LNG (Liquefied Natural Gas) ship canned boil-off gas recovery system

Abstract

The invention discloses an LNG (Liquefied Natural Gas) ship canned boil-off gas recovery system. Comprising a gas storage tank, a primary heat exchanger communicated with the gas storage tank, a secondary heat exchanger communicated with the gas storage tank and the primary heat exchanger, a gasifier communicated with the secondary heat exchanger, a compressor communicated with the secondary heat exchanger, a safety tank mounted between the gas storage tank and the compressor, and a natural gas generator communicated with the safety tank, and the seawater extraction system is communicated with the safety tank and the primary heat exchanger. Through seawater heat exchange and arrangement of the lifting mechanism in the safety tank, compressed natural gas is converted into a gas state with low energy consumption, so that secondary canning or power generation of a natural gas generator is facilitated; the first connecting mechanism and the second connecting mechanism of the safety tank are optimally designed, so that the safety tank can be integrally disassembled and assembled conveniently, and the safety tank can be conveniently transferred on a ship and flexibly used between secondary canning and natural gas power generation.

Description

Technical Field

[0001] The invention relates to the technical field of LNG boil-off gas treatment, and in particular to an LNG ship tank boil-off gas recovery system. Background Art

[0002] When LNG (liquefied natural gas) is stored in cryogenic tanks, heat exchange is inevitable due to factors such as sunlight, changes in external ambient temperature, and the equipment's own structure, thus producing evaporative gas. In order to minimize the loss of LNG evaporative gas, the industry has proposed a process design that recycles the evaporative gas into nearby gas storage facilities or civil pipelines for reuse.

[0003] Among them, for the gas storage facilities on board the ship used to recover the evaporated gas of natural gas, since the natural gas stored inside cannot be connected to the nearby civil pipeline network, it can only be refilled and returned to the low-temperature storage tank, which makes the reuse of the evaporated gas of natural gas on board the ship a single way.

[0004] In addition, existing ship gas storage facilities use liquid form under high pressure and low temperature conditions to store natural gas. When the natural gas in the gas storage facilities needs to be reused, the liquefied natural gas must be depressurized or heated in advance. The traditional method is to heat the liquefied natural gas through a vaporizer to form a gas, and use a pressure reducing pump to reduce the pressure. However, there is a problem of excessive energy consumption during the use of the vaporizer and the pressure reducing pump, and it is difficult to rely entirely on the ship's LNG power supply system to drive it, otherwise it will affect the normal operation of other areas on the ship. Summary of the invention

[0005] The object of the present invention is to provide a LNG ship tank boil-off gas recovery system to solve the problems raised in the background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] An LNG ship tank boil-off gas recovery system includes a gas storage tank, a primary heat exchanger connected to the gas storage tank, a secondary heat exchanger connected to the gas storage tank and the primary heat exchanger, a vaporizer connected to the secondary heat exchanger, a compressor connected to the secondary heat exchanger, a safety tank installed between the gas storage tank and the compressor, a natural gas generator connected to the safety tank, and a seawater extraction system connected to the safety tank and the primary heat exchanger;

[0008] A partition that can move up and down is arranged inside the safety tank, and the partition divides the inner cavity of the safety tank into a pressure reduction cavity and an air storage cavity. A heat exchange tube is arranged inside the air storage cavity, and a central tube is arranged at both ends of the heat exchange tube. The central tube includes a hollow section and a solid section, and the hollow section is connected to the heat exchange tube as a whole. The outer walls at both ends of the safety tank are respectively installed with a first connection mechanism and a second connection mechanism, and both are installed with a rotating motor. The inner walls at both ends of the air storage cavity are provided with guide grooves and a rotating tube is horizontally installed.

[0009] An inner bend pipe joint is provided at one end of the rotating tube facing the inside of the safety tank, and the other end of the inner bend pipe joint is connected to the hollow section of the central tube through a hose. An outer bend pipe joint is provided at one end of the rotating tube facing the outside of the safety tank, and the other end of the outer bend pipe joint is connected to the first connecting mechanism or the second connecting mechanism through an inner through pipe. The rotating tube is rotatably connected to the inner wall of the safety tank by installing a bearing, and the two ends of the rotating tube are rotatably connected to the outer bend pipe joint and the inner bend pipe joint respectively through connecting bearings. An upper gear is fixedly sleeved on the outer wall of the rotating tube, and a lower gear is meshedly connected below the upper gear, and the lower gear is linked to the rotating motor;

[0010] The solid section of the central tube is connected with a rectangular block, a sliding column is arranged on the rectangular block, the sliding column is slidably connected with the guide groove, a swing rod is fixedly sleeved on the outer wall of the rotating tube, a sliding groove is penetrated through the swing rod, and the rectangular block is slidably connected with the sliding groove.

[0011] Preferably, the partition is moved up and down by a lifting mechanism, and the lifting mechanism includes a lifting column, a screw and a lifting motor. The lifting column is fixedly installed on the upper surface of the partition, and a threaded groove is opened inside the lifting column. The lifting motor is installed on the top of the safety tank. One end of the screw is inserted into the threaded groove and forms a threaded connection with the lifting column, while the other end passes through the safety tank and is linked to the lifting motor. The screw is rotatably connected to the top wall of the safety tank through a lifting bearing.

[0012] Preferably, a support seat is installed on the inner wall of the safety can below the partition, and a groove is opened on the upper surface of the support seat, and the cross-section of the groove is a right-angled trapezoid. A sealing seat is fixedly connected to the lower surface of the partition, and the sealing seat corresponds to the position of the groove and matches the shape. The movable connection between the sealing seat and the support seat is achieved by moving the partition, and the support seat and the sealing seat are both in the shape of a rectangular frame.

