Freezing concentration method

Abstract

The present invention relates to the technical field of freezing concentration, and specifically relates to a freezing concentration method. A dilute solution is frozen into a solid or solid-liquid mixture, such that, during heating and dissolution of the solid or solid-liquid mixture, no dense solid layer is formed on the surface along a direction of solution separation and outflow, or a surface solid layer along a direction of solution separation and outflow has a lower degree of denseness than that of the surface solid layers along other directions; the direction of solution separation and outflow is determined on the basis of the internal structural characteristics formed after the dilute solution is frozen into the solid or solid-liquid mixture, that is, the direction in which the solution can be more easily separated and flow out is set as the direction of solution separation and outflow during heating and dissolution of the solid or solid-liquid mixture; and heat is transferred to the solid or solid-liquid mixture for dissolution, thereby achieving freezing concentration of the dilute solution, and improving the efficiency of freezing concentration. The present invention is simple to operate, and is suitable for application in the fields of food, cosmetics, biomedicine, environmental treatment, etc.

Description

A method for freeze concentration Technical Field

[0001] This invention belongs to the field of freeze concentration technology, specifically a freeze concentration method. Background Technology

[0002] There are two main types of existing freeze concentration methods, based on different physical principles. The first type utilizes the solid-liquid phase relationship of a substance below its crystallization point (e.g., using aqueous solutions below their freezing point) to achieve concentration. For example, when the solvent is water, water is frozen into ice crystals, and the solvent (water) is removed as a solid through solid-liquid separation (separation of ice crystals from the concentrated solution). The second type utilizes the negative correlation between melting point and solute concentration to achieve freeze concentration. This involves heating the frozen material to dissolve it and collecting solutions of different concentrations to achieve concentration.

[0003] The first type of freeze concentration method utilizes the solid-liquid phase relationship between a dilute solution and ice below its freezing point to achieve concentration. This mainly includes two methods: suspension crystallization freeze concentration and progressive freeze concentration. The principle of suspension crystallization freeze concentration is that during the freezing of a dilute solution, free small ice crystals suspended in the liquid are continuously removed, increasing the liquid concentration. The principle of progressive freeze concentration is that during the freezing of a dilute solution, as the ice layer forms and grows on the cooling surface, the solute near the solid-liquid interface is removed to the liquid phase, leading to a gradual increase in the solute concentration in the liquid phase. Existing freeze concentration methods involve complex equipment structures, high equipment and production costs, and low efficiency.

[0004] The second type of freeze-concentration method utilizes the negative correlation between melting point and solute content (concentration), achieving concentration through heating and dissolving the frozen material. For example, when ice melts naturally, a relatively concentrated solution is initially released. Utilizing this phenomenon, by repeatedly freezing the solution into a solid and then dissolving it, the concentration of the dilute solution can be increased; this is a freeze-concentration method based on the natural melting of ice. Additionally, the natural melting of ice is a form of thermal dissolution; similarly, heating ice in other ways will also yield a concentrated solution, achieving freeze-concentration. Currently, the concentration effect and efficiency of this method are very low.

[0005] Both of the above-mentioned freeze concentration methods based on different physical principles suffer from a significant problem: low efficiency and effectiveness. In particular, existing freeze concentration methods based on heating and dissolving (traditional conventional heating methods) have even lower concentration efficiency and effectiveness compared to existing methods that utilize the solid-liquid phase relationship of substances below their crystallization point (such as using aqueous solutions below their freezing point).

[0006] The reason affecting the concentration effect and efficiency of the first freeze concentration method is due to the physical principle it employs: the unavoidable solute entrainment problem during solid-liquid separation. The effectiveness of ice crystal separation and the control of solute loss caused by ice crystal entrainment are extremely important for the successful application of freeze concentration based on this physical principle, and are also one of the reasons for the complex structure, high cost, and complicated operation of existing freeze concentration equipment.

[0007] The second freeze concentration method can solve the solute entrainment problem of the first method. However, there are factors that affect the concentration effect and efficiency of the second freeze concentration method: the dense ice layer with low solute content formed near the cooling surface of the frozen material and the solid structure inside the frozen material will hinder the heat transfer when it is heated and melted, as well as the separation and outflow of the frozen material solution. These two obstacles seriously affect the concentration effect and efficiency of freeze concentration under this method. Summary of the Invention

[0008] To address the problems existing in the prior art, the main objective of this invention is to propose a method and apparatus for cryogenic concentration.

