Porous medium diffusion coefficient measuring device under gas-liquid bidirectional convection condition

Abstract

The invention discloses a porous medium diffusion coefficient measuring device under a gas-liquid bidirectional convection condition, and belongs to the technical field of measurement. The device comprises a porous medium test sample, a sealing frame, an upper pressing plate, a lower pressing plate, a sealing ring, a gas source, a gas treatment device, a liquid storage cavity, a liquid pumping device, a gas flow control meter, a gas pressure sensor, a gas concentration sensor, a liquid pressure sensor, a liquid phase proportion measuring device and the like. According to the device, through controllable gas phase and liquid phase relative flow, gas phase collection and measurement are realized by utilizing gas dissolution, so that the diffusivity of the porous medium to gas-liquid two-phase substances is quantitatively evaluated.

Description

Technical Field

[0001] The invention relates to the field of measurement technology, and in particular to a porous medium diffusion coefficient measuring device under gas-liquid bidirectional convection conditions. Background Art

[0002] Porous media are widely used in the chemical industry in various catalytic systems and separation systems. The diffusion properties of the pores inside porous media play an important role in regulating the apparent chemical reaction rate and improving the transport capacity of reactants and products. In most chemical reaction regulation, the mass transfer process in porous media faces the problem of simultaneous transmission of gas and liquid phases, and the diffusion coefficient when gas and liquid undergo bidirectional convection is difficult to measure accurately. Therefore, it is of great significance and application value to develop a device for measuring the diffusion coefficient of porous media under the condition of simultaneous gas-liquid bidirectional convection.

[0003] After comparing with the prior art, it is found that the existing measuring devices for the diffusion coefficient of porous media only test the mass transfer process under the conditions of single substance and unidirectional transmission, and there are few measuring devices that can simultaneously measure the diffusion coefficient under the conditions of gas-liquid convection. CN 114486635A discloses a method and system for measuring the diffusion coefficient of molecules in porous materials, but the device can only measure the diffusion coefficient of liquid phase probe molecules in porous materials. CN 107314950A discloses a method for determining the diffusion coefficient of carbon dioxide in porous media, but the method mainly detects the change of carbon dioxide concentration by nuclear magnetic resonance method and cannot be applied to other media. CN 113984587A discloses a method for in-situ measurement of CO2-water diffusion coefficient in porous media, but the main test condition of this method is the diffusion process of CO2 in water under the condition that the porous medium is filled with water, and there is no two-way convection of gas and liquid. Summary of the invention

[0004] In order to make up for the deficiencies and gaps in the prior art in the above-mentioned problems, the present invention proposes a porous medium diffusion coefficient measuring device under gas-liquid bidirectional convection conditions, which realizes gas phase collection and measurement by controllable gas-liquid convection and utilizes gas dissolution to quantitatively evaluate the diffusion capacity of the porous medium for gas-liquid two-phase substances.

[0005] The specific technical scheme of the present invention is:

[0006] A device for measuring the diffusion coefficient of a porous medium under gas-liquid bidirectional convection conditions, specifically comprising a porous medium test sample, a sealing frame, an upper pressure plate, a lower pressure plate, a sealing ring, a gas source, a gas processing device, a liquid storage chamber, a liquid pumping device, a gas flow controller, a gas pressure sensor, a gas concentration sensor, a liquid pressure sensor and a liquid phase ratio measuring device, etc.

