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

Abstract

Provided is a burner capable not only of mono-fuel combustion, but also co-combustion of biomass and carbon-free fuel, for example. The present invention comprises: an outer cylinder nozzle (62); a flame holder (71) that holds a flame formed by the outer cylinder nozzle (62); an inner cylinder nozzle (61) that extends along a centerline (CL) on the inner peripheral side of the outer cylinder nozzle (62) and opens toward the inside of a furnace (11); and a plurality of ammonia nozzles (80) that can supply ammonia fuel to the inside of the furnace (11) from a position closer to the outer peripheral side than the flame holder (71); swivel vanes (76, 77) provided on the outer periphery of the inner cylinder nozzle (61); and a distributor (78) which is provided between the swirl vanes (76, 77) and the tip of the inner cylinder nozzle (61), distributes a flow passage between the outer cylinder nozzle (62) and the inner cylinder nozzle (61) to an inner peripheral side flow passage (79a) and an outer peripheral side flow passage (79b), and at which the cross-sectional area of the outer peripheral side flow passage (79b) expands toward the tip of the outer cylinder nozzle (62).

Description

Burner, boiler equipped with same, and burner operating method

[0001] The present disclosure relates to a burner that burns, for example, ammonia fuel, a boiler including the burner, and a method for operating the burner.

[0002] Large boilers, such as power generation boilers, have a hollow furnace installed vertically, with multiple burners disposed on the furnace wall. Large boilers also have a flue connected vertically above the furnace, with a heat exchanger disposed in the flue for generating steam. The burner injects a mixture of fuel and air (oxidizing gas) into the furnace, forming a flame, generating combustion gas that flows down the flue. The heat exchanger is installed in the area where the combustion gas flows, and water or steam flowing through heat transfer tubes constituting the heat exchanger is heated to generate superheated steam.

[0003] For burners used in boilers, studies have been conducted to perform mixed combustion of pulverized coal and ammonia fuel, or to perform single combustion of pulverized coal and single combustion of ammonia fuel (for example, Patent Document 1).

[0004] Japanese Patent Application Laid-Open No. 2020-41748

[0005] Coal-fired boilers generate large amounts of CO2, so the promotion of decarbonization is driving a shift to biomass and carbon-free fuels (hydrogen, ammonia, etc.). However, biomass and carbon-free fuels are more difficult to obtain than coal, and it is sometimes not possible to procure enough fuel to cover the amount of electricity generated.

[0006] For this reason, there is a demand for a burner that can not only perform single-fuel combustion but also perform mixed combustion of multiple types of fuels with the same burner, but at present, such a burner has not been fully studied.

[0007] The present disclosure has been made in consideration of the above circumstances, and aims to provide a burner that is capable of not only monofuel combustion but also mixed combustion of biomass and carbon-free fuels, a boiler equipped with the same, and a method for operating the burner.

[0008] A burner according to one aspect of the present disclosure comprises: a first nozzle extending along a central axis and opening toward the interior of a furnace; a flame stabilizer that stabilizes the flame formed by the first nozzle; a second nozzle extending along the central axis on the inner side of the first nozzle and opening toward the interior of the furnace; a plurality of ammonia nozzles that can supply ammonia fuel to the interior of the furnace from a position outer than the flame stabilizer; swirl vanes provided on the outer periphery of the second nozzle; and a distributor provided between the swirl vanes and the tip of the first nozzle that divides a flow path between the first nozzle and the second nozzle into an inner side flow path and an outer side flow path, and the cross-sectional area of ​​the outer side flow path perpendicular to the central axis increases toward the tip of the first nozzle.

[0009] A boiler according to one aspect of the present disclosure includes the burner described above.

[0010] 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 outer than the flame stabilizers; swirl vanes provided on the outer periphery of the second nozzle; and a distributor provided between the swirl vanes and the tip of the second nozzle, which distributes a flow path between the first nozzle and the second nozzle into an inner periphery-side flow path and an outer periphery-side flow path, and the cross-sectional area of ​​the outer periphery-side flow path perpendicular to the central axis increases toward the tip of the second nozzle, wherein the supply of ammonia fuel to the ammonia nozzle is performed or stopped.

[0011] The burner and its operating method disclosed herein enable not only monofuel combustion but also mixed combustion of biomass and carbon-free fuels.

[0012] 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 showing the burner of FIG. 1. FIG. 3 is a front view showing the positions of the ammonia nozzle of FIG. 2. FIG. 4 is a vertical cross-sectional view showing a burner according to a second embodiment of the present disclosure. FIG. 5 is a vertical cross-sectional view showing a modified example of FIG. 4. FIG. 6 is a vertical cross-sectional view showing a burner according to a third embodiment of the present disclosure. FIG. 7 is a vertical cross-sectional view showing a burner according to a fourth embodiment of the present disclosure. FIG. 8 is a vertical cross-sectional view showing a modified example of FIG. 7. FIG. 9 is a vertical cross-sectional view showing a burner according to a fifth embodiment of the present disclosure. FIG. 10 is a vertical cross-sectional view showing a modified example of FIG. 9. FIG. 11 is a vertical cross-sectional view showing a burner according to a sixth embodiment of the present disclosure.

[0013] An embodiment of the present disclosure will be described below with reference to the drawings. Note that the present invention is not limited to this embodiment, and when there are multiple embodiments, it also includes configurations that combine the embodiments. In the following description, "up" and "upper" refer to the upper side in the vertical direction, and "lower" and "lower" refer to the lower side in the vertical direction, and the vertical direction is not precise and may include errors.

[0014] [First embodiment] FIG. 1 shows a diagram of a finely divided solid fuel and / or ammonia (NH ３ ) fuel-primarily fueled boiler 10 is shown.

