JP2000130710A - Pulverized coal combustion burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pulverized coal combustion burner suitable for reduction of nitrogen oxide concentration. SOLUTION: A pulverized coal combustion burner is adapted such that it includes a pulverized coal nozzle 10 for injecting a mixture of pulverized coal and air and a secondary air nozzle 11 and a tertiary air nozzle 12 both provided concentrically on an outer periphery of the pulverized coal nozzle 10, and there is provided a flared pipe section 20 on a tip end of a partition wall 21 that separates the adjacent two air nozzles. In the burner, there is provided deflection means, e.g. a guide plate 30 through which secondary air in the secondary air nozzle 11 is flowed along the flared pipe section 20. The secondary air is injected toward an outer periphery with the aid of the guide plate 30, whereby mixing of the secondary and tertiary airs and pulverized coal is delayed to reduce nitrogen oxide concentration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a burner that burns pulverized coal by carrying it in a gas stream, and more particularly to a pulverized coal combustion burner suitable for reducing the concentration of nitrogen oxides (hereinafter referred to as NOx).

[0002]

2. Description of the Related Art Generally, in a combustion burner, there is a problem of suppressing NOx generated during combustion. In particular, coal has a higher nitrogen content than gaseous and liquid fuels. For this reason, it is more important to reduce NOx generated during combustion of the pulverized coal combustion burner than in the case of gaseous fuel or liquid fuel.

Most of the NOx generated during the combustion of pulverized coal is generated by oxidizing nitrogen contained in the coal.
x, so-called fuel NOx. In order to reduce this NOx, various burner structures and combustion methods have been conventionally studied.

As one of the combustion methods, there is a method of forming a region having a low oxygen concentration in a flame to reduce NOx. For example, JP-A-1-305306 (USP4)
930430), JP-A-3-211304, JP-A-3-110308, US Pat.
The method of forming a flame in a low oxygen concentration atmosphere and completely combusting coal is disclosed in SP568823 and the like. Further, a structure including a fuel nozzle for conveying pulverized coal in a gas stream and an air nozzle for ejecting air outside the fuel nozzle is provided. Is disclosed. According to these conventional techniques, a reducing flame region having a low oxygen concentration is formed inside a flame, and NOx is formed in the reducing flame region.
To reduce the amount of NOx generated in the flame. Also, JP-A-3-211304 and JP-A-3-110308, US Pat.
No. 37 describes that a flame holding ring is provided at the tip of a pulverized coal nozzle to stabilize the flame. According to these conventional techniques, by providing a flame holding ring or an obstacle at the tip of the pulverized coal nozzle, a circulating flow is formed downstream of the tip of the pulverized coal nozzle, and a high-temperature gas is Stagnation, the ignition of the pulverized coal proceeds, and the stability of the flame can be increased.

[0005]

However, the above-mentioned prior art is still not enough to suppress the generation of NOx.

An object of the present invention is to provide a pulverized coal combustion burner which can solve the above-mentioned problems of the prior art and can further reduce the amount of generated NOx.

[0007]

The present invention employs the following means in order to solve the above-mentioned problems.

A secondary air nozzle for ejecting secondary air is provided concentrically on the outer periphery of a pulverized coal nozzle for ejecting a mixture of pulverized coal and primary air, and tertiary air is ejected on the outer periphery of the secondary air nozzle. In a pulverized coal combustion burner in which a tertiary air nozzle is provided concentrically and an expanded portion is provided at the end of the outer peripheral wall of the secondary air nozzle, the secondary air ejected from the secondary air nozzle is subjected to the secondary air nozzle. A deflecting means is provided on the outer peripheral side of the air nozzle.

As described above, since the secondary air nozzle and the tertiary air nozzle are arranged concentrically on the outer periphery of the pulverized coal nozzle, a reducing flame region having a low oxygen concentration is formed by the primary air to suppress the generation of NOx. The secondary air and the tertiary air are mixed on the downstream side of the reducing flame region to form an oxidizing flame, complete combustion is achieved, and the mixing of the secondary air and the tertiary air is delayed to form a large reducing flame region, and NOx The effect of suppressing the occurrence of blemishes can be enhanced.

Also, pulverized coal has poor ignitability itself,
In order to stably form the flame, it is desirable to draw the high-temperature combustion gas downstream of the flame to the vicinity of the pulverized coal nozzle outlet, but it is preferable that the downstream end of the partition wall separating the pulverized coal nozzle from the secondary air nozzle A low pressure section is formed on the side and a circulating flow is formed, so that the hot combustion gas is drawn back.

Further, since the secondary air flows to the outer periphery along the expanded portion at the outer peripheral end of the secondary air nozzle, a circulation formed downstream of the partition wall separating the pulverized coal nozzle and the secondary air nozzle. The flow is large, which can delay the mixing of the secondary air with the pulverized coal. Further, since the circulating flow is increased, high-temperature combustion gas flows into the circulating flow, and the ignitability of the pulverized coal is improved.

Further, since the deflecting means for bringing the flow of the secondary air to the outer peripheral side is provided, the mixing of the secondary air, the tertiary air and the pulverized coal can be delayed, and the reduction flame region can be enlarged. Since the circulating flow downstream of the partition wall separating the pulverized coal nozzle and the secondary air nozzle is increased, the ignitability of the pulverized coal is improved, and the consumption of oxygen is accelerated, so that the reducing flame region can be enlarged.

Further, in the pulverized coal combustion burner according to claim 1, the deflecting means is provided at a tip of an inner peripheral wall of the secondary air nozzle, and an expanding portion provided at a tip of an outer peripheral wall of the secondary air nozzle. The guide plate is provided at a more acute angle.

