JP2020163254A - Pure water production device and pure water production method - Google Patents

Abstract

To provide a pure water production device which, even at an increased temperature, does not deteriorate water quality of pure water or yield an excess of production of the pure water.SOLUTION: A pure water production device 1 is employed which comprises: a raw water supply channel 2; a supply pump 3; a reverse osmosis membrane 4 which separates raw water W1 into permeated water W2 and concentrated water W3; a circulating water channel 6 which branches off from a permeated water channel 5 and through which part of the permeated water W2 can be returned to the raw water supply channel 2; opening-closing valves 7, 8 which open the circulating water channel 6 when a temperature of the raw water W1 etc. exceeds a reference temperature; and a control part 10 which, when a flow of the permeated water W2 measured by a first flowmeter 9 falls outside a first reference flow range, controls a supply of the raw water W1 by the supply pump 3.SELECTED DRAWING: Figure 1

Description

The present invention relates to a pure water production apparatus and a pure water production method.

Generally, a pure water production apparatus is provided with a reverse osmosis membrane for separating raw water into permeated water and concentrated water for the purpose of removing impurities. When the effective pressure of the reverse osmosis membrane is constant, the viscosity of water decreases and the amount of permeated water increases as the water temperature increases. On the other hand, when the water temperature becomes low, the viscosity of water increases and the amount of permeated water decreases. For this reason, the device configuration and operating conditions of the reverse osmosis membrane are designed so that a sufficient amount of permeated water can be obtained even at a low water temperature in anticipation of a decrease in water temperature in winter. Therefore, in the summer when the water temperature rises, there is a problem that the amount of permeated water in the reverse osmosis membrane increases and exceeds the design value of the permeated water amount. In order to deal with this problem, it is necessary to reduce the effective pressure of the reverse osmosis membrane and adjust the amount of permeated water each time.

By the way, the reverse osmosis membrane has a property that the blocking rate of impurities decreases when the effective pressure is lowered. Therefore, it is necessary to set the effective pressure of the reverse osmosis membrane to, for example, 0.6 MPa or more, and perform the operation under the condition that the inhibition rate of impurities does not decrease. However, as described above, if the effective pressure is lowered as the water temperature rises in the summer, there is a problem that the blocking rate of impurities is lowered and the water quality of the permeated water is lowered.

In Patent Document 1, raw water is boosted and supplied to a plurality of reverse osmosis membrane module units connected in parallel, and when permeated water is obtained, reverse osmosis is performed according to the temperature of the raw water and / or the quality of the permeated water. The operation method of the reverse osmosis processing apparatus which controls the operation number of the membrane module unit is described.

Further, Patent Document 2 describes a reverse osmosis membrane portion that removes impurities in water supply, a pump that supplies water supply to the reverse osmosis membrane portion, and a flow rate sensor that detects the flow rate of permeated water from the reverse osmosis membrane portion. A water quality reforming system including an inverter that changes the rotation speed of a pump according to an output frequency and a control unit that outputs a command signal to the inverter based on a flow rate detection signal from a flow rate sensor is described.

Further, Patent Document 3 includes a raw water supply pump provided in a raw water supply line leading to a filtration membrane device and a flow rate transmitter provided in the filtered water line of the filtration membrane device, and a flow rate signal transmitted from the flow rate transmitter. A filtered water flow rate control means that controls the rotation speed of the raw water supply pump to keep the filtered water flow rate constant, and a concentrated water constant flow valve provided in the concentrated water line of the filter membrane device to keep the concentrated water flow rate constant. , A pressure reducing valve interposed between the filtration membrane device and the constant flow valve for concentrated water to reduce the pressure of concentrated water, and a pressure indicator provided between the pressure reducing valve and the constant flow valve for reduced water. A purified water production apparatus is described.

Japanese Unexamined Patent Publication No. 2001-239134 Japanese Unexamined Patent Publication No. 2005-296945 Japanese Unexamined Patent Publication No. 2013-128911

However, in Patent Document 1, it is necessary to prepare a large number of reverse osmosis membrane module units, and there is a problem that the installation space of the pure water production apparatus is increased. Further, in Patent Document 2, the rotation speed of the pump is controlled according to a change in water temperature, and the amount of permeated water fluctuates according to the water temperature, so that the amount of permeated water may increase in summer. Further, in Patent Document 3, the rotation speed of the water supply pump is controlled to keep the amount of water to the filtration membrane constant so that the amount of filtered water is kept constant even if the water temperature fluctuates, and the effective pressure of the filtration membrane is kept constant. If the value decreases, the water quality may deteriorate.

The present invention has been made in view of the above circumstances, and is a pure water production apparatus that does not deteriorate the quality of pure water and does not excessively produce pure water even when the water temperature rises in summer. An object of the present invention is to provide a method for producing pure water.

