JP2010270992A - Coal burning boiler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coal burning boiler for burning fine powder coal (solid fuel) capable of reducing an NOx generation amount by suppressing a high-temperature oxygen remaining area formed around the periphery of flame. <P>SOLUTION: In the coal burning boiler, a burner 20 for putting the fine powder coal and air into a furnace is made to be a turning combustion type burner part arranged on each corner part of each stage or on a wall surface part, and one or a plurality of turning flames are formed in each stage. The burner 20 includes a fine powder coal burner 21 for putting the fine powder coal and the air, and secondary air input ports 30 respectively arranged on the upper/lower sides or on the right/left sides of the fine powder coal burner 21 and having a flow rate adjustment means. A kicker 24 for concentrating flow of the fine powder coal to a burner axial center part is provided in a coal primary port 22 of the fine powder coal burner 21. A separation distance L is provided between the fine powder coal burner 21 and the secondary air input port 30 at a degree that the secondary air put from the secondary air input port 30 does not interfere with the flame F formed from the fine powder coal burner 21 into the furnace. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a coal fired boiler that uses coal such as pulverized coal as fuel.

Conventionally, solid fuel-fired boilers include, for example, pulverized coal-fired boilers that burn pulverized coal as solid fuel. In such a pulverized coal fired boiler, two types of combustion systems are known: a swirl combustion boiler and an opposed combustion boiler.
Of these, in the pulverized coal-fired swirl combustion boiler, secondary air input ports for secondary air input are installed above and below the primary air input from the coal burner together with the pulverized coal of fuel. The flow rate is adjusted for the secondary air. (For example, see Patent Document 1)

The primary air described above is an amount of air necessary for conveying pulverized coal as fuel, and the amount of air is defined in a roller mill device that pulverizes coal into pulverized coal.
The secondary air mentioned above blows in the air quantity required in order to form the whole flame in a swirl combustion boiler. Therefore, the secondary air amount of the swirl combustion boiler is approximately the total air amount necessary for the combustion of the pulverized coal minus the primary air amount.

  On the other hand, in the burner of the opposed combustion boiler, it has been proposed to finely adjust the air introduction amount by introducing secondary air and tertiary air outside the primary air (pulverized coal supply). (For example, see Patent Document 2)

Japanese Patent No. 3679998 JP 2006-189188 A

By the way, in the conventional coal fired boiler described above, in order to reduce nitrogen oxides (NOx), in general, two-stage combustion using additional air (AA) is performed, and reduction combustion is performed near the burner. Has been done.
Further, in the conventional burner, a flame holding mechanism (adjustment of the tip corner, turning, etc.) is installed on the outer periphery of the pulverized coal burner, and further, the secondary air or the tertiary air is adjacent to the outer periphery of the pulverized coal burner. In general, a configuration in which an air input port for supplying air is installed is provided. For this reason, in the pulverized coal burner, the charged pulverized coal is ignited on the outer periphery of the flame, and a large amount of air is mixed in the ignition region on the outer periphery of the flame.

As a result, in the flame of the pulverized coal burner, a high-temperature oxygen residual region that generates NOx is formed on the outer periphery of the flame. This high temperature oxygen residual region is a flame outer periphery region where the oxygen concentration becomes high and combustion at a high temperature proceeds, and therefore, it is a combustion environment in which NOx is likely to be generated. Therefore, in the flame formed in the conventional pulverized coal burner, the amount of NOx generated from the outer periphery of the flame forming the high temperature oxygen residual region increases.
In this way, NOx generated from the outer periphery of the flame of the pulverized coal burner passes through the outer periphery of the flame as it is, so that the reduction is delayed as compared with the inside of the flame having a different combustion environment. As a result, the NOx generated outside the flame remains without being reduced, and the remaining NOx causes NOx generation in the conventional pulverized coal burner and coal fired boiler.

From such a background, in a coal fired boiler that burns solid fuel such as pulverized coal, it is desirable to suppress the high-temperature oxygen remaining region formed on the outer periphery of the flame and reduce the amount of NOx generated.
The present invention has been made in view of the above circumstances, and its object is to reduce the amount of NOx generated by suppressing (weakening) the high temperature oxygen remaining region formed on the outer periphery of the flame. It is to provide a coal fired boiler.

