A treatment system and treatment process for high salinity wastewater

Abstract

The application provides a treatment system and treatment process for high-salt wastewater, which can efficiently separate salt and overcome the problem of unstable system operation caused by salt crystallization blockage in the prior art. The first evaporation tank is communicated with the second evaporation tank through a first impurity removal separator. The first evaporation tank and the second evaporation tank are respectively communicated with a raw water relay drum. A second evaporation heat exchanger is arranged in the second evaporation tank. The first evaporation tank is connected with the first evaporation heat exchanger. A circulating pump is arranged on a connecting pipe between the first evaporation tank and the first evaporation heat exchanger. A second impurity removal separator is arranged at a steam exhaust port of the second evaporation tank. The exhaust end of the second impurity removal separator is further connected to a third heat exchanger of a heat pump unit. The third heat exchanger is connected to a drain tank. The steam condensate water drain port of the second evaporation tank is connected to a distilled water transfer box. The distilled water transfer box is connected to the drain tank and the third heat exchanger, respectively. The distilled water transfer box is used for gas-liquid separation of steam condensate water.

Description

Technical Field

[0001] This invention relates to the field of high-concentration saline wastewater treatment technology, and in particular to a treatment system and process for high-salinity wastewater. Background Technology

[0002] In the field of waste liquid treatment technology, vacuum evaporators are widely used for the concentration treatment of high-concentration brine because they can lower the boiling point of liquids and achieve low-temperature evaporation under low-pressure conditions.

[0003] Chinese invention patent CN118420027A discloses a high-efficiency heat exchange vacuum evaporator for high-concentration brine. Although a separator is installed between the first and second evaporators to remove salt from the steam, the steam from the second evaporator is directly input into the refrigerant heat exchanger. This causes trace amounts of salt carried in the steam to enter the refrigerant heat exchanger, crystallizing on the surface of the heat exchange tubes. Over time, this leads to a decrease in the heat exchanger's efficiency. Furthermore, the separator is prone to blockage by salt or impurities after long-term operation, resulting in reduced steam flow efficiency and affecting system stability. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a treatment system and process for high-salinity wastewater, which can efficiently separate salts and overcome the problem of unstable system operation caused by salt crystallization and blockage in the prior art.

[0005] The technical solution is as follows: a treatment system for high-salinity wastewater, comprising: A first evaporator and a second evaporator are connected by a first impurity removal separator. Both the first evaporator and the second evaporator are connected to a negative pressure assembly. The first evaporator and the second evaporator are respectively connected to a raw water relay tank. A second evaporation heat exchanger is installed inside the second evaporator. The first evaporator is connected to the first evaporation heat exchanger. A circulation pump is installed on the connecting pipe between the first evaporator and the first evaporation heat exchanger. The first evaporative heat exchanger is also connected to the third heat exchanger, the compressor, and the electronic expansion valve to form a heat pump unit. The third heat exchanger is connected to a drain tank to discharge cooled distilled water. The first evaporator is connected to a crystallization and salt separation unit, which includes a hydrocyclone separator connected to the first evaporator. The hydrocyclone separator is connected to a negative pressure pump, which is connected to the concentrate in the first evaporator. The crystallized salt separated by the hydrocyclone separator is discharged from the crystallization salt outlet, and the separated liquid is returned to the first evaporator. Its features are: The second evaporator is equipped with a second impurity separator at its steam exhaust port. The exhaust end of the second impurity separator is also connected to a third heat exchanger of the heat pump unit. The third heat exchanger is connected to a drain tank. The steam condensate drain port of the second evaporator is connected to a distilled water transfer tank. The distilled water transfer tank is connected to both the drain tank and the third heat exchanger. The distilled water transfer tank is used for gas-liquid separation of steam condensate.

[0006] Furthermore, the negative pressure pump is also connected to the second evaporator, and the negative pressure pump is connected to the centrifuge after being connected to the concentrate control valve, for discharging the concentrate discharged from the second evaporator to the centrifuge for salt separation; Furthermore, the negative pressure pump is also connected to the circulation pump, the mechanical seal cooling pump, and the mechanical seal cooling water tank to form a mechanical seal cooling unit, and the mechanical seal cooling water tank is connected to the drain tank.

[0007] Furthermore, the raw water relay tank is connected to a raw water relay tank heat exchanger for waste heat recovery.

[0008] Furthermore, the raw water relay tank is connected to a chiller, and the chiller is connected to circulating cooling water.

