U.S. patent application number 12/864741 was filed with the patent office on 2010-12-09 for pulverized fuel burner.
This patent application is currently assigned to IHI Corporation. Invention is credited to Toshiyuki Suko, Masato Tamura.
Application Number | 20100307391 12/864741 |
Document ID | / |
Family ID | 41064911 |
Filed Date | 2010-12-09 |
United States Patent
Application |
20100307391 |
Kind Code |
A1 |
Tamura; Masato ; et
al. |
December 9, 2010 |
PULVERIZED FUEL BURNER
Abstract
The invention provides a pulverized fuel burner including a
nozzle body 6 open to a furnace 1 to inject pulverized fuel
together with primary combustion air, flow passages for secondary
combustion air formed coaxially around the nozzle body and shutters
arranged circumferentially along the flow passages and spaced apart
from each other at specified intervals. Non-flow portions are
formed by the shutters for the flow passages for the secondary
combustion air to bring about backflow of hot flue gas. As a
result, ignition performance can be improved with pulverized fuel
containing less volatile matter and the flame can be continuously
kept stably.
Inventors: |
Tamura; Masato; (Tokyo,
JP) ; Suko; Toshiyuki; (Tokyo, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, L.L.P.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
IHI Corporation
Tokyo
JP
|
Family ID: |
41064911 |
Appl. No.: |
12/864741 |
Filed: |
February 9, 2009 |
PCT Filed: |
February 9, 2009 |
PCT NO: |
PCT/JP09/00496 |
371 Date: |
July 27, 2010 |
Current U.S.
Class: |
110/261 |
Current CPC
Class: |
F23C 7/006 20130101;
F23D 1/00 20130101; F23C 7/008 20130101 |
Class at
Publication: |
110/261 |
International
Class: |
F23C 1/12 20060101
F23C001/12 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 10, 2008 |
JP |
2008-059309 |
Claims
1. A pulverized fuel burner comprising a nozzle body open to a
furnace to inject pulverized fuel together with primary combustion
air, flow passages for secondary combustion air formed coaxially
around said nozzle body and shutters arranged circumferentially
along said flow passages and spaced apart from each other at
specified intervals, non-flow portions being formed by said
shutters for said flow passages to bring about backflow of hot
furnace gas.
2. A pulverized fuel burner as claimed in claim 1, wherein occupied
areas of said shutters for said flow passages are variable.
3. A pulverized fuel burner as claimed in claim 1, wherein a
movable ring is rotatably arranged coaxially of a front end of said
nozzle body, said movable ring having movable guide vanes, fixed
guide vanes being arranged on the front end of said nozzle body,
each of said movable and fixed guide vanes having a shutter
perpendicular to an axis of the nozzle, overlapped state of said
two shutters being varied by turning said movable ring.
4. A pulverized fuel burner as claimed in claim 1, wherein said
nozzle body is accommodated in a wind box, an air guide duct being
arranged in said wind box coaxially of a front end of said nozzle
body, a movable ring being rotatably arranged at the front end of
said nozzle body, said movable ring having movable guide vanes,
said air guide duct having fixed guide vanes, each of said movable
and fixed guide vanes having a shutter perpendicular to an axis of
the nozzle, overlapped state of said two shutters being varied by
turning said movable ring.
Description
TECHNICAL FIELD
[0001] The present invention relates to a pulverized fuel burner
for a furnace such as coal-fired boiler which uses pulverized
material as fuel.
BACKGROUND ART
[0002] In some of furnaces using pulverized material, e.g., in a
furnace using coal as fuel, lump coal is pulverized by a coal
pulverizer into pulverized coal which in turn is mixed and fed with
primary air into a pulverized coal burner where the pulverized coal
is injected into the furnace and is suspension-fired.
[0003] Further fed to the flow of the primary air mixed with the
pulverized coal is secondary combustion air which has been heated
to a required temperature (for example, 250.degree. C.-300.degree.
C.). The pulverized coal in the mixed flow is heated by the
secondary air and by radiation heat from the furnace to discharge
and ignite volatile matter to thereby establish flames.
[0004] A conventional pulverized coal burner will be described in
FIG. 1.
[0005] In FIG. 1, reference numeral 1 denotes a furnace; and 2, a
furnace wall of the furnace 1.
[0006] A throat 3 is set on the furnace wall 2, which has a wind
box 4 on a side away from the furnace 1. A pulverized coal burner 5
is arranged in the wind box 4 and coaxially of the throat 3.
