JP2014184380A - Water treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treatment apparatus capable of producing permeated water at flow rate corresponding to the water amount being used at demand points, at minimum necessary pump power.SOLUTION: A water treatment apparatus 1 comprises: a reverse osmosis membrane module 7; flow rate detection means to detect the flow rate of permeated water; a pump 5 that is driven at a rotational speed corresponding to a drive frequency input and sucks in supply water W1 and discharges it toward the reverse osmosis membrane module 7; an inverter 6 that outputs, to the pump 5, a drive frequency which corresponds to a command signal; and a control section 30 that calculates a drive frequency of the pump 5 by using feedback control algorithm so that the flow rate value detected by the flow rate detection means becomes a preset target flow rate value, and outputs, to the inverter 6, a command signal which corresponds to a calculated value of the drive frequency, and is characterized in that the control section 30 decreases the target flow rate value as the water use amount at demand points decreases and increases the target flow rate value as the water use amount at demand points increases.

Description

  The present invention relates to a water treatment apparatus including a reverse osmosis membrane module that separates supplied water into permeated water and concentrated water.

  High-purity pure water that does not contain impurities is used in the manufacture of pharmaceuticals and cosmetics, the cleaning of electronic parts and precision equipment, and the like. This type of pure water is generally produced by subjecting supply water such as ground water and tap water to membrane separation treatment with a reverse osmosis membrane module and purifying the obtained permeated water. The reverse osmosis membrane module is configured by housing a single or a plurality of reverse osmosis membrane elements in a pressure vessel. Hereinafter, the reverse osmosis membrane module is also referred to as “RO membrane module”, the reverse osmosis membrane element as “RO membrane element”, and the reverse osmosis membrane used for the RO membrane element as “RO membrane”.

  In the water treatment apparatus provided with the RO membrane module, the flow rate of the permeated water is set in advance so that the maximum amount of water consumed at the demand point can be covered. On the other hand, the RO membrane has a water permeability coefficient that varies depending on the temperature of the supplied water and the state of the membrane (pore blockage and oxidative deterioration of the material). That is, the flow rate of the permeate varies depending on the temperature of the feed water and the state of the membrane. Therefore, flow rate feedback water volume control and pressure feedback water volume control are performed as a method of operating while maintaining the flow rate of permeate water constant (see Patent Document 1). For example, in the flow rate feedback water amount control, an inverter controls the drive frequency of the pump that sends the supplied water to the RO membrane module so that the detected flow rate value of the permeated water becomes a preset target flow rate value.

JP 2000-271459 A

  By the way, in the recent water treatment apparatus provided with the RO membrane module, a so-called high output operation (high flux operation) in which the permeated water flow rate per module is increased is tried. When the RO membrane module is operated at a high output, even if the number of modules (that is, the membrane area) is reduced, a flow rate equivalent to the conventional case can be obtained. Therefore, the introduction cost of the water treatment device can be reduced by reducing the number of modules.

  However, the above-described flow rate feedback water amount control maintains the flow rate of the permeate water constant, and the pump is operated in a predetermined drive frequency range regardless of the amount of water used at the demand location. Therefore, when the amount of water used at the demand point decreases during high output operation, the power consumed by the pump becomes relatively larger than when the pump is operated at a driving frequency corresponding to the amount of water used. Further, if the high output operation is continued, fouling is likely to be promoted depending on the quality of the supplied water, and there is a concern that RO membrane clogging may occur at an early stage.

  Accordingly, an object of the present invention is to provide a water treatment apparatus capable of producing permeated water having a flow rate corresponding to the amount of water used at a demand location with the minimum necessary pump power.

  The present invention includes a reverse osmosis membrane module that separates feed water into permeate and concentrated water, flow rate detection means that detects the flow rate of permeate, and a rotational speed that is driven according to an input drive frequency. A pump that inhales and discharges the gas toward the reverse osmosis membrane module, an inverter that outputs a driving frequency corresponding to an input command signal to the pump, and a target in which a detected flow rate value of the flow rate detecting means is set in advance A control unit that calculates a driving frequency of the pump by a feedback control algorithm so as to be a flow rate value, and outputs a command signal corresponding to the calculated value of the driving frequency to the inverter. A water treatment apparatus that decreases the target flow rate value as the amount of water used at a point decreases and increases the target flow rate value as the amount of water used at a demand point increases. To.

  Further, a storage tank for storing permeated water, and a water level detecting means for detecting a water level of the permeated water in the storage tank, the control unit, as the detected water level value of the water level detecting means increases, It is preferable to decrease the target flow rate value and increase the target flow rate value as the detected water level value of the water level detection means decreases.

  In addition, a drainage means capable of adjusting the drainage flow rate and the circulation flow rate of the concentrated water is provided, and when the target flow rate value is changed, the control unit is preset with a permeate recovery rate and a concentrate water circulation ratio. It is preferable to control the drainage means so that the value is maintained.

  Further, the control unit recovers the permeated water when the detected water level value of the water level detecting means becomes smaller than a preset lower limit water level value and the reverse osmosis membrane module is in a high output operation state. It is preferable to control the drainage means so that the rate is lower than a preset value.

  Further, the apparatus further comprises water temperature detecting means for detecting the water temperature of the supplied water, and the control unit detects the detected water level value of the water level detecting means only when the detected water temperature value of the water temperature detecting means is equal to or lower than a preset water temperature value. It is preferable to execute the control to decrease the target flow rate value as the value increases.

  ADVANTAGE OF THE INVENTION According to this invention, the water treatment apparatus which can manufacture the permeated water of the flow volume according to the amount of water used in a demand location with minimum required pump electric power can be provided.

1 is an overall schematic diagram of a pure water production apparatus 1 according to a first embodiment. It is the front | former part of the whole block diagram of the pure water manufacturing apparatus 1 which concerns on 1st Embodiment. It is the middle stage part of the whole block diagram of the pure water manufacturing apparatus 1 which concerns on 1st Embodiment. It is a back | latter stage part of the whole block diagram of the pure water manufacturing apparatus 1 which concerns on 1st Embodiment. It is explanatory drawing which shows the relationship between the water level of the storage tank 17, and the flow volume of the permeated water W2 manufactured. 4 is a flowchart illustrating a processing procedure when a target flow rate value and a recovery rate are set in the control unit 30. 5 is a flowchart showing a processing procedure when flow rate feedback water amount control is executed in the control unit 30. It is the whole schematic diagram of the pure water manufacturing apparatus 1A which concerns on 2nd Embodiment. It is the 1st middle stage part of the whole block diagram of the pure water manufacturing apparatus 1A which concerns on 2nd Embodiment. It is the 2nd middle stage part of the whole block diagram of the pure water manufacturing apparatus 1A which concerns on 2nd Embodiment. It is a back | latter stage part of the whole block diagram of the pure water manufacturing apparatus 1A which concerns on 2nd Embodiment.

Hereinafter, an embodiment when the water treatment apparatus according to the present invention is applied to a pure water production apparatus will be described.
(First embodiment)
First, the pure water manufacturing apparatus 1 which concerns on 1st Embodiment is demonstrated, referring drawings. FIG. 1 is an overall schematic diagram of a pure water production apparatus 1 according to the first embodiment. FIG. 2A is a front part of the overall configuration diagram of the pure water producing apparatus 1 according to the first embodiment. FIG. 2B is a middle part of the entire configuration diagram of the pure water producing apparatus 1 according to the first embodiment. FIG. 2C is a rear part of the entire configuration diagram of the pure water producing apparatus 1 according to the first embodiment. The pure water production apparatus 1 according to the present embodiment is applied to, for example, a pure water production apparatus that produces demineralized water (deionized water) from raw water (for example, tap water). The desalinated water produced by the pure water production apparatus 1 is sent as pure water to a demand location or the like. In the pure water production apparatus 1 according to the present embodiment, supplying pure water to a demand point or the like is also referred to as “water sampling”.

  As shown in FIG. 1, the pure water manufacturing apparatus 1 according to the first embodiment includes a first optional device OP1, a prefilter 4, a second optional device OP2, a pressurizing pump 5, an inverter 6, and a reverse RO membrane module 7 as the osmotic membrane module, third optional device OP3, first flow path switching valve V71, electrodeionization stack (hereinafter also referred to as “EDI stack”) 16, and second flow path switching valve V72, 4th option apparatus OP4, the storage tank 17, the control part 30, the input operation part 40, the DC power supply device 50, and the display part 60 are provided.

  The first option device OP <b> 1 to the fourth option device OP <b> 4 are devices installed in the pure water production apparatus 1 as optional equipment that can be attached to and detached from the pure water production apparatus 1. The first optional device OP <b> 1 includes a water softener 2 and an activated carbon filter 3. The second optional device OP2 includes a hardness sensor S1 and a residual chlorine sensor S2. The third optional device OP3 includes a decarboxylation device 15. The fourth optional device OP4 includes a second specific resistance sensor RS2, a total organic carbon sensor TOC, and a third temperature sensor TE3.

  In addition, as shown in FIG. 1, the pure water production apparatus 1 includes a supply water line L1, a permeate water line L21, an RO permeate return line L41, an RO concentrated water return line L51, and a desalted water line L3. A demineralized water return line L42, an EDI concentrated water line L52, and a water supply line L4 are provided. The “line” in the present specification is a general term for lines capable of flowing a fluid such as a flow path, a radial path, and a pipeline.

  2A to 2C, in addition to the configuration shown in FIG. 1, the pure water production apparatus 1 includes a first on-off valve V11 to a seventh on-off valve V17, a vacuum breaker valve V41, and a pressure reducing valve V42. Supply water supply valve V31, first drain valve V32 to third drain valve V34 and proportional control valve V50 as drain means, first constant flow valve V51 to fourth constant flow valve V54, and first check valve Valve V61 to fifth check valve V65, first pressure gauge P1 to sixth pressure gauge P6, first pressure sensor PS1 to fourth pressure sensor PS4, pressure switch PSW, and first temperature as water temperature detecting means Sensor TE1 and second temperature sensor TE2, first flow sensor FM1 and second flow sensor FM2 as flow detection means, first conductivity sensor EC1, first specific resistance sensor RS1, and water level detection means A water level sensor 171 .

  In FIG. 1 and FIG. 2A to FIG. 2C, the electrical connection path is omitted, but the control unit 30 includes the supply water replenishment valve V31, the first flow path switching valve V71, the second flow path switching valve V72, and the first. Drain valve V32 to third drain valve V34, pressure switch PSW, first temperature sensor TE1 to third temperature sensor TE3, first pressure sensor PS1 to fourth pressure sensor PS4, first flow rate sensor FM1 and second flow rate sensor FM2, The first electrical conductivity sensor EC1, the first specific resistance sensor RS1 and the second specific resistance sensor RS2, the total organic carbon sensor TOC, the hardness sensor S1, the residual chlorine sensor S2, the water level sensor 171 and the like are electrically connected.

