Overpressure gas condensation recovery device based on LNG cold energy power generation system

Abstract

The present invention relates to the technical field of LNG cold energy power generation. Disclosed is an overpressure gas condensation recovery device based on an LNG cold energy power generation system, comprising: a tank body; and a condensation cavity arranged at the bottom of the tank body, LNG condensate being stored in the condensation cavity and used for condensing BOG gas, wherein the condensation cavity comprises a vertical hollow pipe mounted in the tank body, and a connecting mechanism is arranged at the bottom of the vertical hollow pipe. The shape and position design of the vertical hollow pipe enables gas to be in initial contact with the condensate in the flowing process of the gas in the vertical hollow pipe; due to a pressure difference, gas at the inlet can continuously enter the vertical hollow pipe, and after entering a conical pipe, the gas is distributed along the cavity shape of the conical pipe and spreads downwards, so that the contact time between the gas and the condensate is increased without expanding the diffusion area of the gas after entering the condensate, allowing for full utilization of the condensate in a limited volume condensation cavity.

Description

An overpressure gas condensation recovery device based on LNG cold energy power generation system

[0001] Cross-references

[0002] This application claims priority to Chinese patent application No. 2023111543462, filed on September 8, 2023. The contents of the above application are incorporated herein by reference. Technical Field

[0003] The present invention relates to the technical field of LNG cold energy power generation, and in particular to an overpressure gas condensation recovery device based on an LNG cold energy power generation system. Background Art

[0004] LNG (liquefied natural gas) cooling systems are a highly efficient and environmentally friendly cooling energy utilization technology widely used in LNG carriers, LNG receiving terminals, LNG transport vehicles, and LNG filling stations. The primary function of LNG cooling systems is to efficiently recover and utilize the cooling energy released during the evaporation and gasification of LNG. LNG inevitably exchanges heat with the surrounding environment, causing the temperature to rise and some of the liquid gas to evaporate, forming overpressure gases such as propane, ethylene, and BOG (boil-off gas).

[0005] Existing recovery systems use high-pressure BOG compression and external transmission, which consumes a lot of electricity. Discharging overpressured gas into a flare for disposal wastes resources and, as a flammable gas with a strong greenhouse effect, releases it into the air, adversely increasing the greenhouse effect. For economic, environmental, and safety reasons, BOG needs to be reliquefied and stored. However, traditional reliquefaction processes use low-temperature refrigerants (such as LNG or liquid nitrogen) for heat exchange, which requires high external transmission requirements and operating costs, and hinders the low-energy, efficient operation of BOG recovery systems.

[0006] A published patent (Patent No. CN216976501U) discloses a natural gas BOG condensation and recovery system. The system comprises: a tank; a labyrinth assembly comprising a plurality of baffles disposed within the tank, the baffles being vertically spaced apart, with any two adjacent baffles arranged in a staggered arrangement. The LNG level within the tank is maintained above the labyrinth assembly; a BOG inlet pipeline connected to the tank, with the connection between the BOG inlet pipeline and the tank located below the labyrinth assembly. The labyrinth assembly effectively prolongs the passage time of the BOG, promoting liquefaction; a first spray device disposed within the tank and located at the top of the tank, for spraying LNG into the tank; and an LNG inlet pipeline for supplying LNG to the first spray device. This natural gas BOG condensation and recovery system has a simple structure and avoids waste and pollution. However, while a multi-stage condensation system can improve BOG condensation efficiency to a certain extent, the increased time the gas remains in the liquid due to the multiple baffles in the first stage does not significantly improve BOG condensation efficiency. The steady input of gas through the calm liquid does not lead to a better condensation of BOG gas.

[0007] Summary of the Invention

[0008] The object of the present invention is to provide an overpressure gas condensation recovery device based on an LNG cold energy power generation system to solve the problem of low BOG condensation and recovery efficiency mentioned in the above background technology.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] An overpressure gas condensation recovery device based on an LNG cold energy power generation system, comprising:

[0011] A tank body, wherein the upper end of the tank body is connected to the output port, and the lower end of the tank body is connected to the input port;

[0012] A condensation chamber is provided at the bottom of the tank body, and contains LNG condensate for condensing BOG gas. The condensation chamber includes a vertical hollow tube installed inside the tank body, a docking mechanism is provided at the bottom of the vertical hollow tube, and a tapered tube is fixedly installed on the top of the vertical hollow tube. The tapered tube and the vertical hollow tube are designed to be connected.

