A method and apparatus for concentrating and crystallizing allulose

Abstract

This invention discloses an allulose concentration and crystallization device and method, comprising a vacuum evaporator, a first delivery pump, a tower body, a delivery cooling pipe, a cooling sedimentation cylinder, a second delivery pump, a buffer tank, and a third delivery pump connected in sequence. The tower body is divided into a cooling section and a crystallization section from top to bottom. The inlet end of the delivery cooling pipe is connected to the bottom of the crystallization section, and the outlet end of the delivery cooling pipe is connected to the cooling sedimentation cylinder, dividing the cooling sedimentation cylinder into a cooling section and a sedimentation section. The second delivery pump extracts the supernatant from the top of the cooling section. A heat exchanger and a fourth delivery pump are provided between the cooling sedimentation cylinder and the tower body. The upper part of the cooling section, the heat exchanger, the fourth delivery pump, and the crystallization section are sequentially connected to form a heat reflux. This invention not only achieves continuous gradient cooling of allulose but also makes the crystal particle size more uniform and consistent.

Description

Technical Field

[0001] This invention relates to the field of allulose production technology, and in particular to an allulose concentration and crystallization device and method. Background Technology

[0002] Allulose is a naturally occurring, low-calorie functional sweetener found in extremely small amounts. It has 70% the sweetness of sucrose but only 0.3% of its energy, making it suitable for use in low-calorie weight-loss foods. Furthermore, D-allulose inhibits the activity of enzymes involved in lipid synthesis in the liver, helping to reduce abdominal fat accumulation and control weight to some extent. It can be used in a variety of functional foods, including health foods.

[0003] Currently, there are two main methods for crystallizing allulose: cooling crystallization and organic solvent precipitation. Organic solvent crystallization often uses ethanol as the solvent, as disclosed in patents 202111205570.0 and 201811470319.5. However, this method has high production costs, inherent risks, and environmental pollution, making it unsuitable for large-scale production. Cooling crystallization is the more widely studied method, as disclosed in patents 202110807994.8 and 201911015344.9. However, cooling crystallization typically involves concentrating the raw material solution and directly immersing it in a tank for gradient cooling crystallization, making continuous production impossible. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an allulose concentration and crystallization equipment and method with continuous gradient cooling, regular and uniform shape, and uniform particle size.

[0005] One objective of this invention is to provide an allulose concentration and crystallization device, comprising a vacuum evaporator, a first delivery pump, a tower body, a delivery cooling pipe, a cooling sedimentation cylinder, a second delivery pump, a buffer tank, and a third delivery pump connected in sequence. The tower body is divided into a cooling section and a crystallization section from top to bottom. The feed end of the delivery cooling pipe is connected to the bottom of the crystallization section, and the discharge end of the delivery cooling pipe is connected to the cooling sedimentation cylinder, dividing the cooling sedimentation cylinder into a cooling section and a sedimentation section. The second delivery pump extracts the supernatant from the top of the cooling section. A heat exchanger and a fourth delivery pump are provided between the cooling sedimentation cylinder and the tower body. The upper part of the cooling section, the heat exchanger, the fourth delivery pump, and the crystallization section are connected in sequence to form a heat reflux.

[0006] Preferably, the cooling section includes multiple baffles, which are connected inside the tower body and are staggered vertically to make the liquid flow in an arc shape.

[0007] Preferably, the tower body is further provided with a mixing section, which mixes the concentrated liquid with the seed crystals.

[0008] Preferably, the mixing section includes a first stirring paddle, a mixing cylinder, and a siphon pipe. The mixing cylinder is located above the cooling section, the first stirring paddle is located inside the mixing cylinder, and the siphon pipe connects the inner and outer sides of the mixing cylinder.

[0009] Preferably, a second stirring paddle is provided in the crystallization section, which mixes the liquid in the cooling section with the hot reflux liquid.

