Waste lithium iron phosphate energizing salt lake lithium extraction integrated method and energy-saving muffle furnace

Abstract

The invention provides a waste lithium iron phosphate energizing salt lake lithium extraction integrated method. Relates to the field of metal material recycling, and discloses a waste lithium iron phosphate energizing salt lake lithium extraction integrated method which comprises the following steps: S1, adding lithium iron phosphate powder into a container filled with a sulfuric acid and hydrogen peroxide mixed solution, heating and stirring to obtain a lithium-rich solution which contains Li < + >, SO4 < 2->, Fe < 3 + >, Fe < 2 + > and PO4 < 3->; s2, concentrating the lithium-rich solution, adjusting the pH value, and removing Fe < 3 + >, Fe < 2 + > and PO4 < 3-> to obtain a mixed solid and a lithium concentrated solution; s3, blowing carbon dioxide into the lithium concentrated solution, filtering and drying to obtain lithium carbonate and filtrate I; according to the waste lithium iron phosphate energizing salt lake lithium extraction integrated method, waste LIBs are used as raw materials, the preparation cost of a salt lake lithium extraction electrode material is reduced, meanwhile, waste LIBs resource recovery and a salt lake lithium extraction technology are organically combined, and lithium resource recovery and cyclic utilization are achieved.

Description

Technical Field

[0001] This invention relates to the field of metal material recycling, and in particular to an integrated method for lithium extraction from waste lithium iron phosphate salt lakes and an energy-saving muffle furnace. Background Technology

[0002] With the popularization of electric vehicles, the demand for lithium-ion batteries (LIBs) has increased dramatically, leading to a rapid increase in the number of waste batteries. Improper disposal of waste LIBs will not only waste resources but also cause serious environmental pollution. At the same time, global lithium resources are limited and unevenly distributed, and the contradiction between lithium supply and demand is becoming increasingly prominent. Therefore, the efficient recovery of lithium resources from waste LIBs and the exploration of its application in new fields have important economic and environmental significance.

[0003] In existing technologies, hydrometallurgy is one of the main methods for recovering lithium resources from waste LIBs, but its process is complex and costly. Although lithium extraction technology from salt lakes has made some progress, it faces challenges such as complex composition, high magnesium-to-lithium ratio, and low lithium concentration. There is an urgent need to develop efficient and low-cost lithium extraction methods.

[0004] Therefore, it is necessary to provide an integrated method for lithium extraction from salt lakes using waste lithium iron phosphate and an energy-saving muffle furnace to solve the above-mentioned technical problems. Summary of the Invention

[0005] This invention provides an integrated method for lithium extraction from waste lithium iron phosphate in salt lakes and an energy-saving muffle furnace, which solves the problems of high cost and low efficiency in the lithium extraction process.

[0006] To address the aforementioned technical problems, this invention provides an integrated method for lithium extraction from waste lithium iron phosphate-enhanced salt lakes, comprising the following steps:

[0007] S1: Lithium iron phosphate powder is added to a container containing a mixture of sulfuric acid and hydrogen peroxide, heated and stirred to obtain a lithium-rich solution. The lithium-rich solution contains Li. + SO4 2- Fe 3+ Fe 2+ and PO4 3- ;

[0008] S2: Concentrate the lithium-rich solution, adjust the pH, and remove Fe. 3+ Fe 2+ and PO4 3- This yields a mixture of solids and lithium concentrate;

[0009] S3: Carbon dioxide is bubbled into the lithium concentrate, filtered, and dried to obtain lithium carbonate and filtrate 1.

[0010] S4: Mix the filtrate 1 and the mixed solid obtained in S2, add a small amount of acid, stir to dissolve, and obtain a mixed solution;

[0011] S5: Add Fe2(SO4)3 to the mixture to reduce the Fe content in the mixture. 3+ Excess Fe 3+ and PO4 3- Complete precipitation yielded FePO4•2H2O and filtrate two, which contained Fe. 3+ Fe 2+ FePO4•2H2O is calcined in a muffle furnace to obtain FePO4;

[0012] S6: Adjust the pH of filtrate 2 obtained from S5 with sodium hydroxide, filter, and obtain precipitates Fe(OH)2 and Fe(OH)3 and filtrate 3;

[0013] S7: Concentrate, evaporate, and crystallize the filtrate to obtain sodium sulfate;

[0014] S8: Mix FePO4, polyvinylidene fluoride and conductive carbon black in a certain mass ratio, add N-methylpyrrolidone, stir, and obtain FePO4 slurry;

[0015] S9: Coat and dry the FePO4 slurry, then cut it into fragments to obtain the FePO4 electrode;

[0016] S10: The waste lithium iron phosphate powder is heated in two stages to obtain repaired lithium iron phosphate powder.

[0017] S11: Mix the repaired lithium iron phosphate powder, polyvinylidene fluoride and conductive carbon black in a certain mass ratio, add N-methylpyrrolidone, stir to obtain a slurry, coat, dry, cut into fragments to obtain a lithium iron phosphate electrode.

