NMP purification method and purification equipment

Abstract

The present application relates to the technical field of solution purification, and particularly relates to a NMP purification method and a purification device. The present application comprises a purification device, the purification device comprises a NMP waste liquid tank, a group of impurity removal distillation stills, a group of water removal distillation stills and a NMP new liquid tank which are connected in sequence along the NMP solution conveying direction on a discharge pipeline. The group of impurity removal distillation stills comprises at least two impurity removal distillation stills which are connected in sequence, and the bottom of the impurity removal distillation still is provided with a liquid discharge impurity removal pipeline which can discharge the bottom sediment impurities in real time, and a concentration sensor is installed in the impurity removal distillation still. In the present application, a filter is not needed, and the impurities in the NMP solution can be efficiently removed.

Description

Technical Field

[0001] This invention relates to the field of solution purification technology, specifically an NMP purification method and purification equipment. Background Technology

[0002] NMP, or N-methylpyrrolidone, is a high-boiling-point, environmentally friendly, and excellent solvent. It has advantages such as low viscosity, chemical stability, good physical and thermal stability, high polarity, low volatility, and infinite miscibility with water and many organic solvents. Its market applications are mainly concentrated in industries such as lithium batteries, circuit boards, insulating materials, petrochemicals, pharmaceuticals, pesticides, cleaning, and polymers.

[0003] Existing methods for extracting high-purity NMP solutions from NMP waste mainly involve the removal of solid impurities and moisture. For example, the text of Chinese Patent Publication No. CN117357919B, entitled "NMP Distillation Purification Method and NMP Distillation Purification Process," describes a process where solid impurities are filtered through a filtration assembly during the waste treatment step, and the NMP solution is purified by heating and distillation during the distillation process.

[0004] However, in practice, when dealing with large-scale processing needs, using filters to remove impurities often presents the following problems: First, during the distillation process of NMP, the properties of the solution change, and the solubility of some impurities at a certain concentration decreases, causing some impurities to precipitate out of NMP during the distillation process, resulting in some impurities still being present in the NMP solution after distillation.

[0005] Second, NMP waste liquid may contain a variety of impurities with different properties. Some impurities may change in morphology, particle size, etc., with changes in time and operating conditions; it is difficult to find a universal filter that can effectively remove all impurities.

[0006] Third, the filter element may leak impurities into the filtered NMP due to wear or breakage.

[0007] Fourth, during the filtration process, there will be the problem of frequent replacement or cleaning of filter elements, which will affect the continuity of production.

[0008] Fifth, filter cartridges are typically consumables that require regular purchase and replacement, increasing long-term operating costs. Therefore, this issue urgently needs to be addressed. Summary of the Invention

[0009] To avoid and overcome the technical problems existing in the prior art, the present invention provides an NMP purification method and purification equipment that does not require a filter and can achieve efficient removal of impurities from NMP solution.

[0010] To achieve the above objectives, the present invention provides the following technical solution: An NMP purification method includes a purification apparatus comprising an NMP waste tank, a set of impurity-removing distillation kettles, a set of water-removing distillation kettles, and a fresh NMP tank connected sequentially along an NMP solution conveying direction on a discharge pipeline. The set of impurity-removing distillation kettles includes at least two impurity-removing distillation kettles connected sequentially, and each kettle has a drain pipe at its bottom for real-time discharge of precipitated impurities. A concentration sensor is installed inside each impurity-removing distillation kettle. The purification method includes the following steps: S1. The concentration of NMP in the solution in each impurity removal distillation vessel is obtained in real time by a concentration sensor; S2. Based on the real-time obtained NMP concentration in the solution of the impurity removal distillation vessel, adjust the NMP concentration in each impurity removal distillation vessel to the target concentration. In particular, along the flow direction from the NMP waste tank to the NMP new tank, the target concentration of NMP in the solution of adjacent impurity removal distillation vessels increases sequentially. S3. Within one iteration time, based on the real-time obtained NMP concentration in the solution of the impurity removal distillation vessel, calculate the concentration growth rate of the impurity removal distillation vessel within one iteration time, and compare the concentration growth rate with the set threshold. S4. When the concentration growth rate is greater than the set threshold, increase the inlet flow rate of the impurity removal distillation vessel and decrease the outlet flow rate to make the NMP concentration in the solution of the impurity removal distillation vessel approach the target concentration. In the next iteration after the NMP concentration in the solution of the impurity removal distillation vessel reaches the target concentration, return to step S3. When the concentration growth rate is less than the set threshold, decrease the inlet flow rate of the impurity removal distillation vessel and increase the outlet flow rate to make the NMP concentration in the solution of the impurity removal distillation vessel approach the target concentration. In the next iteration after the NMP concentration in the solution of the impurity removal distillation vessel reaches the target concentration, return to step S3.

