Simulation experiment system and method for gas desorption dynamic behavior of water-flooded coal seam in closed coal mine

Abstract

This invention belongs to the technical field of simulation experiments for water-flooded coal seams in closed coal mines. It proposes a simulation experimental system and method for the dynamic behavior of gas desorption in water-flooded coal seams in closed coal mines. The experimental system includes an experimental chamber, a stress loading device, a methane supply module, a water injection module, a gas desorption testing device, a monitoring unit, and a control system. The gas desorption testing device monitors the concentration and flow rate of desorbed gas. The monitoring unit includes a pressure sensor, a water level sensor, and a humidity sensor array. The humidity sensor array is used to monitor the wettability of the coal sample surface. This invention provides an experimental system capable of simulating gas desorption during water flooding of gas-bearing coal seams under the background of coal mine closure. This experimental system can more realistically reproduce the gas desorption situation under water flooding conditions, accurately simulate the gas desorption law during the flooding process, and provide effective data support, thereby providing a scientific basis for gas emission management and safety monitoring after coal mine closure.

Description

Technical Field

[0001] This invention belongs to the technical field of simulation experiments on water-flooded coal seams in closed coal mines, specifically relating to a simulation experiment system and method for dynamic behavior of gas desorption in water-flooded coal seams in closed coal mines. Background Technology

[0002] A closed coal mine refers to a coal mine that is closed and abandoned due to reasons such as depletion of coal resources, failure to meet safe mining conditions, or policy reasons. After the mine is closed, the coal seam is gradually submerged by mine water under the influence of groundwater levels and surface rainfall. The closure of the mine causes the underground coal seam to be flooded, creating a complex water pressure environment. During this process, the gas desorption behavior inside the coal seam is of great significance to the safety of the closed coal mine. In the existing technology, although there is some research on the gas desorption problem of water-flooded coal seams, there is a lack of experimental equipment that can realistically simulate the gas desorption process of water-flooded coal seams.

[0003] A search revealed no publicly available technical solutions similar to this invention. Summary of the Invention

[0004] The present invention aims to solve the technical problems existing in the prior art. The first objective of the present invention is to provide a simulation experimental system for the dynamic behavior of gas desorption in coal seams flooded by water in a closed coal mine. The second objective of the present invention is to provide an experimental method based on the aforementioned experimental system.

[0005] To achieve the first objective mentioned above, the present invention adopts the following technical solution: a simulated experimental system for dynamic behavior of gas desorption in coal seams submerged by water in a closed coal mine, comprising an experimental chamber, a methane supply module, a water injection module, a gas desorption testing device, a monitoring unit, and a control system; a clamp for fixing the coal sample is installed in the experimental chamber, and the clamp is connected to a stress loading device for applying ground stress to the coal sample; the methane supply module is connected to the gas injection port of the experimental chamber for injecting methane gas into the experimental chamber for the coal sample to adsorb methane gas; the water injection module is connected to the water injection port of the experimental chamber for injecting water into the experimental chamber to submerge the coal sample, and the enabling terminal of the water injection module is connected to the control system; the gas desorption testing device is connected to the sampling port of the experimental chamber, separating... The methane gas after water vaporization enters the gas desorption test device, which monitors the concentration and flow rate of the desorbed gas. The signal output terminal of the gas desorption test device is connected to the control system. The monitoring unit includes a pressure sensor in the experimental chamber, a water level sensor in the experimental chamber for monitoring water level changes, and several humidity sensors distributed along the height and circumference of the coal sample on its outer wall. The signal output terminal of the pressure sensor is connected to the pressure input terminal of the control system, the signal output terminal of the water level sensor is connected to the control system, and the several humidity sensors form a humidity sensor array. The humidity sensor array is used to monitor the wetness of the coal sample surface, and the signal output terminal of the humidity sensor array is connected to the humidity input terminal of the control system.

[0006] The above technical solution applies axial stress to the coal sample using a stress loading device to realistically simulate the in-situ stress of the coal seam in a closed coal mine; injects methane gas into the experimental chamber using a methane supply module to allow the coal sample to adsorb the methane gas; injects water into the experimental chamber using a water injection module to simulate the water-flooded coal seam in a closed coal mine; monitors the changes in methane concentration and flow rate during the desorption process using a gas desorption test device and transmits the data to the control system; and monitors the water level, water pressure, and surface humidity of the coal sample in the experimental chamber using sensors in the monitoring unit and transmits the data to the control system. A dynamic correlation model of water level, water pressure, methane desorption, and humidity is established using data analysis algorithms, and curves are generated in real time.

