Resource utilization method of waste lithium cobalt oxide battery and waste polyvinyl chloride

Abstract

The invention discloses a resource utilization method of waste lithium cobalt oxide batteries and waste polyvinyl chloride. Chlorine-free conjugated polyolefin (DPVC) is prepared through gradient pyrolysis of polyvinyl chloride (PVC), crude hydrochloric acid is generated, then the DPVC and a lithium cobalt oxide battery (LCO) are subjected to microwave radiation heating and high-temperature co-pyrolysis to achieve resource utilization of pyrolysis three-phase products, a gas phase is recycled into hydrogen-rich gas, a liquid phase is recycled into light oil, and a solid phase is recycled into valuable metal. And in the aspect of metal recovery, simple and efficient separation of the two substances is realized by utilizing the water solubility difference of pyrolysis solid products, the lithium compound is easily dissolved in water and the cobalt compound is insoluble in water, and the leaching recovery of lithium is enhanced by utilizing the generated crude hydrochloric acid. According to the method, the harm caused by hydrogen chloride generated by chlorine elements in traditional treatment is solved, efficient separation of metal is achieved, and the application prospect is wide.

Description

Technical Field

[0001] The present invention relates to the technical field of waste battery recycling, and in particular to a method for resource utilization of waste lithium cobalt oxide batteries and waste polyvinyl chloride. Background Art

[0002] The information disclosed in the background of the invention is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] As a core component of the clean energy system, lithium batteries hold an irreplaceable strategic position in new energy vehicles and novel energy storage. Since 2015, my country's new energy vehicle industry has experienced explosive growth, accompanied by a massive wave of power battery retirements. This presents both severe environmental challenges and immense resource value. Improper disposal of used batteries can pose environmental risks such as heavy metal pollution and toxic electrolyte decomposition products, while also leading to the loss of valuable metal resources. Therefore, repurposing retired lithium batteries as a substitute for lithium and cobalt mineral resources can alleviate environmental pollution pressures while also recovering valuable metals to meet the needs of the rapidly developing battery industry. To address the high energy consumption and low lithium recovery rates associated with traditional lithium battery recycling methods, numerous researchers have developed a chlorination roasting technique that combines low calcination temperatures with complete material recovery. This chlorine-assisted roasting converts the metal elements in the cathode material into water-soluble chlorides, enabling the recovery of valuable metals through water leaching.

[0004] As a typical fossil fuel product, the large-scale production, use, and generation of plastic waste have led to severe fossil fuel shortages, environmental pollution, and resource waste. Improper handling of waste plastics not only poses a significant threat to human health and the natural environment, but also inevitably results in resource waste. Among various plastic types, polyvinyl chloride (PVC) ranks third in production, and with a chlorine content exceeding 50% by weight, resource utilization faces challenges such as the release of hydrogen chloride, which can lead to equipment corrosion and product contamination. During the pyrolysis recovery of waste PVC, corrosive gases such as HCl are generated, which in turn corrodes equipment, contaminates products, and generates toxic substances such as dioxins.

[0005] In recent years, a small number of studies have begun exploring innovative methods for combining spent lithium cobalt oxide (LCO) batteries with polyvinyl chloride (PVC) plastics, attempting to achieve synergistic treatment of the two through hydrothermal, mechanothermochemical, and co-pyrolysis methods. While this synergistic treatment is theoretically and technically feasible, the following challenges remain: 1. Inadequate control of chlorine contamination. Existing synergistic treatment technologies have not effectively addressed the migration and conversion of chlorine in PVC. During the pyrolysis process, chlorine is still released as hydrogen chloride, which corrodes equipment and contaminates pyrolysis oil and pyrolysis gas. 2. The separation and recovery of lithium and cobalt are complex. Due to the presence of chlorine, valuable metals such as lithium and cobalt in LCO are easily converted into water-soluble chlorides. Consequently, subsequent metal recovery requires a multi-step leaching and precipitation process, which is not only lengthy but also significantly increases the consumption of acid and base reagents, reducing overall economic efficiency. 3. The solid phase products of the synergistic treatment contain Co, CoO, and carbon. Conventional pyrolysis methods heat all components simultaneously without considering the thermal differences between these components and their different roles in the pyrolysis process, resulting in poor product quality and selectivity. 4. As a poor conductor of heat, PVC can easily lead to a significant temperature gradient in the reaction system during the co-pyrolysis process, which not only reduces the thermal efficiency but also causes local overheating and coking, resulting in reactor blockage and affecting continuous operation. Summary of the Invention

