Device for purifying and refining natural pigment for food based on membrane separation technology

Abstract

The invention discloses a purification and refining device for natural pigments for food based on a membrane separation technology, and relates to the technical field of membrane separation and purification control, the purification and refining device comprises a top cover mechanism, a multi-stage filtering mechanism and a collecting mechanism, the top cover mechanism comprises a first box body, a feeding assembly is arranged in the first box body, and the multi-stage filtering mechanism comprises a second box body; the collecting mechanism comprises a third box body, the first box body, the second box bodies and the third box body are sequentially stacked, the second box body provided with the microfiltration membrane is arranged close to the first box body, the second box body provided with the nanofiltration membrane is arranged close to the third box body, and the third box body is arranged close to the first box body. A temperature control assembly is arranged in the second box body, and the side faces of all the second box bodies are connected with air pressure control assemblies. The device is easy to disassemble and assemble, high in selective operation, high in control efficiency and convenient to operate, the temperature and the pressure can be independently controlled, and the filtering purity of the natural pigment is effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation purification and control technology, and particularly relates to a purification and refining device for natural food pigments based on membrane separation technology. Background Technology

[0002] Natural pigments, as an important category of food additives, are gradually replacing synthetic pigments due to their high safety, natural and harmonious colors, and combined nutritional and physiological activities. They are widely used in food processing fields such as beverages, pastries, meat products, and condiments. The sources of natural pigments include plants (such as anthocyanins, chlorophyll, and capsanthin), animals (such as carmine), and microorganisms (such as red yeast rice pigment). However, crude pigments extracted from raw materials often contain impurities such as proteins, polysaccharides, colloids, small molecule salts, and crude fiber. These impurities affect the stability, coloring power, and application range of the pigments. Therefore, purification is the core step in the industrial production of natural pigments.

[0003] Traditional methods for purifying natural pigments mainly include solvent extraction, column chromatography, precipitation, and adsorption. However, these methods have many limitations in practical applications.

[0004] Solvent extraction: requires the use of large amounts of organic solvents (such as ethanol, petroleum ether, acetone), which not only increases production costs but also easily causes solvent residues, posing a food safety hazard. At the same time, the extraction process requires multiple separations and distillations, which are cumbersome and energy-intensive. Furthermore, some heat-sensitive pigments (such as anthocyanins and carotenoids) are prone to degradation during high-temperature distillation, resulting in loss of pigment activity and reduced recovery rate.

[0005] Column chromatography: Although it can achieve efficient separation of pigments, the packing materials (such as silica gel and polyamide) are expensive, difficult to regenerate, and have a short service life, making it difficult to adapt to large-scale continuous production. In addition, column chromatography has a limited sample loading capacity and a long separation cycle, which cannot meet the efficiency requirements of industrial production.

[0006] Precipitation method: Inorganic salts or organic solvents need to be added to the crude pigment solution for salting out or alcohol precipitation, which can easily introduce new impurities and increase the burden on subsequent desalting and desolventizing processes; moreover, the precipitation conditions (such as temperature, pH and concentration) require strict control, and improper operation can easily lead to pigment co-precipitation and reduce product yield.

[0007] Adsorption method: Commonly used adsorbents include activated carbon and macroporous resins. Although they can remove some impurities, the selectivity of adsorbents for pigments is poor, which can easily cause irreversible adsorption of the target pigments, resulting in a decrease in recovery rate. At the same time, the desorption process of adsorbents requires the use of high-concentration solvents, which poses a risk of secondary pollution.

[0008] As the food industry continues to demand higher purity, no residue, and high activity of natural pigments, the drawbacks of traditional purification methods are becoming increasingly apparent. The industry urgently needs a new type of purification technology that is green, efficient, and gentle.

