JP7775337B2 - Burner, boiler equipped with same, and burner operating method - Google Patents

Description

The present disclosure relates to a burner that burns, for example, pulverized solid fuel and ammonia fuel, a boiler equipped with the burner, and a method for operating the burner.

Large boilers, such as power generation boilers, have a hollow, vertically installed furnace with multiple burners mounted on the furnace wall. Large boilers also have a flue connected vertically above the furnace, with a heat exchanger installed in this flue to generate steam. The burner then injects a mixture of fuel and air (oxidizing gas) into the furnace, creating a flame, generating combustion gases that flow down the flue. A heat exchanger is installed in the area through which the combustion gases flow, and superheated steam is generated by heating the water and steam flowing through the heat transfer tubes that make up the heat exchanger.

Considerations are being made regarding burners used in boilers that combine pulverized coal and ammonia fuel, or that exclusively burn pulverized coal or ammonia fuel (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2020-41748

However, although Patent Document 1 discloses co-firing of pulverized coal and ammonia fuel on the same shaft, it does not consider increasing the co-firing ratio of ammonia fuel. For example, with the configuration of Patent Document 1, increasing the co-firing ratio of ammonia fuel reduces the flame stability of the pulverized coal, making it impossible to continue co-firing with ammonia fuel.

This disclosure has been made in consideration of these circumstances, and aims to provide a burner that can increase the ammonia fuel co-firing ratio when co-firing ammonia fuel and pulverized fuel, as well as a boiler equipped with the same and a method for operating the burner.

A burner according to one aspect of the present disclosure comprises an inner cylindrical nozzle extending along a central axis, an outer cylindrical nozzle extending along the central axis and covering the inner cylindrical nozzle, which supplies pulverized fuel and primary air into a furnace, a pulverized fuel flame stabilizer which stabilizes the flame of the pulverized fuel supplied from the outer cylindrical nozzle, and a concentrator which is provided inside the outer cylindrical nozzle and concentrates the pulverized fuel on the pulverized fuel flame stabilizer side, and supplies ammonia fuel to the inner cylindrical nozzle or the outer cylindrical nozzle.

A method for operating a burner according to one aspect of the present disclosure is a method for operating a burner comprising: an inner cylindrical nozzle extending along a central axis; an outer cylindrical nozzle extending along the central axis and covering the inner cylindrical nozzle, which supplies pulverized fuel and primary air into a furnace; a pulverized fuel flame stabilizer that stabilizes the flame of the pulverized fuel supplied from the outer cylindrical nozzle; and a concentrator disposed inside the outer cylindrical nozzle that concentrates the pulverized fuel on the pulverized fuel flame stabilizer side, wherein ammonia fuel is supplied to the inner cylindrical nozzle or the outer cylindrical nozzle.

The burner disclosed herein allows for an increased ammonia fuel co-firing ratio.

1 is a schematic configuration diagram showing a boiler according to a first embodiment of the present disclosure. FIG. FIG. 2 is a vertical cross-sectional view showing the burner of FIG. 1; FIG. 4 is a longitudinal cross-sectional view showing a burner according to a second embodiment of the present disclosure. FIG. 3B is a front view showing the inner cylinder nozzle and the outer cylinder nozzle of FIG. 3A. FIG. 3B is a longitudinal cross-sectional view of a burner showing a modification of FIG. 3A. FIG. 4B is a front view showing the inner and outer cylinder nozzles of FIG. 4A. FIG. 10 is a longitudinal cross-sectional view showing a burner according to a third embodiment of the present disclosure. FIG. 10 is a longitudinal cross-sectional view showing a burner according to a fourth embodiment of the present disclosure. FIG. 6B is a front view showing the inner and outer cylinder nozzles of FIG. 6A. FIG. 6C is a perspective view of the circumferential concentrator of FIGS. 6A and 6B. FIG. 10 is a longitudinal cross-sectional view showing a burner according to a fifth embodiment of the present disclosure. FIG. 1 is a longitudinal cross-sectional view showing a liquid ammonia injection tip. FIG. 10 is a longitudinal cross-sectional view showing a burner according to a sixth embodiment of the present disclosure.

One embodiment of the present disclosure will be described below with reference to the drawings. Note that the present invention is not limited to this embodiment, and when there are multiple embodiments, it also includes configurations that combine the embodiments. In the following description, "up" and "upper" refer to the upper side in the vertical direction, and "lower" and "lower" refer to the lower side in the vertical direction, but the vertical direction is not precise and may include errors.

[First embodiment]
FIG. 1 shows a boiler 10 of this embodiment that uses pulverized fuel and/or ammonia (NH ₃ ) as its main fuel.
The boiler 10 of this embodiment is a boiler that can generate superheated steam by burning pulverized fuel made from pulverized solid fuel and ammonia fuel using a burner and exchanging the heat generated by this combustion with feedwater or steam. Biomass fuel, coal, etc. are used as solid fuel.

The boiler 10 has a furnace 11, a combustion device 20, and a combustion gas passage 12. The furnace 11 is a hollow rectangular cylinder installed vertically. The furnace wall 101, which forms the inner wall surface of the furnace 11, is composed of multiple heat transfer tubes and fins connecting the heat transfer tubes. The heat generated by the combustion of pulverized fuel is recovered by heat exchange with water and steam circulating inside the heat transfer tubes, while also suppressing the temperature rise of the furnace wall 101.

The combustion device 20 is installed in the lower region of the furnace 11. In this embodiment, the combustion device 20 has multiple burners 21A, 21B, 21C, 21D, 21E, and 21F (hereinafter, when these burners are not distinguished, they will be simply referred to as "burners 21") attached to the furnace wall 101. The burners 21 are arranged in multiple vertical rows at equal intervals along the furnace wall 101 in the furnace width direction (for example, arranged in the furnace width direction so as to face each of the opposing furnace walls 101 for opposed combustion). The shape of the furnace, the number of burner rows, the number of burners per row, the arrangement of the burners, etc. are not limited to this embodiment.

