Lithium bis (fluorosulfonyl) imide heavy slag treatment method

Abstract

The invention provides a lithium bis (fluorosulfonyl) imide heavy slag treatment method which comprises the following steps: reacting bis (fluorosulfonyl) imide heavy slag to be treated with an aqueous solution of an alkaline compound to obtain a reaction solution containing a salt compound and ammonia gas; and recovering the reaction liquid to obtain the salt compound. By means of the method, resource recycling can be conducted on the lithium bis (fluorosulfonyl) imide heavy slag, economic benefits are improved, and the method has important significance in promoting sustainable development and circular economy.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical recycling process and relates to a method for treating lithium bis(fluorosulfonyl)imide heavy slag. Background Art

[0002] The four key materials of lithium-ion batteries include positive electrode, negative electrode, electrolyte and separator. The electrolyte plays the role of transferring charge between positive and negative electrodes in the battery and is a key component of lithium-ion batteries. The electrolyte is generally composed of an organic solvent, an electrolyte salt and a small amount of additives. Among them, the electrolyte salt is an important component of the electrolyte. At present, lithium hexafluorophosphate has become the most important electrolyte lithium salt used in commercial lithium-ion batteries due to its high conductivity, but it has poor thermal stability and is easy to absorb water and decompose. Lithium bis(fluorosulfonyl)imide has the advantages of high conductivity, high chemical stability and high thermal stability, and has the potential to replace lithium hexafluorophosphate.

[0003] As the market demand for lithium bis(fluorosulfonyl)imide increases, the output of lithium bis(fluorosulfonyl)imide produced by enterprises is also increasing. At present, lithium bis(fluorosulfonyl)imide is usually produced using bis(fluorosulfonyl)imide and lithium-containing compounds as raw materials, but a large amount of bis(fluorosulfonyl)imide heavy residue is usually produced during the production process. Therefore, how to realize the resource recovery of bis(fluorosulfonyl)imide heavy residue is an urgent problem to be solved. Summary of the invention

[0004] In view of the above-mentioned defects, the present invention provides a method for treating lithium bis(fluorosulfonyl)imide heavy residue, which can be used to recycle the lithium bis(fluorosulfonyl)imide heavy residue.

[0005] The present invention provides a method for treating heavy slag of lithium bis(fluorosulfonyl)imide, comprising the following steps:

[0006] The bis(fluorosulfonyl)imide heavy residue to be treated is reacted with an aqueous solution of an alkaline compound to obtain a reaction solution including a salt compound and ammonia gas;

[0007] The reaction solution is recovered to obtain a salt compound.

[0008] Furthermore, the alkaline compound includes at least one of ammonia, oxides, hydroxides or carbonates of alkaline earth metals or alkali metals.

[0009] Furthermore, the molar ratio of the alkaline compound to the bis(fluorosulfonyl)imide in the bis(fluorosulfonyl)imide heavy residue is (6-10):1;

[0010] And / or, the mass concentration of the aqueous solution of the alkaline compound is 10 to 50 wt%;

[0011] And / or, the reaction time is 1 to 24 hours;

[0012] And / or, the reaction temperature is 80°C to 110°C.

[0013] Furthermore, during the reaction process, the reaction system is tested by ion chromatography, and when the reaction system contains no components of the bis(fluorosulfonyl)imide heavy residue, the reaction is stopped.

[0014] Furthermore, the recycling process includes:

[0015] The reaction liquid including the salt compound is subjected to a first solid-liquid separation to obtain a first filtrate and the salt compound.

[0016] Further, the first filtrate is subjected to a crystallization treatment, and the crystallization treatment comprises:

[0017] The first filtrate is used as a raw material liquid to participate in the reaction until the salt compound is precipitated, and then the reaction system is subjected to a second solid-liquid separation treatment to obtain a second filtrate and the salt compound.

[0018] Further, the alkaline compound is at least one of sodium hydroxide, sodium oxide, and sodium carbonate; after the first solid-liquid separation treatment, the salt compound includes sodium fluoride, and the first filtrate includes sodium sulfate; after the second solid-liquid separation treatment, the salt compound includes sodium sulfate, and the second filtrate includes sodium hydroxide and / or sodium carbonate;

[0019] Alternatively, the alkaline compound is at least one of potassium hydroxide, potassium oxide, and potassium carbonate, and after the first solid-liquid separation treatment, the first filtrate includes potassium sulfate and potassium fluoride, and after the second solid-liquid separation treatment, the salt compound includes potassium sulfate, and the second filtrate includes potassium fluoride;

[0020] Alternatively, the alkaline compound is at least one of calcium hydroxide, calcium oxide, and calcium carbonate, and after the first solid-liquid separation treatment, the salt compound includes calcium sulfate and calcium fluoride, and the first filtrate includes calcium hydroxide and / or calcium carbonate;

[0021] Alternatively, the alkaline compound is ammonia water and / or ammonium carbonate, and after the first solid-liquid separation treatment, the first filtrate includes ammonium sulfate and ammonium fluoride, and after the second solid-liquid separation treatment, the salt compound includes ammonium sulfate, and the second filtrate includes ammonium fluoride.

