A method for recovering potassium acetate from waste brine produced by isomethyl ionone production

Abstract

The present invention discloses a method for recovering potassium acetate from waste brine produced by isomethyl ionone production. The method comprises the following steps: 1) using waste brine containing potassium acetate produced in the isomethyl ionone condensation process as a raw material, removing organic matter through steam stripping to obtain an aqueous potassium acetate solution having an organic matter content of less than 0.1 wt%; 2) adding tartaric acid and an auxiliary agent to the aqueous potassium acetate solution from step 1), heating and stirring until a clear solution is obtained; 3) evaporating and concentrating the clear solution from step 2), allowing it to stand for crystal growth, then subjecting it to programmed cooling to obtain a slurry, which is then centrifuged and dried to obtain potassium acetate. The present invention utilizes a novel process that couples steam stripping and crystallization to recover high-quality potassium acetate from waste brine, meeting the requirements for use as a high-end deicing agent. The method has the advantages of simple operation and high product yield, making it suitable for industrial application.

Description

Technical Field

[0001] The invention relates to a method for recovering potassium acetate from waste brine, in particular to a method for recovering potassium acetate from waste water rich in potassium acetate in a condensation process in producing isomethyl ionone from citral, and belongs to the technical field of chemical industry. Technical Background

[0002] Potassium acetate is an important chemical agent that can be used in desiccants, transparent glass, and the pharmaceutical industry. It can also be used as an anti-icing agent and in high-end snow-melting agents. It is mainly used in highways, airports and other fields. It is non-corrosive to infrastructure and is green and environmentally friendly.

[0003] Existing processes mostly use the neutralization reaction of acetic acid and potassium hydroxide to produce potassium acetate. However, there are few methods for recovering chemical by-products, and the product quality is low. This is especially true in the field of flavors and fragrances. Due to the relatively small output of individual products, the small amount of waste brine produced as a by-product and its complex composition, recovery is difficult. Generally, the waste brine is incinerated or entrusted to a third party for treatment, which has high treatment costs, wastes resources, and is uneconomical and environmentally unfriendly.

[0004] In synthetic fragrance products, high-concentration potassium hydroxide is used as a catalyst for the reaction of citral and butanone in the production process of isomethyl ionone. After the reaction, acetic acid is used to neutralize the waste brine, which produces high-concentration potassium acetate as a by-product. The cost of incinerating the waste liquid is high, and the potassium element in the waste brine is corrosive to the material of the incinerator.

[0005] In view of the problems existing in the existing process, a new process is urgently needed to recover potassium acetate from waste brine, which can be used in the field of snow melting agents to produce low-cost high-end snow melting agents to supply the market and achieve the maximum economic benefits of waste liquid treatment. Summary of the Invention

[0006] In response to the above-mentioned problems existing in the prior art, the object of the present invention is to provide a method for recovering potassium acetate from waste brine produced by isomethyl ionone production. Compared with the problem of poor economic efficiency in treating potassium acetate waste brine in existing isomethyl ionone production technologies, the present invention adopts a novel process of coupling steam stripping and crystallization to recover high-quality potassium acetate from waste brine, which can meet the requirements of high-end deicing agents. The method has the advantages of simple operation and high product yield, and is suitable for industrial application.

[0007] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows:

[0008] The present invention provides a method for recovering potassium acetate from waste brine produced by isomethyl ionone production, comprising the following steps:

[0009] 1) using waste brine containing potassium acetate produced in the isomethyl ionone condensation process as a raw material, removing organic matter by steam stripping to obtain a potassium acetate aqueous solution having an organic matter content of less than 0.1 wt %;

[0010] 2) adding tartaric acid and an auxiliary agent to the potassium acetate aqueous solution of step 1), heating and stirring until a clear solution is obtained;

[0011] 3) After the clarified solution in step 2) is evaporated and concentrated, it is allowed to stand for crystal growth, and then programmed to cool to obtain a slurry, which is then centrifuged and dried to obtain potassium acetate.

