TWI897492B - Burner and boiler equipped with the same, and burner operating method - Google Patents

Abstract

A burner is provided that can not only burn a single fuel but also burn a mixture of biomass or carbon-free fuels. The burner comprises: an outer tube nozzle (62); a flame holder (71) for holding the flame formed by the outer tube nozzle (62); an inner tube nozzle (61) extending along the central axis (CL) on the inner circumference of the outer tube nozzle (62) and opening toward the inside of the furnace (11); a plurality of ammonia nozzles (80) capable of supplying ammonia fuel to the inside of the furnace (11) from a position closer to the outer circumference than the flame holder (71); a return The rotor blades (76, 77) are provided on the outer periphery of the aforementioned inner tube nozzle (61); and the distributor (78) is provided between the rotor blades (76, 77) and the front end of the inner tube nozzle (61), and distributes the flow path between the outer tube nozzle (62) and the inner tube nozzle (61) into an inner peripheral flow path (79a) and an outer peripheral flow path (79b), and the cross-sectional area perpendicular to the outer peripheral flow path (79b) increases toward the front end of the outer tube nozzle (62).

Description

Burner and boiler equipped with the same, and burner operating method

This disclosure relates to a burner for burning ammonia fuel, a boiler equipped with the burner, and a method for operating the burner.

Large boilers, such as those used for power generation, have a hollow, vertically mounted furnace with multiple burners mounted on the furnace wall. Furthermore, a flue is connected vertically above the furnace, and a heat exchanger for generating steam is located within the flue. The burners spray a mixture of fuel and air (oxidizing gas) into the furnace, forming a flame. The resulting combustion gas flows into the flue. A heat exchanger is located in the area where the combustion gas flows, heating water or steam flowing within the heat transfer tubes that constitute the heat exchanger to generate superheated steam.

As a burner for use in a boiler, research is underway to combust a mixture of pulverized coal and ammonia fuel, or to combust pulverized coal or ammonia fuel alone (e.g., Patent Document 1).

[Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Application Laid-Open No. 2020-41748

Because coal-fired boilers produce large amounts of CO ₂ , the promotion of carbon reduction is driven by a shift to biomass or carbon-free fuels (hydrogen, ammonia, etc.). On the other hand, biomass or carbon-free fuels are more difficult to obtain than coal, and it is difficult to obtain fuels that can meet the power generation requirements.

Therefore, it is desirable to have a burner that can burn not only a single fuel but also a mixture of multiple fuels. However, such burners have not been fully researched to date.

This disclosure was made in view of such circumstances, with the purpose of providing a burner, a boiler equipped with the same, and a burner operating method, which are capable of not only burning a single fuel but also a mixed combustion of biomass or carbon-free fuels.

The burner of one embodiment of the present disclosure comprises: a first nozzle extending along a central axis and opening toward the interior of a furnace; a flame holder for holding the flame formed by the first nozzle; a second nozzle extending along the central axis on the inner periphery of the first nozzle and opening toward the interior of the furnace; a plurality of ammonia nozzles capable of injecting ammonia from a position further outward than the flame holder. Ammonia fuel is supplied to the interior of the furnace. Swirl vanes are provided on the outer periphery of the second nozzle. A distributor is provided between the swirl vanes and the front end of the first nozzle to divide the flow path between the first nozzle and the second nozzle into an inner peripheral flow path and an outer peripheral flow path. The cross-sectional area of the outer peripheral flow path, perpendicular to the center axis, increases toward the front end of the first nozzle.

One aspect of the boiler disclosed herein is equipped with the aforementioned burner.

The operating method of a burner of one embodiment of the present disclosure is a burner operating method, wherein the burner comprises: a first nozzle extending along a central axis and opening toward the interior of a furnace; a flame holder for holding a flame formed by the first nozzle; a second nozzle extending along the central axis on the inner circumference of the first nozzle and opening toward the interior of the furnace; a plurality of ammonia nozzles capable of supplying ammonia fuel to the burner from a position further outward than the flame holder; The burner comprises an interior portion; a swirl vane disposed on the outer periphery of the second nozzle; and a distributor disposed between the swirl vane and the front end of the second nozzle, which divides the flow path between the first nozzle and the second nozzle into an inner peripheral flow path and an outer peripheral flow path, wherein the cross-sectional area of the outer peripheral flow path perpendicular to the central axis increases toward the front end of the second nozzle. The burner operation method is characterized by supplying or stopping ammonia fuel to the ammonia nozzle.

The burner and operating method disclosed herein are capable of burning not only a single fuel but also a mixture of biomass and carbon-free fuels.

10: Boiler

11: Furnace

12: Combustion gas passage

13: Chimney

20: Combustion device

21, 21A, 21B, 21C, 21D, 21E, 21F: Burner

22, 22A, 22B, 22C, 22D, 22E, 22F: Pulverized fuel supply pipes

23: Bellows

24: Air Duct

25: Additional air port

26: Add air duct

31: Grinder

32: Blower

41: Gas catheter

42: Air preheater

43: Denitrification device

44: Dust collection device

46: Desulfurization device

47: Chimney

50: Liquid ammonia supply source

61: Inner nozzle (second nozzle)

62: Outer nozzle (Nozzle 1)

63: Core air nozzle

71: Flame Holder

72:2 air nozzles

72a: Guide sleeve

73: Secondary air flow path

74: Tertiary air flow path

74a: Gyroscope

76: 1st rotor blade

77: Second rotor blade

78: Allocator

79a: Inner Circumferential Flow Path

79b: Peripheral flow path

80: Liquid ammonia nozzle

101: Fireplace Wall

102, 102A, 102B, 102C: Superheater

103, 103A, 103B: Reheater

104: Economizer

AR1: Ambient air

C1: Concentric circles

CL: Centerline

FL1: Diffusing flame

FL2: Diffusing Flame

FL3: Premixed flame

FL4: Diffusing Flame

FL5: Spreading Flame

RD1: High-temperature reduction zone

RD2: High-temperature reduction zone

RD3: High-temperature reduction zone

RD4: High-temperature reduction zone

RD5: High-temperature reduction zone

L1: Tangent

[Figure 1] is a schematic diagram showing the structure of a boiler according to the first embodiment of this disclosure.

