AU2019216590B2

AU2019216590B2 - Solid fuel burner

Info

Publication number: AU2019216590B2
Application number: AU2019216590A
Authority: AU
Inventors: Akira Baba; Kosuke KITAKAZE; Kenji Kiyama; Koji Kuramashi; Kenichi Ochi; Junya Watanabe
Original assignee: Mitsubishi Power Ltd
Current assignee: Mitsubishi Power Ltd
Priority date: 2018-08-20
Filing date: 2019-08-12
Publication date: 2020-08-27
Anticipated expiration: 2039-08-12
Also published as: CA3051916A1; TWI712761B; JP2020030037A; CN110848672A; AU2019216590A1; KR20200021405A; TW202014642A; US20200056780A1

Abstract

OF DISCLOSURE The present invention provides a solid fuel burner which ensures ignition performance and flame holding 5 performance of a fuel nozzle. The present invention provides a solid fuel burner which achieves cost reduction by simplifying the structure of the fuel nozzle, for example, and which ensures the ignition performance and flame holding performance of the fuel nozzle. Further, 10 the present invention provides a burner which enables stable combustion by both solid fuel and oil combustion with the suppression of soot and dust and mist generated during the oil start-up envisaged. The solid fuel burner of the present invention includes: a fuel nozzle straight 15 tube portion allowing a mixing gas of a solid fuel and its carrier gas to flow therethrough; a fuel nozzle throttling portion narrowing a flow passage of the mixing gas passed through the fuel nozzle straight tube portion; a fuel nozzle diffusion portion horizontally expanding the flow 20 passage of the mixing gas passed through the fuel nozzle throttling portion; a fuel nozzle outlet portion connected to the fuel nozzle diffusion portion and having an outlet flattened in shape; a ring-shaped outer peripheral flame stabilizer disposed on an outer periphery of the fuel 25 nozzle outlet portion; and an inner flame stabilizer 48 disposed in the fuel nozzle outlet portion and horizontally dividing the mixing gas passed through the fuel nozzle diffusion portion. 4/10 FIG. 4A VERTICAL CROSS SECTION TAKEN ON AXIS 101 10 102 100 103 104 12 38 9 FIG. 4B HORIZONTAL CROSS SECTION TAKEN ON AXIS 101 10 -102 100 104 12 3

Description

disposed in the fuel nozzle outlet portion and

horizontally dividing the mixing gas passed through the

fuel nozzle diffusion portion.

4/10

FIG. 4A VERTICAL CROSS SECTION TAKEN ON AXIS 101 10 102

100

103 104

12 38 9

FIG. 4B HORIZONTAL CROSS SECTION TAKEN ON AXIS 101 10 -102

100

104

12 3

SOLID FUEL BURNER

Field of the Invention

The present invention relates to a solid fuel burner.

Background of the Invention

A background art of this field is set forth in Japanese

Patent Application Laid-Open No. Hei 10-220707 (Patent

Literature 1). This patent literature discloses a

structure which includes: an outer peripheral flame

stabilizing ring disposed on an outer periphery of a

burner; an inner flame stabilizer disposed in a pulverized

coal fuel pipe and equipped with a flame stabilizing plate

for drawing a high temperature gas from the outer

periphery of the burner into a central part of the burner;

and a separator disposed on a burner front-stream side of

the inner flame stabilizer. The structure is adapted to

increase a pulverized coal flow volume at the center of

the burner and to decrease the pulverized coal flow volume

on the outer periphery of the burner.

Another background art of this field is set forth in

Japanese Patent Application Laid-Open No. 2014-055759

(Patent Literature 2). This patent literature discloses a

combustor which includes pulverized coal burners arranged

in plural rows and plural columns on at least one surface

of furnace walls. The pulverized coal burner includes a

pulverized coal nozzle which includes a venturi including

the throttling portion and the concentrator in the fuel

flow passage. In the pulverized coal nozzle, a portion

having a circular transverse cross section extends to the

vicinity of the throttling portion, from which the

transverse cross section is progressively flattened in the

horizontal direction so that the nozzle has the maximum

degree of flatness at an opening of the furnace wall. The

pulverized coal burners are arranged such that width sides

of the flattened nozzles are properly directed in a

vertical direction or horizontal direction.

It is generally desirable to overcome or ameliorate one or

more of the above described difficulties, or to at least

provide a useful alternative.

Summary of the Invention

According to the present invention, there is provided a solid fuel burner comprising: a fuel nozzle straight tube portion allowing a mixing gas of a solid fuel and its carrier gas to flow therethrough; a fuel nozzle throttling portion narrowing a flow passage of the mixing gas passed through the fuel nozzle straight tube portion; a fuel nozzle diffusion portion horizontally expanding the flow passage of the mixing gas passed through the fuel nozzle throttling portion; a fuel nozzle outlet portion connected to the fuel nozzle diffusion portion and having an outlet flattened in shape; a ring-shaped outer peripheral flame stabilizer disposed on an outer periphery of the fuel nozzle outlet portion; and an inner flame stabilizer disposed in the fuel nozzle outlet portion and horizontally dividing the mixing gas passed through the fuel nozzle diffusion portion, wherein the fuel nozzle throttling portion has a structure which is narrowed only in the vertical direction.

The above-described Patent Literature 1 discloses the

solid fuel burner including the inner flame stabilizer and

the outer peripheral flame stabilizing ring, while the above-described Patent Literature 2 discloses the pulverized coal burner including the pulverized coal nozzle which is flattened at the outlet. The solid fuel burner stated in Patent Literature 1 and the pulverized coal burner stated in Patent Literature 2 may encounter the following problem. In a case where the burner grows in size, an ignition area relative to fuel injection becomes smaller, which may result in instable ignition or flame holding.

Preferred embodiments of the present invention provide a

solid fuel burner featuring a fuel nozzle which ensures

stable ignition performance and flame holding performance.

