Combined treatment method of glycerol salt and polyglycerol oil residue

Abstract

The invention relates to a combined treatment method of glycerol salt obtained by refining crude glycerol and polyglycerol oil residue, which comprises the following steps: firstly, washing the glycerol salt with water to obtain washed salt and washed salt water; the salt washing water and clear water are mixed and dissolved to obtain salt water, and organic matters in the salt water are deeply oxidized to reach the salt water standard for ionic membrane chlor-alkali through an advanced oxidation technology, so that resource recycling is realized. The method comprises the following steps: mixing and dissolving salt washing water and polyglycerol oil residues, reacting in a strong acid environment to generate water-insoluble fatty acid and NaCl salt which is crystallized and separated out due to supersaturation, and separating a three-phase mixture into solid NaCl salt, fatty acid and a polyglycerol solution through a three-phase separator. And the polyglycerol solution is sequentially subjected to neutralization, electrodialysis desalination, distillation concentration and decoloration to obtain a luminous yellow or faint yellow polyglycerol product containing more than 90% of glycerol and polyglycerol by weight.

Description

Technical field

[0001] The present invention relates to the technical field of resource processing of biodiesel byproducts, and more particularly to a method for jointly processing glycerol salt and polyglycerol oil residue. [Background Technology]

[0002] Biodiesel is a short-chain monohydric alkyl fatty acid ester with properties similar to diesel, such as viscosity and heat of combustion. Its production is increasing significantly as a key biofuel alternative to petroleum diesel. During biodiesel production, approximately 0.1 tons of crude glycerol are produced for every ton of biodiesel produced. Crude glycerol has a glycerol content of 60-80%, and also contains water, methanol, fatty acids, salts, and catalysts. Crude glycerol must be refined into refined glycerol before it can be commercialized. High-purity glycerol (99.5%) is widely used in the pharmaceutical, food, chemical, and cosmetic industries.

[0003] Currently, the primary glycerin refining technology is vacuum distillation. During the distillation process, a certain percentage of distillation residue is discharged. This residue primarily consists of inorganic salts, free alkali, oils, and pigments. Furthermore, in the high-temperature, high-alkaline environment, a portion of the glycerol polymerizes to form polyglycerol. These substances have high boiling points and are difficult to vaporize and evaporate, resulting in continuous concentration at the bottom of the tower, where they form the glycerol distillation residue. Failure to regularly discharge this residue can compromise the quality of the refined glycerin. Typically, the distillation residue is stored in a conical storage tank, where the inorganic salts settle to the bottom. It is then discharged through a discharge port and centrifuged at high speed to form glycerol salts with a NaCl content exceeding 95%. The upper layer of the tank contains the polyglycerol oil residue, which appears as a brown-black liquid at high temperatures and gradually transforms into a semi-solid at lower temperatures. Its main components are polyglycerol, fatty acids, pigments, and inorganic salts.

[0004] The existing technology has little recycling of glycerol salts, and the economic benefits are low. CN108640391A discloses a method and a treatment device for treating high-salt wastewater generated by crude glycerol purification. It can be seen that the glycerol salts are basically discharged in the form of wastewater during treatment, which is complex and costly.

[0005] Regarding the treatment of polyglycerol oil residue, the method for recovering polyglycerol adopted by Shandong Boxinghua Oil Chemical Co., Ltd. (Wei Daijun et al., "Surfactant Technology"; Issue 2, 2000, pp. 23-24) produces new separation residues, and the separation and extraction process is complex and the equipment investment cost is high.

[0006] SU1130548S discloses the production of concrete additives using glycerol distillation residues. Glycerol distillation residues, as a plasticizer in concrete additives, can improve the shrinkage and water resistance of concrete. However, due to the large amount of chloride ions contained in the glycerol residues, this product is no longer suitable for the modern concrete construction market.

[0007] Therefore, the crude glycerol refining field is in urgent need of an efficient and economical processing technology to realize the high-value resource utilization of glycerol salts and polyglycerol oil residues. In order to address this technical gap, the inventors have finally completed the present invention after a large amount of experimental research and analysis and summary. [Summary of the invention]

[0008] [Technical problems to be solved]

[0009] The purpose of the present invention is to provide a method for jointly treating glycerol salt and polyglycerol oil residue.

[0010] [Technical solution]

[0011] The present invention is achieved through the following technical solutions.

[0012] The invention relates to a combined treatment method of glycerol salt and polyglycerol oil residue.

[0013] The processing steps of the combined processing method are as follows:

[0014] A. Glycerol saline wash

[0015] Tap water and glycerol salt are added to the salt washing drum 1 in a weight ratio of 0.3 to 0.8:1, mixed and dissolved, and the obtained solid-liquid mixture is washed with water in the salt washing drum 1 at a speed of 15 to 30 rpm for 10 to 60 minutes. The washed salt slurry is sent to the compression filter 2 and passed through a 0.45 μm filter membrane under a pressure of 0.3 to 0.5 MPa to obtain water-washed salt and washing brine;

[0016] B. Water washing salt treatment

[0017] The washed salt obtained in step A is mixed and dissolved with tap water in a salting tank 3 at a solid-liquid weight ratio of 1:3.5-5.5 to obtain a high-concentration brine, which is then sent to a catalytic oxidation tower 4. At the same time, an oxidant is added to the catalytic oxidation tower 4, mixed evenly, and reacted at a temperature of 30-60° C. for 1-3 hours to reduce the total organic carbon content of the high-concentration brine to below 10 mg / L, thereby obtaining a high-concentration clean brine.

[0018] C. Co-acidification treatment

[0019] The brine obtained in step A is mixed with the polyglycerol oil residue in a dissolution tank 5 and dissolved. The resulting mixed solution is then fed to an acidification reaction tower 6. Simultaneously, a hydrochloric acid solution having a concentration of 28 to 34% by weight is also fed to the acidification reaction tower 6 and mixed uniformly. The pH value of the mixed solution is controlled to be below 1.0. The mixture is then subjected to an acidification reaction at a temperature of 40 to 90° C. with stirring for 30 to 150 minutes, thereby obtaining a three-phase mixture.

[0020] D. Three-phase separation

[0021] The three-phase mixture obtained in step C is fed to a three-phase separator 7 and separated into a lower solid phase, an intermediate aqueous phase, and an upper oil phase at a rotation speed of 1000-2500 rpm and a temperature of 10-80° C.; the lower solid phase is crystalline NaCl, which is separated and removed by a high-speed centrifuge 8 at a rotation speed of 1000-2500 rpm, and then returned to step B after washing; the upper oil phase is dissolved in a fatty acid pool 9 using methanol, ethanol, or a NaOH solution, and then distilled and concentrated in a distillation tower 10 at a vacuum degree of 5-20 kPa to obtain a fatty acid product; the intermediate aqueous phase is a polyglycerol solution with a pH value below 1, which is then subjected to subsequent treatment;

[0022] E. Polyglycerol solution treatment

[0023] The polyglycerol solution obtained in step D is sent to a neutralization tank 11. At the same time, caustic soda is added to the neutralization tank 11 and stirred until the solution becomes neutral. The solution is allowed to stand for 2 hours to remove the insoluble precipitate at the bottom. The upper clear liquid is sent to an electrodialysis device 12. The salt content of the polyglycerol solution is reduced to less than 0.1% by weight under the condition of an operating temperature below 35° C., thereby obtaining a desalted polyglycerol solution and a salty water. The salty water is returned to step A and recycled as washing water.

[0024] F. Concentration

[0025] The desalted polyglycerol solution obtained in step E is evaporated and concentrated in a distillation tower 13 to obtain a polyglycerol concentrate having a content of more than 90% by weight;

[0026] G. Decolorization

[0027] The polyglycerol concentrate obtained in step F is decolorized by passing through a decolorization tower 14 to remove colored substances contained in the polyglycerol concentrate, thereby obtaining a bright yellow or light yellow polyglycerol product.

