U.S. patent application number 16/541914 was filed with the patent office on 2020-02-20 for solid fuel burner.
The applicant listed for this patent is Mitsubishi Hitachi Power Systems, Ltd.. Invention is credited to Akira BABA, Kosuke KITAKAZE, Kenji KIYAMA, Koji KURAMASHI, Kenichi OCHI, Junya WATANABE.
Application Number | 20200056780 16/541914 |
Document ID | / |
Family ID | 69523813 |
Filed Date | 2020-02-20 |
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United States Patent
Application |
20200056780 |
Kind Code |
A1 |
WATANABE; Junya ; et
al. |
February 20, 2020 |
Solid Fuel Burner
Abstract
The present invention provides a solid fuel burner which ensures
ignition performance and flame holding performance of a fuel
nozzle. The present invention provides a solid fuel burner which
achieves cost reduction by simplifying the structure of the fuel
nozzle, for example, and which ensures the ignition performance and
flame holding performance of the fuel nozzle. Further, the present
invention provides a burner which enables stable combustion by both
solid fuel and oil combustion with the suppression of soot and dust
and mist generated during the oil start-up envisaged. The solid
fuel burner of the present invention includes: a fuel nozzle
straight tube portion allowing a mixing gas of a solid fuel and its
carrier gas to flow therethrough; a fuel nozzle throttling portion
narrowing a flow passage of the mixing gas passed through the fuel
nozzle straight tube portion; a fuel nozzle diffusion portion
horizontally expanding the flow passage of the mixing gas passed
through the fuel nozzle throttling portion; a fuel nozzle outlet
portion connected to the fuel nozzle diffusion portion and having
an outlet flattened in shape; a ring-shaped outer peripheral flame
stabilizer disposed on an outer periphery of the fuel nozzle outlet
portion; and an inner flame stabilizer disposed in the fuel nozzle
outlet portion and horizontally dividing the mixing gas passed
through the fuel nozzle diffusion portion.
Inventors: |
WATANABE; Junya;
(Yokohama-shi, JP) ; KURAMASHI; Koji;
(Yokohama-shi, JP) ; BABA; Akira; (Yokohama-shi,
JP) ; KITAKAZE; Kosuke; (Yokohama-shi, JP) ;
OCHI; Kenichi; (Yokohama-shi, JP) ; KIYAMA;
Kenji; (Yokohama-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mitsubishi Hitachi Power Systems, Ltd. |
Yokohama-shi |
|
JP |
|
|
Family ID: |
69523813 |
Appl. No.: |
16/541914 |
Filed: |
August 15, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F23C 3/008 20130101;
F23C 7/006 20130101; F23D 1/005 20130101; F23D 1/04 20130101; F23C
7/008 20130101; F23D 2201/10 20130101; F23D 2201/20 20130101 |
International
Class: |
F23D 1/00 20060101
F23D001/00; F23C 7/00 20060101 F23C007/00; F23C 3/00 20060101
F23C003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 20, 2018 |
JP |
2018-153865 |
Claims
1. A solid fuel burner comprising: a fuel nozzle straight tube
portion allowing a mixing gas of a solid fuel and its carrier gas
to flow therethrough; a fuel nozzle throttling portion narrowing a
flow passage of the mixing gas passed through the fuel nozzle
straight tube portion; a fuel nozzle diffusion portion horizontally
expanding the flow passage of the mixing gas passed through the
fuel nozzle throttling portion; a fuel nozzle outlet portion
connected to the fuel nozzle diffusion portion and having an outlet
flattened in shape; a ring-shaped outer peripheral flame stabilizer
disposed on an outer periphery of the fuel nozzle outlet portion;
and an inner flame stabilizer disposed in the fuel nozzle outlet
portion and horizontally dividing the mixing gas passed through the
fuel nozzle diffusion portion.
2. The solid fuel burner according to claim 1, comprising a guide
sleeve disposed on an outer side of the outer peripheral flame
stabilizer.
3. The solid fuel burner according to claim 2, comprising a
top-bottom guide sleeve disposed vertically with respect to an
outer periphery of the guide sleeve.
4. The solid fuel burner according to claim 3, wherein the fuel
nozzle throttling portion is a venturi type which is
circumferentially narrowed.
5. The solid fuel burner according to claim 3, wherein the fuel
nozzle throttling portion has a structure which is narrowed only in
the vertical direction.
6. The solid fuel burner according to claim 5, comprising a
horizontal vane disposed in the fuel nozzle diffusion portion and
serving to disperse the mixing gas horizontally outward.
7. The solid fuel burner according to claim 5, comprising a
swirling vane disposed in the fuel nozzle straight tube portion and
serving to stir the mixing gas.
8. The solid fuel burner according to claim 5, further comprising:
a pipe disposed on an upstream side of the fuel nozzle straight
tube portion and including a bending portion connected to the fuel
nozzle straight tube portion; and a guide disposed in the bending
portion of the pipe and serving to centrifugally divide the mixing
gas.
9. The solid fuel burner according to claim 6, comprising: a pipe
disposed on an upstream side of the fuel nozzle straight tube
portion and including a bending portion connected to the fuel
nozzle straight tube portion; and a particle dispersion plate
disposed in the fuel nozzle straight tube portion and serving to
disperse the mixing gas.
10. The solid fuel burner according to claim 1, wherein a
horizontal cross section of the inner flame stabilizer takes a
triangular prism defining isosceles triangle.
11. The solid fuel burner according to claim 1, wherein the inner
flame stabilizer is provided with a recess portion on its backside
on a downstream side of a fuel flow and/or air flow direction.
12. The solid fuel burner according to claim 1, wherein a plate is
arranged with the inner flame stabilizer such that the stabilizer
takes a V-shape structure.
13. The solid fuel burner according to claim 12, wherein an baffle
plate is disposed at a tip end of a plate member taking the V-shape
structure so as to enlarge a cross-sectional area of the tip
end.
14. The solid fuel burner according to claim 1, wherein a
horizontal cross section of the inner flame stabilizer has a
pentagonal prism structure.
