Lithium iron phosphate battery black powder recovery method

Abstract

The invention specifically discloses a lithium iron phosphate battery black powder recovery method. The method comprises the following steps: S100, carrying out defluorination pretreatment on lithium iron phosphate battery black powder; s200, introducing excessive chlorine into the defluorinated lithium iron phosphate battery black powder, and performing chloridizing roasting at a first preset temperature to obtain a low-temperature roasting product; s300, the low-temperature roasting product is subjected to water immersion dissolution, and filtrate containing lithium chloride and filter residues are obtained after filtering; s400, introducing excessive chlorine gas into the filter residues, performing chloridizing roasting at a second preset temperature, cooling after roasting is completed, and collecting condensate and residues; and S500, mixing the residues with hydrochloric acid or phosphoric acid, carrying out acid leaching washing, and filtering to obtain graphite. According to the lithium iron phosphate battery black powder recovery method, lithium and carbon in the battery black powder raw material can be effectively recovered, high-purity lithium chloride and graphite products are obtained, and the method has the advantages of being simple in process, few in product impurity and good in economic benefit.

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 black powder from lithium iron phosphate batteries. Background Art

[0002] The wet process of recycling black powder from used lithium iron phosphate batteries involves the simultaneous processing of a large number of positive lithium iron phosphate particles, fluorine-containing organic particles and negative graphite particles. In this process, whether pre-treatment flotation screening of graphite is used or graphite is extracted from wet leaching residues, a large amount of lithium iron phosphate, positive electrode carbon and impurities such as calcium carbonate and silicon dioxide introduced due to improper operation and control of the recycling process will remain in the collected materials.

[0003] In view of this, the present application provides a method for recovering black powder from lithium iron phosphate batteries with simple process, low impurity content and good economic benefits. Summary of the invention

[0004] This application is made in view of the above technical problems and aims to provide a method for recycling black powder of lithium iron phosphate batteries, which is used to reduce the recycling cost of black powder of lithium iron phosphate batteries, improve the purity of recycled products, and thus improve economic benefits.

[0005] In order to solve the above technical problems, the present application provides a method for recovering black powder from lithium iron phosphate batteries, the method comprising the following steps:

[0006] S100, defluorination, pre-treatment of lithium iron phosphate battery black powder;

[0007] S200, low-temperature chlorination, introducing excess chlorine into the defluorinated lithium iron phosphate battery black powder and performing chlorination roasting at a first preset temperature to obtain a low-temperature roasting product, wherein the first preset temperature is 30-300° C., and the chemical reaction formula of chlorination roasting at the first preset temperature is:

[0008] 2LiFePO4+Cl2=2LiCl+2FePO4;

[0009] S300, extracting lithium, dissolving the low-temperature calcined product in water, and filtering to obtain a filtrate and a filter residue containing lithium chloride;

[0010] S400, high temperature chlorination, introducing excess chlorine into the filter residue and performing chlorination roasting at a second preset temperature, cooling after the roasting is completed to collect condensate and residue, wherein the second preset temperature is 600-800° C., and the chemical reaction formula of chlorination roasting at the second preset temperature is:

[0011] FePO4+3Cl2+2C=FeCl3+PCl3+2CO2;

[0012] S500, extracting carbon, mixing the residue with phosphoric acid or hydrochloric acid for acid leaching and washing, the hydrochloric acid concentration is greater than 20%, the acid leaching temperature is room temperature to 90°C, the ferrophosphorus compound generated by the acid leaching reaction is dissolved in the acid solution, and graphite can be obtained after filtering.

[0013] In the present application, based on defluorination treatment, low-temperature chlorination roasting, lithium extraction, high-temperature chlorination roasting and carbon extraction processes, the lithium and carbon in the black powder of the lithium iron phosphate battery can be effectively recovered to generate lithium carbonate and graphite. Moreover, the defluorination process can effectively remove the fluorine element in the black powder of the lithium iron phosphate battery, providing favorable conditions for subsequent lithium recovery.

[0014] In some embodiments, in step S100, the lithium iron phosphate battery black powder is mixed with a reaction gas for defluorination pretreatment, wherein the reaction gas includes at least one of water, alkanes, alkenes, alcohols, and alkyl organic acids.

[0015] In some embodiments, in step S200, the excess chlorine is calculated based on 3-12 L of chlorine required for 100 g of lithium iron phosphate battery black powder.

