Low-cost coal mine water resource treatment system

Abstract

The utility model relates to the field of water treatment, in particular to a low-cost coal mine water resource treatment system which comprises a pretreatment system, an electrodeionization device, a crystallization self-hardness removal device, a high-pressure membrane concentration system, a high-pressure nanofiltration salt separation system and an MVR (mechanical vapor recompression) evaporation device. The pretreatment system comprises a homogeneous adjusting tank, an efficient cyclone, a clean water tank and a first-stage high-density sedimentation tank which are connected in sequence, the first-stage high-density sedimentation tank is connected with a V-shaped filter tank, and the V-shaped filter tank is connected with a filtering water producing tank; the electrodeionization device is connected with the filtering water production tank, a concentrated water outlet of the electrodeionization device is connected with the first crystallization hardness self-removal device, and a water recovery tank is connected to a water production outlet of the electrodeionization device; the device is simple in structure and convenient to use, the operation cost can be greatly reduced, all utilization of mine water can be realized, and industrial sodium sulfate and gypsum products can be obtained at the same time.

Description

Technical Field

[0001] The utility model relates to the field of water treatment, and particularly relates to a low-cost coal mine water resource treatment system. Background Technique

[0002] Nowadays, with the increasingly strict requirements for environmental protection, in some water-scarce areas, measures such as wastewater treatment, zero discharge, and recycling, which save water and control pollution, have become important measures for development. For coal chemical industry, chemical industry, and coal mines, wastewater is discharged from chemical production (generated during the mining process), which is both a by-product and a new resource. In order to continue to utilize the wastewater after treatment, the environmental protection upgrade of enterprises is imperative.

[0003] The usual process routes for zero discharge (advanced treatment) of coal chemical wastewater and mine water adopt coagulation, sedimentation, filtration, advanced membrane treatment, resin treatment, evaporation crystallization, etc. High-salt (high-suspended solids) coal chemical wastewater and mine water are treated by processes such as coagulation, sedimentation, clarification, and filtration to remove coarse particles and suspended solids. The concentrated brine after pretreatment is then subjected to advanced treatment such as reverse osmosis membrane / ion exchange to achieve the purpose of recycling coal chemical wastewater and mine water. Finally, the salts in the concentrated brine are recycled through evaporation crystallization to achieve the separation and recycling of water and salt.

[0004] The high-efficiency hydrocyclone is used for the pretreatment of wastewater, mainly playing the roles of homogenization, neutralization, coagulation, sedimentation, and clarification. Generally, the effluent water quality is SS < 50mg / l and COD < 50mg / l. The high-efficiency hydrocyclone has the advantages of simple process and convenient operation. However, when the SS of the underground inflow water is too high (SS: 3000mg / l), problems such as high effluent turbidity and easy clogging of the packing occur. It is necessary to set up a sufficient homogenization and regulation tank in the front system to first fully statically precipitate the suspended solids, and at the same time optimize the concentration setting of the coal slime.

[0005] The high-density sedimentation tank and the silicon-removing sedimentation tank are used to appropriately remove the hardness in the wastewater and at the same time remove SiO2 in the wastewater. Generally, the effluent water quality of the high-density sedimentation tank is NTU < 5 and calcium hardness < 500mg / l, and the effluent water quality of the silicon-removing sedimentation tank is NTU < 5, calcium hardness < 30mg / l, and SiO2 < 30mg / l. Setting up multiple high-density sedimentation tanks can flexibly adjust the effluent quality according to the water quality change. The silicon-removing sedimentation tank needs to set up a sufficient reaction time to make the silicon-removing agent fully react with the silicon dioxide in the water to form large flocs by bridging.

[0006] The V-type filter and the sand filter, with appropriate addition of PAC and PAM and the packing of the V-type filter and the sand filter, all play the role of removing SS and colloids in the wastewater. After passing through the V-type filter, the effluent water quality is calcium hardness < 500mg / l, SS < 1mg / l, and pH: 6 - 7.

[0007] Electrodeionization method: The electrodeionization method separates salts in a solution from water under the action of an externally applied electric field in a device. It is generally used for high-salt wastewater. In industrial wastewater, it is mainly used for concentrating and reducing the amount of wastewater. It has relatively low requirements for pretreatment, a simple process, and relatively simple operation.

