Note: Descriptions are shown in the official language in which they were submitted.
CA 02719040 2010-09-20
SPECIFICATION
SOLID FUEL BURNER, COMBUSTION APPARATUS USING SOLID FUEL BURNER
AND METHOD OF OPERATING THE COMBUSTION APPARATUS
Technical Field
The present invention relates to a solid fuel burner
suitable for pulverizing a solid fuel, carrying by gas flow,
performing suspension burning, and a combustion apparatus using
the solid fuel burner and a method of operating the same.
Background Art
In combustion apparatuses (boilers, etc.), the steam
temperature and pressure are increased and a reheating cycle
is used for high efficiency. Normally, water supplied to a
boiler passes through a heat transfer tube installed along a
furnace wall surface and vaporizes, and passes through a
superheater, becomes main steam and drives a steam turbine,
and then becomes reheating steam and passes through a reheater,
and is reheated and drives the steam turbine again, passes
through a condenser and becomes water, and is supplied to the
furnace again.
Thus, when the s team passes through a complicated fluid
1
CA 02719040 2010-09-20
channel, it is important to obtain a prescribed heat-transfer
amount at each heat-transfer portion . To obtain the prescribed
heat-transfer amount, the temperature and flow rate of
combustion gas at each heat transfer portion have to be
controlled.
As a method of controlling the temperature and flow rate
of the combustion gas, there is a conventional method in which
a temperature distribution inside a furnace is controlled by
vertically changing the ejection direction of fuel from the
burner (Prior art document 1). There is also known a method
in which on the downstream portion of a furnace, the combustion
gas passage is divided, and the heat-transfer amount of the
heat transfer portion installed in each combustion gas passage
is adjusted by controlling the combustion gas amount flowing
in each passage by using a means such as a damper.
Prior Art Document
U.S. Patent Specification No. 6439136 (Fig. 3)
Summary of the Invention
Problems to be solved by the Invention
In the conventional techniques described above, the
direction of the fuel nozzle has to be mechanically changed
2
CA 02719040 2010-09-20
,
i
when changing the ejection direction of fuel from the burner.
Therefore, there was a problem of an increase in size of a drive
mechanism. Especially, when a solid fuel is used as a fuel,
wearing of a member for mechanically changing the direction
of the fuel nozzle and ash adhesion must be taken into
consideration to mechanically change the direction of the fuel
nozzle. Moreoverõ the portion facing the furnace have to
be provided with a drive mechanism to change the fuel ejection
direction from the fuel nozzle, and thermal deformation of the
drive mechanism must be taken into consideration as well.
Ash adhesion in the combustion gas in the combustion gas
passage for supplying fuel to the fuel nozzle must be taken
into consideration sufficiently when the gas passage is divided
and the combustion gas amount flowing in each gas passage is
changed. Further, partitions are provided, and accordingly,
the passages are narrowed, so that installation of the heat
transfer portions must be sufficiently considered.
An object of the present invention is to provide a solid
fuel burner which can keep constantly the combustion gas
temperature at a furnace outlet, the temperatures of a heat
transfer tube installed on a furnace wall surface and a heat
transfer tube provided in a flue on the downstream side thereof,
and the temperature of a fluid flowing in the heat transfer
3
CA 02719040 2010-09-20
tubes by changing a flame forming position inside the furnace
by controlling the direction of the fuel to be ejected to the
furnace from the solid fuel burner vertically or horizontally
by an air flow rate flowing in the air nozzle with a comparatively
simple structure, and a combustion apparatus using the solid
fuel burner and a method of operating the same.
Means for Solving the Problems
To achieve the object of the present invention, according
to the present invention, a solid fuel burner includes: a fuel
nozzle which ejects a mixture fluid of a solid fuel and its
conveying gas, and at least one air nozzle which is disposed
on the outer side of the fuel nozzle and ejects combustion air,
wherein at least one air nozzle is formed to be annular on the
outer periphery of the fuel nozzle, and the internal air passage
is divided into a plurality of regions in the circumferential
direction of the nozzle by an obstacle, and the solid fuel burner
has means of regulating a flow rate for regulating a flow rate
in at least one of the plurality of regions.
By dividing the air nozzle into a plurality of regions
and changing the air flow rates in the respective regions,
deviations of flow rate and momentum can be generated, in the
flow ejected from the air nozzle, in the circumferential
direction of the fuel nozzle.
4
CA 02719040 2010-09-20
For example, when the air volume flowing in the air nozzle
on the lower side of the fuel nozzle is increased, the flow
rate and flow velocity of air increase and the momentum increases
at the nozzle outlet . At this time , ej ected air involves ambient
gasses and a negative pressure is generated in the region on
the lower side of the fuel nozzle. Therefore, in the pressure
distribution in the circumferential direction around the fuel
nozzle, the negative pressure increases in the region on the
lower side of the fuel nozzle. Accordingly, depending on the
pressure distribution, a downward force is applied to the fuel
ejected from the fuel nozzle into the furnace, and the fuel
flows while being deflected downward, and a flame is formed
at a lower portion inside the furnace than usual.
Therefore, the temperature distribution inside the
furnace is biased to the lower side , the amount of heat absorption
in the furnace increases, and the heat absorption in a heat
transfer tube provided in a flue on the downstream side of the
furnace can be reduced.
On the contrary, when the air flow rate in the air nozzle
on the upper side of the fuel nozzle is increased, a flame is
formed inside the furnace at an upper portion than usual and
the temperature distribution inside the furnace is biased to
the upper side than usual, and the amount of heat absorption
CA 02719040 2010-09-20
in the furnace is reduced and the heat absorption in the heat
transfer tube provided on the downstream portion of the furnace
can be increased.
When the air nozzle is divided into a plurality of regions
in the circumferential direction of the fuel nozzle as described
above, an obstacle connected to the partition walls have to
be provided in the radial direction of the air nozzle to connect
the inner peripheral side partition wall and the outer peripheral
side partition wall. However, in the solid fuel burner, the
distance between the inner peripheral side partition wall and
the outer peripheral side partition wall of the air nozzle may
change during the operation of a combustion apparatus (boiler,
etc.) due to an influence of thermal expansion, etc. For example,
normally, the outer peripheral side partition wall of the passage
on the outermost peripheral side of the solid fuel burner is
formed of a partition wall or a water wall of a furnace body
constituting a furnace.
On the other hand, the inner peripheral side partition
wall of the passage on the outermost peripheral side of the
solid fuel burner is connected to a wind box to which the fuel
nozzle or the burner is connected. The partition wall or water
wall of the furnace body constituting the furnace is different
in temperature from that of the fuel nozzle and the wind box
6
CA 02719040 2010-09-20
during the operation of the combustion apparatus (boiler, etc.),
so that they are different in ratio of thermal expansion.
Therefore, in the solid fuel burner, the relative positions
of the partition wall or water wall of the furnace body on the
outer peripheral side of the air nozzle or the partition wall
connected thereto (the partition wall of the furnace body side)
and the partition wall (the partition wall of the fuel nozzle
side) connected to the fuel nozzle or the wind box on the inner
peripheral side change according to temperature. Therefore,
it is difficult to divide the passage in the circumferential
direction by providing an obstacle in the radial direction
connecting the partition wall of the inner peripheral side and
the partition wall of the outer peripheral side constituting
the air nozzle.
Therefore, in the present invention, as a method of
dividing the inside of the air nozzle into a plurality of regions
in the circumferential direction (the direction crossing the
gas flow), the structure shown as any of the following (A) to
(C) was used.
