Liquid carrying structure, gas-liquid contact method and application, and cooling apparatus for production wellhead in underground coal gasification

Abstract

A liquid carrying structure, a gas-liquid contact method and application, and a cooling apparatus for a production wellhead in underground coal gasification. The liquid carrying structure comprises an annular cylinder body (11), a screen (12) being sealingly connected to an inner circumferential wall of the annular cylinder body, the screen being used for supporting liquid, and capillary pressure Pc at a distal end of the screen being greater than or equal to the gravity ρgH of the carried liquid, where Pc = 2σcosθ / R, σ is surface tension and is expressed in the unit of mN / m, θ is a pinning angle and is expressed in the unit of rad, R is the radius of a screen mesh and is expressed in the unit of m, ρ is the density of the liquid and is expressed in the unit of Kg / m3, g is gravitational acceleration and is expressed in the unit of N / Kg, and H is the depth of the liquid and is expressed in the unit of m. The gas-liquid contact method has the advantage of intensifying gas-liquid contact.

Description

Liquid-bearing structures, gas-liquid contact methods and applications, and wellhead cooling devices for underground coal gasification production.

[0001] Cross-references to related applications

[0002] This application claims the benefit of Chinese patent application 202510077539.5, filed on January 17, 2025, the contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to the field of high-temperature gas processing, specifically to a liquid-bearing structure, a gas-liquid contact method and application, and a wellhead cooling device for underground coal gasification production. Background Technology

[0004] During the heating process of underground coal gasification, the coal seam undergoes chemical reactions at high temperatures, producing a large amount of combustible gas, primarily composed of hydrogen (H2), carbon monoxide (CO), and methane (CH4). These gases react violently with injected oxygen, air, and supercritical water, generating gases at extremely high temperatures, typically above 1000°C. While some heat is lost during the transport of these high-temperature gases to the wellhead, the gas temperature still remains above 300°C. Directly discharging or transporting such high-temperature gases from the production wellhead to the surface treatment system poses serious safety hazards, such as an increased risk of explosion. Furthermore, it easily causes severe thermal damage and damp-heat corrosion to surface equipment and pipelines, significantly shortening equipment lifespan and increasing maintenance costs.

[0005] Traditional cooling technologies, such as casing annulus cooling and wellhead spray systems, can partially cool high-temperature gases, but they suffer from low cooling efficiency and high economic costs, failing to meet the urgent need for a high-efficiency and stable cooling system at the production wellhead during the continuous heating process of underground coal gasification. Therefore, a more efficient wellhead cooling system is needed to cool the high-temperature gases at the production wellhead. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of low gas-liquid heat transfer efficiency in the existing technology, which leads to low cooling efficiency and high economic cost of high-temperature gas. It provides a liquid-bearing structure, gas-liquid contact method and application, and a coal underground gasification wellhead cooling device, which has the advantage of enhanced gas-liquid contact.

[0007] To achieve the above objectives, a first aspect of the present invention provides a liquid-bearing structure, comprising an annular cylinder, wherein a screen is sealed to the inner peripheral wall of the annular cylinder, the screen being used to support the liquid, and the screen being configured to have a capillary tube at its end. c Greater than or equal to the weight of the liquid it carries, ρgH, where P c= 2σcosθ / R, where σ is the surface tension (mN / m), θ is the pinning angle (rad), R is the sieve aperture radius (m), and ρ is the liquid density (kg / m³). 3 g is the acceleration due to gravity, in N / kg; H is the depth of the liquid, in meters.

[0008] In the embodiments of this application, the screen is configured with a terminal capillary pressure P c It is greater than the weight ρgH of the liquid it carries.

[0009] A second aspect of the present invention provides a gas-liquid contact method employing the liquid-carrying structure of the present invention, the method comprising passing gas from bottom to top through a sieve.

[0010] In the embodiments of this application, the gas pressure P gas Satisfy P gas >(ρgH+2σcosθ' / R')=2ρgH, where θ' is the contact angle in rad and R' is the bubble radius in m.

