Burner and its maintenance method

Abstract

The present invention provides a burner that can suppress the uneven distribution of fuel and oxidizing gases in each of the flow paths divided by partition plates, thereby achieving a good combustion state. [Solution] The burner comprises a fuel nozzle body 21-2a that defines an internal passage through which a fuel gas, a mixture of fine fuel and air, flows and injects the fuel gas into the furnace, and a partition plate 21-2b provided in the internal passage of the fuel nozzle body 21-2a that divides the internal passage. The fuel nozzle body 21-2a is shaped such that the internal passage is inclined along the downstream axis CL2 with respect to the upstream axis CL1, and the partition plate 21-2b is shaped such that the ratio of the upstream division cross-sectional area of ​​the internal passage divided at the upstream end corresponding to the upstream axis CL1 is equal to the ratio of the downstream division cross-sectional area of ​​the internal passage divided at the downstream end corresponding to the downstream axis.

Description

Technical Field

[0001] The present disclosure relates to a burner and a maintenance method thereof.

Background Art

[0002] Large boilers such as power generation boilers have a furnace installed vertically with a hollow shape, and a plurality of burners are arranged along the circumferential direction of the furnace on the furnace wall. Further, a flue is connected above the furnace in the vertical direction of the large boiler, and a heat exchanger for generating steam is arranged in this flue. Then, a flame is formed by the burner injecting a mixture of fuel and air (oxidizing gas) into the furnace, combustion gas is generated and flows into the flue. A heat exchanger is installed in the region where the combustion gas flows, and water or steam flowing in the heat transfer tubes constituting the heat exchanger is heated to generate superheated steam.

[0003] The burner has, for example, a fuel nozzle at its tip as shown in Patent Document 1. Inside the fuel nozzle, there is a partition plate that divides the flow path through which a fuel gas in which fuel (pulverized coal) and oxidizing gas (air) are mixed flows. The flow of the fuel gas is rectified by the partition plate.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The burner may be provided with a rotation mechanism that can control the injection direction by rotating the fuel nozzle in the vertical direction. The advantages of this rotation mechanism are as follows. 1. By operating the positional relationship between the heat transfer surface of the boiler and the flame, the steam temperature characteristics can be controlled. 2. By manipulating the fuel injection position, the residence time in the reactor is adjusted, improving the combustibility of various fuels.

[0006] The baffle plate is installed horizontally with the fuel nozzle, and is designed so that the height of the partitioned passage is uniform when viewed from the fuel nozzle inlet side. When the fuel nozzle angle is rotated, the baffle plate rotates in accordance with the fuel nozzle.

[0007] Regarding point 1 above, it can be replaced by gas recirculation (GR), and regarding point 2 above, it can be predicted to some extent from the properties of the coal. For this reason, burners without a rotating mechanism are sometimes used, in which case the fuel nozzle is used at a fixed angle.

[0008] When the nozzle angle is fixed, the fuel nozzle is usually installed horizontally. However, for example, in the case of high-fuel-ratio coal (coal with a high ratio of fixed carbon to volatile content), a downward orientation is adopted. In a burner with a fixed downward nozzle angle, the fuel nozzle is angled so that it bends into a V-shape midway. If a horizontal partition plate is then tilted along the slope of the fuel nozzle, unevenness in the flow path height will occur at the fuel nozzle inlet. Uneven flow path height can lead to uneven distribution of fuel and air, potentially worsening combustion performance.

[0009] This disclosure has been made in view of these circumstances and aims to provide a burner and a maintenance method thereof that can suppress the uneven distribution of fuel and oxidizing gases in each flow path divided by a partition plate, thereby achieving a good combustion state. [Means for solving the problem]

[0010] A burner according to one aspect of the present disclosure comprises a fuel nozzle body that determines an internal passage through which a fuel gas, a mixture of fuel and an oxidizing gas, flows and injects the fuel gas into a furnace, and a partition plate provided in the internal passage of the fuel nozzle body and dividing the internal passage, wherein the fuel nozzle body has a shape in which the downstream axis of the internal passage is inclined with respect to the upstream axis, and the partition plate has a shape in which the upstream division cross-sectional area of ​​the internal passage divided at the upstream end corresponding to the upstream axis is equal to the downstream division cross-sectional area of ​​the internal passage divided at the downstream end corresponding to the downstream axis.