[0012] In the present invention, the potassium acetate-containing waste brine produced in the isomethyl ionone condensation process in step 1) comprises, based on its total mass as 100%, 10-30% of potassium acetate, 0-3% of methanol, 0-5% of butanone, and the remainder is water.

[0013] In the present invention, the waste brine in step 1) enters the top of the stripping tower, and the stripping treatment temperature is 60-90°C, preferably 60-85°C; organic matter in the waste brine is removed by stripping, and the organic matter mainly includes methanol, butanone, etc., and the total content in the waste brine is generally 0-8wt%;

[0014] Preferably, the feed volume space velocity of the waste brine is 0.5-20h -1 , preferably 1-10h -1 ;

[0015] After stripping, the potassium acetate solution is discharged from the bottom of the stripping tower, wherein the organic matter content in the potassium acetate solution is reduced to below 0.1 wt %, preferably below 0.01 wt %, and the potassium acetate content is increased to 40-50 wt %;

[0016] Preferably, the carrier gas used in the stripping treatment is water vapor, nitrogen, air, carbon dioxide, tunnel gas, preferably nitrogen; the carrier gas enters from the stripping tower kettle, and the carrier gas feed volume space velocity is 20-60h -1 , preferably 20-40h -1 .

[0017] In the present invention, the concentration of tartaric acid added to the potassium acetate aqueous solution in step 2) is 1000-20000 ppm, preferably 3000-8000 ppm;

[0018] In the present invention, the auxiliary agent in step 2) is one or more of povidone, hydroxycellulose, and polyvinyl ester, preferably povidone;

[0019] Preferably, the auxiliary agent is povidone, hydroxy cellulose, or polyvinyl ester with a molecular weight of 3,000-60,000.

[0020] Preferably, the concentration of the auxiliary agent added to the potassium acetate aqueous solution is 50-500 ppm, preferably 50-200 ppm.

[0021] In the present invention, the temperature of the heating and stirring in step 2) is 50-80°C, preferably 60-70°C, and the stirring speed is 10-300r / min, preferably 30-100r / min.

[0022] In the present invention, step 3) adopts an evaporation-cooling coupled crystallization process, wherein the evaporation concentration is performed by programmed decompression;

[0023] Preferably, during the decompression process, the pressure is linearly reduced from 0.1 MPaG to 0.01 MPaG;

[0024] More preferably, the decompression time is 0.5-3 h, preferably 0.8-2 h, and the decompression rate is 0.04-0.12 MPa / h.

[0025] Preferably, the evaporation concentration endpoint is when the concentration of potassium acetate in the solution reaches 50-70 wt%, preferably 63-68 wt%.

[0026] In the present invention, in the crystal growing process of step 3), the timing starts after stopping stirring, the crystal growing time is 2-5 hours, preferably 3.5-5 hours, and the temperature is 40-65°C, preferably 45-50°C.

[0027] In the present invention, in the programmed cooling process of step 3), the temperature control program is realized by a constant temperature bath, and the programmed cooling is linearly reduced from the crystal growing temperature to 0-15°C, preferably 5-10°C, and the cooling rate is 3-20°C / min, preferably 5-15°C / min.

[0028] In the present invention, the centrifugation in step 3) has a rotation speed of 2000-3000 rpm, preferably 2500-3000 rpm.

[0029] In the present invention, the drying in step 3) is carried out by spray drying, with an inlet temperature of 120-150°C, preferably 120-135°C, and an outlet temperature of 50-60°C, preferably 55-60°C.

[0030] In the present invention, the potassium acetate recovered by the method has a purity of >99.9% and a recovery rate of >90%;

[0031] The potassium acetate is a colorless rhombus crystal with a bulk density of 1.2-1.3 g / mL;

[0032] The potassium acetate particles have a particle size of 100-500 meshes, of which 100-200 meshes account for more than 92%, preferably more than 95%, and the preferred particle size is 100-200 meshes.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1) The present invention solves the problem of difficult treatment of highly concentrated waste brine in existing isomethyl ionone production technology. First, the present invention uses steam stripping to remove organic matter from the waste brine, thereby improving the purity of the crystals and preventing the organic matter in the waste brine from entering the ground with rainwater and contaminating groundwater when used as a de-icing agent.

