JP2023160353A - Pulverulent fuel burner - Google Patents

Abstract

To provide a pulverulent fuel burner that can improve ignitability even if a fire-retardant pulverulent fuel such as a petroleum residue fuel is directly supplied from a pulverizer.SOLUTION: A pulverulent fuel burner is installed in a combustion chamber of a boiler, and comprises: a cylindrical air-fuel mixture conveying pipe 51 through which an air-fuel mixture made by mixing a pulverulent fuel and conveying air is conveyed, and for injecting the air-fuel mixture into the combustion chamber from a tip; a turning blade 64 installed at the tip of the air-fuel mixture conveying pipe 51; a rod-like central flow inhibition part 62 installed on a central axis 5a of the air-fuel mixture conveying pipe 51 upstream of the turning blade 64A in the conveying direction of the air-fuel mixture, and comprising a cylindrical surface 62a extending in the direction of the central axis concentrically with the air-fuel mixture conveying pipe 51; and a cylindrical surrounding flow inhibition part 63 installed along an inner wall surface 51s of the air-fuel mixture conveying pipe 51 between the central flow inhibition part 62 and the turning blade 64, and comprising a cylindrical inner peripheral surface 63a extending in the direction of the central axis concentrically with the air-fuel mixture conveying pipe 51.SELECTED DRAWING: Figure 5

Description

The present disclosure relates to a powdered fuel burner used in boilers and the like.

An example of a pulverized fuel burner (hereinafter also simply referred to as a "burner") that is used in a boiler or the like and burns pulverized fuel is the pulverized coal combustion apparatus described in Patent Document 1, for example. This pulverized coal combustion device uses a cylindrical body as a pulverized coal passage, a secondary air passage and a tertiary air passage are provided surrounding the cylindrical body, and one or more venturi parts are provided within the cylindrical body. .

Japanese Unexamined Patent Publication No. 58-224207

As mentioned above, when using pulverized coal as fuel, a direct combustion method is adopted in which the pulverized coal is pulverized by a pulverizer and mixed with conveying air, and this mixture is supplied directly from the pulverizer to the burner. ing.

In recent years, it has been considered to use petroleum residues such as petroleum coke as fuel. Since petroleum residue fuel contains a large amount of fixed carbon, it is a flame-retardant powder fuel that is less combustible than pulverized coal. In order to obtain good ignitability of flame-retardant powdered fuel such as petroleum residue fuel, the air-fuel ratio of the mixture supplied from the burner to the combustion chamber of the boiler (A/F) It is necessary to make the air amount [Nm ³ /h]/fuel flow rate [t/h] smaller than in the case of pulverized coal.

However, although the A/F of the air-fuel mixture supplied from a conventional crusher is suitable for pulverized coal, it is not suitable for flame-retardant pulverized fuel. Therefore, we installed a storage tank between the crusher and the burner to separate the air-fuel mixture into solid gas and temporarily store the powdered fuel, creating an A/F suitable for flame-retardant powdered fuel. A conceivable configuration is an indirect combustion method in which a mixture of powdered fuel sent from a storage tank and conveying air is generated and supplied to a burner. In the case of such an indirect combustion method, additional equipment such as a solid-gas separator and a storage tank is required compared to the case of a direct combustion method, and an increase in equipment cost is unavoidable.

The present disclosure has been made in order to solve the above problems, and provides a powder that can improve ignitability even when flame-retardant powder fuel such as petroleum residue fuel is supplied directly from a crusher. The purpose is to provide a fuel burner of the type.

In order to achieve the above object, a powdered fuel burner according to an aspect of the present disclosure is a powdered fuel burner that is installed in a combustion chamber of a boiler, and which generates a mixture of powdered fuel and conveying air. a cylindrical mixture conveying pipe through which the air-fuel mixture is conveyed and injects the mixture from its tip into the combustion chamber; a swirling vane installed at the tip of the mixture conveying pipe; a rod-shaped central flow inhibiting part installed on the central axis of the mixture conveying pipe on the upstream side and having a cylindrical surface concentric with the mixture conveying pipe and extending in the direction of the central axis; a cylindrical peripheral flow installed along the inner wall surface of the mixture transfer pipe between the swirling vane and having a cylindrical inner peripheral surface concentric with the mixture transfer pipe and extending in the central axis direction; It is equipped with an inhibiting part.

