JP5853479B2 - Reverse osmosis membrane separator - Google Patents

Description

  The present invention relates to a reverse osmosis membrane separation device including a reverse osmosis membrane module.

  In the semiconductor manufacturing process, the cleaning of electronic parts and medical instruments, etc., high-purity pure water containing no impurities is used. This type of pure water is generally produced by subjecting raw water such as groundwater or tap water to a reverse osmosis membrane separation treatment with a reverse osmosis membrane module (hereinafter also referred to as “RO membrane module”).

  A reverse osmosis membrane made of a polymer material has a characteristic that the water permeability coefficient changes with temperature. Specifically, the water permeability coefficient of the RO membrane module decreases when the temperature of the supplied water (hereinafter also referred to as “supply water”) is low, and increases when the temperature of the supply water is high.

  Therefore, when the pressurization pump that sends the supply water to the RO membrane module is operated at a constant operating pressure, the permeated water produced for the required production water volume (if the temperature of the supply water becomes lower than the reference temperature) The amount of pure water) is reduced. In this case, the supply amount to the demand point is insufficient. Further, when the temperature of the supply water becomes higher than the reference temperature, the amount of permeated water increases with respect to the required amount of production water. In this case, the power of the pressurizing pump is wasted.

  Therefore, a water quality reforming system that performs flow rate feedback water volume control has been proposed in order to keep the flow rate of permeated water in the RO membrane module constant regardless of the temperature of the supplied water. In this flow rate feedback water amount control, the drive frequency of the pressure pump is controlled by an inverter so that the flow rate of the permeated water produced by the RO membrane module becomes a target value (see Patent Document 1).

JP 2005-296945 A

  In the water quality reforming system, the concentrated water produced by the RO membrane module is delivered from a concentrated water line connected to the primary outlet port of the RO membrane module. The concentrated water line branches into a concentrated water circulation line and a concentrated water drain line. The concentrated water circulation line is a line for returning a part of the concentrated water sent from the concentrated water line to the supply water line on the upstream side of the pressurizing pump. The concentrated water drainage line is a line for discharging the remaining portion of the concentrated water sent from the concentrated water line to the outside of the system. The supply water line is a line for supplying supply water to the RO membrane module via a pressure pump.

In the concentrated water circulation line, in order to maintain the ratio Q _c / Q _p of the flow rate (Q _c ) of the concentrated water flowing out from the RO module to the flow rate (Q _p ) of the permeated water, about 3 to 5 times, a constant flow valve Is provided. In order to operate this constant flow valve, a pressure difference of at least about 0.2 MPa is required between the primary side and the secondary side of the constant flow valve. Therefore, in an actual system in which a constant flow valve is provided in the concentrated water circulation line, a pressure reducing valve (set pressure of about 0.1 to 0.15 MPa) is provided in the supply water line upstream from the position where the concentrated water circulation line joins. Yes. By providing the pressure reducing valve, the pressure can be reduced on the secondary side of the concentrated water circulation line.

  However, when the pressure of the supply water is lowered by the pressure reducing valve, the pressure pump provided on the downstream side of the pressure pump needs to increase the operating pressure by the amount that the pressure of the supplied water is lowered by the pressure reducing valve. Therefore, electric power is wasted in the pressurizing pump.

  Therefore, an object of the present invention is to provide a reverse osmosis membrane separation device that can suppress power consumption of a pressure pump.

The present invention includes a reverse osmosis membrane module that separates feed water into permeate and concentrated water, a feed water line that feeds feed water to the reverse osmosis membrane module, and a rotational speed that is driven by an input drive frequency. A pressure pump for pumping feed water flowing through the feed water line toward the reverse osmosis membrane module, a permeate line for sending permeate from the reverse osmosis membrane module, and concentrated water for the reverse osmosis membrane A concentrated water line sent out from the module, a concentrated water circulation line for returning a part of the concentrated water flowing through the concentrated water line to the upstream side of the pressurizing pump in the supply water line, and a concentrated water in the concentrated water circulation line A flow rate adjusting means for adjusting the flow rate of the water supply to a constant flow rate, and a negative pressure generated when the supply water flows through the supply water line connected to the upstream side of the pressurizing pump The serial concentrated water circulation line concentrated water was returned to the suction and the ejector feed water concentrated water are mixed and sends toward the pressurizing pump, the pressure pump driving frequency corresponding to the input operation value signal An inverter that outputs to the permeated water line, a flow rate sensor that detects the flow rate of permeated water, and the pressure pump so that the detected flow rate value of the flow rate sensor becomes a preset target flow rate value. The present invention relates to a reverse osmosis membrane separation device including a control unit that calculates a driving frequency and outputs a calculated value signal corresponding to a calculated value of the driving frequency to the inverter.

