Salt separation and purification device for high-salinity wastewater

Abstract

The utility model relates to the technical field of wastewater resourceful treatment, in particular to a salt separation and purification device for high-salt wastewater, which is characterized in that at least two groups of reverse osmosis units, evaporation units and crystallization units which are sequentially connected are connected in parallel, each evaporation unit comprises a high-temperature heating part and a steam heat transfer part for recovering heat energy of the high-temperature heating part, the steam heat transfer part comprises a steam heat transfer cavity communicated with the high-temperature heating part and a heat transfer pipe which is arranged in the steam heat transfer cavity, the liquid inlet end of the heat transfer pipe is connected with the reverse osmosis unit, the liquid outlet end of the heat transfer pipe is connected with the high-temperature heating part, and the steam heat transfer cavity is used for heating the outside of the heat transfer pipe to transfer heat to liquid in the heat transfer pipe. The steam heat transfer part provided by the utility model can be used for recovering high-temperature steam in the high-temperature heating part and preheating high-salinity wastewater, so that not only is the heat recycled, but also the evaporation time of the high-salinity wastewater in the high-temperature heating part is saved, and the energy utilization rate and the evaporation efficiency are improved.

Description

Technical Field

[0001] This utility model relates to the field of wastewater resource treatment technology, and in particular to a salt separation and purification device for high-salt wastewater. Background Technology

[0002] High-salinity wastewater refers to wastewater containing high concentrations of salt (mainly sodium chloride and sodium sulfate) and other impurities. Direct discharge of this type of wastewater will cause serious environmental pollution and waste resources.

[0003] In existing technologies, evaporation crystallization is mainly used to recover salt from high-salinity wastewater. Evaporation crystallization evaporates and recovers water from the wastewater, achieving water resource recycling, which is particularly important for water-scarce regions. Simultaneously, sodium chloride, sodium sulfate, and other valuable minerals can be recovered from high-salinity wastewater for industrial or other commercial uses. However, the evaporation crystallization process requires a large amount of heat energy, usually derived from steam or electricity, resulting in high energy consumption. High energy consumption directly leads to increased operating costs, especially in regions with high energy prices. Patent CN208087250 U provides a device for low-temperature evaporation and concentration of high-salinity wastewater using high-temperature industrial wastewater. This device lowers the boiling point of the high-salinity wastewater by creating a negative pressure in the evaporator, thereby reducing the energy consumption required for evaporation crystallization. However, because a negative pressure evaporation environment is required, this device has high requirements for the sealing of the evaporator, making it suitable for batch treatment of certain volumes of high-salinity wastewater, but not for continuous treatment of large volumes of high-salinity wastewater. Utility Model Content

[0004] This invention provides a salt separation and purification device for high-salinity wastewater, which aims to solve one or more of the above-mentioned problems and other potential problems.

[0005] This utility model provides a salt separation and purification device for high-salt wastewater, comprising a sedimentation unit, a nanofiltration unit, a reverse osmosis unit, an evaporation unit, and a crystallization unit connected in sequence via pipelines. The device is characterized by having at least two sets of reverse osmosis units, evaporation units, and crystallization units connected in parallel. The evaporation unit includes a high-temperature heating section and a steam heat transfer section for recovering heat energy from the high-temperature heating section. The steam heat transfer section includes a steam heat transfer chamber communicating with the high-temperature heating section and a heat transfer tube disposed within the steam heat transfer chamber, with its inlet end connected to the reverse osmosis unit and its outlet end connected to the high-temperature heating section. The steam heat transfer chamber transfers heat to the liquid inside the heat transfer tube by heating the outside of the heat transfer tube.

[0006] In this embodiment, the high-salt wastewater is treated by a sedimentation unit and a nanofiltration unit to obtain one high-salt wastewater mainly containing sodium chloride and another high-salt wastewater mainly containing sodium sulfate. The two high-salt wastewaters are respectively filtered and evaporated and crystallized by two sets of parallel reverse osmosis units, evaporation units and crystallization units to obtain sodium chloride crystals and sodium sulfate crystals.

