WO2024262596A1 - Burner, boiler provided with same, and method for operating burner - Google Patents

Abstract

Provided is a burner capable of performing stable combustion when premixed combustion and diffusion combustion of ammonia fuel are combined. The burner is provided with: an outer cylinder nozzle that extends along a center axis (CL), and supplies a premixed gas of ammonia fuel and air to the inside of a furnace; a flame holder that holds the flame of the premixed gas; and a plurality of liquid ammonia nozzles (80) that supply liquid ammonia fuel to the inside of the furnace from a position closer to the outer peripheral side than the flame holder. The liquid ammonia fuel jetted from each liquid ammonia nozzle (80) is jetted from an injection position separated from others by 45° or more on a concentric circle (C1) centered on the center axis (CL), in a direction that opens more than 30° toward the center axis (CL) side from a tangential line (L1) direction on the concentric circle (C1) at the injection position.

Description

Burner, boiler equipped with same, and burner operation method

The present disclosure relates to a burner that burns, for example, 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 furnace that is installed vertically, with multiple burners arranged on the wall of the furnace. Large boilers also have a flue connected vertically above the furnace, and a heat exchanger for generating steam is arranged in this flue. The burner then injects a mixture of fuel and air (oxidizing gas) into the furnace to form a flame, generating combustion gas that flows into the flue. A heat exchanger is installed in the area where the combustion gas flows, and superheated steam is generated by heating the water and steam flowing inside the heat transfer tubes that make up the heat exchanger.

As burners for use in boilers, it has been considered to mix pulverized coal and ammonia fuel, or to exclusively burn pulverized coal or ammonia fuel (for example, Patent Document 1).

JP 2020-41748 A

When modifying a coal-fired boiler to be able to co-fire ammonia and other fuels, it is advantageous to supply the ammonia fuel in liquid form and perform spray combustion in order to reduce the size of the fuel piping, etc. However, in Patent Document 1, it is assumed that the ammonia fuel will be supplied as a gas, and the use of the ammonia fuel as a liquid is not considered.

Ammonia is a gas at room temperature, and needs to be pressurized to around 2 MPa to supply it as a liquid. In addition, ammonia has a slow burning speed of about one-fifth compared to common hydrocarbon fuels such as methane, making it difficult to ignite and burn. Furthermore, when burning ammonia directly as a liquid, the heat of vaporization is large, which can lead to poor ignition in the burner.

　A burner that combines premixed combustion and diffusion combustion is envisaged to improve ignition performance in direct combustion of liquid ammonia. In the premixing section, liquid ammonia is sprayed upstream of the burner, vaporized by mixing with high-temperature combustion air, and supplied to the burner primary nozzle as a premixed gas, which is then injected into the boiler furnace. In the diffusion section, multiple liquid ammonia supply pipes are installed concentrically around the outer periphery of the air, and ammonia fuel is injected into the furnace in liquid form.

When liquid ammonia is supplied from the liquid ammonia supply pipe in the diffusion section, it vaporizes in the furnace and diffuses as a gas, so it is necessary to promote mixing with high-temperature air to compensate for the temperature drop caused by the heat of vaporization. On the other hand, to ignite the premixed gas, it must be mixed with high-temperature air or high-temperature combustion exhaust gas from inside the furnace, so a balance with the diffusion section is required.

The present disclosure has been made in consideration of these circumstances, and aims to provide a burner that can perform stable combustion when premixed combustion and diffusion combustion of ammonia fuel are combined, as well as a boiler equipped with the burner and a method for operating the burner.

A burner according to one embodiment of the present disclosure includes a first nozzle extending along a central axis and supplying a premixed gas of ammonia fuel and air into the interior of the furnace, a flame stabilizer that stabilizes the flame of the premixed gas, and a plurality of liquid ammonia nozzles that supply liquid ammonia fuel into the interior of the furnace from a position on the outer periphery of the flame stabilizer, and the liquid ammonia fuel ejected from each of the liquid ammonia nozzles is ejected from ejection positions that are 45° or more apart from each other on a concentric circle centered on the central axis, in a direction toward the central axis that is open more than 30° from the tangent direction on the concentric circle at the ejection position.