[0007] The pulverized coal burner 5 comprises a nozzle body 6 and a
secondary air adjusting device 7 surrounding a front end of the
nozzle body 6.
[0008] The nozzle body 6 comprises an outer tube nozzle 8, an inner
tube nozzle 9 coaxial of the nozzle 8 and an oil burner 11 arranged
on an axis of the nozzle 9.
[0009] The outer tube nozzle 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
tapered cylinders 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.
[0010] The inner tube nozzle 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
tube intermediate portion 8b, and the front end 9c is tapered with
a tapered angle similar to that of the outer tube front end 8c.
Formed between the inner and outer tube nozzles 8 and 9 is a
hollow, cylindrical fuel conduction space 10 with an end open to
the furnace 1.
[0011] The base (the end away from the furnace 1) of the outer tube
nozzle 8 communicates with a primary air feed pipe 12 through which
primary air 14 and 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. Open to the base of the inner
tube nozzle 9 is one end of a tertiary air feed pipe 13 the other
end of which is 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 tube
nozzle 9 as auxiliary combustion air, i.e., tertiary combustion
air.
[0012] 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.
[0013] 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 swirl adjusting vanes 19 circumferentially
equidistantly arranged in a base of the duct 18, the vanes 19 being
rotatable about rotary axes 21 in sync.
[0014] The main air adjusting mechanism 16 comprises a second air
guide duct 22 with diameters reduced toward its front end and air
swirl adjusting vanes 23 circumferentially equidistantly arranged
in a base of the duct 22, the vanes 23 being rotatable about rotary
axes 24 in sync.
[0015] 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 nozzles 8 and 9 are set back further from the
front end of the guide duct 18.
[0016] Combustion at the above-mentioned pulverized coal burner 5
will be briefly described. The pulverized coal is fed together with
the primary air 14 through the primary air feed pipe 12 into the
base of the fuel conduction space 10. The primary air 14 swirls in
the space 10 toward the furnace 1, is reduced in flow during its
passing through the space 10 and is injected through the front end
of the outer tube nozzle 8. The wind box 4 is fed with the
secondary air 26 as auxiliary combustion air elevated to a required
temperature. The secondary air 26 is adjusted in air swirl by the
vanes 23 and is injected together with the primary air 14 and the
pulverized coal into the furnace 1 via the second air guide duct
22.
[0017] The pulverized coal is heated by the secondary air 26
through its injection into the furnace 1, and is heated by the
radiation heat from the furnace 1. By the heating, the pulverized
coal releases the volatile matter which is ignited to continuously
keep the flames.
[0018] Part of the secondary air 26 taken in the second air guide
duct 22 is taken via the air swirl 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 26 to adjust the combustion
condition of the pulverized coal.
[0019] 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 tube nozzle 9. Injection of the tertiary air 27 adjusts the
combustion condition of the pulverized coal. Thus, by adjustment
of, for example, the secondary and tertiary airs 26 and 27,
combustion condition of the pulverized coal is adjusted to
optimum.
[0020] The oil burner 11 is used to ignite the pulverized coal.
[0021] For the above-mentioned conventional pulverized coal burner
5, the pulverized coal is used such as bituminous coal with a
predetermined amount of, say about 20% of volatile matter.
[0022] However, use of lower-graded fuel has been demanded
recently; for example, used is oil coke which is a residue in
petroleum refinery and which has volatile matter as low as about
10%. Use of the oil coke in the above-mentioned conventional
pulverized coal burner 5 may bring about problems that the
pulverized fuel injected via the pulverized coal burner 5 is low in
temperature and that volatile matter released is not enough for
keeping the flames. When the flames are not kept, NO.sub.x produced
is remarkably increased.
[0023] State-of-art technology for the above-mentioned pulverized
coal burner is disclosed, for example, in Patent Literature 1.
[0024] [Patent Literature 1] JP 8-145320A
SUMMARY OF INVENTION
Technical Problems
[0025] The invention was made in view of the above and has its
object to provide a pulverized fuel burner wherein pulverized fuel
with less volatile matter is used to improve ignition performance
and continuously keep flames stably.
Solution to Problems
[0026] The invention is directed to a pulverized fuel burner
comprising a nozzle body open to a furnace to inject pulverized
fuel together with primary combustion air, flow passages for
secondary combustion air formed coaxially around said nozzle body
and shutters arranged circumferentially along said flow passages
and spaced apart from each other at specified intervals, non-flow
portions being formed by said shutters for said flow passages to
bring about backflow of hot flue gas.