  The flow rate adjusting means is preferably a constant flow valve.

  And a temperature detecting means for detecting the temperature of the supply water, the permeated water or the concentrated water, and a drain valve capable of adjusting a drain flow rate of the concentrated water discharged to the outside of the apparatus. Based on the silica concentration of the obtained feed water and the silica solubility determined from the detected temperature value of the temperature detecting means, the allowable concentration rate of silica in the concentrated water is calculated, (ii) the calculated value of the allowable concentration rate, It is preferable to calculate the drainage flow rate from the target flow rate value of the permeated water and (iii) control the drainage valve so that the actual drainage flow rate of the concentrated water becomes the calculated value of the drainage flow rate.

  Moreover, it is provided with a hardness measuring means for measuring the calcium hardness of the supplied water and a drain valve capable of adjusting the drainage flow rate of the concentrated water discharged outside the apparatus, and the control unit is (i) calcium carbonate obtained in advance Based on the solubility and the measured hardness value of the hardness measuring means, an allowable concentration rate of calcium carbonate in the concentrated water is calculated, and (ii) the drainage flow rate from the calculated value of the allowable concentration rate and the target flow rate value of permeated water (Iii) It is preferable to control the drain valve so that the actual drainage flow rate of the concentrated water becomes the calculated value of the drainage flow rate.

  In addition, the electric conductivity measuring means for measuring the electric conductivity of the permeated water and a drain valve capable of adjusting the drain flow rate of the concentrated water discharged outside the apparatus, the control unit is the electric conductivity measuring means It is preferable to control the flow rate of drainage from the drain valve so that the measured electrical conductivity value becomes a preset target electrical conductivity value.

  ADVANTAGE OF THE INVENTION According to this invention, the reverse osmosis membrane separator which can suppress the power consumption of a pressurization pump can be provided.

1 is an overall configuration diagram of a reverse osmosis membrane separation device 1 according to a first embodiment. It is a flowchart which shows the process sequence in case the control part 10 of 1st Embodiment performs flow volume feedback water volume control. It is a flowchart which shows the process sequence in case the control part 10 of 1st Embodiment performs temperature feedforward collection | recovery rate control. It is a whole block diagram of the reverse osmosis membrane separation apparatus 1A which concerns on 2nd Embodiment. It is a flowchart which shows the process sequence in case the control part 10A of 2nd Embodiment performs water quality feedforward collection | recovery rate control. It is a whole block diagram of the reverse osmosis membrane separation apparatus 1B which concerns on 3rd Embodiment. It is a flowchart which shows the process sequence in case the control part 10B of 3rd Embodiment performs water quality feedback collection | recovery rate control.

(First embodiment)
First, a reverse osmosis membrane separation device 1 according to a first embodiment of the present invention will be described with reference to the drawings. The reverse osmosis membrane separation device 1 of this embodiment is applied to a pure water production system that produces pure water from fresh water, for example. FIG. 1 is an overall configuration diagram of a reverse osmosis membrane separation device 1 according to a first embodiment. FIG. 2 is a flowchart showing a processing procedure when the control unit 10 executes the flow rate feedback water amount control. FIG. 3 is a flowchart showing a processing procedure when the control unit 10 executes the temperature feedforward recovery rate control.

  As shown in FIG. 1, a reverse osmosis membrane separation device 1 according to the first embodiment includes an ejector 2, a temperature sensor 3 as a temperature detecting means, a pressurizing pump 4, an inverter 5, and a reverse osmosis membrane module. RO membrane module 6, flow sensor 7, constant flow valve 8 as a flow rate adjusting means, control unit 10, and first drain valve 11 to third drain valve 13 as drain valves. In FIG. 1, a path of electrical connection is indicated by a broken line (the same applies to FIGS. 1A and 1B described later).

  The reverse osmosis membrane separation device 1 includes a feed water line L1, a permeate water line L2, a concentrated water line L3, a concentrated water circulation line L4, a concentrated water drainage line (first concentrated water drainage line L11, second concentrated water). Water drainage line L12 and third concentrated water drainage line L13). The “line” in the present specification is a general term for lines capable of flowing a fluid such as a flow path, a path, and a pipeline.

  The upstream end of the supply water line L1 is connected to a supply source (not shown) of the supply water W1. In the supply water line L1, a nozzle portion 2a (described later) of the ejector 2 is connected to the downstream side of the supply source.

  The ejector 2 is a device that sucks the concentrated water W3 by the negative pressure generated when the supplied water W1 is ejected from the nozzle portion 2a, and sends the supplied water W1 mixed with the concentrated water W3 toward the pressurizing pump 4. .

