Waste lithium ion battery crushing, sorting, and recycling method and system

Abstract

The present application belongs to the field of new energy, and discloses a waste lithium ion battery crushing, sorting, and recycling method, comprising the following steps: step 1, crushing a lithium ion battery and heating, to obtain a first solid; step 2, removing a housing, to obtain a second solid; step 3, sieving the second solid, to obtain a first undersize product and a first oversize product; step 4, performing airflow sorting on the first oversize product to remove a separator, to obtain a third solid; step 5, pyrolyzing the first undersize product and the third solid, to obtain a fourth solid; step 6, sieving the fourth solid, to obtain a second undersize product and a second oversize product; and step 7, crushing and sieving the second oversize product, to obtain a third undersize product and a third oversize product. By means of collecting black powder before and after crushing in step 7, the present method implements black powder grading, thereby facilitating targeted treatment of black powder of different grades. The black powder recovery rate and the collection efficiency of the present application are high, and a separator is efficiently removed. Furthermore, the present application also discloses a system suitable for said method.

Description

A method and system for crushing, sorting and recycling waste lithium-ion batteries

[0001] This application claims priority to the Chinese patent application filed with the Patent Office of China on December 5, 2023, with application number CN202311655268.4 and invention name “A method and system for crushing, sorting and recycling of waste lithium-ion batteries”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of new energy, and specifically to a method and system for crushing, sorting and recycling waste lithium-ion batteries. Background Art

[0003] Waste lithium-ion batteries primarily consist of a casing, positive electrode, negative electrode, separator, and electrolyte. The current mainstream recycling process involves crushing the batteries under a protective atmosphere and performing multi-stage physical sorting to separate the casing, separator, positive and negative electrode powder, and copper and aluminum particles (powder) for recycling.

[0004] Existing technologies, such as CN114914570A, disclose a method for recycling waste lithium-ion battery electrolytes. After removing the solvent through low-temperature heating, the shell, diaphragm, etc. are sorted. However, in actual production, we have found that it is very difficult to use a one-time sorting method for the shell and diaphragm. At the same time, although the binder in the positive electrode material on the electrode is carbonized after pyrolysis, the efficiency of sorting black powder is still very low.

[0005] Therefore, the technical problem solved in this case is: how to recover black powder efficiently and with high purity. Summary of the Invention

[0006] The main purpose of this application is to provide a method for crushing, sorting and recycling waste lithium-ion batteries, which can efficiently recover black powder with high purity.

[0007] The present application can also realize the graded recovery of black powder while realizing the recovery of black powder, and at the same time make the diaphragm easier to remove.

[0008] At the same time, the present application also provides a system for implementing the method.

[0009] To achieve the above objectives, this application provides the following technical solutions:

[0010] A method for crushing, sorting and recycling waste lithium-ion batteries comprises the following steps:

[0011] Step 1: After crushing the lithium-ion battery, heating it to 60-150° C. under inert gas protection to volatilize at least part of the solvent in the electrolyte to obtain a first solid;

[0012] Step 2: removing the battery shell from the first solid to obtain a second solid;

[0013] Step 3: Screening the second solid to obtain a first undersize material and a first oversize material, wherein the first undersize material contains free black powder in the second solid;

[0014] Step 4: removing the membrane from the first screen material through air flow sorting to obtain a third solid;

[0015] Step 5: Pyrolyzing the first undersize and the third solid to decompose the lithium salt and crack and carbonize the binder on the electrode and the diaphragm to obtain a fourth solid;

[0016] Step 6: Screening the fourth solid to obtain a second undersize material and a second oversize material; the second undersize material is the first black powder;

[0017] Step 7: Crush the second oversize material, and sieve the crushed product to obtain a third undersize material and a third oversize material; the third undersize material is the second black powder, and the third oversize material is the metal substrate particles of the electrode.

[0018] Compared with the prior art, the main innovations of this application are:

[0019] 1. The black powder recovery process has been optimized from the last step in traditional technology to black powder screening recovery before diaphragm sorting, black powder screening recovery after electrode pyrolysis, and black powder screening recovery after electrode crushing. This design maximizes the recovery rate of black powder, achieves graded recovery of black powder, and achieves high-purity recovery of black powder.

[0020] Specifically, some free black powder will fall off during the shredding process at the front end of the lithium battery, and due to the presence of electrolyte, a small amount of black powder will adhere to the wet diaphragm and shell. Therefore, before the diaphragm or shell is sorted, some organic solvents are removed by heating to make the diaphragm and shell dry, reducing the adhesion of the black powder, which is conducive to the full separation and recovery of the black powder; at the same time, before the diaphragm is sorted, the free black powder that falls off during the shredding process is fully screened out by screening to prevent the free black powder from entering the diaphragm sorting process and being sucked away by the airflow, resulting in a lower black powder recovery rate. In this step, the black powder recovery rate is improved by heating and screening;

[0021] After the electrode is pyrolyzed, the binder on the electrode is decomposed, the bonding strength between the black powder and the electrode is weakened, and the black powder is dry and brittle. During the screening process of the electrode, some black powder will fall off. In this step, the recovery efficiency of the black powder is improved through pyrolysis and screening;

[0022] The black powder obtained by screening before diaphragm separation and after pyrolysis of the pole piece has relatively few metal impurities and relatively high purity. By combining pyrolysis with screening before diaphragm separation and screening after pyrolysis, efficient and high-purity recovery of black powder is achieved;

[0023] After the electrode is pyrolyzed, although the adhesive has been decomposed and removed, some black powder will still stick to the electrode, and the size is relatively large. It cannot be completely removed and screened out by simple screening. However, through the crushing after pyrolysis, the black powder on the electrode is fully detached and crushed into powder by impact during the crushing process. Combined with screening, the black powder and metal substrate particles can be screened out; however, due to the existence of the electrode crushing step, the metal impurities in this part of the black powder are relatively high, but the overall proportion of black powder is small, so it is conducive to the targeted treatment of the above two black powders of different purities in hydrometallurgy. Through the combination of the above steps, the graded recovery of black powder is achieved;

[0024] 2. Reduce the difficulty of diaphragm removal and reduce black powder entrainment;

[0025] Achieving this goal is not only related to the volatilization of the organic solvent in the above analysis and the screening before membrane separation, but also closely related to the removal of the shell in step 2;

[0026] Compared with conventional technologies, this application first heats to volatilize the solvent, then removes the shell, then screens, and finally removes the diaphragm. This can reduce the difficulty of diaphragm airflow separation and the airflow separation wind force, thereby reducing the probability of black powder being extracted;

[0027] At the same time, removing the outer shell first creates favorable conditions for subsequent screening. If the outer shell is not removed, the outer shell in the solid is heavier and accounts for a relatively large volume, and its squeezing of the diaphragm can easily cause the outer shell to move with the diaphragm in the screen, causing a large amount of black powder to accumulate in the outer shell. The accumulation of black powder forces the subsequent airflow sorting to increase, and the black powder will be further carried away by the airflow, reducing the recovery rate of the black powder.

