An in-situ separation and conversion system and method for coal mine gas in a mine

Abstract

This invention discloses an in-situ coal mine gas separation and conversion system and method. The conversion system includes: a plasma-activated gas injection module, located in the underground intake airway and connected to a nitrogen injection pipe, configured to inject an activated gas with adjustable composition into the coal seam to displace methane from the coal seam; and a membrane reaction module, located in the underground return airway and connected to a gas extraction pipe, configured to convert the extracted methane into syngas in situ. The membrane reaction module includes: a central reaction tube, a molecular sieve membrane, and a pressure-resistant sleeve arranged sequentially from the inside out. A cavity is formed between the pressure-resistant sleeve and the molecular sieve membrane, configured for the flow of raw material methane gas. The molecular sieve membrane is configured to sieve nitrogen from the raw material methane gas. A partially oxidizing catalyst layer is disposed on the inner wall of the central reaction tube, configured to react methane gas with oxygen to form syngas composed of carbon monoxide and hydrogen.

Description

Technical Field

[0001] This invention relates to the intersection of coal mine safety engineering and chemical process intensification, and particularly to an in-situ coal mine gas separation and conversion system and method. Background Technology

[0002] The "Coal Mine Safety Regulations" establish the ironclad rule of "extraction before mining" for safe production. However, during the pre-extraction period, which can last from several months to several years, the existing technical system suffers from irreconcilable structural contradictions and efficiency bottlenecks. The root cause lies in the "spatial misalignment" of the technical approach: First, the spatial paradox of safety versus economy: To ensure the safety of long-distance pipeline transportation from underground to the surface, high-value, high-concentration methane must be diluted, severely damaging its utilization quality and economic benefits; if high-concentration transportation is maintained, the entire transportation system itself constitutes a linear major hazard source running through the mine. This contradiction is unsolvable under the existing "surface treatment" model. Second, ineffective energy dissipation and process delays: Surface chemical plants must repressurize, cool (for cryogenic separation), or heat (for reactions) the methane from its underground state (atmospheric pressure, low temperature). The vast majority of the energy consumed is used to reverse the natural state change of the methane when it is raised to the surface, constituting a huge waste of energy circulation. At the same time, the long pipelines and multiple independent sections cause the system to respond slowly, unable to adapt to the instantaneous fluctuations in coal mine gas sources, resulting in poor operational stability. Furthermore, the governance process lacks synergy and value-added aspects: existing pre-extraction technologies focus solely on gas removal, lacking proactive intervention measures for coal seam damage (stress changes, fracture propagation) that may occur during the extraction process, potentially creating hidden dangers for secondary disasters. Simultaneously, the extracted gas has extremely low economic value because it cannot be efficiently utilized on-site, resulting in insufficient motivation for enterprise governance.

[0003] While existing research has made progress in membrane materials (such as ZIF-8) or catalyst performance, these are all local optimizations within the old paradigm of "surface treatment" and cannot solve the inherent safety, energy efficiency, and system synergy problems caused by "spatial displacement." Therefore, it is necessary to "sink" the core links of chemical conversion underground and complete the value conversion at the source of gas production, that is, to achieve true "in-situ conversion," in order to break through the existing technological framework. Summary of the Invention

[0004] This solution addresses the problems and needs raised above by proposing an in-situ separation and conversion system and method for coal mine gas. Due to the adoption of the following technical features, it can achieve the above-mentioned technical objectives and bring about several other technical benefits.

[0005] One object of the present invention is to provide an in-situ separation and conversion system for coal mine gas, comprising: The plasma activation gas injection module is located in the underground air intake roadway and is connected to the nitrogen injection pipe. It is configured to inject an activation gas with adjustable composition into the coal seam to displace methane from the coal seam. A membrane reaction module, located in the underground return airway and connected to the gas extraction pipe, is configured to convert extracted methane into syngas in situ and discharge it through the extraction pipe. The membrane reaction module comprises, from the inside out, a central reaction pipe, a molecular sieve membrane, and a pressure-resistant casing. A cavity is formed between the pressure-resistant sleeve and the molecular sieve membrane, and the cavity is configured to allow the flow of raw material methane gas. The molecular sieve membrane is configured to separate nitrogen from the raw material methane gas. The inner wall of the central reaction tube is provided with a partial oxidation catalyst layer, which is configured to react methane gas with oxygen to form synthesis gas of carbon monoxide and hydrogen.

