Method for industrially recovering rare and precious metals in positive electrode of waste lithium battery

Abstract

The invention discloses a method for industrially recovering rare and precious metals in a positive electrode of a waste lithium battery. The process is composed of four continuous systems: 1, a biochar preparation system: carrying out oxygen-isolated pyrolysis on waste biomass; 2, a rare and noble metal recovery system: adsorbing rare and noble metals in the leachate by using biochar; 3, a heat energy circulation system which can effectively utilize heat energy generated in the preparation process of biochar and rare and noble metal oxides and the drying process of centrifugal precipitates in the system 4; and 4, a leaching agent production system is adopted, NaCO3 is added into the system 2, and the content of CO2 is adjusted, so that the growth of chlorella is facilitated, and citric acid is prepared more quickly. According to the method, a closed recycling process flow is innovatively constructed, all raw materials are wastes, most of energy of the system can be self-sufficient in the system after the system runs for one cycle, no waste water and waste gas are discharged, the system is green and environment-friendly, and heat can be recycled; clean regeneration and cyclic utilization of the waste lithium battery material are realized under the condition that the energy consumption is greatly reduced, and the method has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the field of lithium-ion batteries, and particularly to a recycling system for waste lithium-ion batteries. Background Art

[0002] Metals such as nickel, cobalt, lithium, aluminum, copper, and manganese contained in the waste lithium battery cathode belong to China's resources. In current industrial recycling methods, the mixed slag generated by pyrometallurgical recycling will cause inevitable metal losses (including Li, Al, etc.) and produce a large amount of harmful gases, such as sulfur dioxide and nitrogen oxides. In addition, the separation and extraction of metal elements in the later stage still require wet recycling steps, and the procedure is relatively cumbersome. Wet recycling has complex operations, requires a large amount of chemical reagents such as acids, alkalis, reducing agents, and extractants, and requires multiple chemical reactions and separation processes; it has a high cost, not only a large input of chemical reagents, but also a large amount of equipment and manpower; it discharges a large amount of waste liquid, which is difficult to treat, and if not properly treated, it will pollute the environment; for some complex cathodes, there may be problems such as low leaching efficiency and incomplete metal separation. Direct regeneration methods, including solid-phase lithium supplementation method, liquid-phase method, molten salt method, etc., require good contact between the cathode material and lithium salt, often require high energy consumption, and there are challenges in accurately measuring the average lithium deficiency of the waste lithium-ion battery cathode material during large-scale regeneration; the liquid-phase method requires a high-temperature and high-pressure environment, has high requirements for equipment and a small processing capacity; it may lead to uneven products and cannot obtain high-purity battery materials. Summary of the Invention

[0003] In view of the prior art, the present invention provides an industrial method for green and effective recycling of rare and precious metals in waste lithium battery cathodes using waste biomass resources, including the following steps:

[0004] It is divided into a biochar preparation system, a rare and precious metal recycling system, a heat energy recycling system, and a leaching agent production system.

[0005] The biochar preparation system includes: pyrolyzing waste biomass in the absence of oxygen.

[0006] The rare and precious metal recycling system includes: leaching the cathode material in the waste lithium battery cathode plate with citric acid, adsorbing it with the above biochar, filtering to obtain a biochar filter residue adsorbed with rare and precious metal ions, and performing heat treatment to obtain recycled rare and precious metal oxides.

[0007] The heat energy recycling system includes: using the heat generated by calcining the biochar filter residue for the preparation of biochar and the drying of the centrifugate in the leaching agent production system.

[0008] The leaching agent production system includes: sodium carbonate adjusts the metal ion content in the filtrate generated by the dilute precious metal recovery system. Part of it obtains metal carbonates, and the other part adds the discharged CO2 and adds compound fertilizer in the first cycle to cultivate Chlorella, and citric acid is prepared by a biological method.

[0009] The cathode material in the waste lithium battery cathode sheet is quickly obtained after pre-treating the waste lithium battery cathode that has not been assembled into a battery through continuous equipment such as shredding, crushing, pulverizing, and screening. The impurity elements and their contents (ppm) are: Al ≤ 0.05;

[0010] Pyrolysis uses a Joule heating device, the pyrolysis temperature is 300 - 1000 °C, the heating rate is 2 °C / min - 10 K / s, the residence time is 0.5 - 4 h, and an inert gas such as N2, Ar, or H2 is introduced for protection.

