Note: Descriptions are shown in the official language in which they were submitted.
CA 02827903,2013-08-21
DESCRIPTION
COMBUSTION DEVICE
TECHNICAL FIELD
[0001]
The present invention relates to a combustion device such
as a pulverized coal burning boiler having a pulverized coal
burner.
BACKGROUND ART
[0002]
As a combustion method using a pulverized coal burner of
a pulverized coal burning boiler, there is adopted a two-stage
combustion method that combusts a fuel in an air insufficient
state and then complete burning air is supplied from an after
air port in order to reduce an emission rate of a nitride oxide
(which will be referred to as NOx hereinafter) in a combustion
exhaust gas.
[0003]
To further reduce NOx concentration in the exhaust gas
at a boiler furnace outlet, the following means can be used.
[0004]
(1) An after-
air port is installed to a high position of a
furnace, and a detention time of a combustion gas to reach a
NOx reduction region between the burner and the after-air port
is increased.
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[0005]
(2) An
excess air ratio (an input air capacity/a theoretical
air capacity) is lowered as much as possible, and thermal NOx
is reduced beyond those in conventional examples.
[0006]
However, a complete combustion region shifts to a
downstream region (an upper portion of a furnace) according to
the technology of (1), a combustion temperature rises as getting
closer to the theoretical air capacity according to the
technology of (2), and hence an exhaust gas temperature at an
outlet of the furnace is increased. Therefore, a steam
temperature and a metal temperature on a rear heat transfer
surface of the boiler rise, and a possibility of occurrence of
tube leak increases in design that a heat transfer surface
material, arrangement of the heat transfer surface, and others
are unchanged from the conventional examples. Therefore, a
design temperature of the rear heat transfer surface must be
increased to be higher than those in the conventional examples,
and there is a problem that quality of the material must be
enhanced in terms of strength and heat resistant properties.
[0007]
To increase a detention time of the combustion gas to reach
the NOx reduction region in the furnace of the after-air port
from the burner or to equalize a design temperature of the rear
heat transfer surface to a conventional examples while adopting
an NOx reduction countermeasure for reducing the air excess
ratio (the input air capacity /the theoretical air capacity)
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%
to be lower than those in the conventional examples, changing
a direction of flames of the burner to an upward or downward
direction of the furnace in accordance with combustion
conditions such as a load can be considered. That is, when a
direction of burner flames is set to a downward direction and
a detention time of the combustion gas in the NOx reduction
region between the burner and the after-air port is increased,
the furnace installing position of the after-air port may be
the same as that in the conventional example, this position is
provided on a lower (upstream) side in the furnace as compared
with the conventional examples even if a combustion temperature
of the burner flames becomes high, and hence an exhaust gas
temperature at the outlet of the furnace can be the same as that
in the conventional examples.
[0008]
Japanese Unexamined Patent Application Publication No.
2008-121924 discloses a burner having a movable nozzle. When
the nozzle is movable in a portion that faces a furnace and has
high radiant heat, consideration must be given to damage due
to falling of clinkers adhering to the inside of the furnace
or securement of movability.
[0009]
Moreover, Japanese Unexamined Patent Application
Publication No. 2002-147713 discloses a burner that changes a
direction of flames (a combustion region) by deviating an air
flow rate in a circumferential direction of a burner.
Incase of the burner provided with a combustion air nozzle
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having at least two or more air inflow directions, to connect
respective combustion air flow paths of a plurality of burners
through a duct on outer wall of a furnace and to provide a common
wind box, arrangement of the duct is complicated.
PRIOR ART DOCUMENT
PATENT DOCUMENTS
[0010]
Patent Literature 1: Japanese Unexamined Patent
Application Publication No. 2008-121924
Patent Literature 2: Japanese Unexamined Patent
Application Publication No. 2002-147713
SUMMARY OF THE INVENTION
PROBLEM TO BE SOLVED BY THE INVENTION
[0011]
As described above, in case of using a burner having a
movable nozzle disclosed in Japanese Unexamined Patent
Application Publication No. 2008-121924, when the nozzle is
movable in the portion that faces the furnace and has large
radiant heat, consideration must be given to damage due to
falling of clinkers adhering to the inside of the furnace or
securement of movability.
[0012]
Additionally, as to the burner provided with the
combustion air nozzle having at least two air inflow directions
disclosed in Japanese Unexamined Patent Application
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Publication No. 2002-147713, to connect the respective
combustion air flow paths of the plurality of burners through
the common dust on the outer wall of the furnace, the
arrangement of the duct becomes complicated.
[0013]
It is an object of the present invention to provide a
combustion device that can change a direction of flames of a
burner to upward and downward directions in a furnace in
accordance with combustion conditions such as a load and
equalize a design temperature of a rear heat transfer surface
to that in conventional examples.
MEANS FOR SOLVING PROBLEM
[0014]
The above-described object can be achieved by the
following solving means.
