JP7283072B2 - Membrane separator - Google Patents

Description

The present invention relates to a membrane separation device.

2. Description of the Related Art Conventionally, high-purity pure water containing no impurities is used in the manufacturing process of semiconductors, cleaning of electronic parts and medical equipment, and the like. This type of pure water is generally produced by subjecting raw water such as groundwater and tap water to reverse osmosis membrane separation treatment using a reverse osmosis membrane module (hereinafter also referred to as "RO membrane module").

The water permeability coefficient of a reverse osmosis membrane made of polymeric material changes with temperature. The water permeability coefficient of a reverse osmosis membrane also changes due to clogging of pores (hereinafter also referred to as "membrane clogging") and deterioration due to oxidation of materials (hereinafter also referred to as "membrane deterioration").

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

JP 2005-296945 A

In this water reforming system, a proportional control valve (opening adjustment valve) is used to control the amount of water discharged and the pressure of the water supply. Shorten. In addition, follow-up to other PI control becomes frequent, and the possibility of hunting increases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a membrane separation apparatus capable of prolonging the life of an opening adjustment valve and stabilizing various PI controls.

The present invention comprises a reverse osmosis membrane module that separates feed water containing feed water into permeated water and concentrated water, a pressurization pump that sucks feed water and discharges it as feed water toward the reverse osmosis membrane module, and the pressurization pump. Adjust the pressure of the water supply supplied to the pressure pump, the water supply pressure adjustment valve whose opening can be adjusted substantially steplessly, and / or adjust the drainage flow rate of the concentrated water discharged outside the device, and adjust the opening can be adjusted substantially steplessly, an adjustment valve control unit that controls the opening degree of the water supply pressure adjustment valve and / or the drainage flow rate adjustment valve, and the control mode is set to the adjustment valve control unit a fixed opening control mode in which the opening is fixed; a feedback control mode in which the control target value is brought closer to the control target value by the adjustment valve control unit controlling the opening; and a feedback control mode in which the adjustment valve control unit controls the opening A constant acceleration control mode in which the controlled value is increased by changing the degree of opening at a constant rate, and a constant acceleration control mode in which the regulating valve control unit changes the degree of opening at a constant rate to decrease the controlled value a constant deceleration control mode, and a switching unit for switching the control mode to the fixed opening control mode when the control target value is located in a central range including the control target value. switching, when the controlled value is located in the lower first range adjacent to the lower side of the central range, or when the controlled value is located in the upper first range adjacent to the upper side of the central range, Switching to the feedback control mode, switching to the constant acceleration control mode when the control target value is positioned in the lower second range adjacent to the lower side of the lower first range, and switching to the constant acceleration control mode when the control target value is the upper first range. When the control mode is in the upper second range adjacent to the upper side of one range, the control mode is switched to the constant deceleration control mode, and the switching unit switches the control target value to the control target value when the control mode is the feedback control mode. and the control mode is switched to the fixed opening control mode after a first predetermined time has elapsed in a state where the control target value is near the range narrower than the central range.

In addition, when the control mode is the fixed opening control mode, the switching unit switches the control target value outside the central range by a first predetermined amount for a second predetermined time, after which the Preferably, the control mode is switched to the feedback control mode according to a difference between the control target value and the control target value.

Further, when the control mode is the fixed opening control mode, the switching unit switches the control target value outside the central range by a second predetermined amount for a third predetermined time, after which the switching unit Preferably, the control mode is switched to the constant acceleration control mode or the constant deceleration control mode according to the difference between the control target value and the control target value.

The pump control unit may further include a pump control unit that controls the rotational speed of the pressurization pump, and the pump control unit may control the rotation speed of the pressurization pump until the control target value enters a central range including the control target value when the pressurization pump is started. , preferably, the rotation speed of the pressurizing pump is increased at a constant rate.

According to the present invention, it is possible to extend the life of the opening adjustment valve and stabilize various PI controls.

