Magnetic substance filtering device and process suitable for lithium battery raw material production

Abstract

The invention discloses a magnetic substance filtering device and process suitable for lithium battery raw material production, and relates to the technical field of precision filtering equipment, the magnetic substance filtering device comprises a buffer pool, a precision filter, a sludge pool and a clear liquid pool, the precision filter comprises an upper cylinder, a micro-filtration membrane pipe group and a lower cylinder, the upper cylinder is provided with a clear liquid return valve and an overflow pipe, and the lower cylinder is provided with a filter screen; the lower cylinder is provided with a pumping liquid inlet pipe and a backflushing return pipe, a liquid inlet return valve is arranged on the lower cylinder, a plurality of end openings, extending into the lower cylinder, of the pumping liquid inlet pipe are arranged in a cross flow mode, the microfiltration membrane pipe set comprises a connecting part and a membrane pipe, and a plurality of disturbing protrusions are distributed on the peripheral wall of the membrane pipe. The water flow impact direction of the pumping liquid inlet pipe and the direction of the membrane pipe are arranged in a staggered mode, a supporting mechanism is arranged on the membrane pipe, the membrane pipe is a porous expanded polytetrafluoroethylene membrane, and an auxiliary backflushing assembly is arranged in the lower cylinder body. The whole device is reasonable in layout and precise in filtration, weakly magnetic and insoluble impurities in the solution are effectively reduced, and the purity of the lithium battery raw material solution is improved.

Description

Technical Field

[0001] The invention relates to the technical field of precision filtering equipment. Background Art

[0002] Battery-grade lithium carbonate, lithium phosphate, lithium hydroxide, iron phosphate, etc. are raw materials for the production of lithium batteries. They are mainly used to prepare lithium cobalt oxide, lithium manganese oxide, ternary materials and lithium iron phosphate and other lithium-ion battery positive electrode materials. When magnetic substances such as Fe, Cr and Zn exist in the positive electrode materials, magnetic impurity particles may cause short circuits during the battery charging and discharging process, causing the battery to heat up, burn or even explode. These magnetic impurity particles (such as metal elements such as Fe, Cr, Zn, Ni) usually exist in the form of tiny particles. During the battery charging and discharging process, organic substances in the electrolyte may aggregate and grow with magnetic particles as the matrix to form edges or spikes. These particles move to the negative electrode for reduction after oxidation at the positive electrode, and may pierce the battery diaphragm, causing internal short circuits and rapid self-discharge. This causes the battery to self-discharge, bulge, and even cause short circuits and explosions. The higher the content of magnetic substances in the lithium battery, the greater its self-discharge rate. The presence of magnetic impurities will reduce the specific capacity and energy density of the battery material. Some magnetic impurities will also react with the electrolyte, affecting the consistency, service life and safety of the battery.

[0003] At present, magnetic rod filters are usually used for filtration, which is not effective for non-ferromagnetic substances or weak ferromagnetic substances. It is difficult to achieve deep magnetic reduction effects only through physical adsorption, resulting in the inability to guarantee the safety of batteries made from this battery-grade lithium carbonate material. Therefore, it is necessary to develop a new type of magnetic material filtration device and filtration process. Summary of the invention

[0004] The purpose of the present invention is to solve the above technical problems. The present invention provides a magnetic material filtering process suitable for the production of lithium battery raw materials, which is easy to operate and has good filtering effect.

[0005] In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions:

[0006] A magnetic material filtering process suitable for lithium battery raw material production comprises the following steps:

[0007] Step S1: preparing the stock solution, performing preliminary filtration, and reducing magnetic impurities;

[0008] Step S2: the stock solution is injected into the buffer tank for initial sedimentation;

[0009] Step S3: extract the supernatant from the buffer tank and pump it to the precision filter, open the pressure relief pipeline, and allow the impurities to flow back;

[0010] Step S4: close the pressure relief pipeline, open the upper clear liquid reflux, and stabilize the system;

[0011] Step S5: After the system is stable, the upper clear liquid reflux is closed, and the clear liquid flows along the overflow pipe to the clear liquid tank;

[0012] Step S6: After running for a certain period of time, open the backflush valve to clean the filter cake;

[0013] Step S7: perform slag removal, and repeat step S3 after slag removal.