(A) A structure has an obstacle which divides the inside of
an air nozzle formed annularly into a plurality of regions in
the circumferential direction, and the obstacle is connected
to the partition wall of the inner peripheral side of the air
7
CA 02719040 2010-09-20
,
=
nozzle, and is not connected to the partition wall of the outer
peripheral side. The structure has means of regulating a flow
rate for regulating the flow rate in at least one of the plurality
of regions of the air nozzle, and a flow rate deviation is
generated in the circumferential direction of the fuel nozzle
in the flow ejected from the air nozzle.
In this case, apart of the air passes through the clearance
between the obstacle and the partition wall of the outer
peripheral side, however, most of the air remains in the same
region. In the pressure distribution in the circumferential
direction around the fuel nozzle caused by involving ambient
gasses in the air flow ejected from the air nozzle into the
furnace, a deviation is generated according to the flow rate
deviation. Therefore, the fuel ejected from the fuel nozzle
flows while deflecting to the side with a larger air volume
ejected from the air nozzle.
(B) A structure has an obstacle which divides the inside of
the air nozzle formed annularly into a plurality of regions
in the circumferential direction, and the obstacle is connected
to the partition wall of the outer peripheral side of the air
nozzle, and is not connected to the partition wall of the inner
peripheral side. The structure has means of regulating a flow
rate for regulating the flow rate in at least one of the plurality
8
CA 02719040 2010-09-20
,
of regions of the air nozzle, and a flow rate deviation is
generated in the circumferential direction of the fuel nozzle
in the flow ejected from the air nozzle.
In this case, apart of the air passes through the clearance
between the obstacle and the partition wall of the inner
peripheral side, however, most of the air remains in the same
region. Therefore, like the method (A), the fuel ejected from
the fuel nozzle flows while deflecting to the side with a larger
air volume ejected from the air nozzle.
(C) A structure has an obstacle which divides the inside of
the air nozzle formed annularly into a plurality of regions
in the circumferential direction, and the obstacle includes
an obstacle which is connected to the partition wall of the
outer peripheral side of the air nozzle and is not connected
to the partition wall of the inner peripheral side, and an
obstacle which is connected to the partition wall of the inner
peripheral side of the air nozzle and is not connected to the
partition wall of the outer peripheral side. The structure
has means of regulating a flow rate for regulating the flow
rate in at least one of the plurality of regions of the air
nozzle, and a flow rate deviation is generated in the
circumferential direction of the fuel nozzle in the flow ejected
from the air nozzle.
9
CA 02719040 2010-09-20
,
In this case, apart of the air passes through the clearance
between the obstacle and the partition wall of the inner or
outer peripheral side, however, most of the air remains in the
same region. Therefore, like the methods (A) and (B) , the fuel
ejected from the fuel nozzle flows while deflecting to the side
with a larger air volume ejected from the air nozzle.
The obstacles described in (A) to (C) above which divides
the inside of the air nozzle into a plurality of regions in
the circumferential direction are not limited to a configuration
in which combustion air passes through the clearance between
the obstacles and the air nozzle wall surface shown in Fig.
8 to Fig. 10, but may have a configuration in which the obstacle
forms a closed space opened only at an inlet and an outlet in
the combustion air flow direction, and combustion air is made
to flow inside the closed space from the burner upstream side
to the furnace side (The air nozzles for the combustion air
may be called as divided air nozzles) . A specific example of
that is the tertiary air nozzles 12 and 13 formed by connecting
and unifying two obstacles connected to the inner peripheral
wall of the air nozzle shown in Fig. 3 and Fig. 4, and these
are an embodiment of the air nozzle described in (A) above.
Further, divided air nozzles formed by connecting and unifying
two obstacles connected to the outer peripheral wall of the
CA 02719040 2010-09-20
air nozzle described in (B) are also included in the scope of
the present invention.
By regulating the air flow rate flowing in at least one
air nozzle of the divided air nozzles disposed on the outer
side of the fuel nozzle by means of regulating a flow volume,
a flow rate deviation is generated in the circumferential
direction of the fuel nozzle in the flows ejected from the divided
air nozzles. Therefore, the fuel ejected from the fuel nozzle
flows while deflecting to the side with a larger air volume
ejected from the air nozzle.
By disposing the divided air nozzles positioned on the
outer side of the fuel nozzle on the upper and lower sides of
the fuel nozzle and regulating the flow rates and jet flow
velocities of air ejected from the respective upper and lower
air nozzles to the inside of the furnace, the momentum obtained
as a product of the air flow rate and the jet flow velocity
becomes different in the vertical direction of the burner outlet,
and the air flow rates ejected from the upper and lower air
nozzles of the burner can be individually controlled in the
vertical direction inside the furnace at the burner outlet.
Therefore, the temperature distribution inside the furnace
differs in the vertical direction of the burner outlet, and
the heat absorption in the furnace and the heat absorption in
11
CA 02719040 2010-09-20
,
a heat transfer tube provided in a flue on the downstream side
of the furnace change.
Thus, by the divided air nozzles provided on the upper
and lower sides of the fuel nozzle, the controllability of the
air flow rate in the burner is enhanced.
Further, by combination use of the divided air nozzles
shown in Fig. 3 and Fig. 4 and an air nozzle to which two obstacles
are not connected each other (not the divided ones) shown in
Fig. 8 to Fig. 10, deviations in air flow rate and momentum
can be encouraged.
Moreover, the configuration may be such that, in addition
to the annular air nozzle, an air nozzle is disposed on the
outer side of the annular nozzle and an obstacle which divides
the inside of the annular air nozzle into a plurality of regions
in the circumferential direction is disposed, and means of
regulating a flow rate for regulating the air volume to be ejected
from the air nozzle on the outer side of the annular nozzle
is provided.
Also, the solid fuel burner of the present invention may
also be configured so that the fuel nozzle outlet is shaped
into a wide-width nozzle which is relatively short in one
direction and is relatively long in the opposite direction at
the fuel nozzle outlet (The length in one radial direction of
12
CA 02719040 2010-09-20
the section in a direction crossing the passage of the fuel
nozzle is longer than that in the other radial direction of
the two directions orthogonal to each other), and an inner
peripheral partition wall constituting at least one passage
of the air nozzle also differs in length in the two directions
orthogonal to each other, and the outer peripheral partition
wall does not differ in length in the two directions orthogonal
to each other.
By shaping the fuel nozzle outlet into the wide-width
nozzle shape, the fuel ejected from the fuel nozzle easily
scatters in the long side direction. For example, when the
long side direction is orthogonal to the gas flow direction
in the combustion apparatus (furnace), by scattering the fuel
inside the furnace, the space inside the furnace can be
effectively utilized and the fuel retention time in the furnace
can be made longer than conventional method. Therefore, the
discharge amount of nitrogen oxide (N0x) can be reduced, and
unburned fuel can also be reduced.
Further, by adopting the configuration in which the fuel
nozzle outlet is formed into a wide-width nozzle shape, and
the inner peripheral partition wall constituting at least one
air passage in the air nozzle differs in length in the long
side direction and the short side direction, and the outer
13
CA 02719040 2010-09-20
peripheral partition wall does not differ in length in the two
directions orthogonal to each other, the thickness in one of
the two directions orthogonal to each other of the section in
a direction crossing the passage of the air nozzle increases.
Therefore, when an air flow rate deviation is generated at the
thicker portion, due to the large air flow rate, according to
the deviation in air flow rate ejected from the air nozzle into
the furnace, the fuel jet flow from the fuel nozzle can be easily
guided.