[0010] Preferably, a third stirring paddle is provided in the cooling section. The third stirring paddle has straight blades, and the blades of the third stirring paddle are distributed from top to bottom throughout the cooling section. The blades of the third stirring paddle extend from the rotation axis to the inner wall of the cooling sedimentation cylinder.

[0011] Preferably, a first baffle plate is provided at the bottom of the crystal section, and the first baffle plate is provided with a plurality of openings for accommodating the crystal to pass through.

[0012] Preferably, the cooling sedimentation cylinder is provided with a second baffle plate and a third baffle plate. Both the second baffle plate and the third baffle plate are provided with openings to allow crystals to pass through. The second baffle plate and the third baffle plate divide the cooling sedimentation cylinder into a supernatant section, a cooling section and a sedimentation section from top to bottom.

[0013] The second objective of this invention is to provide a method for concentrating and crystallizing allulose, comprising the following steps:

[0014] S1. The allulose aqueous solution obtained by chromatographic separation is concentrated by low-temperature vacuum evaporation;

[0015] S2. Mix the concentrated allulose with the seed crystals;

[0016] S3. Perform the first cooling crystallization on the mixture;

[0017] S4. Add the cooled and crystallized mixture to an unsaturated solution and heat it to crystallize further;

[0018] S5. Perform a second cooling crystallization on the crystallized mixture;

[0019] S6. The mixture is subjected to a third cooling crystallization and sedimentation separation;

[0020] S7. The saturated solution after crystallization, together with the allulose solution separated by chromatography, is concentrated again by low-temperature vacuum evaporation and then recycled.

[0021] Preferably, the saturated solution after the third cooling crystallization is fed into the crystallization section for heating and crystallization after heat exchange in a heat exchanger.

[0022] Preferably, in step S5, after the second cooling crystallization, particle size separation is performed and a second crystallization is carried out.

[0023] The present invention has the following advantages:

[0024] 1. By rationally interconnecting the vacuum evaporator, the first transfer pump, the tower body, the transfer cooling pipe, the cooling sedimentation cylinder, the second transfer pump, the buffer tank, and the third transfer pump, the gradient cooling crystallization function of allulose is realized. The temperature can be reasonably controlled according to the metastable region curve of allulose, avoiding the problems of spontaneous nucleation and uneven crystal size caused by excessively rapid cooling in the early stage, as well as the problems of slow crystal growth and low yield caused by excessively slow cooling in the later stage. At the same time, it realizes the continuous production of allulose crystals and improves the crystallization production efficiency.

[0025] 2. The heat exchanger and the fourth delivery pump can effectively utilize the saturated solution after crystallization to heat and shape the microcrystals generated during the crystallization process. This crystallization makes the crystal size tend to be more uniform, while also making the crystal surface smooth and adjusting the crystal morphology.

[0026] 3. A crystal-forming tube is set at the tail end of the conveying cooling pipe, which realizes the separation of different particle sizes, facilitates the extended crystal growth of small-diameter crystals, makes the crystal particle size more consistent and uniform, and achieves a secondary crystal-forming effect;

[0027] 4. A conveying cooling pipe is installed between the crystallization section and the cooling precipitation cylinder, which not only realizes the third cooling function, but also avoids the problem of the hot solution in the crystallization section being directly discharged into the cooling precipitation cylinder, causing the falling crystals to flow back and heat up again with the rising hot solution, which would greatly reduce the crystal size and improve the final crystal size.

[0028] 5. The second and third baffles divide the cooling sedimentation cylinder into a supernatant section, a cooling section, and a sedimentation section. The solution in the cooling section undergoes slow centrifugal rotation under the action of the third stirring paddle, causing the internal crystals to gradually move from the high-temperature zone in the center to the low-temperature zone around the perimeter, achieving uniform cooling and ultimately increasing the crystal size and causing sedimentation separation. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the overall structure of Embodiment 1 of the present invention;

[0030] Figure 2 This is a schematic diagram of the overall structure of Embodiment 2 of the present invention;

[0031] Figure 3 This is a partial cross-sectional structural schematic diagram of the present invention;

[0032] Figure 4 This is a flowchart illustrating the present invention.

