Process and equipment for recovering valuable components from cathode carbon blocks by binary molten salt-assisted roasting

Abstract

This invention provides a process and equipment for recovering valuable components from cathode carbon blocks using binary molten salt-assisted roasting, relating to the field of solid waste treatment and resource recycling technology. The process includes the following steps: Step S1: The aluminum electrolysis cathode carbon blocks are coarsely crushed using a crusher, then pulverized using a ball mill, sieved, and dried in an oven for later use. Step S2: Analytical grade sodium chloride and carbonate are mixed according to a specific mass ratio. The mixed salt is placed in a muffle furnace and heated for a period of time to form a uniform binary eutectic molten salt. After cooling, it is ground into a fine powder using an agate crucible for later use. This solution ultimately achieves efficient removal of toxic impurities such as fluorides and cyanides from waste cathode carbon blocks in aluminum electrolysis cells and resource recovery of valuable components such as graphite carbon by innovatively employing a sodium chloride-sodium carbonate binary molten salt system assisted by low-temperature roasting, combined with subsequent water leaching and hydrothermal acid leaching treatment steps.

Description

Technical Field

[0001] This invention relates to the field of solid waste treatment and resource recycling, and in particular to a process and equipment for recovering valuable components from cathode carbon blocks by binary molten salt-assisted roasting. Background Technology

[0002] In the aluminum electrolysis industry, cathode carbon blocks eventually become unusable due to corrosion and other factors after a certain number of years of use, generating a large amount of waste cathode carbon blocks. Statistics show that approximately 10 kg of waste cathode carbon blocks are produced for every ton of primary aluminum produced. These waste cathode carbon blocks typically contain over 60% graphite carbon, giving them high recycling value. However, they also contain large amounts of water-soluble fluorides and some toxic cyanides, and are therefore classified as hazardous solid waste by environmental agencies.

[0003] Currently, the main methods for treating waste cathode carbon blocks include pyrometallurgical and hydrometallurgical processes. Pyrometallurgical processes, such as co-incineration with red mud, lime, and limestone, are relatively simple to operate and have a large processing capacity, but the high-temperature treatment requires a large amount of energy, resulting in expensive equipment investment and generating a large amount of secondary waste residue. Hydrometallurgical processes, including leaching with aluminum ion solutions, alkali leaching, and combined alkali-acid leaching, have high reaction efficiency, but the treatment process is complex, and the residual acid / alkali wastewater can easily cause secondary pollution.

[0004] Molten salt heat treatment, as an emerging processing technology, has been applied to the extraction of valuable components from solid waste and refractory minerals. Previous studies have used single molten salt systems to treat waste cathode carbon blocks. However, when using sodium carbonate, a high roasting temperature of 950°C is still required, resulting in high energy consumption. Binary molten salt systems, on the other hand, show promise for further reducing operating temperatures and improving processing efficiency. However, there is currently limited research on this topic, especially regarding systematic methods for recovering valuable components from cathode carbon blocks using binary molten salt-assisted roasting, which still require further development.

[0005] Therefore, it is necessary to provide a process for recovering valuable components from cathode carbon blocks by binary molten salt-assisted roasting to solve the above-mentioned technical problems. Summary of the Invention

[0006] This invention provides a process for recovering valuable components from cathode carbon blocks by binary molten salt-assisted roasting, which solves the problems of high energy consumption, complex processes, serious secondary pollution, and low recovery efficiency of valuable components in existing waste cathode carbon block treatment methods.

[0007] To solve the above-mentioned technical problems, the present invention provides a process for recovering valuable components from cathode carbon blocks by binary molten salt-assisted roasting, comprising the following steps:

[0008] Step S1: Use a crusher to coarsely crush the aluminum electrolysis cathode carbon block, then pulverize it through a ball mill, sieve it, and dry it in an oven for later use.

[0009] Step S2: Select analytical grade sodium chloride and carbonic acid, mix them according to the mass ratio, put the mixed salt into a muffle furnace, heat for a period of time to form a uniform binary eutectic molten salt, and grind it into fine powder using an agate crucible for later use.

[0010] Step S3: Mix the dried cathode carbon block powder with the prepared binary molten salt fine powder according to the mass ratio. Place the uniformly mixed material in a corundum crucible and put it into a horizontal tube furnace. Introduce nitrogen as a protective gas and carry out a pyrolysis reaction at a certain temperature to promote the decomposition of toxic components of the cathode carbon block and the conversion of valuable components. The tail gas passes through a tail gas absorption device containing sodium hypochlorite solution and a sodium hydroxide solution absorption device in sequence.

[0011] Step S4: After pyrolysis, wait for the tube furnace to cool to room temperature, then remove the corundum crucible. The crucible product is divided into two layers: the bottom layer is mainly molten salt, and the top layer is residue of carbonaceous materials and other impurities. The bottom layer of molten salt can be repeated in step S3. The top layer residue is removed and collected for subsequent processing.

