Novel recovery treatment process of fluoroethylene carbonate byproduct mixed potassium salt

Abstract

The invention relates to the technical field of lithium battery electrolyte additives, in particular to a novel fluoroethylene carbonate byproduct mixed potassium salt recovery treatment process which comprises the following steps: S1, byproduct mixed potassium salt dissolution: the byproduct mixed potassium salt and water are mixed and dissolved to obtain a salt solution; s2, salt liquid filtration: filtering the salt liquid to obtain filtrate and filter residues; s3, double-calcium-source synergistic one-step oxidation precipitation: adding a calcium source A and a calcium source B into the filtrate, heating, stirring and filtering to obtain filtrate and filter residues; s4, concentrating and crystallizing the filtrate: concentrating and crystallizing the filtrate obtained in S3 to obtain potassium chloride; the method has the advantages that the recovery step of the fluoroethylene carbonate byproduct mixed potassium salt is simplified, and the purity of the recovered potassium chloride is improved.

Description

Technical Field

[0001] The present application relates to the technical field of lithium battery electrolyte additives, and in particular to a novel process for recovering and treating mixed potassium salts produced as a by-product of fluoroethylene carbonate. Background Art

[0002] Fluoroethylene carbonate (FEC) is a widely used electrolyte additive with excellent performance, playing a key role in improving battery performance. Due to its unique molecular structure, FEC can form a tightly packed, high-performance solid electrolyte interface (SEI) during battery operation. This low-resistance membrane can reduce battery impedance, inhibit partial electrolyte decomposition, and enhance the room-temperature capacity, cycling stability, and thermal stability of lithium-ion batteries at the same rate, effectively extending their service life.

[0003] The main process of industrial fluorocarbonate is to take chloroethylene carbonate as raw material, and Potassium fluoride, as fluorinating agent, is produced as reaction solvent with dimethyl carbonate.And in order to improve the yield of fluorocarbonate, the feeding intake of Potassium fluoride is often excessive.Therefore, in the production process of fluorocarbonate, a large amount of dark brown mixed waste salts can be produced, except a large amount of Repone K, also contain impurities such as carbonates, polycarbonates, charred product and tar that side reaction produces.If these fluorine-containing mixed potassium salts directly handle as "production solid waste", not only can bring great pressure to environmental protection, but also can cause the waste of resources, cause producing fluorocarbonate production cost higher.

[0004] Currently, the main methods for treating such fluorine-containing mixed potassium salts are calcium salt precipitation and high-temperature decarbonization. The calcium salt precipitation method first dissolves the salt to remove water-insoluble organic matter, then separates the potassium fluoride and potassium chloride from the filtrate through calcium precipitation, filtration, concentration, and evaporation and crystallization. The high-temperature decarbonization process first incinerates the organic matter, carbonized products, and tar, then separates the potassium fluoride and potassium chloride through dissolution, concentration, and crystallization. However, in actual implementation, there are still certain shortcomings.

[0005] As disclosed in the patent for invention of publication number CN116060777A, a production process for improving the purity of potassium chloride, a byproduct of fluoroethylene carbonate, is first prepared by heating and reducing pressure to dry the material, dissolving the material and removing the organic impurities in the solid waste by filter pressing, then adding an inorganic acid to regulate the pH of the filtrate, oxidizing and decomposing the organic matter with a strong oxidant and a catalyst, and filtering after decolorizing with activated carbon, and then filtering after removing fluoride ions by precipitation with a calcium salt reagent, and finally obtaining potassium chloride by condensing and crystallizing the filtrate. However, the process involves multiple steps (such as regulating pH, oxidative decomposition, adsorption decolorization, mixed reaction, etc.), and the process is cumbersome and time-consuming. In addition, various reagents (such as inorganic acid, strong oxidant, catalyst, calcium chloride, etc.) are used in the process, which may remain in the potassium chloride and affect the quality.

