Variable-frequency ultrasonic-assisted liquid material freeze concentration device and method

Abstract

The invention relates to a variable-frequency ultrasonic-assisted liquid material freeze concentration device and a liquid material freeze concentration method. According to the liquid material freeze concentration device, frequency conversion ultrasonic technology treatment is assisted on the basis of suspension type freeze concentration, frequency conversion ultrasonic treatment is applied in a freeze concentration phase change stage and an ice crystal curing (growth) stage, and a mechanical effect, a heat effect and a cavitation effect generated by ultrasonic are utilized to promote heat and mass transfer of materials, accelerate ice crystal formation and regulate and control the size of ice crystals; therefore, solute entrainment is reduced, and a concentrated solution with higher quality is obtained.

Description

Technical Field

[0001] The present application relates to the technical field of liquid material freeze concentration, and in particular to a liquid material freeze concentration device and method assisted by variable frequency ultrasound. Background Art

[0002] Currently, common liquid material concentration technologies include thermal concentration, membrane concentration (ultrafiltration, microfiltration, reverse osmosis), and freeze concentration.

[0003] Thermal concentration is carried out at high temperature, which consumes huge amounts of heat and has low thermal energy utilization. It can also lead to problems such as loss of heat-sensitive components, nutrients and aroma, affecting the quality of concentrated juice. Membrane concentration can be carried out continuously at room temperature without phase change, and is suitable for the treatment of heat-sensitive substances, but its disadvantage is that the membrane cost is high and membrane loss caused by membrane pollution is inevitable, which increases the operating cost of the separation process. Freeze concentration is a concentration method that utilizes the solid-liquid phase equilibrium between ice and aqueous solution. The dilute solution is cooled to below the freezing point (freezing point) of the aqueous solution so that part of the water freezes into ice crystals, and the ice crystals are separated to obtain a concentrated solution. Freeze concentration is a low-temperature concentration process that freezes and separates the water in the liquid material to increase the soluble solid content of the liquid material. It is a low-energy concentration method. It is not easy to cause the loss of volatile or heat-sensitive components and nutrients, and can also inhibit the growth of microorganisms.

[0004] Freeze concentration can be divided into progressive freeze concentration and suspended freeze concentration according to the ice crystal formation method. Progressive freeze concentration is a freezing method in which an ice layer is formed along the cooling surface and grows into a whole ice crystal. At the solid-liquid interface, the solute is expelled from the solid phase side to the liquid phase side to obtain concentrated juice. The progressive concentration supercooling is unstable and dendritic ice crystals are easily formed, causing serious ice crystal entrainment; in addition, as the ice layer thickens, the concentration rate decreases, the concentration efficiency becomes lower, and continuous operation is not possible. The ice crystals in suspended concentration have a large specific surface area and a faster concentration rate. At the same time, there is an ice crystal-solute separation procedure to reduce entrainment and achieve continuous production. Therefore, compared with progressive freeze concentration, suspended freeze concentration is more suitable for industrial large-scale production.

[0005] At present, suspension freeze concentration still has problems such as slow freezing rate, slow ice crystal formation, and high solute entrainment in separated ice crystals, and the freeze concentration effect needs to be improved. Summary of the invention

[0006] Based on this, it is necessary to provide a liquid material freezing and concentration device and method assisted by variable frequency ultrasound, which has a fast ice crystal growth and maturation speed, greatly shortens the freezing and concentration time, can regulate the ice crystal size to reduce solute entrainment, and obtain better concentrated liquid quality.

