A method for recovering polyglycerol from polyglycerol oil residue

Abstract

The present application relates to a kind of polyglycerol recovered from polyglycerol oil residue, the steps of the recovery method include dissolving acidification, acidification liquid separation, neutralization reaction, electrodialysis treatment, distillation purification and decolorization etc.Step.The present application recovers polyglycerol from polyglycerol oil residue method by dissolving, makes solid polyglycerol oil residue into liquid polyglycerol oil residue solution, by adjusting pH, the oil residue that is not dissolved in acid is precipitated, the polyglycerol in solution is recovered conveniently, the recovery rate of polyglycerol reaches 55~82%, and the recovery rate of fatty acid reaches 58~76%.

Description

[Technical Field]

[0001] This invention belongs to the field of wastewater treatment technology. More specifically, this invention relates to a method for recovering polyglycerol from polyglycerol oil residue. [Background Technology]

[0002] Glycerin is a multifunctional organic compound with wide industrial applications. To meet practical needs, crude glycerin requires refining. The residue obtained from crude glycerin refining is commonly known as polyglycerol residue, which is very difficult to clean and decolorize, rendering it unusable and economically unviable without treatment. Polyglycerol residue is often simply incinerated or landfilled, causing serious environmental pollution and wasting 3-5% of the total glycerin mass. Currently, there is a need to develop a simple and effective method for treating polyglycerol residue.

[0003] According to relevant literature (titled "Recycling and Utilization of Glycerol Distillation Residue", *Daily Chemical Industry*, 1997.4), the existing processing technology uses solvent extraction, that is, using organic solvents such as isopropanol and ethylene glycol to extract polyglycerol from polyglycerol residue, followed by decolorization and purification with activated carbon. However, this method suffers from problems such as solvent loss, solvent pollution, and low recovery rate, resulting in poor economic efficiency and preventing industrial-scale production. Furthermore, during the extraction process, the organic solvents also extract fatty acids from the polyglycerol residue, leading to high lipid content and low quality in the prepared polyglycerol. Additionally, Zhou Jianping's article, "A Method for Preparing Polyglycerol from By-products", *Small and Medium Enterprise Management and Technology (Early Issue)*, 2019, reports on the extraction, separation, and molecular distillation purification of polyglycerol, but this process is energy-intensive and costly.

[0004] In order to overcome the shortcomings of the existing technology, the inventors conducted extensive experimental research and analysis, and finally completed this invention. [Summary of the Invention]

[0005] [Technical problem to be solved]

[0006] The purpose of this invention is to provide a method for recovering polyglycerol from polyglycerol residue.

[0007] [Technical Solution]

[0008] The present invention is achieved through the following technical solution.

[0009] This invention relates to a method for recovering polyglycerol from polyglycerol residue.

[0010] The steps of this recycling method are as follows:

[0011] A. Dissolution and acidification

[0012] Polyglycerol oil residue and an inorganic acid aqueous solution with a concentration of 10-60% by weight are added to acidification reaction tank 1 through material inlet 1-1 located at the top of acidification reaction tank 1 at a weight ratio of 1:0.5-2.0. The mixture is stirred and reacted at a temperature of 40-90℃ for 30-120 minutes to obtain a polyglycerol oil residue acidification solution.

[0013] B. Separation of acidified liquid

[0014] The polyglycerol residue acidified liquid obtained in step A is sent through a pipeline from outlet 1-2 at the bottom of the acidification reaction tank 1 to inlet 2-1 at the top of the oil-water separator 2. The polyglycerol residue acidified liquid is centrifuged in the oil-water separator 2 to separate an upper fatty acid liquid and a lower polyglycerol acidified liquid. The upper fatty acid liquid is transferred to the alkali tank 3 through a skimming device or overflow device from fatty acid outlet 2-2 at the top of the oil-water separator 2, while the lower polyglycerol acidified liquid is discharged from acidified liquid outlet 2-3 at the bottom of the oil-water separator 2 for subsequent processing.

[0015] C. Neutralization reaction

[0016] The polyglycerol acidified liquid obtained in step B is sent through a pipeline to the acidified liquid inlet 4-1 located in the middle of the neutralization reaction tank 4. According to the weight ratio of polyglycerol acidified liquid to solid inorganic alkali 1:0.01~0.10, solid inorganic alkali is added to the neutralization reaction tank 4 through the inorganic alkali inlet 4-2 located at the top of the neutralization reaction tank 4. The mixture is stirred and dissolved, and reacted at a temperature of 40~90℃ for 20~60 minutes to obtain a polyglycerol solution with a pH of 6~8. This solution is discharged from the polyglycerol solution outlet 4-3 opposite to the acidified liquid inlet 4-1 and sent through a pipeline to the filter inlet 5-1 located at the top of the filter 5. The polyglycerol solution is filtered by the filter 5 to remove the precipitate it contains. It is discharged from the precipitate outlet 5-3 located at the bottom of the filter 5. The resulting transparent polyglycerol solution is discharged from the polyglycerol solution outlet 5-2 located at the top of the filter 5.

[0017] D. Electrodialysis treatment

[0018] According to the weight ratio of transparent polyglycerol solution to water of 1:0.5-2.0, the transparent polyglycerol solution obtained in step C is sent through a pipe from the polyglycerol solution outlet 5-2 located above the filter 5 to the fresh water inlet 6-1 located below the electrodialysis device 6. At the same time, water is sent through a pipe to the concentrated water inlet 6-2 located above the electrodialysis device 6. The salt contained in the polyglycerol solution is transferred to the water in the electrodialysis device 6, resulting in a desalted polyglycerol solution and a salt solution. The salt solution with a sodium chloride concentration of 10%-30% by weight is discharged from the salt solution outlet 6-3 opposite to the fresh water inlet 6-1. The desalted polyglycerol solution is discharged from the polyglycerol solution outlet 6-4 opposite to the concentrated water area 6-2.

[0019] E. Distillation purification

[0020] The desalted polyglycerol solution discharged in step D is sent through a pipe to the polyglycerol solution inlet 7-1 located at the bottom of the evaporator 7. The desalted polyglycerol solution is evaporated at a temperature of 100-150°C. The water is discharged from the distilled water outlet 7-2 located at the top of the evaporator 7, and the obtained polyglycerol is discharged from the polyglycerol outlet 7-3 located at the top of the evaporator 7.

[0021] G. Decolorization

[0022] Polyglycerol discharged from polyglycerol outlet 7-3 is piped to decolorizing inlet 8-1 located at the bottom of fixed bed 8. Polyglycerol is slowly decolorized in fixed bed 8 at a temperature of 70-110℃ for 60-150 minutes and is discharged from polyglycerol outlet 8-2 located at the top of fixed bed 8 to obtain colorless polyglycerol.

[0023] According to a preferred embodiment of the present invention, in step A, the polyglycerol residue contains 40-50% polyglycerol, 20-30% fatty acids, 3-7% water by weight, and the balance being inorganic impurities such as sodium chloride, sodium hydroxide, and phosphate; the inorganic acid is one or more inorganic acids selected from hydrochloric acid, sulfuric acid, or phosphoric acid.

[0024] According to another preferred embodiment of the present invention, in step B, the oil-water separator 2 is an air flotation separation type or a centrifugal separation type oil-water separation device.