In particular, in a combustion apparatus (furnace) in
which combustion gas flows in the vertical direction, the outlet
of the fuel nozzle of the solid fuel burner is formed into a
shape with a longer side set in the horizontal direction, that
is, a wide-width nozzle shape, and the thickness of the air
nozzle described above is increased in the vertical direction,
and a deviation in fuel flow rate is generated in the vertical
direction, accordingly, the direction of the fuel jet flow from
the solid fuel burner can be changed in the vertical direction.
At this time, the retention time of combustion gas flowing in
the combustion apparatus (furnace) changes, so that the heat
transfer amount in the combustion apparatus changes, and the
temperature of the combustion gas at the outlet can be changed.
Further, the solid fuel burner of the present invention
14
CA 02719040 2010-09-20
,
is preferably provided with a ring for stabilizing flame as
an obstacle for obstructing a flow of a mixture fluid flowing
in the fuel nozzle or a flow of air flowing in the air nozzle,
at the tip end of the outer peripheral side partition wall of
the fuel nozzle or the tip end of the inner peripheral side
partition wall of the air nozzle which includes the fuel nozzle.
By providing a ring for stabilizing flame which becomes
an obstacle for flows of fuel and air ejected from respective
nozzles on the partition wall between the fuel nozzle and the
air nozzle, a negative pressure region is formed on the
downstream of the ring for stabilizing flame by a pressure of
the fluid flowing around thereof. In this negative pressure
region, a circulation flow in a direction (from the downstream
to the upstream) opposite to the direction ejected from each
nozzle is formed.
A high-temperature gas generated by combustion is returned
from the downstream to the circulation flow, retained, and
quickens ignition of fuel particles flowing around. The fuel
jet flow ignited by the circulation flow flows while deflecting
in the vertical direction due to air flow rate differences among
the individual regions of the air nozzle, so that the forming
position of flame can be changed. In particular, flame ignition
is stably performed near the circulation flow at the fuel nozzle
CA 02719040 2010-09-20
outlet and only the ignition forming direction can be changed,
so that the temperature distribution in the furnace, the heat
absorption in the furnace, and the heat absorption in a heat
transfer tube provided in a flue on the downstream side of the
furnace can be easily controlled.
The solid fuel burner of the present invention is
preferably provided with the guide member that deflects the
flow to the outer peripheral side (in the direction away from
the fuel nozzle) on the outermost peripheral air nozzle outlet.
As a method of reducing nitrogen oxide (N0x) which is
generated when burning the solid fuel, a method in which mixture
of the fuel and air near the burner is suppressed and the fuel
is burned under a condition with air shortage near the burner
is available. In a burner using this method, when the air flow
rate in the air nozzle is reduced, air is accompanied by the
fuel jet flow and flows to the central axis side, and mixture
with the fuel maybe quickened. However, by providing a guide
member for guiding the air ejection direction toward the outer
peripheral side on the tip end of the air nozzle, the air direction
ejected from the air nozzle is fixed to the outer peripheral
side. Therefore, even when the air flow rate is particularly
reduced, the mixture of the fuel and air near the burner can
be suppressed.
16
CA 02719040 2010-09-20
The guide member preferably has a projection area in the
burner axial direction occupying not less than 90% of the
sectional area in the direction across the passage at the
smallest portion (throat portion) of the air nozzle. By
providing the projection area not less than 90%, the flow
direction is guided to the outer periphery by the guide member.
Further, a flow velocity component radially outward of
the fuel nozzle is induced in the air ejected from the air nozzle
by the guide member. The flow of air ejected from the air nozzle
into the furnace comes to easily involve ambient gasses radially
outward, so that the gas pressure in the region between the
air nozzle and the fuel nozzle becomes lower than the case where
the guide member is not provided. Therefore, when a flow rate
deviation in the circumferential direction of the fuel nozzle
is generated in the air ejected from the air nozzle, the
deflection of the fuel ejected from the fuel nozzle increases.
According to the requirements of the present invention,
by regulating the air flow rates in the air nozzle, the forming
position of flame can be controlled in the vertical direction
or the horizontal direction inside the furnace at the fuel nozzle
outlet. At this time, the air flow rates in the air nozzle
of the solid fuel burner are preferably individually controlled
in the vertical direction based on the combustion gas temperature
17
CA 02719040 2015-06-25
75870-19
at the furnace outlet, the temperature of a heat transfer tube
installed on the furnace wall surface, the temperature of a
fluid flowing in the heat transfer tube, the temperatures of
the heat transfer tubes provided inside the furnace and a flue
on the downstream side of the furnace or the temperatures of
fluids flowing in the heat transfer tubes.
An aspect of the invention relates to a solid fuel
burner which is provided on a furnace wall comprising: a fuel
nozzle which ejects a mixture fluid of a solid fuel and a
conveying gas into the furnace; and at least one air nozzle
which is disposed on the outer side of the fuel nozzle and
ejects combustion air into the furnace, wherein (A) the air
nozzles are formed to be annular on the outer periphery of the
fuel nozzle, (B) an internal air passage of the air nozzles is
divided into a plurality of regions in the circumferential
direction of the air nozzle by obstacles which are for dividing
the internal air passage of the air nozzle into a plurality of
regions in the circumferential direction of the air nozzles,
and are (a) obstacles connected to only an inner peripheral
side partition wall constituting the air nozzles and not
connected to an outer peripheral side partition wall of the air
nozzles, (b) obstacles connected to only an outer peripheral
side partition wall of the air nozzles and not connected to an
inner peripheral side partition wall of the air nozzles or (c)
double obstacles formed by combining obstacles connected to
only the inner peripheral side partition wall and not connected
to an outer peripheral side partition wall of the air nozzles
and obstacles connected to only the outer peripheral side
partition wall and not connected to an inner peripheral side
partition wall of the air nozzles, and (C) the solid fuel
18
CA 02719040 2015-06-25
75870-19
burner has regulators for regulating an air flow rate flowing
in at least one of the plurality of divided regions to generate
deviations of flow rate in the flow ejected from the air nozzle
in the circumferential directions.
Another aspect of the invention relates to a
combustion apparatus comprising a furnace having the solid fuel
burner as defined above installed on a furnace wall, wherein
the combustion apparatus includes a control device which
changes an air flow rate flowing in at least one of the
plurality of regions of the air nozzles of the solid fuel
burner, whose inside is divided by obstacles in the
circumferential direction of the fuel nozzle into the plurality
of regions, based on a combustion gas temperature at the .
furnace outlet, a temperature of a heat transfer tube installed
on a furnace wall surface, a temperature of a fluid flowing in
the heat transfer tube, temperatures of heat transfer tubes
provided in the furnace and a flue on the downstream side of
the furnace or temperatures of fluids flowing in the heat
transfer tubes.
Another aspect of the invention relates to a method
of operating a combustion apparatus comprising a furnace
including the solid fuel burner as defined above installed on a
furnace wall, wherein a deviation is generated in the
circumferential direction of the fuel nozzle in an air volume
flowing in the air nozzles of the solid fuel burner based on a
combustion gas temperature at the furnace outlet, temperatures
of heat transfer tubes installed on a furnace wall surface, a
temperature of a fluid flowing in the heat transfer tube,
temperatures of heat transfer tubes provided in the furnace and
18a
CA 02719040 2015-06-25
75870-19
a flue on the downstream side of the furnace or temperatures of
fluids flowing in the heat transfer tubes.