[0009] Furthermore, the distilled water transfer tank and the compressor are respectively connected to a control valve and then to a fourth heat exchanger. The fourth heat exchanger is connected to a drain tank, which is equipped with a negative pressure centrifugal pump and a pneumatic ball valve for discharging distilled water.

[0010] Furthermore, it also includes a cleaning unit for a purification separator, which includes a distilled water tank. The drain tank is connected to the distilled water tank, and an ejector is provided between the drain tank and the distilled water tank. The distilled water tank is connected to a vacuum pump and a cooler. The vacuum pump is also connected to the first purification separator and the second purification separator through a pipeline. The vacuum pump can draw water from the drain tank into the distilled water tank and introduce the water into the first purification separator and the second purification separator for cleaning.

[0011] Furthermore, the first evaporator and the second evaporator are respectively connected to a vacuum valve, the first evaporator and the second evaporator are respectively provided with a defoamer inlet, and the first evaporator and the second evaporator are connected to a cleaning water pipe.

[0012] Furthermore, the heat pump unit also includes a drying filter, a solenoid valve, and an electronic expansion valve connected between the first evaporative heat exchanger and the third heat exchanger. A hot gas bypass pipeline is also provided between the first evaporative heat exchanger and the third heat exchanger, and a solenoid valve is provided on the hot gas bypass pipeline.

[0013] A process for treating saline wastewater, characterized by comprising the following steps; Step S1: Input the feed liquid into the raw water relay tank and start the negative pressure component to make the pressure in the first evaporator and the second evaporator negative. Step S2: The raw water relay tank feeds the liquid into the first evaporator and the second evaporator through pipelines. The liquid in the first evaporator circulates between the first evaporator heat exchanger and the first evaporator through a circulation pump. The liquid in the second evaporator enters the second evaporator heat exchanger. Step S3: The compressor of the heat pump unit operates, and the hot refrigerant enters the first evaporator heat exchanger to exchange heat with the liquid in the first evaporator heat exchanger, generating steam and concentrate. The hot refrigerant undergoes a phase change and becomes liquid refrigerant, which then enters the third heat exchanger. Step S4: When the concentrate in the first evaporator reaches the standard, it is output to the hydrocyclone separator through a negative pressure pump for salt separation. The separated crystalline salt is discharged from the crystalline salt outlet, and the separated liquid is sent back to the first evaporator. Step S5: The raw water relay tank replenishes liquid to the first evaporator through pipeline for evaporation; Step S6: The steam generated in the first evaporator is fed into the first impurity removal separator for impurity removal. The steam output from the first impurity removal separator enters the second evaporator and exchanges heat with the liquid in the second evaporation heat exchanger for evaporation. Step S7: The steam generated in the second evaporator enters the second impurity removal separator for impurity removal. The steam output from the second impurity removal separator enters the third heat exchanger. The cooling water after the steam is cooled is discharged into the drain tank. The steam condensate generated in the second evaporator enters the distilled water transfer tank. The steam condensate undergoes gas-liquid separation in the distilled water transfer tank and the condensate is discharged into the drain tank. The steam enters the third heat exchanger for heat exchange and is then discharged into the drain tank. Step S8: The concentrated liquid after evaporation in the second evaporator is sent to a centrifuge for salt separation via a negative pressure pump; Step S9: The vacuum pump draws water from the drain tank into the distilled water tank and introduces the water into the first and second impurity separators to clean them. Step S10: When the compressor outlet pressure reaches the set threshold, open the control valve in front of the fourth heat exchanger to assist in heat exchange through the fourth heat exchanger. When the compressor outlet pressure drops to the set threshold, close the control valve in front of the fourth heat exchanger.

