JP2010201325A - Method of controlling pure water supply system, and pure water supply system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of controlling a pure water supply system, by which even if total consumption of pure water varies at a use point, a load of a water supply pump is reduced, with energy consumption curtailed, and to provide a pure water supply system. <P>SOLUTION: The method of controlling the pure water supply system 100 of the application example includes a third piping system 107 by which a part of pure water supplied from a water treatment device 104 to a use point is returned to an upstream side of a water pump 103, driving/controlling the water pump 103 so that a first pure water flow rate Q<SB>1</SB>is made constant as the flow rate of pure water supplied from the water treatment device 104, and also controlling a third pure water flow rate Q<SB>3</SB>in the third piping system 107 on the basis of unused pure water flow rate Q<SB>5</SB>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for controlling a pure water supply system and a pure water supply system.

As a pure water supply system used in a device manufacturing process such as a semiconductor device or an electro-optical device, an apparatus for producing ultrapure water having a positive pressure holding means that always maintains a positive pressure between the raw water supply means and the use location ( Patent Document 1) is known.
In addition, it has a controller that branches the return water pipe to the ultrapure water return pipe and polisher bypass pipe via the control valve, and controls the opening of the control valve based on the input signal of the return water amount and the specific resistance of the return water. A device for producing ultrapure water (Patent Document 2) is known.

  In the apparatus for producing ultrapure water described in Patent Document 1 or 2, ultrapure water is produced by passing primary pure water through a final water treatment apparatus including a membrane separator and a polisher. To supply. However, the amount of ultrapure water used at the point of use is not necessarily constant. For example, there is a problem that water quality (electrical resistance, TOC, etc.) deteriorates if the amount of water passed through the final water treatment device is reduced to a value that is necessary for design in accordance with a decrease in the amount of ultrapure water used.

  As a method for solving the above-described problem, for example, Patent Document 3 discloses that primary pure water is sequentially passed to a first system including a circulation pump, an ultraviolet irradiation device, an ion exchange resin tower, a membrane treatment device, and the like. In addition, a control method for an ultrapure water production apparatus is disclosed in which the flow rate of the first system is detected to control the rotation speed of the circulation pump to a target flow rate.

JP-A-60-7789 JP-A-6-79273 JP-A-64-38185

  However, controlling the circulation pump so that the flow rate of the first system becomes the target flow rate while reusing unused ultrapure water at the use point as in the above-mentioned Patent Document 3 is not possible at the point of use. When the amount of pure water used decreases, the flow rate flowing through the return pipe for reusing the ultrapure water increases. As a result, there is a problem that pressure loss due to return piping over a long distance increases. Also, since the rotational speed of the circulation pump must be increased to achieve the target flow rate against the pressure loss described above, the work of the circulation pump increases, resulting in an increase in energy consumption in the entire ultrapure water production apparatus. There is a problem that it ends up.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  [Application Example 1] A method for controlling a pure water supply system according to this application example includes a water supply pump and a water treatment device for treating raw water supplied by the water supply pump, and the water treatment device treats the pure water supply system. A first piping system in which raw water is supplied to the use point as pure water, and the pure water that is connected to the first piping system and is unused at the use point is returned to the upstream side of the water pump. And a third piping system for returning a part of the pure water supplied from the water treatment device to the upstream side of the water pump. The water pump is driven and controlled so that the flow rate of the pure water supplied from the water treatment device is constant, and the pure water in the third piping system is controlled based on the flow rate of the unused pure water. It is characterized by controlling the flow rate.

According to this method, the flow rate at which the water pump feeds raw water into the water treatment device is controlled to be constant, and the flow rate of pure water flowing through the third piping system is controlled in response to fluctuations in the amount of pure water used at the point of use. By controlling, the control method of the pure water supply system which can reduce the energy which a water pump consumes can be provided.
In addition, even if the amount of pure water used at the point of use fluctuates, the water pump feeds the raw water to the water treatment device so that a fixed amount of pure water is supplied from the water treatment device. Pure water with a stable amount and stable characteristics such as electrical resistance is supplied to the point of use.

