A production system of a diglyceride oil and a preparation method thereof

Abstract

This invention discloses a production system and preparation method for diglyceride oil, relating to the field of oil and fat modification technology. The system includes a hydrolysis reaction section, an esterification reaction section, and a purification section. The purification section includes a first-stage thin-film evaporator, a second-stage molecular distillation unit, a third-stage molecular distillation unit, and a fourth-stage molecular distillation unit connected sequentially. The heavy phase outlet of the third-stage molecular distillation unit is connected to the finished product output pipeline and the inlet of the fourth-stage molecular distillation unit via a splitting device. The light phase outlet of the fourth-stage molecular distillation unit is also connected to the finished product output pipeline. This invention also discloses a preparation method using the above system, including hydrolysis, esterification, and multi-stage molecular distillation purification steps. Through the four-stage molecular distillation and splitting structure, this invention can flexibly prepare diglyceride products with gradient purities of 60% to 99% as needed. Byproducts can be recycled and reused, energy consumption is low, and continuous automated production can be achieved.

Description

Technical Field

[0001] This invention relates to the field of oil and fat modification technology, specifically to a production system and preparation method for diglyceride oil. Background Technology

[0002] Diglycerides are a type of functional oil, formed by the esterification of one molecule of glycerol with two molecules of fatty acids. They have physiological functions such as inhibiting fat accumulation, lowering blood lipids, and improving metabolism. Moreover, their taste and processing characteristics are similar to those of ordinary vegetable oils, making them a high-quality healthy oil raw material that is widely used in food processing, dietary supplements, cosmetics, and pharmaceutical excipients.

[0003] Currently, the industrial production methods for diglycerides are mainly divided into two categories: chemical synthesis and enzymatic synthesis. Chemical synthesis uses chemical catalysts (such as sodium hydroxide, sodium methoxide, etc.) to catalyze the glycerolization of oils or the esterification of fatty acids. This method suffers from drawbacks such as high reaction temperatures, high energy consumption, numerous byproducts, and dark-colored products. Furthermore, subsequent refining is difficult, it easily generates harmful substances, has poor safety, and the product purity is generally low, making it difficult to meet the standards for high-end food and pharmaceutical applications.

[0004] Enzyme-catalyzed synthesis has become the mainstream production process due to its advantages such as mild reaction conditions, high selectivity, few side reactions, and high product safety. However, existing enzymatic production technologies still have many core shortcomings, mainly in the following aspects: First, catalysts are costly and unstable. Currently, the industry commonly uses immobilized enzymes as catalysts, but the preparation cost of the carrier is high, resulting in expensive initial investment. More importantly, during the reaction process, stirring and fluid scouring can easily cause carrier breakage and enzyme protein loss, leading to significant enzyme activity degradation after long-term operation. Damaged carrier particles enter the heat exchanger and molecular distillation system with the material, easily depositing in the tube bundle, resulting in decreased heat exchange efficiency and increased equipment maintenance burden. In addition, the non-specific adsorption of the carrier itself will increase the load on subsequent separation and purification.

[0005] Second, the purification process is simplistic, resulting in insufficient product flexibility. Current purification methods mostly employ single-stage or two-stage simple molecular distillation, which limits separation precision and can only produce products of a single purity. This makes it difficult to flexibly adjust product specifications according to market demands, leading to poor production versatility.

[0006] Third, the utilization rate of by-products is low. Most existing processes only focus on the purification of the main product, diglycerides, without refining and recovering the by-products generated in the reaction (such as free fatty acids and monoglycerides), resulting in low overall utilization of raw materials and increased pressure on waste disposal.

[0007] To address the aforementioned issues, several improved solutions have been proposed in existing patent literature. Chinese patent literature with authorization announcement number CN118879797B discloses a "method for preparing diglyceride oil," which uses immobilized lipase TL IM as a catalyst, glycerol and vegetable oil as reactants, and water as a medium to promote reactant mixing. After cyclic reaction in an enzyme reactor, diglyceride oil is obtained through two-stage short-path distillation, deodorization, and adsorption treatment. While this method has made some progress in terms of the reusability of immobilized enzymes and product purity, it still has significant shortcomings: First, the initial investment cost of the immobilized enzyme carrier is high, and carrier breakage and enzyme loss are prominent problems during operation, making it difficult to maintain enzyme activity over long-term operation; second, broken carrier particles easily contaminate subsequent equipment, affecting heat exchange efficiency and system stability, and the adsorption and refining process generates solid hazardous waste, which not only increases process complexity but also raises environmental treatment costs.

[0008] Chinese patent document CN117757853A discloses a "method for preparing diglycerides," which employs two liquid lipases for stepwise catalysis. First, a first lipase catalyzes the hydrolysis of vegetable oil, and after separation, the upper light phase is collected. Then, a second lipase is added to react with glycerol for esterification. This is followed by two stages of progressive deodorization (first deodorization at 170℃–240℃, second deodorization at 270℃–310℃) and adsorption purification. The drawbacks of this method are: First, a large amount of water needs to be added in the first reaction stage (the mass ratio of vegetable oil to water is 1:0.6–1.2), resulting in a very high water content in the system and high energy consumption for subsequent dehydration. Second, the second deodorization temperature is as high as 270℃–310℃, and high temperatures easily promote the formation of processing pollutants such as trichloropropanol esters and glycidyl esters. Although subsequent adsorption treatment can partially remove these pollutants, it increases the number of steps and the consumption of adsorbent. Third, adsorption purification generates solid hazardous waste, placing a heavy environmental burden on the system.

[0009] Chinese patent document CN121320469A discloses a "preparation process and application of diglyceride oil". The process involves immobilized lipase catalyzing the hydrolysis of vegetable oil, separating fatty acids by primary molecular distillation, then enzymatically esterifying the fatty acids with glycerol, and finally obtaining diglyceride oil by secondary molecular distillation. While this process has made beneficial explorations in green manufacturing and solvent-free systems, it still has the following shortcomings: First, both the hydrolysis and esterification stages of this process use immobilized lipases, resulting in high initial investment costs for immobilized enzyme carriers. During long-term operation, carrier breakage and enzyme activity decay are prominent issues, increasing the equipment maintenance burden and catalyst replacement costs in industrial production. Second, the purification process uses a relatively simple two-stage molecular distillation mode, which has limited separation precision and restricts the potential for improving product purity. According to the data in the example provided in the instruction manual, the highest diglyceride content in the final product, diglyceride oil, is only 89.3%, which is insufficient to meet the application requirements for higher purity diglyceride products. Third, this process only focuses on the purification of the main product, diglyceride, without refining the separation and resource recovery of byproducts generated during the reaction (such as unreacted fatty acids and monoglycerides), and the comprehensive utilization rate of raw materials needs further improvement.

[0010] In summary, existing enzymatic methods for producing diglycerides generally suffer from problems such as simplistic purification processes, inflexible product purity control, low byproduct utilization, and solid waste emissions. Therefore, developing a diglyceride purification system and process that offers high separation precision, adjustable product purity, resource-efficient byproduct utilization, low energy consumption, and environmental friendliness is a pressing technical challenge in this field. Summary of the Invention

[0011] The purpose of this invention is to overcome the shortcomings of the prior art and provide a production system and preparation method for diglyceride oil, which can improve the conversion efficiency of diglyceride, obtain diglycerides of different purities and high-purity by-products, reduce energy consumption, achieve zero solid waste discharge, and enable continuous automated production.