[0011] The concentration of the leaching agent citric acid is 1 - 4.5 mol / L, the leaching temperature is 50 - 80 °C, and the solid-liquid ratio is 1:20 - 50 g / moL.

[0012] The mass ratio of the waste lithium battery cathode material to biochar is 1:0.5 - 3. Through magnetic stirring at a speed of 200 - 500 revolutions per minute, after reacting for 10 - 12 h, filtration is carried out. The obtained biochar is calcined in an oxygen atmosphere at 600 °C - 750 °C to obtain dilute precious metal oxides.

[0013] The concentration of sodium carbonate is 0.1 - 1 g / L, and the concentration of CO2 is controlled within 5 - 20%, which is suitable for the growth of Chlorella.

[0014] The compound fertilizer is sodium nitrate and potassium dihydrogen phosphate.

[0015] For the biological preparation of citric acid, Aspergillus niger is used for fermentation. It is cultured in a shaker at a controlled temperature of 33 - 36 °C and 200 r / min for 20 - 60 h. When the cell concentration reaches 600,000 - 1,500,000 / mL, transfer can be carried out, and then it continues to ferment in a fermentation tank for 3 - 5 days. The residue after fermentation by Aspergillus niger can be reused for the cultivation of Chlorella after calcination. After multiple cycles, when the concentration of the Chlorella culture solution increases to inhibit its growth, the residue after fermentation by Aspergillus niger (enriched with dilute precious metals) is also leached.

[0016] The present invention has the following advantages:

[0017] 1. The present invention uses the generated waste liquid and waste gas for the cultivation of Chlorella, solves the problems of the sources of carbon sources and trace metal elements in the cultivation of Chlorella. Trace elements such as cobalt and lithium can promote the photosynthesis of Chlorella, thereby shortening the growth cycle of Chlorella. The present invention can achieve zero emissions of harmful waste water and waste gas;

[0018] 2. The input amount of the required materials in the present invention is less than that of the current method, and the cost is lower. The compound fertilizer required for citric acid and Chlorella only needs to be input in the first production cycle. Sodium carbonate is only used to adjust the metal content, and the required amount is very small. The price of oxygen is low;

[0019] 3. The energy consumption in the present invention mainly comes from the internal recycling of the system, and the consumption is also very small. It is only required in the first cycle for pyrolysis and the calcination of the fermentation residue of Aspergillus niger. The heat required subsequently comes from the heat generated by the calcination of the biochar adsorbed with metal ions in an oxygen atmosphere. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a flow chart for preparing tea residue according to the present invention.

[0021] Figure 2 It is a flow chart for metal leaching according to the present invention.

[0022] Figure 3 It is a flow chart for regulating the content of trace metals according to the present invention.

[0023] Figure 4 It is a diagram for waste gas utilization and citric acid recycling according to the present invention.

[0024] Figure 5 It is an overall flow chart according to the present invention.

[0025] Figure 6 It is an XRD diagram of the recycled cathode material in the example of the present invention

[0026] Figure 7 It is an SEM diagram of the recycled cathode material in the example of the present invention DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated herein can be arranged and designed in various different configurations.

[0028] Therefore, the detailed description of the embodiments of the present invention provided in the drawings below is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0029] Example 1: A method for industrially recycling rare and precious metals in the cathode of waste lithium batteries, comprising the following steps:

[0030] 1) Pyrolyze tea dregs at 300 °C using a Joule heating device, with a heating rate of 2 °C / min, a residence time of 4 h, and introduce N2 for protection; use citric acid with a concentration of 1.5 mol / L as the leaching agent, add the waste layered cathode LiNi 0.5 Co 0.2 Mn 0.3 O2 material, with a solid-liquid ratio of 1:20 g / mol, leach at 50 °C for 60 min and then filter. Add the pyrolyzed biochar, and the mass ratio of LiNi 0.5 Co 0.2 Mn 0.3 O2 to biochar is 1:0.5. Through magnetic stirring at a speed of 200 revolutions per minute, filter after reacting for 10 h. The obtained biochar is calcined in an oxygen atmosphere at 600 °C for 400 min to obtain rare precious metal oxides.