[0007] In this embodiment, the high-salt wastewater flows into the heat transfer tube from the inlet end of the heat transfer tube via the reverse osmosis unit. After passing through the steam heat transfer chamber inside the heat transfer tube, it enters the high-temperature heating section for heating and evaporation. The high-temperature steam generated by the high-salt wastewater during heating and evaporation enters the steam heat transfer chamber and comes into contact with the outside of the heat transfer tube, transferring the heat energy of the high-temperature steam to the high-salt wastewater inside the heat transfer tube to preheat the high-salt wastewater. This achieves energy recycling, improves energy utilization efficiency, and reduces total energy consumption.

[0008] In some embodiments, the crystallization unit includes a low-temperature crystallization section connected to a high-temperature heating section and a low-temperature condensation section connected to a steam heat transfer section and used to cool the low-temperature crystallization section.

[0009] In this embodiment, most of the water in the high-salt wastewater is evaporated in the high-temperature heating section to obtain concentrated high-salt wastewater with a concentration close to saturation. The concentrated high-salt wastewater is then passed into the low-temperature crystallization section for cooling. Since the concentrated high-salt wastewater is close to saturation, a large amount of salt crystals will precipitate out after cooling and settle to the bottom of the low-temperature crystallization section.

[0010] In some embodiments, the high-temperature heating section includes a high-temperature evaporation chamber connected to the liquid outlet end of a heat transfer tube, and a high-temperature heater for heating the high-temperature evaporation chamber so that the liquid inside the high-temperature evaporation chamber is above the evaporation temperature.

[0011] In this embodiment, the high-temperature evaporation chamber is heated by a high-temperature heater, so that the high-salt wastewater flowing into the high-temperature evaporation chamber through the liquid outlet of the heat transfer tube can be heated rapidly, evaporate most of the water vapor, and gradually increase the concentration of the high-salt wastewater.

[0012] In some embodiments, the high-temperature evaporation chamber is provided with a high-temperature steam recovery pipe that communicates with the steam heat transfer chamber to recover heat energy and a concentrated liquid outlet pipe that communicates with the low-temperature crystallization section.

[0013] In this embodiment, a high-temperature steam recovery pipe is provided in the high-temperature evaporation chamber to transfer the high-temperature steam generated by the evaporation of high-salt wastewater to the evaporation heat transfer chamber. The high-temperature steam exchanges heat with the low-temperature high-salt wastewater inside the heat transfer pipe in the steam heat transfer chamber, thereby preheating the high-salt wastewater. This allows the high-salt wastewater to quickly reach the evaporation temperature after flowing out of the heat transfer pipe and into the high-temperature heating chamber, shortening the evaporation time and accelerating the evaporation rate.

[0014] In some embodiments, the low-temperature condensing section includes a hollow low-temperature condensing cavity, a low-temperature water vapor recovery pipe for connecting the low-temperature condensing cavity and the steam heat transfer cavity, and a condensate outlet disposed on the low-temperature condensing cavity.

[0015] In this embodiment, after the high-temperature steam in the steam heat transfer chamber exchanges heat with the heat transfer tube, it will condense to obtain low-temperature water vapor. The low-temperature water vapor is introduced into the low-temperature condensation chamber through the low-temperature water vapor recovery pipe to cool down the low-temperature crystallization part. This allows the high-temperature concentrated high-salt wastewater in the low-temperature crystallization part, which has reached a saturation concentration, to exchange heat with the low-temperature water vapor in the low-temperature condensation chamber, causing the high-temperature concentrated high-salt wastewater to cool down rapidly. This reduces the solubility of the concentrated high-salt wastewater, causing a large amount of salt to precipitate and settle to the bottom of the low-temperature crystallization part.

[0016] In some embodiments, the low-temperature crystallization section includes a low-temperature crystallization inner cavity disposed within the low-temperature condensation chamber and communicating with a concentrated liquid outlet pipe, a condensate vapor recovery pipe for connecting the low-temperature crystallization inner cavity and the low-temperature condensation chamber, and a crystal outlet disposed on the low-temperature crystallization inner cavity.

