside surface 19 of cross-over duct 116. Duct liner
40
also includes a second contoured wall 52 that is mated to the first contoured
wall 50.
8
CA 02892292 2015-05-22
WO 2014/105067
PCT/US2012/072181
In this case, the second contoured wall 52 is convex and extends into the flow
F of
the flue gases traveling through the duct intersection 130. Contoured duct
liner 42
includes a first contoured wall 54 which is mated to an inside surface 19 of
the
cross-over duct 116. A second contoured wall 56 is mated to the first
contoured wall
54 and is also convex. Similarly, contoured duct liner 44 includes a first
contoured
wall 58 mated to inside surface 17 of the emergency stack 114 and includes a
second contoured wall 60 mated to the first contoured wall 58.
[0045] The first contoured walls of the contoured duct liners may be
attached to
the inside surfaces 17 and 19 by welding, fasteners, or the like. Similarly,
the
second contoured walls may be attached to their respective first contoured
walls by
appropriate fasteners or by welding. As one of ordinary skill in the art will
recognize,
the contoured duct liners may be comprised of various materials which are
suitable
for corrosive, high heat applications. For example, first contoured walls 50,
54, and
58 may be comprised of steel or other suitable material. The second contoured
walls 52, 56, and 60 may comprise a refractory material such as ceramic that
is
capable of resisting the heat associated with the flue gases and local
combustion.
The selection of materials can be dependent on the thermal, flow, and chemical
properties of the flue gases. Because the flue gases can be of varied
temperatures,
velocities, chemical composition, in which all can depend on many factors such
as
the time in the coking cycle, flow control settings, ambient conditions, at
the
locations in the coking oven system, etc., the material selection can vary as
well.
The internal lining layers for the hot duct tie-ins could have more
significant
refractory layers than for cold ducts. Selection of appropriate materials may
take
into account min/max temperatures, thermal cycling, chemical reactions, flow
erosion, acoustics, harmonics, resonance, condensation of corrosive chemicals,
and
accumulation of particles, for example.
[0046] In an embodiment, the flow modifiers may comprise a multilayer
lining
that is built up with a relatively inexpensive material and covered with a
skin. In yet
another embodiment, refractory or similar material can be shaped via gunning
(i.e.
spraying). Better control of shaping via gunning may be accomplished by
gunning in
small increments or layers. In addition, a template or mold may be used to aid
the
shaping via gunning. A template, mold, or advanced cutting techniques may be
used
to shape the refractory (e.g. even in the absence of gunning for the main
shape of
9
CA 02892292 2015-05-22
WO 2014/105067 PCT/US2012/072181
an internal insert) for insertion into the duct and then attached via gunning
to the
inner lining of the duct. In yet another embodiment, the flow modifier may be
integrally formed along the duct. In other words, the duct wall may be formed
or
"dented" to provide a convex surface along the interior surface of the duct.
As used
herein, the term convex does not require a continuous smooth surface, although
a
smooth surface may be desirable. For example, the flow modifiers may be in the
form of a multi-faceted protrusion extending into the flow path. Such a
protrusion
may be comprised of multiple discontinuous panels and/or surfaces.
Furthermore,
the flow modifiers are not limited to convex surfaces. The contours of the
flow
modifiers may have other complex surfaces that may be determined by CFD
analysis and testing, and can be determined by design considerations such as
cost,
space, operating conditions, etc.
[0047] FIG. 5 illustrates a traditional fan manifold 70 that extends
between the
duct fans 26 and main stack 28 (see FIG. 1). Fan manifold 70 comprises a
plurality
of branches 72, 74, and 76 which all intersect into plenum 80. As shown in the
figure, branches 74 and 76 include flow diverters 78 while plenum 80 includes
flow
straightener 79. With reference to FIG. 6, which indicates velocity magnitude
in the
fan manifold 70, traditional fan manifold designs result in a high velocity
flow 82
which can damage the duct as a result of high shear stress. In contrast, FIG.
7
illustrates a fan plenum 180 intersection which includes a turning vane
assembly 90.
In this case, the magnitude of the velocity flowing next to the surface of
main stack
128 is much lower than in the conventional duct configuration shown in FIG. 6.
The
higher flow velocity 184 is displaced inward away from the inside wall of the
main
stack 128, thereby reducing shear stress on the wall and helping to prevent
erosion
and corrosion of the stack. Turning vanes inside the duct help direct the flow
path
for a more efficient process. Turning vanes can be used to better mix flow,
better
directing of flow, and mitigation of total pressure losses, for example.
