Physical refining device and method for edible oil rich in polyunsaturated fatty acid

Abstract

The invention discloses a physical refining device and method for edible oil rich in polyunsaturated fatty acid, and relates to the technical field of edible vegetable oil processing.The physical refining device for the edible oil rich in polyunsaturated fatty acid comprises a crystallizing tank, an upper-layer ultrasonic generating mechanism, a middle-layer ultrasonic generating mechanism and a lower-layer ultrasonic generating mechanism, and the upper-layer ultrasonic generating mechanism, the middle-layer ultrasonic generating mechanism and the lower-layer ultrasonic generating mechanism are arranged from top to bottom in the axial direction of the crystallizing tank. The middle-layer gas distribution mechanism is arranged between the upper-layer ultrasonic generation mechanism and the middle-layer ultrasonic generation mechanism and is used for forming a transverse bubble layer; and the bottom layer gas distribution mechanism is arranged below the lower layer ultrasonic wave generation mechanism and is used for forming rising bubble flow. According to the method, oxidation reaction can be inhibited in the physical refining process of the edible oil rich in polyunsaturated fatty acid, excessive crushing of crystals is prevented, uniform distribution of energy is ensured, ordered growth of the crystals is promoted, and the separation efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of edible vegetable oil processing technology, and in particular to a physical refining apparatus and method for edible oils rich in polyunsaturated fatty acids. Background Technology

[0002] Flaxseed oil and safflower seed oil are rich in essential fatty acids such as alpha-linolenic acid and linoleic acid, as well as natural nutrients such as tocopherols, sterols, and chlorophyll.

[0003] Traditional chemical refining (alkali refining, high-temperature decolorization, high-temperature deodorization) leads to severe loss of nutrients and the formation of trans fatty acids and chloropropanol esters. Although purely physical refining methods have emerged, their efficiency and selectivity in removing gums and free fatty acids (FFA) from crude oil remain limited. Bio-enzymatic refining (such as enzymatic degumming and enzymatic esterification deacidification) offers mild conditions and high specificity, but it is ineffective in removing waxes from oil and requires a long processing time.

[0004] Furthermore, when refining high PUFA oils such as linseed oil, the viscosity of high PUFA oils is relatively high at low temperatures, which can easily lead to localized overheating or uneven distribution of ultrasonic probes / bath equipment. During industrial scale-up, it is difficult to transfer energy evenly, which can easily result in some areas being over-processed and others being ineffective, seriously affecting separation efficiency and product quality. Summary of the Invention

[0005] The main objective of this invention is to provide a physical refining apparatus and method for edible oils rich in polyunsaturated fatty acids, which aims to inhibit oxidation reactions, prevent excessive crystal breakage, ensure uniform energy distribution, promote orderly crystal growth, and improve separation efficiency during the physical refining process of edible oils rich in polyunsaturated fatty acids.

[0006] To achieve the above objectives, the present invention provides a physical refining apparatus for edible oils rich in polyunsaturated fatty acids, comprising: A crystallization tank, wherein a receiving space is provided inside the crystallization tank, and the receiving space is formed sequentially from top to bottom along the axial direction of the crystallization tank into a top nucleation layer, a middle nucleation layer and a crystal growth layer; An upper ultrasonic wave generating mechanism is disposed within the top nucleation layer; A middle-layer ultrasonic wave generating mechanism is disposed at the junction of the middle nucleation layer and the top nucleation layer; A lower ultrasonic wave generating mechanism is disposed at the junction of the middle nucleation layer and the crystal growth layer. A middle-layer gas distribution mechanism is disposed within the top nucleation layer and between the upper-layer ultrasonic generator and the middle-layer ultrasonic generator. A bottom gas distribution mechanism is disposed within the crystal growth layer and below the lower ultrasonic generator.

[0007] The technical solution of this invention achieves regional control of the crystallization process of edible oils rich in polyunsaturated fatty acids through the synergistic effect of layered ultrasound and a gas distribution mechanism. It effectively inhibits the excessive generation and aggregation of fine crystal nuclei in the top region, promotes the controlled transport of crystal nuclei to the crystal growth layer, and maintains a suspended and orderly growth environment for the crystals within the crystal growth layer. This overcomes the problems of crystal breakage, uneven distribution, and difficulty in centrifugal separation in traditional methods, helping to obtain crystals with uniform particle size and easy separation, thereby improving refining efficiency, reducing nutrient loss, and improving product quality. Attached Figure Description

[0008] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0009] Figure 1 A schematic diagram of an embodiment of the physical refining apparatus for edible oils rich in polyunsaturated fatty acids provided by the present invention; Figure 2 A schematic diagram of another embodiment of the physical refining apparatus for edible oils rich in polyunsaturated fatty acids provided by the present invention; Figure 3 A schematic diagram of another embodiment of the physical refining apparatus for edible oils rich in polyunsaturated fatty acids provided by the present invention; Figure 4 This is a schematic diagram of an embodiment of the upper ultrasonic wave generating module, the middle ultrasonic wave generating module and the lower ultrasonic wave generating module of the present invention. Figure 5 This is a schematic diagram of the exploded structure of an embodiment of the mid-level gas distribution mechanism involved in the present invention; Figure 6 This is a schematic diagram of the explosion structure of an embodiment of the bottom gas distribution mechanism involved in the present invention.

[0010] Explanation of icon numbers: 100. Crystallization tank; 200. Upper ultrasonic generator; 300. Middle ultrasonic generator; 400. Lower ultrasonic generator; 500. Middle gas distribution mechanism; 600. Bottom gas distribution mechanism; 101. Containing space; 102. Top nucleation layer; 103. Middle nucleation layer; 104. Crystal growth layer; 210. Upper mounting flange; 220. Upper ultrasonic generator module; 310. Middle mounting flange; 320. Middle ultrasonic generator module; 410. Lower mounting flange; 420. Lower ultrasonic generator module; 510. First mounting outer ring; 520. First mounting inner ring; 530. First main air inlet pipe; 540. First air inlet branch pipe; 550. First air outlet; 610. Second mounting outer ring; 620. Second mounting inner ring; 630. Second main air inlet pipe; 640. Second air inlet branch pipe; 650. Second air outlet.

[0011] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0012] 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 a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0013] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0014] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0015] Flaxseed oil and safflower oil are rich in essential fatty acids such as alpha-linolenic acid and linoleic acid, as well as natural nutrients such as tocopherols, sterols, and chlorophyll. Traditional chemical refining (alkali refining, high-temperature bleaching, high-temperature deodorization) leads to severe loss of nutrients and is accompanied by the formation of trans fatty acids and chloropropanol esters. Although purely physical refining methods have emerged, their efficiency and selectivity in removing gums and free fatty acids (FFA) from crude oil remain limited. Bio-enzymatic refining (such as enzymatic degumming and enzymatic esterification deacidification) is mild and highly specific, but it is ineffective in removing waxes from oil and has a long processing time.

[0016] However, when refining high-PUFA oils such as linseed oil, these oils are highly susceptible to oxidation (due to their complex double-bond structure, including linolenic acid). Ultrasonic cavitation generates localized free radicals and hot spots. Even with energy density controlled at 10W / L~30W / L, prolonged treatment (1~2 hours) can still accelerate peroxide formation, leading to increased peroxide value (PV), flavor degradation, and nutrient loss (especially ω-3 fatty acids). Studies have shown that prolonged ultrasonic treatment of certain high-PUFA oils can significantly reduce polyunsaturated fatty acid content or increase primary oxidation products. A frequency of 20kHz~40kHz falls within the high-intensity power ultrasonic range. If the energy density is too high (>30W / L) or the treatment time is too long, excessive crystal breakage can occur, generating more fine fragments and worsening centrifugal separation. If the energy density is too low, the cavitation effect is insufficient and cannot effectively improve crystal nucleation. The cooling rate (1-2℃ / min) and the timing of ultrasonic treatment must be precisely matched; slight deviations can result in "false wax" (low-temperature crystallization of the oil itself) or wax dissolving back into the oil.

[0017] In addition, high PUFA oil has a high viscosity at low temperatures, which can easily lead to localized overheating or uneven distribution in ultrasonic probes / bath equipment. During industrial scale-up, it is difficult to transfer energy evenly, resulting in some areas being over-processed and others being ineffective. Although the crystals may be more uniform, if too many fine crystals (<5μm) are generated, the retention efficiency of high-speed disc centrifuges will actually decrease, and wax runoff or clogging may still occur, seriously affecting separation efficiency and product quality.

[0018] To address this technical problem, this invention proposes a physical refining apparatus and method for edible oils rich in polyunsaturated fatty acids.

[0019] Please see Figure 1 , Figure 2 and Figure 3In one embodiment of the present invention, the physical refining apparatus for edible oil rich in polyunsaturated fatty acids includes a crystallization tank 100, an upper ultrasonic generator 200, a middle ultrasonic generator 300, a lower ultrasonic generator 400, a middle gas distribution mechanism 500, and a bottom gas distribution mechanism 600. The crystallization tank 100 has a receiving space 101, which, along the axial direction of the crystallization tank 100, sequentially forms a top nucleation layer 102, a middle nucleation layer 103, and a crystal growth layer 104 from top to bottom. The upper ultrasonic generator 200 is disposed on the top nucleation layer 102. 2. The middle layer ultrasonic generator 300 is located at the junction of the middle nucleation layer 103 and the top nucleation layer 102; the lower layer ultrasonic generator 400 is located at the junction of the middle nucleation layer 103 and the crystal growth layer 104; the middle layer gas distribution mechanism 500 is located within the top nucleation layer 102 and is located between the upper layer ultrasonic generator 200 and the middle layer ultrasonic generator 300; the bottom layer gas distribution mechanism 600 is located within the crystal growth layer 104 and is located below the lower layer ultrasonic generator 400.

[0020] Specifically, the crystallization tank 100 is a vertical cylindrical container, with its internal space 101 filled with edible oils rich in polyunsaturated fatty acids (such as flaxseed oil or safflower oil) to be processed. The cooling process is controlled by a jacket, allowing the oil to naturally form temperature and supersaturation gradients along the axial direction. From top to bottom, the tank is divided into a top nucleation layer 102 (the region with the highest supersaturation, easily producing a large number of fine crystal nuclei), a middle nucleation layer 103 (the transition region between crystal growth and transport), and a crystal growth layer 104 (the region where crystals grow slowly and require relative stability). This axial partitioning addresses the practical problem of high PUFA oils easily over-nucleating at the top to form fine powder and having high viscosity at the bottom, leading to deposition and caking, during low-temperature crystallization.

[0021] The upper ultrasonic generator 200 is located within the top nucleation layer 102, with its radiating surface extending into the upper region of the grease. During the initial cooling phase, as the oil temperature slowly decreases from approximately 35°C to around 15°C, this generator activates, producing a strong local cavitation effect and micro-turbulent disturbance. The shock waves and high-speed microjets released when the cavitation bubbles collapse act on the newly formed fine needle-like or plate-like crystal nuclei near the liquid surface, effectively breaking them up or re-dissolving them. This reduces the tendency for secondary nucleation explosions and crystal aggregation caused by excessive supersaturation, thereby lowering the proportion of fine crystals (<10μm).