[0009] Membrane separation technology is a separation technique based on the selective permeability of membranes and driven by pressure difference. It boasts significant advantages such as room temperature operation, no phase change, low energy consumption, no solvent residue, and high separation efficiency, perfectly meeting the technical requirements of natural pigment purification and gradually becoming a research hotspot and application trend in the field of natural pigment processing. Based on differences in membrane pore size and molecular weight cutoff, commonly used membrane types for natural pigment purification include microfiltration (MF), ultrafiltration (UF), and nanofiltration (NF), each with its own focus: microfiltration membranes can remove large-particle impurities such as suspended particles, bacteria, and coarse fibers from crude pigment solutions; ultrafiltration membranes can retain large-molecule impurities such as proteins, polysaccharides, and colloids, achieving separation of the target pigment from these large-molecule impurities; and nanofiltration membranes can retain small-molecule salts and oligosaccharides while simultaneously concentrating the pigment solution, achieving an integrated "purification + concentration" effect.

[0010] Compared to traditional methods, membrane separation technology has shown unique advantages in the purification of natural pigments. However, conventional membrane separation technology generally uses multi-layer membrane integration, and its temperature or pressure control is controlled as a whole, which is not convenient for independent control of zones. As a result, during use, impurities are not completely removed and the pigment purity is low. Summary of the Invention

[0011] The purpose of this invention is to provide a purification and refining device for food-grade natural pigments based on membrane separation technology. This device is easy to assemble and disassemble, offers high selectivity in operation, and allows for independent control of temperature and pressure. It effectively improves the filtration purity of natural pigments, while also providing high control efficiency and convenient operation.

[0012] To achieve the above objectives, the present invention provides the following technical solution:

[0013] A purification and refining device for food-grade natural pigments based on membrane separation technology includes a top cover mechanism, a multi-stage filtration mechanism, and a collection mechanism. The top cover mechanism includes a first housing with a feeding component inside. The multi-stage filtration mechanism includes three second housings, each containing a microfiltration membrane, an ultrafiltration membrane, and a nanofiltration membrane, respectively. The collection mechanism includes a third housing. The first, second, and third housings are stacked sequentially, with the second housing containing the microfiltration membrane positioned close to the first housing and the second housing containing the nanofiltration membrane positioned close to the third housing. The second housings contain a temperature control component, and all the second housings have a pressure control component connected to their sides.

[0014] As a preferred embodiment of the present invention, a fixing frame is fixed to the inner wall of the second box, and the microfiltration membrane, ultrafiltration membrane or nanofiltration membrane is embedded and fixed inside the fixing frame, and a cylinder is fixed to the side of the fixing frame away from the inner wall of the second box.

[0015] As a preferred embodiment of the present invention, one end of the cylinder is provided with a stepped groove, and a sealing ring is bonded inside the stepped groove; the other end of the cylinder is provided with a connector, which is integrally formed with the cylinder.

[0016] As a preferred embodiment of the present invention, the temperature control component includes a support frame fixed to the inner wall of the cylinder, a water pipe rotatably connected inside the support frame, a connector welded to one end of the water pipe, and a snap-fit ​​groove provided at the other end, the snap-fit ​​groove being L-shaped, a snap-fit ​​rod welded to the side of the connector, and a connecting pipe fixed to the side of the water pipe, the connecting pipe having a plurality of connections along the vertical axis and circumferential direction of the water pipe, an annular pipe fixed to the end of the connecting pipe away from the water pipe, the connecting pipe communicating with the water pipe and the interior of the annular pipe, the side of the annular pipe abutting against the inner wall of the cylinder.

[0017] As a preferred embodiment of the present invention, the third box is provided with an empty groove inside, and a conical collection groove is provided at the bottom of the empty groove. The empty groove and the conical collection groove are connected and the connection between the empty groove and the conical collection groove is smoothly transitioned. A water inlet pipe is fixed on the side of the empty groove. The water inlet pipe is connected to a water source at the outer end of the third box. The water inlet pipe is bent on the inner side of the third box. The water inlet pipe is provided with the same snap-fit ​​groove inside the third box. An outlet collection pipe is connected to the side of the conical collection groove.

[0018] As a preferred embodiment of the present invention, the air pressure control component includes a fixed pipe fixedly welded to the side of the second housing. The fixed pipe is located inside the second housing and has several air outlet pipes fixed to its side. A support pipe is fixed to the side of the fixed pipe away from the second housing by flange bolts. An air extraction pipe is welded to the end of the support pipe away from the fixed pipe, and an air extraction device is connected to the bottom of the air extraction pipe.

