Preparation device and recovery process of a mixed lithium iron phosphate electrode floating inhibitor

Abstract

The application relates to the technical field of electrode recovery, in particular to a preparation device and recovery process of a mixed lithium iron phosphate electrode flotation inhibitor, which comprises a cover, a hollow cylinder is arranged in the interior of a beaker and is mounted on the lower surface of the cover, a stirring branch cylinder is rotatably arranged on the periphery of the hollow cylinder, a stirring plate is arranged on the surface of a stirring main shaft, and the stirring rod and the stirring plate are staggered with each other; a driven gear meshed with the driving gear is arranged on the outer side of the driving gear, and the driven gear is fixedly sleeved with the upper end of the stirring branch cylinder; the beneficial effect is that: the reagent mainly composed of starch, cellulose natural high-molecular polymer which is easy to be biodegraded is used as the selective flocculation reagent and the lithium iron phosphate flotation inhibitor, and the reagent has the characteristics of green, environmental protection, no pollution and environmental friendliness; the influence of the binder PVDF and the electrolyte on the sorting of the positive and negative electrodes of the mixed electrode of the waste lithium battery is reduced; the roasting method is not needed to remove the binder and the electrolyte, the sorting cost is reduced, and the environment is friendly.

Description

Technical Field

[0001] This invention relates to the field of electrode recycling technology, specifically to a preparation apparatus and recycling process for mixed lithium iron phosphate electrode flotation inhibitors. Background Technology

[0002] The main components of the lithium iron phosphate hybrid electrode are lithium iron phosphate and graphite, and the minor components are ethylene carbonate electrolyte, PVDF binder, and separator.

[0003] Traditional methods for recovering mixed lithium iron phosphate electrodes typically include chemical and metallurgical processes (roasting, acid leaching, alkaline leaching), or hydrometallurgical and pyrometallurgical recovery. These processes are energy-intensive and costly, and prone to secondary pollution. For example, pyrometallurgical recovery results in low metal recovery rates, demanding equipment requirements, and the inability to recover lithium. Metal recovery from the alloy requires further refining, and environmental impacts include the production of smelting slag, dust, and harmful gases. Hydrometallurgical recovery, on the other hand, requires the crushing of individual battery cells, consumes large quantities of reagents, and treats large amounts of saline wastewater. Therefore, this invention proposes a device for preparing a mixed lithium iron phosphate electrode flotation inhibitor and a recovery process to address these problems. Summary of the Invention

[0004] The purpose of this invention is to provide a preparation apparatus and recycling process for a mixed lithium iron phosphate electrode flotation inhibitor, in order to solve the problems of high energy consumption, high cost, and serious secondary pollution in the recycling process of traditional mixed lithium iron phosphate electrodes mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a preparation apparatus for a mixed lithium iron phosphate electrode flotation inhibitor, comprising a stirring assembly, wherein the stirring assembly includes:

[0006] A lid is provided, which covers the opening of the beaker. A hollow cylinder is installed on the lower surface of the lid and located inside the beaker. A stirring support is rotatably installed around the periphery of the hollow cylinder, and a stirring rod is provided on the surface of the stirring support. A stirring spindle is rotatably installed in the middle of the inner cavity of the hollow cylinder, and a stirring plate is provided on the surface of the stirring spindle. The stirring rod and the stirring plate are staggered. A clearance groove is provided on the surface of the hollow cylinder for the stirring rod to pass through. A discharge port is provided on the surface of the stirring support.

[0007] A drive gear is located outside the beaker and is fixedly connected to the upper end of the stirring shaft. A driven gear is provided on the outside of the drive gear and meshes with it. The driven gear is fixedly sleeved on the upper end of the stirring support cylinder.

[0008] Preferably, a sealing platform is fixedly provided on the lower surface of the cap, the side wall of the sealing platform is attached to and bonded to the inner wall of the beaker with a sealing layer, and multiple stirring cylinders are provided and distributed in a ring array around the hollow cylinder.

[0009] Preferably, the upper ends of the stirring spindle and the stirring support cylinder are both covered by a cover. The upper surface of the cover is provided with an installation groove. The driving gear and the driven gear are both located in the inner cavity of the installation groove. The opening end of the installation groove is covered with a top cover. The surface of the top cover is connected to a plug by a flexible connecting rope. Multiple plugs are provided and are respectively sealed at the upper opening ends of multiple stirring support cylinders. The upper end of the stirring spindle is provided with a handle for driving the stirring spindle to rotate.