By arranging the guide plate at an acute angle with respect to the central axis of the burner, the effect of bringing the secondary air to the outer peripheral side is increased, and it is effective to delay the mixing of the secondary air and the pulverized coal. It is.

Further, in the pulverized coal combustion burner according to the first aspect, the deflecting means is a gas ejection nozzle for ejecting gas toward the secondary air.

Further, in the pulverized coal combustion burner according to the first aspect, the deflecting means is a guiding member for guiding the flow of the secondary air toward the expanded pipe side.

Further, in the pulverized coal combustion burner according to the first aspect, the deflecting means is a secondary air swirler provided at an outlet of the secondary air nozzle.

Further, in the pulverized coal combustion burner according to claim 2, an angle of the guide plate with respect to a center axis of the pulverized coal nozzle is provided at an angle of 60 to 90 degrees.

As described above, when the guide plate is provided, the effect of directing the secondary air to the outside is great.
It is extremely effective to set the angle between 60 degrees and 90 degrees, preferably 80 degrees to 90 degrees with respect to the central axis of the pulverized coal nozzle. Further, in the pulverized coal combustion burner according to claim 2, a tip of the guide plate projects downstream from a tip of the expanded portion.

Thus, the secondary air flows toward the flow of the tertiary air by the guide plate, and serves to direct the tertiary air to the outside. For this reason, it is effective in delaying the mixing of the tertiary air and the pulverized coal.

Further, in the pulverized coal combustion burner according to claim 2, a tip of the guide plate is located upstream of a tip of an outer peripheral wall of the tertiary air nozzle.

Usually, the outer peripheral wall of the tertiary air nozzle often serves also as the furnace wall of the boiler, and slag of combustion ash adheres to the furnace wall. Large slags can reach several to hundreds of kilograms. By preventing the tip from protruding toward the furnace from the furnace wall also serving as the outer peripheral wall of the tertiary air nozzle, it is possible to prevent the influence of slag falling.

Further, in the pulverized coal combustion burner according to claim 7, a distance between a tip of the expanded portion and a tip of the guide plate is in a range of 5 mm or more and 50 mm or less.

Further, in the pulverized coal combustion burner according to the first aspect, a swirler for jetting the tertiary air in a swirling flow is provided to the tertiary air nozzle.

By providing the swirler, the tertiary air ejected from the tertiary air nozzle receives a force in the outer peripheral direction without mixing with the pulverized coal near the burner. It is desirable that the tip of the outer peripheral wall of the tertiary air nozzle be expanded toward the outer periphery.

Further, in the pulverized coal combustion burner according to claim 1, the expanded portion is provided at a tip of a partition wall separating the secondary air nozzle and the tertiary air nozzle, It is characterized in that both the outer peripheral wall tip and the inner peripheral wall tip of the tertiary air nozzle are expanded.

Further, in the pulverized coal combustion burner according to the first aspect, a flow path reducing member for narrowing the flow path of the secondary air nozzle to increase the flow velocity is provided in the secondary air nozzle. Features.

By providing the flow channel reducing member, the direction of the secondary air having the increased flow velocity can be changed by the guide plate, so that the flow of the tertiary air can be directed further to the outer periphery. The channel reducing member may be provided on any of the outer peripheral inner wall and the inner peripheral inner wall of the secondary air nozzle.

In the pulverized coal combustion burner according to the twelfth aspect, the secondary air is provided downstream of the flow path reducing member at the tip of the inner peripheral wall of the secondary air nozzle as the deflecting means. It is characterized in that a guide plate provided at an acute angle with respect to the expanded portion provided at the tip of the outer peripheral wall of the nozzle is provided.

[0030] In the pulverized coal combustion burner according to claim 13, the flow passage reducing member is provided on an inner peripheral wall of the secondary air nozzle. In the charcoal combustion burner, a tip of an outer peripheral wall of the tertiary air nozzle is expanded outward.

Further, in the pulverized coal combustion burner according to the first aspect, a flame holding ring is provided on the outer periphery of the tip of the pulverized coal nozzle. The flammability of the pulverized coal can be improved by the flame holding ring.

Further, in the pulverized coal combustion burner according to the second aspect, a slit is provided in the guide plate. By providing the slit, thermal deformation of the flame holding ring or the guide plate can be suppressed.

A secondary air nozzle for ejecting secondary air is provided concentrically on the outer periphery of a pulverized coal nozzle for ejecting a mixture of pulverized coal and primary air, and tertiary air is provided on the outer periphery of the secondary air nozzle. In a pulverized coal combustion burner in which a tertiary air nozzle to be ejected is provided concentrically and an expanded portion is provided at the end of an outer peripheral wall of the secondary air nozzle, a partition wall tip separating the pulverized coal nozzle and the secondary air nozzle An obstacle having a plane substantially perpendicular to the flow of the primary air and an obstacle having a plane substantially perpendicular to the flow of the secondary air are provided in the section, and the plane of the former obstacle is the same as that of the latter obstacle. It is characterized by being located on the upstream side in the burner axis direction from the plane.

Thus, a circulating flow is formed by the obstacle downstream of the partition separating the primary air and the secondary air.
Since the obstacles are spaced apart in the burner axis direction, vortices are alternately formed in the circulating flow in the burner axis direction. The length of the circulating flow is extended in the burner axis direction by alternately forming vortices. For this reason, since a high-temperature combustion gas flows in from the downstream side, the temperature of the circulating flow rises, and the ignitability of the pulverized coal improves.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1A is a schematic diagram of a pulverized coal combustion burner according to this embodiment, and FIGS. 1B and 1C are FIGS.
FIG. 4 is an enlarged view for explaining an air flow in a nozzle tip region shown in FIG.

