JP2016133224A - Solid fuel burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve stability characteristics on ignitability and burning quality through high concentration of solid fuel and reduction of energy of fuel particles and speed thereof.SOLUTION: This invention relates to a solid fuel burner constituted in such a way that combustion air nozzles 4 and 5 are provided at an outer periphery of a cylindrical fuel nozzle 10 for injecting mixed fluid 3 of fine powdered coal and transfer gas thereof; there are provided a venturi 8 located at an inner wall side of the fuel nozzle 10 and metering once a transfer flow passage for the mixture gas 3 composed of fine powdered coal and transfer gas thereof in the fuel nozzle 10 toward a central axis direction, a condenser 9 for changing a flow of the mixed gas 3 outward placed at a central axis of the fuel nozzle 10 at a downstream side of the venturi 8 and a distributor 11 at the downstream side of the condenser 9 for dividing the flow passage of the fuel nozzle 10 to an outer peripheral side and an inner peripheral side; a transfer flow passage 12 between the fuel nozzle 10 and the distributor 11 is divided into at least two or more in a circumferential direction of the fuel nozzle 10; and there is provided a hindrance object 14 to cause a length in a circumferential direction of the divided flow passage 12 to be reduced as it is advanced toward the downstream side.SELECTED DRAWING: Figure 1

Description

  TECHNICAL FIELD The present invention relates to a solid fuel burner in which solid fuel is conveyed and burned, and more particularly to a structure of a solid fuel burner suitable for improving the ignitability and combustibility of fuel particles having a large particle size such as biomass particles. .

  As a method for improving the ignitability of a solid fuel burner used in a boiler of a thermal power plant or the like and improving the stability of flame, there is a method of increasing the fuel concentration or increasing the oxygen concentration of the fuel carrier gas.

  For example, in Patent Document 1 (Japanese Patent Laid-Open No. 9-310809), the fuel concentration to be introduced into the furnace is increased by adopting the burner structure as shown in FIG. In the burner structure shown in FIG. 6, a solid fuel such as pulverized coal and a carrier gas thereof are supplied into a cylindrical fuel nozzle 10 and charged into the furnace 1 from the outlet of the fuel nozzle 10. A venturi 8 for restricting the flow of the mixed gas 3 provided on the nozzle inner wall side of the fuel nozzle 10 toward the center side of the fuel nozzle 10, and a mixed gas 3 provided on the central axis of the fuel nozzle 10 downstream of the venturi 8. A concentrator 9 that spreads the flow toward the inner wall side of the fuel nozzle 10, and a flow path of the fuel nozzle 10 that is provided on the downstream side of the concentrator 9 coaxially with the central axis of the fuel nozzle 10 from the upstream side toward the downstream side. A distributor 11 that has a narrowed narrow tube portion 19 and that divides the flow path coaxially is integrally provided.

  By the venturi 8, the flow path of the fuel nozzle 10 is reduced and then enlarged. Furthermore, since the flow path in the fuel nozzle 10 is reduced again by the concentrator 9 provided on the downstream side of the venturi 8, the flow velocity of the solid fuel particles is accelerated. Furthermore, since the solid fuel particles once accelerated have a larger mass than the carrier gas, the fuel particles easily flow to the inner wall side of the solid fuel nozzle 10 in the flow path enlargement portion on the downstream side of the concentrator 9. The flow path split body composed of the narrow cylindrical portion 19 and the distributor 11 on the wake side of the concentrator 9 divides the flow path of the fuel nozzle 10 coaxially, and the outer flow path and the inner flow path are separated. Arrange the flow of fuel particles. That is, by disposing the flow path division body in the flow path in the fuel nozzle 10, the flow of the carrier air on the outer peripheral side and the inner peripheral side flowing through the flow path in the fuel nozzle 10 becomes equal, respectively. Ten radial velocity gradients are reduced. Furthermore, since the fuel concentration on the outer peripheral side divided by the flow path dividing body becomes high, the flame can be kept stable even at low loads with low fuel concentration and even in flame-retardant high fuel specific coal.

