JPH04165202A - Exhaust heat recovery boiler - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an exhaust heat recovery boiler, and particularly to a horizontal force support structure for an upper header of a large-scale exhaust heat recovery boiler.

(Prior Art) Generally, in a combined cycle power plant, an exhaust heat recovery boiler is used that uses exhaust gas from a gas turbine or the like as a heat source to generate driving steam for a steam turbine, process steam, and hot water.

A conventional exhaust heat recovery boiler will be briefly explained below.

FIG. 9 shows an example of a conventional exhaust heat recovery boiler. This waste heat recovery boiler has a steam drum placed on top of the equipment.
This is a so-called natural circulation boiler with heat exchanger tubes installed vertically. Exhaust gas from a gas turbine or the like flows into an exhaust heat recovery boiler 41, first passes through a superheater 42 and a high-pressure evaporator 43, and then reaches a denitrification device 44, where nitrogen oxides contained in the exhaust gas are removed. The exhaust gas exiting the denitrification device 44 is sent to a high-pressure economizer 45.
, a low-pressure evaporator 46, and a low-pressure economizer 47, and exchanges heat with the internal fluid in each heat transfer tube.

Compared to a forced circulation type waste heat recovery boiler, a natural circulation type waste heat recovery boiler like the one shown in Figure 9 has the advantage that a circulation pump is not required and the required power can be reduced.
Recently, many combined cycle power plants have been used because the height from the ground to the top of the boiler can be kept low, the boiler duct can be made into a self-supporting structure, and no supporting steel frame is required. tend to be adopted in

FIG. 10 shows a sectional view taken along the line X--X in FIG. 9. 55
are heat exchanger tubes, which are connected to upper and lower headers arranged vertically to form a panel.

A casing 51 of the boiler duct is lined with a heat insulating material 52 to keep the temperature of the casing close to atmospheric temperature.

The loads of the panels such as the heat exchanger tubes 55 and the upper and lower headers 54 and 56 are supported by a lower support member 57 installed below the lower header 56. Therefore, during operation of the waste heat recovery boiler, the heat exchanger tubes and the upper header are displaced vertically upward from the support point of the lower header.

When a horizontal force such as an earthquake force acts on such an exhaust heat recovery boiler, the load of the heat transfer tube panel, which is the heaviest item, must be transferred to the casing via the upper and lower headers. Of these, the horizontal force generated in the pipe bundle during an earthquake is transmitted to the casing via the upper header, and finally to the ground.

FIG. 11 shows an example of a conventional horizontal force transmission support structure for an upper header of an exhaust heat recovery boiler. In the example shown in this figure, the header is configured as a single header in the direction perpendicular to the gas flow, and a lug 62 protruding from the center of the upper header 54 is attached to the upper part of the casing 51 lined with a heat insulating material 52. It is configured to be supported by a bracket 61 provided in the
1-141503). In addition, the casing 51
An upper support member 63 having an upper reinforcement member 64 is fixed thereon.

Incidentally, in recent years, combined cycle power plants have tended to become even larger due to the increase in the capacity of gas turbines, and in conjunction with this, larger exhaust heat recovery boilers are being planned. At present, some exhaust heat recovery boilers have appeared in which the height and width of the gas passage exceeds 10 m, and the total length exceeds 30 m.

In such large-scale waste heat recovery boilers, the width of the gas passage section is long, so the header cannot be configured with a single header in the width direction, so the header must be divided into multiple pieces in the width direction of the gas passage section. There is a need. In addition, it is necessary to access the upper header for inspection and repair, and in order to repair leaking pipes, the upper header must be accessed. Sufficient space is required between the crane rail and the upper casing to install the crane rail and lifting trolley.

(Problems to be Solved by the Invention) In such a large-sized waste heat recovery boiler, in the upper header support structure such as the conventional example shown in FIG. It becomes necessary to make the bracket on the casing side longer and larger. However, when a horizontal force is applied to the upper header, the long moment arm of the former lug causes excessive bending stress at the base of the lug 62, that is, at the welded part with the upper header, which is the pressure-resistant part. There is a problem in that there is a possibility that problems such as weld cracks may occur. The latter long bracket also has the disadvantage that the bending stress must be shared by the bracket, resulting in an oversized member.

