JP2003024736A - Gas-liquid contact apparatus and freezing, concentration, and separation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a gas-liquid contact apparatus reducing the supplied amount of water while keeping solvent absorbing efficiency and making the concentration of a solvent in finally discharged water high. SOLUTION: Water having absorbed a solvent in gas is drained from a treatment tank 14 to be sent to a freezing device 22. From the difference between the coagulation points of water and the solvent, the solvent is not frozen but water is frozen to become ice near to pure water. Herein, there is such a tendency that an ice layer C1 containing the solvent in high concentration adheres to the surface of an ice plate C. Therefore, hot air is sprayed on the ice layer C1 and the surface of the ice plate C is melted by predetermined thickness to be removed to make it possible to reduce the concentration of the solvent contained in the ice plate C. This ice is melted to be again used in the treatment tank 14 to reduce the amount of fresh water. The concentration of the solvent in unfrozen water separated from water becomes high by concentration and water containing the solvent in high concentration can be used as a washing agent, fuel, and a coating solution applied to a planographic printing plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas-liquid contactor and a freeze concentration separation method for recovering, for example, a volatile organic compound (VOC) gas discharged from a plant or the like to the atmosphere.

[0002]

2. Description of the Related Art As shown in FIG. 6, the water used in a sprinkler type gas-liquid contactor 158 for absorbing VOC gas G discharged from a plant or the like into the atmosphere is treated by treating towers 160, 16.
In 2, 164, the solvent concentration gradually increases due to contact with the gas. When the water that has absorbed this solvent is directly returned to the processing tanks 166, 168, 170, the solvent concentration in the water in the entire processing tank rises, and even if this water is supplied to the processing tower, it is in a good condition continuously. Cannot absorb solvent (solvent collection efficiency decreases).

Therefore, in order to maintain the solvent absorption efficiency, it is necessary to continuously supply fresh water W from the water conduit 172 to the treatment tank 170, and it is not possible to reduce the amount of makeup water.

In addition, how high the concentration of the solvent contained in the water W1 finally discharged from the drain pipe 174 of the treatment tank 166 of the sprinkler type gas-liquid contactor 158 and how to distill it and reuse it is determined. This is a major point in reducing running costs.

Therefore, the applicant of the present invention has proposed a gas-liquid contactor for separating water having absorbed a solvent into ice and concentrated solvent-containing water by means of a freeze concentration separator (Japanese Patent Application No. 200).
0-074783).

By using this gas-liquid contactor, the amount of make-up water can be reduced, the solvent absorption efficiency can be maintained, and the concentration of the solvent contained in the finally discharged water can be made high. However, in order to prevent the solvent from being contained in ice during freeze-concentration separation, some more work needs to be done.

[0007]

In consideration of the above facts, the present invention freezes and separates the water that has absorbed the solvent, and then partially removes the ice containing a large amount of the solvent so that the solvent is contained as much as possible. The challenge is to make ice without ice and reduce the amount of makeup water.

[0008]

According to the first aspect of the present invention, there is provided a treatment tower into which a gas is introduced from a gas generating source, and a treatment tank in which water is supplied to the treatment tower and water in which a solvent is absorbed is refluxed. A gas-liquid contact unit, a freezing means for freezing the water containing the solvent drained from the treatment tank, a recycling means for melting the ice frozen by the freezing means and sending the water to the treatment tank. In the gas-liquid contactor including the above, it is characterized by having a removing means for removing the surface of the ice frozen by the freezing means.

In the above structure, the water having absorbed the solvent in the gas is drained from the processing tank and sent to the freezing means. When the freezing means freezes the water containing the solvent, the solvent does not freeze due to the difference in freezing point, and the water freezes to become ice close to pure water.

Here, ice containing a high concentration of solvent tends to adhere to the surface of the ice frozen and adhered to the cooling surface of the freezing means. Therefore, the concentration of the solvent contained in the ice recycled by the recycling unit can be reduced by removing the surface of the ice by a predetermined thickness by the removing unit.

Then, the recycling means melts the ice which does not contain much solvent, sends the water to the processing tank, and again contacts the gas introduced into the processing tower to absorb the solvent in the gas.
In this way, by melting clean ice and reusing it as water, the amount of fresh water supplied to the processing tank can be reduced.