[0014] Through the above scheme, the raw liquid is initially filtered to remove large particles of magnetic impurities, and then passed into the buffer tank for buffering and sedimentation, and then the upper clear liquid is extracted and pumped to the precision filter, and the pressure relief pipeline is opened. At this time, the fine suspended matter on the liquid surface in the filter returns to the buffer tank from the pressure relief port, and then the pressure relief pipeline is closed, the liquid level rises to open the upper clear liquid reflux, and the accuracy in the initial stage of filtration is difficult to meet the requirements. The clear liquid returns to the buffer tank along the upper clear liquid reflux pipeline. After the system is stable and the filtration progress meets the requirements, the upper clear liquid reflux is closed, and the clear liquid overflow pipe flows to the clear liquid tank by gravity. The system runs for a period of time, the backwash valve is opened, the filter cake is cleaned, and the filter cake accumulates to a certain extent for slag discharge, and then step S3 is continued. The whole process is reasonably planned to avoid large particles of suspended matter from entering the clear liquid tank as much as possible, improve the filtration performance of magnetic impurities and other impurities, and improve the purity of the battery raw material solution.

[0015] Furthermore, in step S5, the filtration pressure does not exceed 0.1 MPa.

[0016] Through the above scheme, low-pressure operation is achieved, which facilitates the maintenance of stable operation of the device, avoids damage due to excessive pressure during use, and prevents deformable linear particles from being squeezed into the membrane pores.

[0017] Furthermore, the precision filter is cleaned once every 12 hours using regeneration fluid.

[0018] Through the above scheme, regular use of regeneration liquid for cleaning can effectively reduce the accumulation of filter cakes in the precision filter and increase the continuous operation time of the device.

[0019] The second purpose of the present invention is to provide a magnetic material filtering device suitable for the production of lithium battery raw materials, which has a novel structure, is easy to operate, and has precise filtration. It effectively reduces weak magnetic and insoluble impurities in the solution, improves the purity of the lithium battery raw material solution, and effectively improves the safety of the raw materials.

[0020] A magnetic material filtering device suitable for the production of lithium battery raw materials, comprising a buffer tank, a precision filter, a sludge tank, and a clear liquid tank. The precision filter comprises an upper cylinder, a microfiltration membrane tube group, and a lower cylinder. The upper cylinder is provided with a clear liquid reflux valve and an overflow pipe leading to the clear liquid tank, the lower cylinder is provided with a pumping inlet pipe leading to the buffer tank and a recoil reflux pipe with a valve, the output end of the clear liquid reflux valve is connected to the recoil reflux pipe through a tee, the end opening of the pumping inlet pipe extending into the lower cylinder is provided with multiple openings and adopts a cross-flow setting, the microfiltration membrane tube group comprises a connecting portion located at the upper end and a plurality of membrane tubes arranged on the connecting portion, the outer peripheral wall of the membrane tube is distributed with a plurality of interfering flow protrusions, the water flow impact direction of the pumping inlet pipe is staggered with the direction of the membrane tube, a supporting mechanism is provided on the membrane tube, the membrane tube is a porous expanded polytetrafluoroethylene film, and an auxiliary recoil assembly is provided in the lower cylinder.

[0021] Through the above scheme, the solution enters the buffer tank for preliminary buffering and stabilization, and then is pumped into the lower cylinder through the liquid inlet pipe. There are multiple openings and a cross-flow setting is adopted to disrupt the direction of water flow, reduce the impact of water flow on the membrane tube, reduce the deformation of linear particles that are easily deformed from being squeezed into the membrane pores, and reduce the accumulation of easily adhered substances on the membrane surface. As the water flow increases, the shear force of the water flow on the membrane surface increases, and the volatile solids accumulated on the membrane surface are taken away, and the concentration polarization is weakened, which is conducive to the stable operation of the equipment. The recoil reflux pipe is opened to guide the upper scum on the liquid surface into the buffer tank, and then the recoil reflux pipe is closed. The liquid level passes through the microfiltration membrane tube group upward and enters the upper cylinder, that is, the solution enters. At this time, the purity of the filtrate is insufficient, and the cleaning is opened. The liquid reflux valve refluxes the primary filtered liquid in the upper cylinder to the buffer tank. After running for a period of time and the system is stable, when the purity of the clear liquid in the upper cylinder meets the requirements, the clear liquid reflux valve is closed and the filtrate enters the clear liquid tank along the overflow pipe. After the system runs for a period of time, the recoil reflux pipe is opened, and the liquid level in the lower cylinder drops rapidly. The clear liquid in the upper cylinder recoils the membrane tube, and the filter cake accumulated on the periphery of the membrane tube of the lower cylinder is recoiled, which is convenient for flushing the filter cake. At the same time, the auxiliary recoil component is opened to improve the cleaning efficiency. The whole device has a reasonable layout, stable operation, precise filtration, and effectively reduces weak magnetic and insoluble impurities in the solution, improves the purity of the lithium battery raw material solution, and effectively improves the safety of the raw materials.