[0028] In one embodiment of the present application, step 2 specifically includes: removing the battery shell from the first solid by an airflow sorting process, and the second solid enters step 3 by negative pressure extraction.

[0029] In one embodiment of the present application, the sieve aperture of step 3 is 2-50 mesh; the sieve aperture of step 6 is 80-150 mesh; and the sieve aperture of step 7 is 80-150 mesh.

[0030] In some embodiments of the present application, the sieve aperture in step 3 can be selected as: 2, 5, 10, 15, 20, 25, 30, 40 or 50 mesh;

[0031] In some embodiments of the present application, the sieve aperture in step 6 can be selected as: 80, 85, 90, 95, 100, 110, 120, 130, 140 or 150 mesh;

[0032] In some embodiments of the present application, the sieve aperture in step 7 can be selected as: 80, 85, 90, 95, 100, 110, 120, 130, 140 or 150 mesh;

[0033] It should be noted that the screening mesh number of step 3 in the present application is 2 to 50 meshes. In this step, the free black powder accounts for a relatively high proportion and is mixed with the pole pieces and fluffy diaphragms. Under fixed basic conditions, the smaller the screening mesh number, such as 2 meshes, the higher the separation efficiency of the free black powder and the more thorough the screening, thereby preventing it from being drawn away by the air flow in the next step and causing black powder loss. In addition, since the diaphragm in the lithium battery is thin and has good toughness, after the battery is fully broken up through the shredding and crushing process, the size of the diaphragm in the crushed mixture is generally larger than the size of the shell and the pole pieces. Therefore, even if the screening mesh number is very small, this step will not cause the diaphragm to be screened down and mixed with the first screened material. However, if the screening mesh number is larger, such as 50 meshes or above, under the same equipment conditions, the screening efficiency will be reduced, and the free black powder may not be separated thoroughly, which will ultimately lead to a lower black powder recovery rate. Therefore, in general, it is particularly important to screen the free black powder before diaphragm separation. In this process, since the black powder accounts for a high proportion and is mixed with the pole pieces and fluffy diaphragms, a lower screening mesh is more conducive to the complete separation of the free black powder, thereby reducing black powder loss and improving its recovery rate and the airflow separation efficiency of the diaphragm. In the above-mentioned method for crushing and sorting waste lithium-ion batteries, the first screen material and / or the third solid are magnetically separated and then enter step 5.

[0034] In one embodiment of the present application, step 1 is specifically:

[0035] Under a protective atmosphere, the battery is cut and destroyed, and the materials after cutting and destruction are crushed, and the size of the crushed materials is controlled to be 10 to 30 mm, and the battery components are completely broken up.

[0036] In some embodiments of the present application, the crushed material size can be controlled to 10 mm, 15 mm, 20 mm, 25 mm or 30 mm;

[0037] In one embodiment of the present application, in step 1, the heating time is 30 to 120 minutes;

[0038] Take the organic solvents commonly used in this field as examples: ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl acetate, propyl propionate and propyl acetate;

[0039] The boiling points of the solvents are: ethylene carbonate 240°C; propylene carbonate 242°C; dimethyl carbonate 90°C; diethyl carbonate 126-128°C; ethyl methyl carbonate 107°C; ethyl acetate 77°C; propyl propionate 136°C; propyl acetate 102°C;

[0040] Generally speaking, the optimal solvent evaporation temperature is 100-150°C. If 100°C is selected, it is recommended to maintain a negative pressure in the system to further reduce the boiling point of the solvent. In the above process, solvents with a boiling point above 150°C are generally evaporated and will proceed to step 2.

[0041] Referring to the above examples, under normal pressure, if the heating temperature is 100°C, ethyl acetate and dimethyl carbonate will volatilize; if the heating temperature is 110°C, propyl acetate and ethyl methyl carbonate will volatilize; if the heating temperature is 150°C, diethyl carbonate and propyl propionate will volatilize;

[0042] If you want to volatilize a solvent with a boiling point above the set temperature at a set temperature, you should maintain the system at a negative pressure.

[0043] Under negative pressure system, the lowest temperature can be as low as 60℃, which can make the low boiling point solvent evaporate.

[0044] As a further preference of the present application, the solvent volatilization temperature can be preferably selected to be 110-140°C;

[0045] In some embodiments of the present application, the solvent volatilization temperature may be selected to be 70, 80, 85, 90, 95, 100, 110, 120, 130, 140 or 150°C;

[0046] The pyrolysis temperature in step 5 is 300-550° C., and the time is 30-120 min.

[0047] Preferably, the pyrolysis temperature is 330-500°C; more preferably 350-450°C;

[0048] In some embodiments of the present application, the pyrolysis temperature may be selected to be 300, 350, 400, 450, 500 or 550°C;

[0049] In one embodiment of the present application, in step 1, a first gas is further obtained, and the solvent is recovered by condensing the first gas;

[0050] In step 5, a second gas is obtained after pyrolysis, and PF5 in the second gas is recovered by multi-stage condensation.

[0051] At the same time, the present application also discloses a system for implementing any of the above methods, comprising a first crushing unit for crushing lithium-ion batteries, a heating device for heating and volatilizing the solvent in the crushed lithium-ion batteries, a first separation device for removing the battery shell in the first solid, a first screening device for screening the second solid to remove free black powder in the second solid, a second separation device for removing the diaphragm in the first screened material, a pyrolysis device for pyrolyzing the first screened material and the third solid, a second screening device for screening the fourth solid, a second crushing unit for crushing the second screened material, and a third screening device for screening the crushed product of the second crushing unit.

[0052] In one embodiment of the present application, a magnetic separation device is further provided between the second separation device and the pyrolysis device;

[0053] The first crushing unit includes a shredding device for cutting the intact lithium-ion battery and a crushing device for crushing the shredded lithium-ion battery;

[0054] The first separation device and the second separation device are both airflow separators; the second solid is the light component separated by the first separation device; and the third solid is the heavy component separated by the second separation device;

[0055] The first screening device and the second screening device are both drum screens.

