JP2019198808A - Reverse osmosis membrane separation apparatus - Google Patents

Abstract

To provide a reverse osmosis separation apparatus effective in preventing scaling and fouling.SOLUTION: A reverse osmosis membrane separation apparatus of this invention comprises: a reverse osmosis membrane module 4 that separates feed water W1 into permeated water W3 and concentrated water W4; a concentrated water line L4 that sends out the concentrated water W4 separated by the reverse osmosis membrane module 4; a circulation water line L5 that branches out from the concentrated water line L4 and returns part of the concentrated water W4 separated by the reverse osmosis membrane module 4 to a confluent section J2 of a feedwater line 1; and a flow rate adjusting unit 5 provided in the concentrated water line L4. The flow rate adjusting unit 5 includes: a constant flow rate element that causes the concentrated water of substantially constant flow rate to flow regardless of pressure difference in the flow rate adjusting unit 5; and a proportional element that increases a flow rate of the concentrated water substantially proportional to the pressure difference in the flow rate adjusting unit 5.SELECTED DRAWING: Figure 1

Description

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

  Conventionally, high-purity pure water that does not contain impurities is used in semiconductor manufacturing processes, cleaning of electronic components and medical devices, and the like. This type of pure water is generally produced by subjecting raw water such as groundwater or tap water to a reverse osmosis membrane separation treatment with a reverse osmosis membrane module (hereinafter also referred to as “RO membrane module”).

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

  Therefore, a reverse osmosis membrane separation device that performs flow rate feedback water volume control has been proposed in order to keep the flow rate of permeated water in the RO membrane module constant regardless of the temperature of the raw water and the state of the reverse osmosis membrane (for example, Patent Documents). 1).

Japanese Patent Application Laid-Open No. 2006-203084

  In the reverse osmosis membrane separation device according to Patent Document 1, a constant flow valve for concentrated water is installed. In general, in order to prevent scale, it is effective to increase the flow rate of the concentrated water relative to the flow rate of the permeated water, thereby increasing the flow rate on the primary side of the membrane and suppressing the progress of membrane clogging. However, when a constant flow valve is used in the concentrated water line as in the reverse osmosis membrane separation device according to Patent Document 1, such a suppression method cannot be used.

  An object of the present invention is to provide a reverse osmosis membrane separation device effective in terms of scale and fouling prevention.

  The present invention provides a water supply line through which water supply circulates, a reverse osmosis membrane module that separates supply water into permeated water and concentrated water, and is connected to the water supply line at a junction to supply the supply water to the reverse osmosis membrane module. Supply water line, a permeate line for sending permeated water separated by the reverse osmosis membrane module, a concentrated water line for sending concentrated water separated by the reverse osmosis membrane module, and a branch from the concentrated water line A circulating water line for returning a part of the concentrated water separated by the reverse osmosis membrane module to the junction, and a remaining part of the concentrated water branched from the concentrated water line and separated by the reverse osmosis membrane module. A drainage line that discharges out of the apparatus as drainage, a pressure pump that is provided in the supply water line and sucks the supply water and discharges it toward the reverse osmosis membrane module, and controls the pressure pump And a flow rate adjusting unit provided in the concentrated water line, wherein the flow rate adjusting unit allows a substantially constant flow rate of concentrated water to flow regardless of a differential pressure in the flow rate adjusting unit. And a proportional element that increases the flow rate of the concentrated water substantially in proportion to the differential pressure in the flow rate adjustment unit.

  Further, the apparatus further comprises first flow rate detecting means for detecting the flow rate of the permeated water as a first detected flow rate value, and the pump control unit pressurizes the pressurization so that the first detected flow rate value becomes a predetermined flow rate target value. It is preferable to control the pump.

  A second flow rate detecting means for detecting the flow rate of the drainage as a second detected flow rate value; a drainage flow rate adjusting valve provided in the drainage line and capable of adjusting a flow rate of the drainage discharged to the outside of the apparatus; Based on the first detected flow rate value and the second detected flow rate value, a target recovery rate calculation unit that calculates a target recovery rate that is a target value of the recovery rate, and the recovery rate is the target recovery rate It is preferable to further include a drainage flow rate adjustment valve control unit that controls the opening degree of the drainage flow rate adjustment valve.

  Further, the water supply pressure adjusting means for adjusting the pressure of the water supply flowing through the water supply line, the pressure measuring means for measuring the water supply pressure, and the water supply pressure based on the water supply pressure. It is preferable to further include a water supply pressure adjusting means control unit for controlling the adjusting means.

  Further, based on the water quality measuring means provided in the water supply line for measuring the quality of the water supply, the water temperature measuring means provided in the water supply line for measuring the water temperature of the water supply, the water quality of the water supply and the water temperature of the water supply. A target circulation ratio calculating unit that calculates a target circulation ratio; and a target water supply pressure calculating unit that calculates a target water supply pressure based on the target circulation ratio, wherein the water supply pressure adjusting means control unit It is preferable to control the water supply pressure adjusting means so that the pressure becomes the target water supply pressure.

  The feed water pressure adjusting means includes a feed water pump control unit that controls a feed water pump that supplies the feed water, and the feed water pressure adjusting means control unit controls the rotation speed of the feed water pump via the feed water pump control unit. It is preferable to control the pressure of the feed water by adjusting.