15. The solid fuel burner according to claim 11, wherein the inner
flame stabilizer is provided with the recess portion including a
vertical notch on its backside on the downstream side of the fuel
flow and/or air flow direction.
16. The solid fuel burner according to claim 11, wherein the inner
flame stabilizer is provided with air inlets to supply air into the
recess portion.
Description
CLAIM OF PRIORITY
[0001] The present application claims priority from Japanese Patent
application serial no. 2018-153865, filed on Aug. 20, 2018, the
content of which is hereby incorporated by reference into this
application.
TECHNICAL FIELD
[0002] The present invention relates to a solid fuel burner.
BACKGROUND ART
[0003] A background art of this field is set forth in Japanese
Patent Application Laid-Open No. Hei 10-220707 (Patent Literature
1). This patent literature discloses a structure which includes: an
outer peripheral flame stabilizing ring disposed on an outer
periphery of a burner; an inner flame stabilizer disposed in a
pulverized coal fuel pipe and equipped with a flame stabilizing
plate for drawing a high temperature gas from the outer periphery
of the burner into a central part of the burner; and a separator
disposed on a burner front-stream side of the inner flame
stabilizer. The structure is adapted to increase a pulverized coal
flow volume at the center of the burner and to decrease the
pulverized coal flow volume on the outer periphery of the
burner.
[0004] Another background art of this field is set forth in
Japanese Patent Application Laid-Open No. 2014-055759 (Patent
Literature 2). This patent literature discloses a combustor which
includes pulverized coal burners arranged in plural rows and plural
columns on at least one surface of furnace walls. The pulverized
coal burner includes a pulverized coal nozzle which includes a
venturi including the throttling portion and the concentrator in
the fuel flow passage. In the pulverized coal nozzle, a portion
having a circular transverse cross section extends to the vicinity
of the throttling portion, from which the transverse cross section
is progressively flattened in the horizontal direction so that the
nozzle has the maximum degree of flatness at an opening of the
furnace wall. The pulverized coal burners are arranged such that
width sides of the flattened nozzles are properly directed in a
vertical direction or horizontal direction.
SUMMARY OF THE INVENTION
[0005] The above-described Patent Literature 1 discloses the solid
fuel burner including the inner flame stabilizer and the outer
peripheral flame stabilizing ring, while the above-described Patent
Literature 2 discloses the pulverized coal burner including the
pulverized coal nozzle which is flattened at the outlet. The solid
fuel burner stated in Patent Literature 1 and the pulverized coal
burner stated in Patent Literature 2 may encounter the following
problem. In a case where the burner grows in size, an ignition area
relative to fuel injection becomes smaller, which may result in
instable ignition or flame holding.
[0006] It is therefore an object of the present invention to
provide a solid fuel burner featuring a fuel nozzle which ensures
stable ignition performance and flame holding performance. The
solid fuel burner of the present invention can be applied to a case
where the burner has a large capacity, or a case where a flame
retardant fuel having a small amount of volatile matter, for
example, solid fuel such as anthracite or petroleum coke. In
addition, since the average particle size of the solid fuel
supplied to the burner is large, it can be applied to a fuel, for
example, biomass, for which floating combustion within a boiler
furnace is harder than pulverized coal. Further, the present
invention provides a solid fuel burner which achieves cost
reduction by simplifying the structure of the fuel nozzle and
mitigate environmental burden as represented by NO.sub.x and CO and
enables efficient combustion such as reducing unburned carbon in
the fly ashes and the CO content of the flue gas. Further, the
present invention provides a solid fuel burner in which the solid
fuel burner and a start-up oil burner are coaxially arranged and
which is reducing soot and dust, oil mist and CO during
operation.
[0007] For achieving the above object, a solid fuel burner is
characterized in including: a fuel nozzle straight tube portion
allowing a mixing gas of a solid fuel and its carrier gas to flow
therethrough; a fuel nozzle throttling portion narrowing a flow
passage of the mixing gas passed through the fuel nozzle straight
tube portion; a fuel nozzle diffusion portion horizontally
expanding the flow passage of the mixing gas passed through the
fuel nozzle throttling portion; a fuel nozzle outlet portion
connected to the fuel nozzle diffusion portion and having an outlet
flattened in shape; a ring-shaped outer peripheral flame stabilizer
disposed on an outer periphery of the fuel nozzle outlet portion;
and an inner flame stabilizer disposed in the fuel nozzle outlet
portion and horizontally dividing the mixing gas passed through the
fuel nozzle diffusion portion.
[0008] The present invention can provide the solid fuel burner
which ensures the ignition performance and flame holding
performance of the fuel nozzle in future too. The present invention
can provide the solid fuel burner which achieves cost reduction by
simplifying the structure of the fuel nozzle and ensure the
ignition performance and flame holding performance of the fuel
nozzle.
[0009] The problems, components and effects other than those
described above will become apparent from the description of the
following examples hereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1A is an illustrative diagram showing a vertical cross
section of a solid fuel burner according to Example 1 hereof as
taken on the axis thereof.
[0011] FIG. 1B is an illustrative diagram showing a horizontal
cross section of the solid fuel burner according to Example 1
hereof as taken on the axis thereof.
[0012] FIG. 2A is an illustrative diagram showing a vertical cross
section of a solid fuel burner according to Example 2 hereof as
taken on the axis thereof.
[0013] FIG. 2B is an illustrative diagram showing a horizontal
cross section of the solid fuel burner according to Example 2
hereof as taken on the axis thereof.
[0014] FIG. 3A is an illustrative diagram showing a vertical cross
section of a solid fuel burner according to Example 3 hereof as
taken on the axis thereof.
[0015] FIG. 3B is an illustrative diagram showing a horizontal
cross section of the solid fuel burner according to Example 3
hereof as taken on the axis thereof.
[0016] FIG. 4A is an illustrative diagram showing a vertical cross
section of a solid fuel burner according to Example 4 hereof as
taken on the axis thereof.
[0017] FIG. 4B is an illustrative diagram showing a horizontal
cross section of the solid fuel burner according to Example 4
hereof as taken on the axis thereof.
