A cryogenic storage device for hydrate samples with low moisture carry - over and its usage method

Abstract

The present invention discloses a low-temperature storage device for hydrate samples with low moisture content and a usage method thereof, belonging to the field of basic physical property testing of hydrates and geotechnical engineering. The device includes a low-temperature storage module, a vacuum pumping module, a liquid nitrogen injection module, and a backpressure control module connected to the low-temperature storage module. Specifically, during use, through the combination of each module and the cooperative design of the first valve, piston, and control rod in the low-temperature storage module, low moisture content is carried during the low-temperature storage and transfer of hydrate samples, avoiding the interference of moisture on low-temperature nanoindentation and scratch tests, ensuring the stability of test conditions and the reliability of experimental results, providing an effective technical means for basic physical property testing of hydrates and geotechnical engineering, and having strong practicability.

Description

Technical Field

[0001] The present invention belongs to the field of basic physical property testing of hydrates and geotechnical engineering, and particularly relates to a cryogenic storage device for hydrate-containing samples with low water carry-over and a method of using the same. Background Art

[0002] With the increasing requirements for the mechanical properties of various materials, the mechanical properties of materials at the micro-nano scale have attracted great attention. Nanoindentation and nanoscratching techniques have significant scientific research value and broad application prospects in the analysis of mechanical properties at the micro-nano scale. In the study of the instability behavior of natural gas hydrate production reservoirs, the microscopic mechanical properties of solid-phase media such as hydrates and minerals play a crucial role. Cryogenic nanoindentation and nanoscratching testing techniques provide an effective way to reveal the variation laws of the microscopic structure and microscopic mechanical properties of hydrate-containing sediments.

[0003] In cryogenic nanoindentation and nanoscratching tests, it is very important to control the water content in the cryogenic gas environment where the equipment is located. Excessive water content will affect the following three aspects: (1) Affect the authenticity of the test sample surface: Moisture will adhere to the surface of the test sample, and frost or even ice will appear on the surface of the test sample under the action of low temperature, seriously interfering with the surface performance test of the sample, changing properties such as the hardness and elastic modulus of the test surface, resulting in large deviations in the test results and being unable to accurately reflect the true mechanical properties of the sample; (2) Affect the initial properties of the equipment probe: In addition to adhering to the surface of the test sample, moisture will also adhere to the surface of the equipment probe, and frost or even ice will also appear on the surface of the probe under the action of low temperature, affecting the contact force, friction force, etc. between the probe and the test sample, resulting in unstable and inaccurate test results; (3) Affect the stability of the test environment: Changes in moisture will cause fluctuations in the temperature and humidity of the cryogenic environment where the equipment is located, and these fluctuations may affect the repeatability and accuracy of the test results.

[0004] Generally speaking, in cryogenic nanoindentation and nanoscratching tests, by reducing the water content in the cryogenic gas environment where the equipment is located, it is easier to maintain stable test conditions and ensure the reliability of the experiment. Therefore, in order to ensure the accuracy of the test results, it is necessary to minimize the water content in the surrounding gas environment. A key link in reducing the water content in the surrounding gas environment is to reduce the water carry-over of the sample cryogenic storage tank.

[0005] After the hydrate sample is prepared outside the cryogenic nanoindentation and scratching equipment, it needs to be loaded into a cryogenic sample storage tank and transferred to the low-water-content cryogenic environment inside the cryogenic nanoindentation and scratching equipment while ensuring that the hydrate in the sample does not decompose. However, there is currently no cryogenic storage device that can ensure the low-water content during the transfer of the hydrate sample. As a result, during the transfer of the hydrate sample, excessive moisture is carried into the low-water-content gas environment inside the cryogenic nanoindentation and scratching equipment through the cryogenic sample storage tank, seriously affecting the reliability of the experimental test results.

