JP2004205101A - Soot blower nozzle protecting cover - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the breakage of a soot blower nozzle head due to thermal fatigue. <P>SOLUTION: The nozzle head is covered at its outside with a material having superior heat resistance, and a plurality of layers of partition walls are provided in the cover around the nozzle head where thermal amplitude is the greatest. The inside nozzle head can be protected against the thermal fatigue by the heat insulating and radiation scattering effects of air existing between the partition walls. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cover for protecting a nozzle head of a soot blower used for removing dust attached to a heat transfer element such as a boiler or an air preheater, and more particularly to a cover for preventing damage due to thermal fatigue of the nozzle head. Protective cover.
[0002]
[Prior art]
In general, when exhaust gas dust adheres to the surface of a heat transfer element of a boiler or an air preheater, the flow path of exhaust gas or air is narrowed or blocked, and as a result, the heat exchange efficiency is reduced. Further, the pressure loss increases, and the boiler plant may become inoperable. As a cause of this dust adhesion, for example, in an air preheater that recovers exhaust gas heat from a coal-fired boiler, part of the NH ₃ used in the denitration process on the upstream side remains unreacted, It is considered that this reacts with SOx to produce an ammonium sulfate compound and the like, and the produced compound acts as a binder to adhere dust in exhaust gas to the heat transfer element. Depending on the operating conditions, this deposit changes into a sticky substance that is extremely difficult to peel off.
[0003]
Conventionally, a soot blower is used to remove the adhered matter from the surface of the heat transfer element. This soot blower has a structure in which a nozzle head is provided in a long tube body, and is inserted intermittently near the heat transfer element surface to blow off steam and compressed air to blow off deposits.
[0004]
The soot blower is exposed to a high temperature of about 600 ° C. during standby and 1000 ° C. or more when inserted into the boiler. At the time of steam injection, the temperature inside the nozzle head rapidly drops, and the maximum temperature difference between the inner and outer surfaces of the head instantaneously exceeds 700 ° C. If the heat (temperature) amplitude exceeding 700 ° C. is continued for 1000 hours or more, a crack is generated at the tip of the nozzle head due to thermal fatigue, which further leads to a hole or damage.
[0005]
The cause of damage to the nozzle head tip is thermal fatigue due to a large thermal amplitude on the inner and outer surfaces of the nozzle head. Therefore, it is necessary to reduce the thermal amplitude, that is, to suppress a rise in the nozzle head outer surface temperature and reduce the temperature difference.
[0006]
In order to suppress the rise in the outer surface temperature of the nozzle head, JP-A-62-166218 and JP-A-2000-65337 attach a casing made of a special material such as ceramics and special steel for marine diesel engines to the nozzle head. It is further disclosed that a heat insulator is provided between the casing and the nozzle head.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a nozzle head protection cover that can be manufactured at low cost without using a special material and that can be mounted without changing an existing nozzle head, unlike the above-described conventional technology.
[0008]
[Means for Solving the Problems]
The inventor of the present invention has made extensive studies on the above problems, and as a result, covering the outside of the nozzle head with a material having excellent heat resistance, and providing a multi-layer partition wall inside the cover around the nozzle head tip where the thermal amplitude is the largest. It has been found that the thermal fatigue of the nozzle head can be reduced by the heat insulating effect and the radiation scattering effect of the air between the partition walls. That is, the present invention comprises a cover body disposed outside the soot blower nozzle head, and a plurality of partition walls provided in layers and separated from the tip end of the cover body toward the tip end of the nozzle head. This is a soot blower nozzle head protection cover.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention will be described using embodiments with reference to the drawings. FIG. 1 is a plan view of a nozzle head protective cover 1 of the present invention, and FIG. 2 is a cross-sectional view along the AA plane. The soot blower 11 to which the nozzle head protection cover 1 of the present invention is mounted is installed on a furnace wall as shown in FIG. 7, and a nozzle head section is provided in a pipe (wall sleeve) having a diameter of about 90 mm provided on the opposite side of the furnace from the furnace wall. Is stored.
[0010]
The cover main body 2 constituting the nozzle head protective cover 1 of the present invention covers the nozzle head opening 3 so as to wrap the nozzle head (the imaginary line 6 in FIG. 2) and not to close the steam injection area of the nozzle head. It has a shape cut out from the main body 2. The tip of the cover body 2 is formed into a curved surface with a curvature slightly larger than the nozzle head 6 (for example, 35 mmR). The cover body 2 is made of a material having excellent heat resistance, and prevents the nozzle head from being directly exposed to radiant heat. The material is generally SUS304, SUS310, or the like. Preferably, radiant heat transfer can be further reduced by making the cover body 2 a mirror finish or a heat ray reflective coating.
