A fluidized extraction system and method driven by self-heating of coal seam chemical activation

Abstract

The present invention belongs to the technical field of gas extraction, and specifically is a fluidized extraction system and method driven by chemical activation and self-heating of coal seams. The fluidized extraction method driven by chemical activation and self-heating of coal seams of the present invention is suitable for coal seams with low permeability, strong low-temperature oxidizability, and high gas concentration. It effectively solves the problem of low gas extraction rate in high-gas, low-permeability, and deeply buried coal seams, and maximizes the utilization efficiency of pre-mined coal seams. Compared with the prior art, the present application provides a new gas extraction method, which can not only improve the degree of fracture penetration inside the pre-mined coal seam, but also fully increase the maximum utilization of coal resources and gas resources.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas extraction, and in particular relates to a fluidized extraction system and method driven by chemical activation and self-heating of coal seams. Background Art

[0002] my country's coal seams generally have the characteristics of high gas content, poor permeability, and deep burial, which makes it difficult to extract gas from coal bodies under natural conditions. In addition, existing coal mining technology often leads to a large amount of coal residue in the goaf, resulting in a waste of resources such as gas rich in the remaining coal bodies. For pre-mining gas-containing coal seams, in order to ensure the safety of coal mines, it is necessary to adopt the technical solution of "extraction before mining", first reducing the gas pressure and gas content in the coal seams to below the safety limit before mining. At present, conventional means of gas extraction include hydraulic fracturing technology, fluidized mining related technologies, etc., and have achieved certain results in practical applications.

[0003] However, the above methods still have certain application limitations. For example, hydraulic fracturing technology requires a large amount of high-pressure water to fracture the coal body, and field applications have high requirements for the water content in the area; fluidized mining related technologies mainly increase the temperature of the coal seam to thousands of degrees for mining through gasification, and this method is currently mainly in the theoretical research and conceptual stage. Affected by factors such as heat injection volume, heat control, and coal seam gasification rate, field applications are still in the exploratory stage. Therefore, in response to the above problems, a new gas extraction method is needed, which can not only improve the degree of fracture penetration inside the pre-mined coal seam, but also fully increase the maximum utilization of coal resources and gas resources. Summary of the invention

[0004] In view of the deficiencies in the above-mentioned prior art, the present invention provides a fluidized extraction system and method driven by chemical activation and self-heating of coal seams, which can not only improve the degree of fracture penetration inside the pre-mined coal seams, but also fully increase the maximum utilization of coal and gas resources.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A fluidized extraction system driven by self-heating and chemical activation of coal seams, comprising:

[0007] A plurality of vertical boreholes are arranged circumferentially, and the boreholes are drilled in the pre-mined coal seam; a plurality of horizontal boreholes are opened on the side wall of each vertical borehole, and a liquid injection branch pipe is arranged in each horizontal borehole. The horizontal boreholes are convenient for placing the liquid injection branch pipe in the coal seam, and a plurality of liquid injection holes are opened on the liquid injection branch pipe, and the liquid injection branch pipe is used to discharge the oxidizing liquid or water into the coal seam through the liquid injection holes. The liquid injection branch pipes are connected to the liquid injection main pipeline, and the oxidizing liquid or water enters the liquid injection branch pipe through the liquid injection main pipeline. The liquid injection main pipeline is installed in each vertical borehole, and the free end of the liquid injection main pipeline is connected to the oxidizing liquid supply component, and the oxidizing liquid supply component is used to provide the oxidizing liquid;

[0008] The oxidizing liquid of the oxidizing liquid supply assembly is composed of chemically activated liquid A and chemically activated liquid B. After the chemically activated liquid A is mixed with the chemically activated liquid B, it will undergo an oxidation reaction with the polycyclic aromatic hydrocarbons in the coal matrix, thereby reducing the oxidation resistance of the coal, enhancing its activity, quickly reaching the critical temperature, increasing the temperature of the coal seam, increasing the cracks, and promoting the decomposition of gas adsorbed in the pores of the coal seam;

