Method and device for reducing hardness of sulfate in coal mine well water based on nucleation granulation

Abstract

The invention discloses a method and a device for reducing the hardness of sulfate in coal mine water based on nucleation granulation, which are characterized in that only a special sulfate seed is added into the coal mine water without suspended matters, and the sulfate in the coal mine water is crystallized and precipitated on the surface of the special sulfate seed by using calcium ions in the coal mine water to form a granulated body; discharging granulation bodies to realize synchronous removal and solid-liquid separation of calcium ions and sulfate radicals; the corresponding device comprises a sulfate nucleation granulation tank and a suspended matter tank which are vertically arranged, the sulfate radical special seed crystal added through the seed crystal adding pipe and the coal mine well water with suspended solids removed circulate in the outer cylinder and between the outer cylinder and the inner wall of the sulfate radical nucleation granulation tank in the axial direction to form granulation bodies, sulfate radicals of the coal mine well water can be removed at low cost, and calcium ions are synchronously removed.

Description

Technical Field

[0001] The invention belongs to the technical field of coal mine water treatment, and in particular relates to a method for reducing sulfate hardness in coal mine water based on nucleus crystal granulation. Background Art

[0002] Coal mine water contains sulfate ions produced by oxidation of pyrite, with sulfate content ranging from several thousand to tens of thousands of ppm. Excessive sulfate concentration will lead to the release of toxic sulfides. In addition, sulfate will form scale with calcium ions, increasing the hardness while increasing the operation and maintenance costs of the equipment. The current methods for treating sulfate in coal mine water include reverse osmosis, biological reduction and chemical precipitation. Acidic coal mine water is mostly treated by neutralization chemical precipitation, adding alkaline agents or filtering and neutralizing with limestone as filter material. However, the equipment of the neutralization precipitation method is complex, noisy, and has serious secondary pollution. The reaction product calcium sulfate is mixed with excess limestone, making it difficult to handle. Sulfate can only be further precipitated by membrane salt separation and concentration. However, this method uses a large amount of softening agents, has high investment and operation costs, and the membrane components are easily fouled. Summary of the invention

[0003] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a method for reducing sulfate hardness in coal mine water based on nucleus crystal granulation, so as to remove sulfate ions in coal mine water at low cost and simultaneously remove calcium ions.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A method for reducing sulfate hardness in coal mine water based on nuclear crystal granulation, wherein only sulfate-specific crystal seeds are added to the coal mine water after the suspended matter is removed, calcium ions in the coal mine water are used to cause sulfate in the coal mine water to crystallize and precipitate on the surface of the sulfate-specific crystal seeds to form granules, and the granules are discharged out of the granules to achieve simultaneous removal of calcium ions and sulfate and solid-liquid separation.

[0006] In one embodiment, the calcium ion concentration in the coal mine water after removing suspended matter ranges from 200 to 500 mg / L, the sulfate concentration ranges from 6000 to 8000 mg / L, the dosage of special sulfate seed crystals is 0.3 to 1.8 g / L, the treatment time is more than 30 minutes, and the sulfate concentration in the treated coal mine water ranges from 2000 to 3000 mg / L.

[0007] In one embodiment, the sulfate-specific seed crystals are prepared by the following method: sucrose, calcium nitrate and aluminum sulfate in a weight ratio of 1:1:1.5 to 1:1.2:2 are fully ground until they are evenly mixed, and then concentrated sulfuric acid is added and stirred to obtain a carbonized precursor material, and the precursor material is mixed with a sodium hydroxide solution with a concentration of 1.5 to 2 mol / L according to a solid-liquid ratio of 12 to 15 g / 100 mL, and a magnetic bar is placed in the mixture for stirring. After standing, the mixture is filtered, centrifuged, and washed with deionized water until no sulfate ions are detected in the washing liquid, and then placed in an oven for drying. The mixture is calcined at 550 to 600° C. for 2.5 to 3 hours under a nitrogen atmosphere, and then cooled for 8 to 10 hours to obtain sulfate-specific seed crystals whose main component is ettringite.

[0008] In one embodiment, hydraulic parameters are adjusted to allow the sulfate-specific seed crystals to be suspended in the coal mine water after the suspended matter has been removed.

