AU2020210392B2 - Solid fuel burner - Google Patents

Abstract

The present invention is provided with: a venturi (33) that constricts a channel (24) for a mixed fluid in a fuel nozzle (21) toward the center in a cross-section of the channel; a fuel enricher (34) that imparts a velocity component in a direction leading away from the center of the fuel nozzle (21) to the mixed fluid; and a channel partition member (36) that partitions the channel of the fuel nozzle (21) into an inner side and an outer side. Even if solid fuel particles produced by pulverizing a biomass fuel are used, the degree of enrichment of the fuel can be ensured by using a plurality of blades (34c, 34d) which impart swirl to the mixed fluid and which are not secured to the inner side of the fuel nozzle (21) along the entire surface thereof.

Description

SOLID FUEL BURNER

[Technical Field]

[0001]

The present invention relates to a solid fuel burner which conveys

and burns a solid fuel, and particularly to a solid fuel burner which is

suitable for fuel particles having a large particle size such as biomass

particles.

[Background Art]

[0002]

In order to improve ignitability of a solid fuel burner used in a boiler

of a thermal power generation plant and to increase stability of flames,

locally increasing a fuel concentration is performed.

Generally, in a solid fuel burner which uses pulverized coal, or the

like as a fuel, a fuel concentrator (mechanism) is often provided to impart a

velocity component toward an inner wall surface of a nozzle in a fuel nozzle

to a mixed fluid of a fuel carrier gas and fuel particles so that the fuel

particles are condensed along the inner wall surface of the nozzle.

[0003]

For example, Patent Document 1 (Japanese Patent Specification No.

6231047: JP6231047B2) describes a technique for providing: a first swirler

(6) configured to impart a swirl to the mixed fluid at a central portion of a

fuel nozzle (which is also referred to as a primary air nozzle) (9); and a

second swirl (7) configured to impart a swirl in a direction opposite to that of the first swirler (6). In the technique described in Patent Document 1, the first swirler (6) imparts a strong swirl to the mixed fluid to move the solid fuel particles to an outer peripheral side of the fuel nozzle (along the inner wall surface of the fuel nozzle).

Subsequently, the second swirl (7) imparts a swirl to the mixed fluid

in the direction opposite to that of the first swirler (6) to weaken the swirl

thereof.

Accordingly, a state, in which the solid fuel particles are condensed

around a flame holder (10) installed in an opening portion of the burner at a

tip portion of the fuel nozzle, is maintained, and even when the fuel

concentration supplied to the burner is low and a load is low, the ignitability

of the fuel particles is increased, and the stability of the flame is improved.

At the same time, since the mixed fluid with weakened swirl is

sprayed from the opening portion, a generation of nitrogen oxides (NOx)

may be suppressed by smoothly mixing with a combustion gas (air) such as

a secondary air and tertiary air without excessive spread of the mixed fluid

in the furnace.

[Prior Art Document]

[Patent Document]

[0004]

Patent Document 1: Japanese Patent Publication No. 6231047

("0004", "0048" to "0061", FIGS. 1 to FIG. 3, and FIG. 21 in the

specification).

Patent Document 2: Japanese Patent Publication No. 4919844 ("0021"

to "0023" in the specification)

Patent Document 3: Japanese Patent Laid-Open Publication No.

2010-242999 ("0033")

[Summary of Invention]

[Technical Problem]

[0005]

Pellets made of wood-based raw materials are frequently used as a

fuel for mixing and burning in a coal (pulverized coal)-fired boiler for

thermal power generation. Herein, the pellets are not used as they are, but

fuel particles obtained by pulverizing and classifying the pellets in an

improved mill (crusher and classifier) based on a coal mill (pulverized coal

machine) as a crushing device are conveyed to the solid fuel burner by

means of the carrier gas, and a mixed fluid of fuel particles and carrier gas

is supplied to the burner to be burned in the same manner as pulverized

coal.

[0006]

However, it is more difficult for the biomass fuel to be pulverized

than the coal, and a required pulverization power of the mill becomes

excessive (about 10 times the power of the coal is generally required to make

the same particle size as the coal from wood chips having a particle size of

50 mm), as well as it may be difficult to atomize to the same level as the

current pulverized coal. In addition, if the biomass fuel is pulverized, a

possibility of rapid combustion is increased, and measures to prevent the

same are required. Due to these reasons, the biomass fuel is discharged

from the mill in a state of fairly coarser particles than the coal (see Patent

Document 2; Japanese Patent Publication No. 4919844, Patent Document 3;

Japanese Patent Laid-Open Publication No. 2010-242999, etc.).

As a result, a biomass fuel having coarse particles has lower

ignitability than the pulverized coal.

[0007]

Meanwhile, when using a fuel having low ignitability, reducing the

flow rate of the mixed fluid makes it to be easily ignited, but conveying it

from the crushing device to the burner by reducing the flow rate of biomass

fuel having large particles may cause residence in the conveying system,

therefore it is not realistic.

Thereby, it is necessary to maintain the flow rate of the mixed fluid

(fuel carrier gas) to be high until just before burning it with a burner.

Therefore, it is conceivable that a flow passage cross-sectional area of

the fuel nozzle is decreased on an upstream side, that is, on the fuel carrier

system (a connection portion with a fuel carrier pipe) side connected from

the crushing device, and is larger on a downstream side, that is, on the

furnace opening portion side than on the upstream side to reduce the flow

rate, and thereby improving the ignitability.

Herein, Patent Document 3 discloses a solid fuel burner including a

venturi and a fuel concentrator that imparts a velocity component to the

mixed fluid in a direction away from a center of the fuel nozzle as a

mechanism for condensing the fuel thereof, wherein an inner diameter of

the opening portion of the fuel nozzle on the furnace side is formed larger

than the inner diameter of the upstream end of the venturi. With this

configuration, the flow rate of the mixed fluid can be reduced just before burning the fuel particles by the burner while maintaining the flow rate thereof to be high in the carrier system, such that the ignitability may be improved.

Meanwhile, a curved pipe part is provided on the upstream side of

the fuel nozzle of the solid fuel burner described in Patent Document 3 at

the connection portion with the fuel carrier pipe from a mill to the burner.

The mixed fluid flows through a flow passage that communicates from the

fuel carrier pipe to the straight pipe part of the fuel nozzle via the curved

pipe part.

As a result of analysis by the inventors using a simulation model,

etc., in this configuration, it was found that a high-speed fluid that has

passed through the curved pipe part may easily flow downward so as to be

reflected after colliding with an upper surface, and in particular, after

condensing the fuel on a central axis side of the nozzle in the venturi, when

imparting a velocity component in the direction away from the center of the

fuel nozzle by a spindle-shaped fuel concentrator, a deviation of the fuel

particles in a circumferential direction may occur, and the flow rate of the

fluid at an upper side of the fuel nozzle may be easily excessively delayed

depending on the length setting of each part of the fuel nozzle, etc. In

addition, it could be seen that if the flow rate is excessively delayed, the fuel

may be easily deviated toward a central portion in a radial direction due to

the fuel's own weight, and in the vicinity of an outlet of the fuel nozzle, a

region where the fuel concentration is low occurs on the upper radial outer

side, and thereby, a condensing effect of the fuel may be reduced.

[0008]

It is a technical object of the present invention to secure the

condensing effect of a fuel by a fuel concentrator provided in a fuel nozzle and

improve ignitability and stability of the flame, even when using a fuel having

coarse particles obtained by crushing biomass fuel (such as pellets of wood

based raw materials) with a mill in a solid fuel burner.