[0025] According to another preferred embodiment of the present invention, in step C, the solid inorganic base is one or more inorganic bases selected from sodium hydroxide, sodium carbonate or potassium hydroxide.

[0026] According to another preferred embodiment of the present invention, in step C, the neutralization reaction tank 4 is a continuous dosing neutralization tank, an upflow expansion filter, or a drum neutralization filter type neutralization reaction device;

[0027] According to another preferred embodiment of the present invention, in step C, the filter 5 is a plate and frame filter, a membrane filter press, or a cartridge filter.

[0028] According to another preferred embodiment of the present invention, in step D, the electrodialysis device 6 is an inverted electrode, bipolar membrane or ion-exchange membrane type electrodialysis device. The ion exchange membrane used is an alloy membrane or homogeneous membrane with a pore size of 0.1 μm or more. Its electrodialysis conditions are that multiple layers of anion and cation membranes are alternately stacked to form a membrane stack, and anode and cathode plates are set on both sides. Charged ions or ion clusters in the solution move directionally to the clear water under the traction of the electrodes, while uncharged organic matter is retained in the original solution.

[0029] According to another preferred embodiment of the present invention, in step E, the evaporator 7 is a tubular evaporator, a scraped evaporator, or a centrifugal evaporator.

[0030] According to another preferred embodiment of the present invention, in step F, the activated carbon fixed bed is a cylinder with a diameter-to-height ratio of 1:10 to 20, and the fixed bed is an activated carbon granular bed with a particle size of 8 to 30 mesh.

[0031] According to another preferred embodiment of the present invention, in step F, the colorless polyglycerol discharged from the polyglycerol outlet 8-2 contains more than 98% polyglycerol by weight, with the remainder being a small amount of water, salt and trace amounts of pigment organic matter.

[0032] The invention will now be described in more detail.

[0033] This invention relates to a method for recovering polyglycerol from polyglycerol residue.

[0034] This invention relates to a method for extracting polyglycerol from polyglycerol residue, thereby realizing the resource utilization of polyglycerol residue. The invention involves introducing a large amount of H into the polyglycerol residue. + The fatty acid salts in glycerol are converted into fatty acids and recycled, thus reducing the lipid content in glycerol.

[0035] The steps of this recycling method are as follows:

[0036] A. Dissolution and acidification

[0037] Polyglycerol oil residue and an inorganic acid aqueous solution with a concentration of 10-60% by weight are added to acidification reaction tank 1 through material inlet 1-1 located at the top of acidification reaction tank 1 at a weight ratio of 1:0.5-2.0. The mixture is stirred and reacted at a temperature of 40-90℃ for 30-120 minutes to obtain a polyglycerol oil residue acidification solution.

[0038] The main role of the dissolution and acidification step in the method of recovering polyglycerol from polyglycerol residue is that the strong acid reacts with the organic non-glycerol substances MONG in the polyglycerol residue to form an organic acid that is insoluble in water, which is presented as an oil phase, thus facilitating oil-water separation.

[0039] The polyglycerol residue used in this invention is, for example, provided by Ningbo Huanyang New Material Co., Ltd.

[0040] The polyglycerol residue contains, by weight, 40-50% polyglycerol, 20-30% fatty acids, 3-7% water, and the balance being inorganic impurities such as sodium chloride, sodium hydroxide, and phosphate. The polyglycerol content is determined using standard high-performance liquid chromatography (HPLC). The fatty acid content is determined by titration and further analyzed using a combined chromatography-mass spectrometry (GC-MS) method. Here, fatty acids should be understood as short-chain fatty acids such as acetic acid and butyric acid, medium-chain fatty acids such as octanoic acid and lauric acid, and long-chain fatty acids such as palmitic acid and oleic acid. The contents of sodium chloride, sodium hydroxide, and phosphate are determined using analytical methods commonly used in the field of chemical engineering.

[0041] The inorganic acid used in this invention is one or more inorganic acids selected from hydrochloric acid, sulfuric acid, or phosphoric acid. The concentration of these inorganic acids is 10-60% by weight. If the concentration of the inorganic acid is less than 10%, the acidification reaction will be incomplete, and the conversion of the saponified product into fatty acids will be incomplete. If the concentration of the inorganic acid is greater than 60%, there will be an excess of inorganic acid, leading to an increase in the amount of neutralizing alkali required in the subsequent process. Therefore, a concentration of 10-60% of inorganic acid is suitable, preferably 20-48%. The inorganic acids used in this invention are all commercially available products.

[0042] In this step, the weight ratio of polyglycerol residue to the inorganic acid aqueous solution is 1:0.5–2.0. If the weight ratio of polyglycerol residue to inorganic acid aqueous solution is greater than 1:0.5, their mixture solution is too viscous, resulting in poor stirring, reaction, and mass transfer effects; if the weight ratio of polyglycerol residue to inorganic acid aqueous solution is less than 1:2.0, the organic matter concentration of the mixture is too low, leading to high energy consumption in subsequent purification processes. Therefore, a weight ratio of 1:0.5–2.0 for polyglycerol residue to inorganic acid aqueous solution is appropriate, and preferably 1:0.8–1.6.

[0043] In this step, when the stirring and mixing reaction time is within the specified range, if the stirring and mixing reaction temperature is below 40°C, the reactivity is low and the reaction is incomplete; if the stirring and mixing reaction temperature is above 90°C, the reaction rate does not increase further. Therefore, a stirring and mixing reaction temperature of 40–90°C is reasonable, preferably 48–82°C. When the stirring and mixing reaction temperature is within the specified range, if the stirring and mixing reaction time is less than 30 min, the reaction is incomplete, resulting in incomplete conversion of polyglycerol residue and wasted reagents; if the stirring and mixing reaction time is longer than 120 min, the extended reaction time does not significantly improve the reaction efficiency. Therefore, a stirring and mixing reaction time of 30–120 min is appropriate, preferably 50–100 min.

[0044] The acidification reaction tank 1 used in this step is a commonly used reaction vessel with a stirrer that is currently available on the market in the field of chemical technology, such as the reaction vessel sold by Zhengzhou Fangyuan Instrument Co., Ltd. under the trade name Double-layer glass heating and stirring reaction vessel.

[0045] B. Separation of acidified liquid

[0046] The polyglycerol residue acidified liquid obtained in step A is sent through a pipeline from outlet 1-2 at the bottom of the acidification reaction tank 1 to inlet 2-1 at the top of the oil-water separator 2. The polyglycerol residue acidified liquid is centrifuged in the oil-water separator 2 to separate an upper fatty acid liquid and a lower polyglycerol acidified liquid. The upper fatty acid liquid is transferred to the alkali tank 3 through a skimming device or overflow device from fatty acid outlet 2-2 at the top of the oil-water separator 2, while the lower polyglycerol acidified liquid is discharged from acidified liquid outlet 2-3 at the bottom of the oil-water separator 2 for subsequent processing.

[0047] The main role of this acidification liquid separation step in the method of recovering polyglycerol from polyglycerol residue is to separate the oil phase fatty acids from the polyglycerol aqueous solution to obtain a high-purity polyglycerol solution and fatty acid intermediate products.