The present disclosure provides a powdered fuel burner having the configuration described above and capable of improving ignitability even when flame-retardant powdered fuel such as petroleum residue fuel is directly supplied from a pulverizer. It has the effect of being able to

FIG. 1 is a schematic diagram showing an example of a combustion system including a boiler equipped with a powdered fuel burner according to the present embodiment. FIG. 2 is a schematic cross-sectional view showing an example of the powdered fuel burner according to the present embodiment. FIG. 3 is a sectional view taken along line AA in FIG. FIG. 4 is a diagram showing an example of the swirl vane viewed from the base end side of the air-fuel mixture conveying pipe. FIG. 5 is a schematic cross-sectional view showing the main parts of a powdered fuel burner using another swirl vane. FIG. 6 is a schematic cross-sectional view showing the main parts of a powdered fuel burner using another swirl vane.

Hereinafter, preferred embodiments of the present disclosure will be described with reference to the drawings. In addition, below, the same reference numerals are given to the same or equivalent element throughout all the drawings, and the overlapping explanation will be omitted. In addition, the drawings schematically show each component for ease of understanding, and the shapes, dimensional ratios, etc. may not be accurately shown.

(Embodiment)
FIG. 1 is a schematic diagram showing an example of a combustion system including a boiler equipped with a powdered fuel burner according to the present embodiment.

The combustion system shown in FIG. 1 includes a fuel supply device 20 and a boiler 100. The fuel supply device 20 includes a fuel storage tank 21, a metering feeder 22, and a crusher 23. The fuel storage tank 21 stores a flame-retardant fuel such as petroleum residue such as petroleum coke. The fuel stored in the fuel storage tank 21 is supplied to a metering feeder 22, and a predetermined weight of fuel is supplied from the metering feeder 22 to a crusher 23. The pulverizer 23 pulverizes the fuel supplied from the metering feeder 22 into powder, and supplies a mixture of the pulverized fuel and transport air to the pulverized fuel burner 5 of the boiler 100 . The air-fuel ratio A/F of the air-fuel mixture supplied from the crusher 23 to the powdered fuel burner 5 is about 1.8.

The boiler 100 is configured as an inverted vertical furnace. The boiler 100 includes a combustion chamber 1 formed in a cylindrical shape with a rectangular cross section, for example, and a flue 12 connected to the combustion chamber 1 via a gas outlet 11.

The combustion chamber 1 includes a high-temperature reduction combustion chamber 2 formed at the upper end, a low-temperature oxidation combustion chamber 3 formed below the high-temperature reduction combustion chamber 2, and a high-temperature reduction combustion chamber 2 and a low-temperature oxidation combustion chamber 3 mutually connected to each other. It has a connecting constriction part 4. The throttle part 4 is a flow path whose horizontal cross-sectional area is reduced by 20 to 50% compared to other parts of the combustion chamber 1.

The walls of the high-temperature reduction combustion chamber 2 are covered with a refractory material 6 that can withstand a predetermined high temperature inside the furnace. A plurality of powdered fuel burners 5 are arranged on each of two opposing side walls of the high temperature reduction combustion chamber 2 . In this example, eight powdered fuel burners 5 are provided. The eight burners 5 are arranged so that their flame axes do not directly oppose each other and are parallel to each other. In the high-temperature reducing combustion chamber 2, fuel supplied from the burner 5 is initially combusted in a high-temperature reducing atmosphere. The combustion gas generated here is pushed out from the high temperature reduction combustion chamber 2 and flows down through the throttle part 4 to the low temperature oxidation combustion chamber 3 because the combustion gas is increased by the newly supplied fuel.