[0017] In this embodiment, after the high-temperature concentrated high-salt wastewater flows into the low-temperature crystallization chamber, it rapidly cools down and precipitates a large amount of salt. The density of the wastewater decreases after the salt precipitation, thus forming a dynamic stratification with the newly flowing high-temperature concentrated wastewater and the precipitated crystallized salt. The upper layer is the low-temperature wastewater after salt precipitation, the middle layer is the newly flowing high-temperature concentrated wastewater, and the lower layer is the precipitated large amount of crystallized salt. When the liquid level in the low-temperature crystallization chamber reaches a certain height, the uppermost layer of low-temperature wastewater after salt precipitation is pumped through the condensate vapor recovery pipe into the low-temperature condensation chamber to cool the low-temperature crystallization chamber.

[0018] In some embodiments, the concentrated liquid outlet pipe is equipped with a hydraulic sensor for detecting the hydraulic pressure on the inlet side and a solenoid valve for controlling the liquid flow rate and velocity.

[0019] In this embodiment, during the evaporation and crystallization process, as water evaporates, the solution concentration increases and the density increases, which leads to changes in the hydraulic pressure in the system. In this embodiment, a hydraulic sensor is installed on the concentrated liquid outlet pipe to measure the hydraulic pressure on the inlet side. By monitoring the changes in hydraulic pressure, the change in solution concentration on the inlet side of the concentrated liquid outlet pipe can be indirectly detected. The flow rate and velocity of the liquid in the concentrated liquid outlet pipe are controlled by a solenoid valve, thereby controlling the concentration of the concentrated high-salt wastewater flowing into the low-temperature crystallization chamber from the concentrated liquid outlet pipe.

[0020] In some embodiments, the inlet end of the heat transfer tube is provided with a solenoid valve for controlling the liquid flow rate and velocity, and the outlet end of the heat transfer tube is provided with a plurality of spray outlets evenly distributed.

[0021] In this embodiment, the high-salt wastewater in the heat transfer tube is sprayed out through the spray outlet, which can increase the contact area between the high-salt wastewater and the steam in the high-temperature evaporation chamber or with the high-temperature heater, thereby increasing the heating speed.

[0022] In some embodiments, air pumps are provided on the high-temperature steam recovery pipe from the high-temperature evaporation chamber to the steam heat transfer chamber, on the low-temperature water vapor recovery pipe from the steam heat transfer chamber to the low-temperature condensation chamber, and on the condensation water vapor recovery pipe from the low-temperature crystallization chamber to the low-temperature condensation chamber.

[0023] In some embodiments, the low-temperature crystallization section further includes a stirrer disposed in the low-temperature crystallization cavity. The stirrer includes a stirring shaft, blades mounted on the stirring shaft and rotating around the stirring shaft, and scrapers connected to the blades and rubbing against the inner surface of the low-temperature crystallization cavity.

[0024] By implementing the above technical solution, this utility model has the following advantages:

[0025] 1. The steam heat transfer section provided by this utility model can recover the high-temperature steam in the high-temperature heating section and use it to preheat the high-salt wastewater. This not only realizes the recycling of heat, but also saves the evaporation time of the high-salt wastewater in the high-temperature heating section, thereby improving energy utilization and evaporation efficiency.

[0026] 2. The low-temperature condensation section provided by this utility model can use the low-temperature water vapor condensed after heat exchange in the steam heat transfer section to cool the low-temperature crystallization section without the need to add additional condensate for cooling, thus saving costs and realizing the reuse of low-temperature water vapor. Attached Figure Description

[0027] 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.

[0028] Figure 1 This is a flowchart illustrating the structure of each unit of this utility model;

[0029] Figure 2 This is a cross-sectional view of the evaporation unit and crystallization unit of this utility model.

