Plate heat exchanger and its use as a liquefied natural gas vaporizer

Abstract

A plate heat exchanger comprising a flexible structure (9) and / or a heating channel and / or an inner tube arranged inside an inlet connection tube (5a) of a first heat exchange medium between a first support end plate (7a) of a plate pack and a first end plate (3a) of an outer shell for improving the ability of the plate heat exchanger to withstand thermal stresses caused by temperature differences, for example when used in the heating of liquefied natural gas.

Description

TECHNICAL FIELD

[0001] The present invention relates to a plate heat exchanger and its use as a liquefied natural gas vaporizer. BACKGROUND

[0002] Due to natural gas being a clean fuel, the demand for natural gas (NG) is increasing globally. In places where a natural gas pipeline is not feasible or does not exist, liquefied natural gas is a way to move natural gas from the production site to the consumption site. Typically, it is cooled to liquid form (approximately -162°C) for the ease and safety of non-pressurized storage or transportation. At the consumption site, the liquefied natural gas (LNG) is turned back into gas by warming up to normal temperature and used as fuel.

[0003] Different kinds of LNG vaporizers are used to heat the LNG to normal temperature. Plate and shell -type heat exchangers are a type of heat exchangers that can be used to warm up the LNG back to gas. Plate and shell heat exchangers are welded heat exchangers that comprise a plate pack and an outer shell surrounding the plate pack. The outer shell comprises a first end plate, a second end plate and a shell connecting the end plates. Inlet and outlet connection pipes for the heat exchange medium flowing inside the plate pack are arranged through the end plates of the outer shell. Typically, the inlet connection pipe of the plate pack and the end plate of the outer shell and the support end plate of the plate pack are attached to each other tightly, for example welded to each other, in the plate and shell heat exchanger, and thus the thermal movement can not necessarily be made without stressing the material in each direction. When the heat exchanger structure is used as a LNG vaporizer, a huge temperature difference can cause stress on the material and its joints, and eventually the stress can break the structure of the heat exchanger. In particular, the temperature difference between the fluids at the point of the inlet connection pipe that is used to supply LNG into the vaporizer can be close to 200 degrees. SUMMARY

[0004] The object of the present invention is to reduce or even eliminate the above-mentioned problems occurring in the prior art.

[0005] The object of the present invention is to propose a plate heat exchanger structure that has an improved ability to withstand thermal stress caused by temperature differences, for example a huge temperature difference present in the heating of liquefied natural gas.

[0006] In particular, the object of the present invention is to propose a novel structure for the end part of a plate and shell heat exchanger that has an improved ability to withstand thermal stress caused by temperature differences, for example when used in the heating of liquefied natural gas.

[0007] In order to achieve the objects set out above, inter alia, the present application is characterised by what is set out in the characterising part of the independent claims enclosed.

[0008] Although not always specifically mentioned, the embodiments and advantages mentioned in the present text relate to both the plate heat exchanger and the use according to the present application, where applicable.

[0009] A typical plate heat exchanger according to the present application comprises

[0010] - a plate pack formed of heat exchanger plates having at least two openings and arranged one above the other, wherein the plate pack comprises a first end and a second end in the length direction of the plate pack, and the plate pack comprises a first support end plate arranged on the first end of the plate pack, a second support end plate (7b) arranged on the second end of the plate pack, and the flow passages for the first heat exchange medium on the inner side of the plate pack are formed by the openings of the heat exchanger plates arranged one above the other,

[0011] - an outer casing surrounding the plate pack, which outer casing comprises a first end plate, a second end plate, and a shell connecting said first end plate and said second end plate,

[0012] - an inlet connection pipe and an outlet connection pipe for the first heat exchange medium, which inlet connection pipe and outlet connection pipe are arranged through the end plates of the outer casing and are arranged in connection with the flow passages of the plate pack, and

[0013] - an inlet connection pipe and an outlet connection pipe for the second heat exchange medium, which inlet connection pipe and outlet connection pipe are arranged through the outer casing and are arranged in connection with the inner side of the outer casing, i.e. with the outer side of the plate pack, and

[0014] wherein the inlet connection pipe for the first heat exchange medium is arranged through the first end plate of the outer casing and in connection with the first support end plate of the plate pack, and the plate heat exchanger according to the present application further comprises

[0015] - a flexible structure arranged between the first support end plate of the plate pack and the first end plate of the outer casing, and / or

[0016] - a heating channel between the first support end plate of the plate pack and the first end plate of the outer casing, and / or at least partially around the inlet connection pipe for the first heat exchange medium, and / or

[0017] - an inner tube arranged on the inner side of the inlet connection pipe for the first heat exchange medium, and which inner tube is at least partially elongated on the inner side of the flow passages of the plate pack.