[0008] DTRO method: DTRO separates water in a solution through a disc tube reverse osmosis membrane with sufficient pressure. It is generally used for high-concentration organic wastewater. In industrial wastewater, it is mainly used for concentrating highly concentrated brine. It has high requirements for pretreatment, a simple process, and simple operation.

[0009] Ion exchange method: The ion exchange method is a method of removing harmful ions in water by exchanging ions on an ion exchanger with ions in water. It is generally used for the pretreatment of circulating water or for producing softened water. In industrial wastewater, it is mainly used to recover precious metals. It has high requirements for pretreatment, a simple process, but difficult operation.

[0010] Evaporation crystallization method: The evaporation method is a treatment method that uses the latent heat of heating steam to vaporize wastewater by heating, so as to concentrate the wastewater. This method is suitable for the treatment of high-concentration wastewater. Combined with the crystallization process, the salts in the wastewater can be recycled, but the operating cost for low-concentration wastewater is very high.

[0011] Currently, the methods used for treating mine water mainly adopt chemical precipitation and double membrane methods. High-salt wastewater is treated by removing hardness, concentrating, and evaporating and crystallizing to recover water and produce sodium chloride, sodium sulfate, and miscellaneous salts. Among them, removing hardness and concentrating are the most core and key links for water reuse. However, a large amount of acid and alkali agents need to be added for removing hardness, resulting in a significant increase in the salt content of the wastewater after precipitation and clarification. Due to the structure of the reverse osmosis membrane being a spiral wound membrane structure (originally applied to pure water and seawater desalination), it has high requirements for pretreatment, is prone to clogging, requires frequent chemical cleaning, and continuous dosing. The agents used in these two units account for more than 80% of the total agent cost of the entire system. Therefore, the construction cost and operating cost of the mine water advanced treatment project are high. Especially, the variable cost per ton of water for operation reaches 14 yuan, and industrial and mining enterprises have a high operating cost pressure. Summary of the Utility Model

[0012] In order to solve the above problems, the utility model provides a low-cost coal mine water resource treatment system with a simple water treatment process, low operating cost, and good resource treatment effect.

[0013] The low-cost coal mine water resource treatment system of the utility model includes a pretreatment system, an electrodeionization device, a crystallization and self-hardness removal device, a high-pressure membrane concentration system, a high-pressure nanofiltration salt separation system, and an MVR evaporation device;

[0014] The pretreatment system includes a homogenization and regulation tank, a high-efficiency hydrocyclone, a clear water tank, and a first high-density sedimentation tank connected in sequence. The first high-density sedimentation tank is connected to a V-shaped filter tank, and the V-shaped filter tank is connected to a filtered water production tank;

[0015] The electrodeionization device is connected to the filtered water production tank. The concentrated water outlet of the electrodeionization device is connected to a first crystallization and self-hardness removal device, and a recovery water tank is connected to the water production outlet of the electrodeionization device;

[0016] The high-pressure membrane concentration system includes a second high-density sedimentation tank and a chelating ion exchanger. The concentrated water outlet of the electrodeionization device is connected to the second high-density sedimentation tank through the first crystallization and self-hardness removal device. The second high-density sedimentation tank is connected to a DTRO device through a second high-density water production tank and a first sand filter connected in sequence. The water production outlet of the DTRO device is connected to the recovery water tank. The concentrated water outlet of the DTRO device is connected to a silicon removal sedimentation tank through a second crystallization and self-hardness removal device. The silicon removal sedimentation tank is connected to a silicon removal water production tank, and the silicon removal water production tank is connected to the chelating ion exchanger through a second sand filter;

[0017] The high-pressure nanofiltration salt separation system includes a high-pressure NF device. The chelating ion exchanger is connected to the high-pressure NF device through a high-pressure NF water inlet tank. The water production outlet of the high-pressure NF device is connected to the recovery water tank, and the concentrated water outlet of the high-pressure NF device is connected to an MVR evaporation crystallization device.