[0006] Therefore, there is an urgent need to develop a new device and method to ensure that as little moisture as possible is brought into the low-water-content gas environment inside the cryogenic nanoindentation and scratching equipment during the cryogenic storage and transfer of the hydrate sample, and to avoid the influence of moisture on the cryogenic nanoindentation and scratching tests. Summary of the Invention

[0007] In view of the problem in the prior art that excessive moisture is brought into the low-water-content gas environment inside the cryogenic nanoindentation and scratching equipment during the cryogenic storage and transfer of the hydrate sample, resulting in unstable and inaccurate cryogenic nanoindentation and scratching test results, the present invention provides a cryogenic storage device for hydrate samples with low moisture content and a usage method thereof, which are applicable to cryogenic nanoindentation and scratching test equipment.

[0008] The present invention is implemented by the following technical solutions: A cryogenic storage device for hydrate samples with low moisture content includes a cryogenic storage module, a vacuum pumping module, a liquid nitrogen injection module, and a backpressure control module connected to the cryogenic storage module. The backpressure control module is used to control the minimum pressure required for the fluid to flow out of the high-pressure cavity.

[0009] The cryogenic storage module includes a high-pressure cavity and a vacuum heat-insulating cylinder. The upper and lower ends of the high-pressure cavity are respectively sealed with a top cover and a bottom cover. Inside the high-pressure cavity, there are a piston, a control rod, and a first valve. The first valve is arranged on the piston. The control rod is used to control the opening and closing of the first valve and the up and down movement of the piston. The piston is provided with a fourth channel and a fifth channel. The fourth channel is communicated with the lower cavity space of the piston, and the fifth channel is communicated with the upper cavity space of the piston. The first valve is used to control the communication between the fourth channel and the fifth channel.

[0010] The first valve includes a valve top cover and a valve flange. The valve top cover is connected to the piston and the control rod by threads respectively. The valve flange is sealed with the piston by a gasket, and the valve flange is sealed with the control rod by an eighth sealing ring.

[0011] Further, a piston limiting ring, a first piston anti-rotation rod and a second piston anti-rotation rod are arranged in the high-pressure cavity. The piston limiting ring is used to limit the highest upward movement position of the piston. The first piston anti-rotation rod and the second piston anti-rotation rod are arranged below the piston limiting ring and extend downward through the piston to prevent the piston from rotating during the opening and closing process of the first valve.

[0012] Further, the high-pressure cavity is cylindrical. The top cover is provided with a first channel and a balance pressure pipeline. The control rod passes through the first channel and is sealed by a third sealing ring. A corresponding pipeline valve is arranged at the balance pressure pipeline.

[0013] Further, a liquid injection pipeline, a liquid discharge pipeline, a safety pipeline and corresponding pipeline valves are arranged on the side wall of the high-pressure cavity. The liquid injection pipeline is connected to the liquid nitrogen injection module. A vacuum extraction pipeline is also connected to the liquid injection pipeline. The vacuum extraction pipeline is connected to the vacuum extraction module. The liquid discharge pipeline is connected to the back pressure control module to limit the highest liquid level of the liquid nitrogen inside the high-pressure cavity.

[0014] The present invention also further provides a method for using a low-water-content-carrying hydrate sample low-temperature storage device, including the following steps:

[0015] Step A: Lift the piston and evacuate the high-pressure cavity: Connect the pipelines between the low-temperature storage module and the vacuum extraction module, the liquid nitrogen injection module and the back pressure control module respectively. Lift the control rod to move the piston to the highest position in the high-pressure cavity. Open the first valve to connect the fourth channel and the fifth channel. Use the vacuum extraction module to evacuate the high-pressure cavity.

[0016] Step B: Inject liquid nitrogen into the high-pressure cavity: Use the back pressure control module to set a back pressure lower than the liquid nitrogen injection pressure. Inject liquid nitrogen into the high-pressure cavity through the liquid nitrogen injection module until the liquid nitrogen flows out from the back pressure control module. Then use the back pressure control module to set the back pressure to atmospheric pressure and wait until the back pressure control module no longer flows out liquid nitrogen.

[0017] Step C: Store the hydrate sample in a low-water-content liquid nitrogen environment: Store the hydrate sample and lower the piston to the lowest position in the high-pressure cavity: Rotate the control rod to close the first valve, open the second valve, control the air pressure in the upper space of the high-pressure cavity to be balanced with the external air pressure, unscrew the top cover, place the hydrate sample on the piston and quickly screw on the top cover, close the second valve, rotate the control rod to open the first valve, press the control rod to move the piston to the lowest position in the high-pressure cavity, and store the hydrate sample in the liquid nitrogen.

