EP0035450B1 - Preheating steam generator - Google Patents

Preheating steam generator Download PDF

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Publication number
EP0035450B1
EP0035450B1 EP81400308A EP81400308A EP0035450B1 EP 0035450 B1 EP0035450 B1 EP 0035450B1 EP 81400308 A EP81400308 A EP 81400308A EP 81400308 A EP81400308 A EP 81400308A EP 0035450 B1 EP0035450 B1 EP 0035450B1
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EP
European Patent Office
Prior art keywords
steam generator
cold
envelope
branch
plate
Prior art date
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Expired
Application number
EP81400308A
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German (de)
French (fr)
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EP0035450A1 (en
Inventor
Jean-Claude Yazidjian
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Areva NP SAS
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Framatome SA
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Priority to AT81400308T priority Critical patent/ATE4932T1/en
Publication of EP0035450A1 publication Critical patent/EP0035450A1/en
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Publication of EP0035450B1 publication Critical patent/EP0035450B1/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B1/00—Methods of steam generation characterised by form of heating method
    • F22B1/02—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers
    • F22B1/023—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers with heating tubes, for nuclear reactors as far as they are not classified, according to a specified heating fluid, in another group
    • F22B1/025—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers with heating tubes, for nuclear reactors as far as they are not classified, according to a specified heating fluid, in another group with vertical U shaped tubes carried on a horizontal tube sheet

Definitions

  • the invention relates to a steam generator, which can be used for example in a nuclear installation, for the production of electrical energy or for naval propulsion.
  • a conventional type steam generator comprises a cylindrical outer enclosure of vertical axis, resistant to pressure and closed at each end by a cap.
  • a horizontal tubular plate is arranged inside the enclosure, integral with the latter and delimiting with the lower cap a chamber separated into two collectors, respectively for admission and evacuation of a primary heat-transfer fluid.
  • a bundle of U-shaped tubes is mounted on the tube plate.
  • Each U-shaped tube has a hot leg which communicates with the intake manifold and a cold leg which communicates with the exhaust manifold, the set of hot legs constituting the hot branch and the set of cold legs constituting the cold branch .
  • a secondary envelope surrounds the bundle without resting on the tube plate and defines an annular space with the outer enclosure.
  • a water intake device is provided for supplying the annular space with secondary water.
  • This secondary water rises along the bundle tubes and vaporizes on contact.
  • the steam produced is discharged through an opening in the upper cap.
  • the water from the separators called recirculation water, returns to the tubular plate using the annular space between the outer enclosure and the secondary envelope, before rising again along the bundle of U-shaped tubes.
  • Recirculation water mixes a food water which comes from the intake device of which we spoke above. This intake device is placed in the upper part of the steam generator so that the mixture of drinking water and recirculating water is homogeneous before it enters the tube bundle.
  • the generator of the conventional type which has just been described has the following drawback in particular: the primary-secondary exchange surface is not used optimally; therefore, the thermal efficiency of the entire generator is not maximum.
  • this configuration has several drawbacks.
  • the inlet and guide structures of this water must be relatively tight.
  • it has the drawback due to the fact that at low load or during certain operating transients (introduction of emergency water), the temperature of the drinking water decreases. This water can then initiate in the structures with which it comes into contact (tubes, tube plate, pressure vessel) unacceptable thermal stresses.
  • This geometry is expressed in relation to the theoretical case considered above by a drop in the saturation pressure delivered by the steam generator and complex structures to be installed in the lower part of the device.
  • the preheater floor can create bending stresses in the tubes (pressure deformation of the tube plate, differential expansion of the tube plate and the preheater floor), and also makes the casing operation difficult because of its lower permeability than that of the tube bundle spacer plates and its proximity to the tubular plate.
  • this floor cannot be perfectly sealed, so that part of the drinking water passes through it and goes towards the hot branch; this decreases the overall performance of the steam generator.
  • the steam generator of the type described in French application No. 2 285 573 has the disadvantage of having a more restricted space for the tubes for a given diameter of the envelope under pressure, part of the space being occupied. by the preheater.
  • this embodiment leads to a very complex structure and the thickness of the central box means that the number of U-shaped tubes has to be reduced, for a given diameter of the secondary envelope.
  • this generator has an efficiency, on the cold branch side, which is improved compared to conventional recirculation water generators, this efficiency is not yet very good.
  • the object of the invention is therefore to propose a new steam generator provided with a preheating device the structure of which is simple, leaves the maximum space available for the U-shaped tubes and does not cause thermal stress and whose performance is improved.
  • the invention applies to any conventional type steam generator, in accordance with the description which we have made above, and in which means are provided for separating the interior of the secondary envelope into two zones, one zone cold branch and a hot branch area.
  • the steam generator is also separated, outside the envelope, into two zones, a cold branch zone and a hot branch zone, these zones communicating respectively with the cold branch and hot branch zones located at the inside of the envelope;
  • the separation means are constituted by a skirt surrounding a part of the secondary envelope, on the side of the cold branch, and constituting with said envelope a closed space on the sides and at its lower part, while leaving a passage towards the zone cold branch from the inside of the envelope, and open at its upper part; so that the secondary water recirculated after passing through the separators, called recirculation water, can return to the bundle of U-shaped tubes both through the cold branch zone and through the hot branch zone, but as the water secondary food, arriving by an intake device located at the top of the generator circulates most of its flow in the cold branch area.
  • the generator according to the invention comprises means for distributing the recirculating water between the two zones, cold branch and hot branch, and for balancing, at the level of the tube plate, the pressures in these two zones.
  • a distribution flange placed in the space between the secondary casing and the skirt, perpendicular to the direction of the secondary water current of the cold branch zone; on the other hand, a distribution plate placed inside the secondary envelope in each of the zones, cold branch and hot branch, perpendicular to the direction of the U-shaped tubes, these two plates generally being of different permeability.
  • the skirt is located at a constant distance from the secondary casing, defining with it a space whose section by a plane parallel to the tubular plate is a ring sector whose the angle may vary with the section plane; the skirt extends vertically from the tube plate to the food water intake device; its sides are folded back towards the secondary envelope and welded to this envelope; its lower part is connected to the tubular plate by a semi-sealed connection limiting leakage school.perschen movements of the skirt relative to the plate so as to accommodate the relative deformations due to pressure and expansion.
  • the skirt is merged with the external enclosure, except for the edges which are constituted by two vertical partitions extending between the external enclosure and the secondary envelope.
  • the vertical partition separating the cold branch zone from the hot branch zone inside the secondary envelope extends from the tubular plate to a height at least equal to the height necessary for preheating the drinking water; it is welded on the sides inside the secondary envelope and connected to the tube plate by a semi-sealed partition.
  • the lower part of the skirt can be engaged in a rail secured to the outer enclosure and not to the tubular plate, in order to reduce the stresses in this plate.
  • the secondary food water is sent for all of its flow in the cold branch zone.
  • the steam generator shown in Figures 1, 2 and 3 comprises a cylindrical outer enclosure 1 of vertical axis, resistant to pressure, closed at each end by a cap.
  • the upper cap has not been shown but we can see the lower cap 2.
  • a horizontal tubular plate 3 is arranged inside the enclosure 1, integral with the latter and delimiting with the lower cap 2 a separate chamber in two manifolds 4 and 5, the manifold 4 being an intake manifold and the manifold 5 a discharge manifold of a primary heat-transfer fluid; this primary fluid can for example come from a nuclear power plant reactor.