[0009] The present invention also provides a device for reducing the sulfate hardness in coal mine water based on nucleus crystal granulation, comprising a vertically arranged sulfate nucleus crystal granulation tank and a suspended matter tank; the sulfate nucleus crystal granulation tank is connected to a seed feeding pipe, an outer cylinder coaxial with the tank is arranged in the tank, the upper and lower ends of the outer cylinder are open, and there is a distance from the tank top, tank bottom, and tank wall;

[0010] The water inlet of the suspended matter tank is connected to the water inlet pipe, the suspended matter is removed in the suspended matter tank by the inlet water, the water outlet of the suspended matter tank is connected to the sulfate nucleus crystal granulation tank, and the water outlet pipe is arranged on the upper part of the sulfate nucleus crystal granulation tank;

[0011] The sulfate-specific seeds added through the seed adding pipe and the coal mine water with suspended matter removed circulate axially in the outer cylinder and between the outer cylinder and the inner wall of the sulfate-nucleus crystal granulation tank to form a granulation body. A granulation body discharge port is arranged at the bottom of the sulfate-nucleus crystal granulation tank.

[0012] In one embodiment, the suspension tank is arranged in the sulfate nucleus crystallization granulation tank and is located inside the outer cylinder. An inner cylinder coaxial with the tank is arranged inside the suspension tank. The upper and lower ends of the inner cylinder are open and there is a distance from the tank top, tank bottom and tank wall of the suspension tank. The coagulant and coal mine water circulate axially in the inner cylinder and between the inner cylinder and the inner wall of the suspension tank to remove suspended matter. A sludge discharge pipe is arranged at the bottom of the suspension tank.

[0013] In one embodiment, a separation device is provided on the top of the suspension tank, a vertical central water pipe is provided in the tank, a rotating blade is provided on the central water pipe, the bottom end of the central water pipe is connected to the water inlet pipe, and the top end extends out of the suspension tank to the separation device;

[0014] A circulating water pipe 1 is arranged below the separation device, and an upper circulating water pipe 2 is arranged above the separation device. The outlet of the circulating water pipe 1 is connected to the suspended matter tank, and the outlet of the circulating water pipe 2 is connected to the sulfate nucleus crystal granulation tank.

[0015] In one embodiment, there are multiple water inlet pipes, which are distributed along the circumferential direction and intake water radially. The bottom end of the central water pipe is connected to each water inlet pipe through a vertical water pipe. The inner diameter of the vertical water pipe is larger than the inner diameter of the central water pipe. In addition, along the water flow direction, a connecting structure with a cross-section that first widens and then narrows is provided at the end of the vertical water pipe or the beginning of the central water pipe. The inner diameter of the connecting structure at the largest cross-section is larger than the inner diameter of the vertical water pipe.

[0016] In one embodiment, the separation device is composed of an isolation screen in the upper part and a stirring blade in the lower part. The isolation screen is fixed to the inner wall of the suspension tank. The driving motor on the top of the separation device drives the stirring blade to rotate by driving the stirring shaft.

[0017] In one embodiment, the circulating water pipe 1 and the circulating water pipe 2 are both hollow water pipes used to connect the water inlet and outlet areas of different regions; the water outlet of the circulating water pipe 1 is located directly above the space between the inner cylinder and the inner wall of the suspended matter tank; the water outlet of the circulating water pipe 2 is connected to the space between the outer cylinder and the inner wall of the sulfate core crystal granulation tank through the water inlet pipe of the core crystal granulation area.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The present invention is based on nuclear crystal granulation technology, which can achieve the simultaneous and efficient removal of sulfate and calcium ions in water without adding other agents, and the formed crystal product has the characteristics of compact structure, low water content and high solid-liquid separation efficiency.

[0020] 2. The present invention combines a sludge enrichment device and a granulation device, integrates suspended matter removal and nucleus crystal granulation into one, and can simultaneously realize the nucleus crystal granulation process of sludge coagulation and sulfate reduction in coal mine water, thereby reducing the treatment process, reducing process costs, and improving treatment efficiency.

[0021] 3. The present invention is based on nuclear crystal granulation technology, which only produces granules without sludge; the reaction time is short, the hydraulic retention time is short, and the retention time in a single-stage reactor is only about 10 minutes (the present invention can be designed as a three-stage reaction), which is much shorter than the membrane treatment technology. The floor space, investment, and operation costs are also significantly smaller than membrane treatment technology. The effluent turbidity is small, no sludge is generated, no secondary pollution, and the treatment method is simple and easy to operate. The calcium sulfate crystals produced by this process, namely gypsum, can be used as raw materials in commercial industries, such as fillers in the paint and papermaking industries, and for the manufacture of sulfuric acid and ammonium sulfate.