[0006] For example, in the invention patent with publication number CN112300111A, the solvent and residual product fluoroethylene carbonate in the recovered solid residue are removed by secondary vacuum drying. Then, the organic matter is hydrolyzed with a strong base and adsorbed with activated carbon. Calcium chloride is used to remove the large amount of fluoride ions remaining in the solution in the form of precipitation. Finally, the filtrate is concentrated, evaporated and crystallized to obtain potassium chloride. However, the strong base conditions in this scheme are not very effective in decomposing the polymers and carbonized products produced during the synthesis of fluoroethylene carbonate; the use of activated carbon to adsorb organic matter has certain limitations, and its adsorption performance is limited by the molecular structure, size, polarity and chemical properties of the organic matter; incineration of activated carbon filter residue involves tail gas absorption, which incurs additional processing costs; it involves multiple filtrations, and the process is cumbersome; the resulting potassium chloride is of low quality and has limited applications. Summary of the Invention

[0007] In order to simplify the recovery steps of mixed potassium salt produced as a by-product of fluoroethylene carbonate and improve the purity of the recovered potassium chloride, the present application provides a novel recovery and treatment process of mixed potassium salt produced as a by-product of fluoroethylene carbonate.

[0008] The present application provides a novel process for recovering and treating mixed potassium salts produced as a by-product of fluoroethylene carbonate, which adopts the following technical solution: A novel process for recovering mixed potassium salts produced as a by-product of fluoroethylene carbonate comprises the following steps: S1. Dissolving the by-product mixed potassium salt: mixing and dissolving the by-product mixed potassium salt with water to obtain a salt solution; S2, salt solution filtration: filtering the salt solution to obtain a filtrate and a filter residue; S3, dual calcium source synergistic one-step oxidation precipitation: adding calcium source A and calcium source B to the filtrate, where calcium source A is calcium hypochlorite and calcium source B is one or more of calcium peroxide, calcium oxide, calcium chloride and calcium hydroxide, mixing well, heating and stirring to react, and filtering to obtain a filtrate and a filter residue; S4, filtrate concentration and crystallization: The filtrate obtained in S3 is concentrated and crystallized to obtain potassium chloride.

[0009] By adopting the above technical solution, the potassium chloride and potassium fluoride in the by-product mixed potassium salt are mixed with water, and the water-insoluble organic impurities such as carbonates, carbonized products, tar, and polycarbonate substances can be fully dissolved in water. Then, by filtering, water-insoluble organic impurities such as carbonates, carbonized products, tar, and polycarbonate substances can be removed. Then, a double calcium source is used for one-step oxidation precipitation to achieve the effects of fluoride ion precipitation and oxidative degradation and color removal of organic matter. Then, by concentration and crystallization, high-purity and high-yield potassium chloride is obtained. The recovery process of the present application omits the activated carbon adsorption / incineration step, and no toxic gases such as hydrogen fluoride and silicon tetrafluoride are released throughout the process. The process steps are reduced and there is no secondary pollution, which is in line with the trend of green chemistry.

[0010] Preferably, the mass ratio of the by-product mixed potassium salt to the water is 1:(2-10); the ratio of the mass of the by-product mixed potassium salt to the total mass of the dual calcium source is (2-8):1.

[0011] By adopting the above technical solution, at this ratio, the potassium ions in the by-product mixed potassium salt can be better recovered.

[0012] Preferably, the mass ratio of the by-product mixed potassium salt to the water is 1:(3-5); the ratio of the mass of the by-product mixed potassium salt to the total mass of the dual calcium source is (3.5-4.5):1; and the mass ratio of the calcium source A to the calcium source B is 1:(0.5-3).

[0013] By adopting the above technical solution and limiting the mass ratio of the by-product mixed potassium salt, water and double calcium source, the fluoride ion concentration in the treated potassium salt solution can meet the processing conditions of the evaporation system, and there is basically no corrosion to the equipment.

[0014] Preferably, the mass ratio of the calcium source A to the calcium source B is 1:(0.8-1.2).

[0015] By adopting the above technical solution and limiting the mass ratio of calcium source A to calcium source B, organic impurities can be more fully oxidized and decomposed. At the same time, based on the high cost of calcium source A, a certain amount of recycling cost can be saved.

[0016] Preferably, the calcium source A is calcium hypochlorite, and the calcium source B is one or more of calcium oxide, calcium peroxide and calcium hydroxide.

[0017] By adopting the above technical solution, calcium hypochlorite is used as the calcium source A, which can be dissolved in water and fully contact with organic impurities in the filtrate. It can not only oxidize and decompose the organic impurities, but also provide a calcium source, playing a dual role at a low cost. The calcium source B is selected from one or more of calcium oxide, calcium peroxide and calcium hydroxide. When added to the aqueous solution, the pH of the solution can be increased to make the solution alkaline. Under alkaline conditions, it helps to degrade organic impurities and is conducive to the formation of calcium fluoride precipitation.

