A coal mine aquifer freezing prevention and control water system and method

Abstract

The present invention provides a coal mine aquifer freezing prevention and control water system and method, comprising a liquid nitrogen storage tank, a pressure pump, a liquid nitrogen delivery pipe, a liquid nitrogen perfusion mechanism, a nitrogen delivery pipe, an air extraction pump and a nitrogen collection tank, wherein the liquid nitrogen perfusion mechanism comprises a sleeve, a liquid injection pipe and a gas collection pipe, and the liquid nitrogen delivery pipe and the nitrogen delivery pipe are laid on the surface of the coal mine mining area; the liquid nitrogen perfusion mechanism is embedded in a borehole in the coal mine mining area, the liquid injection pipe passes through the sleeve, one end of the liquid injection pipe is connected to the liquid nitrogen delivery pipe, and the other end penetrates into the coal mine aquifer, thereby being able to perfuse liquid nitrogen into the coal mine aquifer; one end of the gas collection pipe is fixedly connected to an upper end cover of the sleeve, and the other end is connected to the nitrogen delivery pipe, thereby being able to convey gas in the coal mine aquifer to the nitrogen delivery pipe; the pressure pump is respectively connected to the liquid nitrogen storage tank and the liquid nitrogen delivery pipe, thereby being able to pump liquid nitrogen into the liquid nitrogen delivery pipe; the air extraction pump is respectively connected to the nitrogen collection tank and the nitrogen delivery pipe, thereby being able to pump gas in the nitrogen delivery pipe into the nitrogen collection tank.

Description

Technical Field

[0001] The present invention relates to the field of coal mine production safety, and in particular to a coal mine aquifer freezing prevention and control water system and method. Background Art

[0002] Due to the geological conditions of coal mining areas, water inrush is a common occurrence during coal mining. Water inrush, also known as mine flooding or, more commonly, mine seepage, is a major disaster common in coal mining operations. Water inrush not only impacts normal coal mining operations and reduces productivity, but in severe cases can also flood the mine and mining area, causing casualties. Therefore, effective waterproofing of the mine is crucial to ensuring safe production in coal mines.

[0003] The primary cause of water inrush in coal mines is coal mine aquifer water, the most common and direct source of water inrush in coal mines. While coal seams themselves typically contain no water, the thick, highly confined aquifers overlying them, including conglomerate layers, quicksand layers, and karst limestone layers, all contain significant amounts of water. When these aquifers connect to the mining area through channels, they become the source of water inrush in coal mines. Furthermore, due to the complex hydrogeological conditions in coal mining areas and the continuous development and migration of mining-induced fractures due to mining activities, the amount of water inrush in coal mines increases dramatically, severely impacting the advancement of the mining face.

[0004] At present, the methods for controlling water inrush in mining areas are usually pumping and grouting.

[0005] Water pumping treatment is to use mechanical equipment such as pumps to extract water from the aquifer to reduce the amount of water in the aquifer and achieve the purpose of flood control;

[0006] Grouting sealing is achieved by using grouting technology to fill the water-conducting cracks in the overburden, cut off the hydraulic connection between the aquifer and the mining area, and achieve the purpose of water prevention and control.

[0007] However, the geological environment of coal mine aquifers is complex, the water supply sources are frequent and unclear, and there is a "black box" in the exploration of the distribution characteristics of the water-conducting fracture network. Therefore, the above two methods of mine water inrush control have the problems of large drainage workload and poor water control effect; incomplete grouting or poor sealing leads to secondary water inrush in the mine; and in the process of grouting and sealing to control water inrush, the sealing materials used also have the possibility of contaminating groundwater. Summary of the Invention

[0008] In order to solve the above problems existing in the prior art, the present invention provides a coal mine aquifer freezing prevention and control water system and method.

[0009] The technical solutions provided by the present invention are as follows:

[0010] A coal mine aquifer freezing prevention and control water system includes a liquid nitrogen storage tank, a pressure pump, a liquid nitrogen delivery pipe, a liquid nitrogen filling mechanism, a nitrogen delivery pipe, an air extraction pump and a nitrogen collection tank.

