JP2019141812A - Water treatment equipment and water treatment method - Google Patents

Abstract

To stabilize energy balance by suppressing an energy consumption required for cooling or heating.SOLUTION: Water treatment equipment comprises: forward osmosis means that moves water via a semi-permeable membrane from an aqueous solution containing water as solvent to draw solution having a cloud point to thereby form diluted draw solution in which the draw solution is diluted, and concentrated aqueous solution in which the aqueous solution is concentrated and discharges the diluted draw solution and the concentrated aqueous solution; heating means that heats the diluted draw solution up to the cloud point or more; water separation means that separates the diluted draw solution heated by the heating means into a water-rich solution and a draw solution with the percentage of water content lower than that of the water-rich solution; forward osmosis side heat exchanging means that exchanges heat between the concentrated aqueous solution having flowed out from the forward osmosis means and the draw solution having flowed out from the water separation means; and an outflow side heat exchanging means that exchanges heat between the diluted draw solution having flowed out from the forward osmosis means and the water-rich solution having flowed out from the water separation means.SELECTED DRAWING: Figure 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. Therefore, a method of providing a cooling mechanism for cooling the high-temperature draw solution is conceivable. However, when a cooling mechanism is newly provided, there is 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 an object of the present invention is to provide a water treatment apparatus and a water treatment method capable of stabilizing energy balance by suppressing energy consumption required for cooling and heating. is there.

  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 the outflow from the forward osmosis means Forward osmosis side heat exchange means for exchanging heat between the concentrated aqueous solution and the draw solution flowing out from the water separation means, the diluted draw solution flowing out from the forward osmosis means and the water separation And the outflow side heat exchange means for exchanging heat between the water rich solution flowing out from the stage, characterized in that it comprises a.

  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 for obtaining generated water from the water-rich solution. In this configuration, the water treatment apparatus according to an aspect of the present invention is characterized in that 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 latter-stage heat which performs heat exchange between the draw solution that has flowed out of the water separation unit and the diluted draw solution that has passed through the outflow side heat exchange unit in the above invention. It further comprises an exchange means.

  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.

  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 forward osmosis step of 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 step for separating the solution into a water-rich solution and a draw solution having a lower water content than the water-rich solution, the concentrated aqueous solution obtained by the forward osmosis step, and a draw solution obtained by the water separation step A forward osmosis side heat exchange step for exchanging heat with each other, and the diluted draw solution obtained by the forward osmosis step and the water-rich solution obtained by the water separation step Characterized in that it comprises a and a outflow-side heat exchange step for exchanging heat between.

  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 one embodiment of the present invention is characterized in that the separation treatment step is performed using a coalescer, activated carbon, an ultrafiltration membrane, a nanofiltration membrane, or a reverse osmosis membrane.

  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 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, 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, it is possible to suppress energy consumption required for cooling and heating and to stabilize the energy balance.

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.

  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, and heat exchangers 21 and 22. .

  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 cellulose acetate-based, polyamide-based, polyethyleneimine-based, polysulfone-based, and polybenzimidazole-based materials. 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 heat exchanger 21 is provided on the downstream side of the membrane module 11 along the flow direction of the concentrated aqueous solution. The heat exchanger 21 is provided on the downstream side of the separation tank 13 along the flow direction of the regenerated draw solution. Thereby, the heat exchanger 21 performs heat exchange between the regenerated draw solution flowing out from the separation tank 13 and the concentrated aqueous solution containing the membrane module 11. The flow rate of the concentrated aqueous solution 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, by providing a bypass valve (not shown) in the flow path through which the concentrated aqueous solution in the heat exchanger 21 passes, and controlling the flow rate of the concentrated aqueous solution flowing through the bypass valve, the temperature of the regenerated draw solution is adjusted. Control to a predetermined temperature. The temperature of the regenerated draw solution supplied to the membrane module 11 is controlled to a predetermined temperature of, 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 that has flowed out of the membrane module 11 and the water-rich solution obtained by the separation tank 13.