Further, the solvent concentration of the unfrozen water separated from the water is higher than that of the conventional gas-liquid contactor due to its concentration, and the water containing the high concentration solvent is used as a cleaning agent, It is also possible to use it as a fuel or a coating liquid for coating a lithographic printing plate.

The invention according to claim 2 is characterized in that the removing means is a hot air generating means for blowing hot air onto the surface of the ice to melt the surface of the ice by a predetermined thickness and remove it.

In the above structure, the hot air generating means blows hot air onto the surface of the ice to melt the surface of the ice, whereby the ice containing the high concentration solvent can be easily removed.

The invention according to claim 3 is characterized in that the ice is made thick as much as the surface is removed. As a result, even if the surface of the ice is removed, the required amount of ice to be sent to the recycling means can be secured.

According to a fourth aspect of the present invention, in a freeze-concentration separation method in which water containing a solvent is frozen in a freezing device and separated into ice and a concentrated liquid having a high solvent concentration, the freezing device freezes the water. The feature is that the surface of ice is removed by a predetermined thickness to separate it into ice and concentrated liquid.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIGS. 1 and 2, the gas-liquid contactor 10 according to this embodiment includes a gas-liquid contacting unit 30 composed of a processing tower 12 and a processing tank 14.

In the processing tank 14 of the gas-liquid contact unit 30,
The supply pipe 24 is connected. The supply pipe 24 is provided with the pump 20, and by operating the pump 20, fresh water and recycle water described later are supplied from the storage tank 52 as treated water. Further, the water supply pipe 26 connected to the side wall of the treatment tank 14 is provided with a liquid feed pump 28, and water is pumped to the top of the treatment tower 12. Processing tower 1
The water pumped to the top of 2 is sprinkled downward by the sprinkler 32.

A gas pipe 34 for taking in the volatile organic compound (VOC) gas discharged from the plant P is connected to the outer peripheral wall of one of the processing towers 12, and the VOC gas is continuously introduced into the processing tower 12. Will be sent.

The VOC gas taken from the gas pipe 34 into the treatment tower 12 is raised and comes into contact with the water sprinkled by the sprinkler 32 for batch treatment, whereby the concentration of the contained solvent is lowered. Then, the VOC gas that has come into contact with water is released to the atmosphere as a gas that does not affect the environment through the exhaust pipe 40 connected to the top of the processing tower 12.

A drain pipe 44 is connected to the processing tank 14. The drain pipe 44 is provided with an electromagnetic valve 78, and by operating this electromagnetic valve 78, the water in the processing tank 14 is drained to the intermediate tank 16.

The amount of water replenished from the replenishment pipe 24 to the treatment tank 14 and the amount of water drained from the treatment tank 14 are substantially the same, and the solvent can be recovered in batch processing without stopping the VOC gas. Has become.

On the other hand, the processing tank 14 is provided with a concentration sensor 80, which detects the solvent concentration of the processing tank 14 and sends a signal to the control unit 84. The control unit 84 is connected to the solenoid valve 78 and the pump 20, and switches the water in the processing tank 14 based on the detection result of the concentration sensor 80.

When the solvent concentration of water in the processing tank 14 detected by the concentration sensor 80 exceeds a predetermined value, the pump 2
0 to activate fresh water through the supply pipe 24
4, the solenoid valve 78 is opened and the water having a high solvent concentration is drained from the drainage pipe 44 to replace the inside of the treatment tank 14 with fresh water.

By repeating the above operation,
The solvent in the VOC gas can be collected with high efficiency, and the solvent concentration of the drained water also becomes high. For this reason, the recovery efficiency of the next process is improved, and the equipment cost and running cost can be reduced.

As the gas-liquid contact method, a water spray method,
Filling schemes are known but not specified. Further, the number of gas-liquid contact units is not limited to one as in the present embodiment, and may be plural.

Further, the concentration of the volatile organic compound gas to be treated is preferably 100 ppm or more, and 1000 p
At pm or above, the effect is remarkable. Also, as the type of solvent gas, the difference in solubility parameter with water is 19 (cal.
cm ^-3 ) ^{1/2 or} less is preferable, and 15 (cal · cm ^-3 ).
Less than ^1/2 is more preferable (Solubility parameter: Hild
solubility parameter of ebrand).