  Further, the water supply pressure adjusting means includes a water supply pressure adjusting valve provided in the water supply line, and the water supply pressure adjusting means control unit controls the pressure of the water supply by adjusting the opening of the water supply pressure adjusting valve. It is preferable to do.

  According to the present invention, it is possible to provide a reverse osmosis membrane separation device that is effective in terms of scale and prevention of fouling.

1 is an overall configuration diagram of a reverse osmosis membrane separation device according to a first embodiment of the present invention. It is a figure which shows the relationship between the pressure and flow volume which concern on the flow volume adjustment unit used in 1st Embodiment of this invention. It is a whole block diagram of the reverse osmosis membrane separation apparatus which concerns on 2nd Embodiment of this invention. It is a functional block diagram of a control part of a reverse osmosis membrane separation device concerning a 2nd embodiment of the present invention. It is a flowchart which shows operation | movement of the reverse osmosis membrane separator which concerns on 2nd Embodiment of this invention. It is a flowchart which shows operation | movement of the reverse osmosis membrane separator which concerns on 2nd Embodiment of this invention. It is a whole block diagram of the reverse osmosis membrane separation apparatus which concerns on 3rd Embodiment of this invention.

[1 First Embodiment]
[1.1 Configuration of Reverse Osmosis Membrane Separator]
A reverse osmosis membrane separation device 1 according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of a reverse osmosis membrane separation device 1 according to a first embodiment. The reverse osmosis membrane separation device 1 according to the present embodiment is applied to, for example, a pure water production system that produces pure water from fresh water.

  As shown in FIG. 1, a reverse osmosis membrane separation device 1 according to this embodiment includes a feed water pump 12, a feed water side inverter 13, a pressurization pump 2, a pressurization side inverter 3, and an RO as a reverse osmosis membrane module. A membrane module 4, a flow rate adjustment unit 5, a check valve 6, a drainage flow rate adjustment valve 7 (proportional control valve) as a drainage flow rate adjustment means, a first flow rate sensor FM1, and a control unit 30 are provided. Note that illustration of electrical connection lines between the control unit 30 and the controlled device is omitted.

  The reverse osmosis membrane separation device 1 includes a water supply line L1, a supply water line L2, a permeate water line L3, a first concentrated water line L41, a second concentrated water line L42, a circulating water line L5, A line L6. The “line” in the present specification is a general term for lines capable of flowing a fluid such as a flow path, a path, and a pipeline.

  The water supply line L1 is a line which supplies the water supply W1 to J2 which is a confluence | merging point with the supply water line L2. The upstream end of the water supply line L1 is connected to a supply source (not shown) of the water supply W1. The water supply line L1 is provided with a water supply pump 12 and a junction J2 in order from the upstream side to the downstream side.

  The feed water W1 flowing through the feed water line L1 is not limited to the feed water directly supplied from the feed source (not shown) of the feed water W1, but, for example, the feed water W1 is filtered by a filtration device (iron removal manganese removal device, activated carbon filtration device). Etc.), water supply pretreated by a pretreatment device such as a water softening device is also included.

  The feed water pump 12 is a device that sucks in the feed water W1 flowing through the feed water line L1 and pumps (discharges) the feed water W1 toward the pressurizing pump 2. The feed water 12 is supplied with drive power having a frequency converted from the feed water side inverter 13. The feed water pump 12 is driven at a rotational speed corresponding to the frequency (hereinafter also referred to as “drive frequency”) of the supplied (input) drive power.

  The water supply side inverter 13 is an electric circuit (or a device having the circuit) that supplies the feed water pump 12 with driving power whose frequency has been converted. The water supply side inverter 13 is electrically connected to the control unit 30. A command signal is input from the control unit 30 to the water supply side inverter 13. The water supply side inverter 13 outputs drive power having a drive frequency corresponding to the command signal (current value signal or voltage value signal) input by the control unit 30 to the water supply pump 12.

  In the present embodiment, the control unit 30 controls the water supply side inverter 13 so that the water supply pump 12 discharges the water supply W1 at a predetermined constant pressure value. The constant pressure value of the feed water W1 applied by the feed water pump 12 is set to a pressure value at which the feed water W1 flowing through the feed water line L1 can be supplied to the pressurizing pump 2. Thereby, the feed water pressure of the feed water W1 becomes a constant pressure value. In the present embodiment, the feed water pressure of the feed water W1 is set to a constant pressure value between 0.2 and 0.5 MPa, for example.

  The supply water line L2 is a line that supplies the supply water W1 to the RO membrane module 4 as the supply water W2. The upstream end of the supply water line L2 is connected to the junction J2. The downstream end of the supply water line L <b> 2 is connected to the primary inlet port of the RO membrane module 4. The supply water line L2 is provided with a merging portion J2, a pressure pump 2, and an RO membrane module 4 in order from the upstream side to the downstream side.

  The pressurizing pump 2 is provided in the supply water line L2. The pressurizing pump 2 is a device that sucks the feed water W1 and feeds (discharges) the feed water W1 to the RO membrane module 4 as the feed water W2 in the feed water line L2. The pressurizing pump 2 is supplied with driving power whose frequency is converted from the pressurizing side inverter 3. The pressurizing pump 2 is driven at a rotational speed corresponding to the frequency (hereinafter also referred to as “driving frequency”) of the driving power supplied (input).