[0011] A third aspect of the present invention provides the application of the liquid-bearing structure or the gas-liquid contact method of the present invention in the field of high-temperature gas processing.

[0012] The fourth aspect of the present invention provides a coal underground gasification production wellhead cooling device, which includes a packer on which the liquid-bearing structure of the present invention is installed.

[0013] In the embodiments of this application, the top end of the central tube of the packer is connected to the liquid-bearing structure via a coupling.

[0014] In the embodiments of this application, the outer wall of the annular cylinder of the liquid-bearing structure is set as a cone shape with a larger upper part and a smaller lower part, and the inner wall of the coupling is provided with a cone-shaped mounting position that is adapted to the annular cylinder.

[0015] In the embodiments of this application, a sealing element is fitted on the outer wall surface of the annular cylinder above the coupling.

[0016] In the embodiments of this application, the seal is made of a heat-resistant material that absorbs water and expands.

[0017] In the embodiments of this application, the outer wall surface of the annular cylinder above the coupling is configured as an axially extending wave-shaped structure, wherein a sealing element is sleeved in the trough of the wave-shaped structure.

[0018] In the embodiments of this application, a sealing element is fitted onto the central tube of the packer.

[0019] In the embodiments of this application, the heat-resistant and water-absorbing swelling material is selected from at least one of graphene, hydrogenated nitrile rubber, and fluororubber.

[0020] Through the above technical solution, the liquid-bearing structure of the present invention utilizes the "pinning effect" to stably carry the liquid, allowing the gas to pass through the screen from bottom to top. This disperses the gas into bubbles, increases the contact area between the gas and the liquid, and enhances the gas-liquid contact efficiency. Furthermore, when applied to the field of high-temperature gas processing, it can improve the heat exchange efficiency between high-temperature gas and low-temperature coolant, and further provide technical support for the continuous development of deep underground coal gasification. Attached Figure Description

[0021] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0022] Figure 1 is a schematic diagram of a coal underground gasification wellhead cooling device according to one embodiment of the present invention.

[0023] Figure 2 is an enlarged view of the circled area in Figure 1;

[0024] Figure 3 is an enlarged view of the area within the box in Figure 1;

[0025] Figure 4 is a schematic diagram of the operation of a liquid-bearing structure at the wellhead of an underground coal gasification production well.

[0026] Figure 5 is a flowchart of the process of lowering the liquid-bearing structure 1.

[0027] Explanation of reference numerals in the attached drawings: 1-Liquid-bearing structure; 2-Packard; 3-Coupling; 4-Seal; 5-Cap; 6-Cylinder I; 7-Slip piston; 8-Spring steel plate; 9-Slip; 10-Conical cap; 11-Annular cylinder; 12-Screw; 111-Piston; 112-Cylinder II; 13-Anti-reverse ring; 14-Anti-reverse seat; 21-Central tube; 15-Intermediate spacer ring; 16-Snap ring; 17-Limiting ring; 18-O-ring; 19-Slip screw; 20-Shear screw. Detailed Implementation

[0028] The specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this application.

[0029] To improve gas-liquid contact efficiency, this invention discloses a liquid-bearing structure. This liquid-bearing structure 1 includes an annular cylinder 11, with a screen 12 sealed to the inner circumferential wall of the annular cylinder 11. The screen 12 supports the liquid, and the capillary tube at the end of the screen 12 presses against the liquid. c The force ρgH is greater than or equal to the weight of the liquid it carries, so that the screen can hold water, where P c= 2σcosθ / R; σ is surface tension, unit: mN / m; θ is pinning angle, unit: rad; R is sieve aperture radius, unit: m; ρ is liquid density, unit: kg / m³ 3 g is the acceleration due to gravity, in N / kg; H is the depth of the liquid, in meters.