[0013] As a further solution of the present invention: wherein, the side wall of the tapered tube is provided with a cavity, and the cavity is designed to be connected with the hollow part of the vertical hollow tube.

[0014] As a further solution of the present invention: wherein, the docking mechanism includes a square block fixedly connected to the bottom of the vertical hollow tube, the interior of the square block is hollow, and through grooves are opened on both sides, and closed grooves are opened on the inner side of the through grooves. The square block is movably installed with a docking tube on the end face away from the vertical hollow tube, and closed plates are fixedly installed on both sides of the docking tube corresponding to the closed grooves, and reset springs are provided on both sides of the closing plate.

[0015] As a further solution of the present invention: wherein, the size and position of the closing plate correspond to the closing groove, and when the closing plate is inserted into the closing groove, the through groove is blocked.

[0016] As a further solution of the present invention: wherein, the tank body (10) is connected to an LNG condensate inlet pipe (30) and an LNG condensate outlet pipe (70), the LNG condensate inlet pipe (30) extends into the condensation chamber (20) and the end portion is fixedly connected and communicated with the top of the tapered tube (23), and a spiral plate (31) distributed from top to bottom around the inside of the tapered tube (23) is provided on the path of condensate outlet in the LNG condensate inlet pipe (30).

[0017] As a further solution of the present invention: wherein, a hollow plate is provided on the top of the condensation chamber. After the LNG condensate enters the condensation chamber, the height of the LNG condensate is lower than the hollow plate. The remaining gas after being condensed by the condensation chamber will be released from the holes of the hollow plate to the top of the tank body.

[0018] As a further solution of the present invention, the LNG condensate output pipe (70) is arranged at the bottom of the condensation chamber (20), and the LNG condensate is arranged to be circulated and input.

[0019] As a further solution of the present invention: wherein, a secondary condensation chamber is provided inside the tank body and above the condensation chamber, the secondary condensation chamber includes a conical table, a conical cavity is provided inside the conical table, the conical cavity is used to receive the residual gas from the condensation chamber, an atomizing sprayer is fixedly installed on the top of the conical table, and the atomizing sprayer sprays aerosol in an annular range to achieve further cooling and condensation of the residual gas.

[0020] The conical platform is in the shape of an inverted trumpet, which is divided into a trumpet mouth and a trumpet body. The trumpet body is provided with a plurality of leakage holes to discharge the gas from the condensation chamber, and an arc-shaped reflux port is provided at the trumpet mouth.

[0021] The plurality of leakage holes are at different heights and are distributed in a ring shape on the horn body.

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

[0023] 1. The shape and position design of the vertical hollow tube in the present invention can allow the gas to complete its initial contact with the condensate during the flow process in the vertical hollow tube. Due to the existence of the pressure difference, the gas at the input port will continuously enter the vertical hollow tube. After entering the tapered tube, the gas is distributed downward along the cavity shape of the tapered tube, which increases the contact time between the gas and the condensate without expanding the diffusion area of ​​the gas after entering the condensate, and can fully utilize the condensate in the limited volume condensation chamber.

[0024] 2. BOG gas input through the inlet can pass through the hollow part of the vertical hollow tube and enter the cavity of the tapered tube. The gas will move from bottom to top along the bottom of the vertical hollow tube. When it moves to the top of the vertical hollow tube and enters the tapered tube, due to the volume of the tapered tube, the gas will move from top to bottom along the cavity of the tapered tube under the existence of pressure. Due to the existence of the cone cavity, the gas will gradually fill the cavity of the tapered tube as it moves downward from the initial narrow space. As the volume of the cavity increases, the gas filling also increases, thereby affecting the contact time between the gas and the condensate per unit time, thereby improving the efficiency of gas condensation and recovery.