[0006] In addition, the in-situ coal mine gas separation and conversion system according to the present invention may also have the following technical features: In one example of the present invention, it further includes: a data sensing module and a control module. The data sensing module is configured to sense information on the activity of fracture development in the roadway and the gas concentration and flow rate information in the extraction pipe. The control module is coupled to the data sensing module, the plasma activation and gas injection module, and the membrane reaction module, respectively. It is configured to receive information on fracture development activity and gas concentration and flow rate from the data sensing module and control the coordinated operation of the plasma activation and gas injection module and the membrane reaction module.

[0007] In one example of the present invention, the data sensing module includes: Microseismic sensors are configured to monitor the activity of fracture development in roadways; A gas concentration sensor is configured to monitor the gas concentration and flow rate information in the gas extraction pipelines of various areas. The control module dynamically adjusts the composition, pressure, and activation intensity of the plasma activation and injection module based on information on fracture development activity and gas concentration and flow rate to achieve the optimal methane gas conversion rate of the membrane reaction module.

[0008] In one example of the present invention, the membrane reaction module uses the underground formation pressure of the coal mine as the driving force for the raw material gas to pass through the molecular sieve membrane, and uses the reaction heat released by the partial oxidation reaction of methane to maintain the working temperature of the molecular sieve membrane through heat conduction.

[0009] In one example of the present invention, the molecular sieve membrane has a thickness of 20-50 μm, a separation selectivity for methane and nitrogen greater than 300, and a methane permeation flux greater than 100 GPU.

[0010] In one example of the present invention, the spacing between the molecular sieve membrane and the partially oxidized catalyst layer is less than 2 mm.

[0011] In one example of the present invention, the partial oxidation catalyst is a structured catalyst, the active component of which is a rhodium or nickel nanocluster confined within a cerium oxide shell, the nanocluster having a particle size of less than 2 nanometers; the structured catalyst is supported on a three-dimensional ordered macroporous CeO2-ZrO2 solid solution support.

[0012] In one example of the present invention, the plasma activation gas injection module includes a dielectric barrier discharge plasma generator configured to dynamically adjust the composition of the injected gas, wherein the adjustment ratio of nitrogen to carbon dioxide is between 40%:60% and 80%:20%.

[0013] Another object of the present invention is to provide a conversion method for an underground in-situ coal mine gas separation and conversion system as described above, comprising the following steps: Coal seam gas is extracted through a borehole network and transported entirely to the membrane reaction module, where methane is continuously separated and converted into syngas. The gas extraction parameters and coal seam mechanical state parameters are acquired and monitored. When the gas extraction parameters and coal seam mechanical state parameters indicate a decrease in extraction efficiency or a risk of coal seam instability, the parameters of the plasma-activated gas injection module are adjusted to implement directional gas injection intervention in the target coal seam area for the purpose of increasing permeability or stabilizing the coal seam.

[0014] In one example of the present invention, adjusting the parameters of the plasma activation gas injection module specifically includes: The gas extraction efficiency in low-permeability areas is improved by injecting plasma-activated carbon dioxide into the area; and the expansion of coal seam fractures is suppressed by injecting a higher proportion of high-pressure nitrogen into the area.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. A fundamental leap in safety: The spatial presence of high-concentration methane is compressed into an extremely short path: "coal wall fissures → short-distance extraction pipe → membrane reactor inlet". Once it enters the reactor, it is instantly converted into chemically inert syngas, completely eradicating the traditional biggest hazard source, the "underground high-concentration methane transportation system", and achieving a qualitative change from process safety to fundamental safety at the source.

[0016] 2. Revolutionary reduction in energy consumption: Directly utilizing the underground ground pressure (0.5-1.2 MPa) as the driving force for membrane separation eliminates the vast majority of the electrical energy required to pressurize the gas to the pressure at the surface plant (which typically requires several MPa). In-situ cascade utilization of reaction heat eliminates the need for the massive heat exchange and cooling systems at the surface plant. Overall energy consumption is expected to be 40%-50% lower than the surface cryogenic-conversion route.

[0017] 3. A fundamental shift in economic benefits: Membrane reactors directly convert low-value gas into high-value syngas underground, transforming gas pre-extraction projects from purely "safety cost centers" into "underground production units" with considerable profits, creating a new sustainable model of "using treatment to support treatment and creating benefits through treatment".

