BOG (Boil Off Gas) precooling liquefaction system for recovering LNG (Liquefied Natural Gas) cold energy

Abstract

The utility model relates to the technical field of energy recovery, in particular to a BOG (boil-off gas) precooling liquefaction system for recovering LNG (liquefied natural gas) cold energy. According to the technical scheme, the system comprises an LNG storage tank and a first compressor connected with the LNG storage tank, and further comprises a refrigeration compression system and a BOG reliquefaction system which are connected with the LNG storage tank and the first compressor; wherein the refrigeration compression system comprises a first heat exchanger, a refrigeration compressor, an expansion valve and a second heat exchanger which are connected in sequence. According to the utility model, the LNG storage tank, the first compressor, the stop valve, the high-pressure pump, the refrigeration compression system, the BOG reliquefaction system and other structures are matched, and the refrigeration compression cycle process is adopted, so that the LNG cold energy which is gasified and output is transferred to BOG flowing out of the LNG storage tank, the cold energy required in the traditional BOG recondensation process is reduced, and the energy consumption is reduced. And the loss of the cold energy of the gasified and output LNG is also reduced, so that the cold energy of the LNG is fully recycled.

Description

Technical Field

[0001] The utility model relates to the technical field of energy recovery, in particular to a BOG pre-cooling liquefaction system for recovering LNG cold energy. Background Art

[0002] LNG storage tanks are containers for storing liquefied natural gas. Due to the temperature difference between the storage tank and the outside world, BOG (boil-off gas) will be generated in the tank. At present, there are two main methods for BOG treatment used by LNG receiving stations: one is the BOG reliquefaction process, and the other is the BOG direct compression process. The BOG reliquefaction process refers to sending the BOG generated by the storage tank to the BOG compressor for pressurization, exchanging heat with LNG in the recondenser, and being condensed into liquefied natural gas. This treatment process is suitable for the treatment of BOG generated by the storage tank with a large amount of BOG and a small amount of external transmission. At present, domestic LNG receiving stations basically use this method to treat BOG.

[0003] The BOG reliquefaction process requires the liquefied natural gas in the LNG storage tank to provide cold energy to liquefy in the recondenser to form LNG, while the liquefied natural gas in the LNG storage tank needs to absorb heat and vaporize in an open rack vaporizer (ORV) or a submerged combustion vaporizer (SCV). The cold energy of LNG is released during the vaporization heat absorption process, while BOG needs to provide cold energy during the liquefaction process. Therefore, the cold energy of LNG transported out of the vaporization can be transferred to the liquefaction process of BOG to reduce the cold energy required for the BOG liquefaction process. Utility Model Content

[0004] The utility model aims to solve the problems existing in the background technology and propose a BOG pre-cooling liquefaction system for recovering LNG cold energy.

[0005] The technical solution of the utility model: a BOG pre-cooling liquefaction system for recovering LNG cold energy, comprising an LNG storage tank and a first compressor connected to the LNG storage tank, and also comprising: a refrigeration compression system and a BOG reliquefaction system connected to the LNG storage tank and the first compressor; wherein the refrigeration compression system comprises a first heat exchanger, a refrigeration compressor, an expansion valve and a second heat exchanger connected in sequence, and the BOG reliquefaction system comprises a gas-liquid separator, a second compressor and a recondenser connected in sequence; a ladder mechanism, comprising a ladder mechanism arranged on the outer wall of the LNG storage tank for unfolding or storing after rotating up and down.

[0006] Optionally, a stop valve and a high-pressure pump are provided between the gas-liquid separator and the recondenser, the high-pressure pump is connected to the recondenser and the second heat exchanger, the gas-liquid separator is connected to the first heat exchanger, one end of the refrigeration compressor and the expansion valve are connected to the first heat exchanger, the other end of the refrigeration compressor and the expansion valve are connected to the second heat exchanger, and the BOG reliquefaction system, the stop valve and the high-pressure pump are connected to the LNG storage tank.

