U.S. patent application number 13/979677 was filed with the patent office on 2013-11-07 for solid fuel burner and combustion device using same.
This patent application is currently assigned to BABCOCK-HITACHI KABUSHIKI KAISHA. The applicant listed for this patent is Jun Kashima, Yusuke Ochi, Noriyuki Ohyatsu, Hitoshi Okimura. Invention is credited to Jun Kashima, Yusuke Ochi, Noriyuki Ohyatsu, Hitoshi Okimura.
Application Number | 20130291770 13/979677 |
Document ID | / |
Family ID | 46515484 |
Filed Date | 2013-11-07 |
United States Patent
Application |
20130291770 |
Kind Code |
A1 |
Kashima; Jun ; et
al. |
November 7, 2013 |
SOLID FUEL BURNER AND COMBUSTION DEVICE USING SAME
Abstract
A solid fuel burner and a combustion device using the solid fuel
burner includes: a throat provided to the outer periphery of a fuel
nozzle and injecting combustion gas into a furnace; a duct for
delivering the combustion gas to the throat, the duct being
provided with an inlet opening into which the gas is introduced
from a direction perpendicular to the central axis of the nozzle
and having a flow path formed so as to be bent at a right angle in
the direction of the central axis of the nozzle; a damper provided
in the duct; and a differential pressure detection device for
detecting the difference between the pressure of the combustion gas
flowing through the upstream portion of the duct and the pressure
of the combustion gas flowing through the downstream portion of the
duct. The damper is provided near and downstream of the inlet
opening of the duct.
Inventors: |
Kashima; Jun; (Hiroshima,
JP) ; Okimura; Hitoshi; (Hiroshima, JP) ;
Ohyatsu; Noriyuki; (Hiroshima, JP) ; Ochi;
Yusuke; (Hiroshima, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kashima; Jun
Okimura; Hitoshi
Ohyatsu; Noriyuki
Ochi; Yusuke |
Hiroshima
Hiroshima
Hiroshima
Hiroshima |
|
JP
JP
JP
JP |
|
|
Assignee: |
BABCOCK-HITACHI KABUSHIKI
KAISHA
Tokyo
JP
|
Family ID: |
46515484 |
Appl. No.: |
13/979677 |
Filed: |
January 16, 2012 |
PCT Filed: |
January 16, 2012 |
PCT NO: |
PCT/JP2012/000203 |
371 Date: |
July 15, 2013 |
Current U.S.
Class: |
110/189 ;
110/261; 431/178 |
Current CPC
Class: |
F23N 3/002 20130101;
F23N 2225/06 20200101; F23N 3/02 20130101; F23D 1/00 20130101; F23N
2235/06 20200101; F23C 5/08 20130101; F23C 5/28 20130101; F23N
5/184 20130101; F23D 1/005 20130101 |
Class at
Publication: |
110/189 ;
110/261; 431/178 |
International
Class: |
F23D 1/00 20060101
F23D001/00; F23C 5/08 20060101 F23C005/08; F23N 3/00 20060101
F23N003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 21, 2011 |
JP |
2011-010544 |
Claims
1. A solid fuel burner comprising: a cylindrical fuel nozzle that
discharges a mixed fluid of a solid fuel and a carrier gas into a
furnace from a wall surface of the furnace; a cylindrical
combustion gas throat that is provided at an outer periphery of the
fuel nozzle and discharges a combustion gas into the furnace; a
duct that constitutes a flow path for the combustion gas that is
connected to the combustion gas throat; flow rate adjusting means
for the combustion gas that is provided in the duct; and a
differential pressure detection device that detects a pressure
difference between the combustion gases flowing on the upstream
side and the downstream side in the duct, wherein the duct has an
inlet opening into which the combustion gas is taken from one
direction orthogonal to a central axis direction of the fuel nozzle
and is formed in such a manner that the flow path for the
combustion gas is bent at a right angle in the central axis
direction of the fuel nozzle, the flow rate adjusting means for the
combustion gas is provided near the inlet opening of the duct on
the downstream side of the inlet opening, the differential pressure
detection device has an upstream-side pressure detection point on
an inner wall of the duct that is the farthest from the inlet
opening of the duct corresponding to a stagnation region of the
combustion gas on a wake side of the flow rate adjusting means, and
has a downstream-side pressure detection point on an outer wall of
the combustion gas throat, and a control device is provided, the
control device converting a value of a pressure difference at the
upstream-side pressure detection point and the downstream-side
pressure detection point detected by the differential pressure
detection device into a flow rate of the combustion gas and
operating the flow rate adjusting means to adjust a flow rate of
the combustion gas.
2. The solid fuel burner according to claim 1, wherein the flow
path for the combustion gas in the duct that is connected to the
combustion gas throat is divided by a partition wall into a
plurality of flow paths that the combustion gas does not flow from
one flow path to another, and the upstream-side pressure detection
point and the downstream-side pressure detection point are provided
to each of the plurality of flow paths.
3. The solid fuel burner according to claim 1, wherein the
downstream-side pressure detection point is provided on the
combustion gas throat where an interval between the combustion gas
flow paths in a radial direction becomes maximum with the central
axis of the fuel nozzle being determined as a reference.
4. The solid fuel burner according to claim 1, wherein the
differential pressure detection device is configured to detect a
value of a differential pressure between an upstream-side pressure
and a downstream-side pressure of the combustion gas in the duct
through respective pressure conduits constituting the upstream-side
pressure detection points and the downstream-side pressure
detection points.
5. A combustion apparatus comprising solid fuel burners according
to claim 1 on a plurality of stages along an up-and-down direction
and in a plurality of rows along a furnace width direction on a
wall surface of a furnace, wherein the combustion apparatus
comprises solid fuel flow rate measuring means for individually
adjusting and measuring flow rates of a solid fuel that flows into
the plurality of solid fuel burners, and a control device is
configured to adjust an opening degree of flow rate adjusting means
for a combustion gas based on a combustion gas flow rate detected
by a differential pressure detection device of each solid fuel
burner in accordance with a change in solid fuel flow rate measured
by the solid fuel flow rate measuring means, and to individually
control each flow rate of the combustion gas.
Description
TECHNICAL FIELD
[0001] The present invention relates to a burner that is mainly
used in a thermal power generation plant and combusts a solid fuel
such as pulverized coal and a combustion device using the
burner.
BACKGROUND ART
[0002] In a boiler that comprises a plurality of burners that
combust a solid fuel such as pulverized coal and adopts a two-stage
combustion system as a measure for reducing NOx in a combustion
exhaust gas of the fuel in the burners, to achieve both a reduction
in air excess ratio and a reduction in emission of unburned
combustible such as CO, there is known a technology (WO
2008/133051A1) that a flow rate of the solid fuel is measured in
accordance with each burner and combustion air that is
complementary with this rate is input from each burner or a
two-stage combustion air port (which will be also referred to as an
after-air port: AAP or an over-fire air port: OFA).
[0003] It is required to have the capability of measuring and
adjusting a flow rate of a combustion gas accurately in accordance
with each burner in order to apply the technology to an actual
boiler.
[0004] On the other hand, there is known an invention (WO
2008/038426A1) that concerns a burner which has a flat
cross-sectional shape orthogonal to a flow of a fluid in a fuel
nozzle to suppress expansion of uncombusted region of fuel even
when a capacity of each single burner is raised in accordance with
an increase in capacity of the boiler.
[0005] Further, there is also known an invention (Japanese
Unexamined Patent Application Publication No. 2002-147713, WO
2009/041081A1) of a burner that enables to respectively adjust a
flow rate of an oxygen containing gas for combustion flowing
through a plurality of divided flow paths surrounding a fuel supply
nozzle of the burner to control a heat transfer amount for a fluid
flowing through a boiler heat exchanger by changing a combustion
position of the fuel in a furnace.
