WO2006073346A1

WO2006073346A1 - A heat exchanger device

Info

Publication number: WO2006073346A1
Application number: PCT/SE2005/001985
Authority: WO
Inventors: Ralf Erik Blomgren
Original assignee: Alfa Laval Corporate Ab
Priority date: 2005-01-07
Filing date: 2005-12-20
Publication date: 2006-07-13
Also published as: KR20070094764A; EP1834152A4; SE528143C2; SE0500034L; CN101099072A; EP1834152A1; JP5832922B2; SE0500034D0; JP2008527297A; CN100575852C; JP2012093085A; KR101170583B1

Abstract

A heat exchanger device comprises a number of plate heat ex¬ changers (1 ), which include at least a first plate heat exchanger. Each plate heat exchanger comprises a frame plate (2), a pressure plate (3) and a plurality of heat exchangers plates which are ar¬ ranged in such a way that first plate interspaces (6) for condensa¬ tion of steam and second plate interspaces (7) for evaporation of liquid are formed. Each plate heat exchanger comprises a steam inlet channel (21 ), which communicates with the first plate inter¬ spaces, a condensate outlet channel, which communicates with the first plate interspaces, a liquid inlet channel (23), which communi¬ cates with the second plate interspaces, and a steam outlet channel (24), which communicates with the second plate interspaces. A housing (30) adjoins the frame plate and forms a first outlet cham¬ ber (31 ) which is arranged to receive the formed steam from the steam outlet channel. A first liquid separator (32) is provided in the housing and adapted to catch liquid from the steam flowing through the first outlet chamber.

Description

A heat exchanger device

THE FIELD OF THE INVENTION

The present invention refers to a heat exchanger device comprising a number of plate heat exchangers, which includes at least a first plate heat exchanger and which each comprises a frame plate, a pressure plate and a plurality of heat exchanger plates provided adjacent to each other to a plate package between the frame plate and the pressure plate in such a way that first plate interspaces for condensation of steam and second plate interspaces for evaporation of liquid are formed, wherein each plate heat exchanger comprises a steam inlet channel, which extends through the frame plate and substantially all heat exchanger plates and which communicates with the first plate interspaces, at least a condensate outlet channel, which extends through substantially all heat exchanger plates and communicates with the first plate interspaces, a liquid inlet channel, which extends through substantially all heat ex- changer plates and communicates with the second plate interspaces, and a steam outlet channel, which extends through the frame plate and substantially all heat exchanger plates and which communicates with the second plate interspaces. The invention also refers to a heat exchanger device according to claim 33 and a heat exchanger device according to claim 34.

THE BACKGROUND OF THE INVENTION AND PRIOR ART

Equipment for desalination of seawater is manufactured since sev- eral years, where packages with heat exchanger plates form the main components in the process. The plates have no ports for steam, but instead the plate heat exchangers are positioned in containers, and the space outside the plates is used as one or more flow paths for the steam, depending on the type of process. The container is frequently a cylindrical pressure vessel. SE-B-464 938 discloses such a desalination plant having a plate package provided in a cylindrical container. In a large plant including several plate packages, these may be positioned in the longitudinal direction of the cylinder. To a certain extent, the container is limiting for how large a plant can be made if not several containers should be permitted to be included in the plant.

US-A-4, 511 ,436 discloses another large desalination plant having a process line with several successive heat exchanger stages, which each comprises a plate package of heat exchanger plates that are welded to each other in pairs and provided in a such a way in the plate package that first plate interspaces for condensation and second plate interspaces for evaporation are formed. The process line is provided in a closed pressure container shown schematically, see also US-A-4, 514, 260.

At least for smaller or medium sized plants, the costs for the container are a large part of the total costs for the plant. The manufacturing and the mounting of the container are both complex and time- consuming. In addition, maintenance of the plant is difficult, for instance since individual plate packages and heat exchanger plates are difficult to reach in the container.

SUMMARY OF THE INVENTION

The object of the invention is to provide a heat exchanger device which has a simple construction and which permits maintenance and cleaning in an easy manner. Further object of the invention is to provide such a heat exchanger device which has a construction permitting that the device can be made large and include a large number of heat exchanger stages.

This object is achieved by the heat exchanger device initially defined, which is characterized in that the device comprises a hous- ing, which adjoins the frame plate and forms a first outlet chamber which is arranged to receive the formed steam from the steam outlet channel, and a first liquid separator, which is provided in the housing and adapted to catch liquid from the steam flowing through the first outlet chamber.

By means of such a housing, the heat exchanger device may be designed without any container enclosing the plate heat exchanger or the plate heat exchangers. Suitable conditions for the manufac- turing and the mounting of the heat exchanger device to low costs are thus created. The proposed design also permits an easy manufacturing of the heat exchanger device in various sizes, i.e. with a substantially arbitrarily number of plate heat exchangers. Each plate heat exchanger and the individual heat exchanger plates are thus easily accessible for inspection, maintenance and cleaning. The heat exchanger device is designed for evaporation and condensation, respectively, of two media and is thus suitable for desalination of seawater or for other evaporating or distilling applications.