[0018] S12: The electrolyzer is divided into a cathode chamber and an anode chamber using an anion-selective membrane. Brine is added to the anode chamber and potassium chloride is added to the cathode chamber. Lithium iron phosphate electrode and FePO4 electrode are used as the anode and cathode, respectively. The power supply is connected, lithium is inserted and extracted, and the electrode positions are cyclically exchanged to obtain a lithium-ion-rich cathode electrode and lithium-free brine.

[0019] Preferably, the lithium-ion-rich cathode electrode in S12 was originally FePO4, but it becomes LiFePO4 during the lithium extraction process.

[0020] An energy-saving muffle furnace includes: an electrical control box;

[0021] The outer furnace body is fixedly installed on the top of the electrical control box;

[0022] The inner furnace body is fixedly installed to the bottom of the inner wall of the outer furnace body by a support column;

[0023] The outer furnace body has an external feed inlet and an external discharge outlet on both sides, respectively.

[0024] The inner furnace body has an inner feed port and an inner discharge port on its two sides, respectively.

[0025] A rotating mechanism is fixedly installed at the bottom of the inner wall of the outer furnace body. The rotating mechanism includes a rotating motor, which is fixedly installed at the bottom of the inner wall of the outer furnace body. The output shaft of the rotating motor is fixedly connected to a rotating shaft, which passes through the bottom of the inner furnace body and extends into the interior. A bushing is fixedly installed on the surface of the rotating shaft inside the inner furnace body. Six rotating plates are fixedly installed on the surface of the bushing. Clamping clips are fixedly installed at the ends of the six rotating plates through fixed plates.

[0026] The four heating tubes are respectively fixedly installed on the four sides of the inner wall of the furnace body.

[0027] Preferably, the top of the outer furnace body has six exhaust holes (I), and the top of the inner furnace body has six exhaust holes (II).

[0028] Preferably, an inner furnace sealing mechanism is fixedly installed at the bottom of the inner wall of the outer furnace. The inner furnace sealing mechanism includes a cylinder and limiting blocks. The cylinder is fixedly installed at the bottom of the inner wall of the outer furnace. A lifting plate is fixedly installed at the top of the cylinder through a connecting plate. Inner sealing plates are fixedly installed at both ends of the lifting plate. The two inner sealing plates are respectively adapted to the inner feed port and the inner discharge port. The four limiting blocks are fixedly installed on one side of the inner furnace. Two sliding rods are symmetrically fixedly installed inside the lifting plate. The two sliding rods are slidably installed with the four limiting blocks respectively.

[0029] Preferably, a feeding and unloading mechanism is fixedly installed on one side of the inner wall of the outer furnace. The feeding and unloading mechanism includes a drive motor, which is fixedly installed on one side of the inner wall of the outer furnace. A disc is fixedly installed on the output shaft of the drive motor. A connecting rod is rotatably installed on the surface of the disc via a convex shaft. A right-angle plate is rotatably installed on one end of the connecting rod via a fixed rod. A feeding tray is fixedly installed on the end of the right-angle plate. A second connecting rod is rotatably installed on the surface of the disc via a convex shaft. A right-angle plate is rotatably installed on one end of the second connecting rod via a fixed rod. A material-retrieving clamp is fixedly installed on the end of the right-angle plate. The feeding tray is adapted to the clamp, and the material-retrieving clamp is adapted to the clamp.

[0030] Preferably, a nitrogen mechanism is connected to one side of the outer furnace body. The nitrogen mechanism includes a connecting pipe connected to one side of the outer furnace body. The connecting pipe is connected to a nitrogen pipe through a solenoid valve. The end of the nitrogen pipe is connected to a nitrogen tank, which is located on the ground.

[0031] Preferably, each of the six exhaust holes is internally connected to an exhaust pipe, and the six exhaust pipes respectively pass through the six exhaust holes and extend to the outside.

[0032] Preferably, both sides of the outer furnace body are rotatably mounted with outer sealing plates via rotating shafts, and the two outer sealing plates are respectively adapted to and installed with the outer feed port and the outer discharge port.

[0033] Preferably, six top plates are fixedly mounted on the surface of the rotating shaft, and the six top plates are respectively adapted to and installed with the six exhaust holes.