[Figure 2] is a longitudinal cross-sectional view of the burner in Figure 1.

[Figure 3] is a front view showing the various positions of the ammonia nozzle in Figure 2.

[Figure 4] is a longitudinal cross-sectional view of a burner according to the second embodiment of the present disclosure.

[Figure 5] is a longitudinal cross-sectional view showing a variation of Figure 4.

[Figure 6] is a longitudinal cross-sectional view of a burner according to the third embodiment of the present disclosure.

[Figure 7] is a longitudinal cross-sectional view of a burner according to the fourth embodiment of the present disclosure.

[Figure 8] is a longitudinal cross-sectional view showing a variation of Figure 7.

[Figure 9] is a longitudinal cross-sectional view of the burner according to the fifth embodiment of the present disclosure.

[Figure 10] is a longitudinal cross-sectional view showing a variation of Figure 9.

[Figure 11] is a longitudinal cross-sectional view of a burner according to the sixth embodiment of the present disclosure.

The following describes one embodiment of the present disclosure with reference to the drawings. The present invention is not limited to this embodiment and, if there are multiple embodiments, includes combinations of the various embodiments. In the following description, the terms "upper" or "above" refer to the vertically upper side, and "lower" or "below" refer to the vertically lower side. The vertical direction is not strictly defined and is subject to error.

[First Implementation Method]

FIG1 shows a boiler 10 according to the present embodiment that uses pulverized solid fuel and/or ammonia (NH ₃ ) fuel as main fuel.

The boiler 10 of this embodiment uses a burner to burn a pulverized solid fuel and liquid ammonia fuel. The heat generated by this combustion is exchanged with feed water or steam to generate superheated steam. The pulverized solid fuel used can be biomass fuel, coal, petroleum coke, or the like.

The boiler 10 comprises a furnace 11, a combustion device 20, and a combustion gas passage 12. The furnace 11 is a hollow, rectangular tube, arranged vertically. The furnace wall 101, which forms the inner surface of the furnace 11, is constructed from a plurality of heat transfer tubes and fins connecting the tubes. Heat generated by the combustion of the pulverized fuel is recovered by heat exchange with water or steam flowing through the tubes, while also suppressing temperature increases in the furnace wall 101.

The burner 20 is installed in the lower area of the furnace 11. In this embodiment, the burner 20 comprises a plurality of burners 21A, 21B, 21C, 21D, 21E, and 21F mounted on the furnace wall 101 (hereinafter, when the burners are not distinguished, they are simply referred to as "burners 21"). The burners 21 are evenly spaced across the width of the furnace on the furnace wall 101 (for example, arranged in opposing directions across the width of the furnace on opposing furnace walls 101 for facing combustion), and are arranged in multiple vertical layers. The shape of the furnace, the number of burner layers, the number of burners in a layer, the arrangement of the burners, etc. are not limited to this embodiment.

Burners 21A, 21B, 21C, 21D, 21E, and 21F are connected to multiple grinders (crushers) 31A, 31B, 31C, 31D, 31E, and 31F (hereinafter, simply referred to as "grinder 31") via multiple pulverized fuel supply pipes 22A, 22B, 22C, 22D, 22E, and 22F (hereinafter, when these pulverized fuel supply pipes are not distinguished, they are simply recorded as "pulverized fuel supply pipes 22"). The grinder 31 is, for example, a vertical roller grinder that supports a pulverizing table (not shown) internally so as to be driven and rotatable, and supports a plurality of pulverizing rollers (not shown) above the pulverizing table so as to be rotatable in conjunction with the rotation of the pulverizing table. The solid fuel pulverized by the synergistic action of the pulverizing rollers and the pulverizing table is transported to a classifier (not shown) provided in the grinder 31 by the primary air (transport gas, oxidizing gas) supplied to the grinder 31. In the classifier, the solid fuel is classified into fine powder fuel with a particle size smaller than that suitable for combustion in the burner 21 and coarse powder fuel with a particle size larger than that. The fine powder fuel is supplied to the burner 21 through the fine powder fuel supply pipe 22 together with the primary air through the classifier. The coarse powdered fuel that does not pass through the classifier falls onto the grinding table inside the grinder 31 due to its own weight and is further ground.

Furthermore, at least a portion of burners 21A, 21B, 21C, 21D, 21E, and 21F are configured to be capable of burning a single fuel, or a combination of a pulverized solid fuel such as pulverized coal, biomass, or petroleum coke, ammonia fuel, or an oil fuel (liquid fuel) such as heavy oil. The specific burner structure will be described below using Figures 2 and below. When using ammonia fuel, it is supplied from a liquid ammonia supply source 50. Alternatively, a gaseous ammonia fuel source (not shown) may be supplied.

A windbox (regulator) 23 is installed outside the furnace 11, where the burner 21 is installed. One end of an air duct (air conduit) 24 is connected to the windbox 23. A blower (FDF: Forced Draft Fan) 32 is connected to the other end of the air duct 24. Air supplied by the blower 32 is heated by an air preheater 42 installed in the air duct 24. The air is then supplied to the burner 21 through the windbox 23 as secondary air (combustion air, oxidizing gas), and then into the furnace 11.

The combustion gas passage 12 is connected to the vertical upper portion of the furnace 11. Heat exchangers for recovering heat from the combustion gas are provided in the combustion gas passage 12, including superheaters 102A, 102B, and 102C (hereinafter, referred to simply as "superheater 102" when the superheaters are not distinguished), reheaters 103A and 103B (hereinafter, referred to simply as "reheater 103" when the reheaters are not distinguished), and an economizer 104. Heat exchange occurs between the combustion gas generated by the furnace 11 and the feed water or steam flowing through each heat exchanger. The arrangement and shape of each heat exchanger are not limited to that shown in Figure 1.

Connected to the downstream side of the combustion gas passage 12 is a flue 13 that discharges the combustion gas after heat recovery in the heat exchanger. An air preheater (air heater) 42 is installed between the flue 13 and the air duct 24 to exchange heat between the air flowing through the air duct 24 and the combustion gas flowing through the flue 13. By heating the primary air supplied to the grinder 31 or the secondary air supplied to the burner 21, further heat is recovered from the combustion gas after heat exchange with water or steam.

