JP7208043B2 - Concentration measurement device, ultrapure water production device, and water treatment method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a concentrator, a concentration measuring device, and an ultrapure water production device that are useful in the production of ultrapure water.

In recent years, there has been a demand for further purification of ultrapure water, which is used as cleaning water for semiconductor wafers and the like. For example, it is required to measure the concentration of silica or the like contained as an impurity in the water to be treated for obtaining ultrapure water with high accuracy and a lower quantitative lower limit. Today, it is possible that measurements of silica concentrations on the order of 0.1 ppb to 0.01 ppb and even 0.001 ppb may be required, and it is expected that the required level will continue to increase in the future.

By the way, it is technically difficult to measure a very small amount of silica in the water to be treated. For example, since the lower limit of quantitative determination of the online silica monitor is on the order of 0.1 to 1 ppb, if the concentration of silica to be measured is, for example, 0.001 ppb, the measurement accuracy falls short by 100 to 1000 times. (For example, Non-Patent Document 1). For this reason, although it is desired to concentrate and measure sample water using a concentration method, silica cannot be efficiently adsorbed by the existing concentration method using an ion-exchange resin. may flow out to the distillation side and the silica cannot be sufficiently concentrated. In addition, it is being studied to concentrate silica in the water to be treated using a reverse osmosis membrane device or the like to a level that can be measured by existing measuring instruments (see, for example, Patent Document 1). Since the removal rate of silica in the permeation membrane device is not sufficient, it is difficult to obtain a sufficient concentration ratio and recover silica with a high recovery rate. was difficult.

JP-A-2004-77299

Semiconductor Fundamental Technology Research Group, "Science of Ultrapure Water" Publisher: Realize, September 11, 1990, p.543

However, when a weak electrolyte component such as silica is concentrated using a reverse osmosis membrane device, a solute that is not filtered creates a concentration gradient in the thickness direction of the reverse osmosis membrane, that is, concentration polarization can occur. As the effect of concentration polarization increases, solute leakage to the permeate side of the membrane increases. In particular, weak electrolyte components such as silica are more affected by concentration polarization than other solutes. For this reason, unless the recovery rate and concentration rate of the water to be treated in the reverse osmosis membrane apparatus are appropriately set, the recovery rate of the weak electrolyte component decreases and a sufficient concentration rate cannot be obtained.

The present invention has been made in order to solve the above-mentioned problems, and a concentrator, a concentration measuring device, and a concentrator capable of concentrating to a high concentration ratio with a high recovery rate of weak electrolyte components contained as impurities in the water to be treated. An object of the present invention is to provide an ultrapure water production system. In addition, the present invention can be used for water below the current analytical quantification lower limit (silica concentration on the order of 0.1 ppb to 0.01 ppb and even 0.001 ppb).

The concentrator of the present invention includes a water supply channel, first and second reverse osmosis membrane devices, first and second return channels, first and second branch channels, and a flow rate adjustment mechanism. . To-be-processed water is water-supplied by the water-supply flow path. The first reverse osmosis membrane device is provided on the water supply channel. The second reverse osmosis membrane device is provided downstream of the first reverse osmosis membrane device on the water supply channel. The first return channel extends from the concentrated water outlet of the first reverse osmosis membrane device and returns to the upstream side of the first reverse osmosis membrane device on the water supply channel. The second return channel extends from the concentrated water outlet of the second reverse osmosis membrane device and returns to the upstream side of the first reverse osmosis membrane device on the water supply channel. The first branch channel branches off from the first return channel and drains water. The second branch channel branches off from the second return channel and merges between the first reverse osmosis membrane device and the second reverse osmosis membrane device on the water supply channel. The flow rate adjustment mechanism adjusts the flow rates of the water supply channel, the first and second return channels, and the first and second branch channels.

The flow control mechanism described above has a plurality of valves, pumps, and control units. A plurality of valves are provided in the water supply channel, the first and second return channels, and the first and second branch channels. The pump is provided on the water supply channel. A controller controls the operation of a plurality of valves and/or pumps. Here, the water recovery rate of the first reverse osmosis membrane device is set to be higher than the water recovery rate of the second reverse osmosis membrane device.

Further, the concentration measuring apparatus of the present invention includes the concentrator, the detection section, and the calculation section configured as described above. The detection unit detects the concentration of a predetermined weak electrolyte component contained in the concentrated water flowing through the first branch channel. Here, the detection unit may be directly connected to the concentrator via a pipe or the like, or the concentrated water of the concentrator is sampled with a sampling bottle or the like, and the concentration of the sampled concentrated water is determined, for example, by Detection may be performed by a detection unit provided at a position away from the concentrator. The calculation unit is included in the water to be treated upstream of the return points of the first and second return channels on the water supply channel based on the flow rate adjusted by the flow rate adjustment mechanism and the detected concentration. Calculate the concentration of a given weak electrolyte component. The predetermined weak electrolyte component mentioned above is silica, for example.