Burners 21A, 21B, 21C, 21D, 21E, and 21F are connected to multiple mills (pulverizers) 31A, 31B, 31C, 31D, 31E, and 31F (hereinafter, simply referred to as "mills 31") via multiple pulverized fuel supply pipes 22A, 22B, 22C, 22D, 22E, and 22F (hereinafter, simply referred to as "pulverized fuel supply pipes 22" when not distinguishing between them). Mill 31 is, for example, a vertical roller mill configured with a rotatable grinding table (not shown) supported internally and multiple grinding rollers (not shown) supported above the grinding table for rotation in conjunction with the grinding table's rotation. The solid fuel pulverized by the cooperation of the grinding rollers and grinding table is transported to a classifier (not shown) provided in mill 31 by primary air (carrier gas, oxidizing gas) supplied to mill 31. The classifier separates the pulverized fuel into pulverized fuel having a particle size smaller than that suitable for combustion in the burner 21 and coarse pulverized fuel having a particle size larger than that. The pulverized fuel passes through the classifier and is supplied to the burner 21 together with primary air via the pulverized fuel supply pipe 22. The coarse pulverized fuel that does not pass through the classifier falls onto the grinding table inside the mill 31 under its own weight and is re-ground.

An air register 23 is provided outside the furnace 11 at the installation position of the burner 21, and one end of an air duct 24 is connected to this air register 23. The other end of the air duct 24 is connected to a forced draft fan (FDF) 32. The air supplied from the forced draft fan 32 is heated by an air preheater 42 installed in the air duct 24 and supplied to the burner 21 via the air register 23 as secondary air (combustion air, oxidizing gas) and introduced into the furnace 11.

The combustion gas passage 12 is connected to the vertical upper part of the furnace 11. The combustion gas passage 12 is provided with superheaters 102A, 102B, and 102C (hereinafter, when these superheaters are not distinguished, they will be simply referred to as "superheaters 102"), reheaters 103A and 103B (hereinafter, when these reheaters are not distinguished, they will be simply referred to as "reheaters 103"), and a coal economizer 104 as heat exchangers for recovering heat from the combustion gas. Heat is exchanged between the combustion gas generated in the furnace 11 and the feedwater or steam circulating inside each heat exchanger. The arrangement and shape of each heat exchanger are not limited to those shown in Figure 1.

Connected downstream of the combustion gas passage 12 is a flue 13 through which the combustion gas whose heat has been recovered by the heat exchanger is discharged. An air preheater (air heater) 42 is provided between the flue 13 and the air duct 24, and heat is exchanged between the air flowing through the air duct 24 and the combustion gas flowing through the flue 13. This heats the primary air supplied to the mill 31 and the secondary air supplied to the burner 21, thereby recovering further heat from the combustion gas after heat exchange with water and steam.

A denitration device 43 may be provided in the flue 13 at a position upstream of the air preheater 42. The denitration device 43 supplies a reducing agent, such as ammonia or urea water, that has the effect of reducing nitrogen oxides to the combustion gas flowing through the flue 13, and promotes the reaction between the nitrogen oxides (NOx) in the combustion gas to which the reducing agent has been supplied and the reducing agent by the catalytic action of a denitration catalyst provided in the denitration device 43, thereby removing and reducing the nitrogen oxides in the combustion gas.
A gas duct 41 is connected to the flue 13 downstream of the air preheater 42. The gas duct 41 is provided with environmental devices such as a dust collector 44, such as an electrostatic precipitator, that removes ash and the like from the combustion gas, a desulfurization device 46 that removes sulfur oxides, and an induced draft fan (IDF) 45 that guides the exhaust gas to these environmental devices. The downstream end of the gas duct 41 is connected to a chimney 47, and the combustion gas treated in the environmental device is discharged to the outside of the system as exhaust gas.

When co-firing pulverized fuel and ammonia fuel in the boiler 10, the multiple mills 31 are driven, and pulverized and classified pulverized fuel is supplied to the burner 21 along with primary air via the pulverized fuel supply pipe 22. Secondary air heated by the air preheater 42 is supplied to the burner 21 from the air duct 24 via the wind box 23. The burner 21 blows the pulverized fuel mixture, which is a mixture of pulverized fuel and primary air, into the furnace 11, and also blows secondary air into the furnace 11. The pulverized fuel mixture blown into the furnace 11 ignites and reacts with the secondary air to form a flame. A flame is formed in the lower region of the furnace 11, and high-temperature combustion gas rises within the furnace 11 and flows into the combustion gas passage 12. In this embodiment, air is used as the oxidizing gas (primary air, secondary air), but the oxidizing gas may have a higher or lower oxygen content than air, and stable combustion can be achieved in the furnace 11 by adjusting the ratio of the amount of oxygen to the amount of fuel supplied within an appropriate range.

In addition, above the installation position of the burners 21 in the furnace 11, multiple additional air ports (AA ports) 25 are provided for supplying additional air for combustion (AA) into the furnace 11. The ends of additional air ducts (AA ducts) 26 branching off from the air duct 24 are connected to the additional air ports 25, and a portion of the air supplied from the forced draft fan 32 can be supplied to the additional air ports 25 via the additional air ducts 26 as additional air for combustion.

In region A (corresponding to the height of the wind box 23) within the furnace 11 shown in FIG. 1, a flame is formed by the combustion of a mixture of primary air and pulverized fuel with secondary air. Here, the air ratio in region A is set to be 1 or less. Specifically, the amount of air (the total amount of primary air and secondary air) supplied to the burner 21 is set to be less than the theoretical air amount relative to the amount of fuel supplied to the burner 21. This creates a reducing atmosphere in regions A and B (the region between the top of the burner 21 and the bottom of the additional air port 25) within the furnace 11, and nitrogen oxides (NOx) generated by combustion are reduced within the furnace 11. Subsequently, in region C (the region above the bottom of the additional air port 25), additional combustion air is supplied from the additional air port 25 to the combustion gas from which NOx has been reduced, completing the combustion. However, the amount of NOx generated is reduced by the reduction effect in regions A and B.