In order to solve the above problems, the present invention employs the following means.
In the coal fired boiler according to the present invention, a burner for charging pulverized fuel and air into a furnace is a burner unit of a swirl combustion system in which each burner part is disposed at each corner part or wall face part. In a coal fired boiler in which a plurality of swirling flames are formed, the burner has a fuel burner for charging powdered fuel and air, and a secondary air input having flow rate adjusting means disposed above and below or on the left and right of the fuel burner. And a rich flame portion forming member for concentrating the flow of the pulverized fuel in the center of the burner shaft in the flow path of the fuel burner, and between the fuel burner and the secondary air input port Further, a separation distance is set such that the secondary air introduced from the secondary air introduction port does not interfere with a flame formed from the fuel burner into the furnace.

  According to such a coal fired boiler, the burner includes a fuel burner that inputs pulverized fuel and air, and a secondary air input port that is disposed on the top and bottom or the left and right of the fuel burner and has a flow rate adjusting means. A rich flame portion forming member for concentrating the flow of the pulverized fuel to a burner shaft center portion in the flow path of the fuel burner, and the fuel between the fuel burner and the secondary air input port. Since the separation distance is set such that the secondary air introduced from the secondary air input port does not interfere with the flame formed from the burner into the furnace, the concentrated flame forming member causes the pulverized fuel to enter the flame. At the same time, the downstream flow can be disturbed, and at the same time, the supply of secondary air to the flame from the secondary air input port can be slowed down to lower the oxygen concentration in the flame.

As a result, a rich flame portion is formed inside the flame in which the pulverized fuel is concentrated, and stable ignition can be ensured by the formation of the rich flame portion and the turbulence of the flow generated downstream of the rich flame portion forming member. Therefore, the pulverized fuel can be stably burned in an environment having a low oxygen concentration.
In addition, since the secondary air is slowly supplied from the secondary air input port arranged so as not to interfere with the flame, the temperature drop (cooling) of the flame due to the low-temperature secondary air can be minimized. Despite the fact that the flame is short of air, the flame is heated to a high temperature and continues to ignite stably, so that combustion at a high temperature and a low oxygen concentration is possible. That is, the high-temperature oxygen remaining region formed on the outer periphery of the flame is suppressed, and combustion with significantly reduced NOx and unburned content becomes possible.
Note that the concentrated flame portion forming member concentrates the pulverized fuel inside the flame, so that it is possible to prevent the inner wall from being worn by the pulverized fuel on the downstream side of the concentrated flame portion forming member of the fuel burner.

2. The coal fired boiler according to claim 1, wherein the rich flame portion forming member is preferably a central open type kicker that is installed on a wall surface of the fuel burner and partially opens a flow path central portion. Then, the flow of the pulverized fuel can be collected in the central portion of the flow path, and the fuel can be injected (formation of the rich flame portion) concentrated from the partial opening in the central portion of the flow path toward the inside of the flame. The central open type kicker in this case may be provided over the entire circumference of the wall surface forming the flow path of the fuel burner, or in the same direction (up and down or left and right) as the secondary air input port is arranged. ) May be provided only on the wall surface.
In this case, it is preferable that the dense flame portion forming member includes a central closed type kicker that partially closes the central portion of the flow path upstream of the central open type kicker, whereby the flow of the pulverized fuel is central. Since it is once separated to the outer peripheral side (wall surface side) by the closed type kicker, this flow is folded back to the center and concentrated from the center open type kicker opening toward the inside of the flame, so that the fuel concentration is further increased. (Formation of a deep flame part) becomes possible.

  4. The coal fired boiler according to claim 2, wherein the opening of the central open type kicker is preferably provided with irregularities, thereby enabling fuel injection with further increased concentration (formation of a rich flame part). At the same time, the disturbance of the flow can be further promoted. Note that the unevenness in this case is not limited to a rectangular shape, and for example, a triangular shape or a semicircular shape may be employed.

  2. The coal fired boiler according to claim 1, wherein the rich flame portion forming member is preferably a cyclone portion formed in the fuel burner, whereby the flow of the pulverized fuel is caused by utilizing centrifugal force. A concentrated flame part can be formed by concentrating inside the flame.

