EP2677238A1

EP2677238A1 - Solid fuel burner

Info

Publication number: EP2677238A1
Application number: EP12747032.6A
Authority: EP
Inventors: Tetsuma Tatsumi; Hirofumi Okazaki; Koji Kuramashi; Akihito Orii
Original assignee: Babcock Hitachi KK
Current assignee: Mitsubishi Power Ltd
Priority date: 2011-02-18
Filing date: 2012-02-13
Publication date: 2013-12-25
Anticipated expiration: 2032-02-13
Also published as: EP2677238B1; EP2677238A4; JP5566317B2; WO2012111606A1; KR20130103806A; KR101494993B1; MY170750A; JP2012172865A

Abstract

The present invention is to provide a solid fuel burner for suppressing collision of fuel particles to an inner wall of a fuel nozzle, increasing fuel concentration and oxygen concentration in an outer circumferential portion in the fuel nozzle while reducing abrasion of the fuel nozzle, thereby enabling stable combustion.

A solid fuel burner 42 of the present invention comprising a fuel nozzle 11 for ejecting a mixed fluid of solid fuel and carrier gas therefor, an oxygen-containing gas nozzle 13, 14 arranged outside the fuel nozzle for ejecting oxygen-containing gas, and at least one oxygen-containing gas addition nozzle 12 projected and installed in the fuel nozzle for ejecting oxygen-containing gas having a velocity component in a circumferential direction of the fuel nozzle, wherein the oxygen-containing gas addition nozzle 12 has a nozzle outlet 12A, 12B, 12C in the circumferential direction of the fuel nozzle, characterized in that: the oxygen-containing gas addition nozzle 12 is shaped so as to contract a projected section thereof in an axial direction of the burner toward a central axis of the burner.

Description

{Technical Field}

The present invention relates to a solid fuel burner for gas-flow-transferring and burning solid fuel, and more particularly to a solid fuel burner preferable to pulverizing, gas-flow-transferring, and suspension-firing fuel containing much of moisture and volatile matter such as wood, peat, and coal.

{Background Art}

Generally, fuel such as wood, peat, and coal with a low degree of coalification represented by brown coal and lignite contains much volatile matter, so that it is well known that in the air atmosphere, the aforementioned fuel is apt to ignite spontaneously in the course of storage, pulverization, or transfer and is difficult to handle compared with bituminous coal.
To prevent spontaneous combustion, when pulverizing and burning the aforementioned fuel, as fuel transferring gas, mixed gas of combustion exhaust gas of reduced oxygen concentration and oxygen-containing gas may be used. The combustion exhaust gas reduces the oxygen concentration in the fuel circumference, suppresses the oxidation reaction (combustion) of the fuel, and prevents spontaneous combustion. Further, the combustion exhaust gas has a function of drying the moisture in the fuel by its potential heat.
However, in fuel transferred by carrier gas of a low oxygen concentration, the oxidation reaction that occurs when the fuel is ejected from the solid combustion burner is restricted by the oxygen concentration in the fuel circumference, and compared with the case of transfer by air, the burning rate is low, and the stability of the flame is deficient.
As a method of balancing the prevention of spontaneous combustion with the stability of flame, which are described above, a structure is proposed where an oxygen-containing gas addition nozzle having a nozzle outlet in the circumferential direction of a fuel nozzle is projected and installed inside the fuel nozzle, and the oxygen-containing gas addition nozzle has a form which smoothly contracts and enlarges the sectional area of the flow path of the mixed fluid flowing through the fuel nozzle, and an ejection port for ejecting air having the velocity component in the vertical direction to the mixed fluid flowing through the fuel nozzle is formed on the side thereof (refer to Patent Literature 1).

{Citation List}

{Patent Literature}

{Patent Literature 1}
Japanese Patent Application 2005-140480

{Summary of Invention}

{Problems to be solved by the Invention}

However, as described in the Patent Literature 1, when the oxygen-containing gas addition nozzle having a nozzle outlet in the circumferential direction of the fuel nozzle is projected and installed inside the fuel nozzle and the oxygen-containing gas addition nozzle has a form which smoothly contracts and enlarges the sectional area of the flow path of the mixed fluid flowing through the fuel nozzle, the angle formed by the side plate of the oxygen-containing gas addition nozzle and the inner wall of the fuel nozzle is an acute angle smaller than the right angle in the upstream portion of the oxygen-containing gas addition nozzle.
Therefore, if fuel particles collide with the side plate in the upstream portion of the oxygen-containing gas addition nozzle, the velocity component toward the inner wall of the fuel nozzle is induced and fuel is apt to collide with the inner wall of the fuel nozzle.
As a result, there is a possibility of promotion of abrasion of the inner wall of the fuel nozzle and there is a possibility of re-scattering of the fuel led to the inner wall of the fuel nozzle. Furthermore, due to the re-scattering of the fuel particles, the flow in the fuel nozzle is disturbed and there is a possibility that the oxygen concentration distribution in the outlet portion of the fuel nozzle becomes non-uniform.
The present invention has been developed with the foregoing in view, and an object of the present invention is to provide a solid fuel burner for suppressing collision of the fuel particles to an inner wall of the fuel nozzle, increasing fuel concentration and oxygen concentration in an outer circumferential portion inside the fuel nozzle while reducing abrasion of the fuel nozzle, thereby enabling stable combustion.

{Means for Solving the Problems}

A solid fuel burner of the present invention, to accomplish the above object, comprising a fuel nozzle for ejecting a mixed fluid of solid fuel and carrier gas therefor, an oxygen-containing gas nozzle arranged outside the fuel nozzle for ejecting oxygen-containing gas, and at least one oxygen-containing gas addition nozzle projected and installed inside the fuel nozzle for ejecting oxygen-containing gas having a velocity component in a circumferential direction of the fuel nozzle, wherein the oxygen-containing gas addition nozzle has a nozzle outlet in the circumferential direction of the fuel nozzle, characterized in that: the oxygen-containing gas addition nozzle is shaped so as to contract a projected section thereof in an axial direction of the burner toward a central axis of the burner, or
the oxygen-containing gas addition nozzle is composed of a side plate, a top plate, and a partition (bottom plate) on the fuel nozzle side and the side plate is formed so as to direct to the central axis of the fuel nozzle.