Furthermore, in the exhaust heat recovery boiler as shown in FIG. 9, a heat insulating material is attached to the inner surface of the casing, so a large temperature difference occurs between the temperature of the casing and the temperature of the gas inside. Therefore, when connecting structural members inside the casing to the casing, how to absorb the difference in thermal expansion between the members due to the temperature difference becomes an issue in the design of the support structure of the upper header.

The present invention has been made in view of the above points, and is an upper part of a waste heat recovery boiler that has a simple structure, can effectively absorb the difference in thermal expansion between each part, and can effectively support the weight of the panel in the event of an earthquake. Its purpose is to provide a support structure for headers.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides an exhaust heat recovery boiler in which a panel is constructed by connecting headers arranged above and below with heat exchanger tubes, and this panel is placed in an exhaust gas flow to recover heat. The present invention is characterized by comprising an upper header steadying frame supported by an elastically deformable truss member provided on the inner surface in the υ1 gas flow direction and in a plane perpendicular to the υl gas.

(Function) According to the waste heat recovery boiler of the present invention configured as described above, when a difference in thermal expansion occurs, the difference in thermal expansion is absorbed by the elastic deformation of the truss member.

(Example) Hereinafter, an example of the present invention will be described based on FIGS. 1 to 3.

In FIG. 1, an upper header 1 is arranged perpendicular to the gas flow, and a plurality of heat exchanger tubes 2 are connected to it to form a panel. In this embodiment, the heat exchanger tube group 2.2 consists of five panels in the gas flow direction, of which a branch pipe 5 comes out from the center of the upper header 1 of the third panel on the second flow side, and is connected to external equipment. It is connected. A projection 6 for transmitting horizontal force is provided from the center of the upper header of the downstream two-tier panel. The distance between the upper casing 3 and the upper header is approximately 1.2 m, and the inner surface of the upper casing 3 has a heat insulating material 4.
Or pasting. Two horizontal members 8 are installed on both sides of the branch pipe 5 and the protrusion 6 so as to sandwich these members across the entire panel in the gas flow direction. These two horizontal members 8 are connected via six supporting metal fittings 7 arranged at the front and rear of the upper header 1, and these horizontal members 8 and supporting metal fittings 7 allow the front and rear of the branch pipes and projections to be connected. It surrounds the left and right sides to restrict displacement of the header in the gas flow direction and in the direction perpendicular to the gas flow. In this embodiment, five levels of panels are collectively supported. The horizontal member 8 and the supporting hardware 7 constitute a steady rest frame for the upper header.

Although the horizontal member 8 is made of channel steel in this embodiment, its cross-sectional shape is not particularly specified.
Any cross-sectional shape may be used as long as it has sufficient cross-sectional performance to support horizontal forces.

Since the heat insulating material 4 of the upper casing 3 is lined, a difference in thermal expansion occurs between the upper casing 3, the heat exchanger tubes 2, and the support member. For this reason, the distance between one of the ladder-like parts constituted by the horizontal member 8 and the supporting hardware 7 and the upper end of the upper header 1 is determined by allowing for a certain amount of margin for thermal expansion of the heat exchanger tubes.

In this embodiment, this distance is, for example, 100 mm. With this distance, the bending stress generated at the connection between the branch pipe 5 or projection 6 and the upper header 1 when a horizontal force is applied to the panel is sufficiently small, and the external stress applied to the pressure-resistant part can be minimized. I can do it.

Further, the gaps between the horizontal member 8 and the support member 7 and the branch pipe 5 or the protrusion 6 are determined appropriately depending on the operating conditions. That is, if the upper header 1 can be restrained against displacement with respect to the upper casing 3 in the gas flow direction or in a direction perpendicular to the gas flow, the gap may be reduced or point contact or line contact may be made. However, the displacement of the upper header 1 in the upward direction must not be restricted. On the other hand, if the branch pipe 5 is connected to an external device and the external device is subject to thermal expansion, an appropriate gap may be provided in consideration of the thermal expansion of the external device. The reason for this is that assuming there is nothing to restrict displacement in the upper header 1, the rigidity of the heat transfer tubes 2 is relatively small, so the displacement of the upper header 1 during an earthquake will be quite large, so the gap will be For example 20~
This is because even 30 mm is sufficiently effective.