[0022] 4. The present invention is based on the nuclear crystal granulation technology and does not require the addition of any other reagents. It only induces sulfate crystal crystals to produce precipitates by adding special sulfate seed crystals. The seed crystals are driven by the upward water flow in the nuclear crystal granulation area to be in a fluidized bed state, which increases the contact area between the seed crystals and the solution, is conducive to the realization of rapid heterogeneous induced crystallization, forms large-particle crystal precipitation, reduces energy consumption and reagent dosage and improves water treatment efficiency. It is suitable for the treatment of sulfate in large-volume coal mine water. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of the core crystal granulation device of the present invention.

[0024] Figure 2 This is a SEM characterization picture of the sulfate-specific seed crystal before granulation.

[0025] Figure 3 This is a SEM characterization picture of the sulfate-specific seed crystal after granulation.

[0026] Figure 4 This is the effect of different initial sulfate concentrations on sulfate removal in the present invention.

[0027] Figure 5 This is the effect of different seed crystal addition heights on sulfate removal in the present invention.

[0028] Figure 6 It is a structural schematic diagram of the isolation screen of the present invention. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0030] In order to effectively and cost-effectively solve the problem of high sulfate hardness in coal mine water, the present invention provides a method for reducing sulfate hardness in coal mine water based on nuclear crystal granulation, first pre-treating the coal mine water to remove suspended matter therein, then directly adding sulfate-specific crystal seeds, using the original calcium ions in the coal mine water to make the sulfate in the coal mine water crystallize and precipitate on the surface of the sulfate-specific crystal seeds, under the action of multiple chemical forces, forming a granulation body with a diameter of about 1 mm and a dense and thick spherical structure, and finally expelling the granulation body, so as to achieve the simultaneous removal of calcium ions and sulfate and solid-liquid separation, and obtain clear water after solid-liquid separation, filtration and pH adjustment. Compared with the prior art, the present invention can reduce energy consumption and the dosage of reagents and improve water treatment efficiency, and is suitable for the treatment of sulfate in large-volume coal mine water.

[0031] The method of the present invention does not require any reagents to be added, and only the sulfate-specific crystal seeds and the coexisting calcium ions in water are used to strengthen the removal of sulfate, which can achieve the simultaneous removal of calcium ions and sulfate and solid-liquid separation, and finally discharge the granulated body to achieve the removal of sulfate. The granulated body of the present invention is a calcium sulfate particle with a diameter of about 1 mm and a dense and thick spherical structure, which is finally formed by sulfate enriched on the surface of the dedicated crystal seeds through the nuclear crystal granulation process.

[0032] In the preferred parameter example of the present invention, after the suspended matter is removed from the coal mine water, the calcium ion concentration ranges from 200 to 500 mg / L, and the sulfate concentration ranges from 6000 to 8000 mg / L. In terms of coal mine water, when the dosage of the sulfate-specific crystal seed is 0.3 to 1.8 g / L and the treatment time is more than 30 minutes, the sulfate concentration in the treated coal mine water is controlled below 3000 mg / L, typically 2000 to 3000 mg / L, and the sulfate removal rate is about 60%.

[0033] Among them, the specific implementation method of pre-treatment to remove suspended matter is to add PAM polyacrylamide to the coal mine water to remove the suspended matter in the raw water through coagulation and sedimentation.

[0034] The sulfate-specific seed crystal of the present invention is prepared by the following method: sucrose, calcium nitrate and aluminum sulfate are fully ground until they are uniformly mixed, then concentrated sulfuric acid is added and stirred to obtain a carbonized precursor material, the carbonized material is put into a beaker, a sodium hydroxide solution is added, a magnetic bar is put in for stirring, after standing, deionized water is used for suction filtration, centrifugation, and washing until sulfate ions are not detected in the washing liquid, and then the sulfate-specific seed crystal is put into an oven for drying, and calcined in a nitrogen atmosphere to obtain a sulfate-specific seed crystal with a particle size of 200 to 450 μm, wherein the main component of the sulfate-specific seed crystal is ettringite.

[0035] Preferably, the sulfate-specific seed crystals obtained in the present invention are washed with ultrapure water and dried in an oven before use to remove impurities.

