Continuous recovery method of sorbic acid tailings

Abstract

The invention discloses a continuous recovery method of sorbic acid tailings, and belongs to the technical field of chemical engineering. According to the method, the alcohol washing liquid generated in a crude product washing section in a sorbic acid production process is taken as a raw material, the alcohol concentration in the alcohol washing liquid is reduced in a gradient manner by utilizing the difference of solubility and dissolving speed of tar and sorbic acid in alcohol, and meanwhile, the quality of the recovered sorbic acid can be improved in a gradient cooling manner; the light transmittance of the recovered sorbic acid is increased to 40-50%, the content (namely purity) of the sorbic acid is greater than or equal to 92%, and the proportion gt of the recovered sorbic acid crystals of 0-100 meshes is greater than or equal to 20%; the recovery rate of the sorbic acid is more than 85%. Meanwhile, the technological method is simple and low in energy consumption, recycling of ethyl alcohol and water can be achieved, continuous recycling is achieved on the whole, and cost is saved. In addition, the process has low requirements on equipment and sites, and is suitable for industrial application.

Description

Technical Field

[0001] The present invention relates to a continuous recovery method for sorbic acid tailings, belonging to the technical field of chemical engineering. Background Art

[0002] Sorbic acid, scientific name 2,4 - hexadienoic acid

[0003] English name: Sorbic Acid

[0004] Appearance property: white needle - shaped or powdery crystals

[0005] Solubility: slightly soluble in water, soluble in a variety of organic solvents

[0006] CAS No.: 110 - 44 - 1

[0007] Molecular formula: C6H8O2

[0008] Structural formula:

[0009] Molecular weight: 112.13

[0010] Melting point (°C): 132 - 135

[0011] Boiling point (°C): 228

[0012] Flash point (°C): 127

[0013] Relative density (g / cm 3 ) : 1.205

[0014] Functions and uses: Sorbic acid is an unsaturated fatty acid with conjugated dienes. It can effectively inhibit the activities of molds, yeasts and aerobic bacteria. Its function of inhibiting the development and reproduction of harmful microorganisms is stronger than its bactericidal effect. It is a preservative recommended by the Food and Agriculture Organization of the United Nations to countries around the world, and its safety is twice that of table salt. Sorbic acid has been widely used in the anti - corrosion and preservation of various industries such as food, vegetables, fruits, medicine, rubber, papermaking, animal feed, cosmetics, paint, tobacco, beverages, etc.

[0015] The ketene method is a method commonly adopted in industrial production internationally. Acetic acid is pyrolyzed at high temperature to generate ketene, which then condenses with crotonaldehyde to form polyester. After hydrolysis, centrifugation, and washing, the crude product is obtained. The crude sorbic acid is refined, neutralized, and dried to obtain the finished product of sorbic acid or potassium sorbate. The polyester intermediate in the above production process needs to be hydrolyzed in a hydrochloric acid environment to generate the crude sorbic acid, resulting in a large amount of impurities such as hydrochloric acid and reaction residues (also known as tar) in the crude sorbic acid. To ensure the qualification of the sorbic acid product, it is necessary to use pure water and ethanol washing solution with a concentration of about 50% to wash the crude sorbic acid in turn during centrifugation to ensure that the chloride ion content in the crude sorbic acid after centrifugation and washing is reduced to less than 200 mg / kg. Since ethanol has a certain solubility in sorbic acid, a large amount of acidic organic waste liquid containing sorbic acid, hydrochloric acid, ethanol, tar and other impurities is obtained after washing the crude product. The sorbic acid in the waste liquid needs to be recovered.

[0016] Currently, the sorbic acid recovery technologies used in industry mainly include:

[0017] (1) Evaporate and recover ethanol from the ethanol washing solution containing tar first, and then directly cool and crystallize to separate and wash to obtain the recovered sorbic acid; the following problems exist in this process:

[0018] A large amount of tar is separated and mixed with the precipitated sorbic acid. Therefore, a large amount of tar will wrap the sorbic acid crystals, and the internal tar in the recovered sorbic acid cannot be separated from the sorbic acid, resulting in poor quality of the recovered sorbic acid obtained by the current process;

[0019] Tar itself has solubility in sorbic acid, and a large amount of sorbic acid will remain in the tar, which will also lead to limited recovery amount of sorbic acid and low recovery rate;

[0020] During the evaporation and recovery process of the sorbic acid washing organic waste liquid and the washing liquid of the recovered sorbic acid, a large amount of water needs to be evaporated, consuming a large amount of energy.

