JP2020199431A - Concentration system and concentration method - Google Patents

Abstract

To provide a concentration system and a concentration method which can prevent quality degradation of a treated liquid.SOLUTION: A concentration system 1 includes a positive osmosis membrane device 2 including a first chamber 21 to which a treated liquid is supplied, a second chamber 22 to which a draw solution having an osmotic pressure higher than that of the treated liquid is supplied, and a semi-permeable membrane 20 partitioning the first chamber 21 and the second chamber 22, and an evaporation concentration device 3 to which the treated liquid concentrated in the first chamber 21 of the positive osmosis membrane device 2 is supplied and that evaporates and concentrates the treated liquid. The positive osmosis membrane device 2 is configured so that the treated liquid evaporated and concentrated in the evaporation concentration device 3 is supplied to a second chamber 33 as a draw solution.SELECTED DRAWING: Figure 1

Description

The present invention relates to a liquid concentration system and a concentration method using a forward osmosis membrane device.

A membrane separation method has been conventionally known as a method for concentrating a liquid containing water. As this membrane separation method, Patent Document 1 discloses a liquid concentration system using a forward osmosis membrane device.

FIG. 4 shows a schematic configuration of the concentration system described in Patent Document 1. The concentration system 100 shown in FIG. 4 includes a forward osmosis membrane device 101, a flow path L101 for supplying a liquid to be treated (feed solution) to the first chamber 102 of the forward osmosis membrane device 101, and a first of the forward osmosis membrane device 101. A flow path L102 for discharging the concentrated liquid to be treated from the chamber 102, a flow path L103 for supplying a draw solution having a higher osmotic pressure than the liquid to be treated to the second chamber 103 of the forward osmosis membrane apparatus 101, and a forward osmosis membrane. A flow path L104 for discharging the diluted draw solution from the second chamber 103 of the device 101 and a regeneration device 110 for regenerating the diluted draw solution are provided.

In the forward osmotic membrane device 101, due to the difference in osmotic pressure between the liquid to be treated flowing in the first chamber 102 and the draw solution flowing in the second chamber 103, a part of the water content in the liquid to be treated is reduced to the first chamber 102 It passes through the semipermeable membrane 104 and moves to the second chamber 103. As a result, the liquid to be treated in the first chamber 102 is concentrated, and the draw solution in the second chamber 103 is diluted.

The regenerating device 110 concentrates the diluted draw solution discharged from the second chamber 103 of the forward osmosis membrane device 101, increases the concentration of the draw solution, and supplies the drawn solution to the second chamber 103 again. As the draw solution, a solution containing an inorganic salt such as an aqueous solution of sodium chloride (saline solution) as a solute or a solution containing a temperature-sensitive substance as a solute is generally used.

JP-A-2015-54293

However, in the liquid concentration system using the forward osmosis membrane device, a reverse leakage phenomenon occurs in which the solute contained in the draw solution leaks to the liquid to be treated side via the semipermeable membrane. When this reverse leakage phenomenon occurs, in the concentration system 100 shown in FIG. 4, foreign solutes contained in the draw solution are mixed in the liquid to be treated, so that the liquid to be concentrated is, for example, a beverage, liquid food, or liquid cosmetics. In such cases, there is a problem that the quality of the liquid to be treated after concentration is deteriorated. Further, in the concentration system 100 shown in FIG. 4, it is necessary to prepare a draw solution separately from the solution to be treated.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a concentration system and a concentration method capable of preventing quality deterioration of the liquid to be treated.

In the present invention, the first chamber to which the liquid to be treated is supplied, the second chamber to which the draw solution having a higher osmotic pressure than the liquid to be treated is supplied, and the semipermeable membrane partitioning the first chamber and the second chamber. The forward osmosis membrane device includes a forward osmosis membrane device and an evaporative concentration device for supplying a solution to be concentrated in the first chamber of the forward osmosis membrane device and evaporating and concentrating the solution to be treated. Provided is a concentration system configured such that the liquid to be treated, which has been evaporated and concentrated by the evaporation concentrator, is supplied to the second chamber as a draw solution.

In the concentration system of the present invention, it is preferable that the evaporative concentrator is configured so that the draw solution diluted in the second chamber of the forward osmosis membrane device is returned and the draw solution is evaporated and concentrated.

