Tantalum capacitor packaging shell embrittlement method, component separation method and method for recycling tantalum, manganese and silver in tantalum capacitor

Abstract

The invention belongs to the technical field of tantalum capacitor recycling, and particularly relates to a tantalum capacitor packaging shell embrittlement method, a component separation method and a method for recycling tantalum, manganese and silver in a tantalum capacitor. The tantalum capacitor packaging shell embrittlement method comprises the following steps that S1, anaerobic pyrolysis is conducted, specifically, a tantalum capacitor is pyrolyzed in an anaerobic environment, the pyrolysis temperature ranges from 400 DEG C to 700 DEG C, the pyrolysis time ranges from 0.5 h to 2 h, and the pyrolysis atmosphere is nitrogen or argon or vacuum; the tantalum capacitor is oxidized under the aerobic condition, the oxidizing atmosphere is air or oxygen, the heat preservation temperature ranges from 200 DEG C to 500 DEG C, and the heat preservation time ranges from 0.2 h to 1.5 h. After the treatment, the packaging shell is easily ground into powder, and the physical form of the blocky anode tantalum core is not obviously changed during grinding; the tantalum core is further leached to recover tantalum and manganese, and silver is recovered from the powder formed by the encapsulation shell. The invention provides a new process path for recycling the tantalum capacitor.

Description

Technical Field

[0001] This invention belongs to the field of tantalum capacitor recycling technology, and specifically relates to a method for embrittlement of tantalum capacitor packaging shell and a method for separating each component, as well as a method for recovering tantalum, manganese and silver from tantalum capacitors. Background Technology

[0002] Tantalum capacitors, also known as tantalum electrolytic capacitors, outperform ceramic capacitors and are widely used in circuits where ceramic capacitors cannot be used. Tantalum capacitors consist of 35-50% tantalum and tantalum oxide, 40-50% encapsulation material, and metals such as silver, manganese, iron, and nickel. Tantalum is a critical metal in capacitors and a scarce resource in the Earth's crust, with limited production. Only about 2,000 tons of tantalum are produced globally each year, and tantalum capacitors have the highest downstream application rate for tantalum metal, accounting for 34% of the market. The United States, the European Union, and Japan all classify tantalum as a strategic mineral, and my country's dependence on imported tantalum resources exceeds 80%. Therefore, tantalum capacitors have extremely high recycling and utilization value.

[0003] The key to recovering metal from tantalum capacitors is removing the packaging shell. The tantalum capacitor packaging shell is made of epoxy molding compound (EMC), a composite of inorganic silica and thermosetting epoxy polymers that forms a three-dimensional adhesive structure when heated. Its function is to protect the internal components from high temperatures, humidity, and impacts, while also protecting the internal structure from external physical and chemical damage.

[0004] Existing methods for separating the casing of tantalum capacitors mainly include mechanical, chemical, and thermal treatment methods. Mechanical methods are relatively simple and are the mainstream approach in current technology. For example, Chinese patent documents CN102744415A, CN106048231A, and CN114015884A all use mechanical methods for direct crushing. However, the recovery rate and purity of tantalum largely depend on the material released, and some tantalum may be lost along with the casing material. Chemical methods consume chemicals, require long processing times, and generate liquid waste. Thermal treatment consumes a lot of energy but has a wide range of applications, effectively decomposing the casing material of all types of tantalum capacitors and releasing tantalum without generating excess waste. Further research shows that thermal treatment separation and recovery is reliable and more suitable for industrial applications.

[0005] Existing heat treatment methods include hydrothermal, oxidation, and pyrolysis. Hydrothermal separation of tantalum capacitor casings has limitations; the reaction conditions are harsh and unsuitable for industrial application. Oxidation at 550℃ and 700℃ causes structural collapse of the anode tantalum block, transforming it into tantalum oxide and tantalum powder. Since tantalum oxide and the casing material silica have similar chemical properties, separation is difficult. While hydraulic separation can be used to separate tantalum powder and silica, this method generates wastewater. Pyrolysis avoids anode tantalum structural collapse. Chinese patent document CN106186066A discloses a method for preparing ultrafine tantalum oxide from waste tantalum capacitors. The first step involves placing the waste tantalum capacitors in a tube furnace for pyrolysis and desquamation at 600–800℃ for 1–3 hours with an argon flow rate of 50–100 mL / min. Pyrolysis yields pyrolysis oil, pyrolysis gas, and pyrolysis residues.