[0022] The intermediate ultrasonic wave generator 300 is located at the junction of the intermediate nucleation layer 103 and the top nucleation layer 102, with its radiation surface basically horizontal, covering the main area in the middle. During the crystallization process (when the oil temperature is approximately 15–11°C and some crystal nuclei have already appeared), this generator provides moderate-intensity acoustic radiation and local circulation. At this time, the intermediate gas distribution generator 500 (located between the upper and intermediate generators) instantaneously introduces nitrogen gas, rapidly forming a high-density transverse bubble layer (bubble diameter 3–8 mm, high gas content) at this height. The bubble layer significantly attenuates the sound waves from above, while the intermediate ultrasonic waves partially penetrate or disturb the bubble interface, forming a significant vertical acoustic intensity gradient (strong disturbance at the top, weaker disturbance at the bottom). This gradient allows small crystals to be transported downwards in a controlled manner under the combined action of acoustic flow and gravity, without being excessively broken up by the upper layer, and also avoids strong mass exchange and convective mixing with the crystal growth layer 104.

[0023] The lower ultrasonic generator 400 is located at the junction of the nucleation layer 103 and the crystal growth layer 104, with its radiating surface tilted upwards. Throughout the crystal growth stage (oil temperature approximately 11–8°C, lasting several hours), this mechanism provides stable acoustic levitation force and bottom driving action. The acoustic radiation pressure (related to the square of the frequency) provides upward support to the crystals, compensating for the attenuation of sound wave propagation by the middle bubble layer and preventing crystals from depositing at the bottom of the high-viscosity grease, forming dead zones. Simultaneously, the bottom gas distribution mechanism 600 (located below the lower mechanism) continuously releases fine bubbles (1–3 mm in diameter) upwards at a low flow rate throughout the process, forming a bottom microbubble blanket. This, in conjunction with the lower ultrasonic waves, generates mild macroscopic mixing, maintaining a relatively stable environment at the bottom of the crystal growth layer 104. This facilitates the slow and orderly growth of crystals into larger particles (D50 typically in the range of 80–150 μm) that are easily separated by centrifugation.

[0024] Through the specific positioning and coordinated operation of the aforementioned components, this device achieves zoned control of the crystallization process: the top focuses on suppressing the formation of fine powder, the middle achieves orderly transport and forms physical isolation through an air curtain, and the bottom maintains suspension and orderly growth. This layered differentiated treatment method effectively alleviates the problems of high PUFA oils (such as linseed oil and safflower oil) easily generating a large number of fine crystals, difficult filtration, bottom sedimentation, and the risk of localized oxidation that may be caused by prolonged ultrasonic treatment during pure physical winterization. In actual operation, the proportion of fine powder can be reduced by more than 60% compared with the traditional mechanical stirring process, the centrifugal separation efficiency is increased by 1.8 to 2.5 times, and the increase in peroxide value is significantly controlled, while retaining the content of major unsaturated fatty acids such as α-linolenic acid and linoleic acid in the raw oil.

[0025] More specifically, the upper ultrasonic generator 200 uses a probe module with a frequency of 22kHz for use in the nucleation stage of flaxseed oil; or, for safflower seed oil (which crystallizes more slowly), it uses a module with a frequency of 25kHz. Both frequencies are in the low-frequency strong cavitation range and can effectively break up the small crystal nuclei at the top.

[0026] The middle gas distribution mechanism 500 generates a 3-5 mm bubble layer, and in another embodiment, it generates a 5-8 mm bubble layer. Both bubble size ranges can quickly form an effective attenuation layer.

[0027] In one embodiment, the lower ultrasonic generating mechanism 400 uses a 70kHz module, and in another embodiment, it uses a 75kHz module. Both higher frequencies are beneficial for generating a strong acoustic levitation effect while the cavitation energy is relatively mild, supporting the lower mechanism's requirement to provide stable levitation and compensate for attenuation on the upper part of the crystal growth layer 104.

[0028] This device achieves regional control of the crystallization process of edible oils rich in polyunsaturated fatty acids through the synergistic effect of layered ultrasonic waves and a gas distribution mechanism. It effectively suppresses the excessive generation and aggregation of fine crystal nuclei in the top region, promotes the controlled transport of crystal nuclei to the crystal growth layer 104, and maintains a suspended and orderly growth environment for the crystals within the crystal growth layer 104. This overcomes the problems of crystal breakage, uneven distribution, and difficulties in centrifugal separation in traditional methods, helping to obtain crystals with uniform particle size and easy separation, thereby improving refining efficiency, reducing nutrient loss, and improving product quality.

[0029] As one implementation of this embodiment, the electrical connection and control of the upper ultrasonic generator 200, the middle ultrasonic generator 300, the lower ultrasonic generator 400, the middle gas distribution mechanism 500, and the bottom gas distribution mechanism 600 are achieved in the following manner: The upper-level ultrasonic generator 200 comprises multiple (typically 8–16) titanium alloy cylindrical probes, each with a rated power of 120–200 W and an operating frequency range of 20–30 kHz. These probes are connected to a dedicated upper-level ultrasonic generator (or an upper-level power module distributed within a high-power generator) via high-temperature, high-pressure resistant coaxial cables (with an oil-resistant outer sheath and a temperature resistance ≥150℃). The rated output power of the upper-level generator is typically 35%–45% of the total installed power (e.g., 8.5–11 kW for a total power of 24 kW), and features independent adjustable duty cycle pulse control (10%–100%), linear power adjustment (0–100%), frequency fine-tuning (±1.5 kHz sweep function), and over-temperature / overload protection. The generator communicates with the main PLC controller via RS-485 or Modbus RTU interface. The main PLC automatically outputs a 4-20 mA analog signal to control the power of the upper-level generator based on a preset temperature curve (conditions for the cooling nucleation stage: oil temperature drops to 23-17℃ and cooling rate > 0.6℃ / min), or controls its start / stop and pulse mode via a DO digital signal. In the initial stage of cooling nucleation, the upper-level generator typically operates continuously at 80%-100% power or intermittently at 70%-90% duty cycle. Simultaneously, the PLC monitors the PT100 temperature sensor built into each probe (probe body temperature ≤ 85℃ is the safety threshold); if the temperature exceeds the limit, it automatically reduces power or shuts down.

[0030] The 300-unit intermediate ultrasonic generator comprises multiple probes (typically 10-18), each with a rated power of 80-160 W and an operating frequency range of 35-55 kHz. The probe cables are connected to a dedicated intermediate ultrasonic generator (or the intermediate module of the main generator). The output power of the intermediate generator typically accounts for 25%-35% of the total installed power. In addition to standard power / frequency adjustment functions, the intermediate generator has an external trigger input terminal (dry contact or 24 V DC signal), which is connected to the PLC's DO output. After determining that the crystallization separation stage has begun (typical determination conditions: oil temperature reaches 16-11℃ and intermediate gas flow has increased to the set value), the PLC simultaneously sends an opening command to the intermediate gas solenoid valve group and a trigger signal to the intermediate ultrasonic generator, causing the generator to start synchronously (typically operating at 55%-85% power and a duty cycle of 80%-100%), achieving strict time-coordinated acoustic radiation and air curtain formation. The generator also integrates a sound intensity feedback channel (through a small number of sound pressure sensors installed on the tank wall), and the PLC can fine-tune the power of the middle layer according to the real-time sound pressure attenuation (when the attenuation is too large, the power is increased appropriately by 5% to 15%).

[0031] The lower-level ultrasonic generator 400 contains multiple (typically 12-20) probes, each with a rated power of 60-120 W and an operating frequency range of 55-90 kHz. The lower-level generator (or the lower module of the main generator) typically accounts for 20%-30% of the total power, operating in a fixed low-power continuous mode (typically 25%-45% of rated power). It does not have pulse functionality, only power fine-tuning and overload protection. The lower-level generator communicates with the PLC via RS-485. The PLC issues a continuous operation command after the entire crystallization process starts (when the oil temperature begins to drop after step S10) and continues until crystallization is complete (before material discharge in step S50). The temperature of the lower-level probes is also monitored by the PLC, but the threshold is relaxed to ≤80℃ to ensure stable operation throughout the process.

[0032] The gas passage of the 500 intermediate gas distribution mechanism uses a 316L stainless steel main inlet pipe (DN32~50) introduced from the flange at the lower part of the tank wall. A solenoid shut-off valve (normally closed, explosion-proof), a mass flow controller (MFC, range 0~300 L / min, accuracy ±1.5% FS), a pressure transmitter (0~0.6 MPa), and a manual ball valve are connected in series on the main pipe. Both the solenoid shut-off valve and the MFC are connected to the PLC via a 24 V DC coil / 4~20 mA control signal. During the crystallization separation stage (oil temperature 16~11℃), the PLC sends a DO signal to open the solenoid valve and simultaneously outputs a 4~20 mA signal to the MFC to rapidly increase the flow rate to 0.3~0.8 vvm (corresponding to approximately 140~380 L / min for this tank), maintaining this flow rate for 6~12 minutes before automatically closing or reducing it to an extremely low flow rate (≤0.05 vvm). The flow controller has a built-in PID control function to ensure that the flow rate rise time is ≤15 seconds, avoiding excessively slow bubble formation or excessively strong impact.

[0033] The gas passage of the bottom gas distribution mechanism 600 is introduced from the bottom or lower side of the tank through an independent main inlet pipe (DN25~40). The pipeline is also equipped with a solenoid shut-off valve (normally open type), a mass flow controller (range 0~80 L / min), a pressure gauge, and a filter pressure reducing valve. The bottom MFC maintains continuous low-flow operation throughout the entire process (from the end of oil filling to before discharge). The PLC outputs a fixed 4~20 mA signal to control the flow rate, stabilizing it at 0.05~0.15 vvm (corresponding to approximately 24~70 L / min for this tank), with flow fluctuations controlled within ±5%. The bottom solenoid valve is only closed during emergency shutdown or cleaning.

[0034] The aforementioned electrical and control systems are uniformly coordinated by a single main PLC (such as a Siemens S7-1500 or equivalent), equipped with a touchscreen HMI for process parameter setting, stage switching, manual intervention, and real-time data display (including power percentage, frequency, probe temperature, instantaneous / cumulative gas flow rate, oil temperature profile, etc.). All high-voltage cables and signal cables are shielded and armored, laid in galvanized conduits or stainless steel cable trays. Explosion-proof areas are strictly selected according to Ex d IIB T4 or higher standards to ensure the long-term reliability and safety of the system in edible oil processing environments.

[0035] In one specific embodiment (flaxseed oil), the upper layer generator is allocated 9.2 kW (24 kHz), the middle layer 6.8 kW (44 kHz), and the lower layer 5.1 kW (71 kHz), for a total installed capacity of 21.1 kW. During the separation phase, the middle layer MFC rapidly increases the flow rate from 0.04 VVM to 0.57 VVM and maintains it for 9.5 min, while the lower layer MFC remains stable at 0.082 VVM throughout. The PLC program incorporates dual temperature-time judgment logic to ensure accurate switching between each stage, ultimately yielding winterized oil with uniform crystal distribution and low oil content in the wax residue.

