JP2012145267A - Boiler device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a boiler device with improved reliability and economical efficiency, including a sound air supply nozzle, forming a strong swirl flow along the inner surface of a furnace wall and also suppressing burnout caused by radiation heat, even if a gap is formed between the nozzle provided in a through hole communicating with the inside of a furnace and the through hole.SOLUTION: In the air supply nozzle, the through hole is formed in the furnace wall constituted of a water pipe, the air supply nozzle is inserted into the through hole, and the gap is provided between the nozzle and the through hole. The position of the tip end of the nozzle is separated from the inner surface of the furnace wall by 0.8 times or more the inside diameter of the nozzle. Gas jetted from the inside of the nozzle has a turning speed component.

Description

  The present invention relates to a boiler device, and more particularly to a boiler device having an air supply nozzle for supplying air into a furnace.

  For example, in a pulverized coal fired boiler in which coal is finely pulverized and suspended in a furnace and burned, a pulverized coal burner is provided in the lower part of the boiler furnace as disclosed in Patent Document 1, and the downstream of the burner (upper part of the boiler) ) Is provided with an after air nozzle, pulverized coal fuel and combustion air are supplied from the burner, and only air is supplied from the after air nozzle.

  In combustion in the burner section, air is supplied from the burner in an amount that is less than the theoretical air ratio required for complete combustion of the pulverized coal fuel, and the pulverized coal is combusted in a shortage of air, creating a reducing atmosphere and generating NOx. Is suppressed. However, in this reducing atmosphere, an unburned portion remains due to oxygen shortage, and CO (carbon monoxide) is generated. In order to completely burn the unburned portion and CO generated in this reducing atmosphere, a slightly larger amount of combustion air is supplied into the furnace than the amount of air that becomes a shortage of the theoretical air ratio from the after air nozzle located downstream of the burner, Combustion exhaust gas with reduced unburned matter and CO is discharged from the furnace.

Japanese Patent Laid-Open No. 9-310807 Japanese Unexamined Patent Publication No. 4-52414 JP 2009-174751 A

  In a combustion apparatus such as a pulverized coal fired boiler or an oil fired boiler, it is important to completely burn the fuel. For this reason, for example, when air is supplied from the after air nozzle downstream of the burner and completely burned like the above-described pulverized coal burning boiler, it is desirable to promote the mixing with the unburned portion by uniformly distributing the air in the furnace. . In this case, in addition to supplying air to the center of the furnace, it is necessary to supply air to the vicinity of the furnace wall in order to reduce the amount of unburned fuel near the furnace wall. As a means for supplying air to the vicinity of the furnace wall, there is a method in which air is swirled in a nozzle and supplied into the furnace as a swirling flow. For example, Patent Document 2 discloses a swirling structure that adjusts the flow pattern of an after-air jet and imparts a straight flow and a swirling flow to air in order to promote mixing. When air is supplied to the vicinity of the furnace wall with the above structure, a method of increasing the ratio of the swirling flow and diffusing the air after being ejected from the nozzle by centrifugal force is used. When a particularly strong swirling flow is generated, a wall surface flow along the furnace wall surface can be formed by the Coanda effect in which air flows along the wall surface even after ejection from the nozzle.

  By the way, the furnace wall which is a partition which comprises the furnace of a boiler thermally expands with the rise in furnace temperature. In general, the upper part of a furnace is supported and suspended. For this reason, the furnace wall moves downward due to thermal expansion. Moreover, when supporting a furnace in the lower part, a furnace wall moves to upper direction by thermal expansion. For this reason, an air supply nozzle such as an after air nozzle is generally provided with a gap (gap) without being brought into close contact with a through-hole communicating with the furnace. By providing the gap, contact or interference with the air supply nozzle fixed to the equipment base does not occur with respect to the through hole of the furnace wall that moves due to thermal expansion.

  On the other hand, the inside of the furnace is controlled to a negative pressure in order to prevent the combustion gas from flowing out of the furnace, and air flows from the gap into the furnace as a leak flow. Since the leak flow goes straight and flows into the furnace, it works in a direction that obstructs the flow of the swirl flow, making it difficult to form a strong wall flow along the wall. Even when a structure (seal member) that prevents the inflow of air between the air supply nozzle and the furnace wall is provided, the flow path rapidly expands in the step portion generated between the air supply nozzle and the furnace wall. Therefore, the flow is separated from the wall surface, and a circulating flow is generated to prevent the air ejected from the nozzle from flowing along the wall surface. For this reason, it becomes difficult to form a flow along the furnace wall surface, and there is a possibility that air is not sufficiently supplied in the vicinity of the furnace wall and an unburned portion remains.