[0031] 2) Add sodium carbonate to the filtrate to regulate the metal ion content so that Li ≤ 5 mg / L, Mn ≤ 0.01 mg / L, Co ≤ 3 mg / L, and Ni ≤ 15 mg / L;

[0032] 3) Add the carbon dioxide generated by the calcination in step 1) and the filtrate treated in step 2) to the Chlorella culture pond. Control the carbon dioxide content at 5%, and add compound fertilizer in the first cycle, with a cycle of 7 days; when Chlorella grows for one cycle, centrifugally treat Chlorella using the high-pressure homogenization method, and precipitate oligosaccharides from the supernatant using ethanol, and then further filter;

[0033] 4) After filtration, ferment using Aspergillus niger, culture in a shaker at 33 °C - 36 °C and 200 r / min for 20 h until the cell concentration reaches 900,000 / mL, and ferment for 3 days; the residue after fermentation is calcined and used to provide nutrients for the cultivation of Chlorella in the next cycle;

[0034] 5) When the metal ions are enriched to greatly inhibit the growth of Chlorella, add the residue calcined in step 4) to step 1) to leach rare precious metals again.

[0035] After analysis and detection, the recovery rate of cobalt (Co) reached 85%. By accurately measuring the Co content in the leachate, the filtrate after adsorption, and the final oxide product, and comparing it with the Co content in the raw material cathode, the recovery rate of nickel (Ni) was calculated to be approximately 82%. Using a detection and analysis method similar to that of Co, the experimental conditions were strictly controlled at each stage to ensure data accuracy. The recovery rate of lithium (Li) was 78%. Considering the losses of Li during the leaching, adsorption, and conversion processes in the entire technological process, its final recovery ratio was determined through chemical analysis methods. The heat generated by the calcination of biochar was used for the pyrolysis of tea residues and some subsequent processes. Measured by a heat monitoring device, the heat recycling utilization rate reached 70%. During the operation of the system, the heat input, output, and storage conditions were recorded and analyzed in real time, and this utilization rate was calculated. 65% of the energy required for the pyrolysis of tea residues came from the heat recovery of biochar calcination, effectively reducing the demand for external energy input. This ratio was obtained through the statistical analysis of the energy consumption of the pyrolysis device and the energy supply data of the heat recovery system. Chlorella grew well during the cultivation period, and the cell density increased from the initial inoculation of 100,000 cells / mL to 1,200,000 cells / mL. Under suitable carbon dioxide concentration (5%), trace metal ion concentration regulation (Li ≤ 5 mg / L, Mn ≤ 0.01 mg / L, Co ≤ 3 mg / L, Ni ≤ 15 mg / L), and nutrient supply, the cell number of Chlorella was regularly counted and monitored using a hemocytometer. After the cultured Chlorella was broken by high-pressure homogenization and fermented by Aspergillus niger, the citric acid yield reached 15 g / L. The citric acid content in the fermentation broth was measured by acid-base titration to evaluate the application effect of Chlorella in this system and its contribution to citric acid production.

[0036] Example 2: A method for industrially recovering rare and precious metals from waste lithium battery cathodes, comprising the following steps:

[0037] 1) Pyrolyze tea residues using a Joule heating device at 1000 °C, with a heating rate of 10 K / s and a residence time of 0.5 h, and introduce Ar for protection; use citric acid with a concentration of 4.5 mol / L as a solvent, add waste layered cathode LiNi 0.6 Co 0.2 Mn 0.2 O2 material, with a solid-liquid ratio of 1:40 g / mol, leach at 70 °C for 60 min and then filter, add the pyrolyzed biochar, and the mass ratio of LiNi 0.6 Co 0.2 Mn 0.2 O2 to biochar is 1:1.5, control the stirring speed at 400 revolutions per minute, react for 8 h and then filter to obtain biochar adsorbed with rare and precious metal ions, and calcine at 720 °C in an oxygen atmosphere to obtain metal oxides of rare and precious metals.

[0038] 2) Add 0.6 g / L of sodium carbonate to the filtrate to regulate the content of metal ions, so that Li ≤ 5 mg / L, Mn ≤ 0.01 mg / L, Co ≤ 3 mg / L, and Ni ≤ 15 mg / L.

[0039] 3) Use carbon dioxide, sodium nitrate, and potassium dihydrogen phosphate in the cultivation of Chlorella. When the carbohydrate content of Chlorella drops to 22% and the protein content drops to 32%, break the Chlorella cells by high-pressure homogenization and then ferment them with Aspergillus niger to produce citric acid. The residue after fermentation is calcined and used as nutrients for the next cycle of Chlorella cultivation. When the rare and precious metals in Chlorella begin to accumulate and inhibit growth, the residue after fermentation with Aspergillus niger is transported to step 1) for leaching of metal ions again.