CITATION LIST
Patent Literature
[0006] Patent Literature 1: WO 2008/133051A1
[0007] Patent Literature 2: WO 2008/038426A1
[0008] Patent Literature 3: Japanese Unexamined Patent
[0009] Application Publication No. 2002-147713
[0010] Patent Literature 4: WO 2009/041081A1
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0011] A flow of the combustion air ejected from each burner is
greatly affected by a configuration of the burner, especially a
conformation of the flow path for the combustion gas.
[0012] To accurately measure and adjust a flow rate of the
combustion gas in accordance with each burner, it is desirable to
provide a long linear flow path in the vicinity of measuring means
or adjusting means so that the combustion gas can uniformly flow.
However, in an actual boiler, for the reason of the restrictions
about installation that many burners must be compactly arranged
while avoiding interference with structures outside a furnace, a
conformation of the flow path that can uniform a flow of the
combustion air cannot be necessarily adopted, drift may be locally
produced, and the measurement and the adjustment of a flow rate may
be affected.
[0013] In the burner having the flat cross-sectional shape
orthogonal to the flow of the fluid in the fuel nozzle in
particular, the drift is apt to be generated.
[0014] Furthermore, in a burner that actively adjusts each flow
rate of the combustion gas flowing through divided flow paths, the
number of targets is increased, and an adjustment width or an
adjustment frequency is also increased, thus resulting in a highly
demanding problem.
[0015] It is an object of the present invention to provide a solid
fuel burner that has a relatively simple configuration, which is
hardly affected by the local drift, and a flow rate of a combustion
gas in accordance with each burner can be accurately measured and
adjusted.
[0016] Further, it is another object of the present invention to
provide a combustion device using this burner that has a simple
configuration, is hardly affected by the local drive, accurately
measures and adjusts a flow rate of a combustion gas in accordance
with each burner, and achieves both a reduction in air excess ratio
and emission of unburned combustibles such as CO.
Means for Solving the Problems
[0017] The object can be achieved by the invention described
below.
[0018] According to a first aspect of the invention, there is
provided a solid fuel burner comprising: a cylindrical fuel nozzle
(10) that discharges a mixed fluid of a solid fuel and a carrier
gas into a furnace (40) from a wall surface of the furnace (40); a
cylindrical combustion gas throat (6) that is provided at an outer
periphery of the fuel nozzle (10) and discharges a combustion gas
into the furnace (40); a duct (2) that constitutes a flow path for
the combustion gas that is connected to the combustion gas throat
(6); flow rate adjusting means (1) for the combustion gas that is
provided in the duct (2); and a differential pressure detection
device (32, 35) that detects a pressure difference (a differential
pressure) between the combustion gases flowing on the upstream side
and the downstream side in the duct (2), wherein the duct (2) has
an inlet opening (8) into which the combustion gas is taken from
one direction orthogonal to a central axis direction of the fuel
nozzle (10) and is formed in such a manner that the flow path for
the combustion gas is bent at a right angle in the central axis
direction of the fuel nozzle (10), the flow rate adjusting means
(1) for the combustion gas is provided near the inlet opening (8)
of the duct (2) on the downstream side of the inlet opening (8),
the differential pressure detection device (32, 35) has an
upstream-side pressure detection point (31, 33) on an inner wall of
the duct (2) that is the farthest from the inlet opening (8) of the
duct (2) corresponding to a stagnation region (90) of the
combustion gas on a wake side of the flow rate adjusting means (1),
and has a downstream-side pressure detection point (30, 34) on an
outer wall of the combustion gas throat (6), and a control device
(37) is provided, the control device (37) converting a value of a
pressure difference at the upstream-side pressure detection point
(31, 33) and the downstream-side pressure detection point (30, 34)
detected by the differential pressure detection device (32, 35)
into a flow rate of the combustion gas and operating the flow rate
adjusting means (1) to adjust a flow rate of the combustion
gas.
[0019] A second aspect of the invention provides the solid fuel
burner according to the first aspect, wherein the flow path for the
combustion gas in the duct (2) that is connected to the combustion
gas throat (6) is divided by a partition wall (4) into a plurality
of flow paths that the combustion gas does not flow from one flow
path to another, and the upstream-side pressure detection point
(31, 33) and the downstream-side pressure detection point (30, 34)
are provided to each of the plurality of flow paths.
[0020] A third aspect of the invention provides the solid fuel
burner according to in the first aspect, wherein the
downstream-side pressure detection point (30, 34) is provided on
the combustion gas throat (6) where an interval between the
combustion gas flow paths in a radial direction becomes maximum
with the central axis of the fuel nozzle (10) being determined as a
reference.
[0021] A fourth aspect of the invention provides the solid fuel
burner according to the first aspect, wherein the differential
pressure detection device (32, 35) is configured to detect a value
of a differential pressure between an upstream-side pressure and a
downstream-side pressure of the combustion gas in the duct (2)
through respective pressure conduits constituting the upstream-side
pressure detection point (31, 33) and the downstream-side pressure
detection point (30, 34).
[0022] A fifth aspect of the invention provides a combustion
apparatus comprising solid fuel burners (44) according to the first
aspect on a plurality of stages along an up-and-down direction and
in a plurality of rows along a furnace width direction on a wall
surface of a furnace (40), wherein the combustion apparatus
comprises solid fuel flow rate measuring means (71) for
individually adjusting and measuring flow rates of a solid fuel
that flows into the plurality of solid fuel burners (44), and a
control device (37) is configured to adjust an opening degree of
flow rate adjusting means (1) for a combustion gas based on a
combustion gas flow rate detected by a differential pressure
detection device (32, 35) of each solid fuel burner (44) in
accordance with a change in solid fuel flow rate measured by the
solid fuel flow rate measuring means (71), and to individually
control each flow rate of the combustion gas.
[0023] In the present above-mentioned invention, the stagnation
region 90 (FIG. 2, FIG. 3) for the combustion gas in which each
upstream-side pressure detection point 31 or 33, one of pressure
detection points, is set means a region where a flow velocity of
the combustion gas is nearly zero or relatively minimum in the flow
path.
[0024] Specifically, a portion near the inner wall of the duct 2
which is the farthest from the inlet opening 8 of the duct 2 for
the combustion gas corresponds to each upstream-side pressure
detection point 31 or 33. For example, in the duct 2 shown in FIG.
2, when the flow path of the cube is constituted of a front wall 56
close to the furnace side, a rear wall 57 which is provided to be
parallel to the front wall 56 at an interval and placed at a
position distanced from the furnace side, and a sidewall 55 which
connects ridge line portions of the front and rear walls 56 and 57,
a region of the sidewall 55 that faces and is the farthest from an
inlet opening surface of the duct 2 which functions as the inlet
opening 8 of the combustion air corresponds to each upstream-side
pressure detection point 31 or 33.
[0025] Here, when there is provided such a conformation as shown in
FIG. 2 where each of the front wall 56 and the rear wall 57 is
ovalized and has a U-like shape as a whole (see FIG. 2) and the
sidewall 55 separates the flow path (the duct 2) for the combustion
gas from the outside over linear portions and curved portions of
the ridge lines of the front wall 56 and the rear wall 57, a top
portion of a curved surface formed of the sidewall 55 corresponds
to each of the upstream-side pressure detection points 31 or 33
(FIG. 1).
[0026] Moreover, the top portion of the curved surface formed of
the sidewall 55 can function as a region where a flow path
cross-sectional area of the duct 2, i.e., an area of the duct cross
section orthogonal to the flow direction of the combustion gas in
the straight portion of the duct 2 through which the combustion gas
travels straight from the inlet opening 8 of the duct 2
approximates zero without limit.
[0027] Additionally, when the fuel nozzle 10 has a rectangular
shape, an oval shape, or an elliptic shape (FIG. 1 shows an example
of the oval shape) having a long-diameter portion and a
short-diameter portion in a cross-sectional shape thereof
orthogonal to a central axis direction (a flow direction of the
fluid traveling toward the outlet portion) thereof, a region where
a plane including a top portion of the long-diameter portion and
the central axis of the fuel nozzle 10 (which is the same plane as
a partition wall (a center partition) 4 in the conformation shown
in FIG. 1) is parallel to a line crossing the sidewall 55 of the
duct 2 corresponds to each upstream-side pressure detection point
31 or 33 (FIG. 1).
