JP2019147078A - Water treatment apparatus and water treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the energy balance in a process by suppressing energy consumption required for cooling and heating without taking water-containing aqueous solution for cooling. SOLUTION: Water is moved from an aqueous solution containing water as a solvent to a draw solution having a cloud point through a semi-permeable membrane to flow out as a diluted draw solution obtained by diluting the draw solution, and the aqueous solution is concentrated. The water content of the positive permeation means discharged as a concentrated aqueous solution, the heating means for heating the diluted draw solution to a temperature above the cloud point, and the diluted draw solution heated by the heating means are higher than those of the water-rich solution and the water-rich solution. Heat exchange is performed between the water separation means that separates into a low draw solution, the cooling means that cools the liquid and flows out as a coolant, and the coolant that flows out of the cooling means and the draw solution that flows out of the water separation means. The inflow side heat exchange means and the outflow side heat exchange means for exchanging heat between the diluted draw solution flowing out from the positive infiltration means and the water-rich solution flowing out from the water separation means are provided. [Selection diagram] Fig. 1

Description

  The present invention relates to a water treatment apparatus and a water treatment method for extracting water from an aqueous solution containing water as a solvent.

  Conventionally, seawater, river water, industrial wastewater, or the like is treated water (feed solution), and a liquid having a higher osmotic pressure than the treated water is used as an attracting solution (draw solution). There is known a water treatment system that allows fresh water to permeate through a draw solution from water to be treated by bringing the water into contact with the treated water.

  In this water treatment system, when a temperature sensitive substance is used as the draw solution, the diluted draw solution diluted by moving the fresh water is heated, and the fresh water is separated from the diluted draw solution by phase separation by heating. The draw solution from which the fresh water has been separated and drawn is reused as a regenerated draw solution that is brought into contact with the water to be treated again after being cooled. For example, Patent Document 1 discloses a water treatment apparatus that performs heat exchange between a low-temperature diluted draw solution, a high-temperature regenerated draw solution, and fresh water.

Japanese Patent Laid-Open No. 2017-18895

  However, the above-described water treatment apparatus according to the prior art has a problem in that the cooling mechanism is not provided and cooling of the regenerated draw solution at a high temperature becomes insufficient. In view of this, a method of cooling the regenerated draw solution at a high temperature using an aqueous solution separately taken in water has been considered. However, in this case, it is necessary to newly take the aqueous solution, which causes a problem that the energy required for the water treatment apparatus increases and the running cost increases. Therefore, there has been a demand for a technology that can stabilize energy balance by suppressing energy consumption required for cooling and heating in a water treatment apparatus.

  The present invention has been made in view of the above, and its purpose is to stabilize the energy balance in the process by suppressing the energy consumption required for cooling and heating without taking water-containing aqueous solution for cooling. It is providing the water treatment apparatus and water treatment method which can be performed.

  In order to solve the above-described problems and achieve the object, a water treatment apparatus according to one embodiment of the present invention supplies water through a semipermeable membrane from an aqueous solution containing water as a solvent to a draw solution having a cloud point. A normal osmosis means for discharging and discharging the concentrated aqueous solution as a concentrated aqueous solution containing the concentrated aqueous solution, and heating the diluted draw solution to a temperature equal to or higher than the cloud point. Heating means, water separation means for separating the diluted draw solution heated by the heating means into a water-rich solution and the draw solution having a lower water content than the water-rich solution, and cooling the liquid as a cooling liquid An outflow cooling means, an inflow heat exchange means for exchanging heat between the cooling liquid flowing out from the cooling means and the draw solution flowing out from the water separation means, and flowing from the forward osmosis means. Characterized in that it comprises the a and outlet side heat exchange means for exchanging heat between the dilute draw solution to the water-rich solution flowing out from the water separating means.

  The water treatment apparatus according to an aspect of the present invention is characterized in that, in the above-described invention, the water treatment apparatus further includes a separation treatment unit that obtains generated water from the water-rich solution. In this configuration, the water treatment apparatus according to an aspect of the present invention is configured such that the water separation unit is disposed downstream of the outflow side heat exchange unit and upstream of the separation treatment unit along the flow direction of the water-rich solution. It is characterized by comprising heat exchange means before final treatment for exchanging heat between the water-rich solution that has flowed out of the water and the coolant that has flowed out of the cooling means. Further, in this configuration, the water treatment apparatus according to an aspect of the present invention is configured such that the separation treatment unit can supply the separation treatment waste liquid separated from the generated water to the cooling unit. And Furthermore, the water treatment apparatus according to an aspect of the present invention is characterized in that, in this configuration, the separation treatment means includes a coalescer, activated carbon, an ultrafiltration membrane, a nanofiltration membrane, or a reverse osmosis membrane.

  The water treatment apparatus according to an aspect of the present invention is the above-described invention, wherein the latter stage heat exchange means performs heat exchange between the draw solution flowing out from the water separation means and the diluted draw solution flowing out from the forward osmosis means. Is further provided.

  The water treatment apparatus according to an aspect of the present invention is the water treatment apparatus according to the above aspect, wherein the draw solution that has flowed out of the water separation unit and the positive flow are upstream of the outflow side heat exchange unit along the flow direction of the diluted draw solution. It further comprises a pre-stage heat exchange means for exchanging heat with the diluted draw solution flowing out from the permeation means.

  The water treatment apparatus according to an aspect of the present invention is characterized in that, in the above invention, the coolant is circulated between the cooling means and the inflow side heat exchange means.

  The water treatment apparatus according to an aspect of the present invention is the water treatment apparatus according to the above-described invention, wherein the diluted draw solution that has flowed out of the forward osmosis means is branched, and at least two heat exchangers are configured in parallel. Each of the diluted draw solutions branched and heat-exchanged by the parallel heat exchanging means is joined at the upstream side of the heating means. In this configuration, the water treatment apparatus according to an aspect of the present invention is configured such that, in the parallel heat exchange unit, the diluted draw solution branched from the diluted draw solution and the water-rich solution and the heat that flowed out of the water separation unit. While being exchanged, the other diluted draw solution branched from the diluted draw solution is configured to be heat exchanged with the draw solution flowing out from the water separation means.

  In the water treatment apparatus according to one aspect of the present invention, in the above invention, the draw solution is a solution mainly composed of a temperature-sensitive water-absorbing agent having at least one cloud point.

  The water treatment apparatus according to one embodiment of the present invention is characterized in that, in the above invention, the aqueous solution is seawater, brine, brackish water, industrial wastewater, associated water, or sewage.

  The water treatment method according to one aspect of the present invention is a diluted draw solution obtained by diluting the draw solution by moving water through a semipermeable membrane from a water-containing solution containing water as a solvent to a draw solution having a cloud point. A normal osmosis step of flowing out and discharging the concentrated aqueous solution as a concentrated aqueous solution, a heating step of heating the diluted draw solution to a temperature above the cloud point, and the diluted draw heated in the heating step A water separation process for separating the solution into a water-rich solution and a draw solution having a lower water content than the water-rich solution, a cooling liquid generation process for cooling the liquid to generate a cooling liquid, and the cooling liquid generation process. An inflow-side heat exchange step for exchanging heat between the obtained cooling liquid and the draw solution obtained by the water separation step, and the diluted draw solution obtained by the forward osmosis step and the previous And the outflow side heat exchange step for exchanging heat between the water-rich solution obtained by the water separation step, characterized in that it comprises a.

  The water treatment method according to one aspect of the present invention is characterized in that, in the above-described invention, the method further includes a separation treatment step of obtaining produced water from the water-rich solution. In this configuration, the water treatment method according to an aspect of the present invention includes the water-rich solution obtained by the water separation step and the coolant obtained by the coolant production step before the separation treatment step. And a heat exchange step before final processing for exchanging heat with each other. Moreover, the water treatment method which concerns on 1 aspect of this invention is used for the said cooling fluid production | generation process in this structure, using the separation processing waste liquid isolate | separated from the said produced | generated water by the said separation treatment process. Furthermore, the water treatment method according to an aspect of the present invention is characterized in that, in this configuration, the separation treatment step is performed using a coalescer, activated carbon, an ultrafiltration membrane, a nanofiltration membrane, or a reverse osmosis membrane. To do.

  The water treatment method according to one aspect of the present invention is the water treatment method according to the above-described invention, wherein the diluted draw solution obtained by the forward osmosis step and the draw solution obtained by the water separation step before the outflow side heat exchange step. It further includes a pre-stage heat exchange step for exchanging heat with each other.

  In the water treatment method according to an aspect of the present invention, in the above invention, heat exchange is performed between the draw solution obtained by the water separation step and the diluted draw solution heat-exchanged in the outflow side heat exchange step. The method further includes a subsequent heat exchange step to be performed.

  The water treatment method according to an aspect of the present invention is characterized in that, in the above-described invention, the coolant after heat exchange in the inflow side heat exchange step is cooled in the coolant generation step.