In order to solve the above problems, the present invention adopts the following configuration.
[1] Raw water supply channel for supplying raw water and
A supply pump provided in the raw water supply path and supplying the raw water,
A reverse osmosis membrane that separates the raw water supplied by the supply pump into permeated water and concentrated water.
A permeation channel through which the permeated water that has permeated the reverse osmosis membrane flows,
One or more circulating channels that are branched from the permeated channel and can return a part of the permeated water to the raw water supply channel.
One or two or more that are provided in the circulating water channels and open the circulating water channels when the temperature of any of the raw water, the permeated water, or the concentrated water exceeds the reference temperature set for each circulating water channel. On-off valve and
A first flow meter installed in the permeation channel on the downstream side of the branch position of the circulation channel, and
When the flow rate of the permeated water measured by the first flow meter deviates from the first reference flow rate range, the flow rate of the permeated water measured by the first flow meter falls within the first reference flow range. A pure water production apparatus including a control unit for controlling the supply amount of the raw water by the supply pump.
[2] Two circulation waterways, a first circulation waterway and a second circulation waterway, are provided as the circulation waterway.
Two on-off valves, a first on-off valve and a second on-off valve, are provided.
The first on-off valve is provided in the first circulating water channel and opens the first circulating water channel when the temperature of any of the raw water, the permeated water, and the concentrated water exceeds the first reference temperature. And
The second on-off valve is provided in the second circulation water channel, and when the temperature of any of the raw water, the permeated water, and the concentrated water exceeds the second reference temperature higher than the first reference temperature, the said. The pure water production apparatus according to [1], which is an on-off valve that opens a second circulation water channel.
[3] A concentrated water channel through which the concentrated water discharged from the reverse osmosis membrane flows, and
The second flow meter installed in the concentrated water channel and
The concentrated water measured by the second flow meter when the flow rate of the concentrated water installed in the concentrated water channel and measured by the second flow meter deviates from a preset second reference flow rate range. A flow rate control valve that controls the flow rate so that it is within the second reference flow rate range,
The pure water production apparatus according to [1] or [2], further comprising.
[4] The control unit is an inverter to which a flow rate measurement value from the first flow meter is input and a control signal for controlling the supply amount of the raw water based on the flow rate measurement value is output to the supply pump. The pure water production apparatus according to any one of [1] to [3].

[5] The supply process of supplying raw water by a supply pump and
A separation step of separating the raw water supplied in the supply step into permeated water and concentrated water by a reverse osmosis membrane, and
When the temperature of any of the raw water, the permeated water, and the concentrated water exceeds the reference temperature, a part of the permeated water flowing through the permeated water channel is divided into one or more circulating water channels branched from the permeated water channel. In the circulation process of returning to the raw water before the supply process,
A first flow rate measuring step of measuring the flow rate of the permeated water with a first flow meter in the permeated water channel on the downstream side of the branch position of the circulating water channel.
When the flow rate of the permeated water measured in the first flow rate measuring step deviates from the first reference flow rate range, the flow rate of the permeated water measured by the first flow meter falls within the first reference flow rate range. A method for producing pure water, which comprises a supply control step for controlling the supply amount of the raw water by the supply pump so as to be provided.
[6] In the circulation step, a plurality of different reference temperatures are set as the reference temperature, and the reference temperature is set.
When the temperature of any of the raw water, the permeated water, or the concentrated water exceeds the lowest reference temperature among the plurality of reference temperatures, a part of the permeated water is provided before the supply step by the circulation channel. Started to return to the raw water of
4. The amount of permeated water circulated by the circulating water channel is increased each time the temperature of any of the raw water, the permeated water, or the concentrated water exceeds the plurality of reference temperatures [5]. Pure water production method.
[7] In the circulation step, when the temperature of any of the raw water, the permeated water, and the concentrated water exceeds the first reference temperature, a part of the permeated water flowing through the permeated water channel is first. Returned to the raw water before the supply process by the circulation channel,
When the temperature of any of the raw water, the permeated water, and the concentrated water exceeds the second reference temperature higher than the first reference temperature, a part of the permeated water flowing through the permeated water channel is circulated in the first circulation. The pure water production method according to [5] or [6], wherein the step is to return the raw water before the supply step by the water channel and the second circulation water channel.
[8] A second flow rate measuring step of measuring the flow rate of the concentrated water discharged from the reverse osmosis membrane and flowing through the concentrated water channel with a second flow meter.
When the flow rate of the concentrated water measured in the second flow rate step deviates from the second reference flow rate range, the flow rate of the concentrated water measured by the second flow meter falls within the second reference flow range. The flow rate control process to control
The pure water production method according to any one of [5] to [7], which further comprises.

[9] In a pure water production method in which raw water supplied by a supply pump is separated into permeated water and concentrated water by a reverse osmosis membrane.
When the temperature of the raw water, the permeated water or the concentrated water exceeds the reference temperature, a part of the permeated water is returned to the raw water before supply, and the temperature of the raw water, the permeated water or the concentrated water is reached. Adjust the amount of permeated water returned according to
A pure water production method characterized by adjusting the supply amount by the supply pump so that the flow rate of the remaining portion of the permeated water excluding the portion returned to the raw water becomes the flow rate before the start of the return of the permeated water. ..

According to the pure water production apparatus of the present invention, when the water temperature of raw water or the like exceeds the reference temperature, the on-off valve is automatically opened, so that a part of the permeated water is released at a high water temperature where the amount of permeated water may increase. It is returned to the raw water supply channel via the circulation channel, and the increase in the amount of permeated water supplied from the pure water production device to the point of use and the water treatment device in the subsequent stage can be suppressed. In addition, the quality of raw water is improved by returning a part of the permeated water to the raw water supply channel. Further, when the flow rate value of the first flow meter deviates from the first reference flow rate range, the control unit controls the amount of raw water supplied by the supply pump so that the permeated water amount maintains the first reference flow rate range. To do. As a result, the flow rate of the permeated water is prevented from being reduced more than necessary, and a sufficient amount of permeated water can be supplied to the point of use and the water treatment device in the subsequent stage. As described above, according to the pure water production apparatus of the present invention, it is possible to maintain the production amount of pure water within an appropriate range without deteriorating the water quality of pure water even at a high water temperature. ..