  • U-shaped tubes, 6, grouped in a bundle, are mounted on the tube plate 3 and each have a hot leg 7 which communicates with the intake manifold 4 and a cold leg 8 which communicates with the exhaust manifold 5; the set of hot legs 7 constitutes the hot branch and the set of cold legs constitutes the cold branch.
  • a secondary envelope 9 surrounds the bundle of tubes 6 without resting on the tube plate 3 and defines an annular space 10 with the outer enclosure.
  • An inlet device 11 for supplying the annular space 10 with secondary water is provided in the upper part of the generator.
  • This water is intended to descend to the tubular plate 3 then to rise along the tubes 6 and to heat up and then vaporize on contact.
  • a set of separator-dryers 12 intended to separate the vapor obtained in the upper part of the tubes; this vapor is then discharged through an opening in the upper cap, not shown.
  • FIG. 2 shows the spacer plates 13 which hold the tube bundle 6. These plates 13 and the secondary envelope 9 are blocked in translation relative to the external enclosure 1 by blocks 14.
  • a skirt 16 surrounds part of the secondary envelope 9, on the side of the cold branch and constitutes with the envelope 9 a space 17 closed on the sides and at its lower part.
  • the space 17 constitutes the circuit for the return of the recirculation water to the cold branch or the return of the cold branch water, while the annular space 10 between the pressurized enclosure 1 and the secondary envelope 9, d 'on the one hand, and the space between the enclosure 1 and the skirt 16, which will be called 10', on the other hand, delimit the return of hot branch water.
  • the sides 18 and 18 ′ of the skirt 16 are folded over the secondary casing 9 and welded to the latter, thus preventing the passage of fluid from the cold branch water return to the hot branch water return.
  • the lower part of the skirt 16 is connected to the tube plate 3 by a semi-tight connection limiting leaks.
  • This link is made up here by the groove 19a of a semi-circular rail 19 welded to the tubular plate in which a flange 19b of the lower part of the skirt 16 is fitted.
  • the lower part of the sides 18 and 18 ′ is engaged in the ends 20a and 20b of a straight rail 20.
  • a vertical partition 21 separates the cold legs 8 from the hot legs 7.
  • This vertical partition 21 is engaged in the rectilinear rail 20.
  • the plate 21 is in fact placed in the extension of the plate partition 22 separating the collectors 4 and 5. It is welded to the secondary casing 9 and extends vertically to a height at least equal to the height necessary for preheating the drinking water. The partition 21 can thus prevent transverse flows in the bundle before all the food water is preheated.
  • a feed water inlet manifold is fixed in the tubing 11 and is provided with J-shaped tubes, 23, the openings of which open in the upper part of the cold branch water return 17.
  • a flange 24 provided with orifices is located at the lower part of the space 17 and is intended to create a pressure drop there. This flange 24 also allows a homogeneous supply of the cold branch.
  • Distribution plates 25a and 25b with different permeabilities are located inside the secondary envelope 9, one on the hot branch side and the other on the cold branch side, perpendicular to the direction of the tubes U. These plates have main function to ensure a good sweeping of the tube plate in order to avoid the creation of areas of low speed of water near the tube plate. They also contribute to the balance of pressures at the bottom of the bundle between cold branch and hot branch and make it possible to avoid water flows from one branch to the other.
  • the steam generator according to the invention operates in the following manner: the primary heat transfer fluid circulates upwards in the tubes on the hot branch side and descends on the cold branch side.
  • the secondary water in upward flow is partially vaporized in the bundle of tubes to a vapor titer of 20 to 40%; the emulsion thus produced is directed into a separation-drying assembly ensuring the separation of the water and the vapor and the drying of the latter.
  • the separated water called recirculation water, returns to the base of the bundle according to the arrowed circuits represented in FIG. 2, which include a common area A, a cold branch water return circuit B and a branch water return circuit hot C.
  • Part of the secondary recirculation water is mixed with the drinking water coming from the intake device 11, while the remaining part penetrates directly into the hot branch, and the whole is again vaporized. In operation, a single water level is established at the head of the circuit in the vicinity of the base of the separators 12.
  • the recirculation water is distributed uniformly in a space between the external enclosure and the secondary envelope, here, at full load, a large fraction of the recirculation water, greater than 50%, goes towards the hot branch of the bundle by the return of hot branch water, that is to say through spaces 10 and 10 ', while the remaining fraction of the recirculation water is mixed in the cold branch water return 17 to all of the food water coming from the tubing 11, before reaching the tube plate 3 and the preheating zone (that is to say the cold branch zone included in the inside the secondary envelope 9).
  • This fractionation of the recirculation water results from the pressure drop effect created on the one hand by the flange 24 and on the other hand by the difference in permeability of the distribution plates 25a and 25b located one in the branch hot and the other in the cold branch.
  • the solution of our invention causes a drop in the pressure delivered by the steam generator, due to the reduction of the primary-secondary temperature difference.
  • this reduction in the temperature difference is partially offset by an increase in the transfer coefficient in the secondary film due to an increase in the total flow rate passing through the cold branch zone of the bundle and a very satisfactory yield is obtained.
  • the flange 8 and the distribution plates 25a and 25b are adjusted so as to obtain an optimal distribution of the pressure losses, that is to say a distribution for which, at nominal point, therefore at full load, the fraction of recirculation water going towards the hot branch side is close to 100%.
  • the relative proportion of recirculating water / drinking water naturally increases in the return of cold branch water, which has the effect of compensating for the drop in temperature of drinking water.
  • the temperature of the mixture arriving on the tube plate remains substantially constant both at full load and at low load.
  • FIGS. 4, 5 and 6 represent a second embodiment of the skirt 16.
  • the skirt 16 is such that the section of this skirt by a plane parallel to the tubular plate is a ring sector, but this ring sector has an angle which varies with the section plane. From the upper part of the steam generator to an intermediate plane 26, the angle of the sector of the ring is less than 180 °, whereas, from the intermediate plane 26 to the level of the tube plate 3, the ring sector increases continuously by the value it has at the level of the intermediate plane 26 to 180 °.
  • the skirt 16 is located at a distance from the secondary envelope 9 which is equal to the distance between the external enclosure 1 and the secondary envelope 9; this amounts to saying that the skirt 16 is merged with the outer enclosure 1, except for the sides 18 and 18 '.
  • the skirt is formed only by these sides 18 and 18 ', that is to say by a simple set of two vertical partitions extending between the enclosure 1 and the casing 9 in extension of the vertical partition 21.
  • FIGS. 8, 9, 10 and 11 show examples of semi-sealed connections, between the lower parts of the skirt and of the vertical partition 21 and the tube plate 3.
  • Figure 8 shows the lower parts engaged in rails.
  • the vertical partition 21 is engaged in a rail 20.
  • the lower part of the skirt, 19b, is engaged in the groove 19a of a rail 19.
  • the rail 19 can be fixed either directly on the tubular plate or, preferably, on the outer enclosure, as shown in Figure 8c.
  • the semi-sealed connections are made by means of labyrinth seals secured either to the tubular plate (FIG. 9a) or directly to the outer enclosure 1 (FIG. 9b).
  • FIG. 10 shows a system for connecting the lower parts by means of joint covers.
  • the joint covers 27 are fixed by sectors to the lower parts of the vertical partition 21 or of the skirt 16 by means of bolts 28. The clearance between the joint covers and the tube plate is canceled during assembly.
  • the present invention has many advantages.
  • the present invention makes it possible to obtain a vapor pressure higher than that of a conventional steam generator and close to that of steam generators with integrated preheater, while being of a very simple structure.
  • the invention solves the problems of thermal shock at the level of the tube plate and at the level of the external enclosure. Indeed, the introduction of drinking water is carried out in the upper part of the generator, that is to say away from the tube plate, and this water is mixed on the cold branch side with a fraction of warmer recirculating water. ; this fraction of recirculating water increases at low load, that is to say when the temperature and the flow rate of drinking water decrease. The temperature of the secondary water arriving on the secondary plate is therefore practically constant. As for the pressure vessel 1, it is maintained at a uniform temperature since it is always in contact with the recirculating water contained in the annular spaces 10 and 10 ′, and not with drinking water.
  • Another important advantage of the invention lies in the fact of its very simple structure.
  • distribution plates 25a and 25b it can be added that these can be located in different planes.

