JPH04240302A - Structure of strengthening brace - Google Patents

Abstract

PURPOSE:To provide a structure in which high temperature liquid flows like, for instance, an exhaust heat recovery boiler of a combined cycle electric power plant and which is an internal temperature holding structure with reinforcing braces in order to provide a truss structure and prevent the generation of thermal stresses caused by the thermal expansion due to the heating of the reinforcing braces in order not to damage the reinforcing performance of the structure. CONSTITUTION:To the respective four corners of a rectangular structure body 12 one end of a reinforcing brace 20 is connected by a pin 21 and the other end is connected by a pin 23 to the respective central support members 22 at a position offset from the extension line of each of the reinforcing braces 20 that are mutually opposed.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

[Industrial Application Field] The present invention is applicable to a duct structure of an exhaust heat recovery boiler that recovers heat from the exhaust gas of a gas turbine used in a combined cycle power plant, for example, in which a high-temperature fluid flows and the internal heat is maintained. This invention relates to a reinforcing brace structure for reinforcing a structural body.

0002

2. Description of the Related Art FIG. 9 shows an example of the construction of a double-pressure natural circulation type exhaust heat recovery boiler 1, which is a waste heat recovery boiler referred to in the present invention and is equipped with two steam generation systems.

[0003] The feed water supplied from the low pressure water pump exchanges heat with the exhaust gas 5 of the gas turbine while sequentially passing through the low pressure economizer 2, the low pressure steam drum 3, and the low pressure evaporator 4, and a portion of the water is evaporated. The remainder is returned to the low pressure steam drum 3. The steam generated during this time is guided to the low pressure steam turbine via the low pressure main steam pipe. In addition, part of the water that has exited the low-pressure economizer 2 separates from its main path midway and is boosted in pressure by a high-pressure water pump.
After exchanging heat with and partially evaporating, the steam is separated from moisture in the high-pressure steam drum 8, and then further passed through the high-pressure superheater 9 to become superheated steam, which is led to the high-pressure steam turbine via the high-pressure main steam pipe.

[0004]In each loop of the high pressure evaporator 7 and the high pressure steam drum 8, and the low pressure evaporator 4 and the low pressure steam drum 3, the high pressure steam drum 8 and the low pressure steam drum 3 are connected to the high pressure evaporator 7 and the low pressure evaporator, respectively. A natural circulation is realized in which the water is circulated by obtaining a circulation force due to the density difference between the water in the downcomer pipe that supplies canned water to the heat transfer tube in the vessel 4 and the water in the evaporator heat transfer tube. On the other hand, the exhaust gas 5 from the gas turbine is transferred to the high-pressure superheater 9 of the exhaust heat recovery boiler 1, the high-pressure evaporator 7, the high-pressure economizer 6,
It sequentially passes through the low-pressure evaporator 4 and the low-pressure economizer 2, and is discharged from the chimney 10. Note that the reference numeral 11 indicates a denitrification device.

[0005] The heat exchanger tube group of the exhaust heat recovery boiler 1 having the above structure is arranged within a duct structure. At the inlet of the duct structure, the temperature of the exhaust gas 5 of the gas turbine is 500~
The temperature reaches as high as 600°C, and in response to larger gas turbines and larger exhaust heat recovery boilers, the cross-sectional width and height of the duct structure are both 10 m or more. Therefore,
In order to increase the earthquake resistance of such large duct structures, it is desired to develop more effective duct structures.

FIGS. 10 and 11 are front views of the structure of the exhaust heat recovery boiler 1 in which the conventionally known rigid frame structure and truss structure are applied. In the case of an exhaust heat recovery boiler, the exhaust gas temperature is high, so in order to prevent the structural members that make up the rectangular structure 12 from being exposed to high temperatures, the inside of the structural members are coated with a heat insulating material and an internal heat retention type is used, as shown in Fig. 10. Insulated structure 13
It is advantageous to provide

[0007]