[0018] FIG. 5A is an illustrative diagram showing a vertical cross
section of a solid fuel burner according to Example 5 hereof as
taken on the axis thereof.
[0019] FIG. 5B is an illustrative diagram showing a horizontal
cross section of the solid fuel burner according to Example 5
hereof as taken on the axis thereof.
[0020] FIG. 6A is an illustrative diagram showing a vertical cross
section of a solid fuel burner according to Example 6 hereof as
taken on the axis thereof.
[0021] FIG. 6B is an illustrative diagram showing a horizontal
cross section of the solid fuel burner according to Example 6
hereof as taken on the axis thereof.
[0022] FIG. 7A is an illustrative diagram showing an example of the
inner flame stabilizer which is disposable in any one of the solid
fuel burners according to Example 1 to 6 hereof.
[0023] FIG. 7B is an illustrative diagram showing an example of the
inner flame stabilizer which is disposable in any one of the solid
fuel burners according to Example 1 to 6 hereof.
[0024] FIG. 7C is an illustrative diagram showing an example of the
inner flame stabilizer which is disposable in any one of the solid
fuel burners according to Example 1 to 6 hereof.
[0025] FIG. 7D is an illustrative diagram showing an example of the
inner flame stabilizer which is disposable in any one of the solid
fuel burners according to Example 1 to 6 hereof.
[0026] FIG. 7E is an illustrative diagram showing an example of the
inner flame stabilizer which is disposable in any one of the solid
fuel burners according to Example 1 to 6 hereof.
[0027] FIG. 7F is an illustrative diagram showing an example of the
inner flame stabilizer which is disposable in any one of the solid
fuel burners according to Example 1 to 6 hereof.
[0028] FIG. 7G is an illustrative diagram showing an example of the
inner flame stabilizer which is disposable in any one of the solid
fuel burners according to Example 1 to 6 hereof, in which the
detail of the inner flame stabilizer in FIG. 7D, the flow of the
solid fuel and the injection direction of the start-up oil fuel are
shown.
DETAILED DESCRIPTION OF EMBODIMENTS
[0029] The examples of the present invention will hereinbelow be
described with reference to the accompanying drawings. Equal or
similar reference numerals are assigned to equal or similar
components, and explanation of overlapping components may be
omitted.
First Embodiment
[0030] In combustors using solid fuels such as coal fired boilers,
the solid fuel burner for use in the combustors is required to
ensure stable ignition and flame holding in order to achieve the
reduction of harmful emissions such as nitrogen oxides (NOx) and
the increase in combustion efficiency. To ensure the stable
ignition and flame holding, it is important to install a flame
stabilizer in a fuel nozzle of a solid fuel burner and to supply
the flame stabilizer with a fuel stream (particles of solid fuel)
having sufficiently high density. Particularly, in a case where the
solid fuel burner is increased in size so that a large ignition
area is required or a case where the solid fuel burner operates
under low load during load fluctuation, the stable ignition and
flame holding is necessary.
[0031] FIG. 1A is an illustrative diagram showing a vertical cross
section of a solid fuel burner according to Example 1 hereof as
taken on the axis thereof. FIG. 1B is an illustrative diagram
showing a horizontal cross section of the solid fuel burner
according to Example 1 hereof as taken on the axis thereof.
[0032] The solid fuel burner according to the example includes: a
fuel nozzle straight tube portion 4 (hereinafter, simply referred
to as "straight tube portion") which allows a mixing gas 100 of a
solid fuel and its carrier gas to flow therethrough; a fuel nozzle
throttling portion 5 (hereinafter, simply referred to as
"throttling portion") which narrows a flow passage of the mixing
gas 100 passed through the straight tube portion 4 so as to
accelerate the mixing gas 100; a fuel nozzle diffusion portion 6
(hereinafter, simply referred to as "diffusion portion") which
flows and slows the mixing gas 100 accelerated as passed through
the throttling portion 5 and horizontally expands the flow passage
of the mixing gas 100; and a fuel nozzle outlet portion 16
(hereinafter, simply referred to as "outlet portion") which is
connected to the diffusion portion 6 and ejects the mixing gas 100
passed through the diffusion portion 6 into a furnace.
[0033] An outlet of the outlet portion 16 has a flat configuration
which is expanded in horizontal width. The throttling portion 5 is
a venturi type which is circumferentially narrowed.
[0034] The straight tube portion 4, the throttling portion 5, the
diffusion portion 6 and the outlet portion 16 constitute the fuel
nozzle, defining the flow passage of the mixing gas 100.
[0035] A wind box 10 for introducing combustion air is disposed on
an outer periphery of the fuel nozzle (straight tube portion 4,
throttling portion 5 and diffusion portion 6).
[0036] A guide sleeve 7 for discharging the combustion air into the
furnace is disposed on an outer periphery of the outlet portion 16.
A top-bottom guide sleeve 8 for discharging the combustion air to
upper and lower areas of the furnace is disposed at upper and lower
places of an outer periphery of the guide sleeve 7. Furnace walls 9
are disposed on transversely outer sides of the guide sleeve 7 and
on vertically outer sides of the top-bottom guide sleeve 8 on the
outer sides of the guide sleeve 7, respectively.
[0037] An outer peripheral flame stabilizer 2 shaped like a ring is
disposed on the outer periphery of the outlet portion 16. It is
noted that the guide sleeve 7 is disposed on an outer side from the
outer peripheral flame stabilizer 2.
[0038] The outlet portion 16 is provided with an inner flame
stabilizer 1 shaped like a wedge having an isosceles triangular
cross section. The inner flame stabilizer 1 is singly disposed at a
horizontally central position so as to horizontally divide the
mixing gas 100 passed through the diffusion portion 6.
[0039] A central supporting rod 3 is disposed at a central part of
fuel nozzle (straight tube portion 4, throttling portion 5, and
diffusion portion 6). According to the example, the central
supporting rod 3 is not provided with a particle concentrator for
throwing the particles of the solid fuel (hereinafter, simply
referred to as "particles") toward an outer periphery for
concentration.