[0021] (2) Through decolorization and Fenton reagent oxidation treatment (CN 213295062U), the sorbic acid washing waste liquid is successively filtered under pressure after alcohol recovery, decolorized with activated carbon and filtered under pressure, oxidized with Fenton reagent and filtered under pressure, and finally the pH is adjusted to reduce the COD of the washing waste liquid to less than 200 ppm, and effectively recover ethanol and sorbic acid in the waste liquid, and separate and treat tar and crotonaldehyde in the waste liquid; the following problems exist in this process:

[0022] In this process, sorbic acid precipitates simultaneously with tar during the evaporation of alcohol, and the recovered sorbic acid has poor quality, and a large amount of sorbic acid will dissolve in the tar, resulting in a low recovery rate of sorbic acid.

[0023] Therefore, there is a need for a method for recovering sorbic acid tailings that is suitable for industrial use, has low costs, and improves both the recovery rate and quality of sorbic acid. Summary of the Invention

[0024] To solve at least one of the above problems, the present invention has developed a new method for recovering sorbic acid tailings. The present invention utilizes the differences in the solubility and dissolution rate of tar and sorbic acid in alcohol, and gradually adds water to the alcohol washing solution to gradually reduce the alcohol concentration in the washing solution; since tar has a high solubility in high-concentration alcohol and its solubility rapidly decreases as the alcohol concentration decreases, while the solubility of sorbic acid in the alcohol solution has an approximately linear relationship with the alcohol concentration, reducing the alcohol concentration at a suitable rate of decrease in alcohol concentration can enable the tar and ethanol solution to be preferentially, rapidly, and preferably separated, and less sorbic acid precipitates before most of the tar and ethanol are separated. And during the whole process, since most of the tar and sorbic acid do not precipitate simultaneously, with a suitable cooling rate, there will be no situation where a large amount of sorbic acid crystals contain tar, resulting in inability to separate during washing, thereby further improving the quality of the recovered sorbic acid and increasing the proportion of larger crystal particles (the proportion of 0-100 mesh > 60%, the proportion of 0-100 mesh in the existing process < 20%); while gradually reducing the alcohol concentration, gradually cooling at the same time can reduce the sorbic acid content in the separated tar and increase the recovery rate of sorbic acid.

[0025] A new method for recovering sorbic acid tailings provided by the present invention includes:

[0026] (3) Using the alcohol washing solution generated in the crude product washing section of the sorbic acid production process as the raw material, wherein the ethanol content in the alcohol washing solution is 45%-65% (v / v, the alcohol content is the volume fraction, and the following alcohol contents are all volume fractions), the sorbic acid content is 4%-5% (w / w, mass fraction, the same below), and the tar content is 3%-8% (w / w, mass fraction, the same below);

[0027] (4) Gradually reducing the alcohol concentration in the alcohol washing solution and gradually cooling at the same time; the gradual reduction of the alcohol concentration in the alcohol washing solution is to continuously add a certain amount of water within 2-5 hours, so that the alcohol concentration in the washing solution gradually decreases at a rate of 3%-22.5% / h and finally decreases to 10%-30%; the gradual cooling is to cool from 20-30°C to 0-10°C at a rate of 3°C-12.5°C / h; wherein, the cooling and water addition are carried out simultaneously, and the whole process is kept stirred for 2-5 hours;

[0028] (3) After the steps in (2) are completed, the kettle liquid is centrifuged to separate the precipitate and the filtrate, and the precipitate is washed to obtain the recovered sorbic acid.

[0029] In one embodiment, in step (2), the mass ratio of the total added mass of water to the mass of the alcohol washing liquid (m(water): m(washing liquid)) = 0.5 - 5.5.

[0030] In one embodiment, in step (2), the temperature starts to decrease from room temperature of 25 °C.

[0031] In one embodiment, in step (2), the added water can be recycled water / residual water, that is, the water after the alcohol in the water layer is recovered in the subsequent process section.

[0032] In one embodiment, in step (3), the washing is carried out using a washing liquid with an alcohol content of 60% - 80% and washing water to obtain the recovered sorbic acid. Optionally, the specific washing method is to wash once with the alcohol washing liquid and once with the washing water each time, and the obtained solid is the required recovered sorbic acid.