[0006] In light of this, the present invention provides a method for resource utilization of spent lithium cobalt oxide batteries and waste polyvinyl chloride. This method achieves the coordinated treatment of spent lithium cobalt oxide batteries and waste polyvinyl chloride, addressing issues such as the harmful effects of chlorine, the complex separation of lithium and cobalt, and the large temperature gradient, low thermal efficiency, and poor product quality and selectivity associated with traditional pyrolysis. This method achieves green and efficient resource utilization of spent lithium cobalt oxide batteries and waste polyvinyl chloride.

[0007] In order to achieve the above object, the present invention is implemented through the following technical solutions: The present invention provides a method for resource utilization of waste lithium cobalt oxide batteries and waste polyvinyl chloride, which specifically comprises the following steps: S1. Pretreatment of lithium cobalt oxide batteries: Separate the waste lithium batteries to obtain positive electrode components, and calcine the separated positive electrode components to obtain LiCoO2 powder; S2. Low-temperature dechlorination: The chlorine element in PVC is converted into crude hydrochloric acid at low temperature using a stepwise pyrolysis method to produce chlorine-free conjugated polyolefin DPVC. S3. Co-pyrolysis: Using microwave radiation to synergistically co-pyrolyze conjugated polyolefin (DPVC) and waste lithium cobalt oxide battery (LCO) to achieve resource recovery of valuable metals, hydrogen-rich gas, and light oil; S4. Metal separation and recovery: Use water leaching to separate and obtain a filtrate containing lithium and a filter residue containing cobalt; adjust the calcination atmosphere of the filter residue to selectively recover cobalt as Co (reducing environment) or Co3O4 (oxidizing environment); Alternatively, acid leaching is used to separate and obtain a filtrate containing lithium and cobalt compounds and a coke residue.

[0008] Furthermore, in S1, the specific operation of the pretreatment of the lithium cobalt oxide battery is: soaking the waste lithium battery in NaCl solution to make it fully discharged, separating the positive electrode component, and calcining the separated positive electrode component to obtain pure LiCoO2 powder.

[0009] Furthermore, in S2, PVC is centrally dechlorinated in an oxygen-free atmosphere at a low temperature of 250-320° C. to prepare DPVC and crude hydrochloric acid.

[0010] Furthermore, in S3, DPVC and LCO are co-pyrolyzed under microwave radiation, and hydrogen-rich gas and light oil are condensed and recovered.

[0011] By leveraging the immediacy and integrity of microwave radiation, the process can penetrate materials of a certain thickness and heat them from the inside without the need for heat conduction. This solves the problems of large temperature gradients, low thermal efficiency, and localized overheating and coking in conventional co-pyrolysis processes. By leveraging the selectivity and efficiency of microwave radiation, the Co, CoO, and carbon in the co-pyrolysis products are heated in a targeted manner, which facilitates discharge and luminescence, forming localized hotspots and potentially plasma, enhancing the in-situ catalytic effect of metals and optimizing the quality of pyrolysis oil and gas.

[0012] Furthermore, the mass ratio of DPVC to LCO in the microwave irradiation co-pyrolysis is 1:0.5 to 4. The mass ratio of DPVC to LCO in the microwave irradiation co-pyrolysis can be any ratio between 1:0.5 and 4, preferably 1:0.6 to 2.0, and more preferably 1:0.8 to 1.5.