[0011] A burner maintenance method according to one aspect of the present disclosure is the above-described burner maintenance method, wherein the block is removed from the downstream end of the fuel nozzle body such that the notch does not come into contact with the wall of the fuel nozzle body. [Effects of the Invention]

[0012] The partition plate helps to suppress uneven distribution of fuel and oxidizing gases in each of the divided flow paths, thereby achieving a good combustion state. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram showing a boiler using the burner of this disclosure. [Figure 2] This is a longitudinal cross-sectional view of the burner from the side. [Figure 3] This is a cross-sectional view of the burner in a plan view. [Figure 4] This is a front view showing the fuel nozzle of the burner. [Figure 5] Figure 2 is a magnified longitudinal cross-sectional view of the fuel nozzle. [Figure 6] Figure 5 is a longitudinal cross-sectional view showing the state in which each block of the fuel nozzle has been removed. [Figure 7] This is a vertical cross-sectional view showing an enlarged view of the upper block in Figure 6. [Figure 8] This is a cross-sectional view of a burner equipped with a splitter but without a flame holder, viewed from above. [Figure 9] A longitudinal sectional view showing a side view of a fuel nozzle showing a modified example of a partition plate.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, an embodiment according to the present disclosure will be described with reference to the drawings. Note that the present disclosure is not limited by this embodiment, and when there are multiple embodiments, those configured by combining each embodiment are also included. In the following description, "up" and "above" indicate the upper side in the vertical direction, and "down" and "below" indicate the lower side in the vertical direction. The vertical direction is not strict and includes errors.

[0015] FIG. 1 shows a boiler 10 that uses solid fuel as the main fuel in this embodiment.

[0016] The boiler 10 is a boiler capable of burning pulverized fuel obtained by pulverizing solid fuel with a burner and generating superheated steam by exchanging heat between the heat generated by this combustion and feed water or steam. As the solid fuel, biomass fuel, coal, etc. are used.

[0017] The boiler 10 has a furnace 11, a combustion device 20, and a combustion gas passage 12. The furnace 11 has a hollow shape of a square cylinder and is installed along the vertical direction. The furnace wall 101 that constitutes 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 to each other, and recovers the heat generated by the combustion of the pulverized fuel by exchanging heat with the water or steam flowing inside the heat transfer tubes, while suppressing the temperature rise of the furnace wall 101.

[0018] The combustion device 20 is installed in the lower region of the furnace 11. In the present embodiment, the combustion device 20 has a plurality of burners 21A, 21B, 21C, 21D, 21E, 21F (hereinafter sometimes collectively referred to as "burner 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 a square furnace 11) as a set, and are arranged in a plurality of stages along the vertical direction. In FIG. 1, for the sake of illustration, only two of the burners in one set are shown, and each set is labeled 21A, 21B, 21C, 21D, 21E, 21F. The shape of the furnace, the number of stages of the burners, the number of burners in one stage, the arrangement of the burners, etc. are not limited to this embodiment.

[0019] The burners 21A, 21B, 21C, 21D, 21E, 21F are each connected to a plurality of mills (pulverizers) 31A, 31B, 31C, 31D, 31E, 31F (hereinafter sometimes collectively referred to as "mill 31") via a plurality of pulverized fuel supply pipes 22A, 22B, 22C, 22D, 22E, 22F (hereinafter sometimes collectively referred to as "pulverized fuel supply pipe 22"). The mill 31 pulverizes solid fuel into pulverized fuel. For example, a pulverizing table (not shown) is supported inside the mill 31 so as to be rotatable, and a plurality of pulverizing rollers (not shown) are supported above the pulverizing table so as to be rotatable in conjunction with the rotation of the pulverizing table. It is a vertical roller mill configured in this way. The solid fuel pulverized by the cooperation of the pulverizing roller and the pulverizing table is conveyed to a classifier (not shown) provided in the mill 31 by primary air (transport gas, oxidizing gas) supplied to the mill 31. In the classifier, the pulverized solid fuel is classified into pulverized fuel having a particle size suitable for combustion in the burner 21 and coarse pulverized fuel having a particle size larger than the above particle size. The pulverized fuel that has passed through the classifier is supplied to the burner 21 through the pulverized fuel supply pipe 22 together with the primary air. The coarse pulverized fuel that has not passed through the classifier falls onto the pulverizing table inside the mill 31 due to its own weight and is pulverized again.

[0020] Furthermore, above the mounting position of the burner 21 in the furnace 11, a number of additional air ports (AA ports) 25 are provided to supply additional combustion air (AA) into the furnace 11. The ends of additional air ducts (AA ducts) 26, which branch off from the air duct 24, are connected to the additional air ports 25, and a portion of the air supplied from the forced draft fan 32 can be supplied to the additional air ports 25 as additional combustion air via the additional air ducts 26.