The combustion gas that flows into the combustion gas passage 12 exchanges heat with water and steam in the superheater 102, reheater 103, and economizer 104 located inside the combustion gas passage 12, before being discharged into the flue 13, where nitrogen oxides are removed in the denitration device 43, and the gas exchanges heat with primary and secondary air in the air preheater 42. The gas is then discharged into the gas duct 41, where ash and other particles are removed in the dust collector 44, and sulfur oxides are removed in the desulfurization device 46 before being discharged outside the system through the chimney 47. The arrangement of the heat exchangers in the combustion gas passage 12 and the devices from the flue 13 to the gas duct 41 does not necessarily have to be in the order described above relative to the combustion gas flow.

The boiler 10 is equipped with an ammonia supply source 50. Ammonia is stored in the ammonia supply source 50 in a gaseous or liquid state as ammonia fuel. The ammonia fuel is supplied from the ammonia supply source 50 to each burner 21. When ammonia gas is used in the burners 21, the ammonia fuel is stored as a gas in the ammonia supply source 50, or is stored as liquid ammonia and vaporized during transport to the burners 21. When liquid ammonia is used in the burners 21, it is preferable that the ammonia be stored as liquid ammonia in the ammonia supply source 50.

The switching between the pulverized fuel and the ammonia fuel may be performed manually by an operator, or may be performed by a command from a control unit.
The control unit is composed of, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and a computer-readable storage medium. A series of processes for realizing various functions is stored in a storage medium, for example, in the form of a program. The CPU reads this program into RAM and executes information processing and arithmetic operations to realize various functions. The program may be pre-installed in a ROM or other storage medium, provided in a state stored in a computer-readable storage medium, or distributed via wired or wireless communication means. Examples of computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories.

2 shows the burner 21. The burner 21 is capable of burning a mixture of pulverized fuel and ammonia gas (ammonia fuel).
The burner 21 includes an inner cylindrical nozzle 61 extending along a central axis CL, and an outer cylindrical nozzle 62 provided to cover the inner cylindrical nozzle 61. An oil nozzle 63 is provided on the inner peripheral side of the inner cylindrical nozzle 61. Each of the nozzles 61, 62, and 63 has a common central axis CL, has a circular cross section, for example, and is made of metal.

The inner cylinder nozzle 61 is supplied with ammonia gas and air (combustion air) and sprays the mixture into the furnace 11. The ammonia gas is supplied from the ammonia supply source 50 shown in Figure 1.

An ammonia flame stabilizer 67 is provided at the tip of the inner cylindrical nozzle 61, between it and the oil nozzle 63. The ammonia flame stabilizer 67 is, for example, vane-shaped, and imparts a swirl to the ammonia gas and air mixture around the central axis CL. The ammonia flame stabilizer 67 stabilizes the flame of the ammonia gas injected from the inner cylindrical nozzle 61.

Pulverized fuel and primary air are supplied from the mill 31 (see Figure 1) into the outer nozzle 62. A venturi 68 and a concentrator 69 are provided inside the outer nozzle 62.

The venturi 68 extends circumferentially along the inner wall of the outer cylindrical nozzle 62 and constricts the flow path within the outer cylindrical nozzle 62 by bulging inward (toward the central axis CL). For example, it includes an upstream inclined portion 68a located upstream and inclined inward, and a downstream inclined portion 68b connected to the apex of the upstream inclined portion 68a and inclined outward toward the downstream side. The venturi 68 imparts a velocity component to the flow toward the central axis CL.

The concentrator 69 is located downstream of the venturi 68, is fixed to the outer wall of the oil nozzle 63, and extends circumferentially, bulging outward. For example, it includes an upstream inclined portion 69a located upstream and inclined inward, a cylindrical portion 69c connected to the apex of the upstream inclined portion 68a and extending parallel to the central axis CL, and a downstream inclined portion 69b connected to the downstream end of the cylindrical portion 69c and inclined outward toward the downstream side.

The concentrator 69 expands the flow path narrowed by the venturi 68, imparting a velocity component to the flow toward the outer nozzle 62 (radial direction). Because pulverized fuel has a greater inertial force than primary air, it is collected by the venturi 68 and concentrator 69 on the inner wall side of the outer nozzle 62, forming a high-concentration region of pulverized fuel.

A baffled pulverized fuel flame stabilizer 71 is provided at the tip and outer periphery of the outer cylindrical nozzle 62. The pulverized fuel flame stabilizer 71 is ring-shaped when the outer cylindrical nozzle 62 is viewed from the front. The pulverized fuel flame stabilizer 71 partially blocks the flow of secondary air through the secondary air flow passage 73, forming a flame-stabilizing region downstream. This stabilizes the flame of the pulverized fuel supplied from the outer cylindrical nozzle 62.

Oil fuel is supplied to the oil nozzle 63 from an oil fuel supply source (not shown). The oil fuel is used when the burner 21 is started, and after startup, the supply of oil fuel is stopped and a small amount of cooling air is supplied.

The secondary air flow path 73 is arranged to cover the outer cylindrical nozzle 62. A tertiary air flow path 74 is arranged on the outer periphery of the secondary air flow path 73 to cover the secondary air flow path 73. A swirler 74a is provided within the tertiary air flow path 74 to impart a swirl to the tertiary air.

Next, the operation of the burner 21 having the above configuration will be described.
First, the burner 21 is started by supplying oil fuel from the oil nozzle 63. The oil fuel injected into the furnace 11 from the oil nozzle 63 forms a flame together with air supplied from the inner cylindrical nozzle 61, thereby raising the temperature of the furnace 11. The flame produced by the oil fuel is stabilized by the ammonia flame stabilizer 67. That is, the ammonia flame stabilizer 67 is also used to stabilize the flame of the oil fuel at startup.