[0013] Preferably, the first connection mechanism is provided with a seawater inlet pipe, a liquid nitrogen inlet pipe and a canned gas outlet pipe, one end of the seawater inlet pipe and the liquid nitrogen inlet pipe are connected to the heat exchange pipe through an inner through pipe, the other end of the seawater inlet pipe is used to connect to the seawater extraction system, one end of the canned gas outlet pipe is connected to the inner cavity of the safety tank through the inner through pipe and the other end is used to connect to the gas storage tank;

[0014] The second connecting mechanism is provided with a power generation outlet pipe, a seawater outlet pipe, a nitrogen outlet pipe and a recovery inlet pipe. One end of the seawater outlet pipe and the nitrogen outlet pipe are connected to the heat exchange pipe through an inner through pipe, one end of the recovery inlet pipe and the power generation outlet pipe are connected to the inner cavity of the safety tank through the inner through pipe, the other end of the recovery inlet pipe is used to connect to the compressor, and the other end of the power generation outlet pipe is used to connect to the natural gas generator.

[0015] Preferably, the first connecting mechanism and the second connecting mechanism each include a connecting plate and a cover plate, the connecting plate is fixedly connected to the outer wall of the safety can, the cover plate is located on a side of the connecting plate away from the safety can, a columnar seat and a sealing block are provided between the connecting plate and the cover plate, the sealing block is fixedly connected to the cover plate, and the columnar seat is fixedly connected to the connecting plate;

[0016] The interior of the columnar seat is integrally connected, and an inner through pipe is connected to the side close to the safety tank, a hollow groove is arranged in the middle, and one or two slots are arranged on the side away from the safety tank, the slot is truncated cone-shaped and the closer to the safety tank, the smaller its diameter is, the sealing block corresponds to the position of the slot and matches the shape, and the movable plug-in between the sealing block and the slot is achieved by moving the cover plate, the seawater inlet pipe, the liquid nitrogen inlet pipe, the canned air outlet pipe, the power generation air outlet pipe, the seawater outlet pipe, the nitrogen air outlet pipe and the recovery air inlet pipe all pass through the cover plate and are respectively inserted into each slot, and the sealing block is circumferentially arranged along the outer side wall of the insertion end of the seawater inlet pipe, the liquid nitrogen inlet pipe, the canned air outlet pipe, the power generation air outlet pipe, the seawater outlet pipe, the nitrogen air outlet pipe and the recovery air inlet pipe.

[0017] Preferably, the outer walls of the seawater inlet pipe, liquid nitrogen inlet pipe, canned air outlet pipe, power generation air outlet pipe, seawater outlet pipe, nitrogen air outlet pipe and recovery air inlet pipe are all sleeved with clamps, the middle part of the clamp is welded and fixed to the side of the cover plate away from the connecting plate, and bolts are provided through the two ends of the clamp to separate the two ends of the clamp by removing the bolts.

[0018] Preferably, the cover plate is provided with a plurality of screw holes, and the connecting plate is provided with a plurality of adjusting bearings at positions corresponding to the screw holes. A screw rod is passed through the screw holes, and one end of the screw rod is rotatably connected to the connecting plate through the adjusting bearing. The screw rod is threadedly connected to the cover plate through the screw holes, and the cover plate can be moved closer to or away from the connecting plate by rotating the screw rod.

[0019] Preferably, the guide groove is elliptical.

[0020] Preferably, the rocker arm and the upper gear are respectively arranged on both sides of the mounting bearing.

[0021] Preferably, the seawater extraction system includes a seawater primary filter, the outlet pipe of the seawater primary filter is connected to a reverse osmosis filter, the outlet pipe of the reverse osmosis filter is connected to a refrigerator, a triangular valve is installed on the outlet pipe of the refrigerator, one outlet of the triangular valve is connected to the seawater inlet pipe, and the other outlet of the triangular valve is connected to the primary heat exchanger.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects:

[0023] 1. The present invention sets a heat exchange tube and a compressor. The recovered natural gas boil-off gas is first partially compressed by the compressor. At this time, the boil-off gas is pressurized but does not reach the high pressure state during storage. Then, the pressurized boil-off gas enters the gas storage cavity of the safety tank from the recovery air inlet pipe. Liquid nitrogen is introduced into the liquid nitrogen inlet pipe, and the liquid nitrogen enters the heat exchange tube and fully contacts with the boil-off gas, thereby realizing condensation and cooling treatment of the boil-off gas. The present invention adopts a relatively low-cost method of combining compression and condensation to recover the natural gas boil-off gas and temporarily store it in the safety tank.

[0024] 2. The present invention sets a lifting mechanism, and drives the screw to rotate through the lifting motor. The screw drives the lifting column to rise through the threaded groove. The lifting column drives the partition to move upward in the safety tank, so that the space of the gas storage chamber is increased, and the compressed natural gas stored in the gas storage chamber is depressurized. At the same time, seawater at room temperature is introduced into the seawater inlet pipe through the seawater extraction system. The seawater passes through the hollow groove, the inner pipe, the rotating pipe, the hose, and the central pipe in sequence and flows into the heat exchange tube. The seawater exchanges heat with the low-temperature compressed natural gas through the heat exchange tube. The compressed natural gas is converted into gas through the pressure reduction and temperature increase operations, which is conducive to subsequent secondary canning or supplying power to the natural gas generator. The safety tank provided by the present invention itself has the functions of storing, reducing pressure, and increasing temperature for natural gas, so as to achieve the effect of one tank for multiple uses and effectively reduce energy consumption.

