A natural gas recovery apparatus and method

Abstract

The application provides a natural gas recovery device and method, which comprises a vacuum adiabatic container, a liquid nitrogen container, a heat exchanger, a spraying pipe and a cryogenic pump, and the natural gas flowing into the recovery device is liquefied, and the liquefied natural gas is output from the recovery device by using the cryogenic pump, so that the liquefied natural gas is recycled. The natural gas recovery device and method provided by the application can significantly reduce the consumption of LNG in the replacement and cooling process of the fuel tank; the device uses low-cost liquid nitrogen as a cold source, and under the premise of meeting the LNG filling of the fuel tank, the cost is greatly saved; in addition, the recovery device has a simple structure, a low construction cost and is easy to be widely promoted.

Description

Technical Field

[0001] This invention relates to the field of natural gas technology, specifically to a natural gas recovery device and method. Background Technology

[0002] Before refueling vessels with large LNG tanks, such as LNG carriers, dual-fuel carriers, and dual-fuel container ships, the ship's fuel tanks and fuel supply systems need to be inerted, purged, and cooled. After inerting, the fuel tanks contain a large amount of nitrogen. During the process of purging the nitrogen in the tanks with vaporized natural gas, a large amount of a mixture of natural gas and nitrogen is discharged from the fuel tanks. In addition, during the process of using LNG spray to cool the fuel tanks, a large amount of natural gas that has absorbed heat and vaporized is also generated and discharged from the fuel tanks. Currently, during the fuel tank purging and cooling process, the mixture of natural gas and nitrogen discharged from the fuel tanks, as well as the vaporized natural gas, is usually directly discharged into the flare for combustion, resulting in energy waste. Summary of the Invention

[0003] In view of the shortcomings of the prior art described above, the present invention provides a natural gas recovery device and method. The device includes a vacuum-insulated container, a liquid nitrogen container, a heat exchanger, a spray pipe, and a cryogenic pump. By liquefying the natural gas flowing into the recovery device, and then using the cryogenic pump to output the liquefied natural gas from the recovery device, the recycling of liquefied natural gas is achieved. The natural gas recovery device and method provided by the present invention significantly reduce the LNG consumption of the fuel tank during the replacement and cooling process; moreover, this device uses inexpensive liquid nitrogen as a cold source, greatly saving costs while meeting the requirement of LNG refueling in the fuel tank; furthermore, the recovery device has a simple structure, low construction cost, and is easy to promote on a large scale.

[0004] To achieve the above and other related objectives, the present invention provides a natural gas recovery device, characterized in that it comprises:

[0005] Vacuum insulated containers;

[0006] A liquid nitrogen container is disposed in the vacuum insulated container. The liquid nitrogen container is provided with a first pipe and a second pipe. Both the first pipe and the second pipe connect the liquid nitrogen container to the outside of the vacuum insulated container. The first pipe is used to input liquid nitrogen, and the second pipe is used to output nitrogen gas.

[0007] A heat exchanger is installed in the vacuum insulated container and is connected to the liquid nitrogen container;

[0008] A cryogenic pump is located at the bottom of the vacuum insulated container and is connected to the outside of the vacuum insulated container through a third pipe, which is used to output liquefied natural gas.

[0009] A spray pipe is installed above the heat exchanger and is connected to the third pipe via a fourth pipe;

[0010] The fifth pipe, located within the vacuum-insulated container, is used to introduce the mixed gas.

[0011] Optionally, a first valve is provided on the first pipeline; a second valve is provided on the second pipeline; a third valve is provided on the third pipeline; a fourth valve is provided on the fourth pipeline; and a fifth valve is provided on the fifth pipeline.

[0012] Optionally, the vacuum insulation container is further provided with a sixth pipe, which is connected to the outside of the vacuum insulation container and is used to output the mixed gas; the sixth pipe is also provided with a sixth valve.

[0013] Optional, also includes:

[0014] A first thermometer is used to measure the temperature of the liquefied natural gas in the vacuum-insulated container;

[0015] A first level gauge is used to measure the level of the liquefied natural gas in the vacuum-insulated container;

[0016] The first pressure gauge is used to measure the gas pressure in the vacuum insulated container.

