JP2019171230A - Water treatment device and starting method thereof - Google Patents

Abstract

To shorten a starting time to a steady state while starting is stably performed in a water treatment device which causes permeation of plain water from a water-containing solution into a draw solution.SOLUTION: A starting method for starting a water treatment device comprises: forward osmosis means which transfers water from a water-containing solution into a draw solution having a cloud point through a semipermeable membrane and causes the water to flow out as a diluted draw solution and discharges a concentrated water-containing solution; heating means which heats the diluted draw solution to a temperature not less than the cloud point; and water separation means which separates the heated diluted draw solution into a water-rich solution and a less-water-containing draw solution. A circulation flow passage is provided which communicatively connects a downstream side of the water separation means and an upstream side of the forward osmosis means along a flow direction of the less-water-containing draw solution with an upstream side of the heating means and a downstream side of the forward osmosis means along a flow direction of the diluted draw solution. A draw solution stored in the water separation means is fed through the circulation flow passage into the heating means to be heated to the temperature not less than the cloud point.SELECTED DRAWING: Figure 1

Description

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

  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). A water treatment apparatus is known that allows fresh water to permeate through a draw solution from the water to be treated by bringing the water into contact with the treated water.

  In this water treatment apparatus, 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 is separated and drawn is reused as a regenerated draw solution that is brought into contact with the aqueous solution 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 branched into two flow paths, 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, the present inventor has devised a configuration including a cooling tower configured to allow a recovered liquid such as water supplied from the outside to flow out as a cooling liquid cooled to a low temperature in the water treatment apparatus. As a result, energy consumption required for cooling and heating can be suppressed, and the energy balance can be stabilized.

  The suppression of energy consumption and stabilization of the energy balance in the water treatment apparatus described above assume a steady state in which the water treatment apparatus is operating stably. In this regard, when the water treatment apparatus is first activated, the temperature of the entire system in the water treatment apparatus is different from the steady state. For this reason, at the start of starting the operation of the water treatment device, the balance of heat in the system is lost, so it takes a long time to start the water treatment device from the start to the steady state, or the start-up becomes difficult. There was a case.

  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 that allows fresh water to permeate through a draw solution from a water-containing solution, while stably starting the start-up time until a steady state is reached. An object of the present invention is to provide a water treatment device that can be shortened and a method for starting the same.

  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 forward osmosis means configured to move and flow out as a diluted draw solution obtained by diluting the draw solution, and to be discharged as a concentrated aqueous solution containing the aqueous solution, and the diluted draw solution above the cloud point The heating means configured to be able to be heated to a temperature, and the diluted draw solution heated by the heating means are configured to be separable into a water rich solution and a low water content draw solution having a lower water content than the water rich solution. A water separation means, downstream of the water separation means along the flow direction of the low water content draw solution and upstream of the forward osmosis means, and the addition along the flow direction of the diluted draw solution. Wherein the upstream and downstream side and communicable a circulation flow path of the forward osmosis unit means.

  The water treatment apparatus according to an aspect of the present invention, in the above invention, further includes dilution draw storage means configured to store the diluted draw solution flowing out from the forward osmosis means, and the flow of the low water content draw solution An upstream bypass flow path capable of communicating the downstream side of the water separation unit and the upstream side of the forward osmosis unit along the direction and the dilution draw storage unit is provided.

  The water treatment apparatus according to an aspect of the present invention further includes dilution draw storage means configured to store the diluted draw solution flowing out from the forward osmosis means in the above invention, and the flow direction of the water-rich solution And a downstream bypass flow path capable of communicating with the downstream side of the water separation means along the dilution draw storage means.

  A water treatment apparatus according to an aspect of the present invention is configured in the above invention so that heat exchange can be performed between the diluted draw solution flowing out from the diluted draw storage means and the water rich solution flowing out from the water separation means. The outlet side heat exchanging means is further provided.

  In the water treatment apparatus according to one aspect of the present invention, in the above invention, heat exchange is possible between the diluted draw solution flowing out from the diluted draw storage means and the low water content draw solution flowing out from the water separating means. It is further characterized by comprising a rear heat exchanging means configured.

  The water treatment apparatus according to one aspect of the present invention is the above-described invention, wherein the diluted draw solution flowing out from the diluted draw storage unit is branched, and at least two heat exchange units are configured in parallel. The dilute draw solution branched and heat-exchanged by the parallel heat exchanging means is configured to be merged upstream of the heating means. To do.

  The water treatment device according to an aspect of the present invention is the water treatment device according to the above invention, wherein the cooling means that cools the liquid and flows out as a cooling liquid, the cooling liquid that flows out from the cooling means, and the low flow that flows out from the water separation means. Inflow side heat exchanging means configured to be capable of exchanging heat with the water-containing draw solution.

  A method for starting a water treatment apparatus according to an aspect of the present invention is a dilution in which water is moved through a semipermeable membrane to a draw solution having a cloud point from an aqueous solution containing water as a solvent to dilute the draw solution. Forward osmosis means configured to flow out as a draw solution and discharge as a concentrated aqueous solution containing the aqueous solution, and heating means configured to heat the diluted draw solution to a temperature equal to or higher than the cloud point. A water treatment device comprising: a water separation means configured to be capable of separating the diluted draw solution heated by the heating means into a water-rich solution and a low-water content draw solution having a lower water content than the water-rich solution. An activation method for activating, which is downstream of the water separation means along the flow direction of the low water content draw solution and upstream of the forward osmosis means, and along the flow direction of the diluted draw solution. A circulation channel that can communicate with the upstream side of the heating unit and the downstream side of the forward osmosis unit is provided, and the draw solution stored in the water separation unit is supplied to the heating unit through the circulation channel. It includes a separation and circulation step of heating to a temperature above the cloud point.

  The water treatment apparatus activation method according to one aspect of the present invention is the above-described invention, wherein the water treatment apparatus further includes a dilution draw storage unit configured to store the diluted draw solution flowing out from the forward osmosis unit. Provided with an upstream bypass flow path capable of communicating the downstream side of the water separation means and the upstream side of the forward osmosis means along the flow direction of the low water content draw solution, and the dilution draw storage means, After the separation and circulation step, an upstream bypass step of supplying the draw solution stored in the water separation unit to the dilution draw storage unit through the upstream bypass flow path is included.

  The water treatment apparatus activation method according to one aspect of the present invention is the above-described invention, wherein the water treatment apparatus further includes a dilution draw storage unit configured to store the diluted draw solution flowing out from the forward osmosis unit. Provided with a downstream bypass passage capable of communicating with the downstream side of the water separation means along the flow direction of the water-rich solution and the dilution draw storage means, and after the separation and circulation step, the water separation A downstream bypass step of supplying the water-rich solution flowing out from the means to the dilution draw storage means through the downstream bypass flow path.

  The water treatment apparatus start-up method according to one aspect of the present invention is the water treatment apparatus according to the above-described invention, wherein the water treatment apparatus includes the diluted draw solution that has flowed out of the diluted draw storage means and the water-rich solution that has flowed out of the water separation means. An outflow side heat exchanging means configured to be capable of exchanging heat with each other, and by the outflow side heat exchanging means, the draw solution flowing out from the diluted draw storage means and the water rich outflowing from the water separation means It includes an outflow side temperature raising step in which heat exchange is performed with the solution to raise the temperature of the draw solution that has flowed out of the diluted draw storage means. Further, in this configuration, the method for starting the water treatment device according to one aspect of the present invention includes a heating step of heating the draw solution flowing out from the diluted draw storage unit by the heating unit after the outflow side temperature raising step. It is characterized by including.