[0016] In some embodiments, in step S400, the excess chlorine is calculated based on 40-50 L of chlorine required for 100 g of the filter residue.

[0017] In some embodiments, in step S500, the molar concentration of phosphoric acid is above 5 mol / L, the concentration of hydrochloric acid is above 20%, and the acid leaching temperature is 30-90°C.

[0018] In some embodiments, in step S500, the molar ratio of concentrated phosphoric acid to the iron content in the residue is 3-4:1.

[0019] In some embodiments, the lithium extraction process includes: adding pure water to the low-temperature calcined product and heating it to a third preset temperature, stirring until the low-temperature calcined product is completely dissolved, and then filtering to obtain a filtrate and a filter residue containing lithium chloride, wherein the third preset temperature is 30-70°C.

[0020] In some embodiments, after the low-temperature chlorination roasting is completed, a protective gas is first charged to completely replace the remaining chlorine in the reaction container, and then the low-temperature roasting product is taken out.

[0021] In some embodiments, the process of acid leaching carbon includes: mixing the residue with hydrochloric acid or phosphoric acid for reaction, then performing solid-liquid separation, and then washing and filtering the obtained solid, while controlling the pH value of the washing water obtained from the last washing to be greater than 6, to obtain graphite.

[0022] In some embodiments, after lithium extraction, the filtrate containing lithium chloride is subjected to lithium precipitation crystallization to obtain lithium carbonate crystals.

[0023] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] 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.

[0025] Figure 1 It is a flow chart of a method for recovering black powder from a lithium iron phosphate battery in this application. DETAILED DESCRIPTION

[0026] "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.

[0027] 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.

[0028] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0029] The overall inventive concept of the embodiment of the present application is to provide a method for recovering black powder of lithium iron phosphate batteries. The recovery method can firstly effectively recover the lithium in the black powder of lithium iron phosphate batteries through defluorination, low-temperature chlorination roasting and lithium extraction. During the recovery process, the fluorine element in the black powder of lithium iron phosphate batteries is removed based on the defluorination process, which greatly improves the comprehensive recovery rate of lithium; then, high-temperature chlorination roasting and carbon extraction can be used to effectively recover the graphite in the filter residue remaining after lithium extraction, thereby realizing the low-cost recovery of black powder of lithium iron phosphate batteries. The recovered product of this method is of high purity and has good economic benefits.

[0030] Based on the above general concept, reference Figure 1 As shown, the embodiment of the present application provides a method for recovering black powder from a lithium iron phosphate battery, the method comprising the following steps:

[0031] S100, defluorination, pre-treatment of lithium iron phosphate battery black powder;

[0032] The step specifically comprises: mixing lithium iron phosphate battery black powder with a reaction gas for defluorination pretreatment, wherein the reaction gas comprises at least one of water, alkanes, alkenes, alcohols, and alkyl organic acids;

[0033] In the above defluorination treatment method, the lithium iron phosphate battery black powder and the reaction gas are first mixed and stirred evenly; then the reaction temperature is controlled to convert the fluorine element in the lithium iron phosphate battery black powder into gaseous hydrogen fluoride. Since the hydrogen fluoride generated by the reaction is mixed with part of the reaction gas in the gas phase, the gas phase and the lithium iron phosphate battery black powder solid phase can be effectively separated by extraction;

[0034] S200, low-temperature chlorination, introducing excess chlorine gas into the defluorinated lithium iron phosphate battery black powder and performing chlorination roasting at a first preset temperature to obtain a low-temperature roasting product, wherein the first preset temperature is 30-300° C.;

[0035] In this step, the first preset temperature may be any value between 30-300°C, and illustratively, may be 40°C, 50°C, 100°C, 150°C, 200°C, 250°C, or 300°C.

[0036] In this step, the excess chlorine is calculated based on 3-12L of chlorine required for 100g of lithium iron phosphate battery black powder. At the same time, after the low-temperature chlorination roasting is completed, a protective gas is first filled in to completely replace the remaining chlorine in the reaction container, and then the low-temperature roasting product is taken out.