[0011]
In FIG. 1, two flat disk-shaped partition plates are attached to the cover main body 2 at a layer interval with the partition walls 4 constituting the nozzle head protective cover 1 of the present invention. There is some convective heat transfer between the partitions due to the heat insulation effect of the air, and the heat of the partitions is appropriately radiated to the cover body 2 and other partitions or nozzle heads. By this action, the temperature of the nozzle head does not rise for about one minute at the time of insertion, and when the steam is injected next and the cooling effect by the steam from the inner surface of the nozzle can be exerted, the partition wall 4 and the cover body 2 from the nozzle side. Acts to cool. Therefore, the return of the cover body 2 to the standby temperature is completed in about 10 minutes, there is no heat accumulation due to the operation cycle, and the protection cover is exposed to the high temperature for one minute from the start of insertion to the steam injection. Almost limited to the extent.
[0012]
The number of the partition walls 4 increases and decreases depending on the external environment, and is adjusted so that the heat amplitude of the inner and outer surfaces of the nozzle head 6 is 500 ° C. or less. The material of the partition is a material having excellent heat resistance, for example, SUS304, SUS310, or the like. In particular, it is preferable that the material of the partition wall 4 is the same as the material of the cover body 2 from the viewpoint that thermal distortion does not occur. Preferably, radiant heat transfer can be further reduced by forming the partition walls 4 into a mirror finish or a heat ray reflective coating.
[0013]
Explaining in detail, the main amount of heat received by the nozzle head protection cover via the nozzle housing pipe (wall sleeve) during standby is radiant heat, and the mirror surface finish or the heat ray reflective coating actively reduces radiant heat transfer, and furthermore, the surface is appropriately curved. When using a multi-layered partition wall with heat insulation and radiation scattering effect to prevent radiant heat transfer positively, heat that penetrates to the partition wall is transferred to the protective cover side. The heat can be dissipated, and the amount of heat that can finally reach the nozzle head due to the multi-layered partition wall acting in this manner is very small as compared with the case without the protective cover. This is an effect that can be achieved because the temperature of the heat insulating material around the nozzle housing pipe (wall sleeve) is lower than the temperature at which the tip of the protective cover is heated by radiant heat transfer.
[0014]
The same is true during the insertion process.The temperature around the wall sleeve is always low, and the heat mainly due to the radiation received by the protective cover and the multi-layer partition walls is moderately radiated from the side of the protective cover. The rise can be reduced as much as possible, and as a result, the rise in the nozzle head outer surface temperature can be suppressed.
[0015]
By providing the protective cover body and the partition wall, the temperature of the nozzle head during standby can be reduced as compared with the case without the protective cover. And proceed. Therefore, due to the protective cover, the double effect, that is, the temperature of the nozzle head is already lower in the standby state than in the standby state without the protective cover, and there is almost no temperature rise in the next insertion process, and the steam injection is performed as it is. Proceed to the process. This is due to the fact that the occurrence of cracks can be reduced to the utmost due to the significant decrease in the thermal amplitude of the inner and outer surfaces of the nozzle during steam injection, and the temperature of the nozzle head during standby, which occupies 90% or more of the operation time, decreases. The durability of the nozzle head can be improved.
[0016]
The partition wall 4 may be fixed to the cover main body 2 by point contact as shown in FIG. 2, or may be entirely fixed by surface contact. From the viewpoint of preventing deformation and breakage of the protective cover main body and the partition wall due to thermal deformation, point contact is preferable. The fixing method includes a fixing method such as welding and a detachable screwing means. Furthermore, when manufacturing the nozzle head protective cover 1, the cover main body 2 and the partition wall 4 may be integrally manufactured from the same material.
[0017]
As is clear from FIG. 2, one hole 5 having a diameter of about 2 mm is formed at a position slightly inside (for example, about 10 mm) from the outer periphery of the partition wall 4. The holes 5 function as gas vents, and prevent the cover main body 2 and the partition 4 from being deformed or damaged due to expansion and contraction of air during thermal amplitude. In addition, the shape of the hole 5 may be any shape as long as it is formed so as to be an entrance and exit when the insulating air in the protective cover 1 expands and contracts.
[0018]
FIG. 3 is a plan view of a nozzle head protection cover 1 according to another embodiment of the present invention, and FIG. 4 is a cross-sectional view taken along the line AA of FIG. The partition 4 has a convex curved surface with respect to the tip of the cover body 2. The curvature is arbitrary from a shape close to a flat plate to a shape equivalent to the tip of the nozzle head 2 and a shape larger than that. By providing the curved partition wall 4 in the cover main body 2, the protrusion size of the front end of the cover main body 2 can be shortened by about 15 mm as compared with the case of the plate shape. In the case of a plate-like shape, the front end of the cover main body 2 becomes longer due to the attachment, and is exposed to a high-temperature region both during standby and when inserted into the furnace, so that the amount of heat received increases. The curved shape can reduce the effect of the amount of heat received. Further, radiation scattering on the inner surface of the protective cover 1 can be promoted, which further contributes to extending the life of the nozzle head.
[0019]
After the nozzle opening 3 of the cover main body 2 and the opening of the nozzle head 6 (broken line) are matched and adjusted to the nozzle joint root-side joint pipe with the nozzle head protection cover 1, several spot welding locations 7 are formed. By providing a fixed structure (three places in FIG. 4), the protective cover 1 can be detached from the nozzle head 6 at appropriate times.