The solid fuel burner of the present invention can be

applied to a case where the burner has a large capacity,

or a case where a flame retardant fuel having a small

amount of volatile matter, for example, solid fuel such as

anthracite or petroleum coke. In addition, since the

average particle size of the solid fuel supplied to the

burner is large, it can be applied to a fuel, for example,

biomass, for which floating combustion within a boiler

furnace is harder than pulverized coal. Further, the

present invention provides a solid fuel burner which

achieves cost reduction by simplifying the structure of the fuel nozzle and mitigate environmental burden as represented by NOx and CO and enables efficient combustion such as reducing unburned carbon in the fly ashes and the

CO content of the flue gas. Further, the present

invention provides a solid fuel burner in which the solid

fuel burner and a start-up oil burner are coaxially

arranged and which is reducing soot and dust, oil mist and

CO during operation.

For achieving the above object, a solid fuel burner is

preferably characterized in including: a fuel nozzle

straight tube portion allowing a mixing gas of a solid

fuel and its carrier gas to flow therethrough; a fuel

nozzle throttling portion narrowing a flow passage of the

mixing gas passed through the fuel nozzle straight tube

portion; a fuel nozzle diffusion portion horizontally

expanding the flow passage of the mixing gas passed

through the fuel nozzle throttling portion; a fuel nozzle

outlet portion connected to the fuel nozzle diffusion

portion and having an outlet flattened in shape; a ring

shaped outer peripheral flame stabilizer disposed on an

outer periphery of the fuel nozzle outlet portion; and an

inner flame stabilizer disposed in the fuel nozzle outlet

portion and horizontally dividing the mixing gas passed through the fuel nozzle diffusion portion.

The present invention can preferably provide the solid

fuel burner which ensures the ignition performance and

flame holding performance of the fuel nozzle in future too.

The present invention can preferably provide the solid

fuel burner which achieves cost reduction by simplifying

the structure of the fuel nozzle and ensure the ignition

performance and flame holding performance of the fuel

nozzle.

The problems, components and effects other than those

described above will become apparent from the description

of the following examples hereof.

Brief Description of the Drawings

Preferred embodiments of the present invention are

hereafter described, by way of non-limiting example only,

with reference to the accompanying drawings, in which:

Fig. 1A is an illustrative diagram showing a vertical

cross section of a solid fuel burner according to Example

1 hereof as taken on the axis thereof;

Fig. 1B is an illustrative diagram showing a horizontal

cross section of the solid fuel burner according to

Example 1 hereof as taken on the axis thereof;

Fig. 2A is an illustrative diagram showing a vertical

cross section of a solid fuel burner according to Example

2 hereof as taken on the axis thereof;

Fig. 2B is an illustrative diagram showing a horizontal

cross section of the solid fuel burner according to

Example 2 hereof as taken on the axis thereof;

Fig. 3A is an illustrative diagram showing a vertical

cross section of a solid fuel burner according to Example

3 hereof as taken on the axis thereof;

Fig. 3B is an illustrative diagram showing a horizontal

cross section of the solid fuel burner according to

Example 3 hereof as taken on the axis thereof;

Fig. 4A is an illustrative diagram showing a vertical

cross section of a solid fuel burner according to Example

4 hereof as taken on the axis thereof;

Fig. 4B is an illustrative diagram showing a horizontal

cross section of the solid fuel burner according to

Example 4 hereof as taken on the axis thereof;

Fig. 5A is an illustrative diagram showing a vertical

cross section of a solid fuel burner according to Example

5 hereof as taken on the axis thereof;

Fig. 5B is an illustrative diagram showing a horizontal

cross section of the solid fuel burner according to

Example 5 hereof as taken on the axis thereof;

Fig. 6A is an illustrative diagram showing a vertical

cross section of a solid fuel burner according to Example

6 hereof as taken on the axis thereof;

Fig. 6B is an illustrative diagram showing a horizontal

cross section of the solid fuel burner according to

Example 6 hereof as taken on the axis thereof;

Fig. 7A is an illustrative diagram showing an example of

the inner flame stabilizer which is disposable in any one

of the solid fuel burners according to Example 1 to 6

hereof;

Fig. 7B is an illustrative diagram showing an example of

the inner flame stabilizer which is disposable in any one

of the solid fuel burners according to Example 1 to 6

hereof;

Fig. 7C-1 is an illustrative diagram showing an example of

the inner flame stabilizer which is disposable in any one

of the solid fuel burners according to Example 1 to 6

hereof;

Fig. 7C-2 is an illustrative diagram showing an example of

the inner flame stabilizer which is disposable in any one

of the solid fuel burners according to Example 1 to 6 hereof;

Fig. 7D is an illustrative diagram showing an example of

the inner flame stabilizer which is disposable in any one

of the solid fuel burners according to Example 1 to 6

hereof;

Fig. 7E is an illustrative diagram showing an example of

the inner flame stabilizer which is disposable in any one

of the solid fuel burners according to Example 1 to 6

hereof; and

Fig. 7F is an illustrative diagram showing an example of

the inner flame stabilizer which is disposable in any one

of the solid fuel burners according to Example 1 to 6

hereof, in which the detail of the inner flame stabilizer

in Fig.7D, the flow of the solid fuel and the injection

direction of the start-up oil fuel are shown.

Detailed Description of Preferred Embodiments of the

Invention

The examples of the present invention will hereinbelow be

described with reference to the accompanying drawings.

Equal or similar reference numerals are assigned to equal

or similar components, and explanation of overlapping

components may be omitted.

First Embodiment

In combustors using solid fuels such as coal fired boilers,

the solid fuel burner for use in the combustors is

required to ensure stable ignition and flame holding in

order to achieve the reduction of harmful emissions such

as nitrogen oxides (NOx) and the increase in combustion

efficiency. To ensure the stable ignition and flame

holding, it is important to install a flame stabilizer in

a fuel nozzle of a solid fuel burner and to supply the

flame stabilizer with a fuel stream (particles of solid

fuel) having sufficiently high density. Particularly, in

a case where the solid fuel burner is increased in size so

that a large ignition area is required or a case where the

solid fuel burner operates under low load during load

fluctuation, the stable ignition and flame holding is

necessary.

