JP2016203083A - Reverse osmosis membrane separation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reverse osmosis membrane separation device in which power consumption of a booster pump can be reduced while adjusting a circulation ratio to a predetermined value.SOLUTION: The reverse osmosis membrane separation device includes: a reverse osmosis membrane module 4; a feed water line L1; a permeated water line L2; a concentrated water line L3; a circulation water line L4; a waste water line L5; a constant flow rate variable means 50 which keeps a flow rate of concentrated water W3 at a predetermined constant flow rate value and can vary the constant flow rate value; a waste water flow rate adjusting means 8; the booster pump 2; an inverter 3; a pump drive control part 10; and a constant flow rate control part 10A. The pump drive control part 10 decreases/increases a target flow rate value according to decrease/increase of the consumption amount of permeated water W2. The constant flow rate control part 10A decreases/increases the constant flow rate value of concentrated water W3, which is circulated through the concentrated water line L3, according to decrease/increase of the target flow rate value.SELECTED DRAWING: Figure 10

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”).

  The water permeability coefficient of a reverse osmosis membrane made of a polymer material varies depending on the temperature. Further, the water permeation coefficient of the reverse osmosis membrane also changes due to pore clogging (hereinafter also referred to as “membrane clogging”) and deterioration due to oxidation of the material (hereinafter also referred to as “membrane degradation”).

  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 feed water and the state of the reverse osmosis membrane (for example, Patent Documents). 1). In this flow rate feedback water amount control, the drive frequency of the pressure pump is controlled by the inverter so that the flow rate of the permeated water produced by the RO membrane module becomes the target flow rate value.

  In the water quality reforming system, the concentrated water separated by the RO membrane module is sent out from the concentrated water line connected to the primary outlet port of the RO membrane module. Moreover, the permeated water separated by the RO membrane module is sent out from the permeated water line connected to the secondary side port of the RO membrane module. The concentrated water line is branched into a circulating water line and a concentrated water drainage line. The circulating water line is a line that returns a part of the concentrated water sent from the concentrated water line to the supply water line upstream 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 apparatus. The supply water line is a line for supplying supply water to the RO membrane module via a pressure pump.

  By the way, in the RO membrane module using the spiral type element, in order to prevent the membrane surface from being blocked by an organic component or a suspended substance, a separation operation by a cross flow method is usually employed. In this cross-flow method, a separation operation is performed by applying a pressure higher than the osmotic pressure of the feed water to the primary side of the membrane while circulating the feed water at a flow rate more than 5 times the flow rate of the permeated water by a pressure pump I do. At this time, in the RO membrane module, the circulation ratio (the flow rate of the concentrated water / the flow rate of the permeated water) defined by the ratio of the flow rate of the concentrated water to the flow rate of the permeated water is preferably adjusted to about “5”.

  Here, in the technology having the flow path configuration through which the concentrated water flows as described in Patent Document 1, a technology for providing a constant flow valve in the concentrated water line is known in order to keep the flow rate of the concentrated water flowing through the concentrated water line constant. (For example, refer to Patent Document 2). This technique has a permeate flow rate controller that adjusts the flow rate of permeate and a drainage flow rate adjustment valve that adjusts the drainage flow rate of concentrated water. In such a configuration in which the constant flow valve is provided in the concentrated water line, the flow rate of the permeated water is kept constant by the permeate flow rate controller while the flow rate of the concentrated water flowing through the concentrated water line is kept constant by the constant flow valve. By doing so, the circulation ratio (flow rate of concentrated water / flow rate of permeated water) can be adjusted to about “5”.

  Further, in the technology having a flow path configuration through which concentrated water flows as described in Patent Document 1, a reverse pressure regulator is provided in the circulating water line in order to maintain the pressure inside the reverse osmosis membrane module at a predetermined pressure value. The provided technique is known (for example, refer patent document 3). In the technique described in Patent Document 3, a constant flow valve is not provided in the concentrated water line, and a back pressure regulator is provided in the circulating water line. The permeate line is provided with a permeate flow rate throttle valve.

JP 2005-296945 A JP, 2014-213260, A JP 2004-276020 A

  In the configuration in which the constant flow valve is provided in the concentrated water line described in Patent Document 2, the flow rate of the concentrated water is kept constant by the constant flow valve. In this configuration, when the target flow rate value of the flow rate feedback water volume control is changed in accordance with the required water volume of the permeated water, the following state occurs. That is, when the target flow rate value is decreased from the reference 100% flow rate value, the circulation ratio (flow rate of concentrated water / flow rate of permeate water) is higher than that when producing permeate water at the 100% flow rate value. growing.

  In this case, the operation is performed in a state where the circulation ratio exceeds a predetermined value (for example, about “5”), which is preferable from the viewpoint of preventing the membrane surface of the RO membrane module from being blocked. However, from the viewpoint of adjusting the circulation ratio to a predetermined value, the excess flow of concentrated water is circulating in the concentrated water line, so that the power of the pressurizing pump is wasted.

  An object of this invention is to provide the reverse osmosis membrane separation apparatus which can suppress the power consumption of a pressurization pump, adjusting a circulation ratio to a predetermined value.

  The present invention provides 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 permeate separated by the reverse osmosis membrane module. A permeated water line for sending out, a concentrated water line for sending concentrated water separated by the reverse osmosis membrane module, a part of the concentrated water branched from the concentrated water line and separated by the reverse osmosis membrane module A circulating water line returning to the upstream side of the reverse osmosis membrane module, a drainage line branched from the concentrated water line and discharging the remaining concentrated water separated by the reverse osmosis membrane module to the outside of the apparatus, and the concentrated water line A constant flow rate variable means for maintaining the flow rate of the concentrated water flowing through the concentrated water line at a predetermined constant flow rate value and increasing or decreasing the constant flow rate value; The drainage flow rate adjusting means capable of adjusting the drainage flow rate of the concentrated water to be discharged to and the reverse osmosis membrane provided in the supply water line, driven at a rotational speed corresponding to the input drive frequency, and sucking the supply water A pressure pump that discharges toward the module, an inverter that outputs a driving frequency corresponding to the input command signal to the pressure pump, and a system so that the flow rate of the permeated water becomes a preset target flow rate value. A driving frequency of the pressurizing pump using the physical quantity in the pump, and a pump drive control unit that outputs a command signal corresponding to the calculated value of the driving frequency to the inverter; and the concentrated water flowing through the concentrated water line A constant flow rate control unit that controls the constant flow rate varying means to increase or decrease the constant flow rate value, and the pump drive control unit is configured to reduce the target flow rate as the amount of permeated water used decreases. The target flow rate value is increased as the amount of permeated water used is increased, and the constant flow rate control unit is configured to increase the target flow value as the target flow rate value decreases. The present invention relates to a reverse osmosis membrane separation device that decreases a constant flow value and increases the constant flow value of concentrated water flowing through the concentrated water line as the target flow value increases.

  In addition, the constant flow variable means permits the inflow of concentrated water to any one or more constant flow valves of the plurality of constant flow valves arranged in parallel to the concentrated water line and the plurality of constant flow valves. One or more on-off valves that can be opened or closed to prevent or prevent the constant flow rate control unit to increase or decrease the constant flow rate value of the concentrated water flowing through the concentrated water line. It is preferable to control the opening and closing of two or more on-off valves.

  In addition, a first flow rate detection unit that detects a flow rate of the permeated water is provided, and the pump drive control unit drives the pressure pump so that the detected flow rate value of the first flow rate detection unit becomes the target flow rate value. It is preferable to calculate the frequency.

  Moreover, the temperature detection means which detects the temperature of supply water, permeated water, or concentrated water, and the waste_water | drain control part which controls the said waste_water | drain flow volume adjustment means, The said waste_water | drain control part is (i) supply previously acquired. Based on the silica concentration of water and the silica solubility determined from the detected temperature value of the temperature detecting means, the allowable concentration ratio of silica in the concentrated water is calculated, and (ii) the calculated value of the allowable concentration ratio and the permeated water Preferably, the drainage flow rate is calculated from the target flow rate value, and (iii) the drainage flow rate adjusting means is controlled so that the actual drainage flow rate of the concentrated water becomes the calculated value of the drainage flow rate.

  In addition, a proportional control valve as the drainage flow rate adjusting means and a second flow rate detection means for detecting the drainage flow rate of the concentrated water, the drainage control unit, wherein the detected flow rate value of the second flow rate detection means is the It is preferable to adjust the valve opening degree of the proportional control valve so that the drainage flow rate is calculated.

  ADVANTAGE OF THE INVENTION According to this invention, the reverse osmosis membrane separation apparatus which can suppress the power consumption of a pressurization pump can be provided, adjusting a circulation ratio to a predetermined value.

1 is an overall configuration diagram of a reverse osmosis membrane separation device 1 according to a first embodiment. It is explanatory drawing which shows the relationship between the water level of the storage tank 9, and the flow volume of the permeated water W2 manufactured. It is a flowchart which shows the process sequence in the case of setting a target flow volume value and a collection rate in the control part 10. 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 flowchart which shows the process sequence in case the control part 10 of 1st Embodiment performs pressure feedback water volume control. It is a flowchart which shows the process sequence in case the control part 10 of 1st Embodiment performs water quality feedforward collection | recovery rate control. It is a flowchart which shows the process sequence in case the control part 10 of 1st Embodiment performs temperature feedforward water quantity control. It is a flowchart which shows the process sequence in case the control part 10 of 1st Embodiment performs water quality feedback 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 changes the fixed flow value of the concentrated water W3.

(First embodiment)
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 first embodiment does not include a constant flow variable mechanism (constant flow variable means), and is a reference embodiment in that respect. A second embodiment to be described later is an embodiment of the present invention. FIG. 1 is an overall configuration diagram of a reverse osmosis membrane separation device 1 according to a first embodiment. The reverse osmosis membrane separation device 1 according to the first embodiment is applied to, for example, a pure water production system that produces pure water from fresh water.