  In the solid fuel burner disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 2014-1908), after the fuel particles are concentrated in the same manner as in Patent Document 1, a high oxygen concentration is provided in the flow path between the distributor and the fuel nozzle. A region of high oxygen and high fuel particle concentration is formed by providing a jet port for jetting gas and introducing high oxygen concentration gas.

  Further, in the solid fuel burner disclosed in Patent Document 3 (Japanese Patent Laid-Open No. 4-24404), when the burner load of the pulverized coal burner is low, that is, when the coal crushing mill is started and when the burner is under low load, during normal combustion Compared with the reduced amount of pulverized coal combustion air and the reduced amount of pulverized coal supplied, the ignitability of the pulverized coal burner is worsened. A structure is disclosed in which a valve capable of changing the flow rate of pulverized coal for increasing the concentration is provided, and a flame holder for forming a concentrated pulverized coal flow is provided at the outlet of the pulverized coal nozzle.

JP-A-9-310809 JP 2014-1908 A JP-A-4-24404

  The conventional techniques described in Patent Documents 1 to 3 attempt to increase the fuel concentration by collecting the fuel particles in the radial direction of the fuel nozzle, that is, in the vicinity of the inner wall of the fuel nozzle. When it is used as fuel, it is necessary to consider further improving the ignitability.

  That is, in the case of biomass having a large particle size, compared to fine particles such as pulverized coal, it is difficult to ignite at the burner opening, and the ratio of falling to the bottom of the boiler furnace without burning tends to be high. Moreover, since the large diameter particle has a large penetration force into the furnace, it tends to be separated from the flow of the burner flame, and the combustibility tends to deteriorate.

Neither of the above prior arts considers reducing the penetration force of the concentrated particles.
The problem of the present invention is to increase the particle concentration of the solid fuel more than the solid fuel burner of the prior art, and reduce the particle penetration force by lowering the particle speed in the fuel nozzle just before entering the furnace, An object of the present invention is to provide a solid fuel burner that improves the ignitability and flame stability of a solid fuel, particularly a biomass particle having a large particle size.

The above-mentioned problem of the present invention is solved by the following means.
By concentrating the fuel particles concentrated near the nozzle inner wall in the radial direction of the fuel nozzle in the circumferential direction (locally concentrated), the fuel concentration is further increased, and the ignitability and flame stability are improved. It is.

  That is, the invention according to claim 1 is a cylinder fuel nozzle that ejects a mixed fluid of solid fuel (pulverized coal) and its carrier gas, and a combustion gas that ejects a combustion gas disposed outside the fuel nozzle. A gas nozzle, a venturi which is disposed on the inner wall side of the fuel nozzle, and once squeezes the transport path for the solid fuel and the transport gas in the fuel nozzle toward the central axis, and the center of the fuel nozzle on the downstream side of the venturi A concentrator provided on the shaft for changing the flow in the nozzle outward, and a distributor for dividing the flow path of the nozzle into an outer peripheral portion and an inner peripheral portion on the downstream side of the concentrator; A toothed flame stabilizer in the part, the conveying flow path between the inner wall of the solid fuel nozzle and the distributor is divided into at least two in the circumferential direction, and the circumferential length of the flow path is A shape that shrinks as it goes to the wake side Is a solid fuel burner characterized and.

  According to a second aspect of the present invention, a toothed flame stabilizer is provided at the outlet of the solid fuel nozzle, and the outlet of the transport channel divided between the inner wall of the solid fuel nozzle and the distributor is viewed from the furnace side. The solid fuel burner according to claim 1, wherein the solid fuel burner is installed at a position overlapping with a tooth of the toothed flame holder.