The ladder-like part composed of the horizontal member 8 and the supporting hardware 7 is
The upper casing is constructed by four vertical members 10 located before and after the tube group panel, four diagonal members 9 located in a plane perpendicular to the gas flow, and four diagonal members 1 located in a plane in the gas flow direction. It is supported so as to be suspended from 3. The diagonal members 9 and 11 and the vertical member] 0 are connected to the horizontal member 8 and the upper casing 3 via connection plates 12 to 15 at both ends, forming a so-called truss.

By providing these members, the horizontal force in the gas flow direction is shared by the diagonal member 11 and the vertical member 10, and the horizontal force in the gas direction is shared by the diagonal member 9 and the vertical member 10, respectively. Become.

In this embodiment, the diagonal members 9 and 11 are each installed by a band plate having a thickness of less than 10 mm and a width of several tens of mm so that the surface on which the diagonal member is installed is parallel to the width direction of the plate. There is. That is, as shown in FIG. 3, the thickness direction is visible when viewed from above.

By attaching the diagonal members 9 and 11 in such a direction, they are deflected during operation to absorb the difference in thermal expansion between the diagonal members and the upper casing 3 side.

To explain this with reference to FIG. 4, during operation of this waste heat recovery boiler, one end of the diagonal member 9 or 11 is connected to the lower temperature upper casing 3 side, and the other end is connected to the horizontal side exposed to high temperature gas. Since it is connected to member 8, the difference in thermal expansion between the two must be absorbed by diagonal member 9 or 11.

At this time, the diagonal members 9 or 11 are moved in the axial direction as shown in FIG.
During operation, the difference in thermal expansion is absorbed by deforming as shown by the solid line (hatching). However, FIG. 4 shows the concept of deformation of the diagonal member, and the displacement is somewhat exaggerated. The diagonal member 9 or 11 is selected to have a cross-sectional shape and plate thickness that is easily deflected during operation, and is made of an arc-shaped plate that is convex in the direction of deflection in advance during manufacture to ensure displacement during operation. is desirable.

Next, we will explain how the horizontal force transmitted from the heat exchanger tubes 2 to the upper header 1 is transmitted to the upper casing 3 by the support structure of the upper header 1 of this embodiment.
). Figure 5(a) shows the upper header support structure seen from the upstream side of the exhaust gas, and assumes that a horizontal force F in the right direction at right angles to the gas flow transmitted from the heat transfer tubes 2 acts on the upper header 1. do. This horizontal force Fo causes the entire panel to displace in the direction of the load, and the branch pipe (vertical member)
5 and the horizontal member 8 contact, a horizontal force F is generated. is transmitted to the upper steady rest frame.

The horizontal force transmitted to the upper pipe shifter frame is supported by trusses installed at the front and rear of the pipe group. Considering the left and right trusses separately from the center of the upper header 1, horizontal force Fo is transmitted to the horizontal members and nodes of the right truss as F□, Fl is transmitted to the diagonal members of the right truss as compressive force F2, and the vertical member is transmitted as a tensile force F. F2 and F3 are each transmitted to the upper casing 3 from the connection portion with the upper casing. Also, the horizontal force F transmitted to the horizontal member
o is also transmitted to the left truss via the support hardware 7, and becomes F□' at the node between the horizontal member 8 and the left side.

