Forming method of anode of aluminum electrolytic capacitor and full-closed-loop camphor recovery system

Abstract

The invention discloses a forming method of an anode of an aluminum electrolytic capacitor and a full-closed-loop camphor recovery system, relates to the technical field of aluminum electrolytic capacitors, and aims to solve the problems that an existing pore-forming agent cannot be recovered, the anode forming uniformity is poor, and the production cost is high. The method comprises two anode preparation processes of fixed mold layering liquid phase infiltration forming and vacuum pure camphor gas phase closed-loop coating, and a matched camphor purification circulation, anode forming and sintering camphor removal recovery full-closed-loop system, so that the comprehensive recovery rate of camphor is greater than or equal to 98%, and zero VOCs emission is realized. The thickness deviation of the anode is smaller than or equal to + / -2%, the product yield is larger than or equal to 99%, the specific volume of the anode is increased by more than 15%, the production cost is greatly reduced, and the application requirement of the high-voltage aluminum electrolytic capacitor is met.

Description

Technical Field

[0001] This invention relates to the field of aluminum electrolytic capacitor technology, and in particular to a method for forming and preparing etched foil anodes for high-voltage aluminum electrolytic capacitors and a matching closed-loop recycling system for pore-forming agents. Background Technology

[0002] Aluminum electrolytic capacitors are core passive components in electronic circuits, with high-voltage aluminum electrolytic capacitors widely used in new energy, industrial control, and rail transportation. The anode performance of high-voltage aluminum electrolytic capacitors directly determines the capacitor's core indicators such as withstand voltage, specific capacitance, and lifespan. During the anode forming process, the selection of the pore-forming agent and the forming process are crucial factors affecting anode performance.

[0003] In existing technologies, organic pore-forming agents such as rosin and resin are commonly used in the anode forming of high-voltage aluminum electrolytic capacitors. These pore-forming agents decompose into... Gases such as VOCs cannot be recovered, causing environmental pollution and high environmental treatment costs. They also present problems such as uneven pore formation and poor anode porosity consistency. Some processes use camphor as a pore-forming agent. Camphor can be recovered through sublimation-condensation, but existing camphor processes are all open production processes with a camphor loss rate of over 60%. This not only significantly increases production costs but also poses safety risks due to the flammability and explosiveness of camphor.

[0004] Meanwhile, existing anode forming generally adopts an integral pressing forming process, which results in large deviations in anode thickness and uneven layering. Under high-voltage conditions, local breakdown is prone to occur, and the product yield is only about 85%. A few vapor phase coating processes have aluminum powder agglomeration problems, which cannot achieve 360° full coating of a single aluminum powder, resulting in poor anode consistency and making it unsuitable for the long-term stable use requirements of high-voltage aluminum electrolytic capacitors. Summary of the Invention

[0005] 1. Technical problems to be solved

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies, such as the inability to recycle pore-forming agents, poor uniformity of anode forming, high production costs, and high safety risks. This invention provides a method for forming the anode of aluminum electrolytic capacitors and a fully closed-loop camphor recycling system, which realizes closed-loop recycling of camphor throughout its entire life cycle. It also provides two compatible anode forming processes, which significantly improves anode consistency and product yield, and reduces production costs and environmental risks.

[0007] 2. Technical Solution

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A closed-loop camphor recovery system for aluminum electrolytic capacitor anodes includes a raw material purification and circulation unit, an anode forming unit, and a sintering decamphor recovery unit connected in sequence.

[0010] The raw material purification and circulation unit includes a camphor heating kettle, a distillation column, a water-cooled condenser, and a heat-insulating storage tank connected in sequence. The outlet of the heat-insulating storage tank is connected to the anode forming unit, and the reflux end of the raw material purification and circulation unit is connected to the camphor heating kettle.

[0011] The anode forming unit can be selected from a fixed-mold layered immersion mold or a vacuum phase coating device, which is compatible with two anode forming processes.

[0012] The sintering decamphor recovery unit includes an argon-protected sintering furnace, a high-temperature filter, a low-temperature condenser, and an argon drying and reuse unit connected in sequence. The outlet of the argon drying and reuse unit is connected to the argon-protected sintering furnace, and the camphor recovery end of the low-temperature condenser is connected to the camphor heating kettle.