[0025] 3. Push the docking tube inward through the input port to insert it into the square block. At this time, the reset spring is squeezed and has elastic potential energy. The closing plate is inserted into the closed groove along with the docking tube. At this time, the closing plate is in a closed state, and the through grooves on both sides of the square block are also in a closed state. The gas in the input port can enter the vertical hollow tube through the docking tube. When condensation is completed, the input port is separated from the docking tube. Under the action of the elastic potential energy of the reset spring, the docking tube is forced to separate from the square block. At this time, the closing plate is separated from the closed groove, and the through grooves on both sides of the square block are opened. At this time, the gas remaining in the vertical hollow tube will directly enter the condensation chamber through the through groove, avoiding the problem of backflow.

[0026] 4. LNG condensate enters the condensation chamber from the LNG condensate inlet pipe. The presence of the spiral plate affects the flow direction of the LNG condensate. When entering, the LNG condensate will make a spiral motion along the shape of the spiral plate. Initially, because the LNG condensate enters the spiral plate under the action of the pressure difference, a vortex will be formed. Due to the presence of the spiral plate, the vortex will be transmitted downward from the top of the tapered tube. After reaching the bottom of the tapered tube, it will gradually disappear due to the presence of the tapered tube protective wall. Therefore, when BOG gas enters the condensation chamber from the tapered tube, the presence of the condensate vortex will accelerate the diffusion of the gas in the condensate, thereby improving the condensation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG1 is a schematic diagram of the overall structure of the present invention;

[0028] FIG2 is a schematic cross-sectional view of the condensation chamber structure of the present invention;

[0029] FIG3 is a schematic cross-sectional view of the tank structure of the present invention;

[0030] FIG4 is a partial enlarged view of point A in FIG2 of the present invention;

[0031] FIG5 is a perspective schematic diagram of the docking mechanism of the present invention;

[0032] FIG6 is a schematic diagram of the structure of the secondary condensation chamber in the tank body of the present invention;

[0033] FIG7 is a schematic diagram showing the connection between the secondary condensation chamber and the condensation cavity structure in the present invention;

[0034] FIG8 is a schematic diagram of the overall structure of the conical platform in the present invention;

[0035] FIG9 is a schematic diagram of the flow of gas inside the tank in the present invention.

[0036] The correspondence between the labels and component names in the figure is as follows: 10. Tank body; 11. Output port; 12. Input port; 20. Condensation chamber; 21. Vertical hollow tube; 22. Docking mechanism; 221. Square block; 222. Through groove; 223. Closed groove; 224. Docking tube; 225. Closed plate; 226. Return spring; 23. Conical tube; 30. LNG condensate input pipe; 31. Spiral plate; 40. Hollow plate; 50. Secondary condensation chamber; 51. Conical platform; 52. Leakage hole; 521. Bell mouth; 522. Bell body; 523. Arc-shaped reflux port; 60. Atomizing sprayer; 70. LNG condensate output pipe. DETAILED DESCRIPTION

[0037] Please refer to Figure 1. An overpressure gas condensation and recovery device based on an LNG cold energy power generation system includes a tank body 10, an output port 11 arranged above the tank body 10, and an input port 12 arranged below the tank body 10. BOG gas is input into the tank body 10 through the input port 12 and then discharged from the output port 11. During this process, the BOG gas is condensed and recovered by the internal condensing device of the tank body 10. After another cycle, if the BOG gas cannot be completely condensed, it will return to the input port 12 from the output port 11 and be introduced into the tank body 10 for condensation again.

[0038] As shown in Figure 2, based on the existing technology, in order to improve the condensation effect, the present invention is provided with a condensation chamber 20 below the tank body 10, and the condensation chamber 20 includes a vertical hollow tube 21 installed inside the tank body 10, and the bottom of the vertical hollow tube 21 is provided with a docking mechanism 22 corresponding to the input port 12, and the vertical hollow tube 21 is hollow in design. A conical tube 23 connected to the vertical hollow tube 21 is fixedly installed on the top of the vertical hollow tube 21, and the side wall of the conical tube 23 is provided with a cavity, and the cavity is designed to be connected to the hollow part of the vertical hollow tube 21. In this embodiment, BOG gas input through the input port 12 passes through the hollow portion of the vertical hollow tube 21 and enters the cavity of the tapered tube 23. The gas moves from bottom to top along the bottom of the vertical hollow tube 21. After reaching the top of the vertical hollow tube 21 and entering the tapered tube 23, the volume of the tapered tube 23 causes the gas to move from top to bottom along the cavity of the tapered tube 23 under the pressure. Due to the presence of the conical cavity, the gas gradually fills the cavity of the tapered tube 23 as it moves downward from the initial narrow space. As the volume of the cavity increases, the amount of gas filled also increases, thereby affecting the contact time between the gas and the condensate per unit time, thereby improving the efficiency of gas condensation and recovery.