Effect of the Invention
According to the solid fuel burner of the present
invention, the forming position of flame in a furnace can be
controlled in the vertical direction or the horizontal
direction of the solid fuel burner by the air flow rate in the
air nozzle, and the retention time of combustion gas flowing in
the combustion apparatus (furnace) changes, so that the heat
transfer amount in the combustion apparatus changes, and the
temperature of the combustion gas at the outlet can be changed.
Further, according to a combustion apparatus
(furnace) including the solid fuel burner and a method of
operating the combustion apparatus of the present invention,
the combustion gas temperature at the furnace outlet, the
temperature of a heat transfer tube installed on the furnace
wall surface, the temperature of a fluid flowing in the heat
transfer tube, or the temperatures of heat transfer tubes
provided inside the
18b
CA 02719040 2015-06-25
75870-19
furnace and in a flue (refer to Fig. 14) on the downstream side
of the furnace and the temperature of a fluid flowing in the
heat transfer tube are kept constant, so that the forming
positon of flame can be changed.
The obstacles as described which divide the inside of
the air nozzle into a plurality of regions in the
circumferential direction forms a closed space opened only at
an inlet and an outlet in the combustion air flow direction,
and combustion air is made to flow inside the closed space from
the burner upstream side to the furnace side.
By obstacles as described, deviation in the flow rate
can be generated in the circumferential direction of the fuel
nozzle without influences from fluctuation of the relative
positions of the outer peripheral side partition wall and the
inner peripheral side partition wall due to the thermal
expansion difference and it is also possible that the direction
of forming flame is deflected to the left or right or up and
down by generating a deviation in the flow rate of the
combustion air flowing in the regions and for forming flame in
the horizontal or vertical direction in the furnace.
By regulating the air flow rate flowing in at least
one air nozzle of the divided air nozzles disposed on the outer
side of the fuel nozzle by a damper, a flow rate deviation can
be caused in the circumferential direction of the fuel nozzle
in the flows ejected from the divided air nozzles. Therefore,
the fuel ejected from the fuel nozzle flows while deflecting to
the side with a larger air volume ejected from the air nozzle.
19
CA 02719040 2015-06-25
75870-19
By disposing the divided air nozzles positioned on
the outer side of the fuel nozzle on the upper and lower sides
of the fuel nozzle and regulating the flow rates and jet flow
velocities of air ejected from the respective upper and lower
air nozzles to the inside of the furnace, the momentum obtained
as a product of the air flow rate and the jet flow velocity
becomes different in the horizontal or vertical direction of
the burner outlet, and the air flow rates ejected from the
upper and lower air nozzles of the burner can be individually
controlled in the horizontal or vertical direction inside the
furnace at the burner outlet. Therefore, the temperature
distribution inside the furnace differs in the horizontal or
vertical direction of the burner outlet, and the heat
absorption in the furnace and the heat absorption in a heat
transfer tube provided in a flue on the downstream side of the
furnace change.
Thus, by the divided air nozzles provided on the
upper and lower sides or left and right sides of the fuel
nozzle, the controllability of the air flow rate in the burner
is enhanced.
Brief Description of the Drawings
Fig. 1 is a schematic view showing a section of a
solid fuel burner of a first embodiment of the present
invention.
Fig. 2 is a schematic view showing the section of the
solid fuel burner of the first embodiment of the present
invention.
19a
CA 02719040 2015-06-25
75870-19
Fig. 3 is a sectional view taken along an arrow line A-A
of the solid fuel burner of Fig. 1.
Fig. 4 is a sectional view taken along an arrow line B-B
of the solid fuel burner of Fig. 1.
Fig. 5 is a sectional view taken along an arrow line C-C
of the solid fuel burner of Fig. 1.
Fig. 6 is a view showing gas temperature behavior at a
furnace outlet in a combustion apparatus including the solid
fuel burner of the first embodiment of the present invention.
Fig. 7 is a schematic view showing a section of a solid
fuel burner of a second embodiment of the present invention.
Fig. 8 is a sectional view taken along an arrow line C-C
19b
CA 02719040 2010-09-20
, .
of the solid fuel burner of Fig. 7.
Fig. 9 is a sectional view taken along an arrow line C-C
of another example of the solid fuel burner of Fig. 7.
Fig. 10 is a sectional view taken along an arrow line
C-C of another example of the solid fuel burner of Fig. 7.
Fig. 11 is schematic view showing a section of a solid
fuel burner of a third embodiment of the present invention.
Fig. 12 is a sectional view taken along an arrow line
C-C of the solid fuel burner of Fig. 11.
Fig. 13 is a sectional view taken along an arrow line
C-C of another example of the solid fuel burner of Fig. 11.
Fig. 14 is a schematic view of a combustion apparatus
in which a solid fuel burner is provided on a furnace wall showing
an embodiment of the present invention.
Description of Embodiments
Hereinafter, embodiments of the present invention will
be described with reference to the drawings.
First embodiment
A first embodiment of the present invention will be
described with reference to Fig. 1 to Fig. 5.
Fig. 1 is a schematic view showing a section of a solid
CA 02719040 2010-09-20
fuel burner of a first embodiment of the present invention.
Fig. 2 is a schematic view showing the status of forming flame
when a deviation is generated in an air flow rate ejected from
an air nozzle into a furnace with respect to the solid fuel
burner. Fig. 3 is a sectional view taken along an arrow line
(sectional view taken along an arrow line A-A of Fig. 1) at
the furnace partition wall portion of the solid fuel burner
shown in Fig. 1, Fig. 4 is a sectional view taken along an arrow
line (sectional view taken along an arrow line B-B of Fig. 1)
at the wind box portion of the solid fuel burner shown in Fig.
1, and Fig. 5 is a sectional view taken along an arrow line
(sectional view taken along an arrow line C-C of arrows of Fig.
1) at the wind box portion of the solid fuel burner shown in
Fig. 1.
In Fig. 1, a fuel nozzle 10 which supplies and conveys
a mixture fluid of primary air and solid fuel in the solid fuel
burner 1 is connected to a conveying tube on the upstream side,
not shown, and on the outer periphery of the fuel nozzle 10,
an annular secondary air nozzle 11 which ejects secondary air
is provided. On the outer periphery of the secondary air nozzle
11, tertiary air nozzles 12 and 13 which eject tertiary air
are provided. On the outer periphery of the tertiary air nozzles
12 and 13, quaternary air nozzles 14 to 17 which eject quaternary
21
CA 02719040 2010-09-20
air are provided. The tertiary air nozzles 12 and 13 of the
present embodiment are divided air nozzles provided on the upper
and lower sides across the fuel nozzle 10. The quaternary air
nozzles 14 to 17 are outermost peripheral air nozzles forming
a passage on the outermost periphery in the solid fuel burner
1 of the present embodiment.
Here, the layout of the nozzles 10 to 17 and the
configuration of the partition walls to be provided for the
nozzles 10 to 17 will be described based on Fig. 3.