First, the front part of the overall configuration diagram in the pure water production apparatus 1 will be described.
As shown in FIGS. 1 and 2A, the supply water W1 flows through the supply water line L1. The supply water line L1 is a line through which the supply water W1 is circulated to the RO membrane module 7. The supply water line L1 includes a first supply water line L11 and a second supply water line L12.

  The raw water W11 (supply water W1) flows through the first supply water line L11. The first supply water line L11 is a line that connects a supply source (not shown) of the raw water W11 and the water softener 2. The upstream end of the first supply water line L11 is connected to a supply source (not shown) of the raw water W11. Further, the downstream end of the first supply water line L <b> 11 is connected to the water softener 2.

  As shown in FIG. 2A, the first supply water line L11 is provided with a connecting portion J1, a first on-off valve V11, and a water softener 2 in order from the upstream side. The first on-off valve V11 is a manual valve that can be operated to open and close the first supply water line L11.

  The water softener 2 is an apparatus that manufactures the soft water W12 (feed water W1) by replacing the hardness component contained in the raw water W11 with sodium ions. The water softener 2 has an ion exchange tower containing a cation exchange resin bed in a pressure tank.

  Soft water W12 (supply water W1) flows through the second supply water line L12. The second supply water line L12 is a line through which the soft water W12 is circulated to the RO membrane module 7. The second supply water line L <b> 12 is a line that connects the water softener 2 and the RO membrane module 7. As shown in FIG. 2A, the upstream end of the second supply water line L <b> 12 is connected to the water softener 2. As shown in FIG. 2B, the downstream end of the second supply water line L12 is connected to the primary inlet port (inlet for the supply water W1) of the RO membrane module 7.

  As shown in FIG. 2A, in order from the upstream side, the second on-off valve V12, the connecting portion J2, the third on-off valve V13, the activated carbon filter 3, the fourth on-off valve V14, and the connecting portion are connected to the second supply water line L12. J3, the prefilter 4, the connection part J4, and the connection part J5 are provided. Further, after the connecting portion J5, as shown in FIG. 2B, the fifth on-off valve V15, the connecting portion J6, the pressure reducing valve V42, the supply water replenishing valve V31, the connecting portion J59, the connecting portion J51, the connecting portion J7, and the connecting portion. J8, pressurizing pump 5, connecting portion J9, and RO membrane module 7 are provided. The second on-off valve V12 to the fifth on-off valve V15 are manual valves that can be operated to open and close the second supply water line L12. The supply water supply valve V31 is an automatic valve that can control the opening and closing of the second supply water line L12. The supply water supply valve V31 is electrically connected to the control unit 30. The opening and closing of the supply water replenishing valve V31 is controlled by a flow path opening / closing signal transmitted from the control unit 30.

  The activated carbon filter 3 is a device that removes chlorine components (mainly free residual chlorine) contained in the soft water W12 (feed water W1). The activated carbon filter 3 has a filtration tower in which a filter medium bed made of activated carbon is housed in a pressure tank. The activated carbon filter 3 purifies the soft water W12 (feed water W1) by decomposing and removing the chlorine component contained in the soft water W12, adsorbing and removing organic components, and capturing suspended substances.

  The prefilter 4 is a filter that removes fine particles contained in the soft water W12 (supply water W1) purified by the activated carbon filter 3. The prefilter 4 is configured by accommodating a filter element in a housing. As the filter element, for example, a nonwoven fabric filter element or a thread-wound filter element having a filtration accuracy of 1 to 50 μm is used.

  The hardness sensor S1 is a device that measures the total hardness (that is, the hardness leak amount) of the supply water W1 flowing through the supply water line L1. The residual chlorine sensor S2 is a device that measures the free residual chlorine concentration (that is, chlorine leak amount) of the supply water W1 flowing through the supply water line L1. As shown in FIG. 2A, the hardness sensor S1 and the residual chlorine sensor S2 are connected to the supply water line L1 at the connection portion J5 via the measurement line L110. The connecting part J5 is disposed between the prefilter 4 and the fifth on-off valve V15 in the supply water line L1. The hardness sensor S1 and the residual chlorine sensor S2 are electrically connected to the control unit 30. The hardness leak amount measured by the hardness sensor S1 and the chlorine leak amount measured by the residual chlorine sensor S2 are transmitted to the control unit 30 as detection signals, respectively.

Next, the middle part of the overall configuration diagram in the pure water production apparatus 1 will be described.
As shown in FIG. 2B, a vacuum breaker valve V41 is connected to the connecting portion J6. The vacuum breaker valve V41 is a normally closed pressure operating valve, and when the pressure inside the supply water line L1 becomes lower than the atmospheric pressure, the valve body opens and sucks air. By providing the vacuum breaker valve V41, even if the raw water W11 (feed water W1) is cut off and the feed water line L1 becomes negative pressure, it is possible to prevent problems such as damage to the membrane of the RO membrane module 7. it can.

  The pressure reducing valve V42 is a device that adjusts the pressure of the soft water W12 that has passed through the water softener 2, the activated carbon filter 3, and the prefilter 4 to a pressure lower than the pressure of the concentrated water W3 flowing out from the RO membrane module 7. The pressure reducing valve V42 adjusts the pressure of the soft water W12 so that the pressure of the concentrated water W3 is larger than the pressure of the soft water W12 (pressure of the soft water W12 <pressure of the concentrated water W3). Thereby, a part of the concentrated water W3 is circulated to the soft water W12, and the supply water in which the concentrated water W3 is mixed with the soft water W12 is supplied to the RO membrane module 7. That is, in the RO membrane module 7, a cross-flow type separation operation for producing permeated water is performed while circulating the supply water by the pressure pump 5.

  The downstream end of the desalted water return line L42 described later is connected to the connecting portion J59. The connecting portion J51 is connected to the downstream end portion of the RO permeate return line L41, which will be described later, and the downstream end portion of the RO concentrated water return line L51.

  The pressurizing pump 5 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 7. The pressurizing pump 5 is supplied with driving power whose frequency is converted from the inverter 6. The pressurizing pump 5 is driven at a rotational speed corresponding to the frequency of the supplied driving power (hereinafter also referred to as “driving frequency”).

  The inverter 6 is an electric circuit (or a device having the circuit) that supplies driving power whose frequency is converted to the pressure pump 5. The inverter 6 is electrically connected to the control unit 30. A command signal is input to the inverter 6 from the control unit 30. The inverter 6 outputs driving power having a driving frequency corresponding to the command signal (current value signal or voltage value signal) input by the control unit 30 to the pressurizing pump 5.

  The RO membrane module 7 separates the supply water W1 pumped by the pressurizing pump 5 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 7 is configured by accommodating a single or a plurality of spiral RO membrane elements in a pressure vessel (vessel). Examples of the RO membrane used in the RO membrane element include a crosslinked aromatic polyamide composite membrane. Examples of RO membrane elements composed of a crosslinked aromatic polyamide composite membrane include: Toray Industries, Inc .: model name “TMG20-400”, Eunjin Chemical Co., Ltd .: model name: “RE8040-BLF”, Nitto Denko Corporation: model name: “ESPA1” Are commercially available, and these elements can be suitably used.

  The RO concentrated water return line L51 is a line for returning a part W31 of the concentrated water W3 separated by the RO membrane module 7 to the supply water line L1. The upstream end of the RO concentrated water return line L51 is connected to the primary outlet port (the outlet of the concentrated water W3) of the RO membrane module 7. The downstream end of the RO concentrated water return line L51 is connected to the supply water line L1 at the connection J51. The RO concentrated water return line L51 is provided with a first check valve V61 and a proportional control valve V50 as drainage means.

  The proportional control valve V50 is a valve that adjusts the flow rate (circulation flow rate) of the concentrated water W3 returned to the RO concentrated water return line L51. The proportional control valve V50 is electrically connected to the control unit 30. The valve opening degree of the proportional control valve V50 is controlled by a drive signal transmitted from the control unit 30. The circulating flow rate of the concentrated water W3 can be adjusted by transmitting a current value signal (for example, 4 to 20 mA) from the control unit 30 to the proportional control valve V50 and controlling the valve opening degree. By this adjustment, the circulation ratio of the concentrated water W3 can be maintained at a preset value. The circulation ratio of the concentrated water W3 is the ratio of the flow rate of the permeated water W2 flowing out from the secondary side port of the RO membrane module to the flow rate of the concentrated water W3 flowing out from the primary side outlet port (the flow rate of the concentrated water W3 / The flow rate of the permeated water W2. In the first embodiment including the single-stage RO membrane module 7, the circulation ratio is about 5 as a guide. Further, in the second embodiment (described later) including the two-stage RO membrane modules 10 and 14, the circulation ratio of the front stage is about 5, and the circulation ratio of the rear stage is about 3.

  The RO concentrated water discharge line L61 is a line for discharging the remaining portion W32 of the concentrated water W3 separated by the RO membrane module 7 from the middle of the RO concentrated water return line L51 to the outside of the apparatus. The upstream end portion of the RO concentrated water discharge line L61 is connected to the connection portion J53. The connecting portion J53 is disposed between the RO membrane module 7 and the connecting portion J52 in the RO concentrated water return line L51. The upstream end portions of the first concentrated water drain line L611, the second concentrated water drain line L612, and the third concentrated water drain line L613 are connected to the RO concentrated water discharge line L61 at the connecting portions J55 and J56.

  The first concentrated water drain line L611 to the third concentrated water drain line L613 are provided with a first drain valve V32 to a third drain valve V34, and a first constant flow valve V51 to a third constant flow valve V53, respectively. Yes. The first constant flow valve V51 to the third constant flow valve V53 are set to different flow values. The first drainage valve V32 to the third drainage valve V34 can individually open and close the first concentrated water drainage line L611 to the third concentrated water drainage line L613. By appropriately selecting the number of the first drain valve V32 to the third drain valve V34 that are opened, the drainage flow rate of the concentrated water W3 discharged to the outside of the apparatus can be adjusted. By this adjustment, the recovery rate of the permeated water W2 can be maintained at a preset value. The recovery rate of the permeated water W2 is the ratio (%) of the permeated water W2 to the flow rate of the soft water W12 supplied to the RO membrane module 7 (the supplied water W1 before the part W31 of the concentrated water W3 is mixed). Say.

  The first drain valve V32 to the third drain valve V34 are electrically connected to the control unit 30, respectively. Opening and closing of the first drain valve V32 to the third drain valve V34 is controlled by a drive signal transmitted from the control unit 30.

  The downstream ends of the first concentrated water drainage line L611, the second concentrated water drainage line L612, and the third concentrated water drainage line L613 are connected to the upstream end of the merged drainage line L62 at the connecting portions J57 and J58. Has been. The downstream end portion of the combined drainage line L62 is connected or opened to a drainage pit (not shown), for example. A second check valve V62 is provided in the middle of the combined drainage line L62.