[0010] A recycling process for mixed lithium iron phosphate electrodes includes preparing a mixed lithium iron phosphate electrode flotation inhibitor using the aforementioned preparation apparatus, specifically comprising the following steps:

[0011] Step 1, Mixing: After mixing the lithium iron phosphate electrode with water, add a dispersant and grind the mixture to obtain mixed electrode powder;

[0012] Step 2, stirring and flocculation: Pour the ground mixed electrode powder into a mixing tank and stir. Add a selective flocculant and continue stirring. After mixing evenly, let it stand to obtain a slurry.

[0013] Step 3, Magnetic Separation: A high-gradient magnetic separator is used to separate the slurry into graphite anode and lithium iron phosphate + graphite.

[0014] Step 4, Flotation: Using lithium iron phosphate and graphite as magnetic concentrate, water is added to prepare a slurry. Dispersant, depressant, collector, and frother are added to the slurry in sequence to obtain underflow product A and froth product A (roughing). Dispersant, depressant, collector, and frother are added to underflow product A in sequence, with the amount of reagents being half of the amount used in the roughing process, to obtain froth product B and underflow product B (cleaning process one). Dispersant, depressant, collector, and frother are added to underflow product B in sequence, with the amount of reagents being half of the amount used in cleaning process one, to obtain underflow product C and froth product C (cleaning process two). Underflow product C is the lithium iron phosphate cathode.

[0015] Step 5, Scavenging operation: Add dispersant and inhibitor to the slurry of froth product A in sequence. The amount of reagent used is 1 / 4 of the amount of reagent used in the roughing process. This will yield froth product D and underflow product D. Froth product D is a graphite negative electrode.

[0016] Preferably, in steps four and five, foam product B and underflow product D are mixed and returned to the roughing step, where they are mixed with magnetic concentrate to form a closed circuit. Foam product C is then returned to the cleaning step and mixed with underflow product A for cleaning.

[0017] Preferably, in steps two and four, the selective flocculant and the inhibitor are the same substance, and its preparation method includes the following steps:

[0018] Step 1: Add water, starch, cellulose salt, polyacrylamide and polyvinyl alcohol to a beaker, and stir with a stirring device until the solution is uniform and free of particles;

[0019] Step 2: Heat the beaker, add sodium hydroxide and sodium sulfite, and continue heating until the substances in the beaker have reacted completely;

[0020] Step 8: After the beaker has cooled down, dilute the solution inside the beaker.

[0021] Preferably, in step ①, the mass ratio of starch: cellulose salt: polyacrylamide: polyvinyl alcohol is 50-80: 5-9: 0.01-0.05: 2-7.

[0022] Preferably, in step one, the dispersant is sodium tripolyphosphate, guar gum and water glass in a mass ratio of 2-10:1-8:1-15, the amount of dispersant is 500-1000 g / ton, the grinding concentration is 60%-80%, the grinding time is 15-30 min, and the mill speed is 20-40 r / min.

[0023] Preferably, in step two, the first stirring time is 5-15 min, the selective flocculant dosage is 800-1500 g / ton, the second stirring time is 5-15 min, and in step three, the magnetic field strength is 0.5-0.8 T, and the pulse size is 100-300 times / min.

[0024] Preferably, in step four, the amount of dispersant is 200-1000 g / ton, the amount of inhibitor is 500-1500 g / ton, the amount of collector is 100-300 g / ton, and the amount of foaming agent is 10-50 g / ton.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] 1. This invention uses agents mainly composed of easily biodegradable natural polymers such as starch and cellulose as selective flocculants and lithium iron phosphate flotation inhibitors, which are green, environmentally friendly, pollution-free and environmentally friendly.

[0027] 2. Selective flocculation selectively bridges the positive electrode of lithium iron phosphate batteries, reducing the inclusion of graphite in the negative electrode material before magnetic separation, optimizing the magnetic separation effect, and providing a good separation basis for subsequent flotation.

[0028] 3. Due to the small particle size of battery powder, usually between 10-50μm, it is very easy to form an "entrainment" phenomenon during the flotation process. By adding inhibitors, the floating of lithium iron phosphate cathode material can be selectively suppressed, reducing the occurrence of the flotation "entrainment" phenomenon and improving the flotation index.