[0007] The above-mentioned purpose of the present application is achieved through the following technical solutions:

[0008] In a first aspect of the present application, a variable frequency ultrasonic-assisted liquid material freezing and concentration device is provided, comprising a feed tank, a crystallization tank, a maturation tank, and a centrifugal separation tank connected in sequence; the feed tank is used for feeding; the crystallization tank comprises an inner cavity and an outer cavity, the inner cavity of the crystallization tank is used for storing materials, and is provided with a scraper; the maturation tank comprises an inner cavity and an outer cavity, the inner cavity of the maturation tank is used for storing materials, and is provided with a stirring paddle; the outer cavity of the crystallization tank and the outer cavity of the maturation tank are connected through a condensation circulation system; the condensation circulation system is used to cool the crystallization tank, the maturation tank, and the materials; a first ultrasonic component is provided on the outer wall of the crystallization tank, the first ultrasonic component is used to give a first preset time of ultrasonic treatment when the material in the crystallization tank undergoes a phase change, so as to accelerate freezing and promote ice crystal formation; a second ultrasonic component is provided on the outer wall of the maturation tank, the second ultrasonic component is used to give a second preset time of ultrasonic treatment during the ice crystal growth stage, so as to control the ice crystal size; the centrifugal separation tank has a discharge port, and the discharge port is used to connect to a concentrated liquid storage tank.

[0009] In one embodiment, each ultrasonic component includes an ultrasonic vibration plate and an ultrasonic generator for controlling the operation of the ultrasonic vibration plate; the ultrasonic vibration plate is composed of a plurality of ultrasonic vibrators of different frequencies, and the ultrasonic vibrators of different frequencies are controlled by corresponding ultrasonic generators.

[0010] In one embodiment, the ultrasonic vibration plate is composed of a plurality of ultrasonic vibrators with a frequency of 28KHz and a plurality of ultrasonic vibrators with a frequency of 40KHz arranged vertically in an alternating manner; the power of each ultrasonic vibrator is 50W; the ultrasonic generator includes a first generator and a second generator, the first generator is used to control the ultrasonic vibrator with a frequency of 28KHz, and the second generator is used to control the ultrasonic vibrator with a frequency of 40KHz.

[0011] In one embodiment, the ultrasonic generator is a variable frequency ultrasonic generator.

[0012] In one embodiment, the inner cavity of the crystallizer is provided with a first thermocouple, and the first thermocouple is used to detect the temperature of the material in the inner cavity of the crystallizer, so as to give an ultrasonic treatment of a first preset duration when the material undergoes a phase change;

[0013] The inner cavity of the maturation tank is provided with a second thermocouple, which is used to detect the temperature of the material in the inner cavity of the maturation tank, so as to adjust the refrigerant temperature of the condensation circulation system according to the detected temperature, so as to maintain the material in the inner cavity of the maturation tank at a low temperature and promote the maturation of ice crystals.

[0014] In one of the embodiments, a reflux pump is installed between the centrifugal separation tank and the feed tank, and the reflux pump is used to return the concentrated material to the feed tank for secondary freeze concentration.

[0015] In one embodiment, the scraper is installed in the crystallization tank along its vertical direction, and the scraper is a spiral scraper.

[0016] In a second aspect of the present application, a variable frequency ultrasound-assisted liquid material freeze concentration method is provided, which is implemented by the liquid material freeze concentration device as described in the above embodiment, comprising the following steps:

[0017] Precool the liquid material to 2-6°C, open the condensation circulation system to cool the crystallization tank and the maturation tank to the same temperature as the liquid material;

[0018] The pre-cooled liquid material is transported from the feed tank to the crystallization tank, the material temperature in the inner cavity of the crystallization tank is detected, and ultrasonic treatment is given for a first preset time during the phase change stage of the material to accelerate freezing and promote ice crystal formation, and when layered crystals appear on the wall surface of the inner cavity of the crystallization tank, a scraper is turned on to scrape off the crystals, so that the ice crystals fall into the liquid material in the inner cavity of the crystallization tank and are suspended;

[0019] When the ice crystals are stably suspended above the liquid material, the suspended ice crystals and the liquid material are transported to the maturation tank, and the condensation circulation system is used to continuously supply cooling to keep the material in the inner cavity of the maturation tank at a low temperature. The stirring paddle is turned on to stir the material to make the heat transfer of the material uniform, and the ultrasonic treatment of the second preset time is simultaneously given to control the ice crystal size;

[0020] After the ice crystals are ripened, the material is transported to a centrifugal separation tank for centrifugal separation, and the separated concentrated liquid is transported to a storage tank.

