Coal sample three-dimensional gas filling seepage coordination control device and method

Abstract

The present application relates to rock mechanics and gas seepage test technical field, disclose a kind of coal sample three-dimensional gas inflation seepage coordination control device and method, including triaxial loading chamber, upper pressure head, lower pressure head, gas-permeable isolation sheath, three independent gas guide branch, confining pressure loading system and control terminal.Gas-permeable isolation sheath is wrapped in the outside of coal sample, is made of shell and the composite semipermeable membrane of inside, for transmitting external confining pressure and blocking liquid phase confining pressure medium, allow gas phase gas to penetrate.Upper and lower pressure head is equipped with three layers of annular groove, respectively connect independent gas guide branch and exhaust passage.Control method is by controlling the pressure difference of composite semipermeable membrane two sides less than breakthrough pressure, layered independent injection gas is constructed in the radial of coal sample Pressure gradient, and based on the integral calculation of layered flow and pressure time series data collected, the radial heterogeneous characteristics of coal rock is inversed.The present application eliminates the plugging interference of confining pressure medium to seepage pore, realizes three-dimensional seepage test and local permeability evaluation under stress constraint.

Description

Technical Field

[0001] This invention relates to the field of rock mechanics and gas seepage testing technology, specifically to a three-dimensional gas aeration and seepage control device and method for coal samples. Background Technology

[0002] In research on deep coal mining and coalbed methane extraction, the use of triaxial flow testing equipment to physically simulate the stress state of coal and rock and the flow law of gas in the laboratory is a commonly used technical method. Conventional triaxial gas flow testing devices usually use a completely enclosed flexible sheath, such as a rubber heat shrink sleeve, to wrap the coal sample to isolate it from the external liquid confining pressure medium.

[0003] Due to the confined sheath structure, gas can only be injected into one end of the coal sample along its axial direction and discharged from the other end. The gas flow field inside the sample exhibits a simple one-dimensional unidirectional flow. Since the pore and microfracture network inside deep undisturbed coal and rock masses is usually heterogeneous, the actual gas migration is a complex three-dimensional seepage process. The aforementioned one-dimensional axial unidirectional flow field cannot construct a pressure gradient in the radial direction of the coal sample, making it difficult to accurately simulate the multidimensional seepage characteristics of gas under stress constraints.

[0004] To overcome the limitations of one-dimensional flow and achieve radial seepage testing, existing testing devices face a structural contradiction between confining pressure isolation and gas permeation. In a triaxial loading environment, if the ventilation boundary is opened on the sidewall of the coal sample, the liquid confining pressure medium will directly invade the interior of the coal sample under the action of pressure difference, or the test pores on the radial surface of the coal sample will be blocked due to capillary action, thereby interfering with the normal seepage of gas and causing distortion of the test flow rate data.

[0005] Meanwhile, traditional testing equipment often employs a single-loop structure for its gas supply and exhaust channels, resulting in a mixed-flow state within the coal sample's internal flow area after gas injection. This single pipeline and cavity design cannot independently measure and control the gas injection and outflow rates in different radial layers within the coal sample; the test results can only reflect the overall macroscopic permeability of the coal sample. Due to the lack of a multi-channel stratified pressure control mechanism and a corresponding flow-time integral evaluation model, existing equipment cannot separate and extract the apparent gas adsorption response and flow data from different regions. Consequently, it cannot quantitatively invert and finely evaluate the local permeability and radial heterogeneous structural differences within the coal sample. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a three-dimensional gas aeration and seepage control device and method for coal samples, which solves the problem that existing testing equipment cannot achieve multi-layer radial three-dimensional gas aeration and seepage testing and evaluation of local permeability within coal samples under the premise of isolating the interference of liquid phase confining pressure medium.

[0007] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of the present invention provides a three-dimensional coal sample gas aeration and seepage coordinated control device, comprising:

[0008] The three-axis loading chamber is equipped with an upper pressure head and a lower pressure head; the lower pressure head is equipped with a layered exhaust port and inner, middle and outer exhaust channels that are isolated from each other;

[0009] A breathable isolation sleeve is placed between the upper and lower pressure heads to cover the coal sample. It consists of an outer shell and an e-PTFE rubber composite semi-permeable membrane.

[0010] The inner air guide branch, the middle air guide branch, and the outer air guide branch are all connected to the upper pressure head, and each is equipped with a pressure regulating valve, a flow sensor, and a pressure sensor.

[0011] The exhaust pipeline connects the stratified exhaust interface to the gas collection device and is equipped with valves, flow meters, and pressure sensors.

[0012] A confining pressure loading system, connected to a triaxial loading chamber, is used to inject a liquid-phase confining pressure medium;

[0013] The control terminal is connected to the confining pressure loading system, various valves, flow meters, and sensor circuits.

[0014] Furthermore, the outer shell is a pressure-transmitting support structure equipped with pressure-transmitting pores or support windows; the e-PTFE rubber composite semi-permeable membrane is located between the confining pressure medium and the coal sample, used to prevent the liquid phase of the confining pressure medium from entering the coal sample, and to maintain the air-connected state of the seepage pores on the radial surface of the coal sample.

[0015] Furthermore, three layers of annular grooves and radial vent holes are provided on the opposite end faces of the upper and lower pressure heads.

[0016] In this invention, the outer shell provides mechanical support and transmits the pressure of the confining medium to the surface of the coal sample; the e-PTFE rubber composite semi-permeable membrane, combining its microporous structure and hydrophobic properties, forms a capillary resistance barrier on the surface to block the liquid-phase confining medium while allowing gaseous gas molecules to penetrate. The three-layered annular grooves on the upper and lower pressure head ends, along with three independent gas-guiding branches, create spatially isolated injection and exhaust boundaries in the surface, middle, and core regions of the coal sample, constructing a multi-layered gas flow path.

[0017] Furthermore, the control device also includes a vacuum system connected to the internal gas path of the triaxial loading chamber.

[0018] Furthermore, the control terminal can collect data from the pressure sensors and flow sensors on each gas guide branch, and adjust the opening and closing degree of the corresponding pressure regulating valves to build a pressure gradient in the radial direction of the coal sample.

[0019] By independently adjusting the gas injection pressure of each layer, a pressure difference is formed radially inside the coal sample; while the gas flows axially under pressure, it also flows radially to the adjacent pressure difference area, thereby forming a multi-directional seepage field in the pores of the solid coal sample.

[0020] A second aspect of the present invention provides a method for coordinated control of three-dimensional gas aeration and seepage in coal samples, applied to the aforementioned control device, comprising the following steps:

[0021] The coal sample is loaded into the triaxial loading chamber, and a breathable isolation sleeve is fitted on the outside to control the contact between the upper and lower pressure heads and the coal sample.

[0022] Inject confining pressure medium into the triaxial loading chamber and apply preset confining pressure and axial pressure so that the actual liquid phase pressure difference on both sides of the e-PTFE rubber composite semipermeable membrane is less than the breakthrough pressure.