[0029] 4. The process of "selective flocculation-magnetic separation-flotation" is adopted to reduce the impact of binder PVDF and electrolyte on the separation of positive and negative electrodes of waste lithium battery mixed electrodes. It does not require separate roasting to remove binder and electrolyte, which reduces the separation cost and is environmentally friendly. Attached Figure Description

[0030] Figure 1 This is a three-dimensional schematic diagram of the stirring assembly structure of the present invention;

[0031] Figure 2 This is a schematic diagram of the hollow cylinder structure installation of the present invention;

[0032] Figure 3 This is a three-dimensional schematic diagram of the hollow cylinder structure of the present invention;

[0033] Figure 4 This is a schematic diagram of the top cover structure installation of the present invention;

[0034] Figure 5 This is a schematic diagram of the internal structure of the mounting slot of the present invention;

[0035] Figure 6 This is a schematic diagram of the flocculation-magnetic separation process of the present invention;

[0036] Figure 7 This is a schematic diagram of the flotation process of the present invention.

[0037] In the diagram: 1. Cover; 11. Sealing platform; 12. Mounting groove; 13. Top cover; 14. Plug; 15. Flexible connecting rope; 2. Hollow cylinder; 21. Mixing support cylinder; 22. Mixing rod; 23. Clearance groove; 24. Discharge port; 3. Mixing main shaft; 31. Mixing plate; 32. Hand lever; 4. Drive gear; 5. Driven gear. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the present invention clear and complete, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only some, not all, embodiments of the present invention, and are merely illustrative of the embodiments of the present invention. They are not intended to limit the embodiments of the present invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] In the description of this invention, it should be noted that the terms "center," "middle," "upper," "lower," "left," "right," "inner," "outer," "top," "bottom," "side," "vertical," and "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "a," "first," "second," "third," "fourth," "fifth," and "sixth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0040] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0041] For purposes of simplicity and illustration, the principles of the embodiments are described primarily by way of example. In the following description, numerous specific details are set forth to provide a thorough understanding of the embodiments. However, it will be apparent to those skilled in the art that these embodiments may not be limited to these specific details in practice. In some instances, well-known methods and structures have not been described in detail to avoid unnecessarily obscuring these embodiments. Furthermore, all embodiments can be used in combination with each other.

[0042] Please see Figures 1 to 7 The present invention provides a technical solution:

[0043] Example 1: A preparation apparatus for a mixed lithium iron phosphate electrode flotation inhibitor, comprising a stirring assembly, which includes a capping 1 and a drive gear 4.

[0044] A cap 1 covers the opening of the beaker, and a hollow cylinder 2 located inside the beaker is mounted on the lower surface of the cap 1. A stirring support 21 is rotatably mounted around the periphery of the hollow cylinder 2, and a stirring rod 22 is provided on the surface of the stirring support 21. A stirring shaft 3 is rotatably mounted in the center of the inner cavity of the hollow cylinder 2, and a stirring plate 31 is provided on the surface of the stirring shaft 3. The stirring rod 22 and the stirring plate 31 are staggered. A clearance groove 23 is provided on the surface of the hollow cylinder 2 for the stirring rod 22 to pass through. A discharge port 24 is provided on the surface of the stirring support 21. Figure 2 , Figure 3 and Figure 4As shown, when the stirring shaft 3 and the stirring support cylinder 21 rotate, both the stirring plate 31 and the stirring rod 22 can mix and stir the solution in the beaker. Due to the blocking effect of the hollow cylinder 2, the solution in the beaker will not overflow from the opening end of the beaker due to excessive rotation speed. In addition, when the stirring shaft 3 and the stirring support cylinder 21 rotate, the solution in the beaker can be mixed in a disordered manner, thereby ensuring a higher degree of mixing.

[0045] Secondly, the drive gear 4 is located outside the beaker and fixedly connected to the upper end of the stirring shaft 3. A driven gear 5 meshes with the drive gear 4 on its outer side. The driven gear 5 is fixedly sleeved on the upper end of the stirring support cylinder 21. Figure 5 As shown, when the drive gear 4 rotates, it can drive the stirring support cylinder 21 to rotate through the meshing transmission of the driven gear 5, thereby ensuring that the stirring main shaft 3 can drive the stirring support cylinder 21 to rotate synchronously.

[0046] Furthermore, a sealing platform 11 is fixedly provided on the lower surface of the cap 1. The side wall of the sealing platform 11 is attached to the inner wall of the beaker and a sealing layer is bonded to it to improve the sealing performance of the cap 1 to the opening end of the beaker. Multiple stirring support cylinders 21 are provided and distributed in a ring array around the hollow cylinder 2.

