U.S. patent application number 12/524885 was filed with the patent office on 2010-03-11 for pulverized coal burner.
This patent application is currently assigned to IHI Corporation. Invention is credited to Toshiro Fujimori, Shinji Watanabe, Toshihiko Yamada.
Application Number | 20100058961 12/524885 |
Document ID | / |
Family ID | 39709705 |
Filed Date | 2010-03-11 |
United States Patent
Application |
20100058961 |
Kind Code |
A1 |
Fujimori; Toshiro ; et
al. |
March 11, 2010 |
PULVERIZED COAL BURNER
Abstract
Slagging is prevented from occurring in a pulverized coal
burner. A nozzle body 6, which is open to a furnace 1 and which
injects pulverized coal together with primary air 14 transporting
the coal to serve finally as combustion air, has an outer sleeve 8
and an inner sleeve 9 arranged in and coaxially of the sleeve 8. A
fuel flow space 10 is formed between the sleeves 8 and 9.
Straightening plates 29 are arranged on at least either of the
sleeves 8 and 9 to project to the space 10 and extend axially of
the nozzle body. The combustion air (primary air 14) carrying the
pulverized coal passes through the space 10 and is injected.
Inventors: |
Fujimori; Toshiro; (Tokyo,
JP) ; Watanabe; Shinji; (Tokyo, JP) ; Yamada;
Toshihiko; (Tokyo, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, L.L.P.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
IHI Corporation
Koto-ku
JP
|
Family ID: |
39709705 |
Appl. No.: |
12/524885 |
Filed: |
December 21, 2007 |
PCT Filed: |
December 21, 2007 |
PCT NO: |
PCT/JP07/01448 |
371 Date: |
July 29, 2009 |
Current U.S.
Class: |
110/261 ;
110/234; 110/263; 431/187 |
Current CPC
Class: |
F23D 1/00 20130101 |
Class at
Publication: |
110/261 ;
110/263; 431/187; 110/234 |
International
Class: |
F23D 1/00 20060101
F23D001/00; F23C 99/00 20060101 F23C099/00; F23K 3/00 20060101
F23K003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 19, 2007 |
JP |
2007-038147 |
Claims
1. A pulverized coal burner comprising a nozzle body open to a
furnace and through which pulverized coal is injected together with
combustion air, said nozzle body comprising an outer sleeve and an
inner sleeve arranged in and coaxially of said outer sleeve, a fuel
flow space being formed between said outer and inner sleeves,
straightening plates being provided on at least one of said outer
and inner sleeves, said straightening plates projecting in said
fuel flow space and extending axially of said nozzle body, said
combustion air transporting the pulverized coal passing through
said fuel flow space and being injected.
Description
TECHNICAL FIELD
[0001] The present invention relates to a pulverized coal burner
for a furnace such as coal-fired boiler which uses coal as
fuel.
TECHNICAL BACKGROUND
[0002] In one of furnaces using coal as fuel, raw coal is
pulverized into pulverized coal by a coal pulverizer and pulverized
coal is mixed and fed with primary air into a pulverized coal
burner where the pulverized coal is injected to the furnace for
suspension combustion.
[0003] The conventional pulverized coal burner will be described in
conjunction with FIG. 1.
[0004] In FIG. 1, reference numeral 1 denotes a furnace; and 2, a
wall of the furnace 1.
[0005] A throat 3 is installed on the furnace wall 2 and a wind box
4 is arranged on a side away from the furnace 1. A pulverized coal
burner 5 is arranged in the wind box 4 coaxially of the throat
3.
[0006] The pulverized coal burner 5 comprises a nozzle body 6 and a
secondary air adjusting device 7 which surrounds a front end of the
nozzle body 6.
[0007] The nozzle body 6 comprises an outer sleeve 8, an inner
sleeve 9 coaxial of the sleeve 8 and an oil burner 11 arranged on
an axis of the sleeve 9.
