Note: Descriptions are shown in the official language in which they were submitted.
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NON-PERPENDICULAR CONNECTIONS BETWEEN COKE OVEN
UPTAKES AND A HOT COMMON TUNNEL, AND ASSOCIATED
SYSTEMS AND METHODS
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to U.S. Patent Application No.
13/830,971, filed
March 14, 2013.
TECHNICAL FIELD
[0002] The present technology is generally directed to non-perpendicular
connections
between coke oven uptakes and a hot common tunnel, and associated systems and
methods.
BACKGROUND
[0003] Coke is a solid carbonaceous fuel that is derived from coal. Coke
is a favored
energy source in a variety of useful applications. For example, coke is often
used to smelt
iron ore during the steelmaking process. As a further example, coke may also
be used to heat
commercial buildings or power industrial boilers.
[0004] In a typical coking process, an amount of coal is baked in a coke
oven at
temperatures that generally exceed 2,000 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,
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.
[0005] The hot exhaust (i.e. flue gas) emitted during baking is extracted
from the coke
ovens through a network of ducts, intersections, and transitions. The
intersections in the flue
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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 can lead to higher required draft,
leaks, and problems
with system control. 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 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.
The localized erosion and/or hot spots can, in turn, lead to failures at duct
intersections.
[0006] 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 draft fan can pull. Pressure drops
in duct
intersections can take away from the amount of draft available to exhaust flue
gases from the
coke ovens. 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,
and reduce pressure drop losses.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Figure 1 is a schematic illustration of a horizontal heat recovery
coke plant,
configured in accordance with embodiments of the technology.
[0008] Figure 2 is an isometric, partial cut-away view of a portion of the
horizontal
heat recovery coke plant of Figure I configured in accordance with embodiments
of the
technology.
[0009] Figure 3 is a sectional view of a horizontal heat recovery coke oven
configured
in accordance with embodiments of the technology.
[0010] Figure 4 is a top view of a portion of a horizontal heat recovery
coke plant
configured in accordance with embodiments of the technology.
[0011] Figure 5A is a cross-sectional top view of a perpendicular interface
between an
uptake duct and a common tunnel configured in accordance with embodiments of
the
technology.
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[0012] Figure 5B is a cross-sectional top view of a non-perpendicular
interface
between an uptake duct and a common tunnel configured in accordance with
embodiments of
the technology.
[0013] Figure 5C is a cross-sectional end view of a non-perpendicular
interface
between an uptake duct and a common tunnel configured in accordance with
embodiments of
the technology.
[0014] Figure 5D is a cross-sectional end view of a non-perpendicular
interface
between an uptake duct and a common tunnel configured in accordance with
embodiments of
the technology.
[0015] Figure 5E is a cross-sectional end view of a non-perpendicular
interface
between an uptake duct and a common tunnel configured in accordance with
embodiments of
the technology.
[0016] Figures 6A-61 are top views of various configurations of interfaces
between
uptake ducts and a common tunnel configured in accordance with embodiments of
the
technology.
[0017] Figure 7A is a cross-sectional top view of a non-perpendicular
interface
retrofitted between an uptake and a common tunnel configured in accordance
with
embodiments of the technology.
[0018] Figure 7B is a cross-sectional top view of an interface between an
uptake and a
common tunnel configured in accordance with embodiments of the technology.
[0019] Figure 7C is a cross-sectional top view of a non-perpendicular
interface
retrofitted between the uptake and common tunnel of Figure 7B configured in
accordance
with embodiments of the technology.
[0020] Figure 8 is a cross-sectional top view of a non-perpendicular
interface between
an uptake and a common tunnel configured in accordance with embodiments of the
technology.
[0021] Figure 9 is a plot showing the spatial distribution of gas static
pressure along
the length of the common tunnel.
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DETAILED DESCRIPTION
[0022] The present technology is generally directed to non-perpendicular
connections
between coke oven uptakes and a hot common tunnel, and associated systems and
methods.
In some embodiments, a coking system includes a coke oven and an uptake duct
in fluid
communication with the coke oven. The uptake duct has an uptake flow vector of
exhaust
gas from the coke oven. The system also includes a common tunnel in fluid
communication
with the uptake duct. The common tunnel has a common flow vector and can be
configured
to transfer the exhaust gas to a venting system. The uptake flow vector and
common flow
vector can meet at a non-perpendicular interface to improve mixing between the
flow vectors
and reduce draft loss in the common tunnel.
[0023] Specific details of several embodiments of the technology are
described below
with reference to Figures 1-9. Other details describing well-known structures
and systems
often associated with coal processing 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 Figures 1-9.
[0024] Figure 1 is a schematic illustration of a horizontal heat recovery
(HHR) coke
plant 100, configured in accordance with embodiments of the technology. The
HHR coke
plant 100 comprises ovens 105, along with heat recovery steam generators
(HRSGs) 120 and
an air quality control system 130 (e.g., an exhaust or flue gas
desulfurization (FGD) system),
both of which are positioned fluidly downstream from the ovens 105 and both of
which are
fluidly connected to the ovens 105 by suitable ducts. The HHR coke plant 100
also includes
one or more common tunnels 110A, 110B (collectively "common tunnel 110")
fluidly
connecting individual ovens 105 to the HRSGs 120 via one or more individual
uptake ducts
225. In some embodiments, two or more uptake ducts 225 connect each individual
oven 105
to the common tunnel 110. A first crossover duct 290 fluidly connects the
common tunnel
110A to the HRSGs 120 and a second crossover duct 295 fluidly connects the
common
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tunnel 110B to the HRSGs 120 at respective intersections 245. The common
tunnel 110 can
further be fluidly connected to one or more bypass exhaust stacks 240. A
cooled gas duct
125 transports the cooled gas from the HRSGs to the FGD system 130. Fluidly
connected
and further downstream are a baghouse 135 for collecting particulates, at
least one draft fan
140 for controlling air pressure within the system, and a main gas stack 145
for exhausting
cooled, treated exhaust into the environment. Various coke plants 100 can have
different
proportions of ovens 105, HRSGs 120, uptake ducts 225, common tunnels 110, and
other
structures. For example, in some coke plants, each oven 105 illustrated in
Figure 1 can
represent ten actual ovens.