[0014] The present invention provides a high-salinity wastewater treatment system. A second impurity separator is installed at the steam exhaust port of the second evaporator to further purify the steam, removing any impurities that may be entrained, including solid particles, droplets, and mist. The separated steam then enters the third heat exchanger of the heat pump unit. Simultaneously, the condensate from the steam generated in the second evaporator is discharged into a distillation water transfer tank for gas-liquid separation, and the cooling water is directly discharged into a drain tank. The steam is cooled in the third heat exchanger and then discharged into the drain tank, thus fully recovering the distilled water. The impurity separator cleaning unit of the present invention uses a vacuum pump to draw water from the drain tank to a distillation water tank, and then introduces the water into the first and second impurity separators respectively, achieving cleaning of both separators. This solves the problems of inconvenient maintenance and easy residue of impurities in existing impurity separators, ensuring the separation effect and service life of the separators, reducing equipment maintenance costs and downtime, and improving system operational stability. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the left half of a treatment system for high-salinity wastewater in practice. Figure 2 This is a schematic diagram of the right half of a treatment system for high-salinity wastewater in practice. Figure 3 This is a schematic diagram of a cleaning unit for a high-salinity wastewater treatment system in practice. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] See Figure 1 , Figure 2 , Figure 3 The present invention provides a treatment system for high-salinity wastewater, comprising: First evaporator 1 and second evaporator 2 are connected by a first impurity removal separator 3. Both first evaporator 1 and second evaporator 2 are connected to a negative pressure assembly. First evaporator 1 and second evaporator 2 are respectively connected to a raw water relay tank 4. A second evaporation heat exchanger 5 is installed inside the second evaporator 2. First evaporator 1 is connected to a first evaporation heat exchanger 6. A circulation pump 7 is installed on the connecting pipe between first evaporator 1 and first evaporation heat exchanger 6. The first evaporative heat exchanger 6 is also connected to the third heat exchanger 8, the compressor 9, and the electronic expansion valve 10 to form a heat pump unit. The third heat exchanger 8 is connected to the drain tank 11 to discharge the cooled distilled water. The first evaporator 1 is connected to a crystallization and salt separation unit, which includes a hydrocyclone separator 12 and a first impurity removal separator 3 connected to the first evaporator. The first impurity removal separator 3 includes, but is not limited to, a cyclone separator, a spiral separator, a separator with a wire mesh demister, a separator with a filter element, etc. The hydrocyclone separator 12 is connected to a negative pressure pump 13, which is connected to the concentrate in the first evaporator 1. The crystallized salt separated by the hydrocyclone separator 12 is discharged from the crystallization salt outlet 14, and the separated liquid is returned to the first evaporator 1. The steam exhaust port of the second evaporator 1 is equipped with a second impurity removal separator 15. The second impurity removal separator 15 includes, but is not limited to, a cyclone separator, a spiral separator, a separator with a wire mesh demister, a separator with a filter element, etc. The exhaust end of the second impurity removal separator 15 is also connected to the third heat exchanger 8 of the heat pump unit. Connecting the exhaust end of the second impurity removal separator to the third heat exchanger of the heat pump unit allows the heat carried by the steam to fully participate in the heat cycle of the system, realizing the efficient recovery and utilization of steam heat, and improving the energy utilization efficiency of the system. The steam condensate drain of the second evaporator 2 is connected to the distillation water transfer tank 16. The distillation water transfer tank 16 is connected to the drain tank 11 and the third heat exchanger 8. The distillation water transfer tank 16 is used for gas-liquid separation of steam condensate. The distillation water transfer tank 16 allows the liquid steam condensate to be pre-treated. The separated steam enters the third heat exchanger 8 for heat exchange, and the condensate is discharged into the drain tank 11, saving energy.

[0018] In one embodiment, a fourth heat exchanger 17 is also provided. The compressor and the distilled water transfer tank 16 are connected to the fourth heat exchanger 17, which is connected to the drain tank 11. In this embodiment, the fourth heat exchanger 17 is an auxiliary heat exchanger. The function of the fourth heat exchanger 17 is to offset the entropy increase of the system, that is, the entropy increase generated by the compressor doing work. The opening and closing conditions of the valve in front of the fourth heat exchanger 17 are as follows: when the outlet pressure of the compressor 9 reaches a set threshold, the control valve in front of the fourth heat exchanger 17 is opened; when the outlet pressure of the compressor drops to the set threshold, the control valve in front of the fourth heat exchanger 17 is closed. In this embodiment, the use frequency of the fourth heat exchanger 17 can be reduced by setting the distilled water transfer tank 16.

[0019] In this embodiment, a second impurity separator is installed at the steam exhaust port of the second evaporator to perform secondary impurity removal on the steam. Compared with the current situation of insufficient steam impurity removal in the prior art, the purity of the steam is improved, which can reduce the damage of impurities to the subsequent third heat exchanger, extend the service life of the equipment, and improve the quality of distilled water.