[0033] In the diagram, 1. Vacuum evaporator concentrator; 2. First transfer pump; 3. Tower body; 4. Transfer cooling pipe; 5. Cooling sedimentation cylinder; 6. Second transfer pump; 7. Buffer tank; 8. Third transfer pump; 9. Heat exchanger; 10. Fourth transfer pump; 11. Raw material pipe to be concentrated; 12. Steam exhaust pipe; 13. Seed crystal feeding pipe; 14. Mixing cylinder; 15. Siphon pipe; 16. First agitator; 17. Baffle plate; 18. Second agitator; 19. First baffle plate; 20. First cooling coil; 21. Second cooling coil; 22. Third agitator; 23. Second baffle plate; 24. Third baffle plate; 25. Fan; 26. Air inlet; 27. Diverter block; 28. Third cooling coil; 29. ​​Heating coil; 30. Crystallization tube. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0035] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0036] Example 1

[0037] like Figure 1As shown, an allulose concentration and crystallization device includes a vacuum evaporator 1, a first transfer pump 2, a tower body 3, a transfer cooling pipe 4, a cooling sedimentation cylinder 5, a second transfer pump 6, a buffer tank 7, and a third transfer pump 8 connected in sequence. The vacuum evaporator 1 is equipped with a raw material pipe 11 to be concentrated and a steam discharge pipe 12. The raw material pipe 11 is connected to an allulose aqueous solution after chromatographic separation. The steam discharge pipe 12 discharges the evaporated aqueous solution or ethanol. The vacuum evaporator 1 can be a triple-effect vacuum evaporator to achieve low-temperature vacuum concentration. The tower body 3 is divided into a mixing section, a cooling section, and a crystallization section from top to bottom. The mixing section includes a first stirring paddle 16, a mixing cylinder 14, and a siphon pipe 15. The mixing cylinder 14 can be fixedly connected to a support rod. The first stirring paddle 16 is located inside the mixing cylinder 14 and connected to the tower body 3. The siphon pipe 15 is an inverted U-shaped pipe, with its middle section passing through the upper part of the mixing cylinder 14. The siphon pipe 15 connects the inner and outer sides of the mixing cylinder 14. The seed crystal feeding pipe 13 and the outlet of the first conveying pump 2 both discharge into the mixing cylinder 14. The seed crystals and concentrate are added into the mixing cylinder 14 and mixed under the action of the first stirring paddle 16. In continuous production, the upper part of the mixing cylinder 14 contains the newly added liquid to be mixed, and the lower part contains the already uniformly mixed solution. The siphon pipe 15 can preferentially draw up the completely uniformly mixed bottom solution in the mixing cylinder 14 and automatically discharge it downwards, ensuring that the discharged liquid is a uniformly mixed solution. Compared with external mixing... The tank not only enables continuous mixing and discharging, shortening the conveying distance, but also eliminates the need for additional power for transportation. The cooling section includes multiple baffles 17 and a third cooling coil 28. The baffles 17 are horizontally connected inside the tower body 3, and their staggered arrangement causes the liquid to flow in an arc shape. A first baffle 19 is installed at the bottom of the crystallization section, with multiple openings to allow crystals to pass through. The third cooling coil 28, which carries cooling water, is coiled around the tower body 3. The cooling section uses baffles 17 to cause the mixed liquid to flow in an arc shape, rather than the overall flow interconnected with the crystallization section, i.e., the traditional tank-type baffle structure. This avoids rapid mixing between the cold solution in the cooling section and the hot solution in the crystallization section, preventing mutual interference and ensuring the normal functioning of each. The conveying cooling pipe 4 has a horizontal straight pipe structure, and its diameter is smaller than the diameter of the crystallizing section and the diameter of the cooling sedimentation cylinder 5. This makes the flow velocity inside the conveying cooling pipe 4 greater than the flow velocity inside the crystallizing section and the cooling sedimentation cylinder 5, making it less likely for crystals to settle inside the conveying cooling pipe 4. A first cooling coil 20 with internal cooling water is also installed around the conveying cooling pipe 4. The inlet end of the conveying cooling pipe 4 is connected to the bottom of the crystallizing section, and the outlet end of the conveying cooling pipe 4 is connected to the cooling sedimentation cylinder 5, dividing the cooling sedimentation cylinder 5 into a cooling section and a sedimentation section. Preferably, the outlet end of the conveying cooling pipe 4 extends to the middle of the cooling sedimentation cylinder 5, so that the discharged solution rises from the middle and cools and crystallizes. The cooling sedimentation cylinder 5 is equipped with a second cooling coil 21, a third stirring paddle 22, a second baffle plate 23, and a third baffle plate 24.The cooling sedimentation cylinder 5, the conveying cooling pipe 4, and the crystal forming section form a U-shaped communicating vessel structure. The second baffle plate 23 and the third baffle plate 24 are also provided with openings to accommodate the crystals. The second baffle plate 23 and the third baffle plate 24 divide the cooling sedimentation cylinder 5 into a supernatant section, a cooling section, and a sedimentation section from top to bottom. The second cooling coil 21 is coiled around the outside of the cooling section of the cooling sedimentation cylinder 5. The third stirring paddle 22 is located inside the cooling section. The third stirring paddle 22 has plate-shaped straight blades, and its blades are distributed from top to bottom throughout the cooling section. The blades of the third stirring paddle 22 extend from the rotating shaft of the motor to... The inner wall of the cooling sedimentation cylinder 5 is isolated into a separate space by the second baffle plate 23 and the third baffle plate 24. The third stirring paddle 22 in this structure is a non-mixing type, designed solely to cause the solution within the cooling section to rotate as a whole, generating centrifugal force that propels the crystals towards the inner wall during the upward movement. This avoids the mixing effect of traditional propellers that would affect the crystals' gravity settling function. The second transfer pump 6 extracts the solution from the supernatant section. A heat exchanger 9 and a fourth transfer pump 10 are installed between the cooling sedimentation cylinder 5 and the tower body 3. The upper part of the cooling section, the heat exchanger 9, the fourth transfer pump 10, and the crystallization section are sequentially connected to form a heat reflux.