According to an embodiment of the invention, the device comprises a first inlet chamber which is arranged to convey steam into the steam inlet channel. According to a first alternative, the first inlet chamber may be housed in a separate casing which is separated from the housing and which adjoins the frame plate. According to a second alternative, also the first inlet chamber may be housed in the housing. The first inlet chamber and the first outlet chamber are then separated by means of an inner wall in the housing.

According to a further embodiment of the invention, said number of plate heat exchangers is at least one. The heat exchanger device according to the invention may thus advantageously be realised by a plate heat exchanger and a housing that is connected to and adjoins the frame plate of the plate heat exchanger. In such a way, a simple and compact device is achieved. Advantageously, the device may comprise a compressor, which is arranged to feed the formed steam from the first outlet chamber to the first inlet chamber and the steam inlet channel.

According to a further embodiment of the invention, said number of plate heat exchangers is at least two, comprising two such first plate heat exchangers, which are parallel to each other in such a way that the first outlet chamber adjoins the frame plate of both the first plate heat exchangers and is connected to the steam outlet channel of both the first plate heat exchangers, wherein the first Nq- uid separator will catch liquid from the steam that comes from both the first plate heat exchangers. This embodiment operates in principal as the previously defined embodiment, but with the difference that the steam at the same time is conveyed into two plate heat exchangers and that the steam generated in the plate heat exchang- ers is discharged to a common outlet chamber for further use in a subsequent stage or as inlet steam to the two parallel plate heat exchangers.

According to a further embodiment, the first inlet chamber is con- nected to the steam inlet channel of both the first plate heat exchangers. Consequently, also the inlet chamber may be common for the two plate heat exchangers. Advantageously, the housing may have two opposite substantially parallel side walls, wherein the plate heat exchangers extend outwardly from a respective one of said side walls in substantially opposite directions. In such a way, an advantageous layout permitting easy mounting and good accessibility is achieved.

According to a further embodiment of the invention, said number of plate heat exchangers is at least two, wherein the device comprises a first a stage with at least said first plate heat exchanger and a final stage with at least one final such plate heat exchanger. In such a way, a device where the process may take place in several stages or so called effects is achieved. Also this device, comprising a common housing and several plate heat exchangers, may be manufactured in an easy manner and offers a good accessibility for maintenance and cleaning. According to a further embodiment of the invention, the housing adjoins the frame plate of the final plate heat exchanger and forms a final outlet chamber, which is arranged to receive the formed steam from the steam outlet channel of the final plate heat ex- changer. Furthermore, the device may comprise a final inlet chamber, which is arranged to convey steam into the steam inlet channel of the final plate heat exchanger. Advantageously, also the final inlet chamber is housed in the housing.

According to a further embodiment of the invention, the first outlet chamber is connected to the final inlet chamber for permitting transport of the steam formed in the first plate heat exchanger to the steam inlet channel of the final plate heat exchanger. Consequently, a heat exchanger device having several stages or effects is achieved in an easy manner. According to an alternative, the device may comprise a, preferably mechanical, compressor which is arranged to feed the formed steam from the final outlet chamber to the first inlet chamber. Furthermore, the device may comprise a final liquid separator, which is provided in the final outlet chamber and adapted to catch liquid from the steam flowing through the final outlet chamber.

According to an alternative embodiment of the invention, the housing has at least one side wall, wherein the first plate heat ex- changer and the second plate heat exchanger extend outwardly from the side wall in substantially the same direction.

According to another alternative embodiment of the invention, the housing has two opposite, substantially parallel side walls, wherein the first plate heat exchanger and the second plate heat exchanger extend outwardly from a respective one of said side walls in substantially opposite directions.

According to a further embodiment of the invention, the device comprises at least one intermediate stage with at least one intermediate plate heat exchanger, wherein an intermediate inlet chamber is arranged to convey steam into the steam inlet channel of the intermediate plate heat exchanger, an intermediate outlet chamber is arranged to receive steam from the steam outlet channel of the intermediate plate heat exchanger, and the intermediate outlet chamber communicates with the final inlet chamber via an interme- diate liquid separator. The device may advantageously comprise one, two, three, four, five, six or more successive intermediate stages, which each comprises at least one intermediate such plate heat exchanger. By means of the inventive design it is possible in a very easy manner to manufacture and mount very large heat ex- changer plants having a very large number of stages or effects, which all are connected to the common housing.