[0012] Step S5: Mix the collected top residue with deionized water according to the solid-liquid ratio, place it in a water bath and stir for a period of time to separate the solid and liquid to obtain filter residue A and filtrate A;

[0013] Step S6: Mix filter residue A with concentrated hydrogen chloride solution according to the solid-liquid ratio, place in a water bath and stir for a period of time, and separate the solid and liquid to obtain relatively pure carbonaceous material and filtrate B.

[0014] Step S7: Mix filtrate A, filtrate B and sodium hydroxide absorption solution, and add appropriate amount of sodium hydroxide to adjust pH to 10.5-11.5. Separate solid and liquid through precipitation reaction to obtain cryolite and filtrate C. Separate sodium chloride from filtrate C by evaporation and crystallization, so as to realize the recycling of molten salt components and the high-value recovery of fluorine resources.

[0015] Preferably, in step S1, the material is pulverized by a ball mill, sieved through a 150-mesh sieve, and dried in an oven at 80°C for 12 hours for later use. In step S2, sodium chloride with a purity of 99.5% and sodium carbonate with a purity of 99.5% are mixed in a 1:1 mass ratio and heated at 600°C for a period of time.

[0016] Preferably, in step S3, the dried cathode carbon block powder and the prepared binary molten salt fine powder are mixed at a mass ratio of 1:1 and subjected to pyrolysis reaction at 650°C for 2 hours. In step S5, the collected top residue is mixed with deionized water at a solid-liquid ratio of 1:3. In step S6, filter residue A is mixed with 2 mol / L concentrated hydrogen chloride solution at a solid-liquid ratio of 1:3.

[0017] A device for recovering valuable components from cathode carbon blocks by binary molten salt-assisted roasting, including a reaction vessel, a sealing cover, a rotating feeding mechanism, and a depth adjustment mechanism;

[0018] The rotating dosing mechanism includes a mounting plate fixed to the inner wall of the reactor. Three gears are rotatably connected inside the mounting plate. A dropper is slidably connected inside each of the three gears. A rotating ring is rotatably connected to the top of the mounting plate. Three sets of teeth are arranged in a ring array on the inner side of the rotating ring. The three sets of teeth mesh with the three gears respectively.

[0019] The depth adjustment mechanism includes multiple connecting columns fixed to the top of the rotating ring, a drive disk fixed to the top of the multiple connecting columns, a drive shaft fixed vertically inside the drive disk, the drive shaft being rotatably connected to the mounting disk, three protruding plates arranged in a circular array at the bottom of the drive disk, a rotating seat fixed to the top of each of the three droppers, a rotating wheel rotatably connected to the inner side of each of the three rotating seats, and a spring sleeved on the circumferential side of each of the three droppers and located on the top of the gear.

[0020] Preferably, the sealing cover is disposed on the top of the reactor, the sealing cover is fixedly connected to the reactor by bolts, a partition plate is fixedly disposed on the inner wall of the reactor and on the top of the drive plate, and the drive shaft is rotatably connected to the sealing cover and the partition plate.

[0021] Preferably, the reactor contains, from top to bottom, a premixing chamber, an installation chamber, and a mixing chamber. The premixing chamber is used for preliminary mixing and dilution of filtrate B with a portion of filtrate A or water. The mixing chamber is used for mixing filtrate A with sodium hydroxide absorbent. After mixing, diluted filtrate B is slowly added dropwise for further mixing. The bottom of the dropper has a curved structure.

[0022] Preferably, the top of the mounting plate is fixedly provided with an extraction mechanism, the extraction mechanism including a mounting cover fixedly provided on the top of the mounting plate, the drive shaft being rotatably connected to the mounting cover, the circumferential side of the drive shaft and located inside the mounting cover being fixedly provided with a rotating bracket, the inner side of the rotating bracket being rotatably connected with two drive wheels, the inside of the mounting cover being provided with an extraction tube, the two drive wheels being in contact with the extraction tube, the top of the extraction tube being connected to the premixing chamber, and the right side of the extraction tube being connected to a dropper.

[0023] Preferably, a replenishing mechanism is fixedly provided at the bottom of the mounting plate. The replenishing mechanism includes a sliding frame fixedly provided at the bottom of the mounting plate, a toothed plate slidably connected inside the sliding frame, a reciprocating rod fixedly provided on the right side of the toothed plate, a support frame fixedly provided at the bottom of the mounting plate, a replenishing cylinder fixedly provided on the inner side of the support frame, a piston fixedly provided at the right end of the reciprocating rod, a return spring sleeved on the circumferential side of the reciprocating rod, and a half gear fixedly provided on the circumferential side of the dropper on the left side, the half gear meshing with the toothed plate.

[0024] Preferably, a mixing mechanism is fixedly provided on the peripheral side of the drive shaft. The mixing mechanism includes three sets of mixing paddles fixedly provided on the peripheral side of the drive shaft. A premixing paddle is fixedly provided on the peripheral side of the drive shaft and at the top of the mixing paddles. A drive motor for driving the drive shaft to rotate is provided on the top of the sealing cover.