1 is an overall configuration diagram of a membrane separation device according to an embodiment of the present invention; FIG. It is a figure which shows the relationship of the pressure and flow volume which concern on the flow regulating unit used by 1st Embodiment of this invention. It is a functional block diagram of the control part of the membrane separation apparatus concerning embodiment of this invention. It is a flowchart which shows operation|movement of the membrane separation apparatus which concerns on embodiment of this invention. It is a graph which shows the operation example of the membrane separation apparatus which concerns on embodiment of this invention.

[1 Configuration of Membrane Separator]
A membrane separation device 1 according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of a membrane separation device 1 according to an embodiment of the present invention.

As shown in FIG. 1, the membrane separation device 1 according to the present embodiment includes a feedwater pump 12, a pressure pump 2, a pressure-side inverter 3, an RO membrane module 4 as a reverse osmosis membrane module, and a flow rate adjustment unit. 5, a check valve 6, a drainage flow rate adjustment valve 7 as drainage flow rate adjustment means, a water supply pressure adjustment valve 14 as water supply pressure adjustment means, a water supply pressure sensor PS1, a first flow rate sensor FM1, and a second A flow rate sensor FM2 and a controller 30 are provided. The illustration of electrical connection lines between the control unit 30 and the device to be controlled is omitted.

The membrane separation device 1 also includes a feed water line L1, a feed water line L2, a permeated water line L3, a concentrated water line L4, a circulating water line L5, and a drain line L6. The term "line" used herein is a general term for lines through which fluid can flow, such as channels, routes, and pipelines.

The water supply line L1 is a line that supplies the water supply W1 to the confluence point J2 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, a water supply pressure regulating valve 14, a water supply pressure sensor PS1, and a junction J2 in this order from upstream to downstream.

The water supply W1 flowing through the water supply line L1 is not limited to raw water directly supplied from the supply source (not shown) of the water supply W1. ), pretreated water that has been pretreated by a pretreatment device such as a water softener.

The water supply pump 12 is a device that sucks the water supply W<b>1 flowing through the water supply line L<b>1 and pumps (discharges) it toward the pressure pump 2 . The water supply pump 12 is driven at a rotational speed corresponding to the frequency of the supplied (input) driving power (hereinafter also referred to as "driving frequency").

The water supply pressure regulating valve 14 is a valve that adjusts the pressure of the water supply W1 flowing through the water supply line L1. The water supply pressure regulating valve 14 is electrically connected to the controller 30 . The opening degree of the water supply pressure regulating valve 14 is controlled by the controller 30 . The water supply pressure regulating valve 14 may be, for example, an electromagnetic field valve.

The water supply pressure sensor PS1 measures the pressure of the water supply W1 flowing through the water supply line L1. The water supply pressure sensor PS1 is electrically connected to the controller 30 . The water pressure measured by the water supply pressure sensor PS1 is transmitted to the control unit 30 as a detection signal.

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

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

The pressurization-side inverter 3 is an electric circuit (or a device having such a circuit) that supplies the pressurization pump 2 with drive power whose frequency has been converted. The pressure-side inverter 3 is electrically connected to the controller 30 . A command signal is input to the pressure-side inverter 3 from the control unit 30 . The pressurization-side inverter 3 outputs to the pressurization pump 2 drive power having a drive frequency corresponding to the command signal (current value signal or voltage value signal) input from the control unit 30 .

The RO membrane module 4 is equipment for membrane separation treatment of the feed water W2 discharged from the pressure pump 2 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 single or multiple RO membrane elements (not shown). The RO membrane module 4 membrane-separates the feed water W2 using these RO membrane elements to produce permeated water W3 and concentrated water W4.

The permeated water line L3 is a line through which the permeated water W3 separated by the RO membrane module 4 is delivered. The upstream end of the permeate line L3 is connected to the secondary port of the RO membrane module 4 . A downstream end of the permeated water line L3 is connected to a device or the like at a demand point. A first flow rate sensor FM1 (hereinafter also referred to as "first flow rate detection means") is installed in the permeated water 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 rate sensor FM1 is connected to the permeated water line L3. Also, the first flow rate sensor FM1 is electrically connected to the controller 30 . A first detected flow rate value of the permeated water W3 detected by the first flow rate sensor FM1 is transmitted to the controller 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 arranged in a flow path housing can be used.