[0008] The outer sleeve 8 comprises a base (an end away from the
furnace 1) 8a, an intermediate portion 8b contiguous with the base
8a and a front end 8c contiguous with the intermediate portion 8b.
The base 8a is a cylinder with a constant radius of cross section;
the intermediate portion 8b and the front end 8c are cylinders
tapered with radii of cross section reduced toward the furnace 1,
respectively. The front end 8c has a tapered angle greater than
that of the intermediate portion 8b and therefore has radii reduced
more greatly than those of the intermediate portion 8b.
[0009] The inner sleeve 9 comprises a cylindrical portion 9a and a
front end 9c contiguous with the cylindrical portion 9a. The
cylindrical portion 9a is a cylinder with a constant radius of
cross section and extending adjacent to a front side of the outer
sleeve intermediate portion 8b, and the front end 9c is tapered
with a tapered angle similar to that of the outer sleeve front end
8c. Formed between the sleeves 8 and 9 is a hollow, cylindrical,
fuel flow space 10 with an end open to the furnace 1.
[0010] The base (the end away from the furnace 1) of the outer
sleeve 8 communicates with a primary air feed pipe 12 through which
primary air 14 carrying the pulverized coal to finally serve as
combustion air as well as the pulverized coal carried by the air 14
tangentially flow into and swirl in the space 10 and are injected
through the front end of the space. A tertiary air feed pipe 13 has
one end open to the base of the inner sleeve 9 and has the other
end open to the wind box 4, so that combustion air fed to the wind
box 4 is taken in and is guided to the inner sleeve 9 as auxiliary
combustion air, i.e., tertiary combustion air.
[0011] The secondary air adjusting device 7 comprises an auxiliary
air adjusting mechanism 15 accommodating the front end of the
nozzle body 6 and a main air adjusting mechanism 16 arranged
coaxially and outward of the mechanism 15.
[0012] The auxiliary air adjusting mechanism 15 comprises a first
air guide duct 18 with diameters reduced toward a front end of the
duct and air volume adjusting vanes 19 circumferentially
equidistantly arranged in a base of the duct 18, the vanes 19 being
rotatable about rotary axes 21 in sync.
[0013] The main air adjusting mechanism 16 comprises a second air
guide duct 22 with diameters reduced toward its front end and air
volume adjusting vanes 23 circumferentially equidistantly arranged
in a base of the duct 22, the vanes 23 being rotatable about rotary
axes 24 in sync.
[0014] The front end of the second air guide duct 22 is contiguous
with the throat 3. The front end of the first air guide duct 18 is
set back from an inner wall surface of the furnace wall 2. The
front ends of the sleeves 8 and 9 are set back further from the
front end of the guide duct 18.
[0015] Combustion in the above-mentioned pulverized coal burner
will be described briefly. The pulverized coal is fed together with
the primary air 14 through the primary air feed pipe 12 into the
base of the fuel flow space 10. The primary air 14 swirls in the
space 10 toward the furnace 1, is reduced in flow during its
passage through the space 10 and is injected through the front end
of the outer sleeve 8. The wind box 4 is fed with the secondary air
26 as auxiliary combustion air which is air-volume adjusted by the
vanes 23 and is injected together with the primary air 14 and fuel
into the furnace 1 via the second air guide duct 22.
[0016] Part of the secondary air 26 taken in the second air guide
duct 22 is taken via the air volume adjusting vanes 19 into the
first air guide duct 18 and is injected as secondary auxiliary air.
Air volume adjustments by the vanes 23 and 19 change feed flow
condition of the secondary air to adjust the combustion condition
of the fuel.
[0017] Part of the secondary air 26 is guided as the tertiary air
27 via the tertiary air feed pipe 13 into and is injected from the
inner sleeve 9. Injection of the tertiary air 27 adjusts the
combustion condition of the fuel.