[0018] The preferred embodiments of the invention will be described in more detail below with reference to the accompanying drawings, so as to facilitate an understanding of the features and advantages of the invention. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. The drawings are merely illustrative of some embodiments of the present invention and are not intended to limit the scope of the present invention to all embodiments.

[0020] Figure 1 This is a schematic diagram of the structure of an underground in-situ gas separation and conversion system in coal mines according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of a membrane reaction module according to an embodiment of the present invention; Figure 3 This is a flowchart of the conversion method of the underground in-situ separation and conversion system for coal mine gas according to an embodiment of the present invention.

[0021] List of reference numerals in the attached diagram: Coal seam 200; Extraction tube 210; Nitrogen injection tube 220; Air intake tunnel 230; Return airway 240; Conversion System 100; Plasma activation gas injection module 10; Membrane reaction module 20; Central reaction tube 21; Partial oxidation catalyst layer 211; Molecular sieve membrane 22; Pressure-resistant sleeve 23; Oxygen pump assembly 24; Pipeline 241; Lumen 201; Control module 30; Data sensing module 40; Micro-vibration sensor 41; Gas concentration sensor 42; Extraction tube 50. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The same reference numerals in the drawings represent the same components. It should be noted that the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, “an” or “a” and similar terms do not necessarily indicate a quantity limitation. Terms such as “comprising” or “including” mean that the element or object preceding the word encompasses the element or object listed following the word and its equivalents, without excluding other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships; these relative positional relationships may change accordingly when the absolute position of the described object changes.

[0024] According to a first aspect of the present invention, a coal mine gas in-situ separation and conversion system 100 is provided, such as... Figure 1 and Figure 2 As shown, it includes: The plasma activation gas injection module 10 is located in the underground air intake roadway 230 and is connected to the nitrogen injection pipe 220. It is configured to inject an activation gas with adjustable composition into the coal seam 200 to displace methane from the coal seam 200. A membrane reaction module 20 is located in the underground return air roadway 240 and connected to the gas extraction pipe 210. It is configured to convert extracted methane into syngas in situ and discharge it through the extraction pipe 210. The membrane reaction module 20 includes, from the inside out, a central reaction pipe 21, a molecular sieve membrane 22, and a pressure-resistant sleeve 23. A cavity 201 is formed between the pressure-resistant sleeve 23 and the molecular sieve membrane 22. The cavity 201 is configured to allow the flow of raw material methane gas. In other words, the external pressure-resistant sleeve 23 and the molecular sieve membrane 22 form a cavity 201 in which coarse gas flows axially.

[0025] The molecular sieve membrane 22 is configured to screen nitrogen gas in the raw material methane gas; for example, the molecular sieve membrane is set on the outer wall of the central reaction tube, and a continuous, defect-free ZIF-8 molecular sieve membrane with a thickness of only 20-50 micrometers is constructed by in-situ secondary growth method.

[0026] The inner wall of the central reaction tube 21 is provided with a partial oxidation catalyst layer 211, configured to react methane gas with oxygen to form a synthesis gas of carbon monoxide and hydrogen. For example, the central reaction tube 21 is made of porous high-temperature resistant alloy or silicon carbide ceramic, and its inner wall is loaded with a nanostructured partial oxidation catalyst using advanced processes. This region is the only site for the directional conversion of methane.

[0027] The working principle of the in-situ separation and conversion system 100 is as follows: Methane is extracted from the coal seam through a borehole network and transported entirely to the membrane reaction module 20, where methane is continuously separated and converted into syngas. Methane extraction parameters and coal seam mechanical state parameters are acquired and monitored. When these parameters indicate reduced extraction efficiency or a risk of coal seam instability, the parameters of the plasma-activated gas injection module 10 are adjusted to implement directional gas injection intervention in the target coal seam area for the purpose of increasing permeability or stabilization.

[0028] This in-situ separation and conversion system 100 achieves a fundamental leap in safety: the space containing high-concentration methane is compressed into an extremely short path of "coal wall fissures → short-distance extraction pipe 210 → membrane reactor inlet". Once it enters the reactor, it is instantly converted into chemically inert syngas, completely eliminating the traditional biggest hazard source of "underground high-concentration methane transportation system", and realizing a qualitative change from process safety to fundamental safety at the source.