Further, the solvent of the volatile organic compound is not limited to methyl ethyl ketone as long as it is water-soluble, and alcohols such as methanol, ethanol and n-propanol, polyhydric alcohols such as ethylene glycol, acetone and methyl are used. Ketones such as acetone and cyclohexane, and esters such as methyl formate, ethyl formate, methyl acetate, ethyl acetate, and ethyl lactate may be used. further,
It can also be treated with mixed solvent gas.

The temperature of the replenished water is preferably 30 ° C. or lower, more preferably 15 ° C. or lower. The solvent concentration of the water to be replenished is preferably 2000 ppm or less. Further, in this example, water was used as the treated water for recovering the solvent in the VOC gas, but the same effect can be obtained with sludge water or activated sludge containing microorganisms.

Next, how to use the wastewater for one batch stored in the intermediate tank 16 as recycled water will be described.

The water in the intermediate tank 16 is sent to the freezing device 22 through the supply pipe 38 by opening / closing the solenoid valve 18 by the control section 84.

The freezing device 22 includes a tubular cooling pipe 36 connected in an annular shape. Water containing a solvent is supplied from the supply pipe 38 to the cooling pipe 36. Then, the water in the cooling pipe 36 has a flow velocity (for example, 1.0) set by the circulation pump 42 whose driving force is controlled by the controller 84.
m / sec) and circulates along the cooling surface 36A (see FIG. 3).

The vertical portion of the cooling pipe 36 is cooled by a cooling coil 46 in which a refrigerant circulates, and the cooling coil 46 shown in FIGS.
As shown in (B), the ice plate C is formed on the cooling surface 36A. An opening / closing door 48 is provided below the cooling pipe 36 so that the ice plate C can be taken out from below. The unfrozen water in the cooling pipe 36 is sent to the distiller 64 through the drain pipe 50.

A control unit 84 is provided above the cooling pipe 36.
A heater 92 and a blower fan 90 that are operated in the above are arranged, and hot air is blown into the cooling pipe 36 through a duct 94 having an opening / closing valve (not shown). If the temperature of this warm air is too high, only the surface of the ice plate cannot be melted, so 10 ° C to 50 ° C is preferable.
The temperature is preferably 00 ° C or lower.

On the other hand, the ice plate C containing almost no solvent taken out from the freezing device 22 is temporarily stored in the ice storage tank 56 through the charging pipe 54, and then as cold water (or water containing ice particles). It is sent to the heat exchanger 60 through the cold water pipe 62 by the pump 58. As described above, by storing ice and supplying it as cold water, it is possible to stably supply the refrigerant to the heat exchanger 60. The heat exchanger 60 uses cold heat of cold water and is used for air conditioning in a factory.

Further, the cold water (water containing almost no solvent) that has undergone heat exchange in the heat exchanger 60 is sent to the storage tank 52 as recycled water, and is again sent to the processing tank 14.

On the other hand, the water (unfrozen water) containing the high-concentration solvent discharged from the freezing device 22 is sent to the distiller 64 through the drain pipe 50. The distiller 64 separates the solvent and water by vaporization by utilizing the difference in boiling points between the solvent and water, and water containing a high-concentration solvent is introduced into the distillation column 66 from the supply port 68. In the distillation column 66, the vapor and the liquid come into contact with each other, the solvent having a low boiling point component is collected in the vapor, and the water having a high boiling point component is concentrated in the liquid.

As a result, the solvent is sent as vaporized vapor to the condenser 72 through the exhaust pipe 70, and is condensed in the condenser 72 to be recovered in the recovery tank 74 as a solution containing a high concentration of solvent. Also, the water separated from the solvent is
It is drained from the drainage port 76 and sent to the storage tank 52 through the water supply pipe 82 equipped with the water supply pump 86.

Here, the procedure for freezing and separating water containing a solvent in the refrigerating apparatus 22 to separate ice containing almost no solvent and water containing a high concentration of solvent will be described.

First, the solenoid valve 18 is opened, water containing solvent is supplied from the intermediate tank 16 to the cooling pipe 36, and as shown in FIGS. 3 (A) and 3 (B), a predetermined flow velocity (1 .0 m / sec), the ice plate C with a reduced solvent content is made on the surface of the cooling surface 36a.

