JP6632841B2 - Combustion burner and boiler provided with the same - Google Patents

Description

  The present invention relates to a combustion burner and a boiler provided with the same.

  BACKGROUND ART As a combustion burner for burning pulverized coal fuel, there has been known a combustion burner in which a plurality of flame stabilizers called a splitter are installed at an outlet in a fuel nozzle of a burner (see Patent Document below). Then, a recirculation region is formed downstream of the splitter to maintain the combustion of pulverized coal. In this way, by performing ignition and flame holding near the center axis of the fuel nozzle (hereinafter referred to as "internal ignition" or "internal flame holding"), reduction combustion is performed under insufficient air to achieve low NOx combustion. ing.

JP-A-59-205510 JP 2009-204256 A

Although it is preferable to perform internal flame holding for low NOx combustion, there is a corner at the end of the splitter, and ignition may occur from the corner as a starting point. Since the corner is close to the outer periphery of the fuel nozzle, ignition at the corner causes ignition at the outer periphery of the fuel nozzle. Since a combustion air supply nozzle and the like are present outside the fuel nozzle and a large amount of oxygen is present, there is a problem that when external ignition occurs, a large amount of NOx is generated.
In order to avoid such external ignition, it is conceivable to shorten the length of the splitter and move the corners away from the outer periphery of the fuel nozzle. However, when the length of the splitter is reduced, the ignition performance or the flame holding performance may be reduced.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a combustion burner capable of realizing low NOx combustion by suppressing ignition caused by a corner of a splitter, and a boiler including the same. Aim.

In order to solve the above problems, a combustion burner of the present invention and a boiler provided with the same employ the following means.
That is, the combustion burner according to the present invention comprises a fuel nozzle for blowing a fuel gas obtained by mixing a fuel and air into a furnace, and a widened portion having a width increasing in the fuel gas flow direction at a front end side of the fuel nozzle. And a plurality of splitters for dividing a gas flow, wherein a corner removing portion from which the corner is removed is formed at a corner at a downstream end of the widened portion of the splitter.

If a corner is formed at the corner at the downstream end of the widened portion of the splitter, the radiation from the inner peripheral surface side of the fuel nozzle causes ignition to occur starting from the corner, and external ignition at the outer peripheral portion of the fuel nozzle occurs. May occur. Since a combustion air supply nozzle and the like are present outside the fuel nozzle and a large amount of oxygen is present, when external ignition occurs, a large amount of NOx is generated.
Therefore, the formation of the corner removing portion from which the corner is removed suppresses ignition or flame holding at the outer periphery of the fuel nozzle.
As the corner removing portion, for example, a tapered portion having a chamfered corner may be mentioned.

  Further, according to the combustion burner of the present invention, the splitter is arranged at a different position in the fuel gas flow direction.

By disposing the splitters at different positions in the fuel gas flow direction, that is, displaced upstream and downstream in the fuel gas flow direction, the widened portion of the splitter is wider than when the splitter is disposed at the same position in the fuel gas flow direction. The area occupied can be reduced. Thus, by suppressing the acceleration of the fuel gas, the flow rate of the fuel gas flowing downstream in the flow direction of the fuel gas can be made closer to the burning speed of the fuel gas flowing upstream, and the fuel gas is further reduced on the downstream side. It can be ignited quickly before flowing to the flame, and the flame holding properties of the flame can be improved.
Further, ignition can be achieved early by the splitter located on the upstream side of the fuel gas flow, and ignition or flame holding can be enhanced by the splitter located on the downstream side.
Further, the fuel can be guided to the recirculation area of the downstream splitter by the splitter located on the upstream side of the fuel gas flow, and the ignition or flame holding of the downstream splitter can be enhanced.

Further, according to the combustion burner of the present invention, the splitter includes a slitted splitter in which a slit for partially reducing the width of the fuel gas flow downstream end of the widening portion is formed, and the slit of the slitted splitter is provided. Is formed as an inclined surface for deflecting the fuel gas flow in the longitudinal axis direction of the splitter when the fuel nozzle is viewed from the downstream side of the fuel gas flow .

  Since the fuel gas flow is deflected in the direction of the longitudinal axis of the splitter by the inclined surface forming the slit, the fuel gas flow can be disturbed also in the direction of the longitudinal axis, and the flame holding performance can be further improved. In particular, a slit can be formed three-dimensionally by each surface constituting the slit, and the flame holding performance can be improved.

  Furthermore, according to the combustion burner of the present invention, a nozzle angle adjusting mechanism for rotating the fuel nozzle up and down or left and right is provided, and inside the fuel nozzle, a direction perpendicular to the rotating direction of the nozzle angle adjusting mechanism is provided. The straightening plate extending is fixed.

