Method for carrying out in-situ pyrolysis on PVDF (Polyvinylidene Fluoride) to fix fluorine by waste power battery black powder

Abstract

The invention relates to a waste power battery black powder in-situ pyrolysis PVDF (Polyvinylidene Fluoride) fluorine fixation method, which comprises the following steps: performing pyrolysis treatment on waste power battery black powder in a mixed atmosphere of ammonia gas and oxygen; gas generated in the pyrolysis treatment process is absorbed, and fluorine fixation is achieved; the temperature of the pyrolysis treatment is 260 DEG C to 350 DEG C. According to the method provided by the invention, the mixed gas of ammonia gas and oxygen is used, so that the pyrolysis treatment temperature can be effectively reduced to 260-350 DEG C, and the energy consumption is reduced; the ammonia gas can be combined with HF generated by pyrolysis treatment to generate NH4F, so that the purpose of fixing fluorine is achieved; the produced NH4F has high industrial utilization value, and the economical efficiency of fluorine fixation is improved.

Description

Technical Field

[0001] This invention belongs to the field of solid waste recycling technology, and relates to a method for treating black powder, and more particularly to a method for in-situ pyrolysis of PVDF to solidify fluorine from waste power battery black powder. Background Technology

[0002] With the rapid development of new energy vehicles and the energy storage industry, the demand for lithium-ion batteries has surged, leading to a significant increase in the number of waste lithium-ion batteries. Waste lithium-ion batteries contain various valuable metals such as lithium, cobalt, and nickel, as well as organic binders such as polyvinylidene fluoride (PVDF). If not effectively recycled, they will not only waste resources but may also cause serious environmental pollution problems. Therefore, the recycling of waste lithium-ion batteries has become a crucial aspect of the sustainable development of the new energy industry.

[0003] In the recycling process of spent lithium-ion batteries, the recovery of cathode materials is one of the core steps. Cathode materials usually exist in the battery in powder form, also known as battery black powder, and its main components are positive electrode active material, PVDF binder, and conductive agent. PVDF, as a commonly used binder for cathode materials, has strong chemical stability and binding performance, but its presence can hinder the separation of positive electrode active material from valuable metals, reducing the recovery efficiency and purity of the metals. Therefore, in the recycling process of battery black powder, PVDF needs to be removed first.

[0004] In existing technologies, the main method for removing PVDF from battery black powder is pyrolysis. However, PVDF produces hydrogen fluoride (HF) gas during pyrolysis. HF is highly corrosive and toxic; if not effectively treated, it will corrode equipment and pollute the environment. Therefore, HF must be captured. Currently, the main method for capturing HF is solid adsorption, such as using calcium-based compounds like CaO and calcium chloride as fluoride-fixing agents. The principle is to utilize the chemical reaction between CaO, calcium chloride, etc., and HF to generate stable fluorides, thereby fixing the fluorine. However, to ensure the complete fluoride-fixing reaction, a calcination temperature above 400℃ is required, leading to a significant increase in energy consumption. Furthermore, the consumption of calcium-based fluoride-fixing agents is large, and the added value of the generated fluorides is low, resulting in poor overall economic efficiency of the process.

[0005] Existing technologies include pyrolysis in a mixed atmosphere of inert gas and ammonia. This method utilizes the reducing and alkaline properties of ammonia to react with HF during pyrolysis to generate ammonium fluoride (NH4F), thus enabling fluorine recovery. However, PVDF exhibits low thermal decomposition activity in inert or ammonia atmospheres, requiring pyrolysis temperatures above 400°C for effective decomposition. This results in relatively high energy consumption for the entire process, making it difficult to meet the demands of low-carbon and environmentally friendly industrial development.