Then, once the temperature inside the furnace 11 has risen to the specified temperature and startup is complete, the supply of oil fuel is stopped. When the supply of oil fuel is stopped, a small amount of air is allowed to flow from the oil nozzle 63 to cool it.

After a predetermined time has elapsed since the burner was started, the supply of pulverized fuel and ammonia gas is carried out as follows.

Pulverized fuel is gradually supplied from the outer nozzle 62 along with primary air, forming a pulverized fuel flame. The pulverized fuel forms a high-concentration region on the inner wall of the outer nozzle 62 via the venturi 68 and concentrator 69. The pulverized fuel flame is stabilized by the pulverized fuel flame stabilizer 71 installed in the outer nozzle 62, and combustion occurs in stages using secondary air supplied from the secondary air flow path 73 and tertiary air supplied from the tertiary air flow path 74.

Ammonia gas is gradually supplied together with air from the ammonia supply source 50 (see Figure 1) into the inner cylindrical nozzle 61, and is introduced into the ammonia flame stabilizer 67 in a premixed state. The premixed gas is given a swirl by the ammonia flame stabilizer 67, travels straight along the central axis CL, and forms a premixed ammonia gas flame. In this way, the ammonia gas flame is stabilized by the ammonia flame stabilizer 67 and combusted with pulverized fuel supplied from the outer cylindrical nozzle 62.

The above-described embodiment has the following advantages.
The concentrator 69 provided inside the outer cylindrical nozzle 62 concentrates the pulverized fuel on the inner wall side of the pulverized fuel flame stabilizer 71. This makes the flame stabilized by the pulverized fuel flame stabilizer 71 more stable. By supplying ammonia gas to the inner cylindrical nozzle 61, the ammonia gas is supplied near, or more specifically inside, the flame of the pulverized fuel whose flame stabilization has been strengthened by the concentrator 69 and the pulverized fuel flame stabilizer 71, thereby stabilizing the combustion of the ammonia gas and increasing the ammonia fuel co-combustion ratio. For example, when multiple types of fuels are combusted simultaneously with a single burner, the ammonia fuel co-combustion ratio can be increased to 50% or more.

Ammonia gas and air are supplied to the inner nozzle 61 to perform premixed combustion, stabilizing the flame. The ammonia gas flame is then further stabilized by an ammonia flame stabilizer 67 installed at the tip of the inner nozzle 61. This allows for an increased ammonia fuel co-firing ratio.

In this embodiment, a control valve (not shown) may be provided to control the flow rate of air supplied to the inner cylindrical nozzle 61, and the opening of this control valve may be controlled by the control unit.
At this time, the control unit calculates the ammonia fuel combustion ratio (current value) by acquiring the flow rates of ammonia gas, air, pulverized fuel, and primary air from sensors (not shown).The control unit then adjusts the aperture of the control valve to reduce the air flow rate as the ammonia fuel combustion ratio increases.By controlling in this manner, even if the ammonia fuel combustion ratio increases and it becomes difficult to maintain the pulverized fuel flame, the flow rate of the air is reduced as the ammonia fuel increases, thereby reducing the flow velocity of the premixed fuel flowing out of the inner cylinder nozzle 61.This makes it possible to maintain the pulverized fuel flame while avoiding ignition inhibition of the pulverized fuel as much as possible, and to increase the ammonia fuel combustion ratio.

Second Embodiment
Next, a second embodiment of the present disclosure will be described with reference to FIGS. 3A and 3B.
In this embodiment, the oil nozzle 63 of the first embodiment is omitted, and the ammonia gas is ejected from a different position. In the following explanation, the same components as those of the first embodiment are denoted by the same reference numerals and their explanation is omitted, and the different components will be mainly explained.

As shown in Fig. 3A, the burner 21 of this embodiment has an inner cylinder nozzle 61 provided at a position closest to the central axis CL. Therefore, the oil nozzle 63 of the first embodiment is not provided inside the inner cylinder nozzle 61. The end of the inner cylinder nozzle 61 on the furnace 11 side (the right end in Fig. 3A) is closed, and ammonia gas is not ejected from there. Ammonia gas is supplied to the inner cylinder nozzle 61 from the ammonia supply source 50 shown in Fig. 1. However, unlike the first embodiment, only ammonia gas is supplied to the inner cylinder nozzle 61, and air is not supplied.

As shown in FIG. 3B , the concentrator 69 is formed with multiple slits (ammonia gas ejection holes) 80. These slits 80 form radially elongated flow paths. In this embodiment, four slits 80 are provided. However, the number is not particularly limited and may be two or more, or three or more. Each slit 80 communicates with the inner cylinder nozzle 61, allowing ammonia gas to flow through it. As shown in FIG. 3A , each slit 80 is formed in the downstream inclined portion 69b of the concentrator 69 and ejects ammonia gas in a direction along the central axis CL, as indicated by the arrows. The slits 80 inject ammonia gas into the outer cylinder nozzle 62. Primary air flowing through the outer cylinder nozzle 62 is used as combustion air for the ammonia gas.

According to this embodiment, the following advantageous effects are achieved.
Ammonia gas is ejected into the outer cylindrical nozzle 62 from each slit 80 formed in the concentrator 69, so that a flame can be formed together with the pulverized fuel, and the ammonia fuel co-combustion ratio can be increased.

Ammonia gas is ejected from the slit 80 along the central axis CL to prevent it from spreading radially as much as possible, which delays mixing with the pulverized fuel concentrated on the inner wall side of the outer nozzle 62 by the concentrator 69, thereby reducing NOx.

In this embodiment, the ammonia gas is ejected from the slit 80 along the central axis CL, but this may be changed as shown in FIGS. 4A and 4B.
Specifically, the direction in which the ammonia gas is ejected is changed. As shown by the arrows in Figures 4A and 4B, the slits 80' are formed in a direction in which the ammonia gas is ejected outward (radially) at an angle with respect to the central axis CL.