The concentrating system of the present invention further includes a concentrating device provided in a flow path for returning the draw solution diluted in the second chamber of the forward osmosis membrane device to the evaporative concentrating device and concentrating the draw solution. It is preferable that the evaporative concentrator is configured so that the draw solution after being concentrated by the concentrator is returned.

In the concentration system of the present invention, it is preferable to further include a first concentration liquid recovery path for recovering a part of the liquid to be treated concentrated in the first chamber of the forward osmosis membrane device.

In the concentrating system of the present invention, it is preferable to further include a second concentrated liquid recovery path for recovering a part of the liquid to be treated that has been evaporated and concentrated by the evaporative concentrator.

The concentration system of the present invention further includes a solid-liquid separation device for solid-liquid separation of the liquid to be treated that has been evaporated and concentrated by the evaporation concentration device, and the forward osmosis membrane device is a filtrate obtained by the solid-liquid separation device. Is preferably configured to be supplied to the second chamber as a draw solution.

The concentrating system of the present invention further includes a third concentrated liquid recovery path for recovering a part of the liquid to be treated before evaporative concentration by the evaporative concentration device and solid-liquid separation by the solid-liquid separation device. It is preferable that the second concentrate recovery path recovers a part of the filtrate obtained by the solid-liquid separation device.

Further, the present invention is a forward osmotic membrane treatment step of concentrating the liquid to be treated and diluting the draw solution by bringing a draw solution having a higher osmotic pressure than the liquid to be treated into contact with the liquid to be treated via a semipermeable membrane. , The evaporative concentration step of evaporating and concentrating the liquid to be treated concentrated in the forward osmosis membrane treatment step, and the liquid to be treated evaporatively concentrated in the evaporative concentration step is used as a draw solution in the forward osmosis membrane treatment step. , Provide a concentration method.

In the concentration method of the present invention, in the evaporation concentration step, it is preferable to evaporate and concentrate the draw solution diluted in the forward osmosis membrane treatment step together with the liquid to be concentrated in the forward osmosis membrane treatment step.

The concentration method of the present invention further includes a concentration step of concentrating the draw solution diluted in the forward osmosis membrane treatment step, and in the evaporation concentration step, the draw solution concentrated in the concentration step is treated with the forward osmosis membrane. It is preferable to evaporate and concentrate together with the solution to be concentrated in the process.

The concentration method of the present invention further includes a solid-liquid separation step of solid-liquid separation of the liquid to be treated that has been evaporated and concentrated by the evaporative concentration device, and the filtrate obtained by the solid-liquid separation device is subjected to the forward osmosis membrane treatment step. It is preferable to use it as a draw solution of.

According to the present invention, the solution to be treated concentrated by the forward osmosis membrane device (forward osmosis membrane treatment step) is evaporated and concentrated by the evaporation concentration device (evaporation concentration step), and the solution to be treated whose concentration, that is, the osmotic pressure is increased is drawn. It is returned to the forward osmosis membrane device as a solution. As described above, since at least a part of the liquid to be treated concentrated by the forward osmosis membrane apparatus (forward osmosis membrane treatment step) is used as the draw solution, it is not necessary to prepare the draw solution separately from the liquid to be treated. In addition, since the liquid to be treated and the draw solution are of the same type (same component), even if the component contained in the draw solution of the forward osmosis membrane device leaks from the semipermeable membrane and is mixed in the liquid to be treated. , The quality of the solution to be treated (for example, taste and flavor) is not adversely affected.

It is a schematic diagram which shows the schematic structure of the enrichment system. It is a schematic diagram which shows the schematic structure of the modification of the enrichment system. It is a schematic diagram which shows the schematic structure of the modification of the enrichment system. It is a schematic diagram which shows the schematic structure of the conventional example enrichment system.

Hereinafter, the actual form of the present invention will be described with reference to the accompanying drawings. The concentrating system and concentrating method of the present invention are used for separating water from a liquid containing water (liquid to be treated) and concentrating the liquid, and the liquid concentrating system and the liquid concentrating method using a forward osmosis membrane device. Regarding the concentration method. The forward osmotic membrane device is a device that concentrates the liquid to be treated by bringing a draw solution having a higher osmotic pressure than the liquid to be treated into contact with the liquid to be treated via a semipermeable membrane.

Examples of the liquid to be treated include an aqueous solution containing inorganic salts such as seawater. The inorganic salts are not particularly limited, and examples thereof include inorganic salts of strong acids such as hydrochloric acid, sulfuric acid, hydrofluoric acid, and phosphoric acid, and alkali metals such as potassium and sodium, or alkaline earth metals. it can.

