Method for fluorine resource recovery in waste battery recycling process

Abstract

The application provides a method for fluorine resource utilization in a waste battery recycling process, comprising the following steps: S1: discharging a waste lithium ion battery, crushing the discharged waste lithium ion battery, pyrolyzing a positive plate material obtained in the step of discharging and crushing to obtain a metal material to be recycled and fluorine-containing flue gas; S2: sequentially introducing the fluorine-containing flue gas into fluorine-containing sludge and lye for absorption; S3: when the fluorine-containing sludge is saturated in the step S2, spraying the lye after absorbing the fluorine-containing flue gas in the step S2 onto the surface layer of the saturated fluorine-containing sludge, ball milling the fluorine-containing sludge after spraying, roasting the obtained ball milled material to obtain a roasting solid; and S4: crushing the roasting solid in the step S3, leaching the crushed roasting solid, and obtaining a leaching solid after solid-liquid separation, and obtaining a calcium fluoride product after washing and drying the leaching solid. The fluorine-containing sludge and the lye are used for absorbing the fluorine-containing flue gas, and the fluorine element is effectively utilized in the waste lithium ion battery recycling process.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of solid waste treatment, and particularly relates to a method for fluorine resource utilization in a waste battery recycling process. BACKGROUND

[0002] Currently, the main method for treating high-concentration fluorine-containing wastewater generated in the process of recycling waste batteries by a wet method is chemical precipitation-coagulation treatment. This method generally adds calcium hydroxide to form a precipitate, and the generated sludge often contains calcium fluoride, calcium hydroxide, calcium sulfate, and the hydroxides of some metals. The proportion of calcium fluoride in fluorine-containing sludge is not small. Fluorite (calcium fluoride) is a non-renewable resource. If the fluorine-containing sludge is directly disposed of, it is easy to cause waste of fluorine resources. However, the content of other impurities in the fluorine-containing sludge is also not low, and it is difficult to directly utilize the fluorine-containing sludge to meet the requirements of the metallurgical industry on the content of calcium fluoride. Therefore, the fluorine-containing sludge needs to be purified. The current industrial method for purifying calcium fluoride is mainly wet purification by flotation and acid leaching. Wet purification often needs to consider the secondary leaching of fluorine in the purification process. Some technical personnel choose fluorine salts such as NaF as a mineral phase regulator to mix and roast with fluorine-containing sludge for purification. Although this method can effectively improve the purity of calcium fluoride, the fluorine salts such as NaF used are relatively expensive, which also increases the cost of fluorine-containing sludge purification. Some other technical personnel only recover the fluorine in the fluorine-containing sludge itself, and the amount of fluorine recovered is limited. In addition, the fluorine-containing sludge needs to be converted by adding carbonate before calcination, and the treatment process is relatively complicated.

[0003] Due to economic interests, the current industrial recycling of waste batteries mainly focuses on high-value metal elements, and the electrolyte is burned and decomposed in a pyrolysis process, and then tail gas treatment is performed. The lithium salt in the electrolyte mainly uses lithium hexafluorophosphate, and F in the electrolyte is treated by gasification and combustion and then enters the tail gas to be absorbed by lye, which also makes F in the electrolyte not effectively utilized.

[0004] In summary, it is an urgent problem to be solved in the current industrial solid waste treatment to seek a process method that can effectively utilize fluorine resources in the recycling process of waste batteries, reduce fluorine pollution and fluorine resource waste, and has low treatment cost. SUMMARY

[0005] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a method for fluorine resource utilization in a waste battery recycling process, which can effectively utilize fluorine resources in the recycling process of waste lithium ion batteries, reduce fluorine pollution and fluorine resource waste, and has low treatment cost.