[0040] The recovery rate of cobalt (Co) is increased to 90%. Thanks to the optimized adsorption performance of biochar prepared by pyrolyzing tea residues at a higher temperature and the adjustment of leaching process parameters, the Co content in each stage is measured and calculated by precise chemical analysis methods. The recovery rate of nickel (Ni) reaches 88%. Under the condition of leaching with 4.5 mol / L citric acid and optimized reaction conditions, the leaching and recovery efficiency of Ni is effectively improved. The analysis method is the same as before. The recovery rate of lithium (Li) is 82%. Through the material balance and chemical detection of Li in the whole process, the improvement of its recovery ratio under the improved process is determined; the heat recycling utilization rate is increased to 75%. Under the synergistic action of pyrolysis at 1000 °C and an efficient heat recovery system, the heat transfer and utilization process in the system is monitored and analyzed in detail to obtain this utilization rate. 70% of the energy required for pyrolysis is provided by the heat of biochar calcination, further reducing the dependence on external energy. This ratio is obtained through energy consumption monitoring and heat distribution data statistics; the Chlorella cell density increases to 1.5 million cells / mL. Under the optimized culture conditions, its growth rate is accelerated, and the growth situation is monitored by regular cell counting; the citric acid yield reaches 20 g / L, indicating that Chlorella provides more abundant raw materials for citric acid fermentation under the conditions of this example. This yield data is obtained through fermentation process control and product detection.

[0041] Example 3: A method for industrially recovering rare and precious metals from the positive electrode of waste lithium batteries, comprising the following steps:

[0042] 1) Pyrolyze tea residues using a Joule heating device at 800 °C, with a heating rate of 5 K / s and a residence time of 2 h, and introduce N2 for protection. Use citric acid with a concentration of 2.5 mol / L as the solvent, add waste layered positive electrode LiNi 0.8 Co 0.1 Mn 0.1 O2 material, with a solid-liquid ratio of 1:45 g / mol, leach for 60 min at 75 °C and then filter, add the pyrolyzed biochar, LiNi 0.8 Co 0.1 Mn0.1 The mass ratio of O2 to biochar is 1:1.75. The stirring speed is controlled at 450 revolutions per minute. After reacting for 12 h, filtration is carried out to obtain biochar adsorbed with dilute precious metal ions, which is calcined at 750 °C in an oxygen atmosphere to obtain metal oxides of dilute precious metals.

[0043] 2) Sodium carbonate is added to the filtrate to regulate the metal ion content so that Li ≤ 5 mg / L, Mn ≤ 0.01 mg / L, Co ≤ 3 mg / L, and Ni ≤ 15 mg / L.

[0044] 3) Carbon dioxide, sodium nitrate, and potassium dihydrogen phosphate are used for the cultivation of Chlorella. When the carbohydrate content of Chlorella drops to 25% and the protein content drops to 35%, Chlorella is broken by high-pressure homogenization and then fermented by Aspergillus niger to prepare citric acid. The residue after fermentation is calcined and used as nutrients for the next cycle of Chlorella cultivation. When the dilute precious metals in Chlorella begin to accumulate and inhibit growth, the residue after fermentation by Aspergillus niger is transported to step 1) for leaching of metal ions again.

[0045] The recovery rate of cobalt (Co) is stable at about 88%. Under specific pyrolysis temperature (800 °C), leaching agent concentration (2.5 mol / L citric acid), and reaction conditions, a relatively high recovery level is maintained. The recovery rate is determined through a strict chemical analysis process. The recovery rate of nickel (Ni) is about 85%, which is obtained through precise detection and calculation of the nickel content in each link. The recovery rate of lithium (Li) is maintained at 80%. Under this combination of process parameters, the recovery effect of Li is good, and the analysis method is the same as before. The heat cycle utilization rate is maintained at 72%. The system realizes stable heat cycle utilization under the conditions of this embodiment. The data is obtained through a heat monitoring and analysis system and the utilization rate is calculated. 68% of the energy required for pyrolysis is supplied by internal heat, ensuring effective control of the system energy consumption, and this ratio is obtained through analysis of the energy consumption composition of the pyrolysis device. The cell density of Chlorella reaches 1.3 million cells / mL, achieving good growth under a stable cultivation environment and nutrient regulation. The growth dynamics are monitored through cell counting. The citric acid yield is 18 g / L, indicating that Chlorella can be effectively converted into raw materials for citric acid production in this embodiment, and the yield is determined through detection of fermentation products.

