Method for purifying and recycling residual anode fine powder

Abstract

The present application relates to aluminum electrolysis solid waste resource utilization and carbon material recycling field, disclose a kind of residual anode fine powder purification recycling method;Including: residual anode fine powder is sent into the first pre-screening section with thin layer state after drying and loose processing, separates metal impurities, hard particles and un-depolymerized agglomerates;The undersize of first screening is sent into stripping screening section, and the material is made to roll, rub and short-range jump by the protruding part and elastic disturbance part arranged on the screen surface, so that the salt ash fine particles attached to the surface of carbonaceous particles are separated;Through negative pressure dust removal channel and partition collection, respectively obtain salt ash enrichment powder, mixed fine powder and carbon-rich powder;After detection, the mixed fine powder is returned to screening or incorporated into carbon-rich powder, and the carbon-rich powder is detected and used in prebaked anode batching according to the proportion.The application can reduce the salt ash entrainment when the residual anode fine powder is reused, and improve the stability of the carbonaceous part recycling.

Description

Technical Field

[0001] This invention relates to the field of resource utilization of aluminum electrolysis solid waste and recycling of carbon materials, specifically to a method for purifying and reusing residual anode fine powder. Background Technology

[0002] In the aluminum electrolysis production process, after the prebaked anode is used, residual anodes are formed. After cleaning, crushing and screening, residual anodes can be used to obtain residual anode materials of different particle sizes. Among them, residual anode materials with larger particle sizes can usually be reused as carbon feedstock or calcination filler. However, due to their small particle size and large specific surface area, the fine residual anode powder is prone to carrying electrolyte salt ash, fine ash particles and metal impurities, and its reuse stability is lower than that of coarse-grained residual anode materials.

[0003] Existing treatment methods mostly involve crushing, screening, and iron removal to classify the waste anodes, recovering the coarser particles and discharging the fine powder with high ash and fluoride content separately or treating it as low-value material. Some solutions also purify the waste anode slag through flotation and high-temperature calcination, but these processes are lengthy, require sophisticated equipment and energy, and are not suitable for continuous dry recycling of waste anode powder in carbon batching.

[0004] Because the salt and ash particles in residual anode fine powder exist not only in a free fine powder state but also adhere to the surface of carbonaceous particles, ordinary sieving can only classify them according to particle size, making it difficult to effectively separate the attached salt and ash from the reusable carbonaceous particles. If the residual anode fine powder is recycled as a whole, it easily increases the amount of ash and fluoride salts entrained in the prebaked anode feedstock; if it is discharged as a whole, it will result in the waste of the usable carbonaceous particles. Therefore, there is a problem with residual anode fine powder in that it is difficult to achieve stable recycling of the carbonaceous portion while reducing salt and ash entrainment. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for purifying and reusing residual anode fine powder, thereby solving the technical problems existing in the prior art.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A method for purifying and reusing residual anode fine powder includes the following steps: S1: Dry and loosen the residual anode fine powder generated during the crushing and screening process, so that the residual anode fine powder is transformed from a moist and agglomerated state into a loose material that can roll and move on the screen surface; S2: The loose material is fed to the primary pre-screening section in a thin layer. The primary pre-screening section separates the metal impurities, hard particles and unagglomerated agglomerates in the residual anode fine powder to obtain the primary undersize. S3: The primary undersize material is conveyed to the stripping screening section. The stripping screening section includes a loose screening section, a stripping screening section and a fine screening section along the material movement direction. The screen surface of the stripping screening section is equipped with a disturbance stripping structure. The disturbance stripping structure includes a protrusion and an elastic disturbance part set on the screen surface of the stripping screening section. Under the action of the protrusion and the elastic disturbance part, the primary undersize material rolls, rubs and jumps on the screen surface, causing the salt and ash fine particles attached to the surface of the carbon particles to detach from the surface of the carbon particles. S4: A negative pressure ash discharge channel is formed below the screen surface of the stripping screening section, so that the salt ash fine particles after passing through the screen holes enter the negative pressure ash discharge channel. S5: Collect the screening products in sections along the material movement direction of the stripping screening section. Collect the material passing through the loose screening section as salt and ash enriched powder, collect the material passing through the stripping screening section as mixed fine powder, and collect the material on the screen at the end of the fine screening section as carbonaceous enriched powder. S6: Detect the ash and fluorine content of the mixed fine powder. Mixed fine powder with ash content not exceeding 10.0% and fluorine content not exceeding 1.5% is incorporated into the carbonaceous enrichment powder. Mixed fine powder that does not simultaneously meet the requirements of ash content not exceeding 10.0% and fluorine content not exceeding 1.5% is returned to the stripping and screening section for stripping and screening again. S7: Detect the carbon content, ash content and fluorine content of the carbon-enriched powder, determine the addition ratio of the carbon-enriched powder in the prebaked anode feed based on the test results, and collect the salt-ash enriched powder as electrolyte recovery feed.

[0007] Preferably, the residual anode fine powder is powder with a particle size of no more than 1.0 mm formed after the residual anode has been crushed and sieved; When drying and loosening residual anode powder, the residual anode powder is fed into a drying chamber equipped with stirring blades and dried with hot air at 80℃ to 160℃. During the drying process, the stirring blades turn the residual anode powder at a speed of 20r / min to 80r / min, so that the moisture content of the residual anode powder is reduced to 0.3% to 1.5%.

[0008] Preferably, the dried residual anode fine powder is fed into the agglomeration chamber, and a low-speed feeding rod is provided in the agglomeration chamber. The low-speed feeding rod agitates the residual anode fine powder at a speed of 10 r / min to 50 r / min. The discharge end of the agglomeration chamber is equipped with a verification screen with a screen aperture of 1.0 mm. The material that passes through the verification screen enters the primary pre-screening section as loose material, while the material that does not pass through the verification screen is returned to the agglomeration chamber for further agglomeration.