[0035] 2) the present invention also adds tartaric acid and auxiliary agent in waste brine solution, wherein tartaric acid can significantly promote the solubility of potassium acetate in water, change the charge distribution near the nucleus in the microemulsion system, further promote and induce the growth of organic salt potassium acetate on the nucleus surface, avoid forming clusters or too fast growth in the growth process, obtain high-quality salt from waste water by the control of crystal form. The auxiliary agent added simultaneously can form a microemulsion system under agitation with a small amount of organic matter remaining in the waste water, and the microemulsion system makes the nucleus in the crystallization process more dispersed, and is evenly distributed, widens the stable interval of crystallization, avoids causing the problem such as poor product crystal form, inclusion of impurities causing purity low and color depth due to unorganized crystallization in crystallization. Tartaric acid and auxiliary agent coordination affect the nucleation, growth process of potassium acetate crystal, and finally show with high purity, certain morphological crystal form, reach the purpose of reclaiming high-quality potassium acetate from waste liquid.

[0036] 3) The present invention couples two distinct crystallization methods, evaporation and cooling, to avoid the high energy consumption of simple evaporation crystallization, the problems of salt clustering and inclusion during the crystallization process, and the problem of dark product color due to the enrichment of color-forming substances in the crystal form caused by continuous heating of the waste liquid.

[0037] 4) The potassium acetate product recovered by the present invention has a regular crystal shape, higher quality purity, and a relatively large bulk density. When used as a snow melting agent, it can also effectively prevent melted snow from freezing, is harmless to ground infrastructure, and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a scanning electron microscope image of the potassium acetate crystals prepared in Example 1. DETAILED DESCRIPTION

[0039] The present invention is further described in detail with reference to the following examples, but the scope of the present invention is not limited to these examples.

[0040] The analysis and testing method used in the embodiment of the present invention is as follows:

[0041] Gas chromatography analysis conditions: Agilent gas chromatograph, RTX-WAX column, 50 °C for 5 min; 10 °C / min to 80 °C, hold for 5 min; 10 °C / min to 100 °C, hold for 5 min; 10 °C / min to 160 °C, hold for 15 min.

[0042] Ion chromatography analysis method: ion chromatograph, Metrohm model 883; separation column IonPacAS11-HC (4 mm*250 mm); column temperature, 40°C; conductivity monitor; mobile phase, 5.0 mmol / L sodium carbonate solution, flow rate, 1.0 mL / min; suppressor mobile phase, 80 mL / min phosphoric acid aqueous solution; injection volume, 20 uL.

[0043] The scanning conditions of the electron microscope were as follows: a CD Xcalibur Nova single crystal X-ray diffractometer (Oxford Instruments, UK) was used for single crystal X-ray diffractometry (SXRD). The sample was scanned at room temperature using Mo-Kα radiation (λ = 0.071 nm) in the scanning range of θ = 3.13°-26.37°.

[0044] Sources of the main raw materials used in the embodiments of the present invention:

[0045] Waste brine containing potassium acetate: Derived from Wanhua's pilot production unit for isomethyl ionone, which uses citral and butanone as raw materials, catalyzed by high-concentration potassium hydroxide, to produce isomethyl ionone. After the reaction is complete, the by-product, waste brine containing potassium acetate, is neutralized with acetic acid.

[0046] Povidone: BASF Kollidon series, the products are referred to as povidone K30 (molecular weight 44,000-54,000), povidone K25 (molecular weight 28,000-34,000), and povidone K17 (molecular weight 7,000-11,000);

[0047] Hydroxycellulose: Eastman, cellulose CAB-553-0.4, molecular weight 20,000;

[0048] Polyvinyl ester: Denno polyvinyl ester, molecular weight 80000;

[0049] Tartaric acid: Hubei Jusheng Technology, purity >99%;

[0050] Unless otherwise specified, other ingredients are common commercially available raw materials.