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Abstract

A steam generator having cold branch and hot branch zones defined, inside the secondary envelope, by vertical partitions separating the cold limbs from the hot limbs, and outside the secondary envelope by a skirt surrounding a portion of the latter on the cold branch side, forming therewith a space closed on its sides and at its lower portion while leaving a passage to the cold branch zone from the inside of the envelope. The space is open at the top so that recycled water can return to the bundle of U-tubes through both zones, but secondary feed water circulates for the most part in the cold branch zone. Recycled water may be distributed between the cold and hot branch zones, and the pressure in these zones may be balanced at the level of a horizontal, perforated tubular plate.

Description

L'invention concerne un générateur de vapeur, qui peut être utilisé par exemple dans une installation nucléaire, pour la production d'énergie électrique ou la propulsion navale.The invention relates to a steam generator, which can be used for example in a nuclear installation, for the production of electrical energy or for naval propulsion.

Un générateur de vapeur de type classique comporte une enceinte extérieure cylindrique d'axe vertical, résistante à la pression et fermée à chaque extrémité par une calotte. Une plaque tubulaire horizontale est disposée à l'intérieur de l'enceinte, solidaire de celle-ci et délimitant avec la calotte inférieure une chambre séparée en deux collecteurs, respectivement d'admission et d'évacuation d'un fluide primaire caloporteur. Un faisceau de tubes en U est monté sur la plaque tubulaire. Chaque tube en U présente une jambe chaude qui communique avec le collecteur d'admission et une jambe froide qui communique avec le collecteur d'évacuation, l'ensemble des jambes chaudes constituant la branche chaude et l'ensemble des jambes froides constituant la branche froide. Une enveloppe secondaire entoure le faisceau sans s'appuyer sur la plaque tubulaire et définit un espace annulaire avec l'enceinte extérieure. Un dispositif d'admission d'eau est prévu pour l'alimentation de l'espace annulaire en eau secondaire. Cette eau secondaire remonte le long des tubes du faisceau et se vaporise à leur contact. Dans la partie haute de l'enceinte, se trouve en ensemble de séparateurs ; la vapeur produite est évacuée par une ouverture ménagée dans la calotte supérieure. L'eau issue des séparateurs, appelée eau de recirculation retourne vers la plaque tubulaire en utilisant l'espace annulaire compris entre l'enceinte extérieure et l'enveloppe secondaire, avant de remonter à nouveau le long du faisceau de tubes en U. A cette eau de recirculation se mélange une eau alimentaire qui provient du dispositif d'admission dont nous avons parlé plus haut. Ce dispositif d'admission est placé en partie haute du générateur de vapeur afin que le mélange de l'eau alimentaire et de l'eau de recirculation soit homogène avant son entrée dans le faisceau tubulaire.A conventional type steam generator comprises a cylindrical outer enclosure of vertical axis, resistant to pressure and closed at each end by a cap. A horizontal tubular plate is arranged inside the enclosure, integral with the latter and delimiting with the lower cap a chamber separated into two collectors, respectively for admission and evacuation of a primary heat-transfer fluid. A bundle of U-shaped tubes is mounted on the tube plate. Each U-shaped tube has a hot leg which communicates with the intake manifold and a cold leg which communicates with the exhaust manifold, the set of hot legs constituting the hot branch and the set of cold legs constituting the cold branch . A secondary envelope surrounds the bundle without resting on the tube plate and defines an annular space with the outer enclosure. A water intake device is provided for supplying the annular space with secondary water. This secondary water rises along the bundle tubes and vaporizes on contact. In the upper part of the enclosure, there is a set of dividers; the steam produced is discharged through an opening in the upper cap. The water from the separators, called recirculation water, returns to the tubular plate using the annular space between the outer enclosure and the secondary envelope, before rising again along the bundle of U-shaped tubes. Recirculation water mixes a food water which comes from the intake device of which we spoke above. This intake device is placed in the upper part of the steam generator so that the mixture of drinking water and recirculating water is homogeneous before it enters the tube bundle.

Le générateur de type classique que l'on vient de décrire présente en particulier l'inconvénient suivant : on n'utilise pas de façon optimale la surface d'échange primaire-secondaire ; par conséquent, l'efficacité thermique de l'ensemble du générateur n'est pas maximale.The generator of the conventional type which has just been described has the following drawback in particular: the primary-secondary exchange surface is not used optimally; therefore, the thermal efficiency of the entire generator is not maximum.

Pour remédier à cet inconvénient, c'est-à-dire pour tenter d'augmenter le rendement du générateur, on a prévu de préchauffer l'eau alimentaire avant son mélange à l'eau de recirculation. Ce préchauffage permet une meilleure utilisation de la surface d'échange et un accroissement de l'efficacité thermique de l'ensemble du générateur.To overcome this drawback, that is to say to try to increase the efficiency of the generator, provision has been made to preheat the drinking water before mixing it with the recirculating water. This preheating allows better use of the exchange surface and an increase in the thermal efficiency of the entire generator.

D'un point de vue théorique, l'efficacité maximale est atteinte lorsque l'eau alimentaire est amenée au voisinage immédiat de la plaque tubulaire puis remonte le long de la branche froide des tubes en U, au contact desquels elle doit se réchauffer sur une certaine distance, appelée zone de préchauffage. L'eau alimentaire n'est mélangée à l'eau de recirculation venant des séparateurs qu'à la sortie de la zone de préchauffage.From a theoretical point of view, maximum efficiency is reached when the drinking water is brought to the immediate vicinity of the tube plate then rises along the cold branch of the U-shaped tubes, in contact with which it must heat up on a certain distance, called the preheating zone. The food water is only mixed with the recirculation water coming from the separators when it leaves the preheating zone.

Cependant cette configuration présente plusieurs inconvénients. En particulier, du fait que l'eau alimentaire ne doit pas être mélangée à l'eau de recirculation avant d'avoir été préchauffée, les structures d'arrivée et de guidage de cette eau doivent être relativement étanches. En outre, elle présente l'inconvénient dû au fait qu'en basse charge ou durant certains transitoires de fonctionnement (introduction d'eau de secours), la température de l'eau alimentaire décroît. Cette eau peut alors initier dans les structures avec lesquelles elle entre en contact (tubes, plaque tubulaire, enceinte sous pression) des contraintes thermiques inacceptables.However, this configuration has several drawbacks. In particular, since the drinking water must not be mixed with the recirculating water before it has been preheated, the inlet and guide structures of this water must be relatively tight. In addition, it has the drawback due to the fact that at low load or during certain operating transients (introduction of emergency water), the temperature of the drinking water decreases. This water can then initiate in the structures with which it comes into contact (tubes, tube plate, pressure vessel) unacceptable thermal stresses.

Pour pallier ces inconvénients, on a proposé plusieurs solutions parmi lesquelles celles qui consistent à incorporer un soutien en température de l'eau alimentaire ou à prévoir une alimentation secondaire en haut du générateur de vapeur.To overcome these drawbacks, several solutions have been proposed, including those which consist in incorporating temperature support for the drinking water or in providing a secondary supply at the top of the steam generator.

Ces deux solutions conduisent cependant à un alourdissement du fonctionnement et de la conduite du générateur de vapeur.These two solutions however lead to an increase in the operation and operation of the steam generator.

Pour diminuer les contraintes thermiques dans la plaque tubulaire, on peut éloigner de cette plaque la zone où l'eau alimentaire pénètre dans le faisceau tout en la maintenant en partie basse. C'est l'objet par exemple du brevet français n° 2 191 704 au nom de SIEMENS A.G.To reduce the thermal stresses in the tubular plate, the zone where the food water enters the bundle can be moved away from this plate while keeping it at the bottom. This is the subject, for example, of French patent No. 2,191,704 in the name of SIEMENS A.G.

Cette géométrie se traduit par rapport au cas théorique envisagé plus haut par une baisse de la pression de saturation délivrée par le générateur de vapeur et des structures complexes à implanter dans la partie basse de l'appareil.This geometry is expressed in relation to the theoretical case considered above by a drop in the saturation pressure delivered by the steam generator and complex structures to be installed in the lower part of the device.

On a aussi proposé de créer une zone tampon traversée par de l'eau de recirculation au-dessus de la plaque tubulaire.It has also been proposed to create a buffer zone crossed by recirculating water above the tube plate.

On pourra par exemple se reporter à la demande de brevet français n° 2 285 573 au nom de WESTINGHOUSE ELECTRIC CORPORATION. Dans la zone tampon, la plaque tubulaire, côté branche froide, est balayée par de l'eau de recirculation. Cette eau de recirculation est guidée par une plaque très peu perméable, qui est en fait constituée par le plancher du préchauffeur, ce préchauffeur et le dispositif d'admission d'eau alimentaire étant situés en partie basse du générateur de vapeur.We can for example refer to French patent application No. 2 285 573 in the name of WESTINGHOUSE ELECTRIC CORPORATION. In the buffer zone, the tube plate, on the cold branch side, is flushed with recirculating water. This recirculation water is guided by a very slightly permeable plate, which is in fact constituted by the floor of the preheater, this preheater and the food water intake device being located in the lower part of the steam generator.

Cependant le plancher du préchauffeur peut créer des contraintes de flexion dans les tubes (déformation en pression de la plaque tubulaire, dilatation différentielle de la plaque tubulaire et du plancher du préchauffeur), et rend en outre l'opération de tubage difficile du fait de sa perméabilité inférieure à celle des plaques entretoises du faisceau tubulaire et de sa proximité de la plaque tubulaire.However, the preheater floor can create bending stresses in the tubes (pressure deformation of the tube plate, differential expansion of the tube plate and the preheater floor), and also makes the casing operation difficult because of its lower permeability than that of the tube bundle spacer plates and its proximity to the tubular plate.

D'autre part, ce plancher ne peut pas être parfaitement étanche, si bien qu'une partie de l'eau alimentaire le traverse et se dirige vers la branche chaude ; ceci diminue les performances d'ensemble du générateur de vapeur.On the other hand, this floor cannot be perfectly sealed, so that part of the drinking water passes through it and goes towards the hot branch; this decreases the overall performance of the steam generator.

En outre, l'introduction de l'eau alimentaire dans le faisceau sans mélange à de l'eau de recirculation quelle que soit la charge, rend délicat le dimensionnement des structures du préchauffeur car celui-ci doit répondre à deux exigences contradictoires :

  • 1. Accomoder des variations importantes de température, ce qui nécessite des épaisseurs faibles.
  • 2. Limiter, en situation accidentelle (rupture de tuyauteries, coup de bélier) de déformations qui pourraient mettre en danger la barrière primaire-secondaire que constituent les tubes. Il est donc nécessaire de prévoir un ensemble rigide.
In addition, the introduction of drinking water into the bundle without mixing with recirculating water whatever the load, makes it difficult to size the structures of the preheater because it must meet two contradictory requirements:
  • 1. Accommodate large variations in temperature, which requires low thicknesses.
  • 2. Limit, in an accidental situation (broken pipes, water hammer), deformations that could endanger the primary-secondary barrier constituted by the tubes. It is therefore necessary to provide a rigid assembly.

