A method for recycling lithium slag from waste lithium iron phosphate batteries

Abstract

The present application specifically discloses a method for recycling and reusing lithium slag from waste lithium iron phosphate batteries, the method comprising the following steps: S100, mixing lithium slag from waste lithium iron phosphate batteries with carbon material to obtain a mixture, wherein the carbon content in the carbon material is ≥80%, and the carbon ratio of the mixture satisfies: 2≤A≤30, A represents the ratio of carbon mole number to phosphorus mole number in the mixture; S200, chlorine is introduced into the mixture for roasting, and the roasting reaction temperature is controlled by adjusting the chlorine flow rate to obtain a roasting product, wherein the roasting reaction temperature is 500-1100°C; S300, the roasting product is subjected to step-by-step condensation separation, and solid ferric chloride, solid aluminum chloride and liquid phosphorus trichloride can be obtained respectively. The present application adopts chlorine one-step roasting to convert iron, aluminum and phosphorus in lithium slag into gas phase, and the gas phase can be directly separated and recycled by step-by-step condensation, so the method has the characteristics of high yield, short process and low cost.

Description

Technical Field

[0001] The present application belongs to the technical field of lithium iron phosphate battery recycling, and in particular, relates to a method for recycling and reusing lithium slag extracted from waste lithium iron phosphate batteries. Background Art

[0002] Lithium iron phosphate batteries have the advantages of long life, high safety and low price, and are widely used in new energy vehicle power batteries and large-scale electrochemical energy storage. After the end of the life of lithium iron phosphate batteries, they need to be properly disposed of. Direct disposal in the natural environment will cause water and soil pollution, seriously damaging the health of animals, plants and humans.

[0003] Publication No. CN103066343A discloses a method for separating active substances from aluminum in lithium-ion battery positive electrode sheets, which comprises crushing and drying the failed lithium-ion battery positive electrode sheets, and then introducing chlorine gas at a temperature of 300-380°C for chlorination separation treatment to obtain hot volatiles and solid products containing positive electrode active substances; the hot volatiles are directly condensed to obtain aluminum chloride, or oxidized to obtain aluminum oxide. This method can efficiently separate aluminum from positive electrode active substances, and the method has a short process route, good separation effect, high aluminum salt yield, and low energy consumption. The above method only effectively separates aluminum from other positive electrode active substances in waste lithium battery positive electrode sheets, while the black powder of lithium iron phosphate batteries contains other elements such as phosphorus and iron in addition to aluminum.

[0004] Based on this, the present application provides a method for recycling and reusing lithium slag from waste lithium iron phosphate batteries with a short process, high separation effect, high yield and low cost. The method can efficiently recover phosphorus, iron and aluminum in the lithium slag, thereby maximizing the recycling value of waste lithium iron phosphate batteries. Summary of the invention

[0005] This application is made in view of the above technical problems and aims to provide a method for recycling and reusing lithium slag from waste lithium iron phosphate batteries with a short process, high separation effect, high yield and low cost.

[0006] In order to solve the above technical problems, the present application provides a method for recycling lithium slag from waste lithium iron phosphate batteries, the method comprising the following steps:

[0007] S100, mixing lithium slag extracted from waste lithium iron phosphate batteries with a carbon material to obtain a mixture, wherein the carbon content in the carbon material is ≥80%, and the carbon ratio of the mixture satisfies: 2≤A≤30, where A represents the ratio of the molar number of carbon to the molar number of phosphorus in the mixture;

[0008] S200, introducing chlorine gas into the mixture for roasting, and controlling the roasting reaction temperature by adjusting the chlorine gas flow rate to obtain a roasting product, wherein the roasting reaction temperature is 500-1100° C.;

[0009] S300, the roasting product is condensed and separated step by step to obtain solid ferric chloride, solid aluminum chloride and liquid phosphorus trichloride respectively.

[0010] In some embodiments, in step S100, the lithium slag from waste lithium iron phosphate batteries is dried and then mixed with the carbon material.