  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 polymer solution containing the temperature sensitive water-absorbing agent separated by the final processing unit 14 may be discarded or introduced into the diluted draw solution at least upstream of the heater 12. Further, it is possible to discard a part of the separated polymer solution and introduce the remaining polymer solution as a draw solution into a diluted draw solution at least upstream of the heater 12 or upstream of the heat exchanger 22. . Here, as a method of introducing the polymer solution into the diluted draw solution, not only a method of introducing the polymer solution into a pipe through which the diluted draw solution flows, but also a method of introducing the diluted solution into a tank (not shown) that temporarily stores the diluted draw solution. Various methods can be employed.

(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.

(Forward osmosis side heat exchange process)
In the heat exchanger 21 as the forward osmosis side heat exchange means, the forward osmosis side heat exchange step is performed. That is, the concentrated aqueous solution obtained by passing the aqueous solution through the membrane module 11 is supplied to the heat exchanger 21. On the other hand, the regenerated draw solution discharged 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, specifically, for example, a temperature of about 40 ° C. by the heat exchanger 21. As will be described later, the heated diluted draw solution flows into the separation tank 13. Due to this, the temperature of the regenerated draw solution flowing out from the separation tank 13 is higher than the temperature of the concentrated aqueous solution. Therefore, the temperature of the regenerated draw solution is lowered by the heat exchanger 21. In order to lower the regenerated draw solution to a predetermined temperature, the flow rate of the concentrated aqueous solution used 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 concentrated aqueous solution, while the concentrated aqueous solution is heated by the regenerated draw solution. It is also possible to provide a blow valve (not shown) as an adjustment valve between the membrane module 11 and the heat exchanger 21 to adjust the flow rate of the concentrated aqueous solution that flows into the heat exchanger 21. The regenerated draw solution cooled by heat exchange is supplied to the other chamber of the membrane module 11. On the other hand, the concentrated aqueous solution that has been subjected to heat exchange and heated to a temperature of 55 to 70 ° C., for example, is discharged to the outside.

(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 water rich solution is adjusted by the heat exchanger 22 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 flowing out from the separation tank 13 is hotter than the diluted draw solution flowing out from the membrane module 11 after being cooled in the heat exchanger 22. 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 as the separation processing means, 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 draw solution 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 draw solution separated from the generated water is a polymer solution having a draw concentration of about 0.5 to 25%, and is discarded outside or the heater 12 or the heat exchanger 22. Or can be introduced into the diluted draw solution upstream. It is also possible to discard part of the polymer solution separated from the produced water and introduce the remaining polymer solution into the diluted draw solution upstream of the heater 12 or the heat exchanger 22.

(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 and the comparative example, a case where 350 L (350 L / h) of fresh water is generated from 1000 L (1000 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 in the membrane module 11 while being heated by a regenerated draw solution of about 40 ° C. supplied to the membrane module 11. Concentrated seawater (concentrated seawater) is heated to a temperature of about 30 ° C. and discharged at a flow rate of 650 L / h. That is, in the membrane module 11, the water is moved at a flow rate of 350 L / h.

  The regenerated draw solution passes through the heat exchanger 21 and is heat-exchanged with a low-temperature concentrated aqueous solution containing 30 ° C., and the temperature 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 1000 L / h.

  The diluted draw solution flowing out from the membrane module 11 has a temperature of 38 ° C. and a flow rate of 1350 L / h because water moves from the seawater to the draw solution and heat moves from the regenerated draw solution to the seawater. The diluted draw solution is heat-exchanged with the 88 ° C. water-rich solution in the heat exchanger 22 and is heated from 38 ° C. to a temperature of 51.6 ° C. The diluted draw solution that has been heated is supplied to the heater 12 and further heated, and the temperature is raised from 51.6 ° 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 1000 L / h. The water-rich solution has a temperature of 88 ° C. and a flow rate of 350 L / h.

  The water-rich solution is supplied to the heat exchanger 22 to exchange heat with the 38 ° C. diluted draw solution, and the temperature is lowered from 88 ° C. to 45 ° C., and then supplied to the final processing unit 14. In the final treatment unit 14, product water is obtained at a flow rate of 350 L / h. In addition, since it is a small amount, it does not consider about the separation processing draw solution isolate | separated from the produced water in the final processing unit 14. As described above, generated water having a flow rate of 350 L / h is obtained from seawater having a flow rate of 1000 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. 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 having a semipermeable membrane 101a provided therein, 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. supplied from the outside.