[0021] An air register 23 is provided on the outside of the furnace 11 where the burner 21 is installed, and one end of an air duct 24 is connected to this 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 as secondary air (combustion air, oxidizing gas) via the air register 23 and introduced into the furnace 11.

[0022] The combustion gas passage 12 is connected to the upper vertical part of the furnace 11. The combustion gas passage 12 is equipped with superheaters 102A, 102B, 102C (hereinafter sometimes collectively referred to as "superheater 102"), reheaters 103A, 103B (hereinafter sometimes collectively referred to as "reheater 103"), and an economizer 104 as heat exchangers for recovering heat from the combustion gas. Heat exchange takes place between the combustion gas generated in the furnace 11 and the feedwater or steam circulating inside each heat exchanger. Note that the arrangement and shape of each heat exchanger are not limited to the configuration shown in Figure 1.

[0023] Downstream of the combustion gas passage 12 is a flue 13 through which the combustion gas, whose heat has been recovered by the heat exchanger, is discharged. An air preheater (air heater) 42 is installed between the flue 13 and the air duct 24, and heat exchange takes place between the air flowing through the air duct 24 and the combustion gas flowing through the flue 13. By heating the primary air supplied to the mill 31 and the secondary air supplied to the burner 21, heat is further recovered from the combustion gas after heat exchange with water or steam.

[0024] Furthermore, a denitrification device 43 may be provided in the flue 13 at a position upstream of the air preheater 42. The denitrification device 43 supplies a reducing agent, such as ammonia or urea solution, which has the effect of reducing nitrogen oxides, to the combustion gas flowing through the flue 13. The reaction between the nitrogen oxides (NOx) in the combustion gas to which the reducing agent has been supplied and the reducing agent is promoted by the catalytic action of a denitrification catalyst installed in the denitrification device 43, thereby removing and reducing nitrogen oxides in the combustion gas.

[0025] A gas duct 41 is connected downstream of the air preheater 42 in the flue 13. The gas duct 41 is equipped with dust collection devices 44, such as an electrostatic precipitator, to remove ash and other particles from the combustion gas, and environmental devices such as a desulfurization device 46 to remove sulfur oxides, as well as an induced draft fan (IDF) 45 to guide the exhaust gas to these environmental devices. The downstream end of the gas duct 41 is connected to the chimney 47, and the combustion gas treated by the environmental devices is discharged outside the system as exhaust gas.

[0026] In the boiler 10, when multiple mills 31 are driven, the crushed and classified pulverized fuel is supplied to the burner 21 via the pulverized fuel supply pipe 22 along with primary air. Secondary air heated by the air preheater 42 is also supplied to the burner 21 via the wind duct 24 and 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. The flame is formed in the lower region of the furnace 11, and the high-temperature combustion gas rises inside 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 a gas with a higher or lower oxygen content than air may also be used, and stable combustion in the furnace 11 can be achieved by adjusting the ratio of oxygen to the supplied fuel amount to an appropriate range.

[0027] The combustion gas flowing into the combustion gas passage 12 undergoes heat exchange with water and steam in the superheater 102, reheater 103, and economizer 104 located inside the combustion gas passage 12, before being discharged into the flue 13. There, nitrogen oxides are removed in the denitrification device 43, and after heat exchange with primary and secondary air in the air preheater 42, it is further discharged into the gas duct 41. Ash and other contaminants are removed in the dust collector 44, and sulfur oxides are removed in the desulfurization device 46 before being discharged out of the system through the chimney 47. Note that the arrangement of each heat exchanger in the combustion gas passage 12 and each device from the flue 13 to the gas duct 41 does not necessarily have to be in the order described above with respect to the combustion gas flow.

[0028] In the embodiments described above, the boiler of this disclosure was described as a boiler that uses solid fuel. Examples of solid fuels used in the boiler include coal, biomass fuel, petroleum coke (PC) fuel, and petroleum residue. Furthermore, boiler fuels are not limited to solid fuels; liquid fuels such as heavy oil, light oil, heavy crude oil, and other petroleum products, as well as industrial wastewater and liquefied ammonia, can also be used. Gaseous fuels such as natural gas, various petroleum gases, by-product gases generated in steelmaking processes, hydrogen gas, and ammonia gas can also be used. Moreover, this technology can be applied to co-firing boilers that use a combination of these various fuels.

