Mixed salt concentrating, separating and drying system

Abstract

The utility model discloses a mixed salt concentration, separation and drying system which is characterized in that an outlet of a raw water feeding pipeline is connected with a circulating pipe of a primary concentration unit, a concentrated solution outlet of the primary concentration unit is connected with a circulating pipe of a secondary concentration unit, and a concentrated solution outlet of the secondary concentration unit is connected with a freezing crystallization unit; the freezing crystallization unit comprises a freezing crystallizer, an outlet of the forced discharging pump is connected with a feeding port of the freezing crystallizer, a circulating outlet of the freezing crystallizer is connected with an inlet of a freezing crystallization circulating pump, and an outlet of the freezing crystallization circulating pump is connected with a tube pass inlet of a freezing heat exchanger. A tube pass outlet of the freezing heat exchanger is connected with a circulating inlet of the freezing crystallizer; a salt slurry outlet in the bottom of the freezing crystallizer is connected with an inlet of the freezing thickening tank through a freezing crystal slurry pump, an outlet in the bottom of the freezing thickening tank is connected with an inlet of the freezing centrifugal machine, and a solid phase outlet of the freezing centrifugal machine is connected with the sodium sulfate hot melting unit through an elephant trunk. The system is low in energy consumption, and the separated sodium sulfate and sodium chloride are high in quality.

Description

Technical Field

[0001] The utility model relates to a salt separation treatment system, in particular to a mixed salt concentration, separation and drying system, belonging to the technical field of comprehensive resource utilization. Background Technique

[0002] Since the structural, root and trend pressures on ecological environment protection in China have not been fundamentally alleviated, and the economic and social development has entered a high-quality development stage of accelerating greening and low-carbonization, the modern society has higher and higher requirements for environmental protection, and thus higher requirements are put forward for the sewage discharge of industries such as pharmaceuticals, petrochemicals, printing and dyeing, and textiles. High-salt wastewater must be treated more deeply before it can meet the discharge standards.

[0003] High-salt wastewater refers to wastewater with a total salt content of at least 3.5 wt%, which mainly comes from chemical industry and oil and gas extraction. The sources of salt-containing wastewater are extensive and the water volume increases year by year. There are many ways to treat wastewater. Usually, through processes such as concentration, low-temperature crystallization, thermal crystallization, membrane treatment coupling, etc., and finally solid-liquid separation is achieved by a centrifuge. The separated solid salt particles are dried, and the separated condensed water is recycled. In addition, a part of the miscellaneous salt solution needs to be dried by a drum dryer and then solid waste treatment is carried out after drying.

[0004] The Chinese patent application with the publication number of CN 11279450 discloses a method for separating sodium chloride and sodium sulfate from high-salt wastewater based on membrane treatment. By using a variety of membrane treatment methods, it can effectively remove the fine particles and salts in the wastewater, effectively reduce the salinity of the wastewater entering the reverse osmosis membrane module, and improve the water production recovery rate. Although the membrane treatment method can achieve the purpose of zero discharge, its disadvantages are that the treatment capacity is small, and when the concentration of high-salt wastewater is too high, it is extremely easy to block the membrane, and the membrane needs to be cleaned and replaced regularly, which is unstable for production and has low economic value.

[0005] The Chinese patent application with the publication number of CN 11270741 discloses a method for separating sodium sulfate and sodium chloride, which mainly uses the thermal crystallization method to carry out salt separation treatment on high-salt wastewater, and uses the setting of a liquid entrainment separator to carry out liquid entrainment separation on the mixed liquid to improve the salt separation purity. However, the process of this technical solution is relatively simple, the separation means is relatively single, the quality of the separated salt is poor, and the directly evaporated and crystallized miscellaneous salt has complex components and contains a large amount of toxic substances, which can only be treated as solid waste, not only polluting the environment secondly but also increasing the enterprise treatment cost.

[0006] In the waste water salt separation workshop, scraper centrifuges, horizontal screw centrifuges or two-stage pusher centrifuges are generally used. The process of the scraper centrifuge is intermittent, which is not conducive to continuous production. The horizontal screw centrifuge can achieve continuous production and has a relatively low requirement for the solid-liquid ratio. However, for the salt separation project, the fineness of the finished salt particles produced is uneven. The two-stage pusher centrifuge can achieve continuous production, but has a relatively high requirement for the solid-liquid ratio, generally about 50%. It is necessary to ensure the solid-liquid ratio through process design by means of thickening tank sedimentation crystallization, so that the fineness of the finished salt particles centrifuged is uniform and meets the industry requirements.

[0007] Two-stage pusher centrifuges are widely used in the field of separating sodium sulfate and sodium chloride, and the control of the salt fineness is uniform. When the saturated brine is concentrated and settled in the thickening tank until the solid-liquid ratio is about 50%, it is fed into the centrifuge for solid-liquid separation, and then tail gas is generated. The traditional design is to directly discharge the tail gas. The tail gas contains a large amount of water vapor and dust particles, and discharging it into the air will pollute the environment and cannot meet the discharge standards.

[0008] There are many types of dryers to choose from. Among them, the box dryer and conveyor dryer have high operating costs and large floor areas. Rotary dryers, fluidized bed dryers, pneumatic dryers, and vibrating dryers are generally used to dry solid particles. The working principle of the spray dryer is to atomize the feed solution and then dry it, with a fast drying speed. However, for treating miscellaneous salts, it is easy to block the pipeline. The drum dryer is more in line with the industry requirements and has advantages such as a small floor area and not easy to block the pipeline.

[0009] In summary, for the production of high-salt wastewater, it is urgent to develop a salt separation treatment system to improve the productivity and quality of crystalline salts, realize the resource utilization of enterprise wastewater, and ensure a high system fault tolerance rate, which can not only ensure the normal production of enterprises, meet environmental protection requirements, but also reduce the operating costs of enterprises. Summary of the Utility Model

[0010] The purpose of this part is to outline some aspects of the embodiments of the present utility model and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this part, as well as in the abstract of the specification and the title of the utility model of this application, and such simplifications or omissions cannot be used to limit the scope of the present utility model.

[0011] In view of the above and / or problems existing in the prior art, the present utility model is proposed.

[0012] The purpose of the present utility model is to overcome the problems existing in the prior art and provide a mixed salt concentration, separation and drying system, which can improve the evaporation heat transfer coefficient, reduce energy consumption, improve the quality of sodium sulfate and sodium chloride, increase the yield of crystalline salts, and reduce the impact of organic matter and nitrate on the system.

[0013] To solve the above technical problems, a mixed salt concentration, separation and drying system of the present utility model includes a raw water feed pipe, the outlet of the raw water feed pipe is connected to the circulation pipe of the first-stage concentration unit, the concentrated liquid outlet of the first-stage concentration unit is connected to the circulation pipe of the second-stage concentration unit, and the concentrated liquid outlet of the second-stage concentration unit is connected to the freeze crystallization unit;

[0014] The freeze crystallization unit includes a freeze crystallizer, the outlet of the forced discharge pump is connected to the inlet of the freeze crystallizer, the circulation outlet of the freeze crystallizer is connected to the inlet of the freeze crystallization circulation pump, the outlet of the freeze crystallization circulation pump is connected to the tube side inlet of the freeze heat exchanger, and the tube side outlet of the freeze heat exchanger is connected to the circulation inlet of the freeze crystallizer; the bottom slurry outlet of the freeze crystallizer is connected to the inlet of the freeze thickening tank through a freeze slurry pump, the bottom outlet of the freeze thickening tank is connected to the inlet of the freeze centrifuge, and the solid phase outlet of the freeze centrifuge is connected to the sodium sulfate hot melting unit through a chute.