[0013] The power of microwave radiation co-pyrolysis is 400-700W, the temperature is 400-700℃; the co-pyrolysis time is 30-90min; when the temperature is lower than 450℃, LCO is partially decomposed into LiOH and CoO; when the temperature is higher than 600℃, LCO is completely decomposed into Li2CO3 and Co.

[0014] When the power and temperature of microwave radiation co-pyrolysis are low, the pyrolysis gas released by DPVC decomposition is small, with a small molecular weight and low carbon content, and can only partially reduce LCO to LiOH and CoO; when the power and temperature are high, the decomposition of DPVC will release a large amount of pyrolysis gas with a large molecular weight and high carbon content, which is rich in reducing atmosphere and can completely decompose LCO to generate Li2CO3 with higher thermal stability, and further reduce the high-valent cobalt to Co.

[0015] There is a two-way synergistic effect between DPVC and LCO during microwave irradiation co-pyrolysis. The essence of the synergistic effect lies in the "reduction-catalysis" two-way strengthening mechanism formed between DPVC and LCO: on the one hand, the reducing atmosphere such as H2 produced by the pyrolysis of DPVC promotes the reduction of cobalt (Co 3+ →Co 2+ →Co 0 ), which decomposes LCO into Co, CoO and Li2CO3; on the other hand, the decomposition products of LCO (Co, CoO, etc.) can reversely catalyze the deep cracking of DPVC, promote the generation of H2-rich gas, and form a self-enhancing reaction system of "reduction enhances catalysis, catalysis promotes reduction".

[0016] Furthermore, the co-pyrolysis solid phase product is leached with water in S4, filtered, and the filtrate containing the lithium compound and the filter residue containing the cobalt compound are recovered.

[0017] Furthermore, the water leaching conditions of the co-pyrolysis solid phase product are: leaching temperature 25-100°C, leaching time 15-90 min, and solid-liquid ratio 0.3-3:100 g / mL; preferably, the leaching temperature is 25-50°C, the leaching time is 15-60 min, and the solid-liquid ratio is 1-3:100 g / mL.

[0018] Furthermore, the acid leaching conditions of the co-pyrolysis solid phase product are: leaching temperature 25-30°C, leaching time 15-30 min, and solid-liquid ratio 0.3-3:100 g / mL; preferably, the solid-liquid ratio is 1-3:100 g / mL.

[0019] Furthermore, in S4, the acid used in the acid leaching is the crude hydrochloric acid prepared in S2.

[0020] Water leaching and co-pyrolysis of solid phase products can achieve the separate recovery of lithium and cobalt. In terms of metal recovery, the difference in water solubility of pyrolysis solid products is utilized. Lithium compounds are easily soluble in water, while cobalt compounds are insoluble in water, which enables simple and efficient separation of the two types of substances. The lithium leaching rate is as high as 96.5%.

[0021] HCl absorption solution enhances lithium leaching rate: HCl absorption solution significantly improves the Li leaching rate. At 400°C, the leaching rate of co-pyrolysis lithium deionized water is 64.64%, and the leaching rate of HCl absorption solution is 81.76%, an increase of 26.49%.

[0022] Furthermore, in S4, the filter residue containing the cobalt compound is calcined in a reducing atmosphere to recover Co, and in an oxidizing atmosphere to recover Co3O4.

[0023] Furthermore, the filter residue is calcined at 700-800° C. for 60-90 min in hydrogen with a concentration of 5%-10% to obtain Co; preferably, the calcination is carried out at 750-800° C. for 60-90 min.

[0024] Furthermore, the reducing atmosphere may also be the hydrogen-rich gas obtained in S3.

[0025] Furthermore, the filter residue is calcined in air at 700-800° C. for 60-90 min to obtain Co 3 O 4 . Preferably, the filter residue is calcined at 750-800° C. for 60-90 min.