{Advantageous Effects of Invention}

According to the present invention, the velocity component of the fuel particles in the radial direction which collide with the side plate in the upstream portion of the oxygen-containing gas addition nozzle is suppressed. As a result, there can be provided a solid fuel burner that can suppress the collision of the fuel particles to the inner wall of the fuel nozzle and the re-scattering of the fuel and increase the oxygen concentration and fuel concentration in the outlet portion of the outer circumferential portion of the fuel nozzle so as to achieve stable combustion.

{Brief Description of Drawings}

{Fig. 1} Fig. 1 is a cross-sectional view showing the structure of embodiment 1 of the solid fuel burner according to the present invention and the state in which the flame of the solid fuel burner is formed from the neighborhood of the circulation flow on the downstream side of a flame stabilizer.
{Fig. 2} Fig. 2 is a drawing showing the schematic structure of the solid fuel burner of the embodiment 1 viewed from the furnace side.
{Fig. 3} Fig. 3 is a perspective view for explaining the structure of the oxygen-containing gas nozzle of the solid fuel burner of the embodiment 1 and the fuel ejection flow inside the fuel nozzle, that is, the flow of fuel and carrier gas therefor.
{Fig. 4} Fig. 4 is a drawing showing the schematic structure of the solid fuel burner of the embodiment 1 viewed from the upstream side of the burner.
{Fig. 5} Fig. 5 is a drawing showing the schematic structure of the embodiment 2 of the solid fuel burner according to the present invention viewed from the furnace side.
{Fig. 6} Fig. 6 is a cross-sectional view showing the structure of the embodiment 3 of the solid fuel burner according to the present invention and the state in which the flame of the solid fuel burner is formed from a near place to the circulation flow on the downstream side of the flame stabilizer.
{Fig. 7} Fig. 7 is a drawing showing the schematic structure of the embodiment 4 of the solid fuel burner according to the present invention viewed from the furnace side.
{Fig. 8} Fig. 8 is a perspective view for explaining the structure of the oxygen-containing gas nozzle of the solid fuel burner of the embodiment 5 and the fuel ejection flow inside the fuel nozzle, that is, the flow of fuel and carrier gas therefor.
{Fig. 9} Fig. 9 is a drawing showing the schematic structure of the solid fuel burner of the embodiment 5 viewed from the upstream side of the burner.
{Fig. 10} Fig. 10 is a cross-sectional view showing the structure of the embodiment 5 of the solid fuel burner according to the present invention and the state in which the flame of the solid fuel burner is formed from a near place to the circulation flow on the downstream side of the flame stabilizer.
{Fig. 11} Fig. 11 is a perspective view for explaining the structure of the oxygen-containing gas nozzle of the solid fuel burner of the embodiment 6 and the fuel ejection flow inside the fuel nozzle, that is, the flow of fuel and carrier gas therefor.
{Fig. 12} Fig. 12 is a drawing showing the schematic structure of the solid fuel burner of the embodiment 6 viewed from the upstream side of the burner.
{Fig. 13} Fig. 13 is a modification of the oxygen-containing gas addition nozzle of the solid fuel burner according to the present invention and a drawing showing the schematic structure of the solid fuel burner viewed from the furnace side.
{Fig. 14} Fig. 14 is another modification of the oxygen-containing gas addition nozzle of the solid fuel burner according to the present invention and a drawing showing the schematic structure of the solid fuel burner viewed from the furnace side.

{Description of Embodiments}

Hereinafter, the solid fuel burner of the present invention will be explained in detail on the basis of the drawings showing the solid fuel burner.