  The pressurizing side inverter 3 is an electric circuit (or a device having the circuit) that supplies driving power having a frequency converted to the pressurizing pump 2. The pressurizing side inverter 3 is electrically connected to the control unit 30. A command signal is input from the control unit 30 to the pressure side inverter 3. The pressurizing side inverter 3 outputs driving power having a driving frequency corresponding to the command signal (current value signal or voltage value signal) input by the control unit 30 to the pressurizing pump 2.

  The RO membrane module 4 is a facility for subjecting the supply water W2 discharged from the pressurizing pump 2 to membrane separation treatment into permeated water W3 from which dissolved salts have been removed and concentrated water W4 from which dissolved salts have been concentrated. The RO membrane module 4 includes a single or a plurality of RO membrane elements (not shown). The RO membrane module 4 membrane-separates the supply water W2 with these RO membrane elements, and produces the permeated water W3 and the concentrated water W4.

  The permeated water line L3 is a line for sending the permeated water W3 separated by the RO membrane module 4. The upstream end of the permeate line L3 is connected to the secondary port of the RO membrane module 4. The downstream end of the permeate line L3 is connected to a device or the like at the demand point. A first flow rate sensor FM1 (hereinafter also referred to as “first flow rate detection means”) is installed in the permeate line L3.

  The first flow rate sensor FM1 is a device that detects the flow rate of the permeated water W3 flowing through the permeated water line L3 as a first detected flow rate value. The first flow sensor FM1 is connected to the permeate line L3. The first flow sensor FM1 is electrically connected to the control unit 30. The first detected flow rate value of the permeated water W3 detected by the first flow rate sensor FM1 is transmitted to the control unit 30 as a detection signal. As the first flow rate sensor FM1, for example, a pulse transmission type flow rate sensor in which an axial flow impeller or a tangential impeller (not shown) is disposed in the flow path housing can be used.

  The first concentrated water line L41 is a line for sending the concentrated water W4 separated by the RO membrane module 4. The upstream end of the first concentrated water line L41 is connected to the primary outlet port of the RO membrane module 4. Further, the downstream side of the first concentrated water line L41 is connected to the primary side of the flow rate adjustment unit 5.

  The second concentrated water line L <b> 42 is a line for sending the concentrated water W <b> 4 whose flow rate is adjusted by the flow rate adjusting unit 5. The upstream end of the second concentrated water line L <b> 42 is connected to the secondary side of the flow rate adjustment unit 5. Further, the downstream side of the second concentrated water line L42 branches into a circulating water line L5 and a drainage line L6 at the connection portion J1.

  Hereinafter, the first concentrated water line L41 and the second concentrated water line L42 may be collectively referred to as “the concentrated water line L4”.

  The flow rate adjusting unit 5 concentrates substantially in proportion to the constant flow rate element that allows the concentrated water having a substantially constant flow rate to flow and the differential pressure in the flow rate adjusting unit 5 regardless of the differential pressure in the flow rate adjusting unit 5. And a proportional element that increases the flow rate of the water W4. The differential pressure in the flow rate adjustment unit 5 is specifically the differential pressure between the water pressure in the first concentrated water line L41 and the water pressure in the second concentrated water line L42. As the constant flow rate element, a constant flow rate value is maintained without requiring auxiliary power or external operation, and for example, a constant flow rate element called by the name of the water governor may be used. Moreover, as a proportional element, what is called by the name of an orifice may be used, for example, and the flow rate of the concentrated water W4 flowing from the orifice is proportional to the differential pressure in the flow rate adjusting unit 5.

  FIG. 2 is a graph showing an example of the relationship between the inlet pressure of the RO membrane module 4 and the flow rate of the concentrated water flowing through the flow rate adjustment unit 5. Since the flow rate adjusting unit 5 includes a constant flow rate element, when the inlet pressure is generated, the flow rate of the concentrated water flowing through the flow rate adjusting unit 5 rises to point A at a stretch. That is, approximately, the flow rate at the height of point A flows to the flow rate adjustment unit 5 simultaneously with the generation of the inlet pressure. At the same time, since the flow rate adjusting unit 5 includes a proportional element, the flow rate of the concentrated water flowing through the flow rate adjusting unit 5 increases in a linear function as the inlet pressure increases.

  In the flow rate adjustment unit 5, the constant flow rate element and the proportional element may be configured integrally or may be configured separately. In the case of being configured integrally, for example, the flow direction of the proportional element coincides with the long axis direction of the flow rate adjustment unit 5, and the flow direction of the constant flow rate element is orthogonal to the long axis direction of the flow rate adjustment unit 5. You may comprise as follows. Alternatively, the flow direction of the proportional element may be orthogonal to the long axis direction of the flow rate adjustment unit 5, and the flow direction of the constant flow rate element may coincide with the long axis direction of the flow rate adjustment unit 5. Alternatively, the flow direction of the constant flow element and the flow direction of the proportional element may both be configured to coincide with the major axis direction of the flow rate adjustment unit 5.

  The circulating water line L5 is a line branched from the concentrated water line L4, and is a line that returns the circulating water W41, which is a part of the concentrated water W4 separated by the RO membrane module 4, to the junction J2. The upstream end of the circulating water line L5 is connected to the concentrated water line L4 at the connecting portion J1. Further, the downstream end of the circulating water line L5 is connected to the water supply line L1 at the junction J2. A check valve 6 is provided in the circulating water line L5.