[0028] According to a preferred embodiment of the present invention, in step A, the glycerol salt contains 95-98% NaCl, 1-3% glycerol and 1-3% water by weight.

[0029] According to another preferred embodiment of the present invention, in step A, the glycerol salt is mixed and dissolved in the salt washing drum 1 at a temperature of 10 to 70°C; the salt washing drum 1 is a double-axis flip stirring drum or a single-axis flip stirring drum; the compression filter 2 is a flip positive pressure membrane filter or a flip positive pressure filter element filter.

[0030] According to another preferred embodiment of the present invention, in step B, the oxidant is ozone or hydrogen peroxide; the weight ratio of high-concentration brine to oxidant is 1:0.01-0.05; the catalytic oxidation tower 4 is a fixed-bed oxidation tower filled with alumina balls or activated carbon granules with a diameter of 3-5 mm, and the ratio of the tower body diameter to the tower height is 1:4-12.

[0031] According to another preferred embodiment of the present invention, in step C, the weight ratio of the washing brine to the polyglycerol oil residue is 0.3-1.0:1; the acidification reaction tower 6 is a paddle stirred reactor, a turbine stirred reactor, a propeller stirred reactor or an anchor stirred reactor.

[0032] According to another preferred embodiment of the present invention, in step D, the three-phase separator 7 is a butterfly-type centrifuge, a centrifugal clarification type or a centrifugal separation type phase separator; the high-speed centrifuge 8 is a tripod centrifuge, an overhead centrifuge or a centrifugal discharge centrifuge type centrifuge; the fatty acid tank 9 is a reactor with an anchor structure; and the distillation tower 10 is a bubble-cap type, a sieve plate type, a vertical sieve plate type or a floating tongue type distillation tower.

[0033] According to another preferred embodiment of the present invention, in step D, the crystallized NaCl separated from the residual liquid is washed 2 to 4 times with methanol according to a volume ratio of the crystallized NaCl to methanol of 1:3 to 5; the volume ratio of the upper oil phase to methanol, ethanol or NaOH solution is 1:2 to 4.

[0034] According to another preferred embodiment of the present invention, in step E, the pH of the desalted polyglycerol solution is lower than 1, the polyglycerol organic matter content thereof is 30-50% by weight, and the salt content is 10-20%; the salty water contains 0.5-2.0% by weight of organic matter.

[0035] According to another preferred embodiment of the present invention, in step F, the desalted polyglycerol solution is evaporated and concentrated in a distillation tower 13 at a temperature of 80-120° C. and a pressure of 20-100 kPa for 60-300 min; the distillation tower 13 is a bubble-cap type, sieve-plate type or vertical sieve-plate type distillation tower.

[0036] According to another preferred embodiment of the present invention, in step G, the polyglycerol concentrate is decolorized at a temperature of 70 to 90° C. in a decolorization tower 14 for 30 to 90 minutes; the decolorization tower 14 is a fixed bed activated carbon decolorization tower or a fluidized bed activated carbon decolorization tower.

[0037] The present invention will be described in more detail below.

[0038] The invention relates to a combined treatment method of glycerol salt and polyglycerol oil residue.

[0039] To address the weaknesses and complexities of existing glycerol distillation residue treatment technologies, the inventors have developed a method for the combined treatment of glycerol salts and polyglycerol oil residues, which improves the resource recovery efficiency of NaCl salts, polyglycerols, and fatty acids. Furthermore, the combined treatment method operates under normal pressure and at mild temperatures, resulting in a pollution-free production process.

[0040] The processing steps of this method are as follows:

[0041] A. Glycerol saline wash

[0042] Tap water and glycerol salt are added to the salt washing drum 1 in a weight ratio of 0.3 to 0.8:1, mixed and dissolved, and the obtained solid-liquid mixture is washed with water in the salt washing drum 1 at a speed of 15 to 30 rpm for 10 to 60 minutes. The washed salt slurry is sent to the compression filter 2 and passed through a 0.45 μm filter membrane under a pressure of 0.3 to 0.5 MPa to obtain water-washed salt and washing brine;

[0043] The glycerol salt used in the present invention is a solid salt produced when preparing refined glycerol by distilling crude glycerol, a by-product of biodiesel. For example, see the glycerol salt used in CN 219128315U. This glycerol salt contains 95-98% NaCl, 1-3% glycerol and 1-3% water by weight.

[0044] In the present invention, washing with glycerol salt water should be understood as dissolving the glycerol organic matter on the surface of the solid salt particles into water with water to form a mutually soluble glycerol solution; at the same time, due to the dissolution of NaCl, the washing water becomes a nearly saturated brine solution.

[0045] In this step, the weight ratio of tap water to glycerol salt needs to be controlled at 0.3 to 0.8:1. If the weight ratio of tap water to glycerol salt is higher than 0.8:1, too much salt will dissolve in the water, resulting in a significant reduction in the amount of water-washed salt and an excessively high salt content in the subsequent treatment solution. If the ratio of tap water to glycerol salt is lower than 0.3:1, the glycerol salt is not fully washed, resulting in a high organic matter content in the water-washed salt and a high subsequent deep oxidation load. Therefore, a weight ratio of tap water to glycerol salt of 0.3 to 0.8:1 is appropriate, and preferably 0.4 to 0.6:1.

[0046] In this step, the obtained solid-liquid mixture is washed with water in the salt washing drum 1 at a temperature of 10-70°C and a rotation speed of 15-30 rpm for 10-60 minutes. When the washing time and the rotation speed are within the above range, if the washing temperature is lower than 10°C, the tap water will not be effective in dissolving the glycerol organic matter; if the washing temperature is higher than 70°C, the overall energy consumption will be relatively high, increasing the processing cost; therefore, the washing temperature is suitable to be 10-70°C, preferably 22-58°C, and more preferably 30-50°C.

[0047] When the washing temperature and the salt washing drum speed are within the above ranges, if the washing time is shorter than 10 minutes, the tap water has a poor effect in dissolving the glycerol organic matter, which affects the glycerol recovery rate in the glycerol salt and the quality of the washed salt; if the washing time is longer than 60 minutes, the efficiency of the combined treatment method of the present invention will be significantly reduced, and the treatment cost will be significantly increased; therefore, a washing time of 10 to 60 minutes is reasonable, preferably 20 to 50 minutes, and more preferably 28 to 40 minutes;

[0048] When the washing temperature and washing time are within the range, if the salt washing drum speed is lower than 15 rpm, the washing is insufficient, the glycerin recovery rate is reduced, and the quality of the salt washing is affected; if the salt washing drum speed is higher than 30 rpm, the stirring is too fast, the equipment load increases, and the long-term stable operation of the equipment is affected; therefore, the salt washing drum speed is appropriate to be 15 to 30 rpm, preferably 18 to 28 rpm, and more preferably 20 to 26 rpm;

[0049] Preferably, the obtained solid-liquid mixture is washed with water in the salt washing drum 1 at a temperature of 22 to 58° C. and a rotation speed of 18 to 28 rpm for 20 to 50 minutes.

[0050] More preferably, the obtained solid-liquid mixture is washed with water in the salt washing drum 1 at a temperature of 30 to 50° C. and a rotation speed of 20 to 26 rpm for 28 to 40 minutes.

[0051] The washed salt slurry is sent to the compression filter 2 and passes through a 0.45 μm filter membrane under a pressure of 0.3 to 0.5 MPa to obtain washed salt and washed brine.

[0052] The main purpose of using 0.45μm filter membrane in this step is solid-liquid separation, filtering and intercepting solid particle salts, and allowing the washing brine to pass through.

