EP2188581B1 - Air-supplied dry cooler - Google Patents

Abstract

The invention relates to an air-supplied dry cooler for the condensation of water vapor, having at least one direct-current condenser (6) and at least one counter-current condenser (dephlegmator) (1), wherein heat exchanger pipes (2) of the counter-current condenser (1) are connected to an upper suction chamber (3), and wherein a cover (7) reducing the discharge cross-section of at least one heat exchanger pipe (2) is provided with cover orifices (8). The sum of the cross-sectional surfaces of the cover orifices (8) corresponds to no more than the cross-sectional surface of a suction pipe connection to the suction chamber (3).

Description

The invention relates to a luftbeaufschlagten dry cooler with the features in the preamble of claim 1. Such a dry cooler is off DE 44 39 801 known.

The use of air to condense turbine steam has been known for a long time. In direct air-cooled condensation, the turbine steam is condensed in parallel finned tube elements (surface condensers) and the condensate is returned to the feedwater circuit. The finned tube elements are on the inside under vacuum, whereby the non-condensable gases are sucked off. The cooling air flow is generally generated by fans, rarely by natural ventilation. Dry coolers in roof construction (A-arrangement) are widespread. Here, the finned tube elements form the legs of a triangle, at the base of which the fans are arranged.

Two types of surface capacitor circuits are common: first, the flow-through capacitor circuit and, secondly, the countercurrent capacitor circuit (dephlegmator circuit). With the flow condenser, the steam flows down from an overhead distribution pipe into the water Flow condenser. The also flowing down condensate is collected in a condensate collecting line. In the countercurrent condenser circuit, exhaust steam is introduced from below into the cooling tubes and thus guided against the outflowing condensate. In practice, flow condensers and countercurrent condensers are combined. The so-called "condensation end" of the steam then lies in the countercurrent condenser.

In order to achieve a uniform distribution of steam in the steam distribution chamber of a countercurrent condenser introduced steam flow, it is known to provide in the steam distribution chamber an intermediate bottom with recesses (DE-GM 1873644). Here, the entire flow cross-section of the recesses is smaller than the total cross section of the condenser tubes.

Conversely, it is from the DE 44 39 801 C2 It is known that the vast majority of dephlegmators have resistance elements in the region of their gas collector-side ends. As a result, the exhaust steam counteracts a resistance that is enforced by a homogenization of the entering into the individual dephlegmator from below steam. This homogenization leads to an extensive utilization of the entire capacitor area for the condensation. The formation of "cold nests" or "dead zones", in which neither steam nor condensate is present, is counteracted. However, under certain circumstances, problems can occur when a larger amount of condensate collects in the suction chamber at low temperatures. Due to the large condensate volume, it can lead to hypothermia and in extreme cases even to the freezing of the condensate. This danger is outside temperatures in the negative range, both during operation, as well as when starting, since the large amount of frozen condensate, which is just below the aperture may not be thawed quickly enough by the gas-vapor mixture, causing the new precipitating condensate quickly freezes and in extreme cases could block the aperture holes.

Another problem can arise when a lot of condensate has collected in the suction chamber, which through the same opening in the Dephlegmatorrohre must be returned, through which the gas-vapor mixture enters the suction chamber. Due to the counterflow through the gas-vapor mixture, it can lead to a "swallowing" in the region of the individual openings and thus to a temporary demolition of the gas-vapor stream. This can result in undesirable pressure fluctuations within the individual dephlegmator tubes.

The invention is based on the object to further improve an air-cooled dry cooler for condensing water vapor with respect to achieving a high overall efficiency, with a freezing of the dephlegmator, as well as a tearing off of the gas-steam stream flowing into the suction chamber should be reliably avoided.

This object is achieved in a dry cooler with the features of claim 1.

Advantageous developments of the inventive concept are the subject of the dependent claims.

The condensate entering the suction via an orifice collects in the deepest part of the suction chamber and can be reintroduced into a heat exchanger tube via a gas barrier in the form of siphons. The gas barrier is to ensure that the suction prevailing in the suction chamber does not lead to gas or steam passing the aperture opening into the suction chamber. This can be prevented by means of a gas barrier in the form of a siphon.

It is essential in the invention that the siphon drain separates the gas-steam stream from the countercurrent condensate stream. It can no longer be swallowed in the region of the individual apertures, since the condensate flows off via a separate path and is immediately introduced back into the heat exchanger tubes. Another advantage is that only small amounts of condensate can accumulate in the deepest of the suction chamber. Lower amounts of condensate can be heated faster by the extracted gas-steam mixture, so that freezing during operation can be excluded. This increases the reliability. In addition, pressure fluctuations avoided within each Dephlegmatorrohre, since in any case it is ensured that the condensate does not hinder the gas-steam flow.

