A system for treating waste salt by fractional concentration

Abstract

The utility model relates to a kind of waste miscellaneous salt concentration treatment systems, it includes pretreatment unit, pretreatment water pool, reverse osmosis device, nanofiltration device, nanofiltration water pool, evaporation crystallization unit, nanofiltration concentrated water pool and refrigeration crystallization unit;Concentration meter is installed in pretreatment water pool, for low-concentration waste salt, waste salt solution is concentrated by reverse osmosis first, reverse osmosis concentrated water is separated monovalent salt and divalent salt by nanofiltration again;Finally, water, sodium chloride is separated sodium chloride by evaporation crystallization, sodium sulfate etc. are separated product sodium sulfate by refrigeration crystallization;For medium-concentration waste salt, control waste salt solution directly into nanofiltration device separates monovalent salt and divalent salt, without reverse osmosis to medium-concentration waste salt, reduce energy consumption;For high-concentration waste salt, control waste salt solution directly into evaporation crystallization unit and refrigeration crystallization unit, adopt evaporation crystallization and temperature reduction crystallization combination, separate sodium chloride and sodium sulfate product.

Description

Technical Field

[0001] This utility model relates to the field of waste salt treatment technology, specifically to a waste salt concentration treatment system. Background Technology

[0002] With the rapid development of industrialization and urbanization, the amount of waste salt generated is constantly increasing, and the market demand for waste salt resource utilization is also growing. Waste salt mainly comes from industries such as chemical, pharmaceutical, and pesticide manufacturing. The composition of these waste salts is relatively complex, mainly containing sodium chloride and sodium sulfate, and also contains a small amount of impurities. Generally, they are treated for harmlessness and utilized for resource utilization. Harmlessness technologies such as incineration, landfill, and marine discharge are mainly used to reduce or eliminate toxic and harmful components in waste salt to reduce environmental risks, but this results in resource waste. Therefore, resource utilization is the conventional approach. For example, Chinese patent CN209502536U discloses an industrial waste salt resource utilization device. After pretreatment (removal of organic matter, hardening and impurity removal, drying, filtration, oxidation, and secondary impurity removal) of the waste salt solution, it is then subjected to ultrafiltration, ion exchange, nanofiltration, reverse osmosis, and multi-effect evaporation crystallization to separate sodium chloride and sodium nitrate.

[0003] However, directly applying the above methods to recover waste salts presents the following problems: First, after pretreatment, the waste salts are directly passed through ultrafiltration, ion exchange, nanofiltration, reverse osmosis, and multi-effect evaporation crystallization units in sequence, without distinguishing the concentration of the waste salts. If the waste salt concentration is low (total salt < 5%), using all the above equipment uniformly after pretreatment leads to overtreatment and high energy costs. If the waste salt concentration is high (total salt > 20%), after pretreatment, the high concentration of ions inhibits the separation effect of the nanofiltration membrane, making it impossible to effectively separate monovalent and divalent salts, and subsequent evaporation still produces mixed salts. Furthermore, when passing through the reverse osmosis membrane, the membrane flux drops sharply due to excessively high osmotic pressure, affecting the separation effect. Second, the sequence of waste salts passing through ion exchange, nanofiltration, and reverse osmosis is unreasonable. Ion exchange resin regeneration requires strong acids or bases (such as HCl or NaOH). If the regeneration waste liquid is not properly treated before entering the membrane system, it will cause hydrolysis and damage to the nanofiltration and reverse osmosis membranes, shortening their service life. Utility Model Content

[0004] The purpose of this invention is to provide a waste salt concentration treatment system.

