CN111606488A - Critical desalting method and system for high-salinity wastewater - Google Patents
Critical desalting method and system for high-salinity wastewater Download PDFInfo
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- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/02—Treatment of water, waste water, or sewage by heating
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- C02F2301/06—Pressure conditions
- C02F2301/066—Overpressure, high pressure
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- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/124—Water desalination
- Y02A20/131—Reverse-osmosis
Abstract
The invention relates to a critical desalting method and a critical desalting system for high-salinity wastewater, wherein the method comprises the steps of boosting the critical pressure range of the high-salinity wastewater, and then raising the temperature to make the temperature in a critical temperature region; inorganic salt in the high-salinity wastewater reaches supersaturated concentration, salt crystal particles are separated out, and salt slurry and desalted water are obtained; and finally, separating the salt crystal particles in the salt slurry from the water phase to obtain an inorganic salt product and steam. The input end of a high-pressure pump in the system is connected with the output port of the high-salinity wastewater, the output end of the high-pressure pump is communicated with the inlet of a heating device, and the outlet of the heating device is communicated with the inlet of a water-steam mixer; the inlet of the crystallizer is communicated with the outlet of the water-vapor mixer, the salt storage tank is connected below the outlet of the crystallizer, the hydrocyclone is installed at one side of the crystallizer, which is provided with an opening, one side of the hydrocyclone is communicated with the opening of the crystallizer, the underflow tank is connected below the hydrocyclone, the top of the hydrocyclone is provided with an opening, and the salt storage tank and the underflow tank are both connected with the flash evaporator.
Description
Technical Field
The invention belongs to the technical field of high-salinity wastewater desalination, and particularly relates to a critical desalination method and system for high-salinity wastewater.
Background
The high-salinity wastewater refers to wastewater with the total salt mass fraction of at least 1%. The high-salinity wastewater in China mainly comes from chemical plants, petroleum and natural gas collection and processing procedures and the like, and the yield of the high-salinity wastewater is increased year by year at a rate of about 10 percent.
The existing disposal scheme is that the solution is concentrated as much as possible by means of the pretreatment processes of microfiltration, RO membrane, electrolysis, electrodialysis and the like, and then the final separation of salt and water is realized by using the desalination technologies of evaporation concentration, distillation crystallization, thermal incineration and the like.
The desalination technology for treating high-salinity wastewater realizes the recovery of salt by a method of gasifying solvent water, and the problems of high energy consumption cost and large equipment investment generally exist in the methods due to high specific heat and large latent heat of gasification of the solvent water, so that the cost is very high, and the whole wastewater zero-discharge process is controlled by a terminal desalination section, so that the high-salinity wastewater is difficult to achieve the expected treatment effect.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a critical desalting method and system for high-salinity wastewater, which can realize the efficient separation and recovery of soluble inorganic salts such as sodium chloride, sodium sulfate and the like and water.
The invention is realized by the following technical scheme:
a critical desalting method of high-salinity wastewater comprises the following steps,
and 3, separating the salt crystal particles in the salt slurry from the water phase to obtain an inorganic salt product and steam.
Preferably, the high-salinity wastewater in the step 1 is pretreated high-salinity wastewater, and the specific pretreatment comprises one or more of softening, COD removal, filtration, denitrification, ion exchange, advanced oxidation, ultrafiltration, nanofiltration and reverse osmosis.
Furthermore, the COD of the pretreated high-salinity wastewater is lower than 500mg/L, and the salt concentration is 50-150 g/L.
Preferably, in the step 1, the critical pressure range of the high-salinity wastewater is 10-25 MPa.
Preferably, in step 1, the critical temperature region is 250-450 ℃.
Preferably, in step 1, the obtained high-salinity wastewater is heated by heating, heat exchange, mixing with high-temperature water, direct heating or mixing with high-enthalpy water vapor.
Preferably, in the step 2, the time for the salt crystal particles to be separated out from the high-salinity wastewater is within 10 min.
Preferably, the desalted water in the step 2 is subjected to heat exchange and pressure relief to obtain a desalted water product.
Preferably, the salt slurry in the step 3 is subjected to hydrocyclone separation, gravity settling, bed filtration, flash evaporation or spraying to obtain an inorganic salt product and steam.
