KR860002218Y1 - Steam generator - Google Patents

Abstract

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Description

Steam generator

1 is a partial cross-sectional front view showing a first embodiment of a steam generator according to the present invention.

FIG. 2 is a cross sectional view through a plane perpendicular to the tube plate and vertical bulkhead of the FIG. 1 steam generator; FIG.

3 is a cross-sectional view taken through a plane parallel to the tube plate, ie line III-III, at the top elevation of the skirt of the FIG. 2 steam generator.

4 is a similar partial cross-sectional front view of FIG. 1 showing a second embodiment of a skirt according to the present invention;

5 is a cross-sectional view of the embodiment of FIG. 4 in a cross-sectional view similar to the second view.

6 is a cross-sectional view similar to the third view of the embodiment of FIG.

7 is a cross-sectional view similar to the third view of a third embodiment of a skirt.

8, 9, 10 and 11 are cross-sectional views showing various connection mechanisms between the skirt and the bottom of the vertical bulkhead and the tube plate and the outer container.

FIG. 8A is a bottom cross-sectional view of a vertical bulkhead engaged with a straight row.

FIG. 8B is a cross sectional bottom view of the skirt engaged with the semicircular rail of the tube sheet. FIG.

8C is a bottom cross-sectional view of the skirt engaged with the semicircular rail of the outer container.

9A and 9B are bottom cross sectional views of a skirt coupled with a labyrinth seal to a tube plate and an outer container.

Figure 10a is a cross sectional bottom view of a vertical bulkhead coupled to a butt substrate by a sector.

FIG. 10B is a cross sectional bottom view of a skirt coupled to a butt board by a bolt.

11 is a bottom sectional view of a skirt connected to a tube plate by a spring seal.

The present invention relates to a steam generator that can be used for power generation or navigational propulsion by nuclear facilities. Steam generators of a conventional type are pressure resistant and consist of a cylindrical outer container having a vertical axis sealed at its upper and lower ends by a dome. A horizontal tube plate is attached to the side of the vessel inside the vessel to provide a compartment with two collectors for the inlet and outlet of the primary heat transfer fluid, respectively, in the lower aid, whereby a U-tube bundle is installed on the tube plate. Each U-tube has a heat pipe connected to the inlet manifold and a cold pipe connected to the outlet manifold. The heat pipe group constitutes a hot arm and the cold pipe group constitutes a cold arm. The secondary shell is not supported by the tube plate and surrounds the tube bundle and forms an annular space with the outer container. A water supply inlet device is provided to supply water to the annular space. The water supply rises again along the tube of the tube bundle and comes into contact with the tube bundle to become steam. A separator is provided at the top of the vessel to allow the produced steam to flow out through the opening formed in the upper help. The recycled water flowing from the separator is returned to the tube plate through the annular space formed between the outer vessel and the secondary shell and re-elevated along the U-tube bundle. The recycle water is mixed with feed water from the inlet device. The feedwater inlet is located at the top of the steam generator so that the mixture of feedwater and recycle water is homogeneous before entering the tube bundle.

The steam generator of the conventional type described above has the drawback that the first-secondary exchange surface is not optimally used and as a result the overall thermal efficiency of the steam generator is not at its maximum.

In order to solve this drawback and increase the efficiency of the steam generator, by providing a facility for preheating the feed water before mixing with the recycle water, and by using the heat exchange surface well due to the preheating, the overall thermal efficiency of the steam generator is increased. I could make it. Theoretically, maximum efficiency is achieved only when the feedwater is introduced to the immediate vicinity of the tube plate and reheated along the cold arm of the U-tube to reheat over a distance called the preheating zone. The feedwater is then mixed with recycle water from the separator at the outlet of the preheating zone.

However, this arrangement has several drawbacks, especially since the inlet and guide structure for the feedwater must be relatively fluid free of leaks and must not be mixed with recycled water until the feedwater is preheated, and underload or any temporary operation. The cycle (introduction of emergency water) had the drawback that the temperature of the feedwater decreased.

The water supply generates thermal stress in contact with structures such as pipes, tube plates, and pressure vessels. To overcome this drawback, several solutions have been proposed, consisting of adjusting the temperature of the structure to the temperature of the feed water or supplying a secondary feed water at the top of the steam generator.

However, these two solutions also interfere with the control and operation of the steam generator. In order to reduce the thermal stress in the tube sheet, the area where the feed water enters the tube bundle is spaced apart from the tube plate while keeping the feed water at the bottom.