[0006] According to a first aspect of the present application, a method for fluorine resource utilization in a waste battery recycling process is provided, comprising the following steps:

[0007] S1: discharging the waste lithium ion battery, crushing, pyrolyzing the obtained positive electrode sheet material to obtain a metal material to be recovered and fluorine-containing flue gas;

[0008] S2: sequentially passing the fluorine-containing flue gas in step S1 into fluorine-containing sludge and lye for absorption;

[0009] S3: when the fluorine-containing sludge in step S2 is saturated, spraying the lye after absorbing the fluorine-containing flue gas in step S2 to the surface layer of the saturated fluorine-containing sludge, ball milling the sprayed fluorine-containing sludge, and roasting the obtained ball milled material to obtain a roasted solid;

[0010] S4: crushing the roasted solid in step S3, leaching, and obtaining a leaching solid after solid-liquid separation, and obtaining a calcium fluoride product after washing and drying the leaching solid;

[0011] In step S2, the pH of the fluorine-containing sludge is greater than or equal to 12, the dry basis of CaF2 in the fluorine-containing sludge is 45% to 65%, and the water content is 30% to 50%.

[0012] The fluorine-containing sludge used in the present application is derived from the sludge formed by adding calcium hydroxide to high-concentration fluorine-containing wastewater generated in the process of wet recycling and processing waste lithium ion batteries. The sludge contains calcium fluoride, calcium hydroxide, calcium sulfate, calcium carbonate, sodium sulfate, a small amount of silicon-magnesium impurities, and some metal hydroxides, etc.

[0013] In some embodiments, in step S1, the crushing is performed under vacuum conditions.

[0014] In some embodiments, in step S1, the pyrolysis temperature is 200 to 1000℃, and the time is 1 to 5h.

[0015] In some embodiments, in step S2, the fluorine-containing flue gas is combusted and discharged after passing through the lye. The heat generated by combustion can be supplied to the subsequent roasting process.

[0016] In some embodiments, in step S2, the flow rate of the fluorine-containing flue gas into the fluorine-containing sludge is 20 to 40L / h; and / or, the lye is a 0.1 to 1mol / L NaOH solution. The main purpose of using lye to absorb after the fluorine-containing sludge absorption section in the present application is to avoid the residual fluorine in the flue gas from entering the air. Therefore, the amount of lye can be selected according to the fluorine absorption situation, for example, it can be 1L, 2L, etc., and the present application does not make special limitations.

[0017] In some embodiments, in step S3, after the fluorine-containing sludge is saturated with the absorption, the water content is reduced to 1% to 5%; and / or, the spraying amount of the lye after the absorption of the fluorine-containing flue gas is 3% to 8% of the mass of the saturated fluorine-containing sludge; and / or, the ball milling time is 0.5 to 2 hours.

[0018] In some embodiments, the fluorine content in the lye after the absorption of the fluorine-containing flue gas is greater than or equal to 50 mg / L. When the fluorine content in the lye reaches 50 mg / L, it can be considered that the fluorine-containing sludge is saturated with the absorption of the fluorine-containing flue gas. The pyrolysis obtained fluorine-containing flue gas is acidic, and the alkalinity of the fluorine-containing sludge is weakened after fully absorbing the fluorine-containing flue gas. A small amount of lye that has absorbed residual fluorine in the fluorine-containing flue gas is sprayed on the surface of the fluorine-containing sludge after fully absorbing the fluorine-containing flue gas, and then ball milling, so that the fluorine-containing sludge can maintain a uniform alkaline state during calcination without significantly increasing the water content, reducing the escape of fluorine in the form of hydrogen fluoride or silicon tetrafluoride in the sludge during the calcination process, ensuring the safety of the operation process, and further effectively utilizing the residual fluorine absorbed by the lye.

[0019] If the fluorine-containing sludge does not sufficiently absorb fluorine, the fluorine content in the fluorine-containing sludge is low, and calcium is not fully utilized to convert into calcium fluoride, calcium exists in the sludge in the form of impurities, increasing the subsequent acid liquid impurity removal pressure, and easily causing the secondary leaching amount of F in the acid liquid to increase or the dry basis CaF2 content to decrease.

[0020] In some embodiments, in step S2, the fluorine-containing sludge includes a first-stage sludge and a second-stage sludge, and the fluorine-containing flue gas is sequentially absorbed by the first-stage sludge, the second-stage sludge, and the lye; when the first-stage sludge is saturated with the absorption, the step S2 includes: sequentially passing the fluorine-containing flue gas in step S1 into the second-stage sludge, standby sludge, and lye for absorption. At this time, the second-stage sludge serves as a new first-stage sludge to absorb the fluorine-containing flue gas, and the standby sludge serves as a new second-stage sludge to absorb the fluorine-containing flue gas, and the standby sludge has the same source as the first-stage sludge and the second-stage sludge. To ensure the absorption effect, the first-stage sludge is replaced at the same time as the lye is replaced with a NaOH solution with the same concentration (0.1 to 1 mol / L).