[0021] In one of the embodiments, the method further includes the step of pumping the separated concentrated liquid to a feed tank and performing ultrasound-assisted freeze concentration again.

[0022] In one embodiment, the ultrasonic treatment is variable frequency ultrasonic treatment.

[0023] The variable frequency ultrasonic-assisted liquid material freezing and concentration device provided in the present application, by arranging ultrasonic components on the outer walls of the crystallization tank and the maturation tank, promotes heat and mass transfer of the liquid material by means of ultrasonic-assisted freezing, so as to promote ice crystal nucleation, accelerate ice crystal formation, reduce freezing and concentration time, and thus accelerate the freezing and concentration process; during the ice crystal maturation period, continuous refrigeration is performed to maintain the low temperature of the material, stirring is performed to ensure uniform heat transfer of the material, and ultrasonic treatment is simultaneously performed to enhance the Ostwald ripening effect, so that large ice crystals grow and small ice crystals melt, and ice crystal particle size control is achieved, thereby reducing solute entrainment losses; in addition, the ultrasonic-assisted method does not require additional refrigerant or energy consumption, and only requires the ultrasonic vibration effect to achieve rapid freezing of the material, which is environmentally friendly and energy-saving, and has low cost, which is conducive to the promotion and application of the suspension freezing and concentration method and device. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the structure of a liquid material freezing and concentration device provided in one embodiment of the present application.

[0025] Figure 2 A schematic diagram of the structure of a crystallization tank provided in one embodiment of the present application.

[0026] Figure 3 This is a schematic diagram of the structure of a maturation tank provided in one embodiment of the present application.

[0027] Figure 4 A schematic diagram of the tank structure of a crystallization tank and a maturation tank provided in one embodiment of the present application.

[0028] Explanation of reference numerals: 1. Feed tank; 2. Feed pump; 3. Condensation circulation system; 4. Crystallization tank; 5. Ripening tank; 6. Centrifugal separation tank; 7. Stop valve; 8. Reflux pump; 9. Ultrasonic generator; 10. Scraper; 13. Stirring paddle; 14. Ice outlet; 15. Ice storage bin; 16. 40kHz ultrasonic vibrator; 17. Tank body cavity; 18. Tank body cavity; 19. 28kHz ultrasonic vibrator; 20. Shell. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0030] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0032] In a first aspect of the present application, a variable frequency ultrasound-assisted liquid material freezing and concentration device is provided, which can be applied to the freezing and concentration of liquid materials in the fields of food processing, biology, medicine, chemistry, etc.

[0033] like Figure 1 As shown, the liquid material freezing concentration device includes a feed tank 1, a crystallization tank 4, a maturation tank 5, and a centrifugal separation tank 6 which are connected in sequence.

[0034] The feed tank 1 is used for feeding. Before feeding, the liquid material is precooled to a preset temperature, for example, 4°C.

[0035] The crystallization tank 4 is used to generate ice crystal nuclei, combined with Figure 2 , Figure 4 From the perspective of the present invention, the tank body of the crystallizer 4 includes an inner cavity and an outer cavity. The inner cavity of the crystallizer 4 is connected through a pipeline and a feed pump 2. A first valve is provided between the feed pump 2 and the feed tank 1, and a second valve is provided between the feed pump 2 and the crystallizer 4. The inner cavity of the crystallizer 4 is used to store materials, and is provided with a scraper 10. The scraper 10 is used to scrape the layered crystals formed on the inner cavity wall of the crystallizer 4 into fine ice crystals, and the scraped fine ice crystals fall onto the liquid material in the crystallizer 4 and suspend.