[0013] Furthermore, the present invention provides two anode forming methods, both based on the above-described fully closed-loop camphor recovery system:

[0014] The first method is a fixed-mold, layered liquid phase impregnation molding method, which includes the following steps:

[0015] S1 Raw material purification: Industrial camphor is added to a camphor heating kettle and heated to 170-190℃ to vaporize. The camphor gas enters a distillation column for purification and is then condensed into liquid camphor by a water-cooled condenser. The liquid is then sent to an insulated storage tank for constant temperature storage at 170-190℃.

[0016] S2 Mold Preparation: Stainless steel mesh is attached to the inner wall of the aluminum alloy mold cavity, and layers of stainless steel mesh and spherical aluminum powder are alternately laid inside. After the mold is closed, the mold is heated to 170-190℃ through the constant temperature heating layer of the mold cavity.

[0017] S3 Impregnation molding: Liquid camphor from the heat-insulating storage tank is injected into the mold from bottom to top through the injection / overflow hole to impregnate the spherical aluminum powder layer. Excess camphor is filtered through the waste material filter and then returned to the camphor heating kettle.

[0018] S4 Demolding and Sintering: After impregnation, the anode blank is cooled and demolded to obtain the anode blank. The anode blank is sent into an argon-protected sintering furnace, first held at 550-590℃ for descaling, and then heated to 620-660℃ for high-temperature sintering to obtain the anode of the aluminum electrolytic capacitor.

[0019] S5 Recycling: Camphor gas sublimated during sintering is filtered by a high-temperature filter and then sent to a low-temperature condenser for condensation and recovery. It is then returned to the camphor heating kettle for recycling. Argon gas after camphor removal is dried by an argon gas drying and reuse unit and then recycled to an argon-protected sintering furnace.

[0020] The second method is a vacuum pure camphor vapor phase closed-loop coating method, which includes the following steps:

[0021] S1 Raw material pretreatment: Spherical aluminum powder is fed into aluminum powder silo, and the aluminum powder is pre-cooled to 0-25℃ by a semiconductor cooling chip. Low-speed stirring is used to prevent particle size separation.

[0022] S2 Gas Phase Circulation: Camphor is heated and vaporized and then sent into the vertically covered cavity. The cavity temperature is maintained at 170-190℃ by the constant temperature heating layer of the cavity. The camphor gas is driven by a high temperature shielded pump to circulate in a closed loop between the vertically covered cavity, the constant temperature cyclone separator, the high temperature sintered metal filter, and the camphor storage silo.

[0023] S3 Sublimation Coating: The pre-cooled aluminum powder is controlled by a double-layer constant temperature screen and an ultrasonic transducer, and each particle falls into the vertical coating cavity at a uniform speed. High-temperature camphor gas sublimates on the surface of the cold aluminum powder to form a uniform camphor film, thus completing the coating.

[0024] S4 Material Collection and Sintering: The coated aluminum powder is continuously fed into the bottom collection bin through a double-stage rotary airlock valve, and then sent into an argon-protected sintering furnace. It is first held at 550-590℃ to remove the camphor, and then heated to 620-660℃ for high-temperature sintering to obtain the anode of the aluminum electrolytic capacitor.

[0025] S5 Recycling: Camphor gas sublimated during sintering is filtered by a high-temperature filter and then sent to a low-temperature condenser for condensation and recovery. It is then returned to the camphor heating kettle for recycling. Argon gas after camphor removal is dried by an argon gas drying and reuse unit and then recycled to an argon-protected sintering furnace.

[0026] 3. Beneficial effects

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] (1) Significant environmental benefits: This invention constructs a closed-loop recycling system for camphor throughout its entire life cycle. Through three stages—purification and recycling, residual material return, and sintering recycling—it achieves a comprehensive camphor recovery rate of ≥98%, zero VOC emissions during the production process, and no risk of flammability or explosion. This completely solves the environmental and safety problems of existing pore-forming agents.

