U.S. patent application number 11/062614 was filed with the patent office on 2005-09-29 for burner, fuel combustion method and boiler retrofit method.
This patent application is currently assigned to Babcock-Hitachi K.K.. Invention is credited to Itou, Osamu, Kiyama, Kenji, Kuramashi, Kouji, Okazaki, Hirofumi, Taniguchi, Masayuki, Yamamoto, Kenji, Yano, Takanori.
Application Number | 20050211142 11/062614 |
Document ID | / |
Family ID | 34858423 |
Filed Date | 2005-09-29 |
United States Patent
Application |
20050211142 |
Kind Code |
A1 |
Yamamoto, Kenji ; et
al. |
September 29, 2005 |
Burner, fuel combustion method and boiler retrofit method
Abstract
In a burner of construction having a primary nozzle, a secondary
nozzle and a tertiary nozzle, a partition wall partitioning the
secondary nozzle and the tertiary nozzle and having a flow path
change member provided thereon, the partition wall is formed so as
to be movable in parallel to the burner axis to control jetting
speeds and flow rates of secondary air and tertiary air, whereby it
is possible to cool the burner constituent members while reducing
NOx. The partition wall is composed of a fixed wall and a movable
wall. The burner comprises a bypass passage through which tertiary
air in the tertiary nozzle bypasses the tertiary nozzle to flow
into the secondary nozzle or the primary nozzle.
Inventors: |
Yamamoto, Kenji;
(Hitachinaka, JP) ; Okazaki, Hirofumi;
(Hitachinaka, JP) ; Itou, Osamu; (Hitachiota,
JP) ; Taniguchi, Masayuki; (Hitachinaka, JP) ;
Yano, Takanori; (Kumano-cho, JP) ; Kiyama, Kenji;
(Kure, JP) ; Kuramashi, Kouji; (Kure, JP) |
Correspondence
Address: |
CROWELL & MORING LLP
INTELLECTUAL PROPERTY GROUP
P.O. BOX 14300
WASHINGTON
DC
20044-4300
US
|
Assignee: |
Babcock-Hitachi K.K.
Tokyo
JP
|
Family ID: |
34858423 |
Appl. No.: |
11/062614 |
Filed: |
February 22, 2005 |
Current U.S.
Class: |
110/265 ;
110/348 |
Current CPC
Class: |
F23D 2900/11402
20130101; F23C 7/008 20130101; F23D 2900/00003 20130101 |
Class at
Publication: |
110/265 ;
110/348 |
International
Class: |
F23C 001/10; F23C
001/12 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 24, 2004 |
JP |
2004-086006 |
Claims
What is claimed is:
1. A fuel combustion burner comprising a primary nozzle for
supplying fuel and primary air, a secondary nozzle for supplying
secondary air, provided outside said primary nozzle, and a tertiary
nozzle for supplying tertiary air, provided outside said secondary
nozzle so as to contact with the outside of said secondary nozzle,
said secondary nozzle and said tertiary nozzle being partitioned by
a partition wall, wherein said partition wall has thereon a flow
path change member for changing a flow of tertiary air from a flow
along an axis of the burner to an outward flow and jetting the
tertiary air, and said partition wall is movable in the burner
axial direction.
2. A fuel combustion burner according to claim 1, wherein said
partition wall has a guide sleeve as said flow path change member
at an end thereof.
3. A fuel combustion burner according to claim 1, wherein said
primary nozzle is a nozzle constituted so as to pneumatically
transfer fuel with a primary air.
4. A fuel combustion burner according to claim 1, wherein said
partition wall is provided thereon with a bypass mechanism for
allowing a part of the tertiary air to bypass said tertiary nozzle
into one of said primary nozzle and said secondary nozzle when said
partition wall is moved to a predetermined position.
5. A fuel combustion burner according to claim 1, wherein said
partition wall is composed of a fixed wall and a movable wall, said
flow path change member is provided on said movable wall.
6. A fuel combustion burner according to claim 5, wherein holes for
allowing tertiary air to bypass are formed in said fixed wall and
said movable wall, respectively.
7. A fuel combustion burner according to claim 6, wherein said
primary nozzle has a hole formed in an outer wall thereof, and a
bypass pipe is provided between said hole formed in said fixed wall
and said hole formed in said outer wall of said primary nozzle so
that tertiary air passed through said holes formed in said fixed
wall and said movable wall flows into said primary nozzle.
8. A fuel combustion burner according to claim 7, wherein said
bypass pipe has a jet outlet formed so that the tertiary air flowed
into said primary nozzle flows along an inner wall of said primary
nozzle.
9. A fuel combustion burner according to claim 7, wherein said
primary nozzle is a nozzle for supplying pulverized coal, said
primary nozzle has a pulverized coal concentrator provided inside
for narrowing a cross-sectional area of a flow path and
concentrating the pulverized coal, and said bypass pipe is extended
to said pulverized coal concentrator so that the tertiary air
flowed into said primary nozzle flows along the surface of said
pulverized coal concentrator.
10. A fuel combustion burner according to claim 1, wherein fins for
cooling said flow path change member an d said partition wall in
the vicinity of said flow path change member are provided on said
flow path change member and said partition wall in the vicinity of
said flow path change member.
11. A fuel combustion burner according to claim 5, wherein said
partition wall is constituted so that said movable wall slides on
said fixed wall, and guide rollers for guiding said movable wall
are provided on said fixed wall.
12. A fuel combustion burner according to claim 5, wherein a
stopper for stopping said movable wall is provided on at lease one
of said fixed wall and said movable wall.
13. A fuel combustion burner according to claim 1, wherein a wind
box for supplying secondary air and tertiary air is provided, and a
mechanism for moving said partition wall is arranged outside said
wind box.