[0009] Preferably, when the loose material is fed to the primary pre-screening section in a thin-layer feeding state, a variable frequency screw feeder and a material distribution plate are used for feeding. The discharge port of the variable frequency screw feeder is located above the material distribution plate. The material distribution plate extends along the width of the screen surface of the primary pre-screening section. After the loose material is spread by the material distribution plate, a continuous material layer with a thickness of 5 mm to 25 mm is formed at the inlet of the primary pre-screening section. The continuous material layer covers 80% to 100% of the width of the screen surface of the primary pre-screening section.

[0010] Preferably, the primary pre-screening section includes an intercepting screen surface arranged in the vertical direction and a primary undersize collection hopper, wherein the screen aperture of the intercepting screen surface is 1.0 mm to 3.0 mm; After the loose material enters the primary pre-screening section, the material that does not pass through the intercepting screen is discharged from the end of the intercepting screen and enters the coarse material collection box. The material that passes through the intercepting screen falls into the primary undersize collection hopper and is then sent to the stripping screening section by the primary undersize collection hopper.

[0011] Preferably, the screen surface of the loose screening section is a flat screen, the screen surface of the peeling screening section is provided with transverse ribs, stepped screen bars and elastic disturbance plates, and the screen surface of the fine screening section is a fine-mesh screen. The transverse ribs extend along the width of the screen surface, the stepped screen bars are arranged at intervals along the material movement direction, and the elastic disturbance plates are arranged between adjacent stepped screen bars.

[0012] Preferably, the height of the transverse rib is 2mm to 8mm, and the distance between adjacent transverse ribs is 20mm to 80mm; The upper surface of the stepped screen bar is 1 mm to 6 mm higher than the screen surface of the stripping screen section; The fixed end of the elastic disturbance piece is connected to the screen surface of the stripping screen section, and the free end of the elastic disturbance piece is inclined towards the material movement direction. The free end of the elastic disturbance piece is 1mm to 5mm higher than the screen surface of the stripping screen section.

[0013] Preferably, the screen aperture of the stripping screening section is segmented along the material movement direction, wherein the screen aperture of the loose screening section is 0.075mm to 0.15mm, the screen aperture of the stripping screening section is 0.15mm to 0.30mm, and the screen aperture of the fine screening section is 0.30mm to 0.60mm. The material passing through the loose sieve section enters the salt and ash enrichment powder collection chamber, the material passing through the peeling sieve section enters the mixed fine powder collection chamber, the material passing through the fine sieve section enters the third sieve powder collection chamber, and the material on the sieve at the end of the fine sieve section enters the carbonaceous enrichment powder collection chamber.

[0014] Preferably, the negative pressure ash discharge channel includes a closed ash collection chamber, a partition plate, and an exhaust pipe. The closed ash collection chamber is located below the screen surface of the stripping screening section. The partition plate divides the closed ash collection chamber into a first ash collection chamber corresponding to the loose screening section, a second ash collection chamber corresponding to the stripping screening section, and a third ash collection chamber corresponding to the fine screening section. The first ash collection chamber is connected to the salt ash enrichment powder collection chamber, the second ash collection chamber is connected to the mixed fine powder collection chamber, and the third ash collection chamber is connected to the third transparent sieve powder collection chamber. The third transparent sieve powder in the third transparent sieve powder collection chamber is incorporated into the mixed fine powder for ash and fluorine content detection. The fine screening section is equipped with an over-screen discharge port at the end, which is connected to the carbonaceous enrichment powder collection bin. The exhaust duct is connected to the first and second ash collection chambers, and the negative pressure in the exhaust duct is 300Pa to 1500Pa.

[0015] Preferably, the carbonaceous enrichment powder is subjected to fixed carbon content, ash content and fluorine content testing before entering the prebaked anode feedstock; Carbonaceous enriched powder with a fixed carbon content of not less than 85.0%, ash content of not more than 8.0%, and fluorine content of not more than 1.0% is added to the prebaked anode feed at a ratio of 3% to 12% of the mass of fine powder in the prebaked anode feed. Carbonaceous enriched powder that does not simultaneously meet the requirements of fixed carbon content not less than 85.0%, ash content not greater than 8.0%, and fluorine content not greater than 1.0% is fed into the carbon filler batching process.

[0016] In summary, the present invention has the following main beneficial effects: This application transforms the damp, agglomerated residual anode powder into a loose material capable of stable tumbling on the screen surface by sequentially drying and loosening, thin-layer feeding, and primary pre-screening. Before entering the stripping screening section, it pre-discharges metallic impurities, hard particles, and undeagglomerated agglomerates, thereby reducing screen clogging, minimizing wear on the stripping screening section structure, and improving the stability of subsequent screening. This treatment method does not involve direct, ordinary screening of the residual anode powder; instead, it first enables the material to achieve a disperseable, agitated, and screen-passable state, providing a stable material basis for the subsequent separation of salt and ash particles from carbonaceous particles.

[0017] This application addresses the issue of salt and ash particles adhering to carbonaceous particles by setting up a loose screening section, a stripping screening section, and a fine screening section. The stripping screening section incorporates transverse ribs, stepped screen bars, and elastic disturbance plates. This causes the primary undersize material to tumble, rub, and short-range jump on the screen surface, promoting the detachment of fine salt and ash particles from the carbonaceous particle surface. Simultaneously, a negative pressure ash discharge channel promptly removes the sieved fine salt and ash particles from the space below the screen surface, reducing the probability of re-adhesion of fine salt and ash particles, improving the purity of the carbonaceous enriched powder, and reducing ash and fluoride entrainment. Compared to screening methods relying solely on particle size differences, this application effectively addresses the problem of salt and ash particles adhering to carbonaceous particles in residual anode fine powder, resulting in a clearer separation between the reusable carbonaceous portion and the salt and ash enriched portion of the residual anode fine powder.