  The water treatment apparatus start-up method according to one aspect of the present invention is the water treatment apparatus according to the above invention, wherein the water treatment apparatus includes the diluted draw solution flowing out from the diluted draw storage means and the low water content draw flowing out from the water separation means. A rear heat exchange means configured to be capable of exchanging heat with the solution; and a draw solution that has flowed out of the diluted draw storage means and a draw solution that has flowed out of the water separation means by the rear heat exchange means; And a subsequent temperature raising step of raising the temperature of the draw solution flowing out from the diluted draw storage means.

  The water treatment apparatus start-up method according to one aspect of the present invention is the water treatment apparatus according to the above invention, wherein the water treatment apparatus branches the diluted draw solution flowing out from the diluted draw storage means, so that at least two heat exchange means are provided. Heat exchange is possible by parallel heat exchange means configured in parallel, and the dilute draw solution branched and heat exchanged by the parallel heat exchange means can be merged upstream of the heating means. The heat exchange between the draw solution flowing out from the diluted draw storage means and the water-rich solution flowing out from the water separation means by a part of the at least two heat exchange means And the draw solution flowing out from the diluted draw storage means by the heat exchange means of the other part of the at least two heat exchange means, and Characterized in that it comprises a parallel heat exchange step for exchanging heat between the flowing out draw solution from the separating unit. Further, in this configuration, the method for starting the water treatment device according to one aspect of the present invention is such that, after the parallel heat exchanging step, the draw solution flowing out from the diluted draw storage unit joined is heated by the heating unit. Including a process.

  According to the water treatment apparatus and the activation method thereof according to the present invention, in the water treatment apparatus that allows fresh water to permeate from the aqueous solution into the draw solution, the activation time until the steady state is reached can be shortened while being stably activated. It becomes possible.

FIG. 1 is a block diagram schematically showing a water treatment device according to a first embodiment of the present invention and a state at the time of startup. FIG. 2 is a block diagram schematically showing a water treatment device according to a modification of the first embodiment of the present invention. FIG. 3 is a block diagram schematically showing the water treatment apparatus according to the second embodiment of the present invention and the pre-stage start-up process at the time of start-up. FIG. 4 is a block diagram schematically showing a subsequent stage startup process at the time of startup in the water treatment apparatus according to the second embodiment of the present invention. FIG. 5 is a block diagram schematically showing the water treatment device according to the third embodiment of the present invention and the state at the start-up of the water treatment device. FIG. 6 is a block diagram schematically showing a water treatment apparatus according to the fourth embodiment of the present invention. FIG. 7 is a block diagram schematically showing a start-up state in the water treatment apparatus according to the fourth 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, heat exchangers 21, 22, and a three-way valve. 31 is comprised.

  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 as 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 and increases the amount of water absorption.On the other hand, the amount of water absorption decreases as the temperature rises, becomes hydrophobic when the temperature rises above a certain level, and the solubility decreases. 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, the temperature-sensitive water-absorbing agent is, for example, an agent having a polymer of ethylene oxide and propylene oxide. 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 the 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, the membrane module 11 is configured to be able to discharge an aqueous solution (concentrated aqueous solution) concentrated by moving water into the draw solution.

  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 is configured to be able to heat the supplied draw solution. For example, the diluted draw solution that flows out of the membrane module 11 and is heat-exchanged by the heat exchanger 22 is heated by the heater 12 to a cloud point temperature or higher. 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. Furthermore, the heater 12 is configured to be able to heat the draw solution flowing out from the separation tank 13 when the water treatment apparatus 1 is activated.

  The separation tank 13 serving as a water separation means is configured to use a diluted draw solution phase-separated by the heater 12 as a water-based solution (water-rich solution) and a temperature-sensitive water-absorbing agent having a lower water content than the water-rich solution. It is configured to be separable into a main draw solution. The draw solution having a lower water content than the water-rich solution is supplied to the membrane module 11 through the heat exchanger 21 as a low water-containing draw solution (hereinafter referred to as a regenerated draw solution) to be reused.

The three-way valve 31 as the separation channel switching means is provided on the downstream side of the separation tank 13 and the upstream side of the heat exchanger 21 along the flow direction of the regenerated draw solution. A circulation channel 41 is provided in communication with the upstream side of the heater 12 along the flow direction of the diluted draw solution from the three-way valve 31. The circulation channel 41 is a channel that can communicate with the heater 12 via the inflow point P ₀ . The circulation channel 41 may be directly communicated with the heater 12. The three-way valve 31 is configured to be able to switch between a flow path for supplying the draw solution flowing out from the separation tank 13 to the heat exchanger 21 and a circulation flow path 41 for supplying to the heater 12.

  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 from the separation tank 13 as supernatant water, and generates 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. or more and 50 ° C. or less, 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, recovered liquid) supplied from the outside as a liquid (hereinafter referred to as a 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 waste liquid 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. In addition, in the cooling mechanism 15, you may make it blow the excess of the excessive 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, or the coolant that flows out of the cooling mechanism 15. The temperature of the regenerated draw solution is controlled to a predetermined temperature by controlling the flow rate of the liquid. 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 flowing out from the membrane module 11 and the water-rich solution obtained by the separation tank 13.

(Water treatment method in steady state)
Next, in the water treatment apparatus 1 according to the first embodiment configured as described above, a water treatment method in a steady state in which a sufficient amount of time has passed since the start and which is stably operated 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.

(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. 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, 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. 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 heated by the heater 12 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, 50 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. The water-rich solution flowing out from the separation tank 13 is at a higher temperature than the diluted draw solution flowing out from the membrane module 11, and the temperature is lowered by heat exchange with the diluted draw solution 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, 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.

(Start-up method of water treatment equipment)
Next, an activation method for activating the water treatment device 1 in a stage before operating the water treatment device 1 in accordance with the water treatment method in the steady state described above will be described. In the start-up method according to the first embodiment, when the water treatment apparatus 1 is started, the draw solution to be used is circulated between the heater 12 and the separation tank 13 to perform preliminary heating, and then the water treatment apparatus 1 This is a method for starting operation in a steady state.

(Preparation process)
First, a preparatory process for activation is performed in the water treatment apparatus 1. That is, as shown in FIG. 1, the three-way valve 31 is switched so that the draw solution flowing out from the separation tank 13 flows into the upstream side of the heater 12 through the three-way valve 31. On the other hand, a draw solution containing water having a temperature of, for example, about 25 ° C., which is an environmental temperature, and a temperature-sensitive water-absorbing agent is charged into the separation tank 13. Specifically, in the separation tank 13, for example, about 90% of a temperature-sensitive water-absorbing agent having a polymer concentration of 50% or more and 100% or less is diluted with water, so that the polymer concentration is 40% or more and 95% or less, for example, 60%. Retain approximately% draw solution. Furthermore, in the separation tank 13, the flow path through which the water-rich solution that is supernatant water flows out is blocked. On the other hand, the draw solution can be heated by operating the heater 12.

(Separation and circulation process)
Next, a separation / circulation step is performed by the separation tank 13 and the heater 12. The flow path of the draw solution in the separation / circulation step is indicated by a thick broken line a in FIG. First, the draw solution is discharged from the separation tank 13 by, for example, a water pump (not shown). The drawn solution that has flowed out is supplied to the heater 12 through the three-way valve 31 and the circulation channel 41. In the heater 12, an activation heating process is performed. That is, the draw solution that has flowed out of the separation tank 13 is heated by the heater 12 to a temperature equal to or higher than the cloud point, for example. Specifically, the draw solution put into the separation tank 13 in the preparation step is heated by the heater 12. The heating temperature in the startup heating step can be adjusted by controlling the heater 12. Also, the polymer concentration in the draw solution is uniquely related to the temperature of the draw solution above the cloud point, that is, the concentration of the draw solution is determined by the temperature after the draw solution is heated, so the polymer of the draw solution is determined from the temperature of the draw solution. The concentration can be derived. The heated draw solution is supplied to the separation tank 13. By repeatedly performing a series of heating operations that are supplied from the separation tank 13 to the heater 12 through the circulation channel 41 and heated, the draw solution in the separation tank 13 is heated to a temperature of, for example, about 25 ° C., which is the ambient temperature at the time of charging. To a temperature of, for example, 88 ° C. below the boiling point and below the boiling point.

