JP3327371B2 - Membrane liquid concentrator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane type liquid concentrating apparatus for concentrating a liquid to be concentrated using a reverse osmosis membrane, and in particular, to obtain a concentrated liquid having a stable concentration even when the supply flow rate of the liquid to be concentrated fluctuates. The present invention relates to a membrane-type liquid concentrator capable of performing a high concentration ratio at a high concentration.

[0002]

2. Description of the Related Art Reverse osmosis membranes have the property of allowing a solvent to pass through, but difficult for solutes dissolved in the solvent to pass through. In the case of an aqueous solution only, the reverse osmosis membrane selectively passes (ie, permeates) water from an aqueous solution in which a solute is dissolved, so that seawater desalination,
Used for ultrapure water production equipment. The remaining liquid that has passed through the water is concentrated. A concentrating device that actively utilizes this property is used.

[0003] That is, in a general reverse osmosis membrane, the solute dissolved in the feed solution (the solution to be concentrated) has a low rate of leakage into the permeate (high rejection), so that the solute concentration in the permeate is low. It is small and therefore contains a large amount of solutes in the liquid that has not been permeated, resulting in a concentrated liquid.

At present, reverse osmosis membranes are used in the form of elements. The element structure includes a reverse osmosis membrane in a tube shape, a tube type wound in a spiral shape, a spiral type, and the like. In using the element, since a pressure is applied to the liquid to be treated, a pressure vessel having one or more of the elements incorporated in series is used. This is called a module. One or a plurality of these modules are arranged in series or in parallel according to the flow rate to be processed, and are combined so that a concentration operation at a predetermined flow rate can be performed. This is hereinafter referred to as a reverse osmosis membrane device.

A reverse osmosis membrane device has a feed liquid inlet, a concentrate outlet and a permeate outlet. The supplied liquid passes through the installed module. The liquid flows from the supply liquid inlet to the concentrated liquid outlet from the surface of the reverse osmosis membrane in the module as a passage. The liquid that has passed through the reverse osmosis membrane is collected and flows out from the permeate outlet.
That is, the liquid supplied to the supply liquid inlet is guided on the surface of the reverse osmosis membrane in the reverse osmosis membrane device, flows on the surface, and water flows through the reverse osmosis membrane at right angles to the flow. Accordingly, the supplied liquid flows toward the concentrated liquid outlet while being concentrated, and flows out from the concentrated liquid outlet.

Normally, a back pressure valve is provided on the outlet side of the concentrated liquid so that the supply liquid is pressurized so that pressure is applied to the reverse osmosis membrane.

[0007] When a plurality of modules are arranged in parallel, the supply liquid branches into each module, and the concentrated liquid and the permeate discharged from each module are collected to form one liquid flow. Is discharged.

When the reverse osmosis membrane device is used for a long period of time, it is necessary to secure the flow rate of the concentrated solution to a certain value or more in order to prevent accumulation of foreign substances and clogging in the module. To increase the concentration ratio, the flow rate of the permeate must be increased, and the flow rate of the concentrate decreases. In order to secure the minimum flow rate of the concentrated liquid, the flow rate of the supply liquid must be increased. However, the increase in the flow rate of the supply liquid is limited due to an increase in pressure loss in the module and the like, and the concentration method in which the flow is performed only once in the module can only obtain a concentration ratio of about 1.2 to 3.

In view of this, a circulating system has been developed in which a circulating system is formed to ensure the minimum flow rate in the module and that the concentration in the circulating system can be made higher than the concentration of the supply liquid even if the concentration ratio in the module in the circulating system is small. is there. In this circulation type concentrating device, a high concentration ratio can be obtained as a result, and a liquid having a high concentration can be obtained. Also,
Even when the supply liquid flow rate is small, the circulating flow rate may be ensured to be equal to or higher than the minimum flow rate, which is convenient for module operation.

[0010] Japanese Patent Application Laid-Open No.
There is a 4-56105 gazette.