The gas barrier is formed by the baffle, a tube plate arranged below the baffle, in which the heat exchanger tubes are welded, and the collecting condensate itself. In this case, the condensate can flow back into the heat exchanger tubes directly above the outlet openings of the heat exchanger tubes fastened to the tubesheet and mix with the condensate that precipitates there. The panel may be part of a bottom plate of the suction chamber. For draining the condensate, condensate discharge openings are arranged in the diaphragm within the gas barrier. The condensate discharge openings are preferably located in the lowest areas of the diaphragm.

When arranged in roof shape heat exchanger elements of the heat exchanger tubes-retaining tube sheet is inclined relative to a horizontal. Since the aperture of a heat exchanger tube associated aperture has a substantially smaller cross-section than the heat exchanger tube, is due to the inclination of the tube plate, the lowest point of the outlet below the lowest point of the aperture. In other words, accumulating in the suction condensate can not dammed so high until it reaches the aperture, because it previously drains over the lower edge of the outlet opening of the heat exchanger tube and is discharged in this way from the suction. In this way, there may be no flooding of the suction chamber. Even a freezing of the dammed up in the gas barrier condensate would be harmless to the operation of the suction because the apertures are higher than the outlet openings of the heat exchanger tubes. During operation, i. if condensate returns to the suction chamber via the apertures, any frozen condensate would be quickly melted again and could immediately drain off again via the heat exchanger tubes.

In the invention, one also makes use of the fact that the weld seam superelevation over which the heat exchanger tubes are connected to the tubesheet are welded, in a sense serves as a seal in the region of the connection between tube plate and heat exchanger tube, which is not subject to the risk of crevice corrosion due to the existing residual gap of about 1-2 mm. The seal is due to a distance which is not more than 2 mm, but preferably not greater than 1 mm, so tight that there is no risk that steam or gas from adjacent, ie not directly under the aperture, heat exchanger tubes is sucked , In addition, dammed condensate in the area of the weld seam elevations can pass into the heat exchanger tubes and drain off. Due to the sufficient distance between the outlet opening and the bottom plate, crevice corrosion can not occur.

A special manufacturing advantage results when a pair of opposite in a roof-shaped arrangement dephlegmators is connected to a common suction. This does not mean that the suction chamber of two dephlegmators is provided with only a single suction tube, but that, instead of two separate extraction chambers to be produced, a single suction chamber is mounted on the dephlegmators. In dephlegmators arranged in the shape of a roof, the lowest point of the ridge area lies between the tubesheets of the dephlegmators. In this area, the condensate collects. In an advantageous embodiment, the condensate collects up to a barrier height, in which a partition wall dips and shares as a gas barrier, the suction chamber in a first dephlegmator associated first sub-chamber and the second dephlegmator associated second sub-chamber. Each sub-chamber is provided with a separate suction. The discharge of the condensate from the deepest via condensate discharge openings in the bottom plate of the suction.

As structurally particularly favorable, it is considered when the partition wall of the gas barrier is formed by a suction plate closing the cover plate. The cover plate can be made as well as the bottom plate of a folded sheet metal blank. The board is perforated in the area of the apertures and the suction tube. In addition, condensate discharge openings are manufactured. The perforated board is according to the inclination of the tube sheets folded. In addition, the side walls to which the suction tubes are attached, can be made in one piece with the bottom plate of the board. The side walls and bottom plates effectively form a trough on which the cover plate is placed. The cover plate basically only needs to be folded once, in such a way that its fold in the installed position is lower than the deepest regions of the outlet openings of the heat exchanger tubes, so that a gas barrier is formed. The cover plate is thus more folded than the board between the two bottom plates.

The thus prefabricated suction can be provided in the region of its side walls with spacers, which are supported on the tube plate of the heat exchanger. The spacers also serve as a vacuum support. They define a fixed distance between the tubesheet and the bottom plate. In the transition region between the side wall and the bottom plate, the suction chamber can be firmly welded to the tube plate via a fillet weld in ideal welding position.

The cross-sectional wedge-shaped design of the suction chamber is structurally simple in terms of the course of the cover plate and the bottom plate and also fluidly particularly favorable. The cover plate can be stiffened by vacuum supports, which are arranged in triangular form above the cover plate.