[0009] A plurality of horizontal wells are drilled at each vertical well terminal, explosives are reserved in the horizontal wells, explosives are reserved after the horizontal wells are completed, and the fuse is taken out of the wells and detonated on the ground with a detonator; the radius of the vertical well 27 and the horizontal well 3 are both 200-250 mm, a large-size pipe is arranged in each vertical well, the radius of the large-size pipe 5 is 100-150 mm, and a small-size pipe is arranged in each horizontal well, the small-size pipe is connected to the large-size pipe, and the free end of the large-size pipe is connected to the air supply assembly, the air supply assembly is used to provide air, so that the gas is discharged through the coal seam under the pressure of air, and the large-size pipe and the small-size pipe are used to circulate air;

[0010] Gas extraction drilling and monitoring drilling, the radius of the gas extraction drilling 21 is 150-200mm, and the radius of the monitoring drilling 17 is 50-100mm. The gas extraction drilling is used to extract gas, and the monitoring drilling is used to detect the gas composition and temperature in the coal seam, so as to facilitate timely regulation according to the situation in the coal seam. The two are drilled in the center of the vertical drilling well, and the monitoring drilling is close to the gas extraction drilling; temperature sensors and gas detectors are installed in the monitoring drilling.

[0011] Preferably, the chemical activation liquid A is composed of 40 g / L sodium persulfate solution as a chemical activator, 50 g / L citric acid solution as a chelating agent and 1‰ to 1% volume fraction of sodium dodecyl sulfate solution as a surfactant; the chemical activation liquid B is 10 g / L ferrous sulfate solution.

[0012] Preferably, the oxidizing liquid supply assembly is composed of an injection pump and a mixing tank, the injection main pipeline is connected to the mixing tank, and the mixing tank is also connected to a chemically activated B liquid storage tank and a chemically activated A liquid storage tank, respectively, the mixing tank is used to mix the chemically activated A liquid and the chemically activated B liquid, and the injection pump is detachably connected to the injection main pipeline;

[0013] The injection pump can also be detachably connected to a water source. When cooling the coal seam, the injection pump is connected to the water source. When oxidizing the coal seam with an oxidizing liquid, the injection pump is connected to a mixing tank.

[0014] Preferably, the air supply assembly is composed of an air compression pump and an air heating tank. The large-size pipe is connected to the air heating tank through an air injection pipeline. The air compression pump is installed on the air injection pipeline. The air heating tank is used to store heated air or to heat room temperature air. Under the action of the air compression pump, the heated air is discharged into the large-size pipe through the air heating tank.

[0015] Preferably, a gas extraction pipe is provided in the gas extraction drilling well, and a gas extraction pump is provided on the gas extraction pipe. Under the action of the gas extraction pump, the gas is extracted through the gas extraction pipe. The bottom end of the gas extraction drilling well is 2 to 3 meters higher than the horizontal drilling well, which is convenient for extracting the gas in the oxidized and fractured coal seam above the horizontal drilling well. Moreover, this position is located in the middle of the coal seam, and the gas extraction is relatively complete. The monitoring drilling well is 5 to 10 meters away from the gas extraction drilling well; and the bottom of the monitoring drilling well is immersed in the coal seam by 1 to 2 meters.

[0016] Preferably, the horizontal drilling is close to the bottom of the coal seam, the horizontal borehole is 0.3 to 0.8 m away from the top of the coal seam, and the length of the horizontal borehole is 30-80 m, depending on the length of the coal seam dip. The better horizontal drilling is parallel to the horizontal drilling.

[0017] Preferably, a first four-way diverter valve is provided between the small-size tube and the large-size tube, and a second four-way diverter valve is provided between the injection branch pipe and the injection main pipeline. By regulating the first four-way diverter valve and the second four-way diverter valve, the injection amount of the oxidizing liquid, water and air can be timely regulated.

[0018] The present invention also protects the above-mentioned coal seam chemical activation self-heat driven fluidized extraction method, comprising the following steps:

[0019] After starting the gas extraction pump, a large number of cracks are generated in the coal seam above the horizontal drilling by blasting with explosives, which makes it easier to inject the oxidizing liquid into the cracks, increasing the contact area between the oxidizing liquid and the coal seam and improving the oxidizing effect of the oxidizing liquid on the coal seam.

