JP2000234702A - Downcast pipe supporting structure of evaporator for heat recovery steam generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid concentration of stress by eliminating generation of structural disconnection at portions having large temperature differences, readily conduct checking of a pressure tight weld line, and reduce cost by simplifying structure so as to reduce the number of parts and welding portions. SOLUTION: A vertical channel 20a which communicates with an inner channel 19a of a downcast pipe 19 and a horizontal channel 20b which is communicated with an inner channel 18a of a manifold 18, are formed in an L shape between the lower end of the downcast pipe 19 and the base end of the manifold 18. A downcast pipe support member 20 which is formed by integrating a leg 20c into the L-shaped portion is bonded to the inside of a boiler duct 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for supporting an evaporator downcomer of an exhaust heat recovery boiler.

[0002]

2. Description of the Related Art Generally, in a combined cycle power generation plant, an exhaust heat recovery boiler is used as a heat source for generating exhaust steam from a gas turbine or the like for driving steam for a steam turbine or steam for a process.

FIG. 2 shows an example of a general waste heat recovery boiler. Reference numeral 1 denotes a horizontal type natural circulation type waste heat recovery boiler, and the waste heat recovery boiler 1 has a boiler duct 2 inside. , A superheater 3, a high-pressure evaporator 4, a denitration device 5, a high-pressure economizer 6, a low-pressure evaporator 7, and a low-pressure economizer 8 are sequentially arranged.
A high-pressure steam drum 9 is provided above the high-pressure evaporator 4, and a low-pressure steam drum 10 is provided above the low-pressure evaporator 7. The high-pressure steam drum 9 flows into the exhaust heat recovery boiler 1 from a gas turbine or the like (not shown). The exhaust gas passes through a superheater 3 and a high-pressure evaporator 4 to reach a denitration device 5 where nitrogen oxides are removed. The exhaust gas from which the nitrogen oxides have been removed in the denitration device 5 is a high-pressure economizer 6 and a low-pressure evaporator. 7 and the low-pressure economizer 8 in sequence,
Heat exchange is performed with the internal fluid in each heat transfer tube, and in the high-pressure steam drum 9 and the low-pressure steam drum 10, the two-phase flows generated by the evaporators of each pressure flow into and are separated into steam and can water.

[0004] Such a natural circulation type waste heat recovery boiler 1
Compared with the forced circulation type waste heat recovery boiler, a circulation pump is not required, and in addition to the advantage that power in the plant can be reduced, the height from the ground to the top of the boiler can be kept low. Since it has the advantages of being able to have a self-supporting structure and not requiring a supporting steel frame, it is used in many combined cycle power plants.

FIGS. 3 and 4 show details of an evaporator 11 corresponding to the high-pressure evaporator 4 and the low-pressure evaporator 7 of the natural-circulation-type exhaust heat recovery boiler 1. An upper pipe side 13 and a lower pipe side 14 are attached to the upper and lower ends of the arranged evaporating pipes 12, respectively, and constitute one heat transfer panel as a whole. Are arranged in the gas flow direction. The upper pipe 13 is connected via a riser pipe 15 to a steam drum 1 corresponding to the high-pressure steam drum 9 and the low-pressure steam drum 10.
6, while the lower pipe 14 is connected to a manifold 18 via a water supply pipe 17. The manifold 18 is provided with a downcomer pipe 1 suspended downward from the steam drum 16.
9 and is directed in the gas flow direction, that is, the direction orthogonal to the axis of the steam drum 16. The weight of the steam drum 16 is reduced by the boiler duct 2 via the downcomer support member 20 attached to the lower end of the downcomer 19.
The support is transmitted to the foundation.

As shown in FIG. 5, an elbow 21 is interposed between the downcomer 19 and the manifold 18, and a tubular downcomer support member 2 is provided below the bent portion of the elbow 21.
0 is welded, whereby the downcomer pipe 19 is supported so as to be independent, and a drain pipe 22 for draining is connected to a required portion of the manifold 18.