Further, the ultrapure water production system of the present invention includes the concentration measuring device, the primary pure water producing section, the secondary pure water producing section, the tank, and the third return channel. The primary pure water production unit performs water treatment on the water to be treated to produce primary pure water. The secondary pure water production section is provided downstream of the primary pure water production section, and performs further water treatment on the produced primary pure water to produce secondary pure water. The tank is interposed between the primary pure water producing section and the secondary pure water producing section. The third return flow path returns the water to be treated that has passed through the point of use provided downstream of the secondary pure water production section to the tank. Here, at least the above-described concentrator that constitutes the concentration measuring device has a predetermined It may be connected via a connection mechanism, or installed in series between the secondary pure water production unit and the use point, inside the secondary pure water production unit, or in the third return flow path. good too. The predetermined connection mechanism is a branch from the third return flow path (or the main flow path in the secondary pure water production section, or the flow path connecting the secondary pure water production section and the point of use). The concentrator is connected to the main body of the ultrapure water production apparatus via the connection mechanism including such branched flow paths. The connection mechanism is equipped with a valve, a check valve, etc., as required. When the above-described concentrator is installed in series with the flow path, the flow rate of the water to be treated flowing into the concentrator increases, so the concentrator must be appropriately scaled up accordingly.

According to the present invention, there is provided a concentrator, a concentration measuring device, and an ultrapure water production device that can increase the recovery rate of weak electrolyte components contained as impurities in the water to be treated and obtain a high concentration ratio. is possible.

1 is a block diagram showing the configuration of an ultrapure water production apparatus according to an embodiment of the present invention; FIG. FIG. 2 is a block diagram showing the configuration of a secondary pure water producing unit and a concentration measuring device provided in the ultrapure water producing apparatus of FIG. 1; FIG. 3 is a diagram showing the configuration of a concentrator included in the concentration measuring device of FIG. 2; 4 is a diagram showing the configuration of a concentrator of Comparative Example 1. FIG. 4 is a diagram showing the configuration of a concentrator of Comparative Example 2. FIG. FIG. 4 is a diagram showing the configuration of another concentrator that is partially different in configuration from the concentrator of FIG. 3 ;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described based on the drawings.
As shown in FIG. 1, an ultrapure water production apparatus 10 according to the present embodiment is an apparatus for obtaining ultrapure water by treating water to be treated, and includes a pretreatment unit 12, a primary pure water production unit 14, A water treatment system 15 including a flow path 17 for water to be treated, a tank 16 , a secondary pure water producing section 18 and a concentration measuring device 19 is provided. The pretreatment unit 12 introduces city water, well water, industrial water, or the like as raw water. The pretreatment unit 12 has an appropriate configuration according to the quality of the raw water, etc., and removes suspended solids from the raw water to generate pretreated water. The pretreatment unit 12 includes, for example, a sand filter device, a microfiltration device, and the like, and further has a heat exchanger and the like for adjusting the temperature of the water to be treated as necessary.

The primary pure water production unit 14 performs water treatment on the water to be treated (pretreated water) to produce primary pure water. The primary pure water production unit 14 removes organic components, ion components, dissolved gases, and the like from the pretreated water to produce primary pure water, and supplies the primary pure water to the tank 16 . In addition, the primary pure water production unit 14 includes, for example, a reverse osmosis membrane device, an ion exchange device (cation exchange device, anion exchange device, mixed bed ion exchange device, etc.), an ultraviolet oxidation device, and a degassing device (vacuum degassing device, degassing membrane device, etc.). The primary pure water has, for example, a total organic carbon (TOC) concentration of 5 μgC/L or less and a resistivity of 17 MΩ·cm or more. The tank 16 stores primary pure water and supplies the required amount to the secondary pure water producing section 18 .

On the other hand, the secondary pure water production unit 18 is provided downstream of the primary pure water production unit 14, and performs further water treatment on the primary pure water produced by the primary pure water production unit 14 to produce secondary pure water. do. This secondary pure water production unit 18 removes impurities from the primary pure water to produce secondary pure water that becomes ultrapure water, and is a point of use (POU) where the ultrapure water is used. 20. The tank 16 is interposed between the primary pure water producing section 14 and the secondary pure water producing section 18 .