[0020] The injection pump is turned on to allow the heated oxidizing liquid to enter the injection pipe and enter the coal seam fissures along the injection hole under the action of gravity and spread throughout the coal seam;

[0021] Among them, the temperature of the heated oxidizing liquid is greater than the critical point temperature of the coal. The heating temperature of the oxidizing liquid is 60-70°C. The coal will undergo a slow oxidation reaction after the critical point temperature. Heating to the critical point temperature in advance can accelerate the oxidation. At this time, the flow ratio of chemical activation liquid A to chemical activation liquid B is 1:1. The oxidation reaction is accompanied by heat release. At this time, the temperature in the coal seam rises. When the temperature sensor monitors that the coal seam temperature reaches 60°C, the flow ratio of chemical activation liquid A to chemical activation liquid B is adjusted to 2:1 to prevent excessive Fe 2+ The production of sulfate radicals then inhibits the generation of sulfate radicals, affecting the activation rate;

[0022] When the temperature of the coal seam reaches 70℃ and starts to heat up rapidly, stop injecting the oxidizing liquid. At this time, the coal enters the self-heating period, releases heat and heats up rapidly. The oxidizing liquid is no longer needed for oxidation. The coal will oxidize by itself. The role of the oxidizing liquid is to accelerate the energy level transition of the coal in the preparation stage.

[0023] Start the air compression pump, discharge the dry air heated to the critical temperature through the large-size pipe to the small-size pipe, and inject it into the horizontal drilling well. The critical temperature of dry air is 60-70℃. Coal will undergo a slow oxidation reaction after the critical temperature. Air heated to the critical temperature in advance can accelerate oxidation. When the temperature sensor detects that the coal seam temperature reaches 150-160℃, fresh dry air is passed. At this time, the coal begins to oxidize and heat up rapidly. There is no need for heated air to supply heat, which can save energy. The air passes through the coal seam and is extracted along the gas extraction well. Heat accumulates in the coal body and the temperature continues to rise.

[0024] The oxidation heat generated by the coal body causes the temperature of the coal seam to continue to rise, further promoting the reaction between the chemical activation liquid and the coal matrix, but its temperature cannot exceed the ignition point of the coal. A temperature sensor is used to continuously monitor the temperature of the coal body in the chemical activation area containing the oxidizing liquid. When the temperature reaches 280°C, the coal seam is judged to be completely oxidized, and when the gas detector detects the production of acetylene gas, the air supply is stopped. Acetylene gas is a signature gas for coal spontaneous combustion. When acetylene gas is detected, oxidation must be stopped to prevent coal spontaneous combustion.

[0025] Preferably, the maximum temperature resistance value of the temperature sensor is 1800°C, and the effective working temperature range is between 0 and 1200°C.

[0026] Preferably, the coal seam temperature cannot exceed the ignition point. When the temperature sensor detects that the coal seam temperature reaches 280-290°C, an injection pump is connected to a water source to inject water to cool the coal seam to prevent the coal seam from continuing to heat up and burn, and to reduce the temperature to room temperature.

[0027] Preferably, a gas extraction drilling connector is used to fix the position of the gas extraction pipe, a connector is used to fix the position of the large-size pipe, and a horizontal drilling connector is used to fix the position of the injection branch pipe. At this time, the side walls of the gas extraction pipe, large-size pipe, and injection branch pipe are also sealed to prevent leakage of liquid or gas.

