Mine water source fluorine reduction method considering influence of coal mining disturbance factors

Abstract

The invention provides a mine water source fluorine reduction method considering the influence of coal mining disturbance factors. The method comprises the following steps: step 1, collecting a water sample and detecting fluorine concentration; and 2, qualitatively determining the source of the mine water by utilizing the characteristic difference presented by the Dove graph. 3, qualitatively determining the source of the primary aquifer of fluorine in the mine water by using the mass concentration scatter distribution diagram of fluorine ions in different types of water samples; and 4, quantitatively calculating the contribution ratio of the primary geological deposition and the coal mining disturbance to the fluorine in the mine water by using the fluorine concentration in the mine water at different positions and adopting a fluorine source calculation model. And step 5, based on the contribution rate of each source to fluorine in the mine water, providing a mine water goaf source fluorine reducing method, and reducing the fluorine concentration in the mine water so as to solve the technical problem that the fluorine source in the mine water is difficult to quantify and treat.

Description

Technical Field

[0001] The present invention belongs to the technical field of mine water treatment and utilization, relates to mine water quality monitoring, and specifically relates to a method for reducing fluorine at the source of mine water taking into account the influence of coal mining disturbance factors. Background Art

[0002] Affected by the dual influence and control of original geological deposition and human mining disturbance, the fluorine content in mine water in western mining areas generally exceeds the standard. The fluorine concentration in mine water is greater than 1 mg / L, exceeding the Class III limit of the "Groundwater Quality Standard" (GB14848-2017) and the "National Drinking Water Quality Standard" (GB5749-2022).

[0003] In recent years, as coal mining has gradually shifted to western China, efforts to improve mine water resource utilization have prioritized its use in water-scarce areas, with specific application scenarios for mine water in production, domestic use, ecology, and agriculture. However, excessive fluoride levels in mine water have become a significant barrier to its resource utilization.

[0004] Before high-fluoride mine water can be utilized as a resource, identifying its primary sources, quantitatively calculating the proportions of each source, and developing corresponding fluoride reduction methods are crucial. Currently, analytical methods for identifying the sources of fluoride in mine water remain at the qualitative stage, with no precise quantitative methods available. Furthermore, current fluoride removal methods for mine water are primarily end-of-pipe treatment, leaving a lack of methods for reducing fluoride at the source. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a method for reducing fluoride at the source of mine water that takes into account the influence of coal mining disturbance factors, so as to solve the technical problems in the existing technology that the source of fluoride in mine water cannot be quantitatively analyzed and the fluoride concentration in mine water cannot be controlled from the source.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A method for reducing fluoride at the source of mine water taking into account the influence of coal mining disturbance factors, the method comprising the following steps:

[0008] Step 1: Water sample collection and fluoride concentration detection:

[0009] Collect water samples, acidify them, filter the acidified water samples to remove suspended particulate matter, and then use an ultraviolet spectrophotometer to measure the absorbance at a wavelength of 530nm. The fluorine concentration in the water sample is finally measured by conversion through a standard curve.

[0010] The water samples include surface water samples, groundwater samples from different aquifers, mine water samples from the central water tank, mine water samples from the working face, mine water samples from the goaf, and mine filling water source samples.

[0011] Step 2: Determine the source of mine water:

[0012] Test the water samples for conventional ion concentrations, pH, and TDS, and draw a Dove diagram based on the test results. Utilize the characteristic differences shown on the Dove diagram to qualitatively determine the source of the mine water.

[0013] The conventional ions include K + 、Na + , Ca 2+ Mg 2+ 、SO4 2 、Cl － and HCO3 － .

[0014] Step 3: Determine the primary aquifer source of fluoride:

[0015] According to the main source of the mine water obtained in step 2, combined with the fluoride concentration in the water sample obtained in step 1, the primary aquifer source of the fluoride in the mine water is qualitatively determined using the scatter plot of the mass concentration of fluoride ions in different types of water samples.

[0016] Step 4: Calculate the contribution ratio of fluoride in mine water:

[0017] Based on the original aquifer source of fluorine obtained in step three, the fluorine concentration in mine water at different locations is used, and a fluorine source calculation model is adopted to quantitatively calculate the contribution ratio of original geological deposition and coal mining disturbance to fluorine in mine water.