[0037] S300, extracting lithium, dissolving the low-temperature calcined product in water, and filtering to obtain a filtrate and a filter residue containing lithium chloride;

[0038] This step specifically includes: adding pure water to the low-temperature roasting product and heating it to a third preset temperature, stirring until the low-temperature roasting product is completely dissolved, and then filtering to obtain a filtrate and a filter residue containing lithium chloride, wherein the third preset temperature is room temperature-70°C; at the same time, after lithium extraction, the filtrate containing lithium chloride is subjected to lithium precipitation crystallization to obtain lithium carbonate crystals.

[0039] In some embodiments, the third preset temperature may be any value between 30-70°C. For example, the third preset temperature may be 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, or 70°C.

[0040] S400, high temperature chlorination, introducing excess chlorine gas into the filter residue and performing chlorination roasting at a second preset temperature, cooling after the roasting is completed, collecting condensate and residue, wherein the second preset temperature is 600-800°C;

[0041] In this step, the excess chlorine is calculated based on 40-50 L of chlorine required for 100 g of the filter residue.

[0042] In some embodiments, the second preset temperature may be any value between 600-800°C, and illustratively, may be 600°C, 650°C, 700°C, 750°C, or 800°C.

[0043] S500, extracting carbon, mixing the residue with hydrochloric acid or phosphoric acid for acid leaching and washing, and filtering to obtain graphite.

[0044] The step specifically comprises: mixing the residue with concentrated phosphoric acid for reaction, performing solid-liquid separation, washing and filtering the obtained solid, and controlling the pH value of the washing water obtained by the last washing to be greater than 6, so as to obtain a graphite product, wherein the molar ratio of the concentrated phosphoric acid to the iron content in the residue is 3-4:1, the molar concentration of the concentrated phosphoric acid is above 5 mol / L, the concentration of the hydrochloric acid is above 20%, and the acid leaching temperature is 30-90°C.

[0045] In some embodiments, the molar ratio of concentrated phosphoric acid to the iron content in the residue may be any value between 3 and 4:1, and illustratively, may also be 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1, or 4:1;

[0046] In some embodiments, the molar concentration of phosphoric acid may be any value above 5 mol / L, illustratively, it may also be 5.5 mol / L, 6 mol / L, 6.5 mol / L, 7 mol / L, 7.5 mol / L, etc.;

[0047] In some embodiments, the concentration of hydrochloric acid may be any value above 20%, illustratively, it may also be 25%, 30%, 35%, etc.;

[0048] In some embodiments, the pickling temperature can be any value between 30-90°C, and illustratively, can also be 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, or 90°C.

[0049] In the above embodiment, the lithium in the lithium iron phosphate battery black powder can be effectively recovered through defluorination, low-temperature chlorination roasting and lithium extraction, and the fluorine element in the lithium iron phosphate battery black powder is removed based on the defluorination process, which greatly improves the comprehensive recovery rate of lithium; then, high-temperature chlorination roasting and carbon extraction can be used to effectively recover the graphite in the filter residue remaining after lithium extraction, thereby realizing the low-cost recovery of lithium iron phosphate battery black powder. The method has high purity of the recovered product and good economic benefits.

[0050] 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.

[0051] Example 1

[0052] (1) taking 500 g of lithium iron phosphate battery black powder and mixing it with a reaction gas to remove fluorine from the lithium iron phosphate battery black powder, wherein the reaction gas includes at least one of water, methane, ethylene, methanol and formic acid;

[0053] (2) introducing chlorine gas into the defluorinated lithium iron phosphate battery black powder, the amount of chlorine gas introduced is 40 L, and the temperature is controlled at 200° C. to perform chlorination roasting to obtain a low-temperature roasting product;

[0054] (3) adding pure water to the low-temperature roasted product and heating it to 60° C., stirring until the low-temperature roasted product is completely dissolved, filtering to obtain a filtrate and a filter residue, and subjecting the filtrate to lithium precipitation crystallization to obtain lithium carbonate crystals;

[0055] (4) introducing chlorine gas into the filter residue and controlling the temperature to 700° C. for chlorination roasting, until the chlorination roasting is completed, cooling and collecting condensate and residue, the amount of chlorine gas introduced is 240 L of chlorine gas;

[0056] (5) The residue is mixed with concentrated phosphoric acid for acid leaching reaction, the molar concentration of the concentrated phosphoric acid is 5 mol / L, the acid leaching temperature is 70° C., the molar ratio of the concentrated phosphoric acid to the iron content in the residue is 3:1, and the product after the acid leaching reaction is solid-liquid separated, and then the solid after the solid-liquid separation is repeatedly washed with water until the pH value of the washing water obtained by washing is greater than 6, and the graphite product can be obtained by filtering.