A burner according to one embodiment of the present disclosure includes a first nozzle extending along a central axis and supplying a premixed gas of ammonia fuel and air into the interior of the furnace, a flame stabilizer that stabilizes the flame of the premixed gas, and a plurality of liquid ammonia nozzles that supply liquid ammonia fuel into the interior of the furnace from a position on the outer periphery of the flame stabilizer, and the liquid ammonia fuel ejected from each of the liquid ammonia nozzles is ejected parallel to the central axis from injection positions spaced apart by 60° or more from each other on concentric circles centered on the central axis.

A boiler according to one embodiment of the present disclosure is equipped with any of the burners described above.

A method of operating a boiler according to one aspect of the present disclosure is a method of operating a burner including a first nozzle extending along a central axis and supplying a premixed gas of ammonia fuel and air into the interior of a furnace, a flame stabilizer that stabilizes the flame of the premixed gas, and a plurality of liquid ammonia nozzles that supply liquid ammonia fuel into the interior of the furnace from a position on the outer periphery of the flame stabilizer, and the liquid ammonia fuel is ejected from each of the liquid ammonia nozzles from injection positions spaced apart by 45° or more on a concentric circle centered on the central axis, in a direction toward the central axis at an angle of more than 30° from the tangent direction on the concentric circle at the injection positions.

A method of operating a boiler according to one aspect of the present disclosure is a method of operating a burner including a first nozzle extending along a central axis and supplying a premixed gas of ammonia fuel and air into the interior of a furnace, a flame stabilizer that stabilizes the flame of the premixed gas, and a plurality of liquid ammonia nozzles that supply liquid ammonia fuel into the interior of the furnace from a position on the outer periphery of the flame stabilizer, and the liquid ammonia fuel is ejected from each of the liquid ammonia nozzles parallel to the central axis from injection positions spaced apart by 60° or more from each other on concentric circles centered on the central axis.

Stable combustion can be achieved by combining premixed combustion and diffusion combustion of ammonia fuel.

FIG. 1 is a schematic configuration diagram showing a boiler according to a first embodiment of the present disclosure. FIG. 2 is a vertical cross-sectional view of the burner of FIG. 1; FIG. 3 is a front view showing the positions of the liquid ammonia nozzle of FIG. 2. FIG. 3B is a front view showing the reference example of FIG. 3A. FIG. 3 is a vertical sectional view showing a modification of FIG. 2 . FIG. 4 is a vertical cross-sectional view showing a burner according to a second embodiment of the present disclosure. FIG. 6 is a front view showing the positions of the liquid ammonia nozzle of FIG. 5 . FIG. 6 is a vertical sectional view showing a modification of FIG. 5 . FIG. 11 is a vertical cross-sectional view showing another modified example.

Below, one embodiment of the present disclosure will be described 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 in which the respective embodiments are combined. In the following description, top and upward refer to the upper side in the vertical direction, and bottom and downward refer to the lower side in the vertical direction, and the vertical direction is not precise and includes error.

[First embodiment]
FIG. 1 shows a boiler 10 according to the present embodiment, which 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 by pulverizing solid fuel and liquid ammonia fuel with a burner and exchanging the heat generated by this combustion with feed water or steam. Biomass fuel, coal, etc. are used as the solid fuel.

The boiler 10 has a furnace 11, a combustion device 20, and a combustion gas passage 12. The furnace 11 has a hollow rectangular cylinder shape and is installed vertically. The furnace wall 101 that forms the inner wall surface of the furnace 11 is composed of multiple heat transfer tubes and fins that connect the heat transfer tubes to each other, and recovers the heat generated by the combustion of pulverized fuel by heat exchange with water and steam flowing inside the heat transfer tubes, while 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, 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 at equal intervals in the furnace width direction along the furnace wall 101 (for example, burners are arranged in the furnace width direction so as to face each of the opposing furnace walls 101 for opposed combustion), and are arranged in multiple tiers along the vertical direction. The shape of the furnace, the number of burner tiers, the number of burners in one tier, the arrangement of the burners, etc. are not limited to this embodiment.