[0007] The porous medium test sample is connected with a sealing frame to prevent leakage on all sides. The porous medium test sample and the sealing frame are located between the upper pressing plate and the lower pressing plate as a whole. The upper pressing plate and the lower pressing plate are fastened and connected with each other with an adjustable distance. At the same time, the corresponding positions of the sealing frames on the upper pressing plate and the lower pressing plate are provided with sealing ring grooves, and a sealing ring to prevent leakage is installed inside the groove. The upper pressing plate is provided with an air inlet and an air outlet, the air inlet is connected to the air source, and the air outlet is connected to the gas processing device. A liquid storage chamber is installed below the lower pressing plate, and the liquid storage chamber is connected to the liquid pumping device. The gas source provides soluble gas with a certain pressure, and a gas flow controller and a gas pressure sensor are arranged in sequence between the gas source and the air inlet of the upper pressure plate. The gas processing device includes a liquid drying and collecting device and a gas harmless processing device connected in sequence; a gas concentration sensor for measuring the gas content diffused from the porous medium to the liquid in the cavity and a liquid pressure sensor for measuring liquid pressure fluctuations are arranged in the liquid storage cavity; a liquid phase proportion measuring device is arranged on the side of the porous medium test sample, which can measure the proportion of liquid content inside the porous medium in real time.

[0008] Furthermore, the liquid phase proportion measuring device can emit X-rays and collect the attenuated X-rays that penetrate the porous medium test sample on the opposite side. The liquid phase volume and proportion inside the porous medium test sample can be calculated and reconstructed based on the ray attenuation.

[0009] Furthermore, a gas indicator for tracing is added to the sealing frame to detect whether leakage occurs at the frame.

[0010] Furthermore, the soluble gas provided by the gas source has a suitable solubility with the liquid inside the liquid storage chamber, and the solubility range of the gas in the liquid is 1-50.

[0011] Furthermore, a flow channel for gas diversion and droplet purging is provided within the contact area between the upper pressure plate and the porous medium test sample, and appropriate gas distribution is achieved through the diversion area to ensure uniform distribution of gas pressure and flow rate inside the flow channel.

[0012] Furthermore, the upper pressing plate is made of a transparent material, and the surface of the material is coated with a super-hydrophobic coating for enhancing the ability of the gas to sweep the droplets.

[0013] Furthermore, a porous support layer for filtering and supporting is provided in the lower pressing plate. The porous support layer has a large rigidity and a suitable pore size range, an elastic modulus of not less than 200 MPa, and a pore size range of 10 μm to 500 μm.

[0014] Furthermore, the liquid pumping device can provide stable micro-flow control and output, and the flow control range is 10 μL / min to 20 mL / min.

[0015] Furthermore, a liquid pressure buffer is connected to the side of the liquid storage cavity. When the instrument is working, a certain volume of insoluble gas is stored in the pressure buffer to mitigate drastic changes in liquid pressure and facilitate liquid pressure control. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the overall appearance and connection relationship of the porous medium diffusion coefficient measurement device under gas-liquid bidirectional convection conditions.

[0017] In the figure, 6 is a gas source, 7 is a gas processing device, 9 is a liquid pumping device, 10 is a gas flow controller, 11 is a gas pressure sensor, and 14 is a liquid phase ratio measuring device.

[0018] Figure 2 It is a cross-sectional view of the internal structure of the device.

[0019] In the figure, 1-porous medium test sample, 2-sealing frame, 3-upper pressure plate, 4-lower pressure plate, 5-sealing ring, 8-liquid storage chamber, 12-gas concentration sensor, 13-liquid pressure sensor, 301-flow channel, 302-guiding area, 401-porous support layer, 801-pressure buffer zone, 802-insoluble gas.

[0020] Figure 3 Schematic diagram of the gas processing device.

[0021] In the figure, 701-liquid drying and collecting device, 702-gas harmless treatment device. DETAILED DESCRIPTION

[0022] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

[0023] Example

[0024] A device for measuring the diffusion coefficient of a porous medium under gas-liquid bidirectional convection conditions, specifically comprising a porous medium test sample, a sealing frame, an upper pressure plate, a lower pressure plate, a sealing ring, a gas source, a gas processing device, a liquid storage chamber, a liquid pumping device, a gas flow controller, a gas pressure sensor, a gas concentration sensor, a liquid pressure sensor and a liquid phase ratio measuring device, etc.

