JP2011000541A - Freeze concentration method and freeze concentration apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a freeze concentration method and a freeze concentration apparatus each of which separates a solute to a sufficiently higher degree while saving energy and has an improved processing speed of a liquid to be treated.SOLUTION: The freeze concentration method for freezing the liquid to be treated to concentrate the solute included in the liquid to be treated, comprises: a supply step of supplying the liquid to be treated to an icehouse 42 having a heat transfer area; a freezing step of freezing the liquid to be treated in the icehouse; a first thawing step of bringing the frozen liquid to be treated into contact with a high-concentration solution having the solute concentration higher than that of the liquid to be treated to thaw a part of the frozen liquid to be treated; a concentrated liquid recovery step of recovering a liquid mixture of the high-concentration solution, which is used at the first thawing step, with a thawed liquid of the frozen liquid to be treated; and a separated liquid recovery step of recovering the separated liquid in a state wherein frozen liquid to be treated is kept in a frozen state or is thawed into a liquid state after the concentrated liquid recovery step.

Description

  The present invention relates to a freeze concentration method and a freeze concentration apparatus that concentrate a solute contained in a liquid to be processed by freezing the liquid to be processed.

  In the process of manufacturing a semiconductor device or a liquid crystal display, an organic waste liquid or an inorganic acid waste liquid may be generated. These waste liquids are often disposed of as industrial waste because they contain biodegradable substances or a large amount of sludge is generated by insolubilization. In order to reduce the amount of waste, volume reduction by concentration or reuse of waste liquid has been attempted. Evaporation of liquid components and membrane separation treatment of waste liquid have been studied. However, these methods have problems such as high temperature corrosion and odor generation, energy cost required for heating, and membrane corrosion.

  As a method for concentrating the solute contained in the waste liquid, a freeze concentration method is known (see Patent Documents 1-3). The freeze-concentration method is advantageous in terms of energy cost because it has only about 1/7 of latent heat compared to the evaporation method, and the processing is performed under low temperature conditions, and therefore, corrosion problems are less likely to occur. For example, even when a waste liquid containing an inorganic acid is treated, it is possible to easily maintain corrosion resistance by selecting a suitable organic material. Furthermore, the problem of odor has the advantage of being easy to take countermeasures because of its low temperature.

Japanese Examined Patent Publication No. 38-10509 Japanese Patent No. 3739440 International Publication No. 2003/072216

  By the way, in the conventional freeze concentration process, it was considered suitable to apply a stirring shear force to the liquid to be processed when the liquid to be processed was frozen from the viewpoint of obtaining a high degree of separation. For example, Patent Document 2 describes a method of melting a surface layer portion of an ice body after freezing the liquid to be treated while flowing down to an ice plate. In the initial stage where ice begins to adhere to the ice plate, the ice growth rate is high, and the solute to be separated is easily trapped in the ice body. For this reason, in order to make the concentrated portion of the solute portion unevenly distributed on the surface layer portion of the ice body, it is considered necessary to apply high-speed shear to the fluid to be treated at least in the initial stage. In this way, when the method is employed, a stirring device and a circulation device for applying a shearing force to the liquid to be treated are necessary, and energy for operating these is also necessary.

On the other hand, the method described in Patent Document 3 is premised on rapidly freezing the liquid to be treated. Patent Document 3 describes that it is preferable to use a deep freezer at −80 ° C. or liquid nitrogen at −200 ° C. (see page 7, lines 28-30). In the method described in Patent Document 3, while quick freezing is performed in this way, the frozen material is slowly melted over time. According to Equation 2 defined in claim 2 of Patent Document 3, the lower limit value of the melting time T (min) is defined by the weight A (g) of the frozen material and the surface area A (cm ² ) of the frozen material. . This method has a problem that it takes a long time to melt and a sufficient amount of liquid cannot be processed per unit time.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a freeze concentration method and a freeze concentration apparatus capable of separating solute components to a sufficiently high degree while saving energy and improving the processing speed. To do.