[0029] This in-situ separation and conversion system achieves a revolutionary reduction in energy consumption: it directly utilizes the underground ground pressure (0.5-1.2 MPa) as the driving force for membrane separation, eliminating the vast majority of the electrical energy required to pressurize the gas to the pressure at the surface plant (which typically requires several MPa). The reaction heat is utilized in-situ in a cascade manner, eliminating the need for a large heat exchange and cooling system at the surface plant. The overall energy consumption is expected to be 40%-50% lower than that of the surface cryogenic-conversion route.

[0030] This in-situ separation and conversion system has achieved a fundamental reversal in economic benefits: the membrane reactor directly converts low-value gas into high-value-added syngas underground, transforming the gas pre-extraction project from a purely "safety cost center" into a "downhole production unit" with considerable profits, and creating a new sustainable model of "using treatment to support treatment and creating benefits through treatment".

[0031] It is understandable that the nitrogen injection pipe 220 and the extraction pipe 210 are located in the same position, but they are independent and not connected to each other, only connected by an external fixing method (from the perspective of...). Figure 1 (They are located in the same position).

[0032] It is worth noting that the membrane reaction module 20 also includes an oxygen pump assembly 24, which includes an oxygen tank and a pump body, configured to pump oxygen into the central reaction tube 21 through a pipe 241, and decompose it with methane gas under the action of a partially oxidized catalyst layer 211 to form carbon monoxide and hydrogen. The carbon monoxide and hydrogen are then discharged through the pipe 241 and discharged to the ground along the extraction pipe 50; wherein the extraction pipe 50 is connected to the pipe 241.

[0033] In one example of the present invention, it further includes: a data sensing module 40 and a control module 30. The data sensing module 40 is configured to sense information on the activity of fracture development in the roadway and the gas concentration and flow rate information of the extraction pipe 210. The control module 30 is coupled to the data sensing module 40, the plasma activation gas injection module 10 and the membrane reaction module 20 respectively, and is configured to receive the fracture development activity information and gas concentration and flow rate information from the data sensing module 40 and control the coordinated operation of the plasma activation gas injection module 10 and the membrane reaction module 20. Coal seam gas is extracted through a borehole network and transported entirely to the membrane reactor module. The control module 30 controls the continuous separation of methane within the membrane reactor module and its conversion into syngas. The data sensing module 40 acquires information on the activity of fracture development in the roadway and the gas concentration and flow rate information of the extraction pipe 210. When the gas extraction parameters and coal seam mechanical state parameters indicate a decrease in extraction efficiency or a risk of coal seam instability, the parameters of the plasma-activated gas injection module 10 are adjusted to implement directional gas injection intervention in the target coal seam area for the purpose of increasing permeability or stabilization.

[0034] In one example of the present invention, the data sensing module 40 includes: Microseismic sensor 41 is configured to monitor information on the activity of fracture development in the roadway; Gas concentration sensor 42 is configured to monitor the gas concentration and flow rate information in the gas extraction pipes 210 in each area; The control module 30 dynamically adjusts the composition, pressure, and activation intensity of the plasma activation injection module 10 based on information on fracture development activity and gas concentration and flow rate to achieve the optimal methane gas conversion rate of the membrane reaction module 20.

[0035] For example, control module 30 controls the system based on a digital twin model: First, regarding the model's input data: The model's input data originates entirely from the sensing and execution units deployed within this system, including: coal seam mechanical state time-series data, gas drainage process time-series data, gas injection control parameter data, and in-situ transformation state data. Specifically, the coal seam mechanical state time-series data is microseismic event information acquired and processed in real-time by microseismic sensors, used to characterize the dynamic development behavior of the fracture network. The gas drainage process time-series data consists of gas component concentration and volumetric flow rate data in each drainage pipeline, acquired in real-time by gas concentration sensors and flow meters. The gas injection control parameter data is the injected gas component ratio, injection pressure, and gas activation intensity parameters fed back in real-time by the plasma-activated gas injection module. The in-situ transformation state data is the inlet feed gas conditions, reactor operating status, and outlet product gas information fed back in real-time by the membrane reactor module.

[0036] Secondly, the core architecture and coupling relationships of the model: The digital twin model logically consists of three sub-models: a coal seam mechanics and fracture evolution sub-model, a multi-component gas competitive adsorption and seepage sub-model, and a system process coupling interface. The coal seam mechanics and fracture evolution sub-model: This model is driven by microseismic event data, inferring the stress state changes within the coal seam through an inversion algorithm, and combining injection pressure as a boundary load to simulate and predict the fracture propagation trend and coal body stability risk. The multi-component gas competitive adsorption and seepage sub-model: This model uses extraction data and injection parameters as core inputs. Based on porous media seepage theory and competitive adsorption kinetics, it simulates the migration of activated injected gas in the coal seam, the displacement process of adsorbed methane, and the migration process of desorbed methane to the extraction borehole, thereby predicting the gas outburst dynamics at each extraction point. System process coupling interface: This interface provides the feed gas parameters (composition, flow rate) predicted by the above permeate sub-model and about to enter the membrane reaction module as feedforward information to the reactor optimization control system, so as to realize the dynamic connection and overall optimization of the extraction process and the conversion process.