[0036] Combination Figure 3 , Figure 4 From the perspective of the present invention, the body of the maturation tank 5 includes an inner cavity and an outer cavity. The inner cavity of the maturation tank 5 is connected to the inner cavity of the crystallization tank 4 through a pipeline and a third valve is provided. The inner cavity of the maturation tank 5 is used to store materials and is provided with a stirring paddle 13. Stirring can make the heat transfer of the materials in the inner cavity uniform. The outer cavity of the crystallization tank 4 and the outer cavity of the maturation tank 5 are connected through the refrigerant flow channel of the condensation circulation system 3. The condensation circulation system 3 is used to cool the crystallization tank 4, the maturation tank 5, and the materials in the crystallization tank 4 and the inner cavity of the crystallization tank 4.

[0037] Optionally, the condensation cycle system includes components such as a refrigeration compressor, a condenser, an expansion valve, and an evaporator. Its working principle is based on the basic principle of the refrigeration cycle, and heat transfer and transfer are achieved through the phase change of the refrigerant in different states, mainly including the compression process, the condensation process, the throttling process, and the evaporation process. Through the continuous cycle of the four processes, the condensation cycle system can continuously take away the heat in the suspension, freeze the water into ice crystals and achieve concentration. At the same time, through the phase change and heat transfer of the refrigerant, the low temperature environment of the system is maintained to ensure the smooth progress of the freezing and concentration process.

[0038] A storage bin 15 is provided above the body of the ripening tank 5, and an ice outlet 14 is provided on the side of the storage bin 15. The ripened ice crystals rise to the storage bin 15 under the action of stirring, and are sent out from the ice outlet 14 to the centrifugal separation tank 6.

[0039] When the material in the inner cavity of the crystallizer 4 undergoes a phase change, the material temperature is below zero and crystallization begins to form a crystal nucleus. A first ultrasonic component is provided on the outer wall of the crystallizer 4, and the first ultrasonic component is used to give an ultrasonic treatment of a first preset duration when the material in the crystallizer 4 undergoes a phase change, so as to accelerate freezing and promote ice crystal formation.

[0040] Optionally, in this embodiment, the method for detecting whether the liquid material undergoes phase change can be a temperature monitoring method, that is, detecting the material temperature in the inner cavity of the crystallization tank by a temperature sensor. When the material temperature reaches a plateau or an obvious temperature turning point, it can be determined that the material undergoes phase change.

[0041] When the ice crystals are stably suspended above the liquid material, the suspended ice crystals and the liquid material are transported to the maturation tank, and the condensation circulation system is used to continuously supply cold to keep the material in the inner cavity of the maturation tank at a low temperature. A second ultrasonic component is provided on the outer wall of the maturation tank 5, and the second ultrasonic component is used to give an ultrasonic treatment of a second preset duration during the ice crystal growth stage to enhance the Ostwald maturation effect, so that large ice crystals grow and small ice crystals melt, thereby controlling the ice crystal size during the ice crystal maturation process and reducing solute entrainment. The first ultrasonic component and the second ultrasonic component are controlled by the ultrasonic generator 9.

[0042] The centrifugal separation tank 6 and the maturation tank 5 are connected through a pipeline and a fourth valve. The centrifugal separation tank 6 has a discharge port, which is used to connect to the concentrated liquid storage tank. The centrifugal separation tank is used to centrifugally separate ice crystals from liquid materials to obtain concentrated liquid and transport it to the storage tank. After the concentration in the maturation tank 5 is completed, the separated ice crystals enter the centrifugal separation tank 6 for centrifugation to obtain purer ice crystals, which can reduce the solute entrainment loss.

[0043] The variable frequency ultrasonic-assisted liquid material freezing and concentration device provided in the present application, by arranging ultrasonic components on the outer walls of the crystallization tank and the maturation tank, promotes heat and mass transfer of the liquid material by using variable frequency ultrasonic-assisted freezing, which can promote ice crystal nucleation, accelerate ice crystal formation, reduce freezing and concentration time, and thus speed up the freezing and concentration process; during the ice crystal maturation period, the material is kept at a low temperature by continuous cooling through the condensation circulation system, the material is stirred to ensure uniform heat transfer, and ultrasonic treatment is given simultaneously to enhance the Ostwald ripening effect, so that large ice crystals grow and small ice crystals melt, control the ice crystal size, and reduce solute entrainment losses; in addition, the ultrasonic-assisted method does not require additional refrigerant or energy consumption, and only requires the ultrasonic vibration effect to achieve rapid freezing of the material, which is environmentally friendly and energy-saving.

