EP1008803B1 - Feedwater preheater for steam power plants - Google Patents

Description

Technical field

The invention relates to a preheater in a steam power plant for heating of water for the water-steam cycle of the power plant through heat exchange between tapping steam from turbines and water flowing in pipes. The Invention deals with so-called duplex and multiplex preheaters, in which are two or more preheaters of different levels and pressures in one Housing are housed. The preheaters are in series on the water side and connected on the steam side in parallel. The invention particularly relates to Construction of bundle carriers and a partition wall, the two or more Separates the preheater within the preheater housing.

State of the art

A duplex preheater is described, for example, in BWK, volume 37 (1985) No. 10, Oct., p. 387-396. This preheater has two in its housing Heat exchange rooms each with a steam inlet connection and a tube bundle with associated water inlet and water outlet. In the two heat exchange rooms is with tapping steam of different temperature and different pressure headed. The pressure ranges of the heat exchange rooms are separated from each other by a self-closing partition. The water chamber for the water to be warmed up through the tube bundle is divided into four compartments by two shirts, in which the Water inlets and water outlets of the two tube bundles are arranged.

DE 195 11 264 describes a duplex preheater with an elongated, cylindrical outer housing. The first heat exchange room is in an elongated inner housing during the second heat exchange space through the Inside of the outer case and the outer of the inner case of the first Heat exchange room is formed. The separation between the two pressure areas consists of a complete inner housing. This is on on one side by a semicircular and on the other side by a straight, vertical wall.

Another duplex preheater is disclosed in DE 195 37 478. The preheater has a straight, vertical partition inside, which separates the two Separates heat exchange rooms or pressure areas.

Presentation of the invention

It is the object of the invention to provide a duplex and multiplex preheater of the type mentioned at the outset, which has a bundle carrier construction and one or more partition walls for separating the heat exchange spaces or pressure areas, which can be produced and assembled inexpensively and are also heat-insulating.
This object is achieved by a duplex or multiplex preheater with an outer housing or steam jacket, in which two or more heat exchange modules are accommodated, each of which is separated from one another by a partition wall, a heat exchanger tube bundle supported by support plates being arranged in each heat exchange module. According to the invention, the cross-section of the dividing wall between the heat exchange rooms is designed in a zigzag shape. For this purpose, the dividing wall has a high middle part, which extends over the area of the support plates, and two short parts, which extend from both ends of the middle part under a bend to the middle part in each case towards the steam jacket and are welded to the steam jacket. Due to the pressure difference between the heat exchange rooms, there is a compressive force on the partition. According to the invention, the partition is made zigzag and is therefore flexible, so that it yields to the compressive force by moving and bending only very slightly. The zigzag shape of the partition wall allows the wall to move when the pressure is exerted, with the middle part of the partition wall shifting
By moving the partition, the partition comes into contact with the support plates, which in turn come into contact with the steam jacket. This results in a transfer of the pressure force from the partition to the stronger steam jacket, which absorbs the force.
The power transmission makes it possible, in particular, to manufacture the partition wall from thinner walls.
In a preferred embodiment, the partition is double-walled, in that at least over the area of the high central part of the partition two walls run parallel to one another and there is a space between them. In an expanded version, the support plates of the tube bundles have inner and outer wings, of which the inner ones extend to the partition wall and the outer ones to the steam jacket. They are arranged with respect to the partition wall and the steam jacket so that the partition wall comes into contact with the inner wings and the outer wings come into contact with the steam jacket. The pressure force is also transmitted to the steam jacket via the wings of the support plates.
In order to transfer the pressure force from one wall to the other of the double-walled partition, sheets are arranged in the space between the individual walls, which come into contact with the walls of the partition when the pressure is applied.
The invention relieves the dividing wall of the compressive force by transmitting the compressive force from the dividing wall to the support plates and the jacket of the preheater housing. This makes it possible to manufacture the walls of the double partition wall thinly and inexpensively with little material.
The zigzag shape of the partition has the advantage that it allows deformations due to thermal expansion. The straight-line displacement of its long middle section has only a minor effect on the welds on the steam jacket. The double-walled partition also has the advantage of thermal insulation. Compared to a single preheater, a duplex preheater causes additional heat losses. These are reduced by the thermal insulation of the double wall.