[0048] The polyglycerol oil residue acidified liquid is centrifuged in oil-water separator 2 at a speed of 1000-2500 rpm for 3-20 minutes to separate it into an upper fatty acid liquid and a lower polyglycerol acidified liquid.

[0049] The oil-water separator 2 used in this invention is an air flotation separation type or a centrifugal separation type oil-water separation device, which are products currently sold on the market, such as the disc centrifugal separation type oil-water separation device sold by Liaoning Ke'en Machinery Co., Ltd. under the trade name DHC disc centrifuge.

[0050] In this invention, the upper layer of fatty acid solution is transferred to the alkali tank 3 via a skimming device or an overflow device. The skimming device or overflow device used in this invention are commercially available products, such as the skimming device sold by Liaoyang Zhonglian Pharmaceutical Machinery Co., Ltd. under the trade name "Flat Plate Automatic Skimming Centrifuge," and the overflow device sold by Zhengzhou Changcheng Science & Industry Experimental Instrument Factory Co., Ltd. under the trade name "Five-Link Overflow Device." The alkali tank 3 used in this invention is a commonly used filling device in the chemical engineering field.

[0051] The lower layer of polyglycerol acidified liquid is discharged from acidified liquid outlet 2-3 and sent to neutralization reaction tank 4 for further treatment.

[0052] C. Neutralization reaction

[0053] The polyglycerol acidified liquid obtained in step B is sent through a pipeline to the acidified liquid inlet 4-1 located in the middle of the neutralization reaction tank 4. According to the weight ratio of polyglycerol acidified liquid to solid inorganic alkali 1:0.01~0.10, solid inorganic alkali is added to the neutralization reaction tank 4 through the inorganic alkali inlet 4-2 located at the top of the neutralization reaction tank 4. The mixture is stirred and dissolved, and reacted at a temperature of 40~90℃ for 20~60 minutes to obtain a polyglycerol solution with a pH of 6~8. This solution is discharged from the polyglycerol solution outlet 4-3 opposite to the acidified liquid inlet 4-1 and sent through a pipeline to the filter inlet 5-1 located at the top of the filter 5. The polyglycerol solution is filtered by the filter 5 to remove the precipitate it contains. It is discharged from the precipitate outlet 5-3 located at the bottom of the filter 5. The resulting transparent polyglycerol solution is discharged from the polyglycerol solution outlet 5-2 located at the top of the filter 5.

[0054] The main role of this neutralization reaction step in the method of recovering polyglycerol from polyglycerol residue is to precipitate the impurities contained in the polyglycerol solution and, in conjunction with the subsequent filtration process, remove insoluble neutral or weakly alkaline impurities.

[0055] The solid inorganic base used in this invention is one or more inorganic bases selected from sodium hydroxide, sodium carbonate, or potassium hydroxide, all of which are currently commercially available products.

[0056] The weight ratio of polyglycerol acidified liquid to solid inorganic alkali is 1:0.01 to 0.10. If the weight ratio is greater than 1:0.01, the amount of alkali used is insufficient, resulting in incomplete removal of impurities. If the weight ratio is less than 1:0.10, the amount of alkali used is excessive, wasting alkali raw materials and hindering subsequent evaporation processes. Therefore, a weight ratio of 1:0.01 to 0.10 is suitable, preferably 1:0.02 to 0.08, and more preferably 1:0.03 to 0.06.

[0057] The polyglycerol acidified solution reacts with a solid inorganic base at a temperature of 40–90°C for 20–60 minutes. Within this range, if the reaction temperature is below 40°C, the reactivity is low and the reaction rate is slow; if the reaction temperature is above 90°C, the polyglycerol in the acidified solution may undergo chain scission as the temperature increases. Therefore, a reaction temperature of 40–90°C is preferable, preferably 48–82°C, and more preferably 56–75°C. Within this range, if the reaction time is less than 20 minutes, the reaction is incomplete and reagents are wasted; if the reaction time is longer than 60 minutes, some other side reactions may occur. Therefore, a reaction time of 20–60 minutes is appropriate, preferably 26–52 minutes, and more preferably 32–46 minutes.

[0058] The resulting polyglycerol solution has a pH of 6–8. If the pH of the polyglycerol solution is below 6, the precipitation of impurity ions will be incomplete; if the pH of the polyglycerol solution is above 8, it will be detrimental to the subsequent evaporation process, causing the polymerization reaction to continue. Therefore, a pH of 6–8 for the polyglycerol solution is reasonable, preferably 6.4–7.6, and more preferably 6.7–7.2. The pH value of the polyglycerol solution was measured using a pH meter sold by Mettler Toledo under the trade name FE28K pH meter, according to the operating procedures described in its instruction manual.

[0059] The neutralization reaction tank 4 used in this invention is a type of neutralization reaction equipment, such as a continuous dosing neutralization tank, an upflow expansion filter, or a drum neutralization filter. These are all products currently sold on the market. For example, the continuous dosing neutralization tank sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name "Continuous Solid Feeding Neutralization Tank", the upflow expansion filter sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name "Upflow Filter", and the drum neutralization filter sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name "Drum Neutralization Filter".

[0060] The filter 5 used in this invention is a plate and frame filter, a membrane filter press, or a cartridge filter, all of which are currently available on the market. For example, the plate and frame filter sold by Cangzhou Yaoda Dream Filter Equipment Manufacturer under the trade name Dream brand plate and frame filter press, the riser membrane filter sold by Haining Yadong Filter Equipment Co., Ltd. under the trade name flip-type positive pressure filter, and the cartridge filter sold by Haining Yadong Filter Equipment Co., Ltd. under the trade name cartridge type flip-type filter.

[0061] D. Electrodialysis treatment

[0062] According to the weight ratio of transparent polyglycerol solution to water of 1:0.5-2.0, the transparent polyglycerol solution obtained in step C is sent through a pipe from the polyglycerol solution outlet 5-2 located above the filter 5 to the fresh water inlet 6-1 located below the electrodialysis device 6. At the same time, water is sent through a pipe to the concentrated water inlet 6-2 located above the electrodialysis device 6. The salt contained in the polyglycerol solution is transferred to the water in the electrodialysis device 6, resulting in a desalted polyglycerol solution and a salt solution. The salt solution with a sodium chloride concentration of 10%-30% by weight is discharged from the salt solution outlet 6-3 opposite to the fresh water inlet 6-1. The desalted polyglycerol solution is discharged from the polyglycerol solution outlet 6-4 opposite to the concentrated water area 6-2.

[0063] The main role of this electrodialysis treatment step in the method of recovering polyglycerol from polyglycerol residue is to remove charged ions from the polyglycerol solution through electrode traction and selective ion permeation of a homogeneous membrane, thereby achieving deep desalination.

[0064] In this invention, "pure water" should be understood as a clear and transparent body of water with very low particulate matter content. The basic purpose of using pure water is to absorb the charged ions separated by the ion-selective permeation homogeneous membrane in the polyglycerol stock solution, that is, to absorb the salts contained in the polyglycerol stock solution.