  The drainage line L6 is a line that is branched from the concentrated water line L4 at the connection portion J1 and discharges the wastewater W42 that is the remaining portion of the concentrated water W4 separated by the RO membrane module 4 to the outside of the apparatus (outside the system). The drainage line L6 is provided with a drainage flow rate adjusting valve 7 as drainage flow rate adjusting means.

  The drainage flow rate adjusting valve 7 is a valve capable of adjusting the drainage flow rate of the drainage W42 discharged from the drainage line L6 to the outside of the apparatus. The drainage flow rate adjustment valve 7 is electrically connected to the control unit 30. The valve opening degree of the drain flow rate adjusting valve 7 is controlled by a drive signal transmitted from the control unit 30. By sending a current value signal (for example, 4 to 20 mA) from the control unit 30 to the drainage flow rate adjustment valve 7, the drainage flow rate of the drainage W42 can be adjusted by controlling the valve opening degree.

  The control unit 30 includes a CPU, a ROM, a RAM, a CMOS memory, and the like, which are known to those skilled in the art and configured to be able to communicate with each other via a bus.

  The CPU is a processor that controls the reverse osmosis membrane separation apparatus 1 as a whole. The CPU reads out various programs stored in the ROM via a bus and controls the entire reverse osmosis membrane separation device 1 according to the various programs, thereby functioning as a pump control unit that controls the pressurizing pump 2. Configured to be realized. Various data such as temporary calculation data and display data are stored in the RAM. The CMOS memory is configured as a non-volatile memory that is backed up by a battery (not shown) and retains the memory state even when the reverse osmosis membrane separation device 1 is powered off.

  The control unit 30 controls the pressurizing pump 2 as a pump control unit. More specifically, the control unit 30 sets the frequency of the pressurization pump 2 via the pressurization-side inverter 3 so that the flow rate of the permeated water W3 detected by the first flow rate sensor FM1 becomes a predetermined flow rate target value. By controlling, the flow rate of the supply water discharged from the pressurizing pump 2 is controlled. Thereby, flow rate feedback water amount control is realized in which the flow rate of the permeated water W3 in the RO membrane module 4 is kept constant.

[1.2 Operation of reverse osmosis membrane separator]
With the passage of time from the start of use of the reverse osmosis membrane separation device 1, there is a concern that the RO membrane element of the RO membrane module 4 may be clogged with scale. Due to this clogging, the water pressure of the supply water line L2 and, consequently, the water pressure of the first concentrated water line L41 rises, but the flow rate adjusting unit 5 has a differential pressure in the flow rate adjusting unit 5, that is, the first concentrated water line L41. The flow rate of the concentrated water W4 increases because it includes a proportional element that increases the flow rate of the concentrated water substantially in proportion to the differential pressure between the water pressure and the water pressure of the second concentrated water line L42. By increasing the flow rate of the concentrated water W4 relative to the flow rate of the permeated water W3, the circulation ratio (ratio of the flow rate of the concentrated water W4 relative to the flow rate of the permeated water W3) increases, and the flow velocity on the primary side of the RO membrane module 4 increases. Thereby, the shearing force of the scale from the RO membrane element increases, and the progress of membrane clogging is suppressed.

[1.3 Effects of First Embodiment]
According to the reverse osmosis membrane separation device 1 according to the first embodiment described above, for example, the following effects can be obtained.
In the reverse osmosis membrane separation device 1 according to the first embodiment, the flow rate adjustment unit 5 is installed in the concentrated water line L4, and the flow rate adjustment unit 5 is substantially constant regardless of the differential pressure in the flow rate adjustment unit 5. Constant flow element for circulating the concentrated water and a proportional element for increasing the flow rate of the concentrated water substantially in proportion to the differential pressure in the flow rate adjusting unit 5.

  When the RO membrane element of the RO membrane module 4 is clogged, the differential pressure in the flow rate adjustment unit 5 increases, so that the flow rate of the concentrated water W4 increases and the circulation ratio increases. Thereby, the shearing force of the scale from the RO membrane element increases, and the progress of membrane clogging is suppressed.

[2 Second Embodiment]
[2.1 Configuration of reverse osmosis membrane separator]
A reverse osmosis membrane separation device 1A according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 is an overall configuration diagram of a reverse osmosis membrane separation device 1A according to the second embodiment. In the following, among the components provided in the reverse osmosis membrane separation device 1A, the same components as those provided in the reverse osmosis membrane separation device 1 according to the first embodiment are described using the same reference numerals. The components different from the reverse osmosis membrane separation device 1 will be mainly described.

  The reverse osmosis membrane separation device 1A includes, in addition to the constituent elements of the reverse osmosis membrane separation device 1, a water quality sensor 15 as water quality measurement means, a water temperature sensor 16 as water temperature measurement means, a pressure sensor 17 as pressure measurement means, Two flow sensors FM2 are provided. The reverse osmosis membrane separation device 1 </ b> A includes a control unit 30 </ b> A instead of the control unit 30.