[0012] To achieve the above-mentioned objectives, the present invention provides the following technical solution: On the one hand, the present invention provides a production system for diglyceride oil.

[0013] In one preferred embodiment, the system includes: a hydrolysis reaction section, an esterification reaction section, and a purification section; The hydrolysis reaction section is used to hydrolyze vegetable oil under the action of lipase, and its outlet is connected to the inlet of the esterification reaction section. The esterification reaction section is used to esterify the hydrolysis product with glycerol under the action of lipase, and its outlet is connected to the inlet of the purification section. The purification section includes a first-stage thin-film evaporator, a second-stage molecular distillation unit, a third-stage molecular distillation unit, and a fourth-stage molecular distillation unit connected in sequence. The heavy phase outlet of the third-stage molecular distillation unit is connected to the finished product output pipeline and the inlet of the fourth-stage molecular distillation unit respectively through a flow splitting device. The light phase outlet of the fourth-stage molecular distillation unit is connected to the finished product output pipeline.

[0014] In a preferred embodiment, the purification section further includes a diglyceride cooler and a first feed preheater located between the outlet of the esterification reaction section and the inlet of the first-stage thin-film evaporator. The tube-side outlet of the diglyceride cooler is connected to the tube-side inlet of the first feed preheater, and the tube-side outlet of the first feed preheater is connected to the inlet of the first-stage thin-film evaporator. The shell-side inlet of the diglyceride cooler is connected to the heavy phase outlet of the tertiary molecular distillation unit or the light phase outlet of the quaternary molecular distillation unit.

[0015] In a preferred embodiment, the purification section further includes a quadruple cooler and a second feed preheater located between the heavy phase outlet of the primary thin-film evaporator and the inlet of the secondary molecular distillation unit. The heavy phase outlet of the primary thin-film evaporator is connected to the tube-side inlet of the quadruple cooler, the tube-side outlet of the quadruple cooler is connected to the tube-side inlet of the second feed preheater, and the tube-side outlet of the second feed preheater is connected to the inlet of the secondary molecular distillation unit. The shell-side inlet of the quadruple cooler is connected to the heavy phase outlet of the quadruple molecular distillation unit.

[0016] In a preferred embodiment, the diversion device is a three-way switching valve. The inlet of the three-way switching valve is connected to the heavy phase outlet of the three-stage molecular distillation unit, the first outlet of the three-way switching valve is connected to the inlet of the four-stage molecular distillation unit, and the second outlet of the three-way switching valve is connected to the finished product output pipeline.

[0017] In a preferred embodiment, the heavy phase outlet of the four-stage molecular distillation unit is connected to the vegetable oil inlet of the hydrolysis reaction section, so as to send the separated triglycerides back to the hydrolysis reaction section as raw materials.

[0018] In a preferred embodiment, the esterification reaction section includes an enzyme reactor and a glycerol ester storage tank. The bottom outlet of the enzyme reactor is divided into two paths after passing through a circulation pump: one path is connected to the circulation inlet of the enzyme reactor after passing through an oil heater and an oil cooler, and the other path is connected to the inlet of the glycerol ester storage tank.

[0019] In a preferred embodiment, the bottom outlet of the enzyme reactor is also connected to a glycerol storage tank, the outlet of which is connected to the glycerol inlet of the enzyme reactor via a glycerol discharge pump; the bottom outlet of the enzyme reactor is also connected to an oil-water separation tank.

[0020] In a preferred embodiment, two enzyme reactors are connected in parallel. The bottom outlets of the two enzyme reactors are respectively connected to the inlet of the circulation pump through valves, and the circulation inlets of the two enzyme reactors are respectively connected to the outlet of the oil cooler through valves.

[0021] In a preferred embodiment, the light phase outlet of the primary thin-film evaporator is connected to a first condensation recovery unit, and the outlet of the first condensation recovery unit is connected to the glycerol inlet of the esterification reaction section.

[0022] In a preferred embodiment, the light phase outlet of the secondary molecular distillation unit is connected to a fatty acid collection unit, and the light phase outlet of the tertiary molecular distillation unit is connected to a monoglyceride collection unit.

[0023] On the other hand, the present invention provides a method for preparing diglyceride oil.

[0024] In a preferred embodiment, the preparation method employs the production system described in any of the above-mentioned embodiments and includes the following steps: S1. Hydrolysis reaction: Vegetable oil, soft water and hydrolysis lipase are fed into the hydrolysis reaction section and hydrolyzed at 35~55℃ to obtain a hydrolyzed mixture. S2. Enzyme inactivation and drying: The hydrolysate mixture is heated to 80~90℃ to inactivate the enzymes. After separating the lower aqueous phase, it is vacuum dried at 80~90℃ and absolute pressure ≤110mbar. S3. Esterification reaction: Glycerol and lipase for esterification are added to the dried hydrolysate mixture to carry out the esterification reaction and synthesize a mixture of glycerol esters; S4. Enzyme inactivation and purification: The glycerol ester mixture is heated to 80-90℃ to inactivate the enzymes. After separating the lower layer of glycerol, it is washed with water and vacuum dried to obtain a crude glycerol ester mixture. S5. First-stage thin-film evaporation: The crude glyceride mixture is preheated and then fed into a first-stage thin-film evaporator. Thin-film evaporation is carried out at 80~140℃ and absolute pressure ≤120Pa to remove the light phase components and obtain the heavy phase material. S6. Secondary molecular distillation: The heavy phase material obtained in step S5 is preheated and then fed into a secondary molecular distillation apparatus. Molecular distillation is carried out at 170~200℃ and absolute pressure ≤10Pa to separate fatty acids and obtain the heavy phase material. S7. Three-stage molecular distillation: The heavy phase material obtained in step S6 is fed into a three-stage molecular distillation apparatus and molecular distilled at 170~200℃ and absolute pressure ≤10Pa to separate monoglycerides and obtain a heavy phase material rich in diglycerides. S8. Finished product preparation: The heavy phase material rich in diglycerides is cooled and filtered to obtain a diglyceride oil product with a diglyceride content ≥60%; or, the heavy phase material rich in diglycerides is fed into a four-stage molecular distillation apparatus and molecular distilled at 200~260℃ and absolute pressure ≤1Pa, and the light phase component is collected, cooled and filtered to obtain a diglyceride oil product with a diglyceride content ≥90%.

[0025] In a preferred embodiment, in step S1, the weight ratio of the vegetable oil, soft water, and hydrolysis lipase is 100:(30~60):(0.2~0.5), and the hydrolysis reaction time is 12~24h; in step S3, the amount of glycerol added is 10~30% of the weight of the vegetable oil, the amount of esterification lipase added is 0.2~0.5% of the weight of the vegetable oil, and the esterification reaction time is 12~24h.

[0026] In a preferred embodiment, in step S1, the lipase used for hydrolysis is a liquid lipase; in step S3, the lipase used for esterification is a liquid lipase.

[0027] In a preferred embodiment, in step S5, the light phase component separated by the primary thin-film evaporation is condensed and then sent back to step S3 as a raw material to participate in the esterification reaction; in step S8, the heavy phase component separated by the quaternary molecular distillation is triglyceride, which is cooled and filtered and then sent back to step S1 as a raw material to participate in the hydrolysis reaction.