[0065] The weight ratio of the transparent polyglycerol solution to water is 1:0.5 to 2.0. If the weight ratio is greater than 1:0.5, the salt content in the water after receiving the salt will be too high, resulting in excessive energy consumption for electrodialysis. If the weight ratio is less than 1:2.0, the salt content in the water after receiving the salt will be too low, leading to the production of a large amount of saline solution. Therefore, a weight ratio of 1:0.5 to 2.0 is preferable, and more preferably 1:0.8 to 1.6.

[0066] The electrodialysis device 6 used in this invention is an inverted electrode, bipolar membrane, or ion-exchange membrane type electrodialysis device. The ion exchange membrane used is an alloy membrane or homogeneous membrane with a pore size of 0.1 μm or larger. The electrodialysis devices mentioned are all products currently sold on the market, such as the inverted electrode type electrodialysis device sold by Hangzhou Lanran Technology Co., Ltd. under the trade name "Inverted Electrodialysis Device with Homogeneous Membrane"; the bipolar membrane type electrodialysis device sold by Hangzhou Lanran Technology Co., Ltd. under the trade name "Bipolar Alloy Membrane Electrodialysis Device"; and the ion-exchange membrane type electrodialysis device sold by Hangzhou Lanran Technology Co., Ltd. under the trade name "Diaphragm Type Electrodialysis Device".

[0067] In the electrodialysis device 6, multiple layers of anion and cation membranes are stacked alternately to form a membrane stack, and anode and cathode plates are set on both sides. Charged ions or ion clusters in the solution move directionally to the clear water under the traction of the electrodes, while uncharged organic matter remains in the original solution.

[0068] The electrodialysis conditions of electrodialysis device 6 are as follows: current density 10~400A / m 2 Operating temperature: 15–35℃; Flow rate: 100–500 ml / s; Pressure: 0.09–0.12 MPa;

[0069] E. Distillation purification

[0070] The desalted polyglycerol solution discharged in step D is sent through a pipe to the polyglycerol solution inlet 7-1 located at the bottom of the evaporator 7. The desalted polyglycerol solution is evaporated at a temperature of 100-150°C. The water is discharged from the distilled water outlet 7-2 located at the top of the evaporator 7, and the obtained polyglycerol is discharged from the polyglycerol outlet 7-3 located at the top of the evaporator 7.

[0071] The main role of this distillation purification step in the method of recovering polyglycerol from polyglycerol residue is to remove water from the polyglycerol solution;

[0072] When the desalted polyglycerol solution evaporates in evaporator 7, if the evaporation temperature is below 100°C, it is difficult to completely evaporate the water; if the evaporation temperature is above 150°C, it will cause unnecessary energy waste. Therefore, an evaporation temperature of 100-150°C is reasonable, preferably 110-140°C, and more preferably 116-135°C.

[0073] The evaporator 7 used in this invention is a tubular evaporator, a scraped evaporator, or a centrifugal evaporator, all of which are currently available on the market. For example, the tubular evaporator sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name "Multi-tube Evaporator", the scraped evaporator sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name "Automatic Scraped Evaporator", and the centrifugal evaporator sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name "Centrifugal Thin Film Evaporator".

[0074] G. Decolorization

[0075] Polyglycerol discharged from polyglycerol outlet 7-3 is piped to decolorizing inlet 8-1 located at the bottom of fixed bed 8. Polyglycerol is slowly decolorized in fixed bed 8 at a temperature of 70-110℃ for 60-150 minutes and is discharged from polyglycerol outlet 8-2 located at the top of fixed bed 8 to obtain colorless polyglycerol.

[0076] The main role of this decolorization step in the method of recovering polyglycerol from polyglycerol residue is to remove pigment impurities contained in the polyglycerol discharged from the polyglycerol discharge port 7-3;

[0077] The activated carbon fixed bed used in this invention is a cylinder with a diameter-to-height ratio of 1:10-20. The fixed bed is a granular activated carbon bed with a particle size of 8-30 mesh. The activated carbon used in this invention is a commercially available product, such as the powdered activated carbon sold by Zhejiang Zhelang Activated Carbon Co., Ltd.

[0078] Polyglycerol was slowly passed through an activated carbon fixed bed in a fixed bed 8 at a temperature of 70–110°C for 60–150 min to decolorize it.

[0079] When the decolorization time is within the aforementioned range, if the decolorization temperature is below 70°C, the decolorization effect will be poor; if the decolorization temperature is above 110°C, it will cause unnecessary energy waste. Therefore, a decolorization temperature of 70–110°C is feasible, preferably 80–100°C. When the decolorization temperature is within the aforementioned range, if the decolorization time is less than 60 minutes, the decolorization will be incomplete; if the decolorization time is longer than 150 minutes, other side reactions may occur. Therefore, a decolorization time of 60–150 minutes is suitable, preferably 70–135 minutes, and more preferably 78–126 minutes.

[0080] According to the standard detection method of high performance liquid chromatography, the colorless polyglycerol discharged from polyglycerol outlet 8-2 contains more than 98% polyglycerol by weight, with the remainder being a small amount of water, salt and trace amounts of pigment organic matter.

[0081] The polyglycerol recovery rate of the method of the present invention is calculated according to the following formula (I):

[0082] Polyglycerol recovery rate (%) = TOC 聚甘油 / TOC0*100%(I)

[0083] In the formula:

[0084] TOC 聚甘油 The method step G of this invention yields the TOC (total organic carbon) mass of polyglycerol;

[0085] TOC0 is the mass of TOC (total organic carbon) of polyglycerol in the polyglycerol residue used in the method of this invention.

[0086] The polyglycerol recovery rate of the recycling method of this invention reaches 55-82%.

[0087] The fatty acid recovery rate of the method of the present invention is calculated according to the following formula (II):

[0088] Fatty acid recovery rate (%) = TOC 脂肪酸 / TOC1*100%(II)

[0089] In the formula:

[0090] TOC 脂肪酸 The TOC mass of the fatty acids obtained in step B of the method of this invention;

[0091] TOC1 is the TOC mass of fatty acids contained in the polyglycerol residue used in the method of this invention.

[0092] The fatty acid recovery rate of the recovery method of this invention reaches 58-76%.

[0093] [Beneficial Effects]

[0094] The beneficial technical effects of this invention are:

[0095] This invention relates to a method for recovering polyglycerol from polyglycerol residue. By dissolving solid polyglycerol residue into a liquid polyglycerol residue solution, and adjusting the pH to allow acid-insoluble residue to precipitate, the polyglycerol in the solution can be easily recovered. The recovery rate of polyglycerol reaches 55-82%, and the recovery rate of fatty acids reaches 58-76%. [Attached Image Description]

[0096] Appendix Figure 1 This is a schematic diagram of the process for recovering polyglycerol from polyglycerol oil residue according to the present invention.

[0097] In the picture:

[0098] 1-Acidification reaction tank; 1-1-Material inlet; 1-2-Outlet; 2-Oil-water separator; 2-1-Oil residue acidification liquid inlet; 2-2-Fatty acid outlet; 2-3-Acidification liquid outlet; 3-Alkali tank; 4-Neutralization reaction tank; 4-1-Acidification liquid inlet; 4-2-Inorganic alkali inlet; 4-3-Polyglycerol solution outlet; 5-Filter; 5-1-Filter inlet; 5-2-Polyglycerol solution outlet; 5-3-Sediment outlet; 6-Electrodialysis unit; 6-1-Desalinated water zone inlet; 6-2-Concentrated water zone inlet; 6-3-Salt solution outlet; 6-4-Polyglycerol solution outlet; 7-Evaporator; 7-1-Polyglycerol solution inlet; 7-2-Distilled water outlet; 7-3-Polyglycerol outlet; 8-Fixed bed; 8-1-Decolorizing agent inlet; 8-2-Polyglycerol outlet.