A first aspect of the present invention provides a
combustion device comprising a plurality of burners arranged on
a furnace wall of a furnace, each burner comprising: a
cylindrical fuel nozzle that injects a mixture of a fuel and a
carrier gas therefor into the furnace; one or more cylindrical
combustion gas nozzles that are provided on the outer
circumference of the fuel nozzle and inject a combustion gas
into the furnace; and a wind box that supplies the combustion
gas to the combustion gas nozzles, wherein
(a) the wind box is partitioned to form a plurality
of parallel flow paths through which the combustion gas flows
and has a combustion gas inflow opening portion into which the
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combustion gas flows, the burners being arranged such that the
axial direction of each of the respective burners are parallel
and aligned to fire into the combustion device, and combustion
gas inflow opening portions are aligned such that the
combustion gas flows into each respective inflow opening in the
same direction,
(b) the combustion gas inflow opening portions are
provided in a single duct located outside of the furnace wall
where the wind box are installed, as all of the combustion air
are supplied from outside of the furnace, and
(c) some of the plurality of combustion gas inflow
paths of the wind box are connected to an upper side of the
combustion gas nozzles, the other flow paths are connected to a
lower side of the combustion gas nozzles, and
(d) first flow rate adjusting means for adjusting a
flow rate of the combustion gas is independently provided to
each of the plurality of flow paths.
[0015]
A second aspect of the present invention provides the
combustion device according to the first aspect, wherein the
plurality of wind boxes are aligned and provided parallel at
inside or outside of the one duct.
[0016]
A third aspect of the present invention provides the
combustion device according to the first or second aspect,
wherein second flow rate adjusting means for adjusting a flow
rate of the combustion gas that flows into each burner on the
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upstream side of the first flow rate adjusting means is
provided in each wind box.
[0017]
In the combustion device according to the present
invention, since the first flow rate adjusting means for
adjusting a combustion gas flow rate is provided to each of the
plurality of combustion gas nozzles and, when an opening degree
of the first flow rate adjusting means is adjusted, a momentum
of the combustion gas injected into the furnace from the burner
can be independently adjusted on each of upper and lower sides.
For example, when the first flow rate adjusting means is
adjusted to increase an air flow rate injected into the furnace
from the combustion gas nozzle or so that a momentum (an air
injection flow rate) of the air flow rate from the lower side
can be higher than that from the upper side of the burner,
flames can be deflected to a downward direction. When the
flames are deflected to the downward direction, the maximum
thermal load region in the furnace shifts to the lower side,
thermal absorption of the furnace increases, and an exhaust gas
temperature at an outlet of the furnace can be reduced.
Further, when the flames are deflected to the lower side of the
burner to shift the combustion region of the burner to the
lower side, a detention time of the NOx reduction region in the
furnace between the burner and the after-air port provided on
the furnace wall on the downstream side of the burner becomes
longer than that in a case where an injecting direction of
flames is parallel, and the NOx concentration in the exhaust
gas is reduced to be lower than that provided by the
conventional technology.
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Furthermore, when the second flow rate adjusting
means is provided on the upstream side of the first flow rate
adjusting means, an air capacity supplied to each burner can be
adjusted.
EFFECT OF THE INVENTION
[0018]
According to the invention of the first aspect, when
the momentum of the combustion gas injected into the furnace
from the burner is deviated depending on each of the upper and
lower sides, the flames can be deflected, and the thermal
absorption of the furnace can be controlled. As a result, a
temperature controller on the rear heat transfer surface of the
furnace can be eliminated. Additionally, in case of modifying
an existing combustion device, the NOx reduction technology
based on the change in the after-air port installing position
and the air excess ratio can be applied without changing a
steam temperature and a metal temperature of the rear heat
transfer surface in the conventional example. Further, when
the flames are deflected toward the lower side in the furnace,
the combustion region of the burner can be shifted to the lower
side, the detention time of the NOx reduction region between
the burner and the after-air port can be increased to be longer
than that in a case where the injecting direction of the flames
is horizontal, and the NOx concentration in the exhaust gas can
be reduced as compared with the conventional example.
The combustion gas supplied to the wind box provided
on the outer side of one furnace wall surface can be
collectively supplied from single duct, and the combustion gas
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supply system for the plurality of burners can have a simple
configuration.
According to the invention of the second aspect, in
addition to the effect of the invention of the first aspect,
since the plurality of wind boxes are aligned and installed on
the outer side of the furnace wall inside or outside one duct,
construction of the plurality of wind boxes and the duct can be
facilitated.
According to the invention of the third aspect, in
addition to the effect of the invention of the first and second
aspects, the first flow rate adjusting means provided to one
wind box on each of the upper and lower sides of the burner,
and providing the second flow rate adjusting means on the
upstream side of the first flow rate adjusting means enables
facilitating adjustment of an amount of the combustion gas
supplied to each burner.