[0038] In some embodiments, cooling water is cooled sequentially through the second cooling coil 21, the first cooling coil 20, and the third cooling coil 28. This not only meets the requirement of gradually increasing cooling rate during allulose crystallization but also utilizes waste heat and saves energy.

[0039] Example 2

[0040] like Figure 2As shown, the difference from Embodiment 1 is that a second stirring paddle 18 is installed in the crystallization section. The first stirring paddle 16 and the second stirring paddle 18 are coaxial and shared. The second stirring paddle 18 can be selected in various forms. Its main purpose is to enable the solution after heat exchange transmitted by the fourth delivery pump 10 to be quickly mixed with the cooling solution flowing down from the cooling section. In some embodiments, the saturated solution in the supernatant section is not used, but pure water is connected externally. The crystallization function is achieved in conjunction with the heating coil 29 installed outside the crystallization section. The delivery cooling pipe 4 adds a crystallization pipe 30 to the original straight pipe structure. The crystallization pipe 30 includes a gravity separation section at the head and an extended cooling section and a normal delivery section at the tail. The gravity separation section is a vertical pipe structure that delivers cold... Cooling pipe 4 connects to the middle of the gravity separation section, and the extended cooling section connects to the top of the gravity separation section. A jacket or tubular cooling heat exchange structure is installed on the extended cooling section. The normal conveying section connects to the bottom of the gravity separation section, and the tail of the normal conveying section and the extended cooling section connects to the middle of the cooling sedimentation cylinder 5. The crystals in the conveying cooling pipe 4 contain large and small particles. When they are conveyed to the gravity separation section, the large and small particles are separated under the action of gravity. The large particles enter the cooling sedimentation cylinder through the normal conveying section, while the small particles enter the extended cooling section for further crystallization, causing the small particles to grow into large particles and finally enter the cooling sedimentation cylinder. Through the action of the crystal tube, the particle size difference of the crystals in the conveying cooling pipe 4 is reduced.