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

Also, the second concentrated water line L42 is a line for sending out the concentrated water W4 whose flow rate is adjusted by the flow rate adjustment 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 is branched into the circulating water line L5 and the drainage line L6 at the connection J1.

In addition, henceforth, the 1st concentrated water line L41 and the 2nd concentrated water line L42 may be collectively called "concentrated water line L4."

The flow rate adjustment unit 5 has a constant flow rate element that circulates a substantially constant flow of concentrated water regardless of the differential pressure in the flow rate adjustment unit 5, and the concentration is substantially proportional to the differential pressure in the flow rate adjustment unit 5. and a proportional element that increases the flow rate of the water W4. Specifically, the differential pressure in the flow rate adjusting unit 5 is the differential pressure between the water pressure of the first concentrated water line L41 and the water pressure of the second concentrated water line L42. A constant flow element maintains a constant flow value without the need for auxiliary power or external manipulation, and may be used, for example, under the name of a water governor. As the proportional element, for example, an orifice may be used.

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 concentrated water flowing through the flow rate adjusting unit 5. As shown in FIG. Since the flow rate adjusting unit 5 is provided with a constant flow rate element, the flow rate of the concentrated water flowing through the flow rate adjusting unit 5 rises to point A at once when the inlet pressure is generated. That is, approximately, the flow rate at the height of point A flows into the flow rate adjusting unit 5 at the same time as the inlet pressure is generated. At the same time, since the flow rate adjusting unit 5 has a proportional element, the flow rate of the concentrated water flowing through the flow rate adjusting unit 5 increases linearly as the inlet pressure rises.

In addition, 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. When configured integrally, for example, the flow direction of the proportional element is aligned with the longitudinal direction of the flow rate adjustment unit 5, and the flow direction of the constant flow rate element is orthogonal to the longitudinal direction of the flow rate adjustment unit 5. It may be configured as Alternatively, the flow direction of the proportional element may be perpendicular to the longitudinal direction of the flow rate adjusting unit 5 and the flow direction of the constant flow rate element may be aligned with the longitudinal direction of the flow rate adjusting unit 5 . Alternatively, both the flow direction of the constant flow rate element and the flow direction of the proportional element may be configured to match the longitudinal 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 for returning 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 connection 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 drain line L6 is a line that branches off from the concentrated water line L4 at the connection J1 and discharges waste water W42, which is the remainder 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 adjustment valve 7 as drainage flow rate adjustment means and a second flow rate sensor FM2 (hereinafter also referred to as "second flow rate detection means") from the upstream side to the downstream side. .

The drainage flow rate adjustment 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 controller 30 . The valve opening degree of the drainage flow rate adjustment valve 7 is controlled by a drive signal transmitted from the control section 30 . By transmitting a current value signal (eg, 4 to 20 mA) from the control unit 30 to the drainage flow rate adjustment valve 7 to control the valve opening, the drainage flow rate of the drainage W42 can be adjusted. The drain flow control valve 7 may be, for example, an electromagnetic valve.

The second flow rate sensor FM2 is a device that detects, as a second detected flow rate value, the flow rate of the waste water W42 discharged from the apparatus through the drainage line L6. The second flow rate sensor FM2 is connected to the drainage line L6. Also, the second flow rate sensor FM2 is electrically connected to the controller 30 . A second detected flow rate value of the waste water W42 detected by the second flow rate sensor FM2 is transmitted to the control section 30 as a detection signal. As the second flow rate sensor FM2, for example, a pulse transmission type flow rate sensor having an axial flow impeller or a tangential impeller (not shown) arranged in a flow path housing can be used.

[2 Functional Blocks of Control Unit]
The control unit 30 has a CPU, a ROM, a RAM, a CMOS memory, etc., which are known to those skilled in the art and are configured to communicate with each other via a bus.

The CPU is a processor that controls the membrane separation device 1 as a whole. The CPU reads various programs stored in the ROM through the bus and controls the entire membrane separation apparatus 1 according to the various programs, thereby opening the control unit 30 as shown in the functional block diagram of FIG. It is configured to realize the functions of the degree adjusting valve control section 31 , the switching section 32 and the pump control section 33 . Various data such as temporary calculation data and display data are stored in the RAM. The CMOS memory is backed up by a battery (not shown) and configured as a non-volatile memory that retains the memory state even when the membrane separation device 1 is turned off.