Brief description of the drawings

Figur 1: eine seitliche Aussenansicht eines Duplex-Vorwärmers mit Wasserkammern und einem Aussengehäuse für zwei Wärmetauscher und einen Querschnitt durch die Wasserkammer des Duplex-Vorwärmers,

Figur 2: einen axialen Querschnitt eines Duplex-Vorwärmers zur Darstellung der Ausbildung der erfindungsgemässen Stützplatten und doppelwandigen Trennwand,

Figur 3: einen axialen Querschnitt desselben Duplex-Vorwärmers zur Darstellung der Verwendung der erfindungsgemässen Trennwand unter Wirkung der Druckkraft von einem zum andern Druckbereich,

Figur 4: ein Beispiel eines Multiplex-Vorwärmers mit drei Wärmetauschräumen getrennt durch erfindungsgemässe Trennwände und einen Querschnitt durch die Wasserkammer des Multiplex-Vorwärmers.

Show it:

FIG. 1: a side external view of a duplex preheater with water chambers and an outer housing for two heat exchangers and a cross section through the water chamber of the duplex preheater,

FIG. 2 shows an axial cross section of a duplex preheater to illustrate the design of the support plates and double-walled partition according to the invention,

FIG. 3 shows an axial cross section of the same duplex preheater to illustrate the use of the partition according to the invention under the effect of the pressure force from one pressure region to the other,

Figure 4: an example of a multiplex preheater with three heat exchange rooms separated by partitions according to the invention and a cross section through the water chamber of the multiplex preheater.

Way of carrying out the invention

Figure 1 shows the exterior of a duplex preheater with an outer housing or steam jacket 1. On the steam jacket 1 there are steam inlet connections 3 and 4 appropriate. Steam is, for example, via the two steam inlet connections 3 from a first tap stage of a low-pressure turbine to a first one Preheater room in the interior of the jacket 1 passed while on the steam inlet nozzle 4 steam from a second tap stage of a low-pressure turbine, is passed into a second preheater room within the jacket 1. Following the steam jacket 1, a tube plate 15 is arranged in which Tubes of U-shaped tube bundles for the two heat exchangers are anchored. The tube sheet 15 is connected to a water chamber 2 with four partial water chambers 11 ', 12', 13 ', 14' a water inlet nozzle 7 and one Water outlet connector 8. The water to be heated passes through the water inlet connector 7 in a first partial water chamber 11 ', the water entry zone for the first stage preheater, and from there through the series Tube bundle. (The flow direction of the water from the partial water chambers into the Tube bundle and from this into the subchambers is with crosses or circles indicated.) The tube bundles are via a second partial water chamber 12 ', the Water outlet zone of the first preheater, and a third partial water chamber 13 ', the water entry zone of the second preheater, connected to one another. After flowing through the two tube bundles, the water flows into a fourth Partial water chamber 14 ', the water outlet zone of the second preheater, and occurs finally via the water outlet connection 8 from the duplex preheater. The Partial water chambers 11 'and 14' are formed by two shirts 16 and 17, the partial water chambers 12 'and 13' through the outer walls of the shirts 16 and 17 and the inner wall of the water chamber 2 are formed and are interconnected.

Figure 2 shows the interior of the duplex preheater with the inventive Partition 20 for dividing and separating the pressure areas of the two Heat exchanger and with the support plates 19 according to the invention for the Pipe bundle 11-14 to carry out the transfer of the pressure force to the Steam jacket 1.