[Problem to be solved by the invention] However, FIG.
In the case of a large-capacity waste heat recovery boiler with a duct structure of 10 m or more, large structural members are required to maintain strength. must be used, which is uneconomical. Furthermore, in the truss structure shown in FIG. 11, the structural members constituting the outer shell of the rectangular structure 12 are at room temperature, whereas the fixed brace 15 used in the truss is at room temperature. During operation, high-temperature exhaust gas (the inlet temperature of exhaust heat boiler 1 reaches a maximum of 500℃
600°C), the temperature becomes high and thermal elongation occurs. Therefore, a large difference in elongation occurs between the structural member of the rectangular structure 12 and the fixed brace 15 portion. This difference in elongation generates destructive thermal stress in the fixed brace 15,
This causes the fixed brace 15 itself to buckle. For this reason,
It cannot be applied as the duct structure of the exhaust heat recovery boiler 1. Note that reference numeral 16 in FIG. 11 is a central support member that supports the center side of the rectangular structure 12 of the fixed brace 15. An object of the present invention is to provide a reinforcing brace structure which eliminates the above-mentioned conventional drawbacks and which reduces the weight and increases the strength of a structure having an internal heat retention structure. [Structure of the invention]

[0008]

[Means for Solving the Problems] The present invention has an internal heat retention structure for high-temperature fluid flowing inside, and has an n-gon (
However, one end of the reinforcing brace is connected to each corner of the structure (n is 4 or more) via a pin, and the other end is made a rigid body at a position offset from the extension line of the opposing reinforcing brace. It is designed to be connected to via a pin.

[0009]

[Operation] Even if the inside of the structure becomes high temperature and the reinforcing brace is heated and thermal elongation occurs, this thermal elongation is absorbed by the rotation of the central support member, so no thermal stress is generated on the reinforcing brace and the structure without impairing the reinforcing performance.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a front view of an embodiment of the present invention applied to a duct structure of an exhaust heat recovery boiler of a combined cycle power plant.

In the figure, 12 is a rectangular structure, and the inside of this rectangular structure 12 is covered with a heat insulating structure 13, which insulates the rectangular structure 12 from the heat of the exhaust gas and keeps it at room temperature. There is. High-temperature exhaust gas flows inside the heat insulating structure 13, and a heat exchanger tube assembly 14 is installed to recover the heat of this exhaust gas.

One end of a reinforcing brace 20 is rotatably connected to each of the four corners of the rectangular structure 12 via a pin 21, and the other end is rotatably connected to the central support member 22 via a pin 23. is supported by Here, the four reinforcing braces 20 have the same length, and the pin 23 on the central supporting member 22 side, which is the connection part between the central supporting member 22 and the reinforcing brace 20, is the pin 23 on the side of the rectangular structure 12. 21
are arranged at positions shifted in the same direction with respect to each diagonal line. Further, as shown in FIG. 2, the pin 23 is attached to the reinforcing brace 2 so that it has a degree of freedom only within the plane of FIG.
Support 0. That is, the reinforcing brace 20 and the central support member 22 are connected in a structure that has no degree of freedom in the normal direction to the cross section of the duct structure shown in the figure.

Next, the operation of the embodiment configured as above will be explained. FIG. 3 shows the connection state of the central support member 22 and the reinforcing brace 20 when the combined cycle power plant is stopped, and FIG. 4 shows the connection state of the central support member 22 and the reinforcing brace 20 when the combined cycle power plant is in operation. Indicates connection status. During operation of a combined cycle power plant, high-temperature exhaust gas flows inside the duct structure, so the reinforcing brace 20 is heated by this exhaust gas and stretches, but this thermal expansion cannot be transferred to the four corners of the rectangular structure 12. Therefore, as shown by the arrow 24 in FIG. 4, it moves toward the central support member 22 side. Each reinforcing brace 20 has the same length, and if the temperature in the cross section of the duct structure is uniform, four reinforcing braces 20
Since the thermal elongation at 0 is also the same, pin 2 due to this thermal elongation
3 is also the same, and the central support member 22 rotates about the rotation center 26 as shown by the arrow 25 in FIG. This rotation is not constrained by anything other than the thermal expansion of the reinforcing brace 20, so no stress is generated in the reinforcing brace 20. Moreover, since the position of the pin 23 due to the rotation of the central support member 22 caused by the thermal expansion of the reinforcing brace 20 is geometrically uniform, this brace structure has the effect of reinforcing the rectangular structure 12.

The rectangular structure 12 of the embodiment described above is as follows:
Since it is a rectangle, four reinforcing braces 20 are required, but in the case of an n-gon shape, n reinforcing braces 20 are required. Further, it is preferable to make the rotation center 26 of the central support member 22 coincide with the center of the rectangular structure 12 and to make all the reinforcing braces 20 the same length in order to simplify the structure. However, if it is not possible to align the center of rotation of the central support member 22 with the center of the rectangular structure 12, this can be achieved by providing a specific relationship between the reinforcing brace 20 and the central support member 22. FIG. 5 shows a geometrical representation of the reinforcing brace structure in such a case.