  Patent Document 3 discloses a nozzle that ejects air along a water pipe wall. However, the component member protrudes into the furnace, and the nozzle member may be burned by the radiant heat of the burner flame, so that a necessary air jet may not be formed.

  An object of the present invention is to form a strong swirling flow and form a wall surface flow on the furnace inner wall surface even if there is a gap between the nozzle provided in the through hole of the furnace wall leading to the furnace and the through hole, and a nozzle by radiant heat An object of the present invention is to provide an air supply nozzle that suppresses burning and enhances soundness, and provides a boiler device that has improved reliability and economy.

  The present invention relates to a burner that burns fuel supplied into a furnace, a furnace wall that constitutes a furnace in which a water pipe is provided and a through hole is formed, a nozzle that is inserted into the through hole and supplies air into the furnace, and In a boiler apparatus having an air supply nozzle having a swirl member that imparts a swirl speed component to air supplied into the nozzle and having a gap between the nozzle and the through hole, the tip position of the air supply nozzle in the through hole Is installed at a distance of 0.8 times or more the nozzle inner diameter from the furnace wall inner surface.

  Moreover, the boiler apparatus provided with the air supply nozzle has a tube expansion structure in which the nozzle tip portion is directed downstream and the cross-sectional area is expanded.

  Moreover, the boiler apparatus provided with the air supply nozzle is characterized in that a cylindrical tube expansion member having a cross-sectional area expanding toward the downstream side is provided inside the nozzle.

  Moreover, in the boiler apparatus provided with the air supply nozzle, an uneven member is provided at the tip of the nozzle.

  Moreover, in the boiler apparatus provided with the air supply nozzle, the furnace inner surface side of the through hole has a tube expansion structure.

  Moreover, the boiler apparatus provided with the air supply nozzle is characterized in that a structure for preventing the inflow of air is provided at a location where the nozzle contacts the outside of the furnace wall.

  Moreover, the boiler apparatus provided with the air supply nozzle is provided with an adjusting member for adjusting a swirl velocity component of the fluid.

  Moreover, the boiler apparatus provided with the air supply nozzle WHEREIN: The air supply nozzle was provided in the downstream of the said burner, It is characterized by the above-mentioned.

  Further, in the boiler apparatus provided with the air supply nozzle, at least two stages of nozzles for supplying a shortage of combustion air in the burner into the furnace are provided on the downstream side of the burner, and the air supply nozzle is provided as a part of the nozzle. It is provided.

  Furthermore, in the boiler apparatus provided with the air supply nozzle, the air supply nozzle is provided at a height at which the burner is disposed.

  According to the present invention, since the tip of the nozzle is disposed at a distance of 0.8 D or more from the furnace wall inner surface, the flow ejected from the nozzle gradually expands in the radial direction, and the inner wall of the through hole upstream from the through hole outlet. Flowing along. It further expands at the outlet of the through hole and flows along the furnace wall inner surface of the water pipe surface. For this reason, even if there is a gap between the nozzle provided in the through hole leading into the furnace and the through hole, a wall surface flow along the wall can be formed.

  When the air supply nozzle of the present invention is installed downstream of the burner, sufficient oxygen can be supplied in the vicinity of the wall, and unburned components and CO existing in the vicinity of the wall are reduced. In addition, when installed at the height where the burner is placed, oxygen can be supplied along the furnace wall surface to suppress corrosion, and because the nozzle does not protrude into the furnace, it can suppress the burning of the nozzle due to radiant heat. It is possible to provide a highly economical boiler device.

The front view of the air supply nozzle by Example 1 of this invention. The schematic diagram which shows the AA cross section of FIG. The graph showing the jet state by the presence or absence of L and the clearance gap 24. FIG. The schematic diagram which shows the jet flow in the case of the wall surface flow in FIG. 3 (H area | region). The schematic diagram which shows the jet of the case where it does not become a wall surface flow in FIG. 3 (F area | region). The schematic diagram of the air supply nozzle by Example 2 of this invention. The schematic diagram of the air supply nozzle by Example 3 of this invention. The schematic diagram of the air supply nozzle by Example 4 of this invention. The schematic diagram of the air supply nozzle by Example 5 of this invention. The schematic diagram of the air supply nozzle by Example 6 of this invention. The schematic diagram of the boiler apparatus which shows Example 7 of this invention. The schematic diagram of the boiler apparatus which shows Example 7 of this invention. The BB arrow line view of the boiler of FIG.