[0040] The mixing gas 100 ejected from the outlet portion 16 into
the furnace forms a fuel jet flow 104. The combustion air
discharged from the guide sleeve 7 and top-bottom guide sleeve 8
into the furnace as spreading circumferentially outward forms a
combustion air jet flow 101.
[0041] A recirculation flow 102 is formed between the fuel jet flow
104 and the combustion air jet flow 101. The recirculation flow 102
is formed in the rear of the outer peripheral flame stabilizer 2. A
high-temperature combustion gas resulting from fuel combustion in
the furnace accumulates in the recirculation flow 102. The
high-temperature combustion gas contacting with the fuel jet flow
104 causes immediate ignition of the particles in the rear of the
outer peripheral flame stabilizer 2 and thus, flames are
formed.
[0042] In the solid fuel burner according to the example, the
outlet portion 16 has the flattened configuration having a short
vertical (height) dimension and a long horizontal (width)
dimension. The diffusion portion 6 is expanded in the horizontal
direction but not in the vertical direction. That is, the diffusion
portion 6 and the outlet portion 16 are formed in the flattened
shape also at their connection portion.
[0043] In general, an opening (a jetting port of the fuel jet flow
into the furnace) of the fuel nozzle of the solid fuel burner has a
circular shape. In a case where the outlet portion of the solid
fuel burner has the flattened configuration having a short vertical
(height) dimension and a long horizontal (width) dimension, a flow
passage of the combustion air jetted from an outer peripheral area
of the outlet portion has an area which is vertically wide and
horizontally narrow. Accordingly, the flow volume of the combustion
air is large in the vertical area but small in the horizontal
area.
[0044] The solid fuel burner of the example is provided with the
top-bottom guide sleeve 8 only in the vertical area so as to guide
the combustion air in the vertical area of the large flow volume to
the outer peripheral area. In a case where the combustion air has a
large flow volume, the combustion air with high kinetic momentum is
jetted into the furnace so that a large recirculation flow 102 is
vertically formed in the rear of the outer peripheral flame
stabilizer 2.
[0045] The larger the magnitude of the recirculation flow 102 is,
the more high-temperature combustion gas can be accumulated. Mixed
with the fuel jet flow 104 and imparted thermal radiation, the
recirculation flow 102 can provide stable ignition and flame
holding of the solid fuel. Therefore, the fuel nozzle having the
horizontally elongated flat configuration at the outlet portion 16
is capable of forming the large recirculation flow 102 in
vertically upper and lower areas and achieving the stable ignition
and flame holding.
[0046] The solid fuel burner according to the example has the inner
flame stabilizer 1 so disposed as to horizontally divide the flow
passage in the outlet portion 16. Namely, the inner flame
stabilizer 1 is designed to horizontally divide the mixing gas 100
passed through the diffusion portion 6. The inner flame stabilizer
1 so disposed as to horizontally divide the flow passage in the
outlet portion 16 plays a role as a bridge to interconnect the
upper and lower parts of the outer peripheral flame stabilizer 2.
By virtue of the effect of the fuel nozzle having the horizontally
elongated flat configuration, a large recirculation flow 102 is
formed at the upper and lower parts of the outer peripheral flame
stabilizer 2 so that the high-temperature combustion gas is stably
supplied to the vicinity of the outer peripheral flame stabilizer
2.
[0047] The high-temperature combustion gas in the large
recirculation flow 102 can be drawn to the center in the rear of
the outlet portion 16 by disposing the inner flame stabilizer 1
according to the example. That is, a high-temperature gas flow 103
can be formed so as to draw the high-temperature combustion gas to
the center in the rear of the outlet portion 16. In this way, the
high-temperature combustion gas drawn to the center in the rear of
the outlet portion 16 permits even the small recirculation flow
(not shown) in the rear of the inner flame stabilizer 1 to achieve
the stable ignition and flame holding of the whole fuel jet flow up
to the point where the divided fuel jet flow 104 is innermost
ignited on the inner sides thereof.
[0048] The particles are concentrated toward the center of the fuel
nozzle by the venturi type throttling portion 5.
[0049] The inner flame stabilizer 1 according to the example is
disposed at the horizontal center position so that the concentrated
particles can be made to flow in the vicinity of the inner flame
stabilizer 1. Since a fuel (particle) flow of high density can be
made to flow in the vicinity of the inner flame stabilizer 1, the
inner flame stabilizer can achieve the stable ignition and flame
holding.
[0050] The inner flame stabilizer 1 according to the example is
shaped like the wedge having the isosceles triangular cross section
so as to split the fuel jet flow 104 in a manner to spread the fuel
jet flow horizontally. The inner flame stabilizer can spread the
flames in the furnace so as to prevent flame localization in the
furnace. This leads to homogeneous combustion of the fuel in the
furnace and hence, is effective in reducing unburned NOx and
non-combusted content.
[0051] According to the example, the inner flame stabilizer 1 is
singly disposed at the horizontal center position. However, more
than one inner flame stabilizer 1 may be arranged in the horizontal
direction. Further, the cross section shape of the inner flame
stabilizer 1 is not limited to isosceles triangle but may also be
pentagonal or such a shape as providing a recess on a downstream
side portion of the inner flame stabilizer which faces the
furnace.
[0052] As to such concrete shape examples, reference is made to
FIG. 7B to FIG. 7F. The inner flame stabilizer basically has such
function as dividing the solid fuel into two directions, but
according to the type of the fuel and the fuel granurality, the
fuel is hard to be incorporated into the downstream recirculation
zone of the inner flame stabilizer, leading to interrupting
ignition, in which case the structure having such recess enables
such recirculation zone to be enlarged so as to permit stable
ignition. Further, in terms of production cost, the example in FIG.
7C-1 or 7C-2 taking a V-shape structure by a plate is more
cost-effective than the solid triangular prism, so that the inner
flame stabilizer taking a V-shape structure is optionally adoptable
when ignition performance is stable enough.
