Equipment for rectifying and purifying NMP mixed solution containing salt impurities

Abstract

The utility model provides rectification and purification equipment for an NMP (N-Methyl Pyrrolidone) mixed solution containing salt impurities. According to the equipment, the feeding end of the reduced-pressure rectifying tower is communicated with the microporous filter through the reduced-pressure feeding pipeline; the bottom discharging end of the reduced pressure rectifying tower is communicated with the outer circulation feeding end of the reduced pressure rectifying tower through a reduced pressure outer circulation pipe, the reduced pressure rectifying tower reboiler is arranged on the reduced pressure outer circulation pipe, and the evaporative crystallization device comprises a crystallization unit separator; the feeding end of the crystallization unit separator is communicated with the decompression outer circulating pipe through an evaporative crystallization feeding pipeline; the feeding end of the normal-pressure rectifying tower is communicated with the top gas-phase discharging end of the crystallization unit separator through a normal-pressure feeding pipeline; the bottom discharging end of the normal-pressure rectifying tower is communicated with the outer circulation feeding end of the normal-pressure rectifying tower through a normal-pressure outer circulation pipe, and the normal-pressure rectifying tower reboiler is arranged on the normal-pressure outer circulation pipe. The equipment does not need to use an extracting agent, and the normal-pressure rectifying tower reboiler is low in thermal load and relatively long in service life.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery slurry recovery, and in particular to a device for distilling and purifying a NMP mixed solution containing salt impurities. Background Art

[0002] During the slurry mixing process of lithium battery slurry, various factors such as slurry ratio, temperature, stirring speed, slurry mixing time, etc. may cause the lithium battery slurry to become scrapped and produce waste slurry. Since the waste slurry contains NMP and salt impurities, it will cause waste and pollute the environment if it is directly discarded.

[0003] For example, Chinese patent CN209721832U discloses a separation and recovery system of NMP in a saline solution, and specifically discloses an extraction device, a stripping tower, an extractant removal device, a crude NMP purification device, and a salt solution recovery device to achieve separation and recovery of salt impurities and NMP. Therefore, the above-mentioned separation and recovery system of NMP in a saline solution, through separation by extraction technology, makes the salt content in NMP ≤ 0.05%, and solves the problem of intermittent system and increased periodicity of cleaning due to salt enrichment in the tower kettle during recovery distillation.

[0004] However, the separation and recovery system of NMP in the above-mentioned salt solution needs to add an additional extractant, that is, a chemical extraction method, which not only causes a high separation cost, but also causes the wastewater generated by the separation of NMP to contain the extractant, which increases the difficulty of wastewater treatment. In addition, since the NMP enters the NMP recovery tower in liquid phase after extraction, the heat load of the reboiler of the NMP recovery tower is high, resulting in high energy consumption of the NMP recovery tower. Utility Model Content

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a device for distilling and purifying NMP mixed solution containing salt impurities, which can effectively remove salt impurities in NMP mixed solution by combining physical and heating methods, without using an extractant, thereby reducing separation costs and the difficulty of wastewater treatment; and reducing the heat load of the atmospheric distillation tower reboiler, while the salt impurities are not brought into the atmospheric distillation tower, which not only reduces the energy consumption of the atmospheric distillation tower reboiler, but also extends the service life of the atmospheric distillation tower reboiler.

[0006] The purpose of this disclosure is achieved through the following technical solutions:

[0007] A device for rectifying and purifying a NMP mixed solution containing salt impurities, comprising:

[0008] Microporous filter;

[0009] A vacuum distillation device, comprising a vacuum distillation tower and a vacuum distillation tower reboiler; the feed end of the vacuum distillation tower is connected to the microporous filter through a vacuum feed pipeline; the bottom discharge end of the vacuum distillation tower is connected to the external circulation feed end of the vacuum distillation tower through a vacuum external circulation pipe, and the vacuum distillation tower reboiler is arranged on the vacuum external circulation pipe;

[0010] An evaporation crystallization device, the evaporation crystallization device comprises a crystallization unit separator, and a feed end of the crystallization unit separator is connected to the pressure-reducing external circulation pipe through an evaporation crystallization feed pipeline;

[0011] An atmospheric distillation device, the atmospheric distillation device comprises an atmospheric distillation tower and an atmospheric distillation tower reboiler; the feed end of the atmospheric distillation tower is connected to the top gas phase discharge end of the crystallization unit separator through an atmospheric feed pipeline; the bottom discharge end of the atmospheric distillation tower is connected to the external circulation feed end of the atmospheric distillation tower through an atmospheric external circulation pipe, and the atmospheric distillation tower reboiler is arranged on the atmospheric external circulation pipe.

[0012] In one embodiment, the pore size of the microporous filter is 0.1 um to 5 um.

[0013] In one embodiment, the evaporation crystallization device also includes an evaporator feed preheater, a forced circulation pipeline, a heater and a slurry tank; the evaporator feed preheater is arranged on the evaporation crystallization feed pipeline of the crystallization unit separator; the bottom discharge end of the crystallization unit separator is connected to the circulation feed end of the crystallization unit separator through the forced circulation pipeline; the heater is arranged on the forced circulation pipeline; the slurry tank is connected to the forced circulation pipeline through the evaporation crystallization discharge pipeline.

[0014] In one embodiment, the vacuum distillation tower comprises a vacuum tower top and a vacuum tower kettle which are connected to each other; a vacuum packing part is detachably provided in the vacuum tower top; a vacuum tower plate is provided in the vacuum tower kettle, and a feed end of the vacuum distillation tower is provided between the vacuum tower kettle and the vacuum tower top; a bottom discharge end of the vacuum distillation tower is provided at the bottom of the vacuum tower kettle; and,

[0015] The atmospheric distillation tower comprises an atmospheric tower top and an atmospheric tower kettle which are connected to each other; an atmospheric packing part is detachably provided in the atmospheric tower top; an atmospheric tower plate is provided in the atmospheric tower kettle, and the feed end of the atmospheric distillation tower is provided between the atmospheric tower kettle and the atmospheric tower top; the bottom discharge end of the atmospheric distillation tower is provided at the bottom of the atmospheric tower kettle.