As described above, it is possible to make the ice plate C having a small content of the solvent by giving a flow rate to the water containing the solvent. When water is drained from 50 and the ice plate is taken out, a high-concentration solvent tends to adhere to the ice liquid interface. Therefore, if the ice plate C is taken out from the cooling pipe 36 as it is, the ice plate C having a high solvent concentration is sent to the ice storage tank 56.

Therefore, the heater 92 and the blower fan 90
The warm air M is sent to the cooling pipe 36 through the duct 94, and the ice layer C1 containing the high-concentration solvent adhering to the surface of the ice plate C is melted and removed by a predetermined thickness to expose a clean ice surface . This can prevent the ice plate C having a high solvent concentration from being sent to the ice storage tank 56.

In this embodiment, an example in which the ice layer C1 is melted and removed with warm air has been described, but an ice shaving machine with a cutter turning is inserted from the duct 94 to scrape off the ice layer C1 having a predetermined thickness. May be. Further, in order to melt the surface of the ice plate and obtain the required amount of ice, it is desirable to make a thick ice plate in consideration of the removed amount. The melted ice layer water is drained from the cooling pipe 36 through the drain pipe 50.

Next, in order to verify the effect of the present invention, an ice making test was conducted under different conditions as shown in the table of FIG. The present invention is not limited to this test and is included in the present invention without departing from the spirit of the present invention.

From the exhaust gas containing methanol discharged from the plant P, methanol was recovered with a scrubber as a gas-liquid contactor.

Exhaust gas containing methanol is 1.0 Nm
^It was introduced into the processing tower 12 at a rate of ³ / min. The content of methanol in the exhaust gas was 3000 ppm. When water drawn up from the treatment tank 14 was sprinkled from the sprinkler 32 of the treatment tower 12 and exhaust gas was introduced to perform batch treatment, the concentration of methanol in the water discharged from the treatment tank 14 was 1000.
It became 0 ppm.

Concentration of methanol as this solvent 1000
0 ppm of water was introduced into the freezing device 22 and freeze-concentrated. Then, the concentration of the solvent contained in the ice and the concentration of the solvent in the unfrozen concentrate were measured by introducing warm air into the cooling pipe to melt the surface of the ice plate and in the case of not melting.

When hot air at 40 ° C. was introduced into the cooling pipe for 2 minutes to melt the surface of the ice plate, the solvent content concentration of the ice plate was 300 ppm, which was as good as that when no hot air was introduced. In addition, the solvent concentration of the unfrozen concentrate is
It became 27,000 ppm.

On the other hand, when the ice making time is 70 minutes, 0.5 m
When an ice plate with a thickness of m is made and the surface is melted and removed with warm air, the thickness is 16.0 mm and the concentration of solvent is 300.
It was possible to obtain ppm of clean ice, and the solvent concentration of the unfrozen concentrated solution was 29400 ppm.

As described above, after melting the ice plate made into ice and returning to the processing tank 14 to treat the exhaust gas, as shown in the table of FIG. 5, the gas released from the exhaust pipe 40 to the atmosphere is discharged. The sample was sampled and the removal rate of the volatile organic compound (VOC) gas was determined and observed.

As a result, the solvent content concentration in ice was 100 p
pm, 300ppm, 800ppm, 2000ppm in this order, the VOC gas removal rate is 93%, 90%, 85
% And 70% were obtained, and it can be seen that the VOC gas can be reused as a treatment liquid.

The concentration of the solvent component contained in the water sent to the freezing device 22 is preferably 1000 ppm, more preferably 5000 ppm or more for concentrating the solvent to a high concentration.

Furthermore, the water concentrated in the freezing device 22 may be reused as it is as an alternative fuel such as a cleaning liquid or heavy oil. When sending the concentrated water to the distiller 64, the concentration of the solvent component contained in the water is preferably 1% or more,
0% or more is more preferable.

Further, the heat-exchanged cold water may be decomposed in a waste water treatment facility using activated sludge or the like, and depending on the concentration of the solvent component contained (if the COD value and the BOD value are within the allowable values). ), It may be discharged as it is.

The method of the water scrubber is not limited to the spray type, the filling type and the like, and the method of absorbing gas in water may not be the scrubber. Furthermore, the freezing device 22
Although the distiller 64 was used as a means for separating the water containing the solvent concentrated in 1. into the solvent and the water, a membrane separator, a centrifugal separator, or the like may be used.