Furthermore, a denitrification device 43 is installed in the flue 13, upstream of the air preheater 42. The denitrification device 43 supplies a reducing agent, such as ammonia or urea solution, to the combustion gases flowing through the flue 13. The catalytic action of the denitrification catalyst within the denitrification device 43 promotes the reaction between nitrogen oxides (NOx) in the combustion gases supplied with the reducing agent and the reducing agent, thereby removing and reducing the nitrogen oxides in the combustion gases.

A gas duct 41 is connected to the flue 13 downstream of the air preheater 42. Gas duct 41 houses a dust collector 44, such as an electric dust collector, for removing ash and other particles from the combustion gases, a desulfurization device 46 for removing sulfur oxides, and an induced draft fan (IDF) 45 for directing exhaust gas to these environmental devices. The downstream end of gas duct 41 is connected to a chimney 47, where the combustion gases processed in the environmental devices are discharged outside the system as exhaust gas.

In boiler 10, when using a single fuel source (or a mixed fuel source with ammonia) for combustion of finely divided fuel (pulverized fuel), the multiple grinders 31 are driven, and the pulverized and classified fuel is supplied to burner 21 through finely divided fuel supply pipe 22 along with primary air. Furthermore, secondary air, heated in air preheater 42, is supplied to burner 21 from air duct 24 through wind box 23. Burner 21 blows a finely divided fuel mixture, formed by mixing the finely divided fuel with primary air, into furnace 11, and also blows secondary air into furnace 11. The finely divided fuel mixture blown into furnace 11 is ignited, reacting with the secondary air to form a flame. A flame forms in the lower region of the furnace 11, and high-temperature combustion gases rise within the furnace 11 and flow into the combustion gas passage 12. In this embodiment, air is used as the oxidizing gas (primary air and secondary air). However, gases with a higher or lower oxygen ratio than air are also acceptable. By adjusting the ratio of oxygen to the supplied fuel within an appropriate range, stable combustion can be achieved in the furnace 11.

Furthermore, above the burner 21, a plurality of additional air ports (AA ports) 25 are provided in the furnace 11 for supplying additional air (AA) for combustion into the furnace 11. Connected to the additional air ports 25 is the end of an additional air duct (AA duct) 26 branching from the air duct 24. A portion of the air supplied by the blower 32 is supplied to the additional air ports 25 via the additional air duct 26 as additional air for combustion.

In zone A within the furnace 11 shown in Figure 1 (the area corresponding to the height of the windbox 23), a flame is formed by the combustion of a mixture of primary air and pulverized fuel with secondary air. The air ratio in zone A is set to be below 1. Specifically, the amount of air supplied to the burner 21 (the combined amount of primary and secondary air) is set to be less than the theoretical amount of air supplied to the fuel. This creates a reducing environment within zone A and zone B (the area between the top of the burner 21 and the bottom of the additional air port 25), allowing nitrogen oxides (NOx) generated by combustion to be reduced within the furnace 11. Subsequently, in zone C (a zone above the lowest portion of the additional air port 25), additional air for combustion is supplied from the additional air port 25 to the NOx-reduced combustion gas, completing combustion. However, NOx generation is reduced by an amount corresponding to the reduction effect achieved in zones A and B.

The combustion gas flowing into the combustion gas passage 12 undergoes heat exchange with water or steam in the superheater 102, reheater 103, and economizer 104 located within the combustion gas passage 12. The combustion gas is then discharged into the flue 13. Nitrogen oxides are removed by the denitrification device 43. After heat exchange with primary and secondary air in the air preheater 42, the gas is further discharged into the gas duct 41. Ash and other substances are removed by the dust collector 44, and sulfur oxides are removed by the desulfurization device 46. The gas is then discharged out of the system through the chimney 47. The arrangement of the heat exchangers in the combustion gas passage 12 and the various 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 the liquid ammonia supply source 50 as ammonia fuel in a liquid state. 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 computer-readable storage media. The series of processes used to implement various functions is, for example, stored in the form of a program on the storage media. The CPU reads this program into the RAM, executing information processing and calculations to implement the various functions. Alternatively, the program may be pre-installed in ROM or other storage media, provided stored on computer-readable storage media, or transmitted via wired or wireless communication methods. Computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, semiconductor memories, etc.

FIG2 shows a burner 21 configured to perform mixed combustion of ammonia fuel and pulverized fuel.

The burner 21 comprises an inner cylindrical nozzle (second nozzle) 61 extending along a central axis CL, and an outer cylindrical nozzle (first nozzle) 62 disposed to cover the inner cylindrical nozzle 61. A core air nozzle (air nozzle) 63 is disposed on the outer circumference of the inner cylindrical nozzle 61 and the inner circumference of the outer cylindrical nozzle 62. Each nozzle 61, 62, and 63 shares a common central axis CL, has a circular cross-section, and is made of metal.

The inner cylinder nozzle 61 is supplied with oil fuel (starting fuel) and sprays the oil fuel into the furnace 11. An injection nozzle (not shown) is provided at the front end of the inner cylinder nozzle 61 to spray the oil fuel. The oil fuel is supplied from an oil fuel supply source (not shown) and is used during the startup of the burner 21. A fuel switching valve is provided upstream of the inner cylinder nozzle 61 and is controlled by a control unit (not shown).

When used as a pulverized coal burner, the outer cylinder nozzle 62 is supplied with pulverized fuel and primary air. A pulverized coal fuel selector valve and a primary air selector valve are installed upstream of the outer cylinder nozzle 62 and are controlled by a control unit (not shown).

The core air nozzle 63 is shorter than the inner tube nozzle 61, and its front end is located further to the base end (left side in Figure 2) than the front end of the inner tube nozzle 61. Core air (center air) serving as primary air and ammonia fuel flow 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 sprayed upstream of the core air nozzle 63. High-temperature air heated by the air preheater 42 is introduced into the core air nozzle 63, for example, from the wind box 23. The temperature of the high-temperature air is, for example, 150°C to 400°C. On the upstream side of the core air nozzle 63, a switching valve for ammonia fuel and a switching valve for primary air are installed, which are controlled by a control unit (not shown).