Burners 21A, 21B, 21C, 21D, 21E, 21F are connected to a plurality of mills (pulverizers) 31A, 31B, 31C, 31D, 31E, 31F (hereinafter, when these mills are not distinguished, they will be simply referred to as "mills 31") via a plurality of pulverized fuel supply pipes 22A, 22B, 22C, 22D, 22E, 22F, respectively (hereinafter, when these mills are not distinguished, they will be simply referred to as "mills 31"). Mill 31 is, for example, a vertical roller mill in which a grinding table (not shown) is supported inside so that it can be driven and rotated, and a plurality of grinding rollers (not shown) are supported above the grinding table so that they can rotate in conjunction with the rotation of the grinding table. The solid fuel pulverized by the cooperation of the pulverizing roller and the pulverizing table is transported to a classifier (not shown) provided in the mill 31 by primary air (carrier gas, oxidizing gas) supplied to the mill 31. In the classifier, the fuel is classified into fine pulverized fuel having a particle size smaller than that suitable for combustion in the burner 21 and coarse pulverized fuel having a larger particle size. The fine pulverized fuel passes through the classifier and is supplied to the burner 21 together with the primary air via the fine pulverized fuel supply pipe 22. The coarse pulverized fuel that does not pass through the classifier falls onto the pulverizing table by its own weight inside the mill 31 and is pulverized again.

At least some of the burners 21A, 21B, 21C, 21D, 21E, and 21F are ammonia-only burners to which ammonia fuel is supplied. In this case, the other burners 21A, 21B, 21C, 21D, 21E, and 21F are pulverized coal-only burners. The ammonia-only burners are not supplied with pulverized coal fuel from the mill 31, but are supplied with ammonia fuel from the liquid ammonia supply source 50.

An air register 23 is provided on the outside of the furnace 11 at the installation position of the burner 21, and one end of an air duct 24 is connected to the air register 23. A forced draft fan (FDF: Forced Draft Fan) 32 is connected to the other end of the air duct 24. The air supplied from the forced draft fan 32 is heated by an air preheater 42 installed in the air duct 24, and is supplied to the burner 21 via the air register 23 as secondary air (combustion air, oxidizing gas) and is 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, 102C (hereinafter, when the superheaters are not differentiated, they will simply be referred to as "superheaters 102"), reheaters 103A, 103B (hereinafter, when the reheaters are not differentiated, they will simply be referred to as "reheaters 103"), and a coal economizer 104 as heat exchangers for recovering heat from the combustion gas, and heat is exchanged between the combustion gas generated in the furnace 11 and the feed water or steam flowing inside each heat exchanger. The arrangement and shape of each heat exchanger are not limited to the form shown in FIG. 1.

Connected to the downstream side of the combustion gas passage 12 is a flue 13 through which the combustion gas that has had its heat 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, heating 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.

Further, 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 having an effect of reducing nitrogen oxides, such as ammonia or urea water, to the combustion gas flowing through the flue 13, and promotes a 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 equipment such as a dust collector 44, such as an electric dust collector, for removing ash and the like from the combustion gas, a desulfurization equipment 46 for removing sulfur oxides, and an induced draft fan (IDF) 45 for directing the exhaust gas to these environmental equipment. The downstream end of the gas duct 41 is connected to a chimney 47, and the combustion gas treated in the environmental equipment is discharged to the outside of the system as exhaust gas.

When the boiler 10 is burning pulverized fuel alone (or mixed with ammonia fuel), the multiple mills 31 are driven and pulverized and classified pulverized fuel is supplied to the burner 21 via the pulverized fuel supply pipe 22 together with primary air. Secondary air heated in the air preheater 42 is supplied to the burner 21 from the air duct 24 via the wind box 23. The burner 21 blows a pulverized fuel 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 inside 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 it may be a gas with 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 mounting position of the burner 21 of the furnace 11, multiple additional air ports (AA ports) 25 are provided for supplying additional air for combustion (AA) into the furnace 11. The additional air ports 25 are connected to the ends of additional air ducts (AA ducts) 26 branching off from the air duct 24, 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 range of the wind box 23) inside 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 (total amount of primary air and secondary air) supplied to the burner 21 is set to be less than the theoretical amount of air for the amount of fuel supplied to the burner 21, so that region A and region B (region between the top of the burner 21 and the bottom of the additional air port 25) inside the furnace 11 become reducing atmospheres, and nitrogen oxides (NOx) generated by combustion are reduced inside the furnace 11. After that, in region C (region above the bottom of the additional air port 25), additional air for combustion is supplied from the additional air port 25 to the combustion gas in which NOx has been reduced, completing the combustion, but the amount of NOx generated is reduced by the amount of 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 arranged inside the combustion gas passage 12, and is then 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, before being 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 from the system through the chimney 47. Note that 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 with respect to the combustion gas flow.