Detailed Implementation Methods

[0099] The invention will be better understood through the following examples.

[0100] Example 1: Method for recovering polyglycerol from polyglycerol residue

[0101] The implementation steps of this embodiment are as follows:

[0102] A. Dissolution and acidification

[0103] The polyglycerol residue used in this embodiment contains 40% polyglycerol, 24% fatty acid, 7% water by weight, and the balance being inorganic impurities such as sodium chloride, sodium hydroxide, and phosphate.

[0104] The polyglycerol oil residue and a 26% hydrochloric acid inorganic acid aqueous solution by weight were added to the acidification reaction tank 1 through the material inlet 1-1 located at the top of the acidification reaction tank 1, which was sold by Zhengzhou Fangyuan Instrument Co., Ltd. under the trade name of double-layer glass heated and stirred reaction vessel, at a weight ratio of 1:1.5. The mixture was stirred and reacted for 60 minutes at a temperature of 75°C to obtain a polyglycerol oil residue acidification liquid.

[0105] B. Separation of acidified liquid

[0106] The polyglycerol oil residue acidified liquid obtained in step A is sent through a pipeline from outlet 1-2 at the bottom of the acidification reaction tank 1 to oil residue acidified liquid inlet 2-1 at the top of the oil-water separator 2. The polyglycerol oil residue acidified liquid is centrifuged for 5 minutes in a disc centrifuge-type oil-water separator 2 (trade name: DHC disc centrifuge) sold by Liaoning Keen Machinery Co., Ltd. at a centrifuge speed of 2000 rpm, separating it into an upper fatty acid liquid and a lower polyglycerol acidified liquid. The upper fatty acid liquid is transferred from fatty acid outlet 2-2 at the top of the oil-water separator 2 to the alkali tank 3 through a skimming device (trade name: flat plate automatic skimming centrifuge) sold by Liaoyang Zhonglian Pharmaceutical Machinery Co., Ltd., while the lower polyglycerol acidified liquid is discharged from acidified liquid outlet 2-3 at the bottom of the oil-water separator 2 for further processing.

[0107] C. Neutralization reaction

[0108] The polyglycerol acidified liquid obtained in step B is piped to the acidified liquid inlet 4-1 in the middle of the continuous dosing neutralization tank 4, which is sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name "Continuous Dosing Neutralization Tank". Sodium hydroxide solid inorganic alkali is added to the neutralization tank 4 through the inorganic alkali inlet 4-2 at the top of the neutralization tank 4 according to a weight ratio of polyglycerol acidified liquid to solid inorganic alkali of 1:0.01. The mixture is stirred and dissolved, and reacted at 75℃ for 35 minutes to obtain a polyglycerol solution with a pH of 8.0. This solution is discharged from the polyglycerol solution outlet 4-3, which is opposite to the acidified liquid inlet 4-1, and piped to the filter inlet 5-1 at the top of the plate and frame filter 5, which is sold by Cangzhou Yaoda Dream Filter Equipment Co., Ltd. under the trade name "Dream Brand Plate and Frame Filter Press". The polyglycerol solution is filtered by the filter 5 to remove its precipitates, and it is discharged from the precipitate outlet 5-3 at the bottom of the filter 5. The resulting transparent polyglycerol solution is discharged from the polyglycerol solution outlet 5-2 at the top of the filter 5.

[0109] D. Electrodialysis treatment

[0110] According to the weight ratio of transparent polyglycerol solution to water of 1:1.0, the transparent polyglycerol solution obtained in step C is piped from the polyglycerol solution outlet 5-2 located above filter 5 to the freshwater inlet 6-1 located below the inverted polarity electrodialysis device 6 sold by Hangzhou Lanran Technology Co., Ltd. under the trade name "Inverted Polarity Electrodialysis Equipment". Simultaneously, clean water is piped to the concentrated water inlet 6-2 located above the electrodialysis device 6. The electrodialysis device 6 operates at a current density of 400 A / m³. 2Electrodialysis is performed under the following conditions: operating temperature 25℃, flow rate 100ml / s, and pressure 0.1MPa. The salt contained in the polyglycerol solution is transferred to clean water in the electrodialysis device 6 to obtain a desalted polyglycerol solution and a salt solution. The salt solution with a sodium chloride concentration of 10% by weight is discharged from the salt solution outlet 6-3, which is opposite to the fresh water inlet 6-1. The desalted polyglycerol solution is discharged from the polyglycerol solution outlet 6-4, which is opposite to the concentrated water zone 6-2.

[0111] E. Distillation purification

[0112] The desalted polyglycerol solution discharged in step D is piped to the polyglycerol solution inlet 7-1 located at the bottom of the tubular evaporator 7, which is sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name Multi-tube Evaporator. The desalted polyglycerol solution is evaporated at a temperature of 150°C. The water is discharged from the distilled water outlet 7-2 located at the top of the evaporator 7, and the obtained polyglycerol is discharged from the polyglycerol outlet 7-3 located at the top of the evaporator 7.

[0113] G. Decolorization

[0114] Polyglycerol discharged from polyglycerol outlet 7-3 is piped to decolorizing inlet 8-1 located at the bottom of activated carbon fixed bed 8 with particle size of 8-30 mesh. Polyglycerol is slowly passed through the activated carbon fixed bed 8 at a temperature of 110℃ for 60 minutes for polyglycerol decolorization. Colorless polyglycerol is then discharged from polyglycerol outlet 8-2 located at the top of the fixed bed 8.

[0115] According to the method described in this application, the polyglycerol recovery rate of this embodiment is 55%, and the fatty acid recovery rate is 58%.

[0116] Example 2: Method for recovering polyglycerol from polyglycerol residue

[0117] The implementation steps of this embodiment are as follows:

[0118] A. Dissolution and acidification

[0119] The polyglycerol residue used in this embodiment contains 50% polyglycerol, 20% fatty acids, 3% water by weight, and the balance being inorganic impurities such as sodium chloride, sodium hydroxide, and phosphate.

[0120] The polyglycerol oil residue and a 10% sulfuric acid inorganic acid aqueous solution were added to the acidification reaction tank 1 through the material inlet 1-1 at the top of the acidification reaction tank 1, which was sold by Zhengzhou Fangyuan Instrument Co., Ltd. under the trade name of double-layer glass heated and stirred reactor, at a weight ratio of 1:2.0. The mixture was stirred and reacted for 90 minutes at a temperature of 55°C to obtain a polyglycerol oil residue acidification liquid.