[0034] Compared with related technologies, the integrated method for lithium extraction from waste lithium iron phosphate salt lakes provided by this invention has the following beneficial effects:

[0035] This invention provides an integrated method for lithium extraction from salt lakes using waste lithium iron phosphate (LIBs). By utilizing waste LIBs as raw materials, the preparation cost of electrode materials for lithium extraction from salt lakes is reduced. Simultaneously, the recycling of waste LIBs resources is organically combined with salt lake lithium extraction technology to achieve the recycling and reuse of lithium resources. During the FePO4 intercalation process, the ion insertion sequence is: Li + Na + >Mg 2+ >K + The selective permeability of anion-selective membranes helps improve the enrichment efficiency of lithium ions and can block other cations such as Na+. + Mg 2 + K + The membrane ensures that lithium ions can be more effectively enriched on the cathode electrode. It selectively allows lithium ions to pass through while blocking impurity ions. The anion-selective membrane helps to improve the purity of lithium extraction. Lithium ions form a concentration gradient in the electrolyte and move towards the cathode under the drive of the electric field. That is, they migrate between the anode and cathode through ion conduction in the electrolyte and the action of the electric field. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of a preferred embodiment of an energy-saving muffle furnace provided by the present invention;

[0037] Figure 2 Another structural schematic diagram of a preferred embodiment of an energy-saving muffle furnace;

[0038] Figure 3 for Figure 2 The diagram shows the structure of the rotating mechanism.

[0039] Figure 4 This is a schematic diagram of the structure of a second embodiment of an energy-saving muffle furnace;

[0040] Figure 5 Another structural schematic diagram of a second embodiment of an energy-saving muffle furnace;

[0041] Figure 6 for Figure 5 The diagram shows the installation of the inner furnace sealing mechanism;

[0042] Figure 7 for Figure 6 The diagram shows the structure of the inner furnace sealing mechanism.

[0043] Figure 8 for Figure 5 The diagram shown is a structural schematic of the feeding mechanism;

[0044] Figure 9 for Figure 5 The diagram shows the structure of the nitrogen gas mechanism.

[0045] Figure 10 for Figure 5 The diagram shows the installation of the top plate.

[0046] The diagram is labeled as follows: 1. Electrical control box; 2. Outer furnace body; 3. Inner furnace body; 4. Rotating mechanism; 401. Rotary motor; 402. Rotating shaft; 403. Bushing; 404. Rotating plate; 405. Fixing plate; 406. Clamping clip; 5. Exhaust port one; 6. Exhaust port two; 7. Inner furnace sealing mechanism; 701. Cylinder; 702. Lifting plate; 703. Inner sealing plate; 704. Slide rod; 705. Limit block; 8. Feeding and unloading mechanism; 801. Drive motor. 802. Disc; 803. Link 1; 804. Right Angle Plate 1; 805. Feed Tray; 806. Link 2; 807. Right Angle Plate 2; 808. Material Pickup Clamp; 9. Nitrogen Mechanism; 901. Nitrogen Tank; 902. Nitrogen Pipe; 903. Solenoid Valve; 904. Connecting Pipe; 10. Heating Pipe; 11. External Feed Inlet; 12. Internal Feed Inlet; 13. Internal Discharge Outlet; 14. External Discharge Outlet; 15. Exhaust Pipe; 16. External Sealing Plate; 17. Top Plate. Detailed Implementation

[0047] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0048] An integrated method for lithium extraction from salt lakes using waste lithium iron phosphate.

[0049] First Embodiment

[0050] An integrated method for lithium extraction from salt lakes using waste lithium iron phosphate includes the following steps:

[0051] S1: Lithium iron phosphate powder is added to a container containing a mixture of sulfuric acid and hydrogen peroxide, heated and stirred to obtain a lithium-rich solution. The lithium-rich solution contains Li. + SO4 2- Fe 3+ Fe 2+ and PO4 3- ;

[0052] S2: Concentrate the lithium-rich solution, adjust the pH, and remove Fe. 3+ Fe 2+ and PO4 3- This yields a mixture of solids and lithium concentrate;

[0053] S3: Carbon dioxide is bubbled into the lithium concentrate, filtered, and dried to obtain lithium carbonate and filtrate 1.

[0054] S4: Mix the filtrate 1 and the mixed solid obtained in S2, add a small amount of acid, stir to dissolve, and obtain a mixed solution;

[0055] S5: Add Fe2(SO4)3 to the mixture to reduce the Fe content in the mixture. 3+ Excess Fe 3+ and PO4 3- Complete precipitation yielded FePO4•2H2O and filtrate two, which contained Fe. 3+ Fe 2+ FePO4•2H2O is calcined in a muffle furnace to obtain FePO4;

[0056] S6: Adjust the pH of filtrate 2 obtained from S5 with sodium hydroxide, filter, and obtain precipitates Fe(OH)2 and Fe(OH)3 and filtrate 3;

[0057] S7: Concentrate, evaporate, and crystallize the filtrate to obtain sodium sulfate;

[0058] S8: Mix FePO4, polyvinylidene fluoride and conductive carbon black in a certain mass ratio, add N-methylpyrrolidone, stir, and obtain FePO4 slurry;

[0059] S9: Coat and dry the FePO4 slurry, then cut it into fragments to obtain the FePO4 electrode;

[0060] S10: The waste lithium iron phosphate powder is heated in two stages to obtain repaired lithium iron phosphate powder.

[0061] S11: Mix the repaired lithium iron phosphate powder, polyvinylidene fluoride and conductive carbon black in a certain mass ratio, add N-methylpyrrolidone, stir to obtain a slurry, coat, dry, cut into fragments to obtain a lithium iron phosphate electrode.