{Embodiment 1}

Fig. 1 shows the structure of the embodiment 1 of the solid fuel burner according to the present invention and the state in which a flame 20 of a solid fuel burner 42 is formed from a near place to a circulation flow 19 on the downstream side of a flame stabilizer 23 and Fig. 2 shows the schematic structure of the solid fuel burner of the embodiment 1 viewed from the side of a furnace 41.
As shown in Figs. 1 and 2, the solid fuel burner 42 in the embodiment 1 includes a columnar fuel nozzle 11, a secondary oxygen-containing gas nozzle 13, and a tertiary oxygen-containing gas nozzle 14 which are arranged concentrically so as to be formed circularly, furthermore, an auxiliary oil gun 24 in the center portion, and an ejection flow 16, that is, the fuel nozzle 11 for ejecting fuel and carrier gas therefor around the auxiliary oil gun 24. The auxiliary oil gun 24 installed through the center portion of the fuel nozzle 11 is used for fuel ignition when starting the solid fuel burner 42.
On the other hand, inside the fuel nozzle 11, a flow path contraction member (Venturi) 32 and an obstacle (concentrator) 33 are provided from the upstream side, and the Venturi 32 has a shape of smoothly contracting and enlarging the flow path cross-sectional area of the fuel nozzle 11 from the outer circumference side, and the concentrator 33 has a shape of smoothly contracting and enlarging the flow path cross-sectional area of the fuel nozzle 11 from the inside. Further, on the outside of the fuel nozzle 11, an outer oxygen-containing gas nozzle for oxygen-containing gas ejection concentrical with the fuel nozzle 11, that is, the secondary oxygen-containing gas nozzle 13 and the tertiary oxygen-containing gas nozzle 14 are installed.
Furthermore, an oxygen-containing gas addition nozzle 12 for ejecting oxygen-containing gas which interconnects with a wind box 26 and has the velocity component of the fuel nozzle 11 in the circumferential direction is projected into the fuel nozzle 11 and a plurality of oxygen-containing gas addition nozzles 12 are positioned on the downstream side of the Venturi 32 and the concentrator 33 and are provided in the circumferential direction. In each of the oxygen-containing gas addition nozzles 12, outlets 12A, 12B, and 12C are formed in the circumferential direction of the fuel nozzle 11.
Further, at the tip outside the fuel nozzle 11, that is, on the outlet side of the furnace 41, an obstacle called the flame stabilizer 23 is provided. The flame stabilizer 23 acts on the fuel ejection flow 16, that is, the flow of fuel, the carrier gas therefor, and secondary oxygen-containing gas 17 flowing through the secondary oxygen-containing gas nozzle 13 as an obstacle from the fuel nozzle 11.
Therefore, the pressure of the flame stabilizer 23 on the downstream side (on the side of the furnace 41) is reduced and to this portion, a flow in the inverse direction to the flow of the fuel ejection flow 16 and the secondary oxygen-containing gas 17 is induced. The flow in the inverse direction is called a circulation flow 19. Into the circulation flow 19, high-temperature gas generated by combustion of fuel flows from the downstream and stays there, and the high-temperature gas and the fuel in the fuel ejection flow 16 are mixed at the outlet of the solid fuel burner 42 and furthermore, due to radiation heat from the inside of the furnace 41, fuel particles rise in temperature and ignite.
The secondary oxygen-containing gas nozzle 13 and the tertiary oxygen-containing gas nozzle 14 are separated by a partition 29 and at the tip of the partition 29, a guide 25 for ejecting tertiary oxygen-containing gas 18 is formed so that the flow thereof makes an angle with the fuel ejection flow 16. The guide 25, at the flow path outlet of the outer circumferential oxygen-containing gas nozzle (the secondary oxygen-containing gas nozzle 13, the tertiary oxygen-containing gas nozzle 14, etc.), is formed so as to lead the ejection direction of the oxygen-containing gas to a direction away from the central axis of the burner, thereby advantageously helping form the circulation flow 19 as well as the flame stabilizer 23.
In the embodiment 1, to give a swirl force to the oxygen-containing gas ejected from the secondary oxygen-containing gas nozzle 13 and the tertiary oxygen-containing gas nozzle 14, on the secondary oxygen-containing gas nozzle 13 and the tertiary oxygen-containing gas nozzle 14, swirl devices 27 and 28 are installed. Further, a burner throat 30 composing the furnace wall serves as an outer circumferential wall of the tertiary oxygen-containing gas nozzle 14 and furthermore, on the furnace wall, a water pipe 31 for flowing a refrigerant for cooling the furnace wall is installed.
Fig. 3 is a drawing for explaining the structure of the oxygen-containing gas addition nozzle 12 of the solid fuel burner 42 of the embodiment 1 and the fuel ejection flow 16 inside the fuel nozzle 11, that is, the flow of fuel and carrier gas therefor and Fig. 4 is a drawing showing the structure of the oxygen-containing gas addition nozzle 12 of the solid fuel burner 42 of the embodiment 1 and the fuel ejection flow 16 inside the fuel nozzle 11, that is, the flow of fuel and carrier gas therefor viewed from the upstream side of the burner.
As shown in Figs. 3 and 4, in the solid fuel burner 42 of this embodiment, the nozzle entrances of the plurality of oxygen-containing gas addition nozzles 12 are arranged in the direction from the outside partition 22 of the fuel nozzle 11 toward the central axis of the solid fuel burner 42. The oxygen-containing gas addition nozzles 12, for the flow of the fuel ejection flow 16, is installed near to the outside partition 22 of the fuel nozzle 11 on the downstream side of the concentrator 33.
In the radial direction of the fuel nozzle 12, the outer circumferential direction is indicated by (+) and the central axial direction is indicated by (-). When fuel particles collide with a side plate 60 of the oxygen-containing gas addition nozzle 12, it is when the angle formed between the side plate 60 and an inner wall 63 of the fuel nozzle is a right angle, that the velocity component in the radial direction is not induced and the velocity component is induced only in the circumferential direction. On the other hand, if the angle formed between the side plate 60 and the inner wall 63 of the fuel nozzle is an acute angle, in the radial direction, the (+) velocity component is induced and if it is an obtuse angle, the (-) velocity component is induced.
In the conventional system, in the upstream portion of the oxygen-containing gas addition nozzle 12, the angle formed between the side plate 60 and the inner wall of the fuel nozzle is an acute angle, so that if fuel particles collide with the side plate 60 in the upstream portion of the oxygen-containing gas addition nozzle 12, in the radial direction, the (+) velocity component is induced and the fuel particles are apt to collide with the inner wall of the fuel nozzle 11.
On the other hand, in this embodiment, the oxygen-containing gas addition nozzle 12 is composed of the side plate 60, a top plate 61, and a bottom plate 62 by the sheet metal working, and the facing side plate 60 is formed so as to be inclined toward the central axis of the burner, and the projected section of the oxygen-containing gas addition nozzle 12 in the axial direction has a shape contracted toward the central axis of the burner, and the area of the bottom plate 62 is larger than the area of the top plate 61.