[0015] The boiler 10 of this embodiment is a boiler that can generate superheated steam by burning pulverized solid fuel and liquid ammonia fuel using a burner and exchanging the heat generated by the combustion with feedwater or steam. The pulverized solid fuel can be biomass fuel, coal, oil coke, or the like.

[0016] The boiler 10 has a furnace 11, a combustion device 20, and a combustion gas passage 12. The furnace 11 has a hollow rectangular cylindrical shape and is installed vertically. The furnace wall 101 that forms the inner wall surface of the furnace 11 is composed of a plurality of heat transfer tubes and fins that connect the heat transfer tubes together. The heat generated by the combustion of pulverized fuel is recovered by heat exchange with water and steam circulating inside the heat transfer tubes, and the temperature rise of the furnace wall 101 is suppressed.

[0017] The combustion device 20 is installed in the lower region of the furnace 11. In this embodiment, the combustion device 20 has a plurality of burners 21A, 21B, 21C, 21D, 21E, and 21F (hereinafter, when these burners are not distinguished, they will be simply referred to as "burners 21") attached to the furnace wall 101. The burners 21 are arranged at equal intervals in the furnace width direction along the furnace wall 101 (for example, they are arranged in the furnace width direction so as to face the opposing furnace walls 101, so as to perform opposed combustion), and are arranged in multiple rows along the vertical direction. The shape of the furnace, the number of burner rows, the number of burners per row, the arrangement of the burners, etc. are not limited to this embodiment.

[0018] The burners 21A, 21B, 21C, 21D, 21E, and 21F are connected to a plurality of mills (pulverizers) 31A, 31B, 31C, 31D, 31E, and 31F (hereinafter, when the pulverized fuel supply pipes are not distinguished, they will be simply referred to as "pulverized fuel supply pipes 22") via a plurality of pulverized fuel supply pipes 22A, 22B, 22C, 22D, 22E, and 22F, respectively (hereinafter, when the pulverized fuel supply pipes are not distinguished, they will be simply referred to as "mills 31"). The mill 31 is, for example, a vertical roller mill having a rotatable pulverizing table (not shown) supported therein and a plurality of pulverizing rollers (not shown) supported above the pulverizing table so as to be rotatable in conjunction with the rotation of the pulverizing table. The solid fuel pulverized by the cooperation of the pulverizing rollers 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. The classifier separates the pulverized fuel into pulverized fuel having a particle size smaller than that suitable for combustion in the burner 21 and coarse pulverized fuel having a particle size larger than that. The pulverized fuel passes through the classifier and is supplied to the burner 21 together with primary air via the pulverized fuel supply pipe 22. The coarse pulverized fuel that does not pass through the classifier falls onto the grinding table inside the mill 31 under its own weight and is re-ground.

[0019] At least some of the burners 21A, 21B, 21C, 21D, 21E, and 21F are capable of burning a single fuel such as pulverized coal fuel, biomass, or oil coke, or ammonia fuel, or an oil fuel (liquid fuel) such as heavy oil, or a combination of these fuels. Specific burner structures will be described later with reference to FIG. 2 and subsequent figures. When ammonia fuel is used, the ammonia fuel is supplied from a liquid ammonia supply source 50. Alternatively, gaseous ammonia fuel may be supplied from a gaseous ammonia fuel source (not shown).

[0020] An air register 23 is provided outside the furnace 11 at the installation position of the burner 21, and one end of an air duct 24 is connected to the air register 23. The other end of the air duct 24 is connected to a forced draft fan (FDF) 32. Air supplied from the forced draft fan 32 is heated by an air preheater 42 installed in the air duct 24 and supplied to the burner 21 via the air register 23 as secondary air (combustion air, oxidizing gas) and introduced into the furnace 11.

[0021] The combustion gas passage 12 is connected to the vertical upper part of the furnace 11. The combustion gas passage 12 is provided with superheaters 102A, 102B, and 102C (hereinafter, when there is no need to distinguish between these superheaters, they will simply be referred to as "superheaters 102"), reheaters 103A and 103B (hereinafter, when there is no need to distinguish between these reheaters, they will simply be referred to as "reheater 103"), and an 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 feedwater or steam circulating inside each heat exchanger. Note that the arrangement and shape of each heat exchanger are not limited to those shown in FIG. 1.

[0022] A flue 13 is connected downstream of the combustion gas passage 12, and discharges the combustion gas whose heat has been recovered by the heat exchanger. 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, thereby 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.

[0023] A denitration device 43 may be provided in the flue 13 upstream of the air preheater 42. The denitration device 43 supplies a reducing agent, such as ammonia or urea water, that has the ability to reduce nitrogen oxides to the combustion gas flowing through the flue 13. The denitration device 43 promotes a reaction between the nitrogen oxides (NOx) in the combustion gas and the reducing agent through the catalytic action of a denitration catalyst provided in the denitration device 43, thereby removing and reducing the nitrogen oxides in the combustion gas. A gas duct 41 is connected to the flue 13 downstream of the air preheater 42. The gas duct 41 is provided with environmental devices, such as a dust collector 44, such as an electrostatic precipitator, that removes ash and the like from the combustion gas, and a desulfurization device 46 that removes sulfur oxides, as well as an induced draft fan (IDF) 45 that guides the exhaust gas to these environmental devices. The downstream end of the gas duct 41 is connected to a chimney 47, through which the combustion gas treated in the environmental device is discharged to the outside of the system as exhaust gas.