[0028] On the other hand, each of the downstream-side pressure
detection points 30 and 34 (FIG. 1) which is the other pressure
detection point is provided at a top portion of the combustion gas
throat 6 that is the farthest from the partition wall (the center
partition) 4 that divides the combustion gas duct 2 into upper and
lower portions when the combustion gas throat 6 is arranged in a
burner attachment opening 58 (FIG. 2) of the furnace 40. In the
example where the cross-sectional shape of the fuel nozzle 10
depicted in FIG. 1 is the oval shape, each of these points is
present in a region of the combustion gas throat 6 where a
difference between the diameter of the concentrically arranged
cylindrical combustion gas throat 6 and the short diameter of the
fuel nozzle 100 having the oval cross-sectional shape, i.e., a
cross-sectional area of the flow path of the duct 2 for the
combustion gas with running through a central axis of the fuel
nozzle 10 in the radial direction of the fuel nozzle 10 becomes
maximum. In other words, it is present in a region where the plane
including the short-diameter portion of the fuel nozzle 10 and the
central axis of the fuel nozzle 10 are parallel to a line crossing
the fuel gas throat 6.
[0029] The two pressure detection points (the upstream-side
pressure detection point 31 and the downstream-side pressure
detection point 30; and the upstream-side pressure detection point
33 and the downstream-side pressure detection point 34 in FIG. 1)
are not restricted to one specific point or line, and they are the
region which have a given width and more specifically, can also be
defined by the following geometric numerical range.
[0030] The stagnation region 90 (FIG. 2, FIG. 3) of the combustion
gas dust 2 where each upstream-side pressure detection point 31 or
33 is arranged is a region where a flow velocity of the combustion
gas is substantially zero or it is relatively minimum in the duct
2, and this region is present in a region that runs through the
central axis of the fuel nozzle 10 with the partition wall (the
center partition) 4 that divides the downstream-side duct 2 of the
duct 2 into upper and lower parts at the center and is surrounded
by planes each of which is in the range of 15.degree. on the upper
or lower side.
[0031] The top portion of the combustion gas throat 6 which is the
position where each of the downstream-side pressure detection
points 30 and 34 is arranged is present in the range of
.+-.2.degree. in the circumferential direction (see FIG. 12) and on
the downstream side of a half point of a throat length of the
combustion gas throat 6 in the central axis direction when a
position at which the difference between the diameter of the throat
6 and the diameter of the flow path of the fuel nozzle 10 becomes
maximum (a perpendicular running through the central axis of the
combustion gas throat 6 in FIG. 1) is determined as a
reference.
(Operation)
[0032] The present invention has the following operation.
[0033] A value of a differential pressure of the combustion gas at
each upstream-side pressure detection point 31 or 33 and each
downstream-side pressure detection point 30 or 34 detected by each
of the differential pressure detection devices 32 and 35 can be
converted into a flow rate of the combustion gas when it is
assigned to a predetermined conversion formula, whereby the flow
rate of the combustion gas (gas such as air) each burner can be
measured.
[0034] The predetermined conversion formula is as follows.
Q=C.times. (OP.times.P)
[0035] (Q: a flow rate, C: constant, OP: a differential pressure,
P: density of the fuel gas)
[0036] The combustion gas duct 2 has the inlet opening 8 into which
the combustion gas is introduced from one direction orthogonal to
the central axis direction (a flow direction of the fluid flowing
toward the outlet opening portion on the furnace side) of the
combustion gas throat 6, and it is formed so that the flow path
(the duct) 2 of the combustion gas can bend at a right angle toward
the central axis direction of the combustion gas throat 6.
[0037] To measure a flow rate of the combustion gas in the duct 2
by the differential pressure detection devices 32 and 35 and adjust
this flow rate, the duct 2 is compactly accommodated in a wind box
41 parallel to the wall surface of the boiler furnace 40 while
obtaining a duct length required to suppress an influence of drift
produced in the duct 2.
[0038] The flow rate adjusting means 1 for the combustion gas is
provided on an upstream-side of the installing portion for each
differential pressure detection device 32 or 35 in the duct 2 for
the combustion gas. As a result, since a duct length of the duct 2
from the flow rate adjusting means 1 can be assured to some extent,
the flow rate adjusting means 1 can reduce a flow velocity
distribution of the combustion gas in the duct cross section that
is produced and is apt to increase when an opening degree of the
inlet opening 8 is small.
[0039] Further, the flow rate adjusting means 1 which involves a
mechanical operation such as opening/closing can be prevented from
directly receiving radiant heat from the inside of the furnace 40
or from colliding with clinkers or the like falling from, e.g., the
upper side of the furnace 40, and a possibility that damage or an
inconvenience of an operation caused thereby can be lowered.
[0040] Since each of the differential pressure detection devices 32
and 35 determines an inner wall position of the duct 2 farthest
from the inlet opening 8 of the duct 2 corresponding to the
stagnation region 90 of the combustion gas on the wake side of the
flow rate adjusting means 1 as each of the upstream-side pressure
detection points 31 and 33, an influence of a dynamic pressure
acting on each of the pressure detection points 31 and 33 is
reduced, and the combustion gas flow rate can be measured without
being affected by the drift of the combustion gas because the
downstream-side pressure detection points 30 and 34 are arranged on
the top portion wall surface and the bottom portion wall surface of
the combustion gas throat 6, thereby highly accurately measuring
the flow rate of the combustion gas.
[0041] The duct 2 for the combustion gas connected to the
combustion gas throat 6 is divided into two portions by the
partition wall (the center partition) 4, and the upstream-side
pressure detection points 31 and 33 and the downstream-side
pressure detection points 30 and 34 are provided to the respective
divided flow paths.
[0042] As a result, the flow rates of the combustion gas flowing
through the plurality of ducts 2 are deviated on upper and lower
sides of the combustion air outlet opening 7 of the burner 44,
accurate adjustment can be individually carried out, a flame
forming position in the furnace 40 can be controlled, and NOx
concentration of a nitrogen oxide in a combustion exhaust gas can
be effectively reduced, or an amount of heat transfer to a heat
transfer tube (not shown) installed in the boiler furnace 40 can be
effectively controlled. When the duct 2 is divided into the
plurality of flow paths, the number of targets of the combustion
gas flow rate measurement and adjustment is increased, the flow
rate is actively changed in accordance with each flow path, its
span of adjustable range or frequency is thereby increased, and
hence the configuration using the upstream-side pressure detection
points 31 and 33 and the downstream-side pressure detection points
30 and 34 has high importance.
[0043] Furthermore, even if the shape of the cross section of the
fuel nozzle 10 orthogonal to the central axis direction (the flow
direction of the fluid flowing toward the outlet opening on the
furnace side) in which drift of the combustion gas is apt to be
generated is the rectangular shape, the oval shape, or the elliptic
shape having the long-diameter portion and the short-diameter
portion, when each of the downstream-side pressure detection points
30 and 34 is provided on the outer wall surface of the combustion
gas throat 6 where the flow path cross-sectional area of the
combustion gas in the radial direction becomes maximum with the
central axis of the combustion gas throat 6 determined as the
reference, the flow rate of the combustion gas can be accurately
measured with being hardly affected by the drift.
[0044] When a differential pressure detection device that detects a
value of a differential pressure between an upstream-side pressure
and a downstream-side pressure of the combustion air through
pressure conduits constituting each upstream-side pressure
detection point 31 or 33 and each downstream-side pressure
detection point 30 or 34 is used, each of the differential pressure
detection devices 32 and 35 can be easily realized without greatly
increasing facility cost.
[0045] In a combustion apparatus such as a boiler that comprises
the solid fuel flow rate measuring means 71 provided in a plurality
of stages in the vertical direction and a plurality of rows in the
furnace width direction on the wall surface of the furnace 40 in
particular and individually measure the flow rate of the solid fuel
flowing into the solid fuel burner 44 and that is configured to
individually control the combustion gas flow rate of each solid
fuel burner 44 in accordance with a change in fuel flow rate
measured by the solid fuel flow rate measuring means 71, when the
flow rate of the combustion gas flowing through each of the
plurality of flow paths must be individually accurately adjusted,
this is important since the number of required devices is large. It
is to be noted that this configuration can be applied not only the
combustion device according to the present invention but also any
other combustion devices using the solid fuel burner 44.