  The water quality sensor 15 is installed in the water supply line L1. The water quality sensor 15 is electrically connected to the control unit 30A. The water quality sensor 15 measures the water quality of the feed water W1 (hereinafter also referred to as “measured water quality value”), and the measured water quality value is transmitted as a detection signal to the control unit 30A. The water quality of the water supply W1 may be one or more of pH, hardness, alkalinity, calcium carbonate solubility, silica solubility, silica concentration, and the like.

  The water temperature sensor 16 is installed in the water supply line L1. The water temperature sensor 16 is electrically connected to the control unit 30A. The water temperature sensor 16 measures the water temperature of the water supply W1 (hereinafter also referred to as “measured water temperature value”), and the measured water temperature value is transmitted as a detection signal to the control unit 30A.

  The pressure sensor 17 is installed in the water supply line L1. The pressure sensor 17 is electrically connected to the control unit 30A. The pressure sensor 17 measures the water pressure of the feed water W1 (hereinafter also referred to as “measured water pressure value”), and the measured water pressure value is transmitted as a detection signal to the control unit 30A.

  The second flow rate sensor FM2 (hereinafter also referred to as “second flow rate detection means”) is a device that detects the flow rate of the wastewater W42 flowing through the drainage line L6 as a second detected flow rate value. The second flow sensor FM2 is connected to the drain line L6. The second flow sensor FM2 is electrically connected to the control unit 30A. The second detected flow rate value of the waste water W42 detected by the second flow rate sensor FM2 is transmitted as a detection signal to the control unit 30A. As the second flow rate sensor FM2, for example, a pulse transmission type flow rate sensor in which an axial flow impeller or a tangential impeller (not shown) is disposed in the flow path housing can be used.

[2.2 Function blocks of control unit]
The control unit 30A, like the control unit 30, includes a CPU, ROM, RAM, CMOS memory, and the like, which are known to those skilled in the art and configured to be able to communicate with each other via a bus. The CPU reads various programs stored in the ROM via the bus and controls the entire reverse osmosis membrane separation device 1 according to the various programs, so that the control unit 30A can be controlled as shown in the functional block diagram of FIG. The pump control unit 301, the target recovery rate calculation unit 302, the target circulation ratio calculation unit 303, the target water supply pressure calculation unit 304, the drainage flow rate adjustment valve control unit 305, and the water supply pressure adjustment means control unit 306 are configured to be realized. Is done.

  The pump control unit 301 controls the driving frequency of the pressurizing pump 2 via the pressurizing side inverter 3 so that the flow rate of the permeated water W3 detected by the first flow rate sensor FM1 becomes a predetermined flow rate target value. . Thereby, flow rate feedback water amount control is realized in which the flow rate of the permeated water W3 in the RO membrane module 4 is kept constant.

The target recovery rate calculation unit 302 calculates the target recovery rate based on the measured water quality value detected by the water quality sensor 15. Here, the “target recovery rate” is a target value of the recovery rate. The “recovery rate” is the ratio of the flow rate of the permeate water W3 to the flow rate of the feed water W1 supplied to the RO membrane module 4 (the flow rate of the permeate water W3 / the flow rate of the feed water W1). It is calculated from the first detected flow value that is the flow rate of the permeated water W3 and the second detected flow value that is the flow rate of the drainage W42.
In addition, by using, for example, hardness, alkalinity, silica concentration, etc. as the measured water quality value, it is possible to calculate a target recovery rate that maximizes the recovery rate of the permeated water W3 while reliably suppressing the precipitation of scale. It becomes possible.
The applicant has previously filed an invention related to a reverse osmosis membrane separation device as Japanese Patent Application No. 2017-113706. The method for calculating the target recovery rate described in the specification may be incorporated in the present invention.

The target circulation ratio calculation unit 303 calculates a target circulation ratio based on the measured water quality value detected by the water quality sensor 15 and the measured water temperature value detected by the water temperature sensor 16. Here, the “target circulation ratio” is a target value of the circulation ratio. Since the scale risk can be reduced by controlling the circulation ratio when the scale risk increases due to the water temperature and the water quality of the water supply W1, the target circulation ratio calculation unit 303 performs the water quality and water temperature of the water supply W1. Based on the above, the target circulation ratio is calculated.
The target circulation ratio is preferably a value between 5 and 6.

  The target water supply pressure calculation unit 304 calculates the target water supply pressure based on the target circulation ratio calculated by the target circulation ratio calculation unit 303. Here, the “target water supply pressure” is a target value of the water supply pressure. In order to ensure the flow rate even when the RO membrane clogging of the RO membrane module 4 progresses, when the primary pressure of the RO membrane module 4 is increased, the water pressure of the first concentrated water line L41 increases, and the flow rate adjustment unit The differential pressure at 5 increases. Since the flow rate adjusting unit 5 includes a proportional element that increases the flow rate of the concentrated water W4 substantially in proportion to the differential pressure in the flow rate adjusting unit 5, the flow rate of the concentrated water W4 increases. That is, since the circulation ratio increases as the primary pressure of the RO membrane module 4 increases due to the increase of the feed water pressure due to the presence of the flow rate adjusting unit 5, the target feed water pressure calculation unit 304 uses this relationship. Then, the target water supply pressure is calculated based on the target circulation ratio.

  The drainage flow rate adjustment valve control unit 305 adjusts the opening degree of the drainage flow rate adjustment valve 7 so that the actual value of the recovery rate becomes the target recovery rate. For example, a speed digital PID algorithm can be used for the calculation of the opening degree in this control. The drainage flow rate adjustment valve control unit 305 may change the opening degree of the drainage flow rate adjustment valve 7 discontinuously.