[0027] The invention is further directed to a pulverized fuel
burner wherein occupied areas of said shutters for said flow
passages are variable.
[0028] The invention is further directed to a pulverized fuel
burner wherein a movable ring is rotatably arranged coaxially of a
front end of said nozzle body, said movable ring having movable
guide vanes, fixed guide vanes being arranged on the front end of
said nozzle body, each of said movable and fixed guide vanes having
a shutter perpendicular to an axis of the nozzle, overlapped state
of said two shutters being varied by turning said movable ring.
[0029] The invention is further directed to a pulverized fuel
burner wherein said nozzle body is accommodated in a wind box, an
air guide duct being arranged in said wind box coaxially of a front
end of said nozzle body, a movable ring being rotatably arranged at
the front end of said nozzle body, said movable ring having movable
guide vanes, said air guide duct having fixed guide vanes, each of
said movable and fixed guide vanes having a shutter perpendicular
to an axis of the nozzle, overlapped state of said two shutters
being varied by turning said movable ring.
ADVANTAGEOUS EFFECTS OF INVENTION
[0030] According to the invention comprising a nozzle body open to
a furnace to inject pulverized fuel together with primary
combustion air, flow passages for secondary combustion air arranged
coaxially around said nozzle body and shutters arranged
circumferentially along said flow passages and spaced apart from
each other at specified intervals, non-flow portions being formed
by said shutters for said flow passages to bring about backflow of
hot flue gas, so that hot flue gas is brought in to heat the
pulverized fuel; ignition performance is improved even with
pulverized fuel having less volatile matter; and ignition is made
stably and certainly and the flames are kept.
[0031] According to the invention, occupied areas of said shutters
for said flow passages are variable, so that a degree of backflow
of the hot flue gas can be adjusted; and pulverized fuels with
different volatile matter can be burned in proper conditions.
[0032] According to the invention, a movable ring is rotatably
arranged coaxially of a front end of said nozzle body, said movable
ring having movable guide vanes, fixed guide vanes being arranged
on the front end of said nozzle body, each of said movable and
fixed guide vanes having a shutter perpendicular to an axis of the
nozzle, overlapped state of said two shutters being varied by
turning said movable ring, so that occupied area of said shutters
for the flow passages may vary to adjust a degree of backflow of
hot flue gas; and pulverized fuels with different volatile matter
can be burned in proper conditions.
[0033] According to the invention, said nozzle body is accommodated
in a wind box, an air guide duct being arranged in said wind box
coaxially of a front end of said nozzle body, a movable ring being
rotatably arranged at the front end of said nozzle body, said
movable ring having movable guide vanes, said air guide duct having
fixed guide vanes, each of said movable and fixed guide vanes
having a shutter perpendicular to an axis of the nozzle, overlapped
state of said two shutters being varied by turning said movable
ring, so that occupied area of said shutters for the flow passages
may vary to adjust a degree of backflow of hot flue gas; and
pulverized fuels with different volatile matter can be burned in
proper conditions.
BRIEF DESCRIPTION OF DRAWINGS
[0034] FIG. 1 is a sectional view showing a conventional pulverized
coal burner;
[0035] FIG. 2 is a sectional view showing an embodiment of a
pulverized coal burner according to the invention;
[0036] FIG. 3 is a view looking in the direction of arrow A in FIG.
2;
[0037] FIG. 4A is a view for explanation of an operation of
variable shutters used in a pulverized coal burner according to the
invention, movable and fixed guide vanes being in a condition
closest to each other;
[0038] FIG. 4B is a view for explanation of the operation of the
variable shutters used in a pulverized coal burner according to the
invention, the movable and fixed guide vanes being in a condition
most away from each other;
[0039] FIG. 5A is a view for explanation of the operation of the
variable shutters used in a pulverized coal burner according to the
invention, the movable and fixed guide vanes being in a condition
closest to each other; and
[0040] FIG. 5B is a view for explanation of the operation of the
variable shutters used in a pulverized coal burner according to the
invention, the movable and fixed guide vanes being in a condition
most away from each other.