[0018] The expression of the fluorine source calculation model is:

[0019]

[0020]

[0021] 0<f ij <1;

[0022] S j ≥0;

[0023] Where:

[0024] C i represents the fluorine concentration in the i-th mine water sample in the central water tank;

[0025] f ij It indicates the fraction of the selected mine water sample index that comes from the j-type source;

[0026] S j represents the average concentration of the jth type of source;

[0027] m represents the total number of source classes.

[0028] The present invention also has the following technical features:

[0029] In step 1, fuming nitric acid is added to acidify the water sample to pH = 2.

[0030] In step 1, the acidified water sample is filtered using a 0.45 μm filter membrane to remove suspended particulate matter in the water.

[0031] In step 2, a high-frequency plasma spectrometer is used to detect K + 、Na + , Ca 2+ Mg 2+ 、SO4 2 and Cl － Concentration; HCO3 is detected by chemical titration － Concentration; a portable multi-parameter TDS and pH analyzer was used to detect the pH and TDS of the water samples.

[0032] It also includes step five, reducing fluoride at the source of mine water:

[0033] Based on the contribution ratio of primary geological deposition and coal mining disturbance to fluoride in mine water obtained in step 4, large-aperture segmented drilling and gradient filter filling boreholes are arranged in the goaf to timely drain high-fluoride groundwater entering the goaf; the orthogonal network hole layout method is used to optimize the spatial layout of drainage boreholes in the goaf.

[0034] Compared with the prior art, the present invention has the following technical effects:

[0035] (I) The method of the present invention constructs a source-sink analytical model for fluorine in mine water to accurately quantify the contribution rate of each source to fluorine in mine water, and proposes a technology for reducing fluorine at the source to reduce the fluorine concentration in mine water, thereby solving the technical problems of difficult quantification and treatment of fluorine sources in mine water.

[0036] (II) The method of the present invention fully considers the control effect of fluorine formation in mine water, which is affected by two factors: original geological deposition and artificial coal mining disturbance. That is, the concentration of fluorine in mine water depends in part on the concentration of fluorine in the original groundwater, and in part on the concentration of fluorine in the mine water in the goaf due to the interaction between groundwater and broken rocks in the goaf after the coal mining disturbance.

[0037] (III) Through accurate analysis of the formation mechanism of fluoride in mine water, a source-sink analytical model of fluoride in mine water was constructed, and the contribution rate of each source to fluoride in mine water was accurately calculated. Based on this, a method of source control to reduce the fluoride concentration in mine water was proposed, providing a basis for the resource utilization of high-fluoride mine water. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of drilling structure.

[0039] Figure 2 This is the comprehensive hydrogeological histogram of the study area.

[0040] Figure 3 Dove diagram for mine water source identification.

[0041] Figure 4 The figure shows the scatter distribution of fluoride ions in different types of water samples.

[0042] The specific contents of the present invention are further described in detail below with reference to the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0043] It should be noted that, unless otherwise specified, all devices and methods in the present invention adopt devices and methods known in the prior art.

[0044] In terms of removing fluoride from mine water, most of the focus has been on terminal treatment and removal, and there is no method for reducing fluoride at the source. In response to the current technical gaps and defects in the sources and removal of fluoride in mine water, the present invention has found through a large amount of preliminary research that the formation of fluoride in mine water is subject to the dual control and influence of primary geological deposition and artificial coal mining disturbance. That is to say, under the long-term influence of water-rock interaction, high-fluoride groundwater is formed. Under the influence of coal mining disturbance factors, part of the high-fluoride groundwater flows out of the coal mining working face, and part enters the goaf. The high-fluoride groundwater entering the goaf undergoes secondary water-rock interaction with the broken coal rock, which further increases the fluoride concentration in the goaf. Whether it is working face mine water or goaf mine water, it eventually converges in the central water tank underground to form mixed high-fluoride mine water. Therefore, the present invention, based on the accurate analysis of the control factors and main sources of fluoride formation in mine water, constructs a mine water fluoride source-sink analysis model, quantitatively analyzes the contribution rate of each source to fluoride in mine water, and proposes a method for reducing fluoride at the source based on the contribution rate of each source, thereby accelerating the resource utilization of high-fluoride mine water in the west.