[Solution to Problem]

[0009]

In order to solve the above technical object,

there is provided a solid fuel burner according to a first aspect of the

present invention, including:

a fuel nozzle through which a mixed fluid of a solid fuel and a carrier

gas thereof flows, and is opened toward a furnace;

a combustion gas nozzle which is disposed on an outer peripheral

side of the fuel nozzle to spray a combustion gas; and

a fuel concentrator provided on a center side of the fuel nozzle and

configured to impart a velocity component in a direction away from a center

of the fuel nozzle to the mixed fluid,

wherein the fuel concentrator has a plurality of vanes configured to

impart a swirl to the mixed fluid, of which each vane is disposed away from

an inner surface of the fuel nozzle without being completely fixed to an

inside of the fuel nozzle, and includes a first swirler disposed on an

upstream side in a flow direction of the mixed fluid, and a second swirler

which is disposed on a downstream side in the flow direction of the mixed fluid with respect to the first swirler, and has a plurality of vanes whose swirl direction is in a direction opposite to that of the first swirler, and a flow passage partition member configured to partition a flow passage of the fuel nozzle into an inner side and an outer side in the flow passage cross section is provided on the downstream side with respect to the second swirler in the flow direction of the mixed fluid.

[0010]

An invention of a second aspect of the present invention provides the

solid fuel burner according to the first aspect,

wherein outer diameters of the first swirler and the second swirler

are equal to or less than an inner diameter of an upstream end of the flow

passage partition member.

[0011]

An invention of a third aspect of the present invention provides the

solid fuel burner according to the first aspect,

wherein the flow passage partition member has a shape in which the

inner diameter of the upstream end is larger than an inner diameter of a

downstream end.

[0012]

An invention of a fourth aspect of the present invention provides the

solid fuel burner according to the third aspect,

wherein the outer diameter of the second swirler is smaller than the

inner diameter of the upstream end of the flow passage partition member

and larger than the inner diameter of the downstream end.

[0013]

An invention of a fifth aspect of the present invention provides a

solid fuel burner, including:

a fuel nozzle through which a mixed fluid of a solid fuel and a carrier

gas thereof flows, and is opened toward a furnace;

a combustion gas nozzle which is disposed on an outer peripheral

side of the fuel nozzle to spray a combustion gas; and

a fuel concentrator provided on a center side of the fuel nozzle and

configured to impart a velocity component in a direction away from a center

of the fuel nozzle to the mixed fluid,

wherein the fuel concentrator has a plurality of vanes configured to

impart a swirl to the mixed fluid, of which each vane is disposed away from

an inner surface of the fuel nozzle without being completely fixed to an

inside of the fuel nozzle, and includes a first swirler disposed on an

upstream side in a flow direction of the mixed fluid, and a second swirler

which is disposed on a downstream side in the flow direction of the mixed

fluid with respect to the first swirler, and has a plurality of vanes whose

swirl direction is in a direction opposite to that of the first swirler, and

wherein the flow passage of the fuel nozzle has an upstream part

whose inner diameter is the same or is monotonically increased on the

upstream side of the first swirler, an enlarged pipe part communicated to

the downstream side of the upstream part and having an inner diameter

gradually increased, and a downstream part communicated to the

downstream side of the enlarged pipe part and having a constant inner

diameter.

[0014]

An invention of a sixth aspect of the present invention provides the

solid fuel burner according to the fifth aspect,

wherein at least a portion of the first swirler is located in a range of

the upstream part of the fuel nozzle flow passage, and

at least a portion of the second swirler is located in a range of the

downstream part of the fuel nozzle flow passage.

[0015]

An invention of a seventh aspect of the present invention provides

the solid fuel burner according to the sixth aspect,

wherein a flow passage partition member configured to partition a

flow passage of the fuel nozzle into an inner side and an outer side in the

flow passage cross section is provided in the range of the downstream part of

the fuel nozzle flow passage.

[0016]

An invention of a eighth aspect of the present invention provides the

solid fuel burner according to the seventh aspect,

wherein the flow passage partition member has a shape in which an

inner diameter of an upstream end is larger than an inner diameter of the

downstream end, and

an outer diameter of the second swirler is smaller than an inner

diameter of an upstream end of the flow passage partition member and

larger than an inner diameter of a downstream end of the flow passage

partition member.

[0017]

An invention of a ninth aspect of the present invention provides the

solid fuel burner according to any one of the first to the eighth aspect,

wherein the outer diameter of each swirler is less than an inner

diameter of the upstream part of the fuel nozzle flow passage.

[Advantageous Effects]

[0018]

According to the invention of the first aspect of the present invention,

by including the fuel concentrator having two swirlers and the flow passage

partition member, even when using a fuel having coarse particles obtained by

crushing biomass fuel (such as pellets of wood-based raw materials) with a

mill in a solid fuel burner, it is possible to secure the condensing effect of the

fuel by the fuel concentrator provided in the fuel nozzle and improve the

ignitability and stability of the flame.

[0019]

According to the invention of the second aspect of the present

invention, in addition to the effect of the first aspect of the present invention,

as compared to the case in which an outer diameter of the vane of each swirler

is larger than an inner diameter of the upstream end of the flow passage

partition member, since the carrier gas can be dispersed to an inner

peripheral side while maintaining the fuel closer to the outer peripheral side,

the condensing effect of the fuel on the outer peripheral side may be improved.

Further, according to the invention of the second aspect of the present

invention, it is possible to further reduce the flow rate on the gas side of the

mixed fluid passing through the flow passage partition member, and improve the ignitability and flame holding properties.

[0020]

According to the invention of the third aspect of the present invention,

the inner diameter of the flow passage on the outer peripheral side (inner wall

side of the nozzle) is reduced toward the opening portion of the nozzle, such

that the flow passage cross-sectional area of the mixed fluid between the flow

passage partition member and the inner wall of the nozzle is increased, and

thereby the flow rate of the fuel particles may be reduced, and the ignitability

and the stability of the flame may be further improved.

[0021]

According to the invention of the fourth and eighth aspect of the

present invention, on the inner peripheral side (central side of the nozzle) of

the flow passage partition member, the effect of canceling the swirl by the

second swirler maybe spread over the entire radial direction. Therefore,the

mixed fluid with weakened swirl is sprayed from the opening portion of the

burner, and a suppressing action of the generation of nitrogen oxides (NOx)

by smoothly mixing with a combustion gas (air) such as a secondary air and

tertiary air may be enhanced without excessive spread of the mixed fluid in

the furnace.

[0022]

According to the invention of the fifth aspect of the present invention,

the fuel nozzle has the upstream part of a straight pipe shape whose diameter

is the same or is monotonically increased on the upstream side of the first

swirler, the enlarged pipe part communicated to the downstream side thereof

and having an inner diameter gradually increased, and the straight tubular downstream part communicated to the downstream side of the enlarged pipe part and having an inner diameter larger than that of the upstream side. In addition, the flow passage cross-sectional area on the opening portion side of the furnace is larger than that of on the upstream side and the flow rate is reduced while conveying the fuel at a high flow rate so as not to cause residence of fuel particles having a large particle size in the carrier pipe, such that the ignitability and stability of the flame may be improved while ensuring the condensing effect of the fuel.

[0023]

According to the invention of the sixth aspect of the present invention,

the first swirler is capable of effectively performing concentration of fuel

particles on the outside of the fuel nozzle (along the inner wall), and the

second swirler is capable of effectively performing cancellation of the swirl.

That is, the vanes of the first swirler are applied to the upstream part in at

least a portion of a longitudinal direction, and a radial outward velocity

component may be efficiently imparted to the mixed fluid flowing in the

upstream part.

[0024]

According to the invention of the seventh aspect of the present

invention, as compared to the case which does not have the flow passage

partition member, the condensing effect of the fuel particles on the outside of

the fuel nozzle (along the inner wall) may be enhanced and the effect thereof

is less likely to disappear, such that in the combination of the first swirler and

the second swirler as a fuel concentrator, it is not necessary to impart

excessive swirl and cancel the same. Thereby, a pressure loss of the burner may be reduced. Further, the combination of the first swirler and the second swirler as the fuel concentrator may be formed into a compact form to shorten the total length of the fuel nozzle, which leads to a suppression in the used amount of members.

[0025]

According to the invention of the ninth aspect of the present invention,

the fuel concentrator may be pulled out and removed in the axial direction of

the fuel nozzle for maintenance and inspection. Therefore, ease of the

maintenance and inspection may be improved.