[0016] In one embodiment, the interior of the decompression packing portion is filled with wire mesh corrugated packing; and / or,

[0017] The vacuum packing part is mounted in the top of the vacuum tower; and / or,

[0018] The vacuum tower plate comprises a plurality of vacuum sieve plates, and the vacuum sieve plates are sequentially spaced from top to bottom.

[0019] In one embodiment, the NMP mixed solution distillation and purification equipment containing salt impurities also includes a steam waste heat recovery pipe assembly, the steam waste heat recovery pipe assembly includes a first waste heat recovery pipeline and a second waste heat recovery pipeline, the gas outlet end of the heater is respectively connected to the atmospheric distillation tower reboiler and the evaporator feed preheater through the first waste heat recovery pipeline, and the evaporator feed preheater is connected to the vacuum distillation tower feed preheater through the second waste heat recovery pipeline.

[0020] In one embodiment, the NMP mixed solution distillation purification equipment containing salt impurities further includes a centrifuge, and the feed end of the centrifuge is connected to the discharge end of the slurry tank through a centrifugal feed pipeline; and / or,

[0021] The NMP mixed solution rectification and purification equipment containing salt impurities also includes a cooling device, which includes a cooler and an NMP product buffer tank; the NMP product buffer tank is connected to the normal pressure external circulation pipe through a cooling feed pipe; the cooler is arranged on the cooling feed pipe, and / or,

[0022] The equipment for rectifying and purifying the NMP mixed solution containing salt impurities further comprises a raw material buffer tank, which is arranged on the reduced pressure feed pipeline.

[0023] In one embodiment, the NMP mixed solution distillation and purification equipment containing salt impurities also includes an atmospheric reflux device; the atmospheric reflux device includes an atmospheric distillation tower reflux tank, an atmospheric distillation tower reflux pump, a first reflux pipe assembly and a second reflux pipe assembly; the top gas phase discharge end of the atmospheric distillation tower is connected to the reflux inlet end of the vacuum distillation tower reboiler through the first reflux pipe assembly, and the reflux outlet end of the vacuum distillation tower reboiler is connected to the top liquid phase reflux end of the atmospheric distillation tower through the second reflux pipe assembly; the atmospheric distillation tower reflux tank and the atmospheric distillation tower reflux pump are sequentially connected and arranged on the second reflux pipe assembly, and the atmospheric distillation tower reflux tank is arranged on the side close to the vacuum distillation tower reboiler.

[0024] In one embodiment, the vacuum distillation device also includes a vacuum condenser, a vacuum reflux tank, a vacuum reflux pump and a third reflux pipe assembly; the top gas phase discharge end of the vacuum distillation tower is connected to the top liquid phase reflux end of the vacuum distillation tower through the third reflux pipe assembly; the vacuum condenser, the vacuum reflux tank and the vacuum reflux pump are sequentially connected and arranged on the third reflux pipe assembly.

[0025] In one embodiment, the NMP mixed solution distillation purification equipment containing salt impurities also includes a vacuum component, and the suction end of the vacuum component is connected to the suction end of the pressure reducing condenser through a vacuum air inlet pipeline.

[0026] Compared with the prior art, the present invention has at least the following advantages:

[0027] 1) Since the microporous filter is added to preliminarily filter the salt-containing impurities in the NMP mixed solution, it is effectively avoided that too many salt-containing impurities enter the vacuum distillation tower, causing too many salt-containing impurities to easily adhere to the surface of the vacuum distillation tower reboiler and affect the heat exchange efficiency of the vacuum distillation tower reboiler; and since the evaporation crystallization device is added to the atmospheric distillation tower and the vacuum distillation tower, the evaporation crystallization of the salt-containing impurities in the NMP mixed solution is realized, and the salt-containing impurities are more effectively removed to ensure that the gas phase NMP mixed solution entering the atmospheric distillation tower has very few salt impurities, effectively avoiding the problem that the atmospheric distillation tower reboiler is easy to precipitate crystal salt and cause the atmospheric distillation tower reboiler The problem of low heat exchange efficiency of the atmospheric distillation tower reboiler is effectively avoided, and the scaling cycle of the vacuum distillation tower reboiler and the atmospheric distillation tower reboiler is extended. In this way, the present invention utilizes a combination of physical and heating methods to effectively remove salt-containing impurities in the NMP mixed solution, which not only improves the purity of the NMP product, but also eliminates the need for an extractant and reduces the separation cost. The wastewater generated by the separation does not contain an extractant, thereby reducing the difficulty of wastewater treatment.

[0028] 2) Since the gas enters the atmospheric distillation tower in the gas phase after being processed by the crystallization unit separator, the heat load of the atmospheric distillation tower reboiler is effectively reduced, the energy consumption of the atmospheric distillation tower is reduced, and the service life of the atmospheric distillation tower reboiler is extended.

[0029] 3) Since the vacuum distillation tower adopts a combination of a detachable vacuum packing part and a vacuum plate, and cooperates with the atmospheric pressure packing part and atmospheric pressure plate of the atmospheric distillation tower, it is easy to clean the salt impurities adhering to the vacuum packing part and the atmospheric pressure packing part while improving the separation efficiency.

[0030] 4) The heater of the evaporation crystallization device still has a relatively high temperature of the steam condensate after heat exchange, and can heat the vacuum distillation tower feed preheater, atmospheric distillation tower reboiler and evaporator feed preheater through the steam waste heat recycling pipe assembly, thereby improving the utilization rate of steam thermal energy.