[0041] In some embodiments, the baffle 17 is changed from a horizontal setting to an inclined setting of 3-5°, which can prevent crystals from depositing on the baffle 17. Furthermore, as... Figure 3 As shown, a diversion block 27 is fixedly installed on the overflow edge of the baffle plate 17. The diversion block 27 can be of any shape, preferably a long strip block structure. The diversion block 27 can divide the liquid into strip flow and form a channel for gas flow. At the same time, an air inlet 26 is opened between the crystallization section and the cooling section. A fan 25 is installed on the top of the tower body 3. The fan 25 starts and draws air to remove the hot air in the cooling section to achieve the effect of air cooling.

[0042] In some embodiments, the first baffle plate 19, the second baffle plate 23, and the third baffle plate 24 have the same structure. The main body is preferably a W-shaped bent plate structure. An opening is opened at the bottom of the bend to allow crystals to pass through. The W-shaped bent structure has many advantages. It can prevent crystals in the lower solution from moving upward, while allowing large crystal particles in the upper part to fall freely onto the plate under the action of gravity and collect from the opening to fall below. This achieves the effect of allowing the solution to pass through normally while preventing and collecting crystals.

[0043] A method for concentrating and crystallizing allulose includes the following steps:

[0044] S1. The allulose aqueous solution obtained by chromatographic separation is passed through the raw material tube to be concentrated into the vacuum evaporator for low-temperature vacuum evaporation and concentration, and the steam is discharged through the steam discharge tube.

[0045] S2. The concentrated allulose solution is pumped into the mixing cylinder inside the tower by the first pump. Simultaneously, the seed crystals are also added into the mixing cylinder for mixing. The mixture is then automatically discharged into the cooling section through a siphon.

[0046] S3. The mixture undergoes its first cooling and crystallization process in the cooling section to allow the seed crystals to grow.

[0047] S4. The mixed liquid in the cooling section is automatically discharged into the crystallization section. The saturated solution in the supernatant section at the top of the cooling sedimentation cylinder is heated by the heat exchanger to become an unsaturated solution. It is then discharged into the crystallization section by the fourth delivery pump. The unsaturated hot solution exchanges heat with the cold solution to increase the overall temperature, making the surface of the small crystal particles in the mixed liquid tend to be smooth and the crystal size tend to be averaged to achieve the effect of adjusting the crystal morphology.

[0048] S5. The mixed liquid after crystallization is discharged into the conveying cooling pipe for a second cooling and crystallization, which further promotes crystal growth;

[0049] S6. The mixed liquid discharged from the cooling pipe enters the cooling sedimentation cylinder. The largest crystals in the mixed liquid settle in the sedimentation section under the action of gravity. The next largest crystals enter the cooling section. The next largest crystals rotate and centrifuge under the action of the third stirring paddle. Because the cooling sedimentation cylinder is equipped with a second cooling coil on its outer wall, the temperature of the solution in the middle of the cooling section is higher than that around the periphery. The closer the next largest crystals are to the inner wall after centrifugation, the better the cooling and crystallization effect and the faster the crystals grow. The third cooling and crystallization is completed until the solution enters the sedimentation section through the third baffle plate under the action of gravity. The remaining solution enters the supernatant section through the second baffle plate.

[0050] S7. The saturated solution in the supernatant section is discharged into the buffer tank by the second delivery pump to maintain the flow in the tower body, delivery cooling pipe and cooling sedimentation cylinder;

[0051] S8. The saturated solution in the buffer tank is discharged into the vacuum evaporator by the third transfer pump, and together with the chromatographically separated allulose solution, it is subjected to low-temperature vacuum evaporation and concentration and then circulated.