According to a further embodiment of the invention, the device comprises a condenser, which is arranged downstream the final outlet chamber for condensation of the steam that is fed to the final outlet chamber. Advantageously, the device may comprise a thermo compressor, which is adapted to be operated through the supply of external steam at high pressure and which is adapted to receive at least a part of the steam that is fed to the final or one of the final outlet chambers for mixing of this part and the external steam, wherein the mixture forms the steam that is supplied to the first inlet chamber.

According to a further embodiment of the invention, each stage comprises at least two such plate heat exchangers. In such a way, the physical dimensions of the plant may be kept at a relatively low level. Advantageously, the housing may have two opposite substantially parallel side walls, wherein the plate heat exchangers in each stage extend outwardly from a respective one of said side walls in substantially opposite directions. The housing may then have an elongated shape permitting that the plate heat exchangers extend substantially perpendicularly outwardly from the two longitudinal substantially parallel side walls of the centrally positioned housing.

According to a further embodiment of the invention, substantially each heat exchanger plate comprises a first porthole for forming the first steam inlet channel, at least a second porthole for forming the condensate outlet channel, a third porthole for forming the liquid inlet channel and at least a fourth porthole for forming the steam outlet channel. Furthermore, substantially each heat exchanger plate may comprise a central heat transfer area, wherein the first porthole is located above the central heat transfer area and the second porthole is located below the central heat transfer area. Advantageously, the third porthole may be located in the proximity of an upper end of the central heat transfer area, wherein the heat ex- changer plates are designed in such a way that a distribution space is formed in each of the second plate interspaces, which extends transversely to the heat exchanger plates along the upper end of the central heat transfer area and is adapted to distribute the liquid over the whole central heat transfer area.

According to a further embodiment of the invention, each of the plate heat exchangers comprises at least one elongated support member which extends substantially perpendicularly from the frame plate, wherein the heat exchanger plates and the pressure plate are mounted in the support member. Furthermore, each of the plate heat exchangers may comprise a number of tie bolts which extend between the frame plate and the pressure plate and which are arranged to permit compressing of the heat exchanger plates.

The object is also achieved by the initially defined heat exchanger device, which is characterized in that it comprises a housing, which adjoins the frame plate of each of the plate heat exchangers, wherein the housing forms a first outlet chamber, which is arranged to receive the formed steam from the steam outlet channel of the first plate heat exchanger, and a final outlet chamber, which is arranged to receive the formed steam from the steam outlet channel of the final plate heat exchanger.

Furthermore, the object is achieved by the heat exchanger device initially defined, which is characterized in that it comprises a housing, which adjoins the frame plate of each of the plate heat exchangers and form a first inlet chamber, which is arranged to con- vey steam into the steam inlet channel of the plate heat exchanger in the first stage, a first outlet chamber, which is arranged to receive steam from the steam outlet channel of the plate heat exchangers in the first stage, a final inlet chamber, which is arranged to convey steam into the steam inlet channel of the plate heat exchangers in the second stage, and a final outlet chamber, which is arranged to receive steam from the steam outlet channel of the plate heat exchangers in the second stage.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is now to be explained more closely by means of embodiments described by way of example and with reference to the drawings attached hereto.

Fig. 1 discloses schematically a view from above of a heat exchanger device according to a first embodiment of the invention.

Fig. 2 discloses schematically a partly sectional side view of the heat exchanger device along the line H-Il in Fig. 1.

Fig. 3 discloses a sectional view along the line Ill-Ill in Fig. 2. Fig. 4 discloses a sectional view along the line IV-IV in Fig. 2. Fig. 5 discloses a plan view of a first heat exchanger plate of the heat exchanger device in Fig. 1. Fig. 6 discloses a plan view of a second heat exchanger plate of the heat exchanger device in Fig. 1.

Fig. 7 discloses schematically a view from above of a heat exchanger device according to a second embodiment of the invention. Fig. 8 discloses schematically a partly sectional side view of the heat exchanger device along the line VIII-VIII in Fig. 7.

Fig. 9 discloses a sectional view along the line IX-IX in Fig. 8 Fig. 10 discloses a plan view of a first heat exchanger plate of the heat exchanger device in Fig. 7.

Fig. 11 discloses a plan view of a second heat exchanger plate of the heat exchanger device in Fig. 7. Fig. 12 discloses schematically a view from above of a heat exchanger device according to a third embodiment of the invention.

Fig. 13 discloses schematically a partly sectional side view of the heat exchanger device in Fig. 12.

Fig. 14 discloses schematically a view from above of a heat exchanger device according to a fourth embodiment of the invention.

Fig. 15 discloses a sectional view along the line XV-XV in Fig. 14.

Fig. 16 discloses a sectional view along the line XVI-XVI in Fig. 14.