[0044] In an optional embodiment, each ultrasonic component includes an ultrasonic vibration plate and an ultrasonic generator for controlling the operation of the ultrasonic vibration plate. The ultrasonic vibration plate is composed of a plurality of ultrasonic vibrators of different frequencies arranged, and the ultrasonic vibrators of different frequencies are controlled by corresponding ultrasonic generators.

[0045] The ultrasonic vibration plate is composed of a plurality of ultrasonic vibrators with a frequency of 28KHz and a plurality of ultrasonic vibrators with a frequency of 40KHz arranged vertically in an alternating manner; the power of each ultrasonic vibrator is 50W.

[0046] like Figure 4 As shown, the tank bodies of the crystallization tank and the ripening tank both include a shell 20, an outer tank cavity 18 and an inner tank cavity 17 are provided inside the tank body, and a 40kHz ultrasonic vibrator 16 and a 28kHz ultrasonic vibrator 19 are installed on the shell 20 and act on the inner tank cavity 17 to assist in maintaining the material in the inner tank cavity 17 at a low temperature. The ultrasonic generator 9 includes a first generator and a second generator, the first generator is used to control the 28KHz ultrasonic vibrator 19, and the second generator is used to control the 40KHz ultrasonic vibrator 16.

[0047] Optionally, the ultrasonic generator 9 is a variable frequency ultrasonic generator. Compared with the case where no ultrasound is applied, the use of variable frequency ultrasound to assist freeze concentration shortens the freeze concentration time by more than 25%, reduces the number of ice crystals in the ripening process by more than 20%, and reduces the solute entrainment of separated ice crystals by more than 15%, which helps to obtain a higher quality concentrate.

[0048] In an optional embodiment, the inner cavity of the crystallization tank is provided with a first thermocouple, which is used to detect the temperature of the material in the inner cavity of the crystallization tank. When the temperature of the material reaches a plateau or an obvious temperature turning point, it is determined that the material has undergone a phase change, and then ultrasonic treatment of a first preset duration is given. The inner cavity of the maturation tank is provided with a second thermocouple, which is used to detect the temperature of the material in the inner cavity of the maturation tank, so as to adjust the refrigerant temperature of the condensation circulation system according to the detected temperature, turn on the stirring paddle to stir the material so that the heat transfer is uniform, and simultaneously give ultrasonic treatment of a second preset duration to assist the material in the inner cavity of the maturation tank to maintain a low temperature and promote the maturation of ice crystals.

[0049] In addition, the condensation circulation system 3 adjusts the refrigerant temperature according to the material temperature measured by the thermocouple, so as to control the temperature of the materials in the crystallization tank 4 and the maturation tank 5 to maintain a low temperature.

[0050] The first thermocouple and the second thermocouple are both K-type thermocouples. By measuring the temperature of the material in the crystallization tank 4 through the K-type thermocouple, it is also possible to accurately monitor whether a phase change occurs, so as to provide ultrasonic assistance in time during the phase change stage of the material; by measuring the temperature of the material in the maturation tank 5 through the K-type thermocouple, it is also possible to control the operation of the condensation circulation system 3 to maintain the maturation tank 5 at a low temperature.

[0051] In an optional embodiment, if a higher concentration of liquid material is required, a fourth valve, a reflux pump 8 and a stop valve 7 are further installed between the centrifugal separation tank 6 and the feed tank 1. The reflux pump 8 is used to return the concentrated liquid to the feed tank 1 for secondary freeze concentration or even multiple freeze concentration to obtain a higher concentration and higher quality concentrated liquid.