  The boiler which is an Example of this invention is demonstrated below with reference to drawings.

FIG. 1 shows a front view of an air supply nozzle 4 according to an embodiment of the present invention, and FIG. 2 shows a schematic diagram of a cross section AA in FIG. A water pipe 11 is provided on the surface of the furnace wall 1, and the water pipe 11 is also deformed and installed along the shape of the through hole 30 so as not to interfere with the circular through hole 30. Since the furnace wall 1 extends downward due to thermal expansion due to heat in the furnace, a gap 24 is provided between the outer diameter of the nozzle 20 installed in the through hole 30 and the inner diameter of the through hole 30. A circular swirl vane 25 is installed in the nozzle 20 as a swirl member for air. The duct 16 is configured so that the air 15 can be supplied from the through hole 30 into the furnace through the nozzle 20.
The air 15 passes through the duct 16 and flows in from an inflow hole 22 provided in the nozzle 20, becomes a swirl flow having a swirl speed component by the swirl vanes 25, flows out from the tip of the nozzle 20, and enters the furnace from the through hole 30. Flowing. The air flow rate is adjusted by the opening degree of the damper 21. The furnace wall 1 and the duct 16 are brought into close contact so that the entire amount of air 15 flows into the furnace, but a gap 26 exists between the duct 16 and the furnace wall 1.

  The inside of the furnace is always controlled to a negative pressure during operation so that the combustion gas does not go out of the furnace. Therefore, there is a leak flow 23 in which air flows in from the gap 26 and is ejected from the gap 24 into the furnace. Since the leak flow 23 is a straight flow toward the furnace, the wall flow along the wall due to the strong swirling flow ejected from the nozzle 20 is obstructed. Further, even when sealing with a sealing member 27 that prevents the inflow of air in order to suppress the leak flow 23, the circulating flow 31 is generated at the tip of the nozzle 20 due to the gap 24, and the swirling flow ejected from the nozzle 20 is generated. Prevents flow along the wall.

  FIG. 3 shows the influence of the presence or absence of the gap 24 on the jet flow. The horizontal axis represents a value (L / D) obtained by dividing the distance L from the tip of the nozzle 20 shown in FIG. 2 to the inner surface of the furnace wall 1 by the inner diameter D of the nozzle 20. The vertical axis indicates the presence or absence of the gap 24. In the figure, ◯ indicates that the jet flow from the through hole 30 is a wall surface flow ejected along the wall, and × indicates that it is not a wall surface flow. A hatched portion H in the figure indicates a region where a wall surface flow occurs, and F indicates a non-wall surface flow region. Even in the region F in the figure, a wall surface flow may occur temporarily, but the wall surface flow cannot be stably maintained if a disturbance due to pressure fluctuation in the furnace is applied. Under the condition of region H, a stable wall flow can be formed without being affected by these disturbances. 3 that the distance L from the tip of the nozzle 20 to the inner surface of the furnace wall 1 needs to be about 0.8 times or more the inner diameter D of the nozzle 20 in order to form a wall flow when there is a gap 24.

  FIG. 4 shows a schematic diagram of a jet flow in the case of a wall surface flow corresponding to the region H in FIG. Since the tip position of the nozzle 20 is sufficiently spaced apart from the inner surface of the furnace wall 1 by 0.8D or more, the swirling flow ejected from the nozzle gradually expands in the radial direction, and the flow of the leak flow 23 and the circulation flow 31 is While being suppressed, it further expands at the outlet of the through hole 30 and becomes a wall surface flow that flows along the inner surface of the furnace wall 1 on the surface of the water pipe 11.

  On the other hand, the schematic diagram of the jet in the case of the non-wall surface flow corresponding to the region F in FIG. 3 is shown in FIG. Since the tip of the nozzle 20 is near the inner surface of the furnace wall 1, the swirling flow ejected from the nozzle 20 flows out into the furnace before spreading in the radial direction. Since the leak flow 23 flows straight toward the furnace and the circulation flow 31 is inhibited from becoming a wall surface flow, it is difficult to become a stable wall surface flow.

  According to the first embodiment, even when there is a gap 24 between the through hole 30 leading to the furnace and the nozzle 20, the tip position of the nozzle 20 is separated from the inner surface of the furnace wall 1 by 0.8 times or more of the inner diameter D of the nozzle 20. Thus, a stable wall flow can be formed without being affected by disturbance due to fluctuations in the pressure in the furnace.