[0011] Wherein, the liquid nitrogen perfusion mechanism includes a sleeve, a liquid injection pipe and a gas collecting pipe, and the liquid nitrogen delivery pipe and the nitrogen delivery pipe are laid on the surface of the coal mining area;

[0012] The liquid nitrogen injection mechanism is embedded in a borehole in the coal mine mining area, and the injection pipe passes through the sleeve, one end of which is connected to the liquid nitrogen delivery pipe, and the other end penetrates into the coal mine aquifer, thereby injecting liquid nitrogen into the coal mine aquifer;

[0013] One end of the gas collecting pipe is fixedly connected to the upper end cover of the sleeve, and the other end is connected to the nitrogen delivery pipe, so as to be able to deliver the gas in the coal mine aquifer to the nitrogen delivery pipe;

[0014] The pressure pump is connected to the liquid nitrogen storage tank and the liquid nitrogen delivery pipe respectively, and can pump liquid nitrogen into the liquid nitrogen delivery pipe;

[0015] The vacuum pump is connected to the nitrogen collection tank and the nitrogen delivery pipe respectively, and can pump the gas in the nitrogen delivery pipe into the nitrogen collection tank.

[0016] Furthermore, the system also includes a control mechanism, which includes a liquid flow meter, an airflow sensor and a 51 single-chip microcomputer, wherein the liquid flow meter is installed at the liquid nitrogen delivery pipe and can measure the volume of liquid nitrogen pumped into the liquid nitrogen delivery pipe by the pressure pump;

[0017] The air flow sensor is installed at the nitrogen delivery pipe, and is used to measure the nitrogen flow in the nitrogen delivery pipe in real time, and transmit digital information to the single chip microcomputer through a signal line;

[0018] The 51 single chip microcomputer can receive the digital information and set the gas flow threshold, and connect and control the pressure pump through the signal line to start and operate for a set time before shutting down.

[0019] Furthermore, the system is also provided with a nitrogen generator, which is arranged on the surface of the coal mining area.

[0020] Furthermore, a boiling stop chamber and a filtering chamber are sequentially arranged inside the sleeve from bottom to top, and zeolite or broken porcelain pieces are placed in the boiling stop chamber; filter materials such as filter cotton or sand and gravel are placed in the filtering chamber.

[0021] Furthermore, an annular airbag is embedded on the outer side of the sleeve.

[0022] Furthermore, the liquid injection pipe, the gas collecting pipe and the sleeve are integrally formed.

[0023] Furthermore, the inner wall of the sleeve is covered with a heat insulation layer, and the sleeve and the injection pipe are made of 45# steel pipe or Q345 steel pipe, and their surfaces are galvanized.

[0024] Furthermore, the pressure standard provided by the pressure pump is calculated as σ1=αγM,

[0025] Wherein, σ1-boosting pump pressure, KN; M-aquifer burial depth, m; γ-average volume force of overlying strata of aquifer, KN / m; α-richness coefficient;

[0026] The calculation formula of the force σ2 provided by the air pump is σ2=λ696V n ρ n gm,

[0027] Where, λ is the liquid-gas conversion loss coefficient of liquid nitrogen; V n - Liquid nitrogen injection volume per hole, m 3 ρ n - density of liquid nitrogen; m - number of boreholes in the area of ​​aquifer freezing operation.

[0028] Using the above-mentioned coal mine aquifer freezing prevention water system, the present invention provides a coal mine aquifer freezing prevention water method, comprising the following steps:

[0029] S1, conduct geological exploration of the coal mining area to obtain the following geological information: the location, area and buried depth M of the coal mine aquifer; the average volume force γ of the overlying rock layer of the aquifer and the surface temperature ɑ;

[0030] S2, calculate the single hole freezing radius R by the following formula,

[0031]

[0032] Where, R is the radius of single hole freezing, a is the surface temperature, °C; V n - Liquid nitrogen injection volume per hole, m 3 ;c n -Specific heat capacity of liquid nitrogen; c w -average specific heat capacity of the aquifer; ρ n - density of liquid nitrogen; ρ w -average density of aquifer, k-liquid nitrogen vaporization error coefficient; m; μ-assumed spherical error, M-burial depth of coal mine aquifer.

[0033] S3, using a drilling rig to drill holes on the surface of the coal mining area, with the center spacing between adjacent holes less than the single hole freezing radius R; the depth of the holes is to the middle of the aquifer in the vertical direction;

[0034] S4, installing the coal mine aquifer freeze prevention water system, and during the installation process, closing the control mechanism and always keeping the pressure pump on, so that the injection pipe is allowed to penetrate into the aquifer while maintaining a certain air pressure inside the pipe;

[0035] S5, turning on the control mechanism and adjusting the pressure pump according to the volume of liquid nitrogen measured by the liquid flow meter, so that the pressure pump can pump a fixed amount of liquid nitrogen into the liquid nitrogen delivery pipe within a set operating time;

[0036] S6: After completing the single-hole nitrogen injection operation, repeat steps S4-S5 to complete the next single-hole nitrogen injection operation.