[0022] Furthermore, the salt compound is washed, and the washing liquid is combined into the first filtrate.

[0023] Furthermore, the method further comprises using the second filtrate to produce potassium fluoride;

[0024] Alternatively, the second filtrate is used to produce ammonium fluoride.

[0025] Furthermore, the mass percentage of bis(fluorosulfonyl)imide in the bis(fluorosulfonyl)imide heavy residue is not less than 95wt%.

[0026] The method for treating lithium bis(fluorosulfonyl)imide heavy residue of the present invention comprises the following steps: reacting the bis(fluorosulfonyl)imide heavy residue to be treated with an aqueous solution of an alkaline compound to obtain ammonia gas and a reaction liquid, and recovering the reaction liquid to obtain a salt compound, wherein the ammonia gas and the salt compound can be used as raw materials for various chemical productions, thereby realizing the resource recovery and utilization of the bis(fluorosulfonyl)imide heavy residue, bringing economic benefits while avoiding safety and environmental risks. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] The present invention provides a method for treating heavy slag of lithium bis(fluorosulfonyl)imide, comprising the following steps:

[0029] The bis(fluorosulfonyl)imide heavy residue to be treated is reacted with an aqueous solution of an alkaline compound to obtain a reaction solution including a salt compound and ammonia gas;

[0030] The reaction liquid is recovered to obtain a salt compound.

[0031] The bisfluorosulfonyl imide heavy residue in the present invention is prepared by purifying the produced bisfluorosulfonyl imide to remove impurities therein, and collecting the bisfluorosulfonyl imide by distillation to obtain the remaining components, which are the bisfluorosulfonyl imide heavy residue. The main components of the bisfluorosulfonyl imide heavy residue include bisfluorosulfonyl imide, fluorosulfonic acid, and fluoride salt, wherein the fluoride salt includes any one of sodium fluoride, potassium fluoride, and ammonium fluoride.

[0032] The present invention does not specifically limit the reaction temperature, reaction time, type of alkaline compound, molar ratio of alkaline compound to bisfluorosulfonyl imide in bisfluorosulfonyl imide heavy residue, and mass concentration of aqueous solution of alkaline compound, and it is only necessary to make the alkaline compound and bisfluorosulfonyl imide react fully.

[0033] The method for treating lithium bis(fluorosulfonyl)imide heavy residue in the invention is to react lithium bis(fluorosulfonyl)imide heavy residue with an aqueous solution of an alkaline compound, and the bis(fluorosulfonyl)imide and fluorosulfonic acid in the heavy residue are hydrolyzed. The hydrolysis products of bis(fluorosulfonyl)imide are sulfuric acid, ammonium bisulfate and hydrofluoric acid, and the hydrolysis products of fluorosulfonic acid are sulfuric acid and hydrofluoric acid. These hydrolysis products further react with an alkaline compound to obtain a reaction solution and ammonia. The reaction solution includes salt compounds sulfate and fluoride salt. The reaction solution is recycled to obtain salt compounds. The reaction principle is shown in Formula 1, Formula 2, Formula 3, Formula 4 and Formula 5. The obtained ammonia and salt compounds are collected and used as raw materials in different chemical productions, which can not only reduce the discharge of chemical waste and reduce environmental pollution, but also realize the resource recycling of bis(fluorosulfonyl)imide heavy residue, improve economic benefits, and achieve the unity of economic and environmental benefits, which is of great significance to promoting sustainable development and circular economy.

[0034]

[0035] NH4HSO4+2OH - →SO4 2- +NH3+H2O Formula 3

[0036]

[0037] HF+OH - →F - +H2O Formula 5

[0038] In a specific embodiment, the basic compound includes at least one of ammonia, an oxide, hydroxide or carbonate of an alkaline earth metal or an alkali metal. When the basic compound includes two or more of the aforementioned compounds, the present invention does not specifically limit the ratio between the compounds.

[0039] The present invention does not specifically limit the types of alkaline earth metals and alkali metals and the sources of the alkaline compounds. For example, commercially available products or products prepared by conventional preparation methods well known to those skilled in the art may be used.

[0040] In a specific embodiment, the molar ratio of the basic compound to the bis(fluorosulfonyl)imide in the bis(fluorosulfonyl)imide heavy residue is (6-10): 1. Within this range, the basic compound is conducive to fully reacting with the bis(fluorosulfonyl)imide heavy residue, so that the bis(fluorosulfonyl)imide and fluorosulfonic acid in the heavy residue are reacted to a greater extent, thereby improving the treatment effect.

[0041] In a specific embodiment, the mass concentration of the aqueous solution of the alkaline compound is 10 to 50 wt %. When the mass concentration of the aqueous solution of the alkaline compound is within the above range, a better treatment effect can be achieved, which can not only fully hydrolyze the bis(fluorosulfonyl)imide and fluorosulfonic acid, but also enable the hydrolysis product to react better with the alkaline compound and be completely converted into ammonia and salt compounds; at the same time, while ensuring complete reaction, the amount of the alkaline compound can be reduced to avoid waste and reduce costs.

