Control method for ultrapure water production equipment

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 control method for a pure water production apparatus suitable for producing ultrapure water used in the electronics industry, such as semiconductors and liquid crystals, and more particularly to a control method for a pure water production apparatus that can control the water supply amount according to the amount of water used in downstream systems and use points. [Background technology]

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

[0003] The pretreatment device 2 consists of a coagulation device 21 and a turbidity removal UF membrane device 22. In this pretreatment device 2, the raw water W is pretreated by coagulation sedimentation, membrane filtration, etc., and suspended solids are mainly removed.

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

[0005] The subsystem (secondary pure water system) 4, which is responsible for the final stage of ultrapure water production, consists of a pump 41 that supplies primary pure water W2 from a sub-tank 37, an ultraviolet oxidation system 42, a membrane degasser 43, a non-regenerative mixed-bed ion exchange system 44, and an ultrafiltration (UF) membrane 45 as a membrane filtration system, and in some cases an RO membrane separation system may also be provided as needed. In this subsystem 4, the ultraviolet oxidation system 42 oxidizes and decomposes trace amounts of organic matter (TOC components) contained in the primary pure water W2 and degasses it. Subsequently, the non-regenerative mixed-bed ion exchange system 44 processes it to remove residual carbonate ions, organic acids, anionic substances, and even metal ions and cationic substances by ion exchange. Then, the ultrafiltration (UF) membrane 45 removes fine particles to produce ultrapure water W3, which is supplied to the use point 5.

[0006] As described above, the primary pure water production apparatus 3 in the ultrapure water production apparatus 1 generally has multiple series (3 series in Figure 7) of water supply pumps 32A, 32B, and 32C. Downstream from these water supply pumps is a primary pure water treatment apparatus, which in the primary pure water treatment apparatus 3 shown in Figure 6 consists of a reverse osmosis membrane apparatus, a membrane degasser, an ultraviolet oxidation apparatus, and an electrodeionizer. Reference numeral 51 denotes a chemical injection device for pH adjusters and other chemicals in the water being treated by the reverse osmosis membrane. The water supply channel 52 connected to the water treatment apparatus 30 branches into a supply channel 53 that communicates with a sub-tank 37 and a circulation channel 54 that communicates with a water tank 31. A control valve 55 is provided at this branching point to adjust the flow rate.

[0007] Then, in order to stably supply primary pure water W2 to subsystem 4, the water pumps 32A, 32B, and 32C are driven at their maximum design discharge rate to produce an excess amount of primary pure water W2. The required amount for subsystem 4 is then sent from the supply path 53 to the sub-tank 37, and the excess is returned to the treated water tank 31 via the circulation path 54 by the control valve 55, thus maintaining circulation.

[0008] As shown in Figure 7, the amount of primary pure water W2 used (required amount) in subsystem 4 is 140 m³. 3 / h, when the designed maximum discharge of the water supply pumps 32A, 32B, and 32C is 60 m 3 / h, the water supply pumps 32A, 32B, and 32C are operated at the designed maximum discharge to produce 180 m 3 / h of primary pure water W2. Then, the control valve 55 sends 140 m 3 / h to the sub-tank 37, and the excess 40 m 3 / h is sent to the circulation path 54 communicating with the treated water tank 31, and the amount of the returned primary pure water W2 is increased or decreased according to the usage amount of the primary pure water W2 in the subsystem 4.

Summary of the Invention

Problems to be Solved by the Invention

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

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

[0014] According to such an invention (Invention 2), it is possible to suppress the excessive production of pure water and efficiently reduce the energy consumption of the pure water production apparatus and the pumps.

[0015] In the above invention (Invention 2), it is preferable that the control of the output of the water supply pumps is 60% to 100% of the design maximum discharge amount of the water supply pumps (Invention 3).

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

[0017] In the above invention (Invention 3), it is preferable to control the number of operating pumps so that the number of pumps is obtained by dividing the amount of pure water supplied by the design maximum discharge rate of one pump and rounding up the result to a natural number (Invention 4).

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

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

[0020] According to this invention (Invention 5), the amount of pure water produced by the water treatment device is reduced, which in turn reduces the amount of chemicals added, thereby lowering costs.