[0062] S12: The electrolyzer is divided into a cathode chamber and an anode chamber using an anion-selective membrane. Brine is added to the anode chamber and potassium chloride is added to the cathode chamber. Lithium iron phosphate electrode and FePO4 electrode are used as the anode and cathode, respectively. The power supply is connected, lithium is inserted and extracted, and the electrode positions are cyclically exchanged to obtain a lithium-ion-rich cathode electrode and lithium-free brine.

[0063] The lithium-ion-rich cathode electrode in S12 was originally FePO4, but it became LiFePO4 during the lithium extraction process.

[0064] The specific implementation method of the integrated lithium extraction method from waste lithium iron phosphate salt lakes provided by this invention is as follows:

[0065] S1: Add lithium iron phosphate powder to a container containing a mixture of hydrogen peroxide and sulfuric acid (molar ratio = 3:1), heat and stir at 65°C for 1.5 hours. The lithium-rich solution contains Li... + SO4 2- Fe 3+ Fe 2+ and PO4 3- ;

[0066] S2: Concentrate the lithium-rich solution, adjust the pH to 10, and remove Fe. 3+ Fe 2+ and PO4 3- This yields a mixture of solids and lithium concentrate;

[0067] S3: Carbon dioxide is bubbled into the lithium concentrate, filtered, and dried to obtain lithium carbonate and filtrate 1.

[0068] S4: Mix the filtrate 1 and the mixed solid obtained from S2, add 2% sulfuric acid dropwise, stir to dissolve, and obtain a mixed solution;

[0069] S5: Add Fe2(SO4)3 to the mixture to reduce the Fe content in the mixture. 3+ Excess, pH=5, Fe 3+ and PO4 3- Complete precipitation yielded FePO4•2H2O and filtrate two, which contained Fe. 3+ Fe 2+ ;

[0070] S6: FePO4•2H2O was washed three times, dried, and calcined in a muffle furnace at 600℃ for 2 hours to obtain FePO4.

[0071] S7: Adjust the pH of filtrate 2 obtained from S5 with sodium hydroxide, let it stand, and filter to obtain precipitates Fe(OH)2 and Fe(OH)3 and filtrate 3;

[0072] S8: Concentrate, evaporate, and crystallize the filtrate to obtain sodium sulfate;

[0073] S9: Mix the FePO4 obtained in S6 with polyvinylidene fluoride and conductive carbon black in a mass ratio of 8:1:1, add N-methylpyrrolidone as a solvent, stir, and obtain FePO4 slurry;

[0074] S10: Coat and dry the FePO4 slurry, then cut it into fragments to obtain the FePO4 electrode;

[0075] S11: The waste lithium iron phosphate powder was heated in two stages under an argon atmosphere. It was heated at 450℃ for 4 hours and then heated at 700℃ for 6 hours. The heating and cooling rates were both 5℃ / min. After cooling to room temperature, the repaired lithium iron phosphate powder was obtained.

[0076] S12: The repaired lithium iron phosphate powder, polyvinylidene fluoride and conductive carbon black are mixed in a mass ratio of 8:1:1. N-methylpyrrolidone is added as a solvent and stirred to obtain a slurry. The slurry is coated, dried and cut into fragments to obtain a lithium iron phosphate electrode. The electrolytic cell is divided into a cathode chamber and an anode chamber using an anion selective membrane. 50 mL of brine is added to the anode chamber and 50 mL of potassium chloride solution is added to the cathode chamber. A 2 cm × 2 cm lithium iron phosphate electrode and a 2 cm × 2 cm FePO4 electrode are used as the anode and cathode, respectively. The power supply is connected and an appropriate voltage is applied. Lithium insertion and extraction are performed, and the electrode positions are cyclically exchanged to obtain a lithium-ion-rich cathode electrode and lithium-free brine.

[0077] Compared with related technologies, the integrated method for lithium extraction from waste lithium iron phosphate salt lakes provided by this invention has the following beneficial effects:

[0078] This invention provides an integrated method for lithium extraction from salt lakes using waste lithium iron phosphate (LIBs). By utilizing waste LIBs as raw materials, the preparation cost of electrode materials for lithium extraction from salt lakes is reduced. Simultaneously, the recycling of waste LIBs resources is organically combined with salt lake lithium extraction technology to achieve the recycling and reuse of lithium resources. During the FePO4 intercalation process, the ion insertion sequence is: Li + Na + >Mg 2+ >K + The selective permeability of anion-selective membranes helps improve the enrichment efficiency of lithium ions and can block other cations such as Na+. + Mg 2 + K +The membrane ensures that lithium ions can be more effectively enriched on the cathode electrode. It selectively allows lithium ions to pass through while blocking impurity ions. The anion-selective membrane helps to improve the purity of lithium extraction. Lithium ions form a concentration gradient in the electrolyte and move towards the cathode under the drive of the electric field. That is, they migrate between the anode and cathode through ion conduction in the electrolyte and the action of the electric field.

