Hydrostatic pressure simulation device and method for sampling under pressure

Abstract

The application discloses a kind of static water pressure simulation device and pressure sampling method with pressure, it is related to sediment-water interface biogeochemical process simulation technical field, the application includes container cylinder, top sealing installation has sealing cylinder cover;Pressure gauge and temperature table are located on sealing cylinder cover;Air inlet assembly and air release assembly are located on sealing cylinder cover;Discharge pipe is located in the lower part of container cylinder, and first control valve, sampling tube, second control valve are sequentially connected in series.The application has broken through to realize the sampling without pressure relief under the condition of in-situ static water pressure, effectively avoids systematic error caused by dissolved gas due to decompression escape;It is suitable for a variety of sediment types and gas types, and provides a high-fidelity experimental platform for greenhouse gas emission research under extreme conditions of deep water reservoir, thermal stratification area;Provide key data support and methodological basis for constructing pressure-corrected methane flux model and deep water carbon emission inventory, serve the national "double carbon" strategy and global change research needs.

Description

Technical Field

[0001] This invention relates to the field of sediment-water interface biogeochemical process simulation technology, and in particular to a hydrostatic pressure simulation device and method for pressurized sampling, which is applicable to the study of the mechanism and flux determination of gas (methane, carbon dioxide) release behavior at the sediment-water interface under complex hydraulic conditions such as oceans, lakes, and reservoirs. Background Technology

[0002] Against the backdrop of global change and the "dual-carbon" strategy, water bodies (such as oceans and lakes) are significant sources of methane (CH4) emissions, and their carbon cycle processes and emission mechanisms have become a cutting-edge research focus in environmental fields such as limnology. The sediment-water interface is a crucial boundary for methane generation, oxidation, and trans-interfacial transport. Its flux characteristics are not only regulated by factors such as temperature, redox potential, organic matter content, and microbial community structure, but are also significantly constrained by the key physical variable of hydrostatic pressure. Hydrostatic pressure profoundly affects the entire process of methane dissolution-adsorption-diffusion-escape by altering sediment pore structure, gas dissolution equilibrium, and bubble nucleation threshold, thus determining the intensity and spatiotemporal pattern of methane emissions from the water-gas interface.

[0003] However, existing experimental techniques generally conduct sediment-water interface gas sampling and flux measurements under normal pressure and open conditions, which cannot accurately reproduce the high-pressure physical environment of deep water areas. This leads to significant decompression-induced gas escape phenomena and a serious underestimation of the true reserves and potential release capacity of dissolved methane in sediments. Although some studies have attempted to use pressure vessels to simulate still water environments, the technical bottleneck of having to depressurize during sampling makes it difficult to achieve accurate sampling under in-situ pressure conditions, thus hindering the accurate construction of methane release mechanisms and flux models in deep-water sediments.

[0004] Therefore, there is an urgent need to develop an experimental device and supporting method that can achieve in-situ, pressure-free, and non-escape sampling under controllable hydrostatic pressure, in order to meet the stringent requirements of high-pressure physical field accuracy, sample representativeness, and data repeatability in the study of gas behavior mechanisms at the deep-water sediment-water interface. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies in achieving high-fidelity sample collection of sediment-water interface samples under in-situ hydrostatic pressure conditions. It aims to provide a hydrostatic pressure simulation device and method for pressurized sampling, solving problems such as dissolved gas escape, poor sample representativeness, and experimental data distortion caused by depressurization during traditional sampling. This provides a high-fidelity, repeatable, and quantitative experimental method for studying the methane release mechanism of deep-water sediments.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] A hydrostatic pressure simulation device capable of sampling under pressure, comprising:

[0008] The container cylinder is sealed with a cap at the top.

[0009] Pressure gauges and temperature gauges are mounted on the sealed cylinder cover;

[0010] The air intake assembly and the air vent assembly are located on the sealing cylinder cover;

[0011] The discharge pipe is located at the bottom of the container cylinder and is connected in series with the first control valve, the sampling pipe, and the second control valve.

[0012] The sampling assembly, connected to the lower end of the second control valve, includes a needle and a pre-vacuumed headspace vial, with a rubber stopper sealing the top of the headspace vial;

[0013] The system utilizes the coordinated control of the first and second control valves to achieve the isolation, quantification, and transfer of the mud-water mixture under in-situ hydrostatic pressure conditions, thus completing pressurized sampling.

[0014] Furthermore, the sampling tube has a fixed volume and is used to quantitatively collect mud-water mixtures.