[0020] In one embodiment of the present invention, the negative pressure pump 13 is also connected to the second evaporator 2. The negative pressure pump 13 is connected to the concentrate control valve 18 and then to a centrifuge to discharge the concentrate from the second evaporator 2 to the centrifuge for salt separation. The negative pressure pump 13 is also connected to the circulating pump 7, the mechanical seal cooling pump 19, and the mechanical seal cooling water tank 20 to form a mechanical seal cooling unit. The mechanical seal cooling water tank is connected to the drain tank 11. The mechanical seal cooling unit uses the circulating pump to transport cooling water from the mechanical seal cooling water tank to the mechanical seal part of the pump body, removing heat and maintaining a low-temperature environment for the mechanical seal. This prevents excessively high temperatures and ensures long-term stable operation of the equipment. The distilled water in the drain tank can be used as a supplementary source of mechanical seal cooling water, forming a closed loop, reducing the amount of new water replenishment, and improving water resource utilization.

[0021] In one embodiment of the present invention, the raw water relay tank 4 is connected to the raw water relay tank heat exchanger 21, and a negative pressure pump is provided between the raw water relay tank 4 and the raw water relay tank heat exchanger 21 for waste heat recovery. The raw water relay tank heat exchanger 21 is provided in this embodiment to recover and utilize waste heat, which can further improve the heat utilization rate and reduce energy consumption.

[0022] In this embodiment, the raw water relay tank 21 is connected to a chiller 22, and the chiller 22 is connected to circulating cooling water.

[0023] In this embodiment, the drain tank is connected to a negative pressure centrifugal pump 23 and a pneumatic ball valve 24 for discharging distilled water.

[0024] In one embodiment of the present invention, a cleaning unit for a purification separator is also included. The cleaning unit includes a distilled water tank 25, a drain tank 11 connected to the distilled water tank 25, and an ejector 34 disposed between the drain tank 11 and the distilled water tank 25. The distilled water tank 25 is connected to a vacuum pump 26 and a cooler 27. The vacuum pump 26 is also connected to a first purification separator 3 and a second purification separator 15 through a pipeline. The vacuum pump 26 can draw water from the drain tank into the distilled water tank and introduce the water into the first purification separator 3 and the second purification separator 15 for cleaning. The first purification separator 3 and the second purification separator 15 are cleaned by the water drawn from the drain tank by the vacuum pump, forming a water flow to clean the first purification separator 3 and the second purification separator 15 in reverse, thoroughly removing the attached salt, maintaining steam flow efficiency, and maintaining equipment stability. This can solve the problem of dirt adhering to the purification separator and affecting the separation effect in the prior art after long-term use. The setup in this embodiment does not require manual disassembly of the equipment, is simple and efficient to operate, can reduce maintenance costs and downtime, and improve the stability and production efficiency of equipment operation.

[0025] In this embodiment, the first evaporator 1 and the second evaporator 2 are respectively connected to a vacuum valve 28, the first evaporator 1 and the second evaporator 2 are respectively provided with a defoamer inlet 29, and the first evaporator 1 and the second evaporator 2 are connected to a cleaning water pipe 30. The setting of the impurity separator cleaning unit and the cleaning water pipe facilitates the maintenance and cleaning of the equipment and helps to extend the service life of the equipment.

[0026] In this embodiment, the heat pump unit also includes a drying filter 31, a solenoid valve 32 and an electronic expansion valve 10 connected between the first evaporator heat exchanger 6 and the third heat exchanger 8. A hot gas bypass pipeline is also provided between the first evaporator heat exchanger 6 and the third heat exchanger 8, and a solenoid valve 33 is provided on the hot gas bypass pipeline.

[0027] In this embodiment, the specific installation positions of various control valves installed between some devices, such as the control valves on the liquid delivery pipe, defoamer pipe, and cleaning water pipe between the raw water relay tank and the first and second evaporators, can be referred to the schematic diagram in Figure 1 of the specification. This type of layout is a setting based on conventional process logic by those skilled in the art and will not be described one by one here. Regarding the selection of control valve types, common valve body structures such as ball valves, butterfly valves, and gate valves can be selected according to actual working conditions to achieve control over fluid flow, flow rate, or pressure. This selection method is also a conventional technical means in this field.

