Recovery method and recovery device of temperature-sensitive polymer

Abstract

To provide a recovery device of a temperature-sensitive polymer capable of efficiently recovering a temperature-sensitive polymer dissolved in water to be treated.SOLUTION: A recovery device 1 of a temperature-sensitive polymer for recovering a temperature-sensitive polymer capable of being changed between hydrophilicity and hydrophobicity by temperature change from water to be treated where the temperature-sensitive polymer is dissolved includes a first heat exchanger 2 for changing the temperature-sensitive polymer contained in the water to be treated to the hydrophobicity from the hydrophilicity, a polymer separation tank 3 for separating the temperature-sensitive polymer having been changed to the hydrophobicity from the water to be treated, and a second heat exchanger 4 for changing the separated temperature-sensitive polymer to the hydrophilicity from the hydrophobicity, wherein the first heat exchanger 2 and the second heat exchanger 4 change the temperatures of the temperature-sensitive polymer to mutually opposite directions, by using mutual heat transfer using a heat pump chiller 5.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for recovering a thermosensitive polymer, and more particularly, to a method and an apparatus for recovering a thermosensitive polymer that dissolves in water to be treated.

Background Art

[0002] An aqueous solution of a thermosensitive polymer has been conventionally used, for example, as a draw solution for concentrating a feed solution such as seawater by forward osmosis treatment using a semipermeable membrane (for example, Patent Document 1). Since the thermosensitive polymer has the property of changing from soluble to insoluble depending on a temperature change, Patent Document 1 discloses that, by utilizing this property, a draw solution from which water has been recovered from a feed solution by forward osmosis treatment is heated to a temperature equal to or higher than the lower critical solution temperature of the thermosensitive polymer in a recovery system to separate and recover the thermosensitive polymer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, since the concentration method disclosed in Patent Document 1 is performed by membrane treatment, it usually does not have a heat source required for heating the draw solution, and it is difficult to recover the thermosensitive polymer while achieving energy saving in an environment where waste heat or cooling water cannot be used.

[0005] Therefore, an object of the present invention is to provide a method and an apparatus for recovering a thermosensitive polymer that can efficiently recover a thermosensitive polymer dissolved in water to be treated.

Means for Solving the Problems

[0006] The object of the present invention is a method for recovering a thermosensitive polymer that can be changed between hydrophilicity and hydrophobicity by a temperature change from treated water in which the thermosensitive polymer is dissolved, the method including a polymer hydrophobization step of changing the thermosensitive polymer contained in the treated water from hydrophilic to hydrophobic, a polymer separation step of separating the thermosensitive polymer that has changed to hydrophobic from the treated water, and a polymer hydrophilization step of changing the separated thermosensitive polymer from hydrophobic to hydrophilic, and the polymer hydrophobization step and the polymer hydrophilization step are achieved by a method for recovering a thermosensitive polymer that utilizes heat transfer between each other using a heat pump chiller to change the temperature of the thermosensitive polymer in opposite directions to each other.

[0007] In this method for recovering a thermosensitive polymer, when the thermosensitive polymer has a lower critical solution temperature, it is preferable that the polymer hydrophobization step includes a polymer heating step of heating the thermosensitive polymer by heat exchange with a heating medium heated by the heat pump chiller, and it is preferable that the polymer hydrophilization step includes a polymer cooling step of cooling the thermosensitive polymer by heat exchange with a cooling medium cooled by the heat pump chiller. In this case, it is preferable that the polymer hydrophobization step further includes a heating control step of controlling the flow rate of the heating medium based on the temperatures of the heating medium and the thermosensitive polymer after heat exchange, and it is preferable that the polymer hydrophilization step further includes a cooling control step of controlling the flow rate of the cooling medium based on the temperatures of the cooling medium and the thermosensitive polymer after heat exchange. It is preferable that the polymer hydrophilization step further includes a step of branching a part of the cooling medium cooled by the heat pump chiller and cooling the residual liquid by heat exchange with the residual liquid from which the thermosensitive polymer has been separated from the treated water, and it is preferable that the cooling control step includes a step of controlling the branched flow rate of the cooling medium based on the temperatures of the residual liquid and the thermosensitive polymer after heat exchange.