FIG. 7 shows a conventional circulation type membrane liquid concentrator. In FIG. 7, the outlet liquid from the reciprocating high-pressure pump 31 passes through the circulating concentrate pipe 22 and passes through the reverse osmosis membrane device 2.
to go into. On the other hand, one of the pipes coming out of the reverse osmosis membrane device 2 and the pipe 23 for the concentrated liquid are branched into two pipes 25 and 26. One of the pipes 25 has a circulating-side back pressure valve 37 and a circulating-side liquid meter 35 in the pipe. Downstream of the circulating-side back pressure valve 37, the reciprocating high-pressure pump 31 is connected. To form a circulatory system.

The other pipe 26 is a pipe for collecting the concentrated liquid for guiding the concentrated liquid to the outside of the system.
6. An outlet flow meter 34 is provided. Reverse osmosis membrane device 2
The pipe 24 for permeate, which is the other pipe from which the permeate is discharged, is a pipe for guiding the permeate from the reverse osmosis membrane device 2, and the permeate flow meter 11 is installed in this pipe 24.

In such a configuration, at the start of the operation, the outlet side back pressure valve 36 is closed, and the operation is performed while adjusting the opening degree of the circulation side back pressure valve 37 so that the inlet side pressure of the reverse osmosis membrane device 2 becomes a predetermined value. First, the outlet side back pressure valve 36 is opened and the circulation side back pressure valve 37 is closed while maintaining the inlet side pressure at a predetermined value. When the indicated value of the permeate flow meter 11 has reached the target value, the opening of the outlet back pressure valve 36 is adjusted so that the indicator value of the outlet flow meter 34 becomes the target value. In this way, the concentrated solution can be promptly brought into an equilibrium state, and a concentrated solution of a constant concentration can be continuously recovered. Even when the flow rate of the concentrated solution (supply liquid) is small, the concentrated solution can be reliably concentrated. It is stated that a membrane liquid concentrator is obtained.

[0014]

According to the above prior art, since the outlet side back pressure valve 36 and the circulation back pressure valve 37 are located immediately after the reverse osmosis membrane unit 2, the pressure applied to the reverse osmosis membrane is reduced.
7 and the back pressure valve 36 on the outlet side. The outlet side back pressure valve 36 has two functions of maintaining this pressure and extracting the concentrated liquid at a constant flow rate. If any abnormalities, for example, small debris enter the outlet side back pressure valve 36 and the flow rate of the withdrawal changes, operate the outlet side back pressure valve 36 to return the flow rate of the concentrate to a predetermined value,
In order to keep the pressure applied to the reverse osmosis membrane constant, it is necessary to operate the back pressure valve 37, and the operation is complicated, and the system tends to be unstable.

Furthermore, according to the above prior art, since the flow rate of the permeate and the flow rate of the concentrated liquid to be recovered are controlled to be constant, when the concentration of the liquid to be concentrated fluctuates, the concentration of the concentrated liquid to be recovered is changed. There is a problem that it fluctuates, and there is a problem that even if it is desired to change the flow rate of the liquid to be concentrated, it cannot be easily changed.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to make the concentration of the concentrated liquid to be recovered constant even when the concentration of the liquid to be concentrated, that is, the raw material liquid to be supplied, changes. A liquid concentrating device, and a membrane-type liquid concentrating device capable of obtaining a concentrated solution having a constant concentration in response to a change in the flow rate of the liquid to be concentrated or a change in the flow rate of the liquid to be concentrated. is there.

[0017]

A feature of the present invention that achieves the above object is that a liquid to be concentrated is sent to a reverse osmosis membrane device by a pump to obtain a concentrated liquid and a permeated liquid, and a part of the concentrated liquid is obtained. In a membrane-type liquid concentrator provided with a circulation system for returning the concentrated liquid as the circulating liquid to the concentrated liquid, and providing a back pressure valve in the circulation system, and withdrawing the recovered concentrated liquid downstream of the back pressure valve. And a pipe for extracting the collected concentrated liquid, which is provided with the flow control valve described above.