The side wall of the low-temperature oxidation combustion chamber 3 has a water-cooled wall structure, and the high-temperature combustion gas flowing down from the high-temperature reduction combustion chamber 2 through the throttle section 4 is cooled. In the low-temperature oxidation combustion chamber 3, a plurality of air nozzles 7 for supplying air for two-stage combustion are arranged in a single stage or in multiple stages on a furnace wall spaced downward from the throttle part 4. In a two-stage combustion region 10 below the air nozzle 7, unburned gas in the combustion gas is subjected to two-stage combustion in a low-temperature oxidizing atmosphere by air supplied from the air nozzle 7. The combustion ash accumulated at the bottom of the furnace is discharged from the ash outlet 8 to the outside of the furnace.

A gas outlet 11 communicating with a flue 12 is provided on the lower side of the two-stage combustion region 10 . The combustion gas generated in the two-stage combustion region 10 reverses its flow in a U-shape and flows into the flue 12. The flue 12 is provided with a steam superheater tube 13 and an economizer 14. The combustion gas that has flowed into the flue 12 exchanges heat with boiler water in the steam superheater tube 13 and economizer 14, and is then supplied to a post-treatment process. Further, the combustion ash accompanying the combustion gas is discharged from the ash discharge port 15.

In this boiler 100, the fuel supplied from the powdered fuel burner 5 is initially combusted in a high-temperature reducing atmosphere in the high-temperature reducing combustion chamber 2, and then subjected to two-stage combustion in a low-temperature oxidizing atmosphere in the low-temperature oxidizing combustion chamber 3. The amount of NOx generated is reduced.

FIG. 2 is a schematic cross-sectional view showing an example of the powdered fuel burner 5 according to this embodiment. FIG. 3 is a sectional view taken along line AA in FIG.

The powdered fuel burner 5 shown in FIG. 2 includes a cylindrical air-fuel mixture conveying pipe 51 and a wind box 52 through which the air-fuel mixture supplied from the crusher 23 is conveyed. The wind box 52 includes a secondary air supply path 53 that supplies secondary air to the high temperature reduction combustion chamber 2 and a tertiary air supply path 54 that supplies tertiary air swirled by the swirling vane 55 to the high temperature reduction combustion chamber 2. It is equipped with That is, the air-fuel mixture is injected from the tip of the air-fuel mixture transfer pipe 51 to the high-temperature reduction combustion chamber 2, and secondary air and tertiary air, which are combustion air, are injected into the high-temperature reduction combustion chamber 2 from around the tip of the air-fuel mixture transfer pipe 51. supplied to

Furthermore, a flame stabilizing plate 51 a is provided at the tip of the mixture transport pipe 51 so as to be integrated with the mixture transport pipe 51 . A swirl vane 64 and a short inner cylinder 65 are installed at the tip of the mixture conveying pipe 51. The base end of the mixture conveying pipe 51 is connected to a mixture supply pipe 57 through which the mixture from the crusher 23 is supplied via an elbow pipe 58 . Further, an ignition burner 61 consisting of a gun-type heavy oil burner or a gas burner is arranged on the central axis 5a of the air-fuel mixture conveying pipe 51.

The swirl vane 64 is fixed near the tip of the ignition burner 61. FIG. 4 is a diagram showing an example of the swirling vane 64 viewed from the base end side of the air-fuel mixture conveying pipe 51. The swirling blade 64 is a well-known type including a cylindrical portion 64a attached to the ignition burner 61 and a plurality of flat blades 64b, and is arranged inside the inner cylinder 65. The inner cylinder 65 is installed inside the air-fuel mixture transport pipe 51 and concentrically with the air-fuel mixture transport pipe 51 . The plurality of blades 64b are attached to the outer peripheral surface of the cylindrical portion 64a at equal intervals and at a predetermined angle with respect to the center line of the cylindrical portion 64a. The center line of the cylindrical portion 64a is the same as the central axis 5a, and the cylindrical portion 64a is installed concentrically with the air-fuel mixture conveying pipe 51.