[0053] If the pressure of the compression filter 2 is lower than 0.3MPa, the filtration speed is slow and the solid salt has more residual moisture; if the pressure of the compression filter 2 is higher than 0.5MPa, the filter membrane is easily damaged; therefore, it is appropriate for the pressure of the compression filter 2 to be 0.3~0.5MPa, preferably 0.35~0.45MPa.

[0054] The 0.45 μm filter membrane used in the present invention is a filter membrane sold by Haining Yadong Filter Equipment Co., Ltd. under the trade name Y45 microporous filter membrane.

[0055] The salt washing drum 1 used in the present invention is a double-axis tumbling stirring drum or a single-axis tumbling stirring drum, which are products sold on the current market that are well known to those skilled in the art, such as the double-axis tumbling stirring drum sold by Qufu Ruicheng Equipment Co., Ltd. under the trade name horizontal mixer.

[0056] The compression filter 2 used in the present invention is a flip-type positive pressure membrane filter or a flip-type positive pressure filter element filter, which are products currently sold on the market that are well known to those skilled in the art, such as the flip-type positive pressure membrane filter sold by Haining Yadong Filter Equipment Co., Ltd. under the trade name flip-type positive pressure filter.

[0057] B. Water washing salt treatment

[0058] The washed salt obtained in step A is mixed and dissolved with tap water in a salting tank 3 at a solid-liquid weight ratio of 1:3.5-5.5 to obtain a high-concentration brine, which is then sent to a catalytic oxidation tower 4. At the same time, an oxidant is added to the catalytic oxidation tower 4, mixed evenly, and reacted at a temperature of 30-60° C. for 1-3 hours to reduce the total organic carbon content of the high-concentration brine to below 10 mg / L, thereby obtaining a high-concentration clean brine.

[0059] The main function of the water-washing salt treatment step in the combined treatment method of the present invention is to dissolve the solid salt to form brine, and to deeply remove organic matter in the brine by oxidation, thereby making the brine a resource.

[0060] During mixed dissolution, the solid-liquid weight ratio of washed salt to tap water is 1:3.5-5.5. If the solid-liquid weight ratio of washed salt to tap water is higher than 1:3.5, the amount of water is insufficient and the dissolution is insufficient, making it difficult to completely dissolve the washed salt; if the solid-liquid weight ratio of washed salt to tap water is lower than 1:5.5, there is too much water, which reduces the salt concentration in the brine; therefore, a solid-liquid weight ratio of washed salt to tap water of 1:3.5-5.5 is reasonable, preferably 1:3.8-5.2, and more preferably 1:4.2-4.8;

[0061] In this step, the oxidant is ozone or hydrogen peroxide, which are oxidants that do not introduce impurities but can fully react with organic matter contained in the high-concentration brine. The weight ratio of the high-concentration brine to the oxidant is 1:0.01 to 0.05. If the weight ratio of the high-concentration brine to the oxidant is greater than 1:0.01, the oxidation is incomplete and the brine quality is poor. If the weight ratio of the high-concentration brine to the oxidant is less than 1:0.05, the amount of oxidant used is large and the oxidation cost is high. Therefore, a weight ratio of the high-concentration brine to the oxidant of 1:0.01 to 0.05 is reasonable, and preferably 1:0.02 to 0.04.

[0062] The high-concentration brine and the oxidant are subjected to oxidation reaction at a temperature of 30 to 60° C. for 1 to 3 hours, so that the total organic carbon content of the high-concentration brine is reduced to below 10 mg / L, thereby obtaining a high-concentration clean brine.

[0063] When the reaction time is within the range, if the reaction temperature is lower than 30°C, the oxidation reaction effect is poor; if the reaction temperature is higher than 60°C, the energy consumption for heating the solution is high, and the high temperature causes ineffective decomposition of the oxidant, increasing the cost; therefore, a reaction temperature of 30 to 60°C is appropriate, preferably 36 to 54°C, and more preferably 40 to 50°C. When the reaction temperature is within the range, if the reaction time is shorter than 1h, the oxidation reaction effect is poor; if the reaction time is longer than 3h, the reaction efficiency is low and the investment cost increases; therefore, a reaction time of 1 to 3h is appropriate, preferably 1.4 to 2.6h, and more preferably 1.8 to 2.2h.

[0064] The catalytic oxidation tower 4 used in the present invention is a fixed-bed oxidation tower loaded with alumina balls or activated carbon granules having a diameter of 3 to 5 mm, and the ratio of the tower diameter to the tower height is 1:4 to 12. The alumina balls or activated carbon granules used in the present invention are currently available on the market, such as alumina balls sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name Heterogeneous Fenton Catalyst and activated carbon sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name Carbon-based Heterogeneous Fenton Catalyst.

[0065] In the present invention, the total organic carbon content of the high-concentration brine is detected according to the combustion oxidation-non-dispersive infrared absorption analysis method.

[0066] C. Co-acidification treatment

[0067] The brine obtained in step A is mixed with the polyglycerol oil residue in a dissolution tank 5 and dissolved. The resulting mixed solution is then fed to an acidification reaction tower 6. Simultaneously, a hydrochloric acid solution having a concentration of 28 to 34% by weight is also fed to the acidification reaction tower 6 and mixed uniformly. The pH value of the mixed solution is controlled to be below 1.0. The mixture is then subjected to an acidification reaction at a temperature of 40 to 90° C. with stirring for 30 to 150 minutes, thereby obtaining a three-phase mixture.

[0068] The main function of the coordinated acidification step in the combined treatment method of the present invention is to mix and dissolve the washing brine with the polyglycerol oil residue, reduce the viscosity of the polyglycerol residue, and acidify the reaction to generate a product that is easy to separate.

[0069] In this step, the washing brine and the polyglycerol oil residue are mixed and dissolved in the dissolution tank 5 at a weight ratio of 0.3 to 1.0:1. If the weight ratio of the washing brine to the polyglycerol oil residue is less than 0.3:1, the mixed solution is too viscous, affecting the subsequent separation process; if the weight ratio of the washing brine to the polyglycerol oil residue is greater than 1.0:1, the organic matter content of the mixed solution is low, and the subsequent purification energy consumption is high. Therefore, a weight ratio of the washing brine to the polyglycerol oil residue of 0.3 to 1.0:1 is desirable, preferably 0.4 to 0.8:1, and more preferably 0.5 to 0.7:1.

[0070] In this step, a hydrochloric acid solution with a concentration of 28-34% by weight is used to control the pH value of the mixed solution to below 1.0. The main purpose is to provide a large amount of H + , maintaining an acidic water environment.

[0071] Then, the mixed solution with a pH below 1.0 is subjected to an acidification reaction at a temperature of 40 to 90° C. with stirring for 30 to 150 minutes.

[0072] Specifically, the acidification reaction should be understood as a reaction in which a fatty acid salt reacts with a strong acid to generate a fatty acid and a salt. The acidification reaction is as follows:

[0073] RNa+H + =RH+Na +

[0074] Na + +Cl - =NaCl

[0075] The fatty acid RH is insoluble in water and floats on the surface. The neutralized free alkali in the oil residue reacts with the fatty acid salt to form NaCl salts that enter the solution. In the strong hydrochloric acid environment, the NaCl supersaturates and precipitates, with the precipitated solid salts settling at the bottom. Therefore, the acidification reaction solution exhibits a three-phase distribution: a solid salt layer at the bottom, a polyglycerol solution in the middle, and a water-insoluble fatty acid layer at the top. The acidification reaction solution is allowed to stand for 1-2 hours to allow for separation of the layers.

