JPH02259309A - Fine powder fuel burner - Google Patents

Abstract

PURPOSE:To provide a stable combustion and to save auxiliary fuel by a method wherein a flow of fine powder fuel is struck against a distributing plate within a vortex pipe, its direction is changed toward a crossing direction to form a swirl and to collect fuel around a circumference of the pipe and the fuel is supplied to some distributing pipes concentrically installed in multi-layered form. CONSTITUTION:A flow of fine powder fuels supplied by a fuel supply pipe 6 strikes against a distributing disk 4 within an inner pipe 2 of a vortex pipe 1, its direction is changed toward a crossing direction and the flow is blown from an opening 5 of a tangential direction of a circumferential surface into an outer pipe 3 so as to make a swirl. With such an arrangement, the powder fuels are collected at a circumference under a centrifugal force so as to form a region of fuel condensation and another region of lean fuel. The fuel is discharged out of each of the pipes 9 to 11 of the distributing pipe 8 for every regions. Then, an amount of air flowing into a central pipe 9 is made variable by a flow rate variable valve 7. With such an arrangement, it is possible to provide a stable combustion and to save auxiliary fuel oil.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a burner. More specifically, the present invention relates to a burner that uses pulverized fuel such as pulverized coal or pulverized coke as fuel.

(Prior art) As shown in Fig. 7, a conventional pulverized fuel burner is
Pulverized fuel is used as primary air (approximately 20 to 30% of the total amount of combustion air)
), the fuel is blown into the furnace, and secondary air is supplied from around it for combustion. This burner 10
Type 1 uses radiant heat in the high-temperature furnace and interference from a pond burner to stabilize the flame and achieve complete combustion, and many are equipped with an oil nozzle 102 for auxiliary combustion in the center.

(Problem U to be solved by the invention) However, in conventional burners, the pulverized fuel from the coal crusher (mill) is directly supplied to the burner and burned, so it is difficult to transport the pulverized fuel and prevent backfire. For this purpose, a certain flow rate (for example, 15 to 301/s) of primary air is required. For this reason, when the combustion amount is significantly reduced to reduce the load, it is necessary to reduce the amount of fuel while maintaining the minimum amount of air required for conveyance. (represented by the ratio A/C of the amount of pulverized fuel and the amount of pulverized fuel) becomes thinner, making combustion unstable (see Figure 6). Therefore, when only pulverized fuel is used, a large turn It is impossible to carry out a reduction, and auxiliary fuel is required to achieve this.For example, in a thermal power plant, etc., if only pulverized fuel is used, it is currently possible to change the range by 120 to 50%. However, since the demand for electric power is low late at night, it is required to change the load to about 20 to 30%, and auxiliary fuel is required. Therefore, when reducing the amount of combustion, there is a disadvantage that fuel cost increases. Due to the current state of pulverized fuel burners, there is a demand for the development of a burner dedicated to pulverized fuel that can handle low loads, with the aim of operating at a minimum load comparable to that of oil-fired power plants and reducing the amount of auxiliary fuel used during low-load operations.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pulverized fuel burner that can ensure stable combustion even when the minimum load is reduced to the same level as oil-fired power, and can save on auxiliary fuel.

(Means for Solving the Problems) In order to achieve the above object, the pulverized fuel burner of the present invention has distribution disks formed on the inner circumferential surface perpendicular to the flow of pulverized fuel, and a pulverized fuel burner on the upstream side of each distribution disk. A vortex tube consisting of an inner tube whose peripheral surface is opened in the tangential direction and an outer tube surrounding the vortex tube, and two or more tubes are arranged concentrically, and at least the entrance of the outermost tube is opened in the radial direction. A distribution pipe having an inlet of the central pipe opened in the axial direction, and a variable flow valve that moves toward and away from the inlet of the central pipe of the distribution pipe to adjust the amount of air flowing into the central pipe. The outlet of the vortex tube is connected to the distribution tube, and the vortex tube can be moved in and out of the distribution tube, so that the opening area of the inlet of the outer tube can be varied.

The present invention also provides an outer tube and an inner tube of the vortex tube, which are separated and fitted together so as to be movable in the axial direction of the tube, and the inner tube is fixed to the pulverized fuel supply tube side, and the outer tube has a tube axis. The opening area of the inlet of the outer pipe of the distribution pipe and the opening area of the peripheral surface of the inner pipe are made variable by the directional movement.