[0036] Preferably, the sulfate-specific crystal seeds can be suspended in the coal mine water after the suspended matter is removed by adjusting the hydraulic parameters and / or the amount of crystal seeds added. The purpose of suspending the sulfate-specific crystal seeds in the coal mine water after the suspended matter is to increase the contact area between the crystal seeds and the water and improve the reaction rate. Specifically, the water inlet flow rate can be adjusted to 5-20m 3 / h, the inlet pH is 6.5-7.5, for example, the inlet flow rate can be 5m 3 / h、12.5m 3 / h、20m 3 / h, and the inlet pH values ​​were 6.5, 7 and 7.5 respectively; by regulating the inlet flow rate between the fluidization velocity and the carry-out velocity, it was ensured that the difference between the actual flow velocity of the fluid in the bed and the sedimentation velocity of the crystal-inducing carrier in the vertical direction caused by gravity was greater than zero, thereby allowing the crystal-inducing carrier to be suspended for nuclear crystallization.

[0037] The present invention also provides a device for reducing the sulfate hardness in coal mine water based on nucleus crystal granulation, which combines a sludge enrichment device with a granulation device to reduce the processing steps, reduce process costs, and improve processing efficiency. Figure 1 As shown, it includes a vertically arranged sulfate nucleus crystal granulation tank 1 and a suspension tank 2. The sulfate nucleus crystal granulation tank 1 is connected to a seed feeding pipe 5, and sulfate-specific seeds are fed through the seed feeding pipe 5. The sulfate nucleus crystal granulation tank 1 is provided with an outer cylinder 21 coaxial with the tank, the upper and lower ends of the outer cylinder 21 are opened, and the cylinder wall is fixed by a bracket or an iron plate 25. The outer cylinder 21 is at a certain distance from the tank top, tank bottom, and tank wall of the sulfate nucleus crystal granulation tank 1. The water inlet of the suspended matter tank 2 is connected to the water inlet pipe 3, and the water inlet is coal mine water. The water outlet of the suspended matter tank 2 is connected to the sulfate nucleus crystal granulation tank 1. The coal mine water enters the sulfate nucleus crystal granulation tank 1 after the suspended matter is removed in the suspended matter tank 2. In the sulfate nucleus crystal granulation tank 1, together with the sulfate special crystal seeds added through the crystal seed adding pipe 5, the granulation body is circulated in the outer cylinder 21 and between the outer cylinder 21 and the inner wall of the sulfate nucleus crystal granulation tank 1 along the axial direction to form a granulation body. The upper part of the sulfate nucleus crystal granulation tank 1 is provided with a water outlet pipe 15 to discharge the coal mine water after the final treatment. The tank bottom of the sulfate nucleus crystal granulation tank 1 is provided with a granulation body discharge port 23 to discharge the granulation body obtained after the final treatment.

[0038] In a further embodiment of the present invention, the suspension tank 2 is arranged in the sulfate nucleus crystal granulation tank 1, specifically arranged in the outer cylinder 21 of the sulfate nucleus crystal granulation tank 1, and preferably arranged coaxially. An inner cylinder 22 coaxial with the tank is arranged in the suspension tank 2, the upper and lower ends of the inner cylinder 22 are opened, and the cylinder wall is fixed by a bracket or an iron plate 25. The inner cylinder 22 is at a certain distance from the tank top, tank bottom, and tank wall of the suspension tank 2. The coagulant and the coal mine water circulate axially in the inner cylinder 22 and between the inner cylinder 22 and the inner wall of the suspension tank 2 to remove the suspended matter. A sludge discharge pipe 10 is arranged at the bottom of the suspension tank 2 to discharge the sludge formed by coagulation.

[0039] In a further embodiment of the present invention, a separation device 19 is provided on the top of the suspended matter tank 2, and the separation device 19 is used to separate impurities, large suspended matter or suspended matter combined with coagulants in the water. A vertical central water pipe 12 is provided in the suspended matter tank 2, and a rotating blade 11 is provided on the central water pipe 12. The bottom end of the central water pipe 12 is connected to the water inlet pipe 3, and the top end extends out of the suspended matter tank 2 to the separation device 19, that is, the raw water of the water inlet pipe 3 directly goes up to the separation device 19 through the central water pipe 12, and the preliminary removal of impurities and suspended matter is completed in the separation device 19.