[0056] In one embodiment of the present application, a first condensing unit and a second condensing unit are further included, and the gas generated in the heating device is transported to the first condensing unit through a pipeline; the gas generated in the pyrolysis device is transported to the second condensing unit through a pipeline.

[0057] In one embodiment of the present application, the pyrolysis device performs pyrolysis in two steps; the temperature of the first pyrolysis step is 200-300°C; and the temperature of the second pyrolysis step is 300-500°C.

[0058] In one embodiment of the present application, the second condensing unit includes a pre-condensing device for condensing the gas generated by the first pyrolysis, a primary condensing device for condensing the uncondensed gas of the pre-condensing device, a secondary condensing device for condensing the uncondensed gas of the primary condensing device, and a tertiary condensing device for condensing the uncondensed gas of the secondary condensing device, which are connected in sequence;

[0059] The first condensing unit includes a primary condensing device for condensing the gas generated in the heating device and a separation device for separating fluorine-containing compounds from the tail gas of the primary condensing device; the gas separated by the separation device is sent to the secondary condensing device for condensation.

[0060] One of the above technical solutions of this application has at least one of the following advantages or beneficial effects:

[0061] In the method of the present application, the shell and the diaphragm are sequentially sorted after the electrolyte is evaporated at low temperature, so as to prevent the shell and the diaphragm soaked by the electrolyte from adhering to and taking away a small amount of black powder during sorting;

[0062] Secondly, the shell and free black powder are screened out in sequence before the separation membrane to prevent some black powder from being carried away during the separation of the membrane and causing black powder loss. At the same time, the shell is not removed, which causes the membrane to be squeezed by the shell during screening, making it difficult to separate and reducing the black powder recovery efficiency.

[0063] At the same time, pyrolysis of the first screen undersize and the electrode can pyrolyze the organic matter in the black powder, improve the purity of the black powder, and reduce the adhesion of the black powder on the electrode, making the black powder on the electrode dry and brittle, making it easier to fall off during the screening operation after pyrolysis, thereby improving the recovery rate and purity of the black powder;

[0064] Finally, after cracking, the electrode size is reduced by crushing again, and the black powder on the positive and negative electrode sheets is easier to fall off and crush into powder. In the subsequent screening process, the separation of black powder and copper and aluminum particles can be more thorough, and the recovery of black powder containing metal powder impurities is realized; this application realizes black powder grading by collecting black powder before and after crushing, which is conducive to targeted treatment of black powder of different levels. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] The drawings described herein are used to provide further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0066] FIG1 is a pipeline flow chart of Example 1;

[0067] FIG2 is a pipeline flow chart of Example 5;

[0068] FIG3 is a pipeline flow chart of Example 6;

[0069] FIG4 is a pipeline flow chart of Example 4;

[0070] Among them, 1. shredding device, 2. heating device, 3. first separation device, 4. first screening device, 5. second separation device, 6. pyrolysis device, 7. second screening device, 8. second crushing unit, 9. third screening device, 10. magnetic separation device, 11. crushing device, 12. oil removal device, 13. tail gas combustion device, 14. heat exchanger, 15. flue gas quenching tower, 16. semi-dry reactor, 17. dust collector, 18. induced draft fan, 19. first-stage alkali spray tower, 20. second-stage alkali spray tower, 21. chimney, 22. primary condensing device, 23. pre-condensing device, 24. first-stage condensing device, 25. second-stage condensing device, 26. third-stage condensing device, 27. cold trap. DETAILED DESCRIPTION

[0071] The following will be combined with the embodiments of the present application to clearly and completely describe the technical solutions of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of this application.

[0072] Part 1

[0073] Before introducing the process of this part in detail, the production system of this part is introduced first. Referring to Figure 1, it specifically includes the following devices: a first crushing unit for crushing lithium-ion batteries, a heating device 2 for heating at least part of the solvent in the crushed lithium-ion batteries to a volatilization temperature, a first separation device 3 for removing the battery shell in the first solid, a first screening device 4 for screening the second solid to remove free black powder in the second solid, a second separation device 5 for removing the diaphragm in the first screened material, a pyrolysis device 6 for pyrolyzing the first screened material and the third solid, a second screening device 7 for screening the fourth solid, a second crushing unit 8 for crushing the second screened material, and screening the crushed product of the second crushing unit. A third screening device 9 is provided, and a magnetic separation device 10 is further provided between the second separation device and the pyrolysis device; the first crushing unit includes a shredding device 1 for cutting off the complete lithium-ion battery and a crushing device 11 for crushing the shredded lithium-ion battery; the first separation device and the second separation device are both airflow separators; the second solid is the light component separated by the first separation device; the third solid is the heavy component separated by the second separation device. The light component and heavy component mentioned in this application refer to the components removed by the airflow during the airflow separation process, namely, the light component, and the components not removed by the airflow are the heavy component; the first screening device and the second screening device are both drum screens.

[0074] Example 1

[0075] Step 1: crushing one ton of cylindrical waste lithium iron phosphate batteries using a first crushing unit under nitrogen protection, and heating to the solvent volatilization temperature of the electrolyte under inert gas protection to obtain a first solid;

[0076] In lithium iron phosphate batteries, the main organic solvent composition of the electrolyte is: ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC), with a mass ratio of 3:1:6;

[0077] The lithium salt is lithium hexafluorophosphate, which accounts for 13% of the weight of the electrolyte;

[0078] The active material of the positive electrode is lithium iron phosphate, and the current collector is on carbon-coated aluminum foil; the mass ratio of lithium iron phosphate, conductive agent SuperP, adhesive PVDF and carbon nanotubes (CNT) on the current collector is 95.8:1:2.5:0.7;

[0079] Crushing is carried out by a shredding device and a crushing device. The battery is first shredded and invalidated by the shredding device, and then crushed by a hammer crushing device. The size after crushing is 10 to 30 mm. At this time, a mixture of shell, diaphragm, electrode, electrolyte, and free black powder is obtained. The mixture is heated by a heating device (100 ° C, 1 hour) to evaporate the solvent in the electrolyte. The first solid remaining after volatilization is the shell, diaphragm, electrode, lithium salt, black powder and some non-volatile additives. If the electrolyte system contains a high-boiling organic solvent, the first solid-liquid mixture also contains a high-boiling organic solvent. During shredding and crushing, the oxygen content is controlled to <2.0% to avoid the risk of explosion. The effective response measure is to continuously introduce nitrogen as a protective gas. At the same time, nitrogen is introduced into the heating device throughout the process to facilitate solvent volatilization.