[0005] The purpose of this utility model is achieved by the following technical solution: a waste salt concentration treatment system, which includes a pretreatment unit, a pretreatment product water tank, a reverse osmosis device, a nanofiltration device, a nanofiltration product water tank, an evaporation crystallization unit, a nanofiltration concentrate water tank, a freeze crystallization unit, and a condensate storage tank. The outlet of the flotation tank in the pretreatment unit is connected to the inlet of the pretreatment permeate tank. A concentration meter is installed in the pretreatment permeate tank. The first outlet of the pretreatment permeate tank is connected to the inlet of the reverse osmosis unit via a first pipeline. The permeate outlet of the reverse osmosis unit is connected to the second makeup water inlet of the dissolution tank in the pretreatment unit via a second return water pipeline. The concentrate outlet of the reverse osmosis unit is connected to the first inlet of the nanofiltration unit. The permeate outlet of the nanofiltration unit is connected to the inlet of the nanofiltration permeate tank. The outlet of the nanofiltration permeate tank is connected to the first inlet of the evaporation crystallization unit. The concentrate outlet of the nanofiltration unit is connected to the inlet of the nanofiltration concentrate tank. The outlet of the nanofiltration concentrate tank is connected to the first inlet of the freeze crystallization unit. The second outlet of the pretreatment water tank is connected to the second inlet of the nanofiltration device via a second pipeline; The third outlet of the pretreatment water production tank is connected to the second inlet of the evaporation crystallization unit through a third pipeline; the mother liquor outlet of the evaporation crystallization unit is connected to the second inlet of the freeze crystallization unit; and the drain outlet of the evaporation crystallization unit is connected to the inlet of the condensate storage tank. A first solenoid valve is provided on the first pipeline, a second solenoid valve is provided on the second pipeline, and a third solenoid valve is provided on the third pipeline; the concentration meter is electrically connected to the signal input terminal of the controller, and the signal output terminal of the controller is electrically connected to the first solenoid valve, the second solenoid valve, and the third solenoid valve respectively.

[0006] Preferably, the pretreatment unit includes the dissolution tank, multi-media filter, wet catalytic oxidation device, hardening removal device, tubular membrane device, equalization tank and flotation tank; The outlet of the dissolving tank is connected to the inlet of the multi-media filter, the outlet of the multi-media filter is connected to the inlet of the wet catalytic oxidation device, the outlet of the wet catalytic oxidation device is connected to the inlet of the hardening removal device, the outlet of the hardening removal device is connected to the inlet of the tubular membrane device, the outlet of the tubular membrane device is connected to the inlet of the equalization tank, and the outlet of the equalization tank is connected to the inlet of the air flotation tank.

[0007] Preferably, the pretreatment unit further includes a sludge collection tank and a plate and frame filter press; the sludge outlet of the multi-media filter is connected to the first inlet of the sludge collection tank, the outlet of the sludge collection tank is connected to the inlet of the plate and frame filter press, and the filtrate outlet of the plate and frame filter press is connected to the first water inlet of the dissolving tank through a first return water pipeline; the sludge outlet of the tubular membrane is connected to the second inlet of the sludge collection tank.

[0008] Preferably, the pretreatment unit further includes a hydrochloric acid storage tank, the outlet of which is connected to the hydrochloric acid inlet of the equalization tank.

[0009] Preferably, the hardening removal device includes a primary softening tank, a secondary softening tank, a sodium hydroxide storage tank, and a sodium carbonate storage tank. The inlet of the primary softening tank is the inlet of the hardening removal device, the outlet of the secondary softening tank is the outlet of the hardening removal device, the outlet of the primary softening tank is connected to the inlet of the secondary softening tank, the dosing port of the primary softening tank is connected to the outlet of the sodium hydroxide storage tank, and the dosing port of the secondary softening tank is connected to the outlet of the sodium carbonate storage tank.

[0010] Preferably, the hardening device further includes a mixer, which is vertically installed in both the primary softening tank and the secondary softening tank.

[0011] Preferably, the outlet of the hydrochloric acid storage tank is connected to the hydrochloric acid inlet of the regulating tank.

[0012] Advantages of this invention: This invention installs a concentration meter in the pretreatment permeate tank, which is adapted to the total salt concentration of the pretreated waste salt solution. For low-concentration waste salt (the concentration meter detects a total salt concentration of <5% in the pretreatment permeate tank), the waste salt solution is automatically controlled to enter the reverse osmosis unit for concentration. The reverse osmosis permeate can be reused as process water. The reverse osmosis concentrate is sent to the nanofiltration unit to separate monovalent and divalent salts. Water, sodium chloride, etc., pass through the nanofiltration membrane and enter the permeate side, where they are separated and enter the nanofiltration permeate tank. Then, they enter the evaporation and crystallization unit to evaporate and crystallize sodium chloride. Sulfate, etc., are retained by the nanofiltration membrane on the concentrate side and sent to the nanofiltration concentrate tank for collection. Then, they enter the freeze crystallization unit to freeze and crystallize, producing sodium sulfate. For medium-concentration waste salt (the concentration meter detects a total salt concentration of 5%-20% in the pretreatment permeate tank), the invention provides further control. The system automatically controls waste salt solutions to directly enter the nanofiltration unit for the separation of monovalent and divalent salts, eliminating the need for reverse osmosis treatment of medium-concentration waste salts and reducing energy consumption. For high-concentration waste salts (where the concentration meter detects a total salt concentration >20% in the pretreatment product water tank), the system automatically controls the waste salt solution to directly enter the evaporation crystallization unit and the freeze crystallization unit. A combination of evaporation crystallization and cooling crystallization is used to separate sodium chloride and sodium sulfate products, eliminating the need for the high-concentration waste salt solution to pass through the reverse osmosis and nanofiltration units. This avoids the inhibition of nanofiltration membrane separation due to high ionic strength and the sudden drop in permeate membrane flux due to excessive osmotic pressure, thus using nanofiltration and permeate membranes rationally and effectively and reducing system energy consumption. The system is also tailored to the total salt concentration of the pretreated waste salt solution, avoiding a one-size-fits-all approach that could lead to overtreatment, high energy costs, poor separation performance, and shortened membrane system lifespan. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the structure of this utility model.