By ejecting ammonia gas from the slit 80' toward the outer periphery at an angle relative to the central axis CL, the ammonia gas spreads toward the inner wall of the outer tube nozzle 62 and mixes with the pulverized fuel concentrated on the inner wall of the outer tube nozzle 62 by the concentrator 69, thereby promoting combustion.

[Third embodiment]
Next, a third embodiment of the present disclosure will be described with reference to FIG.
This embodiment differs from the second embodiment in that a distributor 82 is added, but the other configurations are similar, so the same reference numerals are used and the description thereof will be omitted.

As shown in Figure 5, a ring-shaped distributor 82 is provided inside the tip of the outer cylindrical nozzle 62. The distributor 82 is provided to surround the downstream end of the downstream inclined portion 69b of the concentrator 69. The distributor 82 divides the flow path within the outer cylindrical nozzle 62 into an inner flow path 62a and an outer flow path 62b.

By separating the inner flow path 62a and outer flow path 62b of the outer cylindrical nozzle 62, the inner flow path 62a is separated by the concentrator 69 and mainly carries primary air, while the outer flow path 62b mainly carries concentrated pulverized fuel. This allows the primary air flowing through the inner flow path 62a to be used to burn ammonia gas, and the concentrated pulverized fuel flowing through the outer flow path 62b can promote ignition of the pulverized fuel.

In this embodiment, as shown in Figure 5, the ammonia gas is ejected in a direction inclined relative to the central axis CL toward the outer periphery as shown in Figure 4A, but the present disclosure is not limited to this. For example, as shown in Figure 3A, ammonia gas may be ejected from the slit 80 along the central axis CL.

[Fourth embodiment]
Next, a fourth embodiment of the present disclosure will be described with reference to FIGS. 6A to 6C.
In the second embodiment, the ammonia gas is blown out from the inner peripheral side of the outer cylindrical nozzle 62, but in this embodiment, the ammonia gas is blown out from the inner wall side of the outer cylindrical nozzle 62. In the following description, the same components as in the second embodiment are denoted by the same reference numerals and description thereof will be omitted, and the different components will be mainly described.

As shown in Figure 6A, no ammonia gas is supplied from the inner cylinder nozzle 61. The inner cylinder nozzle 61 basically flows a small amount of cooling air, but can be used as an oil nozzle during startup if necessary.

Multiple circumferential concentrators 85 are provided on the inner wall of the outer cylindrical nozzle 62. Each circumferential concentrator 85 is located on the outer periphery of the downstream inclined portion 69b of the concentrator 69.

As shown in Figure 6B, each circumferential concentrator 85 is provided at a predetermined circumferential interval along the inner wall of the outer tubular nozzle 62. The pulverized fuel concentrated by the concentrator 69 flows between adjacent circumferential concentrators 85 in a contracting flow.

Figure 6C shows two circumferential concentrators 85 as an example. In the figure, the upper part indicates the outer circumferential side of the outer cylindrical nozzle 62, and the lower part indicates the inner circumferential side of the outer cylindrical nozzle 62. As shown in Figure 6C, an ammonia gas ejection hole 85a for ejecting ammonia gas is provided at the tip (downstream end) of the circumferential concentrator 85. An ammonia gas supply pipe 87 (see Figures 6A and 6B) is connected to the circumferential concentrator 85 via a pipe-shaped mounting portion 85b. Ammonia gas is supplied to the circumferential concentrator 85 from the ammonia supply source 50 (see Figure 1) via the ammonia gas supply pipe 87.

As shown in Figure 6C, the circumferential concentrator 85 has a diamond shape when viewed from the inner circumferential side of the outer cylindrical nozzle 62, gradually widening from the upstream end 85c and gradually narrowing from the intermediate position 85d to the downstream end 85e. Multiple ammonia gas ejection holes 85a are formed on the downstream side surface 85f extending from the intermediate position 85d to the downstream end 85e. The inner circumferential surface of the circumferential concentrator 85, i.e., the bottom surface 85g, is closed.

According to this embodiment, the following advantageous effects are achieved.
By providing the concentrator 69 on the outer wall of the inner cylindrical nozzle 61, the pulverized fuel is concentrated on the inner wall side of the outer cylindrical nozzle 62. By providing a plurality of circumferential concentrators 85 at predetermined intervals in the circumferential direction on the inner wall of the tip of the outer cylindrical nozzle 62, the circumferential flow path width is partially reduced, and the pulverized fuel is concentrated in the circumferential direction. Ammonia gas is then ejected from the ammonia gas ejection holes 85a provided in the circumferential concentrators 85, whereby the ammonia gas is mixed with the circumferentially concentrated pulverized fuel, thereby promoting combustion.

Fifth Embodiment
Next, a fifth embodiment of the present disclosure will be described with reference to FIGS. 7A and 7B.
While ammonia gas is used in the first embodiment, liquid ammonia is used in this embodiment, which is different. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals and their description will be omitted, and the description will focus mainly on the different components.

As shown in FIG. 7A, a liquid ammonia supply pipe 90 for spraying liquid ammonia is provided inside the inner cylindrical nozzle 61. Multiple liquid ammonia supply pipes 90 are provided at predetermined intervals around the central axis CL. Liquid ammonia is supplied to the liquid ammonia supply pipe 90 from the ammonia supply source 50 (see FIG. 1). Air is supplied to the inner cylindrical nozzle 61.

A liquid ammonia injection tip 92 is provided within the liquid ammonia supply pipe 90, as shown in Figure 7B. A liquid ammonia flow path is formed within the liquid ammonia injection tip 92, as shown in Figure 7B, and atomized liquid ammonia fuel is injected from multiple injection holes 92a toward the inner cylinder nozzle 61. The liquid ammonia is injected by pressure spraying from the liquid ammonia injection tip 92. Liquid ammonia is injected from the liquid ammonia injection tip 92 of the liquid ammonia supply pipe 90 upstream of the ammonia flame stabilizer 67.