[0028] In a preferred embodiment, the lower aqueous phase separated in step S2 is discharged to an oil-water separation tank; the lower glycerol separated in step S4 is collected and sent back to step S3 as a raw material to participate in the esterification reaction.

[0029] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. The selectivity of the catalytic reaction is greatly improved, and the purity of the product is significantly increased. The hydrolysis and esterification reactions are separated into two independent reaction stages. The hydrolysis is specifically catalyzed by lipase, resulting in the hydrolysis of triglycerides. After hydrolysis, the substrate of the system is mostly glycerol and free fatty acids. Then, esterification is carried out by lipase to synthesize diglycerides, which greatly reduces the generation of by-products such as monoglycerides. The amount of glycerol used is reduced, and the proportion of the target product diglycerides is much higher than that of one-step compound enzyme and single-enzyme one-step processes. The substrate ratio of the two-step reaction is precisely controlled, resulting in low residual free fatty acids, lower acid value of the finished product, no need for neutralization and deacidification process, and reduced loss of neutral oils.

[0030] 2. High separation and purification precision, with flexible and adjustable product purity. This invention employs a purification system combining single-stage thin-film evaporation and three-stage molecular distillation (two-stage, three-stage, and four-stage molecular distillation). The heavy phase outlet of the three-stage molecular distillation unit is connected to both the finished product output pipeline and the inlet of the four-stage molecular distillation unit via a splitter device. The light phase outlet of the four-stage molecular distillation unit is also connected to the finished product output pipeline. This splitter structure allows for flexible adjustment of process parameters according to production needs, producing diglyceride products with gradient purities ranging from 60% to 99%, adapting to different application scenarios and overcoming the shortcomings of existing technologies, such as limited purification processes and insufficient product flexibility.

[0031] 3. The two lipases do not inhibit each other, resulting in improved enzyme utilization, lower enzyme dosage, and reduced production costs. Existing compound enzyme schemes involve two enzymes coexisting, leading to substrate competition and microenvironmental conflicts that reduce enzyme activity. This invention uses staged feeding, ensuring only one lipase exists in the system at any given time, resulting in no enzyme activity loss and lower enzyme dosage for the same conversion effect. Furthermore, this invention uses liquid enzymes, facilitating addition and separation, resulting in a more uniform reaction system, simpler equipment, lower dosage, and lower initial investment costs. Taking a factory processing 5 tons of 65% diglyceride per day as an example, this invention has significant advantages in terms of enzyme catalyst dosage, process length, and equipment investment, significantly reducing overall production costs compared to existing processes.

[0032] 4. High utilization rate of by-products and significantly improved comprehensive utilization rate of raw materials. In this invention, the purity of fatty acids separated by secondary molecular distillation can reach over 82%, and the purity of monoglycerides separated by tertiary molecular distillation can reach over 95%, both of which can be individually recovered for resource reuse. At the same time, the heavy phase component triglycerides separated by quaternary molecular distillation can be returned to the hydrolysis reaction section for recycling, and the light phase component separated by primary thin-film evaporation and the excess glycerol separated after esterification can also be returned to the esterification reaction section for recycling, effectively improving the overall utilization rate of raw materials, reducing production waste emissions, achieving zero solid waste emissions, and further reducing comprehensive production costs.

[0033] 5. Solvent-free and mild reaction system ensures better product safety and nutrient retention. Stepwise hydrolysis gradually reduces system viscosity, achieving good mass transfer without the need for organic solvents. This eliminates the need for solvent recovery and residue removal processes, eliminating the risk of organic residues and making production safer and more environmentally friendly. The mild reaction conditions result in efficient and rapid subsequent purification, avoiding the generation of processing contaminants such as 3-MCPD and glycidyl esters. It also reduces the oxidative decomposition of unsaturated fatty acids, natural vitamin E, and phytosterols, resulting in higher retention of the original active nutrients in the oils. The finished product combines high levels of diglycerides with highly active functional components.

[0034] 6. Multi-stage heat exchange network enables low-energy operation. This invention incorporates a diglyceride cooler and a quadruple cooler in the purification section, utilizing heat exchange between high-temperature and low-temperature materials to achieve heat recovery and reduce the overall energy consumption of the system.

[0035] 7. Strong process controllability and wider range of applicable raw materials. The hydrolysis stage is independently controllable and highly adaptable to crude oil, oils containing impurities, and various animal and vegetable triglyceride raw materials, without the need for pre-refining. Existing one-step enzymatic methods have high requirements for raw material purity, and crude oil is prone to enzyme inactivation. The two-stage process allows for independent control of reaction parameters (temperature, substrate ratio), and the depth of hydrolysis and degree of esterification can be flexibly adjusted according to different raw materials, precisely controlling the diglyceride yield ratio. The process flexibility is far superior to the one-step co-catalytic process.

[0036] 8. Advantages of industrialized production and environmental protection. The content of by-products such as monoglycerides and unreacted fatty acids is low, and the molecular distillation separation load is significantly reduced; no organic solvents are used, and the emissions of organic waste liquid and exhaust gas are minimal, resulting in low environmental treatment costs and no risk of flammable or explosive solvents in the production workshop; the process is modularized, and the hydrolysis section and esterification section can operate independently and continuously, with low barriers to equipment modification, making it suitable for large-scale mass production in small and medium-sized oil processing plants. Attached Figure Description

[0037] Figure 1 This is a process flow diagram of Example 1 of the diglyceride oil production system of the present invention; Figure 2 This is a process flow diagram of Example 2 of the diglyceride oil production system of the present invention; Explanation of reference numerals in the attached diagram: E1. Enzyme reactor; E2. Glycerol temporary storage tank; E3. Glyceryl ester temporary storage tank; E4. Light ester tank; E5. Heavy ester tank; E6. Light ester tank; E7. Heavy ester tank; E8. Light ester tank; E9. Heavy ester tank; E10. Light ester tank; E11. Heavy ester tank; E12. Buffer tank; E13. Oil-water separator; F1. First-stage thin-film evaporator; F2. Second-stage molecular distillation unit; F3. Third-stage molecular distillation unit; F4. Quaternary molecular distillation unit; P1. Vegetable oil pump; P2. Glycerin feed pump; P3. Soft water pump; P4. Circulation pump; P5. Glycerin discharge pump; P6. Glyceryl ester transfer pump; P7. Primary light pump; P8. Primary heavy pump; P9. Secondary light pump; P10. Secondary heavy pump; P11. Tertiary light pump; P12. Tertiary pump; P13. Quadruple light pump; P14. Quadruple pump; H1. First condenser; H2. Oil heater; H3. Oil cooler; H4. First feed preheater; H5. Second condenser; H6. Second feed preheater; H7. Third condenser; H8. Fourth condenser; H9. Fifth condenser; H10. Diglyceride cooler; H11. Quadruple cooler; H12. Triglyceride cooler; H13. Discharge cooler; D1. First filter; D2. Second filter; V1. First vacuum system; V2. Second vacuum system; V3. Third vacuum system; V4. Fourth vacuum system; V5. Fifth vacuum system; G1. Vegetable oil inlet pipe; G2. Glycerin inlet pipe; G3. Soft water inlet pipe; G4. Enzyme inlet pipe; G5. Hot water inlet pipe; G6. Hot water outlet pipe; G7. Steam inlet pipe; G8. Condensate outlet pipe; G9. Circulating water inlet pipe; G10. Circulating water outlet pipe; G11. Glycerin outlet pipe; G12. Heat transfer oil inlet pipe; G13. Heat transfer oil outlet pipe; G14. Chilled water inlet pipe; G15. Chilled water outlet pipe; G16. Light ester outlet pipe; G17. Fatty acid outlet pipe; G18. Monoglyceride outlet pipe; G19. Triglyceride outlet pipe; G20. Low-boiling-point substance outlet pipe; G21. Diglyceride outlet pipe; G22. Glyceryl ester mixture inlet pipe; G23. Glyceryl ester mixture outlet pipe; G24. Primary mixture inlet pipe; G25. Primary mixture outlet pipe. Detailed Implementation

[0038] Unless otherwise specified, all pressures mentioned in this article refer to absolute pressures.