The point of use 20 is provided downstream of the secondary pure water production section 18 and the concentration measuring device 19 . The flow path 17 directs the water to be treated by the pretreatment unit 12, the primary pure water producing unit 14, the secondary pure water producing unit 18, and the concentration measuring device 19, which constitute the water treatment system 15, to the point of use 20. send. Further, the flow path 17 has a return flow path (third return flow path) 17 a for returning the water to be treated that has passed through the point of use 20 to the tank 16 . That is, the surplus ultrapure water that has passed through the point of use 20 is collected in the tank 16 through the return channel 17 a of the channel 17 .

More specifically, as shown in FIG. 2, the secondary pure water production unit 18 includes a circle pump 22, a heat exchanger (HEX: Heat Exchanger) 23, an ultraviolet oxidation device (TOC-UV) 24, and a membrane deaerator. A device (MDG: membrane degasifier) 25 , a polisher 26 and an ultrafiltration membrane (UF: Ultrafiltration Membrane) device 28 are provided.

The circle pump 22 is a to-be-treated water supply pump that supplies the to-be-treated water (primary pure water) contained in the tank 16 to the heat exchanger 23 . The heat exchanger 23 adjusts the temperature of the water to be treated supplied from the circle pump 22 . At this time, the temperature of the water to be treated is preferably adjusted to, for example, 25±3° C. by the heat exchanger 23 .

The ultraviolet oxidation device 24 irradiates the water to be treated (primary pure water) temperature-controlled by the heat exchanger 23 with ultraviolet rays to decompose and remove trace organic substances in the water to be treated. The ultraviolet oxidation device 24 has, for example, an ultraviolet lamp, and generates ultraviolet rays having a wavelength of about 185 nm. The ultraviolet oxidation device 24 may generate ultraviolet rays having a wavelength of about 254 nm. When the water to be treated is irradiated with ultraviolet rays in such an ultraviolet oxidation device 24, the ultraviolet rays decompose the water to generate OH radicals, and the OH radicals oxidize and decompose organic matter in the water to be treated.

The membrane degassing device 25 is a device that decompresses the secondary side of a gas-permeable membrane and allows only the dissolved gas in the water to be treated flowing through the primary side to permeate the secondary side and remove it. The polisher 26 has a mixed-bed type ion exchange resin in which a cation exchange resin and an anion exchange resin are mixed, and is a non-regenerating non-regenerating resin that adsorbs and removes trace amounts of cation and anion components in the water to be treated. It is a mixed-bed ion exchange apparatus of the type.

The ultrafiltration membrane device 28 is provided at a position sandwiching the concentration measuring device 19 between the most downstream point of use 20 on the channel 17 and the ultrafiltration membrane device 28 . The ultrafiltration membrane device 28 has a plurality of hollow fiber modules, and the water flow rate per hollow fiber module is 10 m ³ /h or more. This ultrafiltration membrane device 28 further treats the water to be treated by the polisher 26 (or the microfiltration membrane device 27 when attached) to remove fine particles with a particle diameter of 50 nm or more, for example, and ultrapure water (two (pure water) is obtained.

Here, ultrapure water (ultrapure water that satisfies the desired water quality conditions) within the manufacturing specifications of the ultrapure water production apparatus 10 of the present embodiment has a particle size of 50 nm or more and the number of particles is 200/L or less. and a total organic carbon concentration of 1 μgC/L or less, and a resistivity of 18 MΩ·cm or more.
In FIG. 2, the concentration measuring device 19 is installed immediately after the ultrafiltration membrane device 28, and by installing it in this way, for example, the concentration of silica in the ultrapure water to be produced can be accurately measured to low concentrations. It is possible to In addition, when the concentration measuring device 19 is installed in series between each device of the secondary pure water production section or via a predetermined connection mechanism, malfunction of each device (for example, silica leak from the polisher) etc. It is also possible to detect When the concentration measuring device 19 is installed in series between the POU 20 and the tank 16 or through a predetermined connection mechanism, it is possible to confirm that contamination has occurred due to some malfunction of the POU, for example.

Next, the configuration of the concentration measuring device 19 of this embodiment will be described in detail with reference to FIGS. 1 to 3. FIG. As shown in FIGS. 1 and 2, the concentration measuring device 19 includes a concentrator 19a, a detector 19b and a calculator 19c. At least the concentrator 19a that constitutes the concentration measuring device 19 is connected between the secondary pure water production section 18 (ultrafiltration membrane device 28) and the point of use 20 via a predetermined connection mechanism. Here, the concentrator 19a of the concentration measuring device 19 is connected to the inside of the secondary pure water production unit 18 or the third return flow path 17a via a predetermined connection mechanism instead of the installation position described above. may have been In addition, the concentrator 19a of the concentration measurement device 19 is located between the secondary pure water production unit 18 and the point of use 20, inside the secondary pure water production unit 18, or on the flow path of the third return flow path 17a. may be connected in series. Furthermore, instead of this, the concentrator 19a of the concentration measuring device 19 may be provided on the flow path 17 of the ultrapure water production device 10 shown in FIG. Here, the predetermined connection mechanism described above is the return flow path 17a (or the main flow path 17 in the secondary pure water production section 18, or the connection between the secondary pure water production section 18 and the point of use 20). , and the concentrator 19a is connected to the main body of the ultrapure water production apparatus 10 via the connection mechanism including the branched flow path. be. Also, the concentration measuring device 19 may be detachably attached to a predetermined position of the flow path 17 of the ultrapure water production device 10 .