  As shown in FIG. 1, a reverse osmosis membrane separation apparatus 1 according to this embodiment includes a pressurizing pump 2, an inverter 3, an RO membrane module 4 as a reverse osmosis membrane module, and a constant flow valve as a constant flow means. 5, a check valve 6, a pressure adjusting valve 7 as a pressure adjusting means, a proportional control drain valve 8 (proportional control valve) as a drain flow rate adjusting means, a storage tank 9, and a control unit 10. . Further, the reverse osmosis membrane separation device 1 includes a temperature sensor TE as a temperature detecting means, a hardness sensor S, a first pressure sensor PS1, a first flow rate sensor FM1 as a flow rate detecting means, and a first pressure sensor as a pressure detecting means. Two pressure sensors PS2, a second flow rate sensor FM2 as a second flow rate detection means, a first electrical conductivity sensor EC1, a second electrical conductivity sensor EC2 as an electrical conductivity measurement means, a water level sensor 91, Is provided. In FIG. 1, the path of electrical connection is indicated by a broken line (the same applies to FIG. 10 described later).

  The reverse osmosis membrane separation device 1 includes a supply water line L1, a permeate water line L2, a concentrated water line L3, a circulating water line L4, a drainage line L5, and a water supply line L6. 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 supply water line L1 is a line for supplying the supply water W1 to the RO membrane module 4. The upstream end of the supply water line L1 is connected to a supply source (not shown) of the supply water W1. The downstream end of the supply water line L <b> 1 is connected to the primary inlet port of the RO membrane module 4. In the supply water line L1, a hardness sensor S, a connection portion J2, a temperature sensor TE, a pressure pump 2, a first pressure sensor PS1, and an RO membrane module 4 are provided in order from the upstream side to the downstream side.

  The pressurizing pump 2 is a device that sucks in the supply water W1 flowing through the supply water line L1 and pumps (discharges) it toward the RO membrane module 4. The driving power whose frequency is converted is supplied from the inverter 3 to the pressurizing pump 2. The pressurizing pump 2 is driven at a rotational speed corresponding to the frequency (hereinafter also referred to as “driving frequency”) of the driving power supplied (input).

  The inverter 3 is an electric circuit (or a device having the circuit) that supplies the pressurizing pump 2 with driving power whose frequency has been converted. The inverter 3 is electrically connected to the control unit 10. A command signal is input to the inverter 3 from the control unit 10. The inverter 3 outputs driving power having a driving frequency corresponding to the command signal (current value signal or voltage value signal) input by the control unit 10 to the pressurizing pump 2.

  The RO membrane module 4 is a facility that performs membrane separation processing of the feed water W1 discharged from the pressurizing pump 2 into permeate water W2 from which dissolved salts have been removed and concentrated water W3 from which dissolved salts have been concentrated. The RO membrane module 4 includes a single or a plurality of RO membrane elements (not shown). The RO membrane module 4 membrane-separates the supply water W1 with these RO membrane elements to produce permeated water W2 and concentrated water W3.

  The permeate water line L2 is a line for sending the permeate water W2 separated by the RO membrane module 4. The upstream end of the permeate line L2 is connected to the secondary port of the RO membrane module 4. The downstream end of the permeate line L <b> 2 is connected to the storage tank 9. In the permeated water line L2, the RO membrane module 4, the first flow rate sensor FM1, the first electrical conductivity sensor EC1, and the storage tank 9 are provided in order from the upstream side to the downstream side.

  The concentrated water line L3 is a line for sending the concentrated water W3 separated by the RO membrane module 4. The upstream end of the concentrated water line L3 is connected to the primary outlet port of the RO membrane module 4. Further, the downstream side of the concentrated water line L3 branches to the circulating water line L4 and the drainage line L5 at the connection portion J1.

The concentrated water line L3 is provided with a constant flow valve 5, a second electrical conductivity sensor EC2, and a connecting portion J1 in order from the upstream side to the downstream side.
The constant flow valve 5 is a device that adjusts the flow rate of the concentrated water W3 flowing through the concentrated water line L3 so as to maintain a predetermined constant flow rate value. The constant flow value held in the constant flow valve 5 is a concept having a range in the constant flow value, and is not limited to the target flow value in the constant flow valve. For example, in consideration of the characteristics of the constant flow mechanism (for example, temperature characteristics caused by the material and structure), the constant flow mechanism includes those having an adjustment error of about ± 10% with respect to the target flow rate value. The constant flow valve 5 holds a constant flow value without requiring auxiliary power or external operation, and includes, for example, what is called by the name of a water governor. The constant flow valve 5 may be operated by auxiliary power or an external operation to hold a constant flow value.

  The circulating water line L4 is a line branched from the concentrated water line L3, and a part W31 of the concentrated water W3 separated by the RO membrane module 4 is supplied from the RO membrane module 4 and the pressure pump 2 in the supply water line L1. Is also a line that returns to the upstream side. The upstream end of the circulating water line L4 is connected to the concentrated water line L3 at the connecting portion J1. Further, the downstream end of the circulating water line L4 is connected to the supply water line L1 at the connecting portion J2. The circulating water line L4 is provided with a check valve 6 and a pressure adjusting valve 7 as pressure adjusting means in order from the upstream side to the downstream side.

  The pressure adjusting valve 7 is a valve that adjusts an intermediate pressure that is a pressure on the secondary side of the constant flow valve 5 and is a pressure on the primary side of the proportional control drain valve 8 to a predetermined set pressure value. The pressure adjusting valve 7 adjusts the intermediate pressure at the connection portion J1 (the portion between the constant flow valve 5 and the proportional control drain valve 8) by adjusting the flow resistance of the concentrated water W31 flowing through the circulating water line L4. Configured to be possible.

  In the present embodiment, the intermediate pressure is the pressure of the concentrated water W3 at the connection portion J1 (portion between the constant flow valve 5 and the proportional control drain valve 8 in the concentrated water line L3 and the drain line L5). The predetermined set pressure value is proportional control even when the back pressure on the secondary side of the proportional control drain valve 8 in the drain line L5 is high or when the pressure of the feed water W1 flowing through the feed water line L1 is low. The pressure value is set so that a predetermined pressure difference (primary side pressure> secondary side pressure) is obtained between the primary side and the secondary side of the drain valve 8.

  The pressure regulating valve 7 is electrically connected to the control unit 10. The valve opening degree of the pressure regulating valve 7 is controlled by a drive signal transmitted from the control unit 10. The flow resistance (that is, pressure loss) can be changed by transmitting a current value signal (for example, 4 to 20 mA) from the control unit 10 to the pressure regulating valve 7 and adjusting the flow path cross-sectional area. By this adjustment, the intermediate pressure at the connection portion J1 (the pressure on the secondary side of the constant flow valve 5 and the pressure on the primary side of the proportional control drain valve 8) can be kept at a predetermined set pressure value set in advance. it can.

  The drainage line L5 is a line that branches off from the concentrated water line L3 at the connecting portion J1 and discharges the remaining portion W32 of the concentrated water W3 separated by the RO membrane module 4 to the outside of the apparatus (outside the system). The drain line L5 is provided with a proportional control drain valve 8 as a drain flow rate adjusting means.

The proportional control drain valve 8 is a valve that adjusts the drain flow rate of the concentrated water W32 discharged from the drain line L5 to the outside of the apparatus. The proportional control drain valve 8 is electrically connected to the control unit 10. The valve opening degree of the proportional control drain valve 8 is controlled by a drive signal transmitted from the control unit 10. The drainage flow rate of the concentrated water W32 can be adjusted by transmitting a current value signal (for example, 4 to 20 mA) from the control unit 10 to the proportional control drainage valve 8 and controlling the valve opening degree.
Details of control by the control unit 10 in the proportional control drain valve 8 will be described later.

  The temperature sensor TE is a device that detects the temperature of the supply water W1. The temperature sensor TE is disposed between the supply source (not shown) of the supply water W1 and the pressurizing pump 2. The temperature sensor TE is electrically connected to the control unit 10. The temperature of the supply water W1 detected by the temperature sensor TE (hereinafter also referred to as “detected temperature value”) is transmitted to the control unit 10 as a detection signal.

  The hardness sensor S is a device that measures the calcium hardness of the supply water W1 flowing through the supply water line L1 (for example, the hardness leak amount of the water softening device installed in the previous stage: a calcium carbonate equivalent value). The hardness sensor S is disposed on the upstream side of the connection portion J2. The hardness sensor S is electrically connected to the control unit 10. The calcium hardness (hereinafter also referred to as “measured hardness value”) of the supply water W <b> 1 measured by the hardness sensor S is transmitted to the control unit 10 as a detection signal.

  The first pressure sensor PS1 is a device that detects the discharge pressure (operating pressure) of the pressurizing pump 2. The first pressure sensor PS1 is disposed in the vicinity of the discharge side of the pressure pump 2. In the present embodiment, the pressure of the supply water W <b> 1 immediately after being discharged from the pressurizing pump 2 is set as the discharge pressure of the pressurizing pump 2. The first pressure sensor PS1 is electrically connected to the control unit 10. The pressure of the supply water W1 detected by the first pressure sensor PS1 (hereinafter also referred to as “detected pressure value”) is transmitted to the control unit 10 as a detection signal.

  The second pressure sensor PS2 is a device that detects the intermediate pressure (the pressure on the secondary side of the constant flow valve 5 and the pressure on the primary side of the proportional control drain valve 8) at the connection portion J1. The second pressure sensor PS2 is connected to the concentrated water line L3, the drainage line L5, and the circulating water line L4 at the connection portion J1. The connecting part J1 is a part where the concentrated water line L3 branches into the drainage line L5 and the circulating water line L4, the downstream end of the concentrated water line L3, the upstream end of the circulating water line L4, and The upstream end of the drain line L5 is a connected part. The second pressure sensor PS2 is electrically connected to the control unit 10. The pressure of the concentrated water W3 (W31, W32) detected by the second pressure sensor PS2 (hereinafter also referred to as “detected pressure value”) is transmitted to the control unit 10 as a detection signal.

  In the present embodiment, the connection position of the second pressure sensor PS2 is the connection portion J1, but the present invention is not limited to this. If the connection position of the second pressure sensor PS2 is a pressure on the secondary side of the constant flow valve 5 and can detect the pressure on the primary side of the proportional control drain valve 8, the concentrated water line L3 and the circulating water line L4. Or the drainage line L5 may be sufficient.