By operating the back pressure valve or changing the rotation speed of the pump, the flow rate of the permeate is controlled to a value based on the flow rate of the liquid to be concentrated, and the concentration of the concentrate is given in advance. The flow rate of the collected concentrate is controlled by a flow control valve so as to be the same as the set value.

In the reverse osmosis operation, the flow rate Q of the permeate is proportional to the difference P-π between the pressure P of the liquid in the reverse osmosis membrane and the osmotic pressure π determined by the properties and concentration of the liquid. Therefore, the permeate flow rate Q can be controlled by controlling the liquid pressure P in the reverse osmosis membrane.

The flow rate of the supply liquid, ie, the liquid to be concentrated, brought in from the outside of the circulation system consisting of the above-described high-pressure pump, reverse osmosis membrane device, etc. Q2 and Q. The solute concentration and density of the feed solution are C1, γ1, the solute concentration and density of the recovered concentrate are C2, γ2, and the solute concentration and density of the permeate are C, γ.
Then, the following equation is obtained from the mass balance.

[0021]

Q1 · γ1 · C1 = Q2 · γ2 · C2 + Q · γ · C (1)

[0022]

## EQU2 ## Q1 = Q2 + Q (2)

Since the solute hardly permeates into the permeate, the solute concentration C of the permeate is zero. Summarizing these equations, the solute concentration C2 of the recovered concentrate is represented by the following equation.

[0024]

## EQU3 ## C2 = Q1.γ1.C1 / (Q2.γ2) = (γ1.C1 / γ2). (1 + Q / Q2) (3)

From the equation (3), the concentration C2 of the recovered concentrate is
Even if the flow rate Q1 and the concentration C1 of the liquid to be concentrated change, it can be controlled by controlling the flow rate Q2 of the recovered concentrated liquid, and even if the flow rate Q of the permeated liquid changes, it can be controlled by controlling the flow rate Q2 of the recovered concentrated liquid.

According to the present invention, the flow rate control valve for controlling the flow rate of the recovered concentrated liquid is provided after the back pressure valve on the concentrated liquid outlet side of the reverse osmosis membrane device, so that the flow rate Q2 of the recovered concentrated liquid can be controlled at a low pressure. In addition, the concentration C2 of the recovered concentrate can be controlled with high accuracy.

In the back pressure valve, the liquid passes through a throttle whose opening degree can be changed, and a pressure difference occurs before and after the throttle according to the linear velocity of the liquid. By utilizing this, the liquid pressure P in the reverse osmosis membrane device can be controlled by adjusting the opening of the back pressure valve and the flow rate passing through the back pressure valve, and the flow rate Q of the permeate can be controlled. In the present invention, the permeate flow rate Q
Can be controlled from outside the system so as to be a value corresponding to the flow rate Q1 of the liquid to be concentrated (supply liquid). Therefore, it is possible to cope with a change in the flow rate Q1 of the liquid to be concentrated,
1. Even if the flow rate Q1 changes, it is possible to accurately obtain a constant concentration of the recovered concentration liquid.

[0028]

FIG. 1 shows an embodiment of the present invention.
In FIG. 1, the high-pressure pump 1 is connected to a reverse osmosis membrane device 2 via a circulating concentrated solution piping 22, and a concentrated solution outlet 23 of the reverse osmosis membrane device 2 is connected to a concentrated solution piping 23. A back pressure valve 3, a flow meter 15, a concentration detector 13
The concentrated liquid pipe 23 is divided into a recovered concentrated liquid pipe 26 and a circulating liquid pipe 25 downstream thereof. The circulating liquid piping 25 is connected to the concentrated liquid piping 21 from the supply liquid tank 5, and becomes the circulating concentrated liquid piping 22 and is connected to the high-pressure pump 1.