[0079] An energy-saving muffle furnace

[0080] First Embodiment

[0081] Please refer to the following: Figure 1 , Figure 2 , Figure 3 An energy-saving muffle furnace includes: an electrical control box 1;

[0082] The outer furnace body 2 is fixedly installed on the top of the electrical control box 1;

[0083] The inner furnace body 3 is fixedly installed on the bottom of the inner wall of the outer furnace body 2 by a support column;

[0084] The outer furnace body 2 has an external feed inlet 11 and an external discharge outlet 14 on its two sides, respectively;

[0085] The inner furnace body 3 has an inner feed port 12 and an inner discharge port 13 on its two sides respectively;

[0086] A rotating mechanism 4 is fixedly installed at the bottom of the inner wall of the outer furnace body 2. The rotating mechanism 4 includes a rotating motor 401, which is fixedly installed at the bottom of the inner wall of the outer furnace body 2. The output shaft of the rotating motor 401 is fixedly connected to a rotating shaft 402. The rotating shaft 402 passes through the bottom of the inner furnace body 3 and extends into the interior. A bushing 403 is fixedly installed on the surface of the rotating shaft 402 inside the inner furnace body 3. Six rotating plates 404 are fixedly installed on the surface of the bushing 403. The ends of the six rotating plates 404 are all fixedly installed with clamping clips 406 through fixing plates 405.

[0087] Heating tubes 10, four of which are fixedly installed on the four sides of the inner wall of the inner furnace body 3.

[0088] The top of the outer furnace body 2 has six exhaust holes 5, and the top of the inner furnace body 3 has six exhaust holes 6.

[0089] In actual use, the clamping clip 406 does not contact the inner furnace body 3 during rotation; the FePO4•2H2O is placed in the crucible for calcination.

[0090] The working principle of the energy-saving muffle furnace provided by this invention is as follows:

[0091] First, the FePO4•2H2O obtained from S5 is placed into the crucible. The crucible is then manually placed into the clamping device 406 through the outer feed port 11 and the inner feed port 12 using crucible tongs. The heating tube 10 is activated to heat the interior of the inner furnace body 3 to calcine the FePO4•2H2O. The electrical control box 1 controls the heating tube 10 to achieve automated heating and safe operation.

[0092] During the calcination process, the rotary motor 401 is started to drive the rotary shaft 402 to rotate. Each time the rotary shaft 402 is started, it drives the rotary plate 404 to rotate 60 degrees through the bushing 403. The rotary plate 404 drives the clamping clamp 406 to rotate. The clamping clamp 406 drives the crucible to be heated evenly inside the inner furnace body 3 to complete the calcination and ensure that anhydrous FePO4 is obtained.

[0093] Meanwhile, during the calcination process, when the empty clamping piece 406 rotates to correspond to the outer feed port 11 and the inner feed port 12, the next batch of FePO4•2H2O can be placed manually using crucible tongs for calcination. Multiple batches of calcination save energy. The water vapor generated during the calcination process is discharged through exhaust port 1 5 and exhaust port 2 6.

[0094] After calcination, the anhydrous FePO4 is removed manually by using crucible tongs through the outer outlet 14 and the inner outlet 13.

[0095] Compared with related technologies, the energy-saving muffle furnace provided by the present invention has the following beneficial effects:

[0096] By setting up multiple clamping clips 406 driven by rotary motors 401, continuous calcination of multiple batches of FePO4•2H2O is achieved, which is more energy-efficient and efficient. The inner furnace body 3 maintains a high temperature for a long time, while the outer furnace body 2 isolates the temperature to reduce heat loss. It supports uninterrupted feeding and discharging during the calcination process, avoiding the huge heat waste caused by frequent heating and cooling in traditional intermittent operation. The energy utilization rate is greatly improved, and the energy consumption and equipment cost of calcining a single crucible are reduced. The clamping clips 406 drive the crucible to rotate, ensuring that FePO4•2H2O is heated evenly, while the next batch of FePO4•2H2O can be placed and the already calcined FePO4 can be taken out. Combined with stable The furnace temperature ensures that each batch of products undergoes a consistent thermal history, guaranteeing high uniformity in the crystallinity, purity, and properties of anhydrous FePO4. A rotary motor 401 drives the crucible to rotate 60 degrees per cycle, allowing the material to dynamically and uniformly receive heat radiated from the heating tubes during calcination. This effectively avoids uneven heating, localized overheating, or underheating caused by fixed positions during static calcination. The presence of vents 5 and 6 allows for timely removal of water vapor generated during dehydration, preventing water vapor accumulation, condensation, and reflux within the furnace, ensuring the thoroughness of the dehydration reaction. Operators only need to use crucible tongs for short periods at specific locations, reducing the direct impact of high-temperature heat radiation on them.