Enfin, le générateur de vapeur du type décrit dans la demande française n° 2 285 573 présente l'inconvénient de comporter un espace plus restreint pour les tubes pour un diamètre donné de l'enveloppe sous pression, une partie de l'espace étant occupée par le préchauffeur.Finally, the steam generator of the type described in French application No. 2 285 573 has the disadvantage of having a more restricted space for the tubes for a given diameter of the envelope under pressure, part of the space being occupied. by the preheater.

On connaît aussi la demande de brevet français n° 2 387 417 au nom du Commissariat à l'Energie Atomique qui décrit un générateur de vapeur ne présentant pas les inconvénients précités. Dans ce générateur, la totalité de l'eau alimentaire est mélangée à l'eau de recirculation et canalisée vers la branche froide de la plaque tubulaire au moyen de deux anneaux plats de forme elliptique. L'intérieur de l'enveloppe secondaire est séparé en deux zones, une zone branche froide et une zone branche chaude par un caisson central. Le mélange d'eau de recirculation et d'eau alimentaire remonte par la zone branche froide puis se divise en deux parties : l'une continue de monter vers l'ensemble de séparateurs et l'autre traverse le caisson central pour venir balayer la partie chaude de la plaque tubulaire avant de remonter par la zone branche chaude.We also know French patent application No. 2 387 417 in the name of the French Atomic Energy Commission which describes a steam generator which does not have the aforementioned drawbacks. In this generator, all of the drinking water is mixed with the recirculating water and channeled towards the cold branch of the tube plate by means of two flat rings of elliptical shape. The interior of the secondary enclosure is separated into two zones, a cold branch zone and a hot branch zone by a central box. The mixture of recirculating water and drinking water rises through the cold branch zone and then divides into two parts: one continues to rise towards the set of separators and the other crosses the central box to sweep the part tube plate before reassembling through the hot branch area.

Cependant, cette réalisation conduit à une structure très complexe et l'épaisseur du caisson central oblige à diminuer le nombre de tubes en U, pour un diamètre donné de l'enveloppe secondaire. En outre, même si ce générateur a un rendement, côté branche froide, qui est amélioré par rapport aux générateurs à eau de recirculation de type classique, ce rendement n'est pas encore très bon.However, this embodiment leads to a very complex structure and the thickness of the central box means that the number of U-shaped tubes has to be reduced, for a given diameter of the secondary envelope. In addition, even if this generator has an efficiency, on the cold branch side, which is improved compared to conventional recirculation water generators, this efficiency is not yet very good.

Le but de l'invention est donc de proposer un nouveau générateur de vapeur muni d'un dispositif de préchauffage dont la structure soit simple, laisse le maximum d'espace disponible pour les tubes en U et n'entraîne pas de contrainte thermique et dont le rendement soit amélioré.The object of the invention is therefore to propose a new steam generator provided with a preheating device the structure of which is simple, leaves the maximum space available for the U-shaped tubes and does not cause thermal stress and whose performance is improved.

L'invention s'applique à tout générateur de vapeur de type classique, conforme à la description que nous avons effectuée plus haut, et dans lequel sont prévus des moyens de séparation de l'intérieur de l'enveloppe secondaire en deux zones, une zone branche froide et une zone branche chaude.The invention applies to any conventional type steam generator, in accordance with the description which we have made above, and in which means are provided for separating the interior of the secondary envelope into two zones, one zone cold branch and a hot branch area.

Selon l'invention, le générateur de vapeur est également séparé, à l'extérieur de l'enveloppe, en deux zones, une zone branche froide et une zone branche chaude, ces zones communiquant respectivement avec les zones branche froide et branche chaude situées à l'intérieur de l'enveloppe ; les moyens de séparation sont constitués par une jupe entourant une partie de l'enveloppe secondaire, du côté de la branche froide, et constituant avec ladite enveloppe un espace fermé sur les côtés et à sa partie inférieure, tout en laissant un passage vers la zone branche froide de l'intérieur de l'enveloppe, et ouvert à sa partie supérieure ; de telle sorte que l'eau secondaire remise en circulation après passage dans les séparateurs, dite eau de recirculation, puisse retourner vers le faisceau de tubes en U aussi bien par la zone branche froide que par la zone branche chaude, mais que l'eau secondaire alimentaire, arrivant par un dispositif d'admission situé à la partie supérieure du générateur circule pour l'essentiel de son débit dans la zone branche froide.According to the invention, the steam generator is also separated, outside the envelope, into two zones, a cold branch zone and a hot branch zone, these zones communicating respectively with the cold branch and hot branch zones located at the inside of the envelope; the separation means are constituted by a skirt surrounding a part of the secondary envelope, on the side of the cold branch, and constituting with said envelope a closed space on the sides and at its lower part, while leaving a passage towards the zone cold branch from the inside of the envelope, and open at its upper part; so that the secondary water recirculated after passing through the separators, called recirculation water, can return to the bundle of U-shaped tubes both through the cold branch zone and through the hot branch zone, but as the water secondary food, arriving by an intake device located at the top of the generator circulates most of its flow in the cold branch area.

En outre, le générateur selon l'invention comporte des moyens de répartition de l'eau de recirculation entre les deux zones, branche froide et branche chaude, et d'équilibrage, au niveau de la plaque tubulaire, des pressions dans ces deux zones. On pourra utiliser d'une part une collerette de répartition placée dans l'espace compris entre l'enveloppe secondaire et la jupe, perpendiculairement à la direction du courant d'eau secondaire de la zone branche froide ; d'autre part, une plaque de distribution placée à l'intérieur de l'enveloppe secondaire dans chacune des zones, branche froide et branche chaude, perpendiculairement à la direction des tubes en U, ces deux plaques étant en général de perméabilité différente.In addition, the generator according to the invention comprises means for distributing the recirculating water between the two zones, cold branch and hot branch, and for balancing, at the level of the tube plate, the pressures in these two zones. One can use on the one hand a distribution flange placed in the space between the secondary casing and the skirt, perpendicular to the direction of the secondary water current of the cold branch zone; on the other hand, a distribution plate placed inside the secondary envelope in each of the zones, cold branch and hot branch, perpendicular to the direction of the U-shaped tubes, these two plates generally being of different permeability.

Dans un mode préféré de réalisation de l'invention, la jupe est située à une distance constante de l'enveloppe secondaire, définissant avec celle-ci un espace dont la section par un plan parallèle à la plaque tubulaire est un secteur d'anneau dont l'angle peut varier avec le plan de section ; la jupe s'étend verticalement de la plaque tubulaire jusqu'au dispositif d'admission d'eau alimentaire ; ses côtés sont rabattus vers l'enveloppe secondaire et soudés à cette enveloppe ; sa partie inférieure est reliée à la plaque tubulaire par une liaison semi-étanche limitant les fuites mais.permettant des mouvements de la jupe par rapport à la plaque de façon à accomoder les déformations relatives dues à la pression et aux dilatations.In a preferred embodiment of the invention, the skirt is located at a constant distance from the secondary casing, defining with it a space whose section by a plane parallel to the tubular plate is a ring sector whose the angle may vary with the section plane; the skirt extends vertically from the tube plate to the food water intake device; its sides are folded back towards the secondary envelope and welded to this envelope; its lower part is connected to the tubular plate by a semi-sealed connection limiting leakage mais.permettre movements of the skirt relative to the plate so as to accommodate the relative deformations due to pressure and expansion.

Dans un mode particulier de réalisation de l'invention, la jupe est confondue avec l'enceinte extérieure, exception faite des bords qui sont constitués par deux cloisons verticales s'étendant entre l'enceinte extérieure et l'enveloppe secondaire.In a particular embodiment of the invention, the skirt is merged with the external enclosure, except for the edges which are constituted by two vertical partitions extending between the external enclosure and the secondary envelope.

De préférence, la cloison verticale séparant la zone branche froide de la zone branche chaude à l'intérieur de l'enveloppe secondaire s'étend de la plaque tubulaire jusqu'à une hauteur au moins égale à la hauteur nécessaire au préchauffage de l'eau alimentaire ; elle est soudée sur les côtés à l'intérieur de l'enveloppe secondaire et reliée à la plaque tubulaire par une cloison semi-étanche.Preferably, the vertical partition separating the cold branch zone from the hot branch zone inside the secondary envelope extends from the tubular plate to a height at least equal to the height necessary for preheating the drinking water; it is welded on the sides inside the secondary envelope and connected to the tube plate by a semi-sealed partition.

Pour effectuer les liaisons semi-étanches, on peut par exemple utiliser des rails solidaires de la plaque tubulaire, dans lesquels les parties inférieures de la jupe et de la cloison verticale sont engagées. Si, au niveau de la plaque tubulaire, la section de la jupe est un secteur d'anneau de 180°, les côtés rabattus de la jupe peuvent être engagés dans le même rail rectiligne que la cloison verticale.To make the semi-sealed connections, one can for example use rails integral with the tube plate, in which the lower parts of the skirt and the vertical partition are engaged. If, at the level of the tubular plate, the section of the skirt is a ring sector of 180 °, the folded sides of the skirt can be engaged in the same rectilinear rail as the vertical partition.