[0015] Further, the tail gas outlet of the freeze centrifuge is connected to the inlet of the water foam dust removal spray tower through a tail gas confluence pipe, the bottom water outlet of the water foam dust removal spray tower is connected to the inlet of the spray circulation pump, and the outlet of the spray circulation pump is connected to the upper spray port of the water foam dust removal spray tower through a spray circulation pipe; the top exhaust port of the water foam dust removal spray tower is connected to the inlet of the induced draft fan through a spray tower exhaust pipe, and the outlet of the induced draft fan is open to the atmosphere;

[0016] A remote transmission absolute pressure gauge is installed on the spray tower exhaust pipe, the tail gas confluence pipe is also connected to the outlet of the negative pressure regulating valve, the inlet of the negative pressure regulating valve is open to the atmosphere through a negative pressure regulating pipe, and the opening degree of the negative pressure regulating valve is controlled by the pressure of the remote transmission absolute pressure gauge.

[0017] Further, the clear liquid overflow port of the freeze thickening tank is connected to the inlet of the freeze precipitation tank, the bottom outlet of the freeze precipitation tank and the liquid phase outlet of the freeze centrifuge are respectively connected to the inlet of the freeze mother liquor tank, and the outlet of the freeze mother liquor tank is connected to the reflux port of the freeze thickening tank through a freeze mother liquor circulation pump; the clear liquid outlet of the freeze precipitation tank is connected to the primary salt MVR unit through a freeze mother liquor discharge pump.

[0018] Further, the solid phase outlet of the freeze centrifuge is connected to the inlet of the dissolution tank in the sodium sulfate hot melting unit through a chute, the side wall circulation outlet of the dissolution tank is connected to the inlet of the dissolution circulation pump, the outlet of the dissolution circulation pump is connected to the tube side inlet of the dissolution heat exchanger, the tube side outlet of the dissolution heat exchanger is connected to the central feed pipe of the dissolution tank, the lower end of the central feed pipe extends to the lower part of the dissolution tank, and the bottom outlet of the dissolution tank is connected to the nitrate recrystallization unit through a dissolution discharge pump.

[0019] Further, the outlet of the nitrate dissolution discharge pump is connected to the inlet of the nitrate thickening tank in the nitrate recrystallization unit. The crystal slurry outlet of the nitrate thickening tank is connected to the inlet of the nitrate centrifuge. The solid phase outlet of the nitrate centrifuge is connected to the sodium sulfate drying unit through a chute pipe.

[0020] The mother liquor outlet of the nitrate centrifuge is connected to the inlet of the nitrate mother liquor tank. The bottom outlet of the nitrate mother liquor tank is connected to the middle part of the nitrate evaporator circulation pipe through a nitrate mother liquor pump. The upper end of the nitrate evaporator circulation pipe is connected to the circulation outlet of the nitrate crystallizer. The lower end of the nitrate evaporator circulation pipe is connected to the inlet of the nitrate circulation pump. The outlet of the nitrate circulation pump is connected to the tube side inlet of the nitrate evaporator. The tube side outlet of the nitrate evaporator is connected to the circulation inlet of the nitrate crystallizer. The bottom crystal slurry outlet of the nitrate crystallizer is connected to the inlet of the nitrate thickening tank through a nitrate crystal slurry pump.

[0021] Further, the tail gas outlet of the nitrate centrifuge is connected to the tail gas confluence pipe. A plastic Pall ring packing layer is provided below the upper spray nozzle of the water foam dust removal spray tower. And the water replenishment port at the upper part of the tower body is connected to the spray water replenishment pipe through a water replenishment control valve. The water replenishment control valve is controlled by the remote transmission liquid level gauge of the water foam dust removal spray tower.

[0022] Further, the external discharge pump for the frozen mother liquor is connected to the middle part of the primary salt concentration circulation pipe in the primary salt MVR unit. The upper end of the primary salt concentration circulation pipe is connected to the circulation outlet of the primary salt crystallizer. The lower end of the primary salt concentration circulation pipe is connected to the inlet of the primary salt circulation pump. The outlet of the primary salt circulation pump is connected to the tube side inlet of the primary salt heat exchanger. The tube side outlet of the primary salt heat exchanger is connected to the circulation inlet of the primary salt crystallizer.

[0023] The salt leg outlet of the primary salt crystallizer is connected to the inlet of the primary salt thickening tank through a primary salt crystal slurry pump. The bottom outlet of the primary salt thickening tank is connected to the inlet of the primary salt centrifuge. The solid phase outlet of the primary salt centrifuge is connected to the inlet of the primary salt dissolution tank. The outlet of the primary salt dissolution tank is connected to the inlet of the nanofiltration membrane device through a primary salt dissolution external delivery pump. The concentrated water outlet of the nanofiltration membrane device is connected to the inlet of the freezing crystallizer. The water production outlet of the nanofiltration membrane device is connected to the secondary salt MVR unit.

[0024] Further, the liquid phase outlet of the primary salt centrifuge is connected to the inlet of the primary salt mother liquor tank. The outlet of the primary salt mother liquor tank is connected to the reflux port of the primary salt thickening tank through a primary salt mother liquor circulation pump. The clear liquid outlet at the top of the primary salt thickening tank is connected to the inlet of the primary salt precipitation tank. The bottom outlet of the primary salt precipitation tank is connected to the inlet of the primary salt mother liquor tank.

[0025] The upper side wall outlet of the primary salt precipitation tank is connected to the mixed salt evaporation crystallization system through a primary salt mother liquor external discharge pump.

[0026] Further, the water production outlet of the nanofiltration membrane device is connected to the middle of the secondary salt concentration circulation pipe in the secondary salt MVR unit. The upper end of the secondary salt concentration circulation pipe is connected to the circulation outlet of the secondary salt crystallizer, and the lower end of the secondary salt concentration circulation pipe is connected to the inlet of the secondary salt circulation pump. The outlet of the secondary salt circulation pump is connected to the tube side inlet of the secondary salt heat exchanger, and the tube side outlet of the secondary salt heat exchanger is connected to the circulation inlet of the secondary salt crystallizer; the salt leg outlet of the secondary salt crystallizer is connected to the inlet of the secondary salt thickening tank through the secondary salt crystal slurry pump. The bottom outlet of the secondary salt thickening tank is connected to the inlet of the secondary salt centrifuge. The solid phase outlet of the secondary salt centrifuge is connected to the sodium chloride drying unit, and the tail gas outlets of the primary salt centrifuge and the secondary salt centrifuge are connected to the tail gas confluence pipe.

[0027] Further, the mother liquor outlet of the secondary salt centrifuge is connected to the inlet of the secondary salt mother liquor tank, and the outlet of the secondary salt mother liquor tank is connected to the reflux port of the secondary salt thickening tank through the secondary salt mother liquor circulation pump;

[0028] The clear liquid overflow port of the secondary salt thickening tank is connected to the inlet of the secondary salt precipitation tank, and the bottom outlet of the secondary salt precipitation tank is connected to the inlet of the secondary salt mother liquor tank;

[0029] The middle clear liquid outlet of the secondary salt precipitation tank is connected to the inlet of the freezing crystallizer through the secondary salt mother liquor discharge pump and the secondary salt mother liquor discharge pipe.