[0019] As a preferred embodiment of the present invention, a solenoid valve is fixed to the side of the fixing tube by screws, and each solenoid valve is controlled independently.

[0020] As a preferred embodiment of the present invention, the first box, the second box and the third box are welded with connecting plates on their sides, and the connecting plates are provided with a plurality of through holes for bolts to pass through.

[0021] As a preferred embodiment of the present invention, the feeding assembly includes a cover plate detachably connected to the top of the first housing, a drive shaft rotatably connected inside the cover plate, a motor connected to the drive shaft facing the outer end of the first housing, the motor being screwed to the cover plate, a conical fixing cylinder fixed to the inner side of the drive shaft located inside the first housing, a fan-shaped plate fixed to the side of the conical fixing cylinder, and a fixing plate fixed to the inner wall of the first housing, the fixing plate having a plurality of fan-shaped through slots, a connecting cylinder fixed to the bottom of the fixing plate, the bottom of the connecting cylinder being welded with the same insertion pipe, a drain pipe fixed to the side of the insertion pipe, and the drain pipe having the same connector facing the inside of the insertion pipe.

[0022] As a preferred embodiment of the present invention, the feeding assembly further includes a bracket fixed to the top of the first box with screws. Four brackets are provided at the four corners of the first box. All brackets have feeding pipes fixed inside. Feed pipes are fixed to the end of the feeding pipe facing the cover plate. Feed pipes are fixed inside the cover plate. Feed guide pipes are fixed to one side of the feeding pipes. Feed guide pipes are externally connected to feeding equipment.

[0023] In summary, the beneficial technical effects of this invention are as follows: This purification and refining device for food-grade natural pigments based on membrane separation technology, through the sequential arrangement of microfiltration membranes, ultrafiltration membranes, and nanofiltration membranes in a multi-stage filtration mechanism, can achieve multi-stage fine filtration of the natural pigment solution, effectively removing impurities, macromolecules, etc., and improving the purity of the pigment. Simultaneously, the temperature control component allows for precise temperature control during the filtration process based on the characteristics of different pigments, ensuring the stability and activity of the pigment. The air pressure control component can regulate the air pressure during the filtration process, ensuring smooth filtration and improving filtration efficiency. Furthermore, the device's top cover mechanism, multi-stage filtration mechanism, and collection mechanism adopt a stacked design and are fixed by connecting plates and bolts, making the entire device easy to disassemble, clean, and maintain. The design of the feeding component ensures uniform feeding of the natural pigment solution, guaranteeing the uniformity of the filtration effect. Attached Figure Description

[0024] The accompanying drawings are provided to further illustrate the invention and form part of the specification, but do not constitute a limitation thereof. In the drawings:

[0025] Figure 1 This is a schematic diagram of the structure of a purification and refining device for food-grade natural pigments based on membrane separation technology according to this embodiment;

[0026] Figure 2 This is a cross-sectional schematic diagram of a purification and refining device for food-grade natural pigments based on membrane separation technology according to this embodiment;

[0027] Figure 3 This is an exploded structural diagram of the second chamber of a purification and refining device for food-grade natural pigments based on membrane separation technology according to this embodiment.

[0028] Figure 4 This is an exploded structural diagram of the first chamber of a purification and refining device for food-grade natural pigments based on membrane separation technology according to this embodiment.