  The permeated water line L <b> 21 is a line through which the permeated water W <b> 2 separated by the RO membrane module 7 flows through the EDI stack 16. As shown in FIGS. 2B and 2C, the permeate water line L21 includes a front-stage permeate water line L211, a middle-stage permeate water line L212, a desalting chamber inflow line L213, and a concentration chamber inflow line L214.

  As shown in FIG. 2B, the upstream end of the front-stage permeate line L211 is connected to the secondary port (the outlet of the permeate W2) of the RO membrane module 7. As shown in FIG. 2C, the downstream end of the front-stage permeate line L211 is connected to the middle-stage permeate line L212 and the RO permeate return line L41 via the first flow path switching valve V71. .

  As shown in FIG. 2B, a upstream side permeate line L211 is provided with a third check valve V63, a connection portion J10, a connection portion J11, and a sixth on-off valve V16 in order from the upstream side. Further, after the sixth on-off valve V16, as shown in FIG. 2C, a decarboxylation device 15, a connection portion J31, a connection portion J32, and a first flow path switching valve V71 are provided. The 6th on-off valve V16 is a manual valve which can operate opening and closing of the front | former stage side permeated water line L211.

Next, the latter part of the entire configuration diagram in the pure water production apparatus 1 will be described.
In FIG. 2C, the decarboxylation device 15 is a facility that obtains degassed water (degassed permeated water) by degassing the free carbonic acid (dissolved carbon dioxide gas) contained in the permeated water W2 with a gas separation membrane module. . By providing the decarboxylation device 15 on the downstream side of the RO membrane module 7, free carbon dioxide that easily permeates the RO membrane can be removed from the permeated water W <b> 2. Accordingly, it is possible to obtain the permeated water W2 having a higher purity. In the decarboxylation device 15 of the present embodiment, an external perfusion type gas separation membrane module made of a hollow fiber membrane is used, and a sweep gas such as air is introduced while the inside of the hollow fiber membrane is sucked by a vacuum pump (not shown). The free carbon dioxide is exhausted while being transferred into the sweep gas through the membrane wall. As a gas separation membrane module suitable for such an application, for example, a product name “Liqui-Cel G-521R” manufactured by Celgard Co., Ltd. may be mentioned. The vacuum pump connected to the gas separation membrane module is electrically connected to the control unit 30.

  The first flow path switching valve V71 is a flow path (water sampling side flow path) for flowing the permeated water W2 separated by the RO membrane module 7 toward the EDI stack 16 via the middle permeate water line L212. The automatic valve can be switched to a flow path (circulation-side flow path) that circulates toward the supply water line L1 on the upstream side of the RO membrane module 7 via the RO permeate return line L41. The first flow path switching valve V71 is configured by, for example, an electric or electromagnetic three-way valve. The first flow path switching valve V71 is electrically connected to the control unit 30. The switching of the flow path in the first flow path switching valve V71 is controlled by a flow path switching signal transmitted from the control unit 30.

  The RO permeated water return line L41 is a line that returns the permeated water W2 separated by the RO membrane module 7 to the supply water line L1 upstream of the RO membrane module 7. The upstream end of the RO permeate return line L41 is connected to the first flow path switching valve V71. The downstream end of the RO permeate return line L41 is connected to the RO concentrated water return line L51 at the connection J52. The connection part J52 is arrange | positioned between the connection part J53 and the connection part J51 in RO concentrated water return line L51. The portion from the connecting portion J52 to the connecting portion J51 in the RO permeate return line L41 is common to the portion from the connecting portion J52 to the connecting portion J51 in the RO concentrated water return line L51. A fourth check valve V64 is provided on the upstream side of the RO permeate return line L41.

  The upstream end of the middle permeate line L212 is connected to the first flow path switching valve V71. The downstream end of the middle permeate water line L212 is connected to the upstream end of the desalting chamber inflow line L213 and the upstream end of the concentrating chamber inflow line L214 at the branch J71.

  The downstream end of the desalting chamber inflow line L213 is connected to the primary port of the EDI stack 16 (inlet side of the desalting chamber 161). A connecting portion J33 is disposed in the desalting chamber inflow line L213. The downstream end of the concentrating chamber inflow line L214 is connected to a primary port (each inlet side of the concentrating chamber 162) of the EDI stack 16. The concentrating chamber inflow line L214 is provided with a fourth constant flow valve V54 and a connecting portion J34 in order from the upstream side.

  The EDI stack 16 is a water treatment device that obtains demineralized water W6 (deionized water) and concentrated water W7 by demineralizing the permeated water W2 separated by the RO membrane module 7 (deionized treatment). The EDI stack 16 is electrically connected to a DC power supply device 50 (see FIG. 1). A DC voltage is applied to the EDI stack 16 from the DC power supply device 50. The EDI stack 16 is energized by the DC voltage applied from the DC power supply device 50 and operates.

  The DC power supply device 50 applies a DC voltage between the pair of electrodes of the EDI stack 16. The DC power supply device 50 is electrically connected to the control unit 30. The DC power supply device 50 outputs a DC voltage to the EDI stack 16 in response to the command signal input by the control unit 30.

  In the EDI stack 16, a cation exchange membrane and an anion exchange membrane (not shown) are alternately arranged between a pair of electrodes. The inside of the EDI stack 16 is partitioned into a desalting chamber 161 and a concentration chamber 162 (including an anode chamber and a cathode chamber) by these ion exchange membranes. The desalting chamber 161 is filled with an ion exchanger (not shown). As an ion exchanger filled in the desalting chamber 161, for example, an ion exchange resin or an ion exchange fiber is used. In FIG. 2C, a plurality of desalting chambers 161 and concentration chambers 162 partitioned inside the EDI stack 16 are schematically shown.

  A desalting chamber inflow line L213 through which the permeated water W2 flows is connected to the inlet side of the desalting chamber 161. On the outlet side of the desalting chamber 161, a desalted water line L3 through which the desalted water W6 discharged from the ions in the desalting chamber 161 is discharged is connected. A concentrating chamber inflow line L214 through which the permeated water W2 flows is connected to the inlet side of the concentrating chamber 162. An EDI concentrated water line L52 for circulating the concentrated water W7 that has been concentrated and discharged is connected to the outlet side of the concentration chamber 162.

  The permeated water W2 flowing through the permeated water line L21 flows into each of the desalting chamber 161 and the concentration chamber 162. Residual ions contained in the permeated water W2 are captured by an ion exchanger (not shown) filled in the desalting chamber 161 to become desalted water W6. The desalted water W6 is sent to the demand location via the desalted water line L3 (described later). Further, residual ions captured by the ion exchanger in the desalting chamber 161 move to the concentration chamber 162 by the electric energy of the applied DC voltage. And the water containing a residual ion is sent out toward the decarbonation apparatus 15 through the EDI concentrated water line L52 (after-mentioned) as the concentrated water W7. The concentrated water W7 sent to the decarboxylation device 15 is used as sealing water for the vacuum pump, and is then discharged out of the device via a sealing water discharge line L71 (described later).

  The desalted water line L3 is a line for sending the desalted water W6 obtained by the EDI stack 16 to the demand point as pure water. The demineralized water line L3 includes an upstream demineralized water line L31 and a downstream demineralized water line L32.

  The upstream end of the upstream demineralized water line L31 is connected to the secondary port of the EDI stack 16 (the outlet side of the demineralized chamber 161). The downstream end of the upstream demineralized water line L31 is connected to a downstream demineralized water line L32 and a demineralized water return line L42 (described later) via a second flow path switching valve V72. In the upstream demineralized water line L31, a connecting portion J36, a connecting portion J37, a connecting portion J38, a seventh on-off valve V17, and a second flow path switching valve V72 are provided in this order from the upstream side. The seventh on-off valve V17 is a manual valve that can be operated to open and close the upstream demineralized water line L31.

  The second flow path switching valve V72 is a flow path (water sampling side flow path) for sending the desalted water W6 obtained in the desalination chamber 161 of the EDI stack 16 toward the demand point via the downstream side desalted water line L32. ) Or an automatic valve that can be switched to a flow path (circulation side flow path) that circulates toward the supply water line L1 upstream of the RO membrane module 7 via the desalted water return line L42. The second flow path switching valve V72 is configured by, for example, an electric or electromagnetic three-way valve. The second flow path switching valve V72 is electrically connected to the control unit 30. The switching of the flow path in the second flow path switching valve V72 is controlled by a flow path switching signal transmitted from the control unit 30.

  The second flow path switching valve V72 is capable of executing a process of sending the desalted water W6 obtained in the EDI stack 16 from the desalted water line L3 to the demand point by being switched to the water sampling side flow path by the control unit 30. Functions as a means.

  The upstream end of the downstream demineralized water line L32 is connected to the second flow path switching valve V72. The downstream end of the downstream demineralized water line L <b> 32 is connected to the storage tank 17.

  The desalted water return line L42 is a line that returns the desalted water W6 obtained in the desalting chamber 161 of the EDI stack 16 from the middle of the desalted water line L3 to the upstream side of the RO membrane module 7 (supply water line L1). is there. In the present embodiment, the upstream end of the desalted water return line L42 is connected to the second flow path switching valve V72. The downstream end of the desalted water return line L42 is connected to the connecting portion J59. A fifth check valve V65 is provided on the upstream side of the desalted water return line L42.

  The EDI concentrated water line L52 is a line for sending the concentrated water W7 discharged from the concentration chamber 162 of the EDI stack 16 to the decarboxylation device 15. The upstream end of the EDI concentrated water line L52 is connected to the secondary port of the EDI stack 16 (the outlet side of the concentration chamber 162). The downstream end of the EDI concentrated water line L52 is connected to the decarboxylation device 15.

  The sealed water discharge line L71 is a line for discharging the sealed water drainage W8 discharged from the decarboxylation device 15 to the outside of the device. The upstream end of the sealed water discharge line L71 is connected to the decarbonation device 15. The downstream side of the sealed water discharge line L71 is connected or opened to a drainage pit (not shown), for example.

  The first pressure gauge P1 to the sixth pressure gauge P6 are devices that measure the pressure of water flowing through each connected line. As shown in FIG. 2A, the first pressure gauge P1 to the fourth pressure gauge P4 are each connected to the supply water line L1 at the connection portions J1 to J4. As shown in FIG. 2C, the fifth pressure gauge P5 is connected to the EDI concentrated water line L52 at the connection portion J35. The sixth pressure gauge P6 is connected to the demineralized water line L3 at the connection portion J36.

  The first pressure sensor PS1 to the fourth pressure sensor PS4 are devices that measure the pressure of water flowing through each connected line. As shown in FIGS. 2B and 2C, the first pressure sensor PS1 is connected to the supply water line L1 at the connection portion J9. The connecting portion J9 is disposed between the pressurizing pump 5 and the RO membrane module 7 in the supply water line L1. The second pressure sensor PS2 is connected to the permeate line L21 at the connection portion J11. The connecting portion J11 is disposed between the RO membrane module 7 and the decarboxylation device 15 in the permeate line L21. The third pressure sensor PS3 is connected to the desalting chamber inflow line L213 at the connection portion J33. The connection part J33 is arrange | positioned in the middle of the desalination chamber inflow line L213. The fourth pressure sensor PS4 is connected to the concentration chamber inflow line L214 at the connection portion J34. The connection portion J34 is disposed between the fourth constant flow valve V54 and the EDI stack 16 in the concentration chamber inflow line L214.