  The water treatment method according to one aspect of the present invention is the above-described invention, wherein the diluted draw solution obtained by the forward osmosis step is branched and heat is exchanged in parallel in at least two heat exchangers. The method further includes an exchange step, and the branched diluted draw solution is merged after the parallel heat exchange step and before the heating step. In this configuration, the water treatment method according to an aspect of the present invention is configured such that, in the parallel heat exchange step, the diluted draw solution branched from the diluted draw solution is the water-rich solution obtained by the water separation step. Heat exchange is performed, and the other diluted draw solution branched from the diluted draw solution is heat exchanged with the draw solution obtained by the water separation step.

  In the water treatment method according to an aspect of the present invention, in the above invention, the draw solution is a solution mainly composed of a temperature-sensitive water-absorbing agent having at least one cloud point.

  The water treatment method according to one embodiment of the present invention is characterized in that, in the above-described invention, the aqueous solution is seawater, brine, brackish water, industrial wastewater, associated water, or sewage.

  According to the water treatment apparatus and the water treatment method of the present invention, energy consumption required for cooling and heating can be suppressed and energy balance can be stabilized without separately taking water-containing aqueous solution for cooling. Become.

FIG. 1 is a block diagram schematically showing a water treatment apparatus according to the first embodiment of the present invention. FIG. 2 is a block diagram schematically showing a water treatment apparatus according to a comparative example. FIG. 3 is a block diagram schematically showing a water treatment apparatus according to the second embodiment of the present invention. FIG. 4 is a block diagram schematically showing a water treatment apparatus according to the third embodiment of the present invention. FIG. 5 is a block diagram schematically showing a water treatment apparatus according to the fourth embodiment of the present invention. FIG. 6 is a block diagram schematically showing a water treatment apparatus according to the fifth embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings. In all the drawings of the following embodiments, the same or corresponding parts are denoted by the same reference numerals. Further, the present invention is not limited to the embodiments described below.

(First embodiment)
(Water treatment equipment)
First, the water treatment apparatus according to the first embodiment of the present invention will be described. FIG. 1 is a block diagram schematically showing a water treatment apparatus 1 according to the first embodiment. As shown in FIG. 1, the water treatment apparatus 1 according to the first embodiment includes a membrane module 11, a heater 12, a separation tank 13, a final treatment unit 14, a cooling mechanism 15, and heat exchangers 21 and 22. Configured.

  The membrane module 11 as the normal osmosis means is, for example, a cylindrical or box-shaped container in which a semipermeable membrane 11a is installed. The inside of the membrane module 11 is partitioned into two chambers by a semipermeable membrane 11a. Examples of the form of the membrane module 11 include various forms such as a spiral module type, a laminated module type, and a hollow fiber module type. As the membrane module 11, a known semipermeable membrane device can be used, and a commercially available product can also be used.

  The semipermeable membrane 11a provided in the membrane module 11 is preferably one that can selectively permeate water, and a forward osmosis (FO) membrane is used, but a reverse osmosis (RO) membrane is used. Also good. The material of the separation layer of the semipermeable membrane 11a is not particularly limited, and examples thereof include materials such as cellulose acetate, polyamide, polyethyleneimine, polysulfone, and polybenzimidazole. The semipermeable membrane 11a may be composed of only one type (one layer) of materials used for the separation layer, and has two or more layers having a support layer that physically supports the separation layer and does not substantially contribute to separation. You may comprise. Examples of the support layer include materials such as polysulfone, polyketone, polyethylene, polyethylene terephthalate, and general nonwoven fabrics. The form of the semipermeable membrane 11a is not limited, and various forms of membranes such as a flat membrane, a tubular membrane, or a hollow fiber can be used.

  Inside the membrane module 11, the aqueous solution can be flowed into one chamber partitioned by the semipermeable membrane 11a, and the draw solution as the water absorbing solution can be flowed into the other chamber. The introduction pressure of the draw solution to the membrane module 11 is 0.1 MPa or more and 0.5 MPa or less, and in this first embodiment, for example, 0.2 MPa. The aqueous solution is, for example, seawater, brackish water, brackish water, industrial wastewater, associated water, or sewage, or an aqueous solution containing water as a solvent obtained by subjecting these waters to filtration if necessary.

  As the draw solution, a solution mainly composed of a temperature-sensitive water-absorbing agent made of a polymer having at least one cloud point is used. A temperature-sensitive water-absorbing agent is hydrophilic at low temperatures and dissolves well in water, increasing the amount of water absorption.On the other hand, the amount of water absorption decreases as the temperature rises. It is a substance. The temperature sensitive water-absorbing agent is used as various surfactants, dispersants, or emulsifiers.

  In the first embodiment, the temperature-sensitive water-absorbing agent includes at least a hydrophobic part and a hydrophilic part, and includes a block copolymer or a random copolymer containing an ethylene oxide group and at least one group consisting of propylene oxide and butylene oxide in a basic skeleton. A copolymer is preferred. Examples of the basic skeleton include a glycerin skeleton and a hydrocarbon skeleton. In the first embodiment, as the temperature-sensitive water-absorbing agent, for example, an agent having a polymer of ethylene oxide and propylene oxide is used. In such a temperature-sensitive water-absorbing agent, the temperature at which water solubility and water insolubility change is called a cloud point. When the temperature of the draw solution rises and reaches the cloud point, the hydrophobized temperature-sensitive water-absorbing agent aggregates and white turbidity occurs.

  In this first embodiment, the draw solution is used as an attractant that attracts water from the aqueous solution. Thereby, in the membrane module 11, water is attracted from the aqueous solution to the draw solution, and the diluted draw solution (diluted draw solution) flows out. On the other hand, in the membrane module 11, the aqueous solution (concentrated aqueous solution) concentrated by moving water into the draw solution flows out.

  A heater 12 as a heating means for the draw solution is provided on the upstream side of the separation tank 13 along the flow direction of the draw solution. The heater 12 heats the diluted draw solution that has flowed out of the membrane module 11 and heat-exchanged by the heat exchanger 22 to a temperature higher than the cloud point. The diluted draw solution heated above the cloud point temperature by the heater 12 is phase-separated into water and a temperature-sensitive water-absorbing agent that is a polymer.

  In the separation tank 13 as the water separation means, the diluted draw solution phase-separated by the heater 12 is a water-based solution (water-rich solution) and a temperature-sensitive water-absorbing agent having a lower water content than the water-rich solution. Into a draw solution mainly composed of A draw solution having a moisture content lower than that of the water-rich solution is supplied to the membrane module 11 through the heat exchanger 21 as a reused draw solution (hereinafter, regenerated draw solution).

  The final processing unit 14 as a separation processing unit is configured by, for example, a coalescer, an activated carbon adsorption unit, an ultrafiltration membrane (UF membrane) unit, a nanofiltration membrane (NF membrane) unit, or a reverse osmosis membrane (RO membrane) unit. The The final processing unit 14 separates the temperature-sensitive water-absorbing agent remaining from the water-rich solution that has flowed out of the separation tank 13 to generate fresh water as generated water. The final treatment unit 14 uses at least a part or the whole of the polymer solution containing the temperature-sensitive water-absorbing agent from which the produced water has been separated as a separation treatment effluent at a temperature of 30 ° C. to 50 ° C., for example, 45 ° C. The mechanism 15 can be supplied.

  The cooling mechanism 15 as a cooling means is configured to be able to flow out, for example, a liquid such as water (hereinafter referred to as recovered liquid) supplied from the outside as a liquid (hereinafter referred to as cooling liquid) cooled to a temperature lower than the temperature at the time of supply. Is done. That is, the cooling mechanism 15 is configured to be able to flow out a cooling liquid such as cooling water. Examples of the cooling mechanism 15 include a cooling tower. Specifically, various cooling towers can be adopted as the cooling tower. For example, a cooling tower that cools the liquid by air by bringing the air sucked from outside by the cooling fan into contact with liquid such as hot water scattered by the filler as the cooling fan rotates. Can do. Here, the temperature of the recovered liquid is, for example, about 45 ° C. between 35 ° C. and 60 ° C., and the cooling mechanism 15 cools the temperature of the cooling liquid to, for example, about 35 ° C. between 15 ° C. and 45 ° C. The cooling mechanism 15 is not limited to the cooling tower, and various coolers that can cool the liquid can be employed.

  In the first embodiment, the cooling mechanism 15 is supplied with at least a part or all of the separation processing effluent obtained by the final processing unit 14. The separation processing waste liquid is used as a replenishing liquid to make up for the shortage of the cooling liquid that has decreased due to evaporation or blowdown. That is, by controlling the flow rate of the separation process waste liquid supplied from the final processing unit 14 and using the separation process waste liquid as a replenishment liquid, the coolant flowing out from the cooling mechanism 15 can be maintained at a predetermined flow rate. Note that the cooling mechanism 15 may blow excess cooling water. The cooling mechanism 15 supplies the coolant to the heat exchanger 21 using, for example, a water pump (not shown), as indicated by reference numeral A in FIG. On the other hand, as shown by a symbol B in FIG. 1, the cooling liquid that has passed through the heat exchanger 21 is returned to the cooling mechanism 15 and flows into the recovered liquid. Thereby, the cooling mechanism 15 is comprised so that a liquid can be circulated as a cooling fluid and a collection | recovery liquid between the heat exchangers 21 using a water pump.