[0025] As will be described in further detail below, in several embodiments
the uptake
ducts 225 meet the common tunnel 110 at non-perpendicular interfaces. The non-
perpendicular interfaces may comprise a fitting within the uptake ducts 225, a
fitting within
the common tunnel 110, a non-perpendicular uptake duct 225, a non-
perpendicular portion of
the uptake duct 225, or other feature. The non-perpendicular interfaces can
lower the mixing
draft loss at the uptake/common tunnel connection by angling the connection in
the direction
of the common tunnel flow. More specifically, the uptake ducts 225 have an
uptake flow
having an uptake flow vector (having x, y, and z orthogonal components) and
the common
tunnel 110 has a common flow having a common flow vector (having x, y, and z
orthogonal
components). By minimizing the differences between the uptake flow vector and
the
common flow vector, the lesser the change in the directional momentum of the
hot gas and,
consequently, the lower the draft losses.
[0026] Furthermore, there are interface angles in which the draft in the
common tunnel
110 can increase from the addition of the extra mass flow from the uptake duct
225. More
specifically, the interface can act as a vacuum aspirator which uses mass flow
to pull a
vacuum. By aligning the uptake duct 225 mass flow with the common tunnel 110
mass flow
(having a velocity vector in the same major flow direction), a coke plant can
achieve more
vacuum pull and lower draft loss, which can potentially cause a draft
increase. The reduced
draft loss can be used to reduce the common tunnel 110 size (e.g., diameter)
or lower the
required overall system draft.
[0027] Further, various embodiments of the technology are not limited to
the interface
between uptake ducts and the common tunnel. Rather, any connection where the
gas flow
undergoes a significant change in direction can be improved to have a lower
draft loss by
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using a non-perpendicular connection. For example, any of the connections in
the exhaust
flow path (e.g., between the common tunnel 110 and the bypass exhaust stacks
240) can
include ducts meeting head to head; angling these connections can lower draft
losses in the
manner described above.
[0028] Figures 2 and 3 provide further detail regarding the structure and
operation of
the coke plant 100. More specifically, Figures 2 and 3 illustrate further
details related to the
structure and mechanics of exhaust flow from the ovens to the common tunnel.
Figures 4
through 9 provide further details regarding various embodiments of non-
perpendicular
connections between coke oven uptakes ducts and the common tunnel.
[0029] Figure 2 is an isometric, partial cut-away view of a portion of the
HHR coke
plant 100 of Figure 1 configured in accordance with embodiments of the
technology. Figure
3 is a sectional view of an HHR coke oven 105 configured in accordance with
embodiments
of the technology. Referring to Figures 2 and 3 together, each oven 105 can
include an open
cavity defined by a floor 160, a front door 165 forming substantially the
entirety of one side
of the oven, a rear door 170 opposite the front door 165 forming substantially
the entirety of
the side of the oven opposite the front door, two sidewalls 175 extending
upwardly from the
floor 160 intermediate the front 165 and rear 170 doors, and a crown 180 which
forms the top
surface of the open cavity of an oven chamber 185. Controlling air flow and
pressure inside
the oven chamber 185 can be critical to the efficient operation of the coking
cycle, and
therefore the front door 165 includes one or more primary air inlets 190 that
allow primary
combustion air into the oven chamber 185. Each primary air inlet 190 includes
a primary air
damper 195 which can be positioned at any of a number of positions between
fully open and
fully closed to vary the amount of primary air flow into the oven chamber 185.
Alternatively,
the one or more primary air inlets 190 are formed through the crown 180.
[0030] In operation, volatile gases emitted from the coal positioned inside
the oven
chamber 185 collect in the crown and are drawn downstream in the overall
system into
downcomer channels 200 formed in one or both sidewalls 175. The downcomer
channels
fluidly connect the oven chamber 185 with a sole flue 205 positioned beneath
the oven floor
160. The sole flue 205 forms a circuitous path beneath the oven floor 160.
Volatile gases
emitted from the coal can be combusted in the sole flue 205 thereby generating
heat to
support the carbonization of coal into coke. The downcomer channels 200 are
fluidly
connected to chimneys or uptake channels 210 formed in one or both sidewalls
175. A
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secondary air inlet 215 is provided between the sole flue 205 and the
atmosphere; the
secondary air inlet 215 includes a secondary air damper 220 that can be
positioned at any of a
number of positions between fully open and fully closed to vary the amount of
secondary air
flow into the sole flue 205. The uptake channels 210 are fluidly connected to
the common
tunnel 110 by the one or more uptake ducts 225. A tertiary air inlet 227 is
provided between
the uptake duct 225 and atmosphere. The tertiary air inlet 227 includes a
tertiary air damper
229 which can be positioned at any of a number of positions between fully open
and fully
closed to vary the amount of tertiary air flow into the uptake duct 225.
