Plate heat exchanger and use of the plate heat exchanger as a liquefied natural gas evaporator

Abstract

The plate heat exchanger comprises a flexible structure (9) and / or a heating flow passage between the first supporting end plate (7a) of the plate pack and the first end plate (3a) of the outer casing, and / or an inner tube arranged inside the inlet connecting tube (5a) of the first heat exchange medium, which improves the plate heat exchanger's ability to withstand thermal stresses caused by temperature differences when used, for example, for heating 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 Art

[0002] Since natural gas (NG) is a clean fuel, global demand is constantly increasing. When a natural gas pipeline is not feasible or does not exist, liquefied natural gas is a way to move natural gas from the production area to the consumption area. Typically, it is cooled to a liquid form (about -162°C) for ease and safety of non-pressurized storage or transportation. At the consumption area, liquefied natural gas (LNG) is heated to room temperature to be vaporized and regasified for use as fuel.

[0003] To heat LNG to room temperature, different types of LNG vaporizers are used. Plate and shell heat exchangers are one type of heat exchanger that can be used to warm LNG back to gas. Plate and shell heat exchangers are welded heat exchangers comprising a plate pack and an external casing surrounding the plate pack. The outer casing 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 via the end plates of the outer casing. Typically, the inlet connection pipe of the plate pack, the end plates of the outer casing, and the supporting end plates of the plate pack are firmly attached to each other in a plate and shell type heat exchanger, and thus heat transfer is not necessarily possible in all directions without causing stress in the material. When the heat exchanger structure is used as an LNG vaporizer, a large temperature difference causes stress in the material and its joints, and ultimately the stress may damage the structure of the heat exchanger. In particular, the temperature difference between the fluids at the point of the inlet connection pipe supplying LNG to the vaporizer can be close to 200 degrees.

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to reduce or eliminate the above-described problems that appear in the prior art.

Means for Solving the Problems

[0005] An object of the present invention is to provide a plate heat exchanger structure with improved ability to withstand thermal stress caused by a temperature difference, for example, a large temperature difference present in the heating of liquefied natural gas.

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

[0007] To achieve the above object, the present invention is characterized in that it is described in the characterizing part of the independent claims.

[0008] The embodiments and advantages referred to in this specification are related to both plate heat exchangers and the use according to the present invention where applicable, but are not necessarily specifically mentioned.

[0009] A typical plate heat exchanger according to the present invention is a plate pack having at least two openings and arranged overlapping each other, Heat exchange plate wherein the plate pack has a first end and a second end in the length direction of the plate pack, the plate pack has a first support end plate arranged at the first end of the plate pack, a second support end plate (7b) arranged at the second end of the plate pack, and a flow path for a first heat exchange medium inside the plate pack formed from the openings of the heat exchange plates arranged overlapping each other. a first end plate, a second end plate, and a shell connecting the first and second end plates, and an outer casing surrounding the plate pack. An inlet connection pipe and an outlet connection pipe for a first heat exchange medium, which are arranged via an end plate of the outer casing and are connected to a flow path of the plate pack, and an inlet connection pipe and an outlet connection pipe for a second heat exchange medium, which are arranged inside the outer casing, outside the plate pack, and penetrate the outer casing, comprising The inlet connection pipe of the first heat exchange medium is connected to and arranged on the first support end plate of the plate pack via the first end plate of the outer casing. The plate heat exchanger further comprises a flexible structure arranged between the first support end plate of the plate pack and the first end plate of the outer casing, a heating flow path arranged at least partly around the inlet connection pipe of the first heat exchange medium between the first support end plate of the plate pack and the first end plate of the outer casing, an inner pipe arranged inside the inlet connection pipe of the first heat exchange medium and extending at least partly inside the flow path of the plate pack, characterized by comprising at least one of

[0010] Typically, the plate heat exchanger according to the present invention is used as a liquefied natural gas (LNG) vaporizer.

[0011] The structure of the plate heat exchanger according to the present invention is based on reducing the influence of heat transfer directed to the structure due to the temperature difference between the first and second heat exchange media. According to the present invention, the heat exchanger structure is improved by arranging at least one of the following structures in the plate heat exchanger.

[0012] a flexible structure between the first support end plate of the plate pack and the first end plate of the outer casing,

[0013] A heating flow path that is disposed between the first support end plate of the plate pack and the first end plate of the outer casing and / or that is disposed around at least a part of the inlet connection pipe for the first heat exchange medium.

