Control method for ultra pure water production apparatus

Abstract

To provide a control method for a pure water production apparatus that adjusts the operating power of the feed pump according to the water usage in downstream systems or at the usage point, thereby enabling control of the feed water volume.SOLUTION: With the circulating water flow fixed at 20 m cubed / h, the design maximum discharge capacity of feed pumps 32A, 32B, and 32C is 60 m cubed / h, and the primary pure water W2 consumption in the subsystem is 80 m cubed / h, the number of pumps in operation must be 1.67≤2 (units). Therefore, two water supply pumps, pumps 32A and 32B, are operated. At this time, the output of water supply pumps 32A and 32B is controlled via inverter to 83% capacity to produce 100 m cubed / h of primary pure water W2. Then, a control valve 55 sends 80 m cubed / h to a sub-tank 37 and sends the surplus 20 m cubed / h to a circulation path 54, which connects to a treated water tank 31.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for controlling a pure water production apparatus suitable for producing ultrapure water used in the electronics industry, such as semiconductors and liquid crystal displays, and more particularly to a method for controlling a pure water production apparatus capable of controlling the amount of water supplied in accordance with the amount of water used in downstream systems or at use points. [Background technology]

[0002] Conventionally, ultrapure water used in the electronics industry, such as semiconductors, is produced by an ultrapure water production system such as the one shown in Fig. 6. In Fig. 6, the ultrapure water production system 1 is composed of three stages of equipment: a pretreatment device 2, a primary pure water production system (pure water production system) 3, and a secondary pure water production system (subsystem) 4.

[0003] The pretreatment device 2 comprises a coagulation treatment device 21 and a turbidity removal UF membrane device 22. In this pretreatment device 2, the raw water W is subjected to pretreatment such as coagulation sedimentation and membrane filtration, and mainly suspended solids are removed.

[0004] The primary pure water system 3 includes a water tank 31 for storing pretreated water (water to be treated) W1, a water pump 32 for transporting the pretreated water W1, a reverse osmosis membrane device 33, a membrane degassing device 34, an ultraviolet oxidation device 35, and an electrodeionization device 36. In the primary pure water system 3, the reverse osmosis membrane device 33 removes fine particles and ions from the pretreated water W1, the membrane degassing device 34 reduces dissolved oxygen, and the ultraviolet oxidation device 35 decomposes organic matter (TOC components). Subsequently, the electrodeionization device 36 removes metal ions, carbonate ions, organic acids, and the like to produce primary pure water (pure water) W2. The produced primary pure water W2 is stored in a sub-tank 37 for supply to the subsystem 4.

[0005] The subsystem (secondary pure water system) 4, which handles the final step in ultrapure water production, consists of a pump 41 that delivers primary pure water W2 from a subtank 37, an ultraviolet oxidation device 42 that processes the primary pure water W2, a membrane degassing device 43, a non-regenerative mixed-bed ion exchanger 44, and an ultrafiltration (UF) membrane 45 as a membrane filtration device. An RO membrane separator or other device may also be installed as needed. In this subsystem 4, the ultraviolet oxidation device 42 oxidizes and degasses trace amounts of organic matter (TOC components) contained in the primary pure water W2. The non-regenerative mixed-bed ion exchanger 44 then processes the water to remove residual carbonate ions, organic acids, anionic substances, and even metal ions and cationic substances by ion exchange. The ultrafiltration (UF) membrane 45 then removes particulates, producing ultrapure water W3, which is then supplied to the point of use 5.

[0006] The primary pure water production system 3 in the above-described ultrapure water production system 1 generally has multiple lines of water pumps 32A, 32B, and 32C (three lines in FIG. 7) as shown in FIG. 7. The primary pure water system downstream of these pumps is a water treatment system 30 consisting of a reverse osmosis membrane device, a membrane degassing device, an ultraviolet oxidation device, and an electrodeionization device in the primary pure water system 3 shown in FIG. 6. Reference numeral 51 denotes a chemical feeder for pH adjusters and the like for the water to be treated by the reverse osmosis membrane. A water supply line 52 connected to the water treatment system 30 branches into a supply line 53 communicating with a sub-tank 37 and a circulation line 54 communicating with the tank 31 for treated water. A control valve 55 is provided at this branch point as a flow rate regulator.