Application Example 2 In the method for controlling a pure water supply system according to the application example described above, the flow rate of the unused pure water is controlled so that the back pressure in the first piping system becomes a predetermined value. preferable.
According to this method, since the back pressure in the first piping system is maintained at a predetermined value, pure water can be supplied to the use point at a stable supply pressure. That is, the energy consumption of the water pump can be reduced while ensuring the back pressure in the pure water supply system.

Application Example 3 In the method for controlling a pure water supply system according to the application example described above, the water pump is a rotary pump, and the rotation speed of the water pump is controlled so that the amount of water supply is constant.
According to this method, for example, by increasing the flow rate of pure water flowing in the third piping system in response to a decrease in the amount of pure water used at the point of use, the piping resistance in the first piping system is reduced, Even if the number of revolutions of the water pump is lowered, a certain amount of water can be secured, so that the energy consumption of the rotary water pump can be reduced.

Application Example 4 In the method for controlling a pure water supply system according to the application example described above, the water pump is driven and controlled so that the flow rate of the pure water in the third piping system is always equal to or higher than a predetermined value. preferable.
According to this method, a decrease in electrical resistance and an increase in TOC due to retention of pure water in the third piping system can be avoided, and pure water having stable characteristics is supplied and circulated.

  Application Example 5 A pure water supply system according to this application example includes a water pump and a water treatment device that processes raw water supplied by the water pump, and the raw water treated by the water treatment device is pure. A first piping system that is supplied to the use point as water, and a second piping that is connected to the first piping system and the pure water that has not been used at the use point is returned to the upstream side of the water pump. And a first control unit that drives and controls the water pump so that the flow rate of the pure water supplied from the water treatment device is constant. A second control unit that controls a flow rate of the unused pure water so that a back pressure in the system becomes a predetermined value, and a part of the pure water supplied from the water treatment device is disposed upstream of the water pump. A third piping system to be returned to and the unused pure water A third control unit for controlling the flow rate of the pure water in the third pipeline based on the flow rate, characterized by comprising a.

According to this configuration, the first piping system is a pure water supply line to the use point, and the second piping system is a pure water return line that returns unused pure water at the use point upstream. The third piping system is a second pure water return line that returns a part of the pure water supplied from the water treatment device upstream before supplying it to the use point. This configuration provides a pure water supply system that can control the flow rate of pure water in the third piping system in response to fluctuations in the amount of pure water used at the point of use and reduce the energy consumed by the water pump. can do.
In addition, the first control unit controls the water supply pump so that the flow rate of pure water supplied from the water treatment device is constant even when the amount of pure water used at the use point fluctuates, and the raw water is treated with the raw water. Therefore, a pure water supply system is provided that can supply pure water with a stable amount of raw water in the water treatment device and stable characteristics such as electric resistance to a use point.
Furthermore, since the second control unit controls the flow rate of unused pure water so that the back pressure in the first piping system becomes a predetermined value, it is stable even if the amount of pure water used at the point of use fluctuates. Pure water can be supplied at the supplied pressure.

Application Example 6 In the pure water supply system according to the application example, the water pump is a rotary pump, and the first control unit controls the rotation speed of the water pump so that the water supply amount is constant. It is characterized by that.
According to this configuration, the number of revolutions of the water pump is controlled in response to the piping resistance of the first piping system accompanying the change in the amount of pure water used at the point of use, and unnecessary energy consumption in the water pump is reduced. Can do.

Application Example 7 In the pure water supply system of the application example described above, one end of the third piping system is between the water treatment device and the use point and is close to the water treatment device side. It is preferable that they are connected.
According to this structure, the pressure loss at the time of returning pure water to the upstream side of a water pump using a 3rd piping system can be decreased.

Application Example 8 In the pure water supply system according to the application example described above, the other end of the third piping system may be connected to the second piping system after the second control unit.
According to this configuration, the length of the pipe that returns the pure water to the upstream side of the water pump using the third pipe system can be further shortened.