In this powdered fuel burner 5, when the boiler 100 starts operating, heavy oil or gas ejected from the ignition burner 61 is first burned. Then, after the high-temperature reduction combustion chamber 2 is warmed, the air-fuel mixture is ejected from the powdered fuel burner 5, and combustion of the powdered fuel in the air-fuel mixture is started. Thereafter, the ejection of heavy oil or gas from the ignition burner 61 is stopped at a timely manner, and the combustion of the powdered fuel in the air-fuel mixture ejected from the powdered fuel burner 5 is continued.

In the powdered fuel burner 5 of this embodiment, a rod-shaped central flow inhibiting portion 62 is installed on the central axis 5a of the mixture conveying pipe 51 upstream of the swirling vanes 64 in the conveying direction of the mixture. The central flow inhibiting portion 62 has a cylindrical surface 62a that is concentric with the air-fuel mixture conveying pipe 51 and extends in the direction of the central axis 5a. Further, a cylindrical peripheral flow inhibiting portion 63 is installed along the inner wall surface 51s of the mixture conveying pipe 51 between the central flow inhibiting portion 62 and the swirling vane 64. The peripheral flow inhibiting portion 63 has a cylindrical inner circumferential surface 63a that is concentric with the air-fuel mixture conveying pipe 51 and extends in the direction of the central axis 5a.

According to this powdered fuel burner 5, the air-fuel mixture flowing inside the air-fuel mixture conveying pipe 51 flows around the inside of the pipe by the central flow obstruction part 62, and then is directed toward the center of the pipe by the peripheral flow obstruction part 63. The liquid flows through the central portion of the tube in the same direction as the central axis 5a. Thereafter, when it leaves the area where the peripheral flow inhibiting part 63 is installed, it spreads throughout the pipe, flows, is swirled by the swirling vanes 64, and is ejected into the combustion chamber 1. Here, even after the powdered fuel particles contained in the air-fuel mixture pass through the installation area of the peripheral flow inhibiting portion 63 in the same direction as the central axis 5a, they tend to move straight due to the inertial force. As shown by S1, a mixture with a high concentration of powdered fuel, that is, a mixture with a low A/F, flows through the central portion of the mixture transfer pipe 51, passes through the swirl vane 64, and ignites the combustion chamber 1. It is ejected to region R1. Further, as shown by arrow S2, an air-fuel mixture with a low concentration of powdered fuel, that is, an air-fuel mixture with a high A/F, flows near the pipe wall of the air-fuel mixture conveying pipe 51. Therefore, even if the air-fuel mixture with a large A/F is supplied to the main burner 5, the A/F of the air-fuel mixture injected into the combustion chamber 1 can be locally reduced. That is, even if flame-retardant powdered fuel such as petroleum residue fuel is directly supplied from the crusher 23 in a state where the A/F is larger than the A/F suitable for ignition and combustion, the A/F of the air-fuel mixture injected into the combustion chamber 1 is /F can be locally reduced to make the A/F suitable for ignition and combustion of powdered fuel. As a result, ignitability can be improved and stable combustion can be achieved. Incidentally, in this example, the A/F of the air-fuel mixture supplied from the crusher 23 is about 1.8, which is suitable for igniting and burning petroleum coke, which is an example of flame-retardant powdered fuel. /F is preferably 1.5 or less, more preferably about 1.0.

Further, details of the central flow inhibiting portion 62 and the peripheral flow inhibiting portion 63 will be described with reference to FIG. 5. Note that FIG. 5 is a schematic cross-sectional view showing a main part of the powdered fuel burner 5 using a swirling vane 66 different from the swirling vane 64 described above. In the case of FIG. 5, a swirl vane 66 is provided in place of the swirl vane 64 and inner cylinder 65 of FIG. 2, and the configuration other than the swirl vane 66 is the same as that of the powdered fuel burner 5 shown in FIG. be.