Further, according to the pure water production apparatus of the present invention, the first circulation water channel and the second circulation water channel, the first on-off valve and the second on-off valve are provided, and as the water temperature rises, the permeated water enters the first circulation water channel. Is configured so that permeated water flows into the first circulation channel and the second circulation channel when the water temperature rises further, so the amount of permeated water returned to the raw water supply channel is adjusted according to the change in water temperature. It is possible to maintain the production amount of pure water within an appropriate range.

Further, according to the pure water production apparatus of the present invention, when the flow rate of the concentrated water flowing through the concentrated water channel is out of the second reference flow rate range, the flow rate control valve controls the flow rate of the concentrated water to an appropriate flow rate. As a result, for example, even when the flow rate of the concentrated water increases and there is a concern that the amount of permeated water decreases, the ratio of the amount of concentrated water to the permeated water is maintained within an appropriate range. Therefore, the operating conditions of the reverse osmosis membrane can be maintained within an appropriate range, and the quality of pure water can be maintained.

Furthermore, according to the pure water production apparatus of the present invention, since the control unit is an inverter, the supply amount of raw water can be easily controlled based on the flow rate measurement value from the first flow meter.

According to the pure water production method of the present invention, when the temperature of raw water or the like exceeds the reference temperature in the circulation step, a part of the permeated water is returned to the raw water, so that it is supplied to the point of use or the water treatment device in the subsequent stage. It is possible to suppress an increase in the amount of permeated water. In addition, the quality of raw water is improved by returning a part of the permeated water to the raw water supply channel. Further, in the first flow rate measurement step and the supply control step, when the flow rate value of the first flow meter installed on the downstream side of the branch position between the permeation water channel and the circulation water channel deviates from the first reference flow rate range, the supply is performed. By controlling the amount of raw water supplied by the pump, the amount of permeated water is maintained in the first reference flow rate range. As a result, the flow rate of the permeated water is prevented from being reduced more than necessary, and a sufficient amount of permeated water can be supplied to the point of use and the water treatment device in the subsequent stage. As described above, according to the pure water production method of the present invention, it is possible to maintain the production amount of pure water in an appropriate range without deteriorating the water quality of pure water even at a high water temperature. ..

Further, according to the pure water production method of the present invention, a plurality of different reference temperatures are set as reference temperatures, and the amount of permeated water circulated through the circulation channel is increased each time the temperature of raw water or the like exceeds a plurality of reference temperatures. Therefore, the amount of permeated water returned to the raw water supply path can be adjusted according to the change in water temperature, and the amount of pure water produced can be maintained within an appropriate range.

Further, according to the pure water production method of the present invention, permeated water flows into the first circulating water channel as the water temperature rises, and when the water temperature rises further, permeated water flows into the first circulating water channel and the second circulating water channel. Since it is configured to flow, the amount of permeated water returned to the raw water supply channel can be adjusted according to changes in water temperature, and the amount of pure water produced can be maintained within an appropriate range.

Furthermore, according to the pure water production method of the present invention, in the second flow rate measuring step and the flow rate control step, when the flow rate of the concentrated water flowing through the concentrated water channel is out of the second reference flow rate range, the flow rate of the concentrated water is adjusted. Control to an appropriate flow rate. As a result, for example, even when the flow rate of the concentrated water increases and there is a concern that the amount of permeated water decreases, the ratio of the amount of concentrated water to the permeated water is maintained within an appropriate range. Therefore, the operating conditions of the reverse osmosis membrane can be maintained within an appropriate range, and the quality of pure water can be maintained.

According to the pure water production method of the present invention, when the temperature of raw water or the like exceeds the reference temperature, a part of the permeated water is returned to the raw water. In addition, the amount of permeated water returned is adjusted according to the temperature of the raw water. Further, the supply amount by the supply pump is adjusted so that the flow rate of the remaining portion of the permeated water excluding the amount returned to the raw water becomes the flow rate before the start of return.
As a result, even if the amount of permeated water that permeates the reverse osmosis membrane increases at high water temperatures in summer, it is possible to suppress an increase in the amount of permeated water that is supplied to the point of use and the water treatment device in the subsequent stage. In addition, the quality of raw water is improved by returning a part of the permeated water to the raw water supply channel. Furthermore, by adjusting the flow rate of the balance of the permeated water excluding the amount returned to the raw water, an extreme decrease in the flow rate of the permeated water is prevented.
Therefore, according to the pure water production method of the present invention, it is possible to maintain the production amount of pure water in an appropriate range without deteriorating the water quality of pure water even at a high water temperature.

FIG. 1 is a schematic view illustrating a configuration of a pure water production apparatus according to an embodiment of the present invention.

The pure water production apparatus 1 and the pure water production method according to the embodiment of the present invention will be described.
As shown in FIG. 1, the pure water production apparatus 1 of the present embodiment includes a raw water supply path 2, a supply pump 3, a reverse osmosis film 4 that separates the raw water W1 into permeated water W2 and concentrated water W3, and permeated water W2. Control to control the flowing permeation channel 5, the circulation channel 6 branched from the permeation channel 5, the on-off valves 7 and 8 provided in the circulation channel 6, the first flow meter 9 provided in the permeation channel 5, and the supply pump 3. The part 10 is provided.

Further, as shown in FIG. 1, the pure water production apparatus 1 of the present embodiment is provided with a concentrated water channel 11 through which concentrated water W3 flows. The concentrated water channel 11 is provided with a second flow meter 12 and a flow control valve 13.
Further, the permeation water channel 5 of the pure water production apparatus 1 is provided with a water temperature gauge 20.