Application Example 9 In the pure water supply system of the application example, the pure water supply system includes a storage tank that is connected to the upstream side of the water pump and stores the raw water, and the second piping system and the third piping system. It is preferable that the other end of is connected to the storage tank.
According to this configuration, since the other ends of the second piping system and the third piping system are connected to the storage tank, the pure water return line is compared to the case where these pipes are directly connected to the water pump. It is possible to reduce the pressure loss of water supply in the second and third piping systems.

Application Example 10 In the pure water supply system according to the application example, the pure water supply system includes a storage tank that is connected to the upstream side of the water pump and stores the raw water, and the other end of the second piping system is the storage. It is connected to the tank, and the other end of the third piping system may be connected to the second piping system between the storage tank and the second control unit.
According to this configuration, the length of the piping in the third piping system can be further shortened.

Application Example 11 In the pure water supply system of the above application example, the raw water is primary pure water.
According to this configuration, the primary pure water can be processed in the water treatment device and supplied to the use point as ultrapure water. In addition, a well-known structure can be employ | adopted for a water treatment apparatus, for example, the structure containing an ion exchange apparatus, an ultraviolet irradiation device, and various filtration apparatuses can be mentioned.

The schematic diagram which shows the structure of a pure water supply system. The graph which shows the relationship between the piping resistance of a 1st piping system, and the water supply pressure of a water supply pump. The graph which shows the correlation of the pure water flow rate in each piping system. A graph showing how to adjust the back pressure. The schematic diagram which shows the 3rd piping system of a modification. (A) And (b) is a schematic diagram which shows the combination of the water supply pump and water treatment apparatus of a modification.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings. Note that the drawings to be used are appropriately enlarged or reduced so that the part to be described can be recognized.

<Pure water supply system>
The pure water supply system of this embodiment is demonstrated with reference to FIG. FIG. 1 is a schematic diagram showing a configuration of a pure water supply system.

  As shown in FIG. 1, the pure water supply system 100 of this embodiment is a system that supplies pure water obtained by treating raw water to a plurality of devices 1, 2,..., N as use points. It is. The point of use refers to a plurality of devices 1, 2,..., N to which pure water is supplied, and does not include branch pipes that supply pure water. Hereinafter, the plurality of devices 1, 2,..., N are collectively referred to as a device n.

The pure water supply system 100 includes a storage tank 101 in which raw water is stored, a water supply pump 103, and a water treatment device 104 in which raw water supplied by the water supply pump 103 is treated with water. A first piping system 109 including a plurality of branch pipes for supplying the raw water as pure water to each device n is provided. The first piping system 109 is a pure water supply line.
Further, a second piping system 114 is provided which is connected to the first piping system 109 and returns unused pure water to the storage tank 101 in each apparatus n. In other words, the second piping system 114 is a pure water return line.
Furthermore, a third piping system 107 that returns a part of pure water supplied from the water treatment device 104 to the storage tank 101 is provided. Therefore, the third piping system 107 can be called another pure water return line or pure water bypass line.

  The storage tank 101 is supplied with raw water from the outside through a pipe 102 and stored therein. Liquid level management is performed so that a certain amount of raw water is stored.

  The water supply pump 103 is, for example, an inverter-controlled rotary pump, and can feed raw water stored in the storage tank 101 to the water treatment device 104 while keeping the amount of water supply constant. A first flow meter 105 is provided on the downstream side of the water treatment apparatus 104, and includes a first control unit 106 that drives and controls the water supply pump 103 based on the flow rate detected by the first flow meter 105.

As the water treatment device 104, a known device can be used. For example, an ion exchange device that adsorbs and removes cations (metal ions) and anions in raw water, ultraviolet rays are irradiated on treated water after ion exchange, and microorganisms are removed. Examples include a combination of an ultraviolet irradiation device for sterilization and a filtration device for filtering treated water after ultraviolet irradiation to remove microorganisms and foreign matters.
Such a water treatment device 104 performs water treatment by passing a certain amount of raw water, and produces pure water having predetermined characteristics. Various processing devices are combined according to the characteristic requirements such as electrical resistance and TOC (Total Organic Carbon).