Such a thing is Siemens ah. to. It is described in French Patent Publication No. 2,191,704, which has the disadvantage of requiring a composite structure to be installed under the apparatus and reducing the trapped vapor pressure generated by the steam generator.

It has also been proposed to form a buffer area through which the recirculating water traverses on the tube plate and to separate the hot and cold arms by means of a vertical sealing plate and a lower sealing plate of the preheater, such as by Westinghouse Electric Coporation. French Patent Publication No. 2,285,573. The tube plate on the cold arm side in the buffer area is cleaned by recycle water. The recirculated water is led towards the hot arm by a flow distribution plate under the preheater, ie a low permeability plate, wherein the preheater and feedwater inlet are located at the bottom of the steam generator. In this case, however, the flow distribution plate may generate bending stress (due to the pressure deformation of the tube plate, the differential expansion of the tube plate and the flow distribution plate) in the tube, and also the permeability and tube plate smaller than the transverse support plate of the tube bundle. Due to its proximity to the tube, the pipework was difficult.

In addition, because the tube must be inserted into the bottom sealing plate under the preheating portion, a gap is formed between the tube and the bottom sealing plate, and a portion of the water supply moves directly to the high temperature arm side through the gap, thereby lowering the overall efficiency of the steam generator. There is a flaw.

Therefore, if the gap is reduced to suppress the flow of water supply to the hot arm through the gap of the bottom sealing plate as described above, it becomes difficult to insert the pipe and bending stress is generated in the tube by the differential expansion between the tube plate and the bottom sealing plate. There is a danger. In addition, the inflow of feedwater from the feedwater inlet into the tube bundle of the preheater without mixing with the recycle water, regardless of the load size, makes it difficult to set the dimensions of the preheater structure. This is because two contradictory requirements must be met at the same time. In other words,

1. Respond to significant changes in temperature, which requires a small thickness.

2. Propose modifications that can endanger the primary-secondary bulkheads constituted by the pipes in unexpected situations (pipe rupture, water hammer), which requires a robust assembly.

As a result, the steam generator of the type described in French Patent Publication No. 2,285,573 has a drawback in that the space for the pipe is more limited than a given diameter of the pressurized vessel, and a part of the space occupies the preheater.

French Patent Publication No. 2,387,417 by Comisariat is also known which provides a steam generator which does not have this drawback. In the steam generator, all feed water is mixed with recirculated water and sent to the cold arm of the tube plate through a central waterproof case located between the U-tubes, the mixed water being watertight in the center by two elliptical flattening rings. It is connected to the channel. However, this has the disadvantage of having a very complicated structure. It is therefore an object of the present invention to provide a novel steam generator having a preheater which does not have the same drawbacks as in the prior art. The present invention can be easily applied to a conventional steam generator.

The steam generator according to the present invention is divided into two regions, namely a cold arm region and a hot arm region, wherein the separation is performed in the secondary shell by a vertical bulkhead separating the cold pipe from the heat pipe on the one hand and the low temperature on the other hand. It is carried out on the outside of the secondary sheath by a skirt surrounding the secondary sheath on the arm side, the skirt forming an opening through the lower end of the secondary sheath, the sides and the bottom being sealed and the upper being open. However, the secondary water passing through the separator and recirculating, i.e., the recycle water, can be returned to the U-tube bundle through the cold arm zone and the hot arm zone, while the feed water through the feed inlet located above the steam generator is only in the cold arm zone. To flow and circulate.

In addition, the steam generator according to the present invention includes a device for distributing recycle water between two regions, that is, the cold arm region and the hot arm region, and to achieve pressure balance in the two regions on the tube plate. Such a device may use a dispensing collar installed perpendicular to the flow direction from the cold arm region in the space between the secondary shell and the skirt, on the other hand, U- in each of the cold and hot arm regions. Distribution plates can be used which are installed perpendicular to the installation direction of the magnetic tube, where these two plates generally have different permeability.

In one preferred embodiment of the present invention, a skirt is arranged at a distance from the secondary shell to form a space, wherein a cross section parallel to the tube plate of the space becomes ring sector, the angle of arc being smaller as it rises to the top of the skirt. The skirt is configured to extend vertically from the tube plate to the feedwater inlet, forming a space of the side, the side of which is bent toward the secondary shell and welded to the shell. Its lower part is also connected to the tube plate by a semi-fluid sealing connection that restricts leakage but permits movement of the skirt relative to the plate to adapt to relative deformation due to pressure and expansion.

In another embodiment of the present invention, the skirt is the same as the outer container except for the edges formed by two vertical bulkheads extending between the outer container and the secondary envelope.