[0042] In a specific embodiment, the reaction temperature is 80° C. to 110° C. Within this range, it is helpful to fully hydrolyze bis(fluorosulfonyl)imide and fluorosulfonic acid, thereby promoting the reaction of the hydrolysis product with the alkaline compound, and further improving the treatment effect.

[0043] In a specific embodiment, the reaction time is 1 to 24 hours. Within this range, the bis(fluorosulfonyl)imide heavy residue can be ensured to fully react with the alkaline compound, and the treatment time can be controlled within an appropriate range, which is conducive to improving the treatment efficiency.

[0044] In a specific embodiment, during the reaction process, the reaction system is subjected to an ion chromatography test, and when there is no component of the bisfluorosulfonyl imide heavy residue in the reaction system, the reaction is stopped. By using ion chromatography during the reaction process, the content of bisfluorosulfonyl imide and fluorosulfonic acid in the reaction system can be monitored to ensure that the bisfluorosulfonyl imide heavy residue component in the reaction system has been completely reacted at the end of the reaction, thereby improving the treatment effect.

[0045] In a specific embodiment, the recovery process includes: performing a first solid-liquid separation on the reaction liquid including the salt compound to obtain a first filtrate and the salt compound.

[0046] It is understood that the salt compound obtained after the reaction may contain components that are insoluble in the reaction solution.

[0047] Specifically, when the alkaline compound is at least one of sodium hydroxide, sodium oxide, and sodium carbonate, the heavy residue of bis(fluorosulfonyl)imide is treated, and after the reaction is completed, gaseous ammonia and / or carbon dioxide, as well as precipitated sodium fluoride and water-soluble sodium sulfate present in the reaction system are generated. The gaseous ammonia and / or carbon dioxide are collected, and the reaction system is subjected to a first solid-liquid separation to obtain the salt compound sodium fluoride.

[0048] When the alkaline compound is at least one of calcium hydroxide, calcium oxide and calcium carbonate, the heavy residue of bis(fluorosulfonyl)imide is treated, and after the reaction is completed, gaseous ammonia and / or carbon dioxide, as well as precipitated calcium fluoride and calcium sulfate present in the reaction system are generated, and salt compounds of calcium fluoride and calcium sulfate can be obtained through the first solid-liquid separation. Among them, the mixture of calcium fluoride and calcium sulfate can be used to prepare cement.

[0049] It can be understood that in order to completely react the bis(fluorosulfonyl)imide and fluorosulfonic acid in the bis(fluorosulfonyl)imide heavy residue, it is often necessary to add an excess of alkaline compounds during the actual reaction process. Therefore, the first filtrate also includes unreacted alkaline compounds. For example, when the alkaline compound is at least one of sodium hydroxide, sodium oxide, and sodium carbonate, the first filtrate also includes sodium hydroxide and / or sodium carbonate; when the alkaline compound is at least one of calcium hydroxide, calcium oxide, and calcium carbonate, the first filtrate also includes calcium hydroxide and / or calcium carbonate.

[0050] In a specific embodiment, the crystallization treatment includes: allowing the first filtrate to participate in the reaction as a raw material liquid until the salt compound is precipitated, and then performing a second solid-liquid separation treatment on the reaction system to obtain a second filtrate and the salt compound.

[0051] It is understandable that the salt compound obtained by the reaction may also contain components soluble in the reaction liquid. In order to obtain the salt compound soluble in the reaction liquid, after the first solid-liquid separation is performed to remove the salt compound insoluble in the reaction liquid, the first filtrate needs to be crystallized to separate the salt compound soluble in the reaction liquid.

[0052] The raw material liquid in the present invention refers to the liquid used for the reaction between the bis(fluorosulfonyl)imide heavy residue to be treated and the alkaline compound.

[0053] Specifically, when the alkaline compound is at least one of sodium hydroxide, sodium oxide, and sodium carbonate, after the reaction system obtained after the treatment of the previous batch of bis(fluorosulfonyl)imide heavy slag is subjected to the first solid-liquid separation treatment, a first filtrate containing sodium sulfate can be obtained; by using the first filtrate obtained from the previous batch as a raw material liquid for the next batch of bis(fluorosulfonyl)imide heavy slag for reaction, gaseous ammonia and / or carbon dioxide, as well as precipitated sodium fluoride and sodium sulfate soluble in water present in the reaction system can be generated, and the reaction system is subjected to the first solid-liquid separation to obtain the salt compound sodium fluoride and the first filtrate containing sodium sulfate; the cycle is repeated, that is, by using the first filtrate containing sodium sulfate obtained from the previous batch for the next batch of bis(fluorosulfonyl)imide heavy slag, as the number of cycles increases, the mass concentration of sodium sulfate in the first filtrate gradually increases, the temperature of the reaction system is reduced to 20-25° C., sodium sulfate crystals will precipitate, and then the second solid-liquid separation is performed to obtain the salt compound sodium sulfate.