The partition wall 18 constituting the fuel nozzle 10
commonly serves as an inner peripheral wall of the secondary
air nozzle 11 provided annularly on the outer periphery of the
fuel nozzle 10. Also, the outer peripheral wall 19 of the
secondary air nozzle 11 commonly serves as inner peripheral
walls of the tertiary air nozzles 12 and 13 and the quaternary
air nozzles 16 and 17. The upper tertiary air nozzle 12 and
the lower tertiary air nozzle 13 are disposed so as to sandwich
the fuel nozzle 10, a cylindrical partition wall 19 and a
bent-plate-shaped peripheral wall obstacle 20 constitute the
upper tertiary air nozzle 12, and the cylindrical partition
wall 19 and a bent-plate-shaped obstacle 21 constitute the lower
tertiary air nozzle 13. The quaternary air nozzles 14 to 17
are divided into respective regions by the peripheral wall
22
CA 02719040 2010-09-20
obstacles 20 and 21, however, the partition wall 19 on the outer
peripheral side and the partition wall 19 on the inner peripheral
side are separated from each other. The quaternary air nozzle
14 is provided on the outer peripheral upper side of the tertiary
air nozzle 12, the quaternary air nozzle 15 is provided on the
outer peripheral lower side of the tertiary air nozzle 13, the
quaternary air nozzle 16 is provided on the outer side of the
partition wall 19 of the tertiary air nozzle and the obstacles
20 and 21 on the left side as viewed from the furnace side,
and the quaternary air nozzle 17 is provided on the outer side
of the partition wall 19 of the tertiary air nozzle and the
peripheral wall obstacles 20 and 21 on the right side as viewed
from the furnace side.
Next, a configuration and a combustion state of the burner
will be described based on Fig. 1.
An oil gun 24 is provided to penetrate through the central
portion of the fuel (pulverized coal) nozzle 10, and is used
for assisting combustion when starting up the burner and during
low-load combustion. For preventing backfire of the solid fuel,
a restriction 25 is provided in the fuel nozzle 10. At the
tip end of the partition wall 18 between the fuel nozzle 10
and the secondary air nozzle 11, a ring for stabilizing flame
26 is provided, and the ring for stabilizing flame 26 has a
23
CA 02719040 2010-09-20
. .
function to expand circulation flows 33 generated by mixing
a mixture fluid of the fuel and primary air with secondary air
inside the furnace near the tip end portion of the fuel
(pulverized coal) nozzle 10.
An opening portion in which the burner 1 on the furnace
wall 28 is installed, is a burner throat portion 29, and the
burner throat portion 29 commonly serves as outer peripheral
partition walls of the quaternary air nozzles 14 to 17. On
the wall surface except for the burner throat portion 29 of
the furnace wall 28, a water tube 30 is provided.
On the tip endof the partitionwall 19between the secondary
air nozzle 11 and the tertiary air nozzles 12 and 13, a guide
member (guide sleeve) 32 which guides secondary air and tertiary
air in the direction away from the fuel nozzle 10 is provided,
and on the tip ends of the peripheral wall obstacles 20 and
21 between the tertiary air nozzles 12 and 13 and the quaternary
air nozzles 14 and 15, guide members (guide sleeves) 34 and
35 which guide tertiary air and quaternary air in the direction
away from the fuel nozzle 10 are provided respectively.
Air flowing in these combustion air nozzles 11 to 17 is
supplied from a wind box 39 surrounding the burner 1.
In the fuel (pulverized coal) nozzle 10, a flow 37 of
a mixture fluid of the solid fuel and the primary air flows,
24
CA 02719040 2010-09-20
and in the secondary air nozzle 11, a flow 41 of the secondary
air flows. Moreover, the upstream sides of the tertiary air
nozzles 12 and 13 and the quaternary air nozzles 14 to 17 form
the same air passage, and an air flow 42 to be used as the tertiary
air and the quaternary air is regulated by flow regulators
(dampers) 38a, 38b, 43, and 44.
Further, the flow rate of the secondary air flow 41 flowing
in the secondary air nozzle 11 is regulated by the flow regulator
(damper) 40, and in the air flow 42 to be used as tertiary air
and quaternary air, the total flow rate of which is regulated
by the flow regulator (damper) 38, air in the tertiary air nozzles
12 and 13 to be used as tertiary air is respectively regulated
by the flow regulators (dampers) 43 and 44.
A flow 46 of a mixture fluid (fuel jet flow) of the solid
fuel and primary air ejected from the fuel nozzle 10 into the
furnace, a flow 48 of secondary air ejected from the secondary
air nozzle 11 into the furnace, flows 49 and 50 of tertiary
air and quaternary air (in Fig. 1, the tertiary air and the
quaternary air in the furnace are not discriminated but are
shown as an upper flow 49 and a lower flow 50) ejected from
the tertiary air nozzles 12 and 13 and the quaternary air nozzles
14 to 17 into the furnace, are formed. Further, in the furnace,
an outer peripheral portion of flame (fuel jet flow) 51 is formed.
CA 02719040 2010-09-20
In combustion of the solid fuel in the solid fuel burner
1, air in the region on the downstream side of the partition
wall 18 separating the fuel nozzle 10 and the secondary air
nozzle 11 is involved in flows ejected from the respective
nozzles 10 and 11. Therefore, in the region on the downstream
side of the partition wall 18, the pressure is reduced, and
circulation flows 33 as flows from the downstream side to the
upstream side are formed.
When the ring for stabilizing flame 26 is provided on
the tip end portion of the partition wall 18, the flow 46 of
the fuel mixture fluid and the flow 48 of the secondary air
in the furnace are separated and the circulation flows 33 expand.
A high-temperature gas is retained in the circulation flows
33, so that ignition of fuel particles is promoted and the flame
stability is improved.
Further, a flame is formed near the outlet of the fuel
nozzle 10 and the oxygen consumption is advanced, and accordingly,
a reducing flame region with a lower oxygen concentration expands
in the flame. In this reducing flame, nitrogen contained in
the solid fuel is emitted as a reducing substance such as ammonia
or cyan, and acts as a reducing agent for reducing the nitrogen
oxide (N0x) to nitrogen. Therefore, the NOx evolution amount
can be reduced.
26
CA 02719040 2010-09-20
Further, the ignition is quickened, so that the combustion
reaction of the solid fuel is advanced and the unburned fuel
in the fuel ash (hereinafter, referred to as unburned amount)
is also reduced. By providing guide members 32, 34, and 35
for guiding air to be ejected from the respective air nozzles
toward the outer periphery at the outlets of the tertiary air
nozzles 12 and 13 and the quaternary air nozzles 14 to 17, the
flow 46 of the fuel mixture fluid, the flow 48 of the secondary
air, and the flows 4 9 and 50 of the tertiary air and the quaternary
air flow in the furnace are made to flow separately from each
other, so that mixture of the fuel, the tertiary air, and the
quaternary air near the burner is delayed and the reducing flame
region expands.
Next, features of the present embodiment will be described
with reference to Fig. 1 and Fig. 2.
Fig. 1 is the case where air is made to flow so that the
velocities of jet flows from the tertiary air nozzles 12 and
13 become equal to each other, and Fig. 2 is in the case where
the flow regulating damper 43 of the tertiary air nozzle 12
installed on the upper side of the burner 1 is operated so that
a smaller amount of air flows in the tertiary air nozzle than
in other nozzles.
As shown in Fig. 2, when the air volume on the lower side
27
CA 02719040 2010-09-20
of the burner 1 is increased, in the jet flows from the tertiary
air nozzles 12 and 13, the air flow rate and jet flow velocity
from the upper air nozzle 12 are reduced, and the air flow rate
and jet flow velocity from the lower air nozzle 13 are increased.
The momentum obtained as a product of the flow rate and the
jet flow velocity also becomes larger on the lower side of the
burner 1 than on the upper side of the burner 1. The jet flows
of the tertiary air involve ambient gasses at the outlet of
the burner 1, so that a negative pressure is generated. When
the air volume of the air nozzle 13 on the lower side of the
burner 1 is increased as shown in Fig. 2, in the pressure
distribution around the tertiary air nozzles 12 and 13, the
negative pressure increases more in the lower tertiary air nozzle
13, and a pressure differs in the vertical direction at the
outer peripheral portion of the secondary air nozzle 11. On
the lower side with the higher negative pressure, the secondary
air 48 easily deflects downward and flows. Therefore, at the
outer peripheral portion of the fuel nozzle 10, the secondary
air 48 also deflects downward from the burner 1 and flows, so
that the negative pressure increases downward in the furnace.