[0015] Furthermore, a sealing ring gasket is provided between the container cylinder and the sealing cylinder cover to improve the sealing performance.

[0016] Furthermore, the headspace vial is equipped with a rubber stopper at the top, and a needle can puncture the rubber stopper to inject the sample into the headspace vial.

[0017] Furthermore, the air intake assembly includes an air intake pipe, an air intake valve, and a pressure reducing valve, used to smoothly regulate the gas pressure inside the container. The lower end of the air intake pipe is connected to the top wall of the sealing cylinder cover. The air intake valve is located at the upper end of the air intake pipe. The upper end of the air intake valve is connected to a ventilation pipe, and the ventilation pipe is connected to a gas storage bottle to be tested. The pressure reducing valve is connected to the ventilation pipe.

[0018] Furthermore, the venting assembly includes a venting pipe and a venting valve, used to adjust or release the pressure inside the container before and after the experiment. The venting pipe is connected to the top wall of the sealed cylinder cover, and the venting valve is installed at the upper end of the venting pipe.

[0019] Furthermore, the headspace vial is pre-evacuated to collect the gas released from the sample.

[0020] A method for sampling under pressure includes the following steps:

[0021] S1. Add the sediment and water sample to the container in proportion, seal it, and then introduce gas to the target pressure;

[0022] S2. Open the first control valve to allow the mud-water mixture to enter the sampling tube;

[0023] S3. Close the first control valve, open the second control valve, and use the residual pressure to inject the sample into the pre-vacuumed headspace vial;

[0024] S4. Complete pressurized sampling to prevent gas from escaping.

[0025] Furthermore, in step S2, the sampling tube has a volume of 20 mL and is used for quantitative sample collection.

[0026] Further, in step S4, after the sample is injected into the headspace vial, high-purity nitrogen is immediately injected with a syringe until it is balanced with atmospheric pressure, and the gas volume is recorded.

[0027] Further, in step S4, after the sample is injected into the headspace vial, the gas concentration is determined using a gas chromatograph.

[0028] Furthermore, in step S1, the target pressure is 0.1 to 2.0 MPa, used to simulate the hydrostatic pressure under different water depth conditions.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] This invention achieves breakthrough in in-situ hydrostatic pressure-free sampling, effectively avoiding systematic errors caused by dissolved gas escaping due to decompression.

[0031] The dual-valve series structure of this invention is simple and efficient, and has three functions: quantification, isolation and transfer, which significantly improves sample representativeness and data reproducibility.

[0032] This invention is applicable to various sediment types and gas species, providing a high-fidelity experimental platform for greenhouse gas emission research in deep-water reservoirs, thermal strata, and extreme conditions.

[0033] This invention provides key data support and methodological foundation for constructing pressure-corrected methane flux models and deep-water carbon emission inventories, serving the national "dual carbon" strategy and the needs of global change research. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of a hydrostatic pressure simulation device capable of sampling under pressure.

[0035] Figure 2 This is an adsorption-dissolution curve of methane gas under different pressures in Example 2.

[0036] In the diagram: 1. Container cylinder; 2. Sealed cylinder cap; 3. Pressure gauge; 4. Thermometer; 5. Discharge pipe; 6. First control valve; 7. Sampling tube; 8. Second control valve; 9. Inlet pipe; 10. Inlet valve; 11. Vent pipe; 12. Vent valve; 13. Needle; 14. Headspace vial; 15. Rubber stopper; 16. Vent pipe; 17. Gas storage bottle; 18. Pressure reducing valve. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Example 1:

[0039] Please see Figure 1 As shown, the present invention is a hydrostatic pressure simulation device capable of sampling under pressure, comprising:

[0040] Container cylinder 1, with a sealing cylinder cover 2 installed on the top;

[0041] Pressure gauge 3 and temperature gauge 4 are mounted on the sealing cylinder cover 2;

[0042] The air intake assembly and the air venting assembly are located on the sealing cylinder cover 2;

[0043] Discharge pipe 5 is located at the lower part of container cylinder 1, and is connected in series with first control valve 6, sampling pipe 7, and second control valve 8.

[0044] The sampling assembly, connected to the lower end of the second control valve 8, includes a needle 13 and a pre-vacuumed headspace vial 14, with a rubber stopper 15 sealing the top of the headspace vial 14.