[0009] To address the aforementioned technical problems, according to one aspect of the present invention, the present invention provides the following technical solution:

[0010] A method for freeze concentration involves freezing a dilute solution into a solid or a solid-liquid mixture, such that when the solid or solid-liquid mixture is heated and dissolved, the surface solid layer in the solution separation outflow direction does not form a dense solid layer, or the density of the surface solid layer in the solution separation outflow direction is less than that in other directions; the direction in which the solution is more easily separated and flows out is set as the solution separation outflow direction when the solid or solid-liquid mixture is heated and dissolved; heat is transferred to the solid or solid-liquid mixture to dissolve it, thereby achieving freeze concentration of the dilute solution and improving the efficiency of freeze concentration.

[0011] As a preferred embodiment of the freeze concentration method of the present invention, in step S1, when the solid or solid-liquid mixture is heated and dissolved, the direction of solution separation and outflow is determined according to the internal structural characteristics of the dilute solution after it is frozen into a solid or solid-liquid mixture. That is, the direction that makes it easier for the solution to be separated and outflowed is set as the direction of solution separation and outflow when the solid or solid-liquid mixture is heated and dissolved.

[0012] In a preferred embodiment of the cryogenic concentration method of the present invention, in step S2, the method of transferring heat to the solid or solid-liquid mixture is as follows:

[0013] Solids or solid-liquid mixtures dissolve spontaneously.

[0014] Alternatively, heat can be transferred directly to a solid or a solid-liquid mixture, wherein one or more heat sources can be set up to transfer heat to the ice.

[0015] Alternatively, a heat source may be placed at a specific location inside or outside the solid or solid-liquid mixture to transfer heat to it, wherein one or more heat sources may be placed to transfer heat to the ice.

[0016] In a preferred embodiment of the freeze-concentration method described in this invention, in step S2, the specific orientation is a description of a directional region: viewed from the cooling surface when a dilute solution is frozen into a solid or solid-liquid mixture, the specific orientation region is the region moving away from the cooling surface towards the solid or solid-liquid mixture (excluding the solid layer with low solute content adjacent to the cooling surface). This region can be inside or outside the solid or solid-liquid mixture (depending on the location of the cooling surface). The shape of the heat source includes: point-like, line (column)-like, surface (plate)-like, and spherical.

[0017] As a preferred embodiment of the freeze concentration method of the present invention, in step S2, the heat source set at a specific location is characterized by the fact that when transferring heat to the solid or solid-liquid mixture, heat is transferred as far as possible to the solid layer with low solute content in the solid or solid-liquid mixture first.

[0018] In a preferred embodiment of the freeze-concentration method of the present invention, in step S2, the method of setting the heat source at a specific location is as follows:

[0019] Insert a heat source into a solid or solid-liquid mixture obtained by freezing;

[0020] Alternatively, the location for setting up a heat source can be machined (e.g., drilled out, cut out) on a solid or solid-liquid mixture, and then the heat source can be placed (inserted) in.

[0021] Alternatively, a heat source can be pre-set in the location where a heat source is needed during the freezing process.

[0022] In a preferred embodiment of the freeze concentration method of the present invention, in step S2, after the solid or solid-liquid mixture is heated, the solution is separated and flows out in the following ways: natural outflow, negative pressure extraction or centrifugal separation.

[0023] In a preferred embodiment of the freeze concentration method of the present invention, in step S1, a flow channel is provided on the frozen solid or solid-liquid mixture to improve the effect and efficiency of freeze concentration and separation purification.

[0024] To solve the above-mentioned technical problems, according to another aspect of the present invention, the present invention provides the following technical solution:

[0025] The above-mentioned freeze concentration method has applications in the fields of food, cosmetics, biomedicine, and environmental treatment.

[0026] The above-mentioned freeze concentration method has applications in the fields of milk, wine, beverages (such as juice, coffee, tea, soy milk, soy milk, etc.), chemical solutions, traditional Chinese medicine solutions, plant extracts, seawater desalination, and wastewater treatment.

[0027] An application of the above-mentioned freeze concentration method in the field of freeze concentration and separation purification of heat-sensitive raw materials.

[0028] The above-mentioned freeze concentration method is applied in the freeze concentration and separation purification of milk, wine, beverages (such as juice, coffee, tea, soy milk, soy milk, etc.), chemical liquids, traditional Chinese medicine liquids, plant extracts, seawater desalination, wastewater treatment, etc.