Therefore, the fuel jet flow (flame) 51 also deflects downward.
That is, the fuel jet flow 51 is formed in the furnace
as a downward flow due to a deviation between the air flow rates
28
CA 02719040 2010-09-20
in the tertiary air nozzles 12 and 13. Further, the fuel flows
downward, and accordingly, the flame to be formed from the
circulation flows 33 on the downstream of the ring for
stabilizing flame 26 is also formed downward. Therefore, the
temperature distribution in the furnace is biased to the lower
side, and the amount of heat absorption in the furnace can be
increased and the amount of heat absorption in the heat transfer
tube provided on the downstream portion of the furnace can be
reduced.
In addition, contrary to Fig. 2, when the damper for
regulating flow 44 of the tertiary air nozzle 13 installed on
the lower side of the burner 1 is operated and the air flow
rate on the upper side is relatively increased, the flame is
formed inside the furnace at an upper portion than usual, and
the temperature distribution in the furnace is biased to the
upper side, and the amount of heat absorption in the furnace
can be reduced and the amount of heat absorption in the heat
transfer tube provided in the flue of a downstream side of the
furnace can be increased.
According to this embodiment, the position for forming
the flame 51 can be controlled in the vertical direction by
generating a deviation between air flow rates in the tertiary
air nozzles 12 and 13. Therefore, based on the combustion gas
29
CA 02719040 2010-09-20
temperature at the furnace outlet, the temperature of a heat
transfer tube installed on the furnace wall surface, the
temperature of the fluid flowing in the heat transfer tube,
or the temperatures of heat transfer tubes provided in the
furnace and a flue on the downstream side thereof and the
temperatures of fluids flowing in the heat transfer tubes, the
air flow rates in the tertiary air nozzles 12 and 13 of the
solid fuel burner 1 can be individually controlled in the
vertical direction.
In the solid fuel burner 1 of the present embodiment,
at the tip end of the outer peripheral side partition wall 18
of the fuel nozzle 10, a ring for stabilizing flame 26 which
obstructs the flow of the mixture fluid 37 flowing in the fuel
nozzle 10 and the flow of air flowing in the secondary air nozzle
11 is provided. Further, guide members 32, 34 and 35 which
deflect flows to the outer peripheral side (the direction away
from the fuel nozzle 10) are provided at the outlets of the
tertiary air nozzles 12 and 13 and the quaternary air nozzles
14 to 17.
By providing the ring for stabilizing flame 26, the
circulation flows 33 are formed inside the furnace, and a
high-temperature gas is retained in the circulation flows 33,
and by igniting the fuel, the flame can be stably ignited and
CA 02719040 2010-09-20
formed on the downstream side of the ring for stabilizing flame
26 at the outlet of the fuel nozzle 10. Therefore, regardless
of the flow rates of air ejected from the tertiary air nozzles
12 and 13, the ignition position can be fixed. Therefore, even
when a deviation is generated between air flow rates ejected
from the tertiary air nozzles 12 and 13, only the forming
direction (angle) of the flame 51 can be changed. The start
position of forming the flame 51 does not change and only the
angle of the flame 51 changes, so that the temperature
distribution or the amount of heat absorption in the furnace
and that in a heat transfer tube provided on the downstream
portion of the furnace are easily controlled.
Further, the guide members 32, 34, and 35 are provided,
so that the direction of the air ejected from the air nozzles
11 to 17 can be always set toward the outer peripheral side
of the burner 1. Therefore, particularly, even when the flow
rate is reduced, mixing the fuel and air near the burner 1 inside
the furnace can be suppressed. Therefore, mixing fuel and air
near the burner 1 inside the furnace can be suppressed and NOx
can be reduced.
As dampers for regulating air flow rate, the respective
dampers 40, 43, and 44 corresponding to the secondary air nozzle
11 and the tertiary air nozzles 12 and 13 are shown in the present
31
CA 02719040 2010-09-20
embodiment, however, as shown in Fig. 5, dampers for regulating
the flow rate which regulate the air volume in the tertiary
air nozzles 12 and 13 and the quaternary air nozzles 14 to 17
may be provided as flow regulating dampers 38a and 38b
respectively provided for the upper and lower quaternary air
nozzles 14 and 15 and flow regulating dampers 56a and 56b provided
for the left and right quaternary air nozzles 16 and 17.
In this case, by the flow regulating dampers 38a, 38b,
56a and 56b, a deviation between the air flow rate in the tertiary
air nozzles 12 and 13 and the quaternary air nozzles 14 to 17
can be generated each other. Fig. 6 shows gas temperature
changes at the furnace outlet respectively when a deviation
in the flow rate is generated in the vertical direction of the
burner 1 by operating the flow regulating dampers 38a and 38b
which regulate the air volume in the quaternary air nozzles
14 and 15 of the solid fuel burner 1 of the first embodiment,
and when a deviation in the flow rate is generated in the vertical
direction of the burner 1 by operating the flow regulating
dampers 43 and 44 of the tertiary air nozzles 12 and 13.
As shown in Fig. 6, the gas temperature at the furnace
outlet changes by the deviation in the air flow rate in the
vertical direction of the air nozzles of the burner 1. The
gas temperature change at the furnace outlet shows an increase
32
CA 02719040 2010-09-20
or a decrease in heat absorption in the furnace. For example,
a decrease of a gas temperature means an increase in heat
absorption in the furnace and facilitation of cooling of
combustion gas.
The results shown in Fig. 6 show that the quaternary air
nozzles 14 to 17 have passages connected to each other, so that
the same effect can be obtained although the effect of flow
rate regulation by the dampers 38 and 56 is smaller than that
by the dampers 43 and 44 of the tertiary air nozzles 12 and
13.
As described above, when the air nozzles 12 to 17 are
divided in the circumferential direction into a plurality of
regions, the partition walls 19 and 29 and the peripheral wall
obstacles 20 and 21, etc., must be provided. Normally, in the
solid fuel burner 1, similar to the quaternary air nozzles 14
to 17 shown in Fig. 3, the outer peripheral side partition wall
29 of the passage on the outermost periphery is a furnace body
partition wall 28 or a water wall 30 constituting the furnace.
On the other hand, the inner peripheral side partition wall
19 and the peripheral wall obstacles 20 and 21 are connected
to the wind box 39 to which the fuel nozzle 10 and the burner
1 are connected. The fuel nozzle 10 and the wind box 39 are
different in thermal expansion rate caused by operation of the
33
CA 02719040 2010-09-20
combustion apparatus (boiler) from that of the furnace body
partition wall 28 or the water wall 30. Therefore, in the solid
fuel burner 1, the relative positions of the outer peripheral
side partition wall 29 of the passage on the outermost periphery
and the inner peripheral side partition wall 19 and peripheral
wall obstacles 20 and 21 change according to the temperature,
so that they must be installed independently each other.
Therefore, it is difficult to connect the inner peripheral side
partition wall 19 and peripheral wall obstacles 20 and 21 to
the outer peripheral side partition wall 29. Therefore, in
the present embodiment, the quaternary air nozzles 14 to 17
are divided into four regions by the obstacles 20 and 21 connected
to only the tertiary air nozzles 12 and 13, so that the effect
of flow rate regulation is obtained.
Second embodiment
Fig. 7 is a schematic view showing a section of a solid
fuel burner of a second embodiment of the present invention.