The opening adjustment valve control unit 31 controls the opening of the water supply pressure adjustment valve 14 and/or the drainage flow rate adjustment valve 7 . In particular, the opening adjustment valve control section 31 controls the opening degrees of the water supply pressure adjustment valve 14 and/or the drainage flow rate adjustment valve 7 according to the control mode switched by the switching section 32 which will be described later.

More specifically, when the control mode is the fixed opening control mode, the opening adjustment valve control unit 31 fixes the opening of the water supply pressure adjustment valve 14 and/or the drainage flow rate adjustment valve 7 .
When the control mode is the feedback control mode, the opening adjustment valve control unit 31 feeds back the control target value so as to bring the control target value closer to the control target value, so that the feed water pressure adjustment valve 14 and/or Controls the degree of opening of the drainage flow control valve 7 . Here, the "control target value" is, for example, the value of the water supply pressure, the waste water flow rate, or the treated water flow rate. When the "value to be controlled" is the water supply pressure, the opening adjustment valve control unit 31 controls the opening of the water supply pressure adjustment valve 14 to change the water supply pressure measured by the water supply pressure sensor PS1 to " control target value, that is, the target value of the water supply pressure. Further, when the "value to be controlled" is the drainage flow rate, the opening adjustment valve control unit 31 controls the opening of the drainage flow rate adjustment valve 7 to control the drainage flow rate measured by the second flow sensor FM2. is brought close to the "control target value", that is, the target value of the waste water flow rate. Note that the control target value may change during operation of the membrane separation device 1 .

When the control mode is in the constant acceleration control mode, the opening adjustment valve control unit 31 changes the opening of the water supply pressure adjustment valve 14 and/or the drainage flow rate adjustment valve 7 at a constant rate, so that the control target Increase value.
When the control mode is in the constant deceleration control mode, the opening degree adjustment valve control unit 31 changes the opening degree of the water supply pressure adjustment valve 14 and/or the drainage flow rate adjustment valve 7 at a constant rate, so that the control target Decrease value. In particular, as the specifications of the water supply pressure adjustment valve 14 and/or the drainage flow rate adjustment valve 7, if a current value of 0 is input to the water supply pressure adjustment valve 14 and/or the drainage flow rate adjustment valve 7, the opening at that time will be keep it. If a value of 0 mA is given while the opening is maintained, the water supply pressure control valve 14 and/or the drainage flow rate control valve 7 may be erroneously recognized as abnormal and may not close. For that reason, it performs an operation called constant deceleration.

For example, if an electric power of 4 mA is output to the water supply pressure control valve 14 and/or the drainage flow rate control valve 7, each valve will be closed. Actually, when a current value of, for example, 3.8 mA is output, the water supply pressure regulating valve 14 and/or the drain flow rate regulating valve 7 may hold their opening degrees. In order to prevent such a phenomenon, if the current value is gradually decreased from a current value higher than 4 mA, at least 4 mA will pass through and the valve will be fully closed.

For example, while the rotational speed of the pressurizing pump 2 can be easily electrically controlled, it is not easy to control the water supply pressure adjustment valve 14 and/or the drainage flow rate adjustment valve 7 as described above. passes the range near the control target value, or problems such as hunting occur. Therefore, in this embodiment, the switching unit 32 switches the control mode as follows.

The switching unit 32 switches the control mode between a fixed opening control mode, a feedback control mode, a constant acceleration control mode, and a constant deceleration control mode.
More specifically, the switching unit 32 switches the control mode to the fixed opening control mode when the control target value is positioned in the "center range" including the control target value. Further, the switching unit 32 switches when the controlled value is positioned in the "lower first range" adjacent to the lower side of the central range, or when the controlled value is positioned in the "upper first range" adjacent to the upper side of the central range. , the control mode is switched to the feedback control mode. Further, the switching unit 32 switches the control mode to the constant acceleration control mode when the control target value is positioned in the "lower second range" adjacent to the lower side of the lower first range. Further, the switching unit 32 switches the control mode to the constant deceleration control mode when the control target value is positioned in the "upper second range" adjacent to the upper side of the upper first range.
Specific examples of the "middle range", "lower first range", "upper first range", "lower second range", and "upper second range" will be described later in Examples. do.