  FIG. 6 shows a schematic diagram of a nozzle according to Example 2 of the present invention. In addition to the conditions for the nozzle tip position in the first embodiment, this nozzle has a tube expansion structure in which the tip of the nozzle 20 is directed downstream and the cross-sectional area is expanded. According to the second embodiment, since the expanded pipe portion 32 provided in the nozzle 20 is directed in the radial direction, the generation of the circulating flow 31 is suppressed, and the swirling flow ejected from the nozzle 20 is easily spread in the radial direction, and is more stable. There is an advantage that a wall flow can be formed.

  FIG. 7 shows a schematic diagram of a nozzle according to Example 3 of the present invention. This nozzle is provided with a cylindrical tube expansion member 33 whose cross-sectional area expands toward the downstream side at the tip end inside the nozzle 20. In the third embodiment as well, since the pipe expansion member 33 faces in the radial direction, the swirling flow easily spreads in the radial direction, and the generation of the circulating flow 31 is suppressed, so that a more stable wall surface flow can be formed. Further, since the pipe expansion member 33 is inside the nozzle, there is an advantage that the influence of the radiant heat can be reduced.

  FIG. 8 shows a schematic diagram of a nozzle according to Example 4 of the present invention. This nozzle is provided with an uneven member 34 in which tooth-like or strip-like members are arranged in the circumferential direction at the tip of the nozzle 20. The member 34 disturbs the flow ejected from the nozzle, and the flow is easily diffused in the circumferential direction. For this reason, the flow ejected from the nozzle is easily expanded, and the flow ejected from the nozzle 20 becomes a stable wall surface flow in order to suppress the generation of the circulating flow 31.

  FIG. 9 shows a schematic diagram of a nozzle according to Example 5 of the present invention. This nozzle has an expanded structure in which an expanded portion 28 that is expanded toward the exit is formed at the exit portion of the through hole 30 of the furnace wall 1. According to the fifth embodiment, the swirling flow ejected from the nozzle 20 easily spreads in the radial direction at the outlet of the through hole 30 and suppresses the generation of the circulating flow 31, so that there is an advantage that a more stable wall surface flow can be formed.

  FIG. 10 shows a schematic diagram of a nozzle according to Example 6 of the present invention. In place of the swirl vane 25 shown in FIG. 9, a guide vane 29 is provided in which the angle of the radial vanes arranged in the circumferential direction is adjustable. The air flow rate is adjusted by the damper 36. In the sixth embodiment, a strong swirl flow that is a wall surface flow can be generated as in FIG. Furthermore, since the turning speed component (turning strength) can be adjusted by adjusting the angle of the guide vane 29 with the adjusting handle 35 as an adjusting member, there is an advantage that the shape of the jet can be controlled widely.

  In FIG. 11, the schematic diagram of the boiler to which the nozzle structure of this invention in Example 7 is applied is shown. A burner 2 is provided at the lower part of the boiler, and after-air (air) 7 is supplied from an after-air nozzle 3 provided at the upper part of the boiler with a gas 5 containing an unburned part rising from the burner part. Is discharged outside the furnace. The lower stage of the after air nozzle 3 is provided with the air supply nozzle 4 of the present invention. By supplying air (oxygen) as a wall surface flow 8 near the wall that cannot be supplied by the after-air nozzle 3, the air can be mixed uniformly in the furnace, and the unburned portion and CO near the wall can be reduced. Therefore, the combustion rate of the fuel in the furnace is improved, and a highly economical boiler can be provided.

  In FIG. 12, the schematic diagram of the boiler to which the air supply nozzle structure of this invention in Example 8 is applied is shown. In the eighth embodiment, an air supply nozzle 4 is provided in the vicinity of the burner 2 below the boiler. In the vicinity of the burner, the oxygen concentration is low and the furnace wall tends to corrode. FIG. 13 is a view taken along arrow BB in FIG. By installing the air supply nozzle 4 of the present invention at the burner installation height, air (oxygen) flows on the surface of the water tube by the wall surface flow along the furnace wall as in the jet 8 shown in FIG. And corrosion can be suppressed. Further, since the members constituting the nozzle do not protrude into the furnace, there is no burning due to radiant heat, and the reliability is high. In FIG. 12, the burner 2 is only on one side, but the effect is the same even if the burner 2 is on both sides as shown in FIG. Moreover, in FIG. 12 which shows a present Example, although the air supply nozzle 4 is provided in 3 surfaces other than the burner 2 installation surface, it is also possible to provide in the burner 2 installation surface. Moreover, in FIG. 12 which shows a present Example, although the air supply nozzle 4 is provided in the lowest step height of the burner 2, any installation height of the burner 2 below (upstream side) from the after air nozzle 3 may be sufficient.