[0033] In one embodiment, in step (3), the ratio of the added mass (m(wash)) of the washing liquid with an alcohol content of 60% - 80% to the recovered material (m(recovered material), the mass of the solid material in the centrifuge) is m(wash): m(recovered material) = 0.5 - 2; the ratio of the added mass of the washing water to the added mass of the washing liquid with an alcohol content of 60% - 80% is m(water): m(wash) = 0.5 - 2.

[0034] In one embodiment, after the treatment in step (3), the recovered sorbic acid has a light transmittance of 40% - 50%, a sorbic acid recovery rate of 80% - 85%, and the proportion of recovered sorbic acid crystal particles of 0 - 100 mesh is 60% - 80%. After reducing the alcohol concentration and lowering the temperature in step (2), most of the tar and sorbic acid have precipitated from the solution. Most of the tar has been separated from the solution and mixed with the sorbic acid solid, and a small part of the tar will dissolve in the ethanol solution; in step (3), the kettle liquid is centrifuged, and the mixed filter cake of sorbic acid and tar in the centrifuge is washed with the alcohol washing liquid to separate the tar solution mixed in the filter cake, and the purpose of the water washing is to replace the washing liquid involved in the recovered sorbic acid tailings during the washing process.

[0035] In the above steps, the rate of gradually reducing the alcohol concentration in the alcohol washing liquid in step (2) needs to be controlled. If it drops too fast, the difference in the solubility of tar and sorbic acid cannot be reflected and the two cannot be separated. Regarding temperature control, in principle, the lower the final cooling temperature, the better (when it is low, the precipitation degree of sorbic acid is higher, and when it is high, sorbic acid cannot be separated), but if the temperature is too low, the tar will be in a solid or semi-solid state and the tar cannot be effectively separated by centrifugation.

[0036] In one embodiment, the method further includes step (4): combining and layering the filtrate and the washing liquid obtained in step (3), treating the phase containing tar as solid waste, recycling the ethanol in the water layer for use, and recycling the residual water (recycled water) after ethanol recycling to the water addition stage of step (2). Thus, continuous recovery of sorbic acid tailings can be achieved.

[0037] In one embodiment, the layering temperature in step (4) is between 35°C and 60°C, and the layering time is 10 - 60 min.

[0038] In one embodiment, the tar obtained in step (4) still contains 5% - 10% alcohol by content.

[0039] In one embodiment, in step (4), for the water layer obtained by layering, ethanol is recycled, continuously discharged under the condition of a top temperature of 80°C, the recycled ethanol is collected for standby, the content of the recycled ethanol is 95%, and the alcohol content in the residual water is 0.5%. Optionally, 30% - 70% of the residual water can be used in the gradient water addition section of step (2), and the rest is subjected to environmental protection treatment.

[0040] In one embodiment, the new method for recovering sorbic acid tailings specifically includes:

[0041] (1) The raw material used is the alcohol washing liquid generated in the crude product washing section of the sorbic acid production process. The alcohol content in this washing liquid is about 45% - 65% (the alcohol content is volume fraction, and the following alcohol contents are all volume fractions), the sorbic acid content is 4% - 5% (mass fraction, the same below), and the tar content is 3% - 8% (mass fraction, the same below).

[0042] (2) A certain amount of recycled water (m(water):m(washing liquid)=0.5 - 5.5) is continuously added to the washing liquid within 2 - 5 hours, so that the alcohol concentration in the washing liquid decreases at a rate of 3% - 22.5% / h in a gradient manner, and finally decreases to 10% - 30%; during this period, at the same time, the temperature is decreased from 25°C at a rate of 3°C - 12.5°C / h to 0 - 10°C, stirring and cooling for crystallization, lasting for 2 - 5 hours. The gradient decrease of the alcohol concentration in the washing liquid and the gradient cooling crystallization are carried out simultaneously;

[0043] (3) When the kettle temperature drops to the set temperature, the kettle liquid is centrifugally separated and washed with a 60% - 80% alcohol washing liquid (m(wash):m(recovered material)=0.5 - 2) and washing water (m(water):m(wash)=0.5 - 2) to obtain recovered sorbic acid. The transmittance of the obtained recovered sorbic acid is 40% - 50%;

[0044] (4) The filtrate and washing liquid obtained in (3) are combined and layered. The layering temperature is between 35°C and 60°C, and the layering time is 10 - 60 min. The alcohol content in the obtained tar is 5% - 10%, and the solid waste is excluded for treatment. The water layer obtained by layering is subjected to ethanol recovery, and continuous discharging is carried out under the condition of a top temperature of 80°C. The recovered ethanol is collected for standby use. The content of the recovered ethanol is 95%, and the alcohol content in the remaining water is 0.5%. Among them, 30% - 70% of the remaining water is in the gradient water addition section, and the rest enters the environmental protection process.