[0045] In accordance with the above technical solution, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0046] Example:

[0047] This embodiment provides a method for reducing fluoride at the source of mine water by taking into account the influence of coal mining disturbance factors. The method comprises the following steps:

[0048] Step 1: Water sample collection and fluoride concentration detection:

[0049] Collect water samples, acidify them, filter the acidified water samples to remove suspended particulate matter, and then use an ultraviolet spectrophotometer to measure the absorbance at a wavelength of 530nm. The fluorine concentration in the water sample is finally measured by conversion through a standard curve.

[0050] Water samples include surface water samples, groundwater samples from different aquifers, mine water samples from the central water tank, mine water samples from the working face, mine water samples from the goaf, and mine water source samples.

[0051] Preferably, in step 1, fuming nitric acid is added to acidify the water sample to pH=2 to inhibit the generation of hydroxide ions, thereby avoiding the generation of precipitates that affect the detection of fluorine concentration.

[0052] Preferably, in step 1, the acidified water sample is filtered using a 0.45 micron filter membrane to remove suspended particulate matter in the water.

[0053] Step 2: Determine the source of mine water:

[0054] Test the water samples for conventional ion concentrations, pH, and TDS, and draw a Dove diagram based on the test results. Utilize the characteristic differences shown on the Dove diagram to qualitatively determine the source of the mine water.

[0055] Common ions include K + 、Na + , Ca 2+ Mg 2+ 、SO4 2 、Cl － and HCO3 － .

[0056] In step 2, preferably, a high frequency plasma spectrometer is used to detect K + 、Na + , Ca 2+ Mg 2+ 、SO4 2 and Cl － Concentration; HCO3 is detected by chemical titration － Concentration; a portable multi-parameter TDS and pH analyzer was used to detect the pH and TDS (Total Dissolved Solids) of the water samples.

[0057] Step 3: Determine the primary aquifer source of fluoride:

[0058] According to the main source of the mine water obtained in step 2, combined with the fluoride concentration in the water sample obtained in step 1, the primary aquifer source of the fluoride in the mine water is qualitatively determined using the scatter plot of the mass concentration of fluoride ions in different types of water samples.

[0059] Step 4: Calculate the contribution ratio of fluoride in mine water:

[0060] Based on the original aquifer source of fluorine obtained in step three, the fluorine concentration in mine water at different locations is used, and a fluorine source calculation model is adopted to quantitatively calculate the contribution ratio of original geological deposition and coal mining disturbance to fluorine in mine water.

[0061] The expression of the fluorine source calculation model is:

[0062]

[0063] 0<f ij <1;

[0064] S j ≥0;

[0065] Where:

[0066] C i represents the concentration of fluorine in the i-th mine water sample in the central water tank, in mg / L;

[0067] g ij It indicates the fraction of the selected mine water sample index that comes from the j-type source;

[0068] S j It represents the average concentration of the jth type of source, in mg / L;

[0069] m represents the total number of source classes.

[0070] In step 4, the specific fluorine source calculation model is constructed based on the source-sink principle of mine water. The mine water in the central water tank is set as the convergence point, the groundwater represents the source of original geological sedimentary fluorine, and the goaf represents the source of fluorine affected by mining disturbance, that is, the groundwater and goaf water are the sources respectively.

[0071] In step 4, the sources and sinks in the fluorine source calculation model need to meet the following four assumptions:

[0072] First, the fluoride in the mine water in the central water tank comes from groundwater and mine water in the goaf.

[0073] Second, there is a significant difference in the fluoride concentrations in the water of the two.

[0074] Third, the fluoride concentrations in the water bodies of both are relatively stable.

[0075] Fourth, the two are relatively independent in the process of converging into the central water tank, and almost no chemical reaction occurs.

[0076] In step 4, the collected groundwater samples, goaf water samples, and central water tank samples are combined and fed into the fluorine source calculation model to solve the equation. Finally, the contribution of fluorine in the groundwater and goaf water samples is calculated based on the solution.

[0077] In step 4, the contribution of fluorine in groundwater represents the contribution of primary geological deposition, the contribution of fluorine in mine water in the goaf represents the contribution of human mining disturbance, and the sum of the contribution rates of primary geological deposition and human mining disturbance fluorine is equal to 100%.