[0031] In order to provide the ability to control gas flow through the
uptake ducts 225
and within the ovens 105, each uptake duct 225 also includes an uptake damper
230. The
uptake damper 230 can be positioned at any number of positions between fully
open and fully
closed to vary the amount of oven draft in the oven 105. The uptake damper 230
can
comprise any automatic or manually-controlled flow control or orifice blocking
device (e.g.,
any plate, seal, block, etc.). As used herein, "draft" indicates a negative
pressure relative to
atmosphere. For example, a draft of 0.1 inches of water indicates a pressure
of 0.1 inches of
water below atmospheric pressure. Inches of water is a non-SI unit for
pressure and is
conventionally used to describe the draft at various locations in a coke
plant. In some
embodiments, the draft ranges from about 0.12 to about 0.16 inches of water in
the oven 105.
If a draft is increased or otherwise made larger, the pressure moves further
below
atmospheric pressure. If a draft is decreased, drops, or is otherwise made
smaller or lower,
the pressure moves towards atmospheric pressure. By controlling the oven draft
with the
uptake damper 230, the air flow into the oven 105 from the air inlets 190,
215, 227 as well as
air leaks into the oven 105 can be controlled. Typically, as shown in Figure
3, an individual
oven 105 includes two uptake ducts 225 and two uptake dampers 230, but the use
of two
uptake ducts and two uptake dampers is not a necessity; a system can be
designed to use just
one or more than two uptake ducts and two uptake dampers. All of the ovens 105
are fluidly
connected by at least one uptake duct 225 to the common tunnel 110 which is in
turn fluidly
connected to each HRSG 120 by the crossover ducts 290, 295. The exhaust gases
from each
oven 105 flow through the common tunnel 110 to the crossover ducts 290, 295.
[0032] In operation, coke is produced in the ovens 105 by first loading
coal into the
oven chamber 185, heating the coal in an oxygen depleted environment, driving
off the
volatile fraction of coal, and then oxidizing the VM within the oven 105 to
capture and utilize
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the heat given off. The coal volatiles are oxidized within the ovens over an
extended coking
cycle, and release heat to regeneratively drive the carbonization of the coal
to coke. The
coking cycle begins when the front door 165 is opened and coal is charged onto
the oven
floor 160. The coal on the oven floor 160 is known as the coal bed. Heat from
the oven (due
to the previous coking cycle) starts the carbonization cycle. As discussed
above, in some
embodiments, no additional fuel other than that produced by the coking process
is used.
Roughly half of the total heat transfer to the coal bed is radiated down onto
the top surface of
the coal bed from the luminous flame of the coal bed and the radiant oven
crown 180. The
remaining half of the heat is transferred to the coal bed by conduction from
the oven floor
160 which is convectively heated from the volatilization of gases in the sole
flue 205. In this
way, a carbonization process "wave" of plastic flow of the coal particles and
formation of
high strength cohesive coke proceeds from both the top and bottom boundaries
of the coal
bed.
[0033] Typically, each oven 105 is operated at negative pressure so air is
drawn into
the oven during the reduction process due to the pressure differential between
the oven 105
and atmosphere. Primary air for combustion is added to the oven chamber 185 to
partially
oxidize the coal volatiles, but the amount of this primary air is controlled
so that only a
portion of the volatiles released from the coal are combusted in the oven
chamber 185,
thereby releasing only a fraction of their enthalpy of combustion within the
oven chamber
185. The primary air is introduced into the oven chamber 185 above the coal
bed through the
primary air inlets 190 with the amount of primary air controlled by the
primary air dampers
195. The primary air dampers 195 can also be used to maintain the desired
operating
temperature inside the oven chamber 185. The partially combusted gases pass
from the oven
chamber 185 through the downcomer channels 200 into the sole flue 205, where
secondary
air is added to the partially combusted gases. The secondary air is introduced
through the
secondary air inlet 215. The amount of secondary air that is introduced is
controlled by the
secondary air damper 220. As the secondary air is introduced, the partially
combusted gases
are more fully combusted in the sole flue 205, thereby extracting the
remaining enthalpy of
combustion which is conveyed through the oven floor 160 to add heat to the
oven chamber
185. The fully or nearly-fully combusted exhaust gases exit the sole flue 205
through the
uptake channels 210 and then flow into the uptake duct 225. Tertiary air is
added to the
exhaust gases via the tertiary air inlet 227, where the amount of tertiary air
introduced is
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controlled by the tertiary air damper 229 so that any remaining fraction of
uncombusted gases
in the exhaust gases are oxidized downstream of the tertiary air inlet 227.
[0034] At the end of the coking cycle, the coal has coked out and has
carbonized to
produce coke. The coke is preferably removed from the oven 105 through the
rear door 170
utilizing a mechanical extraction system. Finally, the coke is quenched (e.g.,
wct or dry
quenched) and sized before delivery to a user.
[0035] Figure 4 is a top view of a portion of a horizontal heat recovery
coke plant 400
configured in accordance with embodiments of the technology. The coke plant
400 includes
several features generally similar to the coke plant 100 described above with
reference to
Figure 1. For example, the plant 400 includes numerous uptake ducts 425 in
fluid
communication with coke ovens (not shown) and the hot common tunnel 110. The
uptake
ducts 425 can include "corresponding" uptake ducts 425a, 425b opposite one
another on
opposing lateral sides of the common tunnel 110 and a most-upstream or "end"
uptake duct
425c. The uptake ducts 425 can channel exhaust gas to the common tunnel 110.
The exhaust
gas in the common tunnel 110 moves from an "upstream" end toward a
"downstream" end.