[0018] Preferably, both the first crystallization and self-hardness removal device and the second crystallization and self-hardness removal device include a shell. A first reaction zone and a second reaction zone that are interconnected are arranged inside the shell, and the first reaction zone is located below the second reaction zone. A stirrer for lifting materials to the second reaction zone is arranged at the connection of the first reactor and the second reaction zone;

[0019] A water inlet pipe for concentrated water to enter is arranged at the position of the shell corresponding to the first reaction zone;

[0020] It further includes an inclined plate clarification zone. The second reaction zone is connected to the inclined plate clarification zone. A sedimentation outlet and a water outlet are arranged at the position of the shell corresponding to the inclined plate clarification zone. Clarifying inclined plates inclined towards the sedimentation outlet are arranged in the inclined plate clarification zone, and the water outlet is located above the clarifying inclined plates;

[0021] The sedimentation outlet is connected to a seed reflux device through a pipeline. A seed stirrer and a seed discharge port are arranged on the seed reflux device, and the seed discharge port is connected to the first reaction zone inside the shell through a conveyor;

[0022] A sludge outlet is further arranged at the bottom of the shell, and a sludge scraper is arranged in the first reaction zone. A driving device for driving the sludge scraper to move and scrape the sludge towards the sludge outlet is arranged on the sludge scraper;

[0023] A dosing port for the settling agent is further provided on the housing, and the dosing port for the settling agent extends into the second reaction zone through a pipeline.

[0024] Preferably, a rake dryer is further connected to the MVR evaporation crystallization device.

[0025] Preferably, the turbidity of the water quality in the filtered water production pool is <1 NTU, the calcium hardness is 500 mg / l, and the pH value is 6 - 7.

[0026] The utility model has a simple structure and is convenient to use, which can greatly reduce the operation cost, and then can realize the full utilization of mine water, and at the same time obtain industrial sodium sulfate and gypsum products. Description of the Drawings

[0027] Figure 1 It is a schematic diagram of the connection relationship of the utility model.

[0028] Figure 2 It is a schematic diagram of the crystallization self - hardness removal device.

[0029] Reference numerals: 1 - first reaction zone, 2 - second reaction zone, 3 - stirrer, 4 - clarification inclined plate, 5 - crystal seed reflux equipment, 6 - water outlet, 7 - sludge scraper, 8 - conveying auger. Detailed Description of the Invention

[0030] A low - cost coal mine water resource treatment system of the utility model comprises a pretreatment system, an electro - demineralization device, a crystallization self - hardness removal device, a high - pressure membrane concentration system, a high - pressure nanofiltration salt separation system and an MVR evaporation device;

[0031] The pretreatment system comprises a homogeneous regulation tank, a high - efficiency hydrocyclone, a clear water tank and a first high - density sedimentation tank which are connected in sequence. The first high - density sedimentation tank is connected with a V - shaped filter tank, and the V - shaped filter tank is connected with a filtered water production pool;

[0032] The electro - demineralization device is connected with the filtered water production pool. The concentrated water outlet of the electro - demineralization device is connected with the first crystallization self - hardness removal device, and a recovery water tank is connected to the water production outlet of the electro - demineralization device;

[0033] The high - pressure membrane concentration system comprises a second high - density sedimentation tank and a chelating ion exchanger. The concentrated water outlet of the electro - demineralization device is connected with the second high - density sedimentation tank through the first crystallization self - hardness removal device. The second high - density sedimentation tank is connected with a DTRO device through a second high - density water production pool and a first sand filter which are connected in sequence. The water production outlet of the DTRO device is connected with the recovery water tank. The concentrated water outlet of the DTRO device is connected with a silicon - removal sedimentation tank through the second crystallization self - hardness removal device. The silicon - removal sedimentation tank is connected with a silicon - removal water production pool, and the silicon - removal water production pool is connected with the chelating ion exchanger through a second sand filter;

[0034] The high-pressure nanofiltration salt separation system includes a high-pressure NF device. The chelating ion exchanger is connected to the high-pressure NF device through a high-pressure NF inlet tank. The water production outlet of the high-pressure NF device is connected to a recovery water tank, and the concentrated water outlet of the high-pressure NF device is connected to an MVR evaporation crystallization device.

[0035] Both the first crystallization self-removing hardness device and the second crystallization self-removing hardness device include a housing. Inside the housing, there are a first reaction zone 1 and a second reaction zone 2 that are interconnected. The first reaction zone 1 is located below the second reaction zone 2. At the connection of the first reactor and the second reaction zone 2, there is a stirrer 3 for lifting materials to the second reaction zone 2.

[0036] At the position of the housing corresponding to the first reaction zone 1, there is a water inlet pipe for concentrated water to enter. The water inlet pipe of the first crystallization self-removing hardness device is connected to the concentrated water outlet of the electrodialysis demineralization device, and the water inlet pipe of the second crystallization self-removing hardness device is connected to the concentrated water outlet of the DTRO device.