[0025] Preferably, the left side of the reactor is connected to three feed pipes, the right side of the reactor is connected to an exhaust pipe, the bottom of the reactor is connected to a discharge pipe, and the bottom of the reactor is provided with four support seats in a circular array.

[0026] Compared with related technologies, the process and equipment for recovering valuable components from cathode carbon blocks by binary molten salt-assisted roasting provided by this invention have the following advantages:

[0027] By innovatively employing a sodium chloride-sodium carbonate binary molten salt system to assist in a low-temperature roasting process, combined with subsequent water immersion and hydrothermal acid leaching treatment steps, this technology achieves efficient removal of toxic impurities such as fluorides and cyanides from waste cathode carbon blocks in aluminum electrolysis cells, as well as resource recovery of valuable components such as graphite carbon. This process breaks through the high-temperature bottleneck of traditional single-salt systems, reducing the pyrolysis temperature by 300℃ and significantly reducing energy consumption. At the same time, it achieves self-separation through the density difference between molten salt and carbon products, simplifying the post-processing procedure. The binary molten salt-assisted roasting technology can efficiently achieve the harmlessness and resource recovery of waste cathode carbon blocks through a synergistic reaction mechanism. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0029] Figure 1 A schematic diagram of the process flow provided for this invention;

[0030] Figure 2 The optimal structural schematic diagram provided for this invention;

[0031] Figure 3 for Figure 2 The diagram shown is a structural schematic of the right view of the reactor.

[0032] Figure 4 for Figure 2 The diagram shows a cross-sectional view of the reactor.

[0033] Figure 5 This is a schematic diagram of the structure of the rotating feeding mechanism and the depth adjustment mechanism provided by the present invention;

[0034] Figure 6 This is a schematic diagram showing the state in which the rotating ring drives the tooth assembly to rotate counterclockwise, as provided by the present invention.

[0035] Figure 7 A schematic diagram showing the state in which the drive shaft drives the drive disk and the cam plate to rotate counterclockwise, as provided by the present invention.

[0036] Figure 8 This is a schematic diagram of the extraction mechanism provided by the present invention;

[0037] Figure 9 for Figure 8 The diagram shows the state in which the drive shaft drives the rotating bracket to rotate counterclockwise.

[0038] Figure 10 This is a schematic diagram of the supplementary mechanism provided by the present invention;

[0039] Figure 11 A schematic diagram showing the state in which the half gear rotates counterclockwise, causing the gear plate to move to the right, as provided by the present invention.

[0040] Figure 12 This is a schematic diagram of the structure of the hybrid mechanism provided by the present invention.

[0041] Explanation of icon numbers:

[0042] 1. Reactor; 2. Sealing cap;

[0043] 3. Rotary dosing mechanism; 31. Mounting plate; 32. Gear; 33. Dropper; 34. Rotating ring; 35. Gear assembly;

[0044] 4. Depth adjustment mechanism; 41. Connecting column; 42. Drive disc; 43. Drive shaft; 44. Protruding plate; 45. Rotating seat; 46. Rotating wheel; 47. Spring;

[0045] 5. Divider;

[0046] 6. Extraction mechanism; 61. Mounting cover; 62. Rotating bracket; 63. Drive wheel; 64. Extraction tube;

[0047] 7. Replenishing mechanism; 71. Sliding frame; 72. Gear plate; 73. Reciprocating rod; 74. Support frame; 75. Replenishing cylinder; 76. Piston; 77. Return spring; 78. Half gear;

[0048] 8. Mixing mechanism; 81. Mixing propeller; 82. Premixing propeller; 83. Drive motor;

[0049] 9. Feed pipe; 10. Exhaust pipe; 11. Discharge pipe; 12. Support base. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0051] This invention provides a process for recovering valuable components from cathode carbon blocks by binary molten salt-assisted roasting.

[0052] Please see Figure 1 The process for recovering valuable components from cathode carbon blocks by binary molten salt-assisted roasting includes the following steps:

[0053] Step S1: Use a crusher to coarsely crush the aluminum electrolysis cathode carbon block, then pulverize it through a ball mill, sieve it, and dry it in an oven for later use.

[0054] Step S2: Select analytical grade sodium chloride and carbonic acid, mix them according to the mass ratio, put the mixed salt into a muffle furnace, heat for a period of time to form a uniform binary eutectic molten salt, and grind it into fine powder using an agate crucible for later use.

[0055] Step S3: Mix the dried cathode carbon block powder with the prepared binary molten salt fine powder according to the mass ratio. Place the uniformly mixed material in a corundum crucible and put it into a horizontal tube furnace. Introduce nitrogen as a protective gas and carry out a pyrolysis reaction at a certain temperature to promote the decomposition of toxic components of the cathode carbon block and the conversion of valuable components. The tail gas passes through a tail gas absorption device containing sodium hypochlorite solution and a sodium hydroxide solution absorption device in sequence.