Connected to the downstream side of the first flow meter 105, the branch point Br ₁ of the first piping system 109, Br _2, · · ·, device branch pipes extending from each of the Br _n 1, 2, · · ·, n are connected to each other. The amount of pure water per unit n _{is, Qd 1, Qd 2, ···} , represented by Qd _n. Therefore, the total use amount Q ₄ of pure water at the use point is expressed by ΣQd _i (i = 1 to n).

One end of the second piping system 114 is connected to the first piping system 109 via the valve 112, the pressure gauge 111, and the second flow meter 110, and the other end is connected to the storage tank 101. It is open. That is, the first piping system 109 is a piping system between the first flow meter 105 and the second flow meter 110.
It goes without saying that the flow rate Q ₅ of unused pure water flowing through the first piping system 109 (hereinafter referred to as the flow rate of unused pure water Q ₅ ) depends on the total use amount Q ₄ of pure water at the use point. .
In order to send pure water stably to each device n, the water supply pressure in the first piping system 109 needs to be maintained at a predetermined pressure. Therefore, the valve 112 is opened based on the value of the pressure gauge 111 so that the water supply pressure (hereinafter referred to as back pressure) in the apparatus n connected most downstream in the first piping system 109 is kept constant. The degree can be adjusted. That is, the pressure gauge 111 and the valve 112 function as a second control unit for ensuring back pressure.

The third piping system 107 is provided with at least a shorter length than the first piping system 109. One end thereof is connected between the water treatment device 104 and the use point at a position close to the water treatment device 104 side. Specifically, in the first piping system 109, the first flow meter 105 is connected to a branch point Br ₀ between the branch point Br ₁ to which the branch pipe connected to the apparatus 1 located at the most upstream is connected. The other end of the third piping system 107 is connected to the storage tank 101 and opened to the inside thereof.
A valve 108 is provided in the third piping system 107. A third control unit 113 that controls the opening degree of the valve 108 is provided. The third control unit 113 controls the opening degree of the valve 108 based on the unused pure water flow rate Q ₅ in the first piping system 109 measured by the second flow meter 110. Alternatively, the third control unit 113 may control the opening degree of the valve 108 based on the back pressure of the first piping system 109 measured by the pressure gauge 111.

  The pure water supply system 100 of the present embodiment is an open system in which pure water supplied to a use point (apparatus n) is drained after use. It is not limited to this, You may provide the 4th piping system which returns the part to the storage tank 101 depending on the characteristic of the pure water drained for every apparatus n. Thereby, effective use of pure water is achieved.

  The substantial effective diameter in each piping system is preferably larger in the second piping system 114 and the third piping system 107 than in the first piping system 109 in consideration of the piping resistance of pure water flowing therethrough. Furthermore, it is desirable that the third piping system 107 has a pipe diameter equal to or larger than that of the second piping system 114.

In the pure water supply system 100 of the present embodiment, the pure water flow rate obtained by the first flow meter 105 is defined as a first pure water flow rate Q ₁ . A flow rate of pure water passing through the branch point Br ₀ and flowing through the first piping system 109 is defined as a second pure water flow rate Q ₂ . Similarly, the flow rate of pure water passing through the branch point Br ₀ and flowing through the third piping system 107 is defined as a third pure water flow rate Q ₃ .

In such a pure water supply system 100, the total amount Q ₄ of the pure water device n is the point of use is not necessarily constant. For example, if some of the devices n are suspended, the total usage amount Q ₄ naturally decreases. The pure water supply system 100 can stably supply pure water having desired characteristics to the use point, and each control unit can respond to the fluctuation of the total use amount Q ₄ of pure water at the use point. The power consumption of the water pump 103 can be reduced by functioning. In detail, it demonstrates in the control method of a pure water supply system.

<Control method of pure water supply system>
Next, the control method of the pure water supply system of this embodiment is demonstrated with reference to FIGS. 2 is a graph showing the relationship between the piping resistance of the first piping system and the water supply pressure of the water pump, FIG. 3 is a graph showing the mutual relationship of the pure water flow rate in each piping system, and FIG. 4 is a method of adjusting the back pressure. It is a graph which shows.