The vertical bulkhead separating the cold arm region from the hot arm region inside the secondary sheath extends from the tube sheet to at least the height necessary to preheat the feedwater, the sides being welded to the inside of the secondary sheath and the lower part by semi-fluid sealing connection. Is connected to.

In order to carry out the semi-fluid sealing connection, for example, a rail fixed to the tube plate may be used to engage the skirt and the bottom of the vertical bulkhead. If the cross-sectional area of the skirt is just 180 ° above the tube plate, the flipped side of the skirt can be joined to the same straight rail applied to the vertical bulkhead.

In a preferred embodiment of the semi-fluid sealing connection, the bottom of the skirt can be coupled to a rail fixed to an outer container without being fixed to the tube plate to reduce the stress of the tube plate. The secondary feedwater feeds to flow to the low temperature arm region as a whole. Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

First, referring to FIGS. 1 to 3, the steam generator includes a vertical pressure-resistant cylindrical outer container 1 sealed by a dome at upper and lower ends thereof. Although the upper help is not shown in the figure, the lower help 2 can be viewed and inferred. A horizontal tube plate 3 is arranged inside the container 1 and is secured to the container 1, forming a chamber in the lower helper 2 separated by two manifolds 4, 5, at which time the manifold 4 Is the inlet manifold of the primary heat transfer fluid coming from the reactor, for example, and the manifold 5 is the outlet manifold of the primary heat transfer fluid. A bundle-shaped U-shaped tube 6 is installed on the tube plate 3, each consisting of a heat tube 7 connected to the inlet manifold 4 and a cold tube 8 connected to the outlet manifold 5. The group of heat tubes 7 constitutes a hot arm, and the group of cold tubes constitutes a low temperature arm. The secondary shell 9 forms the outer container and the annular space 10 by enclosing the bundle of the tubes 6 without being supported by the tube plate 3 to supply water to the annular space 10. An apparatus 11 is provided on top of the steam generator.

The water supply is lowered to the tube plate 3 and then re-raised along the periphery of the tube 6 to be reheated to become steam. At the top of the vessel 1 is provided a set of separators 12 to separate the steam obtained from the top of the tube and the separated steam is extracted through an opening (not shown) in the upper help.

In FIG. 2, a support plate 13 is shown for supporting the bundle of tubes 6. The support plate 13 and the secondary shell 9 are closed in the transverse direction with respect to the outer container 1 by the block 14.

A space 15 is formed between the secondary shell 9 and the tube plate 3 so that the secondary water flows toward the tube bundle.

The skirt 16 surrounds a portion of the secondary sheath 9 on the cold arm side and together with the secondary sheath 9 constitutes a closed space 17 at its sides and bottom. The space 17 forms a return duct of the recycled water to the cold arm, but is formed between the container 1 and the skirt 16 and the annular space 10 formed between the container 1 and the secondary shell 9. The space 10 'constitutes a hot arm water return duct. The sides 18, 18 ′ of the skirt 16 are bent to the secondary sheath 9 side and welded thereto so that fluid flows from the low temperature arm return duct 17 to the high temperature arm return duct 10, 10 ′. To prevent them.

The lower part of the skirt 16 is connected to the tube plate 3 by a semi-fluid sealing connection that restricts leakage. The connection is made by the groove 19a of the semicircular rail 19 welded to the tube plate on which the rim 19b under the skirt 16 is installed. In the same way, the lower portion of the sides 18, 18 ′ of the skirt 16 is coupled to both ends 20a, 20b of the straight rail 20. In the secondary shell 9, the vertical bulkhead 21 separates the heat pipe 7 and the cold pipe 8. The vertical binding wall 21 is engaged with the straight rail 20. The vertical bulkheads 21 are in fact arranged in the extension of the partition plate 22 separating the manifolds 4, 5.

The vertical bulkheads 21 are welded to the secondary shell 9 and extend vertically to at least the height necessary to preheat the feedwater.

The vertical bulkhead 21 thus prevents transverse flow in the tube bundle before the feedwater is preheated.

A feed water inlet lamp is attached to the inlet device 11 and has a J-tube 23, the opening of which allows the feed water to flow above the low temperature arm water return duct 17. A dispensing collar 24 with an orifice is designed to be disposed below the low temperature arm water return duct 17 to cause a pressure drop therein.

The dispensing collar 24 also allows for homogeneous feeding of the cold arm. Distributive plates 25a and 25b having different permeability are arranged inside the secondary shell 9, one on the hot arm side and the other on the cold arm side, perpendicular to the U-tube direction. The constant distribution plate has an important function of ensuring good cleaning of the tube plate in order to prevent the low speed water region from occurring near the tube plate. The distribution plate also balances the lower tube bundle pressure between the cold and hot arms to prevent water from flowing from one arm to the other.