[0076] In the present invention, when the acidification reaction time is within the range, if the acidification reaction temperature is lower than 40°C, the acidification reaction is slow and the acidification reaction is not thorough; if the acidification reaction temperature is higher than 90°C, the energy consumption of the acidification reaction is high and the processing cost is significantly increased; therefore, it is desirable that the acidification reaction temperature is 40-90°C, preferably 48-80°C, and more preferably 56-70°C.

[0077] When the acidification reaction temperature is within the range, if the acidification reaction time is shorter than 30 minutes, the acidification reaction is not thorough and the acidification separation of fatty acids is incomplete; if the acidification reaction time is longer than 150 minutes, the acidification reaction efficiency is low and the processing cost increases; therefore, an acidification reaction time of 30 to 150 minutes is feasible, preferably 45 to 120 minutes, and more preferably 60 to 100 minutes.

[0078] This step has no special requirements on the stirring speed of the stirrer used, as long as it can mix the reaction solution evenly.

[0079] The dissolving tank 5 used in the present invention is a chemical reagent dissolving device commonly used in the field of chemical technology.

[0080] The acidification reaction tower 6 used in the present invention is a paddle stirred reactor, a turbine stirred reactor, a propeller stirred reactor or an anchor stirred reactor, all of which are chemical equipment currently sold on the market, such as the paddle stirred reactor sold by Zhengzhou Supu Instrument Co., Ltd. under the trade name of two-blade paddle chemical stirred reactor and the anchor stirred reactor sold by Zhengzhou Supu Instrument Co., Ltd. under the trade name of anchor chemical stirred reactor.

[0081] D. Three-phase separation

[0082] The three-phase mixture obtained in step C is fed to a three-phase separator 7 and separated into a lower solid phase, an intermediate aqueous phase, and an upper oil phase at a rotation speed of 1000-2500 rpm and a temperature of 10-80° C.; the lower solid phase is crystalline NaCl, which is separated and removed by a high-speed centrifuge 8 at a rotation speed of 1000-2500 rpm, and then returned to step B after washing; the upper oil phase is dissolved in a fatty acid pool 9 using methanol, ethanol, or a NaOH solution, and then distilled and concentrated in a distillation tower 10 at a vacuum degree of 5-20 kPa to obtain a fatty acid product; the intermediate aqueous phase is a polyglycerol solution with a pH value below 1, which is then subjected to subsequent treatment;

[0083] The three-phase mixture is separated into a lower solid phase, a middle water phase and an upper oil phase in the three-phase separator 7 at a rotation speed of 1000-2500 rpm and a temperature of 10-80°C;

[0084] When the speed of the three-phase separator 7 is within the above range, if its separation temperature is lower than 10°C, the viscosity of the oil phase increases, which is not conducive to separation. If its separation temperature is higher than 80°C, the material requirements of the reaction equipment are high, and the investment cost increases. Therefore, its separation temperature is preferably 10-80°C, preferably 20-70°C, and more preferably 28-62°C.

[0085] When the separation temperature of the three-phase separator 7 is within the above range, if the rotation speed of the three-phase separator 7 is lower than 1000 rpm, the separation effect is poor and the separation is incomplete; if its rotation speed is higher than 2500 rpm, the energy consumption is high and the requirements for the equipment are high; therefore, its rotation speed is appropriately 1000-2500 rpm, preferably 1200-2300 rpm, and more preferably 1400-2000 rpm;

[0086] The three-phase separator 7 used in the present invention is a disc centrifuge or a centrifugal separation centrifuge, which are products currently sold on the market, such as the disc centrifuge sold by Alfa Laval under the trade name BD series high-speed disc centrifuge and the centrifugal separation centrifuge sold by Haoshilai Environmental Technology Co., Ltd. under the trade name continuous filtering centrifuge.

[0087] The upper oil phase is dissolved in a fatty acid pool 9 using methanol, ethanol or NaOH solution, and then distilled and concentrated in a distillation tower 10 under a vacuum degree of 5 to 20 kPa to obtain a fatty acid product;

[0088] The main purpose of dissolving the upper oil phase with methanol, ethanol or NaOH solution is to dissolve the fatty acid substances and form a stable solution, reduce its viscosity and improve fluidity. The concentration of the methanol solution is usually 30-80% by volume; the concentration of the ethanol solution is 30-80% by volume; the concentration of the NaOH solution is 30-80% by weight; the volume ratio of the upper oil phase to the methanol, ethanol or NaOH solution is generally 1:2-4. The solution obtained by dissolving the upper oil phase is distilled in a distillation tower 10 under a vacuum degree of 5-20kPa to remove methanol, ethanol or water, and concentrated to obtain a fatty acid product. According to the standard liquid chromatography analysis, the fatty acid product is mainly C6-C 12 Medium- and long-chain fatty acids;

[0089] The fatty acid pool 9 used in the present invention is a reactor having an anchor structure, such as the reactor sold by Zhengzhou Supu Instrument Co., Ltd. under the trade name Anchor Chemical Stirred Reactor;

[0090] The distillation tower 10 used in the present invention is a bubble-cap type, sieve-plate type, vertical sieve-plate type or floating tongue type distillation tower, which are all products currently sold on the market, such as the bubble-cap type distillation tower sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name of bubble-cap type chemical distillation tower, the sieve-plate type distillation tower sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name of sieve-plate type chemical distillation tower, the vertical sieve-plate type distillation tower sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name of vertical sieve-plate type chemical distillation tower, and the floating tongue type distillation tower sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name of floating tongue type chemical distillation tower;

[0091] The middle aqueous phase is a polyglycerol solution with a pH value lower than 1. After the three phases are separated, they are then processed;

[0092] According to liquid chromatography analysis, the polyglycerol solution contains 30-50% by weight of glycerol, diglycerol and triglycerol, with the ratio of the three being approximately 2:3:2.

[0093] The lower layer of solid phase crystallized NaCl can be separated using a bottom valve or a filtering device, and it is separated and removed from the residual liquid by a high-speed centrifuge 8 at a speed of 1000 to 2500 rpm, and then washed 2 to 4 times with methanol according to a volume ratio of 1:3 to 5 between it and methanol, and then returned to step B; the high-speed centrifuge 8 used in the present invention is a three-legged centrifuge, a top-hung centrifuge or a centrifugal unloading centrifuge, such as the three-legged centrifuge sold by Haoshilai Environmental Protection Technology Co., Ltd. under the trade name of three-legged sedimentation centrifuge, the top-hung centrifuge sold by Haoshilai Environmental Protection Technology Co., Ltd. under the trade name of top-hung material centrifuge, and the centrifugal unloading centrifuge sold by Haoshilai Environmental Protection Technology Co., Ltd. under the trade name of high-speed centrifugal unloading centrifuge.

[0094] E. Polyglycerol solution treatment

[0095] The polyglycerol solution obtained in step D is sent to a neutralization tank 11. At the same time, caustic soda is added to the neutralization tank 11 and stirred until the solution becomes neutral. The solution is allowed to stand for 2 hours to remove the insoluble precipitate at the bottom. The upper clear liquid is sent to an electrodialysis device 12. The salt content of the polyglycerol solution is reduced to less than 0.1% by weight under the condition of an operating temperature below 35° C., thereby obtaining a desalted polyglycerol solution and a salty water. The salty water is returned to step A and recycled as washing water.

[0096] The polyglycerol solution obtained in step D contains salt and some impurity ions. It is stirred and reacted with caustic soda in the neutralization tank 11 until it becomes neutral, and the following reaction is carried out:

[0097] Fe 3+ +OH - =FeOH3,

[0098] Mg 2+ +OH - =MgOH2

[0099] The mixture is then allowed to stand for 2 hours, and the resulting precipitate is deposited at the bottom of the reactor. The upper clarified liquid is sent to an electrodialysis device 12, where the salt content of the polyglycerol solution is reduced to less than 0.1% by weight at an operating temperature below 35°C, thereby obtaining a desalted polyglycerol solution and a salty water.