[0054] When the alkaline compound is at least one of potassium hydroxide, potassium oxide, and potassium carbonate, after the treatment of the previous batch of bis(fluorosulfonyl)imide heavy residue is completed, gaseous ammonia and / or carbon dioxide, and potassium fluoride and potassium sulfate that are easily soluble in water present in the reaction system are obtained, and the reaction system is subjected to a first solid-liquid separation treatment to obtain a first filtrate including potassium fluoride and potassium sulfate; the first filtrate obtained from the previous batch is used as a raw material liquid for the reaction in the treatment of the next batch of bis(fluorosulfonyl)imide heavy residue, and gaseous ammonia and / or carbon dioxide, and potassium fluoride and potassium sulfate that are easily soluble in water present in the reaction system can be generated, and the reaction system is subjected to a first solid-liquid separation treatment to obtain a first filtrate including potassium fluoride and potassium sulfate; and the first filtrate obtained from the previous batch is used as a raw material liquid for the reaction in the treatment of the next batch of bis(fluorosulfonyl)imide heavy residue. The system performs a first solid-liquid separation to obtain a first filtrate comprising potassium fluoride and potassium sulfate; the process is repeated, i.e., the first filtrate comprising potassium fluoride and potassium sulfate obtained in the previous batch is used in the treatment of the next batch of bis(fluorosulfonyl)imide heavy residues, and as the number of cycles increases, the mass concentrations of potassium fluoride and potassium sulfate in the first filtrate gradually increase, and by utilizing the solubility difference between potassium fluoride and potassium sulfate, when the mass concentration of potassium fluoride in the first filtrate is 25-30wt%, the temperature of the reaction system is reduced to 20-25°C, potassium sulfate crystals are precipitated, and a second solid-liquid separation is performed to obtain salt compound potassium sulfate crystals and a second filtrate comprising potassium fluoride.

[0055] When the alkaline compound is ammonia water and / or ammonium carbonate, after the treatment of the previous batch of bis(fluorosulfonyl)imide heavy residue is completed, gaseous ammonia and / or carbon dioxide, and ammonium fluoride and ammonium sulfate that are easily soluble in water present in the reaction system are obtained, and the reaction system is subjected to a first solid-liquid separation treatment to obtain a first filtrate including ammonium fluoride and ammonium sulfate; by using the first filtrate obtained from the previous batch as a raw material liquid for reaction in the treatment of the next batch of bis(fluorosulfonyl)imide heavy residue, gaseous ammonia and / or carbon dioxide, and ammonium fluoride and ammonium sulfate that are easily soluble in water present in the reaction system can be generated, and the reaction system is subjected to a first solid-liquid separation treatment. The invention discloses a method for preparing a first filtrate comprising ammonium fluoride and ammonium sulfate by performing solid-liquid separation, and performing a second solid-liquid separation, i.e., using the first filtrate comprising ammonium fluoride and ammonium sulfate obtained in the previous batch for treating the next batch of bis(fluorosulfonyl)imide heavy residues. With the increase of the number of cycles, the mass concentrations of ammonium fluoride and ammonium sulfate in the first filtrate gradually increase. By utilizing the difference in solubility between ammonium fluoride and ammonium sulfate, when the mass concentration of ammonium fluoride in the first filtrate is 25-30wt%, the temperature of the reaction system is lowered to 20-25°C, ammonium sulfate crystals are precipitated, and a second solid-liquid separation is performed to obtain salt compound ammonium sulfate crystals and a second filtrate comprising ammonium fluoride.

[0056] It can be understood that the alkaline compound is consumed to a certain extent during the reaction process, so the mass content of the alkaline compound in the filtrate after solid-liquid separation is relatively low. When the first filtrate is used as the raw material liquid to participate in the reaction, it is necessary to add alkaline compounds to the filtrate to ensure that the heavy residue of bis(fluorosulfonyl)imide is fully reacted to improve the treatment effect.

[0057] In a specific embodiment, the alkaline compound is at least one of sodium hydroxide, sodium oxide, and sodium carbonate, and after the first solid-liquid separation treatment, the salt compound includes sodium fluoride, and the first filtrate includes sodium sulfate, and after the second solid-liquid separation treatment, the salt compound includes sodium sulfate, and the second filtrate includes sodium hydroxide and / or sodium carbonate;

[0058] Alternatively, the alkaline compound is at least one of potassium hydroxide, potassium oxide, and potassium carbonate, and after the first solid-liquid separation treatment, the first filtrate includes potassium sulfate and potassium fluoride, and after the second solid-liquid separation treatment, the salt compound includes potassium sulfate, and the second filtrate includes potassium fluoride;

[0059] Alternatively, the alkaline compound is at least one of calcium hydroxide, calcium oxide, and calcium carbonate, and after the first solid-liquid separation treatment, the salt compound includes calcium sulfate and calcium fluoride, and the first filtrate includes calcium hydroxide and / or calcium carbonate;

[0060] Alternatively, the alkaline compound is ammonia water and / or ammonium carbonate, and after the first solid-liquid separation treatment, the first filtrate includes ammonium sulfate and ammonium fluoride, and after the second solid-liquid separation treatment, the salt compound includes ammonium sulfate and the second filtrate includes ammonium fluoride.

[0061] Through the above operation, the salt compounds obtained can be used as raw materials in different chemical productions, thereby realizing the resource recovery of bis(fluorosulfonyl)imide heavy residues and reducing environmental pollution.