[0006] Therefore, existing processes for removing PVDF from battery black powder through pyrolysis, whether using calcium-based compounds for fluorine fixation or a nitrogen and ammonia mixed atmosphere for pyrolysis, suffer from high pyrolysis temperatures, high energy consumption, high costs, or shortcomings in environmental performance. These issues hinder the efficient, low-carbon, and economical development of waste lithium-ion battery recycling processes. Therefore, there is a need to develop a method for treating waste power battery black powder that reduces pyrolysis temperature, lowers energy consumption, efficiently recovers fluorine resources, and is environmentally friendly. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a method for in-situ pyrolysis of PVDF from waste power battery black powder to solidify fluorine. This method can effectively reduce the pyrolysis temperature to 260℃~350℃, thereby reducing energy consumption. Furthermore, ammonia can combine with HF generated during pyrolysis to generate NH4F, achieving the purpose of solidifying fluorine. Moreover, the generated NH4F has high industrial utilization value, improving the economics of solidifying fluorine.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] This invention provides a method for in-situ pyrolysis of PVDF to solidify fluorine from waste power battery black powder, the method comprising:

[0010] In a mixed atmosphere of ammonia and oxygen, waste power battery black powder is pyrolyzed; and the gas generated during the pyrolysis process is absorbed to achieve solid fluorine.

[0011] The temperature of the pyrolysis treatment is 260℃~350℃.

[0012] The method provided by this invention can effectively reduce the temperature of pyrolysis treatment to 260℃~350℃ by using a mixture of ammonia and oxygen, thereby reducing energy consumption. Moreover, ammonia can combine with HF produced by pyrolysis treatment to generate NH4F, thus achieving the purpose of solid fluorine. Furthermore, the generated NH4F has high industrial utilization value, improving the economics of solid fluorine treatment.

[0013] In one embodiment of the present invention, the volume fraction of oxygen is 5% to 12%.

[0014] In one embodiment of the present invention, the pyrolysis treatment time is 40 min to 50 min.

[0015] In one embodiment of the present invention, the absolute pressure of the pyrolysis treatment is 0.11 MPa to 0.13 MPa.

[0016] In one embodiment of the present invention, the molar ratio of the ammonia gas to the theoretical HF generation amount of the waste power battery black powder is 1.2:1 or higher.

[0017] In one embodiment of the present invention, prior to the pyrolysis treatment, waste power battery black powder and sulfur powder are mixed.

[0018] In one embodiment of the present invention, the molar ratio of sulfur powder to PVDF in the waste power battery black powder is 0.8:1 to 1.2:1.

[0019] In one embodiment of the present invention, the absorption includes spray absorption using water to obtain an absorbent liquid.

[0020] In one embodiment of the present invention, the method further includes distilling the absorbent to obtain an ammonia and ammonium fluoride solution.

[0021] In one embodiment of the present invention, the ammonia gas is recycled for the pyrolysis process.

[0022] In one embodiment of the present invention, the ammonium fluoride solution is evaporated and crystallized to obtain ammonium fluoride.

[0023] In one embodiment of the present invention, the method includes the following steps:

[0024] (1) Mix waste power battery black powder and sulfur powder to obtain a mixture; the molar ratio of sulfur powder to PVDF in the waste power battery black powder is 0.8:1 to 1.2:1;

[0025] (2) The mixture was subjected to pyrolysis treatment for 40 min to 50 min in a mixed atmosphere of ammonia and oxygen at 260℃~280℃ and an absolute pressure of 0.11MPa~0.13MPa.

[0026] In the mixed atmosphere, the volume fraction of oxygen is 5% to 12%;

[0027] The molar ratio of ammonia to the theoretical HF generation of the waste power battery black powder is greater than 1.2:1;

[0028] (3) The gas generated during the pyrolysis process is sprayed and absorbed by water to obtain an absorbent; the absorbent is distilled to obtain ammonia and ammonium fluoride solution; the ammonia is recycled for the pyrolysis process; the ammonium fluoride solution is evaporated and crystallized to obtain ammonium fluoride.