The steam inlet connections 3 and 4 are again shown on the steam jacket 1, via which steam with a pressure P1 is conducted into the first heat exchanger space S1, or preheater first stage, and steam with a pressure P2 into a second heat exchanger space S2, or preheater second stage , where P1 <P2. A U-shaped tube bundle is arranged in each of the two areas S1 and S2, the legs of which are designated by 11 and 12 in area S1 and by 13 and 14 in area S2.
The bleed steam from the low-pressure turbines, which reaches areas S1 and S2 via inlet ports 3 and 4, flows through the tubes of the tube bundles. To protect the pipes 3 and 4 baffles 22 can be attached to the inlet connection.
From a preheater of a higher (here third) stage 6 condensate is led into the area S2 via a cascade inlet connection. The condensation of the steam forms condensate on the pipe surfaces, which collects in the lower area of the preheater. The condensate in the area S2 is discharged via the condensate outlet connection 10 and can be pumped forward to the higher stage or can be supplied to the area S1 after throttling via a level control valve via the cascade inlet connection 5. The condensate collected in the area S1 is discharged via the condensate outlet connection 9 and fed to the lower preheater stage or the condenser of the system.
To remove non-condensable gases (air) from the preheater, ventilation tubes 24 are attached in the bundle lanes in the interior of the tube bundle, via which the gases are sucked off.
The cover plates 23 serve to prevent a direct flow of steam into the bundle lane and the air extraction zone with the lowest pressure.
In both areas S1 and S2, the tube bundles are supported by support plates 19. The support plates 19 are in turn clamped together by tie rods and sleeves 18 which run in the longitudinal direction through the preheater. The support plates 19 also lie on angles and rails 21 which are fastened in the lower region of the steam jacket 1.
According to the invention, the support plates 19 have wings 19 'and 19 ". In this embodiment, two wings 19' on each support plate 19 extend towards the center of the preheater and two further wings 19" extend from the outer edge of the support plates 19 to the jacket 1.
The heat exchange areas S1 and S2 are formed by the partition 20 according to the invention and the surrounding jacket 1. The partition 20 has a basic zigzag shape. The partition 20 consists of three parts: a high middle part 20 ', which extends slightly beyond the area of the support plates 19, and two short parts 20 "which run in a bend from the high middle part 20' to the jacket 1 of the preheater ; the two short parts 20 "can be parallel. They are welded to the jacket 1 at the welding or clamping points 38 and 39.
The partition wall 20 is designed over a large part of the zigzag shape as a double wall, the first wall, which faces the heat exchange chamber with higher pressure, the maintenance of the pressure difference and the second wall, which faces the heat exchange chamber with low pressure Serves as thermal insulation. The individual walls of the double wall are made of thin sheet metal, which is not intended to absorb the compressive force. The sheet is made, for example, with thicknesses of 2-5 mm, of which the first wall is preferably made thicker than the second wall. The insulation results in a reduction of the heat loss and a performance saving.
For example, if there is a simple partition made of carbon steel, a heat flow of 1000-2000 kW can be transferred from the second preheater module to the first preheater module by heat conduction. For this, a steam flow of approx. 0.5-0.8 kg per second would have to be tapped out of the turbine one stage earlier. This would lead to an increase in the heat consumption of the steam system of approx. 0.03 to 0.05%. These losses can be reduced by choosing a stainless steel material for the partition, but this would entail higher costs. By using a double-walled partition according to the invention, the heat losses mentioned are minimized, even practically avoided.

The individual walls are separated by a few spaces Millimeters wide. There are intermediate plates in the gap 30 arranged together with the wings 19 'of the transmission of the compressive force serve on the thicker and more heavily manufactured jacket 1 by at Displacement of the partition come into contact with it.

Figure 3 shows the force on the partition, which results from the pressure difference between the areas S1 and S2. The pressure force is indicated here with arrows. For the sake of simplicity, their effect is shown here only on the wall on the left of the double wall. Due to its zigzag shape, the partition wall 20 yields to the compressive force by moving into the position indicated by the broken line; it only bends slightly. It essentially has the function of transmitting the compressive force to the support plates 19 and the jacket 1. In contrast to the prior art, it does not have the function of absorbing the force solely through a heavy load. When the force is transmitted, the bending points 36 and 37 practically move on circular lines, the welding points or clamping points 38 and 39 being the center points of the circles. The high middle part 20 'of the partition wall moves slightly obliquely upwards due to the compressive force. During this displacement, the first wall of the double wall comes into contact with the intermediate plates 30, which then come into contact with the second wall of the double wall. The result is a parallel displacement of the middle part 20 'of both walls of the double wall. The double wall then touches the wings 19 'and transmits the compressive force to the support plates 19. The wings 19 "at the outer edge of the support plates finally transmit the force to the jacket 1, which absorbs them due to its greater material thickness.
The compressive force is transmitted to the jacket both via the support plates 19 and the wings 19 ′, 19 ″ and also absorbed by the welding points 38, 39. This prevents strong bending loads on the partition 20, in particular in the vicinity of the two welding points 38, 39 The relief of the partition by support on the support plates and wings also allows the thin design of the partition with little material.