[0030] The labels in the diagram represent: 1. High-temperature heating section, 11. High-temperature evaporation chamber, 12. High-temperature heater, 13. High-temperature steam recovery pipe, 14. Concentrated liquid outlet pipe, 2. Steam heat transfer section, 21. Steam heat transfer chamber, 22. Heat transfer pipe, 221. Spray outlet, 3. Low-temperature crystallization section, 31. Low-temperature crystallization inner cavity, 32. Condensate vapor recovery pipe, 33. Stirrer, 331. Stirring shaft, 332. Blade, 333. Scraper, 34. Crystal outlet, 4. Low-temperature condensation section, 41. Low-temperature condensation chamber, 42. Low-temperature water vapor recovery pipe, 43. Condensate outlet. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0032] It should be noted that the following embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it; those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

[0033] In the following description, terms such as “inner,” “outer,” “upper,” “lower,” “left,” and “right” are used only to facilitate the description of the embodiments and simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0034] like Figure 1 As shown, this embodiment provides a salt separation and purification device for high-salt wastewater, including a sedimentation unit, a nanofiltration unit, a reverse osmosis unit, an evaporation unit, and a crystallization unit connected in sequence through pipelines. Two sets of reverse osmosis units, evaporation units, and crystallization units are connected in parallel in sequence. The evaporation unit includes a high-temperature heating section 1 and a steam heat transfer section 2 for recovering the heat energy of the high-temperature heating section 1. The steam heat transfer section 2 includes a steam heat transfer chamber 21 communicating with the high-temperature heating section 1 and a heat transfer pipe 22 disposed in the steam heat transfer chamber 21 with its inlet end connected to the reverse osmosis unit and its outlet end connected to the high-temperature heating section 1. The steam heat transfer chamber 21 heats the liquid inside the heat transfer pipe 22 by heating the outside of the heat transfer pipe 22.

[0035] In this embodiment, the high-salt wastewater is treated by a sedimentation unit and a nanofiltration unit to obtain one high-salt wastewater mainly containing sodium chloride and another high-salt wastewater mainly containing sodium sulfate. The two high-salt wastewaters are respectively filtered and evaporated and crystallized by two sets of parallel reverse osmosis units, evaporation units and crystallization units to obtain sodium chloride crystals and sodium sulfate crystals.

[0036] like Figure 2 As shown in the embodiment, high-salt wastewater flows into heat transfer tube 22 from the inlet end of the reverse osmosis unit. After passing through the steam heat transfer chamber 21 inside the heat transfer tube 22, it enters the high-temperature heating section 1 for heating and evaporation. The high-temperature steam generated by the high-salt wastewater in the high-temperature heating section 1 enters the steam heat transfer chamber 21 through the high-temperature steam recovery pipe 13 and comes into contact with the outside of the heat transfer tube 22. The heat energy of the high-temperature steam is transferred to the high-salt wastewater inside the heat transfer tube 22 to preheat the high-salt wastewater. The steam condenses and falls off the outside of the heat transfer tube 22 to form condensate or low-temperature water vapor, realizing the recycling of energy and improving the energy utilization rate. This allows the high-salt wastewater to reach a certain temperature when it enters the high-temperature heating section 1, thereby shortening the heating time required for the high-salt wastewater in the high-temperature heating section 1 and further reducing the total energy consumption.

[0037] In some embodiments, the crystallization unit includes a low-temperature crystallization section 3 connected to a high-temperature heating section 1 and a low-temperature condensation section 4 connected to a steam heat transfer section 2 and used to cool the low-temperature crystallization section 3.

[0038] In this embodiment, condensate or low-temperature water vapor in the steam heat transfer section 2 is transferred to the low-temperature condensation section 4 via the low-temperature water vapor recovery pipe 42 to cool the high-temperature concentrated high-salt wastewater in the low-temperature crystallization section 3. Since most of the water in the high-temperature heating section 1 is evaporated, a concentrated high-salt wastewater with a near-saturated concentration is obtained. This concentrated high-salt wastewater is then passed into the low-temperature crystallization section 3 for cooling. Because the concentrated high-salt wastewater is close to its saturated concentration, a large amount of salt crystals will precipitate out after cooling and settle to the bottom of the low-temperature crystallization section 3.