[0029] The beneficial effects of this invention are as follows:

[0030] This invention proposes a freeze-concentration method that freezes a dilute solution into a solid or a solid-liquid mixture. This method ensures that when the solid or solid-liquid mixture is heated and dissolved, the surface solid layer in the solution separation outflow direction does not form a dense solid layer, or the density of the surface solid layer in the solution separation outflow direction is less than that in other directions. The solution separation outflow direction is determined by the internal structural characteristics of the dilute solution after freezing into a solid or solid-liquid mixture; that is, the direction that facilitates solution separation and outflow is set as the solution separation outflow direction when the solid or solid-liquid mixture is heated and dissolved. Heat is transferred to the solid or solid-liquid mixture to dissolve it, achieving freeze-concentration of the dilute solution and improving the efficiency of freeze-concentration. This invention is simple to operate and easy to apply in the fields of food, cosmetics, biomedicine, and environmental treatment. Detailed Implementation

[0031] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] This invention proposes a freeze concentration method that breaks with traditional freeze concentration thinking, improves the efficiency of freeze concentration and separation purification, is simple to operate, and is easy to apply in the fields of food, cosmetics, biomedicine, and environmental treatment.

[0033] The freezing concentration apparatus used to implement the freezing concentration method of the present invention can be, for example, a cylindrical freezing concentration apparatus, consisting of a cylindrical dilute solution container and a columnar heat source. The columnar heat source is installed at the bottom center of the container, positioned along the central axis of the cylindrical dilute solution container and its surrounding area. One columnar heat source (heating rod) or multiple columnar heat sources (multiple heat source rods) can be optionally placed in this area. The top of the columnar heat source is flush with the opening of the dilute solution container, and the opening of the apparatus is equipped with a container lid. The container lid is made of a material with a lower thermal conductivity than other parts (and is further protected by heat-insulating material). When the dilute solution is injected into the cylindrical dilute solution container of the apparatus, the container lid is tightened, and the apparatus is inverted (with the container lid at the bottom) and placed in a freezing device for freezing. After the dilute solution is frozen into a solid or a solid-liquid mixture, the apparatus is removed from the freezing device, the container lid is opened, and the solid or solid-liquid mixture is heated to dissolve. The solid surface at the container opening is the solution separation outflow surface during dissolution.

[0034] Example 1

[0035] A method for freeze-concentrating thorn wine involves placing 3000 mL of thorn wine with an alcohol content of 14.88% vol into a cylindrical freeze-concentration apparatus, sealing and tightening the container lid, and then placing the apparatus upside down (with the lid at the bottom) into a freezer for freezing. The freezing temperature is -45°C. After the thorn wine has frozen into a solid, the apparatus is removed from the freezer, the container lid is opened, and the container opening is kept facing downwards. In this embodiment, the heat source is a cylindrical heat source located at the central axis of the container. The heating switch is turned on, and heat is transferred to the thorn wine solid through the heat source. The solution flows out from the container opening, and the solution is collected in segments and the dissolution status is recorded, as shown in Table 1.

[0036] Table 1. Details of the segmented solution collection in Example 1

[0037] Example 2

[0038] The difference from Example 1 is that, before dissolving the solid by transferring heat, several holes are made in the solid as flow channels, and then heat is transferred to the solid of the thorn wine through a heat source, and the dissolution status is recorded, as shown in Table 2.

[0039] Table 2. Details of the segmented solution collection in Example 2

[0040] Comparative Example 1

[0041] The difference from Example 1 is that the container lid is made of the same material (same thermal conductivity) as the rest of the container. During freezing, the container opening faces upwards, and during dissolution, the opening faces downwards as the solution outlet for solid dissolution. In this case, a dense solid layer has formed on the solid surface in the direction of solution separation during dissolution. The dissolution status is recorded in Table 3.

[0042] Table 3 details the fractional solution collection from Comparative Example 1.

[0043] As can be seen from Examples 1 and 2, in Example 1, the first segment of the receiving solution had an alcohol content of 35.8% vol and a volume percentage of 9.3%, with the alcohol content of this segment increased by 140.6% compared to the original alcohol content. In Example 2, the first segment of the receiving solution had an alcohol content of 38.9% vol and a volume percentage of 9.5%, with the alcohol content of this segment increased by 161.4% compared to the original alcohol content. It is evident that when using a freeze-concentration apparatus to freeze dilute solutions, setting up a flow channel for the solids can improve the freeze-concentration effect.