Effects of the Invention
[0046] According to the invention of the first aspect, the duct 2
of the combustion gas has the inlet opening 8 into which the
combustion gas is introduced from one direction orthogonal to the
central axis direction of the combustion gas throat 6, the duct 2
is formed to bend at a right angle toward the central axis
direction of the combustion gas throat 6, the flow rate adjusting
means 1 for the combustion gas is provided at the anterior flow
portion in the duct 2 for the combustion gas, and hence the length
of the duct 2 can be assured to some extent, whereby the flow rate
adjusting means 1 can decrease spread of the flow velocity
distribution of the combustion gas in the duct cross section for
the combustion gas that is produced and apt to increase when an
opening degree of the inlet opening 8 is small in particular.
[0047] Moreover, since each of the upstream-side pressure detection
points 31 and 33 is provided in the stagnation region 90 of the
combustion gas in the duct 2, the flow rate of the combustion gas
can be highly accurately measured with being hardly affected by a
dynamic pressure acting on each of the upstream-side pressure
detection points 31 and 33, and assigning a value of the
differential pressure detected by each of the differential pressure
detection devise 32 and 35 into a predetermined conversion formula
(1) enables conversion into a flow rate of the combustion gas and
allows each burner to measure a flow rate of the combustion gas
(gas such as air). In this manner, the combustion gas flow rate can
be measured without being affected by drift of the combustion
gas.
[0048] Additionally, since the combustion gas flow rate is measured
by each of the differential pressure detection devices 32 and 35
and this flow rate is adjusted by the flow rate adjusting means 1,
the duct 2 can be compactly accommodated in the wind boxy 41
parallel to the wall surface of the boiler furnace 40 while
obtaining a duct length required for suppressing an influence of
the drift produced in the duct 2 for the fuel gas.
[0049] Further, since the flow rate adjusting means 1 is provided
in the duct 2, the flow rate adjusting means 1 that involves a
mechanical operation such as opening/closing can be prevented from
directly receiving the radiant heat from the furnace 40 or from
colliding with clinkers or the like falling from, e.g., the upper
side of the furnace 40, thus lowering a possibility that damage or
an inconvenience of an operation caused thereby occurs.
[0050] According to the invention of the second aspect, in addition
to the effect of the invention of the first aspect, when the duct 2
for the combustion gas is divided into the two combustion gas flow
paths by the partition wall 4 and each upstream-side pressure
detection point 31 or 33 and each downstream-side pressure
detection point 30 or 34 are provided in the respective flow paths,
the flow rate of the combustion gas flowing through each of the
plurality of ducts 2 can be individually and accurately adjusted on
the upper and lower sides, and the forming position of a flame in
the furnace 40 can be controlled. When the duct 2 is divided into
the plurality of flow paths, the number of targets for measurement
and adjustment of the combustion gas flow rate is increased, and
the flow rate can be actively changed in accordance with each flow
path, whereby the flow rate can be finely adjusted.
[0051] According to the invention of the third aspect, in addition
to the effect of the invention of the first aspect, even if the
shape of the cross section of the fuel nozzle 10 orthogonal to the
central axis direction (the flow direction of the fluid flowing
toward the outlet opening on the furnace side) in which drift of
the combustion gas is apt to be produced is the rectangular shape,
the oval shape, or the elliptic shape having the long-diameter
portion and the short-diameter portion, when each of the
downstream-side pressure detection points 30 and 34 is provided on
the outer wall surface of the combustion gas throat 6 where the
flow path cross-sectional area of the combustion gas in the radial
direction becomes maximum with the central axis of the fuel nozzle
10 determined as a reference, the flow rate of the combustion gas
can be accurately measured with being hardly affected by the
drift.
[0052] According to the invention of the fourth aspect, in addition
to the effect of the invention of the first aspect, each of the
differential pressure detection devices 32 and 35 can detect a
value of the differential pressure between the upstream-side
pressure and the downstream-side pressure of the combustion gas in
the duct 2 through the pressure conduits connected to each
upstream-side pressure detection point 31 or 33 and each
downstream-side pressure detection point 30 or 34, and it can be
easily realized without greatly increasing facility cost.
[0053] According to the invention of the fifth aspect, the flow
rates of the solid fuel flowing into the plurality of solid fuel
burners 44 in the combustion device are individually adjusted and
measured by the solid fuel flow rate measuring means 71, the
control device 37 adjusts an opening degree of the flow rate
adjusting means 1 for the combustion gas based on each combustion
gas flow rate detected by the differential pressure detection
device 32 or 35 of each solid fuel burner 44 in accordance with a
change in measured solid fuel flow rate, and the control device 37
individually controls each flow rate of the combustion gas, thereby
rapidly coping with a change in solid fuel flow rate of each burner
44. Furthermore, adjusting the combustion gas alone can suffice,
and the adjusting means can have a simpler configuration as
compared with a case where the solid fuel is conveyed with use of a
carrier gas. Moreover, when an amount of combustion gas is deviated
depending on each of the upper and lower sides of each burner 44,
flames can be changed to the upward direction or the downward
direction in the furnace 40, NOx concentration of a nitrogen oxide
in the combustion exhaust gas can be reduced, or an amount of heat
transfer to the heat transfer tube (not shown) installed in the
boiler furnace 40 can be effectively controlled.
BRIEF DESCRIPTION OF DRAWINGS
[0054] FIG. 1 is a schematic perspective view of a solid fuel
burner according to an embodiment of the present invention;
[0055] FIG. 2 is a view showing constituent element of the burner
shown in FIG. 1;
[0056] FIG. 3 is a front view of a combustion air duct seen from a
boiler front side of the burner in FIG. 1;
[0057] FIG. 4 is a cross-sectional view taken along a line A-A of
the burner shown in FIG. 3;
[0058] FIG. 5 is a schematic front view (FIG. 5(a)) and a side view
(FIG. 5(b)) showing an example of a furnace having the burner in
FIG. 1 disposed thereto;
[0059] FIG. 6 is a view for explaining drift in the burner in FIG.
1;
[0060] FIG. 7 is a view for explaining the drift in the burner in
FIG. 1;
[0061] FIG. 8 is a view for explaining the drift in the burner in
FIG. 1;
[0062] FIG. 9 is a view for explaining the drift in the burner in
FIG. 1;
[0063] FIG. 10 is a view for explaining a relationship between a
damper opening degree and a static pressure of the burner in FIG.
1;
[0064] FIG. 11 is a view for explaining positions at which
downstream-side pressure detection points of the burner in FIG. 1
are disposed;
[0065] FIG. 12 is a view for explaining the positions at which the
downstream-side pressure detection points of the burner in FIG. 1
are disposed;
[0066] FIG. 13 is a view for explaining an influence of the damper
opening degree on the static pressure at the positions where the
downstream-side pressure detection points of the burner in FIG. 1
are disposed in the direction of a central axis;
[0067] FIG. 14 is a view for explaining the influence of the damper
opening degree on the static pressure at the positions where the
downstream-side pressure detection points of the burner in FIG. 1
are disposed in the direction of circumference;
[0068] FIG. 15 is a schematic view of control over a supply amount
of a solid fuel in a furnace using the burners in FIG. 1;
[0069] FIG. 16 is a view for explaining a general technique for
measuring a combustion air (gas) flow rate; and
[0070] FIG. 17 is a view for explaining a general technique for
measuring a combustion air (gas) flow rate.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0071] An embodiment according to the present invention will now be
described with reference to the drawings.