[0029] Figure 2 shows a longitudinal section of the burner 21 viewed from the side. In this figure, the left side shows the internal FI (furnace filtration) and the right side shows the external FO (furnace filtration).

[0030] The burner 21 comprises a burner body 21-1, a fuel nozzle 21-2 connected to the tip of the burner body 21-1, and combustion air nozzles 21-3 provided around the fuel nozzles 21-2. Air is supplied to the combustion air nozzles 21-3 from the wind box 23 (see Figure 1).

[0031] The burner body 21-1 is connected to the fine fuel supply pipe 22 (see Figure 1), and fuel gas, which is a solid-gas mixed fluid of fine fuel (fuel) and primary air (oxidizing gas), flows through its interior. The burner body 21-1 extends in a substantially straight line along the axis CL1. The axis CL1 passes through the center of the burner body 21-1 in the vertical direction, as shown in Figure 2, and also through the center in the width direction, as shown in Figure 3.

[0032] The fuel nozzle 21-2 is connected to the tip of the burner body 21-1 and injects fuel gas, consisting of pulverized fuel and primary air, towards the reactor FI. As shown in Figure 4, the fuel nozzle 21-2 is equipped with a fuel nozzle body 21-2a as a wall that defines the internal flow path. As shown in Figure 4, the fuel nozzle body 21-2a is rectangular when viewed from the front. A partition plate 21-2b and a splitter 21-2c are provided inside the fuel nozzle body 21-2a to partition the internal flow path.

[0033] The partition plates 21-2b are horizontally mounted plate-like bodies, and two are provided, one above the other. Each partition plate 21-2b evenly divides the space of the fuel nozzle 21-2 in the vertical direction. Note that the number of partition plates 21-2b is not limited to the two shown in Figure 4, but may be one or three or more.

[0034] The splitters 21-2c extend vertically in the up-and-down direction and are installed at equal intervals. Each splitter 21-2c evenly divides the space of the fuel nozzle 21-2 in the horizontal direction. However, the number of rows of splitters 21-2c is not limited to the three rows shown in Figure 4; it may be two or fewer rows, or four or more rows.

[0035] Each splitter 21-2c is equipped with a wedge-shaped flame holder 21-2c1 that widens from the upstream side to the downstream side (see, for example, Figure 3).

[0036] Figure 5 shows a magnified view of the fuel nozzle 21-2 shown in Figure 2. As shown in the figure, the fuel nozzle 21-2 is formed along the axis (upstream axis) CL1 on the upstream side (inlet side) and along the axis (downstream axis) CL2 on the downstream side (outlet side). The downstream axis CL2 is set at a predetermined angle downward relative to the upstream axis CL1. Specifically, axes CL1 and CL2 intersect at intersection point A and form an angle θ with each other. Axes CL1 and CL2 coincide when viewed from above (as in Figure 3).

[0037] As shown in Figure 5, a bent surface P is defined that passes through intersection A and bends in the direction of the downstream axis CL2 relative to the upstream axis CL1. The bent surface P corresponds to the flow path cross-section of the internal flow path that flows through the fuel nozzle body 21-2a.

[0038] The wall portion of the fuel nozzle body 21-2a is bent at the intersection line B where the bent surface P and the fuel nozzle body 21-2a intersect. That is, the upper and lower wall portions of the fuel nozzle body 21-2a are each bent into a V-shape. The bending angle is equivalent to the angle θ between axis CL1 and axis CL2.

[0039] The partition plates 21-2b are bent at the intersection line C where the bending surface P and each partition plate 21-2b intersect. That is, the upper and lower partition plates 21-2b are each bent into a V-shape. The bending angle is equal to the angle θ between axis CL1 and axis CL2.

[0040] As described above, the upper and lower walls of the fuel nozzle body 21-2a and each partition plate 21-2b are bent at the same angle θ at the intersection lines B and C, respectively. Therefore, the fuel nozzle body 21-2a has a bent shape that corresponds to an inclined state where the downstream axis CL2 is inclined with respect to the upstream axis CL1. The partition plates 21-2b have a bent shape that corresponds to the bent shape of the fuel nozzle body 21-2a. As a result, the ratio of the areas of the internal flow channels divided into three sections vertically by each partition plate 21-2b is equal. That is, the ratio of the heights of the three divided flow channels divided at the upstream end of the partition plate 21-2b, H1a:H1b:H1c, is equal to the ratio of the heights of the three divided flow channels divided at the downstream end of the partition plate 21-2b, H2a:H2b:H2c. Alternatively, the cross-sectional areas of each upstream divided section and each downstream divided section divided by the partition plate 21-2b may be made equal.