A critical desalting system for high-salinity wastewater comprises a high-pressure pump, a water-steam mixer, a crystallizer, a salt storage tank, a hydrocyclone, an underflow tank, a flash evaporator and a heating device;
the input end of the high-pressure pump is connected with an output port of high-salinity wastewater, the output end of the high-pressure pump is communicated with an inlet of a heating device, and an outlet of the heating device is communicated with an inlet of a water-steam mixer;
the crystallizer is arranged below the water-vapor mixer along the vertical direction, an inlet of the crystallizer is positioned on the upper surface of the crystallizer, the inlet of the crystallizer is communicated with an outlet of the water-vapor mixer, a salt storage tank is connected below the outlet of the crystallizer, and an opening is formed in one side of the crystallizer;
a hydrocyclone separator is arranged on one side of the crystallizer, which is provided with an opening, one side of the hydrocyclone separator is communicated with the opening of the crystallizer, a bottom flow tank is connected below the hydrocyclone separator, and the top of the hydrocyclone separator is provided with an opening;
the salt storage tank and the underflow tank are both connected with the flash evaporator.
Compared with the prior art, the invention has the following beneficial technical effects:
according to the characteristic that the solubility of soluble inorganic salt in water is low according to the solubility rule of the soluble inorganic salt in water, the solubility of the soluble inorganic salt in a critical area is regulated and controlled by sequentially increasing the pressure and heating the high-salt wastewater to the critical area, so that the inorganic salt in the high-salt wastewater reaches supersaturated concentration, salt crystal particles are separated out, salt slurry and desalted water are obtained, and the salt crystal particles in the salt slurry are further separated from the water phase to obtain an inorganic salt product and steam, so that the technical scheme for desalting is realized.
Furthermore, the process from crystallization to separation of the high-salt wastewater is within 10min, so that the inorganic salt crystals can be ensured to be agglomerated to obtain particles with large particle size, and high salt separation rate is obtained.
Furthermore, after heat exchange and pressure relief are carried out on desalted water, heat and pressure in the desalted water can be recycled for heating and boosting the high-salinity wastewater raw material, so that the energy consumption and the cost of a desalting system can be effectively reduced, and the desalting method has good technical economy.
The invention relates to a critical desalting system for high-salinity wastewater, which utilizes the critical characteristic of water to carry out desalting, the input end of a high-pressure pump is connected with an output port of the high-salinity wastewater, the pressure of the high-salinity wastewater can be increased, the pressure corresponding to the critical area of the high-salinity wastewater is reached, then the output end of the high-pressure pump is communicated with an inlet of a heating device, the high-salinity wastewater can be continuously preheated, an outlet of the heating device is communicated with an inlet of a water-steam mixer, thus, the high-temperature and high-pressure water phase, namely supercritical water or superheated steam can be mixed with the high-salinity wastewater in the water-steam mixer to achieve the purpose of rapid temperature rise, the inlet of a crystallizer arranged along the vertical direction is communicated with the outlet of the water-steam mixer, so that the crystallizer provides a place for crystallization and crystal growth of the high-salinity wastewater, because the salt storage tank is connected below the outlet of the crystallizer, the purposes of low energy consumption and quick and efficient realization of brine separation are achieved; a hydrocyclone separator is arranged at one side of the crystallizer, an underflow tank is connected below the hydrocyclone separator, and an opening is formed in the top of the hydrocyclone separator, so that small-particle salt crystals carried in a water phase can be enriched in underflow by the hydrocyclone separator and finally stored in the underflow tank, and fluid at the top end of the hydrocyclone separator obtains high-temperature and high-pressure desalted water, so that the requirement on the separation rate of the salt crystals and water is met; the salt storage tank and the underflow tank are both connected with a flash evaporator, and the flash evaporator carries out flash evaporation on salt slurry containing salt crystals in the two containers to obtain inorganic salt products and water vapor, so that the separation of the salt products and the water is realized.
Drawings
FIG. 1 is a schematic flow chart of desalting of high-salinity wastewater in a critical water state according to the present invention.
FIG. 2 is a schematic diagram of a critical desalination system for high salinity wastewater according to the present invention.
In the figure: 1-a high-pressure pump, 2-a water-vapor mixer, 3-an inner cylinder, 4-a crystallizer, 51-a first connecting pipeline, 52-a second connecting pipeline, 53-a third connecting pipeline, 6-a salt storage tank, 7-a hydrocyclone, 8-a underflow tank, 9-a heat exchanger, 10-pressure changing equipment, 11-a cooler and 12-a flash evaporator.