[0028] In an embodiment of the present invention, a treatment process for saline wastewater is also provided, comprising the following steps: Step S1: Input the feed liquid into the raw water relay tank and start the negative pressure component to make the pressure in the first evaporator and the second evaporator negative. Step S2: The raw water relay tank feeds the liquid into the first evaporator and the second evaporator through pipelines. The liquid in the first evaporator circulates between the first evaporator heat exchanger and the first evaporator through a circulation pump. The liquid in the second evaporator enters the second evaporator heat exchanger. Step S3: The compressor of the heat pump unit operates, and the hot refrigerant enters the first evaporator heat exchanger to exchange heat with the liquid in the first evaporator heat exchanger, generating steam and concentrate. The hot refrigerant undergoes a phase change and becomes liquid refrigerant, which then enters the third heat exchanger. Step S4: When the concentrate in the first evaporator reaches the standard, it is output to the hydrocyclone separator through a negative pressure pump for salt separation. The separated crystalline salt is discharged from the crystalline salt outlet, and the separated liquid is sent back to the first evaporator. Step S5: The raw water relay tank replenishes liquid to the first evaporator through pipeline for evaporation; Step S6: The steam generated in the first evaporator is fed into the first impurity removal separator for impurity removal. The steam output from the first impurity removal separator enters the second evaporator and exchanges heat with the liquid in the second evaporation heat exchanger for evaporation. Step S7: The steam generated in the second evaporator enters the second impurity removal separator for impurity removal. The steam output from the second impurity removal separator enters the third heat exchanger. The cooling water after the steam is cooled is discharged into the drain tank. The steam condensate generated in the second evaporator enters the distilled water transfer tank. The steam condensate undergoes gas-liquid separation in the distilled water transfer tank and the condensate is discharged into the drain tank. The steam enters the third heat exchanger for heat exchange and is then discharged into the drain tank. Step S8: The concentrated liquid after evaporation in the second evaporator is sent to a centrifuge for salt separation via a negative pressure pump; Step S9: The vacuum pump draws water from the drain tank into the distilled water tank and introduces the water into the first and second impurity separators to clean them. Step S10: When the compressor outlet pressure reaches the set threshold, open the control valve in front of the fourth heat exchanger to assist in heat exchange through the fourth heat exchanger. When the compressor outlet pressure drops to the set threshold, close the control valve in front of the fourth heat exchanger.

[0029] In this embodiment, after the concentrate is desalted, the mother liquor can be returned to the evaporation system for further processing, minimizing the final waste liquid discharge and reducing the risk of environmental pollution. The first and second impurity removal separators remove impurities from the steam generated by the first and second evaporators, respectively, preventing impurities from entering subsequent stages and ensuring stable equipment operation. A vacuum pump is used to extract water from the drain tank for automated cleaning of the first and second impurity removal separators, which can effectively extend the equipment life. At the same time, the condensate from the steam generated by the second evaporator enters the distilled water transfer tank for gas-liquid separation. After being cooled by the third heat exchanger, the steam is discharged into the drain tank along with other cooling water, which can be used as cleaning water for cleaning the impurity removal separators, realizing the recycling of water resources.

[0030] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A treatment system for high-salinity wastewater, comprising: A first evaporator and a second evaporator are connected by a first impurity removal separator. Both the first evaporator and the second evaporator are connected to a negative pressure assembly. The first evaporator and the second evaporator are respectively connected to a raw water relay tank. A second evaporation heat exchanger is installed inside the second evaporator. The first evaporator is connected to the first evaporation heat exchanger. A circulation pump is installed on the connecting pipe between the first evaporator and the first evaporation heat exchanger. The first evaporative heat exchanger is also connected to the third heat exchanger, the compressor, and the electronic expansion valve to form a heat pump unit. The third heat exchanger is connected to a drain tank to discharge cooled distilled water. The first evaporator is connected to a crystallization and salt separation unit, which includes a hydrocyclone separator connected to the first evaporator. The hydrocyclone separator is connected to a negative pressure pump, which is connected to the concentrate in the first evaporator. The crystallized salt separated by the hydrocyclone separator is discharged from the crystallization salt outlet, and the separated liquid is returned to the first evaporator. Its features are: The second evaporator is equipped with a second impurity separator at its steam exhaust port. The exhaust end of the second impurity separator is also connected to a third heat exchanger of the heat pump unit. The third heat exchanger is connected to a drain tank. The steam condensate drain port of the second evaporator is connected to a distilled water transfer tank. The distilled water transfer tank is connected to both the drain tank and the third heat exchanger. The distilled water transfer tank is used for gas-liquid separation of steam condensate. The negative pressure pump is also connected to the second evaporator. The negative pressure pump is connected to the concentrate control valve and then to the centrifuge, which is used to discharge the concentrate discharged from the second evaporator to the centrifuge for salt separation. The distilled water transfer tank and the compressor are respectively connected to a control valve and then to a fourth heat exchanger. The fourth heat exchanger is connected to a drain tank, which is equipped with a negative pressure centrifugal pump and a pneumatic ball valve for discharging distilled water. It also includes a cleaning unit for a purification separator, which includes a distilled water tank. The drain tank is connected to the distilled water tank, and an ejector is provided between the drain tank and the distilled water tank. The distilled water tank is connected to a vacuum pump and a cooler. The vacuum pump is also connected to the first purification separator and the second purification separator through a pipeline. The vacuum pump can draw water from the drain tank into the distilled water tank and introduce the water into the first purification separator and the second purification separator for cleaning.