  After the temperature in the separation tank 13 rises to, for example, 88 ° C. above the cloud point, the draw solution is supplied from the separation tank 13 to the membrane module 11 via the heat exchanger 21 by switching the three-way valve 31. At the same time, the forward osmosis process by the membrane module 11 is started by supplying the aqueous solution to the membrane module 11. On the other hand, the water rich solution is supplied to the final processing unit 14 via the heat exchanger 22 by opening the flow path through which the supernatant water flows out in the separation tank 13 in accordance with the start of the forward osmosis process. Processing begins. As described above, the water treatment apparatus 1 is activated and the water treatment in the steady state described above is started. The supply of the draw solution to the membrane module 11 and the supply of the aqueous solution may be performed at the same time, or one of them may be performed first. Further, the supply of the draw solution to the membrane module 11, the supply of the water-rich solution to the final processing unit 14, and the activation of the final processing unit 14 may be performed at the same time. Good.

(Modification)
Next, a modification of the first embodiment will be described. FIG. 2 is a block diagram schematically showing a water treatment device according to a modification of the first embodiment.

  As shown in FIG. 2, in the water treatment device 2 according to the modified example, on the downstream side of the separation tank 13 along the flow direction of the regenerated draw solution, on the upstream side of the heat exchanger 21 and along the flow direction of the diluted draw solution. A heat exchanger 23 is provided downstream of the heat exchanger 22 and upstream of the heater 12.

  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 of the water treatment device 2 according to the modification, 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 water treatment methods in the steady state are the same as those in the first embodiment.

In the water treatment device 2 according to the modification, a three-way valve 31 is provided on the downstream side of the separation tank 13 and the upstream side of the heat exchanger 23 along the flow direction of the regenerated draw solution. The circulation channel 41 communicates from the three-way valve 31 to an inflow point P ₀ downstream of the heat exchanger 23 and upstream of the heater 12 along the flow direction of the diluted draw solution. About the other structure and starting method of the water treatment apparatus 2 by a modification, it is the same as that of 1st Embodiment.

  Conventionally, when the water treatment apparatuses 1 and 2 are started without performing preliminary heating, a draw solution having a low polymer concentration before phase separation is supplied to the membrane module 11. Therefore, the movement of water from the aqueous solution to the draw solution becomes extremely small until the temperature balance in the system is stabilized in the water treatment apparatuses 1 and 2. In this case, the temperature of the draw solution circulating in the water treatment apparatuses 1 and 2 gradually rises, and phase separation is started when the temperature of the draw solution in the separation tank 13 exceeds cloudy weather, and the membrane module 11 Increased water movement within However, until the draw solution in the separation tank 13 reaches a predetermined temperature, that is, the cloud point, the phase separation of the draw solution in the separation tank 13 remains insufficient, so that the water-rich solution is sent to the final processing unit 14. The state where liquid cannot be continued. In this case, since the amount of the solution stored in the separation tank 13 increases, the operation of the water treatment apparatuses 1 and 2 becomes difficult when the inside of the separation tank 13 becomes full.

  On the other hand, according to 1st Embodiment demonstrated above, at the time of start-up of the water treatment apparatuses 1 and 2, using the three-way valve 31 and the circulation flow path 41, a draw solution is made into the heater 12, the separation tank 13, and Preliminary heating is performed in which the heating is performed to a predetermined temperature above the cloud point. Thereby, since the inside of the separation tank 13 can be made into the state which isolate | separated the water rich solution which is the supernatant water at the time of starting of the water treatment apparatus 1, when starting the water treatment apparatuses 1 and 2, the membrane module 11 Can be supplied with a high polymer concentration draw solution. Therefore, in the membrane module 11, the time required for water to move from the aqueous solution through the semipermeable membrane 11 a to the draw solution quickly and to stabilize the temperature balance in the system in the water treatment apparatuses 1 and 2. Can be shortened.

(Second Embodiment)
(Water treatment equipment)
Next, a second embodiment of the present invention will be described. FIG. 3 shows a water treatment device 3 according to the second embodiment. As shown in FIG. 3, 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, heat exchangers 21 and 22, and a three-way valve 31 are provided. Unlike the first embodiment, the water treatment device 3 further includes a supernatant water tank 16, a diluted draw storage tank 17, and three-way valves 32 and 33.

  The supernatant water tank 16 is provided downstream of the separation tank 13 and upstream of the heat exchanger 22 along the flow direction of the water-rich solution. The diluted draw storage tank 17 is provided on the downstream side of the membrane module 11 and the upstream side of the heat exchanger 22 along the flow direction of the diluted draw solution. The diluted draw storage tank 17 as the diluted draw storage means is configured to be able to store at least temporarily the diluted draw solution that has flowed out of the membrane module 11.

  The three-way valve 32 as the upstream side switching means is provided on the downstream side of the three-way valve 31 and the upstream side of the heat exchanger 21 along the flow direction of the draw solution flowing out from the separation tank 13. The three-way valve 32 and the diluted draw storage tank 17 are communicated with each other by an upstream bypass passage 42 through which the draw solution can flow into the diluted draw storage tank 17. The three-way valve 32 is provided between a flow path for supplying the draw solution flowing out from the separation tank 13 and passing through the three-way valve 31 to the heat exchanger 21 and an upstream bypass flow path 42 for supplying to the diluted draw storage tank 17. It is configured to be switchable.

  The three-way valve 33 as the downstream side switching means is provided on the downstream side of the heat exchanger 22 and the upstream side of the final processing unit 14 along the flow direction of the water-rich solution flowing out from the supernatant water tank 16. The three-way valve 33 and the diluted draw storage tank 17 are communicated with each other by a downstream bypass flow path 43 through which supernatant water, that is, a water-rich solution can flow into the diluted draw storage tank 17. The three-way valve 33 includes a flow path that supplies the water-rich solution that has flowed out of the supernatant water tank 16 and passed through the heat exchanger 22 to the final processing unit 14, and a downstream bypass flow path 43 that supplies the diluted draw storage tank 17. It can be switched between. About another structure, it is the same as that of 1st Embodiment.

(Water treatment method in steady state)
Next, a water treatment method in a steady state according to the second embodiment performed in the water treatment apparatus 3 configured as described above will be described. 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 flows into the diluted draw storage tank 17 and is supplied to the heat exchanger 22. The water-rich solution that is the supernatant water that has flowed out of the separation tank 13 flows into the supernatant water tank 16 and is supplied to the heat exchanger 22. Other water treatment methods in the steady state are the same as those in the first embodiment.

(Start-up method of water treatment equipment)
(Pre-stage startup process)
Next, the starting method of the water treatment apparatus 3 by 2nd Embodiment is demonstrated. In other words, in the second embodiment, first, as in the first embodiment, the separation and circulation step is performed after the preparation step. In the second embodiment, the separation and circulation process according to the first embodiment is a first stage startup process that is the first half of the startup process. In the upstream activation step, the draw solution in the separation tank 13 is supplied to the heater 12 through the circulation flow path 41 according to the flow path indicated by the thick broken line a in FIG. Thereby, the draw solution in the separation tank 13 is raised from the environmental temperature to a temperature equal to or higher than the cloud point.