Fig. 17 discloses schematically a sectional view similar to the one in Fig. 16 of a heat exchanger device according to a fifth embodiment of the invention.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION

Figs. 1 - 6 disclose a heat exchanger device according to a first embodiment. The disclosed embodiments are in the first place intended for desalination of a salt-containing liquid, so called brine, but they are not limited to this application but can be used for distillation or evaporation in other applications. The heat exchanger device comprises a plate heat exchanger 1 , which comprises a frame plate 2, a pressure plate 3 and a plurality of heat exchanger plates 4, 5 arranged beside each other to a plate package, see Figs. 5, 6. The heat exchanger plates 4 and 5 are arranged adjacent to each other in an alternating order in the plate heat ex- changer 1 between the frame plate 2 and the pressure plate 3 in such a way that first plate interspaces 6 for condensation of steam and second plate interspaces 7 for evaporation of liquid are formed, see also Fig. 8 where a small number of the total number of heat exchanger plates 4, 5 and plate interspaces 6, 7 are schematically indicated. Each heat exchanger plate 4, 5 and the frame plate 2 comprise two first portholes 11 for forming a steam inlet channel 21 , a second porthole 12 for forming a condensate outlet channel 22, a third porthole 13 for forming a liquid inlet channel 23 and two fourth port- holes 14 for forming a steam outlet channel 24. Each heat exchanger plate 4, 5 also comprises a central heat transfer area 15. The first portholes 11 are located above the central heat transfer area 15 when the heat exchanger plates 4, 5 are located in a normal position of use in the plate heat exchanger 1. The second port- hole 12 is then located below the central heat transfer area 15. The third porthole 13 is located in the proximity of an upper edge of the central heat transfer area 15 whereas the fourth portholes 14 are located below the central heat transfer area 15 in the normal position of use. The pressure plate 3 is in the disclosed embodiments continuous, i.e. the pressure plate 3 lacks portholes.

The steam inlet channel 21 , which extends through the frame plate 2 and substantially all heat exchanger plates 4, 5, communicates with the first plate interspaces 6. The condensate outlet channel 22, which extends through the frame plate 2 and substantially all heat exchanger plates 4, 5, communicates with the first plate interspaces 6. The liquid inlet channel 23, which extends through the frame plate 2 and substantially all heat exchanger plates 4, 5, communicates with the second plate interspaces 7. The steam outlet channel 24, which extends through the frame plate 2 and substantially all heat exchanger plates 4, 5, communicates with the second plate interspaces 7.

The heat exchanger plates 4, 5 are designed in such a way that a distribution space 16 is formed in each of the second plate interspaces 7. The distribution space 16 extends transversely to the heat exchanger plates 4, 5 along the upper end of the central heat transfer area 15 and is adapted to distribute the liquid from the liquid inlet channel 23 over the whole central heat transfer area 15.

The plate heat exchanger 1 comprises three elongated support members 17, 18 in which the heat exchanger plates 4, 5 and the pressure plate 3 are mounted. The support members 17, 18 are designed as beams extending substantially horizontally from the frame plate 2 in the normal position of use. Furthermore, the plate heat exchanger 1 comprises a number of tie bolts 19, see Fig. 7, which extend between the frame plate 2 and the pressure plate 3 and which are arranged to permit compression of the heat exchanger plates 4, 5. In the embodiments disclosed, gaskets 21 are provided between the heat exchanger plates 4, 5 for sealing the first plate interspaces 6 relatively the surroundings, the liquid inlet channel 23 and the steam outlet channel 24 and for sealing of the second plate interspaces 7 relatively the surroundings, the steam inlet channel 21 and the condensate outlet channel 22. It is also possible to utilize a permanent connection of adjacent heat exchanger plates 4, 5, for instance by welding in pairs, gluing in pairs, completely welded plate packages or completely glued plate packages.

The heat exchanger device also comprises a housing 30, which is located beside the heat exchanger plates 4, 5 and which more specifically adjoins the frame plate 2. In the first embodiment, the housing 30 forms a first outlet chamber 31 which is arranged to receive the formed steam from the steam outlet channel 24. The heat exchanger device also comprises a first liquid separator 32, which is provided in the first outlet channel 31 in the housing 30 and which is adapted to catch liquid from the steam flowing through the first outlet chamber 31. Furthermore, the heat exchanger device comprises a first inlet chamber 33 which is arranged to convey steam into the steam inlet channel 21. According to the first embodiment, the first inlet chamber 33 is housed in a separate casing 34 which also adjoins the frame plate 2 but is separated from the housing 30.

The heat exchanger device also comprises a mechanical compressor 40, in form of a pump or fan member. The compressor 40 is provided between the first liquid separator 32 and the first inlet chamber 33. The compressor 40 is thus arranged to feed the formed steam from the first outlet chamber 31 through the first liquid separator 32 to the first inlet chamber 33 and the steam inlet channel 21 via a connection channel 39. A salt-containing liquid, so called brine, is supplied to the liquid inlet channel 23 via a liquid conduit 41. The formed condensate is discharged from the condensate outlet channel 22 via a condensate conduit 42. The salt- containing liquid which is separated by means of the first liquid separator 32 is collected in a bottom space 43 and discharged by means of a conduit 44.