As shown in FIG. 5, the central flow inhibiting portion 62 has a predetermined length L1 of the cylindrical surface 62a in the direction of the central axis 5a, which is equal to or greater than a certain value. Thereby, the flow direction of the powdery particles contained in the air-fuel mixture that has passed through the surface of the cylindrical surface 62a is made parallel to the direction of the central axis 5a. Further, the peripheral flow inhibiting portion 63 has a length L2 of the cylindrical inner circumferential surface 63a in the direction of the central axis 5a, which is a predetermined length greater than or equal to a certain value. Thereby, the flow direction of the powdery particles contained in the air-fuel mixture that has passed through the surface of the inner circumferential surface 63a is made parallel to the direction of the central axis 5a.

Further, the diameter of the cylindrical surface 62a of the central flow inhibiting portion 62 is greater than or equal to the diameter of the cylindrical inner circumferential surface 63a of the peripheral flow inhibiting portion 63. In other words, the total of the diameter of the cylindrical surface 62a of the central flow inhibiting portion 62 and twice the distance from the inner wall surface 51s of the mixture conveying pipe 51 to the inner circumferential surface 63a of the peripheral flow inhibiting portion 63 is the mixture conveyance. It is larger than the inner diameter of the tube 51. Therefore, when the inside of the air-fuel mixture conveying pipe 51 is viewed from the direction of the central axis 5a, it appears that there is no gap between the central flow inhibiting portion 62 and the peripheral flow inhibiting portion 63, as shown in FIG. 3, for example. As a result, the flow direction of all the air-fuel mixture flowing inside the air-fuel mixture conveying pipe 51 is regulated by the central flow inhibiting portion 62 and the peripheral flow inhibiting portion 63, so that the flow of the air-fuel mixture can be made into a desired flow. , contributes to locally reducing the A/F of the air-fuel mixture injected into the combustion chamber 1.

Further, the central flow inhibiting portion 62 has curved surfaces 62b and 62c, which protrude from the ends of the cylindrical surface 62a in the direction of the central axis 5a and have a conical side surface shape, at both ends of the cylindrical surface 62a. It is preferable that the angles e and f formed by the curved surfaces 62b and 62c and the central axis 5a are 20 degrees or less. Thereby, the generation of separation vortices can be suppressed before and after the air-fuel mixture flowing in the air-fuel mixture conveying pipe 51 passes through the central flow inhibiting portion 62, and the flow of the air-fuel mixture can be made into a desired flow. The curved surface 62b is formed to protrude upstream from the upstream end of the cylindrical surface 62a in the air-fuel mixture conveying direction, and the curved surface 62c is formed to protrude downstream from the downstream end of the cylindrical surface 62a. There is.

Further, the peripheral flow inhibiting portions 63 are provided at both ends of the cylindrical inner circumferential surface 63a, protrude from the ends of the inner circumferential surface 63a in the direction of the central axis 5a, and are connected to the inner wall surface 51s of the mixture conveying pipe 51, and have a truncated conical side surface shape. It has curved surfaces 63b and 63c that form . It is preferable that the angles g and h formed by the curved surfaces 63b and 63c and the inner wall surface 51s of the air-fuel mixture conveying pipe 51 are 20 degrees or less. Thereby, the generation of separation vortices can be suppressed before and after the air-fuel mixture flowing in the air-fuel mixture conveying pipe 51 passes through the peripheral flow inhibiting part 63, and the flow of the air-fuel mixture can be made into a desired flow. In this way, the flow of the air-fuel mixture in the air-fuel mixture conveying pipe 51 can be made into a desired flow, which contributes to locally reducing the A/F of the air-fuel mixture injected into the combustion chamber 1. The curved surface 63b is formed to protrude upstream from the upstream end of the inner circumferential surface 63a in the air-fuel mixture conveying direction, and the curved surface 63c is formed to protrude downstream from the downstream end of the inner circumferential surface 63a. has been done.