Dans un mode préféré de réalisation des liaisons semi-étanches, la partie inférieure de la jupe peut être engagée dans un rail solidaire de l'enceinte extérieure et non de la plaque tubulaire, afin de diminuer les contraintes dans cette plaque.In a preferred embodiment of the semi-sealed connections, the lower part of the skirt can be engaged in a rail secured to the outer enclosure and not to the tubular plate, in order to reduce the stresses in this plate.

De préférence, l'eau secondaire alimentaire est envoyée pour la totalité de son débit dans la zone branche froide.Preferably, the secondary food water is sent for all of its flow in the cold branch zone.

Afin de mieux être comprise, l'invention va être décrite dans quelques modes de réalisation préférés, choisis uniquement à titre d'exemples et représentés par les dessins annexés.

  • La figure 1 représente une vue d'un 1er mode de réalisation du générateur selon l'invention.
  • La figure 2 représente une coupe, par un plan perpendiculaire à la plaque tubulaire et à la cloison verticale, du générateur de la figure 1.
  • La figure 3 représente une coupe par un plan parallèle à la plaque tubulaire, au niveau de la partie supérieure de la jupe, du générateur de vapeur de la figure 2 (coupe suivant III-III).
  • La figure 4 représente un deuxième mode de réalisation de la jupe selon l'invention, dans une vue semblable à celle de la figure 1.
  • La figure 5 représente le mode de réalisation de la figure 4, vue dans une coupe analogue à celle de la figure 2.
  • La figure 6 représente le mode de réalisation de la figure 4, vue d'une façon analogue à celle de la figure 3.
  • La figure 7 représente un troisième mode de réalisation de la jupe, vue de façon analogue à la figure 3.
  • Les figures 8, 9, 10 et 11 représentent divers modes de réalisation des moyens de liaison de la partie inférieure de la jupe et de la cloison verticale avec la plaque tubulaire.
  • Les figures 8a, 8b et 8c montrent les parties inférieures engagées dans des rails.
  • Les figures 9a et 9b montrent les parties inférieures engagées dans des joints à labyrinthe.
  • Les figures 10a et 10b montrent un système de liaison avec couvre-joints.
  • La figure 11 représente un système de liaison par joints du type à ressort.
In order to be better understood, the invention will be described in a few preferred embodiments, chosen only by way of examples and represented by the accompanying drawings.
  • FIG. 1 represents a view of a 1st embodiment of the generator according to the invention.
  • FIG. 2 represents a section, through a plane perpendicular to the tube plate and to the vertical partition, of the generator of FIG. 1.
  • FIG. 3 represents a section through a plane parallel to the tube plate, at the level of the upper part of the skirt, of the steam generator of FIG. 2 (section along III-III).
  • FIG. 4 represents a second embodiment of the skirt according to the invention, in a view similar to that of FIG. 1.
  • FIG. 5 represents the embodiment of FIG. 4, seen in a section similar to that of FIG. 2.
  • FIG. 6 represents the embodiment of FIG. 4, seen in a manner similar to that of FIG. 3.
  • FIG. 7 represents a third embodiment of the skirt, seen in a manner similar to FIG. 3.
  • Figures 8, 9, 10 and 11 show various embodiments of the means for connecting the lower part of the skirt and the vertical partition with the tube plate.
  • Figures 8a, 8b and 8c show the lower parts engaged in rails.
  • Figures 9a and 9b show the lower parts engaged in labyrinth seals.
  • Figures 10a and 10b show a connection system with joint covers.
  • Figure 11 shows a spring-type joint connection system.

Sur toutes les figures, les éléments correspondants portent les mêmes repères.In all the figures, the corresponding elements bear the same references.

On se reportera tout d'abord aux figures 1, 2 et 3.We will first refer to Figures 1, 2 and 3.

Le générateur de vapeur représenté sur les figures 1, 2 et 3 comporte une enceinte extérieure cylindrique 1 d'axe vertical, résistante à la pression, fermée à chaque extrémité par une calotte. La calotte supérieure n'a pas été représentée mais on peut voir la calotte inférieure 2. Une plaque tubulaire 3 horizontale est disposée à l'intérieur de l'enceinte 1, solidaire de celle-ci et délimitant avec la calotte inférieure 2 une chambre séparée en deux collecteurs 4 et 5, le collecteur 4 étant un collecteur d'admission et le collecteur 5 un collecteur d'évacuation d'un fluide primaire caloporteur ; ce fluide primaire peut par exemple provenir d'un réacteur de centrale nucléaire.The steam generator shown in Figures 1, 2 and 3 comprises a cylindrical outer enclosure 1 of vertical axis, resistant to pressure, closed at each end by a cap. The upper cap has not been shown but we can see the lower cap 2. A horizontal tubular plate 3 is arranged inside the enclosure 1, integral with the latter and delimiting with the lower cap 2 a separate chamber in two manifolds 4 and 5, the manifold 4 being an intake manifold and the manifold 5 a discharge manifold of a primary heat-transfer fluid; this primary fluid can for example come from a nuclear power plant reactor.

Des tubes en U, 6, groupés en un faisceau, sont montés sur la plaque tubulaire 3 et présentent chacun une jambe chaude 7 qui communique avec le collecteur d'admission 4 et une jambe froide 8 qui communique avec le collecteur d'évacuation 5 ; l'ensemble des jambes chaudes 7 constitue la branche chaude et l'ensemble des jambes froides constitue la branche froide.U-shaped tubes, 6, grouped in a bundle, are mounted on the tube plate 3 and each have a hot leg 7 which communicates with the intake manifold 4 and a cold leg 8 which communicates with the exhaust manifold 5; the set of hot legs 7 constitutes the hot branch and the set of cold legs constitutes the cold branch.

Une enveloppe secondaire 9 entoure le faisceau de tubes 6 sans s'appuyer sur la plaque tubulaire 3 et définit un espace annulaire 10 avec l'enceinte extérieure.A secondary envelope 9 surrounds the bundle of tubes 6 without resting on the tube plate 3 and defines an annular space 10 with the outer enclosure.

Un dispositif 11 d'admission pour l'alimentation de l'espace annulaire 10 en eau secondaire est prévu en partie haute du générateur.An inlet device 11 for supplying the annular space 10 with secondary water is provided in the upper part of the generator.

Cette eau est destinée à descendre vers la plaque tubulaire 3 puis à remonter le long des tubes 6 et à se réchauffer puis se vaporiser à leur contact. Dans la partie haute de l'enceinte 1 est prévu un ensemble de séparateurs-sécheurs 12 destinés à séparer la vapeur obtenue en partie haute des tubes ; cette vapeur est évacuée ensuite par une ouverture ménagée dans la calotte supérieure, non représentée.This water is intended to descend to the tubular plate 3 then to rise along the tubes 6 and to heat up and then vaporize on contact. In the upper part of the enclosure 1 is provided a set of separator-dryers 12 intended to separate the vapor obtained in the upper part of the tubes; this vapor is then discharged through an opening in the upper cap, not shown.

Sur la figure 2, on a représenté les plaques entretoises 13 qui maintiennent le faisceau de tubes 6. Ces plaques 13 et l'enveloppe secondaire 9 sont bloquées en translation par rapport à l'enceinte extérieure 1 par des blocs 14.FIG. 2 shows the spacer plates 13 which hold the tube bundle 6. These plates 13 and the secondary envelope 9 are blocked in translation relative to the external enclosure 1 by blocks 14.

On a appelé 15 l'espace compris entre l'enveloppe secondaire 9 et la plaque tubulaire 3 prévu pour que le fluide secondaire puisse pénétrer dans le faisceau.The space between the secondary casing 9 and the tube plate 3 provided for the secondary fluid to enter the bundle has been called.

Une jupe 16 entoure une partie de l'enveloppe secondaire 9, du côté de la branche froide et constitue avec l'enveloppe 9 un espace 17 fermé sur les côtés et à sa partie inférieure. L'espace 17 constitue le circuit de retour de l'eau de recirculation vers la branche froide ou retour d'eau branche froide, alors que l'espace annulaire 10 compris entre l'enceinte sous pression 1 et l'enveloppe secondaire 9, d'une part, et l'espace compris entre l'enceinte 1 et la jupe 16, que l'on appellera 10', d'autre part, délimitent le retour d'eau branche chaude. Les côtés 18 et 18' de la jupe 16 sont rabattus sur l'enveloppe secondaire 9 et soudés à celle-ci, évitant ainsi le passage de fluide du retour d'eau branche froide vers le retour d'eau branche chaude.A skirt 16 surrounds part of the secondary envelope 9, on the side of the cold branch and constitutes with the envelope 9 a space 17 closed on the sides and at its lower part. The space 17 constitutes the circuit for the return of the recirculation water to the cold branch or the return of the cold branch water, while the annular space 10 between the pressurized enclosure 1 and the secondary envelope 9, d 'on the one hand, and the space between the enclosure 1 and the skirt 16, which will be called 10', on the other hand, delimit the return of hot branch water. The sides 18 and 18 ′ of the skirt 16 are folded over the secondary casing 9 and welded to the latter, thus preventing the passage of fluid from the cold branch water return to the hot branch water return.