[0023] Set the target gas pressure and flow thresholds for the inner, middle and outer gas guide branches, and inject the gas into the coal sample through the corresponding gas guide branches;

[0024] When the gas pressure and flow data of each gas guide branch remain stable at the preset threshold, the control terminal determines that a dynamic balance state has been reached and controls the corresponding gas guide branch to enter the pressure holding control state.

[0025] After the test is completed, stop the gas injection, unload the axial pressure and confining pressure, and control the exhaust pipeline to connect to the gas collection device for exhaust gas recovery; when the exhaust flow rate is lower than the preset residual flow rate threshold, close the valve on the exhaust pipeline;

[0026] Based on the collected time-series data, the integral calculation of gas adsorption capacity and the evaluation of the radial heterogeneous structure of the coal sample were performed.

[0027] Furthermore, the specific process for ensuring that the actual liquid phase pressure difference across the e-PTFE rubber composite semipermeable membrane is less than the breakthrough pressure is as follows: the breakthrough pressure is calculated based on the Young-Laplace equation according to the surface tension of the confining medium, the contact angle between the confining medium and the membrane material, and the micropore radius; the pressure data on both sides are monitored simultaneously to maintain the actual liquid phase pressure difference less than the breakthrough pressure.

[0028] Furthermore, the specific process for determining that a dynamic equilibrium state has been reached is as follows: obtain the total injection flow rate through each air guide branch and the total outflow flow rate through the exhaust pipe, calculate the absolute value of the difference between the two and compare it with the set error threshold; when the absolute value is less than or equal to the set error threshold, and the pressure monitoring value of each air guide branch is within the target pressure tolerance range, and the above conditions are continuously met within the set time window, it is determined that a dynamic equilibrium state has been reached.

[0029] Furthermore, the specific process of exhaust gas recovery is as follows: the control terminal acquires monitoring data from the exhaust pipeline, and adjusts the opening of the exhaust valve according to the exhaust pressure and exhaust flow rate, so that the residual gas enters the gas collection device.

[0030] Furthermore, the calculation of gas adsorption integral and the evaluation of radial heterogeneous structure of coal samples are performed, including:

[0031] The real-time injection flow rate of each air guide branch and the real-time exhaust flow rate of each exhaust channel are accumulated over time to obtain the cumulative injection volume and cumulative exhaust volume of each layer.

[0032] The cumulative injection volume and cumulative exhaust volume of each layer are summed to obtain the total injection volume and total exhaust volume, and the difference between the two is calculated as the overall apparent adsorption volume.

[0033] Calculate the difference between the cumulative gas injection volume of each layer and the cumulative exhaust volume of the corresponding layer and the preset residual gas correction volume to obtain the cumulative net injection volume of each layer;

[0034] The total net injection amount is obtained by summing the cumulative net injection amounts of each layer.

[0035] Calculate the percentage weight of the cumulative net injection volume of each layer in the total net injection volume to evaluate the radial structure differences of the coal samples.

[0036] The calculation and evaluation process of this invention is based on the law of conservation of gas mass, using the dynamic difference between the total input gas volume and the total output gas volume of the system as the retained gas volume of the coal sample and pipeline. Using the stratified flow time-series data of each independent channel, after deducting the exhaust volume and free gas volume, the apparent adsorption and permeation response of each radial layer during the experimental period is obtained. The degree of pore connectivity within the corresponding region of the coal sample is correlated with the proportion of each layer's response, thereby quantifying the heterogeneous characteristics of the radial structure of the coal sample.

[0037] This invention provides a device and method for coordinated control of three-dimensional gas aeration and seepage in coal samples. It has the following beneficial effects:

[0038] 1. This invention transmits confining pressure through pressure-transmitting pores or support windows in the outer shell and utilizes a composite semi-permeable membrane to isolate the liquid-phase confining pressure medium. Under the boundary condition that the actual liquid-phase pressure difference is less than the breakthrough pressure, the liquid-phase confining pressure medium is effectively blocked outside the coal sample, allowing gaseous gas molecules to diffuse or permeate through the micropores of the semi-permeable membrane under the pressure difference. This physical structure avoids the external confining pressure medium from blocking the test pores on the radial surface of the coal sample, ensuring the connectivity of the radial gas seepage test interface inside the coal sample.

[0039] 2. This invention utilizes three layers of annular grooves on the end faces of the upper and lower pressure heads, along with independent gas-guiding branches, to inject methane gas into the inner, middle, and outer layers of the coal sample, respectively. The control terminal independently adjusts the injection flow rate of the corresponding pressure regulating valve based on the pressure feedback from each layer of pipelines, constructing a stable radial pressure gradient within the coal sample, thereby realizing a three-dimensional methane filling and seepage simulation process under stress.

[0040] 3. This invention is based on time-series pressure and flow data collected experimentally, and performs time integration and accumulation calculations on the injection and exhaust volumes, respectively. The overall apparent adsorption capacity is obtained by calculating the difference between the total injection volume and the total exhaust volume. Furthermore, the interference from dead volume and residual gas in the pipeline is eliminated by calculating the cumulative net injection volume of each layer. The local permeability of different regions of the coal sample is evaluated based on the difference in the proportion of the cumulative net injection volume of each layer, thus achieving an objective evaluation and data inversion of the radial heterogeneity characteristics of coal and rock. Attached Figure Description

[0041] Figure 1 This is a structural diagram of the collaborative control device of the present invention;

[0042] Figure 2 This is a flowchart of the overall collaborative control method of the present invention;

[0043] Figure 3 This is a flowchart illustrating the control process for preventing confining pressure media interference and physical isolation according to the present invention.

[0044] Figure 4 This is a flowchart of the layered gradient gas injection and dynamic balance determination closed-loop control of the present invention;

[0045] Figure 5 This is a flowchart of the calculation of the layered apparent adsorption response and the inversion of radial heterogeneous characteristics according to the present invention.

[0046] Among them, 1000 is the triaxial loading chamber; 1001 is the flow sensor; 1002 is the pressure regulating valve; 1003 is the gas cylinder; 1004 is the gas collection device; 2000 is the confining pressure loading system; 3000 is the upper pressure head; 3001 is the middle layer gas injection interface; 3002 is the inner layer gas injection interface; 3003 is the outer layer gas injection interface; 4000 is the lower pressure head; 5000 is the coal sample; 6000 is the gas collection interface; 7000 is the outer shell; 8000 is the control terminal; 9000 is the vacuum system; and 1100 is the e-PTFE rubber composite semi-permeable membrane. Detailed Implementation

[0047] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] See attached document Figure 1 The present invention provides a three-dimensional gas aeration and seepage coordinated control device for coal samples, which may include: a triaxial loading chamber 1000, a flow sensor 1001, a pressure regulating valve 1002, a gas cylinder 1003, a gas collection device 1004, a confining pressure loading system 2000, an upper pressure head 3000, a lower pressure head 4000, a shell 7000, a control terminal 8000, and a vacuum system 9000.