  The ejector 2 includes a nozzle part 2a, a diffuser part 2b, and a vacuum suction part 2c provided between the nozzle part 2a and the diffuser part 2b. The nozzle part 2a is a part into which the supply water W1 as a driving fluid flows. The reduced pressure suction part 2c is a part that sucks the concentrated water W3 as the suction fluid. The diffuser part 2b is a part for supplying the supply water W1 mixed with the concentrated water W3, that is, the mixed fluid.

  The ejector 2 is connected to the upstream side of the pressurizing pump 4 in the supply water line L1. As for the ejector 2, the nozzle part 2a and the diffuser part 2b are connected to the supply water line L1. A downstream side of a concentrated water circulation line L4 (described later) is connected to the reduced pressure suction part 2c of the ejector 2.

  The temperature sensor 3 is a device that detects the temperature of the supply water W1. The temperature sensor 3 is connected to the supply water line L1 at the connection portion J1. The connecting portion J1 is disposed between the ejector 2 and the pressure pump 4. The temperature sensor 3 is electrically connected to the control unit 10. The temperature of the supply water W1 detected by the temperature sensor 3 (hereinafter also referred to as “detected temperature value”) is transmitted to the control unit 10 as a detection signal.

  The pressurizing pump 4 is a device that sucks the supply water W1 sent from the ejector 2 and discharges it toward the RO membrane module 6. The pressure pump 4 is electrically connected to an inverter 5 (described later). Driving power having a converted frequency is supplied from the inverter 5 to the pressurizing pump 4. The pressurizing pump 4 is driven at a rotational speed corresponding to the input driving frequency.

  The inverter 5 is an electric circuit that supplies driving power whose frequency has been converted to the pressure pump 4. The inverter 5 is electrically connected to the control unit 10. A current value signal is input to the inverter 5 from the control unit 10. The inverter 5 outputs a driving frequency corresponding to the input current value signal to the pressurizing pump 4.

  The RO membrane module 6 is a facility that performs membrane separation processing on the supplied water W1 into permeated water W2 from which dissolved salts are removed and concentrated water W3 from which dissolved salts are concentrated. The RO membrane module 6 includes a single or a plurality of RO membrane elements (not shown). The RO membrane module 6 performs membrane separation treatment of the supply water W1 with these RO membrane elements to produce permeated water W2 and concentrated water W3. The primary side inlet port of the RO membrane module 6 is connected to the downstream side of the pressurizing pump 4 via the supply water line L1.

  An upstream end of the permeate line L2 is connected to the secondary port of the RO membrane module 6. The permeated water W2 produced by the RO membrane module 6 is sent out as pure water to a demand location or the like via the permeated water line L2. Further, an upstream end of the concentrated water line L3 is connected to the primary outlet port of the RO membrane module 6. The concentrated water W3 produced by the RO membrane module 6 is discharged out of the RO membrane module 6 through the concentrated water line L3.

  The concentrated water circulation line L4 is a line for returning a part of the concentrated water W3 sent from the RO membrane module 6 to the upstream side of the pressurizing pump 4 in the supply water line L1. The upstream end of the concentrated water circulation line L4 is connected to the concentrated water line L3 at the connection J2. Further, the downstream end of the concentrated water circulation line L4 is connected to the reduced pressure suction part 2c of the ejector 2.

  The concentrated water drainage line (the first concentrated water drainage line L11, the second concentrated water drainage line L12, and the third concentrated water drainage line L13) discharges the remainder of the concentrated water W4 sent from the RO membrane module 6 to the outside of the system. Line. The upstream end portions of the first concentrated water drainage line L11 to the third concentrated water drainage line L13 are connected to the concentrated water line L3 at connecting portions J4 and J5.

  The flow rate sensor 7 is a device that detects the flow rate of the permeated water W2 flowing through the permeated water line L2. The flow sensor 7 is connected to the permeated water line L2 at the connection portion J3. The flow sensor 7 is electrically connected to the control unit 10. The flow rate of the permeated water W2 detected by the flow rate sensor 7 (hereinafter also referred to as “detected flow rate value”) is transmitted to the control unit 10 as a detection signal.

  The constant flow valve 8 is a device that adjusts the flow rate of the concentrated water W3 flowing from the concentrated water line L3 to the concentrated water circulation line L4 to a constant flow rate.

  A first drain valve 11, a second drain valve 12, and a third drain valve 13 are provided in the first concentrated water drain line L11, the second concentrated water drain line L12, and the third concentrated water drain line L13, respectively. The first drain valve 11 to the third drain valve 13 adjust the drain flow rate of the concentrated water W3 by individually opening and closing the first concentrated water drain line L11 to the third concentrated water drain line L13, and the RO membrane module 6 The recovery rate of the permeated water W2 can be set to a desired value.