[0011] As a further aspect of the present invention: the target concentration of the solution in the lowest-level impurity removal distillation vessel in step S1 is 90%.

[0012] As a further aspect of the present invention, the threshold set in step S3 is 0.

[0013] A purification device that applies the aforementioned NMP purification method, wherein in the purification device, the middle part of the adjacent upper-level impurity removal distillation vessel is connected to the adjacent lower-level impurity removal distillation vessel through a discharge pipeline, and the bottom of the adjacent lower-level impurity removal distillation vessel is connected to the adjacent upper-level impurity removal distillation vessel through a reflux pipeline, and the reflux pipeline constitutes the liquid discharge impurity removal pipeline.

[0014] As a further embodiment of the present invention, the impurity removal distillation vessel is configured as three.

[0015] As a further embodiment of the present invention, the dehydration distillation vessel is configured as two.

[0016] As a further embodiment of the present invention: condensers are connected to the top of both the impurity removal distillation vessel and the water removal distillation vessel, and the condensers connected to the adjacent upper-level impurity removal distillation vessel are connected to the adjacent lower-level impurity removal distillation vessel. The condensers connected to the lowest-level impurity removal distillation vessel and the condensers connected to the water removal distillation vessel are both connected to the drain tank.

[0017] As a further aspect of the present invention, the heating temperature of the impurity removal distillation vessel group and the water removal distillation vessel group is 120°C.

[0018] As a further aspect of the present invention, the condensing temperature of the condenser is 7°C.

[0019] Compared with the prior art, the beneficial effects of the present invention are: 1. The purification method of this invention enables continuous distillation at progressively increasing target concentrations between adjacent impurity-removing distillation vessels. For impurities that may form precipitates, higher NMP concentrations promote their easier precipitation from the solution. Simultaneously, at higher concentrations, changes in solution properties such as viscosity enhance the interaction between solid particles, making them more likely to aggregate and precipitate. Furthermore, the drainage pipe at the bottom of the impurity-removing distillation vessel allows for real-time discharge of precipitated impurities, eliminating the need for filters and achieving efficient removal of impurities generated during the NMP solution purification process.

[0020] 2. This invention treats impurities during the distillation process of NMP, thus simultaneously processing impurities precipitated from the NMP solution at specific concentrations during distillation. Furthermore, the particulate impurity precipitation and reflux method eliminates the need for filtration mechanisms, avoiding concerns about leakage due to filter element breakage and ensuring the stability and reliability of the purification process. The precipitation and reflux method also eliminates the need for frequent filter element cleaning or replacement; only periodic cleaning of particulate impurities in the top-level impurity removal distillation vessel is required, resulting in low cleaning cycles and maintenance costs. Additionally, it offers the advantages of efficient cleaning without interrupting purification operations, enabling continuous impurity removal without production disruptions, making it more suitable for large-scale industrial production.

[0021] 3. In this invention, it is preferable to use three purification distillation vessels, which is applicable to most working conditions. The concentration of the NMP solution in the three purification distillation vessels can be set differently, allowing particulate impurities to be substantially precipitated under distillation at different concentrations. Furthermore, by precipitating particulate impurities in the second-stage purification distillation vessel and refluxing them back to the first-stage purification distillation vessel, the impurity content in the second-stage purification distillation vessel is kept at a low level. Consequently, the impurity content in the third-stage purification distillation vessel, which is then fed into the second-stage purification distillation vessel, is even lower. Subsequently, through further impurity reflux in the third-stage purification distillation vessel, the impurities precipitated in the third-stage purification distillation vessel, as well as the impurities fed into the third-stage purification distillation vessel, are returned to the second-stage purification distillation vessel, resulting in the third-stage purification distillation vessel being in a state almost free of impurities.