In addition, examples of the liquid to be treated include an oral liquid and an external liquid. Oral liquid means something that humans or animals eat, such as beverages such as concentrated juices and soft drinks, liquid foods such as noodle soup, various soup stocks, seasonings, soups, and liquid health supplements. Examples include foods and oral medicines. In addition, external liquids are a general term for liquids that are applied to the body of humans or animals, such as lotions and lotions, liquid cosmetics such as liquid hand creams, and liquid medicines that are applied or sprayed on the skin or mouth. Can be mentioned. Furthermore, whether it is an oral liquid or an external liquid, it is not limited to the final use by consumers or patients, but also includes raw materials.

FIG. 1 is a schematic view showing a schematic configuration of the concentration system 1 of the present embodiment. The concentration system 1 includes a forward osmosis membrane device 2, an evaporation concentration device 3, a liquid to be treated supply line L1, a liquid to be treated discharge line L2, a draw solution supply line L3, a draw solution return flow path L4, and a third. It is provided with a 1-concentrate recovery path L5 and / or a second concentrate recovery path L6, and a condensed water recovery path L7.

In the concentration system 1 and the concentration method of the present embodiment, the liquid to be treated is concentrated by contacting a draw solution having a higher osmotic pressure than the liquid to be treated through the semipermeable membrane 20 in the forward osmosis membrane device 2. The draw solution is diluted (forward osmosis membrane treatment step). The liquid to be treated is supplied to the evaporation concentration device 3 after its concentration is increased by the forward osmosis membrane device 2, and is evaporated and concentrated in the evaporation concentration device 3, and the concentration is further increased (evaporation concentration step). The concentration system 1 and the concentration method of the present embodiment are characterized in that the liquid to be treated after evaporative concentration is used as a draw solution of the forward osmosis membrane device 2 (forward osmosis membrane treatment step). Further, in the evaporation concentration device 3 (evaporation concentration step), the draw solution after being diluted by the forward osmosis membrane device 2 (forward osmosis membrane treatment step) is concentrated by the forward osmosis membrane device 2 (forward osmosis membrane treatment step). It is evaporated and concentrated together with the liquid to be treated.

As the forward osmosis membrane device 2, a conventionally known structure can be used, and the inside thereof is divided into two chambers 21 and 22 by a semipermeable membrane 20. As the semipermeable membrane 20, a conventionally known material such as cellulose acetate, polyamide, polysulfone, or aquaporin (protein) can be used, and it is preferable to use a semipermeable membrane generally called a forward osmosis membrane. Further, as the semipermeable membrane 20, a conventionally known structure such as a flat membrane or a hollow fiber membrane can be used. When the semipermeable membrane 20 is a flat membrane, the semipermeable membrane 20 can be held in a posture by, for example, a net-like support.

A liquid to be processed supply path L1 is connected to one end side (left end side in the drawing) of the first chamber 21 of the forward osmosis membrane device 2, and the liquid to be treated is supplied through the liquid to be treated supply passage L1. .. The liquid to be treated supply path L1 connects the first chamber 21 of the forward osmosis membrane device 2 and the tank 5 for storing the liquid to be treated, and the liquid to be treated is supplied from the tank 5. On the other hand, in the second chamber 22, a draw solution supply path L3 is connected to the other end side (right end side in the drawing), and a draw solution having a higher osmotic pressure than the liquid to be treated passes through the draw solution supply path L3. Be supplied. The draw solution supply path L3 connects the second chamber 22 of the forward osmosis membrane device 2 and the evaporation concentration device 3, and the draw solution is supplied from the evaporation concentration device 3.

In the forward osmotic membrane device 2, the draw solution having a higher osmotic pressure than the liquid to be treated is in contact with the liquid to be treated via the semipermeable membrane 20 (osmotic pressures a <d, b <c). Due to the difference in the osmotic pressure of the solution, a part of the water content in the liquid to be treated moves from the first chamber 21 to the second chamber 22 through the semipermeable membrane 20. As a result, the liquid to be treated in the first chamber 21 is concentrated, and the draw solution in the second chamber 22 is diluted. The forward osmosis membrane device 2 is of a horizontal installation type in the drawing, and the first chamber 21 is on the top and the second chamber 22 is on the bottom, but the first chamber 21 is on the bottom and the second chamber 22 is on the bottom. It may be on top. Further, the forward osmosis membrane device 2 may be arranged in a vertically oriented posture.