[0029] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The method provided by this invention can effectively reduce the temperature of pyrolysis treatment to 260℃~350℃ by using a mixture of ammonia and oxygen, thereby reducing energy consumption. Moreover, ammonia can combine with HF produced by pyrolysis treatment to generate NH4F, thus achieving the purpose of solid fluorine. Furthermore, the generated NH4F has high industrial utilization value, improving the economics of solid fluorine treatment. Attached Figure Description

[0032] Figure 1 A process flow diagram of the method provided in Embodiment 1 of the present invention is provided. Detailed Implementation

[0033] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0034] The main source of HF in battery black powder is the pyrolysis of PVDF, which requires specific temperature conditions. For example, in a protective atmosphere such as nitrogen, the initial decomposition temperature of PVDF is approximately 380°C, and complete decomposition requires 400°C to 450°C. The inventors of this invention have discovered that by using a mixture of ammonia and oxygen, the breaking of CC and CF bonds in PVDF can be accelerated, thereby reducing the pyrolysis temperature.

[0035] An embodiment of the present invention provides a method for in-situ pyrolysis of PVDF to solidify fluorine from waste power battery black powder, the method comprising:

[0036] In a mixed atmosphere of ammonia and oxygen, waste power battery black powder is subjected to pyrolysis treatment; the gas generated during the pyrolysis treatment is absorbed to achieve solid fluorine.

[0037] The temperature of the pyrolysis treatment is 260℃~350℃.

[0038] The method provided by this invention can effectively reduce the temperature of pyrolysis treatment to 260℃~350℃ by using a mixture of ammonia and oxygen, thereby reducing energy consumption. Moreover, ammonia can combine with HF produced by pyrolysis treatment to generate NH4F, thus achieving the purpose of solid fluorine. Furthermore, the generated NH4F has high industrial utilization value, improving the economics of solid fluorine treatment.

[0039] The use of oxygen enables the pyrolysis temperature to be between 260°C and 350°C, for example, 260°C, 280°C, 300°C, 320°C, 330°C, 340°C or 350°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] Under the temperature conditions of pyrolysis, the HF produced by pyrolysis cannot react with NH3 to form NH4F. Therefore, it is necessary to absorb the gas produced during pyrolysis to obtain an absorbent containing ammonia and ammonium fluoride, thereby achieving the technical effect of solid fluoride.

[0041] Within the temperature range of the pyrolysis treatment of this invention, NH3 and O2 may undergo an oxidation reaction, which reduces the effective NH3 that reacts with HF, leading to a decrease in HF capture efficiency. Controlling the volume fraction of oxygen in the mixed atmosphere can effectively reduce the adverse effects of the reaction between oxygen and NH3.

[0042] In one embodiment of the present invention, the volume fraction of oxygen is 5% to 12%, for example, it can be 5%, 6%, 8%, 9%, 10% or 12%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] If the volume fraction of oxygen is less than 5%, it cannot effectively promote the decomposition of PVDF within the temperature range of 260℃ to 350℃; while when the volume fraction of oxygen exceeds 12%, it will intensify the competitive oxidation reaction between oxygen and ammonia, reducing the amount of HF captured. As a preferred technical solution of the present invention, controlling the volume fraction of oxygen in the mixed atmosphere to be 5% to 12% enables oxygen to preferentially react with the CC and CF bonds in PVDF, while only a small amount of ammonia is oxidized.

[0044] If the pyrolysis treatment time is insufficient, PVDF cannot be fully pyrolyzed; however, if the pyrolysis treatment time is too long, the pyrolysis rate of PVDF cannot be further improved, but the consumption of ammonia by oxygen increases. Therefore, it is necessary to control the pyrolysis treatment time within the preferred range.

[0045] In one embodiment of the present invention, the pyrolysis treatment time is 40 min to 50 min, for example, it can be 40 min, 42 min, 45 min, 48 min or 50 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0046] During pyrolysis, although appropriately increasing the pressure reduces the intermolecular distance between ammonia and oxygen, the concentration of hydrocarbon gas produced by PVDF decomposition is too high, which can preferentially react with oxygen, thus reducing the amount of ammonia consumed by oxygen.