[0030] Further, the primary salt mother liquor discharge pump is connected to the middle of the mixed salt concentration circulation pipe in the mixed salt evaporation and crystallization system. The upper end of the mixed salt concentration circulation pipe is connected to the circulation outlet of the mixed salt crystallizer, and the lower end of the mixed salt concentration circulation pipe is connected to the inlet of the mixed salt circulation pump. The outlet of the mixed salt circulation pump is connected to the tube side inlet of the mixed salt evaporator, and the tube side outlet of the mixed salt evaporator is connected to the circulation inlet of the mixed salt crystallizer;

[0031] The salt leg outlet of the mixed salt crystallizer is connected to the inlet of the mixed salt thickening tank through the mixed salt crystal slurry pump. The bottom outlet of the mixed salt thickening tank is connected to the inlet of the mixed salt centrifuge. The solid phase outlet of the mixed salt centrifuge is connected to the inlet of the mixed salt dissolution tank, and the bottom outlet of the mixed salt dissolution tank is connected to the reflux port of the freezing crystallizer through the mixed salt dissolution discharge pump;

[0032] The liquid phase outlet of the mixed salt centrifuge is connected to the inlet of the mixed salt mother liquor tank. The outlet of the mixed salt mother liquor tank is connected to the inlet of the drum dryer through the mixed salt mother liquor pump. The waste salt outlet of the drum dryer is connected to the waste salt baler through the waste salt auger, and the tail gas outlet of the drum dryer is connected to the tail gas confluence pipe.

[0033] Compared with the prior art, the utility model has achieved the following beneficial effects: 1. By combining evaporation concentration and membrane treatment technologies, the resource utilization of wastewater can be realized, which not only protects the environment from pollution, saves water resources, but also reduces the enterprise's water treatment cost and improves economic efficiency. The separated sodium sulfate salt meets the first-class product of Class I of "Sodium Sulfate in Industrial Sewage" (GB / T 6009-2003) and can be sold externally; the separated sodium chloride salt meets the first-class product standard of industrial dry salt in "Industrial Salt" (GB / T 5462-2015) and can also be sold externally; the proportion of miscellaneous salts shall not exceed 10%, and the water content ≤ 10%.

[0034] 2. By means of freeze crystallization + heat melting + nitrate recrystallization, the sodium sulfate salt is purified. All sodium sulfate is produced by the heat melting and recrystallization of mirabilite, and the quality of the crystalline salt is higher. Since the solubility of sodium sulfate is lower at low temperatures, only by controlling the freezing temperature at -5 to 0 °C can the quality of the sodium chloride feed water be stabilized, thus ensuring the stable operation of the sodium chloride system; at the same time, the mirabilite centrifugal mother liquor is discharged by using secondary precipitation separation + precision heat preservation filter to ensure that the discharged mother liquor does not contain fine mirabilite crystals, improve the quality of sodium chloride, increase the recovery rate of sodium sulfate, and increase the added value.

[0035] 3. The sodium chloride washing salt system is adopted to further clean and purify the crude sodium chloride salt produced by the primary salt evaporation crystallization system of sodium chloride, further ensuring the quality of the sodium chloride salt; at the same time, by coupling thermal crystallization and nanofiltration membrane, the crude sodium chloride is redissolved and sent to the nanofiltration system. By using the selective retention characteristics of the nanofiltration membrane for divalent salts, the separation of monovalent salt sodium chloride and divalent salt sodium sulfate in the liquid phase is realized. The relative content of sodium chloride in the nanofiltration permeate is usually higher than 95%, greatly increasing the recovery rate of the sodium chloride crystalline salt. And the solution entering the nanofiltration membrane is the redissolved solution of crude sodium chloride, with a lower sulfate content and is not easy to block the nanofiltration membrane.

[0036] 4. The crystalline salt produced by single-effect evaporation crystallization is returned to the freeze crystallization unit for the recovery of sodium sulfate by diluting and dissolving it in water, or discharged to the front end, treated again and then returned to the system, which can increase the recovery rate of the crystalline salt and reduce the amount of miscellaneous salts.

[0037] 5. In the device, the nitrate recrystallization, primary salt evaporation, and secondary salt evaporation systems all reduce the system vacuum degree through a vacuum pump to lower the system boiling point. The primary salt system and the secondary salt system perform thermal evaporation at a temperature of about 95 °C, and the forced system and the nitrate recrystallization unit perform evaporation at about 90 °C, which not only ensures safety but also reduces energy consumption and saves operating costs.

[0038] 6. An induced draft fan is used to extract negative pressure to carry away the tail gas of the centrifuge, and the tail gas of the drum dryer is incorporated into the system to avoid the pollution of the air by the dust particles generated by the dryer. A water foam dust removal spray tower is used to wash the tail gas. A plastic Pall ring packing layer is arranged in the tower to effectively absorb the dust particles, water vapor and other impurities in the tail gas, so that the tail gas meets the emission standards. By setting the interlock feedback control of the remote absolute pressure gauge and the negative pressure regulating valve, the negative pressure of the intake pipeline of the induced draft fan is controlled at -30~-50 kPa, and the use of the frequency converter of the induced draft fan is cancelled, saving investment. And it ensures that the lubricating oil of the double-stage pusher centrifuge will not be sucked away due to too large negative pressure. The water foam dust removal spray tower is increased with the interlock of the remote liquid level gauge and the water replenishment control valve, and automatic water replenishment is realized after regular drainage, realizing automatic operation and saving labor costs. Description of the Drawings

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. The drawings are only for reference and explanation, and are not used to limit the present invention. Among them:

[0040] Figure 1 It is a flow chart of the mixed salt concentration, separation and drying system of the present invention;

[0041] Figure 2 It is a flow chart of the tail gas treatment unit in the present invention;

[0042] In the figure: 1. Primary concentration unit; 2. Secondary concentration unit;

[0043] Freezing crystallization unit; 3a. Freezing heat exchanger; 3b. Freezing crystallizer; 3c. Freezing crystallization circulation pump; 3d. Refrigerant circulation pump; 3e. Freezing crystal slurry pump; 3f. Freezing thickening tank; 3g. Freezing centrifuge; 3h. Freezing mother liquor tank; 3j. Freezing mother liquor circulation pump; 3k. Freezing precipitation tank; 3m. Freezing mother liquor discharge pump;

[0044] Sodium sulfate hot melting unit; 4a. Nitrate melting heat exchanger; 4b. Nitrate melting tank; 4c. Nitrate melting circulation pump; 4d. Nitrate melting discharge pump;

[0045] Nitrate recrystallization unit; 5a. Nitrate evaporator; 5b. Nitrate crystallizer; 5c. Nitrate circulation pump; 5d. Nitrate crystal slurry pump; 5e. Nitrate thickening tank; 5f. Nitrate centrifuge; 5g. Nitrate mother liquor tank; 5h. Nitrate mother liquor pump;

[0046] 6. Sodium sulfate drying unit;

[0047] Primary salt MVR unit; 7a. Primary salt heat exchanger; 7b. Primary salt crystallizer; 7c. Primary salt circulation pump; 7d. Primary salt crystal slurry pump; 7e. Primary salt thickening tank; 7f. Primary salt centrifuge; 7g. Primary salt precipitation tank; 7h. Primary salt mother liquor tank; 7j. Primary salt mother liquor circulation pump; 7k. Primary salt dissolution tank; 7m. Primary salt dissolution and external delivery pump; 7n. Primary salt mother liquor external discharge pump;

[0048] 8. Nanofiltration membrane device;

[0049] Secondary salt MVR unit; 9a. Secondary salt heat exchanger; 9b. Secondary salt crystallizer; 9c. Secondary salt circulation pump; 9d. Secondary salt crystal slurry pump; 9e. Secondary salt thickening tank; 9f. Secondary salt centrifuge; 9g. Secondary salt precipitation tank; 9h. Secondary salt mother liquor tank; 9j. Secondary salt mother liquor circulation pump; 9k. Secondary salt mother liquor external discharge pump;

[0050] 10. Sodium chloride drying unit;

[0051] Mixed salt evaporation and crystallization system; 11a. Mixed salt evaporator; 11b. Mixed salt crystallizer; 11c. Mixed salt circulation pump; 11d. Mixed salt crystal slurry pump; 11e. Mixed salt thickening tank; 11f. Mixed salt centrifuge; 11g. Mixed salt mother liquor tank; 11h. Mixed salt mother liquor pump; 11j. Mixed salt dissolution tank; 11k. Mixed salt dissolution and external discharge pump;

[0052] Waste salt mother liquor drying unit; 12a. Drum dryer; 12b. Waste salt auger; 12c. Waste salt baler;

[0053] 13. Water spray dust removal spray tower; 14. Spray circulation pump; 15. Induced draft fan;

[0054] G1. Raw water feed pipeline; G2. Secondary salt mother liquor external discharge pipe; G3. Tail gas confluence pipe; G4. Negative pressure regulating pipe; G5. Spray tower exhaust pipe; G6. Spray make-up water pipe; V1. Negative pressure regulating valve; V2. Make-up water control valve; PT. Remote absolute pressure gauge; LT. Remote level gauge. Detailed implementation manners

[0055] In order to make the technical means, creative features, achieved purposes and functions realized by the present utility model easy to understand, the present utility model will be further described below with reference to specific drawings. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of the embodiments.