[0100] According to the standard liquid chromatography analysis method, the desalted polyglycerol solution contains 30-50% polyglycerol by weight; the desalted polyglycerol solution is subjected to subsequent processing steps.

[0101] According to the combustion oxidation-non-dispersive infrared detection analysis method, the salt water contains 0.5-2.0% organic matter by weight; the salt water contains a small amount of polyglycerol, and the solution is clear and can be returned to step A for recycling as washing water;

[0102] The neutralization tank 11 used in the present invention is a device commonly used in the field of chemical technology. The electrodialysis equipment 12 used in the present invention is a product currently sold on the market, such as the product sold by Hangzhou Lanran Technology Co., Ltd. under the trade name electrodialysis equipment.

[0103] F. Concentration

[0104] The desalted polyglycerol solution obtained in step E is evaporated and concentrated in a distillation tower 13 to obtain a polyglycerol concentrate having a content of more than 90% by weight;

[0105] The desalted polyglycerol solution is evaporated and concentrated in the distillation tower 13 at a temperature of 80 to 120° C. and a pressure of 20 to 100 kPa for 60 to 300 minutes.

[0106] When the evaporation concentration pressure and the evaporation concentration time are within the range, if the evaporation concentration temperature is lower than 80°C, the evaporation rate is slow and the efficiency is low; if the evaporation concentration temperature is higher than 120°C, the evaporation energy consumption is large and the cost is high; therefore, the evaporation concentration temperature is reasonable at 80-120°C, preferably 86-114°C, and more preferably 90-108°C;

[0107] When the evaporation concentration temperature and the evaporation concentration time are within the above ranges, if the evaporation concentration pressure is lower than 20 kPa, the vacuum degree requirement is higher and the equipment cost is high; if the evaporation concentration pressure is higher than 100 kPa, the evaporation efficiency is low; therefore, the evaporation concentration pressure is suitably 20 to 100 kPa, preferably 20 to 80 kPa, and more preferably 20 to 60 kPa;

[0108] When the evaporation concentration temperature and the evaporation concentration pressure are within the range, if the evaporation concentration time is shorter than 60 minutes, the evaporation is incomplete; if the evaporation concentration time is longer than 300 minutes, the evaporation efficiency is low; therefore, the evaporation concentration time is appropriately 60 to 300 minutes, preferably 80 to 260 minutes, and more preferably 110 to 220 minutes;

[0109] The distillation tower 13 used in the present invention is a bubble-cap type, sieve plate type or vertical sieve plate type distillation tower, which are all products currently sold on the market, such as the bubble-cap type distillation tower sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name of bubble-cap type chemical distillation tower, the sieve plate type distillation tower sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name of sieve plate type chemical distillation tower, and the vertical sieve plate type distillation tower sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name of vertical sieve plate type chemical distillation tower.

[0110] According to the liquid chromatography analysis method, the concentrate contains more than 90% by weight of glycerol and polyglycerol (mainly diglycerol and triglycerol).

[0111] G. Decolorization

[0112] The polyglycerol concentrate obtained in step F is decolorized by passing through a decolorization tower 14 to remove colored substances contained in the polyglycerol concentrate, thereby obtaining a bright yellow or light yellow polyglycerol product.

[0113] The polyglycerol concentrate is decolorized by passing through a decolorization tower 14 at a temperature of 70 to 90° C. for 30 to 90 minutes. When the decolorization time is within the above range, if the decolorization temperature is lower than 70° C., the decolorization efficiency is low and the decolorization is incomplete; if the decolorization temperature is higher than 90° C., the energy consumption is high. Therefore, a decolorization temperature of 70 to 90° C. is desirable, preferably 74 to 86° C., and more preferably 76 to 84° C.

[0114] When the decolorization temperature is within the above range, if the decolorization time is shorter than 30 minutes, the decolorization is incomplete; if the decolorization time is longer than 90 minutes, the decolorization efficiency is low; therefore, a decolorization time of 30 to 90 minutes is appropriate, preferably 38 to 82 minutes, and more preferably 46 to 75 minutes;

[0115] The decolorization tower 14 used in the present invention is a fixed bed activated carbon decolorization tower or a fluidized bed activated carbon decolorization tower, both of which are products currently sold on the market, such as the fixed bed activated carbon decolorization tower sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name of high-efficiency fixed bed activated carbon decolorization tower, and the fluidized bed activated carbon decolorization tower sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name of high-efficiency fluidized bed activated carbon decolorization tower.

[0116] According to the standard liquid chromatography analytical method, the bright yellow or light yellow polyglycerol product contains more than 90% glycerol and polyglycerol by weight;

[0117] [Beneficial Effects]

[0118] The beneficial technical effects of the present invention are as follows: organic matter on the surface of glycerol salts is concentrated in the brine using a water washing process. The washed salt, with significantly reduced organic matter, undergoes salting and advanced oxidation to form a crude brine, which is used as a raw material for ion-exchange membrane caustic soda and converted into a recycled resource. The organic-enriched brine is mixed with polyglycerol oil residue, dissolved, and acidified to produce, in addition to the polyglycerol solution, water-insoluble fatty acids and NaCl crystals precipitated due to supersaturation. These are separated and disposed of in a three-phase separator. The alkali-neutralized polyglycerol solution is deeply desalted using electrodialysis equipment, and then purified and decolorized by distillation to produce a bright yellow or light yellow polyglycerol product containing over 90% glycerol and polyglycerol by weight.

Brief Description of the Drawings

[0119] Attachment Figure 1 The present invention is a schematic flow chart of a combined treatment method of glycerol salt obtained by refining crude glycerol and polyglycerol oil residue.

[0120] In the picture:

[0121] 1-Salt washing drum; 2-Compression filter; 3-Salting tank; 4-Catalytic oxidation tower; 5-Dissolution tank; 6-Acidification reaction tower; 7-Three-phase separator; 8-High-speed centrifuge; 9-Fatty acid tank; 10-Distillation tower; 11-Neutralization tank; 12-Electrodialysis equipment; 13-Distillation tower; 14-Decolorization tower. [Specific implementation method]

[0122] The present invention will be better understood through the following examples.

[0123] Example 1: Combined treatment method of glycerol salt and polyglycerol oil residue of the present invention

[0124] The implementation steps of this embodiment are as follows:

[0125] A. Glycerol saline wash

[0126] This embodiment uses glycerol salt containing 97% NaCl, 2% glycerol and 1% water by weight; tap water and glycerol salt are added to the salt washing drum 1 at a weight ratio of 0.4:1, mixed and dissolved, and the resulting solid-liquid mixture is washed with water for 10 minutes at a temperature of 50°C and a rotation speed of 20 rpm in the salt washing drum 1 with a double-axis tumbling stirring drum or a single-axis tumbling stirring drum. The washed salt slurry is sent to the flip-type positive pressure membrane filter compression filter 2 and passed through a 0.45 μm filter membrane under a pressure of 0.4 MPa to obtain water-washed salt and washed brine.

[0127] B. Water washing salt treatment

[0128] The washed salt obtained in step A is mixed and dissolved with tap water in a salting tank 3 at a solid-liquid weight ratio of 1:4.8 to obtain a high-concentration brine, which is then sent to a catalytic oxidation tower 4. The catalytic oxidation tower 4 is a fixed-bed oxidation tower filled with alumina balls with a diameter of 3 to 5 mm, which are sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name Heterogeneous Fenton Catalyst. The ratio of the tower diameter to the tower height is 1:12. At the same time, ozone or hydrogen peroxide oxidant is added to the catalytic oxidation tower 4 at a weight ratio of high-concentration brine to oxidant of 1:0.05. The mixture is evenly mixed and reacted at a temperature of 30° C. for 3.0 hours to reduce the total organic carbon content of the high-concentration brine to below 10 mg / L, thereby obtaining a high-concentration clean brine.