Detailed Description
The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.
The invention utilizes the principle that the solubility of soluble inorganic salt in a critical area of water is sharply reduced to realize the rapid and high-efficiency crystallization of brine, and the online continuous separation is carried out under the conditions of high temperature and high pressure.
The complete high-salinity wastewater critical desalting method comprises a crystallization pretreatment part, a crystallization separation part, a desalted water post-treatment part and a salt slurry post-treatment part, wherein the crystallization separation part is the core of the critical desalting method, and other parts can be adjusted according to the characteristics of raw material wastewater and the desalted water quality requirement.
In the method for critical desalination of high-salt wastewater, the high-salt wastewater can be a single-component salt solution or a multi-component salt solution, as shown in fig. 1, the method comprises the following specific steps:
a, performing targeted pretreatment according to the COD and TDS contents of the high-salinity wastewater;
the pretreatment of the high-salinity wastewater comprises one or more of softening, COD removal, filtration, denitrification, ion exchange, advanced oxidation, ultrafiltration, nanofiltration and reverse osmosis, so that the impurities in the high-salinity wastewater do not influence the quality of the separated product, but the COD of the pretreated wastewater is lower than 500mg/L, and the salt concentration is within the range of 100g/L +/-50 g/L.
This step can be omitted if the brine meets the above crystallization requirements.
b, boosting the pressure of the pretreated high-salinity wastewater to be close to the critical pressure point of water, wherein the pressure range of the boosted high-salinity wastewater is between 10 and 25 MPa;
and c, rapidly heating the high-salinity wastewater subjected to pressure boosting to a critical temperature region by means of heating, heat exchange or mixing with high-temperature water, wherein the temperature range of the high-salinity wastewater subjected to temperature boosting is between 250 and 450 ℃.
a, after the high-salt wastewater reaches a critical temperature range, the solubility of inorganic salt is rapidly reduced to reach a large supersaturation degree, so that impact crystallization is carried out in a critical state, a large number of salt crystal particles are separated out, and salt slurry and desalted water are obtained through gravity settling and sintered metal filtration;
b, the solubility of inorganic salt in the desalted water can be reduced to 200mg/L or below by regulating the temperature and the pressure of the high-salinity wastewater, seed crystals can be provided in the crystallization process to obtain inorganic salt crystal particles with large particle size as much as possible, and the core purpose is to quickly separate out the inorganic salt and realize solid-liquid two-phase separation by regulating the temperature and the pressure of the high-salinity wastewater.
a, separating salt slurry which is separated out from the water phase by inorganic salt crystal particles through density difference, hydrocyclone separation and gravity settling or bed filtration;
b, cooling the inorganic salt crystal slurry obtained by separation, and obtaining an inorganic salt solid product by means of flash evaporation or spraying;
and c, the water vapor generated by flash evaporation and spraying operations can be used as a heat source for heating the high-salinity wastewater after pressurization and heating operations, and the energy in the water vapor can be recovered by means of heat exchange, expansion work and the like.
And (4) carrying out heat exchange and pressure relief on the desalted water obtained by separation to obtain a desalted water product. The heat and pressure of the desalinated water can be recycled for heating and pressurizing the high-salinity wastewater raw material.
After phase separation, the content of inorganic salts in the desalted water is controlled to be 500mg/L or less, and a small amount of solid salt crystals which are not completely separated are dissolved into a liquid phase again, so that the salt concentration of the desalted water is increased. Meanwhile, heat preservation and pressure maintaining are needed in the separation process, so that salt crystals precipitated in the separation process are prevented from being dissolved again.
The method has no special requirements on the salt components and the content in the high-salt wastewater, and the retention time of the high-salt wastewater from crystallization to separation is generally controlled within 10min, so that the inorganic salt crystals can be agglomerated and grown into particles with large particle sizes, and the high salt separation rate can be obtained. The residence time of this separation process is much lower than the 2-6h residence time required for conventional crystallization operations.
The above process may be carried out by a system as shown in fig. 2, which specifically comprises a high pressure pump 1, a water-steam mixer 2, a crystallizer 4, a salt storage tank 6, a hydrocyclone 7, an underflow tank 8, a flash vessel 12 and a heating device.