[0022] 4. In this invention, instead of directly collecting the condensate from the upper-stage impurity removal distillation vessel into the adjacent lower-stage impurity removal distillation vessel, the condensate helps stabilize the system operation to some extent. The condensate helps maintain pressure balance between the distillation vessels, promoting gas flow and substance transfer, thus improving purification efficiency and progressively increasing concentration. Furthermore, the pressure balancing effect of the condensate makes the reflux process more stable, facilitating further precipitation of particulate impurities and ensuring even removal. Simultaneously, the water entering the lower-stage impurity removal distillation vessel may also play a supporting separation role throughout the purification process. To a certain extent, the presence of water can affect the boiling point and vapor pressure of different substances, thus promoting the separation of NMP from other impurities. If the condensed water does not enter the adjacent lower-stage impurity removal distillation vessel, it may interfere with this separation mechanism, preventing the effective removal of some impurities and reducing the purity of the purified NMP.

[0023] 5. This invention employs a multi-stage distillation tower design, with five distillation towers connected in series, enabling the gradual purification of NMP waste liquid. Each distillation tower targets specific impurities and concentration ranges, improving the overall purification effect and reducing reliance on high-temperature steam. For example, in the first-stage distillation tower, some impurities can be initially separated, reducing the processing burden on subsequent distillation towers. This allows for effective purification at a relatively lower temperature; therefore, compared to the traditional 150°C distillation, this invention only requires 120°C, reducing energy consumption during the distillation process. Simultaneously, due to the lower distillation temperature, the condenser 50 does not need the traditional 5°C condensation temperature; 7°C is sufficient, effectively reducing the energy consumption for post-distillation condensation. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating the purification method of the present invention.

[0025] Figure 2This is a schematic diagram of the purification device in this invention.

[0026] In the diagram: 10, NMP waste liquid tank; 20, impurity removal distillation kettle assembly; 21, impurity removal distillation kettle; 30, discharge pipeline; 40, reflux pipeline; 50, condenser; 60, water removal distillation kettle assembly; 61, water removal distillation kettle; 70, NMP fresh liquid tank; 80, drain tank. Detailed Implementation

[0027] 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.

[0028] For ease of understanding, the specific structure and operation of the present invention will be further described below with reference to the accompanying drawings: The purification method of the present invention refers to Figure 1 As shown, an NMP purification method includes a purification apparatus. This apparatus comprises an NMP waste liquid tank 10, a purification distillation vessel group 20, a dehydration distillation vessel group 60, and an NMP fresh liquid tank 70, sequentially connected along the NMP solution conveying direction to a discharge pipeline 30. The purification distillation vessel group 20 includes at least two purification distillation vessels 21 connected in sequence. Each purification distillation vessel 21 has a drainage pipeline at its bottom for real-time discharge of precipitated impurities. A concentration sensor is installed inside each purification distillation vessel 21. The purification method includes the following steps: S1. The concentration of NMP in the solution in each impurity removal distillation vessel 21 is obtained in real time by the concentration sensor; S2. Based on the real-time obtained NMP concentration of the solution in the impurity removal distillation vessel 21, adjust the NMP concentration of the solution in each impurity removal distillation vessel 21 to the target concentration. In particular, along the flow direction from the NMP waste liquid tank 10 to the NMP new liquid tank 70, the target concentration of NMP in the solution in adjacent impurity removal distillation vessels 21 increases sequentially. S3. Within one iteration time, based on the real-time obtained NMP concentration of the solution in the impurity removal distillation vessel 21, calculate the concentration growth rate of the impurity removal distillation vessel 21 within one iteration time, and compare the concentration growth rate with the set threshold. S4. When the concentration growth rate is greater than the set threshold, increase the inlet flow rate of the impurity removal distillation vessel 21 and decrease the outlet flow rate to make the NMP concentration of the solution in the impurity removal distillation vessel 21 approach the target concentration. In the next iteration after the NMP concentration of the solution in the impurity removal distillation vessel 21 reaches the target concentration, return to step S3. When the concentration growth rate is less than the set threshold, decrease the inlet flow rate of the impurity removal distillation vessel 21 and increase the outlet flow rate to make the NMP concentration of the solution in the impurity removal distillation vessel 21 approach the target concentration. In the next iteration after the NMP concentration of the solution in the impurity removal distillation vessel 21 reaches the target concentration, return to step S3.