[0024] When the boiler 10 is performing mono-combustion of pulverized fuel (or co-combustion with ammonia fuel), the multiple mills 31 are driven, and pulverized and classified pulverized fuel is supplied to the burner 21 together with primary air via the pulverized fuel supply pipe 22. Secondary air heated by the air preheater 42 is supplied to the burner 21 from the air duct 24 via the wind box 23. The burner 21 blows a pulverized fuel mixture, which is a mixture of pulverized fuel and primary air, into the furnace 11, and also blows secondary air into the furnace 11. The pulverized fuel mixture blown into the furnace 11 ignites and reacts with the secondary air to form a flame. A flame is formed in the lower region of the furnace 11, and high-temperature combustion gas rises within the furnace 11 and flows into the combustion gas passage 12. In this embodiment, air is used as the oxidizing gas (primary air, secondary air), but the oxidizing gas may have a higher or lower oxygen content than air, and stable combustion can be achieved in the furnace 11 by adjusting the ratio of the amount of oxygen to the amount of fuel supplied within an appropriate range.

[0025] Additionally, above the mounting position of the burners 21 in the furnace 11, a plurality of 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.

[0026] In region A (corresponding to the height of the wind box 23) inside the furnace 11 shown in FIG. 1 , a flame is formed by combustion of a mixture of primary air and pulverized fuel with secondary air. Here, the air ratio in region A is set to be 1 or less. Specifically, the amount of air (the total amount of primary air and secondary air) supplied to the burner 21 is set to be less than the theoretical air amount relative to the amount of fuel supplied to the burner 21. This creates a reducing atmosphere in regions A and B (regions between the top of the burner 21 and the bottom of the additional air port 25) inside the furnace 11, and nitrogen oxides (NOx) generated by combustion are reduced inside the furnace 11. Subsequently, in region C (region above the bottom of the additional air port 25), additional combustion air is supplied from the additional air port 25 to the combustion gas from which NOx has been reduced, completing the combustion. However, the amount of NOx generated is reduced by the reduction effect in regions A and B.

[0027] The combustion gas that has flowed into the combustion gas passage 12 exchanges heat with water and steam in a superheater 102, a reheater 103, and an economizer 104 arranged inside the combustion gas passage 12, and is then discharged into the flue 13, where nitrogen oxides are removed in a denitration device 43, and the combustion gas exchanges heat with primary air and secondary air in an air preheater 42, and is then discharged into the gas duct 41, where ash and the like are removed in a dust collector 44, and sulfur oxides are removed in a desulfurization device 46, and the combustion gas is then discharged to the outside of the system through a chimney 47. The arrangement of the heat exchangers in the combustion gas passage 12 and the arrangement of the devices from the flue 13 to the gas duct 41 with respect to the combustion gas flow do not necessarily have to be in the order described above.

[0028] The boiler 10 includes a liquid ammonia supply source 50. Ammonia is stored in liquid form as an ammonia fuel in the liquid ammonia supply source 50. The liquid ammonia is supplied from the liquid ammonia supply source 50 to each burner 21.

[0029] The control unit is composed of, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and a computer-readable storage medium. A series of processes for realizing various functions is stored in a storage medium, for example, in the form of a program. The CPU reads this program into RAM and executes information processing and arithmetic operations to realize various functions. The program may be pre-installed in a ROM or other storage medium, provided in a state stored in a computer-readable storage medium, or distributed via wired or wireless communication means. Examples of computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories.

[0030] 2 shows a burner 21 capable of co-firing ammonia fuel and pulverized fuel. The burner 21 includes an inner cylindrical nozzle (second nozzle) 61 extending along a central axis CL, and an outer cylindrical nozzle (first nozzle) 62 provided to cover the inner cylindrical nozzle 61. A core air nozzle (air nozzle) 63 is provided on the outer circumferential side of the inner cylindrical nozzle 61 and on the inner circumferential side of the outer cylindrical nozzle 62. Each of the nozzles 61, 62, and 63 has a common central axis CL, has a circular cross section, for example, and is made of metal.

[0031] The inner cylinder nozzle 61 is supplied with oil fuel (start-up fuel) and injects the oil fuel into the furnace 11. An injection tip (not shown) is provided at the tip of the inner cylinder nozzle 61 so that the oil fuel is sprayed. The oil fuel is supplied from an oil fuel supply source (not shown) and is used when starting up the burner 21. An oil fuel switching valve is provided upstream of the inner cylinder nozzle 61 and is controlled by a control unit (not shown).

[0032] When used as a pulverized coal burner, pulverized fuel and primary air are supplied into the outer cylindrical nozzle 62. A switching valve for the pulverized coal fuel and a switching valve for the primary air are provided upstream of the outer cylindrical nozzle 62 and are controlled by a control unit (not shown).

[0033] 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 through 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. High-temperature air heated by, for example, the air preheater 42 is introduced from the air box 23 to the core air nozzle 63. The temperature of the high-temperature air is, for example, 150°C to 400°C. A switch valve for ammonia fuel and a switch valve for primary air are provided upstream of the core air nozzle 63 and are controlled by a control unit (not shown).

[0034] A first swirl vane 76 and a second swirl vane 77 are provided on the outer wall of the inner cylindrical 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 cylindrical nozzle 61.

[0035] The first swirl vane 76 imparts a swirl about the central axis line 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 that of the first swirl vane 76.

[0036] A distributor 78 is provided downstream of the second swirl vane 77 (toward the tip of the inner cylinder nozzle 61). The distributor 78 distributes the annular flow path between the outer cylinder nozzle 62 and the inner cylinder nozzle 61 into an inner circumference-side flow path 79a and an outer circumference-side flow path 79b. The longitudinal cross section of the distributor 78 is, for example, circular about the central axis CL and has a cylindrical shape tapering toward the downstream side. The distributor 78 gradually increases the cross-sectional area of ​​the outer circumference-side flow path 79b perpendicular to the central axis CL toward the tip of the inner cylinder nozzle 61.