  The 1st flow sensor FM1 is an apparatus which detects the flow volume of the permeated water W2 which distribute | circulates the permeated water line L2. The first flow sensor FM1 is connected to the permeate line L2. The first flow sensor FM1 is electrically connected to the control unit 10. The flow rate of the permeated water W2 detected by the first flow rate sensor FM1 (hereinafter also referred to as “detected flow rate value”) is transmitted to the control unit 10 as a pulse signal.

The second flow rate sensor FM2 is a device that detects the flow rate of the concentrated water W32 flowing through the drainage line L5. The second flow sensor FM2 is disposed downstream of the proportional control drain valve 8 in the drain line L5. The second flow rate sensor FM2 is electrically connected to the control unit 10. The flow rate of the concentrated water W32 detected by the second flow rate sensor FM2 (hereinafter also referred to as “detected flow rate value”) is transmitted to the control unit 10 as a pulse signal.
As the first flow sensor FM1 and the second flow sensor FM2, for example, a pulse transmission type flow sensor in which an axial flow impeller or a tangential impeller (not shown) is disposed in the flow path housing can be used.

The first electrical conductivity sensor EC1 is a device that measures the electrical conductivity of the permeated water W2 flowing through the permeated water line L2. The first electrical conductivity sensor EC1 is connected to the permeated water line L2. The first electrical conductivity sensor EC1 is electrically connected to the control unit 10. The electric conductivity of the permeated water W2 measured by the first electric conductivity sensor EC1 (hereinafter also referred to as “measured electric conductivity value”) is transmitted to the control unit 10 as a detection signal.
The second electrical conductivity sensor EC2 is a device that measures the electrical conductivity of the concentrated water W3 (the concentrated water W3 separated by the RO membrane module 4) flowing through the concentrated water line L3. The second electrical conductivity sensor EC2 is connected to the concentrated water line L3. The second electrical conductivity sensor EC2 is electrically connected to the control unit 10. The electrical conductivity of the concentrated water W3 measured by the second electrical conductivity sensor EC2 (hereinafter also referred to as “measured electrical conductivity value”) is transmitted to the control unit 10 as a detection signal.

  The storage tank 9 is a tank for storing the permeated water W2 separated by the RO membrane module 4. The storage tank 9 is connected to the downstream end of the permeate line L2. The permeated water W2 separated by the RO membrane module 4 is supplied to the storage tank 9 through the permeated water line L2. Further, the storage tank 9 is connected to a device or the like (not shown) at a downstream demand point via a water supply line L6. The water supply line L6 is a line through which the permeated water W2 stored in the storage tank 9 is circulated to a device or the like at a demand location. The permeated water W2 stored in the storage tank 9 is supplied to a device or the like at a demand point via a water supply line L6.

  The storage tank 9 is provided with a water level sensor 91. The water level sensor 91 is a device that detects the water level of the permeated water W <b> 2 stored in the storage tank 9. The water level sensor 91 is electrically connected to the control unit 10. The water level of the storage tank 9 (hereinafter also referred to as “detected water level value”) measured by the water level sensor 91 is output to the control unit 10 as a detection signal.

  In the present embodiment, the water level sensor 91 is, for example, a level switch. The level switch is a preset liquid level position detector, and is configured to detect, for example, a plurality of liquid level positions (for example, two positions). FIG. 1 shows an example in which a float type level switch is provided as the water level sensor 91. The water level sensor 91 is not limited to a level switch, and may be a continuous level sensor, for example. As the continuous level sensor, for example, a capacitive sensor, a pressure sensor, an ultrasonic sensor, or the like is used.

  Here, the relationship between the water level of the storage tank 9 and the flow rate of the permeate W2 produced by the RO membrane module 4 will be described. FIG. 2 is an explanatory diagram showing the relationship between the set water level in the storage tank 9 and the flow rate of the permeated water W2 to be produced. As shown in FIG. 2, in the present embodiment, the set water level of the storage tank 9 is divided into two stages of L and H in order from the lowest to the highest.

  The set water level L is an upper limit water level for producing the permeated water W2 at a 100% flow rate value (first target flow rate value). When the water level of the storage tank 9 is equal to or lower than the set water level L, the permeated water W2 is produced with a 100% flow rate value. At the 100% flow rate value (first target flow rate value), the recovery rate at the RO membrane module 4 is adjusted to the required recovery rate.

The set water level H is an upper limit water level (full water level) at which the permeated water W2 is produced with a 60% flow rate value (second target flow rate value). When the water level of the storage tank 9 exceeds the set water level L and becomes the set water level H or less, the permeated water W2 is produced at a 60% flow rate value. At the 60% flow rate value (second target flow rate value), the recovery rate at the RO membrane module 4 is adjusted to the required recovery rate.
Further, when the water level of the storage tank 9 exceeds the set water level H, the production of the permeated water W2 is stopped (0% flow rate value).

  The control unit 10 is configured by a microprocessor (not shown) including a CPU and a memory. Hereinafter, functions of the control unit 10 will be described.

<Water volume control of permeated water W2>
For example, the control unit 10 can select and execute one of flow rate feedback water amount control, pressure feedback water amount control, and temperature feedforward water amount control as the water amount control of the permeated water W2. The outline of each water quantity control is as follows.

The flow rate feedback water amount control control unit 10 (pump drive control unit) is configured so that the flow rate of the permeated water W2 becomes a preset target flow rate value (a first target flow rate value or a second target flow rate value described later). The drive frequency for driving the pressurizing pump 2 is calculated using the detected flow rate value (physical quantity in the system) of the flow rate sensor FM1 as a feedback value. Then, the control unit 10 outputs a command signal (current value signal or voltage value signal) corresponding to the calculated value of the drive frequency to the inverter 3 (hereinafter also referred to as “flow rate feedback water amount control”). For example, a speed type digital PID algorithm can be used for calculation of the drive frequency in the main water amount control.

The pressure feedback water amount control control unit 10 (pump drive control unit) pressurizes so that the flow rate of the permeated water W2 becomes a preset target flow rate value (a first target flow rate value or a second target flow rate value described later). Using the detected pressure value of the pump 2 (physical quantity in the system) as a feedback value, the drive frequency of the pressurizing pump 2 is calculated. Then, the control unit 10 outputs a command signal (current value signal or voltage value signal) corresponding to the calculated value of the drive frequency to the inverter 3 (hereinafter also referred to as “pressure feedback water amount control”). For example, a speed type digital PID algorithm can be used for calculation of the drive frequency in the main water amount control.

The temperature feedforward water amount control control unit 10 (pump drive control unit) controls the temperature so that the flow rate of the permeated water W2 becomes a preset target flow rate value (a first target flow rate value or a second target flow rate value described later). The drive frequency of the pressurizing pump 2 is calculated using the detected temperature value of the sensor TE (physical quantity in the system) as a feedforward value. Then, the control unit 10 outputs a command signal (current value signal or voltage value signal) corresponding to the calculated value of the drive frequency to the inverter 3 (hereinafter also referred to as “temperature feedforward water amount control”).

Adjustment of the circulation ratio of the concentrated water W3 The circulation ratio of the concentrated water W3 is the ratio between the flow rate of the permeated water W2 flowing out from the secondary side port of the RO membrane module 4 and the flow rate of the concentrated water W3 flowing out from the primary side outlet port. (Flow rate of concentrated water W3 / flow rate of permeated water W2). The predetermined value of the circulation ratio is about “5”.
Here, in this embodiment, the constant flow valve 5 is provided in the concentrated water line L3. Therefore, the circulation ratio of the concentrated water W3 is set to a predetermined value by holding the flow rate of the permeated water W2 constant by any of the above-described water amount control while holding the flow rate of the concentrated water W3 constant by the constant flow valve 5. Will be adjusted to.

<Target flow rate increase / decrease control>
The increase / decrease control is executed in association with the water amount control of the permeated water W2.
The control unit 10 (pump drive control unit) decreases the target flow rate value and increases the used water amount of the permeated water W2 as the used water amount of the permeated water W2 decreases during the execution of the water amount control of the permeated water W2. In accordance with the above, the target flow rate value is increased.
Specifically, the control unit 10 decreases the target flow rate value and decreases the detected water level value as the detected water level value of the storage tank 9 measured by the water level sensor 91 increases (detected water level value ≦ L). (L <detected water level value ≦ H), the target flow rate value is increased.

  Specifically, the control unit 10 sets the first target flow rate value (100% flow rate value that is the rated output of the reverse osmosis membrane separation device 1) when the detected water level value is equal to or lower than the set water level value L, and The recovery rate is set to a predetermined first recovery rate. Further, when the detected water level value exceeds the set water level value L and is equal to or less than the set water level value H, the control unit 10 sets the second target flow rate value (60% flow rate value) and sets the recovery rate to a predetermined first level. 2 Set to recovery rate.

  In the control unit 10, the memory of the microprocessor is a data table in which the set water level (L, H), the target flow value (first target flow value, second target flow value), and predetermined recovery rates are associated with each other. Is remembered.

<Recovery rate control of permeate W2>
The recovery rate of the permeated water W2 is the ratio of the flow rate of the permeated water W2 to the flow rate of the supplied water W1 supplied to the RO membrane module 4 (the flow rate of the permeated water W2 / the flow rate of the supplied water W1).
The control unit 10 can select and execute, for example, temperature feedforward recovery rate control, water quality feedforward, or water quality feedback recovery rate control as the recovery rate control of the permeated water W2. The outline of each recovery rate control is as follows.

The temperature feedforward recovery rate control control unit 10 calculates the allowable concentration rate of silica in the concentrated water W3 based on the silica concentration determined from the silica concentration of the supply water W1 acquired in advance and the detected temperature value of the temperature sensor TE. To do. Then, the control unit 10 calculates the drainage flow rate from the calculated value of the permissible concentration ratio and the target flow rate value of the permeate W2 (first target flow rate value or second target flow rate value described later), and the actual drainage amount of the concentrated water W3. The valve opening degree of the proportional control drain valve 8 is controlled so that (the detected flow rate value of the second flow sensor FM2) becomes the calculated value of the drainage flow rate (target drainage flow rate) (hereinafter, “temperature feedforward recovery rate control”). Also called).