[0025] 3. The present invention sets a first connecting mechanism and a second connecting mechanism, and drives the cover plate away from the connecting plate by rotating the screw rod. At the same time, the cover plate drives the clamp to move, and the clamp drives multiple pipes to be pulled out from the slot. At this time, the bolts on the clamp can be loosened, so that the seawater inlet pipe, liquid nitrogen inlet pipe, canned air outlet pipe, power generation air outlet pipe, seawater outlet pipe, nitrogen air outlet pipe and recovery air inlet pipe can be removed from the cover plate, which is convenient for the overall disassembly and installation of the safety tank, the transfer of the safety tank on the ship and the flexible use between the secondary canning and the natural gas generator, meeting the multi-purpose requirements in practical applications.

[0026] 4. The present invention provides a rotating tube and its associated structure. When liquid nitrogen is introduced into the heat exchange tube to cool the compressed natural gas or normal temperature seawater is introduced into the heat exchange tube to heat the compressed natural gas, the rotating motor sequentially drives the lower gear, the upper gear, the rotating tube, and the swing rod to rotate. The swing rod drives the rectangular block to rotate. Since the slide column connected to the rectangular block needs to move along the guide groove, the rectangular block is pulled by the slide column while rotating around the rotating tube and sliding in the slide groove. That is, the rectangular block drives the heat exchange tube through the central tube to rotate and move along an elliptical trajectory in the gas storage cavity, so that the heat exchange tube is fully in contact with the compressed natural gas at various locations in the gas storage cavity, thereby improving the heat exchange efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the overall structure of an LNG ship tank boil-off gas recovery system according to Example 1 of the present invention;

[0028] Figure 2 This is a schematic diagram of the front cross-section structure of the safety can in Example 1;

[0029] Figure 3 It is a schematic diagram of the side cross-section structure of the safety can at the position of the swing rod in Example 1;

[0030] Figure 4 This is a schematic diagram of the connection structure between the rotating motor and the heat exchange tube in Example 1;

[0031] Figure 5 is a front cross-sectional structural schematic diagram of the first connecting mechanism in Example 1;

[0032] Figure 6 is a schematic diagram of the three-dimensional structure of the first connecting mechanism in Example 1;

[0033] Figure 7 is a front cross-sectional structural schematic diagram of the second connecting mechanism in Example 1;

[0034] Figure 8 This is a schematic diagram of the split structure of the second connecting mechanism in Example 1;

[0035] In the figure: 1. gas storage tank; 2. primary heat exchanger; 3. secondary heat exchanger; 4. gasifier; 5. compressor; 6. safety tank; 61. partition; 62. lifting mechanism; 621. lifting column; 622. threaded groove; 623. screw; 624. lifting bearing; 625. lifting motor; 63. support seat; 631. groove; 632. sealing seat; 64. decompression chamber; 65. gas storage chamber; 66. heat exchange tube; 67. rotating tube; 671. mounting bearing; 672. outer elbow joint; 673. inner elbow joint; 674. connecting bearing; 675. hose; 676. center tube; 677. upper gear; 678. lower gear; 679. rotating motor; 6710. rectangular block; 6711. sliding column; 6712. swing rod; 6713, slide; 68, first connecting mechanism; 69, second connecting mechanism; 691, connecting plate; 692, cylindrical seat; 693, hollow groove; 694, inner through pipe; 695, slot; 696, cover plate; 697, screw hole; 698, screw rod; 699, adjusting bearing; 6910, clamp; 6911, bolt; 6912, sealing block; 610, guide groove; 611, seawater inlet pipe; 612, liquid nitrogen inlet pipe; 613, canned air outlet pipe; 614, power generation air outlet pipe; 615, seawater outlet pipe; 616, nitrogen outlet pipe; 617, recovery air inlet pipe; 7, natural gas generator; 8, seawater extraction system; 81, seawater primary filter; 82, reverse osmosis filter; 83, refrigerator; 84, triangular valve. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front end", "rear end", "two ends", "one end", "the other end" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply 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" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0038] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" 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.

[0039] Example 1

[0040] like Figures 1 to 8 As shown, this embodiment provides an LNG ship tank boil-off gas recovery system, including a gas storage tank 1, a primary heat exchanger 2 connected to the gas storage tank 1, a secondary heat exchanger 3 connected to the gas storage tank 1 and the primary heat exchanger 2, a vaporizer 4 connected to the secondary heat exchanger 3, a compressor 5 connected to the secondary heat exchanger 3, a safety tank 6 installed between the gas storage tank 1 and the compressor 5, a natural gas generator 7 connected to the safety tank 6, and a seawater extraction system 8 connected to the safety tank 6 and the primary heat exchanger 2.

[0041] A partition 61 is provided inside the safety tank 6, and the length and width of the partition 61 are adapted to the length and width of the inner cavity of the safety tank 6. The partition 61 divides the inner cavity of the safety tank 6 into a pressure reduction chamber 64 and an air storage chamber 65. The partition 61 is raised and lowered by a lifting mechanism 62 to adjust the space size of the air storage chamber 65 and the pressure reduction chamber 64.

[0042] A support seat 63 is installed on the inner wall of the safety tank 6 below the partition 61, and a heat exchange tube 66 is arranged inside the gas storage cavity 65. The heat exchange tube 66 adopts an S-shaped bending structure, which is used to contact with the compressed natural gas in the gas storage cavity 65 to achieve heat exchange. Both ends of the heat exchange tube 66 are provided with a central tube 676, and the central tube 676 includes a hollow section and a solid section. The hollow section is integrally connected with the heat exchange tube 66. A rotating tube 67 is installed at the center of the inner wall at both ends of the gas storage cavity 65, and an elliptical guide groove 610 is also opened on the inner wall at both ends of the gas storage cavity 65.

