Burner, boiler equipped with same, and burner operating method

Abstract

Provided is a burner capable of increasing the co-firing rate of ammonia fuel when co-firing the ammonia fuel and pulverized fuel. The present invention comprises: an inner cylinder nozzle (61) that extends along a central axis (CL); an outer cylinder nozzle (62) that extends along the central axis (CL) and is disposed so as to cover the inner cylinder nozzle (61), and supplies pulverized fuel and primary air into a furnace; a pulverized fuel flame stabilizer (71) for stabilizing the flame of the pulverized fuel supplied from the outer cylinder nozzle (62); and a concentrator (69) that is disposed inside the outer cylinder nozzle (62) and concentrates the pulverized fuel on the pulverized fuel flame stabilizer (71) side. Ammonia fuel is supplied to the inner cylinder nozzle (61).

Description

[Technical Field]

[0001] The present disclosure relates to a burner that burns pulverized fuel, for example, obtained by pulverizing solid fuel, and ammonia fuel, a boiler including the burner, and a method for operating the burner. [Background technology]

[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. A heat exchanger is installed in the area where the combustion gas flows, and superheated steam is generated by heating water or steam flowing through the heat transfer tubes that make up the heat exchanger.

[0003] For burners used in boilers, studies are being 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). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-41748 Summary of the Invention [Problem to be solved by the invention]

[0005] However, although Patent Document 1 discloses co-firing of pulverized coal and ammonia fuel on the same shaft, it does not consider increasing the co-firing ratio of ammonia fuel. For example, in the configuration of Patent Document 1, if the co-firing ratio of ammonia fuel is increased, the flame stability of the pulverized coal deteriorates, making it impossible to continue co-firing with ammonia fuel.

[0006] The present disclosure has been made in consideration of the above circumstances, and aims to provide a burner that can increase the ammonia fuel co-combustion ratio when ammonia fuel and pulverized fuel are co-combusted, a boiler including the burner, and a method for operating the burner. [Means for solving the problem]

[0007] A burner according to one aspect of the present disclosure comprises an inner cylindrical nozzle extending along a central axis, an outer cylindrical nozzle extending along the central axis and covering the inner cylindrical nozzle, which supplies pulverized fuel and primary air into a furnace, a pulverized fuel flame stabilizer which stabilizes the flame of the pulverized fuel supplied from the outer cylindrical nozzle, and a concentrator which is provided inside the outer cylindrical nozzle and concentrates the pulverized fuel on the pulverized fuel flame stabilizer side, and supplies ammonia fuel to the inner cylindrical nozzle or the outer cylindrical nozzle.

[0008] A method for operating a burner according to one aspect of the present disclosure is a method for operating a burner comprising: an inner cylindrical nozzle extending along a central axis; an outer cylindrical nozzle extending along the central axis and covering the inner cylindrical nozzle, which supplies pulverized fuel and primary air into a furnace; a pulverized fuel flame stabilizer which stabilizes the flame of the pulverized fuel supplied from the outer cylindrical nozzle; and a concentrator which is provided inside the outer cylindrical nozzle and concentrates the pulverized fuel on the pulverized fuel flame stabilizer side, wherein ammonia fuel is supplied to the inner cylindrical nozzle or the outer cylindrical nozzle. [Effects of the Invention]

[0009] According to the burner of the present disclosure, the mixed combustion ratio of ammonia fuel can be increased. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram showing a boiler according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a vertical cross-sectional view showing the burner of FIG. [Figure 3A]FIG. 4 is a vertical cross-sectional view showing a burner according to a second embodiment of the present disclosure. [Figure 3B] 3B is a front view showing the inner cylinder nozzle and the outer cylinder nozzle of FIG. 3A. FIG. [Figure 4A] FIG. 3B is a vertical cross-sectional view of a burner showing a modified example of FIG. 3A. [Figure 4B] 4B is a front view showing the inner cylinder nozzle and the outer cylinder nozzle of FIG. 4A. FIG. [Figure 5] FIG. 10 is a vertical cross-sectional view showing a burner according to a third embodiment of the present disclosure. [Figure 6A] FIG. 10 is a vertical cross-sectional view showing a burner according to a fourth embodiment of the present disclosure. [Figure 6B] FIG. 6B is a front view showing the inner cylinder nozzle and the outer cylinder nozzle of FIG. 6A. [Figure 6C] FIG. 6C is a perspective view of the circumferential concentrator of FIGS. 6A and 6B. [Figure 7A] FIG. 10 is a longitudinal cross-sectional view showing a burner according to a fifth embodiment of the present disclosure. [Figure 7B] FIG. 1 is a longitudinal cross-sectional view showing a liquid ammonia injection tip. [Figure 8] FIG. 10 is a vertical cross-sectional view showing a burner according to a sixth embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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.

[0012] [First embodiment] FIG. 1 shows a boiler 10 of this embodiment that uses pulverized fuel and / or ammonia (NH3) fuel as its main fuel. The boiler 10 of this embodiment is a boiler that can burn pulverized solid fuel and ammonia fuel using a burner, and exchange the heat generated by this combustion with feedwater or steam to generate superheated steam. Biomass fuel, coal, etc. are used as solid fuel.

[0013] 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, and recovers the heat generated by the combustion of pulverized fuel by heat exchange with water and steam circulating inside the heat transfer tubes, while suppressing the temperature rise of the furnace wall 101.

[0014] 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 to be 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 each other on the opposing furnace walls 101 for opposed combustion), and are arranged in multiple stages along the vertical direction. The shape of the furnace, the number of burner stages, the number of burners per stage, the arrangement of the burners, etc. are not limited to this embodiment.