(Operation) Therefore, the pulverized fuel flow introduced into the vortex pipe from the fuel supply pipe collides with each distribution disk, changes its direction in the orthogonal direction, and is blown out in the tangential direction into the outer pipe through the opening in the circumferential surface, Forms a swirling flow.

This swirling flow of pulverized fuel collects the pulverized fuel contained therein around it by centrifugal force. Therefore, the A/C ratio of the pulverized fuel flow injected from the vortex tube does not change as a whole, but the A/C ratio as a whole is higher than the area where the pulverized fuel is concentrated, that is, the area where the A/C ratio is low. A region with a high A/C ratio is formed. The region in which the pulverized fuel is concentrated and the region mainly composed of air are separated in a distribution pipe and injected separately.

Therefore, when performing turndown by reducing only the pulverized fuel while maintaining the minimum amount of conveying air, the second The concentration of the pulverized fuel flow injected from the pipe is kept constant.At this time, since the total pulverized fuel flow is decreasing, a vortex pipe is inserted into the distribution pipe to reduce the area of the inlet of the outermost pipe. This prevents the injection force of the pulverized fuel flow flowing into the second pipe from decreasing.

(Example) Hereinafter, the configuration of the present invention will be described in detail based on an example shown in the drawings.

FIG. 1 schematically shows the basic structure of the pulverized fuel burner of the present invention. This burner has distribution disks 4.4 formed on the inner peripheral surface perpendicular to the flow of pulverized fuel, and each distribution disk 4.4. a vortex tube 1 consisting of an inner tube 2 having a tangential opening 5.5 on the upstream circumferential surface of the vortex tube 4; and an outer tube 3 surrounding the inner tube 2;
Two or more concentric tubes9.10. -11, and a variable flow rate valve 7 that moves toward and away from the inlet 13 of the pipe 9 in the center of the distribution pipe 8, and the outlet 1b of the vortex pipe is connected to the inside of the distribution pipe 8. The vortex tube 1 is connected so that it can go in and out, and the inlet la side is connected to the pulverized fuel supply pipe 6, so that the vortex tube 1 can be moved between the fixed pulverized fuel supply pipe 6 and the distribution pipe 8.

The air flow distribution disks 4, 4 are for changing the direction and dividing the pulverized fuel flow flowing in the direction of the tube axis in the radial direction perpendicular to the direction. In this embodiment, one ring-shaped disk is used. and one disk, and are arranged so that the difference in area (difference in projected area) S is equal. The pulverized fuel flow is therefore distributed in approximately the same amount of flow, depending on the impingement area of each distribution disk 4.4. The inlet 1a of the vortex tube 1 is fitted into the pulverized fuel supply pipe 6 so as to be movable in the axial direction, and is provided so that the pulverized fuel is conveyed from the crusher or the like by primary air.

The vortex tube 1 is provided so as to be movable in the axial direction by an appropriate actuator or manually, and is provided so as to be able to move in and out of the distribution pipe s.

By controlling the insertion amount of this vortex tube 1 into the distribution pipe 8, the area of the inlet 11a of the outermost pipe 11 of the distribution pipe 8 fitted to the opening 1b can be varied, that is, the inflowing @ powder The amount of fuel flow can be changed.

The amount of insertion of the vortex tube 1 is controlled by an actuator 22 or manually in response to changes in the amount of conveyed air.

Further, a variable flow valve 7 is provided in the vortex pipe 1 to control the amount of air flowing into the central pipe 9 of the distribution pipe 8. The variable flow rate valve 7 is provided so as to be able to move in the axial direction by penetrating the distribution disks 4, 4 of the vortex pipe 1.
By approaching or moving away from the inlet 9a of the central tube 9, the flow resistance near the inlet 9a of the central tube 9 is changed, and the amount of air flowing into the central tube 9 is adjusted. . The variable flow rate valve 7 is provided so as to be movable by an actuator 21 provided externally or manually. The position of this variable flow rate valve 7 is controlled according to the concentration of the supplied pulverized fuel flow.