Fig. 1A is an illustrative diagram showing a vertical

cross section of a solid fuel burner according to Example

1 hereof as taken on the axis thereof. Fig. 1B is an

illustrative diagram showing a horizontal cross section of

the solid fuel burner according to Example 1 hereof as taken on the axis thereof.

The solid fuel burner according to the example includes: a

fuel nozzle straight tube portion 4 (hereinafter, simply

referred to as "straight tube portion") which allows a

mixing gas 100 of a solid fuel and its carrier gas to flow

therethrough; a fuel nozzle throttling portion 5

(hereinafter, simply referred to as "throttling portion")

which narrows a flow passage of the mixing gas 100 passed

through the straight tube portion 4 so as to accelerate

the mixing gas 100; a fuel nozzle diffusion portion 6

(hereinafter, simply referred to as "diffusion portion")

which flows and slows the mixing gas 100 accelerated as

passed through the throttling portion 5 and horizontally

expands the flow passage of the mixing gas 100; and a fuel

nozzle outlet portion 16 (hereinafter, simply referred to

as "outlet portion") which is connected to the diffusion

portion 6 and ejects the mixing gas 100 passed through the

diffusion portion 6 into a furnace.

An outlet of the outlet portion 16 has a flat

configuration which is expanded in horizontal width. The

throttling portion 5 is a venturi type which is

circumferentially narrowed.

The straight tube portion 4, the throttling portion 5, the

diffusion portion 6 and the outlet portion 16 constitute

the fuel nozzle, defining the flow passage of the mixing

gas 100.

A wind box 10 for introducing combustion air is disposed

on an outer periphery of the fuel nozzle (straight tube

portion 4, throttling portion 5 and diffusion portion 6).

A guide sleeve 7 for discharging the combustion air into

the furnace is disposed on an outer periphery of the

outlet portion 16. A top-bottom guide sleeve 8 for

discharging the combustion air to upper and lower areas of

the furnace is disposed at upper and lower places of an

outer periphery of the guide sleeve 7. Furnace walls 9

are disposed on transversely outer sides of the guide

sleeve 7 and on vertically outer sides of the top-bottom

guide sleeve 8 on the outer sides of the guide sleeve 7,

respectively.

An outer peripheral flame stabilizer 2 shaped like a ring

is disposed on the outer periphery of the outlet portion

16. It is noted that the guide sleeve 7 is disposed on an outer side from the outer peripheral flame stabilizer 2.

The outlet portion 16 is provided with an inner flame

stabilizer 1 shaped like a wedge having an isosceles

triangular cross section. The inner flame stabilizer 1 is

singly disposed at a horizontally central position so as

to horizontally divide the mixing gas 100 passed through

the diffusion portion 6.

A central supporting rod 3 is disposed at a central part

of fuel nozzle (straight tube portion 4, throttling

portion 5, and diffusion portion 6). According to the

example, the central supporting rod 3 is not provided with

a particle concentrator for throwing the particles of the

solid fuel (hereinafter, simply referred to as

"particles") toward an outer periphery for concentration.

The mixing gas 100 ejected from the outlet portion 16 into

the furnace forms a fuel jet flow 104. The combustion air

discharged from the guide sleeve 7 and top-bottom guide

sleeve 8 into the furnace as spreading circumferentially

outward forms a combustion air jet flow 101.

A recirculation flow 102 is formed between the fuel jet flow 104 and the combustion air jet flow 101. The recirculation flow 102 is formed in the rear of the outer peripheral flame stabilizer 2. A high-temperature combustion gas resulting from fuel combustion in the furnace accumulates in the recirculation flow 102. The high-temperature combustion gas contacting with the fuel jet flow 104 causes immediate ignition of the particles in the rear of the outer peripheral flame stabilizer 2 and thus, flames are formed.

In the solid fuel burner according to the example, the

outlet portion 16 has the flattened configuration having a

short vertical (height) dimension and a long horizontal

(width) dimension. The diffusion portion 6 is expanded in

the horizontal direction but not in the vertical direction.

That is, the diffusion portion 6 and the outlet portion 16

are formed in the flattened shape also at their connection

portion.

In general, an opening (a jetting port of the fuel jet

flow into the furnace) of the fuel nozzle of the solid

fuel burner has a circular shape. In a case where the

outlet portion of the solid fuel burner has the flattened

configuration having a short vertical (height) dimension and a long horizontal (width) dimension, a flow passage of the combustion air jetted from an outer peripheral area of the outlet portion has an area which is vertically wide and horizontally narrow. Accordingly, the flow volume of the combustion air is large in the vertical area but small in the horizontal area.

The solid fuel burner of the example is provided with the

top-bottom guide sleeve 8 only in the vertical area so as

to guide the combustion air in the vertical area of the

large flow volume to the outer peripheral area. In a case

where the combustion air has a large flow volume, the

combustion air with high kinetic momentum is jetted into

the furnace so that a large recirculation flow 102 is

vertically formed in the rear of the outer peripheral

flame stabilizer 2.

The larger the magnitude of the recirculation flow 102 is,

the more high-temperature combustion gas can be

accumulated. Mixed with the fuel jet flow 104 and

imparted thermal radiation , the recirculation flow 102

can provide stable ignition and flame holding of the solid

fuel. Therefore, the fuel nozzle having the horizontally

elongated flat configuration at the outlet portion 16 is capable of forming the large recirculation flow 102 in vertically upper and lower areas and achieving the stable ignition and flame holding.

The solid fuel burner according to the example has the

inner flame stabilizer 1 so disposed as to horizontally

divide the flow passage in the outlet portion 16. Namely,

the inner flame stabilizer 1 is designed to horizontally

divide the mixing gas 100 passed through the diffusion

portion 6. The inner flame stabilizer 1 so disposed as to

horizontally divide the flow passage in the outlet portion

16 plays a role as a bridge to interconnect the upper and

lower parts of the outer peripheral flame stabilizer 2.