[0080] Step 2: using a first separation device to remove the battery shell from the first solid to obtain a second solid;

[0081] The first solid is fed into the first separation device, which is an air separator. The separator sucks the diaphragm, electrode, lithium salt, and some non-volatile additives, high-boiling organic solvents, etc. into the first screening device by means of negative pressure extraction. The additives and high-boiling organic solvents mainly enter the first screening device in the form of adhering to the diaphragm and electrode.

[0082] Step 3: Screening the second solid using a first screening device to obtain a first undersize and a first oversize, wherein the first undersize contains free black powder in the second solid and a high-boiling organic solvent impregnated in the black powder;

[0083] The sieve aperture of the first sieve device is 10 mesh;

[0084] It should be noted that in this step, the aperture of the sieve should be set larger, that is, the mesh number should be smaller. In actual production, more than 50% of the black powder needs to be screened out in this step. If the free black powder cannot be completely screened out, then part of it will be pumped away in step 4. At the same time, if a large amount of black powder cannot be screened out in this step, then in step 4, it will make it difficult to pump out the diaphragm.

[0085] During the project experiment, we tried to go directly to step 4 to remove the diaphragm without screening the second solid. After analyzing the extracted diaphragm, we found that it contained black powder equivalent to 1 to 5 wt% of the total black powder. This part of the black powder entrainment will reduce the black powder recovery rate.

[0086] The first screening device in this step is a drum screen;

[0087] Step 4: The first screen material is separated by air flow to remove the diaphragm to obtain a third solid; the third solid is treated by a magnetic separation device to remove the magnetic metal powder before entering step 5;

[0088] It should be noted that the first undersize material may also enter the magnetic separation device together with the third solid;

[0089] This step is carried out by a second separation device, which is an airflow separator. The membrane is sucked away by the airflow separator; the remaining solid is the third solid. More specifically, the first screen material is placed on an 80-100 mesh screen conveyor belt, above which is the airflow separator.

[0090] Step 5: Pyrolyzing the first undersize and the third solid to decompose the lithium salt and crack the electrode binder to obtain a fourth solid;

[0091] The pyrolysis temperature of the pyrolysis device is 500° C., and the time is 1.5 h. During the pyrolysis process, nitrogen protection is introduced, and the oxygen content is controlled to be less than 2.0%.

[0092] The key point of this step is that: through pyrolysis, not only the decomposition of lithium salts is achieved to avoid the presence of lithium salts in the black powder, but also the binder is cracked, so that the black powder on the electrode falls off during the screening process in step 6, and more black powder with higher purity is obtained; the most important thing is: through pyrolysis, the organic matter in the black powder obtained by screening in step 6 is fully decomposed, thereby improving the purity of the black powder.

[0093] Step 6: Screening the fourth solid to obtain a second undersize material and a second oversize material; the second undersize material is the first black powder;

[0094] This step is carried out by a second screening device, which is a 120-mesh drum screen. The collected first black powder has a low impurity metal content, thereby reducing the difficulty of extracting lithium and other positive electrode metal materials from the black powder and improving its purity;

[0095] Step 7: The second oversize material is crushed by a second crushing unit, and the crushed product is screened by a third screening device with 120 mesh to obtain a third undersize material and a third oversize material; the third undersize material is the second black powder, and the third oversize material is the metal substrate particles of the electrode.

[0096] In this step, the crushed size is 1 to 3 mm;

[0097] It should be noted that the crushing process is indispensable in this step, because after repeated experiments, if the pole piece is not crushed, the size of the pole piece is still too large. Although there is no binder on the pole piece, it is still difficult to completely separate the black powder from the pole piece. By crushing, on the one hand, the size of the pole piece is reduced, which is conducive to the black powder falling off from the pole piece; on the other hand, the friction and impact caused by the crushing can accelerate the falling of the black powder and crush it into powder, which is conducive to subsequent screening. During the experiment, it was tested that if the pole piece is not crushed but directly screened, after analyzing the pole piece on the sieve, it was found that it contained black powder entrainment equivalent to 10 to 20wt% of the total black powder. Therefore, crushing before screening is very necessary.

[0098] It's also important to note that the second black powder obtained in this step should not be mixed with the first black powder. The crushing process described above produces a large amount of metal powder, which complicates black powder recovery. Simple screening and other operations are not sufficient to separate the metal powder, requiring specialized recovery of aluminum and copper to achieve a high-purity black powder. While this portion of black powder accounts for approximately 5-20% of the total black powder, recycling it requires additional steps and processes, further improving its purity and recovery rate, making it a necessary procedure.

[0099] At the same time, it should be noted that if the crushing size in step 1 is adjusted to the size in step 7, it will reduce the size of the electrode at the source, but it will also cause excessive crushing of the diaphragm. The undersized diaphragm will increase the difficulty of diaphragm sorting in step 4. Some small-sized diaphragms will be buried by the electrode pieces or other solids, making them difficult to remove. At the same time, excessive crushing in step 1 will cause the screened material obtained in step 3 to contain small-sized electrode pieces and diaphragms, making subsequent processes more complicated.

[0100] Result analysis:

[0101] 1. First, the shell and diaphragm are sorted after the electrolyte is evaporated at low temperature to prevent the shell and diaphragm soaked in electrolyte from adhering to and taking away a small amount of black powder during sorting; secondly, the shell and free black powder are screened out in turn before sorting the diaphragm to avoid the black powder being taken away during diaphragm sorting and causing black powder loss, and to avoid the problem that the diaphragm is squeezed by the shell during screening and difficult to separate due to the shell not being removed; at the same time, the first screen undersize and the electrode are pyrolyzed to decompose the organic matter in the black powder and improve the purity of the black powder At the same time, the adhesion of the black powder on the electrode is reduced, making the black powder on the electrode dry and brittle, making it easier for the black powder to fall off the electrode during the screening operation after pyrolysis, thereby improving the purity and recovery rate of the black powder; finally, after cracking, the electrode size is reduced by crushing again, and the black powder on the positive and negative electrode sheets falls off and crushed into powder, which is beneficial to the effective separation of black powder and copper and aluminum particles in the subsequent screening process; the present application also realizes the collection of black powder before and after crushing, realizes black powder grading, and is beneficial to the targeted treatment of black powder of different levels.

