A sodium nitrate purification system and method

Abstract

The application discloses a kind of sodium nitrate purification system and method, belong to sodium nitrate purification field, a kind of sodium nitrate purification system, including first nanofiltration membrane device, second nanofiltration membrane device, wastewater treatment system, reverse osmosis membrane concentration device, evaporator and reuse water system, the concentrated water end of first nanofiltration membrane device is connected with second nanofiltration membrane device, the concentrated water end of second nanofiltration membrane device is connected with wastewater treatment system, the water production end of first nanofiltration membrane device and the water production end of second nanofiltration membrane device are connected, and outlet is connected with reverse osmosis membrane concentration device, the concentrated water end of reverse osmosis membrane concentration device is connected with evaporator, the water production end of reverse osmosis membrane concentration device is connected with reuse water system.The application makes full use of twice nanofiltration membrane treatment and once reverse osmosis treatment, to improve purification efficiency, purity, and after twice nanofiltration membrane treatment and once reverse osmosis treatment Water can be directly reused, reduce waste liquid discharge, more energy saving and environmental protection.

Description

Technical Field

[0001] This invention belongs to the field of sodium nitrate purification, and particularly relates to a sodium nitrate purification system and method. Background Technology

[0002] Sodium nitrate is an important chemical widely used in industrial and laboratory fields. It is used in the preparation of gunpowder, fertilizers, glass, metal surface treatment, and various other applications. In these applications, the purity of sodium nitrate is crucial, as any impurities can affect the quality and performance of the final product.

[0003] However, some applications require sodium nitrate of higher purity, which traditional methods cannot meet.

[0004] Nanofiltration and reverse osmosis, as membrane separation technologies, are widely used in liquid treatment and separation. They are used to remove tiny particles, ions, and impurities from solutions to obtain products with higher purity. However, these membrane separation technologies have not been fully utilized in the purification of sodium nitrate, so there is still room for improvement in purification efficiency and purity. Summary of the Invention

[0005] The purpose of this invention is to provide a sodium nitrate purification system and method to overcome at least one of the above-mentioned defects in the prior art.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] The present invention provides a sodium nitrate purification system, comprising a first nanofiltration membrane device, a second nanofiltration membrane device, a wastewater treatment system, a reverse osmosis membrane concentration device, an evaporator, and a recycled water system. The concentrate end of the first nanofiltration membrane device is connected to the second nanofiltration membrane device, the concentrate end of the second nanofiltration membrane device is connected to the wastewater treatment system, the product water end of the first nanofiltration membrane device and the product water end of the second nanofiltration membrane device are connected, and their outlets are connected to the reverse osmosis membrane concentration device. The concentrate end of the reverse osmosis membrane concentration device is connected to the evaporator, and the product water end of the reverse osmosis membrane concentration device is connected to the recycled water system.

[0008] Preferably, the water recycling system has at least one outlet, and the flushing port of the first nanofiltration membrane device and the flushing port of the second nanofiltration membrane device are respectively connected to the two outlets of the water recycling system.

[0009] Preferably, the device further includes a crystallizer, a centrifuge, and a dryer, with the drain end of the evaporator connected to the crystallizer, the discharge end of the crystallizer connected to the centrifuge, and the discharge end of the centrifuge connected to the dryer.

[0010] Preferably, the dryer includes a drying chamber, a hot air assembly, a feeding assembly, a guiding assembly, a first heating plate, a stirring assembly, a heat-conducting cylinder, and a first spiral blade. The feeding assembly is fixed to the top wall of the drying chamber, with its feeding end located above the drying chamber and its discharge end located above the interior of the drying chamber. The guiding assembly is fixed to the inner wall of the drying chamber, located below the discharge end of the feeding assembly. Several first heating plates are fixed to the inner side wall of the drying chamber below the guiding assembly. The stirring assembly is fixed to the bottom wall of the drying chamber, with its stirring end located below the interior of the drying chamber. The heat-conducting cylinder is fixed to the inner end of the first heating plate and located in the middle of the drying chamber. The rotating end of the stirring assembly is fixed with a first spiral blade located inside the heat-conducting cylinder. The rotating end of the stirring assembly passes through the guiding assembly and the feeding assembly and extends upward to the top of the feeding assembly, communicating with the air outlet of the hot air assembly.