[0045] According to the above method, the transmittance of the recovered sorbic acid is 40% - 50%, the recovery rate of sorbic acid is 80% - 85%, and the proportion of the recovered sorbic acid crystal particles with a mesh size of 0 - 100 is 60% - 80%.

[0046] Advantages of the present invention:

[0047] Compared with the existing process (first evaporating and recovering ethanol from the ethanol washing liquid containing tar, and then directly cooling and crystallizing to separate and wash to obtain the recovered sorbic acid), the process of the present invention:

[0048] 1) It can improve the quality of the recovered sorbic acid. The transmittance of the recovered sorbic acid is increased from 20% to 40 - 50%, the sorbic acid content (i.e., purity) ≥ 92%, and the proportion of the recovered sorbic acid crystals with a mesh size of 0 - 100 is increased from <20% to >60%, which is beneficial to the improvement of quality;

[0049] 2) By gradually reducing the amount of residual sorbic acid in the tar, the recovery rate of sorbic acid is increased from 75% to 85%.

[0050] At the same time, the process of the present invention is simple, mainly involving temperature reduction operations, without the need for a large amount of steam treatment, and the energy consumption during the sorbic acid recovery process is reduced; it can also realize the recycling of ethanol and water, achieving continuous recycling as a whole and saving costs. In addition, the process of the present invention has low requirements for equipment and site, does not require expensive equipment such as membrane separation, and has a low overall cost, making it suitable for industrial applications. Description of the drawings

[0051] Figure 1 It is a process flow chart for sorbic acid recovery. Detailed implementation manners

[0052] Measurement / calculation method:

[0053] The transmittance of sorbic acid is measured by an ultraviolet spectrophotometer.

[0054] Calculation method for the recovery rate of sorbic acid: Recovery rate = (m(recovered sorbic acid) × sorbic acid content) / (m(washing liquid) × sorbic acid content) × 100%

[0055] Such as Figure 1As shown in the figure, it is the process flow diagram of sorbic acid recovery in the embodiment of the present invention. The alcohol washing solution containing tar is subjected to gradient crystallization by means of gradually decreasing the alcohol concentration and synchronously decreasing the temperature in a gradient manner, and then sorbic acid is obtained through continuous separation and washing; the mother liquor and the washing solution are stratified to obtain a tar phase and an aqueous phase. The aqueous phase is subjected to ethanol recovery, and the recovered ethanol can be continuously used for the previous alcohol washing solution, and the recovered water can be continuously used for gradually decreasing the alcohol concentration.

[0056] Example 1:

[0057] (1) The raw material used in this process is the alcohol washing solution generated in the crude product washing section of the sorbic acid production process. The alcohol content in this washing solution is about 45%, the sorbic acid content is 4%, and the tar content is 3%.

[0058] (2) A certain amount of recycled water (m(water):m(washing solution)=0.5) is continuously added to this washing solution within 5 hours, so that the alcohol concentration in the washing solution decreases at a rate of 3% in a gradient manner and finally decreases to 30%; during this period, the temperature is simultaneously decreased from room temperature of 25°C to 10°C at a rate of 3°C / h, and stirring and cooling crystallization are carried out for 5 hours. The gradient decrease of the alcohol concentration in the washing solution and the gradient cooling crystallization are carried out simultaneously.

[0059] (3) After the kettle temperature drops to the set temperature, the kettle liquid is centrifugally separated and washed with an 80% alcohol washing solution (m(wash):m(solid)=2) and washing water (m(water):m(wash)=2) to obtain the recovered sorbic acid.