As another example of a structure for supporting the downcomer 19 so as to be independent, as shown in FIG. 6, a tee 2 is provided between the downcomer 19 and the manifold 18.
3, a lid plate 25 having a drain hole 24 formed therein is fixed to the inside of the lower end of the tee 23, and the drain pipe 22 is connected to the drain hole 24 of the lid plate 25.
There was one in which a tubular downcomer support member 20 was welded to the lower end of the pipe.

Further, as another example of a structure for supporting the downcomer pipe 19 so as to be independent, as shown in FIGS. 7 and 8, a tubular portion 26a is provided between the downcomer pipe 19 and the manifold 18. Sleeve 26 having an outer cylindrical portion 26b which swells smoothly from the middle of the sleeve, and an elbow 27
In some cases, the downcomer support member 20 formed in half is welded to the lower end of the outer cylindrical portion of the thermal sleeve 26.

[0009]

By the way, the downcomer pipes 19 are suspended from the steam drum 16 by a plurality (four in the example of FIG. 4), and the downcomer pipes 20 are attached by the downcomer support members 20 attached to the lower ends thereof. Although the weight of the drum 16 is supported in a dispersed manner, at the time of startup, the upper surface of the steam drum 16 is first heated to a high temperature by saturated steam, while the lower surface is not sufficiently heated. Since the temperature is low due to the accumulation of water, the steam drum 16
, A metal temperature difference occurs between the upper and lower sides of the steam drum 16, and the elongation on the upper surface side of the steam drum 16 becomes larger than the elongation on the lower surface side.
Both ends are curved in the downward direction, and as a result,
The weight of the steam drum 16 cannot be evenly supported by the respective downcomers 19, but is supported by only two downcomers 19 provided at both ends of the steam drum 16. Then, a large load acts on the connection portion between the pipe and each downcomer support member 20. On the other hand, when the steam drum 16 is stopped, the upper surface side of the steam drum 16 first becomes low temperature, while the lower surface side becomes difficult to cool because the sufficiently heated can water is accumulated. A difference in metal temperature occurs between the upper and lower sides of the steam drum 16, the extension of the upper surface of the steam drum 16 becomes smaller than the extension of the lower surface, and both ends of the steam drum 16 are curved in the upward direction. Cannot be equally supported by the downcomers 19, but is supported only by the two downcomers 19 provided at the center of the steam drum 16, and the two downcomers 19
Then, a large load acts on the connection portion between the pipe and each downcomer support member 20.

In addition, especially at the time of startup, the downcomer 1
Although still water that has not yet been sufficiently warmed is present inside 9, the outer surface of the downcomer 19 is rapidly heated by the exhaust gas, and a large temperature difference between the inner and outer surfaces occurs.

For this reason, in the case of the support structure as shown in FIG. 5, stress tends to concentrate on the welded portion between the elbow 21 and the downcomer support member 20 which are structural discontinuities, and the curved surface of the elbow 21 In this case, the upper end portion of the downcomer support member 20 must be processed and welded so as to conform to the above, so that it is difficult to manufacture.

In the case of the support structure as shown in FIG. 6, the pressure welding line of the cover plate 25 to the tee 23 is covered with the downcomer support member 20, so that it is very difficult to perform maintenance and inspection. There is a problem that it is difficult to maintain the connection portion of the drain pipe 22 with respect to the drain pipe 25.

Further, in the case of the support structure as shown in FIGS. 7 and 8, since the structure of the thermal sleeve 26 and the downcomer support member 20 is complicated, the manufacturing cost is increased and the tubular shape of the thermal sleeve 26 is increased. Part 26a and elbow 2
Pressure welding line at the joint with the thermal sleeve 2
6 is covered with the outer tube portion 26b and the downcomer support member 20, so that there is a problem that maintenance and inspection are difficult.