The distribution pipe 8 consists of two or more pipes 9, 10° 11 arranged concentrically, and distributes the swirling flow injected from the outlet 1b of the vortex pipe 1 into the furnace while maintaining the same concentration. This is for injecting water, and in this embodiment, it is made up of triple pipes. This distribution pipe 8 may constitute a burner nozzle, but a separate burner nozzle may be provided at its tip.

On the upstream side of the second pipe 10 of the distribution pipe 8, there is a reduced flow section (
A throat) 12 is provided to further speed up the swirling flow of the pulverized fuel and enhance the effect of classifying fine particles and coarse particles. The inlet 10a of the second pipe 10 of the distribution pipe 8 is opened in the radial direction on the outlet side of the flow path cross-section reduced part 12, and the inlet 11a of the third pipe 11 is opened in the radial direction on the inlet side. There is. Inlet portion 10 of second and third pipes 10.11
A and lla are provided with a large number of guide plates 10b and 10b disposed in the circumferential direction for guiding the flow in the tangential direction and urging the swirling flow. In this embodiment, a concentrated pulverized fuel stream is injected from the second tube 11 during turndown.

FIG. 3 shows an embodiment of the pond. In this embodiment, an inversion pipe 16 consisting of the same number of pipes 13, 14, and 15 arranged concentrically as the distribution pipe 8 is arranged parallel to the distribution pipe 8. The injection positions of the pulverized fuel flow divided by 8 are reversed so that the inner part is injected outward and the outer part is injected inward. 3 pipe 11 and the central pipe 13 of the reversing pipe 16, the central IF9 of the distribution pipe 8 and the third pipe 15 of the reversing pipe 16, and the second pipes 10 and 14, respectively, in the tangential direction to the container pipe. Opening communication pipe 17.
It is connected at 18.19. In this case, it becomes possible to install the oil gun 20 as a pilot burner in the central pipe. Also, outside of the flames II! Since primary combustion air is injected from the IJ, concentrated combustion can occur and NOx can be reduced.

FIG. 4 shows another embodiment. In this embodiment, the vortex tube 1 is separated into an inner tube 2 and an outer tube 3, and the inner tube 2 is fixed to the pulverized fuel supply tube 6 side, while the outer tube 3 is made movable in the axial direction. By this, the third pipe 11 of the distribution pipe 8
and the opening 55 of the inner tube 2 at the same time so that the swirling force of the fuel flow and the injection force are not reduced even during turndown.

With the above structure, the burner of the present invention can change the combustion amount as follows and achieve stable combustion.

First, Fig. 5 shows an example of a combustion system to which the burner of the present invention is applied. This combustion system uses a mill to crush coal, which is the fuel, to a combustible particle size, and makes up 30% of the combustion air.
This type of primary air is used as transport air to be transported to the burner side and burned.

Based on the measurement result from the pulverized coal concentration measuring device 23 installed in the middle of the pulverized fuel flow supply system 6, the actuator 21 is driven to move the variable flow valve 7 to maintain the pulverized fuel concentration constant. At this time, the insertion amount of the vortex pipe 1 into the distribution pipe 8, that is, the inflow port 11a of the third pipe 11
The opening area of is determined from the relationship with the amount of combustion air, and is controlled so as to keep the injection force from the distribution pipe 8 constant. Here, the concentration measuring device 23 may be, for example, a differential pressure type Newmarine powder/granular material flowmeter that determines the flow rate because the load pressure loss due to particles at two points in the flow direction is proportional to the mixing ratio, or a correlation type powder/granular material flow meter. A meter or a microwave powder flow meter can be used.

In this combustion system, the combustion amount can be changed within a range where the ratio of conveying air to fuel can be changed proportionally (approximately 120 to 5
(0), the opening cross-sectional area of the inlet 11a of the third pipe 11 is changed by changing the insertion amount of the vortex pipe 1 into the distribution pipe 8 in accordance with the fluctuation of the supply amount of conveying air. This can only be achieved by keeping the injection force of the pulverized fuel stream constant.

For example, to turn down the combustion amount to 80%,
The vortex tube 1 is inserted into the distribution tube 8 so that the open area of the third tube 11 is 80% of the open area of the third tube 11 at 0% load.