[0037] Then, the model's online calibration mechanism: To ensure that the model's simulation accuracy remains consistent with the realism of the physical system, the model employs data assimilation technology for online self-calibration: Model parameter set initialization: Based on prior geological knowledge, reasonable ranges are set for key uncertainty parameters in the model (such as permeability and adsorption constant), and an initial set containing multiple parameter combinations is generated. The data assimilation process is executed periodically: Within each control cycle, the model first performs forward simulation prediction based on the current state and gas injection command. Subsequently, the predicted extraction data (such as gas flow rate) is compared with actual sensor measurements. Through an ensemble Kalman filter algorithm, the parameters of each member in the model set are automatically adjusted so that the overall predictive output of the model optimally approximates the actual observed data. This process is repeated cyclically, achieving dynamic tracking and adaptive correction of model parameters.

[0038] Finally, the application steps of the model in intelligent decision-making are as follows: the intelligent decision engine of the control module calls the digital twin model in the following manner to form closed-loop control: Status assessment and early warning: The model calculates and outputs the "coal seam stability risk distribution" and "gas extraction efficiency trend" across the entire mine in real time, providing operators with global situational awareness and automatically issuing early warnings when parameters exceed safety thresholds.

[0039] Control scheme simulation and optimization: When the decision engine determines that intervention is necessary based on the rules, it can generate one or more candidate gas injection control strategies. These strategies (including target area, gas composition, pressure, duration, etc.) are sent to the digital twin model.

[0040] Rapid simulation and effect evaluation: The digital twin model starts from the current calibrated state and performs rapid simulation for each candidate strategy, simulating the system response over a period of time after the strategy is executed, and returns quantitative evaluation indicators, such as the predicted increase in gas extraction and the estimated change in coal seam stability.

[0041] Decision support and instruction generation: The decision engine comprehensively compares the simulation evaluation results of each candidate strategy, selects the strategy with the best overall benefits under the condition of meeting safety constraints, and transforms it into a specific equipment control instruction sequence, which is then issued to the plasma activation and gas injection module, the extraction pipeline valve and the membrane reaction module for execution, thereby completing the intelligent control closed loop of "perception-prediction-decision-execution".

[0042] Through the above construction and operation methods, the digital twin model realizes dynamic mapping, trend prediction and strategy simulation of the complex downhole industrial process of "gas injection displacement-gas extraction-in-situ conversion", and becomes the intelligent core of this system to achieve safe, efficient and adaptive collaborative operation.

[0043] Control module 30 triggers mode selection: when the above data exceeds a preset safety or efficiency threshold, the system automatically selects the most suitable mode from several pre-stored "control modes". For example: If a region has "high fissure activity" and "rapid gas concentration decline", then the "stabilize fissures first, then increase permeability" mode should be selected.

[0044] If only the gas concentration decreases rapidly while the coal seam remains stable, then the "high-efficiency displacement" mode should be selected.

[0045] Execution of equipment parameter settings: After selecting a mode, the system sends a command packet containing specific parameter settings and execution timing to the relevant equipment. For example, when executing the "stabilize cracks first, then increase permeability" mode, the command is as follows: For the gas injection module: it is instructed to first inject gas into the target borehole with parameters of "high nitrogen ratio (e.g., 75%) and high pressure (e.g., 1.8 MPa)" within a specified time period; then it automatically switches to parameters of "high activated carbon dioxide ratio (e.g., 80%) and moderate pressure (e.g., 1.3 MPa)" to continue gas injection.

[0046] For extraction valves: instruct them to slowly increase the opening of the corresponding pipeline after a period of time following the start of gas injection, in order to match the expected increase in gas outflow.

[0047] For membrane reaction module 20: send early warning information to it, informing it of the expected changes in intake gas concentration and flow rate, so that its local control system can prepare in advance.