2. The treatment system for high-salinity wastewater according to claim 1, characterized in that: The negative pressure pump is also connected to the circulation pump, the mechanical seal cooling pump, and the mechanical seal cooling water tank to form a mechanical seal cooling unit, and the mechanical seal cooling water tank is connected to the drain tank.

3. The treatment system for high-salinity wastewater according to claim 1, characterized in that: The raw water relay tank is connected to a raw water relay tank heat exchanger for waste heat recovery.

4. The treatment system for high-salinity wastewater according to claim 1, characterized in that: The raw water relay tank is connected to a chiller, and the chiller is connected to circulating cooling water.

5. The treatment system for high-salinity wastewater according to claim 1, characterized in that: The first evaporator and the second evaporator are respectively connected to a vacuum valve, and the first evaporator and the second evaporator are respectively provided with a defoamer inlet. The first evaporator and the second evaporator are connected to a cleaning water pipe.

6. The treatment system for high-salinity wastewater according to claim 1, characterized in that: The heat pump unit also includes a drying filter, a solenoid valve, and an electronic expansion valve connected between the first evaporator heat exchanger and the third heat exchanger. A hot gas bypass pipeline is also provided between the first evaporator heat exchanger and the third heat exchanger, and a solenoid valve is provided on the hot gas bypass pipeline.

7. A treatment process for saline wastewater, characterized in that, The system for treating high-salinity wastewater according to any one of claims 1 to 6 comprises the following steps: Step S1: Input the feed liquid into the raw water relay tank and start the negative pressure component to make the pressure in the first evaporator and the second evaporator negative. Step S2: The raw water relay tank feeds the liquid into the first evaporator and the second evaporator through pipelines. The liquid in the first evaporator circulates between the first evaporator heat exchanger and the first evaporator through a circulation pump. The liquid in the second evaporator enters the second evaporator heat exchanger. Step S3: The compressor of the heat pump unit operates, and the hot refrigerant enters the first evaporator heat exchanger to exchange heat with the liquid in the first evaporator heat exchanger, generating steam and concentrate. The hot refrigerant undergoes a phase change and becomes liquid refrigerant, which then enters the third heat exchanger. Step S4: When the concentrate in the first evaporator reaches the standard, it is output to the hydrocyclone separator through a negative pressure pump for salt separation. The separated crystalline salt is discharged from the crystalline salt outlet, and the separated liquid is sent back to the first evaporator. Step S5: The raw water relay tank replenishes liquid to the first evaporator through pipeline for evaporation; Step S6: The steam generated in the first evaporator is fed into the first impurity removal separator for impurity removal. The steam output from the first impurity removal separator enters the second evaporator and exchanges heat with the liquid in the second evaporation heat exchanger for evaporation. Step S7: The steam generated in the second evaporator enters the second impurity removal separator for impurity removal. The steam output from the second impurity removal separator enters the third heat exchanger. The cooling water after the steam is cooled is discharged into the drain tank. The steam condensate generated in the second evaporator enters the distilled water transfer tank. The steam condensate undergoes gas-liquid separation in the distilled water transfer tank and the condensate is discharged into the drain tank. The steam enters the third heat exchanger for heat exchange and is then discharged into the drain tank. Step S8: The concentrated liquid after evaporation in the second evaporator is sent to a centrifuge for salt separation via a negative pressure pump; Step S9: The vacuum pump draws water from the drain tank into the distilled water tank and introduces the water into the first and second impurity removal separators to clean them. Step S10: When the compressor outlet pressure reaches the set threshold, open the control valve in front of the fourth heat exchanger to assist in heat exchange through the fourth heat exchanger. When the compressor outlet pressure drops to the set threshold, close the control valve in front of the fourth heat exchanger.

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