  In FIG. 2, curves Pa, Pb, and Pn indicate the relationship between the water supply amount and the water supply pressure in the first piping system 109. Curves Ra, Rb, and Rn indicate the relationship between the water supply amount and the piping resistance in the first piping system 109. Curves Pa, Pb, and Pn indicate the characteristics of the water supply pump 103 corresponding to the curves Ra, Rb, and Rn, respectively.

  More specifically, the curve Rn shows the relationship between the water supply amount and the pipe resistance in the normal state where all the devices n are operating. As the amount of water supplied by the water supply pump 103 increases, the pipe resistance increases. Along with this, the water supply pressure decreases as shown by the curve Pn.

The first control unit 106 drives and controls the water pump 103 so that a certain amount of pure water is supplied from the water treatment device 104. According to FIG. 2, in a normal state, the water supply pressure when the water supply amount from the water supply pump 103 is the first pure water flow rate Q ₁ is P ₁ .

On the other hand, when the total usage amount Q ₄ of the apparatus n as a use point decreases, the flow rate of unused pure water Q ₅ flowing through the first piping system 109 increases, and the longest first piping system 109 remains as it is. As shown by the curve Rb, the pipe resistance of the pipe increases as compared with the curve Rn. As described above, the first control unit 106 controls the water supply pump 103 so that the first pure water flow rate Q ₁ is constant. Therefore, the rotation speed is to resist the increase in pipe resistance in the first pipe system 109. Rises and the characteristic of the water pump 103 becomes a curve Pb. Therefore, although the total usage amount Q ₄ is reduced, the load of the water pump 103 is increased and the energy consumption is increased. Therefore, in the present embodiment, the following pure water flow rate is controlled.

FIG. 3 shows the relationship between the total amount of use Q ₄ at each use point and each pure water flow rate. The first pure water flow rate Q ₁ , which is the amount of pure water supplied from the water treatment device 104, is kept constant by the first control unit 106 drivingly controlling the water supply pump 103. The third control unit 113 detects a change in the total used amount Q ₄ indirectly by detecting a change in the unused pure water flow rate Q ₅ with the second flow meter 110, and in response to this, opens the valve 108. Adjust the degree.
The back pressure in the first piping system 109 is preferably maintained at a predetermined value as described above. Moreover, it is necessary to prevent unused pure water from staying in the first piping system 109 and generating bacteria and the like. For this purpose, it is required that the necessary minimum amount of pure water flow Q ₅ is ensured to be constant.
For example, when the total amount Q ₄ of pure water decreases, the unused pure water flow rate Q ₅ increases. The third control unit 113 compares the unused pure water flow rate Q ₅ predetermined and the actual unused value of pure water flow rate Q ₅ obtained from the second flow meter 110, in accordance with the difference The opening degree of the valve 108 is controlled. Therefore, when the unused pure water flow rate Q ₅ is increased, the opening degree of the valve 108 is further increased. As a result, the third pure water flow rate Q _{3 in} the third piping system 107 increases, and the piping resistance in the first piping system 109 decreases as shown by the curve Ra in FIG. In other words, the pressure loss for the pure water supply in the first piping system 109 is reduced. Therefore, the first control unit 106 may be a driving condition of the curve Pa which dropped the rotational speed of the water pump 103, to secure the first pure water flow rate Q _1. That is, the energy consumption of the water pump 103 can be reduced with a decrease in the total usage amount Q _{4 at} the use point.

A curve Bp in FIG. 4 shows the relationship between the unused pure water flow rate Q ₅ and the back pressure.
Back pressure Pc in the first piping system 109 is maintained at a predetermined value by controlling the unused pure water flow rate Q ₅ by the second control unit configured to a pressure gauge 111 and valve 112 .
Specifically, the minimum flow rate of the unused pure water flow rate Q ₅ is obtained from the flow rate necessary to prevent the generation of bacteria and the like, and the back pressure is determined from the specifications of the device n as a use point. Desired. Therefore, the pressure gauge 111 and the valve 112 are controlled so as to satisfy the required flow rate and back pressure from the relationship shown in FIG.