The input end of the high-pressure pump 1 is connected with an output port of high-salinity wastewater, the output end of the high-pressure pump 1 is communicated with an inlet of a heating device, and an outlet of the heating device is communicated with an inlet of the water-steam mixer 2 through a pipeline or a flange; the crystallizer 4 is arranged below the water-vapor mixer 2 along the vertical direction, the inlet of the crystallizer 4 is positioned on the upper surface of the crystallizer 4, the inlet of the crystallizer 4 is communicated with the outlet of the water-vapor mixer 2, the lower part of the outlet of the crystallizer 4 is connected with a salt storage pool 6, and one side of the crystallizer 4 is provided with an opening. The warming may be accomplished by a single or multiple devices. The preferred solution is a combination of a preheater and a steam-water mixer 2. The specific flow is that the high-salinity wastewater after boosting is preheated by desalted water in a preheater and then is mixed with a high-temperature and high-pressure water phase (supercritical water or superheated steam) in a water-steam mixer 2 to achieve the purpose of rapid temperature rise.
The crystallizer 4 is cylindrical and provides a place for crystallization of high-salinity wastewater and crystal growth. The center of the crystallizer 4 is provided with a cylindrical inner cylinder 3 along the vertical direction, the upper end of the inner cylinder 3 is flush with the inlet of the crystallizer 4, and the height of the inner cylinder 3 is less than that of the crystallizer 4. The inner cylinder 3 plays a role in baffling the high-salinity wastewater entering the crystallizer 4 so as to prolong the retention time of the wastewater and ensure that the supersaturated salt solution has enough crystallization and crystal growth time. The high-salinity wastewater after the pressure and temperature rise is introduced into a critical crystallization part from the upper end of the inner cylinder 3, grows in the inner cylinder 3 in a crystallization way, and further grows in the space at the lower part of the crystallizer 4 after flowing out from the lower end of the inner cylinder 3. The large-grained salt crystals are finally deposited under the action of gravity from the lower part of the crystallizer 4 via a transition pipe and a first connecting pipe 51 into the salt storage tank 6.
The cross section of the inner cylinder 3 is 20-70% of the cross section area of the crystallizer 4, and the height of the inner cylinder 3 is 30-70% of the height of the crystallizer 4.
A filter plate with the aperture of 0.1-1.0mm is arranged between the inner cylinder 3 and the inner wall of the crystallizer 4, and the filter plate is positioned at the opening of the crystallizer 4.
The outlet of the crystallizer 4 is connected with a transition pipe, which is connected with the salt storage tank 6 through a first connecting pipe 51, and the communication state of the pipes can be controlled by a high-pressure valve.
A hydrocyclone 7 is arranged at one side of the crystallizer 4 with an opening, one side of the hydrocyclone 7 is communicated with the opening of the crystallizer 4, an underflow tank 8 is connected below the hydrocyclone 7, and the top of the hydrocyclone 7 is provided with an opening.
The hydrocyclone 7 and the underflow tank 8 are connected by a second connecting conduit 52. The fluid at the top end of the hydrocyclone 7 is the resulting high temperature, high pressure desalted water. When the separation effect has higher requirement, a plurality of hydrocyclone groups connected in series can be arranged behind the hydrocyclone 7 for further processing desalted water, and generally 2 hydrocyclone groups are required.
The back end of the hydrocyclone 7 is connected with a heat exchanger 9 and a pressure changing device 10 in sequence. The heat energy and the pressure energy in the desalted water are recovered, and the configuration sequence is that the heat exchange is carried out firstly and then the pressure is changed, so that the pressure stability of the fluid can be ensured. Preferred equipment configurations are high pressure shell and tube heat exchangers and positive displacement energy recovery devices.
The salt storage tank 6 and the underflow tank 8 are both connected with a flash evaporator 12.
The outlets of the salt storage tank 6 and the underflow tank 8 are both connected with the input end of a cooler 11, and the output end of the cooler 11 is connected with the input end of a flash evaporator 12. The flash vessel 12 is connected to the salt storage tank 6 and the underflow tank 8 via pipes and a cooler 11, and functions to flash-vaporize the salt slurry containing salt crystals in the two vessels to obtain inorganic salt product and water vapor.
