A visual supercritical carbon dioxide immersion in-situ static experiment system

Abstract

The utility model relates to the technical field of statics experiment device, and specifically discloses a visual supercritical carbon dioxide soaking in-situ statics experiment system, which comprises a loading system, and the loading system comprises a frame type pressure testing machine, and a soaking tank is arranged inside the frame type pressure testing machine; the soaking tank comprises a soaking tank body, the soaking tank body is in a cylindrical shape, a sample body is placed inside the soaking tank body, a top cover is detachably fixed to the top of the soaking tank body, a pressure head for pressing down the sample body is vertically and slidingly arranged through the top cover, and a visual window is arranged on the side of the soaking tank body, and a perspective glass is arranged on the visual window. The utility model can realize DIC image processing of the coal sample under the supercritical carbon dioxide soaking in-situ mechanical test without taking out the coal sample, and has high measurement accuracy and test efficiency.

Description

Technical Field

[0001] This utility model relates to the field of static experimental device technology, and in particular to a visual supercritical carbon dioxide immersion in-situ static experimental system. Background Technology

[0002] With the development of industrialization, large amounts of carbon dioxide are emitted, and excessive carbon emissions pose a huge challenge to addressing environmental problems such as global warming and the greenhouse effect, seriously affecting the future living environment of humankind. Global warming and the greenhouse effect have gradually impacted human production activities, and CO2 is considered one of the main culprits of global warming. To reduce atmospheric carbon content, many scholars have proposed various methods to reduce atmospheric carbon dioxide levels. Among them, geological carbon dioxide sequestration has received high attention globally due to its enormous potential and high safety. Geological carbon dioxide sequestration refers to injecting carbon dioxide into geological formations under high pressure to achieve the purpose of sequestering carbon dioxide. Since deep, unminable coal seams are naturally favorable locations for geological carbon dioxide sequestration, sequestering carbon dioxide into deep, unminable coal seams can reduce the CO2 content in the atmosphere and also replace the extraction of methane gas from coal seams, achieving two effects at once, which is of great significance. In deep environments, the increased temperature and pressure make carbon dioxide readily form a supercritical state (temperature 31.1℃, pressure 7.38MPa), exhibiting some properties of both gases and liquids. When supercritical CO2 interacts with coal, it undergoes complex physicochemical reactions with the coal matrix, altering the internal structure of the coal, promoting the development and connection of internal fractures, and consequently affecting its mechanical properties. This ultimately leads to deformation, failure, and structural damage within the coal seam, causing secondary disasters. Therefore, changes in the mechanical properties of coal are directly related to the effectiveness and safety of CO2 geological sequestration.

[0003] Existing studies have shown that after supercritical carbon dioxide immersion, coal exhibits a trend of decreasing micropore and mesopore content and increasing macropore content at the microscopic level. Macroscopically, this manifests as a decrease in the elastic modulus and peak strength of the coal, along with increased degradation, as supercritical CO2 treatment progresses. The mechanical damage evolution effect of supercritical CO2 on coal is a cumulative process from micro to macro. Because the erosive effect of supercritical CO2 on coal causes minute deformations on its surface and the formation of microcracks during loading, random speckle patterns are sprayed onto the sample surface. Images of the sample failure are captured using a high-speed camera, and digital image correlation (DIC) technology is used to import the captured digital images into an analysis system for full-field strain and displacement calculations. This monitors the microscopic evolution of the global strain field of the sample, providing a direct understanding of the crack initiation and evolution process and damage state of multi-fractured coal from multiple perspectives. Currently, mechanical tests on coal and rock after supercritical carbon dioxide immersion conducted domestically and internationally can be broadly categorized into two types:

[0004] The first method involves immersing the sample in a supercritical carbon dioxide immersion tank for a certain period of time, then removing it and placing it under a mechanical testing machine for mechanical testing. Although this method can take pictures of the sample when it is damaged and perform DIC post-processing, the desorption of carbon dioxide and the pressure changes after the sample is removed have a significant impact on the test results.

[0005] The second method combines a supercritical carbon dioxide immersion tank with a pressure machine to conduct in-situ mechanical tests. While this method allows for in-situ mechanical testing, the closed design of the tanks prevents the photographic observation of the specimen's failure type. Furthermore, neither of these methods can systematically detect the amount of carbon dioxide adsorbed on the specimen.