Such control of the pure water flow rate is summarized as a mathematical formula as follows.
Q ₁ (constant) = Q ₂ (variation) + Q ₃ (variation) ··· (1)
Q ₂ (variation) = Q ₄ (variation) + Q ₅ (constant) ··· (2)
Therefore, Q ₁ (constant) = Q ₃ (variation) + Q ₄ (variation) + Q ₅ (constant) (3). That is, the first pure water flow rate Q ₁ is the sum of the second pure water flow rate Q ₂ and the third pure water flow rate Q ₃ and is kept constant. The second pure water flow rate Q ₂ is the sum of the total pure water use amount Q _{4 at the} use point and the unused pure water flow rate Q ₅ and varies. Further, the third control unit 113 controls the opening degree of the valve 108 while maintaining the back pressure by keeping the unused pure water flow rate Q ₅ constant corresponding to the fluctuation of the total pure water usage Q _{4 at} the use point. The third pure water flow rate Q ₃ is controlled by adjusting.

Incidentally, those in FIG. 3, the third pure water flow rate Q ₃ in the bypass line of the third pipeline 107 i.e. pure water is started from the level of certain unused pure water flow rate Q _5, which is limited to is not. For example, in the 2nd piping system 114 and the 3rd piping system 107 which return pure water to the storage tank 101, it is necessary to prevent that a pure water retains in a piping and a characteristic falls. Therefore, the third pure water flow rate Q ₃ and the unused pure water flow rate Q ₅ are controlled so as not to become zero. Further, for example, even when all the devices n that are use points are suspended, the state where the total usage amount Q ₄ is not made zero is maintained in the same manner. Therefore, since the total usage amount Q ₄ and the unused pure water flow rate Q ₅ are determined according to the operating state of the apparatus n, the third pure water flow rate Q ₃ is also set accordingly.

According to such a control method of the pure water supply system 100, the third pure water flow rate Q ₃ of the pure water flowing through the third piping system 107 in accordance with the fluctuation of the total pure water usage Q _{4 at} the use point is obtained. Be controlled. As a result, the pipe resistance (pressure loss) of the first piping system 109 is reduced even if the total usage amount Q ₄ is reduced while ensuring the back pressure in the first piping system 109. The load can be reduced while keeping the constant. That is, the energy consumption of the water pump 103 can be reduced.

In addition, since a constant amount of raw water is always fed into the water treatment device 104 by the water pump 103 regardless of fluctuations in the total use amount Q ₄ at the use point, pure water having stable characteristics is supplied to the use point. Is realized.

  Various modifications other than the above embodiment are conceivable. Hereinafter, a modification will be described.

  (Modification 1) The structure in the pure water supply system 100 of the said embodiment is not limited to this. For example, the storage tank 101 for storing the raw water is not necessarily required if the raw water is stably supplied to the water supply pump 103.

(Modification 2) In the pure water supply system 100 of the above embodiment, the piping method of the third piping system 107 is not limited to this. FIG. 5 is a schematic diagram showing a third piping system according to a modification.
For example, as shown in FIG. 5, the third piping system 107 </ b> A of the modified example is connected to the second piping system 114 after the valve 112 without connecting the other pipe to the storage tank 101. In this way, the third piping system 107 can be piped with a shorter length. That is, the piping resistance in the third piping system 107 can be further reduced.

(Modification 3) In the pure water supply system 100 of the above embodiment, the combination of the water pump 103 and the water treatment device 104 is not limited to this. FIGS. 6A and 6B are schematic views showing a combination of a water pump and a water treatment device according to a modification.
As shown in FIG. 6A, a plurality of (three) water treatment devices 104a, 104b, and 104c may be combined with one water pump 103. According to this, even if a malfunction occurs in the water treatment apparatus 104a, for example, it is possible to compensate with the other water treatment apparatuses 104b and 104c.
Moreover, as shown in FIG.6 (b), you may comprise one set with one water pump 103a and one water treatment apparatus 104a by one set. The first control unit 106 drives and controls the water pumps 103a, 103b, and 103c of each group based on the respective flow rates detected by the flow meters 105a, 105b, and 105c provided corresponding to the respective groups. For example, even if the water pump 103a fails, it can be compensated by another set.