[0015] 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 these mills are not distinguished, they will be simply referred to as "mills 31") via a plurality of pulverized fuel supply pipes 22A, 22B, 22C, 22D, 22E, and 22F, respectively (hereinafter, when these mills are not distinguished, they will be simply referred to as "mills 31"). Mill 31 is, for example, a vertical roller mill having a rotatable grinding table (not shown) supported therein and a plurality of grinding rollers (not shown) supported above the grinding table so that they can rotate in conjunction with the rotation of the grinding table. The solid fuel pulverized by the cooperation of the grinding rollers and the grinding table is transported to a classifier (not shown) provided in mill 31 by primary air (carrier gas, oxidizing gas) supplied to mill 31. The classifier separates the pulverized fuel into pulverized fuel having a particle size smaller than that suitable for combustion in the burner 21 and coarse pulverized fuel having a particle size larger than that. The pulverized fuel passes through the classifier and is supplied to the burner 21 together with primary air via the pulverized fuel supply pipe 22. The coarse pulverized fuel that does not pass through the classifier falls onto the grinding table inside the mill 31 under its own weight and is re-ground.

[0016] 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. A forced draft fan (FDF) 32 is connected to the other end of the air duct 24. The air supplied from the forced draft fan 32 is heated by an air preheater 42 installed in the air duct 24 and is supplied to the burner 21 via the air register 23 as secondary air (combustion air, oxidizing gas) and introduced into the furnace 11.

[0017] 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 a coal economizer 104 as heat exchangers for recovering heat from the combustion gas, and heat is exchanged between the combustion gas generated in the furnace 11 and 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.

[0018] A flue 13 is connected to the downstream side 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, 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.

[0019] Furthermore, a denitration device 43 may be provided in the flue 13 at a position upstream of the air preheater 42. The denitration device 43 supplies a reducing agent, such as ammonia or urea water, which has the effect of reducing nitrogen oxides, to the combustion gas flowing through the flue 13, and promotes the reaction between the nitrogen oxides (NOx) in the combustion gas to which the reducing agent has been supplied and the reducing agent by the catalytic action of a denitration catalyst provided in the denitration device 43, thereby removing and reducing the nitrogen oxides in the combustion gas. A gas duct 41 is connected to the flue 13 downstream of the air preheater 42. The gas duct 41 is provided with environmental equipment such as a dust collector 44, such as an electrostatic precipitator, that removes ash and the like from the combustion gas, and a desulfurization equipment 46 that removes sulfur oxides, as well as an induced draft fan (IDF) 45 that guides the exhaust gas to these environmental equipment. The downstream end of the gas duct 41 is connected to a chimney 47, and the combustion gas that has been treated in the environmental equipment is discharged to the outside of the system as exhaust gas.

[0020] When pulverized fuel and ammonia fuel are mixed and combusted in the boiler 10, 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 the pulverized fuel mixture, which is a mixture of the 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.

[0021] 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.

[0022] In region A (corresponding to the installation range of the wind box 23 in the height direction) 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 supplied to the burner 21 (the total amount of primary air and secondary air) is set to be less than the theoretical amount of air relative to the amount of fuel supplied to the burner 21. By doing so, 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 become reducing atmospheres, and nitrogen oxides (NOx) generated by combustion are reduced inside the furnace 11. Thereafter, 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 in 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.

[0023] 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 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 gas is then discharged to the outside of the system from a chimney 47. Note that 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.

[0024] The boiler 10 is equipped with an ammonia supply source 50. Ammonia is stored in the ammonia supply source 50 in a gaseous or liquid state as ammonia fuel. The ammonia fuel is supplied from the ammonia supply source 50 to each burner 21. When ammonia gas is used in the burners 21, the ammonia fuel is stored in the ammonia supply source 50 as a gas, or is stored as liquid ammonia and vaporized during transport to the burners 21. When liquid ammonia is used in the burners 21, it is preferable that the ammonia supply source 50 store the ammonia as liquid ammonia.

[0025] The switching between the pulverized fuel and the ammonia fuel may be performed manually by an operator, or may be performed by a command from a control unit. The control unit is composed of, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and computer-readable storage media. A series of processes for realizing various functions is stored in, for example, a storage medium 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.

[0026] 2 shows the burner 21. The burner 21 is capable of burning a mixture of pulverized fuel and ammonia gas (ammonia fuel). The burner 21 includes an inner cylindrical nozzle 61 extending along a central axis CL, and an outer cylindrical nozzle 62 provided to cover the inner cylindrical nozzle 61. An oil nozzle 63 is provided on the inner peripheral side of the inner cylindrical nozzle 61. Each of the nozzles 61, 62, and 63 has a common central axis CL, has a circular cross section, for example, and is made of metal.

[0027] Ammonia gas and air (air for combustion) are supplied to the inner cylinder nozzle 61, which then ejects the mixture into the furnace 11. The ammonia gas is supplied from the ammonia supply source 50 shown in FIG.

[0028] An ammonia flame stabilizer 67 is provided at the tip of the inner cylindrical nozzle 61, between it and the oil nozzle 63. The ammonia flame stabilizer 67 is, for example, shaped like a vane, and imparts a swirl to the mixture of ammonia gas and air around the central axis CL. The ammonia flame stabilizer 67 stabilizes the flame of the ammonia gas injected from the inner cylindrical nozzle 61.

[0029] Pulverized fuel and primary air introduced from the mill 31 (see FIG. 1) are supplied into the outer cylindrical nozzle 62. A venturi 68 and a concentrator 69 are provided inside the outer cylindrical nozzle 62.