  The first pressure sensor PS1 to the fourth pressure sensor PS4 are electrically connected to the control unit 30. The pressure of the supply water W1 or the permeated water W2 measured by the first pressure sensor PS1 to the fourth pressure sensor PS4 is transmitted to the control unit 30 as a detection signal.

  The pressure switch PSW is a device that detects that the pressure of the supply water W1 flowing through the supply water line L1 is equal to or lower than the first set pressure value or equal to or higher than the second set pressure value. As shown in FIG. 2B, the pressure switch PSW is connected to the supply water line L1 at the connection portion J7. The connection part J7 is arrange | positioned between the connection part J51 and the pressurization pump 5 in the supply water line L1. A detection signal of the pressure of the supply water W <b> 1 detected by the pressure switch PSW is transmitted to the control unit 30.

  The first temperature sensor TE1 to the third temperature sensor TE3 are devices that measure the temperature of water flowing through each connected line. The first temperature sensor TE1 is connected to the supply water line L1 at the connection portion J8. The connection part J8 is arrange | positioned between the connection part J51 and the pressurization pump 5 in the supply water line L1. The second temperature sensor TE2 is connected to the permeate line L21 at the connection portion J31. The connection part J31 is arrange | positioned between the decarbonation apparatus 15 and the 1st flow-path switching valve V71 in the permeated water line L21. The third temperature sensor TE3 is connected to the demineralized water line L3 at the connection portion J43. The connection part J43 is arrange | positioned at the downstream demineralized water line L32 in the downstream from the 2nd flow-path switching valve V72 in the demineralized water line L3.

  The first temperature sensor TE1 to the third temperature sensor TE3 are electrically connected to the control unit 30. The temperature (detected water temperature value) of the supply water W1, the permeated water W2, or the desalted water W6 measured by the first temperature sensor TE1 to the third temperature sensor TE3 is transmitted to the control unit 30 as a detection signal.

  The first flow rate sensor FM1 and the second flow rate sensor FM2 are devices that measure the flow rate of water (permeated water W2 or desalted water W6) flowing through each connected line. The first flow rate sensor FM1 is connected to the permeate line L21 at the connection portion J10. The connection part J10 is arrange | positioned between the RO membrane module 7 and the decarbonation apparatus 15 in the permeated water line L21. The second flow rate sensor FM2 is connected to the demineralized water line L3 at the connection portion J38. The connection portion J38 is disposed between the EDI stack 16 and the second flow path switching valve V72 in the desalted water line L3.

  The first flow rate sensor FM1 and the second flow rate sensor FM2 are electrically connected to the control unit 30. The flow rate (detected flow rate value) of the permeated water W2 or the desalted water W6 measured by the first flow rate sensor FM1 and the second flow rate sensor FM2 is transmitted to the control unit 30 as a detection signal.

  The first electrical conductivity sensor EC1 is a device that measures the electrical conductivity (electrical characteristic value) of the permeated water W2 flowing through the permeated water line L21. The first electrical conductivity sensor EC1 is connected to the permeated water line L21 at the connection portion J32. The connection part J32 is arrange | positioned between the decarboxylation apparatus 15 and the 1st flow-path switching valve V71 in the permeated water line L21.

  1st specific resistance sensor RS1 and 2nd specific resistance sensor RS2 are apparatus which measures the specific resistance (electrical characteristic value) of the desalinated water W6 which distribute | circulates the desalted water line L8. 1st specific resistance sensor RS1 is connected to the desalted water line L3 in the connection part J37. The connection portion J37 is disposed between the EDI stack 16 and the second flow path switching valve V72 in the desalted water line L3. The second specific resistance sensor RS2 is connected to the demineralized water line L3 at the connection portion J41. The connection part J41 is arrange | positioned at the downstream demineralized water line L32 in the downstream from the 2nd flow-path switching valve V72 in the demineralized water line L3. Note that the first specific resistance sensor RS1 and the second specific resistance sensor RS2 incorporate a temperature sensor for temperature compensation of the measured specific resistance value. Therefore, the first specific resistance sensor RS1 and the second specific resistance sensor RS2 can measure the water temperature of the desalted water W6.

  The first electrical conductivity sensor EC1, the first specific resistance sensor RS1, and the second specific resistance sensor RS2 are electrically connected to the control unit 30. The electrical conductivity of the permeated water W2 measured by the first electrical conductivity sensor EC1, the specific resistance (and temperature) of the desalted water W6 measured by the first specific resistance sensor RS1, and the second specific resistance sensor RS2. The specific resistance (and temperature) of the desalted water W6 is transmitted to the control unit 30 as a detection signal.

  The total organic carbon sensor TOC is a device that detects the amount of organic carbon in the desalted water W6 flowing through the desalted water line L8. Organic carbon is carbon in organic matter present in water. The total organic carbon sensor TOC is connected to the demineralized water line L3 at the connection portion J42. The connection part J42 is arrange | positioned at the downstream demineralized water line L32 in the downstream from the 2nd flow-path switching valve V72 in the demineralized water line L3.

  The all organic carbon sensor TOC is electrically connected to the control unit 30. The total organic carbon content of the demineralized water W6 detected by the total organic carbon sensor TOC is transmitted to the control unit 30 as a detection signal.

  The storage tank 17 is a tank that stores demineralized water W <b> 6 obtained by the desalting process in the EDI stack 16. The storage tank 17 is connected to the downstream end of the downstream demineralized water line L32 (demineralized water line L3). Desalinated water W6 sent from the EDI stack 16 (exit side of the desalting chamber 161) is replenished to the storage tank 17 via the downstream desalted water line L32. Further, the storage tank 17 is connected to a device or the like (not shown) at a downstream demand point via a water supply line L4. The water supply line L4 is a line through which the desalinated water W6 stored in the storage tank 17 is circulated to a device or the like at a demand point. The demineralized water W6 stored in the storage tank 17 is supplied as pure water to a device or the like at a demand point through the water supply line L4.

  The storage tank 17 is provided with a water level sensor 171. The water level sensor 171 is a device that detects the water level of the desalted water W6 stored in the storage tank 17. The water level sensor 171 is electrically connected to the control unit 30. The water level of the storage tank 17 (hereinafter also referred to as “detected water level value”) measured by the water level sensor 171 is output to the control unit 30 as a detection signal.

  In the present embodiment, the water level sensor 171 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, 4 positions). FIG. 2C shows an example in which a float type level switch is provided as the water level sensor 171. The water level sensor 171 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 17 and the flow rate of the permeate W2 produced by the RO membrane module 7 will be described. FIG. 3 is an explanatory diagram showing the relationship between the water level in the storage tank 17 and the flow rate of the permeated water W2 to be produced. As shown in FIG. 3, in the present embodiment, the water level of the storage tank 17 is divided into four stages of LL, L, M, and H in order from the lowest to the highest.

  The water level LL 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 17 becomes equal to or lower than the water level LL, the permeated water W2 is manufactured at a 100% flow rate value. At the 100% flow rate value (first target flow rate value), the recovery rate in the RO membrane module 7 is set to 50%.

  The water level L is a water level for producing the permeated water W2 at a 75% flow rate value (second target flow rate value). When the water level in the storage tank 17 is above the water level LL and below the water level L, the permeated water W2 is produced at a 75% flow rate value. At the 75% flow rate value (second target flow rate value), the recovery rate in the RO membrane module 7 is set to 60%.

  The water level M is a water level for producing the permeated water W2 at a 50% flow rate value (third target flow rate value). When the water level in the storage tank 17 exceeds the water level L and becomes equal to or lower than the water level M, the permeated water W2 is produced at a 50% flow rate value. At the 50% flow rate value (third target flow rate value), the recovery rate in the RO membrane module 7 is set to 70%.

  The water level H is an upper limit water level (full water level) at which the permeated water W2 is produced with a 25% flow rate value (fourth target flow rate value). When the water level in the storage tank 17 exceeds the water level M and falls below the water level H, the permeated water W2 is produced at a 25% flow rate value. At the 25% flow rate value (fourth target flow rate value), the recovery rate in the RO membrane module 7 is set to 80%. Further, when the water level in the storage tank 17 exceeds the water level H, the production of the permeated water W2 is stopped (0% flow rate value).

  The input operation unit 40 is an input interface for accepting an administrator's input operation for selection related to the operation mode of the device (for example, selection of operation / stop, release of alarm, etc.) and various settings related to the operation condition of the device. is there. The input operation unit 40 includes an operation panel that combines a display and button switches, a touch panel that directly operates on the display, and the like. The input operation unit 40 is electrically connected to the control unit 30. Information input from the input operation unit 40 is transmitted to the control unit 30.

  The display unit 60 displays desired information. The display unit 60 is electrically connected to the control unit 30.

  Next, the control unit 30 will be described. The control unit 30 is configured by a microprocessor (not shown) including a CPU and a memory. In the control unit 30, the CPU of the microprocessor executes various controls described later according to a predetermined program read from the memory. In the control unit 30, data and various programs for controlling the pure water production apparatus 1 are stored in the memory of the microprocessor. The microprocessor of the control unit 30 incorporates an integrated timer unit (hereinafter also referred to as “ITU”) that manages timekeeping and the like.

  As the flow rate feedback water amount control, the control unit 30 calculates the drive frequency of the pressurizing pump 5 by the speed type digital PID algorithm so that the detected flow rate value of the first flow rate sensor FM1 becomes a preset target flow rate value. Then, a current value signal (command signal) corresponding to the calculated value of the driving frequency is output to the inverter 6. The flow rate feedback water amount control by the control unit 30 will be described later.

  Further, the control unit 30 decreases the target flow rate value and decreases the detected water level value as the detected water level value of the storage tank 17 measured by the water level sensor 171 increases (water level LL <L <M <H). (Water level H> M> L> LL), the target flow rate value is increased. Further, the control unit 30 decreases the recovery rate as the target flow rate value is decreased, and increases the recovery rate as the target flow rate value is increased.

  Specifically, when the water level is equal to or lower than the water level LL, the control unit 30 sets the first target flow rate value (maximum value) and sets the recovery rate to 50%. When the water level LL is exceeded and below the water level L, the control unit 30 sets the second target flow rate value (<first target flow rate value) and sets the recovery rate to 60%. The control unit 30 sets the third target flow rate value (<second target flow rate value) and the recovery rate to 70% when the water level L is exceeded and the water level M or less. When the water level M is exceeded and the water level H or lower, the control unit 30 sets the fourth target flow rate value (<third target flow rate value) and sets the recovery rate to 80%.

  In the control unit 30, the above-described water level (LL to H), target flow rate (first target flow value to fourth target flow value), and recovery rate (50% to 80%) are associated with the memory of the microprocessor. A data table is stored.