[0036] In the illustrated embodiments, the uptake ducts 425 meet the common
tunnel
110 at a non-perpendicular interface. More specifically, the uptake ducts 425
have an
upstream angle 0 relative to the common tunnel 110. While the upstream angle 0
is shown to
be approximately 45 , it can be lesser or greater in other embodiments.
Further, as will be
discussed in more detail below, in some embodiments different uptake ducts 425
can have
different upstream angles 0 from one another. For example, there may be a
combination of
perpendicular (90 ) and non-perpendicular (less than 90 ) interfaces. The non-
perpendicular
interfaces between the uptake ducts 425 and the common tunnel 110 can improve
flow and
reduce draft loss in the manner described above.
[0037] Figure 5A is a cross-sectional top view of a perpendicular interface
between an
uptake duct 525a and the common tunnel 110 configured in accordance with
embodiments of
the technology. An uptake flow of exhaust gas in the uptake duct 525a
intersects a common
flow of exhaust gas in the common tunnel 110 to form a combined flow. The
uptake duct
525a and the common tunnel 110 meet at an interface having an upstream angle
al and a
downstream angle a2 which are each approximately 90 . In other words, using a
spherical
coordinate system, a direction of the uptake flow vector comprises an
azimuthal y-component
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but no azimuthal x-component, while a direction of the common flow vector and
combined
flow vector comprises an x-component but no y-component.
[0038] Figure 5B is a cross-sectional top view of a non-perpendicular
interface
between an uptake duct 525b and the common tunnel 110 configured in accordance
with
embodiments of the technology. The uptake flow from the uptake duct 525b
intersects the
common flow in the common tunnel 110 to form a combined flow. The uptake duct
525b
and the common tunnel 110 meet at an interface having an upstream angle al
less than 90
and a downstream angle a2 greater than 90 . The non-perpendicular interface
thus provides
an azimuthal commonality between the uptake flow vector and the common flow
vector. In
other words, the uptake flow vector comprises an x-component having a
direction in common
with an x-component of the common flow vector, and the exhaust gas accordingly
loses less
momentum at the uptake duct 525b and common tunnel 110 interface as compared
to the
arrangement of Figure 5A. The reduced momentum loss can lower the draft loss
at the
interface or, in some embodiments, can even increase the draft in the common
tunnel 110.
[0039] Figure 5C is a cross-sectional end view of a non-perpendicular
interface
between an uptake duct 525c and a common tunnel 510c configured in accordance
with
embodiments of the technology. While previous embodiments have shown the
common
tunnel to have a generally circular cross-sectional shape, in the embodiment
shown in Figure
5C the common tunnel 510c has a generally oval or egg-shaped cross-sectional
shape. For
example, the common tunnel 510 has a height H between a base B and a top T. In
some
embodiments, the egg-shaped cross-section can be asymmetrical (i.e., top-
heavy), such that
the common tunnel 510c has a greater cross-sectional area above a midpoint M
between the
top T and base B than below the midpoint M. Such a top-heavy design can
provide for more
room in the upper portion of the common tunnel 510c for combustion to occur,
as the
buoyancy of hot exhaust gas tends to urge combustion upward. The oblong shape
of the
illustrated common tunnel 510c can thus minimize flame impingement along the
upper
surface of the interior of the common tunnel 510c. In further embodiments, the
uptake duct
525c can comprise any of the circular or non-circular cross-sectional shapes
described above
with reference to the common tunnel 510c, and the uptake duct 525c and common
tunnel
510c need not have the same cross-sectional shape.
[0040] The uptake flow from the uptake duct 525c intersects the common flow
in the
common tunnel 510c to form a combined flow. Again referencing a spherical
coordinate
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system, the uptake duct 525c meets the common tunnel 510c at an interface
having a negative
altitude angle P less than 900 with respect to the horizon (e.g., with respect
to the x-y plane).
The non-perpendicular interface thus provides an altitudinal difference
between the uptake
flow vector and the common flow vector. In other words, the uptake flow vector
comprises a
z-component that differs from a z-component of the common flow vector. In some
embodiments, by introducing the uptake flow into the common flow at an
altitudinal angle
relative to the common flow vector, swirling flow or turbulence is developed
inside the
common tunnel 510c to enhance mixing and combustion of unburned volatile
matter and
oxygen. In other embodiments, the altitude angle 13 is a positive angle,
greater than 900, or
approximately equal to 90 .
[0041] The uptake duct 525c can interface with the common tunnel 510c at
any height
between the top T and bottom B of the common tunnel 510c. For example, in the
illustrated
embodiment, the uptake duct 525c intersects with the common tunnel 510c in the
lower
portion of the common tunnel 510c (i.e., below or substantially below the
midpoint M). In
further embodiments, the uptake duct 525c intersects with the common tunnel
510c in the
upper portion of the common tunnel 510c, at the midpoint M, at a top T or
bottom B of the
common tunnel 510c, or in multiple locations around the cross-sectional
circumference of the
common tunnel 510c. For example, in a particular embodiment, one or more
uptake ducts
525c may intersect with the common tunnel 510c in the lower portion and one or
more other
uptake ducts 525c may intersect with the common tunnel 510c in the upper
portion.