[0072] In an embodiment according to the present invention
described below, it is assumed that a solid fuel, especially
pulverized coal, woody biomass, or a mixture of the pulverized coal
and the woody biomass is combusted as a main fuel by a solid fuel
burner, but a type of fuel is not necessarily restricted, and a
liquid or a gas may be used as a main fuel. Further, air is assumed
to be used as a combustion gas, but the air alone is not
necessarily restricted, and a recirculating gas of a combustion
exhaust gas, a high-oxygen concentration gas, or a mixed gas of the
various kinds of gases may be used.
[0073] FIG. 1 is a schematic perspective view of a solid fuel
burner according to an embodiment of the present invention, and
FIG. 5 is a schematic front view (FIG. 5(a)) and a side view (FIG.
5(b)) when the solid fuel burners 44 to which the present invention
is applied are incorporated in a boiler furnace 40.
[0074] Combustion air enters burners 44 from a wind box 41 provided
on the outer side of a sidewall of the boiler furnace 40 shown in
FIG. 5 through a combustion air duct 2 depicted in FIG. 1 and flows
into the furnace 40 from a combustion air throat 6 provided at an
opening portion of the sidewall of the furnace 40. Furthermore,
pulverized coal and its carrier air are ejected into the furnace 40
through a solid fuel carrying tube (a fuel nozzle) 10.
[0075] The combustion air throat 6 that ejects the combustion air
into the furnace 40 is provided on the outer peripheral side of the
solid fuel carrying tube 10, and the combustion air is supplied
into the combustion air throat 6 from the combustion air duct 2. An
air inlet opening 8 into which the combustion air from the window
box 41 is introduced is provided in the combustion air duct 2, an
air inflow direction of the air inlet opening 8 indicated by an
arrow B in FIG. 1 is provided to be parallel to a furnace wall
surface on which a burner 44 is installed so that the combustion
air is bent at a substantially right angle from the air inlet
opening 8 and is spouted into the furnace 40 from a combustion air
outlet opening 7 toward the furnace wall surface. Therefore, the
combustion air duct 2 is provided at the outer peripheral portion
of the solid fuel carrying tube (the fuel nozzle) 10, and the air
that has flowed into the air inlet opening 8 is bent at a
substantially right angle to surround the outer peripheral portion
of the solid fuel carrying tube 10 and supplied to the combustion
air throat 6.
[0076] Although an outlet opening portion of the solid fuel
carrying tube 10 has a flow path formed into an oval configuration
as seen from the inside of the furnace 40, whereas an outlet
opening of the throat 6 has a gas flow path formed into a circular
configuration as seen from the inside of the furnace. Therefore,
the furnace outlet opening of the throat 6 has an opening portion
that is large in an up-and-down direction around the outlet opening
of the solid fuel carrying tube 10.
[0077] The combustion air duct 2 is divided into two parts in the
up-and-down direction by a center partition 4, and upper air and
lower air (combustion gas) do not become confluent in the
combustion duct 2. Moreover, the combustion air inlet opening 8 of
the combustion air duct 2 is divided by an upper partition 3 and a
lower partition 5 and consists of four spaces in total including
the spaces divided by the center partition 4, and a combustion air
(combustion gas) amount adjustment damper 1 is installed in each of
the spaces.
[0078] FIG. 2 is a detailed perspective view of the combustion air
duct 2. The combustion air duct 2 is connected to the combustion
air throat 6, and it is constituted of a U-shaped front wall 56
arranged to be parallel to a furnace wall surface on the side close
to the furnace wall surface, a U-shaped rear wall 57 arranged to be
parallel to the front wall 56 on the side far from the furnace wall
surface on the back side of the front wall 56, and a sidewall 55
that has both end portions connected to ridge line portions of the
front wall 56 and the rear wall 57 and covers the spaces of the
combustion air duct 2. The front wall 56 has a circular opening
portion 58 connected to the combustion air throat 6, and the
sidewall member 57 has an opening 59 connected to the solid fuel
carrying tube 10.
[0079] The center partition 4 is installed at a position having a
height 0.5 L1 which is a center position having a height L1 of the
inlet opening 8 of the combustion air duct 2, divides the
combustion air inlet opening 8 into two parts in the up-and-down
direction, and is joined to the front and rear walls 56 and 57 for
the configuration of the duct 2, and the spaces in the combustion
air duct 2 divided into two parts in the up-and-down direction by
the center partition 4 are independent from each other so that the
combustion air does not flow into or out from these spaces.
[0080] Additionally, in the combustion duct 2 divided into two
parts in the up-and-down direction by the center partition 4, an
upper partition plate 3 and a lower partition plate 5 are arranged,
respectively. The upper partition plate 3 is arranged on the lower
side with a height L3 from a top portion of the combustion air
inlet opening 8, the lower partition plate 5 is arranged on the
upper side with a height L4 from a bottom portion of the combustion
air inlet opening 8, and these plates are arranged so as to be
parallel to the center partition 4. Although the height L3 and the
height L4 can be arbitrarily determined, they must be set not less
than a length of a blade of the damper 1 in a gas flow
direction.
[0081] Although a length L6 of each of the upper partition plate 3
and the lower partition plate 5 in the gas flow direction can be
also arbitrarily determined, it must be less than a length L5 of
the center partition 4 in order to allow the combustion air to flow
out from the outlet opening 7 into the furnace 40. In this
embodiment, the two partition plates, i.e., the upper partition
plate 3 and the lower partition plate 5 are used as partition
members, but an arbitrary number of the partition plates can be
used.
[0082] FIG. 3 is a front view of the combustion air duct 2 as seen
from the boiler front side (a front furnace wall of the boiler
furnace 40). A curvature radius r2 of a cross-sectional
semicircular portion of the sidewall 55 which is a constituent
member of the combustion air duct 2 must be set larger than a
radius r1 of the combustion air throat 6 (r2>r1). As a result,
an effect of alleviating drift at the combustion air outlet opening
7 can be obtained.
[0083] FIG. 4 is a cross-sectional view taken along a line A-A in
FIG. 3. The combustion air 20 that has flowed into the combustion
air duct 2 from the combustion air (the combustion gas) inlet
opening 8 bends at a right angle, flows through a space between the
combustion air throat 6 and the solid fuel carrying tube 10, and
flows out into the furnace 40 from the combustion air outlet
opening 7. The space between the combustion air throat 6 and the
solid fuel carrying tube 10 is also divided into two parts in the
up-and-down direction by the center partition 4 to reach the
combustion air outlet opening 7. As a result, a combustion air
amount is deviated depending on each of the upper and lower sides
of the combustion air outlet opening 7, and flames are changed to
the upward direction or the downward direction, which is effective
for a reduction in NOx concentration of a nitrogen oxide in the
combustion exhaust gas or control over an amount of heat transfer
to the heat transfer tube (not shown) installed in the boiler
furnace 40.
[0084] The combustion air duct 2 is divided into two parts in the
up-and-down direction by the center partition 4 to reach the
combustion air outlet opening 7. The center partition 4 allows a
combustion air amount to deviate depending on each of the upper and
lower sides of the combustion air outlet opening 7, and flames are
changed to the upward direction or the downward direction in the
boiler furnace 40, which is effective for a reduction in NOx
concentration of a nitrogen oxide in the combustion exhaust gas or
control over an amount of heat transfer to the heat transfer tube
(not shown) installed in the boiler furnace 40.
[0085] In regard to a flow rate of the combustion air in the
combustion air duct 2 divided into the two parts in the up-and-down
direction to sandwich the center partition 4 therebetween, a
deviation between measured pressure values at an upstream-side
pressure detection point 31 and a downstream-side pressure
detection point 30 which are pressure conduits and a deviation
between measured pressure values at an upstream-side pressure
detection point 33 and a downstream-side pressure detection point
34 which are pressure conduits are measured, respectively.
[0086] The upstream-side pressure detection points 31 and 33 as the
pressure conduits configured to measure a flow rate of the
combustion air are disposed in a stagnation region 90 (FIG. 3) of
the combustion air duct 2. Here, the stagnation region 90 means the
region 90 represented by a filled portion in FIG. 2 and a hatched
portion in FIG. 3, it is the region (a space surrounded by the
front and rear walls 56 and 57 and the sidewall 55) restricted by
virtual planes which run through the center of an opening portion
58 and are formed in the vertical direction at tilt angles
.theta..sub.1 and .theta..sub.2 relative to a horizontal plane to
sandwich the center partition 4 with the central axis of the
combustion air throat 6 at an origin, and the upstream-side
pressure detection points 31 and 33 as the pressure conduits can be
arbitrarily disposed in the stagnation region 90. A value of each
of the tilt angles .theta..sub.1 and .theta..sub.2 will be
described later in detail.