By virtue of the effect of the fuel nozzle having the

horizontally elongated flat configuration, a large

recirculation flow 102 is formed at the upper and lower

parts of the outer peripheral flame stabilizer 2 so that

the high-temperature combustion gas is stably supplied to

the vicinity of the outer peripheral flame stabilizer 2.

The high-temperature combustion gas in the large

recirculation flow 102 can be drawn to the center in the

rear of the outlet portion 16 by disposing the inner flame

stabilizer 1 according to the example. That is, a high- temperature gas flow 103 can be formed so as to draw the high-temperature combustion gas to the center in the rear of the outlet portion 16. In this way, the high temperature combustion gas drawn to the center in the rear of the outlet portion 16 permits even the small recirculation flow (not shown) in the rear of the inner flame stabilizer 1 to achieve the stable ignition and flame holding of the whole fuel jet flow up to the point where the divided fuel jet flow 104 is innermost ignited on the inner sides thereof.

The particles are concentrated toward the center of the

fuel nozzle by the venturi type throttling portion 5.

The inner flame stabilizer 1 according to the example is

disposed at the horizontal center position so that the

concentrated particles can be made to flow in the vicinity

of the inner flame stabilizer 1. Since a fuel (particle)

flow of high density can be made to flow in the vicinity

of the inner flame stabilizer 1, the inner flame

stabilizer can achieve the stable ignition and flame

holding.

The inner flame stabilizer 1 according to the example is shaped like the wedge having the isosceles triangular cross section so as to split the fuel jet flow 104 in a manner to spread the fuel jet flow horizontally. The inner flame stabilizer can spread the flames in the furnace so as to prevent flame localization in the furnace.

This leads to homogeneous combustion of the fuel in the

furnace and hence, is effective in reducing unburned NOx

and non-combusted content.

According to the example, the inner flame stabilizer 1 is

singly disposed at the horizontal center position.

However, more than one inner flame stabilizer 1 may be

arranged in the horizontal direction. Further, the cross

section shape of the inner flame stabilizer 1 is not

limited to isosceles triangle but may also be pentagonal

or such a shape as providing a recess on a downstream side

portion of the inner flame stabilizer which faces the

furnace.

As to such concrete shape examples, reference is made to

Fig. 7B to Fig. 7F. The inner flame stabilizer basically

has such function as dividing the solid fuel into two

directions, but according to the type of the fuel and the

fuel granurality, the fuel is hard to be incorporated into the downstream recirculation zone of the inner flame stabilizer, leading to interrupting ignition, in which case the structure having such recess enables such recirculation zone to be enlarged so as to permit stable ignition. Further, in terms of production cost, the example in Fig. 7C-1 or 7C-2 taking a V-shape structure by a plate is more cost-effective than the solid triangular prism, so that the inner flame stabilizer taking a V-shape structure is optionally adoptable when ignition performance is stable enough.

(Operation 1)

In a conventional solid fuel burner provided with the

outer peripheral flame stabilizer, the particle

concentrator is disposed on the central supporting rod.

The particle concentrator is designed to increase the fuel

(particles) density around the outer peripheral flame

stabilizer at the outlet portion of the fuel nozzle by

throwing the particles toward the outer periphery for

concentration.

Specifically, the fuel nozzle provided with the particle

concentrator on the central supporting rod is designed such that the fuel nozzle is narrowed by means of the throttling portion thereof so as to guide the particles to the center and against the particle concentrator, which guide the particles toward the outer periphery for concentration so as to increase the density of the fuel around the outer peripheral flame stabilizer.

As just described, the particle concentrator must be

disposed in order to increase the fuel (particles) density

around the outer peripheral flame stabilizer. This

entails an additional support member for the particle

concentrator at a distal end of the solid fuel burner and

an increase in axial length of the solid fuel burner,

resulting in cost increase.

The particle concentrator is subjected to impacts from

high-density fuel flow (particles) at a velocity of tens

of meters per second and suffers from increase in wear

volume. Therefore, a high-grade hard material must be

used for the particle concentrator. This results in cost

increase.

The particle concentrator further suffers from the

increase in wear volume because the particles need to collide against the concentrator at a large collision angle. The particles thrown toward the outer periphery by the particle concentrator are concentrated as colliding against an inner wall of the fuel nozzle. Hence, the inner wall of the fuel nozzle suffers from increased wear volume. Furthermore, if the particle concentrator is disposed on the central supporting rod, a cross-sectional area of the flow passage is decreased so that the velocity of the particles in the fuel nozzle is increased. Hence, the particles colliding against the inner wall of the fuel nozzle are also increased in velocity. Accordingly, the inner wall of the fuel nozzle is increased in wear volume.

This dictates the need for using the high-grade hard

material for the fuel nozzle as well, resulting in cost

increase.

Particularly, in a case where the fuel nozzle having the

horizontally flattened configuration at the outlet portion

of the fuel nozzle is used, the movement distance from the

particle concentrator to the outlet portion of the fuel

nozzle of the particles that are thrown toward the outer

periphery by the particle concentrator disposed on the

central supporting rod of the fuel nozzle is longer in the

horizontal direction than in the vertical direction.

Therefore, a sufficient amount of horizontally thrown

particles does not reach the outer peripheral flame

stabilizer, which may be lowered in fuel (particle)

density in the horizontal direction. Thus, the outer

peripheral flame stabilizer is prone to suffer ignition

failure in the horizontal direction. In the case where

the fuel nozzle having the flattened configuration is

employed, it is required to increase the diameter of the

particle concentrator and the axial length of the solid

fuel burner in order to obviate this problem. This

results in cost increase.

For the sake of suppressing cost increase, as just

described, it is effective to omit the particle

concentrator.