The outer wall of the inner tube nozzle 61 is provided with a first swirl vane 76 and a second swirl vane 77. A plurality of these swirl vanes 76 and 77 are provided circumferentially around the central axis CL. The first swirl vane 76 and the second swirl vane 77 are located between the leading end of the core air nozzle 63 and the leading end of the inner tube nozzle 61.

The first swirl vane 76 imparts swirl about 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 direction of primary air flow and imparts swirl in the opposite direction to the first swirl vane 76.

A distributor 78 is provided downstream of the second swirl vane 77 (toward the front end of the inner tube nozzle 61). The distributor 78 divides the annular flow path between the outer tube nozzle 62 and the inner tube nozzle 61 into an inner peripheral flow path 79a and an outer peripheral flow path 79b. The longitudinal cross-section of the distributor 78 is, for example, circular, centered about the central axis CL, and is cylindrical, tapering toward the downstream side. Due to the distributor 78, the cross-sectional area perpendicular to the central axis CL of the outer peripheral flow path 79b gradually increases toward the front end of the inner tube nozzle 61.

A flame holder 71, for example, serving as a baffle, is provided at the front end and on the outer periphery of the outer cylinder nozzle 62. The flame holder 71 is annular when viewed from the front. The flame holder 71 partially blocks the flow of secondary air flowing through the secondary air flow path 73, forming a flame holding area downstream. This holds the flame of the premixed ammonia fuel and air supplied from the outer cylinder nozzle 62 via the core air nozzle 63.

A secondary air nozzle 72 is provided on the outer periphery of the outer cylinder nozzle 62. The secondary air nozzle 72 forms a secondary air flow path 73. The secondary air flow path 73 is provided so as to cover the outer cylinder nozzle 62. A guide sleeve 72a with an expanded diameter is provided at the front end of the secondary air nozzle 72.

A tertiary air flow path 74 is provided 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 swirl to the tertiary air.

A plurality of ammonia nozzles 80 are installed within the tertiary air flow path 74, passing through the guide sleeve 72a. Each ammonia nozzle 80 is tubular and located on the outer periphery of the outer cylinder nozzle 62, corresponding to the position of the tertiary air flow path 74. An injection nozzle (not shown) is provided at the front end of the ammonia nozzle 80 to spray the ammonia fuel.

As shown in Figure 3, a plurality of ammonia nozzles 80 are arranged on a concentric circle C1 centered about the central axis CL. These nozzles inject liquid ammonia fuel supplied from a liquid ammonia supply source 50 (see Figure 1) into the furnace 11. Each ammonia nozzle 80 is spaced apart from one another on the concentric circle C1. More specifically, as shown in Figure 3, eight ammonia nozzles 80 are arranged at equal intervals of 45°. The number of ammonia nozzles 80 is not particularly limited; it may be four, six, or nine or more. The spacing is not limited to equal intervals; any spacing is acceptable. For example, the direction of liquid ammonia fuel spray is from the tangent line L1 on the concentric circle C1 at an angle of more than 35° inward (toward the center axis CL).

An ammonia fuel switching valve is installed upstream of the ammonia nozzle 80 and is controlled by a control unit (not shown).

The burner 21 constructed as described above performs mixed combustion of pulverized coal fuel and ammonia fuel as follows.

The inner cylinder nozzle 61 is supplied with oil fuel and primary air only during startup, forming a startup flame. After ammonia combustion is established, the supply of oil fuel and primary air to the inner cylinder nozzle 61 is stopped.

During the combustion of the mixed pulverized coal fuel and ammonia fuel, as shown in Figure 2, pulverized coal fuel and primary air are supplied between the outer tube nozzle 62 and the inner tube nozzle 61, while a premixed gas of ammonia fuel and primary air is supplied from the core air nozzle 63, forming a flame within the furnace 11. The flame is maintained by a flame holder 71.

The pulverized coal fuel is imparted with centrifugal force by the first and second swirl vanes 76, 77, converging on the inner circumference of the outer tube nozzle 62, increasing its concentration. Furthermore, the distributor 78 reduces the flow rate of the high-concentration pulverized coal fuel passing through the outer circumference, promoting ignition.

Liquid ammonia fuel is sprayed from the ammonia nozzle 80 toward the center axis CL. As the liquid ammonia fuel is sprayed, it vaporizes and diffuses and burns.

The effects of the above-described embodiment are as follows.

Air and pulverized coal fuel are supplied between the inner nozzle 61 and the outer nozzle 62. The swirl vanes 76 and 77 concentrate the pulverized coal fuel on the inner circumference of the outer nozzle 62. The distributor 78 reduces the flow rate and ignites the fuel, maintaining a stable flame.

A premixed gas of air and ammonia fuel is formed at the core air nozzle 63, while a premixed flame is formed at the outlet of the outer tube nozzle 62.

The ammonia fuel injected from the ammonia nozzle 80 diffuses and burns inside the furnace 11 together with the pulverized coal fuel flame and the premixed ammonia fuel flame.

Thus, according to this embodiment, mixed combustion of ammonia fuel and pulverized coal fuel can be performed.

Alternatively, the oil fuel may be continuously supplied from the time the second nozzle is automatically activated, and mixed combustion with the oil fuel may be performed.

[Second Implementation Method]

Next, the second embodiment of this disclosure will be described using FIG4 . This embodiment utilizes the aforementioned burner 21 to perform single-fuel combustion of oil fuel (liquid fuel). Therefore, components identical to those of the first embodiment are assigned the same reference numerals, and their descriptions will be omitted.

As shown in Figure 4, the inner nozzle 61 is supplied with oil fuel, and heavy oil or other oil fuel is sprayed into the interior of the furnace 11. The core air nozzle 63 is supplied with primary air (high-temperature air from the bellows 23). There is no material flow between the inner nozzle 61 and the outer nozzle 62, and the flow stops.

Within the furnace 11, a diffusion flame FL1 is formed by the oil fuel sprayed from the inner cylinder nozzle 61 and the primary air supplied from the core air nozzle 63. A high-temperature reduction zone RD1 is formed downstream of the diffusion flame FL1 and between the diffusion flame FL1 and the surrounding air AR1. Thus, according to this embodiment, a single-fuel burner operating with oil fuel can be achieved.