[0021] The application preferably utilizes two-stage fluorine-containing sludge and lye to absorb fluorine-containing flue gas generated by pyrolysis of positive electrode sheet material, and has the following effects: (1) three-stage absorption (two-stage alkaline fluorine-containing sludge absorption + lye absorption) can fully absorb fluorine in the pyrolysis flue gas, and the fluorine-containing sludge also contains unreacted calcium hydroxide and generated calcium sulfate, and the fluorine in the fluorine-containing flue gas can further react with the calcium hydroxide and calcium sulfate in the fluorine-containing sludge to generate calcium fluoride; (2) two-stage fluorine-containing sludge absorption can absorb most of the fluorine in the fluorine-containing flue gas, and the lye absorption is to absorb the residual fluorine in the fluorine-containing flue gas when the fluorine-containing sludge is about to be saturated, so the lye concentration does not need to be too high, avoiding waste of lye; (3) when the two-stage fluorine-containing sludge absorbs the fluorine-containing flue gas generated by pyrolysis, the residual heat of the fluorine-containing flue gas can be absorbed to reduce the water content of the fluorine-containing sludge, thereby reducing the heat energy consumption required for subsequent sludge calcination; and the fluorine-containing sludge can also adsorb and intercept part of the carbon dioxide and hydrocarbon organic matter generated by incomplete combustion in the fluorine-containing flue gas, the carbon dioxide can react with the calcium hydroxide in the fluorine-containing sludge to generate calcium carbonate, and the organic matter can be burned during sludge calcination to release heat energy, thereby further reducing the heat energy consumption required for subsequent sludge calcination; (4) after the initial one-stage sludge absorption is saturated, the original two-stage sludge absorption is used as a new one-stage sludge absorption, and the standby sludge absorption is used as a new two-stage sludge absorption to continue to absorb the fluorine-containing flue gas, so as to ensure that the one-stage fluorine-containing sludge can fully absorb the fluorine-containing flue gas. The application preferably adopts two-stage fluorine-containing sludge and lye to absorb the fluorine-containing flue gas, which guarantees the continuity of the process, facilitates quick replacement after the one-stage sludge absorption is saturated, reduces the loss of fluorine and the consumption of lye, and allows fluorine to be enriched in the fluorine-containing sludge as much as possible. It can be understood that the fluorine-containing sludge can be provided with only one stage, but this will increase the amount of lye, and the lye that absorbs a large amount of fluorine-containing flue gas also needs to be further treated to remove fluorine; of course, the fluorine-containing sludge can be provided with three stages, four stages or five stages, which is beneficial to further reducing the loss of fluorine and the consumption of lye, but too many sludge absorption stages will make the fluorine-containing flue gas treatment process complicated.

[0022] In some embodiments, in step S3, the temperature of the calcination is 650-1000℃, and the time is 1-4h. The calcination process can utilize the residual heat generated by the combustion of the flue gas after lye absorption to maintain high-temperature conditions, the calcium sulfate and calcium hydroxide in the fluorine-containing sludge that has fully absorbed the fluorine-containing flue gas can react with fluorine to convert into calcium fluoride, and the remaining unreacted calcium sulfate, calcium carbonate and calcium hydroxide can decompose into calcium oxide under high-temperature conditions. Under high-temperature conditions, the calcium fluoride crystals grow, and during the growth process, the calcium carbonate and calcium oxide particles cannot enter the inside of the calcium fluoride crystals due to the impurity removal phenomenon of crystal growth, thereby realizing the purification of calcium fluoride. That is, the fluorine enriched in the fluorine-containing sludge can act as a regulator for the growth of calcium fluoride crystals, inducing phase transition of the crystals.