If the particle concentrator is omitted, however, a high

density fuel flow (particles) centrally concentrated in

the throttling portion 5 is directly jetted into the

furnace but is not made to flow in the vicinity of the

outer peripheral flame stabilizer 2 where the

recirculation flow 102 with the accumulated high

temperature combustion gas is formed. Hence, the solid

fuel burner is significantly degraded in combustion performance (ignition performance).

The solid fuel burner according to the example is provided

with the inner flame stabilizer 1 at the outlet portion 16

in place of the particle concentrator such that the high

density fuel flow (particles) centrally concentrated in

the throttling portion 5 is ignited by the inner flame

stabilizer 1. Thus, the solid fuel burner is adapted to

suppress cost increase without degrading the combustion

performance (ignition performance).

The solid fuel burner according to the example utilizes

the inner flame stabilizer 1 disposed in the outlet

portion 16 to cause the high-density fuel flow (particles)

centrally concentrated in the throttling portion 5 to flow

in the vicinity of the outer peripheral flame stabilizer 2

where the recirculation flow 102 with the accumulated

high-temperature combustion gas is formed. Thus, the

solid fuel burner is improved in the combustion

performance (ignition performance).

The solid fuel burner according to the example does not

employ the particle concentrator disposed on the central

supporting rod 3 but effectively utilizes the high-density fuel flow (particles) centrally concentrated in the throttling portion 5 to achieve the increased combustion performance (ignition performance).

As compared with the conventional solid fuel burner

including the particle concentrator, the solid fuel burner

of the example can also achieve the reduction of the wear

volume of inner wall of the fuel nozzle. This is the

result of omitting the particle concentrator so as to

avoid positively throwing the particles toward the outer

periphery.

(Operation 2)

The combustor is faced with a strong demand for cost

reduction. One of the measures for cost reduction is to

increase the capacity of the solid fuel burner. The high

capacity enables the reduction of the number of solid fuel

burners, leading to the reduction of the number of pipes

for flowing the mixing gas of the solid fuel and its

carrier gas and the number of pulverizers for pulverizing

the solid fuel. Thus, cost reduction can be achieved.

With the increase in the capacity of the solid fuel burner, however, the fuel nozzle for use in the solid fuel burner is increased in diameter so that an unignited area near the center of the fuel nozzle is increased. This may raise the fear of increase in harmful emissions such as nitrogen oxides (NOx) and decrease in combustion efficiency.

With the decrease in the number of solid fuel burners, a

distance between the solid fuel burner and the solid fuel

burner in the combustor is increased so that the flames

are localized, making it difficult to make effective use

of the whole furnace.

By using the inner flame stabilizer 1 shaped like the

wedge having the isosceles triangular cross section, the

solid fuel burner according to the example is adapted to

bring the recirculation flow 102 with the accumulated

high-temperature combustion gas and the fuel jet flow 104

into contact, to ensure the stable ignition and flame

holding, to achieve the reduction of harmful emissions

such as nitrogen oxides (NOx) and the improvement of

combustion efficiency, and to split the fuel jet flow 104

into horizontally spread flows so as to spread the flames

in the furnace and to prevent the flame localization.

(Operation 3)

In general, comparing the ring-shaped inner flame

stabilizer with the ring-shaped outer peripheral flame

stabilizer, the recirculation flow formed in the rear of

the latter is larger than that formed in the rear of the

former. In turn, when such stabilizers are put to use

together, the surrounding temperature rises under the

influence of the flame formed behind the inner flame

stabilizer so as to lead to inflating the combustion gas,

under the influence of which the recirculation zone behind

the outer peripheral flame stabilizer is reduced, with the

result that the burner provided with the outer peripheral

flame stabilizer and the inner flame stabilizer is

inferior to the burner provided only with the outer

peripheral flame stabilizer in terms of the ignition

performance and the flame holding performance.

However, by employing the inner flame stabilizer 1 shaped

like the wedge having the isosceles triangular cross

section, the solid fuel burner according to the example is

adapted to form the large recirculation flow 102 so that

the high-temperature combustion gas is stably supplied to the vicinity of the outer peripheral flame stabilizer.

Therefore, the burner can achieve the stable ignition and

flame holding.

Second Embodiment

Fig. 2A is an illustrative diagram showing a vertical

cross section of a solid fuel burner according to Example

2 hereof as taken on the axis thereof. Fig. 2B is an

illustrative diagram showing a horizontal cross section of

the solid fuel burner according to Example 2 hereof as

taken on the axis thereof.

A solid fuel burner according to this example differs from

the solid fuel burner of Example 1 in the configuration of

the throttling portion 5.

In the solid fuel burner of Example 1, the throttling

portion 5 has the venturi type configuration such that the

throttling portion is circumferentially narrowed. In the

solid fuel burner according to this example, on the other

hand, the throttling portion 5 is configured to be

narrowed in the vertical (height) direction but not

narrowed in the horizontal (width) direction. The throttling portion 5 is configured to narrow the flow passage of the mixing gas 100 only in the vertical

(height) direction.

The throttling portion 5 according to the example does not

concentrate the particles toward the center with respect

to the horizontal direction. Therefore, the particles

also tend to flow to the vicinity of the outer peripheral

flame stabilizer 2 in the horizontal direction,

facilitating the ignition in the horizontal direction of

the outer peripheral flame stabilizer 2.

Further, the throttling portion does not horizontally

narrow the flow passage of the mixing gas 100 so that the

solid fuel burner can be shortened in the axial length.

Hence, cost increase can be suppressed.

Since the cross-sectional area of the flow passage in the

throttling portion 5 is less reduced (than that of the

venturi type configuration), the acceleration of the

mixing gas 100 in the throttling portion 5 is limited and

increase in the particle velocity is also limited.

Accordingly, the wear volume of the inner wall of the fuel

nozzle is also reduced.

In the solid fuel burner according to the example, a

contraction flow angle (throttle angle) of the throttling

portion 5 is properly designed in view of balance between

the inner flame holding and the outer flame holding. In

the solid fuel burner of the example, the contraction flow

angle (throttle angle) of the throttling portion 5 is

defined to be smaller than that of the solid fuel burner

according to Example 1.