[0029] (2) Significantly improved anode performance: The fixed-mold layered liquid phase wetting process provided by this invention can achieve anode thickness deviation Porosity uniformity ≥98%, product yield increased from the current 85% to over 99%; vapor phase coating process can achieve 360° full coating of a single aluminum powder particle, with minimal coating thickness deviation. The anode specific capacitance is increased by more than 15% compared to existing processes, and the breakdown voltage is increased by more than 20%, making it suitable for the long-term stable use requirements of high-voltage aluminum electrolytic capacitors.

[0030] (3) Production costs are significantly reduced: This invention enables the recycling of camphor, reducing the cost of pore-forming agents by more than 70%; the entire process is continuous, increasing production efficiency by more than 50%, reducing energy consumption by 30%, and reducing overall production costs by more than 40% compared to existing processes.

[0031] (4) Strong compatibility: The fully closed-loop recycling system of the present invention can be adapted to both liquid phase wetting and gas phase coating molding processes. It can be flexibly switched according to the needs of different anode specifications, without the need to repeatedly build production lines, which greatly reduces equipment investment costs. Attached Figure Description

[0032] Figure 1 is a schematic diagram of the structure of the fixed-mold layered liquid phase impregnation molding device (with camphor closed-loop recovery system) of the present invention;

[0033] Figure 2 is a schematic diagram of the vacuum pure camphor gas phase closed-loop coating device of the present invention.

[0034] Appendix Label Reference Table:

[0035] 1 - Camphor heating kettle; 2 - Distillation column; 3 - Water-cooled condenser; 4 - Insulated liquid storage tank; 5 - Mold sealing flange cover; 6 - Vent hole; 7 - Layered stainless steel mesh plate; 8 - Spherical aluminum powder layer; 9 - Inner wall stainless steel lining mesh; 10 - Aluminum alloy mold cavity; 11 - Mold cavity constant temperature heating layer; 12 - Mold bottom end cover; 13 - Liquid injection / overflow hole; 14 - Residue filter; 15 - Argon-protected sintering furnace; 16 - High temperature filter; 17 - Low temperature condenser recovery unit; 18 - Argon drying and recycling unit;

[0036] (Figure 2 Supplementary Markings) 2 - Aluminum powder silo; 3 - Low-speed stirring paddle; 4 - Semiconductor cooling chip; 5 - Double-layer constant temperature screen; 6 - Ultrasonic transducer; 7 - Constant temperature heating layer of screen; 8 - Vertical covering cavity; 9 - Constant temperature heating layer of cavity; 10 - Bottom receiving silo; 11 - Two-stage rotary airlock valve; 12 - Constant temperature cyclone separator; 13 - High-temperature sintered metal filter screen; 14 - High-temperature shielded pump; 15 - Camphor storage silo. Detailed Implementation

[0037] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0038] Example 1: Fixed-mold layered liquid phase impregnation molding method

[0039] This embodiment is based on the fully closed-loop camphor recovery system described in this invention, and the specific steps are as follows:

[0040] S1 Raw material purification: Industrial camphor is added to camphor heating kettle (1) and heated to 180°C for vaporization. The camphor gas enters the distillation column (2) for purification. The theoretical number of plates in the distillation column is 15. The purified camphor gas is condensed into liquid camphor by water-cooled condenser (3) at a condensation temperature of 35°C. The condensed liquid camphor is sent to the heat-insulated storage tank (4) and stored at a constant temperature of 180°C.

[0041] S2 Mold Preparation: A stainless steel mesh (9) is attached to the inner wall of the aluminum alloy mold cavity (10). Alternating layers of 100-mesh stainless steel mesh (7) and spherical aluminum powder (8) are laid inside. The aluminum powder particle size is 50μm, and a total of 10 layers are laid. Each layer of aluminum powder is 2mm thick, with a thickness deviation of [missing information]. After the mold is closed, the mold is heated to 180°C through the constant temperature heating layer (11) of the mold cavity;

[0042] S3 Impregnation molding: Liquid camphor in the heat-insulating storage tank (4) is injected into the mold from bottom to top through the injection / overflow hole (13), with an injection pressure of 0.2MPa and an impregnation time of 20min. Excess camphor is filtered through the residue filter (14) and then returned to the camphor heating kettle (1).