[0037] It also includes an inclined plate clarification zone. The second reaction zone 2 is connected to the inclined plate clarification zone. At the position of the housing corresponding to the inclined plate clarification zone, there is a precipitation outlet and a water outlet 6. Inside the inclined plate clarification zone, there are clarification inclined plates 4 that are inclined towards the precipitation outlet, and the water outlet 6 is located above the clarification inclined plates 4.

[0038] The precipitation outlet is connected to a seed reflux device 5 through a pipeline. The seed reflux device 5 is provided with a seed stirrer 3 and a seed discharge port. The seed discharge port is connected to the first reaction zone 1 inside the housing through a conveyor. The seed stirrer 3 is a stirrer blade connected to a stirring shaft in the prior art, and the stirring shaft is also connected to a motor for driving the rotation of the stirring shaft.

[0039] At the bottom of the housing, there is also a sludge outlet. Inside the first reaction zone 1, there is a sludge scraping plate 7. On the sludge scraping plate 7, there is a driving device for driving the sludge scraping plate 7 to move and scrape the sludge towards the sludge outlet. In actual use, the driving device is a motor. The motor is connected to a connecting arm through a rotating shaft. The connecting arm is connected to a plurality of connecting rods extending towards the bottom of the housing. The end of the connecting rod away from the connecting arm is connected to the sludge scraping plate 7. The sludge scraping plates 7 are all vertical and set towards the sludge outlet. During the rotation of the connecting arm, the sludge scraping plates 7 scrape the sludge at the bottom of the housing towards the sludge outlet, and the sludge is output through a conveying auger 8 at the sludge outlet.

[0040] On the housing, there is also a flocculant dosing port, and the flocculant dosing port extends into the second reaction zone 2 through a pipeline.

[0041] The concentrated water enters from the inlet pipe of the crystallization self-removing hardness device and mixes and reacts with the added coagulant aid in the first reaction zone 1. Then it is lifted to the second reaction zone 2 through stirring for further mixing and reaction, and then discharged after passing through the inclined plate clarification zone. During this process, the crystal seeds deposited on the clarification inclined plate 4 are continuously reinjected into the first reaction zone 1 through the crystal seed reflux device to improve the reaction intensity. When the activity of the crystal seeds decreases, the aged crystal seed precipitates are regularly discharged through the sludge discharge device. At the same time, new crystal seeds can be added into the system through the crystal seed reflux device to maintain the activity of the crystal seeds.

[0042] A rake dryer is also connected to the MVR evaporation crystallization device.

[0043] The turbidity of the water quality in the filtered water production pool is <1 NTU, the calcium hardness is 500 mg / l, and the pH value is 6 - 7.

[0044] Appendix Figure 1 As shown, when in use, the underground inflow water is pumped out from the homogeneous regulation pool by the high-efficiency cyclone inlet pump and first enters the high-efficiency cyclone, so that the SS of the treated water quality is <50 mg / l and the COD is <50 mg / l. During this process, a small amount of PAC and PAM are added.

[0045] Then it enters the clear water pool and is pumped out from the clear water pool by the clear water pump and enters the first high-density sedimentation tank, so that the calcium hardness of the treated water quality is controlled at 500 mg / l, the turbidity is <1 NTU, and the pH is 6 - 7. The water produced by the first high-density sedimentation tank enters the V-shaped filter, so that the turbidity of the treated water quality is <1 NTU. During this process, only a small amount of PAC and PAM are added.

[0046] The water produced by the V-shaped filter enters the V-shaped filter water production pool and is pumped out from the V-shaped filter water production pool by the electrodialysis demineralization device inlet pump and enters the electrodialysis demineralization device. The concentrated water treated by the electrodialysis demineralization device has a salt content concentration of 2.8 - 3.5%. The water produced by the electrodialysis demineralization device with a salt content lower than 700 mg / l can be recycled.

[0047] The concentrated water coming out of the electrodialysis demineralization device flows into the first crystallization self-removing hardness device by gravity, so that the calcium hardness of the treated water quality is about 1000 mg / l. During this process, a small amount of coagulant aid PAC is added.

[0048] The water produced by the first crystallization self-removing hardness device enters the second high-density sedimentation tank, so that the calcium hardness of the treated water quality is controlled at 500 mg / l, the turbidity is <1 NTU, and the pH is 6 - 7. During this process, only a small amount of PAC and PAM are added.