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

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

[0023] According to the present invention, a pure water system has three or more series of water supply pumps that supply the produced pure water to a downstream system or user point, and return any 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 user point. This prevents an excess of pure water from being returned to the storage tank from the circulation path, thereby reducing excessive energy consumption of the pumps. [Brief explanation of the drawing]

[0024] [Figure 1] This is a flow diagram showing a pure water production apparatus to which the control method for a pure water production apparatus according to the first embodiment of the present invention can be applied. [Figure 2] This is a flow diagram showing a control method for a pure water production apparatus according to a second embodiment of the present invention. [Figure 3] This is a flow diagram showing the control method for the pure water production apparatus according to the second embodiment described above. [Figure 4] This is a flow diagram showing the control method of the pure water production apparatus according to the third embodiment described above. [Figure 5] This is a flow diagram showing the control method of the pure water production apparatus according to the third embodiment described above. [Figure 6] This is a flow chart showing an ultrapure water production apparatus to which the control method for the pure water production apparatus of the present invention can be applied. [Figure 7] This is a flowchart illustrating the control method of a conventional pure water production system. [Figure 8] This is a flowchart illustrating the control method of a conventional pure water production system. [Modes for carrying out the invention]

[0025] The control method for the pure water production apparatus of the present invention will be described below with reference to the attached drawings.

[0026] [First Embodiment] (Pure water production equipment) 333 Figure 1 schematically shows a pure water device to which the control method of the pure water production device of the present invention is applicable. Since the basic configuration is the same as that of FIG. 7 described above, the same components are denoted by the same reference numerals. In FIG. 1, the primary pure water device 3 includes a treated water tank 31 for storing the pre-treated water (raw water) W1, and a plurality of series (n series: n is a positive integer) of water supply pumps 32A ··· 32n connected by a header pipe. These water supply pumps 32A to 32n are equipped with inverters as output control means. A water treatment device 30 composed of a reverse osmosis membrane device, a membrane degassing device, an ultraviolet oxidation device, and an electrodeionization device is arranged downstream of the water supply pump 32A. A chemical injection device 51 such as a pH adjuster for adjusting the pH of the treated water of the reverse osmosis membrane is attached to the water treatment device 30. In addition, a water supply line 52 is connected to the water treatment device 30. This water supply line 52 branches into a supply line 53 communicating with the sub-tank 37 and a circulation line 54 communicating with the treated water tank 31, and a control valve 55 as a flow rate adjustment unit is provided at this branch. Further, 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] The flow meters 56 and 57 can communicate information with control means (not shown). Based on the measured values of the flow meters 56 and 57, the control means can control the operation and stop of the water supply pumps 32A to 32n, and can control the output of the water supply pumps 32A to 32n within a range of 60 to 100% with respect to the designed maximum discharge volume of the water supply pumps by inverter control. At the same time, the control valve 55 can be controlled so as to obtain a predetermined circulation water volume and a water consumption volume.

[0028] (Control Method of Pure Water Production Device) In the pure water production device as described above, the water supply volume of the water supply pumps 32A to 32n, the water consumption volume of the primary pure water, and the circulation water volume satisfy the following formula (1). Water supply volume (m 3 / h) = Water consumption volume x (m 3 / h) + Circulation water volume y (m 3 / h) = x + y (m3 / h) ···(1)

[0029] Here, the circulating water volume y(m 3 The circulating water volume (m³ / h) is preferably set to be 20% or less of the sum of the design maximum discharge volumes of water supply pumps 32A to 32n, and this circulating water volume may be a fixed value or a variable value. Here, the sum of the design maximum discharge volumes is the design maximum discharge volume per water supply pump (m³ / h). 3 The formula is ( / h) × number of water pumps (n).

[0030] Then, the number of operating water pumps is controlled to be the smallest natural number that satisfies equation (2) below. Number of operating units ≥ Water flow rate (m³) 3 / h) / Design maximum discharge rate (m³) of water supply pump 3 / h)···(2)

[0031] Based on the calculation results of formula (2) above, the number of operating water supply pumps 32A to 32n can be switched to keep the amount of circulating water below the design maximum discharge rate per water supply pump. Furthermore, by controlling the output of the operating water supply pumps with an inverter within the range of 60-100% of the design maximum discharge rate of the water supply pumps, 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 achieve the predetermined amount of circulating water and water usage.

[0032] By implementing this control, it is possible to reduce the energy required for the operation of the water supply pumps 32A to 32n, reduce the amount of chemicals injected from the chemical injection device 51, and further suppress the operating energy of the water treatment device 30.

[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, in the embodiment shown in Figure 1 above, the water supply pumps are configured as three units, 32A, 32B, and 32C, and the outputs of water supply pumps 32A to 32C are not controlled by an inverter.

[0034] Figure 2 shows the circulating water volume at 20 m³. 3 The setting is fixed at / h, and the design maximum discharge rate of water pumps 32A, 32B, and 32C is 60m³. 3 At / h, the usage (request) of primary pure water W2 in the subsystem is at its maximum of 160m. 3 This is the case for / h. Here, the number of pumps in operation is (160 + 20(m 3 / h)) / 60(m 3 Since ( / h) = 3 (units), the water supply pumps 32A, 32B, and 32C are operated at their maximum design discharge rate, and the water is treated with the water treatment device 30 to produce 180 m³. 3 It produces primary pure water W2 at a rate of / h. Then, the control valve 55 controls it to 160m 3 The water at / h is sent to sub-tank 37, and the surplus 20m 3 The water at / h is sent to the circulation path 54 which is connected to the water to be treated tank 31.