[0037] Beneficial effects of the present invention:

[0038] 1. Due to its ultra-low temperature physical properties, liquid nitrogen can effectively freeze the water in the coal mine aquifer, thereby cutting off the hydraulic connection between the water supply source, the aquifer and the mining area, and effectively avoiding the continuous water gushing from the working face due to the unclear water supply source of the aquifer. In addition, the use of water freezing will not cause groundwater pollution, and can effectively avoid the continuous water gushing from the working face due to the unclear distribution characteristics of the overburden water fractures, thereby achieving the purpose of coal mine water prevention and control, with excellent water prevention and control effects.

[0039] 2. The coal mine aquifer freezing prevention and control system described in the present invention uses corresponding formulas to calculate and determine the freezing range of the aquifer and the freezing radius of a single borehole, and determines the operating time of the pressure pump by calculation, so as to accurately control the injection volume of liquid nitrogen in a single borehole; by extracting, recovering, purifying and reproducing the nitrogen gas after the liquid nitrogen is vaporized, the water control cost is greatly reduced and the overall efficiency of the coal mine is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 : Schematic diagram of the coal mine aquifer freezing prevention water system and stratum cross-section of the present invention;

[0041] Figure 2 : Schematic diagram of the distribution of the drill holes of the present invention on the surface of the coal mining area;

[0042] Figure 3 : A partial schematic diagram of the coal mine aquifer freezing prevention water system of the present invention;

[0043] Figure 4 : The present invention Figure 1 A magnified view of point A;

[0044] Figure 5 : The structural diagram of the liquid nitrogen perfusion mechanism of the present invention.

[0045] Explanation of symbols

[0046] 1-Liquid nitrogen storage tank, 2-Pressure pump, 3-Liquid nitrogen delivery pipe, 4-Liquid nitrogen filling mechanism, 41-Sleeve, 42-Liquid injection pipe, 43-Gas collecting pipe, 44-Stop boiling chamber, 45-Filter chamber, 46-Annular air bag, 5-Nitrogen delivery pipe, 6-Vacuum pump, 7-Nitrogen collection tank, 8-Drill hole, 9-Nitrogen purification tank, 10-Liquid flow meter, 11-Air flow sensor, 12-Nitrogen generator, 13-Workstation, 14-Temperature monitor. DETAILED DESCRIPTION

[0047] The present invention will be described in detail below by way of embodiments with reference to the accompanying drawings.

[0048] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the invention. The scope of protection of the present invention shall be as defined in the attached claims.

[0049] As attached Figure 1 To the attached Figure 5 As shown, a coal mine aquifer freezing prevention and control water system includes a nitrogen generator, a liquid nitrogen storage tank 1, a pressure pump 2, a liquid nitrogen delivery pipe 3, a liquid nitrogen filling mechanism 4, a nitrogen delivery pipe 5, an air extraction pump 6, a nitrogen collection tank 7 and a control mechanism.

[0050] The nitrogen generator is used to prepare liquid nitrogen. The nitrogen generator is fixedly installed on the surface of the coal mining area. The liquid nitrogen prepared by the nitrogen generator is stored in a liquid nitrogen storage tank 1.

[0051] The pressure pump 2 is connected to the liquid nitrogen storage tank 1 and the liquid nitrogen delivery pipe 3 respectively, and its purpose is to extract the liquid nitrogen in the liquid nitrogen storage tank 1 and pump the liquid nitrogen into the liquid nitrogen delivery pipe 3 at a certain pressure.

[0052] The liquid nitrogen delivery pipe 3 is laid parallel to the surface of the coal mining area and secured with a support plate. The end away from the pressure pump 2 is sealed. The pipe body of the liquid nitrogen delivery pipe 3 is provided with an infusion hole, and the number of infusion holes is ≥ 1. In this embodiment, a plurality of boreholes 8 are drilled in a regular pattern on the surface of the coal mining area. The depth of each borehole 8 is defined as H, and the distance from the surface to the upper surface of the aquifer is defined as D. If H > D, the liquid nitrogen delivery pipe 3 is laid close to the borehole 8.