Sixth Embodiment
Next, a sixth embodiment of the present disclosure will be described with reference to FIG.
Although the fifth embodiment shows a configuration in which liquid ammonia is supplied, liquid ammonia can also be supplied to the oil nozzle 63, which injects oil fuel, which is the same liquid, as a burner that burns liquid ammonia. In this case, if a large amount of liquid ammonia is supplied into the furnace 11 from the central axis CL side of the burner 21, the temperature near the outlet of the burner 21 will drop due to the heat of vaporization, making ignition difficult. Therefore, in addition to the ammonia supplied from the oil nozzle 63, it is desirable to supply a necessary amount of ammonia from the outer circumferential side of the oil nozzle 63, i.e., from the ammonia supply pipe 95 provided in the tertiary air flow path 74.

The ammonia supply pipes 95 are cylindrical members, and multiple pipes are arranged within the tertiary air flow path 74 at appropriate circumferential intervals. However, there are no limitations on the shape or quantity of the ammonia supply pipes 95, as long as they can stably ignite and burn the fuel. Furthermore, the ammonia supplied to the ammonia supply pipes 95 may be either liquid or gas.

According to this embodiment, the following advantageous effects are achieved.
Liquid ammonia is injected upstream of the ammonia flame stabilizer 67 provided at the tip of the inner cylindrical nozzle 61. As a result, the liquid ammonia is mixed with the air supplied into the inner cylindrical nozzle 61 upstream of the ammonia flame stabilizer 67, and the liquid ammonia is vaporized as much as possible in the ammonia flame stabilizer 67, stabilizing the flame by the ammonia flame stabilizer 67. This makes it possible to increase the ammonia fuel co-firing ratio.

In each of the above-described embodiments, the boiler of the present invention has been described as a boiler that uses solid fuel as fuel. Examples of solid fuels used in boilers include coal, biomass fuel, petroleum coke (PC), and petroleum residue.

The burner described in each of the above-described embodiments, the boiler equipped with the same, and the method of operating the burner can be understood, for example, as follows.

A burner (21) according to one aspect of the present disclosure comprises an inner cylindrical nozzle (61) extending along a central axis (CL), an outer cylindrical nozzle (62) extending along the central axis and covering the inner cylindrical nozzle, for supplying pulverized fuel and primary air into a furnace, a pulverized fuel flame stabilizer (71) for stabilizing the flame of the pulverized fuel supplied from the outer cylindrical nozzle, and a concentrator (69) provided inside the outer cylindrical nozzle for concentrating the pulverized fuel on the pulverized fuel flame stabilizer side, and supplies ammonia fuel to the inner cylindrical nozzle or the outer cylindrical nozzle.

A concentrator installed inside the outer nozzle concentrates pulverized fuel on the pulverized fuel flame stabilizer side. This makes the flame stabilized by the pulverized fuel flame stabilizer more stable. Furthermore, by supplying ammonia fuel to the inner or outer nozzle, the ammonia fuel is supplied near the pulverized fuel flame, whose flame stabilization has been strengthened using the concentrator and pulverized fuel flame stabilizer, thereby increasing the ammonia fuel co-firing ratio.

In a burner according to one aspect of the present disclosure, ammonia gas is used as the ammonia fuel, ammonia gas and air are supplied to the inner cylindrical nozzle, and an ammonia flame stabilizer (67) is provided at the tip of the inner cylindrical nozzle to stabilize the flame of the ammonia gas supplied from the inner cylindrical nozzle.

Ammonia gas and air are supplied to the inner nozzle to perform premixed combustion, stabilizing the flame. The ammonia gas flame is then further stabilized by an ammonia flame stabilizer installed at the tip of the inner nozzle. This allows for an increased ammonia fuel co-firing ratio.

A burner according to one aspect of the present disclosure includes a control valve that controls the flow rate of air supplied to the inner cylindrical nozzle, and a control unit that controls the control valve, and the control unit controls the control valve to reduce the flow rate of the air in response to an increase in the ammonia fuel co-combustion ratio.

Increasing the ammonia fuel co-firing ratio can make it difficult to maintain a pulverized fuel flame. Therefore, by reducing the air flow rate in response to an increase in ammonia fuel, the flow velocity of the premixed fuel flowing out of the inner nozzle is reduced. This makes it possible to maintain the pulverized fuel flame while minimizing ignition inhibition of the pulverized fuel, thereby enabling an increase in the ammonia fuel co-firing ratio.

In a burner according to one aspect of the present disclosure, ammonia gas is used as the ammonia fuel, ammonia gas is supplied to the inner cylindrical nozzle, the concentrator is provided on the outer wall of the inner cylindrical nozzle, and the concentrator is provided with ammonia gas ejection holes (80, 80') that eject the ammonia gas guided from the inner cylindrical nozzle into the outer cylindrical nozzle.

By providing a concentrator on the outer wall of the inner cylindrical nozzle, the pulverized fuel can be concentrated on the inner wall side of the outer cylindrical nozzle.
Since ammonia gas is ejected into the outer cylindrical nozzle from the ammonia gas ejection holes formed in the concentrator, a flame can be formed together with the pulverized fuel, and the ammonia fuel co-combustion ratio can be increased.

In a burner according to one aspect of the present disclosure, the ammonia gas ejection holes are formed in a direction such that the ammonia gas is ejected along the central axis.

By ejecting ammonia gas from the ammonia gas ejection hole along the central axis, mixing with the pulverized fuel concentrated on the inner wall of the outer nozzle by the concentrator is delayed, thereby reducing NOx.

In a burner according to one aspect of the present disclosure, the ammonia gas ejection holes are formed in a direction such that the ammonia gas is ejected toward the outer periphery at an angle relative to the central axis.

By ejecting ammonia gas from the ammonia gas ejection holes at an angle relative to the central axis toward the outer periphery, the ammonia gas spreads along the inner wall of the outer nozzle and mixes with the pulverized fuel concentrated on the inner wall of the outer nozzle by the concentrator, promoting combustion.