The raw water supply channel 2 is composed of a raw water tank 2a and a raw water channel 2b. The raw water tank 2a is a tank for temporarily storing the raw water W1. The raw water channel 2b is a flow path for flowing the raw water W1 from the raw water tank 2a to the reverse osmosis membrane 4. A supply pump 3 is arranged in the middle of the raw water channel 2b, and the raw water W1 is pressurized by the supply pump 3 and sent to the reverse osmosis membrane 4.

The supply pump 3 supplies the raw water W1 to the reverse osmosis membrane 4. The amount of raw water W1 supplied to the reverse osmosis membrane 4 is controlled by the amount of rotation of the supply pump 3, and the effective pressure on the reverse osmosis membrane 4 is adjusted. The amount of rotation of the supply pump 3 is controlled by the control unit 10.

The reverse osmosis membrane 4 separates the raw water W1 into the permeated water W2 and the concentrated water W3. Impurities are removed from the raw water W1 by passing it through the reverse osmosis membrane 4, and the raw water W1 becomes permeated water W2. The removed impurities are contained in the concentrated water W3. As the reverse osmosis membrane 4, a spiral type module in which osmosis membranes (membranes) are stacked in multiple layers and wrapped in a seaweed roll shape and housed in a container can be preferably used, but the reverse osmosis membrane 4 is not limited thereto. Further, the reverse osmosis membrane 4 is connected to a permeated water channel 5 through which the permeated water W2 flows and a concentrated water channel 11 through which the concentrated water W3 flows.

The permeated water channel 5 is a water channel that supplies the permeated water W2 separated by the reverse osmosis membrane 4 to a use point or a water treatment device at a subsequent stage (hereinafter, simply referred to as “use point or the like”). A circulation water channel 6 is connected in the middle of the permeation water channel 5. Further, a water temperature gauge 20 and a first flow meter 9 are installed in the permeation channel 5.

In the pure water production apparatus 1 shown in FIG. 1, two circulation water channels 6 are provided, a first circulation water channel 6a and a second circulation water channel 6b. The number of circulating water channels 6 is not particularly limited and may be 1 or more. The first circulation channel 6a and the second circulation channel 6b are branched from the middle of the permeation channel 5 and are connected to either the raw water tank 2a or the raw water channel 2b constituting the raw water supply channel 2. A part of the permeated water W2 can be returned to the raw water supply channel 2 by the circulation channel 6.

On-off valves 7 and 8 are provided in the middle of the circulation water channel 6. The first circulation water channel 6a is provided with the first on-off valve 7, and the second circulation water channel 6b is provided with the second on-off valve 8. The on-off valves 7 and 8 are valves that open when the temperature of any of the raw water W1, the permeated water W2, and the concentrated water W3 exceeds a preset reference temperature. The on-off valves 7 and 8 may be, for example, automatic valves that automatically open and close according to the water temperature. Further, the on-off valves 7 and 8 may be control valves whose opening degree can be changed according to the water temperature.

The first on-off valve 7 is an on-off valve that opens when the temperature of any of the raw water W1, the permeated water W2, and the concentrated water W3 exceeds the first reference temperature, and the second on-off valve 8 is the raw water W1 and the permeated water. An on-off valve that opens when the temperature of either W2 or concentrated water W3 exceeds the second reference temperature. The second reference temperature is set to a temperature higher than the first reference temperature. The reference temperature, the first reference temperature, and the second reference temperature may be appropriately set according to the performance of the reverse osmosis membrane, the production capacity of the pure water production apparatus, and the like.

When opening and closing the first on-off valve 7 and the second on-off valve 8, it is the raw water W1, the permeated water W2, and the permeated water W2 that refer to the temperature of any of the raw water W1, the permeated water W2, and the concentrated water W3. This is because the water temperature of the concentrated water W3 hardly changes before and after passing through the reverse osmosis membrane 4, so that the on-off valves 7 and 8 may be operated based on any of the water temperatures.

The water temperature gauge 20 is installed in the permeated water channel 5 on the downstream side of the branch position with the circulating water channel 6, and measures the water temperature of the permeated water W2. The installation position of the water temperature gauge 20 is not limited to the position shown in FIG. 1, and may be installed in the raw water channel 2b or the concentrated water channel 11. When the water temperature gauge 20 is installed in the raw water channel 2b, the water temperature of the raw water W1 is measured, and when it is installed in the concentrated water channel 11, the water temperature of the concentrated water W3 is measured. The on-off valves 7 and 8 may be operated based on the water temperature measured by the water temperature gauge 20.

The first flow meter 9 is installed in the permeated water channel 5 on the downstream side of the branch position with the circulating water channel 6, and measures the flow rate of the permeated water W2. The measured flow rate of the permeated water W2 is output to the control unit 10.

The control unit 10 supplies pumps so that when the flow rate of the permeated water W2 measured by the first flow meter 9 deviates from the first reference flow rate range, the flow rate of the permeated water W2 falls within the first reference flow rate range. Control the supply amount of raw water W1 according to 3. The flow rate measurement value from the first flow meter 9 is input to the control unit 10. Then, the control unit 10 outputs a control signal for controlling the supply amount of the raw water W1 to the supply pump 3 based on the input flow rate measurement value. The control unit 10 is preferably an inverter. The first reference flow rate range may be appropriately set according to the performance of the reverse osmosis membrane, the production capacity of the pure water production apparatus, and the like.

The concentrated water channel 11 is a water channel through which the concentrated water W3 separated by the reverse osmosis membrane 4 flows. The concentrated water channel 11 is connected to either the raw water tank 2a or the raw water channel 2b. As a result, the concentrated water W3 can be returned to the raw water supply channel 2.