14. A fuel combustion method by a burner comprising a primary
nozzle for supplying fuel and primary air, a secondary nozzle for
supplying secondary air, provided outside said primary nozzle, a
tertiary nozzle for supplying tertiary air, provided outside said
secondary nozzle so as to contact with the outside of said
secondary nozzle, said secondary nozzle and said tertiary nozzle
being partitioned by a partition wall, and a flow path change
member provided on said partition wall for changing a flow of the
tertiary air from a flow along the burner axis to an outward flow,
said partition wall being constituted to be movable in the burner
axis direction, wherein said partition wall is moved in dependence
with any condition or conditions of a load change, a temperature at
burner axis end portion, properties of fuel, the concentration of
nitrogen oxides, the concentration of unburned fuel, and fuel
supply stoppage, and adjusts a flow rate of the tertiary air
supplied from said tertiary nozzle.
15. A fuel combustion method according to claim 14, wherein at the
time of stoppage of fuel supply to said burner, said partition wall
is moved so that the cross-sectional area of a tertiary air jetting
outlet of said tertiary nozzle becomes small, thereby to increase a
flow rate of the secondary air from said secondary air nozzle.
16. A fuel combustion method according to claim 14, wherein said
method further comprises step of moving said partition wall so that
the cross-sectional area for jetting tertiary air of said tertiary
nozzle decreases when a temperature of said flow path change member
becomes higher than a set temperature during combustion of fuel by
the burner, and increasing a flow speed of the tertiary air.
17. A fuel combustion method according to claim 14, wherein a part
of the tertiary air supplied to said tertiary nozzle is caused to
bypass a flow path of said tertiary nozzle into said secondary
nozzle during stoppage of fuel supply to said the burner.
18. A fuel combustion method according to claim 14, wherein a part
of the tertiary air supplied to said tertiary nozzle is caused to
bypass a flow path of said tertiary nozzle to flow along an inner
wall of said primary nozzle during stoppage of fuel supply to said
the burner.
19. A method of retrofitting a boiler having a burner which is
provided on a furnace wall and comprises a primary nozzle for
supplying fuel and primary air, a tubular secondary nozzle for
supplying secondary air, provided outside said primary nozzle so as
to enclose said primary nozzle, a tubular tertiary nozzle for
supplying tertiary air, provided outside said secondary nozzle, a
tubular partition wall fixed between said secondary nozzle and said
tertiary nozzle, wherein said method comprises: removing at least
an end portion of said partition wall; and providing, around the
position of the removed portion of said partition wall, a tubular
partition wall with a flow path change member for changing a flow
of tertiary air from a flow along the burner axis to an outward
flow so as to be movable in the burner axial direction.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field
[0002] The present invention relates to a burner, a fuel combustion
method by the burner, and a method of retrofitting a boiler
provided with an existing burner to turn it into a boiler with the
burner made according to the present invention.
[0003] 2. Description of Prior Art
[0004] For burners used for boilers or the like, it is required to
cope with load change, cope with various coals, reduce the
concentration of nitrogen oxides (NOx), reduce unburned fuel, etc.
In order to satisfy those requirements, various methods of
controlling combustion conditions have been developed. For example,
some of them are a method of apportioning a flow quantity of air
between secondary air and tertiary air by air resistors, a method
of changing swirl number, etc.
[0005] As one of methods of controlling combustion conditions, a
method of adjusting a secondary air flow rate and adjusting an air
jetting direction by making a partition wall partitioning secondary
air and tertiary air movable is proposed (see a patent document 1,
for example).
[0006] Patent Document 1: JP 60-26922 B (Claims)
SUMMARY OF THE INVENTION
[0007] The patent document 1 discloses that since it is possible to
control the flow of secondary air by moving the partition wall in
the burner axial direction, secondary flame can be burned under the
best condition from a viewpoint of low NOx emission and combustion
efficiency.
[0008] An object of the invention is to enable a burner to be
cooled while reducing NOx.
[0009] A burner according to the present invention comprises a
primary nozzle for supplying fuel and primary air, a tubular
secondary nozzle provided outside the primary nozzle so as to
embrace or contact with the primary nozzle, a tubular tertiary
nozzle provided outside the secondary nozzle so as to embrace or
contact with the secondary nozzle, and a tubular partition wall
partitioning the secondary nozzle and the tertiary nozzle and
provided therebetween, wherein a flow path change member is
provided on the partition wall, which flow path change member is
made so as to jet outwardly a fluid flowing in the tertiary nozzle,
and the partition wall is made movable in parallel with the burner
axis direction. The secondary nozzle is supplied with secondary air
and the tertiary nozzle is supplied with tertiary air. In the
invention, the burner axis means the central axis of the tubular
primary nozzle.
[0010] By moving the partition wall provided with the flow path
change member in a direction in parallel with the burner axis, a
cross-sectional area of a tertiary air jet of the tertiary nozzle
changes, and a flow rate and a flow speed of the tertiary air
change. The change in flow rate of the tertiary air changes a flow
rate and a flow speed of the secondary air. By the change in flow
rate of the tertiary air or a flow rate of the secondary air, the
combustion conditions change. As a result, it is possible to lower
the temperatures of burner constituent components.
[0011] The burner of triple tube construction, which is an
objective of the invention, is constructed so that fuel is ignited
with primary air to form reducing flame and make NOx small, and the
secondary air and tertiary air are mixed with the reducing flame to
burn the unburned fuel contained in the reducing flame. The burner
is known as an in-flame 2-stage combustion burner or an in-flame
NOx reduction burner. In this burner, delay in mixing of the
tertiary air makes a region of the reducing flame large, whereby
low NOx emission is promoted. Many burners of this construction
each have a stabilizer provided at the outlet of the tubular
primary nozzle, as shown in the patent document 1, and in the
present invention, also, it is possible to provide a stabilizer at
the outlet of the primary nozzle. Of flame stabilizers, there are
an inner flame stabilizing ring in which a ring-shaped projection
is formed at the inside of the outlet of the tubular primary nozzle
and an outer flame stabilizing ring in which a tubular projection
is provided outside the outlet of the tubular primary nozzle so as
to throw out in the burner axis direction, and it is preferable to
provide both of them. Provision of the stabilizer forms a flow
recirculation region due to turbulent flow eddy in a wake flow
thereof or in a flow downstream of the stabilizer, and the flow
recirculation involves fuel, for example, pulverized coal particles
to make them into flash points for high temperature gas and promote
ignition of the pulverized coal. H ere, the secondary air bears a
role to cool the stabilizer and adjust a mixing ratio of fuel and
air.