In one aspect of the burner disclosed herein, a distributor (82) is provided at the tip of the outer cylindrical nozzle to separate the inner flow path from the outer flow path.

A distributor is installed at the tip of the external nozzle, separating the internal and external flow paths of the external nozzle, creating an internal flow path through which primarily primary air flows, and an external flow path through which primarily concentrated pulverized fuel flows. This allows the primary air flowing through the internal flow path to be used to burn ammonia gas, and the concentrated pulverized fuel flowing through the external flow path to promote ignition of the pulverized fuel.

In a burner according to one aspect of the present disclosure, ammonia gas is used as the ammonia fuel, the concentrator is provided on the outer wall of the inner cylindrical nozzle, and a plurality of circumferential concentrators (85) are provided at predetermined intervals in the circumferential direction on the inner wall of the tip of the outer cylindrical nozzle, and ammonia gas ejection holes (85a) for ejecting the ammonia gas are formed in the circumferential concentrators.

By installing a concentrator on the outer wall of the inner cylindrical nozzle, the pulverized fuel is concentrated on the inner wall side of the outer cylindrical nozzle. Furthermore, by installing multiple circumferential concentrators at predetermined intervals around the circumferential direction on the inner wall at the tip of the outer cylindrical nozzle, the circumferential flow path width is partially reduced, concentrating the pulverized fuel in the circumferential direction. Ammonia gas is then ejected from the ammonia gas ejection holes installed in the circumferential concentrators, where it mixes with the circumferentially concentrated pulverized fuel and promotes combustion.

In a burner according to one aspect of the present disclosure, liquid ammonia is used as the ammonia fuel, air is supplied to the inner cylindrical nozzle, an ammonia flame stabilizer (67) is provided at the tip of the inner cylindrical nozzle to stabilize the flame of the ammonia supplied from the inner cylindrical nozzle, and a liquid ammonia supply pipe (90) is provided inside the inner cylindrical nozzle to inject the liquid ammonia upstream of the ammonia flame stabilizer.

Liquid ammonia is injected upstream of the ammonia flame stabilizer installed at the tip of the inner nozzle. This allows it to mix with the air supplied into the inner nozzle upstream of the ammonia flame stabilizer, vaporizing the liquid ammonia as much as possible in the flame stabilizer, stabilizing the flame with the ammonia flame stabilizer. This allows for an increased ammonia fuel co-firing ratio.

In a burner according to one aspect of the present disclosure, liquid ammonia fuel is supplied from the inner cylindrical nozzle, and ammonia is injected from an ammonia supply pipe provided on the outer periphery of the outer cylindrical nozzle.

By supplying liquid ammonia from the inner nozzle and injecting ammonia from the ammonia supply pipe attached to the outer periphery of the outer nozzle, the ammonia co-firing ratio can be increased. Furthermore, supplying liquid ammonia from the inner nozzle can lower the temperature near the burner outlet due to the heat of vaporization, which can make ignition difficult. However, by reducing the amount of liquid ammonia supplied from the inner nozzle by an amount equivalent to the ammonia supplied from the ammonia supply pipe, proper ignition can be achieved. The ammonia supplied from the ammonia supply pipe can be either liquid or gas.

A boiler (10) according to one aspect of the present disclosure is equipped with any of the burners described above.

A method for operating a burner according to one aspect of the present disclosure is a method for operating a burner comprising: an inner cylindrical nozzle extending along a central axis; an outer cylindrical nozzle extending along the central axis and covering the inner cylindrical nozzle, which supplies pulverized fuel and primary air into a furnace; a pulverized fuel flame stabilizer that stabilizes the flame of the pulverized fuel supplied from the outer cylindrical nozzle; and a concentrator disposed inside the outer cylindrical nozzle that concentrates the pulverized fuel on the pulverized fuel flame stabilizer side, wherein ammonia fuel is supplied to the inner cylindrical nozzle or the outer cylindrical nozzle.

Furthermore, according to the burner according to one aspect of the present disclosure, the following advantageous effects can be obtained.
In a co-firing burner that simultaneously burns pulverized fuel and ammonia fuel using a single burner, the conditions for fuel ignition and flame stability become strict, particularly in the range of loads lower than the rated output, and therefore the range of upper and lower limits for the co-firing ratio tends to be narrow.

In addition, the minimum load limit for multi-fuel burners tends to be higher than that of single-fuel burners, as they stably form and maintain flames from multiple fuels with different combustion characteristics.

In wall-fired boilers, which use burners arranged in multiple rows and columns on the furnace wall, ignition, extinguishing, and output (load) adjustments are often performed for each row of burners as a single group.
One stage of burner may be shut down to use as a spare, and the load on other operating burner stages may be adjusted, or the number of burner stages may be further shut down to reduce the load.

A wall-fired boiler equipped with the burners of the present disclosure in each stage and each row can increase the ammonia fuel co-firing ratio.
Even in the low boiler load region, the upper and lower limits of the co-firing ratio are wide, and the lower limit of the boiler load can be lowered. This improves the operability of the boiler plant and the flexibility in responding to co-firing ratio and load fluctuations.

The burner disclosed herein allows for an increased ammonia fuel co-firing ratio, i.e., the upper limit of the co-firing ratio is high. Therefore, when converting a boiler equipped only with burners that burn existing pulverized fuel into a co-firing boiler by replacing some of the burners with burners capable of burning ammonia, there is an advantage in that it is sufficient to replace fewer burners than with burners with a lower upper limit of the co-firing ratio.

The burner disclosed herein has a wide upper and lower limit range for the ammonia fuel co-firing ratio, which has the advantage that in a boiler plant that has a mixture of burners that exclusively fire a specific fuel type and burners that co-firing ammonia and pulverized fuel, the range for selecting burners to be used or idled and for adjusting the load is wider than with burners that have a narrow upper and lower limit range for the ammonia fuel co-firing ratio.