In these figures, reference numeral 10 denotes a pulverized coal nozzle connected to a conveying pipe (not shown) on the upstream side for supplying and conveying pulverized coal together with primary air, and 11 denotes a secondary air nozzle for ejecting secondary air A flow path is formed concentrically around the outer periphery of the pulverized coal nozzle 10. Reference numeral 12 denotes a tertiary air nozzle that ejects tertiary air, and a flow path is formed concentrically around the outer periphery of the secondary air nozzle 11. The flow distribution ratio of primary air, secondary air, and tertiary air is, for example, 1-2: 1:
3 to 7. 13 is pulverized coal and primary air flowing in,
Numeral 14 indicates the inflowing secondary air, and numeral 15 indicates the inflowing tertiary air. Reference numeral 16 denotes an oil gun provided to penetrate the pulverized coal nozzle 10 and is used for assisting combustion when the burner is started or when burning under low load. Reference numeral 17 denotes a throttle unit for reducing the nozzle inner diameter of the pulverized coal nozzle 10 for preventing flashback of the pulverized coal, and 18 denotes a primary air and a secondary air which are provided at the tip of a partition wall 28 separating the pulverized coal nozzle and the secondary air nozzle. A flame holding ring 19 for separating and expanding the circulating flow 31 is a burner throat constituting a furnace wall, and also serves as an outer peripheral wall of a tertiary air nozzle. Reference numeral 20 denotes a guide sleeve provided at the tip of a partition 21 that separates the secondary air nozzle and the tertiary air nozzle, and is a tube expansion section in the present invention. Reference numeral 22 denotes a swirler for swirling the tertiary air along the circumference of the secondary air nozzle. In this embodiment, an air swirl blade usually called a register blade is used. 23 is a side plate through which secondary air flows, 24 is a water pipe provided on the furnace wall 19, 25 is a wind box into which the secondary air is introduced, 26 is a damper for adjusting the secondary air, 27 is pulverized coal. This is a swirler for swirling along the circumference of the nozzle. In this embodiment, air swirling vanes usually called vanes are used. 28 is a partition wall between the pulverized coal nozzle 10 and the secondary air nozzle 11;
Reference numeral 0 denotes a guide plate provided at the tip of the inner peripheral wall of the secondary air nozzle 11 for ejecting secondary air in the outer peripheral direction, and 31 is formed between the ejection areas of the primary air nozzle 10 and the secondary air nozzle 11. The circulation flow 32 is an obstacle provided in the primary air nozzle 10. 52 is a secondary air flow ejected from the secondary air nozzle 11, and 53 is a tertiary air flow ejected from the tertiary air nozzle 12. 65a is an obstacle attached to the flame holding ring 18 and provided on the inner peripheral portion of the secondary air nozzle.

FIG. 2 is an enlarged view for explaining the air flow in the nozzle tip region of the conventional pulverized coal combustion burner shown for comparison with the pulverized coal combustion burner shown in FIG. 1 (b).

The configuration shown in FIG. 2 is different from that shown in FIG. 1A in that the guide plate 30 is not provided.

Next, the combustion operation of this embodiment will be described with reference to FIGS. 1 (a) and 1 (b).

When the combustion of the pulverized coal combustion burner starts, the air downstream of the partition walls 28 separating the pulverized coal nozzles 10 and the secondary air nozzles 11 is entrained by the air ejected from the respective nozzles. The pressure drops and a circulating flow is formed that flows from downstream to upstream. Partition wall 2
Since the flame holding ring 18 is provided at the distal end of 8, the primary air and the secondary air are separated, and the circulation flow is expanded. Since high-temperature gas stays in this circulation flow, the ignition of the pulverized coal proceeds, and the stability of the flame increases. Downstream of the obstacle 32, the pulverized coal gathers near the partition wall 28 due to inertial force. For this reason, the concentration of pulverized coal increases near the circulating flow, and a flame of pulverized coal and primary air is stably formed near the outlet of the pulverized coal nozzle. In addition, the consumption of oxygen in this flame progresses,
A reducing flame region having a low oxygen concentration spreads in the flame, and NOx
The amount of generation can be reduced. Further, since the ignition is accelerated, the combustion of the coal proceeds, and the unburned portion (hereinafter, referred to as unburned portion) in the combustion ash also decreases. Further, the air swirl vanes 22, 27
Is provided, the secondary air and the tertiary air are ejected as a swirling flow, and the centrifugal force increases the negative pressure downstream of the flame holding ring 18 to further expand the circulation flow. As a result, mixing of the secondary air or tertiary air with the pulverized coal near the burner is delayed, and the oxygen concentration in the flame is reduced.

In the present embodiment, the secondary air flow 52 ejected from the secondary air nozzle 11 is
As means for deflecting to the outer peripheral side of the secondary air nozzle 11
The guide plate 30 is provided at the tip of the inner peripheral wall of the above. The secondary air is blown toward the outer peripheral side, the mixing of the secondary air or tertiary air with the pulverized coal stream is further delayed, and the circulating flow 31 downstream of the flame holding ring 18 expands. Since the amount of high-temperature gas returning from the downstream in this circulating basin increases, the ignition of the pulverized coal is promoted and the reducing flame region is expanded. Therefore, the generation of NOx and unburned components can be further reduced.