The water quality feedforward recovery rate control control unit 10 calculates the allowable concentration rate of calcium carbonate in the concentrated water W3 based on the previously obtained solubility of calcium carbonate and the measured hardness value of the hardness sensor S. Then, the control unit 10 calculates the drainage flow rate from the calculated value of the permissible concentration ratio and the target flow rate value of the permeate W2 (first target flow rate value or second target flow rate value described later), and the actual drainage amount of the concentrated water W3. The valve opening degree of the proportional control drain valve 8 is controlled so that (the detected flow rate value of the second flow sensor FM2) becomes the calculated value (target drainage flow rate) of the drainage flow rate (hereinafter, “water quality feedforward recovery rate control”). Also called).

The water quality feedback recovery rate control control unit 10 directly controls the valve opening of the proportional control drain valve 8 so that the measured electrical conductivity value of the first electrical conductivity sensor EC1 becomes a preset target electrical conductivity. (Hereinafter also referred to as “water quality feedback recovery rate control”). For example, a speed type digital PID algorithm can be used to determine the valve opening in this control.

<Drain flow control by proportional control drain valve 8>
This adjustment control is executed in association with the temperature feedforward recovery rate control or the water quality feedforward recovery rate control in the recovery rate control described above.
The control unit 10 (drainage control unit) serves as a drainage flow rate adjusting unit so that the detected flow rate value of the second flow rate sensor FM2 becomes the calculated value (target drainage flow rate) of the drainage flow rate determined by the recovery rate control described above. Flow rate feedback control of the valve opening degree of the proportional control drain valve 8 is performed. For example, a speed type digital PID algorithm can be used for the calculation of the valve opening degree in this adjustment control.

<Control of flow resistance by pressure regulating valve 7>
The control unit 10 (pressure adjustment control unit) opens the valve opening (flow path) of the pressure adjustment valve 7 so that the detected pressure value detected by the second pressure sensor PS2 becomes a predetermined set pressure value (target pressure value). Control to adjust the cross-sectional area. Thereby, the flow resistance in the circulating water line L4 is adjusted. By this adjustment, it is possible to adjust the intermediate pressure at the connection portion J1 (the pressure on the secondary side of the constant flow valve 5 and the pressure on the primary side of the proportional control drain valve 8). For example, a speed type digital PID algorithm can be used for calculation of the valve opening degree in the adjustment control.
In this adjustment control, a third pressure sensor (not shown) is provided on the secondary side of the proportional control drain valve 8, and the difference between the detected pressure values of the second pressure sensor and the third pressure sensor is a predetermined set pressure value. The valve opening degree of the pressure regulating valve 7 can also be adjusted so that it becomes (target pressure value).

  In the present embodiment, the flow rate of the concentrated water W3 flowing through the concentrated water line L3 is maintained at a constant flow value by the constant flow valve 5. Moreover, the flow rate of the concentrated water W32 which distribute | circulates the drainage line L5 is increased / decreased by the proportional control drainage valve 8 by the recovery rate control mentioned above. Thereby, although the flow volume of the concentrated water W31 which distribute | circulates the circulating water line L4 is also increased / decreased, the circulation ratio of the concentrated water W3 is kept constant.

  In the present embodiment, the pressure regulating valve 7 is not intended to adjust the flow rate of the concentrated water W31 flowing through the circulating water line L4, but is an intermediate pressure (pressure on the secondary side of the constant flow valve 5) at the connection portion J1. The pressure on the primary side of the proportional control drain valve 8 is to be adjusted. The control unit 10 changes the valve opening degree (flow passage cross-sectional area) of the pressure regulating valve 7 to change the intermediate pressure (the pressure on the secondary side of the constant flow valve 5 and the proportional control drain valve 8) at the connection unit J1. The primary pressure).

In the present embodiment, the control unit 10 performs control so as to adjust the valve opening (flow passage cross-sectional area) of the pressure adjustment valve 7, so that the intermediate pressure at the connection portion J <b> 1 is changed to the primary side of the proportional control drain valve 8. And a pressure at which a predetermined pressure difference (primary side pressure> secondary side pressure) can be obtained. Thereby, even when the back pressure on the secondary side of the proportional control drain valve 8 in the drain line L5 becomes high or when the pressure of the feed water W1 flowing through the feed water line L1 is low, the proportional control drain valve 8 A predetermined pressure difference is obtained between the primary side and the secondary side, and the concentrated water W32 can be discharged out of the apparatus via the proportional control drain valve 8.
Even when the pressure of the supply water W1 flowing through the supply water line L1 or the back pressure of the proportional control drain valve 8 fluctuates, the control unit 10 controls the intermediate pressure at the connection portion J1 to a predetermined pressure value. Thus, more reliable adjustment of the drainage flow rate can be realized.

<Flushing operation control>
The control unit 10 performs the flushing operation control when a predetermined condition is satisfied. Examples of the predetermined conditions include the following [a] to [d].
[A] When production of the permeated water W2 is finished (when operation of the device is finished)
[B] When the continuation time during which the permeated water W2 is not manufactured after the end of the previous flushing operation is a set time (eg, 1 hour) [c] Integrated manufacturing time of the permeated water W2 after the end of the previous flushing operation Reaches the set time (e.g., 30 minutes) [d] When the membrane contamination level of the RO membrane module 4 exceeds the allowable value The contamination level of the RO membrane module is, for example, the primary inlet port of the RO membrane module 4 And the pressure difference between the primary side outlet port and the primary side outlet port is obtained by measuring with a differential pressure gauge (not shown).
For example, the flushing operation control is executed for 120 seconds under the conditions [a] and [d]. For example, under the conditions [b] and [c], the process is executed for 60 seconds.

  In the flushing operation control, the control unit 10 performs the cleaning of the primary side of the RO membrane module 4. In the flushing operation control, the supply water W <b> 1 is supplied to the primary side of the RO membrane module 4. In the flushing operation control, the pressurizing pump 2 is fixed at a driving frequency (for example, 30 Hz) lower than the maximum driving frequency (50 Hz or 60 Hz). At this time, most of the supply water W1 flows through the surface of the RO membrane without passing through the RO membrane, and is discharged to the outside through the concentrated water line L3 as flushing washing wastewater. By this flushing operation control, scale nuclei and deposited suspended substances deposited on the surface of the RO membrane are removed. When the flushing operation control is executed for a predetermined time (for example, 120 seconds, 60 seconds), the permeated water W2 can be manufactured.

  Next, the increase / decrease of the target flow rate value and the adjustment of the recovery rate by the control unit 10 will be described. FIG. 3 is a flowchart showing a processing procedure in the case where the control unit 10 adjusts the recovery rate while increasing or decreasing the target flow rate value. 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 ST <b> 101 shown in FIG. 3, the control unit 10 acquires the detected water level value W of the water level sensor 91.

  In step ST102, the control unit 10 determines whether or not the detected water level value W is less than or equal to the set water level L. In step ST102, when the control unit 10 determines that the detected water level value W ≦ the set water level L (YES), the process proceeds to step ST103. In Step ST102, when the control unit 10 determines that the detected water level value W> the set water level L (NO), the process proceeds to Step ST105.

  In step ST103 (step ST102: YES), the control unit 10 sets the flow rate of the permeated water W2 to the first target flow rate value. Thus, when the detected water level value W is equal to or lower than the set water level L, in order to increase the water storage amount of the storage tank 9, the target flow rate value of the permeated water W2 becomes the 100% flow rate value that is the rated output. Set the value and execute the selected water amount control.

  In step ST104, the control unit 10 adjusts the valve opening degree of the proportional control drain valve 8 in accordance with the selected recovery rate control. Thus, the process of this flowchart ends (returns to step ST101).

  On the other hand, in step ST105 (step ST102: NO), the control unit 10 determines whether or not the detected water level value W exceeds the set water level L and is not more than the set water level H. In step ST105, when the control unit 10 determines that the set water level L <the detected water level value W ≦ the set water level H (YES), the process proceeds to step ST106. In step ST105, when the control unit 10 determines that the detected water level value W> the set water level H (NO), the process proceeds to step ST108.

  In step ST106 (step ST105: YES), the control unit 10 sets the flow rate of the permeated water W2 to the second target flow rate value. The second target flow value is a flow value smaller than the first target flow value. As described above, when the detected water level value W exceeds the set water level L and is equal to or lower than the set water level H, the target flow rate value of the permeated water W2 is set to the second target flow rate value that is 60% flow rate, and then selected. Execute water volume control. As a result, when a sufficient amount of water is secured in the storage tank 9, energy saving can be achieved by lowering the rotation speed of the pressurizing pump 2.

  In step ST107, the control unit 10 adjusts the valve opening degree of the proportional control drain valve 8 according to the selected recovery rate control. Thus, the process of this flowchart ends (returns to step ST101).

  On the other hand, in step ST108 (step ST105: NO), the control unit 10 controls the inverter 3 so as to stop the pressurizing pump 2. Thus, the process of this flowchart ends (returns to step ST101).

<Control example of water amount control and recovery rate control of permeate W2>
Next, a specific control example will be described for the water amount control and the recovery rate control of the permeated water W2.
Here, a pattern (control example 1) executed by combining “flow rate feedback water amount control” and “temperature feedforward recovery rate control”, “pressure feedback water amount control” and “water quality feedforward recovery rate control” A pattern (control example 2) executed in combination, a pattern (control example 3) executed by combining "temperature feedforward water amount control" and "water quality feedback recovery rate control" will be exemplified. In the present application, combinations other than the control examples 1 to 3 are not excluded.

Control example 1
The flow rate feedback water amount control by the control unit 10 will be described with reference to FIG. The temperature feedforward recovery rate control by the control unit 10 will be described with reference to FIG. This temperature feedforward recovery rate control is executed in parallel with the flow rate feedback water amount control. FIG. 4 is a flowchart showing a processing procedure when the control unit 10 executes the flow rate feedback water amount control. FIG. 5 is a flowchart showing a processing procedure when the control unit 10 executes the temperature feedforward recovery rate control. 4 and 5 are repeatedly executed during the operation of the reverse osmosis membrane separation device 1.

First, flow rate feedback water amount control by the control unit 10 will be described.
In step ST201 shown in FIG. 4, 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, the first target flow rate value or the second target flow rate value set in step ST103 or step ST106 of the flowchart shown in FIG.

In step ST 202, the control unit 10 acquires the detected flow rate value _{Q p} of the permeate W2 detected by the first flow rate sensor FM1.