The steam generator according to the present invention operates in the following manner. The primary heat transfer fluid flows upward through the heat pipe on the hot arm side and reloads to the cold arm side. The upwardly flowing secondary water vaporizes partially in the tube bundle at a vapor fraction of 20-40%. The emulsion produced here is directed to a separator-dryer unit which separates water and steam and dries the steam. The recirculation water separation separates the separated water back to the tube bundle base along the circuit shown by the arrows in FIG. 2, which consists of the common area (A), the low temperature and low water return circuit (B), and the high temperature arm number recovery circuit (C). Some of the secondary water, i.e. the recycle water, is mixed with the feedwater from the inlet device 11 while the remaining part is directly introduced into the hot arm to regasify the whole. During operation near the base of the separator 12 the height of the flow circuit is kept at the same height.

In the prior art, the recycled water is distributed evenly in the space between the outer container and the secondary shell, but here a significant portion of the recycled water, i.e., at least 50% of the fraction at maximum load, returns the return duct (10, 10 ') of the hot arm water. While going through the hot arm of the tube bundle, the remaining fraction of the recirculated water is mixed in all of the feedwater coming from the inlet 11 and in the return duct 17 of the cold arm water so that the tube plate 3 and the preheating zone (ie (9) low temperature arm region inside). This distribution of recycle water is on the one hand due to the pressure drop effect generated by the dispensing collar 24 and on the other hand due to the permeability difference of the distribution plates 25a and 25b disposed on the hot arm side and the cold arm side. will be.

Compared to the prior art in which only feed water enters the cold subpressure of the U-tube bundle, the solution of the present invention causes a pressure drop on the pressure delivered by the steam generator due to the reduction of the primary-secondary temperature separation. However, the reduction in temperature separation is compensated for by increasing the number of heat transfers in the secondary feedwater due to the very high efficiency and the increase in overall flow rate through the hot arm region of the tube bundle. The distribution collar 24 and the distribution plates 25a and 25b are adjusted to obtain an optimal distribution of the pressure drop, i.e., the ratio of recycle water directed to the hot arm at the rated point, which is here a full load point, close to 100%. do.

When output reduction occurs that causes a decrease in the flow rate and temperature of the feedwater, the relative ratio of recycle water / water feed will naturally increase in the cold arm water return duct to compensate for the feedwater temperature drop. Thus, the temperature of the mixture reaching the tube plate is kept constant under both full and incomplete load conditions.

4 to 6 showing a second embodiment of the skirt 16 will be described. In these figures, the main purpose is to show the skirt 16 in the case, and the other parts of the steam generator are similar to those of FIGS. In the case of FIGS. 4 to 6 the skirt 16 is configured such that the cross section of the skirt through a plane parallel to the tube plate is a ring sector, but the ring sector has an angle that varies with the cross section one side. The angle of the ring sector from the top of the steam generator to the middle plane 26 is 180 ° or less, while the ring sector from the middle plane 26 to the tube plate 3 height is continuous from 180 ° to the 180 ° from the value at the height of the middle plane 26. To increase.

There may be another possibility, considering that the cross section of the skirt is always a ring sector.

In the limited case shown in FIG. 7, the skirt 16 is arranged at a distance equal to the distance between the outer container 1 and the secondary shell 9 from the secondary shell 9. This means that except for the sides 18, 18 ′, the skirt 16 is identical to the outer container 1. Indeed, the skirt is constituted by two vertical bulkheads extending between the container 1 and the secondary shell 9 at the sides 18, 18 ′, ie the extension of the vertical bulkhead 21.

8, 9, 10 and 11 show an example of a semi-fluid sealing connection between the bottom of the skirt and vertical bulkhead 21 and the tube plate 3.

8 shows the lower part engaged with the rail. FIG. 8a shows that the vertical bulkhead 21 is engaged with the straight rail 20, and FIG. 8b shows that the ring 19b at the bottom of the skirt is engaged with the groove 19a of the semicircular rail 19. In FIG. . The rail 19 is preferably attached directly to the tube plate or to the outer container as shown in FIG. 8C. In FIG. 9, the semi-fluid sealing connection is made by means of a labyrinth seal secured to the tube plate (FIG. 9A) or directly to the outer container 1 (FIG. 9B). 10 shows the bottom connection structure by the butt board. The butt board 27 is fixed to the lower portion of the vertical bulkhead 21 by the sector (FIG. 10A) or to the skirt 16 by the bolt 28 (FIG. 10B), wherein the butt board and the tube plate are No play occurs. 11 shows the connection by the seal of the spring.