The state of the combustion state at this time is shown in the guide plate 30.
This will be described in comparison with FIG. In FIG. 2, the flow path of the tertiary air 53 is bent by the guide sleeve 20 formed in a tapered cylinder, and is ejected to the outer peripheral side. On the other hand, the flow path of the secondary air nozzle 11 at the nozzle outlet is widened to the outer peripheral side by the guide sleeve 20. Since the air travels straight due to inertia, the secondary air 52 is likely to flow along the burner axis direction. At this time, since the air in the region along the guide sleeve 20 is entrained in the flow of the secondary air 52, a pressure drop (hereinafter referred to as a reverse pressure gradient) occurs in a direction opposite to the direction in which the secondary air is ejected, and A circulating flow 54 is formed downstream of the sleeve 20. A flow toward the center of the tertiary air 53 is induced by the circulating flow 54, and the mixing of the tertiary air 53 and the pulverized coal is accelerated, so that the reduction flame region is narrowed.

On the other hand, in the present embodiment, FIG.
As shown in (b), the guide plate 30 causes the secondary air 52 to blow out in the outer peripheral direction. Therefore, formation of the circulation flow 54 downstream of the guide sleeve 20 separating the secondary air nozzle 11 and the tertiary air nozzle 12 is prevented or suppressed. Also, by the momentum of the secondary air 52 ejected in the outer peripheral direction,
In particular, since the secondary air 52 is configured to be ejected toward the outer peripheral side from the tertiary air 53, the tertiary air 53 flows further toward the outer periphery. For this reason, the mixing of the secondary air or tertiary air with the pulverized coal near the burner is delayed, the reduction flame region in the flame is widened, and NOx generated in the flame can be reduced. Further, since the distal end of the guide plate 30 is located downstream of the distal end of the guide sleeve 20 in the burner axial direction, the flow of the secondary air is likely to flow to the outer periphery, and the circulating air flows downstream of the guide sleeve 20. It is difficult to do.

In this embodiment, the flow path near the outlet of the secondary air nozzle is narrowed by the obstacle 65a attached to the flame holding ring 18. Since the ejection speed of the secondary air is increased, the mixing of the tertiary air 53 and the pulverized coal can be delayed.

As described above, according to the present embodiment, the secondary air 52 is ejected in the outer peripheral direction by the guide plate 30 provided on the secondary air nozzle. Further, since the back pressure gradient downstream of the partition wall between the secondary air nozzle and the tertiary air nozzle is reduced, the tertiary air 53 ejected from the tertiary air nozzle on the outer peripheral side of the secondary air nozzle also ejects in the outer peripheral direction. For this reason, mixing of the pulverized coal and the combustion air near the burner is suppressed, and the pulverized coal burns in a low oxygen concentration atmosphere near the burner, thereby reducing the amount of NOx generated. As an example, Table 1 shows the results of a combustion test of the burner shown in FIG. 1 (the distance between the guide sleeve 20 and the tip of the guide plate 30 in the burner axial direction of 10 mm) and the burner shown in FIG. .

[0047]

[Table 1]

At this time, the NOx concentration at the burner outlet of the burner shown in FIG. 1 was 103 ppm (converted to 6% oxygen concentration), whereas the NOx concentration of the burner shown in FIG. It was 111 ppm (in terms of 6% oxygen concentration), and the effect of reducing the amount of NOx generated by the present invention was recognized.

FIG. 1 (c) is an enlarged view of the nozzle tip area for explaining the air flow when the guide plate 30 of FIG. 1 (c) is moved upstream from that of FIG. 1 (b). . FIG.
When the guide plate 30 is moved to the upstream side of the guide sleeve 20 in the burner axial direction as in the burner shown in FIG. 1C, the secondary air 52 flows as shown in FIG.
That is, the direction of the flow of the secondary air 52 can be changed in the outer circumferential direction by the guide plate 30, but the flow in the outer circumferential direction is blocked by the guide sleeve 20. For this reason, the secondary air ejected from the burner is supplied to the guide plate 30 as shown in FIG.
Flows in the axial direction more than when installed at the downstream side in the burner axial direction from the tip of the guide sleeve 20. For this reason, as shown in FIG. 1C, a circulation flow 54 is likely to be formed downstream of the guide sleeve 20. Therefore, the circulating flow 54 induces a flow of the tertiary air 53 in the central axis direction, so that the mixing of the tertiary air 53 and the pulverized coal is accelerated, and the reduction flame region is narrowed. As an example, FIG.
(The tip of the guide plate 30 is the guide sleeve 20)
Is located 10 mm upstream in the burner axis direction from the tip of
Table 1 shows the results of a combustion test conducted at a coal supply of 500 kg / h. At this time, the NOx concentration at the burner outlet of the burner shown in FIG. 1B was 103 ppm (converted to 6% oxygen concentration), whereas the NO of the burner shown in FIG.
The Ox concentration is 107 ppm (converted to 6% oxygen concentration) on the same basis of the unburned components, which is NO compared to the case where the guide plate 30 is located downstream of the tip of the guide sleeve in the burner axis direction.
x generation amount increases.

Next, a second embodiment of the present invention will be described with reference to FIG.

FIG. 3 is a schematic view of the nozzle tip of the pulverized coal combustion burner according to this embodiment.

This embodiment is different from the first embodiment shown in FIGS. 1A and 1B in that the angle 55 of the guide plate 30 and the angle 56 of the guide sleeve 20 can be adjusted. And the other configurations are the same.

According to the present embodiment, the angle 5 of the guide plate 30
By adjusting the angle 5 and the angle 56 of the guide sleeve 20, a more optimal circulating basin as compared to the first embodiment is formed in accordance with the supplied pulverized coal, the amount of primary air and the amount of combustion air, It is possible to effectively reduce NOx and unburned components.