[0006] Therefore, in order to study the strain field changes on the surface of the specimen while conducting in-situ mechanical experiments, it is urgent to develop a visual supercritical carbon dioxide immersion in-situ static experimental system. Utility Model Content

[0007] To address the shortcomings of existing methods, the purpose of this invention is to provide a visualized in-situ static experimental system and method for supercritical carbon dioxide immersion. This invention can perform DIC image processing on the failure process of coal under in-situ mechanical testing after supercritical carbon dioxide immersion, allowing for a more intuitive observation of the strain field and physical field changes of the sample body 26 throughout the failure process. Furthermore, it can test the expansion rate of the coal matrix and the amount of carbon dioxide adsorbed after CO2 adsorption. Simultaneously, this invention possesses excellent sealing performance, corrosion resistance, and high material strength, greatly ensuring the accuracy of the experiment and the safety of the experimental personnel.

[0008] To achieve the above objectives, this utility model provides the following technical solution:

[0009] A visual supercritical carbon dioxide immersion in-situ static experimental system includes a loading system, wherein the loading system includes a frame-type pressure testing machine, and an immersion tank is installed inside the frame-type pressure testing machine.

[0010] The soaking tank includes a tank body, which is cylindrical. The interior of the tank body is used to place the sample body. A top cover is detachably fixed to the top of the tank body. A pressure head for pressing down the sample body is vertically slidably through the top cover. A viewing window is provided on the side of the tank body, and a transparent glass is installed on the viewing window.

[0011] The side walls of the soaking tank are respectively provided with an air inlet and an air outlet that communicate with the inside of the soaking tank.

[0012] The side wall of the soaking tank is also provided with an external electrode, which includes an insulating electrode. The insulating electrode is connected to a strain gauge, which can be attached to the sample body. A heating plate is also installed on the inner wall of the soaking tank.

[0013] The bottom of the soaking tank is fixed with a base, and a metal pad is placed on the base. The sample body is placed on the metal pad.

[0014] Preferably, the main parameters of the frame-type pressure testing machine are: maximum applied pressure of 100kN, pressure accuracy greater than ±0.5%, displacement accuracy greater than 0.0025mm ±0.5%, and loading speed adjustment range of 0.01-500mm / min.

[0015] Preferably, the strain gauge has a size of 4mm*9mm and is connected to an insulating electrode, which can be connected to an external power source.

[0016] Preferably, the top cover is coaxially provided with a boss, the boss has a round hole for the pressure head to pass through, a flange is detachably fixed to the top of the boss, a first sealing gasket is provided between the flange and the boss, and the flange and the first sealing gasket are coaxially sleeved on the pressure head.

[0017] Preferably, the transparent glass is detachably mounted on the visualization window via a glass cover, and a second sealing gasket is provided coaxially between the transparent glass and the visualization window.

[0018] Preferably, the soaking tank has a through hole on its side, an electrode sleeve is threadedly connected to the through hole, a round washer is coaxially provided between the electrode sleeve and the through hole, the inside of the electrode sleeve is filled with insulating sealant, and the insulating electrode is placed inside the insulating sealant.

[0019] Preferably, the frame-type pressure testing machine is also provided with a gas supply system on the side. The gas supply system includes a carbon dioxide cylinder. The carbon dioxide cylinder is connected to the air inlet through a first pipe. The carbon dioxide cylinder can deliver carbon dioxide into the immersion tank. A first air valve, a first pressure gauge, a first pressure reducing valve, a heater, a first gas flow meter, a carbon dioxide booster pump, a second air valve, and a second pressure gauge are installed sequentially on the first pipe.

[0020] Preferably, the carbon dioxide booster pump has a maximum output pressure of 20 MPa and an output flow rate of 5 L / min.

[0021] Preferably, the frame-type pressure testing machine is further provided with a strain measurement system on its side, the strain measurement system including a strain gauge that is electrically connected to the strain gauge.

[0022] Preferably, the frame-type pressure testing machine is also provided with a degassing system on the side. The degassing system includes a gas collecting bottle, which is connected to the gas outlet through a second pipe. Carbon dioxide inside the soaking tank can be transported to the gas collecting bottle through the second pipe. A pressure vacuum gauge, an electric valve, a second pressure reducing valve, a second gas flow meter, a vacuum pump, and a third gas valve are installed sequentially on the second pipe.