BRIEF DESCRIPTION OF DRAWINGS
[0019]
FIG. 1 is a schematic view showing a pulverized coal
boiler system according to the present invention;
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FIG. 2 is a cross-sectional view of a pulverized coal
burner according to an embodiment of the present invention;
FIG. 3 is a perspective view (FIG. 3 (a) ) of a wind box
and a view (FIG. 3 (b) ) showing a wind tunnel test result
concerning the wind box according to an embodiment of the
present invention;
FIG. 4 shows an example of the wind box in the form of
a cross-sectional view (FIG. 4 (a) ) taken along a line A-A in
FIG. 2 and a cross-sectional view (FIG. 4 (b) ) taken along a line
B-B in FIG. 2;
FIG. 5 shows an example of the wind box in the form of
a cross-sectional view (FIG. 5 (a) ) taken along a line A-A in
FIG. 2 and a cross-sectional view (FIG. 5 (b) ) taken along a line
B-B in FIG. 2;
FIG. 6 is a view showing a method for connecting each wind
box with a combustion gas carrying duct and supplying combustion
air according to an embodiment of the present invention;
FIG. 7 is a view showing a method for installing each wind
box in the combustion gas carrying duct and supplying the
combustion air according to an embodiment of the present
invention;
FIG. 8 shows an example of the wind box in the form of
a cross-sectional view taken along the line A-A in FIG. 2;
FIG. 9 shows an example of the wind box in the form of
a cross-sectional view taken along the line A-A in FIG. 2;
FIG. 10 is a view showing a method for connecting each
wind box with the combustion gas carrying duct and supplying
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the combustion air according to an embodiment of the present
invention;
FIG. 11 is a view showing a method for installing each
wind box in the combustion gas carrying duct and supplying the
combustion air according to an embodiment of the present
invention;
FIG. 12 shows an example of the wind box in the form of
a cross-sectional view taken along the line A-A in FIG. 2;
FIG. 13 shows an example of the wind box in the form of
a cross-sectional view taken along the line A-A in FIG. 2;
FIG. 14 is a view showing a method for connecting each
wind box with the combustion gas carrying duct and supplying
the combustion air according to an embodiment of the present
invention;
FIG. 15 is a view showing a method for installing each
wind box in the combustion gas carrying duct and supplying the
combustion air according to an embodiment of the present
invention;
FIG. 16 shows an example of the wind box in the form of
a cross-sectional view (FIG. 16(a)) taken along the line A-A
in FIG. 2 and a cross-sectional view (FIG. 16(b)) taken along
a line B-B in FIG. 2;
FIG. 17 shows an example of the wind box in the form of
a cross-sectional view (FIG. 17(a)) taken along the line A-A
in FIG. 2 and a cross-sectional view (FIG. 17(b)) taken along
a line B-B in FIG. 2;
FIG. 18 is a view showing a method for installing each
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wind box in the combustion gas carrying duct and supplying the
combustion air according to an embodiment of the present
invention; and
FIG. 19 is a view showing a method for connecting each
wind box with the combustion gas carrying duct and supplying
the combustion air according to an embodiment of the present
invention.
BEST MODE(S) FOR CARRYING OUT THE INVENTION
[0020]
FIG. 1 shows a pulverized coal boiler system according
to the present invention, FIG. 2 is a cross-sectional view of
a pulverized coal burner 19 concerning the pulverized coal
boiler system in FIG. 1, and FIG. 3 is a perspective view (FIG.
3(a)) of a wind box 12 of the pulverized coal burner 19 and a
view (FIG. 3(b)) showing a wind tunnel test result concerning
the wind box 12.
It is to be noted that a fuel in the present invention
is not restricted to pulverized coal, and a solid fuel
pulverized so that it can be carried using an air current can
be used without regard to its type or composition. Further,
although a description will be given on a situation where air
is mainly used as a fuel carrying gas and a combustion gas, the
present invention is not necessarily restricted to air alone,
and it is possible to adopt any gas that can be used as the fuel
carrying gas and the combustion gas for a combustion device such
as a boiler, e.g., a combustion exhaust gas or a mixed gas of
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air or oxygen and the combustion exhaust gas without regard to
its type or composition.
[0021]
In the pulverized coal boiler system shown in FIG. 1,
pulverized coal and combustion air are supplied to burners 19
provided on a plurality of stages on a furnace wall 10 of a boiler
furnace 18, the pulverized coal is combusted, and a
non-illustrated water wall constituting the furnace wall 10 and
a heat exchanger such as a non-illustrated superheater provided
in the furnace are heated, thereby generating water vapor.
[0022]
The pulverized coal supplied to each burner 19 is obtained
by pulverizing coal in a bunker 20 with use of a mill 21, and
the pulverized coal is carried on an air current and supplied
to each burner 19 by using a blower 23. Further, the combustion
air supplied to each burner 19 and each after-air port 24
is supplied through a duct 16 by a blower 25, and the combustion
air is supplied to each pulverized coal burner 19 from each wind
box 12 arranged on the outer side of the boiler furnace wall
10.