[0011] In some embodiments, in step S100, the carbon material includes one or more of charcoal, bamboo charcoal, activated carbon, carbon black, coke, coal, graphite, carbon nanotubes, graphene, carbon fiber, hard carbon and soft carbon.

[0012] In some embodiments, the step S200 is specifically: adding the mixed material to a chlorination reactor and heating it to a calcination reaction temperature, then introducing chlorine into the chlorination reactor for calcination reaction, and stopping the introduction of chlorine after the calcination reaction is completed, thereby obtaining gaseous aluminum chloride, ferric chloride and phosphorus trichloride, wherein during the calcination reaction, the calcination reaction temperature is controlled by adjusting the chlorine flow rate and the heating power, and the calcination reaction temperature satisfies: , is the target reaction temperature, is the maximum temperature deviation allowed for the calcination reaction, is the calcination reaction temperature.

[0013] In some embodiments, in step S200, the calcination reaction time is 10-180 minutes.

[0014] In some embodiments, step S300 is specifically as follows: rapidly cooling the calcined product to a first preset temperature to convert gaseous ferric chloride into solid ferric chloride; then rapidly cooling the calcined product to a second preset temperature to convert gaseous aluminum chloride into solid aluminum chloride; and finally cooling the calcined product to a third preset temperature to convert gaseous phosphorus trichloride into liquid phosphorus trichloride, wherein the first preset temperature is 200-300°C, the second preset temperature is 85-170°C, and the third preset temperature is 5-70°C.

[0015] In some embodiments, the tail gas remaining after the roasting product is separated by step-by-step condensation is also absorbed by spraying with alkali solution.

[0016] Compared with the prior art, the present invention provides a method for recycling and reusing lithium slag from waste lithium iron phosphate batteries, which has the following beneficial technical effects:

[0017] (1) The present application adopts medium-temperature one-step chlorination roasting to achieve the chlorination conversion and volatilization of phosphorus, iron and aluminum in lithium extraction slag. The chlorination conversion rate of phosphorus, iron and aluminum is as high as 99%, and the chlorides of phosphorus, iron and aluminum can be directly desublimated and separated. Compared with the traditional wet process, the yield of phosphorus and iron is higher and the process flow is shorter;

[0018] (2) The present application directly uses chlorine as a reactant to chlorinate and roast the lithium extraction slag. The chlorination conversion process does not require acid and alkali. The reaction product can be directly condensed, separated and recovered. Only a very small amount of alkali is needed to absorb the tail gas. Compared with the traditional wet process, the amount of acid and alkali used is less;

[0019] Therefore, the recycling and reuse method provided in the present application has the characteristics of high yield, short process and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 It is a flow chart of a method for recycling lithium slag from waste lithium iron phosphate batteries in some embodiments of the present application. DETAILED DESCRIPTION

[0022] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0023] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0024] refer to Figure 1 As shown, the embodiment of the present application provides a method for recycling lithium slag from waste lithium iron phosphate batteries, the method comprising the following steps:

[0025] S100, mixing lithium slag extracted from waste lithium iron phosphate batteries with a carbon material to obtain a mixture, wherein the carbon content in the carbon material is ≥80%, and the carbon ratio of the mixture satisfies: 2≤A≤30, where A represents the ratio of the molar number of carbon to the molar number of phosphorus in the mixture;

[0026] In this step, the lithium slag from waste lithium iron phosphate batteries refers to the residue formed after the waste lithium iron phosphate batteries are subjected to a wet lithium extraction process. The main components of the lithium slag include phosphorus, iron, aluminum, and carbon elements; and the lithium slag from waste lithium iron phosphate batteries needs to be dried before being mixed with the carbon material.

[0027] In this step, the carbon material includes one or more of charcoal, bamboo charcoal, activated carbon, carbon black, coke, coal, graphite, carbon nanotubes, graphene, carbon fiber, hard carbon and soft carbon, and it is only necessary to ensure that the carbon ratio in the mixture satisfies 2≤A≤30.

[0028] In some embodiments, the carbon ratio in the mixture can be any value between 2-30. For example, it can be 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, etc.