[0007] This invention provides an experimental system for simulating gas desorption during the flooding process of a gas-bearing coal seam under the background of coal mine closure. This experimental system can more realistically reproduce the gas desorption situation under the condition of coal seam flooding, accurately simulate the gas desorption law during the flooding process, and provide effective data support, thereby providing a scientific basis for gas emission management and safety monitoring after coal mine closure.

[0008] In a preferred embodiment of the present invention, the water inlet includes a bottom water inlet located at the bottom of the experimental chamber, the bottom water inlet being positioned below the bottom of the coal sample, and the water injection module having a water injection valve for controlling the opening and closing of each water inlet.

[0009] The above technical solution simulates water flooding of coal seams by setting up a bottom water injection port and using a bottom single-point water injection method.

[0010] In a preferred embodiment of the present invention, the bottom of the experimental chamber has a water injection buffer zone located below the coal sample. The water injection buffer zone is provided with a water injection buffer baffle, and the water injection buffer baffle is provided with a plurality of water passage holes. Water discharged from the bottom water injection port enters the experimental chamber above it after passing through the water injection buffer baffle.

[0011] The above technical solution minimizes the impact of high methane concentration at the top by having the water injection buffer plate directly transport methane gas upwards during the water injection process from the bottom water inlet, thus making the experimental results more accurate.

[0012] In a preferred embodiment of the present invention, the water inlet further includes a plurality of side water inlets spaced apart along the height direction of the experimental chamber, and the water injection module has a water injection valve for controlling the opening and closing of each water inlet.

[0013] The above technical solution, by adding multiple side water injection ports, can not only use bottom single-point water injection, but also carry out layer-by-layer water injection to simulate the infiltration of fissure water in the closed mine and the inflow of mine water in the adjacent goaf area; by comparing the gas desorption behavior of layer-by-layer water injection and bottom single-point water injection, the influence of layer-by-layer water injection on the coal body wettability and gas desorption behavior is analyzed, and the effect of layer-by-layer water injection on the efficiency of coal seam gas emission is evaluated.

[0014] In a preferred embodiment of the present invention, multiple water level sensors corresponding to multiple water injection ports are spaced apart along the height direction in the experimental chamber. The water level sensors are positioned above the corresponding water injection ports, and the uppermost water level sensor is positioned above the top of the coal sample. The control system controls the closing of the water injection valve of the corresponding water injection port based on the signal from the water level sensor.

[0015] In the above technical solution, the water level sensor is linked with the water injection valve of the water injection port. When studying the effect of layer-by-layer water injection on gas adsorption and desorption, when the water level reaches the water level sensor, the water injection valve will be linked to close the corresponding water injection port. After maintaining stability for a period of time, the water injection valve of the next water injection port will be linked to open, and water will be injected into the experimental chamber, thus realizing automatic layer-by-layer water injection.

[0016] To achieve the second objective mentioned above, the present invention adopts the following technical solution: an experimental method for simulating the dynamic behavior of gas desorption in a coal seam flooded by water in a coal mine, comprising the following steps:

[0017] S1. Coal sample preparation: Select a standard coal column as the coal sample, put it in the drying oven to dry, and ensure that the coal sample is completely dry. Install the coal sample into the holder of the experimental chamber, apply axial stress to the coal sample through the stress loading device, and attach the humidity sensor array to the surface of the coal sample.

[0018] S2. Coal sample gas adsorption: Methane gas is injected into the experimental chamber through the methane gas supply module, and a set static pressure is applied for a period of time until the coal sample reaches the gas adsorption saturation state. Then, the methane gas supply module is turned off to complete the coal sample gas adsorption.

[0019] S3. Inject water into the experimental chamber: Open the water inlet and slowly inject water into the experimental chamber until the water level rises to the first monitoring point. Keep it stable for a period of time, then continue to inject water to the second monitoring point. Repeat the stabilization process and continue to inject water layer by layer until the coal sample is completely submerged. Keep it stable for a period of time.

[0020] S4. Gas desorption: After the gas adsorption of the coal sample is completed, open the valve of the sampling port to introduce the methane gas desorbed from the coal sample into the gas desorption test device.