[0039] like Figure 1 As shown, this invention provides a diglyceride oil production system, comprising: an enzyme reactor E1, a glycerol storage tank E2, a glycerol ester storage tank E3, a primary light tank E4, a primary heavy tank E5, a secondary light tank E6, a secondary heavy tank E7, a tertiary light tank E8, a tertiary heavy tank E9, a quaternary light tank E10, a quaternary heavy tank E11, a buffer tank E12, a primary thin-film evaporator F1, a secondary molecular distillation unit F2, a tertiary molecular distillation unit F3, and a quaternary molecular distillation unit F4, etc. The above components are connected by pipelines in the following manner: Vegetable oil inlet pipe G1 is connected to the inlet of vegetable oil pump P1, and the outlet of vegetable oil pump P1 is connected to the vegetable oil inlet of enzyme reactor E1; glycerol inlet pipe G2 is connected to the inlet of glycerol feed pump P2, and the outlet of glycerol feed pump P2 is connected to the glycerol inlet of enzyme reactor E1; soft water inlet pipe G3 is connected to the inlet of soft water pump P3, and the outlet of soft water pump P3 is connected to the soft water inlet of enzyme reactor E1; enzyme inlet pipe G4 is connected to the enzyme inlet of enzyme reactor E1.

[0040] The bottom outlet of enzyme reactor E1 is connected to the inlet of circulating pump P4. One outlet of circulating pump P4 is connected to the cold-side inlet of oil heater H2. A bypass valve is provided between the cold-side inlet and cold-side outlet of oil heater H2. The cold-side outlet of oil heater H2 is connected to the hot-side inlet of oil cooler H3. A bypass valve is provided between the hot-side inlet and hot-side outlet of oil cooler H3. The hot-side outlet of oil cooler H3 is connected to the upper circulating inlet of enzyme reactor E1. Another outlet of circulating pump P4 is connected to the inlet of glycerol ester storage tank E3. The outlet of glycerol ester storage tank E3 is connected to the inlet of glycerol ester transfer pump P6. The outlet of glycerol ester transfer pump P6 is connected to the tube-side inlet of diglyceride cooler H10 through glycerol ester mixture inlet pipe G22. The tube-side outlet of diglyceride cooler H10 is connected to the tube-side inlet of first feed preheater H4 through glycerol ester mixture outlet pipe G23. The tube-side outlet of first feed preheater H4 is connected to the inlet of first-stage thin-film evaporator F1. A bypass valve is provided between the inlet pipe G22 and the outlet pipe G23 of the glycerol ester mixture.

[0041] The upper vapor phase outlet of the first-stage thin-film evaporator F1 is connected to the shell-side inlet of the second condenser H5. The shell-side outlet of the second condenser H5 is connected to the inlet of a light tank E4. The outlet of the light tank E4 is connected to the inlet of a light pump P7. The outlet of the light pump P7 is connected to a light outlet pipe G16. The outlet of the light outlet pipe G16 is connected to the inlet of the glycerin feed pump P2.

[0042] The bottom outlet of the primary thin-film evaporator F1 is connected to the inlet of the primary heavy tank E5. The outlet of the primary heavy tank E5 is connected to the inlet of the primary heavy pump P8. The outlet of the primary heavy pump P8 is connected to the tube-side inlet of the quadruple cooler H11 via the primary mixture inlet pipe G24. The tube-side outlet of the quadruple cooler H11 is connected to the tube-side inlet of the second feed preheater H6 via the primary mixture outlet pipe G25. The tube-side outlet of the second feed preheater H6 is connected to the inlet of the secondary molecular distillation unit F2. A bypass valve is provided between the primary mixture inlet pipe G24 and the primary mixture outlet pipe G25.

[0043] The upper vapor phase outlet of the secondary molecular distillation unit F2 is connected to the shell-side inlet of the third condenser H7, the shell-side outlet of the third condenser H7 is connected to the inlet of the buffer tank E12, and the outlet of the buffer tank E12 is connected to the low-boiling-point outlet pipe G20.

[0044] The bottom light phase outlet of the secondary molecular distillation unit F2 is connected to the inlet of the secondary light phase tank E6, the outlet of the secondary light phase tank E6 is connected to the inlet of the secondary light phase pump P9, and the outlet of the secondary light phase pump P9 is connected to the fatty acid outlet pipe G17.

[0045] The bottom heavy phase outlet of the second-stage molecular still F2 is connected to the inlet of the double tank E7, the outlet of the double tank E7 is connected to the inlet of the double pump P10, and the outlet of the double pump P10 is connected to the inlet of the third-stage molecular still F3.

[0046] The upper vapor outlet of the third-stage molecular distillation unit F3 is connected to the shell-side inlet of the fourth condenser H8, and the shell-side outlet of the fourth condenser H8 is also connected to the inlet of the buffer tank E12.

[0047] The bottom light phase outlet of the three-stage molecular distillation unit F3 is connected to the inlet of the three-light tank E8, the outlet of the three-light tank E8 is connected to the inlet of the three-light pump P11, and the outlet of the three-light pump P11 is connected to the monoglyceride outlet pipe G18.

[0048] The bottom heavy phase outlet of the third-stage molecular still F3 is connected to the inlet of the triple tank E9, and the outlet of the triple tank E9 is connected to the inlet of the triple pump P12. The outlet of the triple pump P12 is divided into two paths: one path is connected to the shell-side inlet of the diglyceride cooler H10, and the shell-side outlet of the diglyceride cooler H10 is connected to the hot-side inlet of the discharge cooler H13, and the hot-side outlet of the discharge cooler H13 is connected to the inlet of the second filter D2, and the outlet of the second filter D2 is connected to the diglyceride outlet pipe G21; the other path is connected to the inlet of the fourth-stage molecular still F4.

[0049] The upper vapor phase outlet of the fourth-stage molecular still F4 is connected to the shell-side inlet of the fifth condenser H9, and the shell-side outlet of the fifth condenser H9 is also connected to the inlet of the buffer tank E12. The bottom light phase outlet of the fourth-stage molecular still F4 is connected to the inlet of the fourth light tank E10, and the outlet of the fourth light tank E10 is connected to the inlet of the fourth light pump P13, and the outlet of the fourth light pump P13 is also connected to the shell-side inlet of the diglyceride cooler H10. The bottom heavy phase outlet of the fourth-stage molecular still F4 is connected to the inlet of the fourth heavy tank E11, and the outlet of the fourth heavy tank E11 is connected to the inlet of the fourth heavy pump P14, the outlet of the fourth heavy pump P14 is connected to the shell-side inlet of the fourth heavy cooler H11, the shell-side outlet of the fourth heavy cooler H11 is connected to the hot-side inlet of the triglyceride cooler H12, the hot-side outlet of the triglyceride cooler H12 is connected to the inlet of the first filter D1, and the outlet of the first filter D1 is connected to the triglyceride outlet pipe G19.