  Among the above controls for increasing or decreasing the target flow rate value in the control unit 30, the control for decreasing the target flow rate value is performed only when the detected water temperature value output from the first temperature sensor TE1 is equal to or lower than the preset water temperature value. Is done. In other words, the control for reducing the target flow rate value in the control unit 30 is not performed when the detected water temperature value output from the first temperature sensor TE1 exceeds the preset water temperature value. Of the above-described controls for increasing or decreasing the target flow rate value in the control unit 30, control for increasing the target flow rate value is performed regardless of the detected water temperature value.

  In general, the operating pressure required for the RO membrane decreases as the flow rate of the permeated water W2 to be produced decreases, but when the operating pressure decreases, the removal rate of dissolved salts decreases. In addition, the RO membrane has a lower operating pressure required to produce the permeated water W2 at a predetermined flow rate as the water temperature of the supply water W1 increases (the viscosity of the water decreases), but when the operating pressure decreases, the dissolved salts are removed. The rate drops. In the control for increasing or decreasing the target flow rate value, the target flow rate value is decreased as the detected water level value of the storage tank 17 measured by the water level sensor 171 increases. In this case, if the water temperature of the supply water W1 is high, the above two conditions for reducing the operating pressure of the RO membrane overlap, so the degree of decrease in the removal rate of dissolved salts increases, and the quality of pure water required at the demand location It is thought that it becomes impossible to maintain. Therefore, the above control for increasing or decreasing the target flow rate value is performed when the detected water temperature value of the supply water W1 output from the first temperature sensor TE1 is equal to or lower than a preset water temperature value (when the operating pressure of the RO membrane does not decrease). By implementing only, the quality of the pure water requested | required in a demand location can be maintained.

  In the control unit 30, a functional expression (program) that associates the water temperature value of the supply water W1 with the lower limit value of the operating pressure in the RO membrane is stored in the memory of the microprocessor. The control unit 30 calculates the lower limit value of the operating pressure corresponding to the detected water temperature value of the supply water W1 output from the first temperature sensor TE1 by the above functional equation, and the operating pressure of the RO membrane becomes equal to or higher than the lower limit value. Increase or decrease the target flow rate value within the range. In the control unit 30, a data table that associates the water temperature value of the supply water W1 with the lower limit value of the operating pressure in the RO membrane is stored in the memory of the microprocessor, and the lower limit of the operating pressure is determined based on this data table. A value may be acquired.

  In addition, when the target flow rate value is changed (increased / decreased), the control unit 30 controls the first drainage means so that the recovery rate of the permeated water W2 and the circulation ratio of the concentrated water W3 are maintained at preset values. The number of opened 1 drain valve V32 to 3rd drain valve V34 and the opening degree of proportional control valve V50 are controlled.

  As described above, the drainage flow rate of the concentrated water W3 discharged out of the apparatus can be adjusted by appropriately selecting the number of opened first drain valve V32 to third drain valve V34. By this adjustment, the recovery rate of the permeated water W2 can be maintained at a preset value (50% to 80%). At that time, by controlling the valve opening degree of the proportional control valve V50 and adjusting the circulation flow rate of the concentrated water W3, the circulation ratio of the concentrated water W3 can be maintained at a preset value (for example, 5). Specifically, when the drainage flow rate of the concentrated water W3 is increased (when the recovery rate is lowered), the control unit 30 reduces the valve opening degree of the proportional control valve V50 to circulate the concentrated water W3. The circulating flow rate of the concentrated water W3 is reduced so that the ratio is maintained at a preset value. Further, when the drainage flow rate of the concentrated water W3 is decreased (when the recovery rate is increased), the control unit 30 increases the valve opening degree of the proportional control valve V50 so that the circulation ratio of the concentrated water W3 is set in advance. The circulating flow rate of the concentrated water W3 is increased so that the set value is maintained.

  Moreover, the control part 30 permeate | transmits, when the detection water level value of the storage tank 17 measured with the water level sensor 171 becomes smaller than the preset lower limit water level value, and the RO membrane module 7 becomes a high output driving | operation. The number of opened first drain valve V32 to third drain valve V34 is controlled so that the recovery rate of water W2 is lower than a preset value. Specifically, when the detected water level value of the storage tank 17 is equal to or lower than the water level LL and the RO membrane module 7 is in a high output operation state, the control unit 30 sets the recovery rate of the permeated water W2 in advance. The number of opening of the first drain valve V32 to the third drain valve V34 is controlled so as to be lower than the value (for example, 80%).

  Next, setting of the target flow rate value and the recovery rate by the control unit 30 will be described. FIG. 4 is a flowchart illustrating a processing procedure when the control unit 30 sets the target flow rate value and the recovery rate. The process of the flowchart shown in FIG. 4 is repeatedly executed during the operation of the pure water production apparatus 1.

  In step ST <b> 101 shown in FIG. 4, the control unit 30 acquires the detected water level value W of the water level sensor 171.

  In step ST102, the control unit 30 determines whether or not the detected water level value W is equal to or lower than the water level LL. In step ST102, when the control unit 30 determines that the detected water level value W ≦ the water level LL (YES), the process proceeds to step ST103. In step ST102, when the control unit 30 determines that the detected water level value W> the water level LL (NO), the process proceeds to step ST105.

  In step ST103 (step ST102: YES), the control unit 30 sets the flow rate of the permeated water W2 to the first target flow rate value. As described above, when the detected water level value W is equal to or lower than the water level LL, the target flow rate value of the permeated water W2 is set to the first target flow rate value that is the maximum flow rate value in order to increase the water storage amount of the storage tank 17.

  In step ST104, the control unit 30 sets the RO membrane module 7 recovery rate to 50%. Thereby, the process of this flowchart is complete | finished (it returns to step ST101).

  On the other hand, in step ST105 (step ST102: NO), the control unit 30 determines whether or not the detected water level value W is above the water level LL and below the water level L. In step ST105, when the control unit 30 determines that the water level LL <the detected water level value W ≦ the water level L (YES), the process proceeds to step ST106. In step ST105, when the control unit 30 determines that the detected water level value W> the water level L (NO), the process proceeds to step ST108.

  In step ST106 (step ST105: YES), the control unit 30 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.

  In step ST107, the control unit 30 sets the recovery rate of the RO membrane module 7 to 60%. Thereby, the process of this flowchart is complete | finished (it returns to step ST101).

  On the other hand, in step ST108 (step ST105: NO), the control unit 30 determines whether or not the detected water level value W exceeds the water level L and is equal to or lower than the water level M. In step ST108, when the control unit 30 determines that the water level L <the detected water level value W ≦ the water level M (YES), the process proceeds to step ST109. In step ST108, when the control unit 30 determines that the detected water level value W> the water level M (NO), the process proceeds to step ST111.

  In step ST109 (step ST108: YES), the control unit 30 sets the flow rate of the permeated water W2 to the third target flow rate value. The third target flow value is a flow value smaller than the second target flow value.

  In step ST110, the control unit 30 sets the recovery rate of the RO membrane module 7 to 70%. Thereby, the process of this flowchart is complete | finished (it returns to step ST101).

  In step ST111 (step ST108: NO), the control unit 30 sets the flow rate of the permeated water W2 to the fourth target flow rate value. The fourth target flow value is a minimum flow value that is smaller than the third target flow value.

  In step ST112, the control unit 30 sets the recovery rate of the RO membrane module 7 to 80%. Thereby, the process of this flowchart is complete | finished (it returns to step ST101).

  By executing the processing of the flowchart shown in FIG. 4 described above, the target flow rate value and the recovery rate corresponding to the detected water level value W are set. As described above, the control for reducing the target flow rate value is performed only when the detected water temperature value output from the first temperature sensor TE1 is equal to or lower than a preset water temperature value. Therefore, when the detected water temperature value output from the first temperature sensor TE1 exceeds a preset water temperature value, control for decreasing the target flow rate value is not performed even if the detected water level value becomes larger than the previous value. The target flow rate value and recovery rate set at that time are maintained.

  Next, flow rate feedback water amount control by the control unit 30 will be described. FIG. 5 is a flowchart showing a processing procedure when the control unit 30 executes the flow rate feedback water amount control. The process of the flowchart shown in FIG. 5 is repeatedly executed during the operation of the pure water production apparatus 1.

In step ST201 shown in FIG. 5, the control unit 30 acquires the target flow rate value Q _p ′ of the permeated water W2. This target flow rate value Q _p ′ is the first target flow rate value to the fourth target flow rate value set in step ST103, step ST106, step ST109 or step ST111 of the flowchart shown in FIG.

  In step ST202, the control unit 30 determines whether or not the time t measured by the ITU has reached 100 ms, which is the control cycle (Δt). In step ST202, when the control unit 30 determines that the time t measured by the ITU has reached 100 ms (YES), the process proceeds to step ST203. In step ST202, when the control unit 30 determines that the time measured by the ITU has not reached 100 ms (NO), the process returns to step ST202.

Step ST 203: In (step ST 202 YES judgment), the control unit 30 acquires the detected flow rate value _{Q p} of the first flow rate sensor FM1 as a feedback value.

In step ST 204, the control unit 30 detects the flow rate value obtained in step ST 203 (feedback value) _{Q p} and, as difference between the target flow rate value _{Q p} 'obtained in step ST201 becomes zero, velocity type digital PID The operation amount _Un is calculated by an algorithm. In the speed type digital PID algorithm, the operation amount change ΔU _n is calculated every control cycle Δt (100 ms), and this is added to the operation amount U _n−1 at the previous control cycle, thereby obtaining the current operation amount U. _n is determined.

An arithmetic expression used for the velocity type digital PID algorithm is expressed by the following expressions (1a) and (1b).
_{ΔU n = K p {(e} n -e n-1) + (Δt / T i) × e n + (T d / Δt) × (e n -2e n-1 + e n-2)} (1a)
U _n = U _n-1 + ΔU _n (1b)

In Expression (1a) and Expression (1b), Δt: control period, U _n : current operation amount, U _n-1 : operation amount at the previous control period, ΔU _n : change in operation amount from the previous time to this time. Minute, e _n : magnitude of current deviation, e _n-1 : magnitude of deviation at the previous control cycle, e _n-2 : magnitude of deviation at the previous control cycle, K _p : proportional gain, T _i : integration time, T _d : differentiation time. The size e _n of the current deviation is obtained by the following formula (2).
e _n = Q _p ′ −Q _p (2)

In step ST205, the control unit 30 uses the current operation amount U _n , the target flow rate value Q _p ′, and the maximum drive frequency of the pressurizing pump 5 (set value of 50 Hz or 60 Hz) according to a predetermined arithmetic expression. The drive frequency F [Hz] of the pressure pump 5 is calculated.