[0008] Further, a polymer addition step of adding the thermosensitive polymer rendered hydrophilic by the polymer hydrophilization step to the water to be treated having a substance to be concentrated passing through the semipermeable membrane, and a step of supplying the water to be treated that has undergone the polymer addition step to a semipermeable membrane unit including the semipermeable membrane to separate permeated water, and discharging the permeated water as concentrated water in which the substance to be concentrated is concentrated can be further provided. The polymer hydrophobization step is preferably performed on the water to be treated after the permeated water is separated.

[0009] Further, the object of the present invention is a recovery device for a thermosensitive polymer that recovers the thermosensitive polymer from the water to be treated in which the thermosensitive polymer capable of changing between hydrophilicity and hydrophobicity due to a temperature change is dissolved, and includes a first heat exchanger that changes the thermosensitive polymer contained in the water to be treated from hydrophilic to hydrophobic, a polymer separation tank that separates the thermosensitive polymer that has changed to hydrophobic from the water to be treated, and a second heat exchanger that changes the separated thermosensitive polymer from hydrophobic to hydrophilic. The first heat exchanger and the second heat exchanger are achieved by a recovery device for a thermosensitive polymer that utilizes heat transfer between each other using a heat pump chiller to change the temperature of the thermosensitive polymer in opposite directions.

Advantages of the Invention

[0010] According to the method and device for recovering a thermosensitive polymer of the present invention, the thermosensitive polymer dissolved in the water to be treated can be efficiently recovered.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0012] <First Embodiment> Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of a temperature-sensitive polymer recovery device (hereinafter simply referred to as "recovery device") according to a first embodiment of the present invention. The recovery device 1 shown in FIG. 1 is a device for recovering a temperature-sensitive polymer from treated water in which the temperature-sensitive polymer is dissolved, and includes a first heat exchanger 2, a polymer separation tank 3, a second heat exchanger 4, a heat pump chiller 5, and a third heat exchanger 6 as main components.

[0013] A temperature-sensitive polymer is a polymer that can be changed between hydrophilicity and hydrophobicity by a temperature change. The temperature-sensitive polymer used in this embodiment is a temperature-sensitive polymer having a lower critical solution temperature (LCST). At a temperature lower than the lower critical solution temperature, it exhibits hydrophilicity and binds to water molecules in the treated water, making it easier to dissolve in the treated water. On the other hand, at a temperature higher than the lower critical solution temperature, it becomes hydrophobic and the bond with water molecules is broken. Such a temperature-sensitive polymer can be, for example, one contained in the draw solution of a conventional forward osmosis water treatment method.

[0014] The first heat exchanger 2 heats the temperature-sensitive polymer contained in the treated water to a temperature higher than the lower critical solution temperature by performing heat exchange between the supplied treated water and a heating medium. As a result, the temperature-sensitive polymer changes from hydrophilic to hydrophobic and becomes insoluble. The heating medium is, for example, water, and circulates through the first flow path 61 by the operation of the heating pump 12.

[0015] The polymer separation tank 3 separates the insolubilized thermosensitive polymer from the water to be treated supplied from the first heat exchanger 2. The separated thermosensitive polymer is supplied to the second heat exchanger 4 by the operation of a polymer supply pump 11. In addition, the residual liquid remaining after the thermosensitive polymer is separated from the water to be treated is supplied to the third heat exchanger 6 by the operation of a residual liquid supply pump 14.

[0016] The second heat exchanger 4 exchanges heat between the thermosensitive polymer separated in the polymer separation tank 3 and a cooling medium, thereby cooling the thermosensitive polymer to a temperature lower than the lower critical solution temperature, thereby changing the thermosensitive polymer from hydrophobic to hydrophilic. The cooling medium is, for example, water, which is circulated through the second flow path 62 by the operation of the cooling pump 13.