[0050] The top gas phase outlet of enzyme reactor E1 is connected to the shell-side inlet of the first condenser H1, and the shell-side outlet of the first condenser H1 is connected to the first vacuum system V1; the shell-side vacuum port of the second condenser H5 is connected to the second vacuum system V2; the shell-side vacuum port of the third condenser H7 is connected to the third vacuum system V3; the shell-side vacuum port of the fourth condenser H8 is connected to the fourth vacuum system V4; and the shell-side vacuum port of the fifth condenser H9 is connected to the fifth vacuum system V5.

[0051] The enzyme reactor E1 is equipped with a heating coil. The inlet of the heating coil is connected to the hot water inlet pipe G5, and the outlet of the heating coil is connected to the hot water outlet pipe G6. The hot-side inlet of the oil heater H2 is connected to the steam inlet pipe G7, and the hot-side outlet of the oil heater H2 is connected to the condensate outlet pipe G8. The cold-side inlet of the oil cooler H3 is connected to the circulating water inlet pipe G9, and the cold-side outlet of the oil cooler H3 is connected to the circulating water outlet pipe G10. The tube-side inlet of the first condenser H1 is connected to the circulating water inlet pipe G9, and the tube-side outlet of the first condenser H1 is connected to the circulating water outlet pipe G10. The cold-side inlet of the triglyceride cooler H12 is connected to the circulating water inlet pipe G9, and the cold-side outlet of the triglyceride cooler H12 is connected to the circulating water outlet pipe G10.

[0052] The bottom outlet of enzyme reactor E1 is also connected to the inlet of glycerol storage tank E2, the outlet of glycerol storage tank E2 is connected to the inlet of glycerol discharge pump P5, and the outlet of glycerol discharge pump P5 is connected to glycerol outlet pipe G11. The bottom outlet of enzyme reactor E1 is also connected to the inlet of oil-water separator E13.

[0053] The heat transfer oil inlet pipe G12 is connected to the heat transfer oil inlets of the first-stage thin-film evaporator F1, the second-stage molecular distillation unit F2, the third-stage molecular distillation unit F3, and the fourth-stage molecular distillation unit F4, respectively. The heat transfer oil outlet of the first-stage thin-film evaporator F1 is connected to the hot-side inlet of the first feed preheater H4, and the heat transfer oil outlet of the second-stage molecular distillation unit F2 is connected to the hot-side inlet of the second feed preheater H6. The hot-side outlets of the first feed preheater H4, the second feed preheater H6, the third-stage molecular distillation unit F3, and the fourth-stage molecular distillation unit F4 are connected to the heat transfer oil outlet pipe G13, respectively.

[0054] The chilled water inlet pipe G14 is connected to the tube-side inlet of the second condenser H5, the tube-side inlet of the third condenser H7, the tube-side inlet of the fourth condenser H8, and the tube-side inlet of the fifth condenser H9, respectively; the tube-side outlet of the second condenser H5, the tube-side outlet of the third condenser H7, the tube-side outlet of the fourth condenser H8, and the tube-side outlet of the fifth condenser H9 are connected to the chilled water outlet pipe G15, respectively.

[0055] The working principle of this production system is as follows: S1. Raw Material Delivery and Atmospheric Pressure Hydrolysis Reaction (First Step Reaction): Vegetable oil is delivered to enzyme reactor E1 via vegetable oil inlet pipe G1 and vegetable oil pump P1. Soft water is delivered to enzyme reactor E1 via soft water inlet pipe G3 and soft water pump P3. Lipase for hydrolysis is manually added to enzyme reactor E1 via enzyme inlet pipe G4. Hot water enters the heating coil of enzyme reactor E1 via hot water inlet pipe G5, heating the reaction mixture to 35~55℃ for the first step reaction (atmospheric pressure) for 12~24 hours. The water from the heating coil returns to the hot water tank via hot water outlet pipe G6, achieving hot water recycling.

[0056] S2, Enzyme inactivation, circulation sedimentation and wastewater discharge of hydrolyzed materials: After the hydrolysis reaction is completed, the mixture is pumped into the cold side of the oil heater H2 by the circulation pump P4. After exchanging heat with the steam on the hot side, the temperature is raised to 80~90℃ to inactivate the enzyme. Then the mixture returns to the enzyme reactor E1 through the upper circulation inlet of the enzyme reactor E1 to settle. After settling, the water in the lower layer is discharged to the oil-water separation tank E13.

[0057] S3. Material drying under vacuum: The gas phase discharged from enzyme reactor E1 is condensed in the shell side of condenser H1. The non-condensable gas is discharged to the tail gas treatment system through the first vacuum system V1. The absolute pressure inside enzyme reactor E1 is ≤110mbar. Hot water enters the heating coil of enzyme reactor E1 through hot water inlet pipe G5 to heat the mixture to 80~90℃ for drying. After drying, the mixture is pumped into the hot side of oil cooler H3 by circulating pump P4. After heat exchange with circulating water, it is cooled to 35~55℃ and returned to enzyme reactor E1 through the upper circulation inlet.

[0058] S4. Atmospheric pressure esterification reaction (second step reaction): Glycerol is sent to enzyme reactor E1 by glycerol feed pump P2 through glycerol inlet pipe G2. Lipase for esterification is manually added to enzyme reactor E1 through enzyme inlet pipe G4. The materials are fully mixed and esterification reaction occurs to synthesize a glycerol ester mixture.

[0059] S5. Esterification Material Enzyme Inactivation, Sedimentation and Separation, and Glycerol Discharge: The reacted mixture is pumped by circulating pump P4 into the cold side of oil heater H2. After heat exchange with the steam on the hot side, the temperature is raised to 80-90℃ to inactivate the enzyme. Then, the mixture returns to enzyme reactor E1 through the upper circulation inlet to settle. The glycerol in the lower layer after settling enters the glycerol storage tank E2, and is discharged by glycerol discharge pump P5 and glycerol outlet pipe G11. The obtained glycerol can be used as a production raw material and transported back to enzyme reactor E1 by glycerol feed pump P2, entering the production process for recycling and maximizing the utilization of raw materials.

[0060] S6. Material washing and preliminary purification: The upper layer mixture after sedimentation in enzyme reactor E1 is washed with water to remove inactivated enzymes and some impurities, completing the preliminary purification of the glyceride mixture. Figure 2As shown, to improve production continuity, in another feasible embodiment, enzyme reactors E1 can also be configured in parallel as two sets, with the two enzyme reactors E1 sharing a single circulating pump P4. The outlet of circulating pump P4 is connected to the cold-side inlet of oil heater H2 and the inlet of glycerol ester storage tank E3. The upper circulating inlets of the two enzyme reactors E1 are controllably connected to the outlet of oil cooler H3 through circulating inlet valves, thereby allowing the two enzyme reactors E1 to share the same set of oil heater H2 and oil cooler H3. By controlling the opening and closing of the circulating pump inlet valve and the upper circulating inlet valve of enzyme reactor E1, the two enzyme reactors E1 can be fed at different times and run alternately to improve the overall operating efficiency of the system.