(Later start-up process)
Thereafter, a post-stage startup process is performed. FIG. 4 is a block diagram schematically showing a post-stage activation process of the water treatment device 3 according to the second embodiment. In FIG. 4, the flow path of the draw solution and the water-rich solution in the circulation heating step is indicated by a thick solid line b. First, in the second embodiment, a draw solution containing water having a temperature of, for example, about 25 ° C., which is an environmental temperature, and a temperature-sensitive water-absorbing agent are charged into the diluted draw storage tank 17. Specifically, for example, in the dilution draw storage tank 17, a temperature-sensitive water-absorbing agent having a polymer concentration of about 90% is diluted with water to store a draw solution having a polymer concentration of about 50%. The introduction of the draw solution into the diluted draw storage tank 17 may be performed at any stage before or after the above-described preparation process or before or after the preceding stage starting process.

(Switching process)
Next, the switching process is performed by the three-way valves 32 and 33. That is, the three-way valve 32 is switched so that the draw solution flowing out from the separation tank 13 and passing through the three-way valve 31 can flow into the diluted draw storage tank 17 through the three-way valve 32. On the other hand, the three-way valve 33 is switched so that the water-rich solution flowing out from the separation tank 13 and flowing through the supernatant water tank 16 and the heat exchanger 22 can flow into the dilution draw storage tank 17 through the three-way valve 33.

(Circulating heating process)
Next, a circulating heating process is performed by the heater 12, the separation tank 13, the supernatant water tank 16, the dilution draw storage tank 17, and the heat exchanger 22. That is, as shown in FIG. 4, by switching the three-way valve 31, the draw solution heated in the upstream startup process flows out of the separation tank 13, and then as the upstream bypass process, the three-way valve 32 and the upstream bypass flow The diluted draw storage tank 17 is supplied through the path 42 and stored. In the diluted draw storage tank 17, the stored draw solution containing the draw solution supplied from the separation tank 13 and the water-rich solution that flows in through the downstream bypass flow path 43 described later are mixed. The temperature of the draw solution in the diluted draw storage tank 17 is raised from an environmental temperature of about 25 ° C., for example. The draw solution stored in the diluted draw storage tank 17 is supplied to the heat exchanger 22 by, for example, a water pump (not shown). In the heat exchanger 22, an outflow side temperature raising step is performed. That is, the draw solution that has flowed out from the diluted draw storage tank 17 is heated to a temperature higher than the cloud point that has flowed out from the separation tank 13 by heat exchange with a high-temperature water-rich solution of about 88 ° C., for example. The draw solution heated in the heat exchanger 22 is supplied to the heater 12. In the heater 12, the heated draw solution is further heated to a boiling point or higher and a boiling point or lower as a heating step. The heated draw solution is supplied to the separation tank 13. That is, the draw solution flowing out from the separation tank 13 is circulated to the separation tank 13 via the three-way valves 31 and 32, the dilution draw storage tank 17, the heat exchanger 22, and the heater 12.

  On the other hand, a high-temperature water-rich solution of about 88 ° C. that has flowed out of the separation tank 13 flows into the supernatant water tank 16 and is stored therein. Thereafter, the water-rich solution is supplied to the heat exchanger 22 by, for example, a water pump (not shown), and is heat-exchanged with the low-temperature draw solution supplied from the diluted draw storage tank 17. The water-rich solution cooled by the heat exchanger 22 flows into the diluted draw storage tank 17 through the three-way valve 33 and the downstream bypass flow path 43 as a downstream bypass process. In the diluted draw storage tank 17, the flowing water-rich solution and the stored draw solution containing the draw solution supplied from the separation tank 13 are mixed. Thereby, the water-rich solution is mixed with the draw solution. The draw solution stored in the diluted draw storage tank 17 is supplied to the heat exchanger 22 by, for example, a water pump (not shown), and is a water-rich solution having a high temperature of, for example, about 88 ° C. above the cloud point flowing out from the separation tank 13 And heat exchange. The draw solution heated in the heat exchanger 22 is supplied to the heater 12. In the heater 12, the heated draw solution is further heated. The heated draw solution is supplied to the separation tank 13. That is, the water-rich solution that has flowed out of the separation tank 13 is supplied to the diluted draw storage tank 17 via the supernatant water tank 16, the heat exchanger 22, and the three-way valve 33, and mixed with the draw solution. It is circulated to the separation tank 13 via the vessel 22 and the heater 12.

  In the circulating heating step described above, a high temperature draw solution of, for example, 88 ° C. above the cloud point is supplied from the separation tank 13 to the dilution draw storage tank 17. Thereby, in the dilution draw storage tank 17, the temperature of the draw solution stored rises. Further, a water-rich solution having a temperature of, for example, 88 ° C. above the cloud point from the separation tank 13 via the supernatant water tank 16 is lowered to a temperature of, for example, about 45 ° C. in the heat exchanger 22 and then supplied to the dilution draw storage tank 17. The Thereby, the temperature of the draw solution in the dilution draw storage tank 17 further increases. That is, the temperature of the draw solution in the diluted draw storage tank 17 is raised by the draw solution that has flowed out of the separation tank 13 and the water-rich solution that has flowed out of the separation tank 13 and passed through the heat exchanger 22. That is, since the heat energy in the separation tank 13 is used to raise the temperature of the draw solution in the dilution draw storage tank 17, the separation tank 13 is initially used by the ambient temperature draw solution previously charged in the dilution draw storage tank 17. The temperature of the inner draw solution may also temporarily decrease. Specifically, for example, the temperature of the draw solution in the separation tank 13 may be reduced to about 60 ° C. Even in this case, the temperature of the draw solution in the separation tank 13 and the diluted draw storage tank 17 can be raised by the thermal energy supplied to the heater 12 by continuing the circulation heating process. In addition, although the load of the heater 12 increases, the draw solution supplied to the separation tank 13 is constantly heated to, for example, 88 ° C. above the cloud point by enhancing the heating by the heater 12 as necessary. It is also possible.

  Continuing the above-described circulation heating process, the temperature of the draw solution in the separation tank 13 rises to the cloud point or higher, for example, about 88 ° C., and the temperature of the draw solution in the diluted draw storage tank 17 rises to a predetermined temperature, for example, 40 ° C. or higher. Thereafter, the three-way valves 32 and 33 are switched. Thus, the draw solution supplied from the separation tank 13 is supplied to the heat exchanger 21 via the three-way valve 32 and then supplied to the membrane module 11, and the aqueous solution is supplied to the membrane module 11. The forward osmosis process in the membrane module 11 is started. On the other hand, the water-rich solution that has flowed out of the separation tank 13 flows into the supernatant water tank 16, passes through the heat exchanger 22, is supplied to the final processing unit 14, and the final processing is started. As described above, the water treatment apparatus 3 is activated, and water treatment in a steady state according to the above-described second embodiment is started. The supply of the draw solution to the membrane module 11 and the supply of the aqueous solution may be performed at the same time, or one of them may be performed first. Further, the supply of the draw solution to the membrane module 11, the supply of the water-rich solution to the final processing unit 14, and the activation of the final processing unit 14 may be performed at the same time. Good.