[0062] In a specific embodiment, the salt compound is washed, and the washing liquid is combined with the first filtrate. By washing the salt compound to remove impurities therein, and combining the washing liquid with the first filtrate as a raw material liquid to participate in the reaction, not only the purity of the salt compound can be improved, but also the waste liquid generated during the treatment process can be recycled, thereby further reducing costs and reducing environmental pollution.

[0063] In a specific embodiment, it further comprises using the second filtrate to produce potassium fluoride;

[0064] Alternatively, the second filtrate is utilized to produce ammonium fluoride.

[0065] Specifically, when the alkaline compound is at least one of potassium oxide, hydroxide and potassium carbonate, the second filtrate includes potassium fluoride, and the filtrate can be used to prepare a potassium fluoride product.

[0066] The present invention does not impose any particular limitation on the method for preparing the potassium fluoride product, and the product can be prepared by conventional methods.

[0067] When the alkaline compound is aqueous ammonia and / or ammonium carbonate, the second filtrate includes ammonium fluoride, and the filtrate can be used to prepare an ammonium fluoride product.

[0068] The present invention does not impose any particular limitation on the method for preparing the ammonium fluoride product, and the product can be prepared by a conventional method.

[0069] Potassium fluoride or ammonium fluoride products can be obtained by further processing the second filtrate, and can also be used as raw materials for other productions, thereby achieving economic maximization.

[0070] In a specific embodiment, the method further includes absorbing ammonia.

[0071] When the alkaline compound is at least one of ammonia water, an oxide or hydroxide of an alkaline earth metal or an alkali metal, ammonia gas can be obtained after the reaction is completed. At this time, pure water can be used to absorb the ammonia gas to obtain ammonia water. Since ammonia water has multiple uses as an important reagent, it can be used as an analytical reagent, an alkaline disinfectant, a neutralizer, a detergent, etc., so the economic benefit can be further improved. Preferably, the mass concentration of ammonia water is 20 to 35wt%.

[0072] When the alkaline compound includes at least one of ammonium carbonate, alkaline earth metal or alkali metal carbonates, the gas phase generated after the reaction includes ammonia and carbon dioxide at the same time. At this time, pure water can also be used to absorb the gas phase obtained by the reaction. Since carbon dioxide is more difficult to dissolve in water than ammonia at normal temperature and pressure, the ammonia water obtained after absorption by pure water can be used in fields where purity requirements are not too high.

[0073] In a specific embodiment, the mass percentage of bis(fluorosulfonyl)imide in the bis(fluorosulfonyl)imide heavy slag is not less than 95wt%. Within this range, not only a better treatment effect can be achieved, but also the cost increase caused by too low bis(fluorosulfonyl)imide content in the heavy slag can be avoided, which has higher economic efficiency.

[0074] The following is a detailed introduction to the method for treating lithium bis(fluorosulfonyl)imide heavy residue of the present invention through specific examples.

[0075] Example 1

[0076] 500 g of the first batch of bisfluorosulfonyl imide heavy residue (the mass percentage of bisfluorosulfonyl imide is 95 wt%) is mixed with 6.3 kg of sodium hydroxide aqueous solution (mass concentration is 10 wt%), wherein the molar ratio of the alkaline compound to the bisfluorosulfonyl imide in the bisfluorosulfonyl imide heavy residue is 6:1, and the mixture is stirred evenly. The temperature is raised to 100° C. for reaction. During the reaction, the reaction system is tested by ion chromatography. When there is no component of the bisfluorosulfonyl imide heavy residue in the reaction system, the reaction is stopped. The reaction time is 5 hours to obtain a reaction system and ammonia. Pure water is used to absorb the ammonia to obtain an ammonia aqueous solution with a concentration of 25 wt%. The reaction system is filtered to obtain a filter cake of sodium fluoride and a first filtrate including sodium sulfate. The filter cake is washed to obtain a washing liquid. The first filtrate is combined with the washing liquid, and sodium hydroxide is added thereto. The first filtrate is used as the raw material liquid for the next batch to participate in the reaction, and the cycle is repeated for multiple times. During the reaction, the concentration of sodium sulfate gradually increases. When the concentration of sodium sulfate in the filtrate is higher than its solubility at 20°C, sodium sulfate crystals precipitate and sodium sulfate is obtained after solid-liquid separation. The liquid phase obtained after separation continues to participate in the reaction as a raw material liquid.