  The present invention relates to a freeze concentration method for concentrating a solute contained in a liquid to be treated by freezing the liquid to be treated, a supply step of supplying the liquid to be treated to an ice making chamber having a heat transfer surface, A freezing step for freezing the liquid to be treated in the room, and a first melting step for melting a part of the ice body by bringing the high-concentration liquid having a higher solute concentration than the liquid to be treated into contact with the ice body of the liquid to be treated. And a concentrated liquid recovery process for recovering a mixture of the high-concentration liquid used in the first melting process and the ice melt, and after the concentrate recovery process, the ice body is frozen or thawed. There is provided a freeze concentration method comprising a separation liquid recovery step of recovering in a liquid state.

  In the freezing step of the above method, the liquid to be treated is frozen in a static state without flowing down or stirring. Power for applying a shearing force to the liquid to be treated is unnecessary, and energy saving is achieved. When frozen in a static state, a large amount of solute remains inside the ice body, but in the first melting step, the solute content is contained at a high concentration by bringing the high-concentration liquid into contact with the ice body. As a result, it is possible to selectively melt the portion to be melted and to flow the concentrated portion remaining without freezing with a high-concentration liquid. Thereafter, the concentrated liquid recovery step and the separated liquid recovery step are performed, whereby the concentrated liquid containing the solute component at a high concentration and the separated liquid with the reduced solute content can be recovered separately.

  In the above method, a part of ice body is melted, and since the ice body and the high-concentration liquid are brought into solid-liquid contact at the time of melting, the time required for melting is greatly increased compared with the case of melting in air. Can be shortened. For this reason, the processing amount per unit time can be improved.

  When a series of steps from the above supply step to the separation liquid recovery step is repeatedly performed, it is preferable to use the mixed liquid obtained through the concentrated liquid recovery step as a high concentration liquid in the melting step.

  It is preferable that the freeze concentration method of the present invention further includes a crushing step of crushing the ice body after the freezing step, and bringing the crushed ice body into contact with the high-concentration liquid in the first melting step. By crushing the ice body into ice pieces, the solid-liquid contact efficiency in the first melting step is increased, so that the solute content can be separated to a higher degree and the treatment can be performed in a shorter time.

  In the case where the supplying step supplies a part of the liquid to be processed to the ice making chamber, the freeze concentration method is to bring the ice body of the liquid to be processed and the remaining liquid to be processed into contact after the first thawing step. A second melting step for further melting a part of the ice body; and a treatment liquid recovery step for recovering a mixed liquid of the remaining liquid to be processed and the melted ice body used in the second melting step. The separation liquid recovery step is preferably performed after the process liquid recovery step. By performing the second melting step, the solute content remaining in the ice body can be further reduced.

  Furthermore, the present invention is a freeze concentration apparatus for concentrating a solute contained in the liquid to be processed by freezing the liquid to be processed, and has a first tank for storing the liquid to be processed and a heat transfer surface. An ice making chamber for freezing the liquid to be treated supplied from the first tank, a solid-liquid contact means for bringing a high-concentration liquid having a higher solute concentration than the liquid to be treated and an ice body of the liquid to be treated; There is provided a freeze concentration apparatus including a second tank for storing a mixed liquid of a high concentration liquid transferred from a liquid contact means and a melt of ice body.

  The ice making chamber does not require a function of flowing down or stirring the liquid to be processed, and freezes the liquid to be processed in a static state. For this reason, the power for giving a shearing force with respect to a to-be-processed liquid becomes unnecessary, and energy saving is achieved. When frozen in a static state, a large amount of solute remains inside the ice body, but the solid-liquid contact means contains a high concentration of solute by bringing the high-concentration liquid into contact with the ice body. As a result, it is possible to selectively melt the portion to be melted and to flow the concentrated portion remaining without freezing with a high-concentration liquid. By transferring the mixed solution containing the solute component at a high concentration to the second tank, the ice body (or a melt thereof) having a reduced solute component and the concentrated solution can be separated.