In addition, as shown in FIG. 3, the concentrator 19a of the present embodiment includes a water supply channel 35, a reverse osmosis membrane device (first reverse osmosis membrane device: RO-1) 31, a reverse osmosis membrane device (second Reverse osmosis membrane device: RO-2) 32, return channel (first return channel) 36, return channel (second return channel) 37, branch channel (first branch channel) 38, A branch channel (second branch channel) 39 and a flow rate adjustment mechanism 21 are provided.

As shown in FIG. 3, the water supply channel 35 is a channel through which the water to be treated is sent, and is connected in series with the channel 17 shown in FIGS. The reverse osmosis membrane device 31 has a water inlet 31a, a permeate outlet 31b, and a concentrated water outlet 31c, and is provided on a water supply channel . Moreover, the reverse osmosis membrane device 31 is equipped with a reverse osmosis membrane, and separates the water to be treated introduced from the water to be treated inlet 31a into permeated water and concentrated water by the reverse osmosis membrane. More specifically, the water to be treated inlet 31 a introduces the water to be treated from the upstream side of the reverse osmosis membrane device 31 on the water supply channel 35 . On the other hand, the permeated water outlet 31 b discharges the permeated water from the downstream side of the reverse osmosis membrane device 31 on the water supply channel 35 . Also, the concentrated water outlet 31 c discharges the concentrated water to the return flow path 36 . Here, the concentrator 19a of this embodiment can be used in both constant water supply operation and intermittent operation. However, in the case of intermittent operation, it is preferable to perform flushing (washing treatment) for several days after starting water supply before use.

On the other hand, the reverse osmosis membrane device 32 has a water inlet 32a, a permeate outlet 32b, and a concentrated water outlet 32c. The reverse osmosis membrane device 32 is provided downstream of the reverse osmosis membrane device 31 on the water supply channel 35 . The reverse osmosis membrane device 32 has a reverse osmosis membrane like the reverse osmosis membrane device 31, and the water to be treated introduced from the water to be treated inlet 32a is divided into permeated water and concentrated water by the reverse osmosis membrane. To separate. More specifically, the water inlet 32 a introduces the water to be treated (permeated water of the reverse osmosis membrane device 31 ) from the upstream side of the reverse osmosis membrane device 32 on the water supply channel 35 . Also, the permeated water outlet 32 b discharges the permeated water from the downstream side of the reverse osmosis membrane device 32 on the water supply channel 35 . It should be noted that this permeated water may be returned to the tank 16 shown in FIGS. Further, it is also possible to return this permeated water to the same channel as the channel from which the water to be treated is branched from the secondary pure water production unit 18 by a predetermined connecting mechanism. By using these methods, it is possible to avoid wasting the wastewater, which has a quality almost equal to that of the water in the secondary pure water producing section 18 . Furthermore, the concentrated water outlet 32 c discharges the concentrated water to the return flow path 37 .

The return channel 36 extends from the concentrated water outlet 31 c of the reverse osmosis membrane device 31 and returns to the upstream side of the reverse osmosis membrane device 31 on the water supply channel 35 . The return channel 37 extends from the concentrated water outlet 32 c of the reverse osmosis membrane device 32 and returns to the upstream side of the reverse osmosis membrane device 31 on the water supply channel 35 . The branch flow path 38 branches off from the return flow path 36 and discharges water to the outside of the ultrapure water production apparatus 10 (concentrator 19a). The branch channel 39 branches off from the return channel 37 and merges between the reverse osmosis membrane devices 31 and 32 on the water supply channel 35 .

The flow rate adjusting mechanism 21 adjusts the flow rates of the water supply channel 35 , return channels 36 and 37 , and branch channels 38 and 39 . More specifically, the flow rate adjustment mechanism 21 has pumps 33 and 34, valves 41 to 49, and a control section 21a. The control unit 21a controls the operations of the valves 41-49 and the pumps 33,34. Also, the pump 33 is provided on the upstream side of the reverse osmosis membrane device 31 on the water supply channel 35 . On the other hand, the pump 34 is provided downstream of the reverse osmosis membrane device 31 and upstream of the reverse osmosis membrane device 32 on the water supply channel 35 .