[0057] Example 2

[0058] (1) taking 500 g of lithium iron phosphate battery black powder and mixing it with a reaction gas to remove fluorine from the lithium iron phosphate battery black powder, wherein the reaction gas includes at least one of water, methane, ethylene, methanol and formic acid;

[0059] (2) introducing chlorine gas into the defluorinated lithium iron phosphate battery black powder, the amount of chlorine gas introduced is 15 L, and the temperature is controlled at 30° C. to perform chlorination roasting to obtain a low-temperature roasting product;

[0060] (3) adding pure water to the low-temperature roasted product, stirring at a temperature of 30° C. until the low-temperature roasted product is completely dissolved, filtering to obtain a filtrate and a filter residue, and subjecting the filtrate to lithium precipitation crystallization to obtain lithium carbonate crystals;

[0061] (4) introducing chlorine gas into the filter residue and controlling the temperature to 600° C. for chlorination roasting, cooling down after the chlorination roasting is completed, collecting the condensate and residue, and the amount of chlorine gas introduced is 200 L;

[0062] (5) The residue is mixed with concentrated phosphoric acid for acid leaching reaction, the molar concentration of the concentrated phosphoric acid is 5 mol / L, the acid leaching temperature is 70° C., the molar ratio of the concentrated phosphoric acid to the iron content in the residue is 4:1, and the product after the acid leaching reaction is solid-liquid separated, and then the solid after the solid-liquid separation is repeatedly washed with water until the pH value of the washing water obtained by washing is greater than 6, and the graphite product can be obtained by filtering.

[0063] Example 3

[0064] (1) taking 500 g of lithium iron phosphate battery black powder and mixing it with a reaction gas to remove fluorine from the lithium iron phosphate battery black powder, wherein the reaction gas includes at least one of water, methane, ethylene, methanol and formic acid;

[0065] (2) introducing chlorine gas into the defluorinated lithium iron phosphate battery black powder, the chlorine gas introduction amount is 60L, and the temperature is controlled at 300°C for chlorination roasting to obtain a low-temperature roasting product;

[0066] (3) adding pure water to the low-temperature roasted product and heating it to 70° C., stirring until the low-temperature roasted product is completely dissolved, filtering to obtain a filtrate and a filter residue, and evaporating, concentrating and drying the filtrate to obtain lithium chloride crystals;

[0067] (4) introducing chlorine gas into the filter residue and controlling the temperature to 800° C. for chlorination roasting, until the chlorination roasting is completed, cooling and collecting condensate and residue, the amount of chlorine gas introduced is 280 L;

[0068] (5) The residue is mixed with concentrated phosphoric acid for acid leaching reaction, the molar concentration of the concentrated phosphoric acid is 5 mol / L, the acid leaching temperature is 70° C., the molar ratio of the concentrated phosphoric acid to the iron content in the residue is 3.5:1, and the product after the acid leaching reaction is solid-liquid separated, and then the solid after the solid-liquid separation is repeatedly washed with water until the pH value of the washing water obtained by washing is greater than 6, and the graphite product can be obtained by filtering.

[0069] Comparative Example 1

[0070] The difference between Comparative Example 1 and Example 1 is that the lithium iron phosphate battery black powder in Comparative Example 1 is not mixed with the reaction gas for defluorination treatment, and the subsequent steps are the same as those in Example 1.

[0071] Comparative Example 2

[0072] The difference between Comparative Example 2 and Example 2 is that the lithium iron phosphate battery black powder in Comparative Example 2 is not mixed with the reaction gas for defluorination treatment, and the subsequent steps are the same as those in Example 2.

[0073] Comparative Example 3

[0074] The difference between Comparative Example 3 and Example 3 is that the lithium iron phosphate battery black powder in Comparative Example 3 is not mixed with the reaction gas for defluorination treatment, and the subsequent steps are the same as those in Example 3.

[0075] The raw material of lithium iron phosphate battery black powder and the products obtained in each step of Examples 1-3 and Comparative Examples 1-3 were tested and analyzed, and the analysis results are shown in Table 1.