[0023] Preferably, the frame-type pressure testing machine is also equipped with a digital speckle measurement system on its side. The digital speckle measurement system includes a high-speed camera and a computer. The high-speed camera is used to photograph the inside of the soaking tank through the transparent glass. The computer is connected to the high-speed camera, the frame-type pressure testing machine, the strain gauge, and the electric valve via electrical signals.

[0024] Preferably, the high-speed camera has a frame rate of 120fps and an image resolution of 7952*5304ppi.

[0025] Preferably, the computer can perform digital speckle image processing, strain gauge data acquisition, and control of the frame-type pressure testing machine and electric valves.

[0026] The pressure vacuum gauge has a display range of -0.1 to 10 MPa, and the vacuum pump has a pumping speed of 40 L / min.

[0027] The soaking tank body, top cover, flange, pressure head, and glass cover are all made of high-alloy austenitic steel or nickel-based alloy.

[0028] Both the sealing ring and the sealant are made of corrosion-resistant materials. The heating plate has an adjustable temperature, up to 100°C, and its circuitry is connected to an insulating electrode, which can be powered externally.

[0029] The transparent glass is made of sapphire glass, which has the characteristics of chemical corrosion resistance, high hardness, and good light transmission.

[0030] The soaking tank has an average wall thickness of 20mm, a maximum air pressure of 25MPa, and an internal volume of 2600mL.

[0031] The metal pads are available in multiple height specifications to accommodate specimens of different heights. The testable specimen sizes range from 25*50mm to 50*100mm.

[0032] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0033] This invention includes a gas supply system, a loading system, an immersion tank, a strain measurement system, a digital speckle measurement system, and a degassing system. The overall structure is simple and easy to operate. It can perform DIC image processing on coal samples subjected to in-situ mechanical tests under supercritical carbon dioxide immersion without removing the coal sample. It can determine the expansion rate of the coal matrix and the amount of carbon dioxide adsorbed, with high accuracy and high test efficiency.

[0034] The gas cylinder outlet of this invention is equipped with a heater (the heater is in the form of a patch that can completely wrap and heat the front end conduit of the carbon dioxide booster pump). After being heated by the heater, the outflowing carbon dioxide can be completely vaporized, eliminating the influence of some liquid carbon dioxide on the carbon dioxide booster pump.

[0035] The exhaust gas collection system of this utility model adopts an electric valve. Since the supercritical carbon dioxide pressure is too high, manual depressurization is too difficult and dangerous. Therefore, an electric valve is used for depressurization. During depressurization, no manual operation is required, which prevents the test personnel from being injured by excessive pressure during depressurization.

[0036] This invention can measure the amount of carbon dioxide adsorbed on a sample after supercritical carbon dioxide immersion. This measurement method is based on the principle that the change of gas phase in a closed space does not affect the amount of substance. The difference in the amount of carbon dioxide before and after adsorption is used to represent the amount of carbon dioxide adsorbed on the sample.

[0037] This invention can also be used to conduct visual static experiments under single temperature and single pressure variable conditions, that is, with the experimental conditions unchanged, the changes in the static experiment can be observed visually through tempered glass. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the structure of this utility model;

[0040] Figure 2 This is an isometric view of the soaking tank of this utility model;

[0041] Figure 3 This is an exploded view of the soaking tank of this utility model;

[0042] Figure 4 This is a left sectional view of the soaking tank of this utility model.

[0043] In the diagram: 1. Carbon dioxide cylinder; 2. First gas valve; 3. First pressure gauge; 4. First pressure reducing valve; 5. Heater; 6. First gas flow meter; 7. Carbon dioxide booster pump;