[0011] Preferably, the agitation assembly includes a motor, a hollow rotating shaft, hollow agitator blades, and a mesh plate. The motor is fixed to the bottom wall of the drying chamber, and a hollow rotating shaft is fixed to the top of the motor. The top end of the hollow rotating shaft passes through the bottom wall of the drying chamber, the heat-conducting cylinder, the material guiding assembly, and the feeding assembly, and extends above the feeding assembly to communicate with the air outlet of the hot air assembly. The hollow rotating shaft is sealed to the bottom wall of the drying chamber. A first spiral blade is fixed to the hollow rotating shaft, and a plurality of hollow agitator blades are fixedly connected to the hollow rotating shaft. The hollow agitator blades are offset from the first heating plate, and hollow agitator blades are provided on both the upper and lower sides of the heat-conducting cylinder. Air holes are opened on the side walls of the hollow agitator blades, and a mesh plate is fixed inside the air holes.

[0012] Preferably, the feeding assembly includes a feeding hopper and a second spiral blade. The feeding hopper is fixed to the top wall of the drying chamber, and the second spiral blade is fixed to the hollow rotating shaft and located below the inside of the feeding hopper. A heating chamber is provided inside the second spiral blade, which is connected to the hollow rotating shaft. The second spiral blade has several first discharge holes, which are not connected to the heating chamber. The spiral directions of the first spiral blade and the second spiral blade are the same.

[0013] Preferably, the material guiding assembly includes a material guiding plate and a second heating plate. The material guiding plate is fixed to the inner wall of the drying oven. The material guiding plate has a through hole in the middle for the hollow rotating shaft to pass through. The second heating plate is fixed to both the front and rear sides of the top wall of the material guiding plate. The material guiding plate has two downward inclined plates on the left and right. Several second discharge holes are opened in the lower part of the inclined plates. A discharge groove is opened at the bottom end of the inclined plates.

[0014] Preferably, the hot air assembly includes a hot air blower, an air duct, and a sealing ring. The hot air blower is fixed to the top wall of the drying chamber, and the air outlet of the hot air blower is fixedly connected to the air duct. The air outlet of the air duct extends to the upper part of the hollow rotating shaft. A sealing ring is provided between the air duct and the hollow rotating shaft. A discharge pipe is fixedly connected to the lower side wall of the drying chamber, and a valve is provided on the discharge pipe.

[0015] This invention also provides a method for purifying sodium nitrate, using the aforementioned sodium nitrate purification system, comprising the following steps: feeding raw sodium nitrate water into a first nanofiltration membrane device for initial nanofiltration treatment; feeding the concentrated water produced by the first nanofiltration membrane device into a second nanofiltration membrane device for secondary nanofiltration treatment; feeding the concentrated water produced by the second nanofiltration membrane device into a wastewater treatment system for treatment; feeding the permeate water produced by the first nanofiltration membrane device and the permeate water produced by the second nanofiltration membrane device together into a reverse osmosis membrane concentration device for concentration treatment; feeding the permeate water produced by the reverse osmosis membrane concentration device into a reclaimed water system for reuse; and feeding the concentrated water produced by the reverse osmosis membrane concentration device into an evaporator for evaporation and concentration.

[0016] Preferably, the method further includes the following steps: the effluent from the recycled water system is used as flushing water and enters the first nanofiltration membrane device and the second nanofiltration membrane device for flushing treatment; the concentrate after evaporation and concentration treatment in the evaporator is sent to the crystallizer for crystallization treatment; the sodium nitrate crystals obtained from the crystallizer are sent to the centrifuge for centrifugation treatment; and the aqueous sodium nitrate obtained from the centrifuge is sent to the dryer for drying treatment to obtain the dried sodium nitrate product.

[0017] The beneficial effects of this invention are as follows:

[0018] 1. This invention fully utilizes two nanofiltration membrane treatments and one reverse osmosis treatment to improve purification efficiency and purity. Furthermore, the permeate after these two treatments can be directly reused as flushing water for both the first and second nanofiltration membrane units, reducing wastewater discharge and making it more energy-efficient and environmentally friendly. Through this invention, sodium nitrate purification can be achieved more quickly and effectively, while simultaneously reducing energy consumption and waste generation.