As mentioned above, if the angle formed between the side plate 60 in the upstream portion of the oxygen-containing gas addition nozzle 12 and the fuel nozzle inner wall 63 is brought close to the right angle, when fuel particles collide with the side plate 60 of the oxygen-containing gas addition nozzle 12, the induction of the (+) velocity component in the radial direction is suppressed and mainly, the velocity component in the circumferential direction of the burner is induced.
As a result, the collision frequency of fuel particles with the inner wall 63 of the fuel nozzle is reduced, and the abrasion of the fuel nozzle inner wall 63 is reduced, and the re-scattering of the fuel particles is suppressed. The re-scattering of the fuel is suppressed, thus the oxygen concentration and fuel concentration in the outer circumferential portion of the fuel nozzle 11 in the neighborhood of the outside partition 22 of the fuel nozzle 11 or the flame stabilizer 23 can be increased.
As mentioned above, the lead direction of fuel particles is controlled, thus the collision of fuel particles to the fuel nozzle inner wall 63 is suppressed and while reducing the abrasion of the fuel nozzle 11, the oxygen concentration and fuel concentration in the outer circumferential portion of the fuel nozzle 11 in the neighborhood of the outside partition 22 of the fuel nozzle 11 or the flame stabilizer 23 can be increased.
On the other hand, on the side of the partition in the downstream portion of the oxygen-containing gas addition nozzle 12, the outlets 12A, 12B, and 12C of the oxygen-containing gas addition nozzle 12 for ejecting addition oxygen-containing gas 21 in the circumferential direction of the fuel nozzle 11 are formed and the ejection flow of the addition oxygen-containing gas 21 ejected from the outlets 12A, 12B, and 12C intersects almost vertically to the fuel ejection flow 16 to be mixed. Further, in the final portion of the oxygen-containing gas addition nozzle 12, an outlet 12Z for discharging fuel particles inversely flowing from the outlets 12A, 12B, and 12C of the oxygen-containing gas addition nozzle 12 when switching the operation mode may be formed.
In Fig. 3, only two oxygen-containing gas addition nozzles 12 are shown and the relationship between the fuel ejection flow 16 and the addition oxygen-containing gas 21 is shown. In Fig. 3, the upper left to lower right direction indicates an axial direction of the fuel nozzle 11, the upper right to lower left direction indicates a circumferential direction of the fuel nozzle 11, and the up and down direction indicates a radial direction of the fuel nozzle 11.
In the oxygen-containing gas addition nozzle 12 of this embodiment, the side of the secondary oxygen-containing gas nozzle 13 of a partition not shown is cylindrical, and the side of the fuel nozzle 11 has a shape of a hexahedron held on the upstream side and the downstream side of the fuel nozzle 11, and the partition not shown is positioned at a junction of the cylinder to the hexahedron.
In Fig. 3, the fuel ejection flow 16 flows in the upper left to lower right direction in the axial direction of the fuel nozzle 11. Further, the ejection flow of the addition oxygen-containing gas 21 enters into the nozzle from the upper portion of the cylinder of the oxygen-containing gas addition nozzle 12 and ejects into the fuel nozzle 11 from the outlets 12A, 12B, and 12C positioned on the side of the partition in the downstream portion of the oxygen-containing gas addition nozzle 12 whose projected section in the axial direction of the burner is shaped to be contracted toward the center.
The ejection flow of the addition oxygen-containing gas 21 ejected from the oxygen-containing gas addition nozzle 12 has a velocity component in the circumferential direction (the upper right to lower left direction shown in Fig. 3) of the fuel nozzle 11. Therefore, it intersects the fuel ejection flow 16 ejecting in the axial direction at an almost right angle, and the velocity difference between the fuel particles and the oxygen-containing gas is larger than the case of parallel ejection, thus the mixture progresses. Particularly, the fuel particles are higher in density than gas, so that they are easily mixed into the ejection flow of the addition oxygen-containing gas 21 due to the inertia force.
Furthermore, in the embodiment 1, the partition of the oxygen-containing gas addition nozzle 12 has a shape of smoothly contracting and enlarging the flow path cross-sectional area of the fuel nozzle 11. Namely, the shape of the oxygen-containing gas addition nozzle 12 is such that the cross-sectional area of the fuel nozzle 11 in the axial direction gradually increases in size from the end on the upstream side, reaches the maximum value, gradually decreases in size on the downstream side, and reaches the end on the downstream side. Therefore, inside the fuel nozzle 11 whose outer cylinder uses a cylindrical member with a constant flow path sectional area, relatively, the flow path sectional area of the fuel nozzle 11 gradually contracts from the upstream side end of the oxygen-containing gas addition nozzle 12 toward the downstream side, switches off at a certain place, and gradually enlarges toward the downstream side end.
If the outlets 12A, 12B, and 12C of the oxygen-containing gas addition nozzle 12 and the outlet 12Z for discharging fuel particles are provided on the side of the partition of the oxygen-containing gas addition nozzle 12 or in the contraction portion on the downstream side, fuel particles flowing through the fuel nozzle 11 can be suppressed from flowing into the oxygen-containing gas addition nozzle 12, so that the abrasion of the outlet portion of the oxygen-containing gas addition nozzle 12 can be suppressed.
If the flow rate of the addition oxygen-containing gas 21 is increased, the ejection flow of the addition oxygen-containing gas 21 and the fuel ejection flow 16 are mixed, so that the outer circumferential portion of the fuel nozzle 11 where the oxygen-containing gas addition nozzle 12 is provided, increases in flow resistance. Therefore, if the flow rate of the addition oxygen-containing gas 21 is increased, the carrier gas flowing through the outer circumferential portion of the fuel nozzle 11 is decreased. On the other hand, fuel particles are larger in inertia force than gas, so that they flow through the outer circumferential portion regardless of the flow resistance, thus the fuel particle quantity stays about the same.
Therefore, if the flow rate of the addition oxygen-containing gas 21 is increased, the carrier gas flowing through the outer circumferential portion of the fuel nozzle 11 along with the fuel particles is decreased. If the carrier gas is decreased, it is replaced with the addition oxygen-containing gas 21, so that compared with the case that the carrier gas and the addition oxygen-containing gas 21 are mixed simply, the oxygen concentration is less diluted and the oxygen concentration is increased.