[0029] In the diagram: 1. First chamber; 2. Second chamber; 3. Third chamber; 4. Microfiltration membrane; 5. Ultrafiltration membrane; 6. Nanofiltration membrane; 7. Fixture; 8. Cylinder; 9. Stepped groove; 10. Sealing ring; 11. Connecting pipe; 12. Support frame; 13. Water pipe; 14. Connector; 15. Snap-fit ​​groove; 16. Snap-fit ​​rod; 17. Connecting pipe; 18. Annular pipe; 19. Empty trough; 20. Conical collection trough; 21. Water inlet pipe; 22. 1. Outlet collection pipe; 23. Fixed pipe; 24. Support pipe; 25. Air extraction pipe; 26. Solenoid valve; 27. Connecting plate; 28. Through hole; 29. ​​Cover plate; 30. Drive shaft; 31. Motor; 32. Conical fixed cylinder; 33. Sector plate; 34. Fixed plate; 35. Sector through groove; 36. Connecting cylinder; 37. Bracket; 38. Feed pipe; 39. Distributor pipe; 40. Feed guide pipe; 41. Drain pipe; 42. Air outlet pipe. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to the accompanying drawings.

[0031] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Please see Figure 1-4 This invention provides a technical solution: a purification and refining device for food-grade natural pigments based on membrane separation technology, comprising a top cover mechanism, a multi-stage filtration mechanism, and a collection mechanism. The top cover mechanism includes a first housing with a feeding component inside. The multi-stage filtration mechanism includes a second housing, of which three are provided. The three second housings are respectively provided with a microfiltration membrane, an ultrafiltration membrane, and a nanofiltration membrane. The collection mechanism includes a third housing. The first, second, and third housings are stacked sequentially, with the second housing containing the microfiltration membrane positioned close to the first housing and the second housing containing the nanofiltration membrane positioned close to the third housing. The second housings are provided with a temperature control component inside, and all the second housings are connected to a pressure control component on their sides.

[0033] In this embodiment, a microfiltration → ultrafiltration → nanofiltration structure is arranged sequentially from top to bottom to form a combined process. At the same time, connecting plates are welded to the sides of the first, second, and third chambers. The connecting plates have several through holes for bolts to pass through. Thus, the first chamber is fixed to the second chamber, the second chamber is fixed to each other, and the second chamber is fixed to the third chamber with bolts, which is convenient for disassembly and assembly. In addition, the number of second chambers in each process can be increased or decreased to meet different quality requirements. The combination is convenient and easy to operate.

[0034] In this embodiment, the pigment liquid to be filtered enters the first chamber through the feeding assembly inside the first chamber, passes through each of the second chambers in sequence, and then enters the third chamber for collection.

[0035] Among them, the microfiltration membrane is used to thoroughly remove tiny colloids and suspended particles from the extract to obtain a clear pigment filtrate, which provides a guarantee for subsequent ultrafiltration. The ultrafiltration membrane is selected with a molecular weight cutoff of 10-50 kDa to retain large molecular impurities such as proteins and polysaccharides in the extract, while the target pigment (small molecules) permeates through the membrane to form the permeate. The nanofiltration membrane is selected with a molecular weight cutoff of 200-500 Da to retain or partially retain small molecule salts in the filtrate (such as citric acid and sodium chloride added during extraction), while the pigment permeates through the membrane, reducing the ash content of the pigment product.

[0036] The area between each pair of second chambers is an independent area for microfiltration / ultrafiltration membranes or ultrafiltration / nanofiltration membranes. Specifically, the air pressure control component includes a fixed pipe welded to the side of the second chamber. The fixed pipe is located inside the second chamber and has several air outlet pipes fixed to its side. A support pipe is fixed to the side of the fixed pipe away from the second chamber by flange bolts. An air extraction pipe is welded to the end of the support pipe away from the fixed pipe, and an air extraction device is connected to the bottom of the air extraction pipe.

[0037] The fixed tube has solenoid valves secured by screws on its side, each independently controlled. After feeding, the first solenoid valve opens while the next two remain closed. During evacuation, the air pressure in its independent area is reduced, facilitating the passage of filtrate. The pressure required for microfiltration / ultrafiltration / nanofiltration can be adjusted, such as 0.2–0.5 MPa for ultrafiltration and 0.5–1.5 MPa for nanofiltration. Upon entering the next process, the corresponding solenoid valve remains open while the other two remain closed. The three solenoid valves are programmed to open and close at set times, enabling automated membrane separation.