[0040] A circulating water pipe 13 is arranged below the separation device 19, and the outlet of the circulating water pipe 13 is connected to the suspended matter tank 2. The preliminary separated water to be treated after separation by the separation device 19 falls into the suspended matter tank 2 through the circulating water pipe 13 for circulation, and specifically can be circulated to the space between the tank wall of the suspended matter tank 2 and its inner cylinder 22, go down along the space, and then go up from the inner cylinder 22 to complete the circulation, and better combine with the coagulant during the circulation. Among them, the space inside the inner cylinder 22 and between the tank wall of the suspended matter tank 2 and the inner cylinder 22 form a sludge enrichment zone. During the upward process, the action of the rotating blades 11 can make this part of the water enter the separation device 19 again.

[0041] An upper circulation water pipe 16 is arranged above the separation device 19, and the outlet of the circulation water pipe 16 is connected to the sulfate nucleus crystal granulation tank 1. The deep separation water to be treated after separation by the separation device 19 falls into the sulfate nucleus crystal granulation tank 1 through the circulation water pipe 16 for circulation, and can be circulated to the space between the tank wall of the sulfate nucleus crystal granulation tank 1 and its outer cylinder 21, and then go down along the space, and then go up from the space between the outer cylinder 21 and the tank wall of the suspension tank 2 to complete the circulation, and better realize granulation under the action of the sulfate special crystal seed in the circulation. Among them, the space inside the outer cylinder 21 and between the tank wall of the sulfate nucleus crystal granulation tank 1 and the outer cylinder 21 forms a nucleus crystal granulation area. Under the action of the water inlet pressure, the crystal particles generated in the sulfate nucleus crystal granulation tank 1 are thrown up by the continuous water pressure impact and overflow from the top of the outer cylinder 21, and then sink along the space between the outer cylinder 21 and the inner wall of the tank body, so that the circulating crystal particles gradually grow, and the enlarged particles sink to the crystal particle discharge port 23 for discharge. Furthermore, the end of the circulating water pipe 16 is connected to the nucleus crystal granulation area water inlet pipe 14, which is a pipe with an arc, which can better guide the treated water into the corresponding area.

[0042] After centrifugation to separate large suspended matter, the separation device 19 uses a filter medium to intercept and remove small suspended matter. Water passes through the separation device, and impurities such as suspended matter are intercepted in the separation device. The medium in the separation device is activated carbon, sand filter, ceramic membrane, etc.

[0043] Through the separation device 19, the present invention can achieve solid-liquid separation during granulation, and clear water can be obtained after adjusting the pH.

[0044] In a further embodiment of the present invention, the separation device 19 may specifically be composed of an isolation screen 29 in the upper part and a rotating blade 11 in the lower part, wherein the isolation screen 29 is fixed to the inner wall of the suspension tank 2, and the driving motor 17 at the top of the separation device 19 drives the rotating blade 11 to rotate by driving the stirring shaft 20.

[0045] like Figure 6 As shown, the separation device 19 is equipped with an isolation screen 29, and a plurality of holes 28 are arranged on the isolation screen 29. After being treated, the wastewater in the suspended matter tank 2 enters the separation device 19 and is further separated, and passes through the holes 28 to enter the circulating water pipe 2 16. A shaft sleeve 27 is arranged at the center of the isolation screen 29, and the stirring shaft 20 passes through the shaft sleeve 27 and can rotate therein. The rotating blade 11 is installed on the stirring shaft 20 and is driven to rotate by the stirring shaft 20.

[0046] In a further embodiment of the present invention, there are multiple water inlet pipes 3, which are distributed along the circumference and inlet water radially. A coagulant dosing device 4 and a flow meter 26 can be provided on the water inlet pipe 3, and the flow meter 26 is placed after the coagulant dosing device 4. The coagulant is added to the raw water through the coagulant dosing device 4, and the raw water inflow is controlled by the flow meter 26, and the final hydraulic parameters are controlled. The bottom end of the central water pipe 12 is connected to each water inlet pipe 3 through a vertical water pipe 24, and the inner diameter of the vertical water pipe 24 is larger than the inner diameter of the central water pipe 12. Since the outer side of the central water pipe 12 is a rotating blade 11, in order to increase the blade rotation speed and improve the processing efficiency, the diameter of the central water pipe 12 is reduced, and the thicker inner diameter of the vertical water pipe 12 can facilitate the control of the flow. Along the direction of water flow, a connecting structure with a cross-section that first widens and then narrows is provided at the end of the vertical water pipe 24 or the beginning of the central water pipe 12. The inner diameter of the connecting structure at the largest cross-section is larger than the inner diameter of the vertical water pipe 24, which plays a buffering role in the water flow and prevents equipment damage caused by excessive changes in the pipe diameter.

