Burner and boiler comprising the same

Abstract

To provide a burner that can restrain a leak of liquefied gas fuel.SOLUTION: A burner 21 comprises: a burner body 60 comprising a main flow passage 60a through which liquefied ammonia fuel flows; a metallic nozzle 62 connected so as to cover the periphery of a tip part 60b of the burner body 60, and in which a branch flow passage 62c through which the liquefied ammonia fuel guided from the burner body 60 flows is formed; and a chip 64 connected so as to cover the periphery of a tip part 62a of the metallic nozzle 62, and in which an injection hole 64a for injecting the liquefied ammonia fuel guided from the metallic nozzle 62 is formed. The metallic nozzle 62 and the chip 64 are liquid-tightly connected by a welding part 65.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a burner that burns a liquefied gas fuel, such as liquid ammonia fuel, and a boiler equipped with 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] The burner described in Patent Document 1 burns vaporized ammonia gas, and is not intended to inject ammonia in a liquid state.

[0006] When a burner is used to inject ammonia in liquid form, the burner tip (tip) where the injection holes for injecting the fuel are formed is cooled by the liquid temperature and heat of vaporization of the liquefied ammonia. On the other hand, the nozzle metal fittings for attaching the tip to the burner body are heated by the flame, so there is a possibility that the liquid ammonia fuel will leak due to the difference in thermal expansion between the tip and the nozzle metal fittings.

[0007] The present disclosure has been made in consideration of the above circumstances, and aims to provide a burner that can suppress leakage of liquefied gas fuel and a boiler equipped with the same. [Means for solving the problem]

[0008] A burner according to one aspect of the present disclosure comprises a burner body having a flow path through which liquefied gas fuel flows, a nozzle fitting connected to cover the periphery of the tip of the burner body and having a flow path through which the liquefied gas fuel led from the burner body flows, and a tip connected to cover the periphery of the tip of the nozzle fitting and having an injection hole through which the liquefied gas fuel led from the nozzle fitting is formed, and the nozzle fitting and the tip are liquid-tightly connected by a weld.

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

[0010] The leakage of liquefied gas fuel can be suppressed. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram illustrating a boiler according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a vertical cross-sectional view showing the tip of the burner of FIG. 1. [Figure 3] FIG. 3 is a vertical cross-sectional view showing the reference example of FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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.

[0013] FIG. 1 shows a boiler 10 according to this embodiment that is capable of burning liquid ammonia (NH3) fuel. The boiler 10 of this embodiment is a boiler that can burn liquid ammonia fuel, pulverized fuel made by pulverizing solid fuel (coal or biomass fuel), or oil fuel such as heavy oil using a burner, and exchange the heat generated by this combustion with feedwater or steam to generate superheated steam.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] At least some of the burners 21A, 21B, 21C, 21D, 21E, and 21F are ammonia-fired burners to which liquid ammonia fuel is supplied. In this case, the other burners 21A, 21B, 21C, 21D, 21E, and 21F are pulverized coal-fired burners. The ammonia-fired burners are not supplied with pulverized coal fuel from the mill 31, but are supplied with liquid ammonia fuel from the liquid ammonia supply source 50.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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 treated in the environmental equipment is discharged to the outside of the system as exhaust gas.

[0023] 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.

[0024] 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.

[0025] 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, liquid ammonia fuel and / or pulverized fuel, and 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.

[0026] 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.

[0027] The boiler 10 is provided with 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.

[0028] 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.

[0029] FIG. 2 shows the tip of a burner 21 that is capable of burning liquid ammonia fuel exclusively. The burner 21 is provided with a burner body 60, a nozzle metal fitting 62, and a tip 64 in this order along the central axis CL toward the tip side. The burner body 60, the nozzle metal fitting 62, and the tip 64 each have a common central axis CL, have a substantially circular cross section, for example, and are made of metal.

[0030] A main flow passage 60a is formed inside the burner body 60 along the central axis CL. Liquefied ammonia fuel flows through the main flow passage 60a. An expanded diameter section 60a1 whose diameter gradually expands is provided at the tip end side (right side in FIG. 2) of the main flow passage 60a. A male thread section 60c is formed on the outer periphery of the tip end section 60b of the burner body 60.