[0038] Meanwhile, a cylindrical structure is set inside each second box. Specifically, a fixing frame is fixed to the inner wall of the second box, and the microfiltration membrane, ultrafiltration membrane or nanofiltration membrane is embedded inside the fixing frame. A cylindrical body is fixed to the side of the fixing frame away from the inner wall of the second box.

[0039] The cylinder has a stepped groove at one end with a sealing ring bonded inside. The other end has a connector integrated with the cylinder. After docking with the second housing, the cylinder can automatically connect. Simultaneously, the upper and lower ends of the cylinder dock with the internal structures of the first and third housings, respectively. The entire assembly and disassembly are convenient. After docking, the air inside the cylinder is independent for temperature control during membrane separation. Specifically, the temperature control component includes a support frame fixed to the inner wall of the cylinder. A water pipe is rotatably connected inside the support frame. A connector is welded to one end of the water pipe, and a snap-fit ​​groove is provided at the other end. The snap-fit ​​groove is L-shaped, and a snap-fit ​​rod is welded to the side of the connector. It also includes a connecting pipe fixed to the side of the water pipe. Several connecting pipes are provided along the vertical axis and circumference of the water pipe. An annular pipe is fixed to the end of the connecting pipe away from the water pipe. The connecting pipe communicates with the water pipe and the annular pipe. The side of the annular pipe abuts against the inner wall of the cylinder.

[0040] The third chamber has an empty slot inside, and a conical collection slot at the bottom of the empty slot. The empty slot and the conical collection slot are connected and the connection between the empty slot and the conical collection slot is smoothly transitioned. A water inlet pipe is fixed to the side of the empty slot. The water inlet pipe is connected to the water source at the outer end of the third chamber. The water inlet pipe is bent at the inner side of the third chamber. The water inlet pipe at the inner side of the third chamber has the same snap-fit ​​groove.

[0041] The water pipe connection is achieved by rotating the connector and the snap-fit ​​groove. At the same time, the water pipe remains inside the support frame and rotates freely. During the assembly process, the pipes are assembled from top to bottom. After the water pipe rotates, the snap-fit ​​rod at the top enters along the snap-fit ​​groove and rotates to snap into place. Meanwhile, the snap-fit ​​connector extends into the water pipe to improve the sealing performance.

[0042] Furthermore, the feeding assembly includes a cover plate detachably connected to the top of the first housing. A drive shaft is rotatably connected inside the cover plate. A motor is connected to the drive shaft facing the outside of the first housing. The motor is screwed to the cover plate. A conical fixing cylinder is fixed to the inner side of the drive shaft inside the first housing. A fan-shaped plate is fixed to the side of the conical fixing cylinder. The assembly also includes a fixing plate fixed to the inner wall of the first housing. The fixing plate has several fan-shaped through slots. A connecting cylinder is fixed to the bottom of the fixing plate. The bottom of the connecting cylinder is welded with the same insertion pipe. A drain pipe is fixed to the side of the insertion pipe. The drain pipe has the same connector facing the inside of the insertion pipe.

[0043] The feeding assembly also includes a bracket fixed to the top of the first box with screws. There are four brackets at the four corners of the first box. All brackets have feeding pipes fixed inside. Feed pipes are fixed to the end of the feeding pipe facing the cover plate. Feed pipes are fixed inside the cover plate. Feed guide pipes are fixed to one side of the feeding pipe. Feed guide pipes are connected to the external feeding equipment.

[0044] The aforementioned drain pipe and inlet pipe form a loop, allowing water at the required temperature to be introduced. Since the side of the water pipe is connected to a ring pipe, which fits against the inner wall of the cylinder, and the cylinder is made of metal, heat is conducted through the cylinder to ensure the temperature environment during internal membrane separation. For example, the temperature can be lowered to 20-30°C, and normal temperature operation can prevent pigment degradation.

[0045] Simultaneously, during the feeding process, the motor drives the drive shaft to rotate, which in turn drives the conical fixed cylinder and the sector plate to rotate. The sector plate interacts with the sector-shaped grooves on the fixed plate during rotation, creating a stirring and preliminary filtration effect, which helps to evenly distribute the pigment solution and initially remove large particulate impurities. The motor uses frequency conversion control, allowing the speed to be adjusted according to actual needs, ensuring filtration efficiency while avoiding unnecessary shearing damage to the pigment.