[0047] In a further embodiment of the present invention, the circulating water pipe 1 13 and the circulating water pipe 2 16 are both hollow water pipes used to connect the water inlet and outlet areas of different regions. Among them, the circulating water pipe 1 13 is used to connect the suspended matter tank 2 and the separation device 19, and the circulating water pipe 2 16 is used to connect the separation device and the water inlet pipe 14 of the sulfate nucleus crystal granulation tank 1. Specifically, the water outlet of the circulating water pipe 1 13 is located directly above the space between the inner cylinder 22 and the inner wall of the suspended matter tank 2; the water outlet of the circulating water pipe 2 16 is connected to the space between the outer cylinder 21 and the inner wall of the sulfate nucleus crystal granulation tank 1 through the water inlet pipe 14 of the nucleus crystal granulation area.

[0048] In order to facilitate the discharge of sludge and granulation bodies, the bottoms of the sludge enrichment zone and the nucleus crystal granulation zone of the present invention are both designed to be conical bucket-shaped.

[0049] To protect the entire device, the present invention sets a top cover 18 on the top of the sulfate core crystal granulation tank 1, and a driving motor 17 is arranged in the tank, connecting the stirring shaft 20 and the central water pipe 12, driving the central water pipe 12 and the rotating blades 11 thereon to rotate.

[0050] Since the nuclear crystal granulation device is small in size, the nuclear crystal granulation device can be installed on a vehicle body, and the vehicle can be driven to a site where sulfate treatment of coal mine water is required as needed, and has good mobility.

[0051] Figure 2 and Figure 3 These are SEM images of the sulfate-specific seed crystals prepared in Example 1 of the present disclosure before and after the performance test.

[0052] like Figure 2 As shown in the figure, the particle size of the sulfate-specific seed before nucleation granulation is about 215 μm, and the shape is a hexagram. After the nucleation granulation reaction, calcium sulfate precipitates and adheres to the surface of the seed, and the particle size increases to about 650 μm, and the shape is a uniformly distributed dense granule. Figure 3 As shown, the results indicate that the sulfate-specific seed crystals successfully form dense granules after reaction.

[0053] The effect of the core crystal granulation process of the present invention on the removal rate of sulfate in coal mine water is shown in the following table. Figure 4 and Figure 5 .

[0054] Figure 4 The figure shows the effect of the prepared sulfate-specific crystal seed on the removal of sulfate in water (the bar graph is turbidity, and the line graph is sulfate removal rate). Figure 4 It can be seen that under the enrichment effect of sulfate on the surface of the dedicated sulfate seed crystal, sulfate forms a local supersaturated state on the surface of the dedicated seed crystal, and finally adheres to the surface of the seed crystal in the form of calcium sulfate. After the nuclear crystal granulation reaction treatment, in the wastewater with an initial sulfate concentration of 80mM, the effluent sulfate concentration dropped to below 4000mg / L, the sulfate removal rate was about 50%, and the turbidity was about 8NTU; in the wastewater with an initial sulfate concentration of 120mM, the effluent sulfate concentration dropped to below 5000mg / L, the sulfate removal rate was about 60%, and the turbidity was about 7NTU; in the wastewater with an initial sulfate concentration of 160mM, the effluent sulfate concentration dropped to below 6000mg / L, the sulfate removal rate was about 60%, and the turbidity was about 6NTU; Figure 5 The figure shows the effect of filling height of prepared sulfate-specific crystal seeds on sulfate removal in water (the bar graph is turbidity, and the line graph is sulfate removal rate). Figure 5It can be seen that when the filling height of the special seed crystals is 10%, 20% and 30%, respectively, the removal rate of sulfate radical gradually increases to 30%, 35% and 40%, respectively, and the effluent turbidity gradually decreases to 15, 14 and 11, respectively. The above results show that the composite seed crystals prepared by the present invention can effectively remove sulfate radicals from wastewater, and the low turbidity of the effluent indicates that sulfate radicals form precipitations attached to the seed crystals to form granules. The special seed crystals prepared by the present invention are conducive to the further treatment of subsequent wastewater and are environmentally friendly.