  Each of the first drain valve 11 to the third drain valve 13 includes a constant flow valve mechanism (not shown). The constant flow valve mechanisms are set to different flow values in the first drain valve 11 to the third drain valve 13. For example, the drainage flow rate of the first drain valve 11 is set so that the recovery rate of the permeated water W2 is 95% in the open state. The drainage flow rate of the second drain valve 12 is set so that the recovery rate of the permeated water W2 is 90% in the open state. The drainage flow rate of the third drain valve 13 is set so that the recovery rate of the permeated water W2 is 80% in the open state.

  The drainage flow rate of the concentrated water W3 discharged from the first concentrated water drain line L11 to the third concentrated water drain line L13 is stepwise by selectively opening and closing the first drain valve 11 to the third drain valve 13. Can be adjusted. For example, only the second drain valve 12 is opened, and the first drain valve 11 and the third drain valve 13 are closed. In this case, the recovery rate of the permeated water W2 can be 90%. Further, the first drain valve 11 and the second drain valve 12 are opened, and only the third drain valve 13 is closed. In this case, the recovery rate of the permeated water W2 can be 85%. Therefore, in this embodiment, by selectively opening and closing the first drain valve 11 to the third drain valve 13 to adjust the drain flow rate of the concentrated water W3, the recovery rate of the permeated water W2 is from 65% to 95%. Can be set in steps of every 5%.

  The first drain valve 11 to the third drain valve 13 are each electrically connected to the control unit 10. The opening and closing of the valve body in the first drain valve 11 to the third drain valve 13 is controlled by a drive signal from the control unit 10.

  The control unit 10 is configured by a microprocessor (not shown) including a CPU and a memory. The control unit 10 calculates a drive frequency for driving the pressurizing pump 4 so that the detected flow rate value of the flow sensor 7 becomes a preset target flow rate value, and a current corresponding to the calculated value of the drive frequency. A value signal is output to the inverter 5 (hereinafter also referred to as “flow rate feedback water amount control”). The flow rate feedback water amount control by the control unit 10 will be described later.

  Further, the control unit 10 performs the recovery rate control of the permeated water W2 based on the temperature of the supply water W1 (hereinafter, also referred to as “temperature feedforward recovery rate control”). This temperature feedforward recovery rate control is executed in parallel with the above-described flow rate feedback water amount control. The temperature feedforward recovery rate control by the control unit 10 will be described later.

  Next, the flow rate feedback water amount control by the control unit 10 will be described with reference to FIG. The process of the flowchart shown in FIG. 2 is repeatedly performed during the operation of the reverse osmosis membrane separation device 1.

In step ST101 shown in FIG. 3, the control unit 10 obtains a target flow rate value Q _p ′ of the permeated water W2. The target flow rate value Q _p ′ is, for example, a set value that is input to the memory of the control unit 10 by a system administrator via a user interface (not shown).

  In step ST102, the control unit 10 determines whether or not the time t measured by an internal timer (not shown) has reached 100 ms which is a control cycle. In step ST102, when the control unit 10 determines that the time measured by the timer has reached 100 ms (YES), the process proceeds to step ST103. In step ST102, when the control unit 10 determines that the time measured by the timer has not reached 100 ms (NO), the process returns to step ST102.

Step ST 103: In (step ST 102 YES judgment), the control unit 10 acquires the detected flow rate value _{Q p} of the permeate W2 detected by the flow rate sensor 24.
In step ST 104, the control unit 10, so that the deviation between the detected flow rate value obtained in step ST 103 (feedback value) _{Q p} and the target flow rate value _{Q p} obtained in step ST 101 'is zero, velocity type digital PID algorithm To calculate the operation amount U. In the velocity type digital PID algorithm, the change amount of the operation amount is calculated every control cycle (100 ms), and this operation amount is determined by adding this to the previous operation amount.

In step ST105, the control unit 10, the operation amount U, based on the target flow rate value _{Q p} 'and the maximum driving frequency of the pressurizing pump 4 (the set value of 50Hz or 60 Hz), calculates a drive frequency F of the pressure pump 4 To do.
In step ST106, the control unit 10 converts the calculated value of the drive frequency F into a corresponding current value signal (4 to 20 mA).
In step ST107, the control unit 10 outputs the converted current value signal to the inverter 5. Thereby, the process of this flowchart is complete | finished (it returns to step ST101).

  In step ST107, when the control unit 10 outputs a current value signal to the inverter 5, the inverter 5 supplies the driving power converted to the frequency corresponding to the input current value signal to the pressurizing pump 4. As a result, the pressurizing pump 4 is driven at a rotational speed corresponding to the driving frequency input from the inverter 5.

