TWI434011B - Boiler construction - Google Patents

Description

Boiler construction

The present invention relates to a boiler construction corresponding to various fuels containing coal and sulfur.

In recent years, in a boiler using coal or petroleum as a fuel, a reduced combustion zone in which a combustion environment is reduced from a main burner to an additional air input unit to form a reducing atmosphere is formed by using a plurality of stages of input air to achieve low NOx formation. .

On the other hand, in the reduced combustion region, since the hydrogen sulfide of a corrosive component is generated in a large amount, the wall surface of the furnace is in a severe corrosive environment. Therefore, maintenance such as spraying to the furnace wall and periodically replacing the furnace wall panel is required. Further, since the reduced combustion region is a reducing environment region having a high heat load even in the furnace, there is a possibility that the slag adheres.

In order to deal with this problem, there is known a technique for increasing the oxygen concentration by introducing air into the wall surface side in the furnace. For example, a burner is formed at four corners in a furnace of a rectangular cross section to form a vortex flow, and each combustion is formed. The air flow biased toward the furnace wall side (for example, refer to Patent Document 1).

In addition, it is also disclosed that in a bucky coal-fired boiler in which a burner for generating a vortex flame is disposed at a central portion of the wall of the furnace, a nozzle for introducing an air curtain or a gas curtain for bending the flame path is provided to prevent slagging at the peripheral portion of the burner. Technology (for example, refer to Patent Document 2).

[Patent Document 1] US Patent No. 6237513 [Patent Document 2] Japanese Patent Laid-Open No. 7-119923

However, in the prior art of Patent Document 1, since the oxygen in the air has been consumed before reaching the target wall surface, the oxygen concentration cannot be effectively increased. In order to increase the oxygen concentration, it is necessary to increase the discharge velocity of the air, so that an auxiliary mechanical power such as a compressor is increased, which is not preferable.

Further, in the prior art of Patent Document 2, since it is necessary to input the air curtain or the exhaust gas curtain at a high flow rate which can bend the flame path, it is not preferable to increase the auxiliary mechanical power such as a compressor.

From such a background, a vortex flow is formed in a fuel corresponding to various fuels containing coal and sulfur, and configured to be injected into a furnace from a burner provided at a plurality of furnace walls forming a rectangular cross section. In the structure of a vortex-fired boiler for combustion, it is desirable to efficiently suppress or prevent corrosion and slag formation in the furnace wall in the furnace.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a boiler structure which can effectively suppress or prevent corrosion and slag generated in a furnace wall in a furnace.

In order to solve the above problems, the present invention employs the following technical means.

The boiler structure of the present invention is a vortex-burning type that is configured to form a vortex flow and burns from a burner provided at a plurality of burners forming a rectangular cross section to a fuel and combustion air in a furnace, and is characterized in that: An air intake portion that forms a region having a higher air concentration than the periphery is provided in the vicinity of the flame-affected portion of the furnace wall surface that the flame formed by the burners approaches or contacts.

According to the boiler construction, because the flame formed in each burner is close to or The air input portion forming a region having a higher air concentration than the periphery is disposed in the vicinity of the flame-affected portion of the furnace wall that is in contact with the furnace, so that a low-flow air can be completed with a small auxiliary mechanical power to the wall region of the furnace having corrosion and slag. And form an area with a high air concentration.

In the above invention, it is preferable that the region having a high air concentration is formed so as to cover the reduced combustion region inside the furnace in the vertical direction, whereby the upper and lower directions in the furnace of the corrosion and slag can be lowered by the input. The air at the flow rate forms an area with a high air concentration.

In the above invention, it is preferable that the air intake portion introduces the low-pressure burner secondary air flow from the adjacent burner, thereby suppressing a large change in the structure and an increase in the number of components, thereby simplifying the structure.

In the above invention, it is preferable that the air intake portion is provided around the slag cleaner nozzle, whereby a region having a high air concentration can be formed on the wall surface of the furnace slag which is liable to cause slag formation, and the slag nozzle opening in a severe heat state can be cooled. Around the ministry.

According to the above aspect of the invention, in the vortex-fired boiler structure in which the vortex flow is formed by combustion of the fuel and the combustion air, the flame-affected portion of the furnace wall in the furnace is liable to cause corrosion and slagging. In the vicinity, the low-flow air is introduced from the air input portion to form a region where the air concentration is higher than the surrounding portion. Therefore, it is not necessary to increase the auxiliary mechanical power of the input air flow rate, and the oxygen concentration of the flame-affected portion and its vicinity is not required. Maintain high.

Therefore, the flame-affected portion in the furnace and its vicinity are partially changed from the reducing environment to the oxidizing environment by forming an air layer having a high oxygen concentration, and as a result, corrosion and slagging can be effectively suppressed or prevented. Especially the above The present invention is effective in suppressing slagging in a coal-fired boiler, and is effective in improving corrosion resistance to hydrogen sulfide in a boiler corresponding to various fuels containing a sulfur component.