(Operation 1)
[0053] In a conventional solid fuel burner provided with the outer
peripheral flame stabilizer, the particle concentrator is disposed
on the central supporting rod. The particle concentrator is
designed to increase the fuel (particles) density around the outer
peripheral flame stabilizer at the outlet portion of the fuel
nozzle by throwing the particles toward the outer periphery for
concentration.
[0054] Specifically, the fuel nozzle provided with the particle
concentrator on the central supporting rod is designed such that
the fuel nozzle is narrowed by means of the throttling portion
thereof so as to guide the particles to the center and against the
particle concentrator, which guide the particles toward the outer
periphery for concentration so as to increase the density of the
fuel around the outer peripheral flame stabilizer.
[0055] As just described, the particle concentrator must be
disposed in order to increase the fuel (particles) density around
the outer peripheral flame stabilizer. This entails an additional
support member for the particle concentrator at a distal end of the
solid fuel burner and an increase in axial length of the solid fuel
burner, resulting in cost increase.
[0056] The particle concentrator is subjected to impacts from
high-density fuel flow (particles) at a velocity of tens of meters
per second and suffers from increase in wear volume. Therefore, a
high-grade hard material must be used for the particle
concentrator. This results in cost increase.
[0057] The particle concentrator further suffers from the increase
in wear volume because the particles need to collide against the
concentrator at a large collision angle. The particles thrown
toward the outer periphery by the particle concentrator are
concentrated as colliding against an inner wall of the fuel nozzle.
Hence, the inner wall of the fuel nozzle suffers from increased
wear volume. Furthermore, if the particle concentrator is disposed
on the central supporting rod, a cross-sectional area of the flow
passage is decreased so that the velocity of the particles in the
fuel nozzle is increased. Hence, the particles colliding against
the inner wall of the fuel nozzle are also increased in velocity.
Accordingly, the inner wall of the fuel nozzle is increased in wear
volume. This dictates the need for using the high-grade hard
material for the fuel nozzle as well, resulting in cost
increase.
[0058] Particularly, in a case where the fuel nozzle having the
horizontally flattened configuration at the outlet portion of the
fuel nozzle is used, the movement distance from the particle
concentrator to the outlet portion of the fuel nozzle of the
particles that are thrown toward the outer periphery by the
particle concentrator disposed on the central supporting rod of the
fuel nozzle is longer in the horizontal direction than in the
vertical direction. Therefore, a sufficient amount of horizontally
thrown particles does not reach the outer peripheral flame
stabilizer, which may be lowered in fuel (particle) density in the
horizontal direction. Thus, the outer peripheral flame stabilizer
is prone to suffer ignition failure in the horizontal direction. In
the case where the fuel nozzle having the flattened configuration
is employed, it is required to increase the diameter of the
particle concentrator and the axial length of the solid fuel burner
in order to obviate this problem. This results in cost
increase.
[0059] For the sake of suppressing cost increase, as just
described, it is effective to omit the particle concentrator.
[0060] If the particle concentrator is omitted, however, a
high-density fuel flow (particles) centrally concentrated in the
throttling portion 5 is directly jetted into the furnace but is not
made to flow in the vicinity of the outer peripheral flame
stabilizer 2 where the recirculation flow 102 with the accumulated
high-temperature combustion gas is formed. Hence, the solid fuel
burner is significantly degraded in combustion performance
(ignition performance).
[0061] The solid fuel burner according to the example is provided
with the inner flame stabilizer 1 at the outlet portion 16 in place
of the particle concentrator such that the high-density fuel flow
(particles) centrally concentrated in the throttling portion 5 is
ignited by the inner flame stabilizer 1. Thus, the solid fuel
burner is adapted to suppress cost increase without degrading the
combustion performance (ignition performance).
[0062] The solid fuel burner according to the example utilizes the
inner flame stabilizer 1 disposed in the outlet portion 16 to cause
the high-density fuel flow (particles) centrally concentrated in
the throttling portion 5 to flow in the vicinity of the outer
peripheral flame stabilizer 2 where the recirculation flow 102 with
the accumulated high-temperature combustion gas is formed. Thus,
the solid fuel burner is improved in the combustion performance
(ignition performance).
[0063] The solid fuel burner according to the example does not
employ the particle concentrator disposed on the central supporting
rod 3 but effectively utilizes the high-density fuel flow
(particles) centrally concentrated in the throttling portion 5 to
achieve the increased combustion performance (ignition
performance).
[0064] As compared with the conventional solid fuel burner
including the particle concentrator, the solid fuel burner of the
example can also achieve the reduction of the wear volume of inner
wall of the fuel nozzle. This is the result of omitting the
particle concentrator so as to avoid positively throwing the
particles toward the outer periphery.
(Operation 2)
[0065] The combustor is faced with a strong demand for cost
reduction. One of the measures for cost reduction is to increase
the capacity of the solid fuel burner. The high capacity enables
the reduction of the number of solid fuel burners, leading to the
reduction of the number of pipes for flowing the mixing gas of the
solid fuel and its carrier gas and the number of pulverizers for
pulverizing the solid fuel. Thus, cost reduction can be
achieved.
[0066] With the increase in the capacity of the solid fuel burner,
however, the fuel nozzle for use in the solid fuel burner is
increased in diameter so that an unignited area near the center of
the fuel nozzle is increased. This may raise the fear of increase
in harmful emissions such as nitrogen oxides (NOx) and decrease in
combustion efficiency.
[0067] With the decrease in the number of solid fuel burners, a
distance between the solid fuel burner and the solid fuel burner in
the combustor is increased so that the flames are localized, making
it difficult to make effective use of the whole furnace.
[0068] By using the inner flame stabilizer 1 shaped like the wedge
having the isosceles triangular cross section, the solid fuel
burner according to the example is adapted to bring the
recirculation flow 102 with the accumulated high-temperature
combustion gas and the fuel jet flow 104 into contact, to ensure
the stable ignition and flame holding, to achieve the reduction of
harmful emissions such as nitrogen oxides (NOx) and the improvement
of combustion efficiency, and to split the fuel jet flow 104 into
horizontally spread flows so as to spread the flames in the furnace
and to prevent the flame localization.