Figs. 7 - 11 disclose a heat exchanger device according to a sec- ond embodiment. It is to be noted that for elements and components having a corresponding function the same reference signs have been used in all embodiments. The second embodiment differs from the first one in that the first inlet chamber 33 is housed in the housing 30, i.e. in the same housing 30 as the first outlet cham- ber 31. The first inlet chamber 33 and the first outlet chamber 33 are separated from each other by means of an inner wall 46 in the housing 30.

Furthermore, the heat exchanger plates 4, 5 are somewhat differ- ently designed in the second embodiment. The heat exchanger plates 4, 5 comprise a first porthole 11 for forming the steam inlet channel 21 and a fourth porthole 14 for forming the steam outlet channel 24. Furthermore, each heat exchanger plate 4, 5 comprises two second portholes 12 for forming the condensate outlet channel 22.

Also the second embodiment may include a mechanical compressor of the type disclosed in Figs. 1 , 2 and 4.

Figs. 12 and 13 disclose schematically a heat exchanger device according to a third embodiment. This heat exchanger device comprises two plate heat exchangers 1 , wherein each plate heat exchanger 1 has substantially the same construction as the plate heat exchanger 1 in the second embodiment. For the sake of simplicity, certain details, which are disclosed in Figs. 7 - 11 , have been dispensed with in Figs. 12 and 13. The two plate heat exchangers 1 are provided in series with each other in such a way that they form a first stage with at least a first plate heat exchanger 1 and a final stage with at least a final plate heat exchanger 1. The third embodiment comprises a common housing 30 for both the plate heat exchangers 1 or the stages. The housing 30 adjoins the frame plate 2 of both the plate heat exchangers 1 and forms a first outlet chamber 31 and a final outlet chamber 31 , which are arranged to receive the formed steam from the steam outlet channel 24 of the respective plate heat exchanger 1. A liquid separator 32 is provided in each of the outlet chambers 31 for catching liquid from the steam flowing through the respective outlet chamber 31. The housing 30 also forms a first inlet chamber 33 and a final inlet chamber 33, which are arranged to convey steam into the steam inlet channel 21 of the respective plate heat exchanger 1.

The first outlet chamber 31 is connected to the final inlet chamber 33 via a connection channel 39 for permitting transport of the steam formed in the first plate heat exchanger 1 to the steam inlet channel 21 of the final plate heat exchanger 1 by means of a compressor 40 which is arranged to feed the formed steam from the final outlet chamber 31 to the first inlet chamber 33. In the third embodiment, the housing 30 has two opposite, substantially parallel side walls 50 which according to an alternative may be formed by the frame plate 2 of the respective plate heat exchanger 1. As appears from Figs. 12 and 13, the first plate heat exchanger 1 and the second plate heat exchanger 1 extend outwardly from a respective one of these side walls 50 in substantially opposite directions. Inner walls 46 are provided in the housing 30 for separating the different chambers 31 , 33 from each other.

Figs. 14 - 16 disclose schematically a heat exchanger device according to a fourth embodiment. This heat exchanger device comprises ten plate heat exchangers 1 , wherein each plate heat exchanger 1 has substantially the same construction as the plate heat exchanger 1 in the second and third embodiments. For the sake of simplicity, certain details, which are disclosed in Figs. 7 - 11 , have been dispensed with also in Figs. 14 - 16. The heat exchanger device according to the fourth embodiment also comprises a common housing 30 for all plate heat exchangers 1. The housing 30 has two opposite substantially parallel longitudinal side walls 50, wherein the plate heat exchangers 1 extend out- wardly from these side walls 50 in substantially opposite directions. The plate heat exchangers 1 are arranged in pairs, wherein each pair of plate heat exchangers 1 forms a stage in the process, or a so called effect. The plate heat exchangers 1 in each stage are arranged opposite to each other on opposite sides of the centrally lo- cated, elongated housing 30 in such a way that they extend outwardly from a respective one of the longitudinal side walls 50 in substantially opposite directions. The plate heat exchangers 1 in each stage are thus parallel to each other and have a common outlet chamber 31 and a common inlet chamber 33, i.e. the first outlet chamber 31 adjoins the frame plate 2 of both the plate heat exchangers 1 in the first stage and is connected to the steam outlet channel 24 of the both plate heat exchangers 1 in the first stage. In the same way, the first inlet chamber 32 adjoins the frame plate 2 of both the plate heat exchangers 1 in the first stage and are con- nected to the steam inlet channel 21 of the both plate heat exchangers 1 in the first stage. Between each stage there is a liquid separator 32, which thus functions as a border between the outlet chamber 31 of one stage and the inlet chamber 33 of the subsequent stage, see Fig. 16. The inlet chamber 33 in one stage is separated from the outlet chamber 31 in the same stage by means of a sloping inner wall 46.