[0023]
An oil spraying nozzle 7 is arranged at a central axis
of the pulverized coal burner 19, a fuel nozzle 3 through which
a gas-particle flow 1 of the pulverized coal and the carrying
air is arranged at an outer periphery of the oil spraying nozzle
7, and a secondary air nozzle 8 and a tertiary air nozzle 11
that inject the combustion air 2 are provided at an outer
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periphery of the fuel nozzle 3. As shown in FIG. 2, an outer
peripheral wall of the tertiary air nozzle 11 is formed of the
wind box 12.
Further, the oil spraying nozzle 7 is used for auxiliary
combustion at the time of starting up or low-load combustion
of each burner 19. A venturi tube 6 configured to narrow a
nozzle inner diameter of the fuel nozzle 3 is arranged on an
inner peripheral wall of the fuel nozzle 3, and a pulverized
coal concentrator 5 is provided on the outer periphery of the
oil spraying nozzle 7 near an outlet portion of the fuel nozzle
3. A flame stabilizer 4 is provided at an end of a partition
wall (an outlet portion of each of the nozzles 3 and 8) that
partitions the fuel nozzle 3 and the secondary air nozzle 8,
and a guide sleeve 13 that directs a fluid toward a diffusing
direction from the central axis of the burner 19 is provided
at an end of a partition wall (an outlet portion of each of the
nozzles 8 and 11) that partitions the secondary air nozzle 8
and the tertiary air nozzle 11.
[0024]
As described above, in this embodiment, each burner 19
is formed of the oil spraying nozzle 7, the fuel nozzle 3, the
secondary air nozzle 8, the tertiary air nozzle 11, and the wind
box 12 constituting the outer peripheral wall of the tertiary
air nozzle 11, and this burner 19 is installed on the furnace
wall 10 of the furnace 18.
Although a description will be given with reference to
the drawings, the present invention is not restricted to
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structures in the description.
EMBODIMENT 1
[0025]
FIG. 3(a) shows a perspective view of the wind box 12 of
the pulverized coal burner 19 according to this embodiment, and
FIG. 4 shows a cross-sectional view (FIG. 4(a)) taken along a
line A-A in FIG. 2 and a cross-sectional view (FIG. 4(b)) taken
along a line B-B in FIG. 2. It is to be noted that each dark
arrow shown in FIG. 4 and subsequent drawings represents an
inflow direction of the combustion air.
[0026]
Further, a heavy oil nozzle 7 and the pulverized coal
nozzle 3 are not shown in FIG. 4, and the heavy oil nozzle 7
and the pulverized coal nozzle 3 are arranged in a cylindrical
through hole of the wind box 12. A furnace wall of the through
hole constitutes an outer wall of the secondary air nozzle 8.
[0027]
As shown in FIG. 4, the wind box 12 having combustion air
inlet openings 12a and 12b provided in a direction vertical to
a central axis direction of the pulverized coal burner 19, and
the secondary air nozzle 8 is arranged as if it is inserted in
the through hole provided in the wind box 12.
[0028]
Furthermore, the two combustion air inlet openings 12a
and 12b are provided in the wind box 12, a partition plate 14
that partitions the two combustion air inlet openings
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(combustion gas opening portions) 12a and 12b is provided, and
the partition plate 14 is connected to the outer side of a portion
that divides the outer wall of the secondary air nozzle 8
constituting the through hole of the wind box 12 into two parts.
[0029]
Upper and lower dampers 15a and 15b, each of which has
a rotary shaft in a direction cutting across a flow of the
combustion air introduced into the wind box and changes an area
through which the combustion air flows, are provided near the
combustion air inlet openings 12a and 12b in the wind box 12
divided into upper and lower parts by the partition plate 14,
and separately adjusting respective rotation angles of the two
dampers 15a and 15b enables deviating a momentum of the
combustion air injected from the pulverized coal burner 19
depending on each of upper and lower sides in the wind box 12.
[0030]
For example, when the upper damper 15a is closed and the
lower damper 15b is opened, an injection amount of the
combustion air on the lower side of the burner 19 increases,
and the momentum of the combustion air on the lower side of the
burner 19 increases, whereby flames in the boiler furnace 18
can be deflected to a downward direction.
It is to be noted that, in a state that planes of the
dampers 15a and 15b are arranged in a direction parallel to a
flow of the combustion air, each of the dampers 15a and 15b is
arranged in the wind box 12 to be retracted by a length L1 from
the inlet opening portion of the wind box 12.
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[0031]
FIG. 3(b) shows a result of a tertiary air flow path outlet
velocity distribution at the time of flame downward deflection
realized by conducting a test for deviating a momentum of
tertiary air injected from the tertiary air nozzle 11 into the
furnace depending on each of the upper and lower sides of the
burner 19 based on the wind tunnel test. It was confirmed from
this wind tunnel test that the momentum of the combustion air
on the lower side of the burner 19 can be increased by adjusting
a revolving angle of each of the upper and lower revolving
dampers 15a and 15b. In case of deflecting flames into the
furnace 18 on the upper side of the burner 19, the upper revolving
damper 15a is opened, and the lower revolving damper 15b is
closed.