[0031] 5) The additional centrifuge effectively separates the lithium-containing salt impurities in the NMP mixed solution, and extracts lithium through the downstream process, thereby improving the recovery rate of the lithium element in the NMP mixed solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 This is a schematic diagram of the structure of one direction of a device for distilling and purifying a NMP mixed solution containing salt impurities according to an embodiment of the present disclosure;

[0034] Figure 2 for Figure 1 A partial enlarged view shown in the middle A;

[0035] Figure 3 for Figure 1 A partial enlarged view shown at B in the middle;

[0036] Figure 4 for Figure 1 A partial enlarged view shown at C in the middle.

[0037] Figure numerals: 10, distillation and purification equipment for NMP mixed solution containing salt impurities; 100, microporous filter; 200, raw material buffer tank; 310, vacuum distillation tower feed preheater; 320, vacuum distillation tower; 321, vacuum tower top; 3211, vacuum packing part; 322, vacuum tower kettle; 3221, vacuum tower plate; 323, feed end of vacuum distillation tower; 324, bottom discharge end of vacuum distillation tower; 325, top gas phase discharge end of vacuum distillation tower; 326, The top liquid phase reflux end of the vacuum distillation tower; 327, the external circulation feed end of the vacuum distillation tower; 330, the vacuum distillation tower kettle pump; 340, the vacuum external circulation pipe; 350, the vacuum distillation tower reboiler; 410, the evaporator feed preheater; 420, the crystallization unit separator; 421, the feed end of the crystallization unit separator; 422, the top gas phase discharge end of the crystallization unit separator; 423, the bottom discharge end of the crystallization unit separator; 424, the circulation feed end of the crystallization unit separator; 4 30, forced circulation pipeline; 440, heater; 450, slurry tank; 510, atmospheric distillation tower; 511, feed end of atmospheric distillation tower; 512, bottom discharge end of atmospheric distillation tower; 513, gas phase discharge end of atmospheric distillation tower; 514, liquid phase reflux end of atmospheric distillation tower; 515, external circulation feed end of atmospheric distillation tower; 516, atmospheric tower top; 517, atmospheric tower kettle; 520, atmospheric distillation tower kettle pump; 530, atmospheric external circulation pipe; 540, Atmospheric distillation tower reboiler; 610, cooler; 620, NMP product buffer tank; 710, first waste heat recovery pipeline; 720, second waste heat recovery pipeline; 800, centrifuge; 911, atmospheric distillation tower reflux tank; 912, atmospheric distillation tower reflux pump; 913, first reflux pipe assembly; 914, second reflux pipe assembly; 920, vacuum condenser; 930, vacuum reflux tank; 940, vacuum reflux pump; 950, third reflux pipe assembly; 960, vacuum assembly. DETAILED DESCRIPTION

[0038] In order to facilitate the understanding of the present disclosure, the present disclosure will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present disclosure are given in the drawings. However, the present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present disclosure more thoroughly and comprehensively understood.

[0039] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present disclosure. The terms used herein in the specification of the present disclosure are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0041] In order to better understand the technical solutions and beneficial effects of the present invention, the present invention is further described in detail below in conjunction with specific embodiments:

[0042] like Figures 1 to 3 As shown, an apparatus 10 for distilling and purifying a mixed NMP solution containing salt impurities in one embodiment includes a microporous filter 100, a vacuum distillation device, an evaporation crystallization device and a normal pressure distillation device. The vacuum distillation device includes a vacuum distillation tower 320 and a vacuum distillation tower reboiler 350; the feed end 323 of the vacuum distillation tower is connected to the microporous filter 100 through a vacuum feed pipeline; the vacuum distillation tower 320 is connected to the microporous filter 100, so that the additional microporous filter can preliminarily filter the saline impurities in the NMP mixed solution; and because the bottom discharge end 324 of the vacuum distillation tower is connected to the external circulation feed end 327 of the vacuum distillation tower through a vacuum external circulation pipe 340, the vacuum distillation tower reboiler 350 is arranged on the vacuum external circulation pipe 340, realizing the external circulation heating operation of the vacuum distillation tower 320 itself, so as to achieve the vacuum distillation operation, so as to effectively avoid the problem that too much saline impurities enter the vacuum distillation tower and cause too much saline impurities to easily adhere to the surface of the vacuum distillation tower reboiler and affect the heat exchange efficiency of the vacuum distillation tower reboiler.

[0043] The evaporation crystallization device includes a crystallization unit separator 420; the feed end 421 of the crystallization unit separator is connected to the reduced pressure external circulation pipe 340 through the evaporation crystallization feed pipeline, so that the NMP mixed solution containing salt impurities of the heavy component after passing through the reduced pressure distillation tower 320 will enter the crystallization unit separator 420 from the reduced pressure external circulation pipe 340; to ensure that the NMP mixed solution containing salt impurities of the heavy component can enter the crystallization unit separator 420 for evaporation and crystallization, more effectively remove the salt impurities, to ensure that the gas phase NMP mixed solution entering the atmospheric distillation tower 510 has very few salt impurities, effectively avoid the problem that the atmospheric distillation tower reboiler is easy to precipitate crystal salt and cause the atmospheric distillation tower reboiler heat exchange efficiency is low, and extend the scaling cycle of the vacuum distillation tower reboiler and the atmospheric distillation tower reboiler.

[0044] The atmospheric distillation device includes an atmospheric distillation tower 510 and an atmospheric distillation tower reboiler 540; the feed end 511 of the atmospheric distillation tower is connected to the top gas phase discharge end 422 of the crystallization unit separator through an atmospheric pressure feed pipeline; the gas phase enters the atmospheric distillation tower 510 after being processed by the crystallization unit separator 420, which effectively reduces the heat load of the atmospheric distillation tower reboiler 540 and the energy consumption of the atmospheric distillation tower 510, thereby extending the service life of the atmospheric distillation tower reboiler 540; and because the bottom discharge end 512 of the atmospheric distillation tower is connected to the external circulation feed end 515 of the atmospheric distillation tower through the atmospheric pressure external circulation pipe 530, the atmospheric distillation tower reboiler 540 is arranged on the atmospheric pressure external circulation pipe 530; the external circulation heating operation of the atmospheric distillation tower 510 itself is realized to achieve atmospheric distillation operation.

