A closed-loop circulation type carbon-based negative electrode material pickling purification production line and process

Abstract

The application discloses a closed-loop circulation type carbon-based negative material pickling purification production line and process and belongs to the technical field of electrochemical energy storage negative material processing. The production line comprises a primary reaction module, a secondary reaction module and a finished product preparation module which are sequentially connected, and is provided with an acid liquid circulation and reuse system and a water resource closed-loop utilization system. The process adopts twice gradient pickling+staged circulation washing mode, combines with an intelligent monitoring and control unit, realizes that the acid liquid utilization rate is increased to more than 90%, fresh water consumption is reduced by more than 40%, the surface layer and internal impurities of the carbon-based material are accurately removed, the purity of the finished product meets the performance requirements of high-end energy storage batteries, and the production line has the characteristics of green environmental protection, intelligent stability and strong adaptability, and has high industrialization popularization value.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage anode material processing technology, specifically relating to a closed-loop circulating carbon-based anode material acid washing and purification production line and process. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] In the battery and electrochemical energy storage industry chain, the purity of carbon-based anode materials directly determines the cycle life, rate performance, and safety stability of the battery. Excessive metal impurities will exacerbate internal side reactions in the battery, leading to a faster capacity decay rate, while ash residue will damage the layered or porous structure of the anode material, reducing its lithium / sodium intercalation capacity. Traditional carbon-based anode acid washing and purification processes mostly adopt a single acid washing combined with a single-stage water washing mode. The acid solution is directly discharged after only one reaction, resulting in an acid raw material utilization rate of less than 60% and generating a large amount of high-concentration acidic waste liquid. Environmental treatment costs account for more than 15% of the total production cost. At the same time, the washing water is mostly used once, and the consumption of fresh water accounts for more than 90% of the total water consumption, resulting in a significant water waste problem.

[0004] For novel carbon-based anode materials such as porous carbon and hard carbon, the limitations of traditional processes are more pronounced: porous carbon has high porosity, making it easy for acid to remain within the pores, which is difficult to completely remove in a single wash, resulting in excessive acid residue in the finished product; hard carbon has an amorphous structure, with impurities embedded more deeply, and the removal rate of a single acid wash is less than 25%, and excessive acid washing may even damage the amorphous structure, leading to a decline in the material's electrochemical performance. Although existing technologies attempt to introduce simple acid recovery or water washing cycles, problems exist such as the inability to precisely control the ratio of recovered acid and incomplete purification of circulating washing water, making it difficult to achieve a truly closed-loop cycle and deep purification, and thus failing to meet the performance requirements of high-end energy storage batteries for carbon-based anode materials. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a closed-loop circulating acid washing and purification production line and process for carbon-based anode materials. Specifically, it provides an acid washing and purification production line and process that enables acid recycling and water resource closed-loop utilization, while significantly improving the purity of the finished product. The production line achieves efficient utilization of acid and water resources through modular design and circulating system construction; the process ensures the purity of the finished product through two acid washing enhancements and graded washing.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, the present invention provides a closed-loop circulating acid washing and purification production line for carbon-based anode materials, comprising a primary reaction module, a secondary reaction module and a finished product preparation module connected in sequence, and an acid solution recycling system is constructed in conjunction with it. The primary reaction module includes a primary batching tank, a primary reaction tank, a primary solid-liquid separation device, and a primary washing and pressing device connected in sequence. The secondary reaction module includes a secondary batching tank, a secondary reaction tank, a secondary solid-liquid separation device, and a secondary washing and pressing device connected in sequence. The finished product preparation module includes a pulping tank and a finished product filter press connected in sequence; The discharge end of the primary washing and pressing device in the primary reaction module is connected to the secondary batching tank of the secondary reaction module; The discharge end of the secondary washing and pressing device in the secondary reaction module is connected to the pulping tank of the finished product preparation module; The acid recycling system is equipped with an online acid concentration monitoring unit, which automatically adjusts the reflux path of the recovered acid based on the monitoring data; The carbon-based anode material includes one or more of graphite, porous carbon, hard carbon, and mesophase carbon microspheres.

[0007] Secondly, the present invention provides a closed-loop recycling carbon-based anode material acid washing and purification production process, which adopts the above-mentioned closed-loop recycling carbon-based anode material acid washing and purification production line, including a primary reaction process, a secondary reaction process and a finished product preparation process, and realizes full-process resource recycling through an acid liquid recycling and reuse system and a water resource closed-loop utilization system. One-stage reaction process: The acid solution in the primary reaction vessel is a mixture of 8%-15% hydrochloric acid and 4%-8% hydrofluoric acid. The reaction temperature is controlled within the range of 65℃-80℃, and the reaction time is 3-5 hours. The mass ratio of carbon-based raw materials, mixed acid, and deionized water is 1:(0.5-0.8):(2.5-3.5). In the mixed acid, the mass ratio of hydrochloric acid to hydrofluoric acid is (2-3):1. Secondary reaction process: The acid solution in the secondary reaction tank is a mixture of 4%-8% hydrochloric acid and 2%-5% hydrofluoric acid. The reaction temperature is controlled within the range of 65℃-85℃, and the reaction time is 2.5h-4.5h. The mass ratio of the solid material after primary treatment, the mixed acid, and the circulating filtrate is 1:(0.2-0.4):(1.5-2.5). In the mixed acid, the mass ratio of hydrochloric acid to hydrofluoric acid is (2-3):1. After the first reaction, the solid material is washed with deionized water 2-4 times, with a liquid-to-solid ratio of (3-5):1 in each wash, and then pressed to a moisture content of 32%-40%. After the second reaction, the solid material is washed with circulating washing water 2-3 times, with a liquid-to-solid ratio of (2-4):1 in each wash, and then pressed to a moisture content of 30%-38%.

[0008] One or more of the above technical solutions have the following advantages or beneficial effects: (1) This invention discloses a closed-loop circulating carbon-based anode material acid washing and purification production line and process, which is applicable to the deep purification of all types of carbon-based raw materials such as graphite, porous carbon, hard carbon, and mesophase carbon microspheres. The production line consists of a primary reaction module, a secondary reaction module, and a finished product preparation module connected in sequence, and is equipped with an acid recycling system and a water resource closed-loop utilization system. The process adopts a two-stage gradient acid washing + graded circulating washing mode, combined with an intelligent monitoring and control unit, to achieve an acid utilization rate of over 90% and a fresh water consumption reduction of over 40%. At the same time, it accurately removes surface and internal impurities of carbon-based materials, and the purity of the finished product meets the performance requirements of high-end energy storage batteries. It also has the characteristics of being green and environmentally friendly, intelligent and stable, and highly adaptable, and has high industrial promotion value.