Example 1
The method comprises the steps of boosting 150g/L sodium chloride solution prepared in a laboratory to 16MPa, then rapidly heating the sodium chloride solution to 320 ℃ through a heat exchanger and an electric heater in sequence, reducing the flow rate of the sodium chloride solution in a crystallizer 4 to 0.12m/s, carrying out critical crystallization and flocculation on the sodium chloride solution in the crystallizer 4, then precipitating the sodium chloride solution to the lower part of the crystallizer 4, and flowing the sodium chloride solution into a salt storage tank 6 at the lowest end through a communicating pipeline at the lower part. A filter plate of sintered metal is arranged in front of an outlet of the crystallizer 4, inorganic salt crystals carried in the filtrate are captured and blocked by the filter plate, and desalted water with high temperature and high pressure flows out of the crystallizer 4 after penetrating through a filter cake, so that the separation of two phases of the brine is realized. After the flow resistance of the system rises, the feeding is switched from the sodium chloride solution to the deionized water, and simultaneously, a high-pressure valve on a communicating pipeline at the lower part of the crystallizer 4 is cut off. The slurry in the salt storage tank 6 is cooled to 120 ℃, then a pressure reducing pipeline valve is opened to flash evaporate the sodium chloride slurry in the salt storage tank, and finally a sodium chloride crystal product is obtained in a flash evaporator 12. The desalted water discharged from the crystallizer 4 is cooled and decompressed to obtain desalted water product. The subsequent introduction of deionized water will re-dissolve the salt crystal particles deposited in the system, and after the cleaning operation of the system is completed, the next operation cycle can be entered.
Example 2
The method comprises the steps of firstly increasing the pressure of a 120g/L sodium sulfate solution prepared in a laboratory to 21MPa by a triple plunger pump, then increasing the temperature to 250 ℃ by heat exchange with desalted water in a heat exchanger, further heating to 300 ℃ by an electric heater, and finally rapidly mixing with 400 ℃ superheated steam in a water-steam mixer 2 and then spraying into a crystallizer 4 for impact crystallization. The temperature and the pressure of the high-salinity wastewater in the crystallizer 4 are controlled to be 320 +/-20 ℃ and 20MPa, crystals aggregate and grow in the crystallizer 4 along with the flow of the water phase, wherein large-particle crystals are settled to the bottom of the reactor through gravity and flow into the salt storage pool 6 at the lowest end through the communicating pipeline at the lower part, part of small-particle crystals are carried by the water phase and enter the subsequent hydrocyclone 7, and the salt content of desalted water can be controlled to be below 150mg/L after the crystals are further separated by the hydrocyclone 7. And (4) exchanging heat between the desalted water and the high-salinity wastewater raw material in a heat exchanger 9, and then decompressing through a back pressure valve to obtain final product water. After the experiment is finished, the system is cooled and depressurized, and the crystallizer 4 and the underflow tank 8 at the lower part of the hydrocyclone 7 are opened to remove salt crystals in the system.
Example 3
A large amount of potassium chloride washing wastewater is generated in the production process of the super activated carbon, the content of organic matters such as tar and the like in the wastewater is very low, the mass fraction of potassium chloride is 8-10%, and the content of other inorganic salts can be ignored. After the wastewater is pretreated by an advanced oxidation method to remove organic matters, the concentration of potassium chloride in the solution is about 100 g/L. The saline solution is pressurized by a high-pressure pump, then is further heated to 250 ℃, and then is rapidly mixed with high-pressure steam at 400 ℃, the temperature of the mixed fluid is controlled to be in a subcritical state at 300 +/-10 ℃, potassium chloride crystals are rapidly crystallized and settled from subcritical water and finally gather at the bottom of a crystallizer 4, and a high-pressure valve at the bottom of the crystallizer 4 is intermittently opened to discharge concentrated potassium chloride slurry into a salt storage tank 6 through a bottom flow pipe. After the communicating valve is closed, the high-temperature and high-pressure potassium chloride slurry is cooled and then subjected to decompression flash evaporation, and finally a potassium chloride crystal product is obtained in the flash evaporator 12. The desalted water discharged from the crystallizer 4 enters a raw material brine preheater to heat the feed brine, and then is returned to the super activated carbon production section for recycling after pressure relief. The method realizes the recycling of potassium chloride and water resources, and does not generate waste water and waste solids.