[0014] An inner pipe inside the inlet connection pipe for the first heat exchange medium, which extends at least partially inside the flow path of the plate pack.

[0015] The plate heat exchanger according to the present invention can be provided with one, two, or all three structures of the present invention disposed at the ends of the plate heat exchanger, and an inlet connection pipe for the first heat exchange medium is disposed through the plate heat exchanger. The presented improved structure provides an easy and simple modification to the end plate structure of the plate heat exchanger.

[0016] The present invention will be described in more detail with reference to the accompanying drawings.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0018] The plate-shell type plate heat exchanger comprises a plate pack formed of heat exchange plates and an outer casing surrounding the plate pack. The outer casing comprises a first end plate, a second end plate, and a shell connecting the end plates. The plate pack is typically mounted inside a cylindrical shell that functions as a pressure vessel. The plate-shell type heat exchanger is usually a fully welded heat exchanger.

[0019] In the plate-shell type heat exchanger according to the present invention, the plate packs are arranged overlapping each other Heat exchange plate and are formed from, and the plate pack is characterized by having a first end and a second end in the longitudinal direction of the plate pack. The longitudinal direction of the plate pack refers to the stacking direction of the stacked plates, Heat exchange plate In a typical embodiment according to the present invention, the plate pack further comprises a first support end plate arranged at the first end of the plate pack and a second support end plate arranged at the second end of the plate pack. For example, the welded plate pack is composed of circular heat exchange plates. The plate pack is composed of plate pairs of a plurality of heat exchange plates. Each plate pair is formed by two attached heat exchange plates, and it is preferable to weld at least their outer peripheries together. Each heat exchange plate has at least two openings with respect to the flow of the first heat exchange medium. Adjacent plate pairs are attached to each other by attaching the openings of the two adjacent plate pairs to each other. Accordingly, the plate pack is formed of heat exchange plates, and the heat exchange plates are alternately attached to each other at the openings of the plates and around the plates. In the plate pack, the first heat exchange medium can flow from one plate pair to another through the openings inside the plate pack of the heat exchanger, and there is a flow path formed by the openings of the heat exchange plates overlapping each other. The inlet and outlet connection pipes for the first heat exchange medium are connected to the flow path of the plate pack, that is, are arranged connected to the inner part of the plate pair. Thus, the primary circuit of the plate heat exchanger is formed between the inlet and outlet connection pipes of the first heat exchange medium.

[0020] In the plate - shell type heat exchanger according to the present invention, the second heat exchange medium is arranged to flow inside the shell in the space between the plate pairs. The inlet and outlet connection pipes for the second heat exchange medium are arranged to be connected to the inside of the shell, that is, the outside of the plate pairs of the plate pack, via the outer casing. That is, the secondary circuit of the plate type heat exchanger is formed in the space between the inlet connection pipe and the outlet connection pipe of the second heat exchange medium, inside the shell, and between the plate pairs. Typically, the primary circuit and the secondary circuit are separated from each other. That is, the first heat exchange medium flowing through the inner part of the plate pack does not mix with the second heat exchange medium flowing inside the shell, that is, outside the plate pack. Thereby, the first primary - side heat exchange medium flows through every other plate space, and the second secondary - side heat exchange medium flows through all the other plate spaces of the plate type heat exchanger.

[0021] According to the present invention, the longitudinal direction, that is, the length direction of the plate pack, is substantially the same as the longitudinal direction of the shell. According to a preferred embodiment of the present invention, the plate pack is mainly a circular cylinder, the shell is a cylindrical shell, and a cylindrical plate pack formed by heat exchange plates arranged to overlap each other is arranged inside the functional part of the cylindrical shell such that the longitudinal direction of the plate pack is the same as the longitudinal direction of the cylindrical shell.

[0022] According to one embodiment of the present invention, by arranging a flexible structure between the first support end plate of the plate pack and the first end plate of the outer casing, the stress caused by heat transfer is prevented and / or eliminated. The first end plate herein refers to the outer casing where the inlet connection pipe of the first heat exchange medium is arranged, and the first support end plate of the plate pack refers to the support plate of the plate pack arranged in connection with 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 pack and the first end plate of the outer casing, which has the ability to compensate for thermal movement. According to one embodiment of the present invention, the flexible structure comprises a spring structure and / or a flexible structure that can be bent and / or moved without being broken. In an embodiment of the present invention, a flexible structure is arranged between the first support end plate of the plate pack and the first end plate of the outer casing where the inlet connection pipe of the first heat exchange medium is arranged, and its size is substantially the same as that of the first support end plate of the plate pack, that is, it is arranged throughout the area between the first support end plate of the plate pack and the first end plate of the outer casing.