[0007] In order to stably supply primary pure water W2 to subsystem 4, water pumps 32A, 32B, and 32C are driven at their maximum designed discharge rates to produce an excess amount of primary pure water W2, and the amount required by subsystem 4 is supplied to sub-tank 37 from supply line 53, and the excess is returned to the treated water tank 31 via circulation line 54 by control valve 55 for circulation.

[0008] As shown in Figure 7, the amount of primary pure water W2 used (required) in subsystem 4 is 140 m 3 / h, the maximum designed discharge capacity of water pumps 32A, 32B, and 32C is 60m 3 / h, the water pumps 32A, 32B, and 32C are operated at their maximum designed discharge rate of 180m 3 / h of primary pure water W2 is produced. Then, 140 m 3 / h is sent to sub-tank 37, and the surplus 40m 3 / h was sent to the circulation line 54 communicating with the tank 31 for treated water, and the amount of the returned primary pure water W2 was increased or decreased depending on the amount of primary pure water W2 used in the subsystem 4. Summary of the Invention [Problem to be solved by the invention]

[0009] However, in the control method of the conventional ultrapure water production system as described above, the water pumps 32A, 32B, and 32C are operated at their maximum designed discharge rates. For example, as shown in FIG. 8, when the amount of primary pure water W2 used in the subsystem 4 is 100 m 3 / h, the rate drops to 80m 3 / h of water is returned from the circulation path 54. In other words, more primary pure water W2 than necessary is produced. This causes a problem in that the water pumps 32A, 32B, and 32C, the ultraviolet oxidation device, the electrodeionization device, and other devices are operating excessively, leaving significant room for energy reduction. In particular, since the power consumption of pumps accounts for approximately 60% of the power consumption in the ultrapure water production system 1, reducing the power consumption of the water pumps 32A, 32B, and 32C would make a significant contribution to energy conservation.

[0010] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a control method for a pure water production apparatus that can control the amount of water supplied by adjusting the operating power of a water supply pump according to the amount of water used in downstream systems or use points. [Means for solving the problem]

[0011] In view of the above object, the present invention provides a control method for a pure water production system comprising a storage tank for water to be treated, three or more water supply pumps for supplying the water to be treated stored in the storage tank, and one or more water treatment devices provided downstream of the water supply pumps, a water supply channel for supplying the pure water produced by the water treatment devices to a downstream system or use point, and a circulation channel for returning excess pure water branched off from the water supply channel to the storage tank, wherein the control method controls the number of operating water supply pumps and / or the output of the water supply pumps according to the amount of pure water required by the downstream system or use point (Invention 1).

[0012] According to this invention (Invention 1), the number of operating water pumps is controlled according to the increase or decrease in the amount of pure water required by the downstream system or use point, and the output of the water pumps is controlled as needed based on this number of operating pumps. This prevents excess pure water from being returned from the circulation path to the storage tank, and reduces excessive pump energy consumption.

[0013] In the above invention (Invention 1), it is preferable to control the number of operating water pumps and / or the output of the water pumps so that the amount of water circulated through the circulation path is 20% or less of the total designed maximum discharge volume of the water pumps (Invention 2).

[0014] According to this invention (Invention 2), it is possible to suppress the production of excessive pure water, and to efficiently reduce the energy consumption of the pure water production device and pump.

[0015] In the above invention (invention 2), it is preferable that the output of the water pump is controlled to 60 to 100% of the designed maximum discharge rate of the water pump (invention 3).

[0016] According to this invention (Invention 3), the amount of water to be fed can be adjusted in response to a wide range of fluctuations in the flow rate of pure water fed to a downstream system or use point.