That is, in FIG. 5, the rectangular structure 12
The lengths of the reinforcing braces 27, 28, 29, and 30 provided in the are A, B, C, and D, respectively, and the corresponding lengths from the center of rotation of the central support member 31 to the pin 23 are a, b, and D, respectively. When c and d, the relationship A:B:C:D=a:b:c:d is established, and the line connecting the center of the central support member 31 and each pin 23 and the reinforcing brace 27, 28,
The angles θ formed by 29 and 30 are made equal to each other. With this configuration, each reinforcing brace 27
, 28, 29, 30, the central support member 3
1 becomes approximately equal, and the reinforcing braces 27, 28,
No thermal stress is generated at 29 and 30. However, a, b
, c, and d need to be long enough to allow the thermal expansion of each part to be sufficiently absorbed by the rotation of the central support member 31.

It should be noted that the present invention is not limited to the above-described embodiments, but can be implemented in various modifications. FIG. 6 is a front view showing another embodiment of the present invention. In the same figure, 32
is a reinforcing brace having one end rotatably connected to a corner of the rectangular structure 12 via a pin 21 and the other end rotatably connected to a central support member 33 via a pin 23. The central support member 33 has a truss structure made of angle-shaped steel or the like, so that even if the distance between the center of the central support member 33 and the pin 23 is increased, the flow of exhaust gas is not impaired.

FIG. 7 is a front view showing the main parts of still another embodiment of the present invention. In this embodiment, if the temperature of the exhaust gas is not uniform in the cross section of the duct structure in the exhaust gas flow direction, the thermal elongation of the reinforcing brace is also not constant. Even in such a case, if the above-described embodiments are applied, the deviation in thermal elongation can be absorbed to some extent by rotating the central support member within the cross section of the duct structure. However, if the deviation in thermal elongation is excessive or if manufacturing errors are taken into consideration, the deviation or error cannot be absorbed. Therefore, the embodiment shown in FIG. 7 is adapted to cope with this by changing the pin support method of the central support member. That is, in the same figure, the central support member 3
5 is provided with disk-shaped parts 36, 36 on both sides, and each of the disk-shaped parts 36, 36 is provided with a long hole 37 having an arc shape at only one location. One reinforcing brace 20 is supported in this elongated hole 37 via a sliding pin 38, and the other three reinforcing braces 20 are supported via pins 23. Here, the degree of freedom of the sliding pin 38 due to the elongated hole 37 is determined by limiting the non-uniformity of the exhaust gas temperature distribution and the deterioration of the reinforcing performance of the rectangular structure 12.

[0018]

[Effects of the Invention] As explained above, according to the present invention, when reinforcing a structure with a reinforcing brace in which a high-temperature fluid flows inside and has an internal heat retention structure, the reinforcing brace is heated by the high-temperature fluid and thermal elongation occurs. However, since the reinforcing brace is supported by the central support member to absorb this thermal elongation and prevent thermal stress from occurring in the reinforcing brace, it is possible to provide a reinforcing brace structure that reduces the weight of the structure and increases strength. can.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an embodiment of the present invention.

FIG. 2 is an enlarged perspective view of section X in FIG. 1;

FIG. 3 is an explanatory diagram showing the operation of an embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a different effect from FIG. 3 in one embodiment of the present invention.

FIG. 5 is an explanatory diagram showing an embodiment of the present invention in a geometric configuration.

FIG. 6 is a front view of another embodiment of the invention.

FIG. 7 is a front view showing essential parts of still another embodiment of the present invention.

8 is a view along the Y arrow in FIG. 7. FIG.

FIG. 9 is a side sectional view of a duct structure of a conventional waste heat recovery boiler.

10 is a front view of a rectangular structure having a rigid frame structure attached to the duct structure shown in FIG. 9; FIG.

11 is a front view of a rectangular structure with a truss structure attached to the duct structure shown in FIG. 9. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 12... Rectangular structure, 13... Heat insulation structure, 14... Heat exchanger tube assembly, 20... Reinforcement brace, 21, 23... Pin, 22...
Central support member.

Claims (1)

[Claims] Claim 1: One end of a reinforcing brace is connected to each corner of the structure with an n-gon shape (where n is 4 or more) through a pin, and has an internal heat insulation structure for high-temperature fluid flowing inside. The reinforcing brace structure is characterized in that the other ends thereof are connected via pins to a rigid central support member at positions offset from the extension lines of the opposing reinforcing braces.