[0051] Example 1

[0052] Recovery of potassium acetate from waste brine produced by isomethyl ionone production:

[0053] 1) The stripping tower has a diameter of 30 mm and is filled with 1 m high 5*5 theta ring packing. The waste brine containing potassium acetate (potassium acetate content 26 wt%, methanol content 2.6 wt%, butanone content 3.7 wt%) produced in the isomethyl ionone condensation process is used as raw material. -1 The volume space velocity of nitrogen enters the stripping tower at 20h -1 The volume space velocity of the steam stripping tower is 65°C, and the flow rate of the liquid collected at the top of the tower after stripping is 8.1 mL / min. The composition of the liquid is 9.0% butanone, 6.5% methanol, and 84.6% water. The flow rate of the liquid collected at the bottom of the tower is 11.9 mL / min, and a potassium acetate aqueous solution with an organic matter content of <0.1 wt% is obtained (the composition of the aqueous solution is 43.8 wt% potassium acetate, 56.1 wt% water, 0.07 wt% butanone, and 0.03 wt% methanol).

[0054] 2) Add 3500 ppm of tartaric acid and 80 ppm of povidone K30 to the potassium acetate aqueous solution, raise the temperature to 80°C, and stir at 80 rpm until a clear solution is obtained;

[0055] 3) The clarified solution from step 2) was pressure-controlled by a diaphragm pump, and the system pressure was gradually and linearly reduced from 0.1 MPaG to 0.01 MPaG over 2 hours at a rate of 0.045 MPa / h. The system was then evaporated and concentrated until the potassium acetate content was 67.2 wt%. Stirring was stopped, and the solution was allowed to stand at 45°C for 3.5 hours to grow crystals. The temperature was then linearly reduced to 12°C at a rate of 5°C / h in a thermostatic bath to obtain a slurry. The solution was then centrifuged at 2800 rpm and spray-dried (inlet temperature 130°C, outlet temperature 55°C) to obtain colorless rhombus-shaped potassium acetate crystals (e.g., Figure 1 As shown), the purity is 99.92%, the recovery rate is 92.3%, the bulk density is 1.2 g / mL, the particle size is 100-400 mesh, of which 100-200 mesh accounts for 96.7%.

[0056] Example 2

[0057] Recovery of potassium acetate from waste brine produced by isomethyl ionone production:

[0058] 1) The stripping tower has a diameter of 30 mm and is filled with 1 m high 5*5 theta ring packing. The waste brine containing potassium acetate (potassium acetate content 14 wt%, methanol content 1.8 wt%, butanone content 2.3 wt%) produced in the isomethyl ionone condensation process is used as raw material. -1 The volume space velocity of nitrogen is fed into the stripping tower at 40h -1The volume space velocity of the steam stripping tower is 85°C, and the flow rate of the liquid collected at the top of the tower after stripping is 13.7 mL / min. The composition of the liquid is 3.4 wt% of butanone, 2.6 wt% of methanol, and 94 wt% of water. The flow rate of the liquid collected at the bottom of the tower is 6.3 mL / min, and a potassium acetate aqueous solution with an organic matter content of <0.1 wt% (composition of potassium acetate 44.2 wt%, water 55.77 wt%, butanone 0.02 wt%, and methanol 0.01 wt%) is obtained.