[0049] The triaxial loading chamber 1000 is equipped with an upper pressure head 3000 and a lower pressure head 4000. The coal sample 5000 is placed inside the triaxial loading chamber 1000 and sandwiched between the upper pressure head 3000 and the lower pressure head 4000.

[0050] The outer side of the coal sample 5000 is fitted with a breathable isolation sleeve, which is located between the radial sidewall of the coal sample 5000 and the confining pressure medium inside the triaxial loading chamber 1000. The breathable isolation sleeve is composed of a stainless steel corrosion-resistant outer shell 7000 and an e-PTFE rubber composite semi-permeable membrane 1100 attached to the inner side of the outer shell 7000.

[0051] In the e-PTFE rubber composite semi-permeable membrane 1100, the effective air-permeable area maintains the interconnection of the e-PTFE microporous structure, and the rubber composite part is used for membrane layer support, edge sealing or bonding and fixing, without sealing the effective air-permeable micropores of the composite semi-permeable membrane.

[0052] The upper and lower edges of the e-PTFE rubber composite semi-permeable membrane 1100 are respectively pressed and fixed by corresponding annular sealing gaskets, end clamping rings or pressure head sealing seats, so that the effective air permeable area of ​​the e-PTFE rubber composite semi-permeable membrane 1100 covers the radial sidewall of the coal sample 5000, and the edge area of ​​the membrane layer forms a sealing boundary of the confining pressure medium.

[0053] The outer shell 7000 is a pressure-transmitting support structure for supporting the e-PTFE rubber composite semi-permeable membrane 1100. The outer shell 7000 forms pressure-transmitting pores or support windows at the position corresponding to the radial sidewall of the coal sample 5000, so that the confining pressure medium in the triaxial loading chamber 1000 can transmit the confining pressure to the outside of the e-PTFE rubber composite semi-permeable membrane 1100.

[0054] The e-PTFE rubber composite semi-permeable membrane 1100 is located between the confining pressure medium and the coal sample 5000. It is used to block the liquid confining pressure medium from entering the coal sample 5000 and to form a breathable isolation interface on the radial sidewall of the coal sample 5000. This maintains the air-to-air connection of the seepage pores on the radial surface of the coal sample 5000 and prevents the liquid confining pressure medium from blocking the seepage pores on the radial surface of the coal sample 5000. This ensures that the radial seepage inside the coal sample 5000 formed by the stratified pressure boundary is not disturbed by the confining pressure medium.

[0055] The confining pressure loading system 2000 is connected to the triaxial loading chamber 1000. The confining pressure loading system 2000 is used to inject confining pressure medium into the triaxial loading chamber 1000.

[0056] The vacuum system 9000 is connected to the gas path inside the triaxial loading chamber 1000, and is used to degas the system pipeline and the inside of the coal sample.

[0057] The gas supply system includes a gas cylinder 1003, gas pipelines, pressure regulating valves 1002 for each layer, flow sensors 1001 for each layer, pressure sensors for each layer, and inner, middle, and outer gas delivery branches. The gas cylinder 1003 outputs gas through the gas pipelines, which are divided into three independent branches from the main gas pipeline: the inner, middle, and outer gas delivery branches.

[0058] The inner air guiding channel includes an inner air guiding branch, an inner gas injection interface 3002, and a corresponding inner annular air intake groove inside the upper pressure head 3000; the middle air guiding channel includes a middle air guiding branch, a middle gas injection interface 3001, and a corresponding middle annular air intake groove inside the upper pressure head 3000.

[0059] The outer air guide channel includes an outer air guide branch, an outer gas injection interface 3003, and a corresponding outer annular air inlet groove inside the upper pressure head 3000.

[0060] Each independent branch is equipped with a pressure regulating valve 1002, a flow sensor 1001, and a pressure sensor. The three independent branches are respectively sealed and connected to the inner gas injection port 3002, the middle gas injection port 3001, and the outer gas injection port 3003 at the top of the upper pressure head 3000. The control terminal 8000 can collect the pressure and flow data of each branch and adjust the opening degree of the corresponding pressure regulating valve 1002.

[0061] The bottom of the pressure head 4000 is provided with an exhaust port. The exhaust port includes a layered exhaust port that is connected to the inner exhaust channel, the middle exhaust channel and the outer exhaust channel respectively, or a manifold exhaust port that is connected to the inner exhaust channel, the middle exhaust channel and the outer exhaust channel respectively via an independent control valve.

[0062] Each floor's exhaust channel remains independent before entering the gas collection interface 6000, and exhaust flow data for the corresponding floor is collected or switched to be collected separately.

[0063] The exhaust port is connected to the external gas collection device 1004 through the gas collection port 6000 for recovering the gas discharged from the system. A controllable exhaust valve is provided between the gas collection port 6000 and the gas collection device 1004.

[0064] If necessary, check valves, pressure relief valves, or airtightness testing interfaces may be installed on gas cylinder 1003, gas guide branches on each floor, or exhaust pipes as conventional safety protection structures in this field.

[0065] The control terminal 8000 is connected to the pressure sensors, confining pressure loading system 2000, flow sensors 1001, pressure regulating valves 1002, and exhaust pipe valves in the system via circuits. This enables the synchronous acquisition of pressure, flow, and stress data, as well as the control and regulation of the pipe valves. It can also perform inflation, pressure holding, gas replenishment, pressure relief, and exhaust gas recovery control on the inner, middle, and outer air guide branches, respectively.

[0066] See attached document Figure 2 This invention provides a method for coordinated control of three-dimensional gas aeration and seepage in coal samples, comprising the following steps:

[0067] S10, process coal sample 5000 into a cylindrical specimen. Load coal sample 5000 into triaxial loading chamber 1000. Control the end face of the upper pressure head 3000 to fit against the upper end face of coal sample 5000. Complete the sealing connection between each layer of air guiding channels and the air inlet interface;

[0068] S20, activate the confining pressure loading system 2000 to inject confining pressure medium into the triaxial loading chamber 1000, and apply the preset confining pressure and axial pressure. Activate the vacuum system 9000 to perform vacuum degassing on the gas delivery channel and inside the coal sample 5000.

[0069] During the vacuum degassing process, the control terminal 8000 simultaneously monitors the confining pressure and the pressure on the pore side or gas guide channel side of the coal sample, and maintains the actual liquid phase pressure difference across the e-PTFE rubber composite semi-permeable membrane 1100. Less than the breakout pressure .

[0070] After vacuum degassing is completed, close the corresponding vacuum control valve and open the confining pressure medium return switch or return valve to remove the confining pressure medium injected during the system pre-pressurization stage; before entering the triaxial loading coupling test, the confining pressure loading system 2000 will reapply the target confining pressure and axial pressure according to the test plan;

[0071] S30, the target gas pressure and flow thresholds for the inner, middle, and outer gas channels are set via the control terminal 8000. Gas cylinder 1003 outputs gas, which passes through three independent gas channels via corresponding pressure regulating valves 1002, flow sensors 1001, and pressure sensors, and then connects to the inner gas injection port 3002, middle gas injection port 3001, and outer gas injection port 3003 at the top of the upper pressure head 3000.