[0047] Additionally, a cover 1 extends through the upper ends of both the stirring shaft 3 and the stirring support cylinder 21. An installation groove 12 is formed on the upper surface of the cover 1. The drive gear 4 and driven gear 5 are located within the installation groove 12. A top cover 13 covers the opening of the installation groove 12. A plug 14 is connected to the surface of the top cover 13 via a flexible connecting rope 15. Multiple plugs 14 are provided and respectively seal the upper opening ends of multiple stirring support cylinders 21. A handle 32 for driving the stirring shaft 3 to rotate is provided at the upper end of the stirring shaft 3. Figure 5 , Figure 4 and Figure 1 As shown, the operator can drive the stirring shaft 3 to rotate by using the handle 32. Then, through the meshing between the drive gear 4 and multiple driven gears 5, multiple stirring cylinders 21 are driven to rotate synchronously, thereby achieving thorough mixing of the solution in the beaker. In addition, the above-mentioned method of manually driving the stirring shaft 3 to rotate by using the handle 32 is only one of the multiple driving methods. Depending on the actual needs of the site, this device can also install a known drive motor on the surface of the top cover 13 to drive the stirring shaft 3 to rotate, which will not be elaborated here.

[0048] This invention also discloses a recycling process for mixed lithium iron phosphate electrodes, including the preparation of a mixed lithium iron phosphate electrode flotation inhibitor using the aforementioned preparation apparatus, specifically including the following steps:

[0049] Step 1, Mixing: After mixing the lithium iron phosphate electrode with water, add a dispersant and grind the mixture to obtain mixed electrode powder;

[0050] Step 2, stirring and flocculation: Pour the ground mixed electrode powder into a mixing tank and stir. Add a selective flocculant and continue stirring. After mixing evenly, let it stand to obtain a slurry.

[0051] Step 3, Magnetic Separation: A high-gradient magnetic separator is used to separate the slurry into graphite anode and lithium iron phosphate + graphite.

[0052] Step 4, Flotation: Using lithium iron phosphate and graphite as magnetic concentrate, water is added to prepare a slurry. Dispersant, depressant, collector, and frother are added to the slurry in sequence to obtain underflow product A and froth product A (roughing). Dispersant, depressant, collector, and frother are added to underflow product A in sequence, with the amount of reagents being half of the amount used in the roughing process, to obtain froth product B and underflow product B (cleaning process one). Dispersant, depressant, collector, and frother are added to underflow product B in sequence, with the amount of reagents being half of the amount used in cleaning process one, to obtain underflow product C and froth product C (cleaning process two). Underflow product C is the lithium iron phosphate cathode.

[0053] Step 5, Scavenging operation: Add dispersant and inhibitor to the slurry of froth product A in sequence. The amount of reagent used is 1 / 4 of the amount of reagent used in the roughing process. This will yield froth product D and underflow product D. Froth product D is a graphite negative electrode.

[0054] In steps four and five, froth product B and underflow product D are mixed and returned to the roughing step, where they are mixed with magnetic concentrate to form a closed circuit. Froth product C is then returned to the cleaning step and mixed with underflow product A for cleaning.

[0055] In steps two and four, the selective flocculant and the inhibitor are the same substance, and its preparation method includes the following steps:

[0056] Step 1: Add water, starch, cellulose salt, polyacrylamide and polyvinyl alcohol to a beaker, and stir with a stirring device until the solution is uniform and free of particles;

[0057] Step 2: Heat the beaker, add sodium hydroxide and sodium sulfite, and continue heating until the substances in the beaker have reacted completely;

[0058] Step 8: After the beaker has cooled down, dilute the solution inside the beaker.

[0059] The mechanism of action of selective flocculants and flotation inhibitors is as follows:

[0060] I. The carboxylic acid anions of modified carboxymethyl cellulose salt electrostatically attract the metal cations on the surface of lithium iron phosphate cathode material. The hydroxyl groups in the modified carboxymethyl cellulose salt form a water film with water through hydrogen bonds. This electrostatic attraction due to opposite charges can reach the level of forming chemical bonds, thus creating a certain degree of chemisorption. Furthermore, the modified carboxymethyl cellulose salt forms molecular flocculation in water. These micelles adsorb the lithium iron phosphate cathode material within the micelles, increasing the particle size of the lithium iron phosphate. This reduces the entrainment effect of collectors and frothers on the lithium iron phosphate cathode material during flotation aeration.