[0023] In some embodiments, in step S4, the particle size of the calcined solid after crushing is ≤0.15 mm; and / or, the leaching agent used in the leaching is hydrochloric acid, and the liquid-solid ratio of the leaching is 4-5 L / kg; and / or, the pH of the solution in the leaching process is maintained at 5-8; and / or, the leaching time is 0.5-2 h. The calcined solid of the fluorine-containing sludge is hard in texture, and needs to be ground and crushed to a certain degree, so that the calcium oxide and sulfates, silicon-magnesium and other impurities in the calcined solid can be fully dissolved in the acid solution to achieve the removal of impurities in the calcined solid. Controlling the pH of the leaching solution in the leaching process can reduce the secondary leaching of fluorine in the calcined solid.

[0024] In some embodiments, in step S4, the washing method is slurry washing, and the slurry washing process is: mixing and stirring the leached solid with water at a liquid-solid ratio of 4-5 L / kg, and the stirring time is 0.5-2 h. Washing the calcined solid after leaching with pure water can further wash out impurities and achieve further purification of calcium fluoride.

[0025] According to a second aspect of the present application, the application of the method of the first aspect of the present application in the recycling of waste lithium batteries is proposed. The calcium fluoride product obtained by the method has a purity of more than 90%, and the effective utilization of fluorine resources in the recycling process of waste lithium batteries is realized.

[0026] According to an embodiment of the present application, at least the following beneficial effects are achieved:

[0027] 1. The treatment method of the present application can effectively absorb the fluorine-containing flue gas generated in the pyrolysis stage of the waste battery recycling process, effectively utilize the fluorine and heat in the fluorine-containing flue gas, and reduce the waste of fluorine resources and heat energy.

[0028] 2. The treatment method of the present application can reduce the dissolution of fluorine in the sludge and reduce the secondary pollution of fluorine while producing high-purity calcium fluoride from fluorine-containing sludge.

[0029] 3. The treatment method of the present application has tolerant treatment conditions, uses conventional and easily available reagents, does not require expensive equipment investment, has low cost, and is easy to popularize.

[0030] 4. The treatment method of the present application can effectively recycle the fluorine-containing sludge, reduce the production of fluorine-containing sludge, and reduce the treatment cost of solid waste sludge in the fluorine-containing wastewater treatment process. BRIEF DESCRIPTION OF DRAWINGS

[0031] The present application will be further described below in conjunction with the drawings and examples, in which:

[0032] Figure 1 The process flow chart of Example 1 of the present application is shown in Figure 1.

[0033] Figure 2XRD pattern of the untreated fluorine-containing sludge;

[0034] Figure 3 XRD pattern of the fluorine-containing sludge after roasting and acid leaching in the present application comparative example 1;

[0035] Figure 4 XRD pattern of the fluorine-containing sludge after roasting and acid leaching in the present application example 1. DETAILED DESCRIPTION

[0036] The concept and technical effects of the present application will be described below in conjunction with examples to fully understand the purpose, features and effects of the present application.

[0037] The raw materials, reagents or devices used in the following examples can be obtained from conventional commercial channels or can be obtained by existing known methods, unless otherwise specified.

[0038] Example 1

[0039] The present embodiment provides a method for fluorine resource utilization in the process of waste battery recycling, as shown in the following steps: Figure 1

[0040] S1: Take a number of fully discharged waste lithium ion batteries and disassemble and crush them to obtain positive electrode sheet materials.

[0041] S2: Pyrolyze the positive electrode sheet materials obtained in step S1 at 650℃ for 3h to obtain metal materials to be recycled, and collect the fluorine-containing flue gas generated by pyrolysis.

[0042] S3: The fluorine-containing flue gas collected in step S2 is continuously absorbed through 1kg of first fluorine-containing sludge and second fluorine-containing sludge with a flow rate of 25L / h, and the residual fluorine-containing flue gas after passing through the second fluorine-containing sludge is introduced into 1L of NaOH solution with a concentration of 0.5mol / L, and the absorption process lasts for 3h. The tail gas absorbed by the lye is collected and introduced into the tail gas treatment system for combustion and emission. The waste heat of combustion can be used for heat preservation in the subsequent roasting process. When the fluorine content in the NaOH solution reaches 50mg / L, the first fluorine-containing sludge saturated with absorption is replaced, the second fluorine-containing sludge is used as new first fluorine-containing sludge, the standby fluorine-containing sludge is used as new second fluorine-containing sludge, and the lye after absorbing the fluorine-containing flue gas is replaced with NaOH solution with the same concentration to continue the absorption of the fluorine-containing flue gas. The standby sludge is the same as the first fluorine-containing sludge and the second fluorine-containing sludge.