[0012] As the flow path change member, such a member is desirable
that has a taper-shaped inclined plane so that the tertiary air
flows, while changing gradually the flow direction from a flow
parallel with the burner axis to an outward flow. Further, the rear
side, that is, the side in contact with the secondary air, of the
flow path change member is desirable to be formed so that it
inclines along the inclined plane of the tertiary nozzle. By
forming the flow path change member in this construction, when the
flow path change member is moved so that the tertiary air jet
cress-sectional area becomes small, the secondary air jet
cross-sectional area increases according to the movement
thereof.
[0013] In order to make the partition wall move easily without
making the burner construction complicated, it is desirable for the
partition wall to be composed of a fixed wall and a movable wall,
and for the movable wall to be move sliding on the surface of the
fixed wall. Concretely, it is desirable to be composed of a portion
that the tertiary air flows in parallel with the burner axis as the
fixed wall and a portion that the parallel flow changes in flow
direction outward as the movable wall, that is, the latter portion
is a portion on which the flow path change member is provided. It
is desirable for the fixed wall to provide guide rollers thereon.
It is preferable to provide a stopper or stoppers for stopping
movement of the movable wall on at least one of the fixed wall and
the movable wall. Since the flow path change member and the
partition wall in the vicinity of the flow path change member are
apt to be heated to a high temperature, it is preferable to provide
fins for cooling them there. As a means for moving the movable
wall, a bar-shaped member is provided, which bar-shaped member is
mounted on the movable wall and moved forward and backward in the
burner axis direction by manual or automatic means. At this time,
extension of one end of the bar-shaped member out of the wind box
of the burner makes its maintenance easy and its failure uneasy. It
is possible to move the movable wall by pulling and pushing the end
of the bar-shaped member by hand. Further, it is possible to easily
move it forward and backward to provide gears on the end portion of
the bar-shaped member and use a handle having another gear mounted
thereon and meshed with the gears. Still further, by providing a
motor or motors instead of the handle, it is possible to save power
for movement and to make it automatic by control.
[0014] The burner according to the invention can be used for a
burner using oil, gas, pulverized coal etc. as fuel, particularly,
it is suitable for a burner using pulverized coal. In a pulverized
coal burner, sometimes combustion is assisted when a load is low by
providing an oil burner for assisting combustion inside a primary
nozzle. In the burner according to the invention, also, such an oil
burner can be provided.
[0015] For the burner according to the invention, it is possible to
add a tertiary air bypass mechanism by which a part of tertiary air
is caused to bypass the tertiary nozzle into another nozzle. The
tertiary air bypass mechanism is formed so that when the partition
wall partitioning the secondary nozzle and the tertiary nozzle is
moved to a predetermined position, a part of the tertiary air
bypasses the tertiary nozzle into another nozzle. By making a hole
in the movable wall while making a hole in the fixed wall so as to
communicate with the above-mentioned hole when the movable wall is
moved to the predetermined position, the part of the tertiary air
can bypass the tertiary nozzle into the secondary nozzle. One hole
formed in each of the fixed wall and the movable wall is
sufficient, however, it is preferable to provide a plurality of
holes in a circumferential direction in order to increase a flow
rate of the tertiary air.
[0016] By forming a hole in the primary nozzle and connecting the
hole with the hole formed in the fixed wall by a bypass pipe, it is
possible to flow the tertiary air into the primary nozzle. By
forming the bypass pipe so that the tertiary air flows along the
inner wall of the primary nozzle and jets in the flow direction of
fuel, it is possible to cool the stabilizer by the tertiary air
flowing in the primary nozzle.
[0017] Another of the aspects of the present invention is a
combustion method in which the partition wall partitioning the
secondary nozzle and the tertiary nozzle is moved to reduce the
tertiary air jet cross-sectional area of the tertiary nozzle when
the temperature of the flow path change member becomes higher than
a set temperature in the case where fuel is burned by using the
above-mentioned burner, thereby a flow speed of the tertiary air is
increased. Further, another of the aspects of the present invention
is a combustion method in which the partition wall is moved to
increase the tertiary air jet cross-sectional area and make the
flow speed of the tertiary air slow when ash comes to deposit on
the burner during combustion. Further, another of the aspects of
the present invention is a method of moving the partition wall to
decrease the tertiary air jet cross-sectional area of the tertiary
nozzle and increase the flow rate of secondary air when the burner
is out of service without fuel supply to the burner. Further,
another of the aspects of the present invention is a method of
causing a part of, tertiary air to be supplied to the tertiary
nozzle to bypass the tertiary nozzle into the secondary nozzle or
the primary nozzle while stopping of fuel supply to the burner.
Further, another of the aspects of the present invention is a
method of conducting an operation of making the tertiary air jet
cross-sectional area small to increase the momentum of tertiary air
and increasing the quantity of tertiary air in the case where the
NOx concentration is high or fuel of bad combustibility is
used.
[0018] Further another of the aspects of the present invention is a
method of retrofitting a boiler provided with an existing burner
having a tubular partition wall which partitions a secondary nozzle
and a tertiary nozzle and is fixedly provided, wherein a part or
all of the partition wall is removed and a tubular partition wall
provided with a flow path change member is arranged for the fixed
partition wall so as to be movable.