[0029] S200, introducing chlorine gas into the mixture for roasting, and controlling the roasting reaction temperature by adjusting the chlorine gas flow rate to obtain a roasting product, wherein the roasting reaction temperature is 500-1100° C.;

[0030] The step specifically comprises: adding the mixed material into a chlorination reactor and heating it to a calcination reaction temperature, then introducing chlorine gas into the chlorination reactor for calcination reaction, and stopping introducing chlorine gas after the calcination reaction is completed, thereby obtaining gaseous aluminum chloride, ferric chloride and phosphorus trichloride, wherein during the calcination reaction process, the calcination reaction temperature is controlled by adjusting the chlorine gas flow rate and the heating power, and the calcination reaction temperature satisfies: , is the target reaction temperature, is the maximum temperature deviation allowed for the calcination reaction, is the calcination reaction temperature;

[0031] Specifically, before the mixture reacts with chlorine in the chlorination reactor, the temperature in the chlorination reactor needs to be raised to a roasting reaction temperature of 500-1100°C, and then chlorine is introduced into the chlorination reactor for chlorination roasting reaction. At the same time, during the chlorination roasting reaction, the roasting reaction temperature is controlled by using the chlorine flow rate and heating power, so that the chlorination roasting reaction temperature always meets: , wherein the maximum temperature deviation allowed by the roasting reaction is 5-65°C. Then, the iron, aluminum and phosphorus elements in the lithium extraction slag are chlorinated and converted into iron chloride, aluminum chloride and phosphorus trichloride respectively. The chlorination conversion chemical reaction formula is:

[0032] (1)

[0033] (2)

[0034] (3)

[0035] At a temperature above 400°C, the Gibbs free energy of reaction (1) and reaction (2) is less than 0, indicating that the reactions (1) and reaction (2) are spontaneous. Since the calcination reaction temperature T in the chlorination reactor is 500-1100°C, ferric chloride, aluminum chloride and phosphorus trichloride are all present in the chlorination reactor in the gas phase.

[0036] In some embodiments, the calcination reaction temperature may be any value between 500-1100°C, illustratively, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, etc.;

[0037] In some embodiments, the maximum temperature deviation allowed for the calcination reaction can be any value between 5-65°C. For example, it can be 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, etc.

[0038] S300, condensing and separating the roasting products step by step to obtain solid ferric chloride, solid aluminum chloride and liquid phosphorus trichloride respectively.

[0039] In this step, based on the roasting product produced in step S200, the ferric chloride, aluminum chloride and phosphorus trichloride in the roasting product are all present in the gas phase. At the same time, the boiling points of ferric chloride, aluminum chloride and phosphorus trichloride decrease successively, and the boiling points between them have a difference of more than 100°C. Therefore, by utilizing this characteristic, the ferric chloride, aluminum chloride and phosphorus trichloride in the roasting product can be separated and collected by desublimation, that is, the roasting product is condensed step by step to achieve the separation of ferric chloride, aluminum chloride and phosphorus trichloride, and solid ferric chloride, solid aluminum chloride and liquid phosphorus trichloride are obtained respectively.

[0040] Specifically, the calcined product is first quickly cooled to a first preset temperature to convert gaseous ferric chloride into solid ferric chloride; then the calcined product is quickly cooled to a second preset temperature to convert gaseous aluminum chloride into solid aluminum chloride; finally, the calcined product is cooled to a third preset temperature to convert gaseous phosphorus trichloride into liquid phosphorus trichloride, wherein the first preset temperature is 200-300°C, the second preset temperature is 85-170°C, and the third preset temperature is 5-70°C.

[0041] In some embodiments, the first preset temperature may be any value between 200-300° C., illustratively, it may be 200° C., 210° C., 220° C., 230° C., 240° C., 250° C., 260° C., 270° C., 280° C., 290° C., 300° C., etc., to ensure that the gaseous ferric chloride in the roasted product can be converted into solid ferric chloride;

[0042] The second preset temperature may be any value between 85°C and 170°C, for example, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, etc., to ensure that the gaseous aluminum chloride in the calcined product can be converted into solid aluminum chloride;

[0043] The third preset temperature can be any value between 5-70°C, illustratively, it can be 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, etc., to ensure that the gaseous phosphorus trichloride in the roasting product can be converted into liquid phosphorus trichloride.