[0029] According to the purification method described above, continuous distillation at progressively increasing target concentrations can be achieved between adjacent impurity-removing distillation vessels 21. For impurities that may form precipitates, higher NMP concentrations promote their easier precipitation from the solution. Simultaneously, at higher concentrations, changes in solution viscosity and other properties enhance the interaction between solid particles, making them more likely to aggregate and precipitate. Without progressive concentration increases, the precipitate may mix with NMP and other impurities, making effective separation difficult. Furthermore, the drainage pipe at the bottom of the impurity-removing distillation vessel 21 allows for the real-time discharge of precipitated impurities, eliminating the need for filters and enabling efficient removal of impurities generated during the NMP solution purification process.

[0030] Purification equipment using the above purification method, such as Figure 2 As shown, its main structure includes an NMP waste liquid tank 10, a purification distillation kettle group 20, a dehydration distillation kettle group 60, and an NMP fresh liquid tank 70, which are sequentially connected to the discharge pipeline 30 along the solution conveying direction. The NMP solution in the NMP waste liquid tank 10 first enters the purification distillation kettle group 20 for distillation to remove particulate impurities. After that, the NMP solution with the particulate impurities removed enters the dehydration distillation kettle group 60 for further distillation to evaporate the residual water. Finally, it is transported to the NMP fresh liquid tank 70 to achieve the final solution purification.

[0031] Specifically, such as Figure 2As shown, the impurity removal distillation vessel group 20 includes at least two impurity removal distillation vessels 21 connected in sequence. The middle of an adjacent upper-level impurity removal distillation vessel 21 is connected to an adjacent lower-level impurity removal distillation vessel 21 via a discharge pipe 30, and the bottom of an adjacent lower-level impurity removal distillation vessel 21 is connected to an adjacent upper-level impurity removal distillation vessel 21 via a reflux pipe 40, which constitutes the discharge impurity removal pipeline. During the distillation process, the concentration in the impurity removal distillation vessel 21 continuously changes, causing impurities dissolved in the NMP solution in the impurity removal distillation vessel 21 to gradually precipitate and settle at the bottom of the impurity removal distillation vessel 21. Because the middle of an adjacent upper-level impurity removal distillation vessel 21 is connected to an adjacent lower-level impurity removal distillation vessel 21 via a discharge pipe 30, the solution entering the adjacent upper-level impurity removal distillation vessel 21 and then entering the adjacent lower-level impurity removal distillation vessel 21 is mostly the clarified liquid after precipitation. Furthermore, the bottom of the adjacent lower-level impurity removal distillation vessel 21 is connected to the adjacent upper-level impurity removal distillation vessel 21 via a reflux pipe 40, thereby sequentially conveying the impurity turbid liquid from the bottom of the lower-level impurity removal distillation vessel 21 to the adjacent upper-level impurity removal distillation vessel 21. This not only reduces the amount of impurities in the adjacent lower-level impurity removal distillation vessel 21, but also reduces the amount of impurities discharged into the adjacent lower-level impurity removal distillation vessel 21. In addition, all particulate impurities in the lower-level impurity removal distillation vessels 21 eventually converge into the uppermost impurity removal distillation vessel 21. Therefore, when cleaning particulate impurities, only the impurities in the uppermost impurity removal distillation vessel 21 need to be cleaned. In summary, this invention treats impurities during the distillation of NMP, enabling simultaneous treatment of the re-precipitation of impurities from the NMP solution at a specific concentration. Moreover, the particulate impurity precipitation and reflux treatment method eliminates the need for a filtration mechanism, avoiding concerns about leakage caused by filter element breakage, and ensuring the stability and reliability of the purification process. Furthermore, the sedimentation and reflux method eliminates the need for frequent cleaning or replacement of filter elements. It only requires periodic cleaning of particulate impurities in the top-level impurity removal distillation vessel 21, which has the advantages of low cleaning cycle and low maintenance cost. In addition, it has the advantages of efficient cleaning process and no need to interrupt purification operation, so that impurities can be continuously removed without interrupting production, making it more suitable for large-scale industrial production.