The valve 41 is provided upstream of each return point of the return flow paths 36 and 37 on the water flow path 35 (the confluence point of the water flow path 35 and the return flow paths 36 and 37). The pump 33 described above is installed at a position sandwiching each of the return points of the return flow paths 36 and 37 between the valve 41 and the valve 41 . Also, the valve 42 is installed at a position sandwiched between the pump 33 and the reverse osmosis membrane device 31 on the water supply channel 35 .

Furthermore, the above-described pump 34 is installed at a position sandwiching the junction of the branched flow path 39 with the water supply flow path 35 with the reverse osmosis membrane device 31 . The valve 43 is installed at a position sandwiched between the pump 34 and the reverse osmosis membrane device 32 on the water supply channel 35 . Also, the valves 46 and 48 are provided on the return flow path 36 , while the valves 45 and 47 are provided on the return flow path 37 . Further, a valve 49 is provided on the branch flow path 38 and a valve 44 is provided on the branch flow path 39 .

The valves 41 to 49 described above are composed of electromagnetic valves, for example, and adjust the water flow rate by changing the degree of opening based on the control signal generated by the control section 21a. Further, the pumps 33 and 34 change their operating amounts based on the control signal generated by the control section 21a to adjust the amount of water supplied to the downstream side of the pumps 33 and 34. As a result, the control unit 21 a and the flow rate adjusting mechanism 21 having the valves and pumps described above adjust the flow rate of the water supply channel 35 , the return channels 36 and 37 and the branch channels 38 and 39 .

Further, as shown in FIGS. 2 and 3, the detection unit 19b constituting the concentration measuring device 19 detects a predetermined weak electrolysis contained in the concentrated water flowing through the branch flow path 38 (point D8 on the downstream side of the valve 49). Detects the concentration of qualitative components. Based on the flow rate adjusted by the flow rate adjustment mechanism 21 and the concentration detected by the detection section 19b, the calculation section 19c is arranged upstream of each return point of the return flow paths 36 and 37 on the water supply flow path 35 (valve 41 and the respective return points, the concentration of a predetermined weak electrolyte component contained in the water to be treated at point D1) is calculated.

In other words, the calculation unit 19c calculates backward from the concentration rate (concentration ratio) of the water to be treated by the reverse osmosis membrane devices 31 and 32 to obtain the actual concentration of the weak electrolyte component. Here, the predetermined weak electrolyte component is silica (silicon dioxide: SiO ₂ ), for example. Therefore, the detection unit 19b and the calculation unit 19c described above are configured by, for example, a silica meter.
As the reverse osmosis membrane module incorporated in the reverse osmosis membrane device used in this concentrator, any of those composed of an ultra-low pressure membrane, a low pressure membrane, a medium pressure membrane, and a high pressure membrane can be used.
As the reverse osmosis membrane module, a commercially available module can be used. For example, ES-20 manufactured by Nitto Denko Co., Ltd. can be used.
Since this concentrator only needs to obtain a small flow rate of concentrated water for analysis, the reverse osmosis membrane module is preferably a module with a small membrane area, such as a 4-inch module or a small laboratory module.
Since this concentrator only needs to obtain concentrated water for analysis, it is preferable that the concentrated water flow rate is about 1 to 10 L/min.
A cooler can be provided in the branch flow path 39 and the return flow paths 36 and 37 as required. By providing a cooler, it is possible to prevent the water temperature from rising due to water circulation, and to suppress the decrease in the silica removal rate in the reverse osmosis membrane apparatus due to the water temperature rising. The water temperature is preferably kept at 20-25°C.
In order to suppress the adverse effect of concentration polarization, it is necessary to flow concentrated water at a minimum amount of concentrated water or more according to the specifications of the reverse osmosis membrane device, but it is preferable to maintain a flow rate of 1.5 times or more than the minimum amount of concentrated water. .
When the above-described concentrator is installed inside the secondary pure water production section, the flow rate of the water to be treated flowing into the concentrator increases, so the concentrator must be appropriately scaled up accordingly. be.

Next, mainly based on FIG. 3, a more specific configuration and operational effects of the concentration measuring device 19 of the present embodiment will be exemplified (examples will be described). The water recovery rate of the reverse osmosis membrane device 31 in the concentration measuring device 19 (concentrator 19a) of the present embodiment is configured to be higher than the water recovery rate of the reverse osmosis membrane device 32 . More specifically, the water recovery rate of the reverse osmosis membrane device 31 is preferably in the range of 80-99.99%, more preferably in the range of 98-99.9%. On the other hand, the water recovery rate of the reverse osmosis membrane device 32 is preferably in the range of 10-80%, more preferably in the range of 40-60%. In this embodiment (example), the water recovery rate of the reverse osmosis membrane device (RO-1) 31 is 99.5%, while the water recovery rate of the reverse osmosis membrane device (RO-2) 32 is 48.5%. An example of 5% will be described. Here, the reverse osmosis membrane device 31 is applied with an ultra-low pressure 2-inch RO (ES 20-D2: Nitto Denko), while the reverse osmosis membrane device 32 is a seawater desalination membrane 2-inch RO (RE 2521- SHN: LENNTECH) has been applied.