[0018] Thus, by adjustment of, for example, the secondary and
tertiary airs, combustion condition of the fuel is adjusted to
optimum.
[0019] The oil burner 11 is used for ignition of the pulverized
coal.
[0020] In the above-mentioned conventional pulverized coal burner,
the outer and inner sleeve front ends 8c and 9c are drastically
reduced in diameter toward their front sides, so that the primary
air 14 flowing through the fuel flow space 10 and the tertiary air
27 flowing through the inner sleeve 9 are reduced in flow and are
injected. Consequently, the primary air 14 transporting the
pulverized coal (hereinafter, pulverized coal and primary air 14 in
combination is referred to as primary air 14) is injected through
the front ends of the outer sleeve 8 and first air guide duct 18
while expanding. The primary air 14 swirls while being reduced in
flow, and further expands by centrifugal force due to the swirling.
Thus, the pulverized coal in the primary air 14 is burned while
expanding.
[0021] As a result, slagging may occur which is a phenomenon that
clinker as combustion residue of the pulverized coal impinges and
deposits on the furnace wall 2. The slagging may impair heat
transmission of the furnace wall 2 and cause heat accumulation on
the furnace wall 2, resulting in increase in temperature of the
furnace wall 2 and hence of the furnace 1. The increase in
temperature of the furnace wall 2 and of the furnace 1 may melt the
clinker, so that disadvantageously slagging may occur more easily
and NO.sub.xmay be generated more easily.
[0022] In recent years, in order to increase combustion capacity of
a pulverized coal burner, i.e., in order that much more pulverized
coal can be burned, pulverized coal burners have been increased in
size. To cope with increased combustion capacity of the pulverized
coal burner, the nozzle is made larger-sized; however, its axial
length remains limitative owing to installational restrictions.
[0023] As a result, the nozzle has larger diameter in comparison
with axial length; the pulverized coal burner is short in axial
length relative to diameter.
[0024] Because of shortness in axial length, the pulverized coal
burner has less straightening effect, so that the primary air 14
flowing into the fuel flow space 10 is injected from the nozzle
body 6 while it remains strongly swirling. Thus, due to centrifugal
force, the pulverized coal in the primary air 14 expands or
impinges, so that slagging may occur very easily.
[0025] [Patent Literature 1] JP 8-145320A
SUMMARY OF INVENTION
Technical Problems
[0026] The invention was made in view of the above and has its
object to prevent slagging from occurring in a pulverized coal
burner.
Solution to Problems
[0027] The invention is directed to a pulverized coal burner
comprising a nozzle body open to a furnace and through which
pulverized coal is injected together with combustion air, said
nozzle body comprising an outer sleeve and an inner sleeve arranged
in and coaxially of said outer sleeve, a fuel flow space being
formed between said outer and inner sleeves, straightening plates
being provided on at least one of said outer and inner sleeves,
said straightening plates projecting in said fuel flow space and
extending axially of said nozzle body, said combustion air
transporting the pulverized coal passing through said fuel flow
space and being injected.
Advantageous Effects of Invention
[0028] According to the invention, a nozzle body open to a furnace
and for injection of pulverized coal together with combustion air
comprises an outer sleeve and an inner sleeve arranged in and
coaxially of the outer sleeve. A fuel flow space is formed between
the sleeves. Straightening plates are arranged in at least either
of the outer and inner sleeves and are projected to the fuel flow
space and extend on an axis of the nozzle body, so that the
combustion air transporting the pulverized coal passes through the
fuel flow space and is injected. When the primary air transporting
the pulverized coal to finally serve as combustion air as well as
the pulverized coal flow through the fuel flow space, swirling is
weakened by the straightening plates and the pulverized coal
injected via the nozzle body is prevented from expanding and
impinging, thereby preventing the slagging from occurring.
BRIEF DESCRIPTION OF DRAWINGS
[0029] FIG. 1 is a sectional view showing a conventional pulverized
coal burner; and
[0030] FIG. 2 is a sectional view showing a pulverized coal burner
according to an embodiment of the invention.