[0018] Preferably, the temperature in S3 is raised to 30-85°C.

[0019] Preferably, the temperature in S3 is raised to 50-60°C.

[0020] By adopting the above technical solution, the oxidation and decomposition of organic impurities by the calcium source A can be effectively carried out at a relatively high temperature. Within this temperature range, the organic impurities can be effectively decomposed and energy can be saved.

[0021] Preferably, the water in S1 is the water evaporated during the concentration and crystallization in S4.

[0022] By adopting the above technical solution, the filtrate can be rendered colorless and transparent through the oxidation and decomposition of organic impurities by the calcium source A, and the water evaporated from the concentrated crystallization does not contain the generated colored organic impurities. The generated water can be returned to the dissolution process for recycling, and there is no need to directly discharge wastewater into the nature, which can greatly reduce the discharge of wastewater and other liquid wastes.

[0023] Preferably, in S4, when the filtrate is concentrated to one third of its original volume, 800-1200 mesh potassium chloride seed crystals are added, and then concentration and crystallization are continued.

[0024] By adopting the above technical solution, potassium chloride with a smaller particle size is added, which can be used as a seed crystal in the filtrate. When the filtrate is supersaturated with potassium chloride during the concentration and crystallization process, its crystallization can be accelerated, thereby improving the precipitation efficiency. In addition, by adding potassium chloride with a smaller particle size, it can be found that the potassium chloride in the filtrate is precipitated more fully, which helps to improve the yield.

[0025] Preferably, the potassium chloride seed crystals are obtained by grinding the potassium chloride obtained by concentrated crystallization in S4.

[0026] By adopting the above technical solution, potassium chloride prepared by concentrated crystallization can save additional purchase costs and reduce production costs.

[0027] In summary, this application includes at least one of the following beneficial technical effects: 1. By mixing the by-product mixed potassium salt with water, the potassium chloride and potassium fluoride therein can be fully dissolved in water, and by filtration, the water-insoluble organic impurities such as carbonates, carbonized products, tar, and polycarbonate substances can be removed, and then a double calcium source is used for one-step oxidation precipitation to achieve the effects of fluoride ion precipitation and organic matter oxidation degradation and decolorization, and then by concentration and crystallization, high-purity and high-yield potassium chloride is obtained; the recovery process of the present application omits the activated carbon adsorption / incineration step, and no toxic gases such as hydrogen fluoride and silicon tetrafluoride are released throughout the process. The process steps are reduced and there is no secondary pollution, which is in line with the trend of green chemistry.

[0028] 2. The novel recovery and treatment process of the mixed potassium salt produced as a by-product of fluoroethylene carbonate designed in this application can effectively improve the removal efficiency of fluoride ions and organic impurities; wherein, the purity of the recovered potassium chloride is maintained in the range of 99.3-99.6%, and the key impurities (Na + , Ca 2+ Mg 2+ 、SO4 2- ) content is low, and both purity and color meet the standards, which is better than the premium grade standard of the national standard for industrial potassium chloride (GB / T 7118-2008), and can increase the added value of potassium chloride; at the same time, its yield can reach 93.7% or above, and the highest can reach 94.6%. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A process flow chart embodying a novel process for recovering and treating mixed potassium salts produced as a by-product of fluoroethylene carbonate according to Examples 1-6 of the present application.

[0030] Figure 2 1 is a comparison diagram showing the filtrate obtained by filtering the saline solution S2 (upper) and the colorless transparent solution obtained by S3 (lower) in Example 1.

[0031] Figure 3 It is a diagram showing the white potassium chloride salt recovered in Example 1. DETAILED DESCRIPTION

[0032] The following is a further detailed description of this application in conjunction with the specific content.