In step ST 203, the control unit 10, so that the deviation between the detected flow rate value obtained in step ST 202 (feedback value) _{Q p} and the target flow rate value _{Q p} obtained in step ST 201 'is zero, velocity type digital PID algorithm _{Is used} to calculate an operation amount U (U _n described later). In the velocity type digital PID algorithm, the control period (e.g., 100 ms) calculates the operation amount of the variation ΔU each, the current operation amount U _n by adding it to the previous operation amount U _n-1 Determine (n is the number of operations).

In step ST 204, the control unit 10, the operation amount U, based on the target flow rate value _{Q p} 'and the maximum driving frequency of the pressure pump 2 (the set value of 50Hz or 60 Hz), calculates a drive frequency F of the pressure pump 2 To do.

In step ST205, 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 ST206, the control unit 10 outputs the converted current value signal to the inverter 3. Thus, the process of this flowchart ends (returns to step ST201).

Next, temperature feedforward recovery rate control executed in parallel with flow rate feedback water amount control will be described.
In step ST301 shown in FIG. 5, 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, the first target flow rate value or the second target flow rate value set in step ST103 or step ST106 of the flowchart shown in FIG.

In step ST 302, 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 supply water line L1, the silica concentration of the supply water W1 may be measured by a water quality sensor (not shown) (for example, a colorimetric water quality sensor using a molybdenum yellow method).

In step ST303, the control unit 10 acquires the detected temperature value T of the supply water W1 from the temperature sensor TE.
In step ST304, the control unit 10 determines silica solubility S _s with respect to water based on the acquired detected temperature value T.

In step ST305, 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 306, 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 ST 307, the control unit 10, actual wastewater flow rate _{Q d} of concentrated water W3 is such that the target drainage flow _{Q d} 'calculated in step ST 306, to adjust the valve opening of the proportional control drain valve 8. Specifically, the control unit 10 performs flow rate feedback control of the valve opening degree of the proportional control drain valve 8 so that the detected flow rate value of the second flow rate sensor FM2 becomes the target drainage flow rate Q _d ′. For calculating the valve opening (operation amount), it is preferable to use a speed digital PID algorithm. Thus, the process of this flowchart ends (returns to step ST301). This step ST307 corresponds to step ST104 or step ST107 in FIG.

Control example 2
The pressure feedback water amount control by the control unit 10 will be described with reference to FIG. Moreover, the water quality feedforward recovery rate control by the control part 10 is demonstrated with reference to FIG. This temperature feedforward recovery rate control is executed in parallel with the pressure feedback water amount control. FIG. 6 is a flowchart showing a processing procedure when the control unit 10 executes the pressure feedback water amount control. FIG. 7 is a flowchart showing a processing procedure when the control unit 10 executes water quality feedforward recovery rate control. 6 and 7 are repeatedly executed during the operation of the reverse osmosis membrane separation apparatus 1.

First, the pressure feedback water amount control by the control unit 10 will be described.
In step ST401 shown in FIG. 6, the control unit 10 obtains a target flow rate value Q _p ′ of the permeated water W2. This target flow rate value Q _p ′ is, for example, the first target flow rate value or the second target flow rate value set in step ST103 or step ST106 of the flowchart shown in FIG.

In step ST402, the control unit 10 acquires the water permeability coefficient L _p at the reference temperature (25 ° C.) of the RO membrane module 4. This water permeability coefficient L _p is, for example, a set value input to the memory by a system administrator via a user interface (not shown).

It should be noted that this pressure feedback water amount control can be executed as a backup of the aforementioned flow rate feedback water amount control. In that case, the water permeability coefficient L _p may be a calculated value immediately before the failure of the first flow sensor FM1 (see FIG. 1) occurs.

The calculated value of the water permeability coefficient L _{p at} the reference temperature can be obtained based on the following formulas (3) and (4).
L _p = Q _p / (K · A · P _e ) (3)
(K: temperature correction coefficient, A: membrane area of RO membrane module 4, P _e : effective pressure)
_{P e = P d - (ΔP} 1/2) -P 2 -Δπ + P s (4)
(Where P _d : discharge pressure of the pressure pump 2, ΔP ₁ : differential pressure on the primary side of the RO membrane module 4, P ₂ : back pressure on the secondary side of the RO membrane module 4, Δπ: of the RO membrane module 4 Osmotic pressure difference, P _s : pressure on the suction side of the pressure pump 2)

In equation (3), the temperature correction coefficient K is a function of the detected temperature value T of the temperature sensor TE. Since the membrane area A is determined by the number of reverse osmosis membrane elements used, a preset value can be used. In the calculation of the effective pressure P _e according to formula (4), the values of ΔP _{1, P 2, Δπ,} and P _s, is operating steadily, because that regarded as substantially constant, the use of a preset value Can do. Accordingly, during operation of the reverse osmosis membrane separation device, at least three of the detected temperature value T of the temperature sensor TE, the detected flow value Q _p of the first flow sensor FM1, and the detected pressure value P _d of the first pressure sensor PS1. If the parameter is obtained, the water permeability coefficient L _p at the reference temperature can be calculated.

In step ST403, the control unit 10 acquires the detected temperature value T of the supply water W1 detected by the temperature sensor TE.
In step ST404, the control unit 10 calculates a temperature correction coefficient K based on the detected temperature value T acquired in step ST403.

In step ST405, the control unit 10 obtains or calculates the target flow rate value Q _p ′, water permeation coefficient L _p , temperature correction coefficient K, and required set values (A, ΔP ₁ , P ₂ , Δπ) obtained in the previous step. , P _s ), the discharge pressure P _d ′ of the pressurizing pump 2 is calculated based on the above formulas (3) and (4). Then, the calculated value of the discharge pressure P _d ′ is set as the target pressure value.

In step ST 406, the control unit 10 obtains the detected pressure value _{P d} of the detected pressure pump 2 in the first pressure sensor PS1.

In step ST 407, the control unit 10, so that the deviation between the detected pressure value obtained in step ST 406 (feedback value) _{P d} and the target pressure value _{P d} set in step ST 405 'is zero, velocity type digital PID algorithm _{Is used} to calculate an operation amount U (U _n described later). In the velocity type digital PID algorithm, the control period (e.g., 100 ms) calculates the operation amount of the variation ΔU each, the current operation amount U _n by adding it to the previous operation amount U _n-1 Determine (n is the number of operations).

In step ST408, the control unit 10 calculates the driving frequency F of the pressurizing pump 2 based on the operation amount U, the target pressure value P _d ′, and the maximum driving frequency of the pressurizing pump 2 (set value of 50 Hz or 60 Hz). To do.

In step ST409, 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 ST410, the control unit 10 outputs the converted current value signal to the inverter 3. Thus, the process of this flowchart ends (returns to step ST401).

Next, water quality feedforward recovery rate control executed in parallel with pressure feedback water amount control will be described.
In step ST501 shown in FIG. 7, 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, the first target flow rate value or the second target flow rate value set in step ST103 or step ST106 of the flowchart shown in FIG.
In step ST 502, the control unit 10 acquires the measured hardness value _{C c} of the supply water W1 measured by the hardness sensor S.

In step ST 503, the control unit 10 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 504, the control unit 10, prior to measurement 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 obtained by the following equation (5).
N _c = S _c / C _c (5)

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 ST505, 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 _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 (6).
Q _d ′ = Q _p ′ / (N _c −1) (6)

In step ST 506, the control unit 10, actual wastewater flow rate _{Q d} of concentrated water W3 is such that the target drainage flow _{Q d} 'calculated in step ST505, to adjust the valve opening of the proportional control drain valve 8. Specifically, the control unit 10 performs flow rate feedback control of the valve opening degree of the proportional control drain valve 8 so that the detected flow rate value of the second flow rate sensor FM2 becomes the target drainage flow rate Q _d ′. For calculating the valve opening (operation amount), it is preferable to use a speed digital PID algorithm. Thus, the process of this flowchart ends (returns to step ST501). This step ST506 corresponds to step ST104 or step ST107 in FIG.

Control example 3
The temperature feedforward water amount control by the control unit 10 will be described with reference to FIG. The water quality feedback recovery rate control by the control unit 10 will be described with reference to FIG. This water quality feedback recovery rate control is executed in parallel with the temperature feedforward water amount control. FIG. 8 is a flowchart showing a processing procedure when the control unit 10 executes the temperature feedforward water amount control. FIG. 9 is a flowchart showing a processing procedure when the control unit 10 executes water quality feedback recovery rate control. 8 and 9 are repeatedly executed during the operation of the reverse osmosis membrane separation device 1.

First, temperature feedforward water amount control by the control unit 10 will be described.
In step ST601 shown in FIG. 8, the control unit 10 acquires the target flow rate value Q _p ′ of the permeated water W2. This target flow rate value Q _p ′ is, for example, the first target flow rate value or the second target flow rate value set in step ST103 or step ST106 of the flowchart shown in FIG.

In step ST602, the control unit 10 acquires the water permeability coefficient L _p at the reference temperature (25 ° C.) of the RO membrane module 4. This water permeability coefficient L _p is, for example, a set value input to the memory by a system administrator via a user interface (not shown).

The temperature feedforward water amount control can be executed as a backup of the flow rate feedback water amount control described above. In that case, the water permeability coefficient L _p may be a calculated value immediately before the failure of the first flow sensor FM1 (see FIG. 1) occurs. The water permeation coefficient L _{p at the} reference temperature can be calculated by the method described in the explanation of the pressure feedback water amount control.

In step ST603, the control unit 10 acquires the detected temperature value T of the supply water W1 detected by the temperature sensor TE.
In step ST604, the control part 10 calculates the temperature correction coefficient K based on the detected temperature value T acquired in step ST603.

In step ST605, the control unit 10 obtains or calculates the target flow rate value Q _p ′, water permeation coefficient L _p , temperature correction coefficient K, and required set values (A, ΔP ₁ , P ₂ , Δπ) obtained in the previous step. , P _s ), the discharge pressure P _d ′ of the pressurizing pump 2 is calculated based on the equations (3) and (4) described in the above description.