[0072] S40, when the gas pressure and flow data of the inner gas guiding channel, the middle gas guiding channel and the outer gas guiding channel remain stable for a period of time that reaches a preset threshold, the control terminal 8000 determines that the coal sample 5000 has reached the dynamic equilibrium state of gas adsorption and seepage under the current pressure boundary.

[0073] At this time, the control terminal 8000 closes or reduces the corresponding air inlet valve that meets the preset conditions according to the stable state of gas pressure and flow in each layer, so that the corresponding air guide channel enters the pressure holding control state.

[0074] During loading, if the pressure of the corresponding layer is lower than the target pressure tolerance range, a gas replenishment action is performed; if the pressure of the corresponding layer is higher than the target pressure tolerance range, a pressure relief action is performed. The triaxial loading system is then activated to conduct a coupled test of the mechanical properties and gas seepage characteristics of coal sample 5000.

[0075] During the test loading process, the control terminal 8000 controls the pressure regulating valve, air supply valve or pressure relief valve of the corresponding air path to perform air supply or pressure relief actions according to the pressure changes at the air guide channel or pressure head interface of each layer, so as to maintain the gas boundary pressure of each layer within the target pressure tolerance range.

[0076] S50, after the test is completed, the control terminal 8000 first stops the gas injection and unloads the axial pressure and confining pressure according to the preset unloading rate; after the axial pressure and confining pressure are unloaded, the tail gas recovery system is turned on to discharge the residual gas in each layer of gas guiding channel, the coal sample 5000 pores and the exhaust channel of the lower pressure head 4000 into the gas collection device 1004 for recovery treatment.

[0077] When the exhaust pressure drops to near the ambient atmospheric pressure and the exhaust flow rate falls below the preset residual flow rate threshold, the control terminal 8000 closes the exhaust valve. Then, the upper pressure head 3000, lower pressure head 4000, and coal sample 5000 are disassembled.

[0078] S60, the control terminal 8000 performs gas adsorption integral calculation and evaluation of the radial heterogeneous structure of coal samples based on the pressure, flow and stress time series data collected during the test cycle.

[0079] As a specific implementation of step S10, based on the encapsulation and assembly principle of the breathable insulating sleeve, the following steps are performed:

[0080] S101, the coal sample to be tested is processed into a cylindrical specimen as coal sample 5000. The process of processing coal sample 5000 into a cylindrical specimen can be carried out by those skilled in the art using conventional core sampling equipment. The processing method is well-known in the art and will not be described in detail here.

[0081] S102, place coal sample 5000 inside triaxial loading chamber 1000. A breathable isolation sleeve is fitted onto the outer cylindrical surface of coal sample 5000. The breathable isolation sleeve consists of an outer shell 7000 and an e-PTFE rubber composite semi-permeable membrane 1100 attached to its inner wall.

[0082] In the assembled state, the inner surface of the e-PTFE rubber composite semi-permeable membrane 1100 contacts the radial outer surface of the coal sample 5000, and the outer surface of the outer shell 7000 faces the cavity inside the triaxial loading chamber 1000 for contact with the confining pressure medium. The outer shell 7000 is made of corrosion-resistant steel and is constructed as a pressure-transmitting support structure. The area of ​​the outer shell 7000 corresponding to the radial sidewall of the coal sample 5000 is provided with multiple pressure-transmitting pores, strip windows or mesh support windows arranged at intervals along the circumference and / or axis, rather than a continuous rigid cylinder that completely seals the sidewall of the coal sample 5000.

[0083] The outer shell 7000 bears and transmits the pressure of the external confining medium through pressure-transmitting pores or support windows, so that the pressure of the confining medium acts on multiple areas outside the e-PTFE rubber composite semi-permeable membrane 1100, and the edges of the pressure-transmitting pores or support windows provide mechanical support to the e-PTFE rubber composite semi-permeable membrane 1100, so that the confining pressure is transmitted to the surface of the coal sample 5000 through the e-PTFE rubber composite semi-permeable membrane 1100, while not blocking the pressure interface of the confining medium on the outside of the e-PTFE rubber composite semi-permeable membrane 1100, and avoiding blocking the gas seepage interface on the radial surface of the coal sample 5000.

[0084] S103, e-PTFE rubber composite semi-permeable membrane 1100 is made of expanded polytetrafluoroethylene material and has a microporous structure with a pore size ranging from 0.1μm to 0.5μm.

[0085] The barrier effect of the e-PTFE rubber composite semi-permeable membrane 1100 on liquid confining media such as oil or water is determined by the hydrophobic properties of the membrane material, the surface tension of the confining medium, the contact angle, and the micropore radius, rather than simply by the size relationship between the molecular size of the confining medium and the micropore diameter.

[0086] The kinetic diameter of gaseous gas molecules is smaller than the micropore size of the e-PTFE rubber composite semi-permeable membrane 1100, allowing them to diffuse or permeate through the membrane micropores under pressure differential. Based on the capillary pressure principle, the confining medium forms a meniscus on the micropore surface, overcoming the pressure. Calculated using the Young-Laplace equation:

[0087] ;

[0088] In the formula, The surface tension of the confining medium is expressed in N / m. Contact angle; The radius of the micropore is in meters (m). To measure the pressure, the unit is Pa, which can be converted to MPa.

[0089] The actual liquid phase pressure difference across the membrane is set as follows: When the control system satisfies When the confining pressure medium cannot penetrate the e-PTFE rubber composite semi-permeable membrane 1100, it is isolated from the outside. Simultaneously, the microporous structure of the e-PTFE rubber composite semi-permeable membrane 1100 allows gas to permeate through the membrane layer under pressure differential via Knudsen diffusion and viscous flow coupling mechanism. This physical mechanism forms a selective permeation interface, achieving the dual functions of confining pressure medium isolation and radial gas seepage.

[0090] For a three-dimensional docking structure with multiple independent air channels, perform the following steps:

[0091] S104, the upper pressure head 3000 and the lower pressure head 4000 are provided with three layers of annular grooves and radial vent holes on their opposite end faces.

[0092] Among them, the three-layer annular groove on the end face of the upper pressure head 3000 serves as a three-layer annular air intake groove, which is used to introduce gas into the surface, middle and core areas of coal sample 5000 respectively.

[0093] The three-layer annular groove on the end face of the lower pressure head 4000 serves as a three-layer annular exhaust groove, used to receive the gas seeping from the corresponding area of ​​coal sample 5000 to the lower end face.

[0094] The three annular grooves are radially distributed along the end face of the pressure head, corresponding to the surface, middle, and core regions of the radial section of coal sample 5000 in spatial position. The surface, middle, and core regions are radial concentric pressure boundaries formed by the positions of the three annular grooves, and do not divide coal sample 5000 into mutually isolated solid layers along the axial direction of coal sample 5000.