[0022] Furthermore, the microfiltration membrane tube group includes a cover plate with a middle opening, a porous plate, and a rubber sealing ring. The outer edge of the connecting portion is embedded between the porous plate and the rubber sealing ring. The cover plate and the rubber sealing ring are fixed between the upper cylinder and the lower cylinder.

[0023] Through the above scheme, the cover plate cooperates with the porous plate and the rubber sealing ring to fix the connection part and provide stable support for the connection part. The porous plate is arranged to facilitate the introduction of clear liquid into the upper cylinder, and the whole structure is tightly sealed.

[0024] Furthermore, the support mechanism includes a support frame arranged in the membrane tube and a fixing clamp located at the lower end of the outer wall of the membrane tube, the fixing clamp is fixed to the connecting part, and guide grooves are distributed along the length direction on the support frame.

[0025] Through the above scheme, a supporting frame and a fixed clamping ring are provided to facilitate maintaining the posture of the membrane tube and reduce deformation and folding of the membrane tube. At the same time, a guide groove is provided to facilitate guiding the clear liquid in the membrane tube. The whole mechanism has a good supporting effect and is conducive to maintaining the long-term operation of the membrane tube.

[0026] Furthermore, a pressure gauge is provided on the lower cylinder, a slag discharge valve leading to the sludge pool is provided at the bottom end of the lower cylinder, and a regeneration liquid interface is provided at the lower end of the lower cylinder.

[0027] Through the above scheme, a pressure gauge is set to observe the pressure in the lower cylinder, so as to judge the degree of filter cake accumulation. At the same time, a slag discharge valve is set to discharge the filter cake under backwashing. At the same time, a regeneration liquid interface is set to facilitate the introduction of regeneration liquid to clean the device.

[0028] Furthermore, the auxiliary recoil assembly includes a recoil nozzle array on the inner wall of the lower cylinder, the recoil nozzle is inclined toward the membrane tube, the outer peripheral wall of the lower cylinder is provided with an annular tube, the annular tube is connected to the pumping liquid inlet pipe through a pipeline, and an electromagnetic three-way valve is provided at the connection between the annular tube and the pumping liquid inlet pipe.

[0029] Through the above scheme, the recoil reflux pipe is opened, the liquid level in the lower cylinder drops rapidly, and the clear liquid in the upper cylinder recoils the membrane tube. After the liquid level is lowered, the electromagnetic three-way valve controls the liquid inlet pipe to introduce the liquid into the annular pipe, prompting the solution to spray from the recoil nozzle to the membrane tube, impacting the filter cake residue, and further improving the recoil effect of the device.

[0030] Furthermore, the membrane tubes are arranged in a staggered manner, and the backflushing nozzles are evenly arranged toward each membrane tube.

[0031] Through the above scheme, the membrane tubes are staggered to increase the contact space between the membrane tubes and the solution, and the backwash nozzles are evenly arranged toward each membrane tube, thereby improving the effect of the backwash nozzles in flushing the filter cake.

[0032] Furthermore, a plurality of nozzles are provided at the water outlet end of the recoil nozzle, and the nozzles are arranged in a vertical direction and are distributed along the length direction of the membrane tube.

[0033] Through the above scheme, the nozzle direction is distributed along the length direction of the membrane tube, which is convenient for forming a jet flow covering the membrane tube, providing comprehensive coverage and improving the cleaning effect.