[0028] Preferably, the temperature sensor and the gas detector are respectively connected to the ground monitoring system through wires. The ground monitoring system includes a multi-component gas monitoring system and a temperature monitoring system. The multi-component gas monitoring system is connected to the gas detector in the multi-functional assembly device through the gas concentration detector wire, and the temperature monitoring system is connected to the temperature sensor in the multi-functional assembly device through the temperature detector wire.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The fluidized extraction method driven by self-heating of chemical activation of coal seams of the present invention is suitable for coal seams with low permeability, strong low-temperature oxidizability and high gas concentration. Several vertical wells are drilled from the ground to the bottom of the coal seam, and gas extraction wells and monitoring wells are drilled in the middle of the vertical wells. Liquid injection pipes are arranged along the vertical wellbore and slightly below the top plate of the coal seam. A large number of cracks are generated in the coal seam above the horizontal well by explosive blasting. A chemical activation liquid of a certain temperature is injected into the coal seam along the liquid injection pipe at a set flow rate. The chemical activation liquid spreads throughout the coal seam along the cracks of the coal seam under the action of gravity. Then, warm air is pumped into the coal seam at a set flow rate, so that the coal is activated at a certain temperature, quickly exceeds the critical temperature and reaches the self-heating stage, promotes the further development of coal seam cracks, and releases the adsorbed gas, and finally performs negative pressure extraction through gas extraction drilling. The present invention has high feasibility, can realize gas extraction to the maximum extent, and realizes the efficient utilization of coal resources.

[0031] 2. The technical solution of this application is adopted to effectively solve the problem of low gas extraction rate in high-gas, low-permeability and deeply buried coal seams, and maximize the utilization efficiency of pre-mined coal seams. First, the traditional explosive blasting method is adopted to initially fracture the coal seam at the lowest cost, and then a chemical activation liquid of a certain temperature is injected into the coal seam along the injection pipe according to the set flow rate, and the air compression pump is dynamically controlled to inject a certain amount of air into the horizontal drilling. Under the appropriate air flow rate and sufficient O2 supply, the oxidizing liquid entering the coal seam fissure reacts with the coal matrix, so that the coal seam fissure develops to the maximum extent and the gas in the coal seam is released to the maximum extent. By real-time monitoring of the gas concentration and temperature in the horizontal drilling, by adjusting the air pumping speed and flow rate, as well as the mixing ratio and injection flow rate of the chemical activation liquid, the target coal seam is always in a controllable chemical activation state. Under the action of the gas extraction pump, a large amount of free gas diffuses and seeps through the multi-scale pore fracture structure, and is finally efficiently extracted. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Side view of a fluidized extraction system driven by self-heat for chemical activation of coal seams;

[0033] Figure 2 A top view of the fluidized extraction system driven by self-heating and chemical activation of coal seams in Example 1;

[0034] Figure 3 Partial diagram of the layout of the oxidizing liquid components for the fluidized extraction system driven by self-heating for chemical activation of coal seams.

[0035] Description of reference numerals:

[0036] 1- rock formation, 2- coal seam, 3- horizontal drilling, 4- main liquid injection pipeline, 5- large size pipe, 6- connector, 7- air heating tank, 8- air compression pump, 9- gas injection pipeline, 10- liquid injection pump, 11- chemically activated A liquid storage tank, 12- chemically activated B liquid storage tank, 13- liquid storage station, 14- first four-way diverter valve, 15- temperature detector wire, 16- gas concentration detector wire, 17- monitoring drilling, 18- temperature sensor, 19- gas detector, 20- gas extraction pipe, 21- gas extraction drilling, 22- gas extraction drilling connector, 23- gas extraction pump, 24- ground monitoring system, 25- horizontal drilling, 26- mixing tank, 27- vertical drilling, 28- second four-way diverter valve, 29- small size pipe, 30- liquid injection branch pipe, 31- horizontal drilling connector, 32- liquid injection hole. DETAILED DESCRIPTION

[0037] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention. The experimental methods described in the embodiments of the present invention are conventional methods unless otherwise specified.

[0038] In the fluidized extraction system driven by self-heating of chemical activation of coal seams of the present invention, a number of vertical wells are arranged in the circumferential direction, and a number of horizontal wells are drilled along the vertical well terminals, and then a number of injection pipes are arranged along the vertical wellbore. At this time, a large number of cracks are effectively generated in the coal seam by blasting, and efficient contact between the oxidizing liquid and the coal seam is achieved through a number of injection pipes. The oxidizing liquid is used to accelerate the energy level transition of the coal in the preparation stage to achieve the initial oxidation of the coal.