[0019] 2. Liquid sodium nitrate is concentrated and purified into solid sodium nitrate through the use of crystallizers, centrifuges, and dryers, which facilitates product application.

[0020] 3. By setting up the stirring component, the material is stirred and dispersed, thereby improving drying efficiency.

[0021] 4. By using a hot air assembly and a first heating plate, two different drying methods can be achieved, resulting in more comprehensive drying.

[0022] 5. The first heating plate not only directly heats the material but also serves as a fixing component for the heat-conducting cylinder, transferring heat to the cylinder and raising its temperature. Combined with the first spiral blades, this pushes the material at the bottom of the drying chamber upwards, while simultaneously heating the material inside the cylinder. The pushing action of the first spiral blades ensures that the material is evenly agitated, resulting in more uniform heating and significantly improved drying efficiency.

[0023] 6. In addition to stirring the material, the hollow stirring blades also disperse the material, improving drying efficiency. After the hot air enters the hollow rotating shaft, it enters the hollow stirring blades and is discharged through the air holes. While stirring, the material is dried with hot air, so that the material is dried evenly.

[0024] 7. As the hollow shaft rotates, it drives the second spiral blades to rotate, pushing the material upward and slowing its descent. The material is then discharged through the first discharge hole. Furthermore, combined with the heating chamber, hot air enters the heating chamber through the hollow shaft, heating the second spiral blades and simultaneously slowing the material's descent while pre-drying it.

[0025] 8. The agitation and slowing of material feeding can be achieved with only one motor, saving energy and demonstrating ingenious design. A hollow rotating shaft, in conjunction with a hot air assembly, enables simultaneous agitation and hot air drying by the hollow stirring blades; it also drives the first spiral blades to rotate, working in conjunction with the first heating plate and heat-conducting cylinder to achieve simultaneous material pushing, heating, and drying; and it further drives the second spiral blades to rotate, working in conjunction with the feed hopper to achieve pre-drying and slow feeding.

[0026] 9. The material feeding hopper is distributed to the left and right sides by the material guiding component. While guiding the material, the feeding speed is further slowed down. The second heating plate is set to heat the material while guiding it. The second discharge hole is set at the lower part of the inclined plate and the discharge chute is set at the bottom of the inclined plate to ensure the heating time of the material during the guiding process and to ensure the smooth feeding of the material. Attached Figure Description

[0027] Figure 1 This is a system block diagram of the present invention.

[0028] Figure 2 This is a schematic diagram of the structure of the present invention.

[0029] Figure 3 This is a partial cross-sectional view of the stirring component of the present invention.

[0030] Figure 4 This is a top view schematic diagram of the feed hopper, the second spiral blade, and the hollow rotating shaft of the present invention.

[0031] Figure 5 This is a cross-sectional view of the second helical blade of the present invention.

[0032] Figure 6 This is a top view of the material guiding component of the present invention.

[0033] Figure 7 This is a schematic diagram of the assembly structure of the air duct, sealing ring, and hollow rotating shaft of the present invention.

[0034] The labels in the attached diagram are as follows: 100-First nanofiltration membrane device, 200-Second nanofiltration membrane device, 300-Wastewater treatment system, 400-Reverse osmosis membrane concentration device, 500-Evaporator, 600-Reclaimed water system, 700-Crystallizer, 800-Centrifuge, 900-Dryer, 1-Drying oven, 2-Hot air assembly, 3-Feed assembly, 4-Feeding assembly, 5-First heating plate, 6-Agitation assembly, 7-Heat conduction cylinder, 8-... - First spiral blade, 61-Motor, 62-Hollow rotating shaft, 63-Hollow stirring blade, 64-Mesh plate, 65-Air hole, 31-Feed hopper, 32-Second spiral blade, 33-First discharge hole, 34-Heating chamber, 41-Guide plate, 42-Second heating plate, 43-Perforation, 44-Second discharge hole, 45-Discharge trough, 21-Hot air blower, 22-Air duct, 23-Sealing ring, 9-Discharge pipe, 10-Valve. Detailed Implementation