[0053] The liquid nitrogen filling mechanism 4 is inserted into the borehole 8, with its top end higher than the surface of the borehole 8. The liquid nitrogen filling mechanism 4 includes a sleeve 41, a liquid filling pipe 42 and a gas collecting pipe 43.

[0054] in,

[0055] The sleeve 41 is a hollow cylinder with a sealed upper end and an open lower end. Inside the sleeve 41, there are a stop-boil chamber 44 and a filter chamber 45, arranged from bottom to top. Zeolite or broken porcelain pieces are placed in the stop-boil chamber 44 to prevent the water surface from rolling due to the large-scale release of nitrogen; filter materials such as filter cotton or sand and gravel are placed in the filter chamber 45 to filter out impurities carried by the nitrogen outflow. The number of the stop-boil chamber 44 and the filter chamber 45 can be set to multiple according to actual production needs, and the stop-boil chamber 44 and the filter chamber 45 can be set to different heights.

[0056] An annular airbag 46 is embedded on the outer side surface of the sleeve 41 near the upper end surface. The annular airbag 46 expands after being inflated to fill the gap between the outer wall of the sleeve 41 and the drilled hole 8 to prevent nitrogen from overflowing.

[0057] The injection tube 42 is made of seamless steel pipe, open at both ends, and extends vertically through the sleeve 41. The bottom end of the injection tube 42 can be set flush with the lower end surface of the sleeve 41, or it can be set to extend into the coal mine aquifer. The top end of the injection tube 42 is a certain distance above the surface of the sleeve 41 and is fixedly connected to the infusion hole of the liquid nitrogen delivery tube 3 via a transfer tube.

[0058] The gas collecting pipe 43 is inserted into the sleeve 41 from the upper end surface thereof, with the top end thereof being higher than the surface of the sleeve 41 by a certain distance, and is fixedly connected to the nitrogen delivery pipe 5 through a transfer pipe.

[0059] Preferably, the liquid injection tube 42, the gas collection tube 43 and the sleeve 41 are integrally formed, which can achieve better liquid infusion and gas collection effects.

[0060] Preferably, the sleeve 41 is made of a seamless steel pipe, and the inner wall of the sleeve 41 is covered with an insulation layer; in order to make the sleeve 41 have excellent mechanical strength and corrosion resistance, 45# steel pipe or Q345 steel pipe is preferably used, and the steel pipe is surface-galvanized.

[0061] A nitrogen delivery pipe 5 is laid along the surface of the coal mining area, secured with support plates, and laid close to the liquid nitrogen delivery pipe 3. One end of the nitrogen delivery pipe 5 is sealed, and the other end is connected to a vacuum pump 6. Multiple air inlet holes are opened in the wall of the nitrogen delivery pipe 5 for connecting to the gas collection pipe 43 of the liquid nitrogen injection mechanism 4.

[0062] The vacuum pump 6 is connected to the nitrogen collection tank 7 via a pipeline and is used to pump the nitrogen in the nitrogen delivery pipe 5 into the nitrogen collection tank 7. The nitrogen collection tank 7 is connected to the nitrogen purification tank 9 via a pipeline, and a valve is provided on the pipeline between the two. The nitrogen collection tank 7 is equipped with a pressure gauge to display and read the air pressure inside the nitrogen collection tank 7. When the air pressure reaches the set value, the valve is opened to transfer the nitrogen through the pipeline to the nitrogen purification tank 9.

[0063] Nitrogen purification tank 9 uses crude nitrogen as raw material, hydrogenates and catalytically removes oxygen, then uses condensed water adsorption for secondary drying and ash removal to remove impurities such as oxygen, water vapor, and dust from the nitrogen, resulting in high-purity nitrogen. The separated and purified nitrogen is transported to nitrogen generator 12, where it is used as raw material for the production of liquid nitrogen.

[0064] The control mechanism includes a liquid flow meter 10, an air flow sensor 11 and a 51 single chip microcomputer.

[0065] in,

[0066] The liquid flow meter 10 is installed at the liquid nitrogen delivery pipe 3 and close to the pressure pump 2 , and is used to measure the volume of liquid nitrogen pumped into the liquid nitrogen delivery pipe 3 by the pressure pump 2 .