[0121] B. Separation of acidified liquid

[0122] The polyglycerol oil residue acidified liquid obtained in step A is sent through a pipeline from outlet 1-2 at the bottom of the acidification reaction tank 1 to oil residue acidified liquid inlet 2-1 at the top of the oil-water separator 2. The polyglycerol oil residue acidified liquid is centrifuged for 10 minutes at a centrifugal separation type oil-water separator 2 sold by Liaoning Keen Machinery Co., Ltd. under the trade name DHC disc centrifuge at a centrifuge speed of 2500 rpm, and centrifuged to separate into an upper fatty acid liquid and a lower polyglycerol acidified liquid. The upper fatty acid liquid is transferred to the alkali tank 3 through the fatty acid outlet 2-2 at the top of the oil-water separator 2 via an overflow device sold by Liaoyang Zhonglian Pharmaceutical Machinery Co., Ltd. under the trade name flat plate automatic skimming centrifuge. The lower polyglycerol acidified liquid is discharged from the acidified liquid outlet 2-3 at the bottom of the oil-water separator 2 for subsequent processing.

[0123] C. Neutralization reaction

[0124] The polyglycerol acidified liquid obtained in step B is piped to the acidified liquid inlet 4-1 in the middle of the neutralization reaction tank 4 of the upflow expansion filter type sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name upflow filter. According to the weight ratio of polyglycerol acidified liquid to solid inorganic alkali of 1:0.10, sodium carbonate solid inorganic alkali is added to the neutralization reaction tank 4 through the inorganic alkali inlet 4-2 located at the top of the neutralization reaction tank 4. The mixture is stirred and dissolved, and reacted at a temperature of 40℃ for 60 minutes to obtain a polyglycerol solution with a pH of 6.0. This solution is discharged from the polyglycerol solution outlet 4-3 opposite to the acidified liquid inlet 4-1, and piped to the filter inlet 5-1 at the top of the filter membrane filter 5 sold by Haining Yadong Filter Equipment Co., Ltd. under the trade name flip-type positive pressure filter. The polyglycerol solution is filtered by the filter 5 to remove the precipitate it contains, and it is discharged from the precipitate outlet 5-3 located at the bottom of the filter 5. The resulting transparent polyglycerol solution is discharged from the polyglycerol solution outlet 5-2 located at the top of the filter 5.

[0125] D. Electrodialysis treatment

[0126] According to the weight ratio of transparent polyglycerol solution to water of 1:0.5, the transparent polyglycerol solution obtained in step C is piped from the polyglycerol solution outlet 5-2 located above filter 5 to the desalination zone inlet 6-1 located below the bipolar membrane electrodialysis device 6 sold by Hangzhou Lanran Technology Co., Ltd. under the trade name "Bipolar Alloy Membrane Electrodialysis Equipment". Simultaneously, water is piped to the concentrate zone inlet 6-2 located above the electrodialysis device 6. The electrodialysis device 6 operates at a current density of 400 A / m³. 2Electrodialysis is performed under the following conditions: operating temperature 30℃, flow rate 100ml / s, and pressure 0.11MPa. The salt contained in the polyglycerol solution is transferred to clean water in the electrodialysis device 6 to obtain a desalted polyglycerol solution and a salt solution. The salt solution with a sodium chloride concentration of 16% by weight is discharged from the salt solution outlet 6-3, which is opposite to the fresh water inlet 6-1. The desalted polyglycerol solution is discharged from the polyglycerol solution outlet 6-4, which is opposite to the concentrated water zone 6-2.

[0127] E. Distillation purification

[0128] The desalted polyglycerol solution discharged in step D is piped to the polyglycerol solution inlet 7-1 located at the bottom of the scraped evaporator 7 sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name Automatic Scraped Evaporator. The desalted polyglycerol solution is evaporated at a temperature of 100°C. The water is discharged from the distilled water outlet 7-2 located at the top of the evaporator 7, and the obtained polyglycerol is discharged from the polyglycerol outlet 7-3 located at the top of the evaporator 7.

[0129] G. Decolorization

[0130] Polyglycerol discharged from polyglycerol outlet 7-3 is sent through a pipeline to decolorizing inlet 8-1, located at the bottom of activated carbon fixed bed 8 with particle size of 8-30 mesh. Polyglycerol is slowly passed through the activated carbon fixed bed 8 at a temperature of 70℃ for 150 minutes for polyglycerol decolorization. Colorless polyglycerol is then discharged from polyglycerol outlet 8-2, located at the top of the fixed bed 8.

[0131] According to the method described in this application, the polyglycerol recovery rate of this embodiment is 65%, and the fatty acid recovery rate is 74%.

[0132] Example 3: Method for recovering polyglycerol from polyglycerol residue

[0133] The implementation steps of this embodiment are as follows:

[0134] A. Dissolution and acidification

[0135] The polyglycerol residue used in this embodiment contains 44% polyglycerol, 30% fatty acids, 4% water by weight, and the balance being inorganic impurities such as sodium chloride, sodium hydroxide, and phosphate.

[0136] The polyglycerol oil residue and a 60% (by weight) phosphoric acid inorganic acid aqueous solution were added to the acidification reaction tank 1 through the material inlet 1-1 at the top of the acidification reaction tank 1, which was sold by Zhengzhou Fangyuan Instrument Co., Ltd. under the trade name "double-layer glass heated and stirred reactor". The mixture was stirred and reacted for 120 minutes at a temperature of 40°C to obtain a polyglycerol oil residue acidification liquid.

[0137] B. Separation of acidified liquid

[0138] The polyglycerol oil residue acidified liquid obtained in step A is sent through a pipeline from outlet 1-2 at the bottom of the acidification reaction tank 1 to oil residue acidified liquid inlet 2-1 at the top of the oil-water separator 2. The polyglycerol oil residue acidified liquid is centrifuged for 10 minutes in a disc centrifuge-type oil-water separator 2 sold by Liaoning Keen Machinery Co., Ltd. under the trade name DHC disc centrifuge, at a centrifuge speed of 2500 rpm, and centrifuged to separate into an upper fatty acid liquid and a lower polyglycerol acidified liquid. The upper fatty acid liquid is transferred from the fatty acid outlet 2-2 at the top of the oil-water separator 2 to the alkali tank 3 through an overflow device sold by Zhengzhou Changcheng Science and Technology Experimental Instruments Co., Ltd. under the trade name five-link overflow device, while the lower polyglycerol acidified liquid is discharged from the acidified liquid outlet 2-3 at the bottom of the oil-water separator 2 for subsequent treatment.

[0139] C. Neutralization reaction

[0140] The polyglycerol acidified liquid obtained in step B is piped to the acidified liquid inlet 4-1 in the middle of the neutralization reaction tank 4 of the roller neutralization filter type sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name roller neutralization filter. According to the weight ratio of polyglycerol acidified liquid to solid inorganic alkali of 1:0.07, potassium hydroxide solid inorganic alkali is added to the neutralization reaction tank 4 through the inorganic alkali inlet 4-2 located at the top of the neutralization reaction tank 4. The mixture is stirred and dissolved, and reacted at a temperature of 56℃ for 45 minutes to obtain a polyglycerol solution with a pH of 6.6. This solution is discharged from the polyglycerol solution outlet 4-3 opposite to the acidified liquid inlet 4-1, and piped to the filter inlet 5-1 at the top of the cartridge filter 5 sold by Haining Yadong Filter Equipment Co., Ltd. under the trade name cartridge type flip filter. The polyglycerol solution is filtered by the filter 5 to remove the precipitate it contains. It is discharged from the precipitate outlet 5-3 located at the bottom of the filter 5. The resulting transparent polyglycerol solution is discharged from the polyglycerol solution outlet 5-2 located at the top of the filter 5.