[0021] S5. Data Acquisition: A water level sensor is used to collect data on water level changes within the experimental chamber, generating data on the rate of water level rise; a humidity sensor array is used to collect real-time changes in the surface wetness of the coal sample, recording the rate of coal wetting expansion; a gas desorption test device is used to monitor the concentration and flow rate of desorbed gas, and a gas desorption rate curve is generated by combining the data with time; a pressure sensor is used to monitor the internal pressure of the experimental chamber in real time, and the impact of pressure changes on desorption behavior is recorded during the gas desorption process.

[0022] S6. Data analysis and processing: including dynamic simulation analysis of flooding, dynamic analysis of wetting diffusion, and modeling of gas desorption behavior;

[0023] Dynamic simulation analysis of flooding: Based on the data from the water level sensor, calculate the rate of rise of the water level in the experimental chamber over time; establish a dynamic model of water pressure and water level in the experimental chamber, and evaluate the response characteristics of gas desorption under different water pressure conditions;

[0024] Dynamic analysis of wetting diffusion: The distribution data of the humidity sensor array is mapped onto the surface of the coal sample to generate a three-dimensional wetting spread map; the relationship between the water absorption rate and the wetting depth of the coal sample is calculated through curve fitting; the hysteretic effect of the wetting process inside the coal body on the gas desorption rate is analyzed.

[0025] Modeling of gas desorption behavior: Combining gas concentration and flow rate data to generate a desorption amount-time curve, which is the gas desorption rate curve; dividing the desorption process into stages based on the water level changes in the experimental chamber during the experiment; fitting the relationship between the desorption rate and water pressure and the surface wettability of the coal sample to establish a desorption kinetic model;

[0026] S7. Results Output: Based on data analysis and processing, output the experimental report.

[0027] In another preferred embodiment of the present invention, n pressure sensors are spaced apart along the height direction of the test chamber, and all pressure sensors can be submerged in water. The water pressure P inside the test chamber is obtained in the following manner. avg :

[0028]

[0029] Where n is the number of pressure sensors, and Pi is the detection value of the i-th sensor.

[0030] The above technical solution uses multiple pressure sensors in the height direction to monitor water pressure and calculates the average value of the values ​​detected by multiple pressure sensors to obtain the water pressure in the experimental chamber, resulting in a more accurate result.

[0031] In another preferred embodiment of the present invention, in step S3, the water injection method includes two types: bottom single-point water injection and layer-by-layer water injection. Bottom single-point water injection involves injecting water into the experimental chamber only through the bottom water inlet. Layer-by-layer water injection involves first injecting water into the experimental chamber through the bottom water inlet until the water level rises to the first monitoring point and remains stable for a period of time. Then, water is injected through the side water inlet corresponding to the height of the first monitoring point to the second monitoring point, repeating the stabilization process. Then, water is injected through the side water inlet corresponding to the height of the second monitoring point to the third monitoring point, repeating the stabilization process. This layer-by-layer water injection continues until the coal sample is completely submerged and remains stable for a period of time. The gas desorption behavior of layer-by-layer water injection and bottom single-point water injection is compared to analyze the impact of layer-by-layer water injection on the coal body wettability and gas desorption behavior, and to evaluate the effect of layer-by-layer water injection on the efficiency of coal seam gas emission.

[0032] In another preferred embodiment of the present invention, during the data analysis and processing, multivariate regression analysis is used to couple the gas desorption amount with the water level rise rate, wetting expansion rate, and water pressure to establish a dynamic correlation model of "water level-water pressure-wetting-desorption"; the influence of different water injection rates on the gas desorption amount is analyzed to form a comparison chart.

[0033] In another preferred embodiment of the present invention, the wetting spread rate is obtained in the following manner:

[0034] W(t) = W0·(1-e -αt )

[0035] Among them, W (t) Let be the moisture content at time t, W0 be the final saturated moisture content, α be the fitting constant, and t be time.

[0036] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0037] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0038] Figure 1 This is a schematic diagram of the structure of the simulation experiment system for dynamic behavior of gas desorption in a coal seam under water flooding in Example 1.

[0039] Figure 2 This is a top view of the sensor arrangement in the experimental chamber.

[0040] Figure 3 This is a top view of the water-filled buffer partition in Embodiment 1.