[0018] Step D: Transfer the hydrate sample for low-temperature nanoindentation / scratch test: Transfer the low-temperature storage module to the low-water-content gas environment in the low-temperature nanoindentation / scratch equipment. According to the operation shown in Step C, take out the hydrate sample to be tested, and continue to store the other hydrate samples to be tested in the liquid nitrogen.

[0019] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0020] Through the combined design of the low-temperature storage module, the first valve, the piston and the control rod, and by using the method of using the hydrate sample-carrying low-moisture content cryogenic storage device, the present solution realizes loading the hydrate sample into the low-moisture cryogenic storage module in a high-moisture environment. During specific operation, the vacuum pumping module is used to reduce the initial moisture content in the cryogenic storage module; the piston is lifted to reduce the contact space between the cryogenic storage module and the high-moisture external environment, thereby reducing the moisture content entering the cryogenic storage module from the external environment during the loading process; and in combination with the piston moving downward, it is ensured that the sample is stored in moisture-free liquid nitrogen, thereby avoiding the condensation of moisture on the surface of the hydrate sample in a low-temperature environment. Thus, the storage and transfer of hydrate samples with low moisture content are realized, providing technical support for exploring the surface properties and mechanical property measurement of hydrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a composition diagram of the cryogenic storage device described in the embodiment of the present invention;

[0022] Figure 2 It is a schematic cross-sectional structure diagram of the cryogenic storage module described in the embodiment of the present invention;

[0023] Figure 3 It is a schematic structure diagram of the first valve described in the embodiment of the present invention;

[0024] Wherein, 1, cryogenic storage module; 2, vacuum pumping module; 3, liquid nitrogen injection module; 4, backpressure control module; 5, high-pressure cavity; 6, vacuum heat preservation cylinder; 7, top cover; 8, bottom cover; 9, piston; 10, control rod; 11, piston limit ring; 12, first piston anti-rotation rod; 13, second piston anti-rotation rod; 14, first sealing ring; 15, second sealing ring; 16, third sealing ring; 17, fourth sealing ring; 18, fifth sealing ring; 19, sixth sealing ring; 20, seventh sealing ring; 21, first valve; 22, second valve; 23, third valve; 24, fourth valve; 25, fifth valve; 26, safety valve; 27, first channel; 28, second channel; 29, third channel; 30, fourth channel; 31, fifth channel; 32, liquid injection pipeline; 33, vacuum pumping pipeline; 34, liquid discharge pipeline; 35, safety pipeline; 36, balance pressure pipeline; 37, valve top cover; 38, valve flange; 39, eighth sealing ring; 40, gasket. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] To more clearly understand the above objects, features, and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. Many specific details are set forth in the following description to facilitate a thorough understanding of the present invention. However, the present invention may be implemented in other ways different from those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0026] Embodiment 1: A cryogenic storage device for a hydrate sample with low water content carried, as Figure 1 and Figure 2 shown, includes a cryogenic storage module 1 and a vacuum pumping module 2, a liquid nitrogen injection module 3, and a backpressure control module 4 connected to the cryogenic storage module 1;

[0027] The cryogenic storage module 1 includes a high-pressure cavity 5 and a vacuum insulation cylinder 6. A top cover 7 and a bottom cover 8 are respectively provided at the upper and lower ends of the high-pressure cavity 5. A piston 9, a control rod 10, and a first valve 21 are arranged inside the high-pressure cavity 5. The first valve 21 is arranged on the piston 9. The control rod 10 is used to control the opening and closing of the first valve 21 and the up and down movement of the piston 9; There are two upper and lower sealing rings between the piston 9 and the inner wall of the high-pressure cavity 5, namely the fourth sealing ring 17 and the fifth sealing ring 18;