In addition, stable combustion can be achieved even at low loads, and the minimum load limit can be set low.

It is also easy to accommodate flexible operations such as increasing or decreasing the fuel supply ratio, i.e., the mixed combustion ratio, depending on the fuel procurement circumstances at the boiler plant.

10 Boiler 11 Furnace 12 Combustion gas passage 13 Flue 20 Combustion device 21 Burner 22 Pulverized fuel supply pipe 23 Air register
24 Air duct
25 Additional air port 26 Additional air duct 31 Mill (crusher)
32 Forced draft fan (FDF)
41 Gas duct 42 Air preheater 43 Denitrification device 44 Dust collector 45 Induced draft fan (IDF)
46 Desulfurization device 47 Chimney 50 Ammonia supply source 61 Inner cylindrical nozzle 62 Outer cylindrical nozzle 62a Inner flow path 62b Outer flow path 63 Oil nozzle 67 Ammonia flame stabilizer 68 Venturi 68a Upstream inclined portion 68b Downstream inclined portion 69 Concentrator 69a Upstream inclined portion 69b Downstream inclined portion 69c Cylindrical portion 71 Pulverized fuel flame stabilizer 73 Secondary air flow path 74 Tertiary air flow path 74a Swirlers 80, 80' Slit (ammonia gas ejection hole)
82 distributor 85 circumferential concentrator 85 a ammonia gas injection hole 85 b mounting portion 85 c upstream end 85 d intermediate position 85 e downstream end 85 f downstream side surface 85 g bottom surface 87 ammonia gas supply pipe 90 liquid ammonia supply pipe 92 liquid ammonia injection tip 92 a injection hole 95 liquid ammonia supply pipe 101 furnace wall 102 superheater 103 reheater 104 economizer

Claims (11)

an inner cylindrical nozzle extending along a central axis;
an outer cylindrical nozzle extending along the central axis and covering the inner cylindrical nozzle, the outer cylindrical nozzle supplying pulverized fuel and primary air into the furnace;
a pulverized fuel flame stabilizer that stabilizes the flame of the pulverized fuel supplied from the outer cylindrical nozzle;
a concentrator provided inside the outer cylindrical nozzle and configured to concentrate the pulverized fuel on the pulverized fuel flame stabilizer side;
Equipped with
supplying ammonia fuel to the inner cylindrical nozzle or the outer cylindrical nozzle ;
Ammonia gas is used as the ammonia fuel,
Ammonia gas is supplied to the inner cylindrical nozzle,
the concentrator is provided on an outer wall of the inner cylindrical nozzle,
a burner in which the concentrator is provided with an ammonia gas ejection hole for ejecting the ammonia gas introduced from the inner cylindrical nozzle into the outer cylindrical nozzle ; Ammonia gas is used as the ammonia fuel,
Ammonia gas and air are supplied to the inner cylindrical nozzle,
2. The burner according to claim 1, wherein an ammonia flame stabilizer for stabilizing the flame of the ammonia gas supplied from the inner cylindrical nozzle is provided at the tip of the inner cylindrical nozzle. a control valve for controlling the flow rate of air supplied to the inner cylindrical nozzle;
a control unit that controls the control valve;
Equipped with
The burner according to claim 2 , wherein the control unit controls the control valve to reduce the flow rate of the air in response to an increase in the mixed combustion ratio of the ammonia fuel. 2. The burner according to claim 1 , wherein the ammonia gas ejection holes are formed in a direction such that the ammonia gas is ejected along the central axis. 2. The burner according to claim 1 , wherein the ammonia gas ejection holes are formed in a direction such that the ammonia gas is ejected toward the outer periphery at an angle with respect to the central axis. 2. The burner according to claim 1 , wherein a distributor is provided at the tip of said outer cylindrical nozzle to separate the inner flow passage from the outer flow passage. Ammonia gas is used as the ammonia fuel,
the concentrator is provided on an outer wall of the inner cylindrical nozzle,
a plurality of circumferential concentrators are provided at predetermined intervals in the circumferential direction on the inner wall of the tip of the outer cylindrical nozzle;
2. The burner according to claim 1, wherein the circumferential concentrator is formed with ammonia gas ejection holes for ejecting the ammonia gas. Liquid ammonia is used as the ammonia fuel,
Air is supplied to the inner cylindrical nozzle,
an ammonia flame stabilizer that stabilizes the flame of the ammonia supplied from the inner cylindrical nozzle is provided at a tip of the inner cylindrical nozzle;
2. The burner according to claim 1, wherein a liquid ammonia supply pipe for injecting the liquid ammonia is provided inside the inner cylindrical nozzle on the upstream side of the ammonia flame stabilizer. supplying liquid ammonia fuel from the inner cylindrical nozzle;
2. The burner according to claim 1, wherein ammonia is injected from an ammonia supply pipe provided on the outer periphery of the outer cylindrical nozzle. A boiler equipped with the burner according to any one of claims 1 to 9 . an inner cylindrical nozzle extending along a central axis;
an outer cylindrical nozzle extending along the central axis and covering the inner cylindrical nozzle, the outer cylindrical nozzle supplying pulverized fuel and primary air into the furnace;
a pulverized fuel flame stabilizer that stabilizes the flame of the pulverized fuel supplied from the outer cylindrical nozzle;
a concentrator provided inside the outer cylindrical nozzle and configured to concentrate the pulverized fuel on the pulverized fuel flame stabilizer side;
A method for operating a burner comprising:
supplying ammonia fuel to the inner cylindrical nozzle or the outer cylindrical nozzle ;
Ammonia gas is used as the ammonia fuel,
Ammonia gas is supplied to the inner cylindrical nozzle,
the concentrator is provided on an outer wall of the inner cylindrical nozzle,
The method for operating a burner , wherein the concentrator is provided with an ammonia gas ejection hole for ejecting the ammonia gas introduced from the inner cylindrical nozzle into the outer cylindrical nozzle .