In view of such circumstances, the present invention eliminates the occurrence of structural discontinuities at locations where there is a large temperature difference, avoids stress concentration, and facilitates maintenance and inspection of pressure-resistant welding lines. Further, it is an object of the present invention to provide an evaporator downcomer support structure of an exhaust heat recovery boiler which can simplify the structure, reduce the number of parts and the number of welding points and reduce the cost.

[0015]

According to the present invention, an upper pipe and a lower pipe are attached to the upper and lower ends of a plurality of vertically arranged evaporating pipes in a boiler duct, and the upper pipe is raised. A pipe is connected to a steam drum, a lower pipe is connected to a manifold via a water supply pipe, and the manifold is connected to a lower end of a downcomer downwardly suspended from the steam drum so that the downcomer can be made to stand alone. An evaporator downcomer support structure for an exhaust heat recovery boiler to be supported, wherein a vertical flow path communicating with an internal flow path of the downcomer and an internal flow path of the manifold are provided between a lower end of the downcomer and a base end of the manifold. An evaporator downcomer supporting structure of an exhaust heat recovery boiler, wherein a communicating horizontal passage is formed in an L shape and a downcomer supporting member formed by integrating legs installed in a boiler duct is joined. Such is the case.

In the evaporator downcomer support structure of the exhaust heat recovery boiler, the downcomer support member may be formed by a forged product.

According to the above means, the following effects can be obtained.

As described above, between the lower end of the downcomer and the base end of the manifold, the vertical flow path communicating with the internal flow path of the downcomer and the horizontal flow path communicating with the inner flow path of the manifold are formed in an L shape. When joining the downcomer supporting member formed and integrated with the legs installed in the boiler duct, a structural discontinuity is not formed at a place where the temperature difference is large, so that the joining part of the downcomer supporting member to the downcomer In addition, stress is less likely to concentrate at the junction of the downcomer support member to the manifold.

The pressure welding wire at the joint of the downcomer pipe supporting member to the downcomer pipe and the joint of the downcomer pipe supporting member to the manifold are not covered by other members, so that maintenance and inspection can be performed easily and the structure can be improved. Since the structure itself is very simplified, the number of parts and the number of welded portions are reduced, and the manufacture is facilitated.

Further, the downcomer support member has an L-shaped vertical flow path communicating with the internal flow path of the downcomer and an L-shaped horizontal flow path communicating with the internal flow path of the manifold. May be provided at required positions of the manifold, and maintenance of the connection portion of the drain pipe can be easily performed.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an embodiment of the present invention. In the drawing, portions denoted by the same reference numerals as those in FIGS. 2 to 8 represent the same components, and the basic configuration is shown in FIGS. 8 is the same as the conventional one shown in FIG. 8, but the feature of this illustrated example is that the inside of the downcomer 19 is located between the lower end of the downcomer 19 and the base end of the manifold 18 as shown in FIG. The vertical flow path 20a communicating with the flow path 19a and the internal flow path 1 of the manifold 18
The point is that a horizontal flow path 20b communicating with 8a is formed in an L-shape, and a downcomer support member 20 formed by integrating legs 20c installed in the boiler duct 2 is joined.

The downcomer support member 20 is formed by forging.

Next, the operation of the illustrated example will be described.

As described above, the internal flow path 19a of the downcomer 19 is provided between the lower end of the downcomer 19 and the base end of the manifold 18.
Pipe supporting member 20 which is formed in an L-shape with a vertical flow path 20a communicating with the inside and a horizontal flow path 20b communicating with the internal flow path 18a of the manifold 18, and which integrates a leg 20c installed in the boiler duct 2. , Since a structural discontinuous portion is not formed at a location where the temperature difference is large, stress is less likely to be concentrated on the joining portion of the downcoming tube support member 20 to the downcoming tube 19 and the joining portion of the downcoming tube support member 20 to the manifold 18. Become.