[0059] 2) Add 7000 ppm of tartaric acid and 200 ppm of povidone K25 to the potassium acetate aqueous solution, heat to 65°C, and stir at 100 rpm until a clear solution is obtained;

[0060] 3) The clarified solution from step 2) was subjected to pressure control by a diaphragm pump, gradually decreasing the system pressure linearly from 0.1 MPaG to 0.01 MPaG over 1.2 hours at a rate of 0.075 MPa / h. The system was then concentrated by evaporation until the potassium acetate content was 66.5 wt %. Stirring was stopped, and the solution was allowed to stand at 50° C. for 4.5 hours to grow crystals. The temperature was then linearly decreased to 10° C. at a rate of 10° C. / h in a thermostatic bath to obtain a slurry. The solution was then centrifuged at 2500 rpm and spray-dried (inlet temperature 125° C., outlet temperature 55° C.) to obtain colorless rhombus-shaped potassium acetate crystals with a purity of 99.94%, a recovery of 93.4%, a bulk density of 1.3 g / mL, and a particle size of 100-500 mesh, of which 100-200 mesh accounted for 95.8%.

[0061] Example 3

[0062] Recovery of potassium acetate from waste brine produced by isomethyl ionone production:

[0063] 1) The stripping tower has a diameter of 30 mm and is filled with 1 m high 5*5 theta ring packing. The waste brine containing potassium acetate (potassium acetate content 14 wt%, methanol content 1.8 wt%, butanone content 2.3 wt%) produced in the isomethyl ionone condensation process is used as raw material. -1 The volume space velocity of nitrogen is fed into the stripping tower at 30h -1 The volume space velocity of the steam stripping tower is 85°C, and the flow rate of the liquid collected at the top of the tower after stripping is 13.7 mL / min. The composition of the liquid is 3.4 wt% of butanone, 2.6 wt% of methanol, and 94 wt% of water. The flow rate of the liquid collected at the bottom of the tower is 6.3 mL / min, and a potassium acetate aqueous solution with an organic matter content of <0.1 wt% (composition of potassium acetate 44.2 wt%, water 55.77 wt%, butanone 0.02 wt%, and methanol 0.01 wt%) is obtained.

[0064] 2) Add 5000 ppm of tartaric acid and 140 ppm of povidone K17 to the potassium acetate aqueous solution, heat to 75°C, and stir at 40 rpm until a clear solution is obtained;

[0065] 3) The clarified solution from step 2) was subjected to a diaphragm pump to control the system pressure, gradually decreasing linearly from 0.1 MPaG to 0.01 MPaG over 1 hour at a rate of 0.09 MPa / h. The system was then evaporated and concentrated until the potassium acetate content was 64.8 wt %. Stirring was stopped, and the solution was allowed to stand at 55° C. for 5 hours to grow crystals. The temperature was then linearly decreased to 10° C. at a rate of 10° C. / h in a thermostatic bath to obtain a slurry. The solution was then centrifuged at 3000 rpm and spray-dried (inlet temperature 130° C., outlet temperature 55° C.) to obtain colorless rhombus-shaped potassium acetate crystals with a purity of 99.91%, a recovery of 93.1%, a bulk density of 1.3 g / mL, and a particle size of 100-300 mesh, of which 100-200 mesh accounted for 97.2%.

[0066] Example 4

[0067] The method of Example 1 was followed, except that in step 2), povidone was replaced with an equal amount of hydroxycellulose. Other operations remained unchanged, and a colorless potassium acetate solid was obtained with a purity of 98.92%, a recovery rate of 93.2%, a bulk density of 1.1 g / mL, and a particle size of 100-500 mesh, of which 100-200 mesh accounted for 93.6%.

[0068] Example 5

[0069] The method of Example 1 was followed, except that in step 2), povidone was replaced with an equal amount of polyvinyl ester. Other operations remained unchanged, and a colorless potassium acetate solid was obtained with a purity of 98.75%, a recovery rate of 93.8%, a bulk density of 1.1 g / mL, and a particle size of 100-500 mesh, of which 100-200 mesh accounted for 92.7%.

[0070] Comparative Example 1

[0071] Referring to the method of Example 2, the only difference is that: in step 2), no povidone adjuvant is added, and other operations remain unchanged to obtain a light yellow potassium acetate solid with a purity of 96.4%, a recovery rate of 91.7%, a bulk density of 1.1 g / mL, and a particle size of 100-500 mesh, of which 100-200 mesh accounts for 46.3%.