[0061] II. Starch molecules are very large, and each glucose unit in the molecule contains 3 hydroxyl groups. After modification, starch contains not only hydroxyl groups but also other hydrophilic groups. It can also be adsorbed onto the mineral surface through hydrogen bonding, so that the mineral particles are first coated with a layer of starch colloid and then coated with a layer of water film, thereby inhibiting the hydrophilicity of lithium iron phosphate cathode material.

[0062] III. Under the combined action of modified starch, modified carboxymethyl cellulose and other agents, the surface properties and particle state of lithium iron phosphate cathode material are changed, and the hydrophilicity of lithium iron phosphate cathode material is enhanced, thereby achieving the inhibition effect on lithium iron phosphate cathode material.

[0063] In step ①, the mass ratio of starch: cellulose salt: polyacrylamide: polyvinyl alcohol is 50-80: 5-9: 0.01-0.05: 2-7.

[0064] In step one, the dispersant is sodium tripolyphosphate, guar gum and water glass in a mass ratio of 2-10:1-8:1-15, the amount of dispersant is 500-1000 g / ton, the grinding concentration is 60%-80%, the grinding time is 15-30 min, and the mill speed is 20-40 r / min.

[0065] In step two, the first stirring time is 5-15 minutes, and the amount of selective flocculant is 800-1500 grams / ton. The second stirring time is 5-15 minutes. In step three, the magnetic field strength is 0.5-0.8T, and the pulse size is 100-300 times / min.

[0066] In step four, the dosage of dispersant is 200-1000 g / ton, the dosage of inhibitor is 500-1500 g / ton, the dosage of collector is 100-300 g / ton, and the dosage of foaming agent is 10-50 g / ton.

[0067] Example 2: An experiment was conducted using a mixed electrode from a waste lithium battery in Anhui Province with a fixed carbon content of 23.21%. The main materials were lithium iron phosphate and graphite.

[0068] 1. Add water to the mixed electrode powder to adjust the concentration to 70%, add 600g / t of dispersant (sodium tripolyphosphate, guar gum and water glass, mass ratio = 7:5:10), grind for 20min, and mill speed is 30r / min.

[0069] 2. Pour the ground mixed electrode powder into the mixing tank and stir at a speed of 80 r / min for 7 min. Then add the prepared selective flocculant at a dosage of 500 g / ton. Continue stirring at a speed of 15 r / min for 10 min. After stirring, stop stirring and let stand for 1 min.

[0070] 3. The selectively flocculated slurry is subjected to magnetic separation with a magnetic field strength of 0.65T and a pulse size of 250 times / min to separate the magnetic separation tailings graphite product (fixed carbon content of 90.86%) and magnetic separation concentrate (lithium iron phosphate + graphite product).

[0071] 4. Add water to the lithium iron phosphate and graphite concentrate mixture to prepare a flotation concentration of 5%. Add dispersant, depressant, collector, and frother to the slurry in sequence (dispersant dosage: 480 g / ton; depressant dosage: 830 g / ton; collector dosage: 150 g / ton; frother dosage: 30 g / ton) to obtain underflow product A and froth product A. Continue to add dispersant, depressant, collector, and frother to underflow product A in sequence, with each dosage being half the amount of the roughing reagent, to obtain froth product B and underflow product B. Continue to add dispersant, depressant, collector, and frother to underflow product B in sequence, with each dosage being half the amount of the above reagents, to obtain underflow product C and froth product C. Underflow product C is the lithium iron phosphate cathode.

[0072] 5. The froth product A is subjected to scavenging. Dispersant and inhibitor are added to the slurry in sequence. The amount of reagent is 1 / 4 of the amount of reagent used in the roughing process. Froth product D and underflow product D are obtained. Froth product D is a graphite negative electrode with a fixed carbon content of 92.49%.

[0073] 6. Mix foam product B and underflow product D, and return them sequentially to the roughing stage. Mix them with the magnetic separation concentrate to form a closed circuit. Return foam product C sequentially to the cleaning stage, and mix it with underflow product A for cleaning.

[0074] 7. Finally, the two sets of graphite anodes are mixed to form a graphite anode product with a fixed carbon content of 91.92% and a graphite recovery rate of 95.35%. The flotation concentrate is a lithium iron phosphate cathode product with a lithium iron phosphate purity of 96.17%, a fixed carbon content of 1.43%, and a lithium iron phosphate recovery rate of 93.81%.