[0017] The heat pump chiller 5 recovers heat from the cooling medium that has cooled the thermosensitive polymer in the second heat exchanger 4, and uses the recovered heat to heat the heating medium that has heated the thermosensitive polymer in the first heat exchanger 2.

[0018] The heat pump chiller 5 has a known configuration, for example, equipped with a vapor compression refrigeration cycle, in which an evaporator, compressor, condenser, and expansion valve are arranged in this order on a closed loop, and the refrigerant circulates through four steps: evaporation, compression, condensation, and expansion. The cooling medium discharged from the second heat exchanger 4 absorbs heat by the heat of vaporization when the refrigerant evaporates in the evaporator of the heat pump chiller 5. The heating medium discharged from the first heat exchanger 2 is heated by the heat of condensation when the refrigerant condenses in the condenser of the heat pump chiller 5.

[0019] The third heat exchanger 6 cools the residual liquid by exchanging heat between the residual liquid from which the thermosensitive polymer has been separated from the water to be treated in the polymer separation tank 3 and the cooling medium diverted from the second flow path 62 to the branch flow path 63. The cooling medium that has passed through the third heat exchanger 6 merges with the cooling medium that has passed through the second heat exchanger 4 and flows through the second flow path 62.

[0020] Next, a method for recovering the thermosensitive polymer by the recovery device 1 having the above configuration will be described. First, the water to be treated is supplied to the first heat exchanger 2 to perform a polymer hydrophobization step of changing the thermosensitive polymer contained in the water to be treated from hydrophilic to hydrophobic. The polymer hydrophobization step of the present embodiment includes a polymer heating step of heating the thermosensitive polymer by heat exchange with a heating medium heated by the heat pump chiller 5, and by heating the thermosensitive polymer so as to be at a temperature higher than the lower critical solution temperature, the thermosensitive polymer becomes hydrophobic. The water to be treated is not particularly limited as long as it is water to be treated in which a thermosensitive polymer having a lower critical solution temperature is dissolved, and for example, a draw solution used for concentrating a feed solution by forward osmosis membrane treatment can be exemplified.

[0021] Next, the water to be treated that has passed through the first heat exchanger 2 is supplied to the polymer separation tank 3 to perform a polymer separation step of separating the thermosensitive polymer that has changed to hydrophobic from the water to be treated.

[0022] Thereafter, the separated thermosensitive polymer is supplied to the second heat exchanger 4 to perform a polymer hydrophilicization step of changing the thermosensitive polymer from hydrophobic to hydrophilic. The polymer hydrophilicization step of the present embodiment includes a polymer cooling step of cooling the thermosensitive polymer by heat exchange with a cooling medium cooled by the heat pump chiller 5, and by cooling the thermosensitive polymer so as to be at a temperature lower than the lower critical solution temperature, the thermosensitive polymer becomes hydrophilic. Since the hydrophilic thermosensitive polymer is easily dissolved in water, it can be reused as a draw solution having a high osmotic pressure or the like.

[0023] In parallel with the above polymer hydrophilization step, a residual liquid cooling step is performed in which the residual liquid from which the thermosensitive polymer has been separated from the water to be treated in the polymer separation tank 3 is supplied to the third heat exchanger 6 and cooled by a cooling medium. The cooling temperature of the residual liquid is not particularly limited. However, when performing membrane treatment on the residual liquid for the purpose of recovering a small amount of thermosensitive polymer that was not separated in the polymer separation tank 3 from the residual liquid, the membrane treatment can be performed quickly and easily by cooling the residual liquid to a temperature below the heat resistance temperature of the membrane. Note that the residual liquid cooling step is not essential in the present invention, and the recovery device 1 may be configured without the branch flow path 63 and the third heat exchanger 6.