The boiler 10 is equipped with a liquid ammonia supply source 50. Ammonia is stored in liquid form in the liquid ammonia supply source 50 as ammonia fuel. The liquid ammonia is supplied from the liquid ammonia supply source 50 to each burner 21.

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 in the form of a program, for example, and the CPU reads this program into the RAM and executes information processing and arithmetic processing 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. Computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories.

FIG. 2 shows a burner 21 capable of burning ammonia fuel exclusively.
The burner 21 includes an inner cylinder nozzle (second nozzle) 61 extending along a central axis CL, and an outer cylinder nozzle (first nozzle) 62 provided so as to cover the inner cylinder nozzle 61. A core air nozzle (air nozzle) 63 is provided on the outer periphery side of the inner cylinder nozzle 61 and on the inner periphery side of the outer cylinder nozzle 62. Each of the nozzles 61, 62, 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 oil fuel (start-up fuel) and injects the oil fuel into the furnace 11. The oil fuel is supplied from an oil fuel supply source (not shown) and is used when starting up the burner 21.

When used as a pulverized coal burner, pulverized fuel and primary air are supplied to the outer nozzle 62, but when used as an ammonia-only burner, the supply of pulverized fuel and primary air is stopped.

The core air nozzle 63 is shorter than the inner cylinder nozzle 61, and its tip is located closer to the base end (left side in FIG. 2) than the tip of the inner cylinder nozzle 61. Core air (central air) as primary air and ammonia fuel are flowed into the core air nozzle 63. The ammonia fuel supplied to the core air nozzle 63 may be sprayed into the core air nozzle 63, or may be sprayed upstream of the core air nozzle 63.

A first swirl vane 76 and a second swirl vane 77 are provided on the outer wall of the inner tube nozzle 61. A plurality of these swirl vanes 76, 77 are provided in the circumferential direction around the central axis CL. The first swirl vane 76 and the second swirl vane 77 are provided between the tip of the core air nozzle 63 and the tip of the inner tube nozzle 61.

The first swirl vane 76 imparts a swirl around the central axis CL to the ammonia fuel and primary air flowing out of the core air nozzle 63. The second swirl vane 77 is located downstream of the first swirl vane 76 in the flow direction of the primary air, and imparts a swirl in the opposite direction to the first swirl vane 76.

A flame stabilizer 71, for example a baffle, is provided at the tip and outer periphery of the outer tubular nozzle 62. The flame stabilizer 71 is ring-shaped when the outer tubular nozzle 62 is viewed from the front. The flame stabilizer 71 partially blocks the flow of secondary air through the secondary air passage 73, forming a flame-stabilizing region downstream of it. This stabilizes the flame FL of the premixed air and ammonia fuel supplied from the outer tubular nozzle 62 via the core air nozzle 63.

The secondary air flow passage 73 is provided so as to cover the outer tube nozzle 62. A tertiary air flow passage 74 is provided on the outer peripheral side of the secondary air flow passage 73 so as to cover the secondary air flow passage 73. A swirler 74a is provided within the tertiary air flow passage 74 to give a swirl to the tertiary air.

A tubular liquid ammonia nozzle 80 is provided on the outer periphery of the outer tube nozzle 62 at a position corresponding to the tertiary air flow path 74. As shown in FIG. 3A, a plurality of liquid ammonia nozzles 80 are provided on a concentric circle C1 centered on the central axis CL, and liquid ammonia fuel supplied from the liquid ammonia supply source 50 (see FIG. 1) is sprayed into the furnace 11. Each liquid ammonia nozzle 80 is disposed at an angle of 45° or more from each other on the concentric circle C1. More specifically, as shown in FIG. 3A, for example, eight liquid ammonia nozzles 80 are disposed at equal angular intervals of 45°. The liquid ammonia fuel sprayed from each liquid ammonia nozzle 80 is sprayed from spray positions on the concentric circle C1 that are 45° or more apart from each other, in a direction that is open by more than 30° from the tangent L1 direction on the concentric circle C1 at the spray position toward the central axis CL (see arrow A1). FIG. 3A shows, as an example, a state in which the ejection direction of the liquid ammonia fuel is a direction that is 35° or more away from the direction of the tangent line L1 on the concentric circle C1 and toward the inside (the central axis CL side).