[0056] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present utility model belongs. The terms used in the description of the present utility model herein are only for the purpose of describing specific embodiments, and are not intended to limit the present utility model.

[0057] As Figure 1 and Figure 2 shown in the figure, the mixed salt concentration, separation and drying system of the present utility model includes a primary concentration unit 1, a secondary concentration unit 2, a freezing crystallization unit, a sodium sulfate heat melting unit, a nitrate recrystallization unit, a sodium sulfate drying unit 6, a primary salt MVR unit, a nanofiltration membrane system, a secondary salt MVR unit, a sodium chloride drying unit 10, a mixed salt evaporation and crystallization system and a miscellaneous salt mother liquor drying unit.

[0058] The outlet of the raw water feed pipe G1 is connected to the circulation pipe of the primary concentration unit 1, so that the brine enters the primary concentration unit 1 for concentration. When the discharge density of the falling film concentration unit reaches 1100 g / L, it enters the secondary concentration unit 2 for further concentration. When the discharge density of the forced concentration unit reaches 1150 - 1160 g / L, it enters the freezing crystallization unit.

[0059] The freezing crystallization unit includes a freezing heat exchanger 3a, a freezing crystallizer 3b, a freezing crystallization circulation pump 3c, a refrigerant circulation pump 3d, a freezing crystal slurry pump 3e, a freezing thickening tank 3f, a freezing centrifuge 3g, a freezing mother liquor tank 3h, a freezing mother liquor circulation pump 3j, a freezing precipitation tank 3k and a freezing mother liquor discharge pump 3m. The cold source of the freezing heat exchanger 3a is the refrigerant provided by the freezer through a pipe, and the refrigerant circulation pump 3d sends the cold source into the shell side of the freezing heat exchanger 3a for circulation. The outlet of the forced discharge pump is connected to the inlet of the freezing crystallizer 3b, the circulation outlet of the freezing crystallizer 3b is connected to the inlet of the freezing crystallization circulation pump 3c, the outlet of the freezing crystallization circulation pump 3c is connected to the tube side inlet of the freezing heat exchanger 3a, and the tube side outlet of the freezing heat exchanger 3a is connected to the circulation inlet of the freezing crystallizer 3b; the bottom salt slurry outlet of the freezing crystallizer 3b is connected to the inlet of the freezing crystal slurry pump 3e, the bottom outlet of the freezing thickening tank 3f is connected to the inlet of the freezing centrifuge 3g, and the solid phase outlet of the freezing centrifuge 3g is connected to the sodium sulfate heat melting unit through a chute.

[0060] The freezing centrifuge 3g adopts a two-stage pusher centrifuge, and its tail gas outlet is connected to the air inlet of the water foam dust removal spray tower 13 through a tail gas converging pipe G3. The bottom water outlet of the water foam dust removal spray tower 13 is connected to the inlet of the spray circulation pump 14, and the outlet of the spray circulation pump 14 is connected to the upper spray port of the water foam dust removal spray tower 13 through a spray circulation pipe; a plastic Pall ring packing layer is provided below the upper spray port of the water foam dust removal spray tower 13, and the top exhaust port of the water foam dust removal spray tower 13 is connected to the inlet of the induced draft fan 15 through a spray tower exhaust pipe G5, and the outlet of the induced draft fan 15 leads to the atmosphere.

[0061] The tail gas containing dust particles enters the water foam dust removal spray tower 13 through the tail gas confluence pipe G3, flows upward through the plastic Pall ring packing layer, and is washed by the spray water. The purified tail gas is discharged into the atmosphere through the spray tower exhaust pipe G5 by the induced draft fan 15. The circulating water that falls to the bottom of the tower is pumped out by the spray circulating pump 14 and sent to the upper spray nozzles of the water foam dust removal spray tower 13 through the spray circulating pipe for circulating spraying. The dust particles in the tail gas after water washing are intercepted by the water and the plastic Pall rings in the spray tower.

[0062] The upper water replenishing port of the water foam dust removal spray tower 13 is connected to the spray water replenishing pipe G6 through the water replenishing control valve V2, and the water replenishing control valve V2 is controlled by the remote transmission liquid level gauge LT of the water foam dust removal spray tower 13. When the liquid level in the water foam dust removal spray tower 13 reaches about 20%, the water replenishing control valve V2 opens for automatic water replenishment. When the water is replenished to 50% liquid level, the water replenishing control valve V2 closes. When the liquid level exceeds 60%, it automatically overflows into the trench, and the bottom of the tower can also be drained regularly.

[0063] A remote transmission absolute pressure gauge PT is installed on the spray tower exhaust pipe G5. The tail gas confluence pipe G3 is also connected to the outlet of the negative pressure regulating valve V1. The inlet of the negative pressure regulating valve V1 communicates with the atmosphere through the negative pressure regulating pipe G4. The opening degree of the negative pressure regulating valve V1 is controlled by the pressure of the remote transmission absolute pressure gauge PT. After the induced draft fan 15 starts, the system has a negative pressure. Too large a negative pressure will cause the lubricating oil of the double-stage pusher centrifuge to be pumped away. When the remote transmission absolute pressure gauge PT measures that the negative pressure is too large, the negative pressure regulating valve V1 gradually opens to control the negative pressure at -30~-50 kPa, ensuring the normal operation of each double-stage pusher centrifuge, avoiding the main shaft wear caused by lack of oil, and eliminating the use of the induced draft fan frequency converter, reducing costs and increasing efficiency.

[0064] The clear liquid overflow port of the frozen thickening tank 3f is connected to the inlet of the frozen settling tank 3k. The bottom outlet of the frozen settling tank 3k and the liquid phase outlet of the frozen centrifuge 3g are respectively connected to the inlet of the frozen mother liquor tank 3h. The outlet of the frozen mother liquor tank 3h is connected to the return port of the frozen thickening tank 3f through the frozen mother liquor circulating pump 3j; the clear liquid outlet of the frozen settling tank 3k is connected to the primary salt MVR unit through the frozen mother liquor external discharge pump 3m.