[0078] Step 5: Reduce fluoride at the source of mine water:

[0079] Based on the contribution ratio of primary geological deposits and coal mining disturbance to fluorine in mine water obtained in step 4, large-aperture segmented drilling-gradient filter filling boreholes are arranged in the goaf to timely drain the high-fluorine groundwater entering the goaf, so as to prevent secondary water-rock reaction between groundwater and broken coal and rock in the goaf, causing the fluorine concentration in the mine water in the goaf to further increase.

[0080] The orthogonal network hole layout method is used to optimize the spatial layout of drilling holes in the goaf:

[0081] In step five, compared with traditional drilling, large-aperture segmented drilling and gradient filter material filling drilling have three advantages: high drainage efficiency, preliminary filtration of high-fluoride groundwater during drainage, not easy to clog and long service life.

[0082] Specifically in this embodiment, the structure of the drilling is as follows Figure 1 As shown, the system consists of three stages: the first-stage diversion section has a depth of 0-100m and a 380mm diameter. It uses a double-helix drill bit to quickly penetrate the aquifer. The second-stage filtration section has a depth of 100-200m and a 180mm diameter. This section is filled with different filter media to prevent clogging and provide initial adsorption of fluoride from the groundwater. The filter media is a mixture of 40% 2-6mm gravel, 30% 0.2mm-2mm quartz sand, and 30% 0.1-0.2mm artificial zeolite. The third-stage section, with a depth of less than 200m and a 140mm diameter, is filled with a polyurethane-fly ash composite material. This material has excellent toughness and primarily acts as a seal to prevent rock collapse into the drainage borehole.

[0083] Specifically, in this embodiment, an orthogonal network drilling method is used. Based on the area of ​​the goaf, the spacing between boreholes is set at 100×100 meters, ensuring a drainage borehole coverage rate of at least 85%. Additionally, inclined boreholes are arranged near the retained coal pillars, with an inclination angle of 20-25°, to directional divert high-fluoride groundwater within the goaf.

[0084] Application examples:

[0085] This application example provides a method for reducing fluorine in mine water sources based on the above-mentioned embodiment, taking into account the influence of coal mining disturbance factors. Specifically, the Shendong mining area is located in the area bordering Shaanxi Province and Inner Mongolia Autonomous Region, with an altitude of 1015-1190m. It is a transition zone from the Maowusu Desert to the Loess Plateau. The landform is mainly hilly, with no obvious mountains and a relatively flat terrain. The mining area covers an area of ​​approximately 3356.11km 2 The mining area includes 9 coal mines, namely, Bulutai Coal Mine, Cuncao Tower Coal Mine, Wulanmulun Coal Mine, Bulianta Coal Mine, Shangwan Coal Mine, Halagou Coal Mine, Shigetai Coal Mine, Daliuta Coal Mine and Huojitu Coal Mine. The study area has a typical temperate continental semi-arid climate, with an average annual temperature of 11°C, an average annual rainfall of about 360mm, and an average annual evaporation of about 2500mm, which is 5 to 10 times the rainfall. It is dry and rainy, and the evaporation is large. The groundwater mainly comes from the infiltration of atmospheric precipitation, so the groundwater in the area is relatively scarce. The surface water system is mainly the Kuye River, a tributary of the middle reaches of the Yellow River, and its tributary, the Wulanmulun River, flows through the entire mining area. The underground aquifers in the study area mainly include the Quaternary (Q4) loose groundwater aquifer, the Cretaceous Zhidan Group (K1z) sandstone fissure groundwater aquifer, the Jurassic Zhiluo Formation (J 2z ), Jurassic Yan'an Formation (J 2y ) fractured confined aquifer and the Upper Triassic Yanchang Formation (T 3y ) fractured confined aquifer. The Yan'an Formation includes the water-bearing rock section from the bottom of the Zhiluo Formation to the 2-2 coal roof (abbreviated as the 2-2 coal roof) and the water-bearing section from the 2-2 coal bottom to the 3-1 coal roof (abbreviated as the 3-1 coal roof). The comprehensive hydrogeological histogram is shown in the figure below. Figure 2 shown.