[0018] Typically, the plate heat exchanger according to the present application is used as a liquefied natural gas (LNG) vaporizer.

[0019] The plate heat exchanger according to the invention is structured to reduce the effects of thermal movement on the structure caused by the temperature difference between the first and second heat exchange media. According to the invention, the heat exchanger structure is improved by arranging at least one of the following structures in the plate heat exchanger.

[0020] - A flexible structure between the first support end plate of the plate assembly and the first end plate of the outer shell.

[0021] A heating channel is formed between the first support end plate of the plate assembly and the first end plate of the outer shell, and / or at least partially around the inlet connecting pipe of the first heat exchange medium.

[0022] - An internal tube on the inside of the inlet connection pipe for the first heat exchange medium, which extends at least partially inside the flow passage of the plate assembly.

[0023] The plate heat exchanger according to the invention may include one, two, or all three structures according to the invention arranged at the end of the plate heat exchanger, with the inlet connection pipe for the first heat exchange medium arranged through that end. The proposed improved structure provides easy and simple modification to the end plate structure of the plate heat exchanger. Attached Figure Description

[0024] The invention will be described in more detail with reference to the accompanying drawings, in which...

[0025] Figure 1 An exemplary embodiment of the structure of a plate-and-shell heat exchanger is shown.

[0026] Figure 2 The diagram illustrates the end structure of a plate heat exchanger according to an embodiment of the present invention, which includes a flexible structure between a support end plate of the plate assembly and an end plate of the outer casing.

[0027] Figure 3 The diagram illustrates the structure of an end portion of a plate heat exchanger according to an embodiment of the invention, comprising a heating channel between a support end plate of the plate assembly and an end plate of the outer casing.

[0028] Figure 4 The structure of the end of a plate heat exchanger according to an embodiment of the present invention is shown, which includes an inner tube disposed inside an inlet connection tube for a first heat exchange medium, and the inner tube extends at least partially inside the flow passage of the plate assembly. Detailed Implementation

[0029] Detailed description of the invention

[0030] A plate heat exchanger comprises an assembly of plates formed by heat exchange plates and an outer shell surrounding the assembly. The outer shell includes a first end plate, a second end plate, and a shell connecting the end plates. The plate assembly is typically mounted inside a cylindrical shell that functions as a pressure vessel. Plate heat exchangers are typically fully welded heat exchangers.

[0031] In the plate-shell heat exchanger according to the invention, the plate assembly is formed by heat exchanger plates arranged vertically to each other, wherein the plate assembly includes a first end and a second end along its length. The length direction of the plate assembly refers to the direction in which the stacked plate heat exchanger plates are stacked. In a typical embodiment according to the invention, the plate assembly further includes a first support end plate disposed on the first end of the plate assembly and a second support end plate disposed on the second end of the plate assembly. For example, the welded plate assembly consists of circular heat exchange plates. The plate assembly is composed of several pairs of heat exchange plates. Each pair of plates is formed by two heat exchange plates, which are attached together, preferably welded together, at least at their outer periphery. Each heat exchange plate has at least two openings for the flow of a first heat exchange medium. Adjacent pairs of plates are attached together by attaching the openings of two adjacent pairs to each other. Thus, the plate assembly is formed of heat exchange plates such that the heat exchange plates are alternately attached to each other at the openings and at the periphery of the plates. In the plate assembly, a first heat exchange medium can flow from one plate to another through openings on the inner side of the plate assembly of the heat exchanger, wherein there is a flow path formed by the openings of the heat exchange plates arranged vertically to each other. The inlet and outlet connecting pipes for the first heat exchange medium are arranged to connect to the flow path of the plate assembly, i.e., to the inner portion of the plate pair. Therefore, the primary circuit of the plate heat exchanger is formed between the inlet and outlet connecting pipes for the first heat exchange medium.