[0017] Optional, also includes:

[0018] A second thermometer is used to measure the temperature of the liquid nitrogen in the heat exchanger;

[0019] The second level gauge is used to measure the level of liquid nitrogen in the liquid nitrogen container;

[0020] The second pressure gauge is used to measure the gas pressure in the liquid nitrogen container.

[0021] The present invention also provides a natural gas recovery method, comprising the following steps:

[0022] S1: Provide a natural gas recovery device, wherein the natural gas recovery device is any one of the natural gas recovery devices described above;

[0023] S2: Open the first valve and the second valve, and introduce liquid nitrogen into the liquid nitrogen container through the first pipe. Part of the liquid nitrogen in the liquid nitrogen container flows into the heat exchanger.

[0024] S3: Open the fifth valve and the sixth valve, and introduce the mixed gas into the vacuum insulation container through the fifth pipe. The natural gas in the mixed gas is cooled on the surface of the heat exchanger and condenses into liquefied natural gas, which accumulates at the bottom of the vacuum insulation container.

[0025] S4: When the liquefied natural gas at the bottom of the vacuum insulated container reaches the first liquid level, the third valve and the cryogenic pump are opened, and the liquefied natural gas is output through the third pipeline, so that the height of the liquefied natural gas at the bottom of the vacuum insulated container is maintained at the second liquid level.

[0026] Optionally, before step S2, the method further includes: opening the fifth valve and the sixth valve, introducing the mixed gas into the vacuum insulation container through the fifth pipe, and discharging the air and water vapor from the vacuum insulation container.

[0027] Optionally, before step S4, the method further includes: when the liquefied natural gas at the bottom of the vacuum insulated container reaches the third liquid level, opening the fourth valve and starting the cryogenic pump to allow the liquefied natural gas to enter the spray pipe and spray the heat exchanger.

[0028] Optionally, the first liquid level is 55% to 65% of the height of the vacuum insulated container, and the second liquid level is 45% to 55% of the height of the vacuum insulated container.

[0029] Optionally, the third liquid level height is greater than or equal to 0.4m.

[0030] The natural gas recovery device and method provided by this invention have at least the following beneficial effects:

[0031] The natural gas recovery device and method provided by this invention significantly reduce the LNG consumption of the fuel tank during the replacement and cooling process; moreover, this device uses inexpensive liquid nitrogen as a cold source, which greatly saves costs while meeting the requirement of LNG refueling in the fuel tank; in addition, the recovery device has a simple structure, low construction cost, and is easy to promote on a large scale. Attached Figure Description

[0032] Figure 1 The diagram shown is a structural schematic of the natural gas recovery device provided in Embodiment 1.

[0033] Figure 2 The diagram shown is a flowchart of the natural gas recovery method provided in Example 2.

[0034] Component designation explanation

[0035] 10 Vacuum Insulated Container

[0036] 20 Liquid nitrogen containers

[0037] 30 Heat exchanger

[0038] 40 spray pipes

[0039] 50 Cryogenic Pump

[0040] Pipelines 61-66: First Pipeline to Sixth Pipeline

[0041] 71-76 First valve to sixth valve

[0042] 101 First Thermometer

[0043] 102 Second Thermometer

[0044] 201 First Liquid Level Gauge

[0045] 202 Second Liquid Level Gauge

[0046] 301 First Pressure Gauge

[0047] 302 Second Pressure Gauge Detailed Implementation

[0048] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0049] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Although the illustrations only show components related to the present invention and are not drawn according to the actual number, shape and size of the components, the shape, quantity, positional relationship and proportion of each component can be arbitrarily changed under the premise of realizing the technical solution of this invention, and the layout of the components may also be more complex.

[0050] Example 1

[0051] This embodiment provides a natural gas recovery device, such as... Figure 1 As shown, it includes a vacuum insulated container 10, and a liquid nitrogen container 20, a heat exchanger 30, a spray pipe 40 and a cryogenic pump 50 disposed in the vacuum insulated container 10.