A flow control valve 4 is installed in the recovered concentrate pipe 26, and the concentrate is recovered through the flow control valve 4. At the permeate outlet of the reverse osmosis membrane device 2, a permeate pipe 24 is provided.
Is connected, and the permeated liquid is led out of the system. The permeated liquid flow meter 11 is attached to the permeated liquid pipe 24. Then, a sufficient amount of the concentrated liquid, for example, an amount several times or more the amount of the collected concentrated liquid, flows in the concentrated liquid piping 23.

The raw material liquid 6 is supplied to the supply liquid tank 5, and the raw material liquid 6 is supplied to the high-pressure pump 1 through the concentrated liquid pipe 21 as a supply liquid. A liquid level gauge 16 is attached to the supply liquid tank 5, and a value related to the liquid level can be sent out as a permeated liquid flow rate instruction value.
That is, a large value is sent out when the liquid level is high, and a small value is sent out when the liquid level is reversed.

The back pressure regulator 12 attached to the back pressure valve 3 takes in the flow rate value from the permeate flow meter 11 and the permeate flow rate indication value related to the liquid level from the liquid level gauge 16, and reads both values. The back pressure valve 3 is operated so that the values become the same.

In the operation, since the solute concentrations C1 and C2 of the supply liquid and the recovered concentrated liquid and the flow rate Q1 of the supply liquid are given, the permeate flow rate Q is determined. Initially, it is assumed that the liquid level of the supply liquid tank 5 is at the center of the tank. If the supply amount of the raw material liquid 6 increases, the liquid level increases, and in this case, a large signal value is sent to the back pressure valve controller 12 as the liquid level increases.

An example of the permeated liquid flow rate instruction value related to the liquid level height is a predetermined value, such as that when the liquid level height is increased by 10%, the set flow rate of the permeated liquid is increased by 5%. Is stored in the liquid level meter 16, and the back pressure valve controller 12 determines whether the flow rate instruction value of the permeated liquid and the flow value from the permeated liquid flow meter 11 are related to the liquid level height based on this relation. The back pressure valve 3 is operated so as to be the same.

A flow controller 14 is attached to the flow control valve 4. A predetermined concentration is given (set) in advance to this, and the flow control valve 4 is controlled so that this value and the concentration value from the concentration detector 13 become the same. If the flow rate of the circulating concentrate is increased by restricting the flow control valve 4, the concentration value increases (if the amount of the recovered concentrate is reduced), the concentration value increases if the flow rate of the circulated concentrated solution is reduced by opening the flow control valve 4. Go down.

Therefore, as the liquid level rises, the permeate flow rate Q
As can be seen from equation (3), the ratio Q / Q2 between the permeate flow rate Q and the recovered concentrated liquid flow rate Q2 is controlled to be constant, so that the recovered concentrated liquid flow rate Q2 is increased. The concentration C2 is kept constant, the flow rate Q1 of the supply liquid increases based on the equation (2), and the liquid level of the supply liquid tank 5 returns to the original tank center position.

With the above configuration, the circulating supply liquid from the high-pressure pump 1 passes through the reverse osmosis membrane device 2 and flows through the concentrated solution pipe 23. A corresponding pressure is generated in the circulating feed liquid, and this pressure causes the permeated liquid to flow out through the reverse osmosis membrane in the reverse osmosis membrane device 2.
With this outflow, the circulating feed solution is concentrated and becomes a concentrated solution, which flows out into the concentrated solution pipe 23. The flow rate of the permeated liquid is measured by the permeated liquid flow meter 11 and compared with the indicated value from the liquid level gauge 16 (the indicated value of the permeated liquid flow rate related to the liquid level) by the back pressure valve controller 12. By controlling the opening degree of the back pressure valve 3 based on the comparison result, the flow rate of the permeated liquid is set to the same value as the indicated value from the liquid level gauge 16 (the indicated value of the permeated liquid flow rate related to the liquid level).