[0044] 8. Second air valve; 9. Second air pressure gauge; 10. Immersion tank; 11. Frame-type pressure testing machine; 12. Up button; 13. Down button; 14. Start button; 15. Emergency stop button; 16. Pressure / vacuum gauge; 17. Electric valve; 18. Second pressure reducing valve; 19. Second gas flow meter; 20. Vacuum pump; 21. Third air valve; 22. Gas collecting bottle; 23. Computer; 24. Strain gauge; 25. High-speed camera; 26. Sample body; 27. Immersion tank body; 28. 1. Air inlet; 29. ​​Heating plate; 30. External electrode; 31. Electrode housing; 32. Round washer; 33. Top cover; 34. First spring washer; 35. First hex bolt; 36. Flange; 37. First sealing washer; 38. Pressure head; 39. Metal pad; 40. Strain gauge; 41. Air outlet; 42. Second sealing washer; 43. Transparent glass; 44. Glass cover; 45. Second spring washer; 46. Second hex bolt; 47. Insulating electrode; 48. Insulating sealant. Detailed Implementation

[0045] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0046] In the description of this utility model, it should be understood that the terms "opening", "upper", "lower", "thickness", "top", "middle", "length", "inner", "around" and other terms indicating orientation or positional relationship are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the components or elements referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0047] The following describes in detail a visualization-based in-situ static experimental system and method for supercritical carbon dioxide immersion. The visualization-based in-situ static experimental system for supercritical carbon dioxide immersion will be more clearly described in conjunction with the accompanying drawings in the embodiments of this utility model:

[0048] Reference Figures 1-4A visualized supercritical carbon dioxide immersion in-situ static experimental system includes a loading system, which comprises a frame-type pressure testing machine 11, inside which an immersion tank 10 is installed. The frame-type pressure testing machine 11 has a platform for mounting the immersion tank 10.

[0049] The soaking tank 10 includes a tank body 27, which is cylindrical in shape. The specific shape of the tank body 27 is as follows: Figure 2 , Figure 3 as well as Figure 4 As shown. The interior of the soaking tank body 27 is used to hold the sample body 26, which can be a coal sample. A top cover 33 is detachably fixed to the top of the soaking tank body 27, and a pressure head 38 for pressing down the sample body 26 is vertically slidably installed on the top cover 33. The pressure head 38 is as follows: Figure 3 and Figure 4 As shown, the frame-type pressure testing machine 11 is equipped with a power-controlled downward-moving crossbeam pressure bar, which can press down onto the top of the pressure head 38, i.e., apply downward pressure. The side of the soaking tank 27 is equipped with a viewing window, on which a transparent glass 43 is installed.

[0050] The side walls of the soaking tank body 27 are respectively provided with an air inlet 28 and an air outlet 41 that communicate with the inside of the soaking tank body 27;

[0051] The side wall of the immersion tank body 27 is also provided with an external electrode 30, which includes an insulating electrode 47. The insulating electrode 47 is connected to a strain gauge 40, which can be attached to the sample body 26. The inner wall of the immersion tank body 27 is also equipped with a heating plate 29, which is matched with a temperature sensor and can be used to transmit temperature information in real time.

[0052] The bottom of the immersion tank 27 is fixed with a base, on which a metal pad 39 is placed, and the sample body 26 is placed on the metal pad 39. A center mark or groove can be provided on the base to facilitate the positioning of the sample body 26. The metal pad 39 can be configured with multiple height specifications to accommodate sample bodies 26 of different heights. The size range of the testable sample body 26 is 25*50mm-50*100mm.

[0053] The main parameters of the frame-type compression testing machine 11 are: maximum applied pressure 100kN, pressure accuracy greater than ±0.5%, displacement accuracy greater than 0.0025mm ±0.5%, and loading speed adjustment range of 0.01-500mm / min.

[0054] The strain gauge 40 has a size of 4mm*9mm and is connected to the insulating electrode 47, which can be connected to an external power source.

[0055] The top cover 33 is detachably and fixedly connected to the top of the soaking tank body 27 by a number of first hexagonal bolts 35, that is, the first hexagonal bolts 35 are threaded through the top cover 33, and the soaking tank body 27 is provided with matching threaded holes, as shown in the figure below. Figure 3 As shown. A boss is coaxially provided on the upper side of the top cover 33. The boss has a round hole for the pressure head 38 to pass through. A flange 36 is detachably fixed to the top of the boss. A first sealing gasket 37 is provided between the flange 36 and the boss. Both the flange 36 and the first sealing gasket 37 are coaxially fitted onto the pressure head 38. The flange 36 and the first sealing gasket 37 provide a sealing effect, ensuring the airtightness of the interior of the soaking tank 27. The flange 36 is also detachably fixed to the corresponding boss by several first hexagonal bolts 35. That is, the threads of the first hexagonal bolts 35 penetrate the flange 36, and the boss has matching threaded holes. A matching first spring washer 34 is fitted onto the first hexagonal bolts 35. The first spring washer 34 can prevent the first hexagonal bolts 35 from loosening. Specifically, as shown... Figure 3 As shown.