[0048] With reference to FIGS. 8 and 9, the turning vane assembly 90
includes
an inner vane 92 and an outer vane 94. In this embodiment, both the inner and
outer vanes are disposed in the main stack 128. FIG. 8 provides exemplary
dimensions by which a turning vane assembly could be constructed. However,
these dimensions are exemplary and other dimensions and angles may be used. As
perhaps best shown in FIG. 9 the inner vane 92 includes a leading portion 902
that
CA 02892292 2015-05-22
WO 2014/105067
PCT/US2012/072181
connects to an angled portion 904, which, in turn, connects to trailing
portion 906.
As shown in the figure, the angled portion 904 tapers from a 100 inch width to
an 80
inch width. Similarly, the trailing portion 906 tapers from an 80 inch width
to a 50
inch width. Here again, the dimensions are only representative and may vary.
In
this embodiment, the angled portion 904 is angled at approximately 45 degrees;
however, other angles may be used depending on the particular application.
Outer
vane 94 includes a leading portion 908 connected to an angled portion 910
which in
turn is connected to a trailing portion 912. Outer turning vane 94 also
includes side
walls 914 and 916 as shown. Side walls 914 and 916 are canted inward towards
the
angled and trailing portions 910 and 912 at an angle A. In this embodiment
angle A
is approximately 10 degrees. Turning vane assembly 90 may be mounted or
assembled into the main stack 128 with suitable fasteners or may be welded in
place, for example.
[0049] In an
exemplary embodiment shown in FIG. 10, a fan manifold plenum
280 intersects main stack 228 with a ramped transition. In this case, it can
be
appreciated that the fan manifold plenum 280 has an upper wall 281 which
transitions into the main stack 228 at an angle. As shown by the velocity
magnitude
282, this results in a lower flow velocity magnitude than with traditional fan
manifold
designs shown in FIGS. 5 and 6. It has been
found that improving the
intersection/transition from the duct fan to the main stack can reduce wear
and
erosion as well as ash buildup in the main stack. In addition to the ramped
transition, contoured duct liners and/or turning vanes may be used together in
combination. For example, contoured duct liners may be located in the slower
velocity regions 202, 204, and 206 as shown in FIG. 10.
[0050] FIGS. 11A
and 11B illustrate a duct intersection 230 according to
another exemplary embodiment. In this embodiment, the duct intersection 230
includes an emergency stack 214 and a cross-over duct 216 with a transition
portion
240 extending therebetween. Changing the size of the duct cross sectional
areas
near or at intersections can help improve flow performance. In general,
increasing
the size of the flow cross sectional area as in transition portion 240 can
help reduce
flow losses. The transition portion can help better transition flow from a
duct to a
joining duct at tie-ins or intersections. The transitions can be flared,
swaged, swept,
or the like to provide the desired flow behavior at the intersections. In
addition, the
11
CA 02892292 2015-05-22
WO 2014/105067
PCT/US2012/072181
transitions may converge or diverge with respect to the direction of flow.
Converging
and diverging portions may be used in combination, e.g. the duct may first
converge
and then diverge or vice versa. Furthermore, it should be understood that the
embodiments may be implemented in various combinations. For example, a turning
vane assembly, such as described above with respect to FIGS. 7-9, may be used
in
conjunction with the duct liners, whether fabricated or gunned in place, as
well as
transition portions.
[0051] The transition portion 240 has a length L extending along a side of
the
exhaust duct and a depth D extending away from the side of the exhaust duct.
In
this embodiment, the length is greater than a diameter d of the cross-over
duct 216.
The length L may be a function of the duct diameter d or the depth D. For
example,
the length L may be twice the depth D. FIG. 12A and 12B illustrate a duct
intersection 330 including a transition portion 340 that is similar to that
shown in
FIGS. 11A and 11B, except in this case the exhaust stack 314 includes an
enlarged
annular region 315 that is adjacent to the intersection 330. FIG. 13
illustrates yet
another embodiment of a duct intersection 430 with an asymmetric transition
portion
440. Depending on the desired design performance, external fins could be added
to
help enhance heat transfer with the surrounding ambient air. For example,
external
fins from the surfaces could be used to help cool localized hot spots.
[0052] Duct intersections can be designed, retrofitted, or modified to
introduce
fluids such as oxidizers (for better combustion or to remove PIC's, products
of
incomplete combustion), liquids such as water, fuels, inert gases, etc. to
help better
distribute combustion and mitigate hot spots or allow cooling of the hot
stream. For
example, fluid could be introduced to provide a boundary layer of cold inert
fluid to
mitigate hot spots at affected wall surfaces. The fluids, which could include
liquids
such as water, inert or other gases, could be used for cooling or mitigating
certain
chemical reactions. The ducts can be modified to accommodate ports or
additional
pathways for introducing fluids. Fluid introduction, if introduced from a
pressurized
source, could also create entrainment, thereby improving mixing or flow
energy.