[0033] raw material The by-product mixed potassium salt used in the examples of the present application is obtained by reacting ethylene chloride and potassium fluoride in a dimethyl carbonate solvent, followed by filtration, separation, and drying. It contains potassium chloride, potassium fluoride, carbonates, polycarbonates, carbonized products, tar, etc., wherein the content of potassium element is measured by flame atomic absorption spectrometry, and the content of fluorine and chlorine elements are measured by ion chromatography; the elements other than potassium chloride and potassium fluoride are classified as organic residue, and the mass ratio of potassium chloride, potassium fluoride and organic residue is calculated based on the measured amounts of potassium element, fluorine element and chlorine element, and the mass ratios are described one by one in the examples; the relevant raw materials used in this application are all commercially available and are of analytical grade. Example

[0034] Example 1 A novel process for recovering mixed potassium salts produced as a by-product of fluoroethylene carbonate, the process flow is as follows: Figure 1 As shown, the recycling process includes the following preparation steps: S1. Dissolving the by-product mixed potassium salt: In a 5000ml beaker, add 2450g of water and 700g of the by-product mixed potassium salt (the mass ratio of potassium chloride, potassium fluoride and organic residue is: potassium chloride: potassium fluoride: organic residue = 15.7:3.3:1), stir at room temperature for 0.5h, so that the potassium chloride and potassium fluoride in the by-product mixed potassium salt are fully dissolved in water to obtain a saline solution; S2, salt solution filtration: The salt solution prepared in S1 is filtered to separate and remove water-insoluble organic impurities such as carbonates, carbonized products, tar, polycarbonates and other substances to obtain a filtrate and 126g of filter residue; the color of the filtrate is as follows: Figure 2 The beaker is shown above, in order to facilitate the observation of the filtrate color, Figure 2 In the middle, take a small amount of the filtrate into a beaker and place it on a white substrate; S3. Dual calcium source synergistic one-step oxidation precipitation: 182 g of two calcium source reagents were added to the filtrate at the same time, marked as calcium source A and calcium source B, where calcium source A is calcium hypochlorite and calcium source B is calcium oxide, 91 g of each of calcium source A and calcium source B. After mixing evenly, the mixture was heated to 50° C. and stirred for 2 h to achieve the effects of fluoride ion precipitation, organic matter oxidation degradation and color removal. The mixture was filtered to obtain a colorless transparent filtrate and a calcium fluoride filter residue. The filter residue was washed and dried to obtain 76.5 g of white calcium fluoride precipitate. The colorless transparent filtrate was as follows: Figure 2 The beaker is shown below to facilitate observation of the filtrate color. Figure 2 In the middle, take a small amount of colorless transparent filtrate into a beaker and place it on a white substrate; S4, filtrate concentration and crystallization: The colorless transparent filtrate is concentrated and crystallized (the water produced by the concentrated crystallization can be used to dissolve the by-product mixed potassium salt in S1) to obtain 660g of white potassium chloride salt, the main component purity is 99.5%, and the recovery rate of potassium ions is 94.1% after detection and calculation. The recovered part of the white potassium chloride salt is as follows Figure 3 shown.

[0035] Example 2 A novel process for recovering mixed potassium salts produced as a by-product of fluoroethylene carbonate, the process flow is as follows: Figure 1 As shown, the recycling process includes the following preparation steps: S1. Dissolving the by-product mixed potassium salt: In a 5000ml beaker, add 2800g of water and 700g of the by-product mixed potassium salt (the mass ratio of potassium chloride, potassium fluoride and organic residue is: potassium chloride: potassium fluoride: organic residue = 14.8:3:1), stir at room temperature for 0.5h, so that the potassium chloride and potassium fluoride in the by-product mixed potassium salt are fully dissolved in water to obtain a salt solution; S2, salt solution filtration: The salt solution prepared in S1 is subjected to filter press to separate and remove water-insoluble organic impurities, such as carbonates, carbonized products, tar, polycarbonates, etc., to obtain a filtrate and 151 g of filter residue; S3. Dual calcium source synergistic one-step oxidation precipitation: 185 g of two calcium source reagents, marked as calcium source A and calcium source B, were added to the filtrate at the same time. Calcium source A was calcium hypochlorite, and calcium source B was calcium peroxide. Calcium source A was 100 g, and calcium source B was 85 g. The mixture was mixed evenly, heated to 55° C., stirred for 2 h, and then filtered to obtain a colorless transparent filtrate and a calcium fluoride residue. The residue was washed and dried to obtain 75 g of a white calcium fluoride precipitate. S4. Concentration and crystallization of the filtrate: The colorless transparent filtrate was concentrated and crystallized to obtain 655 g of white potassium chloride salt. The purity of the main component was 99.3%. After detection and calculation, the recovery rate of potassium ions was 93.7%.