  According to a third aspect of the present invention, the cross-sectional areas of the upstream inlet and the downstream outlet of the circumferentially divided transport channel between the inner wall of the fuel nozzle and the distributor are the same or the same of the transport channel. 3. The solid fuel burner according to claim 1, wherein a cross-sectional area of the outlet is larger than that of the inlet.

According to the present invention, the following effects can be obtained.
According to the first aspect of the present invention, when the venturi for narrowing the flow path and the concentrator for enlarging the flow path are provided in the fuel nozzle of the solid fuel burner in order from the upstream side of the burner, A velocity component is induced along the outer circumferential direction of the fuel nozzle. Since the fuel particles have an inertial force larger than that of the carrier gas, they are concentrated on the inner wall side of the fuel nozzle. For this reason, the fuel concentration of the conveyance flow path which flows between the inner wall of a fuel nozzle and a divider | distributor becomes high. So far, it is the same as that of the prior art.

  Furthermore, the conveyance flow path between the inner wall of the solid fuel nozzle and the distributor is divided into at least two in the circumferential direction of the cylindrical solid fuel nozzle, and the circumferential length of the conveyance flow path is Since the oil is concentrated in the circumferential direction by the reduced amount, the ignitability and combustion stability by increasing the concentration of solid fuel and reducing the energy and speed of the fuel particles at the outlet of the concentrated downstream fuel nozzle Can be increased.

  According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, when the outlet of the transfer channel is provided at a position overlapping the teeth of the toothed flame holder as viewed from the furnace side, The flame holder teeth act as an obstacle to which the fuel particles hit, and in the conveying flow path just before the furnace is charged, the fuel particles are once applied to the flame holder teeth installed perpendicular to the flow direction. As a result, the velocity of the fuel particles decreases and the penetration force decreases. Thus, if the penetration force of the fuel particles immediately before entering the furnace decreases, the ignitability of the fuel improves, and the fuel particles with reduced penetration force burn without penetrating the burner flame. Will improve.

  According to the invention of claim 3, in addition to the effect of the invention of claim 1 or 2, if the cross-sectional areas of the inlet and outlet of the transfer channel are the same, the flow velocity in the transfer channel is changed. Without increasing the fuel concentration. In addition, if the cross-sectional area of the transfer flow path outlet is larger than the cross-sectional area of the inlet, the flow speed of the transfer flow path outlet is slower than that of the transfer flow path inlet. Therefore, it is possible to form a mixed flow of the low flow velocity and high concentration fuel particles and the carrier gas necessary for improving the ignitability.

FIG. 1A is a side sectional view of a solid fuel burner according to a first embodiment of the present invention (FIG. 1A), and FIG. 1A is a sectional view taken along line AA in FIG. A cross-sectional view taken along the line B-B (FIG. 1C) and a cross-sectional view taken along the line C-C in FIG. 1A, FIG. 1B, and FIG. 1C (FIG. 1D). is there. It is a perspective view of the obstruction installed in the channel between the fuel nozzle and the channel division nozzle of Example 1 of the present invention. FIG. 3A is a perspective view of a fuel concentration flow path according to a second embodiment of the present invention (FIG. 3A), a cross-sectional view taken along line AA in FIG. 1A, and FIG. A cross-sectional view taken along the line B-B (FIG. 3C) and a cross-sectional view taken along the line C-C in FIG. 1A, FIG. 3B, and FIG. 3C (FIG. 3D). is there. Side sectional view (FIG. 4 (a)) of the solid fuel burner of Example 3 of the present invention, a front view seen from the furnace (FIG. 4 (b)), and a sectional view taken along the line CC in FIG. 4 (a). (FIG. 4C). It is a sectional side view of the solid fuel burner of Example 4 of the present invention. It is a schematic block diagram of the conventional solid fuel burner.