[0036] The circuit and control implementation described above provide a reliable electrical foundation for the phased and zoned acoustic-gas coordinated regulation of the present invention. It can execute the differences in operating parameters of ultrasonic generators at different heights and the gas distribution requirements of instantaneous high flow rate in the middle layer and low flow rate throughout the bottom layer, thereby achieving the process goal of strong nucleation at the top, controlled separation in the middle, and gentle and orderly crystal growth at the bottom during the physical refining of edible oils rich in polyunsaturated fatty acids.

[0037] Please continue reading. Figure 1 , Figure 2 and Figure 3 And see Figure 4 In an embodiment of the present invention, the upper ultrasonic generating mechanism 200 includes an upper mounting flange 210 and a plurality of upper ultrasonic generating modules 220. The upper mounting flange 210 is coaxially arranged with the crystallization tank 100 and is sleeved on the outside of the crystallization tank 100. The plurality of upper ultrasonic generating modules 220 are installed at intervals along the circumference of the crystallization tank 100 on the upper mounting flange 210. The radiating surfaces of the plurality of upper ultrasonic generating modules 220 all extend into the top nucleation layer 102. The radiating surfaces of the plurality of upper ultrasonic generating modules 220 are all arranged towards the central axis of the crystallization tank 100. The radiating surfaces of the plurality of upper ultrasonic generating modules 220 are all inclined downward and are all arranged at a first angle with the horizontal plane, the first angle being α, where 5°≤α≤10°.

[0038] Specifically, the upper ultrasonic generating mechanism 200 consists of an upper mounting flange 210 and multiple upper ultrasonic generating modules 220. The upper mounting flange 210 is an annular structure, coaxially arranged with the crystallization tank 100 and sleeved on the outer wall of the crystallization tank 100. It is fixed to the outer wall of the tank by bolts or clamps to ensure that the coaxiality error is less than 0.5mm. Multiple upper ultrasonic generating modules 220 (usually 6 to 12, depending on the tank diameter) are installed at equal intervals along the circumference of the tank in the mounting holes on the inner side of the flange. The transducer, amplitude transformer, and radiating surface assembly of each module pass through the sealing flange seat on the tank wall, and the radiating surface extends directly into the top nucleation layer 102 of the grease.

[0039] The radiating surfaces of each upper module are arranged towards the central axis of the crystallization tank 100, meaning that the direction of sound wave emission points towards the central axis of the tank, rather than being radially parallel or divergent. This orientation arrangement allows sound beams from different circumferential positions to superimpose to a certain extent in the central region of the tank, forming a relatively uniform sound field coverage and avoiding the phenomenon that a single module only produces strong cavitation in the near-wall region while the effect in the central region is too weak.

[0040] More specifically, the radiating surfaces are not installed horizontally, but are tilted downwards as a whole, forming a first angle α with the horizontal plane, with α controlled within the range of 5° to 10°. In one specific embodiment, α = 7°, and in another embodiment, α = 9°. The downward tilting arrangement means that the main beam axis of the sound wave is not strictly horizontal, but has a downward component.

[0041] With the above arrangement, when the upper ultrasonic generator 200 is activated during the cooling nucleation stage (when the oil temperature typically drops from 30-35°C to 14-16°C), the sound waves mainly act on a depth range of approximately 50-400 mm below the liquid surface (the probe tip generally leaves a margin of 200-350 mm from the liquid surface). Because the radiating surface faces the center and tilts downwards at 5°-10°, the sound beam coverage area exhibits a conical distribution that is narrower at the top and wider at the bottom. This effectively acts on the extremely thin supersaturated layer near the liquid surface, while extending downwards to the lower middle part of the top nucleation layer 102, avoiding excessive disturbance only at the outermost layer while lacking cavitation at deeper levels.

[0042] The selection of this tilt angle range is based on the fact that highly polyunsaturated fatty acid oils (such as flaxseed oil and safflower oil) readily generate a large number of tiny needle-like or feather-like crystal nuclei near the liquid-gas interface during the initial cooling phase. Too small a tilt angle (<5°) would cause the sound beam to be too close to the liquid surface, increasing interference between the probe's radiation area and the gas-liquid interface, and easily introducing bubble shielding or standing wave interference. Too large a tilt angle (>10°) would cause the sound beam to be directed too much towards the lower and middle parts, weakening the targeted fragmentation effect on the top, highly supersaturated region. A range of 5° to 10° ensures strong cavitation fragmentation capability at the top while minimizing the risk of accelerated oxidation and gas-liquid interface instability caused by the probe tip being too close to the liquid surface.

[0043] In actual operation, the combined effect of multiple circumferentially distributed, center-oriented, and downward-sloping radiation surfaces makes the sound intensity distribution in the top nucleation layer 102 relatively uniform in both the radial and axial directions. This avoids the unevenness that is easy to occur when using a traditional single probe or horizontal arrangement, such as "strong near the probe and weak at the far end" or "strong on the wall and weak at the center". This more effectively suppresses the excessive generation and aggregation of fine crystal nuclei near the liquid surface due to excessive local supersaturation.

[0044] In one specific embodiment, with a tank diameter of 1200 mm, eight upper-layer modules were used, with a circumferential spacing of 45°, α = 7°, and a frequency of 22 kHz. The measured proportion of 102 fine powder (<10 μm) in the top nucleation layer was reduced by approximately 62% to 78% compared to when there was no ultrasonic treatment or the probe was arranged horizontally. In another embodiment, with a tank diameter of 800 mm, six modules were used, α = 9°, and the frequency was 25 kHz. For the safflower seed oil system, the same results were obtained, with a significant decrease in the proportion of fine powder and improved uniformity of crystal distribution.

[0045] Please continue reading. Figure 1 , Figure 2 , Figure 3 and Figure 4 In an embodiment of the present invention, the intermediate ultrasonic generating mechanism 300 includes an intermediate mounting flange 310 and a plurality of intermediate ultrasonic generating modules 320. The intermediate mounting flange 310 is coaxially arranged with the crystallization tank 100 and is sleeved on the outside of the crystallization tank 100. The plurality of intermediate ultrasonic generating modules 320 are installed at intervals along the circumference of the crystallization tank 100 on the intermediate mounting flange 310. The radiating surfaces of the plurality of intermediate ultrasonic generating modules 320 all extend into the junction of the middle nucleation layer 103 and the top nucleation layer 102. The radiating surfaces of the plurality of intermediate ultrasonic generating modules 320 are all arranged facing the central axis of the crystallization tank 100 and are all arranged in the horizontal direction.

[0046] Specifically, the intermediate layer mounting flange 310 adopts an annular stainless steel structure with an inner diameter slightly larger than the outer diameter of the crystallization tank 100. It is fixed to the outer wall of the tank body by multiple high-strength bolts or special clamping assemblies to ensure that the flange plane is strictly perpendicular to the tank body axis, and the coaxiality deviation is controlled within 0.4mm. Multiple intermediate layer ultrasonic generating modules 320 (generally 6 to 12, depending on the tank diameter) are arranged at equal angles along the circumference of the tank body in the reserved mounting holes of the flange. The radiating end (i.e., the transducer emitting surface) of each module passes through the pre-opened and welded sealing flange seat on the tank wall and extends into the grease. The insertion depth is usually 30% to 45% of the inner diameter of the tank, ensuring that the radiating surface is exactly located at the junction height area between the middle nucleation layer 103 and the top nucleation layer 102.

[0047] The radiating surfaces of each intermediate ultrasonic generating module 320 are all oriented towards the central axis of the crystallization tank 100, meaning that the sound wave emission direction points towards the geometric central axis of the tank, rather than being emitted tangentially or radially. This directional arrangement causes multiple circumferentially distributed sound beams to intersect and superimpose to a certain extent near the center of the tank, forming an approximately cylindrical sound radiation region with the central axis as the axis of symmetry at the junction height.

[0048] All radiating surfaces are arranged horizontally, meaning the plane containing the radiating surface is parallel to the horizontal plane, and the main emission direction of the sound waves remains horizontal without any significant upward or downward tilt. In one specific embodiment, the tank diameter is 1100mm, eight middle-layer modules are selected, circumferentially spaced at 45°, the radiating surfaces are strictly horizontal, and the operating frequency is 45kHz; in another specific embodiment, the tank diameter is 800mm, six modules are selected, circumferentially spaced at 60°, the radiating surfaces remain horizontal, and the operating frequency is 48kHz.

[0049] More specifically, during the crystallization separation stage (when the oil temperature typically reaches the range of 14℃ to 11℃, a certain number of crystal nuclei have been generated but have not yet entered the rapid growth phase), after the middle layer gas distribution mechanism 500 instantaneously introduces a large flow rate of nitrogen (generally 0.35 to 0.75 vvm, lasting 6 to 12 minutes), a transverse high-density bubble layer with a thickness of approximately 100 to 220 mm is rapidly formed near the middle layer installation height. At this time, the middle layer ultrasonic generating mechanism 300 is activated, and the horizontal acoustic radiation directed towards the center mainly acts on the area below the bubble layer.

[0050] Because the bubble layer significantly reflects, scatters, and absorbs strong upper-layer sound waves, the downward penetration ability of these waves is greatly weakened. Meanwhile, horizontally emitted sound waves from the middle layer can maintain a relatively high local sound intensity below the bubble layer and induce additional radial and local circumferential microflows near the bubble interface. This acoustic-gas interface positional matching relationship produces the following main effects: 1. The formation of a medium-intensity continuous disturbance zone below the bubble layer helps to gradually transport the fine nuclei / crystals generated in the top nucleation layer 102 downwards along the direction of acoustic flow and gravity, without further crushing them into finer, harder-to-separate particles due to excessive cavitation in the upper layer. 2. The bubble layer itself acts as a natural acoustic barrier, which significantly suppresses the vertical material exchange and thermal disturbance between the top nucleation layer 102 and the crystal growth layer 104, and prevents the uncontrolled downward penetration of the top fine powder into the crystal growth layer 104 and contamination of the existing crystals. 3. The combined effect of horizontal acoustic radiation and the rising path of the bubbles creates a relatively stable transitional flow field in the interface region, making the crystal transport process gradual and controllable.

[0051] In one embodiment (flaxseed oil system), after adopting the above-mentioned middle layer horizontal center-oriented arrangement in conjunction with an air curtain, the cumulative penetration ratio of fine crystals (size <12μm) from the top nucleation layer 102 to the crystal growth layer 104 decreased by about 58% to 74% compared with the absence of middle layer ultrasonic participation, and the uniformity of crystal axial migration (standard deviation of particle size along height) was improved by about 0.7 to 1.1 times. In another embodiment (safflower seed oil system), under the same arrangement conditions, the oil content of wax residue after centrifugation was reduced by about 13% to 20%, and the increase in peroxide value was controlled within 1.1 meq / kg.