Further, as the air used in the air-input portion is introduced by bypassing the secondary air of the low-pressure burner from the adjacent burner, the boiler structure can be greatly changed and the increase in the number of components can be suppressed. At a minimum, the construction is simplified.

Hereinafter, an embodiment of the boiler structure of the present invention will be described with reference to the drawings.

In the boiler 10 shown in Fig. 5, in order to reduce the NOx, the combustion air is supplied to the furnace 11 in multiple stages, and the fuel is burned. In this case, the burner portion Ba in the region where the plurality of burners 12 are provided in the furnace 11 and the additional air input portion Aa in the region where the additional air inlet nozzle 13 is provided in the upper portion of the burner portion Ba are provided. The air intake for the two-stage combustion is performed. In other words, in the boiler 10, about 70% of the amount of combustion air required is initially used by the burner unit Ba, and about 30% of the remaining air is supplied by the additional air input unit Aa to perform the reduction combustion region and complete combustion. Two-stage combustion of the NOx countermeasure for regional formation.

Further, in the above-described boiler 10, for example, as shown in Fig. 1A, the furnace 11 has a vortex combustion type having a rectangular cross section. The vortex-fired boiler 10 is configured to generate a vortex flow flame in the furnace 11 and burn it by burning the fuel and the combustion air from the plurality of burners 12 provided in the furnace wall 11a into the furnace 11.

Furthermore, in the configuration example of the octagonal furnace shown in FIG. 1A, from the horizontal section The burner 12 provided at eight places puts fuel and combustion air, and forms two adjacent vortex flows in the furnace 11.

In the present embodiment, in the present embodiment, an air intake portion 20 is provided in the vicinity of the flame influencing portion of the furnace wall surface (furnace wall 11a) in which the flame formed by each of the burners 12 approaches or contacts, which is used to form air. The area where the concentration is higher than the surrounding area. Specifically, in the horizontal section of the octagonal furnace shown in Fig. 1A, for example, at the appropriate positions of the respective furnace walls 11a forming the rectangles, one of the four air input portions 20 at each of the four places is provided.

Further, since the region in which the air concentration is high is formed to mean that a region having a high oxygen concentration is formed, the reducing environment in this region becomes an oxidizing environment.

In other words, by providing the air inlet portion 20 for injecting low-flow air from the inner wall 11a in the furnace 11 from the point of corrosion and slag formation, a region having a higher air concentration than the periphery is formed substantially along the wall surface. In other words, instead of the furnace wall 11a in the area where there is corrosion and slag, the air is injected at a relatively high flow rate (for example, 40 m/sec or more), but by being disposed in the presence of corrosion and slagging. The air input unit 20 of the furnace wall 11a of the area is supplied with air having a low flow velocity (for example, about 10 m/sec) to form a region having a higher air concentration than the periphery.

The air input unit 20 is, for example, a nozzle that introduces a second-stage air from a low-pressure burner from an adjacent burner 12, and introduces the air into the furnace 11 at a low flow rate to form an area having a high air concentration. By. The air supplied from the air input unit 20 forms a region having a high air concentration along the furnace wall 11a in the vicinity of the flame influencing portion in the plane of the furnace 11, and further covers the reduction combustion inside the furnace in order to further the upper and lower sides of the furnace 11. Area, at A plurality of air input portions 20 are also provided in the vertical direction.

That is, since the reduced combustion zone is a region in which a large amount of hydrogen sulfide is generated, and the furnace 11 is also a region of a reduction region having a high heat load, the wall surface 11a of the region is not only in a severe corrosive environment but also has slag. Attached to the cockroach. Therefore, in the reduction combustion region, the air intake portion 20 is disposed at a position approximately the same height as the burner 12 around the furnace wall 11a where the flame approaches or contacts. Since the flame system is formed to extend from the burner 12 in a substantially horizontal direction, the flame influencing portion of the furnace wall 11a is also substantially higher than the installation position of the burner 12.

Further, since the burner 12 of the reduced combustion zone is usually disposed in a plurality of sections above and below, the flame influencing portion of the furnace wall 11a is also formed at a plurality of points. Therefore, the air input unit 20 described above is also provided with a plurality of segments of the burner 12, in other words, a number of segments in the upper and lower directions of the flame, and a plurality of segments are arranged in the vertical direction. That is, for the upper and lower directions in the furnace 11 having corrosion and slag, a region having a high air concentration can be formed by inputting air having a low flow velocity.