[0053] FIG. 14 illustrates a duct intersection 530 including a fluid
injection
system 540. Fluid injection system 540 is operative to inject fluid at
particular
regions in the intersection 530 to energize or direct flow, as well as
insulate the
surface of the ducts from exhaust gases. Fluid injection system 540 includes a
12
CA 02892292 2015-05-22
WO 2014/105067
PCT/US2012/072181
controller 542 which is connected to a plurality of valves, or fluid injectors
544, via
wiring 548. Each injector 544 is connected by tubing 546 to a fluid reservoir
550. It
should be understood that the term fluid encompasses liquids as well as gases.
Thus, the injection system 540 may inject liquids or gases into the exhaust
flow. The
injectors may be spaced optimally depending on design conditions. The
injectors
can inject fluid transversely into the duct, as shown in FIG. 14.
Alternatively, the
injectors could inject external fluid axially or along the exhaust flow
direction at
various locations. The injectors could also inject fluid at different
injection angles.
The direction and method of injection depends on the conditions that exist at
the tie-
ins and intersections. The injected fluid may come from an external
pressurized
source. In another embodiment, the fluid may be entrained through a port or
valve
by the draft of the exhaust flow.
[0054] The fluid injection system 540 may also include various sensors,
such as
temperature sensor 552 connected to controller 542 via cable 554. Various
sensors,
such as sensor 552, may provide feedback to controller 542 such that fluid may
be
injected at appropriate times. While the embodiment is illustrated as having a
single
temperature sensor, other additional sensors of different types of sensors may
be
employed in providing control feedback to controller 542. For example, other
sensor
may include pressure, velocity, and emissions sensors, such as an oxygen
sensor.
[0055] The fluid injection system 540 may be used in conjunction with the
contoured duct liners, turning vanes, and transition portions disclosed above.
The
contoured duct liners in conjunction with the fluid injection system may
extend the
use of the duct intersection as a true mixing zone and potentially a
combustion
chamber. Air and other additives (e.g. oxygen) may be injected into the
intersection
to allow better combustion and use of the tunnels as extended combustion
zones.
Also, a well-mixed duct intersection may be configured to act as a second
combustion chamber. The addition of extra air into the duct intersection
mixing zone
can burn any excess flue gas and even cool off the intersection with excess
air or
other gases, such as nitrogen. For example, if the common tunnel is too hot
and
fully combusted, air may be injected to cool the process. In contrast, if the
flue gas
is not completely combusted before entering the heat recovery steam generator
(HRSG), it could reduce the HRSG tubes, which are typically made of metal,
leading
13
CA 02892292 2015-05-22
WO 2014/105067
PCT/US2012/072181
to accelerated corrosion and failure. In this case, an oxidizer is added, such
as air,
to burn all the combustibles before entering the HRSG.
[0056] Although the embodiments have been described with respect to a duct
intersection between an emergency stack and cross-over duct, the disclosed
technology may be applicable to hot duct tie-ins, cold duct tie-ins, stack
junctions,
and HRSGs. For example, as shown in FIGS. 15A-15D, an intermediate HRSG tie
in may include transition pieces (632, 634, 652) at the tie-in joints.
Transitions 632
and 634 connect duct 622 to duct 630. Duct 630 connects to a rectangular tube
650
via transition piece 652.
[0057] Also contemplated herein are methods of improving gas flow in an
exhaust system that includes at least one duct intersection. The methods may
include any procedural step inherent in the structures described herein. In an
embodiment, the method comprises determining a location of a low or poor flow
zone, an area of poor combustion, or an area of poor mixing (i.e. areas of
relatively
undesirable conditions) within the duct intersection and providing a flow
modifier at
the determined location. Providing a flow modifier may include, for example
and
without limitation, mounting a duct liner within the duct, gunning a
refractory material
to the inside of the duct, mounting turning vanes within the duct, forming a
convex
surface along the duct, and combinations of the above. The location may be
determined with a computer aided design system, such as a CFD system. The
location may also be determined by measuring conditions at the duct
intersection,
such as temperature, pressure, and velocity. In another embodiment the method
comprises determining a location of a poor flow zone within the duct
intersection and
injecting a fluid into the duct intersection at the determined location.
[0058] From the foregoing it will be appreciated that, although specific
embodiments of the technology have been described herein for purposes of
illustration, various modifications may be made without deviating from the
spirit and
scope of the technology. Further, certain aspects of the new technology
described
in the context of particular embodiments may be combined or eliminated in
other
embodiments. Moreover, while advantages associated with certain embodiments of
the technology have been described in the context of those embodiments, other
embodiments may also exhibit such advantages, and not all embodiments need
necessarily exhibit such advantages to fall within the scope of the
technology.
14
Accordingly, the disclosure and associated technology can encompass other
embodiments not expressly shown or described herein. Thus, the disclosure is
not
limited except as by the appended claims.