[0060] (4) The filtrate and the washing solution obtained in (3) are combined and stratified at a stratification temperature of 35°C and a stratification time of 60 min. The obtained tar is discharged for solid waste treatment, and the water layer obtained by stratification is subjected to ethanol recovery. The top temperature is 80°C for discharging, and the recovered ethanol is collected for standby. The recovered ethanol content is 95%, and the alcohol content in the remaining water is 0.5%. 30% of the remaining water is used for the gradient water addition section, and the rest enters the environmental protection process.

[0061] The light transmittance of the recovered sorbic acid obtained in step (3) of this example is 51%, the sorbic acid recovery rate is 83%, and the proportion of the recovered sorbic acid crystal particles with a particle size of 0-100 mesh is 81%.

[0062] Example 2:

[0063] (1) The raw material used in this process is the alcohol washing solution generated in the crude product washing section of the sorbic acid production process. The alcohol content in this washing solution is about 50%, the sorbic acid content is 4.5%, and the tar content is 5%.

[0064] (2) A certain amount of recycled water (m(water): m(washing solution) = 1.5) was continuously added to the washing solution within 3 hours, causing the alcohol concentration in the washing solution to decrease at a rate gradient of 10% / h until it finally dropped to 20%. During this period, the temperature was simultaneously decreased from room temperature of 25°C to 7°C at a rate of 6°C / h, with stirring for cooling crystallization for 3 hours. The gradient decrease of the alcohol concentration in the washing solution and the gradient cooling crystallization were carried out simultaneously.

[0065] (3) After the kettle temperature dropped to the set temperature, the kettle liquid was centrifuged and washed with a 70% alcohol washing solution (m(wash): m(solid) = 1) and washing water (m(water): m(wash) = 1) to obtain recycled sorbic acid.

[0066] (4) The filtrate and washing solution obtained in (3) were combined and stratified at a temperature of 45°C for 30 minutes. The resulting tar was discharged for solid waste treatment. The water layer obtained by stratification was used for ethanol recovery, and the product was discharged under the condition of a top temperature of 80°C. The recovered ethanol was collected for standby use, with the recovered ethanol content being 95%, and the alcohol content in the remaining water being 0.5%. 50% of the remaining water was used for the gradient water addition section, and the rest entered the environmental protection process.

[0067] The light transmittance of the recycled sorbic acid obtained in step (3) of this example was 45%, the sorbic acid recovery rate was 82%, and the proportion of the recycled sorbic acid crystal particles with a particle size of 0 - 100 mesh was 74%.

[0068] Example 3:

[0069] (1) The raw material used in this process was the alcohol washing solution generated in the crude product washing section of the sorbic acid production process. The alcohol content in this washing solution was approximately 65%, the sorbic acid content was 5%, and the tar content was 8%.

[0070] (2) A certain amount of recycled water (m(water): m(washing solution) = 5.5) was continuously added to the washing solution within 2 hours, causing the alcohol concentration in the washing solution to decrease at a rate gradient of 22.5% / h until it finally dropped to 10%. During this period, the temperature was simultaneously decreased from room temperature of 25°C to 0°C at a rate of 12.5°C / h, with stirring for cooling crystallization for 2 hours. The gradient decrease of the alcohol concentration in the washing solution and the gradient cooling crystallization were carried out simultaneously.

[0071] (3) After the kettle temperature dropped to the set temperature, the kettle liquid was centrifuged and washed with a 60% alcohol washing solution (m(wash): m(solid) = 0.5) and washing water (m(water): m(wash) = 0.5) to obtain recycled sorbic acid.

[0072] (4) The filtrate and washing liquid obtained in (3) are combined and stratified. The stratification temperature is 35 °C and the stratification time is 10 min. The obtained tar is discharged for solid waste treatment. The water layer obtained by stratification is subjected to ethanol recovery, and the material is discharged under the condition that the top temperature is 99 °C. The recovered ethanol is collected for standby. The content of the recovered ethanol is 60%, and the alcohol content in the remaining water is 0.1%. Among them, 50% of the remaining water is in the gradient water addition section, and the rest enters the environmental protection process.

[0073] In this example, the transmittance of the recovered sorbic acid obtained in step (3) is 43%, the recovery rate of sorbic acid is 85%, and the proportion of the recovered sorbic acid crystal particles with a mesh size of 0 - 100 is 62%.