[0056] Step S4: After pyrolysis, wait for the tube furnace to cool to room temperature, then remove the corundum crucible. The crucible product is divided into two layers: the bottom layer is mainly molten salt, and the top layer is residue of carbonaceous materials and other impurities. The bottom layer of molten salt can be repeated in step S3. The top layer residue is removed and collected for subsequent processing.

[0057] Step S5: Mix the collected top residue with deionized water according to the solid-liquid ratio, place it in a water bath and stir for a period of time to separate the solid and liquid to obtain filter residue A and filtrate A;

[0058] Step S6: Mix filter residue A with concentrated hydrogen chloride solution according to the solid-liquid ratio, place in a water bath and stir for a period of time, and separate the solid and liquid to obtain relatively pure carbonaceous material and filtrate B.

[0059] Step S7: Mix filtrate A, filtrate B and sodium hydroxide absorption solution, and add appropriate amount of sodium hydroxide to adjust pH to 10.5-11.5. Separate solid and liquid through precipitation reaction to obtain cryolite and filtrate C. Separate sodium chloride from filtrate C by evaporation and crystallization, so as to realize the recycling of molten salt components and the high-value recovery of fluorine resources.

[0060] In step S1, the material is pulverized by a ball mill, sieved through a 150-mesh sieve, and then dried in an oven at 80°C for 12 hours for later use. In step S2, sodium chloride with a purity of 99.5% and sodium carbonate with a purity of 99.5% are mixed in a 1:1 mass ratio and heated at 600°C for a period of time.

[0061] In step S3, the dried cathode carbon block powder and the prepared binary molten salt fine powder are mixed at a mass ratio of 1:1 and pyrolyzed at 650°C for 2 hours. In step S5, the collected top residue is mixed with deionized water at a solid-liquid ratio of 1:3. In step S6, filter residue A is mixed with 2 mol / L concentrated hydrogen chloride solution at a solid-liquid ratio of 1:3.

[0062] Preferably, in step S7, filtrate A and sodium hydroxide absorption solution are first mixed in proportion in the mixing chamber of reactor 1 to form a uniform alkaline mixture. Filtrate B is then initially mixed and diluted with a portion of filtrate A or water. The diluted filtrate B is then slowly added to the alkaline mixture. During this process, the pH of the alkaline mixture will gradually decrease as filtrate B is added. When the pH drops to 9-10, the addition is stopped, and the impurity removal and precipitation stage begins. (If the pH is higher than 9 after adding filtrate B, a small amount of filtrate B is added for fine adjustment; if the pH is lower than 8, 10%-20% sodium hydroxide solution is added to adjust it back to 8-9.) After the impurity removal and precipitation are completed, the impurity filter residue is discarded, the supernatant is collected, and 20%-30% concentrated sodium hydroxide solution is added dropwise to the supernatant using a metering pump to adjust the pH to 10.5-11.5.

[0063] Preferably, during the slow addition of filtrate B to the alkaline mixture, the concentration of F in the solution is periodically monitored. - Concentration, when F - When the concentration is <8g / L, stop adding filtrate B and intermittently add saturated NaF solution.

[0064] In this embodiment, by innovatively employing a sodium chloride-sodium carbonate binary molten salt system to assist in a low-temperature roasting process, combined with subsequent water immersion and hydrothermal acid leaching treatment steps, the efficient removal of toxic impurities such as fluorides and cyanides from waste cathode carbon blocks in aluminum electrolysis cells and the resource recovery of valuable components such as graphite carbon are achieved. This process breaks through the high-temperature bottleneck of traditional single-salt systems, reducing the pyrolysis temperature by 300°C and significantly reducing energy consumption. At the same time, it achieves self-separation through the density difference between molten salt and carbon products, simplifying the post-processing process. The binary molten salt-assisted roasting technology can efficiently achieve the harmlessness and resource recovery of waste cathode carbon blocks through a synergistic reaction mechanism.

[0065] The present invention also provides a device for recovering valuable components of cathode carbon blocks by binary molten salt-assisted roasting.

[0066] First embodiment:

[0067] Please see Figures 2 to 7 A device for recovering valuable components from cathode carbon blocks by binary molten salt-assisted roasting includes a reactor 1, a sealing cover 2, a rotating feeding mechanism 3, and a depth adjustment mechanism 4.

[0068] The rotating dosing mechanism 3 includes a mounting plate 31 fixed to the inner wall of the reactor 1. Three gears 32 are rotatably connected inside the mounting plate 31. Droppers 33 are vertically slidably connected inside each of the three gears 32. A rotating ring 34 is rotatably connected to the top of the mounting plate 31. Three sets of tooth groups 35 are arranged in a ring array on the inner side of the rotating ring 34. The three sets of tooth groups 35 mesh with the three gears 32 respectively.

[0069] The depth adjustment mechanism 4 includes multiple connecting posts 41 fixed to the top of the rotating ring 34. A drive disk 42 is fixed to the top of the multiple connecting posts 41. A drive shaft 43 is vertically fixed inside the drive disk 42. The drive shaft 43 is rotatably connected to the mounting disk 31. Three protruding plates 44 are arranged in a ring array at the bottom of the drive disk 42. A rotating seat 45 is fixed to the top of each of the three droppers 33. A rotating wheel 46 is rotatably connected to the inner side of each of the three rotating seats 45. A spring 47 is sleeved on the circumferential side of each of the three droppers 33 and on the top of the gear 32.