  Next, temperature feedforward recovery rate control by the control unit 10 will be described with reference to FIG. The process of the flowchart shown in FIG. 3 is repeatedly executed during the operation of the reverse osmosis membrane separation device 1.

In step ST201 shown in FIG. 3, the control unit 10 acquires a target flow rate value Q _p ′ of the permeated water W2. This target flow rate value Q _p ′ is, for example, a set value that is input to the memory by the system administrator via a user interface (not shown).

In step ST 202, the control unit 10 acquires a silica (SiO ₂₎ concentration _{C s} of the supply water W1. This silica concentration C _s is a set value input to the memory by the system administrator via a user interface (not shown), for example. The silica concentration of the supply water W1 can be obtained by analyzing the water quality of the supply water W1 in advance. In the permeate line L2, the silica concentration of the supply water W1 may be measured by a sensor (not shown).

In step ST203, the control unit 10 acquires the detected temperature value T of the supply water W1 from the temperature sensor 3.
In step ST 204, the control unit 10 based on the detected temperature value T obtained, to determine the silica solubility _{S s} for water.

In step ST205, the control unit 10 calculates the allowable concentration magnification N _s of silica in the concentrated water W3 based on the silica concentration C _s acquired or determined in the previous step and the silica solubility S _s . Permissible concentration rate N _s of silica can be determined from the following equation (1).
N _s = S _s / C _s (1)
For example, if the silica concentration C _s is 20 mg SiO ₂ / L and the silica solubility S _{s at} 25 ° C. is 100 mg SiO ₂ / L, the allowable concentration ratio N _s is “5”.

In step ST 206, the control unit 10, prior to the target flow rate value Q _p acquired or calculated in step _', and based on the allowable concentration rate N _s, wastewater flow rate recovery is maximized (target drainage flow Q _d') Is calculated. The target drainage flow rate Q _d ′ can be obtained by the following equation (2).
Q _d ′ = Q _p ′ / (N _s −1) (2)

In step ST207, the control unit 10, the actual drainage flow _{Q d} are formed so that the target drainage flow _{Q d} 'calculated in step ST 206, controls the opening and closing of the first drain valve 11 to the third drain valve 13 of the concentrated water W3 To do. Thereby, the process of this flowchart is complete | finished (it returns to step ST201).

According to the reverse osmosis membrane separation device 1 according to the first embodiment described above, for example, the following effects can be obtained.
In the reverse osmosis membrane separation device 1 according to the first embodiment, the ejector 2 is provided in the supply water line L1 on the upstream side of the pressurizing pump 4. In the ejector 2, the concentrated water W3 recirculated to the concentrated water circulation line L4 is sucked by the negative pressure generated when the supply water W1 flows. For this reason, the circulating water amount of the concentrated water W3 recirculated to the concentrated water circulation line L4 can be ensured. According to this, in the pressurizing pump 4, it is not necessary to increase the operating pressure by the amount lowered by the pressure reducing valve. Therefore, the power consumption of the pressure pump 4 can be suppressed.

  Further, the provision of the ejector 2 eliminates the need for a pressure reducing valve. Furthermore, the capacity of the pressurizing pump 4 can be reduced by providing the ejector 2.

  In the reverse osmosis membrane separation device 1 according to the first embodiment, temperature feedforward recovery rate control is executed. For this reason, in the reverse osmosis membrane separation device 1, precipitation of silica-based scale in the RO membrane module 6 can be more reliably suppressed while maximizing the recovery rate of the permeated water W2.

(Second Embodiment)
Next, the configuration of the reverse osmosis membrane separation device 1A according to the second embodiment of the present invention will be described with reference to FIG. FIG. 4 is an overall configuration diagram of a reverse osmosis membrane separation device 1A according to the second embodiment. In the second embodiment, differences from the first embodiment will be mainly described. In the second embodiment, the same or equivalent components as those in the first embodiment will be described with the same reference numerals. In the second embodiment, the description overlapping with the first embodiment is omitted as appropriate.

  As shown in FIG. 4, the reverse osmosis membrane separation device 1 </ b> A according to the second embodiment includes an ejector 2, a pressurizing pump 4, an inverter 5, an RO membrane module 6, a flow sensor 7, and a constant flow valve 8. And a hardness sensor 9 as a hardness measuring means, a control unit 10A, and a first drain valve 11 to a third drain valve 13.