  The heat exchanger 21 as the inflow side heat exchange means is provided upstream of the membrane module 11 and downstream of the separation tank 13 along the flow direction of the regenerated draw solution. The coolant that flows out of the cooling mechanism 15 flows into the heat exchanger 21. Thereby, the heat exchanger 21 performs heat exchange between the high-temperature regenerated draw solution that has flowed out of the separation tank 13 and the low-temperature coolant that has flowed out of the cooling mechanism 15. The coolant heated by the regenerated draw solution that has passed through the heat exchanger 21 is returned to the cooling mechanism 15 again. The flow rate of the coolant flowing into the heat exchanger 21 is controlled so that the temperature of the regenerated draw solution supplied to the membrane module 11 becomes a predetermined temperature. Specifically, a bypass valve (not shown) is provided in a flow path through which the coolant in the heat exchanger 21 passes, and the flow rate of the coolant flowing through the bypass valve is controlled, whereby the temperature of the regenerated draw solution is set to a predetermined temperature. To control. The temperature of the regenerated draw solution supplied to the membrane module 11 is controlled to a predetermined temperature, for example, about 40 ° C. between 25 ° C. and 50 ° C.

  The heat exchanger 22 is provided on the downstream side of the membrane module 11 along the flow direction of the diluted draw solution. The heat exchanger 22 is provided on the downstream side of the separation tank 13 along the flow direction of the water-rich solution obtained by the separation tank 13. The heat exchanger 22 performs heat exchange between the diluted draw solution flowing out from the membrane module 11 and the water-rich solution obtained by the separation tank 13.

(Water treatment method)
Next, a water treatment method using the water treatment apparatus 1 according to the first embodiment configured as described above will be described.

(Forward osmosis process)
In the membrane module 11 as the forward osmosis means, the forward osmosis step is performed. That is, in the membrane module 11, the aqueous solution and the regenerated draw solution are brought into contact with each other through the semipermeable membrane 11a. Thereby, in the membrane module 11, the water in the aqueous solution passes through the semipermeable membrane 11a and moves to the regenerated draw solution due to the osmotic pressure difference. That is, from one chamber to which the aqueous solution containing the membrane module 11 is supplied, the concentrated aqueous solution containing water that has been concentrated as the water moves into the regenerated draw solution flows out. From the other chamber to which the regenerated draw solution is supplied, the diluted draw solution diluted by the movement of water from the aqueous solution flows out. Here, heat exchange is also performed in the membrane module 11, and the temperature rises from the inflow side of the aqueous solution to the outflow side of the concentrated aqueous solution, while from the inflow side of the regenerated draw solution to the outflow side of the diluted draw solution. Temperature decreases.

(Inflow side heat exchange process)
In the heat exchanger 21 as the inflow side heat exchange means, an inflow side heat exchange step is performed. That is, the coolant supplied from the cooling mechanism 15 is supplied to the heat exchanger 21. On the other hand, the regenerated draw solution flowing out from the separation tank 13 is supplied to the heat exchanger 21. In the first embodiment, the regenerated draw solution is adjusted to a predetermined temperature of, for example, about 40 ° C. between 25 ° C. and 50 ° C. by the heat exchanger 21. In order to lower the regenerated draw solution to a predetermined temperature, the flow rate of the coolant supplied from the cooling mechanism 15 provided for heat exchange in the heat exchanger 21 is adjusted. That is, in the heat exchanger 21, the regenerated draw solution is cooled by the coolant. On the other hand, in the heat exchanger 21, the coolant is heated by the regenerated draw solution. Note that a bypass valve (not shown) as an adjustment valve may be provided in the heat exchanger 21 to adjust the flow rate of the coolant flowing into the heat exchanger 21. The regenerated draw solution cooled by the heat exchange in the heat exchanger 21 is supplied to the other chamber of the membrane module 11. On the other hand, as shown by reference numeral B in FIG. 1, the cooling liquid that has been heat-exchanged in the heat exchanger 21 and has been heated to a temperature of, for example, 45 ° C. between 35 ° C. and 60 ° C. Returned to

(Cooling liquid production process)
In the cooling mechanism 15 as a cooling means, a cooling liquid production | generation process is performed. That is, in the heat exchanger 21, the temperature of the coolant is raised by cooling the regenerated draw solution that has flowed out of the separation tank 13 with the coolant. The cooled cooling liquid that has passed through the heat exchanger 21 is supplied to the cooling mechanism 15 as a recovered liquid. The temperature of the recovered liquid is, for example, 45 ° C. between 35 ° C. and 60 ° C., and the flow rate is, for example, 2500-4800 L / h. In the cooling mechanism 15, the recovered liquid is cooled to 15 ° C. or higher and 45 ° C. or lower, for example, 35 ° C. to generate a cooling liquid. Further, the separation processing waste liquid supplied from the final processing unit 14 is supplied to the cooling mechanism 15. The temperature of the supplied separation treatment effluent is, for example, 45 ° C., for example, 30 ° C. or more and 50 ° C. or less, and the flow rate is, for example, 85 L / h, for example, 5 L / h or more, 500 L / h or less. Note that the flow rate of the separation processing waste liquid supplied from the final processing unit 14 is adjusted and controlled in the cooling mechanism 15 in accordance with the amount of liquid discharged to the outside by blow or evaporation.

(Heating process)
In the heater 12 as a heating means, a heating process is performed. That is, after the temperature of the diluted draw solution obtained by diluting the regenerated draw solution in the forward osmosis step is raised in the outflow side heat exchange step described later, the heater 12 is further heated to a temperature equal to or higher than the cloud point. Thereby, at least a part of the temperature-sensitive water-absorbing agent is agglomerated and phase separation is performed. The heating temperature in the heating process can be adjusted by controlling the heater 12. The heating temperature is not higher than the boiling point of water and is preferably 100 ° C. or lower in the case of atmospheric pressure. In the first embodiment, the heating temperature is, for example, 88 ° C. from the cloud point to 100 ° C.

(Water separation process)
In the separation tank 13 as water separation means, a water separation step is performed. That is, in the separation tank 13, the diluted draw solution is separated into a water-rich solution containing a large amount of water and a concentrated regenerated draw solution containing a temperature-sensitive water-absorbing agent at a high concentration. The pressure in the separation tank 13 is, for example, atmospheric pressure. The phase separation between the water-rich solution and the regenerated draw solution can be performed by allowing the liquid temperature to stand above the cloud point. In 1st Embodiment, the liquid temperature in the separation tank 13 is 88 degreeC of the cloud point or more and 100 degrees C or less, for example. The concentrated draw solution separated from the diluted draw solution is supplied to the membrane module 11 via the heat exchanger 21 as a regenerated draw solution. The draw concentration of the regenerated draw solution is, for example, 60 to 95%. On the other hand, the water-rich solution separated from the diluted draw solution is supplied to the final processing unit 14 via the heat exchanger 22. For example, the water-rich solution has a draw concentration of 1% and water of 99%.

(Outflow side heat exchange process)
In the heat exchanger 22 as the outflow side heat exchange means, an outflow side heat exchange step is performed. That is, the diluted draw solution flowing out from the membrane module 11 is first supplied to the heat exchanger 22. On the other hand, the water-rich solution obtained in the separation tank 13 is supplied to the heat exchanger 22. In the first embodiment, the heat exchanger 22 adjusts the water-rich solution to a predetermined temperature, specifically, a temperature of about 30 ° C. to 50 ° C., for example, about 45 ° C. As described above, in the separation tank 13, the water separation step is performed with the liquid temperature set to the cloud point or higher and 100 ° C. or lower. Therefore, the water-rich solution that flows out from the separation tank 13 is lowered in temperature in the heat exchanger 21 and is higher in temperature than the diluted draw solution that is lowered in temperature in the membrane module 11 and flows out. On the other hand, the processing temperature in the latter final processing unit 14 is, for example, 20 ° C. or more and 50 ° C. or less, preferably 35 ° C. or more and 45 ° C. or less, and in this first embodiment, for example, 45 ° C. Therefore, temperature adjustment is performed in the heat exchanger 22 to lower the temperature of the water-rich solution to the processing temperature of the final processing unit 14. That is, in the heat exchanger 22, the water rich solution is cooled by the diluted draw solution, while the diluted draw solution is heated by the water rich solution.

(Final treatment process)
In the final processing unit 14, a final processing step as a separation processing step is performed. That is, the temperature sensitive water-absorbing agent may remain in the water-rich solution separated in the separation tank 13. Therefore, in the final processing unit 14, the polymer solution that becomes the separation processing waste liquid is separated from the water-rich solution. Thereby, produced water such as fresh water is obtained. The product water separated from the water-rich solution is supplied to the required external use as a final product obtained from the aqueous solution. In the final treatment unit 14, the separation treatment waste liquid separated from the generated water is a polymer solution having a draw concentration of about 0.5 to 25%, and at least a part thereof is supplied to the cooling mechanism 15. When there is a remaining separation process waste liquid that is not supplied to the cooling mechanism 15, the remaining separation process waste liquid is discarded outside or introduced into the diluted draw solution upstream of the heater 12 or the heat exchanger 22. it can.