[0049] The water produced by the second high-density sedimentation tank enters the second high-density water production pool and is pumped out from the second high-density water production pool by the DTRO feed pump and enters the first sand filter, so that the turbidity of the treated water quality is <1 NTU.

[0050] The water produced by the primary sand filter enters the DTRO device. The dissolved solids in the concentrated water after DTRO treatment reach 8.5 - 10%, and the water produced by DTRO is recycled.

[0051] The concentrated water produced by the DTRO device enters the second crystallization self-desalination device, making the calcium hardness of the treated water quality about 1000 mg / l. A small amount of sedimentation promoter PAC is added in this process;

[0052] The DTRO concentrated water enters the silicon removal sedimentation tank, controlling the total hardness of the treated water quality below 250 mg / l, silicon dioxide < 30 mg / l, pH: 7 - 8. PAC, PAM, a small amount of NaOH and magnesium agent are added in this process;

[0053] The water produced by the silicon removal sedimentation tank enters the silicon removal water production tank, which is pumped out from the silicon removal sedimentation water production tank by the secondary sand filter feed pump and enters the secondary sand filter, making the turbidity of the treated water quality < 1 NTU;

[0054] The water produced by the secondary sand filter enters the chelating ion exchanger, making the total hardness of the treated water < 30 mg / l;

[0055] The water produced by the chelating ion exchanger enters the high-pressure NF inlet water tank, which is pumped out from the NF inlet water tank by the high-pressure NF feed pump and enters the high-pressure NF device, concentrating the sulfate radical to the NF membrane concentrated water side of the treated water. The water produced by the NF device is recycled;

[0056] The NF concentrated water enters the MVR evaporation crystallization device, producing qualified sodium sulfate above 98%. The crystallization device discharges a small amount of mother liquor regularly, and a small amount of miscellaneous salts are produced through the rake dryer. The miscellaneous salts are sodium chloride and sodium sulfate, etc.

[0057] The following specifically describes the realization of each process:

[0058] (1)Pretreat the mine water to remove SS, COD and control the calcium hardness concentration;

[0059] Pretreating the mine water is required by the electrodialysis deionization device, DTRO device and evaporation crystallization process.

[0060] The indexes after treatment by the high-efficiency cyclone, primary high-density sedimentation tank and V-shaped filter are: turbidity < 1 NTU, calcium hardness: 500 mg / l, pH: 6 - 7.

[0061] The high-efficiency cyclone is the mainstream process for treating high-turbidity underground inflow water nowadays. The underground inflow water is mainly high-turbidity, high-salt and high-hard wastewater. Among them, due to the high turbidity of the incoming water in the high-efficiency cyclone system, mainly coal slime, a certain amount of PAC and PAM agents need to be added. At the same time, the adaptation of such equipment to water quality changes has certain limitations, and the process operation parameters need to be adjusted in a timely manner according to the incoming water quality.

[0062] The high-density sedimentation tank is used to treat this type of high-salt wastewater with high calcium and magnesium ion content and low carbonate content. At this time, the advantages of the high-density sedimentation tank, such as good flocculation effect, inclined plate separation, high rising velocity, external sludge circulation, centralized sludge thickening, strong ability to cope with water quality changes, and small floor area, are more suitable as the choice for advanced treatment. At the same time, corresponding flocculants and coagulants need to be added. In the high-density sedimentation tank of this process section, only the hardness needs to be controlled within a certain range, so the corresponding dosage of chemicals is less.

[0063] The pretreatment by the V-type filter is also required for the subsequent electrodeionization and DTRO processes. The front-end high-efficiency cyclone and high-density sedimentation tank can only remove coal slime, suspended solids and colloids with larger particle sizes. The V-type filter set at this stage can remove finer suspended solids and colloids, and the effluent turbidity is <1 NTU.

[0064] Treatment of the discharged water from the pretreatment device:

[0065] In order to achieve zero discharge of wastewater, the flushing water or cleaning water of the pretreatment device cannot be directly discharged and should be treated accordingly to realize the recycling of wastewater within the device. These flushing waters include: high-efficiency cyclone flushing water, V-type filter flushing water, and filter press filtrate recovery water.

[0066] The high-efficiency cyclone flushing water, V-type filter flushing water, and filter press filtrate recovery water are recycled and returned to the high-density sedimentation tank.