[0077] Example 2

[0078] 1000g of the first batch of bis(fluorosulfonyl)imide heavy residue (the mass percentage of bis(fluorosulfonyl)imide is 96wt%) was mixed with 15.8kg of potassium hydroxide aqueous solution (mass concentration is 15wt%), wherein the molar ratio of the alkaline compound to the bis(fluorosulfonyl)imide in the bis(fluorosulfonyl)imide heavy residue was 8:1, stirred evenly, the temperature was raised to 80°C for reaction, during the reaction, the reaction system was subjected to ion chromatography test, when there was no component of the bis(fluorosulfonyl)imide heavy residue in the reaction system, the reaction was stopped, the reaction time was 6h, and the reaction system and ammonia were obtained, and the reaction system was subjected to the first solid-liquid reaction. The first filtrate including potassium fluoride and potassium sulfate can be obtained by separation treatment; the first filtrate obtained in the first batch is used as a raw material liquid for the next batch of bis(fluorosulfonyl)imide heavy residue treatment for reaction, and the reaction is repeated multiple times; as the reaction proceeds, the mass concentration of potassium fluoride and potassium sulfate in the first filtrate gradually increases, and the solubility difference between potassium fluoride and potassium sulfate is used. When the mass concentration of potassium fluoride in the first filtrate is 25-30wt%, the temperature of the reaction system is reduced to 20°C, potassium sulfate crystals are precipitated, and a second solid-liquid separation is performed to obtain salt compound potassium sulfate crystals and a second filtrate including potassium fluoride. A 21wt% ammonia solution is obtained by absorbing ammonia gas with pure water. The second filtrate is further treated, and a hydrogen fluoride aqueous solution is added until the filtrate is neutral to obtain a potassium fluoride product.

[0079] Example 3

[0080] 1000g of the first batch of bisfluorosulfonyl imide heavy residue (the mass percentage of bisfluorosulfonyl imide is 95wt%) is mixed with 24.7kg of calcium hydroxide aqueous solution (mass concentration is 11wt%), wherein the molar ratio of the alkaline compound to the bisfluorosulfonyl imide in the bisfluorosulfonyl imide heavy residue is 7:1, stirred evenly, the temperature is raised to 110°C for reaction, during the reaction, the reaction system is tested by ion chromatography, when there is no component of the bisfluorosulfonyl imide heavy residue in the reaction system, the reaction is stopped, the reaction time is 3h, gaseous ammonia and precipitated calcium fluoride and calcium sulfate present in the reaction system are generated, and pure water is used to absorb ammonia to obtain an ammonia aqueous solution with a concentration of 18wt%. The reaction solution is filtered to obtain a filter cake including calcium sulfate and calcium fluoride and a first filtrate, the calcium sulfate and calcium fluoride are washed with water to obtain a washing liquid, the washing liquid is mixed with the first filtrate and calcium hydroxide is added thereto, and it can continue to participate in the reaction as a raw material liquid; the mixture of calcium sulfate and calcium fluoride can be used to prepare cement.

[0081] Example 4

[0082] 1000g of the first batch of bis(fluorosulfonyl)imide heavy residue (the mass percentage of bis(fluorosulfonyl)imide is 96wt%) is mixed with 6kg of ammonia solution (mass concentration is 15wt%), wherein the molar ratio of the alkaline compound to the bis(fluorosulfonyl)imide in the bis(fluorosulfonyl)imide heavy residue is 8:1, and the mixture is stirred evenly. The temperature is raised to 80°C for reaction. During the reaction, the reaction system is subjected to ion chromatography test. When there is no component of the bis(fluorosulfonyl)imide heavy residue in the reaction system, the reaction is stopped. The reaction time is 6h to obtain a reaction system and ammonia gas. The reaction system is subjected to a first solid-liquid separation process. The first filtrate including ammonium fluoride and ammonium sulfate can be obtained by treating the first filtrate obtained in the first batch as a raw material liquid for the next batch of bis(fluorosulfonyl)imide heavy residue treatment for reaction, and the reaction is repeated for multiple times; as the reaction proceeds, the mass concentration of ammonium fluoride and ammonium sulfate in the first filtrate gradually increases, and by utilizing the difference in solubility between ammonium fluoride and ammonium sulfate, when the mass concentration of ammonium fluoride in the first filtrate is 25-30wt%, the temperature of the reaction system is lowered to 20°C, ammonium sulfate crystals are precipitated, and a second solid-liquid separation is performed to obtain salt compound ammonium sulfate crystals and a second filtrate including ammonium fluoride. A 21wt% ammonia solution is obtained by absorbing ammonia gas with pure water. The filtrate is further treated, and a hydrogen fluoride aqueous solution is added until the filtrate is neutral to obtain an ammonium fluoride product.

[0083] Example 5

[0084] 944.4 g of the first batch of bis(fluorosulfonyl)imide heavy residue (the mass percentage of bis(fluorosulfonyl)imide is 95 wt%) is mixed with 6.3 kg of sodium carbonate aqueous solution (mass concentration is 50 wt%), wherein the molar ratio of the alkaline compound to the bis(fluorosulfonyl)imide in the bis(fluorosulfonyl)imide heavy residue is 6:1, and the mixture is stirred evenly. The temperature is raised to 85° C. for reaction. During the reaction, the reaction system is tested by ion chromatography. When there is no component of the bis(fluorosulfonyl)imide heavy residue in the reaction system, the reaction is stopped. The reaction time is 5 hours to obtain a reaction system, ammonia and carbon dioxide. The reaction system is filtered to obtain a filter cake of sodium fluoride and a first filtrate including sodium sulfate; the filter cake is washed to obtain a washing liquid, the first filtrate is combined with the washing liquid, and sodium carbonate is added thereto, and the filtrate is used as the raw material liquid for the next batch to participate in the reaction, and the cycle is repeated for multiple times. During the reaction, the concentration of sodium sulfate gradually increases. When the concentration of sodium sulfate in the filtrate is higher than its solubility at 20°C, sodium sulfate crystals are precipitated and solid-liquid separation is performed to obtain sodium sulfate. The liquid phase obtained after separation continues to participate in the reaction as a raw material liquid. A mixed gas of ammonia and carbon dioxide is passed into pure water, and ammonia is completely absorbed and a small amount of carbon dioxide is absorbed. The solution after absorption is an ammonia solution with slightly lower purity, which can be used in fields such as metal surface degreasing, rust removal, cleaning and polishing, which have lower requirements for ammonia purity.