[0025] The porous medium test sample (1) is connected to the surrounding sealing frames (2) by means of adhesives or the like to prevent leakage of gaseous or liquid phase substances through the frames. The porous medium test sample and the sealing frame are clamped between the upper pressing plate (3) and the lower pressing plate (4) as a whole by means of bolts or the like, and the distance between the upper and lower pressing plates can be adjusted by means of gasket thickness or springs or the like. O-ring grooves are provided at the corresponding positions of the edge positions of the sealing frames on the upper and lower pressing plates, respectively, for placing O-rings (5) to prevent leakage of gaseous and liquid phase substances to the outside.

[0026] The upper pressure plate is provided with an air inlet and an air outlet, the air inlet is connected to the air source (6), and the air outlet is connected to the gas processing device (7). At the same time, the air inlet and the air outlet are connected to a gas flow controller (10) and a gas pressure sensor (11) for adjusting the gas flow and measuring the gas pressure in real time.

[0027] The gas provided by the gas source needs to have a suitable solubility with the liquid used, so as to solve the problem of difficulty in collecting and measuring after traditional two-way convection of gas through the dissolution process of gas in liquid, and it is also conducive to better simulation of the actual working conditions in chemical reactions. The solubility of gas in liquid should be in the range of 1-50. Too small solubility will make it difficult for the gas to be completely absorbed by the liquid, so that gas cavities will appear in the liquid storage cavity, affecting the liquid transmission process and the test of gas transmission volume; while too large solubility will cause the gas to dissolve quickly and completely in a short time, so that negative pressure will appear instantly in the gas cavity at the upper pressure plate, resulting in a "fountain" effect, affecting the normal transmission process of the liquid.

[0028] The gas processing device (7) comprises a liquid drying and collecting device (701) and a gas harmless treatment device (702) connected in sequence. The main purpose of drying and collecting is to obtain the real-time transmission amount of liquid through the porous medium through real-time quality detection, and gas drying is also conducive to further processing of the gas. Since most soluble gases are often toxic and dangerous, the gas cannot be discharged directly into the air, but needs to pass through the harmless treatment device. The main treatment method is to completely absorb it through chemical reagent reaction, or to convert it into harmless gas before discharge.

[0029] A liquid storage chamber (8) is installed below the lower pressure plate. The liquid storage chamber is connected to a liquid pumping device (9). The flow control range of the pump should meet the use requirements and be as accurate as possible. The recommended adjustment range is 10μL / min to 20mL / min. A gas concentration sensor (12) for measuring the gas content diffused from the porous medium to the liquid in the chamber and a liquid pressure sensor (13) for measuring the liquid pressure fluctuation are arranged in the liquid storage chamber. The gas concentration sensor needs to be selected according to the type of gas used. Most gases will be ionized after being dissolved in liquid, so the gas concentration can be measured by conductivity measurement or pH value measurement.

[0030] In order to detect the proportion of gas-liquid two-phase in the pores inside the porous medium, a liquid phase proportion measuring device (14) is provided on the side of the test sample, which can measure the proportion of liquid content inside the porous medium in real time. Preferably, the measurement can be performed by X-ray transmission. Since the attenuation rate of X-rays is different after penetrating different substances, the distribution and proportion of gas-liquid two-phase in the porous medium can be reconstructed by calculating and analyzing the X-ray intensity after penetrating the sample.

[0031] At the same time, the liquid storage chamber is connected to a liquid pressure buffer zone (801). In addition to the liquid portion, there is also a portion of the buffer zone filled with insoluble gas (802). The main purpose of leaving this portion of liquid is to buffer the liquid pressure fluctuation when the liquid is pumped into the liquid storage chamber through the volume compression of the gas, thereby avoiding a sharp pressure rise in a short period of time, which is conducive to the precise control of the liquid pressure.