[0067] The air flow sensor 11 is installed at the nitrogen delivery pipe 5 and is used to measure the nitrogen flow in the nitrogen delivery pipe 5 in real time and transmit digital information to the 51 single chip microcomputer through the signal line.

[0068] The 51-chip microcontroller is used to set a gas flow threshold. When the nitrogen flow in nitrogen delivery pipe 5 reaches the threshold, for example, when the threshold is set to 0, the 51-chip microcontroller connects and controls the start and stop of booster pump 2 via a signal line. When the digital airflow information transmitted by the airflow sensor triggers the 51-chip microcontroller and reaches the threshold, the 51-chip microcontroller transmits an operation command to booster pump 2, turning it on and allowing it to operate for a set time before turning it off.

[0069] 51 single-chip microcomputer is a general term for single-chip microcomputers compatible with Intel's 8051 instruction system. It is widely used in household appliances, automobiles, industrial measurement and control, and communication equipment. Its instruction system and internal structure are relatively simple. Simple automatic control can be performed by setting relevant instructions. It is a commonly used and mature single-chip microcomputer. This embodiment does not improve its structure and function, so its operating principle will not be described in detail.

[0070] In this embodiment,

[0071] Preferably, the liquid nitrogen storage tank 1, the pressure pump 2, the vacuum pump 6 and the nitrogen collection tank 7 are collectively arranged in a workstation 13. A temperature monitor 14 is provided in the workstation 13. The temperature monitor 14 is used to measure the temperature in the workstation in real time to ensure that the temperature in the workstation is a suitable temperature for storing liquid nitrogen.

[0072] Preferably, the collected nitrogen is used as a raw material to produce liquid nitrogen through a nitrogen generator 12, and the nitrogen generator 12 is an industrial nitrogen generator.

[0073] Preferably, the drilling rig is a crawler drilling rig, which does not require laying tracks on the surface of the coal mining area, thereby saving production costs; moreover, the crawler drilling rig is easy to move and can achieve precise drilling.

[0074] As an example, the pressure standard provided by the pressure pump 2 is calculated as σ1=αγM,

[0075] Wherein, σ1 is the pressure of the booster pump, KN; M is the depth of the aquifer, m; γ is the average volume force of the overlying strata above the aquifer, KN / m; α is the richness coefficient (considering that liquid nitrogen injection requires pressure and that the ground stress is unstable, a reasonable value is selected based on the hydrogeological conditions of the coal mine).

[0076] As a preferred method, the vacuum pump 6 is turned on, and the calculation formula of the force σ2 provided by the vacuum pump 6 is σ2=λ696V n ρ n gm,

[0077] Where, λ is the liquid-to-gas conversion loss coefficient of liquid nitrogen; m is the number of boreholes in the aquifer freezing operation area;

[0078] As a preference, the boreholes 8 are distributed in parallel on the surface of the coal mining area to ensure the comprehensive freezing of the aquifer water. Figure 2 A surface drill hole distribution map is shown.

[0079] According to the above-mentioned coal mine aquifer freezing prevention water system, the present invention provides a coal mine aquifer freezing prevention water method, which includes the following steps.

[0080] S1, conduct geological exploration of the coal mining area to obtain the following geological information:

[0081] The location, area and depth M of the coal mine aquifer;

[0082] The average volume force of the overlying rock layer of the aquifer γ;

[0083] Surface temperatureɑ.

[0084] S2, determining the freezing radius R of a single borehole 8, hereinafter referred to as the single-hole freezing radius R.

[0085] According to the bottom temperature gradient standard, the aquifer temperature T is calculated by the following formula:

[0086]

[0087] Where ɑ is the surface temperature and M is the depth of the aquifer;

[0088] The temperature of liquid nitrogen itself is -196℃.

[0089] The heat Q1 required to convert liquid nitrogen into nitrogen at room temperature is calculated using the following formula:

[0090] Q1=c n ρ n V n (-196-a)

[0091] In order for an aquifer to freeze, the temperature of the aquifer must reach below zero.

[0092] The heat Q2 required to be released by the aquifer within the freezing radius R is calculated using the following formula:

[0093] Q2=c w ρ w V w T

[0094] According to heat transfer theory, the amount of heat absorbed is equal to the amount of heat released, that is,

[0095] Q1=Q2

[0096]

[0097] Set the heat loss during liquid nitrogen injection and the specific heat capacity change during liquid nitrogen vaporization.