[0087] Further, the downstream-side pressure detection points 30
and 34 as the other pressure conduits are respectively installed at
a top portion and a bottom portion of the combustion air throat 6
that are positions at which a difference between the radius r1 of
the combustion air throat 6 and an outlet radius r3 of the solid
fuel carrying tube 10 becomes maximum. The downstream-side pressure
detection points 30 and 34 are disposed on the wall surface of the
combustion air throat 6 shown in FIG. 1 with a longitudinal
direction of each of the downstream-side pressure detection points
30 and 34 being set in the vertical direction so as not to be
affected by a dynamic pressure.
[0088] An upstream-side fluid pressure (a high-pressure side
pressure) of the combustion air flowing through the combustion air
duct 2 is led from each of the upstream-side pressure detection
points 31 and 33, and a downstream-side fluid pressure (a
low-pressure side pressure) of the combustion air is led from each
of the downstream-side pressure detection points 30 and 34. The
upstream- and downstream-side pressure detection points 30 and 31
as the pressure conduits are connected to the differential pressure
detection device 32, the upstream- and downstream-side pressure
detection points 33 and 34 are connected to the differential
pressure detection device 35, and differential pressures obtained
at these points are assigned to the predetermined flow rate
conversion formula (1), thereby calculating a flow rate of the
combustion air.
[0089] Although an arbitrary material or diameter can be adopted
for each of the pressure conduits constituting the upstream- and
downstream-side pressure detection points 30 and 31; and 33 and 34,
a temperature of the combustion air (approximately 300.degree. C.)
must be taken into consideration in regard to the material.
Furthermore, as to the diameter of each of the pressure conduits
constituting the upstream- and downstream-side pressure detection
points 30 and 31; and 33 and 34, clogging or the like by dust
contained in the combustion air must be taken into consideration,
and applying a purge system and the like is also effective.
[0090] FIG. 5 is a schematic view of the furnace 40 using the
burners 44 in which the present invention is incorporated. The wind
box 41 is installed in the furnace 40, and a plurality of two-stage
combustion air (combustion gas) ports 42 and burners 44 to which
the present invention is applied are disposed. A solid fuel
supplied from the outside of the furnace 40 is connected to each
burner 44 from the solid fuel carrying tubes 10.
[0091] FIG. 5 shows an example where the burners 44 are disposed on
a boiler front side of the furnace 40, and the present invention
can be also used for the opposed combustion burners installed on
the boiler front side and a boiler rear side of the furnace 40.
FIG. 5 shows an example where the two-stage combustion air
(combustion gas) ports 42 are installed on two stages, and the
number of stages may be one. The six ports 42 are installed in one
row in FIG. 5, but an arbitrary number can be set.
[0092] Each of FIG. 16 and FIG. 17 shows an example of a
generalized combustion air (combustion gas) flow rate measurement
device. FIG. 16 shows an example of a flow rate measurement device
using a pitot tube 61. The pitot tube 61 is installed in a flow
path 60 with an introduction port of a total pressure detection
hole 62 facing a direction opposite to a fluid flow 22. A fluid
pressure detected by the total pressure detection hole 62 and a
static pressure detection hole 63 is supplied to a differential
pressure detection device 67 and assigned to the predetermined flow
rate conversion formula (1), thereby calculating a flow rate.
[0093] FIG. 17 shows an example of a combustion air (combustion
gas) flow rate measurement device using an orifice. An orifice 64
is disposed in a perpendicular direction relative to a fluid flow
22 in a flow path 60. Pressure conduits 65 and 66 are installed on
the upstream side and the downstream side to sandwich the orifice
64 therebetween. A fluid pressure detected by the pressure conduits
65 and 66 is supplied to a differential pressure detection device
67 and assigned to the predetermined flow rate conversion formula
(1), thereby calculating a flow rate.
[0094] In case of the pitot tube 61, a sufficient straight pipe
length required in the burner 44 cannot be taken, a measurement
accuracy for a fuel flow rate is low, and it may probably be
influenced by drift. Although many pitot tubes 61 may be used to
measure a given cross section in the flow path 60 at a plurality of
positions in order to enhance the flow rate measurement accuracy,
costs are disadvantageously high. Additionally, in case of using
the orifice 64, unwanted pressure loss occurs because of the flow
rate measurement, power for a fan or the like increases in order to
supply the combustion air to each burner 44, which is not
preferable.
[0095] In regard to the generalized flow rate measurement device,
the flow rate measurement device according to the present invention
detects pressure loss of the combustion air (gas) caused due to the
burner configuration by using the upstream- and downstream-side
pressure detection points 30 and 31 and the differential pressure
detection device 32 or the upstream- or downstream-side pressure
detection points 33 and 34 and the differential pressure detection
device 35 respectively and converts the pressure loss into a
combustion air (gas) flow rate, and unwanted pressure loss
concerning the flow rate measurement does not occur. Further, when
each appropriate differential pressure detection locus is selected,
a differential pressure to be detected is not affected by a change
in flow pattern due to an operation of the adjustment damper 1 or
by drift, and hence highly accurate flow rate measurement can be
carried out.
[0096] The drift of the burner combustion air will now be
described.
[0097] FIG. 6 is a view showing the burner 44 from the boiler front
side when an angle .delta. formed between a perpendicular 52 and
the combustion air amount adjustment damper 1 is 30.degree., the
perpendicular 52 being obtained by connecting rotary axes 1a, 1b,
1c, and 1d of a plurality of adjustment dampers 1 which are
arranged in parallel near the combustion air inlet opening 8 of the
combustion air duct 2, and FIG. 7 schematically shows flow rate
deviations at the combustion air outlet opening 7.
[0098] In regard to the combustion air amount adjustment damper 1,
the dampers 1a, 1b, 1c, and 1d are respectively disposed in a space
50a partitioned by the sidewall 55 and the upper partition 3, a
space 50b partitioned by the upper partition 3 and the center
partition 4, a space 50c partitioned by the center partition 4 and
the lower partition 5, and a space 50d partitioned by the lower
partition 5 and the sidewall 55.
[0099] In FIG. 6, the angle .delta. formed between the
perpendicular 52 and an extended line 53 of each blade of the
damper 1 is 30.degree. (a damper opening degree 30.degree.). A flow
21 of the combustion air in the combustion air duct 2 at this time
has such a flow rate that varies as shown in FIG. 7. As shown in
FIG. 7, the flow rate is high in a region B of the combustion air
outlet opening 7, and the flow rate is low in a region A of the
outlet opening 7. The flow rate is low in a region C of the outlet
opening 7, and the flow rate is high in a region D of the outlet
opening 7. This is drift of the combustion air.
[0100] FIG. 8 and FIG. 9 schematically show the burner 44 from the
boiler front side when the angle .delta. formed between the
perpendicular 52 and an extended line 53 of the combustion air
amount adjustment damper 1 is 90.degree. (a damper opening degree
90.degree.) and flow rate deviations at the combustion air outlet
opening 7. When the angle .delta. varies, the flow 21 of the
combustion air differs from that when the damper opening degree is
30.degree. in FIG. 6. Therefore, the flow rate deviations at the
combustion air outlet opening 7 are different from those when the
damper opening degree is 30.degree., the flow rate deviation is
high in each of the region B of the combustion air outlet opening 7
and the region C of the outlet opening 7, and the flow rate
deviation is low in the region A of the outlet opening 7 and the
region D of the outlet opening 7.