[0032] In the plate-and-shell heat exchanger according to the invention, the second heat exchange medium is arranged to flow inside the shell in the gaps between the plate pairs. The inlet and outlet connecting pipes for the second heat exchange medium are arranged to pass through the outer shell and connect to the inner side of the shell, i.e., to the outer side of the plate pairs of the plate assembly. In other words, the secondary circuit of the plate heat exchanger is formed inside the shell, in the gaps between the plate pairs, between the inlet and outlet connecting pipes of the second heat exchange medium. Typically, the primary and secondary circuits are separated from each other; that is, the first heat exchange medium flowing in the inner portion of the plate assembly cannot mix with the second heat exchange medium flowing in the shell (i.e., outside the plate assembly). Therefore, the first primary-side heat exchange medium flows in every other plate gap, and the second secondary-side heat exchange medium flows in every other plate gap of the plate heat exchanger.

[0033] According to the present invention, the longitudinal direction, i.e., the length direction, of the plate assembly is substantially the same as the longitudinal direction of the shell. According to a preferred embodiment of the present invention, the plate assembly is mainly cylindrical in shape, and the shell is a cylindrical shell, wherein the cylindrical plate assembly formed by heat exchange plates arranged vertically to each other is arranged inside the functional part of the cylindrical shell, such that the longitudinal direction of the plate assembly is the same as the longitudinal direction of the cylindrical shell.

[0034] According to embodiments of the invention, stress caused by thermal movement is prevented and / or eliminated by arranging a flexible structure between a first support end plate of the plate assembly and a first end plate of the outer housing. The first end plate, herein referring to the end plate of the outer housing, through which the inlet connection pipe of the first heat exchange medium is arranged, and the first support plate of the plate assembly is also arranged to connect to the inlet connection pipe of the first heat exchange medium. The flexible structure can be any suitable reversible flexible structure arranged between the first support end plate of the plate assembly and the first end plate of the outer housing, which has the ability to compensate for thermal movement. According to embodiments of the invention, the flexible structure includes a spring structure and / or a flexible plate structure that is bendable and / or movable without breaking. In embodiments of the invention, the flexible structure is arranged between the first support end plate of the plate assembly and the first end plate of the outer housing, through which the inlet connection pipe of the first heat exchange medium is arranged, and the size of the flexible structure is substantially the same as the size of the first support end plate of the plate assembly, i.e., it is arranged over the entire area between the first support end plate of the plate assembly and the first end plate of the outer housing.

[0035] Furthermore, in the plate heat exchanger structure according to the invention, the structure can be improved to resist thermal stress by combining the welded locations with the proposed additional flexible structure. According to an embodiment of the invention, the flexible structure is not tightly attached to the inlet connecting pipe of the first heat exchange medium and / or the end plate of the outer casing to allow movement of the flexible structure. Welded joints may exist between the flexible structure and the end plate of the inlet connecting pipe of the first heat exchange medium and / or the outer casing, but they are only welded at points that still allow reversible movement of the flexible structure. The heat exchanger according to the invention is a fully welded structure that also has an additional flexible structure.

[0036] According to another embodiment of the invention, in order to suppress and / or eliminate stress caused by thermal movement in the end structure of the plate heat exchanger, the area around the inlet pipe connection of the first heat exchange medium is heated. Large temperature differences at the connection point between the inlet pipe and the plate assembly structure can be reduced and / or prevented by arranging heating channels at least partially around the inlet pipe and / or between the first support end plate of the plate assembly and the first end plate of the outer housing. The first end plate herein refers to the end plate of the outer housing through which the inlet pipe of the first heat exchange medium is arranged, and the first support end plate of the plate assembly is a support plate of the plate assembly also arranged to connect with the inlet pipe of the first heat exchange medium. According to an embodiment of the invention, the plate heat exchanger includes heating channels formed in the first support end plate and / or the end plate of the outer housing through which the inlet pipe of the first heat exchange medium is arranged. According to an embodiment of the invention, heating channels are machined in the first support end plate of the plate assembly and / or the end plate of the outer housing, wherein warm fluid can flow and heat the area around the inlet pipe. The heating channel may be a groove or a corresponding structure, machined in the first support end plate of the plate assembly and / or machined into the end plate of the outer housing, and the heating channel provides a path for the heating fluid to flow. The structure and dimensions of the heating channel can vary.