[0034] 1. The treatment process of the present invention is reasonably designed. The raw liquid is filtered to remove large particles of magnetic impurities through the initial filtration, and then passed into the buffer tank for buffering and sedimentation. Then the upper clear liquid is extracted and pumped to the precision filter, and the pressure relief pipeline is opened. At this time, the fine suspended matter on the liquid surface in the filter returns to the buffer tank from the pressure relief port, and then the pressure relief pipeline is closed. The liquid level rises and the upper clear liquid reflux is opened. The accuracy in the initial stage of filtration is difficult to meet the requirements. The clear liquid returns to the buffer tank along the upper clear liquid reflux pipeline. After the system is stable and the filtration progress meets the requirements, the upper clear liquid reflux is closed, and the clear liquid overflow pipe flows to the clear liquid tank by itself. The system runs for a period of time, the backwash valve is opened, the filter cake is cleaned, and the filter cake is accumulated to a certain extent for slag removal, and then step S3 is continued. The whole process is reasonably planned to avoid large particles of suspended matter from entering the clear liquid tank as much as possible, improve the filtering performance of magnetic impurities and other impurities, and improve the purity of the battery raw material solution;

[0035] 2. The solution enters the buffer tank for preliminary buffering and stabilization, and then is pumped into the lower cylinder through the liquid inlet pipe. There are multiple openings and a cross-flow setting is adopted to disrupt the direction of water flow, reduce the impact of water flow on the membrane tube, reduce the deformation of linear particles squeezed into the membrane holes, and reduce the accumulation of easily adhered substances on the membrane surface. As the water flow increases, the shear force of the water flow on the membrane surface increases, and the volatile solids accumulated on the membrane surface are taken away, and the concentration polarization is weakened, which is conducive to the stable operation of the equipment. The backwash reflux pipe is opened to guide the upper scum on the liquid surface into the buffer tank, and then the backwash reflux pipe is closed. The liquid level passes through the microfiltration membrane tube group upward and enters the upper cylinder, that is, the solution enters. At this time, the purity of the filtrate is insufficient, and the clear liquid reflux is opened The valve will reflux the primary filtered clear liquid in the upper cylinder to the buffer tank. After running for a period of time, the system will be stable. When the purity of the clear liquid in the upper cylinder meets the requirements, the clear liquid reflux valve will be closed, and the filtrate will enter the clear liquid tank along the overflow pipe. After the system runs for a period of time, the recoil reflux pipe will be opened, and the liquid level in the lower cylinder will drop rapidly. The clear liquid in the upper cylinder will recoil the membrane tube, and the filter cake accumulated on the periphery of the membrane tube of the lower cylinder will be recoiled, which is convenient for flushing the filter cake. At the same time, the auxiliary recoil component will be opened to improve the cleaning efficiency. The whole device has a reasonable layout, stable operation, precise filtration, and effectively reduces weak magnetic and insoluble impurities in the solution, improves the purity of lithium battery raw material solution, and effectively improves the safety of raw materials.

[0036] 3. Open the recoil reflux pipe, the liquid level in the lower cylinder drops rapidly, and the clear liquid in the upper cylinder recoils the membrane tube. After the liquid level drops, the electromagnetic three-way valve controls the liquid inlet pipe to introduce the liquid into the annular pipe, prompting the solution to spray from the recoil nozzle to the membrane tube, impacting the filter cake residue, and further improving the recoil effect of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the overall process of the present invention;

[0038] Figure 2 It is a schematic diagram of a partial cross-sectional structure of the precision filter of the present application;

[0039] Figure 3 yes Figure 2 A schematic diagram of the enlarged structure of part A.

[0040] Figure numerals: 11, buffer tank; 12, precision filter; 13, sludge tank; 14, clear liquid tank; 15, upper cylinder; 16, lower cylinder; 17, clear liquid reflux valve; 18, overflow pipe; 19, pumping liquid inlet pipe; 20, recoil reflux pipe; 22, end opening; 23, connecting part; 24, membrane tube; 25, cover plate; 26, porous plate; 27, rubber sealing ring; 28, supporting frame; 29, fixing clamp; 30, guide groove; 31, pressure gauge; 32, slag discharge valve; 33, regeneration liquid interface; 34, recoil nozzle; 35, annular pipe; 36, electromagnetic three-way valve; 37, nozzle. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0042] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] Example 1