(Examples and Comparative Examples)
Next, the first embodiment of the water treatment apparatus 1 configured as described above and a comparative example according to the prior art will be described. In the first embodiment, a case where 300 L (300 L / h) of fresh water is generated from 1100 L (1100 L / h) of seawater per hour using a water treatment device will be described as an example.

(First embodiment)
In the first embodiment, seawater introduced to the water treatment apparatus 1 from the outside at a temperature of about 25 ° C. is supplied to the membrane module 11. Seawater is concentrated while being heated in the membrane module 11. Concentrated seawater (concentrated seawater) is heated to a temperature of about 30 ° C. and discharged from the membrane module 11 at a flow rate of 715 L / h. That is, in the membrane module 11, the water is moved at a flow rate of 385 L / h.

  The cooling water cooled in the cooling mechanism 15 is supplied to the heat exchanger 21 at a flow rate of 2500 to 4800 L / h. The regenerated draw solution is supplied to the heat exchanger 21, is heat-exchanged with low-temperature 35 ° C. cooling water, and is lowered from 88 ° C. to 40 ° C. The regenerated draw solution whose temperature has been lowered is supplied to the membrane module 11, diluted by the movement of water, and flows out as a diluted draw solution. Here, the flow rate of the regenerated draw solution supplied to the membrane module 11 is 1100 L / h.

  The diluted draw solution flowing out from the membrane module 11 has a temperature of 35 ° C. and a flow rate of 1485 L / h. The diluted draw solution is heat-exchanged with the 88 ° C. water-rich solution in the heat exchanger 22 and is heated to a temperature of 35 ° C. to 48.6 ° C. The diluted draw solution whose temperature has been raised is supplied to the heater 12 and further heated to raise the temperature from 48.6 ° C. to 88 ° C. The diluted draw solution having a temperature of 88 ° C. is supplied to the separation tank 13 and phase-separated into a regenerated draw solution and a water-rich solution. The regenerated draw solution has a temperature of 88 ° C. and a flow rate of 1100 L / h. The water-rich solution has a temperature of 88 ° C. and a flow rate of 385 L / h.

  The water-rich solution that has flowed out of the separation tank 13 is supplied to the heat exchanger 22, exchanged with the 35 ° C. diluted draw solution, and cooled to 88 ° C. to 45 ° C., and then supplied to the final processing unit 14. In the final processing unit 14, the separation processing waste liquid is separated at a flow rate of 85 L / h, and product water is obtained at a flow rate of 300 L / h. At least a part of the obtained separation processing waste liquid is supplied to the cooling mechanism 15. In the cooling mechanism 15, a predetermined amount of water is consumed by blowing or evaporation, and approximately the same amount of separation processing waste liquid as the consumed water is supplied. As described above, generated water having a flow rate of 300 L / h is obtained from seawater having a flow rate of 1100 L / h.

(Comparative example)
In order to compare with the first example based on the first embodiment, an example in which a cooling mechanism for cooling the regenerated draw solution is provided as a conventional water treatment apparatus is used as a comparative example. In the comparative example, a case where 300 L (300 L / h) of fresh water is generated from 1100 L (1100 L / h) of seawater per hour using a water treatment device will be described as an example. FIG. 2 is a block diagram schematically showing a water treatment apparatus 100 according to a comparative example.

  As shown in FIG. 2, the water treatment apparatus 100 according to the comparative example includes a membrane module 101 in which a semipermeable membrane 101a is provided, a heater 102, a separation tank 103, a cooler 104, and a final treatment unit 105. Composed. The membrane module 101, the heater 102, the separation tank 103, and the final processing unit 105 are respectively the same as the membrane module 11, the heater 12, the separation tank 13, and the final processing unit 14 in the first embodiment. On the other hand, unlike the water treatment apparatus 1, in the water treatment apparatus 100, a cooler 104 is provided on the downstream side of the separation tank 103 along the flow direction of the regenerated draw solution. The cooler 104 is a heat exchanger for cooling the regenerated draw solution that has flowed out of the separation tank 103 with, for example, seawater at about 30 ° C. that has been separately taken in by a water intake pump or the like.

  In the water treatment apparatus 100 according to the comparative example, the raw seawater temperature or seawater adjusted to a temperature of, for example, 40 ° C. is supplied to the membrane module 101. The concentrated seawater is discharged from the membrane module 101 by the membrane module 101 at a flow rate of 715 L / h. That is, in the membrane module 101, water is moved at a flow rate of 385 L / h.

  On the other hand, the regenerated draw solution is adjusted to a temperature of 40 ° C. by the cooler 104 and then supplied to the membrane module 101 to be diluted, and flows out as a diluted draw solution at a flow rate of 1485 L / h. The temperature of the diluted draw solution flowing out from the membrane module 101 is 40 ° C. The diluted draw solution is supplied to the heater 102 and heated, and the temperature is raised to a temperature of 88 ° C. The diluted draw solution having a temperature of 88 ° C. is supplied to the separation tank 103 and phase-separated, and separated into a regenerated draw solution having a temperature of 88 ° C. and a water-rich solution having a temperature of 88 ° C. The regenerated draw solution having a temperature of 88 ° C. is lowered to 40 ° C. by the cooler 104. Similarly, the water-rich solution having a temperature of 88 ° C. is supplied to the final processing unit 105 after being cooled to about 45 ° C. by a cooler (not shown) if necessary. In the final treatment unit 105, the produced water is obtained at a flow rate of 300 L / h, and the separation treatment waste liquid separated at a flow rate of 85 L / h is discharged. As described above, generated water having a flow rate of 300 L / h is obtained from seawater having a flow rate of 1100 L / h.

  In the comparative example, the regenerated draw solution separated by the separation tank 103 is cooled by the cooler 104 and then supplied to the membrane module 101. Seawater is supplied to the cooler 104 using a water intake pump. Therefore, an intake pump facility for supplying seawater to the cooler 104 and electric power for operating the intake pump are required. On the other hand, in 1st Example, the cooling water cooled with the cooling mechanism 15 is supplied to the heat exchanger 21 using a water pump, and the reproduction | regeneration draw solution is cooled. Here, the energy such as electric power required for the water intake pump for separately taking seawater is about 2 to 3 times the energy required for the water supply pump for supplying the cooling water. Considering the point of using a water pump in the water treatment apparatus 1 even when taking seawater separately, in the first embodiment, energy consumption is reduced to about 1/4 to 1/2 compared to the comparative example. Can be reduced. Thereby, compared with the case where a water intake pump is provided, equipment cost can be reduced and reduction in power cost can be realized.

  The specific heat and density of the polymer aqueous solution used in the first example and the comparative example are 3.2 kJ / kg · K and 1.05 kg / L, respectively. Thereby, energy required when heating a draw solution to 88 degreeC is computable. In addition, about specific heat, since the average specific heat in 40-88 degreeC is used as polymer aqueous solution, it does not depend on the density | concentration of a draw solution. Further, since the contribution of the concentration and temperature of the draw solution is extremely small, the influence of the concentration and temperature is negligibly small.

In the comparative example, the diluted draw solution having a temperature of 40 ° C. is heated by the heater 102 to a temperature of 88 ° C. In this case, the energy required to heat the diluted draw solution at a flow rate of 1485 L / h from 40 ° C. to 88 ° C. is as follows.
Comparative example: (3.2 kJ / kg · K × 1.05 kg / L × 1485 L / h × (88 ° C.-40 ° C.) =) 2.40 × 10 ⁵ kJ / h
In this case, the input energy required for the heater 102 was 66.5 kW.

In contrast, in the first embodiment, the diluted draw solution having a temperature of 48.6 ° C. is heated by the heater 12 to a temperature of 88 ° C. In this case, the energy required to heat the diluted draw solution at a flow rate of 1485 L / h from 48.6 ° C. to 88 ° C. is as follows.
First Example: (3.2 kJ / kg · K × 1.05 kg / L × 1485 L / h × (88 ° C.−48.6 ° C.) =) 1.96 × 10 ⁵ kJ / h
In this case, the input energy required for the heater 12 was 54.6 kW, which was found to be reduced by about 20% compared to the comparative example.

  As described above, according to the first embodiment of the present invention, in the water treatment apparatus, the heat exchanger 21 is provided to cool the regenerated draw solution with the cooling liquid, and the cooling liquid is circulated by the cooling mechanism 15. In this way, the regenerated draw solution is cooled. Thereby, in order to cool the regenerated draw solution which flowed out from the separation tank 13, it is not necessary to separately provide a water intake pump for taking water-containing aqueous solution for cooling, and the energy balance in the water treatment apparatus 1 can be stabilized. Therefore, the energy required for taking the aqueous solution can be reduced, and the consumption of energy heated by the heater 12 can be reduced.

  Further, according to the first embodiment described above, the regenerated draw solution supplied to the membrane module 11 is adjusted to a desired temperature using the cooling liquid cooled by the cooling mechanism 15. Thereby, since the temperature of the aqueous solution and the temperature of the draw solution can be made close to each other in the membrane module 11, the treatment in the membrane module 11 can be stabilized. Further, before the diluted draw solution to be supplied to the separation tank 13 is heated to a temperature not lower than the cloud point and not higher than 100 ° C. by the heater 12, the high temperature water-rich solution flowing out from the separation tank 13 is used to flow out from the membrane module 11. The diluted draw solution is heated. Thereby, when heating a dilution draw solution, since the temperature range heated up with the heater 12 can be made small, the energy required for the heating by the heater 12 can be reduced. From the above, in the water treatment apparatus 1, the energy consumed for cooling the regenerated draw solution or heating the diluted draw solution can be reduced, and the energy required for water treatment can be minimized. .