Below, as shown in FIG. 3, measured values of the flow rate and silica concentration at points D1, D4 to D8 in the concentrator 19a will be exemplified. Note that, for points D2 and D3, predicted values of silica concentration are exemplified. First, the flow rate at point D1 is 0.707 L/min, and the concentration of silica at point D1 is 4.1 ppb. It should be noted that the optimum flow rate of water supply at point D1 is on the order of 1 to 10 L/min. Also, the concentration of silica at point D2 is 3 ppb, and the concentration of silica at point D3 is 6 ppb.

The flow rate at point D4 is 0.7 L/min, the concentration of silica at point D4 is 0.08 ppb, and the flow rate (measured value) at point D5 is 4.7 L/min. Furthermore, the flow rate at point D6 is 0.65 L/min and the flow rate at point D7 is 3.5 L/min. Also, the flow rate at point D8 is 0.007 L/min, and the concentration of silica at point D8 is 410 ppb.

Here, the theoretical value A of the concentrated water at the time of 100% silica recovery (theoretical concentration of silica at point D8) is B for the concentration of silica at point D1, C for the flow rate at point D1, and E for the flow rate at point D8. Then, it is given by the following equation 1.
A=B×(C÷E) Equation 1
That is, 414.1 [ppb]=4.1×101 [101 times the flow ratio].

On the other hand, the actual recovery rate F of silica is given by the following equation 2, where G is the concentration of silica at point D8.
F=(G÷A)×100 Formula 2
That is, 99[%]≈(410÷414.1)×100[%].

As can be seen from this result, the flow rate of each channel is appropriately set via the flow rate adjusting mechanism 21 of the concentrator 19a. That is, since the reverse osmosis membrane device 31 is intended for concentration, the water recovery rate is set to be high. is set to low. More specifically, in order to suppress concentration polarization that may occur in the reverse osmosis membrane devices 31 and 32, the concentrator 19a has a return flow path for returning the concentrated water of the water to be treated to the preceding stage (immediately) of the reverse osmosis membrane devices 31 and 32. 36 and a branch flow path 39 are provided to maintain a flow rate of 1.5 times or more the minimum concentrated water amount in the specifications of the reverse osmosis membrane device. On the other hand, in order to improve the recovery rate of silica (to recover the silica leaked from the reverse osmosis membrane device 31), the return flow path 37 returns the concentrated water of the reverse osmosis membrane device 32 to the front stage of the reverse osmosis membrane device 31. is provided. The concentration measuring device 19 including the concentrator 19a has such a configuration, so that the flow rate ratio at the points D1 and D8 and the concentration of silica at the point D8 (actually, the point D8 calculated by the calculation unit 19c (silica concentration of )), it is possible to measure the concentration of silica at point D1 with high accuracy.

Next, the concentrators 80 and 90 of Comparative Examples 1 and 2 will be described with reference to FIGS. 4 and 5. FIG. As shown in FIG. 4, the concentrator 80 of Comparative Example 1 includes a reverse osmosis membrane device 81 having a water inlet 81a, a permeate outlet 81b, and a concentrated water outlet 81c, a water supply channel 82, and a concentrated water channel 83. I have. Measured values of flow rate and silica concentration at points D11-D13 in the concentrator 80 are illustrated. First, the flow rate at point D11 is 0.765 L/min, and the concentration of silica at point D11 is 0.13 ppb. Also, the flow rate at point D12 is 0.75 L/min, and the concentration of silica at point D12 is 0.11 ppb. Furthermore, the flow rate at point D13 is 0.015 L/min and the concentration of silica at point D13 is 0.71 ppb.

Here, the theoretical value H of the concentrated water at the time of 100% silica recovery (theoretical concentration of silica at point D13) is J for the concentration of silica at point D11, K for the flow rate at point D11, and M for the flow rate at point D13. Then, it is given by the following equation 3.
H=J×(K÷M) Equation 3
That is, 6.63 [ppb]=0.13×51 [51 times the flow ratio].

On the other hand, the actual silica recovery rate N is given by the following equation 4, where P is the concentration of silica at point D13.
N=(P÷H)×100 Equation 4
That is, 10.7[%]≈0.71÷6.63×100.