[0037] A flame stabilizer 71, for example a baffle, is provided at the tip and outer periphery of the outer cylindrical nozzle 62. The flame stabilizer 71 has a ring shape when the outer cylindrical nozzle 62 is viewed from the front. The flame stabilizer 71 partially blocks the flow of secondary air flowing through the secondary air flow passage 73, forming a flame stabilization region downstream thereof. This stabilizes the flame of the premixed gas of ammonia fuel and air supplied from the outer cylindrical nozzle 62 via the core air nozzle 63.

[0038] A secondary air nozzle 72 is provided on the outer circumferential side of the outer cylindrical nozzle 62. A secondary air flow path 73 is formed by the secondary air nozzle 72. The secondary air flow path 73 is provided so as to cover the outer cylindrical nozzle 62. An enlarged guide sleeve 72a is provided at the tip of the secondary air nozzle 72.

[0039] A tertiary air flow path 74 is provided on the outer periphery of the secondary air flow path 73 so as to cover the secondary air flow path 73. A swirler 74a is provided in the tertiary air flow path 74 to impart a swirl to the tertiary air.

[0040] A plurality of ammonia nozzles 80 are provided penetrating the guide sleeve 72a from within the tertiary air flow path 74. Each ammonia nozzle 80 is tubular and provided on the outer circumferential side of the outer cylindrical nozzle 62 at a position corresponding to the tertiary air flow path 74. An injection tip (not shown) is provided at the tip of the ammonia nozzle 80 so that ammonia fuel is sprayed.

[0041] As shown in FIG. 3 , a plurality of ammonia nozzles 80 are arranged on a concentric circle C1 centered on the central axis CL, and inject liquid ammonia fuel supplied from the liquid ammonia supply source 50 (see FIG. 1 ) into the furnace 11. The ammonia nozzles 80 are arranged spaced apart from one another on the concentric circle C1. More specifically, as shown in FIG. 3 , for example, eight ammonia nozzles 80 are arranged at equal angular intervals of 45°. The number of ammonia nozzles 80 is not particularly limited and may be four, six, or nine or more. The intervals are also not limited to equal intervals and may be arranged at any interval. As an example, the injection direction of the liquid ammonia fuel is a direction inward (toward the central axis CL) at an angle of 35° or more from the direction of the tangent L1 on the concentric circle C1. An ammonia fuel switching valve is provided upstream of the ammonia nozzle 80 and is controlled by a control unit (not shown).

[0042] The burner 21 configured as described above performs mixed combustion of pulverized coal fuel and ammonia fuel as follows. Oil fuel and primary air are supplied into the inner cylindrical nozzle 61 only at startup, and a starting flame is formed. After that, once ammonia combustion is established, the supply of oil fuel and primary air into the inner cylindrical nozzle 61 is stopped.

[0043] 2, when pulverized coal fuel and ammonia fuel are mixed and burned, pulverized coal fuel and primary air are supplied between the outer cylindrical nozzle 62 and the inner cylindrical nozzle 61, and a premixed gas of ammonia fuel and primary air is supplied from the core air nozzle 63, thereby forming a flame in the furnace 11. The flame is stabilized by a flame stabilizer 71.

[0044] The pulverized coal fuel is subjected to centrifugal force by the first swirl vane 76 and the second swirl vane 77, and accumulates and becomes highly concentrated on the inner peripheral side of the outer cylindrical nozzle 62. Then, the flow velocity of the highly concentrated pulverized coal fuel passing through the outer peripheral flow passage is reduced by the distributor 78, thereby promoting ignition.

[0045] Liquid ammonia fuel is sprayed toward the central axis line CL from the ammonia nozzle 80. When the liquid ammonia fuel is sprayed, the ammonia fuel is vaporized and diffusion combustion occurs.

[0046] The effects of the present embodiment described above are as follows. By supplying air and pulverized coal fuel between the inner cylindrical nozzle 61 and the outer cylindrical nozzle 62, the swirl vanes 76, 77 concentrate the pulverized coal fuel on the inner circumferential side of the outer cylindrical nozzle 62. The flow velocity is reduced by the distributor 78, and the pulverized coal fuel is ignited and flame-stabilized. A premixed gas of air and ammonia fuel is formed in the core air nozzle 63, and a premixed flame is formed at the outlet of the outer cylindrical nozzle 62. The ammonia fuel injected from the ammonia nozzle 80 is diffused and combusted together with the flame of the pulverized coal fuel and the premixed flame of the ammonia fuel inside the furnace 11. As described above, according to this embodiment, ammonia fuel and pulverized coal fuel can be mixed and combusted. Note that oil fuel may be continuously supplied from the second nozzle at startup to mix and combust the ammonia fuel.

[0047] Second Embodiment Next, a second embodiment of the present disclosure will be described with reference to Fig. 4. In this embodiment, the oil fuel (liquid fuel) is exclusively burned using the burner 21 described above. Therefore, the same components as those in the first embodiment are designated by the same reference numerals, and their description will be omitted.

[0048] As shown in Figure 4, oil fuel is supplied to the inner cylinder nozzle 61, and oil fuel such as heavy oil is sprayed into the inside of the furnace 11. Primary air (high-temperature air from the air box 23) is supplied to the core air nozzle 63. Nothing flows between the inner cylinder nozzle 61 and the outer cylinder nozzle 62, and the nozzle is inactive.

[0049] In the furnace 11, a diffusion flame FL1 is formed by the oil fuel sprayed from the inner cylindrical 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 peripheral air AR1. In this way, according to this embodiment, a burner exclusively for oil fuel can be provided.