[0009] (2) Significantly improved efficiency of resource recycling: This invention constructs a precise acid recycling and reuse system. After the first reaction, the remaining acid is directly returned to the primary batching tank. After the second reaction, the remaining acid can be returned to the primary or secondary batching tank according to the concentration gradient. Combined with the automatic control of the online acid concentration monitoring unit, the utilization rate of acid raw materials is increased from less than 60% in the traditional process to more than 90%, and the consumption of acid raw materials is reduced by more than 30%. At the same time, a closed-loop water resource utilization system is built. Through the washing water buffer tank and water purification unit, the washing water is reused in stages, and the consumption of fresh water is reduced by more than 40%. This completely solves the core pain points of acid waste and high water consumption in the traditional process, and is in line with the industrial orientation of green manufacturing and circular economy.

[0010] (3) Significantly improved material purification precision: The enhanced process of two-stage gradient acid washing + graded circulation washing is adopted. The first acid washing (the acid solution obtained from the first solid-liquid separation is returned to the first batching tank) specifically removes easily soluble impurities on the surface of the material. The second acid washing (the acid solution obtained from the second solid-liquid separation is returned to the second batching tank or the first batching tank) deeply penetrates into the interior of the material to remove embedded impurities. Combined with the graded washing strategy (the surface acid solution is thoroughly rinsed with deionized water in the first reaction module, and the internal residual acid solution is rinsed with circulating water in the second reaction module), the purity of the finished product is improved compared with the traditional single acid washing process, which can meet the high-end application purity requirements of various materials such as metal oxides, mineral raw materials, and metallurgical slag.

[0011] (4) Improved intelligence and stability of production process: The production line is equipped with a steam heating temperature control unit, which can accurately control the reaction temperature in the range of 60℃-90℃, with a temperature fluctuation range of ≤±2℃, avoiding the problem of unstable reaction efficiency caused by temperature fluctuation in traditional processes; the acid concentration online monitoring unit and water quality monitoring sensor can provide real-time feedback on the status of the circulating liquid, and the linkage flow regulating valve can automatically adjust the return path to realize the automated control of the production process; the sealed conveying channel effectively avoids the contamination or oxidation of materials during the conveying process, further ensuring the stability of the finished product quality.

[0012] (5) Enhanced process adaptability and scalability: The production line adopts a modular design. The parameters of the primary reaction module, secondary reaction module, and finished product preparation module can be independently adjusted according to the characteristics of different materials (such as acid concentration, reaction temperature, washing times, etc.), adapting to the acid washing and purification needs of multiple types of materials such as metal oxides, mineral raw materials, and metallurgical slag. At the same time, the architecture design of the dual closed-loop circulation system can be flexibly expanded to larger-scale production scenarios without major modifications to the core process, and has strong industrial promotion value. Attached Figure Description

[0013] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0014] Figure 1 This is a schematic diagram of a closed-loop circulating carbon-based anode material acid washing and purification production line according to an embodiment of the present invention.

[0015] Wherein, A: primary batching tank; F: secondary batching tank; E: primary circulating wash water buffer tank; J: secondary circulating wash water buffer tank. Detailed Implementation

[0016] In view of the problems in the existing technology, such as the inability to accurately control the ratio of recycled acid and the incomplete purification of circulating washing water, this invention proposes a closed-loop circulating acid washing and purification production line and process for carbon-based anode materials. It can be applied to the deep purification of all types of carbon-based raw materials, such as graphite, porous carbon, hard carbon, and mesophase carbon microspheres. It can simultaneously meet the purity requirements of anode materials for electrochemical energy storage devices such as lithium-ion batteries and sodium-ion batteries. By constructing a multi-level gradient reaction coupled dual closed-loop circulation system, it achieves efficient recycling of acid and water resources and precise targeted removal of impurities in carbon-based materials.

[0017] In one typical embodiment, the present invention provides a closed-loop circulating carbon-based anode material acid washing and purification production line, including a primary reaction module, a secondary reaction module and a finished product preparation module connected in sequence, and is equipped with an acid liquid recycling system and a water resource closed-loop utilization system. The primary reaction module includes a primary batching tank, a primary reaction tank, a primary solid-liquid separation device, and a primary washing and pressing device connected in sequence. The secondary reaction module includes a secondary batching tank, a secondary reaction tank, a secondary solid-liquid separation device, and a secondary washing and pressing device connected in sequence. The finished product preparation module includes a pulping tank and a finished product filter press connected in sequence; The discharge end of the primary washing and pressing device in the primary reaction module is connected to the secondary batching tank of the secondary reaction module; The discharge end of the secondary washing and pressing device in the secondary reaction module is connected to the pulping tank of the finished product preparation module; The carbon-based anode material includes one or more of graphite, porous carbon, hard carbon, and mesophase carbon microspheres.

[0018] In some embodiments of this implementation, the steam heating components built into the primary and secondary reaction tanks, along with a temperature control unit, can precisely control the reaction temperature within a preset range, with a temperature fluctuation range of ≤±2℃; the steam heating components adopt a serpentine steam heat exchange structure with a heat exchange efficiency of ≥90%; the temperature control unit is equipped with an early warning module, which automatically stops the steam supply and issues an alarm when the temperature exceeds the preset range of ±5℃.

[0019] In some embodiments of this implementation, the primary solid-liquid separation device and the secondary solid-liquid separation device are plate and frame filter presses or horizontal screw centrifuges, with a solid-liquid separation accuracy of ≤0.1μm.

[0020] In some embodiments of this implementation, in the primary reaction module, the solid material separated by the primary solid-liquid separation device enters the primary washing and pressing device. An acid recovery pipe is installed between the primary solid-liquid separation device and the primary batching tank, so that the acid outlet of the primary solid-liquid separation device is connected to the primary batching tank through a recovery pipe equipped with a flow regulating valve. Similarly, the same arrangement is used in the secondary reaction module. Specifically: the solid material separated by the secondary solid-liquid separation device enters the secondary washing and pressing device. An acid recovery pipe is installed between the secondary solid-liquid separation device and the secondary batching tank, so that the acid outlet of the secondary solid-liquid separation device is connected to the secondary batching tank through a recovery pipe equipped with a flow regulating valve. In addition, the acid outlet of the secondary solid-liquid separation device is also connected to the primary batching tank through a recovery pipe equipped with a flow regulating valve.

[0021] In some embodiments of this implementation, the primary washing and pressing device is equipped with a primary circulating washing water buffer tank with a water quality monitoring sensor, and the secondary washing and pressing device is equipped with a secondary circulating washing water buffer tank with a water quality monitoring sensor.

[0022] Furthermore, the water resource closed-loop utilization system is equipped with a water purification unit to filter and remove impurities from the wastewater in the circulating washing water buffer tank before reuse.