An embodiment of the present invention will be described with reference to the drawings. The configuration and operation common to the prior art are as described above.
FIG. 1 is a schematic longitudinal sectional view showing the structure of a solid fuel burner according to an embodiment of the present invention. A fuel nozzle 10 through which solid fuel and carrier gas flow is provided on the wall surface of the furnace 1, and a combustion gas nozzle (secondary combustion gas nozzle) 4 for injecting combustion air into the furnace 1 on the outer periphery of the fuel nozzle 10, The combustion gas nozzle 4 is provided with a combustion gas nozzle (third combustion gas nozzle) 5 provided with an air register 6 for forming a swirling flow at the burner outlet on the outer periphery of the combustion gas nozzle 4, and the secondary combustion gas nozzle 4 and the tertiary combustion gas nozzle 5 In the structure, combustion gas is supplied from the wind box 7.

  A venturi 8 that restricts the flow of the mixed gas 3 toward the center of the fuel nozzle 10 on the nozzle inner wall side of the fuel nozzle 10; a concentrator 9 provided on the center axis of the fuel nozzle 10 downstream of the venturi 8; A distributor 11 that divides the flow path in the radial direction is provided on the downstream side of the concentrator 9.

  Since the oil gun 2 is disposed on the central axis of the fuel nozzle 10, the concentrator 9 is disposed on the oil gun 2, and the distributor 11 is supported on the inner wall of the fuel nozzle 10. .

  A mixed gas 3 composed of solid fuel and carrier gas (primary air) is supplied to the fuel nozzle 10, and a velocity component in the central axis direction of the fuel nozzle 10 is induced in the mixed gas 3 by the venturi 8. Further, a speed component directed toward the outer peripheral direction of the fuel nozzle 10 along the concentrator 9 is induced in the mixed gas 3 by the concentrator 9. Since the fuel particles have a greater inertial force than the carrier gas, they cannot follow the flow of the carrier gas. For this reason, the fuel particles are concentrated near the inner wall of the fuel nozzle 10. Therefore, the flow path between the distributor 11 and the fuel nozzle 10 installed downstream of the concentrator 9 becomes a fuel concentration flow path 12 with a high fuel particle concentration, and the inside of the distributor has a fuel lean flow path 13 with few fuel particles. Become.

  Further, a wedge-shaped obstacle 14 is installed in the fuel concentration passage 12 between the fuel nozzle 10 and the distributor 11 as shown in the perspective view of FIG. 2, and an upper surface 14c of the obstacle 14 is a fuel nozzle. 10, the bottom surface 14 d of the obstacle is in contact with the distributor 11, and there are two side surfaces 14 e between the top surface 14 c and the bottom surface 14 d of the obstacle 14, and the front end 14 a and the bottom surface 14 d of the obstacle are the fuel nozzles. 10 and the upstream end of the distributor 11 are vertically connected, and due to the obstacle 14, the flow path between the fuel nozzle 10 and the distributor 11 is shown in FIGS. 1 (b) and 1 (c). And it is divided as shown in FIG. 1 (b) is a cross-sectional view taken along line AA in FIG. 1 (a), and FIG. 1 (c) is a cross-sectional view taken along line BB in FIG. 1 (a). ) Is a cross-sectional view taken along line CC in FIGS. 1 (a), 1 (b), and 1 (c).

  As shown in FIG. 1 (d), the obstacle 14 installed in the fuel concentration channel 12 divides the fuel concentration channel 12 in the circumferential direction of the cylindrical fuel nozzle 10, and the respective divisions. The length in the circumferential direction of the fuel concentration channel 12 thus made becomes shorter in the circumferential direction as it proceeds to the wake.

  The fuel particles collected in the fuel enrichment flow path 12 are collected toward the center of the fuel enrichment flow path 12 divided as they proceed to the downstream while hitting the side surface 14e of the obstacle 14. As a result, the fuel particles that have been concentrated near the inner wall of the fuel nozzle 10 and started to flow with the widening of the width of the fuel concentration passage inlet 12a are concentrated in the center of the width of the passage 12, and then the fuel concentration passage. Exit from exit 12b.