[0025A]

In a broad form, the present invention seeks to provide a solid fuel

burner, including:

a fuel nozzle through which a mixed fluid of a solid fuel and a carrier

gas thereof flows, and is opened toward a furnace;

a combustion gas nozzle which is disposed on an outer peripheral

side of the fuel nozzle to spray a combustion gas; and

a fuel concentrator provided on a center side of the fuel nozzle and

configured to impart a velocity component in a direction away from a center

of the fuel nozzle to the mixed fluid,

wherein the fuel concentrator has a plurality of vanes configured to

impart a swirl to the mixed fluid, of which each vane is disposed away from

an inner surface of the fuel nozzle without being completely fixed to an

inside of the fuel nozzle, and includes a first swirler disposed on an

upstream side in a flow direction of the mixed fluid, and a second swirler

which is disposed on a downstream side in the flow direction of the mixed

13A

fluid with respect to the first swirler, and has a plurality of vanes whose

swirl direction is in a direction opposite to that of the first swirler,

a flow passage partition member configured to partition a flow passage

of the fuel nozzle into an inner side and an outer side in the flow passage cross

section is provided on the downstream side with respect to the second swirler

in the flow direction of the mixed fluid,

an outer diameter of the first swirler is equal to or less than an inner

diameter of an upstream end of the flow passage partition member,

the solid fuel condensed toward an inner peripheral wall of the fuel

nozzle by the first swirler is supplied to an outside of the flow passage

partition member,

the flow passage partition member has a shape in which the inner

diameter of the upstream end is larger than an inner diameter of a

downstream end, and

an outer diameter of the second swirler is smaller than the inner

diameter of the upstream end of the flow passage partition member and

larger than the inner diameter of the downstream end of the flow passage

partition member.

[0025B]

In one embodiment:

a flow passage of the fuel nozzle has an upstream part whose inner

diameter is the same on the upstream side of the first swirler, an enlarged

pipe part communicated to the downstream side of the upstream part and

having an inner diameter gradually increased, and a downstream part

communicated to the downstream side of the enlarged pipe part and having

13B

a constant inner diameter,

at least a portion of the first swirler is located in a range of the

upstream part of the flow passage of the fuel nozzle, and

at least a portion of the second swirler is located in a range of the

downstream part of the flow passage of the fuel nozzle.

[0025C]

In one embodiment, the outer diameter of each swirler is less than

an inner diameter of the upstream part of the flow passage of the fuel nozzle.

[Brief Description of Drawings]

[0026]

FIG. 1 is an entire view describing a combustion system according to

Embodiment 1 of the present invention.

FIG. 2 is a view describing a solid fuel burner of Embodiment 1.

FIG. 3 is a view as seen from an arrow III direction in FIG. 2.

FIGS. 4 (A) and 4 (B) are views describing a flow passage partition

member of Embodiment 1, wherein FIG. 4 (A) is a side view, FIG. 4 (B) is a

cross-sectional view taken on line IVB-IVB in FIG. 4 (A), FIG. 4(C) is a view

corresponding to FIG. 4 (B) of Modification 1, and FIG. 4 (D) is a view

corresponding to FIG. 4 (B) of Modification 2.

FIG. 5 is a view describing a comparative example.

FIG. 6 is a view describing simulation results.

FIG. 7 is views describing a boiler (combustion device) including the

solid fuel burner of the present invention, wherein FIG. 7(A) is a view describing a case of including the solid fuel burner of the present invention, in which biomass fuels are used at the uppermost stages on a front side of a can (boiler) and a rear side of the can among front and rear respective three stage solid fuel burners of the can, FIGS. 7(B) and 7(D) views describing a case of including the solid fuel burner of the present invention, in which the biomass fuel is used at the uppermost stage on the front side of the can, and

FIGS. 7(C) and 7(E) are views describing a case of including the solid fuel

burner of the present invention, in which the biomass fuel is used at the

uppermost stage on the rear side of the can.

[Description of Embodiments]

[0027]

Next, specific examples of an embodiment of the present invention

(hereinafter referred to as embodiments) will be described with reference to

the drawings, but the present invention is not limited to the following

embodiments. Further, in the following description using the drawings,

members other than members necessary for the description to facilitate the

understanding will not be appropriately illustrated.

Embodiment 1

[0028]

FIG. 1 is an entire view describing a combustion system according to

Embodiment 1 of the present invention.

In FIG. 1, in the combustion system (combustion device) 1 of

Embodiment 1 used in a thermal power generation plant or the like,

biomass fuel (solid fuel) is housed in a bunker (fuel hopper) 4. The biomass fuel of the bunker 4 is crushed by a mill (crusher) 5. The crushed fuel is supplied to a solid fuel burner 7 of a boiler (fire furnace) 6 through a fuel pipe 8 and burned. A plurality of solid fuel burners 7 are installed in the boiler 6.

[0029]

An exhaust gas discharged from the boiler 6 is denitrated by a

denitration device 9. The denitrated exhaust gas passes through an air

preheater 10. In the air preheater 10, heat exchange between an air sent

from a blower 11 and the exhaust gas is performed. Therefore, the exhaust

gas is cooled, and the air from the blower 11 is heated. The air from the

blower 11 is supplied to the solid fuel burner 7 and the boiler 6 as a

combustion air through an air pipe 12.

When the exhaust gas that has passed through the air preheater 10

passes through a gas-gas heater (heat recovery device) 13, heat is recovered

and the exhaust gas is cooled.

[0030]

The exhaust gas that has passed through the gas-gas heater (heat

recovery device) 13 passes through a dry dust collector 14, thereby dust in

the exhaust gas is recovered and removed.

The exhaust gas that has passed through the dry dust collector 14 is

sent to the desulfurization device 15 to be desulfurized therein.

The exhaust gas that has passed through the desulfurization device

15 passes through a wet dust collector 16 while dust in the exhaust gas is

recovered and removed again.

The exhaust gas that has passed through the wet dust collector 16 is reheated by a gas-gas heater (reheating device) 17.

The exhaust gas that has passed through the gas-gas heater

(reheating device) 17 is discharged to the atmosphere from a chimney 18.

Further, a configuration of the mill 5 itself may use various

conventionally known configurations. For example, such a configuration is

described in Japanese Patent Laid-Open Publication No. 2010-242999, and

therefore will not be described in detail.

[0031]

FIG. 2 is a view describing the solid fuel burner of Embodiment 1.

FIG. 3 is a view as seen from an arrow III direction in FIG. 2.

In FIGS. 2 and 3, the solid fuel burner 7 of Embodiment 1 has a fuel

nozzle 21 through which a carrier gas flows. An opening at a downstream

end of the fuel nozzle 21 is provided in a wall surface (furnace wall, water

pipe wall) 23 of a furnace 22 of the boiler 6. The fuel nozzle 21 has an

elbow 20 which is formed at an upstream end portion thereof in a flow

direction of the carrier gas as an example of a curved pipe part. The elbow

20 is bent so that the flow direction of the mixed fluid is bent by about 90.

The elbow 20 is connected with the fuel pipe 8 at an upstream end thereof.

The fuel nozzle 21 is formed in a hollow cylindrical shape, and a flow

passage 24 is formed inside the fuel nozzle 21, through which the mixed

fluid including a solid fuel (crushed biomass fuel) and the carrier gas flows.

[0032]

An inner combustion gas nozzle (secondary combustion gas nozzle)

26 is installed on an outer periphery of the fuel nozzle 21 to spray the

combustion air to the furnace 22. In addition, an outer combustion gas nozzle (tertiary combustion gas nozzle) 27 is installed on an outer peripheral side of the inner combustion gas nozzle 26. Each of the combustion gas nozzles 26 and 27 sprays air from a wind box (wind case) 28 toward an inside of the furnace 22. In Embodiment 1, a guide vane 26a is formed at the downstream end of the inner combustion gas nozzle 26, which is inclined radially outward with respect to a center of the fuel nozzle 21 (a diameter thereof is increased toward the downstream side). In addition, a throat part 27a along an axial direction and an enlarged part 27b parallel to the guide vane 26a are formed in the downstream part of the outer combustion gas nozzle 27. Therefore, the combustion air sprayed from the respective combustion gas nozzles 26 and 27 is sprayed so as to be diffused from the center in the axial direction.