In the throttling portion 5, the particles are

concentrated to form a high-density fuel flow (particles)

toward the center of the fuel nozzle. However, if the

contraction flow angle (throttle angle) of the throttling

portion 5 is excessively large, the fuel (particles)

density on the outer peripheral side is not sufficiently

increased so that the outer peripheral flame stabilizer 2

becomes less likely to make ignition. On the other hand,

if the contraction flow angle (throttle angle) of the

throttling portion 5 is excessively small, the outlet

portion 16 is increased in the length required for

allowing transformation to the predetermined flat

configuration. The solid fuel burner is increased in the

axial length, resulting in increased production cost of the burner.

The contraction flow angle (throttle angle) of the

throttling portion 5 is properly designed in view of

balance between the inner flame holding and the outer

flame holding so that the high-density fuel flow

(particles) in the outlet portion 16 is made to flow also

to the vicinity of the upper and lower parts of the outer

peripheral flame stabilizer 2, which achieves reliable

ignition. Thus, the burner can achieve both the stable

inner flame holding and outer flame holding.

Third Embodiment

Fig. 3A is an illustrative diagram showing a vertical

cross section of a solid fuel burner according to Example

3 hereof as taken on the axis thereof. Fig. 3B is an

illustrative diagram showing a horizontal cross section of

the solid fuel burner according to Example 3 hereof as

taken on the axis thereof.

In addition to the solid fuel burner of Example 2, the

solid fuel burner according to the example further

includes a horizontal vane 11 which is disposed in the diffusion portion 6 and adapted to throw the particles horizontally outward. Namely, the solid fuel burner of this example includes the horizontal vane 11 which is disposed in the diffusion portion 6 so as to disperse the mixing gas 100 horizontally outward.

The solid fuel burner according to the example is

decreased in the fuel (particles) density in the vicinity

of the outer peripheral flame stabilizer 2 because the

particle concentrator is omitted. The large recirculation

flow 102 is formed with respect to the vertical parts of

the outer peripheral flame stabilizer 2 and hence, the

particles are captured by the large recirculation flow 102

despite the decreased fuel (particles) density. Thus, the

ignition and flame holding are ensured. However, the

recirculation flow 102 is relatively small with respect to

the horizontal parts of the outer peripheral flame

stabilizer 2 so that the outer peripheral stabilizer may

be less likely to achieve ignition and flame holding.

The solid fuel burner of the example is provided with the

horizontal vane 11 for particle concentration on the

horizontally outer side so as to concentrate the particles

to the vicinity of the horizontal parts of the outer peripheral flame stabilizer 2 and to facilitate the horizontally outer peripheral flame holding.

The solid fuel burner of the example is adapted to control

the fuel (particles) density in the vicinity of the inner

flame stabilizer 1 and the fuel (particles) density in the

vicinity of the horizontal parts of the outer peripheral

flame stabilizer 2 by changing the installation angle of

the horizontal vane 11. Thus, the burner can adjust the

combustion state. By virtue of the movable structure of

the horizontal vane 11, the solid fuel burner can properly

control the combustion state according to the operating

conditions.

Fourth Embodiment

Fig. 4A is an illustrative diagram showing a vertical

cross section of a solid fuel burner according to Example

4 hereof as taken on the axis thereof. Fig. 4B is an

illustrative diagram showing a horizontal cross section of

the solid fuel burner according to Example 4 hereof as

taken on the axis thereof.

In addition to the solid fuel burner of Example 2, the solid fuel burner according to the example further includes a swirling vane 12 which stirs the particles as disposed on an upstream side of the throttling portion 5.

Namely, the solid fuel burner of the example includes the

swirling vane 12 disposed in the straight tube portion 4

so as to stir the mixing gas 100.

The mixing gas 100 flows through a long pipe (not shown)

to be supplied to the straight tube portion 4. In this

process, the mixing gas passes many bending portions where

only the particles are centrifugally shifted to the outer

side so that the density deviation of the fuel (particles)

occurs in the pipe. This density deviation of the fuel

(particles) may sometimes cause particle aggregation at

some unanticipated place (straight tube portion 4)

upstream of the throttling portion 5, which may interfere

with ignition or flame holding in the inner flame

stabilizer and the outer peripheral flame stabilizer 2.

In the solid fuel burner of the example, therefore, the

swirling vane 12 for stirring the particles is disposed at

place (straight tube portion 4) upstream of the throttling

portion 5 so as to control the density deviation of the

fuel (particles) flowing through the throttling portion 5 and to facilitate the ignition and flame holding in the inner flame stabilizer 1 or the outer peripheral flame stabilizer 2.

While the example employs the swirling vane 12 as the

particle stirring structure, the stirring structure may

have another configuration such as a turning blade (a

component such as a conical structure for diffusing the

mixing gas 100 toward the outer periphery).

Fifth Embodiment

Fig. 5A is an illustrative diagram showing a vertical

cross section of a solid fuel burner according to Example

5 hereof as taken on the axis thereof. Fig. 5B is an

illustrative diagram showing a horizontal cross section of

the solid fuel burner according to Example 5 hereof as

taken on the axis thereof.

In addition to the solid fuel burner of Example 2, the

solid fuel burner according to the example further

includes a pipe which is disposed on an upstream side of

the straight tube portion 4 and includes a bending portion

13 connected to the straight tube portion 4 (the bending portion according to the example is a planar member which can be opened and closed for maintenance work). The bending portion 13 of the pipe is provided with a guide

(guide plate) 14 for dividing the flow passage into an

inner side and an outer side with respect to the bending

portion 13. Namely, the solid fuel burner includes, on

the upstream side of the straight tube portion 4, the pipe

including the bending portion 13 connected to the straight

tube portion 4, and the guide (guide plate) 14 disposed at

the bending portion 13 of the pipe for centrifugally

dividing the mixing gas 100.