[0018] This application collects the sieved material from the loose screening section as salt-ash enriched powder, the sieved material from the stripping screening section as mixed fine powder, and the oversize material from the end of the fine screening section as carbonaceous enriched powder. After testing the ash and fluorine content of the mixed fine powder, a decision is made whether to incorporate it into the carbonaceous enriched powder or return it to the stripping screening section for further processing. Simultaneously, the carbonaceous enriched powder is tested for fixed carbon, ash, and fluorine content to determine its addition ratio in the prebaked anode feedstock. This achieves the effects of preventing high-ash and high-fluorine fine powder from directly entering the prebaked anode feedstock, increasing the proportion of carbonaceous resources reused in the residual anode fine powder, and reducing the quality fluctuation of the prebaked anode feedstock. This method transforms the overall discharge of residual anode fine powder into graded purification and controlled reuse, enabling the resource utilization of residual anode fine powder without relying on full-volume flotation and high-temperature calcination. Attached Figure Description

[0019] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0020] 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 some embodiments of the present invention, and not all embodiments. Based on 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.

[0021] Example 1 refer to Figure 1 A method for purifying and reusing residual anode fine powder includes the following steps: S1: Dry and loosen the residual anode fine powder generated during the crushing and screening process, so that the residual anode fine powder is transformed from a moist and agglomerated state into a loose material that can roll and move on the screen surface; S2: The loose material is fed to the primary pre-screening section in a thin layer. The primary pre-screening section separates the metal impurities, hard particles and unagglomerated agglomerates in the residual anode fine powder to obtain the primary undersize. S3: The primary undersize material is conveyed to the stripping screening section. The stripping screening section includes a loose screening section, a stripping screening section and a fine screening section along the material movement direction. The screen surface of the stripping screening section is equipped with a disturbance stripping structure. The disturbance stripping structure includes a protrusion and an elastic disturbance part set on the screen surface of the stripping screening section. Under the action of the protrusion and the elastic disturbance part, the primary undersize material rolls, rubs and jumps on the screen surface, causing the salt and ash fine particles attached to the surface of the carbon particles to detach from the surface of the carbon particles. S4: A negative pressure ash discharge channel is formed below the screen surface of the stripping screening section, so that the salt ash fine particles after passing through the screen holes enter the negative pressure ash discharge channel. S5: Collect the screening products in sections along the material movement direction of the stripping screening section. Collect the material passing through the loose screening section as salt and ash enriched powder, collect the material passing through the stripping screening section as mixed fine powder, and collect the material on the screen at the end of the fine screening section as carbonaceous enriched powder. S6: Detect the ash and fluorine content of the mixed fine powder. Mixed fine powder with ash content not exceeding 10.0% and fluorine content not exceeding 1.5% is incorporated into the carbonaceous enrichment powder. Mixed fine powder that does not simultaneously meet the requirements of ash content not exceeding 10.0% and fluorine content not exceeding 1.5% is returned to the stripping and screening section for stripping and screening again. S7: Detect the carbon content, ash content and fluorine content of the carbon-enriched powder, determine the addition ratio of the carbon-enriched powder in the prebaked anode feed based on the test results, and collect the salt-ash enriched powder as electrolyte recovery feed.

[0022] This application is used for dry purification of the fine powder formed after crushing and screening of residual anodes generated during aluminum electrolysis production, and the carbonaceous enriched powder that meets the requirements for batching is reused in the batching of prebaked anodes.

[0023] The residual anode fine powder referred to in this embodiment refers to powder with a particle size of no more than 1.0 mm obtained after the residual anode is crushed and sieved. This residual anode fine powder contains carbonaceous particles, salt and ash fine particles, metallic impurities, hard particles, and agglomerates formed by moisture adhesion; wherein, the salt and ash fine particles include free electrolyte salt fine particles and electrolyte salt fine particles and ash fine particles attached to the surface of carbonaceous particles.

[0024] In existing waste anode classification processes, fine powder with high ash and fluoride content is typically discharged as a whole based on particle size, or flotation and high-temperature calcination are used to purify the waste anode slag. These methods do not address the issue of carbonaceous particles and salt ash particles adhering to each other and overlapping in particle size within the waste anode fine powder. This embodiment employs a combination of drying and loosening, thin-layer feeding, primary pre-screening, stripping screening, negative pressure ash discharge, zoned collection, and closed-circuit return screening to detach salt ash particles from the surface of carbonaceous particles, and to collect the salt ash enriched powder, mixed fine powder, and carbonaceous enriched powder separately.

[0025] The fine powder of residual anodes generated during the crushing and screening process is fed into a drying chamber equipped with stirring blades. The drying chamber is a hot air drying chamber, with the hot air inlet located at the bottom and the exhaust port at the top. During the drying process, the hot air temperature is controlled between 80℃ and 160℃, and the stirring blades rotate at 20 r / min to 80 r / min to continuously agitate the fine powder within the drying chamber, preventing localized accumulation at the bottom.

[0026] The completion of drying is determined by the moisture content of the residual anode fine powder. In this embodiment, the moisture content of the residual anode fine powder is controlled between 0.3% and 1.5%. When the moisture content is higher than 1.5%, the salt and ash particles and carbonaceous particles in the residual anode fine powder are prone to agglomeration due to moisture, which can easily clog the screen holes during subsequent screening. When the moisture content is lower than 0.3%, dust dispersion increases during the conveying and screening process of the residual anode fine powder, increasing the requirements for negative pressure ash discharge and on-site dust removal. Therefore, controlling the moisture content between 0.3% and 1.5% is used to ensure that the residual anode fine powder has the loose state required for dry screening.