[0007] Optionally, the ladder mechanism includes a ladder fixedly connected to the outer wall of the LNG storage tank, the lower surface of the bottom end of the ladder is fixedly connected to a U-shaped seat, the inside of the U-shaped seat is fixedly connected to a cylinder, the piston rod of the cylinder movably passes through the U-shaped seat and is fixedly connected to a push rod, the bottom end of the ladder is fixedly connected to a pair of rotating seats, and the middle part of the rotating seat is rotatably connected to a step ladder that is supported by the push rod and then rotates upward.

[0008] Optionally, a handrail is fixedly connected to the upper surface of the ladder.

[0009] Optionally, a buffer block is fixedly connected to one end of the step ladder away from the rotating seat.

[0010] Optionally, a circular fence is fixedly connected to the top upper surface of the LNG storage tank.

[0011] Optionally, the circular fence is provided with a plurality of rectangular perforations distributed in a circular array.

[0012] In summary, the present application includes at least one of the following beneficial technical effects of a BOG precooling liquefaction system for recovering LNG cold energy:

[0013] The utility model utilizes the coordination of structures such as the LNG storage tank, the first compressor, the stop valve, the high-pressure pump, the refrigeration compression system and the BOG reliquefaction system, and adopts a refrigeration compression cycle process to transfer the cold energy of the gasified and externally transmitted LNG to the BOG flowing out of the LNG storage tank. This method reduces the cold energy required in the traditional BOG recondensation process, and also reduces the loss of the cold energy of the gasified and externally transmitted LNG, so that the cold energy of the LNG is fully recovered and utilized. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A structural schematic diagram of a BOG pre-cooling liquefaction system for recovering LNG cold energy is given in the utility model;

[0015] Figure 2 for Figure 1 Schematic diagram of the first state structure of the LNG storage tank;

[0016] Figure 3 for Figure 1 Schematic diagram of the second state structure of the LNG storage tank;

[0017] Figure 4 for Figure 3 A magnified schematic diagram of center A.

[0018] Figure numerals: 1. LNG storage tank; 101. rotating seat; 102. ladder; 103. handrail; 104. circular fence; 105. step ladder; 106. U-shaped seat; 107. cylinder; 108. push rod; 109. buffer block; 2. first compressor; 3. first heat exchanger; 4. refrigeration compressor; 5. second compressor; 6. gas-liquid separator; 7. stop valve; 8. recondenser; 9. expansion valve; 10. high-pressure pump; 11. second heat exchanger. DETAILED DESCRIPTION

[0019] The technical solution of the present utility model will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present utility model, rather than all of the embodiments.

[0020] The components of the embodiments of the present invention generally described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention.

[0021] Based on the embodiments of the present utility model, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present utility model.

[0022] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0023] It should be noted that the terms "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0024] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] Example

[0026] like Figure 1-4 As shown, the utility model proposes a BOG pre-cooling liquefaction system for recovering LNG cold energy, including an LNG storage tank 1 and a first compressor 2 connected to the LNG storage tank 1, a circular fence 104 is fixedly connected to the top upper surface of the LNG storage tank 1, and a plurality of rectangular perforations distributed in a circumferential array are opened on the circular fence 104, and also includes: a refrigeration compression system and a BOG reliquefaction system connected to the LNG storage tank 1 and the first compressor 2; wherein the refrigeration compression system includes a first heat exchanger 3, a refrigeration compressor 4, an expansion valve 9 and a second heat exchanger 11 connected in sequence, and the BOG reliquefaction system includes a gas-liquid separator 6, a second compressor 5 and a recondenser 8 connected in sequence; a ladder mechanism, and equipment maintenance in the BOG pre-cooling liquefaction system for recovering LNG cold energy is very important. Among them, the LNG storage tank 1 is relatively high, and a ladder mechanism will be provided on it. When regular maintenance and inspection are to ensure its normal operation, the ladder mechanism needs to be used. However, the existing ladder mechanism is usually for people to climb at will, and the lack of protective measures easily leads to the risk of people falling or slipping. The climbing mechanism can be rotated upward and retracted to avoid this risk. It includes an outer wall of the LNG storage tank 1 for unfolding or folding after being rotated up and down.