[0102] 2. The crushing size in step 1 should not be too small. The crushing size in step 1 is related to the screening aperture in step 2. If the crushing size in step 1 is too small, the screening mesh in step 2 must be large, which will increase the difficulty of black powder screening. As a result, some black powder will be sucked away along with the diaphragm during the subsequent diaphragm removal process. Therefore, the crushing size in step 1 and step 7 should be reasonably set and coordinated to achieve process optimization.

[0103] 3. The crushing in step 7 is of great significance to the sufficient screening of black powder, and the crushing in this step is indispensable.

[0104] 4. The amount of black powder collected in step 7 is relatively small. For this part of black powder, multiple batches of black powder in step 7 should be mixed and processed uniformly. At the same time, it should be processed separately from the black powder collected in step 6. This can effectively reduce the process difficulty of black powder processing in step 6.

[0105] Example 2

[0106] The method is substantially the same as that of Example 1, except that in step 1, the battery is cut and the damaged material is crushed, and the size of the crushed material is controlled to be 10 to 20 mm;

[0107] The heating temperature for volatilizing the solvent in step 1 is 150° C. and the time is 2 h;

[0108] The mesh number of the first screening device is 50 mesh; the mesh number of the second screening device is 80 mesh; the mesh number of the third screening device is 150 mesh;

[0109] In step 5, the pyrolysis temperature is 300° C. and the time is 2 h.

[0110] Example 3

[0111] The method is similar to Example 1, except that in step 1, the battery is cut and the damaged material is crushed, and the size of the crushed material is controlled to be 20 to 30 mm.

[0112] The heating temperature for evaporating the solvent in step 1 is 60°C, the system is kept under negative pressure, and the time is 2 hours;

[0113] The mesh size of the first screening device is 2 meshes; the mesh size of the second screening device is 150 meshes; the mesh size of the third screening device is 80 meshes;

[0114] In step 5, the pyrolysis temperature is 550° C. and the time is 0.5 h.

[0115] Comparative Example 1

[0116] The method is substantially the same as Example 1, except that step 3 is eliminated; after step 2, the second solid is directly sent to step 4 for airflow separation to remove the membrane.

[0117] Comparative Example 2

[0118] The process is substantially the same as that of Example 1, except that step 6 is omitted and the fourth solid is directly sent to step 7 for crushing.

[0119] Comparative Example 3

[0120] The process is basically the same as Example 1, except that there is no crushing operation in step 7, and the second screened material is directly screened again.

[0121] The black powder recovery results are shown in Table 1 below;

[0122] Table 1

[0123] It can be seen from the above Examples 1-3 that, on the basis of other conditions being the same, the temperature of low-temperature volatilization and high-temperature cracking has a certain influence on the overall black powder recovery rate. That is, under the condition of low-temperature volatilization, the diaphragm and the shell are not dried sufficiently, and it is easy for a small amount of black powder to adhere and take away in the subsequent sorting, resulting in black powder loss, and the recovery rate is slightly low. Therefore, it is particularly important to perform low-temperature volatilization treatment and select a suitable volatilization temperature before sorting the shell and diaphragm. If the high-temperature cracking temperature is too low, it will lead to incomplete decomposition of adhesives, etc., and incomplete shedding of black powder in the subsequent crushing and sorting process, resulting in a low black powder recovery rate. Therefore, selecting a high-temperature cracking process and setting a suitable processing temperature are factors that need to be considered in the process of optimizing the process.

[0124] It can be seen from Comparative Example 1 that if the free black powder that is torn and broken off in the early stage is not screened before membrane sorting, then part of the black powder will be sucked away by the airflow during the membrane sorting process, resulting in black powder loss, and too much free black powder will cause the diaphragm to be unable to separate it efficiently, which is easy to clog the pipeline during transportation and increase energy consumption in the subsequent high-temperature cracking process. Therefore, it is very important to fully separate the free black powder before the airflow sorting diaphragm.

[0125] It can be seen from Comparative Example 2 that directly crushing and screening the fourth solid has little effect on the overall recovery rate, but if screening is not performed before crushing, the metal powder in the crushing process will cause the impurity content of black powder to increase. Therefore, the graded recovery treatment method of first screening the fourth solid and then crushing and screening is beneficial to targeted treatment of black powder with different impurity contents and improve economic benefits.

[0126] It can be seen from Comparative Example 3 that if there is no crushing step in Step 7, the recovery rate of the black powder will be seriously reduced. This is because although the adhesive can be removed after high-temperature cracking, it is difficult to fully fall off and separate the residual black powder on the electrode by simple screening without any mechanical force. This part of black powder accounts for about 5-20% of the total black powder, which has a great impact on the overall recovery rate of the black powder. Therefore, the crushing step after high-temperature cracking is also indispensable.

[0127] In the above embodiments and comparative examples, when calculating the recovery rate, the theoretical content of black powder in 1 ton of cylindrical waste lithium iron phosphate batteries was estimated to be about 530 kg. Since it is not guaranteed that every battery in the waste battery is exactly the same, but the basic component contents of batteries of the same model are similar, the data in Table 1 above are only used as a basis for inferring data trends and are not used as error-free results for specific recovery rates.

[0128] Example 4

[0129] This embodiment mainly introduces the use of the method of the present application to recover black powder from square aluminum shell ternary batteries;

[0130] The relevant parameters of square aluminum shell ternary battery are:

[0131] The positive electrode material of the ternary battery is: nickel-cobalt-manganese ternary material, whose chemical formula is LiNi 0.5 Mn 0.3 Co 0.2 O2;

[0132] The main organic solvent composition of the electrolyte is: ethylene carbonate, propylene carbonate, ethyl methyl carbonate, and diethyl carbonate, with a mass ratio of 25:5:15:55;

[0133] The lithium salt is lithium hexafluorophosphate, with a content of 12.5 wt%;

[0134] The active material of the positive electrode is a ternary material (chemical formula is LiNi 0.5 Mn 0.3 Co 0.2 O2), the current collector is carbon-coated aluminum foil; the mass ratio of the ternary material, conductive agent SuperP, and adhesive PVDF on the current collector is 96.8:2:1.2;

[0135] The flowchart of this embodiment refers to FIG4 . FIG4 differs from FIG1 in that the first undersize material enters the magnetic separation device 10 for magnetic separation. The specific steps of the recovery operation are as follows:

[0136] Step 1: crushing 1 ton of square aluminum shell ternary batteries under nitrogen protection, and heating under inert gas protection to volatilize the electrolyte solvent to obtain a first solid;

[0137] Crushing is performed by the shredding device 1 and the crushing device 11. The battery is first shredded and rendered ineffective by the shredding device 1, and then crushed by the crushing device 11. The crushing device 11 is a hammer-type crushing device, and the size of the crushed battery is 10 to 30 mm. At this time, a mixture of the shell, diaphragm, electrode, electrolyte, and free black powder is obtained. The mixture is heated by the heating device 2 (120°C, 1.5 hours) to volatilize the electrolyte solvent. After volatilization, the first solid remaining is the shell, diaphragm, electrode, lithium salt, black powder, and some non-volatile additives and high-boiling solvents.