  Furthermore, in order to increase the amount of water movement in the membrane module 11, it is desirable that the osmotic pressure of the aqueous solution is low. In order to reduce the osmotic pressure of the aqueous solution, it is preferable that the temperature of the aqueous solution flowing into the membrane module 11 is low. In this regard, since the regenerated draw solution is cooled using the cooling liquid cooled by the cooling mechanism 15, it is not necessary to cool the regenerated draw solution using the aqueous solution flowing into the membrane module 11. It is possible to allow the aqueous solution supplied from the outside to flow into the membrane module 11 at a low temperature.

(Second Embodiment)
(Water treatment apparatus and water treatment method)
Next, a second embodiment of the present invention will be described. FIG. 3 shows a water treatment device 2 according to the second embodiment. As shown in FIG. 3, the water treatment apparatus 2 includes a membrane module 11 having a semipermeable membrane 11a provided therein, a heater 12, a separation tank 13, a final treatment unit 14, a cooling unit, as in the first embodiment. A mechanism 15 and heat exchangers 21, 22, and 23 are provided.

  In the water treatment device 2 according to the second embodiment, unlike the first embodiment, the downstream side of the heat exchanger 22 along the flow direction of the diluted draw solution, the upstream side of the heater 12, and the regenerated draw solution. A heat exchanger 23 is provided on the downstream side of the separation tank 13 along the flow direction and on the upstream side of the heat exchanger 21. A post-stage heat exchange step is performed by the heat exchanger 23 as the post-stage heat exchange means. That is, in the water treatment method according to the second embodiment, the diluted draw solution flowing out from the membrane module 11 is first heat-exchanged with the high-temperature water-rich solution in the heat exchanger 22. Subsequently, as a post-stage heat exchange step, the diluted draw solution is heated in the heat exchanger 23 between the regenerated draw solution having the same temperature as the water-rich solution and heated. Thereafter, the diluted draw solution is heated by the heater 12 to a temperature not lower than the cloud point and not higher than 100 ° C. Other configurations are the same as those of the first embodiment.

(Second embodiment)
Next, a second embodiment of the water treatment apparatus 2 configured as described above will be described. In the second embodiment, a case where 300 L (300 L / h) of fresh water is generated from 1100 L (1100 L / h) of seawater per hour using a water treatment device will be described as an example.

  In the second embodiment, seawater introduced to the water treatment device 2 from the outside at a temperature of about 25 ° C. is supplied to the membrane module 11. On the other hand, the regenerated draw solution having a temperature of 40 ° C. that has been heat-exchanged by the cooling water in the heat exchanger 21 is supplied to the membrane module 11 at a flow rate of 1100 L / h, diluted, and flows out as a diluted draw solution. In the membrane module 11, water is transferred from the seawater to the draw solution, and heat is transferred from the draw solution to the seawater. Seawater is concentrated in the membrane module 11 while being heated by the regenerated draw solution. The concentrated seawater is heated to a temperature of about 30 ° C. and discharged from the membrane module 11 at a flow rate of 715 L / h. On the other hand, the diluted draw solution flowing out from the membrane module 11 has a temperature of 35 ° C. and a flow rate of 1485 L / h. That is, in the membrane module 11, the water is moved at a flow rate of 385 L / h. In the heat exchanger 21, heat is exchanged between the regenerated draw solution discharged from the separation tank 13 and passed through the heat exchanger 23 and the cooling water supplied from the cooling mechanism 15 at a flow rate of 2500 to 4800 L / h.

  Thereafter, the diluted draw solution is heated by the heat exchanger 22 and heated to a temperature of 48.6 ° C., and then supplied to the heat exchanger 23. The diluted draw solution is heated by heat exchange with the regenerated draw solution at 88 ° C. by the heat exchanger 23. With the heat exchanger 23, the diluted draw solution is heated from 48.6 ° C. to 71 ° C. Subsequently, the diluted draw solution is supplied to the heater 12 and further heated to raise the temperature from 71 ° C. to 88 ° C.

  Thereafter, the diluted draw solution is supplied to the separation tank 13 and phase-separated into a regenerated draw solution and a water-rich solution. The regenerated draw solution has a temperature of 88 ° C. and a flow rate of 1100 L / h. The water-rich solution has a temperature of 88 ° C. and a flow rate of 385 L / h. The regenerated draw solution is lowered from 88 ° C. to a predetermined temperature of 55 ° C. or higher and lower than 88 ° C. by the heat exchanger 23, and then lowered to 40 ° C. by the heat exchanger 21. The water rich solution is cooled from 88 ° C. to 45 ° C. by the heat exchanger 22 and then supplied to the final processing unit 14. In the final treatment unit 14, product water is obtained at a flow rate of 300 L / h. At least a part or all of the separation processing waste liquid obtained by separating from the generated water is supplied to the cooling mechanism 15. The flow rate at which the separation processing waste liquid flows out is 85 L / h. In the cooling mechanism 15, the cooling water is consumed by a predetermined amount by evaporation, and is blown when the cooling water is excessive. As described above, generated water having a flow rate of 300 L / h is obtained from seawater having a flow rate of 1100 L / h.

In the second embodiment, the diluted draw solution having a temperature of 71 ° C. is heated by the heater 12 to a temperature of 88 ° C. In this case, the energy required to heat the diluted draw solution with a flow rate of 1485 L / h from 71 ° C. to 88 ° C. is as follows.
Second Example: (3.2 kJ / kg · K × 1.05 kg / L × 1485 L / h × (88 ° C.-71 ° C.) =) 8.48 × 10 ⁴ kJ / h
In this case, the input energy required for the heater 12 is 23.2 kW, which is about 1/3 times (23.2 / 66.5 =) compared to the above-described comparative example, compared with the first example. (23.2 / 54.6 =) is about 1/2 times.

  According to the second embodiment, heat exchange is performed by the heat exchanger 21 using the coolant cooled by the cooling mechanism 15, and heat exchange between the water-rich solution and the diluted draw solution is performed by the heat exchanger 22. Therefore, the same effect as that of the first embodiment can be obtained. Further, the temperature of the diluted draw solution to be supplied to the separation tank 13 is raised by the heat exchanger 23 while the temperature of the regenerated draw solution flowing out of the separation tank 13 is lowered by the heat exchanger 23. The temperature range for raising the temperature when the diluted draw solution is heated can be further reduced as compared with the first embodiment. Therefore, the energy required for heating by the heater 12 can be further reduced, and the energy consumed for heating can be further reduced in the water treatment device 2.

(Third embodiment)
(Water treatment apparatus and water treatment method)
Next, a third embodiment of the present invention will be described. FIG. 4 shows a water treatment device 3 according to the third embodiment. As shown in FIG. 4, the water treatment apparatus 3 includes a membrane module 11 having a semipermeable membrane 11a provided therein, a heater 12, a separation tank 13, a final treatment unit 14, a cooling unit, as in the first embodiment. A mechanism 15 and heat exchangers 21, 22, and 24 are provided.

  In the water treatment device 3 according to the third embodiment, unlike the first embodiment, the downstream side of the membrane module 11 along the flow direction of the diluted draw solution, the upstream side of the heat exchanger 22, and the regenerated draw solution. A heat exchanger 24 is provided on the downstream side of the separation tank 13 along the flow direction and on the upstream side of the heat exchanger 21. The pre-stage heat exchange process is performed by the heat exchanger 24 as the pre-stage heat exchange means. That is, in the water treatment method according to the third embodiment, the diluted draw solution flowing out from the membrane module 11 is combined with the high-temperature regenerated draw solution supplied from the separation tank 13 in the heat exchanger 24 as a pre-stage heat exchange step. Heat is exchanged between them and the temperature is raised. Subsequently, the diluted draw solution is heated by exchanging heat with the high-temperature water-rich solution supplied from the separation tank 13 in the heat exchanger 22. Thereafter, the diluted draw solution is heated to a temperature not lower than the cloud point and not higher than 100 ° C. by the heater 12. Other configurations are the same as those of the first embodiment.

(Third embodiment)
Next, a description will be given of a third embodiment of the water treatment apparatus 3 configured as described above. In the third embodiment, a case where 300 L (300 L / h) of fresh water is generated from 1100 L (1100 L / h) of seawater per hour using a water treatment device will be described as an example.

  In the third embodiment, seawater introduced into the water treatment device 3 from the outside at a temperature of about 25 ° C. is supplied to the membrane module 11. The concentrated seawater concentrated in the membrane module 11 is discharged at a flow rate of 715 L / h. On the other hand, the regenerated draw solution heat-exchanged by the cooling water in the heat exchanger 21 and lowered to a temperature of 40 ° C. is supplied to the membrane module 11 at a flow rate of 1100 L / h and diluted by the movement of water from seawater. It flows out as a diluted draw solution. That is, in the membrane module 11, water is moved at a flow rate of 385 L / h. The diluted draw solution flowing out from the membrane module 11 has a temperature of 35 ° C. and a flow rate of 1485 L / h. In the heat exchanger 21, cooling water supplied from the cooling mechanism 15 at a flow rate of 2500 to 4800 L / h, and a regenerated draw solution having a flow rate of 1100 L / h discharged from the separation tank 13 and passed through the heat exchanger 24 Is heat exchanged.