The liquid to be treated discharge path L2 is connected to the other end side (right end side in the drawing) of the first chamber 21 of the forward osmosis membrane device 2, and the liquid to be treated concentrated in the first chamber 21 is the liquid to be treated. It is discharged through the discharge path L2. The liquid to be treated discharge passage L2 connects the first chamber 21 of the forward osmosis membrane device 2 and the evaporation concentration device 3, and the liquid to be treated discharged from the first chamber 21 of the forward osmosis membrane device 2 is evaporated and concentrated. The concentration is further increased by being supplied to the device 3 and evaporating and concentrating in the evaporative concentration device 3. In the present embodiment, the liquid to be treated after evaporation and concentration is supplied to the second chamber 22 of the forward osmosis membrane device 2 as a draw solution through the draw solution supply path L3, so that the first chamber 22 is first. A draw solution having a higher osmotic pressure than the liquid to be treated in the chamber 21 is supplied. Further, when the liquid to be treated is evaporated and concentrated by the evaporation concentration device 3, the temperature of the liquid to be treated after evaporation and concentration is higher than that before evaporation and concentration. Therefore, the osmotic pressure of the draw solution supplied from the evaporation concentrator 3 to the second chamber 22 of the forward osmosis membrane device 2 becomes higher as the temperature rises. The temperature of the liquid to be treated after evaporation and concentration is preferably set to a temperature lower than the heat resistant temperature of the semipermeable membrane 20 of the forward osmosis membrane device 2.

The evaporative concentration device 3 evaporates and concentrates the liquid to be treated supplied from the first chamber 21 of the forward osmosis membrane device 2. The evaporation concentrator 3 is not particularly limited as long as it evaporates and concentrates the liquid to be treated, that is, it concentrates by heating the liquid to be treated and evaporating a part of the water content of the liquid to be treated, for example, an evaporation can. A multi-tube evaporation concentrator that has a plurality of heat transfer tubes inside and evaporates the liquid to be treated by heat exchange with the vapor flowing in the heat transfer tubes can be used. As the multi-tube evaporation concentrator, for example, a heat pump type equipped with a compressor, an ejector drive type equipped with an ejector, a steam type using low-pressure steam, or the like can be used. Further, as the evaporation concentrator 3, instead of not providing a heat transfer tube, a flash type evaporation concentrator which is provided with a heater and flash evaporates the liquid to be treated heated by the heater outside the evaporation can in the evaporation can may be used. .. The water vapor generated by the evaporation of the liquid to be treated in the evaporation concentrator 3 is condensed, and the condensed water is recovered by the condensed water recovery path L7 and used as fresh water.

A draw solution return flow path L4 is connected to one end side (left end side in the drawing) of the second chamber 22 of the forward osmosis membrane device 2. The draw solution return flow path L4 connects the second chamber 22 of the forward osmosis membrane device 2 and the evaporation concentration device 3, and the draw solution diluted in the second chamber 22 passes through the draw solution return flow path L4. It is discharged from the two chambers 22 and supplied to the evaporation concentrator 3. The evaporative concentration device 3 evaporates and concentrates the draw solution returned from the second chamber 22 of the forward osmosis membrane device 2 together with the liquid to be treated supplied from the first chamber 21 of the forward osmosis membrane device 2.

The first concentrated liquid recovery path L5 is branched into the liquid to be treated liquid discharge path L2. The first concentrated liquid recovery path L5 is for recovering a part of the liquid to be treated concentrated in the first chamber 21 of the forward osmosis membrane device 2. Since the first concentrate recovery path L5 is separated from the solution discharge path L2, the solution to be treated after being concentrated in the first chamber 21 of the forward osmosis membrane device 2 is partially concentrated (product). It is possible to supply a part of the draw solution as a stock solution to the evaporation concentrator 3. When the liquid to be treated is evaporated and concentrated by the evaporative concentration device 3, the temperature of the liquid to be treated becomes high. Therefore, when the liquid to be treated is an oral liquid or an external liquid and it is desired to recover the concentrated liquid without applying heat, the first concentrated liquid recovery path L5 is used to make the first of the forward osmosis membrane apparatus 2. The high-concentration liquid to be treated discharged from the chamber 21 can be recovered.