[0015] Figure 2 This is a schematic diagram of the control principle of this utility model.

[0016] The components in the attached diagram are labeled as follows: Pretreatment unit 1, Dissolving tank 1.1, Multi-media filter 1.2, Wet catalytic oxidation device 1.3, Hardness removal device 1.4, Primary softening tank 1.4.1, Secondary softening tank 1.4.2, Agitator 1.4.3, Sodium hydroxide storage tank 1.4.4, Sodium carbonate storage tank 1.4.5, Tubular membrane device 1.5, Equalization tank 1.6, Air flotation tank 1.7, Sludge collection tank 1.8, Plate and frame filter press 1.9, Hydrochloric acid storage tank 1.10, First return water pipeline 1.11, Pretreatment product water tank 2, Reverse osmosis device 3, Nanofiltration device 4, Nanofiltration product water tank 5, Evaporation crystallization unit 6, Nanofiltration concentrate tank 7, Freeze crystallization unit 8, Condensate storage tank 9, Concentration meter 10, Second return water pipeline 11, Third return water pipeline 12, First solenoid valve 15, Second solenoid valve 14, Third solenoid valve 13, Controller 16. Detailed Implementation

[0017] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0018] In the description of this utility model, it should be noted that the terms "center", "upper", "lower", "front", "rear", "top", "bottom", "left", "right", "vertical", "horizontal", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0019] like Figure 1-2As shown, a waste salt concentration treatment system includes a pretreatment unit 1, a pretreatment product water tank 2, a reverse osmosis unit 3, a nanofiltration unit 4, a nanofiltration product water tank 5, an evaporation crystallization unit 6, a nanofiltration concentrate tank 7, a freeze crystallization unit 8, and a condensate storage tank 9; wherein, the pretreatment unit 1 includes a dissolution tank 1.1, a multi-media filter 1.2, a wet catalytic oxidation unit 1.3, a hardening removal unit 1.4, a tubular membrane unit 1.5, an equalization tank 1.6, an air flotation tank 1.7, a sludge collection tank 1.8, and a plate and frame filter press 1.9; The outlet of dissolving tank 1.1 is connected to the inlet of multi-media filter 1.2 via a pipeline. The sludge outlet of multi-media filter 1.2 is connected to the first inlet of sludge collection tank 1.8 via a pipeline. The outlet of sludge collection tank 1.8 is connected to the inlet of plate and frame filter press 1.9 via a pipeline. The filtrate outlet of plate and frame filter press 1.9 is connected to the first water supply port of dissolving tank 1.1 via the first return water pipeline 1.11. The outlet of multi-media filter 1.2 is connected to the inlet of wet catalytic oxidation device 1.3 via a pipeline. Wet catalytic oxidation device 1.3 can be a wet catalytic oxidation device produced by Zhejiang Fantai Instrument Co., Ltd., which is existing equipment. The specific structure will not be described here. The outlet of wet catalytic oxidation device 1.3 is connected to the inlet of hardening removal device 1.4 via a pipeline. Waste salt is dissolved in dissolving tank 1.1. The waste salt solution is pumped to a multi-media filter 1.2 for solid-liquid separation to remove large suspended particles such as mud, sand, and rust. The permeate from the multi-media filter 1.2 is pumped to a wet catalytic oxidation unit 1.3 for oxidation treatment. Under the action of manganese dioxide, hydrogen peroxide reacts with organic pollutants, oxidizing them. Hydrogen peroxide also decomposes in water to produce hydroxyl radicals, which can significantly enhance the oxidation capacity and further improve the degradation effect on organic pollutants, completely converting them into harmless inorganic substances. The sludge produced by the multi-media filter 1.2 is sent to a sludge collection tank 1.8. After centralized collection, the sludge is sent to a plate and frame filter press 1.9 for filtration. The filter cake is sent to the plant's safe landfill for disposal. The filtrate is returned to the dissolving tank 1.1 for replenishment. The waste salt solution after organic matter removal is pumped into the hardening removal device 1.4. The hardening removal device 1.4 includes a primary softening tank 1.4.1, a secondary softening tank 1.4.2, a mixer 1.4.3, a sodium hydroxide storage tank 1.4.4, and a sodium carbonate storage tank 1.4.5. The inlet of the primary softening tank 1.4.1 is the inlet of the hardening removal device 1.4, and the outlet of the secondary softening tank 1.4.2 is the outlet of the hardening removal device 1.4. The outlet of the primary softening tank 1.4.1 and the inlet of the secondary softening tank 1.4.2 are connected by a pipeline. The dosing port of the primary softening tank 1.4.1 is connected to the sodium hydroxide... The outlet of storage tank 1.4.4 is connected to the outlet of sodium carbonate storage tank 1.4.5 via a pipeline. The dosing port of secondary softening tank 1.4.2 is connected to the outlet of sodium carbonate storage tank 1.4.5 via a pipeline. Agitators 1.4.3 are installed in both primary softening tank 1.4.1 and secondary softening tank 1.4.2. Sodium hydroxide is added to primary softening tank 1.4.1 and sodium carbonate is added to secondary softening tank 1.4.2. The mixture is stirred to generate calcium carbonate and magnesium hydroxide precipitates. The saturated brine is softened using a double alkali method to remove most of the calcium and magnesium ions, silica and heavy metal ions from the brine, forming a large amount of suspended solids. The outlet of the hardening device 1.4 is connected to the inlet of the tubular membrane device 1.5 via a pipeline; the sludge outlet of the tubular membrane device 1.5 is connected to the second inlet of the sludge collection tank 1.8 via a pipeline; the liquid outlet of the tubular membrane device 1.5 is connected to the inlet of the equalization tank 1.6 via a pipeline; the hydrochloric acid inlet of the equalization tank 1.6 is connected to the outlet of the hydrochloric acid storage tank 1.10 via a pipeline; and the outlet of the equalization tank 1.6 is connected to the inlet of the dissolved air flotation tank 1.7 via a pipeline. A large amount of suspended solids is directly sent to the tubular membrane device 1.5 for separation. To prevent scaling in subsequent membrane systems, the permeate from the tubular membrane unit 1.5 enters the equalization tank 1.6, where hydrochloric acid is added to adjust the pH of the brine to neutral, preventing extreme pH from corroding the reverse osmosis or nanofiltration membranes. The solid filter cake after tubular membrane filtration then enters the sludge collection tank 1.8 and the plate and frame filter press 1.9 for further recycling of the filtrate. After pH adjustment, the brine is sent to the flotation tank 1.7, where emulsified oil is removed by flotation (with the addition of coagulants), preventing fouling of the reverse osmosis and nanofiltration membranes. The outlet of the flotation tank 1.7 is connected to the inlet of the pretreatment product water tank 2 via a pipeline. A concentration meter 10 is installed in the pretreatment product water tank 2. The first outlet of the pretreatment product water tank 2 is connected to the inlet of the reverse osmosis unit 3 via a first pipeline. The product water outlet of the reverse osmosis unit 3 is connected to the second makeup water inlet of the dissolving tank 1.1 via a second return water pipeline 11. The concentrate outlet of the reverse osmosis unit 3 is connected to the first inlet of the nanofiltration unit 4 via a pipeline. The product water outlet of the nanofiltration unit 4 is connected to the inlet of the nanofiltration product water tank 5 via a pipeline. The outlet of the nanofiltration product water tank 5 is connected to the first inlet of the evaporation crystallization unit 6 via a pipeline. The evaporation condensate outlet of the evaporation crystallization unit 6 is connected to the first inlet of the condensate storage tank 9 via a pipeline. The nanofiltration unit 4's concentrate outlet is connected to the nanofiltration concentrate tank 7's inlet via a pipeline; the nanofiltration concentrate tank 7's outlet is connected to the first inlet of the freeze crystallization unit 8 via a pipeline; the freeze crystallization unit 8's clear liquid outlet is connected to the second inlet of the condensate storage tank 9 via a pipeline; the pretreatment product water tank 2's second outlet is connected to the nanofiltration unit 4's second inlet via a second pipeline; the pretreatment product water tank 2's third outlet is connected to the second inlet of the evaporation crystallization unit 6 via a third pipeline; the evaporation crystallization unit 6's mother liquor outlet is connected to the second inlet of the freeze crystallization unit 8 via a pipeline; the condensate storage tank 9's outlet is connected to the third water inlet of the dissolving tank 1.1 via a third return water pipeline 12. A first solenoid valve 15 is installed on the first pipeline, a second solenoid valve 14 is installed on the second pipeline, and a third solenoid valve 13 is installed on the third pipeline. A concentration meter 10 is electrically connected to the signal input terminal of a controller 16, and the signal output terminal of the controller 16 is electrically connected to the first solenoid valve 15, the second solenoid valve 14, and the third solenoid valve 13, respectively. When the concentration meter 10 detects that the total salt concentration of the waste salt solution in the pretreatment product water tank 2 is >20%, it transmits a signal to the controller 16. The controller 16 controls the third solenoid valve 13 to open and the first solenoid valve 15 and the second solenoid valve 14 to close. The waste salt solution in the pretreatment product water tank 2 is then transported to the evaporation and crystallization unit 6 via a transfer pump. The evaporation and crystallization unit 6 includes an evaporator and a centrifuge. The evaporator and centrifuge are existing equipment, and their specific structures will not be described here. The material is indirectly heated using steam provided by the waste heat boiler in the plant's incineration workshop, with a steam temperature of approximately 80-100℃. On the right, after the waste salt solution is evaporated and crystallized, the evaporation condensate is sent to the condensate storage tank 9 and periodically returned to the dissolving tank 1.1 for reuse as salt-dissolving water. The suspension in the evaporation crystallizer enters the centrifuge, and after centrifugation, the solid is the product sodium chloride. The mother liquor after centrifugation enters the freeze crystallization unit 8. The freeze crystallization unit 8 includes a freeze crystallizer and a centrifuge. The freeze crystallizer and centrifuge are existing equipment, and their specific structures will not be described here. The temperature of the solution in the freeze crystallizer is reduced by the freezing liquid (the freezing liquid is 40% ethylene glycol). Most of the dissolved sodium sulfate in the solution precipitates in the form of crystals. The solution is pumped into the centrifuge for centrifugation by the discharge pump. The centrifuge separates the sodium sulfate crystals from the mother liquor by the centrifugal force generated by the high-speed rotation. The centrifugal mother liquor is sent back to the freeze crystallizer by the centrifugal mother liquor pump. The solid separated by centrifugation is the product sodium sulfate. The clear liquid on the top of the freeze crystallizer is sent to the condensate storage tank 9 and periodically reused in the dissolving tank 1.1 for further recycling. When the concentration meter 10 detects that the total salt concentration of the waste salt solution in the pretreatment product water tank 2 is 5%-20%, it transmits a signal to the controller 16. The controller 16 controls the second solenoid valve 14 to open and the first solenoid valve 15 and the third solenoid valve 13 to close. The waste salt solution in the pretreatment product water tank 2 enters the nanofiltration device 4 through the booster pump. The nanofiltration operating pressure is about 4.5 MPa, and the sodium chloride rejection rate is less than 20%. Water, sodium chloride, etc. pass through the nanofiltration membrane and enter the product water side to be separated and enter the nanofiltration product water tank 5. Then it enters the evaporation crystallization unit 6 to evaporate and crystallize to precipitate sodium chloride. The nanofiltration membrane has a rejection rate of about 98% for divalent ions. Sulfate and other ions are retained by the nanofiltration membrane on the concentrate side and sent to the nanofiltration concentrate tank 7 for collection. Then it enters the freeze crystallization unit 8 to repeat the above freeze crystallization steps. When the concentration meter 10 detects that the total salt concentration of the waste salt solution in the pretreatment product water tank 2 is <5%, it transmits a signal to the controller 16. The controller 16 controls the first solenoid valve 15 to open and the second solenoid valve 14 and the third solenoid valve 13 to close. The waste salt solution in the pretreatment product water tank 2 first enters the reverse osmosis unit 3. After reverse osmosis concentration, the product water is reused in the dissolving tank 1.1 through the second return water pipeline 11. After reverse osmosis concentration, the concentrated water is transported to the nanofiltration unit 4 through the transfer pump to continue repeating the above treatment steps.