[0019] The burner according to the present invention is the
in-flame 2-stage combustion type and excellent for reduction of
NOx. According to the present invention, it is possible to suppress
ash deposit on the burner or damage of the burner due to heat while
reducing NOx. In the present invention, by fixing the jet direction
of tertiary air to a constant outward direction and changing the
momentum of the tertiary air, the size or region of flow
recirculation can be optimized within a range in which it does not
become small, and it is possible to keep the combustion condition
better. Further, even if a flow rate of tertiary air is kept
constant, it is possible to make the flow speed at a downstream end
of a guide sleeve high, so that the guide sleeve can be cooled.
Further, by controlling independently the momentum and the flow
rate of the tertiary air, the size of flame and the size of flow
recirculation determined mainly by the momentum, and the size of a
reducing region determined by the flow rate can be controlled
independently, and a good combustion condition can be kept.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a sectional view of a burner of an embodiment of
the present invention;
[0021] FIG. 2 is a sectional view showing a use example of the
burner of the embodiment of the present invention shown in FIG.
1;
[0022] FIG. 3 is a sectional view taken along III-III of the burner
of FIG. 1;
[0023] FIG. 4 is a sectional view taken along IV-IV of the burner
of FIG. 1;
[0024] FIG. 5 is a sectional view of the burner of another
embodiment of the present invention;
[0025] FIG. 6 is a sectional view showing a use example of the
burner shown in FIG. 5;
[0026] FIG. 7 is a schematic diagram of a construction of a
controller for the burner according to the present invention;
[0027] FIG. 8 is a sectional view of the burner of another
embodiment of the present invention;
[0028] FIG. 9 is a sectional view of the burner of another
embodiment of the present invention;
[0029] FIG. 10 is a sectional view of the burner of another
embodiment of the present invention;
[0030] FIG. 11 is a sectional view of the burner of another
embodiment of the present invention;
[0031] FIG. 12 is a sectional view of the burner of another
embodiment of the present invention;
[0032] FIG. 13 is a sectional view of taken along XIII-XIII of FIG.
12;
[0033] FIG. 14 is a sectional view of taken along XIV-XIV of FIG.
12;
[0034] FIG. 15 is a sectional view of taken along XV-XV of FIG.
12;
[0035] FIG. 16 is a sectional view of the burner of another
embodiment of the present invention;
[0036] FIG. 17 is a sectional view of taken along XVII-XVII of FIG.
16;
[0037] FIG. 18 is a view viewed form XVIII-XVIII of FIG. 16;
and
[0038] FIG. 19 is a graph showing conditions that the flow rates of
fuel and air supplied from the burner change according to burner
loads.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0039] The burner and the method of using the burner according to
the present invention will be explained hereunder, referring to the
Drawings.
Embodiment 1
[0040] FIGS. 1, 2, 3 and 4 each are a sectional view showing an
embodiment of the burner according to the present invention. The
burner has a triple tube construction composed of a primary nozzle
4, a secondary nozzle 8 and a tertiary nozzle 9. Primary air and
pulverized coal flow from the primary nozzle 4 as shown by an arrow
11. In the present embodiment, the case where pulverized coal is
used as fuel is shown, however, the case where oil, gas or the like
is used is also the same as the above-mentioned case. The primary
nozzle 4 is tubular and its cross-section is shaped in circle or
squire. A partition wall is provided between the secondary nozzle 8
and the tertiary nozzle 9, and the partition wall is composed of a
fixed wall 1 and a movable wall 2. A guide sleeve 3 is provided at
an end portion of the movable wall 2. The guide sleeve 3 serves a
role to change the flow of tertiary air outward. Secondary air
flows from the secondary nozzle 8 as an arrow 12. Further, the
tertiary air flows from the tertiary nozzle 9 as an arrow 13. The
movable wall 2 is connected to movement control rods 5 at
connection portions 14, and handles 33 for operating are provided
out of a wall 28 of a wind box.
[0041] A stabilizer 10 having a tubular shape is provided on an end
of the primary nozzle 4. An air resistor (or air resistors) 7 is
provided upstream of the tertiary nozzle 9. Further, a tertiary
damper 35 and a secondary damper 34 are provided upstream of the
tertiary nozzle 9 and the secondary nozzle 8, respectively.
[0042] By moving the movable wall 2 and the guide sleeve 3 provided
on the end thereof forward and backward, that is, in a parallel
direction to the burner axis, the flow rate and flow speed of the
tertiary air, the flow rate and flow speed of the secondary air and
a ratio of the tertiary air flow rate and the secondary air flow
rate are changed, whereby it is possible to control the combustion
conditions. This is the same as changing a ratio of tertiary air
momentum and secondary air momentum. In the present invention, by
keeping a jet angle of the tertiary air constant and changing an
outlet cross-sectional area for the tertiary air, it is possible to
change the flow rate and flow speed of the tertiary air. By
directing always the tertiary air outward, the size of flow
recirculation formed downstream of the stabilizer 10 and the guide
sleeve 3 can be always made large, so that the combustion
conditions can be always kept good. The momentum of the tertiary
air is a main factor for determining the size of flame and the size
of flow recirculation. The flow rate of the tertiary air is a main
factor for determining the size of a reducing region. Since the
momentum and the flow rate of tertiary air can be controlled
independently, it is possible to make a combustion condition
suitable for improvement on flame stabilization and NOx reduction.
Further, it is possible to change independently the momentum of
tertiary air and the flow rate of secondary air, whereby the
secondary air can be used for other objects such as cooling of the
stabilizer 10, air supply to the fuel flowing in the primary
nozzle, etc.
[0043] FIG. 3 shows a III-III section of FIG. 1. FIG. 4 is shows a
IV-IV section of FIG. 1. Rollers 23 are mounted so that the movable
wall 2 smoothly moves. In this embodiment, four (4) movement
control rods 5 are provided, and they are suitable for parallel
movement of the movable wall 2 to the burner axis. The rollers 23
are mounted on the fixed wall 1, but they also can be mounted on
the movable wall 2.