According to the burner 21 having the above-mentioned configuration, ammonia combustion is carried out as follows.
Only at the time of starting, the oil fuel and the primary air are supplied into the inner cylinder nozzle 61 to form a starting flame. After that, after ammonia combustion is established, the supply of the oil fuel and the primary air into the inner cylinder nozzle 61 is stopped.

When ammonia is used exclusively in combustion, as shown in FIG. 2, ammonia fuel and primary air are supplied from the core air nozzle 63, and a flame FL is formed in the furnace 11. The flame FL is stabilized by a flame stabilizer 71, and a recirculation region RC of high-temperature gas is formed around the periphery of the flame FL. Arrow A2 shows a schematic diagram of the flow of high-temperature gas in the recirculation region RC.

Liquid ammonia fuel is sprayed from the liquid ammonia nozzle 80 toward the central axis CL, as shown by the arrow A1. When the liquid ammonia fuel is sprayed, the ammonia fuel is vaporized and a vaporization region GR is formed between the tip of the burner 21 and the flame FL.

As shown in FIG. 3A, in this embodiment, the liquid ammonia nozzles 80 are spaced at intervals of 45° or more, so that the high-temperature gas in the recirculation region RC can be easily drawn into the vaporization region GR inside the concentric circle C1 through the liquid ammonia nozzles 80 as shown by arrow A3. This allows good contact between the high-temperature gas and the vaporized ammonia fuel in the vaporization region GR, promoting ignition and combustion.

In contrast, if the spacing between the liquid ammonia nozzles 80 were narrower than 45°, as shown in FIG. 3B, the high-temperature gas in the recirculation region RC would be blocked by the liquid ammonia fuel ejected from the liquid ammonia nozzles 80 as indicated by arrow A4, and would not be able to be drawn into the vaporization region GR inside the concentric circle C1.

The effects of the present embodiment described above are as follows.
A premixed gas of ammonia fuel and primary air is supplied from the outer cylinder nozzle into the furnace 11, and a flame FL of the premixed gas is formed and stabilized by a flame stabilizer 71. A recirculation region RC of high-temperature gas is formed on the outer periphery of the flame FL formed by the flame stabilizer 71.

Liquid ammonia fuel is supplied from a position on the outer periphery of the flame stabilizer 71 through a plurality of liquid ammonia nozzles 80. The liquid ammonia fuel is injected from each injection position on a concentric circle C1 centered on the central axis CL toward the inside (toward the central axis CL) at an angle of more than 30° from the tangent L1 direction on the concentric circle C1 at the injection position. The liquid ammonia fuel injected in this manner is vaporized in the vaporization region GR inside the concentric circle C1 and ignites to form a flame FL. At this time, the heat of vaporization of the liquid ammonia fuel is large, so the temperature of the vaporization region GR is low. Therefore, the vaporization and ignition of the liquid ammonia fuel is promoted by drawing high-temperature gas from the recirculation region RC formed on the outer periphery of the flame FL into the inside of the concentric circle C1. Therefore, the injection positions for injecting the liquid ammonia fuel are separated by 45° or more from each other, making it easier to guide the high-temperature gas in the recirculation region RC to the inside of the concentric circle C1 from between adjacent injection positions. This promotes stable combustion of liquid ammonia fuel, and allows stable ammonia combustion to be achieved by combining premixed combustion and diffusion combustion.

Instead of premixed combustion using the core air nozzle 63, the same effect can be obtained by using a diffusion combustion method in which liquid ammonia is supplied from inside the inner cylinder nozzle 61, to which the starting fuel (oil fuel) is supplied, as shown in FIG. 4. In this case, core air can be supplied from the core air nozzle 63 as combustion air.

[Second embodiment]
Next, a second embodiment of the present disclosure will be described with reference to Figures 5 and 6. This embodiment differs from the first embodiment in the injection direction and separation distance of the liquid ammonia nozzle. Therefore, the following describes the differences from the first embodiment, and the same reference numerals are used to designate the same components as the first embodiment, and the description thereof will be omitted.

As shown in FIG. 5, the direction of the liquid ammonia nozzle fuel sprayed from the liquid ammonia nozzle 81 is parallel to the central axis CL, as shown by arrow A5. Therefore, the liquid ammonia fuel sprayed from each liquid ammonia nozzle 81 is sprayed parallel to each other and parallel to the central axis CL.