The circulating feed liquid is concentrated because part of the liquid has escaped as a permeate. The concentration of the concentrate is the concentration detector 1
The flow rate of the collected concentrate is controlled by the flow rate control valve 4 so as to be detected at 3 and compared with a predetermined concentration set value by the flow rate controller 14 so that the two values become the same.

With the above operation, even if the flow rate of the raw material liquid 6 fluctuates, it can be processed according to the fluctuation, the concentration of the recovered concentrated liquid becomes constant, and the liquid level of the supply tank 5 becomes higher. Constant and stable operation is possible.

Further, even if the concentration of the raw material liquid 6 fluctuates, the flow rate Q2 of the recovered concentrated liquid is calculated as shown in the equation (3) according to the fluctuation.
Is controlled so that the concentration C2 of the collected concentrate becomes constant. Therefore, as shown in the equation (2), the supply liquid flow rate Q1
Fluctuates, and the liquid level of the supply liquid tank 5 fluctuates. However, since the amount of the permeated liquid can be changed as described above, the concentration of the recovered concentrated liquid can be kept constant, and the liquid level of the supply tank 5 can be changed over time. The height is constant and stable operation is possible.

As can be seen from the above equation (3), by increasing the flow rate Q of the permeated liquid and decreasing the flow rate Q2 of the recovered concentrated liquid, the concentration C2 of the recovered concentrated liquid is reduced to the concentration C1 of the supplied liquid.
And a high concentration ratio can be obtained.

Further, withdrawal of the recovered concentrated liquid is performed using the back pressure valve 3.
Is performed via the flow control valve 4 downstream of the apparatus, and the opening degree of the back pressure valve 3 is not related to the flow rate control. Pressurization)
Is stable, the flow rate of the permeate does not change, and the flow rate and concentration of the concentrate can be maintained at constant values.

The high-pressure pump 1 only needs to be able to exhibit a discharge flow rate and a discharge pressure enough to return to the high-pressure pump 1 even if the permeated liquid and the recovered concentrated liquid are extracted. In practice, the raw material liquid 6
When the fluctuations in the flow rate and the concentration are not particularly large, the circulating flow rate is monitored by the flow meter 15, and the discharge flow rate is controlled by manually changing the rotation speed of the motor of the high-pressure pump 1 so as to fall within a predetermined flow rate range. Good.

FIGS. 2 to 6 show other embodiments of the present invention. 2 to 6, the same components as those shown in FIG. 1 and the corresponding components are denoted by the same reference numerals.

In the embodiment shown in FIG. 2, a variable-speed motor is used as a drive source of the high-pressure pump 1 and the flowmeter 15 is used.
Is compared with a preset flow value by the pump drive controller 17 to control the rotation speed of the motor of the high-pressure pump 1.

According to this configuration, the flow rate of the circulating fluid toward the high-pressure pump 1 is substantially constant, and the concentration of the circulating fluid is also substantially constant unless the flow rate of the supply fluid changes suddenly. Can be. In addition, the flow on the reverse osmosis membrane surface, that is, the flow rate of the concentrated liquid through the reverse osmosis membrane device 1 requires a certain amount or more to remove precipitates on the membrane surface.
In the present apparatus, this flow rate can be sufficiently ensured.

Note that the position of the flow meter 15 is
3, the same operation and effect can be obtained on the circulating fluid pipe 25.

In the embodiment shown in FIG. 3, the supply pump 7 is attached to the concentrated liquid pipe 21, and the liquid in the supply tank 5 is forcibly supplied to the high pressure pump 1.

In this configuration, the discharge pressure of the supply pump 7 is transmitted to the recovered concentrated liquid via the circulating liquid, and the recovered concentrated liquid having a certain concentration can be supplied to a higher place or a distant place.

The embodiment of FIG. 4 shows an example in which the transmission point of the permeated liquid flow rate instruction value is different from that of FIG.

That is, in place of the signal from the liquid level gauge 16 to the back pressure valve controller 12 in FIG. 1, in the embodiment of FIG. It is converted to a flow rate indication value, which is
To be sent to The pressure detector 18 converts the flow rate into a small flow rate indication value when the pressure is low and a large flow rate indication value when the pressure is high.