[0052] In an optional embodiment, a scraper is installed in the crystallization tank 4 along its vertical direction. The scraper is a spiral scraper. The size of the spiral scraper matches the diameter of the inner cavity of the crystallization tank 4. The spiral scraper rotates to scrape off the layered crystals formed on the inner cavity wall of the crystallization tank 4, and small ice crystals are obtained that fall above the liquid material and suspend.

[0053] In the process of freezing and concentrating liquid materials, the condensation circulation system is first turned on, and the pre-cooled liquid material is pumped from the feed tank into the crystallization tank. The ultrasonic generator is turned on during the phase change stage of the material in the inner cavity of the crystallization tank to assist in variable frequency ultrasonic treatment to accelerate heat and mass transfer, accelerate ice crystal formation, and reduce freezing time; when the inner cavity of the crystallization tank is cooled to the point where crystals appear on the wall, the ice scraping motor is turned on to perform ice scraping operation; when the ice crystals are stably suspended above the liquid material, the suspended ice crystals and the liquid material are transported to the maturation tank for ice crystal maturation, the condensation circulation system continues to refrigerate, maintains the material at a low temperature, turns on the stirring paddle to stir so that the heat transfer of the inner cavity material is uniform, and simultaneously turns on ultrasound to accelerate heat and mass transfer, enhance the Ostwald maturation effect, make large ice crystals grow and small ice crystals melt, control the ice crystal size, reduce the specific surface area, and thus reduce ice crystal entrainment; after the concentration is completed, the separated ice crystals enter the centrifugal separation tank for centrifugation to obtain purer ice crystals to further reduce solute entrainment losses; if a higher concentration of concentrated liquid is required, the material after the initial concentration is pumped to the feed tank, and the above concentration process is repeated.

[0054] The liquid material freezing and concentration device of the present application is assisted by variable frequency ultrasonic technology processing on the basis of suspension freezing and concentration. Variable frequency ultrasonic treatment is applied in the phase change stage of freezing and concentration and the ice crystal maturation (growth) stage. The mechanical effect, thermal effect and cavitation effect generated by ultrasound are used to promote heat and mass transfer of materials, accelerate ice crystal formation, regulate ice crystal size, and thus reduce solute entrainment.

[0055] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0056] 1. Compared with hot concentration, this frozen concentration equipment operates at low temperature, which can avoid thermal decomposition of material components and loss of volatile components. It is particularly suitable for concentrating heat-sensitive liquid materials and high-end products that require retaining natural color and flavor.

[0057] Second, using variable frequency ultrasound to assist freezing to promote heat and mass transfer of liquid materials can promote ice crystal nucleation, accelerate ice crystal formation, reduce freeze concentration time, and thus speed up the freeze concentration process; using ultrasound to enhance the Ostwald ripening effect, thereby reducing solute entrainment losses;

[0058] 3. The ultrasonic-assisted method does not require additional refrigerant or energy consumption. It can achieve rapid freezing of materials by simply utilizing the ultrasonic vibration effect, which is environmentally friendly and energy-saving.

[0059] Fourth, using this variable frequency ultrasonic assisted concentration equipment, the freezing concentration time is shortened by more than 25% compared with the freezing concentration without ultrasound, the number of ice crystals in the ripening process is reduced by more than 20%, and the solute entrainment of the separated ice crystals is reduced by more than 15%.

[0060] In a second aspect of the present application, a variable frequency ultrasound-assisted liquid material freeze concentration method is provided, which is implemented by the device described in the above embodiment, and comprises the following steps:

[0061] S1: Precool the liquid material to 2-6°C, open the condensation circulation system to cool the crystallization tank and the maturation tank to the same temperature as the liquid material.

[0062] S2: The pre-cooled liquid material is transported from the feed tank to the crystallization tank, the material temperature in the inner cavity of the crystallization tank is detected, and ultrasonic treatment is given for a first preset time during the phase change stage of the material to accelerate freezing and promote ice crystal formation. When layered crystals appear on the wall surface of the inner cavity of the crystallization tank, a scraper is turned on to scrape out fine ice crystals from the layered crystals, and the fine ice crystals fall into the liquid material in the inner cavity of the crystallization tank and are suspended.