[0006] However, the applicant's experiments revealed that even after anaerobic pyrolysis at 400-700℃ for 0.5-2 hours, the hardness of the tantalum capacitor's casing remained relatively high, making it difficult to mechanically peel off. This may be because the molecular structure of the epoxy resin polymer material underwent ring-opening and dehydrogenation reactions during the carbonization stage, forming a strong and brittle carbonaceous residue. Summary of the Invention

[0007] The primary objective of this invention is to overcome the shortcomings of the prior art and provide a method for embrittlement of the tantalum capacitor package shell, so as to facilitate separation of the tantalum capacitor package shell from the tantalum core and terminals after embrittlement, while maintaining the integrity of the tantalum core's shape.

[0008] The solution of the present invention to the aforementioned technical problem is as follows: A method for preventing the embrittlement of the tantalum capacitor package casing includes the following steps: S1. Anaerobic pyrolysis: The tantalum capacitor is placed in an oxygen-free environment for pyrolysis, and the generated pyrolysis gas is then processed in the oxidation chamber. S2, Controlled Oxygen Oxidation: The tantalum capacitor after anaerobic pyrolysis is oxidized under aerobic conditions. Part of the generated flue gas enters the pyrolysis chamber for waste heat recovery. The recovered flue gas and the surplus flue gas enter the tail gas treatment stage.

[0009] As a preferred embodiment, in step S1, the anaerobic pyrolysis is carried out in a tubular, rotary, spiral, or tunnel oxidation furnace; the pyrolysis temperature is 400–700°C, the pyrolysis time is 0.5–2 h, and the pyrolysis atmosphere is nitrogen, argon, or vacuum. In step S2, oxygen-controlled oxidation is carried out in a tubular, rotary, spiral, or tunnel oxidation furnace; the oxidation atmosphere is air or oxygen; the holding temperature is 200–500℃, and the holding time is 0.2–1.5h.

[0010] A second objective of this invention is to provide a method for separating the components of a tantalum capacitor, comprising the following steps: S1. Anaerobic pyrolysis: The tantalum capacitor is placed in an oxygen-free environment for pyrolysis, and the generated pyrolysis gas is then processed in the oxidation chamber. S2, controlled oxygen oxidation: The tantalum capacitor after oxygen-free pyrolysis is oxidized under oxygen conditions. Part of the flue gas generated enters the pyrolysis chamber for waste heat recovery. The recovered flue gas and the excess flue gas enter the tail gas treatment stage. S3. Grinding, sieving, and magnetic separation: The heat-treated product is ground to form a powder for the encapsulation shell while the tantalum core remains intact. After sieving and magnetic separation, the powder formed from the encapsulation shell, the tantalum core, and the iron-nickel terminal are obtained respectively.

[0011] As a preferred embodiment, in step S3, the powder formed by the packaging shell is removed by sieving through a 20-mesh sieve.

[0012] A third objective of this invention is to provide a method for recovering tantalum, manganese, and silver from tantalum capacitors, comprising the following steps: S1. Anaerobic pyrolysis: The tantalum capacitor is placed in an oxygen-free environment for pyrolysis, and the generated pyrolysis gas is then processed in the oxidation chamber. S2, controlled oxygen oxidation: The tantalum capacitor after oxygen-free pyrolysis is oxidized under oxygen conditions. Part of the flue gas generated enters the pyrolysis chamber for waste heat recovery. The recovered flue gas and the excess flue gas enter the tail gas treatment stage. S3. Grinding, sieving and magnetic separation: The heat-treated product is ground, the outer shell is packaged into powder while the tantalum core remains unchanged, and after sieving and magnetic separation, the powder formed by the outer shell, the tantalum core and the iron-nickel terminal are obtained respectively. S4. Tantalum and Manganese Recovery: Place the separated tantalum core in the leaching solution, H + The concentration is 0.5-1.5 M, the solid-liquid ratio (S / L) is 1 / 25, the leaching solution temperature is 80-99°C, and the leaching time is 1-3 h. After leaching, the anolyte block and manganese leaching solution are obtained by filtration. An alkaline substance is added to the leaching solution to adjust the pH to alkaline, thus obtaining manganese hydroxide. S5. Silver Recovery: Place the powder obtained from S3 separation in a 2-4 M nitric acid solution with a solid-liquid ratio of S / L of 1 / 25 and a solution temperature of 50-70℃; filter to remove residue, and add Cl to the filtrate. - When the solution temperature is 20-40℃, the solid product silver chloride precipitates.