The liquid ammonia nozzles 81 are arranged on the concentric circle C1 at intervals of 60° or more. More specifically, as shown in FIG. 6, for example, six liquid ammonia nozzles 81 are arranged at equal angular intervals of 60°.

According to this embodiment, the following advantageous effects are obtained.
The liquid ammonia fuel is supplied from a position on the outer periphery side of the flame stabilizer 71 through a plurality of liquid ammonia nozzles 81. The liquid ammonia fuel is injected parallel to the central axis CL from each injection position on a concentric circle C1 centered on the central axis CL. The liquid ammonia fuel injected in this manner is vaporized and ignited while being injected in a direction parallel to the central axis CL to form a flame. At this time, the temperature of the vaporization region GR is low because the heat of vaporization of the liquid ammonia fuel is large. For this reason, it is necessary to effectively contact the high-temperature gas in the recirculation region RC formed on the outer periphery of the flame with the liquid ammonia fuel injected parallel to the central axis CL to promote vaporization and ignition of the liquid ammonia fuel. When the liquid ammonia fuel is injected parallel to the central axis CL, vaporization is delayed compared to when the liquid ammonia fuel is injected inside the concentric circle C1 as in the first embodiment. Therefore, the injection positions for injecting the liquid ammonia fuel are set to be 60° or more apart from each other, and compared to when the injection positions are set closer than this (for example, 45°), the liquid ammonia fuel is more likely to come into contact with the high-temperature gas in the recirculation region RC. This promotes stable combustion of the liquid ammonia fuel, and enables stable ammonia combustion by combining premixed combustion and diffusion combustion.

Instead of premixed combustion using the core air nozzle 63, the same effect can be obtained by using a diffusion combustion method in which liquid ammonia is supplied from inside the inner cylinder nozzle 61, to which the starting fuel (oil fuel) is supplied, as shown in FIG. 7. In this case, core air can be supplied from the core air nozzle 63 as combustion air.

Also, as shown in FIG. 8, the liquid ammonia nozzle 81 can be expanded from parallel to the central axis CL (0 degrees) to an injection angle α (for example, +30 degrees) outward from the central axis CL, with the same effect.

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

The burner (21) according to the first aspect of the present disclosure includes a first nozzle (62) extending along a central axis (CL) and supplying a premixed gas of ammonia fuel and air into the interior of the furnace, a flame stabilizer (71) that stabilizes the flame of the premixed gas, and a plurality of liquid ammonia nozzles (80) that supply liquid ammonia fuel into the interior of the furnace from a position on the outer periphery of the flame stabilizer, and the liquid ammonia fuel ejected from each of the liquid ammonia nozzles is ejected from ejection positions that are 45° or more apart from each other on a concentric circle (C1) centered on the central axis, in a direction toward the central axis that is open by more than 30° from the tangent direction on the concentric circle at the ejection position.

A premixed gas of ammonia fuel and air is supplied from the first nozzle into the furnace, and a flame of the premixed gas is formed and stabilized by a flame stabilizer. A recirculation region of high-temperature gas is formed on the outer periphery of the flame formed by the flame stabilizer.
The liquid ammonia fuel is supplied from a plurality of liquid ammonia nozzles from a position on the outer periphery side of the flame stabilizer. The liquid ammonia fuel is injected from each of the concentric injection positions centered on the central axis toward the inside (the central axis side) at an angle of more than 30° from the tangent direction on the concentric circle at the injection position. The liquid ammonia fuel injected in this manner is vaporized and ignited inside the concentric circle to form a flame. At this time, the heat of vaporization of the liquid ammonia fuel is large, so the temperature of the vaporization region is low. Therefore, the vaporization and ignition of the liquid ammonia fuel are promoted by drawing high-temperature gas from the recirculation region formed on the outer periphery side of the flame of the premixed air-fuel into the inside of the concentric circle. Therefore, the injection positions for injecting the liquid ammonia fuel are set to be separated from each other by 45° or more, and the high-temperature gas in the recirculation region is led to the inside of the concentric circle from between the adjacent injection positions. This promotes stable combustion of the liquid ammonia fuel, and stable ammonia combustion can be performed by combining premixed combustion and diffusion combustion.