[0048] Effect tracking and parameter fine-tuning: During the execution of control commands, the system continuously compares monitoring data with expected results. If the actual gas concentration recovery rate is lower than expected, the system automatically fine-tunes the injection pressure or duration according to preset rules, such as increasing the injection pressure by 0.05-0.1 MPa, to ensure that the target is achieved.

[0049] In one example of the present invention, the membrane reaction module 20 uses the formation pressure of 0.5-1.2 MPa in the coal mine as the driving force for the raw material gas to pass through the molecular sieve membrane 22, and uses the reaction heat released by the partial oxidation reaction of methane to maintain the working temperature of the molecular sieve membrane 22 at 50-150°C through heat conduction.

[0050] In other words, the membrane reactor module 20 represents a revolutionary reduction in energy consumption: it directly utilizes the downhole pressure (0.5-1.2 MPa) as the driving force for membrane separation, eliminating the vast majority of the electrical energy required to pressurize the gas to the surface plant pressure (which typically requires several MPa). The reaction heat is utilized in situ through cascades, eliminating the need for a massive heat exchange and cooling system at the surface plant. The overall energy consumption is expected to be 40%-50% lower than that of the surface cryogenic-conversion route.

[0051] Specifically, the membrane reaction module 20 achieves energy-self-consistent thermal management: the partial oxidation reaction of methane (CH4 + ½O2 → CO + 2H2) is a mildly exothermic reaction (ΔH ≈ -36 kJ / mol). The heat of reaction is directly transferred to the outer molecular sieve membrane through the highly thermally conductive central tube wall. The optimal operating temperature for membrane separation is 50-150°C, while the reaction zone temperature is 300-450°C. This design cleverly utilizes the residual heat of the reaction to maintain the temperature required for membrane separation, achieving in-situ cascade utilization of energy. The system thermal efficiency exceeds 85%, eliminating the need for a complex external heat exchange network. The membrane reactor module 20 enables precise process control: the module integrates a high-precision mass flow controller (MFC) and distributed fiber optic temperature / pressure sensors. The intelligent control unit dynamically adjusts the oxygen injection rate based on the real-time composition and flow rate of the inlet gas, precisely stabilizing the oxygen-to-carbon ratio (O2 / CH4) within the optimal range of 0.50-0.55, ensuring that the reaction is always within the optimal thermodynamic and kinetic window for syngas generation.

[0052] In one example of this invention, the molecular sieve membrane 22 is a ZIF-8 molecular sieve membrane. This membrane 22 incorporates a graphite oxide (GO) interface layer to enhance the membrane-substrate bonding and mechanical strength; fluorosilane surface grafting imparts superhydrophobicity to the membrane, preventing water vapor blockage; and optimized crystal growth guidance provides the membrane with specific preferential adsorption channels for CH4, resisting poisoning by impurities such as H2S. The molecular sieve membrane 22 is primarily designed for use in humid, dusty, and trace corrosive environments in wells, and has undergone engineered strengthening.

[0053] In one example of the present invention, the molecular sieve membrane 22 has a thickness of 20-50 μm, a separation selectivity for methane and nitrogen greater than 300, and a methane permeation flux greater than 100 GPU.

[0054] In one example of the present invention, the distance between the molecular sieve membrane 22 and the partially oxidized catalyst layer 211 is less than 2 mm, which allows the methane reaction to be more complete and also avoids the participation of other gases in the reaction.

[0055] In one example of the present invention, the partial oxidation catalyst is a structured catalyst, the active component of which is a rhodium or nickel nanocluster confined within a cerium oxide shell, the nanocluster having a particle size of less than 2 nanometers; the structured catalyst is supported on a three-dimensional ordered macroporous CeO2-ZrO2 solid solution support.

[0056] In one example of the present invention, the plasma activation gas injection module 10 includes a dielectric barrier discharge plasma generator configured to dynamically adjust the composition of the injected gas, wherein the adjustment ratio of nitrogen to carbon dioxide is between 40%:60% and 80%:20%.

[0057] In other words, this dielectric barrier discharge plasma generator is a highly efficient chemical displacement device: it activates a CO2 / N2 mixture into a plasma rich in highly reactive particles (such as O2) through dielectric barrier discharge (DBD). 3 Plasma containing P, CO⁺, and excited-state molecules. The competitive adsorption capacity of the active gas for CH4 in coal is increased by orders of magnitude, and it can deeply and rapidly replace the adsorbed gas like a "chemical wedge". It is expected to increase the extraction efficiency of low-permeability coal seam 200 by more than 50% and permanently improve the permeability of coal seam 200.