[0052] like Figure 1As shown, the liquid nitrogen container 20 is provided with a first pipe 61 and a second pipe 62. The first pipe 61 is connected to an external liquid nitrogen storage tank (not shown in the figure) for inputting liquid nitrogen into the liquid nitrogen container 20; the second pipe 62 is connected to an external nitrogen storage tank (not shown in the figure) for outputting nitrogen gas generated in the liquid nitrogen container 20. As an example, a first valve 71 is provided on the first pipe 61, and a second valve 72 is provided on the second pipe 62. The first valve 71 and the second valve 72 are used to regulate the flow rate of gas or liquid in the pipes.

[0053] like Figure 1 As shown, the heat exchanger 30 is connected to the liquid nitrogen container 20. When liquid nitrogen flows into the liquid nitrogen container 20, some of the liquid nitrogen flows into the heat exchanger 30, thereby cooling the heat exchanger 30.

[0054] like Figure 1 As shown, a cryogenic pump 50 is installed at the bottom of the vacuum insulated container 10. The cryogenic pump 50 is connected to an external liquefied natural gas storage device (not shown in the figure) via a third pipe 63, which is used to output liquefied natural gas. A third valve 73 is installed on the third pipe 63 to regulate the flow rate of the liquid in the pipe. As an example, the cryogenic pump 50 can output the liquefied natural gas 100 accumulated at the bottom of the vacuum insulated container 10 through the third pipe 63.

[0055] like Figure 1 As shown, a spray pipe 40 is provided above the heat exchanger 30 for spraying the heat exchanger 30; the spray pipe 40 is connected to the third pipe 63 through a fourth pipe 64, and a fourth valve 74 is provided on the fourth pipe 64. As an example, the cryogenic pump 50 can transport the liquefied natural gas 100 accumulated at the bottom of the vacuum insulated container 10 to the spray pipe 40 through the fourth pipe 64, so that the spray pipe 40 sprays the heat exchanger 30.

[0056] like Figure 1 As shown, the vacuum insulation container 10 is also provided with a fifth pipe 65 and a sixth pipe 66. The fifth pipe 65 is used to supply mixed gas into the vacuum insulation container 10, and the sixth pipe 66 is used to discharge mixed gas from the vacuum insulation container 10. As an example, a fifth valve 75 is provided on the fifth pipe 65, and a sixth valve 76 is provided on the sixth pipe 66. The fifth valve 75 and the sixth valve 76 are used to regulate the flow rate of gas in the pipes.

[0057] like Figure 1As shown, the natural gas recovery device is also equipped with a first thermometer 101, a first level gauge 201, and a first pressure gauge 301. The first thermometer 101 is used to measure the temperature of the liquefied natural gas 100 in the vacuum insulated container; the first level gauge 201 is used to measure the level of the liquefied natural gas 100 in the vacuum insulated container 10; and the first pressure gauge 301 is used to measure the gas pressure in the vacuum insulated container 10.

[0058] like Figure 1 As shown, the natural gas recovery device is also equipped with a second thermometer 102, a second level gauge 202, and a second pressure gauge 302. The second thermometer 102 is used to measure the temperature of liquid nitrogen in the heat exchanger 30; the second level gauge 202 is used to measure the liquid nitrogen level in the liquid nitrogen container 20; and the second pressure gauge 302 is used to measure the gas pressure in the liquid nitrogen container 20.

[0059] Example 2

[0060] This embodiment provides a natural gas recovery method, such as... Figure 2 As shown, it includes the following steps:

[0061] S1: Provide a natural gas recovery unit;

[0062] As an example, the natural gas recovery device is the natural gas recovery device provided in Embodiment 1. Its specific structure can be found in the description of Embodiment 1, and will not be repeated here.

[0063] As an example, before natural gas recovery, the first pipe 61, the second pipe 62, the third pipe 63, the fifth pipe 65 and the sixth pipe 66 on the natural gas recovery device are connected to external pipes or storage devices, and the natural gas recovery device is tested to ensure that it can operate normally.

[0064] S2: Open the first valve and the second valve, and introduce liquid nitrogen into the liquid nitrogen container through the first pipe. Part of the liquid nitrogen in the liquid nitrogen container flows into the heat exchanger.