[0023] The water quality purification unit refers to the process of periodically purifying and discharging the circulating liquid: periodically extract the circulating liquid in the primary or secondary circulating washing water buffer tank, selectively remove the enriched metal cation impurities through flocculation sedimentation, ion exchange resin or membrane filtration technology, return the product water to the circulating washing water buffer tank, and discharge the generated impurity-containing concentrated water after neutralization up to the standard.

[0024] The washing water in the primary washing and pressing device can come from the water in the buffer tank or external deionized water. The water in the buffer tank can be periodically purified in terms of water quality. The water squeezed out in the primary washing and pressing device can be connected to the primary circulating washing water buffer tank through a pipeline, and the water in the washing water buffer tank is circulated back to the primary washing and pressing device for cyclic reuse.

[0025] It is understandable that the primary washing and pressing device is not limited to using deionized water, and the water source can be flexibly switched according to production requirements and water quality conditions, with the specific rules as follows: Conventional production scenario: Prioritize the use of circulating washing water treated by the water quality purification unit (from the primary circulating washing water buffer tank), whose water quality shall meet the purification standard of "conductivity ≤500μS / cm, total metal cation concentration ≤10ppm", which is suitable for the primary washing demand of solid materials, realizes closed-loop utilization of water resources, and can reduce the consumption of fresh water by more than 70% compared with pure deionized water.

[0026] Special production scenario: When the water quality in the circulating washing water buffer tank fails to meet the standard (e.g., conductivity >500μS / cm, total metal cation concentration >10ppm), or when producing graphite-based carbon negative electrode materials with high purity requirements, switch to using deionized water to avoid residual impurities in the circulating water from affecting product purity.

[0027] The deionized water used in the primary washing and pressing device has two supply paths. Path 1 is external fresh deionized water, which comes from the deionized water preparation system (such as reverse osmosis + ion exchange resin process) supporting the production line, and is an additional fresh water source for emergency water quality supplementation or high-purity product production. Path 2 is the purified water from the buffer tank. When the water in the primary circulating washing water buffer tank is treated by the water quality purification unit (flocculation sedimentation + membrane filtration process) to reach the deionized water standard (conductivity ≤10μS / cm), it can be reused as deionized water to further improve the water resource utilization rate.

[0028] The washing water in the secondary washing and pressing device can come from the water in the buffer tank. The water in the buffer tank can be periodically purified in terms of water quality. The water squeezed out in the secondary washing and pressing device can be connected to the secondary circulating washing water buffer tank through a pipeline, and the water in the washing water buffer tank is circulated back to the secondary washing and pressing device for cyclic reuse.

[0029] This invention establishes a closed-loop water resource utilization system, which realizes the tiered reuse of washing water through a washing water buffer tank and a water purification unit.

[0030] In some embodiments of this implementation, both the primary washing and pressing device and the secondary washing and pressing device include a rinsing component and a pressing component. The water inlet of the rinsing component is selectively connected to a deionized water source or a circulating washing water buffer tank through a three-way valve. The pressing component is equipped with a pressure sensor, which can automatically adjust the pressing pressure according to the moisture content of the material. The pressure adjustment range is 0.5MPa-1.5MPa.

[0031] This invention does not specifically limit the combination of the rinsing component and the pressing component in the washing and pressing device; existing conventional technology is sufficient. The bottom outlet of the rinsing component is connected to the inlet of the pressing component.

[0032] The pressing assembly can use existing mature conventional devices, such as industrial-grade diffused silicon pressure sensors, which have a measurement accuracy of 0.2%FS, can stably collect real-time pressure data of the pressing assembly, and are compatible with an adjustment range of 0.5MPa-1.5MPa.

[0033] Furthermore, the rinsing assembly is designed with a counter-current layered washing structure, in which circulating water is conveyed from the bottom to the top and materials are conveyed from the top to the bottom, forming counter-current contact and enhancing the rinsing effect on residual acid inside.

[0034] In some embodiments of this implementation, the filtrate outlet of the finished product filter press is connected to a primary batching tank, a secondary batching tank, a primary circulating wash water buffer tank, or a secondary circulating wash water buffer tank via a circulation pipe equipped with a flow regulating valve. The solid obtained from the finished product filter press is purified to obtain a purified finished product, which is then temporarily stored.

[0035] In some embodiments of this implementation, the primary solid-liquid separation device and the secondary solid-liquid separation device (such as a plate and frame filter press or a horizontal screw centrifuge) are equipped with an online filtrate concentration monitoring instrument, which can provide real-time feedback of filtrate acid concentration data and automatically switch the filtrate reflux path in conjunction with the flow regulating valve.

[0036] In some embodiments of this implementation, the acid recycling system is equipped with an online acid concentration monitoring unit, which can automatically adjust the reflux path of the recovered acid based on the monitoring data.

[0037] Specifically: The acid concentration online monitoring unit includes: (1) an acid outlet located at the primary solid-liquid separation device, corresponding to high-concentration recovered acid. After the acid separated by the solid-liquid separation is detected by the acid concentration online monitoring unit, it is returned to the primary batching tank for reuse through a recovery pipeline with a flow regulating valve. (2) an acid outlet located at the secondary solid-liquid separation device, corresponding to medium-concentration recovered acid. After the acid separated by the solid-liquid separation is detected by the acid concentration online monitoring unit, it is returned to the secondary batching tank for reuse or returned to the primary batching tank for reuse through a recovery pipeline with a flow regulating valve according to the concentration gradient. (3) an acid outlet located at the solid-liquid separation device (filter press) of the finished product preparation module, corresponding to low-concentration recovered acid.

[0038] Based on feedback from the online acid concentration monitoring unit, a three-stage acid cascade circulation path is established: High-concentration recovered acid (concentration ≥ 80% of fresh acid): directly replenished to the primary or secondary batching tank in the same process; Medium-concentration recovered acid (concentration 40%-80% of fresh acid): compounded with fresh acid and replenished to the same process, or directly replenished to the batching tank of the previous reaction process as low-concentration acid; Low-concentration recovered acid (concentration < 40% of fresh acid): all returned to the batching tank of the primary reaction module as a bottom liquid to replace part of the deionized water.

[0039] High-concentration recovered acid is the acid solution obtained through solid-liquid separation in the primary reaction module. Medium-concentration recovered acid is the acid solution obtained through solid-liquid separation in the secondary reaction module.

[0040] The fresh acid mentioned in this invention refers to the initial mixed acid solution that has just been prepared without participating in any reaction, i.e., the initial batch of mixed acid used to enter the formal reaction process.

[0041] Taking Example 1 as an example: Fresh acid for one reaction step: 12% hydrochloric acid and 6% hydrofluoric acid mixed at a mass ratio of 2:1, with a total effective acid concentration of 10%; Fresh acid for the secondary reaction process: 7% hydrochloric acid and 4% hydrofluoric acid mixed at a mass ratio of 3:1, with a total effective acid concentration of 6.25%.