[0074] Comparative Example 1:

[0075] Compared with Examples 1, 2, and 3, the traditional process for recovering sorbic acid is adopted. Specifically:

[0076] The alcohol washing waste liquid with an alcohol content of 45% as in Example 1 is subjected to evaporation for alcohol recovery. Evaporation is stopped when the kettle temperature reaches 98 °C. The kettle liquid is cooled evenly to 10 °C, and the total cooling time is about 8 hours. When the kettle temperature drops to the set temperature, the kettle liquid is centrifuged. The recovered sorbic acid is obtained by washing with a 70% alcohol washing liquid and washing water. The filtrate and washing liquid are combined and stratified. The obtained tar from stratification is discharged for solid waste treatment. The water layer obtained by stratification is subjected to ethanol recovery. The recovered ethanol is collected for standby, and the remaining water enters the environmental protection process for treatment.

[0077] In this comparative example, the transmittance of the recovered sorbic acid is 20%, the content is 85%, the recovery rate of sorbic acid is 75%, and the proportion of the recovered sorbic acid crystal particles with a mesh size of 0 - 100 is 15%, and the crystals are powdery.

[0078] Comparative Example 2:

[0079] Compared with Example 3, the end temperature of cooling crystallization in step (2) is changed, and the rest is the same as Example 3. Specifically:

[0080] (1) The raw material used in this process is the alcohol washing liquid generated in the crude product washing section of the sorbic acid production process, which is the same as that in Example 3. The alcohol content in this washing liquid is about 65%, the sorbic acid content is 5%, and the tar content is 8%.

[0081] (2) A certain amount of recovered water (m(water):m(washing liquid)=5.5) is continuously added to the washing liquid within 2 hours, so that the alcohol concentration in the washing liquid decreases at a rate of 22.5% / h in a gradient manner until it finally drops to 10%. During this period, at the same time, the temperature is decreased from 25 °C at room temperature to -10 °C at a rate of 25 °C / h, and the stirring crystallization cooling time is 1.4 hours, and it is carried out while the alcohol concentration in the washing liquid is decreasing in a gradient manner;

[0082] (3) After the temperature of the kettle drops to the set temperature, the liquid in the kettle is centrifuged and washed with a 60% alcohol washing solution (m(wash):m(solid)=0.5) and washing water (m(water):m(wash)=0.5) to obtain recovered sorbic acid;

[0083] (4) The filtrate and washing solution obtained in (2) are combined and layered. The layering temperature is 35°C and the layering time is 10 min. The obtained tar is discharged for solid waste treatment. The water layer obtained by layering is subjected to ethanol recovery. The material is discharged under the condition of a top temperature of 80°C. The recovered ethanol is collected for standby. The content of the recovered ethanol is 95%. The alcohol content in the remaining water is 0.5%. 50% of the remaining water is used for the gradient water addition section, and the rest enters the environmental protection process.

[0084] The transmittance of the recovered sorbic acid obtained in step (3) of this comparative example is 10%, the sorbic acid recovery rate is 72%, and the proportion of the recovered sorbic acid crystal particles with a mesh size of 0-100 is 43%.

[0085] Comparative Example 3:

[0086] Compared with Example 3, the rate of decrease in the alcohol concentration in step (2) is changed, and the others are the same as in Example 3. Specifically:

[0087] (2) A certain amount of recovered water is continuously added to the washing solution within 1.5 hours, so that the alcohol concentration in the washing solution decreases at a rate of 36.7% / h in a gradient manner and finally decreases to 10%; during this period, the temperature is simultaneously decreased from 25°C at room temperature to 0°C at a rate of 12.5°C / h, and stirring and cooling crystallization are carried out for 2 hours. The gradient decrease in the alcohol concentration in the washing solution and the gradient cooling crystallization are carried out simultaneously.

[0088] The transmittance of the recovered sorbic acid obtained in this comparative example is 21%, the sorbic acid recovery rate is 76%, and the proportion of the recovered sorbic acid crystal particles with a mesh size of 0-100 is 22%.

[0089] Comparative Example 4:

[0090] Compared with Example 3, the final alcohol concentration in step (2) is changed, and the others are the same as in Example 3. Specifically:

[0091] (2) A certain amount of recovered water is continuously added to the washing solution within 1.56 hours, so that the alcohol concentration in the washing solution decreases at a rate of 22.5% / h in a gradient manner and finally decreases to 30%; during this period, the temperature is simultaneously decreased from 25°C at room temperature to 0°C at a rate of 12.5°C / h, and stirring and cooling crystallization are carried out for 2 hours. The gradient decrease in the alcohol concentration in the washing solution and the gradient cooling crystallization are carried out simultaneously.