In step ST606, the control unit 10 uses the calculated value of the discharge pressure P _{d ',} on the basis of the following equation (7), calculates a drive frequency F of the pressure pump 2.
^{_{F = a · P d '2}} + b · P d' + c (7)
(However, a, b, c are coefficients determined by the specifications of the pressurizing pump 2)

In step ST607, 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 ST608, the control unit 10 outputs the converted current value signal to the inverter 3. Thus, the process of this flowchart ends (returns to step ST601).

Next, water quality feedback recovery rate control executed in parallel with temperature feedforward water amount control will be described.
In step ST701 shown in FIG. 9, the control unit 10 obtains a 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 702, the control unit 10 acquires the measured electric conductivity value _{E p} of the measured permeate W5 in the first conductivity sensor EC1.

In step ST 703, the control unit 10, so that the deviation between the obtained measured electrical conductivity value (feedback value) _{E p} and step target electric conductivity value obtained in ST701 _{E p} 'in step ST702 becomes zero, proportional The valve opening degree of the control drain valve 8 is feedback-controlled. That is, by continuously 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. Thus, the process of this flowchart ends (returns to step ST701). This step ST703 corresponds to step ST104 or step ST107 in FIG.

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 apparatus 1 according to the first embodiment, the reverse osmosis membrane module 4, the feed water line L1, the permeate water line L2, the concentrated water line L3, and the circulating water branched from the concentrated water line L3. A line L4, a drain line L5 branched from the concentrated water line L3, a constant flow valve 5 provided in the concentrated water line L3, a proportional control drain valve 8 provided in the drain line L5, and a circulating water line L4. A pressure adjusting valve 7 for adjusting an intermediate pressure, which is a pressure on the secondary side of the constant flow valve 5 and a pressure on the primary side of the proportional control drain valve 8, to a predetermined set pressure value, and an additional pressure provided in the supply water line L1. A pressure pump 2, an inverter 3 that outputs a driving frequency to the pressurizing pump 2, and a control unit that outputs a command signal to the inverter 3 so that the flow rate of the permeated water W2 becomes a preset target flow rate value (pump drive control) ) Includes a 10, a.

  Therefore, the constant flow valve 5 keeps the flow rate of the concentrated water W3 constant, and the flow rate of the permeate water W2 is kept constant by controlling the amount of water, so that the circulation ratio of the concentrate water W3 (flow rate of concentrate water / permeate water). Flow rate) can be adjusted to a predetermined value. Further, by adjusting the intermediate pressure to a predetermined set pressure value by the pressure adjusting valve 7, the intermediate pressure can be set to a pressure at which a pressure difference is obtained between the primary side and the secondary side of the proportional control drain valve 8. it can. Thereby, even when the back pressure on the secondary side of the proportional control drain valve 8 in the drain line L5 becomes high or when the pressure of the feed water W1 flowing through the feed water line L1 is low, the proportional control drain valve 8 A predetermined pressure difference (primary side pressure> secondary side pressure) is obtained between the primary side and the secondary side, and the concentrated water W32 can be discharged out of the apparatus via the proportional control drain valve 8.

In the reverse osmosis membrane separation device 1 according to the first embodiment, the pressure adjustment valve 7 is configured to be able to adjust the intermediate pressure by adjusting the flow resistance of the concentrated water W31 flowing through the circulating water line L4. The control unit 10 (pressure adjustment control unit) controls to adjust the pressure adjustment valve 7 so that the detected pressure value detected by the second pressure sensor PS2 becomes a predetermined set pressure value.
Thereby, even when the pressure of the supply water W1 flowing through the supply water line L1 and the back pressure of the proportional control drain valve 8 fluctuate, the control unit 10 controls the intermediate pressure at the connection portion J1 to a predetermined pressure value. Therefore, the drainage flow rate can be more reliably adjusted.

Further, in the reverse osmosis membrane separation device 1 according to the first embodiment, the control unit 10 controls the flow rate of the permeated water W2 by flow rate feedback water amount control. In the velocity type digital PID algorithm used in the flow rate feedback water amount control, the change amount from the previous manipulated variable is calculated, and the previous manipulated variable is added to this to obtain the present manipulated variable. Even when _p is a discrete value, the deviation from the target flow rate value Q _p ′ can be eliminated at high speed. Therefore, even when the water permeation coefficient of the RO membrane module 4 changes abruptly due to temperature change, membrane clogging, or the like, the change can be sufficiently followed. Therefore, if the water permeability coefficient of the RO membrane module 4 changes rapidly, the flow rate of the permeate water W2 is converged in a short time to the target flow rate value Q _{p ',} it is possible to produce a permeate W2 stable water .

  Further, in the reverse osmosis membrane separation device 1 according to the first embodiment, the control unit 10 controls the flow rate of the permeated water W2 by pressure feedback water amount control. This pressure feedback water amount control can be executed as a backup of the flow rate feedback water amount control. Therefore, even when a failure occurs in the first flow sensor FM1 (see FIG. 1) during the flow rate feedback water amount control, the permeated water W4 having a stable water amount is manufactured by switching to the pressure feedback water amount control. Can do.

  Moreover, in the reverse osmosis membrane separation apparatus 1 which concerns on 1st Embodiment, the control part 10 controls the flow volume of the permeated water W2 by temperature feedforward water amount control. This temperature feedforward water amount control can be executed as a backup of the flow rate feedback water amount control in the first embodiment. Therefore, even when a failure occurs in the first flow sensor FM1 (see FIG. 1) during the execution of the flow rate feedback water amount control, the permeated water W2 having a stable water amount is manufactured by switching to the temperature feedforward water amount control. be able to.

  In the reverse osmosis membrane separation device 1 according to the first embodiment, the control unit 10 performs temperature feedforward recovery rate control. For this reason, in the reverse osmosis membrane separation apparatus 1, precipitation of the silica scale in the RO membrane module 4 can be more reliably suppressed while maximizing the recovery rate of the permeated water W2.

  Moreover, in the reverse osmosis membrane separation apparatus 1 which concerns on 1st Embodiment, the control part 10 performs water quality feedforward collection | recovery rate control. For this reason, even when the amount of hardness leak from the previous water softening device increases, the reverse osmosis membrane separation device 1A maximizes the recovery rate of the permeated water W2 and precipitates the calcium carbonate scale in the RO membrane module 4. Can be more reliably suppressed.

  In the reverse osmosis membrane separation device 1 according to the first embodiment, the control unit 10 performs water quality feedback recovery rate control. For this reason, in the reverse osmosis membrane separation device 1A, the recovery rate of the permeate W2 can be maximized while satisfying the water quality required for the permeate 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. 10 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. 10, in the reverse osmosis membrane separation device 1A according to the second embodiment, a constant flow variable mechanism 50 as a constant flow variable means is provided in the concentrated water line L3 instead of the constant flow valve 5. However, it differs from the reverse osmosis membrane separation apparatus 1 of 1st Embodiment. Moreover, the structure of the concentrated water line L3A of 2nd Embodiment differs from the concentrated water line L3 of 1st Embodiment.

  In the reverse osmosis membrane separation device 1A of the second embodiment, the concentrated water line L3A includes an upstream concentrated water line L31, a first intermediate concentrated water line L32 branched from the upstream concentrated water line L31, and a second intermediate concentrated water. It has a water line L33 and a downstream concentrated water line L34 where the first intermediate concentrated water line L32 and the second intermediate concentrated water line L33 join.

The upstream concentrated water line L31 is connected to the primary outlet port of the RO membrane module 4 on the upstream side, and the downstream side branches to the first intermediate concentrated water line L32 and the second intermediate concentrated water line L33 at the connection portion J11. doing.
The upstream side of the first intermediate concentrated water line L32 and the second intermediate concentrated water line L33 branches from the upstream concentrated water line L31 at the connection portion J11. The downstream sides of the first intermediate concentrated water line L32 and the second intermediate concentrated water line L33 join the downstream concentrated water line L34 at the connection portion J12.
The upstream side of the downstream concentrated water line L34 is connected to the first intermediate concentrated water line L32 and the second intermediate concentrated water line L33 at the connection portion J12. The downstream side of the downstream concentrated water line L34 branches to the circulating water line L4 and the drainage line L5 at the connection portion J1.

  The constant flow rate variable mechanism unit 50 is provided in the concentrated water line L3A. The constant flow rate variable mechanism unit 50 can maintain the flow rate of the concentrated water W3 flowing through the concentrated water line L3A at a predetermined constant flow rate value and can change the constant flow rate value.

  The constant flow variable mechanism unit 50 includes a first constant flow valve 51, a second constant flow valve 52, and an on-off valve 53. The first constant flow valve 51 and the second constant flow valve 52 are provided in parallel to the concentrated water line L3A. Specifically, the first constant flow valve 51 is provided in the first intermediate concentrated water line L32. The second constant flow valve 52 is provided in the second intermediate concentrated water line L33.

  The first constant flow valve 51 is a device that adjusts the flow rate of the concentrated water W3 flowing through the first intermediate concentrated water line L32 so as to maintain a predetermined constant flow rate value. The second constant flow valve 52 is a device that adjusts the flow rate of the concentrated water W3 flowing through the second intermediate concentrated water line L33 so as to maintain a predetermined constant flow rate value. The constant flow value held in each of the first constant flow valve 51 and the second constant flow valve 52 is a concept having a range in the constant flow value, and is not limited to the target flow value in the constant flow valve. For example, in consideration of the characteristics of the constant flow mechanism (for example, temperature characteristics caused by the material and structure), the constant flow mechanism includes those having an adjustment error of about ± 10% with respect to the target flow rate value. The 1st constant flow valve 51 and the 2nd constant flow valve 52 hold | maintain a fixed flow value without requiring auxiliary power or external operation, for example, what is called by the name of a water governor is mentioned. The first constant flow valve 51 and the second constant flow valve 52 may be operated by auxiliary power or external operation to hold a constant flow value.

  In the present embodiment, the first constant flow valve 51 is a constant flow valve that sets the target flow rate value as the first flow rate value F1 as a constant flow rate value. The second constant flow valve 52 is a constant flow valve that sets the target flow rate value to the second flow rate value F2 as a constant flow rate value. The first flow rate value F1 is set to a 60% flow rate value of the constant flow valve 5 of the first embodiment. Moreover, the 2nd flow value F2 is set to the 40% flow value of the constant flow valve 5 of 1st Embodiment, for example.