[0027] The dried residual anode powder enters the agglomeration chamber. A low-speed agitator is installed in the chamber, rotating at 10 to 50 rpm to agitate the residual anode powder. The purpose of the low-speed agitator is not to further pulverize the carbonaceous particles, but rather to disperse the dried agglomerated powder into loose material under low-intensity agitation, avoiding over-pulverization that would further refine reusable carbonaceous particles.

[0028] A verification screen with a 1.0mm aperture is installed at the discharge end of the agglomeration chamber. Material passing through the verification screen enters the primary pre-screening section as loose material; material failing to pass through the verification screen is returned to the agglomeration chamber as unagglomerated agglomerates for further agitation and breaking up. By setting up the verification screen, a clear screening basis is provided for determining whether agglomerates have been properly loosened.

[0029] Loose material is conveyed to the distribution plate via a variable frequency screw feeder. The discharge port of the variable frequency screw feeder is located above the distribution plate, which extends along the width of the primary pre-screening section. After falling onto the distribution plate, the loose material is spread out, forming a continuous material layer with a thickness of 5 mm to 25 mm at the inlet of the primary pre-screening section. This continuous material layer covers 80% to 100% of the width of the primary pre-screening section.

[0030] The reason for setting a thin-layer feeding is that there is overlap in particle size between the salt and ash particles and carbonaceous particles in the residual anode fine powder. If the material enters the screen surface in a thick layer, the salt and ash particles in the lower layer are easily blocked by the carbonaceous particles in the upper layer, resulting in a decrease in screening efficiency. At the same time, the thick layer will weaken the tumbling and rubbing effect of the particles in the subsequent stripping screening section. By controlling the material layer thickness to 5mm to 25mm, the material can form a relatively uniform moving layer on the screen surface, which facilitates the disturbance of the particle surface in the subsequent stripping screening section.

[0031] The primary pre-screening section includes an intercepting screen arranged vertically and a primary undersize collection hopper. The screen aperture of the intercepting screen is 1.0 mm to 3.0 mm. After loose material enters the primary pre-screening section, metallic impurities, hard particles, and unagglomerated agglomerates cannot pass through the intercepting screen due to their particle size or shape, and are discharged from the end of the intercepting screen and enter the coarse impurity collection box; the material that passes through the intercepting screen falls into the primary undersize collection hopper and is then sent to the stripping screening section.

[0032] The primary pre-screening section is used to remove coarse impurities that affect the stability of the stripping screening. If metal flakes, hard particles, and unagglomerated agglomerates directly enter the stripping screening section, they will damage the transverse ribs, stepped screen bars, and elastic disturbance plates of the stripping screening area, and cause local blockage of the screen surface.

[0033] The material undersize from the first stage enters the stripping and screening section. The stripping and screening section includes, in sequence along the material movement direction, a loose screening section, a stripping screening section, and a fine screening section. The screen surface of the loose screening section is a flat screen, the screen surface of the stripping screening section is equipped with transverse ribs, stepped screen bars, and elastic disturbance plates, and the screen surface of the fine screening section is a fine-mesh screen.

[0034] Transverse ribs extend along the width of the screen surface, with a height of 2mm to 8mm and a distance of 20mm to 80mm between adjacent ribs. Stepped screen bars are arranged at intervals along the material movement direction, with the upper surface of each stepped screen bar 1mm to 6mm higher than the screen surface of the stripping screen section. Elastic agitators are positioned between adjacent stepped screen bars, with their fixed ends connected to the screen surface of the stripping screen section and their free ends inclined towards the material movement direction, extending 1mm to 5mm above the screen surface of the stripping screen section.

[0035] During the stripping and screening process, the primary undersize material first enters the loose screening section. This section is used to loosen the material entering the stripping section and allow any loose salt and ash particles to pass through the screen first. Afterward, the material enters the stripping screening section. Driven by the vibrating screen surface, the primary undersize material moves along the material's direction of motion. When the material passes through the transverse ribs and stepped screen bars, its trajectory changes, causing the carbonaceous particles and salt and ash particles to tumble and bounce briefly. When the material contacts the elastic disturbance plates, these plates agitate the material, causing friction between carbonaceous particles and between the carbonaceous particles and the screen surface. Through this tumbling, rubbing, and brief bouncing, the salt and ash particles adhering to the surface of the carbonaceous particles detach from the particle surface.

[0036] The stripping and screening method in this embodiment differs from ordinary particle size screening. Ordinary screening mainly separates oversize and undersize particles based on differences in particle size. However, in residual anode fine powder, there are salt and ash particles adhering to the surface of carbonaceous particles. When screening solely by particle size, the adhering salt and ash will enter the recycled powder along with the carbonaceous particles. In this embodiment, the movement state of the material on the screen surface is changed by transverse ribs, stepped screen bars, and elastic disturbance plates, causing the adhering salt and ash particles to first detach from the surface of the carbonaceous particles and then pass through the screen holes and be discharged. Therefore, the carbonaceous enriched powder is not ordinary oversize material, but rather oversize carbonaceous material with reduced salt and ash entrainment after stripping and screening.

[0037] The screen apertures in the stripping screening section are segmented along the material movement direction. Specifically, the screen apertures in the loose screening section are 0.075mm to 0.15mm, the screen apertures in the stripping screening section are 0.15mm to 0.30mm, and the screen apertures in the fine screening section are 0.30mm to 0.60mm.

[0038] The material passing through the loose screening section enters the salt and ash enrichment powder collection bin. This part of the material mainly consists of salt and ash fine particles and ultrafine ash powder that were already in a free state before entering the stripping screening section. The material passing through the stripping screening section enters the mixed fine powder collection bin. This part of the material includes salt and ash fine particles that fell off during the stripping process and some fine carbonaceous particles, so it is not directly discharged as salt and ash enrichment powder, nor is it directly reused as carbonaceous enrichment powder. The material passing through the fine screening section enters the third screening powder collection bin, where the third screening powder is combined with the mixed fine powder for ash and fluoride content testing. The material remaining at the end of the fine screening section enters the carbonaceous enrichment powder collection bin as carbonaceous enrichment powder.