[0045] It can also be understood that the present disclosure utilizes a combination of physical and heating methods to achieve effective removal of salt-containing impurities in the NMP mixed solution, which not only improves the purity of the NMP product, but also eliminates the need for an extractant and reduces separation costs. The wastewater generated by the separation does not contain an extractant, reducing the difficulty of wastewater treatment.

[0046] Furthermore, since the components enter the atmospheric distillation tower 510 in the gas phase after being processed by the crystallization unit separator 420, the heat load of the atmospheric distillation tower reboiler 540 is effectively reduced, and at the same time, salt impurities are not brought into the atmospheric distillation tower reboiler 540, thereby extending the service life of the atmospheric distillation tower reboiler 540.

[0047] In one embodiment, the pore size of the microporous filter 100 is 0.1 um to 5 um. Since the pore size of the microporous filter 100 is 0.1 um to 5 um, the pore size is relatively precise, and the salt-containing impurities in the NMP mixed solution can be filtered more comprehensively.

[0048] In one embodiment, the NMP mixed solution containing salt impurities distillation purification equipment also includes a raw material buffer tank 200, and the raw material buffer tank 200 is arranged on the reduced pressure feed pipeline, so that the raw material buffer tank 200 can store the filtered NMP mixed solution containing salt impurities for standby use.

[0049] In one embodiment, the vacuum distillation device further includes a vacuum distillation tower feed preheater 310 and a vacuum distillation tower kettle pump 330; the vacuum distillation tower feed preheater 310 is arranged on the vacuum feed pipeline to preheat the NMP mixed solution containing salt impurities entering the vacuum distillation tower 320; it is conducive to completing the vacuum distillation operation. Since the vacuum distillation tower kettle pump 330 is arranged on the vacuum external circulation pipe 340, it is convenient to extract the NMP mixed solution containing salt impurities of the heavy component after distillation; so as to speed up the external circulation operation of the vacuum distillation tower 320, thereby speeding up the vacuum distillation operation.

[0050] In one embodiment, the vacuum distillation tower feed preheater 310 is formed with a vacuum feed end and a vacuum discharge end; the vacuum feed end is connected to the first end of the vacuum feed pipeline, and the vacuum discharge end is connected to the second end of the vacuum feed pipeline, thereby realizing the setting of the vacuum distillation tower feed preheater 310 in the vacuum feed pipeline.

[0051] In one embodiment, the heater 440 is formed with a forced circulation feed end and a forced circulation discharge end; the forced circulation feed end is connected to the first end of the forced circulation pipeline 430, and the forced circulation discharge end is connected to the second end of the forced circulation pipeline 430, thereby realizing the setting of the heater 440 in the forced circulation pipeline 430.

[0052] In one embodiment, the vacuum distillation tower reboiler 350 forms a vacuum external circulation feed end and a vacuum external circulation discharge end respectively; the vacuum external circulation feed end is connected to the first end of the vacuum external circulation pipe 340, and the vacuum external circulation discharge end is connected to the second end of the vacuum external circulation pipe 340, so as to realize the setting of the vacuum distillation tower reboiler 350 in the vacuum external circulation pipe 340.

[0053] In one embodiment, the atmospheric distillation device further includes an atmospheric distillation tower bottom pump 520, which is disposed on the atmospheric pressure external circulation pipe 530 to accelerate the extraction of the gaseous NMP after the atmospheric distillation operation and realize the rapid discharge of the gaseous NMP.

[0054] In one of the embodiments, the atmospheric distillation tower reboiler 540 forms an atmospheric pressure external circulation feed end and an atmospheric pressure external circulation discharge end respectively; the atmospheric pressure external circulation feed end is connected to the first end of the atmospheric pressure external circulation pipe 530, and the atmospheric pressure external circulation discharge end is connected to the second end of the atmospheric pressure external circulation pipe 530, so as to realize the setting of the atmospheric pressure distillation tower reboiler 540 in the atmospheric pressure external circulation pipe 530.

[0055] In one embodiment, the NMP mixed solution distillation purification equipment containing salt impurities also includes a cooling device, which includes a cooler 610 and an NMP product buffer tank 620; the NMP product buffer tank 620 is connected to the normal pressure external circulation pipe 530 through a cooling feed pipe; the cooler 610 is arranged on the cooling feed pipe to achieve cooling of the liquid phase NMP, so that the obtained NMP product is temporarily stored in the NMP product buffer tank 620.

[0056] Please also read Figure 4The evaporation crystallization device also includes an evaporator feed preheater 410, a forced circulation pipeline 430, a heater 440 and a crystal slurry tank 450; the evaporator feed preheater 410 is arranged on the evaporation crystallization feed pipe of the crystallization unit separator 420; the heating operation of the NMP mixed solution containing salt impurities of the heavy component flowing through the evaporator feed preheater 410 is realized; it is conducive to the evaporation crystallization of the NMP mixed solution containing salt impurities of the heavy component. The bottom discharge end 423 of the crystallization unit separator is connected with the circulation feed end 424 of the crystallization unit separator through the forced circulation pipeline 430; the heater 440 is arranged on the forced circulation pipeline 430; the heating circulation operation of the crystallization unit separator 420 itself is realized to fully ensure the gas-liquid separation effect of the NMP mixed solution containing salt impurities of the heavy component; the crystal slurry tank 450 is connected to the forced circulation pipeline 430 through the evaporation crystallization discharge pipeline, so that the separated concentrated slurry is temporarily stored in the crystal slurry tank 450.