The flow angle of the fuel gas can be changed so as to follow the direction in which the angle of the fuel nozzle changes by providing the rectifying plate extending in the direction orthogonal to the rotation direction of the nozzle angle adjusting mechanism. Thus, a desired combustion state can be maintained even when the nozzle angle is changed.
One or more rectifying plates may be provided, and it is preferable to provide the rectifying plate near the center of the fuel nozzle in order to obtain a rectifying effect.

  Further, the boiler of the present invention comprises a furnace, a combustion burner according to any one of the above provided in the furnace, a flue provided downstream of the furnace, and a heat exchange provided in the flue. And a container.

  By providing the above-described combustion burner, a boiler that performs low NOx combustion can be provided.

  By suppressing external ignition by a corner removing portion formed at a corner of the splitter, internal flame holding can be strengthened and low NOx combustion can be realized.

It is a front view showing the fuel nozzle concerning a 1st embodiment of the present invention. It is sectional drawing which cut | disconnected the fuel nozzle of FIG. 1 in the horizontal surface. It is the perspective view which showed the splitter with a slit. It is the perspective view which showed the taper part of FIG. It is a front view showing a fuel nozzle concerning a 2nd embodiment of the present invention. It is the front view which showed the modification of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
The combustion burner of the present embodiment mainly burns pulverized coal fuel (fuel) obtained by crushing coal by a mill, and is provided in a boiler (not shown). A plurality of combustion burners are provided for a boiler provided with heat exchange such as a superheater and an evaporator in a flue, and form a flame in a furnace.
FIG. 1 shows a front view of the combustion burner 1. The combustion burner 1 includes a fuel nozzle 3 located inside and a combustion air supply nozzle 4 surrounding the fuel nozzle 3.
The combustion air supply nozzle 4 is a flow path through which only the secondary air flows, and supplies the air so as to go straight into the furnace. That is, the air flowing out of the combustion air supply nozzle 4 flows so as not to intersect with the fuel gas flowing out of the fuel nozzle 3 in parallel. Although not shown, a tertiary combustion air nozzle for supplying combustion air is provided outside the combustion air supply nozzle 4.

As shown in FIG. 1, the fuel nozzle 3 has a rectangular cross section when viewed from the front, and a fuel gas in which pulverized coal and air are mixed flows therein. In the following embodiments, the downstream side of the fuel gas flow is simply referred to as the downstream side, and the upstream side of the fuel gas flow is simply referred to as the upstream side.
In the fuel nozzle 3, a plurality of splitters 5, 6, 7 are provided, and in the present embodiment, five splitters are provided. Each of the splitters 5, 6, and 7 has a longitudinal axis extending from the lower wall 3a of the fuel nozzle 3 to the upper wall 3b facing the fuel nozzle 3. That is, each of the splitters 5, 6, and 7 is a vertical splitter provided in the vertical direction. The upper and lower ends of each of the splitters 5, 6, 7 are fixed to the wall of the fuel nozzle 3 by support members 8, respectively.
The fuel nozzle 3 is provided with a nozzle angle adjusting mechanism rotatable in the vertical direction together with the splitters 5, 6, and 7.
The splitters 5, 6, and 7 are members having a function of dividing a fuel gas flow, and do not have a function of injecting air from the inside.

  The splitter includes splitters 5 and 6 with slits provided at both ends in the center and the horizontal direction, and splitters 7 without slits provided on both sides of the splitter 5 with slit at the center. Thus, the slitless splitter 7 is arranged at a position adjacent to the splitters 5 and 6 with slits.

As shown in FIG. 2, the splitters 5, 6, and 7 include a widened portion 10 whose width increases in the fuel gas flow direction. On the upstream side of the widened portion 10, a plate-like portion 11 extending in the vertical direction is provided along the fuel gas flow direction.
The widened portion 10 has a substantially triangular shape when viewed in cross section as shown in FIG. The widened portions 10 of the central splitter 5 with slits and the splitter 7 without slits extend on both sides when viewed in cross section as shown in FIG. On the other hand, the widened portions 10 of the splitters 6 with slits located at both ends in the horizontal direction extend toward the center of the fuel nozzle 3 but do not extend toward the wall of the fuel nozzle 3. By making the downstream side of the splitter with slits 6 located on both sides straight as described above, the fuel gas flowing between the wall surface of the fuel nozzle 3 and the splitter with slits 6 flows out of the air supply nozzle 4 for combustion. It does not deflect to the outflow side. Thereby, external ignition occurring on the outer peripheral side of the fuel nozzle 3 can be suppressed.