[0032]
Since the secondary air nozzle 8 having the guide sleeve
13 at the distal end thereof is provided in the pulverized coal
burner 19, the combustion air can be gradually injected. Two
upper and lower opening portions 8a are provided at the outer
peripheral portion of the secondary air nozzle 8, and it is
desirable to provide an air capacity adjusting mechanism such
as slide type dampers 9a and 9b that adjust an amount of air
supplied into the secondary air nozzle 8 from the opening
portions 8a as shown in FIG. 2.
[0033]
For example, when the upper revolving damper 15a is closed
and the lower revolving damper 15b is opened to increase an
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injection amount of the combustion air from the lower side of
the burner 19, the air can be prevented from flowing into the
upper secondary air nozzle 8 and the tertiary air nozzle 11
by fully closing the upper opening portion 8a of the secondary
air nozzle 8 with use of the slide type damper 9a, and the
momentum of the air injected into the furnace 18 from the
secondary air nozzle 8 can be substantially homogeneously
maintained in the circumferential direction, thereby keeping
flame stabilizing properties.
[0034]
It is to be noted that the momentum of the air injected
from the secondary air nozzle 8 into the furnace 18 can be
substantially evenly maintained along the circumferential
direction of the secondary air nozzle 8 only if the combustion
air flows into the secondary nozzle 8 from any position
irrespective of whether the upper opening portion 8a of the
secondary air nozzle 8 is fully closed by using the slide type
damper 9a, but the upper opening portion 8a of the secondary
air nozzle 8 must be fully closed by using the slide type damper
9a if softening the deflection of the flames in the furnace 18
toward the lower side is undesirable.
[0035]
A direction of the flames in the furnace 18 can be
deflected by just deviating the momentum of the combustion air
in each of the upper half portion and the lower half portion
in the burner 19 while maintaining flame stabilizing properties
by adjusting an inflow amount of the combustion air. When each
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of the combustion air inlet openings 12a and 12b obtained by
dividing the inside of the wind box shown in FIG. 5 into two
parts by the partition plate 14 is further divided into two parts
and dampers 15aa and 15ab and dampers 15ba and 15bb are provided
to the respective combustion air inlet openings 12a and 12b,
the momentum of the combustion air is deviated in each of the
upper half and the lower half of the burner 19, whereby a
direction of flames in the furnace 18 can be deflected.
[0036]
In this embodiment, as shown in FIG. 6, the burners 19
each having the wind box 12 are installed on the furnace wall
of the boiler furnace 18, and the combustion air is supplied
into the burners 19 from the duct 16 provided on the outer side
of the furnace wall 10. However, arrangement of the duct 16
is dependent on a boiler configuration and an installation angle
of the burner 19 relative to the furnace wall 10. Further, even
if the burners 19 each having the wind box 12 are arranged in
the duct 16 as shown in FIG. 7, the momentum of the combustion
air in each of the upper half and the lower half of each burner
19 can be deviated, and a direction of flames in the furnace
18 can be deflected.
EMBODIMENT 2
[0037]
In this embodiment, as shown in FIG. 8 and FIG. 9, a wind
box 12 into which combustion air flows only from the upper side
that is vertical to a central axis direction of a burner 19 is
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provided, and a plurality of partition plate 14 and revolving
dampers 15 are provided in the wind box 12 so that the momentum
of the combustion air injected into a furnace can be deviated
depending on each of upper and lower sides by adjusting the
dampers 15.
[0038]
As shown in FIG. 8, in this embodiment, the partition
plates 14 are provided so as to divide into three parts the wind
box 12 into which the combustion air flows from one direction,
i.e., either upper combustion air inlet opening 12a or 12b
vertical to the central axis direction of the burner 19.
Furthermore, the dampers 15a, 15b, and 15b as air capacity
adjusters are provided on the upstream side of trifurcated air
inflow paths in the wind box 12, respectively. Therefore, air
flows into the upper side of the burner 19 from a central portion
of the wind box 12, and air flows into the lower side of the
burner 19 from left and right portions of the wind box 12.
[0039]
In an embodiment shown in FIG. 9, two partition plates
14 are provided so as to divide into four parts a wind box 12
into which the combustion air flows from one direction, i.e.,
either upper combustion air inlet opening 12a or 12b vertical
to the central axis direction of the burner 19. Furthermore,
the combustion air inlet opening 12a at a central portion of
the wind box 12 is divided into two parts, and dampers 15aa,
15ab, and 15b as air capacity adjusters are provided on the
upstream side of respective air inflow paths. Therefore, also
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when shown in Fig. 9, air flows into the upper side of the burner
19 from an upper central portion of the wind box 12, and air
flows into the lower side of the burner 19 from left and right
portions of the wind box 12.