[0097] Second Embodiment

[0098] Please refer to the following: Figures 4-10 Based on the energy-saving muffle furnace provided in the first embodiment of this application, the second embodiment of this application proposes another energy-saving muffle furnace. The second embodiment is merely a preferred embodiment of the first embodiment, and the implementation of the second embodiment will not affect the separate implementation of the first embodiment.

[0099] Specifically, the second embodiment of this application provides an energy-saving muffle furnace that differs in that an inner furnace sealing mechanism 7 is fixedly installed at the bottom of the inner wall of the outer furnace body 2. The inner furnace sealing mechanism 7 includes a cylinder 701 and a limiting block 705. The cylinder 701 is fixedly installed at the bottom of the inner wall of the outer furnace body 2. A lifting plate 702 is fixedly installed at the top of the cylinder 701 through a connecting plate. Inner sealing plates 703 are fixedly installed at both ends of the lifting plate 702. The two inner sealing plates 703 are respectively adapted to the inner feed port 12 and the inner discharge port 13. The four limiting blocks 705 are fixedly installed on one side of the inner furnace body 3. Two sliding rods 704 are symmetrically fixedly installed inside the lifting plate 702. The two sliding rods 704 are slidably installed with the four limiting blocks 705 respectively.

[0100] A feeding mechanism 8 is fixedly installed on one side of the inner wall of the outer furnace body 2. The feeding mechanism 8 includes a drive motor 801, which is fixedly installed on one side of the inner wall of the outer furnace body 2. A disc 802 is fixedly installed on the output shaft of the drive motor 801. A connecting rod 803 is rotatably installed on the surface of the disc 802 via a convex shaft. A right-angle plate 804 is rotatably installed on one end of the connecting rod 803 via a fixed rod. A feeding tray 805 is fixedly installed on the end of the right-angle plate 804. A connecting rod 806 is rotatably installed on the surface of the disc 802 via a convex shaft. A right-angle plate 807 is rotatably installed on one end of the connecting rod 806 via a fixed rod. A material picking clamp 808 is fixedly installed on the end of the right-angle plate 807. The feeding tray 805 is adapted to the clamping clamp 406, and the material picking clamp 808 is adapted to the clamping clamp 406.

[0101] A nitrogen mechanism 9 is connected to one side of the outer furnace body 2. The nitrogen mechanism 9 includes a connecting pipe 904, which is connected to one side of the outer furnace body 2. The connecting pipe 904 is connected to a nitrogen pipe 902 through a solenoid valve 903. The end of the nitrogen pipe 902 is connected to a nitrogen tank 901, which is located on the ground.

[0102] Each of the six exhaust holes 5 is connected to an exhaust pipe 15, and the six exhaust pipes 15 pass through the six exhaust holes 6 and extend to the outside.

[0103] Both sides of the outer furnace body 2 are rotatably mounted with outer sealing plates 16 via rotating shafts. The two outer sealing plates 16 are respectively adapted to and installed with the outer feed port 11 and the outer discharge port 14.

[0104] Six top plates 17 are fixedly installed on the surface of the rotating shaft 402, and the six top plates 17 are respectively adapted to the six exhaust holes 5.

[0105] In actual use, the feeding tray 805 is open in the direction facing the inner furnace body 3 for pushing out the crucible; the material picking clamp 808 is provided with two clamps for stably clamping out the crucible; the clamping force of the material picking clamp 808 is greater than the clamping force of the clamping clamp 406; the connecting rod 1 803 and the connecting rod 2 806 are limited by a limiting plate fixedly installed on one side of the inner furnace body 3.

[0106] The working principle of an energy-saving muffle furnace provided in this embodiment is as follows:

[0107] Open the outer sealing plate 16 and manually place the uncalcined crucible into the feeding tray 805. Start the cylinder 701 to drive the lifting plate 702 to rise. At this time, the slide rod 704 slides inside the limit block 705 to ensure vertical movement. The lifting plate 702 drives the two inner sealing plates 703 to rise to open the inner feed port 12 and the inner discharge port 13, reducing the heat loss of the inner furnace body 3.

[0108] Then, when multiple clamping clips 406 are calcined in sequence, the calcined crucible moves to the inner discharge port 13, and the empty clamping clips 406 rotate back to the inner feed port 12. The two outer sealing plates 16 are manually opened to open the outer feed port 11 and the outer discharge port 14. The solenoid valve 903 is opened to output nitrogen through the nitrogen tank 901, and nitrogen is input through the connecting pipe 904 to the space between the outer furnace body 2 and the inner furnace body 3.