[0033]

Further, a flame holder 31 is supported on an opening portion at the

downstream end of the fuel nozzle 21.

In FIGS. 2 and 3, an ignition burner (oil gun) 32 is formed to

penetrate a flow passage cross section of the fuel nozzle 21 at the central

portion thereof. The ignition burner 32 is supported in a state of

penetrating a collision plate 32a supported by a collision plate flange 20a of

the fuel nozzle 21.

[0034]

A straight pipe part 21a is provided with the fuel nozzle 21 on the

downstream side of the elbow 20 with respect to the flow direction of the

mixed fluid as an example of an upstream part. The straight pipe part 21a

is formed in a straight tubular shape having the same cross-sectional area as the flow passage 24.

An enlarged part 21b whose inner diameter (that is, cross-sectional

area) is increased toward the downstream side is connected to the

downstream side of the straight pipe part 21a. A straight tubular

downstream part 21c having the same cross-sectional area toward the

downstream end is connected to the downstream side of the enlarged part

21b.

In Embodiment 1, an angle 01 formed by the inner wall of the

enlarged part 21b with respect to an extension line of the straight pipe part

21a is set to be 10 to 15. When 01 is less than 10°, a length of the fuel

nozzle 21 in the axial direction becomes longer, and when 01 exceeds 15°,

there is a problem that peeling occurs in the flow of the mixed flow, and

stagnation occurs in the flow, and fuel may be easily accumulated in the

stagnant portion. Therefore, it is preferable that 01 is 10° to 15°.

[0035]

It is not always essential that the shape of the fuel nozzle

communicates from the upstream side in the form of a straight pipe, an

enlarged pipe and a straight pipe, such as the straight pipe part 21a (=

upstream part), the enlarged part 21b and a downstream part 21c from the

upstream side. For example, if a flow passage partition member described

below is provided, the ignitability and the stability of the flame are

improved, and there may be a case in which there is no problem even if it

has the straight tubular shape throughout the nozzle.

Even if a fuel having coarse particles such as biomass fuel is used

throughout the nozzle, it is not necessary to excessively strengthen the swirl, and it may be configured to reduce pressure loss and adhesion of fuel particles to the swirlers (34a and 34b).

[0036]

A fuel concentrator 34 is disposed inside the fuel nozzle 21. Thefuel

concentrator 34 is supported by an ignition burner 32. The fuel

concentrator 34 has a first swirler 34a on the upstream side and a second

swirler 34b on the downstream side.

The first swirler 34a has a plurality of first swirl vanes 34c formed in

a spiral shape taking the ignition burner 32 as an axis. Further, the second

swirler 34b has second swirl vanes 34d which are inclined in a direction

opposite to that of the first swirl vanes 34c (reversely winding spiral shape).

The respective swirl vanes 34c and 34d are not fixed to an inner surface of

the fuel nozzle 21, and outer peripheral ends of the swirl vanes 34c and 34d

are installed apart from the inner surface of the fuel nozzle 21.

[0037]

Therefore, in the fuel concentrator 34 of Embodiment 1, a swirl

toward the outer side in the radial direction is imparted to the mixed fluid of

the fuel and the carrier gas when passing through the first swirler 34a.

Thereby, the fuel is condensed toward the inner wall surface of the fuel

nozzle 21. In addition, when passing through the second swirler 34b, a

reverse swirl is imparted to weaken the swirl. Thereby, on the downstream

side of the fuel concentrator 34, the fuel is condensed on the outer

peripheral side, and the mixed fluid is a flow close to a straight flow.

[0038]

When disposing the first swirler 34a and the second swirler 34b in the fuel nozzle 21 having such the enlarged tube shape, it is desirable to appropriately set the arrangement in the fuel nozzle so that the first swirler

34a effectively performs concentration of fuel particles on the outside of the

fuel nozzle 21 (along the inner wall), and the second swirler 34b effectively

performs cancellation of the swirl, such that the condensing effect of the fuel

and the swirl cancellation effect are less deteriorated.

It is desirable that the vanes 34c of the first swirler 34a are applied

to the upstream part (straight pipe part 21a) in (at least a portion) of a

longitudinal direction. As a result, the velocity component in a radial

direction outward (toward an inner wall of the nozzle) may be efficiently

imparted to the mixed fluid flowing through the upstream part 21a.

[0039]

Further, it is desirable that the first swirler 34a is provided so that

the end portion on the downstream side in the longitudinal direction (axial

direction of the fuel nozzle) of the vane 34c thereof is located at the same

position as a boundary portion of the upstream part (straight pipe part 21a

on the upstream side) with the enlarged part 21b (enlarged pipe part

communicating with the upstream part) of the fuel nozzle 21 or on the

downstream side from the position, that is, on the enlarged part 21b side.

This is to reduce the rebound of fuel particles from the inner wall of the

nozzle to enhance the condensing effect. Since it is not necessary to impart

excessive swirling, it is also possible to suppress the action of canceling the

swirling by the second swirler 34b without excessively increasing, and there

is also an effect of suppressing an increase in the pressure loss in the flow

passage of the fuel nozzle 21 through two swirlers 34a and 34b.

Further, it is desirable for the second swirler 34b that the vanes 34d

thereof overlap with the downstream part 21c (the straight pipe part on the

downstream side) in (at least a portion) of the longitudinal direction. That

is, it is desirable to be provided so that the downstream end portion of the

vane thereof in the longitudinal direction (axial direction of the fuel nozzle

21) is located on the downstream part 21c (straight pipe part on the

downstream side) side of the fuel nozzle 21. As a result, the second swirler

34b having a sufficient swirl canceling effect may be disposed at an

appropriate interval from the first swirler 34a while suppressing the

pressure loss.

[0040]

In Embodiment 1, an outer diameter Dwi of the first swirl vane 34c

is set to be 70% as an example with respect to an inner diameter D1 of the

straight pipe part, but it is preferably set to be 60% to 85%. If it is less

than 60%, the imparted swirling is weak and the condensing effect of the

fuel is low. Further, if it exceeds 85%, the swirling flow may become too

strong.

An outer diameter Dw2 of the second swirl vane 34d is formed to have

a size equal to or greater than the outer diameter Dwi of the first swirl vane

34c (that is, Dw2 i Dwi). Further, in Embodiment 1, they are formed with

the outer diameter Dw2 < inner diameter D1. Furthermore, the outer

diameter Dw2 of the second swirl vane 34d is set to be 65% as an example

with respect to an inner diameter D2 of the downstream part 21c, and is

preferably set to be 55% to 80%. If it is less than 55%, the effect of

canceling the swirl by the reverse swirl is reduced. Further, if it exceeds

80%, it may be difficult to pull out the ignition burner 32 from the fuel

nozzle 21 at the time of maintenance. Therefore, in the case of the

configuration in which the ignition burner 32 is not pulled out, it may be set

in such way that the outer diameter Dw 2 exceeds 80% of the inner diameter

D2, or the outer diameter Dw2 > the inner diameter D1.

[0041]

Further, in Embodiment 1, when a distance from a downstream end

fs of the fuel nozzle 21 to the downstream end of the straight pipe part 21a

(= upstream end of the enlarged part 21b) with respect to the flow direction

of the mixed flow is set to be L1, a distance from the downstream end fs of

the fuel nozzle 21 to the upstream end of the downstream part 21c (=

downstream end of the enlarged part 21b) is set to be L2, a distance from

the downstream end fs of the fuel nozzle 21 to a central portion of the second

swirler 34b is set to be L4, and a distance from the downstream end fs of the

fuel nozzle 21 to a central portion of the first swirler 34a is set to be L5, as

an example in Embodiment 1, they are set as follows.

(1) L2 = L4

(2) L5 - L4 = 0.7 x D2

(3) L5 - L1 = 0.1 x D2

[0042]

Regarding (1), it is also possible to set L2 # L4.