  In the coal fired boiler according to any one of claims 2 to 5, it is preferable to provide one or a plurality of split members at a tip outlet portion of the fuel burner, whereby a flame holding mechanism is formed in front of the burner, More stable ignition can be maintained. In particular, if two or more split members are provided at a distance in the center of the tip outlet, the flame does not spread outward, but forms a concentrated flame in the center, so that NOx is generated inside the flame. , Ignition can be maintained strongly.

In the coal fired boiler according to any one of claims 2 to 6, it is preferable to provide an auxiliary nozzle for restricting a cross-sectional area of the flow path at a tip outlet portion of the burner. It can be further stabilized.
If a split member as described in claim 6 is used in combination and a flame holding mechanism is provided at the tip of the auxiliary nozzle, ignition can be further stabilized.

The coal fired boiler according to any one of claims 1 to 7, wherein the secondary air input port is preferably installed so as to have an outward angle from an axial center of the fuel burner, Even if the installation position of the secondary air input port is close to the fuel burner, the secondary air input from the secondary air input port does not interfere with the flame formed from the fuel burner into the furnace. Reduction is possible.
Further, when the secondary air input port is adjacent, the mixing of the secondary air and the flame can be delayed by injecting the secondary air obliquely with respect to the flame.

The coal fired boiler according to any one of claims 1 to 7, wherein a rib may be provided inside the flow path of the secondary air input port, or a swirl blade may be provided.
Here, by providing a rib inside the flow path of the secondary air input port, for example, on the inner side (fuel burner side) of the flow path, the mixing of the secondary air to the flame can be adjusted. Further, by providing a swirling impeller inside the flow path, it is possible to suppress the burner height and separate the flow so that the flow of secondary air does not interfere with the flame.

According to the coal fired boiler of the present invention described above, in the coal fired boiler that burns solid fuel such as pulverized coal, the remarkable effect of suppressing the high temperature oxygen remaining region formed on the outer periphery of the flame and reducing the amount of NOx generated Is obtained.
That is, by concentrating pulverized fuel such as pulverized coal injected from the fuel burner in the center of the flame, a rich flame portion is formed inside the flame, and the flow turbulence that occurs downstream of the rich flame portion formation and the dense flame portion forming member As a result, a stable ignition can be ensured by the synergistic effect, and the pulverized fuel can be stably burned even in a low oxygen concentration environment. Furthermore, since the secondary air is slowly supplied from the secondary air input port arranged so as not to interfere with the flame, the temperature drop (cooling) of the flame due to the low temperature secondary air is minimized, Despite the lack of air in the flame, stable ignition is continued while maintaining a high temperature flame. Therefore, the coal fired boiler according to the present invention can be burned in an environment of high temperature and low oxygen concentration, and can be burned with greatly reduced NOx and unburned content.

It is a figure which shows one Embodiment of the coal fired boiler which concerns on this invention, (a) is a longitudinal cross-sectional view which shows a burner structure, (b) is the front view which looked at the burner of (a) from the inside of a furnace. It is a figure which shows the supply system of secondary air about the burner structure shown in FIG. It is a longitudinal section showing an example of composition of a coal fired boiler concerning the present invention. FIG. 4 is a horizontal (horizontal) cross-sectional view of FIG. 3. It is a longitudinal cross-sectional view which shows the 1st modification of the burner structure shown in FIG. It is a figure which shows the 2nd modification of the burner structure shown in FIG. 1, (a) is a longitudinal cross-sectional view of a burner structure, (b) is the front view which looked at the burner from the inside of a furnace. It is a longitudinal cross-sectional view which shows the 3rd modification of the burner structure shown in FIG. It is a longitudinal cross-sectional view which shows the 4th modification of the burner structure shown in FIG. It is a figure which shows the 5th modification of the burner structure shown in FIG. 1, (a) is a longitudinal cross-sectional view of a burner structure, (b) is the front view which looked at the burner from the inside of a furnace. It is a longitudinal cross-sectional view which shows the 6th modification of the burner structure shown in FIG. It is a longitudinal cross-sectional view which shows the 7th modification of the burner structure shown in FIG. It is a longitudinal cross-sectional view which shows the 8th modification of the burner structure shown in FIG. It is a longitudinal cross-sectional view which shows the 9th modification of the burner structure shown in FIG. It is a figure which shows the 10th modification of the burner structure shown in FIG. 1, (a) is a top view, (b) is the front view which looked at the burner from the inside of a furnace. It is a top view which shows the 11th modification of the burner structure shown in FIG.