[0020] The above are merely preferred embodiments of the present utility model and are not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A waste salt concentration treatment system, characterized in that, It includes a pretreatment unit, a pretreatment product water tank, a reverse osmosis unit, a nanofiltration unit, a nanofiltration product water tank, an evaporation crystallization unit, a nanofiltration concentrate tank, a freeze crystallization unit, and a condensate storage tank; The outlet of the flotation tank in the pretreatment unit is connected to the inlet of the pretreatment permeate tank. A concentration meter is installed in the pretreatment permeate tank. The first outlet of the pretreatment permeate tank is connected to the inlet of the reverse osmosis unit via a first pipeline. The permeate outlet of the reverse osmosis unit is connected to the second makeup water inlet of the dissolution tank in the pretreatment unit via a second return water pipeline. The concentrate outlet of the reverse osmosis unit is connected to the first inlet of the nanofiltration unit. The permeate outlet of the nanofiltration unit is connected to the inlet of the nanofiltration permeate tank. The outlet of the nanofiltration permeate tank is connected to the first inlet of the evaporation crystallization unit. The concentrate outlet of the nanofiltration unit is connected to the inlet of the nanofiltration concentrate tank. The outlet of the nanofiltration concentrate tank is connected to the first inlet of the freeze crystallization unit. The second outlet of the pretreatment water tank is connected to the second inlet of the nanofiltration device via a second pipeline; The third outlet of the pretreatment water production tank is connected to the second inlet of the evaporation crystallization unit through a third pipeline; the mother liquor outlet of the evaporation crystallization unit is connected to the second inlet of the freeze crystallization unit; and the drain outlet of the evaporation crystallization unit is connected to the inlet of the condensate storage tank. A first solenoid valve is provided on the first pipeline, a second solenoid valve is provided on the second pipeline, and a third solenoid valve is provided on the third pipeline; the concentration meter is electrically connected to the signal input terminal of the controller, and the signal output terminal of the controller is electrically connected to the first solenoid valve, the second solenoid valve, and the third solenoid valve respectively.