[0052] This embodiment addresses the key technical challenge of "disorderly downward penetration of fine crystal nuclei / crystals at the top, easily contaminating the crystal growth layer 104 and leading to a decrease in separation efficiency" during the crystallization process of high polyunsaturated fatty acid oils. It, together with the instantaneous high-flow-rate gas curtain of the middle gas distribution mechanism 500, the downward tilted radiation surface of the upper ultrasonic generator 200, and the upward tilted radiation surface of the lower ultrasonic generator 400, constitutes an axial sound intensity gradient and sound-gas separation synergistic system. This effectively solves the technical problems of uncontrolled axial distribution of crystals, excessive accumulation of fine powder, aggravated local oxidation, and subsequent centrifugal wax runoff or smearing in the traditional ultrasonic-assisted winterization process.

[0053] Please continue reading. Figure 1 , Figure 2 , Figure 3 and Figure 4 In an embodiment of the present invention, the lower ultrasonic generating mechanism 400 includes a lower mounting flange 410 and a plurality of lower ultrasonic generating modules 420. The lower mounting flange 410 is coaxially arranged with the crystallization tank 100 and is sleeved on the outside of the crystallization tank 100. The plurality of lower ultrasonic generating modules 420 are installed at intervals along the circumference of the crystallization tank 100 on the lower mounting flange 410. The radiating surfaces of the plurality of lower ultrasonic generating modules 420 all extend into the junction of the nucleation layer 103 and the crystal growth layer 104 in the middle. The radiating surfaces of the plurality of lower ultrasonic generating modules 420 are all arranged facing the central axis of the crystallization tank 100. The radiating surfaces of the plurality of lower ultrasonic generating modules 420 are all inclined upward and are all arranged at a second angle with the horizontal plane, the second angle being β, where 5°≤β≤10°.

[0054] Specifically, the lower mounting flange 410 adopts a ring-shaped 316L stainless steel structure, with an inner diameter slightly larger than the outer diameter of the crystallization tank 100. It is fixed to the outer wall of the tank body by multiple sets of high-strength bolts and an outer reinforcing ring, ensuring that the flange plane is perpendicular to the tank body axis and the coaxiality deviation is controlled within 0.5mm. Multiple lower ultrasonic generating modules 420 (generally 6 to 12, depending on the tank diameter) are installed at equal angles along the circumference of the tank body in the reserved through holes of the flange. The radiating end (transducer emitting surface) of each module passes through the oil-resistant sealing flange seat pre-welded on the tank wall and extends into the grease. The insertion depth is usually 35% to 50% of the inner diameter of the tank, so that the radiating surface is located at the junction height area between the lower part of the nucleation layer 103 and the upper part of the crystal growth layer 104.

[0055] The radiation surfaces of each lower-level ultrasonic generating module 420 are all oriented towards the central axis of the crystallization tank 100, meaning the main emission direction of the sound waves points towards the geometric central axis of the tank. This directional arrangement causes multiple circumferentially distributed sound beams to converge and intersect to a certain extent near the center of the tank, forming an approximately cylindrical sound radiation zone with the central axis as the axis of symmetry at the junction height.

[0056] Each radiating surface is tilted upwards, forming a second angle β between the radiating surface and the horizontal plane, with β limited to the range of 5° to 10°. In one specific embodiment, β = 6°, and in another specific embodiment, β = 8°. The upward tilt gives the main beam axis an upward component, and the sound beam coverage area exhibits a conical distribution that is narrower at the bottom and wider at the top in the vertical direction.

[0057] During the crystal growth stage (when the oil temperature is usually stable in the range of 8-11℃, and the crystals have entered a period of slow and orderly growth), the lower ultrasonic generator operates continuously at 400° (the frequency is generally 65-80kHz, and the average sound intensity is 8-18W / cm²). 2 Since the radiating surface faces the center and is tilted upwards at 5° to 10°, the acoustic radiation pressure mainly acts on the upper part of the crystal growth layer 104 and the lower part of the nucleation layer 103 within a height range of about 200 to 600 mm. At the same time, the downward-transmitted acoustic flow component is relatively weak, providing continuous upward suspension support for the crystals that have a tendency to settle at the bottom.

[0058] During this stage, the bottom gas distribution mechanism 600 maintains a low flow rate (0.04–0.12 vvm) to release fine rising bubbles (1–4 mm in diameter). This, combined with the upward-sloping acoustic radiation, provides axial levitation force for the crystals. The fine bubbles provide additional upward disturbance and local shear flow. The superposition of these two factors keeps the crystals below the crystal growth layer 104 in a suspended state, significantly reducing the formation of a dense deposition layer at the bottom. At the same time, it avoids excessive disturbance intensity that could cause the grown crystals (typically 50–120 μm in size) to be broken back into fine particles.

[0059] In one specific embodiment (flaxseed oil), eight lower-layer modules were used, with a circumferential spacing of 45°, β = 6°, and a frequency of 70kHz. The thickness of the bottom crystal deposition was reduced by approximately 68%–84% compared to when there was no lower-layer ultrasonication, and the oil content of the wax residue after centrifugation was reduced by approximately 14%–21%. In another specific embodiment (safflower seed oil), seven modules were used, with a circumferential spacing of approximately 51.4°, β = 8°, and a frequency of 75kHz. The proportion of the bottom dead zone volume decreased by approximately 75%–88%, the average crystal volume diameter D increased by approximately 16–24μm, and the filtration cycle was shortened by approximately 22%–31%.

[0060] This embodiment addresses the core technical problem of "bottom crystals easily depositing and hardening, forming dead zones, and causing a significant decrease in subsequent separation efficiency" in high polyunsaturated fatty acid oils under low temperature and high viscosity conditions. Together with the continuous microbubble flow of the bottom gas distribution mechanism 600 and the axial sound intensity gradient of the upper and middle ultrasonic generating mechanisms 300, it forms a complete acoustic-gas suspension and zoned transport system. This effectively solves the technical problems of severe bottom sedimentation of the crystal growth layer 104, uneven axial distribution of crystals, easy clogging or wax runoff in the centrifuge, and poor overall yield and product quality stability in traditional physical winterization and ultrasonic-assisted winterization processes.

[0061] Please continue reading. Figure 1 , Figure 2 , Figure 3 and Figure 4 In an embodiment of the present invention, multiple upper ultrasonic generating modules 220, multiple middle ultrasonic generating modules 320, and multiple lower ultrasonic generating modules 420 are arranged alternately on the orthographic projection of the bottom of the crystallization tank 100.

[0062] Specifically, the ultrasonic generating modules at the upper, middle, and lower heights are arranged circumferentially at intervals, with each layer typically containing 6 to 12 modules (depending on the tank diameter). The radiating surface of each module extends into the grease through the tank wall sealing seat. The orthographic projection on the tank bottom plane refers to the distribution of points formed after projecting the center points (or geometric centers of the radiating surfaces) of all radiating surfaces vertically onto the circular plane at the bottom of the tank.

[0063] In this embodiment, the projection points of the three modules do not overlap or align on the circumference of the tank bottom; instead, they are staggered. Specifically: The projection points of the upper module are usually located on the outer ring of the tank bottom circumference (approximately 15% to 25% of the tank diameter from the projection line on the tank wall), the projection points of the middle module are located on the middle ring (approximately 25% to 40% of the tank diameter from the projection line on the tank wall), and the projection points of the lower module are located on the innermost ring (approximately 35% to 50% of the tank diameter from the projection line on the tank wall). The circumferential angle between adjacent projection points within each layer is equal, while the projection points between adjacent layers are offset by a certain angle in the circumferential direction.

[0064] In one specific embodiment (tank inner diameter 1100mm), the upper layer uses 8 modules spaced 45° circumferentially, with projection points located in a ring approximately 480–520 mm from the center; the middle layer uses 8 modules spaced 45° circumferentially, but with the starting angle rotated 22.5° relative to the upper layer (i.e., offset by half a module interval), with projection points located in a ring approximately 380–420 mm from the center; the lower layer also uses 8 modules spaced 45° circumferentially, with the starting angle rotated 22.5° relative to the middle layer, with projection points located in a ring approximately 280–320 mm from the center. The three layers of projection points form three nested, staggered rings on the bottom plane of the tank, with the minimum circumferential angle between the nearest projection points of any two layers not less than 10°–12°.

[0065] In another specific embodiment (tank inner diameter 850mm), the upper 6 modules are spaced 60° apart, the middle 6 modules are spaced 60° apart but rotated 30°, and the lower 7 modules are spaced approximately 51.4° apart and rotated approximately 15.7°. The three layers of projection also form a staggered nested distribution, and the minimum circumferential angle between any adjacent layer projection points is controlled between 12° and 18°.

[0066] This staggered arrangement of three layers of projection creates complementary coverage areas for sound waves emitted from different heights within the tank in both the radial and circumferential directions: when the upper module generates strong local cavitation and acoustic flow in the top nucleation layer 102, its downward propagating sound radiation is stronger in the near-wall region, while the sound radiation from the middle module mainly covers the mid-radial region, and the lower module further covers the region closer to the center. This radially staggered superposition of the three sound fields avoids the "sound shadow zone" or "over-concentration zone" caused by a single-height module that extends vertically throughout the entire tank height.

[0067] During the crystallization separation and crystal growth process, when the intermediate gas distribution mechanism 500 forms a transient high-density bubble layer, the strong sound waves in the upper layer are significantly attenuated by the bubble layer, while the sound radiation in the middle and lower layers can still maintain effective disturbance intensity at their respective main operating heights. Due to the staggered projection of the three layers, the macroscopic circulation path formed by the acoustic flow in the tank is more complex and sufficient, the radial and circumferential liquid replacement efficiency is significantly improved, and the crystal particles achieve better radial uniformity while being transported axially.

[0068] In one embodiment (flaxseed oil system, tank diameter 1100mm, three layers staggered by 22.5°), the standard deviation of crystal particle size at different radii along the tank height was reduced by about 42% to 61% compared with the traditional same-angle aligned arrangement, and the oil content of wax residue decreased by about 11% to 19% after centrifugation. In another embodiment (safflower seed oil system, tank diameter 850mm, three layers staggered by 30° + 15.7°), the axial-radial variation coefficient of crystal volume concentration in the tank was reduced by about 0.24 to 0.38, the filtration resistance was reduced by about 18% to 27%, and the peroxide value increase was controlled at 0.9 to 1.3 meq / kg.

[0069] This embodiment addresses the technical challenge of "uneven radial acoustic field coverage, local dead zones or excessive disturbances penetrating along the height, and uncontrolled radial distribution of crystals leading to decreased separation efficiency and product quality fluctuations" during the ultrasonic-assisted crystallization process of high polyunsaturated fatty acid oils. It works in conjunction with the layering and partitioning relationships, as well as the instantaneous air curtain isolation in the middle layer, the downward tilt of the upper layer, the horizontal orientation of the middle layer, and the upward tilt of the lower layer's radiation surfaces. This creates a composite acoustic field distribution within the tank that is radially complementary, circumferentially staggered, and axially gradient. This effectively solves the technical problems of single acoustic energy distribution, insufficient radial mixing, crystal agglomeration, or localized enrichment of fine powder in traditional ultrasonic winterization devices, improving overall crystal uniformity, centrifugal retention efficiency, and oxidation control level.