[0065] The brine concentrated by the first-stage concentration unit 1 and the second-stage concentration unit 2 is concentrated nearly 4.5 times and enters the freezing crystallizer 3b. Sodium sulfate is close to saturation while sodium chloride is unsaturated. Under the action of a cold source, the concentrated liquid is cooled and frozen. When the temperature in the freezing crystallizer 3b drops below 20°C, sodium sulfate decahydrate, i.e., mirabilite, begins to crystallize out in the system. When the temperature in the freezing crystallizer 3b drops to 0°C, a large amount of mirabilite precipitates, and the solubility of sodium sulfate in the system drops to 4.9 g / L. The precipitated salt slurry is pumped into the freezing thickening tank 3f by the freezing crystal slurry pump 3e for thickening, and then enters the freezing centrifuge 3g through a pipeline for solid-liquid separation. The separated mother liquor enters the freezing mother liquor tank 3h through a pipeline for temporary storage, and then is sent back to the freezing thickening tank 3f by the freezing mother liquor circulation pump 3j for re-thickening. The supernatant liquid on the upper layer of the freezing thickening tank 3f overflows to the freezing sedimentation tank 3k through a connecting pipe. The supernatant liquid is a sodium chloride-rich solution. In the freezing sedimentation tank 3k, some fine sodium sulfate crystals settle again, reducing the content of fine sodium sulfate crystals in the discharged mother liquor, increasing the crystallization salt productivity, and ensuring the quality of the subsequent sodium chloride salt. The clear liquid in the freezing sedimentation tank 3k is sent into the primary salt MVR unit by the freezing mother liquor discharge pump 3m. The solid mirabilite separated by the freezing centrifuge 3g is sent into the sodium sulfate hot-melting unit through a chute for treatment.

[0066] The sodium sulfate hot-melting unit consists of a nitrate dissolving heat exchanger 4a, a nitrate dissolving tank 4b, a nitrate dissolving circulation pump 4c, and a nitrate dissolving discharge pump 4d. The solid-phase outlet of the freezing centrifuge 3g is connected to the inlet of the nitrate dissolving tank 4b in the sodium sulfate hot-melting unit through a chute. The sidewall circulation outlet of the nitrate dissolving tank 4b is connected to the inlet of the nitrate dissolving circulation pump 4c. The outlet of the nitrate dissolving circulation pump 4c is connected to the tube-side inlet of the nitrate dissolving heat exchanger 4a. The tube-side outlet of the nitrate dissolving heat exchanger 4a is connected to the central feed pipe of the nitrate dissolving tank 4b. The lower end of the central feed pipe extends to the lower part of the nitrate dissolving tank 4b. The bottom outlet of the nitrate dissolving tank 4b is connected to the nitrate recrystallization unit through the nitrate dissolving discharge pump 4d.

[0067] The mirabilite discharged from the solid phase of the freezing centrifuge 3g enters the nitrate dissolving tank 4b through a chute. Utilizing the property that mirabilite melts when the temperature is above 32.8°C, i.e., it dissolves in its own crystal water, it absorbs heat during melting, and its heat of fusion is 77 kJ / mol. In the nitrate dissolving tank 4b of this system, mirabilite dissolves into 44% sodium sulfate and 56% crystal water at a temperature above 40°C. To ensure its dissolution temperature, the brine in the nitrate dissolving tank 4b enters the tube side of the nitrate dissolving heat exchanger 4a through the nitrate dissolving circulation pump 4c to be heated and then returns to the nitrate dissolving tank 4b for circulation. The heat source on the shell side is live steam. Subsequently, the solution is sent into the nitrate recrystallization unit through the nitrate dissolving discharge pump 4d.

[0068] The nitrate recrystallization unit includes a nitrate evaporator 5a, a nitrate crystallizer 5b, a nitrate circulation pump 5c, a nitrate crystal slurry pump 5d, a nitrate thickening tank 5e, a nitrate centrifuge 5f, a nitrate mother liquor tank 5g, and a nitrate mother liquor pump 5h. The outlet of the nitrate dissolution discharge pump is connected to the inlet of the nitrate thickening tank 5e in the nitrate recrystallization unit. The crystal slurry outlet of the nitrate thickening tank 5e is connected to the inlet of the nitrate centrifuge 5f. The mother liquor outlet of the nitrate centrifuge 5f is connected to the inlet of the nitrate mother liquor tank 5g. The bottom outlet of the nitrate mother liquor tank 5g is connected to the middle of the nitrate evaporator circulation pipe through the nitrate mother liquor pump 5h. The upper end of the nitrate evaporator circulation pipe is connected to the circulation outlet of the nitrate crystallizer 5b. The lower end of the nitrate evaporator circulation pipe is connected to the inlet of the nitrate circulation pump 5c. The outlet of the nitrate circulation pump 5c is connected to the tube-side inlet of the nitrate evaporator 5a. The tube-side outlet of the nitrate evaporator 5a is connected to the circulation inlet of the nitrate crystallizer 5b. The bottom crystal slurry outlet of the nitrate crystallizer 5b is connected to the inlet of the nitrate thickening tank 5e through the nitrate crystal slurry pump 5d.

[0069] The redissolved sodium sulfate brine is sent into the nitrate thickening tank 5e by the nitrate dissolution discharge pump 4d. After the crystal slurry is solid-liquid separated by the nitrate centrifuge 5f, high-purity sodium sulfate salt is obtained for the solid. The mother liquor from the solid-liquid separation enters the nitrate mother liquor tank 5g for caching, and then is sent into the nitrate evaporator circulation pipe through the nitrate mother liquor pump 5h, and then enters the tube-side of the nitrate evaporator 5a for heat exchange through the nitrate circulation pump 5c. The brine after heat exchange to 93 °C enters the nitrate crystallizer 5b for flash evaporation. When the solid-liquid ratio of the bottom crystal slurry of the nitrate crystallizer 5b reaches about 10%, it is sent into the nitrate thickening tank 5e for thickening through the nitrate crystal slurry pump 5d to form a cycle. The sodium sulfate salt discharged from the solid phase of the nitrate centrifuge 5f enters the sodium sulfate drying unit 6 for drying to obtain high-quality sodium sulfate. The nitrate centrifuge 5f uses a two-stage pusher centrifuge, and its tail gas outlet is connected to the air inlet of the water foam dust removal spray tower 13 through the tail gas converging pipe G3.

[0070] The primary salt MVR unit includes a primary salt heat exchanger 7a, a primary salt crystallizer 7b, a primary salt circulation pump 7c, a primary salt crystal slurry pump 7d, a primary salt thickening tank 7e, a primary salt centrifuge 7f, a primary salt precipitation tank 7g, a primary salt mother liquor tank 7h, a primary salt mother liquor circulation pump 7j, a primary salt dissolution tank 7k, a primary salt dissolution and external delivery pump 7m, and a primary salt mother liquor external discharge pump 7n.

[0071] The external discharge pump 3m of the freezing mother liquor is connected to the middle of the primary salt concentration circulation pipe in the primary salt MVR unit. The upper end of the primary salt concentration circulation pipe is connected to the circulation outlet of the primary salt crystallizer 7b. The lower end of the primary salt concentration circulation pipe is connected to the inlet of the primary salt circulation pump 7c. The outlet of the primary salt circulation pump 7c is connected to the tube-side inlet of the primary salt heat exchanger 7a. The tube-side outlet of the primary salt heat exchanger 7a is connected to the circulation inlet of the primary salt crystallizer 7b.

[0072] The frozen sodium chloride-rich mother liquor is subjected to evaporation crystallization through the primary salt MVR unit. The external discharge pump 3m of the frozen mother liquor sends the clear liquid in the frozen precipitation tank 3k into the primary salt heat exchanger 7a for heat exchange to 102 °C, and then sends it into the primary salt crystallizer 7b for flash evaporation, and is driven by the primary salt circulation pump 7c for circulating concentration.

[0073] The salt leg outlet of the primary salt crystallizer 7b is connected to the inlet of the primary salt thickener 7e through the primary salt slurry pump 7d. The bottom outlet of the primary salt thickener 7e is connected to the inlet of the primary salt centrifuge 7f. The solid phase outlet of the primary salt centrifuge 7f is connected to the inlet of the primary salt dissolution tank 7k. The outlet of the primary salt dissolution tank 7k is connected to the inlet of the nanofiltration membrane device through the primary salt dissolution external delivery pump 7m. The concentrated water outlet of the nanofiltration membrane device is connected to the inlet of the frozen crystallizer 3b. The produced water outlet of the nanofiltration membrane device is connected to the secondary salt MVR unit.