  (Modification 4) In the pure water supply system 100 of the above embodiment, the raw water supplied to the water treatment device 104 may be primary pure water. According to this, primary pure water can be sent to the water treatment device 104 by the water feed pump 103 to be processed, and supplied to the use point as ultrapure water.

DESCRIPTION OF SYMBOLS 100 ... Pure water supply system, 101 ... Storage tank, 103 ... Water supply pump, 104 ... Water treatment apparatus, 106 ... 1st control part, 107 ... 3rd piping system, 109 ... 1st piping system, 113 ... 3rd Control unit 114 ... second piping system, Q ₁ ... _first pure water flow rate as the flow rate of pure water supplied from the water treatment device, Q ₃ ... first flow rate as pure water flow rate through the third piping system 3 Pure water flow rate, Q ₄ ... Total use amount of pure water at the point of use, Q ₅ ... Flow rate of unused pure water.

Claims (11)

A first piping system that includes a water pump and a water treatment device that treats raw water supplied by the water pump, and the raw water treated by the water treatment device is supplied to a use point as pure water; A method for controlling a pure water supply system, comprising: a second piping system connected to the first piping system, wherein the pure water that has not been used at the use point is returned to the upstream side of the water pump. ,
A third piping system for returning a part of the pure water supplied from the water treatment device to the upstream side of the water pump;
The water pump is driven and controlled so that the flow rate of the pure water supplied from the water treatment device is constant, and the flow rate of pure water in the third piping system based on the flow rate of the unused pure water A method for controlling a pure water supply system, characterized by controlling the water.   2. The method of controlling a pure water supply system according to claim 1, wherein the flow rate of the unused pure water is controlled such that a back pressure in the first piping system becomes a predetermined value. The water pump is a rotary pump,
The method for controlling a pure water supply system according to claim 1 or 2, wherein the number of rotations of the water pump is controlled so that the amount of water is constant.   The pure water according to any one of claims 1 to 3, wherein the water pump is driven and controlled so that the flow rate of the pure water in the third piping system is always equal to or greater than a predetermined value. Supply system control method. A first piping system that includes a water pump and a water treatment device that treats the raw water supplied by the water pump, and the raw water treated by the water treatment device is supplied to a use point as pure water; A pure water supply system comprising: a second piping system connected to the first piping system and the pure water that has not been used at the use point is returned to the upstream side of the water pump;
A first controller that drives and controls the water pump so that the flow rate of the pure water supplied from the water treatment device is constant;
A second control unit that controls a flow rate of the unused pure water so that a back pressure in the first piping system becomes a predetermined value;
A third piping system for returning a part of the pure water supplied from the water treatment device to the upstream side of the water pump;
A third controller that controls the flow rate of the pure water in the third piping system based on the flow rate of the unused pure water;
A pure water supply system characterized by comprising: The water pump is a rotary pump,
The pure water supply system according to claim 5, wherein the first control unit controls the number of rotations of the water pump so that a water supply amount becomes constant.   The one end of the third piping system is connected between the water treatment device and the use point and at a position close to the water treatment device side. The pure water supply system described.   The pure water according to any one of claims 5 to 7, wherein the other end of the third piping system is connected to the second piping system after the second control unit. Supply system. Connected to the upstream side of the water pump, and having a storage tank in which the raw water is stored,
The pure water supply system according to any one of claims 5 to 7, wherein the other ends of the second piping system and the third piping system are connected to the storage tank. Connected to the upstream side of the water pump, and having a storage tank in which the raw water is stored,
The other end of the second piping system is connected to the storage tank,
8. The other end of the third piping system is connected to the second piping system between the storage tank and the second control unit. Pure water supply system as described in.   The pure water supply system according to any one of claims 5 to 10, wherein the raw water is primary pure water.

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