Further, when the control mode is the feedback control mode, the switching unit 32 switches the control mode to the fixed opening control mode after the first predetermined time has passed while the control target value is near the control target value.
Here, "near the control target value" means a range in which the difference from the control target value is within a predetermined value and a range narrower than the central range. When the central range is -5% to +5% with respect to the control target value, the range near the control target value may be, for example, a range of -3% to +3% of the central region centered on the control target value. .

Further, when the control mode is the fixed opening control mode, the switching unit 32 switches the controlled object value to the The control mode is switched to the feedback control mode according to the difference from the control target value.

Further, when the control mode is the fixed opening control mode, the switching unit 32 switches the control target value to the control target value after a third predetermined time has passed in a state where the control target value is outside the central range by a second predetermined amount. The control mode is switched to constant acceleration control mode or constant deceleration mode according to the difference from the control target value.

The pump control section 33 controls the rotation speed of the pressure pump 2 . In particular, when the "value to be controlled" is the treated water flow rate, the pump control unit 33 controls the rotation speed of the pressurizing pump 2 to increase the treated water flow rate measured by the first flow sensor FM1 ( The flow rate of the permeated water W3) is brought close to the "control target value", that is, the target value of the treated water flow rate.
In addition, when the pressure pump 2 is started, the pump control unit 33 increases or decreases the rotation speed of the pressure pump 2 at a constant rate until the control target value enters the central range including the control target value.

[3 Operation of Membrane Separator]
FIG. 4 is a flow chart showing an operation example of the membrane separation device 1 .
In step S1, the membrane separation device 1 measures a control target value. For example, when the controlled value is the water supply pressure, the water supply pressure is measured by the water supply pressure sensor PS1. When the controlled value is the drainage flow rate, the second flow rate sensor FM2 measures the drainage flow rate. When the control target value is the flow rate of treated water, the flow rate of treated water (flow rate of permeated water W3) is measured by the first flow rate sensor FM1.

In step S2, if the control target value is within the lower second range (S2: YES), the process proceeds to step S3. If the control target value is not within the lower second range (S2: NO), the process proceeds to step S5.

In step S3, the membrane separation device 1 performs constant acceleration control. Specifically, the opening adjustment valve control unit 31 changes the opening of the water supply pressure adjustment valve 14 and/or the drainage flow rate adjustment valve 7 at a constant rate.

In step S4, if the control target value has entered the lower first range (S4: YES), the process proceeds to step S6. If the control target value is not within the lower first range (S4: NO), the process proceeds to step S1 (return).

In step S5, if the control target value is in the lower first range or the upper first range (S5: YES), the process proceeds to step S6. If the control target value is not in the lower first range or the upper first range (S5: NO), the process proceeds to step S8.

In step S6, the membrane separation device 1 performs feedback control. Specifically, the opening adjustment valve control unit 31 feeds back the control target value so that the control target value approaches the control target value, thereby opening the water supply pressure adjustment valve 14 and/or the drainage flow rate adjustment valve 7. control the degree.

In step S7, when the predetermined time T1 has passed since the control target value reached the vicinity of the control target value (S7: YES), the process proceeds to step S10. Otherwise (S7: NO), the process proceeds to step S1 (return).

In step S8, if the control target value is in the middle range (S8: YES), the process proceeds to step S9. If the control target value is not within the central range (S8: NO), the process proceeds to step S12.

In step S9, when the predetermined time T1 has passed since the control target value reached the vicinity of the control target value (S9: YES), the process proceeds to step S10. Otherwise (S9: NO), the process proceeds to step S1 (return).

In step S10, the membrane separation device 1 performs opening fixed control. Specifically, the opening adjustment valve control unit 31 fixes the opening of the water supply pressure adjustment valve 14 and/or the drainage flow rate adjustment valve 7 .

In step S11, when the predetermined time T2 has elapsed since the difference between the control target value and the control target value exceeded the predetermined value (S11: YES), the process proceeds to step S1 (return). Otherwise (S11: NO), the process proceeds to step S10.