[0050] 5, in a burner 21 in which the core air nozzle 63 is omitted, it is possible to make it an oil-fuel-only burner by supplying air (cold air not heated by the air preheater 42) from between the inner cylindrical nozzle 61 and the outer cylindrical nozzle 62. The temperature of the cold air is, for example, room temperature to 100°C.

[0051] [Third embodiment] Next, a third embodiment of the present disclosure will be described with reference to Fig. 6. In this embodiment, pulverized coal fuel (pulverized solid fuel) is exclusively burned using the burner 21 described above. Therefore, the same components as those in the first embodiment are designated by the same reference numerals, and their description will be omitted.

[0052] 6, air (cold air) and pulverized coal fuel are supplied between the inner cylindrical nozzle 61 and the outer cylindrical nozzle 62. The inner cylindrical nozzle 61 is stopped, and the ammonia nozzle 80 is also stopped.

[0053] By supplying air and pulverized coal fuel between the inner cylindrical nozzle 61 and the outer cylindrical nozzle 62, the pulverized coal fuel is concentrated on the inner peripheral side of the outer cylindrical nozzle 62 by the swirl vanes 76, 77, and after the flow velocity is reduced by the distributor 78, it is ignited and flame-stabilized. As a result, the diffusion flame FL2 of the pulverized coal fuel is stably ignited and flame-stabilized. A high-temperature reducing zone RD2 is formed between the diffusion flame FL2 and the outer peripheral air AR1. Therefore, good combustion can be achieved even when biomass or flame-retardant oil coke, which are difficult to ignite, is used instead of the pulverized coal fuel.

[0054] [Fourth embodiment] Next, a fourth embodiment of the present disclosure will be described with reference to Fig. 7. In this embodiment, the liquid ammonia fuel is exclusively burned using the burner 21 described above. Therefore, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0055] As shown in Fig. 7, the flow of air and pulverized coal fuel between the inner cylindrical nozzle 61 and the outer cylindrical nozzle 62 is stopped. The inner cylindrical nozzle 61 is also stopped. Air (high-temperature air from the wind box 23) and liquid ammonia fuel are supplied to the core air nozzle 63. In addition, liquid ammonia fuel is supplied to the ammonia nozzle 80, and the liquid ammonia fuel is injected into the furnace 11.

[0056] A premixed gas of high-temperature air and liquid ammonia fuel supplied from the core air nozzle 63 forms a premixed flame FL3 in the furnace 11. Liquid ammonia fuel is injected into this premixed flame FL3 from the ammonia nozzle 80, and diffusion combustion is carried out. This makes it possible to provide a burner exclusively for liquid ammonia fuel.

[0057] Furthermore, as shown in Fig. 8, a gaseous ammonia fuel-only burner can be configured using cold air that is not heated by the air preheater 42. In this case, the core air nozzle 63 can be omitted. As shown in Fig. 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 not in operation. Furthermore, gaseous ammonia fuel is supplied to the ammonia nozzle 80, and the gaseous ammonia fuel is injected into the furnace 11.

[0058] A diffusion flame FL4 is formed by the air supplied from the outer cylindrical nozzle 62 and the gaseous ammonia fuel supplied from the ammonia nozzle 80. Since the ammonia fuel is gaseous, it can be combusted well. This allows the burner to be a mono-fuel burner for gaseous ammonia fuel.

[0059] [Fifth Embodiment] Next, a fifth embodiment of the present disclosure will be described with reference to Fig. 9. In this embodiment, gaseous ammonia fuel and pulverized solid fuel are mixed and burned using the burner 21 described above. Therefore, the same components as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted.

[0060] As shown in Fig. 9, air (cold air) and pulverized coal fuel (pulverized solid fuel) are supplied between the inner cylindrical nozzle 61 and the outer cylindrical nozzle 62. The inner cylindrical nozzle 61 is stopped. The core air nozzle 63 is also stopped. Gaseous ammonia fuel is supplied to the ammonia nozzle 80. This allows a burner to be configured to co-combust gaseous ammonia fuel and pulverized coal fuel.

[0061] The velocity component of the gaseous ammonia fuel injected from the ammonia nozzle 80 toward the central axis CL is greater than the velocity component in the direction of a tangent L1 of a concentric circle C1 that is centered on the central axis CL and passes through the injection position of the gaseous ammonia fuel (see FIG. 3 for the concentric circle C1 and the tangent L1). As a result, as shown by arrow A3, the gaseous ammonia fuel is likely to move toward the high-temperature reduction zone RD3 formed in the flame of the pulverized coal fuel. If the ignition ability of the pulverized solid fuel is good, the ignition ability of the pulverized solid fuel is not adversely affected, so that the gaseous ammonia fuel can be mixed into the high-temperature reduction zone RD3 to reduce NOx. Note that symbol RD4 denotes a high-temperature reduction zone formed between the flame of the pulverized coal fuel and the peripheral air AR1.

[0062] 10 , when a pulverized solid fuel such as biomass, which is difficult to ignite, or flame-retardant oil coke is supplied between the inner cylindrical nozzle 61 and the outer cylindrical nozzle 62, the direction of the gaseous fuel injected from the ammonia nozzle 80 is changed. This change in direction can be achieved, for example, by rotating the ammonia nozzle 80 around its axis.

[0063] The velocity component of the gaseous ammonia fuel injected from the ammonia nozzle 80 toward the central axis CL is smaller than the velocity component in the direction of a tangent L1 of a concentric circle C1 that is centered on the central axis CL and passes through the injection position of the gaseous ammonia fuel (see FIG. 3 for the concentric circle C1 and the tangent L1). As a result, as shown by arrow A4, the gaseous ammonia fuel flows around the flame of the pulverized solid fuel rather than directly toward it. In this way, when the ignition characteristic of the pulverized solid fuel is poor, such as biomass or oil coke, it is possible to stabilize ignition and flame stability without adversely affecting the ignition characteristic of the pulverized solid fuel.