[0035] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0036] Contents not described in detail in this specification are prior art known to those skilled in the art. In the description of this invention, it should be understood that terms such as "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, terms such as "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0037] like Figures 1 to 7As shown, the sodium nitrate purification system provided in this embodiment includes a first nanofiltration membrane device 100, a second nanofiltration membrane device 200, a wastewater treatment system 300, a reverse osmosis membrane concentration device 400, an evaporator 500, a reclaimed water system 600, a crystallizer 700, a centrifuge 800, and a dryer 900. The concentrate end of the first nanofiltration membrane device 100 is connected to the second nanofiltration membrane device 200, the concentrate end of the second nanofiltration membrane device 200 is connected to the wastewater treatment system 300, the product water end of the first nanofiltration membrane device 100 and the product water end of the second nanofiltration membrane device 200 are connected, and their outlets are connected to the reverse osmosis membrane concentration device 400. The concentrate end of the reverse osmosis membrane concentration device 400 is connected to the evaporator 500, and the product water end of the reverse osmosis membrane concentration device 400 is connected to the reclaimed water system 600. The recycled water system 600 has at least one outlet. The flushing port of the first nanofiltration membrane device 100 and the flushing port of the second nanofiltration membrane device 200 are respectively connected to the two outlets of the recycled water system 600. The drain end of the evaporator 500 is connected to the crystallizer 700, the discharge end of the crystallizer 700 is connected to the centrifuge 800, and the discharge end of the centrifuge 800 is connected to the dryer 900.

[0038] This embodiment also provides a method for purifying sodium nitrate, which uses the above-mentioned sodium nitrate purification system and includes the following steps:

[0039] The raw sodium nitrate water is fed into the first nanofiltration membrane device 100 for primary nanofiltration treatment. The concentrate produced by the first nanofiltration membrane device 100 is fed into the second nanofiltration membrane device 200 for secondary nanofiltration treatment. The concentrate produced by the second nanofiltration membrane device 200 is fed into the wastewater treatment system 300 for treatment. The permeate produced by the first nanofiltration membrane device 100 and the permeate produced by the second nanofiltration membrane device 200 are fed into the reverse osmosis membrane concentration device 400 for concentration treatment. The permeate produced by the reverse osmosis membrane concentration device 400 is fed into the water reuse system 600 for reuse. The concentrate produced by the reverse osmosis membrane concentration device 400 is fed into the evaporator 500 for evaporation and concentration. The effluent from the recycled water system 600 is used as flushing water and enters the first nanofiltration membrane device 100 and the second nanofiltration membrane device 200 for flushing treatment. The concentrated liquid after evaporation and concentration in the evaporator 500 is sent to the crystallizer 700 for crystallization treatment. The sodium nitrate crystals obtained from the crystallizer 700 are sent to the centrifuge 800 for centrifugation treatment. The hydrous sodium nitrate obtained from the centrifuge 800 is sent to the dryer 900 for drying treatment to obtain dried sodium nitrate product. This invention makes full use of two nanofiltration membrane treatments and one reverse osmosis treatment to improve purification efficiency and purity. Furthermore, the permeate after the two nanofiltration membrane treatments and one reverse osmosis treatment can be directly reused as flushing water for the first nanofiltration membrane device 100 and the second nanofiltration membrane device 200, reducing waste liquid discharge and making it more energy-efficient and environmentally friendly. Through this invention, sodium nitrate purification can be achieved more quickly and effectively, while reducing energy consumption and waste generation. The arrangement of the crystallizer 700, centrifuge 800, and dryer 900 concentrates and purifies liquid sodium nitrate into solid sodium nitrate, facilitating product application.