[0039] The present invention also provides an oxidizing solution, which is composed of a chemically activated A solution and a chemically activated B solution. The chemically activated A solution is composed of a sodium persulfate solution, a citric acid solution and a sodium dodecyl sulfate solution. The chemically activated B solution is a ferrous sulfate solution. After the chemical A solution and the chemical B solution are mixed, the Fe in the B solution is 2+ It has an activating effect on the highly oxidizing sodium persulfate, and the reaction between the two promotes the production of sulfate free radicals (SO 4- ·), sulfate radical (SO 4- ·) reacts with the coal matrix to oxidize and dissolve organic substances such as polycyclic aromatic hydrocarbons, achieving the effect of cracking and permeability enhancement on the coal seam, while accelerating the preparation process of coal oxidation and heating itself, and transitioning to the self-heating period after exceeding 70°C. Sodium dodecyl sulfate in chemical activation liquid A acts as a surfactant to wet the coal body, which can effectively increase the contact area of ​​the oxidation reaction; citric acid acts as a chelating agent for Fe 3+ Ions have strong capture and dispersion effects, which can maintain the Fe 2+ stability.

[0040] The system of the present application is structurally designed based on the method of the present application, which not only realizes the regulation of air, oxidizing liquid and water, but also can monitor temperature and gas components; the method of the present application mainly realizes the self-oxidation of coal, and after the self-oxidation of coal, the adsorbed gas is released, thereby improving the gas extraction efficiency. In order to realize the initial self-oxidation of coal, the present application provides oxidizing liquid, and in order to improve the self-oxidation efficiency of coal, the present application provides hot air, and from a safety perspective, provides temperature and gas component monitoring; compared with the prior art, the present application provides a new gas extraction method, which can not only improve the degree of crack penetration inside the pre-mined coal seam, but also fully increase the maximum utilization of coal resources and gas resources.

[0041] Example 1

[0042] A gas extraction method using a fluidized extraction system driven by coal seam chemical activation and self-heating, comprising the following steps:

[0043] like Figure 1As shown, a drilling machine is first used to penetrate the rock layer 1 from the ground, and several drilling groups are drilled toward the pre-mined coal seam 2. Each drilling group includes four vertical drilling wells 27 arranged in a circumferential direction. At the terminal of the vertical drilling well 27 near the bottom of the coal seam, a steering drill bit is used to drill three horizontal drilling wells 3 along the direction of the coal seam, along the dip of the coal seam, and along the direction of the gas extraction drilling in the middle, for a total of 12 horizontal drilling wells. A gas extraction drilling well 2 is drilled in the middle of the four vertical drilling wells 27. 1 and a monitoring well 17. The gas extraction well 21 is located at the intersection of four horizontal wells 3. The depth of the gas extraction well 21 is 2-3m higher than that of the horizontal wells. The distance between the monitoring well 17 and the gas extraction well 21 is 8m. The bottom of the monitoring well 17 is 2m below the coal seam. The radii of the vertical well 27 and the horizontal well 3 are both 250mm, the radius of the gas extraction well 21 is 150mm, and the radius of the monitoring well 17 is 100mm. Figure 2 An alternating extraction method is used between each drilling group, and adjacent wells can be reused.

[0044] Three horizontal boreholes 25 are respectively opened on the side wall of each vertical borehole 27. The horizontal borehole 25 is perpendicular to the vertical borehole shaft and is parallel to the horizontal borehole 3. Liquid injection branch pipes 30 are respectively arranged in the horizontal boreholes 25. Four liquid injection holes 32 are evenly opened on the liquid injection branch pipes 30 every 2 meters along the pipe wall. A liquid injection main pipeline 4 is arranged in each vertical borehole 27. The horizontal borehole 25 is 0.6m away from the top of the coal seam. The length of the horizontal borehole 25 is 80m, which is determined according to the inclination length of the coal seam. Three directions The injection branch pipes 30 are connected to the injection main pipeline 4 through the second four-way diverter valve 28, and the horizontal drilling connector 31 is used to fix the position of the injection branch pipe and seal the side wall to prevent leakage. The injection main pipeline 4 extends out of the wellhead and is connected to the injection pump 10. After the injection pump 10 is connected to the mixing tank 26, the mixing tank 26 is respectively connected to the chemically activated A liquid storage tank 11 and the chemically activated B liquid storage tank 12 on the liquid storage station 13. The mixing tank 26 is used to mix the chemically activated A liquid and the chemically activated B liquid in advance.