[0024] The method for recovering the thermosensitive polymer according to the present embodiment is characterized in that, in the polymer hydrophilization step, heat is recovered from the cooling medium after cooling the thermosensitive polymer by the heat pump chiller 5, and in the polymer hydrophobicization step, the recovered heat is used to heat the heating medium to heat the thermosensitive polymer. That is, in the polymer hydrophobicization step and the polymer hydrophilization step, the temperature of the thermosensitive polymer is changed in opposite directions by utilizing the mutual heat transfer using the heat pump chiller 5. Thereby, even in an environment where there is no heat source or the like for recovering the thermosensitive polymer due to a temperature change, it is possible to efficiently recover the thermosensitive polymer from the water to be treated while achieving energy savings.

[0025] <Second Embodiment> FIG. 2 is a schematic configuration diagram of a recovery device according to the second embodiment of the present invention. Since the recovery device 1a shown in FIG. 2 is obtained by adding the following configuration to the recovery device 1 shown in FIG. 1, the same reference numerals are given to the same components as those shown in FIG. 1, and repeated description is omitted.

[0026] The recovery device 1a shown in Fig. 2 includes a first thermometer 21 for measuring the temperature of the water to be treated supplied to the first heat exchanger 2, a second thermometer 22 for measuring the temperature of the water to be treated discharged from the first heat exchanger 2, a third thermometer 23 for measuring the temperature of the heating medium supplied to the first heat exchanger 2, a fourth thermometer 24 for measuring the temperature of the heating medium discharged from the first heat exchanger 2, a fifth thermometer 25 for measuring the temperature of the cooling medium supplied to the second heat exchanger 4, a sixth thermometer 26 for measuring the temperature of the cooling medium discharged from the second heat exchanger 4, a seventh thermometer 27 for measuring the temperature of the thermosensitive polymer discharged from the second heat exchanger 4, and an eighth thermometer 28 for measuring the temperature of the residual liquid discharged from the third heat exchanger 6.

[0027] Also, the recovery device 1a shown in Fig. 2 includes a first flowmeter 31 for measuring the flow rate of the heating medium flowing through the first flow path 61, a second flowmeter 32 for measuring the flow rate of the cooling medium flowing through the second flow path 62, and a third flowmeter 33 for measuring the flow rate of the cooling medium flowing through the branch flow path 63. A regulating valve 40 for adjusting the branch flow rate of the cooling medium flowing through the branch flow path 63 is provided in the branch flow path 63. The flow rate control (inverter control) of the heating pump 12 and the cooling pump 13, as well as the opening degree control of the regulating valve 40, are performed by a control device (not shown).

[0028] The method for recovering the temperature-sensitive polymer according to the second embodiment includes a heating control step in the polymer hydrophobization step included in the method for recovering the temperature-sensitive polymer according to the first embodiment. In this step, the temperatures of the heating medium and the temperature-sensitive polymer after heat exchange in the first heat exchanger 2 are measured by the fourth thermometer 24 and the second thermometer 22 respectively. Based on these temperatures, while observing the flow rate of the heating medium by the first flow meter 31, the flow rate control of the heating pump 12 is performed. By providing such a heating control step, based on the temperatures of the heating medium and the temperature-sensitive polymer after heat exchange by the first heat exchanger 2, the flow rate control of the heating medium supplied to the first heat exchanger 2 can be performed. Therefore, when the temperature rise of the temperature-sensitive polymer in the first heat exchanger 2 becomes small due to efficiency reduction caused by fouling of the first heat exchanger 2 or deterioration of the temperature-sensitive polymer, etc., the flow rate of the heating medium can be increased to promote the temperature rise of the temperature-sensitive polymer. Thus, in the polymer hydrophobization step, the temperature-sensitive polymer can be surely hydrophobized.