[0047] In one embodiment of the present invention, the absolute pressure of the pyrolysis treatment is 0.11 MPa to 0.13 MPa, for example, it can be 0.11 MPa, 0.12 MPa or 0.13 MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0048] In one embodiment of the present invention, the molar ratio of the ammonia gas to the theoretical HF generation amount of the waste power battery black powder is 1.2:1 or higher.

[0049] In one embodiment of the present invention, before the pyrolysis treatment, waste power battery black powder and sulfur powder are mixed.

[0050] Under the temperature conditions of pyrolysis treatment, sulfur can form sulfides with metal impurities such as Al and Fe. These sulfides have a certain adsorption capacity for HF, which further improves the fluorine fixation effect. Moreover, the presence of sulfur can reduce the side reaction activity of ammonia and oxygen and improve the utilization rate of ammonia. In addition, the use of sulfur can reduce the temperature of pyrolysis treatment to 260℃~280℃.

[0051] However, in the preferred technical solution, the amount of sulfur powder used needs to be controlled. Excessive sulfur powder reacts with ammonia to produce ammonium sulfide, which, when mixed with ammonium fluoride, affects the purity of ammonium fluoride.

[0052] In one embodiment of the present invention, the molar ratio of sulfur powder to PVDF in the waste power battery black powder is 0.8:1 to 1.2:1, for example, it can be 0.8:1, 0.9:1, 1:1, 1.1:1 or 1.2:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0053] In one embodiment of the present invention, the absorption includes spraying water to obtain an absorbent liquid.

[0054] For example, in order to obtain an absorbent of suitable concentration, the gas-liquid volume ratio of water for spray absorption is 500:1 to 800:1, such as 500:1, 600:1, 700:1 or 800:1, but not limited to the listed values. Other unlisted values ​​within the range are also applicable. As a preferred technical solution, the gas-liquid volume ratio is 600:1.

[0055] In some embodiments, the temperature for water spray absorption can be 20°C to 30°C, for example, 20°C, 25°C or 30°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, with 25°C being the preferred value.

[0056] In one embodiment of the present invention, the method further includes distilling the absorbent to obtain an ammonia and ammonium fluoride solution.

[0057] In one embodiment of the present invention, the ammonia gas is recycled for the pyrolysis treatment.

[0058] In one embodiment of the present invention, the ammonium fluoride solution is evaporated and crystallized to obtain ammonium fluoride.

[0059] In one embodiment of the present invention, the method includes the following steps:

[0060] (1) Mix waste power battery black powder and sulfur powder to obtain a mixture; the molar ratio of sulfur powder to PVDF in the waste power battery black powder is 0.8:1 to 1.2:1;

[0061] (2) The mixture was subjected to pyrolysis treatment for 40 min to 50 min in a mixed atmosphere of ammonia and oxygen at 260℃~280℃ and an absolute pressure of 0.11MPa~0.13MPa.

[0062] In the mixed atmosphere, the volume fraction of oxygen is 5% to 12%;

[0063] The molar ratio of ammonia to the theoretical HF generation of the waste power battery black powder is greater than 1.2:1;

[0064] (3) The gas generated during the pyrolysis process is absorbed by spraying water to obtain an absorbent; the absorbent is distilled to obtain ammonia and ammonium fluoride solution.

[0065] The gas-liquid volume ratio for water spray absorption is 500:1 to 800:1, and the temperature is 20℃ to 30℃.

[0066] The ammonia gas is recycled for the pyrolysis treatment; the ammonium fluoride solution is evaporated and crystallized to obtain ammonium fluoride.

[0067] To clearly illustrate the technical solution of the present invention, in the following embodiments and comparative examples, the positive electrode active material of the waste power battery black powder is NCM811 with a content of 90wt%; the content of the binder PVDF is 3wt%.