[0056] The transparent glass 43 is detachably mounted on the viewing window via a glass cover 44. A second sealing gasket 42 is coaxially positioned between the transparent glass 43 and the viewing window. The glass cover 44 is detachably and fixedly connected to the viewing window via several second hexagonal bolts 46, wherein the threads of the second hexagonal bolts 46 penetrate the glass cover 44. The edge of the viewing window has matching threaded holes. A matching second spring washer 45 is fitted onto the second hexagonal bolts 46. The second spring washer 45 prevents the second hexagonal bolts 46 from loosening. Specifically, as shown... Figure 3 As shown.

[0057] The immersion tank body 27 has a through hole on its side, and an electrode sleeve 31 is threadedly connected to the through hole. A round washer 32 is coaxially provided between the electrode sleeve 31 and the through hole. The inside of the electrode sleeve 31 is filled with insulating sealant 48, and the insulating electrode 47 is placed inside the insulating sealant 48. The round washer 32 and the insulating sealant 48 provide a sealing effect, ensuring the airtightness of the immersion tank body 27.

[0058] The frame-type pressure testing machine 11 is also equipped with a gas supply system on the side. The gas supply system includes a carbon dioxide cylinder 1. The carbon dioxide cylinder 1 is connected to the air inlet 28 through a first pipe. The carbon dioxide cylinder 1 can deliver carbon dioxide into the immersion tank 27. The first pipe is sequentially equipped with a first gas valve 2, a first gas pressure gauge 3, a first pressure reducing valve 4, a heater 5, a first gas flow meter 6, a carbon dioxide booster pump 7, a second gas valve 8, and a second gas pressure gauge 9.

[0059] The carbon dioxide booster pump 7 is made of corrosion-resistant materials and can boost the pressure of carbon dioxide.

[0060] The maximum output pressure of the carbon dioxide booster pump 7 is 20MPa, and the output flow rate is 5L / min.

[0061] The frame-type pressure testing machine 11 is also equipped with a strain measurement system on its side, which includes a strain gauge 24 that is electrically connected to the strain gauge 40.

[0062] The frame-type pressure testing machine 11 is also equipped with a degassing system on the side. The degassing system includes a gas collecting bottle 22, which is connected to the gas outlet 41 through a second pipe. Carbon dioxide inside the soaking tank 27 can be transported to the gas collecting bottle 22 through the second pipe, thereby realizing the carbon dioxide gas extraction operation. A pressure vacuum gauge 16, an electric valve 17, a second pressure reducing valve 18, a second gas flow meter 19, a vacuum pump 20, and a third gas valve 21 are installed sequentially on the second pipe.

[0063] The frame-type pressure testing machine 11 is also equipped with a digital speckle measurement system on its side. The digital speckle measurement system includes a high-speed camera 25 and a computer 23. The high-speed camera 25 is used to photograph the inside of the soaking tank 27 through the transparent glass 43. The computer 23 is electrically connected to the high-speed camera 25, the frame-type pressure testing machine 11, the strain gauge 24, and the electric valve 17.

[0064] The high-speed camera 25 shoots at 120fps with an image resolution of 7952*5304ppi.

[0065] Computer 23 can perform digital speckle image processing, strain gauge 24 data acquisition, and control of frame-type pressure testing machine 11 and electric valve 17.

[0066] The pressure vacuum gauge 16 has a display range of -0.1 to 10 MPa, and the vacuum pump 20 has a pumping speed of 40 L / min.

[0067] The materials of the soaking tank body 27, top cover 33, flange 36, pressure head 38, and glass cover 44 are all high-alloy austenitic steel or nickel-based alloy.

[0068] Both the sealing ring and the sealant are made of corrosion-resistant materials. The heating plate 29 has an adjustable temperature, which can be raised to a maximum of 100°C. The circuit of the heating plate 29 is connected to the insulating electrode, which can be connected to an external power source.