[0064] Sixth Embodiment Next, a sixth embodiment of the present disclosure will be described with reference to Fig. 11. In this embodiment, mixed combustion of gaseous ammonia fuel and oil fuel (liquid fuel) is performed using the burner 21 described above. Therefore, the same components as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted.

[0065] 11 , the burner 21 of this embodiment does not include a core air nozzle 63. Only air (cold air) is supplied between the inner cylindrical nozzle 61 and the outer cylindrical nozzle 62. Oil fuel is supplied to the inside of the inner cylindrical nozzle 61. Then, gaseous ammonia fuel is supplied to the ammonia nozzle 80.

[0066] In the furnace 11, a diffusion flame FL5 is formed by the oil fuel sprayed from the inner cylindrical nozzle 61 and the air supplied from between the inner cylindrical nozzle 61 and the outer cylindrical nozzle 62. A high-temperature reducing zone RD5 is formed downstream of the diffusion flame FL5 and between the diffusion flame FL5 and the peripheral air AR1. In this way, according to this embodiment, a burner for co-firing oil fuel and gaseous ammonia fuel can be provided.

[0067] The burner, the boiler including the burner, and the method of operating the burner described in each of the above-described embodiments can be understood, for example, as follows.

[0068] a plurality of ammonia nozzles (80) capable of supplying ammonia fuel to the inside of the furnace from a position on the outer periphery of the second nozzle, the ammonia nozzles being arranged on the inner periphery of the second nozzle; and a distributor (78) arranged between the ammonia nozzles and the tip of the first nozzle, the distributor distributing a flow path between the first nozzle and the second nozzle into an inner periphery-side flow path and an outer periphery-side flow path, the cross-sectional area of ​​the outer periphery-side flow path being increased toward the tip of the first nozzle.

[0069] Ammonia combustion can be achieved by supplying liquid ammonia fuel or gaseous ammonia fuel through the ammonia nozzle. Liquid fuel or ammonia fuel can be combusted by supplying oil fuel (liquid fuel) such as heavy oil or ammonia fuel (liquid or gas) into the second nozzle. Swirl vanes are provided between the first and second nozzles, allowing the fuel concentration to be higher on the inner periphery of the first nozzle. This promotes stable ignition of pulverized solid fuel such as pulverized coal. A distributor is provided between the swirl vanes and the tip of the second nozzle to distribute the fuel between the inner periphery flow path and the outer periphery flow path, expanding the cross-sectional area of ​​the outer periphery flow path (cross-sectional area perpendicular to the central axis) in the flow direction (toward the tip of the second nozzle). This allows for stable ignition and flame stability, even when the solid fuel concentrated in the outer periphery flow path by the swirl vanes is biomass or non-flammable petroleum coke, which is difficult to ignite, because the distributor expands the outer periphery flow path. The burner described above can perform single combustion of each fuel such as ammonia fuel, pulverized solid fuel, and liquid fuel, or mixed combustion of a combination of these fuels.

[0070] The burner according to the second aspect of the present disclosure is the first aspect, and is provided with an air nozzle (63) that is arranged on the inner periphery of the first nozzle and on the outer periphery of the second nozzle so as to cover the second nozzle, and whose tip is located closer to the base end of the second nozzle than the swirl vanes, and that is capable of supplying combustion air.

[0071] Combustion air can be supplied through an air nozzle. Preferably, high-temperature air that has been heated to a high temperature by recovering heat from exhaust gas from a boiler equipped with a burner is supplied to the air nozzle. Furthermore, if ammonia fuel is supplied to the air nozzle, a premixed gas can be formed in the air nozzle.

[0072] A burner according to a third aspect of the present disclosure is the burner of 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.

[0073] By supplying air and pulverized solid fuel between the first and second nozzles, the swirl vanes concentrate the pulverized solid fuel on the inner periphery of the first nozzle, and after the flow velocity is reduced by the distributor, the pulverized solid fuel is ignited and flame-stabilized. A premixed mixture of air and ammonia fuel is formed in the air nozzle, and a premixed flame is formed at the outlet of the first nozzle. The ammonia fuel injected from the ammonia nozzle is diffused and burned inside the furnace together with the pulverized solid fuel flame and the ammonia fuel premixed flame. The second nozzle is deactivated, and no oil fuel is supplied. In this manner, ammonia fuel and pulverized solid fuel can be mixed and burned. Alternatively, oil fuel (liquid fuel) can be supplied from the second nozzle to mix and burn the ammonia fuel. Air and fuel switching is performed by an air switching valve, an oil fuel switching valve, a solid fuel switching valve, and an ammonia fuel switching valve. These switching valves may be operated by commands from a control unit or manually by an operator.

[0074] A burner according to a fourth aspect of the present disclosure is any one of the first to third aspects, 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.

[0075] By supplying air and pulverized solid fuel between the first and second nozzles, the swirl vanes concentrate the pulverized solid fuel on the inner periphery of the first nozzle, and after the flow rate is reduced by the distributor, the pulverized solid fuel is ignited and flame-stabilized. The gaseous ammonia fuel injected from the ammonia nozzle is diffused and burned inside the furnace together with the flame of the pulverized solid fuel. The second nozzle is deactivated and no oil fuel is supplied. When a core air nozzle is provided as in the second embodiment, the nozzle is deactivated without supplying air or ammonia fuel. In this way, mixed combustion of gaseous ammonia fuel and pulverized solid fuel can be performed. Switching of air and fuel is performed by an air switching valve, an oil fuel switching valve, a solid fuel switching valve, and an ammonia fuel switching valve. The operation of these switching valves may be performed by command from the control unit or manually by an operator.