Furthermore, in Fig. 3, even in the farthest downward stream portion of the partition forming the oxygen-containing gas addition nozzle 12, the outlet 12Z for discharging one fuel particle is provided. If the outlet 12Z for discharging one fuel particle is provided in the farthest downward stream portion of the partition forming the oxygen-containing gas addition nozzle 12, the fuel particle entering inside the oxygen-containing gas addition nozzle 12 can be discharged easily and the accumulation of fuel particles can be prevented. Further, if the accumulation of fuel particles can be prevented, the blocking of the oxygen-containing gas addition nozzle 12 and the burnout of the burner can be prevented.
According to the embodiment 1, in the fuel ejection flow 16 ejected from the fuel nozzle 11, due to the high oxygen concentration and fuel concentration, the combustion reaction progresses easily and the flame 20 is formed stably at the outlet of the fuel nozzle 11.
The distance from the outlet of the oxygen-containing gas addition nozzle 12 to the outlet of the fuel nozzle 11 is determined so as to prevent the burnout or backfire of the fuel nozzle 11, due to the ignition of the fuel inside the fuel nozzle 11, which are apt to be caused when the oxygen concentration is high. To prevent the burnout or backfire of the fuel nozzle 11, the stay time of the fuel after the mixture with the ejection flow of the addition oxygen-containing gas 21 inside the fuel nozzle 11 is desirably shorter than the ignition delay time of the fuel.
Generally, the ignition delay time (about 0.1 s) of gas fuel which is shorter than the ignition delay time of pulverized coal is considered as a standard. For example, the fuel transferring gas flows at a flow velocity of 12 to 20 m/s in the fuel nozzle 11, so that the distance from the outlet of the oxygen-containing gas addition nozzle 12 to the outlet of the fuel nozzle 11 is 1 m or shorter.
Furthermore, in the embodiment 1, the Venturi 32 for contracting the flow path installed in the fuel nozzle 11 is provided in the outside partition 22 on the upstream side of the fuel nozzle 11. Further, the concentrator 33 for contracting the flow path in the fuel nozzle 11 once and then enlarging it, is provided in the outside portion of the oil gun 24 at the central portion of the fuel nozzle 11 and on the downstream side of the burner (on the side of the furnace 41) rather than the Venturi 32.
The Venturi 32 induces the velocity component in the central direction of the fuel nozzle 11 for the fuel transferring gas and fuel particles. Furthermore, if the concentrator 33 is provided on the downstream side of the Venturi 32, the fuel transferring gas and fuel particles are induced the velocity component toward the outside partition 22 of the fuel nozzle 11. The fuel particles are larger in the inertia force than the fuel transferring gas, so that they cannot follow the flow of the fuel transferring gas. Therefore, the fuel particles form a high-concentration region in the vicinity of the wall surface on the opposite side to the change direction of the flow path. By the Venturi 32 and the concentrator 33, the velocity component toward the outside partition 22 of the fuel nozzle 11 is induced, so that most of the fuel particles flow along the outside partition 22 of the fuel nozzle 11.
As mentioned above, the fuel particles, after concentrated in the outer circumferential portion of the fuel nozzle 11, are mixed with the oxygen-containing gas from the oxygen-containing gas addition nozzle 12. At this time, in the conventional structure, the fuel particles collide with the side plate in the upstream portion of the oxygen-containing gas addition nozzle, are induced the (+) velocity component in the radial direction, and collide with the inner wall of the fuel nozzle, thus there is a possibility that the fuel particles induced to the inner wall of the fuel nozzle may re-scatter.
In this embodiment, the angle formed by the side plate 60 in the upstream portion of the oxygen-containing gas addition nozzle 12 and the fuel nozzle inner wall 63 are brought close to the right angle, so that when the fuel particles collide with the side plate 60 of the oxygen-containing gas addition nozzle 12, the induction of the (+) velocity component in the radial direction is suppressed and mainly, the velocity component in the circumferential direction of the burner is induced. Therefore, the fuel particles concentrated in the outer circumferential portion of the fuel nozzle 11 by the Venturi 32 and the concentrator 33 can be maintained in the outer circumferential portion of the fuel nozzle 11. The fuel concentration in the outer circumferential portion of the fuel nozzle 11 contributes to the flame stability, so that fuel particles can be maintained in the outer circumferential portion of the fuel nozzle 11, thus stable combustion can be continued at a lower load than usual. This allows a load-reduced operation of the burner and also allows responding to the load change of the boiler.
The oxygen-containing gas ejected from the oxygen-containing gas addition nozzle 12 flows through the outer circumferential portion of the fuel nozzle 11, so that the region with both a high oxygen concentration and a high fuel concentration is biased to and formed on the inside wall surface of the outside partition 22 of the fuel nozzle 11. As a result, the fuel particles ejected from the fuel nozzle 11 are apt to progress in the combustion reaction due to the high fuel concentration and oxygen concentration and the flame 20 is formed stably at the outlet of the fuel nozzle 11.
At this time, the fuel ejection flow 16 flowing on the inside wall surface of the outside partition 22 of the fuel nozzle 11, in the neighborhood of the outlet of the fuel nozzle 11, is easily mixed with the oxygen-containing gas ejected from the outside oxygen-containing gas nozzle. Furthermore, if it is mixed with high-temperature gas of the circulation flow generated on the wake side of the flame stabilizer 23, the fuel particles rise in temperature and are easily ignited. As a result, the flame 20 is formed stably at the outlet of the fuel nozzle 11.
If the oxygen-containing gas is ejected from the oxygen-containing gas addition nozzle 12 in the circumferential direction of the fuel nozzle 11 and intersects the fuel ejection flow 16 almost perpendicularly, the oxygen concentration in the neighborhood of the outside partition 22 of the fuel nozzle 11 increases. The mixture of the fuel particles and oxygen-containing gas progresses in this state and the flame 20 is formed stably at the outlet of the fuel nozzle 11.
In this embodiment, the re-scattering of the fuel particles can be suppressed, so that the flow field in the fuel nozzle 11 is stabilized and the oxygen concentration distribution in the outlet portion of the fuel nozzle becomes uniform, so that stable combustion can be continued at a lower load than usual. This allows a load-reduced operation of the burner and also allows responding to the load change of the boiler.
Further, in the embodiment 1, combustion exhaust gas is used for the fuel transferring gas, thus the oxygen concentration in the fuel ejection flow 16 flowing through the fuel nozzle 11 is reduced. As an embodiment of application of such a combustion method, the combustion of coal with a low degree of coalification represented by brown coal and lignite, peat, and wood may be cited.