[0069] The transparent glass 43 is made of sapphire glass, which has the characteristics of chemical corrosion resistance, high hardness, and good light transmission. Its thickness is 20mm and it can withstand the high pressure of supercritical carbon dioxide.

[0070] The average wall thickness of the soaking tank 27 is 20mm, the maximum air pressure it can withstand is 25MPa, and the internal volume of the tank is 2600mL.

[0071] In the preparation phase of the experiment, an airtightness check was first performed. Electric valve 17 was closed, and the first gas valve 2 and the second gas valve 8 were opened. The first pressure reducing valve 4 was adjusted to supply carbon dioxide into the first pipeline, and heater 5 remained open. Heating plate 29 was turned on to heat the temperature to 31°C. Carbon dioxide booster pump 7 was turned on to pressurize the soaking tank 10. When the reading on the second pressure gauge 9 reached 7.3 MPa, the second gas valve 8, carbon dioxide booster pump 7, and first gas valve 2 were closed. At this point, the carbon dioxide was in a supercritical state. After a period of time, if the reading on the second pressure gauge 9 remained unchanged or fluctuated by only 0.05 MPa, the airtightness was considered good. Heating plate 29 was closed, and the third gas valve 21 and electric valve 17 were opened to depressurize the supercritical carbon dioxide into the gas collecting bottle 22. After the reading on the pressure vacuum gauge 16 stabilized, vacuum pump 20 was turned on to extract the remaining carbon dioxide gas from the soaking tank. Then, the third gas valve 21 and vacuum pump 20 were closed.

[0072] Strain gauges 40 are attached to both sides of the sample body 26 to be tested. The strain gauges 40 are connected to insulating electrodes 47, which are connected to an external power source. The sample body 26 is placed inside the immersion tank 27. The third gas valve 21, electric valve 17, and vacuum pump 20 are opened to evacuate the sample. When the pressure gauge 16 reads approximately -0.1 MPa, the evacuation is complete, and the third gas valve 21, electric valve 17, and vacuum pump 20 are closed. The first gas valve 2 and the second gas valve 8 are opened, and the first pressure reducing valve 4 is adjusted to supply carbon dioxide into the first pipeline. The heater 5 remains open. The heating plate 29 is opened to heat the sample to 31°C. The carbon dioxide booster pump 7 is turned on to pressurize the immersion tank 27. When the second pressure gauge 9 reads 7.3 MPa, the second gas valve 8, carbon dioxide booster pump 7, and first gas valve 2 are closed. At this point, the carbon dioxide is in a supercritical state. The strain gauge 24 is turned on, and the data from the strain gauge 24 is recorded in the computer 23. After the sample body 26 is immersed for 24 hours (immersion time can be customized), the high-speed camera 25 is aimed at the visualization window on the immersion tank 27, keeping it focused on the surface of the sample body 26. The frame-type pressure testing machine 11 is started by pressing the start button 14, and the descent button 13 is adjusted so that the crossbeam pressure bar stops just before contacting the indenter 38. The loading rate is set, the high-speed camera 25 is turned on, and the test begins. During the experiment, the crossbeam pressure bar continuously applies pressure to the indenter 38, slowly pressing it down and continuously contacting the sample body 26. During this slow process, the high-speed camera 25 records the failure process of the sample body 26 until the sample body 26 fails, at which point the indenter 38 stops pressing down. Furthermore, in the event of any emergency during the experiment, the experiment can be stopped using the emergency stop button 15.

[0073] The test ends when obvious deformation and cracks appear on the surface of the specimen 26. Save the experimental data, turn off the strain gauge 24 and high-speed camera 25, and adjust the rise button 12 of the frame-type pressure testing machine 11 to raise the crossbeam pressure bar of the frame-type pressure testing machine 11. Turn off the heating plate 29, open the third gas valve 21 and the electric valve 17 to depressurize the supercritical carbon dioxide into the gas collecting bottle 22. After the pressure vacuum gauge 16 reading stabilizes, turn on the vacuum pump 20 to extract the residual carbon dioxide gas in the soaking tank 27, then close the third gas valve 21 and the vacuum pump 20, and remove the specimen 26. The test ends.