[0046] The working principle of this invention is as follows: In actual operation, the natural food pigment liquid to be purified is first introduced into the feed pipe through the feed conduit, and then evenly distributed into the first chamber through the distribution pipe. The motor is started, and the drive shaft rotates the conical fixed cylinder and the fan-shaped plate, performing preliminary stirring and filtration of the pigment liquid. Large particles of impurities are intercepted by the fixed plate, and the pre-filtered pigment liquid flows into the connecting cylinder below through the fan-shaped channel. Simultaneously, according to process requirements, water at a set temperature is introduced into the temperature control component through the water inlet pipe. The water flows through the water pipe, connecting pipe, and annular pipe, utilizing the thermal conductivity of the cylinder to maintain a suitable temperature environment inside the second chamber, ensuring that the membrane separation process takes place under optimal temperature conditions and preventing pigment degradation. Subsequently, the pigment solution flows sequentially through a second chamber equipped with microfiltration, ultrafiltration, and nanofiltration membranes. Under the control of the pressure control unit, each membrane module independently adjusts the pressure in its respective zone via solenoid valves, achieving precise pressure management and ensuring efficient operation of the microfiltration, ultrafiltration, and nanofiltration processes at pressures of 0.1–0.2 MPa, 0.2–0.5 MPa, and 0.5–1.5 MPa, respectively. Finally, the pigment solution purified through multi-stage membrane separation enters the conical collection tank of the third chamber and is discharged through the outlet collection pipe, completing the entire purification process. The entire device features a modular design, with each chamber connected by bolts, facilitating rapid disassembly and process adjustments to meet pigment purification requirements of varying quality.

[0047] Meanwhile, for cleaning the various membranes, the second chamber can be disassembled for cleaning, or clean water can be poured in along the collection pipe for reverse rinsing. Since the upper and lower ends of this device are connected, cleaning is convenient.

[0048] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0049] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. 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. A purification and refining device for natural food pigments based on membrane separation technology, characterized in that, The device includes a top cover mechanism, a multi-stage filtration mechanism, and a collection mechanism. The top cover mechanism includes a first housing (1) with a feeding component inside. The multi-stage filtration mechanism includes a second housing (2) with three housings. The three housings (2) are respectively equipped with a microfiltration membrane (4), an ultrafiltration membrane (5), and a nanofiltration membrane (6). The collection mechanism includes a third housing (3). The first housing (1), the second housing (2), and the third housing (3) are stacked in sequence. The second housing (2) with the microfiltration membrane (4) is located close to the first housing (1), and the second housing (2) with the nanofiltration membrane (6) is located close to the third housing (3). The second housing (2) is equipped with a temperature control component inside, and all the second housings (2) are connected to a pressure control component on their sides.

2. The purification and refining apparatus for food-grade natural pigments based on membrane separation technology according to claim 1, characterized in that, The inner wall of the second box (2) is fixed with a fixing frame (7), and the microfiltration membrane (4), ultrafiltration membrane (5) or nanofiltration membrane (6) is embedded and fixed inside the fixing frame (7). A cylinder (8) is fixed on the side of the fixing frame (7) away from the inner wall of the second box (2).

3. The purification and refining apparatus for food-grade natural pigments based on membrane separation technology according to claim 2, characterized in that, One end of the cylinder (8) is provided with a stepped groove (9), and a sealing ring (10) is bonded inside the stepped groove (9). The other end of the cylinder (8) is provided with a plug pipe (11), which is integrated with the cylinder (8).