[0044] The movable wall 2 has a possibility that the temperature
thereof rises when the flow rate of tertiary air is small. Damage
due to burning or deformation are apt to occur when the temperature
of the member rises higher than a temperature that the member
subjected to heat is sustainable to the heat. It is better to use
material of high heat resistance for the movable wall 2.
[0045] Hereunder, first of all, a burner adjusting method at time
of trial operation of the burner will be explained. Immediately
after the burner is installed on the boiler, in some cases an
intended flow rate does not flow. Causes for this are considered to
be manufacturing errors of the burner, asymmetry of upstream ducts,
setting errors of the resistors, the dampers installed on the
burner, etc. Further, in some cases, it is necessary to set a flow
rate of air according to deviation of fuel for each burner.
Therefore, by adjusting the air resistor 7 of the tertiary nozzle
9, the tertiary damper 35, the secondary damper 34 and the movable
wall 2, combustion conditions suitable for reduction of NOx, CO,
unburned fuel, soot, corrosion, and the metal temperature of the
burner part are made. Hereunder, examples of the adjusting method
are shown.
EXAMPLE 1
[0046] In the case where flame stabilization is bad, the following
operations are conducted to improve the stabilization of flame:
[0047] (1.1) In the case where the momentum of tertiary air is
small: The movable wall 2 is moved to a near side or to the left
side in FIG. 1 to make the flow path area of the tertiary nozzle
narrow. Under this condition, the pressure loss of the tertiary air
becomes large, so that a flow rate of the tertiary air decreases
and a flow rate of the secondary air increases. In order not to
change these flow rates, the air resistor 7 or the tertiary damper
35 of the tertiary nozzle 9 is opened, or, the secondary damper 34
is closed not to flow the secondary air. By increase in momentum of
the tertiary air, a flow recirculation region downstream of the
stabilizer 10 becomes large and the stabilization of flame is
raised.
[0048] (1.2) In the case where the momentum of secondary air is
small:
[0049] When the flow rate of secondary air can be allowed to be
increased, it is good that the air resistor 7 of the tertiary
nozzle 9 is closed to make swirling strong, or the movable wall 2
is moved to the near side to make the flow speed of the tertiary
air high. The increase in flow rate and momentum of the secondary
air makes the flow recirculation region downstream of the
stabilizer 10 large and raises the stabilization of flame. However,
when the secondary air increases too much, on the contrary in some
cases the flow recirculation is made small. An optimum flow rate
exists for the secondary air.
[0050] In FIG. 2, by having moved the movable wall 2, the minimum
flow path area between the stabilizer 10 and the guide sleeve 3 has
been widened. Therefore, there is the possibility that a jetting
flow speed of the secondary air becomes slow. When the flow speed
is slow, a cooling effect of the stabilizer 10 decreases, so that
it is better to make the stabilizer 10 long in the moving direction
of the movable wall 2 not to change in the minimum flow path area
even if the movable wall 2 is moved.
EXAMPLE 2
[0051] In the case where the concentration of NOx is high,
adjustment is conducted the following method.
[0052] (2.1) Since making the stabilization of flame high decreases
the concentration of NOx, setting for increasing the stability of
flame is taken.
[0053] (2.2) In the case where although flame is sufficiently
stabilized, it is desired to further reduce the concentration of
NOx, it is effective to delay mixing of air. In order to delay the
mixing of air, it is effective to decrease the flow rate of the
secondary air and increase the flow rate of the tertiary air. To
carry out it, it is considered that the secondary damper 34 is
closed, or the movable wall 2 is moved so that the tertiary air
outlet is opened. Further, it can be achieved by increasing the
momentum of tertiary air. The delay of mixing of air can be
attained also even by closing the air resistor 7 of the tertiary
nozzle 9 and making swirling of tertiary air strong. In this case,
it is necessary to close the secondary damper 34 so that the flow
rate of the tertiary air does not decrease.
EXAMPLE 3
[0054] In the case where unburned fuel is much, adjustment is
conducted in the following method.
[0055] (3.1) There is a possibility that unburned fuel becomes much
without conducting stabilization of flame. Therefore, it is
effective to take a setting similar to the setting for improvement
on the stabilization of flame.
[0056] (3.2) In the case where although flame is sufficiently
stabilized, it is desired to further reduce the unburned fuel, it
is effective to increase secondary air. In this case, there is a
possibility that the momentum of tertiary air decreases and the
stabilization of flame decreases when the secondary damper 34 is
opened. Therefore, it is effective to increase the flow speed of
tertiary air by moving the movable wall 2 to the near side or to
make the swirling strong by closing the air resistor 7 of the
tertiary nozzle 9.
[0057] (3.3) For reduction of unburned fuel, it is effective to
raise a burner air ratio. The flow rate of air increases by raising
the burner air ratio, mixing of air and fuel becomes better, and
the concentration of NOx becomes high. In order to reduce the
concentration of NOx, the method described in the example 2 can be
applied.
EXAMPLE 4
[0058] To reduce corrosion, adjustment is conducted by the
following method:
[0059] (4.1) Being short in air around the wall makes the
concentration of reducing gas higher and corrosion speed high. To
supply air to around the wall, it is effective to increase the flow
rate of tertiary air. Therefore, it is effective to open the
movable wall 2 to make the flow path area of the tertiary nozzle 9
wide and increase the flow rate of tertiary air. Further, to make
air reach to around the wall by increasing the momentum of tertiary
air, it is possible to close the secondary damper 34.
[0060] (4.2) Since it is also possible to make the stabilization of
flame bad and to decrease reducing gas, it is possible to perform
an operation reverse to that in the example 1.
[0061] (4.3) The reducing gas can be reduced and corrosion can be
reduced, also, by increasing an air quantity of the burner close to
the wall that is apt to corrode. Therefore, it is effective to
adjust air distribution by adjusting the movable wall 2, the
resistor, and the damper for each burner, thereby making the
operation condition into such an operation condition that the
pressure loss of the burner that is better for an air quantity to
be increase is reduced.