[0074] Furthermore, this invention can perform visualized static experiments under single temperature and single pressure variable conditions. Specifically, it can measure the amount of carbon dioxide adsorbed on the sample body 26 after supercritical carbon dioxide immersion, and simultaneously visualize the changes in the static experiment through the transparent glass 43. The specific steps are as follows:

[0075] In the preparation phase of the experiment, an airtightness check was first performed. Electric valve 17 was closed, and the first gas valve 2 and the second gas valve 8 were opened. The first pressure reducing valve 4 was adjusted to supply carbon dioxide into the first pipeline, and heater 5 remained open. Heating plate 29 was turned on to heat the temperature to 31°C. Carbon dioxide booster pump 7 was turned on to pressurize the immersion tank 27. When the reading on the second pressure gauge 9 reached 7.3 MPa, the second gas valve 8, carbon dioxide booster pump 7, and first gas valve 2 were closed. At this point, the carbon dioxide was in a supercritical state. After a period of time, if the reading on the second pressure gauge 9 remained unchanged or fluctuated by only 0.05 MPa, the airtightness was considered good. Heating plate 29 was closed, and the third gas valve 21 and electric valve 17 were opened to depressurize the supercritical carbon dioxide into the gas collecting bottle 22. After the reading on the pressure vacuum gauge 16 stabilized, vacuum pump 20 was turned on to extract the remaining carbon dioxide gas from the immersion tank 27. Then, the third gas valve 21 and vacuum pump 20 were closed.

[0076] The sample body 26 is placed into the immersion tank 27. The third gas valve 21, electric valve 17, and vacuum pump 20 are opened to evacuate the tank. Vacuuming is completed when the pressure gauge 16 reads approximately -0.1 MPa. The electric valve 17, third gas valve 21, and vacuum pump 20 are then closed. The first gas valve 2 and second gas valve 8 are opened, and the first pressure reducing valve 4 is adjusted. The reading of the first pressure gauge 3 is recorded as P1. Carbon dioxide is introduced into the first pipeline. The heater 5 is normally open, and its temperature is recorded as T1. The cumulative gas flow rate of the first gas flow meter 6 is recorded as V1. The compressibility factor of carbon dioxide at this pressure and temperature is found to be z1. The heating plate 29 is opened, and the temperature is controlled and heated to 31°C. The carbon dioxide booster pump 7 is opened to pressurize the immersion tank 27. When the reading of the second pressure gauge 9 is 7.3 MPa, the second gas valve 8, carbon dioxide booster pump 7, and first gas valve 2 are closed. At this point, the carbon dioxide is in a supercritical state. After the sample body 26 is soaked for 24 hours (the soaking time can be customized), the electric valve 17 and the third gas valve 21 are opened, the second pressure reducing valve 18 is adjusted, and the reading of the pressure vacuum gauge 16 is recorded as P2. The compressibility factor of carbon dioxide at this pressure and temperature is found to be z2, so that the supercritical carbon dioxide in the soaking tank 27 flows out in a low-pressure gaseous form. The indoor temperature at this time is recorded as T2. The vacuum pump 20 is turned on to extract the residual gas in the soaking tank 27, and the cumulative gas volume of the second gas flow meter 19 is recorded as V2. All the subtle changes in the gas adsorbed by the sample can be observed through the transparent glass 43.

[0077] From the gas law:

[0078] PV = znRT

[0079] have to:

[0080]

[0081] Where P is the gas pressure in Pa; V is the gas volume in m3; z is the gas compressibility factor; n is the amount of substance in mol; R is the molar gas constant in J / (mol·K); and T is the gas temperature in K.

[0082] The amount of carbon dioxide entering tank 27 of the soaking tank is:

[0083]

[0084] After soaking, the amount of carbon dioxide discharged is:

[0085]

[0086] The amount of carbon dioxide adsorbed by sample 26 is:

[0087] nad =n1-n2

[0088] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.