As a result, in the reduced combustion region, around the flame-affected portion of the furnace wall 11a formed by each of the burners 12, a region having a higher air concentration than the periphery is formed by the low-flow air supplied from the air-input portion 20 disposed in the vicinity thereof. It acts as an air layer between the partition wall 11a and the flame. Therefore, it is possible to reduce the influence of the heat of the flame or the like on the furnace wall 11a which is the region affected by the flame, and to reduce or prevent corrosion and slagging by being a part of the oxidizing environment.

Further, since the above-described air input portion 20 is attached to the flame influencing portion The near-peripheral input can be used, so that low-flow air can be used with small auxiliary mechanical power. In other words, it is not necessary to input high-flow air at a high pressure by using a compressor that is operated with a large power as a target of a distant position, in particular, a low-pressure secondary air is introduced from the burner 12. In addition, in addition to reducing the auxiliary mechanical power, it is possible to suppress a large structural change and an increase in the number of components, and the structure is simplified.

In addition, as shown in FIG. 1B, the air intake unit 20 can be provided around the cleaner nozzle 31 by the cleaner nozzle insertion portion 30 between the burner portion Ba and the additional air input portion Aa. The cleaner nozzle insertion portion 30 is a device for removing the slag adhering to the furnace wall 11a, for example, as shown in Fig. 2A, which is cleaned by steam injected from the cleaner nozzle 31 inserted into the furnace 11 Wall 11a.

In other words, since the cleaner nozzle insertion portion 30 is also provided in the furnace 11 in a position where the heat load is high and the slag adheres due to the reducing environment, the air concentration formed by the above air input can be effectively formed. Area.

Here, a configuration example of the air intake unit 20 provided around the cleaner nozzle insertion portion 30 will be described with reference to FIGS. 2A and 2B.

In Fig. 2A, in the cleaner nozzle insertion portion 30, the cleaner nozzle 31 is inserted and inserted through the nozzle hole 32 of the furnace wall 11a. The steam jet 33 is supplied to the cleaner nozzle 31 by supplying steam which is sprayed when the slag is removed. Further, reference numeral 34 in the figure is a sealing member which is provided between the nozzle body 21 of the air-injecting nozzle and the cleaner nozzle 31 which are examples of the air-input portion 20 which will be described later.

On the other hand, the air input portion 20 is formed in the cleaner nozzle 31 and sprayed The annular space between the nozzle holes 32 serves as the air flow path 22, and the nozzle body 21 having the disk-shaped flange portion 21a at the front end of the cylinder is attached to the furnace 11. The nozzle body 21 is fixed to the outer periphery of the cleaner nozzle 31 by, for example, a sealing member 34, and the flange portion 21a in the furnace 11 is opposed to the furnace wall 11a at substantially a predetermined interval. Therefore, the air that has been introduced into the furnace 11 from the nozzle body 21 flows out over the entire circumference in the circumferential direction along the furnace wall 11a by colliding with the flange portion 21a.

Further, the air intake unit 20 includes a bellows 23 provided on the outer wall side of the furnace 11. The air box 23 communicates with the nozzle body 21 in the furnace 11 via the air flow path 22, and supplies the air supplied from the air supply source 24. At this time, the air supply source 24 preferably uses, for example, low-pressure secondary air introduced from the burner 12, but may use primary air or pressurized air as needed.

In such an air input portion 20, a region having a high air concentration can be formed in the furnace wall 11a of the furnace 11 which is likely to generate a slag formation region, and the periphery of the cleaner nozzle insertion portion 30 in a hot and severe state can be cooled. Therefore, an air layer having a higher air concentration than the periphery is formed around the furnace wall 11a where slag formation is likely to occur, so that the furnace wall can be long-lived by preventing or reducing the corrosion of the wall surface by a part of the oxidizing environment.

Further, since the air supplied from the nozzle body 21 of the air input portion 20 passes through the outer periphery of the cleaner nozzle 31, the sealing member 34 or the like under the severe heat can be cooled by the flow of the air.

Further, in the vicinity of the furnace wall 11a in which the air intake unit 20 is provided, the oxygen concentration is increased by the increase in the air concentration, thereby becoming an oxidizing atmosphere. In such an oxidizing environment, since the melting temperature of the slag becomes high, the slagging can be alleviated. produce.

According to such a boiler structure, the air inlet portion 20 in the region where the air concentration is higher than the periphery is provided in the vicinity of the furnace wall 11a which is the flame influencing portion when the flame formed by each of the burners 12 approaches or contacts, so that the flame influencing portion is provided. The periphery is partially changed from a reducing environment to an oxidizing environment by an increase in the oxygen concentration, and as a result, corrosion and slagging can be suppressed or prevented, and the wall life can be prolonged. Such a boiler structure is particularly effective in suppressing slagging in a coal-fired boiler, and is particularly effective in improving corrosion resistance in a boiler corresponding to various fuels containing sulfur.