  FIG. 3 is a view showing the structure of the fuel nozzle 10 according to the second embodiment of the present invention. The structure of the fuel nozzle 10 of the second embodiment is different from the structure shown in FIG. 1, and instead of the distributor 11 and the obstacle 14, three plate-shaped U-shapes shown in a perspective view in FIG. It is formed by connecting in the circumferential direction so that the end of the upstream side surface 15a of the obstacle 15 is in contact.

  When the three plate-shaped U-shaped obstacles 15 shown in a perspective view in FIG. 3A are connected along the fuel nozzle 10, the fuel nozzle 10 and the three plate-shaped U-shaped obstacles are connected. The flow path between the obstacles 15 is divided as shown in FIGS. 3B, 3C, and 3D. 3 (b) is a cross-sectional view taken along line AA in FIG. 1 (a), and FIG. 3 (c) is a cross-sectional view taken along line BB in FIG. 1 (a). ) Is a cross-sectional view taken along the line CC in FIGS. 1 (a), 3 (b) and 3 (c).

  Each U-shaped obstacle 15 includes a side surface 15a and a bottom surface 15b along the inner wall surface of the fuel nozzle 10 that connects the side surfaces 15a. The length of the side surface 15a opposite to the bottom surface 15b is long. The side is attached so as to contact the inner wall of the fuel nozzle 10. Since the particles collected near the inner wall of the fuel nozzle 10 upstream of the U-shaped obstacle 15 flow in a region surrounded by the U-shaped obstacle 15 and the fuel nozzle 10, the fuel is concentrated in this region. A flow path 12 is formed.

  Unlike the solid wedge-shaped obstacle 14 of the first embodiment, the obstacle 15 of the present embodiment is different from the solid wedge-shaped obstacle 14 of the first embodiment because the obstacle 15 having a U-shaped plate is used. A fuel lean flow path 13 is provided outside the fuel concentration flow path 12 formed in FIG. 1, and a fuel flow path is formed inside and outside the U-shaped obstacle 15, so that the fuel concentration is compared with the embodiment shown in FIG. The area where the obstacle 15 partitioning the flow paths 12 and 13 contacts the mixed gas 3 increases, and the obstacle 15 is easily cooled.

FIG. 4 shows the configuration of the third embodiment of the present invention, in which a toothed flame holder 16 is employed.
4A is a side sectional view of the solid fuel burner of the present embodiment, FIG. 4B is a configuration diagram of the fuel nozzle 10 viewed from the furnace 1, and FIG. 4C is a diagram of FIG. It is CC sectional view taken on the line.

  As shown in the view from the furnace side in FIG. 4B, the plurality of teeth 17 of the toothed flame holder 16 are annularly held so as not to overlap with the plurality of wedge-shaped obstacles 14 arranged in an annular shape. It is annularly arranged in the flame unit 16 at equal intervals. Therefore, the fuel concentration passage outlet 12b (FIG. 4C) formed between two adjacent wedge-shaped obstacles 14 and the teeth 17 of the flame holder 16 are installed so as to overlap each other when viewed from the front-rear direction of the fuel passage. ing.

  In the present embodiment, the fuel concentration passage outlet 12b and the teeth 17 of the flame holder 16 are in a one-to-one relationship so that the fuel particles introduced into the furnace 1 through the fuel concentration passage outlet 12b hit the teeth 17 of the flame holder 16. It is desirable to provide it so as to correspond and overlap. In this case, the circumferential width W1 of the fuel concentration passage outlet 12b is set so that the fuel particles do not hit the teeth 17 of the flame holder 16 and are not put into the furnace. 17 is equal to or smaller than the width W2 on the circumferential straight line, and the radial height h1 of the fuel concentration passage outlet 12b is the height h2 of the teeth 17 of the flame holder 16 in the radial direction. It is desirable to be smaller. However, if the height h1 in the radial direction of the fuel concentration passage outlet 12b is too small, fuel particles may be clogged. Therefore, the radial width h1 of the fuel concentration passage outlet 12 (b) has a toothed flame stabilizer. The width 17 of the teeth 17 may be larger than the radial width h2. As shown in the particle flow 18, the fuel particles flowing in from the fuel concentration passage inlet 12 (a) pass through the fuel concentration passage 12 and exit from the fuel concentration passage outlet 12b while being collected in the central direction of the passage. Then, after hitting the teeth 17 of the flame holder 16, the flame holder 16 is put into the furnace 1.