[0043] ​S4: Spraying the 0.5 mol / L NaOH solution absorbing the fluorine-containing flue gas in step S3 to the surface of the fluorine-containing sludge with the water content reduced to about 3%, the mass of the sprayed alkali solution being 4% of the mass of the fluorine-containing sludge saturated with the absorption, and then ball-milling the fluorine-containing sludge after the spraying for 1 h.

[0044] S5: Roasting the fluorine-containing sludge after the ball-milling in step S4 at 850°C for 3 h to obtain a roasted solid.

[0045] S6: After the roasted solid in step S5 is cooled to room temperature, the roasted solid is crushed to ≤0.15 mm (100 mesh or less) by using a crusher, and then the crushed roasted solid is placed in 0.5 mol / L dilute hydrochloric acid at a liquid-solid ratio of 4 (L / kg) for leaching and stirring for 1 h, hydrochloric acid is added during the leaching and stirring to maintain the pH of the solution at about 7, and then solid-liquid separation is performed after the leaching to obtain a leaching solid.

[0046] S7: The leaching solid in step S6 is placed in pure water at a liquid-solid ratio of 4 (L / kg) for stirring and washing for 1 h, and then solid-liquid separation is performed to obtain a solid, which is then dried to remove water to obtain a high-purity calcium fluoride product.

[0047] The fluorine-containing sludge used in step S3 of the example is a sludge formed by adding calcium hydroxide to high-concentration fluorine-containing wastewater generated in the process of wet recycling and processing waste lithium ion batteries, and the sludge contains, in addition to calcium fluoride, calcium hydroxide, calcium sulfate, calcium carbonate, sodium sulfate, a small amount of silicon-magnesium impurities, and some metal hydroxides, etc., and has a pH≥12.

[0048] Example 2

[0049] The difference from Example 1 is only that the flow rate of the fluorine-containing flue gas in step S3 is 35 L / h.

[0050] Example 3

[0051] The difference from Example 1 is only that the roasting temperature of the fluorine-containing sludge in step S5 is 750°C.

[0052] Comparative Example 1

[0053] The difference from Example 1 is only that steps S1-S3 are not performed, the fluorine-containing sludge in step S4 is dried by heating to have a water content of about 3%, and then the fluorine-containing sludge is sprayed with a NaOH solution that has not absorbed flue gas, ball-mixed, and then directly roasted and subjected to subsequent steps.

[0054] Comparative Example 2

[0055] The difference from Example 1 is only that the flow rate of the fluorine-containing flue gas in step S3 is 60 L / h.

[0056] Comparative Example 3

[0057] The difference from Example 1 is that the roasting temperature of the fluorine-containing sludge in step S5 is 550℃.

[0058] Test Example

[0059] The dry basis CaF2 content of the fluorine-containing sludge before and after treatment in each example is shown in Table 1:

[0060] Table 1 Dry basis CaF2 content of fluorine-containing sludge before and after treatment

[0061]