[0085] Example 6

[0086] 1078g of the first batch of bis(fluorosulfonyl)imide heavy residue (the mass percentage of bis(fluorosulfonyl)imide is 96wt%) was mixed with 15.8kg of potassium carbonate aqueous solution (the mass concentration is 30wt%), wherein the molar ratio of the alkaline compound to the bis(fluorosulfonyl)imide in the bis(fluorosulfonyl)imide heavy residue was 6:1, and the mixture was stirred evenly. The temperature was raised to 90°C for reaction. During the reaction, the reaction system was subjected to ion chromatography test. When there was no component of the bis(fluorosulfonyl)imide heavy residue in the reaction system, the reaction was stopped. The reaction time was 12h to obtain the reaction system, ammonia and carbon dioxide. The reaction system was subjected to the first Solid-liquid separation treatment can obtain a first filtrate including potassium fluoride and potassium sulfate; the first filtrate obtained from the first batch is used as a raw material liquid for the next batch of bis(fluorosulfonyl)imide heavy residue treatment for reaction, and the reaction is repeated multiple times; as the reaction proceeds, the mass concentration of potassium fluoride and potassium sulfate in the first filtrate gradually increases, and the difference in solubility between potassium fluoride and potassium sulfate is used. When the mass concentration of potassium fluoride in the first filtrate is 25-30wt%, the temperature of the reaction system is reduced to 20°C, potassium sulfate crystals are precipitated, and a second solid-liquid separation is performed to obtain salt compound potassium sulfate crystals and a second filtrate including potassium fluoride. The second filtrate is further treated, and a hydrogen fluoride aqueous solution is added until the filtrate is neutral to obtain a potassium fluoride product. The mixed gas of ammonia and carbon dioxide is passed into pure water, the ammonia is completely absorbed, and a small amount of carbon dioxide is absorbed. The solution after absorption is an ammonia solution with slightly lower purity, which can be used in fields such as metal surface degreasing, rust removal, cleaning and polishing, which have lower requirements for ammonia purity.

[0087] Example 7

[0088] The first batch of 2016g of bisfluorosulfonyl imide heavy slag (the mass percentage of bisfluorosulfonyl imide is 95wt%) is mixed with 24.7kg of calcium carbonate aqueous solution (mass concentration is 30wt%), wherein the molar ratio of the alkaline compound to the bisfluorosulfonyl imide in the bisfluorosulfonyl imide heavy slag is 7:1, and the mixture is stirred evenly. The temperature is raised to 95°C for reaction. During the reaction, the reaction system is subjected to ion chromatography test. When there is no component of the bisfluorosulfonyl imide heavy slag in the reaction system, the reaction is stopped. The reaction time is 18h, and gaseous ammonia and carbon dioxide are generated, as well as precipitated calcium fluoride and calcium sulfate present in the reaction system. The reaction liquid is filtered to obtain a filter cake and a filtrate including calcium sulfate and calcium fluoride, the calcium sulfate and calcium fluoride are washed with water to obtain a washing liquid, the washing liquid is mixed with the filtrate and calcium hydroxide is added thereto, and the washing liquid can continue to participate in the reaction as a raw material liquid; the mixture of calcium sulfate and calcium fluoride can be used to prepare cement; the mixed gas of ammonia and carbon dioxide is introduced into pure water, the ammonia is completely absorbed, and a small amount of carbon dioxide is absorbed, and the solution after absorption is an ammonia solution with slightly lower purity, which can be used in fields such as degreasing, rust removal, cleaning and polishing of metal surfaces, which have lower requirements on the purity of ammonia water.