With this configuration, a part of the liquid flowing out of the high-pressure pump 1 circulates and returns to the high-pressure pump 1, but the other liquid becomes a permeated liquid and a recovered concentrated liquid and goes out of the system. Therefore, the high-pressure pump 1 tries to suck only the amount of liquid that has come out of the system due to mass balance. When the amount of the supply liquid flowing through the concentrated liquid pipe 21 is smaller than the amount of the liquid that has flowed out of the system, the supply liquid is pulled and the pressure decreases. Conversely, if it increases, it will be sent into the system and the pressure will increase. Therefore, the relationship between the pressure in the circulation system and the flow rate instruction value is grasped in advance, and the opening degree of the back pressure valve 3 is adjusted with this flow rate instruction value to control the flow rate of the permeated liquid. Even if it fluctuates, the pressure in the circulating system is prevented from being disturbed, so that a concentrated solution with a constant concentration can be stably obtained.

In the embodiment shown in FIG. 5, an inlet pressure gauge 19 for the reverse osmosis membrane unit 2, a reverse osmosis membrane unit 2 and a back pressure valve are connected to a circulating concentrate pipe 22 connecting the high pressure pump 1 and the reverse osmosis membrane unit 2. An outlet pressure gauge 20 is installed in a concentrated liquid pipe 23 connecting the pressure gauge 3 and the pressure sensor 3.

In such a configuration, it is possible to monitor an increase in pressure loss of the reverse osmosis membrane unit 2 caused by contamination of the liquid and an increase in pressure due to a decrease in permeability. By grasping in advance problems such as breakage of the reverse osmosis membrane and performing maintenance, it is possible to obtain a fixed concentration of the concentrated liquid without any trouble.

In the embodiment shown in FIG. 6, the back pressure valve 3 is adjusted by the back pressure valve controller 12 so that the value of the flow meter 15 matches a predetermined value. Also, the pump drive controller 17 is controlled so that the value of the permeate flow meter 11 matches the value of the permeate flow rate given by the signal from the liquid level gauge 16, and the rotation speed of the high-pressure pump 1 is controlled. .

Accordingly, a new signal from the liquid level gauge 16 changes the number of revolutions of the high-pressure pump 1 and the flow rate of the circulating supply liquid, but adjusts the back pressure valve 3 so as to keep the flow rate of the concentrated liquid constant. Then, the pressure applied to the reverse osmosis membrane of the reverse osmosis membrane unit 2 changes, and the permeate flow rate changes to settle to the specified flow value. The operation of extracting the concentrated liquid is the same as in the embodiment of FIG.

Since the operation is performed as described above, the flow rate of the concentrated liquid is kept constant, and the concentration of the recovered concentrated liquid can be accurately kept constant even if the amount of the supplied liquid changes.

The present invention has been described in connection with the preferred embodiments.
The present invention is not limited to these. For example,
It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0058]

As described above, according to the present invention, the concentration of the concentrated liquid to be recovered can be kept constant even when the concentration of the liquid to be concentrated changes. Further, even if the flow rate of the liquid to be concentrated is changed or the flow rate of the liquid to be concentrated is changed, a concentrated liquid having a constant concentration can be obtained correspondingly.

[Brief description of the drawings]

FIG. 1 is a diagram showing the configuration of an embodiment of the membrane type liquid concentrator of the present invention.

FIG. 2 is a diagram showing the configuration of another embodiment of the membrane type liquid concentrator of the present invention.

FIG. 3 is a diagram showing a configuration of another embodiment of the membrane liquid concentration device of the present invention.

FIG. 4 is a diagram showing the configuration of another embodiment of the membrane type liquid concentrator of the present invention.

FIG. 5 is a diagram showing the configuration of another embodiment of the membrane liquid concentration device of the present invention.

FIG. 6 is a view showing the configuration of another embodiment of the membrane type liquid concentrating device of the present invention.