In step S12, the membrane separation device 1 performs constant deceleration control. Specifically, the opening adjustment valve control unit 31 reduces the control target value by changing the opening of the water supply pressure adjustment valve 14 and/or the drainage flow rate adjustment valve 7 at a constant rate.

In step S13, if the control target value has entered the upper first range (S13: YES), the process proceeds to step S6. If the control target value is not within the upper first range (S13: NO), the process proceeds to step S1.

[4 Examples]
FIG. 5 is a graph showing an example of the control result of the control target value by the membrane separation device 1 according to this embodiment.

As shown on the left side of the graph in FIG. 5, the central area containing the control target value is defined as the "central range". A range adjacent to the upper side of the central range is referred to as an "upper first range", and a range adjacent to the lower side is referred to as a "lower first range". Further, a range adjacent to the upper side of the upper first range is referred to as an "upper second range", and a range adjacent to the lower side of the first range is referred to as a "lower second range".

Furthermore, although the details will be described later, the center range generally corresponds to the fixed opening control area. More specifically, when the control target value is in the middle range, the control mode is basically the fixed opening control mode.
The upper first range and the lower first range generally correspond to the feedback control area. More specifically, when the control target value is in the upper first range and the lower first range, the control mode is basically the feedback control mode.
The upper second range generally corresponds to the constant deceleration control area. More specifically, when the control target value is in the upper second range, the control mode is basically the constant deceleration control mode.
The lower second range generally corresponds to the constant acceleration region. More specifically, when the control target value is in the upper second range, the control mode is basically the constant acceleration control mode.

At time t=0, the controlled value is in the lower second range, so the membrane separation device 1 executes constant acceleration control. Specifically, the opening adjustment valve control unit 31 increases the control target value by changing the opening of the water supply pressure adjustment valve 14 and/or the drainage flow rate adjustment valve 7 at a constant rate.
In addition, if the opening of the water supply pressure adjustment valve 14 and/or the drainage flow rate adjustment valve 7 is continuously changed at a constant rate, the time until the opening reaches 100% is T3. In , feedback control is executed as described later before the opening degree reaches 100%. This is because, for example, if the constant acceleration control is executed until the opening reaches 90% or more, the control target value may pass the middle range. For this reason, a relatively large area of the lower first range (and the upper first range) in which feedback control is performed is secured.
Further, the pump control unit 33 increases or decreases the rotational speed of the pressurizing pump 2 at a constant rate until the control target value enters the central range including the control target value.

At time t=t1, the value to be controlled has entered the lower first range, so the membrane separation device 1 performs feedback control. Specifically, the opening adjustment valve control unit 31 feeds back the control target value so that the control target value approaches the control target value, thereby opening the water supply pressure adjustment valve 14 and/or the drainage flow rate adjustment valve 7. control the degree.

At time t=t2, the controlled object value reaches the controlled target value. After that, until the predetermined time T1 elapses, the control target value continues to exist in the region near the control target value, so the membrane separation device 1 executes opening fixed control at time t=t3 (=t2+T1). do. Specifically, the opening adjustment valve control unit 31 fixes the opening of the water supply pressure adjustment valve 14 and/or the drainage flow rate adjustment valve 7 .

Even if the opening of the water supply pressure adjustment valve 14 and/or the drainage flow rate adjustment valve 7 is fixed, for example, due to disturbance, at time t=t4, the controlled value leaves the central range and enters the lower first range. . After that, the control target value continued to exist in the lower first range until the predetermined time T2 passed, so the membrane separation device 1 executes feedback control at time t=t5 (=t4+T2).

At time t=t6, the controlled object value reaches the controlled target value. After that, until the predetermined time T1 elapses, the control target value continues to exist in the region near the control target value, so the membrane separation device 1 executes opening fixed control at time t=t7 (=t6+T1). do.

At time t=t8, the controlled value leaves the middle range and enters the upper first range. After that, the control target value continued to exist in the upper first range until the predetermined time T2 passed, so the membrane separation device 1 executes feedback control at time t=t9 (=t8+T2).