Example 4
The 50g/L sodium chloride and sodium sulfate solution from the production site is concentrated to 120g/L by reverse osmosis, then the pressure is increased to 25MPa, and then the solution is preheated to 270 ℃ by desalted water. The high-temperature and high-pressure salt solution is quickly mixed with the superheated steam with the temperature of 380-420 ℃ according to the mass ratio of 3:1 and then is sprayed into the crystallizer 4. The mixture of sodium chloride and sodium sulphate in the crystalliser 4 undergoes shock crystallisation in the crystalliser 4 to form a two phase mixture of crystal particles and desalinated water. The two-phase mixture flows into a downstream hydrocyclone 7, inorganic salt crystals in the two-phase mixture are enriched in underflow and finally flow to an underflow tank 8 through a communicating pipeline at the lower part of the hydrocyclone 7; while the desalted water phase leaves from the top of the hydrocyclone 7. The high-temperature high-pressure water phase is subjected to heat exchange and pressure reduction to obtain final product water. After the experiment is finished, a high-pressure valve on a communicating pipeline at the lower part of the hydrocyclone 7 is closed, the inorganic salt slurry in the underflow tank 8 is led into a flash evaporator 12 for flash evaporation, and the obtained inorganic salt crystals are the salt product of the high-salinity wastewater.
Claims (10)
1. A critical desalting method of high-salinity wastewater is characterized by comprising the following steps,
step 1, boosting the high-salinity wastewater to a critical pressure range, and then heating the obtained high-salinity wastewater to enable the obtained temperature to be in a critical temperature region;
step 2, inorganic salt in the high-salinity wastewater obtained in the step 1 reaches supersaturated concentration, so that salt crystal particles are separated out, and salt slurry and desalted water are obtained;
and 3, separating the salt crystal particles in the salt slurry from the water phase to obtain an inorganic salt product and steam.
2. The method for critically desalting high-salinity wastewater according to claim 1, wherein the high-salinity wastewater in step 1 is pretreated high-salinity wastewater, and the specific pretreatment comprises one or more of softening, COD removal, filtration, denitrification, ion exchange, advanced oxidation, ultrafiltration, nanofiltration and reverse osmosis.
3. The critical desalination method of high salinity wastewater according to claim 2, characterized in that the COD of the pretreated high salinity wastewater is lower than 500mg/L and the salt concentration is 50-150 g/L.
4. The method for critically desalting high salinity wastewater according to claim 1, wherein in step 1, the critical pressure of the high salinity wastewater is in the range of 10-25 MPa.
5. The method for critical desalination of high salinity wastewater as defined in claim 1, wherein in step 1, the critical temperature region is 250-450 ℃.
6. The method for critically desalting high salinity wastewater according to claim 1, wherein in step 1, the obtained high salinity wastewater is heated by heating, heat exchange, mixing with high temperature water, direct heating or mixing with high enthalpy steam.
7. The critical desalination method of high salinity wastewater according to claim 1, characterized in that, in step 2, the time for the high salinity wastewater to precipitate salt crystal particles is within 10 min.
8. The critical desalination method of high salinity wastewater according to claim 1, characterized in that the desalted water obtained in step 2 is subjected to heat exchange and pressure relief to obtain desalted water product.
9. The critical desalination method of high salinity wastewater according to claim 1, characterized in that the salt slurry in step 3 is subjected to hydrocyclone separation, gravity settling, bed filtration, flash evaporation or spraying to obtain inorganic salt product and steam.
10. A critical desalination system for high-salinity wastewater is characterized by comprising a high-pressure pump (1), a water-steam mixer (2), a crystallizer (4), a salt storage tank (6), a hydrocyclone (7), an underflow tank (8), a flash evaporator (12) and a heating device;
the input end of the high-pressure pump (1) is connected with an output port of high-salinity wastewater, the output end of the high-pressure pump (1) is communicated with an inlet of a heating device, and an outlet of the heating device is communicated with an inlet of a water-steam mixer (2);
the crystallizer (4) is arranged below the water-steam mixer (2) along the vertical direction, an inlet of the crystallizer (4) is positioned on the upper surface of the crystallizer (4), an inlet of the crystallizer (4) is communicated with an outlet of the water-steam mixer (2), a salt storage tank (6) is connected below an outlet of the crystallizer (4), and an opening is formed in one side of the crystallizer (4);
a hydrocyclone (7) is arranged on one side of the crystallizer (4) provided with an opening, one side of the hydrocyclone (7) is communicated with the opening of the crystallizer (4), a bottom flow tank (8) is connected below the hydrocyclone (7), and the top of the hydrocyclone (7) is provided with an opening;
the salt storage tank (6) and the underflow tank (8) are both connected with a flash evaporator (12).
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