(Operation 3)
[0069] In general, comparing the ring-shaped inner flame stabilizer
with the ring-shaped outer peripheral flame stabilizer, the
recirculation flow formed in the rear of the latter is larger than
that formed in the rear of the former. In turn, when such
stabilizers are put to use together, the surrounding temperature
rises under the influence of the flame formed behind the inner
flame stabilizer so as to lead to inflating the combustion gas,
under the influence of which the recirculation zone behind the
outer peripheral flame stabilizer is reduced, with the result that
the burner provided with the outer peripheral flame stabilizer and
the inner flame stabilizer is inferior to the burner provided only
with the outer peripheral flame stabilizer in terms of the ignition
performance and the flame holding performance.
[0070] However, by employing the inner flame stabilizer 1 shaped
like the wedge having the isosceles triangular cross section, the
solid fuel burner according to the example is adapted to form the
large recirculation flow 102 so that the high-temperature
combustion gas is stably supplied to the vicinity of the outer
peripheral flame stabilizer. Therefore, the burner can achieve the
stable ignition and flame holding.
Second Embodiment
[0071] FIG. 2A is an illustrative diagram showing a vertical cross
section of a solid fuel burner according to Example 2 hereof as
taken on the axis thereof. FIG. 2B is an illustrative diagram
showing a horizontal cross section of the solid fuel burner
according to Example 2 hereof as taken on the axis thereof.
[0072] A solid fuel burner according to this example differs from
the solid fuel burner of Example 1 in the configuration of the
throttling portion 5.
[0073] In the solid fuel burner of Example 1, the throttling
portion 5 has the venturi type configuration such that the
throttling portion is circumferentially narrowed. In the solid fuel
burner according to this example, on the other hand, the throttling
portion 5 is configured to be narrowed in the vertical (height)
direction but not narrowed in the horizontal (width) direction. The
throttling portion 5 is configured to narrow the flow passage of
the mixing gas 100 only in the vertical (height) direction.
[0074] The throttling portion 5 according to the example does not
concentrate the particles toward the center with respect to the
horizontal direction. Therefore, the particles also tend to flow to
the vicinity of the outer peripheral flame stabilizer 2 in the
horizontal direction, facilitating the ignition in the horizontal
direction of the outer peripheral flame stabilizer 2.
[0075] Further, the throttling portion does not horizontally narrow
the flow passage of the mixing gas 100 so that the solid fuel
burner can be shortened in the axial length. Hence, cost increase
can be suppressed.
[0076] Since the cross-sectional area of the flow passage in the
throttling portion 5 is less reduced (than that of the venturi type
configuration), the acceleration of the mixing gas 100 in the
throttling portion 5 is limited and increase in the particle
velocity is also limited. Accordingly, the wear volume of the inner
wall of the fuel nozzle is also reduced.
[0077] In the solid fuel burner according to the example, a
contraction flow angle (throttle angle) of the throttling portion 5
is properly designed in view of balance between the inner flame
holding and the outer flame holding. In the solid fuel burner of
the example, the contraction flow angle (throttle angle) of the
throttling portion 5 is defined to be smaller than that of the
solid fuel burner according to Example 1.
[0078] In the throttling portion 5, the particles are concentrated
to form a high-density fuel flow (particles) toward the center of
the fuel nozzle. However, if the contraction flow angle (throttle
angle) of the throttling portion 5 is excessively large, the fuel
(particles) density on the outer peripheral side is not
sufficiently increased so that the outer peripheral flame
stabilizer 2 becomes less likely to make ignition. On the other
hand, if the contraction flow angle (throttle angle) of the
throttling portion 5 is excessively small, the outlet portion 16 is
increased in the length required for allowing transformation to the
predetermined flat configuration. The solid fuel burner is
increased in the axial length, resulting in increased production
cost of the burner.
[0079] The contraction flow angle (throttle angle) of the
throttling portion 5 is properly designed in view of balance
between the inner flame holding and the outer flame holding so that
the high-density fuel flow (particles) in the outlet portion 16 is
made to flow also to the vicinity of the upper and lower parts of
the outer peripheral flame stabilizer 2, which achieves reliable
ignition. Thus, the burner can achieve both the stable inner flame
holding and outer flame holding.
Third Embodiment
[0080] FIG. 3A is an illustrative diagram showing a vertical cross
section of a solid fuel burner according to Example 3 hereof as
taken on the axis thereof. FIG. 3B is an illustrative diagram
showing a horizontal cross section of the solid fuel burner
according to Example 3 hereof as taken on the axis thereof.
[0081] In addition to the solid fuel burner of Example 2, the solid
fuel burner according to the example further includes a horizontal
vane 11 which is disposed in the diffusion portion 6 and adapted to
throw the particles horizontally outward. Namely, the solid fuel
burner of this example includes the horizontal vane 11 which is
disposed in the diffusion portion 6 so as to disperse the mixing
gas 100 horizontally outward.
[0082] The solid fuel burner according to the example is decreased
in the fuel (particles) density in the vicinity of the outer
peripheral flame stabilizer 2 because the particle concentrator is
omitted. The large recirculation flow 102 is formed with respect to
the vertical parts of the outer peripheral flame stabilizer 2 and
hence, the particles are captured by the large recirculation flow
102 despite the decreased fuel (particles) density. Thus, the
ignition and flame holding are ensured. However, the recirculation
flow 102 is relatively small with respect to the horizontal parts
of the outer peripheral flame stabilizer 2 so that the outer
peripheral stabilizer may be less likely to achieve ignition and
flame holding.
[0083] The solid fuel burner of the example is provided with the
horizontal vane 11 for particle concentration on the horizontally
outer side so as to concentrate the particles to the vicinity of
the horizontal parts of the outer peripheral flame stabilizer 2 and
to facilitate the horizontally outer peripheral flame holding.