[0039] In some embodiments, the high-temperature heating unit 1 includes a high-temperature evaporation chamber 11 connected to the liquid outlet end of the heat transfer tube 22, and a high-temperature heater 12 for heating the high-temperature evaporation chamber 11 so that the liquid in the high-temperature evaporation chamber 11 is higher than the evaporation temperature.

[0040] In this embodiment, the high-temperature evaporation chamber 11 is heated by the high-temperature heater 12, so that the high-salt wastewater flowing into the high-temperature evaporation chamber 11 through the liquid outlet of the heat transfer tube 22 can be heated rapidly, evaporate and remove most of the water vapor, and gradually increase the concentration of the high-salt wastewater.

[0041] In some embodiments, the high-temperature evaporation chamber 11 is provided with a high-temperature steam recovery pipe 13 that communicates with the steam heat transfer chamber 21 to recover heat energy and a concentrated liquid outlet pipe 14 that communicates with the low-temperature crystallization section 3.

[0042] In this embodiment, a high-temperature steam recovery pipe 13 is provided in the high-temperature evaporation chamber 11 to transfer the high-temperature steam generated by the evaporation of high-salt wastewater to the evaporation heat transfer chamber. The high-temperature steam exchanges heat with the low-temperature high-salt wastewater inside the heat transfer pipe 22 in the steam heat transfer chamber 21, thereby preheating the high-salt wastewater. This allows the high-salt wastewater to quickly reach the evaporation temperature after flowing out of the heat transfer pipe 22 and entering the high-temperature heating chamber, shortening the evaporation time and accelerating the evaporation rate.

[0043] In some embodiments, the low-temperature condensing section 4 includes a hollow low-temperature condensing cavity 41, a low-temperature water vapor recovery pipe 42 for connecting the low-temperature condensing cavity 41 with the steam heat transfer cavity 21, and a condensate outlet 43 disposed on the low-temperature condensing cavity 41.

[0044] In this embodiment, after the high-temperature steam in the steam heat transfer chamber 21 exchanges heat with the heat transfer tube 22, it will condense to obtain low-temperature water vapor. The low-temperature water vapor is introduced into the low-temperature condensation chamber 41 through the low-temperature water vapor recovery pipe 42 to cool down the low-temperature crystallization section 3. This allows the high-temperature concentrated high-salt wastewater in the low-temperature crystallization section 3, which has reached a saturated concentration, to exchange heat with the low-temperature water vapor or condensate in the low-temperature condensation chamber 41, thereby rapidly cooling down the high-temperature concentrated high-salt wastewater. This reduces the solubility of salt in the concentrated high-salt wastewater, causing a large amount of salt to precipitate and settle to the bottom of the low-temperature crystallization section 3.

[0045] In some embodiments, the low-temperature crystallization section 3 includes a low-temperature crystallization inner cavity 31 disposed in the low-temperature condensation cavity 41 and communicating with the concentrated liquid outlet pipe 14, a condensate vapor recovery pipe 32 for connecting the low-temperature crystallization inner cavity 31 and the low-temperature condensation cavity 41, and a crystal outlet 34 disposed on the low-temperature crystallization inner cavity 31.

[0046] In this embodiment, after the high-temperature concentrated high-salt wastewater flows into the low-temperature crystallization chamber 31, it rapidly cools down and precipitates a large amount of salt. The density of the wastewater decreases after the salt precipitation, thus forming a dynamic stratification with the newly flowing high-temperature concentrated wastewater and the precipitated crystallized salt. The upper layer is the low-temperature wastewater after salt precipitation, the middle layer is the newly flowing high-temperature concentrated wastewater, and the lower layer is the precipitated large amount of crystallized salt. When the liquid level in the low-temperature crystallization chamber 31 reaches a certain height, the uppermost layer of low-temperature wastewater after salt precipitation is pumped through the condensate vapor recovery pipe 32 into the low-temperature condensation chamber 41 to cool the low-temperature crystallization chamber.

[0047] In some embodiments, the concentrated liquid outlet pipe 14 is equipped with a hydraulic sensor for detecting the hydraulic pressure on the inlet side and a solenoid valve for controlling the liquid flow rate and velocity.