A drainage channel may be branched in the middle of the concentrated water channel 11 and a part of the concentrated water W3 may be discharged to the outside of the pure water production apparatus 1. Alternatively, the concentrated water channel 11 may discharge the entire amount of the concentrated water W3 to the outside of the pure water production apparatus 1 without connecting to the raw water tank 2a and the raw water channel 2b.

Further, a second flow meter 12 and a flow control valve 13 are installed in the middle of the concentrated water channel 11. The second flow meter 12 measures the flow rate of the concentrated water W3. The measured flow rate of the concentrated water W3 is output to the flow rate control valve 13. In the flow control valve 13, when the flow rate of the concentrated water W3 measured by the second flow meter 12 deviates from the preset second reference flow rate range, the flow rate of the concentrated water W3 falls within the second reference flow rate range. The flow rate of the concentrated water W3 is controlled so as to be. The second reference flow rate range may be appropriately set according to the performance of the reverse osmosis membrane, the production capacity of the pure water production apparatus, and the like.

Next, the pure water production method of the present embodiment will be described with reference to FIG. The pure water production method of the present embodiment includes a supply step of supplying raw water W1 by a supply pump 3, a separation step of separating raw water W1 into permeated water W2 and concentrated water W3 by a reverse osmosis membrane 4, and a circulating water channel 6. A circulation step of returning a part of the permeated water W2 to the raw water W1, a first flow rate measuring step of measuring the flow rate of the permeated water W2 with the first flow meter 9, and a supply control for controlling the supply amount of the raw water W1 with the supply pump 3. Perform the process and.

Further, in the pure water production method of the present embodiment, the second flow rate measuring step of measuring the flow rate of the concentrated water W3 by the second flow meter 12 and the control so that the flow rate of the concentrated water W3 is within the second reference flow rate range. The flow rate control step may be performed. Hereinafter, each step will be described.

First, in the supply step, the raw water W1 stored in the raw water tank 2a is supplied to the reverse osmosis membrane 4 through the raw water channel 2b. At this time, the supply pump 3 is operated to adjust the effective pressure of the raw water W1 supplied to the reverse osmosis membrane 4. The effective pressure is adjusted so that the blocking rate of the reverse osmosis membrane 4 does not become too low.

Next, in the separation step, the raw water W1 is separated into the permeated water W2 and the concentrated water W3 by the reverse osmosis membrane 4. By passing the raw water W1 through the reverse osmosis membrane 4, the permeated water W2 having a reduced amount of impurities can be obtained. On the other hand, impurities are concentrated in the concentrated water W3. The permeated water W2 is sent to the permeated water channel 5, and the concentrated W3 is sent to the concentrated water channel 11.

Next, in the circulation step, when the temperature of any of the raw water W1, the permeated water W2 or the concentrated water W3 (hereinafter referred to as the raw water W1 or the like) exceeds the reference temperature, a part of the permeated water W2 is removed by the circulating water channel 6. Return to raw water W1 before the supply process. On the other hand, when the temperature of the raw water W1 or the like is equal to or lower than the reference temperature, the entire permeated water W2 is supplied to the use point or the like without returning a part of the permeated water W2 to the raw water W1. When the permeated water W2 flows through the circulating water channel 6, the permeated water W2 is allowed to flow through the circulating water channel 6 by operating the on-off valves 7 and 8. When the water temperature of the raw water W1 exceeds the reference temperature, the viscosity of the raw water W1 decreases and the amount of the permeated water W2 becomes excessive. Therefore, in the circulation step, the operation of returning the excess permeated water W2 to the raw water W1 is performed.

Since the viscosity of the raw water W1 decreases as the water temperature of the raw water W1 rises, it is advisable to increase the amount of permeated water W2 returned in accordance with the rise in the water temperature of the raw water W1. Therefore, in the circulation step, a plurality of different reference temperatures are set as the reference temperature, and when the temperature of the raw water W1 or the like exceeds the lowest reference temperature among the plurality of reference temperatures, the permeated water W2 is provided by the circulation channel 6. It is possible to start returning a part of the raw water W1 before the supply step and increase the circulation amount of the permeated water W2 by the circulation water channel 6 every time the temperature of the raw water W1 or the like exceeds a plurality of reference temperatures. When any of the temperatures of the raw water W1 and the like is equal to or lower than the minimum reference temperature, the entire permeated water W2 may be supplied to the use point or the like without returning a part of the permeated water W2 to the raw water W1.

In this case, the circulation of the permeated water W2 may be started and the amount of the circulating water may be increased by using one circulation channel 6. As the on-off valve provided in the circulation water channel 6, for example, a control valve having a variable opening degree may be used.

Further, using two or more circulating water channels 6, the circulation of the permeated water W2 is started by the first circulating water channel, and when the water temperature rises further, the remaining circulating water channels are sequentially opened to increase the amount of circulating water. May be good. As the on-off valve provided in each circulation water channel 6, for example, a valve that can switch the open / closed state between "open" and "closed" may be used.

Hereinafter, the circulation process in the pure water production apparatus 1 shown in FIG. 1 will be described. In FIG. 1, two circulation water channels 6 are provided, a first circulation water channel 6a and a second circulation water channel 6b. Therefore, two reference temperatures, a first reference temperature and a second reference temperature, are set as reference temperatures. The second reference temperature is set to a temperature higher than the first reference temperature.