Further, the central flow inhibiting portion 62 may be configured to be able to adjust its position in the direction of the central axis 5a. In this case, for example, the central flow inhibiting part 62 is attached to the ignition burner 61 so as to be slidable in the direction of the central axis 5a, the central flow inhibiting part 62 is connected to an operating lever, and this operating lever is connected to the outside of the mixture conveying pipe 51. The operating lever may be moved in the direction of the central axis 5a by being pulled out. Thereby, the interval between the downstream curved surface 62c of the central flow inhibiting part 62 and the upstream curved surface 63b of the peripheral flow inhibiting part 63 can be adjusted by moving the central flow inhibiting part 62 in the direction of the central axis 5a. The narrower the interval, the higher the concentration of the powdered fuel in the air-fuel mixture after passing through the peripheral flow inhibiting part 63 near the center of the air-fuel mixture conveying pipe 51. The interval can be adjusted.

Note that the swirling blade 66 shown in FIG. 5 includes a cylindrical portion 66a installed at the tip of the air-fuel mixture transport pipe 51 and inside the air-fuel mixture transport pipe 51, and a plurality of blades 66b made of flat plates. The plurality of blades 66b are attached to the outer peripheral surface of the cylindrical portion 66a at equal intervals and at a predetermined angle with respect to the center line of the cylindrical portion 66a. The center line of the cylindrical portion 66a is the same as the central axis 5a, and the cylindrical portion 66a is installed concentrically with the air-fuel mixture conveying pipe 51. In other words, the swirling vane 66 is generally constructed by increasing the diameter of the cylindrical portion 64a in the aforementioned swirling vane 64. The cylindrical portion 66a of the swirl vane 66 has an inner diameter larger than the diameter of the cylindrical inner circumferential surface 63a of the peripheral flow inhibiting portion 63.

For example, in the swirling blade 64 shown in FIG. 4, a plurality of blades 64b are crowded in the central portion near the center. When many particles of the powdered fuel are repelled to the outside of the ignition region R1 by the swirling vane 64 in the center part, by using the swirling vane 66 shown in FIG. Many particles of fuel can be supplied to the ignition region R1. Therefore, it contributes to locally reducing the A/F of the air-fuel mixture supplied to the ignition region R1 of the combustion chamber 1.

Further, FIG. 6 is a schematic cross-sectional view showing a main part of the powdered fuel burner 5 using a swirling vane 67 different from the swirling vanes 64 and 66 described above. This swirling vane 67 generally has a configuration in which the diameter of the swirling vane 64 shown in FIG. 2 is increased by increasing the length of the vane 64b, and the inner cylinder 65 is not installed. In some cases, such a swirl vane 67 may be used.

In addition, in this embodiment, when the ignition burner 61 is installed separately instead of inside the air-fuel mixture conveying pipe 51, a central shaft rod is installed on the central axis 5a in place of the ignition burner 61, A central flow inhibiting portion 62 may be attached to the central shaft. In this case, the swirl vanes 64 and 67 shown in FIGS. 2 and 6 may also be attached to the central shaft rod.

Moreover, the flame-retardant powdered fuel in this embodiment may be a petroleum residue fuel that is less combustible than pulverized coal, a biomass fuel, or a mixed fuel of biomass and pulverized coal.

From the above description, many improvements and other embodiments of the present disclosure will be apparent to those skilled in the art. Accordingly, the above description is to be construed as illustrative only, and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the present disclosure. Substantial changes may be made in the structural and/or functional details thereof without departing from the spirit of the disclosure.

(summary)
A powdered fuel burner according to a first aspect of the present disclosure is a powdered fuel burner installed in a combustion chamber of a boiler, in which a mixture of powdered fuel and transportation air is conveyed and mixed from the tip. a cylindrical air-fuel mixture conveying pipe that injects air into the combustion chamber; a swirling vane installed at the tip of the mixture conveying pipe; and a swirling vane disposed at the tip of the mixture conveying pipe, and a mixture conveying pipe located upstream of the swirling vane in the direction of conveying the mixture. a rod-shaped central flow inhibiting part installed on the central axis of the pipe, concentric with the mixture conveying pipe and having a cylindrical surface extending in the central axis direction; and between the central flow inhibiting part and the swirling vane. a cylindrical peripheral flow inhibiting part installed along an inner wall surface of the mixture transport pipe, having a cylindrical inner peripheral surface concentric with the mixture transport pipe and extending in the central axis direction; There is.