[0042] Figure 5D is a cross-sectional end view of a non-perpendicular
interface
between an uptake duct 525d and the common tunnel 510d configured in
accordance with
embodiments of the technology. In the embodiment shown in Figure 5D the common
tunnel
510d has a generally square or rectangular cross-sectional shape. Other
embodiments can
have other cross-sectional shapes. The uptake flow from the uptake duct 525d
intersects the
common flow in the common tunnel 510d to form a combined flow. Again
referencing a
spherical coordinate system, the uptake duct 525d and the common tunnel 510d
meet at an
interface having a positive altitude angle 13 less than 90 with respect to
the horizon. In other
words, the uptake flow vector comprises a z-component that differs from a z-
component of
the common flow vector. In some embodiments, by introducing the uptake flow
into the
common flow at an altitudinal angle different from the common flow, mixing
draft loss can
be reduced and combustion can be encouraged to occur at a height that does not
burn the
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interior surfaces of the common tunnel 510d. For example, the downward
altitudinal
introduction of flow from the uptake duct 525d can counter the buoyancy of the
hot exhaust
gas to encourage combustion to occur toward the bottom of the common tunnel
510d so as
not to burn the top of the common tunnel 501d.
[0043] Figure 5E is a cross-sectional end view of a non-perpendicular
interface
between an uptake duct 525c and a common tunnel 510e configured in accordance
with
embodiments of the technology. The interface has several features generally
similar to those
discussed above with reference to Figures 5A-5D. However, in the embodiment
illustrated in
Figure 5E, the common tunnel 510e comprises a symmetrical, elongated oval.
More
specifically, the common tunnel 510e includes a semi-circular shape at top and
bottom
positions of the common tunnel 510c, and generally straight, parallel,
elongated sides
between the top and bottom semi-circles. The elongated shape can provide
several of the
advantages described above. For example, the design can provide for more room
in the mid-
section of the common tunnel 510e for combustion to occur, as the buoyancy of
hot exhaust
gas tends to urge combustion upward. Similarly, the downward altitudinal
introduction of
flow from the uptake duct 525e at angle 13 can further counter the buoyancy of
the hot exhaust
gas to encourage combustion to occur toward the bottom of the common tunnel
510e. The
oblong shape of the illustrated common tunnel 510e can thus minimize flame
impingement
along the upper surface of the interior of the common tunnel 510e. In further
embodiments,
the common tunnel 510e can be symmetrical or asymmetrical and have the same or
different
shapes.
[0044] While various features of the uptake duct and common tunnel
interface have
been shown separately for purposes of illustration, any of these features can
be combined to
achieve reduced draft loss, combustion control, and the most effective mixing
of the uptake
flow and common flow. More specifically, the azimuthal angle of interface, the
altitudinal
angle of interface, the height of interface, the shape of the common tunnel
and/or uptake duct,
or other feature can be selected to achieve the desired thermal and draft
conditions at the
interface. Various parameters such as common tunnel draft, desired degree of
common
tunnel combustion, exhaust gas buoyancy conditions, total pressure, etc. can
be some of the
considerations in selecting the features of the uptake duct and common tunnel
interface.
[0045] Figures 6A-6I are top views of various configurations of interfaces
between
uptake ducts and a common tunnel configured in accordance with embodiments of
the
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technology. As will be shown, the uptake ducts can comprise various patterns
of
perpendicular and non-perpendicular interfaces with the common tunnel, or can
comprise
various non-perpendicular angles relative to the common tunnel. While the
embodiments
shown and discussed with reference to Figures 6A-6I include numerous features
and
arrangements, in further embodiments any of these features and/or arrangements
can be used
independently or in any combination with other features and/or arrangements
described
herein.
[0046] Referring first to Figure 6A, in some embodiments each of several
uptake ducts
625a meets the common tunnel 110 at a less-than-90 upstream angle a. The
uptake ducts
625a thus reduce mixing loss at the combination of common flow and uptake flow
in the
manner described above. In some embodiments, corresponding (i.e., opposing)
uptake ducts
625a are laterally offset from one another and are not directly opposing. This
is shown in the
two most-downstream uptake ducts 625a shown in Figure 6A. In further
embodiments, the
spacing between individual uptake ducts 625a (i.e., along the length of the
common tunnel
110) can likewise be variable. For example, the distance d between the two
most
downstream uptake ducts 625a along one side of the common tunnel 110 is
greater than the
distance between the other uptake ducts 625a. In further embodiments, the
spacing is
constant between all uptake ducts 625a.
[0047] Figure 6B illustrates an embodiment where uptake ducts 625b meet the
common tunnel 110 at decreasing upstream angles a. For example, at a most
downstream
position, the uptake ducts may be perpendicular or nearly-perpendicular to the
common
tunnel 110. As the uptake tunnels approach an upstream end, the upstream
angles a between
the uptake ducts 625b and the common tunnel 110 become progressively smaller.
In some
embodiments, the range of upstream angles a varies from about 150 to about 90
. Since the
draft pull is weaker farther upstream, this arrangement can progressively
reduce the barrier to
entry of the uptake flow into the common flow and thereby reduce draft loss
due to mixing or
stagnant flow regions. In further embodiments, one or more uptake ducts 625b
can be
positioned at an upstream angle a that is greater than 90 . In still further
embodiments, the
trend shown in Figure 6B can be reversed. More specifically, the uptake ducts
625b can meet
the common tunnel 110 at increasing upstream angles, wherein the most-upstream
angle can
be near or approaching 90 . Such an arrangement can be useful in embodiments
where
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mixing flow losses are potentially greater at downstream positions having
higher
accumulated common flow.
[0048] Figure 6C illustrates an embodiment having a combination of uptake
ducts 625c
meeting the common tunnel 110 at non-perpendicular angles al and perpendicular
angles a2.
The illustrated embodiment includes pairs of non-perpendicular ducts 625c
along a side of
the common tunnel 110 followed by pairs of perpendicular ducts 625c, and so
on. In further
embodiments, there can be more or fewer perpendicular or non-perpendicular
uptake ducts
625c in a row.