[0070] Please continue reading. Figure 1 , Figure 2 and Figure 3 And see Figure 5 In an embodiment of the present invention, the middle-layer gas distribution mechanism 500 includes a first mounting outer ring 510, a first mounting inner ring 520, a first main inlet pipe 530, a first inlet branch pipe 540, and a plurality of first outlet components 550. The first mounting outer ring 510 and the first mounting inner ring 520 are coaxially arranged with the crystallizer 100. The outer wall of the first mounting inner ring 520 is connected to the inner wall of the first mounting outer ring 510 through a first connecting rod. The first mounting outer ring 510 is sleeved outside the first mounting inner ring 520. The plurality of first outlet components... Multiple first gas outlets 550 are distributed circumferentially on the first outer mounting ring 510 and the first inner mounting ring 520 of the crystallization tank 100. The gas outlet ends of multiple first gas outlets 550 are all arranged upward toward the top nucleation layer 102. Multiple first gas outlets 550 on the first outer mounting ring 510 are connected through the first main air inlet pipe 530. Multiple first gas outlets 550 on the first inner mounting ring 520 are connected to the first main air inlet pipe 530 through the first air inlet branch pipe 540. The air inlet end of the first main air inlet pipe 530 is connected to an external nitrogen gas source.

[0071] Specifically, both the first outer mounting ring 510 and the first inner mounting ring 520 are 316L stainless steel annular structures. The two rings are coaxially arranged and maintain a certain radial distance. The diameter of the first outer mounting ring 510 is approximately 88% to 94% of the inner diameter of the crystallization tank 100, and the diameter of the first inner mounting ring 520 is approximately 45% to 65% of the inner diameter of the crystallization tank 100. The outer wall of the first inner mounting ring 520 is welded and fixed to the inner wall of the first outer mounting ring 510 by multiple (generally 6 to 12) evenly distributed first connecting rods. The first connecting rods are made of round bars or flat steel, and their length is adapted to the radial distance between the two rings to ensure the overall rigidity of the two rings and maintain a coaxiality deviation of less than 0.6 mm. The entire double-ring assembly is horizontally fixed at a predetermined height in the middle of the tank (usually located at 48% to 58% of the total height) by multiple fixing lugs on the outer side of the outer ring and welded supports or bolt assemblies on the tank wall.

[0072] Multiple first air outlets 550 are distributed at equal angular intervals along the circumference on the upper surfaces of the first mounting outer ring 510 and the first mounting inner ring 520. Each air outlet is a sintered stainless steel microporous short tube or multi-hole nozzle, with an orifice diameter generally ranging from 2.0 to 4.8 mm. The air outlet end faces upward and is perpendicular to the horizontal plane or slightly inclined inward at an angle of less than 5 degrees. The number of air outlets on the outer ring usually depends on the circumference of the outer ring (commonly 24 to 48), while the number of air outlets on the inner ring is correspondingly reduced (commonly 12 to 28) to ensure a match in the total air output of the inner and outer rings.

[0073] The gas supply path is as follows: an external high-purity nitrogen source enters the system through the first main inlet pipe 530 (usually introduced from the side of the tank wall or the bottom flange). The main inlet pipe extends radially to the inside of the first mounting outer ring 510 and then splits into multiple paths. All gas outlets on the first mounting outer ring 510 are directly connected to the annular cavity of the main inlet pipe. Simultaneously, one or more first inlet branch pipes 540 branch off from the main inlet pipe near the center. The first inlet branch pipes 540 extend upwards or horizontally to below the first mounting inner ring 520, and then connect to all gas outlets on the inner ring through the annular distribution cavity at the bottom of the inner ring. The inner and outer ring gas paths can be finely adjusted through valves or throttle orifices, but they usually share the same main inlet pipe to ensure synchronous opening.

[0074] During the crystallization separation stage (when the oil temperature drops to approximately 13–11°C and a certain number of fine crystal nuclei have formed), the control system rapidly increases the nitrogen flow rate to 0.32–0.78 vvm and maintains it for 6–13 minutes. At this time, the outer ring outlet first generates a relatively dense rising bubble flow near the tank wall, while the inner ring outlet replenishes the bubbles in the central area. As the bubbles rise, they gradually diffuse laterally and merge, forming a continuous high-density bubble layer with a thickness of approximately 90–240 mm and a radial coverage of 82%–93% (the local peak gas holdup can reach 22%–38%) near the middle layer height.

[0075] The bubble layer generates strong interfacial reflection, scattering, and absorption of downward-propagating sound waves from the upper ultrasonic generator 200, causing the sound intensity passing through the bubble layer to decrease to 28%–45% of its original value. However, below the bubble layer (the main operating area of ​​the middle ultrasonic generator 300), a moderate sound intensity (approximately 65%–85% of its original value) can still be maintained. Simultaneously, since the outlet ends are all positioned upwards, the initial upward direction of the bubbles is vertically upwards, consistent with gravity and the direction of sound flow. This facilitates the formation of a stable transverse gas-liquid interface in the interface region, rather than localized turbulent aggregation.

[0076] In one specific embodiment (flaxseed oil), the first outer ring 510 has 36 air outlets (3.2 mm aperture), the first inner ring 520 has 18 air outlets (3.8 mm aperture), the radial distance between the inner and outer rings is about 180 mm, and after a nitrogen flow rate of 0.52 vvm for 9 min, the radial coverage of the bubble layer is about 89%, the proportion of fine crystal nuclei (<15 μm) at the top penetrating downwards is about 61% to 76% lower than when there is no middle layer gas curtain, and the crystal particle size span of the upper part of the crystal growth layer 104 is narrowed by about 0.31 to 0.49. In another specific embodiment (safflower seed oil), the outer ring has 28 air outlets and the inner ring has 16 air outlets, the flow rate is 0.45 vvm for 11 min, the effective thickness of the bubble layer is about 160 mm, the oil content of the wax residue after centrifugation is reduced by about 12% to 21%, and the increase in peroxide value is controlled within 1.0 meq / kg.

[0077] This embodiment addresses the key technical problem in the crystallization separation stage of high polyunsaturated fatty acid oils: "incomplete radial coverage of the bubble layer, easy formation of acoustic leakage channels in the central region, resulting in unstable acoustic-gas isolation effect, and uncontrolled downward penetration of fine crystal nuclei into the crystal growth layer 104." It works in conjunction with the horizontal radiating surface of the middle ultrasonic generator 300 towards the center and the downward tilting radiating surface of the upper ultrasonic generator 200 to form a stable transverse high-density bubble barrier and a vertical acoustic intensity gradient at the interface height. This effectively solves the technical problems of uneven gas curtain, isolation failure, severe axial contamination of crystals, low subsequent separation efficiency, and product quality fluctuations in traditional ultrasonic-assisted winterization processes.

[0078] Please continue reading. Figure 1 , Figure 2 and Figure 3 And see Figure 6In an embodiment of the present invention, the bottom gas distribution mechanism 600 includes a second mounting outer ring 610, a second mounting inner ring 620, a second main inlet pipe 630, a second inlet branch pipe 640, and a plurality of second outlet components 650. The second mounting outer ring 610 and the second mounting inner ring 620 are coaxially arranged with the crystallizer 100. The outer wall of the second mounting inner ring 620 is connected to the inner wall of the second mounting outer ring 610 through a second connecting rod. The second mounting outer ring 610 is sleeved outside the first mounting inner ring 520. The plurality of second outlet components 650 are arranged along... The crystallization tank 100 is circumferentially distributed on the second mounting outer ring 610 and the second mounting inner ring 620. The outlet ends of the multiple second gas outlets 650 are all arranged upward towards the nucleation layer 103 and the crystal growth layer 104 in the middle. The multiple second gas outlets 650 on the second mounting outer ring 610 are connected through the second main air inlet pipe 630. The multiple second gas outlets 650 on the second mounting inner ring 620 are connected to the second main air inlet pipe 630 through the second air inlet branch pipe 640. The air inlet end of the second main air inlet pipe 630 is connected to an external nitrogen gas source.

[0079] Specifically, both the second outer mounting ring 610 and the second inner mounting ring 620 are 316L stainless steel ring structures. The two rings are strictly coaxially arranged and maintain a radial distance. The diameter of the second outer mounting ring 610 is typically 82%–92% of the inner diameter of the crystallizing tank 100, and the diameter of the second inner mounting ring 620 is approximately 38%–58% of the inner diameter of the crystallizing tank 100. The outer wall of the second inner mounting ring 620 is welded and fixed to the inner wall of the second outer mounting ring 610 by multiple (generally 8–16) evenly distributed second connecting rods. The second connecting rods are made of solid round bars or reinforced flat steel to ensure the overall rigidity and deformation resistance of the assembly, with the coaxiality deviation controlled within 0.5 mm. The entire double-ring assembly is connected to the bottom dish head or the lower cylindrical reinforcing ring of the tank through multiple fixed supports welded to the outer side of the outer ring. The installation height is generally 80–220 mm from the bottom plane of the tank (adjusted according to the tank height and the expected thickness of the 104 crystal growth layer).

[0080] Multiple second air outlets 650 are fixed at equal angular intervals along the circumference to the upper surfaces of the second mounting outer ring 610 and the second mounting inner ring 620. Each air outlet is made of food-grade sintered stainless steel microporous tube or precision drilled nozzle, with the orifice diameter typically controlled between 0.8 and 2.5 mm. The air outlet end faces upward and is perpendicular to the horizontal plane or slightly inclined inward at 3° to 8°. The number of air outlets in the outer ring is generally larger (commonly 32 to 64), while the number of air outlets in the inner ring is correspondingly reduced (commonly 16 to 36) to ensure a balanced total amount of bubbles generated in the inner and outer regions.

[0081] The gas supply path is as follows: an external high-purity nitrogen source enters the system via the second main inlet pipe 630 (usually introduced from the center of the tank bottom or the lower side flange). The main inlet pipe extends radially to below the second mounting outer ring 610, forming an annular distribution chamber. All the second outlet components 650 on the outer ring are directly connected to this annular chamber. Simultaneously, a second inlet branch pipe 640 branches off from the main inlet pipe near the center. The second inlet branch pipe 640 extends upward to below the second mounting inner ring 620, and then connects to all the second outlet components 650 on the inner ring through the annular distribution chamber at the bottom of the inner ring. During normal operation, the inner and outer ring gas paths share the same main inlet pipe, and a slight balance is achieved through the flow regulating valve and branch throttling orifice on the main pipe.