[0044] In the implementation mode of the present application, the ferrophosphorus aluminum in the lithium extraction slag is converted into ferric chloride, aluminum chloride and phosphorus trichloride by medium-temperature one-step chlorination roasting. Since the boiling points of ferric chloride, aluminum chloride and phosphorus trichloride decrease in sequence and the boiling point difference between them is more than 100°C, this characteristic can be utilized to directly separate and recover them by desublimation. Therefore, the recycling and reuse method provided by the present application has a high yield of ferrophosphorus aluminum, a short process flow and very little acid and alkali usage, and has the characteristics of high yield, short process flow and low cost.

[0045] In some embodiments, the tail gas remaining after the roasting product is separated by step-by-step condensation is also absorbed by spraying with alkali solution.

[0046] In the above embodiment, the tail gas remaining after the roasting product is condensed and separated step by step needs to be absorbed by spraying with alkali solution, thereby avoiding the pollution of the tail gas to the atmosphere.

[0047] The following examples describe the disclosure of the present application in more detail, and these examples are merely illustrative, as it will be apparent to those skilled in the art that various modifications and variations within the scope of the disclosure of the present application are possible. Unless otherwise stated, all reagents and raw materials used in the examples are commercially available or synthesized according to conventional methods, and the instruments and equipment used in the examples are commercially available.

[0048] Example 1

[0049] (1) 100 kg of waste lithium iron phosphate battery lithium slag is taken, wherein the iron phosphate content is 96.8%, the graphite content is 2.3%, the aluminum content is 0.73%, and the rest is impurities such as calcium, fluorine, and titanium. The waste lithium iron phosphate battery lithium slag raw material is placed in a vacuum oven, baked at 150° C. for 2 hours, and naturally cooled to room temperature to obtain the dried waste lithium iron phosphate battery lithium slag;

[0050] (2) adding 27.7 kg of graphite to the dried waste lithium iron phosphate battery lithium extraction slag and mixing them evenly to obtain a mixture, wherein the carbon ratio A in the mixture is 3.89;

[0051] (3) adding the mixed material into a chlorination reactor, raising the temperature to a reaction temperature of 500°C, introducing chlorine gas with a purity of 99.99% to carry out a calcination reaction, and during the calcination reaction, adjusting the flow rate of chlorine gas and the heating power of the chlorination reactor to control the maximum temperature deviation allowed by the calcination reaction to be 65°C, and the calcination reaction time is 180 minutes;

[0052] (4) The calcination product generated by the calcination reaction is subjected to three-stage desublimation separation, wherein the first-stage desublimation separation temperature (first preset temperature) is 250°C to obtain a solid FeCl3 product; the second-stage desublimation separation temperature (second preset temperature) is 170°C to obtain a solid AlCl3 product; and the third-stage desublimation separation temperature (third preset temperature) is 70°C to obtain a liquid PCl3 product.

[0053] (5) The remaining tail gas of the roasting product after the three-stage desublimation separation is absorbed by alkaline solution spraying and discharged after purification to meet the standards.

[0054] Example 2

[0055] (1) 100 kg of waste lithium iron phosphate battery lithium slag is taken, wherein the iron phosphate content is 96.8%, the graphite content is 2.3%, the aluminum content is 0.73%, and the rest is impurities such as calcium, fluorine, and titanium. The waste lithium iron phosphate battery lithium slag raw material is placed in a vacuum oven, baked at 150° C. for 2 hours, and naturally cooled to room temperature to obtain the dried waste lithium iron phosphate battery lithium slag;

[0056] (2) adding 3 kg of graphite and 12.7 kg of carbon black to the dried waste lithium iron phosphate battery lithium extraction slag and mixing them evenly to obtain a mixture, wherein the carbon ratio A in the mixture is 2.34;

[0057] (3) The mixed material is added to a chlorination reactor, the temperature is raised to a calcination reaction temperature of 700°C, and chlorine gas with a purity of 99.99% is introduced for calcination reaction. During the calcination reaction, the maximum temperature deviation allowed by the calcination reaction is controlled to be 30°C by adjusting the flow rate of chlorine gas and the heating power of the chlorination reactor. The calcination reaction time is 100 minutes.