F1' is transmitted to the diagonal member 9' in the left-hand truss as a tensile force F, and to the vertical member as a compressive force F5, which is transmitted to the upper casing 3 via the respective nodes. During operation of the waste heat recovery boiler, as mentioned above, the diagonal members are bent into the shape without hatching as shown in Fig. 5(b), and the forces F2 and F4 acting on the left and right diagonal members are The components parallel to the upper casing surface correspond to F6 and Fl, respectively. During operation when the diagonal members 9 and 9' are deflected, the diagonal members of the left truss are subject to tensile force from the time Fo begins to act on the horizontal member 8 of the steady rest frame until the forces acting on each member are balanced. As a result, the diagonal member 9 of the right truss, which is subjected to compressive force, undergoes further deformation in addition to the deformation during operation (see the hatched portion in FIG. 5(b)). In such a case, the load shared by the diagonal member 9 of the right truss, where deformation increases, is small compared to the load of the left truss 9', which receives the tensile force, and most of the load is shared by the left truss 9. are doing. Therefore, it is necessary for the diagonal members 9 and 11 to have a cross-sectional diameter so that they can support horizontal loads only on the tension side.

With this configuration, the diagonal member 9 has a structure that can absorb thermal elongation by itself, so it can be a welded structure, eliminating the need for bolting or sliding parts, improving reliability. It can be virtually maintenance-free. However, if it is removed during inspection and repair, 1. If you need
It is also possible that it will not be a welded structure.

In this way, it was possible to obtain a support structure for an exhaust heat recovery boiler header that can sufficiently reduce the bending stress that occurs when a horizontal force acts on the header. That is, the external stress applied to the pressure-resistant section can be minimized, and the pressure-resistant section can be safely supported.

In addition, compared to the case where the upper header is supported at only one point as described in the prior art, the present invention makes it possible to share the load transmitted to the upper casing, making the reinforcement of the outside of the upper casing more compact. can do. In addition, the bending stress and shearing force transmitted to the casing can be minimized, reducing the burden on the casing during earthquakes and the like.

Furthermore, since the support structure is a so-called truss structure, there is no need to share bending stress in the support portion, and the member can be made smaller and lighter.

The supporting member has a structure that can absorb thermal expansion by itself (
Moreover, it is possible to have a welded structure, eliminating the need for bolt threads and sliding parts, improving reliability and making it virtually maintenance-free.

Next, other embodiments of the present invention will be described based on FIGS. 6 to 8.

In this embodiment as well, the functions and effects of the invention are the same as those in the previous embodiment, so only the parts that are different in structure will be explained here.

In FIG. 6, an upper header 21 is arranged in a direction perpendicular to the gas flow, and a plurality of heat exchanger tubes 22 are connected to it to form a panel. In this embodiment, the heat exchanger tube group 22.22.
... consists of two stages of panels in the gas flow direction, and is connected to a communication pipe 25 that connects the upstream side and the downstream side. In this embodiment, the distance between the upper casing 23 and the upper header 21 is about 1.2 m, as in the first embodiment, and a heat insulating material 24 is pasted on the inner surface of the upper casing 23.

As shown in FIGS. 6 to 8, the connecting pipe 25 is assembled so that the center side of the header is surrounded by a supporting metal fitting 26, and connected to a horizontal member 27. The horizontal member 27 is an H-shaped member, and one horizontal member 27 is installed at the center of the upper header 21 in the gas flow direction. The cross-sectional shape can be arbitrary as in the first embodiment.

In this embodiment, the supporting hardware 26 and the horizontal member 7 surround the header connecting pipe 25 to restrain displacement of the upper header 21 in the gas flow direction and in the direction perpendicular to the gas flow. It supports two levels of panels together.

The distance between the lower surface of the component constituted by the horizontal member 27 and the supporting hardware 26 and the upper end of the upper header 21 is determined by allowing for a certain amount of allowance for thermal expansion of the heat exchanger tubes 22, as in the first embodiment. In this embodiment as well, when a horizontal force is applied to the panel, the bending stress generated at the connecting portion between the connecting pipe 25 and the header 21 is sufficiently small, and the external stress applied to the pressure-resistant portion can be suppressed to a minimum.

The part consisting of the horizontal m+4'27 and the supporting hardware 26 is
It is suspended from the upper casing by two vertical members 29 located at the front and rear of the tube group panel, four diagonal members 28 located in the direction perpendicular to the gas flow, and four diagonal members 30 located in the plane in the gas flow direction. It is supported so that it can be lowered.