[0043] S4 Demolding and Sintering: After impregnation, the anode blank is naturally cooled to room temperature and demolded to obtain the anode blank. The anode blank is sent into an argon-protected sintering furnace (15). It is first held at 580℃ for 2 hours to remove the camphor, and then heated to 640℃ for 3 hours for high-temperature sintering. Argon gas is introduced throughout the sintering process. The oxygen content in the furnace is ≤50ppm. After sintering, the anode of the aluminum electrolytic capacitor is obtained.

[0044] S5 Recycling: Camphor gas sublimated during sintering is filtered by a high-temperature filter (16) and sent to a low-temperature condenser (17). Liquid camphor is condensed and recovered at -5℃ and returned to the camphor heating kettle (1) for recycling. Argon gas after camphor removal is dried by an argon gas drying and reuse unit (18) and then recycled to an argon gas protected sintering furnace (15).

[0045] In this embodiment, the camphor recovery rate was 98.7%, the anode thickness deviation was ±1.2%, the product yield was 99.3%, the anode specific capacity was increased by 16.2% compared with the existing process products of the same specification, and the breakdown voltage was increased by 21.5%.

[0046] Example 2 Vacuum Pure Camphor Gas Phase Closed-Circuit Coating Method

[0047] This embodiment is based on the fully closed-loop camphor recovery system described in this invention, and the specific steps are as follows:

[0048] S1 Raw material pretreatment: Spherical aluminum powder with a particle size of 50μm is fed into aluminum powder silo (2), and the aluminum powder is pre-cooled to 10°C by semiconductor cooling chip (4). It is then stirred at a low speed of 8rpm by low speed stirring paddle (3) to prevent the aluminum powder particle size from separating.

[0049] S2 Gas Phase Circulation: Camphor is heated to 180℃ and vaporized before being sent into the vertically coated cavity (8). The cavity temperature is maintained at 180℃ by the constant temperature heating layer (9), and the cavity vacuum is -0.06MPa. The camphor gas is driven by a high-temperature shielded pump (14) to circulate in a closed loop between the vertically coated cavity (8), the constant temperature cyclone separator (12), the high-temperature sintered metal filter (13), and the camphor storage bin (15), maintaining the camphor gas concentration in the cavity at a certain level. ;

[0050] S3 Sublimation Coating: The pre-cooled aluminum powder is controlled by a double-layer constant temperature screen (5) and an ultrasonic transducer (6). The ultrasonic transducer vibrates at a frequency of 30kHz and the aluminum powder feed rate is 500g / h. Each particle falls into the vertical coating cavity (8) at a uniform speed. High-temperature camphor gas sublimates on the surface of the cold aluminum powder to form a uniform camphor film with a thickness of 2μm, thus completing the coating. The coating thickness deviation is ≤±4%.

[0051] S4 Sintering: The coated aluminum powder is continuously fed into the bottom receiving hopper (10) through a double-stage rotary airlock valve (11), and then sent into an argon-protected sintering furnace (15). It is first held at 580℃ for 2 hours to remove camphor, and then heated to 640℃ for 3 hours for high-temperature sintering. Argon gas is introduced throughout the sintering process, and the oxygen content in the furnace is ≤50ppm. After sintering, it is cooled with the furnace to obtain the anode of the aluminum electrolytic capacitor.

[0052] S5 Recycling: Camphor gas sublimated during sintering is filtered by a high-temperature filter (16) and sent to a low-temperature condenser (17). Liquid camphor is condensed and recovered at -5℃ and returned to the camphor heating kettle (1) for recycling. Argon gas after camphor removal is dried by an argon gas drying and reuse unit (18) and then recycled to an argon gas protected sintering furnace (15).

[0053] In this embodiment, the camphor recovery rate is 98.2%, the aluminum powder coating uniformity is 99.1%, the product yield is 99.5%, the anode specific capacity is increased by 17.5% compared with the existing process products of the same specification, and the breakdown voltage is increased by 23.1%.

[0054] Comparative example of existing conventional rosin pore-forming integral compression molding process

[0055] This comparative example uses existing conventional processes, and the specific steps are as follows:

[0056] Rosin pore-forming agent and spherical aluminum powder are mixed evenly at a mass ratio of 8:92, and then pressed into shape by a mold at a pressing pressure of 20MPa to obtain an anode blank. The anode blank is then sent to a sintering furnace, where it is first held at 500℃ for 2 hours to decompose the pore-forming agent, and then heated to 640℃ for 3 hours for high-temperature sintering to obtain the anode of an aluminum electrolytic capacitor.