The heat exchanger device according to the fourth embodiment comprises a condenser 55, which is provided downstream the final outlet chamber 31 for condensation of the steam fed to the final outlet chamber 31. The condenser 55 comprises in the embodiment disclosed two parallel plate heat exchangers which extend outwardly from the housing 30 in opposite directions in a corresponding manner as the plate heat exchangers 1. The condenser 55 is adapted to provide a final condensation of the steam fed to the final outlet chamber 31. The condenser 55 is supplied with an external cooling medium. It is to be noted that the condenser 55 may be de- signed in another way than as disclosed in Fig. 14. The heat exchanger device according to the fourth embodiment also comprises a thermo compressor 60, which is adapted to be operated through the supply of external steam at a high pressure in a manner known per se. The external steam is supplied to the thermo compressor 60 via a supply conduit 61. The thermo compressor 60 supplies steam at a pressure and a temperature to the first inlet chamber 33 via a feed conduit 62. This pressure and this temperature corresponds to the pressure and the temperature in the first inlet chamber and in the first plate interspaces 6 in the plate heat exchanger 1 in the first stage, but is lower than the surrounding atmospheric pressure and the surrounding temperature, respectively. The pressure and the temperature then sink successively in the subsequent stages. A part of the steam fed from one or several of the final stages is re- turned to the thermo compressor 60 via a conduit 63. The thermo compressor 60 comprises a nozzle for recirculation of the returned steam to the feed conduit 62 by means of the external steam.

Fig. 17 illustrates a fifth embodiment which differs from the fourth embodiment in that each stage comprises four plate heat exchangers 1 , two on each side of the housing 30.

According to a sixth embodiment, which is a variant of the fourth or fifth embodiment, each stage may comprise a plate heat exchanger 1 , wherein all plate heat exchangers 1 extends outwardly from one and the same side wall 50 of the elongated housing 30 in substantially the same direction. For the rest, the fifth embodiment may be constructed in the same way as the fourth embodiment.

The invention is not limited to the embodiments disclosed but may be varied and modified within the scope of the following claims.

Claims

1. A heat exchanger device comprising a number of plate heat exchangers (1 ), which includes at least a first plate heat exchanger (1 ) and which each comprises a frame plate (2), a pressure plate (3) and a plurality of heat exchanger plates (4, 5) provided adjacent to each other to a plate package between the frame plate (2) and the pressure plate (3) in such a way that first plate interspaces (6) for condensation of steam and second plate interspaces (7) for evaporation of liquid are formed, wherein each plate heat exchanger (1 ) comprises a steam inlet channel (21 ), which extends through the frame plate (2) and substantially all heat exchanger plates (4, 5) and which communicates with the first plate interspaces (6), at least a condensate outlet channel (22), which extends through substantially all heat exchanger plates (4, 5) and communicates with the first plate interspaces (6), a liquid inlet channel (23), which extends through substantially all heat exchanger plates (4, 5) and communicates with the second plate interspaces (7), and a steam outlet channel (24), which extends through the frame plate (2) and substantially all heat exchanger plates (4, 5) and which communicates with the second plate interspaces (7), characterized in that the device comprises a housing, which adjoins the frame plate and forms a first outlet chamber which is arranged to receive the formed steam from the steam outlet channel, and a first liquid separator, which is provided in the housing and adapted to catch liquid from the steam flowing through the first outlet chamber.

2. A device according to claim 1 , characterized in that the device comprises a first inlet chamber (33) which is arranged to convey steam into the steam inlet channel (21 ).

3. A device according to claim 2, characterized in that the first inlet chamber (33) is housed in a separate casing (34) which is separated from the housing (30) and which adjoins the frame plate (2).

4. A device according to claim 2, characterized in that the first inlet chamber (33) is housed in the housing (30).

5. A device according to claim 4, characterized in that the first inlet chamber (33) and the first outlet chamber (31 ) are separated by means of an inner wall (46) in the housing (30).

6. A device according to any one of the preceding claims, characterized in that said number of plate heat exchangers (1 ) is at least one.

7. A device according to claims 2 and 6, characterized in that the device comprises a compressor (40), which is arranged to feed the formed steam from the first outlet chamber (31 ) to the first inlet chamber (33) and the steam inlet channel (21 ).