[0062] The dry basis CaF2 content of the calcium fluoride product in Examples 1 to 3 is above 90%, which reflects that the fluorine is effectively utilized in the recycling process of waste batteries. The XRD pattern of the fluorine-containing sludge after roasting and acid leaching in Example 1, which fully absorbs the fluorine-containing flue gas, is shown in Figure 4 . It can be seen that the purity of the product is high. The XRD pattern of the untreated fluorine-containing sludge is shown in Figure 2 . It can be seen that it contains more calcium sulfate and calcium carbonate impurities. In Comparative Example 1, the fluorine-containing sludge is not subjected to flue gas absorption and is directly roasted, and the removal effect of impurities such as calcium sulfate and calcium carbonate is not obvious, and there are more calcium impurities other than calcium fluoride, and the purity of calcium fluoride in the product is low, and the XRD pattern is shown in Figure 3 . In Comparative Example 2, the flow of fluorine-containing flue gas absorbed by the fluorine-containing sludge is too large, and more fluorine in the fluorine-containing flue gas enters the lye, and when the sludge is replaced, the fluorine-containing sludge does not fully absorb the fluorine-containing flue gas, and the removal effect of impurities such as calcium sulfate and calcium carbonate is not obvious, and there are more calcium impurities other than calcium fluoride, and the purity of calcium fluoride in the product is relatively low. In Comparative Example 3, the roasting temperature is low, and the phase transformation of calcium fluoride crystals is insufficient, and the product has no obvious impurity removal effect, and the purity of calcium fluoride in the product is relatively low.

[0063] The above has made a detailed description of the embodiments of the present application, but the present application is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the purpose of the present application. In addition, the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

Claims

1. A method for fluorine resource recovery during the recycling and processing of waste batteries, characterized in that, Includes the following steps: S1: Discharge the waste lithium-ion batteries and crush them. Pyrolyze the obtained positive electrode material to obtain the metal material to be recycled and fluorine-containing flue gas. S2: The fluorine-containing flue gas described in step S1 is sequentially passed into fluorine-containing sludge and alkaline solution for absorption; S3: When the fluorine-containing sludge in step S2 is saturated, the alkaline solution after absorbing the fluorine-containing flue gas in step S2 is sprayed onto the surface of the saturated fluorine-containing sludge, and then the sprayed fluorine-containing sludge is ball-milled, and the resulting ball-milled material is calcined to obtain a calcined solid. S4: The calcined solid described in step S3 is pulverized and then leached. After solid-liquid separation, the leached solid is obtained. The leached solid is then washed and dried to obtain calcium fluoride product. In step S2, the pH of the fluorine-containing sludge is ≥12, the dry basis percentage of CaF2 in the fluorine-containing sludge is 45%~65%, and the water content is 30%~50%; the flow rate of the fluorine-containing flue gas into the fluorine-containing sludge is 20~40 L / h; and / or, the alkaline solution is a 0.1~1 mol / L NaOH solution. In step S3, the amount of alkaline solution sprayed after absorbing the fluorine-containing flue gas is 3% to 8% of the mass of the saturated fluorine-containing sludge.

2. The method according to claim 1, characterized in that, In step S1, the pyrolysis temperature is 200~1000℃ and the time is 1-5h.

3. The method according to claim 1, characterized in that, In step S2, the fluorine-containing sludge includes a first-stage sludge and a second-stage sludge. The fluorine-containing flue gas is absorbed sequentially through the first-stage sludge, the second-stage sludge, and the alkaline solution. When the first-stage sludge is saturated, step S2 further includes: passing the fluorine-containing flue gas from step S1 sequentially through the second-stage sludge, the spare sludge, and the alkaline solution for absorption.

4. The method according to claim 1, characterized in that, In step S3, after the fluorine-containing sludge is saturated, the moisture content drops to 1%~5%; and / or, the ball milling time is 0.5~2h.

5. The method according to claim 1, characterized in that, The fluoride content in the alkaline solution after absorbing fluoride-containing flue gas is greater than or equal to 50 mg / L.

6. The method according to claim 1, characterized in that, In step S3, the calcination temperature is 650~1000℃ and the time is 1~4h.

7. The method according to claim 1, characterized in that, In step S4, the particle size of the calcined solid after pulverization is ≤0.15mm; and / or, the leaching reagent used in the leaching is hydrochloric acid, and the liquid-to-solid ratio of the leaching is 4~5L / kg; and / or, the pH of the solution is maintained at 5~8 during the leaching process; and / or, the leaching time is 0.5~2h.

8. The method according to claim 1, characterized in that, In step S4, the washing method is pulp washing, and the pulp washing process is as follows: the leached solid is mixed with water at a liquid-solid ratio of 4~5L / kg and stirred for 0.5~2h.

9. The application of the method according to any one of claims 1-8 in the recycling of waste lithium batteries.

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