  The feed water pressure adjusting means control unit 306 adjusts the pressure of the feed water W1 flowing through the feed water line L1 so that the measured water pressure value detected by the pressure sensor 17 becomes the target feed water pressure calculated by the target feed water pressure calculation unit 304. The feed water pressure adjusting means to be controlled is controlled. In the second embodiment, the “feed water pressure adjusting means” is a feed water pump control unit that controls the feed water pump 12, specifically, a feed water side inverter 13. That is, the feed water pressure adjusting means control unit 306 controls the feed water pressure by controlling the rotation speed of the feed water pump 12 via the feed water side inverter 13.

The feed water pressure adjusting means control unit 306 controls the rotation speed of the feed water pump 12 in a range where the frequency of the pressurizing pump 2 in front of the RO membrane module 4 does not fall below the lower limit frequency.
Thereby, the failure of the pressurizing pump 2 is prevented, and as a result, the differential pressure in the flow rate adjusting unit 5 is also secured, and the target circulation ratio is also secured.

  In particular, when the water supply pressure adjusting means control unit 306 controls the rotation speed of the water supply pump 12, when the water quality measured by the water quality sensor 15 deteriorates or when the water temperature measured by the water temperature sensor 16 changes, the scale The risk increases (for silica, the lower the water temperature, the lower the solubility and the higher the scale risk, and for the calcium hardness, the higher the water temperature, the lower the solubility and the higher the scale risk). Is within a range that does not fall below the lower limit frequency, the rotational speed of the feed water pump 12 is reduced.

[2.3 Control method of drainage flow control valve]
The flowchart of FIG. 5 shows a method for controlling the drain flow rate adjusting valve 7.
In step S1, the target recovery rate calculation unit 302 determines the flow rate of the permeated water W3 detected by the first flow rate sensor FM1 and the remainder of the concentrated water W4 detected by the second flow rate sensor FM2, based on the quality of the water supply. That is, the target recovery rate, which is the target value of the recovery rate calculated from the flow rate of the waste water W42, is calculated.

  In step S2, the first flow rate sensor FM1 detects the flow rate of the permeated water W3, and the second flow rate sensor FM2 detects the remaining amount of the concentrated water W4, that is, the flow rate of the waste water W42, thereby measuring the actual recovery rate. Is done.

  In step S3, the drain flow rate adjusting valve control unit 305 compares the difference between the actual recovery rate measured in step S2 and the target recovery rate calculated in step S1 with a predetermined deviation. If the difference between the actual recovery rate and the target recovery rate is less than the predetermined deviation (S3: YES), the process proceeds to step S4. If the difference between the actual recovery rate and the target recovery rate is greater than or equal to a predetermined deviation (S3: NO), the process proceeds to step S5.

  In step S4, the drainage flow rate adjustment valve control unit 305 fixes the opening degree of the drainage flow rate adjustment valve 7, and the process returns to step S1 (return).

  In step S5, the drainage flow rate adjustment valve control unit 305 changes the opening degree of the drainage flow rate adjustment valve 7, and the process returns to step S1 (return).

  In step S1, the target recovery rate calculation unit 302 may calculate the target recovery rate based on silica solubility, calcium carbonate solubility, and the like as the water quality.

  Moreover, you may replace the order of said step S1-step S5 suitably as needed.

[2.4 Control method of water supply pressure]
The flowchart in FIG. 6 shows a method for controlling the feed water pressure.
In step S11, the water quality sensor 15 measures the water quality of the water supply W1 in the water supply line L1.

  In step S12, the water temperature sensor 16 measures the water temperature of the water supply W1 in the water supply line L1.

  In step S <b> 13, the target circulation ratio calculation unit 303 calculates a target circulation ratio based on the measured water quality value detected by the water quality sensor 15 and the measured water temperature value detected by the water temperature sensor 16.

  In step S14, the target water supply pressure calculation unit 304 calculates a target water supply pressure based on the target circulation ratio calculated by the target circulation ratio calculation unit 303.

  In step S15, the pressure sensor 17 measures the water pressure of the water supply W1 in the water supply line L1.

  In step S16, when the actual water supply pressure exceeds the target water supply pressure (S16: YES), the process proceeds to step S17. When the actual water supply pressure is equal to or lower than the target water supply pressure (S16: NO), the process proceeds to step S18.

  In step S17, the feed water pressure adjusting means control unit 306 controls the rotation speed of the feed water pump 12 through the feed water side inverter 13 as the feed water pressure adjusting means within a range where the frequency of the pressurizing pump 2 does not fall below the lower limit frequency. As a result, the water supply pressure is lowered, and the process returns to step S1 (return).

  In step S18, the feed water pressure adjusting means control unit 306 controls the rotation speed of the feed water pump 12 via the feed water side inverter 13 as the feed water pressure adjusting means within a range where the frequency of the pressurizing pump 2 does not fall below the lower limit frequency. By doing so, the water supply pressure is raised, and the process returns to step S1 (return).

  In particular, when the water supply pressure adjusting means control unit 306 controls the rotation speed of the water supply pump 12, when the water quality measured by the water quality sensor 15 deteriorates or when the water temperature measured by the water temperature sensor 16 changes, The rotation speed of the feed water pump 12 is reduced within a range where the frequency of the pressure pump 2 does not fall below the lower limit frequency.