[0084] The solid fuel burner of the example is adapted to control
the fuel (particles) density in the vicinity of the inner flame
stabilizer 1 and the fuel (particles) density in the vicinity of
the horizontal parts of the outer peripheral flame stabilizer 2 by
changing the installation angle of the horizontal vane 11. Thus,
the burner can adjust the combustion state. By virtue of the
movable structure of the horizontal vane 11, the solid fuel burner
can properly control the combustion state according to the
operating conditions.
Fourth Embodiment
[0085] FIG. 4A is an illustrative diagram showing a vertical cross
section of a solid fuel burner according to Example 4 hereof as
taken on the axis thereof. FIG. 4B is an illustrative diagram
showing a horizontal cross section of the solid fuel burner
according to Example 4 hereof as taken on the axis thereof.
[0086] In addition to the solid fuel burner of Example 2, the solid
fuel burner according to the example further includes a swirling
vane 12 which stirs the particles as disposed on an upstream side
of the throttling portion 5. Namely, the solid fuel burner of the
example includes the swirling vane 12 disposed in the straight tube
portion 4 so as to stir the mixing gas 100.
[0087] The mixing gas 100 flows through a long pipe (not shown) to
be supplied to the straight tube portion 4. In this process, the
mixing gas passes many bending portions where only the particles
are centrifugally shifted to the outer side so that the density
deviation of the fuel (particles) occurs in the pipe. This density
deviation of the fuel (particles) may sometimes cause particle
aggregation at some unanticipated place (straight tube portion 4)
upstream of the throttling portion 5, which may interfere with
ignition or flame holding in the inner flame stabilizer and the
outer peripheral flame stabilizer 2.
[0088] In the solid fuel burner of the example, therefore, the
swirling vane 12 for stirring the particles is disposed at place
(straight tube portion 4) upstream of the throttling portion 5 so
as to control the density deviation of the fuel (particles) flowing
through the throttling portion 5 and to facilitate the ignition and
flame holding in the inner flame stabilizer 1 or the outer
peripheral flame stabilizer 2.
[0089] While the example employs the swirling vane 12 as the
particle stirring structure, the stirring structure may have
another configuration such as a turning blade (a component such as
a conical structure for diffusing the mixing gas 100 toward the
outer periphery).
Fifth Embodiment
[0090] FIG. 5A is an illustrative diagram showing a vertical cross
section of a solid fuel burner according to Example 5 hereof as
taken on the axis thereof. FIG. 5B is an illustrative diagram
showing a horizontal cross section of the solid fuel burner
according to Example 5 hereof as taken on the axis thereof.
[0091] In addition to the solid fuel burner of Example 2, the solid
fuel burner according to the example further includes a pipe which
is disposed on an upstream side of the straight tube portion 4 and
includes a bending portion 13 connected to the straight tube
portion 4 (the bending portion according to the example is a planar
member which can be opened and closed for maintenance work). The
bending portion 13 of the pipe is provided with a guide (guide
plate) 14 for dividing the flow passage into an inner side and an
outer side with respect to the bending portion 13. Namely, the
solid fuel burner includes, on the upstream side of the straight
tube portion 4, the pipe including the bending portion 13 connected
to the straight tube portion 4, and the guide (guide plate) 14
disposed at the bending portion 13 of the pipe for centrifugally
dividing the mixing gas 100.
[0092] When flowing through the bending portion 13, the mixing gas
100 allows only the particles to be centrifugally shifted toward
the outer side. Disposing the guide (guide plate) 14 restricts the
particles from being shifted only toward the outer side with
respect to the bending portion 13. Thus, the burner can provide
vertically well-balanced supply of particles.
[0093] This configuration obviates the extreme density deviation of
the fuel (particles) in the outlet portion 16, facilitating the
ignition and flame holding in the inner flame stabilizer 1 and the
outer peripheral flame stabilizer 2.
[0094] A structure such as the guide (guide plate) 14 disposed in
the bending portion 13 of the pipe dispenses with the need for
disposing the structure such as the swirling vane 12 in the
straight tube portion 4. Hence, the solid fuel burner can be
reduced in the axial length. This leads to reduction of production
cost of the burner.
Sixth Embodiment
[0095] FIG. 6A is an illustrative diagram showing a vertical cross
section of a solid fuel burner according to Example 6 hereof as
taken on the axis thereof. FIG. 6B is an illustrative diagram
showing a horizontal cross section of the solid fuel burner
according to Example 6 hereof as taken on the axis thereof.
[0096] In addition to the solid fuel burner of Example 3, the solid
fuel burner according to the example further includes a pipe which
is disposed on an upstream side of the straight tube portion 4 and
includes a bending portion 13 connected to the straight tube
portion 4 (the bending portion according to the example is a planar
member which can be opened and closed for maintenance work).
[0097] A particle dispersion plate 15 for dispersing the particles
is disposed at an outlet of the bending portion 13. That is, the
straight tube portion 4 includes the particle dispersion plate 15
for dispersing the mixing gas 100.
[0098] The particle dispersion plate 15 is disposed only on a
centrifugally outer side of the bending portion 13. This is for the
purpose of utilizing the particle dispersion plate 15 to
effectively disperse the centrifugally outwardly shifted particles
because the particles are shifted to the centrifugally outer side
of the bending portion 13. By disposing the particle dispersion
plate 15 only on the centrifugally outer side, the reduction of the
cross-sectional area of the flow passage in the straight tube
portion 4 can be obviated so that the increase in particle velocity
in the straight tube portion 4 is also limited. Accordingly, the
wear volume of the inner wall of the fuel nozzle is also
reduced.
[0099] The particle dispersion plate 15 provides a balanced flow of
the particles through the fuel nozzle so as to permit the
horizontal vane 11 on a downstream from the particle dispersion
plate 15 to achieve an efficient particle distribution. Thus, the
burner can control the combustion state.
Seventh Embodiment
[0100] FIGS. 7A to 7F illustrate the detailed structures of the
inner flame stabilizers 1 in FIGS. 1A to 6B.
[0101] FIG. 7A illustrates the basic structure of the inner flame
stabilizers of the burners exemplified in FIGS. 1A to 6B
respectively, which structure takes a wedge structure of triangular
prism. FIGS. 7B to 7F illustrate modifications of the structure of
the inner flame stabilizer in FIG. 7A.