[0023] Also, in the structure of the plate type heat exchanger according to the present invention, by combining the presented additional flexible structure and the position of the welded part, the structure against thermal stress can be improved. According to one embodiment of the present invention, the flexible structure is not firmly attached to the inlet connection pipe of the first heat exchange medium and / or the end plate of the outer casing to enable the movement of the flexible structure. A welded joint can be provided between the flexible structure and the inlet connection pipe of the first heat exchange medium and / or the end plate of the outer casing, but it is welded only at some parts where the reversible movement of the flexible structure is still allowed. Further, the heat exchanger according to the present invention is a completely welded structure having an additional flexible structure.

[0024] According to another embodiment of the present invention, in order to suppress and / or eliminate the stress caused by thermal movement in the end structure of the plate heat exchanger, the periphery of the inlet pipe connection portion of the first heat exchange medium is heated. By arranging a heating flow path at least partially around the inlet pipe and / or between the first support end plate of the plate pack and the first end plate of the outer casing, a large temperature difference at the connection point between the inlet connection pipe and the plate pack structure can be reduced and / or prevented. The first end plate herein refers to the end plate of the outer casing where the inlet connection pipe of the first heat exchange medium is arranged, and the first support end plate of the plate pack refers to the support plate of the plate pack that is also connected to the inlet connection pipe of the first heat exchange medium. According to an embodiment of the present invention, the plate heat exchanger includes a heating flow path formed in the first support end plate and / or the end plate of the outer casing, and through this heating flow path, the inlet connection pipe of the first heat exchange medium is arranged. According to an embodiment of the present invention, the heating flow path is machined in the first support end plate of the plate pack and / or in the end plate of the outer casing, and a heating fluid can flow through it to heat the periphery of the inlet connection pipe. The heating flow path can be a groove or a corresponding structure that is machined in the first support end plate of the plate pack and / or in the end plate of the outer casing to provide a route for the heating fluid to flow. The structure and dimensions of the heating flow path can be various.

[0025] In one embodiment of the present invention, the heating flow path is also formed at least partially around the inlet connection pipe of the first heat exchange medium. In an embodiment of the present invention, at least a part of the heating flow path is arranged to circulate around the inlet connection pipe, and the heating fluid flows inside the heating flow path arranged between the first support end plate of the plate pack and the first end plate of the outer casing, flows in from the other edge of the end plate, at least partially circulates around the inlet connection pipe, and can flow out from the other edge of the end plate through the heating flow path. According to one embodiment of the present invention, the heating flow path around the inlet pipe can be made simply by machining a larger opening at least in a part of the length direction of the opening at the end plate of the outer casing. The height and width of the heating flow path around the inlet connection pipe can be various. According to one embodiment of the present invention, the heating flow path is arranged around the inlet connection pipe over the entire length of the inlet connection pipe.

[0026] According to one embodiment of the present invention, the heating flow path is arranged to be connected to the inside of the shell, and the heating fluid or medium flowing inside the heating flow path is the same fluid or medium as that flowing inside the shell. Thereby, the guiding of the heating fluid or medium in the heating flow path can be easily performed. Further, by processing the standard parts of the plate heat exchanger as described above, the heating flow path can be easily formed. The heating flow path structure according to the present invention provides an easy embodiment for preventing damage caused by thermal stress.

[0027] According to yet another embodiment of the present invention, for suppressing and / or eliminating stress generated by heat transfer in the end structure of a plate heat exchanger, the first heat exchange medium heated inside the plate pack is conveyed into the plate pack together with an inner pipe that distributes the flow of the first heat exchange medium deeper into the plate pack. A plate heat exchanger according to an embodiment of the present invention includes an inner pipe disposed inside an inlet connection pipe of the first heat exchange medium and elongating at least a part inside the flow path of the plate pack. Thus, the inlet connection pipe for the first heat exchange medium is at least partially double-walled, and the gas between the structures acts as an insulator, raising the temperature of the original single inlet connection pipe and thus helping the structure withstand thermal stress and movement. In a preferred embodiment according to the present invention, the inlet connection pipe for the first heat exchange medium is double-walled over substantially the entire length of the inlet connection pipe.