[0030] The venturi 68 is provided on the inner wall of the outer cylindrical nozzle 62, extending in the circumferential direction, and its shape bulges outward (toward the central axis CL) to reduce the flow path within the outer cylindrical nozzle 62. For example, it includes an upstream inclined portion 68a located upstream and inclined inward, and a downstream inclined portion 68b connected to the apex of the upstream inclined portion 68a and inclined outward toward the downstream side. The venturi 68 imparts a velocity component to the flow that points toward the central axis CL.

[0031] The concentrator 69 is located downstream of the venturi 68, is fixed to the outer wall of the oil nozzle 63 and extends circumferentially, and has a shape that bulges outward. For example, it includes an upstream inclined portion 69a located upstream and inclined inward, a cylindrical portion 69c connected to the apex of the upstream inclined portion 68a and extending parallel to the central axis CL, and a downstream inclined portion 69b connected to the downstream end of the cylindrical portion 69c and inclined outward toward the downstream side.

[0032] The concentrator 69 expands the flow path narrowed by the venturi 68, and gives the flow a velocity component toward the outer cylindrical nozzle 62 (radial direction). Since the pulverized fuel has a larger inertial force than the primary air, it is collected on the inner wall side of the outer cylindrical nozzle 62 by the venturi 68 and the concentrator 69, forming a high concentration region of the pulverized fuel.

[0033] A pulverized fuel flame stabilizer 71 serving as a baffle is provided on the outer periphery of the tip of the outer cylindrical nozzle 62. The pulverized fuel flame stabilizer 71 is ring-shaped when the outer cylindrical nozzle 62 is viewed from the front. The pulverized fuel flame stabilizer 71 partially blocks the flow of secondary air through the secondary air passage 73, forming a flame-stabilizing region downstream thereof. This stabilizes the flame of the pulverized fuel supplied from the outer cylindrical nozzle 62.

[0034] Oil fuel is supplied from an oil fuel supply source (not shown) to the oil nozzle 63. The oil fuel is used when the burner 21 is started up, and after the start-up, the supply of oil fuel is stopped and a small amount of cooling air is supplied instead.

[0035] The secondary air flow path 73 is provided so as to cover the outer cylindrical nozzle 62. A tertiary air flow path 74 is provided on the outer circumferential side of the secondary air flow path 73 so as to cover the secondary air flow path 73. A swirler 74a that imparts a swirl to the tertiary air is provided within the tertiary air flow path 74.

[0036] Next, the operation of the burner 21 having the above configuration will be described. First, the burner 21 is started by supplying oil fuel from the oil nozzle 63. The oil fuel injected into the furnace 11 from the oil nozzle 63 forms a flame together with air supplied from the inner cylindrical nozzle 61, and heats up the furnace 11. The flame of the oil fuel is stabilized by the ammonia flame stabilizer 67. That is, the ammonia flame stabilizer 67 is also used to stabilize the flame of the oil fuel at startup.

[0037] When the temperature inside the furnace 11 is raised to a predetermined temperature and startup is completed, the supply of oil fuel is stopped. When the supply of oil fuel is stopped, a small amount of air is flowed from the oil nozzle 63 to cool the oil nozzle 63.

[0038] After a predetermined time has elapsed since the start of the burner, the supply of pulverized fuel and ammonia gas is carried out as follows.

[0039] Pulverized fuel is gradually supplied from the outer nozzle 62 together with primary air, and a flame of pulverized fuel is formed. The pulverized fuel forms a high-concentration region on the inner wall side of the outer nozzle 62 by the venturi 68 and the concentrator 69. The flame of pulverized fuel is stabilized by a pulverized fuel flame stabilizer 71 provided in the outer nozzle 62, and combustion is carried out in stages by secondary air supplied from a secondary air passage 73 and tertiary air supplied from a tertiary air passage 74.

[0040] Ammonia gas is gradually supplied together with air from an ammonia supply source 50 (see FIG. 1) into the inner cylindrical nozzle 61, and is introduced in a premixed state to the ammonia flame stabilizer 67. The premixed gas given a swirl by the ammonia flame stabilizer 67 travels straight along the central axis CL, forming a premixed flame of ammonia gas. In this way, the flame of the ammonia gas is stabilized by the ammonia flame stabilizer 67, and is mixed and burned with the pulverized fuel supplied from the outer cylindrical nozzle 62.

[0041] The above-described embodiment has the following advantages. The concentrator 69 provided inside the outer cylindrical nozzle 62 concentrates the pulverized fuel on the inner wall side of the pulverized fuel flame stabilizer 71. This makes the flame stabilization by the pulverized fuel flame stabilizer 71 more stable. By supplying ammonia gas to the inner cylindrical nozzle 61, the ammonia gas is supplied near, or more specifically inside, the flame of the pulverized fuel whose flame stabilization has been strengthened by the concentrator 69 and the pulverized fuel flame stabilizer 71, thereby stabilizing the combustion of the ammonia gas and increasing the ammonia fuel mixed combustion ratio. For example, when multiple types of fuels are combusted simultaneously with a single burner, the ammonia fuel mixed combustion ratio can be increased to 50% or more.

[0042] The flame is stabilized by premixed combustion of ammonia gas and air supplied to the inner cylinder nozzle 61. The ammonia gas flame is then further stabilized by an ammonia flame stabilizer 67 provided at the tip of the inner cylinder nozzle 61. This allows the ammonia fuel co-firing ratio to be increased.