[0026] Compared with the prior art, the present invention has achieved the following beneficial effects: (1) The present invention makes full use of waste resources. It can effectively recover metallic lithium and cobalt from waste lithium cobalt oxide batteries, turning waste lithium cobalt oxide batteries into treasure. In addition, the source of polyvinyl chloride is also relatively wide. After dechlorination, the waste polyvinyl chloride material is co-pyrolyzed with waste lithium cobalt oxide. While effectively treating waste lithium cobalt oxide batteries, the waste polyvinyl chloride material can also be effectively treated.

[0027] (2) The process is simple, the raw materials are widely available, and the cost is low, making it suitable for large-scale application. The present invention only requires dechlorination of polyvinyl chloride and co-pyrolysis with waste lithium cobalt oxide, and then water and hydrochloric acid are used as leaching solutions to recover valuable metals such as lithium and cobalt. Lithium and cobalt can also be easily separated, making the process promising for large-scale application.

[0028] (3) The PVC of the present invention is centrally dechlorinated in the low-temperature section, with a dechlorination rate of 99.97%. The prepared DPVC contains almost no chlorine. No chlorine components are detected in the pyrolysis gas and liquid phase in the high-temperature section. This solves the problem of chlorine corrosion of equipment and the reuse of pyrolysis products, and realizes the resource utilization of PVC. Compared with the pyrolysis of organic matter alone, the co-pyrolysis of organic DPVC and inorganic LCO hinders the formation of large-volume, high-strength solid coke, which can ensure the continuous and stable operation of the equipment. The addition of inorganic LCO reduces the agglomeration of organic coke blocks, making the solid phase product present in a dispersed granular form, which is easy to continuously remove from the reaction device. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0030] Figure 1 It is a technical flow chart of the present invention. DETAILED DESCRIPTION

[0031] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0032] The technical solution of the present invention is further described below with reference to specific embodiments.

[0033] Example 1: Efficient recovery of lithium and cobalt from LCO lithium batteries to LiCl and CoCl2 by cascade pyrolysis of PVC S1. Pretreatment of lithium cobalt oxide batteries: Use 20 g / L NaCl solution to soak the used lithium batteries for 180 minutes. After they are fully discharged, separate the positive electrode components, calcine them at 500°C for 40 minutes, and then calcine them at 600°C for 12 hours to obtain relatively pure LiCoO2 powder.

[0034] S2. Low-temperature dechlorination of PVC: 8g of PVC was pyrolyzed at 320℃, and the released hydrogen chloride was absorbed by 200mL of deionized water to obtain DPVC and HCl absorption solution (crude hydrochloric acid). The dechlorination rate was as high as 99.97%. - The concentration is about 24 g / L.

[0035] Microwave co-pyrolysis of S3, DPVC and LCO: the mass ratio of DPVC to LCO was 1:1, the microwave co-pyrolysis power was set to 500 W, the temperature was set at 400 °C, and the pyrolysis time was 30 min.

[0036] S4. The co-pyrolysis solid product was leached using the crude hydrochloric acid prepared in S2 at a leaching temperature of 25°C, a leaching time of 30 minutes, and a solid-to-liquid ratio of 3:100 g / mL. Valuable metals in the co-pyrolysis solid product were recovered as LiCl and CoCl2, with a lithium leaching rate of 81.76%. Under the same conditions, using water leaching, the lithium leaching rate was only 64.64%.

[0037] The recovery rates of the lithium and cobalt products after leaching were analyzed, with the lithium product recovery rate being 81.76% and the cobalt product recovery rate being 75.85%.

[0038] Example 2: Efficient recovery of lithium / cobalt from LCO lithium batteries by PVC cascade pyrolysis to Li2CO3 and Co / Co3O4 S1. Pretreatment of lithium cobalt oxide batteries: Use 20 g / L NaCl solution to soak the used lithium batteries for 180 minutes. After they are fully discharged, separate the positive electrode components, calcine them at 500°C for 40 minutes, and then calcine them at 600°C for 12 hours to obtain relatively pure LiCoO2 powder.

[0039] S2. Dechlorination of PVC at low temperature: 8g of PVC was pyrolyzed at 320℃, and the released hydrogen chloride was absorbed by 200ml of deionized water to prepare DPVC and HCl absorption solution (crude hydrochloric acid). The dechlorination rate was as high as 99.97%.