Furthermore, as shown in Figure 5, in a burner 21 without the core air nozzle 63, air (cold air not heated by the air preheater 42) is supplied between the inner tube nozzle 61 and the outer tube nozzle 62, thereby enabling a single-fuel burner using oil as fuel. The temperature of the cold air is, for example, between room temperature and 100°C.

[Implementation Method 3]

Next, the third embodiment of this disclosure will be described using FIG6 . This embodiment utilizes the aforementioned burner 21 to perform single-fuel combustion of pulverized coal fuel (pulverized solid fuel). Therefore, components identical to those of the first embodiment are designated by the same reference numerals, and their descriptions will be omitted.

As shown in Figure 6, air (cold air) and pulverized coal fuel are supplied between the inner tube nozzle 61 and the outer tube nozzle 62. Stopping the inner tube nozzle 61 also stops the ammonia nozzle 80.

Air and pulverized coal fuel are supplied between the inner and outer nozzles 61, 62. The swirl vanes 76 and 77 concentrate the pulverized coal fuel on the inner circumference of the outer nozzle 62. The distributor 78 reduces the flow rate before igniting and maintaining the flame. This ensures a stable and sustained diffusion flame FL2 of the pulverized coal fuel. A high-temperature reduction zone RD2 is then formed between the diffusion flame FL2 and the surrounding air AR1. This ensures reliable combustion even when using biomass or petroleum coke, which are difficult to ignite, instead of pulverized coal.

[Implementation Method 4]

Next, the fourth embodiment of this disclosure will be described using FIG7 . This embodiment utilizes the aforementioned burner 21 to perform single-fuel combustion of liquid ammonia. Therefore, components identical to those of the first embodiment are designated by the same reference numerals, and their descriptions will be omitted.

As shown in Figure 7, air and pulverized coal fuel are no longer flowing between the inner and outer cylinder nozzles 61, 62, and the process is stopped. The inner cylinder nozzle 61 is also stopped. Air (high-temperature air from the windbox 23) and liquid ammonia fuel are supplied to the core air nozzle 63. Furthermore, liquid ammonia fuel is supplied to the ammonia nozzle 80, which then sprays the liquid ammonia fuel into the furnace 11.

A premixed gas of high-temperature air and liquid ammonia fuel supplied from the core air nozzle 63 forms a premixed flame FL3 within the furnace 11. Liquid ammonia fuel is injected from the ammonia nozzle 80 into this premixed flame FL3, causing diffuse combustion. This creates a single-fuel burner for liquid ammonia fuel.

Furthermore, as shown in Figure 8 , a single-fuel burner using gaseous ammonia fuel can be used, using cold air that has not been heated by the air preheater 42. In this case, the core air nozzle 63 can be omitted.

As shown in Figure 8, only air (cold air) is supplied between the inner cylinder nozzle 61 and the outer cylinder nozzle 62. The inner cylinder nozzle 61 is stopped. Furthermore, gaseous ammonia fuel is supplied to the ammonia nozzle 80, and the gaseous ammonia fuel is sprayed into the furnace 11.

Air supplied from the outer cylinder nozzle 62 and gaseous ammonia fuel supplied from the ammonia nozzle 80 form a diffuse flame FL4. Because the ammonia fuel is a gas, it burns reliably. This makes it a single-fuel burner for gaseous ammonia fuel.

[Fifth Implementation Method]

Next, the fifth embodiment of this disclosure will be described using FIG9 . This embodiment utilizes the aforementioned burner 21 to perform mixed combustion of gaseous ammonia fuel and pulverized solid fuel. Therefore, components identical to those of the first embodiment are assigned the same reference numerals, and their descriptions will be omitted.

As shown in Figure 9, air (cold air) and pulverized coal fuel (a pulverized solid fuel) are supplied between the inner cylinder nozzle 61 and the outer cylinder nozzle 62. The inner cylinder nozzle 61 is stopped. The core air nozzle 63 is also stopped. Next, gaseous ammonia fuel is supplied to the ammonia nozzle 80. This creates a mixed burner of gaseous ammonia fuel and pulverized coal fuel.

The velocity component of the gaseous ammonia fuel ejected from the ammonia nozzle 80 traveling toward the center axis CL is greater than the velocity component traveling toward the tangent line L1 of the concentric circle C1 centered on the center axis CL and passing through the injection point of the gaseous ammonia fuel (see Figure 3 for concentric circle C1 and tangent line L1). As a result, as indicated by arrow A3, the gaseous ammonia fuel easily travels to the high-temperature reduction zone RD3 formed within the pulverized coal fuel flame. If the pulverized solid fuel has good ignition properties, this prevents adverse effects on the ignition properties of the pulverized solid fuel, allowing the gaseous ammonia fuel to be mixed into the high-temperature reduction zone RD3, thereby reducing NOx emissions. Furthermore, symbol RD4 denotes the high-temperature reduction zone formed between the pulverized coal fuel flame and the surrounding air AR1.

As shown in Figure 10, when supplying a pulverized solid fuel such as biomass, which is difficult to ignite, or petroleum coke, which is difficult to burn, between the inner and outer cylinder nozzles 61 and 62, the direction of the gaseous fuel ejected from the ammonia nozzle 80 is changed. This direction change can be achieved, for example, by rotating the ammonia nozzle 80 about its axis.

The velocity component of the gaseous ammonia fuel ejected from ammonia nozzle 80 traveling toward the center axis CL is smaller than the velocity component traveling toward the tangent line L1 of concentric circle C1 centered about the center axis CL and passing through the injection point of the gaseous ammonia fuel (see Figure 3 for concentric circle C1 and tangent line L1). As a result, as indicated by arrow A4, the gaseous ammonia fuel flows around the flame rather than directly toward the pulverized solid fuel. This prevents the ignition of pulverized solid fuels, such as biomass or petroleum coke, from being adversely affected, ensuring stable ignition and flame.