[0063] In this step, the variable frequency ultrasound assisted freezing method is used to promote heat and mass transfer of the liquid material, which can promote ice crystal nucleation, accelerate ice crystal formation, reduce the freezing concentration time, and thus speed up the freezing concentration process. The first preset time can be determined according to demand.

[0064] S3: When the ice crystals are stably suspended above the liquid material, the suspended ice crystals and the liquid material are transported to the maturation tank, and the condensation circulation system is used to continuously supply cooling to keep the material in the inner cavity of the maturation tank at a low temperature. The stirring paddle is turned on to stir the material to ensure uniform heat transfer, and ultrasonic treatment is simultaneously given for a second preset time to control the ice crystal size.

[0065] In this step, ultrasound is turned on during the stirring process to accelerate heat and mass transfer, and at the same time enhance the Ostwald ripening effect, so that large ice crystals grow and small ice crystals melt, so as to control the ice crystal size, reduce the specific surface area, and thus reduce ice crystal entrainment. The first preset time can be determined according to demand.

[0066] S4: After the ice crystals are ripened, the material is transported to a centrifugal separation tank for centrifugal separation, and the separated concentrated liquid is transported to a storage tank to obtain a finished product.

[0067] The preparation method provided in the present application is based on suspension freeze concentration and is assisted by variable frequency ultrasonic technology. Variable frequency ultrasonic treatment is applied during the phase change stage of freeze concentration and the ice crystal maturation (growth) stage, and the mechanical effect, thermal effect and cavitation effect generated by ultrasound are used to promote heat and mass transfer of materials, accelerate ice crystal formation, and regulate the size of ice crystals, thereby reducing solute entrainment.

[0068] In some embodiments, if a concentrate with a higher concentration is required, the separated concentrate can be pumped to a feed tank and subjected to ultrasound-assisted suspension freeze concentration again.

[0069] The above ultrasonic treatments are all variable frequency ultrasonic treatments.

[0070] The liquid material freeze concentration method of the present application is assisted by variable frequency ultrasonic technology processing on the basis of suspension freeze concentration. Variable frequency ultrasonic treatment is applied in the freeze concentration phase change stage and ice crystal maturation (growth) stage, and the mechanical effect, thermal effect and cavitation effect generated by ultrasound are used to promote heat and mass transfer of materials, accelerate ice crystal formation, and regulate ice crystal size, thereby reducing solute entrainment.

[0071] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0072] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims, and the description may be used to interpret the contents of the claims.

Claims

1. A variable frequency ultrasonic assisted liquid material freezing and concentration device, characterized in that: It includes a feed tank, a crystallization tank, a maturation tank, and a centrifugal separation tank which are connected in sequence; The feed tank is used for feeding; The crystallization tank comprises an inner cavity and an outer cavity, the inner cavity of the crystallization tank is used to store materials and is provided with a scraper; the maturation tank comprises an inner cavity and an outer cavity, the inner cavity of the maturation tank is used to store materials and is provided with a stirring paddle; the outer cavity of the crystallization tank and the outer cavity of the maturation tank are connected through a condensation circulation system; the condensation circulation system is used to cool the materials in the crystallization tank and the maturation tank; A first ultrasonic component is provided on the outer wall of the crystallization tank, and the first ultrasonic component is used to provide ultrasonic treatment for a first preset time when the material in the crystallization tank undergoes a phase change, so as to accelerate freezing and promote ice crystal formation; A second ultrasonic component is disposed on the outer wall of the ripening tank, and the second ultrasonic component is used to provide ultrasonic treatment for a second preset time during the ice crystal growth stage to control the ice crystal size; The centrifugal separation tank has a discharge port, and the discharge port is used to connect to the concentrated liquid storage tank. The centrifugal separation tank is used to centrifugally separate ice crystals from liquid materials to obtain concentrated liquid and transport it to the storage tank.