[0040] The dryer 900 includes a drying chamber 1, a hot air assembly 2, a feeding assembly 3, a guiding assembly 4, a first heating plate 5, a stirring assembly 6, a heat-conducting cylinder 7, and first spiral blades 8. The feeding assembly 3 is fixed to the top wall of the drying chamber 1, with its inlet end located above the chamber and its outlet end located above the interior of the chamber. The guiding assembly 4 is fixed to the inner wall of the drying chamber 1, located below the outlet end of the feeding assembly 3. Several first heating plates 5 are fixed to the inner wall of the drying chamber 1 below the guiding assembly 4. A stirring assembly 6 is fixed to the bottom wall of the drying chamber 1. The stirring end of the stirring assembly 6 is located at the lower part of the interior of the drying chamber 1. A heat-conducting cylinder 7 is fixed to the inner end of the first heating plate 5 and located in the middle of the drying chamber 1. A first spiral blade 8 is fixed to the rotating end of the stirring assembly 6. The first spiral blade 8 is located inside the heat-conducting cylinder 7. The rotating end of the stirring assembly 6 passes through the material guiding assembly 4 and the feeding assembly 3, and extends upward to the top of the feeding assembly 3 to communicate with the air outlet of the hot air assembly 2. A discharge pipe 9 is fixedly connected to the lower side wall of the drying chamber 1, and a valve 10 is installed on the discharge pipe 9. Sodium nitrate containing water enters the drying chamber 1 through the feeding assembly 3 and is buffered by the material guiding assembly 4. It is stirred and dispersed by the stirring assembly 6 at the lower part of the interior of the drying chamber 1 to improve drying efficiency. The arrangement of the hot air assembly 2 and the first heating plate 5 realizes two different drying methods, making the drying more comprehensive. The first heating plate 5 not only directly heats the material but also serves as a fixing component for the heat-conducting cylinder 7, transferring heat to it and raising its temperature. Combined with the first spiral blades 8, this pushes the material at the bottom of the drying chamber 1 upwards, simultaneously heating the material inside the heat-conducting cylinder 7. The pushing action of the first spiral blades 8 ensures the material is evenly agitated, resulting in more uniform heating and significantly improved drying efficiency. The dried sodium nitrate product is in powder form. During discharge, valve 10 is opened, and the sodium nitrate product is discharged from the discharge pipe 9.

[0041] The stirring component 6 includes a motor 61, a hollow rotating shaft 62, hollow stirring blades 63, and a mesh plate 64. The motor 61 is fixed to the bottom wall of the drying chamber 1, and the hollow rotating shaft 62 is fixed to the top of the motor 61. The top of the hollow rotating shaft 62 is open, and the bottom is closed. The top of the hollow rotating shaft 62 passes through the bottom wall of the drying chamber 1, the heat-conducting cylinder 7, the material guiding component 4, and the feeding component 3, and extends above the feeding component 3 to communicate with the air outlet of the hot air component 2. The hollow rotating shaft 62 is sealed to the bottom wall of the drying chamber 1. The first spiral blade 8 is fixed to the hollow rotating shaft 62, and several hollow stirring blades 63 are fixedly connected to the hollow rotating shaft 62. The hollow stirring blades 63 are staggered with the first heating plate 5, so that the material can be dried more evenly. Furthermore, the heat-conducting cylinder 7 has hollow stirring blades 63 on both its upper and lower sides. Air holes 65 are opened on the side walls of the hollow stirring blades 63, and a mesh plate 64 is fixed inside the air holes 65. The motor 61 rotates, driving the hollow rotating shaft 62 to rotate, causing the hollow stirring blades 63 and the first spiral blade 8 to rotate. The hollow stirring blades 63 not only stir the material but also disperse it, improving drying efficiency. Hot air enters the hollow rotating shaft 62, then enters the hollow stirring blades 63 and is discharged through the air holes 65. While stirring, the material is simultaneously dried with hot air, ensuring uniform drying. The mesh plate 64 prevents material from passing through the air holes 65.