  In addition, you may replace the order of said step S11-step S18 suitably as needed.

[2.5 Effects of Second Embodiment]
According to the reverse osmosis membrane separation device 1A according to the second embodiment described above, for example, the following effects can be obtained.
By the reverse osmosis membrane separation device 1A, the same effect as the reverse osmosis membrane separation device 1 according to the first embodiment is exhibited.

Further, the reverse osmosis membrane separation device 1A detects the flow rate of the permeated water W3, and controls the pressurizing pump 2 so that the flow rate of the permeated water W3 becomes a predetermined target flow rate value.
Thereby, it becomes possible to ensure the flow rate of the permeated water W3 stably.

Further, the reverse osmosis membrane separation device 1A calculates the target recovery rate, and controls the opening degree of the drainage flow rate adjustment valve 7 so that the actual recovery rate becomes the target recovery rate.
Thereby, even if the inlet pressure of the drainage flow rate adjustment valve fluctuates, the recovery rate can be kept constant.

Moreover, 1 A of reverse osmosis membrane separators measure the pressure of the feed water W1, and adjust a feed water pressure based on the measured pressure value of the feed water W1.
Since the reverse osmosis membrane is deteriorated, the differential pressure in the flow rate adjustment unit 5 is lowered and the return of the circulating water W41 is deteriorated. By ensuring the above, it can be prevented.

Further, the reverse osmosis membrane separation device 1A calculates the target circulation ratio based on the water quality and the water temperature of the feed water W1, calculates the target water supply pressure based on the target circulation ratio, and the actual water supply pressure becomes the target water supply pressure. Adjust the water supply pressure.
This makes it possible to reduce the scale risk when the scale risk increases due to the temperature and quality of the feed water.

The reverse osmosis membrane separation device 1 </ b> A includes a water supply side inverter 13 as a water supply pump control unit that controls the water supply pump 12 as a water supply pressure adjusting unit, and controls the rotation speed of the water supply pump 12 via the water supply side inverter 13. By doing so, the water supply pressure is controlled.
By controlling the number of rotations of the feed water pump 12 based on the measured value of the pressure of the feed water W1, the feed water pressure can be lowered.

[3 Third Embodiment]
[3.1 Configuration of Reverse Osmosis Membrane Separator]
A reverse osmosis membrane separation device 1B according to a third embodiment of the present invention will be described with reference to the drawings. FIG. 7 is an overall configuration diagram of a reverse osmosis membrane separation device 1B according to the third embodiment. In the following, among the components provided in the reverse osmosis membrane separation device 1B, the same components as those provided in the reverse osmosis membrane separation device 1A according to the second embodiment are described using the same reference numerals. The components different from the reverse osmosis membrane separation device 1A will be mainly described.

  Unlike the reverse osmosis membrane separation device 1 </ b> A, the reverse osmosis membrane separation device 1 </ b> B includes a water supply pressure adjustment valve 14 instead of the water supply side inverter 13.

  The water supply pressure adjustment valve 14 is installed upstream of the water quality sensor 15, the water temperature sensor 16, and the pressure sensor 17 in the water supply line L <b> 1. The feed water pressure adjustment valve 14 is electrically connected to the control unit 30A. The feed water pressure adjustment valve 14 is a valve that regulates the pressure of the feed water W1 flowing through the feed water line L1.

  In addition, in this embodiment, although the feed water pump 12 was provided in the feed water line L1, it is not restrict | limited to this. If the water supply pressure of the water supply W1 supplied from the supply source is sufficiently secured, the water supply pump 12 may not be provided. For example, you may comprise so that the water supply pressure of the water supply W1 may be ensured by utilizing a water head pressure difference in the upstream of the water supply line L1.

[3.2 Functional blocks of control unit]
The functional blocks realized by the control unit 30B are basically the same as the functional blocks realized by the control unit 30A of the reverse osmosis membrane separation device 1A of the second embodiment, and thus illustration thereof is omitted.
However, among the functional blocks realized by the control unit 30B, the feed water pressure adjusting unit control unit 306 controls the feed water pressure adjusting valve 14 as the feed water pressure adjusting unit. The feed water pressure is adjusted by the feed water pressure adjusting means control unit 306 controlling the opening of the feed water pressure adjusting valve 14.

[3.3 Wastewater flow rate adjustment valve and control method of water supply pressure]
The control method of the drainage flow rate adjustment valve and the control method of the feed water pressure in the reverse osmosis membrane separation device 1B are basically the control method of the drainage flow rate adjustment valve in the reverse osmosis membrane separation device 1A according to the second embodiment, and Since it is the same as the method for controlling the feed water pressure, its illustration and description are omitted.

  However, in the control method of the feed water pressure shown in FIG. 6, in step S17 and step S18, the feed water pressure adjusting means control unit 306 controls the opening of the feed water pressure adjusting valve 14 as the feed water pressure adjusting means, thereby The reverse osmosis membrane separation device 1B is different from the reverse osmosis membrane separation device 1A in that the pressure is lowered / increased.