8. A device according to any one of the preceding claims, characterized in that said number of plate heat exchangers (1 ) is at least two, comprising two such first plate heat exchangers (1 ), which are parallel to each other in such a way that the first outlet chamber (31 ) adjoins the frame plate (2) of both the first plate heat exchangers (1 ) and is connected to the steam outlet channel (24) of both the first plate heat exchangers (1 ), wherein the first liquid separator (32) will catch liquid from the steam that comes from both the first plate heat exchangers (1 ).

9. A device according to claims 2 and 8, characterized in that the first inlet chamber (33) is connected to the steam inlet channel (24) of both the first plate heat exchangers (1 ).

10. A device according to any one of claims 8 and 9, character- ized in that the housing (30) has two opposite substantially parallel side walls (50), wherein the plate heat exchangers (1 ) extend out- wardly from a respective one of said side walls (50) in substantially opposite directions.

11. A device according to any one of claims 1 to 5, characterized in_. that said number of plate heat exchangers (1 ) is at least two, wherein the device comprises a first stage with at least said first plate heat exchanger (1 ) and a final stage with at least one final such plate heat exchanger (1 ).

12. A device according to claim 11 , characterized in that the housing (30) adjoins the frame plate (2) of the final plate heat exchanger (1 ) and forms a final outlet chamber (31 ), which is arranged to receive the formed steam from the steam outlet channel (24) of the final plate heat exchanger (1 ).

13. A device according to claims 2 and 12, characterized in that the device comprises a final inlet chamber (33), which is arranged to convey steam into the steam inlet channel (21 ) of the final plate heat exchanger (1 ).

14. A device according to claim 13, characterized in that the final inlet chamber (33) is housed in the housing (30).

15. A device according to any one of claims 13 and 14, charac- terized in that the first outlet chamber (31 ) is connected to the final inlet chamber (33) for permitting transport of the steam formed in the first plate heat exchanger (1 ) to the steam inlet channel (21 ) of the final plate heat exchanger (1 ).

16. A device according to any one of claims 13 to 15, characterized in that the device comprises a compressor (40) which is arranged to feed the formed steam from the final outlet chamber (31 ) to the first inlet chamber (33).

17. A device according to any one of claims 12 to 16, characterized in that the device comprises a final liquid separator (32), which is provided in the final outlet chamber (31 ) and adapted to catch liquid from the steam flowing through the final outlet chamber (31).

18. A device according to any one of claims 11 to 17, character- ized in that the housing (30) has at least one side wall (50), wherein the first plate heat exchanger (1 ) and the second plate heat exchanger (1) extend outwardly from the side wall (50) in substantially the same direction.

19. A device according to any one of claims 11 to 17, characterized in that the housing has two opposite, substantially parallel side walls (50), wherein the first plate heat exchanger (1) and the second plate heat exchanger (1) extend outwardly from a respective one of said side walls (50) in substantially opposite directions.

20. A device according to any one of claims 11 to 20, characterized in that the device comprises at least one intermediate stage with at least one intermediate plate heat exchanger (1), wherein an intermediate inlet chamber (33) is arranged to convey steam into the steam inlet channel (21 ) of the intermediate plate heat exchanger (1), an intermediate outlet chamber (31 ) which is arranged to receive steam from the steam outlet channel (24) of the intermediate plate heat exchanger (1), and the intermediate outlet chamber (31 ) communicates with the final inlet chamber (33) via an intermediate liquid separator (32).

21. A device according to claim 20, characterized in that the device comprises at least two successive intermediate stages which each comprises at least one such intermediate plate heat exchanger (1).

22. A device according to claim 20, characterized in that the device comprises at least three successive intermediate stages which each comprises at least one such intermediate plate heat exchanger (1 ).

23. A device according to any one of claims 1 1 to 22, characterized in that the device comprises a condenser (55), which is arranged downstream the final outlet chamber (31 ) for condensation of the steam that is fed to the final outlet chamber (31 ).

24. A device according to claim 23, characterized in that the device comprises a thermo compressor (60), which is adapted to be operated through the supply of external steam at high pressure and which is adapted to receive at least a part of the steam that is fed to the final outlet chamber (31 ) for mixing of this part and the external steam, wherein the mixture forms the steam that is supplied to the first inlet chamber (33).

25. A device according to claims 22 and 23, characterized in that the device comprises a thermo compressor (60), which is adapted to be operated through the supply of external steam at high pressure and which is adapted to receive at least a part of the steam that is fed to one of the final outlet chambers (31 ) for mixing of this part and the external steam, wherein the mixture forms the steam that is supplied to the first inlet chamber (33).

26. A device according to any one of claims 11 to 25, characterized in that each stage comprises at least two such plate heat exchanger (1 ).

27. A device according to claim 26, characterized in that the housing (30) has two opposites substantially parallel side walls (50), wherein the plate heat exchangers (1 ) in each stage extend outwardly from a respective one of said side walls (50) in substan- tially opposite directions.