[0043] In this embodiment, a control valve (not shown) for controlling the flow rate of air supplied to the inner cylindrical nozzle 61 may be provided, and the opening degree of this control valve may be controlled by the control unit. At this time, the control unit calculates the ammonia fuel co-combustion ratio (current value) by acquiring the flow rates of ammonia gas, air, pulverized fuel, and primary air from sensors (not shown).The control unit then adjusts the aperture of the control valve to reduce the air flow rate as the ammonia fuel co-combustion ratio increases.By controlling in this manner, even if the ammonia fuel co-combustion ratio increases and it becomes difficult to maintain the pulverized fuel flame, the flow rate of the air can be reduced as the ammonia fuel increases, thereby reducing the flow rate of the premixed fuel flowing out of the inner cylinder nozzle 61.This makes it possible to maintain the pulverized fuel flame while avoiding ignition inhibition of the pulverized fuel as much as possible, and to increase the ammonia fuel co-combustion ratio.

[0044] [Second embodiment] Next, a second embodiment of the present disclosure will be described with reference to FIGS. 3A and 3B. In this embodiment, the oil nozzle 63 of the first embodiment is omitted, and the position at which the ammonia gas is ejected is different. In the following explanation, the same components as those in the first embodiment are given the same reference numerals and their explanation is omitted, and the different components will be mainly explained.

[0045] As shown in FIG. 3A, the burner 21 of this embodiment is provided with an inner cylindrical nozzle 61 at a position closest to the central axis CL. Therefore, the oil nozzle 63 of the first embodiment is not provided inside the inner cylindrical nozzle 61. The end of the inner cylindrical nozzle 61 on the furnace 11 side (in FIG. 3A) It The inner cylindrical nozzle 61 is supplied with ammonia gas from the ammonia supply source 50 shown in Fig. 1. However, unlike the first embodiment, only ammonia gas is supplied to the inner cylindrical nozzle 61, and air is not supplied thereto.

[0046] As shown in FIG. 3B, the concentrator 69 is formed with a plurality of slits (ammonia gas ejection holes) 80. These slits 80 are formed with radially elongated flow paths in the radial direction. In this embodiment, the number of slits 80 is four, but the number is not particularly limited and may be two or more, or three or more. Each slit 80 communicates with the inner cylinder nozzle 61, allowing ammonia gas to flow through. As shown in FIG. 3A, each slit 80 is formed in the downstream inclined portion 6 of the concentrator 69. 9 b, which injects ammonia gas in the direction along the central axis CL as shown by the arrow. Ammonia gas is injected into the outer cylindrical nozzle 62 through the slit 80. Primary air flowing inside the outer cylindrical nozzle 62 is used as the combustion air for the ammonia gas.

[0047] According to this embodiment, the following advantageous effects are achieved. Since ammonia gas is ejected into the outer cylindrical nozzle 62 from each slit 80 formed in the concentrator 69, a flame can be formed together with the pulverized fuel, and the ammonia fuel co-combustion ratio can be increased.

[0048] Ammonia gas is ejected from the slit 80 along the central axis CL to prevent it from spreading radially as much as possible, which delays mixing with the pulverized fuel concentrated on the inner wall side of the outer cylindrical nozzle 62 by the concentrator 69, thereby enabling reduction of NOx.

[0049] In this embodiment, the ammonia gas is ejected from the slit 80 along the central axis CL, but this may be modified as shown in FIGS. 4A and 4B. Specifically, the direction in which the ammonia gas is ejected is changed. As shown by the arrows in Figures 4A and 4B, the slits 80' are formed in a direction in which the ammonia gas is ejected toward the outer periphery (radial direction) at an angle with respect to the central axis CL.

[0050] By ejecting the ammonia gas from the slit 80' toward the outer periphery at an angle relative to the central axis CL, the ammonia gas spreads toward the inner wall of the outer cylindrical nozzle 62 and is mixed with the pulverized fuel concentrated on the inner wall of the outer cylindrical nozzle 62 by the concentrator 69, thereby promoting combustion.

[0051] [Third embodiment] Next, a third embodiment of the present disclosure will be described with reference to FIG. This embodiment differs from the second embodiment in that a distributor 82 is added, but the other configurations are similar, so the same reference numerals are used and the description thereof will be omitted.

[0052] 5, a ring-shaped distributor 82 is provided inside the tip of the outer cylindrical nozzle 62. The distributor 82 is provided so as to surround the downstream end of the downstream inclined portion 69b of the concentrator 69. The distributor 82 divides the flow path within the outer cylindrical nozzle 62 into an inner flow path 62a and an outer flow path 62b.

[0053] By separating the inner flow passage 62a and the outer flow passage 62b of the outer cylindrical nozzle 62, the inner flow passage 62a through which mainly primary air flows, separated by the concentrator 69, and the outer flow passage 62b through which mainly concentrated pulverized fuel flows, are formed. This allows the primary air flowing through the inner flow passage 62a to be used for burning ammonia gas, and the concentrated pulverized fuel flowing through the outer flow passage 62b can promote ignition of the pulverized fuel.

[0054] In this embodiment, as shown in Fig. 5, the ammonia gas is ejected in a direction inclined with respect to the central axis CL toward the outer periphery as shown in Fig. 4A, but the present disclosure is not limited to this. For example, as shown in Fig. 3A, the ammonia gas may be ejected from the slit 80 along the central axis CL.

[0055] [Fourth embodiment] Next, a fourth embodiment of the present disclosure will be described with reference to FIGS. 6A to 6C. In the second embodiment, the ammonia gas is blown out from the inner peripheral side of the outer cylindrical nozzle 62, but in this embodiment, the ammonia gas is blown out from the inner wall side of the outer cylindrical nozzle 62. In the following explanation, the same components as in the second embodiment are denoted by the same reference numerals and explanations thereof will be omitted, and the different components will be mainly explained.