[0028] According to an embodiment of the present invention, the end of the inner tube is attached to the inlet connection tube of the first heat exchange medium. Typically, the inner tube is attached to the inlet connection tube of the first heat exchange medium only from one end of the inner tube, and this inlet connection tube extends outward from the end plate of the plate heat exchanger. According to an embodiment of the present invention, when the inner tube is disposed in the flow path of the plate pack, the first plate pair is blocked and the inflow of the first heat exchange medium into the first plate pair is blocked. Therefore, according to an embodiment of the present invention, the inner tube is attached to the plate pack inside the flow path of the plate pack by a gasket or an elastic structure disposed around the inner tube, whereby the inner tube blocks the flow to the plate pack and at the same time the inner tube is attached to the plate pack. Thus, the inner tube structure according to the present invention is a flexible structure that withstands heat transfer caused by a large temperature difference. In an embodiment of the present invention, for example, 1 to 5 of the first flow paths inside the plate pack are closed by a gasket or a corresponding structure disposed around the inner tube as viewed from the direction of the inlet tube for the first heat exchange medium. The gasket or the corresponding structure holds the inner tube in its position but also withstands heat transfer. This also suppresses damage caused by a large temperature difference because the first plate pair is not open to the first heat exchange medium and functions as a heat insulating layer toward the end structure of the plate heat exchanger.

[0029] According to an embodiment of the present invention, the inner tube includes an opening that forms a flow path to the flow path inside the plate pack. Therefore, the inner tube extends inside the flow path and can provide normal operation of the plate pack.

[0030] According to a preferred embodiment of the present invention, the plate heat exchanger is used as a liquefied natural gas (LNG) vaporizer or evaporator. In the LNG vaporizer according to the present invention, the first heat exchange medium contains LNG to be heated, and the second heat exchange medium can contain water and / or glycol or any other suitable heating fluid. The temperature difference between the LNG conveyed inside the plate pack and the heating fluid inside the outer casing of the plate heat exchanger may be close to 200 degrees, and the solution of the plate heat exchanger according to the present invention is valuable in reducing the thermal stress caused by this large temperature difference.

[0031] A typical method of vaporizing liquefied natural gas (LNG) in the plate heat exchanger according to the present invention is to arrange a heat medium flowing inside the shell between the inlet connection pipe and the outlet connection pipe for the second heat exchange medium, to allow liquefied natural gas to flow into the plate pack from the inlet connection pipe for the first heat exchange medium, and to allow the heated natural gas to flow out of the plate pack through the outlet connection pipe for the first heat exchange medium.

[0032] According to an embodiment of the present invention, a part of the heat medium flowing inside the shell is made to flow into a heating flow path formed between the first support end plate of the plate pack and the first end plate of the outer casing, and at least a part of it is arranged to circulate through the inlet connection pipe for LNG. The heating flow path is provided in communication with the inside of the shell. In a typical method according to the present invention, the heating medium is led into the heating flow path from the side of the inlet connection part for the heating fluid (second heat exchange medium) and flows out from the side of the outlet connection part for the heating fluid.

[0033] Detailed Description of the Drawings

[0034] FIG. 1 can accommodate the improved end structure according to the present invention Plate type shell and tube heat exchangerAn exemplary embodiment of the structure is shown. The plate heat exchanger 1 includes a plate pack 2 and an outer casing surrounding the plate pack. The outer casing includes a first end plate 3a, a second end plate 3b, and a shell 4 connecting the first and second end plates. The plate pack 2 is formed of heat exchange plates 8, 8', 8'' as shown in FIGS. 2-4. The heat exchange plates have at least two openings and are arranged overlapping each other. The plate pack has a first end and a second end in the length / height direction of the plate pack. The plate pack includes a first support end plate 7a arranged at the first end of the plate pack and a second support end plate 7b arranged at the second end of the plate pack. Also, inside the plate pack 2, flow paths 9a, 9b for the first heat exchange medium are formed at the openings of the heat exchange plates arranged overlapping each other. The plate heat exchanger further includes an inlet connection pipe 5a and an outlet connection pipe 5b for the first heat exchange medium. These are arranged via the end plates of the outer casing and are connected to the flow paths 9a, 9b of the plate pack. The inlet connection pipe 6a and the outlet connection pipe 6b for the second heat exchange medium are arranged via the outer casing and are connected to the inside of the outer casing, that is, the outside of the plate pack.