[0070] The sealing cover 2 is located on the top of the reactor 1 and is fixedly connected to the reactor 1 by bolts. A partition plate 5 is fixedly provided on the inner wall of the reactor 1 and on the top of the drive disk 42. The drive shaft 43 is rotatably connected to the sealing cover 2 and the partition plate 5.

[0071] The reactor 1 contains, from top to bottom, a premixing chamber, an installation chamber, and a mixing chamber. The premixing chamber is used for the initial mixing and dilution of filtrate B with a portion of filtrate A or water. The mixing chamber is used for mixing filtrate A with sodium hydroxide absorbent. After mixing, the diluted filtrate B is slowly added dropwise for further mixing. The bottom of the dropper 33 has a curved structure.

[0072] Please combine Figure 5 and Figure 6 When the rotating ring 34 drives the three sets of toothed assemblies 35 to rotate counterclockwise, the toothed assemblies 35 contact the gear 32 and continue to rotate, which will drive the gear 32 to rotate counterclockwise. The counterclockwise rotation of the gear 32 will then drive the dropper 33 to rotate, thereby allowing the diluted filtrate B to be added to the alkaline mixture at multiple points from different angles.

[0073] Please combine Figure 5 and Figure 7 When the drive shaft 43 rotates counterclockwise, it will simultaneously drive the drive disk 42 to rotate counterclockwise. The drive disk 42 will then drive the three convex plates 44 to rotate counterclockwise. When the convex plates 44 come into contact with the rotating wheel 46, the rotating wheel 46 will press the rotating seat 45 and the dropper 33 downward, and the spring 47 will contract. The dropper 33 will move downward, thereby adding filtrate B to the alkaline mixture at different depths.

[0074] Furthermore, when the drive disc 42 continues to drive the convex plate 44 to rotate, after the convex plate 44 separates from the rotating wheel 46, the spring force of the spring 47 causes the dropper 33, the rotating seat 45 and the rotating wheel 46 to return to their original position upwards.

[0075] Preferably, when the drive disk 42 rotates counterclockwise, the connecting column 41 will simultaneously drive the rotating ring 34 to rotate, and the rotation of the rotating ring 34 will in turn drive the tooth assembly 35 to rotate counterclockwise.

[0076] In this embodiment, the drive shaft 43 rotates counterclockwise, causing the drive disk 42 and the rotating ring 34 to rotate counterclockwise. The rotating ring 34 rotates counterclockwise, causing the three sets of toothed gears 35 to rotate counterclockwise, which in turn causes the three gears 32 to rotate the dropper 33 counterclockwise. This enables the multi-point, multi-angle addition of diluted filtrate B in a ring, uniformly dispersing the acidic filtrate B into the alkaline solution in the mixing chamber. This ensures a uniform decrease in pH of the system, with no localized sudden pH drops, completely suppressing HF generation and reducing fluorine resource loss. The counterclockwise rotation of the drive disk 42 simultaneously drives multiple convex plates 44 to rotate counterclockwise. When the convex plates 44 contact the rotating wheel 46, the dropper 33 moves downward, causing the spring 47 to contract. By moving the dropper 33 downward, filtrate B can be added to the alkaline mixture at different depths. This avoids the traditional method of adding filtrate only at the liquid surface or a fixed depth, which easily leads to stratification where the upper layer of solution is neutralized first and the lower layer of solution has a higher alkalinity.

[0077] Second embodiment:

[0078] Please see Figures 8 to 11 The top of the mounting plate 31 is fixedly provided with an extraction mechanism 6. The extraction mechanism 6 includes a mounting cover 61 fixedly provided on the top of the mounting plate 31. The drive shaft 43 is rotatably connected to the mounting cover 61. A rotating bracket 62 is fixedly provided on the circumferential side of the drive shaft 43 and inside the mounting cover 61. Two drive wheels 63 are rotatably connected to the inner side of the rotating bracket 62. An extraction tube 64 is provided inside the mounting cover 61. The two drive wheels 63 are in contact with the extraction tube 64. The top of the extraction tube 64 is connected to the premixing chamber, and the right side of the extraction tube 64 is connected to the dropper 33.

[0079] A replenishing mechanism 7 is fixedly provided at the bottom of the mounting plate 31. The replenishing mechanism 7 includes a sliding frame 71 fixedly provided at the bottom of the mounting plate 31. A toothed plate 72 is slidably connected inside the sliding frame 71. A reciprocating rod 73 is fixedly provided on the right side of the toothed plate 72. A support frame 74 is fixedly provided at the bottom of the mounting plate 31. A replenishing cylinder 75 is fixedly provided on the inner side of the support frame 74. The circumferential side of the reciprocating rod 73 is slidably connected to the inside of the replenishing cylinder 75. A piston 76 is fixedly provided at the right end of the reciprocating rod 73. A return spring 77 is sleeved on the circumferential side of the reciprocating rod 73. A half gear 78 is fixedly provided on the circumferential side of the dropper 33 on the left side. The half gear 78 meshes with the toothed plate 72 and retracts.