At this time, it is desirable that the angle 55 of the guide plate 30 be 60 to 90 degrees, more preferably 80 to 90 degrees. The guide plate 30 blows out the secondary air 52 in the outer peripheral direction. Therefore, formation of the circulation flow 54 downstream of the guide sleeve 20 separating the secondary air nozzle 11 and the tertiary air nozzle 12 is prevented or suppressed. In addition, due to the momentum of the secondary air 52 ejected in the outer peripheral direction, in particular, since the secondary air 52 is ejected toward the outer peripheral side from the tertiary air 53, the tertiary air 53 flows further toward the outer periphery. . For this reason, mixing of the secondary air or tertiary air with the pulverized coal near the burner is delayed, and the reduction flame region in the flame is widened, so that NOx generated in the flame can be reduced.

Next, a third embodiment of the present invention will be described with reference to FIG.

FIG. 4 is a schematic view of the nozzle tip of the pulverized coal combustion burner according to this embodiment.

In this embodiment, as shown in the figure, an outlet area of the secondary air nozzle 11 is used as a guide member for guiding the secondary air flow ejected from the secondary air nozzle 11 to the outer peripheral side of the secondary air nozzle. Is provided with a tapered ring 61. Other configurations are substantially the same as those of the first embodiment.

According to this embodiment, the ring 61 becomes an obstacle to the secondary air 52 flowing in the burner axis direction. The flow of the secondary air 52 along the tapered portion of the ring 61 induces a flow of the secondary air 52 in the outer circumferential direction,
A part flows along the guide sleeve 20. For this reason,
Secondary air 52 flows downstream of the guide sleeve 20 separating the secondary air nozzle 11 and the tertiary air nozzle 12. Since the back pressure gradient downstream of the guide sleeve 20 is less likely to occur, the formation of the circulating flow 54 described above is prevented or suppressed. In addition, the tertiary air 53 flows further toward the outer periphery due to the momentum of the secondary air 52 ejected toward the outer periphery. Therefore, mixing of the secondary air or tertiary air with the pulverized coal near the burner is delayed, and the oxygen concentration in the flame decreases. By expanding the reducing flame region, NOx generated in the flame can be reduced.

Next, a fourth embodiment of the present invention will be described with reference to FIG.

FIG. 5 is a schematic view of the nozzle tip of the pulverized coal combustion burner according to this embodiment.

In this embodiment, as shown in the figure, as a guide member for guiding the secondary air flow ejected from the secondary air nozzle 11 to the outer peripheral side of the secondary air nozzle, the inside of the secondary air nozzle 11 or the nozzle is used. A gas jet nozzle 63 for jetting gas toward the outer periphery is provided in the outlet area. As the gas, air, combustion exhaust gas, inert gas such as nitrogen, steam, or the like can be used. Other configurations are substantially the same as those of the first embodiment.

According to the present embodiment, the gas ejection nozzle 63
Due to the momentum of the gas ejected from the nozzle, a secondary airflow ejected from the secondary air nozzle 11 induces a flow in the outer circumferential direction, and a part of the secondary air flows along the guide sleeve 20. In order to increase the momentum, it is desirable that the flow velocity of the gas ejected from the gas ejection nozzle 63 is higher than the flow velocity of the air ejected from the secondary air nozzle. In the burner having this configuration, since the secondary air 52 flows along the guide sleeve 20, a back pressure gradient downstream of the guide sleeve 20 is less likely to occur. For this reason, the formation of the circulation flow 54 described above downstream of the guide sleeve 20 is prevented or suppressed. In addition, the tertiary air 53 flows further toward the outer periphery due to the momentum of the secondary air 52 ejected toward the outer periphery. Therefore, mixing of the secondary air or tertiary air with the pulverized coal near the burner is delayed, and the oxygen concentration in the flame decreases. NOx generated in the flame due to the expansion of the reducing flame area
Can be reduced.

Next, a fifth embodiment of the present invention will be described with reference to FIG.

FIG. 6 is a schematic view of the nozzle tip of the pulverized coal combustion burner according to this embodiment.

In this embodiment, as shown in the figure, as a means for guiding the secondary air flow ejected from the secondary air nozzle 11 to the outer peripheral side of the secondary air nozzle, the secondary air nozzle is connected to the outlet of the secondary air nozzle. A swirl vane 64 as a next air swirler is provided. Other configurations are substantially the same as those of the first embodiment.

According to the present embodiment, the secondary air 52 is swirled by the swirling vanes 64 and flows to the outer peripheral side due to centrifugal force. For this reason, the secondary air 52 flows along the guide sleeve 20, so that a reverse pressure gradient downstream of the guide sleeve 20 is less likely to occur. For this reason, the formation of the circulation flow 54 described above downstream of the guide sleeve 20 is prevented or suppressed. In addition, the tertiary air 53 flows further toward the outer periphery due to the momentum of the secondary air 52 ejected toward the outer periphery. Therefore, mixing of the secondary air or tertiary air with the pulverized coal near the burner is delayed, and the oxygen concentration in the flame decreases. By expanding the reducing flame area,
NOx generated in the flame can be reduced.

As described above, according to the pulverized coal combustion burner of each of the above embodiments, the means for deflecting the secondary air flow ejected from the secondary air nozzle to the outer peripheral side of the secondary air nozzle is provided. A circulating flow is unlikely to be formed downstream of the partition wall between the secondary air nozzle and the tertiary air nozzle located on the outer peripheral side. In the circulating flow region, there is a pressure drop (back pressure gradient) in the direction opposite to the jetting direction of the flow, and the air flowing along the circulating flow changes its direction due to the back pressure gradient. In the flow of the pulverized coal combustion burner, when a circulating flow is formed downstream of the partition wall between the secondary air nozzle and the tertiary air nozzle, the tertiary air flow is likely to flow toward the pulverized coal flow side by the circulating flow. However,
In the above-described embodiments, the secondary air is ejected in the outer peripheral direction, so that it is difficult to form a circulating flow downstream of the partition wall between the secondary air nozzle and the tertiary air nozzle. Flows away from pulverized coal stream.