[0065] First, open the fifth valve 75 and the sixth valve 76, and introduce a mixed gas into the vacuum insulation container 10 through the fifth pipe 65. Use the inert nitrogen and natural gas in the mixed gas to purge the vacuum insulation container 10, and after expelling the air and water vapor from the vacuum insulation container 10, close the fifth valve 75 and the sixth valve 76.

[0066] Next, the first valve 71 and the second valve 72 are opened, and liquid nitrogen is introduced into the liquid nitrogen container 10 through the first pipe 61 to cool the liquid nitrogen container 20 and the first pipe 61, and to fill the liquid nitrogen container 20 with a small amount of liquid nitrogen. Since the heat exchanger 30 and the liquid nitrogen container 20 are equivalent to communicating vessels, some of the liquid nitrogen in the liquid nitrogen container 20 will flow into the heat exchanger 30 under the action of gravity, and lower the temperature inside the heat exchanger 30.

[0067] S3: Open the fifth valve and the sixth valve, and introduce the mixed gas into the vacuum insulation container through the fifth pipe. The natural gas in the mixed gas is cooled on the surface of the heat exchanger and condenses into liquefied natural gas, which accumulates at the bottom of the vacuum insulation container.

[0068] As an example, the fifth valve 75 is fully opened to reduce resistance within the fifth pipe 65, and the pressure within the vacuum insulation container 10 is kept relatively stable by adjusting the opening of the sixth valve 76. In this embodiment, the pressure within the vacuum insulation container 10 is measured by the first pressure gauge 301.

[0069] Next, a mixed gas, which is a mixture of natural gas and nitrogen or natural gas, is continuously introduced into the vacuum insulation container 10 through the fifth pipe 65. Since the temperature of the mixed gas is higher than the surface temperature of the heat exchanger 30, the natural gas in the mixed gas is cooled on the surface of the heat exchanger 30 and condenses into liquefied natural gas, which accumulates at the bottom of the vacuum insulation container 10.

[0070] S4: When the liquefied natural gas at the bottom of the vacuum insulated container reaches the first liquid level, the third valve and the cryogenic pump are opened, and the liquefied natural gas is output through the third pipeline, so that the height of the liquefied natural gas at the bottom of the vacuum insulated container is maintained at the second liquid level.

[0071] First, when the liquefied natural gas 100 at the bottom of the vacuum insulated container 10 reaches the third liquid level, the fourth valve 74 is opened and the cryogenic pump 50 is started, allowing the liquefied natural gas 100 to enter the spray pipe 40 and spray the heat exchanger 30. This enhances the heat exchange between the liquid nitrogen inside the heat exchanger 30 and the liquefied natural gas outside the heat exchanger 30, keeping the liquefied natural gas in a subcooled state. On one hand, the natural gas in the mixed gas can be absorbed by the subcooled liquefied natural gas; on the other hand, due to the strong heat exchange between the liquefied natural gas and the pipe wall, it also prevents the natural gas from condensing into a solid on the outer surface of the heat exchanger 30. In this embodiment, the third liquid level is greater than or equal to 0.4m.

[0072] As an example, during the spraying process on the heat exchanger 30, the first valve 71 is adjusted so that the liquid nitrogen level in the liquid nitrogen container 20 is approximately 50% of the container's height. In this embodiment, the liquid nitrogen level can be measured by the second level gauge 202. Simultaneously, the temperature inside the heat exchanger 30 is monitored using the second thermometer 102 to ensure that the temperature inside the heat exchanger 30 is greater than or equal to -182°C, in order to prevent the liquefied natural gas from solidifying.

[0073] Next, when the liquefied natural gas 100 at the bottom of the vacuum insulated container 10 reaches the first liquid level, the third valve 73 and the cryogenic pump 50 are opened, allowing the liquefied natural gas 100 to be output from the third pipeline 63. During this process, by adjusting the opening of the third valve 73, the height of the liquefied natural gas 100 at the bottom of the vacuum insulated container 10 is maintained at the second liquid level, thereby achieving a dynamic balance between the condensed liquid and the discharged liquid inside the vacuum insulated container 10, and the system enters a normal reliquefaction cycle mode. In this embodiment, the first liquid level is 55% to 65% of the height of the vacuum insulated container 10, preferably 60%; the second liquid level is 45% to 55% of the height of the vacuum insulated container 10, preferably 50%; the liquid level inside the vacuum insulated container 10 is measured by the first liquid level gauge 201.