[0039] Using the aforementioned zoned collection method, this embodiment does not discharge the fine powder entirely or reuse all the sieve residue directly. Instead, it diverts the powder according to the salt and ash release stage and the carbonaceous particle retention state. The loose sieve zone is used to discharge the original free salt and ash, the stripping sieve zone is used to collect the mixed fine powder formed during the stripping process, and the fine sieve zone is used to obtain the carbonaceous enriched powder after stripping.

[0040] A negative pressure ash discharge channel is installed below the screen surface of the stripping screening section. The negative pressure ash discharge channel includes a closed ash collection chamber, partition plates, and exhaust pipes. The closed ash collection chamber is located below the screen surface of the stripping screening section, and the partition plates divide the closed ash collection chamber into a first ash collection chamber corresponding to the loose screening section, a second ash collection chamber corresponding to the stripping screening section, and a third ash collection chamber corresponding to the fine screening section.

[0041] The first ash collection chamber is connected to the salt-ash enriched powder collection chamber, the second ash collection chamber is connected to the mixed fine powder collection chamber, and the third ash collection chamber is connected to the third sieve powder collection chamber. A screen outlet is located at the end of the fine sieving section, and this screen outlet is connected to the carbonaceous enriched powder collection chamber. The exhaust duct is connected to both the first and second ash collection chambers, and the negative pressure within the exhaust duct is between 300 Pa and 1500 Pa.

[0042] The negative pressure ash discharge channel is designed to ensure that fine salt and ash particles that have passed through the sieve openings promptly leave the space below the sieve surface, reducing the likelihood of these particles re-adhering to the carbonaceous particle surface after being thrown back near the sieve. The negative pressure primarily acts on the first and second ash collection chambers because the loose sieve zone and the stripping sieve zone are the main release areas for fine salt and ash particles. The third ash collection chamber is used to collect the third-pass powder from the fine sieve zone. This third-pass powder is not directly reused as carbonaceous enrichment powder but is incorporated into the mixed fine powder for testing.

[0043] When the negative pressure in the exhaust duct is below 300 Pa, it is insufficient to discharge fine salt and ash particles from the sieve, causing these particles to easily remain in the undersize area. When the negative pressure is above 1500 Pa, some fine carbonaceous particles are easily carried into the salt and ash enrichment path, reducing the recovery rate of the carbonaceous enrichment powder. Therefore, in this embodiment, the negative pressure is controlled between 300 Pa and 1500 Pa.

[0044] In this embodiment, the moisture content, ash content, fluorine content, fixed carbon content, and the proportion of carbonaceous enrichment powder added are all used as process control parameters in the purification and reuse of residual anode fine powder. Moisture content is used to determine whether the residual anode fine powder has the loose state required for dry sieving; the ash and fluorine content of the mixed fine powder are used to determine whether it can be incorporated into the carbonaceous enrichment powder; the fixed carbon content, ash content, and fluorine content of the carbonaceous enrichment powder are used to determine whether it can be included in the prebaked anode feedstock; and the proportion of carbonaceous enrichment powder added is used to control the impact of the carbonaceous enrichment powder on the prebaked anode fine powder system.

[0045] The above parameters were determined based on the test results of residual anode fine powder raw materials, stripping and screening products, and prebaked anode batching system, and were verified by testing ash content, fluorine content, and fixed carbon content. These parameters are correlated with each other and are not arbitrary, independent values.

[0046] When testing mixed fine powder, third-stage sieve powder, and carbonaceous enriched powder, the powder entering the corresponding collection bin within the same continuous operating period is considered as one test batch. Samples are taken from the upper, middle, and lower parts of each test batch within the collection bin, and the samples are mixed thoroughly to form the test sample. Ash content is determined using the constant weight on ignition method, fluoride content is determined using the ion detection method after water extraction, and the fixed carbon content is determined by deducting the moisture, ash, and volatile matter content of the test sample. The same test batch is tested at least twice; if the difference between the two test results exceeds the allowable deviation of the production site testing procedures, resampling and testing are required.

[0047] The above-described testing methods are all feasible at the carbon raw material production site and do not rely on special or unavailable equipment. Those skilled in the art can complete the testing based on the sampling objects, sampling locations, testing items, and judgment criteria described above.

[0048] The mixed fine powder in the mixed fine powder collection bin and the third-pass sieve powder collected in the third-pass sieve powder collection bin are all subjected to ash and fluoride content testing. When the ash content of the mixed fine powder is no greater than 10.0% and the fluoride content is no greater than 1.5%, this batch of mixed fine powder is included in the carbonaceous enrichment powder. When the mixed fine powder does not simultaneously meet the requirements of ash content no greater than 10.0% and fluoride content no greater than 1.5%, this batch of mixed fine powder is returned to the stripping sieve section for stripping and sieving again.

[0049] The ash content of the mixed fine powder should not exceed 10.0%, and the fluoride content should not exceed 1.5%. This is used to determine whether the mixed fine powder can be incorporated into the carbonaceous enrichment powder. This criterion is derived from the control requirements of the influence of salt and ash entrainment in the residual anode fine powder on the ash and fluoride entrainment of the prebaked anode batch, and is determined in combination with the batch test results of the residual anode fine powder, the mixed fine powder after stripping and screening, and the carbonaceous enrichment powder. When the ash content is greater than 10.0% or the fluoride content is greater than 1.5%, it indicates that the mixed fine powder still contains a large amount of salt and ash particles. If this mixed fine powder is directly incorporated into the carbonaceous enrichment powder, it will increase the ash and fluoride entrainment in the subsequent prebaked anode batch. Therefore, it needs to be returned to the stripping and screening section for stripping and screening again. The above thresholds are the process diversion conditions for the mixed fine powder in this method, and are not a limitation on the composition of the residual anode fine powder raw material.