[0074] When the solid-liquid ratio of the slurry in the salt leg of the primary salt crystallizer 7b reaches about 10%, it is sent into the primary salt thickener 7e through the primary salt slurry pump 7d for thickening. When the stirring current of the primary salt thickener 7e rises to 4~, the slurry can enter the primary salt centrifuge 7f through the pipeline for solid-liquid separation.

[0075] The solid separated by the primary salt centrifuge 7f is crude sodium chloride, which enters the primary salt dissolution tank 7k through the chute for dissolving and washing the salt to remove the sodium sulfate attached to the surface of the salt. The dissolved sodium chloride solution is then sent into the nanofiltration membrane device 8 through the primary salt dissolution external delivery pump 7m. By utilizing the differences in the ionic radii or charge characteristics of chloride ions and sulfate ions, etc., and through the selective retention characteristics of the nanofiltration membrane for divalent salts, the separation of monovalent salt sodium chloride and divalent salt sodium sulfate in the liquid phase is achieved. Sodium chloride mainly enters the nanofiltration permeate, while sodium sulfate is concentrated in the nanofiltration concentrated water. Since divalent salts are retained by the nanofiltration membrane, the relative content of sodium chloride in the nanofiltration permeate is usually higher than 95%. Therefore, the recovery rate of this part of sodium chloride crystal salt is relatively high.

[0076] The nanofiltration permeate (produced water) and the nanofiltration concentrated liquid (concentrated water) are separated through the nanofiltration membrane device 8. The nanofiltration concentrated water is a mixed solution of sodium chloride and sodium sulfate, which is returned to the frozen crystallizer 3b in the frozen crystallization unit for re-separation.

[0077] The nanofiltration produced water enters the secondary salt MVR unit for further evaporation, and refined sodium chloride salt is obtained through secondary MVR evaporation crystallization. To ensure the quality of the crystal salt and improve the retention rate of fine crystals of sodium sulfate. The primary and secondary salt MVR units also design a circulation loop of secondary precipitation, supernatant reflux, and external discharge, which can effectively reduce the influence of organic matter on the chromaticity of the crystal salt, and at the same time ensure the purity and recovery rate of sodium chloride, and improve the efficiency of salt separation and crystallization.

[0078] The liquid phase outlet of the primary salt centrifuge 7f is connected to the inlet of the primary salt mother liquor tank 7h, and the outlet of the primary salt mother liquor tank 7h is connected to the reflux port of the primary salt thickening tank through the primary salt mother liquor circulation pump 7j; the supernatant outlet at the top of the primary salt thickening tank is connected to the inlet of the primary salt precipitation tank 7g, and the bottom outlet of the primary salt precipitation tank 7g is connected to the inlet of the primary salt mother liquor tank 7h; the upper side wall outlet of the primary salt precipitation tank 7g is connected to the mixed salt evaporation and crystallization system through the primary salt mother liquor discharge pump 7n.

[0079] The liquid separated by the primary salt centrifuge 7f enters the primary salt mother liquor tank 7h for temporary storage, and is sent back to the primary salt thickening tank 7e for circulation through the primary salt mother liquor circulation pump 7j. The supernatant at the top of the primary salt thickening tank 7e enters the primary salt precipitation tank 7g through the connecting pipe for secondary sedimentation, ensuring that the supernatant in the primary salt precipitation tank 7g is an unsaturated nitrate and COD solution. After the primary salt precipitation tank 7g reaches 80% of its liquid level, the nitrate-rich and organic matter solution in the precipitation tank is sent to the mixed salt evaporation and crystallization system through the primary salt mother liquor discharge pump 7n. The main purpose is to eliminate the influence of nitrate, COD and other ions on the primary salt MVR unit, and prevent the boiling point of the primary salt system from rising due to the enrichment of organic matter and impurity ions, increasing the system energy consumption.

[0080] The secondary salt MVR unit includes a secondary salt heat exchanger 9a, a secondary salt crystallizer 9b, a secondary salt circulation pump 9c, a secondary salt crystal slurry pump 9d, a secondary salt thickening tank 9e, a secondary salt centrifuge 9f, a secondary salt precipitation tank 9g, a secondary salt mother liquor tank 9h, a secondary salt mother liquor circulation pump 9j and a secondary salt mother liquor discharge pump 9k. The water production outlet of the nanofiltration membrane device is connected to the middle of the secondary salt concentration circulation pipe in the secondary salt MVR unit. The upper end of the secondary salt concentration circulation pipe is connected to the circulation outlet of the secondary salt crystallizer 9b, and the lower end of the secondary salt concentration circulation pipe is connected to the inlet of the secondary salt circulation pump 9c. The outlet of the secondary salt circulation pump 9c is connected to the tube side inlet of the secondary salt heat exchanger 9a, and the tube side outlet of the secondary salt heat exchanger 9a is connected to the circulation inlet of the secondary salt crystallizer 9b; the salt leg outlet of the secondary salt crystallizer 9b is connected to the inlet of the secondary salt thickening tank 9e through the secondary salt crystal slurry pump 9d, the bottom outlet of the secondary salt thickening tank 9e is connected to the inlet of the secondary salt centrifuge 9f, and the solid phase outlet of the secondary salt centrifuge 9f is connected to the sodium chloride drying unit 10.

[0081] The mother liquor outlet of the secondary salt centrifuge 9f is connected to the inlet of the secondary salt mother liquor tank 9h, and the outlet of the secondary salt mother liquor tank 9h is connected to the reflux port of the secondary salt thickening tank 9e through the secondary salt mother liquor circulation pump 9j; the overflow outlet of the supernatant of the secondary salt thickening tank 9e is connected to the inlet of the secondary salt precipitation tank 9g, and the bottom outlet of the secondary salt precipitation tank 9g is connected to the inlet of the secondary salt mother liquor tank 9h; the middle supernatant outlet of the secondary salt precipitation tank 9g is connected back to the inlet of the freezing crystallizer 3b through the secondary salt mother liquor discharge pump 9k and the secondary salt mother liquor discharge pipe.

[0082] The produced water of the nanofiltration membrane device 8, which is a sodium chloride-rich solution, enters the secondary salt heat exchanger 9a for heat exchange to 102 °C, and then is sent to the secondary salt crystallizer 9b for flash evaporation. When the solid-liquid ratio of the crystal slurry in the salt leg of the secondary salt crystallizer 9b reaches about 10%, it is sent to the secondary salt thickening tank 9e through the secondary salt crystal slurry pump 9d for thickening. When the stirring current of the secondary salt thickening tank 9e rises to 4~, the crystal slurry can enter the secondary salt centrifuge 9f through the pipeline for solid-liquid separation. The solid separated by the secondary salt centrifuge 9f is refined sodium chloride, which is sent to the sodium chloride drying unit 10 to obtain high-quality sodium chloride.

[0083] The mother liquor separated by the secondary salt centrifuge 9f enters the secondary salt mother liquor tank 9h for temporary storage, and then is sent back to the secondary salt thickening tank 9e for circulation by the secondary salt mother liquor circulation pump 9j. Subsequently, the clear liquid in the secondary salt thickening tank 9e overflows into the secondary salt sedimentation tank 9g. At this time, the clear liquid in the secondary salt sedimentation tank 9g is an unsaturated sodium chloride and sodium sulfate solution, which is sent back to the freezing crystallizer 3b through the secondary salt mother liquor discharge pump 9k and the secondary salt mother liquor discharge pipe G2 to improve the salt recovery rate.