[0039] As shown in Figure 5, further, the shape and position design of the vertical hollow tube 21 can allow the gas to complete its initial contact with the condensate during the flow process of the vertical hollow tube 21. Due to the existence of the pressure difference, the gas at the input port 12 will continuously enter the vertical hollow tube 21. After entering the tapered tube 23, the gas is distributed and spread downward along the cavity shape of the tapered tube 23, which increases the contact time between the gas and the condensate without expanding the diffusion area of ​​the gas after entering the condensate, and can make full use of the condensate in the limited volume condensation chamber 20.

[0040] As shown in Figures 3 and 4 , after BOG gas is introduced from the inlet 12, due to the length of the vertical hollow tube 21, after the pressure difference disappears, the BOG gas that has not yet been discharged will remain inside the vertical hollow tube 21, causing the BOG gas to flow back and be discharged into the air. To address this problem, the docking mechanism 22 includes a square block 221 fixedly connected to the bottom of the vertical hollow tube 21. The square block 221 has a hollow interior and is provided with through slots 222 on both sides. The through slots 222 are provided with closed slots 223 inside. A docking tube 224 is movably mounted on the end surface of the square block 221 away from the vertical hollow tube 21. Closing plates 225 are fixedly mounted on both sides of the docking tube 224 corresponding to the closed slots 223. Return springs 226 are provided on both sides of the closing plate 225. One end of the return spring 226 is fixedly connected to the closing plate 225 and the other end is fixedly connected to the square block 221. In this embodiment, initially, the connecting tube 224 is located outside the block 221. During use, the inlet 12 pushes inward, driving the connecting tube 224 into the block 221. This compresses the return spring 226, generating elastic potential energy. The closing plate 225, along with the connecting tube 224, is then inserted into the closed slot 223. The closing plate 225 is now closed, and the through-slots 222 on either side of the block 221 are also closed. Gas in the inlet 12 can enter the vertical hollow tube 21 through the connecting tube 224. After condensation is complete, the inlet 12 separates from the connecting tube 224. The elastic potential energy of the return spring 226 forces the connecting tube 224 to separate from the block 221. The closing plate 225 then separates from the closed slot 223, opening the through-slots on either side of the block 221. Gas remaining in the vertical hollow tube 21 then enters the condensation chamber 20 directly through the through-slots 222, preventing backflow.

[0041] As shown in FIG3 , an LNG condensate inlet pipe 30 is fixedly mounted on the top of the vertical hollow tube 21 , and an LNG condensate outlet pipe 70 is provided on the outer wall of the tank body 10 . The LNG condensate outlet pipe 70 is divided into a liquid inlet and a liquid outlet. The liquid inlet of the LNG condensate outlet pipe 70 interfaces with the external condensate, and the condensate is fed into the LNG condensate inlet pipe 30 in conjunction with a connecting pipe, and ultimately fed into the interior of the tank body 10 . The condensate can be discharged from the liquid outlet with the cooperation of a pump body. Furthermore, a liquid level limiting sensor is provided in the condensation chamber 20 to limit the condensate level in the condensation chamber 20 to a certain position, so that the liquid inlet and liquid outlet reach a state of equilibrium and the liquid level is maintained at a certain height. This achieves the effect of circulating condensate; by continuously circulating LNG condensate, the condensate temperature in the condensation chamber 20 is lowered, accelerating the condensation of BOG gas. To enhance condensation efficiency, spiral plates 31 are disposed along the path of condensate entering the LNG condensate inlet pipe 30, extending from top to bottom around the interior of the tapered tube 23. In this embodiment, as LNG condensate enters the condensation chamber 20 from the LNG condensate inlet pipe 30, the presence of the spiral plates 31 influences its subsequent flow direction. Upon entering, the LNG condensate undergoes a spiral motion along the shape of the spiral plates 31. Initially, due to the pressure differential, a vortex forms upon entering the spiral plates 31. This vortex is then conducted downward from the top of the tapered tube 23 due to the presence of the spiral plates 31. Upon reaching the bottom of the tapered tube 23, it gradually dissipates due to the protective wall of the tapered tube 23. Consequently, as the BOG gas enters the condensation chamber from the tapered tube 23, the presence of the condensate vortex accelerates its diffusion within the condensate, improving condensation efficiency.