[Implementation Method No. 6]

Next, the sixth embodiment of this disclosure will be described using Figure 11. This embodiment utilizes the aforementioned burner 21 to perform mixed combustion of gaseous ammonia fuel and oil fuel (liquid fuel). Therefore, components identical to those of the first embodiment are designated by the same reference numerals, and their description will be omitted.

As shown in Figure 11, the burner 21 of this embodiment omits the core air nozzle 63. Only air (cold air) is supplied between the inner tube nozzle 61 and the outer tube nozzle 62. Oil fuel is supplied to the interior of the inner tube nozzle 61. Then, gaseous ammonia fuel is supplied to the ammonia nozzle 80.

Within the furnace 11, a diffused flame FL5 is formed by the oil fuel sprayed from the inner tube nozzle 61 and the air supplied between the inner tube nozzle 62. Downstream of the diffused flame FL5, a high-temperature reduction zone RD5 is formed between the diffused flame FL5 and the surrounding air AR1. Thus, according to this embodiment, a mixed burner of oil fuel and gaseous ammonia fuel is achieved.

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

The burner (21) of the first form disclosed herein comprises: a first nozzle (62) extending along the central axis (CL) and opening toward the interior of the furnace (11); a flame holder (71) for holding the flame formed by the first nozzle; a second nozzle (61) extending along the central axis on the inner circumference of the first nozzle and opening toward the interior of the furnace; a plurality of ammonia nozzles (80) capable of being more than the flame holder. Ammonia fuel is supplied to the interior of the furnace at a position near the outer periphery; swirl vanes (76, 77) are provided on the outer periphery of the second nozzle; and a distributor (78) is provided between the swirl vanes and the front end of the first nozzle to distribute the flow path between the first nozzle and the second nozzle into an inner peripheral flow path and an outer peripheral flow path, and the cross-sectional area of the outer peripheral flow path perpendicular to the central axis increases toward the front end of the first nozzle.

Liquid or gaseous ammonia fuel is supplied from the ammonia nozzle, enabling ammonia combustion.

Oil fuel (liquid fuel) such as heavy oil or ammonia fuel (liquid or gaseous) is supplied to the interior of the second nozzle, thereby enabling the liquid fuel or ammonia fuel to be burned.

A swirl vane is installed between the first and second nozzles, increasing the fuel concentration on the inner circumference of the first nozzle. This improves the ignition stability of pulverized solid fuels such as pulverized coal.

A distributor is installed between the swirling vanes and the front end of the second nozzle, dividing the flow into an inner and outer peripheral flow path. The cross-sectional area of the outer peripheral flow path (measured perpendicular to the central axis) is designed to expand toward the direction of flow (toward the front end of the second nozzle). This allows even if the solid fuel concentrated in the outer peripheral flow path by the swirling vanes is biomass or petroleum coke, which are difficult to ignite, the flow velocity is reduced by the distributor, which expands the outer peripheral flow path, ensuring stable ignition and flame.

The aforementioned burner can be used to burn ammonia fuel, pulverized solid fuel, liquid fuel, or other fuels alone, or in combination.

The burner of the second form disclosed herein is provided with the air nozzle (63) in the aforementioned first form, which is provided on the inner circumference of the aforementioned first nozzle and the outer circumference of the aforementioned second nozzle so as to cover the aforementioned second nozzle. The front end of the air nozzle is located closer to the base end of the aforementioned second nozzle than the aforementioned swirl vane and is capable of supplying air for combustion.

Combustion air can be supplied via air injectors. High-temperature air, obtained by recovering heat from the exhaust of a boiler equipped with a self-igniting burner, is preferably used to supply the air injectors. Furthermore, if ammonia fuel is supplied to the air injectors, a premixed gas can be formed at the air injectors.

The third aspect of the burner disclosed herein is a burner according to the second aspect, wherein air and pulverized solid fuel are supplied between the first nozzle and the second nozzle, the second nozzle is stopped, air and ammonia fuel are supplied to the air nozzle, and ammonia fuel is supplied to the ammonia nozzle.

Air and pulverized solid fuel are supplied between the first and second nozzles. The swirling vanes concentrate the pulverized solid fuel on the inner circumference of the first nozzle. The distributor reduces the flow rate before ignition, maintaining a stable flame.

A premixed gas of air and ammonia fuel is formed at the core air nozzle, and a premixed flame is formed at the outlet of the first nozzle.

The ammonia fuel injected from the ammonia nozzle diffuses and burns inside the furnace along with the flame of the pulverized solid fuel and the pre-mixed flame of the ammonia fuel.

The second nozzle is stopped and no fuel is supplied.

Thus, according to this embodiment, mixed combustion of ammonia fuel and pulverized solid fuel can be performed.

Alternatively, oil fuel (liquid fuel) can be supplied from the second nozzle and mixed with the oil fuel for combustion.

Switching between air and fuel is accomplished using an air switching valve, an oil fuel switching valve, a solid fuel switching valve, or an ammonia fuel switching valve. These switching valves can be operated by commands from the control unit or manually by the operator.

The fourth aspect of the burner disclosed herein, in any of the first to third aspects, comprises supplying air and pulverized solid fuel between the first and second nozzles, stopping the second nozzle, and supplying gaseous ammonia fuel to the ammonia nozzle.

Air and pulverized solid fuel are supplied between the first and second nozzles. The swirling vanes concentrate the pulverized solid fuel on the inner circumference of the first nozzle. The distributor reduces the flow rate before ignition, maintaining a stable flame.

The gaseous ammonia fuel ejected from the ammonia nozzle diffuses and burns inside the furnace along with the flame of the finely divided solid fuel.

The second nozzle is stopped and no fuel is supplied.

In the case of a core air nozzle as in the second embodiment, the engine stops without supplying air or ammonia fuel.

In this way, mixed combustion of gaseous ammonia fuel and pulverized solid fuel can be carried out.

Switching between air and fuel is accomplished using an air switching valve, an oil fuel switching valve, a solid fuel switching valve, or an ammonia fuel switching valve. These switching valves can be operated by commands from the control unit or manually by the operator.

The burner of the fifth aspect of the present disclosure is characterized in that, in the fourth aspect, the velocity component of the gaseous ammonia fuel ejected from the ammonia nozzle toward the central axis is greater than the velocity component in the direction of a tangent to a circle centered on the central axis and passing through the injection position of the gaseous ammonia fuel.