[0109] At this time, the drive motor 801 is started, which drives the disc 802 to rotate counterclockwise. The disc 802 simultaneously drives the connecting rod 1 803 and the connecting rod 2 806 to move. The connecting rod 1 803 and the connecting rod 2 806 respectively drive the right-angle plate 1 804 and the right-angle plate 2 807 to move in opposite directions. The right-angle plate 1 804 drives the feeding tray 805 to move into the inner furnace body 3, and the right-angle plate 2 807 drives the material picking clamp 808 to move into the inner furnace body 3. At this time, the clamping clamp 406 corresponding to the inner feeding port 12 is empty. The feeding tray 805, carrying the crucible, contacts the empty clamping clip 406. The left side of the feeding tray 805 itself provides a limit, and the clamping clip 406 opens and clamps the crucible. At the same time, the material picking clip 808 on the other side also moves into the inner furnace body 3. At this time, the material picking clip 808 contacts the crucible on the clamping clip 406 after calcination. At this time, the drive motor 801 reverses and drives the disc 802 to reverse, and the disc 802 is driven to reset. At this time, the material picking clip 808 and the feeding tray 805 are moved out of the inner furnace body 3.

[0110] The cylinder 701 is restarted to drive the inner sealing plate 703 to reset and seal the inner furnace body 3 to continue calcination. After isolating the high temperature, the calcined FePO4 is manually removed from the outlet 14 using crucible tongs. Then, the two outer sealing plates 16 are closed to continue the calcination process.

[0111] Then, when the rotating shaft 402 rotates, it drives multiple clamping clips 406 to rotate and automatically complete the process of updating the crucible for feeding and loading. During this process, the rotating shaft 402 also drives the top plate 17 to rotate. As the top plate 17 rotates, after the crucible has been calcined, the top plate 17 rotates to open the second exhaust port 6. The second exhaust port 6 releases high-temperature water vapor, which is completely discharged through the exhaust pipe 15 to prevent water vapor from flowing into the space between the inner furnace body 3 and the outer furnace body 2 and causing secondary pollution of FePO4•2H2O. At the same time, when the rotation is complete, the top plate 17 closes the second exhaust port 6 again to prevent heat loss.

[0112] Compared with related technologies, the energy-saving muffle furnace provided in this embodiment has the following beneficial effects:

[0113] By setting cylinder 701 to drive inner sealing plate 703 to open inner feed port 12 and inner discharge port 13, the exposure time of high temperature inside inner furnace body 3 is minimized, greatly reducing heat loss during feeding and unloading. Drive motor 801 drives disc 802 to rotate, simultaneously moving feed tray 805 and unloading clamp 808 to automatically feed crucibles. This achieves automatic grabbing of calcined crucibles and simultaneous loading of uncalcined crucibles, replacing manual clamping, reducing operation intervals, making operation smoother and more efficient, improving equipment utilization and production capacity. It also avoids the danger of manual crucible clamps directly reaching into inner furnace body 3. After the inner furnace is closed (16), nitrogen is introduced to effectively isolate the air and prevent FePO4 from oxidizing and contaminating at high temperatures, ensuring the high purity and chemical stability of the product. By setting the rotating shaft (402) to drive the top plate (17), the exhaust is only activated after the crucible calcination is completed, ensuring that water vapor is directionally and promptly discharged, avoiding its condensation and backflow in the furnace or its seepage into the interlayer to contaminate other materials and the environment. This ensures the thoroughness of the dehydration reaction and the consistency of the product. After the inner furnace body (3) is sealed, manual operation is simplified to placing and collecting materials on the relatively low-temperature outer side, greatly reducing the heat radiation risk and labor intensity of the operators and improving safety.

[0114] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for integrated lithium extraction from waste lithium iron phosphate salt lakes, characterized in that, Includes the following steps: S1: Lithium iron phosphate powder is added to a container containing a mixture of sulfuric acid and hydrogen peroxide, heated and stirred to obtain a lithium-rich solution. The lithium-rich solution contains Li. + SO4 2- Fe 3+ Fe 2+ and PO4 3- ; S2: Concentrate the lithium-rich solution, adjust the pH, and remove Fe. 3+ Fe 2+ and PO4 3- This yields a mixture of solids and lithium concentrate; S3: Carbon dioxide is bubbled into the lithium concentrate, filtered, and dried to obtain lithium carbonate and filtrate 1. S4: Mix the filtrate 1 and the mixed solid obtained in S2, add a small amount of acid, stir to dissolve, and obtain a mixed solution; S5: Add Fe2(SO4)3 to the mixture to reduce the Fe content in the mixture. 3+ Excess Fe 3+ and PO4 3- Complete precipitation yielded FePO4•2H2O and filtrate two, which contained Fe. 3+ Fe 2+ FePO4•2H2O was calcined in a muffle furnace to obtain FePO4; S6: Adjust the pH of filtrate 2 obtained in S5 with sodium hydroxide, filter, and obtain precipitates Fe(OH)2 and Fe(OH)3 and filtrate 3; S7: Concentrate, evaporate, and crystallize the filtrate to obtain sodium sulfate; S8: Mix FePO4, polyvinylidene fluoride and conductive carbon black in a certain mass ratio, add N-methylpyrrolidone, stir, and obtain FePO4 slurry; S9: Coat and dry the FePO4 slurry, then cut it into fragments to obtain the FePO4 electrode; S10: The waste lithium iron phosphate powder is heated in two stages to obtain repaired lithium iron phosphate powder. S11: Mix the repaired lithium iron phosphate powder, polyvinylidene fluoride and conductive carbon black in a certain mass ratio, add N-methylpyrrolidone, stir to obtain a slurry, coat, dry, cut into fragments to obtain a lithium iron phosphate electrode. S12: The electrolyzer is divided into a cathode chamber and an anode chamber using an anion-selective membrane. Brine is added to the anode chamber and potassium chloride is added to the cathode chamber. Lithium iron phosphate electrode and FePO4 electrode are used as the anode and cathode, respectively. The power supply is connected, lithium is inserted and extracted, and the electrode positions are cyclically exchanged to obtain a lithium-ion-rich cathode electrode and lithium-free brine.