  In step ST <b> 206, the control unit 30 converts the calculated value of the driving frequency F into a corresponding current value signal (command signal: 4 to 20 mA), and outputs this current value signal to the inverter 6. Thereby, the process of this flowchart is complete | finished (it returns to step ST201). In step ST206, when the control unit 30 outputs a current value signal to the inverter 6, the inverter 6 supplies the drive power converted to the frequency specified by the input current value signal to the pressurizing pump 5. As a result, the pressurization pump 5 is driven at a rotational speed corresponding to the drive frequency input from the inverter 6.

  According to the pure water manufacturing apparatus 1 which concerns on 1st Embodiment mentioned above, the following effects are show | played, for example.

  In the pure water manufacturing apparatus 1 according to the first embodiment, the control unit 30 decreases the target flow rate value in the flow rate feedback water volume control and increases the water usage volume at the demand location as the usage water volume at the demand location decreases. As a result, the target flow rate value in the same water amount control is increased. Therefore, when the amount of water used at the demand point decreases during high output operation, the operation is performed with the flow rate of the permeated water W2 reduced, so that the pure water production apparatus 1 can be operated with the minimum necessary pump power. . Further, when the amount of water used at the demand point decreases during the high output operation, the high output operation is not continued, so that overconcentration due to concentration polarization on the surface of the RO membrane is suppressed. As a result, even if fouling-causing substances remain in the supply water W1, RO membrane clogging is less likely to occur.

  Further, the control unit 30 increases or decreases the target flow rate value according to the detected water level value of the water level sensor 171. According to this, since the increase / decrease of the amount of water used in a demand location can be easily grasped by the water level of the storage tank 17, the structure of the pure water manufacturing apparatus 1 can be simplified.

  In addition, when the target flow rate value is changed, the control unit 30 causes the first drainage valve V32 to the third drainage valve V32 to the third drain so that the recovery rate of the permeated water W2 and the circulation ratio of the concentrated water W3 are maintained at preset values. The number of opened drain valves V34 and the opening degree of the proportional control valve V50 are controlled. According to this, since the concentration rate of the concentrated water W3 is kept below a predetermined value regardless of the increase or decrease of the target flow rate value, it is possible to suppress the deposition of silica-based scale or calcium-based scale on the surface of the RO membrane. Can do. Moreover, since the flow velocity on the surface of the RO membrane is maintained at a predetermined value or more regardless of the increase or decrease of the target flow rate value, it is possible to effectively suppress overconcentration due to concentration polarization.

  Moreover, the control part 30 becomes low of the permeated water W2 when the detection water level value of the water level sensor 171 becomes smaller than the preset lower limit water level value (water level LL) and the RO membrane module 7 becomes a high output operation. The number of opened first drain valve V32 to third drain valve V34 is controlled so that the recovery rate is lower than a preset value. According to this, at the time of high output operation, the concentration rate of the concentrated water W3 is kept lower than at the time of non-high output operation, so that even if concentration polarization occurs on the surface of the RO membrane, overconcentration does not proceed easily. As a result, occurrence of fouling is more effectively suppressed, and RO membrane clogging is less likely to occur.

  In addition, the control unit 30 increases the target flow rate as the detected water level value of the storage tank 17 measured by the water level sensor 171 increases only when the detected water temperature value of the first temperature sensor TE1 is equal to or lower than a preset water temperature value. Control to decrease the value is executed. According to this, when the detected water temperature value exceeds a preset water temperature value, the control for decreasing the target flow rate value is not executed, and therefore, the RO membrane operating pressure is prevented from being significantly reduced. As a result, the removal rate of dissolved salts is maintained at a certain value or higher, so that the quality of pure water required at the demand location can be maintained.

(Second Embodiment)
Next, a pure water producing apparatus 1A according to a second embodiment of the present invention will be described with reference to FIGS. 6 and 7A to 7C. FIG. 6 is an overall schematic diagram of a pure water producing apparatus 1A according to the second embodiment. FIG. 7A is a first middle portion of the entire configuration diagram of the pure water producing apparatus 1A according to the second embodiment. FIG. 7B is a second middle part of the overall configuration diagram of the pure water producing apparatus 1A according to the second embodiment. FIG. 7C is a rear part of the entire configuration diagram of the pure water producing apparatus 1A according to the second embodiment.

  In the second embodiment, differences from the first embodiment will be mainly described. For this reason, the same code | symbol is attached | subjected about the same (or equivalent) structure as 1st Embodiment, and detailed description is abbreviate | omitted. The description of the first embodiment is appropriately applied to points that are not particularly described in the second embodiment. Moreover, in 2nd Embodiment, the structure from the upstream of the supply water line L1 to the supply water replenishment valve V31 is the same as that of 1st Embodiment. Therefore, in 2nd Embodiment, main drawings (drawing corresponding to FIG. 2A) about the structure from the upstream of the supply water line L1 in 1st Embodiment to the supply water replenishment valve V31 and its description are abbreviate | omitted.

  The pure water producing apparatus 1A according to the second embodiment is a two-stage RO membrane arranged in series, whereas the pure water producing apparatus 1 in the first embodiment includes the one-stage RO membrane module 7. The pure water production apparatus 1 according to the first embodiment is provided in that the modules 10 and 14 are provided, the intermediate tank 11 is provided between the two-stage RO membrane modules 10 and 14, and the configuration around these. And mainly different.

  In the second embodiment, the “RO membrane module 7” in the first embodiment is provided as the “rear-stage RO membrane module 14” that becomes the second-stage RO membrane module. Therefore, in the second embodiment, the “permeate water line L21” in the first embodiment is referred to as a “desalted water line L3”, and the permeated water separated by the rear-stage RO membrane module 14 is referred to as “a rear-stage permeate water W4”.

  In the second embodiment, the “RO permeate return line L41” in the first embodiment is referred to as the “front-stage RO permeate return line L43”, and the “RO concentrated water return line L51” in the first embodiment is referred to as the “front-stage RO. Concentrated water return line L53 ". In the second embodiment, the “pressurizing pump 5” in the first embodiment is referred to as a “rear-stage pressurizing pump 12”, and the “inverter 6” is referred to as a “rear-stage inverter 13”.

  As shown in FIG. 6, the pure water producing apparatus 1A according to the second embodiment includes a first optional device OP1, a prefilter 4, a second optional device OP2, a pre-stage pressurizing pump 8, and a pre-stage inverter 9. The upstream RO membrane module 10, the intermediate tank 11, the downstream pressure pump 12, the downstream inverter 13, the downstream RO membrane module 14, the third optional device OP3, the first flow path switching valve V71, and the EDI stack 16, the second flow path switching valve V <b> 72, the fourth optional device OP <b> 4, the storage tank 17, the control unit 30 </ b> A, the input operation unit 40, the DC power supply device 50, and the display unit 60.

  Moreover, as shown in FIG. 6, the pure water manufacturing apparatus 1A of the second embodiment includes a supply water line L1, a front-stage RO permeate line L22, a front-stage RO permeate return line L43, and a front-stage RO concentrated water return line. L53, the back | latter stage RO permeated water line L23, the back | latter stage RO permeated water return line L44, the front | former stage RO concentrated water return line L54, the desalted water line L3, and the desalted water return line L45 are provided.

  As shown in FIG. 6, the pure water producing apparatus 1A according to the second embodiment replaces the RO permeate return line L41 and the desalted water return line L42 according to the first embodiment with a front-stage RO permeate return line L43 and a rear-stage RO. A permeated water return line L44, a desalted water return line L45, and a water supply line L4 are provided.

  Moreover, as shown to FIG. 7A-FIG. 7C, the pure water manufacturing apparatus 1A of 2nd Embodiment is not provided with 2nd pressure sensor PS2 in 1st Embodiment, On the other hand, 5th pressure sensor PS5, 4th A temperature sensor TE4, a fifth temperature sensor TE5, a third flow rate sensor FM3, and a second electrical conductivity sensor EC2 are further provided. Similarly to the first embodiment, the pure water manufacturing apparatus 1A of the second embodiment includes the first electrical conductivity sensor EC1 and the first specific resistance sensor RS1.

  The pre-stage RO membrane module 10 separates the supply water W1 pumped by the pre-stage pressurization pump 8 into a pre-stage permeate water W2 from which dissolved salts have been removed and a concentrated water W3 from which dissolved salts have been concentrated.

  The front-stage RO permeate line L22 is a line through which the front-stage permeate water W2 separated by the front-stage RO membrane module 10 flows to the rear-stage RO membrane module 14. The upstream end of the upstream RO permeate line L22 is connected to the secondary port of the upstream RO membrane module 10 (the outlet of the upstream permeate W2), as shown in FIG. 7A. As shown in FIG. 7B, the downstream end of the upstream RO permeate line L22 is connected to the primary inlet port (the inlet of the upstream permeate W2) of the downstream RO membrane module 14.

  As shown in FIG. 7A, the upstream RO permeated water line L22 is connected to the connecting portion J54, the upstream permeated water replenishing valve V35, the third check valve V63, the connecting portion J10, the connecting portion J12, and the connecting portion J13. , And a sixth on-off valve V16. Further, after the sixth on-off valve V16, as shown in FIG. 7B, the intermediate tank 11, the seventh on-off valve V17, the connection portion J61, the connection portion J21, the post-stage pressurizing pump 12, the connection portion J22, and the post-stage RO membrane A module 14 is provided. As shown in FIG. 7A, the upstream end of the upstream RO permeate return line L43 is connected to the connecting portion J54. Moreover, as shown to FIG. 7B, the downstream end part of the back | latter stage RO concentrated water return line L54 is connected to the connection part J61.

  The front-stage permeated water supply valve V35 is an automatic valve that can control the opening and closing of the front-stage RO permeated water line L22. The front stage permeated water replenishment valve V35 is electrically connected to the control unit 30A. The opening and closing of the front permeate replenishment valve V35 is controlled by a flow path opening / closing signal transmitted from the control unit 30A.

  As shown in FIG. 6, the intermediate tank 11 is provided between the front RO membrane module 10 and the rear RO membrane module 14 in the front RO permeate line L22. The intermediate tank 11 is a tank that stores the previous-stage permeated water W <b> 2 separated by the previous-stage RO membrane module 10.

  The intermediate tank 11 is provided with a water level sensor 111 as shown in FIG. 7B. The water level sensor 111 is a device that detects the water level of the upstream permeated water W2 stored in the intermediate tank 11. The water level sensor 111 is electrically connected to the control unit 30A. The water level (detected water level value) of the intermediate tank 11 measured by the water level sensor 111 is transmitted as a detection signal to the control unit 30A.

  The post-stage pressurizing pump 12 is a device that sucks the pre-stage permeate water W2 flowing through the pre-stage RO permeate line L22 and pumps it toward the post-stage RO membrane module 14. The post-stage pressurizing pump 12 is supplied with drive power having a frequency converted from the post-stage inverter 13. The post-stage pressurizing pump 12 is driven at a rotational speed corresponding to the frequency of the supplied driving power (hereinafter also referred to as “driving frequency”).