[0044] like Figure 1 and Figure 2 and Figure 3 As shown, this embodiment provides a magnetic material filtering device suitable for the production of lithium battery raw materials, including a buffer tank 11, a precision filter 12, a sludge tank 13, and a clear liquid tank 14. The precision filter 12 includes an upper cylinder 15, a group of microfiltration membrane tubes 24, and a lower cylinder 16. The upper cylinder 15 is provided with a clear liquid reflux valve 17 leading to the buffer tank 11 and an overflow pipe 18 leading to the clear liquid tank 14. The lower cylinder 16 is provided with a pumping liquid inlet pipe 19 leading to the buffer tank 11 and a recoil reflux pipe 20 with a valve. The output end of the clear liquid reflux valve 17 is connected to the recoil reflux pipe 20 through a tee. The end opening 22 of the pumping liquid inlet pipe 19 extending into the lower cylinder 16 is provided with multiple and adopts a cross-flow arrangement.

[0045] Reference Figure 2 and Figure 3The microfiltration membrane tube 24 group includes a connection part 23 at the upper end and a plurality of membrane tubes 24 arranged on the connection part 23. The microfiltration membrane tube 24 group includes a cover plate 25 with a middle opening, a porous plate 26, and a rubber sealing ring 27. The outer edge of the connection part 23 is embedded between the porous plate 26 and the rubber sealing ring 27. The cover plate 25 and the rubber sealing ring 27 are fixed between the upper cylinder 15 and the lower cylinder 16. The cover plate 25 cooperates with the porous plate 26 and the rubber sealing ring 27 to fix the connection part 23 and provide stable support for the connection part 23. The porous plate 26 is arranged to facilitate the introduction of clear liquid into the upper cylinder 15. The whole structure is tightly sealed. The outer peripheral wall of the membrane tube 24 is distributed with some interfering flow protrusions. The water flow impact direction of the pumping liquid inlet pipe 19 is staggered with the direction of the membrane tube 24. A support mechanism is arranged on the membrane tube 24. The membrane tube 24 is a porous expanded polytetrafluoroethylene film. An auxiliary recoil component is arranged in the lower cylinder 16.

[0046] In order to improve the recoil deslagging effect, refer to Figure 2 and Figure 3 The auxiliary backwashing assembly includes a backwashing nozzle 34 arrayed on the inner wall of the lower cylinder 16, the backwashing nozzle 34 is inclined toward the membrane tube 24, and the outer peripheral wall of the lower cylinder 16 is provided with an annular tube 35, which is connected to the pumping liquid inlet pipe 19 through a pipeline, and an electromagnetic three-way valve 36 is provided at the connection between the annular tube 35 and the pumping liquid inlet pipe 19. When the backwashing reflux pipe 20 is opened, the liquid level of the lower cylinder 16 drops rapidly, and the clear liquid in the upper cylinder 15 backwashes the membrane tube 24. After the liquid level drops, the electromagnetic three-way valve 36 controls the liquid inlet pipe to be introduced into the annular tube 35, so that the solution is sprayed from the backwashing nozzle 34 to the membrane tube 24, impacting the filter cake residue, and further improving the backwashing effect of the device. In order to improve the spraying effect, the membrane tubes 24 are staggered, and the backwashing nozzles 34 are evenly arranged toward each membrane tube 24. A plurality of nozzles 37 are provided at the water outlet of the backwashing nozzle 34, and the nozzles 37 are arranged in the vertical direction, and the nozzles 37 are distributed along the length direction of the membrane tube 24. The membrane tubes 24 are staggered to increase the contact space between the membrane tubes 24 and the solution. At the same time, the backwash nozzles 34 are evenly arranged toward each membrane tube 24 to improve the effect of backwashing the filter cake by the backwash nozzles 34. The nozzles 37 are distributed along the length direction of the membrane tubes 24 to form a jet covering the membrane tubes 24, thereby providing comprehensive coverage and improving the cleaning effect.