[0080] Please combine Figure 8 and Figure 9 When the drive shaft 43 rotates counterclockwise, it will simultaneously drive the rotating bracket 62 to rotate. The rotation of the rotating bracket 62 will in turn drive the two drive wheels 63 to rotate, causing the two drive wheels 63 to intermittently squeeze and release the extraction tube 64, creating a negative pressure inside the extraction tube 64, and drawing the diluted filtrate B into the dropper 33 through the extraction tube 64.

[0081] Preferably, a one-way valve is provided on the surface of the extraction tube 64;

[0082] Please combine Figure 10 and Figure 11 When the left dropper 33 rotates counterclockwise, it will simultaneously drive the half gear 78 to rotate counterclockwise. The counterclockwise rotation of the half gear 78 will drive the toothed plate 72 to move to the right. The rightward movement of the toothed plate 72 will drive the reciprocating rod 73 to move to the right. The reciprocating rod 73 will then drive the piston 76 to move to the right inside the replenishing cylinder 75, thus adding the NaF solution inside the replenishing cylinder 75 to the mixed solution.

[0083] Furthermore, the top of the replenishing cylinder 75 is connected to a suction pipe, and the right side of the replenishing cylinder 75 is connected to a discharge pipe. Both the suction pipe and the discharge pipe are equipped with one-way valves. When the half gear 78 continues to rotate and disengages from the toothed plate 72, the toothed plate 72 slides to the left in the sliding frame 71 under the action of the return spring 77, and drives the reciprocating rod 73 to move to the left. The reciprocating rod 73 moves to the left, which drives the piston 76 to move to the left, thereby replenishing NaF solution into the replenishing cylinder 75 through the suction pipe.

[0084] In this embodiment, during the slow addition of filtrate B to the alkaline mixture, when the F- concentration is <8 g / L, the addition of filtrate B is stopped. The dropper 33 rotates counterclockwise, causing the half-gear 78 to rotate. The counterclockwise rotation of the half-gear 78 causes the toothed plate 72 to move to the right. The rightward movement of the toothed plate 72 causes the reciprocating rod 73 to move to the right. The reciprocating rod 73 causes the piston 76 to move to the right within the replenishment cylinder 75, dripping the NaF solution from the replenishment cylinder 75 into the mixed solution. This ensures that the Al / F molar ratio remains close to the stoichiometric ratio of cryolite, improving the crystallization rate and yield of cryolite. The resulting cryolite crystals are uniform in size and have high purity, while preventing excessive F. - Residue increases the difficulty of treating filtrate C.

[0085] Third embodiment:

[0086] Please participate Figure 1 , Figure 3 and Figure 12 A mixing mechanism 8 is fixedly provided on the peripheral side of the drive shaft 43. The mixing mechanism 8 includes three sets of mixing paddles 81 fixedly provided on the peripheral side of the drive shaft 43. A premixing paddle 82 is fixedly provided on the peripheral side of the drive shaft 43 and on top of the mixing paddles 81. A drive motor 83 for driving the drive shaft 43 to rotate is provided on the top of the sealing cover 2.

[0087] The left side of the reactor 1 is connected to three feed pipes 9, the right side of the reactor 1 is connected to an exhaust pipe 10, the bottom of the reactor 1 is connected to a discharge pipe 11, and the bottom of the reactor 1 is provided with four support seats 12 in a circular array.

[0088] Please combine Figure 12 : Start the drive motor 83. The drive motor 83 rotates and drives the drive shaft 43 to rotate. The rotation of the drive shaft 43 in turn drives the mixing paddle 81 and the premixing paddle 82 to rotate, thereby mixing filtrate A with sodium hydroxide absorption liquid in the mixing chamber, and premixing and diluting filtrate B with part of filtrate A or water in the premixing chamber.

[0089] Preferably, the top feed pipe 9 on the left side of the reactor 1 is connected to the premixing chamber, and the two feed pipes 9 at the bottom left side of the reactor 1 are connected to the mixing chamber.

[0090] In this embodiment, the drive motor 83 rotates to drive the drive shaft 43 to rotate, and the drive shaft 43 rotates to drive the mixing paddle 81 and the premixing paddle 82 to rotate. The mixing paddle 81 rotates to mix filtrate A with sodium hydroxide absorbent, and the premixing paddle 82 rotates to mix and dilute filtrate B with a portion of filtrate A or water.