When flowing through the bending portion 13, the mixing

gas 100 allows only the particles to be centrifugally

shifted toward the outer side. Disposing the guide (guide

plate) 14 restricts the particles from being shifted only

toward the outer side with respect to the bending portion

13. Thus, the burner can provide vertically well-balanced

supply of particles.

This configuration obviates the extreme density deviation

of the fuel (particles) in the outlet portion 16,

facilitating the ignition and flame holding in the inner

flame stabilizer 1 and the outer peripheral flame stabilizer 2.

A structure such as the guide (guide plate) 14 disposed in

the bending portion 13 of the pipe dispenses with the need

for disposing the structure such as the swirling vane 12

in the straight tube portion 4. Hence, the solid fuel

burner can be reduced in the axial length. This leads to

reduction of production cost of the burner.

Sixth Embodiment

Fig. 6A is an illustrative diagram showing a vertical

cross section of a solid fuel burner according to Example

6 hereof as taken on the axis thereof. Fig. 6B is an

illustrative diagram showing a horizontal cross section of

the solid fuel burner according to Example 6 hereof as

taken on the axis thereof.

In addition to the solid fuel burner of Example 3, the

solid fuel burner according to the example further

includes a pipe which is disposed on an upstream side of

the straight tube portion 4 and includes a bending portion

13 connected to the straight tube portion 4 (the bending

portion according to the example is a planar member which can be opened and closed for maintenance work).

A particle dispersion plate 15 for dispersing the

particles is disposed at an outlet of the bending portion

13. That is, the straight tube portion 4 includes the

particle dispersion plate 15 for dispersing the mixing gas

100.

The particle dispersion plate 15 is disposed only on a

centrifugally outer side of the bending portion 13. This

is for the purpose of utilizing the particle dispersion

plate 15 to effectively disperse the centrifugally

outwardly shifted particles because the particles are

shifted to the centrifugally outer side of the bending

portion 13. By disposing the particle dispersion plate 15

only on the centrifugally outer side, the reduction of the

cross-sectional area of the flow passage in the straight

tube portion 4 can be obviated so that the increase in

particle velocity in the straight tube portion 4 is also

limited. Accordingly, the wear volume of the inner wall

of the fuel nozzle is also reduced.

The particle dispersion plate 15 provides a balanced flow

of the particles through the fuel nozzle so as to permit the horizontal vane 11 on a downstream from the particle dispersion plate 15 to achieve an efficient particle distribution. Thus, the burner can control the combustion state.

Seventh Embodiment

Figs. 7A to 7F illustrate the detailed structures of the

inner flame stabilizers 1 in Figs. 1A to 6B.

Fig. 7A illustrates the basic structure of the inner flame

stabilizers of the burners exemplified in Figs. 1A to 6B

respectively, which structure takes a wedge structure of

triangular prism. Figs. 7B to 7F illustrate modifications

of the structure of the inner flame stabilizer in Fig. 7A.

The structure in Fig. 7B is provided with a recess portion

105 on the backside of the inner flame stabilizer on the

downstream side of the fuel jet flow 104 in terms of the

basic structure thereof shown in Fig. 7A. The provision

of such recess portion 105 on the backside of the inner

flame stabilizer promotes the mixing of the high

temperature gas flow 103 and the fuel jet flow 104,

thereby, further facilitating ignition compared to such basic structure.

As to the structure in Fig. 7C-1, making the inner flame

stabilizer, in which a plate is arranged such that it has

a V-shape structure, take a V-shape structure without

providing such stabilizer with a backside as shown in Fig.

7A promotes the mixing of the high-temperature gas flow

103 and the fuel jet flow 104 and leads to cost reduction

by reducing the number of the parts of such stabilizer in

the same way as the recess portion 105 in Fig. 7B.

As to the structure in Fig. 7C-2, an baffle plate 106 is

disposed at the tip end of the V-shape structure in Fig.

7C-1. Providing the tip end of the plate member taking a

V-shape structure with such baffle plate 106 so as to

enlarge the cross-sectional area of the tip end of the

plate taking such V-shape structure further promotes the

mixing of the fuel jet flow 104 and the high-temperature

gas flow 103 than the structure in Fig. 7C-1, thereby,

facilitating ignition.

In Fig. 7D, the horizontal cross-section of the inner

flame stabilizer has a pentagonal prism structure. The

inner flame stabilizer in Fig. 7D has a larger volume than the counterpart whose horizontal cross section takes a triangular prism defining isosceles triangle and is excellent in anti-abrasion property as well as is inexpensively producible without use of expensive ceramic materials. In addition, since such stabilizer is excellent in anti-abrasion property, it is applicable to the combustion of the low-grade coal whose ash content is higher.

Fig. 7E illustrates the structure of the recess portion

105 in Fig. 7B with the exclusion of the vertical notch.

In other words, Fig. 7B corresponds to the structure with

the inclusion of the vertical notch in the recess portion

in Fig. 7E. Comparing this structure with that in Fig. 7B,

high negative pressure created by the recess portion 105

further promotes the mixing of the high-temperature gas

flow 103 and the fuel jet flow 104, thereby, leading to

excellent ignition property. This structure is also

effective for the stable ignition of the start-up oil

burner which requires higher negative pressure in the same

way as coal.

The structure in Fig. 7F is provided with the inner flame

stabilizer 1, the recess portion 105 and air inlets 107 which supply air into the recess portion 105. The air inlets 107 are provided on the outer periphery of the recess portion. In Fig. 7F, in order to explain the function of the recess portion 105 and the ignition promotion of the start-up oil burner, a start-up oil burner tip 109 and a start-up oil burner gun 110 are also illustrated.

Oil fuel 111 is jet-sprayed from the start-up oil burner

tip 109 toward the furnace so as to turn into flame. Upon

the start-up, the solid fuel is not supplied, but a

combustion fuel flow and/or an air flow 108 is fed and a

part of such flow flows from the air inlets 107 into the

periphery of the start-up oil burner tip 109 to generate

an air flow 112 toward the recess portion.