[0013] As a preferred embodiment, in step S3, the grinding method is one or more of a pestle mill, ball mill, or vortex mill; the sorting method is one of a vibrating screen, airflow separation, or gravity separation.

[0014] As a further preferred embodiment, in step S4, the leachate is one or more of hydrochloric acid, sulfuric acid, nitric acid, aqua regia, or hydrofluoric acid; the extraction is assisted by mechanical stirring, ultrasound, or microwave; the alkaline substance is one or more of ammonia, sodium hydroxide, or calcium hydroxide, and the alkaline substance adjusts the pH of the leachate to 12.

[0015] As a preferred embodiment, in step S5, Cl is added to the filtrate. - The substance is one or more of sodium chloride, calcium chloride, or hydrochloric acid.

[0016] The beneficial effects of this invention are: After oxygen-free pyrolysis and controlled-oxygen oxidation, the tantalum capacitor's encapsulation shell is easily ground into powder, and the physical morphology of the blocky anode tantalum core does not change significantly during grinding. The tantalum core is an anode tantalum block encapsulated with a cathode manganese oxide layer, containing small amounts of graphite and silver. Further leaching of the tantalum core recovers tantalum and manganese, and silver is recovered from the powder formed from the encapsulation shell. This application provides a new process route for the recycling of tantalum capacitors. Attached Figure Description

[0017] Figure 1 These are external views of the tantalum capacitor before pyrolysis, after anaerobic pyrolysis, and after oxygen-controlled oxidation according to the present invention. Figure 2 SEM image of the cross-section of the tantalum core after oxygen-free pyrolysis of a tantalum capacitor; Figure 3 SEM image of the cross-section of the tantalum core after pyrolysis and oxidation of a tantalum capacitor; Figure 4 XPS plot for Ta4f; Figure 5 This is a state diagram of the tantalum capacitor after pyrolysis, oxidation, grinding, and sieving. Figure 6 A process flow diagram for recovering tantalum, manganese, and silver from tantalum capacitors. Detailed Implementation Example 1

[0018] The tantalum capacitor encapsulation embrittlement method described in this application uses yellow chip tantalum capacitors with dimensions ranging from 4×7mm to 2×3mm as the waste tantalum capacitors used in the experiment.

[0019] The following steps are used to embrittle its packaging shell: S1. Anaerobic pyrolysis: The tantalum capacitor is placed in an oxygen-free environment for pyrolysis; the pyrolysis is carried out in a rotary pyrolysis furnace; the pyrolysis temperature is 500℃, the pyrolysis time is 60min, the heating rate is 10℃ / min, and nitrogen gas is introduced at a gas rate of 20mL / min.

[0020] S2. Controlled Oxygen Oxidation: The tantalum capacitors after oxygen-free pyrolysis are oxidized under aerobic conditions. Controlled oxygen oxidation is carried out in a rotary pyrolysis furnace; the oxidizing atmosphere is air; the holding temperature is 400℃, the holding time is 30 min, the heating rate is 10℃ / min, and the gas velocity is 0 mL / min. A portion of the generated flue gas enters the pyrolysis chamber for waste heat recovery; the recovered flue gas and the surplus flue gas enter the tail gas treatment stage.

[0021] The states of the tantalum capacitor before pyrolysis, after oxygen-free pyrolysis, and after oxygen-controlled oxidation are as follows: Figure 1 As shown in the figure. a) is the original tantalum capacitor, b)-c) are the tantalum capacitors after oxygen-free pyrolysis, and d) is the tantalum capacitor after pyrolysis-oxidation.