  According to the second embodiment, the same effect as that of the first embodiment can be obtained by raising the temperature of the draw solution in the separation tank 13 to the cloud point or higher in the upstream startup step. Furthermore, if the water treatment device 3 is started without performing the preliminary heating in the above-described post-starting step, the heating load increases in the initial stage, and thus the heater 12 needs to be greatly increased. In this case, since an excessively large heat exchanger is used for the water treatment method in the steady state, the heating in the water treatment in the steady state becomes unstable and the initial equipment cost increases. . On the other hand, in the second embodiment described above, when the diluted draw storage tank 17 is provided, preliminary heating is also performed for the draw solution in the diluted draw storage tank 17 by the subsequent stage starting process. . Thereby, while being able to start the water treatment apparatus 3 stably, the temperature balance in the system | strain of the water treatment apparatus 3 can be stabilized quickly.

(Third embodiment)
(Water treatment equipment)
Next, a third embodiment of the present invention will be described. FIG. 5 shows a water treatment device 4 according to the third 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 second embodiment. A mechanism 15, a supernatant water tank 16, a dilution draw storage tank 17, three-way valves 31, 32, 33, and heat exchangers 21, 22 are provided. Further, unlike the second embodiment, the water treatment device 4 further includes a heat exchanger 23 as a post-stage heat exchange means. The heat exchanger 23 is a heat exchanger downstream of the heat exchanger 22 along the flow direction of the diluted draw solution and upstream of the heater 12 and downstream of the separation tank 13 along the flow direction of the regenerated draw solution. 21 on the upstream side.

(Water treatment method in steady state)
Next, a water treatment method in a steady state according to the third embodiment performed in the water treatment apparatus 4 configured as described above will be described. That is, in the water treatment method according to the third embodiment, a post-stage heat exchange step is performed by the heat exchanger 23. Specifically, the diluted draw solution flowing out of the membrane module 11 flows into the diluted draw storage tank 17 and is supplied to the heat exchanger 22 to exchange heat with the high-temperature water-rich solution. 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 to a temperature not lower than the cloud point and not higher than 100 ° C. by the heater 12 and then supplied to the separation tank 13. Other water treatment methods in the steady state are the same as in the second embodiment.

(Start-up method of water treatment equipment)
(Preparation process and previous stage startup process)
Next, the starting method of the water treatment apparatus 4 by 3rd Embodiment is demonstrated. In the third embodiment, similar to the second embodiment, the preparation process and the pre-stage activation process are performed. That is, in the upstream startup step, as shown by a thick broken line a in FIG. 5, the draw solution in the separation tank 13 is heated by the heater 12 through the circulation channel 41 and circulated in the separation tank 13. Thereby, the temperature of the draw solution in the separation tank 13 is raised from the environmental temperature to a temperature higher than the cloud point.

(Later start-up process)
Furthermore, in the third embodiment, the post-stage startup process is performed in the same manner as in the second embodiment. That is, after the ambient temperature draw solution is put into the diluted draw storage tank 17, the temperature of the draw solution is raised.

(Switching process)
Specifically, first, the switching process is performed by the three-way valves 32 and 33. That is, the three-way valve 32 is switched so that the draw solution flowing out from the separation tank 13 and passing through the three-way valve 31 and the heat exchanger 23 can flow into the diluted draw storage tank 17 through the three-way valve 32. On the other hand, the three-way valve 33 is switched so that the water-rich solution flowing out from the separation tank 13 can flow into the dilution draw storage tank 17 through the three-way valve 33 via the supernatant water tank 16 and the heat exchanger 22. .

(Circulating heating process)
Next, a circulating heating process is performed by the heater 12, the separation tank 13, the supernatant water tank 16, the dilution draw storage tank 17, and the heat exchangers 22 and 23. In FIG. 5, the flow path of the draw solution and the water-rich solution in the circulation heating step is indicated by a thick solid line b.

  That is, when the three-way valve 31 is switched, the draw solution in the separation tank 13 heated in the preceding stage starting process flows out of the separation tank 13 and is supplied to the diluted draw storage tank 17 through the three-way valve 32 and the upstream bypass flow path 42. The In the diluted draw storage tank 17, the previously stored draw solution, the draw solution that flows from the separation tank 13 through the upstream bypass flow path 42, and the water rich that flows from the supernatant water tank 16 to be described later through the downstream bypass flow path 43. The solution is mixed. The temperature of the draw solution in the diluted draw storage tank 17 is raised from an environmental temperature of about 25 ° C., for example. The water-rich solution flowing into the diluted draw storage tank 17 is mixed with the stored draw solution. The draw solution in the diluted draw storage tank 17 is heated by the inflow of the hot draw solution and the hot water-rich solution.

  The draw solution heated in the dilution draw storage tank 17 is supplied to the heat exchanger 22 by, for example, a water pump (not shown), and is rich in high-temperature water, for example, about 88 ° C. above the cloud point flowing out from the separation tank 13. Heat exchange with solution. The draw solution that has been heated in the heat exchanger 22 is supplied to the heat exchanger 23, and a subsequent heating step is performed. That is, the draw solution heated in the heat exchanger 22 is heat-exchanged with the high-temperature draw solution flowing out from the separation tank 13 in the heat exchanger 23 and further heated. The draw solution heated through the heat exchanger 23 is supplied to the heater 12. In the heater 12, the draw solution is further heated to a cloud point or higher and a boiling point or lower. The heated draw solution is supplied to the separation tank 13. That is, the draw solution flowing out from the separation tank 13 sequentially passes through the three-way valve 31, the heat exchanger 23, the three-way valve 32, the dilution draw storage tank 17, the heat exchangers 22 and 23, and the heater 12. It is circulated in.

  On the other hand, the water-rich solution having a high temperature above the cloud point that has flowed out of the separation tank 13 flows into the supernatant water tank 16 and is stored therein. Thereafter, the water-rich solution is supplied to the heat exchanger 22 by, for example, a water pump (not shown), and is heat-exchanged with the low-temperature draw solution supplied from the diluted draw storage tank 17 to be cooled. The water-rich solution cooled by the heat exchanger 22 flows into the diluted draw storage tank 17 through the downstream bypass passage 43 by the three-way valve 33. The water-rich solution that has flowed into the diluted draw storage tank 17 is mixed with the stored draw solution. Thereafter, the draw solution in the diluted draw storage tank 17 is supplied to the separation tank 13 through the flow path on the downstream side of the diluted draw storage tank 17 described above. That is, the water-rich solution that has flowed out of the separation tank 13 is supplied to the diluted draw storage tank 17 via the supernatant water tank 16, the heat exchanger 22, and the three-way valve 33, and is mixed with the draw solution. It is circulated to the separation tank 13 via 22 and 23 and the heater 12 sequentially.

  In the circulating heating process described above, a high temperature draw solution of, for example, about 35 to 60 ° C., which flows out from the separation tank 13 and is cooled in the heat exchanger 23, is supplied to the diluted draw storage tank 17. Even the draw solution cooled by the heat exchanger 23 has a higher temperature than the draw solution in the diluted draw storage tank 17, and therefore the draw solution stored in the diluted draw storage tank 17 has a temperature higher than the environmental temperature. The temperature is raised. Further, the water-rich solution above the cloud point from the separation tank 13 via the supernatant water tank 16 is lowered to a temperature of about 30 to 60 ° C., for example, about 45 ° C. in the heat exchanger 22, and then into the dilution draw storage tank 17. Supplied. Thereby, the draw solution in the diluted draw storage tank 17 is further heated to the ambient temperature or higher. That is, the draw solution in the dilution draw storage tank 17 is heated by the draw solution that flows out from the separation tank 13 and passes through the heat exchanger 23, and the water-rich solution that flows out of the separation tank 13 and passes through the heat exchanger 22. Is done. Thereby, since the thermal energy in the separation tank 13 is used to raise the temperature of the draw solution in the diluted draw storage tank 17, the separation tank is initially filled with the ambient temperature draw solution previously charged in the diluted draw storage tank 17. The temperature of the draw solution in 13 may also temporarily decrease. Specifically, for example, the temperature of the draw solution in the separation tank 13 may be lowered to about 50 to 85 ° C., for example, about 60 ° C. Even in this case, by continuing the circulation heating process, the thermal energy from the heater 12 is continuously supplied to the draw solution, and the temperature of the draw solution in the separation tank 13 and the diluted draw storage tank 17 is increased. be able to. In addition, although the load of the heater 12 increases, if necessary, the draw solution supplied to the separation tank 13 is strengthened by heating by the heater 12, and is always up to, for example, 88 ° C. above the cloud point and below the boiling point. Heating is also possible.