Further, since high negative pressure is created by the

recess portion 105, the high-temperature gas flow 103 and

the fuel jet flow 104 flow into the recess portion 105.

Accordingly, the air flow 112 into the recess portion

promotes the ignition of the oil fuel and reduces soot and

dust as well as suppresses the coking (carbonization) of

the start-up oil burner tip 109.

To note, as to the air inlets 107, because of a small

amount of air intake structure, they are not limited to

the pore structure and may be arranged with another

structure such as slit. Further, in Fig. 7F, a plurality

of the air inlets 107 are provided over the entire

periphery of the recess portion 105, but they may be

provided on any one of the sides constituting the recess

portion and the number of such inlets may be one or more.

Moreover, when the air inlets are made not of pores but of

slits, such slits may be provided over the entire

periphery and the number of such slits and their length

may be set in an arbitrary manner.

To note, the start-up oil burner tip 109 and the start-up

oil burner gun 110 are shown only in Fig. 7F according to

the present example, but such start-up oil burner tip is

provided for the inner flame stabilizers in Figs. 7A to 7E

as well such that such tip penetrates such stabilizers,

thereby, enabling the stable combustion upon the solid

fuel combustion and the oil combustion.

It is noted that the present invention is not limited to

the above-described examples and includes a variety of

modifications. The foregoing examples, for example, are the detailed illustrations to clarify the present invention. The present invention is not necessarily limited to those including all the components described above. Some component of one example can be replaced by some component of another example. Further, some configuration of one example can be added to the configuration of another example.

Throughout this specification and the claims which follow,

unless the context requires otherwise, the word "comprise",

and variations such as "comprises" and "comprising", will

be understood to imply the inclusion of a stated integer

or step or group of integers or steps but not the

exclusion of any other integer or step or group of

integers or steps.

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 that 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.

List of Reference Signs

1: inner flame stabilizer

2: outer peripheral flame stabilizer

3: central supporting rod

4: fuel nozzle straight tube portion

5: fuel nozzle throttling portion

6: fuel nozzle diffusion portion

7: guide sleeve

8: guide sleeve

9: furnace wall

10: wind box

11: horizontal vane

12: swirling vane

13: bending portion

14: guide

15: particle dispersion plate

16: fuel nozzle outlet portion

100: mixing gas

101: combustion air jet flow

102: recirculation flow

103: high-temperature flow

104: fuel jet flow

105: recess portion

106: baffle plate

107: air inlet

108: solid fuel flow and/or air flow

109: start-up oil burner tip

110: start-up oil burner gun

111: oil fuel

112: air flow toward recess portion

Claims

Claims Defining the Invention:

1. A solid fuel burner comprising:

a fuel nozzle straight tube portion allowing a

mixing gas of a solid fuel and its carrier gas to flow

therethrough;

a fuel nozzle throttling portion narrowing a flow

passage of the mixing gas passed through the fuel nozzle

straight tube portion;

a fuel nozzle diffusion portion horizontally

expanding the flow passage of the mixing gas passed

through the fuel nozzle throttling portion;

a fuel nozzle outlet portion connected to the fuel

nozzle diffusion portion and having an outlet flattened in

shape;

a ring-shaped outer peripheral flame stabilizer

disposed on an outer periphery of the fuel nozzle outlet

portion; and

an inner flame stabilizer disposed in the fuel

nozzle outlet portion and horizontally dividing the mixing

gas passed through the fuel nozzle diffusion portion,

wherein the fuel nozzle throttling portion has a

structure which is narrowed only in the vertical direction.

2. The solid fuel burner according to Claim 1, comprising

a guide sleeve disposed on an outer side of the outer

peripheral flame stabilizer.

3. The solid fuel burner according to Claim 2, comprising

a top-bottom guide sleeve disposed vertically with respect

to an outer periphery of the guide sleeve.

4. The solid fuel burner according to Claim 3, comprising

a horizontal vane disposed in the fuel nozzle diffusion

portion and serving to disperse the mixing gas

horizontally outward.

5. The solid fuel burner according to Claim 3, comprising

a swirling vane disposed in the fuel nozzle straight tube

portion and serving to stir the mixing gas.

6. The solid fuel burner according to Claim 3, further

comprising: a pipe disposed on an upstream side of the

fuel nozzle straight tube portion and including a bending

portion connected to the fuel nozzle straight tube

portion; and a guide disposed in the bending portion of the pipe and serving to centrifugally divide the mixing gas.

7. The solid fuel burner according to Claim 4,

comprising: a pipe disposed on an upstream side of the

fuel nozzle straight tube portion and including a bending

portion connected to the fuel nozzle straight tube

portion; and a particle dispersion plate disposed in the

fuel nozzle straight tube portion and serving to disperse

the mixing gas.

8. The solid fuel burner according to Claim 1, wherein a

horizontal cross section of the inner flame stabilizer

takes a triangular prism defining isosceles triangle.

9. The solid fuel burner according to Claim 1, wherein

the inner flame stabilizer is provided with a recess

portion on its backside on a downstream side of a fuel

flow and/or air flow direction.

10. The solid fuel burner according to Claim 1, wherein a

plate is arranged with the inner flame stabilizer such

that the stabilizer takes a V-shape structure.

11. The solid fuel burner according to Claim 10, wherein

an baffle plate is disposed at a tip end of a plate member

taking the V-shape structure so as to enlarge a cross

sectional area of the tip end.

12. The solid fuel burner according to Claim 1, wherein a

horizontal cross section of the inner flame stabilizer has

a pentagonal prism structure.

13. The solid fuel burner according to Claim 9, wherein

the inner flame stabilizer is provided with the recess

portion including a vertical notch on its backside on the

downstream side of the fuel flow and/or air flow direction.

14. The solid fuel burner according to Claim 9, wherein

the inner flame stabilizer is provided with air inlets to

supply air into the recess portion.