[0048] In this embodiment, during the evaporation and crystallization process, as water evaporates, the solution concentration increases and the density increases, which leads to changes in the hydraulic pressure in the system. In this embodiment, a hydraulic sensor is provided on the concentrated liquid outlet pipe 14 to measure the hydraulic pressure on the inlet side. By monitoring the changes in hydraulic pressure, the change in solution concentration on the inlet side of the concentrated liquid outlet pipe 14 can be indirectly detected. The flow rate and velocity of the liquid in the concentrated liquid outlet pipe 14 are controlled by a solenoid valve, thereby controlling the concentration of the concentrated high-salt wastewater flowing into the low-temperature crystallization chamber from the concentrated liquid outlet pipe 14.

[0049] In some embodiments, the inlet end of the heat transfer tube 22 is provided with a solenoid valve for controlling the liquid flow rate and velocity, and the outlet end of the heat transfer tube 22 is uniformly distributed with a plurality of spray outlets 221. The spray outlets 221 can compress the high-salt wastewater into a fan-shaped, circular, or other spray surface, thereby increasing the contact area between the high-salt wastewater and the steam in the high-temperature evaporation chamber 11 or with the high-temperature heater 12, thereby increasing the heating rate.

[0050] In some embodiments, air pumps are provided on the high-temperature steam recovery pipe 13 from the high-temperature evaporation chamber 11 to the steam heat transfer chamber 21, on the low-temperature water vapor recovery pipe 42 from the steam heat transfer chamber 21 to the low-temperature condensation chamber 41, and on the condensation water vapor recovery pipe 32 from the low-temperature crystallization chamber to the low-temperature condensation chamber 41.

[0051] In this embodiment, by setting up multiple air pumps, the steam, water vapor, or condensate in the high-temperature evaporation chamber 11, the evaporation heat transfer chamber, and the condensation crystallization chamber all flow unidirectionally into the low-temperature condensation chamber 41, thereby creating a dynamic negative pressure environment in the high-temperature evaporation chamber 11 and the condensation crystallization chamber, thereby reducing the liquid evaporation temperature and saving energy.

[0052] In some embodiments, the low-temperature crystallization section 3 further includes a stirrer 33 disposed in the low-temperature crystallization cavity 31. The stirrer 33 includes a stirring shaft 331, blades 332 mounted on the stirring shaft 331 and rotating around the stirring shaft 331, and scraper 333 connected to the blades 332 and rubbing against the inner surface of the low-temperature crystallization cavity 31.

[0053] In this embodiment, by setting a stirrer 33 inside the low-temperature crystallization chamber, the inner wall temperature of the low-temperature crystallization chamber 31 is low. After the high-temperature and high-salt wastewater comes into contact with the inner wall of the low-temperature crystallization chamber 31, salt is easily precipitated on the inner wall. The crystallized salt on the inner wall of the low-temperature crystallization chamber 31 can be scraped off by slowly driving the stirrer 33 without affecting the dynamic stratification of the liquid in the low-temperature crystallization chamber.

[0054] like Figure 2As shown, the scraper 333 of the stirrer 33 can rub against the inner surface of the low-temperature crystallization cavity 31, and the blade 332 is located in the middle of the low-temperature crystallization cavity 31. This ensures that the stirring object of the blade 332 is the high-temperature concentrated high-salt wastewater in the middle layer, so that the crystallized salt can be precipitated more evenly, and prevents the stratification of the high-temperature concentrated high-salt wastewater and the low-temperature wastewater that has precipitated crystallized salt from being disrupted.

[0055] In this embodiment, a valve with a control switch is provided at the crystal outlet 34. When the valve is opened, the crystallized salt deposited at the bottom of the low-temperature crystallization chamber will flow out through the crystal outlet 34 at the bottom under the action of hydraulic pressure.

[0056] The applicant declares that the above are only specific embodiments of this utility model, but the protection scope of this utility model is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model fall within the protection and disclosure scope of this utility model.