[0061] S7. Vacuum drying and feeding of crude product: The gas phase of enzyme reactor E1 is condensed in the shell side of condenser H1. The absolute pressure inside enzyme reactor E1 is ≤110mbar. Hot water enters the heating coil of enzyme reactor E1 through hot water inlet pipe G5 to heat the glycerol ester mixture to 80~90℃ for vacuum drying to remove residual moisture. The dried glycerol ester mixture is pumped into glycerol ester temporary storage tank E3 by circulation pump P4 and then sent to the subsequent purification process by glycerol ester transfer pump P6.

[0062] S8. Multi-stage heat exchange pretreatment and primary thin-film evaporation purification: The glycerol ester mixture output from the glycerol ester transfer pump P6 is first sent to the tube side of the diglyceride cooler H10, where it exchanges heat with the diglyceride product from the subsequent finished product process in the shell side. After initial heating, it enters the tube side of the first feed preheater H4 for further heat exchange with the heat transfer oil in the shell side, and then enters the primary thin-film evaporator F1. The primary thin-film evaporation temperature is 80~140℃, and the absolute pressure is ≤120Pa. Some glycerol and low-boiling-point substances are evaporated. The gas phase enters the shell side of the second condenser H5, where it exchanges heat with the chilled water in the tube side and then condenses into a light phase tank E4. The non-condensable gas is discharged to the tail gas treatment system by the second vacuum system V2. The glycerol and low-boiling-point substances in the light phase tank E4 are sent out by a light phase pump P7 and a light phase outlet pipe G16, and can be fed back into the enzyme reactor E1 as production raw materials. The heavy phase material separated by the primary thin-film evaporator F1 enters the heavy phase tank E5, completing the primary separation of light and heavy components.

[0063] When the target purity of diglyceride product is above 60%, the diglyceride product in triple tank E9 is sent to the shell side of diglyceride cooler H10 by triple pump P12. When the target purity of the finished product is high-purity diglyceride of 90% or higher, the diglyceride product in the four-light tank E10 is sent to the shell side of the diglyceride cooler H10 by the four-light pump P13.

[0064] S9. Secondary Molecular Distillation Purification: The heavy phase material in the primary heavy tank E5 is transported to the tube side of the secondary cooler H11 via the primary pump P8, where it exchanges heat with the triglyceride material from the shell side of the secondary cooler P14. After heat exchange, it enters the tube side of the second feed preheater H6 for further heat exchange with the heat transfer oil in the shell side, and then enters the secondary molecular distiller F2 for further purification. The secondary molecular distillation temperature is 170~200℃, and the absolute pressure is ≤10Pa. During the secondary molecular distillation process, some low-boiling substances are evaporated, and the gas phase enters the shell side of the third condenser H7, where it exchanges heat with the chilled water in the tube side and then condenses into the buffer tank E12. The non-condensable gas is discharged to the tail gas treatment system through the third vacuum system V3. Due to the different molecular free paths, some fatty acids in the material reach the condensation surface first, and after condensation, they enter the secondary light tank E6. The remaining mixed heavy phase material enters the secondary heavy tank E7, completing the secondary separation and purification.

[0065] S10. Tertiary Molecular Distillation Purification and Component Separation: The heavy phase material in the secondary distillation tank E7 is sent to the tertiary molecular distillation unit F3 by the secondary pump P10 for further purification. The tertiary molecular distillation temperature is 170~200℃, and the absolute pressure is ≤10Pa. Some low-boiling-point substances are evaporated, and the gas phase enters the shell side of the fourth condenser H8. After heat exchange with the chilled water in the tube side, it condenses and enters the buffer tank E12. The non-condensable gas is discharged to the tail gas treatment system through the fourth vacuum system V4. Some monoglycerides enter the tertiary light phase tank E8 as the light phase, and the remaining heavy phase components enter the tertiary distillation tank E9. According to the purity requirements of the target product, they enter different finished product preparation processes.

[0066] S11, Processing of Diglyceride Products with a Purity of 60% or More: When the production target is a product with a purity of 60% or more, the heavy phase material in the triple tank E9 is sent to the shell side of the diglyceride cooler H10 by the triple pump P12, where it exchanges heat with the glyceride mixture from the glyceride transfer pump P6 in the tube side. Then it is further cooled by the discharge cooler H13 and filtered by the second filter D2 to finally obtain the finished diglyceride product with a purity of 60% or more.

[0067] Preparation of high-purity diglyceride (90% or higher): When the production target is high-purity diglyceride (90% or higher), the heavy phase material in the triple tank E9 is sent to the quadruple molecular distillation unit F4 by the triple pump P12 for final purification. The quadruple molecular distillation temperature is 200~260℃, absolute pressure ≤1Pa. Some low-boiling components in the material are evaporated, and the gas phase enters the shell side of the fifth condenser H9. After heat exchange with the chilled water in the tube side, it condenses and enters the buffer tank E12. The non-condensable gas is discharged to the tail gas treatment system by the fifth vacuum system V5. The high-purity diglyceride is collected as the light phase component in the four-light tank E10 and sent to the shell side of the diglyceride cooler H10 by the four-light pump. After heat exchange with the glyceride mixture from the glyceride transfer pump P6 in the tube side, it is further cooled by the discharge cooler H13 and then filtered by the second filter D2 to finally obtain the high-purity diglyceride (90% or higher).

[0068] S12. Recovery and Recycling of Triglyceride Byproducts: The heavy phase component separated by the four-stage molecular distillation unit F4 is triglyceride. This material enters the four-stage tank E11 and is pumped into the shell side of the four-stage cooler H11 by the four-stage pump P14. It exchanges heat with the mixture from the first pump P8 in the tube side, and then enters the hot side of the triglyceride cooler H12. After exchanging heat with the circulating water on the cold side, it is filtered by the first filter D1 and can be used as raw material to be sent to the enzyme reactor E1 by the vegetable oil pump P1 for recycling, so as to maximize the utilization of raw materials.

[0069] The preparation process of the diglyceride of the present invention will be further described in detail below through specific embodiments. The following embodiments are relatively specific. Unless otherwise specified, the experimental methods and detection methods involved in the following specific embodiments are conventional experimental methods and detection methods already existing in the prior art. Example

[0070] In step S1, the raw material weight ratio entering enzyme reactor E1 is: 100 parts peanut oil, 30 parts soft water, and 0.2 parts Blue LQ-05 liquid lipase; the reaction mixture is heated to 35°C for the first step reaction (at normal pressure) for 24 hours.

[0071] In step S2, the mixture after the hydrolysis reaction is completed exchanges heat with steam on the hot side and is heated to 85±5℃ to inactivate the enzyme.

[0072] In step S3, the absolute pressure inside enzyme reactor E1 is 100±5 mbar. Hot water is used to heat the mixture to 85±5℃ for drying. After drying, the mixture is cooled to 35℃ after exchanging heat with circulating water and then returned to enzyme reactor E1.

[0073] In step S4, 10 parts of glycerol are fed into enzyme reactor E1, and 0.2 parts of Lipozyme® CALB L are used as the esterification lipase in enzyme reactor E1. The materials are thoroughly mixed and reacted for 24 hours.

[0074] In step S5, the reacted mixture enters the cold side of the oil heater H2 and is heated to 85±5℃ to inactivate the enzyme.