The burner according to the second aspect of the present disclosure includes a first nozzle extending along a central axis and supplying a premixed gas of ammonia fuel and air to the inside of the furnace, a flame stabilizer that stabilizes the flame of the premixed gas, and a plurality of liquid ammonia nozzles (81) that supply liquid ammonia fuel to the inside of the furnace from a position on the outer periphery of the flame stabilizer, and the liquid ammonia fuel ejected from each of the liquid ammonia nozzles is ejected parallel to the central axis from ejection positions spaced apart by 60° or more from each other on concentric circles centered on the central axis.

A premixed gas of ammonia fuel and air is supplied from the first nozzle into the furnace, and a flame of the premixed gas is formed and stabilized by a flame stabilizer. A recirculation region of high-temperature gas is formed on the outer periphery of the flame formed by the flame stabilizer.
The liquid ammonia fuel is supplied from a position on the outer periphery side of the flame stabilizer through a plurality of liquid ammonia nozzles. The liquid ammonia fuel is injected parallel to the central axis from each injection position on a concentric circle centered on the central axis. The liquid ammonia fuel injected in this manner is vaporized and ignited while being injected in a direction parallel to the central axis to form a flame. At this time, the heat of vaporization of the liquid ammonia fuel is large, so the temperature of the vaporization region is low. For this reason, it is necessary to effectively bring the high-temperature gas in the recirculation region formed on the outer periphery side of the flame into contact with the liquid ammonia fuel injected parallel to the central axis to promote vaporization and ignition of the liquid ammonia fuel. When the liquid ammonia fuel is injected parallel to the central axis, vaporization is delayed compared to when the liquid ammonia fuel is injected inside the concentric circle. Therefore, the injection positions for injecting the liquid ammonia fuel are set to be 60° or more apart from each other, and compared to when the injection positions are set closer than this (for example, 45°), the liquid ammonia fuel is more likely to come into contact with the high-temperature gas in the recirculation region. This promotes stable combustion of the liquid ammonia fuel, and stable ammonia combustion can be performed by combining premixed combustion and diffusion combustion.

The burner according to the third aspect of the present disclosure, in the first or second aspect described above, is provided with a second nozzle (61) that extends along the central axis on the inner periphery of the first nozzle and supplies starting fuel to the inside of the furnace.

The burner can be started by supplying starting fuel (e.g., oil fuel) from a second nozzle located on the inner periphery of the first nozzle. After the burner has started, the supply of starting fuel is stopped.

The burner according to the fourth aspect of the present disclosure is the third aspect described above, and is provided with an air nozzle that is located on the inner periphery of the first nozzle and on the outer periphery of the second nozzle, and that is arranged to cover the second nozzle, supplies combustion air, and supplies ammonia fuel for premixing to the air nozzle.

The premixed air-fuel mixture is supplied to the inside of the furnace by supplying premixed ammonia fuel and combustion air from an air nozzle installed between the first and second nozzles. This allows a premixed flame to be effectively formed along the central axis of the burner.

The burner according to the fifth aspect of the present disclosure is the third or fourth aspect described above, in which a swirl vane is provided on the outer periphery of the second nozzle between the tip of the second nozzle and the tip of the air nozzle.

By providing swirl vanes around the outer periphery of the inner nozzle, between the tip of the inner nozzle and the tip of the air nozzle, it is possible to form a good premixture and to configure the burner in a compact manner.

The boiler according to the first aspect of the present disclosure is equipped with a burner according to any one of the above aspects.

The method of operating a burner according to the first aspect of the present disclosure is a method of operating a burner including a first nozzle extending along a central axis and supplying a premixed gas of ammonia fuel and air into the interior of a furnace, a flame stabilizer that stabilizes the flame of the premixed gas, and a plurality of liquid ammonia nozzles that supply liquid ammonia fuel into the interior of the furnace from a position on the outer periphery of the flame stabilizer, and the liquid ammonia fuel ejected from each of the liquid ammonia nozzles is ejected from injection positions spaced apart by 45° or more from each other on a concentric circle centered on the central axis, in a direction toward the central axis at an angle of more than 30° from the tangent direction on the concentric circle at the injection positions.