  Then, the diluted draw solution is heated to a temperature of 59.4 ° C. in the heat exchanger 24 by exchanging heat with the 88 ° C. regenerated draw solution supplied from the separation tank 13. The heated diluted draw solution is supplied from the heat exchanger 24 to the heat exchanger 22. The diluted draw solution is heat-exchanged with the 88 ° C. water-rich solution supplied from the separation tank 13 in the heat exchanger 22 and is heated to a temperature of 66.7 ° C. Subsequently, the diluted draw solution is supplied to the heater 12 and further heated to raise the temperature from 66.7 ° C. to 88 ° C. The diluted draw solution at 88 ° C. is supplied to the separation tank 13 and phase-separated into a regenerated draw solution and a water-rich solution.

  The regenerated draw solution separated in the separation tank 13 has a temperature of 88 ° C. and a flow rate of 1100 L / h. On the other hand, the separated water-rich solution has a temperature of 88 ° C. and a flow rate of 385 L / h. The regenerated draw solution is supplied from the separation tank 13 to the heat exchanger 24 and lowered in temperature from 88 ° C. to 78 ° C., then heat exchanged with the concentrated seawater by the heat exchanger 21 and lowered in temperature from 78 ° C. to 40 ° C. The The water rich solution is cooled from 88 ° C. to 62.6 ° C. by the heat exchanger 22 and then supplied to the final processing unit 14. In addition, when the heat resistance in the final processing unit 14 is low, such as when a film processing apparatus is used as the final processing unit 14, a cooling means (see FIG. 5) is further provided between the heat exchanger 22 and the final processing unit 14. The water-rich solution may be cooled to a predetermined temperature by installing (not shown). In the final treatment unit 14, product water is obtained at a flow rate of 300 L / h. At least a part or all of the separation processing waste liquid obtained by separating from the generated water is supplied to the cooling mechanism 15. The flow rate at which the separation processing waste liquid flows out is 85 L / h. In the cooling mechanism 15, the cooling water is consumed by a predetermined amount by evaporation, and is blown when the cooling water is excessive. As described above, generated water having a flow rate of 300 L / h is obtained from seawater having a flow rate of 1100 L / h.

In the third embodiment, the diluted draw solution having a temperature of 71 ° C. is heated by the heater 12 to a temperature of 88 ° C. In this case, the energy required to heat the diluted draw solution with a flow rate of 1485 L / h from 71 ° C. to 88 ° C. is as follows.
Third Example: (3.2 kJ / kg · K × 1.05 kg / L × 1485 L / h × (88 ° C.-66.7 ° C.) =) 1.06 × 10 ⁵ kJ / h
In this case, the input energy required for the heater 12 is 29.5 kW, which is about 2/5 times (29.5 / 66.5 =) that of the above-described comparative example, compared with the first embodiment. (29.5 / 54.6 =) is about ½ times.

  According to the third embodiment, heat exchange is performed by the heat exchanger 21 using the coolant cooled by the cooling mechanism 15, and heat exchange between the water-rich solution and the diluted draw solution is performed by the heat exchanger 22. Therefore, the same effect as that of the first embodiment can be obtained. Further, the temperature of the diluted draw solution is raised while the temperature of the regenerated draw solution to be supplied to the membrane module 11 is lowered by the heat exchanger 24, so that the same effect as in the second embodiment can be obtained. Can be obtained.

(Fourth embodiment)
(Water treatment apparatus and water treatment method)
Next, a fourth embodiment of the present invention will be described. FIG. 5 shows a water treatment device 4 according to the fourth embodiment. As shown in FIG. 5, the water treatment apparatus 4 includes a membrane module 11 having a semipermeable membrane 11a provided therein, a heater 12, a separation tank 13, a final treatment unit 14, a cooling unit, as in the first embodiment. A mechanism 15 and heat exchangers 21, 22, and 25 are provided.

In the water treatment device 4, unlike the first embodiment, a heat exchanger 25 is provided on the downstream side of the separation tank 13 along the flow direction of the regenerated draw solution and on the upstream side of the heat exchanger 21. Further, a branch point P ₀ is provided in the piping on the downstream side of the membrane module 11 along the flow direction of the diluted draw solution. At the branch point P ₀ , the diluted draw solution is branched in at least two directions and one pipe is connected to the heat exchanger 22 and the other pipe is connected to the heat exchanger 25. On the other hand, along the flow direction of the diluted draw solution, a junction P ₁ where the diluted draw solution that has passed through the heat exchangers 22 and 25 merges is provided in the pipe on the upstream side of the heater 12. At the junction P ₁ , the dilute diluted draw solution joins. That is, each of the heat exchangers 22 and 25 as the parallel heat exchanging means is configured to be able to exchange heat between the diluted draw solution and other solutions. A parallel heat exchange process is performed by the heat exchangers 22 and 25.

That is, in the water treatment method according to the fourth embodiment, the diluted draw solution flowing out from the membrane module 11 is branched at the branch point P ₀ of the piping upstream of the heat exchangers 22 and 25. The diluted draw solution flowing through one of the branched pipes is supplied to the heat exchanger 22 and heat-exchanged with the high-temperature water-rich solution to raise the temperature. The diluted draw solution flowing through the other pipe branched at the branch point P ₀ is supplied to the heat exchanger 25, and is heat-exchanged with the regenerated draw solution having the same temperature as that of the water-rich solution to be heated. The In other words, the diluted draw solution that has flowed out of the membrane module 11 is branched at the branch point P ₀ as a parallel heat exchange process, and then is passed in parallel to the heat exchangers 22 and 25 to respectively produce a water-rich solution and a regeneration draw. Heat exchange with solution. Accordingly, the flow rate of the diluted draw solution that is heated by the regenerated draw solution and the flow rate of the diluted draw solution that is heated by the water-rich solution can be reduced as compared to the second and third embodiments, and the temperature that is raised. The width can be expanded.

The diluted draw solution that has passed through the heat exchangers 22 and 25 in parallel joins at a junction P ₁ on the downstream side of the heat exchangers 22 and 25 and on the upstream side of the heater 12. Where it is branched at the branch point P _0, the flow rate ratio of one dilute draw solution and the other dilute draw solution is adjusted by the control valve provided in the vicinity of the branch point P ₀ (not shown) . Specifically, the flow rate ratio at the branch point P ₀ in the diluted draw solution is adjusted by the adjusting valve so that the temperature of one diluted draw solution and the temperature of the other diluted draw solution are substantially equal at the junction P ₁ . Is done. The diluted draw solution merged at the merge point P ₁ is heated by the heater 12 to a temperature not lower than the cloud point and not higher than 100 ° C. Other configurations are the same as those of the first embodiment.

(Fourth embodiment)
Next, the 4th Example of the water treatment apparatus 4 comprised as mentioned above is described. In the fourth embodiment, a case where 300 L (300 L / h) of fresh water is generated from 1100 L (1100 L / h) of seawater per hour using the water treatment device 4 will be described as an example.

  In the fourth embodiment, seawater having a temperature of about 25 ° C. introduced into the water treatment device 4 from the outside is supplied to the membrane module 11. The concentrated seawater concentrated by the membrane module 11 is discharged at a flow rate of 715 L / h. On the other hand, the regenerated draw solution heat-exchanged by the cooling water in the heat exchanger 21 and lowered to a temperature of 40 ° C. is supplied to the membrane module 11 at a flow rate of 1100 L / h and diluted by the movement of water from seawater. It flows out as a diluted draw solution. That is, in the membrane module 11, water is moved at a flow rate of 385 L / h. The diluted draw solution flowing out from the membrane module 11 has a temperature of 35 ° C. and a flow rate of 1485 L / h. In the heat exchanger 21, the cooling water supplied from the cooling mechanism 15 at a flow rate of 900 L / h and the regenerated draw solution at a flow rate of 1100 L / h discharged from the separation tank 13 and passed through the heat exchanger 25 are heated. Exchanged.

Thereafter, the diluted draw solution is branched at branch point P ₀ . One diluted draw solution is supplied to the heat exchanger 22 to exchange heat with a water-rich solution having a temperature of 88 ° C., and the temperature is raised from 35 ° C. to 75 ° C. The other diluted draw solution is supplied to the heat exchanger 25 and is heat-exchanged with a regenerated draw solution having a temperature of about 88 ° C., which is about the same as the water-rich solution, and the temperature is raised from 35 ° C. to 75 ° C. The temperature of the diluted draw solution on the upstream side of the heater 12 is higher than that in the first to third embodiments for the following reason. That is, since the diluted draw solution is branched in the middle and heat-exchanged in parallel, the flow rate of the diluted draw that increases the temperature per unit of the heat exchangers 22 and 25 is reduced, and the temperature range in which the temperature can be increased is obtained. This is to enlarge. The diluted draw solutions heated in parallel to 75 ° C. are merged at the merge point P ₁ , then supplied to the heater 12 and further heated to raise the temperature from 75 ° C. to 88 ° C.