[0029] Also, the method for recovering the temperature-sensitive polymer according to the second embodiment includes a cooling control step in the polymer hydrophilization step included in the method for recovering the temperature-sensitive polymer according to the first embodiment. In this step, the temperatures of the cooling medium and the temperature-sensitive polymer after heat exchange in the second heat exchanger 4 are measured by the sixth thermometer 26 and the seventh thermometer 27 respectively, and the temperature of the residual liquid after heat exchange in the third heat exchanger 6 is measured by the eighth thermometer 28. Based on these temperatures, while observing the flow rate of the cooling medium by the second flow meter 32, the flow rate control of the cooling pump 13 and the opening degree control of the regulating valve 40 are performed. By providing such a cooling control step, based on the temperatures of the cooling medium and the temperature-sensitive polymer after heat exchange by the second heat exchanger 4, the flow rate control of the cooling medium supplied to the second heat exchanger 4 can be performed. Therefore, when the temperature drop of the temperature-sensitive polymer in the second heat exchanger 4 becomes small due to efficiency reduction caused by fouling of the second heat exchanger 4 or deterioration of the temperature-sensitive polymer, etc., the flow rate of the cooling medium can be increased to promote the temperature drop of the temperature-sensitive polymer. Thus, in the polymer hydrophilization step, the temperature-sensitive polymer can be surely hydrophilized.

[0030] In the above-described heating control process, instead of controlling the flow rate of the heating pump 12 based on the measured temperatures by the fourth thermometer 24 and the second thermometer 22, the flow rate control of the heating pump 12 may be performed based on the temperature difference measured by the third thermometer 23 and the fourth thermometer 24, and the temperature difference measured by the first thermometer 21 and the second thermometer 22. Further, in the above-described cooling control process, instead of controlling the flow rate of the cooling pump 13 based on the measured temperature by the sixth thermometer 26, the flow rate control of the cooling pump 13 may be performed based on the temperature difference measured by the fifth thermometer 25 and the sixth thermometer 26. In a configuration not provided with the branch flow path 63 and the third heat exchanger 6, in the cooling control process, the flow rate control of the cooling pump 13 may be performed based on the measured temperatures by the sixth thermometer 26 and the seventh thermometer 27. The adjustment valve 40 may be provided in the second flow path 62 instead of being provided in the branch flow path 63. Specifically, as shown in FIG. 3, in the second flow path 62, the adjustment valve 40 may be provided upstream of the position where the cooling medium merges from the branch flow path 63 to control the branch flow rate.

[0031] <Third Embodiment> FIG. 4 is a schematic configuration diagram of a recovery device according to the third embodiment of the present invention. The recovery device 1b shown in FIG. 4 is obtained by adding the following configuration to the recovery device 1 shown in FIG. 1. Therefore, the same reference numerals are given to the same components as those shown in FIG. 1, and repeated descriptions are omitted.

[0032] The recovery device 1b shown in FIG. 4 is a device that concentrates small-sized substances (such as molecules and ions) contained in the water to be treated by utilizing the recovery of the temperature-sensitive polymer from the water to be treated, and includes a semipermeable membrane unit 50 to which the water to be treated is supplied from a supply line 64. The semipermeable membrane unit 50 includes a semipermeable membrane 51 whose pore size is set so that the substance to be concentrated passes together with the permeated water, and performs reverse osmosis treatment on the supplied water to be treated to separate the permeated water from the water to be treated as concentrated water. The type of the semipermeable membrane 51 is not necessarily limited, but a nanofiltration membrane (NF membrane) or a reverse osmosis membrane (RO membrane) can be preferably exemplified.

[0033] The supply line 64 is equipped with a polymer addition section 65 and a high-pressure pump 15. A thermosensitive polymer that has become hydrophilic through the second heat exchanger 4 is added to the water to be treated that is supplied to the semipermeable membrane unit 50 at the polymer addition section 65. The thermosensitive polymer may have a size that does not pass through the pores of the semipermeable membrane 51. When the molecular weight of the thermosensitive polymer is large, the semipermeable membrane 51 may be a microfiltration membrane (MF membrane), an ultrafiltration membrane (UF membrane), or the like. By using a microfiltration membrane or an ultrafiltration membrane as the semipermeable membrane 51, the flux (membrane permeation flux) increases and the operating pressure decreases, so energy savings can be achieved.