[0043] A first connecting mechanism 68 and a rotating motor 679 are installed on the outer wall of one end of the safety tank 6, and a second connecting mechanism 69 and a rotating motor 679 are installed on the outer wall of the other end of the safety tank 6. The first connecting mechanism 68 and the second connecting mechanism 69 enable the heat exchange medium to enter and exit the heat exchange pipe 66 and the natural gas evaporated gas to enter and exit the gas storage chamber 65.

[0044] The rotating tube 67 is arranged horizontally and is rotatably connected to the inner wall of the safety tank 6 by installing a bearing 671. An inner bend pipe joint 673 is arranged at one end of the rotating tube 67 facing the inside of the safety tank 6, and an outer bend pipe joint 672 is arranged at one end of the rotating tube 67 facing the outside of the safety tank 6. Both the outer bend pipe joint 672 and the inner bend pipe joint 673 are right-angled circular tubes and are connected to the inner cavity of the rotating tube 67. Both ends of the rotating tube 67 are connected to the outer bend pipe joint 672 and the inner bend pipe joint 673 respectively through connecting bearings 674. 73 is rotatably connected, the mounting bearing 671 and the connecting bearing 674 are both sealed bearings that are resistant to low temperature and high pressure, and can adapt to the special environment of high pressure and low temperature in the air storage chamber 65. The other end of the inner bend pipe joint 673 is connected to a hose 675, and the other end of the hose 675 is vertically connected to the outer side wall of the hollow section of the central tube 676 to achieve communication between the rotating tube 67 and the heat exchange tube 66. The other end of the outer bend pipe joint 672 is connected to the first connecting mechanism 68 or the second connecting mechanism 69 through an inner through pipe 694.

[0045] Located on the side of the mounting bearing 671 facing the outside of the safety tank 6, the outer wall of the rotating tube 67 is fixedly sleeved with an upper gear 677, and a lower gear 678 is meshed and connected below the upper gear 677. The lower gear 678 is linked to a nearby rotating motor 679, and the two rotating motors 679 are synchronously driven by circuit control.

[0046] Located on the side of the mounting bearing 671 facing the inside of the safety can 6, the outer wall of the rotating tube 67 is fixedly sleeved with a swing rod 6712, and a slide groove 6713 is penetrated through the swing rod 6712. The solid section of the central tube 676 is connected with a rectangular block 6710, and a slide column 6711 is provided on the rectangular block 6710. The slide column 6711 is slidably connected to the guide groove 610, and the rectangular block 6710 is slidably connected to the slide groove 6713. It should be noted that the length of the hose 675 is to meet the requirement that when the slide column 6711 moves to the farthest position at both ends of the guide groove 610, it does not affect the normal communication function of the hose 675.

[0047] Furthermore, the combination of the central tube 676, the rectangular block 6710 and the sliding column 6711 passes through the swing rod 6712 as a whole, one end of which is slidably connected to the guide groove 610, and the other end is connected to the heat exchange tube 66. When the rotating tube 67 drives the swing rod 6712 to rotate, the swing rod 6712 simultaneously drives the rectangular block 6710 to rotate, and the sliding column 6711 connected to the rectangular block 6710 moves along the guide groove 610. Therefore, the rectangular block 6710 is pulled by the sliding column 6711 while rotating around the rotating tube 67 and moving along the sliding groove 6713, so that the rectangular block 6710 drives the heat exchange tube 66 to rotate and move along an elliptical trajectory in the air storage chamber 65 through the central tube 676, thereby achieving full contact between the heat exchange tube 66 and the compressed natural gas in the air storage chamber 65, and rapid heat exchange.

[0048] Furthermore, the lifting mechanism 62 includes a lifting column 621, a screw 623 and a lifting motor 625. The number of the lifting columns 621 is two and they are symmetrically distributed on the upper surface of the partition 61. The bottom of the lifting column 621 is welded and fixed to the partition 61. A threaded groove 622 is opened inside the lifting column 621. The number of the lifting motor 625 is two and they are symmetrically installed on the top of the safety tank 6. One end of the screw 623 is inserted into the threaded groove 622 and forms a threaded connection with the lifting column 621, while the other end passes through the safety tank 6 and is linked to the lifting motor 625. The screw 623 is rotatably connected to the top wall of the safety tank 6 through a lifting bearing 624. The lifting bearing 624 uses a sealed bearing that is resistant to low temperature and high pressure, which can adapt to the special environment of high pressure and low temperature inside the safety tank 6. The two lifting motors 625 are synchronously driven by a circuit.

[0049] Furthermore, a groove 631 is provided on the upper surface of the support seat 63, and the cross section of the groove 631 is a right-angle trapezoid. A sealing seat 632 is fixedly connected to the lower surface of the partition 61. The sealing seat 632 corresponds to the groove 631 in position and matches in shape. The movable connection between the sealing seat 632 and the support seat 63 is achieved by moving the partition 61. Both the support seat 63 and the sealing seat 632 are in the shape of a rectangular frame. The sealing seat 632 is made of a low-temperature and high-pressure resistant material, such as acrylic rubber, and can be used in the range of -25-170°C. The shape matching involved in the present invention means that the two have the same shape and are consistent in size or have an interference of 0.5-2mm. Specifically, in this embodiment, the width dimension of the sealing seat 632 can be equal to or slightly larger than the width dimension of the groove 631. When the sealing seat 632 is inserted into the groove 631, the sealing seat 632 is squeezed and deformed by the inner wall of the groove 631, so that the sealing seat 632 is tightly attached to the groove 631 and the inner wall of the safety tank 6, thereby sealing the gap between the partition 61 and the inner wall of the safety tank 6.