[0052] Furthermore, such as Figure 4 As shown, in step S5, a crystal-forming tube is installed between the conveying cooling pipe and the cooling precipitation cylinder so that after the second cooling crystallization, particle size sedimentation separation is performed, and the cooling crystallization time is extended for small-diameter crystals to achieve the second crystal-forming function.

[0053] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An allulose concentration and crystallization apparatus, characterized in that: The system includes a vacuum evaporator, a first delivery pump, a tower body, a delivery cooling pipe, a cooling sedimentation cylinder, a second delivery pump, a buffer tank, and a third delivery pump connected in sequence. The tower body is divided into a cooling section and a crystallization section from top to bottom. The inlet end of the delivery cooling pipe is connected to the bottom of the crystallization section, and the outlet end of the delivery cooling pipe is connected to the cooling sedimentation cylinder, dividing the cooling sedimentation cylinder into a cooling section and a sedimentation section. The second delivery pump extracts the supernatant from the top of the cooling section. A heat exchanger and a fourth delivery pump are provided between the cooling sedimentation cylinder and the tower body. The upper part of the cooling section, the heat exchanger, the fourth delivery pump, and the crystallization section are connected in sequence to form a heat reflux.

2. The allulose concentration and crystallization apparatus according to claim 1, characterized in that: The cooling section includes multiple baffles, which are connected inside the tower body. The baffles are staggered vertically to make the liquid flow in an arc shape.

3. The allulose concentration and crystallization apparatus according to claim 2, characterized in that: The tower body is also equipped with a mixing section, which mixes the concentrated liquid with the seed crystals.

4. The allulose concentration and crystallization apparatus according to claim 3, characterized in that: The mixing section includes a first stirring paddle, a mixing cylinder, and a siphon pipe. The mixing cylinder is located above the cooling section, the first stirring paddle is located inside the mixing cylinder, and the siphon pipe connects the inside and outside of the mixing cylinder.

5. The allulose concentration and crystallization apparatus according to claim 1, characterized in that: A second stirring paddle is provided in the crystallization section, which mixes the liquid in the cooling section with the hot reflux liquid.

6. The allulose concentration and crystallization apparatus according to claim 1, characterized in that: A third stirring paddle is provided in the cooling section. The third stirring paddle has straight blades and the blades of the third stirring paddle are distributed from top to bottom throughout the cooling section. The blades of the third stirring paddle extend from the rotation axis to the inner wall of the cooling sedimentation cylinder.

7. The allulose concentration and crystallization apparatus according to claim 1, characterized in that: The bottom of the crystal section is provided with a first baffle plate, and the first baffle plate is provided with a plurality of openings to accommodate the crystals.

8. The allulose concentration and crystallization apparatus according to claim 6, characterized in that: The cooling sedimentation cylinder is equipped with a second baffle plate and a third baffle plate. Both the second baffle plate and the third baffle plate are provided with openings to allow crystals to pass through. The second baffle plate and the third baffle plate divide the cooling sedimentation cylinder into a supernatant section, a cooling section and a sedimentation section from top to bottom.

9. The method for concentrating and crystallizing allulose according to any one of claims 1-8, characterized in that, Includes the following steps, S1. The allulose aqueous solution obtained by chromatographic separation is concentrated by low-temperature vacuum evaporation; S2. Mix the concentrated allulose with the seed crystals; S3. Perform the first cooling crystallization on the mixture; S4. Add the cooled and crystallized mixture to an unsaturated solution and heat it to crystallize further; S5. Perform a second cooling crystallization on the crystallized mixture; S6. The mixture is subjected to a third cooling crystallization and sedimentation separation; S7. The saturated solution after crystallization, together with the allulose solution separated by chromatography, is concentrated again by low-temperature vacuum evaporation and then recycled.

10. The method for concentrating and crystallizing allulose according to claim 9, characterized in that, After the saturated solution undergoes the third cooling and crystallization process, it is transferred to the crystallization section for further heating and crystallization.

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