[0030] It should be noted that the screen in this invention is not limited to a mesh structure formed by interlaced filaments. It can also be a thickened mesh structure, as shown in Figure 2, where multiple through-holes are uniformly formed on a substrate to create the screen. These through-holes act as sieves (pores) for the flow of material. In the complex interface between liquid and solid, especially at the edges of the tiny pores in the screen, the wetting behavior of the liquid exhibits unique physical phenomena. When the liquid approaches the tip of the screen or the edge of the pore, its wetting angle changes significantly. This is due to the combined effect of the surface microstructure of the screen material and the physical properties of the liquid. This change in wetting angle causes a change in the interface morphology at the pores, which generates a counterforce, laying the foundation for the capillary pressure supporting the coolant.

[0031] Capillary pressure is the pressure difference generated by a liquid in tiny pores due to surface tension, and it is the core of a sieve's ability to hold water. The pinning effect at the ends of the sieve openings—the phenomenon where the liquid is "pinned" at the edges of the micropores—can further enhance the effect of capillary pressure. This effect effectively prevents the liquid from descending under the influence of gravity in the direction of the sieve, allowing the liquid to form a stable layer above the sieve. This upward support ensures the stability of the liquid.

[0032] To achieve stable support of the liquid above the screen, the inventors discovered that the screen's structural design must be carefully optimized. The size and number of small holes at the end of the screen tube are key design elements. By reducing the hole size, the surface tension's binding effect on the coolant can be increased, thereby increasing capillary pressure. Simultaneously, a reasonable distribution of the number of small holes can disperse the gas into as many bubbles as possible, increasing the gas-liquid contact area. For example, when the liquid-bearing structure of this invention is used to cool high-temperature gas, the high-temperature gas passes through the screen from bottom to top into the coolant, causing the gas to change from a continuous phase to a dispersed phase, increasing the heat exchange area between the high-temperature gas and the low-temperature coolant. A reasonable distribution of the number of small holes ensures that the coolant is heated throughout the entire screen, preventing bubbles from slipping through the coolant. Compared to existing cooling methods, this optimized screen structure design not only improves cooling efficiency but also reduces the resistance of gas breaking through the liquid surface.

[0033] It is understandable that, in order to stably support the liquid above the screen, the capillary pressure P at the end of the screen 12 is preferably provided. cThe force is greater than the weight ρgH of the liquid it supports. By analyzing this formula and its conditions, a scientific basis can be provided for the design of the screen, ensuring stable support of the liquid on the screen and the formation of a continuous phase fluid.

[0034] In summary, the liquid-supporting structure of this invention enables water-filled screens at the wellhead of underground coal gasification production. By precisely controlling the size and number of small holes, and utilizing the pinning effect at the ends of the screen holes and the capillary pressure principle, stable support of the coolant above the screen and the formation of a continuous phase fluid can be achieved. This method not only improves cooling efficiency and reduces gas breakthrough resistance, but also enhances the safety and reliability of the production wellhead.

[0035] Based on the foregoing disclosure, the present invention discloses a gas-liquid contact method, which employs the liquid-bearing structure 1 of the present invention and includes passing gas from bottom to top through a screen 12.

[0036] This invention uses the application of the aforementioned gas-liquid contact method in underground coal gasification technology as an example to illustrate the advantages of the invention, but the invention is not limited thereto. Referring to the background art, a key challenge in underground coal gasification technology is how to handle the high-temperature gases generated during the gasification process. These gases, with temperatures generally exceeding 300°C, will rapidly cause thermal corrosion and damp heat damage when directly exposed to wellhead equipment, seriously threatening the safety and service life of the wellhead equipment, and thus hindering the continuous and efficient development of underground coal gasification. Therefore, developing an efficient high-temperature gas cooling method is particularly important.

[0037] The inventors discovered that the liquid-bearing structure 1 of this invention can fill the wellhead screen with water to form a coolant layer, and utilize the pinning effect to ensure that the coolant stably covers the screen in the form of a continuous phase fluid. This design not only effectively isolates the high-temperature gas from direct contact with the wellhead equipment, but also provides a foundation for the subsequent cooling process through a physical barrier.