[0041] The reference numerals in the accompanying drawings include: experimental chamber 10, water inlet 10a, top cover 11, water injection buffer zone 12, water injection buffer baffle 13, water passage 131, methane gas supply module 20, high-pressure gas cylinder 21, pressure reducing valve 22, gas injection pipe 23, gas injection valve 24, water injection module 30, water injection control system 31, water injection pipe 32, water injection valve 33, pressure gauge 34, gas desorption test device 40, sampling pipe 41, water vapor separator 42, sampling valve 43, control system 50, stress loading device 60, pressure sensor 71, water level sensor 72, humidity sensor 73, and coal sample A. Detailed Implementation

[0042] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0043] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "vertical", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0044] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0045] Example 1

[0046] This embodiment provides a simulation experiment system for the dynamic behavior of gas desorption in water-flooded coal seams in coal mines, such as... Figure 1As shown, in a preferred embodiment, the experimental system includes an experimental chamber 10, a methane supply module 20, a water injection module 30, a gas desorption testing device 40, a monitoring unit, and a control system 50. The experimental chamber 10 is a high-strength stainless steel cylinder with a diameter of 15 cm and a height of 30 cm, specifically corrosion-resistant and with a pressure resistance of up to 20 MPa. A cap for sealing its top opening is detachably connected to the top of the experimental chamber 10. A clamp for fixing coal sample A is installed in the experimental chamber 10. The clamp is connected to a stress loading device 60 for applying ground stress to coal sample A. The clamp holds coal sample A securely from above and below, and the stress loading device 60 uniformly transmits top pressure to coal sample A to simulate ground stress.

[0047] The methane supply module 20 is connected to the gas injection port at the top of the experimental chamber 10 and is used to inject methane gas into the experimental chamber 10 for coal sample A to adsorb methane gas. Specifically, the methane supply module 20 includes a high-pressure gas cylinder 21 containing methane gas. The outlet of the high-pressure gas cylinder 21 is connected to the gas injection port through a gas injection pipe 23. The gas injection port is located on the cap. The gas injection pipe 23 is equipped with a pressure valve and a gas injection valve 24, with the gas injection valve 24 located near the gas injection port.

[0048] The water injection module 30 is connected to the water injection port 10a of the experimental chamber 10 and is used to inject water into the experimental chamber 10 to submerge the coal sample A. The enable terminal of the water injection module 30 is connected to the control system 50. Specifically, the water injection module 30 includes a water injection control system 31. The outlet of the water injection control system 31 is connected to the water injection port 10a through a water injection pipe 32. The water injection port 10a is located at the bottom and / or side wall of the experimental chamber 10. The water injection pipe 32 is equipped with a pressure gauge 34 and a water injection valve 33. The water injection valve 33 is an electric regulating valve used to regulate the water injection rate and water injection pressure.

[0049] The gas desorption testing device 40 is connected to the sampling port of the experimental chamber 10. Methane gas after water vapor separation enters the gas desorption testing device 40 through the sampling port. The gas desorption testing device 40 monitors the concentration and flow rate of the desorbed gas. The signal output terminal of the gas desorption testing device 40 is connected to the control system 50. The sampling port is located on the cover and is connected to the gas desorption testing device 40 via a sampling tube 41. The sampling tube 41 has a valve near the sampling port; this valve is a one-way flow sampling valve 43. A water vapor separator 42 is also installed on the sampling tube 41. The methane gas after water vapor separation by the water vapor separator 42 enters the gas desorption testing device 40. The gas desorption testing device 40 contains a built-in gas concentration sensor and flow meter to record changes in the concentration and flow rate of the desorbed gas in real time.

[0050] The monitoring unit includes a pressure sensor 71 installed in the experimental chamber 10, a water level sensor 72 installed in the experimental chamber 10 for monitoring water level changes, and several humidity sensors 73 distributed along the height and circumference of the outer wall of the coal sample A. Multiple pressure sensors 71 are arranged along the height of the experimental chamber 10, and all pressure sensors 71 can be submerged in water. For example, one pressure sensor 71 can be installed near the bottom, middle, and top of the coal sample A. The pressure sensors 71 can also be spaced apart along the circumference of the coal sample. The signal output of the pressure sensors 71 is connected to the pressure input of the control system 50. Multiple water level sensors 72 are also arranged along the height of the experimental chamber 10, and can also be spaced apart along the circumference of the coal sample. The signal output of the water level sensors 72 is connected to the control system 50. Several humidity sensors 73 form a humidity sensor 73 array (combined with...). Figure 2 As shown, multiple rings of humidity sensors 73 can be set along the height direction of coal sample A, with each ring having multiple humidity sensors 73 arranged circumferentially. The array of humidity sensors 73 is used to monitor the wetness of the surface of coal sample A. The signal output terminal of the array of humidity sensors 73 is connected to the humidity input terminal of the control system 50.