[0032] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A device for measuring diffusion coefficient of porous media under gas-liquid bidirectional convection conditions, characterized in that: It comprises a porous medium test sample (1), a sealing frame (2), an upper pressing plate (3), a lower pressing plate (4), a sealing ring (5), a gas source (6), a gas processing device (7), a liquid storage chamber (8), a liquid pumping device (9), a gas flow controller (10), a gas pressure sensor (11), a gas concentration sensor (12), and a liquid pressure sensor (13); The porous medium test sample (1) is connected with a sealing frame (2) to prevent leakage on all sides. The porous medium test sample (1) and the sealing frame (2) are located between the upper pressing plate (3) and the lower pressing plate (4) as a whole. The upper pressing plate (3) and the lower pressing plate (4) are fastened and connected with each other with adjustable distance. Sealing ring grooves are provided at corresponding positions of the sealing frames on the upper pressing plate (3) and the lower pressing plate (4). A sealing ring (5) to prevent leakage is installed inside the groove. The upper pressing plate (3) is provided with an air inlet and an air outlet. The air inlet is connected to an air source (6), and the air outlet is connected to a gas processing device (7). A liquid storage chamber (8) is installed below the lower pressing plate (4) and the porous medium test sample (1). The liquid storage chamber stores a liquid to be tested, and the liquid storage chamber (8) is connected to a liquid pumping device (9). The gas source (6) provides soluble gas at a certain pressure, a gas flow controller (10) and a gas pressure sensor (11) are arranged in sequence between the gas source (6) and the gas inlet of the upper pressure plate (3), and the gas processing device (7) comprises a liquid drying and collecting device (701) and a gas harmless processing device (702) connected in sequence; The liquid storage cavity (8) is provided with a gas concentration sensor (12) for measuring the gas content diffused from the porous medium into the liquid in the cavity and a liquid pressure sensor (13) for measuring the liquid pressure fluctuation.

2. The porous medium diffusion coefficient measuring device according to claim 1, characterized in that: The invention also comprises a liquid phase proportion measuring device (14), wherein the liquid phase proportion measuring device (14) is arranged on the side of the porous medium test sample (1), and the liquid phase proportion measuring device (14) can realize CT imaging, by emitting X-rays and collecting the attenuated X-rays that penetrate the porous medium test sample (1) on the opposite side, and according to the ray attenuation, the liquid phase volume and proportion inside the porous medium test sample (1) can be calculated and reconstructed.

3. The porous medium diffusion coefficient measuring device according to claim 1, characterized in that: A gas indicator for tracing is added to the sealing frame (2) to detect whether leakage occurs at the frame.

4. The porous medium diffusion coefficient measuring device according to claim 1, characterized in that: The soluble gas provided by the gas source (6) has a suitable solubility with the liquid inside the liquid storage chamber (8), and the solubility range of the gas in the liquid is 1 to 50.

5. The porous medium diffusion coefficient measuring device according to claim 1, characterized in that: A flow channel (301) for gas diversion and droplet purging is provided within the contact area between the upper pressure plate (3) and the porous medium test sample (1), and appropriate gas distribution is achieved through the diversion area (302) to ensure uniform distribution of gas pressure and flow rate inside the flow channel.

6. The porous medium diffusion coefficient measuring device according to claim 1 and claim 5, characterized in that: The upper pressing plate (3) is made of a transparent material, and the surface of the material is coated with a super-hydrophobic coating for enhancing the ability of the gas to sweep the liquid droplets.

7. The porous medium diffusion coefficient measuring device according to claim 1, characterized in that: It also includes a porous support layer (401) for filtering and supporting, wherein the porous support layer is located between the upper pressing plate (3) and the lower pressing plate (4), and the porous support layer has a large rigidity and a suitable pore size range, an elastic modulus of not less than 200 MPa, and a pore size range of 10 μm to 500 μm.

8. The porous medium diffusion coefficient measuring device according to claim 1, characterized in that: The liquid pumping device (9) can provide stable micro-flow control and output, and the flow control range is 10 μL / min to 20 mL / min.

9. The porous medium diffusion coefficient measuring device according to claim 1, characterized in that: The side of the liquid storage chamber (8) is connected to a liquid pressure buffer zone (801). When the instrument is working, a certain volume of insoluble gas (802) is stored in the pressure buffer zone (801) to mitigate the drastic change of liquid pressure and facilitate liquid pressure control.

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