[0034] The method for recovering the thermosensitive polymer according to the third embodiment further includes a polymer addition step of adding the thermosensitive polymer that has become hydrophilic by the polymer hydrophilization step to the water to be treated at the polymer addition section 65 in the method for recovering the thermosensitive polymer according to the first embodiment. The water to be treated can preferably be exemplified by an aqueous solution of a lower alcohol such as methanol, ethanol, or propanol, but is not particularly limited as long as the substance to be concentrated passes through the semipermeable membrane 51. For example, it may be water to be treated in which a water-soluble gas such as carbon dioxide, hydrogen, ammonia, or hydrogen chloride is dissolved in water. When the water to be treated is an acidic solution such as a dilute hydrochloric acid solution, the thermosensitive polymer preferably has acid resistance.

[0035] Further, the method for recovering the thermosensitive polymer according to the third embodiment further includes a concentration step of supplying the water to be treated that has undergone the above-described polymer addition step to the semipermeable membrane unit 50 to separate permeated water and discharging this permeated water as concentrated water in which the substance to be concentrated is concentrated. The thermosensitive polymer added to the water to be treated in the hydrophilic state binds to the water molecules of the water to be treated to become bound water, thereby reducing the proportion of free water. As a result, the amount of free water passing through the semipermeable membrane 51 decreases, so the permeated water passing through the semipermeable membrane 51 is discharged to the outside as concentrated water in which the substance to be concentrated is concentrated. As a result, substances of a small size that are difficult to concentrate by conventional membrane treatment can be efficiently concentrated.

[0036] The water to be treated after the permeated water is separated contains a thermosensitive polymer bound to water molecules, and a polymer hydrophobization step is performed on the water to be treated after the permeated water is separated.

[0037] In addition, the method for recovering the thermosensitive polymer according to the third embodiment includes, in the method for recovering the thermosensitive polymer according to the first embodiment, a step of supplying the residual liquid that has undergone the residual liquid cooling step to a low-pressure RO membrane unit 52 equipped with a low-pressure RO membrane 53 by the operation of a pressure pump 16. Since a small amount of the thermosensitive polymer that was not separated in the polymer separation tank 3 may remain in the residual liquid supplied to the low-pressure RO membrane unit 52, by refluxing the non-permeated water that does not pass through the low-pressure RO membrane 52 to the polymer separation tank 3, the recovery rate of the thermosensitive polymer in the polymer separation tank 3 can be increased. The residual liquid that has passed through the low-pressure RO membrane 53 is discharged as diluted water in which the concentration of the substances contained in the water to be treated is diluted, and can be used, for example, as washing water. The low-pressure RO membrane 53 may be another membrane such as an NF membrane that can capture the thermosensitive polymer.

[0038] The supply line 64 and the semipermeable membrane unit 50 included in the recovery device 1b according to the third embodiment may be added to the recovery device 1a according to the second embodiment instead of adding them to the recovery device 1 according to the first embodiment.

[0039] <Fourth Embodiment> FIG. 5 is a schematic configuration diagram of a recovery device according to a fourth embodiment of the present invention. The recovery device 1c shown in FIG. 5 is obtained by mutually swapping the heating pump 12 and the cooling pump 13 in the recovery device 1 shown in FIG. 1, and is configured such that a cooling medium flows through the first flow path 61 while a heating medium flows through the second flow path 62. Since the other configurations of the recovery device 1c are the same as those of the recovery device 1 shown in FIG. 1, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and repeated descriptions are omitted.

[0040] The thermosensitive polymer used in the recovery device 1c of the fourth embodiment is a polymer substance having an upper critical solution temperature (UCST) that becomes hydrophilic at a temperature higher than the transition temperature and hydrophobic at a temperature lower than the transition temperature. The method for recovering the thermosensitive polymer by this recovery device 1c includes a polymer cooling step in which the polymer hydrophobization step cools the thermosensitive polymer by heat exchange with a cooling medium cooled by the heat pump chiller 5, and a polymer heating step in which the polymer hydrophilization step heats the thermosensitive polymer by heat exchange with a heating medium heated by the heat pump chiller 5. Thereby, the thermosensitive polymer contained in the water to be treated can be cooled in the first heat exchanger 2 to be changed to hydrophobicity and separated in the polymer separation tank 3, and the separated thermosensitive polymer can be heated in the second heat exchanger 4 to be changed to hydrophilicity.