Here, the PS plate manufacturing process, which is one of the manufacturing processes for generating the VOC gas, will be briefly described.

The PS plate is JIS containing 99.5% by weight of aluminum, 0.01% by weight of copper, 0.03% by weight of titanium, 0.3% by weight of iron and 0.1% by weight of silicon.
-A1050 aluminum material with a thickness of 0.30 mm and rolled with 400 mesh pumice stone (manufactured by Kyoritsu Kiln)
Wt% aqueous suspension and rotating nylon brush (6,10-
Nylon) and the surface thereof was grained and then thoroughly washed with water.

This was immersed in a 15% by weight sodium hydroxide aqueous solution (containing 4.5% by weight of aluminum) to perform etching so that the amount of aluminum dissolved was 5 g / m ² , and then washed with running water. Furthermore, neutralize with 1 wt% nitric acid,
Next, in a 0.7% by weight nitric acid aqueous solution (containing 0.5% by weight of aluminum), a rectangular wave alternating waveform voltage (current ratio r = 0.9, voltage at anode: 10.5 V, voltage at cathode: 9.3 V).
0, the current waveform described in JP-B-58-5796) was used to perform electrolytic surface roughening treatment at an anode hour electricity of 160 coulomb / dm ² . After washing with water, 1 at 35 ℃
It was immersed in a 0 wt% sodium hydroxide aqueous solution, etched so that the amount of aluminum dissolved was 1 g / m ² , and then washed with water. Next, it was immersed in a 30% by weight sulfuric acid aqueous solution at 50 ° C., desmutted, and washed with water.

Further, a porous anodic oxide film forming treatment was carried out by using a direct current in a 20% by weight sulfuric acid aqueous solution (containing 0.8% by weight of aluminum) at 35 ° C. That is, electrolysis was performed at a current density of 13 A / dm ² , and the anodic oxide film weight was set to 2.7 g / m ² by adjusting the electrolysis time. In order to prepare a negative photosensitive lithographic printing plate using a diazo resin and a binder, this support was washed with water, immersed in a 3% by weight aqueous solution of sodium silicate at 70 ° C. for 30 seconds, washed with water and dried.

[0061] The thus-obtained aluminum support, reflection density was measured with Macbeth RD920 reflection densitometer 0.30, the center line average roughness R _a as defined in JIS B00601 is 0.58μm met It was

Next, methyl methacrylate /
The coating amount of a 1.0 wt% aqueous solution of ethyl acrylate / 2-acrylamido-2-methylpropanesulfonate copolymer (average molecular weight of about 60,000) (molar ratio 50/30/20) was dried by a roll coater. 0.05 g
It was applied so as to be / m ² .

Further, the following photosensitive solution-1 was used as a coating solution.
Apply using the bar coater used in the present embodiment, 110 ℃
And dried for 45 seconds. The dry coating amount was 2.0 g / m ² . Photosensitive solution-1 Diazo resin-1 0.50 g Binder-1 5.00 g Stilite HS-2 (manufactured by Daido Industry Co., Ltd.) 0.10 g Victoria Pure Blue BOH 0.15 g Tricresyl phosphate 0.50 g Dipicolinic acid 0 20 g FC-430 (3M surfactant) 0.05 g Solvent 1-methoxy-2-propanol 25.00 g Methyl lactate 12.00 g Methanol 30.00 g Methyl ethyl ketone 30.00 g Water 3.00 g

The above-mentioned diazo resin-1 is obtained as follows. First, 29.4 g of 4-diazodiphenylamine sulfate (purity 99.5%) was added at 25 ° C.
It was slowly added to 70 ml of 6% sulfuric acid and stirred for 20 minutes. Paraformaldehyde (purity 92%) 3.
26 g was added slowly over about 10 minutes and the mixture was added to 30
The mixture was stirred at 4 ° C. for 4 hours to proceed with the condensation reaction. In addition,
The condensation molar ratio of the diazo compound and formaldehyde is 1: 1. The reaction product was poured into 2 liters of ice water with stirring and treated with a cold concentrated aqueous solution in which 130 g of sodium chloride was dissolved. The precipitate was collected by suction filtration, the partially dried solid was dissolved in 1 liter of water, filtered, cooled with ice and treated with an aqueous solution containing 23 g of potassium hexafluorophosphate. Finally, the precipitate was collected by filtration and air dried to give the diazo resin-
1 g was obtained.