  Continuing the above-described circulation heating process, the temperature of the draw solution in the separation tank 13 rises to the cloud point or higher, for example, about 88 ° C., and the temperature of the draw solution in the diluted draw storage tank 17 rises to a predetermined temperature, for example, 40 ° C. or higher. Thereafter, the three-way valves 32 and 33 are switched. As a result, the draw solution flowing out from the separation tank 13 is supplied to the heat exchanger 21 via the heat exchanger 23 and the three-way valve 32 in order, and then supplied to the membrane module 11 and further the aqueous solution is added to the membrane. By supplying the module 11, the forward osmosis process by the membrane module 11 is started. On the other hand, the water-rich solution that has flowed out of the separation tank 13 flows into the supernatant water tank 16 and is supplied to the final processing unit 14 via the heat exchanger 22 and the three-way valve 33 in order, and the final processing is started. Thereby, the water treatment apparatus 4 is started and the water treatment in the steady state according to the third embodiment described above is started. The supply of the draw solution to the membrane module 11 and the supply of the aqueous solution may be performed at the same time, or one of them may be performed first. Further, the supply of the draw solution to the membrane module 11, the supply of the water-rich solution to the final processing unit 14, and the activation of the final processing unit 14 may be performed at the same time. Good.

  According to the third embodiment, the same effect as that of the first embodiment can be obtained by raising the temperature of the draw solution in the separation tank 13 to the cloud point or higher in the upstream startup step. Furthermore, the effect similar to 2nd Embodiment can be acquired by heating up the draw solution in the dilution draw storage tank 17 to predetermined temperature by a back | latter stage starting process. If the water treatment apparatus 4 is started without performing the preliminary heating in the latter stage starting process described above, the heating and cooling are both started in an unsteady operation state. Therefore, the presence of the heat exchanger 23 makes it easier for the heat balance in the system to be lost compared to the water treatment device 3 according to the second embodiment, and the operation of the water treatment device 4 may be stopped. On the other hand, in 3rd Embodiment, preliminary heating is implemented with respect to the draw solution in the dilution draw storage tank 17 by a back | latter stage starting process. Thereby, even when the heat exchanger 23 is provided, the water treatment device 4 can be stably started and the temperature balance in the system of the water treatment device 4 can be quickly stabilized. it can.

(Fourth embodiment)
(Water treatment equipment)
Next, a fourth embodiment of the present invention will be described. FIG. 6 shows a water treatment device 5 according to the fourth embodiment. As shown in FIG. 6, the water treatment apparatus 5 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 third embodiment. A mechanism 15, a supernatant water tank 16, a dilution draw storage tank 17, heat exchangers 21, 22 and 23, and three-way valves 31, 32 and 33 are provided. Further, in the water treatment device 5, unlike the third embodiment, the pre-final treatment unit 22 is disposed downstream of the heat exchanger 22 and the three-way valve 33 along the flow direction of the water-rich solution and upstream of the final treatment unit 14. A heat exchanger 24 is provided as heat exchange means. The heat exchanger 24 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.

Further, in the water treatment device 5, a branch point P ₁ is provided in the flow path on the downstream side of the diluted draw storage tank 17 along the flow direction of the diluted draw solution. At the branch point P ₁ , the diluted draw solution is branched in at least two directions. One of the branched flow paths is in communication with the heat exchanger 22, and the other flow path is in communication with the heat exchanger 23. Furthermore, along the flow direction of the diluted draw solution, the merged flow in which the diluted draw solution that has passed through the heat exchanger 22 and the diluted draw solution that has passed through the heat exchanger 23 join the flow path upstream of the heater 12. Point P ₂ is provided. In confluence P _2, diluted draw solution are merged which is branched at the branch point P _1. That is, each of the heat exchangers 22 and 23 as the parallel heat exchange means is configured to be able to exchange heat between the diluted draw solution, the other regenerated draw solution, and the water-rich solution. In FIG. 6, the merging point P ₂ is disposed on the upstream side of the inflow point P ₀ in the circulation channel 41, but may be disposed on the downstream side.

(Water treatment method in steady state)
Next, a water treatment method in a steady state according to the fourth embodiment performed in the water treatment apparatus 5 configured as described above will be described. That is, in the water treatment method according to the fourth embodiment, the parallel heat exchange process is performed by the heat exchangers 22 and 23 as the parallel heat exchange means. Specifically, the diluted draw solution flowing out from the membrane module 11 flows into the diluted draw storage tank 17 and is branched at the branch point P ₁ of the flow path from the diluted draw storage tank 17 to the upstream side of the heat exchangers 22 and 23. The The diluted draw solution supplied to the heat exchanger 22 through one of the branched flow paths is heat-exchanged with the high-temperature water-rich solution and heated. The diluted draw solution supplied to the heat exchanger 23 by the other branched flow path is heated by exchanging heat with the regenerated draw solution having the same temperature as the water-rich solution. In other words, the diluted draw solution flowing out from the membrane module 11 flows into the diluted draw storage tank 17 and is branched at the branch point P ₁ , and then passed in parallel to the heat exchangers 22 and 23 as a parallel heat exchange process. Heat exchange with water rich solution and regenerated draw solution respectively. As a result, 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 with the third embodiment, and the temperature range for raising the temperature is increased. Can be expanded.

In the water treatment device 5, the diluted draw solution branched at the branch point P ₁ is configured to be merged at the junction P ₂ on the downstream side of each of the heat exchangers 22 and 23 and on the upstream side of the heater 12. Yes. That is, dilute draw solution heat exchanger 22 through the parallel is heat-exchanged, to merge at the merging point P _2. Here, the flow rate of one diluted draw solution supplied to the heat exchanger 22 as a part of the heat exchange means and the other diluted draw solution supplied to the heat exchanger 23 as the other part of the heat exchange means The ratio is adjusted by a control valve (not shown) provided near the branch point P ₁ . The flow rate ratio at the branch point P ₁ adjusted by the control valve is adjusted 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 ₂ . The diluted draw solution merged at the merge point P ₂ is heated by the heater 12 to a temperature not lower than the cloud point and not higher than the boiling point.

  Further, the heat exchange step before final processing is performed by the heat exchanger 24 as the heat exchange means before final processing. That is, the water-rich solution having a high temperature of about 88 ° C. flowing out from the separation tank 13 and stored in the supernatant water tank 16 is supplied to the heat exchanger 22 and lowered to, for example, 45 ° C. between 30 ° C. and 50 ° C. . Thereafter, as a heat exchange step before final treatment, the water-rich solution that has passed through the heat exchanger 22 and the three-way valve 33 is cooled to 30 ° C. or higher and 45 ° C. or lower, for example, 35 ° C. by the heat exchanger 24, and then the final treatment unit. 14. Other water treatment methods in the steady state are the same as in the third embodiment.