[0020]
FIGS. 5 and 6 show a modification of FIG. 3, in which a notch 8 is provided on the cover body 2 so that the nozzle head 6 can be adjusted to the screwing position of the nozzle joint with the nozzle head, and a detent for preventing rotation of about 5 mm in diameter. It is the same as FIG. 3 except that a hole 9 is provided. After adjusting the nozzle head opening 3 of the cover so as to coincide with the ejection port of the nozzle head 6, the nozzle head 6 is detachably fixed with screws or the like.
[0021]
【Example】
[Comparative Example 1]
In the general view of the soot blower installed in the furnace as shown in FIG. 7 (however, without the protective cover 2), when the temperature in the furnace is 1100 ° C., the nozzle tip of the nozzle head 6 without the protective cover is in a standby state. The temperature of the part was about 630 ° C. (575 ° C. inside the nozzle), and when it was inserted into the furnace for 1 minute, it became 810 ° C. (630 ° C. inside the nozzle). When steam was introduced in this state, the temperature difference between the inner and outer surfaces of the nozzle head became 550 ° C., and the durability was significantly reduced due to this thermal fatigue.
[0022]
[Example 1]
In the overall view shown in FIG. 7, when the temperature in the furnace is 1100 ° C., the temperature of the tip of the protective cover in the standby state of the nozzle head 6 with the protective cover shown in FIG. The temperature was slightly higher than the temperature at the tip of the nozzle head without the cover. However, the temperature of the tip of the nozzle head in the protective cover during standby is about 500 ° C. (490 ° C. inside the nozzle), and the temperature of the tip of the nozzle head is reduced by 130 ° C. in the standby state by attaching the protective cover. .
[0023]
Next, when this was inserted into the furnace for 1 minute from the standby state, the temperature of the tip of the protective cover was about 860 ° C, which was slightly higher than that of the nozzle without the protective cover as in the standby mode. The temperature at the tip of the nozzle head inside the cover remained at 500 ° C. (490 ° C. inside the nozzle), which was the same as during standby, and was lowered by 300 ° C. by the protective cover. Even if steam is injected at this point, the temperature difference between the inner and outer surfaces of the nozzle head is about 250 ° C., and the thermal fatigue due to the heat amplitude can be greatly reduced. improves.
[0024]
[Example 2]
The test was performed under the same conditions as in Example 1 except that the furnace temperature was changed from 1100 ° C. to 1400 ° C. Similarly, when the temperature was 1400 ° C., the temperature of the nozzle head portion in the protective cover was 500 ° C. (inside: 490 ° C.), which was the same as the temperature of the furnace 1100 ° C. Therefore, even when the temperature inside the furnace is 1400 ° C., the temperature at the tip of the nozzle head is improved by 500 ° C. by the protective cover, and the temperature difference between the inner and outer surfaces of the nozzle head due to steam injection is about 250 ° C.
[0025]
【The invention's effect】
By covering the outside of the nozzle head with a cover made of a material having excellent heat resistance, the nozzle head is prevented from being directly exposed to radiant heat. By providing a plurality of heat-resistant partitions in the cover at intervals, it is possible to reduce the temperature difference between the inside and outside due to the heat insulating effect of air between the partitions and the radiation scattering effect inside. Therefore, the life of the nozzle head can be extended. Further, if the partition wall is formed in a curved shape, it is possible to suppress an increase in the protrusion size of the cover tip and the amount of heat reception as compared with a plate-shaped one. Further, radiation scattering on the inner surface of the cover can be promoted, and the life of the nozzle head can be further extended. The convenience is great in that the nozzle head can be detachably attached to the outside without changing the existing nozzle head.
[Brief description of the drawings]
FIG. 1 is a plan view of a soot blower nozzle protection cover according to an embodiment of the present invention.
FIG. 2 is a sectional view taken along line AA of FIG.
FIG. 3 is a plan view of a soot blower nozzle protection cover according to another embodiment of the present invention.
FIG. 4 is a sectional view taken along the line AA of FIG. 3;
FIG. 5 is a plan view of a soot blower nozzle protection cover according to still another embodiment of the present invention.
FIG. 6 is a sectional view taken along line AA of FIG. 5;
FIG. 7 is an overall view when a soot blower equipped with the nozzle head protection cover of the present invention is installed in a furnace.
[Explanation of symbols]
1: Nozzle head protection cover 2: Cover body 3: Nozzle head opening 4: Partition wall 5: Hole 6: Nozzle head 7: Spot welding point 8: Cover adjustment notch 9: Detent hole 10: Furnace wall 11: Soot blower

Claims (6)

A soot blower nozzle head protection cover comprising: a cover main body disposed outside a soot blower nozzle head; The soot blower nozzle head protection cover according to claim 1, wherein the protection cover main body and the partition are made of the same material. The soot blower nozzle head protective cover according to claim 1 or 2, wherein the protective cover is detachable from the soot blower nozzle head. The soot blower nozzle head protective cover according to any one of claims 1 to 3, wherein the partition has a hole. The soot blower nozzle head protective cover according to any one of claims 1 to 4, wherein the partition is plate-shaped. The soot blower nozzle head protective cover according to any one of claims 1 to 4, wherein the partition wall has a curved shape.

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