REFERENCE SIGNS LIST
[0041] 1 furnace [0042] 4 wind box [0043] 5 pulverized coal burner
[0044] 6 nozzle body [0045] 8 outer tube nozzle [0046] 14 primary
air [0047] 26 secondary air [0048] 32 air guide duct [0049] 33
movable ring [0050] 34 movable guide vane [0051] 36 flow shutter
[0052] 37 fixed guide vane [0053] 39 flow shutter [0054] 43 ring
gear [0055] 44 drive gear [0056] 47 motor
DESCRIPTION OF EMBODIMENT
[0057] An embodiment of the invention will be described in
conjunction with the drawings.
[0058] FIGS. 2 and 3 show the embodiment of a pulverized coal
burner according to the invention. In FIG. 2, the parts similar to
those in FIG. 1 are represented by the same reference numerals and
explanations thereon are omitted.
[0059] A pulverized coal burner 5 comprises a nozzle body 6 and a
secondary air adjusting device 31. The burner 5 is arranged
coaxially of a throat 3 open to the furnace wall 2. The burner 5 is
accommodated in a wind box 4.
[0060] Secondary air 26 is fed to the wind box 4 by a forced draft
fan (not shown). Air volume of the secondary air 26 is controlled
by the forced draft fan to control air pressure for the air volume
required for combustion.
[0061] The nozzle body 6 comprises an outer tube nozzle 8 and an
inner tube nozzle 9 coaxially of the nozzle 8. Formed between the
nozzles 8 and 9 is a hollow, cylindrical fuel conduction space
10.
[0062] The nozzle body 6 has a base extending out of the wind box
4. An outer tube base 8a communicates with a primary air feed pipe
12. An end of the inner tube nozzle 9 communicates with a
downstream end of a tertiary air feed pipe 13 and an upstream end
of the pipe 13 communicates with the wind box 4. The primary air
feed pipe 12 is connected through a coal pulverizer (not shown) to
the forced draft fan (not shown). By the feed pipe 12, primary air
14 carrying the pulverized coal is introduced into the fuel
conduction space 10. The tertiary air feed pipe 13 takes in and
feeds part of the secondary air 26 into the inner tube nozzle
9.
[0063] The wind box 4 is provided, on its side adjacent to the
furnace 1, with a secondary air adjusting device 31 coaxially of
the front end of the pulverized coal burner 5.
[0064] The secondary air adjusting device 31 will be described.
[0065] Arranged on a surface of the wind box 4 facing the furnace 1
is an air guide duct 32 coaxially of the outer tube nozzle 8. The
air guide duct 32 is substantially tapered with radii reduced
toward the furnace 1 and is connected at its front end to the
throat 3.
[0066] Rotatably arranged in and coaxially of the air guide duct 32
is a movable ring 33 which is formed, at its inner surface, with a
required number of movable guide vanes 34 arranged equidistantly of
say 90.degree..
[0067] Each of the movable guide vanes 34 comprises a flow guide 35
(see FIG. 4A) extending toward an axis of the pulverized coal
burner 5 and arranged along a direction of flow of the secondary
air 26 and a flow shutter 36 on an upstream end of and
perpendicular to the flow guide 35 (perpendicular to the axis of
the pulverized coal burner 5), the movable guide vanes being
rotatable integrally with the movable ring 33.
[0068] The flow guide 35 comprises a first flow straightener 35a
(see FIG. 4A) in parallel with the axis of the pulverized coal
burner 5 and a second flow straightener 35b (see FIG. 4A) slant to
the axis to cause the secondary air 26 to swirl.
[0069] The outer tube nozzle 8 is provided, at its front end, with
fixed guide vanes 37 of the same number as the movable guide vanes
34 and arranged equidistantly of say 90.degree..
[0070] The fixed guide vanes 37 are substantially similar in shape
with movable guide vane 34 and extend radially from the axis of the
pulverized coal burner 5. Each of the fixed guide vanes 37
comprises a flow guide 38 (see FIG. 4A) along the direction of flow
of the secondary air 26 and a flow shutter 39 on an upstream end of
the flow guide 38 perpendicular to the flow guide 38 (perpendicular
to the axis of the pulverized coal burner 5). In order not to
interfere with rotation of the movable ring 33, outer peripheral
ends of the fixed guide vanes 37 are spaced apart from the inner
surface of the movable ring 33, and the flow shutters 39 are
axially shifted to the flow shutters 36.
[0071] Like the movable guide vane 34, the flow guide 38 comprises
the first and second flow straighteners 35a and 35b.