Then, when the temperature of the raw water W1 or the like exceeds the first reference temperature, the first on-off valve 7 is opened, and a part of the permeated water W2 is returned to the raw water W1 before the supply process by the first circulation water channel 6a. .. When the temperature of the raw water W1 or the like rises further and the temperature of the raw water W1 or the like exceeds the second reference temperature, the second on-off valve 8 is further opened to partially circulate the permeated water W2 in the first circulation channel. It is returned to the raw water W1 before the supply process by 6a and the second circulation channel 6b.

The rest of the permeated water W2 that has not been returned by the first circulating water channel 6a and the second circulating water channel 6b flows through the permeated water channel 5 as it is and is sent to a use point or the like.

Next, in the first flow rate measuring step, the flow rate of the permeated water W2 is measured by the first flow meter 9. The first flow meter 9 is arranged in the permeation channel 5 on the downstream side of the branch position of the circulation channel 6. Therefore, when a part of the permeated water W2 is returned by the circulating water channel 6, the first flow meter 9 measures the flow rate of the rest of the permeated water W2. When the permeated water W2 is not returned by the circulating water channel 6, the total flow rate of the permeated water W2 is measured by the first flow meter 9. The flow rate measurement value of the permeated water W2 measured by the first flow meter 9 is sent to the control unit 10.

Next, in the supply control step, when the flow rate of the permeated water W2 measured in the first flow rate measuring step deviates from the first reference flow rate range, the control unit 10 detects this and the flow rate of the permeated water W2 is increased. The amount of raw water W1 supplied by the supply pump 3 is controlled so as to be within the first reference flow rate range. When a part of the permeated water W2 is returned to the raw water W1 by the circulating water channel 6, the amount of the permeated water W2 supplied to the use point or the like decreases, and water shortage may occur at the use point or the like. Therefore, the first reference flow rate range, which is an appropriate range of the flow rate of the permeated water W2, is set, and when the flow rate of the permeated water W2 deviates from the first reference flow rate range, the control unit 10 detects this and the supply pump 3 A control signal is sent to adjust the supply amount of raw water W1.

For example, when the flow rate of the permeated water W2 is lower than the first reference flow rate range, the control unit 10 sends a control signal to the supply pump 3 to increase the supply amount of the raw water W1. In this case, the effective pressure of the raw water W1 in the reverse osmosis membrane 4 increases, and the amount of the permeated water W2 can be increased while maintaining a high blocking rate of the reverse osmosis membrane 4. When the flow rate of the permeated water W2 exceeds the first reference flow rate range, the control unit 10 sends a control signal to the supply pump 3 to reduce the supply amount of the raw water W1.

Next, in the second flow rate measuring step, the flow rate of the concentrated water W3 flowing through the concentrated water channel 11 is measured by the second flow meter 12. The flow rate measurement value of the concentrated water W3 measured by the second flow meter 12 is sent to the flow control valve 13.

Next, in the flow rate control step, when the flow rate of the concentrated water W3 measured in the second flow rate measuring step is out of the second reference flow rate range, the flow rate of the concentrated water W3 is within the second reference flow rate range. Control. When the supply amount of the raw water W1 is increased by the supply pump 3, the flow rate of the concentrated water W3 increases, but there is a concern that the flow rate of the permeated water W2 decreases. Therefore, the flow rate of the concentrated water W3 is monitored by the second flow meter 12, and if this is out of the appropriate range, the flow control valve 13 is operated to reduce the flow rate of the concentrated water W3, thereby reducing the flow rate of the permeated water W2. The flow rate balance between the concentrated water W3 and the concentrated water W3 is set within an appropriate range. As a result, the operating conditions of the reverse osmosis membrane 4 can be maintained within an appropriate range.

As described above, according to the pure water production apparatus 1 of the present embodiment, when the water temperature of the raw water W1 or the like exceeds the reference temperature, the on-off valves 7 and 8 are automatically opened, which may increase the amount of permeated water. At a certain high water temperature, a part of the permeated water W2 is returned to the raw water supply channel 2 via the circulating water channel 6, and an increase in the amount of permeated water supplied from the pure water production apparatus 1 to the use point or the like can be suppressed. Further, by returning a part of the permeated water W2 to the raw water supply path 2, the water quality of the raw water W1 is improved. Further, when the flow rate value of the first flow meter 9 deviates from the first reference flow rate range, the control unit 10 controls the supply amount of the raw water W1 by the supply pump 3, so that the permeated water amount after branching becomes the first reference. Try to maintain the flow range. This prevents the flow rate of the permeated water W2 from being reduced more than necessary, and a sufficient amount of permeated water can be supplied to the point of use or the like. As described above, according to the pure water production apparatus 1 of the present embodiment, the quality of pure water is not deteriorated even at a high water temperature, and the production amount of pure water is maintained in an appropriate range. Can be done.

Further, according to the pure water production apparatus 1 of the present embodiment, the permeated water W2 flows through the first circulating water channel 6a as the water temperature rises, and when the water temperature further rises, the first circulating water channel 6a and the second circulating water channel 6a. Since the permeated water W2 is configured to flow through 6b, the amount of permeated water returned to the raw water supply path 2 can be adjusted according to the change in water temperature, and the amount of pure water produced can be maintained within an appropriate range. ..

Further, according to the pure water production apparatus 1 of the present embodiment, when the flow rate of the concentrated water W3 flowing through the concentrated water channel 11 is out of the second reference flow rate range, the flow rate control valve 13 makes the flow rate of the concentrated water W3 appropriate. Control the flow rate. As a result, for example, even when the flow rate of the concentrated water W3 increases and there is a concern that the flow rate of the permeated water W2 decreases, the water amount ratio of the concentrated water W3 and the permeated water W2 is maintained in an appropriate range. Therefore, the operating conditions of the reverse osmosis membrane 4 can be maintained within an appropriate range, and the quality of pure water can be maintained.