[0049] Figure 6D illustrates an embodiment having a combination of uptake
ducts 625d
meeting the common tunnel 110 at non-perpendicular angles al and perpendicular
angles a2.
The illustrated embodiment includes alternating non-perpendicular ducts 625d
and
perpendicular ducts 625d along a side of the common tunnel 110.
[0050] Figure 6E illustrates an embodiment having a combination of uptake
ducts 625e
meeting the common tunnel 110 at non-perpendicular angles al and perpendicular
angles a2.
The illustrated embodiment includes individual perpendicular uptake ducts 625e
alternating
with non-perpendicular uptake ducts 625e, followed by pairs of non-
perpendicular ducts
625e, followed by pairs of perpendicular ducts 625e, and so on. This pattern
or a portion of
this pattern can repeat along further sections of the common tunnel 110. In
further
embodiments, there can be different combinations of perpendicular and non-
perpendicular
uptake ducts.
[0051] Figure 6F illustrates an embodiment having a combination of uptake
ducts 625f
meeting the common tunnel 110 at non-perpendicular angles al and perpendicular
angles a2.
The illustrated embodiment includes a series of non-perpendicular uptake ducts
625f,
followed by a perpendicular duct 625f, followed by another series of non-
perpendicular ducts
625f, and so on.
[0052] Figure 6G illustrates an embodiment having a combination of uptake
ducts 625g
meeting the common tunnel 110 at non-perpendicular angles al and perpendicular
angles a2.
The illustrated embodiment includes non-perpendicular uptake ducts 625g on a
first lateral
side of the common tunnel 110, and perpendicular ducts 625g along a second,
opposing,
lateral side of the common tunnel 110.
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[0053] Figure 6H illustrates an embodiment having a combination of uptake
ducts 625h
meeting the common tunnel 110 at non-perpendicular angles al and perpendicular
angles a2.
The illustrated embodiment includes alternating non-perpendicular ducts 625h
and
perpendicular ducts 625h along a side of the common tunnel 110, where the non-
perpendicular uptake ducts 625h are opposite perpendicular ducts 625h and vice-
versa.
[0054] Figure 61 illustrates an embodiment having uptake ducts 625i along
only one
lateral side of the common tunnel 110, with no uptake ducts on the opposing
lateral side. In
some embodiments, two single-sided common tunnels 110 can be operated in a
coke plant in
a side-by-side parallel arrangement. The uptake ducts 625i can be angled at
non-
perpendicular angle a relative to the common tunnel 110 in the manner
described above.
[0055] Figure 7A is a cross-sectional top view of a non-perpendicular
interface
retrofitted between a perpendicular uptake duct 725a and the common tunnel 110
configured
in accordance with embodiments of the technology. The uptake duct 725a and the
common
tunnel 110 can originally have the same arrangement as the embodiment
discussed above
with reference to Figure 5A, but can be retrofitted to include one or more non-
perpendicular
interface features. For example, the interface has been fitted with an
internal baffle 726a to
alter the flow pattern and create a non-perpendicular interface. More
specifically, the baffle
726a is placed in a lumen of the uptake duct 725a and modifies a perpendicular
interface into
an angled interface that reduces draft loss due to mixing. In the illustrated
embodiment, the
baffle 726a is triangle-shaped and converges the uptake flow by reducing an
inner
characteristic dimension of the uptake duct 725a. This converged flow can act
as a nozzle
and minimize flow energy losses of the uptake flow and/or common flow. In
further
embodiments, the baffle 726a can be adjustable (i.e., movable to adjust the
flow and interface
pattern), can have different shapes and/or sizes, and/or can converge and/or
diverge flow to
other degrees. Further, the baffle can extend around more or less of the lumen
of the uptake
duct 725a.
[0056] The common tunnel 110 can further be retrofitted with a flow
modifier 703
positioned on an interior surface of the common tunnel 110 and configured to
interrupt or
otherwise modify flow in the common tunnel 110, or improve the interface
(i.e., reduce draft
loss) at the junction of the uptake flow and the common flow. The uptake duct
725a has
further been modified with a bumped-out diverging flow plate D. The diverging
flow plate D
modifies the uptake flow vector to have an x-component in common with a common
flow
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vector, thus reducing draft loss between the uptake flow and the common flow.
While the
diverging flow plate D, the baffle 726a, and the flow modifier 703 are shown
in use together,
in further embodiments, any of these features can be used independently or in
any
combination with any other features described herein.
[0057] While the terms "baffle" 726a and "flow modifier" 703 are used
herein, the
additions to the uptake duct 726a or common tunnel 110 can comprise any
insulation
material, refractory material, or other thermally-suitable material. In some
embodiments, the
flow modifier 703 and/or baffle 726a may comprise a single or 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 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 703 and/or baffle 726a may be integrally formed along the duct.
In other
words, the uptake duct 725a 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 modifier 703 and/or baffle 726a 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 modifier 703 and/or baffle 726a
are not limited
to convex surfaces. The contours of the flow modifier 703 and/or baffle 726a
may have other
complex surfaces, and can be determined by design considerations such as cost,
space,
operating conditions, etc. In further embodiments, there can be more than one
flow modifier
703 and/or baffle 726a. Further, while the flow modifier 703 is shown in the
common tunnel
110, in further embodiments the flow modifier 703 can be positioned at other
locations (e.g.,
entirely or partially extending into the uptake duct 725a, or around the inner
circumference of
the common tunnel 110.
[0058] Figure 7B is a cross-sectional top view of an interface between an
uptake duct
725b and a common tunnel 110 configured in accordance with embodiments of the
technology. Figure 7C is a cross-sectional top view of a non-perpendicular
interface
retrofitted between the uptake duct 725b and common tunnel 110 of Figure 7B.