  The on-off valve 53 is provided upstream of the second constant flow valve 52 in the second intermediate concentrated water line L33. The on-off valve 53 can open and close the second intermediate concentrated water line L33 in an open state or a closed state. When the on-off valve 53 is open, the on-off valve 53 allows the concentrated water W3 to flow into the second constant flow valve 52. When the on-off valve 53 is closed, the on-off valve 53 prevents the concentrated water W3 from flowing into the second constant flow valve 52. The on-off valve 53 is controlled to be opened and closed by a control unit 10A (constant flow rate control unit) described later.

  In the second embodiment, the flow rate of the concentrated water W3 flowing through the concentrated water line L3A is the total flow rate of the concentrated water flowing through the first intermediate concentrated water line L32 and the second intermediate concentrated water line L33. Specifically, the flow rate of the concentrated water W3 flowing through the concentrated water line L3A is the total flow rate of the concentrated water flowing through the first constant flow valve 51 and the second constant flow valve 52 when the on-off valve 53 is open. When the on-off valve 53 is in the closed state, the flow rate of the concentrated water flowing through the first constant flow valve 51.

  For example, the first constant flow valve 51 is a constant flow valve having a constant flow value and the target flow value is a first flow value F1, and the second constant flow valve 52 is a constant flow value and the target flow value is a second flow value F2. When the on-off valve 53 is open, the flow rate F of the concentrated water W3 flowing through the concentrated water line L3A is the first constant flow valve 51 in the first intermediate concentrated water line L32. And the total flow rate Fs of the concentrated water W3 flowing through the second constant flow valve 52 in the second intermediate concentrated water line L33 (Fs = F1 + F2: 100% flow rate value). When the on-off valve 53 is closed, the flow rate F of the concentrated water W3 flowing through the concentrated water line L3A is the first flow rate of the concentrated water W3 flowing only through the first constant flow valve 51 in the first intermediate concentrated water line L32. Value F1 (60% flow rate value).

  The control unit 10A is configured by a microprocessor (not shown) including a CPU and a memory. Hereinafter, functions of the control unit 10A will be described.

10 A of control parts perform the following various control [1]-[6] similarly to the control part 10 of 1st Embodiment. Since the details of the various controls are as described above, description thereof is omitted.
[1] Water volume control of permeated water W2 [2] Target flow rate increase / decrease control [3] Permeated water W2 recovery rate control [4] Proportional control drainage flow rate control by drain valve 8 [5] Pressure control valve 7 Flow resistance adjustment control [6] Flushing operation control In the present embodiment, the control examples 1 to 3 described in the first embodiment are executed. Since the details of these control examples are as described above, the description thereof is omitted.

<Adjustment control of constant flow value of concentrated water W3>
This adjustment control is executed in association with the above-described increase / decrease control of the target flow rate value, and the constant flow rate variable mechanism unit 50 is the control target.
The control unit 10A (constant flow rate control unit) controls the opening / closing of the on-off valve 53 so as to increase or decrease the constant flow value of the concentrated water W3 flowing through the concentrated water line L3A.
Specifically, the control unit 10A decreases the constant flow value of the concentrated water W3 flowing through the concentrated water line L3A as the target flow value decreases (first target flow value → second target flow value), As the target flow value increases (second target flow value → first target flow value), the constant flow value of the concentrated water W3 flowing through the concentrated water line L3A is increased.

Specifically, when the target flow rate value is set to the second target flow rate value (60% flow rate value), the control unit 10A controls the on-off valve 53 to be closed. As a result, the constant flow rate value of the concentrated water W3 flowing through the concentrated water line L3A is set as a flow rate value (60% flow rate value F1) flowing only through the first constant flow valve 51.
Moreover, 10 A of control parts control the on-off valve 53 to an open state, when a target flow value is set to the 1st target flow value (100% flow value). Accordingly, the constant flow value of the concentrated water W3 flowing through the concentrated water line L3A is set as a flow value (100% flow value Fs) flowing through the first constant flow valve 51 and the second constant flow valve 52.

Adjustment of the circulation ratio of the concentrated water W3 In the present embodiment, while maintaining the flow rate of the concentrated water W3 at a constant 100% flow rate value with the first constant flow valve 51 and the second constant flow valve 52, The flow rate of the permeated water W2 is maintained at a constant 100% flow rate value by controlling the amount of water. In the present embodiment, the flow rate of the permeated water W2 is maintained at a constant 60% by any one of the water amount controls described above while the flow rate of the concentrated water W3 is maintained at a constant 60% flow rate value by the first constant flow valve 51. Hold at flow rate value. As a result, the circulation ratio of the concentrated water W3 is always adjusted to a predetermined value regardless of the increase or decrease of the target flow rate value. The predetermined value of the circulation ratio is approximately “5” as in the first embodiment.

  Next, increase / decrease of the target flow rate value by the control unit 10A, adjustment of the constant flow rate value of the concentrated water W3, and adjustment of the recovery rate will be described. FIG. 11 is a flowchart showing a processing procedure when the control unit 10A of the second embodiment adjusts the constant flow rate value of the concentrated water W3. The process of the flowchart shown in FIG. 11 is repeatedly performed during the operation of the reverse osmosis membrane separation device 1.

  In step ST801 shown in FIG. 11, the control unit 10A acquires the detected water level value W of the water level sensor 91.

  In step ST802, control unit 10A determines whether or not detected water level value W is equal to or lower than set water level L. In Step ST802, when the control unit 10A determines that the detected water level value W ≦ the set water level L (YES), the process proceeds to Step ST803. In Step ST802, when the control unit 10A determines that the detected water level value W> the set water level L (NO), the process proceeds to Step ST805.

  In step ST803 (step ST802: YES), the control unit 10A sets the flow rate of the permeated water W2 to the first target flow rate value. Thus, when the detected water level value W is equal to or lower than the set water level L, in order to increase the water storage amount of the storage tank 9, the target flow rate value of the permeated water W2 becomes the 100% flow rate value that is the rated output. Set the value and execute the selected water amount control.

In step ST804, the control unit 10A controls the on-off valve 53 in the constant flow rate variable mechanism unit 50 to be in an open state.
Here, since the on-off valve 53 is in the open state, the flow rate F of the concentrated water W3 is the first constant flow valve 51 in the first intermediate concentrated water line L32 and the second constant flow valve 52 in the second intermediate concentrated water line L33. Is the total flow rate Fs (100% flow rate value) of the concentrated water W3 flowing through.

  In this case, while the flow rate of the concentrated water W3 is maintained at a constant 100% flow rate value by the first constant flow valve 51 and the second constant flow valve 52, the flow rate of the permeate water W2 is controlled by any of the water amount controls described above. It is held at a constant 100% flow rate value. As a result, the circulation ratio (flow rate of the concentrated water W3 / flow rate of the permeated water W2) is adjusted to a predetermined value (for example, “5”). As a result, the circulation ratio can be maintained at a predetermined value that prevents the membrane surface of the RO membrane module 4 from being blocked.

In step ST805, the control unit 10A adjusts the valve opening degree of the proportional control drain valve 8 in accordance with the selected recovery rate control. The control unit 10A adjusts the valve opening of the proportional control drain valve 8 (that is, the drain flow rate of the concentrated water W3 every time the target flow rate value of the permeate water W2 is changed, regardless of whether the recovery rate is changed or not. Adjust).
For example, when the target flow rate value is set from the second target flow rate value to the first target flow rate value that is twice the second target flow rate value, the control unit 10A sets the drainage flow rate of the concentrated water W32 based on the recovery rate control. The valve opening degree of the proportional control drain valve 8 is adjusted so as to double the current drain flow rate set in the above.
Thus, the process of this flowchart ends (returns to step ST801).

  On the other hand, in step ST806 (step ST802: NO), the control unit 10A determines whether or not the detected water level value W exceeds the set water level L and is not more than the set water level H. In step ST806, when the control unit 10A determines that the set water level L <the detected water level value W ≦ the set water level H (YES), the process proceeds to step ST807. In Step ST806, when the control unit 10A determines that the detected water level value W> the set water level H (NO), the process proceeds to Step ST810.

  In step ST807 (step ST806: YES), the control unit 10A sets the flow rate of the permeated water W2 to the second target flow rate value. The second target flow value is a flow value smaller than the first target flow value. As described above, when the detected water level value W exceeds the set water level L and is equal to or lower than the set water level H, the target flow rate value of the permeated water W2 is set to the second target flow rate value that is 60% flow rate, and then selected. Execute water volume control.

In step ST808, the control unit 10A controls the on-off valve 53 in the constant flow rate variable mechanism unit 50 to be closed.
Here, since the on-off valve 53 is in a closed state, the flow rate F of the concentrated water W3 is the first flow value F1 (60% flow rate) of the concentrated water W3 flowing through the first constant flow valve 51 in the first intermediate concentrated water line L32. Value).

  In this case, while the flow rate of the concentrated water W3 is maintained at a constant 60% flow rate value by the first constant flow valve 51, the flow rate of the permeate water W2 is set to a constant 60% flow rate value by any of the water amount controls described above. Will be retained. As a result, the circulation ratio (flow rate of the concentrated water W3 / flow rate of the permeated water W2) is adjusted to a predetermined value (for example, “5”). Thereby, energy saving is achieved by lowering the rotation speed of the pressurizing pump 2 while maintaining the circulation ratio at a predetermined value that prevents the membrane surface of the RO membrane module 4 from being blocked.

In Step ST809, the control unit 10A adjusts the valve opening degree of the proportional control drain valve 8 in accordance with the selected recovery rate control. The control unit 10A adjusts the valve opening of the proportional control drain valve 8 (that is, the drain flow rate of the concentrated water W3 every time the target flow rate value of the permeate water W2 is changed, regardless of whether the recovery rate is changed or not. Adjust).
For example, when the target flow rate value is set from the first target flow rate value to the second target flow rate value that is half of the first target flow rate value, the control unit 10A sets the drainage flow rate of the concentrated water W32 based on the recovery rate control. The opening degree of the proportional control drain valve 8 is adjusted so as to halve the set current drainage flow rate.
Thus, the process of this flowchart ends (returns to step ST801).