[0042] The 0.6% acid concentration in the filter press filtrate from the finished product preparation process originates from the material after the secondary reaction. Therefore, the benchmark is the fresh acid from the secondary reaction process (effective total concentration 6.25%). 0.6% ÷ 6.25% = 9.6%, meaning the recovered acid concentration is 9.6% of the fresh acid from the corresponding process. This meets the definition of "low-concentration recovered acid (concentration < 40% of fresh acid)" in the three-stage acid cascade circulation path, belonging to the low-concentration recovered acid gradient.

[0043] Preferably, a closed-loop circulating carbon-based anode material acid washing and purification production line includes a primary reaction module, a secondary reaction module and a finished product preparation module connected in sequence, and is equipped with an acid recycling system and a water resource closed-loop utilization system. The primary reaction module includes a primary batching tank, a primary reaction tank with built-in steam heating components, a primary solid-liquid separation device, and a primary washing and pressing device; the acid outlet of the primary solid-liquid separation device is connected to the primary batching tank through a recovery pipe with a flow regulating valve; the primary washing and pressing device is equipped with a circulating washing water buffer tank with a water quality monitoring sensor, and its discharge end is connected to the secondary batching tank of the secondary reaction module. Secondary reaction module: includes a secondary batching tank, a secondary reaction tank with built-in steam heating components, a secondary solid-liquid separation device, and a secondary washing and pressing device; the acid outlet of the secondary solid-liquid separation device is connected to the primary batching tank or the secondary batching tank through a recovery pipe with a flow regulating valve; the secondary washing and pressing device is equipped with a circulating washing water buffer tank with a water quality monitoring sensor, and its discharge end is connected to the pulping tank of the finished product preparation module. Finished product preparation module: includes a slurry tank and a finished product filter press; the filtrate outlet of the finished product filter press is connected to a primary batching tank, a secondary batching tank or a circulating washing water buffer tank through a circulation pipeline with a flow regulating valve; The acid recycling system is equipped with an online acid concentration monitoring unit, which can automatically adjust the return path and ratio of the recovered acid based on the monitoring data; the water resource closed-loop utilization system is equipped with a water purification unit, which filters and removes impurities from the wastewater in the circulating washing water buffer tank before reuse.

[0044] In one typical embodiment, the present invention provides a closed-loop circulating carbon-based anode material acid washing and purification production process, which adopts the above-mentioned closed-loop circulating carbon-based anode material acid washing and purification production line, including a primary reaction process, a secondary reaction process and a finished product preparation process, and realizes full-process resource recycling through an acid liquid recycling system and a water resource closed-loop utilization system. The primary reaction process involves a mixture of 8%-15% hydrochloric acid and 4%-8% hydrofluoric acid in the primary reaction vessel. The reaction temperature is controlled between 65℃ and 80℃, and the reaction time is 3-5 hours. The mass ratio of carbon-based raw materials, mixed acid, and deionized water is 1:(0.5-0.8):(2.5-3.5). In the mixed acid, the mass ratio of hydrochloric acid to hydrofluoric acid is (2-3):1. Secondary reaction process: The acid solution in the secondary reaction tank is a mixture of 4%-8% hydrochloric acid and 2%-5% hydrofluoric acid. The reaction temperature is controlled within the range of 65℃-85℃, and the reaction time is 2.5h-4.5h. The mass ratio of the solid material (dried) after primary treatment, the mixed acid, and the circulating filtrate is 1:(0.2-0.4):(1.5-2.5). In the mixed acid, the mass ratio of hydrochloric acid to hydrofluoric acid is (2-3):1. After the first reaction, the solid material is washed with deionized water 2-4 times, with a liquid-to-solid ratio of (3-5):1 in each wash, and then pressed to a moisture content of 32%-40%. After the second reaction, the solid material is washed with circulating washing water 2-3 times, with a liquid-to-solid ratio of (2-4):1 in each wash, and then pressed to a moisture content of 30%-38%.

[0045] Different raw materials require different processing parameters. Details are shown below.

[0046] When the object being processed is a graphite-based carbon material: One-stage reaction process: The acid solution in the primary reaction vessel is a mixture of 10%-15% hydrochloric acid and 5%-8% hydrofluoric acid. The reaction temperature is controlled within the range of 70℃-80℃, and the reaction time is 3-4 hours. The mass ratio of carbon-based raw materials, mixed acid, and deionized water is 1:(0.6-0.8):(2.5-3). In the mixed acid, the mass ratio of hydrochloric acid to hydrofluoric acid is (2-3):1. Secondary reaction process: The acid solution in the secondary reaction tank is a mixture of hydrochloric acid (preferably 7%) with a concentration of 5%-8% and hydrofluoric acid (preferably 4%) with a concentration of 3%-5%. The reaction temperature is controlled in the range of 65℃-75℃, and the reaction time is 2.5h-3.5h. The mass ratio of the solid material (dried) after primary treatment, the mixed acid and the circulating filtrate is 1:(0.2-0.3):(1.5-2). In the mixed acid, the mass ratio of hydrochloric acid and hydrofluoric acid is (2-3):1. After the first reaction, the solid material is washed with deionized water 2-3 times, with a liquid-to-solid ratio of (3-4):1 in each wash, and then pressed to a moisture content of 32%-35%. After the second reaction, the solid material is washed with circulating washing water 2 times, with a liquid-to-solid ratio of (2-3):1 in each wash, and then pressed to a moisture content of 30%-33%.

[0047] When the material being processed is porous carbon, hard carbon, or other porous / amorphous carbon-based materials: The primary reaction process involves a mixture of 8%-12% hydrochloric acid and 4%-6% hydrofluoric acid in the primary reaction vessel. The reaction temperature is controlled between 65℃ and 75℃, and the reaction time is 4-5 hours. The mass ratio of carbon-based raw materials, mixed acid, and deionized water is 1:(0.5-0.7):(3-3.5). The mass ratio of hydrochloric acid to hydrofluoric acid in the mixed acid is (2-3):1. Secondary reaction process: The acid solution in the secondary reaction tank is a mixture of 4%-6% hydrochloric acid and 2%-4% hydrofluoric acid. The reaction temperature is controlled within the range of 75℃-85℃, and the reaction time is 3.5h-4.5h. The mass ratio of the solid material (dried), mixed acid, and circulating filtrate after primary treatment is 1:(0.2-0.4):(2-2.5). In the mixed acid, the mass ratio of hydrochloric acid to hydrofluoric acid is (2-3):1. After the first reaction, the solid material is washed with deionized water 3-4 times, with a liquid-to-solid ratio of (4-5):1 in each wash, and then pressed to a moisture content of 35%-40%. After the second reaction, the solid material is washed with circulating washing water 3 times, with a liquid-to-solid ratio of (3-4):1 in each wash, and then pressed to a moisture content of 33%-38%.