[0028] The piston 9 is provided with a second channel 28, a third channel 29, a fourth channel 30, and a fifth channel 31. The fourth channel 30 is communicated with the lower cavity space of the piston 9, and the fifth channel 31 is communicated with the upper cavity space of the piston 9. The first valve 21 is used to control the communication between the fourth channel 30 and the fifth channel 31. Through the special design of the piston 9, its ingenious cooperation with the control rod 10 and the first valve 21 is realized, ensuring that when the first valve 21 is opened, the fluids (including nitrogen and liquid nitrogen) in the high-pressure cavity 5 above and below the piston 9 can easily pass through the piston, ensuring the same pressure in the high-pressure cavity 5 above and below the piston 9 and realizing the controlled movement of the piston; At the same time, it also ensures that when the first valve 21 is closed, the fluids in the high-pressure cavity 5 above and below the piston 9 are not connected, reducing the contact space between the high-pressure cavity 5 and the high-moisture external environment.

[0029] In addition, a piston limiting ring 11, a first piston anti-rotation rod 12, and a second piston anti-rotation rod 13 are arranged in the high-pressure cavity 5. The piston limiting ring 11 is arranged at the upper part of the high-pressure cavity 5 and is used to limit the highest upward movement position of the piston 9. The first piston anti-rotation rod 12 and the second piston anti-rotation rod 13 are arranged below the piston limiting ring 11 and extend downward through the piston, and are used to prevent the rotation of the piston 9 during the opening and closing of the first valve 21. Specifically, the first piston anti-rotation rod 12 is arranged in the second channel 28, and a sixth sealing ring 19 is arranged between the second channel 28 and the first piston anti-rotation rod 12. The second piston anti-rotation rod 13 is arranged in the third channel 29, and a seventh sealing ring 20 is arranged between the third channel 29 and the second piston anti-rotation rod 13.

[0030] In this embodiment, through the special arrangement of the piston limiting ring 11, the first piston anti-rotation rod 12, and the second piston anti-rotation rod 13, the rotation of the piston 9 in the high-pressure cavity 5 is cleverly avoided, ensuring that the first valve 21 on the piston 9 is opened and closed under the control of the control rod 10; at the same time, this arrangement avoids the piston 9 being pushed out of the high-pressure cavity 5 by the high-pressure fluid at its bottom during the loading and transfer of the hydrate sample.

[0031] As Figure 3 shown, the first valve 21 includes a valve top cover 37 and a valve flange 38. Both between the valve top cover 37 and the piston 9 and between the valve top cover 37 and the control rod 10 are connected by threads. The valve flange 38 is sealed with the piston 9 through a gasket 40, and the valve flange 38 is sealed with the control rod 10 through an eighth sealing ring 39.

[0032] In this embodiment, the high-pressure cavity 5 is cylindrical. The top of the high-pressure cavity 5 is threadedly connected to the top cover 7 and sealed through a first sealing ring 14. The top cover 7 is provided with a first channel 27 and a balanced pressure pipeline 36. The control rod 10 passes through the first channel 27 and is sealed through a third sealing ring 16. A second valve 22 is arranged at the balanced pressure pipeline 36. The bottom of the high-pressure cavity 5 is threadedly connected to the bottom cover 8 and sealed through a second sealing ring 15.

[0033] In addition, a liquid injection pipeline 32, a liquid discharge pipeline 34, and a safety pipeline 35 are provided on the side wall of the high-pressure cavity 5. The liquid injection pipeline 32 is connected to the liquid nitrogen injection module 3. A third valve 23 and a vacuum pumping pipeline 33 are arranged on the liquid injection pipeline 32. The vacuum pumping pipeline 33 is connected to the vacuum pumping module 2. The third valve 23 controls the connection between the liquid injection pipeline 32 and the liquid nitrogen injection module 3. A fourth valve 24 is arranged on the vacuum pumping pipeline 33, and the fourth valve 24 controls the connection between the vacuum pumping pipeline 33 and the vacuum pumping module 2. The liquid discharge pipeline 34 is connected to the backpressure control module 4. A fifth valve 25 is arranged on the liquid discharge pipeline 34. The liquid discharge pipeline 34 is used to limit the highest liquid level of the liquid nitrogen inside the high-pressure cavity 5. The backpressure control module 4 is used to control the minimum pressure required for the fluid (liquid nitrogen or nitrogen) inside the high-pressure cavity 5 to flow out. A safety valve 26 is arranged on the safety pipeline 35, and the safety valve 26 is used to limit the highest pressure inside the high-pressure cavity 5.