The present invention has several advantages, in particular the design point of view has the advantage of having a distribution of annular feed water and recycle water to the conventional steam generator, the operating point is provided with an integrated preheating unit as described above Has the advantage of letting. In addition, the vertical bulkhead in the present application extends from the tube plate to a predetermined height to completely separate the low temperature region and the high temperature region in the secondary shell, so that the problem of flowing water directly to the high temperature region without being preheated as in the conventional vertical partition plate is Completely solved. The present invention can produce a higher steam pressure than conventional steam generators, and at the same time, it is possible to have a steam generator with an integrated preheater while having a very simple structure.

The present invention solves the thermal shock problem to the tube and the outer container. In practice, the inflow of the feedwater takes place at the top of the steam generator, i.e., remote from the tube plate, and the feedwater is mixed with hot recycle water than on the cold arm side, and the recycle water fraction is at low load, i.e. temperature and feed water. It increases when the flow rate decreases. Thus, the temperature of the secondary water that reaches the secondary skin is actually constant. In the pressure-resistant outer container 1, it is maintained at a uniform temperature because it is in contact with the recirculated water contained in the high temperature arm water return ducts 10 and 10 ', and not in contact with the water supply. In addition, even if the supply pipe ruptures on the integrating portion of the U-tube and the preheater structure, the pressure effect is mitigated as described earlier in this specification, which is less severe than in a steam generator with a conventional preheater.

In the steam generator according to the present invention, there is no need to apply a component such as a preheating part or a waterproof case which is difficult to set the dimension, and thus there is no problem as in the related art. In addition, the difficulty caused by the presence of the flow distribution plate of the preheater as in the prior art is also excluded. In addition, the seal requirements in the tube plate area are alleviated due to the hot arm-cold arm adjustment by the distribution plate. The transverse flow inside the secondary sheath above the preheating zone is also reduced.

Another important advantage of the present invention lies in the fact that the structure is very simple. Of course, the present invention is not limited only to the embodiments described by way of example, but also applies to all other embodiments that vary in details, and to embodiments using structural changes or equivalent means. Thus, it is not necessary for all water supply to flow through the annular space between the secondary shell 9 and the skirt 16 and some of the water supply may flow through the hot arm water return ducts 10, 10 ′. However, the rate of water supply circulating in the hot arm region is kept small. In addition, the dispensing collar 24 may be disposed above the steam generator, not below.

The collar 24 is accessible at the time of stopping the operation and has a closing orifice to adjust the distribution of the pressure drop at the time of stopping the operation.

In addition, the permeability of the support plate 13 disposed above the preheating area, that is, the vertical partition wall 21 may be adjusted by performing the adjustment. Note that also in the distribution plates 25a and 25b, the distribution plate 25b may be arranged in another plane.

Claims (1)

A cylindrical outer container (1), each of which is closed by means of a pressure resistor with a vertical axis and is attached to the container (1) and inlet manifold (4) and outlet respectively for the primary heat transfer fluid to the lower support (2) A horizontal tube plate 3 forming a chamber separated by two manifolds used as the manifold 5, and a heat pipe 7 and an outlet manifold 5 installed in the tube plate 3 and connected to the inlet manifold 4; A bundle of U-tubes 6 each having a cold tube 8 connected to the cold tube, a low temperature arm composed of a high temperature arm composed of a heat tube 7 group and a cold tube 8 group, and a tube plate 3. The secondary shell 9, which is not supported and surrounds the bundle of tubes 6 and forms the annular space 10 together with the outer container 1, and rises along the tubes 6 of the bundle, Inlet device 11 for supplying secondary water, which becomes steam by contact, to annular space 10, a series of separators 12 and generated on top of the vessel 1. In a steam generator having an opening in the upper support for the discharge of the air, the steam generator is on the one hand from the tube plate (3) while separating the heat pipe (7) from the cold pipe (8) in the secondary shell (9). By means of a vertical bulkhead 21 extending to a predetermined height, on the other hand, a portion of the secondary shell 9 is enclosed on the low-temperature arm side and the inner shaft of the shell 9 together with the secondary shell 9. It is separated into two regions of the cold arm region and the hot arm region by a skirt 1 constituting the cold arm water return duct 17 whose side and bottom are hermetically sealed and the upper portion are opened while leaving a passage from the cold arm region. And an outlet of the feedwater inlet device (11) is located above the upper opening of the low temperature arm water return duct (17).