2. The integrated method for lithium extraction from waste lithium iron phosphate-enhanced salt lakes according to claim 1, characterized in that, The lithium-ion-rich cathode electrode in S12 was originally FePO4, but it became LiFePO4 during the lithium extraction process.

3. An energy-saving muffle furnace, requiring the use of the integrated method for lithium extraction from waste lithium iron phosphate-enriched salt lakes as described in any one of claims 1-2, characterized in that, include: Electrical control box; The outer furnace body is fixedly installed on the top of the electrical control box; The inner furnace body is fixedly installed to the bottom of the inner wall of the outer furnace body by a support column; The outer furnace body has an external feed inlet and an external discharge outlet on both sides, respectively. The inner furnace body has an inner feed port and an inner discharge port on its two sides, respectively. A rotating mechanism is fixedly installed at the bottom of the inner wall of the outer furnace body. The rotating mechanism includes a rotating motor, which is fixedly installed at the bottom of the inner wall of the outer furnace body. The output shaft of the rotating motor is fixedly connected to a rotating shaft, which passes through the bottom of the inner furnace body and extends into the interior. A bushing is fixedly installed on the surface of the rotating shaft inside the inner furnace body. Six rotating plates are fixedly installed on the surface of the bushing. Clamping clips are fixedly installed at the ends of the six rotating plates through fixed plates. The four heating tubes are respectively fixedly installed on the four sides of the inner wall of the furnace body.

4. An energy-saving muffle furnace according to claim 3, characterized in that, The top of the outer furnace body has six exhaust holes (I), and the top of the inner furnace body has six exhaust holes (II).

5. An energy-saving muffle furnace according to claim 3, characterized in that, An inner furnace sealing mechanism is fixedly installed at the bottom of the inner wall of the outer furnace. The inner furnace sealing mechanism includes a cylinder and limit blocks. The cylinder is fixedly installed at the bottom of the inner wall of the outer furnace. A lifting plate is fixedly installed at the top of the cylinder through a connecting plate. Inner sealing plates are fixedly installed at both ends of the lifting plate. The two inner sealing plates are respectively adapted to the inner feed port and the inner discharge port. The four limit blocks are fixedly installed on one side of the inner furnace. Two sliding rods are symmetrically fixedly installed inside the lifting plate. The two sliding rods are slidably installed with the four limit blocks respectively.

6. An energy-saving muffle furnace according to claim 3, characterized in that, A feeding and unloading mechanism is fixedly installed on one side of the inner wall of the outer furnace. The feeding and unloading mechanism includes a drive motor, which is fixedly installed on one side of the inner wall of the outer furnace. A disc is fixedly installed on the output shaft of the drive motor. A connecting rod 1 is rotatably installed on the surface of the disc via a convex shaft. A right-angle plate 1 is rotatably installed on one end of the connecting rod 1 via a fixed rod. A feeding tray is fixedly installed on the end of the right-angle plate 1. A connecting rod 2 is rotatably installed on the surface of the disc via a convex shaft. A right-angle plate 2 is rotatably installed on one end of the connecting rod 2 via a fixed rod. A material-retrieving clamp is fixedly installed on the end of the right-angle plate 2. The feeding tray is adapted to the clamp, and the material-retrieving clamp is adapted to the clamp.

7. An energy-saving muffle furnace according to claim 3, characterized in that, A nitrogen gas mechanism is connected to one side of the outer furnace body. The nitrogen gas mechanism includes a connecting pipe connected to one side of the outer furnace body. The connecting pipe is connected to a nitrogen gas pipe through a solenoid valve. The end of the nitrogen gas pipe is connected to a nitrogen gas tank, which is located on the ground.

8. An energy-saving muffle furnace according to claim 4, characterized in that, Each of the six exhaust holes is connected to an exhaust pipe, and the six exhaust pipes pass through the six exhaust holes and extend to the outside.

9. An energy-saving muffle furnace according to claim 3, characterized in that, Both sides of the outer furnace body are equipped with outer sealing plates that are rotatably mounted via a rotating shaft. The two outer sealing plates are respectively adapted to the outer feed inlet and the outer discharge outlet.

10. An energy-saving muffle furnace according to claim 4, characterized in that, Six top plates are fixedly installed on the surface of the rotating shaft, and the six top plates are respectively adapted to the six exhaust holes.

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