In addition, Fig. 8 is a sectional view taken along an arrow
line C-C of the solid fuel burner shown in Fig. 7.
The second embodiment is different from the first
embodiment shown in Fig. 1 to Fig. 5 in that the divided tertiary
air nozzles 12 and 13 of the first embodiment are not provided
34
CA 02719040 2010-09-20
and the outermost peripheral nozzle regions 14 to 17 are divided
in the circumferential direction in Fig. 7 and Fig. 8.
The outermost peripheral air nozzle is divided by
obstacles 53 and 54 into the regions 14 to 17 in which air
corresponding to the tertiary air flows in this burner 1. The
regions 14 to 17 to be connected to the wind box 39 include
the upper region 14, the lower region 15, the left region 16
and the right region 17 as viewed from the furnace side, and
can individually regulate air flow rates by dampers for
regulating the flow rate 38a and 38b provided in the upper and
lower regions 14 and 15 and dampers for regulating the flow
rate 56a and 56b provided in the left and right regions 16 and
17, respectively.
The obstacles 53 and 54 are connected to the partition
wall 19 on the inner peripheral side of the outermost peripheral
air nozzle, and are not connected to the partition wall 29 on
the outer peripheral side (burner throat portion which is an
opening portion of the furnace wall 28 in which the burner 1
is installed). By providing the obstacles 53 and 54, movement
of combustion air among the regions 14 to 17 is obstructed.
Therefore, by the flow rate regulator (dampers) 38a, 38b, 56a
and 56b, the air volume ejected from the regions 14 to 17 into
the furnace can be regulated by the flow rate regulator (dampers)
CA 02719040 2010-09-20
38a, 38b, 56a and 56b.
Specifically, the air flow rate and air jet flow velocity
flowing in the upper region 14 are reduced by squeezing the
damper 38a. Accordingly, the air flow rate and air jet flow
velocities in other regions 15 to 17 increase. Therefore, as
the air momentum obtained as a product of the air flow rate
and the air jet flow velocity, downward momentum increases with
respect to the circumferential direction of the fuel nozzle
10. The air jet flow ejected from the outermost peripheral
air nozzle into the furnace involves ambient gasses at the
outermost peripheral air nozzle outlet, so that a negative
pressure is generated. The momentum in the outermost peripheral
air nozzle is increased downward, and accordingly the negative
pressure on the lower side is increased at the outermost air
nozzle outlet. Therefore, the flow 48 of the secondary air
in the furnace, flowing near the outermost peripheral air nozzle,
flows while deflecting downward in the furnace. Further, the
negative pressure on the lower side portion in the circulation
flow 33 is also increased due to the flow 48 of the secondary
air, so that the fuel jet flow 46 flowing near the circulation
flow 33 also deflects downward.
That is, due to a deviation of air flow rates in the regions
14 to 17 of the outermost air nozzle, the fuel jet flow 46 is
36
CA 02719040 2010-09-20
,
formed as a downward flow in the furnace. Further, the fuel
flows downward, and accordingly, the flame 51 is also formed
downward. Therefore, the temperature distribution in the
furnace is biased to the lower side, and the amount of heat
absorption in the furnace can be increased and the heat
absorption in a heat transfer tube provided in the flue on the
downstream side of the furnace can be reduced.
Further, in the present embodiment, obstacles 53 and 54
that divide the combustion air nozzle of the solid fuel burner
1 in the circumferential direction into a plurality of regions
are provided as described above. Normally, the outer
peripheral side partition wall 29 of the solid fuel burner 1
is composed of a furnace partition wall 28 or the water wall
35 which constitutes the furnace, and the inner peripheral side
partition wall 19 of the regions 14 to 17 of the outermost
peripheral air nozzle is connected to the wind box 39 to which
the fuel nozzle 10 and the burner 1 are connected. The outer
peripheral side partition wall 29 and the inner peripheral side
partition wall 19 are different in thermal expansion caused
by operation of the combustion apparatus (boiler) . Therefore,
the relative positions of the outer peripheral side partition
wall 29 and the inner peripheral side partition wall 19 in the
solid fuel burner 1 change according to temperature, so that
37
CA 02719040 2010-09-20
both of them must be installed independently. Therefore, it
is difficult to connect the inner peripheral side partition
wall 19 and the outer peripheral side partition wall 29.
In the present embodiment, the outermost peripheral air
nozzle is divided into a plurality of regions, however, the
obstacles 53 and 54 are not connected to the outer peripheral
side partition wall 29. Therefore, a deviation in the flow
rate can be generated in the circumferential direction of the
fuel nozzle 10 without influences from fluctuation of the
relative positions of the outer peripheral side partition wall
29 and the inner peripheral side partition wall 19 due to the
thermal expansion difference. Also, in the description given
above, the direction of forming flame in the vertical direction
inside the furnace is described, however, it is also possible
that the direction of forming flame is deflected to the left
or right by generating a deviation in the flow rate of the
combustion air flowing in the regions 16 and 17 for forming
flame in the horizontal direction in the furnace.
In the second embodiment shown in Fig. 7 and Fig. 8, the
obstacles 53 and 54 are connected from the inner peripheral
side partition wall 19, however, it is also possible that, as
shown in Fig. 9, the obstacles 53 and 54 are connected to the
outer peripheral side partition wall 29 and separated from the
38
CA 02719040 2010-09-20
inner peripheral side partition wall 19. Alternatively, as
shown in Fig. 10, it is also possible that the obstacles 53
and 54 are connected to only the inner peripheral side partition
wall 19, the obstacles 60 and 61 are connected to only the outer
peripheral side partition wall 29, and obstacles 53, 54, 60,
and 61 respectively connected to both of the inner peripheral
side and the outer peripheral side are provided doubly. By
providing obstacles doubly, air movement among the regions 14
to 17 is further reduced.
Moreover, in the present embodiment, the secondary air
nozzle 11 is provided on the outer peripheral portion of the
fuel nozzle 10, however, even when the secondary air nozzle
11 is not provided and the fuel nozzle 10 is in contact with
the regions 14 to 17 of the outermost peripheral air nozzle,
the deflection effect of the position for forming flame by the
above-described air flow rate deviation is similarly obtained.
Third embodiment
Fig. 11 is a schematic view showing a section of a solid
fuel burner of a third embodiment of the present invention.
Fig. 12 is a sectional view taken along an arrow line C-C of
Fig. 11.
The difference of the embodiment shown in Fig. 11 and
39
CA 02719040 2010-09-20
Fig. 12, from the second embodiment shown in Fig. 7 and Fig.
8 is that, for example, the fuel nozzle 10 and the secondary
air nozzle 11 are relatively short in diameter in the vertical
direction and relatively long in diameter in the horizontal
direction orthogonal thereto, that is, wide-width nozzles. In
the present embodiment, an example of the fuel nozzle 10 and
the secondary air nozzle 11 whose longer side is formed in the
horizontal direction is shown. Moreover, the outer peripheral
partition wall 29 of the respective regions 14 to 17 of the
outermost peripheral air nozzle has a circular shape whose length
in the vertical direction and the horizontal direction is equal.
The fuel nozzle 10 and the secondary air nozzle 11 become
so-called planiform, so that the thickness of the outermost
peripheral air nozzle in the sectional direction across the
passages of respective regions 14 to 17 is thicker in one of
two directions orthogonal to each other. Therefore, when a
deviation in the flow rate is generated at the thicker portion,
due to larger flow rate, the fuel jet flow ejected from the
fuel nozzle 10 into the furnace can be easily guided by a deviation
among flow rates ejected from the regions 14 to 17 of the outermost
peripheral air nozzle.