[0138] During shredding and crushing, the oxygen content is controlled at <2.0% to avoid the risk of combustion and explosion. The effective countermeasure is to continuously introduce nitrogen as a protective gas. At the same time, nitrogen is introduced into the heating device throughout the process to facilitate solvent volatilization.

[0139] Step 2: removing the battery shell from the first solid to obtain a second solid;

[0140] The first solid is fed into the first separation device 3, which is an air separator. The separator, electrode, lithium salt, and some non-volatile additives, high-boiling organic solvents, etc. are sucked into the first screening device 4 by negative pressure extraction. The additives and high-boiling organic solvents mainly enter the first screening device 4 in the form of adhering to the separator and electrode.

[0141] Step 3: Screening the second solid to obtain a first undersize material and a first oversize material, wherein the first undersize material contains free black powder in the second solid and a high-boiling organic solvent impregnated in the black powder;

[0142] This step is carried out in the first screening device 4, and the screening aperture is 10 mesh;

[0143] The first screening device 4 in this step is a drum screen;

[0144] Step 4: The first sieve material is separated by air flow to remove the diaphragm to obtain a third solid; the first sieve material and the third solid are separated by a magnetic separation device to remove the magnetic metal powder and then enter step 5;

[0145] This step is carried out by the second separation device 5, which is an airflow separator. The membrane is sucked away by the airflow separator; the remaining solid is the third solid. More specifically, the first screen material is placed on a 100-mesh screen conveyor belt, above which is the airflow separator.

[0146] Step 5: Pyrolyzing the first undersize and the third solid to decompose the lithium salt and crack the electrode binder to obtain a fourth solid;

[0147] The pyrolysis temperature of the pyrolysis device 6 is 500° C., and the time is 1.5 h. During the pyrolysis process, nitrogen protection is introduced, and the oxygen content is controlled to be less than 2.0%.

[0148] Step 6: Screening the fourth solid to obtain a second undersize material and a second oversize material; the second undersize material is the first black powder;

[0149] This step is carried out by the second screening device 7, which is a drum screen with a mesh size of 120. The collected first black powder has a low content of impurity metals, so it is easier to extract lithium and other positive electrode material metal elements from the black powder.

[0150] Step 7: The second oversize material is crushed by the second crushing unit 8, and the crushed product is screened by the third screening device 9 with a mesh size of 120 to obtain the third undersize material and the third oversize material; the third undersize material is the second black powder, and the third oversize material is the metal substrate particles of the electrode.

[0151] In this step, the crushed size is 1 to 3 mm.

[0152] By weight statistics of the first black powder and the second black powder, the black powder recovery rate reached more than 98%, indicating that this solution is also applicable to the treatment of waste square aluminum shell ternary batteries and other types of batteries.

[0153] Part 2

[0154] The first part mainly describes the collection of black powder. Next, the treatment of the exhaust gas after the pyrolysis operation in step 5 is mainly explained.

[0155] In Example 1, only the step 5 to obtain solid is introduced, and the method for treating the tail gas is not clearly stated. In this field, there are two ways to treat the tail gas. The first way is to directly treat it harmlessly and then discharge it, and the second way is to recover the resources and then discharge it. Both methods have their own advantages. The former has low processing costs and has a relatively mature process for implementation; the latter is complicated to process, but can recycle renewable resources.

[0156] The following two embodiments illustrate these two methods respectively.

[0157] Example 5

[0158] This embodiment mainly introduces a process for harmless treatment and then discharge. Referring to Figure 2, it specifically includes an oil removal device 12, an exhaust combustion device 13, a heat exchanger 14, a flue gas quenching tower 15, a semi-dry reactor 16, a dust collector 17, an induced draft fan 18, a primary alkali spray tower 19, and a secondary alkali spray tower 20, which are connected in sequence. After the exhaust gas passes the test, it is discharged from a chimney 21.

[0159] The oil removal device 12 is connected to the flue gas outlet of the pyrolysis device;

[0160] The heating device 2 is connected to an exhaust fan and a primary condensing device 22. The exhaust fan is used to condense the organic solvent volatilized by heating of the heating device 2. The condensation is preferably performed using cold water at about 5°C. The primary condensing device 22 is preferably a tubular condenser.

[0161] In step 1, the volatilization temperature is not high, and the maximum does not exceed 150°C. Then there will be some high-boiling organic solvents, and the boiling points of these high-boiling organic solvents reach above 150°C.

[0162] Among them, the boiling point of unsaturated carbonate is very high. If it is treated at a volatilization temperature of 100°C, many solvents cannot be volatilized. These solvents are collectively referred to as high-boiling organic solvents, that is, solvents with a boiling point above the set volatilization temperature. These solvents will become the first sieve undersize after the treatment in step 3.