  The hardness sensor 9 is a device that measures the calcium hardness (calculated value of calcium carbonate) of the supply water W1 flowing through the permeate line L2. The hardness sensor 9 is connected to the supply water line L1 at the connection portion J1. The connecting portion J1 is disposed between the ejector 2 and the pressure pump 4. The hardness sensor 9 is electrically connected to the control unit 10A. The calcium hardness (hereinafter also referred to as “measured hardness value”) of the supply water W1 measured by the hardness sensor 9 is transmitted as a detection signal to the control unit 10A.

The control unit 10A is configured by a microprocessor (not shown) including a CPU and a memory. The control unit 10A performs the same flow rate feedback water volume control (see FIG. 2) as the control unit 10 of the first embodiment.
Further, the control unit 10A of the present embodiment performs recovery rate control of the permeated water W2 based on the hardness of the supply water W1 (hereinafter also referred to as “water quality feedforward recovery rate control”). This water quality feedforward recovery rate control is executed in parallel with the flow rate feedback water amount control described above.

  Next, water quality feedforward recovery rate control by the control unit 10A will be described. FIG. 5 is a flowchart showing a processing procedure when the control unit 10A executes water quality feedforward recovery rate control. The process of the flowchart shown in FIG. 5 is repeatedly executed during the operation of the reverse osmosis membrane separation device 1.

In step ST301 shown in FIG. 5, the control unit 10A acquires the target flow rate value Q _p ′ of the permeated water W2. This target flow rate value Q _p ′ is, for example, a set value that is input to the memory by the system administrator via a user interface (not shown).
In step ST 302, the control unit 10A acquires the measured hardness value _{C c} of the supply water W1 measured by the hardness sensor 9.

In step ST 303, the control unit 10A acquires the calcium carbonate solubility _{S c} to water. This calcium carbonate solubility _Sc is, for example, a set value input to the memory by the system administrator via a user interface (not shown). In addition, the calcium carbonate solubility with respect to water can be regarded as a substantially constant value at a normal operation temperature (5 to 35 ° C.).

In step ST 304, the control unit 10A, the previous measured hardness value _{C c} obtained in step, and based on calcium carbonate solubility _{S c,} calculates a permissible concentration rate _{N c} of calcium carbonate in the concentrated water W3. The permissible concentration factor _Nc of calcium carbonate can be determined by the following equation (3).
N _c = S _c / C _c (3)
For example, if the measured hardness value C _c is ₃ mg CaCO ₃ / L and the calcium carbonate solubility S _{c at} 25 ° C. is 15 mg CaCO ₃ / L, the allowable concentration ratio N _c is “5”.

In step ST 305, the control unit 10A, the previous target flow rate value Q _p acquired or calculated in step _', and based on the allowable concentration rate N _c, wastewater flow rate recovery is maximized (target drainage flow Q _d') Is calculated. The target drainage flow rate Q _d ′ can be obtained by the following equation (4).
Q _d ′ = Q _p ′ / (N _c −1) (4)

In step ST 306, the control unit 10A controls the opening and closing of the concentrated water W3 of the actual drainage flow _{Q d} is the target wastewater flow rate _{Q d} 'and so as to first drain valve 11 to the third drain valve 13 calculated in step ST305 . Thereby, the process of this flowchart is complete | finished (it returns to step ST301).

  According to the reverse osmosis membrane separation device 1A according to the second embodiment described above, the flow rate feedback water volume control of the permeated water W2 is executed, and thus the same effect as in the first embodiment can be obtained. In the reverse osmosis membrane separation device 1A according to the second embodiment, water quality feedforward recovery rate control is executed. For this reason, in the reverse osmosis membrane separation device 1A, precipitation of calcium carbonate scale in the RO membrane module 6 can be more reliably suppressed while maximizing the recovery rate of the permeated water W2.

(Third embodiment)
Next, the configuration of the reverse osmosis membrane separation device 1B according to the third embodiment of the present invention will be described with reference to FIG. FIG. 6 is an overall configuration diagram of a reverse osmosis membrane separation device 1B according to the third embodiment. In the third embodiment, differences from the first embodiment will be mainly described. In the third embodiment, the same or equivalent components as those in the first embodiment will be described with the same reference numerals. In the third embodiment, the description overlapping with that of the first embodiment is omitted as appropriate.

  As shown in FIG. 6, the reverse osmosis membrane separation device 1 </ b> B according to the third embodiment includes an ejector 2, a pressurizing pump 4, an inverter 5, an RO membrane module 6, a flow sensor 7, and a constant flow valve 8. And 10A of control parts, the 1st drain valve 11-the 3rd drain valve 13, and the electrical conductivity sensor 14 as an electrical conductivity measurement means are provided.