  In the water treatment apparatus 100 according to the comparative example, seawater is used as the aqueous solution, and the seawater adjusted to the temperature of the raw seawater or, for example, 40 ° C. is supplied to the membrane module 101. Concentrated seawater that is a concentrated aqueous solution concentrated by the membrane module 101 is discharged from the membrane module 101 at a flow rate of 650 L / h. That is, in the membrane module 101, water is moved at a flow rate of 350 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 1350 L / h. Here, when the temperature of the seawater supplied to the membrane module 101 is 40 ° C., the temperature of the diluted draw solution flowing out from the membrane module 101 is 40 ° C. Thereafter, the diluted draw solution is supplied to the heater 102 and heated to be heated 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, produced water is obtained at a flow rate of 350 L / h. As described above, generated water having a flow rate of 350 L / h is obtained from seawater having a flow rate of 1000 L / h. Note that the separation processing draw solution separated in the final processing unit 105 may be discharged, or the separation processing draw solution may be reused as a regenerated drawing solution. Absent.

  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. Since the cooler 104 supplies seawater to cool the regenerated draw solution, a pump facility for supplying seawater to the cooler 104 and power for operating the pump are required. In contrast, in the first embodiment, the regenerated draw solution is cooled by the heat exchanger 21 using seawater introduced into the membrane module 11. This eliminates the need for the cooler 104 for cooling the regenerated draw solution, eliminates the need for a pump facility for supplying seawater to the cooler 104, and eliminates the need for power to operate the pump. Thereby, while being able to reduce equipment cost, reduction of electric power cost is realizable.

  The specific heat and density of the polymer 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 the specific heat, since the average specific heat in 40-88 degreeC is used as a polymer 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 1350 L / h from 40 ° C. to 88 ° C. is as follows.
Comparative example: (3.2 kJ / kg · K × 1.05 kg / L × 1350 L / h × (88 ° C.-40 ° C.) =) 2.18 × 10 ⁵ kJ / h
In this case, the input energy required for the heater 102 was 60.5 kW.

In contrast, in the first embodiment, the diluted draw solution having a temperature of 51.6 ° 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 1350 L / h from 51.6 ° C. to 88 ° C. is as follows.
First Example: (3.2 kJ / kg · K × 1.05 kg / L × 1350 L / h × (88 ° C.−51.6 ° C.) =) 1.65 × 10 ⁵ kJ / h
In this case, the input energy required for the heater 12 was 45.8 kW, which was found to be reduced to (45.8 / 60.5 =) 3/4 times that of the comparative example.

  As described above, according to the first embodiment of the present invention, in the water treatment apparatus, the heat exchanger 21 for cooling the regenerated draw solution with the concentrated aqueous solution is provided. Thereby, it is not necessary to separately provide a cooling mechanism for cooling the regenerated draw solution flowing out from the separation tank 13, and the energy balance in the water treatment apparatus 1 can be stabilized. In addition, the use of the concentrated aqueous solution as cooling water eliminates the need to take the aqueous solution for cooling, reducing the energy required for cooling the regenerated draw solution and further reducing the energy required for water treatment. it can.

  Moreover, according to 1st Embodiment mentioned above, the reproduction | regeneration draw solution supplied to the membrane module 11 is adjusted to desired temperature using concentrated aqueous solution containing concentrated seawater etc. which flowed out from the membrane module 11. . Thereby, concentrated seawater can be used effectively. In addition, before the diluted draw solution 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. Therefore, by cooling the regenerated draw solution using the concentrated aqueous solution after passing through the membrane module 11, compared with the case of cooling the regenerated draw solution using the aqueous solution flowing into the membrane module 11, external Can be introduced into the membrane module 11 at a low temperature.