(Start-up method of water treatment equipment)
(Pre-stage startup process)
Next, the starting method of the water treatment apparatus 5 by 4th Embodiment is demonstrated. That is, in the fourth embodiment, first, similarly to the second and third embodiments, the pre-stage startup process is performed after the preparation process is performed. In the upstream start-up process, as shown by a thick broken line a in FIG. 6, the draw solution in the separation tank 13 is supplied to the heater 12 through the three-way valve 31 and the circulation flow path 41 and heated and circulated in the separation tank 13. Let Thereby, the draw solution in the separation tank 13 is raised from the environmental temperature to a temperature equal to or higher than the cloud point.

(Later start-up process)
Thereafter, a post-stage startup process is performed. FIG. 7 is a block diagram schematically showing a post-stage activation process of the water treatment device 5 according to the fourth embodiment. In FIG. 7, the flow path of the draw solution and the water-rich solution in the circulation heating step is indicated by a thick solid line c. First, in the same manner as in the second and third embodiments, a draw solution containing environmental temperature water and a temperature-sensitive water-absorbing agent is introduced into the diluted draw storage tank 17 so that the polymer concentration is, for example, about 50%. To store. The introduction of the draw solution into the diluted draw storage tank 17 may be performed at any stage before or after the above-described preparation process or before or after the preceding stage starting process.

(Switching process)
Next, as shown in FIG. 7, a switching process is performed by the three-way valves 32 and 33. That is, the three-way valve 32 is switched so that the draw solution flowing out from the separation tank 13 and passing through the three-way valve 31 and the heat exchanger 23 can flow into the diluted draw storage tank 17 through the three-way valve 32. On the other hand, the three-way valve 33 is switched so that the water-rich solution flowing out from the separation tank 13 can flow into the dilution draw storage tank 17 through the three-way valve 33 via the supernatant water tank 16 and the heat exchanger 22. .

(Circulating heating process)
Next, a circulating heating process is performed by the heater 12, the separation tank 13, the supernatant water tank 16, the dilution draw storage tank 17, and the heat exchangers 22 and 23. That is, by switching the three-way valve 31, the high-temperature draw solution heated in the upstream startup process flows out of the separation tank 13, and the three-way valve 31, the heat exchanger 23, the three-way valve 32, and the upstream bypass flow path 42. Is supplied to the diluted draw storage tank 17. On the other hand, as will be described later, a high-temperature water-rich solution that has flowed out of the separation tank 13 and above the cloud point flows into the supernatant water tank 16 and is stored. Thereafter, the water-rich solution is supplied to the heat exchanger 22 by, for example, a water pump (not shown), and is heat-exchanged with the low-temperature draw solution supplied from the diluted draw storage tank 17 to be cooled. The water-rich solution cooled by the heat exchanger 22 flows into the diluted draw storage tank 17 through the downstream bypass passage 43 by the three-way valve 33.

  In the diluted draw storage tank 17, the previously stored draw solution, the draw solution that flows from the separation tank 13 through the upstream bypass flow path 42, and the water-rich solution that flows from the supernatant water tank 16 through the downstream bypass flow path 43 Are mixed. The temperature of the draw solution in the diluted draw storage tank 17 is raised from an environmental temperature of about 25 ° C., for example. The water-rich solution flowing into the diluted draw storage tank 17 is mixed with the stored draw solution. The draw solution in the diluted draw storage tank 17 is heated by the inflow of the hot draw solution and the hot water-rich solution.

The draw solution stored in the diluted draw storage tank 17 is discharged, for example, by a water pump (not shown) and branched at the branch point P ₁ . The draw solution flowing through one flow path on the side of the branched heat exchanger 22 is heated in the heat exchanger 22 between the water-rich solution having a temperature higher than the cloud point and passing through the supernatant water tank 16 from the separation tank 13. The temperature is raised after replacement. The draw solution flowing through the other flow path on the side of the branched heat exchanger 23 is heat-exchanged with the hot draw solution having a temperature higher than the cloud point that has flowed out of the separation tank 13 in the heat exchanger 23 and the temperature is raised. . In other words, the draw solution that has flowed out of the diluted draw storage tank 17 is branched at the branch point P ₁ , and then passes in parallel to the heat exchangers 22 and 23, so that each of the high-temperature water-rich solution and the draw solution at the cloud point or higher And heat exchange.

The draw solutions that have passed through the heat exchangers 22 and 23 in parallel join at a junction P ₂ on the downstream side of the heat exchangers 22 and 23 and on the upstream side of the heater 12. A draw solution through the one flow passage which is branched at the branch point P ₁ described above, the flow rate ratio of the draw solution through the other flow path, without adjusting valve (not provided in the vicinity of the branch point P ₁ ). Specifically, the flow rate ratio at the branch point P ₁ in the draw solution is adjusted by the regulating valve so that the temperature of one draw solution and the temperature of the other draw solution are substantially equal at the junction P ₂ . The draw solution merged at the merge point P ₂ is supplied to the heater 12 and further heated to the boiling point or more and the boiling point or less. The heated draw solution is supplied to the separation tank 13. That is, after the draw solution flowing out from the separation tank 13 passes through the three-way valve 31, the heat exchanger 23, the three-way valve 32, and the dilution draw storage tank 17 in order and joins the heat exchangers 22 and 23 in parallel. , Supplied to the heater 12 and circulated to the separation tank 13. On the other hand, the water-rich solution that has flowed out of the separation tank 13 is supplied to the diluted draw storage tank 17 via the supernatant water tank 16, the heat exchanger 22, and the three-way valve 33, and mixed with the draw solution. It is circulated to the separation tank 13 via the vessels 22 and 23 and the heater 12 in order. Other activation methods are the same as those in the third embodiment.

  In the circulation heating step described above, the draw solution in the diluted draw storage tank 17 is exchanged through the draw solution that has flowed out of the separation tank 13 and passed through the heat exchanger 23, and from the separation tank 13 via the supernatant water tank 16. The temperature is raised by the water-rich solution that has passed through the vessel 22. Thereby, the effect similar to the circulation heating process by 3rd Embodiment can be acquired.

  The circulation heating process described above is continued, and the temperature of the draw solution in the separation tank 13 is raised to a cloud point or higher, for example, 88 ° C. or higher, and the temperature of the draw solution in the diluted draw storage tank 17 is increased to a predetermined temperature, for example, 40 ° C. or higher. Thereafter, the three-way valves 32 and 33 are switched. As a result, the draw solution flowing out from the separation tank 13 is supplied to the heat exchanger 21 via the heat exchanger 23 and the three-way valve 32 in order, and then supplied to the membrane module 11 and further the aqueous solution is added to the membrane. By supplying to the module 11, the forward osmosis process by the membrane module 11 is started. On the other hand, the water-rich solution flowing out from the separation tank 13 is stored in the supernatant water tank 16 and then supplied to the final processing unit 14 via the heat exchanger 22, the three-way valve 33, and the heat exchanger 24 in order. The final processing is started. Thereby, the water treatment apparatus 5 is started and the water treatment in the steady state according to the above-described fourth embodiment is started. The supply of the draw solution to the membrane module 11 and the supply of the aqueous solution may be performed at the same time, or one of them may be performed first. Further, the supply of the draw solution to the membrane module 11, the supply of the water-rich solution to the final processing unit 14, and the activation of the final processing unit 14 may be performed at the same time. Good.

  According to the fourth embodiment, the same effect as that of the first embodiment can be obtained by raising the temperature of the draw solution in the separation tank 13 to the cloud point or higher in the upstream startup step. Furthermore, when the water treatment apparatus 4 is started, the same effect as in the second and third embodiments can be obtained by raising the temperature of the draw solution in the diluted draw storage tank 17 to a predetermined temperature.