[0050] Furthermore, the first connecting mechanism 68 is provided with a seawater inlet pipe 611, a liquid nitrogen inlet pipe 612 and a canned gas outlet pipe 613. One ends of the seawater inlet pipe 611 and the liquid nitrogen inlet pipe 612 are connected to the heat exchange pipe 66 through an inner tube 694. The other end of the seawater inlet pipe 611 is connected to the seawater extraction system 8 for introducing seawater at room temperature into the heat exchange pipe 66 to heat up the compressed natural gas. The liquid nitrogen inlet pipe 612 is used to introduce liquid nitrogen into the heat exchange pipe 66 to cool the compressed natural gas. One end of the canned gas outlet pipe 613 is connected to the gas storage chamber 65 through the inner tube 694 and the other end is used to connect to the gas storage tank 1. The compressed natural gas stored in the safety tank 6 is introduced into the gas storage tank 1 through the canned gas outlet pipe 613 for secondary canning and utilization.

[0051] The second connecting mechanism 69 is provided with a power generation outlet pipe 614, a seawater outlet pipe 615, a nitrogen outlet pipe 616 and a recovery air inlet pipe 617. One ends of the seawater outlet pipe 615 and the nitrogen outlet pipe 616 are connected to the heat exchange pipe 66 through an inner tube 694. The seawater outlet pipe 615 is used to discharge the seawater in the heat exchange pipe 66. The nitrogen outlet pipe 616 is used to discharge the liquid nitrogen after refrigeration and vaporization. One ends of the recovery air inlet pipe 617 and the power generation outlet pipe 614 are connected to the air storage chamber 65 through the inner tube 694. The other end of the recovery air inlet pipe 617 is used to connect to the compressor 5. The other end of the power generation outlet pipe 614 is used to connect to the natural gas generator 7.

[0052] The first connecting mechanism 68 and the second connecting mechanism 69 both include a connecting plate 691 and a cover plate 696. The connecting plate 691 is fixedly connected to the outer wall of the safety tank 6. The cover plate 696 is located on the side of the connecting plate 691 away from the safety tank 6. A columnar seat 692 and a sealing block 6912 are provided between the connecting plate 691 and the cover plate 696. The sealing block 6912 is fixedly connected to the cover plate 696. The columnar seat 692 is fixedly connected to the connecting plate 691 or is integrally formed.

[0053] The interior of the columnar seat 692 is completely connected, and the side close to the safety tank 6 is connected to an inner through pipe 694, a hollow groove 693 is provided in the middle, and one or two slots 695 are provided on the side away from the safety tank 6. The seawater inlet pipe 611, the liquid nitrogen inlet pipe 612, the tank gas outlet pipe 613, the power generation gas outlet pipe 614, the seawater outlet pipe 615, the nitrogen gas outlet pipe 616 and the recovery gas inlet pipe 617 correspond to each slot 695 one by one and are respectively inserted into the cover plate 696 after passing through the cover plate 696. The slots 695 corresponding to the seawater inlet pipe 611 and the liquid nitrogen inlet pipe 612 are located in the same columnar seat 692 and connected to the same hollow groove 693. The slots 695 corresponding to the seawater outlet pipe 615 and the nitrogen outlet pipe 616 are located in the same columnar seat 692 and connected to the same hollow groove 693. The canned air outlet pipe 613, the power generation air outlet pipe 614 and the recovery air inlet pipe 617 all correspond to the columnar seat 692 with independent slot structures.

[0054] The slot 695 is truncated cone-shaped and its diameter becomes smaller as it gets closer to the safety tank 6. The sealing block 6912 corresponds to the position of each slot 695 and is circumferentially arranged along the outer side walls of the insertion ends of the coastal water inlet pipe 611, the liquid nitrogen inlet pipe 612, the canned air outlet pipe 613, the power generation air outlet pipe 614, the seawater outlet pipe 615, the nitrogen air outlet pipe 616 and the recovery air inlet pipe 617. The shape of the sealing block 6912 matches the slot 695. The movable plug-in between the sealing block 6912 and the slot 695 is realized by moving the cover plate 696. When the sealing block 6912 is inserted into the slot 695, the sealing block 6912 is squeezed and deformed by the inner wall of the slot 695, so that the sealing block 6912 is closely attached to the slot 695 and the outer wall of the pipe, thereby sealing the gap between each pipe and the columnar seat 692. At the same time, the friction between the sealing block 6912 and the inner wall of the slot 695 and the outer wall of each pipe is increased, thereby reinforcing the gap between each pipe and the cover plate 696. In this embodiment, the sealing block 6912 is made of ordinary rubber.

[0055] A plurality of screw holes 697 are provided at the edge of the cover plate 696, and a plurality of adjusting bearings 699 are provided at the positions of the connecting plate 691 corresponding to the screw holes 697. A screw rod 698 is provided through the screw hole 697, and one end of the screw rod 698 is rotatably connected to the connecting plate 691 through the adjusting bearing 699. The screw rod 698 is threadedly connected to the cover plate 696 through the screw hole 697, and the cover plate 696 can be moved closer to or away from the connecting plate 691 by rotating the screw rod 698.