La partie inférieure de la jupe 16 est reliée à la plaque tubulaire 3 par une liaison semi-étanche limitant les fuites. Cette liaison est ici constituée par la gorge 19a d'un rail semi-circulaire 19 soudé à la plaque tubulaire dans laquelle un rebord 19b de la partie inférieure de la jupe 16 est emboîté. De la même façon, la partie inférieure des côtés 18 et 18' est engagée dans les extrémités 20a et 20b d'un rail rectiligne 20.The lower part of the skirt 16 is connected to the tube plate 3 by a semi-tight connection limiting leaks. This link is made up here by the groove 19a of a semi-circular rail 19 welded to the tubular plate in which a flange 19b of the lower part of the skirt 16 is fitted. Likewise, the lower part of the sides 18 and 18 ′ is engaged in the ends 20a and 20b of a straight rail 20.

A l'intérieur de l'enveloppe secondaire 9, une cloison verticale 21 sépare les jambes froides 8 des jambes chaudes 7. Cette cloison verticale 21 est engagée dans le rail rectiligne 20. La plaque 21 est en fait placée dans le prolongement de la plaque de partition 22 séparant les collecteurs 4 et 5. Elle est soudée à l'enveloppe secondaire 9 et s'étend verticalement jusqu'à une hauteur au moins égale à la hauteur nécessaire au préchauffage de l'eau alimentaire. La cloison 21 peut ainsi prévenir les écoulements transversaux dans le faisceau avant que toute l'eau alimentaire soit préchauffée.Inside the secondary envelope 9, a vertical partition 21 separates the cold legs 8 from the hot legs 7. This vertical partition 21 is engaged in the rectilinear rail 20. The plate 21 is in fact placed in the extension of the plate partition 22 separating the collectors 4 and 5. It is welded to the secondary casing 9 and extends vertically to a height at least equal to the height necessary for preheating the drinking water. The partition 21 can thus prevent transverse flows in the bundle before all the food water is preheated.

Une rampe d'admission d'eau alimentaire est fixée dans la tubulure 11 et est munie de tubes en J, 23, dont les ouvertures débouchent dans la partie supérieure du retour d'eau branche froide 17.A feed water inlet manifold is fixed in the tubing 11 and is provided with J-shaped tubes, 23, the openings of which open in the upper part of the cold branch water return 17.

Une collerette 24 munie d'orifices est située à la partie inférieure de l'espace 17 et est destinée à y créer une perte de charge. Cette collerette 24 permet aussi une alimentation homogène de la branche froide.A flange 24 provided with orifices is located at the lower part of the space 17 and is intended to create a pressure drop there. This flange 24 also allows a homogeneous supply of the cold branch.

Des plaques de distribution 25a et 25b dont les perméabilités sont différentes sont situées à l'intérieur de l'enveloppe secondaire 9, l'une côté branche chaude et l'autre côté branche froide, perpendiculairement à la direction des tubes U. Ces plaques ont pour fonction principale d'assurer un bon balayage de la plaque tubulaire afin d'éviter la création de zones de basse vitesse de l'eau près de la plaque tubulaire. Elles contribuent aussi à l'équilibre des pressions en bas du faisceau entre branche froide et branche chaude et permettent d'éviter les écoulements d'eau d'une branche vers l'autre.Distribution plates 25a and 25b with different permeabilities are located inside the secondary envelope 9, one on the hot branch side and the other on the cold branch side, perpendicular to the direction of the tubes U. These plates have main function to ensure a good sweeping of the tube plate in order to avoid the creation of areas of low speed of water near the tube plate. They also contribute to the balance of pressures at the bottom of the bundle between cold branch and hot branch and make it possible to avoid water flows from one branch to the other.

Le générateur de vapeur selon l'invention fonctionne de la façon suivante : le fluide primaire caloporteur circule vers le haut dans les tubes côté branche chaude et redescend côté branche froide.The steam generator according to the invention operates in the following manner: the primary heat transfer fluid circulates upwards in the tubes on the hot branch side and descends on the cold branch side.

L'eau secondaire en écoulement ascendant est partiellement vaporisée dans le faisceau de tubes jusqu'à un titre vapeur de 20 à 40 % ; l'émulsion ainsi produite se dirige dans un ensemble de séparation-séchage assurant la séparation de l'eau et de la vapeur et le séchage de celle-ci. L'eau séparée, dite eau de recirculation, retourne à la base du faisceau selon les circuits fléchés représentés à la figure 2, qui comportent une zone commune A, un circuit retour d'eau branche froide B et un circuit retour d'eau branche chaude C. Une partie de l'eau secondaire de recirculation est mélangée à l'eau alimentaire provenant du dispositif d'admission 11, alors que la partie restante pénètre directement dans la branche chaude, et l'ensemble est à nouveau vaporisé. En fonctionnement, un niveau d'eau unique s'établit en tête du circuit au voisinage de la base des séparateurs 12.The secondary water in upward flow is partially vaporized in the bundle of tubes to a vapor titer of 20 to 40%; the emulsion thus produced is directed into a separation-drying assembly ensuring the separation of the water and the vapor and the drying of the latter. The separated water, called recirculation water, returns to the base of the bundle according to the arrowed circuits represented in FIG. 2, which include a common area A, a cold branch water return circuit B and a branch water return circuit hot C. Part of the secondary recirculation water is mixed with the drinking water coming from the intake device 11, while the remaining part penetrates directly into the hot branch, and the whole is again vaporized. In operation, a single water level is established at the head of the circuit in the vicinity of the base of the separators 12.

Alors que, dans l'art antérieur, l'eau de recirculation se répartit uniformément dans un espace compris entre l'enceinte extérieure et l'enveloppe secondaire, ici, à pleine charge, une faction importante de l'eau de recirculation, supérieure à 50 %, se dirige vers la branche chaude du faisceau par le retour d'eau branche chaude, c'est-à-dire par les espaces 10 et 10', alors que la fraction restante de l'eau de recirculation est mélangée dans le retour d'eau branche froide 17 à la totalité de l'eau alimentaire venant de la tubulure 11, avant d'atteindre la plaque tubulaire 3 et la zone de préchauffage (c'est-à-dire la zone branche froide comprise à l'intérieur de l'enveloppe secondaire 9). Ce fractionnement de l'eau de recirculation résulte de l'effet de perte de charge créé d'une part par la collerette 24 et d'autre part par la différence de perméabilité des plaques de distribution 25a et 25b situées l'une dans la branche chaude et l'autre dans la branche froide.Whereas, in the prior art, the recirculation water is distributed uniformly in a space between the external enclosure and the secondary envelope, here, at full load, a large fraction of the recirculation water, greater than 50%, goes towards the hot branch of the bundle by the return of hot branch water, that is to say through spaces 10 and 10 ', while the remaining fraction of the recirculation water is mixed in the cold branch water return 17 to all of the food water coming from the tubing 11, before reaching the tube plate 3 and the preheating zone (that is to say the cold branch zone included in the inside the secondary envelope 9). This fractionation of the recirculation water results from the pressure drop effect created on the one hand by the flange 24 and on the other hand by the difference in permeability of the distribution plates 25a and 25b located one in the branch hot and the other in the cold branch.

Par rapport à certaines solutions de l'art antérieur, où seule l'eau alimentaire pénètre dans la branche froide du faisceau de tubes en U, la solution de notre invention entraîne une baisse de la pression délivrée par le générateur de vapeur, due à la diminution de l'écart des températures primaire-secondaire. Toutefois, cette diminution de l'écart des températures est partiellement compensée par une élévation du coefficient de transfert dans le film secondaire due à une augmentation du débit total traversant la zone branche froide du faisceau et on obtient un rendement très satisfaisant.Compared to certain solutions of the prior art, where only the drinking water enters the cold branch of the bundle of U-shaped tubes, the solution of our invention causes a drop in the pressure delivered by the steam generator, due to the reduction of the primary-secondary temperature difference. However, this reduction in the temperature difference is partially offset by an increase in the transfer coefficient in the secondary film due to an increase in the total flow rate passing through the cold branch zone of the bundle and a very satisfactory yield is obtained.

On règle la collerette 8 et les plaques de distribution 25a et 25b de façon à obtenir une répartition optimale des pertes de charge, c'est-à-dire une répartition pour laquelle, au point nominal, donc à pleine charge, la fraction d'eau de recirculation se dirigeant côté branche chaude est proche de 100 %.The flange 8 and the distribution plates 25a and 25b are adjusted so as to obtain an optimal distribution of the pressure losses, that is to say a distribution for which, at nominal point, therefore at full load, the fraction of recirculation water going towards the hot branch side is close to 100%.