[0048] In some embodiments of this implementation, during the finished product preparation process, the solid content of the liquid in the slurry tank is controlled at 40%-50%, and the filtration pressure of the finished product filter press is 0.8MPa-1.2MPa; when the acid concentration in the filter press filtrate is ≤0.5%, it is recycled to the washing process, that is, recycled to the primary circulating washing water buffer tank or the secondary circulating washing water buffer tank; when the acid concentration is ≥0.5%, it is recycled to the batching process, that is, recycled to the primary batching tank or the secondary batching tank.

[0049] It should be noted that the reuse in this invention only indicates the process flow and does not specify the allocation ratio.

[0050] In some embodiments of this implementation, a linkage control system for acid solution, washing water, and reaction temperature can be established. Data from the online acid concentration monitoring unit, water quality monitoring sensor, and temperature control unit are exchanged in real time. When the acid concentration fluctuates, the reaction temperature and washing water flow parameters are automatically adjusted to ensure the stability of acid washing and washing effects.

[0051] In some embodiments of this implementation, a periodic purification and discharge process for the circulating liquid is also included. The circulating liquid in the primary or secondary circulating wash water buffer tank is periodically extracted, and after selectively removing the enriched metal cation impurities through flocculation sedimentation, ion exchange resin or membrane filtration technology, the product water is returned to the circulating wash water buffer tank, and the resulting concentrated water containing impurities is neutralized and discharged in compliance with standards.

[0052] The acid utilization rate of this closed-loop circulating carbon-based anode material pickling and purification process is stable at 92%~95%. Among them, the acid utilization rate can reach 95% when pickling graphite-based carbon materials, and 92%~93% when pickling porous carbon and hard carbon materials. The total metal impurity content of the finished graphite-based carbon materials is ≤50ppm, of which iron ≤10ppm, copper ≤5ppm, nickel ≤3ppm, calcium ≤15ppm, and magnesium ≤10ppm, and the ash content is ≤0.02%. The total metal impurity content of the finished porous carbon and hard carbon materials is ≤80ppm, of which iron ≤15ppm, copper ≤8ppm, nickel ≤5ppm, calcium ≤25ppm, and magnesium ≤15ppm, and the ash content is ≤0.05%.

[0053] In this invention, unless otherwise specified, all other test materials and instruments are conventional test materials in the field and can be purchased through commercial channels.

[0054] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0055] Example 1 This embodiment provides a closed-loop circulating acid washing and purification production line for carbon-based anode materials, including a primary reaction module, a secondary reaction module, and a finished product preparation module connected in sequence, and is equipped with an acid recycling system and a water resource closed-loop utilization system. Primary reaction module: includes a primary batching tank, a primary reaction tank with built-in steam heating components, a primary solid-liquid separation device, and a primary washing and pressing device; the acid outlet of the primary solid-liquid separation device is connected to the primary batching tank through a recovery pipe with a flow regulating valve, and the primary washing and pressing device is equipped with a circulating washing water buffer tank with a water quality monitoring sensor, and its discharge end is connected to the secondary batching tank of the secondary reaction module. Secondary reaction module: includes a secondary batching tank, a secondary reaction tank with built-in steam heating components, a secondary solid-liquid separation device, and a secondary washing and pressing device; the acid outlet of the secondary solid-liquid separation device is connected to the primary batching tank or the secondary batching tank through a recovery pipe with a flow regulating valve; the secondary washing and pressing device is equipped with a circulating washing water buffer tank with a water quality monitoring sensor, and its discharge end is connected to the pulping tank of the finished product preparation module. Finished product preparation module: includes a slurry tank and a finished product filter press; the filtrate outlet of the finished product filter press is connected to a primary batching tank, a secondary batching tank or a circulating washing water buffer tank through a circulation pipeline with a flow regulating valve; The acid recycling system is equipped with an online acid concentration monitoring unit, which can automatically adjust the return path of the recovered acid based on the monitoring data; the water resource closed-loop utilization system is equipped with a water purification unit, which filters and removes impurities from the wastewater in the circulating washing water buffer tank before reuse.

[0056] Both the primary washing and pressing device and the secondary washing and pressing device include a rinsing component and a pressing component. The water inlet of the rinsing component is selectively connected to a deionized water source or a circulating washing water buffer tank through a three-way valve. The pressing component is equipped with a pressure sensor, which can automatically adjust the pressing pressure according to the moisture content of the material.

[0057] The rinsing assembly is designed with a counter-current layered washing structure, in which circulating water is transported from the bottom to the top and materials are transported from the top to the bottom, forming a counter-current contact and enhancing the rinsing effect on residual acid inside.

[0058] The primary and secondary reaction vessels are equipped with built-in steam heating components and temperature control units, which can accurately control the reaction temperature within a preset range with a temperature fluctuation range of ≤±2℃. The steam heating components adopt a serpentine steam heat exchange structure with a heat exchange efficiency of ≥90%. The temperature control unit is equipped with an early warning module, which automatically stops the steam supply and issues an alarm when the temperature exceeds the preset range of ±5℃.

[0059] The primary and secondary solid-liquid separation devices are plate and frame filter presses or horizontal screw centrifuges, with a solid-liquid separation accuracy of ≤0.1μm. The finished product filter press is equipped with an online filtrate concentration monitoring instrument, which can provide real-time feedback on filtrate acid concentration data and automatically switch the filtrate reflux path in conjunction with the flow regulating valve.

[0060] A linkage control system is established for acid solution, washing water, and reaction temperature. Data from the online acid concentration monitoring unit, water quality monitoring sensor, and temperature control unit are exchanged in real time. When the acid concentration fluctuates, the reaction temperature and washing water flow parameters are automatically adjusted to ensure the stability of acid washing and washing effects.

[0061] It also includes a periodic purification and discharge process for circulating liquid: the circulating liquid in the primary or secondary circulating washing water buffer tank is periodically extracted, and after selectively removing the enriched metal cation impurities through flocculation sedimentation, ion exchange resin or membrane filtration technology, the produced water is returned to the circulating washing water buffer tank, and the resulting impurity-containing concentrated water is neutralized and discharged in compliance with standards.