[0042] A hollow plate 40 is provided on the top of the condensation chamber 20 so that the condensed BOG gas can pass through the holes in the hollow plate 40 and enter the upper part of the tank body 10 for other treatments.

[0043] As shown in Figures 6 and 7, the condensation device in the current prior art is equipped with a secondary condensation device above the condensation chamber 20, and a spray-type device is used to atomize and cool the upper part of the condensation chamber 20, thereby achieving the effect of secondary condensation. However, the effect of atomization alone is not significant. Therefore, in response to the above-mentioned problems, the following improvements are made: a secondary condensation chamber 50 is installed inside the tank body 10 and above the condensation chamber 20. The secondary condensation chamber 50 is separated from the condensation chamber 20 by a hollow plate 40. When the gas that undergoes initial condensation in the condensation chamber 20 enters the upper part of the tank body 10 through the holes and grooves in the hollow plate 40, it undergoes secondary condensation.

[0044] The secondary condensation chamber 50 includes a conical platform 51, and a conical cavity is provided inside the conical platform 51. The conical cavity is used to receive the residual gas from the condensation chamber 20. An atomizing sprayer 60 is fixedly installed on the top of the conical platform 51. The atomizing sprayer 60 is connected to the pump body through a connecting pipe, wherein the connecting pipe is not drawn in the figure; the pump body is arranged inside the condensation chamber 20, and can directly extract the LNG condensate inside the condensation chamber 20 into the secondary condensation chamber 50, and then form a mist under the action of the atomizing sprayer 60, and spray out an annular range through the atomizing sprayer 60. The cone-shaped platform 51 is in the shape of an inverted trumpet, and the trumpet-shaped cone-shaped platform 51 is divided into a trumpet mouth 521 and a trumpet body 522. The trumpet body 522 is provided with an annularly distributed leakage hole 52 to discharge the gas from the condensation chamber 20. The bell mouth 521 is provided with an arc-shaped reflux port 523. The LNG condensate formed by the spray from above slides from the top to the bottom through the surface of the cone-shaped platform 51, and finally flows into the condensation chamber 20 through the arc-shaped reflux port 523, and is then recycled in conjunction with the pump body and the cooler.

[0045] It is worth noting that, as shown in Figures 8 and 9, through the above design, due to the presence of the conical platform 51, the condensation chamber 20 will be capped, thereby reducing the volatilization of cold air in the condensation chamber 20. Compared with the open condensation chamber 20 in the prior art, the design of the conical platform 51 can better maintain the temperature in the condensation chamber 20 and slow down the temperature increase; secondly, because the horn body 522 is designed as a curved surface, when the gas ejected from the atomizing sprayer 60 cools the remaining gas, the annular spray will form a barrier above the remaining gas, which will hinder the gas from the leakage hole 52, and the gas can form a sinking effect, which further delays the time for the gas to be discharged from the tank body, and the position of the leakage hole 52 is set to be closer to the position with the lowest temperature of the atomizing sprayer 60, because as time goes by during the atomization process, the low-temperature mist will be assimilated by the temperature inside the tank body 10, and the area around the mist just ejected is the lowest temperature, so the leakage hole 52 is set at a position that can face this place. The remaining gas condenses at the lowest temperature. Some gas may not be condensed and then disperse to both sides under the obstruction of water mist, and finally rise up and leave the tank, delaying the time and thus improving the condensation effect.