[0075] Example 3: An experiment was conducted using a mixed electrode from a waste lithium battery in Hubei Province with a fixed carbon content of 18.98% as the raw material. The main materials were lithium iron phosphate and graphite.

[0076] The steps in this embodiment are the same as those in Embodiment 2, with the main differences being as follows:

[0077] 1. After adding water, adjust the concentration to 65%, add 800g / t of dispersant (sodium tripolyphosphate, guar gum and water glass, mass ratio = 3:2:6), grind for 15min, and mill speed is 20r / min;

[0078] 2. The first stirring speed is 60 r / min, the stirring time is 10 min, and the selective flocculant dosage is 800 g / ton; the second stirring time is 5 min.

[0079] 3. With a magnetic field strength of 0.6T and a pulse size of 150 times / min, the separated graphite product has a fixed carbon content of 93.27%.

[0080] 4. The dosage of dispersant is 300 g / ton, the dosage of inhibitor is 500 g / ton, the dosage of collector is 100 g / ton, and the dosage of foaming agent is 20 g / ton;

[0081] 5. The fixed carbon content in foam product D was found to be 90.43%.

[0082] 6. Consistent;

[0083] 7. Graphite anode product with a fixed carbon content of 91.42% and a graphite recovery rate of 87.68%, lithium iron phosphate purity of 95.58%, fixed carbon content of 2.86%, and lithium iron phosphate recovery rate of 94.26%.

[0084] Example 4: An experiment was conducted using a high-alumina, low-grade phosphate rock from Henan Province with a fixed carbon content of 18.29% as raw material. The main materials were lithium iron phosphate and graphite.

[0085] The steps in this embodiment are the same as those in Embodiments 2 and 3, with the main differences being as follows:

[0086] 1. After adding water, adjust the concentration to 75%, add 1000g / t of dispersant (sodium tripolyphosphate, guar gum and water glass, mass ratio = 6:7:11), grind for 25min, and mill speed is 30r / min;

[0087] 2. The first stirring speed is 100 r / min, the stirring time is 5 min, and the selective flocculant dosage is 800 g / ton; the second stirring speed is 25 r / min, and the time is 15 min.

[0088] 3. With a magnetic field strength of 0.80T and a pulse size of 250 times / min, the separated graphite product has a fixed carbon content of 95.28%.

[0089] 4. The dosage of dispersant is 900 g / ton, the dosage of inhibitor is 1200 g / ton, the dosage of collector is 250 g / ton, and the dosage of foaming agent is 40 g / ton;

[0090] 5. The fixed carbon content in foam product D was found to be 92.33%.

[0091] 6. Consistent;

[0092] 7. Graphite anode product with a fixed carbon content of 93.45% and a graphite recovery rate of 95.98%, lithium iron phosphate purity of 94.14%, fixed carbon content of 1.56%, and lithium iron phosphate recovery rate of 96.52%.

[0093] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for recycling of mixed lithium iron phosphate electrode, characterized in that: Specifically comprising the following steps: Step one, mixing: mix the lithium iron phosphate electrode with water, add a dispersing agent, and perform grinding to obtain a mixed electrode powder; Step two, stirring and flocculation: pour the ground mixed electrode powder into a stirring barrel for stirring, continue stirring after adding a selective flocculating agent, and obtain a slurry after mixing and standing; Step three, magnetic separation: use a high-gradient strong magnetic separator to separate graphite negative electrodes and lithium iron phosphate+graphite from the slurry; Step four, flotation: prepare a slurry by adding water to the lithium iron phosphate+graphite as the magnetic separation concentrate, and sequentially add a dispersing agent, a depressor, a collector, and a frother to the slurry to obtain an underflow product A and a froth product A, continue to sequentially add a dispersing agent, a depressor, a collector, and a frother to the underflow product A, with the dosage of each reagent being half of the dosage in the roughing step, to obtain a froth product B and an underflow product B, continue to sequentially add a dispersing agent, a depressor, a collector, and a frother to the underflow product B, with the dosage of each reagent being half of the dosage in the first cleaning step, to obtain an underflow product C and a froth product C, and the underflow product C is a lithium iron phosphate positive electrode; Step five, scavenging operation: sequentially add a dispersing agent and a depressor to the slurry of the froth product A, with the dosage being 1 / 4 of the dosage in the roughing step, to obtain a froth product D and an underflow product D, and the froth product D is a graphite negative electrode; In the step two and the step four, the selective flocculating agent and the depressor are the same substance, and the preparation method comprises the following steps: Step ①, add water, starch, cellulose salt, polyacrylamide, and polyvinyl alcohol into a beaker, and use a stirring assembly to stir until the solution is uniform and free of particles; Step ②, heat the beaker, add sodium hydroxide and sodium sulfite, and continue heating until the reaction in the beaker is complete; Step ③, dilute the solution in the beaker after the beaker cools down; In the step ①, the mass ratio of starch: cellulose salt: polyacrylamide: polyvinyl alcohol is 50-80: 5-9: 0.01-0.05: 2-7.