The method of operating a burner according to the second aspect of the present disclosure is a method of operating a burner including a first nozzle extending along a central axis and supplying a premixed gas of ammonia fuel and air into the interior of a furnace, a flame stabilizer that stabilizes the flame of the premixed gas, and a plurality of liquid ammonia nozzles that supply liquid ammonia fuel into the interior of the furnace from a position on the outer periphery of the flame stabilizer, and the liquid ammonia fuel ejected from each of the liquid ammonia nozzles is ejected parallel to the central axis from ejection positions spaced apart by 60° or more from each other on concentric circles centered on the central axis.

Reference Signs List 10: Boiler 11: Furnace 12: Combustion gas passage 13: Flue 20: Combustion device 21: Burner 22: Pulverized fuel supply pipe 23: Wind box 24: Wind duct 25: Additional air port 26: Additional air duct 31: Mill 32: Forced draft fan 41: Gas duct 42: Air preheater 43: Denitrification device 44: Device 46: Desulfurization device 47: Chimney 50: Liquid ammonia supply source 61: Inner cylinder nozzle (second nozzle)
62: Outer cylinder nozzle (first nozzle)
63: Core air nozzle 71: Flame holder 73: Secondary air flow path 74: Tertiary air flow path 74a: Swirler 76: First swirl vane 77: Second swirl vane 80: Liquid ammonia nozzle 81: Liquid ammonia nozzle 101: Furnace wall 102: Superheater 103: Reheater 104: Economizer C1: Concentric circle CL: Central axis FL: Flame GR: Vaporization region L1: Tangent line RC: Recirculation region

Claims (8)

A first nozzle extending along a central axis and supplying a premixed gas of ammonia fuel and air into the interior of the furnace;
A flame stabilizer that stabilizes the flame of the premixed gas;
A plurality of liquid ammonia nozzles that supply liquid ammonia fuel into the furnace from a position on the outer periphery side of the flame stabilizer;
Equipped with
The liquid ammonia fuel ejected from each of the liquid ammonia nozzles is ejected from injection positions spaced apart from each other by 45° or more on concentric circles centered on the central axis, in a direction toward the central axis at an angle of more than 30° from a tangent direction on the concentric circle at the injection positions. A first nozzle extending along a central axis and supplying a premixed gas of ammonia fuel and air into the interior of the furnace;
A flame stabilizer that stabilizes the flame of the premixed gas;
A plurality of liquid ammonia nozzles that supply liquid ammonia fuel into the furnace from a position on the outer periphery side of the flame stabilizer;
Equipped with
The liquid ammonia fuel is ejected from each of the liquid ammonia nozzles in parallel to the central axis from ejection positions spaced apart by 60° or more from each other on concentric circles centered on the central axis. The burner according to claim 1 or 2, further comprising a second nozzle extending along the central axis on the inner periphery of the first nozzle and supplying starting fuel to the inside of the furnace. an air nozzle that is located on an inner circumferential side of the first nozzle and on an outer circumferential side of the second nozzle and is provided so as to cover the second nozzle, and that supplies combustion air;
4. The burner of claim 3, further comprising ammonia fuel for premixing said air nozzle. The burner according to claim 4, wherein a swirl vane is provided on the outer periphery of the second nozzle between the tip of the second nozzle and the tip of the air nozzle. A boiler equipped with a burner according to claim 1 or 2. A first nozzle extending along a central axis and supplying a premixed gas of ammonia fuel and air into the interior of the furnace;
A flame stabilizer that stabilizes the flame of the premixed gas;
A plurality of liquid ammonia nozzles that supply liquid ammonia fuel into the furnace from a position on the outer periphery side of the flame stabilizer;
A method for operating a burner comprising:
A burner operation method in which liquid ammonia fuel is sprayed from each of the liquid ammonia nozzles from spray positions spaced apart from each other by 45° or more on concentric circles centered on the central axis, in a direction toward the central axis at an angle of more than 30° from a tangent direction on the concentric circle at the spray positions. A first nozzle extending along a central axis and supplying a premixed gas of ammonia fuel and air into the interior of the furnace;
A flame stabilizer that stabilizes the flame of the premixed gas;
A plurality of liquid ammonia nozzles that supply liquid ammonia fuel into the furnace from a position on the outer periphery side of the flame stabilizer;
A method for operating a burner comprising:
A burner operating method in which the liquid ammonia fuel is ejected from each of the liquid ammonia nozzles parallel to the central axis from ejection positions spaced apart by 60° or more from each other on concentric circles centered on the central axis.

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