The dry cooler according to the invention optimizes the construction of the suction chamber, because in a simple manner provided with apertures bottom plate is part of a completely factory pre-finished chamber. Due to the bending radii during the production of the chamber, the welding phases for the subsequent welding with the tubesheets are created automatically. This reduces costs as a whole.

A significant advantage of the suction chamber designed according to the invention is that there is no significant difference between countercurrent and DC capacitors with regard to the design of the individual tube bundles. This is primarily a logistical advantage, since on the construction site not on the Care must be taken to ensure the order of the capacitors to be installed, but first the capacitors can be placed independently of their wiring and then determine the wiring as a countercurrent condenser or DC capacitor. Only after the gas-tight welding of the tubesheets are the factory-made completely prefabricated Absaugkammem mounted on the individual, operated in countercurrent heat exchanger elements and connected to the tube sheets.

Preferably, the sum of the cross-sectional areas of the apertures, which are associated with the individual heat exchanger tubes, at most the cross-sectional area of a suction pipe connected to the suction chamber.

It has surprisingly been found that the cross-sectional area of the aperture is in direct proportion to the cross-sectional area of the suction tube, which has not hitherto been recognized in this form. The adaptation of the cross-sectional areas makes it possible to use due to the relatively small aperture suction tubes with also relatively small cross-sections, which is particularly advantageous to note that each Dephlegmator only a single suction pipe must be connected to the suction. This leads to a significant reduction of the previously required welding. It should be noted that countercurrent condensers, which are used for the condensation of steam of a power plant, regularly have a width of about 2 m per tube bundle, so far distributed over the width of the tube bundle three suction tubes were connected to respective Absaugkammem. The Absaugkammem were here separated gas-tight. It has been installation technology extremely complicated to connect the individual Absaugkammem over a variety of individual extraction with a manifold, as this is a variety of welds required. However, the number of welds increases the risk of leaks. To make matters worse, that the welds must be partially welded on site in the overhead position, so that the welding process is very complex and time consuming.

Due to the coordinated cross-sectional areas, it is now possible within the scope of the invention to dispense with three separate, separate Absaugkammem each Dephlegmator and provide only a single suction with only one central suction. This significantly reduces the number of welds and reduces the risk of leaks. Decisive in the dimensioning of the individual cross-sections is that there is a uniform extraction of gas and / or steam from the individual heat exchanger tubes. For this purpose, the cross section of the individual apertures may vary, to the edge region, i. in the areas farther from the suction tube, increase and be smaller towards the central area immediately adjacent to the suction. The diameter changes can be continuous or in stages. For example, one-third of the gradation is conceivable, i. in the middle, the suction pipe adjacent area are the apertures with the smallest cross-sectional areas. In an edge area are the apertures with the largest cross-sectional areas and in each case between apertures with average cross-sectional areas.

Figur 1

einen Längsschnitt durch eine Absaugkammer im oberen Bereich eines Gegenstromkondensators;

Figur 2

eine perspektivische Ansicht auf die Absaugkammer der Figur 1 im geöffneten und geschlossenen Zustand;

Figur 3

eine vergrößerte Darstellung der Figur 2;

Figur 4

die Absaugkammer der Figuren 1 bis 3 im Querschnitt.

The invention will be explained in more detail with reference to an embodiment shown in the drawings. Show it:

FIG. 1

a longitudinal section through a suction in the upper part of a countercurrent condenser;

FIG. 2

a perspective view of the suction of the FIG. 1 in the open and closed state;

FIG. 3

an enlarged view of FIG. 2 ;

FIG. 4

the suction chamber of FIGS. 1 to 3 in cross section.

FIG. 1 shows the upper portion of a DC capacitor (dephlegmator) 1 of a not shown in its entirety airborne dry cooler for condensing water vapor. The flow direction of the steam is illustrated by the arrows P shown. The steam rises inside of mutually parallel heat exchanger tubes 2 upwards and enters a suction chamber 3 a. To the suction chamber 3, a suction pipe 4 is centrally connected, via which the vapor-gas mixture is sucked out of the dephlegmator 1. Based on the perspective view of FIG. 2 it can be seen that in each case two of the Absaugkammem 3 are connected to a central suction 5.