[0076] In the burner according to a fifth aspect of the present disclosure, in the above-described fourth aspect, a velocity component of the gaseous ammonia fuel injected from the ammonia nozzle toward the central axis is greater than a velocity component in a tangential direction of a circle that is centered on the central axis and passes through an injection position of the gaseous ammonia fuel.

[0077] The gaseous ammonia fuel injected from the ammonia nozzle has a velocity component directed toward the central axis that is greater than the velocity component directed in the tangential direction. This makes it easier for the gaseous ammonia fuel to be directed toward the flame of the finely divided solid fuel formed from the first nozzle. If the finely divided solid fuel has good ignition properties, the gaseous ammonia fuel does not have an adverse effect on the ignition properties of the finely divided solid fuel, and therefore, the gaseous ammonia fuel can be mixed into the high-temperature reduction zone to reduce NOx.

[0078] In the burner according to a sixth aspect of the present disclosure, in the fourth aspect, a velocity component of the gaseous ammonia fuel injected from the ammonia nozzle toward the central axis is smaller than a velocity component in a tangential direction of a circle that is centered on the central axis and passes through an injection position of the gaseous ammonia fuel.

[0079] The gaseous ammonia fuel injected from the ammonia nozzle has a velocity component toward the central axis that is smaller than the velocity component in the tangential direction. As a result, the gaseous ammonia fuel flows around the flame of the finely divided solid fuel formed from the first nozzle, rather than directly toward the flame. When the finely divided solid fuel has poor ignition properties, such as biomass or oil coke, the ignition property of the finely divided solid fuel is not adversely affected, thereby making it possible to stabilize ignition and flame stability.

[0080] A burner according to a seventh aspect of the present disclosure is the burner of any one of the first to sixth aspects, wherein air is supplied between the first nozzle and the second nozzle, liquid fuel is supplied to the inside of the second nozzle, and the ammonia nozzle is stopped.

[0081] Air is supplied between the first and second nozzles, and oil fuel (liquid fuel) such as heavy oil is supplied into the second nozzle. Then, the ammonia nozzle is deactivated (ammonia fuel is not supplied). This allows for a liquid fuel-only burner. The air flowing between the first and second nozzles can be either high-temperature air or cold air. "High-temperature air" refers to air heated by recovering heat from the exhaust gas of a boiler equipped with a burner using an air preheater or the like, for example, 150°C to 400°C. "Cold air" refers to air used when ambient air is used directly without recovering heat from the exhaust gas of a boiler equipped with a burner, for example, room temperature to 100°C. When an air nozzle is provided as in the second embodiment, high-temperature air may be supplied from the air nozzle. Air and fuel selection is performed using an air selector valve, an oil fuel selector valve, a pulverized solid fuel selector valve, and an ammonia fuel selector valve. These selector valves may be operated by command from a control unit or manually by an operator.

[0082] The burner according to an eighth aspect of the present disclosure is the burner of any one of the first to seventh aspects, 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.

[0083] Air and pulverized solid fuel are supplied between the first and second nozzles. Then, the second nozzle and the ammonia nozzle are deactivated (ammonia fuel is not supplied). This allows for a burner that is exclusively fired with pulverized solid fuel. Cold air is preferably used as the air flowing between the first and second nozzles. Cold air refers to the air used when ambient air is used directly without heat recovery from the exhaust gas of the boiler in which the burner is installed. When an air nozzle is installed as in the second embodiment, the air nozzle is deactivated (hot air is not supplied). Air and fuel are switched using an air switching valve, an oil fuel switching valve, a pulverized solid fuel switching valve, and an ammonia fuel switching valve. These switching valves may be operated by commands from a control unit or manually by an operator.

[0084] A burner according to a ninth aspect of the present disclosure is any one of the first to eighth aspects, 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.

[0085] 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 shut down. This allows for a burner that is exclusively fired with gaseous ammonia fuel. Cold air is preferably used as the air flowing between the first and second nozzles. Cold air refers to the air used when ambient air is used as is without heat recovery from the exhaust gas of the boiler in which the burner is installed. Switching of air and fuel is performed by an air switching valve, an oil fuel switching valve, a pulverized solid fuel switching valve, and an ammonia fuel switching valve. The operation of these switching valves may be performed by commands from a control unit or manually by an operator.

[0086] A burner according to a tenth aspect of the present disclosure is the burner of any one of the first to eighth aspects, 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.

[0087] The air and pulverized solid fuel flowing between the first and second nozzles are stopped. Liquid ammonia fuel is supplied to the ammonia nozzle. Air and liquid ammonia fuel are supplied to the air nozzle. Then, the second nozzle is stopped. This allows for a burner that is exclusively used for liquid ammonia fuel. High-temperature air is preferably used as the air flowing through the air nozzle. High-temperature air refers to air heated by recovering heat from the exhaust gas of a boiler in which the burner is installed. Switching of air and fuel is performed by an air switching valve, an oil fuel switching valve, a pulverized solid fuel switching valve, and an ammonia fuel switching valve. The operation of these switching valves may be performed by commands from a control unit or manually by an operator.

[0088] A burner according to an eleventh aspect of the present disclosure is the burner of any one of the first to tenth aspects, wherein air is supplied between the first nozzle and the second nozzle, liquid fuel is supplied to the inside of the second nozzle, and gaseous ammonia fuel is supplied to the ammonia nozzle.