Furthermore, according to the pure water production apparatus 1 of the present embodiment, since the control unit 10 is an inverter, the supply amount of the raw water W1 can be easily controlled based on the flow rate measurement value from the first flow meter 9.

Further, according to the pure water production method of the present embodiment, when the water temperature of the raw water W1 or the like exceeds the reference temperature in the circulation step, a part of the permeated water W2 is returned to the raw water W1, so that it is supplied to a use point or the like. The increase in the amount of permeated water can be suppressed. Further, a part of the permeated water W2 is returned to the raw water supply path 2, so that the water quality of the raw water W1 is improved. Further, in the first flow rate measurement step and the supply control step, when the flow rate value of the first flow meter 9 installed on the downstream side of the branch position between the permeation water channel 5 and the circulation water channel 6 deviates from the first reference flow rate range. In addition, by controlling the amount of raw water supplied by the supply pump 3, the amount of permeated water is maintained within the first reference flow rate range. As a result, the flow rate of the permeated water W2 is prevented from being reduced more than necessary, and a sufficient amount of the permeated water W2 can be supplied to the point of use or the like. As described above, according to the pure water production method of the present embodiment, it is possible to maintain the pure water production amount within an appropriate range without deteriorating the water quality of the pure water even at a high water temperature. it can.

Further, according to the pure water production method of the present embodiment, a plurality of different reference temperatures are set as the reference temperature, and each time the temperature of the raw water W1 or the like exceeds the plurality of reference temperatures, the permeated water W2 is circulated through the circulation channel 6. Since the amount is increased, the amount of permeated water W2 returned to the raw water supply path 2 can be adjusted according to the change in water temperature, and the amount of pure water produced can be maintained within an appropriate range.

Further, according to the pure water production method of the present embodiment, the permeated water flows into the first circulating water channel 6a as the water temperature rises, and when the water temperature rises further, the first circulating water channel 6a and the second circulating water channel 6b Since the permeated water W2 is configured to flow through the water, the amount of the permeated water W2 returned to the raw water supply path 2 can be adjusted according to the change in water temperature, and the pure water production amount can be maintained within an appropriate range. it can.

Furthermore, according to the pure water production method of the present embodiment, when the flow rate of the concentrated water W3 deviates from the second reference flow rate range in the second flow rate measurement step and the flow rate control step, the flow rate of the concentrated water W3 is appropriate. Control the flow rate. As a result, even when the flow rate of the concentrated water W3 increases and there is a concern that the flow rate of the permeated water W2 decreases, the water amount ratio of the concentrated water W3 and the permeated water W2 is maintained in an appropriate range. Therefore, the operating conditions of the reverse osmosis membrane 4 can be maintained within an appropriate range, and the quality of pure water can be maintained.

In the pure water production apparatus shown in FIG. 1, the flow rate of permeated water and the effective pressure of the reverse osmosis membrane when the temperature of the raw water is gradually increased to 25 ° C, 28 ° C, 30 ° C, 32 ° C and 35 ° C. Investigated the relationship. The results are shown in Table 1.
As shown in Table 1, as the temperature of raw water rises, the viscosity coefficient of water decreases, and the viscosity of water decreases.

The comparative example is an example in which the permeated water was not returned through the circulation channel. In the comparative example, the supply pump was operated with a constant amount of rotation regardless of the temperature of the raw water.

As shown in Table 1, in the comparative example, as the water temperature increased and the viscosity of the water decreased, the flow rate of the permeated water at each temperature (flow rate value by the first flow meter) increased. On the other hand, the effective pressure of the reverse osmosis membrane (RO membrane) decreased as the water temperature increased and the viscosity of the water decreased. In particular, when the water temperature reached 35 ° C., the effective pressure became 0.575 MPa, the blocking rate of the reverse osmosis membrane decreased, and the amount of impurities in the permeated water (pure water) increased.

On the other hand, the example is an example in which the permeated water is returned through the circulation channel. In the examples, the first reference temperature was set to 28 ° C and the second reference temperature was set to 32 ° C. Further, in the embodiment, the control unit controls the supply amount of raw water by increasing the rotation amount of the supply pump. As a result, the effective pressure of the reverse osmosis membrane (RO membrane) was maintained in the range of 0.721 to 0.764 MPa.

As shown in Table 1, in the example, when the temperature of the raw water reached 28 ° C., the first on-off valve was opened and the permeated water was returned to the raw water tank by the first circulation channel. Further, when the temperature of the raw water reached 32 ° C., the second on-off valve was further opened, and the permeated water was returned to the raw water tank by the second circulation water channel. Therefore, as shown in Table 1, the amount of permeated water returned increased as the water temperature increased. As a result, the flow rate value of the permeated water by the first flow meter was maintained in the range of 95 to 102 m ³ / h. Further, in the examples, since the effective pressure of the reverse osmosis membrane (RO membrane) was maintained in the range of 0.721 to 0.764 MPa, the inhibition rate of the reverse osmosis membrane did not decrease, and the amount of impurities in the permeated water (pure water). Remained low.