[0101] Since the damper 1 is automatically controlled so that a
burner air ratio can have a predetermined value, it is desirable to
install the upstream-side and downstream-side pressure detection
points 30 and 31; and 33 and 34 as the pressure conduits at
positions where these points are not affected by the angle .delta.
formed between the perpendicular 52 and the damper 1. The
upstream-side pressure detection points 30 and 31; and 33 and 34
must be installed in the stagnation region 90 (FIG. 2, FIG. 3) that
is not affected by a contracted flow of each damper 1.
[0102] FIG. 10 shows a result of examination obtained when a
full-size model was used. An abscissa represents an opening degree
(%) of the combustion air amount adjustment damper 1 relative to
the perpendicular 52 in FIG. 6 and FIG. 8, and an ordinate
represents a ratio (dimensionless) of a static pressure relative to
burner pressure loss when the flow rate is unchanged. When the
angles .theta..sub.1 and .theta..sub.2 assumed to represent the
range of the stagnation region 90 shown in FIG. 3 fall within the
range of .theta..sub.1=.theta..sub.2.ltoreq.15.degree., a value of
the static pressure/the burner pressure loss is substantially fixed
in the range of the actually used angles .theta..sub.1 and
.theta..sub.2. That is because a flow velocity is substantially
zero and the range that the angles .theta..sub.1 and .theta..sub.2
meet .theta..sub.1=.theta..sub.2.gtoreq.15.degree. is considered as
the stagnation region 90. Therefore, the upstream-side pressure
detection points 31 and 33 can be installed at arbitrary positions
on the sidewall which is a constituent member of the combustion air
(combustion gas) duct 2 included in this range.
[0103] Positions of the downstream-side pressure detection points
30 and 34 as the pressure conduits will now be examined. The
downstream-side pressure detection points 30 and 34 must be
installed in a region where these points are not affected by the
drift of the combustion air (gas) shown in FIG. 6 to FIG. 9.
[0104] FIG. 11 is a schematic view showing installing positions 81
to 83 for the downstream-side pressure detection point 30 in the
central axis direction of the combustion air throat 6, and FIG. 12
is a schematic view showing installing positions 84 to 87 for the
downstream-side pressure detection point 30 in the circumferential
direction of the throat 6. The installing positions 81 to 83 for
the downstream-side pressure detection point (FIG. 11) are set on
the top portion of the combustion throat 6 where the following
expression becomes maximum in the radial direction, the installing
position 82 for the downstream-side pressure detection point is set
at a position with an intermediate length (0.5.times.L.sub.10) of a
length L.sub.10 of the throat 6, the installing position 81 for the
downstream-side pressure detection point is set on the downstream
side of the throat 6, and the installing position 83 for the
downstream-side pressure detection point is set on the upstream
side of the throat 6.
[0105] (The radius r1 of the throat 6)--(the radius r3 of the fuel
nozzle 10)
Further, as shown in FIG. 12, each of the downstream-side pressure
detection point installing positions 84, 85, 86, and 87 is set at
an intermediate position of the length of the throat 6 in the
central axis direction, each of the downstream-side pressure
detection point installing positions 85 and 86 has a tilt angle
.theta..sub.3=2.degree. in the radial direction of the throat 6
with respect to a perpendicular running through the central axis of
the throat 6, and each of the installing positions 84 and 87 for
the downstream-side pressure detection point has the tilt angle
.theta..sub.3=20.degree. in the radial direction of the throat 6
with respect to the same.
[0106] Each of FIG. 13 and FIG. 14 shows a result of examination
obtained when a full-size model was used. An abscissa in each of
FIG. 13 and FIG. 14 represents an angle (a damper opening degree)
formed between the perpendicular 52 and the combustion air
(combustion gas) amount adjustment damper 1 in FIG. 6 and FIG. 8,
and an ordinate in the same represents static pressure/burner
pressure loss when the flow rate is unchanged.
[0107] As shown in FIG. 13, at each of the installing positions 81
and 82 for the downstream-side pressure detection point in the
central axis direction of the throat 6, the static pressure is
substantially fixed in the damper opening degree range to be used.
As shown in FIG. 14, at each of the installing points 82, 85, and
86 for the downstream-side pressure detection point in the
circumferential direction of the throat 6, the static
pressure/burner pressure loss is substantially fixed in the range
that is approximately 10 to 80% of the damper opening degree range
to be used. Although the static pressure/burner pressure loss
slightly differs in the damper opening degree range to be used, a
differential pressure detected by each of the burner differential
pressure detection devices 32 and 35 shown in FIG. 1 is 100 Pa or
more, and hence this differential pressure only slightly affects
accuracy of a flow rate measurement.
[0108] As described above, assuming that PL is an installing
position, in regard to the central axis direction of the throat
portion 6, the installing position of each of the downstream-side
pressure detection points 30 and 34 of the burner shown in FIG. 1
is set in the range of 0.5 L.sub.10.ltoreq.PL.ltoreq.L.sub.10 on
the downstream side from a center point of the length L of the
throat 6. In regard to the circumferential direction of the throat
6, each installing position is assumed to be set in the range of
0.degree..ltoreq..theta..sub.3=.theta..sub.4.ltoreq.2.degree. shown
in FIG. 12.
[0109] Furthermore, FIG. 15 shows a view for explaining solid fuel
measuring means, and the solid fuel is pulverized by a solid fuel
pulverization device 70 (e.g., a vertical mill) until a
predetermined particle diameter is obtained, and the fuel is
carried to each burner 44 by a carrier gas through the solid fuel
carrying tube 10. The solid fuel carrying tube 10 comprises solid
fuel measuring means 71 (for example, there is a measuring
instrument which is of a static charge type or a micro wave type
and so forth). Therefore, flow rates of the solid fuel that flows
into the plurality of solid fuel burners 44 in the combustion
device are individually adjusted and measured by the solid fuel
flow rate measuring means 71, the control device 37 adjusts an
opening degree of the flow rate adjusting means 1 for the
combustion gas and individually controls the flow rates of the
combustion gas based on the combustion gas flow rates detected by
the differential pressure detection devices 32 and 35 of the
respective solid fuel burners 44 in accordance with a change in
measured solid fuel flow rates, and hence it is possible to rapidly
cope with a change in solid fuel flow rate of each burner 44.
[0110] Moreover, as to control over a burner load, adjusting the
combustion gas alone can suffice, and the adjusting means and
others can have simpler configurations than those in case of using
the solid fuel that is carried by the carrier gas. Additionally,
when a combustion gas amount is deviated depending on each of the
upper and lower sides of each burner 44 in the furnace 40, flames
can be changed to the upward direction or the downward direction,
and NOx concentration of a nitrogen oxide in the combustion exhaust
gas can be reduced, or an amount of heat transfer to the heat
transfer tube (not shown) installed in the boiler furnace 40 can be
effectively controlled. Further, since the combustion air outlet
opening 7 is divided into the two parts in the up-and-down
direction by the center partition 4, the combustion air amount is
deviated depending on each of the upper and lower sides of the
combustion air outlet opening 7, and the flames are changed to the
upward direction or the downward direction in the boiler furnace
40, thereby effectively enabling a reduction in NOx concentration
of a nitrogen oxide in the combustion exhaust gas or control over
an amount of heat transfer to the heat transfer tube (not shown)
installed in the boiler furnace 40.
[0111] In this embodiment, the burner configuration has been
explained with use of the fuel nozzle 10 having a flat transverse
cross section. In the present invention, the above-described
measuring technique can be used with respect to the fuel nozzle 10
having a circular transverse cross section without being restricted
to the flat shape.
[0112] When the fuel nozzle 10 has the circular transverse cross
section, since the combustion air outlet opening 7 has a concentric
cross-sectional shape formed of the fuel nozzle 10 and the
combustion air throat 6, the drift is hardly produced as compared
with the example adopting the flat shape.
[0113] However, the combustion air that has flowed in from the
combustion air inlet opening 8 is not necessarily uniformly
discharged from the combustion air throat 6 having the concentric
shape in the combustion air duct 2.