[0095] S105, the top of the upper pressure head 3000 is provided with an outer layer gas injection port 3003, a middle layer gas injection port 3001, and an inner layer gas injection port 3002. The lower pressure head 4000 has an inner layer exhaust channel, a middle layer exhaust channel, and an outer layer exhaust channel that are isolated from each other. An exhaust port is provided at the bottom of the lower pressure head 4000, and the exhaust port is connected to the exhaust channels of the above-mentioned layers to discharge the gas inside the coal sample 5000.

[0096] Each layer has an independent exhaust channel corresponding to the outer exhaust channel, middle exhaust channel and inner exhaust channel respectively. Each exhaust channel is independent of each other before metering and is connected to the corresponding exhaust flow detection unit or switched to the same exhaust flow detection unit in sequence through independent valves.

[0097] S106, the contact surfaces of the upper pressure head 3000, lower pressure head 4000, and coal sample 5000 are equipped with annular sealing gaskets. Annular sealing bosses or annular sealing grooves are provided between adjacent annular grooves, and high-temperature and high-pressure resistant sealing gaskets are installed inside the annular sealing grooves; an outer sealing gasket is installed on the outermost annular groove. The upper pressure head 3000 and lower pressure head 4000 are then fitted to the upper and lower end faces of the coal sample 5000, respectively, ensuring a tight fit between the annular sealing gaskets on the control end faces and the end faces of the coal sample 5000, thus completing the sealing installation between the pressure heads and the coal sample 5000.

[0098] S107, the outer layer gas guide channel, middle layer gas guide channel and inner layer gas guide channel configured in the system are respectively sealed and connected to the outer layer gas injection interface 3003, middle layer gas injection interface 3001 and inner layer gas injection interface 3002 corresponding to the top of the upper pressure head 3000.

[0099] The annular sealing gasket on the end face ensures that the outer, middle and inner air guiding channels are independent of each other before entering the coal sample 5000, and that there is no pipeline interconnection between the three annular air inlet grooves on the end face of the upper pressure head 3000.

[0100] The sealing structure is used to isolate interlayer gas leakage in the pressure head end face and external pipelines, but not to physically isolate the internal pores of coal sample 5000. The internal pores of coal sample 5000 are not physically isolated, and gas can undergo radial seepage under the pressure difference between layers after entering coal sample 5000.

[0101] Reference Appendix Figure 3 As a specific implementation of S20, regarding the physical isolation mechanism and parameter verification process for preventing confining pressure interference, the following steps are performed:

[0102] S201, activate the confining pressure loading system 2000, injecting oil or water into the triaxial loading chamber 1000 as the confining pressure medium. Obtain the surface tension of the confining pressure medium. Contact angle between the confining pressure medium and the 1100 e-PTFE rubber composite semi-permeable membrane material And the micropore radius of the e-PTFE rubber composite semi-permeable membrane 1100 Calculate the breakthrough pressure corresponding to the current operating condition based on the above parameters. The calculation logic is based on the Young-Laplace equation formula in step S103.

[0103] For obtaining the surface tension and material contact angle parameters of the confining pressure medium, those skilled in the art can use conventional interfacial tension meters and contact angle measuring equipment to determine them, which are well-known technologies in the field and will not be elaborated here.

[0104] S202, the control terminal 8000 will calculate the breakthrough pressure The liquid phase breakthrough threshold of the e-PTFE rubber composite semi-permeable membrane 1100 is defined. A controlled confining pressure is applied to the triaxial loading chamber 1000 via the confining pressure loading system 2000. .

[0105] The control terminal 8000 synchronously receives confining pressure data from the triaxial loading chamber 1000 and pressure data from the pore side or gas guide channel side of the coal sample 5000, and calculates the actual liquid phase pressure difference across the e-PTFE rubber composite semi-permeable membrane 1100. Control terminal 8000 maintained .

[0106] Under this pressure condition, the pressure difference driving force on the confining medium is less than the capillary resistance in the micropores. The confining medium forms a meniscus on the outside of the micropores of the e-PTFE rubber composite semi-permeable membrane 1100, thereby restricting the liquid phase confining medium from penetrating through the micropores into the interior of the coal sample 5000, thus completing the parameter verification and control of the confining medium interference.

[0107] As a further specific implementation of S20, the following steps are performed regarding the vacuum cleaning mechanism for the internal three-dimensional seepage channels of the coal sample:

[0108] S203, under the condition of applying controlled confining pressure in the triaxial loading chamber 1000, the vacuum degassing device is connected to the inner gas injection port 3002, the middle gas injection port 3001, the outer gas injection port 3003 of the upper pressure head 3000, and the exhaust port of the lower pressure head 4000.

[0109] Start the vacuum degassing equipment and perform vacuum treatment on the internal pores of coal sample 5000 along the flow channels inside the upper pressure head 3000 and the lower pressure head 4000 to remove residual air from the pores and reduce the impact of air on subsequent gas seepage tests.

[0110] During the vacuuming process of coal sample 5000, a negative pressure is formed inside the coal sample 5000. The control terminal 8000 simultaneously monitors the confining pressure side pressure and the coal sample pore side pressure, and adjusts the confining pressure loading system 2000 or the vacuum degassing intensity to maintain the actual liquid phase pressure difference across the e-PTFE rubber composite semi-permeable membrane 1100. Less than the breakout pressure .

[0111] Under these conditions, the e-PTFE rubber composite semi-permeable membrane 1100 restricts the intrusion of external confining pressure medium into the coal sample 5000 under the action of pressure difference. It should be noted that the e-PTFE rubber composite semi-permeable membrane 1100 is used to isolate the confining pressure medium, not to physically isolate the three-layer pore region inside the coal sample 5000; radial seepage between the three layers is formed by a subsequently set pressure gradient.

[0112] Reference Appendix Figure 4 As a specific implementation of S30, the following steps are performed for the stratified gas injection and pressure gradient construction of multi-layer independent gas guiding channels:

[0113] S301, after vacuum degassing is completed, the control terminal 8000 controls the gas supply system to inject gas into the inner gas channel, the middle gas channel and the outer gas channel respectively.

[0114] In gradient flow mode, to construct a pressure gradient radially in the coal sample (5000 mm), the control terminal (8000) sets unequal target injection pressures for the three gas-conducting channels; that is, the set injection pressures for the inner, middle, and outer layers have numerical differences. The target injection pressures corresponding to the inner, middle, and outer layers are respectively... , and For example, or satisfy The gradient pressure relationship.

[0115] Under the action of external gas injection pressure, the gas enters the three-layer annular gas inlet groove through the inner gas injection port 3002, the middle gas injection port 3001 and the outer gas injection port 3003 of the upper pressure head 3000, and is injected into the corresponding core area, middle area and surface area inside the coal sample 5000 respectively.

[0116] The three-layer gas guiding channels remain independent of each other in the pressure head and external pipeline. After entering the coal sample 5000, the gas forms radial seepage based on the internal pore connectivity of the coal sample 5000 and the pressure difference between each layer, and seeps downward along the axial direction of the coal sample 5000 to the annular exhaust groove corresponding to the pressure head 4000. The radial pressure gradient and the axial exhaust path together form a three-dimensional gas seepage field.