The downcomer supporting member 2 for the downcomer 19
The pressure-resistant welding line at the joint of the downcomer tube supporting member 20 with respect to the joint 0 and the manifold 18 is not covered with other members, so that maintenance and inspection can be easily performed and the structure itself is very simplified. Therefore, the number of parts and the number of welding points are reduced, and the production is facilitated.

Further, the downcomer support member 20 has a vertical flow path 20a communicating with the inner flow path 19a of the downcomer 19 and a horizontal flow path 20a communicating with the inner flow path 18a of the manifold 18.
Since “b” and “b” are formed in an L-shape, the drain pipe 22 may be provided at a required portion of the manifold 18 and maintenance of the connection part of the drain pipe 22 can be easily performed.

In this way, stress concentration can be avoided by avoiding the occurrence of structural discontinuities at locations where the temperature difference is large, and maintenance and inspection of the pressure-resistant welding line can be performed easily, and the structure can be simplified. The number of parts and the number of welding points can be reduced to reduce costs.

The evaporator downcomer support structure of the exhaust heat recovery boiler of the present invention is not limited to the above-described example, and various modifications can be made without departing from the gist of the present invention. Of course.

[0030]

As described above, according to the evaporator downcomer support structure of the exhaust heat recovery boiler of the present invention, it is possible to avoid a structural discontinuity at a place where a temperature difference is large, thereby avoiding stress concentration. In addition to this, it is possible to easily perform maintenance and inspection of the pressure-resistant welding line, and to achieve an excellent effect that the structure can be simplified, the number of parts and the number of welding points can be reduced, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a side view of an example of an embodiment of the present invention, and is a view corresponding to a portion V in FIG.

FIG. 2 is an overall schematic configuration diagram of a general exhaust heat recovery boiler.

FIG. 3 is a side view illustrating an evaporator of a conventional heat recovery steam generator.

FIG. 4 is a perspective view showing an evaporator of a conventional exhaust heat recovery boiler.

5 is a side view showing an example of a supporting structure of a downcomer in an evaporator of a conventional exhaust heat recovery boiler, and is a view corresponding to a portion V in FIG.

FIG. 6 is a side view showing another example of a supporting structure of a downcomer in an evaporator of a conventional exhaust heat recovery boiler, and is a side view of FIG.
FIG.

FIG. 7 is a side view showing still another example of a supporting structure of a downcomer in an evaporator of a conventional heat recovery steam generator, and FIG.
FIG.

FIG. 8 is a perspective view showing still another example of a support structure of a downcomer in the evaporator of the conventional heat recovery steam generator shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exhaust heat recovery boiler 2 Boiler duct 11 Evaporator 12 Evaporation pipe 13 Upper pipe side 14 Lower pipe side 15 Rise pipe 16 Steam drum 17 Water supply pipe 18 Manifold 18a Internal flow path 19 Downcomer pipe 19a Internal flow path 20 Downcomer support member 20a Vertical Flow path 20b Horizontal flow path 20c Leg

Claims (2)

[Claims] 1. An upper pipe and a lower pipe are attached to upper and lower ends of a plurality of vertically arranged evaporating pipes in a boiler duct, respectively, and the upper pipe is connected to a steam drum via a rising pipe. Then, the lower pipe is connected to a manifold via a water supply pipe, and the manifold is connected to a lower end of a downcomer hanging down from the steam drum, thereby evaporating an exhaust heat recovery boiler that supports the downcomer to be self-supporting. And a vertical flow path communicating with the internal flow path of the downcomer and a horizontal flow path communicating with the internal flow path of the manifold between the lower end of the downcomer and the base end of the manifold. An evaporator downcomer support structure for an exhaust heat recovery boiler, wherein a downcomer support member formed in a shape of a letter and integrated with legs installed in a boiler duct is joined. 2. The evaporator downcomer support structure for an exhaust heat recovery boiler according to claim 1, wherein the downcomer support member is formed by forging.