[0056] The outer walls of the seawater inlet pipe 611, the liquid nitrogen inlet pipe 612, the canned air outlet pipe 613, the power generation air outlet pipe 614, the seawater outlet pipe 615, the nitrogen air outlet pipe 616 and the recovery air inlet pipe 617 are all sleeved with a clamp 6910, and the middle part of the clamp 6910 is welded and fixed to the side of the cover plate 696 away from the connecting plate 691, and bolts 6911 are provided at both ends of the clamp 6910, and the two ends of the clamp 6910 can be separated by removing the bolts 6911. When the cover plate 696 drives the clamp 6910 to move, the clamp 6910 simultaneously drives multiple pipes to be inserted into the corresponding slots 695 to achieve communication with the corresponding hollow grooves 693 and the inner through pipe 694, or the clamp 6910 simultaneously drives multiple pipes to be pulled out from the slots 695, loosening the bolts 6911 on the clamp 6910, so that the seawater inlet pipe 611, the liquid nitrogen inlet pipe 612, the tank outlet pipe 613, the power generation outlet pipe 614, the seawater outlet pipe 615, the nitrogen outlet pipe 616 and the recovery inlet pipe 617 can be quickly removed from the cover plate 696, so as to facilitate the overall disassembly and assembly of the safety tank 6, the transfer of the safety tank 6 on board, and the flexible use between the secondary tanking and the natural gas generator 7.

[0057] It should be noted that the present invention involves multiple internal pipes 694 and correspondingly connects various pipelines, and each internal pipe 694 is installed with a valve to ensure that the sealing inside the safety tank 6 is maintained when the safety tank 6 is disassembled as a whole. Among them, the seawater inlet pipe 611 and the liquid nitrogen inlet pipe 612 are connected to the same internal pipe 694, and the seawater outlet pipe 615 and the nitrogen outlet pipe 616 are also connected to the same internal pipe 694. When the compressed natural gas is stored, liquid nitrogen is passed into the heat exchange pipe 66 to cool the compressed natural gas, and when the compressed natural gas is used, normal temperature seawater is passed into the heat exchange pipe 66 to heat the compressed natural gas, and the two states of storage and use are not carried out at the same time, and the use of seawater heating and liquid nitrogen cooling will not interfere with each other. In addition, valves are installed on each pipeline or the external pipeline of each pipeline to intercept the flow inside each pipeline and control the liquid flow path, ensuring that seawater enters from the seawater inlet pipe 611 and is discharged from the seawater outlet pipe 615, and ensuring that liquid nitrogen enters from the liquid nitrogen inlet pipe 612 and is discharged from the nitrogen outlet pipe 616.

[0058] Furthermore, the seawater extraction system 8 includes a seawater primary filter 81, which performs preliminary filtering of large particle impurities on the extracted seawater. The outlet pipe of the seawater primary filter 81 is connected to a reverse osmosis filter 82 for two-stage filtering of the seawater. The outlet pipe of the reverse osmosis filter 82 is connected to a refrigerator 83 for cooling the seawater. A triangular valve 84 is installed on the outlet pipe of the refrigerator 83. One outlet of the triangular valve 84 is connected to the seawater inlet pipe 611, and the other outlet of the triangular valve 84 is connected to the primary heat exchanger 2, that is, the cooled seawater is diverted through the triangular valve 84 and flows into the primary heat exchanger 2 for heat exchange. It should be noted that when seawater is used to heat the compressed natural gas in the gas storage chamber 65, the refrigerator 83 does not work, and the seawater at room temperature is directly introduced. At this time, there is a large temperature difference between the seawater and the compressed natural gas.

[0059] The use process of the LNG ship tank boil-off gas recovery system provided in this embodiment is as follows:

[0060] When it is necessary to recover the evaporated gas in the LNG tank, the seawater is filtered through the seawater primary filter 81, and then enters the reverse osmosis filter 82 for secondary filtration, and then flows into the primary heat exchanger 2 after being cooled by the refrigerator 83. The natural gas in the gas storage tank 1 passes through the primary heat exchanger 2 or directly enters the secondary heat exchanger 3 for cooling, and then passes through the vaporizer 4 for vaporization and output for use. The evaporated gas generated during the storage and transportation process is heat exchanged by the secondary heat exchanger 3 and then passed through the pipeline to the compressor 5 for partial compression. At this time, the evaporated gas is pressurized but has not reached a high pressure state that can be stored. The evaporated gas enters the gas storage chamber 65 from the recovery air inlet pipe 617. At this time, liquid nitrogen is introduced into the liquid nitrogen inlet pipe 612, and the liquid nitrogen enters the inner pipe 694 through the corresponding hollow groove 693 on the first connecting mechanism 68, and flows into the heat exchange pipe 66 through the outer elbow joint 672, the rotating pipe 67, the inner elbow joint, the hose 675, and the central pipe 676 in sequence to fully contact with the evaporated gas, and condense and cool it.

[0061] At the same time, the rotating motor 679 drives the lower gear 678 to rotate, the lower gear 678 drives the upper gear 677 to rotate, the upper gear 677 drives the rotating tube 67 to rotate, the rotating tube 67 drives the swing rod 6712 to rotate, and the swing rod 6712 drives the rectangular block 6710 to rotate. Since the rectangular block 6710 is restricted by the sliding column 6711 connected to it to slide in the guide groove 610, the rectangular block 6710 slides in the slide groove 6713 and moves along the guide groove 610. The rectangular block 6710 drives the heat exchange tube 66 to rotate and move along an elliptical trajectory in the air storage chamber 65 through the central tube 676. This trajectory is conducive to the full contact between the heat exchange tube 66 and the compressed natural gas in the air storage chamber 65 to achieve rapid heat exchange.