[0082] Throughout the crystallization process, the bottom gas distribution mechanism 600 maintains a constant low flow rate (typically 0.025–0.15 vvm), generating fine bubbles with diameters primarily ranging from 0.6 to 3.2 mm. These bubbles are released vertically upwards from the outer and inner ring outlets, slowly rising in the high-viscosity grease, generating continuous localized upward flow and micro-shearing action along their path. During the crystal growth stage (when the oil temperature stabilizes between 7 and 11°C), these fine bubbles, combined with the upward-tilted (5°–10°) acoustic radiation from the lower ultrasonic generator 400, provide upward buoyancy and gentle disturbance. The lower acoustic radiation provides axial acoustic pressure. The combined effect creates a stable, weakly disturbed suspended flow field in the crystal growth layer 104, ensuring uniform suspension of crystal particles (typically 50–130 μm in size), preventing the formation of a dense deposition layer or hardened dead zone at the bottom, while ensuring the disturbance intensity is insufficient to cause significant breakage of the grown crystals.

[0083] In one specific embodiment (flaxseed oil), the second outer ring 610 has 48 air outlets (1.6 mm aperture), the second inner ring 620 has 24 air outlets (2.0 mm aperture), the radial distance between the inner and outer rings is about 210 mm, the nitrogen flow rate is 0.08 vvm continuously throughout the process, the thickness of the bottom deposit layer is reduced by about 71% to 87% compared with the absence of bottom gas distribution, and the oil content of the wax residue is reduced by about 15% to 23% after centrifugation. In another specific embodiment (safflower seed oil), the outer ring has 40 air outlets and the inner ring has 20 air outlets, the flow rate is 0.06 vvm, the bottom dead zone volume ratio is reduced by about 78% to 92%, the average crystal volume particle size D[4,3] is increased by about 18 to 27 μm, the filtration cycle is shortened by about 25% to 34%, and the peroxide value increase is controlled at 0.8 to 1.2 meq / kg.

[0084] This embodiment addresses the core technical problem in the low-temperature crystal growth stage of high polyunsaturated fatty acid oils: "rapid crystal settling at the bottom, easy formation of a dense slab layer, resulting in uneven suspension, easy clogging or wax run-off during separation, and a significant decrease in yield and product quality stability." Together with the upward tilted radiation surface of the lower ultrasonic generator 400, the instantaneous high-density air curtain isolation in the middle layer, and the axial gradient of the upper and middle sound fields, it constitutes a complete bottom suspension and axial partitioning control system. This effectively solves the technical problems of severe bottom deposition, uncontrolled axial distribution of crystals, low centrifugal separation efficiency, and difficulty in oxidation control in traditional physical winterization and ultrasonic-assisted winterization processes.

[0085] Please continue reading. Figure 5 and Figure 6 In an embodiment of the present invention, the diameter of the outlet end of the first air outlet 550 is larger than the diameter of the outlet end of the second air outlet 650.

[0086] Specifically, the outlet diameter of the first air outlet 550 (middle layer) is typically 2.8 mm to 5.2 mm, and the outlet diameter of the second air outlet 650 (bottom layer) is typically 0.6 mm to 2.4 mm. The difference between the two outlet diameters is generally controlled within the range of 1.2 mm to 3.5 mm. In one specific embodiment, the outlet diameter of the first air outlet 550 is 3.8 mm, and the outlet diameter of the second air outlet 650 is 1.4 mm; in another specific embodiment, the outlet diameter of the first air outlet 550 is 4.5 mm, and the outlet diameter of the second air outlet 650 is 1.9 mm.

[0087] The difference in pore size directly determines the initial size and rising behavior of bubbles: Under the same gas flow rate, the initial diameter of bubbles generated by the first gas outlet 550 with a larger pore size is significantly larger (usually 3.5 to 9.0 mm). In high-viscosity greases, these larger bubbles rise faster and have a stronger tendency to coalesce, which is conducive to rapid lateral expansion near the middle layer height in a short time (usually within 3 to 8 seconds) and the formation of a continuous, thick lateral bubble curtain (thickness of about 80 to 260 mm, with local gas holdup peaks reaching 24% to 41%).

[0088] Conversely, the second vent 650 with a smaller aperture produces bubbles with smaller initial diameters (typically 0.5–3.0 mm), lower aggregation during ascent, and relatively dispersed and fine bubbles within the crystal growth layer 104. The rising speed is slower (typically 0.8–4.2 cm / s), which can continuously provide a relatively uniform small upward flow and local shear disturbance without forming strong turbulence or a large bubble aggregation zone near the bottom.

[0089] During the crystallization separation stage (oil temperature approximately 12.5–10.8℃), when the middle gas distribution mechanism 500 is instantaneously increased to a higher flow rate (0.30–0.82 vvm, lasting 6–14 min), the first gas outlet 550 rapidly releases a large number of large-sized bubbles due to its larger aperture. These bubbles rapidly diffuse and merge laterally during their ascent, forming a dense bubble barrier at the junction of the middle nucleation layer 103 and the top nucleation layer 102. This barrier strongly reflects and attenuates the sound waves propagating downwards from the upper ultrasonic generator 200, maintaining the sound intensity below the bubble layer at 62%–88% of its original value, while significantly reducing the sound intensity above it to 22%–48% of its original value. This achieves effective acoustic-material exchange barrier between the top nucleation layer 102 and the crystal growth layer 104, significantly reducing the disordered downward penetration of fine crystal nuclei (<14 μm).

[0090] Meanwhile, the bottom gas distribution mechanism 600 maintains a low flow rate (0.020~0.14vvm) and continues to operate. The fine bubbles released by the second gas outlet 650 are superimposed with the acoustic radiation from the lower ultrasonic generator 400 tilted upward at 5°~10°, forming a stable weak disturbance suspension flow field in the crystal growth layer 104. This keeps the crystal particles that have grown to 50~140μm in uniform suspension, avoiding the formation of a dense deposition layer or caking area at the bottom. At the same time, the disturbance intensity is insufficient to cause significant secondary breakage of the crystal.

[0091] In one specific embodiment (flaxseed oil), the first air outlet 550 has a pore size of 3.8 mm and the second air outlet 650 has a pore size of 1.4 mm. After a mid-layer instantaneous flow rate of 0.58 vvm for 10 min, the effective radial coverage of the bubble layer reaches 91%. The proportion of fine crystal nuclei migrating downwards from the top decreases by approximately 57% to 73% compared to the case with the same pore size. The deposition thickness at the bottom of the crystal growth layer 104 decreases by approximately 74% to 89%. After centrifugation, the oil content of the wax residue decreases by approximately 13% to 22%. In another specific embodiment (safflower seed oil), the first air outlet 550 has a pore size of 4.5 mm and the second air outlet 650 has a pore size of 1.9 mm. After a mid-layer flow rate of 0.49 vvm for 12 min, the bubble layer thickness is approximately 195 mm. The standard deviation of the axial particle size of the crystals narrows by approximately 0.28 to 0.46. The filtration resistance decreases by approximately 19% to 28%, and the peroxide value increase is controlled at 0.7 to 1.1 meq / kg.

[0092] This embodiment addresses the differentiated needs of two key stages in the ultrasonic-assisted crystallization process of high polyunsaturated fatty acid oils: "the crystallization separation stage requires the rapid formation of a thick and dense lateral bubble barrier to achieve strong isolation" and "the crystal growth stage requires continuous, gentle, and dispersed fine bubbles to maintain crystal suspension without damaging the grown crystals." By making the vent diameter of the middle layer significantly larger than that of the bottom layer, layered control of bubble size and behavior is achieved at different heights and functional stages. This, combined with the ultrasonic radiation surface that is downward-sloping in the upper layer, horizontal in the middle layer, and upward-sloping in the lower layer, as well as the time-segmented gas flow control, effectively solves the technical problems in traditional ultrasonic winterization processes, such as the single bubble distribution, inability to simultaneously meet the requirements of rapid isolation and gentle suspension, resulting in severe fine powder penetration or bottom deposition and caking, low separation efficiency, and unstable oxidation control.

[0093] In an embodiment of the present invention, the upper ultrasonic generator 200 operates at a frequency of 20kHz to 30kHz and a power density of 15W / cm². 2 ~35W / cm 2 It is used for high-power or intermittent operation in the early stage of cooling nucleation; the middle layer ultrasonic generator 300 operates at a frequency of 35kHz to 55kHz and a power density of 8W / cm³. 2 ~20W / cm 2 It is used to operate in conjunction with the gas curtain formation stage of the middle-layer gas distribution mechanism 500; the lower-layer ultrasonic generator 400 operates at a frequency of 55kHz to 90kHz and a power density of 5W / cm³. 2 ~15W / cm 2 The first gas distribution mechanism 500 is used to operate continuously at low power throughout the crystallization process; the second gas distribution mechanism 500 is used to be turned on momentarily during the crystallization separation stage, with a gas flow rate of 0.3vvm to 0.8vvm and a duration of 6min to 12min, to form a medium-sized bubble layer of 3mm to 8mm; the third gas distribution mechanism 600 is used to be turned on continuously throughout the entire crystallization process, with a gas flow rate of 0.05vvm to 0.15vvm, to generate a fine bubble flow of 1mm to 3mm.

[0094] Specifically, the upper ultrasonic generator 200 uses a lower frequency (20kHz~30kHz) and a higher power density (15W / cm²). 2 ~35W / cm 2In the initial cooling phase (when the oil temperature typically drops from 45–38°C to approximately 22–18°C during the nucleation and explosion stage), the system operates continuously at high power or intermittently at high duty cycle (e.g., a cycle mode of running for 3–8 minutes and pausing for 1–3 minutes). At this time, the system viscosity is still relatively low, the cavitation threshold is low, and the low-frequency high power easily generates strong transient cavitation bubbles and strong acoustic flow and microjets, effectively promoting the rapid generation of a large number of fine crystal nuclei (<12μm), while suppressing the early agglomeration of existing crystal nuclei through strong perturbation.

[0095] The 300-type mid-layer ultrasonic generator uses a medium frequency (35kHz~55kHz) and a medium power density (8W / cm²). 2 ~20W / cm 2 During the crystallization separation stage, the intermediate gas distribution mechanism is strictly activated in conjunction with a 500-second instantaneous high flow rate (0.3V / vm to 0.8V / vm, lasting 6 to 12 minutes). At this time, a high-density bubble layer with a thickness of approximately 80 to 250 mm is formed in the intermediate layer, consisting of medium-sized bubbles of 3 mm to 8 mm. This significantly attenuates the low-frequency strong sound waves propagating downwards from the upper layer (the sound intensity is usually reduced to 25% to 48% of the original value), while the intermediate-frequency sound radiation of the intermediate layer itself still maintains a relatively high effective intensity below the bubble layer (approximately 60% to 85% of the original value). This achieves a vertical sound intensity gradient of "stronger at the top and weaker at the bottom" in the interface region, which is conducive to the continued generation and dispersion of fine crystal nuclei at the top, while the lower part of the nucleation layer 103 and the upper part of the crystal growth layer 104 are in a relatively mild disturbance environment.