EXAMPLE 5
[0062] In the case where it is desired to change greatly kinds of
fuel, adjustment is conducted by the following method:
[0063] (5.1) When kinds of fuel are greatly changed, pulverization
and an amount of volatile matters in the fuel change, so that it is
better to change the damper opening, the position of the movable
wall 2 and the setting of the air resistor 7 in order to keep the
stabilization of flame and reduce NOx. In the case where fuel is
changed from a fuel of good combustibility to a fuel of bad
combustibility, there is a possibility that the stabilization of
flame decreases. In this case, it is better to conduct such an
operation that the stabilization of flame becomes good.
[0064] (5.2) The fuel of bad combustibility has a high possibility
that the concentration of NOx becomes high, so that it is better to
conduct such an operation that NOx is reduced.
EXAMPLE 6
[0065] In the case where ashes in fuel deposit, operations are
taken by the following method:
[0066] (6.1) In the case where the stabilization of flame is good
and ashes in the fuel melt and deposit around the burner, the
movable wall 2 is moved forward (to an opposite side to the near
side) to increase the outlet cross-sectional area for tertiary air,
decrease the flow speed of the tertiary air and reduce the
stabilization of flame. By operating in this way, the combustion
temperature decreases, so that deposition of ashes is reduced. At
the same time, secondary air also increases, the temperature around
the stabilizer 10 decreases and the ashes can be prevented from
melting.
[0067] (6.2) In the case where molten ash deposits on the wall of
boiler, it is better to supply air to around the wall. Therefore,
it is better to operate so that air is supplied around the wall by
moving the movable wall 2 to the near side to change the jetting
direction of tertiary air outward.
EXAMPLE 7
[0068] In the case where the temperature of the stabilizer 10 is
high, the following operation is conducted:
[0069] When the temperature of the stabilizer 10 is high, it is
effective to make the flow speed of secondary air high. In order to
increase the flow rate of secondary air, the tertiary damper 35 or
the air resistor 7 is closed. In this case, there is such a
possibility that the momentum of tertiary air decreases and the
stabilization of flame decreases. Therefore, the movable wall 2 is
moved to the near side instead of closing the tertiary damper 35
and the air resistor 7. Thereby, both of keeping the stabilization
of flame and reduction of the temperature of the stabilizer can be
achieved.
EXAMPLE 8
[0070] Decrease of the minimum load of the boiler is conducted as
follows:
[0071] Boiler load not always is 100%, but it is changed according
to power demands. If it can be run at a very low load, the
operation efficiency of the boiler increases. Usual burners are
designed so that the performance is good at a load of 100%. When
the load is low, respective flow rates of fuel and air entering the
furnace from the burner decrease, so that there is a possibility
that the momentums thereof come to be unbalanced and the
stabilization of flame decreases. For example, when the momentum of
tertiary air is low, it is effective to increase the momentum by
moving the movable wall 2 to the near side. This operation is the
same as the method of increasing the stabilization of flame as
described in the example 1. However, when the stabilization of
flame is increased under the low load operation, in some cases, the
combustibility becomes bad at a high load. It is better to set in
such a range that the combustibility does not become bad even at a
high load.
Embodiment 2
[0072] FIG. 5 is a sectional view of another embodiment of the
burner according to the present invention. The present embodiment 2
differs from the embodiment 1 in that motor boxes 6 are provided
and the movement of the movable wall 2 is electrically driven.
Further, in FIG. 5, although the motor boxes 6 are installed inside
the wind box, it is possible to install them outside the wind box.
Further, an air resistor 15 is provided in the secondary nozzle 8.
It is possible to control the flow rate and swirling force by
combining the air resistor 15 and the secondary damper 34.
[0073] A merit of driving the movable wall 2 by the motor 6 is that
the movable wall 2 is controlled according to the algorithm of
combustion adjustment described in the embodiment 1, and an optimum
combustion condition can be always kept. As others, as explained
hereunder, it is possible to provide a suitable operation condition
by changing flow rate conditions.
[0074] In some cases, the burner is out of service without fuel
being supplied. Under such a condition, there is a possibility that
the burner being out of service is heated by radiation heat from
other burners and the temperatures of the guide sleeve 3, the
stabilizer 10, etc. rise. To prevent this phenomenon, it is
necessary to supply air to the burner even when it is out of
service. When a flow rate of air to be supplied to the burner being
out of service is large, an air adjustment quantity becomes small.
Therefore, it is necessary to make small the flow rate of air to be
supplied to the burner being out of service. When the flow rate is
decreased under the condition that the movable wall 2 is fixed, the
flow speeds of tertiary air and secondary air decrease, and it is
impossible to sufficiently cool the guide sleeve 3 and the
stabilizer 10.
[0075] In the present invention, the burner is turned into the
condition as shown in FIG. 6 under the condition that the burner is
out of service. That is, the movable wall 2 is moved to the near
side, the jet portion area of tertiary air is made almost zero.
Since the flow speed at the end of the guide sleeve 3 is large, the
guide sleeve 3 can be cooled even with a small quantity of tertiary
air. Further, by increasing the flow rate of secondary air, it is
possible to increase the flow speed of secondary air and
effectively cool the stabilizer 10. Since secondary air is smaller
in flow rate than tertiary air, it is possible to decrease the
whole flow rate of air even if the secondary air is increased.
[0076] In the above-described embodiments, the tertiary nozzle is
provided with the air resistor 7. However, it is possible to form
it without provision of such an air resistor 7. The air resistor 7
is for controlling a combustion field by swirling the tertiary air,
because in the present invention the same effect can be attained by
moving the movable wall 2 forward and backward in the burner axis
direction. Further, the air resistor 15 of the secondary nozzle is
not essential, either. In this case, the secondary damper 34 is
necessary because any method of adjusting a flow rate of secondary
air comes not to exist thereby.