[0057] In this comparative example, the pore-forming agent completely decomposed and could not be recovered, and the VOC emission concentration was [missing information]. The anode thickness deviation was ±8.7%, the product yield was 84.2%, and the anode specific capacitance and breakdown voltage were significantly lower than those of Example 1 and Example 2.

Claims

1. A fully closed-loop camphor recovery system for the anode of an aluminum electrolytic capacitor, characterized in that, The system includes a raw material purification and circulation unit, an anode forming unit, and a sintering desalting and recovery unit connected in sequence. The raw material purification and circulation unit includes a camphor heating kettle (1), a distillation column (2), a water-cooled condenser (3), and a heat-insulating storage tank (4) connected in sequence via pipelines. The outlet of the heat-insulating storage tank (4) is connected to the inlet of the anode forming unit, and the reflux end of the raw material purification and circulation unit is connected to the reflux port of the camphor heating kettle (1) via pipelines. The anode forming unit is a replaceable structure and can be a fixed-mold layered impregnation mold or a vacuum pure camphor vapor phase coating device. The fixed-mold layered impregnation mold includes an aluminum alloy mold cavity (10). The top of the aluminum alloy mold cavity (10) is sealed with a mold sealing flange cover (5) with an exhaust hole (6), and the bottom of the aluminum alloy mold cavity (10) is sealed with a mold bottom end cover (12) with an injection / overflow hole (13). The inner wall of the aluminum alloy mold cavity (10) is fitted with an inner stainless steel mesh (9). The interior of the aluminum alloy mold cavity (10) is alternately laid with layered stainless steel mesh (7) and spherical aluminum powder layer (8). The outer wall of the aluminum alloy mold cavity (10) is wrapped with a mold cavity constant temperature heating layer (11). The liquid inlet of the liquid injection / overflow hole (13) is connected to the liquid outlet of the heat preservation storage tank (4) through a pipeline. The overflow end of the liquid injection / overflow hole (13) is connected to the return port of the camphor heating kettle (1) after being connected in series with the residual material filter (14) through a pipeline. The sintering decamphoration recovery unit includes an argon-protected sintering furnace (15), a high-temperature filter (16), a low-temperature condenser recovery unit (17), and an argon drying and reuse unit (18) connected in sequence through pipelines. The outlet of the argon drying and reuse unit (18) is connected to the argon-protected sintering furnace (15) through a pipeline. The air inlet of the low-temperature condenser (17) is connected to the camphor recovery port of the camphor heating vessel (1) through a pipeline.

2. A method for molding a layered liquid phase impregnation of the anode of an aluminum electrolytic capacitor, characterized in that, The fully closed-loop camphor recovery system according to claim 1 includes the following steps: S1 Raw material purification: Industrial camphor is added to a camphor heating kettle (1) and heated to 170-190℃ for vaporization. The camphor gas enters a distillation column (2) for purification and is then condensed into liquid camphor by a water-cooled condenser (3). The liquid camphor is then sent to a thermal storage tank (4) for constant temperature storage at 170-190℃; S2 Mold preparation: A stainless steel mesh (9) is attached to the inner wall of the aluminum alloy mold cavity (10). Layered stainless steel mesh plates (7) and spherical aluminum powder layers (8) are alternately laid inside. After the mold is closed, the mold is heated to 170-190℃ through a constant temperature heating layer (11); S3 Impregnation molding: Liquid camphor in the thermal storage tank (4) is injected / overflowed through the injection / overflow hole (13). The camphor is injected into the mold from bottom to top, and the spherical aluminum powder layer (8) is impregnated. The excess camphor is filtered through the residue filter (14) and then returned to the camphor heating kettle (1). S4 Demolding and sintering: After impregnation, the mold is cooled and demolded to obtain the anode blank. The anode blank is sent to the argon-protected sintering furnace (15). The camphor is first removed by holding at 550-590℃, and then heated to 620-660℃ for high-temperature sintering to obtain the anode of the aluminum electrolytic capacitor. S5 Recycling: The camphor gas sublimated during the sintering process is filtered through the high-temperature filter (16) and sent to the low-temperature condenser (17) for condensation and recovery. It is then returned to the camphor heating kettle (1) for recycling. The argon gas after camphor removal is dried by the argon drying and recycling unit (18) and then recycled to the argon-protected sintering furnace (15).