[0084] The primary salt centrifuge 7f and the secondary salt centrifuge 9f adopt a double-stage pusher centrifuge, and their tail gas outlets are respectively connected to the inlet of the water foam dust removal spray tower 13 through the tail gas manifold G3.

[0085] The mixed salt evaporation and crystallization system includes a mixed salt evaporator 11a, a mixed salt crystallizer 11b, a mixed salt circulation pump 11c, a mixed salt crystal slurry pump 11d, a mixed salt thickening tank 11e, a mixed salt centrifuge 11f, a mixed salt mother liquor tank 11g, a mixed salt mother liquor pump 11h, a mixed salt dissolution tank 11j, and a mixed salt dissolution discharge pump 11k. The primary salt mother liquor discharge pump 7n is connected to the middle of the mixed salt concentration circulation pipe. The upper end of the mixed salt concentration circulation pipe is connected to the circulation outlet of the mixed salt crystallizer 11b, and the lower end of the mixed salt concentration circulation pipe is connected to the inlet of the mixed salt circulation pump 11c. The outlet of the mixed salt circulation pump 11c is connected to the tube side inlet of the mixed salt evaporator 11a, and the tube side outlet of the mixed salt evaporator 11a is connected to the circulation inlet of the mixed salt crystallizer 11b; the salt leg outlet of the mixed salt crystallizer 11b is connected to the inlet of the mixed salt thickening tank 11e through the mixed salt crystal slurry pump 11d, the bottom outlet of the mixed salt thickening tank 11e is connected to the inlet of the mixed salt centrifuge 11f, the solid phase outlet of the mixed salt centrifuge 11f is connected to the inlet of the mixed salt dissolution tank 11j, and the bottom outlet of the mixed salt dissolution tank 11j is connected to the reflux port of the freezing crystallizer 3b through the mixed salt dissolution discharge pump 11k.

[0086] The primary brine mother liquor discharge pump 7n sends the solution rich in nitrate and organic matter into the tube side of the mixed salt evaporator 11a, heats it to 93 °C, and then enters the mixed salt crystallizer 11b for flashing. The mixed salt circulation pump 11c maintains the circulation. When the solid-liquid ratio of the crystal slurry in the salt leg of the mixed salt crystallizer 11b reaches about 10%, it is sent into the mixed salt thickening tank 11e by the mixed salt crystal slurry pump 11d for thickening. When the stirring current of the mixed salt thickening tank 11e rises to 4~, the crystal slurry can enter the mixed salt centrifuge 11f through the pipeline for solid-liquid separation.

[0087] The solid separated by the mixed salt centrifuge 11f is the mixed salt of sodium sulfate and sodium chloride, which enters the mixed salt dissolution tank 11j through the chute pipe, is dissolved and then sent back to the freezing crystallizer 3b by the mixed salt dissolution and discharge pump 11k for re-separation to improve the salt recovery rate.

[0088] The liquid phase outlet of the mixed salt centrifuge is connected to the inlet of the mixed salt mother liquor tank 11g. The outlet of the mixed salt mother liquor tank 11g is connected to the inlet of the drum dryer 12a by the mixed salt mother liquor pump 11h. The waste salt outlet of the drum dryer 12a is connected to the waste salt baler through the waste salt auger. The liquid separated by the mixed salt centrifuge 11f is the mixed salt mother liquor, whose main components are nitrate and organic matter. It enters the mixed salt mother liquor tank 11g for temporary storage and then is sent to the waste salt mother liquor drying unit by the mixed salt mother liquor pump 11h.

[0089] The waste salt mother liquor drying unit consists of a drum dryer 12a, a waste salt auger 12b, and a waste salt baler 12c. After the waste mother liquor is sent into the drum dryer 12a by the mixed salt mother liquor pump 11h, it is sprayed on the drum. Subsequently, the dried powdery or flaky waste salt is scraped off by the scraper. The temperature of the drum roller is about 130 °C. The waste salt is transported to the waste salt baler 12c through the waste salt auger 12b and packed in ton bags. The tail gas outlet of the drum dryer 12a is connected to the inlet of the water spray dust removal spray tower 13 through the tail gas manifold G3. The tail gas is discharged after washing and dust removal to avoid dust particles in the air.

[0090] At least one of the freezing centrifuge 3g, nitrate centrifuge 5f, primary salt centrifuge 7f, secondary salt centrifuge 9f, and drum dryer 12a is kept in use to ensure the continuous operation of the device.

[0091] The above is only a preferred and feasible embodiment of the present utility model, which shows and describes the basic principles, main features and advantages of the present utility model. It does not limit the patent protection scope of the present utility model. Those skilled in the art should understand that the present utility model is not limited by the above embodiments. Except for the above embodiments, without departing from the spirit and scope of the present utility model, the present utility model can also have other implementation manners. The present utility model will also have various changes and improvements. All technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope required by the present utility model. The protection scope required by the present utility model is defined by the appended claims and their equivalents. The technical features not described in the present utility model can be realized by or adopted the existing technologies, and will not be elaborated herein.

Claims

1. A mixed salt concentration, separation and drying system, including a raw water feed pipeline, characterized in that, The outlet of the raw water feed pipe is connected to the circulation pipe of the first-stage concentration unit. The concentrated liquid outlet of the first-stage concentration unit is connected to the circulation pipe of the second-stage concentration unit. The concentrated liquid outlet of the second-stage concentration unit is connected to the freeze crystallization unit. The freeze crystallization unit includes a freeze crystallizer. The outlet of the forced discharge pump is connected to the feed inlet of the freeze crystallizer. The circulation outlet of the freeze crystallizer is connected to the inlet of the freeze crystallization circulation pump. The outlet of the freeze crystallization circulation pump is connected to the tube-side inlet of the freeze heat exchanger. The tube-side outlet of the freeze heat exchanger is connected to the circulation inlet of the freeze crystallizer. The bottom slurry outlet of the freeze crystallizer is connected to the inlet of the freeze thickener through a freeze slurry pump. The bottom outlet of the freeze thickener is connected to the inlet of the freeze centrifuge. The solid-phase outlet of the freeze centrifuge is connected to the sodium sulfate hot melting unit through a chute.

2. The mixed salt concentration, separation and drying system according to claim 1, wherein: The tail gas outlet of the freeze centrifuge is connected to the air inlet of the water foam dust removal spray tower through a tail gas converging pipe. The bottom water outlet of the water foam dust removal spray tower is connected to the inlet of the spray circulation pump. The outlet of the spray circulation pump is connected to the upper spray port of the water foam dust removal spray tower through a spray circulation pipe. The top exhaust port of the water foam dust removal spray tower is connected to the inlet of the induced draft fan through a spray tower exhaust pipe. The outlet of the induced draft fan is open to the atmosphere. A remote pressure gauge is installed on the spray tower exhaust pipe. The tail gas converging pipe is also connected to the outlet of the negative pressure regulating valve. The inlet of the negative pressure regulating valve is open to the atmosphere through a negative pressure regulating pipe. The opening degree of the negative pressure regulating valve is controlled by the pressure of the remote pressure gauge.

3. The mixed salt concentration, separation and drying system according to claim 2, characterized in that: The clear liquid overflow port of the freeze thickener is connected to the inlet of the freeze precipitation tank. The bottom outlet of the freeze precipitation tank and the liquid-phase outlet of the freeze centrifuge are respectively connected to the inlet of the freeze mother liquor tank. The outlet of the freeze mother liquor tank is connected to the reflux port of the freeze thickener through a freeze mother liquor circulation pump. The clear liquid outlet of the freeze precipitation tank is connected to the primary salt MVR unit through a freeze mother liquor discharge pump.