Hereinafter, an embodiment of a coal fired boiler according to the present invention will be described with reference to the drawings.
The coal fired boiler 10 shown in FIG. 3 and FIG. 4 reduces the region from the burner unit 12 to the additional air input unit (hereinafter referred to as “AA unit”) 14 by inputting air into the furnace 11 in multiple stages. The atmosphere is designed to reduce NOx in combustion exhaust gas. As for the distance from the burner section 12 to the AA section 14 serving as the reducing atmosphere, that is, the distance (height) of the reducing combustion zone, the longer the residence time of the combustion gas becomes, the smaller the NOx generation amount becomes. In the figure, reference numeral 20 denotes a burner that inputs pulverized fuel such as pulverized coal and air, and 15 is an additional air input nozzle that inputs additional air.

  In the following embodiment, although the coal fired boiler 10 demonstrates as pulverized coal burning using pulverized coal as a pulverized fuel, it is not limited to this. Therefore, the pulverized coal-burning burner 20 is connected to the pulverized coal mixture transport pipe 16 that transports the pulverized coal with primary air and the air supply duct 17 that supplies the secondary air. An air supply duct 17 for supplying secondary air is connected.

  As described above, the coal fired boiler 10 described above is a swirl combustion type burner unit 12 in which the burner 20 for introducing pulverized coal (powder fuel) and air into the furnace 11 is disposed at each corner of each stage. In each stage, a swirl combustion method is employed in which one or a plurality of swirl flames (one in the illustrated example) are formed. That is, in the coal fired boiler 10 shown in FIG. 3 and FIG. 4, the burner 20 that inputs pulverized coal and air into the furnace 11 (inside the furnace) has each section in the furnace 11 having a substantially square cross section. One swirl flame is formed by being arranged at each corner. However, in the present invention described below, for example, by arranging the burner 20 on the corner portion and the wall surface portion in the furnace 11 having a rectangular cross-sectional shape, the burner portion or the like of the swirl combustion method that forms two swirl flames. Is also applicable and is not particularly limited.

In the coal fired boiler 10 of the present embodiment, each burner 20 of the burner unit 12 includes, for example, a pulverized coal burner (fuel burner) 21 for introducing pulverized coal and air, and a pulverized coal burner 21 as shown in FIG. And a secondary air inlet port 30 for injecting secondary air, which is arranged above and below.
The pulverized coal burner 21 is provided so as to surround the rectangular primary coal port 22 for introducing the pulverized coal conveyed by the primary air and the primary coal port 22, and a part of the secondary air is introduced. The call secondary port 23 is provided. The pulverized coal charged from the pulverized coal burner 21 flows substantially straight toward the furnace 11.

Secondary air input ports 30 are provided substantially in parallel above and below the pulverized coal burner 21 for supplying secondary air. The secondary air input port 30 is divided into independent flow paths and ports, and the secondary air input from the secondary air input port 30 flows substantially straight into the furnace 11.
As shown in FIG. 2, for example, as shown in FIG. 2, the flow rate adjusting means of the secondary air supplied to each flow path of the secondary air input port 30 and the call secondary port 23 through flow paths branched from the air supply duct 17. As shown in FIG. In addition, about the position of the secondary air injection | throwing-in port 30, it is not limited to the upper and lower sides of the pulverized coal burner 21, and may be right and left.

  In the illustrated configuration example, the fuel burner 21 of the burner 20 is kicked as a rich flame portion forming member that concentrates the flow of pulverized coal to the center portion of the burner shaft in the primary coal port (fuel flow path) 22 of the fuel burner 21. 24. The kicker 24 in this case is a center open type kicker that is installed on the wall surface 22a of the call primary port 22 and partially opens the central portion of the flow path, and the center open type kicker forms the call primary port 22. May be provided over the entire circumference of the wall surface 22a, or may be provided only on the wall surface 22a in the same direction (up and down in the illustrated example) as the secondary air input port 30 is disposed. .