[0058] (4) The calcination product generated by the calcination reaction is subjected to three-stage desublimation separation, wherein the first-stage desublimation separation temperature (first preset temperature) is 280°C to obtain a solid FeCl3 product; the second-stage desublimation separation temperature (second preset temperature) is 140°C to obtain a solid AlCl3 product; and the third-stage desublimation separation temperature (third preset temperature) is 40°C to obtain a liquid PCl3 product.

[0059] (5) The remaining tail gas of the roasting product after the three-stage desublimation separation is absorbed by alkaline solution spraying and discharged after purification to meet the standards.

[0060] Example 3

[0061] (1) 100 kg of waste lithium iron phosphate battery lithium slag is taken, wherein the iron phosphate content is 58.2%, the graphite content is 40.5%, the aluminum content is 0.86%, and the rest is impurities such as calcium, fluorine, and titanium. The waste lithium iron phosphate battery lithium slag raw material is placed in a vacuum oven, baked at 150° C. for 2 hours, and naturally cooled to room temperature to obtain the dried waste lithium iron phosphate battery lithium slag;

[0062] (2) adding 80 kg of charcoal to the dried waste lithium iron phosphate battery lithium extraction slag and mixing them evenly to obtain a mixture, wherein the carbon ratio A of the mixture is 26.03;

[0063] (3) The mixed material is added to a chlorination reactor, the temperature is raised to a calcination reaction temperature of 900°C, and chlorine gas with a purity of 99.99% is introduced for calcination reaction. During the calcination reaction, the maximum temperature deviation allowed by the calcination reaction is controlled to be 40°C by adjusting the flow rate of chlorine gas and the heating power of the reactor. The calcination reaction time is 45 minutes.

[0064] (4) The calcination product generated by the calcination reaction is subjected to three-stage desublimation separation, wherein the first-stage desublimation separation temperature (first preset temperature) is 300°C to obtain a solid FeCl3 product; the second-stage desublimation separation temperature (second preset temperature) is 120°C to obtain a solid AlCl3 product; and the third-stage desublimation separation temperature (third preset temperature) is 20°C to obtain a liquid PCl3 product.

[0065] (5) The remaining tail gas of the roasting product after the three-stage desublimation separation is absorbed by alkaline solution spraying and discharged after purification to meet the standards.

[0066] Example 4

[0067] (1) 100 kg of waste lithium iron phosphate battery lithium slag is taken, wherein the iron phosphate content is 58.2%, the graphite content is 40.5%, the aluminum content is 0.86%, and the rest is impurities such as calcium, fluorine, and titanium. The waste lithium iron phosphate battery lithium slag raw material is placed in a vacuum oven, baked at 150° C. for 2 hours, and naturally cooled to room temperature to obtain the dried waste lithium iron phosphate battery lithium slag;

[0068] (2) adding 1 kg of activated carbon to the dried waste lithium iron phosphate battery lithium extraction slag and mixing them evenly to obtain a mixture, wherein the carbon ratio A of the mixture is 8.97;

[0069] (3) The mixed material is added to a chlorination reactor, the temperature is raised to a calcination reaction temperature of 1100°C, and chlorine gas with a purity of 99.99% is introduced for calcination reaction. During the calcination reaction, the maximum temperature deviation allowed by the calcination reaction is controlled to be 5°C by adjusting the flow rate of chlorine gas and the heating power of the reactor. The calcination reaction time is 10 minutes.

[0070] (4) The calcination product generated by the calcination reaction is subjected to three-stage desublimation separation, wherein the first-stage desublimation separation temperature (first preset temperature) is 260°C to obtain a solid FeCl3 product; the second-stage desublimation separation temperature (second preset temperature) is 150°C to obtain a solid AlCl3 product; and the third-stage desublimation separation temperature (third preset temperature) is 5°C to obtain a liquid PCl3 product.