[0067] (2) Electrodeionization concentration technology

[0068] According to the initial concentration of the wastewater after pretreatment and the requirements for the quality of the produced water, a single-stage multi-section or multi-stage multi-section electrodeionization process is set to concentrate the wastewater. The electrodeionization process is set to gradually concentrate the wastewater, and the wastewater concentration is increased by 4 times at this stage. In order to achieve zero discharge, this treatment process also needs to treat the flushing water and cleaning water of the electrodeionization membrane module.

[0069] Treatment of the flushing water: When the electrodeionization membrane module stops operating, it is flushed with product water to discharge the concentrated solution in the device to protect the system. The flushing water flows into the recovery water tank, undergoes homogenization treatment, and is recycled to the high-density sedimentation tank.

[0070] Treatment of the cleaning water: The chemical cleaning water of the electrodeionization process is discharged into a chemical cleaning water tank for storage, and together with the chemical cleaning water of DTRO and NF, it is neutralized and then discharged by a tank truck. The amount of cleaning water is very small and does not contain ammonia nitrogen.

[0071] (3) Crystallization self-desalination device

[0072] The highly concentrated brine with calcium sulfate supersaturation generated after the electrodeionization concentration technology has a calcium hardness of 2000 mg / l. It is necessary to remove hardness to meet the operation requirements of the subsequent DTRO process. A crystallization self-hardness removal device is designed to remove 50% of the calcium hardness to meet the operation requirements of the subsequent DTRO.

[0073] The crystallization self-hardness removal device is equipped with a stirrer 3, a sludge discharge device, a coagulant aid dosing device, and a seed crystal reflux device. The concentrated brine reacts with a small amount of coagulant aid to obtain calcium sulfate crystals, and gradually reacts and agglomerates to precipitate to the bottom of the device. The generated gypsum is regularly sent to the whisker-making device through a pump. This device can reduce the system TDS by about 10% and remove 50% of the calcium hardness.

[0074] (4)High-pressure membrane concentration technology

[0075] The highly concentrated brine after passing through the crystallization self-hardness removal device passes through a secondary high-density sedimentation tank and a primary sand filter, and then the wastewater meets the conditions for entering the high-pressure membrane DTRO process. Generally, a single-stage multi-section process is set to concentrate the highly concentrated brine. To achieve zero discharge, this treatment process also needs to treat the flushing water and cleaning water of the DTRO membrane module.

[0076] Treatment of flushing water: When the DTRO membrane module stops operating, it is flushed with product water to discharge the concentrated solution in the DTRO membrane module to protect the DTRO membrane. The flushing water flows into the recovery water tank, undergoes homogenization treatment, and is recycled to the high-density sedimentation tank.

[0077] Treatment of cleaning water: The chemical cleaning water of DTRO is discharged into a chemical cleaning water tank for storage, and together with the chemical cleaning water of electrodeionization and NF, it is neutralized and then discharged by a tank truck. The amount of cleaning water is very small and does not contain ammonia nitrogen.

[0078] (5)High-pressure nanofiltration salt separation technology

[0079] The highly concentrated brine after passing through the front-end secondary self-hardness removal device, silicon removal sedimentation tank, and chelating resin treatment has a total hardness < 30 mg / l, SiO2 < 30 mg / l, and TDS of about 85,000 - 100,000 mg / l. It enters the high-pressure spiral-wound nanofiltration device to further concentrate the sulfate to the NF concentrated water side. The high-pressure nanofiltration device is equipped with multiple high-pressure centrifugal pumps, skid-mounted membrane module racks, chemical cleaning devices and other facilities. To achieve zero discharge, this treatment process also needs to treat the flushing water and cleaning water of the high-pressure NF membrane module.

[0080] Treatment of flushing water: When the high-pressure nanofiltration membrane module stops operating, it is flushed with product water to discharge the concentrated solution in the NF membrane module to protect the NF membrane. The flushing water flows into the recovery water tank, undergoes homogenization treatment, and is recycled to the high-density sedimentation tank.

[0081] Treatment of cleaning water: The chemical cleaning water of NF is discharged into a chemical cleaning water tank for storage. Together with the chemical cleaning water of electrodeionization and DTRO, it is neutralized and then discharged by a tank truck. The amount of cleaning water is very small and does not contain ammonia nitrogen.