[0062] Example 2 This embodiment uses graphite-based carbon-based anode materials as the processing target to carry out closed-loop cyclic acid washing and purification production. It adopts the closed-loop cyclic carbon-based anode material acid washing and purification production line of Example 1, and specifically includes the following steps: First, the primary reaction module is started. The materials are added to the primary reaction tank with a built-in serpentine steam heat exchanger, according to the mass ratio of carbon-based raw materials, a mixture of 12% hydrochloric acid and 6% hydrofluoric acid (mass ratio 2:1), and deionized water 1:0.7:2.8. The reaction temperature is precisely controlled at 75℃ by the automatic temperature control unit, with temperature fluctuations maintained within ±1.5℃, and the reaction continues for 3.5 hours. After the reaction is completed, the materials are sent to a plate and frame filter press for solid-liquid separation. The separated acid solution is monitored online for acid concentration. After unit testing (the acid solution separated by the plate and frame filter press is high-concentration recovered acid, with an acid concentration of 85%-92% of that of fresh acid), it is returned to the primary batching tank for reuse through a recovery pipeline equipped with a flow regulating valve. The solid material is sent to the primary washing and pressing device, where it is first rinsed twice with deionized water at a liquid-to-solid ratio of 3.5:1. Then, the pressure is adjusted to 1.0 MPa through the pressing assembly equipped with a pressure sensor, and the material is pressed to a moisture content of 33%. Subsequently, it is sent to the secondary batching tank of the secondary reaction module through a sealed conveying channel protected by nitrogen. After entering the secondary reaction process, the solid material from the primary treatment, a mixture of 7% hydrochloric acid and 4% hydrofluoric acid (mass ratio of 3:1), and circulating filtrate 1 (dry weight): 0.25:1.8 are prepared according to the mass ratio. The mixture is reacted in the secondary reaction tank at 70°C for 3 hours, with the reaction temperature fluctuation controlled within ±2°C. After the reaction, the material is separated into solid and liquid by a horizontal screw centrifuge. The separated acid is monitored for concentration (belonging to medium-concentration recovery acid) and then returned to the primary batching tank. The solid material enters the secondary washing and pressing device, and is washed twice with circulating washing water treated by the water purification unit at a liquid-to-solid ratio of 2.5:1. It is then pressed to a moisture content of 31% and then sent to the pulping tank of the finished product preparation module. In the finished product preparation process, the solid content of the liquid in the slurry tank is adjusted to 45%, and then sent to the finished product filter press for filtration at a filtration pressure of 1.0 MPa. The concentration monitoring of the filtrate shows that the acid concentration is 0.6% (which is a low-concentration recovered acid). It is then returned to the primary batching tank through the circulation pipeline for the batching process. The final filter solid is the purified graphite-based carbon anode material.

[0063] The acid utilization rate during pickling of graphite-based carbon materials can reach 95%. The total content of metal impurities in the finished graphite-based carbon materials is ≤50ppm, of which iron ≤10ppm, copper ≤5ppm, nickel ≤3ppm, calcium ≤15ppm, magnesium ≤10ppm, and ash content ≤0.02%.

[0064] Throughout the production process, the acid recycling system monitors the acid concentration in real time and automatically adjusts the return path. The water resource closed-loop utilization system continuously filters and removes impurities from the wastewater in the circulating washing water buffer tank, ensuring efficient operation of the entire process. At the same time, all conveying links are protected by nitrogen gas to avoid material contamination or oxidation. The final product has a metal impurity removal rate that is more than 40% higher than that of traditional processes, fully meeting the purity requirements of lithium-ion batteries for anode materials.

[0065] Example 3 This embodiment uses porous carbon and hard carbon-based porous / amorphous carbon-based materials as the processing target to carry out closed-loop circulating acid washing and purification production. It adopts the closed-loop circulating carbon-based anode material acid washing and purification production line of Example 1, and specifically includes the following steps: First, in a primary mixing tank, carbon-based raw materials, mixed acid, and deionized water are prepared at a mass ratio of 1:0.6:3.2. The mixed acid used (mass ratio of 2:1) consists of 10% hydrochloric acid and 5% hydrofluoric acid. The materials are then pumped into a primary reaction tank and reacted at 70°C for 4.5 hours. After the reaction, the slurry is processed by a primary solid-liquid separation device (plate and frame filter press). The separated acid solution, which has a high concentration, is monitored online and returned to the primary mixing tank for reuse through a recovery pipeline. The resulting solid material enters a primary washing and pressing device, where it is countercurrently washed three times with deionized water at a liquid-to-solid ratio of 4.5:1, and then pressed until the moisture content is approximately 36%. The material from the first processing stage is conveyed to a secondary batching tank, where it is mixed with a mixture of acids (5% hydrochloric acid and 3% hydrofluoric acid in a 3:1 mass ratio) and circulating filtrate from the system at a mass ratio of 1 (dry weight): 0.3: 2.2. This mixture is then subjected to a secondary reaction in a secondary reactor at 80°C for 4.0 hours. After the secondary reaction, the material undergoes solid-liquid separation. The separated medium-concentration acid solution is automatically returned to the secondary batching tank; the solid material is washed twice with purified circulating washing water at a liquid-to-solid ratio of 3.5:1 and pressed until the moisture content is approximately 33%. Finally, the material is pulped and filtered in the finished product preparation module to obtain a high-purity porous carbon product.

[0066] Testing revealed that the total metal impurity content of the porous carbon material purified using the process described in this embodiment was reduced to below 80 ppm, the acid utilization rate reached 92% throughout the process, the fresh water consumption per ton of product was reduced by approximately 45% compared to the traditional single-washing process, the average removal rate of key metal impurities was increased by approximately 45%, and the batch purity standard deviation was less than 5%. This fully verifies that the closed-loop recycling process also possesses excellent deep purification effects, resource recycling efficiency, and production stability for porous / amorphous carbon-based materials such as porous carbon and hard carbon.

[0067] The total content of metallic impurities in porous carbon and hard carbon products is ≤80ppm, of which iron is ≤15ppm, copper is ≤8ppm, nickel is ≤5ppm, calcium is ≤25ppm, magnesium is ≤15ppm, and ash content is ≤0.05%.

[0068] Comparative Example 1 This comparative example uses the same graphite raw material as Example 2 and follows the same process conditions for the first reaction as in Example 2, but completely omits the secondary reaction module and its associated closed-loop circulation system for acid and water resources; that is, it adopts the traditional one-time acid washing process. The specific steps are as follows: In the mixing tank, materials were prepared according to the same ratio as in Example 2 (mass ratio of carbon-based raw material: mixed acid: deionized water = 1:0.7:2.8, the mixed acid being 12% hydrochloric acid and 6% hydrofluoric acid, with a mass ratio of hydrochloric acid to hydrofluoric acid of 2:1). The mixture was pumped into the reaction tank and reacted at 75°C for 3.5 hours. After the reaction, the material was subjected to solid-liquid separation using a plate and frame filter press. The separated waste acid liquid, due to its reduced concentration and high content of dissolved metal impurities, was directly treated as waste liquid and not recycled. The obtained solid material was washed multiple times with a large amount of fresh deionized water (liquid-to-solid ratio 3.5:1, rinsing twice) to remove residual acid and impurity ions. The wastewater generated from washing was also directly discharged. Finally, the material was filtered and dried to obtain the finished product. The corresponding results are as follows: The acid utilization rate is extremely low. The acid is for single use only, and no recycling pathway has been established. The actual utilization rate of the acid raw material is only about 55%-60%, far lower than the 95% in Example 2. A large amount of unreacted acid and low-concentration acid are discharged, resulting in raw material waste and environmental pressure.