In the third embodiment of the present invention shown
in Fig. 11 and Fig. 12, the air nozzles are provided as the
CA 02719040 2010-09-20
. .
secondary air nozzle 11 and the regions 14 to 17 of the outermost
peripheral air nozzle, however, as shown Fig. 13, on the inner
sides of the regions 14 to 17 of the outermost peripheral air
nozzle, tertiary air nozzles 12 and 13 served as the divided
air nozzles may be provided. In this case, as shown in Fig.
13, the peripheral wall obstacles 20 and 21 of the divided
tertiary air nozzles 12 and 13 may also be used as obstacles
which divide the regions 14 to 17 of the outermost peripheral
air nozzle.
Fourth embodiment
Fig. 14 is a schematic view of a combustion apparatus
including a solid fuel burner according to the first embodiment
of the present invention provided on the furnace wall.
The solid fuel burner 1 includes a fuel nozzle 10 and
air nozzles 12 and 13. In the present embodiment, for describing
a deviation of the air amount in the vertical direction, the
air nozzles 12 and 13 are provided on the upper and lower sides,
however, any of the burners 1 of the first to third embodiments
described above is applicable.
The fuel nozzle 10 is connected to the solid fuel pulverizer
66, a carrier air fan 67, and a fuel hopper 68 through a fuel
carrying tube for carrying fuel 65 on the upstream thereof.
41
CA 02719040 2010-09-20
Moreover, the air nozzles 12 and 13 are connected to an air
fan 70 via valves for regulating flow volume71 and 72.
Generally, a plurality of the above-described solid fuel
burners 1 are connected to the furnace 74, however, in the present
embodiment, an example to which one solid fuel burner 1 is
connected is described.
The partition wall 28 constituting the furnace 74 is
composed of a water tube and absorbs combustion heat. Further,
heat transfer surfaces 76 hung down from the ceiling inside
the furnace 74 and a heat transfer surface 76 disposed in a
flue on the downstream side of the furnace 74 are provided.
Moreover, for measuring the amount of heat absorption on the
water tube 30 (refer to Fig. 1) on the wall surface of the furnace
74 or on the heat transfer surface 76, a plurality of thermometers
(not shown) for measuring the temperatures of water and steam
or the temperatures of materials constituting the water tube
30 or the heat transfer tube are respectively provided at
appropriate positions.
A control processor 73 is provided shown in Fig. 14, which
controls valves for regulating flow amount 71 and 72 based on
a steam temperature at the water tube outlet and a steam
temperature at the outlet of the heat transfer surfaces 76.
In the embodiment shown in Fig. 14, air from the air nozzles
42
CA 02719040 2010-09-20
12 and 13 formed to sandwich the fuel nozzle 10 in the vertical
direction is ejected while being respectively inclined to the
opposite direction to the fuel nozzle 10.
When the air flow rate in the lower side air nozzle 13
is increased, the jet flow velocity also increases. The
momentum obtained as a product of the flow rate and the jet
flow velocity is also increased in the axial direction, and
also inside the furnace 74, the downward momentum increases.
The air jet flow involves ambient gasses at the outlet of the
fuel nozzle 10, so that a negative pressure is generated, and
due to the negative pressure, the fuel jet flow flowing near
the air jet flow also deflects downward and flows.
That is, due to a deviation between air flow rates ejected
from the air nozzles 12 and 13, a fuel jet flow ejected from
the fuel nozzle 10 is formed as a downward flow at the outlet
of the burner 1 of the furnace. Further due to the downward
flow of the fuel, the flame to be formed inside the furnace
74 from the solid fuel burner 1 is also formed downward.
Therefore, the temperature distribution inside the furnace 74
is biased to the lower side, and the amount of heat absorption
in the furnace 74 can be increased and the amount of heat
absorption by the heat transfer surface 76 provided in the flue
on the downstream side of the furnace 74 can be reduced.
43
CA 02719040 2010-09-20
= .
When the air flow rate of the upper side air nozzle 12
is increased, the flame to be formed at the outlet of the burner
1 is formed to be at an upper portion than usual, the temperature
distribution inside the furnace 74 is biased to the upper side,
and the heat absorption in the furnace 74 can be reduced and
the amount of heat absorption by the heat transfer surface 76
provided in the flue on the downstream side of the furnace 74
can be increased.
Gas temperature changes at the furnace outlet when the
burner structure shown in the first embodiment of the present
invention described above are applied to the furnace 74 shown
in Fig. 14 are as shown in Fig. 6. As shown in Fig. 6, in
acombustion apparatus including the solid fuel burner 1 of the
present invention provided on the furnace wall, due to the air
flow rate deviation in the vertical direction of the burner
1, the gas temperature at the outlet of the furnace 74 changes.
A gas temperature change at the outlet of the furnace 74 shows
an increase/decrease in heat absorption inside the furnace 74.
For example, a gas temperature decrease means that the amount
of heat absorption in the furnace 74 increases and cooling of
the combustion gas is advanced.
According to the present embodiment, by changing the flame
forming position by controlling the valves for regulating flow
44
CA 02719040 2010-09-20
,
volume 71 and 72 via the control processor 73, the amount of
heat absorption on each heat transfer surface 76 can be changed.
As for the steam temperature flowing on the wall of the furnace
74 and the heat transfer surface 76, a predetermined design
temperature is set for protecting materials of a turbine
installed on the downstream side and a heat transfer surface
on the upstream side, and the steam temperature can be kept
in the design temperature range by changing the amount of heat
absorption.
In particular, when ash adhering to the heat transfer
surface 76 is removed, the amount of heat absorption may be
temporarily increased. In this case, the steam temperature
fluctuates, however, the steam temperature fluctuation can be
suppressed by changing the position for forming flame as
described above. Further, steam temperature fluctuation due
to a load change or a change in the kind of fuel can also be
suppressed.
Industrial Applicability
The present invention provides a solid fuel burner which
can easily change a heat absorption position inside a combustion
apparatus, and is highly applicable to a furnace of a boiler,
etc., with high combustion efficiency.
CA 02719040 2010-09-20
Description of the Reference Numerals
1 Solid fuel burner 10 Fuel nozzle
12, 13 Tertiary air nozzle
14 to 17 Quaternary air nozzle (outermost peripheral nozzle
region)
18, 19 Partition wall 20, 21 Peripheral wall obstacle
24 Oil gun 25 Restriction
26 Obstacle (ring for stabilizing flame)
28 Furnace wall (furnace body partition wall)
29 Burner throat portion (outer peripheral side partition wall
of outermost peripheral passage)
30 Water wall (water tube)
32, 34, 35 Guide member (guide sleeve)
33 Circulation flow
37 Flow of mixture fluid of solid fuel and primary air
38, 40, 43, 44 Flow rate regulator (damper)
39 Wind box 41 Flow of secondary air
42 Air flow to be used as tertiary air and quaternary air
46 Flow of mixture fluid (fuel jet flow) in furnace
48 Flow of secondary air in furnace
49, 50 Flows of tertiary air and quaternary air in furnace
51 Outer peripheral portion of flame (fuel jet flow) in furnace
46
CA 02719040 2010-09-20
53, 54 Obstacle 56 Flow rate regulator (damper)
65 Tube for carrying fuel
66 Solid fuel pulverizer
67 Carrier air fan 68 Fuel hopper
70 Air fan
71, 72 valves for regulating flow volume
73 Control processor 74 Furnace
76 Heat transfer surface
47