[0082] (6)MVR Evaporation Crystallization and Miscellaneous Salt Treatment System

[0083] The NF concentrated water is successively transported by the evaporation feed pump into the condensate preheater and the live steam preheater to be heated to the designed required temperature, and then enters the forced circulation evaporator for evaporation crystallization in the forced circulation evaporation system. When the material concentration reaches the designed required value, the system sends the crystal slurry to a centrifuge for solid-liquid separation. The separated crystals enter the vibrating fluidized bed, are dried and then packaged and stored in the salt warehouse; the centrifugal mother liquor returns to the crystallizer for continued evaporation treatment. When the sodium chloride content in the mother liquor is enriched to a certain extent, a part of the mother liquor is discharged to the miscellaneous salt single-effect system for treatment to ensure the quality of sodium sulfate.

[0084] After passing through this device, the anhydrous sodium sulfate produced by evaporation crystallization meets the first-class product index of Class A (T / CCT001 - 2019), and for the miscellaneous salt: the moisture content ≤ 10%, and the general miscellaneous salt rate < 10%.

[0085] (7)Technology for Producing Whiskers from Gypsum Produced by Crystallization Self-Hardness Removal Device

[0086] The by-product gypsum of the two-stage crystallization self-hardness removal device is mixed with water by the hydrothermal method and placed in a hydrothermal reaction kettle. By heating, a high-temperature and high-pressure environment is created to promote the growth of whiskers. The whisker indexes can reach: whiteness % ≥ 92%, length 30 - 150 microns, diameter 1 - 4 microns. Example

[0087] The water gushing out from a certain mine shaft has a TDS of about 7300 mg / l and a calcium hardness of about 550 mg / l and needs to be recycled. The water treatment volume is about 1000 m3 / h.

[0088] The water gushing out from the mine shaft is pumped out from the homogeneous regulation tank by the high-efficiency cyclone feed pump and first enters the high-efficiency cyclone to make the treated water quality SS < 50 mg / l, COD < 50 mg / l; then it enters the clear water tank and is pumped out from the clear water tank by the clear water pump and enters the first-stage high-density sedimentation tank to control the calcium hardness of the treated water quality at 500 mg / l, turbidity < 1 NTU, ph: 6 - 7.

[0089] The water produced by the first-stage high-density sedimentation tank enters the V-shaped filter, reducing the turbidity of the treated water to less than 1 NTU. The water from the V-shaped filter enters the V-shaped filter water production tank. It is pumped out from the V-shaped filter water production tank by the electro-deionization device feed pump and enters the electro-deionization device. The concentrated water treated by the electro-deionization device has a salt content concentration of 2.8 - 3.5%. The fresh water treated by the electro-deionization device with a salt content of less than 700 mg / l can be recycled to the recovery water tank.

[0090] The concentrated water from the electro-deionization device flows into the first-stage crystallization self-desalination device by gravity, making the calcium hardness of the treated water about 1000 mg / l. The water produced by the first-stage crystallization self-desalination device enters the second-stage high-density sedimentation tank, controlling the calcium hardness of the treated water at 500 mg / l, turbidity < 1 NTU, ph: 6 - 7. The water produced by the second-stage high-density sedimentation tank enters the second-stage high-density water production tank. It is pumped out from the second-stage high-density water production tank by the DTRO feed pump and enters the first-stage sand filter, reducing the turbidity of the treated water to < 1 NTU. The water from the first-stage sand filter enters the DTRO device. The concentrated water treated by DTRO has a dissolved solid of 8.5 - 10%. The fresh water produced by DTRO is recycled to the recovery water tank. The concentrated water produced by the DTRO device enters the second-stage crystallization self-desalination device, making the calcium hardness of the treated water about 1000 mg / l. The DTRO concentrated water enters the silicon-removing sedimentation tank, controlling the total hardness of the treated water below 250 mg / l, silicon dioxide < 30 mg / l, ph: 7 - 8. The water produced by the silicon-removing sedimentation tank enters the silicon-removing water production tank. It is pumped out from the silicon-removing sedimentation water production tank by the second-stage sand filter feed pump and enters the second-stage sand filter, reducing the turbidity of the treated water to < 1 NTU. The water from the second-stage sand filter enters the chelating ion exchanger, making the total hardness of the treated water < 30 mg / l;

[0091] The water produced by the chelating ion exchanger enters the high-pressure NF inlet water tank. It is pumped out from the NF inlet water tank by the high-pressure NF feed pump and enters the high-pressure NF device, concentrating the sulfate radical to the NF membrane concentrated water side. The water produced by the NF device is recycled to the recovery water tank. The NF concentrated water enters the MVR evaporation crystallization device, producing qualified sodium sulfate above 98%. The crystallization device regularly discharges a small amount of mother liquor, and a small amount of miscellaneous salts such as sodium chloride and sodium sulfate are produced through the rake dryer.