[0044] As can be seen from Example 1 and Comparative Example 1, in Example 1, the first segment of the received solution had an alcohol content of 35.8% vol and a volume percentage of 9.3%; the second segment had an alcohol content of 33.99% vol and a volume percentage of 9.9%; and the third segment had an alcohol content of 28.99% vol and a volume percentage of 11.9%. The total volume percentage of the first three segments was 31.1%, and the alcohol content was 32.61% vol. In Comparative Example 1, due to the obstruction of the dense solid layer in the direction of solution outflow, the concentrated solution inside the solid could not be separated immediately during the heat transfer and dissolution process. Only after prolonged heating, when the dense solid layer on the surface dissolved and created channels, did a large amount of the concentrated solution inside flow out together. Therefore, in Comparative Example 1, the volume percentage of the first segment of the received solution was 26.7%, and the alcohol content was 22.1% vol. In Example 1, when the volume percentage of the received solution was 31.1%, the alcohol content increased to 32.61% vol, an increase of 119% compared to the original alcohol content of 14.88% vol. In Comparative Example 1, when the volume ratio of the receiving solution was 26.7%, the alcohol content increased to 22.1% vol, a 48.5% increase compared to the original alcohol content of 14.88% vol. Comparing the two, the alcohol content increase rate of Example 1 was 245.3% of that of Comparative Example 1. Furthermore, the alcohol content of the first three stages of Example 1 increased to 35.61% vol, while the alcohol content of the first stage of the Comparative Example only increased to 22.1% vol, a difference of 13.51% vol. This demonstrates that the dense solid layer (ice layer) on the surface in the direction of solution outflow significantly hinders the separation and outflow of the concentrated solution dissolved from the solids.

[0045] In summary, the freeze concentration method of the present invention freezes a dilute solution into a solid or a solid-liquid mixture in the apparatus, and a dense solid layer is not formed on the solid surface layer in the direction of solution separation and outflow (or the density of the solid layer is relatively small); the direction in which the solution is more easily separated and outflowed is set as the direction of solution separation and outflow when the solid or solid-liquid mixture is heated and dissolved; thus, the effect and efficiency of freeze concentration can be significantly improved.

[0046] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for freeze concentration, characterized in that, Includes the following steps: S1. Freeze the dilute solution into a solid or a solid-liquid mixture, such that when the solid or solid-liquid mixture is heated and dissolved, the surface solid layer in the solution separation outflow direction does not form a dense solid layer, or the density of the surface solid layer in the solution separation outflow direction is less than the density of the surface solid layer in other directions. S2. Heat is transferred to the solid or solid-liquid mixture to dissolve it, and the solution is collected in segments to obtain solutions of different concentrations; S3. Solutions that meet the target concentration are transferred to the next step; solutions that do not meet the target concentration are processed by repeating steps S1-S2 to further increase the solution concentration.

2. The freeze-concentration method according to claim 1, characterized in that, In step S1, when a solid or solid-liquid mixture is heated and dissolved, the direction of solution separation and outflow is determined according to the internal structural characteristics of the dilute solution after it is frozen into a solid or solid-liquid mixture. That is, the direction that makes it easier for the solution to be separated and outflowed is set as the direction of solution separation and outflow when the solid or solid-liquid mixture is heated and dissolved.

3. The freeze-concentration method according to claim 1, characterized in that, In step S2, the heat is transferred to the solid or solid-liquid mixture in the following ways: the solid or solid-liquid mixture dissolves naturally; or heat is transferred directly to the solid or solid-liquid mixture; or a heat source is placed at a specific location inside or outside the solid or solid-liquid mixture to transfer heat to it.

4. The freeze-concentration method according to claim 3, characterized in that, A specific orientation is a description of a directional region: when viewed from the cooling surface of a dilute solution frozen into a solid or a solid-liquid mixture, the specific orientation region is the area in the direction from the cooling surface away from the solid or solid-liquid mixture.

5. The freeze-concentration method according to claim 3, characterized in that, A heat source positioned in a specific location is characterized by its heat transfer direction in that, when transferring heat to a solid or solid-liquid mixture, it tries to avoid transferring heat to the solid layer with low solute content in the solid or solid-liquid mixture first.

6. The freeze-concentration method according to claim 1, characterized in that, In step S2, heat is transferred to the solid or solid-liquid mixture to dissolve it, and the solution is separated and flows out in the following ways: natural outflow, negative pressure extraction, or centrifugal separation.

7. The application of the freeze concentration method according to any one of claims 1-6 in the fields of food, cosmetics, biomedicine, and environmental treatment.

8. The application of the freeze concentration method according to any one of claims 1-6 in the fields of milk, wine, beverages, chemical liquids, traditional Chinese medicine liquids, plant extracts, seawater desalination, and wastewater treatment.

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