FIG. 7 is a diagram showing a configuration of a membrane-type liquid concentrator according to a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... High pressure pump 2 ... Reverse osmosis membrane device 3 ... Back pressure valve 4 ... Flow control valve 5 ... Supply liquid tank 6 ... Raw material liquid 7 ... Supply pump 11 ... Permeate flow meter 12 ・ ・ ・ Back pressure valve regulator 13 ・ ・ ・ Concentration detector 14 ・ ・ ・ Flow regulator 15 ・ ・ ・ Flow meter 16 ・ ・ ・ Liquid level meter 17 ・ ・ ・ Pump drive controller 18 ・ ・・ Pressure gauge 19 ・ ・ ・ Inlet pressure gauge 20 ・ ・ ・ Outlet pressure gauge 21 ・ ・ ・ Piping for concentrated liquid 22 ・ ・ ・ Piping for circulating concentrated liquid 23 ・ ・ ・ Piping for concentrated liquid 24 ・ ・ ・ For permeated liquid Piping 25: Piping for circulating liquid 26: Piping for recovered concentrated liquid

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yasuaki Kurokawa 4-3-1 Kanda Surugadai, Chiyoda-ku, Tokyo Hitachi Techno Engineering Co., Ltd. Plant Division (72) Inventor Shigeru Kikawa 4-3-1 Kanda Surugadai, Chiyoda-ku, Tokyo Hitachi Techno Engineering Co., Ltd. Plant Division (56) References JP-A-7-68257 (JP, A) JP-A-9-215912 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01D 61/00-65/10 C02F 1/44

Claims (6)

(57) [Claims] 1. A liquid to be concentrated is sent to a reverse osmosis membrane device by a pump to obtain a concentrated liquid and a permeate, a part of the concentrated liquid is withdrawn as a recovered concentrated liquid, and the remainder is returned to the liquid to be concentrated as a circulating liquid. In the membrane type liquid concentrating apparatus provided with a system, a back pressure valve is provided in the circulating system, and a pipe for extracting a collected concentrated liquid provided with a flow control valve for extracting the collected concentrated liquid is provided downstream of the back pressure valve. Characteristic membrane type liquid concentrator. 2. The apparatus according to claim 1, wherein a concentration detector is provided in a pipe constituting the circulating system, and the concentration of the concentrated solution detected by the concentration detector is the same as a preset value. A membrane-type liquid concentrator comprising a flow controller for operating the flow control valve so as to control the flow rate of the recovered concentrated liquid. 3. The apparatus according to claim 1, wherein a permeate flow meter is provided in a pipe for guiding the permeate, and the flow rate of the permeate monitored by the permeate flow meter is supplied to the pump. A membrane liquid concentrator comprising a back pressure regulator for controlling the opening of the back pressure valve so as to be the same as the indicated value related to the permeate flow rate based on the amount. 4. A pump according to claim 1, wherein a flow meter is provided in a pipe constituting said circulating system, and a rotation speed of said pump is adjusted so that a flow rate in said flow meter becomes equal to a predetermined value. And a pump drive controller for controlling the flow rate to the reverse osmosis membrane device by operating the device. 5. A membrane type liquid concentrator according to claim 1, wherein a pressure gauge is installed in a pipe constituting said circulation system. 6. A back pressure valve according to claim 1, wherein a flow meter is provided in a pipe constituting the circulating system, and the flow rate of the back pressure valve is set so that the flow rate in the flow meter becomes equal to a predetermined value. Providing a back pressure valve regulator for controlling the opening degree, providing a permeate flow meter in the pipe for guiding the permeate, and adjusting the flow rate of the permeate monitored by the permeate flow meter to the supply amount of the concentrated liquid to the pump. A pump drive controller for controlling the flow rate to the reverse osmosis membrane device by operating the rotation speed of the pump so as to be the same as the indicated value related to the permeate flow rate based on the membrane liquid concentration. apparatus.