  According to the present invention, even if there is a gap between the nozzle provided in the through-hole leading into the furnace and the through-hole, a flow along the wall can be formed, and when applied to an after-air nozzle located downstream of the burner, oxygen is present in the vicinity of the wall. , And the amount of unburned CO present in the vicinity of the wall is reduced. In addition, when applied in the vicinity of the burner, oxygen can be supplied along the surface of the water tube, corrosion of the furnace wall can be suppressed, and the structural material constituting the nozzle does not protrude into the furnace, so that burning of the nozzle member due to radiant heat can be suppressed, A boiler device with high reliability and economy can be provided.

1 ... Furnace wall
3 ... After air nozzle
4 ... Air supply nozzle 8 ... Air jet
9 ... Combustion exhaust gas
11 ... Water pipe
15 ... Air flow
20 ... Nozzle
23 ... Leak flow
24, 26 ... gap
25 ... swirl blade 27 ... seal member
28, 32 ... tube expansion part
29 ... Guide feather
30 ... through hole
31 ... Circulating flow 33 ... Cylindrical tube expansion member
34 .. Uneven member
35 ... Adjustment handle
D ... Nozzle inner diameter
L: Distance between nozzle tip and furnace wall inner surface

Claims (10)

A burner that burns fuel supplied into the furnace, a furnace wall that constitutes the furnace in which a water pipe is disposed and a through hole is formed, a nozzle that is inserted into the through hole and supplies air into the furnace, and the A boiler device having an air supply nozzle having a swirl member that imparts a swirl speed component to the air supplied into the nozzle, and having a gap between the nozzle and the through hole;
A boiler apparatus having an air supply nozzle, wherein the tip position of the air supply nozzle in the through hole of the nozzle is disposed at a distance of 0.8 times or more of the nozzle inner diameter from the furnace wall inner surface. .   The boiler apparatus provided with the air supply nozzle of Claim 1 which has a pipe expansion structure where the nozzle front-end | tip part expands a cross-sectional area toward a downstream side, The air supply nozzle characterized by the above-mentioned.   The boiler apparatus provided with the air supply nozzle of Claim 1 provided with the cylindrical pipe expansion member which a cross-sectional area expands toward the downstream in the said nozzle inside.   The boiler apparatus provided with the air supply nozzle of Claim 1 WHEREIN: The uneven | corrugated shaped member was provided in the front-end | tip of the said nozzle, The boiler apparatus provided with the air supply nozzle characterized by the above-mentioned.   The boiler apparatus provided with the air supply nozzle in any one of Claims 1 thru | or 4 WHEREIN: The furnace inner surface side of the said through-hole has a pipe expansion structure, The boiler apparatus provided with the air supply nozzle characterized by the above-mentioned.   6. A boiler apparatus comprising the air supply nozzle according to claim 1, wherein a structure for preventing air from flowing is provided at a location where the nozzle contacts the outside of the furnace wall. A boiler device equipped with a supply nozzle.   The boiler apparatus provided with the air supply nozzle in any one of Claims 1 thru | or 6 WHEREIN: The adjustment member which adjusts the turning speed component of the said fluid was provided, The boiler apparatus provided with the air supply nozzle characterized by the above-mentioned.   The boiler apparatus provided with the air supply nozzle in any one of Claims 1 thru | or 7 WHEREIN: The said air supply nozzle was provided in the downstream of the said burner, The boiler apparatus provided with the air supply nozzle characterized by the above-mentioned.   9. A boiler apparatus having an air supply nozzle according to claim 8, wherein at least two or more stages of nozzles for supplying a shortage of combustion air in the burner into the furnace are provided downstream of the burner, and a part of the nozzle is provided with the nozzle. The boiler apparatus provided with the air supply nozzle provided with the air supply nozzle.   The boiler apparatus provided with the air supply nozzle in any one of Claims 1 thru | or 9 WHEREIN: The said air supply nozzle was provided in the height which has arrange | positioned the said burner, The boiler apparatus provided with the air supply nozzle characterized by the above-mentioned.

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