Lors des diminutions de puissance, qui entraînent des diminutions du débit et de la température de l'eau alimentaire, la proportion relative eau de recirculation/eau alimentaire augmente naturellement dans le retour d'eau branche froide, ce qui a pour effet de compenser la baisse de la température de l'eau alimentaire. Ainsi, la température du mélange arrivant sur la plaque tubulaire reste sensiblement constante aussi bien à pleine charge qu'à faible charge.During power reductions, which lead to reductions in the flow rate and temperature of the drinking water, the relative proportion of recirculating water / drinking water naturally increases in the return of cold branch water, which has the effect of compensating for the drop in temperature of drinking water. Thus, the temperature of the mixture arriving on the tube plate remains substantially constant both at full load and at low load.

On pourra se reporter maintenant aux figures 4, 5 et 6 qui représentent un second mode de réalisation de la jupe 16.Reference may now be made to FIGS. 4, 5 and 6 which represent a second embodiment of the skirt 16.

Sur ces figures, on s'est attaché essentiellement à représenter la jupe 16, les autres parties du générateur étant senblables à celles des figures 1, 2 et 3.In these figures, we have essentially attempted to represent the skirt 16, the other parts of the generator being similar to those of FIGS. 1, 2 and 3.

Dans le cas des figures 4, 5 et 6, la jupe 16 est telle que la section de cette jupe par un plan parallèle à la plaque tubulaire est un secteur d'anneau, mais ce secteur d'anneau a un angle qui varie avec le plan de section. De la partie supérieure du générateur de vapeur jusqu'à un plan intermédiaire 26, l'angle du secteur d'anneau est inférieur à 180°, alors que, du plan intermédiaire 26 jusqu'au niveau de la plaque tubulaire3, le secteur d'anneau augmente de façon continue de la valeur qu'elle a au niveau du plan intermédiaire 26 jusqu'à 180°.In the case of FIGS. 4, 5 and 6, the skirt 16 is such that the section of this skirt by a plane parallel to the tubular plate is a ring sector, but this ring sector has an angle which varies with the section plane. From the upper part of the steam generator to an intermediate plane 26, the angle of the sector of the ring is less than 180 °, whereas, from the intermediate plane 26 to the level of the tube plate 3, the ring sector increases continuously by the value it has at the level of the intermediate plane 26 to 180 °.

On pourrait imaginer encore d'autres possibilités, pourvu que la section de la jupe soit toujours un secteur d'anneau.One could imagine still other possibilities, provided that the section of the skirt is always a ring sector.

Dans un cas limite, représenté à la figure 7, la jupe 16 est située à une distance de l'enveloppe secondaire 9 qui est égale à la distance entre l'enceinte extérieure 1 et l'enveloppe secondaire 9 ; ceci revient à dire que la jupe 16 est confondue avec l'enceinte extérieure 1, exception faite des côtés 18 et 18'. En fait, la jupe est constituée uniquement par ces côtés 18 et 18', c'est-à-dire par un simple jeu de deux cloisons verticales s'étendant entre l'enceinte 1 et l'enveloppe 9 en prolongement de la cloison verticale 21.In a borderline case, shown in FIG. 7, the skirt 16 is located at a distance from the secondary envelope 9 which is equal to the distance between the external enclosure 1 and the secondary envelope 9; this amounts to saying that the skirt 16 is merged with the outer enclosure 1, except for the sides 18 and 18 '. In fact, the skirt is formed only by these sides 18 and 18 ', that is to say by a simple set of two vertical partitions extending between the enclosure 1 and the casing 9 in extension of the vertical partition 21.

Les figures8, 9, 10 et 11 représentent des exemples de liaisons semi-étanches, entre les parties inférieures de la jupe et de la cloison verticale 21 et la plaque tubulaire 3.FIGS. 8, 9, 10 and 11 show examples of semi-sealed connections, between the lower parts of the skirt and of the vertical partition 21 and the tube plate 3.

La figure 8 représente les parties inférieures engagées dans des rails. La cloison verticale 21 est engagée dans un rail 20. La partie inférieure de la jupe, 19b, est engagée dans la gorge 19a d'un rail 19. Le rail 19 peut être fixé soit directement sur la plaque tubulaire soit, de façon préférentielle, sur l'enceinte extérieure, comme le représente la figure 8c.Figure 8 shows the lower parts engaged in rails. The vertical partition 21 is engaged in a rail 20. The lower part of the skirt, 19b, is engaged in the groove 19a of a rail 19. The rail 19 can be fixed either directly on the tubular plate or, preferably, on the outer enclosure, as shown in Figure 8c.

Sur la figure 9, les liaisons semi-étanches sont effectuées au moyen de joints à labyrinthes solidaires soit de la plaque tubulaire (figure 9a) soit directement de l'enceinte extérieure 1 (figure 9b).In FIG. 9, the semi-sealed connections are made by means of labyrinth seals secured either to the tubular plate (FIG. 9a) or directly to the outer enclosure 1 (FIG. 9b).

La figure 10 représente un système de liaison des parties inférieures au moyen de couvre-joints. Les couvre-joints 27 sont fixés par secteurs aux parties inférieures de la cloison verticale 21 ou de la jupe 16 au moyen de boulons 28. On annule au montage le jeu entre les couvre-joints et la plaque tubulaire.FIG. 10 shows a system for connecting the lower parts by means of joint covers. The joint covers 27 are fixed by sectors to the lower parts of the vertical partition 21 or of the skirt 16 by means of bolts 28. The clearance between the joint covers and the tube plate is canceled during assembly.

Quant à la figure 11, elle représente une liaison effectuée au moyen d'un joint du type à ressort.As for Figure 11, it shows a connection made by means of a spring-type seal.

La présente invention comporte de nombreux avantages.The present invention has many advantages.

En particulier, elle combine, du point de vue conception, les avantages du générateur de vapeur classique à tore de distribution d'eau alimentaire et recirculation, et, du point de vue performance, les avantages des générateurs de vapeur à préchauffeur intégré tels que ceux que nous avons décrits plus haut.In particular, it combines, from a design point of view, the advantages of the conventional steam generator with toroidal feed water distribution and recirculation, and, from a performance point of view, the advantages of steam generators with integrated preheater such as those that we described above.

La présente invention permet d'obtenir une pression de vapeur supérieure à celle d'un générateur de vapeur classique et voisine de celle des générateurs de vapeur à préchauffeur intégré, tout en étant d'une structure très simple.The present invention makes it possible to obtain a vapor pressure higher than that of a conventional steam generator and close to that of steam generators with integrated preheater, while being of a very simple structure.

L'invention résoud les problèmes de chocs thermiques au niveau de la plaque tubulaire et au niveau de l'enceinte extérieure. En effet, l'introduction de l'eau alimentaire est effectuée en partie haute du générateur, c'est-à-dire loin de la plaque tubulaire, et cette eau est mélangée côté branche froide à une fraction d'eau de recirculation plus chaude ; cette fraction d'eau de recirculation augmente à faible charge c'est-à-dire quand la température et le débit d'eau alimentaire diminuent. La température de l'eau secondaire arrivant sur la plaque secondaire est donc pratiquement constante. Quant à l'enceinte sous pression 1, elle est maintenue à une température uniforme puisqu'elle est toujours en contact avec l'eau de recirculation contenue dans les espaces annulaires 10 et 10', et non avec l'eau alimentaire. On peut ajouter que les conséquences d'une rupture de tuyauterie alimentaire sur l'intégrité des tubes en U et les structures du préchauffeur sont moins sévères que dans le cas des générateurs comportant un préchauffeur intégré, comme décrit au début de la description, car les effets de pression sont amortis.The invention solves the problems of thermal shock at the level of the tube plate and at the level of the external enclosure. Indeed, the introduction of drinking water is carried out in the upper part of the generator, that is to say away from the tube plate, and this water is mixed on the cold branch side with a fraction of warmer recirculating water. ; this fraction of recirculating water increases at low load, that is to say when the temperature and the flow rate of drinking water decrease. The temperature of the secondary water arriving on the secondary plate is therefore practically constant. As for the pressure vessel 1, it is maintained at a uniform temperature since it is always in contact with the recirculating water contained in the annular spaces 10 and 10 ′, and not with drinking water. It may be added that the consequences of a rupture of the food piping on the integrity of the U-shaped tubes and the structures of the preheater are less severe than in the case of generators comprising an integrated preheater, as described at the beginning of the description, because the pressure effects are absorbed.

Dans le générateur de vapeur selon notre invention, on ne rencontre aucune difficulté telle que celles que l'on rencontrait dans les générateurs munis de préchauffeurs ou de caissons dont les dimensionnements étaient délicats. En outre, on supprime les difficultés liées à la présence d'un plancher de préchauffage.In the steam generator according to our invention, there is no difficulty such as those encountered in generators provided with preheaters or boxes whose dimensions were delicate. In addition, the difficulties associated with the presence of a preheating floor are eliminated.