Regarding (2), it was confirmed in the combustion test that 0.7 x D2

to 1.3 x D2 is preferable. If it is less than 0.7, the second swirler 34b

cancels the swirl before the fuel sufficiently reaches the outer diameter side

by the swirl of the first swirler 34a, and the condensing effect of the fuel is reduced. If it exceeds 1.3, the cancellation of swirling is delayed, and the swirling remains strong at the downstream end of the fuel nozzle 21, such that there is a problem that NOx is increased.

[0043]

Regarding (3), it is preferable to set 0 x D2 to 0.5 x D2. If it is less

than 0, that is, if L5-L1 < 0, most of the first swirler 34a is disposed in the

enlarged part 21b, and a ratio of the outer diameter of the first swirl vane

34c to the inner diameter of the fuel nozzle 21 is relatively reduced, and the

condensing effect of the fuel is decreased. Meanwhile, when it exceeds 0.5,

the fuel deviated to the outer peripheral side by the swirl imparted by the

first swirler 34a collides with the inner peripheral surface of the fuel nozzle

21 and may be easily returned in the radially inward direction in a

reflecting form, thereby reducing the condensing effect of the fuel.

[0044]

That is, in Embodiment 1, at least a portion of the first swirler 34a is

located in the range of the straight pipe part (upstream part) 21a of the fuel

nozzle 21. Further, at least a portion of the second swirler 34b is located in

the range of the downstream part 21c of the fuel nozzle 21. Therefore,

when disposing the first swirler 34a and the second swirler 34b in the fuel

nozzle 21 having the enlarged pipe shape (enlarged part 21b), the first

swirler 34a effectively performs concentration of fuel particles on the outside

of the fuel nozzle (along the inner wall), and the second swirler 34b

effectively performs cancellation of the swirl, such that the fuel is less likely

to be damaged.

The vane 34c of the first swirler 34a is applied to the upstream part

(straight pipe part 21a) in (at least a portion) of the longitudinal direction,

and the velocity component in a radial direction outward (toward an inner

wall of the nozzle) may be efficiently imparted to the mixed fluid flowing

through the upstream part 21a.

[0045]

FIGS. 4 (A) and 4 (B) are views describing a flow passage partition

member of Embodiment 1, wherein FIG. 4 (A) is a side view, FIG. 4 (B) is a

cross-sectional view taken on line IVB-IVB in FIG. 4 (A), FIG. 4(C) is a view

corresponding to FIG. 4 (B) of Modification 1, and FIG. 4 (D) is a view

corresponding to FIG. 4 (B) of Modification 2.

In FIGS. 2 and 3, a flow passage partition member 36 is disposed on

the downstream side of the fuel concentrator 34. The flow passage

partition member 36 is supported on an inner surface of the fuel nozzle 21

by support members 37. The flow passage partition member 36 of

Embodiment 1 is formed in a partial cone shape (conical shape) whose inner

diameter is reduced toward a downstream end S2 from an upstream end S1.

Therefore, the flow passage partition member 36 partitions the flow passage

24 into an outer flow passage 24a and an inner flow passage 24b.

In FIGS. 3 and 4, the support member 37 is formed in a plate shape

extending in the radial direction. A plurality of support members 37 are

disposed at an interval in the circumferential direction. In FIG. 3,

according to Embodiment 1, the support members 37 are disposed between

the inner peripheral side protrusions 31a of the flame holder 31 at positions

corresponding thereto.

[0046]

In FIG. 2, in the solid fuel burner 7 of Embodiment 1, the flow

passage partition member 36 is disposed on the downstream side of the fuel

concentrator 34. Therefore, in the solid fuel burner 7 of Embodiment 1, the

flow passage partition member 36 is disposed on the downstream side where

the swirl of the fluid on the central side of the nozzle is weakened by the

second swirler 34b, and the flow passage is partitioned and separated into

an outer peripheral side (inner wall side of the nozzle) and an inner

peripheral side (central side of the nozzle). Therefore, most of the fuel

condensed toward an inner peripheral wall of the fuel nozzle 21 by the first

swirl vane 34c of the fuel concentrator 34 is supplied to the outer flow

passage 24a. Thereby, the flow passage partition member 36 hardly

hinders the flow of particles directed radially outward by the fuel

concentrator 34, and the fuel directed radially outward in the outer flow

passage 24a is reflected by the inner peripheral wall, such that even if it

goes to a central axis side again, the fuel is blocked by the flow passage

partition member 36. Thereby, the fuel particles once condensed on the

outer peripheral side (inner wall side of the nozzle) are prevented from

being uniformly redispersed by the first swirler 34a, and the condensing

effect is maintained until the vicinity of the opening portion of the nozzle.

Therefore, as compared to the configuration described in Patent

Document 1 which does not have the flow passage partition member 36, the

condensing effect of the fuel may be secured even when using solid fuel

particles obtained by crushing biomass fuel having poor ignitability.

[0047]

In particular, in Embodiment 1, the fuel concentrator 34 is not entirely fixed to the inner surface of the fuel nozzle 21. In the configuration in which the fuel concentrator 34 is supported on the inner surface of the fuel nozzle 21, the supporting portion is worn by the collision of the fuel particles to be condensed. Therefore, the supporting portion needs to be made of a special wear-resistant material, and there is a problem that costs are increased. On the other hand, in Embodiment 1, the fuel concentrator 34 is not supported by the fuel nozzle 21, such that there is no wear portion, and an increase in costs may be suppressed.

[0048]

Further, in the solid fuel burner 7 of Embodiment 1, the venturi, that

is, the member that imparts the velocity component of the fuel particles

toward the center of the nozzle is not present in the fuel nozzle 21

immediately after passing through the curved pipe part (elbow 20), and

subsequently, it is not a configuration in which the fuel concentrator that

imparts the velocity component in a direction away from the center of the

fuel nozzle is disposed on the downstream side. That is, this configuration

is different from that described in Patent Document 3. In the technique of

Patent Document 3, a two-step concentration action, in which the direction

is reversed so that the velocity component of the fuel particles is once

imparted to the center of the nozzle by the venturi, and then the velocity

component in the direction away from the center of the fuel nozzle is

imparted by the spindle-shaped fuel concentrator, would be performed.

Therefore, it is necessary to secure the length of the fuel nozzle within a

certain degree, but due to the relationship with other external equipment,

pipes, and structures, in order to shorten the length, it will be necessary to set an expansion of a diaphragm of the Venturi or the fuel concentrator in the radial direction to be steep. Since the mixed fluid bends sharply in the curved pipe part on the upstream side of the fuel nozzle, a deviation in the distribution of fuel particles in the nozzle cross section occurs, but if setting expansion of a diaphragm of the Venturi or the fuel concentrator in the radial direction to be steep, the deviation may easily remain on the downstream side as it is.

[0049]

Meanwhile, in the solid fuel burner 7 described in Embodiment 1,

the mixed fluid is not subjected to the action toward the center of the fuel

nozzle 21 in the flow passage passing through the curved pipe part, the

velocity component in the direction away from the center of the fuel nozzle

21 is imparted by the first swirler 34a, and the condensing action is

completed in one step, such that the length of the fuel nozzle 21 may be

shortened as compared to the configuration described in Patent Document 3.

If the length of the fuel nozzle 21 can be shortened, there are advantages

that the degree of freedom in installing the burner is increased, and

interference with other external equipment, pipes, and structures may be

avoided. In addition, since the effect of swirling promotes mixing in the

circumferential direction (along the inner wall of the nozzle), the

distribution of fuel particles in the circumferential direction is less likely to

be deviated, which has an effect of improving ignitability and stability of the

flame.

[0050]

Further, since the solid fuel burner 7 of Embodiment 1 has the flow passage partition member 36, the condensing effect of the fuel particles on the outside (along the inner wall) of the fuel nozzle 21 is high, and the effect is less likely to disappear, in the combination of the first swirler 34a and the second swirler 34b as the fuel concentrator 34, it is not necessary to impart and cancel the excessive swirl, which has an effect of reducing the pressure loss of the burner. Further, the combination of the first swirler 34a and the second swirler 34b as the fuel concentrator 34 may be made compact to shorten the total length of the fuel nozzle 21, which leads to a suppression in used amount of the members.