1 ... Pure water production equipment, 2 ... Raw water supply channel, 2a ... Raw water tank, 2b ... Raw water channel, 3 ... Supply pump, 4 ... Reverse osmosis membrane, 5 ... Permeation channel, 6 ... Circulation channel, 6a ... First circulation channel , 6b ... 2nd circulation channel, 7 ... 1st on-off valve (on-off valve), 8 ... 2nd on-off valve (on-off valve), 9 ... 1st flow meter, 10 ... control unit, 11 ... concentrated water channel, 12 ... 2 flow meter, 13 ... flow control valve, 20 ... water temperature gauge, W1 ... raw water, W2 ... permeated water, W3 ... concentrated water.

Claims (9)

The raw water supply channel that supplies raw water and
A supply pump provided in the raw water supply path and supplying the raw water,
A reverse osmosis membrane that separates the raw water supplied by the supply pump into permeated water and concentrated water.
A permeation channel through which the permeated water that has permeated the reverse osmosis membrane flows,
One or more circulating channels that are branched from the permeated channel and can return a part of the permeated water to the raw water supply channel.
One or two or more that are provided in the circulating water channels and open the circulating water channels when the temperature of any of the raw water, the permeated water, or the concentrated water exceeds the reference temperature set for each of the circulating water channels. On-off valve and
A first flow meter installed in the permeation channel on the downstream side of the branch position of the circulation channel, and
When the flow rate of the permeated water measured by the first flow meter deviates from the first reference flow rate range, the flow rate of the permeated water measured by the first flow meter falls within the first reference flow range. A pure water production apparatus including a control unit for controlling the supply amount of the raw water by the supply pump. Two circulation channels, a first circulation channel and a second circulation channel, are provided as the circulation channel.
Two on-off valves, a first on-off valve and a second on-off valve, are provided.
The first on-off valve is provided in the first circulating water channel and opens the first circulating water channel when the temperature of any of the raw water, the permeated water, and the concentrated water exceeds the first reference temperature. And
The second on-off valve is provided in the second circulation water channel, and when the temperature of any of the raw water, the permeated water, and the concentrated water exceeds the second reference temperature higher than the first reference temperature, the said. The pure water production apparatus according to claim 1, wherein the on-off valve opens a second circulation water channel. A concentrated water channel through which the concentrated water discharged from the reverse osmosis membrane flows,
The second flow meter installed in the concentrated water channel and
The concentrated water measured by the second flow meter when the flow rate of the concentrated water installed in the concentrated water channel and measured by the second flow meter deviates from a preset second reference flow rate range. A flow rate control valve that controls the flow rate so that it is within the second reference flow rate range,
The pure water production apparatus according to claim 1 or 2, further comprising. The control unit is an inverter to which a flow rate measurement value from the first flow meter is input and outputs a control signal for controlling the supply amount of the raw water based on the flow rate measurement value to the supply pump. The pure water production apparatus according to any one of claims 1 to 3. The supply process of supplying raw water by a supply pump and
A separation step of separating the raw water supplied in the supply step into permeated water and concentrated water by a reverse osmosis membrane, and
When the temperature of any of the raw water, the permeated water, and the concentrated water exceeds the reference temperature, a part of the permeated water flowing through the permeated water channel is divided into one or more circulating water channels branched from the permeated water channel. In the circulation process of returning to the raw water before the supply process,
A first flow rate measuring step of measuring the flow rate of the permeated water with a first flow meter in the permeated water channel on the downstream side of the branch position of the circulating water channel.
When the flow rate of the permeated water measured in the first flow rate measuring step deviates from the first reference flow rate range, the flow rate of the permeated water measured by the first flow meter falls within the first reference flow rate range. A method for producing pure water, which comprises a supply control step for controlling the supply amount of the raw water by the supply pump so as to be provided. In the circulation step, a plurality of different reference temperatures are set as the reference temperature, and the reference temperature is set.
When the temperature of any of the raw water, the permeated water, or the concentrated water exceeds the lowest reference temperature among the plurality of reference temperatures, a part of the permeated water is provided before the supply step by the circulation channel. Started to return to the raw water of
The fifth aspect of claim 5, wherein the circulation amount of the permeated water by the circulation water channel is increased each time the temperature of any of the raw water, the permeated water or the concentrated water exceeds the plurality of reference temperatures. Pure water production method. In the circulation step, when the temperature of any of the raw water, the permeated water, and the concentrated water exceeds the first reference temperature, a part of the permeated water flowing through the permeated water channel is subjected to the first circulating water channel. Return to the raw water before the supply process,
When the temperature of any of the raw water, the permeated water, and the concentrated water exceeds the second reference temperature higher than the first reference temperature, a part of the permeated water flowing through the permeated water channel is circulated in the first circulation. The pure water production method according to claim 5 or 6, wherein the step is to return the raw water before the supply step by the water channel and the second circulation water channel. A second flow rate measuring step of measuring the flow rate of the concentrated water discharged from the reverse osmosis membrane and flowing through the concentrated water channel with a second flow meter,
When the flow rate of the concentrated water measured in the second flow rate step deviates from the second reference flow rate range, the flow rate of the concentrated water measured by the second flow meter falls within the second reference flow range. The flow rate control process to control
The pure water production method according to any one of claims 5 to 7, further comprising. In a pure water production method in which raw water supplied by a supply pump is separated into permeated water and concentrated water by a reverse osmosis membrane.
When the temperature of the raw water, the permeated water or the concentrated water exceeds the reference temperature, a part of the permeated water is returned to the raw water before supply, and the temperature of the raw water, the permeated water or the concentrated water is reached. Adjust the amount of permeated water returned according to
A pure water production method characterized by adjusting the supply amount by the supply pump so that the flow rate of the remaining portion of the permeated water excluding the portion returned to the raw water becomes the flow rate before the start of the return of the permeated water. ..

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