[0017] In the above invention (Invention 3), it is preferable to control the number of operating pumps so that the value obtained by dividing the amount of pure water delivered by the maximum designed discharge rate of each pump is rounded up to a natural number (Invention 4).

[0018] According to this invention (Invention 4), the amount of water to be fed can be adjusted appropriately in response to fluctuations in the flow rate of pure water fed to a downstream system or a use point.

[0019] In the above inventions (Inventions 1 to 4), it is preferable to provide a chemical injection device in the water supply path for the pure water produced by the primary pure water system, and to adjust the amount of chemicals added from the chemical injection device depending on the amount of pure water supplied by the primary pure water system (Invention 5).

[0020] According to this invention (Invention 5), the amount of pure water produced by the water treatment device is reduced, which leads to a reduction in the amount of chemicals added, thereby enabling cost reduction.

[0021] In the above inventions (Inventions 1 to 4), it is preferable to supply the pure water produced in the primary water purification system to a downstream system, and to perform adjustment operation of the downstream system depending on the amount of water supplied to the downstream system (Invention 6).

[0022] According to this invention (Invention 6), the amount of pure water produced in the water treatment device is reduced, thereby enabling energy savings in the operation of the water treatment device. [Effects of the Invention]

[0023] According to the present invention, a pure water device has three or more series of water supply pumps, and supplies the produced pure water to a downstream system or use point, while returning excess pure water to a storage tank.The number of operating water supply pumps and / or the output of the water supply pumps are controlled according to the amount of pure water required by the downstream system or use point.This prevents excess pure water from being returned from the circulation path to the storage tank, and reduces excessive pump energy consumption. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a flow diagram showing a pure water production system to which a control method for a pure water production system according to a first embodiment of the present invention can be applied. [Figure 2] FIG. 10 is a flowchart showing a control method for a pure water manufacturing system according to a second embodiment of the present invention. [Figure 3] FIG. 4 is a flowchart showing a control method for the pure water manufacturing apparatus according to the second embodiment. [Figure 4] FIG. 10 is a flowchart showing a control method for the pure water manufacturing apparatus according to the third embodiment. [Figure 5] FIG. 10 is a flowchart showing a control method for the pure water manufacturing apparatus according to the third embodiment. [Figure 6] 1 is a flow diagram showing an ultrapure water production system to which the method for controlling a pure water production system of the present invention can be applied. [Figure 7] FIG. 1 is a flow chart showing a conventional method for controlling a pure water manufacturing apparatus. [Figure 8] FIG. 1 is a flow chart showing a conventional method for controlling a pure water manufacturing apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0025] A method for controlling a pure water producing apparatus according to the present invention will now be described with reference to the accompanying drawings.

[0026] First Embodiment (Pure water production equipment) 333 FIG. 1 shows a schematic diagram of a pure water system to which the method for controlling a pure water production system of the present invention can be applied. The basic configuration is the same as that shown in FIG. 7, and the same components are designated by the same reference numerals. In FIG. 1, the primary pure water system 3 includes a tank 31 for storing pretreated water (water to be treated) W1 and multiple series (n series: n is a positive integer) of water pumps 32A to 32n connected by header pipes. Each of the water pumps 32A to 32n is equipped with an inverter as an output control means. The downstream side of the water pump 32A is a water treatment device 30, which includes a reverse osmosis membrane device, a membrane degasser, an ultraviolet oxidation device, and an electrodeionization device. The water treatment device 30 is equipped with a chemical feeder 51, such as a pH adjuster, for adjusting the pH of the water to be treated by the reverse osmosis membrane. A water supply line 52 is also connected to the water treatment device 30. This water supply line 52 branches into a supply line 53 that communicates with the sub-tank 37 and a circulation line 54 that communicates with the tank for treated water 31, and this branching point is provided with a control valve 55 as a flow rate adjustment unit. Furthermore, a flow meter 56 is provided in the circulation line 54, and a flow meter 57 is also provided in the water supply line 52.