A second concentrate recovery path L6 is branched into the draw solution supply path L3. The second concentrated liquid recovery path L6 is for recovering a part of the liquid to be treated that has been evaporated and concentrated by the evaporation concentration device 3. Since the second concentrated solution recovery path L6 is separated from the draw solution supply path L3, a part of the liquid to be treated after evaporative concentration by the evaporative concentration device 3 can be recovered as a concentrated solution (product). A part of the draw solution can be supplied to the second chamber 22 of the forward osmosis membrane device 2. When the liquid to be treated is evaporated and concentrated by the evaporative concentration device 3, the concentration of the liquid to be treated becomes higher. Therefore, when the liquid to be treated is an aqueous solution containing inorganic salts, or when there is no problem even if the concentrated liquid is heated even if it is an oral liquid or an external liquid, the second concentrated liquid recovery path. By using L6, it is possible to recover a higher concentration liquid to be treated discharged from the evaporation concentrator 3.

As described above, according to the concentration system 1 and the concentration method of the present embodiment having the above-described configuration, the liquid to be treated discharged from the first chamber 21 of the forward osmosis membrane device 2 is evaporated and concentrated by the evaporation concentration device 3, and the concentration, that is, The liquid to be treated having an increased osmotic pressure is returned to the second chamber 22 of the forward osmosis membrane device 2 as a draw solution. As described above, since at least a part of the liquid to be treated concentrated in the first chamber 21 of the forward osmosis membrane device 2 is used as the draw solution, it is not necessary to prepare the draw solution separately from the liquid to be treated. In addition, since the liquid to be treated and the draw solution are of the same type (same component), the component contained in the draw solution in the second chamber 22 leaks from the semipermeable membrane 20 and is in the first chamber 21. Even if it is mixed with the solution to be treated, it does not adversely affect the quality (for example, taste and flavor) of the solution to be treated.

Further, the temperature of the liquid to be treated after evaporative concentration, which is a draw solution, is higher than that before evaporative concentration, and the osmotic pressure is further increased. In this way, since the performance of the draw solution is improved by the temperature rise, in the forward osmosis membrane device 2 (forward osmosis treatment step), the liquid to be treated in the first chamber 21 and the draw solution in the second chamber 22 are used. The osmotic pressure difference becomes large. Therefore, since the amount of permeated water moving from the first chamber 21 to the second chamber 22 via the semipermeable membrane 20 can be increased, the concentration efficiency of the liquid to be treated in the first chamber 21 can be increased.

In addition, since the temperature of the liquid to be treated after evaporative concentration, which is the draw solution, is higher than that before concentration, the viscosity of the draw solution decreases due to the temperature rise. As a result, the fluidity of the draw solution in the second chamber 22 of the forward osmosis membrane device 2 is increased, so that the concentration polarization can be reduced.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

For example, the concentrating system 1 may further include a concentrating device 4, as shown in FIG. The concentrator 4 is provided in the draw solution return flow path L4 for returning the draw solution diluted in the second chamber 22 of the forward osmosis membrane device 2 to the evaporation concentrator 3, and performs a concentration step of concentrating the draw solution. .. In the evaporation concentrator 3, the draw solution after being concentrated in the concentrator 4 is returned, and the draw solution concentrated in the concentrator 4 is combined with the liquid to be concentrated in the first chamber 21 of the forward osmosis membrane device 2. Evaporate and concentrate. As a result, when the liquid to be treated is evaporated and concentrated by the evaporation concentration device 3, the concentration of the liquid to be treated becomes higher, so that the amount of vapor and the amount of treatment of the evaporation concentration device 3 can be reduced, and evaporation occurs. The energy consumption in the concentrator 3 can be reduced.

As the concentrator 4, for example, a reverse osmosis membrane device can be used. As the reverse osmosis membrane device, a conventionally known structure can be used, and the inside thereof is partitioned into two chambers 41 and 42 by a semipermeable membrane 40. As the semipermeable membrane 40, conventionally known materials such as cellulose acetate, polyamide, polysulfone, and aquaporin (protein) can be used, and it is preferable to use a semipermeable membrane generally called a reverse osmosis membrane. Further, as the semipermeable membrane 40, a conventionally known structure such as a flat membrane or a hollow fiber membrane can be used. When the semipermeable membrane 40 is a flat membrane, the semipermeable membrane 40 can be held in a posture by, for example, a net-like support.