[0045] The system utilizes the coordinated control of the first control valve 6 and the second control valve 8 to achieve the isolation, quantification, and transfer of the mud-water mixture under in-situ hydrostatic pressure conditions, thus completing pressurized sampling.

[0046] The sampling tube 7 has a fixed volume and is used to quantitatively collect mud-water mixtures.

[0047] A sealing ring gasket is provided between the container cylinder 1 and the sealing cylinder cover 2 to improve the sealing performance.

[0048] As can be seen from the above, after the sealing cylinder cover 2 and the container cylinder 1 are tightened with bolts to press the sealing ring gasket, they can withstand a certain range of hydrostatic pressure simulation; the pressure gauge 3 and the temperature gauge 4 provide real-time feedback to ensure that the "pressure-temperature" coupling conditions are consistent with the target water depth during the experiment, providing a repeatable physical field for the gas adsorption equilibrium of the sediment-water interface and improving the measurement accuracy.

[0049] The headspace vial 14 is provided with a rubber stopper 15 at the top, and the needle 13 can puncture the rubber stopper 15 to inject the sample into the headspace vial 14.

[0050] Depend on Figure 1 It is known that the air intake assembly includes an air intake pipe 9, an air intake valve 10, and a pressure reducing valve 18, which are used to smoothly regulate the gas pressure inside the container. The lower end of the air intake pipe 9 is connected to the top wall of the sealing cylinder cover 2. The air intake valve 10 is located at the upper end of the air intake pipe 9. The upper end of the air intake valve 10 is connected to a ventilation pipe 16, and the gas storage bottle to be tested is connected to the ventilation pipe 16. The pressure reducing valve 18 is connected to the ventilation pipe 16.

[0051] In this embodiment, the gas storage bottle 17 to be tested contains high-purity methane gas.

[0052] As can be seen from the above, the air inlet valve 10 → air passage 16 → pressure reducing valve 18 form a step-by-step pressure reduction path, which can steadily reduce the high-purity methane in the gas storage bottle 17 to the experimental set pressure from the bottle pressure, avoiding instantaneous high pressure disturbance to the surface of the deposit.

[0053] After a certain amount of the gas to be tested is introduced, the gas inlet pipe 16 is separated from the gas inlet valve 10, and one end of the external pipe is connected to the gas inlet valve 10. The other end of the external pipe is connected to a nitrogen storage bottle. Then, nitrogen is introduced to make the container cylinder 1 reach the specified pressure for testing.

[0054] Depend on Figure 1 It is known that the venting assembly includes a venting pipe 11 and a venting valve 12, which are used to adjust or release the pressure inside the container before and after the experiment. The venting pipe 11 is connected to the top wall of the sealing cylinder cover 2, and the venting valve 12 is installed on the upper end of the venting pipe 11. The upper end of the venting valve 12 can be connected to a negative pressure extraction device under the prior art through a pipeline, which is used to perform vacuum treatment inside the container cylinder 1. The negative pressure extraction device can be a Sciencetool DTVS-204P4.

[0055] The headspace vial 14 is pre-evacuated to collect the gas released from the sample.

[0056] As can be seen from the above, the external negative pressure extraction device connected to the vent pipe 11 can evacuate the container 1, remove background gases such as oxygen and carbon dioxide in the headspace in advance, reduce the dilution effect when methane is introduced later, ensure the purity of the initial gas phase, and thus improve the accuracy of adsorption calculation.

[0057] A method for sampling under pressure includes the following steps:

[0058] S1. Add the sediment and water sample to container 1 in proportion, seal it, and then introduce gas to the target pressure;

[0059] S2. Open the first control valve 6 to allow the mud-water mixture to enter the sampling tube 7;

[0060] S3. Close the first control valve 6, open the second control valve 8, and use the residual pressure to inject the sample into the pre-vacuumed headspace vial 14.

[0061] S4. Complete pressurized sampling to prevent gas from escaping.

[0062] In step S2, the sampling tube 7 has a volume of 20 mL and is used for quantitative sample collection.

[0063] In step S4, after the sample is injected into the headspace vial 14, high-purity nitrogen is immediately injected with a syringe until it is balanced with atmospheric pressure, and the gas volume is recorded.

[0064] In step S4, after the sample is injected into the headspace vial 14, the gas concentration is determined using a gas chromatograph.

[0065] In step S1, the target pressure is 0.1 to 2.0 MPa, used to simulate hydrostatic pressure under different water depth conditions.