[0036] Example 3 A novel process for recovering mixed potassium salts produced as a by-product of fluoroethylene carbonate, the process flow is as follows: Figure 1 As shown, the recycling process includes the following preparation steps: S1. Dissolving by-product mixed potassium salt: In a 5000ml beaker, add 2800g of water and 700g of by-product mixed potassium salt (the mass ratio of potassium chloride, potassium fluoride and organic residue is: potassium chloride: potassium fluoride: organic residue = 13.5:3.1:1), stir at room temperature for 0.5h, so that the potassium chloride and potassium fluoride in the by-product mixed potassium salt are fully dissolved in water to obtain a saline solution; S2, salt solution filtration: The salt solution prepared in S1 is subjected to filter press to separate and remove water-insoluble organic impurities, such as carbonates, carbonized products, tar, polycarbonates and the like, to obtain a filtrate and 140 g of filter residue; S3. Dual calcium source synergistic one-step oxidation precipitation: 185 g of two calcium source reagents, marked as calcium source A and calcium source B, were added to the filtrate at the same time. Calcium source A was calcium hypochlorite, and calcium source B was calcium hydroxide. 84 g of calcium source A and 101 g of calcium source B were mixed evenly. The mixture was heated to 60° C. and stirred for 2 h to achieve the effects of fluoride ion precipitation, organic matter oxidation degradation, and color removal. The mixture was filtered to obtain a colorless and transparent filtrate and a calcium fluoride filter residue. The filter residue was washed and dried to obtain 83 g of white calcium fluoride precipitate. S4. Concentration and crystallization of the filtrate: The colorless transparent filtrate was concentrated and crystallized to obtain 657 g of white potassium chloride salt. The purity of the main component was 99.6%. After detection and calculation, the recovery rate of potassium ions was 94.1%.

[0037] Example 4 A novel process for recovering and treating a mixed potassium salt produced as a by-product of fluoroethylene carbonate, wherein the mixed potassium salt produced as a by-product has the same proportion as in Example 3, except that in S3, the mass ratio of calcium source A to calcium source B is 1:3, and the remaining steps are the same as in Example 3.

[0038] Example 5 A novel process for recovering and treating a mixed potassium salt produced as a by-product of fluoroethylene carbonate, wherein the mixed potassium salt produced as a by-product has the same proportion as in Example 3, except that the mass ratio of calcium source A to calcium source B in S3 is 1:0.5, and the remaining steps are the same as in Example 3.

[0039] Example 6 A novel process for recovering and treating mixed potassium salt produced as a by-product of fluoroethylene carbonate. The mixed potassium salt produced as a by-product has the same proportion as that in Example 3. The difference from Example 3 is that the content of S4 is as follows: The dried potassium chloride was ground to a particle size of 800 mesh as potassium chloride seed crystals, and then when the colorless transparent filtrate was concentrated to one third of the original volume, 30 g of the ground potassium chloride seed crystals were added, and then the concentration and crystallization were continued to obtain white potassium chloride salt.

[0040] Comparative Example Comparative Example 1 A novel process for recovering and treating a mixed potassium salt produced as a by-product of fluoroethylene carbonate, wherein the mixed potassium salt has the same proportion as in Example 3, except that the calcium source A is replaced by an equimolar amount of calcium source B. The remaining steps are the same as in Example 3.

[0041] Performance testing Detection method / test method The potassium ions in the by-product mixed potassium salt were recovered according to the recovery treatment processes of Examples 1-6 and Comparative Example 1, and the purity and yield of the recovered potassium chloride are shown in Table 1.

[0042] Table 1 Test results of Examples 1-6 and Comparative Example 1 purity(%) Yield (%) Example 1 99.5 94.1 Example 2 99.3 93.7 Example 3 99.6 94.1 Example 4 99.4 94.2 Example 5 99.6 94.1 Example 6 99.6 94.6 Comparative Example 1 98.3 94.8 It can be seen from the test data of Examples 1-6 and Comparative Example 1 that the novel process for recovering the mixed potassium salt produced as a by-product of fluoroethylene carbonate designed in the present application can effectively improve the removal efficiency of fluoride ions and organic impurities; wherein, the purity of the recovered potassium chloride is maintained in the range of 99.3-99.6%, which is better than the premium grade standard of the national standard for industrial potassium chloride (GB / T 7118-2008), and can increase the added value of potassium chloride; at the same time, the yield can reach 93.7% or above, and can reach as high as 94.6%.