[0027] Among them, a stop valve 7 and a high-pressure pump 10 are provided between the gas-liquid separator 6 and the recondenser 8, the high-pressure pump 10 is connected to the recondenser 8 and the second heat exchanger 11, the gas-liquid separator 6 is connected to the first heat exchanger 3, one end of the refrigeration compressor 4 and the expansion valve 9 are connected to the first heat exchanger 3, and the other end of the refrigeration compressor 4 and the expansion valve 9 are connected to the second heat exchanger 11, and the BOG reliquefaction system, the stop valve 7 and the high-pressure pump 10 are all connected to the LNG storage tank 1.

[0028] Furthermore, the ladder mechanism includes a ladder 102 fixedly connected to the outer wall of the LNG storage tank 1, a support plate 103 is fixedly connected to the upper surface of the ladder 102, a U-shaped seat 106 is fixedly connected to the lower surface of the bottom end of the ladder 102, a cylinder 107 is fixedly connected to the inside of the U-shaped seat 106, a piston rod of the cylinder 107 is movably passed through the U-shaped seat 106 and is fixedly connected to a push rod 108, a pair of rotating seats 101 are fixedly connected to the bottom end of the ladder 102, a step ladder 105 is rotatably connected to the middle part of the rotating seat 101 and is rotated upward after being supported by the push rod 108, and a buffer block 109 is fixedly connected to the end of the step ladder 105 away from the rotating seat 101.

[0029] In this embodiment, when it is necessary to use a BOG pre-cooling liquefaction system that recovers LNG cold energy, the BOG generated by the LNG storage tank 1 is pressurized by the first compressor 2 and then enters the first heat exchanger 3. In the first heat exchanger 3, it exchanges heat with the refrigerant of the refrigeration compression system, the BOG exothermic temperature is reduced, and the refrigerant endothermic temperature is increased. The BOG with the lowered temperature enters the gas-liquid separator 6, and the LNG in the gas-liquid separator 6 is combined with the LNG flowing out of the LNG storage tank 1. The BOG in the gas-liquid separator 6 is pressurized by the second compressor 5. The pressurized BOG exchanges heat with the LNG flowing into the recondenser 8 in the recondenser 8. The BOG in the recondenser 8 is completely liquefied to form LNG, which is combined with the LNG flowing out of the LNG storage tank 1 and the LNG flowing out of the gas-liquid separator 6, and is pressurized by the high-pressure pump 10, and then enters the second heat exchanger 11;

[0030] When the LNG in the second heat exchanger 11 exchanges heat with the refrigerant of the refrigeration compression system, the LNG is vaporized into gaseous natural gas. The refrigerant absorbs the cold energy of the LNG and condenses from the gaseous state to the liquid state. The liquid refrigerant passes through the expansion valve 9. The low-temperature liquid refrigerant becomes a low-temperature gaseous refrigerant. The low-temperature gaseous refrigerant transfers the cold energy to the BOG released from the LNG storage tank 1 in the first heat exchanger 3. The temperature of the low-temperature gaseous refrigerant is increased. The gaseous refrigerant with increased temperature is compressed by the refrigeration compressor 4 and becomes a high-temperature and high-pressure gaseous refrigerant. It then enters the second heat exchanger 11 to exchange heat with the LNG, forming a complete refrigeration compression cycle process, and transfers the cold energy of the vaporized and externally transmitted LNG to the BOG flowing out of the LNG storage tank;