[0141] D. Electrodialysis treatment

[0142] According to the weight ratio of transparent polyglycerol solution to water of 1:1.5, the transparent polyglycerol solution obtained in step C is piped from the polyglycerol solution outlet 5-2 located above filter 5 to the desalination zone inlet 6-1 located below the bipolar membrane electrodialysis device 6 sold by Hangzhou Lanran Technology Co., Ltd. under the trade name "Bipolar Alloy Membrane Electrodialysis Equipment". Simultaneously, water is piped to the concentrate zone inlet 6-2 located above the electrodialysis device 6. The electrodialysis device 6 operates at a current density of 400 A / m³. 2Electrodialysis is performed under the following conditions: operating temperature 30℃, flow rate 100ml / s, and pressure 0.1MPa. The salt contained in the polyglycerol solution is transferred to clean water in the electrodialysis device 6 to obtain a desalted polyglycerol solution and a salt solution. The salt solution with a sodium chloride concentration of 24% by weight is discharged from the salt solution outlet 6-3, which is opposite to the fresh water inlet 6-1. The desalted polyglycerol solution is discharged from the polyglycerol solution outlet 6-4, which is opposite to the concentrated water zone 6-2.

[0143] E. Distillation purification

[0144] The desalted polyglycerol solution discharged in step D is piped to the polyglycerol solution inlet 7-1 located at the bottom of the centrifugal evaporator 7 sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name centrifugal thin film evaporator. The desalted polyglycerol solution is evaporated at a temperature of 125°C. The water is discharged from the distilled water outlet 7-2 located at the top of the evaporator 7, and the obtained polyglycerol is discharged from the polyglycerol outlet 7-3 located at the top of the evaporator 7.

[0145] G. Decolorization

[0146] Polyglycerol discharged from polyglycerol outlet 7-3 is piped to decolorizing inlet 8-1 located at the bottom of activated carbon fixed bed 8 with particle size of 8-30 mesh. Polyglycerol is slowly passed through the activated carbon fixed bed 8 at a temperature of 85℃ for 120 minutes for polyglycerol decolorization. Colorless polyglycerol is then discharged from polyglycerol outlet 8-2 located at the top of the fixed bed 8.

[0147] According to the method described in this application, the polyglycerol recovery rate of this embodiment is 82%, and the fatty acid recovery rate is 76%.

[0148] Example 4: Method for recovering polyglycerol from polyglycerol residue

[0149] The implementation steps of this embodiment are as follows:

[0150] A. Dissolution and acidification

[0151] The polyglycerol residue used in this embodiment contains 48% polyglycerol, 28% fatty acids, 6% water by weight, and the balance being inorganic impurities such as sodium chloride, sodium hydroxide, and phosphate.

[0152] The polyglycerol oil residue and a 44% sulfuric acid inorganic acid aqueous solution by weight were added to the acidification reaction tank 1 through the material inlet 1-1 located at the top of the acidification reaction tank 1, which was sold by Zhengzhou Fangyuan Instrument Co., Ltd. under the trade name of double-layer glass heated and stirred reaction vessel, at a weight ratio of 1:1.0. The mixture was stirred and reacted for 30 minutes at a temperature of 90°C to obtain a polyglycerol oil residue acidification liquid.

[0153] B. Separation of acidified liquid

[0154] The polyglycerol oil residue acidified liquid obtained in step A is sent through a pipeline from outlet 1-2 at the bottom of the acidification reaction tank 1 to oil residue acidified liquid inlet 2-1 at the top of the oil-water separator 2. The polyglycerol oil residue acidified liquid is centrifuged for 15 minutes at a centrifugal separation type oil-water separator 2 sold by Liaoning Keen Machinery Co., Ltd. under the trade name DHC disc centrifuge at a centrifuge speed of 200 rpm, and centrifuged to separate into an upper fatty acid liquid and a lower polyglycerol acidified liquid. The upper fatty acid liquid is transferred from fatty acid outlet 2-2 at the top of the oil-water separator 2 to the alkali tank 3 through a skimming device sold by Liaoyang Zhonglian Pharmaceutical Machinery Co., Ltd. under the trade name flat plate automatic skimming centrifuge, while the lower polyglycerol acidified liquid is discharged from acidified liquid outlet 2-3 at the bottom of the oil-water separator 2 for subsequent processing.

[0155] C. Neutralization reaction

[0156] The polyglycerol acidified liquid obtained in step B is piped to the acidified liquid inlet 4-1 in the middle of the neutralization reaction tank 4 of the roller neutralization filter type sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name of roller neutralization filter. According to the weight ratio of polyglycerol acidified liquid to solid inorganic alkali of 1:0.04, sodium hydroxide solid inorganic alkali is added to the neutralization reaction tank 4 through the inorganic alkali inlet 4-2 located at the top of the neutralization reaction tank 4. The mixture is stirred and dissolved, and reacted at a temperature of 90℃ for 20 minutes to obtain a polyglycerol solution with a pH of 7.2. This solution is discharged from the polyglycerol solution outlet 4-3 opposite to the acidified liquid inlet 4-1, and piped to the filter inlet 5-1 at the top of the plate and frame filter 5 sold by Cangzhou Yaoda Dream Filter Equipment Co., Ltd. under the trade name of Dream brand plate and frame filter press. The polyglycerol solution is filtered by the filter 5 to remove the precipitate it contains. It is discharged from the precipitate outlet 5-3 located at the bottom of the filter 5. The resulting transparent polyglycerol solution is discharged from the polyglycerol solution outlet 5-2 located at the top of the filter 5.

[0157] D. Electrodialysis treatment

[0158] According to the weight ratio of transparent polyglycerol solution to water of 1:2.0, the transparent polyglycerol solution obtained in step C is piped from the polyglycerol solution outlet 5-2 located above filter 5 to the desalination zone inlet 6-1 located below the ion-exchange membrane electrodialysis device 6 sold by Hangzhou Lanran Technology Co., Ltd. under the trade name "Membrane Electrodialysis Equipment". Simultaneously, water is piped to the concentrate zone inlet 6-2 located above the electrodialysis device 6. The electrodialysis device 6 operates at a current density of 400 A / m³. 2Electrodialysis is performed under the following conditions: operating temperature 25℃, flow rate 100ml / s, and pressure 0.11MPa. The salt contained in the polyglycerol solution is transferred to clean water in the electrodialysis device 6 to obtain a desalted polyglycerol solution and a salt solution. The salt solution with a sodium chloride concentration of 30% by weight is discharged from the salt solution outlet 6-3, which is opposite to the fresh water inlet 6-1. The desalted polyglycerol solution is discharged from the polyglycerol solution outlet 6-4, which is opposite to the concentrated water zone 6-2.

[0159] E. Distillation purification

[0160] The desalted polyglycerol solution discharged in step D is piped to the polyglycerol solution inlet 7-1 located at the bottom of the tubular evaporator 7, which is sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name Multi-tube Evaporator. The desalted polyglycerol solution is evaporated at a temperature of 135°C. The water is discharged from the distilled water outlet 7-2 located at the top of the evaporator 7, and the obtained polyglycerol is discharged from the polyglycerol outlet 7-3 located at the top of the evaporator 7.