[0089] Air is supplied between the first and second nozzles, and oil fuel (liquid fuel) such as heavy oil is supplied into the second nozzle. Then, gaseous ammonia fuel is supplied from the ammonia nozzle. This allows for a burner that burns both liquid fuel and gaseous ammonia fuel. When an air nozzle is provided as in the second aspect, high-temperature air may be supplied from the air nozzle. Switching of air and fuel is performed by an air switching valve, an oil fuel switching valve, a pulverized solid fuel switching valve, and an ammonia fuel switching valve. These switching valves may be operated by commands from a control unit or manually by an operator. It is preferable to inject gaseous ammonia fuel toward a high-temperature reduction zone formed downstream of the liquid fuel flame. This accelerates the decomposition of ammonia and suppresses NOx emissions.

[0090] A boiler according to a first aspect of the present disclosure includes the burner according to any one of the above aspects.

[0091] 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 outer than the flame stabilizers; swirl vanes provided on the outer periphery of the second nozzle; and a distributor provided between the swirl vanes and a tip of the second nozzle, which distributes a flow path between the first nozzle and the second nozzle into an inner periphery-side flow path and an outer periphery-side flow path, and the cross-sectional area of ​​the outer periphery-side flow path perpendicular to the central axis increases toward the tip of the second nozzle, wherein the supply of ammonia fuel to the ammonia nozzle is performed or stopped.

[0092] 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 cylindrical nozzle (second nozzle) 62: Outer cylindrical nozzle (first nozzle) 63: Core air nozzle 71: Flame holder 72: Secondary air nozzle 72a: Guide sleeve 73: Secondary air flow path 74: Tertiary air flow path 74a: Swirler 76: First swirl vane 77: Second swirl vane 78: Distributor 79a: Inner peripheral flow path 79b: Outer peripheral flow path 80: Ammonia nozzle 101: Furnace wall 102: Superheater 103: Reheater 104: Economizer AR1: Peripheral air C1: Concentric circle CL: Central axis FL1: Diffusion flame FL2: Diffusion flame FL3: Premixed flame FL4: Diffusion flame FL5: Diffusion 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 line

Claims

1. A burner comprising: a first nozzle extending along a central axis and opening toward the inside of a furnace; a flame stabilizer for maintaining 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 inside of the furnace; a plurality of ammonia nozzles capable of supplying ammonia fuel to the inside of the furnace from a position on the outer periphery side of the flame stabilizer; a swirl vane provided on the outer periphery of the second nozzle; and a distributor provided between the swirl vane and the tip of the first nozzle, for distributing a flow path between the first nozzle and the second nozzle into an inner periphery side flow path and an outer periphery side flow path, the cross-sectional area of ​​the outer periphery side flow path perpendicular to the central axis expanding toward the tip of the first nozzle.

2. A burner as described in claim 1, comprising an air nozzle arranged to cover the second nozzle on the inner periphery of the first nozzle and on the outer periphery of the second nozzle, the tip of which is located closer to the base end of the second nozzle than the swirl vanes, and which is capable of supplying combustion air.

3. A burner as claimed in claim 2, wherein air and pulverized solid fuel are supplied between said first nozzle and said second nozzle, said second nozzle is paused, air and ammonia fuel are supplied to said air nozzle, and ammonia fuel is supplied to said ammonia nozzle.

4. A burner as claimed in claim 1 or 2, wherein air and pulverized solid fuel are supplied between said first nozzle and said second nozzle, said second nozzle is deactivated, and said ammonia nozzle is supplied with gaseous ammonia fuel.

5. A burner as described in claim 4, wherein the velocity component of the gaseous ammonia fuel injected from the ammonia nozzle toward the central axis is greater than the velocity component in the tangential direction of a circle centered on the central axis and passing through the injection position of the gaseous ammonia fuel.

6. A burner as described in claim 4, wherein the velocity component of the gaseous ammonia fuel injected from the ammonia nozzle toward the central axis is smaller than the velocity component in the tangential direction of a circle centered on the central axis and passing through the injection position of the gaseous ammonia fuel.

7. A burner according to claim 1 or 2, wherein air is supplied between the first nozzle and the second nozzle, liquid fuel is supplied to the inside of the second nozzle, and the ammonia nozzle is stopped.

8. A burner according to claim 1 or 2, wherein air and pulverized solid fuel are supplied between said first nozzle and said second nozzle, said second nozzle is deactivated, and said ammonia nozzle is deactivated.

9. A burner as claimed in claim 1, wherein only air is supplied between said first nozzle and said second nozzle, said second nozzle is deactivated, and said ammonia nozzle is supplied with gaseous ammonia fuel.

10. A burner as claimed in claim 2, wherein the flow of air and pulverized solid fuel between said first nozzle and said second nozzle is stopped, said second nozzle is stopped, air and liquid ammonia fuel are supplied to said air nozzle, and liquid ammonia fuel is supplied to said ammonia nozzle.

11. A burner as claimed in claim 1 or 2, wherein air is supplied between said first nozzle and said second nozzle, liquid fuel is supplied to the inside of said second nozzle, and gaseous ammonia fuel is supplied to said ammonia nozzle.

12. A boiler equipped with a burner according to claim 1 or 2.

13. A method for operating a burner comprising: a first nozzle extending along a central axis and opening toward the inside of a furnace; a flame stabilizer for maintaining 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 inside of the furnace; a plurality of ammonia nozzles capable of supplying ammonia fuel to the inside of the furnace from a position outer periphery of the flame stabilizer; a swirl vane provided on the outer periphery of the second nozzle; and a distributor provided between the swirl vane and the tip of the second nozzle, distributing a flow path between the first nozzle and the second nozzle into an inner periphery side flow path and an outer periphery side flow path, the cross-sectional area of ​​the outer periphery side flow path perpendicular to the central axis expanding toward the tip of the second nozzle, wherein the method for operating a burner comprises supplying or suspending ammonia fuel to the ammonia nozzle.

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