[0098] The single hole freezing range is calculated using the following formula:

[0099]

[0100] Since the heat of liquid nitrogen diffuses outward from one point, that is, it diffuses in a spherical shape,

[0101] The single hole freezing radius R is calculated by the following formula:

[0102]

[0103] In the above formula, a-surface temperature, ℃; V w - Single hole freezing range, m 3 ; V n - Liquid nitrogen injection volume per hole, m 3 ;c n -Specific heat capacity of liquid nitrogen; c w -average specific heat capacity of the aquifer; ρ n - density of liquid nitrogen; ρ w -Average density of the aquifer, k-liquid nitrogen vaporization error coefficient; R-single hole freezing radius, m; μ-assumed spherical error.

[0104] In step S3, a drilling rig is used to drill holes 8 on the surface of the coal mining area. The center spacing of the holes 8 is less than the single-hole freezing radius R. To achieve better freezing of the aquifer water and to account for the covered volume and void volume between the spherical bodies during the freezing process, additional holes 8 are added between the parallel holes 8 to reduce the amount of liquid nitrogen injected and thus reduce liquid nitrogen consumption.

[0105] Preferably, considering that the heat of liquid nitrogen diffuses in a spherical shape, the depth of the borehole 8 reaches the middle of the aquifer in the vertical direction.

[0106] S4. Install the coal mine aquifer freeze prevention water system. During installation, disable the control mechanism and keep the booster pump 2 running at all times, allowing the injection pipe 42 to penetrate the aquifer while maintaining a constant pressure. In this step, consider that once the injection pipe 42 is immersed in the aquifer, the aquifer water may be affected by geostress, which could affect subsequent liquid nitrogen injection. Alternatively, the booster pump 2 may be activated to increase pressure before the terminal end of the injection pipe 42 approaches the aquifer.

[0107] S5, turning on the control mechanism, adjusting the pressure pump 2 according to the volume of liquid nitrogen measured by the liquid flow meter 10, so that the pressure pump 2 can pump a fixed amount of liquid nitrogen into the liquid nitrogen delivery pipe 3 within the set operation time.

[0108] S6, after completing the single-hole nitrogen injection operation, repeat steps S4-S5 to complete the next single-hole nitrogen injection operation.

[0109] In the above steps,

[0110] As a preference, multiple liquid nitrogen filling mechanisms 4 can be added according to actual production needs. Figure 2 It shows a schematic diagram of the operation of two groups of liquid nitrogen perfusion mechanisms 4.

[0111] Preferably, as liquid nitrogen is injected into the aquifer, heat transfer occurs between the liquid nitrogen and the water, and the aquifer water begins to freeze. Based on factors such as the working face mining height, inclined length, advancement speed, and the freezing range of a single liquid nitrogen hole, and considering the impact of mining fissures and overburden movement formed during the advancement of the working face on the aquifer range, the aquifer can be frozen in stages according to actual production conditions, specifically divided into frozen areas, freezing operation areas, and areas to be frozen. Affected by the longitudinal diffusion of liquid nitrogen vaporization, the upper and lower rock layers of the aquifer will be partially frozen accordingly. According to actual production needs, the freezing range of the aquifer water can be reasonably controlled by adjusting the injection volume of liquid nitrogen per hole and increasing the drilling density.

[0112] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A coal mine aquifer freezing prevention water system, characterized in that: It includes liquid nitrogen storage tank, pressure pump, liquid nitrogen delivery pipe, liquid nitrogen filling mechanism, nitrogen delivery pipe, vacuum pump and nitrogen collection tank. in, The liquid nitrogen filling mechanism includes a sleeve, a liquid injection pipe and a gas collecting pipe, and the liquid nitrogen delivery pipe and the nitrogen delivery pipe are laid on the surface of the coal mining area; The liquid nitrogen injection mechanism is embedded in a borehole in a coal mining area. The sleeve is a hollow cylinder with a sealed upper end and an open lower end. A boiling stop chamber and a filter chamber are sequentially arranged inside the sleeve from bottom to top. The liquid injection pipe axially passes through the sleeve, one end of which is connected to the liquid nitrogen delivery pipe. While maintaining a certain air pressure in the pipe, the other end penetrates into the coal mine aquifer, thereby injecting liquid nitrogen into the coal mine aquifer. One end of the gas collecting pipe is fixedly connected to the upper end cover of the sleeve, communicating with the sleeve, and the other end is connected to the nitrogen delivery pipe, thereby transporting gas in the coal mine aquifer to the nitrogen delivery pipe. The pressure pump is connected to the liquid nitrogen storage tank and the liquid nitrogen delivery pipe respectively, and can pump liquid nitrogen into the liquid nitrogen delivery pipe; The vacuum pump is connected to the nitrogen collection tank and the nitrogen delivery pipe respectively, and can pump the gas in the nitrogen delivery pipe into the nitrogen collection tank; The center distance between adjacent boreholes is less than the freezing radius of a single hole; the depth of the borehole is to the middle of the aquifer in the vertical direction.