REFERENCE SIGNS LIST
[0031] 1 furnace [0032] 2 furnace wall [0033] 3 throat [0034] 4
wind box [0035] 6 nozzle body [0036] 14 primary air (combustion
air) [0037] 18 first air guide duct [0038] 22 second air guide duct
[0039] 26 secondary air [0040] 27 tertiary air [0041] 29
straightening plate
DESCRIPTION OF EMBODIMENTS
[0042] An embodiment of the invention will be described in
conjunction with the drawings.
[0043] FIG. 2 shows a pulverized coal burner according to the
invention. In FIG. 2, the parts similar to those shown in FIG. 1
are represented by the same reference numerals and explanations
thereon are omitted.
[0044] A pulverized coal burner 5 comprises a nozzle body 6 and a
secondary air adjusting device 7. The burner 5 is arranged
coaxially of a throat 3 open to the furnace wall 2. The burner 5 is
arranged in a wind box 4.
[0045] The nozzle body 6 comprises an outer sleeve 8 and an inner
sleeve 9 coaxially of the outer sleeve 8. Formed between the
sleeves 8 and 9 is a hollow, cylindrical fuel flow space 10. The
nozzle body 6 has a greater diameter relative to its axial length
(see, for example, the conventional example shown in FIG. 1).
[0046] FIG. 2 shows an example of the nozzle body 6 with larger
diameters. That is, the outer sleeve 8 has larger diameters in
comparison with the inner sleeve 9, which fact increases
cross-sectional area of flow passage in the fuel flow space 10.
[0047] Formed on an inner surface of the outer sleeve 8 are
straightening plates 29 which project in the fuel flow space 10.
The plates 29 are arranged in parallel with an axis of the outer
sleeve 8 so as to project radially and extend axially of the sleeve
8. The plates 29 are positioned circumferentially equidistantly;
for example, there are three plates 29 at three positions divided
circumferentially equidistantly.
[0048] The wind box 4 is supplied with secondary air 26 from a
forced draft fan (not shown). The secondary air 26 is injected from
the throat 3 via the secondary air adjusting device 7.
[0049] A base of the nozzle body 6 extends out of the wind box 4
and an outer tube base 8a communicates with a primary air feed pipe
12, and an end of the inner sleeve 9 communicates with a tertiary
air feed pipe 13. The primary air feed pipe 12 is connected through
a coal pulverizer (not shown) to a forced draft fan (not shown). By
the feed pipe 12, primary air 14 transporting the pulverized coal
is introduced into the fuel flow space 10. The tertiary air feed
pipe 13 takes in and feeds part of the secondary air 26 into the
inner sleeve 9.
[0050] The primary air 14, which is fed to the fuel flow space 10,
swirls about the inner sleeve 9 and flows forward. The
straightening plates 29, which are arranged in the fuel flow space
10, prevents and straightens the swirling in the space 10 into
axial straightening flow.
[0051] Weakening of the swirling of the primary air 14 prevents the
swirling of the pulverized coal transported by the primary air 14.
Thus, expansion of the primary air 14 and dispersing of the
pulverized coal injected through the outer sleeve 8 are weakened to
prevent slagging from occurring.
[0052] Any straightening plates 29 will do, provided that they have
the proper function of weakening the swirling of the primary air
14. The plates 29 may have inner edges substantially in contact
with the inner sleeve 9; alternatively, the inner edges may be
spaced apart from the inner sleeve 9 by a required distance so as
not to weaken the swirling at the central position. Moreover, the
plates 29 may be perforated to allow required swirling. Axial
length and numbers of the plates 29 are properly selected so as to
attain optimum combustion.
[0053] Alternatively, the plates 29 may be arranged on the inner
sleeve 9; alternatively, they may be arranged on the inner and
outer sleeves 9 and 8, alternately.
* * * * *