The diluted draw solution discharged from the second chamber 22 of the forward osmosis membrane device 2 is supplied to the first chamber 41 of the reverse osmosis membrane device, and physical pressure is applied to the draw solution in the first chamber 41. , A part of the water content in the draw solution passes through the semipermeable membrane 40 from the first chamber 41 and moves to the second chamber 42. As a result, the draw solution is concentrated and concentrated due to the separation of water as it flows through the first chamber 41. The draw solution is discharged from the first chamber 41 and then supplied to the evaporation concentrator 3. The method of applying the physical pressure to the draw solution in the first chamber 41 is not particularly limited, and various methods used in the reverse osmosis method can be used. A flow path L8 for discharging the permeated water that has permeated the semipermeable membrane 40 is connected to the second chamber 42 of the reverse osmosis membrane device, and the permeated water is collected through the flow path L8 and used as fresh water. ..

The concentrator 4 is not limited to the reverse osmosis membrane device, and other devices can also be used.

Further, in the concentration system 1, a nanofiltration membrane device (not shown) may be arranged in the liquid to be processed supply path L1. The nanofiltration membrane device performs an impurity removing step that mainly removes divalent ions contained in the liquid to be treated. When the liquid to be treated is an aqueous solution containing inorganic salts such as seawater, the nanofiltration membrane device is particularly preferably one that highly eliminates sulfate ions. As a result, the scale component contained in the liquid to be treated supplied from the tank 5 can be removed at a high rate. By removing the scale component from the liquid to be treated in advance, when the liquid to be treated is concentrated to a high concentration by the forward osmosis apparatus 2, scales such as calcium sulfate having low solubility are precipitated, and the semipermeable membrane 20 Can be prevented from being blocked by suspended substances or crystals. In addition, in the evaporation concentrator 3, it is possible to prevent scale from being generated and adhering to the heat transfer surface of the heat exchanger.

Further, in the concentration system 1, a filter (not shown) may be provided in the draw solution supply path L3. When the liquid to be treated is an aqueous solution containing inorganic salts such as seawater, and the liquid to be treated (draw solution) after evaporative concentration contains suspended substances or crystals due to the precipitation of inorganic salts, it is suspended from the draw solution by a filter. By removing turbid substances and crystals, it is possible to prevent the semipermeable membrane 20 from being blocked by suspended substances and crystals in the forward osmosis membrane device 2. The filter may be on the upstream side or the downstream side of the position where the second concentrate recovery path L6 branches in the draw solution supply path L3.

Further, in the concentration system 1, when the liquid to be treated is an aqueous solution containing inorganic salts such as seawater, the liquid to be treated is concentrated to a concentration exceeding the solubility of the inorganic salts in the liquid to be treated by the evaporation concentration device 3 to be inorganic. The salts may be crystallized. In that case, as shown in FIG. 3, the evaporative concentration device 3 supplies the liquid to be treated after evaporative concentration to the solid-liquid separation device 6. The liquid to be treated after this evaporation and concentration contains suspended substances and crystals of precipitated inorganic salts. The solid-liquid separation device 6 performs a solid-liquid separation step of removing suspended substances, crystals, etc. from the liquid to be treated after evaporation and concentration, and supplies the filtrate as a draw solution to the second chamber 22 of the forward osmosis membrane device 2. As a result, the draw solution supplied to the second chamber 22 of the forward osmosis membrane device 2 does not contain suspended substances or crystals. Therefore, in the forward osmosis membrane device 2, the semipermeable membrane 20 is made of suspended substances or crystals. Blockage can be suppressed. The solid-liquid separation device 6 is not particularly limited as long as it can remove suspended substances, crystals, etc. from the liquid to be treated, and is not particularly limited, and is a centrifuge, an MF (microfiltration) membrane, or a UF (ultrafiltration). ) A filtration membrane such as a membrane can be used.

In the embodiment shown in FIG. 3, the liquid to be treated after evaporative concentration by the evaporative concentration device 3 is recovered as a concentrated liquid by the third concentrated liquid recovery path L8 without supplying a part thereof to the solid-liquid separation device 6. You may. As a result, when a concentrated solution in which suspended substances and crystals have been removed is required, the concentrated solution can be recovered from the second concentrated solution recovery path L6, and the concentrated solution mixed with suspended substances and crystals can be recovered. When a liquid or slurry-like concentrated liquid is required, the concentrated liquid can be recovered from the third concentrated liquid recovery path L8.