  In the freeze concentration apparatus, since the ice body and the liquid (high-concentration liquid) are brought into solid-liquid contact to melt a part of the ice body, the time required for melting can be greatly shortened. For this reason, the processing amount per unit time can be improved.

  In the freeze concentration apparatus, the heat transfer surface of the ice making chamber extends in the vertical direction, and it is preferable that the freeze concentrator further includes a melting tank that accommodates crushed pieces of ice bodies of the liquid to be processed below the heat transfer surface. . By adopting such a configuration, after freezing the liquid to be treated, the ice layer can be dropped into the melting tank by melting the surface layer portion of the ice body in contact with the heat transfer surface. Ice bodies can be crushed by the impact of falling.

  According to the present invention, when concentrating the solute contained in the liquid to be treated by freezing the liquid to be treated, the solute can be separated to a sufficiently high degree while saving energy, and the processing speed can be improved. .

It is a mimetic diagram showing a suitable embodiment of a freeze concentration device concerning the present invention. It is a schematic cross section which shows the state inside a freezing tank and thawing, respectively, (a) shows the state after a supply process, (b) shows the state after a crushing process. It is a schematic cross section which shows the state inside a freezing tank and a melting tank, respectively, (a) shows the state which is implementing the 1st melting | fusing process, (b) shows the state which is implementing the separated liquid recovery process. . It is a graph which shows the result of a reference test.

  A preferred embodiment of the present invention will be described in detail with reference to the drawings.

<Freeze concentration device>
The freeze concentration apparatus 100 shown in FIG. 1 is for concentrating the solute contained in the liquid to be processed by freezing the liquid to be processed, and separating the stock solution (liquid to be processed) into a concentrated liquid and a separated liquid. It is. The freeze concentration apparatus 100 includes a tank (first tank) 10 that stores a stock solution, a tank (second tank) 20 that stores a concentrated solution, and a tank 30 that stores a separated solution. In addition, the freeze concentration apparatus 100 includes a freezing tank 40 for freezing the stock solution and a melting tank 50 provided below the freezing tank 40, and a heat transfer tube (ice making chamber) 42 included in the freezing tank 40. Chiller units 45 and 46 for supplying cold brine or warm brine to the outside are provided. These tanks and the like are connected by a line (pipe), and pumps P1-P6 and valves V1-V16 are arranged in the middle of the line.

  As the tanks 10, 20, and 30, a suitable storage tank may be selected according to the type of the stock solution. The separation liquid tank 30 is preferably provided with a meter LI for measuring the amount of the obtained separation liquid. In addition, it is good also as a structure which can collect cold heat by immersing piping in a tank as needed. For example, the pipe of the separation liquid may be immersed in the stock solution tank 10 or the concentrate tank 20 so that the liquid stored in these tanks can be cooled in advance.

  The freezing tank 40 includes a plurality of heat transfer tubes 42 and a brine circulation tank 43 that accommodates brine and adjusts the temperature of the heat transfer tubes 42. The temperature of the heat transfer surface 42a of the heat transfer tube 42 can be adjusted by circulating brine at a predetermined temperature. The chiller units 45 and 46 are for adjusting the temperature of the cold brine and the warm brine, respectively. The chiller units 45 and 46 have brine tanks 45a and 46a, respectively.

  As shown in FIG. 1, the heat transfer surface 42a of the heat transfer tube 42 extends in the vertical direction. The length from the upper end to the lower end of the heat transfer tube 42 can be about 0.5 to 3 m. The heat transfer tube 42 is provided so as to penetrate the partition wall 44 that partitions the freezing tank 40 and the melting tank 50. With this configuration, the ice solution can be dropped into the melting tank 50 by circulating the warm brine after freezing the stock solution.