2. The waste salt concentration treatment system according to claim 1, characterized in that, The pretreatment unit includes the dissolution tank, multi-media filter, wet catalytic oxidation device, hardening removal device, tubular membrane device, equalization tank and air flotation tank; The outlet of the dissolving tank is connected to the inlet of the multi-media filter, the outlet of the multi-media filter is connected to the inlet of the wet catalytic oxidation device, the outlet of the wet catalytic oxidation device is connected to the inlet of the hardening removal device, the outlet of the hardening removal device is connected to the inlet of the tubular membrane device, the outlet of the tubular membrane device is connected to the inlet of the equalization tank, and the outlet of the equalization tank is connected to the inlet of the air flotation tank.

3. The waste salt concentration treatment system according to claim 2, characterized in that, The pretreatment unit further includes a sludge collection tank and a plate and frame filter press; the sludge outlet of the multi-media filter is connected to the first inlet of the sludge collection tank, the outlet of the sludge collection tank is connected to the inlet of the plate and frame filter press, and the filtrate outlet of the plate and frame filter press is connected to the first water supply port of the dissolving tank through a first return water pipeline; the sludge outlet of the tubular membrane is connected to the second inlet of the sludge collection tank.

4. The waste salt concentration treatment system according to claim 2, characterized in that, The pretreatment unit also includes a hydrochloric acid storage tank, the outlet of which is connected to the hydrochloric acid inlet of the equalization tank.

5. A waste salt concentration treatment system according to any one of claims 2-4, characterized in that, The hardening removal device includes a primary softening tank, a secondary softening tank, a sodium hydroxide storage tank, and a sodium carbonate storage tank. The inlet of the primary softening tank is the inlet of the hardening removal device, and the outlet of the secondary softening tank is the outlet of the hardening removal device. The outlet of the primary softening tank is connected to the inlet of the secondary softening tank. The dosing port of the primary softening tank is connected to the outlet of the sodium hydroxide storage tank, and the dosing port of the secondary softening tank is connected to the outlet of the sodium carbonate storage tank.

6. The waste salt concentration treatment system according to claim 5, characterized in that, The hardening device also includes a mixer, which is vertically installed in both the primary softening tank and the secondary softening tank.

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