The binder-1 is a 2-hydroxyethyl methacrylate / acrylonitrile / methyl methacrylate / methacrylic acid copolymer (weight ratio 50/20/26 /
4, average molecular weight 75,000, acid content 0.4 meq /
g) Water-insoluble, alkaline water-soluble film-forming polymer.

Stilite HS-2 (manufactured by Daido Industry Co., Ltd.)
Is a polymer compound having a higher oil sensitivity than the binder,
It was a copolymer of styrene / maleic acid mono-4-methyl-2-pentyl ester = 50/50 (molar ratio) and had an average molecular weight of about 100,000. The matte layer was formed by spraying the matte layer forming resin liquid on the surface of the photosensitive layer thus prepared as described below.

Methyl methacrylate / ethyl acrylate / 2-acrylamide-as a mat layer forming resin liquid
2-Methylpropanesulfonic acid (charge ratio 65: 2)
0:15) 12% with part of the copolymer as sodium salt
Prepare an aqueous solution, and rotate the atomizing head with a rotary atomizing electrostatic coating machine to a rotation speed of 2
5,000 rpm, the amount of resin liquid to be sent is 4.0 ml / min,
The applied voltage to the atomizing head was -90 kV, the ambient temperature during coating was 25 ° C, and the relative humidity was 50%. The coating solution was sprayed with steam for 2.5 seconds to wet it, and then 3 seconds after wetting. Warm air having a temperature of 60 ° C. and a humidity of 10% was blown for 5 seconds to dry. The height of the mat was about 6 μm on average, the size was about 30 μm on average, and the coating amount was 150 mg / m ² .

[0068]

EFFECTS OF THE INVENTION Since the present invention has the above constitution, the amount of replenishing water can be reduced, the solvent absorption efficiency can be maintained, and the solvent concentration of the finally discharged treatment liquid can be made high and reused. Moreover, energy saving can be achieved by utilizing cold heat.

[Brief description of drawings]

FIG. 1 is a perspective view showing a gas-liquid contact device according to the present embodiment.

FIG. 2 is a block diagram showing a gas-liquid contact device according to the present embodiment.

FIG. 3 is a schematic diagram showing how an ice plate is made into ice and the surface is melted by warm air.

FIG. 4 is a test result for determining the solvent concentration of the ice plate melted by warm air and the ice plate not melted with warm air and the solvent concentration of the concentrated liquid.

FIG. 5 is a table showing recovery and removal rates when gas is recovered using recycled water.

FIG. 6 is a side view showing a conventional gas-liquid contact device.

[Explanation of symbols]

12 processing tower 14 Processing tank 22 Freezing device (freezing means) 36 Cooling pipe 36A cooling surface 42 Circulation pump (freezing means) 56 Ice storage tank (recycling means) 60 heat exchanger (recycling means, heat exchange means) 90 Blower fan (removal means, warm air generation means) 92 Heater (removal means, warm air generation means)

Claims (4)

[Claims] 1. A gas-liquid contacting unit comprising a processing tower into which gas is introduced from a gas generating source, and a processing tank for supplying water to the processing tower and refluxing water having absorbed a solvent, and the processing tank. In a gas-liquid contactor comprising a freezing means for freezing the water containing the solvent that is drained from the solvent, and a recycling means for melting the ice frozen by the freezing means and sending the water to the treatment tank. A gas-liquid contact device comprising a removing means for removing the surface of frozen ice. 2. The gas / liquid according to claim 1, wherein the removing unit is a warm air generating unit that blows warm air onto the surface of the ice to melt the surface of the ice by a predetermined thickness and remove the hot air. Contact device. 3. The gas-liquid contactor according to claim 1 or 2, wherein the ice is made thick as much as the surface is removed. 4. A freeze-concentration separation method in which water containing a solvent is frozen in a freezing device to separate it into ice and a concentrated liquid having a high solvent concentration, wherein the surface of the ice frozen in the freezing device has a predetermined thickness. A freeze-concentration separation method, characterized in that it is removed only and separated into ice and a concentrated solution.