[0022] SEM images of the cross-sections of the tantalum capacitor after oxygen-free pyrolysis and after pyrolysis-oxidation are shown below. Figure 2 , Figure 3 As shown, magnification of the tantalum core at a) 40x, b) 200x, c) 500x, d) 500x, e) 1000x, and f) 3000x indicates that the heat treatment effect was good, only damaging the packaging shell without destroying the blocky structure of the tantalum core or the microstructure of the anode tantalum block. Figure 4 The XPS images of Ta4f show: a) standard spectra of Ta and Ta2O5, and b) the chemical morphology of Ta in the tantalum capacitor core before pyrolysis, after oxygen-free pyrolysis, and after pyrolysis-oxidation. It is evident that only Ta2O5 was detected in the original sample, after oxygen-free pyrolysis, and after pyrolysis-oxidation; no metallic Ta signal peak was observed. This is because XPS can only measure surface elements, detecting the Ta2O5 dielectric film on the inner surface of the anode tantalum. This corroborates the SEM results, showing that the internal microstructure of the anode tantalum was not destroyed, and also demonstrates that heat treatment did not alter the chemical morphology of tantalum. Example 2

[0023] Example 2 differs from Example 1 in that some parameters of the anaerobic pyrolysis and controlled oxygen oxidation were changed. Specifically, the pyrolysis temperature of S1 was changed to 400℃, the pyrolysis time to 70 min, the heating rate to 8℃ / min, the atmosphere to vacuum, and the pressure to 40 Pa. The holding temperature of S2 was changed to 300℃, the holding time to 40 min, the heating rate to 8℃ / min, and the gas velocity to 20 mL / min.

[0024] Similar to Example 1, using the same technical parameters, the packaging shell is also easy to grind into powder, and the physical morphology of the anode tantalum block does not change significantly during grinding. Example 3

[0025] This embodiment describes a method for separating the components of a tantalum capacitor, including the following steps: S1. Anaerobic pyrolysis: The tantalum capacitor is placed in an oxygen-free environment for pyrolysis. S2, controlled oxygen oxidation: oxidizing the tantalum capacitor after oxygen-free pyrolysis under oxygen-containing conditions; S3. Grinding, Sieving, and Magnetic Separation: The heat-treated product is ground using a pestle. The outer casing is ground into powder larger than 40 mesh, while the tantalum core remains in its original block form. Separation is achieved by sieving through a vibrating screen. The undersize material—the powder formed from the outer casing—is sieved through a 20-mesh screen, while the oversize material—the tantalum core and the iron-nickel terminals—is separated.

[0026] Steps S1 and S2 are the same as those described in Example 1.

[0027] The state before and after grinding and sieving is as follows Figure 5 As shown, a) is a tantalum capacitor, b) is the powder formed from the packaging shell, c) is the iron-nickel terminal, and d) is the tantalum core. The separation effect is evident. ICP testing and corresponding calculations indicate that, based on the number of layers from the inside out, the separation effect of tantalum is best at the innermost layer (tantalum), with nearly 100% remaining in the tantalum core; manganese is next, with 95-97% remaining in the tantalum core; and about 70% of the outermost silver is separated into the powder formed from the packaging shell. Based on this, tantalum, manganese, and silver can be recovered from the separation products. Example 4

[0028] This embodiment describes a method for recovering tantalum, manganese, and silver from tantalum capacitors. The process flow is as follows: Figure 6 As shown, it includes the following steps: S1. Anaerobic pyrolysis: The tantalum capacitor is placed in an oxygen-free environment for pyrolysis. S2, controlled oxidation: The tantalum capacitor after oxygen-free pyrolysis is oxidized under oxygen-containing conditions; wherein, steps S1 and S2 are the same as those described in Example 1.

[0029] S3. Grinding, Sieving, and Magnetic Separation: The heat-treated product is ground using ball milling at a speed of 50 r / min. The outer casing is ground into powder while the tantalum core remains in its original block form. Air separation is used for sorting, resulting in a mixture of light powder and heavy tantalum core and iron-nickel terminals. Magnetic separation is then used to separate the tantalum core from the iron-nickel terminals. S4. Tantalum and Manganese Recovery: The separated tantalum cores are placed in a leaching solution, which is nitric acid; the H of the leaching solution... + The concentration was 1 M, the solid-liquid ratio (S / L) was 1 / 25, the leaching solution temperature was 90°C, and the leaching time was 2 h. Ultrasonic assistance was used during leaching. After leaching, the anolyte tantalum block and manganese leachate were obtained by filtration using vacuum filtration with an aqueous microporous membrane. Ammonia was added to the leachate to adjust the pH to 12, yielding manganese hydroxide with a purity of 98.5% and a recovery rate of 98%. S5. Silver Recovery: The powder obtained from S3 separation is placed in a 3 M nitric acid solution with a solid-liquid ratio of S / L of 1 / 25 and a solution temperature of 60℃. The extraction is assisted by ultrasound. The residue is removed by filtration using a vacuum filtration method with an aqueous microporous membrane. Sodium chloride is added to the filtrate. The solution temperature is 30℃. Solid silver chloride is precipitated with a purity of 99.5% and a recovery rate of 95%.