[0056] 6A, no ammonia gas is supplied from the inner cylinder nozzle 61. The inner cylinder nozzle 61 basically allows a small amount of cooling air to flow, but can be used as an oil nozzle during start-up if necessary.

[0057] A plurality of circumferential concentrators 85 are provided on the inner wall of the outer cylindrical nozzle 62. Each circumferential concentrator 85 is located on the outer circumferential side of the downstream inclined portion 69b of the concentrator 69.

[0058] 6B, the circumferential concentrators 85 are provided at predetermined intervals along the circumferential direction of the inner wall of the outer casing nozzle 62. The pulverized fuel concentrated by the concentrators 69 flows between the adjacent circumferential concentrators 85 in a contracting flow.

[0059] 6C shows two circumferential concentrators 85 as an example. In the figure, the upper part indicates the outer circumferential side of the outer cylindrical nozzle 62, and the lower part indicates the inner circumferential side of the outer cylindrical nozzle 62. As shown in FIG. 6C, an ammonia gas ejection hole 85a for ejecting ammonia gas is provided at the tip (downstream end) of the circumferential concentrator 85. An ammonia gas supply pipe 87 (see FIGS. 6A and 6B) is connected to the circumferential concentrator 85 via a pipe-shaped mounting portion 85b. Ammonia gas is supplied to the circumferential concentrator 85 from the ammonia supply source 50 (see FIG. 1) via the ammonia gas supply pipe 87.

[0060] 6C, the circumferential concentrator 85 has a diamond shape when viewed from the inner peripheral side of the outer cylindrical nozzle 62, gradually widening from an upstream end 85c and gradually narrowing from an intermediate position 85d to a downstream end 85e. A plurality of ammonia gas ejection holes 85a are formed in a downstream side surface 85f extending from the intermediate position 85d to the downstream end 85e. A bottom surface 85g, which is the inner peripheral surface of the circumferential concentrator 85, is closed.

[0061] According to this embodiment, the following advantageous effects are achieved. By providing the concentrator 69 on the outer wall of the inner cylindrical nozzle 61, the pulverized fuel is concentrated on the inner wall side of the outer cylindrical nozzle 62. By providing a plurality of circumferential concentrators 85 at predetermined intervals in the circumferential direction on the inner wall of the tip of the outer cylindrical nozzle 62, the circumferential flow path width is partially reduced, and the pulverized fuel is concentrated in the circumferential direction. By ejecting ammonia gas from the ammonia gas ejection holes 85a provided in the circumferential concentrators 85, the ammonia gas can be mixed with the pulverized fuel concentrated in the circumferential direction, thereby promoting combustion.

[0062] [Fifth embodiment] Next, a fifth embodiment of the present disclosure will be described with reference to FIGS. 7A and 7B. While ammonia gas is used in the first embodiment, this embodiment differs in that liquid ammonia is used in the second embodiment. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals and their description is omitted, and the description will focus mainly on the different components.

[0063] As shown in Fig. 7A, a liquid ammonia supply pipe 90 for injecting liquid ammonia is provided inside the inner cylindrical nozzle 61. A plurality of liquid ammonia supply pipes 90 are provided at predetermined intervals around the central axis line CL. Liquid ammonia is supplied to the liquid ammonia supply pipe 90 from the ammonia supply source 50 (see Fig. 1). Air is supplied to the inner cylindrical nozzle 61.

[0064] As shown in Fig. 7B, a liquid ammonia injection tip 92 is provided inside the liquid ammonia supply pipe 90. As shown in Fig. 7B, a liquid ammonia flow path is formed inside the liquid ammonia injection tip 92, and atomized liquid ammonia fuel is injected from a plurality of injection holes 92a toward the inside of the inner cylinder nozzle 61. The liquid ammonia is injected by pressure spraying by the liquid ammonia injection tip 92. Liquid ammonia is injected from the liquid ammonia injection tip 92 of the liquid ammonia supply pipe 90 to the upstream side of the ammonia flame stabilizer 67.

[0065] [Sixth embodiment] Next, a sixth embodiment of the present disclosure will be described with reference to FIG. Although the fifth embodiment shows a configuration in which liquid ammonia is supplied, liquid ammonia can also be supplied to the oil nozzle 63, which injects oil fuel, which is the same liquid, as a burner that burns liquid ammonia. In this case, if a large amount of liquid ammonia is supplied into the furnace 11 from the central axis CL side of the burner 21, the temperature near the outlet of the burner 21 will drop due to the heat of vaporization, making ignition difficult. Therefore, in addition to the ammonia supplied from the oil nozzle 63, it is desirable to supply a necessary amount of ammonia from the outer circumferential side of the oil nozzle 63, i.e., from the ammonia supply pipe 95 provided in the tertiary air flow path 74.

[0066] The ammonia supply pipes 95 are cylindrical members, and a plurality of them are arranged at appropriate circumferential intervals inside the tertiary air flow path 74. However, there are no limitations on the shape, number, etc. of the ammonia supply pipes 95, as long as they can stably ignite and burn the fuel. Furthermore, the ammonia supplied to the ammonia supply pipes 95 may be either liquid or gas.

[0067] According to this embodiment, the following advantageous effects are achieved. Liquid ammonia is injected upstream of the ammonia flame stabilizer 67 provided at the tip of the inner cylindrical nozzle 61. As a result, the liquid ammonia is mixed with the air supplied into the inner cylindrical nozzle 61 upstream of the ammonia flame stabilizer 67, and the liquid ammonia is vaporized as much as possible in the ammonia flame stabilizer 67, stabilizing the flame by the ammonia flame stabilizer 67. This makes it possible to increase the ammonia fuel co-firing ratio.