Out FIG. 1 It can also be seen that a part of a DC capacitor 6 is shown in the right-most picture plane. The DC capacitor 6 is not provided with a suction chamber 4 because the steam flows from top to bottom. However, the heat exchanger tubes 2 have the same cross section as that of the dephlegmator 1. It can be clearly seen that in the suction chamber 3 much smaller openings for the passage of the vapor-gas mixture are present. This is due to the fact that an aperture 7 reducing the outlet cross section of the heat exchanger tubes 2 is arranged with aperture openings 8 above the outlet openings 9 of the individual heat exchanger tubes 2. The aperture 7 is part of a bottom plate 10 of the suction chamber 3. The individual apertures 8 have in their sum a cross-sectional area which is not greater than the cross-sectional area of the suction tube 4 connected to the suction chamber 4. This results in a particularly uniform extraction of steam-gas Mixture possible. As a result, cold zones within the heat exchanger tubes 2 of the dephlegmator 1 are largely avoided. In particular, with this particular tuning of the cross sections, it is possible to provide only one suction chamber 3 per dephlegmator unit, wherein it should be noted that a tube bundle configured as a dephlegmator 1 has a width of preferably approximately 2.20 m.

Based on the perspective view of FIG. 2 is the structure of Absaugkammem 3 even more clearly visible. The left in the image plane suction chamber 3 is closed with a cover plate 12, in which it is a V-shaped beveled sheet. This cover plate 12 is welded to a lower part 11 of the suction chamber 3. The lower part 11 is formed by the bottom plates 10 and the angled 90 ° relative to the bottom plates 10 side walls 13. The cover plate 12 is edge with the side walls 13 welded and stiffened over additional triangular vacuum supports 14. Furthermore, spacers 15 are arranged on the side walls 13 at regular intervals, which will be described in more detail below. The spacers 15 are located in the same spatial plane as the vacuum supports 14.

It can also be seen that the cross-section of the suction chamber 3 tapers towards the middle, that is to say it is lowest where the fold occurs between the base plates 10. In this area of the fold is the lowest point of the suction chamber 3. This area is referred to as the lowest 16 and is provided at regular intervals with condensate discharge openings 17. The condensate discharge openings 17 are elongated holes, so that they extend on both sides of the fold, as shown by the enlarged view of FIG. 3 can be seen.

The suction chamber 3 is divided into a respective first dephlegmator 1 associated first sub-chamber 19 and a gas-tight separated from this second sub-chamber 19a. The sub-chambers 19, 19a are mirror-symmetrical or the suction chamber 3 is symmetrical and coupled to a suction pipe, not shown. It can be seen that from the heat exchanger tubes 2, a vapor-gas mixture corresponding to the arrows P rises, forming within the heat exchanger tube 2 condensate drops T, which are reflected on the wall of the heat exchanger tube 2 and condensate K one not closer shown condensate line in the foot of the dephlegmators 1 are supplied. It can be seen that the cross-section of the apertures 8 is substantially smaller than the cross-sectional area of the outlet opening 9 of the heat exchanger tubes 2.

The vapor-gas mixture passing through the aperture 8 is at least partially condensed, with gas being sucked up in the direction of the arrows P1, ie in the direction of the suction tube 4, while condensate drops T move downward by gravity and in the lowest 16 of the suction chamber 3 collect. The condensate K passes through the condensate drain opening 17, which in FIG. 4 are shown only as an interruption in the bottom plate 10, and collects above a heat exchanger tubes 2 supporting tube bottom 18. Die Tube plates 18 of the two dephlegmators are gas-tight welded together. The condensate K passes through the condensate discharge openings 17 under the respective bottom plates 10, which are located at a small distance from the tube sheets 18. This mandatory distance is defined by the spacers 15, which are also supported on the tubesheets 18. By the resulting gap, the condensate can rise up to the level height, which is marked with the line of the broken line F. The filling level height F corresponds to the altitude of the deepest regions of the outlet openings 9. In other words, the condensate K can rise until it can flow between the bottom plates 10 and the tube plates 18 again through the outlet openings 9 in the heat exchanger tubes 2 and with the rest Condensate flow mixed.

The peculiarity is that the cover plate 12 extends below the level line F and immersed in the accumulating condensate. As a result, a gas barrier 20 is formed by the bottom plate 10 or by the diaphragm 7, the tube plate 18 arranged underneath the bottom plate 10 and the condensate K so that no vapor-gas mixture can pass from the left partial chamber 19 into the right partial chamber 19a , In addition, it is ensured by the outflow of the condensate K that the apertures 8 are not below the level line F, so that the way for the entry of the vapor-gas mixture in the suction chamber 3 is a different way than the one for the derivative the condensate K is provided. As a result, a so-called "swallowing" of the effluent condensate is prevented with the extracted in countercurrent vapor-gas mixture.