[0057] In one embodiment, the evaporator feed preheater 410 is formed with an evaporation crystallization feed end and an evaporation crystallization discharge end, the evaporation crystallization feed end is connected to the first end of the evaporation crystallization feed pipeline; the evaporation crystallization discharge end is connected to the second end of the evaporation crystallization feed pipeline; so as to realize the setting of the evaporator feed preheater 410 in the evaporation crystallization feed pipeline.

[0058] like Figure 3 As shown, in one embodiment, the vacuum distillation tower 320 includes a vacuum tower top 321 and a vacuum tower bottom 322 connected to each other; a vacuum packing part 3211 is detachably provided in the vacuum tower top 321, which is convenient for the operator to disassemble and assemble the vacuum packing part 3211, so as to clean the salt impurities adhering to the vacuum packing part 3211, and at the same time improve the separation efficiency of the NMP mixed solution containing salt impurities; a detachable vacuum tower plate 3221 is provided in the vacuum tower bottom 322, which is convenient for the operator to disassemble and clean; the feed end 323 of the vacuum distillation tower is arranged between the vacuum tower bottom 322 and the vacuum tower top 321, so as to ensure that the feed end 323 of the vacuum distillation tower is arranged at a suitable height at the vacuum distillation tower 320, so as to realize a more comprehensive distillation separation of the NMP mixed solution containing salt impurities; the bottom discharge end 324 of the vacuum distillation tower is arranged at the bottom of the vacuum tower bottom 322, so as to facilitate the NMP mixed solution containing salt impurities of the heavy component to be discharged more quickly under the action of gravity.

[0059] In a preferred embodiment, the feed end 323 of the vacuum distillation tower is arranged at the middle position between the vacuum tower bottom 322 and the vacuum tower top 321 to ensure that the feed end 323 of the vacuum distillation tower is arranged at a better height in the vacuum distillation tower 320, so as to realize comprehensive distillation separation of the NMP mixed solution containing salt impurities.

[0060] Similarly, in one embodiment, the atmospheric distillation tower 510 also has a structure similar to that of the vacuum distillation tower 320. Specifically, the atmospheric distillation tower 510 includes an atmospheric tower top 516 and an atmospheric tower bottom 517 that are connected to each other; the atmospheric tower top 516 is provided with an atmospheric packing part that can be detachably arranged; the atmospheric tower bottom 517 is provided with an atmospheric tower plate, and the feed end 511 of the atmospheric distillation tower is arranged between the atmospheric tower bottom 517 and the atmospheric tower top 516; the bottom discharge end 512 of the atmospheric distillation tower is arranged at the bottom of the atmospheric tower bottom 517.

[0061] like Figure 1 , Figure 3 As shown, in one embodiment, the interior of the pressure reducing filler portion 3211 is filled with wire mesh corrugated filler. Due to the large specific surface area of ​​the wire mesh corrugated filler, the efficiency of gas-liquid exchange is effectively improved, thereby improving the separation efficiency of the NMP mixed solution containing salt impurities.

[0062] In one embodiment, the decompression filler portion 3211 is clamped in the decompression tower top 321, which is convenient for the operator to disassemble and clean.

[0063] In one embodiment, the vacuum tower plate 3221 includes a plurality of vacuum sieve plates, and the vacuum sieve plates are sequentially spaced from top to bottom to achieve better separation efficiency for the NMP mixed solution containing salt impurities.

[0064] Similarly, the normal pressure packing part also has a similar structure to the reduced pressure packing part 3211, so that, on the one hand, it is convenient for the operator to disassemble and clean it, and on the other hand, it improves the separation efficiency of the NMP mixed solution containing salt impurities.

[0065] like Figure 1 As shown, in one embodiment, the NMP mixed solution distillation and purification equipment 10 containing salt impurities further includes a steam waste heat recycling pipe assembly, which includes a first waste heat recycling pipeline 710 and a second waste heat recycling pipeline 720. The gas outlet of the heater 440 is respectively connected to the atmospheric distillation tower reboiler 540 and the evaporator feed preheater 410 through the first waste heat recycling pipeline 710, and the evaporator feed preheater 410 is connected to the vacuum distillation tower feed preheater 310 through the second waste heat recycling pipeline 720. Since the steam condensate of the heater 440 of the evaporation crystallization device still has a high temperature after heat exchange, it can be used to heat the vacuum distillation tower feed preheater 310, the atmospheric distillation tower reboiler 540 and the evaporator feed preheater 410, thereby improving the utilization rate of steam thermal energy.

[0066] In one embodiment, the atmospheric distillation tower reboiler 540 is also formed with a first steam waste heat inlet end, and the steam waste heat first inlet end is connected to the outlet end of the heater 440 through the first waste heat recovery pipeline 710, so as to realize the atmospheric distillation tower reboiler 540 to recover and utilize the steam waste heat of the heater 440.

[0067] In one embodiment, the evaporator feed preheater 410 is also formed with a second steam waste heat inlet end and a first waste heat outlet end. The second steam waste heat inlet end is connected to the outlet end of the heater 440 through the first waste heat recycling pipeline 710, and the first waste heat outlet end is connected to the third steam waste heat inlet end of the vacuum distillation tower feed preheater 310 through the second waste heat recycling pipeline 720. The second steam waste heat outlet end of the vacuum distillation tower feed preheater 310 is used for external pipeline connection to realize the recovery and utilization of steam waste heat of the heater 440 by the evaporator feed preheater 410 and the vacuum distillation tower feed preheater 310.

[0068] like Figure 1 As shown, in one embodiment, the NMP mixed solution containing salt impurities distillation purification equipment 10 further includes a centrifuge 800, and the feed end of the centrifuge 800 is connected to the discharge end of the slurry tank 450 through a vacuum air inlet pipeline. The additional centrifuge 800 ensures that the pressure in the vacuum distillation tower 320 reaches the set pressure, which is conducive to separating the lithium-containing salt impurities in the NMP mixed solution, and extracting lithium through the downstream process, thereby improving the recovery rate of the lithium element in the NMP mixed solution.