The gaseous ammonia fuel ejected from the ammonia nozzle has a greater velocity component toward the central axis than in the tangential direction. This facilitates the gaseous ammonia fuel's passage into the flame of the pulverized solid fuel formed by the first nozzle. If the pulverized solid fuel has good ignition properties, this prevents any adverse effects on the ignition quality of the pulverized solid fuel, allowing the gaseous ammonia fuel to be mixed into the high-temperature reduction zone to reduce NOx.

The burner of the sixth aspect of the present disclosure is characterized in that, in the fourth aspect, the velocity component of the gaseous ammonia fuel ejected from the ammonia nozzle toward the central axis is smaller than the velocity component in the direction of a tangent to a circle centered on the central axis and passing through the injection position of the gaseous ammonia fuel.

The velocity component of the gaseous ammonia fuel ejected from the ammonia nozzle toward the aforementioned center axis is smaller than the velocity component in the tangential direction. Consequently, the gaseous ammonia fuel does not directly flow into the flame of the pulverized solid fuel formed by the first nozzle, but instead flows around the flame. This prevents adverse effects on the ignition of pulverized solid fuels, such as biomass or petroleum coke, and ensures stable ignition and flame.

The burner of the seventh aspect of the present disclosure, in any of the first to sixth aspects, is configured such that air is supplied between the first and second nozzles, liquid fuel is supplied into the interior of the second nozzle, and the ammonia nozzle is deactivated.

Air is supplied between the first and second nozzles, while oil fuel (liquid fuel) such as heavy oil is supplied to the interior of the second nozzle. The ammonia nozzle is then deactivated (no ammonia fuel is supplied). This creates a single-fuel burner using liquid fuel.

The air flowing between the first and second nozzles can be either high-temperature air or cold air. High-temperature air refers to exhaust gas from the boiler installed in the combustion burner, heated by heat recovery using an air preheater, for example, to a temperature of 150°C to 400°C. Cold air refers to air directly using ambient air without heat recovery from the boiler's exhaust gas, for example, to a temperature of room temperature to 100°C.

When a core air nozzle is installed as in the second embodiment, it is not necessary to supply high-temperature air from the air nozzle.

Switching between air and fuel is accomplished using an air switching valve, an oil fuel switching valve, a pulverized solid fuel switching valve, or an ammonia fuel switching valve. These switching valves can be operated by commands from the control unit or manually by the operator.

The burner of the eighth aspect of the present disclosure, in any of the first to seventh aspects, is configured such that air and pulverized solid fuel are supplied between the first nozzle and the second nozzle, the second nozzle is stopped, and the ammonia nozzle is also stopped.

Air and pulverized solid fuel are supplied between the first and second nozzles. Then, the second nozzle and ammonia nozzle are deactivated (no ammonia fuel is supplied). This creates a single-fuel burner for pulverized solid fuel.

It is best to use cold air for the air flowing between the first and second nozzles. Cold air refers to air that is directly used from the surrounding air, rather than recovering the exhaust heat from the boiler installed in the self-ignition burner.

In the case of a core air nozzle as in the second embodiment, the air nozzle is stopped (no high-temperature air is supplied).

Switching between air and fuel is accomplished using an air switching valve, an oil fuel switching valve, a pulverized solid fuel switching valve, or an ammonia fuel switching valve. These switching valves can be operated by commands from the control unit or manually by the operator.

The burner of the ninth aspect of the present disclosure, in any of the first to eighth aspects, is configured such that only air is supplied between the first and second nozzles, the second nozzle is deactivated, and gaseous ammonia fuel is supplied to the ammonia nozzle.

Only air is supplied between the first and second nozzles (no pulverized solid fuel is supplied). Gaseous ammonia fuel is supplied to the ammonia nozzle. Then, the second nozzle is deactivated. This creates a single-fuel burner that uses gaseous ammonia fuel.

It is best to use cold air for the air flowing between the first and second nozzles. Cold air refers to air that is directly used from the surrounding air, rather than recovering the exhaust heat from the boiler installed in the self-ignition burner.

Switching between air and fuel is accomplished using an air switching valve, an oil fuel switching valve, a pulverized solid fuel switching valve, or an ammonia fuel switching valve. These switching valves can be operated by commands from the control unit or manually by the operator.

The tenth aspect of the burner disclosed herein, in any of the first through eighth aspects, stops the flow of air and pulverized solid fuel between the first and second nozzles, stops the second nozzle, and supplies air and liquid ammonia fuel to the air nozzle, while supplying liquid ammonia fuel to the ammonia nozzle.

Stop the flow of air and pulverized solid fuel between the first and second nozzles. Supply liquid ammonia fuel to the ammonia nozzle. Supply air and liquid ammonia fuel to the air nozzle. Then, stop the second nozzle. This creates a single-fuel burner using liquid ammonia fuel.

It is best to use high-temperature air flowing into the air nozzle. High-temperature air refers to air heated by recovering heat from the exhaust gas of the boiler installed in the autogenous combustion burner.

Switching between air and fuel is accomplished using an air switching valve, an oil fuel switching valve, a pulverized solid fuel switching valve, or an ammonia fuel switching valve. These switching valves can be operated by commands from the control unit or manually by the operator.

The eleventh aspect of the burner disclosed herein, in any one of the first to tenth aspects, comprises a burner in which air is supplied between the first and second nozzles, liquid fuel is supplied to the interior of the second nozzle, and gaseous ammonia fuel is supplied to the ammonia nozzle.

Air is supplied between the first and second nozzles, while oil fuel (liquid fuel) such as heavy oil is supplied to the interior of the second nozzle. Gaseous ammonia fuel is then supplied from the ammonia nozzle. This creates a mixed burner that uses both liquid and gaseous ammonia fuels.

When a core air nozzle is installed as in the second embodiment, it is not necessary to supply high-temperature air from the air nozzle.

Switching between air and fuel is accomplished using an air switching valve, an oil fuel switching valve, a pulverized solid fuel switching valve, or an ammonia fuel switching valve. These switching valves can be operated by commands from the control unit or manually by the operator.