[0072] The movable guide vanes 34 are paired with the fixed guide
vanes 37 to provide variable shutters 41 (see FIGS. 4A, 4B, 5A and
5B); each of the movable guide vanes 34 and the fixed guide vane 37
of the adjacent variable shutter 41 provide a flow passage 42 (see
FIGS. 4A, 4B, 5A and 5B).
[0073] Arranged at an upstream end of the movable ring 33 is a ring
gear 43 which engages with a drive gear 44. The drive gear 44 is
connected with a drive shaft 45 which in turn is connected to a
motor 47 on a front plate 46 of the drive gear 44.
[0074] Rotation of the motor 47 causes the ring gear 43 to turn
through the drive shaft 45 and the drive gear 44, so that the
movable ring 33 is turned integrally with the ring gear 43.
[0075] Thus, the movable and fixed guide vanes 34 and 37 are
relatively turned normally/reversely to move toward/away from each
other.
[0076] FIGS. 4A, 4B, 5A and 5B show a relationship between the
movable and fixed guide vanes 34 and 37; FIGS. 4A and 5A show the
movable and fixed guide vanes 34 and 37 in their closest state to
each other and FIGS. 4B and 5B show the movable and fixed guide
vanes 34 and 37 in their state most away from each other.
[0077] In the closest state of the vanes, each of the flow passages
42 has a maximum cross section and is shut out minimumly by the
variable shutters 41. In the state of the vanes most away from each
other, each of the flow passages 42 has a minimum cross section and
is shut out maximumly by the variable shutters 41.
[0078] If a supplied amount of secondary air is the same, flow
velocity of the secondary air 26 is low and high in the state of
the vanes closest to each other and in the state of the vanes most
away from each other, respectively.
[0079] Next, a mode of operation of the secondary air adjusting
device 31 will be described.
[0080] When pulverized fuel such as pulverized coal with relatively
less volatile matter, the motor 47 rotates the movable ring 33 to
make the movable and fixed guide vanes 34 and 37 close to each
other.
[0081] This increases the cross sections of the flow passages 42,
reduces the flow velocity of the secondary air 26 passing through
the flow passages 42 and reduces shut-out areas of the flow
passages by the variable shutters 41. A downstream portion of the
variable shutter 41 provides a non-flow portion for the secondary
air 26 on opposite sides of which the secondary air 26 flows to
generate eddies which in turn bring about backflow of hot flue gas
so that the furnace gas is brought in from the furnace 1.
[0082] The furnace gas, which is hot, heats the pulverized coal
injected together with the primary air 14, so that even fuel with
less volatile matter is ignited certainly. Thus, even with the
pulverized fuel having less volatile matter, ignition is certainly
ensured to keep the flames stably. The shut-out areas by the
variable shutters 41 are small, so that the eddies are small and an
amount of the furnace gas brought in from the furnace 1 is also a
little.
[0083] When the pulverized fuel with extremely less volatile matter
is supplied, the movable ring 33 is turned by the motor 47 through
the ring gear 43, so that the movable guide vanes 34 are maximumly
separated from the fixed guide vanes 37.
[0084] Thus, the flow passages 42 are narrowed and the shut-out
areas of the flow passages by the variable shutters 41 are
increased. The flow velocity of the secondary air 26 passing
through the flow passages 42 is increased to enhance the eddies
generating in the secondary air 26 passing on the opposite sides of
the variable shutters 41 and the backflow phenomenon of the hot
flue gas becomes remarkable. As a result, an amount of the furnace
gas brought in from the furnace 1 is increased, so that the
pulverized fuel is heated to further high temperature by the
furnace gas, which enables ignition of the pulverized fuel with
less volatile matter and keeping of the flames after the
ignition.
[0085] Thus, by adjusting the separated amount between the movable
and fixed guide vanes 34 and 37 in the variable shutters 41,
optimal combustion state can be obtained with respect to various
pulverized fuels with less volatile matter.
[0086] In a case where the pulverized fuels supplied have no
variations in volatile matter, flow-shutting plates (corresponding
to the flow shutters 36 and 39) each with a required area may be
arranged circumferentially between the outer tube nozzle 8 and the
air guide duct 32 at required intervals.
[0087] Means for turning the movable ring 33 or the movable guide
vane 34 may be through out variously. For example, a cylinder may
be used or position change may be conducted manually.
[0088] The movable ring 33 has been described to be rotatably
arranged in the air guide duct 32; alternatively, it may rotatably
arranged at the front end of the outer tube nozzle 8, the fixed
guide vanes 37 being mounted on the air guide duct 32.
* * * * *