[0045] Chemical activation liquid A is a mixed solution composed of sodium persulfate, citric acid and sodium dodecyl sulfate, wherein the mass fraction of sodium persulfate as an oxidant is 40 g / L, the mass fraction of citric acid as a chelating agent is 50 g / L, and the volume percentage of sodium dodecyl sulfate as a surfactant is 1%; chemical activation liquid B is a 10 g / L ferrous sulfate solution.

[0046] The temperature sensor 18 and the gas detector 19 are respectively connected to the ground monitoring system 24 through wires, and the temperature sensor 18 and the gas detector 19 form a multifunctional assembly device and are sent to the bottom of the monitoring well 17 for fixing; the ground monitoring system 24 includes a multi-component gas monitoring system and a temperature monitoring system, the multi-component gas monitoring system is connected to the gas detector 19 in the multi-functional assembly device through the multi-component gas concentration detector wire 16, and the temperature monitoring system is connected to the temperature sensor 18 in the multi-functional assembly device through the temperature detector wire 15; the gas detector 19 model is Sensepoint XCD gas detector, and the temperature sensor 18 model is SBWR thermocouple integrated temperature sensor, the sensor has a maximum temperature resistance value of up to 1800°C, and an effective working temperature range of 0 to 1200°C.

[0047] The gas extraction pipe 20 is connected to the gas extraction pump 23, and the gas extraction drilling connector 22 is used to fix the position of the gas extraction pipe 20 and seal the side wall to prevent leakage; large-size pipes 5 with a radius of 150 mm are arranged in the four vertical drilling wells 27, and small-size pipes 29 are arranged in the 12 horizontal drilling wells 3. Every three small-size pipes 29 are tightly connected to the large-size pipe through the first four-way diverter valve 14. The first four-way diverter valve 14 and the second four-way diverter valve 28 are both automatically adjustable flow shut-off valves. The connector 6 is used to fix the position of the large-size pipe 5 and seal the side wall to facilitate the transmission of hot air. Then the large-size pipe 5 is connected to the air compression pump 8 and the air heating tank 7 in sequence through the air injection pipeline 9. The air heating tank 7 provides hot air to the coal seam.

[0048] After starting the gas extraction pump 20, a large number of cracks are generated in the coal seam 2 above the horizontal drilling 3 by means of explosive blasting;

[0049] Open the control valves on the chemical activation liquid A tank 11 and the chemical activation liquid B tank 12, and allow the heated chemical activation liquid A and the chemical activation liquid B to enter the mixing tank 26 at a flow ratio of 1:1, and mix them in the mixing tank 26 to obtain the oxidizing liquid. The oxidizing liquid is flowed into the injection main pipeline 4 at a flow rate of 400L / min under the action of the injection pump 10, and then enters different injection branch pipes 30 through the injection main pipeline 4, and finally discharged into the coal seam through the injection hole 32. The oxidizing liquid is spread throughout the coal seam along the cracks of the coal seam under the action of gravity. After the chemical activation liquid A and liquid B are mixed, they will undergo an oxidation reaction with the polycyclic aromatic hydrocarbons in the coal matrix, thereby increasing the pore structure of the media, and even the micropores will have a significant expansion, which promotes the analysis of gas adsorbed in the pores of the coal seam; the temperature of the chemical activation liquid is greater than the critical point temperature of the coal, generally 70°C;

[0050] The oxidation reaction is accompanied by heat release. At this time, the temperature in the coal seam rises. When the temperature sensor detects that the coal seam temperature reaches 60°C, the flow ratio of chemical activation liquid A and chemical activation liquid B is adjusted to 2:1 to prevent excessive Fe 2+ The production of sulfate radicals then inhibits the generation of sulfate radicals, affecting the activation rate;

[0051] When the temperature of the coal seam reaches 70℃ and starts to heat up rapidly, stop injecting the oxidizing liquid. At this time, the coal enters the self-heating period, releases heat and heats up rapidly. The oxidizing liquid is no longer needed for oxidation. The coal will oxidize by itself. The role of the oxidizing liquid is to accelerate the energy level transition of the coal in the preparation stage.