[0034] Embodiment 2: A low-temperature storage device for hydrate samples with low water carryover proposed based on Embodiment 1. Corresponding to this embodiment, a corresponding usage method is proposed, including the following steps:

[0035] Step (1): Connect the liquid nitrogen injection module 3 to the liquid injection pipeline 32, connect the vacuum pumping module 2 to the vacuum pumping pipeline 33, and connect the backpressure control module 4 to the liquid discharge pipeline 34.

[0036] Step (2): Lift the control rod 10 to move the piston 9 to the highest position of the high-pressure cavity 5. Rotate the control rod 10 to open the first valve 21 to connect the fourth channel 30 and the fifth channel 31; close the second valve 22, the third valve 23, and the fifth valve 25, open the fourth valve 24, and use the vacuum pumping module 2 to evacuate the high-pressure cavity 5, thereby reducing the initial moisture content in the low-temperature storage module.

[0037] Step (3): After the evacuation is completed, use the backpressure control module 4 to set the backpressure (i.e., the minimum pressure required for the fluid (liquid nitrogen or nitrogen) inside the high-pressure cavity 5 to flow out (lower than the liquid nitrogen injection pressure, recommended 0.5 MPa)). Close the fourth valve 24, open the third valve 23 and the fifth valve 25, use the liquid nitrogen injection module 3 to inject liquid nitrogen into the high-pressure cavity 5 until the liquid nitrogen flows out from the backpressure control module 4. Close the third valve 23, use the backpressure control module 4 to set the backpressure to atmospheric pressure. Wait until the backpressure control module 4 no longer discharges liquid nitrogen, and then close the fifth valve 25.

[0038] Step (4), rotate the control rod 10 to close the first valve 21, open the second valve 22, unscrew the top cover 7, place the sample on the piston 9, and move the piston 9 carrying the sample to the highest end of the high-pressure cavity 5 to reduce the contact space between the high-pressure cavity 5 of the low-temperature storage module 1 and the high-moisture external environment, thereby reducing the entry of external moisture during the loading and transfer of the sample. Then screw on the top cover 7 and close the second valve 22; rotate the control rod 10 to open the first valve 21, and press the control rod 10 to move the piston 9 to the lowest position in the high-pressure cavity 5 so that the sample is placed in moisture-free liquid nitrogen for storage, avoiding the condensation of moisture on the surface of the sample in the low-temperature environment.

[0039] Step (5), remove the liquid nitrogen injection module 3 from the liquid injection pipeline 32, remove the vacuum pumping module 2 from the vacuum pumping pipeline 33, remove the backpressure control module 4 from the drain pipeline 34, and move the low-temperature storage module 1 to the low-moisture gas environment inside the low-temperature nano-indentation and scratching equipment.

[0040] Step (6), lift the control rod 10 to move the piston 9 to the highest position in the high-pressure cavity 5, rotate the control rod 10 to close the first valve 21, open the second valve 22, unscrew the top cover 7, and remove the test sample from the piston 9 for testing.

[0041] Step (7), screw on the top cover 7, close the second valve 22, open the first valve 21 by rotating the control rod 10, and move the piston 9 to the lowest position in the high-pressure cavity 5 by pressing the control rod 10. Use the same steps to place other samples to be tested in liquid nitrogen for storage.

[0042] This solution effectively realizes the low-temperature storage of hydrate samples with low moisture content, reduces the moisture content in the low-temperature gas environment where the equipment is located introduced during the loading and transfer of samples in the use of low-temperature nano-indentation and scratching equipment, and ensures the stability of the test conditions and the reliability of the experimental results.