[0163] During pyrolysis, the objects of pyrolysis are the first undersize material and the third solid, which specifically include: high-boiling organic solvent, lithium salt, black powder, electrode piece, binder and other substances attached to the positive electrode material;

[0164] When the pyrolysis temperature reaches 500°C, the high-boiling organic solvent will evaporate, the lithium salt will decompose into LiF and PF5, the binder on the electrode will decompose into carbon and fluorine-containing gas, and a small part of the binder will decompose into low-molecular cracking products;

[0165] The pyrolysis process is a process of continuously discharging the exhaust gas in the furnace. Therefore, it is unrealistic to ensure that all high-boiling organic solvents and binders are completely decomposed. The resulting problem is that thick oil stains will form on the pipeline between the smoke exhaust position and the exhaust gas combustion device 13. In order to solve this problem, an oil removal device 12 is set between the smoke exhaust position and the exhaust gas combustion device 13;

[0166] During the pyrolysis process, the oil removal device 12 may be a filter, an electrostatic oil remover containing an electrostatic plate type electric field, or the like;

[0167] The flue gas generated by the pyrolysis device 6 enters the heat exchanger 14 after passing through the deoiling device 12 for heat exchange to reduce energy consumption, and then enters the tail gas combustion device 13 for combustion. The natural gas ignition combustion system begins to assist combustion and temperature increase. When the temperature in the furnace reaches the set temperature, the mixed exhaust gas begins to enter the furnace. According to the three T principles of combustion (temperature, time, and vortex), the waste and combustion air are pyrolyzed and burned at high temperature in the furnace. The residence time is sufficient and the combustion efficiency reaches more than 99.99%, ensuring that the organic matter is fully oxidized and decomposed.

[0168] The flue gas remains in the furnace for a sufficient period of time to fully burn, and the waste is completely decomposed into acidic gases such as CO2 and H2O at high temperatures. The ash from the incineration residue is packaged and transported to the ash storage room by forklift. It is then transported by truck to a qualified unit for treatment as required.

[0169] The temperature of the TO furnace (pyrolysis gas combustion chamber) is maintained at >1100°C under auxiliary fuel, making the incineration more complete and achieving the effect of smokeless, odorless and zero secondary pollution. The flue gas stays in the secondary incineration chamber for 2 seconds, allowing the trace organic matter and dioxins in the flue gas to be fully decomposed. The decomposition efficiency exceeds 99.99%, ensuring that the hazardous waste entering the incineration system is fully burned.

[0170] The high-temperature flue gas after incineration passes through the heat exchanger 14 and enters the flue gas quenching tower 15, where it is quickly cooled to 200°C to avoid the formation of dioxins.

[0171] Then it enters the flue of the semi-dry reactor 16 to mix with activated carbon powder and lime powder to remove acidic substances and a certain amount of water, and then enters the dust collector 17 to remove dust.

[0172] The flue gas is then pushed by induced draft fan 18 into primary and secondary alkaline spray towers 19 and 20, where it purifies and absorbs acidic gases. After purification, it is discharged through chimney 21. PF5 in the cracked gas is hydrolyzed to produce HF and H3PO4 acidic gases, which are then neutralized, precipitated, purified, and absorbed through water and alkaline washing processes. NaOH is added to the alkaline spray tower, and wastewater from the waste gas water washing treatment system is neutralized with Ca(OH)2, ultimately producing CaF2 and Ca3(PO4)2 precipitates. These precipitates are then dehydrated and outsourced for treatment.

[0173] After the above-mentioned process, the exhaust gas discharged can be guaranteed to meet environmental protection standards.

[0174] Example 6

[0175] This embodiment mainly introduces a process for resource recovery and subsequent discharge. Referring to FIG3 , specifically, step 5 is split into two steps, including step 51 and step 52 that are performed sequentially.

[0176] Step 51: Under the protection of inert gas, the first undersize material and the third solid are subjected to a first pyrolysis to decompose the lithium salt and volatilize the high-boiling organic solvent, and these products are recycled as resources;

[0177] Step 52: Under the protection of inert gas, the solid material after pyrolysis in step 51 is subjected to a second pyrolysis, and the second pyrolysis is used to carbonize the binder; the tail gas from the second pyrolysis is directly subjected to harmless treatment and then discharged. The harmless treatment can refer to the traditional treatment method of the relevant tail gas in Example 5.

[0178] The temperature of the first pyrolysis is 200-300°C; the temperature of the second pyrolysis is 300-500°C;

[0179] Correspondingly, the supporting equipment for step 51 is a pre-condensing device 23 for condensing the gas generated by the first pyrolysis, a primary condensing device 24 for condensing the uncondensed gas of the pre-condensing device, a secondary condensing device 25 for condensing the uncondensed gas of the primary condensing device, and a tertiary condensing device 26 for condensing the uncondensed gas of the secondary condensing device, which are connected in sequence.

[0180] The pre-condensing device 23, the primary condensing device 24, the secondary condensing device 25, and the tertiary condensing device 26 are all tubular condensers;

[0181] The more detailed process is:

[0182] Step 510: The gas generated by the first pyrolysis contains a high-boiling organic solvent, low-molecular cracking products after the cracking of the binder, nitrogen, water, PF5, HF, and POF3;

[0183] Step 511: The gas obtained in step 510 is sent to the pre-condensing device 23 to remove the high-boiling organic solvent and low-molecular cracking products therein; the pre-condensing device 23 is a water-cooled tubular condenser, and cooling water at 0 to 5°C is introduced into the pre-condensing device. The uncondensed gas discharged from the pre-condensing device is the first gas.

[0184] Step 512: The first gas is fed into a primary condensing device 24, which is a tubular condenser. The refrigerant of the primary condensing device is chilled brine at a temperature of -5°C to 0°C. The HF and water are fully condensed to obtain a second gas containing only nitrogen, PF5, POF3, and trace amounts of unidentified impurities.

[0185] Generally speaking, the refrigerant temperature in the tubular condenser should be significantly lower than the boiling point of the object to be condensed, and can even be close to the freezing point of the object. The reason is that the amount of nitrogen in the first gas is relatively large and the gas flow rate is relatively fast. If the condensation temperature is too high, the object to be condensed will not be fully condensed.

[0186] Step 513: The second gas is sent to the secondary condensation device 25 for condensation to obtain the third gas; the secondary condensation device 25 is a tubular condenser, the refrigerant used is liquid nitrogen, and the condensation temperature is -60 to -50°C; this step is mainly used to remove POF3;

[0187] Step 514: Send the third gas to the three-stage condensing device 26 for condensation to collect liquid PF5. The three-stage condensing device 26 is a tubular condenser, the refrigerant used is liquid nitrogen, and the condensation temperature is -120 to -110°C.

[0188] As a further preference of this embodiment, the above embodiment 1 records that most of the solvent is volatilized at the solvent volatilization temperature. In actual production, at the volatilization temperature, a small amount of lithium hexafluorophosphate or other lithium salt still has the risk of decomposition, which also results in a small amount of PF5 being generated after the solvent is recovered in step 1;

[0189] During the production process, it is difficult to detect PF5 in the solvent recovered from step 1. The reason is that its saturated vapor pressure is high and it will evaporate quickly, making it difficult to detect from the recovered solvent. This has also led people to believe that there is no risk of lithium salt decomposition in the solvent recovery in step 1.