Claims

1. An overpressure gas condensation recovery device based on an LNG cold energy power generation system, characterized in that: include: A tank body (10), wherein the upper end of the tank body (10) is connected to an output port (11), and the lower end of the tank body (10) is connected to an input port (12); A condensation chamber (20) is arranged at the bottom of the tank body (10), and contains LNG condensate for condensing BOG gas; the condensation chamber (20) comprises a vertical hollow tube (21) installed inside the tank body (10), a docking mechanism (22) is arranged at the bottom of the vertical hollow tube (21), a tapered tube (23) is fixedly installed at the top of the vertical hollow tube (21), and the tapered tube (23) and the vertical hollow tube (21) are designed to be connected.

2. The overpressure gas condensation recovery device based on the LNG cold energy power generation system according to claim 1 is characterized in that: The side wall of the conical tube (23) is provided with a cavity, and the cavity is designed to be in communication with the hollow part of the vertical hollow tube (21).

3. The overpressure gas condensation recovery device based on the LNG cold energy power generation system according to claim 1 is characterized in that: The docking mechanism (22) comprises a square block (221) fixedly connected to the bottom of the vertical hollow tube (21); the interior of the square block (221) is hollow and has through grooves (222) on both sides; a closed groove (223) is provided inside the through groove (222); a docking tube (224) is movably mounted on the end face of the square block (221) away from the vertical hollow tube (21); closed plates (225) are fixedly mounted on both sides of the docking tube (224) corresponding to the closed groove (223); and return springs (226) are provided on both sides of the closed plate (225).

4. The overpressure gas condensation recovery device based on the LNG cold energy power generation system according to claim 3 is characterized in that: The size and position of the closing plate (225) correspond to the closing groove (223), and when the closing plate (225) is inserted into the closing groove (223), the through groove (222) is blocked.

5. The overpressure gas condensation recovery device based on the LNG cold energy power generation system according to claim 1 is characterized in that: The tank body (10) is connected to an LNG condensate inlet pipe (30) and an LNG condensate outlet pipe (70); the LNG condensate inlet pipe (30) extends into the condensation chamber (20) and an end portion thereof is fixedly connected and communicated with the top of the conical tube (23); and a spiral plate (31) distributed from top to bottom around the inside of the conical tube (23) is provided on the path of condensate outlet in the LNG condensate inlet pipe (30).

6. The overpressure gas condensation recovery device based on the LNG cold energy power generation system according to claim 1 is characterized in that: A hollow plate (40) is provided at the top of the condensation chamber (20). After the LNG condensate enters the condensation chamber (20), the height of the LNG condensate is lower than the hollow plate (40). After being condensed in the condensation chamber (20), the remaining gas will be released from the holes of the hollow plate (40) to the top of the tank body (10).

7. The overpressure gas condensation recovery device based on the LNG cold energy power generation system according to claim 6 is characterized in that: The LNG condensate output pipe (70) is arranged at the bottom of the condensation chamber (20), and the LNG condensate is arranged for circulation input.

8. The overpressure gas condensation recovery device based on the LNG cold energy power generation system according to claim 1 is characterized in that: A secondary condensation chamber (50) is arranged inside the tank body (10) and above the condensation chamber (20), the secondary condensation chamber (50) comprising a conical platform (51), a conical cavity being arranged inside the conical platform (51), the conical cavity being used to receive the residual gas from the condensation chamber (20), an atomizing sprayer (60) being fixedly mounted on the top of the conical platform (51), and the atomizing sprayer (60) sprays aerosol in an annular range to achieve cooling and condensation of the residual gas again.

9. The overpressure gas condensation recovery device based on the LNG cold energy power generation system according to claim 8 is characterized in that: The conical platform (51) is in the shape of an inverted trumpet. The trumpet-shaped conical platform (51) is divided into a trumpet mouth (521) and a trumpet body (522). The trumpet body (522) is provided with a plurality of leakage holes (52) for discharging gas from the condensation chamber (20). The trumpet mouth (521) is provided with an arc-shaped reflux port (523).

10. The overpressure gas condensation recovery device based on the LNG cold energy power generation system according to claim 9 is characterized in that: The plurality of leakage holes (52) are at different heights and are distributed in a ring shape on the horn body (522).

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