[0032] In specific implementation, such as Figure 2As shown, the number of impurity removal distillation vessels 21 can be increased or decreased according to the content of particulate impurities in the specific NMP waste liquid. In this invention, it is preferable to set three impurity removal distillation vessels 21, which can be applied to most working conditions. The concentration of NMP solution in the three impurity removal distillation vessels 21 can be set to be different, so that particulate impurities can be basically precipitated under distillation at different concentrations. In addition, by precipitating particulate impurities in the second-stage impurity removal distillation vessel 21 and refluxing them back to the first-stage impurity removal distillation vessel 21, the impurity content in the second-stage impurity removal distillation vessel 21 can be kept at a low level. Thus, the impurity content in the third-stage impurity removal distillation vessel 21 fed into the second-stage impurity removal distillation vessel 21 is even lower. Subsequently, by refluxing impurities again in the third-stage impurity removal distillation vessel 21, the impurities precipitated in the third-stage impurity removal distillation vessel 21 and the impurities fed into the third-stage impurity removal distillation vessel 21 can be refluxed back to the second-stage impurity removal distillation vessel 21, so that the third-stage impurity removal distillation vessel 21 is in a state of almost no impurities.

[0033] Furthermore, such as Figure 2 As shown, two dehydration distillation kettles 61 are provided, which can not only further improve the efficiency of distillation and dehydration, but also allow the impurities that are not completely filtered to be precipitated again through the first-stage dehydration distillation kettle 61, so as to ensure that the NMP solution sent into the NMP new liquid tank 70 by the second-stage dehydration distillation kettle 61 has a higher purity.

[0034] In addition, such as Figure 2 As shown, both the top of the impurity removal distillation vessel 21 and the top of the water removal distillation vessel 61 are connected to condensers 50, and the condensers 50 connected to the adjacent upper-level impurity removal distillation vessel 21 are connected to the adjacent lower-level impurity removal distillation vessel 21. In this invention, instead of directly sending the condensate from the upper-level impurity removal distillation vessel 21 to the adjacent lower-level impurity removal distillation vessel 21 for collection, the condensate can stabilize the system operation to a certain extent. The condensate helps maintain the pressure balance between the distillation vessels, promotes gas flow and substance transfer, and thus helps improve the purification effect and the progressive increase in concentration. In addition, due to the pressure balancing effect brought about by the condensate, the reflux process may become more stable, facilitating further precipitation of particulate impurities, thereby further ensuring the removal effect of particulate impurities. At the same time, the water entering the lower-level impurity removal distillation vessel 21 may also play a certain auxiliary separation role in the entire purification process. To a certain extent, the presence of water can affect the boiling point and vapor pressure of different substances, thereby promoting the separation of NMP from other impurities. If the condensed water does not enter the adjacent downstream impurity removal distillation vessel 21, it may interfere with this separation mechanism, making it impossible to effectively remove some impurities and reducing the purity of the purified NMP.

[0035] The condenser 50 connected to the lowest-level impurity removal distillation vessel 21 and the condenser 50 connected to the water removal distillation vessel 61 are both connected to the drain tank 80, which ensures that the distillation and water removal process is carried out quickly and improves the purification efficiency of the equipment.

[0036] Based on the above, in this invention, the heating temperature of the impurity removal distillation vessel group 20 and the water removal distillation vessel group 60 is 120°C, and the condensation temperature of the condenser 50 is 7°C. This invention employs a multi-stage distillation column design, with five distillation columns connected in series, enabling the gradual purification of NMP waste liquid. Each distillation column treats specific impurities and concentration ranges, improving the overall purification effect and reducing dependence on high-temperature steam. For example, in the first-stage distillation column, some impurities can be initially separated, reducing the processing burden on subsequent distillation columns. This allows for effective purification at a relatively lower temperature; therefore, compared to the traditional 150°C distillation, this invention only requires 120°C, reducing energy consumption during the distillation process. Simultaneously, due to the lower distillation temperature, the condensation temperature of the condenser 50 does not need to be the traditional 5°C, but only 7°C, effectively reducing the energy consumption of post-distillation condensation.

[0037] Of course, those skilled in the art will recognize that the present invention is not limited to the details of the exemplary embodiments described above, but also includes the same or similar structures that can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0038] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0039] The technologies, shapes, and structures not described in detail in this invention are all known technologies.