Referring to
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Figures 7B and 7C together, the uptake duct 725b includes a diverging uptake
end D that
flares at the interface with the common tunnel 110. The uptake duct 725b can
be retrofitted
with an internal baffle 726c generally similar to the internal baffle 726a
described above with
reference to Figure 7A. The internal baffle 726c of Figure 7C can eliminate
the flare or a
portion of the flare at the diverging end D, to create a non-perpendicular
interface between
the uptake duct 725b and the common tunnel 110 to reduce draft loss. In
further
embodiments, the entire internal circumference of the uptake duct 725b can be
fitted with the
baffle 726c to further narrow or otherwise alter the interface. The baffle
726c can minimize
flow energy losses as the uptake flow meets the common flow in the common
tunnel 110.
[0059] Figure 8 is a cross-sectional top view of a non-perpendicular
interface between
an uptake duct 825 and the common tunnel 110 configured in accordance with
embodiments
of the technology. The uptake duct 825 includes a converging portion C
followed by a
diverging portion D. The converging portion C can minimize flow energy losses
as the
exhaust gas from the uptake duct 825 meets the common flow in the common
tunnel 110.
The diverging portion provides an interface that modifies the uptake flow
vector to have an x-
component in common with a common flow vector, thus reducing draft loss
between the
pressurized uptake flow and the common flow. In various embodiments, the
diverging and
converging portions can have smooth or sharp transitions, and there can be
more or fewer
converging or diverging nozzles in the uptake duct 825 or common tunnel 110.
In another
embodiment, the converging portion C is adjacent to the common tunnel 110 and
the
diverging portion D is upstream in the uptake duct 825. In further
embodiments, the
converging portion C can be used independently from the diverging portion D,
and vice
versa.
[0060] The interface of Figure 8 further includes a jet 803 configured to
introduce a
pressurized fluid such as air, exhaust gas, water, steam, fuel, oxidizer,
inert, or other fluid (or
combination of fluids) to the uptake flow or common flow as a way to improve
flow and
reduce draft loss. The fluid can be gaseous, liquid, or multiphase. The jet
803 can stem from
or be supported by any external or internal pressurized source (e.g., a
pressurized vessel, a
pressurized line, a compressor, a chemical reaction or burning within the
coking oven system
that supports energy to create pressure, etc.). While the jet 803 is shown as
penetrating the
common tunnel 110 at a position downstream of the uptake duct 825, in further
embodiments
the jet 803 can be positioned in the uptake duct 825, upstream of the uptake
duct 825 in the
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common tunnel 110, in multiple locations (e.g., a ring) around the
circumference of the
common tunnel 110 or uptake duct 825a, a combination of these positions, or
other positions.
In a particular embodiment, the jet 803 can be positioned in the uptake duct
825 upstream of
the converging portion C. The jet 803 can act as an ejector, and can pull a
vacuum draft
behind the pressurized fluid. The jet 803 can thus modify flow to create
improved draft
conditions, energize flow or mixing, or can reduce stagnant air or "dead"
zones. In various
embodiments, the jet 803 can pulse the fluid, provide constant fluid, or be
run on a timer.
Further, the jet 803 can be controlled manually, in response to conditions in
the common
tunnel 110, uptake duct 825, or other portion of the exhaust system, or as
part of an advanced
control regime. While the jet 803 is shown in use with the particular uptake
duct 825
arrangement illustrated in Figure 8, in further embodiments, the jet 803 and
uptake duct 825
could be employed independently or in any combination with any other features
described
herein. For example, in a particular embodiment, the jet 803 could be used in
combination
with the flow modifier 703 shown in Figure 7A, and could be proximate to or
protrude
through such a flow modifier 703.
[0061] Figure 9 is a plot showing the spatial distribution of the
difference in static
pressure (in inches-water) along the length of the common tunnel. In other
words, the plot
illustrates the difference in static pressure at downstream positions in the
common tunnel
compared to the static pressure at the upstream end. As shown in the plot, the
45 degree
uptake has a much lower draft loss over the same length of common tunnel as
compared to
the perpendicular uptake. This is because the angled uptake has less mixing
loss than the
perpendicular uptake.
Examples
[0062] The following Examples are illustrative of several embodiments of
the present
technology.
1. A coking system, comprising:
a coke oven;
an uptake duct in fluid communication with the coke oven and having an uptake
flow
vector of exhaust gas from the coke oven; and
a common tunnel in fluid communication with the uptake duct, the common tunnel
having a common flow vector of exhaust gas and configured to transfer the
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exhaust gas to a venting system, wherein the uptake flow vector and common
flow vector meet at a non-perpendicular interface.
2. The coking system of example 1 wherein at least a portion of the uptake
duct
is non-perpendicular to the common tunnel.
3. The coking system of example 1 wherein the non-perpendicular interface
comprises at least one of an altitudinal difference or an azimuthal
commonality between the
uptake flow vector and the common flow vector.
4. The coking system of example 1 wherein the common tunnel has a common
tunnel height, an upper portion above a midpoint of the common tunnel height,
and a lower
portion below the midpoint of the common tunnel height, and wherein the uptake
duct
interfaces with the common tunnel in at least one of the upper portion and the
lower portion.
5. The coking system of example 1 wherein the non-perpendicular interface
comprises at least one of a baffle, gunned surface, contoured duct liner, or
convex flow
modifier inside at least one of the uptake duct or common tunnel and
configured to alter at
least one of the uptake flow vector or common flow vector.