[3.4 Effects of Third Embodiment]
According to the reverse osmosis membrane separation device 1B according to the third embodiment described above, for example, the following effects can be obtained.
The reverse osmosis membrane separation device 1B has the same effects as the reverse osmosis membrane separation device 1 according to the first embodiment and the reverse osmosis membrane separation device 1A according to the second embodiment.

Further, the reverse osmosis membrane separation device 1B includes a feed water pressure adjusting valve 14 as a feed water pressure adjusting means, and controls the feed water pressure by controlling the opening of the feed water pressure adjusting valve 14.
The feed water pressure can be lowered by controlling the opening of the feed water pressure adjusting valve 14 based on the measured value of the pressure of the feed water W1.

[4. (Modification)
In the above-described reverse osmosis membrane separation devices 1, 1A, and 1B, when the RO membrane is clogged, it is possible to perform membrane exchange, membrane cleaning, etc., as in the case of normal reverse osmosis membrane separation devices. is there.

  Further, the main unit of the flow rate adjusting unit 5 may include a mechanical relief valve.

DESCRIPTION OF SYMBOLS 1 1A 1B Reverse osmosis membrane separation apparatus 2 Pressure pump 4 RO membrane module 5 Flow rate adjustment unit 7 Drain flow rate adjustment valve 12 Water supply pump 14 Water supply pressure adjustment valve 15 Water quality sensor 16 Water temperature sensor 17 Pressure sensor 30 30A 30B Control unit 301 Pump control Section 302 Target recovery rate calculation section 303 Target circulation ratio calculation section 304 Target supply water pressure calculation section 305 Drain flow rate adjustment valve control section 306 Supply water pressure adjustment means control section L1 Supply water line L2 Supply water line L3 Permeate water line L4 Concentrated water line L5 Circulation Water line L6 Drainage line W1 Water supply W2 Supply water W3 Permeated water W4 Concentrated water W41 Circulating water W42 Drainage

Claims (7)

A water supply line through which the water supply circulates;
A reverse osmosis membrane module that separates supply water into permeate and concentrated water;
A supply water line connected to the water supply line at a junction, and supplying supply water to the reverse osmosis membrane module;
A permeate line for delivering permeate separated by the reverse osmosis membrane module;
A concentrated water line for delivering concentrated water separated by the reverse osmosis membrane module;
A circulating water line branched from the concentrated water line and returning a part of the concentrated water separated by the reverse osmosis membrane module to the junction;
A drainage line that branches off from the concentrated water line and drains the remainder of the concentrated water separated by the reverse osmosis membrane module as wastewater;
A pressure pump provided in the supply water line, for sucking the supply water and discharging it toward the reverse osmosis membrane module;
A pump controller for controlling the pressurizing pump;
A flow rate adjustment unit provided in the concentrated water line,
The flow rate adjustment unit includes a constant flow element that allows a substantially constant flow rate of concentrated water to flow regardless of the differential pressure in the flow rate adjustment unit, and a flow rate of the concentrated water that is substantially proportional to the differential pressure in the flow rate adjustment unit. A reverse osmosis membrane separation device, comprising: A first flow rate detecting means for detecting the flow rate of the permeated water as a first detected flow rate value;
The reverse osmosis membrane separation device according to claim 1, wherein the pump control unit controls the pressurizing pump so that the first detected flow rate value becomes a predetermined flow rate target value. Second flow rate detection means for detecting the flow rate of the waste water as a second detected flow rate value;
A drainage flow rate adjusting valve provided in the drainage line and capable of adjusting a flow rate of drainage discharged outside the device;
A target recovery rate calculation unit that calculates a target recovery rate that is a target value of the recovery rate calculated from the first detected flow rate value and the second detected flow rate value based on the quality of the water supply;
The reverse osmosis membrane separation device according to claim 2, further comprising: a drainage flow rate adjustment valve control unit that controls an opening degree of the drainage flow rate adjustment valve so that the recovery rate becomes the target recovery rate. A water supply pressure adjusting means provided in the water supply line for adjusting the pressure of the water supplied through the water supply line;
Pressure measuring means for measuring the pressure of the water supply;
A feed water pressure adjusting means control unit for controlling the feed water pressure adjusting means based on the pressure of the feed water;
The reverse osmosis membrane separation device according to any one of claims 1 to 3, further comprising: A water quality measuring means provided in the water supply line for measuring the quality of the water supply;
A water temperature measuring means provided in the water supply line for measuring the temperature of the water supply;
A target circulation ratio calculator that calculates a target circulation ratio based on the quality of the water supply and the temperature of the water supply;
A target water supply pressure calculation unit for calculating a target water supply pressure based on the target circulation ratio;
5. The reverse osmosis membrane separation device according to claim 4, wherein the water supply pressure adjusting means control unit controls the water supply pressure adjusting means so that the pressure of the water supply becomes the target water supply pressure. The water supply pressure adjusting means includes a water supply pump control unit that controls a water supply pump that supplies the water supply,
The reverse osmosis membrane separation device according to claim 4 or 5, wherein the feed water pressure adjusting means control unit controls the feed water pressure by adjusting the rotation speed of the feed water pump via the feed water pump control unit. The water supply pressure adjustment means includes a water supply pressure adjustment valve provided in the water supply line,
The reverse osmosis membrane separation device according to claim 4 or 5, wherein the water supply pressure adjusting means controller controls the pressure of the water supply by adjusting the opening of the water supply pressure adjusting valve.

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