  Thereafter, the diluted draw solution is supplied to the separation tank 13 and phase-separated into a regenerated draw solution and a water-rich solution. The regenerated draw solution has a temperature of 88 ° C. and a flow rate of 1100 L / h. The water-rich solution has a temperature of 88 ° C. and a flow rate of 385 L / h. The regenerated draw solution is lowered from 88 ° C. to a predetermined temperature of 50 ° C. or more and lower than 88 ° C. by the heat exchanger 25, and then lowered to 40 ° C. by the heat exchanger 21. The water rich solution is cooled from 88 ° C. to 45 ° C. by the heat exchanger 22 and then supplied to the final processing unit 14.

  In the final treatment unit 14, product water is obtained at a flow rate of 300 L / h. At least a part or all of the separation processing waste liquid obtained by separating from the generated water is supplied to the cooling mechanism 15. The flow rate at which the separation processing waste liquid flows out is 85 L / h. In the cooling mechanism 15, the cooling water is consumed by a predetermined amount by evaporation, and is blown when the cooling water is excessive. As described above, generated water having a flow rate of 300 L / h is obtained from seawater having a flow rate of 1100 L / h.

In the fourth embodiment, a diluted draw solution having a temperature of 75 ° C. is heated to a temperature of 88 ° C. by the heater 12. The energy required to heat the diluted draw solution at a flow rate of 1485 L / h from 75 ° C. to 88 ° C. is as follows.
Fourth Example: (3.2 kJ / kg · K × 1.05 kg / L × 1485 L / h × (88 ° C.-75 ° C.) =) 6.49 × 10 ⁴ kJ / h
In this case, the input energy required for the heater 12 is 18.0 kW, which is about 2/7 times (18.0 / 66.5 =) that of the comparative example described above, compared with the first embodiment. (18.0 / 54.6 =) about 1/3 times as much as the second embodiment (18.0 / 23.2 =) about 3/4 times as much as the third embodiment. (18.0 / 29.5 =) is about 3/5 times.

  According to the fourth embodiment, heat exchange is performed in the heat exchanger 21 using the coolant cooled by the cooling mechanism 15, and heat exchange between the water-rich solution and the diluted draw solution is performed by the heat exchanger 22. Therefore, the same effect as that of the first embodiment can be obtained. Furthermore, the dilute draw solution flowing out from the membrane module 11 is branched and heat-exchanged with the regenerated draw solution in the heat exchanger 25 and heat-exchanged with the water-rich solution in the heat exchanger 22 to raise the temperature in parallel. ing. Accordingly, since the diluted draw solution can be further heated at the upstream side of the heater 12 as compared with the second and third embodiments, the temperature to be raised when the diluted draw solution is heated by the heater 12. The width can be further reduced as compared with the second and third embodiments. Therefore, the energy required for heating by the heater 12 can be further reduced, and the energy consumed for heating in the water treatment device 4 can be further reduced.

(Fifth embodiment)
(Water treatment apparatus and water treatment method)
Next, a fifth embodiment of the present invention will be described. FIG. 6 shows a water treatment device 5 according to the fifth embodiment. As shown in FIG. 6, the water treatment device 5 includes a membrane module 11 having a semipermeable membrane 11 a provided therein, a heater 12, a separation tank 13, a final treatment unit 14, a cooling device, as in the fourth embodiment. A mechanism 15 and heat exchangers 21, 22, 25, and 26 are provided.

  In the water treatment device 5, unlike the fourth embodiment, heat as heat exchange means before final treatment is provided downstream of the heat exchanger 22 along the flow direction of the water-rich solution and upstream of the final treatment unit 14. An exchanger 26 is provided. The heat exchanger 26 exchanges heat between the coolant supplied from the cooling mechanism 15 and the water-rich solution that has passed through the heat exchanger 22, and supplies the water-rich solution to the final processing unit 14. The heat exchanger 26 performs a heat exchange process before final processing. That is, in the water treatment method according to the fifth embodiment, the water-rich solution at about 88 ° C. flowing out from the separation tank 13 is lowered to, for example, 45 ° C. between 30 ° C. and 50 ° C. in the heat exchanger 22. Thereafter, as a heat exchange step before final processing, the water-rich solution is cooled to 30 ° C. or higher and 45 ° C. or lower, for example, 35 ° C. by the heat exchanger 26 and then supplied to the final processing unit 14. Other configurations are the same as those of the fourth embodiment.

(5th Example)
Next, a description will be given of a fifth embodiment of the water treatment device 5 configured as described above. In the fifth embodiment, a case where 300 L (300 L / h) of fresh water is generated from 1100 L (1100 L / h) of seawater per hour using the water treatment device 5 will be described as an example.

  In the fifth embodiment, seawater having a temperature of about 25 ° C. introduced from the outside to the water treatment device 5 is supplied to the membrane module 11. The concentrated seawater concentrated by the membrane module 11 is discharged at a flow rate of 715 L / h. On the other hand, the regenerated draw solution heat-exchanged by the cooling water in the heat exchanger 21 and lowered to a temperature of 40 ° C. is supplied to the membrane module 11 at a flow rate of 1100 L / h and diluted by the movement of water from seawater. It flows out as a diluted draw solution. That is, in the membrane module 11, water is moved at a flow rate of 385 L / h. The diluted draw solution flowing out from the membrane module 11 has a temperature of 35 ° C. and a flow rate of 1485 L / h. In the heat exchanger 21, the cooling water supplied from the cooling mechanism 15 at a flow rate of 500 L / h and the regenerated draw solution having a flow rate of 1100 L / h that has flowed out of the separation tank 13 and passed through the heat exchanger 25 are heated. Exchanged.

Thereafter, the diluted draw solution is branched at branch point P ₀ . One diluted draw solution is supplied to the heat exchanger 22 to exchange heat with a water-rich solution having a temperature of 88 ° C., and the temperature is raised from 35 ° C. to 75 ° C. The other diluted draw solution is supplied to the heat exchanger 25 and is heat-exchanged with a regenerated draw solution having a temperature of about 88 ° C., which is about the same as the water-rich solution, and the temperature is raised from 35 ° C. to 75 ° C. The diluted draw solutions heated in parallel to 75 ° C. are merged at the junction P ₁ , then supplied to the heater 12 and further heated, and the temperature is raised from 75 ° C. to 88 ° C.

  Thereafter, the diluted draw solution is supplied to the separation tank 13 and phase-separated into a regenerated draw solution and a water-rich solution. The regenerated draw solution has a temperature of 88 ° C. and a flow rate of 1100 L / h. The water-rich solution has a temperature of 88 ° C. and a flow rate of 385 L / h. The regenerated draw solution is lowered from 88 ° C. to a predetermined temperature of 50 ° C. or more and lower than 88 ° C. by the heat exchanger 25, and then lowered to 40 ° C. by the heat exchanger 21. On the other hand, the water-rich solution is lowered from 88 ° C. to 45 ° C. by the heat exchanger 22 and then lowered to 35 ° C. by the heat exchanger 26. In the heat exchanger 26, cooling water is supplied from the cooling mechanism 15 at a flow rate of 400 L / h, and heat exchange with the water-rich solution is performed. The cooled water-rich solution is supplied to the final processing unit 14.

  Here, the distribution of the cooling water from the cooling mechanism 15 to each of the heat exchangers 21 and 26 is performed by adjusting the flow rate supplied to each of the heat exchangers 21 and 26. That is, an adjustment valve (none of which is shown) that can be controlled by a predetermined control unit is provided between the heat exchangers 21 and 26 on the outflow side of the cooling mechanism 15. The flow rate of the cooling water with respect to the heat exchangers 21 and 26 is arbitrarily controlled by controlling the opening degree of the control valve by the control unit. The distribution ratio to the heat exchangers 21 and 26 is calculated from a necessary flow rate for cooling the regenerated draw solution and the water-rich solution to a predetermined temperature in the two heat exchangers 21 and 26, respectively. In the fifth embodiment, the total flow rate of the cooling water supplied from the cooling mechanism 15 to the respective heat exchangers 21 and 26 is set to 900 L / h. The inlet temperature at the time of flowing into the heat exchanger 26 is variable, and the regeneration draw solution flowing out from the heat exchanger 21 and the outlet temperature of the water-rich solution flowing out from the heat exchanger 26 are controlled to be kept constant at a predetermined temperature. Is done.

  In the final treatment unit 14, product water is obtained at a flow rate of 300 L / h. At least a part or all of the separation processing waste liquid obtained by separating from the generated water is supplied to the cooling mechanism 15. The flow rate at which the separation processing waste liquid flows out is 85 L / h. In the cooling mechanism 15, the cooling water is consumed by a predetermined amount by evaporation, and is blown when the cooling water is excessive. As described above, generated water having a flow rate of 300 L / h is obtained from seawater having a flow rate of 1100 L / h.