[0089] Example 8

[0090] 235.8 g of the first batch of bis(fluorosulfonyl)imide heavy residue (the mass percentage of bis(fluorosulfonyl)imide is 96 wt%) is mixed with 6 kg of ammonium carbonate solution (the mass concentration is 15 wt%), wherein the molar ratio of the alkaline compound to the bis(fluorosulfonyl)imide in the bis(fluorosulfonyl)imide heavy residue is 7.5:1, and the mixture is stirred evenly. The temperature is raised to 105°C for reaction. During the reaction, the reaction system is subjected to ion chromatography test. When there is no component of the bis(fluorosulfonyl)imide heavy residue in the reaction system, the reaction is stopped. The reaction time is 24 h to obtain the reaction system, ammonia and carbon dioxide. The reaction system is subjected to the first Solid-liquid separation treatment can obtain a first filtrate including ammonium fluoride and ammonium sulfate; the first filtrate obtained in the first batch is used as a raw material liquid for the next batch of bis(fluorosulfonyl)imide heavy residue treatment for reaction, and the cycle is repeated multiple times; as the reaction proceeds, the mass concentration of ammonium fluoride and ammonium sulfate in the first filtrate gradually increases, and the solubility difference between ammonium fluoride and ammonium sulfate is used. When the mass concentration of ammonium fluoride in the first filtrate is 25-30wt%, the temperature of the reaction system is reduced to 20°C, ammonium sulfate crystals are precipitated, and a second solid-liquid separation is performed to obtain salt compound ammonium sulfate crystals and a second filtrate including ammonium fluoride. The second filtrate is further treated, and a hydrogen fluoride aqueous solution is added until the filtrate is neutral to obtain an ammonium fluoride product. The mixed gas of ammonia and carbon dioxide is passed into pure water, the ammonia is completely absorbed, and a small amount of carbon dioxide is absorbed. The solution after absorption is an ammonia solution with slightly lower purity, which can be used in fields such as metal surface degreasing, rust removal, cleaning and polishing, etc., which have lower requirements for ammonia purity.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for treating heavy slag of lithium bis(fluorosulfonyl)imide, characterized in that: The following steps are involved: The bis(fluorosulfonyl)imide heavy residue to be treated is reacted with an aqueous solution of an alkaline compound to obtain a reaction solution including a salt compound and ammonia gas; The reaction solution is recovered to obtain a salt compound.

2. The method for treating heavy slag of lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that: The alkaline compound includes at least one of ammonia, an oxide, a hydroxide or a carbonate of an alkaline earth metal or an alkali metal.

3. The method for treating heavy slag of lithium bis(fluorosulfonyl)imide according to claim 1 or 2, characterized in that: The molar ratio of the basic compound to the bis(fluorosulfonyl)imide in the bis(fluorosulfonyl)imide heavy residue is 6 to 10):1; And / or, the mass concentration of the aqueous solution of the alkaline compound is 10 to 50 wt%; And / or, the reaction time is 1h to 24h; And / or, the reaction temperature is 80°C to 110°C.

4. The method for treating heavy slag of lithium bis(fluorosulfonyl)imide according to any one of claims 1 to 3, characterized in that: During the reaction, the reaction system was tested by ion chromatography, and when no component of the bis(fluorosulfonyl)imide heavy residue was found in the reaction system, the reaction was stopped.

5. The method for treating heavy slag of lithium bis(fluorosulfonyl)imide according to any one of claims 1 to 4, characterized in that: The recycling process includes: The reaction liquid including the salt compound is subjected to a first solid-liquid separation to obtain a first filtrate and the salt compound.

6. The method for treating heavy slag of lithium bis(fluorosulfonyl)imide according to claim 5, characterized in that: The first filtrate is subjected to a crystallization treatment, wherein the crystallization treatment comprises: The first filtrate is used as a raw material liquid to participate in the reaction until the salt compound is precipitated, and then the reaction system is subjected to a second solid-liquid separation treatment to obtain a second filtrate and the salt compound.

7. The method for treating heavy slag of lithium bis(fluorosulfonyl)imide according to claim 6, characterized in that: The alkaline compound is at least one of sodium hydroxide, sodium oxide, and sodium carbonate; after the first solid-liquid separation treatment, the salt compound includes sodium fluoride, and the first filtrate includes sodium sulfate; after the second solid-liquid separation treatment, the salt compound includes sodium sulfate, and the second filtrate includes sodium hydroxide and / or sodium carbonate; Alternatively, the alkaline compound is at least one of potassium hydroxide, potassium oxide, and potassium carbonate, and after the first solid-liquid separation treatment, the first filtrate includes potassium sulfate and potassium fluoride, and after the second solid-liquid separation treatment, the salt compound includes potassium sulfate, and the second filtrate includes potassium fluoride; Alternatively, the alkaline compound is at least one of calcium hydroxide, calcium oxide, and calcium carbonate, and after the first solid-liquid separation treatment, the salt compound includes calcium sulfate and calcium fluoride, and the first filtrate includes calcium hydroxide and / or calcium carbonate; Alternatively, the alkaline compound is ammonia water and / or ammonium carbonate, and after the first solid-liquid separation treatment, the first filtrate includes ammonium sulfate and ammonium fluoride, and after the second solid-liquid separation treatment, the salt compound includes ammonium sulfate, and the second filtrate includes ammonium fluoride.

8. The method for treating heavy slag of lithium bis(fluorosulfonyl)imide according to claim 6 or 7, characterized in that: The salt compound is washed, and the washing liquid is combined into the first filtrate.

9. The method for treating heavy slag of lithium bis(fluorosulfonyl)imide according to any one of claims 6 to 8, characterized in that: Also included is using the second filtrate to produce potassium fluoride; Alternatively, the second filtrate is used to produce ammonium fluoride.

10. The method for treating heavy slag of lithium bis(fluorosulfonyl)imide according to any one of claims 1 to 9, characterized in that: The mass percentage of bis(fluorosulfonyl)imide in the bis(fluorosulfonyl)imide heavy residue is not less than 95wt%.

Images