[0058] The main dynamics stabilization of this dielectric barrier discharge plasma generator is achieved through a module that can flexibly adjust the composition (N2 / CO2 ratio: 40%-80%), pressure (0.5-2 MPa), and activation intensity of the injected gas according to intelligent commands. When the monitoring system detects accelerated fracture propagation in the coal seam, the N2 ratio and pressure are increased to utilize its "gas pocket effect" to support the fracture; when stress concentration is detected, the activated CO2 ratio is increased to utilize its competitive adsorption characteristics to alleviate stress. This achieves coordinated control of both "permeability enhancement" and "stability control" through a single module.

[0059] According to a second aspect of the present invention, a conversion method for an underground in-situ coal mine gas separation and conversion system 100 as described above is provided. Figure 3 As shown, it includes the following steps: Coal seam gas is extracted through a borehole network and transported entirely to the membrane reaction module 20, where methane is continuously separated and converted into syngas. The gas extraction parameters and coal seam mechanical state parameters are acquired and monitored. When the gas extraction parameters and coal seam mechanical state parameters indicate a decrease in extraction efficiency or a risk of coal seam instability, the parameters of the plasma-activated gas injection module 10 are adjusted to implement directional gas injection intervention in the target coal seam area for the purpose of increasing permeability or stabilizing the coal seam.

[0060] This in-situ separation and conversion method achieves a fundamental leap in safety: the spatial presence of high-concentration methane is compressed into an extremely short path of "coal wall fissures → short-distance extraction pipe 210 → membrane reactor inlet". Once it enters the reactor, it is instantly converted into chemically inert syngas, completely eradicating the traditional biggest hazard source of "underground high-concentration methane transportation system", and realizing a qualitative change from process safety to fundamental safety at the source.

[0061] This in-situ separation and conversion method achieves a revolutionary reduction in energy consumption: it directly utilizes the downhole pressure (0.5-1.2 MPa) as the driving force for membrane separation, eliminating the vast majority of the electrical energy required to pressurize the gas to the pressure at the surface plant (which typically requires several MPa). The reaction heat is utilized in-situ in a cascade manner, eliminating the need for a large heat exchange and cooling system at the surface plant. The overall energy consumption is expected to be 40%-50% lower than that of the surface cryogenic-conversion route.

[0062] This in-situ separation and conversion method has fundamentally reversed the economic benefits: the membrane reactor directly converts low-value gas into high-value-added syngas underground, transforming the gas pre-extraction project from a purely "safety cost center" into an "underground production unit" with considerable profits, and creating a new sustainable model of "using treatment to support treatment and creating benefits through treatment".

[0063] In one example of the present invention, adjusting the parameters of the plasma activation gas injection module 10 specifically includes: The gas extraction efficiency in low-permeability areas is improved by injecting plasma-activated carbon dioxide gas into the area; the expansion of the 200-degree coal seam fracture is suppressed by injecting a higher proportion of high-pressure nitrogen gas into the area.

[0064] In one example of the present invention, the membrane reaction module 20 is operated under the following conditions: operating pressure 0.8-1.5 MPa, catalyst bed temperature 300-450 °C, oxygen-carbon molar ratio controlled at 0.50-0.55, methane single-pass conversion greater than 90%, and syngas selectivity greater than 85%.

[0065] It should be noted that the above method is continued until the assessment confirms that the coal seam gas content and pressure have dropped below the safe mining standard, and that throughout the entire treatment process, high-concentration gas exists only in the locally closed pipeline from the coal seam to the inlet of the membrane reactor module.

[0066] The foregoing description, with reference to preferred embodiments, details an exemplary implementation of the coal mine gas in-situ separation and conversion system 100 and method proposed by the present invention. However, those skilled in the art will understand that various modifications and alterations can be made to the above specific embodiments without departing from the concept of the present invention, and various combinations can be made to the various technical features and structures proposed by the present invention without exceeding the protection scope of the present invention, which is determined by the appended claims.