[0038] The screen design of the liquid-bearing structure 1 of the present invention allows high-temperature gas to pass through, while a stable liquid surface is formed at the tip of the screen holes due to the surface tension between the gas and liquid. This structure greatly enhances the support of the coolant on the screen and ensures the stability of the coolant. When high-temperature gas passes through the screen, it must first pass through this layer of coolant and undergo a cooling process before it can continue to float.

[0039] As the underground coal gasifier continues to heat the coal, combustible gases are constantly released from the deep coal. These gases react with the gases injected into the production well, forming a mixed gas that migrates to the bottom of the well. During this process, the pressure at the bottom of the well gradually increases, and the gas temperature also rises, resulting in a significant increase in the gas's internal energy, which propels the gas towards the wellhead.

[0040] When the high-temperature gas reaches the screen, it faces two possibilities for entering the coolant and rising to the wellhead. The first is dissolution breakthrough: based on Henry's Law, the solubility of high-temperature gas in low-temperature coolant increases significantly, so some gas will enter the coolant as dissolved gas and rise with the coolant flow. The second is pressure breakthrough: as the gas pressure at the bottom of the well increases, when it reaches a level sufficient to overcome the surface tension of the liquid, the gas will break through the gas-liquid interface in the form of bubbles and enter the coolant.

[0041] For high-temperature gases to achieve a pressure breakthrough, certain conditions must be met, namely, the gas pressure P. gas Satisfy P gas >(ρgH+2σcosθ' / R')=2ρgH, where θ' is the contact angle and R' is the bubble radius. Due to the continuous underground coal gasification, a stable gas source is guaranteed, ensuring that the gas pressure in the production well continuously increases, enabling it to overcome surface tension and smoothly enter the coolant.

[0042] Once inside the coolant, the high-temperature gas rises to the wellhead as bubbles due to surface tension. During this ascent, efficient heat exchange occurs between the bubbles and the coolant, causing the gas temperature to gradually decrease. In this process, the continuous high-temperature gas transforms into dispersed bubbles, significantly increasing the gas-liquid contact area and thus improving heat exchange efficiency, ensuring that the gas reaches a safe temperature range upon reaching the wellhead.

[0043] The gas-liquid contact method of this invention is used for the dispersion and cooling of high-temperature gases. By combining the screen structure of this invention with the coolant, effective cooling and protection of the high-temperature gases generated during underground coal gasification are achieved. This method not only solves the problem of damage to wellhead equipment caused by high-temperature gases, but also promotes the continuous and efficient development of underground coal gasification by improving heat exchange efficiency.

[0044] This invention discloses the application of the liquid-bearing structure or the gas-liquid contact method of this invention in the field of high-temperature gas treatment, preferably in the protection of wellhead equipment for underground coal gasification production. The liquid-bearing structure of this invention can disperse high-temperature gas into bubbles for cooling, increase the heat exchange area of ​​the gas, and improve the heat exchange efficiency between high-temperature gas and low-temperature coolant, so as to realize the protection of wellhead equipment for underground coal gasification production and provide technical support for the continuous development of deep underground coal gasification.

[0045] It should be noted that the high-temperature gas cooling control method controls the heat transfer process. Its basic principle is Fourier's law (expressed in this context as Q = hAΔT), which reveals the direct relationship between heat flux Q and heat transfer coefficient h, heat transfer area A, and temperature difference ΔT. Given a fixed heat transfer medium and conditions (i.e., h and ΔT remain constant), increasing the heat transfer area A is key to improving heat transfer efficiency and achieving rapid heat transfer. Based on this theory, this invention innovatively designs a sieve structure composed of densely packed small holes, capable of transforming continuous high-temperature gas into dispersed bubble phases for gas-liquid heat exchange.