[0114] An example where the fuel nozzle 10 is the fuel nozzle 10
having the circular transverse cross-sectional shape will be
assumed and described with reference to FIG. 8. A flow of the air
that has flowed in from the combustion air inlet opening 8 is
disturbed by the adjustment damper 1. When the angle .delta. formed
between the perpendicular 52 in FIG. 6 and the extended line 53 of
the blade of the damper 1 is 30.degree., an air current flows
downward along the vertical direction, and hence an air flow rate
from the combustion air outlet opening 7 close to the downstream of
the adjustment damper 1 increases.
[0115] As described above, the air flow rate at the combustion air
outlet opening 7 is deviated when the transverse cross-sectional
shape of the fuel nozzle 10 is either the flat shape or the
circular shape.
[0116] A description will now be given as to installing positions
of the upstream-side pressure detection points (although not shown,
they correspond to the upstream-side pressure detection points 31
and 33 of the fuel nozzle 10 having the flat transverse
cross-sectional shape in FIG. 1) of the fuel nozzle 10 having the
circular transverse cross-sectional shape. As described above, the
circular fuel nozzle 10 is affected by the drift due to an opening
degree of the damper 1 like the flat fuel nozzle 10.
[0117] Since the installing positions PL for the upstream-side
pressure detection points are the same as those of the flat fuel
nozzle 10 in FIG. 11, a description will be given with reference to
FIG. 11. To avoid an influence of an air contracted flow at the
time of flowing from the combustion air duct 2 toward the
combustion air throat 6 shown in FIG. 11, the range of 0.5
L.sub.10.ltoreq.PL.ltoreq.L.sub.10 in the air flowing direction is
preferable with respect to the length L.sub.10 of the throat 6, and
the range of
0.degree..ltoreq..theta..sub.3=.theta..sub.4.ltoreq.2.degree. is
preferable for the installing positions .theta..sub.3 and
.theta..sub.4 in the circumferential direction as shown in FIG. 12.
That is because the static pressure at the upstream-side pressure
detection points is hardly changed in the adopted damper opening
degree range. Therefore, in case of the fuel nozzle 10 having the
circular transverse cross-sectional shape, it is desirable to
install the upstream-side pressure detection points in the same
range as the flat fuel nozzle 10.
[0118] Furthermore, the downstream-side pressure detection points
(which correspond to the downstream-side pressure detection points
30 and 34 installed on the flat fuel nozzle 10 shown in FIG. 10,
and hence a description will be given with reference to FIG. 1) are
arranged on the top portion wall surface and the bottom portion
wall surface of the combustion gas throat 6. The top portion of the
combustion gas throat 6 that is a position where the
downstream-side pressure detection point is arranged is determined
as a reference, and the detection points are present in the range
of .+-.2.degree. in the circumferential direction (see FIG. 12) on
the downstream side that is 1/2 of the throat length of the
combustion gas throat 6 along the central axis direction (see FIG.
11). Moreover, since the downstream-side pressure detection points
are arranged on the top portion wall surface and the bottom portion
wall surface of the combustion gas throat 6, the combustion gas
flow rate can be measured without being affected by the drift of
the combustion gas, and the flow rate of the fuel gas can be highly
accurately measured.
[0119] Additionally, in case of the fuel nozzle 10 having the
circular transverse cross section, although not shown, differential
pressure detection devices corresponding to the differential
pressure detection devices 32 and 35 shown in FIG. 1 are provided,
and a control device that converts values of pressure differences
between the upstream-side pressure detection points and the
downstream-side pressure detection points into the flow rates of
the combustion gas and adjusts an amount of combustion air flowing
into the combustion air duct based on a damper operation is also
provided.
[0120] An example where the center partition 4 of a burner
comprising the fuel nozzle 10 having the flat or circular
transverse cross section is not provided will now be described.
[0121] In the foregoing embodiment, the combustion air duct 2 is
completely divided into two parts in the up-and-down direction, and
the combustion air measurement points must be installed at the two
positions on the combustion air duct 2 divided into the upper and
lower sides. However, when the center partition 4 is not provided,
measuring points corresponding to the pressure detection points 30,
31, 33, and 34 in FIG. 1 are narrowed down to one position. The
installing position for the pressure detection point should be set
to a position that is not affected by the drift of the damper
1.
[0122] Here, an influence of the drift of the combustion air due to
an opening degree of the damper 1 is assumed. The installing
position of the downstream-side pressure detection point (which is
not shown and corresponds to the downstream-side pressure detection
point 30 or 34 in FIG. 1) will be examined. The left side of the
combustion air outlet opening 7 like the region (B) or (C) in FIG.
9, namely, the combustion air outlet opening 7 on the side close to
the combustion air inlet opening 8 is affected by the drift due to
the damper 1, which is inappropriate. On the other hand, on the
right side of the combustion air outlet opening 7, i.e., the side
distanced from the combustion air inlet opening 8 (the region (A)
or (D)), the air flow rate differs depending on an opening degree
of the damper 1 due to an influence of a flow rate deviation in the
region (B) or (C). On the top portion of the combustion air throat
6, there is no flow rate deviation due to the damper 1, the upper
and lower sides are less unbalanced, and hence the flow rate
deviation is small irrespective of the opening degree of the damper
1.
[0123] Therefore, installing the downstream-side pressure detection
point (not shown) on the top portion or the bottom portion of the
combustion air throat 6 can suffice. Considering the maintenance or
ease of installation, it is good to install this detection point on
the top portion.
[0124] Moreover, as the position at which the upstream-side
pressure detection point (not shown) is installed, one position can
suffice. When the center partition 4 is present, the stagnation
space 90 (see FIG. 2) in the combustion air duct 2 is installed on
the downmost-stream portion on each of the upper and lower sides.
Even if there is no center partition 4, a large part of the
combustion air flows out to the throat 6 before reaching the
downmost-stream portion of the combustion air duct 2, and hence the
stagnation region where there is almost no flow of the combustion
air is produced. In the stagnation region, a static pressure is
stable irrespective of an opening degree of the damper 1.
Therefore, one downstream-side pressure detection point is
installed in a region where each of the pressure detection points
30 and 34 is disposed on the downmost-stream portion of the
combustion air duct 2 in FIG. 1.
[0125] When the combustion air duct 2 is divided into two parts in
the up-and-down direction by the center partition 4, a duct center
portion (a top part of a semicircular portion of the combustion air
duct 2) at which the center partition 4 and the combustion air duct
2 cross each other is provided at the farthest position from the
combustion air inlet opening 8, and a static pressure is in the
most stable state in the stagnation region. Therefore, it is
desirable to provide the upstream-side detection point on the top
part (a position corresponding to each of the upstream-side
pressure detection points 31 and 33 in FIG. 1) of the semicircular
portion of the combustion air duct 2.
REFERENCE SIGNS LIST
[0126] 1 combustion air flow rate adjustment damper [0127] 2
combustion air duct [0128] 3 upper partition [0129] 4 partition
wall (center partition) [0130] 5 lower partition [0131] 6
combustion air throat [0132] 7 combustion air outlet opening [0133]
8 combustion air inlet opening [0134] 10 solid fuel carrying tube
(fuel nozzle) [0135] 11 carried air/fuel outlet opening 20 to 22
air flow [0136] 31, 33 upstream-side pressure detection point
[0137] 30, 34 downstream-side pressure detection point [0138] 32,
35 differential pressure detection device [0139] 37 control device
[0140] 40 furnace [0141] 41 wind box [0142] 42 two-stage combustion
air port [0143] 44 burner [0144] 50 space formed by partitioning
the combustion air duct [0145] 52 perpendicular [0146] 53 extended
line of a blade of the damper [0147] 55 sidewall [0148] 56, 57
front wall [0149] 58 opening for connecting a combustion air (gas)
throat [0150] 59 opening for connecting a combustion carrying tube
[0151] 60 flow path [0152] 61 pitot tube [0153] 62, 63, 65, 66
pressure conduit [0154] 64 orifice [0155] 67 differential pressure
detection device [0156] 70 solid fuel pulverization device [0157]
71 solid fuel flow rate measuring means [0158] 81 to 87 installing
position for the downstream-side pressure detection point [0159] 90
stagnation region
* * * * *