Burner and boiler

Abstract

To provide a burner which enables ammonia and a fossil fuel to be efficiently used as a fuel, and to provide a boiler.SOLUTION: A burner includes: a first nozzle forming a cylindrical shape extending in an axial direction and having a tip opening capable of jetting a fluid mixture of primary air and fine powdered coal; and a second nozzle disposed in the first nozzle so as to extend in the axial direction and having a tip part which is located at the upstream side of the fluid mixture relative to the tip opening of the first nozzle and capable of jetting ammonia.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a burner and a boiler. [Background technology]

[0002] Large boilers, such as power generation boilers, have a hollow furnace installed vertically, with multiple burners arranged circumferentially around the furnace wall. Large boilers also have a flue connected vertically above the furnace, with a heat exchanger for generating steam located in the flue. 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] In recent years, research and development has been conducted on burners that use ammonia as fuel in addition to conventional fossil fuels. A specific example of a boiler that uses this type of burner is known from Patent Document 1 below. This boiler is provided with multiple burners that burn fossil fuels and multiple burners that burn ammonia, each of which is independent of the other. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-178823 Summary of the Invention [Problem to be solved by the invention]

[0005] However, since the total number of burners that can be installed in a boiler is limited, if ammonia-fueled burners are installed as described above, the number of fossil-fueled burners will decrease. As a result, there is a problem that, for example, in a situation where ammonia is not available, the output of the entire burners will decrease accordingly.

[0006] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide a burner and a boiler that can efficiently use ammonia and fossil fuels as fuels. [Means for solving the problem]

[0007] In order to solve the above problems, the burner according to the present disclosure comprises a first nozzle having a cylindrical shape extending in the axial direction and a tip opening capable of spraying a mixed fluid of primary air and pulverized coal, and a second nozzle arranged within the first nozzle so as to extend in the axial direction, positioned upstream of the tip opening of the first nozzle in the mixed fluid, and having a tip portion capable of spraying ammonia.

[0008] A boiler according to the present disclosure includes the burner described above and a furnace provided with the burner. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a burner and a boiler that can efficiently use ammonia and fossil fuels as fuels. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram illustrating a configuration of a boiler according to an embodiment of the present disclosure. [Figure 2] FIG. 1 is a cross-sectional view showing a configuration of a burner according to an embodiment of the present disclosure. [Figure 3] FIG. 1 is an axial view of a burner according to an embodiment of the present disclosure. [Figure 4] FIG. 10 is a cross-sectional view illustrating a modified example of a burner according to an embodiment of the present disclosure. [Figure 5] FIG. 10 is a view of a modified example of a burner according to an embodiment of the present disclosure, viewed from the axial direction. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, one embodiment according to the present disclosure will be described with reference to the drawings. Note that the present invention is not limited to this embodiment, and when there are multiple embodiments, it also includes configurations that combine the respective 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] FIG. 1 is a schematic diagram showing the configuration of a boiler using solid fuel as the main fuel according to this embodiment.

[0013] (Boiler configuration) The boiler 10 of this embodiment is a boiler that can generate superheated steam by burning pulverized fuel made by pulverizing solid fuel with a burner and exchanging the heat generated by this combustion with feedwater or steam. Biomass fuel, coal, etc. are used as solid fuel.

[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, may be collectively referred to as "burners 21") attached to the furnace wall 101. The burners 21 are arranged at equal intervals along the circumferential direction of the furnace 11 (for example, four burners installed at each corner of the rectangular furnace 11), and are arranged in multiple rows along the vertical direction as one set. Note that, for convenience of illustration, FIG. 1 shows only two burners from one set, and each set is denoted by the reference numerals 21A, 21B, 21C, 21D, 21E, and 21F. The shape of the furnace, the number of burner rows, the number of burners in one row, the arrangement of the burners, and the like 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, sometimes collectively referred to as "mills 31") via a plurality of pulverized fuel supply pipes 22A, 22B, 22C, 22D, 22E, and 22F (hereinafter, sometimes collectively referred to as "pulverized fuel supply pipes 22"). Mill 31 is, for example, a vertical roller mill having a pulverizing table (not shown) supported therein so as to be rotatable, 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 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] Furthermore, the burners 21A, 21B, 21C, 21D, 21E, and 21F are connected to an ammonia supply source 52 via an ammonia fuel supply pipe 51. The ammonia fuel supply pipes 51 are provided separately from the pulverized fuel supply pipe 22. In the example of Fig. 1, a plurality of ammonia fuel supply pipes 51 extend from a single ammonia supply source 52, but an ammonia supply source 52 may be provided for each ammonia fuel supply pipe 51. A detailed configuration of the burner 21 will be described later.