In the fifth embodiment, a diluted draw solution having a temperature of 75 ° C. is heated by the heater 12 to a temperature of 88 ° C. The energy required to heat the diluted draw solution at a flow rate of 1485 L / h from 75 ° C. to 88 ° C. is as follows.
Example 5: (3.2 kJ / kg · K × 1.05 kg / L × 1485 L / h × (88 ° C.-75 ° C.) =) 6.49 × 10 ⁴ kJ / h
In this case, the input energy required for the heater 12 is 18.0 kW, which is about 2/7 times (18.0 / 66.5 =) that of the comparative example described above, compared with the first embodiment. (18.0 / 54.6 =) about 1/3 times as much as the second embodiment (18.0 / 23.2 =) about 3/4 times as much as the third embodiment. (18.0 / 29.5 =) is about 3/5 times.

  According to the fifth embodiment, heat exchange is performed in the heat exchanger 21 using the coolant cooled by the cooling mechanism 15, and heat exchange between the water-rich solution and the diluted draw solution is performed by the heat exchanger 22. Therefore, the same effect as that of the first embodiment can be obtained. Furthermore, the dilute draw solution flowing out from the membrane module 11 is branched and heat-exchanged with the regenerated draw solution in the heat exchanger 25 and heat-exchanged with the water-rich solution in the heat exchanger 22 to raise the temperature in parallel. As a result, the same effects as in the fourth embodiment can be obtained. Furthermore, when the temperature of the water-rich solution supplied to the final treatment unit 14 is lowered, when a membrane filtration device is used as the final treatment unit 14, the durability of the filtration membrane is about 1 in the fourth embodiment. In contrast to the year, it is about 3 years in the fifth embodiment, and the life of the membrane filtration device can be extended.

  As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, Various deformation | transformation based on the technical idea of this invention is possible. For example, the numerical values and components listed in the above-described embodiment are merely examples, and different numerical values and components may be used as necessary, and form part of the disclosure of the present invention according to this embodiment. The present invention is not limited by the description and drawings.

  For example, it is possible to implement both the second embodiment and the third embodiment described above. That is, a heat exchanger 24 that performs heat exchange between the regenerated draw solution and the diluted draw solution is provided on the downstream side or the upstream side of the heat exchanger 23 to perform both the pre-stage heat exchange process and the post-stage heat exchange process. You may do it.

  For example, in the first to fifth embodiments described above, the flow rate of water moved in the membrane module 11 is 385 L / h, the flow rate of the finally obtained product water is 300 L / h, and the recovery rate is 78%. However, it is not necessarily limited to this recovery rate, and can be set arbitrarily.

  For example, the heat exchanger 26 as the heat exchange means before final treatment in the fifth embodiment described above can be applied to the water treatment apparatuses 1, 2, and 3 according to the first to third embodiments.

1, 2, 3, 4, 5 Water treatment device 11 Membrane module 11a Semipermeable membrane 12 Heater 13 Separation tank 14 Final treatment unit 15 Cooling mechanism 21, 22, 23, 24, 25, 26 Heat exchanger

Claims (24)

Concentrated by concentrating the aqueous solution as it flows out from the aqueous solution containing water as a solvent to a draw solution having a cloud point and moving the water through a semipermeable membrane to dilute the draw solution. Forward osmosis means for discharging as an aqueous solution,
Heating means for heating the diluted draw solution to a temperature above the cloud point;
Water separation means for separating the diluted draw solution heated by the heating means into a water rich solution and the draw solution having a lower water content than the water rich solution;
Cooling means for cooling the liquid and flowing out as a cooling liquid;
Inflow side heat exchange means for exchanging heat between the cooling liquid flowing out from the cooling means and the draw solution flowing out from the water separation means,
An outflow side heat exchanging means for exchanging heat between the diluted draw solution flowing out from the forward osmosis means and the water rich solution flowing out from the water separation means.   The water treatment apparatus according to claim 1, further comprising a separation treatment unit that obtains generated water from the water-rich solution.   Along the flow direction of the water-rich solution, on the downstream side of the outflow side heat exchange means and the upstream side of the separation processing means, the water-rich solution that has flowed out of the water separation means, and the flowout of the cooling means The water treatment device according to claim 2, further comprising heat exchange means before final treatment for exchanging heat with the cooling liquid.   4. The water treatment apparatus according to claim 2, wherein the separation processing unit is configured to be able to supply a separation processing waste liquid separated from the generated water to the cooling unit. 5.   The water treatment apparatus according to any one of claims 2 to 4, wherein the separation treatment means is made of coalescer, activated carbon, ultrafiltration membrane, nanofiltration membrane, or reverse osmosis membrane.   The post-stage heat exchange means for performing heat exchange between the draw solution flowing out from the water separation means and the diluted draw solution flowing out from the forward osmosis means is further provided. The water treatment apparatus according to item.   Heat exchange is performed between the draw solution flowing out from the water separation means and the diluted draw solution flowing out from the forward osmosis means on the upstream side of the outflow side heat exchange means along the flow direction of the diluted draw solution. The water treatment apparatus according to any one of claims 1 to 6, further comprising a front-stage heat exchange means.   The water treatment apparatus according to any one of claims 1 to 7, wherein the cooling liquid is configured to be circulated between the cooling means and the inflow side heat exchange means.   The diluted draw solution flowing out from the forward osmosis means is branched, and at least two heat exchangers are configured to be able to exchange heat by parallel heat exchange means configured in parallel, respectively, and the parallel heat exchange means are branched. The water treatment device according to any one of claims 1 to 8, wherein the diluted draw solution heat-exchanged by the water is combined on the upstream side of the heating unit.   In the parallel heat exchanging means, one diluted draw solution branched from the diluted draw solution is heat exchanged with the water rich solution flowing out from the water separating means, and the other diluted diluted dilute solution is branched. The water treatment device according to claim 9, wherein the draw solution is configured to exchange heat with the draw solution flowing out from the water separation unit.   The water treatment apparatus according to claim 1, wherein the draw solution is a solution mainly composed of a temperature-sensitive water-absorbing agent having at least one cloud point.   The water treatment apparatus according to any one of claims 1 to 11, wherein the aqueous solution is seawater, brine, brackish water, industrial wastewater, associated water, or sewage. Concentrated by concentrating the aqueous solution as it flows out from the aqueous solution containing water as a solvent to a draw solution having a cloud point and moving the water through a semipermeable membrane to dilute the draw solution. Forward osmosis process to discharge as aqueous solution,
Heating the diluted draw solution to a temperature above the cloud point;
A water separation step of separating the diluted draw solution heated in the heating step into a water-rich solution and a draw solution having a lower water content than the water-rich solution;
A cooling liquid generating step of cooling the liquid to generate a cooling liquid;
An inflow side heat exchange step for exchanging heat between the cooling liquid obtained by the cooling liquid generation step and the draw solution obtained by the water separation step;
An outflow side heat exchange step of performing heat exchange between the diluted draw solution obtained by the forward osmosis step and the water rich solution obtained by the water separation step. .   The water treatment method according to claim 13, further comprising a separation treatment step of obtaining product water from the water-rich solution.   Prior to the separation treatment step, a heat exchange step before final treatment is further performed to exchange heat between the water-rich solution obtained by the water separation step and the cooling liquid obtained by the cooling liquid generation step. The water treatment method according to claim 14, further comprising:   The water treatment method according to claim 14 or 15, wherein the separation treatment waste liquid separated from the generated water in the separation treatment step is used in the cooling liquid production step.   The water treatment method according to any one of claims 14 to 16, wherein the separation treatment step is performed using a coalescer, activated carbon, an ultrafiltration membrane, a nanofiltration membrane, or a reverse osmosis membrane.   Before the outflow side heat exchange step, further comprising a pre-stage heat exchange step of performing heat exchange between the diluted draw solution obtained by the forward osmosis step and the draw solution obtained by the water separation step. The water treatment method according to claim 13, wherein the water treatment method is any one of claims 13 to 17.   The post-stage heat exchange process which performs heat exchange between the draw solution obtained by the water separation process, and the diluted draw solution heat-exchanged in the outflow side heat exchange process is further included. The water treatment method according to any one of 18 above.   The water treatment method according to any one of claims 13 to 19, wherein the coolant after heat exchange in the inflow side heat exchange step is cooled in the coolant generation step.   It further includes a parallel heat exchange step of branching the diluted draw solution obtained by the forward osmosis step and performing heat exchange in parallel in at least two heat exchangers, and after the parallel heat exchange step and the heating step 21. The water treatment method according to any one of claims 13 to 20, wherein the branched diluted draw solution is merged before the step.   In the parallel heat exchange step, one diluted draw solution branched from the diluted draw solution is heat exchanged with the water-rich solution obtained by the water separation step, and the other diluted solution from which the diluted draw solution is branched. The water treatment method according to claim 21, wherein the draw solution is subjected to heat exchange with the draw solution obtained by the water separation step.   The water treatment method according to any one of claims 13 to 22, wherein the draw solution is a solution mainly composed of a temperature-sensitive water-absorbing agent having at least one cloud point.   The water treatment method according to any one of claims 13 to 23, wherein the aqueous solution is seawater, brine, brackish water, industrial wastewater, associated water, or sewage.

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