{Embodiment 2}

Fig. 5 shows the Embodiment 2 of the solid fuel burner according to the present invention and shows the schematic structure viewed from the side of the furnace 41 shown in Fig. 1.
This embodiment shown in the drawing is characterized in the constitution that the concentrator 33 provided in the embodiment 1 is not provided and compared with the constitution shown in Fig. 2, at least one portion of the outside oxygen-containing gas nozzles such as the secondary oxygen-containing gas nozzle 13 and the tertiary oxygen-containing gas nozzle 14 is installed so as to sandwich the fuel nozzle 11. Namely, in this embodiment, the secondary oxygen-containing gas nozzle 13 and the tertiary oxygen-containing gas nozzle 14 are formed in a square shape and are arranged so as to sandwich the fuel nozzle 11 from the up and down directions in Fig. 5.
Further, in this embodiment, in addition to the foregoing, the structure that the fuel nozzle is formed in a square shape, the structure that with respect to the outside oxygen-containing gas nozzle such as the secondary oxygen-containing gas nozzle 13 or the tertiary oxygen-containing gas nozzle 14, one nozzle is used, or the structure that the outside oxygen-containing gas nozzle is divided into three parts or more may be used.

{Embodiment 3}

Fig. 6 shows the Embodiment 3 of the solid fuel burner according to the present invention and shows the state in which when using the solid fuel burner 42 of the present invention under the low load condition, the flame 20 of the solid fuel burner 42 is formed from the neighborhood of the circulation flow 19 on the downstream side of the flame stabilizer 23.
In this embodiment shown in the drawing, an inside oxygen-containing gas nozzle 38 is provided in the fuel nozzle 11 of the solid fuel burner 42, and the inside oxygen-containing gas nozzle 38 and the wind box 26 are connected with a pipe, and a part of the oxygen-containing gas fed to the solid fuel burner 42 is ejected from the inside oxygen-containing gas nozzle 38.
As in this embodiment, if the oxygen-containing gas is mixed from the inside of the fuel nozzle 11 by the inside oxygen-containing gas nozzle 38, compared with the case that it is mixed only from the secondary oxygen-containing gas nozzle 13 and the tertiary oxygen-containing gas nozzle 14, there is an advantage that the mixing of the fuel and oxygen-containing gas is accelerated. Further, if a large quantity of oxygen-containing gas is ejected from the inside oxygen-containing gas nozzle 38, the flow velocity of the fuel ejection flow 16 flowing by is accelerated and the ignition position of fuel can be separated from the solid fuel burner 42.
Therefore, under the high load condition, when forming a flame at the position separated from the solid fuel burner 42, it is desirable to decrease the oxygen-containing gas flow rate ejected from the oxygen-containing gas addition nozzle 12 and increase the oxygen-containing gas flow rate ejected from the inside oxygen-containing gas nozzle 38.
Further, in this embodiment, on the downstream side of the concentrator 33 of the fuel nozzle 11, a distributor 35 for dividing the flow path is provided. If the flow path is separated by the distributor 35, the diffusion of the fuel particles concentrated in the outer circumferential portion of the fuel nozzle 11 and the oxygen-containing gas added from the oxygen-containing gas addition nozzle 12 toward the central axis of the burner can be suppressed, so that the fuel particles can be maintained in the outer circumferential portion of the fuel nozzle 11 and the oxygen concentration distribution in the outlet portion of the fuel nozzle becomes highly concentrated and uniform, so that stable combustion can be continued at a lower load than usual. This allows a load-reduced operation of the burner and also allows responding to the load change of the boiler.

{Embodiment 4}

Fig. 7 shows the embodiment 4 of the solid fuel burner according to the present invention and shows the schematic structure that the solid fuel burner using a toothed flame stabilizer is viewed from the furnace side.
In the embodiment shown in the drawing, at the outlet of the fuel nozzle 11, a toothed flame stabilizer 54 having a plurality of laminal edges projected in the circumferential direction at predetermined intervals is provided. The other constitutions are the same as those of the embodiment 1.
By use of such a constitution of this embodiment, fuel comes around the toothed flame stabilizer 54, thereby is easily ignited. Namely, the fuel ignites on the downstream side of the toothed flame stabilizer 54.