[0068] Example 1

[0069] This embodiment provides a method for in-situ pyrolysis of PVDF to solidify fluorine from waste power battery black powder. The process flow diagram of this method is shown below. Figure 1 As shown, the method includes:

[0070] (1) The waste power battery black powder was pyrolyzed for 45 minutes in a mixed atmosphere of ammonia and oxygen at 320℃ and an absolute pressure of 0.12MPa.

[0071] In the mixed atmosphere, the volume fraction of oxygen is 8%;

[0072] The molar ratio of ammonia to the theoretical HF generation of the waste power battery black powder is 1.2:1;

[0073] (2) The gas generated during the pyrolysis process is absorbed by spraying water to obtain an absorbent; the absorbent is then distilled to obtain ammonia and ammonium fluoride solution.

[0074] The gas-liquid volume ratio for water spray absorption is 600:1, and the temperature is 25℃.

[0075] The ammonia gas is recycled for the pyrolysis treatment; the ammonium fluoride solution is evaporated and crystallized at an absolute pressure of 0.01 MPa and a temperature of 55°C to obtain ammonium fluoride.

[0076] Example 2

[0077] This embodiment provides a method for in-situ pyrolysis of PVDF to solidify fluorine in waste power battery black powder, the method comprising:

[0078] (1) The waste power battery black powder was pyrolyzed for 50 min in a mixed atmosphere of ammonia and oxygen at 300℃ and an absolute pressure of 0.11MPa.

[0079] In the mixed atmosphere, the volume fraction of oxygen is 5%;

[0080] The molar ratio of ammonia to the theoretical HF generation of the waste power battery black powder is 1.2:1;

[0081] (2) The gas generated during the pyrolysis process is absorbed by spraying water to obtain an absorbent; the absorbent is distilled to obtain ammonia and an ammonium fluoride solution with a concentration of 40 wt%.

[0082] The gas-liquid volume ratio for water spray absorption is 600:1, and the temperature is 25℃.

[0083] The ammonia gas is recycled for the pyrolysis treatment; the ammonium fluoride solution is evaporated and crystallized at an absolute pressure of 0.01 MPa and a temperature of 55°C to obtain ammonium fluoride.

[0084] Example 3

[0085] This embodiment provides a method for in-situ pyrolysis of PVDF to solidify fluorine in waste power battery black powder, the method comprising:

[0086] (1) The waste power battery black powder was pyrolyzed for 40 min in a mixed atmosphere of ammonia and oxygen at 350℃ and an absolute pressure of 0.13MPa.

[0087] In the mixed atmosphere, the volume fraction of oxygen is 12%;

[0088] The molar ratio of ammonia to the theoretical HF generation of the waste power battery black powder is 1.2:1;

[0089] (2) The gas generated during the pyrolysis process is absorbed by spraying water to obtain an absorbent; the absorbent is distilled to obtain ammonia and an ammonium fluoride solution with a concentration of 40 wt%.

[0090] The gas-liquid volume ratio for water spray absorption is 600:1, and the temperature is 25℃.

[0091] The ammonia gas is recycled for the pyrolysis treatment; the ammonium fluoride solution is evaporated and crystallized at an absolute pressure of 0.01 MPa and a temperature of 55°C to obtain ammonium fluoride.

[0092] Example 4

[0093] This embodiment provides a method for in-situ pyrolysis of PVDF to solidify fluorine from waste power battery black powder. Except for the pyrolysis temperature of 280°C in step (1), the rest is the same as in embodiment 1.

[0094] Example 5

[0095] This embodiment provides a method for in-situ pyrolysis of PVDF to solidify fluorine from waste power battery black powder. Except for the pyrolysis treatment time of 30 min in step (1), the rest is the same as in embodiment 1.

[0096] Example 6

[0097] This embodiment provides a method for in-situ pyrolysis of PVDF to solidify fluorine from waste power battery black powder. Except for the pyrolysis treatment time of 60 min in step (1), the rest is the same as in embodiment 1.

[0098] Example 7

[0099] This embodiment provides a method for in-situ pyrolysis of waste power battery black powder to solidify PVDF and form fluorine. Except that the volume fraction of oxygen in the mixed atmosphere is 3%, everything else is the same as in Example 1.