  Moreover, according to the water treatment method in the steady state according to the fourth embodiment, the diluted draw solution that has flowed out of the membrane module 11 is branched to exchange heat with the water-rich solution in the heat exchanger 22 and the heat exchanger 23. The temperature is raised in parallel by exchanging heat with the regenerated draw solution. 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.

  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 embodiment are merely examples, and different numerical values and components may be used as necessary. The present invention is disclosed in the disclosure of the present invention according to this embodiment. The present invention is not limited by the description and drawings constituting a part.

  For example, the heat exchanger 24 as the heat exchange means before final treatment in the fourth embodiment described above can be applied to the water treatment apparatuses 1 to 4 according to the first to third embodiments.

  In the water treatment apparatuses 1 to 5 according to the first to fourth embodiments described above, a refractometer is provided on the downstream side of the heat exchanger 21 and the upstream side of the membrane module 11 along the flow direction of the diluted draw solution. It is also possible to provide it. This makes it possible to measure the polymer concentration of the diluted draw solution.

1, 2, 3, 4, 5 Water treatment apparatus 11 Membrane module 11a Semipermeable membrane 12 Heater 13 Separation tank 14 Final treatment unit 15 Cooling mechanism 16 Supernatant water tank 17 Dilution draw storage tank 21, 22, 23, 24 Heat exchanger 31, 32, 33 Three-way valve 41 Circulation channel 42 Upstream bypass channel 43 Downstream bypass channel

Claims (15)

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 configured to be discharged as an aqueous solution,
Heating means configured to be able to heat the diluted draw solution to a temperature equal to or higher than the cloud point;
Water separation means configured to be able to separate the diluted draw solution heated by the heating means into a water-rich solution and a low water-containing draw solution having a lower water content than the water-rich solution, and
A downstream side of the water separation means and an upstream side of the forward osmosis means along the flow direction of the low water content draw solution; an upstream side of the heating means and a forward osmosis means along the flow direction of the diluted draw solution; A water treatment apparatus comprising a circulation channel capable of communicating with a downstream side. Further comprising dilution draw storage means configured to store the diluted draw solution flowing out from the forward osmosis means,
An upstream bypass flow path is provided that is capable of communicating the downstream side of the water separation means and the upstream side of the forward osmosis means along the flow direction of the low water content draw solution with the diluted draw storage means. The water treatment apparatus according to claim 1, wherein Further comprising dilution draw storage means configured to store the diluted draw solution flowing out from the forward osmosis means,
The downstream bypass flow path which can connect the downstream of the said water separation means along the flow direction of the said water rich solution, and the said dilution draw storage means is provided. The Claim 1 or 2 characterized by the above-mentioned. The water treatment apparatus as described. An outflow side heat exchanging means configured to be able to exchange heat between the diluted draw solution flowing out from the diluted draw storage means and the water rich solution flowing out from the water separation means. Item 4. A water treatment apparatus according to item 2 or 3. The post-stage heat exchange means configured to be able to exchange heat between the diluted draw solution flowing out from the diluted draw storage means and the low water content draw solution flowing out from the water separation means. The water treatment apparatus of any one of 2-4. The diluted draw solution flowing out from the diluted draw storage means is branched, and at least two heat exchange means are configured to be capable of exchanging heat by parallel heat exchange means configured in parallel. The water treatment apparatus according to claim 2 or 3, wherein the diluted draw solution heat-exchanged by the parallel heat exchange means is configured to be merged on the upstream side of the heating means. Cooling means that cools the liquid and flows out as a cooling liquid, and inflow heat configured to be able to exchange heat between the cooling liquid that has flowed out of the cooling means and the low hydrous draw solution that has flowed out of the water separation means The water treatment apparatus according to claim 1, further comprising an exchange unit. 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 configured to be discharged as an aqueous solution,
Heating means configured to be able to heat the diluted draw solution to a temperature equal to or higher than the cloud point;
A water separation device configured to be able to separate the diluted draw solution heated by the heating unit into a water-rich solution and a low-water content draw solution having a lower water content than the water-rich solution, and starts a water treatment device A start-up method,
A downstream side of the water separation means and an upstream side of the forward osmosis means along the flow direction of the low water content draw solution; an upstream side of the heating means and a forward osmosis means along the flow direction of the diluted draw solution; Provide a circulation channel that can communicate with the downstream side,
A method for starting up a water treatment apparatus, comprising: a separation and circulation step in which the draw solution stored in the water separation means is supplied to the heating means through the circulation flow path and heated to a temperature equal to or higher than the cloud point. The water treatment apparatus further includes a dilution draw storage means configured to store the diluted draw solution that has flowed out of the forward osmosis means,
Providing an upstream bypass flow path capable of communicating the downstream side of the water separation means and the upstream side of the forward osmosis means along the flow direction of the low water content draw solution, and the dilution draw storage means;
9. The upstream bypass step of supplying, after the separation and circulation step, the draw solution stored in the water separation unit to the dilution draw storage unit through the upstream bypass channel. Method of starting water treatment equipment. The water treatment apparatus further includes a dilution draw storage means configured to store the diluted draw solution that has flowed out of the forward osmosis means,
Providing a downstream bypass flow path capable of communicating the downstream side of the water separation means along the flow direction of the water-rich solution and the dilution draw storage means;
9. The downstream bypass step of supplying the water-rich solution flowing out from the water separation means to the dilution draw storage means through the downstream bypass flow path after the separation and circulation step. The start-up method of the water treatment apparatus of 9. The water treatment device further includes outflow side heat exchange means configured to exchange heat between the diluted draw solution flowing out from the diluted draw storage means and the water rich solution flowing out from the water separation means. ,
The draw solution that has flowed out of the dilution draw storage means by performing heat exchange between the draw solution that has flowed out of the dilution draw storage means and the water-rich solution that has flowed out of the water separation means by the outflow side heat exchange means. The start method of the water treatment device according to claim 9 or 10 including the outflow side temperature raising process which raises temperature. The method for starting a water treatment apparatus according to claim 11, further comprising a heating step of heating the draw solution flowing out from the diluted draw storage means by the heating means after the outflow side temperature raising step. The water treatment apparatus further includes a rear-stage heat exchanging unit configured to exchange heat between the diluted draw solution flowing out from the diluted draw storing unit and the low water content draw solution flowing out from the water separating unit. ,
The post-stage heat exchange means performs heat exchange between the draw solution that has flowed out of the diluted draw storage means and the draw solution that has flowed out of the water separation means, and the draw solution that has flowed out of the diluted draw storage means is increased. The method for starting up the water treatment apparatus according to any one of claims 9 to 12, further comprising a subsequent temperature raising step of heating. The water treatment device is configured such that the diluted draw solution flowing out from the diluted draw storage means is branched and heat exchange is possible by parallel heat exchange means in which at least two heat exchange means are configured in parallel. And the dilute draw solution branched and heat exchanged by the parallel heat exchange means is configured to be merged on the upstream side of the heating means,
Heat exchange is performed between the draw solution flowing out from the dilution draw storage means and the water-rich solution flowing out from the water separation means by some of the at least two heat exchange means, A parallel heat exchange step of performing heat exchange between the draw solution flowing out from the diluted draw storage means and the draw solution flowing out from the water separation means by the heat exchange means of the other part of at least two heat exchange means The start method of the water treatment apparatus according to claim 9 or 10, characterized by comprising: The method for starting up a water treatment apparatus according to claim 14, further comprising a heating step of heating the draw solution that has flowed out from the diluted draw storage unit joined after the parallel heat exchange step by the heating unit.

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