{Embodiment 5}

Figs. 8 and 9 show the embodiment 5 of the solid fuel burner according to the present invention, and Fig. 8 explains the structure of the oxygen-containing gas addition nozzle 12 of the solid fuel burner 42 and the fuel ejection flow 16 in the fuel nozzle 11, that is, the flow of fuel and carrier gas therefor, and Fig. 9 shows the structure of the oxygen-containing gas addition nozzle 12 of the solid fuel burner 42 of the embodiment 1 and the fuel ejection flow 16 in the fuel nozzle 11, that is, the flow of fuel and carrier gas therefor which are viewed from the upstream side of the burner.
In the solid fuel burner 42 of the embodiment shown in the drawings, in the plurality of oxygen-containing gas addition nozzles 12, the surface including the nozzle entrance is arranged in the direction from the outside partition 22 of the fuel nozzle 11 toward the central axis of the solid fuel burner 42. Further, the oxygen-containing gas addition nozzles 12 are installed, for the flow of the fuel ejection flow 16, on the downstream side of the concentrator 33 and in the neighborhood of the outside partition 22 of the fuel nozzle 11.
In the radial direction of the fuel nozzle 12, the outer circumferential direction is indicated by (+) and the central axial direction is indicated by (-). When fuel particles collide with the side plate 60 of the oxygen-containing gas addition nozzle 12, it is when the angle formed between the side plate 60 and the inner wall 63 of the fuel nozzle is a right angle that the velocity component in the radial direction is not induced and the velocity component is induced only in the circumferential direction. On the other hand, if the angle formed between the side plate 60 and the inner wall 63 of the fuel nozzle is an acute angle, in the radial direction, the (+) velocity component is induced and if it is an obtuse angle, the (-) velocity component is induced.
In the conventional system, in the upstream portion of the oxygen-containing gas addition nozzle 12, the angle formed between the side plate 60 and the inner wall of the fuel nozzle is an acute angle, so that if fuel particles collide with the side plate 60 in the upstream portion of the oxygen-containing gas addition nozzle 12, the (+) velocity component is induced in the radial direction, and the fuel particles are apt to collide with the inner wall of the fuel nozzle 11.
On the other hand, in this embodiment, the oxygen-containing gas addition nozzle 12 is composed of the side plate 60, the top plate 61, and the bottom plate 62 by the sheet metal working, and the facing side plate 60 is formed so as to be inclined toward the central axis of the burner, and the projected section of the oxygen-containing gas addition nozzle 12 in the axial direction has a shape contracted toward the central axis of the burner, and the area of the bottom plate 62 is larger than the area of the top plate 61.
As mentioned above, if the angle formed between the side plate 60 in the upstream portion of the oxygen-containing gas addition nozzle 12 and the fuel nozzle inner wall 63 is brought close to the right angle, when fuel particles collide with the side plate 60 of the oxygen-containing gas addition nozzle 12, the induction of the (+) velocity component in the radial direction is suppressed and mainly, the velocity component in the circumferential direction of the burner is induced.
As a result, the collision frequency of fuel particles with the inner wall 63 of the fuel nozzle is reduced, and the abrasion of the fuel nozzle inner wall 63 is reduced, and the re-scattering of the fuel particles is suppressed. The re-scattering of the fuel is suppressed, thus the oxygen concentration and fuel concentration in the outer circumferential portion of the fuel nozzle 11 in the neighborhood of the outside partition 22 of the fuel nozzle 11 or the flame stabilizer 23 can be increased.
As mentioned above, the lead direction of fuel particles is controlled, thus the collision of fuel particles to the fuel nozzle inner wall 63 is suppressed and while reducing the abrasion of the fuel nozzle 11, the oxygen concentration and fuel concentration in the outer circumferential portion of the fuel nozzle 11 in the neighborhood of the outside partition 22 of the fuel nozzle 11 or the flame stabilizer 23 can be increased.
Furthermore, in this embodiment, on the central axis side of the burner at the upstream end of the oxygen-containing gas addition nozzle 12, a projection 12Y is provided, and the projection 12Y is projected in the upstream direction, and the projected section of the projection 12Y in the axial direction of the burner is shaped so as to be enlarged in the central direction of the burner.
If the projection 12Y is provided in this way, the side of the projection 12Y faces the fuel nozzle inner wall 63, so that if fuel particles collide with the side of the projection 12Y, the (+) velocity component is induced in the radial direction, and there are possibilities that a part of the fuel particles may approach the fuel nozzle inner wall surface 63, though the distance from the oxygen-containing gas addition nozzle 12 to the fuel nozzle inner wall 63 is long, and the collision velocity to the fuel nozzle inner wall surface 63 is reduced, thus the abrasion of the fuel nozzle 11 is reduced, and the re-scattering of the fuel is suppressed.
By doing this, the fuel is concentrated in the inner circumferential portion of the outlet of the furnace 41 of the fuel nozzle 11, so that the Venturi, concentrator, and distributor used for fuel concentration are not necessary and the cost can be reduced.
Fig. 10 shows the structure of the solid fuel burner 42 of the embodiment 5 where the flame stabilizer and concentrator are not provided and the state in which the fuel ejected from the solid fuel burner 42 under the low load condition is burnt by the combustion apparatus.
The solid fuel burner 42 of the embodiment 5 shown in the drawing, as mentioned above, has a structure that the concentrator is not provided in the fuel nozzle 11 and at the tip of the partition 22 for separating the fuel nozzle 11 and the outside oxygen-containing gas nozzle 13, the flame stabilizer 23 is not provided.
In the solid fuel burner 42 of the embodiment 1 shown in Fig. 1, the concentrator 33 is provided in the fuel nozzle 11, though as in the embodiment 5, even when the concentrator 33 is not provided, if the projection 12Y is provided, the fuel is concentrated in the inner circumferential portion of the outlet of the furnace 41 of the fuel nozzle 11. Further, if the ejection flow of the addition oxygen-containing gas 21 is ejected in the circumferential direction of the fuel nozzle 11, it intersects the fuel ejection flow 16 flowing through the fuel nozzle 11 almost perpendicularly, so that the velocity difference between the fuel particles and the oxygen-containing gas is larger than the case of ejection in parallel. Therefore, similarly to the embodiment 1, the mixing of the fuel particles and the oxygen-containing gas progresses.
Furthermore, even when the flame stabilizer 23 is not provided, compared with the case that the flame stabilizer 23 is provided, the effect becomes smaller, though on the downstream side of the partition 22, the circulation flow 19 is formed. If high-temperature gas staying in the circulation flow 19 and the fuel particles are mixed, the fuel particles rise in temperature and easily ignites. As a result, the flame 20 is stably formed at the outlet of the fuel nozzle 11.
By use of the constitution of the embodiment 5, the fuel induction direction can be controlled, and the collision of fuel to the fuel nozzle inner wall 63 is suppressed, and the fuel concentration and oxygen concentration in the fuel nozzle 11 are made uniform while reducing the abrasion of the fuel nozzle 11, and the fuel can be burnt stably.
Further, in the embodiment 5, even if the projection 12Y is provided on the central axis side of the burner at the upstream end of the oxygen-containing gas addition nozzle 12, the projected sectional area in the axial direction of the burner of the oxygen-containing gas addition nozzle 12 is not changed, though the projection 12Y is provided in a shape that the top plate 61 of the projection 12Y is extended in the radial direction, thus the projected sectional area in the axial direction of the burner of the oxygen-containing gas addition nozzle 12 can be enlarged.
Further, the oxygen-containing gas addition nozzle 12 may be manufactured by casting. An embodiment thereof is shown in Figs. 11 and 12.

{Embodiment 6}

Figs. 11 and 12 show the embodiment 6 of the solid fuel burner according to the present invention and the embodiment 6 is a modification of Figs. 8 and 9.
In this embodiment shown in the drawings, the oxygen-containing gas addition nozzle 12 is manufactured in a streamline shape by casting. The oxygen-containing gas addition nozzle 12 manufactured in a streamline shape by casting is shaped such that the projection 12Y with an elliptic section in the axial direction of the burner is formed on the central axis side of the burner on the upstream side (refer to Fig. 12) and the elliptic projection 12Y is projected in the upstream direction.
Even if formed in this way, this embodiment can obtain the similar effects to each embodiment described above.
Further, in each embodiment described above, in the fuel nozzle 11, eight oxygen-containing gas addition nozzles 12 are arranged at even intervals in the circumferential direction, though as shown in Fig. 13, in the fuel nozzle 11, two oxygen-containing gas addition nozzles 12 may be arranged opposite to each other, and it is needless to say that, as shown in Fig. 14, in the fuel nozzle 11, three oxygen-containing gas addition nozzles 12 may be arranged at even intervals.
As a result, within a range which is does not deviate from the objects of the present invention, the number of oxygen-containing gas addition nozzles 12 may be determined and to obtain the effects of the present invention, at least one oxygen-containing gas addition nozzle 12 may be arranged.

{Reference Signs List}

11: Fuel nozzle, 12: Oxygen-containing gas addition nozzle, 12A, 12B, 12C: Outlet of oxygen-containing gas addition nozzle, 12Z: Outlet for discharging fuel particles, 12Y: Projection, 13: Secondary oxygen-containing gas nozzle, 14: Tertiary oxygen-containing gas nozzle, 16, 16B, 16C: Fuel ejection flow, 17: Secondary oxygen-containing gas, 18: Tertiary oxygen-containing gas, 19: Circulation flow, 20: Flame, 21: Addition oxygen-containing gas, 22: Outside partition of fuel nozzle, 23: Flame stabilizer, 24: Oil gun, 25: Guide, 26: Wind box, 27, 28: Swirl device, 29: Partition, 30: Burner throat, 31: Water pipe, 32: Venturi, 33: Concentrator, 34: Flow rate regulating valve, 35: Distributor, 36: Opposite side flow path, 37: Flow path on oxygen-containing gas nozzle side, 38: Inside oxygen-containing gas nozzle, 41: Furnace, 42: Solid fuel burner, 54: Toothed flame stabilizer, 60: Side plate, 61: Top plate, 62: Bottom plate, 63: Fuel nozzle inner wall.