  Further, the temperature of the diluted draw solution and the regenerated draw solution is adjusted by heat exchange without branching the diluted draw solution into two flow paths. Thereby, since the balance of the flow volume in a flow path can be adjusted easily, the energy consumption required for cooling and heating can be suppressed, and the energy balance can be stabilized.

(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, and a first treatment unit, as in the first embodiment. Heat exchangers 21 and 22 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 that has flowed out of the membrane module 11 is heat-exchanged with the high-temperature water-rich solution in the heat exchanger 22 and heated, As a post-stage heat exchange step, the heat is exchanged in the heat exchanger 23 between the regenerated draw solution having the same temperature as the water-rich solution and the temperature is raised. 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)
In the second embodiment, seawater at a temperature of 25 ° C. is supplied to the membrane module 11 at a flow rate of 1000 L / h. The concentrated seawater concentrated by the membrane module 11 is discharged at a flow rate of 650 L / h and supplied to the heat exchanger 21. That is, in the membrane module 11, water is moved at a flow rate of 350 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 concentrated seawater.

  On the other hand, the regenerated draw solution having a temperature of 40 ° C. that has been heat-exchanged by the concentrated seawater in the heat exchanger 21 is supplied to the membrane module 11 to be diluted and flows out as a diluted draw solution. Here, the flow rate of the regenerated draw solution is 1000 L / h. In the membrane module 11, water is transferred from the seawater to the draw solution, and heat is transferred from the regenerated draw solution to the seawater. That is, the diluted draw solution flowing out from the membrane module 11 has a temperature of 38 ° C. and a flow rate of 1350 L / h.

  Thereafter, the diluted draw solution is heated by the heat exchanger 22 and heated to a temperature of 51.6 ° 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. The diluted draw solution is heated from 51.6 ° C. to 71 ° C. by the heat exchanger 23. 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 1000 L / h. The water-rich solution has a temperature of 88 ° C. and a flow rate of 350 L / h. The regenerated draw solution is lowered from 88 ° C. to a temperature of 55 ° C. or more and less 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 350 L / h. Note that the separation processing draw solution separated from the generated water in the final processing unit 14 is not taken into consideration because it is a small amount. As described above, generated water having a flow rate of 350 L / h is obtained from seawater having a flow rate of 1000 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 at a flow rate of 1350 L / h from 71 ° C. to 88 ° C. is as follows.
Second Example: (3.2 kJ / kg · K × 1.05 kg / L × 1350 L / h × (88 ° C.−71 ° C.) =) 7.71 × 10 ⁴ kJ / h
In this case, the input energy required for the heater 12 is 21.4 kW, which is about 1/3 times (21.4 / 60.5 =) compared to the above-described comparative example, compared to the first example. (21.4 / 45.8 =) is about ½ times.

  According to the second embodiment, by performing heat exchange with the heat exchangers 21 and 22, the same effect as in 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 device 3 according to the third embodiment is similar to the first embodiment in the membrane module 11 having a semipermeable membrane 11 a provided therein, a heater 12, a separation tank 13, A final processing unit 14 and heat exchangers 21 and 22 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 on the upstream side of the heat exchanger 22 and the regenerated draw solution along the flow direction of the diluted 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 that has flowed out of the membrane module 11 is first a high-temperature regenerated draw solution supplied from the separation tank 13 in the heat exchanger 24 as a pre-stage heat exchange step. The temperature is raised by exchanging heat with each other. 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)
In the third embodiment, similarly to the second embodiment, seawater at a temperature of 25 ° C. is supplied to the membrane module 11 at a flow rate of 1000 L / h. The concentrated seawater concentrated in the membrane module 11 is discharged at a flow rate of 650 L / h and supplied to the heat exchanger 21. That is, in the membrane module 11, water is moved at a flow rate of 350 L / h. In the heat exchanger 21, the concentrated seawater discharged from the membrane module 11 and the regenerated draw solution discharged from the separation tank 13 and passed through the heat exchanger 24 are subjected to heat exchange.