[0074] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A natural gas recovery device, characterized in that, include: Vacuum insulated containers; A liquid nitrogen container is disposed in the vacuum insulated container. The liquid nitrogen container is provided with a first pipe and a second pipe. Both the first pipe and the second pipe connect the liquid nitrogen container to the outside of the vacuum insulated container. The first pipe is used to input liquid nitrogen, and the second pipe is used to output nitrogen gas. A heat exchanger is installed in the vacuum insulated container and is connected to the liquid nitrogen container; A cryogenic pump is located at the bottom of the vacuum insulated container and is connected to the outside of the vacuum insulated container through a third pipe, which is used to output liquefied natural gas. A spray pipe is installed above the heat exchanger and is connected to the third pipe via a fourth pipe; The fifth pipe, installed in the vacuum insulated container, is used to input the mixed gas; The first pipe is equipped with a first valve; the second pipe is equipped with a second valve; the third pipe is equipped with a third valve; the fourth pipe is equipped with a fourth valve; and the fifth pipe is equipped with a fifth valve. The vacuum insulated container is also provided with a sixth pipe, which is connected to the outside of the vacuum insulated container and is used to output the mixed gas; a sixth valve is also provided on the sixth pipe.

2. The natural gas recovery device according to claim 1, characterized in that, Also includes: A first thermometer is used to measure the temperature of the liquefied natural gas in the vacuum-insulated container; A first level gauge is used to measure the level of the liquefied natural gas in the vacuum-insulated container; The first pressure gauge is used to measure the gas pressure in the vacuum insulated container.

3. The natural gas recovery device according to claim 1, characterized in that, Also includes: A second thermometer is used to measure the temperature of the liquid nitrogen in the heat exchanger; The second level gauge is used to measure the level of liquid nitrogen in the liquid nitrogen container; The second pressure gauge is used to measure the gas pressure in the liquid nitrogen container.

4. A method for natural gas recovery, characterized in that, Includes the following steps: S1: A natural gas recovery device is provided, wherein the natural gas recovery device is the natural gas recovery device according to any one of claims 1 to 3; S2: Open the first valve and the second valve, and introduce liquid nitrogen into the liquid nitrogen container through the first pipe. Part of the liquid nitrogen in the liquid nitrogen container flows into the heat exchanger. S3: Open the fifth valve and the sixth valve, and introduce the mixed gas into the vacuum insulation container through the fifth pipe. The natural gas in the mixed gas is cooled on the surface of the heat exchanger and condenses into liquefied natural gas, which accumulates at the bottom of the vacuum insulation container. S4: When the liquefied natural gas at the bottom of the vacuum insulated container reaches the first liquid level, the third valve and the cryogenic pump are opened, and the liquefied natural gas is output through the third pipeline, so that the height of the liquefied natural gas at the bottom of the vacuum insulated container is maintained at the second liquid level.

5. The natural gas recovery method according to claim 4, characterized in that, Before step S2, the procedure further includes: opening the fifth valve and the sixth valve, introducing the mixed gas into the vacuum insulation container through the fifth pipe, and discharging the air and water vapor from the vacuum insulation container.

6. The natural gas recovery method according to claim 4, characterized in that, Before step S4, the process further includes: when the liquefied natural gas at the bottom of the vacuum insulation container reaches the third liquid level, opening the fourth valve and starting the cryogenic pump to allow the liquefied natural gas to enter the spray pipe and spray the heat exchanger.

7. The natural gas recovery method according to claim 4, characterized in that, The first liquid level is 55% to 65% of the height of the vacuum insulated container, and the second liquid level is 45% to 55% of the height of the vacuum insulated container.

8. The natural gas recovery method according to claim 6, characterized in that, The third liquid level height is greater than or equal to 0.4m.

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