[0031] When it is necessary to use the ladder mechanism on the outer wall of the LNG storage tank 1, such as Figure 2As shown, the staff who land on the LNG storage tank 1 can climb to the top of the LNG storage tank 1 through the step ladder 105 and the ladder 102, and finally reach the top of the LNG storage tank 1 by crossing the circular fence 104 on the top of the LNG storage tank 1. When it is necessary to store the ladder mechanism to prevent unauthorized use, it is only necessary to start the cylinder 107 in the U-shaped seat 106. After the cylinder 107 is started, the piston rod pushes the step ladder 105 to rotate upward with the rotating seat 101 as the center until the step ladder 105 is as shown in FIG. Figure 3 As shown, the step ladder 105 can be rotated upward and stored.

[0032] The preferred embodiments of the utility model of the above utility model are only used to help explain the utility model. The preferred embodiments do not describe all the details in detail, nor do they limit the utility model to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the utility model, so that technicians in the relevant technical field can well understand and use the utility model. The utility model is limited only by the claims and their full scope and equivalents.

Claims

1. A BOG pre-cooling liquefaction system for recovering LNG cold energy, comprising an LNG storage tank (1) and a first compressor (2) connected to the LNG storage tank (1), characterized in that: Also includes: A refrigeration compression system and a BOG reliquefaction system connected to the LNG storage tank (1) and the first compressor (2); The refrigeration compression system comprises a first heat exchanger (3), a refrigeration compressor (4), an expansion valve (9) and a second heat exchanger (11) connected in sequence, and the BOG reliquefaction system comprises a gas-liquid separator (6), a second compressor (5) and a recondenser (8) connected in sequence; The ladder mechanism is arranged on the outer wall of the LNG storage tank (1) and is used for unfolding or folding after rotating up and down.

2. A BOG pre-cooling liquefaction system for recovering LNG cold energy according to claim 1, characterized in that: A stop valve (7) and a high-pressure pump (10) are provided between the gas-liquid separator (6) and the recondenser (8); the high-pressure pump (10) is connected to the recondenser (8) and the second heat exchanger (11); the gas-liquid separator (6) is connected to the first heat exchanger (3); one end of the refrigeration compressor (4) and the expansion valve (9) are connected to the first heat exchanger (3); the other ends of the refrigeration compressor (4) and the expansion valve (9) are connected to the second heat exchanger (11); and the BOG reliquefaction system, the stop valve (7) and the high-pressure pump (10) are connected to the LNG storage tank (1).

3. The BOG pre-cooling liquefaction system for recovering LNG cold energy according to claim 1, characterized in that: The ladder mechanism comprises a ladder (102) fixedly connected to the outer wall of the LNG storage tank (1); a U-shaped seat (106) is fixedly connected to the lower surface of the bottom end of the ladder (102); a cylinder (107) is fixedly connected inside the U-shaped seat (106); a piston rod of the cylinder (107) movably passes through the U-shaped seat (106) and is fixedly connected to a push rod (108); a pair of rotating seats (101) are fixedly connected to the bottom end of the ladder (102); a step ladder (105) is rotatably connected to the middle part of the rotating seat (101) and is rotated upward after being pressed by the push rod (108).

4. A BOG pre-cooling liquefaction system for recovering LNG cold energy according to claim 3, characterized in that: A support plate (103) is fixedly connected to the upper surface of the ladder (102).

5. The BOG pre-cooling liquefaction system for recovering LNG cold energy according to claim 3, characterized in that: One end of the step ladder (105) away from the rotating seat (101) is fixedly connected to a buffer block (109).

6. The BOG pre-cooling liquefaction system for recovering LNG cold energy according to claim 1, characterized in that: A circular fence (104) is fixedly connected to the top upper surface of the LNG storage tank (1).

7. A BOG pre-cooling liquefaction system for recovering LNG cold energy according to claim 6, characterized in that: The circular fence (104) is provided with a plurality of rectangular through holes distributed in a circular array.

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