[0051]

Further, in the solid fuel burner 7 of Embodiment 1, as compared to

the technique of Patent Document 1, for the mixed fluid containing fuel

particles having a coarse particle size, effects of condensing the fuel

particles along the inner wall of the fuel nozzle 21 and maintaining it to the

opening end portion of the burner thereof may be achieved by imparting less

swirling. That is, the fuel particles once condensed along the inner wall of

the fuel nozzle 21 are difficult to redisperse toward the center side of the

nozzle, or the ignitability in the vicinity of the flame holder 31 at the

opening end is improved by reducing the flow rate, such that the swirling

strength in the first swirler 34a, that is, the angle of the first swirl vanes

34c, and the like may be set relatively smoothly. This leads to allow the

effect of canceling the swirl in the second swirler 34b to be made relatively

smoothly. From these aspects, the pressure loss in the fuel nozzle 21 may

be reduced. Further, even in the biomass fuel having coarse particles such

as crushed pellets of a wood-based raw material, local residence of the mixed fluid is less likely to occur, such that adhesion of fuel particles to the swirler

(swirl vane) may be suppressed.

[0052]

Furthermore, in Embodiment 1, the flow passage partition member

36 is formed in a conical shape, and the flow rate of the fluid passing

between the flow passage partition member 36 and the fuel nozzle 21 during

passing through the flow passage partition member 36 is decreased. In

addition, the condensed fuel is supplied to the furnace 6 with the reduced

flow rate. Therefore, the ignitability may be secured even in a biomass fuel

having low ignitability.

[0053]

Further, in the flow passage partition member 36 of Embodiment 1,

the cross-sectional area of the outer flow passage 24a at a downstream end

S2 is formed in a conical shape so as to be larger than the cross-sectional

area of the outer flow passage 24a at an upstream end Si, so that the flow

rate of the mixed fluid at the downstream end S2 is lower than the flow rate

at the upstream end S1. That is, in Embodiment 1, an inner diameter Dsi

at the upstream end of the flow passage partition member 36 is formed

larger than an inner diameter Ds 2 at the downstream end. With such an

inclined shape, the solid fuel particles can more easily move along the

inclined surface and are less likely to be deposited on the upper surface than

the case of a tubular shape along the axial direction. Further, by setting

Dsi > Ds 2 , the cross-sectional area of the flow passage on the outer

peripheral side (inner wall side of the nozzle) is gradually increased toward

the opening portion of the nozzle, and it is more effective in terms of reducing the flow rate of the fuel particles, and improving the ignitability and stability of the flame.

It is preferable that an inclination angle 02 at which the flow

passage partition member 36 is inclined with respect to the axial direction is

set to be 10 to 15. The reason why it is preferable to set 02 to be 10 to 15

is the same as in the case of01.

[0054]

Further, the inner diameter Dsi of the upstream end S1 of the flow

passage partition member 36 is set to be equal to or greater than the outer

diameter Dwi of the first swirl vane 34c and the outer diameter Dw 2 of the

second swirl vane 34d. When Dsi < DW2, the carrier gas also inflows into

the outer peripheral flow passage of Dsi, and the condensing effect of the

particle concentration is reduced. Therefore, by setting Dsi i Dw2 , the

particles inflow into the outer peripheral side and the carrier gas is

distributed to the outer circumference and the inner circumference, such

that there is an effect of condensing the concentration of the particles

passing through the flow passage partition member 36. From another

point of view, the effect of canceling the swirl by the second swirler 34b is

retained on the inner peripheral side of the flow passage (central side of the

nozzle), such that the effect of maintaining fuel particle concentration on the

outer peripheral side (inner wall side of the nozzle) may be exceedingly

maintained.

[0055]

Further, in Embodiment 1, the inner diameter Ds 2 at the

downstream end of the flow passage partition member 36 is formed to be smaller than the outer diameter Dw 2 of the second swirl vane 34d. That is, it is set to be Dw2 > Ds 2 . By setting Dw2 > Ds2, the effect of canceling the swirl by the second swirler 34b may be spread over the entire radial direction on the inner peripheral side (central side of the nozzle) of the flow passage partition member 36. Thereby, the mixed fluid whose swirl is weakened is sprayed from the opening portion of the burner, and a suppressing action of the generation of nitrogen oxides (NOx) by smoothly mixing with a combustion gas (air) such as a secondary air and tertiary air may be enhanced without excessive spread of the mixed fluid in the furnace

6.

[0056]

Furthermore, the flow passage partition member 36 of Embodiment

1 is supported by the support members 37 from the inner peripheral wall

side of the fuel nozzle 21. If the flow passage partition member 36 is

supported from the central axis (ignition burner 32) side, when separating

the ignition burner 32 and/or the fuel concentrator 34 from the collision

plate flange 20a together with the collision plate 32a and pulling them out

of the furnace during maintenance and inspection thereof, if the flow

passage partition member 36 and the support member 37 are not separated

from each other, these members cannot pass through the straight pipe part

21a. That is, there is a problem that ease of maintenance inspection work

is deteriorated. On the other hand, in Embodiment 1, the flow passage

partition member 36 is supported from the inner peripheral wall side of the

fuel nozzle 21, such that the ignition burner 32 and/or the fuel concentrator

34 may be easily maintained and inspected.

[0057]

Further, in Embodiment 1, the flow passage partition member 36

and the support member 37 (and the fuel concentrator 34) are installed on

the upstream side in a fluid flow direction in the fuel nozzle 21, that is, an

outside of the furnace 22 at a distance from an opening end portion

(downstream end) fs of the fuel nozzle 21 on the furnace 22 side or an

opening portion formed in a wall surface of the furnace 22 of the solid fuel

burner 7. More specifically, as shown in FIG. 2, when a distance from the

opening end portion fs on the furnace side of the fuel nozzle 21 to the

downstream end of the flow passage partition member 36 is set to be L3, it

is preferable that the distance L3 is set to be a range of 0.15 x D2 to 1.0 x

D2 with respect to the inner diameter D2 at the opening end portion fs on

the furnace side of the fuel nozzle 21. If it is less than 0.15, the flow

passage partition member 36 is likely to receive radiation from the furnace.

[0058]

Therefore, by setting to be 0.15 x D2 or more, the influence of

radiation from the furnace (inside the furnace) 22 may be reduced by the

flow passage partition member 36, etc., and the possibility that frequent

maintenance is required may be reduced. Further, it is possible to reduce a

risk of ignition even when the fuel particles are adhered to and deposited on

the upper surface of the flow passage partition member 36, etc., or a risk of

ignition in the fuel nozzle 21 due to a remaining tendency even without

adhesion and deposition, and it is also possible to easily make an ignition

region be on the downstream side of the flame holder 31.

If it exceeds 1.0 x D2, the downstream end S2 of the flow passage partition member 36 is too far from each position fs and the opening portion of the furnace wall surface. Thereby, a section after the flow rate reduction in the flow passage partition member 36 is increased. If increasing the section after the flow rate reduction, there are problems that the possibilities in which the fuel particles are adhered to and deposited on the wall surface of the fuel nozzle 21 are increased, or the fuel nozzle 21 becomes longer to increase the size of the solid fuel burner 7.

[0059]

In Embodiment 1, the fuel nozzle 21 has a configuration in which the

cross-sectional area of the flow passage 24 is the same or monotonically

increased over the straight pipe part 21a, the enlarged part 21b, and the

downstream part 21c, that is, there is no section where the cross-sectional

area is decreased. If there is a section where the cross-sectional area of the

fuel nozzle 21 is decreased between the upstream end of the fuel

concentrator 34 and the upstream end S1 of the flow passage partition

member 36, the flow rate is increased (accelerated) in the section where the

cross-sectional area is decreased. In addition, when the flow rate is

decelerated at the position of the flow passage partition member 36 after

that, a so-called flow such as a pulsating flow is formed. In such a case, a

region where the flow rate F is too reduced may occur, and there are

concerns that the fuel particles may be deposited and remain.