[0031] The nozzle hardware 62 is provided on the tip side of the burner body 60 so as to extend along the central axis CL. The outer diameter of the nozzle hardware 62 is approximately the same as the outer diameter of the burner body 60. The rear end side (left side in FIG. 2) of the nozzle hardware 62 is arranged so as to cover the outer periphery of the tip part 60b of the burner body 60. A female threaded portion 62b is provided on the rear end side of the nozzle hardware 62. The female threaded portion 62b of the nozzle hardware 62 is threadedly engaged with the male threaded portion 60c of the burner body 60, thereby detachably connecting the burner body 60 and the nozzle hardware 62. In this way, the threaded portions 62b, 60c are provided on the rear end side of the nozzle hardware 62, which is furthest from the tip of the tip 64 (right side in FIG. 2).

[0032] The nozzle metal fitting 62 has a small diameter portion whose outer diameter is smaller than that of the rear end side of the nozzle metal fitting 62. A male thread portion 62d is formed on the outer periphery of the tip portion 62a.

[0033] The tip portion 62a is provided with a plurality of branch flow paths 62c. Liquefied ammonia fuel guided from the main flow path 60a flows through each of the branch flow paths 62c. The branch flow paths 62c extend parallel to one another in the direction of the central axis CL. The branch flow paths 62c are arranged at equal intervals in the circumferential direction around the central axis CL. The number of branch flow paths 62c is set appropriately.

[0034] The tip 64 is provided on the tip side of the nozzle metal fitting 62 so as to extend along the central axis CL. The outer diameter of the tip 64 is approximately the same as the outer diameter of the nozzle metal fitting 62. The rear end side (left side in FIG. 2 ) of the tip 64 is arranged so as to cover the outer periphery of the tip portion 62a of the nozzle metal fitting 62. A female thread portion 64b is provided on the rear end side of the tip 64. The nozzle metal fitting 62 and the tip 64 are connected by threading the female thread portion 64b of the tip 64 into the male thread portion 62d of the nozzle metal fitting 62. Then, a weld 65 is formed by welding the rear end of the tip 64 and the nozzle metal fitting 62 from the outer periphery. The weld 65 is formed over the entire circumferential direction of the outer periphery of the tip 64 and the nozzle metal fitting 62. Although the tip 64 and the nozzle hardware 62 are connected using the threaded portions 64b and 62d and then welded, they may be inserted as a spigot without using the threaded portions 64b and 62d and then welded, or they may simply be butted together and then welded.

[0035] A plurality of injection holes 64a are provided at the end of the tip 64. The injection holes 64a are provided at predetermined intervals around the central axis CL. The upstream side of each injection hole 64a is connected to a single common collecting space 64c. The liquefied ammonia fuel guided from each branch flow path 62c of the nozzle metal fitting 62 is collected in the collecting space 64c and then injected from each injection hole 64a toward the outside (furnace).

[0036] The above-described embodiment has the following advantages. Because the burner 21 injects liquefied ammonia fuel in a liquid state, the tip 64 is cooled by the liquid temperature and heat of vaporization of the liquefied ammonia, and its temperature rises due to the flame. This cooling by the liquefied ammonia and heating by the flame can cause a difference in thermal expansion between the tip 64 and the nozzle metal fitting 62, which are separate components, and this can lead to leakage of the liquefied ammonia fuel. In contrast, in this embodiment, the nozzle metal fitting 62 and the tip 64 are liquid-tightly connected by a weld 65. This can prevent leakage of the liquefied ammonia fuel even if a difference in thermal expansion occurs between the nozzle metal fitting 62 and the tip 64.

[0037] For example, a burner 21' as a reference example is shown in Figure 3. In Figure 3, the same components as in Figure 2 are given the same reference numerals, and their description will be omitted. The burner 21' in Figure 3 has a structure in which a tip 64' is screwed to a tip portion 62a of a nozzle metal fitting 62 by a cap 66 with a threaded portion 67. In the burner 21' shown in Figure 3, the tip 64' and the nozzle metal fitting 62 are cooled by the flowing liquid ammonia fuel, while the cap 66 is heated by the flame. This causes a thermal expansion difference, which reduces the surface pressure of a contact surface 68 between the tip 64' and the tip of the nozzle metal fitting 62, and there is a risk of leakage of the liquid ammonia fuel. In contrast, according to this embodiment, the tip 64' and cap 66 in Figure 3 are integrated into the tip 64, and the tip 64 and the nozzle hardware 62 are liquid-tightly connected by a welded portion 65 (see Figure 2), so there is no risk of leakage as described in Figure 3.