Further, by discharging the secondary air to the outer periphery, the primary air and the secondary air flow apart near the burner.
For this reason, it becomes difficult for the secondary air ejected from the secondary air nozzle to flow downstream of the partition wall between the pulverized coal nozzle and the secondary air nozzle, so that the reverse pressure gradient is strengthened and the circulation flow is widened. High-temperature gas stays in the circulating flow formed between the primary air and the secondary air flow, and contributes to ignition of the pulverized coal and stabilization of the flame. The expansion of the circulating flow weakens the cooling in the circulating flow by the secondary air and increases the temperature. Therefore, ignition of the pulverized coal is promoted. Since the ignition consumes more oxygen, the low oxygen concentration region formed in the flame expands,
As the amount of generated NOx decreases, the unburned portion in the combustion ash decreases.

Further, by improving the ignition of the pulverized coal and the stability of the flame, the distance required for combustion is shortened, and the effect of reducing the size of the combustion device body is also obtained. Furthermore, even when the concentration of pulverized coal decreases as in the case of combustion at a low load, the flame is stable, and the possible range of the pulverized coal combustion in the pulverized coal combustion burner is widened.

Next, a sixth embodiment of the present invention will be described with reference to FIG.

FIG. 7 is a schematic view of a pulverized coal combustion burner according to this embodiment.

In the present embodiment, as shown in the figure, the secondary air flow ejected from the secondary air nozzle 11 is deflected to the outer peripheral side of the secondary air nozzle 11 and the primary air And a ring 30 having a plane perpendicular to the flow of the secondary air. Other configurations are substantially the same as those of the first embodiment.

In the figure, the ring 30 is formed of an inner ring 301 formed on the pulverized coal nozzle 10 side and an outer ring 302 formed on the secondary air nozzle 11 side. The primary air and the secondary air are disturbed by the ring 30, and a circulating flow formed downstream of the ring 30 is developed.
In this embodiment, the inner ring 301 and the outer ring 302
Are spaced apart in the burner axis direction. As a result, the circulating flow formed downstream of the ring 30 is formed so as to be shifted in the burner axial direction between the pulverized coal flow side and the secondary air flow side. The circulation flow becomes longer in the axial direction than when two circulation flows are formed at the same position in the axial direction. For this reason, the gas circulates in the circulation flow 31 from the downstream side.

Further, secondary air is jetted to the outer periphery by the outer ring 302. Thus, the primary and secondary air flow away near the burner. For this reason, it becomes difficult for the secondary air ejected from the secondary air nozzle to flow downstream of the partition wall between the pulverized coal nozzle and the secondary air nozzle, so that the reverse pressure gradient is strengthened and the circulation flow is widened. High-temperature gas stays in the circulating flow formed between the primary air and the secondary air flow, and contributes to ignition of the pulverized coal and stabilization of the flame. As the circulation flow spreads, the cooling in the circulation flow by the secondary air is weakened, and the temperature rises.
Therefore, ignition of the pulverized coal is promoted. Since the consumption of oxygen proceeds due to the ignition, the region where the oxygen concentration is low formed in the flame expands, the amount of generated NOx decreases, and the unburned portion in the combustion ash decreases. In addition, since the ignition of the pulverized coal and the stability of the flame are improved, the distance required for combustion is shortened, and the effect of reducing the size of the combustion device body can be obtained. Furthermore, even when the concentration of pulverized coal decreases as in the case of combustion at a low load, the flame is stable, and the possible range of the pulverized coal combustion in the pulverized coal combustion burner is widened.

Further, by discharging the secondary air to the outer periphery by the outer ring 302, a circulating flow is less likely to be formed on the downstream side of the partition wall between the secondary air nozzle and the tertiary air nozzle located on the outer peripheral side. In the circulating flow region, there is a pressure drop (back pressure gradient) in the direction opposite to the jetting direction of the flow, and the air flowing along the circulating flow changes its direction due to the back pressure gradient. In the flow of the pulverized coal combustion burner, when a circulating flow is formed downstream of the partition wall between the secondary air nozzle and the tertiary air nozzle, the tertiary air flow is likely to flow toward the pulverized coal flow side by the circulating flow. However, in the present invention, the secondary air is ejected in the outer peripheral direction, so that it is difficult to form a circulating flow downstream of the partition wall between the secondary air nozzle and the tertiary air nozzle. And flows away.

Next, a seventh embodiment of the present invention will be described with reference to FIG.

FIG. 8 is a schematic view of a pulverized coal combustion burner according to this embodiment.

In this embodiment, as shown in the figure, the secondary air flow ejected from the secondary air nozzle 11 is deflected to the outer peripheral side of the secondary air nozzle 11 and the circulating flow is formed downstream of the partition wall 28. As a means for performing this, a thick portion (for example, a thickness of 10 mm) 303 of the ring 30 is provided on the inner peripheral wall side of the secondary air nozzle 11 of the ring 30 provided at the tip end of the partition wall 28. In addition, the obstacle 3 is located in the primary air nozzle 10.
Do not have two. When the ignitability of the pulverized coal is good, it is not necessary to have the obstacle 32 as shown in FIG. Other configurations are substantially the same as those of the sixth embodiment.