[0060]

Meanwhile, in Embodiment 1, there is no section where the cross

sectional area of the flow passage 24 is decreased, the flow such as pulsating

flow does not occur, and a flow rate F is smoothly decelerated (gradually reduced) without falling into a low flow rate region where the fuel particles may be deposited and remain. Thereby, in the solid fuel burner 7 of

Embodiment 1, the cross-sectional areas are set so as to be monotonically

increased or to be the same as each other (not decreased) inside of the fuel

nozzle 21, so that the flow rates F are not increased (are monotonically

decreased or are the same as each other).

Therefore, after the fuel is condensed, the cross-sectional area is not

decreased and the flow rate is not increased and decreased repeatedly, such

that the accumulation and residence of the fuel are reduced, and the fuel is

decelerated while being condensed and supplied to the furnace 6. That is,

the flow passage cross-sectional area on the opening portion side of the

furnace 6 is larger than that of on the upstream side and the flow rate is

reduced while conveying the fuel at a high flow rate so as not to cause

residence of fuel particles having a large particle size in the pipe of the fuel

nozzle 21, such that the ignitability and stability of the flame may be

improved.

[0061]

In FIGS. 2 to 4, the support member 37 of Embodiment 1 is formed

in a radial plate shape extending in the radial direction, and has a form that

does not hinder the flow of the mixed fluid as much as possible. Further, in

Embodiment 1, the support member 37 uses one plate-shaped member

whose longitudinal length is the same as that of the flow passage partition

member 36, but it is not limited thereto, and even if the plate is divided into

a plurality of portions, it is also possible to make the member in a rod shape.

The cross-sectional shape of the support member when viewed in the nozzle axial direction is not particularly limited as long as it does not obstruct the flow, and may be a streamlined wing shape (see FIG. 4 (C)), a rhombus (FIG. 4 (D)), etc. In the case of the wing shape or rhombus shape, the flow passage is once reduced along the flow direction, such that the condensation of fuel particles is further enhanced, and there is an effect of improving the ignitability and flame holding properties.

[0062]

Herein, when the shape of the support member 37 is a wedge-shaped

structure in which a thickness in the circumferential direction is increased

toward the downstream side, a vortex flow, in which the mixed fluid flows

backward toward a wall surface facing the opening portion of the support

member to the furnace or the space, is generated with respect to the flow

direction of the mixed fluid. Since the planar portion reaches a high

temperature due to radiation received from the furnace, it is necessary to

consider measures such as a use and covering of a member having high heat

resistance. There are possibilities in which the fuel particles are adhered

and grown, or remain due to the generation of the above-described vortex

flow.

[0063]

On the other hand, in Embodiment 1, the support member 37 is

formed in a plate shape whose thickness direction faces the furnace 22, and

when viewed from the opening face side of the fuel nozzle 21, a plurality of

plate-shaped support members 37 are disposed so as to be linear. Thereby,

as compared to the configuration described in Patent Document 1, the

vortex flow in which the mixed fluid flows backward is less likely to occur, and it is possible to prevent the fuel particles from being adhered and grown, or remaining. In addition, it is economical since it requires less measures against the high temperature due to radiation received from the furnace 22.

In addition, the support member 37 of Embodiment 1 is disposed at

the position which does not overlap with the inner peripheral side

protrusions 31a of the flame holder 31, and as compared to the case of being

overlapped, the resistance of the flow of the mixed gas is reduced.

Meanwhile, in an example in which the flow passage is once reduced

along the flow direction such as a streamlined wing shape or a rhombus

shape, etc. in the cross-sectional shape of the support member 37 when

viewed in the nozzle axis direction (examples shown in FIGS. 4C and 4D),

since a protrusion of the flame holder is located downstream of a region

where the flow passage is once reduced and the fuel particles are condensed

(that is, a distribution is generated), there is an effect of improving the

ignitability and flame holding properties.

[0064]

Further, in Embodiment 1, in relation to the inner diameter of the

fuel nozzle (primary nozzle) 21, the inner diameter D2 at the opening

portion (downstream end) is set to be larger than the inner diameter D1 of

the straight pipe part 21a. In order to prevent the fuel particles from being

adhered to and deposited on the inside of the flow passage on the upstream

side (fuel carrier pipe) of the fuel nozzle 21, it is necessary to maintain the

flow rate of the mixed fluid to be high to some extent, whereas it is

necessary to sufficiently reduce the flow rate at downstream end of the fuel

nozzle (primary nozzle) 21 from the viewpoint of ignitability and flame holding properties. Thereby, in Embodiment 1, the inner diameter D2 at the downstream end is set to be larger than the inner diameter D1 of the straight pipe part 21a, and the ignitability and flame holding properties are improved as compared to the case of D1 D2.

[0065]

(Simulation results)

FIG. 5 is a view describing a comparative example.

Next, an experiment (computer simulation) was conducted to confirm

the effect of Embodiment 1. In Experimental Example 1, in the

configuration of Embodiment 1, the outer diameter Dwi of the first swirl

vane 34c and the outer diameter Dw 2 of the second swirl vane 34d were set

to be the same as each other. Further, in Experimental Example 2, the

outer diameter Dw2 of the second swirl vane 34d was set to be larger than

the outer diameter Dwi of the first swirl vane 34c. Further, in Comparative

Example 1, an experiment was conducted with the configuration shown in

FIG. 5. That is, the configuration of FIG. 5 does not have the enlarged part

21b and the downstream part 21c of Embodiment 1. Further, the

configuration of FIG. 5 has a venturi 01, as a fuel concentrator, in which the

cross-sectional area of the fuel nozzle is reduced instead of the swirl vane to

condense the fuel inward in the radial direction, and then the fuel is moved

by a member whose diameter is increased toward the downstream side

supported by the ignition burner to condense the fuel on the outer side in

the radial direction.

In the simulation, the distribution (ratio) of the fuel in the radial

direction was measured at the downstream end of the fuel nozzle 21. The results are shown in FIG. 6.

[0066]

FIG. 6 is a view describing simulation results.

In Comparative Example 1 of FIG. 6, a result, in which a ratio of fuel

in an outer region 1 in the radial direction was small, and a ratio of fuel in

an intermediate region 2 in the radial direction was large, was obtained.

That is, the fuel was not condensed on the outer peripheral side, and the

condensing effect of the fuel was insufficient.

On the other hand, in Experimental Example 1, the ratio of fuel in

the outer peripheral side region 1 was the highest among all the regions 1 to

3, and the fuel was condensed on the outer peripheral side. Further, in

Experimental Example 2, a result, in which the ratio of fuel in region 1 was

higher than that in Experimental Example 1, was obtained.

[0067]

Therefore, even if the flow passage partition member 36 is provided

and the fuel concentrator is provided as in Comparative Example 1, the

condensing effect of the fuel is not sufficient in the configuration which does

not have the enlarged part 21b. Compared to this, by adopting the

configuration having the enlarged part 21b as in Example 1 (Experimental

Examples 1 and 2), the flow rate is reduced through the enlarged part 21b

whose cross-sectional area is increased, and the ignitability is improved.

Compared to the configuration of Comparative Example 1, the condensing

effect of the fuel is improved and the fuel is condensed on the outer

peripheral side, such that the ignitability and flame holding properties are

further improved.

[0068]

FIG. 7 is views describing a boiler (combustion device) including the

solid fuel burner of the present invention, wherein FIG. 7(A) is a view

describing a case of including the solid fuel burner of the present invention,

in which biomass fuels are used at the uppermost stages on a front side of a

can (boiler) and a rear side of the can among front and rear respective three

stage solid fuel burners of the can, FIGS. 7(B) and 7(D) views describing a

case of including the solid fuel burner of the present invention, in which the

biomass fuel is used at the uppermost stage on the front side of the can, and

FIGS. 7(C) and 7(E) are views describing a case of including the solid fuel

burner of the present invention, in which the biomass fuel is used at the

uppermost stage on the rear side of the can.

In the embodiment shown in FIG. 7(A), biomass fuel is supplied to a

solid fuel burner 7 of the uppermost stage among the solid fuel burners 7.