[0117] S302, due to the pressure difference between the three layers inside coal sample 5000, the gas seeps radially from the high-pressure area to the adjacent low-pressure area in the internal pores of coal sample 5000.

[0118] At the same time, the injected gas, under the action of injection pressure, permeates along the axial direction of coal sample 5000 to the bottom and is discharged through the exhaust channel of the corresponding layer at the bottom of the lower pressure head 4000.

[0119] Radial and axial seepage superimpose in the pore space of coal sample 5000, forming a three-dimensional gas seepage flow field. The term "three independent layers" here refers to the independence of the external aeration branch, the pressure head annular groove, and the exhaust channel in terms of boundary control and data acquisition. It does not exclude the possibility of radial seepage of gas in the pores inside coal sample 5000 due to pressure gradient.

[0120] During gas injection and seepage, the control terminal 8000 simultaneously acquires the injection volume and pressure data of each gas guide branch node in the gas supply system, as well as the outflow data of the exhaust port. The acquisition of gas flow and pressure data can be achieved by conventional gas flow meters and pressure sensors, which are well-known technologies in the field and will not be elaborated upon here.

[0121] In the gas permeation and adsorption test of coal sample 5000 (S303), the internal pores of coal sample 5000 adsorb gas, and simultaneously, the gas seeps into adjacent low-pressure areas under pressure. This physical process consumes the gas inside the channels, causing a decrease in the actual gas pressure at each injection node within the upper pressure head 3000. The control terminal 8000 acquires data from pressure sensors arranged on the gas path and simultaneously receives the current actual monitoring pressure values ​​of the inner, middle, and outer gas guiding channels.

[0122] S304, the control terminal 8000 compares the actual monitoring pressure values ​​of each layer of gas guide branch with their corresponding target set pressure values. Based on the comparison results, the control terminal 8000 outputs control commands to the gas supply system to independently adjust the gas injection flow rate of each layer of pipeline.

[0123] When the actual monitored pressure value of the corresponding air guide branch is lower than the target set pressure value, the control terminal 8000 increases the opening of the pressure regulating valve 1002 of that layer or starts the air replenishment action of that layer to compensate for the pressure loss caused by pore adsorption and fluid seepage.

[0124] When the actual monitored pressure value of the corresponding air guide branch reaches the tolerance range corresponding to the target set pressure value, the control terminal 8000 causes the corresponding air guide branch to enter the pressure holding state.

[0125] When the actual monitoring pressure value of the corresponding layer's gas guide branch is higher than the target set pressure value and exceeds the tolerance range, the control terminal 8000 reduces the gas injection volume of that layer or opens the corresponding pressure relief passage.

[0126] The aforementioned feedback pressure stabilization mechanism dynamically allocates and replenishes the injected gas volume of the three-layer gas guiding channels, maintaining the radial pressure gradient initially set by the system, and providing a stable testing environment for the three-dimensional seepage flow field inside the 5000 coal sample.

[0127] As a specific implementation of step S40, the following steps are performed regarding flow acquisition, dynamic balance determination, and constant confining pressure control:

[0128] S401, the control terminal 8000 acquires real-time gas injection flow data input to the inner gas injection interface 3002, the middle gas injection interface 3001 and the outer gas injection interface 3003 according to the set sampling frequency, and at the same time acquires real-time outflow flow data of the inner exhaust channel, the middle exhaust channel and the outer exhaust channel in the pressure head 4000.

[0129] For the acquisition and transmission of gas flow data, those skilled in the art can use conventional gas mass flow meters, which is a well-known technology in the field and will not be described in detail here.

[0130] S402, the control terminal 8000 will sum the real-time gas injection flow data of the inner layer, middle layer and outer layer to obtain the total injection flow of the input coal sample 5000 at the current moment;

[0131] Simultaneously, the real-time outflow data of the inner, middle, and outer layers are summed to obtain the total outflow of coal sample 5000 at the current moment. Subsequently, the control terminal 8000 calculates the difference between the total injection flow and the total outflow, and compares the absolute value of this difference with a preset error threshold.

[0132] The error threshold, target pressure tolerance range, and time window are pre-calibrated or set based on the coal sample size 5000, target gas pressure, flow metering range, and test repeatability requirements. When the absolute value of the difference is less than or equal to the set error threshold, and the pressure monitoring values ​​of the inner, middle, and outer layers are all within their respective target pressure tolerance ranges, the control terminal 8000 starts timing.

[0133] When the above conditions are met continuously within the set time window, the control terminal 8000 determines that coal sample 5000 has reached the dynamic equilibrium state of gas adsorption and seepage under the current pressure gradient.

[0134] If the above conditions are interrupted within the set time window, the timer will be reset and the current test environment will continue to operate until the equilibrium conditions are met again.

[0135] S403, during the gas permeation and adsorption test, the coal matrix of coal sample 5000 expands and deforms due to the adsorption of gas, or shrinks and deforms due to changes in internal pore pressure.

[0136] Because the triaxial loading chamber 1000 is closed and filled with confining pressure fluid, the radial deformation of the coal sample 5000 can act on the external confining pressure fluid through the e-PTFE rubber composite semi-permeable membrane 1100 and the pressure transmission support structure of the outer shell 7000, causing the real-time confining pressure value in the triaxial loading chamber 1000 to deviate from the target confining pressure value.

[0137] S404, the control terminal 8000 acquires the monitoring data of the pressure sensor arranged in the fluid loop of the triaxial loading chamber 1000 according to the set sampling period, acquires the real-time confining pressure value, compares the real-time confining pressure value with the target confining pressure value set by the system, and performs closed-loop control according to the preset constant pressure tolerance threshold.

[0138] When the real-time confining pressure value is higher than the target confining pressure value, and the difference between the two is greater than the constant pressure tolerance threshold, the control terminal 8000 controls the external confining pressure loading system to open the pressure relief circuit; when the real-time confining pressure value is lower than the target confining pressure value, and the absolute value of the difference between the two is greater than the constant pressure tolerance threshold, the control terminal 8000 controls the external confining pressure loading system to inject confining pressure fluid medium into the triaxial loading chamber 1000.

[0139] When the real-time confining pressure value recovers to the tolerance range corresponding to the target confining pressure value, the system stops the liquid discharge or injection action and maintains the fluid closed state.

[0140] As a specific implementation of S50, the following steps are performed for the post-test treatment pipeline disconnection and independent exhaust gas recovery process:

[0141] S501, after the test process of gas permeation and adsorption test is completed, the control terminal 8000 outputs a command to close the active gas injection circuit of the gas supply system and the inner layer gas injection interface 3002, middle layer gas injection interface 3001 and outer layer gas injection interface 3003 of the upper pressure head 3000, and stop injecting gas into the coal sample 5000.