[0086] The method comprises the following steps:

[0087] Step 1: Water sample collection and fluoride concentration detection:

[0088] To investigate the distribution and primary sources of fluoride in mine water, 71 samples of mine water and mine fill water were collected from the study area. These samples included 33 mine water samples, 6 surface water samples, and 16 groundwater samples. These samples included 32 from the 2-2 coal mine, 17 from the 3-1 coal mine, 3 from Quaternary groundwater, 3 from the Zhiluo Formation, 10 from the Yan'an Formation, and 6 from surface water. Fluoride concentrations were measured for all 71 samples. The results are shown in Table 1.

[0089] Table 1 Statistics of fluoride ion concentrations in different types of water samples in the study area

[0090]

[0091]

[0092] Table 1 shows that the average fluoride concentrations in the mine water from the six mining areas of Burtai, Wulanmulun, Cuncaota, Bulianta, Shangwan, and Halagou were 8.45, 2.34, 4.75, 4.5, 4.03, and 6.36 mg / L, respectively, all exceeding 1 mg / L, indicating high-fluoride mine water. The average fluoride concentrations in the mine water from the three mining areas of Shigetai, Daliuta, and Huojitu were 0.38, 0.79, and 0.89 mg / L, respectively, all below 1 mg / L, indicating low-fluoride mine water.

[0093] Step 2: Determine the source of mine water:

[0094] Routine ion concentration, pH, and TDS physical and chemical tests were performed on 71 groups of water samples. The test and statistical results are shown in Table 2.

[0095] Table 2 Statistics of conventional ion concentrations of different types of water samples in the study area

[0096]

[0097]

[0098] According to Table 2, the Dove diagram for distinguishing the water sources of surface water, 3-1 coal roof groundwater, and 3-1 coal mine water is drawn as follows: Figure 3 As shown in the figure, we can know that the hydrochemical types of 3-1 coal mine water and 3-1 coal roof groundwater are both HCO3-Na type, and the main source of 3- coal mine water is 3-1 coal roof groundwater.

[0099] Step 3: Determine the primary aquifer source of fluoride:

[0100] According to the fluorine concentration test results, the scatter plot of fluorine ion mass concentration in surface water, Quaternary system, Zhiluo formation, Yan'an formation groundwater and mine water is drawn as follows: Figure 4 As shown. Clearly, the fluoride ion concentrations in surface water, Quaternary system, and Zhiluo Formation groundwater are all below the standard limit of 1 mg / L. The Yan'an Formation coal-bearing groundwater is further divided into three parts: 1-2 coal roof groundwater, 2-2 coal roof groundwater, and 3-1 coal roof groundwater. While the fluoride concentrations in 1-2 coal mine water, 2-2 coal roof groundwater, and 2-2 coal mine water are all below 1 mg / L, the fluoride concentrations in 3-1 coal mine water and 3-1 coal roof groundwater are far above 1 mg / L. Therefore, preliminary evidence suggests that the fluoride in the 3-1 coal mine water primarily originates from the Yan'an Formation (3-1 coal roof) groundwater.

[0101] Step 4: Calculate the contribution ratio of fluoride in mine water:

[0102] According to the principles of fluorine mathematical model construction, the Yan'an Group (3-1 coal roof groundwater) samples, goaf water samples, and central water tank water samples were combined into 55 groups. The 55 groups were substituted into formulas (1)-(4) for calculation, and the calculation results were statistically analyzed. The statistical results are shown in Table 3.

[0103] Table 3 Statistics of calculation results of fluorine mathematical model

[0104]

[0105] It can be seen from Table 3 that the proportion of fluorine in the central water tank coming from the Yan'an Formation is in the range of (75, 100], and the statistical number is 24, accounting for 54.54% of the total; the proportion coming from the goaf is in the range of (0, 25], and the statistical proportion is 45.45%. By averaging the calculation results of the 55 groups, it can be approximately determined that the proportion of fluorine in the central water tank coming from the Yan'an Formation is 61.83%, and the proportion coming from the goaf is 39.36%. In other words, the contribution of primary geological deposition to the source of fluorine in mine water is 61.83%, and the contribution of artificial coal mining disturbance to the source of fluorine in mine water is 39.36%.