FIG. 4 shows a multiplex preheater using the example of a preheater with three preheater stages in one housing. It has partition walls according to the invention for dividing the pressure areas and support plates for transmitting the pressure forces between the preheater areas to the jacket of the preheater. The multiplex preheater enclosed by the jacket 1 is divided into three pressure ranges S1, S2, S3, or preheaters first, second and third stage, in which pressures P1, P2 and P3 prevail, with P1 <P2 <P3. Tapping steam is conducted into the three preheater areas via inlet connections 41, 42, 43. Similar to the duplex preheater, U-shaped tube bundles are arranged in each area through which the water to be heated flows. The direction of flow through the bundle legs 44-49 is indicated by means of crosses and circles. The tube bundles are in turn supported by support plates 19 which lie on angles and supports 21 in the lower region of the preheater housing.
The condensate resulting from the condensation of the steam on the pipe surfaces also collects in the lower area. Condensate from a fourth stage preheater is led via the cascade inlet connection 6 into the area S3. The condensate collected in area S3 is discharged via condensate outlet connection 50, after which it is fed via a connection 51 to the collected condensate in area S2. The area S2 has a condensate outlet connection 52, via which the condensate is discharged from this area and led into the area S1 via the cascade inlet connection 5. The condensate from this area is fed to the condenser of the power plant via a condensate outlet connection 53 in the area S1.
The dividing walls 54 and 55 between the areas S3 and S2 or S2 and S1 are similar to the dividing wall 20 in FIG. 2, with middle parts 54 ', 55' and short parts 54 ", 55" in a zigzag shape exhibit. They shift in a similar way to that shown in FIG. 3. The support plates 19 have two or three blades on each side, depending on the size of the multiplex preheater. The support plates in the middle preheater S2 have wings 19 'on both sides, which face the partition walls 54 and 55, respectively.
The water chamber for the multiplex preheater is designed in an analogous manner to the water chamber for the duplex preheater according to FIG. 1. Accordingly, the water chamber is divided into six partial water chambers with the help of two shirts and a water-side, zigzag-shaped partition, which ensures that the tube bundles are connected in series. The first shirt encloses the partial chamber for the water entry into the bundle leg 44. The water-side zigzag-shaped partition runs from the water chamber jacket 2 first between bundle tube zones 45 'and 47', then between bundle tube zones 46 'and 47' and finally between bundle tube zones 46 'and 48' to the jacket 2. The second shirt encloses the partial chamber for the water outlet from the bundle tube zone 49 '.

In an expanded version, the duplex and multiplex preheaters in the second or second and third preheater stage on a subcooler. In order to reduce the length of the pipeline, especially the pipelines for Tapping steam from the low pressure turbine, which has a large diameter have, the duplex or multiplex preheater is preferably as close as possible the low pressure turbine arranged. An arrangement of the duplex preheater in the Capacitor neck is an optimal solution in terms of saving Pipelines when the pressure losses of the low pressure turbine steam around the Duplex preheaters are not large.

LIST OF REFERENCE NUMBERS

1

Steam jacket, outer casing

2

Water chamber jacket

3

Steam inlet connection (turbine tapping steam)

4

Steam inlet connection (turbine tapping steam)

5

Cascade inlet connection

6

Cascade inlet connection (from preheater of higher level)

7

Water inlet connection

8th

Output nozzle

9

Condensate outlet connection from preheater S1

10

Condensate outlet connection from preheater S2

11-14

Tube bundle leg

11 '

Water inlet zone preheater S1

12 '

Water outlet zone from preheater S1

13 '

Water entry zone preheater S2

14 '

Water outlet zone from preheater S2

15

tube sheet

16

Water entry shirt (partial water chamber) in water chamber

17

Water outlet shirt (partial water chamber) in water chamber

18

Tie rods and sleeves

19

Bundle support plates

19 '