[0062] When the stored compressed natural gas needs to be used, the screw 623 is driven to rotate by the lifting motor 625, and the screw 623 drives the lifting column 621 to rise through the threaded groove 622. The lifting column 621 drives the partition 61 to move upward in the safety tank 6, so that the space of the gas storage chamber 65 is increased. At this time, the pressure of the compressed natural gas stored in the gas storage chamber 65 decreases. At the same time, after being processed by the seawater primary filter 81 and the reverse osmosis filter 82, the seawater is passed into the seawater inlet pipe 611 without being refrigerated. The seawater at room temperature is passed through the first connecting mechanism The corresponding hollow groove 693 on 68 enters the inner through pipe 694, and flows into the heat exchange pipe 66 through the outer elbow joint 672, the rotating pipe 67, the inner elbow joint, the hose 675, and the central pipe 676 in sequence to exchange heat with the low-temperature compressed natural gas. The compressed natural gas is vaporized into gas after pressure reduction and temperature increase, and finally enters the gas storage tank 1 through the canned gas outlet pipe 613 for secondary canning, or enters the natural gas generator 7 through the power generation outlet pipe 614, and is combined with the recovered natural gas for power generation operation to meet the power supply needs on board.

[0063] In the above-mentioned process of utilizing the stored compressed natural gas, the safety tank 6 needs to be moved to the side of the gas storage tank 1 or the natural gas generator 7, so the safety tank 6 needs to be disassembled for transfer. First, the valves on each inner tube 694 are closed, and then the screw 698 is rotated. The screw 698 rotates in the screw hole 697 to drive the cover plate 696 away from the connecting plate 691. The cover plate 696 drives the clamp 6910 to move, and the clamp 6910 drives multiple pipes to be pulled out from the slot 695. The bolt 6911 on the clamp 6910 is loosened, so that the seawater inlet pipe 611, the liquid nitrogen inlet pipe 612, the canned air outlet pipe 613, the power generation air outlet pipe 614, the seawater outlet pipe 615, the nitrogen air outlet pipe 616 and the recovery air inlet pipe 617 can be removed from the cover plate 696, which is convenient for the overall disassembly and assembly of the safety tank 6 and convenient for transfer on the ship.

[0064] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An LNG ship tank boil-off gas recovery system, characterized by: The invention comprises a gas storage tank (1), a primary heat exchanger (2) connected to the gas storage tank (1), a secondary heat exchanger (3) connected to the gas storage tank (1) and the primary heat exchanger (2), a vaporizer (4) connected to the secondary heat exchanger (3), a compressor (5) connected to the secondary heat exchanger (3), a safety tank (6) installed between the gas storage tank (1) and the compressor (5), a natural gas generator (7) connected to the safety tank (6), and a seawater extraction system (8) connected to the safety tank (6) and the primary heat exchanger (2); A partition (61) movable up and down is arranged inside the safety tank (6), and the partition (61) divides the inner cavity of the safety tank (6) into a pressure reduction cavity (64) and an air storage cavity (65) up and down. A heat exchange tube (66) is arranged inside the air storage cavity (65). Both ends of the heat exchange tube (66) are provided with a central tube (676), and the central tube (676) includes a hollow section and a solid section. The hollow section is connected to the heat exchange tube (66) in one piece. The outer walls of both ends of the safety tank (6) are respectively provided with a first connection mechanism (68) and a second connection mechanism (69), and both are provided with a rotating motor (679). The inner walls of both ends of the air storage cavity (65) are provided with a guide groove (610) and a rotating tube (67) is horizontally installed. An inner bend pipe joint (673) is provided at one end of the rotating tube (67) facing the interior of the safety tank (6), and the other end of the inner bend pipe joint (673) is connected to the hollow section of the central tube (676) through a hose (675). An outer bend pipe joint (672) is provided at one end of the rotating tube (67) facing the exterior of the safety tank (6), and the other end of the outer bend pipe joint (672) is connected to the first connecting mechanism (68) or the second connecting mechanism (69) through an inner through pipe (694). The rotating tube (67) is rotatably connected to the inner wall of the safety tank (6) through a mounting bearing (671), and the two ends of the rotating tube (67) are rotatably connected to an outer bend pipe joint (672) and an inner bend pipe joint (673) respectively through connecting bearings (674). An upper gear (677) is fixedly sleeved on the outer wall of the rotating tube (67), and a lower gear (678) is meshedly connected below the upper gear (677), and the lower gear (678) is linked to a rotating motor (679); The solid section of the central tube (676) is connected to a rectangular block (6710), a sliding column (6711) is provided on the rectangular block (6710), and the sliding column (6711) is slidably connected to the guide groove (610). The outer wall of the rotating tube (67) is fixedly sleeved with a rocker rod (6712), and a sliding groove (6713) is penetrated through the rocker rod (6712), and the rectangular block (6710) is slidably connected to the sliding groove (6713).

2. The LNG ship tank boil-off gas recovery system according to claim 1, characterized in that: The partition (61) is moved up and down by a lifting mechanism (62). The lifting mechanism (62) includes a lifting column (621), a screw (623) and a lifting motor (625). The lifting column (621) is fixedly mounted on the upper surface of the partition (61). A threaded groove (622) is provided inside the lifting column (621). The lifting motor (625) is mounted on the top of the safety tank (6). One end of the screw (623) is inserted into the threaded groove (622) and is threadedly connected to the lifting column (621), while the other end passes through the safety tank (6) and is linked to the lifting motor (625). The screw (623) is rotatably connected to the top wall of the safety tank (6) through a lifting bearing (624).