[0077] A construction of a controller used for the embodiment 2 is
shown in FIG. 7. The controller 101 receives signals from measuring
installment and sends signals for moving movable parts of the
burner 102. For example, the signals are signals for driving a
movable wall moving motor 111, an air resistor 7 driving motor 112,
a tertiary damper driving motor 113, a secondary damper driving
motor 114, an air resistor 15 driving motor 115, etc. The
controller 101 has a soft wear incorporated therewith, which soft
wear is for realizing the algorithm described in the embodiment 1.
The measuring installment installed in the burner includes a flame
detector 107, a temperature detector or thermometer 108 for burner
metal, a pressure gage 109 for combustion air, a flow meter 110 for
burner air, etc. The measuring instrument mounted on a boiler 116
includes a temperature detector or thermometer 103 for steam, an
ash deposition sensor 104, a NOx sensor 105, a unburned fuel sensor
106 for measuring CO concentration and unburned components of
solids, etc. For example, in order to examine the stabilization of
flame, the flame detector 107 is u sed. Among flame detectors, a
detector that can detect luminous intensity is good. It is possible
to evaluate goodness of the stabilization of flame by the luminous
intensity and change an operation condition to such an operation
condition that the stabilization of flame becomes good when the
stabilization is lowered. The NOx sensor 105 is better to be
installed at a downstream side of the boiler 116, at which the
reaction has terminated. It is good to install a plurality of the
NOx sensors and adjust the movable wall 2, the resistor and the
damper for each burner while examining concentration distribution
of NOx. It is also better to install the unburned fuel sensor 105
at a downstream side of the boiler 116 as installation of the NOx
sensor.
Embodiment 3
[0078] FIGS. 8, 9, 10 and 11 are sectional views showing another
embodiment of the burner according to the present invention. In an
example of FIG. 8, holes 16, 32 for tertiary air bypass are formed
in the fixed wall 1 and the movable wall 2 of the partition wall
partitioning the secondary nozzle 8 and the tertiary nozzle 9,
respectively, and tertiary air flows through those holes into the
secondary nozzle 8 as shown by an arrow 17, bypassing the tertiary
nozzle 9. In this case, the tertiary air not always bypasses, but
the tertiary air is flowed into the secondary nozzle under the
condition that the movable wall 2 is moved to the near side and
fuel supply is out of service as shown in FIG. 8. With this
construction, even in the case where the movable wall 2 has been
moved to the near side and the secondary air has been stopped down,
air is automatically supplied into the secondary nozzle 8, and it
is possible to prevent the temperature of the stabilizer 10 from
rising. It is possible to make the flow rate larger by providing
not only one hole 16, 32 for tertiary air bypass but a plurality of
the holes 16, 32.
[0079] FIG. 9 shows an example in which the tertiary air having
bypassed the tertiary nozzle 9 is supplied to the primary nozzle.
In this example, holes are formed in the tubular wall of the
primary nozzle 4, and bypass pipes 18 connect between the holes
provided in the fixed wall 1 and the holes formed in the primary
nozzle. In the case where the burner is out of service, almost all
air is not supplied in the primary nozzle, and the inner side of
the stabilizer cannot be cooled. Therefore, the constitution that
tertiary air is supplied along the wall of the primary nozzle under
the condition that the burner is out of service is taken as shown
in FIG. 9.
[0080] In the case where the concentration of oxygen in the air
carrying fuel is low, it is good to take such a construction that
the smaller the tertiary air jet sectional area of the tertiary
nozzle 9 becomes with the movable wall 2 being moved to the n ear
side, the more the flow rate of bypass air increases. When lignite
is used, since the fuel is easy to catch fire, the fuel is carried
with flue gas. When the burner load is high, even if the oxygen
concentration of primary air is low, stable combustion is possible
because the gas temperature is high inside the combustion
apparatus, for example, the boiler. However, when the load
decreases, the gas temperature inside the combustion apparatus
lowers and unburned fuel increases and lift-off occurs unless the
oxygen concentration of the primary air becomes high. In such a low
load case, tertiary air flows into the primary nozzle 4, so that it
is possible to effect stable combustion. Although such a
construction that tertiary air always bypasses and flows into the
primary nozzle 4 is also considered, combustion is promoted when
the load is high and the possibility of explosion and ash deposit
becomes high, so that it is better to take the construction that
the smaller the load becomes, the more the flow rate of air is
increased.
[0081] FIG. 10 shows an example in which bypassed secondary air is
supplied to the primary nozzle. In this example, holes are formed
in the tube wall of the primary nozzle 4, and air is supplied from
the secondary nozzle to the primary nozzle through bypass pipes 18.
In the case where the burner is out of service, the movable wall 2
is moved to the near side and the air resistor 15 is closed,
whereby secondary air is supplied along the wall of the primary
nozzle.
[0082] Further, in a similar manner to the example of FIG. 9, when
the oxygen concentration of primary air is low, it is possible to
effect stable combustion by increasing the flow rate of air
bypassing. When it is desired to decrease the combustion speed, the
pressure at the intake port of bypass air is lowered. For example,
the movable wall 2 is moved to widen the jet area of tertiary air,
or open the air resistor 15.
[0083] FIG. 11 shows an example that bypassed tertiary air is used
for cooling a pulverized coal concentrator 20 provided inside the
primary nozzle 4. The pulverized coal concentrator 20 is formed so
as to gradually narrow the flow path of the primary nozzle toward a
downstream side and gradually widen the flow path toward a further
downstream side as shown in FIG. 11, and serves to make higher the
pulverized coal concentration on the wall side of the primary
nozzle. Under the condition of being out of service, the flow rate
of primary air is small, so that it is difficult to cool the
pulverized coal concentrator 20. Therefore, such a construction is
taken that tertiary air flows to the pulverized coal concentrator
20 under the condition of being out of the service. In FIG. 11,
bypass tubes 19 are provided, and each of the bypass tubes 19
connects the hole of the fixed wall 1 and the hole of the primary
nozzle 4 and is extended to the pulverized coal concentrator 20.