According to the present embodiment, the flow path of the secondary air nozzle is narrowed by the thick portion 303, and the flow velocity of the secondary air when passing through the thick portion 303 is increased. Since the secondary air collides with the outer ring 302 in the state where the flow velocity is increased, the velocity of the secondary air induced in the secondary air by the collision is high. As a result, the flow velocity of the secondary air in the outer peripheral direction is stronger than in the sixth embodiment. For this reason, the circulating flow downstream of the partition wall between the pulverized coal nozzle and the secondary air nozzle spreads, and the ignition of the pulverized coal is promoted by the temperature rise in the circulating flow.
In addition, since the secondary air is ejected in the outer peripheral direction, it is difficult to form a circulating flow downstream of the partition wall between the secondary air nozzle and the tertiary air nozzle, so that the tertiary air is separated from the pulverized coal flow near the burner. Flows. For this reason, the region where the oxygen concentration is low formed in the flame expands, the amount of generated NOx decreases, and the unburned portion in the combustion ash decreases.

In each of the sixth and seventh embodiments, the outer ring 302 of the ring 30 is a uniform ring in the circumferential direction of the burner.
A notch may be formed at the top end of the base 2 in an uneven shape along the circumferential direction. By providing the notch, thermal deformation of the ring can be reduced. In addition, the turbulence on the downstream side of the outer ring 302 increases, and the circulation flow easily develops. Further, the concave and convex cutouts may be provided not only on the outer ring 302 but also on the inner ring 301.

Next, an eighth embodiment of the present invention will be described with reference to FIG.

FIG. 9 is a schematic diagram of a pulverized coal combustion burner according to this embodiment.

In the present embodiment, as shown in the figure, the secondary air flow ejected from the secondary air nozzle 11 is deflected to the outer peripheral side of the secondary air nozzle 11, and a circulating flow is formed downstream of the partition wall 28. A ring 30 is provided as a means for performing this. Also,
As means for narrowing the flow path near the outlet of the secondary air nozzle 11, an obstacle 65b is provided in the circumferential direction of the outer peripheral wall of the secondary air nozzle. The obstacle 32 in the primary air nozzle 10 is provided near the throttle unit 17. As shown in FIG. 9 with respect to FIG. 1, even if the obstacles 32 are provided on the upstream side, they are collected near the partition wall 28. Other configurations are substantially the same as those of the sixth embodiment.

According to the present embodiment, the secondary air is
5b, the flow velocity is increased, and the air flow is disturbed in the flow path enlarged portion on the downstream side of the obstacle 65b, so that a certain turbulence can be generated. For this reason, the circulating flow downstream of the partition wall between the pulverized coal nozzle and the secondary air nozzle spreads, and the ignition of the pulverized coal is promoted by the temperature rise in the circulating flow. In addition, obstacle 65
The secondary air having the increased flow velocity in b collides with the outer ring 302 and is ejected in the outer peripheral direction, so that it is difficult to form a circulating flow downstream of the partition wall between the secondary air nozzle and the tertiary air nozzle.
For this reason, the direction of the tertiary air is not changed by the circulating flow, and the tertiary air flows away from the pulverized coal flow near the burner. For this reason, the region where the oxygen concentration is low formed in the flame expands, the amount of generated NOx decreases, and the unburned portion in the combustion ash decreases.

[0085]

As described above, according to the present invention, the means for deflecting the secondary air flow ejected from the secondary air nozzle to the outer peripheral side of the secondary air nozzle is provided. Flows. It becomes difficult to form a circulating flow downstream of the partition wall between the secondary air nozzle and the tertiary air nozzle. For this reason, the direction of the flow of the tertiary air is not changed by the circulating flow, and the tertiary air flows away from the pulverized coal flow near the burner. In addition, since the secondary air flows in the outer circumferential direction, it becomes difficult for the secondary air to flow directly from the secondary air nozzle into the circulating flow formed downstream of the partition wall of the pulverized coal nozzle and the secondary air nozzle. The pressure gradient increases, and this circulation expands. As a result, mixing of the pulverized coal and the tertiary air near the burner is suppressed, and the ignition of the pulverized coal is promoted. For this reason,
Pulverized coal burns at low oxygen concentration near the burner,
Ox generation can be reduced. Further, since the ignition of the pulverized coal is promoted, the unburned portion in the combustion ash can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a pulverized coal combustion burner according to a first embodiment of the present invention.

FIG. 2 is a schematic view of a nozzle tip of a pulverized coal combustion burner according to the prior art shown for comparison with the first embodiment.

FIG. 3 is a schematic view of a pulverized coal combustion burner according to a second embodiment of the present invention.

FIG. 4 is a schematic view of a nozzle tip of a pulverized coal combustion burner according to a third embodiment of the present invention.

FIG. 5 is a schematic view of a nozzle tip portion of a pulverized coal combustion burner according to a fourth embodiment of the present invention.

FIG. 6 is a schematic view of a nozzle tip portion of a pulverized coal combustion burner according to a fifth embodiment of the present invention.

FIG. 7 is a schematic view of a pulverized coal combustion burner according to a sixth embodiment of the present invention.

FIG. 8 is a schematic view of a pulverized coal combustion burner according to a seventh embodiment of the present invention.