[0069] The purity of the finished product is poor. The total metal impurity content of the finished graphite is 220-280 ppm. Due to the lack of a secondary reaction step targeting deep impurities, and the decrease in acid concentration in the later stages of the single reaction due to consumption, the removal of impurities encapsulated inside the graphite sheets or tightly bound impurities is incomplete, making it impossible to stably meet the purity requirements of high-end lithium-ion batteries for anode materials (usually requiring <100 ppm).

[0070] The removal rate of key metal impurities was low. Compared to Example 2, the average removal rate of key metal impurities (such as Fe, Ca, Na) was approximately 35% lower. This directly confirms the crucial role of the secondary reaction module in achieving deep purification.

[0071] High water consumption. All washing steps use fresh deionized water and there is no wastewater recycling system. The fresh water consumption per ton of product is about 70% higher than that of the closed-loop process in Example 2.

[0072] Process acidity (waste liquid): The concentration of waste acid after the reaction fluctuates greatly and contains a high concentration of metal salts, making it difficult and costly to treat.

[0073] The results of Comparative Example 1 clearly demonstrate that, after omitting the secondary reaction module and the corresponding resource recycling system, the process exhibits significant deterioration in several key dimensions, including economic efficiency (high acid and water consumption), environmental friendliness (large waste liquid and wastewater volume), and the quality of the final product (substandard purity and low impurity removal rate). This comparison powerfully proves that the "gradient acid washing (secondary reaction)" and "closed-loop resource recycling throughout the entire process" designed in this invention are not redundant steps, but rather essential core technical features for achieving efficient, deep purification, and green production of carbon-based anode materials. Their comprehensive benefits far exceed those of traditional single-pass acid washing processes.

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A closed-loop circulating acid washing and purification production line for carbon-based anode materials, characterized in that, It includes a primary reaction module, a secondary reaction module, and a finished product preparation module that are connected in sequence, and is equipped with an acid recycling system; The primary reaction module includes a primary batching tank, a primary reaction tank, a primary solid-liquid separation device, and a primary washing and pressing device connected in sequence. The secondary reaction module includes a secondary batching tank, a secondary reaction tank, a secondary solid-liquid separation device, and a secondary washing and pressing device connected in sequence. The finished product preparation module includes a pulping tank and a finished product filter press connected in sequence; The discharge end of the primary washing and pressing device in the primary reaction module is connected to the secondary batching tank of the secondary reaction module; The discharge end of the secondary washing and pressing device in the secondary reaction module is connected to the pulping tank of the finished product preparation module; The acid recycling system is equipped with an online acid concentration monitoring unit, which automatically adjusts the reflux path of the recovered acid based on the monitoring data; The carbon-based anode material includes one or more of graphite, porous carbon, hard carbon, and mesophase carbon microspheres.

2. The closed-loop circulating carbon-based anode material acid washing and purification production line according to claim 1, characterized in that, Both the primary and secondary reaction vessels are equipped with built-in steam heating components and temperature control units. Preferably, the steam heating component adopts a serpentine steam heat exchange structure; Preferably, the temperature control unit is equipped with an early warning module, which automatically stops the steam supply and issues an alarm when the temperature exceeds the preset range of ±5℃.

3. The closed-loop circulating carbon-based anode material acid washing and purification production line according to claim 1, wherein the primary solid-liquid separation device and the secondary solid-liquid separation device are plate and frame filter presses or horizontal screw centrifuges, and the solid-liquid separation accuracy is ≤0.1μm; Preferably, an acid recovery pipe is provided between the primary solid-liquid separation device and the primary batching tank, so that the acid outlet of the primary solid-liquid separation device is connected to the primary batching tank through a recovery pipe with a flow regulating valve; Preferably, an acid recovery pipe is provided between the secondary solid-liquid separation device and the secondary batching tank, so that the acid outlet of the secondary solid-liquid separation device is connected to the secondary batching tank through a recovery pipe with a flow regulating valve; the acid outlet of the secondary solid-liquid separation device is also connected to the primary batching tank through a recovery pipe with a flow regulating valve. Preferably, the primary washing and pressing device is equipped with a primary circulating washing water buffer tank with a water quality monitoring sensor, and the secondary washing and pressing device is equipped with a secondary circulating washing water buffer tank with a water quality monitoring sensor. Preferably, a closed-loop water resource utilization system is also installed; among which, The water resource closed-loop utilization system is equipped with a water purification unit to filter and remove impurities from the wastewater in the circulating washing water buffer tank before reuse. Preferably, the water pressed out in the primary washing and pressing device is connected to the primary circulating washing water buffer tank through a pipeline, and the water in the washing water buffer tank is recycled back to the primary washing and pressing device for reuse. Preferably, the water pressed out in the secondary washing and pressing device can be connected to the secondary circulating washing water buffer tank through a pipeline, and the water in the washing water buffer tank is recycled back to the secondary washing and pressing device for reuse.

4. The closed-loop circulating carbon-based anode material acid washing and purification production line according to claim 1, wherein both the primary washing and pressing device and the secondary washing and pressing device include a rinsing component and a pressing component; Preferably, the water inlet of the rinsing component is selectively connected to a deionized water source or a circulating washing water buffer tank via a three-way valve; Preferably, the pressing assembly is equipped with a pressure sensor, which can automatically adjust the pressing pressure according to the moisture content of the material, with a pressure adjustment range of 0.5MPa-1.5MPa; Preferably, the rinsing assembly is designed with a counter-current layered washing structure, in which circulating water is conveyed from the bottom to the top and the material is conveyed from the top to the bottom, forming a counter-current contact.

5. The closed-loop circulating carbon-based anode material acid washing and purification production line according to claim 1, wherein the primary solid-liquid separation device and the secondary solid-liquid separation device are equipped with an online filtrate concentration monitoring instrument to provide real-time feedback of filtrate acid concentration data and to automatically switch the filtrate reflux path in conjunction with the flow regulating valve; Preferably, the online acid concentration monitoring unit includes: The acid solution is installed at the acid outlet of the primary solid-liquid separation unit, so that the separated acid solution, after being detected by the online acid concentration monitoring unit, is returned to the primary batching tank for reuse through a recovery pipeline equipped with a flow regulating valve; the acid solution is installed at the acid outlet of the secondary solid-liquid separation unit, so that the separated acid solution, after being detected by the online acid concentration monitoring unit, is selectively returned to the secondary batching tank or returned to the primary batching tank for reuse based on the concentration gradient through a recovery pipeline equipped with a flow regulating valve; the acid solution is also installed at the acid outlet of the solid-liquid separation unit in the finished product preparation module.