[0027] These flow meters 56 and 57 are capable of communicating information to a control means (not shown), which is capable of inverter-controlling the operation and stop of the water pumps 32A to 32n and the output of the water pumps 32A to 32n within a range of 60 to 100% of the maximum designed discharge volume of the water pumps based on the measured values ​​of the flow meters 56 and 57, and is also capable of controlling the control valve 55 so that the circulating water volume and the amount of water used are set to the specified volume.

[0028] (Method for controlling a pure water production device) In the pure water production system as described above, the water supply rates of the water pumps 32A to 32n, the amount of primary pure water used, and the amount of circulating water are expressed by the following formula (1). Water supply amount (m 3 / h)=Water usage x(m 3 / h)+circulated water amount y(m 3 / h) =x+y(m3 / h) ···(1)

[0029] Here, the circulating water volume y(m 3 / h) is preferably set to be 20% or less of the sum of the designed maximum discharge rates of the water pumps 32A to 32n, and this circulating water rate may be a fixed value or a variable value. Here, the sum of the designed maximum discharge rates is the designed maximum discharge rate (m 3 / h) × number of water pumps (n).

[0030] Then, the number of operating water pumps is controlled to be the minimum natural number that satisfies the following formula (2). Number of units in operation ≧ Water supply volume (m 3 / h) / Maximum designed discharge of water pump (m 3 / h)···(2)

[0031] By switching the number of operating water pumps 32A-32n based on the calculation results of equation (2), the amount of circulating water can be kept below the maximum designed discharge rate per water pump. Furthermore, by using inverter control to control the output of the operating water pumps within a range of 60-100% of the maximum designed discharge rate of the water pump, the amount of circulating water can be further reduced, and the amount of circulating water can be kept constant. Then, the control valve 55 can be controlled to maintain the desired amount of circulating water and water usage.

[0032] By performing such control, not only can the energy required for operating the water pumps 32A to 32n be reduced, but the amount of chemicals injected from the chemical injection device 51 can also be reduced, and the operating energy of the water treatment device 30 can also be suppressed.

[0033] Second Embodiment (Pure water production equipment) Figures 2 and 3 show a second embodiment of the present invention, which is a specific example in which the embodiment shown in Figure 1 described above is configured with three water pumps, 32A, 32B, and 32C, and the outputs of the water pumps 32A to 32C are not inverter controlled.

[0034] Figure 2 shows the amount of circulating water at 20m 3 / h, and the designed maximum discharge of the water pumps 32A, 32B, and 32C is 60m 3 / h, the usage (required amount) of primary pure water W2 in the subsystem is 160 m 3 / h. Here, the number of pumps in operation is (160 + 20(m 3 / h)) / 60(m 3 / h) = 3 (units), so the water pumps 32A, 32B, and 32C are operated at their maximum designed discharge rates, and the water is treated in the water treatment device 30 to produce 180 m 3 / h of primary pure water W2 is produced. Then, 160 m 3 / h is sent to the sub-tank 37, and the surplus 20m 3 / h is sent to a circulation path 54 communicating with the tank 31 for treated water.

[0035] As shown in Figure 3, the amount of primary pure water W2 used in the subsystem is 100 m 3 / h, the circulating water from the circulation path 54 is 20 m 3 / h, the number of pumps in operation is (100 + 20(m 3 / h)) / 60(m 3 Therefore, the number of operating water pumps is set to two, that is, the water pump 32C is stopped, the water pumps 32A and 32B are operated at the maximum designed discharge rate, and the water is treated by the water treatment device 30 to produce 120 m 3 / h of primary pure water W2 is produced. Then, 100 m 3 / h is sent to the sub-tank 37, and the surplus 20m 3 / h is sent to the circulation path 54 communicating with the treated water tank 31. In this embodiment, if the value obtained by dividing the circulating water volume + the water usage volume by the designed maximum discharge volume of the water supply pump is not a positive integer, the circulating water volume can be increased by that amount.