[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 (details will be described later), 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 sometimes collectively referred to as "superheaters 102"), reheaters 103A and 103B (hereinafter sometimes collectively referred to as "reheaters 103"), and a coal economizer 104 as heat exchangers for recovering heat from the combustion gas, and heat is exchanged between the combustion gas generated in the furnace 11 and feedwater or steam flowing 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. 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.

[0022] (Burner configuration) Next, the configuration of the burner 21 will be described with reference to Figures 2 and 3. As shown in these figures, the burner 21 includes a first nozzle 61 and a second nozzle 62. The first nozzle 61 is cylindrical and centered on the axis O. More specifically, the first nozzle 61 has a rectangular annular cross-sectional shape when viewed from the axis O. The axis O is, for example, an imaginary line extending substantially horizontally. An opening on one side of the first nozzle 61 in the axis O direction is defined as a tip opening 63. The region on the other side of the tip opening 63 in the axis O direction (i.e., the region inside the tip opening 63) is defined as a first flow path 64 through which a mixed fluid of primary air and pulverized coal flows.

[0023] The first flow path 64 is connected to the above-mentioned pulverized fuel supply pipe 22. The mixed fluid that has flowed into the first flow path 64 is ejected into the furnace 11 through the tip opening 63. Thereafter, the mixed fluid is ignited by an ignition device (not shown), and a flame extending from the tip opening 63 toward the inside of the furnace 11 is formed. In the following description, the upstream side in the flow direction of this mixed fluid may be simply referred to as the "upstream side," and the opposite side may be simply referred to as the "downstream side."

[0024] An opening serving as a secondary air outlet 66 is formed in the end face (downstream end face 65) of the first nozzle 61 facing downstream. The area upstream of the secondary air outlet 66 is a second flow path 68 through which secondary air flows. The secondary air outlet 66 has a rectangular ring shape centered on the axis O. The secondary air outlet 66 is connected to the above-mentioned air box 23. Secondary air pressurized and sent from the air box 23 is ejected from the secondary air outlet 66. By mixing the secondary air with the flame, the properties of the flame (flame temperature and flame length) are optimized.

[0025] The second nozzle 62 is provided in the first flow path 64 of the first nozzle 61. The second nozzle 62 extends in the direction of the axis O. Furthermore, the second nozzle 62 is disposed at a position overlapping the center of gravity of the rectangular tip opening 63 (i.e., on the axis O) when viewed from the direction of the axis O. An upstream end of the second nozzle 62 is connected to the ammonia fuel supply pipe 51. As a result, gaseous ammonia is ejected from the second nozzle 62 as fuel. Note that the second nozzle 62 may be configured to eject liquid ammonia.

[0026] The downstream tip 67 of the second nozzle 62 is located upstream of the tip opening 63 of the first nozzle 61 in the direction of the axis O. In other words, the tip 67 of the second nozzle 62 does not protrude from the tip opening 63 toward the furnace 11. In addition, the tip 67 is located at a position that does not overlap with the tip opening 63 in the direction of the axis O.

[0027] The cross-sectional shape of the second nozzle 62 is circular in the example of Fig. 3. However, the cross-sectional shape of the second nozzle 62 can also be rectangular, polygonal, or elliptical.

[0028] (Action and effect) In the boiler 10, when the multiple mills 31 are driven, 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). However, the oxidizing gas may have a higher or lower oxygen content than air. By adjusting the ratio of the oxygen content to the amount of fuel supplied within an appropriate range, stable combustion in the furnace 11 is achieved.

[0029] 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.

[0030] Here, in the burner 21 according to this embodiment, in addition to using the mixed fluid of pulverized coal and primary air ejected from the first nozzle 61 as fuel, it is also possible to use ammonia ejected from the second nozzle 62 as fuel. Conventionally, a plurality of burners for burning pulverized coal and ammonia have been provided independently.