  The electrical conductivity sensor 14 is a device that measures the electrical conductivity of the permeated water W2 flowing through the permeated water line L2. The electrical conductivity sensor 14 is connected to the permeated water line L2 at the connection portion J6. The electrical conductivity sensor 14 is electrically connected to the control unit 10B. The electric conductivity of the permeated water W2 measured by the electric conductivity sensor 14 (hereinafter also referred to as “measured electric conductivity value”) is transmitted as a detection signal to the control unit 10B.

The control unit 10B is configured by a microprocessor (not shown) including a CPU and a memory. The control unit 10B executes the same flow rate feedback water volume control (see FIG. 2) as the control unit 10 of the first embodiment.
Further, the control unit 10B of the present embodiment performs the recovery rate control of the permeated water W2 based on the electrical conductivity of the permeated water W2 (hereinafter also referred to as “water quality feedback recovery rate control”). This water quality feedback recovery rate control is executed in parallel with the flow rate feedback water amount control described above.

  Next, water quality feedback recovery rate control by the control unit 10B will be described. FIG. 7 is a flowchart showing a processing procedure when the control unit 10B executes water quality feedback recovery rate control. The process of the flowchart shown in FIG. 7 is repeatedly executed during the operation of the reverse osmosis membrane separation device 1.

In step ST401 shown in FIG. 7, the control unit 10B acquires the target electrical conductivity value E _p ′ of the permeated water W2. The target electrical conductivity value E _p ′ is an index of purity required for the permeated water W2. The target electrical conductivity value E _p ′ is, for example, a set value that is input to the memory by the system administrator via a user interface (not shown).

In step ST 402, the control unit 10B obtains the measured electric conductivity value _{E p} of the electric conductivity sensor 14 permeate water W5 measured by.
In step ST 403, the control unit 10B, as the deviation between the obtained measured electrical conductivity value (feedback value) _{E p} and step target electric conductivity value obtained at ST 401 _{E p} 'in step ST402 becomes zero, the The opening / closing of the first drain valve 11 to the third drain valve 13 is controlled. That is, by increasing or decreasing the drainage flow rate of the concentrated water W3, the concentration of dissolved salts on the membrane surface is changed so that the permeated water W2 having the required purity can be obtained. Thereby, the process of this flowchart is complete | finished (it returns to step ST401).

  According to the reverse osmosis membrane separation device 1B according to the third embodiment described above, since the flow rate feedback water amount control of the permeated water W2 is executed, the same effect as in the first embodiment can be obtained. Moreover, in the reverse osmosis membrane separation apparatus 1B according to the third embodiment, water quality feedforward recovery rate control is executed. For this reason, in the reverse osmosis membrane separation device 1B, the recovery rate of the permeated water W2 can be maximized while satisfying the water quality required for the permeated water W2.

The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and can be implemented in various forms.
For example, in the first embodiment, the example in which the temperature of the supply water W1 is detected in the temperature feedforward recovery rate control has been described. For example, the temperature of the permeated water W2 or the concentrated water W3 obtained by the RO membrane module 6 may be detected.

In 2nd Embodiment, the water quality feedforward collection | recovery rate control demonstrated the example which calculates the waste_water | drain flow volume from which the collection | recovery rate becomes the maximum based on the permissible concentration rate of calcium carbonate and the target flow rate value of the permeate W2. The present invention is not limited to this, and the following method may be adopted. That is, compared with the allowable concentration rate N _s permissible concentration rate N _c and silica calcium carbonate, selects the smaller side allowable concentration rate. Then, based on the selected permissible concentration ratio and the target flow rate value of the permeate W2, the drainage flow rate at which the recovery rate is maximized is calculated.

  In the first to third embodiments, when the drive frequency is output from the inverter 5 to the pressurizing pump 4, the pressure value of the supply water W1 flowing downstream of the ejector 2 is detected by a pressure sensor (not shown), An alarm may be generated when the pressure value is out of a pressure range corresponding to a preset driving frequency. In 1st-3rd embodiment, since the ejector 2 is provided, it is hard to produce the pressure fall of the supply water W1. Therefore, in the case of the above configuration, the number of alarms can be reduced.

In the first to third embodiments, the supply water W1 may be raw water such as ground water or tap water. Further, the supply water W1 may be water obtained by pre-processing raw water using a filtration device or a hard water softening device.
1st-3rd embodiment demonstrated the example which provided the constant flow valve 8 as a flow volume adjustment means. For example, a configuration in which a proportional control valve or the like is provided may be used.