The factory prefabricated suction chamber 3 is welded as a complete assembly via a weldable in ideal position to be pulled fillet weld 21 with the tube plates 18. In this case, the suction chamber 3 is held by the spacers 15 at a defined minimum distance of preferably 1 mm, to the weld seam elevations, which are not shown in detail, which have arisen due to the tube welds in the tube plates 18. This automatically creates a single chamber per heat exchanger tube 2, which can be uniformly sucked through the discharge opening 8.

Reference numerals:

1 -

Countercurrent condenser (Dephlegmator)

2 -

heat exchanger tube

3 -

suction

4 -

suction tube

5 -

suction

6 -

DC capacitor

7 -

cover

8th -

aperture

9 -

outlet opening

10 -

baseplate

11 -

lower part

12 -

cover plate

13 -

Side wall

14 -

vacuum support

15 -

spacer

16 -

lowest

17 -

Condensate drain opening

18 -

tube sheet

19 -

member chamber

19a -

member chamber

20 -

gas barrier

21 -

Weld

F -

Fill line / barrier height

K -

condensate

P -

arrow

T -

condensate drops

Claims (13)

1. Air-generated dry cooler for the condensation of water vapour with at least one direct current condenser (6) and at least one reverse current condenser (dephlegmator) (1), whereby heat exchanger pipes (2) of the reverse current condenser(1) are connected to an upper suction chamber (3) and whereby a screen (7) with screen openings (8) is provided, which reduces the cross section of the outlet of at least one heat exchanger pipe (2), characterized in that condensate (K) that enters into the suction chamber (3) through the condensate flow openings (17) arranged in the screen (7) and is collected together in the depths (16) of the suction chamber (3) above a tube sheet (18) that holds the heat exchanger pipes (2) and which can be fed again into a heat exchanger pipe (2) via a gas barrier (20) in the form of a siphon, whereby the gas barrier (20) is formed by the screen (7), by the tube sheet (18) that is arranged below the screen (7) and by the condensate (k) that is collected together, whereby the condensate (k) that is collected together can be fed into the outlet openings (9) of the heat exchanger pipes (2) that are mounted on the tube sheet (18).
2. Dry cooler as per Claim 1, characterized in that the screen (7) has, at least in terms of its section, a maximum clearance of 2 mm with respect to the outlet opening (9) of the heat exchanger pipe (2).
3. Dry cooler as per Claim 2, characterized in that the clearance is not greater than 1 mm.
4. Dry cooler as per Claims 2 or 3, characterized in that the outlet opening (9) is enclosed by a weld reinforcement, whereby the clearance is measured with respect to the weld reinforcement.
5. Dry cooler as per one of the Claims 1 to 4, characterized in that the screen (7) is a component part of a base plate (10) of the suction chamber (3).
6. Dry cooler as per one of the Claims 1 to 5, characterized in that a pair of dephlegmators (1), which are arranged in a roof-like shape opposite each other, are connected to a common suction chamber (3).
7. Dry cooler as per Claim 6, characterized in that condensate (K) collects together up to a trap seal depth (F) in the depths (16) of the suction chamber (3) between the dephlegmators (1), into which a bulkhead is immersed and as a gas barrier (20) divides the suction chamber (2) into a first sectional chamber (19) allocated to the first dephlegmator (1) and a second sectional chamber (19a) allocated to the second dephlegmator (1).
8. Dry cooler as per Claim 7, characterized in that the bulkhead is formed by a cover plate (12) that seals the suction chamber (3)
9. Dry cooler as per Claim 5 , characterized in that the base plate (10) that forms the screen (7) is produced as one-piece from a perforated plate, which is chamfered in accordance with the incline/pitch of the tube sheet (18) in the area of the outlet openings (9), of the condensate flow openings (17) and of the suction pipe (4).
10. Dry cooler as per one of the Claims 1 to 9, characterized in that a sidewall (13) of the suction chamber (3) is produced from the plate as one-piece with the base plate (10).
11. Dry cooler as per Claim 10, characterized in that a spacer (15) that is fixed to the tube sheet (10) is located on the side wall (13).
12. Dry cooler as per one of the Claims 1 to 11, characterized in that a prefabricated suction chamber (3) is welded gas-tight onto the edge of the tube sheet (18).
13. Dry cooler as per one of the Claims 1 to 10, characterized in that a suction chamber (3) that extends over the complete width of a dephlegmator (1) has a single suction pipe (4).

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