On peut ajouter également que les exigences d'étanchéité dans la zone de la plaque tubulaire sont limitées en raison du réglage des pressions branche chaude-branche froide apporté par les plaques de distribution. Les écoulements transversaux à l'intérieur de l'enveloppe secondaire en haut de la zone de préchauffage sont aussi minimisés.It can also be added that the sealing requirements in the region of the tube plate are limited due to the adjustment of the hot branch-cold branch pressures provided by the distribution plates. The transverse flows inside the secondary envelope at the top of the preheating zone are also minimized.

Un autre avantage important de l'invention réside dans le fait de sa structure très simple.Another important advantage of the invention lies in the fact of its very simple structure.

Bien entendu, l'invention n'est pas limitée aux seuls modes de réalisation qui ont été décrits à titre d'exemples, mais elle s'applique également à tous les autres modes de réalisation qui n'en diffèreraient que par des détails, par des variantes d'exécution ou par l'utilisation de moyens équivalents.Of course, the invention is not limited to only the embodiments which have been described by way of examples, but it also applies to all the other embodiments which would differ from it only in details, for example. variants or by the use of equivalent means.

Ainsi, il n'est pas nécessaire que toute l'eau alimentaire s'écoule par l'espace annulaire 17 compris entre l'enveloppe secondaire 9 et la jupe 16, mais une partie de cette eau alimentaire pourrait s'écouler dans les conduits annulaires 10 et 10'. Bien sûr, la proportion d'eau alimentaire qui circulerait ainsi dans la zone branche chaude devrait rester dans des proportions faibles.Thus, it is not necessary for all the food water to flow through the annular space 17 between the secondary envelope 9 and the skirt 16, but a part of this food water could flow in the annular conduits. 10 and 10 '. Of course, the proportion of drinking water which would thus circulate in the hot branch zone should remain in low proportions.

On pourrait également placer la collerette 24, non à la partie inférieure du générateur mais plutôt à sa partie supérieure. Ainsi, cette collerette serait accessible lors des arrêts ; on pourrait la munir d'orifices obturables et, à l'arrêt, venir régler la répartition des pertes de charge. On pourrait d'ailleurs, pour effectuer ce réglage, agir sur la perméabilité des plaques entretoies 13 situées dans la zone de'préchauffage, c'est-à-dire en dessous du sommet de la cloison verticale 21.One could also place the flange 24, not at the bottom of the generator but rather at its top. Thus, this collar would be accessible during stops; it could be fitted with closable orifices and, when stationary, adjust the distribution of the pressure drops. One could also, to effect this adjustment, act on the permeability of the braced plates 13 located in the preheating zone, that is to say below the top of the vertical partition 21.

En ce qui concerne les plaques de distribution 25a et 25b, on peut ajouter que celles-ci peuvent être situées dans des plans différents.With regard to the distribution plates 25a and 25b, it can be added that these can be located in different planes.

Claims (12)

1. Steam generator comprising a cylindrical outer enclosure (1) with a vertical axis, which is pressure-resistant and closed at each end by a cap, a horizontal tube-plate (3) located inside the enclosure, integral with the latter and delimiting, with the lower cap (2), a chamber separated into two collectors, respectively for the admission (4) and discharge (5) of a primary heat-transfer fluid, a bundle of U-tubes (6) mounted on the tube-plate (3), each having a hot leg (7) which communicates with the admission collector, and a cold leg (8) which communicates with the discharge collector, the hot legs together forming the hot branch and the cold legs together forming the cold branch, a secondary envelope (9) surrounding the bundle of tubes (6) without resting on the tube-plate (3), and defining an annular space (10) with the outer enclosure (1), means (21) for separating the interior of the secondary envelope (9) into two zones, namely a cold branch zone and a hot branch zone, an admission device (11) for feeding the annular space (10) with secondary water which is to rise along the tubes (6) of the bundle and vaporise in contact there with, and, in the top part of the enclosure, a set of separators (12) and an opening provided in the upper cap for the discharge of the steam produced, characterised in that the steam generator is also separated, outside the secondary envelope (9), into two zones, namely a cold branch zone (17) and a hot branch zone (10 + 10'), these zones communicating respectively with the cold branch and hot branch zones located inside the envelope (9), and the separating means consisting of a skirt (16) surrounding part of the secondary envelope (9) on the side corresponding to the cold branch, and forming, with the said envelope (9), a space (17) closed at the sides and in its lower part, while leaving a passage towards the cold branch zone of the interior of the envelope (9), and open in its upper part, so that the secondary water recirculated after passing through the separator, which is called the recirculation water, can return towards the bundle (6) of U-tubes via both the cold branch zone (17) and the hot branch zone (10 or 10'), but so thff the main part of the throughput of the secondary feed water arriving via the admission device (11) located in the upper part of the generator circulates in the cold branch zone (17).
2. Steam generator according to Claim 1, characterised in that it comprises means (25a, 25b) for distributing the recirculation water between the two zones, namely the cold branch and hot branch zones, and for equilibrating the pressures in these two zones in the region of the tube-plate (3).
3. Steam generator according to Claim 2, characterised in that a distribution flange (24) is placed in the space (17) between the secondary envelope (9) and the skirt (16), perpendicular to the direction of the stream of secondary water from the cold branch zone.
4. Steam generator according to one of Claims 2 or 3, characterised in that, inside the secondary envelope (9), each zone, namely cold branch zone or hot branch zone, comprises a distribution plate (25b, 25a) placed perpendicular to the direction of the U-tubes, the two plates being of different permeabilities.
5. Steam generator according to one of Claims 1 to 4, characterised in that the skirt (16) is located at a constant distance from the secondary envelope (9), defining, with the latter, a space (17) whose cross-section through a plane parallel to the tube-plate is a sector of a ring, the angle of which can vary with the cross-sectional plane, in that it runs vertically from the tube-plate (3) to the device (11) for admitting feed water, in that its sides (18, 18') are turned back towards the secondary envelope (9) and welded to this envelope, and in that its lower part is joined to the tube-plate (3) by a semi-leaktight connector (19).
6. Steam generator according to Claim 5, characterised in that the skirt is identical to the outer enclosure (9) with the exception of the sides, which consist of two vertical partitions (18, 18') running between the outer enclosure (1) and the secondary envelope (9).
7. Steam generator according to one of the preceding claims, characterised in that the vertical partition (21) separating the cold branch zone from the hot branch zone inside the secondary envelope (9) runs from the tube-plate (3) to a height at least equal to the height necessary for preheating the feed water, and in that it is welded to the sides inside the secondary envelope (9) and joined to the tube-plate (3) by a semi-leaktight connector (20).
8. Steam generator according to one of Claims 5, 6 or 7, characterised in that the lower parts of the skirt (16) and of the vertical partition (21) are engaged in rails (19, 20) firmly fixed to the tube-plate.
9. Steam generator according to Claim 8, characterised in that the vertical partition (21) and the turned-back sides (18, 18') of the skirt (16) are engaged in one and the same rectilinear rail.
10. Steam generator according to one of Claims 5, 6 or 7, characterised in that the lower part of the skirt (16) is engaged in a rail (19) firmly fixed to the outer enclosure.
11. Steam generator according to one of Claims 5, 6 or 7, characterised in that the lower parts of the skirt (16) and of the vertical partition (21) are joined to the tube-plate (3) by means of spring-type joints.
11. Steam generator according to any one of the preceding claims, characterised in that the whole of the throughput of the secondary feed water is sent into the cold branch zone.
EP81400308A 1980-02-29 1981-02-27 Preheating steam generator Expired EP0035450B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT81400308T ATE4932T1 (en) 1980-02-29 1981-02-27 STEAM GENERATOR WITH PREHEATING.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8004533 1980-02-29
FR8004533A FR2477265A1 (en) 1980-02-29 1980-02-29 PRE-HEATING STEAM GENERATOR

Publications (2)

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EP0035450A1 EP0035450A1 (en) 1981-09-09
EP0035450B1 true EP0035450B1 (en) 1983-10-05

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US (1) US4357908A (en)
EP (1) EP0035450B1 (en)
JP (1) JPS56137002A (en)
AT (1) ATE4932T1 (en)
BR (1) BR8101111A (en)
CA (1) CA1149248A (en)
DE (1) DE3161076D1 (en)
ES (1) ES499732A0 (en)
FR (1) FR2477265A1 (en)
SU (1) SU1225496A3 (en)
YU (1) YU41763B (en)
ZA (1) ZA811219B (en)

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Also Published As

Publication number Publication date
DE3161076D1 (en) 1983-11-10
YU37681A (en) 1984-02-29
FR2477265B1 (en) 1982-02-26
YU41763B (en) 1987-12-31
US4357908A (en) 1982-11-09
JPS56137002A (en) 1981-10-26
JPH0217762B2 (en) 1990-04-23
SU1225496A3 (en) 1986-04-15
BR8101111A (en) 1981-09-01
ATE4932T1 (en) 1983-10-15
ZA811219B (en) 1982-06-30
EP0035450A1 (en) 1981-09-09
ES8207341A1 (en) 1982-09-01
CA1149248A (en) 1983-07-05
ES499732A0 (en) 1982-09-01
FR2477265A1 (en) 1981-09-04

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