[0055] Under the enrichment of sulfate on the surface of sulfate-specific seed crystals, sulfate forms a local supersaturated state on the surface of the seed crystals, and finally adheres to and precipitates on the surface of the seed crystals in the form of calcium sulfate. The removal rate of sulfate in the water treated by the nuclear crystal granulation reaction is about 60%, and the turbidity is less than 20NTU. And with the increase of the amount of seed crystals added, the removal efficiency is significantly improved, indicating that the sulfate-specific seed crystals have a good removal effect on sulfate.

[0056] The technical principle of the present invention is:

[0057] In the nuclear crystal granulation device, by adding crystal seeds to induce the sulfate and calcium ions that are already in a saturated state to crystallize and produce precipitates, the rapid crystallization of sulfate in water is achieved, and the rapid separation of solid and liquid is achieved. The crystal seeds are driven by the upward water flow to be in a fluidized bed state in the nuclear crystal granulation area, which increases the contact area between the crystal seeds and the solution, is conducive to the rapid induction of heterogeneous crystallization, and forms large-particle crystal precipitation and discharge, realizing the removal of sulfate in coal mine water, and finally the sulfate concentration of the treated water is controlled below 3000mg / L.

[0058] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0059] Example 1

[0060] The coal mine water of a coal mining enterprise has a pH of 2.2-3.8, the dosage of sulfate special seed is 0.8g / L, the adjusted pH is 6-7, the residence time in the nucleus crystal granulation zone is 15min, and the flow rate is 15m 3 / h.

[0061] SO4 before raw water treatment 2- =18000mg / L, after one week of stable operation, the SO4 2- =2800mg / L, and the final densified granules have a particle size of 800-900μm.

[0062] Example 2

[0063] The coal mine water of a coal mining enterprise has a pH of 3.1-4.2, a sulfate seed crystal dosage of 1.0 g / L, an adjusted pH of 6-7, an adjusted pH of 6-7, a nuclear crystal granulation zone residence time of 12 min, and a flow rate of 10 m 3 / h.

[0064] SO4 before raw water treatment 2- =12000mg / L, after one week of stable operation, the SO4 2- =2500mg / L, and the final densified granules have a particle size of 700-850μm.

[0065] The applicant declares that the present invention illustrates the method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned operation steps, that is, it does not mean that the present invention must rely on the above-mentioned operation steps to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for reducing sulfate hardness in coal mine water based on nucleus crystal granulation, characterized in that: The method comprises adding and only adding special sulfate seed crystals to the coal mine water after the suspended matter is removed, utilizing the calcium ions in the coal mine water to make the sulfate in the coal mine water crystallize and precipitate on the surface of the special sulfate seed crystals to form granules, and then expelling the granules to realize the simultaneous removal of calcium ions and sulfate and solid-liquid separation.

2. The method for reducing sulfate hardness in coal mine water based on nucleus crystal granulation according to claim 1, characterized in that: The calcium ion concentration in the coal mine water after the suspended matter is removed is in the range of 200-500 mg / L, the sulfate concentration is in the range of 6000-8000 mg / L, the dosage of the special sulfate seed is 0.3-1.8 g / L, the treatment time is more than 30 minutes, and the sulfate concentration in the treated coal mine water is in the range of 2000-3000 mg / L.

3. The method for reducing sulfate hardness in coal mine water based on nucleus crystal granulation according to claim 1, characterized in that: The special sulfate seed is prepared by the following method: sucrose, calcium nitrate and aluminum sulfate in a weight ratio of 1:1:1.5 to 1:1.2:2 are fully ground until they are evenly mixed, and then concentrated sulfuric acid is added and stirred to obtain a carbonized precursor material, the precursor material is mixed with a sodium hydroxide solution with a concentration of 1.5 to 2 mol / L according to a solid-liquid ratio of 12 to 15 g / 100 mL, a magnetic bar is added for stirring, and after standing, deionized water is used for suction filtration, centrifugation, and washing until sulfate ions are undetectable in the washing liquid, and then the washing liquid is placed in an oven for drying, calcined at 550 to 600° C. for 2.5 to 3 hours in a nitrogen atmosphere, and then cooled for 8 to 10 hours to obtain a special sulfate seed whose main component is ettringite.

4. The method for reducing sulfate hardness in coal mine water based on nucleus crystal granulation according to claim 1, characterized in that: The hydraulic parameters are adjusted to make the special sulfate seed crystals suspended in the coal mine water after the suspended matter is removed.