[0129] C. Co-acidification treatment

[0130] The brine obtained in step A and the polyglycerol oil residue are mixed and dissolved in a dissolution tank 5 at a weight ratio of 0.5:1. The resulting mixed solution is then fed to an acidification reaction tower 6. Simultaneously, a 28% by weight hydrochloric acid solution is also fed to the acidification reaction tower 6. The mixture is mixed uniformly to control the pH value of the mixed solution to below 1.0. The mixture is then subjected to an acidification reaction at 70° C. with stirring for 60 minutes, thereby obtaining a three-phase mixture.

[0131] D. Three-phase separation

[0132] The three-phase mixture obtained in step C is sent to a butterfly-type centrifuge three-phase separator 7 and separated into a lower solid phase, an intermediate aqueous phase, and an upper oil phase at a speed of 2000 rpm and a temperature of 28° C.; the lower solid phase is crystalline NaCl, which is separated and removed by a high-speed centrifuge 8 at a speed of 1400 rpm to remove residual liquid, and then washed three times with methanol at a volume ratio of 1:3, and then returned to step B; the upper oil phase is dissolved in a fatty acid pool 9 using a 30% by volume methanol solution at a volume ratio of 1:3, and then distilled and concentrated in a distillation tower 10 at a vacuum degree of 15 kPa to obtain a fatty acid product; the intermediate aqueous phase is a polyglycerol solution with a pH value below 1, which is then subjected to subsequent treatment;

[0133] E. Polyglycerol solution treatment

[0134] The polyglycerol solution obtained in step D is sent to a neutralization tank 11. At the same time, caustic soda is added to the neutralization tank 11 and stirred until the solution becomes neutral. The solution is allowed to stand for 2 hours to remove the insoluble precipitate at the bottom. The upper clear liquid is sent to an electrodialysis device 12. The salt content of the polyglycerol solution is reduced to less than 0.1% by weight under the condition of an operating temperature below 35° C., thereby obtaining a desalted polyglycerol solution and a salty water. The salty water is returned to step A and recycled as washing water.

[0135] F. Concentration

[0136] The desalted polyglycerol solution obtained in step E was evaporated and concentrated by passing through a bubble-cap distillation column 13 at a temperature of 80° C. and a pressure of 20 kPa for 220 min to obtain a polyglycerol concentrate.

[0137] G. Decolorization

[0138] The polyglycerol concentrate obtained in step F is decolorized by passing through a fixed-bed activated carbon decolorization tower 14 at a temperature of 90° C. for 30 minutes to remove colored substances contained in the polyglycerol concentrate and obtain a bright yellow polyglycerol product.

[0139] According to the method described in the specification of this application, the polyglycerol content of the desalted polyglycerol solution obtained in step E of this embodiment is 46% by weight, and the glycerol and polyglycerol content of the polyglycerol product obtained in step G of this embodiment is 97%.

[0140] Example 2: Combined treatment method of glycerol salt and polyglycerol oil residue of the present invention

[0141] The implementation steps of this embodiment are as follows:

[0142] A. Glycerol saline wash

[0143] This embodiment uses glycerol salt containing 95% NaCl, 2% glycerol and 3% water by weight; tap water and glycerol salt are added to the salt washing drum 1 at a weight ratio of 0.6:1, mixed and dissolved, and the resulting solid-liquid mixture is washed with water in the salt washing drum 1 with a double-axis tumbling stirring drum or a single-axis tumbling stirring drum at a temperature of 10°C and a rotation speed of 26 rpm for 28 minutes. The washed salt slurry is sent to the flip-type positive pressure membrane filter compression filter 2 and passed through a 0.45 μm filter membrane under a pressure of 0.3 MPa to obtain water-washed salt and washed brine.

[0144] B. Water washing salt treatment

[0145] The washed salt obtained in step A is mixed and dissolved with tap water in a salting tank 3 at a solid-liquid weight ratio of 1:3.5 to obtain a high-concentration brine, which is then sent to a catalytic oxidation tower 4. The catalytic oxidation tower 4 is a fixed-bed oxidation tower filled with an activated carbon granular solid catalyst sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name Carbon-based Heterogeneous Fenton Catalyst, and the ratio of the tower diameter to the tower height is 1:4. At the same time, hydrogen peroxide oxidant is added to the catalytic oxidation tower 4 at a weight ratio of high-concentration brine to oxidant of 1:0.04; the mixture is evenly mixed and reacted at a temperature of 50° C. for 1.0 hour to reduce the total organic carbon content of the high-concentration brine to below 10 mg / L, thereby obtaining a high-concentration clean brine.

[0146] C. Co-acidification treatment

[0147] The brine obtained in step A and the polyglycerol oil residue are mixed and dissolved in a dissolution tank 5 at a weight ratio of 0.3:1. The resulting mixed solution is then fed to an acidification reaction tower 6 of a turbine-type stirred reactor. Simultaneously, a 30% by weight hydrochloric acid solution is also fed to the acidification reaction tower 6 and mixed uniformly. The pH value of the mixed solution is controlled to be below 1.0. The acidification reaction is then carried out at a temperature of 56° C. with stirring for 100 minutes, thereby obtaining a three-phase mixture.

[0148] D. Three-phase separation

[0149] The three-phase mixture obtained in step C is fed to a centrifugal three-phase separator 7 and separated at a speed of 1000 rpm and a temperature of 62° C. into a lower solid phase, an intermediate aqueous phase, and an upper oil phase. The lower solid phase is crystalline NaCl, which is separated and removed by a high-speed centrifuge 8 at a speed of 1000 rpm to remove residual liquid, and then washed twice with methanol at a volume ratio of 1:5, and then returned to step B. The upper oil phase is dissolved in a fatty acid pool 9 using an 80% by volume ethanol solution at a volume ratio of 1:2, and then distilled and concentrated in a distillation tower 10 at a vacuum of 5 kPa to obtain a fatty acid product. The intermediate aqueous phase is a polyglycerol solution having a pH value below 1, which is then subjected to subsequent treatment.

[0150] E. Polyglycerol solution treatment

[0151] The polyglycerol solution obtained in step D is sent to a neutralization tank 11. At the same time, caustic soda is added to the neutralization tank 11 and stirred until the solution becomes neutral. The solution is allowed to stand for 2 hours to remove the insoluble precipitate at the bottom. The upper clear liquid is sent to an electrodialysis device 12. The salt content of the polyglycerol solution is reduced to less than 0.1% by weight under the condition of an operating temperature below 35° C., thereby obtaining a desalted polyglycerol solution and a salty water. The salty water is returned to step A and recycled as washing water.

[0152] F. Concentration

[0153] The desalted polyglycerol solution obtained in step E is evaporated and concentrated by passing through a sieve plate distillation tower 13 at a temperature of 120° C. and a pressure of 100 kPa for 60 minutes to obtain a polyglycerol concentrate having a polyglycerol content of at least 90% by weight.

[0154] G. Decolorization

[0155] The polyglycerol concentrate obtained in step F is decolorized by a fixed bed activated carbon or fluidized bed activated carbon decolorization tower 14 at a temperature of 70° C. for 90 minutes to remove colored substances contained in the polyglycerol concentrate and obtain a light yellow polyglycerol product.

[0156] According to the method described in the specification of this application, the polyglycerol content of the desalted polyglycerol solution obtained in step E of this embodiment is 30% by weight, and the glycerol and polyglycerol content of the polyglycerol product obtained in step G of this embodiment is 91%.