[0047] Reference Figure 2 and Figure 3 In order to improve the operating stability of the device and extend the service life of the membrane tube 24, the supporting mechanism includes a supporting frame 28 arranged in the membrane tube 24 and a fixed clamping ring 29 located at the lower end of the outer wall of the membrane tube 24. The fixed clamping ring 29 is fixed to the connecting part 23. A guide groove 30 is distributed along the length direction on the supporting frame 28. The supporting frame 28 and the fixed clamping ring 29 are provided to facilitate maintaining the posture of the membrane tube 24 and reduce the deformation and folding of the membrane tube 24. At the same time, the guide groove 30 is provided to facilitate the diversion of the clear liquid in the membrane tube 24. The whole mechanism has a good supporting effect, which is conducive to maintaining the long-term operation of the membrane tube 24.

[0048] Reference Figure 1 and Figure 2 A pressure gauge 31 is provided on the lower cylinder 16, a slag discharge valve 32 leading to the sludge pool 13 is provided at the bottom of the lower cylinder 16, and a regeneration liquid interface 33 is provided at the lower end of the lower cylinder 16. The pressure gauge 31 is provided to facilitate observation of the pressure in the lower cylinder 16, so as to judge the degree of filter cake accumulation. At the same time, the slag discharge valve 32 is provided to facilitate the discharge of the filter residue and filter cake under backwashing. At the same time, a regeneration liquid interface 33 is provided to facilitate the introduction of regeneration liquid to clean the device.

[0049] The operation process of the whole device is as follows: the solution enters the buffer tank 11 for preliminary buffering and standing, and then is pumped into the lower cylinder 16 through the liquid inlet pipe 19. There are multiple openings and a cross-flow setting is adopted to disrupt the direction of water flow, reduce the impact of water flow on the membrane tube 24, reduce the deformation of linear particles that are easily deformed from being squeezed into the membrane pores, and reduce the accumulation of easily adhered substances on the membrane surface. As the water flow increases, the shear force of the water flow on the membrane surface increases, the volatile solids accumulated on the membrane surface are taken away, and the concentration polarization is weakened, which is conducive to the stable operation of the equipment. The recoil reflux pipe 20 is opened to introduce the upper scum on the liquid surface into the buffer tank 11, and then the recoil reflux pipe 20 is closed. The liquid level passes through the microfiltration membrane tube 24 group upward and enters the upper cylinder 15, that is, the solution enters. At this time, the purity of the filtrate is insufficient, and the clear liquid reflux valve 17 is opened to reflux the initial filtrate in the upper cylinder 15 to the buffer tank 11. The flushing pool 11 runs for a period of time. After the system is stable and the purity of the clear liquid in the upper cylinder 15 meets the requirements, the clear liquid reflux valve 17 is closed, and the filtrate enters the clear liquid pool 14 along the overflow pipe 18. The system runs for a period of time, and the backwash reflux pipe 20 is opened. The liquid level of the lower cylinder 16 drops rapidly, and the clear liquid in the upper cylinder 15 backwashes the membrane tube 24, and the filter cake gathered on the outer periphery of the membrane tube 24 of the lower cylinder 16 is backwashed, which is convenient for flushing the filter cake. At the same time, the auxiliary backwashing component is opened, and the electromagnetic three-way valve 36 controls the liquid inlet pipe to introduce the liquid into the annular pipe 35, so that the solution is sprayed from the backwash nozzle 34 to the membrane tube 24, impacting the filter cake residue, further improving the backwashing effect of the device, and setting the slag discharge valve 32 to facilitate the discharge of the filter residue and filter cake under the backwashing. At the same time, the regeneration liquid interface 33 is set to facilitate the introduction of the regeneration liquid to clean the device. The entire device has a reasonable layout, stable operation, precise filtration, and effectively reduces weak magnetic and insoluble impurities in the solution, improves the purity of the lithium battery raw material solution, and effectively improves the safety of the raw materials.