Meanwhile, coal as an example of the solid fuel is supplied to solid fuel

burners 7'of middle and lower stages. The coal contained in a bunker 4'is

pulverized by a mill 5'to be the pulverized coal, and is supplied to the solid

fuel burners 7'of the middle and lower stages. In each stage, a plurality of

solid fuel burners 7 are installed in a furnace width direction of a

combustion device 1.

The embodiment of the solid fuel burner 7'may not be the solid fuel

burner of the above-described present invention.

[0069]

As shown in FIG. 1, when using biomass fuel, the biomass fuel

having a large particle size may fall to the furnace bottom in an unignited state. If the unignited biomass fuel is deposited on the furnace bottom, there is a problem that the frequency of maintenance should be increased, or waste of fuel is increased.

On the other hand, in the embodiment shown in FIG. 7(A), the

biomass fuel is used only in the solid fuel burner 7 of the uppermost stage.

Therefore, even if the unignited biomass fuel is generated in the uppermost

solid fuel burner 7, the unignited biomass fuel may be easily burned out by

the solid fuel burners 7' of the middle and lower stages until the fuel falls to

the furnace bottom. In particular, in the boiler 6, the temperature tends to

be increased toward the upper side in a region in which the solid fuel

burners 7 and 7' are installed. Therefore, if using the biomass fuel in the

solid fuel burner 7 of the uppermost stage, it is less likely for unignited

biomass fuel to be generated than the case of using the biomass fuel in the

solid fuel burner of the lower stage. Thereby, in the embodiment shown in

FIG. 7(A), it is difficult for the unignited biomass fuel to fall to the furnace

bottom, and the waste of fuel, and the like may be prevented.

[0070]

In addition, in the existing combustion device 1 including the

respective three-stage solid fuel burners on the front side and the rear side

of the can, it is also possible to change so that the biomass fuel is used only

in the solid fuel burner 7 of the uppermost stage. Therefore, an existing

combustion device 1 that uses only coal may be easily converted to the

combustion device 1 that uses the biomass fuel.

Further, as shown in FIGS. 7(B) and 7(C), also in the configuration

in which the numbers of stages of the solid fuel burners 7 and 7' are different before and after the can (or a configuration of including the same number of stages, but one is stopped), it is also possible to change so that the biomass fuel is used only in one solid fuel burner 7 of the uppermost stage on the front side or the rear side of the can.

[0071]

Furthermore, in FIGS. 1 and 7, the configuration, in which the solid

fuel burners 7 and 7'are provided in three stages in a vertical direction, has

been exemplified, but it is not limited thereto. It may also be configured to

have two or four or more stages.

At this time, it is desirable that the solid fuel burner 7 using the

biomass fuel is provided at the uppermost stage, but it is not limited thereto.

It is also possible to provide two or more stages at the uppermost stage and

the middle stage.

Further, it may also be configured in such a way that, for example, as

shown in FIGS. 7(D) and 7(E), one solid fuel burner 7 uses the biomass fuel,

and the other solid fuel burners 7'use the pulverized coal in the uppermost

stage. That is, it may also be configured in such a way that the solid fuel

burner 7 using the biomass fuel and the solid fuel burners 7' using the

pulverized coal face to each other.

[0072]

In the above description, the embodiment of the present invention

has been described in detail, but it is not limited to the above embodiment,

and it is possible to perform various changes within the scope of the purport

of the present invention described in inventions of a first to a ninth aspect of

the present invention.

For example, the shape of the support member 37 is not limited to a

plate shape, and may be changed to any shape such as a wedge shape, a

rhombus shape, or a trapezoidal shape, etc.

In addition, although the configuration of the two-stage combustion

gas nozzles 26 and 27 having the secondary combustion gas nozzle 26 and

the tertiary combustion gas nozzle 27 has been exemplified, but it is not

limited thereto, and combustion gas nozzle(s) having one stage or three or

more stages are also possible.

[0073]

Further, as the fuel concentrator 34, the configuration having two

swirlers of the first swirler 34a and the second swirler 34b has been

exemplified, but it is not limited thereto. It is possible to provide three or

more swirlers, or provide one swirler. Further, even when providing one

swirler, the swirl in the flow passage partition member 36 is weakened, such

that the mixed fluid after passing through the flow passage partition

member 36 is sprayed in a state where the swirl is weakened. Further, in

consideration of the weakening of the swirl in the flow passage partition

member 36, it is possible to make the performance of imparting the reverse

swirl of the second swirler 34b be lower than the performance of imparting

the swirl of the first swirler 34a. That is, it is possible to make changes

such as shortening the outer diameter of the second swirl vane 34d,

reducing the inclination angle, shortening the length in the axial direction

and the like.

[0074]

Further, as the fuel nozzle 21, it is desirable that the fuel nozzle 21 has a downstream part 21c, but it is not limited thereto. It is also possible to have a configuration in which the downstream end of the enlarged part

21b is the downstream end of the fuel nozzle 21 without having the

downstream part 21c. At this time, since L2 = 0, it becomes L2 # L4.

[0075]

The reference in this specification to any prior publication (or

information derived from it), or to any matter which is known, is not, and

should not be taken as an acknowledgment or admission or any form of

suggestion that the prior publication (or information derived from it) or

known matter forms part of the common general knowledge in the field of

endeavour to which this specification relates.

[0076]

Throughout this specification and claims which follow, unless the

context requires otherwise, the word "comprise", and variations such as

"comprises" or "comprising", will be understood to imply the inclusion of a

stated integer or group of integers or steps but not the exclusion of any other

integer or group of integers.

[Reference Signs List]

[0075]

7 ... Solid fuel burner,

21 . . Fuel nozzle,

22 ... Furnace,

24 ...Flow passage of mixed fluid,

24a ... Outer flow passage,

26,27 ... Combustion gas nozzle,

43A

34 ... Fuel concentrator,

34c, 34d ... Vane

36 ... Flow passage partition member.

Claims (3)

1. A solid fuel burner comprising:

a fuel nozzle through which a mixed fluid of a solid fuel and a carrier

gas thereof flows, and is opened toward a furnace;

a combustion gas nozzle which is disposed on an outer peripheral side

of the fuel nozzle to spray a combustion gas; and

a fuel concentrator provided on a center side of the fuel nozzle and

configured to impart a velocity component in a direction away from a center

of the fuel nozzle to the mixed fluid,

wherein the fuel concentrator has a plurality of vanes configured to

impart a swirl to the mixed fluid, of which each vane is disposed away from

an inner surface of the fuel nozzle without being completely fixed to an inside

of the fuel nozzle, and includes a first swirler disposed on an upstream side

in a flow direction of the mixed fluid, and a second swirler which is disposed

on a downstream side in the flow direction of the mixed fluid with respect to

the first swirler, and has a plurality of vanes whose swirl direction is in a

direction opposite to that of the first swirler,

a flow passage partition member configured to partition a flow passage

of the fuel nozzle into an inner side and an outer side in the flow passage cross

section is provided on the downstream side with respect to the second swirler

in the flow direction of the mixed fluid,

an outer diameter of the first swirler is equal to or less than an inner

diameter of an upstream end of the flow passage partition member,

the solid fuel condensed toward an inner peripheral wall of the fuel

nozzle by the first swirler is supplied to an outside of the flow passage partition member, the flow passage partition member has a shape in which the inner diameter of the upstream end is larger than an inner diameter of a downstream end, and an outer diameter of the second swirler is smaller than the inner diameter of the upstream end of the flow passage partition member and larger than the inner diameter of the downstream end of the flow passage partition member.

2. The solid fuel burner according to claim 1, wherein:

a flow passage of the fuel nozzle has an upstream part whose inner

diameter is the same on the upstream side of the first swirler, an enlarged

pipe part communicated to the downstream side of the upstream part and

having an inner diameter gradually increased, and a downstream part

communicated to the downstream side of the enlarged pipe part and having

a constant inner diameter,

at least a portion of the first swirler is located in a range of the

upstream part of the flow passage of the fuel nozzle, and

at least a portion of the second swirler is located in a range of the

downstream part of the flow passage of the fuel nozzle.

3. The solid fuel burner according to claim 2, wherein the outer

diameter of each swirler is less than an inner diameter of the upstream part

of the flow passage of the fuel nozzle.