Further, between the fuel burner 21 and the secondary air input port 30, the secondary air input from the secondary air input port 30 does not interfere with the flame F formed from the fuel burner 21 into the furnace 11. A certain distance L is provided. The separation distance L is used to slow down the supply of secondary air introduced from the secondary air introduction port 30 to lower the oxygen concentration in the flame F. In other words, the separation distance L is a low temperature secondary. It is an appropriate distance that makes it difficult for air to reach the flame F. That is, the separation distance L is a distance that can prevent the secondary air from being mixed into the flame F, and depends on various conditions such as the pressure at which the secondary air is introduced. About 1 h to 32 h is required on the basis of the height dimension h (see FIG. 1).
By providing such a separation distance L, the amount of secondary air mixed into the flame F is reduced, so that the oxygen concentration in the flame F is reduced and the drop in the flame temperature is minimized to a relatively high temperature. Can be maintained.

  In the burner 20 configured in this way, the kicker 24 collects the flow of pulverized coal in the central portion of the flow channel in the coal primary port 22 and the inside of the flame F from the partial opening 24a formed in the central portion of the flow channel. Therefore, a concentrated flame portion Fa for burning high-concentration pulverized coal is formed inside the flame F. The above-described kicker 24 not only concentrates and introduces pulverized coal into the flame F, but also has a function of disturbing the flow of pulverized coal that has been conveyed to the primary air on the downstream side of the kicker 24. Yes. That is, the flow of pulverized coal is disturbed by passing through the kicker 24.

  Thus, according to the coal fired boiler 10 provided with the burner 20 mentioned above, after the kicker 24 concentrates the flow of pulverized coal to the center part of the burner shaft in the flow path of the coal primary port 22, it is thrown into the flame F. At the same time, the separation distance L provided between the pulverized coal burner 21 and the secondary air input port 30 suppresses the interference between the flame F and the secondary air. For this reason, high concentration pulverized coal is introduced into the center of the flame F, and secondary air is slowly supplied from the secondary air introduction port 30 to the flame F, so that the oxygen concentration inside the flame is reduced. Can be reduced.

As a result, a rich flame portion Fa is formed inside the flame in which pulverized coal is intensively charged, and stable ignition of the partial pulverized coal is ensured by the formation of the rich flame portion Fa and the turbulence in the flow downstream of the kicker 24. be able to. Therefore, the pulverized coal can be stably burned even in the internal environment of the flame F having a low oxygen concentration by providing the separation distance L.
At this time, since the secondary air is slowly supplied from the secondary air input port 30 arranged with the separation distance L, the temperature drop of the flame F due to the low temperature secondary air can be minimized, and accordingly Despite the fact that the flame F is in a state of low oxygen concentration due to lack of air, the flame F is heated to continue stable ignition, and combustion at a high temperature and low oxygen concentration becomes possible. That is, since the local high-temperature oxygen remaining region H formed on the outer periphery of the flame F is suppressed and becomes small and weak, combustion with significantly reduced NOx and unburned components becomes possible.

  In addition, since the above-described kicker 24 concentrates and flows the pulverized coal inside the flame F, the coal primary port 22 where the kicker 24 is installed in the pulverized coal burner 21 has an inner wall surface 22a downstream of the kicker 24. The pulverized coal that collides with As a result, the wear caused by the collision of the pulverized coal can be suppressed on the downstream side wall surface of the kicker 24.

By the way, the pulverized coal burner 21 of the above-described burner 20 is, for example, a central closed type kicker 25 that partially closes the center of the flow channel upstream of the centrally open type kicker 24 as in the first modification shown in FIG. It is preferable to provide.
By using the central open type kicker 24 and the central closed type kicker 25 in combination, the flow of pulverized coal is once separated into the outer peripheral wall surface 22a by the central closed type kicker 25, so this flow is separated into the central open type kicker. 24 is turned back to the central portion again, and throwing in is concentrated to the central portion of the flame F. Therefore, compared with the case where the central open type kicker 24 is used alone,
By introducing the outward flow to the center, it is possible to input fuel (formation of a rich flame portion) with further increased concentration.