[0100] Example 8

[0101] This embodiment provides a method for in-situ pyrolysis of waste power battery black powder to solidify PVDF and form fluorine. Except that the volume fraction of oxygen in the mixed atmosphere is 15%, the rest is the same as in Example 1.

[0102] Example 9

[0103] This embodiment provides a method for in-situ pyrolysis of PVDF to solidify fluorine in waste power battery black powder, the method comprising:

[0104] (1) Mix waste power battery black powder and sulfur powder to obtain a mixture; the molar ratio of sulfur powder to PVDF in the waste power battery black powder is 1:1;

[0105] (2) The waste power battery black powder was pyrolyzed for 45 minutes in a mixed atmosphere of ammonia and oxygen at 270°C and an absolute pressure of 0.12MPa.

[0106] In the mixed atmosphere, the volume fraction of oxygen is 8%;

[0107] The molar ratio of ammonia to the theoretical HF generation of the waste power battery black powder is 1.2:1;

[0108] (3) The gas generated during the pyrolysis process is absorbed by spraying water to obtain an absorbent; the absorbent is distilled to obtain ammonia and ammonium fluoride solution.

[0109] The gas-liquid volume ratio for water spray absorption is 600:1, and the temperature is 25℃.

[0110] The ammonia gas is recycled for the pyrolysis treatment; the ammonium fluoride solution is evaporated and crystallized at an absolute pressure of 0.01 MPa and a temperature of 55°C to obtain ammonium fluoride.

[0111] Example 10

[0112] This embodiment provides a method for in-situ pyrolysis of PVDF to solidify fluorine in waste power battery black powder, the method comprising:

[0113] (1) Mix waste power battery black powder and sulfur powder to obtain a mixture; the molar ratio of sulfur powder to PVDF in the waste power battery black powder is 0.8:1;

[0114] (2) The waste power battery black powder was pyrolyzed for 50 min in a mixed atmosphere of ammonia and oxygen at 260℃ and an absolute pressure of 0.11MPa.

[0115] In the mixed atmosphere, the volume fraction of oxygen is 5%;

[0116] The molar ratio of ammonia to the theoretical HF generation of the waste power battery black powder is 1.2:1;

[0117] (2) The gas generated during the pyrolysis process is absorbed by spraying water to obtain an absorbent; the absorbent is distilled to obtain ammonia and an ammonium fluoride solution with a concentration of 40 wt%.

[0118] The gas-liquid volume ratio for water spray absorption is 600:1, and the temperature is 25℃.

[0119] The ammonia gas is recycled for the pyrolysis treatment; the ammonium fluoride solution is evaporated and crystallized at an absolute pressure of 0.01 MPa and a temperature of 55°C to obtain ammonium fluoride.

[0120] Example 11

[0121] This embodiment provides a method for in-situ pyrolysis of PVDF to solidify fluorine in waste power battery black powder, the method comprising:

[0122] (1) Mix waste power battery black powder and sulfur powder to obtain a mixture; the molar ratio of sulfur powder to PVDF in the waste power battery black powder is 1.2:1;

[0123] (2) The waste power battery black powder was pyrolyzed for 40 minutes in a mixed atmosphere of ammonia and oxygen at 280°C and an absolute pressure of 0.13MPa.

[0124] In the mixed atmosphere, the volume fraction of oxygen is 12%;

[0125] The molar ratio of ammonia to the theoretical HF generation of the waste power battery black powder is 1.2:1;

[0126] (2) The gas generated during the pyrolysis process is absorbed by spraying water to obtain an absorbent; the absorbent is distilled to obtain ammonia and an ammonium fluoride solution with a concentration of 40 wt%.

[0127] The gas-liquid volume ratio for water spray absorption is 600:1, and the temperature is 25℃.

[0128] The ammonia gas is recycled for the pyrolysis treatment; the ammonium fluoride solution is evaporated and crystallized at an absolute pressure of 0.01 MPa and a temperature of 55°C to obtain ammonium fluoride.