The downstream ends 5a and 6a of the slit splitters 5 and 6 are aligned with the downstream end 3c of the fuel nozzle 3 as shown in FIG. The downstream end 7a of the slitless splitter 7 is provided at a position separated by a predetermined distance S upstream of the downstream ends 5a, 6a of the slitted splitter 7.
Here, the predetermined distance S is 0.001 D or more and 1.0 D or less, preferably 0.03 D or more and 0.5 D or less, more preferably 0.05 D or more and 0 D or less, where D is the equivalent circular diameter at the opening of the fuel nozzle 3. .3D or less.
The above lower limit and upper limit are determined from the following viewpoints. Below the lower limit, the distance between the splitters 5 and 6 with slits and the splitter 7 without slits becomes too short, and the advantage of shifting these splitters to secure the cross-sectional area of the flow path cannot be obtained. On the other hand, if the upper limit is exceeded, the recirculation area formed by the slitless splitter 7 disappears before the slitted splitters 5 and 6, and the recirculation area of the slitless splitter 7 is removed from the slitted splitters 5 and 6. The advantage of guiding fuel is not obtained.
As shown by the arrow A in FIG. 2, the predetermined distance S may be adjusted by moving the slitless splitter 7 located on the upstream side in the fuel gas flow direction.

  As shown in FIG. 1, the width of the downstream end 7 a of the slitless splitter 7 is constant in the direction of the longitudinal axis (vertical axis) of the slitless splitter 7. On the other hand, a plurality of slits SL that partially reduce the width of the downstream end 5a are formed in the central splitter 5 with a slit. The slit SL at the center has slits SL on both sides at the same height. With these slits, a wide portion W1 and a narrow portion W2 are formed in the splitter 5 with a slit.

  FIG. 3 shows a specific shape of the slit SL. The slit SL cuts out the downstream end 5a of the slitted splitter 5 in a U-shape. Further, the upper surface SL1 and the lower surface SL2 forming the slit SL are surfaces that deflect the fuel gas flow in the longitudinal axis direction of the splitter 5 (in the present embodiment, the vertical direction). That is, the fuel gas flow is deflected downward by the upper surface SL1, and the fuel gas flow is deflected upward by the lower surface SL2.

  As shown in FIG. 1, a slit SL similar to that of the central splitter 5 is also formed in the splitters 6 with slits at both ends, but the slit SL is provided only on the center side of the fuel nozzle 3. Have been. This is because if the slit SL is provided also on the wall side of the fuel nozzle 3, the slit SL becomes an ignition surface, and there is a risk of external ignition.

The slit SL is preferably provided at a central portion in the longitudinal direction of the splitters 5 and 6 so that ignition or flame holding is performed at the center side of the fuel nozzle 3 as much as possible, and the slits SL are not provided at both upper and lower ends.
The range _{L 1} the slits SL, if the length of the splitter 5 and 6 was set to _{L 0,} L 1 / _{L 0} is 0.8 or less, preferably 0.5 or less.

  As shown in FIG. 1, two straightening plates 15a and 15b are fixed in the fuel nozzle 3. Each of the rectifying plates 15a and 15b is provided at a height position symmetrical from a center position in the height direction of the fuel nozzle 3, and is a plate-like body extending in the horizontal direction.

Tapered portions (corner removing portions) 20 are formed at upper and lower corners of the splitter 6 with slits at both ends on the center side of the fuel nozzle 3.
The shape of the tapered portion 20 is not limited as long as the corners are removed. However, as shown in FIG. 4, the apex angles θ1, θ2, and θ3 of the three surfaces forming the corners are removed. Any shape is acceptable. Therefore, it may be a flat surface such as a tapered surface, or may be a curved surface.

According to the combustion burner 1 having the above configuration, the following operation and effect can be obtained.
Since the tapered portion 20 with the corner removed is formed at the corner of the splitter 6, the radiation from the inner peripheral surface side of the fuel nozzle 3 causes ignition starting from the corner, and the fuel nozzle 3 External ignition generated at the outer peripheral portion can be suppressed. Thereby, internal ignition can be strengthened, NOx generation in the combustion burner flame region is reduced, and low NOx combustion in the entire furnace can be realized.
The tapered portion (corner removing portion) 20 may be provided in another splitter, that is, the splitter 5 with a slit or the splitter 7 without a slit at the center.

  Since the fuel gas flow is deflected in the direction of the longitudinal axis of the splitters 5 and 6 by the inclined surfaces SL1 and SL2 forming the slit SL, the fuel gas flow can be disturbed also in the direction of the longitudinal axis, and the flame holding performance is further improved. be able to. In particular, the slit SL can be formed three-dimensionally by each surface constituting the slit SL, and the flame holding performance can be improved.