3. A method for vacuum pure camphor vapor-phase closed-loop coating of the anode of an aluminum electrolytic capacitor, characterized in that, The fully closed-loop camphor recovery system based on claim 1 includes the following steps: S1 Raw material pretreatment: Spherical aluminum powder is fed into the aluminum powder silo (2), and the aluminum powder is pre-cooled to 0-25℃ by a semiconductor cooling chip (4), and low-speed stirring is carried out by a low-speed stirring paddle (3) to prevent particle size stratification; S2 Gas phase circulation: Camphor is heated and vaporized and then sent into the vertical coating cavity (8), and the cavity temperature is maintained at 170-190℃ by a constant temperature heating layer (9), and the camphor gas is driven by a high-temperature shielded pump (14) to circulate in a closed loop between the vertical coating cavity (8), the constant temperature cyclone separator (12), the high-temperature sintered metal filter (13), and the camphor storage silo (15); S3 Sublimation coating: The pre-cooled aluminum powder is passed through a double-layer constant temperature screen (5) and an ultrasonic transducer (6). Controlled, single particles fall uniformly into the vertical coating cavity (8), and high-temperature camphor gas condenses on the surface of cold aluminum powder to form a uniform camphor film, thus completing the coating; S4 Material collection and sintering: The coated aluminum powder is continuously fed into the bottom material collection bin (10) through a double-stage rotary airlock valve (11), and then sent to the argon-protected sintering furnace (15). First, it is kept at 550-590℃ to remove camphor, and then heated to 620-660℃ for high-temperature sintering to obtain the anode of the aluminum electrolytic capacitor; S5 Recycling: The camphor gas sublimated during the sintering process is filtered by a high-temperature filter (16) and then sent to a low-temperature condenser (17) for condensation and recovery, and then returned to the camphor heating kettle (1) for recycling; The argon gas after camphor removal is dried by the argon drying and reuse unit (18) and then circulated back into the argon-protected sintering furnace (15).

4. The fully closed-loop camphor recovery system according to claim 1, characterized in that, The distillation column (2) has 10-20 theoretical plates, the water-cooled condenser (3) has a condensation temperature of 30-40℃, and the low-temperature condenser (17) has a condensation temperature of -10-0℃.

5. The fully closed-loop camphor recovery system according to claim 1, characterized in that, The layered stainless steel mesh (7) is an 80-120 mesh stainless steel mesh, and the aluminum powder particle size of the spherical aluminum powder layer (8) is 30-100μm, with a thickness deviation of ≤±1% for each layer of aluminum powder.

6. The fixed-mold layered liquid phase impregnation molding method according to claim 2, characterized in that, In step S3, the injection pressure of liquid camphor is 0.1-0.3 MPa, and the soaking time is 10-30 min.

7. The fixed-mold layered liquid phase impregnation molding method according to claim 2, characterized in that, In step S4, the descaling holding time is 1-3 hours, the high-temperature sintering holding time is 2-4 hours, and argon gas protection is used throughout the sintering process, with an oxygen content ≤50ppm.

8. The vacuum pure camphor vapor-phase closed-loop coating method according to claim 3, characterized in that, In step S1, the speed of the low-speed stirring paddle (3) is 5-10 rpm, and the pre-cooling temperature of the aluminum powder is 5-15℃.

9. The vacuum pure camphor vapor-phase closed-loop coating method according to claim 3, characterized in that, In step S2, the vacuum degree of the vertically enclosed cavity (8) is -0.05~-0.08MPa, and the camphor gas concentration is 80-120g / m³.

10. The vacuum pure camphor vapor-phase closed-loop coating method according to claim 3, characterized in that, In step S3, the vibration frequency of the ultrasonic transducer (6) is 20-40kHz, the aluminum powder feeding speed is 50-1000g / h, and the thickness of the camphor film formed is 1-5μm.

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