FIG. 9 is a schematic view of a pulverized coal combustion burner according to an eighth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Pulverized coal nozzle 11 Secondary air nozzle 12 Tertiary air nozzle 30 Guide plate 301 Inner ring 302 Outer ring 303 Thick part 31 Circulating flow 61 Ring 63 Gas discharge nozzle 64 Swirl vane 65a, 65b Obstacle

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hironobu Kobayashi 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Shunichi Tsumura 6-9 Takaramachi, Kure City, Hiroshima Prefecture No. Babkotsuk Hitachi Co., Ltd. Kure Factory (72) Inventor Kenji Kiyama 6-9 Takara-cho, Kure City, Hiroshima Prefecture Babkotsuk Hitachi Co., Ltd. (72) Inventor Tadashi Jimbo 6-9 Takaracho, Kure City, Hiroshima Prefecture Babkotsuk Hitachi Inside the Kure Factory Co., Ltd. (72) Koji Kuramasu, Inventor 6-9 Takara-cho, Kure City, Hiroshima Pref. Inside the Kure Factory Co., Ltd. (72) Inventor Shigeki Morita 6-9 Takara-cho, Kure City, Hiroshima Pref. (72) Inventor Shinichiro Nomura 6-9 Takara-cho, Kure City, Hiroshima Pref. Kino Hiroshima Pref. 6-9 Takaracho, Kure City Babkotsuk Hitachi Kure Research Laboratory F Term (reference) 3K065 QA01 QB09 QB11 QC03 TA01 TB01 TD07 TE10 TJ03

Claims (18)

[Claims] 1. A secondary air nozzle for ejecting secondary air is provided concentrically around an outer periphery of a pulverized coal nozzle for ejecting a mixture of pulverized coal and primary air, and a tertiary air nozzle is provided on an outer periphery of the secondary air nozzle. In a pulverized coal combustion burner in which a tertiary air nozzle that ejects air is provided concentrically and an expanded portion is provided at the end of the outer peripheral wall of the secondary air nozzle, the secondary air that is ejected from the secondary air nozzle is A pulverized coal combustion burner, comprising a deflecting means provided on an outer peripheral side of a secondary air nozzle. 2. The pulverized coal combustion burner according to claim 1, wherein the deflecting means is provided at a tip of an inner peripheral wall of the secondary air nozzle, and an expanding portion provided at a tip of an outer peripheral wall of the secondary air nozzle. A pulverized coal combustion burner characterized by a guide plate installed at an acute angle. 3. The pulverized coal combustion burner according to claim 1, wherein the deflecting means is a gas ejection nozzle that ejects gas toward the secondary air. 4. The pulverized coal combustion burner according to claim 1, wherein the deflecting means is a guide member for guiding the flow of the secondary air toward the expanded pipe side. Burning burner. 5. The pulverized coal combustion burner according to claim 1, wherein the deflecting means is a secondary air swirler provided at an outlet of the secondary air nozzle. . 6. The pulverized coal combustion burner according to claim 2, wherein an angle of the guide plate with respect to a center axis of the pulverized coal nozzle is set at an angle of 60 to 90 degrees. Burning burner. 7. The pulverized coal combustion burner according to claim 2, wherein a tip of the guide plate projects downstream from a tip of the expanded portion. 8. The pulverized coal combustion burner according to claim 7, wherein a distance between a tip of the expanded portion and a tip of the guide plate is five.
A pulverized coal combustion burner characterized by being in the range of not less than 50 mm and not more than 50 mm. 9. The pulverized coal combustion burner according to claim 2, wherein a tip of the guide plate is located upstream of a tip of an outer peripheral wall of the tertiary air nozzle. 10. The pulverized coal combustion burner according to claim 1, wherein a swirler for ejecting the tertiary air in a swirling flow is provided to the tertiary air nozzle. 11. The pulverized coal combustion burner according to claim 1, wherein the expanded portion is provided at a tip end of a partition wall separating the secondary air nozzle and the tertiary air nozzle. A pulverized coal combustion burner characterized in that both the outer peripheral wall tip and the inner peripheral wall tip of the tertiary air nozzle are expanded. 12. The pulverized coal combustion burner according to claim 1, wherein a flow passage reducing member for narrowing the flow passage of the secondary air nozzle to increase the flow velocity is provided in the secondary air nozzle. Pulverized coal burning burner. 13. The pulverized coal combustion burner according to claim 12, wherein the deflecting means is provided at a distal end of an inner peripheral wall of the secondary air nozzle, downstream of the flow path reducing member, and A pulverized coal combustion burner, comprising: a guide plate provided at an acute angle with respect to an expanded portion provided at a tip of an outer peripheral wall of a nozzle. 14. The pulverized coal combustion burner according to claim 13, wherein the flow passage reducing member is provided on an inner peripheral wall of the secondary air nozzle. 15. The pulverized coal combustion burner according to claim 1, wherein a tip of an outer peripheral wall of the tertiary air nozzle is expanded outward. 16. The pulverized coal combustion burner according to claim 1, wherein a flame holding ring is provided on an outer periphery of a tip of the pulverized coal nozzle. 17. The pulverized coal combustion burner according to claim 2, wherein a slit is provided in the guide plate. 18. A secondary air nozzle for ejecting secondary air is provided concentrically on the outer periphery of a pulverized coal nozzle for ejecting a mixture of pulverized coal and primary air, and tertiary air is provided on the outer periphery of the secondary air nozzle. A pulverized coal combustion burner in which a tertiary air nozzle for ejecting air is provided concentrically and an expanded portion is provided at the end of the outer peripheral wall of the secondary air nozzle; An obstacle having a plane substantially perpendicular to the flow of the primary air and an obstacle having a plane substantially perpendicular to the flow of the secondary air are provided at the distal end portion, and the plane of the former obstacle is provided with the obstacle of the latter obstacle. A pulverized coal combustion burner, which is located upstream of the plane in the burner axis direction.