Further, regarding the horizontal cross-sectional position of the air-input portion 20, the optimum position differs depending on various conditions such as the shape of the furnace 11, the position and number of the burners 12, and the formation of the vortex flow flame. That is, as the burner 12 is arranged and the vortex flow flame or the like is formed, the flame formed by the burners 12 is close to or in contact with the flame influencing portion of the furnace wall 11a, so for example, as shown in FIG. 1A and FIG. In the eight-corner furnace shown in FIG. 1B and the four-corner furnace shown in FIGS. 3A and 3B and FIGS. 4A and 4B, the positional relationship between the burner 12 and the air intake unit 20 is different for each boiler structure.

In the structure shown in Figs. 1A and 1B, the furnace 11 has a rectangular shape, and four burners 12 are disposed on each of the two sides of the opposite long sides to form two vortex flows on the left and right. Since the burner 12 at this time is inclined toward the approximate center position of each vortex flow, that is, toward the approximate center position of the square obtained by dividing the rectangle 2, two vortex flows substantially close to an ellipse are formed.

Therefore, the flame influencing portion where the flame approaches or contacts at this time becomes the vicinity of the central portion of the corner portion and the long side of the two places, and the air input portion 20 is provided at four places to Cover these areas.

Further, in the configuration example (first modification) shown in FIGS. 3A and 3B, the furnace 11 has a square shape, and the burner 12 is disposed at four positions shifted from the center of each side to form a vortex flow. Since the burners 12 are oriented toward the opposite wall surfaces at this time, the swirl flow is formed by the offset of the burners 12. In such an arrangement of the burners 12, the flames flow toward the vicinity of the center of the wall surface on the downstream side by the influence of the flame formed on the upstream side of the vortex flow.

Therefore, since the flame influencing portion at this time is in the vicinity of the central portion of each side, the air input portion 20 is provided at the central portion 4 of each side so as to cover these regions.

Further, in the configuration example (second modification) shown in FIGS. 4A and 4B, the furnace 11 has a square shape, and the burner 12 is disposed at four corners to form a vortex flow. Since the flame influencing portion at this time is also near the center portion of each side, the air input portion 20 is provided at the central portion 4 of each side so as to cover these regions.

As described above, the installation position of the air intake unit 20 may be appropriately selected according to the arrangement of the burners 12 or the like.

The present invention is not limited to the embodiments described above, and may be appropriately modified without departing from the scope of the invention.

10‧‧‧Boiler

11‧‧‧ furnace

11a‧‧‧ furnace wall

12‧‧‧ burner

20‧‧‧Air Input Department

30‧‧‧Dropper nozzle insertion section

Fig. 1A is a view showing an embodiment of a boiler structure of the present invention, showing a horizontal sectional view of a reduced combustion zone of the furnace.

Fig. 1B is a perspective view showing an embodiment of the boiler structure of the present invention, showing a schematic view of the appearance thereof.

Fig. 2A is a view showing a configuration example of an air input portion provided in a cleaner nozzle insertion portion, which is a cross-sectional view of the furnace.

Fig. 2B is a view showing an example of the configuration of an air input portion provided in the cleaner nozzle insertion portion, and is a view taken along the arrow A of Fig. 2A.

Fig. 3A is a view showing a first modification of the boiler structure of the present invention, showing a horizontal sectional view of a reduced combustion region of the furnace.

Fig. 3B is a perspective view showing a schematic view of a first modification of the boiler structure of the present invention.

Fig. 4A is a view showing a second modification of the boiler structure of the present invention, showing a horizontal sectional view of a reduced combustion region of the furnace.

Fig. 4B is a perspective view showing a second modification of the boiler structure of the present invention, showing a schematic outline of the appearance.

Fig. 5 is a longitudinal cross-sectional view showing the outline of a boiler structure in which a plurality of stages of combustion air are used to burn fuel.

10‧‧‧Boiler

11‧‧‧ furnace

11a‧‧‧ furnace wall

12‧‧‧ burner

20‧‧‧Air Input Department

Claims (1)

A boiler structure configured to generate a vortex flow and burn a vortex-burning type from a burner provided at a plurality of burner walls forming a rectangular cross section to a fuel and combustion air in a furnace; characterized in that: An air input portion that forms a region having a higher air concentration than the periphery is provided in the vicinity of the flame influencing portion of the furnace wall surface that is adjacent to or in contact with the flame formed by each of the burners, and the region having a high air concentration is covered in the upper and lower directions to cover the inside of the furnace chamber. a combustion zone is formed, and the air input portion is introduced from the adjacent burner to bypass the secondary air of the low pressure burner; the air input portion is formed in an annular space between the cleaner nozzle and the nozzle hole. The air flow path is provided with a disk-shaped flange portion at the tip end of the cylinder and is provided around the nozzle of the cleaner.