[0142] After the active gas injection is stopped, the control terminal 8000 controls the axial loading system and the confining pressure loading system to unload according to the preset unloading rate, so that the coal sample 5000 transitions from the triaxial constraint state to the unloading state; after the unloading is completed, the exhaust channels of each layer of the pressure head 4000 are connected to the gas collection device 1004 and the tail gas recovery treatment is performed.

[0143] S502, after the active air intake circuit is cut off, the control terminal 8000 controls the exhaust channels of each layer of the pressure head 4000 to connect to the external gas collection device 1004.

[0144] As the gas supply system stops injecting gas, the internal pressure of the pores in coal sample 5000 decreases, and the adsorbed gas gradually desorbs into a free state. Driven by the pressure difference, the free gas and the residual gas in the pipeline seep towards the bottom of coal sample 5000 and enter the gas collection device 1004 through the exhaust channel of the corresponding layer of the lower pressure head 4000.

[0145] During the exhaust gas recovery process, the control terminal 8000 acquires the monitoring data from the pressure sensor and flow meter on the exhaust pipeline, and adjusts the opening of the exhaust valve or the exhaust gas recovery intensity according to the exhaust pressure and exhaust flow, so that the residual gas enters the gas collection device 1004 through the corresponding exhaust channel of the lower pressure head 4000.

[0146] When the monitoring pressure at each floor's exhaust channel drops to near the ambient atmospheric pressure, and the exhaust flow rate at each floor or the total exhaust flow rate is lower than the preset residual flow rate threshold, the control terminal 8000 determines that the residual gas recovery in the pipeline and inside the coal sample 5000 is complete.

[0147] The residual flow threshold is a positive value set based on the lower limit of the flow meter measurement, and the same residual flow threshold judgment standard is used in the same group of comparative tests. After the judgment is completed, the control terminal 8000 closes the valve of the pipeline where the exhaust port is located.

[0148] For the recovery and treatment of exhaust gas, those skilled in the art can use conventional vacuum pumps and gas collection devices, which are well-known technologies in the field and will not be described in detail here.

[0149] Reference Appendix Figure 5 As a specific implementation of step S60, the following steps are performed for the integral calculation of the apparent adsorption response of gas stratification and the inversion process of heterogeneous structure:

[0150] S601, the control terminal 8000 calls the multi-channel flow monitoring time-series data stored in the data module during the test cycle. For the entire cycle from the start of the test until the system determines that the dynamic equilibrium state of gas adsorption and seepage has been reached, the control terminal 8000 performs cumulative calculations on the real-time gas injection flow data of the inner gas injection interface 3002, the middle gas injection interface 3001, and the outer gas injection interface 3003 over time, based on the acquired time-series data, to obtain the cumulative gas injection volume of the above three independent gas injection channels during the test cycle.

[0151] Based on the same calculation logic, the control terminal 8000 performs cumulative calculations on the real-time outflow data of the inner exhaust channel, the middle exhaust channel and the outer exhaust channel over time to obtain the cumulative exhaust volume of each exhaust channel during the test period.

[0152] Apparent adsorption response of each layer Calculate using the following formula:

[0153] ;

[0154] In the formula, For the first Apparent adsorption response of the layer; For the first Real-time gas injection flow rate of the layer; For the first Real-time exhaust flow rate of the floor; For the first Correction values ​​for dead volume of the pipeline, free gas in the pores of the coal sample, and residual gas; The time for integration.

[0155] If the three exhaust channels are switched to the same flow detection unit through independent valves, the control terminal 8000 records the exhaust volume of each channel according to the valve switching sequence. Before performing the cumulative calculation, the control terminal 8000 converts all the acquired flow data to a standard state based on the ambient temperature and pressure to unify the calculation benchmark.

[0156] S602, after acquiring the cumulative gas data of each independent channel, the control terminal 8000 calculates the overall apparent adsorption amount of coal sample 5000 under the current radial pressure conditions based on the principle of gas mass conservation.

[0157] The control terminal 8000 sums up the cumulative gas injection volume of the inner, middle and outer layers to obtain the total injection volume input to the coal sample 5000 by the system; at the same time, it sums up the cumulative exhaust volume of the inner, middle and outer layers to obtain the total exhaust volume discharged from the coal sample 5000 by the system.

[0158] The difference between the total injection volume and the total exhaust volume was then calculated. This difference reflects the total amount of gas retained in the pores of coal sample 5000, the dead volume of the pipeline, and the amount of gas adsorbed on the surface of the coal matrix during the test period, and can be used as the overall apparent adsorption amount of coal sample 5000 under the test conditions.

[0159] The cumulative net injection volume of each layer is used to characterize the apparent adsorption-permeation response of the corresponding layer boundary, and is not directly equivalent to the physically isolated independent adsorption region inside coal sample 5000.

[0160] If it is necessary to obtain the corrected true adsorption amount, the control terminal 8000 will subtract the residual dead volume of the pipeline, the amount of free gas in the coal sample pores, and the amount of gas pre-stored in the system from the above difference to obtain the corrected adsorption amount of coal sample 5000 under the current pressure boundary and stress state.

[0161] S603, the control terminal 8000 extracts independently acquired cumulative gas injection volume data, cumulative gas exhaust volume data, target pressure, actual monitoring pressure, and stress parameters applied by the triaxial loading chamber 1000 for the corresponding layers, and performs inversion of the radial heterogeneous characteristics of coal and rock.

[0162] In the non-gradient evaluation mode, the control terminal 8000 sets the inner layer, middle layer and outer layer to the same or equivalent injection pressure boundary, and calculates the percentage weight of the cumulative net injection volume of each layer in the total net injection volume.

[0163] If the cumulative net injection volume of a certain radial concentric circle is higher than that of other concentric circles, it indicates that the pore and microfracture network in the 5000 region of the coal sample corresponding to that concentric circle is well developed, has good fluid connectivity, and strong local permeability.

[0164] In gradient seepage mode, after the control terminal 8000 normalizes the injection pressure, exhaust pressure, effective flow area and flow path of each layer, the radial structure difference of coal sample 5000 is evaluated based on the flow response difference of each layer.

[0165] The effective flow area of ​​each layer is determined by the radial area corresponding to the three annular grooves on the end face of the upper pressure head 3000 and the lower pressure head 4000. The flow path is determined by the seepage path between the annular air inlet groove and the annular air outlet groove of the corresponding layer. This avoids directly judging the local permeability based solely on the cumulative gas injection volume when the injection pressures of the three layers are not equal.

[0166] Based on the mapping relationship between the cumulative net injection volume of each layer, pressure boundary, and stress state, the control terminal 8000 constructs the radial structural difference evaluation results of the raw coal medium under the current triaxial stress state. Among them, the cumulative net injection volume of each layer is the result of subtracting the cumulative gas discharge volume and the residual gas correction volume of the corresponding layer from the cumulative gas injection volume of the corresponding layer.

[0167] For specific numerical iterative models for inverting the local permeability distribution inside coal and rock based on layered pressure boundary and flow test data, those skilled in the art can use conventional Darcy's law extension models and heterogeneous fluid-structure coupling equations to achieve this, which are well-known techniques in the field and will not be elaborated here.