By arranging the splitters 5, 6, 7 at different positions in the fuel gas flow direction, the area occupied by the widened portion 10 of the splitter can be reduced as compared with the case where the splitters 5, 6, 7 are arranged at the same position in the fuel gas flow direction. Can be reduced. Thus, by suppressing the acceleration of the fuel gas, the flow rate of the fuel gas flowing downstream in the flow direction of the fuel gas can be made closer to the burning speed of the fuel gas flowing upstream, and the fuel gas is further reduced on the downstream side. It can be ignited quickly before flowing to the flame, and the flame holding properties of the flame can be improved.
The fuel is guided to the recirculation area of the downstream slitted splitters 5 and 6 by the slitless splitter 7 located on the upstream side of the fuel gas flow, and the ignition or flame holding of the downstream slitted splitters 5 and 6 is enhanced. Can be. As described above, when the function of guiding the fuel is mainly used, it is preferable to use the slitless splitter 7.

Since the rectifying plates 15a and 15b extending in the horizontal direction perpendicular to the vertical direction in which the nozzle angle adjusting mechanism rotates are provided, the flow of the fuel gas follows the vertical direction in which the angle of the fuel nozzle 3 changes. The angle can be changed. Thereby, a desired combustion state can be obtained.
The number of rectifying plates may be one or three or more, and is preferably provided near the center of the fuel nozzle in order to obtain a rectifying effect.

In the present embodiment, the number of splitters is five, but the present invention is not limited to this, and may be two to four, or six or more.
Further, in each of the embodiments described above, the vertical splitters in which the splitters 5, 6, and 7 extend in the vertical direction are described as an example. However, the horizontal splitters in which the splitters 5, 6, and 7 extend in the horizontal direction are also described. The present invention can be applied.

[Second embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS.
This embodiment is common to the first embodiment in that a taper portion is formed by removing a corner of the splitter, but the arrangement of the splitter is different. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
The combustion burner 1 shown in FIG. 5 is a combination of horizontal splitters 22 and 23 extending in the horizontal direction and vertical splitters 24 and 25 extending in the vertical direction. Thus, the horizontal splitters 22 and 23 and the vertical splitters 24 and 25 may intersect. In FIG. 5, the tapered portions 20 are provided at the four corners of the vertical splitters 24, 25. When a large amount of air exists above and below the fuel nozzle 3, it is preferable to provide tapered portions at the four corners of the vertical splitters 24 and 25 in order to suppress external ignition.
In addition, as shown in FIG. 6, tapered portions 20 may be provided at the four corners of the horizontal splitters 22 and 23. This configuration is preferable when a large amount of air exists not only above and below the fuel nozzle 3 but also on the left and right sides.

In the present embodiment, a combination of two horizontal splitters and two vertical splitters is used. However, the present invention is not limited to this. For example, one horizontal splitter and three vertical splitters may be used. Any number of combinations are possible. The number of splitters is designed to be optimal according to the size of the fuel nozzle.
Furthermore, in this embodiment, pulverized coal was mainly described as a fuel, but the present invention is not limited to this, and the present invention is also applied to petroleum coke, petroleum residue, and biomass fuel (solid chips, pellets, and slurry). be able to.

DESCRIPTION OF SYMBOLS 1 Combustion burner 3 Fuel nozzle 4 Combustion air supply nozzle 5 Splitter with slit 6 Splitter with slit 7 Splitter without slit 10 Widening section 15 Rectifier plate 20 Taper section (corner removal section)

Claims (5)

A fuel nozzle for injecting fuel gas into which the fuel and air are mixed into the furnace;
A plurality of splitters for dividing a fuel gas flow by a widened portion whose width increases in a fuel gas flow direction, on a tip side in the fuel nozzle;
With
The splitter includes a slitted splitter in which a slit for partially reducing the width of the fuel gas flow downstream end of the widening portion is formed,
The surface of the splitter with the slit that forms the slit is an inclined surface that deflects the fuel gas flow in the longitudinal axis direction of the splitter when the fuel nozzle is viewed from the downstream side of the fuel gas flow. A combustion burner.   The combustion burner according to claim 1, wherein the splitters are arranged at different positions in a fuel gas flow direction. The combustion burner according to claim 1, wherein a corner removing portion from which the corner is removed is formed at a corner at a downstream end of the widened portion of the splitter . A nozzle angle adjusting mechanism for rotating the fuel nozzle up and down or left and right is provided,
4. The combustion burner according to claim 1, wherein a rectifying plate extending in a direction perpendicular to a rotation direction of the nozzle angle adjustment mechanism is fixed in the fuel nozzle. 5. Furnace and
A combustion burner according to any one of claims 1 to 4 provided in the furnace,
A flue provided downstream of the furnace,
A heat exchanger provided in the flue;
A boiler comprising:

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