[0102] The structure in FIG. 7B is provided with a recess portion
105 on the backside of the inner flame stabilizer on the downstream
side of the fuel jet flow 104 in terms of the basic structure
thereof shown in FIG. 7A. The provision of such recess portion 105
on the backside of the inner flame stabilizer promotes the mixing
of the high-temperature gas flow 103 and the fuel jet flow 104,
thereby, further facilitating ignition compared to such basic
structure.
[0103] As to the structure in FIG. 7C-1, making the inner flame
stabilizer, in which a plate is arranged such that it has a V-shape
structure, take a V-shape structure without providing such
stabilizer with a backside as shown in FIG. 7A promotes the mixing
of the high-temperature gas flow 103 and the fuel jet flow 104 and
leads to cost reduction by reducing the number of the parts of such
stabilizer in the same way as the recess portion 105 in FIG.
7B.
[0104] As to the structure in FIG. 7C-2, an baffle plate 106 is
disposed at the tip end of the V-shape structure in FIG. 7C-1.
Providing the tip end of the plate member taking a V-shape
structure with such baffle plate 106 so as to enlarge the
cross-sectional area of the tip end of the plate taking such
V-shape structure further promotes the mixing of the fuel jet flow
104 and the high-temperature gas flow 103 than the structure in
FIG. 7C-1, thereby, facilitating ignition.
[0105] In FIG. 7D, the horizontal cross-section of the inner flame
stabilizer has a pentagonal prism structure. The inner flame
stabilizer in FIG. 7D has a larger volume than the counterpart
whose horizontal cross section takes a triangular prism defining
isosceles triangle and is excellent in anti-abrasion property as
well as is inexpensively producible without use of expensive
ceramic materials. In addition, since such stabilizer is excellent
in anti-abrasion property, it is applicable to the combustion of
the low-grade coal whose ash content is higher.
[0106] FIG. 7E illustrates the structure of the recess portion 105
in FIG. 7B with the exclusion of the vertical notch. In other
words, FIG. 7B corresponds to the structure with the inclusion of
the vertical notch in the recess portion in FIG. 7E. Comparing this
structure with that in FIG. 7B, high negative pressure created by
the recess portion 105 further promotes the mixing of the
high-temperature gas flow 103 and the fuel jet flow 104, thereby,
leading to excellent ignition property. This structure is also
effective for the stable ignition of the start-up oil burner which
requires higher negative pressure in the same way as coal.
[0107] The structure in FIG. 7F is provided with the inner flame
stabilizer 1, the recess portion 105 and air inlets 107 which
supply air into the recess portion 105. The air inlets 107 are
provided on the outer periphery of the recess portion. In FIG. 7F,
in order to explain the function of the recess portion 105 and the
ignition promotion of the start-up oil burner, a start-up oil
burner tip 109 and a start-up oil burner gun 110 are also
illustrated.
[0108] Oil fuel 111 is jet-sprayed from the start-up oil burner tip
109 toward the furnace so as to turn into flame. Upon the start-up,
the solid fuel is not supplied, but a combustion fuel flow and/or
an air flow 108 is fed and a part of such flow flows from the air
inlets 107 into the periphery of the start-up oil burner tip 109 to
generate an air flow 112 toward the recess portion.
[0109] Further, since high negative pressure is created by the
recess portion 105, the high-temperature gas flow 103 and the fuel
jet flow 104 flow into the recess portion 105. Accordingly, the air
flow 112 into the recess portion promotes the ignition of the oil
fuel and reduces soot and dust as well as suppresses the coking
(carbonization) of the start-up oil burner tip 109.
[0110] To note, as to the air inlets 107, because of a small amount
of air intake structure, they are not limited to the pore structure
and may be arranged with another structure such as slit. Further,
in FIG. 7F, a plurality of the air inlets 107 are provided over the
entire periphery of the recess portion 105, but they may be
provided on any one of the sides constituting the recess portion
and the number of such inlets may be one or more. Moreover, when
the air inlets are made not of pores but of slits, such slits may
be provided over the entire periphery and the number of such slits
and their length may be set in an arbitrary manner.
[0111] To note, the start-up oil burner tip 109 and the start-up
oil burner gun 110 are shown only in FIG. 7F according to the
present example, but such start-up oil burner tip is provided for
the inner flame stabilizers in FIGS. 7A to 7E as well such that
such tip penetrates such stabilizers, thereby, enabling the stable
combustion upon the solid fuel combustion and the oil
combustion.
[0112] It is noted that the present invention is not limited to the
above-described examples and includes a variety of modifications.
The foregoing examples, for example, are the detailed illustrations
to clarify the present invention. The present invention is not
necessarily limited to those including all the components described
above. Some component of one example can be replaced by some
component of another example. Further, some configuration of one
example can be added to the configuration of another example.
LIST OF REFERENCE SIGNS
[0113] 1: inner flame stabilizer [0114] 2: outer peripheral flame
stabilizer [0115] 3: central supporting rod [0116] 4: fuel nozzle
straight tube portion [0117] 5: fuel nozzle throttling portion
[0118] 6: fuel nozzle diffusion portion [0119] 7: guide sleeve
[0120] 8: guide sleeve [0121] 9: furnace wall [0122] 10: wind box
[0123] 11: horizontal vane [0124] 12: swirling vane [0125] 13:
bending portion [0126] 14: guide [0127] 15: particle dispersion
plate [0128] 16: fuel nozzle outlet portion [0129] 100: mixing gas
[0130] 101: combustion air jet flow [0131] 102: recirculation flow
[0132] 103: high-temperature flow [0133] 104: fuel jet flow [0134]
105: recess portion [0135] 106: baffle plate [0136] 107: air inlet
[0137] 108: solid fuel flow and/or air flow [0138] 109: start-up
oil burner tip [0139] 110: start-up oil burner gun [0140] 111: oil
fuel [0141] 112: air flow toward recess portion
* * * * *