At time t=t10, the control target value reaches the control target value. After that, until the predetermined time T1 elapses, the controlled value continues to exist in the region near the controlled target value, so the membrane separation device 1 executes opening fixed control at time t=t11 (=t10+T1). do.

At time t=t12, the controlled value leaves the middle range and enters the lower first range. After that, the control target value continued to exist in the lower first range until the predetermined time T2 passed, so the membrane separation device 1 executes feedback control at time t=t13 (=t12+T2).

Although the membrane separation device 1 performs feedback control, the controlled value continues to decrease and enters the lower second range at time t=t14. Therefore, the membrane separation device 1 executes constant acceleration control at time t=t14.

At time t=t15, the value to be controlled has entered the lower first range, so the membrane separation device 1 performs feedback control.

At time t=t16, the controlled object value reaches the controlled target value. After that, until the predetermined time T1 elapses, the control target value continues to exist in the region near the control target value, so the membrane separation device 1 executes opening fixed control at time t=t17 (=t16+T1). do.

At time t=t18, the control target value suddenly increases and enters the upper second range, so the membrane separation device 1 executes constant deceleration control. More specifically, the opening adjustment valve control unit 31 reduces the control target value by changing the opening of the water supply pressure adjustment valve 14 and/or the drainage flow rate adjustment valve 7 at a constant rate.

At time t=t19, the control target value entered the upper first range, so the membrane separation device 1 executes feedback control.

[5 Effect of this embodiment]
According to the membrane separation device 1 according to the embodiment described above, for example, the following effects can be obtained.
The membrane separation device 1 has two control modes: a fixed opening control mode in which the opening degree adjustment valve control unit 21 fixes the opening degrees of the feed water pressure adjustment valve 14 and/or the waste water flow rate adjustment valve 7, and an opening degree adjustment valve control unit 21 controls the opening degree of the water supply pressure regulating valve 14 and/or the drainage flow rate regulating valve 7 to bring the control target value closer to the control target value; 14 and / or by changing the opening of the drainage flow rate adjustment valve 7 at a constant rate, a constant acceleration control mode in which the controlled object value is increased, and the opening adjustment valve control unit 21 controls the water supply pressure adjustment valve 14 and / or A switching unit 32 is provided for switching to a constant deceleration control mode in which the control target value is decreased by changing the opening degree of the drainage flow rate adjustment valve 7 at a constant rate. Furthermore, the switching unit 32 switches the control mode to the fixed opening control mode when the controlled object value is positioned in the central range including the control target value, and switches the control mode to the lower first opening control mode where the controlled object value is adjacent to the lower side of the central range. when the control target value is located in the upper first range adjacent to the upper side of the center range, or when the control target value is located in the upper first range adjacent to the upper side of the center range, and the control target value is adjacent to the lower side of the lower first range When the control target value is in the upper second range adjacent to the upper first range, the control mode is switched to the constant deceleration control mode.
By switching the control mode according to the difference between the control target value and the control target value, it is possible to reduce the possibility of hunting.

Further, when the control mode is the feedback control mode, the switching unit 32 switches the control mode to the fixed opening control mode after the first predetermined time has passed while the control target value is near the control target value.
By stopping the operation of the opening adjustment valve when the control target value is approximately close to the control target value, it is possible to extend the life of the opening adjustment valve and reduce the possibility of hunting. .

Further, when the control mode is the fixed opening control mode, the switching unit 32 switches the controlled object value and the controlled The control mode is switched to the feedback control mode according to the difference from the target value.
Even if the controlled object value once becomes close to the control target value, if the difference between the controlled object value and the control target value again becomes equal to or greater than the predetermined amount, the control is redone to quickly reach the control target value. Corrections can be made. This reduces the possibility of the recovery rate being too high or the water supply amount exceeding the allowable water supply amount.

Further, when the control mode is the fixed opening control mode, the switching unit 32 switches the control target value and the control target value after a third predetermined time has elapsed in a state where the control target value is out of the central range by a second predetermined amount. The control mode is switched between the constant acceleration control mode and the constant deceleration mode according to the difference from the target value.
When the control target value greatly deviates from the control target value, the control is quickly stabilized by performing constant acceleration control or constant deceleration control instead of suddenly performing feedback control. Also, the control target value can be quickly approached without overshooting.