[0072] Comparative Example 2

[0073] Referring to the method of Example 2, the only difference is that in step 2), the auxiliary agent tartaric acid is replaced by an equal mass of succinic acid, and the other operations remain unchanged to obtain a light yellow potassium acetate solid with a purity of 93.7%, a recovery rate of 82.3%, a bulk density of 1.2 g / mL, and a particle size of 100-500 mesh, of which 100-200 mesh accounts for 35.6%.

[0074] Comparative Example 3

[0075] Referring to the method of Example 2, the only difference is that: in step 2), the auxiliary agent tartaric acid is not added, and the other operations remain unchanged, to obtain a light yellow potassium acetate solid with a purity of 92.4%, a recovery rate of 78.2%, a bulk density of 1.1 g / mL, and a particle size of 100-400 mesh, of which 100-200 mesh accounts for 25.3%.

[0076] Comparative Example 4

[0077] The method of Example 2 was referred to except that the stripping operation in step 1) was omitted and the waste brine containing potassium acetate was directly used in step 2). Other operations remained unchanged to obtain a light yellow potassium acetate solid with a purity of 91.6%, a recovery rate of 83.4%, a bulk density of 1.2 g / mL, and a particle size of 100-500 mesh, of which 100-200 mesh accounted for 43.1%.

[0078] Comparative Example 5

[0079] Referring to the method of Example 2, the only difference is that the depressurization rate in step 3) is adjusted to a depressurization rate of 0.9 MPa / h, and the other operations remain unchanged to obtain colorless potassium acetate solid with a purity of 99.63%, a recovery rate of 93.4%, a bulk density of 1.2 g / mL, and a particle size of 100-500 mesh, of which 100-200 mesh accounts for 89.6%.

[0080] Comparative Example 6

[0081] Referring to the method of Example 2, the only difference is that the crystal growth time in step 3) is adjusted to 0.05 h, and the other operations remain unchanged to obtain colorless potassium acetate solid with a purity of 99.37%, a recovery rate of 87.6%, a bulk density of 1.2 g / mL, and a particle size of 100-400 mesh, of which 100-200 mesh accounts for 91.3%.

[0082] Comparative Example 7

[0083] The method of Example 2 was referred to, except that the cooling rate in step 3) was adjusted from 10°C / h to 60°C / h, and other operations remained unchanged to obtain colorless potassium acetate solid with a purity of 96.24%, a recovery rate of 89.3%, a bulk density of 1.2 g / mL, and a particle size of 100-500 mesh, of which 100-200 mesh accounted for 54.7%.

Claims

1. A method for recovering potassium acetate from waste brine produced by isomethyl ionone production, characterized in that the steps include: 1) using waste brine containing potassium acetate produced in the isomethyl ionone condensation process as a raw material, removing organic matter by steam stripping to obtain a potassium acetate aqueous solution having an organic matter content of less than 0.1 wt %; 2) adding tartaric acid and an auxiliary agent to the potassium acetate aqueous solution of step 1), heating and stirring until a clear solution is obtained; 3) After evaporation and concentration of the clarified solution in step 2), the solution is allowed to stand for crystal growth, and then the temperature is programmed to obtain a slurry, which is then centrifuged and dried to obtain potassium acetate; Step 1) The potassium acetate-containing waste brine produced in the isomethyl ionone condensation process comprises, based on its total mass as 100%, 10-30% potassium acetate, 0-3% methanol, 0-5% butanone, and the remainder water; the stripping treatment temperature is 60-90° C.; Step 2) the auxiliary agent is one or more of povidone and hydroxycellulose with a molecular weight of 3000-60000; the concentration of tartaric acid added to the potassium acetate aqueous solution is 1000-20000 ppm; the heating and stirring is performed at a temperature of 50-80°C; Step 3) The evaporation concentration is carried out by programmed decompression, with a decompression time of 0.5-3h and a decompression rate of 0.04-0.12MPa / h; the programmed cooling process is carried out by dropping the crystal growth temperature to 0-15°C at a cooling rate of 3-20°C / min.