[0059] Examples:
Example 1: A duct intersection is provided, which comprises:
a first duct portion;
a second duct portion extending laterally from a side of the first duct
portion;
and
at least one flow modifier disposed inside one of the first and second duct
portions.
Example 2: The duct intersection according to example 1 is configured such
that the flow modifier is a contoured duct liner.
Example 3: The duct intersection according to example 2 is configured such
that the contoured duct liner comprises a first contoured wall mated to an
inside
surface of the duct and a second contoured wall mated to the first contoured
wall.
Example 4: The duct intersection according to example 3 is configured such
that the second contoured wall comprises a refractory material.
Example 5: The duct intersection according to example 2 is configured such
that the second duct portion tees into the first duct portion.
Example 6: The duct intersection according to example 5 is configured such
that the contoured duct liner is mounted inside the first duct portion.
Example 7: The duct intersection according to example 5 is configured such
that the contoured duct liner is mounted inside the second duct portion.
Example 8: The duct intersection according to example 1 is configured such
that the flow modifier includes at least one turning vane.
Example 9: The duct intersection according to example 1 is configured such
that the flow modifier comprises molded refractory material.
Example 10: The duct intersection according to example 1 is configured such
that the second duct portion extends laterally from the side of the first duct
portion at
an angle of less than 90 degrees.
Example 11: A contoured duct liner for use in a duct intersection is provided,
which comprises:
a first wall contoured to mate with an inside surface of a duct intersection;
and
CA 2892292 2017-07-12
a second wall attached to the first wall, wherein the second wall is contoured
to modify the direction of gas flow within the duct intersection.
Example 12: The contoured duct liner according to example 11 is configured
such that the second wall includes at least one convex surface.
Example 13: The contoured duct liner according to example 11 is configured
such that the second wall comprises a refractory material.
Example 14: A coking facility exhaust system is provided, which comprises:
an emergency stack;
a crossover duct extending laterally from a side of the emergency stack; and
a contoured duct liner, including a convex surface operative to modify the
direction of gas flow proximate an intersection of the emergency stack and
crossover
duct.
Example 15: The coking facility exhaust system according to example 14
further comprises a second contoured duct liner disposed on an inside surface
of the
crossover duct.
Example 16: An improved coking facility exhaust system including an
emergency stack and a crossover duct extending laterally from a side of the
emergency stack is provided in which the improvement comprises:
a contoured duct liner, including a convex surface operative to modify the
direction of gas flow proximate an intersection of the emergency stack and
crossover
duct.
Example 17: A method of improving gas flow in an exhaust system including at
least one duct intersection is provided, which comprises:
determining a location having undesirable flow characteristics within the duct
intersection; and
providing a flow modifier in the duct intersection at the determined location.
Example 18: With respect to the method according to example 17, the
location is determined with a computer aided design system.
Example 19: With respect to the method according to example 17, the
location is determined by measuring conditions at the duct intersection.
Example 20: With respect to the method according to example 19, the
conditions are selected from the group consisting of temperature, pressure,
and
velocity.
16
CA 2892292 2017-07-12
Example 21: With respect to the method according to example 17, the flow
modifier is a contoured duct liner.
Example 22: With respect to the method according to example 17, the flow
modifier is at least one turning vane.
Example 23: The method according to example 17 further comprises
gunning refractory material on an inside surface of the duct intersection at
the
determined location, thereby providing the convex surface.
Example 24: A duct intersection is provided, which comprises:
a first duct portion;
a second duct portion extending laterally from a side of the first duct
portion; and
a transition portion extending between the first and second duct portions,
wherein the transition portion has a length extending along a side of the
first duct
portion and a depth extending away from the side of the first duct portion,
wherein
the length is greater than a diameter of the second duct portion.
Example 25: The duct intersection according to example 24 is configured
such that the length is twice the depth.
Example 26: The duct intersection according to example 24, is configured
such that the transition portion is flared.
Example 27: The duct intersection according to example 24 is configured
such that the first duct portion includes an enlarged annular region and the
transition
portion extends between the enlarged annular region and the second duct
portion.
Example 28: The duct intersection according to example 24 is configured
such that the second duct portion extends laterally from the side of the first
duct
portion at an angle of less than 90 degrees.
Example 29: The duct intersection according to example 24 is configured
such that the second duct portion tees into the first duct portion.
Example 30: The duct intersection according to example 24 further
comprises at least one flow modifier having a convex surface disposed inside
one of
the first and second duct portions.
Example 31: The duct intersection according to example 30 further
comprises at least one turning vane.
17
CA 2892292 2017-07-12
Example 32: A method of improving gas flow in an exhaust system including
at least one duct intersection is provided, which comprises:
determining a location of a poor flow zone within the duct intersection; and
injecting a fluid into the duct intersection at the determined location.
18
CA 2892292 2017-07-12