[0037] In embodiments of the invention, the heating channel is also formed at least partially around the inlet connecting pipe of the first heat exchange medium. In embodiments of the invention, the heating channel is arranged to at least partially circulate the inlet connecting pipe, wherein heating fluid can flow from other edges of the end plate inside the heating channel arranged between the first support end plate of the plate assembly and the first end plate of the outer housing, at least partially circling the inlet connecting pipe, and exiting through the heating channel from another edge of the end plate. According to embodiments of the invention, the heating channel surrounding the inlet pipe can be simply fabricated by machining a large opening in at least a portion of the opening in the length direction of the end plate of the outer housing. The height and width of the heating channel surrounding the inlet connecting pipe can be varied. According to embodiments of the invention, the heating channel is arranged around the inlet connecting pipe along its entire length.

[0038] According to an embodiment of the invention, the heating channel is arranged to connect with the inside of the shell, wherein the heating fluid or medium flowing in the heating channel is the same as the fluid or medium flowing inside the shell. Therefore, guiding the heating fluid or medium inside the heating channel can be easily achieved. Furthermore, as mentioned above, the heating channel can be easily manufactured using standard parts of a plate heat exchanger. The heating channel construction according to the invention provides a simple embodiment for preventing damage caused by thermal stress.

[0039] According to another embodiment of the invention, in order to suppress and / or eliminate stress caused by thermal movement in the end structure of the plate heat exchanger, a first heat exchange medium to be heated on the inner side of the plate assembly is supplied to the plate assembly via an internal tube that distributes the first heat exchange medium deeper into the plate assembly. The plate heat exchanger according to an embodiment of the invention includes an internal tube disposed inside the inlet connection tube of the first heat exchange medium and extending at least partially inside the flow channel of the plate assembly. Therefore, the inlet connection tube for the first heat exchange medium is at least partially double-walled, which increases the temperature of the original single inlet connection tube since the gas between the structures acts as an insulator, and thus helps the structure withstand thermal stress and thermal movement. In a preferred embodiment of the invention, the inlet connection tube for the first heat exchange medium is double-walled for substantially the entire length of the inlet connection tube.

[0040] According to an embodiment of the invention, the end of the inner tube is attached to the inlet connection pipe of the first heat exchange medium. Typically, the inner tube is attached to the inlet connection pipe of the first heat exchange medium only from one end, and the inner tube extends outward from the end plate of the plate heat exchanger. According to an embodiment of the invention, when the inner tube is arranged inside the flow channel of the plate assembly, the first plate pair is blocked, thereby hindering the entry of the first heat exchange medium into the first plate pair. Therefore, according to an embodiment of the invention, the inner tube is attached to the plate assembly inside the flow channel of the plate assembly by a gasket or elastic structure arranged around the inner tube, the gasket or elastic structure simultaneously hindering flow to the inside of the plate assembly and attaching the inner tube to the plate assembly. Therefore, the inner tube structure according to the invention is a flexible structure that withstands thermal movement caused by large temperature differences. In an embodiment of the invention, viewed from the direction of the inlet pipe of the first heat exchange medium, for example, one to five of the first flow channels inside the plate assembly are closed by gaskets or corresponding structures arranged around the inner tube. The gaskets or corresponding structures hold the inner tube in its position and withstand thermal movement. This also suppresses damage caused by large temperature differences, because the first plates are not open to the first heat exchange medium, and therefore they act as an insulating layer in the direction to the end structure of the plate heat exchanger.

[0041] According to an embodiment of the invention, the inner tube includes an opening that forms a flow channel into a flow passage inside the plate assembly. Therefore, the inner tube can extend inside the flow channel and provide normal operation of the plate assembly.