[0036] According to this embodiment, the number of operating water pumps is determined and the start and stop of the water pumps is controlled based on this, so that the operating energy of the pure water production system and the amount of circulating water can be reduced compared to the conventional examples shown in Figures 7 and 8. Furthermore, since the amount of water treated by water treatment device 30 is reduced, the amount of chemical solution M injected from chemical injection device 51 can be reduced.

[0037] Third Embodiment (Pure water production equipment) 4 and 5 show a third embodiment of the present invention, which is a specific example in which the outputs of the water pumps 32A to 32C in the embodiment shown in FIG. 2 are inverter-controlled.

[0038] Figure 4 shows the circulating water volume at 20m 3 / h, and the designed maximum discharge of the water pumps 32A, 32B, and 32C is 60m 3 / h, and the amount of primary pure water W2 used (required amount) in the subsystem is 80m 3 / h. Here, the number of pumps in operation is (80 + 20(m 3 / h)) / 60(m 3 / h) = 1.67 ≦ 2 (units). Therefore, the number of operating water pumps is reduced to two, that is, water pump 32C is stopped and water pumps 32A and 32B are operated. In this case, if water pumps 32A and 32B are operated at their maximum designed discharge rate (100%), the discharge rate will be 120 m 3 / h of primary pure water W2 will be produced, and the amount of circulating water will be 40m 3 / h, but in this embodiment, the output of the water pumps 32A and 32B is operated at 83% by inverter control, and the water is treated in the water treatment device 30 to produce 100 m 3 / h of primary pure water W2 is produced. Then, 80 m 3 / h is sent to the sub-tank 37, and the surplus 20m 3 / h is sent to the circulation path 54 communicating with the tank 31 for water to be treated. This allows the primary pure water W2 to be sent without increasing the amount of circulating water.

[0039] As shown in Figure 5, the amount of primary pure water W2 used in the subsystem is 30 m 3 / h, the amount of circulating water from the circulation path 54 is 20 m 3 / h, the number of pumps in operation is (30+20(m 3 / h)) / 60(m 3 / h) = 0.67 ≦ 1 (units). Therefore, the number of operating water pumps is reduced to one, that is, water pumps 32B and 32C are stopped and only water pump 32A is operated. In this case, if water pump 32A is operated at the maximum designed discharge rate (100%), the discharge rate will be 60 m 3 / h of primary pure water W2 will be produced, and the amount of circulating water will be 30m 3 / h, but in this embodiment, the output of the water supply 32A is operated at 83% by inverter control, and the water is treated by the water treatment device 30 to produce 50 m 3 / h of primary pure water W2 is produced. Then, 30 m 3 / h is sent to the sub-tank 37, and the surplus 20m 3 / h is fed to the circulation path 54 communicating with the tank 31 for water to be treated. This allows the primary pure water W2 to be continuously fed without increasing the amount of circulating water.

[0040] According to this embodiment, the number of operating water pumps is determined, the start and stop of the water pumps is controlled based on this, and the output of the water pumps is then inverter controlled, so the pure water production system can reduce the operating energy compared to the conventional example shown in Figures 7 and 8 and can operate with a small amount of circulating water. Furthermore, since the amount of water treated by water treatment device 30 is reduced, the amount of chemical solution M injected from chemical injection device 51 can be reduced.

[0041] Although the present invention has been described above based on the above-mentioned embodiments, various modifications are possible. For example, the pure water production system 3 to which the present invention can be applied is not particularly limited as long as it has three or more water pumps, one or more water treatment devices downstream of the water pumps, a water supply line for supplying the pure water produced by the water treatment devices to a downstream system or point of use, and a circulation line branching from the water supply line for returning excess pure water to a storage tank. Furthermore, the water treatment device downstream of the water supply pump is not particularly limited and can be composed of one or two types selected from a reverse osmosis membrane, an ultraviolet oxidation device, a degassing membrane, an electrodeionization device, a regenerative ion exchange device, a non-regenerative ion exchange device, etc. Furthermore, the present invention is not limited to cases in which primary pure water W2 is supplied to a subsystem of an ultrapure water production system, but can also be applied to cases in which primary pure water W2 is supplied to a point of use. [Example]