  The rear-stage inverter 13 is an electric circuit (or a device having the circuit) that supplies driving power whose frequency is converted to the rear-stage pressurization pump 12. The rear stage inverter 13 is electrically connected to the control unit 30A. A command signal is input to the subsequent inverter 13 from the control unit 30A. The rear stage inverter 13 outputs driving power having a driving frequency corresponding to the command signal (current value signal or voltage value signal) input by the control unit 30 </ b> A to the rear stage pressure pump 12.

  The latter-stage RO membrane module 14 is separated from the first-stage permeate W2 separated from the first-stage RO membrane module 10 and pumped by the second-stage pressurization pump 12, with the second-stage permeate W4 from which dissolved salts are removed from the first-stage permeate W2. Separated into concentrated water W5 enriched with salts. The post-stage RO membrane module 14 is configured by accommodating a single or a plurality of spiral RO membrane elements in a pressure vessel (vessel).

  The front-stage RO permeate return line L43 is a line that returns the front-stage permeate W2 separated by the front-stage RO membrane module 10 to the supply water line L1 upstream of the front-stage RO membrane module 10 as shown in FIG. 7A. . The upstream end of the upstream RO permeate return line L43 is connected to the connection J54. The downstream end of the upstream RO permeated water return line L43 is connected to the upstream RO concentrated water return line L53 at the connection portion J52. The connection part J52 is disposed between the connection part J53 and the connection part J51 in the upstream RO concentrated water return line L53. The part from the connection part J52 to the connection part J51 in the upstream RO permeate return line L43 is common to the part from the connection part J52 to the connection part J51 in the upstream RO concentrated water return line L53.

  As shown in FIG. 7A, a relief valve V43 is provided in the upstream RO permeate return line L43. The relief valve V43 is a normally closed pressure operating valve, and is an adjustment valve that is opened when the pressure on the primary side is higher than the pressure on the secondary side by a certain pressure or more. Specifically, the relief valve V43 is opened when the pipe pressure of the front-stage RO permeate return line L43 becomes equal to or higher than a preset pressure, and the front-stage permeate W2 flowing through the front-stage RO permeate line L22 is removed. This is a valve for flowing through the connecting portion J54 to the upstream RO permeated water return line L43.

  The pressure on the secondary side of the relief valve V43 (the pressure of the supply water W1 at the connection portion J51) is adjusted to be less than the operating pressure of the upstream pressurizing pump 8 by the pressure reducing valve V42. When the front-stage pressurizing pump 8 is driven in a state in which the front-stage permeate replenishment valve V35 is controlled to be closed, the primary pressure in the relief valve V43 (the pressure of the front-stage permeate W2 at the connection portion J54) is secondary. Higher than the pressure on the side. Thereby, the relief valve V43 is opened, and the front-stage permeate water W2 flowing through the front-stage RO permeate water line L22 can be circulated to the front-stage RO permeate return line L43.

  As shown in FIG. 7B, the rear-stage RO concentrated water return line L54 is a line that returns a part W51 of the concentrated water W5 separated by the rear-stage RO membrane module 14 to the front-stage RO permeate water line L22. The upstream end of the rear-stage RO concentrated water return line L54 is connected to the primary-side outlet port (concentrated water outlet) of the rear-stage RO membrane module 14. The downstream end of the rear stage RO concentrated water return line L54 is connected to the connecting portion J61. The connecting portion J61 is disposed between the intermediate tank 11 and the post-stage pressurizing pump 12 in the pre-stage RO permeate line L22.

  As shown in FIG. 7B, the rear stage RO concentrated water return line L54 is provided with a connecting portion J63, a connecting portion J62, a sixth check valve V66, a sixth constant flow valve V56, and a connecting portion J61 in this order from the upstream side. ing. The upstream end of the first second-stage RO concentrated water line L63 is connected to the connecting portion J62. The upstream end of the second second-stage RO concentrated water line L64 is connected to the connecting portion J63.

  The first second-stage RO concentrated water line L63 and the second second-stage RO concentrated water line L64 remove the remaining portion W52 of the concentrated water W5 separated by the second-stage RO membrane module 14 from the middle of the second-stage RO concentrated water return line L54. Is a line to send to The downstream end of the first second-stage RO concentrated water line L63 and the downstream end of the second second-stage RO concentrated water line L64 are connected to the upstream end of the second-stage RO concentrated water delivery line L65 at the connection J64. It is connected. The downstream end of the downstream RO concentrated water delivery line L65 is connected to the decarboxylation device 15 as shown in FIG. 7C. The first second-stage RO concentrated water line L63 and the second second-stage RO concentrated water line L64 are provided with a first regulating valve V36 and a second regulating valve V37, and a seventh constant flow valve V57 and an eighth constant flow valve V58, respectively. It has been.

  The first adjusting valve V36 and the second adjusting valve V37 can adjust the delivery flow rate of the concentrated water W5 by individually opening and closing the first second-stage RO concentrated water line L63 and the second second-stage RO concentrated water line L64. . The first regulating valve V36 and the second regulating valve V37 are each electrically connected to the control unit 30A. Opening and closing of the first regulating valve V36 and the second regulating valve V37 is controlled by a drive signal transmitted from the control unit 30A.

  An eighth open / close valve V18 is provided in the downstream RO concentrated water delivery line L65. The eighth on-off valve V18 is a manual valve that can be operated to open and close the rear-stage RO concentrated water delivery line L65.

  The post-stage RO permeate water line L23 is a line through which the post-stage permeate water W4 separated by the post-stage RO membrane module 14 flows through the EDI stack 16. As shown in FIG. 7B, the upstream end of the rear-stage RO permeate line L23 is connected to the secondary port of the rear-stage RO membrane module 14 (the outlet of the rear-stage permeate water W4). As shown in FIG. 7C, the downstream end of the downstream RO permeate line L23 is connected to the EDI stack 16 via the first flow path switching valve V71.

  The rear-stage RO permeate line L23 includes a front-stage permeate line L231, a middle-stage permeate line L232, a desalting chamber inflow line L233, and a concentration chamber inflow line L234. As shown in FIG. 7B, the upstream side permeated water line L231 is provided with a fourth check valve V64, a connecting portion J23, and a ninth on-off valve V19 in order from the upstream side. Further, after the ninth on-off valve V19, as shown in FIG. 7C, a decarboxylation device 15, a connection portion J31, a connection portion J32, and a first flow path switching valve V71 are provided.

  The first flow path switching valve V71 is a flow path (water sampling side flow path) for allowing the downstream permeate water W4 separated by the rear RO membrane module 14 to flow toward the EDI stack 16 via the middle permeate water line L232. Alternatively, it is a valve that can be switched to a flow path (circulation side flow path) that circulates toward the intermediate tank 11 via the rear-stage RO permeate return line L44. The first flow path switching valve V71 is configured by, for example, an electric or electromagnetic three-way valve. The first flow path switching valve V71 is electrically connected to the control unit 30A. The switching of the flow path in the first flow path switching valve V71 is controlled by a flow path switching signal transmitted from the control unit 30A.

  The post-stage RO permeate return line L44 is a line for returning the post-stage permeate water W4 separated by the post-stage RO membrane module 14 to the intermediate tank 11 provided between the pre-stage RO membrane module 10 and the post-stage RO membrane module 14. is there. As shown in FIG. 7C, the upstream end of the rear stage RO permeate return line L44 is connected to the first flow path switching valve V71. The downstream side of the rear stage RO permeate return line L44 is connected to the intermediate tank 11 as shown in FIG. 7B.

  In addition, in 2nd Embodiment shown to FIG. 7C, the structure of the part downstream from 1st flow-path switching valve V71 is "the middle stage permeate water line L212" in 1st Embodiment, and "desalination room inflow line L213." ”,“ Concentration chamber inflow line L214 ”and“ permeate water W2 ”, respectively,“ middle stage permeate water line L232 ”,“ desalination chamber inflow line L233 ”,“ concentration chamber inflow line L234 ”and“ rear stage permeate water W4 ”. " Moreover, in 2nd Embodiment, it is the structure similar to 1st Embodiment except the structure of the EDI concentrated water discharge line L72 and the desalted water return line L45 which are mentioned later. Therefore, regarding these parts, description of 1st Embodiment is used and description of 2nd Embodiment is abbreviate | omitted.

  As shown in FIG. 7C, the pure water producing apparatus 1A in the second embodiment includes an EDI concentrated water discharge line L72 instead of the EDI concentrated water line L52 in the first embodiment.

  The EDI concentrated water discharge line L72 is a line for discharging the concentrated water W7 discharged from the concentration chamber 162 of the EDI stack 16 to the outside of the apparatus. The upstream end of the EDI concentrated water discharge line L72 is connected to the secondary port of the EDI stack 16 (the outlet side of the concentration chamber 162). The downstream side of the EDI concentrated water discharge line L72 is connected or opened to a drain pit (not shown), for example.

  The second flow path switching valve V72 is a flow path (water sampling side flow path) for sending the desalted water W6 obtained in the desalination chamber 161 of the EDI stack 16 toward the demand point via the downstream side desalted water line L32. Or a valve that can be switched to a flow path (circulation side flow path) that circulates toward the intermediate tank 11 via the desalted water return line L45.

  The desalted water return line L45 is provided between the front-stage RO membrane module 10 and the rear-stage RO membrane module 14 with the desalted water W6 obtained in the desalination chamber 161 of the EDI stack 16 in the middle of the desalted water line L3. This is a line that returns to the intermediate tank 11. In the present embodiment, the upstream end of the desalted water return line L45 is connected to the second flow path switching valve V72. The downstream end of the desalted water return line L45 is connected to the intermediate tank 11.

  The fifth pressure sensor PS5 is a device that measures the pressure of the front-stage permeate water W2 that flows through the front-stage RO permeate line L22. The fifth pressure sensor PS5 is connected to the upstream RO permeated water line L22 at the connection portion J22. The connecting portion J22 is disposed between the rear-stage pressurizing pump 12 and the rear-stage RO membrane module 14 in the front-stage RO permeate water line L22. The fifth pressure sensor PS5 is electrically connected to the control unit 30A. The pressure of the pre-stage permeated water W2 measured by the fifth pressure sensor PS5 is transmitted as a detection signal to the control unit 30A.

  The fourth temperature sensor TE4 and the fifth temperature sensor TE5 are devices that measure the temperature of the front-stage permeate water W2 that flows through the front-stage RO permeate line L22. As shown in FIG. 7A, the fourth temperature sensor TE4 is connected to the upstream RO permeate line L22 at the connection portion J12. The connecting portion J12 is disposed between the upstream RO membrane module 10 and the intermediate tank 11 in the upstream RO permeate line L22. As shown in FIG. 7B, the fifth temperature sensor TE5 is connected to the upstream RO permeate line L22 at the connection portion J21. The connecting portion J21 is disposed between the intermediate tank 11 and the post-stage pressurizing pump 12 in the pre-stage RO permeate line L22. The fourth temperature sensor TE4 and the fifth temperature sensor TE5 are electrically connected to the control unit 30A. The temperature of the pre-stage permeate water W2 measured by the fourth temperature sensor TE4 and the fourth temperature sensor TE4 is transmitted as a detection signal to the control unit 30A.