Further, it is desirable that the above-described pulverized coal burner 21 of the burner 20 employs an open-type kicker 24A in which irregularities are provided in the opening 24a ′ as in the second modification shown in FIG. That is, the kicker 24A itself has a shape with unevenness, and the unevenness of the opening 24a 'through which the flow of pulverized coal passes is not limited to the rectangular shape shown in the figure. For example, a triangular shape or a semicircular shape is adopted. May be.
By installing such a kicker 24A, it becomes possible to make fuel injection (formation of a dense flame portion) with a further increased concentration of pulverized coal to be introduced into the flame F, and further, in the downstream of the kicker 24A, Can be further promoted.

  Further, the pulverized coal burner 21 of the burner 20 described above is a cyclone portion 26 formed in the coal primary port 22 of the pulverized coal burner 21 as a rich flame portion forming member, for example, as in a third modification shown in FIG. May be adopted. That is, the flow of pulverized coal and primary air is guided to the cyclone portion 26 using centrifugal force, passes through the spiral flow path, and flows out from the outlet 26a that opens at the center of the primary port 22 of the coal. It is possible to make the flow of pulverized coal concentrated inside the flame F. Accordingly, it is possible to input fuel in which pulverized coal is concentrated inside the flame so that the rich flame portion Fa is formed inside the flame F.

  Further, the pulverized coal burner 21 of the burner 20 described above has one or a plurality of split members 27 at the tip outlet portion with respect to the primary call port 22 of the fuel burner 21 as in the fourth modified example shown in FIG. Is preferably provided. In the configuration example shown in the figure, a pair of split members 27 are arranged with a gap in the center of the outlet. As a result, a flame holding mechanism is formed by the split member 27 in front of the combustion burner 21 and at the center. A deep flame part can also be formed. Such a flame holding mechanism can be formed also by arranging one split member 27, and more stable ignition can be maintained.

  In particular, the configuration in which two or more split members 27 are disposed at a predetermined interval in the central portion of the tip outlet portion can form a concentrated flame portion in the central portion without spreading the flame F outward, so NOx is reduced. While being generated inside the flame F, stable ignition can be strongly maintained.

Further, the pulverized coal burner 21 of the burner 20 described above is flowed to the tip outlet portion of the burner 20, specifically to the tip outlet portion of the call primary port 22, as in the fifth modification shown in FIG. You may provide the auxiliary nozzle 50 which restrict | squeezes a cross-sectional area.
The auxiliary nozzle 50 shown in the figure is arranged substantially in parallel with a pair of upper and lower outer wall portions 51 that narrow the cross-sectional area of the flow channel in the vertical direction from the tip outlet of the coal primary port 22 to the furnace 11 side, with a predetermined interval in the center portion. And a pair of upper and lower guide plates 52. The predetermined gap formed between the guide plates 52 becomes a guide channel 53 with no change in the channel cross-sectional area, and this guide channel 53 is an opening formed by the kicker 24 when viewed from the furnace 11 side. 24a is provided so as to substantially coincide with 24a. In addition, between the outer wall part 51 and the guide plate 52, a throttle channel 54 whose channel cross-sectional area decreases toward the outlet side is formed.

  By providing such an auxiliary nozzle 50, the flow of pulverized coal flowing out from the primary coal port 22 is divided into a guide channel 53 and upper and lower throttle channels 54 when passing through the auxiliary nozzle 50. Among these, the flow of the pulverized coal passing through the throttle channel 54 is increased with a decrease in the channel cross-sectional area. Therefore, at the tip outlet of the auxiliary nozzle 50, the guide channel in the center without flow rate fluctuations. The flow rate of the pulverized coal that has flowed through 53 becomes relatively low. For this reason, the pulverized coal thrown into the center part of the flame F becomes a flow of low flow velocity with a high concentration of pulverized coal due to concentration of the pulverized coal in the kicker 24. Therefore, the pulverized coal burner 21 provided with the auxiliary nozzle 50 can further stabilize the ignition by lowering the flow velocity at the central portion relatively.

In this case, for example, as in the sixth modified example shown in FIG. 10, the auxiliary nozzle 50 and the split member 27 are used together by providing the split member 27 of FIG. The auxiliary nozzle 50A may be employed.
In such an auxiliary nozzle 50, a flame holding mechanism by the split member 27 is formed at the tip of the auxiliary nozzle 50A. Specifically, since the split member 27 is attached to the distal end side of the guide plate 52 to form the flame holding mechanism, ignition can be further stabilized.