[0046] Furthermore, by controlling the height of the coolant, the time required for bubbles to rise in the coolant can be controlled, thereby adjusting the heat exchange time between the bubbles and the coolant. Studies have shown that a 1μm diameter screen can hold up to 20m of coolant, a depth far exceeding the actual liquid volume required for cooling high-temperature gases. The liquid-bearing structure of this invention can meet the heat exchange requirements of high-temperature gases at the wellhead.

[0047] To further achieve precise control over the cooling effect of high-temperature gas at the wellhead of underground coal gasification production, the cooling requirements of high-temperature gas under different operating conditions can be flexibly addressed by adjusting the size and number of screen holes and the coolant level, ensuring that the equipment at the production wellhead is always in a safe and stable operating state. This highly controllable cooling control scheme not only improves the safety and reliability of underground coal gasification operations but also provides a strong guarantee for the continuous and stable operation of the gasifier.

[0048] This invention proposes to achieve efficient cooling through convective heat exchange between high-temperature gas and coolant. Utilizing the significantly increased gas-liquid heat exchange area and optimized heat conversion efficiency of the aforementioned liquid-supporting structure 1, this invention solves the problem of high-temperature gas at the wellhead in existing technologies. To install the liquid-supporting structure 1 of this invention at the wellhead of underground coal gasification production, this invention discloses a cooling device for the wellhead of underground coal gasification production. The underground coal gasification production well can be a U-shaped well structure as shown in Figure 4. The depth structure of the "U"-shaped well meets the injection requirements of underground coal gasification. The wellhead cooling device is installed at the production end of the production well. During well completion, a steel pipe is lowered at the connection between the injection well and the production well to support the well wall and ensure unobstructed gasification channels in the horizontal section of the injection well. The wellhead cooling device includes a packer 2, on which the liquid-supporting structure 1 of this invention is installed. The liquid-supporting structure 1 is connected to a gas pipe and a water injection pipe. The water injection pipe can be connected to the surface gas tree water pipe to achieve cooling water connection. The gas pipe is a crude coal gas production pipe from which the cooled crude coal gas is produced.

[0049] The coal underground gasification production wellhead cooling device of the present invention can achieve efficient cooling of high-temperature gas at the production wellhead, ensuring the long-term stable operation of the production wellhead equipment.

[0050] The packer in the prior art can be used in this invention. The process of lowering the liquid-bearing structure 1 is shown in Figure 5. First, a "U-shaped well" is constructed and an ignition combustion device is lowered into the injection well. The hydraulic packer 2 shown in Figure 3 is placed in the designed position through the existing tubing, tubing, or other lowering devices. Hydraulic pressure is applied from the tubing or tubing. The hydraulic pressure can be applied by inserting a soluble sphere, which can be made of aluminum-magnesium alloy. Alternatively, hydraulic pressure can be applied directly into the hydraulic cylinder through the tubing. The liquid enters the working chamber of the packer 2 hydraulic cylinder, pushing the slip piston downward, cutting the shear screw, pushing the spring steel plate to move, and opening the slip to achieve anchoring. While the central tube moves, the anti-reverse seat and the middle spacer ring gradually approach each other, squeezing the graphene sealing assembly to form a ring space. The packer is then set and sealed. Then, the liquid-bearing structure 1 is lowered into the system through the tubing or tubing or other lowering devices.

[0051] There are many ways to connect the packer 2 to the liquid-bearing structure 1 of the present invention. The following is an example, but it does not limit the scope of the present invention. For example, as shown in Figures 1-2, the top end of the central tube 21 of the packer 2 is connected to the liquid-bearing structure 1 through a coupling 3. The outer wall of the annular cylinder 11 of the liquid-bearing structure 1 is set as a cone shape with a larger top and a smaller bottom. Multiple screen tubes are evenly opened on the bottom surface of the cone. The inner wall of the coupling 3 is provided with a cone-shaped mounting position that is larger at the top and smaller at the bottom and adapted to the annular cylinder 11. In this way, the liquid-bearing structure 1 and the coupling 3 can be placed to achieve self-locking. Due to the supporting effect of the packer, the liquid-bearing structure 1, as the core cooling device, can sit on top of the packer without falling off.