Claims

1. A method for preventing embrittlement of the tantalum capacitor package casing, characterized in that, Includes the following steps: S1. Anaerobic pyrolysis: The tantalum capacitor is placed in an oxygen-free environment for pyrolysis. S2, controlled oxygen oxidation: oxidizing the tantalum capacitor after anaerobic pyrolysis under aerobic conditions.

2. The method for preventing embrittlement of the tantalum capacitor package casing as described in claim 1, characterized in that, In step S1, the parameters for anaerobic pyrolysis are: pyrolysis temperature 400-700℃, pyrolysis time 0.5-2h, and pyrolysis atmosphere is nitrogen, argon, or vacuum. In step S2, the parameters for controlled oxidation are: a holding temperature of 200–500°C, a holding time of 0.2–1.5 h, and an oxidation atmosphere of air or oxygen.

3. A method for separating the components of a tantalum capacitor, characterized in that, Includes the following steps: S1. Anaerobic pyrolysis: The tantalum capacitor is placed in an oxygen-free environment for pyrolysis. S2, controlled oxygen oxidation: oxidizing the tantalum capacitor after oxygen-free pyrolysis under oxygen-containing conditions; S3. Grinding, sieving, and magnetic separation: The heat-treated product is ground to form a powder for the encapsulation shell while the tantalum core remains intact. After sieving and magnetic separation, the powder formed from the encapsulation shell, the tantalum core, and the iron-nickel terminal are obtained respectively.

4. The method for separating the components of a tantalum capacitor as described in claim 3, characterized in that, In step S3, the powder formed by the packaging shell is removed by sieving through a 20-mesh sieve.

5. A method for recovering tantalum, manganese, and silver from tantalum capacitors, characterized in that, Includes the following steps: S1. Anaerobic pyrolysis: The tantalum capacitor is placed in an oxygen-free environment for pyrolysis. S2, controlled oxygen oxidation: oxidizing the tantalum capacitor after oxygen-free pyrolysis under oxygen-containing conditions; S3. Grinding, sieving and magnetic separation: The heat-treated product is ground, the outer shell is packaged into powder while the tantalum core remains unchanged, and after sieving and magnetic separation, the powder formed by the outer shell, the tantalum core and the iron-nickel terminal are obtained respectively. S4. Tantalum and Manganese Recovery: Place the separated tantalum core in the leaching solution, H + The concentration is 0.5-1.5 M, the solid-liquid ratio (S / L) is 1 / 25, the leaching solution temperature is 80-99°C, and the leaching time is 1-3 h. After leaching, the anolyte block and manganese leaching solution are obtained by filtration. An alkaline substance is added to the leaching solution to adjust the pH to alkaline, thus obtaining manganese hydroxide. S5. Silver Recovery: Place the powder obtained from S3 separation in a 2-4 M nitric acid solution with a solid-liquid ratio of S / L of 1 / 25 and a solution temperature of 50-70℃; filter to remove residue, and add Cl to the filtrate. - When the solution temperature is 20-40℃, the solid product silver chloride precipitates.

6. The method for recovering tantalum, manganese, and silver from tantalum capacitors as described in claim 5, characterized in that, In step S3, the grinding method is one or more of the following: pestle mill, ball mill, or vortex mill; the sorting method is one of the following: vibrating screen, airflow separation, or gravity separation.

7. The method for recovering tantalum, manganese, and silver from tantalum capacitors as described in claim 5, characterized in that, In step S4, the leachate is one or more of hydrochloric acid, sulfuric acid, nitric acid, aqua regia, or hydrofluoric acid; the extraction is assisted by mechanical stirring, ultrasound, or microwave; the alkaline substance is one or more of ammonia, sodium hydroxide, or calcium hydroxide, and the alkaline substance adjusts the pH of the leachate to 12.

8. The method for recovering tantalum, manganese, and silver from tantalum capacitors as described in claim 5, characterized in that, In step S5, Cl is added to the filtrate. - The substance is one or more of sodium chloride, calcium chloride, or hydrochloric acid.

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