  Further, in the pulverized coal burner 21 of the burner 20 described above, the secondary air input port 30A of the burner 20 is directed outward in the vertical direction from the axial center of the pulverized coal burner 21, for example, as in the seventh modification shown in FIG. The installation may be inclined at an angle θ. In the configuration example shown in FIG. 11, the secondary air input port 30 shown in the sixth modification of FIG. 10 is brought closer to the pulverized coal burner 21 side, and the secondary air input port 30 is moved outward in the vertical direction to an angle θ. Although it is made to incline, it is applicable similarly to other embodiment and modifications which do not have auxiliary nozzle 50.

As described above, when the secondary air input port 30 </ b> A that is inclined outward in the vertical direction is employed, even if the installation position of the secondary air input port 30 </ b> A is close to the pulverized coal burner 21, the pulverized coal burner 21 enters the furnace 11. Since the secondary air that is input from the secondary air input port 30A does not interfere with the flame F that is formed to face, the burner height can be reduced. That is, since the secondary air input from the secondary air input port 30A flows away from the flame F, when comparing with the same specifications, the maximum separation distance L1 shown in FIG. It can be set smaller than the separation distance L.
As a result, the burner 20 in which the secondary air input port 30A is disposed above and below the pulverized coal nozzle 21 can reduce the overall height of the burner 20 by reducing the separation distance L1.

  Further, in the eighth modified example shown in FIG. 12, ribs 31 are provided inside the flow path of the inclined secondary air input port 30A. That is, in the illustrated example, the rib 31 is provided inside the outlet of the secondary air input port 30A (the pulverized coal nozzle 21 side), and the flow of the secondary air is caused by colliding the flow of the secondary air with the rib 31. Changes have been made. In particular, the rib 31 provided inside the outlet of the secondary air input port 30A changes the flow of the secondary air in a direction away from the flame F, so that the flame F can be adjusted by appropriately adjusting the height of the rib 31 and the like. The mixing of the secondary air with respect to can be adjusted.

Further, in the ninth modification shown in FIG. 13, a plurality of swirl vanes 32 are provided in the flow path of the secondary air input port 30B. The secondary air input port 30 </ b> B in this case is formed in parallel with the pulverized coal burner 21. The swirl vane 32 has, for example, a blade cross section, and can efficiently separate the secondary air flow from the flame F. Note that the secondary air input port 30B described above may be inclined so as to have an outward angle θ in the vicinity of the outlet on the furnace 11 side, and the outward inclination angle θ provided at the swirl vane 32 and the flow path outlet. In cooperation with each other, the flow of the secondary air can be separated from the flame F more efficiently.
By adopting such a configuration, it is possible to keep the burner height to a minimum and to separate the secondary air flow so as not to interfere with the flame.

  Further, the tenth modification shown in FIG. 14 is a case where the secondary air input port 30C includes the adjacent left outlet 30L and right outlet 30R, and the secondary air is injected obliquely with respect to the flame F. By doing so, mixing of secondary air and the flame F can be delayed. That is, in the modification shown in FIG. 14 (a), a secondary air input port 30C that branches in a Y shape in plan view and inputs secondary air into the furnace 11 from the left outlet 30L and the right outlet 30R; The left air outlet 30L and the right air outlet 30R that are inclined outwardly in the left-right direction from the axis of the pulverized coal burner 21 are disposed adjacent to each other, so that the secondary air flows out in the direction away from the flame F and is mixed. Is delayed.

  Further, also in such a secondary air input port 30C, as in the eleventh modification shown in FIG. 15, for example, on the outlet inner side of the left outlet 30L and the right outlet 30R (on the axial center side of the pulverized coal nozzle 21). Ribs 31 may be provided. By providing such a rib 31, the flow of secondary air collides with the rib 31 and changes the flow. Therefore, when the delay in mixing the secondary air is large, the height of the rib 31 is appropriately adjusted. Thus, the mixing of the secondary air with respect to the flame F can be adjusted.