[0042] According to a preferred embodiment of the invention, the plate heat exchanger is used as a liquefied natural gas (LNG) vaporizer or evaporator. In the LNG vaporizer according to the invention, the first heat exchange medium comprises LNG to be heated, and the second heat exchange medium may comprise water and / or ethylene glycol or any other suitable heating fluid. The temperature difference between the LNG being transported inside the plate assembly and the heating fluid inside the outer shell of the plate heat exchanger can be as close as 200 degrees Celsius, and the plate heat exchanger solution according to the invention is valuable for reducing thermal stress caused by large temperature differences.

[0043] A typical method according to the invention for vaporizing liquefied natural gas (LNG) in a plate heat exchanger includes...

[0044] - The heating medium is arranged to flow inside the shell between the inlet and outlet connecting pipes for the second heat exchange medium.

[0045] - Liquefied natural gas is supplied to the inside of the plate assembly via an inlet connection pipe for the first heat exchange medium, and

[0046] Heated natural gas is delivered from the plate assembly via an outlet connection pipe for the first heat exchange medium.

[0047] According to an embodiment of the invention, a portion of the heating medium flowing inside the shell is arranged to flow into a heating channel formed between a first support end plate of the plate assembly and a first end plate of the outer shell, and arranged to at least partially surround an inlet connection pipe for LNG. The heating channel is arranged to connect to the inside of the shell. In a typical method according to the invention, the heating medium is guided from the inlet connection side for the heating fluid (second heat exchange medium) to the heating channel, and flows out from the outlet connection side for the heating fluid.

[0048] Detailed description of the attached figures

[0049] Figure 1 An exemplary embodiment of a plate-and-shell heat exchanger structure is presented, and an improved end structure according to the present invention can be adapted to this plate-and-shell heat exchanger structure. The plate heat exchanger 1 includes a plate assembly 2 and an outer housing surrounding the plate assembly. The outer housing includes a first end plate 3a, a second end plate 3b, and a shell 4 connecting the first and second end plates. Figures 2-4As shown, plate assembly 2 is formed by heat exchange plates 8, 8', 8'', each having at least two openings and arranged vertically to each other. The plate assembly includes a first end and a second end along its length / height, and includes a first support end plate 7a arranged at the first end and a second support end plate 7b arranged at the second end. Flow passages 9a and 9b for a first heat exchange medium on the inner side of plate assembly 2 are formed by the openings of the vertically arranged heat exchange plates. The plate heat exchanger further includes an inlet connecting pipe 5a and an outlet connecting pipe 5b for the first heat exchange medium, arranged to pass through end plates of the outer casing and connected to the flow passages 9a and 9b of the plate assembly. An inlet connecting pipe 6a and an outlet connecting pipe 6b for a second heat exchange medium are arranged to pass through the outer casing and connected to the inner side of the outer casing, i.e., to the outer side of the plate assembly.

[0050] Figure 2 The structure of the end of a plate heat exchanger according to an embodiment of the present invention is presented, which includes a flexible structure 9 between a first support end plate 7a of the plate assembly and a first end plate of the outer casing 3a.

[0051] Figure 3 The structure of an end portion of a plate heat exchanger according to an embodiment of the present invention is presented, comprising a heating channel 10. The heating channel 10 is arranged between a first support end plate 7a of the plate assembly and a first end plate 3a of the outer casing. The heating channel 10 is also arranged to surround an inlet connecting pipe 5a. The heating channel 10 may be arranged to connect to the inside of the casing, wherein the heating fluid or medium flowing in the heating channel is the same as the fluid or medium flowing inside the casing.

[0052] Figure 4 The structure of the end of a plate heat exchanger according to an embodiment of the invention is presented, comprising an inner tube 11 disposed inside an inlet connection pipe 5a for a first heat exchange medium. The inner tube 11 extends at least partially inside a flow passage 9a of the plate assembly. In a typical embodiment of the invention, the end of the inner tube 11 is attached to the inlet connection pipe 5a. Inside the flow passage of the plate assembly, the inner tube 11 is attached to the plate assembly by a gasket or resilient structure 12 disposed around the inner tube 11. The gasket or resilient structure 12 is typically disposed around the inner tube in the structure such that it also closes the first flow passage between the pairs of plates in the plate assembly. Figure 4 In the embodiment presented, the inner tube 11 includes openings 13, 13', 13'', which form flow channels into the inner side of the plate assembly.