  On the other hand, the regenerated draw solution having a temperature of 40 ° C. that has been heat-exchanged by the concentrated seawater in the heat exchanger 21 is supplied to the membrane module 11 to be diluted and flows out as a diluted draw solution. Here, the flow rate of the regenerated draw solution is 1000 L / h. Here, as water moves from the seawater to the draw solution and heat also moves from the regenerated draw solution to the seawater, the temperature of the diluted draw solution flowing out from the membrane module 11 is 38 ° C. and the flow rate is 1350 L / h. is there. Thereafter, the diluted draw solution is heated to a temperature of 60 ° C. in the heat exchanger 24 by performing heat exchange with the regenerated draw solution of 88 ° C. supplied from the separation tank 13. The 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 heated to a temperature of 67.5 ° C. Subsequently, the diluted draw solution is supplied to the heater 12 and further heated to raise the temperature from 67.5 ° C. to 88 ° C. 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 separated in the separation tank 13 has a temperature of 88 ° C. and a flow rate of 1000 L / h. On the other hand, the separated water-rich solution has a temperature of 88 ° C. and a flow rate of 350 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 58 ° C., and then heat exchanged with the concentrated seawater by the heat exchanger 21 and lowered in temperature from 58 ° C. to 40 ° C. The The water-rich solution is cooled from 88 ° C. to 64 ° 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 350 L / h. Note that the draw solution separated from the produced water in the final treatment unit 14 is not taken into consideration because of the small amount. As described above, generated water having a flow rate of 350 L / h is obtained from seawater having a flow rate of 1000 L / h.

In the third embodiment, the diluted draw solution having a temperature of 67.5 ° 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 1350 L / h from 67.5 ° C. to 88 ° C. is as follows.
Example 3 (3.2 kJ / kg · K × 1.05 kg / L × 1350 L / h × (88 ° C.−67.5 ° C.) =) 9.30 × 10 ⁴ kJ / h
In this case, the input energy required for the heater 12 is 25.8 kW, which is about 2/5 times that of the comparative example described above (25.8 / 60.5 =), compared with the first embodiment. (25.8 / 40.2 =) is about 2/3 times.

  According to the third embodiment, by performing heat exchange with the heat exchangers 21 and 22, the same effects as in 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.

  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 given in the above-described embodiment are merely examples, and different numerical values may be used as necessary. The present invention will be described with reference to the description and drawings that form part of the disclosure of the present invention according to the present embodiment. Is not limited.

  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. May be.

1, 2, 3 Water treatment apparatus 11 Membrane module 11a Semipermeable membrane 12 Heater 13 Separation tank 14 Final treatment unit 21, 22, 23, 24 Heat exchanger

Claims (14)

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 separating means for separating the diluted draw solution heated by the heating means into a water rich solution and a draw solution having a lower water content than the water rich solution;
Forward osmosis side heat exchange means for exchanging heat between the concentrated aqueous solution flowing out from the forward osmosis 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.   The water treatment apparatus according to claim 2, wherein the separation treatment means is made of coalescer, activated carbon, ultrafiltration membrane, nanofiltration membrane, or reverse osmosis membrane.   4. The heat exchanger according to claim 1, further comprising a post-stage heat exchange unit that exchanges heat between the draw solution that has flowed out of the water separation unit and the diluted draw solution that has passed through the outflow side heat exchange unit. The water treatment apparatus of Claim 1.   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 4, further comprising a front-stage heat exchange means.   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 6, wherein the aqueous solution is seawater, brackish water, 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 forward osmosis side heat exchange step of performing heat exchange between the concentrated aqueous solution obtained by the forward osmosis 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 8, further comprising a separation treatment step of obtaining produced water from the water-rich solution.   The water treatment method according to claim 9, wherein the separation treatment step is performed using a coalescer, activated carbon, an ultrafiltration membrane, a nanofiltration membrane, or a reverse osmosis membrane.   The method further comprises a subsequent heat exchange step in which 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 water treatment method according to any one of 10 above.   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 any one of claims 8 to 11, wherein the water treatment method is characterized.   The water treatment method according to any one of claims 8 to 12, 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 8 to 13, wherein the aqueous solution is seawater, brine, brackish water, industrial wastewater, associated water, or sewage.

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