[0043] The above is only a preferred embodiment of the present invention, and it is not a limitation of the present invention in other forms. Any person skilled in the art may use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes and apply them to other fields. However, as long as it does not depart from the technical solution content of the present invention, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A cryogenic storage device for hydrate samples with low water content carried, characterized in that, It includes a low-temperature storage module, a vacuum pumping module, a liquid nitrogen injection module, and a backpressure control module connected to the low-temperature storage module. The backpressure control module is used to control the minimum pressure required for the fluid to flow out of the high-pressure cavity. The low-temperature storage module includes a high-pressure cavity and a vacuum insulation cylinder. The upper and lower ends of the high-pressure cavity are respectively sealed with a top cover and a bottom cover. The top cover is provided with a first channel and a balance pressure pipeline, and a second valve is arranged at the balance pressure pipeline. Inside the high-pressure cavity, there are a piston, a control rod, and a first valve. The first valve is arranged on the piston. The control rod passes through the first channel and is used to control the opening and closing of the first valve and the up and down movement of the piston. The piston is provided with a fourth channel and a fifth channel. The fourth channel is communicated with the lower cavity space of the piston, and the fifth channel is communicated with the upper cavity space of the piston. The first valve is used to control the communication between the fourth channel and the fifth channel.

2. The cryogenic storage device for hydrate samples with low moisture content according to claim 1, characterized in that: The first valve includes a valve top cover and a valve flange. The valve top cover is connected to the piston and the control rod by threads respectively. The valve flange is sealed with the piston by a gasket, and the valve flange is sealed with the control rod by an eighth sealing ring.

3. The cryogenic storage device for hydrate samples with low moisture content according to claim 1 or 2, characterized in that: The high-pressure cavity is cylindrical. Inside the high-pressure cavity, there are a first piston anti-rotation rod, a second piston anti-rotation rod, and a piston limiting ring. The piston limiting ring is used to limit the highest upward movement position of the piston. The first piston anti-rotation rod and the second piston anti-rotation rod are arranged below the piston limiting ring and extend downward through the piston to prevent the piston from rotating during the opening and closing process of the first valve.

4. The cryogenic storage device for hydrate samples with low moisture content according to claim 1, characterized in that: On the side wall of the high-pressure cavity, there are a liquid injection pipeline, a liquid discharge pipeline, a safety pipeline, and corresponding pipeline valves. The liquid injection pipeline is connected to the liquid nitrogen injection module, and a vacuum pumping pipeline is also connected to the liquid injection pipeline. The vacuum pumping pipeline is connected to the vacuum pumping module. The liquid discharge pipeline is connected to the backpressure control module and is used to limit the highest liquid level of liquid nitrogen inside the high-pressure cavity.

5. The method of using the cryogenic storage device for hydrate samples with low moisture content as claimed in claim 3, characterized in that, It includes the following steps: Step A: Lift the piston and evacuate the high-pressure cavity: Connect the pipelines between the low-temperature storage module and the vacuum pumping module, the liquid nitrogen injection module, and the backpressure control module respectively. Lift the control rod to move the piston to the highest position in the high-pressure cavity, and open the first valve to connect the fourth channel and the fifth channel. Use the vacuum pumping module to evacuate the high-pressure cavity. Step B: Inject liquid nitrogen into the high-pressure cavity: Use the backpressure control module to set a backpressure lower than the liquid nitrogen injection pressure. Inject liquid nitrogen into the high-pressure cavity through the liquid nitrogen injection module until the liquid nitrogen flows out of the backpressure control module. Then use the backpressure control module to set the backpressure to atmospheric pressure and wait until the backpressure control module stops flowing out liquid nitrogen. Step C: Store the hydrate sample in a low-moisture liquid nitrogen environment: Rotate the control rod to close the first valve, open the second valve, control the air pressure in the upper space of the high-pressure cavity to be balanced with the external air pressure. Unscrew the top cover, place the hydrate sample on the piston, and quickly screw on the top cover. Close the second valve, rotate the control rod to open the first valve, press the control rod to move the piston to the lowest position in the high-pressure cavity, so that the hydrate sample is stored in the liquid nitrogen. Step D. Transfer the hydrate sample for low-temperature nanoindentation / scratch test: Transfer the low-temperature storage module to the low-water-content gas environment inside the low-temperature nanoindentation / scratch equipment. Lift the control rod to move the piston to the highest position of the high-pressure cavity. Operate according to the procedure shown in Step C, take out the hydrate sample to be tested, and continue to store other hydrate samples to be tested in liquid nitrogen.

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