Claims

1. A method for NMP purification, characterized in that, The purification device includes an NMP waste liquid tank (10), a purification distillation kettle group (20), a dehydration distillation kettle group (60), and an NMP fresh liquid tank (70) connected sequentially along the NMP solution conveying direction on a discharge pipeline (30). The purification distillation kettle group (20) includes at least two purification distillation kettles (21) connected sequentially. The bottom of each purification distillation kettle (21) is provided with a discharge pipeline for real-time discharge of impurities precipitated at the bottom. A concentration sensor is installed inside each purification distillation kettle (21). The middle of an adjacent upper-level purification distillation kettle (21) is connected to an adjacent lower-level purification distillation kettle (21) through a discharge pipeline (30). The bottom of an adjacent lower-level purification distillation kettle (21) is connected to an adjacent upper-level purification distillation kettle (21) through a reflux pipeline (40). The reflux pipeline (40) constitutes the discharge pipeline. The purification method includes the following steps: S1. The concentration of NMP in the solution in each impurity removal distillation vessel (21) is obtained in real time by the concentration sensor; S2. Based on the real-time obtained NMP concentration in the solution of the impurity removal distillation vessel (21), adjust the NMP concentration in the solution of each impurity removal distillation vessel (21) to the target concentration. In particular, along the flow direction from the NMP waste tank (10) to the NMP new tank (70), the target concentration of NMP in the solution of the adjacent impurity removal distillation vessel (21) increases sequentially. In addition, the bottom of the adjacent lower-level impurity removal distillation vessel (21) is returned to the upper-level impurity removal distillation vessel (21) through the return pipe (40), and the middle of the adjacent upper-level impurity removal distillation vessel (21) is sent to the adjacent lower-level impurity removal distillation vessel (21) through the discharge pipe (30), so that the impurities in the adjacent lower-level impurity removal distillation vessel (21) are gradually reduced. S3. Within one iteration time, based on the NMP concentration of the solution in the impurity removal distillation vessel (21) obtained in real time, the concentration growth rate of the impurity removal distillation vessel (21) within one iteration time is calculated, and the concentration growth rate is compared with the set threshold. S4. When the concentration growth rate is greater than the set threshold, increase the inlet flow rate and decrease the outlet flow rate of the impurity removal distillation vessel (21) so that the NMP concentration of the solution in the impurity removal distillation vessel (21) approaches the target concentration. In the next iteration after the NMP concentration of the solution in the impurity removal distillation vessel (21) reaches the target concentration, return to step S3. When the concentration growth rate is less than the set threshold, decrease the inlet flow rate and increase the outlet flow rate of the impurity removal distillation vessel (21) so that the NMP concentration of the solution in the impurity removal distillation vessel (21) approaches the target concentration. In the next iteration after the NMP concentration of the solution in the impurity removal distillation vessel (21) reaches the target concentration, return to step S3.

2. The NMP purification method according to claim 1, characterized in that, The target concentration of the solution in the lowest-level impurity removal distillation vessel (21) in step S1 is 90%.

3. The NMP purification method according to claim 1, characterized in that, The threshold set in step S3 is 0.

4. A purification apparatus, wherein the purification apparatus applies an NMP purification method as described in any one of claims 1-3, characterized in that, In the purification apparatus, there are three impurity removal distillation kettles (21).

5. The purification equipment according to claim 4, characterized in that, Two water-removing distillation kettles (61) are provided.

6. The purification equipment according to claim 5, characterized in that, The top of the impurity removal distillation vessel (21) and the top of the water removal distillation vessel (61) are both connected to condensers (50), and the condensers (50) connected to the adjacent upper-level impurity removal distillation vessel (21) are connected to the adjacent lower-level impurity removal distillation vessel (21). The condensers (50) connected to the lowest-level impurity removal distillation vessel (21) and the condensers (50) connected to the water removal distillation vessel (61) are both connected to the drain tank (80).

7. The purification equipment according to claim 6, characterized in that, The heating temperature of the impurity removal distillation vessel group (20) and the water removal distillation vessel group (60) is 120°C.

8. The purification equipment according to claim 6, characterized in that, The condenser (50) has a condensation temperature of 7°C.

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