[0031] However, since the total number of burners that can be installed in the furnace 11 is limited, if burners that use ammonia as fuel are installed as described above, the number of burners that use pulverized coal as fuel will be reduced. As a result, there was a problem that, for example, under circumstances where ammonia is not available, the output of the entire burners would be reduced accordingly. Therefore, the burner 21 according to this embodiment is equipped with a first nozzle 61 and a second nozzle 62 so that both pulverized coal and ammonia can be used as fuel. This makes it possible to avoid a reduction in the total output of these burners 21 when operating all burners 21 using only pulverized coal as fuel, even while ammonia can be used as fuel.

[0032] Furthermore, with the above configuration, the second nozzle 62 is located upstream of the tip opening 63 of the first nozzle 61. This prevents the cross-sectional area of ​​the tip opening 63 from being reduced by the second nozzle 62. Therefore, when pulverized coal is used as fuel, the injection velocity increases for the same primary air flow rate, preventing ignition instability. As a result, while ammonia can be used as fuel, when pulverized coal is used as fuel, the second nozzle 62 can be prevented from interfering with the flow of the pulverized coal. This prevents a decrease in output of the burner 21 when pulverized coal is used as fuel. In other words, the same flame temperature and flame length as when the second nozzle 62 is not provided can be achieved.

[0033] Furthermore, with the above configuration, by supplying secondary air ejected from the secondary air nozzles 66 to the flame formed by the mixed fluid, it is possible to optimize combustion efficiency and flame temperature. In particular, since the secondary air nozzles 66 are formed so as to surround the periphery of the tip opening 63, secondary air can be supplied evenly from the periphery of the flame. This makes the flame temperature distribution uniform, making it possible to generate high-temperature combustion gas more stably.

[0034] Furthermore, with the above configuration, the second nozzle 62 is disposed at the center of gravity (position of the axis O) in the cross section of the first nozzle 61. As a result, when ammonia is used as fuel, the secondary air ejected from the secondary air ejection port 66 surrounds the periphery of the flame formed by the ammonia. As a result, the shape and temperature of the flame can be stabilized even when ammonia is used as fuel.

[0035] In addition, according to the above configuration, the pulverized fuel supply pipe 22 and the ammonia fuel supply pipe 51 are provided independently. This allows smooth operation using only pulverized coal as fuel, operation using only ammonia as fuel, and operation using both as fuel. In addition, it is possible to smoothly and immediately switch between these three operating states.

[0036] (Other embodiments) Although the embodiments of the present disclosure have been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design modifications and the like are also included within the scope of the gist of the present disclosure. For example, in the above embodiment, an example in which only one second nozzle 62 is provided has been described. However, as shown in Figures 4 and 5, multiple second nozzles 62 may be arranged in a lattice pattern along each side of the tip opening 63 and occupying the inside thereof.

[0037] According to the above configuration, the plurality of second nozzles 62 are arranged in a lattice pattern, which makes it possible to further uniform the concentration distribution of ammonia at the tip opening 63. This makes it possible to form a flame more stably.

[0038] In the above-described embodiment, the boiler of the present invention has been described as a boiler that uses solid fuel as fuel. Examples of solid fuel that can be used in the boiler 10 include coal, biomass fuel, petroleum coke (PC) fuel, and petroleum residue. The fuel for the boiler 10 is not limited to solid fuels, but also includes petroleum fuels such as heavy oil, light oil, and heavy oil, and liquid fuels such as industrial wastewater. Also, gaseous fuels such as natural gas, various petroleum gases, and by-product gases generated in steelmaking processes can be used. Furthermore, the present invention can also be applied to a multi-fuel boiler that uses a combination of these various fuels.

[0039] <Additional Notes> The burner 21 and the boiler 10 described in each embodiment can be understood, for example, as follows.

[0040] (1) The burner 21 according to the first aspect comprises a first nozzle 61 having a cylindrical shape extending in the direction of the axis O and a tip opening 63 capable of ejecting a mixed fluid of primary air and pulverized coal, and a second nozzle 62 arranged within the first nozzle 61 so as to extend in the direction of the axis O, positioned upstream of the tip opening 63 of the first nozzle 61 in the mixed fluid, and having a tip portion 67 capable of ejecting ammonia.

[0041] According to the above configuration, the second nozzle 62 is located upstream of the tip opening 63 of the first nozzle 61. This prevents the cross-sectional area of ​​the tip opening 63 from being reduced by the second nozzle 62. Therefore, when pulverized coal is used as fuel, an increase in flow velocity is suppressed even with the same flow rate of primary air, and destabilization of ignition can be avoided.