[0092] The transmittance of the recovered sorbic acid obtained in this comparative example is 33%, the sorbic acid recovery rate is 31%, and the proportion of the recovered sorbic acid crystal particles with a mesh size of 0-100 is 41%.

[0093] The present invention has been disclosed in the preferred embodiments, but it is not intended to limit the present invention. Any technical solutions obtained by using equivalent substitutions or equivalent transformations fall within the protection scope of the present invention.

Claims

1. A method for recycling sorbic acid tailings, characterized in that, The method includes the following steps: (1) Using the alcohol washing liquid generated in the crude product washing section of the sorbic acid production process as the raw material. The ethanol content in the alcohol washing liquid is 45%-65% v / v, the sorbic acid content is 4%-5% w / w, and the tar content is 3%-8% w / w; (2) Gradually reducing the alcohol concentration in the alcohol washing liquid and simultaneously cooling it at a gradient. Gradually reducing the alcohol concentration in the alcohol washing liquid means continuously adding a certain amount of water within 2-5 hours, so that the alcohol concentration in the washing liquid decreases at a rate of 3%-22.5% / h in a gradient until it finally decreases to 10%-30%. The gradient cooling means cooling from 20-30°C to 0-10°C at a rate of 3°C-12.5°C / h. Among them, the cooling and the addition of water are carried out simultaneously, and the whole process is kept stirred for 2-5 hours; (3) After the completion of the step (2), the kettle liquid is centrifuged to separate the precipitate and the filtrate, and the precipitate is washed to obtain the recovered sorbic acid.

2. The recycling method according to claim 1, characterized in that, In step (2), the mass ratio of the total added mass of water to the mass of the alcohol washing liquid is 0.5-5.

5.

3. The recycling method according to claim 1, characterized in that, In step (3), the washing is carried out using a washing liquid with an alcohol content of 60%-80% and washing water to obtain the recovered sorbic acid.

4. The recycling method according to claim 1, characterized in that, In step (3), the mass ratio of the added mass of the washing liquid with an alcohol content of 60%-80% to the recovered material is 0.5-2.

5. The recycling method according to claim 4, characterized in that, The mass ratio of the added mass of the washing water to the added mass of the washing liquid with an alcohol content of 60%-80% is 0.5-2.

6. The recycling method according to claim 1, characterized in that, The method further includes step (4): combining and layering the filtrate and the washing liquid obtained in step (3), treating the phase containing tar as solid waste, recycling the ethanol in the water layer, and recycling the residual water after the ethanol is recycled to the water addition stage of step (2).

7. The recycling method according to claim 6, characterized in that, The layering temperature in step (4) is between 35°C and 60°C, and the layering time is 10-60 minutes.

8. The recycling method according to claim 6, characterized in that, In step (4), the ethanol in the water layer obtained by layering is recycled.

9. The recycling method according to claim 1, characterized in that, The method specifically includes: (1) The raw material used is the alcohol washing liquid generated in the crude product washing section of the sorbic acid production process. The alcohol content in this washing liquid is about 45%-65%, the sorbic acid content is 4%-5%, and the tar content is 3%-8%; (2) Continuously adding a certain amount of recycled water to this washing liquid within 2-5 hours, so that the alcohol concentration in the washing liquid decreases at a rate of 3%-22.5% / h in a gradient until it finally decreases to 10%-30%. During this period, simultaneously cool from room temperature 25°C to 0-10°C at a rate of 3°C-12.5°C / h, stir and cool for crystallization for 2-5 hours, and the gradient reduction of the alcohol concentration in the washing liquid and the gradient cooling for crystallization are carried out simultaneously; (3) After the kettle temperature drops to the set temperature, the kettle liquid is centrifuged and washed using a 60%-80% alcohol washing liquid and washing water to obtain the recovered sorbic acid, and the light transmittance of the obtained recovered sorbic acid is 40%-50%; (4) The filtrate and washing liquid obtained in (3) are combined and layered, the layering temperature is between 35°C and 60°C, and the layering time is 10 - 60 min; the obtained tar is treated as solid waste, the water layer obtained by layering is used for the recovery of ethanol, and the residual water is used as recycled water for step (2).

10. Application of the method according to any one of claims 1-9 in the production of sorbic acid.

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