[0042] The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0043] Example 1 Table 1 shows the amount of primary pure water W2 fed, the amount of circulating water, the amount of water used, the number of operating pumps, and the reduced power consumption when the water feed amount is controlled only by starting and stopping the water feed pumps 32A to 32C without inverter control as in the second embodiment shown in Figure 2. The total power consumption per water feed pump is 10 kWh.

[0044] [Table 1]

[0045] Comparative Example 1 Table 2 shows the amount of primary pure water W2 supplied, the amount of circulated water, the amount of water used, the number of operating pumps, and the reduced power consumption when the third water pumps 32A to 32C are constantly operated at their maximum designed discharge rate, as in the conventional example shown in Figure 7.

[0046] [Table 2]

[0047] As is clear from Table 1 and Table 2, the control method for the pure water production system of Example 1 can reduce power consumption by controlling the number of operating pumps, and can also reduce the amount of circulating water, compared to the control method for the pure water production system of Comparative Example 1. [Explanation of symbols]

[0048] 1 Ultrapure water production equipment 2 Pretreatment equipment 21 Coagulation treatment equipment 22 Turbidity removal UF membrane device 3 Primary water purification equipment (pure water production equipment) 30 Water Treatment Equipment 31 Untreated water tank 32 Water pump 32A, 32B, 32C water pump 33 Reverse osmosis membrane equipment 34 Membrane degassing device 35 Ultraviolet oxidation device 36 Electrodeionization Equipment 37 Subtank 4 Secondary pure water production equipment (subsystem) 41 Pump 42 Ultraviolet oxidation device 43 Membrane degassing device 44 Non-regenerative mixed-bed ion exchanger 45 Ultrafiltration (UF) membrane 5 Use Points (UP) 51 Chemical dosing device 52 Waterway 53 Supply route 54 Circulation path 55 Control valve 56 Flow meter 57 Flow meter W Raw Water W1 Pretreated water (water to be treated) W2 Primary pure water W3 Ultrapure water (secondary pure water)

Claims

1. A method for controlling a pure water treatment system comprising a storage tank for water to be treated, three or more water pumps for transporting the water to be treated stored in the storage tank, and one or more water treatment devices provided downstream of the water pumps, the system having a water supply line for transporting pure water produced by the water treatment devices to a downstream system or a use point, and a circulation line for returning excess pure water branched off from the water supply line to the storage tank, A method for controlling a pure water production system, which controls the number of operating water pumps and / or the output of the water pumps in accordance with the amount of pure water required by the downstream system or point of use.

2. 2. The method for controlling a pure water production apparatus according to claim 1, wherein the number of operating water pumps and / or the output of the water pumps are controlled so that the amount of water circulated through the circulation path is 20% or less of the sum of the maximum designed discharge volumes of the water pumps.

3. 3. The method for controlling a pure water production system according to claim 2, wherein the output of the water pump is controlled to 60 to 100% of the maximum designed discharge rate of the water pump.

4. 4. The method for controlling a pure water production apparatus according to claim 3, wherein the number of operating pumps is controlled so that the value obtained by dividing the amount of pure water delivered by the maximum designed discharge amount of each pump is rounded up to a natural number.

5. 5. The method for controlling a pure water production system according to claim 1, further comprising providing a chemical injection device in a water supply path for pure water produced by the primary pure water system, and adjusting the amount of chemicals added from the chemical injection device in accordance with the amount of pure water produced by the primary pure water system.

6. 5. The method for controlling a pure water production system according to claim 1, wherein the pure water produced in the primary pure water system is supplied to a downstream system, and the downstream system is operated in an adjusted manner depending on the amount of water supplied to the downstream system.

Images