[0040]
In the wind box 12 shown in each of FIG. 8 and FIG. 9,
for example, when the damper 15a or the dampers 15aa and 15ab
near the combustion air inlet opening 12a at the central portion
are closed and the other two dampers 15b and 15b near the left
and right combustion air inlet openings 12b and 12b are opened,
an injection amount of the combustion air in the lower portion
of the burner 19 increases, the momentum of the combustion air
current flowing toward the lower side of the burner increases,
and a direction of flames in a furnace 18 can be changed to a
downward direction. A result obtained by conducting a test of
deviating the momentum of tertiary air on each of upper and lower
sides of the burner 19 based on a wind tunnel test is as shown
in FIG. 3.
[0041]
As described above, it can be confirmed that the momentum
on the lower side of the burner 19 in the furnace 18 can be
increased by adjusting an amount of the combustion air flowing
into the wind box 12 by using three or four dampers 15.
Performing an operation opposite to the above-described
operation can cope with deflection of flames toward the upper
side of the burner 19 in the furnace.
[0042]
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A secondary air nozzle 8 having a guide sleeve 13 at an
end thereof is provided in the wind box 12 so that the combustion
air can be gradually injected. An opening portion 8a is
provided in an outer wall of the secondary air nozzle 8, and
it is desirable to use an air capacity adjusting mechanism such
as slide type dampers 9a and 9b shown in FIG. 2 that can adjust
an amount of air supplied into the secondary air nozzle 8 in
order to adjust an opening degree of the opening portion 8a.
For example, when the damper 15a near the combustion air inlet
opening 12a in the central portion shown in FIG. 8 is closed
whilst the two dampers 15b and 15b near the left and right
combustion air inlet openings 12b and 12b are opened and an
injection amount of the combustion air on the lower side in the
furnace 18 thereby increases, fully closing the opening portion
8a of the secondary air nozzle 8 provided on the upper side of
the wind box 12 with use of the slide type dampers 9a and 9b
enables preventing air from flowing into a tertiary air nozzle
11 in the upper portion of the burner 19, and the momentum of
the air injected into the furnace 18 from the secondary air
nozzle 8 can be substantially homogeneously maintained along
the circumferential direction, whereby flame stabilizing
properties can be maintained.
[0043]
The flames can be deflected by just deviating the momentum
of the tertiary air depending on each of the upper and lower
sides of the burner 19 while maintaining the flame stabilizing
properties by the above-described operation. According to
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these structures and the operating method, even when the
combustion air inlet opening 12a in the central portion of the
wind box 12 is divided into two portions as shown in FIG. 9 and
the dampers 15aa and 15ab are provided near these divided
portions, the same effect can be obtained by a damper adjustment
method.
[0044]
This embodiment provides a configuration that burners 19
each having the wind box 12 are installed on the outer side of
the furnace wall 10 of the boiler furnace 18 and the combustion
air is put into a duct 16 connected to each wind box 12 from
an illustrated inflow direction. However, arrangement of the
duct 16 is dependent on a boiler configuration and an
installation angle of the burner 19 relative to the furnace wall
10. Further, even if the burners 19 each having the wind box
12 are arranged in the duct 16 as shown in FIG. 11, the same
operation method can be executed.
EMBODIMENT 3
[0045]
This embodiment shown in FIG. 12 and FIG. 13 has a
configuration that a wind box 12 into which combustion air flows
only from lower combustion air inlet openings 12a and 12b
vertical to a central axis of the burner 19 is provided, the
inside of the wind box 12 is partitioned by a plurality of
partition plates 14, dampers 15b, 15a, and 15b or 15b, 15aa,
15ab, and 15b are provided in respective combustion air nozzles
23
CA 02827903 2013-08-21
in the wind box 12 partitioned by the partition plates 14, and
the momentum of the combustion air injected into a furnace 18
from the burner 19 is deviated depending on each of upper and
lower sides of the burner 19 by adjusting opening/closing
degrees of the dampers 15b, 15a, and 15b or 15b, 15aa, 15ab,
and 15b.
[0046]
In this embodiment shown in FIG. 12, the partition plates
14 and 14 are provided so as to divide the wind box 12, into
which the combustion air flows from only one lower direction
which is a direction vertical to the central axis direction of
the burner 19, into threeportions. Moreover, dampers 15b, 15a,
and 15b as air capacity adjusters are provided on upstream
portions of trifurcated air inflow paths 12b, 12a, and 12b of
the wind box 12. Therefore, air from a combustion air inlet
opening 12a at a central portion of the wind box 12 flows into
the lower side of the burner 19, and air flows into the upper
side of the burner 19 from the left and right combustion air
inlet openings 12b and 12b of the wind box 12.
[0047]
As described above, for example, when the damper 15a near
the combustion air inlet opening 12a in the central portion of
the wind box 12 is opened and the dampers 15b and 15b near the
left and right combustion air inlet openings 12b and 12b are
closed, an injection amount of the combustion air on the lower
side of the burner 19 increases, and the momentum of the
combustion air flowing toward the lower side of the burner 19
24
CA 02827903 2013-28-21
increases, thereby changing a direction of flames in the furnace
18 to a downward direction. A result obtained by conducting
a test of deviating the momentum of tertiary air on each of upper
and lower sides based on the wind tunnel test is as shown in
FIG. 3.