[0168] The inputs to the inversion process include the target pressure of each layer, the actual monitored pressure, the cumulative net injection volume, the cumulative exhaust volume, the exhaust pressure, the stress parameters, and the test time. The outputs include the apparent permeability response differences or relative permeability evaluation results of 5000 different radial regions of the coal sample.

Claims

1. A three-dimensional gas aeration and seepage coordinated control device for coal samples, characterized in that, include: The triaxial loading chamber (1000) is equipped with an upper pressure head (3000) and a lower pressure head (4000); the lower pressure head (4000) is provided with a layered exhaust port and inner, middle and outer exhaust channels that are isolated from each other; A breathable insulating sleeve is placed between the upper pressure head (3000) and the lower pressure head (4000) to cover the coal sample (5000). It consists of an outer shell (7000) and an e-PTFE rubber composite semi-permeable membrane (1100). The inner air guide branch, the middle air guide branch, and the outer air guide branch are respectively connected to the upper pressure head (3000), and each is equipped with a pressure regulating valve (1002), a flow sensor (1001), and a pressure sensor; Each layer of exhaust pipes is connected to the corresponding layered exhaust port and the gas collection device (1004), and each of the exhaust pipes is equipped with a valve, a flow meter and a pressure sensor; A confining pressure loading system (2000) is connected to the triaxial loading chamber (1000) for injecting a liquid-phase confining pressure medium; The control terminal (8000) is connected to the confining pressure loading system (2000), each of the pressure regulating valves (1002), each of the valves, each of the flow sensors (1001), each of the flow meters and each of the pressure sensors.

2. The three-dimensional gas aeration and seepage coordinated control device for coal samples according to claim 1, characterized in that, The outer shell (7000) is a pressure-transmitting support structure configured with pressure-transmitting orifices or support windows; The e-PTFE rubber composite semi-permeable membrane (1100) is located between the confining pressure medium and the coal sample (5000) to prevent the liquid phase confining pressure medium from entering the coal sample (5000) and to maintain the air-connected state of the seepage pores on the radial surface of the coal sample (5000).

3. The three-dimensional gas aeration and seepage coordinated control device for coal samples according to claim 1, characterized in that, The upper pressure head (3000) and the lower pressure head (4000) are each provided with three layers of annular grooves and radial vent holes on their opposite end faces.

4. The three-dimensional gas aeration and seepage coordinated control device for coal samples according to claim 1, characterized in that, The device also includes a vacuum system (9000) connected to the internal gas path of the triaxial loading chamber (1000).

5. The three-dimensional gas aeration and seepage coordinated control device for coal samples according to claim 1, characterized in that, The control terminal (8000) can collect data from the pressure sensor and flow sensor (1001) on each of the gas guide branches, and adjust the opening degree of the corresponding pressure regulating valve (1002) to build a pressure gradient in the radial direction of the coal sample (5000).

6. A method for coordinated control of three-dimensional gas aeration and seepage in coal samples, applied to the coordinated control device for three-dimensional gas aeration and seepage in coal samples as described in any one of claims 1 to 5, characterized in that, Includes the following steps: The coal sample (5000) is loaded into the triaxial loading chamber (1000), and the outside is fitted with the breathable isolation sleeve to control the upper pressure head (3000) and the lower pressure head (4000) to fit in contact with the coal sample (5000); Inject confining pressure medium into the triaxial loading chamber (1000), apply a preset confining pressure and axial pressure, so that the actual liquid phase pressure difference on both sides of the e-PTFE rubber composite semipermeable membrane (1100) is less than the preset breakthrough pressure; Set the target gas pressure and flow thresholds for the inner, middle and outer gas guide branches, and inject the gas into the coal sample (5000) through the corresponding gas guide branches. When the gas pressure and flow data of each of the gas guide branches remain stable at a preset threshold, the control terminal (8000) determines that a dynamic balance state has been reached and controls the corresponding gas guide branch to enter a pressure holding control state. After the test is completed, stop the gas injection, unload the axial pressure and confining pressure, and control each of the exhaust pipes to be connected to the gas collection device (1004) for exhaust gas recovery; when the exhaust flow rate is lower than the preset residual flow rate threshold, close the valves on each of the exhaust pipes. Based on the time-series data composed of the collected flow data, the integral calculation of gas adsorption capacity and the evaluation of the radial heterogeneous structure of the coal sample are performed.

7. The method for coordinated control of three-dimensional gas aeration and seepage in coal samples according to claim 6, characterized in that, The specific process for ensuring that the actual liquid phase pressure difference across the e-PTFE rubber composite semi-permeable membrane (1100) is less than the preset breakthrough pressure is as follows: The preset breakthrough pressure is calculated based on the surface tension of the confining medium, the contact angle between the confining medium and the membrane material, and the micropore radius, using the Young-Laplace equation. Simultaneously monitor pressure data on both sides to maintain the actual liquid phase pressure difference below the preset breakthrough pressure.

8. The method for coordinated control of three-dimensional gas aeration and seepage in coal samples according to claim 6, characterized in that, The determination that a dynamic equilibrium state has been reached is specifically achieved through the following process: Obtain the total injection flow rate through each of the aforementioned air guide branches and the total outflow flow rate through each of the aforementioned exhaust pipes, calculate the absolute value of the difference between the two and compare it with a set error threshold; When the absolute value is less than or equal to the set error threshold, and the pressure monitoring value of each of the air guide branches is within the target pressure tolerance range, and the above conditions are continuously met within the set time window, it is determined that a dynamic equilibrium state has been reached.

9. The method for coordinated control of three-dimensional gas aeration and seepage in coal samples according to claim 6, characterized in that, The specific process for exhaust gas recovery is as follows: The control terminal (8000) acquires monitoring data from each exhaust pipe and adjusts the valve opening on each exhaust pipe according to the exhaust pressure and exhaust flow rate, so that residual gas enters the gas collection device (1004).

10. The method for coordinated control of three-dimensional gas aeration and seepage in coal samples according to claim 6, characterized in that, The calculation of gas adsorption capacity integral and the evaluation of radial heterogeneous structure of coal samples include: The real-time injection flow rate of each of the aforementioned air guide branches and the real-time exhaust flow rate of each of the aforementioned exhaust channels are accumulated over time to obtain the cumulative injection volume and cumulative exhaust volume of each layer respectively. The cumulative injection volume and cumulative exhaust volume of each layer are summed to obtain the total injection volume and total exhaust volume, and the difference between the two is calculated as the overall apparent adsorption volume. Subtract the cumulative gas injection volume of the corresponding layer from the cumulative gas exhaust volume of each layer, and deduct the correction amount of the dead volume of the pipeline of the corresponding layer, the free gas in the coal sample pores and the residual gas from the obtained difference to obtain the cumulative net injection volume of each layer. The total net injection amount is obtained by summing the cumulative net injection amounts of each layer. Calculate the percentage weight of the cumulative net injection volume of each layer in the total net injection volume to evaluate the radial structure differences of the coal sample (5000).

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