Claims

1. A coal mine gas in-situ separation and conversion system, characterized in that, include: The plasma activation gas injection module (10) is located in the underground air intake roadway (230) and connected to the nitrogen injection pipe (220). It is configured to inject an activation gas with adjustable composition into the coal seam (200) to displace methane from the coal seam (200). The membrane reaction module (20) is located in the underground return air roadway (240) and connected to the gas extraction pipe (210). It is configured to convert the extracted methane into syngas in situ and discharge it through the extraction pipe (210). The membrane reaction module (20) includes: a central reaction pipe (21), a molecular sieve membrane (22) and a pressure-resistant sleeve (23) arranged sequentially from the inside to the outside. A cavity (201) is formed between the pressure-resistant sleeve (23) and the molecular sieve membrane (22), and the cavity (201) is configured for the flow of raw material methane gas; The molecular sieve membrane (22) is configured to sieve nitrogen gas in the raw material methane gas; The inner wall of the central reaction tube (21) is provided with a partial oxidation catalyst layer (211), which is configured to react methane gas with oxygen to form synthesis gas of carbon monoxide and hydrogen.

2. The in-situ coal mine gas separation and conversion system according to claim 1, characterized in that, It also includes: a data sensing module (40) and a control module (30). The data sensing module (40) is configured to sense the activity of fracture development in the roadway and the gas concentration and flow rate of the extraction pipe (210); The control module (30) is coupled to the data sensing module (40), the plasma activation gas injection module (10) and the membrane reaction module (20) respectively, and is configured to receive the fracture development activity information and gas concentration and flow information from the data sensing module (40) and control the coordinated operation of the plasma activation gas injection module (10) and the membrane reaction module (20).

3. The in-situ coal mine gas separation and conversion system according to claim 2, characterized in that, The data sensing module (40) includes: Microseismic sensor (41) is configured to monitor information on the activity of fracture development in the roadway; A gas concentration sensor (42) is configured to monitor the gas concentration and flow rate information in the gas extraction pipeline (210) of each area; The control module (30) dynamically adjusts the composition, pressure and activation intensity of the plasma activation injection module (10) based on the information on fissure development activity and gas concentration and flow rate to achieve the optimal methane gas conversion rate of the membrane reaction module (20).

4. The in-situ coal mine gas separation and conversion system according to claim 1, characterized in that, The membrane reaction module (20) uses the underground formation pressure of the coal mine as the driving force for the raw material gas to pass through the molecular sieve membrane (22), and uses the reaction heat released by the partial oxidation reaction of methane to maintain the working temperature of the molecular sieve membrane (22) through heat conduction.

5. The in-situ coal mine gas separation and conversion system according to claim 1, characterized in that, The molecular sieve membrane (22) has a thickness of 20-50 μm, a separation selectivity of greater than 300 for methane and nitrogen, and a methane permeation flux of greater than 100 GPU.

6. The in-situ coal mine gas separation and conversion system according to claim 1, characterized in that, The distance between the molecular sieve membrane (22) and the partially oxidized catalyst layer (211) is less than 2 mm.

7. The in-situ coal mine gas separation and conversion system according to claim 1, characterized in that, The partial oxidation catalyst is a structured catalyst, the active component of which is a rhodium or nickel nanocluster confined within a cerium oxide shell, and the particle size of the nanocluster is less than 2 nanometers; the structured catalyst is supported on a three-dimensional ordered macroporous CeO2-ZrO2 solid solution support.

8. The in-situ coal mine gas separation and conversion system according to claim 1, characterized in that, The plasma activation gas injection module (10) includes a dielectric barrier discharge plasma generator, which is configured to dynamically adjust the composition of the injected gas, wherein the adjustment ratio of nitrogen to carbon dioxide is between 40%:60% and 80%:20%.

9. A conversion method for an underground in-situ separation and conversion system for coal mine gas as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Coal seam gas is extracted through a borehole network and transported entirely to the membrane reaction module (20), where methane is continuously separated and converted into syngas within the membrane reaction module (20). The gas extraction parameters and coal seam mechanical state parameters are obtained and monitored. When the gas extraction parameters and coal seam mechanical state parameters indicate that the extraction efficiency is reduced or the coal seam is at risk of instability, the parameters of the plasma-activated gas injection module (10) are adjusted to implement directional gas injection intervention in the target coal seam area for the purpose of increasing permeability or stabilizing the coal seam.

10. The conversion method of the underground in-situ separation and conversion system for coal mine gas according to claim 9, characterized in that, Adjusting the parameters of the plasma activation gas injection module (10) specifically includes: The gas extraction efficiency in low-permeability areas is improved by injecting plasma-activated carbon dioxide gas into the area; the expansion of coal seam (200) fractures is suppressed by injecting a higher proportion of high-pressure nitrogen gas into the area.

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