2. The process for recovery of mixed lithium iron phosphate electrode according to claim 1, wherein: In the step four and the step five, the froth product B and the underflow product D are mixed and returned to the roughing step to mix with the magnetic separation concentrate to form a closed circuit, and the froth product C is returned to the first cleaning step to mix with the underflow product A for cleaning.

3. The process for recovery of mixed lithium iron phosphate electrode according to claim 2, wherein: In the step one, the dispersing agent is sodium tripolyphosphate, guar gum, and water glass, with a mass ratio of 2-10: 1-8: 1-15, and the dosage of the dispersing agent is 500-1000 g / t, the grinding concentration is 60%-80%, and the grinding time is 15-30 min, and the mill speed is 20-40 r / min.

4. The process for recycling mixed lithium iron phosphate electrode according to claim 3, wherein: In the step two, the first stirring time is 5-15 min, and the dosage of the selective flocculating agent is 800-1500 g / t, and the second stirring time is 5-15 min, and in the step three, the magnetic field strength is 0.5-0.8 T, and the pulse size is 100-300 times / min.

5. The process for recovery of mixed lithium iron phosphate electrode according to claim 4, wherein: In the step four, the dosage of the dispersing agent is 200-1000 g / t, the dosage of the depressor is 500-1500 g / t, the dosage of the collector is 100-300 g / t, and the dosage of the frother is 10-50 g / t.

6. A device for the preparation of a mixed lithium iron phosphate electrode flotation depressant for use in the recovery process of a mixed lithium iron phosphate electrode according to claim 5, said device comprising a stirring assembly, characterized in that: The stirring assembly comprises: A cap (1) is placed over the opening of the beaker. A hollow cylinder (2) is installed on the lower surface of the cap (1) inside the beaker. A stirring support cylinder (21) is rotatably installed around the hollow cylinder (2). A stirring rod (22) is provided on the surface of the stirring support cylinder (21). A stirring spindle (3) is rotatably installed in the middle of the inner cavity of the hollow cylinder (2). A stirring plate (31) is provided on the surface of the stirring spindle (3). The stirring rod (22) and the stirring plate (31) are interleaved. A clearance groove (23) is provided on the surface of the hollow cylinder (2) for the stirring rod (22) to pass through. A discharge port (24) is provided on the surface of the stirring support cylinder (21). A drive gear (4) is located outside the beaker and is fixedly connected to the upper end of the stirring shaft (3). A driven gear (5) meshes with the drive gear (4) on the outside of the drive gear (4). The driven gear (5) is fixedly sleeved on the upper end of the stirring support cylinder (21). A sealing platform (11) is fixedly provided on the lower surface of the cap (1). The side wall of the sealing platform (11) is attached to the inner wall of the beaker and a sealing layer is bonded to it. Multiple stirring support cylinders (21) are provided and arranged in a ring array around the hollow cylinder (2).

7. A device for the preparation of a mixed lithium iron phosphate electrode flotation depressant according to claim 6, characterized in that: The upper ends of the stirring spindle (3) and the stirring support cylinder (21) are both through the cover (1). The upper surface of the cover (1) is provided with an installation groove (12). The driving gear (4) and the driven gear (5) are both located in the inner cavity of the installation groove (12). The opening end of the installation groove (12) is covered with a top cover (13). The surface of the top cover (13) is connected to a plug (14) by a flexible connecting rope (15). Multiple plugs (14) are provided and are respectively sealed at the upper opening ends of multiple stirring support cylinders (21). The upper end of the stirring spindle (3) is provided with a handle (32) for driving the stirring spindle (3) to rotate.

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