[0050] By setting up a closed-circuit return sieve, the mixed fine powder is neither directly discarded nor reused without judgment. This treatment method can avoid the problem of waste of carbon resources caused by the overall discharge of fine powder in the existing residual anode classification process, and it can also avoid the problem of quality fluctuation caused by the direct entry of high-ash and high-fluorine mixed powder into the prebaked anode feed.

[0051] Before the carbonaceous enriched powder enters the prebaked anode batching process, its fixed carbon content, ash content, and fluorine content are tested. The fixed carbon content can be determined by deducting from the moisture, ash, and volatile matter test results. Ash content is tested using the constant weight on ignition method, and fluorine content is tested using the ion detection method after water extraction. Carbonaceous enriched powder with a fixed carbon content of not less than 85.0%, an ash content of not more than 8.0%, and a fluorine content of not more than 1.0% is added to the prebaked anode batching process at 3% to 12% of the mass of the fine powder. Carbonaceous enriched powder that does not simultaneously meet these requirements is sent to the carbon filler batching process and is not included in the prebaked anode batching process.

[0052] Before carbonaceous enriched powder enters the prebaked anode batch, it is judged using three indicators: fixed carbon content, ash content, and fluorine content. A fixed carbon content of not less than 85.0% confirms that the carbonaceous enriched powder possesses the basic carbonaceous properties required for carbon fine powder. Ash content of not more than 8.0% and fluorine content of not more than 1.0% limit the amount of inorganic ash and fluoride salts carried into the prebaked anode batch. This reuse judgment condition is stricter than the judgment condition for mixed fine powder being incorporated into carbonaceous enriched powder because the mixed fine powder judgment is used for process diversion, while the carbonaceous enriched powder judgment is used for quality control before entering the prebaked anode batch. If the carbonaceous enriched powder does not simultaneously meet the above three conditions, this batch of carbonaceous enriched powder will not enter the prebaked anode batch but will instead be sent to the carbon filler batching process.

[0053] The aforementioned fixed carbon content, ash content, fluorine content, and addition ratio are to ensure the controlled reuse of carbonaceous enriched powder recovered from the residual anode fine powder, and to prevent the ash and fluoride salt entrainment in the prebaked anode feedstock from exceeding the control requirements for ash content, fluorine content, and fixed carbon content in the prebaked anode feedstock. These indicators are verified based on the source of the residual anode, the feedstock requirements of the anode production line, and the quality control requirements for the finished anode.

[0054] The proportion of carbonaceous enrichment powder added is calculated using the following formula: ; In the formula, The percentage of carbonaceous enrichment powder added relative to the mass of prebaked anode raw fine powder is expressed as % (%). This indicates the mass of carbonaceous enrichment powder added, in kg. This indicates the mass of the prebaked anode raw fine powder, in kg.

[0055] To verify the ash and fluorine content of the prebaked anode fine powder system after adding carbonaceous enrichment powder, the following mass balance formula was used: ; ; In the formula, This indicates the calculated ash content of the fine powder system after the addition of carbonaceous enrichment powder; This indicates the ash content of the original prebaked anode fine powder; This indicates the ash content of carbonaceous enriched powder; This indicates the calculated fluorine content of the fine powder system after the addition of carbonaceous enrichment powder; This indicates the fluorine content of the original prebaked anode fine powder; Indicates the fluorine content of the carbonaceous enrichment powder; This indicates the original mass of the prebaked anode fine powder, in kg. This indicates the mass of carbonaceous enrichment powder added, expressed in kg.

[0056] The above formula is used to calculate and verify the ash and fluorine content when determining the proportion of carbonaceous enrichment powder added. In actual production, it is also necessary to verify this in conjunction with the existing quality control requirements of the prebaked anode batching system and the test results of the finished anode. If the calculation results show that the ash or fluorine content after addition does not meet the quality control requirements of the prebaked anode batching, the proportion of carbonaceous enrichment powder added should be reduced; if the carbonaceous enrichment powder does not meet the fixed carbon content, ash content, and fluorine content reuse indicators, it should be sent to the carbon filler batching process.

[0057] The salt-ash enriched powder in the salt-ash enriched powder collection bin is collected separately as electrolyte recovery feed. In this embodiment, the salt-ash enriched powder does not enter the prebaked anode feed. The salt-ash enriched powder is subsequently processed according to the feed requirements of the electrolyte recovery process, and this embodiment does not further limit the subsequent chemical treatment steps for electrolyte recovery.

[0058] Collecting the salt-ash enriched powder separately is to separate the portion of the residual anode fine powder with high ash and fluoride content from the carbonaceous recycling path, preventing it from entering the prebaked anode feedstock along with the carbonaceous enriched powder. This treatment method differs from discharging the residual anode fine powder as a whole, and also from the full-volume flotation and high-temperature calcination route. In this embodiment, dry stripping screening and negative pressure ash discharge are used to separate the salt-ash fine particles from the carbonaceous particles.

[0059] In a specific operational example, the residual anode fine powder with a particle size no greater than 1.0 mm, obtained after crushing and screening, is fed into the drying chamber. The hot air temperature is set to 120℃, and the stirring blade speed is set to 50 r / min. Drying is carried out until the moisture content is 0.8%. The dried residual anode fine powder enters the agglomeration chamber, where the low-speed feed bar speed is set to 30 r / min, and the aperture of the verification screen at the discharge end of the agglomeration chamber is 1.0 mm. Material passing through the verification screen enters the primary pre-screening section, while material not passing through the verification screen is returned to the agglomeration chamber.