[0076] Table 1 Detection and analysis results of battery black powder after defluorination in Examples 1-3

[0077]

[0078] As can be seen from Table 1, in Examples 1-3, the purity of lithium carbonate is above 99.7%, the lithium recovery rate is above 96.5%, the purity of graphite is 99.97%, and the carbon recovery rate is above 75%; in Comparative Examples 1-3, the purity of lithium carbonate does not change much, but the lithium recovery rate is between 75-82%, showing a significant decline, the purity of graphite is between 90-92%, that is, the purity of graphite has a small decline, the carbon recovery rate is between 76-79%, and the carbon recovery rate has no significant change. Therefore, based on Comparative Examples 1-3 and Examples 1-3, it can be seen that the lithium iron phosphate battery black powder can greatly improve the lithium recovery rate after defluorination treatment, and the purity of the recovered graphite is also improved to a certain extent. The product recovered by the lithium iron phosphate battery black powder recovery method provided in this application is of high purity and has good economic benefits.

[0079] The above is a detailed introduction to a method for recycling black powder of 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 recovering black powder from lithium iron phosphate batteries, characterized in that: The method comprises the following steps: S100, defluorination, pre-treatment of lithium iron phosphate battery black powder; S200, low-temperature chlorination, introducing excess chlorine gas into the defluorinated lithium iron phosphate battery black powder and performing chlorination roasting at a first preset temperature to obtain a low-temperature roasting product, wherein the first preset temperature is 30-300° C.; S300, extracting lithium, dissolving the low-temperature calcined product in water, and filtering to obtain a filtrate and a filter residue containing lithium chloride; S400, high temperature chlorination, introducing excess chlorine gas into the filter residue and performing chlorination roasting at a second preset temperature, cooling after the roasting is completed, collecting condensate and residue, wherein the second preset temperature is 600-800°C; S500, extracting carbon, mixing the residue with hydrochloric acid or phosphoric acid for acid leaching and washing, and filtering to obtain graphite.

2. The method for recovering black powder from lithium iron phosphate batteries according to claim 1, characterized in that: In the step S100, the lithium iron phosphate battery black powder is mixed with a reaction gas for defluorination pretreatment, wherein the reaction gas includes at least one of water, alkanes, alkenes, alcohols, and alkyl organic acids.

3. The method for recovering black powder from lithium iron phosphate batteries according to claim 2, characterized in that: In the step S200, the excess chlorine is calculated based on 3-12 L of chlorine required for 100 g of lithium iron phosphate battery black powder.

4. The method for recovering black powder from lithium iron phosphate batteries according to claim 3, characterized in that: In step S400, the excess chlorine is calculated based on 40-50 L of chlorine required for 100 g of the filter residue.

5. The method for recovering black powder from lithium iron phosphate batteries according to claim 4, characterized in that: In the step S500, the molar concentration of phosphoric acid is above 5 mol / L, the concentration of hydrochloric acid is above 20%, and the acid leaching temperature is 30-90°C.

6. The method for recovering black powder from lithium iron phosphate batteries according to claim 5, characterized in that: In the step S500, the molar ratio of concentrated phosphoric acid to the iron content in the residue is 3-4:

1.

7. The method for recovering black powder from lithium iron phosphate batteries according to claim 6, characterized in that: The lithium extraction process includes: adding pure water to the low-temperature roasting product and heating it to a third preset temperature, stirring until the low-temperature roasting product is completely dissolved, and then filtering to obtain a filtrate and a filter residue containing lithium chloride, wherein the third preset temperature is 30-70°C.

8. The method for recovering black powder from lithium iron phosphate batteries according to claim 7, characterized in that: After the low-temperature chlorination roasting is completed, a protective gas is first charged to completely replace the remaining chlorine in the reaction container, and then the low-temperature roasting product is taken out.

9. The method for recovering black powder from lithium iron phosphate batteries according to claim 1, characterized in that: The carbon extraction process includes: mixing the residue with phosphoric acid or hydrochloric acid for reaction, then performing solid-liquid separation, then washing and filtering the obtained solid, and controlling the pH value of the washing water obtained by the last washing to be greater than 6 to obtain graphite.

10. The method for recovering black powder from lithium iron phosphate batteries according to claim 1, characterized in that: After lithium extraction, the filtrate containing lithium chloride is subjected to lithium precipitation crystallization to obtain lithium carbonate crystals.

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