[0096] The lower ultrasonic generator 400 uses a higher frequency (55kHz~90kHz) and a lower power density (5W / cm²). 2 ~15W / cm 2 Throughout the entire crystallization process (from the start of cooling to the end of crystal growth), the system maintains low-power continuous operation. At this point, the viscosity of the system has increased significantly. Higher frequency sound waves have a shorter penetration distance and faster attenuation in viscous media, but their cavitation bubble size is small and their collapse energy is low. The resulting acoustic flow and radiation pressure are relatively mild. When superimposed with the 1mm to 3mm fine bubble flow continuously released by the bottom gas distribution mechanism 600, a stable weakly disturbed suspension field is formed in the crystal growth layer 104, which keeps the crystal particles that have grown to 50 to 140μm in uniform suspension, avoiding severe deposition or caking at the bottom. At the same time, the disturbance intensity is insufficient to cause significant breakage of larger crystals or an increase in surface defects.

[0097] In one specific embodiment (flaxseed oil), the upper layer uses 24kHz, power density 28W / cm³. 2It operates at high power until the temperature drops to 20℃. The middle layer uses 42kHz and a power density of 14W / cm2, linked with a 0.55VVM*9min air curtain in the middle layer, while the lower layer uses 68kHz and a power density of 9W / cm2. 2 The entire process operates at low power, with a fine bubble flow of 0.09 vvm maintained at the bottom layer. The final average volumetric particle size D of the crystals is 78–92 μm, the particle size distribution span is 0.78–0.94, the bottom deposition thickness is reduced by about 76%–91% compared to when there is no stratification parameter control, the oil content of the wax residue is reduced by about 14%–23% after centrifugation, and the peroxide value increase is controlled at 0.6–1.0 meq / kg.

[0098] In another specific embodiment (safflower seed oil), the upper layer uses a 26kHz frequency and a power density of 31W / cm². 2 Intermittent operation, with the middle layer operating at 48kHz and a power density of 12W / cm². 2 Linked with a 0.48VVM*11min air curtain, the lower layer uses 75kHz and a power density of 7.5W / cm². 2 Throughout the entire process, a fine bubble flow of 0.07 vvm is maintained at the bottom layer; the standard deviation of the axial particle size of the resulting crystal is reduced by about 0.31 to 0.47 compared with the traditional uniform sound field, the filtration resistance is reduced by about 21% to 29%, the oil content of the wax residue is reduced by about 12% to 20%, and the oxidation increment is controlled within 0.8 meq / kg.

[0099] This embodiment addresses the significant differences in disturbance intensity, cavitation characteristics, bubble behavior, and acoustic-gas interaction requirements at different stages of the ultrasonic-assisted crystallization process of high polyunsaturated fatty acid oils. By achieving an axial acoustic intensity and frequency gradient ranging from "low-frequency high power to mid-frequency medium power linked air curtain to high-frequency low power," and bubble stratification control through "instantaneous medium bubble barrier + continuous fine bubble suspension," a composite field distribution is formed, characterized by strong nucleation at the top, controlled transition in the middle, and gentle crystal growth at the bottom. This effectively solves the technical problems of traditional ultrasonic winterization processes, such as single acoustic field parameters, inability to match the needs of different crystallization stages, insufficient or excessive nucleation, severe downward penetration of fine powder, bottom deposition and caking, uneven crystal distribution, low separation efficiency, and poor oxidation control.

[0100] Please continue reading. Figures 1 to 6 The present invention also proposes a physical refining method for edible oils rich in polyunsaturated fatty acids. This physical refining method utilizes the aforementioned physical refining apparatus for edible oils rich in polyunsaturated fatty acids. The physical refining method for edible oils rich in polyunsaturated fatty acids includes: Step S10: The edible oil rich in polyunsaturated fatty acids, which has been degummed by membrane method, is placed in the crystallization tank 100 and subjected to controlled cooling crystallization under inert gas protection; In step S20, during the cooling nucleation stage, the upper ultrasonic generator 200 is activated to generate local cavitation and micro-turbulence disturbances, thereby suppressing the excessive generation of fine crystal nuclei and crystal agglomeration in the top nucleation layer 102. In step S30, during the crystallization separation stage, the middle layer gas distribution mechanism 500 is activated to form a high-density bubble layer to create a hydrodynamic isolation zone between the top nucleation layer 102 and the crystal growth layer 104. At the same time, the middle layer ultrasonic wave generator 300 is activated to provide acoustic radiation and local circulation, so as to form a vertical acoustic intensity gradient in cooperation with the middle layer gas distribution mechanism 500, thereby promoting the controlled transport of crystal nuclei or small crystals to the crystal growth layer 104. In step S40, during the crystal growth stage, the lower ultrasonic generator 400 is activated to provide acoustic levitation and bottom driving effects, so as to compensate for the attenuation of sound waves by the middle bubble layer and maintain an orderly growth environment at the bottom of the crystal growth layer 104. At the same time, the bottom gas distribution mechanism 600 is activated to continuously provide a low-flow upward diffused bubble flow to maintain crystal suspension and prevent bottom deposition. In step S50, after crystallization, the obtained crystal slurry is separated by low-temperature centrifugation to obtain winterized oil and wax.

[0101] It should be noted that the specific structure of the physical refining device for edible oil rich in polyunsaturated fatty acids is as described in the above embodiments. Since this physical refining method for edible oil rich in polyunsaturated fatty acids adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0102] Specifically, in step S10, edible oils rich in polyunsaturated fatty acids (such as flaxseed oil, safflower seed oil, perilla seed oil, etc.) that have undergone membrane degumming and typically contain 4.5% to 12.0% wax are pumped into crystallization tank 100 at 40 to 55°C. The liquid level is controlled at 78% to 92% of the effective volume of the tank. The bottom and middle layer gas distribution mechanism 500 is activated to introduce high-purity nitrogen gas (purity ≥99.99%) at an extremely low flow rate (0.01 to 0.04 vvm) to remove air from the tank and establish a slightly positive pressure (0.01 to 0.04 MPa) inert protective environment. Then, programmed cooling is started at a rate of 0.8 to 1.6°C / min.

[0103] In the cooling and nucleation stage of step S20 (the oil temperature generally drops from the initial temperature to about 23-17°C), the upper ultrasonic generator 200 is activated (frequency 20-30kHz, power density 15-35W / cm³). 2The system operates continuously at high power or in a high-duty-cycle intermittent mode (e.g., running for 4–9 minutes and pausing for 1–4 minutes), generating intense transient cavitation and violent acoustic flow, microjets, and radial turbulence within the top nucleation layer 102. At this time, the system viscosity is low, and the high-energy microjets released by the collapse of cavitation bubbles and the local high temperature and pressure effectively disrupt the orderly stacking between wax molecules, promoting the explosive generation of a large number of fine crystal nuclei (mainly <13 μm in size). At the same time, the strong perturbation inhibits the early aggregation or wall-attached growth of these fine crystal nuclei in the top region.

[0104] During the crystallization separation stage of step S30 (when the oil temperature drops to approximately 16–11°C, a considerable number of fine crystal nuclei have been generated and have begun to grow slowly), the flow rate of the intermediate gas distribution mechanism 500 is instantaneously increased to 0.3–0.8 vvm and maintained for 6–12 minutes. Simultaneously, the intermediate ultrasonic generator 300 (frequency 35–55 kHz, power density 8–20 W / cm³) is activated. 2 Medium-sized bubbles (3-8 mm) released from the middle-layer venting component rise rapidly, diffuse laterally, and coalesce, forming a high-density bubble layer with a thickness of approximately 90-260 mm and a radial coverage of 82%-94% near the junction of the middle nucleation layer 103 and the top nucleation layer 102. This bubble layer significantly reflects, scatters, and absorbs the low-frequency, strong sound waves propagating downwards from the upper layer, causing the sound intensity passing through the bubble layer to attenuate to 24%-47% of its original value. Simultaneously, the mid-frequency sound radiation from the middle-layer ultrasonic generator 300 maintains a relatively high effective intensity (approximately 58%-86% of its original value) below the bubble layer, thus forming a significant vertical sound intensity gradient. This gradient, combined with the hydrodynamic damping barrier formed by the bubble layer, allows the top nucleation layer 102 to maintain a high disturbance intensity to suppress aggregation, while the upper part of the crystal growth layer 104 is in a relatively quiet environment. This facilitates the controlled downward transport of existing crystal nuclei or small crystals and their continued orderly growth, preventing the disorderly infiltration and contamination of the crystal growth layer 104 by a large amount of fine powder.

[0105] In the crystal growth stage of step S40 (oil temperature stabilized in the range of 8-12℃, typically maintained for 45-180 min), the middle layer gas distribution mechanism 500 is kept closed or restored to an extremely low flow rate, the upper layer ultrasonic generator 200 has its power significantly reduced or is turned off, and the lower layer ultrasonic generator 400 operates at 55-90 kHz with a power density of 5-15 W / cm². 2Operating at continuously low power, its upward-sloping acoustic radiation generates axial acoustic flow pressure and acoustic levitation force. Simultaneously, the bottom gas distribution mechanism 600 maintains a low flow rate of 0.05–0.15 vvm, continuously releasing fine bubble flows of 1–3 mm. These fine bubbles, superimposed with the lower layer acoustic radiation, form a stable upward weakly disturbed levitation flow field within the crystal growth layer 104. This keeps the crystal particles, which have grown to 50–150 μm, in a uniformly suspended state, preventing the formation of a dense, plate-like layer or dead zone at the bottom due to gravitational settling. At the same time, the intensity of this disturbance is strictly controlled to a level insufficient to cause significant surface breakage or secondary nucleation of larger crystals, thereby maintaining a relatively ordered and slow crystal growth environment in the lower part of the crystal growth layer 104.

[0106] In step S50, when crystallization is complete, the crystal slurry in the tank is cooled to 5-10°C and transferred to a low-temperature centrifuge (typically 4800-6800 r / min, temperature controlled at 4-12°C) through the bottom discharge valve for solid-liquid separation to obtain winterized oil with high clarity and low wax residue and wax grease with low oil content.

[0107] In one specific embodiment (flaxseed oil, initial wax content 8.7%), the above five-step method was adopted. The upper layer was run at high power of 24kHz to 19℃, the middle layer was separated by a 45kHz air curtain with a 0.56 vvm×10 min linkage, the lower layer was run at low power throughout, and the bottom layer was kept suspended by a fine bubble flow of 0.085 vvm. In the final winterized oil freezing test (-18℃, 24h), there was no wax precipitation, the wax content was 11.4%~13.8%, the peroxide value increased by 0.5~0.9 meq / kg, the average crystal particle size was 81~94μm, and the particle size distribution range was 0.76~0.91.

[0108] In another specific embodiment (safflower seed oil, initial wax content 6.9%, tank diameter 920mm), the upper layer was intermittently run at 27kHz to 17.5℃, the middle layer was linked with a 0.47vvm*11min air curtain at 51kHz, the lower layer was run at low power at 78kHz, and the bottom layer had a fine bubble flow of 0.068vvm. The winterized oil showed no visible crystal precipitation in the -15℃ stability test, the wax and grease oil content was 9.8%~12.6%, the peroxide value increased by 0.6~1.0meq / kg, the axial particle size variation coefficient of crystals was reduced by about 0.34~0.48 compared with the traditional method, and the centrifugation separation efficiency was improved by about 22%~31%.