  Thus, according to the coal fired boiler 10 of the embodiment and each modification described above, in the coal fired boiler that burns solid fuel such as pulverized coal, the high temperature oxygen residual region H formed on the outer periphery of the flame F is suppressed. Thus, the amount of NOx generated can be reduced. That is, the pulverized coal (pulverized fuel) introduced from the pulverized coal burner 21 is concentrated in the center of the flame F by the kicker 24 to form the concentrated flame portion Fa inside the flame F. Stable ignition can be ensured by the synergistic effect of the formation and the disturbance of the flow generated downstream of the kicker 24. For this reason, pulverized fuel such as pulverized coal can be stably combusted even in the rich flame portion Fa in a low oxygen concentration environment.

  Further, since the secondary air is slowly supplied from the secondary air input port 30 arranged so as not to interfere with the flame F, the temperature drop (cooling) of the flame due to the low temperature secondary air is minimized. Can be suppressed. For this reason, even in the flame F in which the supply of secondary air is slow and the air is insufficient, the high temperature flame F can be maintained and stable ignition can be continued. Therefore, the coal fired boiler 10 of the present invention can burn pulverized fuel such as pulverized coal even in an environment of high temperature and low oxygen concentration, and combustion with significantly reduced NOx and unburned content is possible. become.

By the way, each embodiment and modification mentioned above can be combined suitably besides having been demonstrated based on illustration. In the above-described embodiment, the description has been given of the coal fired boiler 10 in which the region from the burner unit 12 to the AA 14 is used as the reducing atmosphere, but the present invention is not limited thereto.
In addition, this invention is not limited to embodiment mentioned above, For example, pulverized fuel is not limited to pulverized coal, For example, it can change suitably in the range which does not deviate from the summary.

10 Coal-fired boiler 11 Furnace 12 Burner section 14 Additional air input section (AA section)
20 Burner 21 Pulverized coal burner (fuel burner)
22 Cole primary port (fuel flow path)
23 Cole secondary port 24, 24A Kicker (Dense flame forming member)
25 Central closed kicker 26 Cyclone part 27 Split member 30, 30A, 30B, 30C Secondary air input port 31 Rib 32 Swivel blade 50, 50A Auxiliary nozzle F Flame Fa Rich flame part H High temperature oxygen remaining area

Claims (10)

Coal in which pulverized fuel and air are introduced into the furnace is a burner portion of a swirl combustion system that is disposed at each corner portion or wall surface portion of each step, and one or more swirl flames are formed at each step In a firewood boiler,
The burner includes a fuel burner for charging pulverized fuel and air, and a secondary air charging port disposed on the top and bottom or the left and right of the fuel burner and having a flow rate adjusting means,
While providing a rich flame portion forming member for concentrating the flow of the pulverized fuel to the center portion of the burner shaft in the flow path of the fuel burner,
A separation distance between the fuel burner and the secondary air input port is such that the secondary air input from the secondary air input port does not interfere with a flame formed from the fuel burner into the furnace. A coal fired boiler characterized by being provided.   2. The coal fired boiler according to claim 1, wherein the rich flame portion forming member is a center open type kicker that is installed on a wall surface of the fuel burner and partially opens a flow path central portion.   3. The coal fired boiler according to claim 2, wherein the dense flame portion forming member includes a central closed type kicker that partially closes a flow path central portion upstream of the central open type kicker.   The coal fired boiler according to claim 2 or 3, wherein unevenness is provided in an opening of the central open type kicker.   The coal fired boiler according to claim 1, wherein the rich flame part forming member is a cyclone part formed in the fuel burner.   The coal fired boiler according to any one of claims 2 to 5, wherein one or more split members are provided at a tip outlet portion of the fuel burner.   The coal fired boiler according to any one of claims 2 to 6, wherein an auxiliary nozzle for reducing a cross-sectional area of the flow path is provided at a tip outlet portion of the burner.   The coal fired boiler according to any one of claims 1 to 7, wherein the secondary air input port is installed so as to have an outward angle from an axial center of the fuel burner.   The coal fired boiler according to any one of claims 1 to 7, wherein a rib is provided inside the flow path of the secondary air input port. The coal fired boiler according to any one of claims 1 to 7, wherein swirl vanes are provided inside the flow path of the secondary air input port.

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