According to this configuration, the air-fuel mixture flowing inside the air-fuel mixture conveying pipe flows around the inside of the pipe by the central flow obstruction part, and then is directed toward the center of the pipe by the peripheral flow obstruction part, so that the mixture flows along the center axis of the pipe. flows in the same direction as the direction. Thereafter, when it leaves the area where the peripheral flow inhibiting part is installed, it spreads throughout the pipe, flows, is swirled by the swirling vanes, and is ejected into the combustion chamber. Here, even after the powdered fuel particles contained in the air-fuel mixture have passed straight through the installation area of the peripheral flow obstruction part in the same direction as the central axis, they tend to move straight due to inertia, so the air-fuel mixture is transported The concentration of powdered fuel is high in the central part of the tube, and the concentration in other parts is low, and the powdered fuel passes through the swirl vanes and is injected into the combustion chamber. Therefore, even if the air-fuel mixture with a large A/F is supplied to the main burner, the A/F of the air-fuel mixture injected into the combustion chamber can be locally reduced. In other words, even if flame-retardant powdered fuel such as petroleum residue fuel is directly supplied from the pulverizer in a state that is larger than the A/F suitable for ignition and combustion, the A/F of the air-fuel mixture injected into the combustion chamber is It is possible to locally reduce the A/F to make it suitable for ignition and combustion of powdered fuel. As a result, ignitability can be improved and stable combustion can be achieved.

In the powdered fuel burner according to the second aspect of the present disclosure, in the powdered fuel burner according to the first aspect, the diameter of the cylindrical surface of the central flow obstruction part is equal to or smaller than the diameter of the cylindrical inner periphery of the peripheral flow obstruction part. It is greater than or equal to the diameter of the surface. As a result, the flow direction of all the air-fuel mixture flowing in the air-fuel mixture conveying pipe is regulated by the central flow obstruction section and the peripheral flow obstruction section, so that the air-fuel mixture can flow as desired and flow into the combustion chamber. This contributes to locally reducing the A/F of the jetting air-fuel mixture.

In the powdered fuel burner according to a third aspect of the present disclosure, in the powdered fuel burner according to the first or second aspect, the central flow inhibiting portion is arranged at both ends of the cylindrical surface from the end of the cylindrical surface to the center. It has a curved surface that protrudes in the axial direction and has a conical side surface shape, and the angle between the curved surface and the central axis is 20 degrees or less, and the peripheral flow inhibiting portion is located at both ends of the cylindrical inner peripheral surface, a curved surface protruding from an end of the inner circumferential surface in the direction of the central axis and connected to the inner wall surface of the mixture transfer pipe and forming a side surface shape of a truncated cone, the shape of the curved surface and the inner wall surface of the mixture transfer pipe; The angle is 20 degrees or less. Thereby, the generation of separated vortices is suppressed before and after the air-fuel mixture flowing in the air-fuel mixture conveying pipe passes through the central flow inhibiting portion, and the generation of separated vortices is suppressed before and after passing through the peripheral flow inhibiting portion. In this way, it is possible to suppress the generation of separated vortices in the mixture conveying pipe and make the mixture flow into the desired flow, contributing to locally reducing the A/F of the mixture injected into the combustion chamber. do.

A powdered fuel burner according to a fourth aspect of the present disclosure is the powdered fuel burner according to any one of the first to third aspects, wherein the central flow inhibiting portion is configured to be adjustable in position in the central axis direction. has been done. Thereby, the interval between the central flow inhibiting part and the peripheral flow inhibiting part can be adjusted by moving the central flow inhibiting part in the central axis direction. The narrower the above interval is, the higher the concentration of powdered fuel in the mixture after passing through the peripheral flow obstruction section will be near the center of the mixture conveying pipe. Can be adjusted.