[0157] Example 3: Combined treatment method of glycerol salt and polyglycerol oil residue of the present invention

[0158] The implementation steps of this embodiment are as follows:

[0159] A. Glycerol saline wash

[0160] This embodiment uses glycerol salt containing 96% NaCl, 3% glycerol and 2% water by weight; tap water and glycerol salt are added to the salt washing drum 1 at a weight ratio of 0.3:1, mixed and dissolved, and the resulting solid-liquid mixture is washed with water in the uniaxial tumbling stirring drum 1 at a temperature of 30°C and a speed of 30 rpm for 60 minutes. The washed salt slurry is sent to the flip-type positive pressure filter compression filter 2 and passed through a 0.45 μm filter membrane under a pressure of 0.4 MPa to obtain water-washed salt and washed brine.

[0161] B. Water washing salt treatment

[0162] The washed salt obtained in step A is mixed and dissolved with tap water in a salting tank 3 at a solid-liquid weight ratio of 1:5.5 to obtain a high-concentration brine, which is then sent to a catalytic oxidation tower 4. The catalytic oxidation tower 4 is a fixed-bed oxidation tower filled with an activated carbon granular solid catalyst sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name Carbon-based Heterogeneous Fenton Catalyst, and the ratio of the tower diameter to the tower height is 1:6. At the same time, hydrogen peroxide oxidant is added to the catalytic oxidation tower 4 at a weight ratio of high-concentration brine to oxidant of 1:0.03; the mixture is evenly mixed and reacted at a temperature of 60° C. for 1.8 hours to reduce the total organic carbon content of the high-concentration brine to below 10 mg / L, thereby obtaining a high-concentration clean brine.

[0163] C. Co-acidification treatment

[0164] The brine obtained in step A and the polyglycerol oil residue are mixed and dissolved in a dissolution tank 5 at a weight ratio of 0.7:1. The resulting mixed solution is then fed to an acidification reaction tower 6 in a propeller-type stirred reactor. Simultaneously, a 34% by weight hydrochloric acid solution is also fed to the acidification reaction tower 6 and mixed uniformly. The pH value of the mixed solution is controlled to be below 1.0. The acidification reaction is then carried out at 90° C. with stirring for 30 minutes, thereby obtaining a three-phase mixture.

[0165] D. Three-phase separation

[0166] The three-phase mixture obtained in step C is sent to a three-phase separator 7 of a butterfly-type centrifuge or a centrifugal separation centrifuge, and separated into a lower solid phase, an intermediate aqueous phase, and an upper oil phase at a speed of 1400 rpm and a temperature of 80° C.; the lower solid phase is crystalline NaCl, which is separated and removed by a high-speed centrifuge 8 at a speed of 2500 rpm to remove residual liquid, and then washed four times with methanol at a volume ratio of 1:4, and then returned to step B; the upper oil phase is dissolved in a fatty acid pool 9 using a 48% by weight NaOH solution at a volume ratio of 1:3, and then distilled and concentrated in a distillation tower 10 under a vacuum of 20 kPa to obtain a fatty acid product; the intermediate aqueous phase is a polyglycerol solution with a pH value below 1, which is then subjected to subsequent treatment;

[0167] E. Polyglycerol solution treatment

[0168] The polyglycerol solution obtained in step D is sent to a neutralization tank 11. At the same time, caustic soda is added to the neutralization tank 11 and stirred until the solution becomes neutral. The solution is allowed to stand for 2 hours to remove the insoluble precipitate at the bottom. The upper clear liquid is sent to an electrodialysis device 12. The salt content of the polyglycerol solution is reduced to less than 0.1% by weight under the condition of an operating temperature below 35° C., thereby obtaining a desalted polyglycerol solution and a salty water. The salty water is returned to step A and recycled as washing water.

[0169] F. Concentration

[0170] The desalted polyglycerol solution obtained in step E is evaporated and concentrated by passing it through a bubble-cap type, sieve-plate type, or vertical sieve-plate type distillation column 13 at a temperature of 90° C. and a pressure of 40 kPa for 110 minutes to obtain a polyglycerol concentrate having a polyglycerol content of more than 90% by weight;

[0171] G. Decolorization

[0172] The polyglycerol concentrate obtained in step F is decolorized by a fixed bed activated carbon or fluidized bed activated carbon decolorization tower 14 at a temperature of 76° C. for 46 minutes to remove colored substances contained in the polyglycerol concentrate and obtain a light yellow polyglycerol product.

[0173] According to the method described in the specification of this application, the polyglycerol content of the desalted polyglycerol solution obtained in step E of this embodiment is 38% by weight, and the glycerol and polyglycerol content of the polyglycerol product obtained in step G of this embodiment is 94%.

[0174] Example 4: Combined treatment method of glycerol salt and polyglycerol oil residue of the present invention

[0175] The implementation steps of this embodiment are as follows:

[0176] A. Glycerol saline wash

[0177] This embodiment uses glycerol salt containing 98% NaCl, 1% glycerol, and 1% water by weight; tap water and glycerol salt are added to a salt washing drum 1 at a weight ratio of 0.8:1, mixed, and dissolved, and the resulting solid-liquid mixture is washed with water in the double-shaft tumbling stirring drum 1 at a temperature of 70°C and a rotation speed of 15 rpm for 40 minutes. The washed salt slurry is sent to a flip-type positive pressure filter compression filter 2 and passed through a 0.45 μm filter membrane at a pressure of 0.5 MPa to obtain water-washed salt and washed brine.

[0178] B. Water washing salt treatment

[0179] The washed salt obtained in step A is mixed and dissolved with tap water in a salting tank 3 at a solid-liquid weight ratio of 1:4.83.55.54.2 to obtain a high-concentration brine, which is then sent to a catalytic oxidation tower 4. The catalytic oxidation tower 4 is a fixed-bed oxidation tower loaded with a solid catalyst of alumina balls with a diameter of 3 to 5 mm, sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name Heterogeneous Fenton Catalyst, and the ratio of the tower diameter to the tower height is 1:10. At the same time, an ozone oxidant is added to the catalytic oxidation tower 4 at a weight ratio of the high-concentration brine to the oxidant of 1:0.02. The mixture is evenly mixed and reacted at a temperature of 40°C for 2.2 hours to reduce the total organic carbon content of the high-concentration brine to below 10 mg / L, thereby obtaining a high-concentration clean brine.

[0180] C. Co-acidification treatment

[0181] The brine obtained in step A and the polyglycerol oil residue are mixed and dissolved in a dissolution tank 5 at a weight ratio of 1.0:1. The resulting mixed solution is then fed to an anchor-stirred reactor acidification reaction tower 6. Simultaneously, a 32% by weight hydrochloric acid solution is also fed to the acidification reaction tower 6 and mixed uniformly. The pH value of the mixed solution is controlled to be below 1.0. The acidification reaction is then carried out at a temperature of 40° C. with stirring for 150 minutes, thereby obtaining a three-phase mixture.

[0182] D. Three-phase separation

[0183] The three-phase mixture obtained in step C is sent to a butterfly-type centrifuge three-phase separator 7 and separated into a lower solid phase, an intermediate aqueous phase, and an upper oil phase at a speed of 2500 rpm and a temperature of 10° C.; the lower solid phase is crystalline NaCl, which is separated and removed by a high-speed centrifuge 8 at a speed of 2000 rpm to remove residual liquid, and then washed three times with methanol at a volume ratio of 1:4, and then returned to step B; the upper oil phase is dissolved in a fatty acid pool 9 using a 62% by weight NaOH solution at a volume ratio of 1:4, and then distilled and concentrated in a distillation tower 10 under a vacuum of 10 kPa to obtain a fatty acid product; the intermediate aqueous phase is a polyglycerol solution with a pH value below 1, which is then subjected to subsequent treatment;

[0184] E. Polyglycerol solution treatment

[0185] The polyglycerol solution obtained in step D is sent to a neutralization tank 11. At the same time, caustic soda is added to the neutralization tank 11 and stirred until the solution becomes neutral. The solution is allowed to stand for 2 hours to remove the insoluble precipitate at the bottom. The upper clear liquid is sent to an electrodialysis device 12. The salt content of the polyglycerol solution is reduced to less than 0.1% by weight under the condition of an operating temperature below 35° C., thereby obtaining a desalted polyglycerol solution and a salty water. The salty water is returned to step A and recycled as washing water.