The air used for cooling the pulverized coal concentrator 20 is
jetted into the furnace from the end of the pulverized coal
concentrator 20.
[0084] In some cases, the pulverized coal burner is provided with
an oil burner formed so as to spray oil 21 for assisting combustion
from an atomizer 31. FIG. 11 shows such an example. By moving the
movable wall 2, it is possible to change a ratio of the flow rate
of air flowing in a central portion of the burner and the flow rate
of air flowing outside thereof. Thereby it is possible to control
NOx and soot occurrence.
Embodiment 4
[0085] FIG. 12 is a sectional view of a burner of another
embodiment of the present invention. In this embodiment, the motor
boxes 6 are mounted out of the wall 28 of the wind box. The
secondary air and tertiary air are high temperature of 300.degree.
C. or more, and in some cases it includes ashes. When the motor
boxes 6 are mounted in such a place, they may become out of order,
and if they have been out of order, it is difficult to repair them.
Further, in the present embodiment, the fixed wall 1 is made to be
shorter than that in FIG. 5. With this construction, even if a
portion close to the end of the movable wall 2 is deformed by heat,
a portion contacting with the fixed wall 1 is disposed in a deeper
bowel of the burner, so that the possibility that movement is
obstructed becomes small.
[0086] Further, it is preferable to provide a stopper 2 on the
movable wall 2. Thereby, it is possible to prevent the movable wall
2 form moving forward too much due to sensor failure or the like.
Although not shown in FIG. 12, by a similar manner, it is also
effective to provide a stopper so as not to pull the movable wall 2
to the near side too much.
[0087] Further, in FIG. 12, the cooling efficiency is raised by
providing cooling fins 22 on the movable wall 2 and the guide
sleeve 3. The cooling fins 22 also serve to increase the strength
of them.
[0088] In FIG. 12, temperature detectors of thermostats 29 are
mounted on the guide sleeve 3 and the stabilizer 10, respectively.
The position of the movable wall 2 can be controlled, based on
values of the thermostats. In this case, when the temperature of
the end of the guide sleeve is higher than a limit value, the flow
speed of the tertiary air is slow, so that the operation that the
flow rate of the secondary air is reduced and the flow speed of the
tertiary air is raised can be conducted. Further, when the
temperature of the stabilizer is higher than a limit value, the
operation condition of the example 7 of the embodiment 1 can be
taken. In the case where the temperatures of the guide sleeve and
the stabilizer are higher than the limit values, respectively, the
quantity of the whole air can be increased.
[0089] FIGS. 13, 14 and 15 are a sectional view taken along
XIII-XIII, XIV-XIV and XV-XV of FIG. 12, respectively and show
various configuration examples. The configurations shown in FIGS.
13 to 15 can be used for not only the burner of FIG. 12, but the
burner of FIG. 1. FIG. 13 shows an example that four movement
control rods 5 are moved by gears 26 and power transmission shafts
27 driven by one motor 25. This has merits that the number of
motors can be reduced and displacements of the movement control
rods 5 can be made always equal. FIG. 14 is an example that the
motor 25 shown in FIG. 13 is not taken and the movement control
rods 5 are moved by rotation of a manual handle 27. FIG. 15 shows
an example that four motors 25 are used, and even if one of the
motors 25 has been out of order, the rods 5 can be driven by the
other motors.
Embodiment 5
[0090] FIGS. 16, 17 and 18 are sectional views of another
embodiment of the burner according to the present invention. FIG.
17 is a sectional view taken along XVII-XVII of FIG. 16, and FIG.
18 is a sectional view taken along XVIII-XVIII of FIG. 16. A
difference from FIG. 1 is that the burner is not made of triple
tubes, a primary nozzle 4 and a secondary nozzle 8 each are made of
a square tube, and a tertiary nozzle 9 is separated into an upper
portion and a lower portion and mounted. In this case, also, it is
possible to make an optimum operational condition by moving a
movable wall 2 having a guide sleeve 3 forward and backward in a
similar manner to the embodiment 1. In the present embodiment,
since the movable wall 2 is separated into an upper portion and a
lower portion, there is a possibility that they are not moved
forward and backward in such a way that they are interlocked.
Therefore, as shown in FIG. 17, it is possible to connect the
movable walls 2 by connecting plates 36. In the present embodiment,
as shown in FIG. 18, handles 33 are mounted at four positions, and
the movable wall 2 is moved by manual, however, it can be moved by
a motor or motors as in the embodiment 2.
Embodiment 6
[0091] An example of other use of the burner according to the
present invention will be explained. In FIG. 19, the abscissa
thereof shows loads of the burner. Air for cooling is flowed even
at a burner load of 0%, and in this case, in order to cool the
stabilizer 10, the movable wall 2 is moved so that the outlet of
tertiary air becomes a condition near to full closing. For the coal
firing burner, since combustion is assisted by oil at the time of a
low load, oil and coal are supplied. When it reached to a load at
which combustion can be performed with only coal, a flow rate of
oil is made zero. When the oil is burned, it is better to increase
a flow rate of air at a position near to a central portion to which
oil is supplied, so that the movable wall 2 is moved to the near
side to make a condition that the outlet of tertiary air is nearly
closed. A flow rate of supplied air is increased as a flow rate of
coal increases. Since stable combustion can be performed even if
the momentum of tertiary air is low, the movable wall 2 is moved to
the near side to make the tertiary air outlet large and approximate
the outlet to a nearly full opening.
[0092] The present invention makes it possible to cool the burner
while reducing NOx by controlling the combustion condition optimum.
The possibility of utility of the burner according to the present
invention is large to make thermal failure of the burner less.
* * * * *