[0035] FIG. 2 shows the structure of the end portion of the plate heat exchanger according to the embodiment of the present invention, and includes a flexible structure 9 between the first support end plate 7a of the plate pack and the first end plate 3a of the outer casing.

[0036] FIG. 3 shows the structure of the end portion of the plate heat exchanger according to an embodiment of the present invention, including a heating flow path 10. This heating flow path 10 is arranged between the first support end plate 7a of the plate pack and the first end plate 3a of the outer casing. Also, the heating flow path 10 is arranged to circulate the inlet connection pipe 5a. The heating flow path 10 can be arranged to connect to the inside of the shell, and the heating fluid or medium flowing in the heating flow path is the same as the fluid or medium flowing in the shell.

[0037] FIG. 4 shows the structure of the end portion of the plate-type heat exchanger according to the embodiment of the present invention, and includes an inner pipe 11 disposed inside the inlet connection pipe 5a for the first heat exchange medium. The inner pipe 11 extends at least partially inside the flow path 9a of the plate pack. In a typical embodiment according to the present invention, the end of the inner pipe 11 is attached to the inlet connection pipe 5a. Inside the flow path of the plate pack, the inner pipe 11 is attached to the plate pack by a gasket or an elastic structure 12 disposed around the inner pipe. The gasket or the elastic structure 12 is typically disposed in the structure around the inner pipe so as to also close the first flow path between the plate pairs of the plate pack. According to the embodiment shown in FIG. 4, the inner pipe 11 includes openings 13, 13', 13'' that form a flow path to the flow path inside the plate pack.

Claims

【Claim 1】 A plate pack (2) formed by heat exchange plates (8, 8', 8'') having at least two openings and arranged overlapping each other, the plate pack having a first end and a second end in the longitudinal direction of the plate pack, the plate pack having a first support end plate (7a) arranged at the first end of the plate pack, a second support end plate (7b) arranged at the second end of the plate pack, and flow paths (9a, 9b) for a first heat exchange medium inside the plate pack formed from the openings of the heat exchange plates (8, 8', 8'') arranged overlapping each other. It has a first end plate (3a), a second end plate (3b), and a shell (4) connecting the first and second end plates, and an outer casing surrounding the plate pack. An inlet connection pipe (5a) and an outlet connection pipe (5b) for a first heat exchange medium, which are arranged via the end plates (3a, 3b) of the outer casing and connected to the flow paths (9a, 9b) of the plate pack. An inlet connection pipe (6a) and an outlet connection pipe (6b) for a second heat exchange medium, which are arranged inside the outer casing, outside the plate pack, and penetrate the outer casing. A plate heat exchanger comprising: The inlet connection pipe (5a) of the first heat exchange medium is connected and arranged to the first support end plate (7a) of the plate pack via the first end plate (3a) of the outer casing. The plate heat exchanger further comprises: An inner pipe (11) arranged inside the inlet connection pipe (5a) of the first heat exchange medium and extending at least partially inside the flow path (9a) of the plate pack. Comprising: The inner pipe (11) is Attached to the plate pack (2) in the flow path (9a) of the plate pack by a gasket or elastic structure (12) arranged around the inner pipe. When viewed from the inlet side of the inlet connection pipe (5a) of the first heat exchange medium, the flow path inside the plate pack composed of the openings of the one or more and five or less heat exchange plates is blocked by the gasket or elastic structure (12), Openings (13, 13', 13'') are formed to form a flow path to the flow path inside the plate pack, characterized in that Plate heat exchanger (1). **Claim 2** The end of the inner pipe (11) is attached to the inlet connection pipe (5a) of the first heat exchange medium. The plate heat exchanger according to claim 1, characterized in that. **Claim 3** The plate heat exchanger is a liquefied natural gas (LNG) vaporizer. The plate heat exchanger according to claim 1 or claim 2, characterized in that. **Claim 4** Use of the plate heat exchanger according to any one of claims 1 to 3 as a liquefied natural gas (LNG) vaporizer.

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