From this result, it can be seen that the concentrator 80 of Comparative Example 1, which does not have a return channel and has a single reverse osmosis membrane device 81, has a very low recovery rate of silica.

On the other hand, as shown in FIG. 5, the concentrator 90 of Comparative Example 2 includes a reverse osmosis membrane device 91 having a water to be treated inlet 91a, a permeated water outlet 91b and a concentrated water outlet 91c, a pump 92, valves 96 and 97, a feed A water channel 93 , a return channel 94 and a branch channel 95 are provided. Measured values of flow rate and silica concentration at points D21, D23-D25 in concentrator 90 are illustrated. Note that, for point D22, an expected value of the concentration of silica is exemplified. First, the flow rate at point D21 is 1.009 L/min and the concentration of silica at point D21 is 3 ppb. Also, the concentration of silica at point D22 is 90.9 ppb. Furthermore, the flow rate at point D23 is 0.99 L/min and the concentration of silica at point D23 is 0.99 ppb. Also, the flow rate at point D24 is 2.66 L/min. Furthermore, the flow rate at point D25 is 0.019 L/min and the concentration of silica at point D25 is 110 ppb.

Here, the theoretical value Q of the concentrated water at the time of 100% silica recovery (theoretical concentration of silica at point D25) is R for the concentration of silica at point D21, S for the flow rate at point D21, and T for the flow rate at point D25. Then, it is given by the following equation 5.
Q=R×(S÷T) Equation 5
That is, 159 [ppb]=3×53 [about 53 times the flow rate ratio].

On the other hand, the actual recovery rate U of silica is given by the following equation 6, where V is the concentration of silica at point D25.
U=(V÷Q)×100 Equation 6
That is, 69[%]≈(110÷159)×100[%].

In the concentrator 90 of Comparative Example 2, since the return flow path 94 is provided to return the concentrated water, the silica concentration is increased in the upstream stage of the reverse osmosis membrane device 91 . Although the water recovery rate of the reverse osmosis membrane device 91 is about 98%, the silica recovery rate is about 70%, which is not sufficient.

On the other hand, the concentrator 19a of the present embodiment (example) described above includes the first and second reverse osmosis membrane devices 31 and 32, and the concentrated water outlets 31c and 32c to the water feed channel 35. In addition, the water recovery rate of each reverse osmosis membrane device 31, 32 is appropriately set through the flow rate adjusting mechanism 21. Therefore, according to the concentration measuring device 19 including the concentrator 19a and the ultrapure water producing device 10 of the present embodiment, the recovery rate of weak electrolyte components such as silica contained as impurities in the water to be treated is increased, and A high concentration ratio can be obtained.

Although the present invention has been specifically described with reference to the embodiments, the present invention is not limited to the embodiments as they are, and various changes can be made in the implementation stage without departing from the scope of the invention. For example, some constituent elements may be deleted from all the constituent elements shown in the embodiments, and it is also possible to appropriately combine a plurality of constituent elements disclosed in the above embodiments.

For example, instead of the concentrator 19a shown in FIG. 3, a concentrator 50 can be configured as shown in FIG. In addition, in FIG. 6, illustration of some valves is omitted. As shown in FIG. 6, the concentrator 50 includes, in addition to the configuration of the concentrator 19a, a return channel 51, a branch channel 54, a pump 57, valves 52, 55, 56, and a reverse osmosis membrane device (RO-3) 53. It has The reverse osmosis membrane device 53 has a reverse osmosis membrane, and separates the water to be treated introduced from the upstream side into permeated water and concentrated water by the reverse osmosis membrane.

The return channel 51 extends from the concentrated water outlet of the reverse osmosis membrane device 53 and returns to the upstream side of the reverse osmosis membrane device 31 on the water supply channel 35 . The branch channel 54 branches off from the return channel 51 and merges between the reverse osmosis membrane device 32 and the reverse osmosis membrane device 53 on the water supply channel 35 . The branch channel 54 may branch from the return channel 51 and join between the reverse osmosis membrane devices 31 and 32 on the water supply channel 35 . In addition, the water recovery rate of the reverse osmosis membrane device 53 is configured to be lower than the water recovery rate of the reverse osmosis membrane device 31 , like the reverse osmosis membrane device 32 . Therefore, even in the concentrator 50 in which the three-stage reverse osmosis membrane devices 31, 32, and 53 are installed in series, the recovery rate of weak electrolyte components such as silica contained as impurities in the water to be treated is increased, and the recovery rate is high. Concentration factor can be obtained. It is also possible to configure a concentrator in which four or more stages of reverse osmosis membrane devices are installed in series.