[0050] Reference Figure 1 and Figure 2 and Figure 3 The present invention also provides a magnetic material filtering process suitable for lithium battery raw material production, comprising the following steps:

[0051] Step S1: preparing the stock solution and performing preliminary filtration, which may be performed using a common magnetic rod filter to initially reduce magnetic impurities;

[0052] Step S2: the stock solution is injected into the buffer tank 11 for initial sedimentation;

[0053] Step S3: The pumping liquid inlet pipe 19 extracts the upper clear liquid of the buffer tank 11 into the lower cylinder 16 of the precision filter 12, and the pressure relief pipeline is opened, that is, the backwash reflux pipe 20 is opened, and the impurities on the upper layer of the liquid surface are refluxed to the buffer tank 11 along the backwash reflux pipe 20;

[0054] Step S4: close the pressure relief pipeline, at this time the liquid level rises and passes through the microfiltration membrane tube 24 group, the upper clear liquid reflux is opened, the clear liquid reflux valve 17 is opened to guide the upper impure clear liquid along the backwash reflux pipe 20 into the buffer tank 11, and then continuously circulates to the stabilization system;

[0055] Step S5: After the system is stable, the upper layer of clear liquid is turned off, the clear liquid return valve 17 is closed, and the clear liquid that meets the standards flows along the overflow pipe 18 to the clear liquid tank 14;

[0056] Step S6: After running for a certain period of time, the backwash valve is opened, that is, the backwash reflux pipe 20 is opened, the liquid level of the lower cylinder 16 drops rapidly, and the clear liquid of the upper cylinder 15 backwashes the membrane tube 24 downward to clean the filter cake, and then the solution is introduced into the annular pipe 35 and the backwash nozzle 34 through the electromagnetic three-way valve 36, so that the solution impacts the residue on the membrane tube 24, which facilitates the stripping of the filter cake;

[0057] Step S7: discharge the residue, open the residue discharge valve 32 to discharge the filter residue into the sludge pool 13, and repeat step S3 after the residue discharge.

[0058] Therefore, the raw liquid is filtered out of large particles of magnetic impurities after preliminary filtration, and then passed into the buffer tank 11 for buffering and sedimentation, and then the upper clear liquid is extracted and pumped to the precision filter 12, and the pressure relief pipeline is opened. At this time, the fine suspended matter on the liquid surface in the filter returns to the buffer tank 11 from the pressure relief port, and then the pressure relief pipeline is closed, the liquid level rises and the upper clear liquid is turned on to reflux. The accuracy in the initial stage of filtration is difficult to meet the requirements, and the clear liquid returns to the buffer tank 11 along the upper clear liquid reflux pipeline. After the system is stable and the filtration progress meets the requirements, the upper clear liquid reflux is closed, and the clear liquid overflow pipe 18 flows to the clear liquid tank 14 by itself. The system runs for a period of time, the backwash valve is opened, the filter cake is cleaned, and the filter cake accumulates to a certain extent for slag discharge, and then step S3 is started. The whole process is planned reasonably to avoid large particles of suspended matter from entering the clear liquid tank 14 as much as possible, improve the filtration performance of magnetic impurities and other impurities, and improve the purity of the battery raw material solution.

[0059] Furthermore, in step S5, the filtration pressure does not exceed 0.1 Mpa. Low-pressure operation facilitates the stable operation of the device, avoids damage due to excessive pressure during use, and avoids deformable linear particles from being squeezed into the membrane pores.

[0060] Further, the precision filter 12 is cleaned once every 12 hours using the regeneration liquid. The regeneration liquid is introduced into the lower cylinder 16 through the regeneration liquid interface 33. Through the above scheme, the regeneration liquid is regularly used for cleaning, which can effectively reduce the accumulation of filter cakes in the precision filter 12 and increase the continuous operation time of the device.

[0061] It should be noted that the regeneration liquid is used to clean the filter cake and other debris in the precision filter 12. The general regeneration liquid composition includes alkali solution, acid solution or a combination of several acid solutions, which are used in combination according to the actual equipment and working conditions. The specific composition needs to be adjusted according to the working conditions. The most common one is 30% concentration of dilute sulfuric acid.

Claims

1. A magnetic material filtering process suitable for lithium battery raw material production, characterized in that: The following steps are involved: Step S1: preparing the stock solution, performing preliminary filtration, and reducing magnetic impurities; Step S2: the stock solution is injected into the buffer tank (11) for initial sedimentation; Step S3: extract the upper clear liquid from the buffer tank (11) and pump it to the precision filter (12), open the pressure relief pipeline, and allow the impurities to flow back; Step S4: close the pressure relief pipeline, open the upper clear liquid reflux, and stabilize the system; Step S5: After the system is stable, the upper clear liquid reflux is closed, and the clear liquid flows along the overflow pipe (18) to the clear liquid tank (14); Step S6: After running for a certain period of time, open the backflush valve to clean the filter cake; Step S7: perform slag removal, and repeat step S3 after slag removal.