  On the other hand, in step ST810 (step ST806: NO), the control unit 10A controls the inverter 3 so as to stop the pressurizing pump 2. Thus, the process of this flowchart ends (returns to step ST801).

According to the reverse osmosis membrane separation device 1A according to the second embodiment described above, for example, the following effects can be obtained.
In the reverse osmosis membrane separation apparatus 1A according to the second embodiment, the reverse osmosis membrane module 4, the feed water line L1, the permeate water line L2, the concentrated water line L3A, and the circulating water branched from the concentrated water line L3A A line L4, a drain line L5 branched from the concentrated water line L3A, and a concentrated water line L3A are provided in the concentrated water line L3A, and the flow rate of the concentrated water W3 flowing through the concentrated water line L3A is maintained at a predetermined constant flow rate value. Constant flow variable mechanism 50 that can increase or decrease, proportional control drain valve 8 provided in drain line L5, pressurization pump 2 provided in supply water line L1, and inverter 3 that outputs a drive frequency to pressurization pump 2 Then, the control unit 10A that outputs a command signal to the inverter 3 so that the flow rate of the permeate W2 becomes a preset target flow rate value, and the constant flow rate value of the concentrated water W3 is increased or decreased. And a control unit 10A for controlling the constant flow rate variable mechanism unit 50. The pump drive control unit 10 decreases the target flow rate value as the used water amount of the permeated water W2 decreases, and the used water amount of the permeated water W2 As the flow rate increases, the target flow rate value is increased, and as the target flow rate value decreases, the control unit 10A decreases the constant flow rate value of the concentrated water W3 flowing through the concentrated water line L3A and increases the target flow rate value. The constant flow rate value of the concentrated water W3 flowing through the concentrated water line L3A is increased.

  Therefore, the circulation ratio (the flow rate of the concentrated water W3 / the flow rate of the permeated water W2) can always be adjusted to a predetermined value (for example, “5”) regardless of the increase or decrease of the target flow rate value. Thereby, the state in which the concentrated water W3 having an excessive flow rate is sent to the concentrated water line L3A is eliminated, and the power consumption of the pressure pump can be suppressed.

In the reverse osmosis membrane separation device 1A according to the second embodiment, the constant flow variable mechanism 50 includes a first constant flow valve 51 and a second constant flow valve 52 arranged in parallel to the concentrated water line L3A, An open / close valve 53 that can be opened and closed to permit or block the flow of the concentrated water W3 to the second constant flow valve 52, and the control unit 10A is configured to keep the concentrated water W3 flowing through the concentrated water line L3A constant. The opening / closing of the on-off valve 53 is controlled so as to increase or decrease the flow rate value.
Therefore, the first constant flow valve 51 and the second constant flow valve 52 are arranged in parallel in the concentrated water line L3A, and the constant flow value of the concentrated water W3 is adjusted stepwise simply by controlling the opening and closing of the on-off valve 53. can do. Thereby, the state where the concentrated water W3 having an excessive flow rate is sent to the concentrated water line L3A is eliminated with a simple configuration, and the power consumption of the pressure pump can be suppressed.

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, as the pressure adjusting means, the pressure adjustment valve 7 is configured to be able to control the valve opening degree by the control unit 10, but is not limited thereto. For example, the pressure adjusting means may be a valve, an orifice, or the like that maintains the flow path cross-sectional area at a constant area without requiring auxiliary power or external operation, and may be called, for example, the name “throttle”. Further, the pressure adjusting means may be used by adjusting the cross-sectional area of the flow path before use, and maintaining the cross-sectional area of the flow path at a constant area during use.

  1st Embodiment demonstrated the example which detects the temperature of the supply water W1 in temperature feedforward collection | recovery rate control. For example, the temperature of the permeated water W2 or the concentrated water W3 (W31, W32) obtained by the RO membrane module 4 may be detected.

  1st Embodiment demonstrated the example which adjusts the waste_water | drain flow volume of the concentrated water W3 by controlling the valve opening degree of the proportional control drain valve 8 in each recovery rate control. However, the present invention is not limited to this, and a plurality of drain valves may be provided in parallel, and the drain flow rate of the concentrated water W3 may be controlled in stages by increasing or decreasing the number of drain valves opened. Thereby, the waste_water | drain flow volume of the concentrated water W3 can be adjusted.

  Moreover, in 1st Embodiment, although 2nd electric conductivity sensor EC2 was provided in the concentrated water line L3, it is not restrict | limited to this. The position where the second electrical conductivity sensor EC2 is provided may be a position where the concentrated water W3 can be detected. For example, the second electrical conductivity sensor EC2 may be provided in the drainage line L5 or the circulating water line L4.

  Moreover, in 1st Embodiment, although the water level of the permeated water W2 detected by detecting the water level of the permeated water W2 stored by the storage tank 9 was grasped | ascertained, it is not restrict | limited. For example, it may be grasped from the flow rate of the permeated water W2 delivered from the storage tank 9, or may be grasped from the flow rate of water consumed at the demand point on the downstream side of the water supply line L6.

  In the second embodiment, the flow rate of the concentrated water W3 can be adjusted in two stages corresponding to the target flow rate values of the two-stage permeate water W2 (first target flow rate value and second target flow rate value). The constant flow variable mechanism 50 is configured to include two constant flow valves 51 and 52 and one open / close valve 53, but is not limited thereto. For example, when the target flow rate value of the permeated water W2 is increased or decreased in three or more stages, the constant flow variable mechanism 50 may include three or more constant flow valves and two or more open / close valves. By increasing the number of constant flow valves and open / close valves, the constant flow value of the concentrated water W3 can be set finely, making it easy to adjust the circulation ratio to a predetermined value even when the target flow value is increased or decreased in multiple stages. Become.

1,1A Reverse Osmosis Membrane Separator 2 Pressure Pump 3 Inverter 4 RO Membrane Module (Reverse Osmosis Membrane Module)
5 Constant flow valve (constant flow means)
7 Pressure adjusting valve (pressure adjusting means)
8 Proportional control drain valve (Proportional control valve, drain flow rate adjusting means)
10, 10A control unit (pump drive control unit, constant flow rate control unit, drainage control unit, pressure adjustment control unit)
50 Constant flow variable mechanism (constant flow variable means)
51 First constant flow valve (constant flow valve)
52 Second constant flow valve (constant flow valve)
53 On-off valve L1 Supply water line L2 Permeate water line L3 Concentrated water line L4 Circulating water line L5 Drainage line TE Temperature sensor (temperature detection means)
FM1 first flow rate sensor (first flow rate detection means)
FM2 second flow rate sensor (second flow rate detection means)
EC2 Second electrical conductivity sensor (electrical conductivity measuring means)
W1 Supply water W2 Permeated water W3 Concentrated water W31 Part of concentrated water W32 The remainder of 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 permeate line for delivering permeate separated by the reverse osmosis membrane module;
A concentrated water line for delivering concentrated water separated by the reverse osmosis membrane module;
A circulating water line branched from the concentrated water line and returning a part of the concentrated water separated by the reverse osmosis membrane module to the upstream side of the reverse osmosis membrane module;
A drainage line that branches off from the concentrated water line and discharges the remainder of the concentrated water separated by the reverse osmosis membrane module to the outside of the device;
Constant flow rate variable means provided in the concentrated water line, capable of maintaining the flow rate of the concentrated water flowing through the concentrated water line at a predetermined constant flow rate value and increasing or decreasing the constant flow rate value;
A drainage flow rate adjusting means provided in the drainage line and capable of adjusting the drainage flow rate of the concentrated water discharged outside the device,
A pressure pump provided in the supply water line, driven at a rotational speed corresponding to the input drive frequency, and sucks the supply water and discharges it toward the reverse osmosis membrane module;
An inverter that outputs a driving frequency corresponding to the input command signal to the pressurizing pump;
The drive frequency of the pressurizing pump is calculated using a physical quantity in the system so that the flow rate of the permeated water becomes a preset target flow rate value, and a command signal corresponding to the calculated value of the drive frequency is sent to the inverter. A pump drive control unit for outputting;
A constant flow rate controller that controls the constant flow rate variable means to increase or decrease the constant flow rate value of the concentrated water flowing through the concentrated water line,
The pump drive control unit decreases the target flow value as the amount of permeated water used decreases, and increases the target flow value as the amount of permeated water used increases.
The constant flow control unit decreases the constant flow value of the concentrated water flowing through the concentrated water line as the target flow value decreases, and reduces the concentrated water line as the target flow value increases. A reverse osmosis membrane separation device for increasing the constant flow rate of concentrated water flowing. The constant flow variable means permits the inflow of concentrated water to any one or more constant flow valves of the plurality of constant flow valves arranged in parallel to the concentrated water line and the plurality of constant flow valves, or One or more on-off valves that can be opened and closed to prevent,
2. The reverse osmosis membrane separation device according to claim 1, wherein the constant flow rate control unit controls opening and closing of the one or more on-off valves so as to increase or decrease the constant flow rate value of the concentrated water flowing through the concentrated water line. . Comprising a first flow rate detecting means for detecting the flow rate of the permeated water,
The pump drive control unit calculates a drive frequency of the pressurizing pump so that a detected flow rate value of the first flow rate detection unit becomes the target flow rate value;
The reverse osmosis membrane separation apparatus according to claim 1 or 2. Temperature detection means for detecting the temperature of the supply water, permeate or concentrated water;
A drainage control unit for controlling the drainage flow rate adjusting means,
The drainage control unit (i) calculates an allowable concentration rate of silica in the concentrated water based on the silica concentration determined in advance from the silica concentration of the feed water obtained in advance and the detected temperature value of the temperature detecting means, ii) calculating the drainage flow rate from the calculated value of the permissible concentration factor and the target flow rate value of the permeated water, and (iii) adjusting the drainage flow rate so that the actual drainage flow rate of the concentrated water becomes the calculated value of the drainage flow rate. Control means,
The reverse osmosis membrane separation apparatus as described in any one of Claims 1-3. A proportional control valve as the drainage flow rate adjusting means;
A second flow rate detecting means for detecting the drainage flow rate of the concentrated water,
The drainage control unit adjusts the valve opening of the proportional control valve so that the detected flow rate value of the second flow rate detection means becomes the calculated value of the drainage flow rate.
The reverse osmosis membrane separator according to claim 4.

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