[0038] Furthermore, according to this embodiment, the threaded portions 60c, 62b are provided on the front end 60b of the burner body 60, so that the threaded portions 60c, 62b can be positioned far from the front end of the tip 64. This minimizes the influence of the flame and suppresses leaks due to the difference in thermal expansion between the burner body 60 and the nozzle metal fitting 62.

[0039] The burner body 60 and the nozzle metal fitting 62 are connected by threaded portions 60c, 62b, making the nozzle metal fitting 62 replaceable together with the tip 64. This allows the nozzle metal fitting 62 and the tip 64 to be replaced during maintenance.

[0040] Although liquefied ammonia fuel is used in this embodiment, any other liquefied gas fuel with a boiling point of less than 0°C may be used. For example, the present invention can be applied to a burner that injects dimethyl ether (DME) in liquid form.

[0041] The burners and boilers including the burners described in the above-described embodiments can be understood, for example, as follows.

[0042] A burner (21) according to the first aspect of the present disclosure comprises a burner body (60) having a flow path through which liquefied gas fuel flows, a nozzle metal fitting (62) connected to cover the periphery of the tip end (60b) of the burner body (60) and having a flow path (62c) through which the liquefied gas fuel led from the burner body (60) flows, and a tip (64) connected to cover the periphery of the tip end (62a) of the nozzle metal fitting (62) and having an injection hole (64a) through which the liquefied gas fuel led from the nozzle metal fitting (62) flows, and the nozzle metal fitting (62) and the tip (64) are liquid-tightly connected by a weld (65).

[0043] The liquefied gas fuel introduced from the burner body passes through a flow path formed in the nozzle metal fitting and is introduced to the tip, where it is injected from an injection hole formed in the tip. Because the liquefied gas fuel is sprayed in a liquid state, the tip is cooled by the liquid temperature and heat of vaporization of the liquefied gas, and its temperature rises due to the flame. This cooling by the liquefied gas and heating by the flame can cause a thermal expansion difference between the tip and the nozzle metal, which are separate components, and can lead to a leak of the liquefied gas fuel. In response to this, the nozzle metal and the tip are connected liquid-tightly by a weld, so that leakage of the liquefied gas fuel can be suppressed even if a thermal expansion difference occurs between the nozzle metal and the tip. Liquefied gas fuels are fuels with a boiling point below 0°C, such as liquefied ammonia and DME.

[0044] In the burner (21) according to the second aspect of the present disclosure, in the first aspect, the burner body (60) and the nozzle metal fitting (62) are connected by a screw portion (60c) provided at the tip end (60b) of the burner body (60).

[0045] By providing the threaded portion at the tip of the burner body, it is possible to position the threaded portion far from the tip, which minimizes the effect of the flame and suppresses leaks caused by differential thermal expansion between the burner body and the nozzle hardware. The burner body and nozzle hardware are connected by a screw, making the nozzle hardware replaceable along with the tip, allowing the nozzle hardware and tip to be replaced during maintenance.

[0046] A boiler according to a first aspect of the present disclosure includes the burner (21) described above. [Explanation of symbols]

[0047] 10. Boiler 11 Furnace 12 Combustion gas passage 13 Flue 20 Combustion equipment 21 Burner 22 Fine fuel supply pipe 23 Wind Box 24 Wind road 25 Additional air port 26 Additional air duct 31 mil 32 Forced draft fan 41 Gas duct 42 Air preheater 43 Denitration equipment 44 Dust collection device 46 Desulfurization equipment 47 Chimney 50 Liquid Ammonia Source 60 Burner body 60a Main channel 60a1 Expanded diameter part 60b Tip 60c male thread part 62 Nozzle hardware 62a Tip 62b Female thread 62c Branch channel 62d male thread 64 chips 64a injection hole 64b female thread 64c collective space 65 Welded section 66 Cap 67 Threaded part 68 Contact surface CL center axis

Claims

1. a burner body having a flow path through which liquefied gas fuel flows; a nozzle metal fitting connected to cover the periphery of the tip of the burner body and having a flow path through which the liquefied gas fuel introduced from the burner body flows; a tip connected to cover the periphery of the tip of the nozzle metal fitting and having an injection hole formed therein for injecting the liquefied gas fuel guided from the nozzle metal fitting; Equipped with A burner in which the nozzle metal fitting and the tip are liquid-tightly connected by a welded joint.

2. 2. The burner according to claim 1, wherein the burner body and the nozzle metal member are connected by a threaded portion provided at the tip of the burner body.

3. A boiler equipped with the burner of claim 1 or 2.

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