[0052] At the same time, the air compression pump 8 is started to pump dry air heated to the critical temperature (60-70°C) into the horizontal drilling 3 through the small-size pipe 29 at a pumping pressure of 15MP. The air passes through the coal seam 2 and is extracted along the gas extraction drilling 21. Heat accumulates in the coal body and the temperature continues to rise. When the temperature sensor 18 detects that the temperature of the coal seam 2 reaches 150°C, fresh dry air is passed instead. At this time, the coal begins to oxidize and heat up rapidly, and there is no need for warm air to supply heat, which can save energy.

[0053] The temperature of the coal body in the chemical activation area is continuously monitored by the temperature sensor 18. The oxidation heat of the coal body causes the temperature of the coal seam 2 to rise continuously, further promoting the reaction between the chemical activation liquid and the coal matrix, but the temperature cannot exceed the ignition point of the coal. When the temperature exceeds 280°C, the gas monitoring device 19 detects the generation of acetylene gas, stops the air supply, and uses the original injection pump 10, the injection main pipeline 4, and the injection branch pipe 30 to inject water to cool the coal seam 2 to prevent the coal seam 2 from continuing to heat up and ignite.

[0054] After the water is gradually injected, the temperature of the coal seam gradually decreases, and when the temperature of the coal seam drops to room temperature, the operation of the gas extraction pump 23 is stopped, and the gas extraction is completed at this time.

[0055] It should be noted that when the present invention involves a numerical range, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes a preferred embodiment. Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the attached claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0056] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these changes and variations. The above-described embodiments are only preferred embodiments for fully illustrating the present invention, and their protection scope is not limited thereto. Equivalent substitutions or changes made by those skilled in the art on the basis of the present invention are all within the protection scope of the present invention, and the protection scope of the present invention shall be subject to the claims.

Claims

1. A method for extracting coal using a fluidized extraction system driven by self-heating through chemical activation of coal seams, characterized in that: The coal seam chemical activation self-heat driven fluidized extraction system comprises: a plurality of vertical boreholes (27) arranged circumferentially, which are drilled in the pre-mined coal seam (2); a plurality of horizontal boreholes (25) are opened on the side wall of each of the vertical boreholes (27); a liquid injection branch pipe (30) is arranged in each of the horizontal boreholes (25); a plurality of liquid injection holes (32) are opened on the liquid injection branch pipe (30); the liquid injection branch pipes (30) are connected to the liquid injection main pipeline (4) The main injection pipeline (4) is installed in each of the vertical drilling wells (27), and the free end of the main injection pipeline (4) is connected to the oxidation liquid supply assembly; the oxidation liquid supply assembly is composed of an injection pump (10) and a mixing tank (26), the main injection pipeline (4) is connected to the mixing tank (26), the mixing tank (26) is used for mixing the chemically activated A liquid and the chemically activated B liquid, and the injection pump (10) is detachably connected to the main injection pipeline (4); The oxidizing liquid of the oxidizing liquid supply component is composed of chemically activated liquid A and chemically activated liquid B; A plurality of horizontal wells (3) are drilled at the end of each of the vertical wells (27), and explosives are reserved in the horizontal wells (3); a large-size pipe (5) is arranged in each of the vertical wells (27), and a small-size pipe (29) is arranged in each of the horizontal wells (3), the small-size pipes (29) are connected to the large-size pipes (5), and the free ends of the large-size pipes (5) are connected to the gas supply assembly; A gas extraction well (21) and a monitoring well (17), both of which are drilled in the center of the vertical well (27); a temperature sensor (18) and a gas detector (19) are arranged in the monitoring well (17); The extraction method of the fluidized extraction system driven by self-heat of chemical activation of coal seams includes the following steps: After starting the gas extraction pump (23), a large number of cracks are generated in the coal seam (2) above the horizontal drilling well (3) by using explosive blasting; The injection pump (10) is turned on to allow the heated oxidizing liquid to enter the injection branch pipe (30) and, under the action of gravity, enter the cracks of the coal seam (2) along the injection hole (32) and spread throughout the entire coal seam (2); The temperature of the heated oxidizing liquid is greater than the critical point temperature of the coal. At this time, the flow ratio of the chemically activated liquid A to the chemically activated liquid B is 1:

1. When the temperature sensor (18) detects that the temperature of the coal seam (2) reaches 60° C., the flow ratio of the chemically activated liquid A to the chemically activated liquid B is adjusted to 2:

1. When the temperature of the coal seam (2) reaches 70°C and starts to rise rapidly, the injection of the oxidizing liquid is stopped, and the temperature of the coal rises due to self-heating; The air compression pump (8) is started to discharge dry air heated to the zero-point temperature through the large-size pipe (5) into the small-size pipe (29) and inject it into the horizontal drilling well (3). When the temperature sensor (18) detects that the temperature of the coal seam (2) reaches 150-160° C., fresh dry air is supplied; The temperature sensor (18) is used to continuously monitor the temperature of the coal body in the chemical activation area containing the oxidizing liquid. When the temperature reaches 280°C and the gas detector (19) detects the generation of acetylene gas, the air supply is stopped.

2. The extraction method of the fluidized extraction system driven by coal seam chemical activation and self-heating according to claim 1 is characterized in that: The chemical activation liquid A is composed of sodium persulfate, citric acid, sodium dodecyl sulfate and water, wherein the sodium persulfate solution is 40 g / L, the citric acid solution is 50 g / L, and the volume fraction of the sodium dodecyl sulfate solution is 1‰ to 1%; the chemical activation liquid B is a 10 g / L ferrous sulfate aqueous solution.

3. The extraction method of the fluidized extraction system driven by coal seam chemical activation and self-heating according to claim 1 is characterized in that: The injection pump (10) can also be detachably connected to a water source.

4. The extraction method of the fluidized extraction system driven by coal seam chemical activation and self-heating according to claim 1 is characterized in that: The air supply assembly is composed of an air compression pump (8) and an air heating tank (7); the large-size pipe (5) is connected to the air heating tank (7) via an air injection pipeline (9); and the air compression pump (8) is installed on the air injection pipeline (9).

5. The extraction method of the fluidized extraction system driven by coal seam chemical activation and self-heating according to claim 1 is characterized in that: A gas extraction pipe (20) is arranged in the gas extraction well (21), and a gas extraction pump (23) is arranged on the gas extraction pipe (20). The bottom end of the gas extraction well (21) is 2 to 3 meters higher than the horizontal well (3); and the bottom of the monitoring well (17) is immersed in the coal seam (2).

6. The extraction method of the fluidized extraction system driven by coal seam chemical activation and self-heating according to claim 1 is characterized in that: The horizontal drilling well (3) is close to the bottom of the coal seam (2), the horizontal borehole (25) is 0.3 to 0.8 m away from the top of the coal seam (2), and the horizontal drilling well (3) is parallel to the horizontal drilling well (3).

7. The extraction method of the fluidized extraction system driven by coal seam chemical activation and self-heating according to claim 1 is characterized in that: A first four-way flow-dividing valve (14) is provided between the small-size pipe (29) and the large-size pipe (5), and a second four-way flow-dividing valve (28) is provided between the liquid injection branch pipe (30) and the liquid injection main pipe (4).

8. The extraction method of the fluidized extraction system driven by coal seam chemical activation and self-heating according to claim 1 is characterized in that: The maximum temperature resistance value of the temperature sensor (18) is 1800°C, and the effective working temperature range is between 0 and 1200°C.

9. The extraction method of the fluidized extraction system driven by coal seam chemical activation and self-heating according to claim 1 is characterized in that: When the temperature sensor (18) detects that the temperature of the coal seam (2) reaches 280-290° C., the injection pump (10) is connected to a water source to inject water to cool the coal seam (2) to room temperature.

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