[0052] To achieve a seal, a sealing element 4 is fitted on the outer wall surface of the annular cylinder 11 above the coupling 3. The sealing element 4 is made of a heat-resistant material that absorbs water and expands.

[0053] The outer wall surface of the annular cylinder 11 above the coupling 3 is set as an axially extending wave-shaped structure (e.g., a sine wave structure). In the troughs of the wave-shaped structure, a sealing element 4 is fitted in place by anchoring or bonding. It can be understood that the sealing component and the crest are slightly smaller than the inner diameter of the pipe column, so that it can be smoothly lowered. Since the sealing element 4 is made of water-absorbing and expanding material, it can expand to a certain extent after absorbing water, thus achieving a seal. The annular cylinder 11 is filled with coolant, and the bottom screen is densely covered with gaps. Under these gaps, the crude gas can permeate through and achieve sufficient heat exchange with the water, thus achieving the cooling process.

[0054] The range of heat-resistant and water-absorbing materials that can be selected for the sealing element 4 in this invention is very wide. The following is an illustrative example, but it does not limit the scope of the invention. For this invention, the sealing element 4 can be a sealing ring made of at least one of graphene, hydrogenated nitrile rubber or fluororubber.

[0055] The coal underground gasification wellhead cooling device of this invention utilizes a packer to construct a platform for the fixed cooling core device - liquid bearing structure 1, as shown in Figure 3. The main difference between the packer of this invention and existing packers lies in the material of the sealing element between the upper and lower stop seats. Specifically, existing packers are made of nitrile rubber, while the packer 2 of this invention is also fitted with the aforementioned sealing element 4. This sealing element deforms under compression and can withstand high temperatures (for example, graphene sealing rings can withstand temperatures up to 650°C), thus achieving a first-level seal. The annular cylinder 11 is made of metal, with an axially extending wave-shaped structure on the outside, utilizing the metal deformation generated by high temperature to achieve a second-level seal, while ensuring the fixation of the equipment. The water-absorbing and expanding sealing element 4 located at the trough expands due to water vapor, achieving a seal for the residual gas, which is a third-level seal, ensuring that the crude coal gas and the coolant supported by the cooling device achieve sufficient heat exchange and production.

[0056] This coal underground gasification wellhead cooling device, based on the principle of convective heat transfer between high-temperature gas and coolant, successfully achieves a highly efficient reduction in the temperature of the gas at the wellhead. Its significant invention benefits are reflected in the following aspects:

[0057] (1) Liquid-bearing structure 1: The core of this invention lies in the liquid-bearing structure 1, which utilizes the "pinning effect" to stably suspend the coolant in the production well, effectively preventing coolant loss and allowing high-temperature gas to smoothly penetrate the screen and move upward. This design not only simplifies the system structure but also improves the overall operational stability and reliability.

[0058] (2) High-efficiency cooling mechanism: By designing a cooling method for the coolant at the bottom of the production wellhead, this invention ensures that the high-temperature gas must pass through the coolant layer in the form of bubbles. This design not only prolongs the contact time between the gas and the coolant, but also greatly promotes the transfer and conversion of heat, thereby achieving rapid and efficient cooling of the high-temperature gas.

[0059] (3) Significantly increased heat exchange area: The high-temperature gas passes through the coolant in the form of dispersed phase bubbles. Compared with traditional shell-and-tube cooling or spray cooling methods, this method significantly increases the heat exchange area between the gas and the coolant. Each bubble becomes a medium for heat transfer, making the heat exchange process more thorough and efficient, thereby achieving a significant reduction in the temperature of the high-temperature gas.