Claims

1. A device for separating and purifying high-salinity wastewater, comprising a precipitation unit, a nanofiltration unit, a reverse osmosis unit, an evaporation unit, and a crystallization unit connected in sequence by pipes, characterized in that, At least two groups of reverse osmosis units, evaporation units and crystallization units are connected in series in parallel, the evaporation unit comprises a high-temperature heating part (1) and a steam heat transfer part (2) for recovering heat energy of the high-temperature heating part (1), the steam heat transfer part (2) comprises a steam heat transfer cavity (21) communicated with the high-temperature heating part (1) and a heat transfer pipe (22) arranged in the steam heat transfer cavity (21) and connected with the reverse osmosis unit at a liquid inlet end and connected with the high-temperature heating part (1) at a liquid outlet end, and the steam heat transfer cavity (21) performs heat transfer on liquid in the heat transfer pipe (22) by heating the outside of the heat transfer pipe (22).

2. The fractional salt purification device of claim 1, wherein, The crystallization unit comprises a low-temperature crystallization part (3) connected with the high-temperature heating part (1) and a low-temperature condensation part (4) communicated with the steam heat transfer part (2) and cooling the low-temperature crystallization part (3).

3. The fractional salt purification device of claim 2, wherein, The high-temperature heating part (1) comprises a high-temperature evaporation cavity (11) communicated with the liquid outlet end of the heat transfer pipe (22) and a high-temperature heater (12) for heating the high-temperature evaporation cavity (11) to make liquid in the high-temperature evaporation cavity (11) higher than evaporation temperature.

4. The fractional salt purification device of claim 3, wherein, The high-temperature evaporation cavity (11) is provided with a high-temperature steam recovery pipe (13) communicated with the steam heat transfer cavity (21) to recover heat energy and a concentrated liquid outlet pipe (14) communicated with the low-temperature crystallization part (3).

5. The fractional salt purification device of claim 4, wherein, The low-temperature condensation part (4) comprises a low-temperature condensation cavity (41) with an internal cavity, a low-temperature water vapor recovery pipe (42) for connecting the low-temperature condensation cavity (41) with the steam heat transfer cavity (21), and a condensation water outlet (43) arranged on the low-temperature condensation cavity (41).

6. The fractional salt purification device of claim 5, wherein, The low-temperature crystallization part (3) comprises a low-temperature crystallization inner cavity (31) arranged in the low-temperature condensation cavity (41) and communicated with the concentrated liquid outlet pipe (14), a condensed water vapor recovery pipe (32) for connecting the low-temperature crystallization inner cavity (31) with the low-temperature condensation cavity (41), and a crystal outlet (34) arranged on the low-temperature crystallization inner cavity (31).

7. The fractional salt purification device of claim 6, wherein, The concentrated liquid outlet pipe (14) is provided with a liquid pressure sensor for detecting liquid pressure on the liquid inlet side and an electromagnetic valve for controlling liquid flow and flow rate.

8. The fractional salt purification device of claim 7, wherein, The liquid inlet end of the heat transfer pipe (22) is provided with an electromagnetic valve for controlling liquid flow and flow rate, and the liquid outlet end of the heat transfer pipe (22) is uniformly distributed with a plurality of spray liquid outlets (221).

9. The fractional salt purification device of claim 8, wherein, The high-temperature steam recovery pipe (13) is provided with an air pump in the direction from the high-temperature evaporation cavity (11) to the steam heat transfer cavity (21), the low-temperature water vapor recovery pipe (42) is provided with an air pump in the direction from the steam heat transfer cavity (21) to the low-temperature condensation cavity (41), and the condensed water vapor recovery pipe (32) is provided with an air pump in the direction from the low-temperature crystallization cavity to the low-temperature condensation cavity (41).

10. The fractional salt purification device of claim 9, wherein, The low-temperature crystallization part (3) further comprises a stirrer (33) arranged in the low-temperature crystallization inner cavity (31), the stirrer (33) comprises a stirring shaft (331), a blade (332) rotatably mounted on the stirring shaft (331) and centered on the stirring shaft (331), and a scraper (333) connected with the blade (332) and frictionally connected with the inner surface of the low-temperature crystallization inner cavity (31).

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