[0075] In step S7, the absolute pressure inside enzyme reactor E1 is 100±5 mbar, and the glycerol ester mixture is heated to 85±5℃ for vacuum drying. The composition of the dried glycerol ester mixture is: fatty acids 7.10%, monoglycerides 13.36%, diglycerides 57.30%, and triglycerides 22.24%.

[0076] In step S8, the triglyceride product from the subsequent finished product process is fed into the shell side of the diglyceride cooler H10 by the triple pump P12. The primary thin-film evaporation temperature is 80℃, and the absolute pressure is 110±5 Pa.

[0077] In step S9, the secondary molecular distillation temperature is 170℃, the absolute pressure is 8±2Pa, and the purity of the secondary light component fatty acid is 82.63%.

[0078] In step S10, the tertiary molecular distillation temperature is 170℃, the absolute pressure is 3±2Pa, and the purity of the tertiary light component monoglyceride is 96.61%.

[0079] In step S11, the tertiary recombinant components are filtered through the second filter D2 to obtain the product, which consists of 0.3% fatty acids, 0.6% monoglycerides, 68.89% diglycerides, and 30.21% triglycerides. Example

[0080] In step S1, the raw material weight ratio entering enzyme reactor E1 is: 100 parts soybean oil, 60 parts soft water, and 0.5 parts Blue RML-L liquid lipase; the reaction mixture is heated to 55°C for the first step reaction (at normal pressure) for 12 hours.

[0081] In step S2, the mixture after the hydrolysis reaction is completed exchanges heat with steam on the hot side and is heated to 85±5℃ to inactivate the enzyme.

[0082] In step S3, the absolute pressure inside enzyme reactor E1 is 100±5 mbar. Hot water is used to heat the mixture to 85±5℃ for drying. After drying, the mixture is cooled to 55℃ after exchanging heat with circulating water and then returned to enzyme reactor E1.

[0083] In step S4, 30 parts of glycerol are fed into enzyme reactor E1, and 0.5 parts of Blue CLAB liquid lipase are used for esterification. The materials are thoroughly mixed and reacted for 12 hours.

[0084] In step S5, the reacted mixture enters the cold side of the oil heater H2 and is heated to 85±5℃ to inactivate the enzyme.

[0085] In step S7, the absolute pressure inside enzyme reactor E1 is 100±5 mbar, and the glycerol ester mixture is heated to 85±5℃ for vacuum drying. The composition of the dried glycerol ester mixture is: fatty acids 6.77%, monoglycerides 12.80%, diglycerides 61.26%, and triglycerides 19.17%.

[0086] In step S8, the diglyceride product from the subsequent finished product process is fed into the shell side of the diglyceride cooler H10 by the four light pump P13. The primary thin-film evaporation temperature is 140℃ and the absolute pressure is 110±5 Pa.

[0087] In step S9, the secondary molecular distillation temperature is 200℃, the absolute pressure is 8±2Pa, and the purity of the secondary light component fatty acid is 83.48%.

[0088] In step S10, the tertiary molecular distillation temperature is 200℃, the absolute pressure is 3±2Pa, and the purity of the tertiary light component monoglyceride is 95.55%.

[0089] In step S11, the fourth-stage molecular distillation temperature is 260℃ and the absolute pressure is 1Pa. After the fourth-stage light component is filtered by the second filter D2, the product is obtained, which consists of 0% fatty acids, 0% monoglycerides, 99.87% diglycerides and 0.13% triglycerides. Example

[0090] In step S1, the raw material weight ratio entering enzyme reactor E1 is: 100 parts rapeseed oil, 40 parts soft water, and 0.3 parts Lipozyme® TL 100 L; the reaction mixture is heated to 45°C for the first step reaction (at atmospheric pressure) for 24 hours.

[0091] In step S2, the mixture after the hydrolysis reaction is completed exchanges heat with steam on the hot side and is heated to 85±5℃ to inactivate the enzyme.

[0092] In step S3, the absolute pressure inside enzyme reactor E1 is 100±5 mbar. Hot water is used to heat the mixture to 85±5℃ for drying. After drying, the mixture is cooled to 45℃ after exchanging heat with circulating water and then returned to enzyme reactor E1.

[0093] In step S4, 20 parts of glycerol are fed into enzyme reactor E1, and 0.3 parts of Cathay TLL-Plus liquid lipase are used for esterification in enzyme reactor E1. The materials are thoroughly mixed and reacted for 24 hours.

[0094] In step S5, the reacted mixture enters the cold side of the oil heater H2 and is heated to 85±5℃ to inactivate the enzyme.

[0095] In step S7, the absolute pressure inside enzyme reactor E1 is 100±5 mbar, and the glycerol ester mixture is heated to 85±5℃ for vacuum drying. The composition of the dried glycerol ester mixture is: fatty acids 9.38%, monoglycerides 13.85%, diglycerides 58.19%, and triglycerides 18.58%.

[0096] In step S8, the diglyceride product from the subsequent finished product process is fed into the shell side of the diglyceride cooler H10 by the four light pump P13. The primary thin-film evaporation temperature is 140℃ and the absolute pressure is 110±5 Pa.

[0097] In step S9, the secondary molecular distillation temperature is 180℃, the absolute pressure is 8±2Pa, and the purity of the secondary light component fatty acid is 85.82%.

[0098] In step S10, the tertiary molecular distillation temperature is 200℃, the absolute pressure is 3±2Pa, and the purity of the tertiary light component monoglyceride is 96.17%.

[0099] In step S11, the fourth-stage molecular distillation temperature is 220℃ and the absolute pressure is 1Pa. After the fourth-stage light component is filtered by the second filter D2, the product is obtained with a purity of 0.1% fatty acid, 0.13% monoglyceride, 98.24% diglyceride and 1.53% triglyceride.

[0100] The vegetable oils in this invention include, but are not limited to, sunflower seed oil, palm oil, palm kernel oil, olive oil, tea seed oil, cottonseed oil, sesame oil, flaxseed oil, perilla oil, walnut oil, sweet almond oil, pumpkin seed oil, grape seed oil, coconut oil, rice bran oil, safflower seed oil, corn germ oil, evening primrose oil, sea buckthorn fruit oil, sea buckthorn seed oil, Sichuan pepper seed oil, pomegranate seed oil, blackcurrant seed oil, shepherd's purse oil, Chinese privet oil, and peony seed oil.

[0101] The diglyceride oil production system and preparation method provided by this invention can be widely applied to the large-scale industrial production of diglyceride oil in food processing, dietary supplements, cosmetics, and pharmaceutical excipients. This system features low equipment investment costs, low energy consumption, adjustable product purity, high raw material utilization, and no solid waste discharge, demonstrating promising industrial application prospects and economic benefits.

Claims

1. A system for producing diglyceride oil, characterized in that, include: Hydrolysis reaction section, esterification reaction section, and purification section; The hydrolysis reaction section is used to hydrolyze vegetable oil under the action of lipase, and its outlet is connected to the inlet of the esterification reaction section. The esterification reaction section is used to esterify the hydrolysis product with glycerol under the action of lipase, and its outlet is connected to the inlet of the purification section. The purification section includes a first-stage thin-film evaporator (F1), a second-stage molecular distillation unit (F2), a third-stage molecular distillation unit (F3), and a fourth-stage molecular distillation unit (F4) connected in sequence. The heavy phase outlet of the third-stage molecular distillation unit (F3) is connected to the finished product output pipeline and the inlet of the fourth-stage molecular distillation unit (F4) respectively through a flow splitting device. The light phase outlet of the fourth-stage molecular distillation unit (F4) is connected to the finished product output pipeline.