[0042] (2) The burner 21 according to the second aspect is the burner 21 of (1), and further includes a secondary air outlet 66 that is annular and capable of ejecting secondary air, and is arranged around the tip opening 63 of the first nozzle 61.

[0043] According to the above configuration, by supplying secondary air to the flame formed by the mixed fluid, it is possible to optimize the combustion efficiency and the flame temperature.

[0044] (3) The burner 21 according to a third aspect is the burner 21 of (1) or (2), in which the second nozzle 62 is disposed at the center of gravity of the cross section of the first nozzle 61.

[0045] According to the above configuration, the second nozzle 62 is disposed at the center of gravity of the cross section of the first nozzle 61, and therefore the shape of the flame can be stabilized when ammonia is used as fuel.

[0046] (4) The burner 21 according to the fourth aspect is a burner 21 according to any one of the aspects (1) to (3), wherein the tip opening 63 of the first nozzle 61 is rectangular when viewed from the direction of the axis O, and the second nozzles 62 are arranged in a grid pattern at intervals along each side of the tip opening 63.

[0047] According to the above configuration, the plurality of second nozzles 62 are arranged in a lattice pattern, which makes it possible to uniformize the concentration distribution of ammonia at the tip opening 63. This makes it possible to form a flame more stably.

[0048] (5) The burner 21 according to the fifth aspect is the burner 21 according to any one of the aspects (1) to (4), wherein the first nozzle 61 is connected to a pulverized fuel supply pipe 22 extending from a mill 31 capable of supplying pulverized coal, and the second nozzle 62 is connected to an ammonia fuel supply pipe 51 provided separately from the pulverized fuel supply pipe 22 and capable of supplying ammonia.

[0049] According to the above configuration, since the pulverized fuel supply pipe 22 and the ammonia fuel supply pipe 51 are provided independently, operation using only pulverized coal as fuel, operation using only ammonia as fuel, and operation using both as fuel can be smoothly performed.

[0050] (6) A boiler 10 according to a sixth aspect includes the burner 21 according to any one of the aspects (1) to (5) and a furnace 11 provided with the burner 21.

[0051] According to the above configuration, it is possible to provide a boiler 10 that can use ammonia as fuel, but does not experience a decrease in output when using only pulverized coal as fuel. [Explanation of symbols]

[0052] 10...Boiler 11…Furnace 12...Combustion gas passage 13…Flute 20...Combustion device 21...Burna 22…Powdered fuel supply pipe 23...Air register 24...Air duct 31...Mill (crusher) 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 51...Ammonia fuel supply pipe 52...Ammonia source 61...Nozzle No. 1 62...Second nozzle 63...Tip opening 64...First flow path 65…Downstream end face 66...Secondary air outlet 67...Tip 68...Second flow path 101… Stove Wall 102… Superheater 102A…First Superheater 102B…Second Superheater 102C…3rd superheater 103…Reheater 103A…First Reheater 103B…Second Reheater 104…carbon saver

Claims

1. a first nozzle having a cylindrical shape extending in an axial direction and having a tip opening capable of ejecting a mixed fluid of primary air and pulverized coal; a second nozzle disposed within the first nozzle so as to extend in the axial direction and positioned upstream of a tip opening of the first nozzle in the mixed fluid direction and having a tip portion capable of ejecting ammonia; a secondary air outlet provided around the tip opening of the first nozzle, the secondary air outlet being annular and capable of ejecting secondary air; Equipped with an area upstream of the secondary air outlet is defined as a second flow path through which the secondary air flows; A burner in which the second flow passage has a flow passage cross-sectional area that decreases toward the secondary air outlet.

2. A burner as described in claim 1, wherein the secondary air outlet is located at the same position in the axial direction as the tip opening of the first nozzle.

3. 3. The burner according to claim 1, wherein the second nozzle is disposed at a center of gravity in a cross section of the first nozzle.

4. A burner as described in any one of claims 1 to 3, wherein the tip opening of the first nozzle is rectangular when viewed from the axial direction, and the second nozzles are arranged in a lattice pattern with intervals along each side of the tip opening.

5. The burner according to any one of claims 1 to 4, wherein the first nozzle is connected to a pulverized fuel supply pipe extending from a mill capable of supplying pulverized coal, and the second nozzle is connected to an ammonia fuel supply pipe provided separately from the pulverized fuel supply pipe and capable of supplying ammonia.

6. A burner according to any one of claims 1 to 5, a furnace provided with the burner; A boiler equipped with

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