[0042] The feeding assembly 3 includes a feeding hopper 31 and a second spiral blade 32. The feeding hopper 31 is fixed to the top wall of the drying chamber 1. The second spiral blade 32 is fixed to the hollow rotating shaft 62 and located below the inside of the feeding hopper 31. A heating chamber 34 is formed inside the second spiral blade 32, which is connected to the hollow rotating shaft 62. The second spiral blade 32 has several first discharge holes 33, which are not connected to the heating chamber 34. The spiral directions of the first spiral blade 8 and the second spiral blade 32 are the same. In this embodiment, both the first spiral blade 8 and the second spiral blade 32 are made of iron. When the hollow rotating shaft 62 rotates, it drives the second spiral blade 32 to rotate, pushing the material upward and slowing down the descent speed of the material, which is then discharged through the first discharge holes 33. In conjunction with the setting of the heating chamber 34, hot air enters the heating chamber 34 through the hollow rotating shaft, heating the second spiral blade 32, which not only slows down the falling speed of the material but also pre-dries the material. Furthermore, the stirring and slowing of the material feeding can be achieved with just one motor 61, which saves more energy and is a clever design. Through a hollow rotating shaft 62 and hot air assembly 2, it can achieve the effect of stirring the material and drying it with hot air at the same time as the hollow stirring blades 63; it can also drive the first spiral blade 8 to rotate, which, in conjunction with the first heating plate and heat conduction cylinder 7, can achieve the effect of pushing the material and heating and drying at the same time; it can also drive the second spiral blade 32 to rotate, which, in conjunction with the feed hopper 31, can achieve the effect of pre-drying and slow feeding.

[0043] The material guiding assembly 4 includes a material guiding plate 41 and a second heating plate 42. The material guiding plate 41 is fixed to the inner wall of the drying chamber 1. The middle of the material guiding plate 41 has a through hole 43 for the hollow rotating shaft 62 to pass through. The second heating plate 42 is fixed to both the front and rear sides of the top wall of the material guiding plate 41. The material guiding plate 41 has two downward inclined plates on the left and right sides. Several second discharge holes 44 are opened at the lower part of the inclined plates, and a discharge groove 45 is opened at the bottom end of the inclined plates. The material guiding assembly 4 disperses the material from the feed hopper 31 to the left and right sides for discharge. While guiding the material, it further slows down the discharge speed. The setting of the second heating plate 42 not only heats the material while guiding it, but also prevents the material from falling from the front and rear sides of the inclined plates. The second discharge holes 44 are set at the lower part of the inclined plates, and the discharge groove 45 is set at the bottom end of the inclined plates to ensure the heating time of the material during the guiding process and to ensure the smooth discharge of the material.

[0044] The hot air assembly 2 includes a hot air blower 21, an air duct 22, and a sealing ring 23. The hot air blower 21 is fixed to the top wall of the drying chamber 1. The air outlet of the hot air blower 21 is fixedly connected to the air duct 22. The air outlet of the air duct 22 extends to the upper part of the hollow rotating shaft 62. A sealing ring 23 is provided between the air duct 22 and the hollow rotating shaft 62. The hot air generated by the hot air blower 21 is sent into the hollow rotating shaft 62 through the air duct 22, and the sealing ring 23 provides a sealing effect.

[0045] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sodium nitrate purification system, characterized in that: It includes a first nanofiltration membrane unit, a second nanofiltration membrane unit, a wastewater treatment system, a reverse osmosis membrane concentration unit, an evaporator, and a water recycling system; The concentrate end of the first nanofiltration membrane device is connected to a second nanofiltration membrane device, and the concentrate end of the second nanofiltration membrane device is connected to a wastewater treatment system. The product water end of the first nanofiltration membrane device is connected to the product water end of the second nanofiltration membrane device, and the outlet is connected to the reverse osmosis membrane concentration device. The concentrate end of the reverse osmosis membrane concentration device is connected to the evaporator; The product water end of the reverse osmosis membrane concentration unit is connected to a water recycling system. It also includes crystallizers, centrifuges, and dryers; The evaporator's drain end is connected to the crystallizer, the crystallizer's discharge end is connected to the centrifuge, and the centrifuge's discharge end is connected to the dryer. The dryer includes a drying chamber, a hot air assembly, a feeding assembly, a guiding assembly, a first heating plate, a stirring assembly, a heat-conducting cylinder, and a first spiral blade; The top wall of the drying chamber is fixed with a feeding assembly, the feeding end of the feeding assembly is located above the drying chamber, and the discharging end of the feeding assembly is located above the interior of the drying chamber. A material guiding assembly is fixed to the inner wall of the drying oven, and the material guiding assembly is located below the discharge end of the feeding assembly; Several first heating plates are fixed to the inner wall of the drying chamber below the material guiding assembly; An agitation assembly is fixed to the bottom wall of the drying oven; The stirring end of the stirring component is located at the bottom inside the drying chamber. The heat-conducting cylinder is fixed to the inner end of the first heating plate and located in the middle of the drying chamber. The rotating end of the stirring component is fixed with a first spiral blade, which is located inside the heat-conducting cylinder. The rotating end of the stirring component passes through the material guiding component and the feeding component, and extends upward to the top of the feeding component to communicate with the air outlet of the hot air component. The agitation assembly includes a motor, a hollow rotating shaft, hollow agitator blades, and a mesh plate; The motor is fixed to the bottom wall of the drying chamber, and a hollow rotating shaft is fixed to the top of the motor. The top end of the hollow rotating shaft passes through the bottom wall of the drying chamber, the heat conduction cylinder, the material guiding assembly, and the feeding assembly, and extends to the top of the feeding assembly to communicate with the air outlet of the hot air assembly. The hollow rotating shaft is sealed to the bottom wall of the drying chamber. The first spiral blade is fixed to the hollow rotating shaft, and the hollow rotating shaft is fixedly connected to a plurality of hollow stirring blades. The hollow stirring blades are offset from the first heating plate, and the upper and lower sides of the heat-conducting cylinder are both equipped with hollow stirring blades. The hollow stirring blade has air holes on its side wall, and a mesh plate is fixed inside the air holes; The feeding assembly includes a feeding hopper and a second spiral blade; The feed hopper is fixed to the top wall of the drying chamber; The second spiral blade is fixed to the hollow rotating shaft and is located inside the lower part of the feed hopper; The second helical blade has a heating cavity inside, and the heating cavity is connected to the hollow rotating shaft; The second spiral blade has several first discharge holes, which are not connected to the heating chamber; The first and second helical blades have the same helical direction.