[0092] The secondary condensate produced by evaporation crystallization is qualified and transported to the recovery water tank, and when unqualified, it is sent to the front-end water tank of evaporation crystallization for temporary storage.

[0093] The final product of the evaporation crystallization unit of this system is anhydrous sodium sulfate, which is packed in ton bags in the evaporation crystallization room. The packaged product is transported to the salt warehouse by forklift and then transported out of the factory for sale by truck.

[0094] The produced miscellaneous salts are also packed in ton bags in the evaporation crystallization room. The packaged miscellaneous salts are transported to the salt warehouse by forklift and then transported out of the factory for centralized disposal by a department with professional qualifications.

Claims

1. A low-cost coal mine water resource treatment system, characterized in that: Including pretreatment system, electric desalination device, crystallization self-hardness removal device, high-pressure membrane concentration system, high-pressure nanofiltration salt separation system and MVR evaporation device; The pretreatment system comprises a homogenizing regulating tank, a high-efficiency cyclone, a clear water tank and a primary high-density sedimentation tank which are connected in sequence, wherein the primary high-density sedimentation tank is connected to a V-shaped filter tank, and the V-shaped filter tank is connected to a filtered water production tank; The electric desalination device is connected to the filtration water production pool, the concentrated water outlet of the electric desalination device is connected to the first crystallization self-hardness removal device, and the water production outlet of the electric desalination device is connected to a recovery water pool; The high-pressure membrane concentration system comprises a secondary high-density sedimentation tank and a chelate ion exchanger, the concentrated water outlet of the electric desalination device is connected to the secondary high-density sedimentation tank through a first crystallization self-hardness removal device, the secondary high-density sedimentation tank is connected to a DTRO device through a secondary high-density water production tank and a primary sand filter connected in sequence, the water production outlet of the DTRO device is connected to a recovery water tank, the concentrated water outlet of the DTRO device is connected to a desiliconization sedimentation tank through a second crystallization self-hardness removal device, the desiliconization sedimentation tank is connected to a desiliconization water production tank, and the desiliconization water production tank is connected to the chelate ion exchanger through a secondary sand filter; The high-pressure nanofiltration salt separation system includes a high-pressure NF device, the chelated ion exchanger is connected to the high-pressure NF device through a high-pressure NF water inlet pool, the water output outlet of the high-pressure NF device is connected to a recovery water pool, and the concentrated water outlet of the high-pressure NF device is connected to an MVR evaporation crystallization device.

2. A low-cost coal mine water resource treatment system as claimed in claim 1, characterized in that: The first crystallization self-hardening device and the second crystallization self-hardening device both comprise a shell, wherein a first reaction zone and a second reaction zone are arranged in the shell, and the first reaction zone is located below the second reaction zone, and a stirrer for lifting materials to the second reaction zone is arranged at the connection between the first reaction zone and the second reaction zone; A water inlet pipe for concentrated water to enter is provided at the position of the first reaction zone corresponding to the shell; It also includes an inclined plate clarification zone, the second reaction zone is connected to the inclined plate clarification zone, a sedimentation outlet and a water outlet are arranged in the shell corresponding to the inclined plate clarification zone, a clarification inclined plate inclined toward the sedimentation outlet is arranged in the inclined plate clarification zone, and the water outlet is located above the clarification inclined plate; The precipitation outlet is connected to a seed reflux device through a pipeline, the seed reflux device is provided with a seed agitator and a seed discharge port, and the seed discharge port is connected to the first reaction zone in the shell through a conveyor; The bottom of the shell is also provided with a sludge outlet, and a scraper is also provided in the first reaction zone, and a driving device is provided on the scraper to drive the scraper to scrape the sludge toward the sludge outlet; The shell is also provided with a precipitation aid dosing port, and the precipitation aid dosing port extends into the second reaction zone through a pipeline.

3. A low-cost coal mine water resource treatment system as claimed in claim 1, characterized in that: The MVR evaporation crystallization device is also connected to a rake dryer.

4. A low-cost coal mine water resource treatment system as claimed in claim 1, characterized in that: The water quality turbidity in the filtration water production pool is <1NTU, the calcium hardness is 500mg / l, and the pH value is 6-7.

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