[0186] F. Concentration

[0187] The desalted polyglycerol solution obtained in step E is evaporated and concentrated in a bubble-cap, sieve-plate, or vertical sieve-plate distillation column 13 at a temperature of 108° C. and a pressure of 80 kPa for 300 minutes to obtain a polyglycerol concentrate having a polyglycerol content of at least 90% by weight.

[0188] G. Decolorization

[0189] The polyglycerol concentrate obtained in step F is decolorized by passing through a fluidized bed activated carbon decolorization tower 14 at a temperature of 84° C. for 75 minutes to remove colored substances contained in the polyglycerol concentrate and obtain a bright yellow polyglycerol product.

[0190] According to the method described in the specification of this application, the polyglycerol content of the desalted polyglycerol solution obtained in step E of this embodiment is 50% by weight, and the glycerol and polyglycerol content of the polyglycerol product obtained in step G of this embodiment is 98%.

Claims

1. A combined treatment method of glycerol salt and polyglycerol oil residue, characterized in that The processing steps of this method are as follows: A. Glycerol saline wash Tap water and glycerol salt are added to a salt washing drum (1) in a weight ratio of 0.3 to 0.8:1, mixed, and dissolved, and the obtained solid-liquid mixture is washed with water in the salt washing drum (1) at a rotation speed of 15 to 30 rpm for 10 to 60 minutes, and the washed salt slurry is sent to a compression filter (2) and passed through a 0.45 μm filter membrane at a pressure of 0.3 to 0.5 MPa to obtain water-washed salt and washed brine; B. Water washing salt treatment The washed salt obtained in step A is mixed and dissolved with tap water in a salting tank (3) at a solid-liquid weight ratio of 1:3.5-5.5 to obtain a high-concentration brine, which is then sent to a catalytic oxidation tower (4). At the same time, an oxidant is added to the catalytic oxidation tower (4), mixed evenly, and reacted at a temperature of 30-60° C. for 1-3 hours to reduce the total organic carbon content of the high-concentration brine to below 10 mg / L, thereby obtaining a high-concentration clean brine. C. Co-acidification treatment The washing brine obtained in step A is mixed with the polyglycerol oil residue in a dissolution tank (5) and dissolved. The resulting mixed solution is then fed to an acidification reaction tower (6). Simultaneously, a hydrochloric acid solution having a concentration of 28 to 34% by weight is also fed to the acidification reaction tower (6). The mixture is mixed uniformly and the pH value of the mixed solution is controlled to be below 1.

0. The mixture is then subjected to an acidification reaction at a temperature of 40 to 90° C. with stirring for 30 to 150 minutes to obtain a three-phase mixture. D. Three-phase separation The three-phase mixture obtained in step C is sent to a three-phase separator (7) and separated into a lower solid phase, a middle aqueous phase and an upper oil phase at a rotation speed of 1000-2500 rpm and a temperature of 10-80°C; The lower solid phase is crystalline NaCl, which is separated and removed by a high-speed centrifuge (8) at a rotation speed of 1000-2500 rpm, and then returned to step B after washing; the upper oil phase is dissolved in a fatty acid pool (9) using methanol, ethanol or NaOH solution, and then distilled and concentrated in a distillation tower (10) at a vacuum degree of 5-20 kPa to obtain a fatty acid product; the middle aqueous phase is a polyglycerol solution with a pH value below 1, which is then subjected to subsequent treatment; E. Polyglycerol solution treatment The polyglycerol solution obtained in step D is sent to a neutralization tank (11), and caustic soda is added to the neutralization tank (11). The solution is stirred and reacted until it becomes neutral. The solution is allowed to stand for 2 hours to remove the insoluble precipitate at the bottom. The upper clear liquid is sent to an electrodialysis device (12) to reduce the salt content of the polyglycerol solution to less than 0.1% by weight under the condition of an operating temperature below 35°C, thereby obtaining a desalted polyglycerol solution and a salty water. The salty water is returned to step A for recycling as washing water. F. Concentration The desalted polyglycerol solution obtained in step E is evaporated and concentrated by a distillation tower (13) to obtain a polyglycerol concentrate having a content of more than 90% by weight; G. Decolorization The polyglycerol concentrate obtained in step F is decolorized by passing through a decolorization tower (14) to remove colored substances contained in the polyglycerol concentrate, thereby obtaining a bright yellow or light yellow polyglycerol product.

2. The combined treatment method according to claim 1, characterized in that In step A, the glycerol salt contains 95-98% NaCl, 1-3% glycerol and 1-3% water by weight.

3. The combined treatment method according to claim 1, characterized in that In step A, the glycerol salt is mixed and dissolved in a salt washing drum (1) at a temperature of 10 to 70° C.; the salt washing drum (1) is a double-axis flip stirring drum or a single-axis flip stirring drum; and the compression filter (2) is a flip positive pressure membrane filter or a flip positive pressure filter element filter.

4. The combined treatment method according to claim 1, characterized in that In step B, the oxidant is ozone or hydrogen peroxide; the weight ratio of high-concentration salt water to the oxidant is 1:0.01-0.05; the catalytic oxidation tower (4) is a fixed-bed oxidation tower filled with alumina balls or activated carbon particles with a diameter of 3-5 mm and a solid catalyst, and the ratio of the tower body diameter to the tower height is 1:4-12.

5. The combined treatment method according to claim 1, characterized in that In step C, the weight ratio of the washing brine to the polyglycerol oil residue is 0.3-1.0:1; the acidification reaction tower (6) is a paddle stirring reactor, a turbine stirring reactor, a propeller stirring reactor or an anchor stirring reactor.

6. The combined treatment method according to claim 1, characterized in that In step D, the three-phase separator (7) is a butterfly-type centrifuge, a centrifugal clarification type, or a centrifugal separation type phase separator; the high-speed centrifuge (8) is a three-legged centrifuge, a top-hung centrifuge, or a centrifugal discharge centrifuge type centrifuge; the fatty acid tank (9) is a reactor with an anchor structure; and the distillation tower (10) is a bubble-cap type, a sieve plate type, a vertical sieve plate type, or a floating tongue type distillation tower.

7. The combined treatment method according to claim 1, characterized in that In step D, the crystallized NaCl is separated and removed from the residual liquid by washing 2 to 4 times with methanol at a volume ratio of 1:3 to 5; the volume ratio of the upper oil phase to methanol, ethanol or NaOH solution is 1:2 to 4.

8. The combined treatment method according to claim 1, characterized in that In step E, the pH of the desalted polyglycerol solution is lower than 1, the polyglycerol organic matter content thereof is 30-50% by weight, and the salt content is 10-20%; the salty water contains 0.5-2.0% by weight of organic matter.

9. The combined treatment method according to claim 1, characterized in that In step F, the desalted polyglycerol solution is evaporated and concentrated in a distillation tower (13) at a temperature of 80-120° C. and a pressure of 20-100 kPa for 60-300 min; the distillation tower (13) is a bubble cap type, sieve plate type or vertical sieve plate type distillation tower.

10. The combined treatment method according to claim 1, characterized in that In step G, the polyglycerol concentrate is decolorized at a temperature of 70 to 90° C. for 30 to 90 minutes in a decolorization tower (14); the decolorization tower (14) is a fixed bed activated carbon decolorization tower or a fluidized bed activated carbon decolorization tower.

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