[0071] (5) The remaining tail gas of the roasting product after the three-stage desublimation separation is absorbed by alkaline solution spraying and discharged after purification to meet the standards.

[0072] Comparative Example 1

[0073] (1) 100 kg of waste lithium iron phosphate battery lithium slag is taken, wherein the iron phosphate content is 96.8%, the graphite content is 2.30%, the aluminum content is 0.73%, and the rest is impurities such as calcium, fluorine, and titanium. The waste lithium iron phosphate battery lithium slag raw material is placed in a vacuum oven, baked at 150° C. for 2 hours, and naturally cooled to room temperature to obtain the dried waste lithium iron phosphate battery lithium slag;

[0074] (2) adding 7 kg of activated carbon to the dried waste lithium iron phosphate battery lithium extraction slag and mixing them evenly to obtain a mixture, wherein the carbon ratio A of the mixture is 1.21;

[0075] (3) The mixed material is added to a chlorination reactor, the temperature is raised to a calcination reaction temperature of 600°C, and chlorine gas with a purity of 99.99% is introduced for calcination reaction. During the calcination reaction, the maximum temperature deviation allowed by the calcination reaction is controlled to be 40°C by adjusting the flow rate of chlorine gas and the heating power of the reactor. The calcination reaction time is 150 minutes.

[0076] (4) The calcination product generated by the calcination reaction is subjected to three-stage desublimation separation. The first-stage desublimation separation temperature (first preset temperature) is 260°C to obtain a solid FeCl3 product; the second-stage desublimation separation temperature (second preset temperature) is 160°C to obtain a solid AlCl3 product; the third-stage desublimation separation temperature (third preset temperature) is 65°C to obtain a liquid PCl3 product.

[0077] (5) The remaining tail gas of the roasting product after the three-stage desublimation separation is absorbed by alkaline solution spraying and discharged after purification to meet the standards.

[0078] Comparative Example 2

[0079] (1) 100 kg of waste lithium iron phosphate battery lithium slag is taken, wherein the iron phosphate content is 58.2%, the graphite content is 40.5%, the aluminum content is 0.86%, and the rest is impurities such as calcium, fluorine, and titanium. The waste lithium iron phosphate battery lithium slag raw material is placed in a vacuum oven, baked at 150° C. for 2 hours, and naturally cooled to room temperature to obtain the dried waste lithium iron phosphate battery lithium slag;

[0080] (2) adding 135 kg of activated carbon to the dried waste lithium iron phosphate battery lithium extraction slag and mixing them evenly to obtain a mixture, wherein the carbon ratio A of the mixture is 37.91;

[0081] (3) The mixed material is added to a chlorination reactor, the temperature is raised to a calcination reaction temperature of 900°C, and chlorine gas with a purity of 99.99% is introduced for calcination reaction. During the calcination reaction, the maximum temperature deviation allowed by the calcination reaction is controlled to be 10°C by adjusting the flow rate of chlorine gas and the heating power of the reactor. The calcination reaction time is 40 minutes.

[0082] (4) The calcination product generated by the calcination reaction is subjected to three-stage desublimation separation. The first-stage desublimation separation temperature (first preset temperature) is 290°C to obtain a solid FeCl3 product; the second-stage desublimation separation temperature (second preset temperature) is 130°C to obtain a solid AlCl3 product; the third-stage desublimation separation temperature (third preset temperature) is 40°C to obtain a liquid PCl3 product.

[0083] (5) The remaining tail gas of the roasting product after the three-stage desublimation separation is absorbed by alkaline solution spraying and discharged after purification to meet the standards.

[0084] The residual contents of phosphorus, iron and aluminum in the unreacted carbon slag remaining in the chlorination reactors of Examples 1-4 and Comparative Examples 1-2 were respectively detected. Based on the contents of phosphorus, iron and aluminum in the carbon slag, the chlorination rates of the corresponding phosphorus, iron and aluminum in Examples 1-4 can be calculated. The results are shown in Table 1.