2. The production system according to claim 1, characterized in that, The purification section further includes a diglyceride cooler (H10) and a first feed preheater (H4) located between the outlet of the esterification reaction section and the inlet of the first-stage thin-film evaporator (F1). The tube-side outlet of the diglyceride cooler (H10) is connected to the tube-side inlet of the first feed preheater (H4), and the tube-side outlet of the first feed preheater (H4) is connected to the inlet of the first-stage thin-film evaporator (F1). The shell-side inlet of the diglyceride cooler (H10) is connected to the heavy phase outlet of the third-stage molecular distillation unit (F3) or the light phase outlet of the fourth-stage molecular distillation unit (F4).

3. The production system according to claim 1, characterized in that, The purification section further includes a quadruple cooler (H11) and a second feed preheater (H6) located between the heavy phase outlet of the primary thin-film evaporator (F1) and the inlet of the secondary molecular distillation unit (F2). The heavy phase outlet of the primary thin-film evaporator (F1) is connected to the tube-side inlet of the quadruple cooler (H11), the tube-side outlet of the quadruple cooler (H11) is connected to the tube-side inlet of the second feed preheater (H6), and the tube-side outlet of the second feed preheater (H6) is connected to the inlet of the secondary molecular distillation unit (F2). The shell-side inlet of the quadruple cooler (H11) is connected to the heavy phase outlet of the quadruple molecular distillation unit (F4).

4. The production system according to claim 1, characterized in that, The diversion device is a three-way switching valve. The inlet of the three-way switching valve is connected to the heavy phase outlet of the three-stage molecular distillation unit (F3), the first outlet of the three-way switching valve is connected to the inlet of the four-stage molecular distillation unit (F4), and the second outlet of the three-way switching valve is connected to the finished product output pipeline.

5. The production system according to claim 1, characterized in that, The heavy phase outlet of the fourth-stage molecular distillation unit (F4) is connected to the vegetable oil inlet of the hydrolysis reaction section, and is used to send the separated triglycerides back to the hydrolysis reaction section as raw materials.

6. The production system according to claim 1, characterized in that, The esterification reaction section includes an enzyme reactor (E1) and a glycerol ester storage tank (E3). The bottom outlet of the enzyme reactor (E1) is divided into two paths by a circulation pump (P4): one path is connected to the circulation inlet of the enzyme reactor (E1) after passing through an oil heater (H2) and an oil cooler (H3), and the other path is connected to the inlet of the glycerol ester storage tank (E3).

7. The production system according to claim 6, characterized in that, The bottom outlet of the enzyme reactor (E1) is also connected to a glycerol storage tank (E2), and the outlet of the glycerol storage tank (E2) is connected to the glycerol inlet of the enzyme reactor (E1) via a glycerol discharge pump (P5); the bottom outlet of the enzyme reactor (E1) is also connected to an oil-water separator (E13).

8. The production system according to claim 6, characterized in that, Two enzyme reactors (E1) are connected in parallel. The bottom outlets of the two enzyme reactors (E1) are respectively connected to the inlet of the circulating pump (P4) through valves, and the circulation inlets of the two enzyme reactors (E1) are respectively connected to the outlet of the oil cooler (H3) through valves.

9. The production system according to claim 1, characterized in that, The light phase outlet of the primary thin-film evaporator (F1) is connected to a first condensation recovery unit, and the outlet of the first condensation recovery unit is connected to the glycerol inlet of the esterification reaction section.

10. The production system according to claim 1, characterized in that, The light phase outlet of the secondary molecular distillation unit (F2) is connected to a fatty acid collection unit, and the light phase outlet of the tertiary molecular distillation unit (F3) is connected to a monoglyceride collection unit.

11. A method for preparing a diglyceride oil, characterized in that, The production system according to any one of claims 1 to 10 includes the following steps: S1. Hydrolysis reaction: Vegetable oil, soft water and hydrolysis lipase are fed into the hydrolysis reaction section and hydrolyzed at 35~55℃ to obtain a hydrolyzed mixture. S2. Enzyme inactivation and drying: The hydrolysate mixture is heated to 80~90℃ to inactivate the enzymes. After separating the lower aqueous phase, it is vacuum dried at 80~90℃ and absolute pressure ≤110mbar. S3. Esterification reaction: Glycerol and lipase for esterification are added to the dried hydrolysate mixture to carry out the esterification reaction and synthesize a mixture of glycerol esters; S4. Enzyme inactivation and purification: The glycerol ester mixture is heated to 80-90℃ to inactivate the enzymes. After separating the lower layer of glycerol, it is washed with water and vacuum dried to obtain a crude glycerol ester mixture. S5. First-stage thin-film evaporation: The crude glyceride mixture is preheated and then fed into a first-stage thin-film evaporator (F1). Thin-film evaporation is carried out at 80~140℃ and absolute pressure ≤120Pa to remove the light phase components and obtain the heavy phase material. S6. Secondary molecular distillation: The heavy phase material obtained in step S5 is preheated and then fed into a secondary molecular distillation apparatus (F2). Molecular distillation is carried out at 170~200℃ and absolute pressure ≤10Pa to separate fatty acids and obtain the heavy phase material. S7. Three-stage molecular distillation: The heavy phase material obtained in step S6 is fed into a three-stage molecular distillation apparatus (F3) and molecular distilled at 170~200℃ and absolute pressure ≤10Pa to separate monoglycerides and obtain a heavy phase material rich in diglycerides. S8. Finished product preparation: The heavy phase material rich in diglycerides is cooled and filtered to obtain a diglyceride oil product with a diglyceride content ≥60%; or, the heavy phase material rich in diglycerides is fed into a four-stage molecular distillation apparatus (F4) and molecular distilled at 200~260℃ and absolute pressure ≤1Pa. The light phase component is collected, cooled, and filtered to obtain a diglyceride oil product with a diglyceride content ≥90%.

12. The method for preparing diglyceride oil according to claim 11, characterized in that, In step S1, the weight ratio of the vegetable oil, soft water, and hydrolysis lipase is 100:(30~60):(0.2~0.5), and the hydrolysis reaction time is 12~24h; in step S3, the amount of glycerol added is 10~30% of the weight of the vegetable oil, the amount of esterification lipase added is 0.2~0.5% of the weight of the vegetable oil, and the esterification reaction time is 12~24h.

13. The method for preparing diglyceride oil according to claim 11, characterized in that, In step S1, the lipase used for hydrolysis is a liquid lipase; in step S3, the lipase used for esterification is a liquid lipase.

14. The method for preparing diglyceride oil according to claim 11, characterized in that, In step S5, the light phase component separated by the primary thin-film evaporation is condensed and sent back to step S3 as a raw material to participate in the esterification reaction; in step S8, the heavy phase component separated by the quaternary molecular distillation is triglyceride, which is cooled and filtered and sent back to step S1 as a raw material to participate in the hydrolysis reaction.

15. The method for preparing diglyceride oil according to claim 11, characterized in that, The lower aqueous phase separated in step S2 is discharged to the oil-water separation tank (E13); the lower glycerol separated in step S4 is collected and sent back to step S3 as raw material to participate in the esterification reaction.

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