[0060] (4) The coal underground gasification wellhead cooling device integrates components such as a liquid-bearing structure 1, a sealing element 4, and a packer 2. The packer, after precise deployment, can be hydraulically driven and anchored, and forms a high-temperature resistant sealing barrier using a sealing element 4 made of materials such as graphene. Furthermore, the core cooling device—the liquid-bearing structure 1—is installed with a wave-shaped structure extending axially from its outer wall, combined with the expansion seal of the sealing element 4, constructing a multi-layered sealing system to ensure stability and sealing. The crude coal gas rises from the central pipe of the packer, penetrates the screen, and undergoes sufficient heat exchange with the cooling water, significantly reducing the wellhead temperature. Simultaneously, the configuration of the gas and water pipe systems enables the supply of cooling water and the smooth discharge of crude coal gas, forming a closed-loop cooling process.

[0061] Compared to traditional cooling methods such as casing annulus cooling and wellhead spraying, this invention not only represents a technological innovation but also demonstrates significant advantages in practical applications. Its high efficiency, stability, and reliability make this technical solution a promising candidate for widespread application in high-temperature gas processing fields such as underground coal gasification and petrochemicals.

[0062] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various specific technical features in any suitable manner. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. However, these simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A liquid-bearing structure, characterized in that, The liquid-bearing structure (1) includes an annular cylinder (11), the inner circumferential wall of which is sealed with a screen (12), the screen (12) being used to support the liquid, and the screen (12) being configured with a capillary pressure at the end. c Greater than or equal to the weight of the liquid it carries, ρgH, where P c = 2σcosθ / R, where σ is the surface tension (mN / m), θ is the pinning angle (rad), R is the sieve aperture radius (m), and ρ is the liquid density (kg / m³). 3 g is the acceleration due to gravity, in N / kg; H is the depth of the liquid, in meters.

2. The liquid-bearing structure according to claim 1, characterized in that, The screen (12) is configured with a terminal capillary pressure P c It is greater than the weight ρgH of the liquid it carries.

3. A gas-liquid contact method, characterized in that, The method employs the liquid-bearing structure (1) as described in claim 1 or 2, and the method includes passing gas from bottom to top through a sieve (12).

4. The method according to claim 3, characterized in that, The pressure P of the gas gas Satisfy P gas >(ρgH+2σcosθ' / R')=2ρgH, where θ' is the contact angle in rad and R' is the bubble radius in m.

5. The application of the liquid-bearing structure according to claim 1 or 2 or the gas-liquid contact method according to claim 3 or 4 in the field of high-temperature gas processing.

6. A coal underground gasification wellhead cooling device, characterized in that, The coal underground gasification production wellhead cooling device includes a packer (2), on which the liquid-bearing structure (1) of claim 1 or 2 is installed.

7. The coal underground gasification wellhead cooling device according to claim 6, characterized in that, The top end of the central tube (21) of the packer (2) is connected to the liquid-bearing structure (1) via a coupling (3).

8. The coal underground gasification wellhead cooling device according to claim 7, characterized in that, The outer wall of the annular cylinder (11) of the liquid-bearing structure (1) is set as a cone shape with a larger upper part and a smaller lower part, and the inner wall of the coupling (3) is provided with a cone-shaped mounting position that is compatible with the annular cylinder (11).

9. The coal underground gasification wellhead cooling device according to claim 8, characterized in that, The outer wall surface of the annular cylinder (11) above the coupling (3) is fitted with a sealing element (4).

10. The coal underground gasification wellhead cooling device according to claim 9, characterized in that, The sealing element (4) is made of a heat-resistant material that absorbs water and expands.

11. The coal underground gasification wellhead cooling device according to claim 9 or 10, characterized in that, The outer wall surface of the annular cylinder (11) above the coupling (3) is configured as an axially extending wave-shaped structure, wherein the sealing element (4) is sleeved in the trough of the wave-shaped structure.

12. The coal underground gasification wellhead cooling device according to claim 10, characterized in that, The sealing element (4) is fitted onto the central tube (21) of the packer (2).

13. The coal underground gasification wellhead cooling device according to claim 10, characterized in that, The heat-resistant and water-absorbing material is selected from at least one of graphene, hydrogenated nitrile rubber, and fluororubber.

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