[0085] Table 1 Analysis results of Examples 1-4 and Comparative Examples 1-2

[0086]

[0087] As can be seen from Table 1, the residual content of phosphorus, iron and aluminum in the unreacted carbon slag of the chlorination reactor in Examples 1-4 is less than 4%, that is, the chlorination rates of phosphorus, iron and aluminum in the lithium slag are all greater than 96%, even as high as 99.9%. Due to the low carbon ratio in Comparative Example 1, the reaction is incomplete, and the chlorination rates of phosphorus, iron and aluminum in the lithium slag are all low. The carbon ratio in Comparative Example 2 is relatively high. Although the chlorination rates of phosphorus, iron and aluminum in the final lithium slag are all greater than 99%, the high carbon ratio will greatly increase the production cost. Therefore, the method for recycling and reusing waste lithium iron phosphate battery lithium slag provided in the present application can effectively recycle phosphorus, iron and aluminum elements in the lithium slag, and has the characteristics of high yield, short process and low cost.

[0088] The above is a detailed introduction to a method for recycling and reusing lithium slag from waste lithium iron phosphate batteries provided by the present application. This article uses specific examples to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the core idea of ​​the present application. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A method for recycling lithium slag from waste lithium iron phosphate batteries, characterized in that: The method comprises the following steps: S100, mixing lithium slag extracted from waste lithium iron phosphate batteries with a carbon material to obtain a mixture, wherein the carbon content in the carbon material is ≥80%, and the carbon ratio of the mixture satisfies: 2≤A≤30, where A represents the ratio of the molar number of carbon to the molar number of phosphorus in the mixture; S200, introducing chlorine gas into the mixture for roasting, and controlling the roasting reaction temperature by adjusting the chlorine gas flow rate to obtain a roasting product, wherein the roasting reaction temperature is 500-1100° C.; S300, condensing and separating the roasting products step by step to obtain solid ferric chloride, solid aluminum chloride and liquid phosphorus trichloride respectively.

2. The method for recycling lithium slag from waste lithium iron phosphate batteries according to claim 1, characterized in that: In the step S100, the lithium slag from the waste lithium iron phosphate battery is dried and then mixed with the carbon material.

3. The method for recycling and reusing lithium slag from waste lithium iron phosphate batteries according to claim 2, characterized in that: In the step S100, the carbon material includes one or more of charcoal, bamboo charcoal, activated carbon, carbon black, coke, coal, graphite, carbon nanotubes, graphene, carbon fiber, hard carbon and soft carbon.

4. The method for recycling lithium slag from waste lithium iron phosphate batteries as claimed in claim 3, characterized in that: The step S200 specifically comprises: adding the mixed material into a chlorination reactor and heating it to a calcination reaction temperature, then introducing chlorine into the chlorination reactor for calcination reaction, and stopping introducing chlorine after the calcination reaction is completed, thereby obtaining gaseous aluminum chloride, ferric chloride and phosphorus trichloride, wherein during the calcination reaction process, the calcination reaction temperature is controlled by adjusting the chlorine flow rate and the heating power, and the calcination reaction temperature satisfies: , is the target reaction temperature, is the maximum temperature deviation allowed for the calcination reaction, is the calcination reaction temperature.

5. The method for recycling lithium slag from waste lithium iron phosphate batteries as claimed in claim 4, characterized in that: In the step S200, the calcination reaction time is 10-180 minutes.

6. The method for recycling lithium slag from waste lithium iron phosphate batteries according to claim 5, characterized in that: The step S300 is specifically as follows: rapidly cooling the roasted product to a first preset temperature so that gaseous ferric chloride becomes solid ferric chloride; then rapidly cooling the roasted product to a second preset temperature so that gaseous aluminum chloride becomes solid aluminum chloride; and finally cooling the roasted product to a third preset temperature so that gaseous phosphorus trichloride becomes liquid phosphorus trichloride, wherein the first preset temperature is 200-300°C, the second preset temperature is 85-170°C, and the third preset temperature is 5-70°C.

7. The method for recycling and reusing lithium slag from waste lithium iron phosphate batteries according to claim 6, characterized in that: The remaining tail gas after the roasting product is condensed and separated step by step is also absorbed by alkali solution spraying.

Images