[0051] like Figure 1 As shown, in one embodiment of the present invention, the water injection port 10a includes a bottom water injection port 10a located at the bottom of the experimental chamber 10. The bottom water injection port 10a is positioned lower than the bottom of the coal sample A. The water injection module 30 has a water injection valve 33 for controlling the opening and closing of each water injection port 10a, thereby enabling single-point bottom water injection through the bottom water injection port 10a. Preferably, the bottom of the experimental chamber 10 has a water injection buffer zone 12 located below the coal sample A, and the water injection buffer zone 12 is provided with a water injection buffer baffle 13, such as... Figure 3 As shown, the water injection buffer plate 13 is provided with several water passage holes 131. Water discharged from the bottom water injection port 10a enters the experimental chamber 10 above it after passing through the water injection buffer plate 13.

[0052] In another preferred embodiment, the water inlet 10a further includes a plurality of side water inlets 10a spaced apart along the height direction of the experimental chamber 10. The water inlet pipe 32 of the water injection module 30 is provided with a water injection valve 33 for controlling the opening and closing of each water inlet 10a, and the water injection rate and water injection pressure are adjusted by the water injection valve 33. The bottom water inlet 10a and the side water inlets 10a are arranged in parallel and can be opened in a selective manner. For example, two side water inlets 10a are set, for a total of three water inlets 10a, which are arranged from bottom to top as the first water inlet 10a, the second water inlet 10a and the third water inlet 10a. The three water inlets 10a are equidistant along the height direction, which can realize layer-by-layer water injection to simulate the closure of the seepage of fracture water in the mine and the inflow of mine water in the adjacent goaf.

[0053] More preferably, the experimental chamber 10 is provided with multiple water level sensors 72 at intervals along the height direction, corresponding to multiple water injection ports 10a. The position of the water level sensors 72 is higher than the corresponding water injection port 10a, and the position of the uppermost water level sensor 72 is higher than the top of the coal sample A. The control system 50 controls the closing of the water injection valve 33 of the corresponding water injection port 10a according to the signal of the water level sensor 72. Three water injection ports 10a are provided with three water level sensors 72, with the first water injection port 10a from bottom to top corresponding to the first water level sensor 72 from bottom to top, and so on. When water is injected layer by layer, when the water injected into the first water injection port 10a reaches the first water level sensor 72, if the effect of layer by layer water injection on gas adsorption and desorption is to be studied, the water injection valve 33 will be activated to close the first water injection port 10a when the water level reaches the first water level sensor 72. After remaining stable for 30 minutes, the water injection valve 33 of the second water injection port 10a will be activated to inject water into the experimental chamber 10, and so on.

[0054] Example 2

[0055] This embodiment provides an experimental method for simulating the dynamic behavior of gas desorption in a water-flooded coal seam in a closed coal mine, based on Embodiment 1, including the following steps:

[0056] S1. Preparation of coal sample A: Select a standard coal column with a diameter of 5cm and a height of 10cm as coal sample A, and dry it in a drying oven for 24 hours to ensure that coal sample A is completely dry; install coal sample A into the holder of experimental chamber 10, and apply axial stress to coal sample A through stress loading device 60 to realistically simulate the in-situ stress of coal seams in closed coal mines; calibrate humidity sensor 73, attach the humidity sensor 73 array to the surface of coal sample A to ensure stable signal output.

[0057] S2. Gas adsorption of coal sample A: Methane gas is injected into the experimental chamber 10 through the methane supply module 20, and a static pressure of a set value (e.g., 2 MPa, detected by the pressure sensor 71 in the experimental chamber 10, specifically the average value of multiple pressure sensor 71 values) is applied for a period of time, such as 12 hours, so that coal sample A reaches the gas adsorption saturation state. Then the methane supply module 20 is turned off to complete the gas adsorption of coal sample A.