2. The variable frequency ultrasound-assisted liquid material freezing and concentration device according to claim 1, characterized in that: Each ultrasonic assembly includes an ultrasonic vibration plate and an ultrasonic generator for controlling the operation of the ultrasonic vibration plate; The ultrasonic vibration plate is composed of a plurality of ultrasonic vibrators of different frequencies, and the ultrasonic vibrators of different frequencies are controlled by corresponding ultrasonic generators.

3. The variable frequency ultrasound-assisted liquid material freezing and concentration device according to claim 2, characterized in that: The ultrasonic vibration plate is composed of a plurality of ultrasonic vibrators with a frequency of 28KHz and a plurality of ultrasonic vibrators with a frequency of 40KHz arranged vertically in an interlaced manner; the power of each ultrasonic vibrator is 50W; The ultrasonic generator includes a first generator and a second generator, the first generator is used to control an ultrasonic vibrator with a frequency of 28KHz, and the second generator is used to control an ultrasonic vibrator with a frequency of 40KHz.

4. The variable frequency ultrasonic assisted liquid material freezing and concentration device according to claim 3, characterized in that: The ultrasonic generator is a variable frequency ultrasonic generator.

5. The variable frequency ultrasonic assisted liquid material freezing and concentration device according to claim 1, characterized in that: The inner cavity of the crystallizer is provided with a first thermocouple, and the first thermocouple is used to detect the temperature of the material in the inner cavity of the crystallizer, so as to provide ultrasonic treatment of a first preset duration when the material undergoes a phase change; The inner cavity of the maturation tank is provided with a second thermocouple, which is used to detect the temperature of the material in the inner cavity of the maturation tank, so as to adjust the refrigerant temperature of the condensation circulation system according to the detected temperature, so as to maintain the material in the inner cavity of the maturation tank at a low temperature and promote the maturation of ice crystals.

6. The variable frequency ultrasound-assisted liquid material freezing and concentration device according to claim 1, characterized in that: A reflux pump is also installed between the centrifugal separation tank and the feed tank, and the reflux pump is used to return the concentrated liquid to the feed tank for secondary freeze concentration.

7. The variable frequency ultrasound-assisted liquid material freezing and concentration device according to claim 1, characterized in that: The scraper is installed in the crystallization tank along its vertical direction, and the scraper is a spiral scraper.

8. A method for freezing and concentrating liquid materials assisted by variable frequency ultrasound, implemented by the device according to any one of claims 1 to 6, characterized in that: The following steps are involved: Precool the liquid material to 2-6°C, open the condensation circulation system to cool the crystallization tank and the maturation tank to the same temperature as the liquid material; The pre-cooled liquid material is transported from the feed tank to the crystallization tank, the material temperature in the inner cavity of the crystallization tank is detected, and ultrasonic treatment is given for a first preset time during the phase change stage of the material to accelerate freezing and promote ice crystal formation, and when crystals appear on the wall surface of the inner cavity of the crystallization tank, a scraper is turned on to scrape off the crystals, so that the ice crystals fall into the liquid material in the inner cavity of the crystallization tank and are suspended; When the ice crystals are stably suspended above the liquid material, the suspended ice crystals and the liquid material are transported to the maturation tank, and the condensation circulation system is used to continuously supply cooling to keep the material in the inner cavity of the maturation tank at a low temperature. The stirring paddle is turned on to stir the material to make the heat transfer of the material uniform, and the ultrasonic treatment of the second preset time is simultaneously given to control the ice crystal size; After the ice crystals are ripened, the material is transported to a centrifugal separation tank for centrifugal separation, and the separated concentrated liquid is transported to a storage tank.

9. The method for freezing and concentrating liquid materials assisted by variable frequency ultrasound according to claim 8, characterized in that: Also includes the steps: The separated concentrate is pumped to the feed tank for ultrasound-assisted freeze concentration again.

10. The method for freezing and concentrating liquid materials assisted by variable frequency ultrasound according to claim 8, characterized in that: The ultrasonic treatment is variable frequency ultrasonic treatment.

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