[0060] After being spread by a variable frequency screw feeder and a material distribution plate, the loose material forms a continuous material layer with a thickness of 15mm at the inlet of the primary pre-screening section. The screen aperture of the primary pre-screening section is 2.0mm. The primary undersize material that passes through the screen enters the stripping screening section, while the coarse material that does not pass through the screen enters the coarse material collection box.

[0061] In the stripping and screening section, the screen aperture is set to 0.10 mm for the loose screening section, 0.20 mm for the stripping screening section, and 0.45 mm for the fine screening section. The height of the transverse ribs in the stripping screening section is set to 5 mm, the distance between adjacent transverse ribs is set to 50 mm, the upper surface of the stepped screen bars is 3 mm higher than the screen surface, and the free end of the elastic disturbance plate is 3 mm higher than the screen surface. The negative pressure in the exhaust duct is set to 900 Pa.

[0062] During operation, the material passing through the loose screening section enters the salt and ash enrichment powder collection bin; the material passing through the peeling screening section enters the mixed fine powder collection bin; the material passing through the fine screening section enters the third screening powder collection bin and is mixed with the fine powder for ash and fluorine content detection; the material on the end of the fine screening section enters the carbonaceous enrichment powder collection bin.

[0063] When the mixed fine powder test results show that the ash content is no more than 10.0% and the fluorine content is no more than 1.5%, the mixed fine powder is incorporated into the carbonaceous enrichment powder. When the mixed fine powder test results do not simultaneously meet the above conditions, the mixed fine powder is returned to the stripping and screening section for re-screening. When the carbonaceous enrichment powder test results meet the requirements of a fixed carbon content of no less than 85.0%, an ash content of no more than 8.0%, and a fluorine content of no more than 1.0%, it is added to the prebaked anode feed at 3% to 12% of the mass of the fine powder in the prebaked anode feed. If the carbonaceous enrichment powder does not simultaneously meet the above conditions, it is sent to the carbon filler feed process.

[0064] The temperature, rotation speed, sieve aperture, sieve surface structure dimensions, and negative pressure value in the specific operating examples described above are all within the range defined in the claims. Those skilled in the art can adjust these parameters within the above range based on the moisture content, agglomeration degree, ash content, fluorine content, and prebaked anode batching requirements of the residual anode powder.

[0065] The focus of this embodiment is not on ordinary crushing and sieving of the residual anode, but on secondary dry stripping and purification of the already formed residual anode fine powder. Conventional residual anode classification usually discharges fine powder according to particle size to avoid high-ash fine powder entering the prebaked anode feed. This embodiment addresses the coexistence of reusable carbonaceous particles and salt ash fine particles in the residual anode fine powder. By using transverse ribs, stepped screen bars, and elastic disturbance plates in the stripping sieve section, the salt ash fine particles are separated from the carbonaceous particles. Then, negative pressure ash discharge and zoned collection separate the fine powder at different release stages, and the mixed fine powder is tested and re-screened. Therefore, this embodiment does not simply list the existing sieving, drying, and testing steps side by side, but forms a continuous processing chain around the problem of salt ash adhesion in the residual anode fine powder, which makes it difficult to recycle carbonaceous particles at a high value.

[0066] This embodiment also differs from the full-volume flotation and high-temperature calcination route for waste anode slag. This embodiment does not require wet flotation of all residual anode fine powder, nor does it rely on high-temperature calcination to remove fluoride salts. Instead, it reduces salt and ash entrainment in the carbonaceous enrichment powder through dry stripping and screening and negative pressure ash removal, and controls the reuse ratio by detecting ash content, fluoride content, and fixed carbon content. This treatment method can retain usable carbonaceous particles while removing the salt and ash enrichment portion from the prebaked anode feed path.

[0067] 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 method for purifying and reusing residual anode fine powder, characterized in that, Includes the following steps: S1: Dry and loosen the residual anode fine powder generated during the crushing and screening process, so that the residual anode fine powder is transformed from a moist and agglomerated state into a loose material that can roll and move on the screen surface; S2: The loose material is fed to the primary pre-screening section in a thin layer. The primary pre-screening section separates the metal impurities, hard particles and unagglomerated agglomerates in the residual anode fine powder to obtain the primary undersize. S3: The primary undersize material is conveyed to the stripping screening section. The stripping screening section includes a loose screening section, a stripping screening section and a fine screening section along the material movement direction. The screen surface of the stripping screening section is equipped with a disturbance stripping structure. The disturbance stripping structure includes a protrusion and an elastic disturbance part set on the screen surface of the stripping screening section. Under the action of the protrusion and the elastic disturbance part, the primary undersize material rolls, rubs and jumps on the screen surface, causing the salt and ash fine particles attached to the surface of the carbon particles to detach from the surface of the carbon particles. S4: A negative pressure ash discharge channel is formed below the screen surface of the stripping screening section, so that the salt ash fine particles after passing through the screen holes enter the negative pressure ash discharge channel. S5: Collect the screening products in sections along the material movement direction of the stripping screening section. Collect the material passing through the loose screening section as salt and ash enriched powder, collect the material passing through the stripping screening section as mixed fine powder, and collect the material on the screen at the end of the fine screening section as carbonaceous enriched powder. S6: Detect the ash and fluorine content of the mixed fine powder. Mixed fine powder with ash content not exceeding 10.0% and fluorine content not exceeding 1.5% is incorporated into the carbonaceous enrichment powder. Mixed fine powder that does not simultaneously meet the requirements of ash content not exceeding 10.0% and fluorine content not exceeding 1.5% is returned to the stripping and screening section for stripping and screening again. S7: Detect the carbon content, ash content and fluorine content of the carbon-enriched powder, determine the addition ratio of the carbon-enriched powder in the prebaked anode feed based on the test results, and collect the salt-ash enriched powder as electrolyte recovery feed.