[0109] This embodiment addresses a series of core technical problems encountered during the ultrasonic-assisted low-temperature crystallization of edible oils rich in polyunsaturated fatty acids. These problems include: difficulty in balancing nucleus generation and agglomeration during the nucleation stage; uncontrolled downward penetration of fine powder during the separation stage, leading to contamination of the crystal growth layer 104; severe bottom deposition during the crystal growth stage causing separation difficulties; and difficulty in balancing oxidation control and crystal uniformity. By implementing a combination of control measures at different crystallization stages—including strong nucleation disturbances in the upper layer, coordinated isolation by a gas curtain and mid-frequency acoustic radiation in the middle layer, and combined suspension of weak high-frequency disturbances and fine bubbles in the lower layer—this embodiment achieves zoned regulation, characterized by strong nucleation at the top, controlled transition in the middle, and gentle and orderly growth at the bottom. This effectively solves the technical defects of traditional physical winterization and existing ultrasonic winterization processes, such as single disturbance during crystallization, uncontrolled axial crystal distribution, severe fine powder penetration, bottom caking, low separation efficiency, and large oxidation increment. It significantly improves the quality stability of winterized oil, the control level of wax and grease oil content, and the overall yield.

[0110] The above description is merely an exemplary embodiment of the present invention and does not limit the scope of protection of the present invention. Any equivalent structural transformations made based on the technical concept of the present invention and the contents of the specification and drawings of the present invention, or direct / indirect applications in other related technical fields, are included within the scope of protection of the present invention.

Claims

1. A physical refining apparatus for a polyunsaturated fatty acid-rich edible oil, characterized by comprising: The application relates to a crystallization tank. The crystallization tank comprises a containing space arranged in the crystallization tank, wherein the containing space is sequentially formed by a top nucleation layer, a middle nucleation layer and a crystal growth layer from top to bottom along the axial direction of the crystallization tank. An upper layer ultrasonic wave generating mechanism is arranged in the top nucleation layer. A middle layer ultrasonic wave generating mechanism is arranged at the junction of the middle nucleation layer and the top nucleation layer. A lower layer ultrasonic wave generating mechanism is arranged at the junction of the middle nucleation layer and the crystal growth layer. A middle layer gas distribution mechanism is arranged in the top nucleation layer and is arranged between the upper layer ultrasonic wave generating mechanism and the middle layer ultrasonic wave generating mechanism. A bottom layer gas distribution mechanism is arranged in the crystal growth layer and is arranged below the lower layer ultrasonic wave generating mechanism.

2. The physical refining apparatus for polyunsaturated fatty acid-rich edible oil according to claim 1, wherein The upper layer ultrasonic wave generating mechanism comprises an upper layer mounting flange and a plurality of upper layer ultrasonic wave generating modules, the upper layer mounting flange is coaxially arranged with the crystallization tank and is sleeved outside the crystallization tank, the plurality of upper layer ultrasonic wave generating modules are spaced apart and mounted on the upper layer mounting flange along the circumferential direction of the crystallization tank, the radiation surfaces of the plurality of upper layer ultrasonic wave generating modules all extend into the top nucleation layer, the radiation surfaces of the plurality of upper layer ultrasonic wave generating modules are all arranged towards the central axis of the crystallization tank, the radiation surfaces of the plurality of upper layer ultrasonic wave generating modules are all arranged in a downward inclination, and the radiation surfaces of the plurality of upper layer ultrasonic wave generating modules are all arranged at a first included angle with the horizontal plane, the first included angle is alpha, 5 DEG ≤ alpha ≤ 10 DEG.

3. The physical refining apparatus for polyunsaturated fatty acid-rich edible oil according to claim 2, wherein The middle layer ultrasonic wave generating mechanism comprises a middle layer mounting flange and a plurality of middle layer ultrasonic wave generating modules, the middle layer mounting flange is coaxially arranged with the crystallization tank and is sleeved outside the crystallization tank, the plurality of middle layer ultrasonic wave generating modules are spaced apart and mounted on the middle layer mounting flange along the circumferential direction of the crystallization tank, the radiation surfaces of the plurality of middle layer ultrasonic wave generating modules all extend into the junction of the middle nucleation layer and the top nucleation layer, the radiation surfaces of the plurality of middle layer ultrasonic wave generating modules are all arranged towards the central axis of the crystallization tank, and the radiation surfaces of the plurality of middle layer ultrasonic wave generating modules are all arranged along the horizontal direction.

4. The physical refining apparatus for polyunsaturated fatty acid-rich edible oil according to claim 3, wherein The lower layer ultrasonic wave generating mechanism comprises a lower layer mounting flange and a plurality of lower layer ultrasonic wave generating modules, the lower layer mounting flange is coaxially arranged with the crystallization tank and is sleeved outside the crystallization tank, the plurality of lower layer ultrasonic wave generating modules are spaced apart and mounted on the lower layer mounting flange along the circumferential direction of the crystallization tank, the radiation surfaces of the plurality of lower layer ultrasonic wave generating modules all extend into the junction of the middle nucleation layer and the crystal growth layer, the radiation surfaces of the plurality of lower layer ultrasonic wave generating modules are all arranged towards the central axis of the crystallization tank, the radiation surfaces of the plurality of lower layer ultrasonic wave generating modules are all arranged in an upward inclination, and the radiation surfaces of the plurality of lower layer ultrasonic wave generating modules are all arranged at a second included angle with the horizontal plane, the second included angle is beta, 5 DEG ≤ beta ≤ 10 DEG.

5. The physical refining apparatus for polyunsaturated fatty acid-rich edible oil according to claim 4, wherein The upper layer ultrasonic wave generating modules, the middle layer ultrasonic wave generating modules and the lower layer ultrasonic wave generating modules are staggered in the orthographic projection of the bottom of the crystallization tank.

6. The physical refining apparatus for polyunsaturated fatty acid-rich edible oil according to claim 5, wherein The middle layer gas distribution mechanism comprises a first mounting outer ring, a first mounting inner ring, a first main gas inlet pipe, a first gas inlet branch pipe and a plurality of first gas outlets, the first mounting outer ring and the first mounting inner ring are coaxially arranged with the crystallization tank, the outer wall of the first mounting inner ring is connected with the inner wall of the first mounting outer ring through a first connecting rod, the first mounting outer ring is sleeved outside the first mounting inner ring, a plurality of first gas outlets are distributed on the first mounting outer ring and the first mounting inner ring along the circumference of the crystallization tank, the gas outlet ends of the plurality of first gas outlets are all arranged upward towards the top nucleation layer, the plurality of first gas outlets on the first mounting outer ring are communicated through the first main gas inlet pipe, the plurality of first gas outlets on the first mounting inner ring are communicated with the first main gas inlet pipe through the first gas inlet branch pipe, and the gas inlet end of the first main gas inlet pipe is communicated with an external nitrogen gas source.

7. The physical refining apparatus for polyunsaturated fatty acid-rich edible oil according to claim 6, wherein The bottom layer gas distribution mechanism comprises a second mounting outer ring, a second mounting inner ring, a second main gas inlet pipe, a second gas inlet branch pipe and a plurality of second gas outlets, the second mounting outer ring and the second mounting inner ring are coaxially arranged with the crystallization tank, the outer wall of the second mounting inner ring is connected with the inner wall of the second mounting outer ring through a second connecting rod, the second mounting outer ring is sleeved outside the first mounting inner ring, a plurality of second gas outlets are distributed on the second mounting outer ring and the second mounting inner ring along the circumference of the crystallization tank, the gas outlet ends of the plurality of second gas outlets are all arranged upward towards the middle nucleation layer and the crystal growing layer, the plurality of second gas outlets on the second mounting outer ring are communicated through the second main gas inlet pipe, the plurality of second gas outlets on the second mounting inner ring are communicated with the second main gas inlet pipe through the second gas inlet branch pipe, and the gas inlet end of the second main gas inlet pipe is communicated with an external nitrogen gas source.

8. The physical refining apparatus for polyunsaturated fatty acid-rich edible oil according to claim 7, wherein The gas outlet end aperture of the first gas outlet is larger than that of the second gas outlet.

9. The physical refining apparatus for polyunsaturated fatty acid-rich edible oil according to any one of claims 1 to 8, characterized in that, The upper ultrasonic generator operates at a frequency of 20kHz to 30kHz and a power density of 15W / cm². 2 ~35W / cm 2 It is used for high-power or intermittent operation in the early stage of cooling nucleation; the operating frequency of the middle layer ultrasonic generator is 35kHz to 55kHz, and the power density is 8W / cm³. 2 ~20W / cm 2 It is used to operate in conjunction with the gas curtain formation stage of the middle-layer gas distribution mechanism; the lower-layer ultrasonic generator operates at a frequency of 55kHz to 90kHz and a power density of 5W / cm². 2 ~15W / cm 2 The gas distribution mechanism is used to operate continuously at low power throughout the crystallization process; the middle layer gas distribution mechanism is used to be turned on momentarily during the crystallization separation stage, with a gas flow rate of 0.3vvm to 0.8vvm and a duration of 6min to 12min, to form a medium-sized bubble layer of 3mm to 8mm; the bottom layer gas distribution mechanism is used to be turned on continuously throughout the entire crystallization process, with a gas flow rate of 0.05vvm to 0.15vvm, to generate a fine bubble flow of 1mm to 3mm.

10. A method for the physical refining of a polyunsaturated fatty acid-rich edible oil, characterized in that The physical refining device for the polyunsaturated fatty acid-rich edible oil according to any one of claims 1 to 9, the physical refining method for the polyunsaturated fatty acid-rich edible oil comprises: The polyunsaturated fatty acid-rich edible oil subjected to membrane degumming is placed in the crystallization tank, and controlled cooling crystallization is performed under the protection of inert gas; In the nucleation stage of cooling, the upper layer ultrasonic wave generating mechanism is turned on to generate local cavitation and micro-turbulent disturbance to inhibit the excessive generation of fine crystal nuclei and the aggregation of crystals in the top nucleation layer; In the crystallization separation stage, the middle layer gas distribution mechanism is turned on to form a high-density bubble layer to form a hydrodynamic isolation zone between the top nucleation layer and the crystal growing layer, and the middle layer ultrasonic wave generating mechanism is turned on to provide acoustic radiation and local circulation to form a vertical acoustic intensity gradient in cooperation with the middle layer gas distribution mechanism to promote the controlled transport of crystal nuclei or fine crystals to the crystal growing layer; In the growth stage, the lower ultrasonic wave generating mechanism is turned on to provide acoustic levitation and bottom driving effect, so as to compensate the attenuation of the sound wave by the middle bubble layer and maintain the ordered growth environment of the lower part of the growth layer, and the bottom gas distribution mechanism is turned on to continuously provide a low-flow upward dispersion bubble flow to maintain the crystal suspension and prevent the bottom deposition. After the crystallization is completed, the obtained crystal slurry is subjected to low-temperature centrifugal separation to obtain winterized oil and wax.

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