[0069] like Figure 1As shown, in one embodiment, the NMP mixed solution distillation and purification equipment 10 containing salt impurities also includes an atmospheric reflux device; the atmospheric reflux device includes an atmospheric distillation tower reflux tank 911, an atmospheric distillation tower reflux pump 912, a first reflux pipe assembly 913 and a second reflux pipe assembly 914; the top gas phase discharge end 513 of the atmospheric distillation tower is connected to the reflux inlet end of the vacuum distillation tower reboiler 350 through the first reflux pipe assembly 913, and the reflux outlet end of the vacuum distillation tower reboiler 350 is connected to the top liquid phase reflux end 514 of the atmospheric distillation tower through the second reflux pipe assembly 914; the atmospheric distillation tower reflux tank 911 and the atmospheric distillation tower reflux pump 912 are sequentially arranged on the second reflux pipe assembly 914, and the atmospheric distillation tower reflux tank 911 is arranged on the side close to the vacuum distillation tower reboiler 350. The atmospheric reflux device is added, so that the steam at the top of the atmospheric distillation tower 510 will flow back from the top gas phase discharge end 513 of the atmospheric distillation tower into the vacuum distillation tower reboiler 350 for heat exchange, saving energy consumption and further improving the utilization rate of steam thermal energy. The condensate produced after the heat exchange in the vacuum distillation tower reboiler 350 enters the atmospheric distillation tower reflux tank 911 for temporary storage, and can be used as the reflux liquid at the top of the atmospheric distillation tower 510, thereby reducing the COD of the tower top condensate, so that the tower top wastewater can be used by downstream processes, and improving the reuse rate of wastewater.

[0070] like Figure 1 As shown, in one embodiment, the vacuum distillation device also includes a vacuum condenser 920, a vacuum reflux tank 930, a vacuum reflux pump 940 and a third reflux pipe assembly 950; the top gas phase discharge end 325 of the vacuum distillation tower is connected to the top liquid phase reflux end 326 of the vacuum distillation tower through the third reflux pipe assembly 950; the vacuum condenser 920, the vacuum reflux tank 930, and the vacuum reflux pump 940 are sequentially connected and arranged on the third reflux pipe assembly 950. The newly added vacuum condenser 920 allows the steam from the vacuum tower top 321 of the vacuum distillation tower 320 to enter the vacuum condenser 920 from the top gas phase discharge end 325 of the vacuum distillation tower, and then enter the vacuum reflux tank 930 for temporary storage after being cooled and liquefied by the vacuum condenser 920. It can be used as the reflux liquid at the top of the vacuum distillation tower 320, thereby reducing the COD of the top condensate, so that the top wastewater can be used by downstream processes, thereby improving the reuse rate of wastewater.

[0071] In one embodiment, the third reflux pipe assembly 950 includes a first reflux sub-tube, a second reflux sub-tube, a third reflux sub-tube and a fourth reflux sub-tube; the reduced pressure condenser 920 is respectively formed with a return gas inlet end and a cooling liquid outlet end, the top gas phase discharge end 325 of the reduced pressure distillation tower is connected with the return gas inlet end of the reduced pressure condenser 920 through the first reflux sub-tube, the cooling liquid outlet end of the reduced pressure condenser 920 is connected with the reduced pressure reflux tank 930 through the second reflux sub-tube, the reduced pressure reflux tank 930 is connected with the reduced pressure reflux pump 940 through the third reflux sub-tube, and the reduced pressure reflux pump 940 is connected with the top liquid phase reflux end 326 of the reduced pressure distillation tower through the fourth reflux sub-tube to realize the cooling circulation reflux setting of the reduced pressure distillation tower 320.

[0072] like Figure 1 As shown, in one embodiment, the NMP mixed solution distillation purification equipment 10 containing salt impurities also includes a vacuum component 960, and the reduced pressure condenser 920 is also formed with a suction end. The suction end of the vacuum component 960 is connected to the suction end of the reduced pressure condenser 920 through a vacuum air inlet pipeline, so as to realize the vacuum operation of the reduced pressure distillation tower 320 to meet the pressure requirement of the reduced pressure distillation tower 320.

[0073] Working principle, the NMP mixed solution distillation purification equipment 10 containing salt impurities comprises the following steps:

[0074] Step 1: First, the NMP mixed solution containing salt impurities produced in the previous stage is filtered through a microporous filter 100, and the obtained filtrate is put into a raw material buffer tank 200 for temporary storage;

[0075] Step 2: Open the vacuum distillation tower 320 and the vacuum assembly 960 to make the pressure in the vacuum distillation tower 320 reach 10kpa-25kpa;

[0076] Step 3: After the vacuum distillation tower feed preheater 310 is preheated to a certain temperature, it enters the vacuum distillation tower 320, and the vacuum distillation tower reboiler 350 is started, and refluxes for 1h-1.5h. The number of theoretical plates of the vacuum distillation tower 320 is controlled to be 14-28, the packing height is 3m-6m, the molar reflux ratio is 0.1-0.5, the temperature of the vacuum tower top 321 is 55℃-65℃, and the temperature of the vacuum tower bottom 322 is 65℃-75℃; at this time, the gas phase discharge end 325 of the vacuum distillation tower top produces gas phase wastewater, wherein the NMP concentration of the light component solution produced by the vacuum distillation tower top gas phase discharge end 325 should be no more than 0. 1%; and cooled and refluxed to the vacuum reflux tank 930 through the vacuum condenser 920 for standby; and the NMP mixed solution containing salt impurities in the vacuum distillation tower 320 flows into the evaporator feed preheater 410 through the vacuum distillation tower kettle pump 330 for preheating and then enters the crystallization unit separator 420 for gas-liquid separation, and the gas phase enters the atmospheric distillation tower 510 for further distillation and dehydration, and part of the liquid phase enters the heater 440, and the heating temperature of the heater 440 is 118°C-138°C; part of the liquid phase is extracted to the slurry tank 450, stirred and cooled, and then transported to the centrifuge 800 by the slurry pump, and extracted after centrifugal separation to obtain salt crystals;