  The third flow rate sensor FM3 is a device that measures the flow rate of the rear permeate water W4 that flows through the rear RO permeate line L23. As shown in FIG. 7B, the third flow rate sensor FM3 is connected to the rear-stage RO permeate line L23 at the connection portion J23. The connecting portion J23 is disposed between the rear-stage RO membrane module 14 and the decarboxylation device 15 in the rear-stage RO permeate line L23. The third flow rate sensor FM3 is electrically connected to the control unit 30A. The flow rate of the rear permeate water W4 measured by the third flow rate sensor FM3 is transmitted as a detection signal to the control unit 30A.

  The second electrical conductivity sensor EC2 is a device that measures the electrical conductivity of the front-stage permeate water W2 that flows through the front-stage RO permeate line L22. As shown in FIG. 7A, the second electrical conductivity sensor EC2 is connected to the upstream RO permeate line L22 at the connection portion J13. The connecting portion J13 is disposed between the upstream RO membrane module 10 and the intermediate tank 11 in the upstream RO permeate line L22. The second electrical conductivity sensor EC2 is electrically connected to the control unit 30A. The electrical conductivity of the upstream permeated water W2 measured by the second electrical conductivity sensor EC2 is transmitted as a detection signal to the control unit 30A.

  As the flow rate feedback water amount control for the upstream RO membrane module 10, the control unit 30A uses a speed type digital PID algorithm so that the detected flow rate value of the first flow sensor FM1 becomes a preset target flow rate value. 8 is calculated, and a current value signal (command signal) corresponding to the calculated value of the drive frequency is output to the pre-stage inverter 9.

  In addition, the control unit 30A uses the velocity type digital PID algorithm as a flow rate feedback water amount control for the downstream RO membrane module 14 so that the detected flow rate value of the third flow rate sensor FM3 becomes a preset target flow rate value. The drive frequency of the pressure pump 12 is calculated, and a current value signal (command signal) corresponding to the calculated value of the drive frequency is output to the subsequent inverter 13.

  In the control unit 30A, the flow rate feedback water amount control, the target flow rate value, the recovery rate, and the circulation ratio control for the downstream RO membrane module 14 are controlled by the first control unit 31 of the first embodiment (see FIG. 5). Since the control is substantially the same as the control of the target flow rate value (see FIG. 4), the recovery rate, and the circulation ratio, the description is omitted.

  The control unit 30A of the second embodiment changes the target flow rate value of the post-stage permeated water W2 manufactured by the post-stage RO membrane module 14 based on the detected water level value of the storage tank 17. The relationship between the water level in the storage tank 17 and the flow rate of the downstream permeated water W2 produced by the downstream RO membrane module 14 is the same as in the first embodiment shown in FIG. In the control unit 30A, the control to decrease the target flow rate value of the rear-stage permeated water W2 is performed only when the detected water temperature value output from the fifth temperature sensor TE5 is equal to or lower than a preset water temperature value. On the other hand, the target flow rate value of the upstream permeated water W2 manufactured by the upstream RO membrane module 10 is always constant in the second embodiment. In addition, the control of the flow rate feedback water amount, the recovery rate and the circulation ratio by the control unit 30A is substantially the same as the control of the flow rate feedback water amount control (see FIG. 5), the recovery rate and the circulation ratio by the control unit 30 of the first embodiment. Since it is the same, description is abbreviate | omitted.

  Also in the pure water manufacturing apparatus 1A of the second embodiment described above, the same effect as the pure water manufacturing apparatus 1 of the first embodiment can be obtained. In addition, in the pure water manufacturing apparatus 1A of the second embodiment, the permeated water W2 is manufactured by the two-stage RO membrane treatment in order to increase the desalination rate with respect to the supply water W1. In this case, if a single pressure pump is used for pressure feeding to the two-stage RO membrane module, it is inevitable that the motor capacity of the pressure pump increases. However, by installing the intermediate tank 11 between the RO membrane modules and providing the pressure pumps 8 and 12 for each of the RO membrane modules 10 and 14, the motor capacity of the pressure pump can be reduced. As a result, the pump power for operating the pure water production apparatus 1 is minimized.

  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.

  In the first embodiment, the configuration in which the storage tank 17 is provided downstream of the EDI stack 16 (fourth optional device OP4) has been described. However, the configuration is not limited to this, and the storage tank 17 is provided directly below the RO membrane module 7 on the downstream side. It is good also as a structure which provided the structure provided, ie, the RO membrane module 7, and the storage tank 17 directly.

  In 1st and 2nd embodiment, the example which calculates the drive frequency of a pressurization pump (5, 8, 12) by a speed type digital PID algorithm was demonstrated as a feedback control algorithm. However, the driving frequency of the pressurizing pump (5, 8, 12) may be calculated by a position type digital PID algorithm. Further, the drive frequency may be calculated not only by the PID algorithm but also by the P algorithm or the PI algorithm.

  In the first and second embodiments, a non-regenerative mixed bed ion exchange column may be provided in place of the EDI stack (electrodeionization stack) 16. In this case, deionized water can be obtained by deionizing the permeated water separated by the preceding RO membrane module with the ion exchange resin bed. In addition, immediately after the start of operation of the apparatus, deionized water whose water quality has been recovered can be supplied to the demand point. Further, by using the ion exchange tower, the power required for the treatment for obtaining deionized water from the permeated water can be made substantially zero.

  In the first and second embodiments, when the target flow rate value is changed, the recovery rate of the permeated water W2 (the front permeate water W2 and the rear permeate water W4) and the circulation ratio of the concentrated water W3 (W5) are set in advance. The example which adjusts the waste_water | drain flow volume and circulating flow volume of the concentrated water W3 was demonstrated so that it might be kept at a value. Not limited to this, when the target flow rate value is changed, the drainage flow rate of the concentrated water W3 so that the recovery rate of the permeate water W2 (the front permeate water W2 and the rear permeate water W4) is maintained at a preset value. Only the circulation flow rate of the concentrated water W3 may be adjusted so that the circulation ratio of the concentrated water W3 is maintained at a preset value. In other words, when the water quality of the supply water W1 is good and the concentration of the fouling cause substance and the scale cause substance is low, the occurrence of fouling and scale deposition can be avoided only by adjusting either the recovery rate or the circulation ratio. can do.

  In 1st and 2nd embodiment, the example which detects the usage-amount of water of a demand location by the increase / decrease in the water level of the storage tank 17 was demonstrated. Not limited to this, the flow rate sensor provided in the connecting pipe from the storage tank 17 to the demand point or the flow rate sensor provided in the equipment at the demand point is used to detect the amount of water used in the demand point. May be.

  In 1st and 2nd embodiment, the example which outputs a current value signal as a command signal from a control part (30, 30A) to an inverter (6, 9, 13) was demonstrated. However, the present invention is not limited to this, and a voltage value signal (for example, 0 to 10 V) may be output as a command signal from the control unit (30, 30A) to the inverter (6, 9, 13).

  1st and 2nd embodiment demonstrated the example which adjusts the waste_water | drain flow volume of the concentrated water W3 in steps by selecting the open | release number of the 1st drain valve V32-the 3rd drain valve V34. For example, the RO concentrated water discharge line L61 may be provided with a proportional control valve without branching the RO concentrated water discharge line L61. In this case, the flow rate of the concentrated water W3 can be adjusted by transmitting a current value signal from the control unit (30, 30A) to the proportional control valve to control the valve opening.

  Moreover, in the structure which provided the proportional control valve in RO concentrated water discharge line L61, it is good also as a structure which provided the flow sensor in RO concentrated water discharge line L61. In this case, the actual drainage flow rate of the concentrated water W3 can be more accurately controlled by inputting the flow rate value measured by the flow rate sensor to the control unit (30, 30A) as a feedback value.

  In 1st and 2nd embodiment, the soft water W12 which removed the hardness component contained in the raw | natural water W11 demonstrated the example made into the supply water W1. Not limited to this, the raw water W11 may be water pre-treated with a ferric-manganese removal device, a sand filtration device, a microfiltration membrane device, an ultrafiltration membrane device, or the like as the supply water W1. In addition, as raw | natural water W11, groundwater, a tap water, etc. can be used, for example.

1,1A pure water production equipment (water treatment equipment)
5, 8, 12 Pressurizing pump (pump)
6, 9, 13 Inverter 7 RO membrane module (reverse osmosis membrane module)
10 Pre-stage RO membrane module (reverse osmosis membrane module)
14 Subsequent RO membrane module (reverse osmosis membrane module)
16 EDI stack 17 Storage tank 30, 30A Control unit 171 Water level sensor (water level detection means)
V32 to V34 First drain valve to third drain valve (drainage means)
FM1 first flow rate sensor (flow rate detection means)
FM3 third flow rate sensor (flow rate detection means)
TE1 first temperature sensor (water temperature detection means)
TE5 Fifth temperature sensor (water temperature detection means)
L1 supply water line L21 permeate water line W1 supply water W2 permeate water, front permeate water W4 rear permeate water W3, W5, W7 concentrated water W6 demineralized water

Claims (5)

A reverse osmosis membrane module that separates supply water into permeate and concentrated water;
Flow rate detection means for detecting the flow rate of the permeated water,
A pump that is driven at a rotational speed according to the input driving frequency, sucks the supplied 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 pump;
The pump drive frequency is calculated by a feedback control algorithm so that the detected flow rate value of the flow rate detection means becomes a preset target flow rate value, and a command signal corresponding to the calculated value of the drive frequency is output to the inverter A control unit,
The control unit decreases the target flow value as the amount of water used at the demand point decreases, and increases the target flow value as the amount of water used at the demand point increases.
Water treatment equipment. A storage tank for storing permeate,
Water level detecting means for detecting the level of permeated water in the storage tank,
The control unit decreases the target flow rate value as the detection water level value of the water level detection unit increases, and increases the target flow rate value as the detection water level value of the water level detection unit decreases.
The water treatment apparatus according to claim 1. Equipped with drainage means that can adjust the drainage flow rate and circulating flow rate of concentrated water,
The control unit controls the drainage means so that the permeated water recovery rate and the concentrated water circulation ratio are maintained at preset values when the target flow rate value is changed.
The water treatment apparatus according to claim 1 or 2. When the detected water level value of the water level detecting means is smaller than a preset lower limit water level value and the reverse osmosis membrane module is in a high output operation state, the control unit has a permeated water recovery rate. Controlling the drainage means to be lower than a preset value;
The water treatment apparatus according to claim 2 or 3. Water temperature detection means for detecting the water temperature of the feed water,
The control unit executes control to decrease the target flow rate value as the detected water level value of the water level detecting unit increases only when the detected water temperature value of the water temperature detecting unit is equal to or lower than a preset water temperature value. ,
The water treatment apparatus as described in any one of Claims 2-4.

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