  The cross-sectional shape of the heat transfer tube 42 is not particularly limited as long as it does not prevent the ice body from falling downward, and may be either rectangular or circular. The material of the heat transfer tube 42 is preferably selected as appropriate depending on the type of the stock solution to be treated. For example, in an apparatus for treating organic wastewater, a metal material (such as stainless steel) is preferred and corrosive. In an apparatus for treating waste water containing a high inorganic acid, organic materials (vinyl chloride, polyethylene, polypropylene, etc.) are preferable.

  The melting tank 50 has solid-liquid contact means for bringing the ice body dropped from the freezing tank 40 into contact with the liquid, and is used for efficiently melting the ice body. Since the ice body frozen in the heat transfer tube 42 without stirring is lower in strength than that frozen in the stirring, it is crushed by the impact of dropping and becomes ice pieces in the melting tank 50.

The distance from the lower end of the heat transfer tube 42 in the melting tank 50 to the bottom surface 50a of the melting tank 50 is such that even if the entire amount of the liquid to be processed in the heat transfer tube 42 is frozen and falls into the melting tank 50, the ice pieces are transferred to the heat transfer tube. It is preferable that the width does not hit the lower end of 42. Specifically, when the repose angle of the ice body is assumed to be 45 °, the distance is preferably about a value (m) obtained by multiplying the internal volume (m ³ ) of the heat transfer tube 42 to the 0.3th power. . The melting tank 50 includes a plurality of nozzles 52 for injecting a liquid onto ice pieces deposited on the bottom surface 50a. The liquid in the melting tank 50 can be discharged through the discharge port 50b.

<Freeze concentration method>
A method for freezing and concentrating a stock solution using the freeze concentration apparatus 100 will be described. First, the stock solution stored in the tank 10 is sent to the concentrate tank 20 by the pump P1. The initial liquid feed amount is an amount that satisfies the total volume of the heat transfer tube 42 of the freezing tank 40 and the volume of the melting tank 50. The brine circulation tank 43 of the freezing tank 40 is filled with cold brine, and the temperature of the heat transfer surface 42a is adjusted to a predetermined temperature (about -20 to -3 ° C) in preparation for freezing. Next, the stock solution in the tank 20 is supplied to the melting tank 50 by the pump P2. Since the lower end of the heat transfer tube 42 communicates with the melting tank 50 and the upper end is opened, the supply of the stock solution is further continued after the melting tank 50 is full, so that the heat transfer tube as shown in FIG. The liquid level of the stock solution rises to the top of 42 (supply process).

  When the water is full, the pump P2 is stopped, and it is cooled by cold brine as it is without stirring, and waits for the stock solution to be iced on the heat transfer surface 42a (freezing step). Meanwhile, cold brine is circulated by the pump P5.

  After a predetermined time has elapsed, the valve V5 is opened, and the liquid in the melting tank 50 is discharged from the discharge port 50b to the concentrate tank 20. At this time, the unfrozen liquid in the heat transfer tube 42 flows into the melting tank 50 due to the influence of gravity and is also discharged into the concentrate tank 20.

  At the same time as the operation of discharging the liquid in the melting tank 50, the valve V12 is opened and the cold brine is discharged to the brine tank 45a. After confirming the completion of discharge of the liquid in the melting tank 50 and the cold brine, warm brine is supplied into the brine circulation tank 43 by the pump P6. The warm brine is for peeling off the ice body adhering to the heat transfer surface 42a, and is preferably at a temperature above the freezing point (about 0 to 20 ° C.).

  By supplying the warm brine, the ice body is peeled off from the heat transfer surface 42a, and the liquid is dropped into the empty melting tank 50 that has been discharged (crushing step). Ice bodies frozen with almost no agitation of the stock solution contain the concentrated solution and have a strength that can be easily broken by the impact of dropping. For this reason, as shown in FIG. 2 (b), ice pieces accumulate on the bottom surface 50 a of the melting tank 50.