[0077] Step 4: The gaseous NMP mixture enters the atmospheric distillation tower 510 for distillation from the crystallization unit separator 420. The number of theoretical plates of the atmospheric distillation tower 510 is 18-32, the packing height is 4m-8m, the molar reflux ratio is 0.1-0.5, the temperature of the atmospheric tower top 516 is 100°C-105°C, and the temperature of the atmospheric tower bottom 517 is 145°C-205°C; when the atmospheric tower bottom 517 NMP concentration of the atmospheric distillation tower 510 is The degree is 90%-99%, and the gaseous NMP in the atmospheric tower kettle 517 of the atmospheric distillation tower 510 is pumped into the cooler 610 for cooling and temporarily stored in the NMP product buffer tank 620; the light component of the atmospheric tower top 516 of the atmospheric distillation tower 510 is mainly water, and the NMP concentration is 0.09%. After cooling, it merges with the wastewater produced from the vacuum tower top 321 of the vacuum distillation tower 320 into the wastewater pipeline and is discharged through the wastewater pipeline.

[0078] Compared with the prior art, the present invention has at least the following advantages:

[0079] 1) Since the microporous filter 100 is added to preliminarily filter the salt impurities in the NMP mixed solution, it is effectively avoided that too many salt impurities enter the vacuum distillation tower 320, causing too many salt impurities to easily adhere to the surface of the vacuum distillation tower reboiler 350 and affect the heat exchange efficiency of the vacuum distillation tower reboiler 350; and since an evaporation crystallization device is added to the atmospheric distillation tower 510 and the vacuum distillation tower 320, the evaporation crystallization of the salt impurities in the NMP mixed solution is realized, and the salt impurities are more effectively removed to ensure that the gas phase NMP mixed solution entering the atmospheric distillation tower 510 has very few salt impurities, effectively avoiding the problem that the atmospheric distillation tower reboiler 540 is easy to precipitate crystal salt and cause the atmospheric distillation tower reboiler 540 The problem of low heat exchange efficiency of the atmospheric distillation tower reboiler 540 is effectively avoided, and the scaling cycle of the vacuum distillation tower reboiler 350 and the atmospheric distillation tower reboiler 540 is extended. In this way, the present invention utilizes a combination of physical and heating methods to effectively remove salt-containing impurities in the NMP mixed solution, which not only improves the purity of the NMP product, but also eliminates the need for an extractant, reduces separation costs, and the wastewater generated by the separation does not contain an extractant, reducing the difficulty of wastewater treatment.

[0080] 2) Since the gas enters the atmospheric distillation tower 510 in the gas phase after being processed by the crystallization unit separator 420, the heat load of the atmospheric distillation tower reboiler 540 is effectively reduced, the energy consumption of the atmospheric distillation tower 510 is reduced, and the service life of the atmospheric distillation tower reboiler 540 is extended.

[0081] 3) Since the vacuum distillation tower 320 adopts a combination of a detachable vacuum packing part 3211 and a vacuum plate 3221, and cooperates with the atmospheric pressure packing part and atmospheric pressure plate of the atmospheric distillation tower 510, it is easy to clean the salt impurities adhering to the vacuum packing part 3211 and the atmospheric pressure packing part while improving the separation efficiency.

[0082] 4) The steam condensate of the heater 440 of the evaporation crystallization device is still at a relatively high temperature after heat exchange, and can be used to heat the vacuum distillation tower feed preheater 310, the atmospheric distillation tower reboiler 540 and the evaporator feed preheater 410 through the steam waste heat recycling pipe assembly, thereby improving the utilization rate of steam thermal energy.

[0083] 5) The additional centrifuge 800 effectively separates the lithium-containing salt impurities in the NMP mixed solution, and extracts lithium through the downstream process, thereby improving the recovery rate of the lithium element in the NMP mixed solution.

[0084] The above embodiments only express several implementation methods of the present disclosure, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the utility model patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present disclosure, and these all belong to the protection scope of the present disclosure. Therefore, the protection scope of the patent of the present disclosure shall be subject to the attached claims.

Claims

1. A device for rectifying and purifying a mixed solution of NMP containing salt impurities, characterized in that: include: Microporous filter (100); A vacuum distillation device, comprising a vacuum distillation tower (320) and a vacuum distillation tower reboiler (350); a feed end (323) of the vacuum distillation tower is connected to the microporous filter (100) via a vacuum feed pipeline; a bottom discharge end (324) of the vacuum distillation tower is connected to an external circulation feed end (327) of the vacuum distillation tower via a vacuum external circulation pipe (340), and the vacuum distillation tower reboiler (350) is arranged on the vacuum external circulation pipe (340); An evaporation crystallization device, the evaporation crystallization device comprising a crystallization unit separator (420), wherein a feed end (421) of the crystallization unit separator is connected to the pressure-reducing external circulation pipe (340) via an evaporation crystallization feed pipeline; An atmospheric distillation device, comprising an atmospheric distillation tower (510) and an atmospheric distillation tower reboiler (540); the feed end (511) of the atmospheric distillation tower is connected to the top gas phase discharge end (422) of the crystallization unit separator through an atmospheric feed pipeline; the bottom discharge end (512) of the atmospheric distillation tower is connected to the external circulation feed end (515) of the atmospheric distillation tower through an atmospheric external circulation pipe (530), and the atmospheric distillation tower reboiler (540) is arranged on the atmospheric external circulation pipe (530).