In addition, the membrane separation device 1 further includes a pump control unit 33 that controls the rotation speed of the pressure pump 2, and when the pressure pump 2 is started, until the controlled value enters the central range including the control target value, The pump controller 33 increases or decreases the rotation speed of the pressure pump 2 at a constant rate.
It is possible to reach the control target value more quickly by performing constant acceleration or constant deceleration operation up to a central range including a predetermined control target value (treated water flow rate) when the pressurizing pump 2 is started, and then performing feedback control. Become.

[6 Modifications]
In the above embodiment, the membrane separation device 1 is an RO membrane device including the RO membrane module 4, but is not limited to this. For example, the membrane separation device 1 may be an NF (loose RO) membrane device.

1 Membrane Separator 2 Pressurizing Pump 4 RO Membrane Module 5 Flow Control Unit 7 Waste Water Flow Control Valve 12 Water Supply Pump 14 Water Supply Pressure Control Valve 30 Control Section 31 Opening Control Valve Control Section 32 Switching Section 33 Pump Control Section L1 Water Supply Line L2 Feed water line L3 Permeated water line L4 Concentrated water line L5 Circulating water line L6 Drainage line W1 Feed water W2 Feed water W3 Permeated water W4 Concentrated water W41 Circulating water W42 Drainage

Claims (4)

a reverse osmosis membrane module that separates feed water, including feed water, into permeate and concentrate;
a pressurizing pump that draws in feed water and discharges it as feed water toward the reverse osmosis membrane module;
Adjust the pressure of the water supply supplied to the pressurizing pump, adjust the water supply pressure adjustment valve whose opening can be adjusted substantially steplessly, and / or adjust the drainage flow rate of the concentrated water discharged outside the apparatus, a drainage flow control valve whose opening can be adjusted substantially steplessly;
a regulating valve control unit that controls the opening degree of the water supply pressure regulating valve and/or the drainage flow rate regulating valve;
control mode,
an opening fixed control mode in which the adjustment valve control unit fixes the opening;
a feedback control mode in which the controlled valve control unit controls the opening to bring the controlled value closer to the control target value;
a constant acceleration control mode in which the regulating valve control unit changes the degree of opening at a constant rate to increase the controlled value;
a switching unit for switching between a constant deceleration control mode in which the control target value is reduced by the adjustment valve control unit changing the opening degree at a constant rate;
The switching unit switches the control mode to the fixed opening control mode when the controlled object value is positioned in a central range including the control target value, and switches the control mode to the fixed opening control mode when the controlled object value is positioned below the central range. When the control target value is located in the side first range, or when the control target value is located in the upper first range adjacent to the upper side of the center range, the control target value is switched to the feedback control mode, and the control target value is located in the lower side first range. When the value to be controlled is positioned in the lower second range adjacent to the lower side of one range, the control mode is switched to the constant acceleration control mode, and when the control target value is positioned in the upper second range adjacent to the upper side of the upper first range. Switching to the constant deceleration control mode,
When the control mode is the feedback control mode, the switching unit performs the first control when the control target value reaches a control target value and is near a control target value in a range narrower than the central range. A membrane separation device, wherein the control mode is switched to the fixed opening control mode after a predetermined time has elapsed. When the control mode is the fixed opening control mode, the switching unit switches the controlled object value after a second predetermined time has elapsed while the controlled object value is out of the central range by a first predetermined amount. 2. The membrane separation device according to claim 1, wherein said control mode is switched to said feedback control mode according to a difference between said value and said control target value. When the control mode is the fixed opening control mode, the switching unit switches the controlled object value to 3. The membrane separation apparatus according to claim 1, wherein said control mode is switched to said constant acceleration control mode or said constant deceleration control mode according to the difference between said value and said control target value. further comprising a pump control unit that controls the rotation speed of the pressure pump,
2. The pump control unit increases the rotation speed of the pressure pump at a constant rate until the control target value enters a central range including the control target value when the pressure pump is started. 4. The membrane separation device according to any one of 1 to 3.

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