Furthermore, it is preferred to inject gaseous ammonia fuel into the high-temperature reduction zone formed downstream of the liquid fuel flame. This can accelerate the decomposition of ammonia and suppress NOx.

The first aspect of the boiler disclosed herein is equipped with any of the aforementioned burners.

The operating method of the burner of the first aspect of the present disclosure is a burner operating method, wherein the burner comprises: a first nozzle extending along a central axis and opening toward the interior of a furnace; a flame holder for holding the flame formed by the first nozzle; a second nozzle extending along the central axis on the inner periphery of the first nozzle and opening toward the interior of the furnace; a plurality of ammonia nozzles capable of supplying ammonia fuel to the burner from a position further outward than the flame holder. to the interior of the aforementioned furnace; swirl vanes are provided on the outer periphery of the aforementioned second nozzle; and a distributor is provided between the aforementioned swirl vanes and the front end of the aforementioned second nozzle, dividing the flow path between the aforementioned first nozzle and the aforementioned second nozzle into an inner peripheral flow path and an outer peripheral flow path, and the cross-sectional area of the outer peripheral flow path perpendicular to the aforementioned central axis increases toward the front end of the aforementioned second nozzle. The burner operating method is characterized by supplying or stopping ammonia fuel to the aforementioned ammonia nozzle.

11: Furnace

21: Burner

61: Inner nozzle (second nozzle)

62: Outer nozzle (Nozzle 1)

63: Core air nozzle

71: Flame Holder

72:2 air nozzles

72a: Guide sleeve

73: Secondary air flow path

74: Tertiary air flow path

74a: Gyroscope

76: 1st rotor blade

77: Second rotor blade

78: Allocator

79a: Inner Circumferential Flow Path

79b: Peripheral flow path

80: Liquid ammonia nozzle

101: Fireplace Wall

CL: Centerline

Claims (12)

A burner comprises: a first nozzle extending along a central axis and opening toward the interior of a furnace; a flame holder for holding a flame formed by the first nozzle; a second nozzle extending along the central axis on the inner periphery of the first nozzle and opening toward the interior of the furnace; a plurality of ammonia nozzles capable of supplying ammonia fuel to the interior of the furnace from a position closer to the outer periphery than the flame holder; a swirl vane provided on the outer periphery of the second nozzle; an air nozzle provided on the inner periphery of the first nozzle The air nozzle is provided on the inner circumference side of the first nozzle and the outer circumference side of the second nozzle so as to cover the second nozzle, the front end of the air nozzle is located closer to the base end side of the second nozzle than the swirl vane, and can supply combustion air; and a distributor is provided between the swirl vane and the front end of the first nozzle, and distributes the flow path between the first nozzle and the second nozzle into an inner circumference flow path and an outer circumference flow path, and the cross-sectional area of the outer circumference flow path perpendicular to the center axis increases toward the front end of the first nozzle. The burner as described in claim 1, wherein air and pulverized solid fuel are supplied between the first nozzle and the second nozzle, the second nozzle is stopped, air and ammonia fuel are supplied to the air nozzle, and ammonia fuel is supplied to the ammonia nozzle. The burner as described in claim 1, wherein air and pulverized solid fuel are supplied between the first nozzle and the second nozzle, the second nozzle is stopped, and gaseous ammonia fuel is supplied to the ammonia nozzle. A burner as described in claim 3, wherein the velocity component of the gaseous ammonia fuel ejected from the aforementioned ammonia nozzle toward the aforementioned central axis is greater than the velocity component in the direction of a tangent to a circle passing through the injection position of the gaseous ammonia fuel with the central axis as the center. A burner as described in claim 3, wherein the velocity component of the gaseous ammonia fuel ejected from the aforementioned ammonia nozzle toward the aforementioned central axis is smaller than the velocity component in the direction of the tangent of a circle passing through the injection position of the gaseous ammonia fuel with the central axis as the center. The burner as described in claim 1, wherein air is supplied between the first nozzle and the second nozzle, liquid fuel is supplied to the interior of the second nozzle, and the ammonia nozzle is stopped. The burner as described in claim 1, wherein air and pulverized solid fuel are supplied between the first nozzle and the second nozzle, the second nozzle is stopped, and the ammonia nozzle is stopped. The burner as described in claim 1, wherein only air is supplied between the first nozzle and the second nozzle, the second nozzle is stopped, and gaseous ammonia fuel is supplied to the ammonia nozzle. A burner as described in claim 1, wherein the air and pulverized solid fuel flowing between the first nozzle and the second nozzle are stopped, the second nozzle is stopped, air and liquid ammonia fuel are supplied to the air nozzle, and liquid ammonia fuel is supplied to the ammonia nozzle. The burner as described in claim 1, wherein air is supplied between the first nozzle and the second nozzle, liquid fuel is supplied to the interior of the second nozzle, and gaseous ammonia fuel is supplied to the ammonia nozzle. A boiler is provided with the burner described in claim 1. A burner operation method, the burner is provided with: a first nozzle, which extends along the central axis and opens toward the interior of the furnace; a flame holder, which holds the flame formed by the first nozzle; a second nozzle, which extends along the central axis on the inner circumference of the first nozzle and opens toward the interior of the furnace; a plurality of ammonia nozzles, which can supply ammonia fuel to the interior of the furnace from a position closer to the outer circumference than the flame holder; a swirl vane, which is provided on the outer circumference of the second nozzle; an air nozzle, which is provided on the inner circumference of the first nozzle and on the outer circumference of the second nozzle; The outer peripheral side is arranged in a manner covering the second nozzle, the front end of the air nozzle is located closer to the base end side of the second nozzle than the aforementioned swirl vane, and is capable of supplying air for combustion; and a distributor is provided between the aforementioned swirl vane and the front end of the second nozzle, which distributes the flow path between the first nozzle and the second nozzle into an inner peripheral flow path and an outer peripheral flow path, and the cross-sectional area of the outer peripheral flow path perpendicular to the aforementioned central axis increases toward the front end of the second nozzle; the operating method of the burner is characterized by: supplying or stopping ammonia fuel to the aforementioned ammonia nozzle.