  A part of ice pieces in the melting tank 50 is melted, and an initial melt containing a high concentration of solute is recovered. When melting ice pieces, since natural melting takes time, the valves V5 and V6 are opened, and the concentrated liquid in the tank 20 is supplied to the melting tank 50 through a line in which the pump P3 is disposed. As shown in FIG. 3A, this concentrated liquid is sprayed from a nozzle 52 provided above the melting tank 50 (first melting step). By performing such solid-liquid contact, melting of ice pieces is promoted. The concentrate is recovered in the concentrate tank 20 through a line in which the valve V5 is disposed (concentrate recovery step). When the amount of the melt recovered in the tank 20 reaches a predetermined amount (approximately ¼ of the ice body volume), the valve V5 is closed and the pump P3 is stopped.

  After recovering the concentrated liquid, it is preferable to carry out the melting process of the ice pieces by supplying the liquid in the raw liquid tank 10 to the melting tank 50 in order to collect the middle-stage molten liquid in the raw liquid tank 10. That is, the valves V7 and V2 are opened, and the liquid in the tank 10 is supplied to the melting tank 50 by the pump P1 and sprayed from the nozzle 52 (second melting step). The middle-stage melt is recovered in the stock solution tank 10 through a line in which the valve V7 is disposed (processed liquid recovery step). When the amount of the melt recovered in the tank 20 reaches a predetermined amount (approximately about 1/4 of the ice body volume), the valve V7 is closed and the pump P1 is stopped.

  In order to collect the last remaining ice content in the separation liquid tank 30 after the middle-stage melting liquid is collected, it is preferable to supply the liquid in the separation liquid tank 30 to the melting tank 50 and perform the ice piece melting treatment. That is, the valves V9 and V8 are opened, and the liquid in the tank 30 is supplied to the melting tank 50 by the pump P4 and sprayed from the nozzle 52 (third melting step). As shown in FIG. 3B, the melted solution or sherbet-like fluid of the remaining ice flows out from the discharge port 50b and is collected in the separation liquid tank 30 (separation liquid collection step).

When the above process is completed, the hot brine is switched to the cold brine to return to the state before the first freezing start. If it is necessary to repeat the concentration process a plurality of times to increase the concentration, the stock solution is sent to the concentrate tank 20 to set the liquid amount in the concentrate tank 20 to a predetermined amount, and then the concentration process is performed. Just do it. The stock solution fed to the concentrate tank 20 may be an amount corresponding to the amount of liquid recovered in the stock solution tank 10 and the separation solution tank 30 by the previous concentration process. When the ratio (V ₁ / V ₂ ) between the integrated flow rate V ₁ measured by the integrated flow meter IF and the volume V ₂ of the collected concentrated liquid reaches a predetermined value, the series of concentration processes is terminated. The concentrated liquid is discharged through the line provided with the valve V4, and the separated liquid is discharged through the line provided with the valve V10, whereby one batch of processing is completed.

According to the freeze concentration apparatus and the freeze concentration method using the same according to the above embodiment, the following effects are exhibited.
(1) When freezing the liquid to be treated, the equipment for flowing the liquid is unnecessary, and the equipment cost and power cost necessary for the flow can be reduced.
(2) When the ice body of the liquid to be treated is melted, by bringing it into contact with the liquid, the melting is promoted, and the time required for collecting the concentrated liquid, which is performance-limited in the conventional apparatus, can be greatly shortened. This improves the processing capability of the entire apparatus.
(3) By freezing the liquid to be treated without stirring, it is possible to obtain an ice body that contains the concentrated liquid and melts easily regardless of the freezing speed. For this reason, there is an advantage that it is not necessary to strictly control the freezing rate.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. For example, in the above embodiment, the case where the liquid is ejected from the nozzle 52 provided in the melting tank 50 and solid-liquid contact is performed is exemplified, but the method is not limited to this, and the crushed ice body You may employ | adopt the means to immerse this in the liquid (For example, concentrate, undiluted | stock solution) in the melting tank 50. FIG. Specifically, by supplying liquid to the melting tank 50 with the valves V5, V7, and V9 closed, the liquid level in the melting tank 50 is gradually raised so that the ice pieces are immersed in the liquid. Also good.