3. The LNG ship tank boil-off gas recovery system according to claim 1, characterized in that: A support seat (63) is installed on the inner wall of the safety can (6) below the partition (61); a groove (631) is provided on the upper surface of the support seat (63); the cross section of the groove (631) is in the shape of a right-angle trapezoid; a sealing seat (632) is fixedly connected to the lower surface of the partition (61); the sealing seat (632) corresponds to the groove (631) in position and matches in shape; the movable plug-in between the sealing seat (632) and the support seat (63) is achieved by moving the partition (61); the support seat (63) and the sealing seat (632) are both in the shape of a rectangular frame.

4. The LNG ship tank boil-off gas recovery system according to claim 1, characterized in that: The first connection mechanism (68) is provided with a seawater inlet pipe (611), a liquid nitrogen inlet pipe (612) and a canned gas outlet pipe (613); one end of the seawater inlet pipe (611) and the liquid nitrogen inlet pipe (612) are both connected to the heat exchange pipe (66) through an inner through pipe (694); the other end of the seawater inlet pipe (611) is used to connect to the seawater extraction system (8); one end of the canned gas outlet pipe (613) is connected to the inner cavity of the safety tank (6) through the inner through pipe (694) and the other end is used to connect to the gas storage tank (1); The second connection mechanism (69) is provided with a power generation outlet pipe (614), a seawater outlet pipe (615), a nitrogen outlet pipe (616) and a recovery inlet pipe (617); one end of the seawater outlet pipe (615) and the nitrogen outlet pipe (616) are both connected to the heat exchange pipe (66) via an inner tube (694); one end of the recovery inlet pipe (617) and the power generation outlet pipe (614) are both connected to the inner cavity of the safety tank (6) via an inner tube (694); the other end of the recovery inlet pipe (617) is used to connect to the compressor (5); and the other end of the power generation outlet pipe (614) is used to connect to the natural gas generator (7).

5. The LNG ship tank boil-off gas recovery system according to claim 4, characterized in that: The first connecting mechanism (68) and the second connecting mechanism (69) both comprise a connecting plate (691) and a cover plate (696); the connecting plate (691) is fixedly connected to the outer wall of the safety tank (6); the cover plate (696) is located on a side of the connecting plate (691) away from the safety tank (6); a columnar seat (692) and a sealing block (6912) are provided between the connecting plate (691) and the cover plate (696); the sealing block (6912) is fixedly connected to the cover plate (696); and the columnar seat (692) is fixedly connected to the connecting plate (691); The interior of the columnar seat (692) is integrally connected, and the side close to the safety tank (6) is connected to an inner through pipe (694), a hollow groove (693) is provided in the middle, and one or two slots (695) are provided on the side away from the safety tank (6). The slots (695) are truncated and the closer they are to the safety tank (6), the smaller their diameters are. The sealing block (6912) and the slots (695) correspond in position and match in shape. The movable plug-in connection between the sealing block (6912) and the slots (695) is achieved by moving the cover plate (696). The seawater inlet pipe (611) The liquid nitrogen inlet pipe (612), the canned air outlet pipe (613), the power generation air outlet pipe (614), the seawater outlet pipe (615), the nitrogen outlet pipe (616) and the recovery air inlet pipe (617) all pass through the cover plate (696) and are respectively inserted into the respective slots (695), and the sealing block (6912) is circumferentially arranged along the outer wall of the insertion end of the seawater inlet pipe (611), the liquid nitrogen inlet pipe (612), the canned air outlet pipe (613), the power generation air outlet pipe (614), the seawater outlet pipe (615), the nitrogen outlet pipe (616) and the recovery air inlet pipe (617).

6. The LNG ship tank boil-off gas recovery system according to claim 5, characterized in that: The outer walls of the seawater inlet pipe (611), the liquid nitrogen inlet pipe (612), the canned air outlet pipe (613), the power generation air outlet pipe (614), the seawater outlet pipe (615), the nitrogen air outlet pipe (616) and the recovery air inlet pipe (617) are all sleeved with a clamp (6910), and the middle part of the clamp (6910) is welded and fixed to the side of the cover plate (696) away from the connecting plate (691), and bolts (6911) are provided at both ends of the clamp (6910) to penetrate through the closed ends, and the two ends of the clamp (6910) can be separated by removing the bolts (6911).

7. The LNG ship tank boil-off gas recovery system according to claim 5, characterized in that: The cover plate (696) is provided with a plurality of screw holes (697), and the connection plate (691) is provided with a plurality of adjustment bearings (699) at positions corresponding to the screw holes (697). A screw rod (698) is provided through the screw hole (697), and one end of the screw rod (698) is rotatably connected to the connection plate (691) through the adjustment bearing (699). The screw rod (698) is threadedly connected to the cover plate (696) through the screw hole (697), and the cover plate (696) is moved closer to or farther away from the connection plate (691) by rotating the screw rod (698).

8. The LNG ship tank boil-off gas recovery system according to claim 1, characterized in that: The guide groove (610) is elliptical.

9. The LNG ship tank boil-off gas recovery system according to claim 1, characterized in that: The rocker rod (6712) and the upper gear (677) are respectively arranged on both sides of the mounting bearing (671).

10. The LNG ship tank boil-off gas recovery system according to claim 4, characterized in that: The seawater extraction system (8) comprises a seawater primary filter (81), the outlet pipe of the seawater primary filter (81) is connected to a reverse osmosis filter (82), the outlet pipe of the reverse osmosis filter (82) is connected to a refrigerator (83), a triangular valve (84) is installed on the outlet pipe of the refrigerator (83), one outlet of the triangular valve (84) is connected to the seawater inlet pipe (611), and the other outlet of the triangular valve (84) is connected to the primary heat exchanger (2).

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