4. The mixed salt concentration, separation and drying system according to claim 2, characterized in that: The solid-phase outlet of the freeze centrifuge is connected to the inlet of the nitrate dissolving tank in the sodium sulfate hot melting unit through a chute. The sidewall circulation outlet of the nitrate dissolving tank is connected to the inlet of the nitrate dissolving circulation pump. The outlet of the nitrate dissolving circulation pump is connected to the tube-side inlet of the nitrate dissolving heat exchanger. The tube-side outlet of the nitrate dissolving heat exchanger is connected to the central feed pipe of the nitrate dissolving tank. The lower end of the central feed pipe extends to the lower part of the nitrate dissolving tank. The bottom outlet of the nitrate dissolving tank is connected to the nitrate recrystallization unit through a nitrate dissolving discharge pump.

5. The mixed salt concentration, separation and drying system according to claim 4, wherein: The outlet of the nitrate dissolving discharge pump is connected to the inlet of the nitrate thickener in the nitrate recrystallization unit. The crystal slurry outlet of the nitrate thickener is connected to the inlet of the nitrate centrifuge. The solid-phase outlet of the nitrate centrifuge is connected to the sodium sulfate drying unit through a chute. The mother liquor outlet of the nitrate centrifuge is connected to the inlet of the nitrate mother liquor tank. The bottom outlet of the nitrate mother liquor tank is connected to the middle of the nitrate evaporator circulation pipe through a nitrate mother liquor pump. The upper end of the nitrate evaporator circulation pipe is connected to the circulation outlet of the nitrate crystallizer. The lower end of the nitrate evaporator circulation pipe is connected to the inlet of the nitrate circulation pump. The outlet of the nitrate circulation pump is connected to the tube side inlet of the nitrate evaporator. The tube side outlet of the nitrate evaporator is connected to the circulation inlet of the nitrate crystallizer. The crystal slurry outlet at the bottom of the nitrate crystallizer is connected to the inlet of the nitrate thickening tank through a nitrate crystal slurry pump.

6. The mixed salt concentration, separation and drying system according to claim 5, characterized in that: The tail gas outlet of the nitrate centrifuge is connected to the tail gas manifold. A plastic Pall ring packing layer is provided below the upper spray nozzle of the water foam dust removal spray tower. And the water replenishing port at the upper part of the tower body is connected to the spray water replenishing pipe through a water replenishing control valve, and the water replenishing control valve is controlled by the remote transmission liquid level gauge of the water foam dust removal spray tower.

7. The mixed salt concentration, separation and drying system according to claim 3, wherein: The external discharge pump of the frozen mother liquor is connected to the middle of the primary salt concentration circulation pipe in the primary salt MVR unit. The upper end of the primary salt concentration circulation pipe is connected to the circulation outlet of the primary salt crystallizer. The lower end of the primary salt concentration circulation pipe is connected to the inlet of the primary salt circulation pump. The outlet of the primary salt circulation pump is connected to the tube side inlet of the primary salt heat exchanger. The tube side outlet of the primary salt heat exchanger is connected to the circulation inlet of the primary salt crystallizer. The salt leg outlet of the primary salt crystallizer is connected to the inlet of the primary salt thickening tank through a primary salt crystal slurry pump. The bottom outlet of the primary salt thickening tank is connected to the inlet of the primary salt centrifuge. The solid phase outlet of the primary salt centrifuge is connected to the inlet of the primary salt dissolution tank. The outlet of the primary salt dissolution tank is connected to the inlet of the nanofiltration membrane device through a primary salt dissolution external delivery pump. The concentrated water outlet of the nanofiltration membrane device is connected to the inlet of the freezing crystallizer. The produced water outlet of the nanofiltration membrane device is connected to the secondary salt MVR unit.

8. The mixed salt concentration, separation and drying system according to claim 7, characterized in that: The liquid phase outlet of the primary salt centrifuge is connected to the inlet of the primary salt mother liquor tank. The outlet of the primary salt mother liquor tank is connected to the return port of the primary salt thickening tank through a primary salt mother liquor circulation pump. The clear liquid outlet at the top of the primary salt thickening tank is connected to the inlet of the primary salt precipitation tank. The bottom outlet of the primary salt precipitation tank is connected to the inlet of the primary salt mother liquor tank. The upper side wall outlet of the primary salt precipitation tank is connected to the mixed salt evaporation and crystallization system through a primary salt mother liquor external discharge pump.

9. The mixed salt concentration, separation and drying system according to claim 7, characterized in that: The produced water outlet of the nanofiltration membrane device is connected to the middle of the secondary salt concentration circulation pipe in the secondary salt MVR unit. The upper end of the secondary salt concentration circulation pipe is connected to the circulation outlet of the secondary salt crystallizer. The lower end of the secondary salt concentration circulation pipe is connected to the inlet of the secondary salt circulation pump. The outlet of the secondary salt circulation pump is connected to the tube side inlet of the secondary salt heat exchanger. The tube side outlet of the secondary salt heat exchanger is connected to the circulation inlet of the secondary salt crystallizer. The salt leg outlet of the secondary salt crystallizer is connected to the inlet of the secondary salt thickening tank through a secondary salt crystal slurry pump. The bottom outlet of the secondary salt thickening tank is connected to the inlet of the secondary salt centrifuge. The solid phase outlet of the secondary salt centrifuge is connected to the sodium chloride drying unit. The tail gas outlets of the primary salt centrifuge and the secondary salt centrifuge are connected to the tail gas manifold.

10. The mixed salt concentration, separation and drying system according to claim 9, wherein: The mother liquor outlet of the secondary salt centrifuge is connected to the inlet of the secondary salt mother liquor tank, and the outlet of the secondary salt mother liquor tank is connected to the reflux port of the secondary salt thickening tank through the secondary salt mother liquor circulation pump; The clear liquid overflow port of the secondary salt thickening tank is connected to the inlet of the secondary salt precipitation tank, and the bottom outlet of the secondary salt precipitation tank is connected to the inlet of the secondary salt mother liquor tank; The middle clear liquid outlet of the secondary salt precipitation tank is connected to the inlet of the freezing crystallizer through the secondary salt mother liquor discharge pump and the secondary salt mother liquor discharge pipe.

11. The mixed salt concentration, separation and drying system according to claim 8, characterized in that: The primary salt mother liquor discharge pump is connected to the middle of the mixed salt concentration circulation pipe in the mixed salt evaporation and crystallization system. The upper end of the mixed salt concentration circulation pipe is connected to the circulation outlet of the mixed salt crystallizer, and the lower end of the mixed salt concentration circulation pipe is connected to the inlet of the mixed salt circulation pump. The outlet of the mixed salt circulation pump is connected to the tube side inlet of the mixed salt evaporator, and the tube side outlet of the mixed salt evaporator is connected to the circulation inlet of the mixed salt crystallizer; The salt leg outlet of the mixed salt crystallizer is connected to the inlet of the mixed salt thickening tank through the mixed salt crystal slurry pump. The bottom outlet of the mixed salt thickening tank is connected to the inlet of the mixed salt centrifuge. The solid phase outlet of the mixed salt centrifuge is connected to the inlet of the mixed salt dissolution tank. The bottom outlet of the mixed salt dissolution tank is connected to the reflux port of the freezing crystallizer through the mixed salt dissolution discharge pump; The liquid phase outlet of the mixed salt centrifuge is connected to the inlet of the mixed salt mother liquor tank. The outlet of the mixed salt mother liquor tank is connected to the inlet of the drum dryer through the mixed salt mother liquor pump. The waste salt outlet of the drum dryer is connected to the waste salt baler through the waste salt auger. The tail gas outlet of the drum dryer is connected to the tail gas manifold.

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