[0068] In the above-described embodiments, the boiler of the present invention has been described as a boiler that uses solid fuel as fuel, such as coal, biomass fuel, petroleum coke (PC), petroleum residue, etc.

[0069] 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.

[0070] A burner (21) according to one embodiment of the present disclosure comprises an inner cylindrical nozzle (61) extending along a central axis (CL), an outer cylindrical nozzle (62) extending along the central axis and arranged to cover the inner cylindrical nozzle, for supplying pulverized fuel and primary air into a furnace, a pulverized fuel flame stabilizer (71) for stabilizing the flame of the pulverized fuel supplied from the outer cylindrical nozzle, and a concentrator (69) arranged inside the outer cylindrical nozzle for concentrating the pulverized fuel on the pulverized fuel flame stabilizer side, and supplies ammonia fuel to the inner cylindrical nozzle or the outer cylindrical nozzle.

[0071] The pulverized fuel is concentrated on the pulverized fuel flame stabilizer side by the concentrator installed inside the outer nozzle. This makes the flame stabilized by the pulverized fuel flame stabilizer more stable. By supplying ammonia fuel to the inner or outer nozzle, the ammonia fuel is supplied near the pulverized fuel flame whose flame stabilization has been strengthened by the concentrator and the pulverized fuel flame stabilizer, and the ammonia fuel co-firing ratio can be increased.

[0072] In a burner according to one aspect of the present disclosure, ammonia gas is used as the ammonia fuel, ammonia gas and air are supplied to the inner cylindrical nozzle, and an ammonia flame stabilizer (67) that stabilizes the flame of the ammonia gas supplied from the inner cylindrical nozzle is provided at the tip of the inner cylindrical nozzle.

[0073] Ammonia gas and air are supplied to the inner nozzle to perform premixed combustion, stabilizing the flame. Determined Furthermore, the ammonia gas flame is further stabilized by an ammonia flame stabilizer installed at the tip of the inner nozzle, which allows for an increased ammonia fuel co-firing ratio.

[0074] A burner according to one aspect of the present disclosure includes a control valve that controls the flow rate of air supplied to the inner cylindrical nozzle, and a control unit that controls the control valve, and the control unit controls the control valve to reduce the flow rate of the air in response to an increase in the mixed-combustion ratio of the ammonia fuel.

[0075] When the ammonia fuel co-firing ratio increases, it may become difficult to maintain the pulverized fuel flame. Therefore, by reducing the air flow rate in response to an increase in ammonia fuel, the flow velocity of the premixed fuel flowing out of the inner nozzle is reduced. This makes it possible to maintain the pulverized fuel flame while avoiding ignition inhibition of the pulverized fuel as much as possible, and to increase the ammonia fuel co-firing ratio.

[0076] In a burner according to one aspect of the present disclosure, ammonia gas is used as the ammonia fuel, ammonia gas is supplied to the inner cylindrical nozzle, the concentrator is provided on the outer wall of the inner cylindrical nozzle, and the concentrator is provided with ammonia gas ejection holes (80, 80') that eject the ammonia gas guided from the inner cylindrical nozzle into the outer cylindrical nozzle.

[0077] By providing a concentrator on the outer wall of the inner cylindrical nozzle, the pulverized fuel can be concentrated on the inner wall side of the outer cylindrical nozzle. Since ammonia gas is ejected into the outer cylindrical nozzle from the ammonia gas ejection holes formed in the concentrator, a flame can be formed together with the pulverized fuel, and the ammonia fuel co-combustion ratio can be increased.

[0078] In the burner according to one aspect of the present disclosure, the ammonia gas ejection holes are formed in a direction such that the ammonia gas is ejected along the central axis.

[0079] By ejecting ammonia gas from the ammonia gas ejection holes along the central axis, mixing with the pulverized fuel concentrated on the inner wall side of the outer cylindrical nozzle by the concentrator is delayed, thereby making it possible to reduce NOx.

[0080] In the burner according to one aspect of the present disclosure, the ammonia gas ejection holes are formed in a direction such that the ammonia gas is ejected toward the outer periphery at an angle with respect to the central axis.

[0081] By ejecting ammonia gas from the ammonia gas ejection holes toward the outer periphery at an angle relative to the central axis, the ammonia gas spreads toward the inner wall of the outer cylindrical nozzle and is mixed with the pulverized fuel concentrated on the inner wall of the outer cylindrical nozzle by the concentrator, thereby promoting combustion.

[0082] In the burner according to one aspect of the present disclosure, a distributor (82) that separates the inner flow path and the outer flow path is provided at the tip of the outer cylindrical nozzle.

[0083] A distributor is provided at the tip of the external nozzle to separate the internal and external flow paths of the external nozzle, forming the internal flow path through which primary air mainly flows and the external flow path through which concentrated pulverized fuel mainly flows. This allows the primary air flowing through the internal flow path to be used for burning ammonia gas, and the concentrated pulverized fuel flowing through the external flow path to promote ignition of the pulverized fuel.

[0084] In a burner according to one aspect of the present disclosure, ammonia gas is used as the ammonia fuel, the concentrator is provided on the outer wall of the inner cylindrical nozzle, and a plurality of circumferential concentrators (85) are provided on the inner wall of the tip of the outer cylindrical nozzle at predetermined intervals in the circumferential direction, and ammonia gas ejection holes (85a) for ejecting the ammonia gas are formed in the circumferential concentrators.