  Moreover, in the said embodiment, although the ice body was dropped in the melting tank 50 as a particularly preferable example, and the ice body was crushed by the impact, the ice body may be crushed by mechanical means. Alternatively, depending on the degree of freezing, the ice body may not necessarily be crushed.

<Freeze concentration test>
In order to experimentally show the effect of the present invention, a freezing operation of a liquid (CODcr = 45000 mg / L) containing N, N-dimethylformamide (DMF) was performed according to the following procedure. That is, 700 g of the liquid to be treated was placed in a steel cylinder (inner diameter 65 mm), and the outside was cooled with brine at −5 ° C. for 2 hours to freeze the liquid to be treated. The liquid to be treated was not stirred during the freezing process.

  After cooling, the ice body and the unfrozen liquid were separately collected. As a result, the ice body was 148 g and the CODcr of the unfrozen liquid was 57000 mg / L. As a result of contacting the ice body with the DMF-containing solution (150 ml, 18 ° C.) having a concentration equivalent to the DMF concentration (CODcr = 57000 mg / L) of the unfrozen solution for 4.8 minutes, 35 g of the melt was recovered. It was done. Thereafter, a DMF-containing liquid (160 ml, 18 ° C.) having a concentration equivalent to the DMF concentration (CODcr = 45000 mg / L) of the liquid to be treated was brought into contact with the remaining ice body over 5.1 minutes. Liquid was recovered. The final melt of 76 g of ice body had a CODcr of 3800 mg / L.

  As described above, by bringing the ice body into contact with the DMF-containing liquid, the weight of the ice body could be halved in a melting time of about 10 minutes (4.8 minutes + 5.1 minutes). At this time, ice bodies in which the residual amount of DMF was 8% with respect to DMF contained in the liquid to be treated were obtained. When the ice body is naturally melted in the air, the melting amount is about 10 to 70 g in 30 minutes (see the following reference test result), but by adopting the above method, the dissolved mass remaining in the ice body is reduced. It was shown that the melting process can be completed in a short time while maintaining a low rate. In addition, if the numerical value in this test is substituted into Formula 2 prescribed | regulated in the above-mentioned patent document 3, the lower limit of the melting time T will be calculated with 23 minutes.

  If forced stirring is not performed when freezing the liquid to be treated, the solute concentrate is partially contained in the ice body, but the degree of solute contamination in the ice crystal itself is low and the temperature is high. It is surmised that, by contacting with the liquid, the flow path of the encapsulated liquid was melted and released, and the encapsulated concentrated liquid could be effectively flowed out while suppressing the melting of ice crystals. This test showed that three types of liquids can be recovered from the liquid to be treated. That is, it was shown that an unfrozen solution having a low freezing point can be recovered as a concentrated solution, a medium-term melt can be recovered together with the liquid to be treated, and the remaining ice melt can be recovered as a separated solution.

<Reference test>
A freezing operation of an aqueous NaCl solution (concentration 3 wt%, freezing point −1.6 ° C.) was performed according to the following procedure. That is, 700 g of the liquid to be treated was placed in a steel cylinder (inner diameter 65 mm), and the outside was cooled with -3 ° C. brine for 20 hours to freeze the liquid to be treated. The liquid to be treated was not stirred during the freezing process.

  After cooling, 380 g of ice was adhered to the inner surface of the cylinder. After recovering the ice body from the cylinder, when it was slowly transferred to the beaker manually, the ice body collapsed as an ice piece. Even when the brine temperature was close to the freezing point of the liquid to be treated and it was frozen slowly over 20 hours, the ice body formed without stirring had a weak physical strength.