In addition, when changing the load range to a range where the A/C ratio increases rapidly, the concentration and particle size of the pulverized fuel are measured with the concentration sensor 2e at the same time as adjusting the opening area of the inlet of the third pipe 11. Based on this value, the variable flow rate valve 7 controls the amount by which the inlet 9a of the central pipe 9 of the distribution pipe 8 is closed, thereby maintaining the concentration constant. That is, when the fuel concentration becomes thinner (the A/C ratio becomes higher), this is detected by the concentration sensor 2.
3 and drives the actuator 21 of the variable flow rate valve 7 to move it away from the distribution pipe 8 to increase the amount of conveying air flowing into the central pipe 9.
The concentration of the pulverized fuel flow injected from the pulverized fuel stream is increased to maintain it at a value in the stable combustion range. In the case of the embodiment shown in FIG. 4, by inserting the outer tube 3 of the vortex tube 1 into the distribution tube 8, the inlet 11a of the third tube 11 of the distribution tube 8 is narrowed and at the same time, the vortex tube 1 is The opening area of the inner tube 2 is also narrowed down to maintain the swirling force of the swirling flow in the vortex tube 1, which weakens as the pulverized fuel flow decreases due to turndown.

(Effects of the Invention) As is clear from the above description, the burner of the present invention introduces and swirls a pulverized fuel flow into a vortex pipe, and the swirling force mainly creates a region where pulverized fuel is concentrated and conveying air. By adjusting the amount of air flowing into the center of the distribution pipe, the concentration is controlled to be constant and distributed injection is performed, so even if the AZC ratio of the entire pulverized fuel flow is high, stable combustion can be achieved. This creates a jet stream that concentrates the pulverized fuel to a low enough A/C ratio to stabilize combustion. That is, it is possible to achieve a turndown of 20 to 30%, which is comparable to oil-fired power generation, and the combustion amount can be changed over a wide load range. Moreover, it does not require auxiliary fuel oil.

[Brief explanation of drawings]

FIG. 1 is a central vertical cross-sectional view showing an outline of the basic structure of the pulverized fuel burner of the present invention, FIG. 2 is a cross-sectional view taken along the line n-■ in FIG. 1, and FIG. 3 is a central vertical cross-sectional view showing another embodiment. 4(A) and (B) are diagrams showing still other embodiments, in which (A) is a central longitudinal sectional view, (B) is a sectional view taken along the line IV-IV, and FIG. 5 is a diagram showing another embodiment of the present invention. 1 is a schematic diagram showing an example of a combustion system to which a pulverized fuel burner is applied. FIG. 6 is a graph showing the relationship between the ratio of the amount of air at the burner inlet to the amount of pulverized fuel and the stable combustion range. FIG. 7 is an explanatory diagram showing the schematic structure of a conventional pulverized fuel burner. ■...Vortex tube, 1a...Inlet, 1b...Outlet, 2...Inner tube, 3...Outer tube, 4...Distribution disk, 5...Opening, 6... -Powdered fuel supply pipe, 7...Variable valve, 8...Distribution pipe, 9...Central pipe, 9a...Inlet, 10...Second
pipe, 10a...inlet, 11...third pipe, 11a
···entrance. Patent applicant: Chuo Electric Power Research Institute Dankini Foundation
Kotobuki agent

Claims (2)

[Claims] (1) Consisting of an inner tube with a distribution disk formed on its inner circumferential surface that is perpendicular to the flow of pulverized fuel and an opening tangentially on the upstream circumferential surface of each distribution disk, and an outer tube surrounding the inner tube. A vortex pipe, a distribution pipe consisting of two or more pipes arranged concentrically, at least the entrance of the outermost pipe being opened in the radial direction, and the entrance of the central pipe being opened in the axial direction, and this distribution pipe. a variable flow rate valve that moves toward and away from the inlet of the central pipe to adjust the amount of air flowing into the central pipe; the outlet of the vortex pipe is connected to the distribution pipe, and the vortex pipe is connected to the distribution pipe. A pulverized fuel burner characterized in that the opening area of the inlet of the outer pipe is made variable so that the inlet can go in and out of the pulverized fuel burner. (2) Separate the outer tube and inner tube of the vortex tube, fit them together so that they can move in the tube axis direction, and fix the inner tube to the pulverized fuel supply tube side, and by moving the outer tube in the tube axis direction. The pulverized fuel burner according to claim 1, wherein the opening area of the inlet of the outer pipe of the distribution pipe and the opening area of the peripheral surface of the inner pipe are variable.