[0058] S3. Inject water into experimental chamber 10: Open water inlet 10a and slowly inject water into experimental chamber 10 until the water level rises to the first monitoring point (monitored by water level sensor 72), and keep it stable for a period of time, such as 30 minutes; then continue to inject water to the second monitoring point, repeat the stabilization process (stabilize for 30 minutes), and continue to inject water layer by layer until the water completely submerges coal sample A, and keep it stable for a period of time (stabilize for 30 minutes).

[0059] S4. Gas desorption: After the gas adsorption of coal sample A is completed, the sampling valve 43 of the sampling port is opened. The methane gas desorbed from coal sample A is separated into water vapor by the water vapor separator 42 and introduced into the gas desorption test device 40 through the sampling pipe 41. The gas desorption test device 40 monitors the changes in gas concentration and flow rate.

[0060] S5. Data Acquisition: The water level sensor 72 is used to collect the water level changes in the experimental chamber 10, generate water level rise rate data, and generate a real-time change curve; the humidity sensor array 73 is used to collect the real-time changes in the surface wetness of coal sample A, record the coal body wetting expansion rate, and generate a real-time change curve; the gas desorption test device 40 is used to monitor the concentration and flow rate of desorbed gas, and generate a gas desorption rate curve in combination with time; the pressure sensor 71 is used to monitor the internal pressure of the experimental chamber 10 in real time, and record the influence of pressure changes on desorption behavior during the gas desorption process.

[0061] Data from all sensors is transmitted via wireless communication modules to the central data processing unit of the control system 50, where dynamic changes are recorded using a high-frequency sampling rate (e.g., once per second). Noise signals are removed using filtering algorithms (e.g., Kalman filtering); the outputs (units and ranges) of different sensors are standardized to ensure data consistency; and timestamps are used to align multi-parameter data to form a time series.

[0062] S6. Data Analysis and Processing: This includes dynamic simulation analysis of flooding, dynamic analysis of wetting diffusion, and modeling of gas desorption behavior, as detailed below:

[0063] Flooding Dynamic Simulation Analysis: Based on data from water level sensor 72, the rate of rise of water level in experimental chamber 10 over time is calculated; a dynamic model of water pressure (measured by pressure sensor 71 within experimental chamber 10) and water level is established to evaluate the response characteristics of gas desorption under different water pressure conditions. Specifically, the water pressure P in the experimental chamber can be obtained through the following methods. avg :

[0064]

[0065] Where n is the number of pressure sensors, and Pi is the detection value of the i-th sensor.

[0066] Dynamic analysis of wetting diffusion: The distribution data of the 73-array humidity sensor is mapped onto the surface of coal sample A to generate a three-dimensional wetting diffusion map; the relationship between the water absorption rate and the wetting depth of coal sample A is calculated by curve fitting; the hysteretic effect of the internal wetting process of the coal body on the gas desorption rate is analyzed.

[0067] Modeling of gas desorption behavior: The gas concentration and flow rate data are combined to generate a desorption amount-time curve, which is the gas desorption rate curve; the desorption process is divided into stages based on the water level changes in the experimental chamber 10 during the experiment; the Langmuir equation is used to extend the model and fit the relationship between the desorption rate and water pressure and the surface wettability of coal sample A to establish a desorption kinetic model.

[0068] S7. Results Output: Based on data analysis and processing, output the experimental report.

[0069] In step S3 of this invention, the water injection method includes two types: bottom single-point water injection and layer-by-layer water injection. Bottom single-point water injection involves slowly injecting water into the experimental chamber 10 only through the bottom water injection port 10a. Layer-by-layer water injection involves first injecting water into the experimental chamber 10 through the first bottom water injection port 10a until the water level rises to the first monitoring point of the first water level sensor 72, maintaining stability for 30 minutes, then continuing to inject water through the second water injection port 10a to the second monitoring point of the second water level sensor 72, repeating the stabilization process, and then continuing to inject water through the third water injection port 10a to the third monitoring point of the second water level sensor 72, repeating the stabilization process, continuously injecting water layer by layer until the coal sample A is completely submerged and maintained stable for a period of time.

[0070] Comparative analysis of layer-by-layer water injection and bottom single-point water injection: The gas desorption behavior of layer-by-layer water injection and bottom single-point water injection is compared. The influence of layer-by-layer water injection on the coal seam wettability and gas desorption behavior is analyzed, and the effect of layer-by-layer water injection on the efficiency of coal seam gas emission is evaluated. Statistical significance analysis (such as ANOVA) is used to verify the difference in desorption rate between different water injection methods.