[0091] Please refer to the reference again. Figures 2 to 12 The working principle of the device for recovering valuable components from cathode carbon blocks by binary molten salt-assisted roasting provided by this invention is as follows:

[0092] Step S1: The calculated volume of filtrate A is delivered to the mixing chamber of reactor 1. Then, the drive motor 83 is started. The drive motor 83 rotates, driving the drive shaft 43 and the mixing paddle 81 to rotate. Then, sodium hydroxide absorbent is slowly added. The mixing paddle 81 is used to mix filtrate A and sodium hydroxide absorbent. The premixing paddle 82 is used to premix and dilute filtrate B in the premixing chamber with part of filtrate A or water.

[0093] Step S2: After mixing is completed, open the valve on the surface of the extraction tube 64, and rotate the drive shaft 43 counterclockwise to drive the rotating bracket 62 to rotate. The rotation of the rotating bracket 62 in turn drives the two drive wheels 63 to rotate, so that the two drive wheels 63 intermittently squeeze and release the extraction tube 64, creating a negative pressure inside the extraction tube 64, and using the extraction tube 64 to draw the diluted filtrate B into the dropper 33.

[0094] In step S3, when the drive shaft 43 rotates, it will drive the drive disk 42 to rotate counterclockwise. The drive disk 42 will then drive the three convex plates 44 to rotate counterclockwise. When the convex plates 44 contact the rotating wheel 46, the rotating wheel 46 will press the rotating seat 45 and the dropper 33 downward, and the spring 47 will contract. The dropper 33 will move downward, thereby adding filtrate B to the alkaline mixture at different depths.

[0095] In step S4, when the drive disk 42 rotates, the connecting column 41 will drive the rotating ring 34 to rotate. The rotating ring 34 will then drive the three sets of tooth groups 35 to rotate counterclockwise. After the tooth groups 35 contact the gear 32 and continue to rotate, they will drive the gear 32 to rotate counterclockwise. The counterclockwise rotation of the gear 32 will then drive the dropper 33 to rotate, thereby allowing the diluted filtrate B to be added to the alkaline mixture at multiple points from different angles.

[0096] In step S5, during the slow addition of filtrate B to the alkaline mixture, when F -When the concentration is <8g / L, stop adding filtrate B. Rotate dropper 33 counterclockwise to drive half gear 78 to rotate. The counterclockwise rotation of half gear 78 drives toothed plate 72 to move to the right. The rightward movement of toothed plate 72 drives reciprocating rod 73 to move to the right. Reciprocating rod 73 drives piston 76 to move to the right in replenishing cylinder 75, adding NaF solution in replenishing cylinder 75 dropwise into the mixed solution.

[0097] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made under the concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A process for recovering valuable components from cathode carbon blocks by binary molten salt-assisted roasting, characterized in that, Includes the following steps: Step S1: Use a crusher to coarsely crush the aluminum electrolysis cathode carbon block, then pulverize it through a ball mill, sieve it, and dry it in an oven for later use. Step S2: Select analytical grade sodium chloride and carbonic acid, mix them according to the mass ratio, put the mixed salt into a muffle furnace, heat for a period of time to form a uniform binary eutectic molten salt, and grind it into fine powder using an agate crucible for later use. Step S3: Mix the dried cathode carbon block powder with the prepared binary molten salt fine powder according to the mass ratio. Place the uniformly mixed material in a corundum crucible and put it into a horizontal tube furnace. Introduce nitrogen as a protective gas and carry out a pyrolysis reaction at a certain temperature to promote the decomposition of toxic components of the cathode carbon block and the conversion of valuable components. The tail gas passes through a tail gas absorption device containing sodium hypochlorite solution and a sodium hydroxide solution absorption device in sequence. Step S4: After pyrolysis, wait for the tube furnace to cool to room temperature, then remove the corundum crucible. The crucible product is divided into two layers: the bottom layer is mainly molten salt, and the top layer is residue of carbonaceous materials and other impurities. The bottom layer of molten salt can be repeated in step S3. The top layer residue is removed and collected for subsequent processing. Step S5: Mix the collected top residue with deionized water according to the solid-liquid ratio, place it in a water bath and stir for a period of time to separate the solid and liquid to obtain filter residue A and filtrate A; Step S6: Mix filter residue A with concentrated hydrogen chloride solution according to the solid-liquid ratio, place in a water bath and stir for a period of time, and separate the solid and liquid to obtain relatively pure carbonaceous material and filtrate B. Step S7: Mix filtrate A, filtrate B and sodium hydroxide absorption solution, and add appropriate amount of sodium hydroxide to adjust pH to 10.5-11.

5. Separate solid and liquid through precipitation reaction to obtain cryolite and filtrate C. Separate sodium chloride from filtrate C by evaporation and crystallization, so as to realize the recycling of molten salt components and the high-value recovery of fluorine resources.

2. The process for recovering valuable components from cathode carbon blocks by binary molten salt-assisted roasting according to claim 1, characterized in that, In step S1, the material is pulverized by a ball mill, sieved through a 150-mesh sieve, and then dried in an oven at 80°C for 12 hours for later use. In step S2, sodium chloride with a purity of 99.5% and sodium carbonate with a purity of 99.5% are mixed in a 1:1 mass ratio and heated at 600°C for a period of time.