6. A closed-loop circulating acid washing and purification process for carbon-based anode materials, characterized in that, The closed-loop recycling carbon-based anode material acid washing and purification production line according to any one of claims 1 to 5 includes a primary reaction process, a secondary reaction process and a finished product preparation process, and realizes full-process resource recycling through an acid recycling and reuse system and a water resource closed-loop utilization system. One-stage reaction process: The acid solution in the primary reaction vessel is a mixture of 8%-15% hydrochloric acid and 4%-8% hydrofluoric acid. The reaction temperature is controlled within the range of 65℃-80℃, and the reaction time is 3-5 hours. The mass ratio of carbon-based raw materials, mixed acid, and deionized water is 1:(0.5-0.8):(2.5-3.5). In the mixed acid, the mass ratio of hydrochloric acid to hydrofluoric acid is (2-3):

1. Secondary reaction process: The acid solution in the secondary reaction tank is a mixture of 4%-8% hydrochloric acid and 2%-5% hydrofluoric acid. The reaction temperature is controlled within the range of 65℃-85℃, and the reaction time is 2.5h-4.5h. The mass ratio of the solid material after primary treatment, the mixed acid, and the circulating filtrate is 1:(0.2-0.4):(1.5-2.5). In the mixed acid, the mass ratio of hydrochloric acid to hydrofluoric acid is (2-3):

1. After the first reaction, the solid material is washed with deionized water 2-4 times, with a liquid-to-solid ratio of (3-5):1 in each wash, and then pressed to a moisture content of 32%-40%. After the second reaction, the solid material is washed with circulating washing water 2-3 times, with a liquid-to-solid ratio of (2-4):1 in each wash, and then pressed to a moisture content of 30%-38%.

7. The closed-loop circulating acid washing and purification process for carbon-based anode materials according to claim 6, characterized in that, When the object being processed is a graphite-based carbon material: One-stage reaction process: The acid solution in the primary reaction vessel is a mixture of 10%-15% hydrochloric acid and 5%-8% hydrofluoric acid. The reaction temperature is controlled within the range of 70℃-80℃, and the reaction time is 3-4 hours. The mass ratio of carbon-based raw materials, mixed acid, and deionized water is 1:(0.6-0.8):(2.5-3). In the mixed acid, the mass ratio of hydrochloric acid to hydrofluoric acid is (2-3):

1. Secondary reaction process: The acid solution in the secondary reaction tank is a mixture of 5%-8% hydrochloric acid and 3%-5% hydrofluoric acid. The reaction temperature is controlled in the range of 65℃-75℃, and the reaction time is 2.5h-3.5h. The mass ratio of the solid material after primary treatment, the mixed acid and the circulating filtrate is 1:(0.2-0.3):(1.5-2). In the mixed acid, the mass ratio of hydrochloric acid and hydrofluoric acid is (2-3):

1. After the first reaction, the solid material is washed multiple times with deionized water, with a liquid-to-solid ratio of (3-4):1 in each wash, and then pressed to a moisture content of 32%-35%. After the second reaction, the solid material is washed multiple times with circulating washing water, with a liquid-to-solid ratio of (2-3):1 in each wash, and then pressed to a moisture content of 30%-33%.

8. The closed-loop circulating acid washing and purification process for carbon-based anode materials according to claim 6, when the material being processed is porous carbon, hard carbon, or other porous / amorphous carbon-based materials: One-stage reaction process: The acid solution in the primary reaction vessel is a mixture of hydrochloric acid with a concentration of 8%-12% and hydrofluoric acid with a concentration of 4%-6%. The reaction temperature is controlled within the range of 65℃-75℃, and the reaction time is 4h-5h. The mass ratio of carbon-based raw materials, mixed acid and deionized water is 1:(0.5-0.7):(3-3.5). In the mixed acid, the mass ratio of hydrochloric acid and hydrofluoric acid is (2-3):

1. Secondary reaction process: The acid solution in the secondary reaction tank is a mixture of 4%-6% hydrochloric acid and 2%-4% hydrofluoric acid. The reaction temperature is controlled in the range of 75℃-85℃, and the reaction time is 3.5h-4.5h. The mass ratio of the solid material after primary treatment, the mixed acid and the circulating filtrate is 1:(0.2-0.4):(2-2.5). In the mixed acid, the mass ratio of hydrochloric acid and hydrofluoric acid is (2-3):

1. After the first reaction, the solid material is washed multiple times with deionized water, with a liquid-to-solid ratio of (4-5):1 in each wash, and then pressed to a moisture content of 35%-40%. After the second reaction, the solid material is washed multiple times with circulating washing water, with a liquid-to-solid ratio of (3-4):1 in each wash, and then pressed to a moisture content of 33%-38%.

9. The closed-loop circulating carbon-based anode material acid washing and purification production process according to claim 6, characterized in that, Based on feedback from the online acid concentration monitoring unit, a three-stage acid cascade circulation path is established: acid concentration ≥ 80% of fresh acid is high-concentration recovered acid, which is directly replenished to the primary or secondary batching tank in the same process; acid concentration of 40%-80% of fresh acid is medium-concentration recovered acid, which is compounded with fresh acid and then replenished to the same process, or directly replenished to the batching tank of the previous reaction process as low-concentration acid; acid concentration < 40% of fresh acid is low-concentration recovered acid, which is all returned to the batching tank of the primary reaction module as the bottom liquid; Preferably, in the finished product preparation process, the solid content of the liquid in the pulping tank is controlled at 40%-50%, and the filtration or separation pressure of the solid-liquid separation device is 0.8MPa-1.2MPa; when the acid concentration in the filter press filtrate is ≤0.5%, it is reused in the washing process; when the acid concentration is ≥0.5%, it is reused in the batching process.

10. The closed-loop circulating carbon-based anode material acid washing and purification production process according to claim 6, characterized in that, It also includes a periodic purification and discharge process for the circulating liquid. Specifically, the circulating liquid in the primary or secondary circulating washing water buffer tank is periodically extracted, and after selectively removing the enriched metal cation impurities through flocculation sedimentation, ion exchange resin or membrane filtration technology, the produced water is returned to the circulating washing water buffer tank, and the resulting concentrated water containing impurities is neutralized and discharged in compliance with standards.

Images