[0071] In step S6 of this invention, during the data analysis and processing, multivariate regression analysis is used to couple the gas desorption amount with the water level rise rate, wetting expansion rate, and water pressure to establish a dynamic correlation model of "water level-water pressure-wetting-desorption" and generate curves in real time; the influence of different water injection rates on the gas desorption amount is analyzed to form a comparison chart.

[0072] In reality, the water flooding process of coal seams is typically a dynamic and nonlinear wetting expansion process. In the experiment, humidity sensor 73 monitors the surface wettability of coal sample A in real time, providing continuous humidity data. Based on the wettability recorded by humidity sensor 73 (usually relative humidity or moisture content), the water absorption rate is fitted to reflect the wetting expansion rate. For example, the wetting expansion rate is usually fitted using an exponential or linear equation, as shown in the following formula:

[0073] W(t) = W0·(1-e -αt )

[0074] Among them, W (t)Let be the moisture content at time t, W0 be the final saturated moisture content, α be the fitting constant, and t be time.

[0075] In the description of this specification, references to terms such as "preferred embodiment," "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0076] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A simulation experiment system for the dynamic behavior of gas desorption in water-flooded coal seams in coal mines, characterized in that: It includes an experimental chamber, a methane supply module, a water injection module, a gas desorption test device, a monitoring unit, and a control system; The experimental chamber is equipped with a clamp for fixing the coal sample, and the clamp is connected to a stress loading device for applying ground stress to the coal sample. The methane supply module is connected to the gas injection port of the experimental chamber and is used to inject methane gas into the experimental chamber so that the coal sample can adsorb the methane gas. The water injection module is connected to the water injection port of the experimental chamber and is used to inject water into the experimental chamber to submerge the coal sample. The enable terminal of the water injection module is connected to the control system. The gas desorption test device is connected to the sampling port of the experimental chamber. The methane gas after water vapor separation enters the gas desorption test device, which monitors the concentration and flow rate of the desorbed gas. The signal output terminal of the gas desorption test device is connected to the control system. The monitoring unit includes a pressure sensor installed in the experimental chamber, a water level sensor installed in the experimental chamber to monitor water level changes, and several humidity sensors distributed along the height and circumference of the coal sample on its outer wall. The signal output terminal of the pressure sensor is connected to the pressure input terminal of the control system, the signal output terminal of the water level sensor is connected to the control system, and the several humidity sensors form a humidity sensor array. The humidity sensor array is used to monitor the wetness of the coal sample surface, and the signal output terminal of the humidity sensor array is connected to the humidity input terminal of the control system.

2. The simulation experimental system for dynamic behavior of gas desorption in water-flooded coal seams according to claim 1, characterized in that, The water inlet includes a bottom water inlet located at the bottom of the experimental chamber, which is positioned below the bottom of the coal sample. The water injection module has a water injection valve for controlling the opening and closing of each water inlet.

3. The simulation experimental system for dynamic behavior of gas desorption in water-flooded coal seams according to claim 2, characterized in that, The bottom of the experimental chamber has a water injection buffer zone located below the coal sample. The water injection buffer zone is equipped with a water injection buffer baffle, which has several water passage holes. Water discharged from the bottom water injection port passes through the water injection buffer baffle and enters the experimental chamber above it.

4. The simulation experimental system for dynamic behavior of gas desorption in water-flooded coal seams according to claim 2, characterized in that, The water inlet also includes multiple side water inlets spaced apart along the height of the experimental chamber, and the water injection module has a water injection valve for controlling the opening and closing of each water inlet.

5. The simulation experimental system for dynamic behavior of gas desorption in water-flooded coal seams according to claim 4, characterized in that, The experimental chamber is equipped with multiple water level sensors at intervals along the height direction, corresponding to multiple water injection ports. The water level sensors are positioned above their respective water injection ports, with the uppermost water level sensor positioned above the top of the coal sample. The control system controls the closing of the water injection valve of the corresponding water injection port based on the signals from the water level sensors.