[0041] As shown in Figure 4, the splitter 21-2c has a structure that is divided into upper and lower halves by a central dividing surface D. As a result, as shown in Figure 6, an upper block BL1 is formed by integrating the upper partition plate 21-2b and the splitter 21-2c, and a lower block BL2 is formed by integrating the lower upper partition plate 21-2b and the splitter 21-2c. The upper block BL1 and the lower block BL2 can be separated and removed from the fuel nozzle body 21-2a during maintenance. Specifically, the upper block BL1 and the lower block BL2 can be accessed from the downstream end (outlet end) of the fuel nozzle 21-2 and removed in the direction of arrow E toward the downstream side.

[0042] As shown in Figure 7, the upper block BL1 has a notch 50 formed at its upper end. The notch 50 is shaped as a cutout on the upstream side of the upper bracket 52, which is located at the very top of the upper block BL1. The upper bracket 52 supports the upper end of the splitter 21-2c. Specifically, the notch 50 is cut out so that the thickness T2 of the upstream end is smaller than the thickness T1 of the downstream end of the upper bracket 52. As a result, as shown in Figure 6, when the upper block BL1 is pulled out in the direction of arrow E, the downstream end of the upper bracket 52 of the upper block BL1 does not interfere with the downstream end which is bent downwards on the upper wall of the fuel nozzle body 21-2a. This allows the upper block BL1 to be easily removed during maintenance.

[0043] The effects and advantages of this embodiment, as described above, are as follows. Even when the internal flow path of the fuel nozzle body 21-2a is shaped such that the downstream axis CL2 is inclined relative to the upstream axis CL1, the ratio of the upstream divided cross-sectional area to the downstream divided cross-sectional area separated by the partition plate 21-2b is made equal. This suppresses uneven distribution of fine fuel and air in each flow path separated by the partition plate 21-2b, thereby achieving a good combustion state.

[0044] The partition plate 21-2b was bent to match the curved shape of the fuel nozzle body 21-2a. This made it possible to create divided flow paths with equivalent flow path cross-sectional areas along the flow path through the partition plate 21-2b, thereby further suppressing the uneven distribution of fine fuel and air.

[0045] Since the fuel nozzle body 21-2a has a bent shape in which the downstream axis CL2 is inclined with respect to the upstream axis CL1, there is a risk of interference with the downstream side of the upper wall of the fuel nozzle body 21-2a when removing the upper block BL1 equipped with the partition plate 21-2b from the downstream end of the fuel nozzle body 21-2a during maintenance. Therefore, a notch 50 is provided in the upper block BL1 to avoid interference with the wall of the fuel nozzle body 21-2a. This makes it possible to easily remove the upper block BL1 from the fuel nozzle body 21-2a while avoiding interference with the wall of the fuel nozzle body 21-2a.

[0046] In the embodiment described above, a wedge-shaped flame holder 21-2c1 is provided as the splitter 21-2c as shown in Figure 3, but the wedge-shaped flame holder may be omitted as shown in Figure 8. Therefore, in the configuration shown in Figure 8, the splitter 21-2c is simply a plate-like body.

[0047] Furthermore, in this embodiment, the shape of the partition plate 21-2b is bent into a V-shape to correspond to the curved shape of the fuel nozzle body 21-2a, but this disclosure is not limited thereto. It is sufficient that the upstream and downstream divided cross-sectional areas separated by the partition plate 21-2b are equal, and the flow path cross-sectional area of ​​the partition plate 21-2b along the flow direction may change. For example, as shown in Figure 9, the partition plate 21-2b may be a flat plate, or it may be a curved shape, although this is not shown.

[0048] Furthermore, it is preferable that the cross-sectional area at the upstream end and the cross-sectional area at the downstream end of the secondary air passage defined by the combustion air nozzle 21-3 be equal. This suppresses uneven distribution of combustion air and allows for a good combustion state to be obtained.

[0049] The burners and their maintenance methods described in each of the embodiments described above can be understood, for example, as follows.

[0050] A burner (21) according to a first aspect of the present disclosure comprises a fuel nozzle body (21-2a) that defines an internal passage through which a fuel gas, a mixture of fuel and an oxidizing gas, flows and injects the fuel gas into a furnace, and a partition plate (21-2b) provided in the internal passage of the fuel nozzle body and dividing the internal passage, wherein the fuel nozzle body (21-2a) has a shape in which the internal passage is inclined along the downstream axis (CL2) with respect to the upstream axis (CL1), and the partition plate (21-2b) has a shape such that the ratio of the upstream division cross-sectional area of ​​the internal passage divided at the upstream end corresponding to the upstream axis (CL1) is equal to the ratio of the downstream division cross-sectional area of ​​the internal passage divided at the downstream end corresponding to the downstream axis.