28. A device according to any one of the preceding claims, characterized in that substantially each heat exchanger plate comprises a first porthole (11 ) for forming the steam inlet channel (21 ), at least a second porthole (12) for forming the condensate outlet channel (22), a third porthole (13) for forming the liquid inlet channel (23), and at least a fourth porthole (14) for forming the steam outlet channel (24).

29. A device according to claim 28, characterized in that substan- tially each heat exchanger plate (4, 5) comprises a central heat transfer area (15), wherein the first porthole (11 ) is located above the central heat transfer area (15) and the fourth porthole (14) is located below the central heat transfer area (15).

30. A device according to claim 29, characterized in that the third porthole is located in the proximity of an upper end of the central heat transfer area, wherein the heat exchanger plates are designed in such a way that a distribution space (16) is formed in each of the second plate interspaces (7), which extends transversely to the heat exchanger plates (4, 5) along the upper end of the central heat transfer area (15) and is adapted to distribute the liquid over the whole central heat transfer area (15).

31. A device according to anyone of the preceding claims, char- acterized in that each of the plate heat exchangers (1 ) comprises at least one elongated support member (17, 18) which extends substantially perpendicularly from the frame plate (2), wherein the heat exchanger plates (4, 5) and the pressure plate (3) are mounted in the support member (17, 18).

32. A device according to anyone of the preceding claims, characterized in that each of the plate heat exchangers (1) comprises a number of tie bolts (19) which extend between the frame plate (2) and the pressure plate (3) and which are arranged to permit com- pressing of the heat exchanger plates (4, 5).

33. A heat exchanger device comprising at least a first plate heat exchanger (1 ) and a final plate heat exchanger (1 ), wherein each of the plate heat exchangers (1 ) comprises a frame plate (2), a pres- sure plate (3) and a number of heat exchanger plates (4, 5) which are provided adjacent to each other to a plate package between the frame plate (2) and the pressure plate (3) in such a way that first plate interspaces (6) for condensation of steam and second plate interspaces (7) for evaporation of liquid are formed, wherein substantially each heat exchanger plate (4, 5) comprises a steam inlet channel (21 ), which extends through the frame plate (2) and substantially all heat exchanger plates (4, 5) and which communicates with the first plate interspaces (6), a condensate outlet channel (22), which extends through substantially all heat exchanger plates (4, 5) and communicates with the first plate interspaces (6), a liquid inlet channel (23), which extends through substantially all heat exchanger plates (4, 5) and communicates with the second plate interspaces (7), and a steam outlet channel (24), which extends through the frame plate (2) and substantially all heat exchanger plates (4, 5) and which communicates with the second plate interspaces (7), characterized in that the device comprises a housing (30), which adjoins the frame plate (2) of each of the plate heat exchangers (1 ), wherein the housing forms a first outlet chamber (31 ), which is arranged to receive the formed steam from the steam outlet channel (24) of the first plate heat exchanger (1 ), and a final outlet chamber (31 ), which is arranged to receive the formed steam from the steam outlet channel (24) of the final plate heat exchanger (1 ).

34. A heat exchanger device comprising at least a first stage with at least two plate heat exchangers (1 ) and a second stage with at least two plate heat exchangers (1 ), wherein each of the plate heat exchangers (1 ) comprises a frame plate (2), a pressure plate (3) and a plurality of heat exchanger plates (4, 5), which are provided adjacent to each other to a plate package between the frame plate (2) and the pressure plate (3) in such a way that first plate interspaces (6) for condensation of steam and second plate interspaces (7) for evaporation of liquid are formed, wherein substantially each heat exchanger plate (4, 5) comprises a steam inlet channel (21 ), which extends through the frame plate (2) and substantially all heat exchanger plates (4, 5) and which communicates with the first plate interspaces (6), at least a condensate outlet channel (22), which extends through substantially all heat exchanger plates (4, 5) and communicates with the first plate interspaces (6), a liquid inlet channel (23), which extends through substantially all heat exchanger plates (4, 5) and communicates with the second plate interspaces (7), and a steam outlet channel (24) which extends through the frame plate

(2) and substantially all heat exchanger plates (4, 5) and which communicates with the second plate interspaces (7), characterized in that the device comprises a housing (30), which adjoins the frame plate (2) of each of the plate heat exchanger (1 ) and form a first inlet chamber (33), which is arranged to convey steam into the steam inlet channel (21 ) of the plate heat exchangers (1 ) in the first stage, a first outlet chamber (31 ), which is arranged to receive steam from the steam outlet channel (24) of the plate heat exchangers (1 ) in the first stage, a final inlet chamber (33), which is arranged to convey steam into the steam inlet channel (21 ) of the plate heat exchangers (1 ) in the second stage, and a final outlet chamber (31 ), which is arranged to receive steam from the steam outlet channel (24) of the plate heat exchangers (1 ) in the second stage.