6. An experimental method based on any one of the simulation experimental systems for the dynamic behavior of gas desorption in water-flooded coal seams in coal mines, as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Coal sample preparation: Select a standard coal column as the coal sample, put it in the drying oven to dry, and ensure that the coal sample is completely dry. Install the coal sample into the holder of the experimental chamber, apply axial stress to the coal sample through the stress loading device, and attach the humidity sensor array to the surface of the coal sample. S2. Coal sample gas adsorption: Methane gas is injected into the experimental chamber through the methane gas supply module, and a set static pressure is applied for a period of time until the coal sample reaches the gas adsorption saturation state. Then, the methane gas supply module is turned off to complete the coal sample gas adsorption. S3. Inject water into the experimental chamber: Open the water inlet and slowly inject water into the experimental chamber until the water level rises to the first monitoring point. Keep it stable for a period of time, then continue to inject water to the second monitoring point. Repeat the stabilization process and continue to inject water layer by layer until the coal sample is completely submerged. Keep it stable for a period of time. S4. Gas desorption: After the gas adsorption of the coal sample is completed, open the valve of the sampling port to introduce the methane gas desorbed from the coal sample into the gas desorption test device. S5. Data Acquisition: A water level sensor is used to collect data on water level changes within the experimental chamber, generating data on the rate of water level rise; a humidity sensor array is used to collect real-time changes in the surface wetness of the coal sample, recording the rate of coal wetting expansion; a gas desorption test device is used to monitor the concentration and flow rate of desorbed gas, and a gas desorption rate curve is generated by combining the data with time; a pressure sensor is used to monitor the internal pressure of the experimental chamber in real time, and the impact of pressure changes on desorption behavior is recorded during the gas desorption process. S6. Data analysis and processing: including dynamic simulation analysis of flooding, dynamic analysis of wetting diffusion, and modeling of gas desorption behavior; Dynamic simulation analysis of flooding: Based on the data from the water level sensor, calculate the rate of rise of the water level in the experimental chamber over time; establish a dynamic model of water pressure and water level in the experimental chamber, and evaluate the response characteristics of gas desorption under different water pressure conditions; Dynamic analysis of wetting diffusion: The distribution data of the humidity sensor array is mapped onto the surface of the coal sample to generate a three-dimensional wetting spread map; the relationship between the water absorption rate and the wetting depth of the coal sample is calculated through curve fitting; the hysteretic effect of the wetting process inside the coal body on the gas desorption rate is analyzed. Modeling of gas desorption behavior: Combining gas concentration and flow data to generate a desorption amount-time curve, which is the gas desorption rate curve; Based on the changes in water level in the experimental chamber during the experiment, the desorption process was divided into stages; the relationship between the desorption rate and water pressure and the wettability of the coal sample surface was fitted, and a desorption kinetic model was established. S7. Results Output: Based on data analysis and processing, output the experimental report.

7. The experimental method according to claim 6, characterized in that, n pressure sensors are spaced at intervals along the height of the experimental chamber, and all pressure sensors can be submerged in water. The water pressure P inside the experimental chamber is obtained in the following manner. avg : Where n is the number of pressure sensors, and Pi is the detection value of the i-th sensor.

8. The experimental method according to claim 6, characterized in that, In step S3, the water injection methods include two types: bottom single-point water injection and layer-by-layer water injection; Among them, bottom single-point water injection means injecting water into the experimental chamber only through the bottom water injection port; The layer-by-layer water injection method involves first injecting water into the experimental chamber through the bottom water inlet until the water level rises to the first monitoring point and remains stable for a period of time. Then, water is injected through the side water inlet corresponding to the height of the first monitoring point to the second monitoring point, and the stabilization process is repeated. Then, water is injected through the side water inlet corresponding to the height of the second monitoring point to the third monitoring point, and the stabilization process is repeated. This layer-by-layer water injection continues until the coal sample is completely submerged and remains stable for a period of time. By comparing the gas desorption behavior of layer-by-layer water injection and bottom single-point water injection, the influence of layer-by-layer water injection on the coal seam wettability and gas desorption behavior is analyzed, and the effect of layer-by-layer water injection on the efficiency of coal seam gas emission is evaluated.

9. The experimental method according to any one of claims 6-8, characterized in that, During the data analysis and processing, multivariate regression analysis was used to couple the gas desorption amount with the water level rise rate, wetting expansion rate, and water pressure to establish a dynamic correlation model of "water level-water pressure-wetting-desorption"; the influence of different water injection rates on the gas desorption amount was analyzed and a comparison chart was generated.

10. The experimental method according to claim 9, characterized in that, The wetting spread rate is obtained in the following way: W(t)=W0·(1-e -αt ) Among them, W (t) Let be the moisture content at time t, W0 be the final saturated moisture content, α be the fitting constant, and t be time.

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