[0085] By providing a concentrator on the outer wall of the inner cylindrical nozzle, the pulverized fuel is concentrated on the inner wall side of the outer cylindrical nozzle. Furthermore, by providing a plurality of circumferential concentrators at predetermined intervals in the circumferential direction on the inner wall of the tip of the outer cylindrical nozzle, the circumferential flow path width is partially reduced, concentrating the pulverized fuel in the circumferential direction. Ammonia gas is then ejected from ammonia gas ejection holes provided in the circumferential concentrators, whereby the ammonia gas is mixed with the circumferentially concentrated pulverized fuel and promotes combustion.

[0086] In a burner according to one aspect of the present disclosure, liquid ammonia is used as the ammonia fuel, air is supplied to the inner cylindrical nozzle, an ammonia flame stabilizer (67) for stabilizing the flame of the ammonia supplied from the inner cylindrical nozzle is provided at the tip of the inner cylindrical nozzle, and a liquid ammonia supply pipe (90) for injecting the liquid ammonia upstream of the ammonia flame stabilizer is provided inside the inner cylindrical nozzle.

[0087] Liquid ammonia is injected upstream of the ammonia flame stabilizer installed at the tip of the inner nozzle. This allows the liquid ammonia to mix with the air supplied into the inner nozzle upstream of the ammonia flame stabilizer, vaporizing the liquid ammonia as much as possible in the flame stabilizer, stabilizing the flame with the ammonia flame stabilizer. This allows for an increased ammonia fuel co-firing ratio.

[0088] In the burner according to one aspect of the present disclosure, liquid ammonia fuel is supplied from the inner cylindrical nozzle, and ammonia is injected from an ammonia supply pipe provided on the outer circumferential side of the outer cylindrical nozzle.

[0089] By supplying liquid ammonia from the inner nozzle and injecting ammonia from the ammonia supply pipe provided on the outer periphery of the outer nozzle, the ammonia co-firing ratio can be increased. Furthermore, supplying liquid ammonia from the inner nozzle can lower the temperature near the burner outlet due to the heat of vaporization, which can make ignition difficult. However, by reducing the amount of liquid ammonia supplied from the inner nozzle by an amount equivalent to the ammonia supplied from the ammonia supply pipe, proper ignition can be achieved. The ammonia supplied from the ammonia supply pipe can be either liquid or gas.

[0090] A boiler (10) according to one aspect of the present disclosure includes any one of the burners described above.

[0091] A method for operating a burner according to one aspect of the present disclosure is a method for operating a burner comprising: an inner cylindrical nozzle extending along a central axis; an outer cylindrical nozzle extending along the central axis and covering the inner cylindrical nozzle, which supplies pulverized fuel and primary air into a furnace; a pulverized fuel flame stabilizer which stabilizes the flame of the pulverized fuel supplied from the outer cylindrical nozzle; and a concentrator which is provided inside the outer cylindrical nozzle and concentrates the pulverized fuel on the pulverized fuel flame stabilizer side, wherein ammonia fuel is supplied to the inner cylindrical nozzle or the outer cylindrical nozzle.

[0092] Furthermore, according to the burner according to one aspect of the present disclosure, the following advantageous effects can be obtained. In a co-firing burner that simultaneously burns pulverized fuel and ammonia fuel in a single burner, the conditions for fuel ignition and flame stability become strict, particularly in the range of loads lower than the rated output, and therefore the range of upper and lower limits for the co-firing ratio tends to be narrow.

[0093] In addition, the minimum load limit for a multi-fuel burner tends to be higher than that for a single-fuel burner, because the burner must stably form and maintain flames from multiple fuels with different combustion characteristics.

[0094] In wall-fired boilers, which have burners arranged in multiple rows and columns on the furnace wall, ignition, extinguishing, and output (load) adjustments are often performed for each row of burners as a single group. One stage of burner may be shut down to use as a spare, and the load on other operating burner stages may be adjusted, or the number of burner stages may be further shut down to reduce the load.

[0095] A wall-fired boiler equipped with the burners of the present disclosure in each stage and each row can increase the ammonia fuel co-firing ratio. Even in the low boiler load region, the upper and lower limits of the co-firing ratio are wide, and the lower limit of the boiler load can be lowered. This improves the operability of the boiler plant and the flexibility in responding to co-firing ratio and load fluctuations.

[0096] The burners of the present disclosure can increase the ammonia fuel co-firing ratio, i.e., the upper limit of the co-firing ratio is high. Therefore, when converting a boiler that is equipped only with burners that combust existing pulverized fuel into a co-firing boiler by replacing some of the burners with burners that can combust ammonia, there is an advantage that it is sufficient to replace fewer burners than with burners with a low upper limit of the co-firing ratio.

[0097] According to the burner of the present disclosure, the range of upper and lower limits of the ammonia fuel co-firing ratio is wide, and therefore, in a boiler plant in which burners that exclusively fire a specific fuel type and burners that co-firing ammonia and pulverized fuel are mixed, there is an advantage that the range of selection of burners to be used or suspended and the range of load adjustment are wider than in the case of burners in which the range of upper and lower limits of the ammonia fuel co-firing ratio is narrow.

[0098] In addition, stable combustion can be achieved even at low loads, and the minimum load limit can be set low.