3. The process for recovering valuable components from cathode carbon blocks by binary molten salt-assisted roasting according to claim 1, characterized in that, In step S3, the dried cathode carbon block powder and the prepared binary molten salt fine powder are mixed at a mass ratio of 1:1 and subjected to pyrolysis reaction at 650℃ for 2 hours. In step S5, the collected top residue is mixed with deionized water at a solid-liquid ratio of 1:

3. In step S6, filter residue A is mixed with 2 mol / L concentrated hydrogen chloride solution at a solid-liquid ratio of 1:

3.

4. A device for recovering valuable components from cathode carbon blocks by binary molten salt-assisted roasting, characterized in that, The equipment for recovering valuable components from cathode carbon blocks is used in the process for recovering valuable components from cathode carbon blocks as described in any one of claims 1-3, and includes a reaction vessel, a sealed cover, a rotating dosing mechanism, and a depth adjustment mechanism; The rotating dosing mechanism includes a mounting plate fixed to the inner wall of the reactor. Three gears are rotatably connected inside the mounting plate. A dropper is slidably connected inside each of the three gears. A rotating ring is rotatably connected to the top of the mounting plate. Three sets of teeth are arranged in a ring array on the inner side of the rotating ring. The three sets of teeth mesh with the three gears respectively. The depth adjustment mechanism includes multiple connecting columns fixed to the top of the rotating ring, a drive disk fixed to the top of the multiple connecting columns, a drive shaft fixed vertically inside the drive disk, the drive shaft being rotatably connected to the mounting disk, three protruding plates arranged in a circular array at the bottom of the drive disk, a rotating seat fixed to the top of each of the three droppers, a rotating wheel rotatably connected to the inner side of each of the three rotating seats, and a spring sleeved on the circumferential side of each of the three droppers and located on the top of the gear.

5. The equipment for recovering valuable components from cathode carbon blocks by binary molten salt-assisted roasting according to claim 4, characterized in that, The sealing cover is located on the top of the reactor and is fixedly connected to the reactor by bolts. A partition plate is fixedly installed on the inner wall of the reactor and on top of the drive plate. The drive shaft is rotatably connected to the sealing cover and the partition plate.

6. The equipment for recovering valuable components from cathode carbon blocks by binary molten salt-assisted roasting according to claim 4, characterized in that, The reactor contains, from top to bottom, a premixing chamber, an installation chamber, and a mixing chamber. The premixing chamber is used for the initial mixing and dilution of filtrate B with a portion of filtrate A or water. The mixing chamber is used for mixing filtrate A with sodium hydroxide absorbent. After mixing, the diluted filtrate B is slowly added dropwise for further mixing. The bottom of the dropper has a curved structure.

7. The equipment for recovering valuable components from cathode carbon blocks by binary molten salt-assisted roasting according to claim 6, characterized in that, The top of the mounting plate is fixedly provided with an extraction mechanism. The extraction mechanism includes a mounting cover fixedly provided on the top of the mounting plate. The drive shaft is rotatably connected to the mounting cover. A rotating bracket is fixedly provided on the circumferential side of the drive shaft and inside the mounting cover. Two drive wheels are rotatably connected to the inner side of the rotating bracket. An extraction tube is provided inside the mounting cover. The two drive wheels are in contact with the extraction tube. The top of the extraction tube is connected to the premixing chamber, and the right side of the extraction tube is connected to the dropper.

8. The equipment for recovering valuable components from cathode carbon blocks by binary molten salt-assisted roasting according to claim 4, characterized in that, A replenishment mechanism is fixedly provided at the bottom of the mounting plate. The replenishment mechanism includes a sliding frame fixedly provided at the bottom of the mounting plate. A toothed plate is slidably connected inside the sliding frame. A reciprocating rod is fixedly provided on the right side of the toothed plate. A support frame is fixedly provided at the bottom of the mounting plate. A replenishment cylinder is fixedly provided on the inner side of the support frame. The circumferential side of the reciprocating rod is slidably connected to the inside of the replenishment cylinder. A piston is fixedly provided at the right end of the reciprocating rod. A return spring is sleeved on the circumferential side of the reciprocating rod. A half gear is fixedly provided on the circumferential side of the dropper on the left side. The half gear meshes with the toothed plate.

9. The equipment for recovering valuable components from cathode carbon blocks by binary molten salt-assisted roasting according to claim 4, characterized in that, A mixing mechanism is fixedly provided on the peripheral side of the drive shaft. The mixing mechanism includes three sets of mixing paddles fixedly provided on the peripheral side of the drive shaft. A premixing paddle is fixedly provided on the peripheral side of the drive shaft and at the top of the mixing paddles. A drive motor for driving the drive shaft to rotate is provided on the top of the sealing cover.

10. The equipment for recovering valuable components from cathode carbon blocks by binary molten salt-assisted roasting according to claim 4, characterized in that, The reactor has three feed pipes connected to its left side, an exhaust pipe connected to its right side, a discharge pipe connected to its bottom, and four support bases arranged in a circular array at its bottom.

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