4. The purification and refining apparatus for food-grade natural pigments based on membrane separation technology according to claim 2, characterized in that, The temperature control component includes a support frame (12) fixed on the inner wall of the cylinder (8), a water pipe (13) is rotatably connected inside the support frame (12), a connector (14) is welded to one end of the water pipe (13), and a snap-fit ​​groove (15) is provided at the other end. The snap-fit ​​groove (15) is L-shaped. A snap-fit ​​rod (16) is welded to the side of the connector (14). It also includes a connecting pipe (17) fixed to the side of the water pipe (13). Several connecting pipes (17) are provided along the vertical axis and circumferential direction of the water pipe (13). An annular pipe (18) is fixed to the end of the connecting pipe (17) away from the water pipe (13). The connecting pipe (17) communicates with the water pipe (13) and the annular pipe (18). The side of the annular pipe (18) abuts against the inner wall of the cylinder (8).

5. The purification and refining apparatus for food-grade natural pigments based on membrane separation technology according to claim 4, characterized in that, The third box (3) has an empty slot (19) inside, and a conical collection slot (20) is provided at the bottom of the empty slot (19). The empty slot (19) and the conical collection slot (20) are connected. The connection between the empty slot (19) and the conical collection slot (20) is smoothly transitioned. A water inlet pipe (21) is fixed on the side of the empty slot (19). The water inlet pipe (21) is located outside the third box (3) and connected to a water source. The water inlet pipe (21) is located inside the third box (3) and is bent. The water inlet pipe (21) is located inside the third box (3) and has the same snap-fit ​​groove (15). The conical collection slot (20) is connected to an outlet collection pipe (22) on the side.

6. The purification and refining apparatus for food-grade natural pigments based on membrane separation technology according to claim 1, characterized in that, The air pressure control assembly includes a fixed pipe (23) fixedly welded to the side of the second housing (2). The fixed pipe (23) is located inside the second housing (2), and several air outlet pipes (42) are fixed on its side. A support pipe (24) is fixed to the side of the fixed pipe (23) away from the second housing (2) by flange bolts. An air extraction pipe (25) is welded to the end of the support pipe (24) away from the fixed pipe (23), and an air extraction device is connected to the bottom of the air extraction pipe (25).

7. The purification and refining apparatus for food-grade natural pigments based on membrane separation technology according to claim 6, characterized in that, The fixed tube (23) is screwed to the side and a solenoid valve (26) is fixed thereon. Each solenoid valve (26) is controlled independently.

8. The purification and refining apparatus for food-grade natural pigments based on membrane separation technology according to claim 1, characterized in that, The first box (1), the second box (2) and the third box (3) are welded with connecting plates (27) on their sides. The connecting plates (27) are provided with a plurality of through holes (28) for bolts to pass through.

9. The purification and refining apparatus for food-grade natural pigments based on membrane separation technology according to claim 2, characterized in that, The feeding assembly includes a cover plate (29) detachably connected to the top of the first housing (1). A drive shaft (30) is rotatably connected inside the cover plate (29). A motor (31) is connected to the end of the drive shaft (30) facing the outside of the first housing (1). The motor (31) is screwed on the cover plate (29). A conical fixing cylinder (32) is fixed to the inner side of the drive shaft (30) inside the first housing (1). A fan-shaped plate (33) is fixed to the side of the conical fixing cylinder (32). The assembly also includes a fixing plate (34) fixed to the inner wall of the first housing (1). The fixing plate (34) has several fan-shaped through slots (35). A connecting cylinder (36) is fixed to the bottom of the fixing plate (34). The same insertion pipe (11) is welded to the bottom of the connecting cylinder (36). A drain pipe (41) is fixed to the side of the insertion pipe (11). The drain pipe (41) has the same connector (14) facing the inside of the insertion pipe (11).

10. The purification and refining apparatus for food-grade natural pigments based on membrane separation technology according to claim 9, characterized in that, The feeding assembly also includes a bracket (37) fixed to the top of the first box (1) with screws. Four brackets (37) are provided at the four corners of the first box (1). All brackets (37) have a feeding pipe (38) fixed inside. The feeding pipe (38) has a distribution pipe (39) fixed to the end facing the cover plate (29). The distribution pipe (39) is fixed inside the cover plate (29). A feeding guide pipe (40) is fixed to one side of the feeding pipe (38). The feeding guide pipe (40) is connected to a feeding device.

Images