[0041] In the recovery device 1a shown in Fig. 2 and the recovery device 1b shown in Fig. 4, by mutually exchanging the heating pump 12 and the cooling pump 13, a thermosensitive polymer having an upper critical solution temperature can be used in the same manner as in the fourth embodiment.

Explanation of Signs

[0042] 1 Recovery device for thermosensitive polymer 2 First heat exchanger 3 Polymer separation tank 4 Second heat exchanger 5 Heat pump chiller 6 Third heat exchanger

Claims

1. A method for recovering a thermosensitive polymer from treated water in which a thermosensitive polymer capable of changing between hydrophilicity and hydrophobicity due to temperature change is dissolved, comprising: a polymer hydrophobization step of changing the thermosensitive polymer contained in the treated water from hydrophilic to hydrophobic; a polymer separation step of separating the thermosensitive polymer that has changed to hydrophobic from the treated water; and a polymer hydrophilicization step of changing the separated thermosensitive polymer from hydrophobic to hydrophilic, wherein the polymer hydrophobization step and the polymer hydrophilicization step utilize heat transfer between each other using a heat pump chiller to change the temperature of the thermosensitive polymer in opposite directions to each other. A method for recovering a thermosensitive polymer.

2. The thermosensitive polymer has a lower critical solution temperature, the polymer hydrophobization step includes a polymer heating step of heating the thermosensitive polymer by heat exchange with a heating medium heated by the heat pump chiller, The method for recovering a thermosensitive polymer according to claim 1, wherein the polymer hydrophilicization step includes a polymer cooling step of cooling the thermosensitive polymer by heat exchange with a cooling medium cooled by the heat pump chiller.

3. The polymer hydrophobization step further includes a heating control step of controlling the flow rate of the heating medium based on the temperatures of the heating medium and the thermosensitive polymer after heat exchange, The method for recovering a thermosensitive polymer according to claim 2, wherein the polymer hydrophilicization step further includes a cooling control step of controlling the flow rate of the cooling medium based on the temperatures of the cooling medium and the thermosensitive polymer after heat exchange.

4. The polymer hydrophilicization step further includes a step of branching a part of the cooling medium cooled by the heat pump chiller and cooling the residual liquid by heat exchange with the residual liquid from which the thermosensitive polymer has been separated from the treated water, The method for recovering a thermosensitive polymer according to claim 3, wherein the cooling control step includes a step of controlling the branched flow rate of the cooling medium based on the temperatures of the residual liquid and the thermosensitive polymer after heat exchange.

5. a polymer addition step of adding the thermosensitive polymer that has become hydrophilic by the polymer hydrophilicization step to treated water having a substance to be concentrated passing through a semipermeable membrane; and a concentration step of supplying the treated water that has undergone the polymer addition step to a semipermeable membrane unit including the semipermeable membrane to separate permeated water and discharging the permeated water as concentrated water in which the substance to be concentrated is concentrated. The method for recovering a thermosensitive polymer according to claim 1, wherein the polymer hydrophobization step is performed on the water to be treated after the permeated water has been separated.

6. A recovery device for a thermosensitive polymer that recovers the thermosensitive polymer from the water to be treated in which the thermosensitive polymer capable of changing between hydrophilicity and hydrophobicity due to a temperature change is dissolved, a first heat exchanger that changes the thermosensitive polymer contained in the water to be treated from hydrophilic to hydrophobic, a polymer separation tank that separates the thermosensitive polymer that has changed to hydrophobic from the water to be treated, and a second heat exchanger that changes the separated thermosensitive polymer from hydrophobic to hydrophilic, wherein the first heat exchanger and the second heat exchanger are a recovery device for a thermosensitive polymer that changes the temperature of the thermosensitive polymer in opposite directions by utilizing heat transfer between them using a heat pump chiller.

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