2. The recycling method according to claim 1, wherein: The stripping treatment temperature is 60-85°C.

3. The recycling method according to claim 1, wherein: Step 1) The feed volume space velocity of the waste brine is 0.5-20h -1 .

4. The recycling method according to claim 3, characterized in that The feed volume space velocity of the waste brine is 1-10h -1 .

5. The recycling method according to claim 1, wherein: In step 1), the organic matter content in the potassium acetate solution is reduced to below 0.1 wt %, wherein the content of potassium acetate is increased to 40-50 wt %.

6. The recycling method according to claim 5, characterized in that: The organic matter content in the potassium acetate solution is reduced to below 0.01 wt%.

7. The recycling method according to claim 1, characterized in that: The carrier gas used in the stripping treatment in step 1) is water vapor, nitrogen, air, carbon dioxide, or tunnel gas.

8. The recycling method according to claim 7, characterized in that: The carrier gas feed volume space velocity is 20-60h -1 .

9. The recycling method according to claim 8, characterized in that: The carrier gas feed volume space velocity is 20-40h -1 .

10. The recycling method according to claim 1, characterized in that: The concentration of the tartaric acid added to the potassium acetate aqueous solution is 3000-8000 ppm.

11. The recycling method according to claim 1, characterized in that: In step 2), the auxiliary agent is added to the potassium acetate aqueous solution at a concentration of 50-500 ppm.

12. The recycling method according to claim 11, characterized in that: The concentration of the auxiliary agent added to the potassium acetate aqueous solution is 50-200 ppm.

13. The recycling method according to claim 1, characterized in that: Step 2) The stirring speed is 10-300 r / min.

14. The recycling method according to claim 13, characterized in that: The temperature of the heating and stirring is 60-70° C., and the stirring speed is 30-100 r / min.

15. The recycling method according to claim 1, characterized in that: During the decompression process, the pressure is reduced from 0.1 MPaG to 0.01 MPaG.

16. The recycling method according to claim 15, characterized in that: The decompression time is 0.8-2h.

17. The recycling method according to claim 1, characterized in that: The endpoint of step 3) the evaporation concentration is when the concentration of potassium acetate in the solution reaches 50-70 wt%.

18. The recycling method according to claim 17, characterized in that: The evaporation concentration end point is when the concentration of potassium acetate in the solution reaches 63-68 wt %.

19. The recycling method according to claim 1, characterized in that: In step 3), the crystal growing process has a crystal growing time of 2-5 hours and a temperature of 40-65°C.

20. The recycling method according to claim 19, characterized in that: The crystal growing process has a crystal growing time of 3.5-5 hours and a temperature of 45-50°C.

21. The recycling method according to claim 1, characterized in that: The programmed cooling process is to reduce the crystal growing temperature to 5-10°C at a cooling rate of 5-15°C / min.

22. The recycling method according to claim 1, characterized in that Step 3) the centrifugation is performed at a speed of 2000-3000 rpm; The drying is carried out by spray drying, with an inlet temperature of 120-150°C and an outlet temperature of 50-60°C.

23. The recycling method according to claim 22, characterized in that: The centrifugal rotation speed is 2500-3000 rpm.

24. The recycling method according to claim 22, characterized in that The drying process has an inlet temperature of 120-135°C and an outlet temperature of 55-60°C.

25. The recycling method according to any one of claims 1 to 24, characterized in that: The potassium acetate recovered by the method is colorless rhombic crystals with a bulk density of 1.2-1.3 g / mL; The potassium acetate particles have a particle size of 100-500 meshes, of which 100-200 meshes account for more than 92%.

26. The recycling method according to claim 25, characterized in that The potassium acetate particles have a particle size of 100-200 meshes.

27. The recycling method according to claim 25, characterized in that The 100-200 mesh accounts for more than 95%.

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