DESCRIPTION OF SYMBOLS 10... Ultrapure water production apparatus, 14... Primary pure water production part, 16... Tank, 17... Flow path, 18... Secondary pure water production part, 19... Concentration measuring device, 19a... Concentrator, 19b... Detection part, 19c... Arithmetic unit, 20... Point of use (POU), 21... Flow rate adjustment mechanism, 21a... Control unit, 31... Reverse osmosis membrane device (first reverse osmosis membrane device), 32... Reverse osmosis membrane device (second reverse osmosis membrane device), 33, 34... pump, 35... water supply channel, 36... return channel (first return channel), 37... return channel (second return channel), 38... branch flow path (first branched flow path), 39 branched flow path (second branched flow path), 41 to 49 valves.

Claims (9)

a water supply channel through which the water to be treated is supplied;
a first reverse osmosis membrane device provided on the water supply channel;
a second reverse osmosis membrane device provided downstream of the first reverse osmosis membrane device on the water supply channel;
a first return channel extending from a concentrated water outlet in the first reverse osmosis membrane device and returning to the upstream side of the first reverse osmosis membrane device on the water supply channel;
a second return channel extending from a concentrated water outlet of the second reverse osmosis membrane device and returning to the upstream side of the first reverse osmosis membrane device on the water supply channel;
a first branch channel that branches from the first return channel and drains water;
a second branch flow path branching from the second return flow path and joining between the first reverse osmosis membrane device and the second reverse osmosis membrane device on the water supply flow path;
a flow rate adjustment mechanism that adjusts flow rates of the water supply channel, the first and second return channels, and the first and second branch channels;
a concentrator comprising
a detection unit that detects the concentration of a predetermined weak electrolyte component contained in the concentrated water flowing through the first branch flow path;
Based on the flow rate adjusted by the flow rate adjustment mechanism and the detected concentration, a predetermined A calculation unit that calculates the concentration of the weak electrolyte component of
A concentration measuring device comprising a The flow rate adjustment mechanism is
a plurality of valves provided in the water supply channel, the first and second return channels, and the first and second branch channels;
a pump provided on the water supply channel;
a control unit that controls operations of the plurality of valves and the pump;
The concentration measuring device according to claim 1, comprising: The water recovery rate of the first reverse osmosis membrane device is greater than the water recovery rate of the second reverse osmosis membrane device,
The concentration measuring device according to claim 1 or 2. the predetermined weak electrolyte component is silica;
The concentration measuring device according to any one of claims 1 to 3 . a concentration measuring device according to any one of claims 1 to 4 ;
a primary pure water production section for producing primary pure water by subjecting the water to be treated to water treatment;
a secondary pure water production unit provided downstream of the primary pure water production unit for further treating the produced primary pure water to produce secondary pure water;
a tank interposed between the primary pure water production unit and the secondary pure water production unit;
a third return flow path for returning the water to be treated that has passed through a point of use provided downstream of the secondary pure water production section to the tank;
with
At least the concentrator, which constitutes the concentration measuring device, is arranged between the secondary pure water production unit and the point of use, inside the secondary pure water production unit, or through the third return flow path. An ultrapure water production device connected on the road in series or via a predetermined connection mechanism. a water supply channel through which the water to be treated is supplied;
a first reverse osmosis membrane device provided on the water supply channel;
a second reverse osmosis membrane device provided downstream of the first reverse osmosis membrane device on the water supply channel;
a first return channel extending from a concentrated water outlet in the first reverse osmosis membrane device and returning to the upstream side of the first reverse osmosis membrane device on the water supply channel;
a second return channel extending from a concentrated water outlet of the second reverse osmosis membrane device and returning to the upstream side of the first reverse osmosis membrane device on the water supply channel;
a first branch channel that branches from the first return channel and drains water;
a second branch flow path branching from the second return flow path and joining between the first reverse osmosis membrane device and the second reverse osmosis membrane device on the water supply flow path;
a flow rate adjustment mechanism that adjusts flow rates of the water supply channel, the first and second return channels, and the first and second branch channels;
A water treatment method using a concentrator comprising
detecting the concentration of a predetermined weak electrolyte component contained in the concentrated water flowing through the first branch channel;
Based on the flow rate adjusted by the flow rate adjustment mechanism and the detected concentration, a predetermined A water treatment method for calculating the concentration of weak electrolyte components in The flow rate adjustment mechanism is
a plurality of valves provided in the water supply channel, the first and second return channels, and the first and second branch channels;
a pump provided on the water supply channel;
a control unit that controls operations of the plurality of valves and the pump;
The water treatment method according to claim 6, having The water recovery rate of the first reverse osmosis membrane device is greater than the water recovery rate of the second reverse osmosis membrane device,
The water treatment method according to claim 6 or 7. the predetermined weak electrolyte component is silica;
The water treatment method according to any one of claims 6 to 8.

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