[0043] It can be seen from the test data of Examples 1-3 that the recovery process of the present application can achieve ideal recovery effects when recovering by-product mixed potassium salts with different ratios, indicating that it has very wide applicability and very strong practical applicability.

[0044] As can be seen from Examples 3-5 and the test data of Comparative Example 1, the strong oxidizing property of calcium source A can effectively decompose organic matter and generate calcium ions, which together with calcium source B provide calcium ions, thereby improving the removal efficiency of fluoride ions and water-soluble organic impurities. However, when only calcium source B is added, its organic impurities cannot be removed, resulting in the actual recovered potassium chloride having a darker color and lower purity. Furthermore, by exploring the ratio of calcium source A to calcium source B, the ratio of Example 3 is a more optimal ratio, which can fully oxidize and decompose organic impurities while also saving costs.

[0045] It can be seen from Examples 3 and 6 that the addition of potassium chloride with a smaller particle size can serve as a seed crystal in the filtrate, so that when the filtrate is supersaturated with potassium chloride during the concentration and crystallization process, its crystallization can be accelerated, thereby improving the precipitation efficiency. In addition, by adding potassium chloride with a small particle size, it can be found that the potassium chloride in the filtrate is precipitated more fully, which helps to improve the yield.

[0046] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed. However, as long as such modifications are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A novel process for recovering mixed potassium salt produced as a by-product of fluoroethylene carbonate, characterized by: It includes the following steps: S1. Dissolving the by-product mixed potassium salt: mixing and dissolving the by-product mixed potassium salt with water to obtain a salt solution; S2, salt solution filtration: filtering the salt solution to obtain a filtrate and a filter residue; S3, dual calcium source synergistic one-step oxidation precipitation: adding calcium source A and calcium source B to the filtrate, where calcium source A is calcium hypochlorite and calcium source B is one or more of calcium peroxide, calcium oxide, calcium chloride and calcium hydroxide, mixing well, heating and stirring to react, and filtering to obtain a filtrate and a filter residue; S4, filtrate concentration and crystallization: The filtrate obtained in S3 is concentrated and crystallized to obtain potassium chloride.

2. The novel process for recovering mixed potassium salt produced as a by-product of fluoroethylene carbonate according to claim 1, characterized in that: The mass ratio of the by-product mixed potassium salt to the water is 1:(2-10); the mass ratio of the by-product mixed potassium salt to the total mass of the dual calcium source is (2-8):

1.

3. The novel process for recovering mixed potassium salt produced as a by-product of fluoroethylene carbonate according to claim 1, characterized in that: The mass ratio of the by-product mixed potassium salt to the water is 1:(3-5); the ratio of the mass of the by-product mixed potassium salt to the total mass of the dual calcium source is (3.5-4.5):1; and the mass ratio of the calcium source A to the calcium source B is 1:(0.5-3).

4. The novel process for recovering mixed potassium salt produced as a by-product of fluoroethylene carbonate according to claim 3, characterized in that: The mass ratio of the calcium source A to the calcium source B is 1:(0.8-1.2).

5. The novel process for recovering mixed potassium salt produced as a by-product of fluoroethylene carbonate according to claim 1, characterized in that: The calcium source A is calcium hypochlorite, and the calcium source B is one or more of calcium oxide, calcium peroxide and calcium hydroxide.

6. The novel process for recovering mixed potassium salt produced as a by-product of fluoroethylene carbonate according to claim 1, characterized in that: In the step S3, the temperature is raised to 30-85°C.

7. The novel process for recovering mixed potassium salt produced as a by-product of fluoroethylene carbonate according to claim 6, characterized in that: In step S3, the temperature is raised to 50-60°C. The novel process for recovering and treating mixed potassium salts produced as a by-product of fluoroethylene carbonate according to claim 1, wherein the water in S1 is water evaporated during the concentration and crystallization in S4.

8. The novel process for recovering mixed potassium salt produced as a by-product of fluoroethylene carbonate according to claim 1, characterized in that: In the step S4, when the filtrate is concentrated to one third of its original volume, 800-1200 mesh potassium chloride seed crystals are added, and then concentration and crystallization are continued.

9. The novel process for recovering mixed potassium salt produced as a by-product of fluoroethylene carbonate according to claim 9, characterized in that: The potassium chloride seed crystals are obtained by grinding the potassium chloride obtained by concentrated crystallization in S4.

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