[0048]
It can be confirmed that the momentum on the lower side
of the burner 19 can be increased by adjusting opening/closing
degrees of the three dampers 15b, 15a, and 15b, and performing
an operation opposite to the above-described operation can cope
with deflection of flames toward the upper side of the burner
19 in the furnace 18.
[0049]
A secondary air nozzle 8 having a guide sleeve 13 is
provided in the wind box 12 so that the combustion air can be
injected along a spreading direction from an outlet of the
burner 19. Further, an opening portion 8a (FIG. 2) is provided
in the secondary air nozzle 8, and it is desirable to adjust
an air inflow amount from the opening portion 8a by providing
a slide type damper 9 shown in FIG. 2. For example, when the
damper 15a near the combustion air inlet opening 12a in the
central portion of the wind box 12 is closed whilst the dampers
15b and 15b near the left and right combustion air inlet openings
12b and 12b are opened and an injection amount of the combustion
air in the upper portion of the burner 19 thereby increases,
fully closing the opening portion 8a of the secondary air nozzle
8 provided on the lower side of the wind box 12 with use of the
CA 02827903 2013-08-21
slide type damper 9 enables preventing air from flowing into
a tertiary air nozzle 11 on the lower side of the burner 19,
and the momentum of the air injected into the furnace 18 from
the secondary air nozzle 8 can be substantially homogeneously
maintained along the circumferential direction, whereby flame
stabilizing properties can be maintained. The flames can be
deflected by just adjusting a tertiary air injection amount to
deviate the momentum of the air depending on each of the upper
and lower sides of the burner 19 while maintaining the flame
stabilizing properties by the above-described operation.
According to these structures and the operating method, even
when the combustion air inlet openings 12b and 12b are provided
on both sides of the lower side of the wind box 12, the combustion
air inlet opening 12a in the central portion is divided into
two portions, and the dampers 15b, 15aa, 15ab, and 15b are
provided on the upstream side of the respective air inflow paths
as shown in FIG. 13, the same effect can be obtained by adj ustment
methods of the dampers 15b, 15aa, 15ab, and 15b.
[0050]
This embodiment is characterized in that the burners 19
each having the wind box 12 are installed on the boiler furnace
wall 10 as shown in FIG. 14 and the combustion air is supplied
into the burners 19 from a duct 16 provided on the outer side
of the furnace wall 10. However, arrangement of the duct 16
is dependent on a boiler configuration and an installation angle
of the burner 19. Further, even if the burners 19 each having
the wind box 12 are arranged in the duct 16 as shown in FIG.
26
CA 02827903 2013-,08-21
15, the same operation method can be carried out.
[0051]
According to this embodiment 3, when flames in the furnace
18 are deflected to the downward direction, the maximum thermal
load region in the furnace 18 shifts to the lower side, thermal
absorption of the furnace thereby increases, an exhaust gas
temperature at an outlet of the furnace 18 can be reduced, a
detention time of an NOx reduction region in the furnace 18
between the burner 19 and an after-air port 24 can be increased
beyond than that in a case where a combustion region is evenly
formed on each of upper and lower sides of the burner 19 by
shifting the combustion region of the burner 19 to the lower
side, thus providing the pulverized coal burner 19 that can
reduce the NOx concentration.
EMBODIMENT 4
[0052]
This embodiment provides a configuration where a second
damper 17 as a supply air capacity adjuster for each burner 19,
which is configured to adjust a flow rate of combustion air
flowing into each burner 19, is provided on the upstream side
of a damper 15 in addition to the configurations of Embodiments
1 to 3.
Since a distribution can appear in a fuel supplied to a
plurality of burners 19 arranged on a boiler furnace wall 10,
it is desirable to enable adjusting a combustion air flow rate
in accordance with each burner 19 so that a combustion air flow
27
CA 02827903 2013-,08-21
rate consistent with a fuel supply amount can be obtained.
Here, although the combustion air flow rate can be
adjusted by a first damper 15 alone if its opening degree is
adjusted in accordance with each burner 19, when the first
damper 15 provided for the purpose of deviating a momentum of
the combustion air on each of upper and lower sides of each burner
19 has a function of adjusting the combustion air flow rate
consistent with the fuel supply amount, controlling this damper
becomes difficult.
Thus, in this embodiment, the first damper 15 and the
second damper 17 that share the two different functions are
independently provided.
Each of FIG. 16 and FIG. 17 shows a configuration where,
in addition to first dampers 15a and 15b configured to deviate
an air momentum on each of upper and lower sides of the burner
19 described in Embodiment 1 (FIGS. 4 and 5), second dampers
17a and 17b for adjusting a flow rate of the combustion air
flowing into each burner 19 are provided on the upstream side
of the first dampers 15a and 15b.