Claims

1. A plate heat exchanger (1), comprising: - A plate assembly (2), the plate assembly being formed of heat exchanger plates (8, 8', 8'') having at least two openings and arranged vertically to each other, wherein the plate assembly includes a first end and a second end along the length direction of the plate assembly, and the plate assembly includes a first support end plate (7a) arranged on the first end of the plate assembly, a second support end plate (7b) arranged on the second end of the plate assembly, and flow passages (9a, 9b) for a first heat exchange medium on the inner side of the plate assembly being formed by the openings of the heat exchanger plates (8, 8', 8'') arranged vertically to each other. - An outer housing surrounding the plate assembly, the outer housing comprising a first end plate (3a), a second end plate (3b), and a shell (4) connecting the first end plate and the second end plate. - For the inlet connecting pipe (5a) and the outlet connecting pipe (5b) of the first heat exchange medium, the inlet connecting pipe (5a) and the outlet connecting pipe (5b) are arranged to pass through the end plates (3a, 3b) of the outer housing and are arranged to connect to the flow passages (9a, 9b) of the plate assembly, and - The inlet connecting pipe (6a) and the outlet connecting pipe (6b) for the second heat exchange medium are arranged to pass through the outer housing and to connect to the inside of the outer housing, i.e., to the outside of the plate assembly. Its features are, The inlet connection pipe (5a) of the first heat exchange medium is arranged to pass through the first end plate (3a) of the outer housing and to connect to the first support end plate (7a) of the plate assembly, and the plate heat exchanger further includes - An internal tube (11) is arranged inside the inlet connecting pipe (5a) of the first heat exchange medium, and the internal tube extends at least partially inside the flow passage (9a) of the plate assembly. The internal tube (11) includes openings (13, 13', 13'') that form flow channels into the flow passages inside the plate assembly. When viewed from the direction of the inlet connecting pipe (5a) of the first heat exchange medium, one to five of the first flow channels inside the plate assembly are closed. The internal tube (11) is attached to the plate assembly (2) inside the flow passage (9a) of the plate assembly by a gasket or elastic structure (12) arranged around the internal tube. The internal tube structure is a flexible structure.

2. The plate heat exchanger according to claim 1, characterized in that, The end of the internal tube (11) is attached to the inlet connection tube (5a) of the first heat exchange medium.

3. The plate heat exchanger according to claim 1 or 2, characterized in that, The plate heat exchanger also includes a flexible structure (9) arranged between the first support end plate (7a) of the plate assembly and the first end plate (3a) of the outer shell.

4. The plate heat exchanger according to claim 3, characterized in that, The flexible structure (9) includes a spring structure and / or a flexible plate structure.

5. The plate heat exchanger according to claim 1 or 2, characterized in that, The plate heat exchanger further includes a heating channel (10) between the first support end plate (7a) of the plate assembly and the first end plate (3a) of the outer housing, and / or at least partially surrounding the inlet connecting pipe (5a) of the first heat exchange medium.

6. The plate heat exchanger according to claim 5, characterized in that, The heating channel (10) is formed in the first support end plate (7a) of the plate assembly and / or formed in the first end plate (3a) of the outer housing.

7. The plate heat exchanger according to claim 5, characterized in that, The heating channel (10) is arranged to connect to the inside of the shell.

8. The plate heat exchanger according to claim 1 or 2, characterized in that, The plate heat exchanger also includes: - A flexible structure (9) is arranged between the first support end plate (7a) of the plate assembly and the first end plate (3a) of the outer shell, and - Heating channel (10), which is located between the first support end plate (7a) of the plate assembly and the first end plate (3a) of the outer housing, and / or at least partially surrounds the inlet connecting pipe (5a) of the first heat exchange medium.

9. The plate heat exchanger according to claim 1 or 2, characterized in that, The plate heat exchanger is a liquefied natural gas (LNG) vaporizer.

10. The use of the plate heat exchanger according to any one of claims 1 to 8 as a liquefied natural gas (LNG) vaporizer.

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