  The solute concentrations in the melt and final residual ice when the ice body was naturally melted indoors (15 ° C.) were measured. From these measured values, the solute residual rate in ice relative to the residual amount of ice was calculated. The residual ice amount means the ratio of the residual ice body weight to the ice body weight before melting, and the solute residual rate in ice means the concentration ratio to the liquid to be treated. The results are shown in FIG.

  Regarding the melting time of ice bodies, in this test, it took 1 hour and 15 minutes to halve the weight of ice bodies, and 2 hours and 50 minutes to melt the whole amount. From the graph of FIG. 4, the solute residual rate in ice of the residual ice in which 50% of the ice body melted is about 0.1. It can be seen that ice bodies formed under no stirring even under slow freezing conditions can yield residual ice with a high degree of solute separation by melting operation.

  DESCRIPTION OF SYMBOLS 10 ... Raw liquid tank (1st tank), 20 ... Concentrated liquid tank (2nd tank), 30 ... Separation liquid tank, 40 ... Freezing tank, 42 ... Heat transfer pipe (ice-making room), 42a ... Heat transfer surface, 43 ... Brine Circulating tank, 44 ... partition wall, 45, 46 ... chiller unit, 45a, 46a ... brine tank, 50 ... melting tank (solid-liquid contact means), 50a ... bottom of melting tank, 50b ... outlet of melting tank, 52 ... nozzle (Solid-liquid contact means), 100 ... Freeze concentrator, IF ... Integrated flow meter, P1-P6 ... Pump, V1-V16 ... Valve.

Claims (6)

A freeze concentration method for concentrating a solute contained in a liquid to be treated by freezing the liquid to be treated,
A supply step of supplying the liquid to be treated to an ice making chamber having a heat transfer surface;
A freezing step of freezing the liquid to be treated in the ice making chamber;
A first melting step in which a high-concentration liquid having a higher solute concentration than the liquid to be treated is brought into contact with an ice body of the liquid to be treated to melt a part of the ice body;
A concentrated liquid recovery process for recovering a mixed liquid of the high-concentration liquid used in the first melting process and the melt of the ice body;
After the concentrated liquid recovery step, a separated liquid recovery step for recovering the ice body in a frozen state or in a liquid state by melting it,
A freeze concentration method comprising the steps of:   When the series of steps from the supply step to the separation liquid recovery step is repeatedly performed, the liquid mixture obtained through the concentrate recovery step is used as the high concentration liquid in the melting step. The freeze concentration method according to claim 1.   The crushing step of crushing the ice body after the freezing step is further provided, and the crushed material of the ice body and the high-concentration liquid are brought into contact in the first melting step. Freeze concentration method. In the case where the supplying step supplies a part of the liquid to be processed to the ice making chamber, after the first melting step, the ice body of the liquid to be processed and the remaining liquid to be processed are brought into contact with each other. A second melting step for further melting a part of the ice body;
A liquid recovery process for recovering a liquid mixture of the remaining liquid to be processed used in the second melting process and the melt of the ice body;
Further comprising
The freeze concentration method according to any one of claims 1 to 3, wherein the separation liquid recovery step is performed after the processing liquid recovery step. A freeze concentration apparatus that concentrates a solute contained in a liquid to be treated by freezing the liquid to be treated,
A first tank for storing the liquid to be treated;
An ice making chamber having a heat transfer surface and freezing the liquid to be treated supplied from the first tank;
Solid-liquid contact means for contacting a high-concentration liquid having a higher concentration of solute than the liquid to be treated and an ice body of the liquid to be treated;
A second tank for storing a mixture of the high-concentration liquid transferred from the solid-liquid contact means and the melt of the ice body;
A freeze concentrating device comprising:   The heat transfer surface of the ice making chamber extends in the vertical direction, and further comprises a melting tank for storing crushed pieces of ice of the liquid to be treated below the heat transfer surface. The freeze concentration apparatus according to claim 5.

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