[0040] Microwave co-pyrolysis of S3, DPVC and LCO: the mass ratio of DPVC to LCO was 1:1, the microwave co-pyrolysis power was set at 700 W, the temperature was set at 600 °C, and the pyrolysis time was 30 min.

[0041] S4. Leach the co-pyrolysis solid phase product with water at a leaching temperature of 25°C, a leaching time of 30 min, and a solid-liquid ratio of 3:100 g / mL to obtain a filtrate containing Li2CO3 and a filter residue containing cobalt.

[0042] S5. The filtrate in S4 was dried at 120°C for 12 hours to obtain the target product Li2CO3. The filter residue containing cobalt in S4 was calcined at 800°C for 60 minutes in 5% hydrogen to obtain Co. The filter residue was calcined in air at 800°C for 60 minutes to obtain Co3O4.

[0043] The recovery rates of the lithium and cobalt products after leaching were analyzed, with the lithium product recovery rate being 96.66% and the cobalt product recovery rate being 99.76%.

[0044] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for resource utilization of waste lithium cobalt oxide batteries and waste polyvinyl chloride, characterized in that: The specific steps include: S1. Pretreatment of lithium cobalt oxide batteries: Separate the waste lithium batteries to obtain positive electrode components, and calcine the separated positive electrode components to obtain LiCoO2 powder; S2. Low-temperature dechlorination: The chlorine element in PVC is converted into crude hydrochloric acid at low temperature using a stepwise pyrolysis method to produce chlorine-free conjugated polyolefin DPVC. S3. Co-pyrolysis: Using microwave radiation to synergistically co-pyrolyze DPVC and waste lithium cobalt oxide battery LCO to achieve resource recovery of valuable metals, hydrogen-rich gas, and light oil; S4. Metal separation and recovery: using water leaching separation to obtain a filtrate containing lithium and a filter residue containing cobalt; adjusting the calcination atmosphere of the filter residue to selectively recover cobalt as Co or Co3O4; Alternatively, acid leaching is used for separation to obtain a filtrate containing lithium and cobalt compounds and a coke residue.

2. The method according to claim 1, wherein In S1, the specific operation of the lithium cobalt oxide battery pretreatment is: soaking the waste lithium battery in NaCl solution to make it fully discharged, separating the positive electrode component, and calcining the separated positive electrode component to obtain LiCoO2 powder.

3. The method according to claim 1, wherein In S2, PVC is dechlorinated in an oxygen-free atmosphere at a low temperature of 250-320°C to prepare DPVC and crude hydrochloric acid.

4. The method according to claim 1, wherein In S3, the power of microwave radiation co-pyrolysis is 400-700 W, the temperature is 400-700° C., and the co-pyrolysis time is 30-90 min.

5. The method according to claim 1, wherein In S3, the mass ratio of DPVC to LCO is 1:0.5~4.

6. The method according to claim 1, wherein In S4, the solid-liquid ratio of co-pyrolysis product and water is 0.3-3:100 g / mL, the leaching temperature is 25-100 °C, and the leaching time is 15-90 min.

7. The method according to claim 1, wherein In S4, the solid-liquid ratio of the co-pyrolysis product and the acid is 0.3-3:100 g / mL, the leaching temperature is 25-30°C, and the leaching time is 15-30 min; the acid is the crude hydrochloric acid prepared in S2.

8. The method according to claim 1, wherein In S4, Co is recovered by calcination in a reducing atmosphere, and Co3O4 is recovered in an oxidizing atmosphere; the reducing atmosphere is hydrogen or the hydrogen-rich gas obtained in S3.

9. The method according to claim 8, wherein The filter residue is calcined in hydrogen with a concentration of 5% to 10% at 700 to 800°C for 60 to 90 minutes to obtain Co.

10. The method according to claim 8, wherein The filter residue is calcined in air at 700-800°C for 60-90 minutes to obtain Co3O4.

Images