2. A coal mine aquifer freezing prevention water system according to claim 1, characterized in that: The system also includes a control mechanism, which includes a liquid flow meter, an air flow sensor and a 51 single chip microcomputer. in, The liquid flow meter is installed at the liquid nitrogen delivery pipe and can measure the volume of liquid nitrogen pumped into the liquid nitrogen delivery pipe by the pressure pump; The air flow sensor is installed at the nitrogen delivery pipe, and is used to measure the nitrogen flow in the nitrogen delivery pipe in real time, and transmit digital information to the 51 single chip microcomputer through a signal line; The 51 single chip microcomputer is used to set the gas flow threshold, and is connected and controlled through a signal line to start the pressure pump and turn it off after operating for a set time.

3. A coal mine aquifer freezing prevention water system according to claim 1, characterized in that: The system is also provided with a nitrogen generator, which is arranged on the surface of the coal mining area.

4. A coal mine aquifer freezing prevention water system according to claim 1, characterized in that: Zeolite or broken porcelain pieces are placed in the boiling-stopping chamber; filter cotton or sand and gravel are placed in the filtering chamber.

5. A coal mine aquifer freezing prevention water system according to claim 4, characterized in that: An annular air bag is embedded on the outer side of the sleeve.

6. A coal mine aquifer freezing prevention water system according to claim 5, characterized in that: The liquid injection pipe, the gas collecting pipe and the sleeve are integrally formed.

7. A coal mine aquifer freezing prevention water system according to claim 6, characterized in that: The inner wall of the sleeve is covered with a heat insulation layer. The sleeve and the injection pipe are made of 45# steel pipe or Q345 steel pipe, and their surfaces are galvanized.

8. A coal mine aquifer freezing prevention water system according to any one of claims 1 to 7, characterized in that: The calculation formula of the pressure standard provided by the booster pump is: , Where, - Booster pump pressure, KN; M-aquifer depth, m; -Average body force of the overlying strata above the aquifer, KN / m; - Wealth coefficient; The force provided by the air pump The calculation formula is , Where, - Liquid nitrogen liquid-gas conversion loss coefficient; - Liquid nitrogen injection volume per hole, m 3 ; - density of liquid nitrogen; m - number of boreholes within the aquifer freezing operation area.

9. A method for preventing and controlling freezing of aquifers in coal mines using the system for preventing and controlling freezing of aquifers in coal mines according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1, carry out geological exploration of the coal mining area to obtain the following geological information: the location, area and depth of the coal mine aquifer M； Average body force of overlying rock layers of aquifer γ and surface temperatureɑ; S2, calculate the single hole freezing radius R by the following formula, ， Where, R is the freezing radius of a single hole, - surface temperature, °C; - Liquid nitrogen injection volume per hole, m 3 ; -Specific heat capacity of liquid nitrogen; - average specific heat capacity of the aquifer; - density of liquid nitrogen; -average density of aquifer, k-liquid nitrogen vaporization error coefficient; m; - assumed spherical error, M - Depth of coal mine aquifers; S3, using a drilling rig to drill holes on the surface of the coal mining area, with the center spacing between adjacent holes less than the single hole freezing radius R; the depth of the holes is to the middle of the aquifer in the vertical direction; S4, installing the coal mine aquifer freeze prevention water system, and during the installation process, closing the control mechanism and always keeping the pressure pump on, so that the injection pipe is allowed to penetrate into the aquifer while maintaining a certain air pressure inside the pipe; S5, turning on the control mechanism and adjusting the pressure pump according to the volume of liquid nitrogen measured by the liquid flow meter, so that the pressure pump can pump a fixed amount of liquid nitrogen into the liquid nitrogen delivery pipe within a set operating time; S6, after completing the single-hole nitrogen injection operation, repeat steps S4-S5 to complete the next single-hole nitrogen injection operation.

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