6. The coking system of example 5 wherein the baffle, gunned surface,
contoured duct liner, or convex flow modifier is integral to at least one of
the uptake duct or
common tunnel or is retrofitted onto the uptake duct or common tunnel.
7. The coking system of example 1 wherein at least one of the uptake duct
or the
interface comprises a converging or diverging pathway.
8. The coking system of example 1 wherein the uptake duct comprises a first
uptake duct in fluid communication with a first coke oven and having a first
uptake flow
vector, and wherein the system further comprises a second uptake duct in fluid
communication with the first coke oven or a second coke oven and having a
second uptake
flow vector of exhaust gas.
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9. The coking system of example 8 wherein the first uptake flow vector and
common flow vector meet at a non-perpendicular interface, and the second
uptake flow
vector and common flow vector meet at a perpendicular interface.
10. The coking system of example 8 wherein the first uptake flow vector and
common flow vector meet at a non-perpendicular interface and the second uptake
flow vector
and common flow vector meet at a non-perpendicular interface.
11. The coking system of example 8 wherein at least a portion of the first
uptake
duct is non-perpendicular to the common tunnel by a first angle and at least a
portion of the
second uptake duct is non-perpendicular to the common tunnel by a second angle
different
from the first angle.
12. The coking system of ex ample 8 wherein:
the system further comprises a third uptake duct in fluid communication with
the first
coke oven, the second coke oven, or a third coke oven and having a third
uptake flow vector of exhaust gas;
the first uptake duct, second uptake duct, and third uptake duct are
positioned along a
lateral side of the common tunnel; and
there is a first distance between the first uptake duct and second uptake duct
and a
second distance different from the first distance between the second uptake
duct and the third uptake duct.
13. The coking system of example 8 wherein the first uptake duct is
positioned on
a first lateral side of the common tunnel and the second uptake duct is
positioned on a second
lateral side of the common tunnel opposite the first lateral side, and wherein
the first uptake
duct and second uptake duct are laterally offset from one another.
14. The coking system of example 8 wherein the first uptake duct and second
uptake duct are positioned on a common lateral side of the common tunnel, and
wherein there
are no uptake ducts on an opposing lateral side of the common tunnel.
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15. The coking system of example 1 wherein the common tunnel has one of a
circular, non-circular, oval, elongated oval, asymmetrical oval, or
rectangular cross-sectional
shape.
16. A method of reducing draft losses in a common tunnel in a coking
system, the
method comprising:
flowing exhaust gas from a coke oven through an uptake duct;
biasing the exhaust gas exiting the uptake duct toward a common flow in the
common
tunnel; and
merging the exhaust gas and common flow at a non-perpendicular interface.
17. The method of example 16, further comprising at least one of converging
or
diverging the exhaust gas in or upon exiting the uptake duct.
18. The method of example 16 wherein biasing the exhaust gas comprises
biasing
the exhaust gas with a baffle in the uptake duct.
19. The method of example 16, further comprising increasing a draft in the
common tunnel upon merging the exhaust gas and common flow.
20. The method of example 16 wherein biasing the exhaust gas comprises
biasing
the exhaust gas within the uptake duct, wherein the uptake duct is at least
partially non-
perpendicular to the common tunnel.
21. The method of example 16, further comprising introducing a pressurized
fluid
via a jet into at least one of the uptake duct or the common tunnel.
22. A coking system, comprising:
a common tunnel configured to direct a gas from one or more coke ovens to a
common stack, wherein the common tunnel has a common tunnel flow with a
common tunnel flow vector, and wherein the common tunnel flow vector has
an x-componcnt and a y-component;
a coke oven in fluid connection with the common tunnel via an uptake, wherein
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the uptake connects to the common tunnel at an intersection, and
the uptake includes an uptake flow having an uptake flow vector with an x-
component and a y-component; and
wherein the uptake flow vector x-component has a same direction as the x-
component
of the common tunnel flow vector.
23. The coking system of example 22 wherein an inner characteristic
dimension of
the uptake at least one of increases or decreases in the direction of the
intersection.
24. The coking system of example 22 wherein the uptake further includes an
angled baffle at or near the intersection, the baffle configured to redirect
the uptake flow.
[0063] Traditional heat recovery coke ovens employ an uptake duct
connection from
the coke oven to the hot common tunnel that is perpendicular to the common
tunnel. Due to
the perpendicular shape of the interface, the hot flue gas moving toward the
common tunnel
experiences a 90-degree change in flow direction. This induces considerable
flow losses
which can lead to a higher pressure drop. Such mixing losses arc undesirable.
in order to
maintain the system under negative pressure, the high draft loss may require
that either the
common tunnel be made larger or a higher draft be pulled on the whole system
to off-set this
higher draft loss.
[0064] The non-perpendicular interfaces disclosed herein can lower the
mixing draft
loss at the uptake/common tunnel connection by angling the connection in the
direction of the
common tunnel flow. The smaller the upstream angle between the uptake duct and
the
common tunnel, the lesser the change in the directional momentum of the hot
gas and,
consequently, the lower the draft losses. By using non-perpendicular
interfaces and aligning
the uptake duct flow in the direction of the common tunnel flow, the draft
loss can be
lowered, which then can be used to reduce the common tunnel size or lower the
required
draft. For example, in some embodiments, the technology described herein can
reduce the
common tunnel insider diameter to 7-9 feet. The technology could similarly
allow a longer
common tunnel that would traditionally have been prohibitive due to draft
losses. For
example, in some embodiments, the common tunnel can be long enough to support
30, 45,
60, or more ovens per side.
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[0065] 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. 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.
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