Wing on support plate to the middle of the preheater

19 "

Wing on support plates to the jacket of the preheater

20

Partition between heat exchange rooms S1 and S2

20 '

Partition between heat exchange rooms S1 and S2, high middle section

20 "

Partition between heat exchange rooms S1 and S2, short parts

21

Angles and supports

22

baffle

23

Cover plate

24

vent pipes

30

intermediate plates

36.37

inflection points

38.39

welds

41-43

Inlet connection to multiplex preheater

44-49

Bundle legs in multiplex preheater

50

Condensate outlet connection from S3

51

Condensate inlet connection to S2

52

Condensate outlet connection from S2

53

Condensate outlet connection from S1

54

Partition between pressure areas S3 and S2

54 '

Partition between pressure areas S3 and S2, middle part

54 "

Partition between pressure areas S3 and S2, short parts

55

Partition between pressure areas S2 and S1

55 '

Partition between pressure areas S2 and S1, middle part

55 "

Partition between pressure areas S2 and S1, short parts

56

Water-side, zigzag-shaped partition

Claims (10)

1. Preheater in steam power plant, with a steam jacket (1) accommodating at least two preheater stages, each with a heat exchange space (S1, S2, S3), turbine tapped steam of different pressure (P1, P2, P3) being conducted via steam inlet connection pieces (3, 4, 41, 42, 43) into each heat exchange space (S1, S2, S3), at least one partition (20, 54, 55) being arranged for subdividing the pressure regions of the heat exchange spaces (S1, S2, S3), and there being arranged in each heat exchange space (S1, S2, S3) of the at least two preheater stages tube bundles, through which water to be heated up flows and which are supported by supporting plates (19), characterized in that the at least one partition (20, 54, 55) is designed with a zigzag-shaped cross section, and it has in each case a high middle part (20'), which extends over the region of the supporting plates (19), and two short parts (20", 54", 55"), which run in bends to the middle part (20', 54', 55'), extend from the ends of the middle part (20', 54', 55') as far as the steam jacket (1) and are welded to the latter, and the at least one partition (20, 54, 55), by virtue of its zigzag shape, is flexible, in that it yields to the pressure force between a heat exchange space of higher pressure and a heat exchange space of low pressure, is displaced and comes into contact with the supporting plates (19), the supporting plates (19) coming into contact with the steam jacket (1) and transmitting the pressure force to the latter.
2. Preheater according to Claim 1, characterized in that, for the purpose of thermal insulation, the at least one partition (20, 54, 55) is of double-walled design, in that it has in each case two walls which are arranged parallel at least over the region of the high middle part (20', 54', 55') and are separated from one another by an interspace, and the two walls are in each case of thin design.
3. Preheater according to Claim 2, characterized in that intermediate plates (30) are arranged between the parallel walls of the at least one partition (20, 54, 55).
4. Preheater according to Claim 3, characterized in that the supporting plates (19) have first wings (19'), which in each case extend towards a partition (20, 54, 55), and further wings (19"), which in each case extend towards the steam jacket (1).
5. Preheater according to Claim 4, characterized in that the supporting plates (19) are clamped together by means of tie rods with sleeves (18).
6. Preheater according to Claim 5, characterized in that the supporting plates (19) are supported on angles and rails (21) in the lower region of the preheater.
7. Preheater according to Claim 6, characterized in that the steam jacket (1) has a first cascade inlet connection piece (6) which leads condensate out of an external higher-stage preheater into the preheater.
8. Preheater according to Claim 7, characterized in that the steam jacket (1) has further cascade inlet connection pieces (5, 51) which lead condensate from a heat exchange space of higher pressure into a heat exchange space of lower pressure.
9. Preheater according to one of the preceding claims, characterized in that the preheater has a subcooler in each of the individual heat exchange spaces.
10. Preheater according to one of the preceding claims, characterized in that the preheater has three preheater stages, each with a heat exchange space (S1, S2, S3), in which two partitions (54, 55) for subdividing the pressure regions of the heat exchange spaces (S1, S2, S3) are arranged.

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