2. The NMP mixed solution rectification and purification equipment containing saline impurities according to claim 1, characterized in that: The pore size of the microporous filter (100) is 0.1 um to 5 um.

3. The NMP mixed solution rectification and purification equipment containing saline impurities according to claim 1, characterized in that, The evaporation crystallization device also includes an evaporator feed preheater (410), a forced circulation pipeline (430), a heater (440) and a slurry tank (450); the evaporator feed preheater (410) is arranged on the evaporation crystallization feed pipeline; the bottom discharge end (423) of the crystallization unit separator is connected to the circulation feed end (424) of the crystallization unit separator through the forced circulation pipeline (430); the heater (440) is arranged on the forced circulation pipeline (430); the slurry tank (450) is connected to the forced circulation pipeline (430) through the evaporation crystallization discharge pipeline.

4. The NMP mixed solution rectification and purification equipment containing saline impurities according to claim 1, characterized in that: The vacuum distillation tower (320) comprises a vacuum tower top (321) and a vacuum tower bottom (322) which are connected to each other; a vacuum packing part (3211) is detachably provided in the vacuum tower top (321); a vacuum tower plate (3221) is provided in the vacuum tower bottom (322); a feed end (323) of the vacuum distillation tower is provided between the vacuum tower bottom (322) and the vacuum tower top (321); a bottom discharge end (324) of the vacuum distillation tower is provided at the bottom of the vacuum tower bottom (322); and, The atmospheric distillation tower (510) comprises an atmospheric tower top (516) and an atmospheric tower bottom (517) which are connected to each other; an atmospheric packing part is detachably provided in the atmospheric tower top (516); an atmospheric tower plate is provided in the atmospheric tower bottom (517); a feed end (511) of the atmospheric distillation tower is provided between the atmospheric tower bottom (517) and the atmospheric tower top (516); and a bottom discharge end (512) of the atmospheric distillation tower is provided at the bottom of the atmospheric tower bottom (517).

5. The NMP mixed solution rectification and purification equipment containing saline impurities according to claim 4, characterized in that, The interior of the decompression packing part (3211) is filled with wire mesh corrugated packing; and / or, The decompression packing part (3211) is mounted in the decompression tower top (321); and / or, The vacuum tower plate (3221) includes a plurality of vacuum sieve plates, and the vacuum sieve plates are arranged in sequence from top to bottom.

6. The NMP mixed solution rectification and purification equipment containing salt impurities according to claim 3, characterized in that: The NMP mixed solution distillation and purification equipment containing salt impurities also includes a steam waste heat recycling pipe assembly, and the steam waste heat recycling pipe assembly includes a first waste heat recycling pipeline (710) and a second waste heat recycling pipeline (720). The gas outlet end of the heater (440) is respectively connected to the atmospheric distillation tower reboiler (540) and the evaporator feed preheater (410) through the first waste heat recycling pipeline (710), and the evaporator feed preheater (410) is connected to the vacuum distillation tower feed preheater (310) through the second waste heat recycling pipeline (720).

7. The NMP mixed solution rectification and purification equipment containing salt impurities according to claim 3, characterized in that: The NMP mixed solution rectification and purification equipment containing salt impurities further comprises a centrifuge (800), the feed end of the centrifuge (800) is connected to the discharge end of the slurry tank (450) via a centrifugal feed pipeline; and / or, The NMP mixed solution rectification and purification equipment containing salt impurities further comprises a cooling device, wherein the cooling device comprises a cooler (610) and an NMP product buffer tank (620); the NMP product buffer tank (620) is connected to the normal pressure external circulation pipe (530) via a cooling feed pipe; the cooler (610) is arranged on the cooling feed pipe, and / or, The NMP mixed solution rectification and purification equipment containing salt impurities further comprises a raw material buffer tank (200), and the raw material buffer tank (200) is arranged on the reduced pressure feed pipeline.

8. The equipment for rectifying and purifying a mixed solution of NMP containing salt impurities according to any one of claims 1 to 7, characterized in that: The NMP mixed solution rectification and purification equipment containing salt impurities also includes an atmospheric reflux device, which includes an atmospheric distillation tower reflux tank (911), an atmospheric distillation tower reflux pump (912), a first reflux pipe assembly (913) and a second reflux pipe assembly (914); the top gas phase discharge end (513) of the atmospheric distillation tower is connected to the reflux inlet of the vacuum distillation tower reboiler (350) through the first reflux pipe assembly (913). The reflux outlet end of the vacuum distillation tower reboiler (350) is connected to the tower top liquid phase reflux end (514) of the atmospheric distillation tower through the second reflux pipe assembly (914); the atmospheric distillation tower reflux tank (911) and the atmospheric distillation tower reflux pump (912) are sequentially arranged on the second reflux pipe assembly (914), and the atmospheric distillation tower reflux tank (911) is arranged on a side close to the vacuum distillation tower reboiler (350).

9. The NMP mixed solution rectification and purification equipment containing salt impurities according to claim 8, characterized in that: The vacuum distillation device further comprises a vacuum condenser (920), a vacuum reflux tank (930), a vacuum reflux pump (940) and a third reflux pipe assembly (950); the top gas phase discharge end (325) of the vacuum distillation tower is connected to the top liquid phase reflux end (326) of the vacuum distillation tower through the third reflux pipe assembly (950); the vacuum condenser (920), the vacuum reflux tank (930) and the vacuum reflux pump (940) are sequentially connected and arranged on the third reflux pipe assembly (950).

10. The NMP mixed solution rectification and purification equipment containing salt impurities according to claim 9, characterized in that: The equipment for rectifying and purifying a mixed solution of NMP containing salt impurities further comprises a vacuum component (960), and a suction end of the vacuum component (960) is connected to a suction end of the reduced pressure condenser (920) via a vacuum air inlet pipeline.

Images