2. A magnetic material filtering process suitable for lithium battery raw material production according to claim 1, characterized in that: In step S5, the filtering pressure does not exceed 0.1 MPa.

3. A magnetic material filtering process suitable for lithium battery raw material production according to claim 1, characterized in that: The precision filter (12) is cleaned once every 12 hours using regeneration fluid.

4. A magnetic material filtering device suitable for lithium battery raw material production according to any one of claims 1 to 3, comprising a buffer tank (11), a precision filter (12), a sludge tank (13), and a clear liquid tank (14), characterized in that: The precision filter (12) comprises an upper cylinder (15), a microfiltration membrane tube (24) group, and a lower cylinder (16); the upper cylinder (15) is provided with a clear liquid reflux valve (17) leading to the buffer tank (11) and an overflow pipe (18) leading to the clear liquid tank (14); the lower cylinder (16) is provided with a pumping liquid inlet pipe (19) leading to the buffer tank (11) and a backwash reflux pipe (20) with a valve; the output end of the clear liquid reflux valve (17) is connected to the backwash reflux pipe (20) through a tee; the pumping liquid inlet pipe (19) extends into the lower cylinder (16); The cylinder (16) is provided with a plurality of end openings (22) which are arranged in a cross-flow configuration. The microfiltration membrane tube (24) group comprises a connection portion (23) located at the upper end and a plurality of membrane tubes (24) arranged on the connection portion (23). The outer peripheral wall of the membrane tube (24) is provided with a plurality of flow interference protrusions. The water flow impact direction of the pumping liquid inlet pipe (19) is staggered with the direction of the membrane tube (24). A supporting mechanism is arranged on the membrane tube (24). The membrane tube (24) is a porous expanded polytetrafluoroethylene film. An auxiliary recoil assembly is arranged in the lower cylinder (16).

5. A magnetic material filtering device suitable for lithium battery raw material production according to claim 4, characterized in that: The microfiltration membrane tube (24) group comprises a cover plate (25) with a middle opening, a porous plate (26), and a rubber sealing ring (27); the outer edge of the connecting portion (23) is embedded between the porous plate (26) and the rubber sealing ring (27); and the cover plate (25) and the rubber sealing ring (27) are fixed between the upper cylinder (15) and the lower cylinder (16).

6. A magnetic material filtering device suitable for lithium battery raw material production according to claim 4, characterized in that: The support mechanism comprises a support frame (28) arranged in the membrane tube (24) and a fixed clamp ring (29) located at the lower end of the outer wall of the membrane tube (24), the fixed clamp ring (29) is fixed to the connecting portion (23), and the support frame (28) is provided with guide grooves (30) along the length direction.

7. A magnetic material filtering device suitable for lithium battery raw material production according to claim 4, characterized in that: The lower cylinder (16) is provided with a pressure gauge (31), the bottom end of the lower cylinder (16) is provided with a slag discharge valve (32) leading into the sludge pool (13), and the lower end of the lower cylinder (16) is provided with a regeneration liquid interface (33).

8. The magnetic material filtering device suitable for lithium battery raw material production according to claim 4, characterized in that: The auxiliary recoil assembly comprises a recoil nozzle array (34) on the inner wall of the lower cylinder (16), wherein the recoil nozzle (34) is inclined toward the membrane tube (24), and an annular tube (35) is provided on the outer peripheral wall of the lower cylinder (16), wherein the annular tube (35) is connected to the pumping liquid inlet pipe (19) through a pipeline, and an electromagnetic three-way valve (36) is provided at the connection between the annular tube (35) and the pumping liquid inlet pipe (19).

9. A magnetic material filtering device suitable for lithium battery raw material production according to claim 8, characterized in that: The membrane tubes (24) are arranged in a staggered manner, and the backflushing nozzles (34) are evenly arranged toward each membrane tube (24).

10. The magnetic material filtering device suitable for lithium battery raw material production according to claim 8, characterized in that: A plurality of nozzles (37) are provided at the water outlet end of the backflushing nozzle (34). The nozzles (37) are arranged in a vertical direction and are distributed along the length direction of the membrane tube (24).

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