As described above, for example, when the upper first
damper 15a in the first dampers 15a and 15b that deviate the
momentum of the combustion air depending on each of the upper
and lower sides of each burner 19 is closed and the lower first
damper 15b is opened, an injection amount of the combustion air
on the lower side of the burner 19 increases, and an increase
in the momentum of the combustion air flowing toward the lower
side of the burner 19 enables deflecting flames in a furnace
28
CA 02827903 2013-,08-21
18 to a downward direction (see FIG. 3(b)).
When the second dampers 17a and 17b are provided on the
upstream side of the first dampers 15a and 15b, the flow rate
of the combustion air flowing into each burner 19 can be
individually adjusted without suppressing a deviation of the
momentum of the combustion air on each of the upper and lower
sides of the burner 19.
Providing the first dampers 15a and 15b, which are
adjusters that deviate the momentum of the combustion air on
each of the upper and lower sides of each burner 19 in each wind
box 12, on the downstream side of the second dampers 17a and
17b can suffice, and the second dampers 17a and 17b can be
arranged at any positions.
Furthermore, as each of the first dampers 15a and 15b and
the second dampers 17a and 17b, a member that adjusts an opening
area by sliding a plurality of laminated porous plates may be
used in place of the illustrated butterfly type damper, and it
can have any structure as long as it has a gas flow rate adjusting
function.
[0053]
In this embodiment, such a secondary air nozzle 8 having
the guide sleeve 13 as shown in FIG. 2 is provided in the wind
box 12, and the combustion air is injected into the furnace 18
from the outlet of the burner 19 in a spreading manner. The
opening portion 8a is provided in the secondary air nozzle 8,
and it is desirable to provide the slide type damper 9 that can
adjust an air capacity flowing into the secondary air nozzle
29
CA 02827903 2013-08-21
=
8.
For example, when the upper first damper 15a in the wind
box 12 shown in FIG. 16 is closed and the lower first damper
15b in the same is opened to increase an injection amount of
the combustion air on the lower side of the burner 19, the
combustion air can be prevented from flowing into the tertiary
air nozzle 11 on the upper side in the wind box 12 by fully closing
the opening portion 8a of the secondary air nozzle 8 provided
on the upper side in the wind box 12 with use of the slide type
damper 9a, and the momentum of the combustion air injected into
the furnace 18 from the secondary air nozzle 8 can be
substantially homogeneously maintained along the
circumferential direction of the burner 19, thereby holding the
flame stabilizing properties.
When the first dampers 15a and 15b and the slide type
damper 9a are operated and the momentum of the tertiary air on
each of the upper and lower sides of the burner 19 is deviated
while maintaining the flame stabilizing properties of the
burner 19, flames in the furnace 18 can be deflected.
[0054]
According to these structures and the operating method,
the damper adjustment method for dividing each of the combustion
air inlet openings 12a and 12b in the wind box 12 into two parts
and providing the first dampers 15aa, 15ab, 15ba, and 15bb and
the second dampers 17aa, 17ab, 17ba, and 17bb to the respective
combustion air inlet openings 12a and 12b as shown in FIG. 17
enables individually adjusting the flow rate of the combustion
CA 02827903 2013-08-21
air flowing into each burner 19 without suppressing a deviation
of the momentum of the combustion air on each of the upper and
lower sides of the burner 19.
[0055]
In this embodiment, as shown in FIG. 18, the burners 19
each having the wind box 12 are arranged in the duct 16. An
air capacity of each of the plurality of burners 19 arranged
on the furnace wall 10 along the horizontal direction in line
can be adjusted by providing the second dampers 17 (17a, 17b
and 17aa, 17ab; and 17ba, 17bb) shown in FIG. 16 and FIG. 17
in each wind box 12.
Moreover, as shown in FIG. 19, the burners 19 each having
the wind box 12 shown in FIG. 16 and FIG. 17 may be installed
on the outer side of the furnace wall 10 of the boiler so that
the combustion air from the outside of the furnace 18 can be
supplied into the burners 19 each having the wind box 12 through
the duct 16.
INDUSTRIAL APPLICABILITY
[0056]
According to the present invention, when the flame
deflection and heat absorption control function and the
combustion gas flow rate adjustment function for each burner
19 are additionally provided, the industrial applicability can
be further enhanced.
DESCRIPTION OF THE REFERENCE NUMERALS
[0057]
31
CA 02827903 2013-08-21
1 gas-particle flow
2 combustion air
3 fuel nozzle
4 flame stabilizer
pulverized coal concentrator
6 venturi tube
7 heavy oil nozzle
8 secondary air nozzle
9 slide type damper
boiler furnace wall
11 tertiary air nozzle
12 wind box
13 guide sleeve
14 partition wall
(15a, 15aa, 15ab, 15b, 15ba, 15bb) damper
(first flow
rate adjusting means)
16 duct
17 (17a, 17aa, 17ab, 17b, 17ba, 17bb) damper
(second flow
rate adjusting means)
18 boiler furnace
19 burner
bunker
21 mill
23 blower
24 after-air port
blower
32