Claims

1. A visualized supercritical carbon dioxide immersion in-situ static experimental system, comprising a loading system, characterized in that, The loading system includes a frame-type pressure testing machine (11), and an immersion tank (10) is installed inside the frame-type pressure testing machine (11); The soaking tank (10) includes a tank body (27), which is cylindrical. The inside of the tank body (27) is used to place the sample body (26). A top cover (33) is detachably fixed to the top of the tank body (27). A pressure head (38) for pressing down the sample body (26) is vertically slidably provided on the top cover (33). A visualization window is provided on the side of the tank body (27), and a transparent glass (43) is installed on the visualization window. The side wall of the soaking tank body (27) is provided with an air inlet (28) and an air outlet (41) that communicate with the inside of the soaking tank body (27); The side wall of the soaking tank body (27) is also provided with an external electrode (30), the external electrode (30) includes an insulating electrode (47), the insulating electrode (47) is connected to a strain gauge (40), the strain gauge (40) can be attached to the sample body (26), and a heating plate (29) is also installed on the inner wall of the soaking tank body (27). The bottom of the soaking tank (27) is fixed with a base, and a metal pad (39) is placed on the base. The sample body (26) is placed on the metal pad (39).

2. The visualized supercritical carbon dioxide immersion in-situ static experimental system according to claim 1, characterized in that, The heating plate (29) circuit is connected to the insulating electrode (47), which can be connected to an external power source.

3. The in-situ static experimental system for visual supercritical carbon dioxide immersion according to claim 1, characterized in that, The top cover (33) is coaxially provided with a boss on the upper side. The boss has a round hole for passing through the pressure head (38). A flange (36) is detachably fixed on the top of the boss. A first sealing gasket (37) is provided between the flange (36) and the boss. Both the flange (36) and the first sealing gasket (37) are coaxially sleeved on the pressure head (38).

4. The in-situ static experimental system for visualizing supercritical carbon dioxide immersion according to claim 1, characterized in that, The transparent glass (43) is detachably mounted on the visualization window through a glass cover (44), and a second sealing gasket (42) is provided coaxially between the transparent glass (43) and the visualization window.

5. The in-situ static experimental system for visual supercritical carbon dioxide immersion according to claim 1, characterized in that, The soaking tank body (27) has a through hole on its side, and an electrode sleeve (31) is threadedly connected to the through hole. A round washer (32) is coaxially provided between the electrode sleeve (31) and the through hole. The electrode sleeve (31) is filled with insulating sealant (48), and the insulating electrode (47) is placed inside the insulating sealant (48).

6. The visualized supercritical carbon dioxide immersion in-situ static experimental system according to claim 1, characterized in that, The frame-type pressure testing machine (11) is also equipped with a gas supply system on its side. The gas supply system includes a carbon dioxide cylinder (1). The carbon dioxide cylinder (1) is connected to the air inlet (28) through a first pipe. The carbon dioxide cylinder (1) can deliver carbon dioxide into the soaking tank (27). The first pipe is sequentially equipped with a first gas valve (2), a first pressure gauge (3), a first pressure reducing valve (4), a heater (5), a first gas flow meter (6), a carbon dioxide booster pump (7), a second gas valve (8), and a second pressure gauge (9).

7. The visualized supercritical carbon dioxide immersion in-situ static experimental system according to claim 1, characterized in that, The frame-type pressure testing machine (11) is also equipped with a strain measurement system on its side, which includes a strain gauge (24) that is electrically connected to the strain gauge (40).

8. The in-situ static experimental system for visualizing supercritical carbon dioxide immersion according to claim 7, characterized in that, The frame-type pressure testing machine (11) is also equipped with a degassing system on the side. The degassing system includes a gas collecting bottle (22). The gas collecting bottle (22) is connected to the gas outlet (41) through a second pipe. Carbon dioxide inside the soaking tank (27) can be transported to the gas collecting bottle (22) through the second pipe. A pressure vacuum gauge (16), an electric valve (17), a second pressure reducing valve (18), a second gas flow meter (19), a vacuum pump (20), and a third gas valve (21) are installed on the second pipe in sequence.

9. The in-situ static experimental system for visualizing supercritical carbon dioxide immersion according to claim 8, characterized in that, The frame-type pressure testing machine (11) is also equipped with a digital speckle measurement system on its side. The digital speckle measurement system includes a high-speed camera (25) and a computer (23). The high-speed camera (25) is used to photograph the inside of the soaking tank (27) through the transparent glass (43). The computer (23) is electrically connected to the high-speed camera (25), the frame-type pressure testing machine (11), the strain gauge (24), and the electric valve (17).

Images