The truss structure constituted by the diagonal members 28, 30 and the vertical member 29 has the same effects as the first embodiment, so a description thereof will be omitted.

According to this embodiment, in addition to the functions and effects of the first embodiment,
The number of horizontal members and vertical members can be reduced, and the structure can be made simpler and more reliable.

By using the first embodiment and this embodiment together, it is possible to obtain a support structure that meets the purpose of the present invention for all exhaust heat recovery boilers having headers on the upper part.

Furthermore, space can be saved by positioning the truss, which supports the horizontal force in the gas flow direction, at the top of the horizontal member. It is also possible to collectively support a plurality of tube groups.

〔Effect of the invention〕

According to the present invention, in the support structure of the upper header of a large-sized waste heat recovery boiler, the bending stress generated in the header welded part due to the horizontal force acting on the upper header can be sufficiently reduced, and the bending stress applied to the pressure-resistant part External stress can be minimized and pressure-resistant parts can be safely supported.

Further, in the exhaust heat recovery boiler, it becomes possible to share and support the horizontal load transmitted to the upper casing, and the reinforcement of the outside of the upper casing can be made compact. Furthermore, the bending stress and shearing force transmitted to the casing can be minimized, and the load placed on the casing in earthquakes and the like can be reduced.

Furthermore, since the support structure is a so-called truss structure, there is no need for the support portion to share bending stress, and the member can be made smaller and lighter.

In addition, the supporting members have a structure that allows them to absorb thermal elongation on their own, so a welded structure can be adopted, eliminating the need for bolting or sliding parts, improving reliability and making it virtually maintenance-free. There are effects such as being able to.

[Brief explanation of drawings]

Fig. 1 is a view of the main part of the upper header in the first embodiment of the waste heat recovery boiler of the present invention, seen from the front of the boiler, Fig. 2 is a view similarly seen from the side of the boiler, and Fig. 3 is the same as Fig. 1. X-
4 is a cross-sectional view taken along the X-ray, FIG. 4 is a diagram showing the deformation of the support member during operation of the first embodiment, FIG. 5 is a diagram showing the transmission path of the horizontal force acting on the header, and FIG. A view of the main part of the upper header in another embodiment of the waste heat recovery boiler of the present invention as seen from the front of the boiler, FIG. 7 is a view similarly seen from the side of the boiler, and FIG. 8 is the line ■-■ in FIG. , FIG. 9 is a diagram showing an example of a conventional exhaust heat recovery boiler, and FIG. 10 is a cross-sectional view taken along line X-X! of FIG. 9. FIG. 11 is an enlarged view of the upper header support of FIG. 8. DESCRIPTION OF SYMBOLS 1... Upper header, 2... Heat exchanger tube, 3... Upper casing, 4... Heat insulating material, 5... Branch pipe, 6... Protrusion, 7... Support hardware, 8 ...Horizontal member, 9.9'・
...Diagonal member, 10.10'...Vertical member, 11...
- Diagonal member, 12-15... Connection plate, 21... Upper header, 22... Heat exchanger tube, 23... Upper casing, 24... Heat insulating material, 25... Connecting pipe, 26 ...Support hardware, 27...Horizontal member, 28...Diagonal member, 2
9... Vertical member, 30... Diagonal member, 31-33.
...Connection board. Applicant's agent Sato - Yu T〃 cram school 3 times ↑ #l - Mr. Shika 4 Figure 5 Figure ■

Claims (1)

[Claims] 1. Construct a panel by connecting the headers placed above and below with heat transfer tubes, restrain this panel with the upper header steady frame, and place the panel in the exhaust gas flow to recover heat. In the exhaust heat recovery boiler, the upper pipe stopper frame is supported by an elastically deformable truss member provided in a plane in the exhaust gas flow direction and in a plane perpendicular to the exhaust gas flow, and thermal expansion is caused by the elastic deformation of the truss member. An exhaust heat recovery boiler characterized by absorbing the difference.