  In the first to third embodiments, an example in which the drainage flow rate of the concentrated water W3 is adjusted stepwise by selectively opening and closing the first drainage valve 11 to the third drainage valve 13 in each recovery rate control will be described. did. However, the present invention is not limited to this, and the configuration may be such that the concentrated water drain line is not branched and is provided with a proportional control valve. In that case, the drain flow rate of the concentrated water W3 is adjusted by transmitting a current value signal (for example, 4 to 20 mA) from the control unit 10 (10A, 10B) to the proportional control valve to control the valve opening. be able to.

  Moreover, it is good also as a structure which provided the flow sensor in the concentrated water drainage line in the structure which provided the proportional control valve. The flow value detected by the flow sensor is input as a feedback value to the control unit 10 (10A, 10B). Thereby, the actual waste water flow rate of the concentrated water W3 can be controlled more accurately.

1, 1A, 1B Reverse osmosis membrane separation device 2 Ejector 3 Temperature sensor (temperature detection means)
4 Pressure pump 5 Inverter 6 RO membrane module (reverse osmosis membrane module)
7 Flow sensor 8 Constant flow valve (Flow control means)
9 Hardness sensor (hardness measuring means)
10, 10A, 10B Control unit 11 First drain valve (drain valve)
12 Second drain valve (drain valve)
13 Third drain valve (drain valve)
14 Electric conductivity sensor (electric conductivity measuring means)
L1 Supply Water Line L2 Permeate Water Line L3 Concentrated Water Line L4 Concentrated Water Circulation Line L11 First Concentrated Water Drain Line L12 Second Concentrated Water Drain Line L13 Third Concentrated Water Drain Line W1 Supply Water W2 Permeated Water W3 Concentrated Water

Claims (5)

A reverse osmosis membrane module that separates supply water into permeate and concentrated water;
A supply water line for supplying supply water to the reverse osmosis membrane module;
A pressurizing pump that is driven at a rotational speed according to the input driving frequency and pumps the feed water flowing through the feed water line toward the reverse osmosis membrane module;
A permeate line for delivering permeate from the reverse osmosis membrane module;
A concentrated water line for delivering concentrated water from the reverse osmosis membrane module;
A concentrated water circulation line for refluxing a part of the concentrated water flowing through the concentrated water line upstream of the pressurizing pump in the supply water line;
A flow rate adjusting means for adjusting the flow rate of the concentrated water to a constant flow rate in the concentrated water circulation line;
Connected to the upstream side of the pressurizing pump in the supply water line, the concentrated water returned to the concentrated water circulation line is sucked by the negative pressure generated when the supply water flows, and the supply water mixed with the concentrated water is An ejector for delivery to the pressurizing pump;
An inverter that outputs a driving frequency corresponding to the input operation value signal to the pressurizing pump;
A flow rate sensor that is provided in the permeate line and detects a permeate flow rate;
Control that calculates the drive frequency of the pressurizing pump so that the detected flow value of the flow sensor becomes a preset target flow value, and outputs a calculated value signal corresponding to the calculated value of the drive frequency to the inverter And
A reverse osmosis membrane separation apparatus. The flow rate adjusting means is a constant flow valve;
The reverse osmosis membrane separation apparatus according to claim 1. Temperature detection means for detecting the temperature of the supply water, permeate or concentrated water;
With a drain valve that can adjust the drainage flow of concentrated water discharged outside the device,
The controller calculates (i) an allowable concentration rate of silica in the concentrated water based on the silica concentration determined from the silica concentration of the feed water acquired in advance and the detected temperature value of the temperature detecting means, and (ii) ) Calculate the drainage flow rate from the calculated value of the permissible concentration rate and the target flow rate value of the permeated water, and (iii) control the drainage valve so that the actual drainage flow rate of the concentrated water becomes the calculated value of the drainage flow rate. To
The reverse osmosis membrane separation apparatus according to claim 1 or 2. A hardness measuring means for measuring the calcium hardness of the feed water;
With a drain valve that can adjust the drainage flow of concentrated water discharged outside the device,
The control unit calculates (i) an allowable concentration rate of calcium carbonate in concentrated water based on (i) the calcium carbonate solubility acquired in advance and the measured hardness value of the hardness measuring means, and (ii) the allowable concentration rate Calculate the drainage flow rate from the calculated value and the target flow rate value of the permeated water, and (iii) control the drainage valve so that the actual drainage flow rate of the concentrated water becomes the calculated value of the drainage flow rate.
The reverse osmosis membrane separation apparatus according to claim 1 or 2. Electrical conductivity measuring means for measuring the electrical conductivity of the permeated water;
With a drain valve that can adjust the drainage flow of concentrated water discharged outside the device,
The control unit controls the flow rate of drainage from the drainage valve so that the measured electrical conductivity value of the electrical conductivity measuring unit becomes a preset target electrical conductivity value.
The reverse osmosis membrane separation apparatus according to claim 1 or 2.

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