Claims

A solid fuel burner comprising: a fuel nozzle for ejecting a mixed fluid of solid fuel and carrier gas therefor, an oxygen-containing gas nozzle arranged outside the fuel nozzle for ejecting oxygen-containing gas, and at least one oxygen-containing gas addition nozzle projected and installed inside the fuel nozzle for ejecting oxygen-containing gas having a velocity component in a circumferential direction of the fuel nozzle, wherein the oxygen-containing gas addition nozzle has a nozzle outlet in the circumferential direction of the fuel nozzle, characterized in that:
the oxygen-containing gas addition nozzle is shaped so as to contract a projected section thereof in an axial direction of the burner toward a central axis of the burner.
A solid fuel burner comprising: a fuel nozzle for ejecting a mixed fluid of solid fuel and carrier gas therefor, an oxygen-containing gas nozzle arranged outside the fuel nozzle for ejecting oxygen-containing gas, and at least one oxygen-containing gas addition nozzle projected and installed inside the fuel nozzle for ejecting oxygen-containing gas having a velocity component in a circumferential direction of the fuel nozzle, wherein the oxygen-containing gas addition nozzle has a nozzle outlet in the circumferential direction of the fuel nozzle, characterized in that:
the oxygen-containing gas addition nozzle is composed of a partition in a radial direction of the burner, a partition in a central axial direction of the burner, and a partition on a side of the fuel nozzle, and the partition in the radial direction of the burner is formed so as to be directed to the central axis of the burner.
The solid fuel burner according to Claim 1 or 2, wherein the oxygen-containing gas addition nozzle is installed in a position close to the outlet of the fuel nozzle.
The solid fuel burner according to Claim 2, wherein an area of the partition in the radial direction of the burner is formed larger than an area of the partition in the central axial direction of the burner.
The solid fuel burner according to any one of Claims 1 to 4, the oxygen-containing gas addition nozzle is provided with a plurality of outlets for ejecting addition oxygen-containing gas in the circumferential direction of the fuel nozzle on a side of a partition in a downstream portion of the oxygen-containing gas addition nozzle.
The solid fuel burner according to Claim 5, the oxygen-containing gas addition nozzle is provided with an outlet for discharging fuel particles back-flowed from the plurality of outlets for ejecting the addition oxygen-containing gas in the circumferential direction of the fuel nozzle at a rear end of the oxygen-containing gas addition nozzle.
The solid fuel burner according to any one of Claims 1 to 4, the oxygen-containing gas addition nozzle is provided with a projection on the central axis side of the burner at an upstream end of the oxygen-containing gas addition nozzle, wherein the projection is projected in an upstream direction, and a projected section of the projection in the axial direction of the burner is shaped so as to be enlarged toward a center of the burner.
The solid fuel burner according to Claim 7, the oxygen-containing gas addition nozzle is provided with a projection for making the projected section in the axial direction of the burner elliptic on the central axis side of the burner at the upstream end of the oxygen-containing gas addition nozzle, and the elliptic projection is projected in the upstream direction.
The solid fuel burner according to any one of Claims 1 to 8, wherein the oxygen-containing gas addition nozzle is formed so as to be an ejection port thereof for ejecting the oxygen-containing gas having a velocity component in parallel with the mixed fluid flowing through the fuel nozzle at a farthest downward portion.
The solid fuel burner according to any one of Claims 1 to 8, the solid fuel burner is provided with a Venturi formed so as to smoothly contract and enlarge a flow path sectional area of the fuel nozzle from an outer circumferential side, and a concentrator formed so as to smoothly contract and enlarge the flow path sectional area of the fuel nozzle from an inner circumferential side in an upper stream of the oxygen-containing gas addition nozzle.
The solid fuel burner according to any one of Claims 1 to 8, the solid fuel burner is provided with a distributor in the fuel nozzle for dividing a flow path, wherein when viewed from a perpendicular direction to the central axis of the burner, the outlet of the oxygen-containing gas addition nozzle exists in a position where the outlet of the oxygen-containing gas addition nozzle is overlaid on the distributor.
The solid fuel burner according to any one of Claims 1 to 8, the solid fuel burner is provided with a concentrator in an upper stream of the oxygen-containing gas addition nozzle formed so as to smoothly contract and enlarge the flow path sectional area of the oxygen-containing gas addition nozzle from an inner side, and a distributor in the fuel nozzle for dividing a flow path, wherein when viewed from a perpendicular direction to the central axis of the burner, the outlet of the oxygen-containing gas addition nozzle exists in a position where the outlet of the oxygen-containing gas addition nozzle is overlaid on the distributor.
The solid fuel burner according to any one of Claims 1 to 8, the solid fuel burner is provided with a flame stabilizer at a tip of a partition for separating the fuel nozzle and the oxygen-containing gas addition nozzle for disturbing a flow of solid fuel ejected from the fuel nozzle and carrier gas therefor and a flow of oxygen-containing gas ejected from the oxygen-containing gas addition nozzle.
The solid fuel burner according to Claim 13, wherein the flame stabilizer is a toothed flame stabilizer projected at the outlet of the fuel nozzle.
The solid fuel burner according to any one of Claims 1 to 8, the oxygen-containing gas nozzle is provided with a guide at a flow path outlet of the oxygen-containing gas nozzle for introducing an ejection direction of oxygen-containing gas to a direction away from the central axis of the burner.
The solid fuel burner according to any one of Claims 1 to 8, the oxygen-containing gas nozzle is provided with a swirl device for giving a swirl force to oxygen-containing gas.
The solid fuel burner according to Claim 1 or 2, the solid fuel burner is provided with an inside oxygen-containing gas nozzle in the fuel nozzle, and the inside oxygen-containing gas nozzle and a wind box are connected with a pipe, wherein a part of oxygen-containing gas fed to the burner is permitted to be ejected from the inside oxygen-containing gas nozzle.