[0129] Comparative Example 1

[0130] This comparative example provides a method for in-situ pyrolysis of PVDF to solidify fluorine from waste power battery black powder. Except for replacing oxygen with ammonia in equal volume, the method is the same as in Example 1.

[0131] Comparative Example 2

[0132] This comparative example provides a method for in-situ pyrolysis of PVDF to solidify fluorine from waste power battery black powder. Except for replacing oxygen with nitrogen in equal volumes, the method is the same as in Example 1.

[0133] Performance Characterization

[0134] The PVDF decomposition rate and total fluorine recovery rate in the above examples and comparative examples were measured. The PVDF decomposition rate was calculated by the mass of residual PVDF, and the total fluorine recovery rate was the percentage of F in ammonium fluoride relative to the F content of the original PVDF in the waste power battery black powder. The results are shown in Table 1.

[0135] Table 1

[0136]

[0137]

[0138] In summary, the method provided by this invention can effectively reduce the temperature of pyrolysis treatment to 260℃~350℃ by using a mixture of ammonia and oxygen, thereby reducing energy consumption. Moreover, ammonia can combine with HF produced by pyrolysis treatment to generate NH4F, achieving the purpose of solid fluorine. Furthermore, the generated NH4F has high industrial utilization value, improving the economics of solid fluorine treatment.

[0139] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for in-situ pyrolysis of PVDF to solidify fluorine from waste power battery black powder, characterized in that, The method includes: In a mixed atmosphere of ammonia and oxygen, waste power battery black powder is pyrolyzed; and the gas generated during the pyrolysis process is absorbed to achieve solid fluorine. The temperature of the pyrolysis treatment is 260℃~350℃.

2. The method according to claim 1, characterized in that, In the mixed atmosphere, the volume fraction of oxygen is 5% to 12%.

3. The method according to claim 1 or 2, characterized in that, The pyrolysis treatment time is 40 min to 50 min.

4. The method according to any one of claims 1 to 3, characterized in that, The absolute pressure of the pyrolysis treatment is 0.11 MPa to 0.13 MPa.

5. The method according to any one of claims 1 to 4, characterized in that, The molar ratio of ammonia to the theoretical HF generation of the waste power battery black powder is greater than 1.2:

1.

6. The method according to any one of claims 1 to 5, characterized in that, Before the pyrolysis treatment, waste power battery black powder and sulfur powder are mixed; And / or, the molar ratio of the sulfur powder to the PVDF in the waste power battery black powder is 0.8:1 to 1.2:

1.

7. The method according to any one of claims 1 to 6, characterized in that, The absorption process includes spraying water to obtain an absorbent solution.

8. The method according to claim 7, characterized in that, The method further includes distilling the absorbent to obtain an ammonia and ammonium fluoride solution.

9. The method according to claim 8, characterized in that, The ammonia gas is recycled for the pyrolysis process; And / or, the ammonium fluoride solution is evaporated and crystallized to obtain ammonium fluoride.

10. The method according to claim 1, characterized in that, The method includes the following steps: (1) Mix waste power battery black powder and sulfur powder to obtain a mixture; the molar ratio of sulfur powder to PVDF in the waste power battery black powder is 0.8:1 to 1.2:1; (2) The mixture was subjected to pyrolysis treatment for 40 min to 50 min in a mixed atmosphere of ammonia and oxygen at 260℃~280℃ and an absolute pressure of 0.11MPa~0.13MPa. In the mixed atmosphere, the volume fraction of oxygen is 5% to 12%; The molar ratio of ammonia to the theoretical HF generation of the waste power battery black powder is greater than 1.2:1; (3) The gas generated during the pyrolysis process is absorbed by spraying water to obtain an absorbent; the absorbent is distilled to obtain ammonia and ammonium fluoride solution; the ammonia is recycled for the pyrolysis process. The ammonium fluoride solution is evaporated and crystallized to obtain ammonium fluoride.

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