2. The sodium nitrate purification system according to claim 1, characterized in that: The water recycling system has at least one outlet, and the flushing port of the first nanofiltration membrane device and the flushing port of the second nanofiltration membrane device are respectively connected to the two outlets of the water recycling system.

3. The sodium nitrate purification system according to claim 1, characterized in that: The material guiding assembly includes a material guiding plate and a second heating plate; The inner wall of the drying oven is fixed with a guide plate, and the guide plate has a through hole in the middle for the hollow rotating shaft to pass through. The top wall of the guide plate is fixed with a second heating plate on both the front and rear sides; The guide plate has two downward-sloping inclined plates on the left and right, and a number of second discharge holes are opened at the lower part of the inclined plates. A discharge groove is opened at the bottom end of the inclined plates.

4. The sodium nitrate purification system according to claim 1, characterized in that: The hot air assembly includes a hot air blower, air ducts, and sealing rings; A hot air blower is fixed to the top wall of the drying oven. The air outlet of the hot air blower is fixedly connected to an air duct. The air outlet of the air duct extends to the top of the hollow rotating shaft. A sealing ring is provided between the air duct and the hollow rotating shaft. A discharge pipe is fixedly connected to the lower side wall of the drying chamber, and a valve is installed on the discharge pipe.

5. A method for purifying sodium nitrate, characterized in that, Purification using the sodium nitrate purification system according to any one of claims 1-4 includes the following steps: Sodium nitrate raw water is fed into the first nanofiltration membrane device for primary nanofiltration treatment. The concentrate produced by the first nanofiltration membrane device is fed into the second nanofiltration membrane device for secondary nanofiltration treatment. The concentrate produced by the second nanofiltration membrane device is sent to the wastewater treatment system for further treatment. The permeate produced by the first nanofiltration membrane device and the permeate produced by the second nanofiltration membrane device are sent together to the reverse osmosis membrane concentration device for concentration treatment. The permeate produced by the reverse osmosis membrane concentration device is sent to the water reuse system for reuse. The concentrate produced by the reverse osmosis membrane concentration device is sent to the evaporator for further evaporation and concentration. The effluent from the recycled water system is used as flushing water and enters the first nanofiltration membrane device and the second nanofiltration membrane device for flushing treatment. The concentrate after evaporation and concentration in the evaporator is sent to the crystallizer for crystallization treatment. The sodium nitrate crystals obtained from the crystallizer are sent to the centrifuge for centrifugation treatment. The aqueous sodium nitrate obtained from the centrifuge is sent to the dryer for drying treatment to obtain the dried sodium nitrate product.

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