[0161] G. Decolorization

[0162] Polyglycerol discharged from polyglycerol outlet 7-3 is piped to decolorizing inlet 8-1 located at the bottom of activated carbon fixed bed 8 with particle size of 8-30 mesh. Polyglycerol is slowly passed through the activated carbon fixed bed 8 at a temperature of 95℃ for 90 minutes for polyglycerol decolorization. Colorless polyglycerol is then discharged from polyglycerol outlet 8-2 located at the top of the fixed bed 8.

[0163] According to the method described in this application, the polyglycerol recovery rate of this embodiment is 74%, and the fatty acid recovery rate is 66%.

Claims

1. A method for recovering polyglycerol from polyglycerol residue, characterized in that... The recycling method involves the following steps: A. Dissolution and acidification Polyglycerol oil residue and an inorganic acid aqueous solution with a concentration of 10-60% by weight are added to the acidification reaction tank (1) through the material inlet (1-1) at the top of the acidification reaction tank (1) at a weight ratio of 1:0.5-2.

0. The mixture is stirred and reacted for 30-120 minutes at a temperature of 40-90℃ to obtain a polyglycerol oil residue acidification liquid. B. Separation of acidified liquid The polyglycerol oil residue acidified liquid obtained in step A is sent through a pipeline from the outlet (1-2) located at the bottom of the acidification reaction tank (1) to the oil residue acidified liquid inlet (2-1) located at the top of the oil-water separator (2). The polyglycerol oil residue acidified liquid is centrifuged in the oil-water separator (2) to separate into an upper fatty acid liquid and a lower polyglycerol acidified liquid. The upper fatty acid liquid is transferred to the alkali tank (3) through a skimming device or an overflow device from the fatty acid outlet (2-2) located at the top of the oil-water separator (2), while the lower polyglycerol acidified liquid is discharged from the acidified liquid outlet (2-3) located at the bottom of the oil-water separator (2) for subsequent processing. C. Neutralization reaction The polyglycerol acidified liquid obtained in step B is sent through a pipeline to the acidified liquid inlet (4-1) located in the middle of the neutralization reaction tank (4). According to the weight ratio of polyglycerol acidified liquid to solid inorganic alkali 1:0.01~0.10, solid inorganic alkali is added to the neutralization reaction tank (4) through the inorganic alkali inlet (4-2) located at the top of the neutralization reaction tank (4). The mixture is stirred and dissolved, and reacted at a temperature of 40~90℃ for 20~60min to obtain a polyglycerol solution with a pH of 6~8. The solution is discharged from the polyglycerol solution outlet (4-3) opposite to the acidified liquid inlet (4-1) and sent through a pipeline to the filter inlet (5-1) located at the top of the filter (5). The polyglycerol solution is filtered by the filter (5) to remove the precipitate it contains. It is discharged from the precipitate outlet (5-3) located at the bottom of the filter (5). The resulting transparent polyglycerol solution is discharged from the polyglycerol solution outlet (5-2) located at the top of the filter (5). D. Electrodialysis treatment According to the weight ratio of transparent polyglycerol solution to water of 1:0.5~2.0, the transparent polyglycerol solution obtained in step C is sent through a pipe from the polyglycerol solution outlet (5-2) located above the filter (5) to the fresh water inlet (6-1) located below the electrodialysis device (6). At the same time, the water is sent through a pipe to the concentrated water inlet (6-2) located above the electrodialysis device (6). The salt contained in the polyglycerol solution is transferred to the water in the electrodialysis device (6) to obtain a desalted polyglycerol solution and a salt solution. The salt solution with a sodium chloride concentration of 10%~30% by weight is discharged from the salt solution outlet (6-3) opposite to the fresh water inlet (6-1). The desalted polyglycerol solution is discharged from the polyglycerol solution outlet (6-4) opposite to the concentrated water zone (6-2). E. Distillation purification The desalted polyglycerol solution discharged in step D is sent through a pipe to the polyglycerol solution inlet (7-1) located at the bottom of the evaporator (7). The desalted polyglycerol solution is evaporated at a temperature of 100-150°C. The water is discharged from the distilled water outlet (7-2) located at the top of the evaporator (7), and the obtained polyglycerol is discharged from the polyglycerol outlet (7-3) located at the top of the evaporator (7). F. Decolorization Polyglycerol discharged from the polyglycerol outlet (7-3) is sent through a pipeline to the decolorizing inlet (8-1) located at the bottom of the fixed bed (8). The polyglycerol is slowly decolorized in the fixed bed (8) at a temperature of 70~110℃ for 60~150min through the activated carbon fixed bed. Colorless polyglycerol is then discharged from the polyglycerol outlet (8-2) located at the top of the fixed bed (8).

2. The recycling method according to claim 1, characterized in that... In step A, the polyglycerol residue contains 40-50% polyglycerol, 20-30% fatty acids, 3-7% water by weight, and the balance being inorganic impurities such as sodium chloride, sodium hydroxide, and phosphate; the inorganic acid is one or more inorganic acids selected from hydrochloric acid, sulfuric acid, or phosphoric acid.

3. The recycling method according to claim 1, characterized in that... In step B, the oil-water separator (2) is an air flotation separation type or centrifugal separation type oil-water separation device.

4. The recycling method according to claim 1, characterized in that... In step C, the solid inorganic base is one or more inorganic bases selected from sodium hydroxide, sodium carbonate, or potassium hydroxide.

5. The recycling method according to claim 1, characterized in that... In step C, the neutralization reaction tank (4) is a type of neutralization reaction equipment, such as a continuous dosing neutralization tank, an upflow expansion filter, or a drum neutralization filter.

6. The recycling method according to claim 1, characterized in that... In step C, the filter (5) is a plate and frame filter, a membrane filter press, or a cartridge filter.

7. The recycling method according to claim 1, characterized in that... In step D, the electrodialysis device (6) is an inverted electrode, bipolar membrane or ion-exchange membrane type electrodialysis device. The ion exchange membrane used is an alloy membrane or homogeneous membrane with a pore size of 0.1µm or more. Its electrodialysis conditions are that multiple layers of anion and cation membranes are stacked alternately to form a membrane stack, and anode and cathode plates are set on both sides. Charged ions or ion clusters in the solution move directionally to the clear water under the traction of the electrodes, while uncharged organic matter is retained in the original solution.

8. The recycling method according to claim 1, characterized in that... In step E, the evaporator (7) is a tubular evaporator, a scraped evaporator, or a centrifugal evaporator.

9. The recycling method according to claim 1, characterized in that... In step F, the activated carbon fixed bed (8) is a cylinder with a diameter-to-height ratio of 1:10~20, and its fixed bed is an activated carbon granule bed with a particle size of 8~30 mesh.

10. The recycling method according to claim 1, characterized in that... In step F, the colorless polyglycerol discharged from the polyglycerol outlet (8-2) contains more than 98% polyglycerol by weight, with the remainder being small amounts of water, salt and trace amounts of pigment organic matter.

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