  FIG. 5 is a side sectional view of a solid fuel burner showing the structure of Embodiment 4 of the present invention. 1 differs from the burner shown in FIG. 1 in that the distributor 11 moves closer to the central axis of the fuel nozzle 10 as it advances in the downstream direction. As the distributor 11 advances in the downstream direction, the fuel concentration passage 12 becomes closer to the central axis direction of the fuel nozzle 10, so that the passage cross-sectional area increases in the radial direction of the fuel nozzle 10 as it advances downstream.

  The cross-sectional area of the fuel concentration channel 12 is constant, or the cross-sectional area of the outlet of the channel 12 is larger than that of the inlet. By making the cross-sectional area constant, the flow speeds of the fuel concentration passage inlet 12a and the fuel concentration passage outlet 12b are constant. Further, if the cross-sectional area of the fuel concentration passage outlet 12b is made larger than the cross-sectional area of the fuel concentration passage inlet 12a, the flow velocity of the fuel concentration passage outlet 12b becomes larger than the flow velocity of the mixed gas 3 at the fuel concentration passage inlet 12a. Slower, can easily form a low flow rate or mixed flow of high concentration fuel particles and carrier gas, increase solid fuel concentration and reduce fuel particle energy and speed, improve ignitability, Improvement can be achieved.

1 furnace 2 oil gun 3 gas mixture 4 combustion gas nozzle (secondary nozzle)
5 Combustion gas nozzle (third nozzle)
6 Air register 7 Wind box 8 Venturi 9 Concentrator 10 Fuel nozzle 11 Distributor 12 Fuel enrichment flow path 13 Fuel lean flow path 14 Obstacle (wedge shape)
15 Obstacle (plate)
16 Toothed flame holder 17 Toothed flame holder tooth 18 Particle flow 19 Narrow tube 20 Water tube

Claims (3)

A cylindrical fuel nozzle that ejects a mixed fluid of solid fuel and its carrier gas;
A combustion gas nozzle for injecting combustion gas disposed on the outer periphery of the fuel nozzle;
A venturi that is disposed on the inner wall side of the fuel nozzle and temporarily squeezes the transport path for the solid fuel and the transport gas in the fuel nozzle toward the central axis direction, and is provided on the central axis of the fuel nozzle on the downstream side of the venturi A solid fuel burner provided with a concentrator that changes the flow in the fuel nozzle outward, and a distributor that divides the flow path of the fuel nozzle into an outer peripheral portion and an inner peripheral portion on the downstream side of the concentrator,
The conveying flow path between the fuel nozzle and the distributor is divided into at least two in the circumferential direction of the fuel nozzle, and the circumferential length of the divided flow path advances to the wake. A solid fuel burner characterized by having a reduced shape. The solid fuel burner according to claim 1, wherein the fuel nozzle outlet has a toothed flame holder.
The outlet of the circumferentially divided conveying flow path between the fuel nozzle and the distributor is approximately the same as the circumferential width of the teeth of the toothed flame stabilizer or the teeth when viewed from the furnace side. The solid fuel burner according to claim 1, wherein the burners overlap so as to be within the circumferential width of the teeth of the attached flame holder. The cross-sectional area of the upstream inlet and the downstream outlet of the circumferentially divided transfer passage between the fuel nozzle and the distributor is the same or the cross-sectional area of the outlet of the transfer passage is larger than that of the inlet. The solid fuel burner according to claim 1 or 2, wherein the solid fuel burner has a structure.

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