[0066] Specifically, in this first embodiment, a method for sampling under pressure is as follows:

[0067] Weigh 300g of sediment and 500ml of pure water, add them to container 1, and seal the container lid 2;

[0068] Introduce high-purity methane and nitrogen gas, adjust to the target pressure (e.g., 0.9 MPa), and incubate at a constant temperature until equilibrium is reached;

[0069] Open the first control valve 6 to allow the mud-water mixture to enter the sampling tube 7 (volume fixed at 20 mL);

[0070] Close the first control valve 6, open the second control valve 8, and use the residual pressure to inject the sample into the pre-vacuumed headspace vial 14.

[0071] Immediately inject high-purity nitrogen gas into the top of headspace vial 14 using a syringe, and record the gas volume.

[0072] The methane concentration was determined using a gas chromatograph, and the amount of methane emitted and adsorbed was calculated.

[0073] Specifically, the sampling tube 7, together with the first control valve 6 and the second control valve 8, forms a three-stage unit of "isolation-quantification-transfer": the first control valve 6 is opened, and the mud-water sample fills the sampling tube 7 under the set pressure and then closes, achieving zero gas loss sampling under in-situ pressure conditions; after stabilization, the first control valve 6 is closed, and the second control valve 8 is opened, using the residual pressure to push the sample into the vacuum headspace vial 14, which has been punctured with a hard steel needle 13. Then, the syringe barrel is immediately inserted into the headspace vial 14 to collect the discharged gas, and the gas volume V in the syringe barrel is recorded. The gas in the syringe barrel is transferred to a vacuum bag, and 1 ml is extracted using an airtight syringe and injected into a gas chromatograph (GC) to measure the relative concentration of methane.

[0074] Example 2:

[0075] This embodiment operates the same as Embodiment 1, with the core optimization being the construction of a sediment culture system and the setting of a pressure gradient, as detailed below:

[0076] Sample and culture system design:

[0077] After sieving, the sediment was mixed with distilled water at a volume ratio of 1:5 to prepare a sediment-water mixture.

[0078] Pretreatment: High-purity nitrogen (purity ≥99.99%) is introduced into the container to replace the air, creating an anaerobic environment and preventing oxygen from interfering with the generation and storage of methane.

[0079] Pressure gradient setting:

[0080] Based on the 0.1 to 2.0 MPa range defined in this patent, four gradients are set: 0.1 MPa, 0.5 MPa, 1.0 MPa, and 2.0 MPa, covering the pressure range from shallow to medium-deep water.

[0081] Cultivation and equilibrium conditions:

[0082] After introducing high-purity methane, the mixture was placed in a constant temperature environment and incubated for 7 days, during which manual shaking was used (to promote gas-liquid-solid three-phase equilibrium).

[0083] During the cultivation process, pressure and temperature data are recorded at regular intervals. When the pressure fluctuation exceeds ±0.1MPa, the air intake valve is used for fine-tuning to maintain the target pressure stability.

[0084] Sampling and testing:

[0085] Samples were collected according to the pressurized sampling procedure in Example 1 to ensure the integrity of the sediment-water interface and avoid methane release due to depressurization.

[0086] The methane concentration was determined using a gas chromatograph (FID detector), and the gas volume was recorded simultaneously. Adsorption-dissolution curves at different pressures are shown below. Figure 2 As shown.

[0087] Example 3:

[0088] This embodiment is basically the same as Embodiment 1, except that in this embodiment, other gases are introduced to the target pressure.

[0089] In summary, the working principle of this invention is as follows: Sediment samples and water samples are added to container 1 according to the designed ratio, the sealing cap 2 is closed, and the sealing ring gasket is tightened with bolts. Specifically: 300g of sediment and 500ml of pure water are weighed, placed into container 1, bolts are installed, and high-purity air is used for pressure testing and leak detection to ensure the system's airtightness.

[0090] After depressurization, 0.1 MPa of gas is introduced to pressurize to the target pressure. The system pressure and temperature are then allowed to stabilize, allowing the gas to reach dissolution / adsorption equilibrium in the sediment-water system. Specifically, the inlet valve 10 is opened, and the gas (methane or carbon dioxide) in the gas storage bottle 17 is smoothly injected into the container cylinder 1 through the pressure reducing valve 18. Subsequently, the nitrogen source can be switched to continue filling with nitrogen until the pressure gauge 3 reaches the target hydrostatic pressure, so as to achieve accurate simulation of deep-water pressure conditions. The mixture is then incubated at a constant temperature under real-time monitoring by the thermometer 4, and the gas adsorption equilibrium is achieved at the sediment-water interface.