The powdered fuel burner according to a fifth aspect of the present disclosure is the powdered fuel burner according to any one of the first to fourth aspects, wherein the swirling vane is concentric with the mixture conveying pipe and conveys the mixture. a cylindrical part installed at the tip of the pipe and inside the mixture conveying pipe and having an inner diameter equal to or larger than the diameter of the cylindrical inner peripheral surface of the peripheral flow inhibiting part; and a cylindrical part attached to the outer peripheral surface of the cylindrical part. It is equipped with multiple blades. This allows many particles of powdered fuel to be supplied to the combustion chamber from near the center of the air-fuel mixture conveying pipe, contributing to locally reducing the A/F of the air-fuel mixture injected into the combustion chamber.

A powdered fuel burner according to a sixth aspect of the present disclosure is a powdered fuel burner according to any one of the first to fifth aspects, wherein the powdered fuel is petroleum residue fuel, biomass fuel, or biomass and fine powder. It is a mixed fuel with charcoal.

1 Combustion chamber of boiler 5 Powdered fuel burner 51 Mixture conveying pipe 62 Central flow inhibiting part 62a Cylindrical surface 63 of central flow inhibiting part Peripheral flow inhibiting part 63a Inner peripheral surface 64, 66, 67 of peripheral flow inhibiting part Swirl vane 66a Cylindrical part 66b of the swirling vane Blade of the swirling vane

Claims (6)

A powdered fuel burner installed in a combustion chamber of a boiler,
a cylindrical mixture conveying pipe through which a mixture of powdered fuel and conveying air is conveyed and the mixture is ejected from the tip into the combustion chamber;
a swirling vane installed at the tip of the mixture conveying pipe;
a rod-shaped center installed on the central axis of the mixture conveying pipe upstream of the swirling vane in the conveying direction of the mixture, and having a cylindrical surface concentric with the mixture conveying pipe and extending in the central axis direction; a flow obstruction part;
A cylindrical inner circumferential surface that is installed along the inner wall surface of the mixture transport pipe between the central flow inhibiting part and the swirling vane, is concentric with the mixture transport pipe and extends in the central axis direction. a cylindrical peripheral flow obstruction portion having;
Powdered fuel burner with. The diameter of the cylindrical surface of the central flow inhibiting portion is greater than or equal to the diameter of the cylindrical inner circumferential surface of the peripheral flow inhibiting portion.
The pulverized fuel burner according to claim 1. The central flow inhibiting portion has curved surfaces at both ends of the cylindrical surface that protrude from the ends of the cylindrical surface in the direction of the central axis and have a conical side surface shape, and the angle between the curved surface and the central axis is 20 degrees. The following is
The peripheral flow inhibiting portion includes a curved surface formed at both ends of the cylindrical inner circumferential surface, protruding from the end of the inner circumferential surface in the direction of the central axis, and connecting to the inner wall surface of the mixture conveying pipe and forming a side surface shape of a truncated cone. and the angle between the curved surface and the inner wall surface of the mixture conveying pipe is 20 degrees or less,
The pulverized fuel burner according to claim 1 or 2. The central flow inhibiting portion is configured to be adjustable in position in the central axis direction.
The powdered fuel burner according to claim 1 or 2. The swirl vane is
A cylinder that is concentric with the mixture transport pipe, installed at the tip of the mixture transport pipe and inside the mixture transport pipe, and has an inner diameter that is equal to or larger than the diameter of the cylindrical inner circumferential surface of the peripheral flow inhibiting part. Department and
a plurality of blades attached to the outer peripheral surface of the cylindrical part;
The powdered fuel burner according to claim 1 or 2. The powdered fuel is petroleum residue fuel, biomass fuel, or a mixed fuel of biomass and pulverized coal.
The pulverized fuel burner according to claim 1 or 2.

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