[0099] It is also easy to accommodate flexible operations such as increasing or decreasing the fuel supply ratio, i.e., the mixed combustion ratio, depending on the circumstances of the boiler plant, such as fuel procurement. [Explanation of symbols]

[0100] 10. Boiler 11 Furnace 12 Combustion gas passage 13 Flue 20 Combustion equipment 21 Burner 22 Fine fuel supply pipe 23 Air register 24 Air duct 25 Additional air port 26 Additional air duct 31 Mill (Grinder) 32 Forced draft fan (FDF) 41 Gas duct 42 Air preheater 43 Denitration equipment 44 Dust collection device 45 Induced Draft Fan (IDF) 46 Desulfurization equipment 47 Chimney 50 Ammonia Source 61 Inner cylinder nozzle 62 External nozzle 62a Inner flow channel 62b Outer channel 63 Oil nozzle 67 Ammonia flame holder 68 Venturi 68a Upstream slope 68b Downstream slope 69 Concentrator 69a Upstream slope 69b Downstream slope 69c Cylindrical part 71 Flame stabilizer for pulverized fuel 73 Secondary air flow path 74 Tertiary air flow path 74a Swivel 80,80' slit (ammonia gas outlet) 82 Distributor 85 Circumferential concentrator 85a Ammonia gas vent 85b Mounting part 85c upstream end 85d intermediate position 85e downstream end 85f downstream side 85g bottom 87 Ammonia gas supply pipe 90 Liquid ammonia supply pipe 92 Liquid Ammonia Injection Tip 92a injection hole 95 Liquid ammonia supply pipe 101 Furnace wall 102 Superheater 103 Reheater 104 Economizer

Claims

1. an inner cylindrical nozzle extending along a central axis; an outer cylindrical nozzle extending along the central axis and covering the inner cylindrical nozzle, the outer cylindrical nozzle supplying pulverized fuel and primary air into the furnace; a pulverized fuel flame stabilizer that stabilizes the flame of the pulverized fuel supplied from the outer cylindrical nozzle; a concentrator provided inside the outer cylindrical nozzle and configured to concentrate the pulverized fuel on the pulverized fuel flame stabilizer side; Equipped with supplying ammonia fuel to the inner cylindrical nozzle or the outer cylindrical nozzle; Ammonia gas is used as the ammonia fuel, Ammonia gas is supplied to the inner cylindrical nozzle, the concentrator is provided on an outer wall of the inner cylindrical nozzle, a burner in which the concentrator is provided with an ammonia gas ejection hole for ejecting the ammonia gas introduced from the inner cylindrical nozzle into the outer cylindrical nozzle;

2. Ammonia gas is used as the ammonia fuel, Ammonia gas and air are supplied to the inner cylindrical nozzle, 2. The burner according to claim 1, wherein an ammonia flame stabilizer for stabilizing the flame of the ammonia gas supplied from the inner cylindrical nozzle is provided at the tip of the inner cylindrical nozzle.

3. a control valve for controlling the flow rate of air supplied to the inner cylindrical nozzle; a control unit that controls the control valve; Equipped with The burner according to claim 2 , wherein the control unit controls the control valve to reduce the flow rate of the air in response to an increase in the mixed combustion ratio of the ammonia fuel.

4. 2. The burner according to claim 1, wherein the ammonia gas ejection holes are formed in a direction such that the ammonia gas is ejected along the central axis.

5. 2. The burner according to claim 1, wherein the ammonia gas ejection holes are formed in a direction such that the ammonia gas is ejected toward the outer periphery at an angle with respect to the central axis.

6. 2. The burner according to claim 1, wherein a distributor is provided at the tip of said outer cylindrical nozzle to separate the inner flow passage from the outer flow passage.

7. Ammonia gas is used as the ammonia fuel, the concentrator is provided on an outer wall of the inner cylindrical nozzle, a plurality of circumferential concentrators are provided at predetermined intervals in the circumferential direction on the inner wall of the tip of the outer cylindrical nozzle; 2. The burner according to claim 1, wherein the circumferential concentrator is formed with ammonia gas ejection holes for ejecting the ammonia gas.

8. Liquid ammonia is used as the ammonia fuel, Air is supplied to the inner cylindrical nozzle, an ammonia flame stabilizer that stabilizes the flame of the ammonia supplied from the inner cylindrical nozzle is provided at a tip of the inner cylindrical nozzle; 2. The burner according to claim 1, wherein a liquid ammonia supply pipe for injecting the liquid ammonia is provided inside the inner cylindrical nozzle on the upstream side of the ammonia flame stabilizer.

9. supplying liquid ammonia fuel from the inner cylindrical nozzle; 2. The burner according to claim 1, wherein ammonia is injected from an ammonia supply pipe provided on the outer periphery of the outer cylindrical nozzle.

10. A boiler equipped with the burner according to any one of claims 1 to 9.

11. an inner cylindrical nozzle extending along a central axis; an outer cylindrical nozzle extending along the central axis and covering the inner cylindrical nozzle, the outer cylindrical nozzle supplying pulverized fuel and primary air into the furnace; a pulverized fuel flame stabilizer that stabilizes the flame of the pulverized fuel supplied from the outer cylindrical nozzle; a concentrator provided inside the outer cylindrical nozzle and configured to concentrate the pulverized fuel on the pulverized fuel flame stabilizer side; A method for operating a burner comprising: supplying ammonia fuel to the inner cylindrical nozzle or the outer cylindrical nozzle; Ammonia gas is used as the ammonia fuel, Ammonia gas is supplied to the inner cylindrical nozzle, the concentrator is provided on an outer wall of the inner cylindrical nozzle, The method for operating a burner, wherein the concentrator is provided with an ammonia gas ejection hole for ejecting the ammonia gas introduced from the inner cylindrical nozzle into the outer cylindrical nozzle.

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