[0046] It should be noted that, without conflict, the implementation manners and features in the implementation manners of the present invention can be combined with each other.

[0047] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for industrially recovering rare and precious metals from the positive electrode of waste lithium batteries, characterized in that: It is divided into a biochar preparation system, a rare metal recovery system, a heat energy circulation system and a leaching agent production system. The biochar preparation system includes: isolating the waste biomass from oxygen and pyrolyzing it; The rare and precious metal recovery system comprises: leaching the positive electrode material in the positive electrode sheet of the waste lithium battery with citric acid, adsorbing it with the above-mentioned biochar, filtering to obtain the biochar filter residue adsorbing the rare and precious metal ions, and heat treating to obtain the recovered rare and precious metal oxides; The heat energy circulation system includes: the heat generated by calcining the biochar filter residue is used for the preparation of biochar and the drying of the centrifuge in the leaching agent production system; The leaching agent production system includes: sodium carbonate is used to adjust the metal ion content in the filtrate produced by the rare and precious metal recovery system, a part of which is obtained as metal carbonate, and the other part is added with the discharged CO2, and compound fertilizer is added in the first cycle to cultivate Chlorella to obtain citric acid by biological method.

2. A method for industrially recovering rare and precious metals from the positive electrode of waste lithium batteries as claimed in claim 1, characterized in that: The positive electrode material in the waste lithium battery positive electrode sheet is quickly obtained by pre-treating the waste lithium battery positive electrode that has not been assembled with a battery by continuous equipment by tearing, crushing, pulverizing, and screening. The impurity elements and their contents (ppm) are: Al≤0.

05.

3. The method for industrially recovering rare and precious metals from the positive electrode of waste lithium batteries according to claim 1, characterized in that: The pyrolysis adopts a Joule heating device, the pyrolysis temperature is 300-1000°C, the heating rate is 2°C / min-10K / s, the residence time is 0.5-4h, and an inert gas protection is introduced among N2, Ar, and H2.

4. A method for industrially recovering rare and precious metals from the positive electrode of waste lithium batteries according to claim 1, characterized in that: The concentration of the leaching agent citric acid is 1-4.5 mol / L, the leaching temperature is 50-80° C., and the solid-liquid ratio is 1:20-50 g / moL.

5. A method for industrially recovering rare and precious metals from the positive electrode of waste lithium batteries according to claim 1, characterized in that: The mass ratio of the waste lithium battery positive electrode material to the biochar is 1:0.5-3. The waste lithium battery positive electrode material is stirred by magnetic force at a speed of 200-500 rpm. After reacting for 10-12 hours, the biochar is filtered and calcined at 600°C-750°C in an oxygen atmosphere to obtain rare and precious metal oxides.

6. A method for industrially recovering rare and precious metals from the positive electrode of waste lithium batteries according to claim 1, characterized in that: The sodium carbonate concentration is 0.1-1 g / L, and the CO2 concentration is controlled within 5-20%, which is suitable for the growth of Chlorella.

7. A method for industrially recovering rare and precious metals from the positive electrode of waste lithium batteries according to claim 1, characterized in that: The compound fertilizer is sodium nitrate and potassium dihydrogen phosphate.

8. A method for industrially recovering rare and precious metals from the positive electrode of waste lithium batteries according to claim 1, characterized in that: The biological method for preparing citric acid is to use Aspergillus niger for fermentation, and culture it in a shaking incubator at a controlled temperature of 33-36°C and 200 r / min for 20-60 hours. When the bacterial cell concentration reaches 600,000-1.5 million / mL, transplanting can be performed, and then fermentation is continued in a fermentation tank for 3-5 days.

9. A method for industrially recovering rare and precious metals from the positive electrode of waste lithium batteries according to claim 1, characterized in that: The residue after fermentation by Aspergillus niger can be repeatedly used for culturing Chlorella after calcination. After multiple cycles, when the concentration of Chlorella culture solution increases to inhibit its growth, the residue after fermentation by Aspergillus niger (enriched with rare and precious metals) is also leached.

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