[0051] Even when the internal flow path of the fuel nozzle body is shaped such that the downstream axis is inclined relative to the upstream axis, the ratio of the upstream divided cross-sectional area to the downstream divided cross-sectional area, separated by the partition plate, is kept equal. This suppresses the uneven distribution of fuel and oxidizing gases in each of the flow paths separated by the partition plate, thereby achieving a good combustion state.

[0052] In the second aspect of the present disclosure, the burner (21) is such that, in the first aspect, the fuel nozzle body (21-2a) has a bent shape corresponding to an inclined state in which the downstream axis (CL2) is inclined with respect to the upstream axis (CL1), and the partition plate (21-2b) has a bent shape corresponding to the bent shape of the fuel nozzle body (21-2a).

[0053] The partition plate is bent to match the curved shape of the fuel nozzle body. This allows for the creation of divided flow paths with equivalent flow path cross-sectional areas along the flow path through the partition plate, thereby further suppressing the uneven distribution of fuel and oxidizing gases. For example, the fuel nozzle body and partition plate are bent in a V-shape.

[0054] A burner (21) according to a third aspect of the present disclosure comprises, in the first or second aspect, the partition plate (21-2b) and a block (BL1) housed in the internal flow path, wherein the block (BL1) is provided with a notch (50) to avoid interference with the wall portion of the fuel nozzle body (21-2a) when removed from the downstream end of the fuel nozzle body (21-2a).

[0055] Because the downstream axis of the fuel nozzle body is inclined relative to the upstream axis (for example, a bent shape), there is a risk of interference with the wall of the fuel nozzle body when removing the block containing the partition plate from the downstream end of the fuel nozzle body during maintenance. Therefore, a notch has been provided in the block to avoid interference with the wall of the fuel nozzle body. This allows the block to be easily removed from the fuel nozzle body while avoiding interference with the wall of the fuel nozzle body.

[0056] A maintenance method for a burner (21) according to a first aspect of this disclosure is a maintenance method for a burner according to the third aspect, wherein the block (BL1) is removed from the downstream end of the fuel nozzle body (21-2a) such that the notch (50) does not come into contact with the wall portion of the fuel nozzle body (21-2a). [Explanation of Symbols]

[0057] 10 Boilers 11 Furnace 12 Combustion gas passage 13 Flue 20 Combustion device 21 Burner 21-1 Burner body 21-2 Fuel Nozzle 21-2a Fuel nozzle body 21-2b Partition Plate 21-2c Splitter 21-2c1 Flame holder 21-3 Combustion air nozzle 22 Fine fuel supply pipe 23. Air register 24. Air ducts 25 Additional Air Ports 26 Additional air ducts 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 Notches 52 Upper bracket BL1 Upper Block BL2 Lower Block CL1 axis Inside the FI furnace FO outside the furnace

Claims

1. A fuel nozzle body defines an internal passage through which a fuel gas, a mixture of fuel and an oxidizing gas, flows, and injects the fuel gas into the furnace. A partition plate is provided in the internal passage of the fuel nozzle body, which divides the internal passage, Equipped with, The fuel nozzle body is shaped such that the internal flow path is inclined along its downstream axis with respect to its upstream axis. The burner is shaped such that the ratio of the upstream division cross-sectional areas of the internal flow channels divided at the upstream end corresponding to the upstream axis is equal to the ratio of the downstream division cross-sectional areas of the internal flow channels divided at the downstream end corresponding to the downstream axis.

2. The fuel nozzle body has a bent shape that corresponds to an inclined state in which the downstream axis is inclined with respect to the upstream axis. The burner according to claim 1, wherein the partition plate has a curved shape corresponding to the curved shape of the fuel nozzle body.

3. The partition plate is provided and the block is housed in the internal flow path, The burner according to claim 1 or 2, wherein the block is provided with a notch to avoid interference with the wall portion of the fuel nozzle body when removed from the downstream end of the fuel nozzle body.

4. A method for maintaining a burner as described in claim 3, A burner maintenance method comprising removing the block from the downstream end of the fuel nozzle body so that the notch does not come into contact with the wall of the fuel nozzle body.

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