2. The method for purifying and reusing residual anode fine powder according to claim 1, characterized in that, The residual anode fine powder is powder with a particle size of no more than 1.0 mm formed after the residual anode is crushed and sieved; When drying and loosening residual anode powder, the residual anode powder is fed into a drying chamber equipped with stirring blades and dried with hot air at 80℃ to 160℃. During the drying process, the stirring blades turn the residual anode powder at a speed of 20r / min to 80r / min, so that the moisture content of the residual anode powder is reduced to 0.3% to 1.5%.

3. The method for purifying and reusing residual anode fine powder according to claim 2, characterized in that, The dried residual anode fine powder is fed into the agglomeration chamber, which is equipped with a low-speed feeding rod. The low-speed feeding rod moves the residual anode fine powder at a speed of 10 r / min to 50 r / min. The discharge end of the agglomeration chamber is equipped with a verification screen with a screen aperture of 1.0 mm. The material that passes through the verification screen enters the primary pre-screening section as loose material, while the material that does not pass through the verification screen is returned to the agglomeration chamber for further agglomeration.

4. The method for purifying and reusing residual anode fine powder according to claim 3, characterized in that, When the loose material is fed to the primary pre-screening section in a thin-layer feeding state, a variable frequency screw feeder and a material distribution plate are used for feeding. The discharge port of the variable frequency screw feeder is located above the material distribution plate. The material distribution plate extends along the width of the screen surface of the primary pre-screening section. After the loose material is spread by the material distribution plate, a continuous material layer with a thickness of 5 mm to 25 mm is formed at the inlet of the primary pre-screening section. The continuous material layer covers 80% to 100% of the width of the screen surface of the primary pre-screening section.

5. The method for purifying and reusing residual anode fine powder according to claim 4, characterized in that, The primary pre-screening section includes an intercepting screen surface arranged in the vertical direction and a primary undersize collection hopper. The screen aperture of the intercepting screen surface is 1.0 mm to 3.0 mm. After the loose material enters the primary pre-screening section, the material that does not pass through the intercepting screen is discharged from the end of the intercepting screen and enters the coarse material collection box. The material that passes through the intercepting screen falls into the primary undersize collection hopper and is then sent to the stripping screening section by the primary undersize collection hopper.

6. The method for purifying and reusing residual anode fine powder according to claim 5, characterized in that, The loose screening section has a flat screen, the peeling screening section has transverse ribs, stepped screen bars and elastic disturbance plates on its screen surface, and the fine screening section has a fine-mesh screen. The transverse ribs extend along the width of the screen surface, the stepped screen bars are arranged at intervals along the material movement direction, and the elastic disturbance plates are arranged between adjacent stepped screen bars.

7. The method for purifying and reusing residual anode fine powder according to claim 6, characterized in that, The height of the transverse ribs is 2mm to 8mm, and the distance between adjacent transverse ribs is 20mm to 80mm; The upper surface of the stepped screen bar is 1 mm to 6 mm higher than the screen surface of the stripping screen section; The fixed end of the elastic disturbance piece is connected to the screen surface of the stripping screen section, and the free end of the elastic disturbance piece is inclined towards the material movement direction. The free end of the elastic disturbance piece is 1mm to 5mm higher than the screen surface of the stripping screen section.

8. The method for purifying and reusing residual anode fine powder according to claim 7, characterized in that, The screen aperture of the stripping screening section is set in segments along the material movement direction, wherein the screen aperture of the loose screening section is 0.075mm to 0.15mm, the screen aperture of the stripping screening section is 0.15mm to 0.30mm, and the screen aperture of the fine screening section is 0.30mm to 0.60mm. The material passing through the loose sieve section enters the salt and ash enrichment powder collection chamber, the material passing through the peeling sieve section enters the mixed fine powder collection chamber, the material passing through the fine sieve section enters the third sieve powder collection chamber, and the material on the sieve at the end of the fine sieve section enters the carbonaceous enrichment powder collection chamber.

9. The method for purifying and reusing residual anode fine powder according to claim 8, characterized in that, The negative pressure ash discharge channel includes a closed ash collection chamber, a partition plate, and an exhaust pipe. The closed ash collection chamber is located below the screen surface of the stripping screening section. The partition plate divides the closed ash collection chamber into a first ash collection chamber corresponding to the loose screening section, a second ash collection chamber corresponding to the stripping screening section, and a third ash collection chamber corresponding to the fine screening section. The first ash collection chamber is connected to the salt ash enrichment powder collection chamber, the second ash collection chamber is connected to the mixed fine powder collection chamber, and the third ash collection chamber is connected to the third transparent sieve powder collection chamber. The third transparent sieve powder in the third transparent sieve powder collection chamber is incorporated into the mixed fine powder for ash and fluorine content detection. The fine screening section is equipped with an over-screen discharge port at the end, which is connected to the carbonaceous enrichment powder collection bin. The exhaust duct is connected to the first and second ash collection chambers, and the negative pressure in the exhaust duct is 300Pa to 1500Pa.

10. The method for purifying and reusing residual anode fine powder according to claim 9, characterized in that, The carbonaceous enrichment powder is subjected to fixed carbon content, ash content and fluorine content testing before entering the prebaked anode feed; Carbonaceous enriched powder with a fixed carbon content of not less than 85.0%, an ash content of not more than 8.0%, and a fluorine content of not more than 1.0% is added to the prebaked anode feed at a ratio of 3% to 12% of the mass of fine powder in the prebaked anode feed. Carbonaceous enriched powder that does not simultaneously meet the requirements of fixed carbon content of not less than 85.0%, ash content of not more than 8.0%, and fluorine content of not more than 1.0% is fed into the carbon filler batching process.

Images