5. A device for reducing sulfate hardness in coal mine water based on nucleus crystal granulation, characterized in that: The invention comprises a sulfate nucleus crystal granulation tank (1) and a suspension tank (2) arranged vertically; the sulfate nucleus crystal granulation tank (1) is connected to a seed crystal feeding pipe (5), an outer cylinder (21) coaxial with the tank is arranged in the tank, the upper and lower ends of the outer cylinder (21) are open, and there is a distance between the tank top, tank bottom and tank wall; The water inlet of the suspended matter tank (2) is connected to the water inlet pipe (3), the suspended matter is removed by the inlet water in the suspended matter tank (2), the water outlet of the suspended matter tank (2) is connected to the sulfate nucleus crystal granulation tank (1), and the upper part of the sulfate nucleus crystal granulation tank (1) is provided with a water outlet pipe (15); The sulfate-specific seed crystals added through the seed crystal adding pipe (5) and the coal mine water from which suspended matter has been removed circulate axially in the outer cylinder (21) and between the outer cylinder (21) and the inner wall of the sulfate-nucleus crystal granulation tank (1) to form a granulation body. A granulation body discharge outlet (23) is provided at the tank bottom of the sulfate-nucleus crystal granulation tank (1).

6. The device for reducing sulfate hardness in coal mine water based on nucleus crystal granulation according to claim 5, characterized in that: The suspended matter tank (2) is arranged in the sulfate nucleus crystal granulation tank (1) and is located inside the outer cylinder (21). An inner cylinder (22) coaxial with the tank is arranged inside the suspended matter tank (2). The inner cylinder (22) is open at both ends and is spaced apart from the tank top, tank bottom and tank wall of the suspended matter tank (2). The coagulant and the coal mine water circulate axially inside the inner cylinder (22) and between the inner cylinder (22) and the inner wall of the suspended matter tank (2) to remove the suspended matter. A sludge discharge pipe (10) is arranged at the bottom of the suspended matter tank (2).

7. The device for reducing sulfate hardness in coal mine water based on nucleus crystal granulation according to claim 5 or 6, characterized in that: A separation device (19) is arranged on the top of the suspended matter tank (2), a vertical central water pipe (12) is arranged in the tank, a rotating blade (11) is arranged on the central water pipe (12), the bottom end of the central water pipe (12) is connected to the water inlet pipe (3), and the top end extends out of the suspended matter tank (2) to the separation device (19); The separation device (19) is connected to the circulating water pipe 1 (13) at the bottom and to the circulating water pipe 2 (16) at the top. The outlet of the circulating water pipe 1 (13) is connected to the suspended matter tank (2), and the outlet of the circulating water pipe 2 (16) is connected to the sulfate nucleus crystal granulation tank (1).

8. The device for reducing sulfate hardness in coal mine water based on nucleus crystal granulation according to claim 7, characterized in that: There are a plurality of water inlet pipes (3) which are distributed in the circumferential direction and inlet water in the radial direction. The bottom end of the central water pipe (12) is connected to each water inlet pipe (3) via a vertical water pipe (24). The inner diameter of the vertical water pipe (24) is larger than the inner diameter of the central water pipe (12). In addition, along the water flow direction, a connecting structure whose cross section widens first and then narrows is provided at the end of the vertical water pipe (24) or the beginning of the central water pipe (12). The inner diameter of the connecting structure at the largest cross section is larger than the inner diameter of the vertical water pipe (24).

9. The device for reducing sulfate hardness in coal mine water based on nucleus crystal granulation according to claim 7, characterized in that: The separation device (19) is composed of an isolation screen in the upper part and a stirring blade in the lower part. The isolation screen is fixed to the inner wall of the suspension tank (2). The driving motor (17) at the top of the separation device drives the stirring blade to rotate by driving the stirring shaft.

10. The device for reducing sulfate hardness in coal mine water based on nucleus crystal granulation according to claim 7, characterized in that: The circulating water pipe 1 (13) and the circulating water pipe 2 (16) are both hollow water pipes. The water outlet of the circulating water pipe 1 (13) is located directly above the space between the inner cylinder (22) and the inner wall of the suspended matter tank (2); the water outlet of the circulating water pipe 2 (16) is connected to the space between the outer cylinder (21) and the inner wall of the sulfate nucleus crystal granulation tank (1) through the nucleus crystal granulation zone water inlet pipe (14).

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