[0091] After the pressure stabilizes, open the first control valve 6 to fill the 20mL sampling tube 7 with the mud-water mixture. After the pressure stabilizes, close the first control valve 6 and open the second control valve 8. Use the residual pressure to push the sample liquid into the vacuum headspace vial 14, which has been punctured with a hard steel needle 13. Immediately afterward, insert the syringe into the headspace vial 14, collect the expelled gas, and record the gas volume V in the syringe. Then, transfer the gas in the syringe to a vacuum bag and use an airtight syringe to extract 1mL and inject it into a gas chromatograph (GC) to measure the relative concentration of methane.

[0092] The accompanying drawings of the embodiments disclosed in this invention only involve structures relevant to the embodiments disclosed in this invention. Other structures can be referred to with common designs. Unless otherwise specified, the same embodiment and different embodiments of this invention can be combined with each other.

[0093] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A hydrostatic pressure simulation device capable of sampling under pressure, characterized in that, include: The container tube (1) is sealed with a sealing cap (2) at the top. Pressure gauge (3) and temperature gauge (4) are mounted on the sealing cylinder cover (2); The air intake assembly and the air vent assembly are located on the sealing cylinder cover (2); The discharge pipe (5) is located at the bottom of the container cylinder (1), and the first control valve (6), the sampling pipe (7), and the second control valve (8) are connected in series in sequence. The sampling assembly, connected to the lower end of the second control valve (8), includes a needle (13) and a pre-vacuumed headspace vial (14), with a rubber stopper (15) sealed at the top of the headspace vial (14). Among them, the isolation, quantification and transfer of mud-water mixture under in-situ hydrostatic pressure conditions are realized through the coordinated control of the first control valve (6) and the second control valve (8), and the pressure sampling is completed.

2. The hydrostatic pressure simulation device capable of sampling under pressure according to claim 1, characterized in that: The headspace vial (14) is provided with a rubber stopper (15) at the top, and the needle (13) can puncture the rubber stopper (15) to inject the sample into the headspace vial (14).

3. The hydrostatic pressure simulation device capable of sampling under pressure according to claim 1, characterized in that: The air intake assembly includes an air intake pipe (9), an air intake valve (10), and a pressure reducing valve (18) for smoothly regulating the gas pressure inside the container. The lower end of the air intake pipe (9) is connected to the top wall of the sealing cylinder cover (2). The air intake valve (10) is located at the upper end of the air intake pipe (9). The upper end of the air intake valve (10) is connected to a ventilation pipe (16), and the gas storage bottle (17) to be tested is connected through the ventilation pipe (16). The pressure reducing valve (18) is connected to the ventilation pipe (16).

4. The hydrostatic pressure simulation device capable of sampling under pressure according to claim 1, characterized in that: The venting assembly includes a venting pipe (11) and a venting valve (12), which are used to adjust or release the pressure inside the container before and after the experiment. The venting pipe (11) is connected to the top wall of the sealing cylinder cover (2), and the venting valve (12) is installed on the upper end of the venting pipe (11).

5. The hydrostatic pressure simulation device capable of sampling under pressure according to claim 1, characterized in that: The headspace vial (14) is pre-evacuated to collect the gas released from the sample.

6. A method for live sampling, implemented based on a hydrostatic pressure simulation device capable of live sampling as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Add the sediment and water sample to the container (1) in proportion, seal it, and then introduce gas to the target pressure; S2. Open the first control valve (6) to allow the mud-water mixture to enter the sampling tube (7); S3. Close the first control valve (6), open the second control valve (8), and use the residual pressure to inject the sample into the pre-vacuumed headspace vial (14). S4. Complete pressurized sampling to prevent gas from escaping.

7. The live sampling method according to claim 6, characterized in that: In step S2, the sampling tube (7) has a volume of 20 mL and is used for quantitative sample collection.

8. The live sampling method according to claim 6, characterized in that: In step S4, after the sample is injected into the headspace vial (14), high-purity nitrogen is immediately injected with a syringe until it is balanced with atmospheric pressure, and the gas volume is recorded.

9. A live sampling method according to claim 6, characterized in that: In step S4, after the sample is injected into the headspace vial (14), the gas concentration is determined using a gas chromatograph.

10. A live sampling method according to claim 6, characterized in that: In step S1, the target pressure is 0.1 to 2.0 MPa, used to simulate hydrostatic pressure under different water depth conditions.

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