Further, in the concentration system 1, when the liquid to be treated has a heat-sensitive property, a cooling device (not shown) for cooling the liquid to be treated after evaporative concentration may be provided in the draw solution supply path L3. Good. As a result, thermal denaturation of the liquid to be treated can be suppressed by lowering the temperature of the liquid to be treated to, for example, normal temperature or a temperature slightly higher than normal temperature. The cooling device is not particularly limited, but from the viewpoint of energy efficiency, a heat exchanger is used to flow through the draw solution supply path L3 and the evaporatively concentrated liquid to be treated and the draw solution return channel L4. It is preferable to lower the temperature of the solution to be treated after evaporative concentration by exchanging heat with the diluted draw solution. Further, instead of the cooling device, a tank (not shown) may be provided in the draw solution supply path L3, and the liquid to be treated after evaporation and concentration may be temporarily stored in the tank to be cooled.

1 Concentration system 2 Forward osmosis membrane device 3 Evaporation concentrator 4 Concentrator 20 Semipermeable membrane 21 Room 1 22 Room 2

Claims (11)

A forward osmosis having a first chamber to which the liquid to be treated is supplied, a second chamber to which a draw solution having a higher osmotic pressure than the liquid to be treated is supplied, and a semipermeable membrane partitioning the first chamber and the second chamber. Membrane device and
A device for evaporating and concentrating the solution to be treated, which is supplied with the solution to be concentrated in the first chamber of the forward osmosis membrane device, is provided.
The forward osmosis membrane device is a concentration system configured such that the liquid to be treated that has been evaporated and concentrated by the evaporation concentration device is supplied to the second chamber as a draw solution. The concentration system according to claim 1, wherein the evaporation concentration device is configured such that the draw solution diluted in the second chamber of the forward osmosis membrane device is returned and the draw solution is evaporated and concentrated. A concentrator provided in the flow path for returning the draw solution diluted in the second chamber of the forward osmosis membrane device to the evaporative concentrator and concentrating the draw solution is further provided.
The concentration system according to claim 2, wherein the evaporation concentration device is configured to return a draw solution after concentration by the concentration device. The concentration system according to any one of claims 1 to 3, further comprising a first concentration solution recovery path for recovering a part of the solution to be concentrated concentrated in the first chamber of the forward osmosis membrane device. The concentration system according to any one of claims 1 to 4, further comprising a second concentration solution recovery path for recovering a part of the liquid to be treated that has been evaporated and concentrated by the evaporation concentration device. A solid-liquid separation device for solid-liquid separation of the liquid to be treated that has been evaporated and concentrated by the evaporation concentration device is further provided.
The concentration system according to any one of claims 1 to 5, wherein the forward osmosis membrane device is configured so that the filtrate obtained by the solid-liquid separation device is supplied to the second chamber as a draw solution. Further provided with a third concentrated liquid recovery path for recovering a part of the liquid to be treated before evaporative concentration by the evaporative concentration device and solid-liquid separation by the solid-liquid separation device.
The concentration system according to claim 6, wherein the second concentrate recovery path recovers a part of the filtrate obtained by the solid-liquid separator. A forward osmotic membrane treatment step in which a draw solution having a higher osmotic pressure than the liquid to be treated is brought into contact with the liquid to be treated via a semipermeable membrane to concentrate the liquid to be treated and dilute the draw solution.
It includes an evaporation concentration step of evaporating and concentrating the liquid to be treated concentrated in the forward osmosis membrane treatment step.
A concentration method in which a liquid to be treated that has been evaporated and concentrated in the evaporation concentration step is used as a draw solution in the forward osmosis membrane treatment step. The concentration method according to claim 8, wherein in the evaporation concentration step, the draw solution diluted in the forward osmosis membrane treatment step is evaporated and concentrated together with the liquid to be treated concentrated in the forward osmosis membrane treatment step. A concentration step of concentrating the draw solution diluted in the forward osmosis membrane treatment step is further included.
The concentration method according to claim 8, wherein in the evaporation concentration step, the draw solution concentrated in the concentration step is evaporated and concentrated together with the liquid to be treated concentrated in the forward osmosis membrane treatment step. The solid-liquid separation step of solid-liquid separation of the liquid to be treated, which has been evaporated and concentrated by the evaporation concentrator, is further included.
The concentration method according to any one of claims 8 to 10, wherein the filtrate obtained by the solid-liquid separator is used as a draw solution in the forward osmosis membrane treatment step.

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