[0190] If the PF5 in the solvent recovery process of step 1 is not further recovered and processed, it will not only cause environmental pollution but also waste resources;

[0191] In order to solve this problem, the following equipment is used in the recovery process of the solvent in step 1: a primary condensing device 22 for condensing the gas generated in step 1 and a separation device for separating fluorine-containing compounds from the tail gas of the primary condensing device; the separation device is a cold trap 27;

[0192] The primary condensing device 22 condenses the volatilized solvent in step 1 at a temperature of 0 to 5°C and is a water-cooled tubular condenser. The uncondensed gas discharged from the primary condensing device 22 is introduced into a cold trap 27 using -20°C supercooled brine as a refrigerant to obtain a fourth gas, which is a relatively pure fluorine-containing gas. The main purpose of the cold trap 27 is to fully remove the uncondensed organic solvent to prevent the organic solvent from entering step 513 and causing trouble in the condensation process of step 513.

[0193] The fourth gas contains a large amount of nitrogen and fluorine-containing gas, which is sent to step 513, mixed with the second gas, and sent to the secondary condensation device 25 for condensation;

[0194] The use of cold traps can effectively prevent PF5 from leaking into the atmosphere and can also effectively recover PF5.

[0195] Experimental verification found that if the tail gas of the primary condensing device 22 is directly discharged, the PF5 recovery rate is reduced by about 3% compared with Example 6; that is, at least 3% of the lithium salt is decomposed in step 1; therefore, it is very necessary to use the method of Example 6 to perform the PF5 resource recovery operation.

[0196] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and intent of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A method for crushing, sorting and recycling waste lithium-ion batteries, characterized in that: The steps include: Step 1: After the lithium-ion battery is crushed, it is heated to 60-150° C. under the protection of an inert gas to volatilize at least part of the solvent in the electrolyte to obtain a first solid; Step 2: removing the battery shell in the first solid to obtain a second solid; Step 3: sieving the second solid to obtain a first undersize and a first oversize, wherein the first undersize contains free black powder in the second solid; Step 4: removing the membrane from the first screen material through airflow sorting to obtain a third solid; Step 5: Pyrolyzing the first undersize material and the third solid to decompose the lithium salt and crack and carbonize the binder on the electrode to obtain a fourth solid; Step 6: Screening the fourth solid to obtain a second undersize material and a second oversize material; the second undersize material is the first black powder; Step 7: Crush the second oversize material, and sieve the crushed product to obtain a third undersize material and a third oversize material; the third undersize material is the second black powder, and the third oversize material is the metal substrate particles of the electrode.

2. The method for crushing, sorting and recycling waste lithium-ion batteries according to claim 1, characterized in that: The step 2 specifically includes: removing the battery shell in the first solid by airflow sorting process, and the second solid enters step 3 by negative pressure extraction.

3. The method for crushing, sorting and recycling waste lithium-ion batteries according to claim 1, characterized in that: The sieve aperture of step 3 is 2-50 mesh; the sieve aperture of step 6 is 80-150 mesh; the sieve aperture of step 7 is 80-150 mesh.

4. The method for crushing, sorting and recycling waste lithium-ion batteries according to claim 1, characterized in that: The first undersize material and / or the third solid enter step 5 after magnetic separation.

5. The method for crushing, sorting and recycling waste lithium-ion batteries according to claim 1, characterized in that: Step 1 is specifically as follows: under a protective atmosphere, the battery is cut and destroyed, the cut and destroyed material is crushed, the crushed material size is controlled to be 10 to 30 mm, and the battery components are completely broken up and opened.

6. The method for crushing, sorting and recycling waste lithium-ion batteries according to claim 1, characterized in that: In step 1, the solvent volatilization temperature is 100-150° C. and the time is 30-120 min; The pyrolysis temperature in step 5 is 300-550° C. and the time is 30-120 min.

7. The method for crushing, sorting and recycling waste lithium-ion batteries according to any one of claims 1 to 6, characterized in that: In the step 1, a first gas is also obtained, and the solvent is recovered by condensing the first gas; In step 5, a second gas is obtained after pyrolysis, and PF5 in the second gas is recovered by multi-stage condensation.

8. A system for implementing the method according to any one of claims 1 to 7, characterized in that: The invention comprises a first crushing unit for crushing lithium-ion batteries, a heating device for heating and volatilizing the solvent in the crushed lithium-ion batteries, a first separation device for removing the battery shell in the first solid, a first screening device for screening the second solid to remove the free black powder in the second solid, a second separation device for removing the diaphragm in the first screened material, a pyrolysis device for pyrolyzing the first screened material and the third solid, a second screening device for screening the fourth solid, a second crushing unit for crushing the second screened material, and a third screening device for screening the crushed product of the second crushing unit.

9. The system according to claim 8, characterized in that A magnetic separation device is also provided between the second separation device and the pyrolysis device; The first crushing unit includes a shredding device for cutting off the complete lithium-ion battery and a crushing device for crushing the shredded lithium-ion battery; The first separation device and the second separation device are both airflow separators; the second solid is the light component separated by the first separation device; the third solid is the heavy component separated by the second separation device; The first screening device and the second screening device are both drum screens.

10. The system according to claim 8, characterized in that It also includes a first condensation unit and a second condensation unit. The gas generated in the heating device is transported to the first condensation unit through a pipeline; the gas generated in the pyrolysis device is transported to the second condensation unit through a pipeline.

11. The system according to claim 10, characterized in that The pyrolysis device performs pyrolysis in two steps; the temperature of the first pyrolysis is 200-300°C; the temperature of the second pyrolysis is 300-500°C.

12. The system according to claim 10, characterized in that The second condensing unit comprises a pre-condensing device for condensing the gas generated by the first pyrolysis, a primary condensing device for condensing the uncondensed gas of the pre-condensing device, a secondary condensing device for condensing the uncondensed gas of the primary condensing device, and a tertiary condensing device for condensing the uncondensed gas of the secondary condensing device, which are connected in sequence; The first condensing unit comprises a primary condensing device for condensing the gas generated in the heating device and a separation device for separating fluorine-containing compounds from the tail gas of the primary condensing device; the gas separated by the separation device is sent to a secondary condensing device for condensation.

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