[0106] Step 5: Reduce fluoride at the source of mine water:

[0107] In order to reduce the impact of mining disturbance on the fluoride concentration in mine water, when high-fluoride groundwater flows into the goaf, the mine water in the goaf is directly drained by laying segmented boreholes in the goaf. Taking the 2113 goaf of Buertai as an example, the fluoride concentration in the original groundwater is 7.2 mg / L. Before the implementation of the source fluoride reduction technology, the fluoride concentration in the mixed mine water in the 2114 central water tank was 10.3 mg / L. This is because the mine water from the 2114 goaf is mixed into the central water tank, that is, after the high-fluoride groundwater enters the goaf, it continues to react with the broken coal rock in the goaf, causing the fluoride concentration in the mine water in the goaf to further increase to 11.41 mg / L. The area of ​​the 2113 goaf is approximately 4.2 km 2 180 drill holes are arranged in a grid pattern, spaced 50 meters apart. These drill holes allow for immediate drainage of mine water entering the goaf. The primary source of mine water in the central water tank is water inflow from the working face, resulting in water quality close to primary groundwater. After implementing source-directed fluoride reduction technology, the concentration of mine water in the central water tank has dropped to 7.5 mg / L, compared to 10.3 mg / L in the adjacent goaf, a 27.84% reduction.

Claims

1. A method for reducing fluoride at the source of mine water taking into account the influence of coal mining disturbance factors, characterized in that: The method comprises the following steps: Step 1: Water sample collection and fluoride concentration detection: Collect water samples, acidify them after collection, filter the acidified water samples to remove suspended particulate matter, and then use an ultraviolet spectrophotometer to measure the absorbance at a wavelength of 530nm. The fluorine concentration in the water sample is finally measured by conversion using a standard curve. The water samples include surface water samples, groundwater samples from different aquifers, mine water samples from the central water tank, mine water samples from the working face, mine water samples from the goaf, and water samples from the mine filling source; Step 2: Determine the source of mine water: Detect the concentration of common ions, pH and TDS in water samples, and draw Dove diagrams based on the test results; use the characteristic differences shown in the Dove diagrams to qualitatively determine the source of mine water; The conventional ions include K + 、Na + , Ca 2+ Mg 2+ 、SO4 2 、Cl － and HCO3 － ; Step 3: Determine the primary aquifer source of fluoride: Based on the main source of the mine water obtained in step 2, combined with the fluoride concentration in the water sample obtained in step 1, and using the scatter plot of fluoride ion mass concentration in different types of water samples, qualitatively determine the primary aquifer source of the fluoride in the mine water; Step 4: Calculate the contribution ratio of fluoride in mine water: Based on the primary aquifer source of fluorine obtained in step 3, the fluorine concentration in mine water at different locations is used, and a fluorine source calculation model is adopted to quantitatively calculate the contribution ratio of primary geological deposition and coal mining disturbance to fluorine in mine water; The expression of the fluorine source calculation model is: 0＜f ij ＜1； S j ≥0； Where: C i represents the fluorine concentration in the i-th mine water sample in the central water tank; f ij It indicates the fraction of the selected mine water sample index that comes from the j-type source; S j represents the average concentration of the jth type of source; m represents the total number of source classes.

2. The method for reducing fluorine in mine water source considering the influence of coal mining disturbance factors according to claim 1, characterized in that: In step 1, fuming nitric acid is added to acidify the water sample to pH = 2.

3. The method for reducing fluorine in mine water source considering the influence of coal mining disturbance factors according to claim 1, characterized in that: In step 1, the acidified water sample is filtered using a 0.45 μm filter membrane to remove suspended particulate matter in the water.

4. The method for reducing fluorine in mine water source considering the influence of coal mining disturbance factors according to claim 1, characterized in that: In step 2, a high-frequency plasma spectrometer is used to detect K + 、Na + , Ca 2+ Mg 2+ 、SO4 2 and Cl － Concentration; HCO3 is detected by chemical titration － Concentration; a portable multi-parameter TDS and pH analyzer was used to detect the pH and TDS of the water samples.

5. The method for reducing fluorine in mine water source considering the influence of coal mining disturbance factors according to claim 1, characterized in that: It also includes step five, reducing fluoride at the source of mine water: Based on the contribution ratio of primary geological deposition and coal mining disturbance to fluoride in mine water obtained in step 4, large-aperture segmented drilling and gradient filter filling boreholes are arranged in the goaf to timely drain high-fluoride groundwater entering the goaf; the orthogonal network hole layout method is used to optimize the spatial layout of drainage boreholes in the goaf.

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