[0035] Then, as shown in Figure 3, the amount of primary pure water W2 used in the subsystem is 100 m³. 3 When the value drops significantly to / h, circulating water from circulation path 54 is 20m 3 Since the value is fixed at / h, the number of pumps in operation is (100 + 20(m 3 / h)) / 60(m 3 ( / h) = 2 (units). Therefore, the number of water supply pumps in operation is set to 2, meaning water supply pump 32C is stopped, and water supply pumps 32A and 32B are operated at their maximum design discharge rate, and the water is treated by the water treatment device 30 to produce 120 m³. 3 It produces primary pure water W2 at a rate of / h. Then, the control valve 55 controls it to 100m 3 The water at / h is sent to sub-tank 37, and the surplus 20m 3 The water at / h is sent to the circulation path 54 which is connected to the water to be treated tank 31. In this embodiment, if the value obtained by dividing the circulating water volume + used water volume by the design maximum discharge volume of the water supply pump is not a positive integer, the circulating water volume should be increased by that amount.

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

[0037] [Third Embodiment] (Pure water production equipment) Figures 4 and 5 show a third embodiment of the present invention, which is a specific example of controlling the output of water supply pumps 32A to 32C with an inverter in the embodiment shown in Figure 2 described above.

[0038] Figure 4 shows the circulating water volume at 20 m³. 3 The design maximum discharge rate for water pumps 32A, 32B, and 32C is fixed at / h, and 60m³ 3 At / h, the amount of primary pure water W2 used (required) in the subsystem is 80m³. 3 This is the case for / 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 water supply pumps in operation is set to 2, meaning water supply pump 32C is stopped and water supply pumps 32A and 32B are started. In this case, if water supply pumps 32A and 32B are operated at the design maximum discharge rate (100%), 120m 3 To produce primary pure water W2 at a rate of / h, the circulating water volume will be 40m³. 3 The output should be set to / h, but in this embodiment, the output of the water supply pumps 32A and 32B is operated at 83% by inverter control, and the water is processed by the water treatment device 30 to produce 100m³. 3 Primary pure water W2 is produced at a rate of / h. Then, the control valve 55 controls 80m 3 The water at / h is sent to sub-tank 37, and the surplus 20m 3 The water at / h is sent to the circulation path 54 that connects to the water to be treated tank 31. This allows primary pure water W2 to be supplied without increasing the volume of circulating water.

[0039] As shown in Figure 5, the amount of primary pure water W2 used in the subsystem is 30 m³. 3 When the volume of circulating water from the circulation path 54 drops significantly to 20 m³ / h, the volume of circulating water from the circulation path 54 drops to 20 m³ / h. 3 If it is / h, the number of pumps in operation is (30 + 20(m 3 / h)) / 60(m 3 ( / h) = 0.67 ≤ 1 (unit). Therefore, the number of water supply pumps in operation is reduced to one, meaning that water supply pumps 32B and 32C are stopped and only water supply pump 32A is operated. In this case, if water supply pump 32A is operated at the design maximum discharge rate (100%), 60m³ 3 To produce primary pure water W2 at a rate of / h, the circulating water volume will be 30m³. 3 It must be set to / h, but in this embodiment, the output of the water supply 32A is operated at 83% by inverter control, and the water treatment device 30 processes it to 50m 3 Primary pure water W2 is produced at a rate of / h. Then, the control valve 55 controls 30m 3 The water at / h is sent to sub-tank 37, and the surplus 20m 3 The water at / h is sent to the circulation path 54 connected to the water to be treated tank 31. This allows the supply of primary pure water W2 to continue without increasing the amount of circulating water.

[0040] According to this embodiment, the number of water supply pumps in operation is determined, and the starting and stopping of the water supply pumps is controlled based on this, followed by inverter control of the output of the water supply pumps. As a result, the operating energy of the pure water production apparatus is reduced compared to the conventional example shown in Figures 7 and 8, and it can be operated with a smaller circulating water volume. Furthermore, since the amount of water treated by the water treatment apparatus 30 is reduced, the amount of chemical solution M injected from the chemical injection apparatus 51 can be reduced.

[0041] The present invention has been described above based on the embodiments described above, but the present invention is not limited to the embodiments described above and can be implemented in various modified forms. For example, the pure water production apparatus 3 to which the present invention can be applied has three or more series of water supply pumps, one or more water treatment devices downstream of these water supply pumps, a water supply channel that supplies the pure water produced by the water treatment device to a downstream system or use point, and a circulation channel that returns the excess pure water branched from this water supply channel to a storage tank, but there are no particular limitations. Furthermore, there are no particular limitations on the water treatment device downstream of the water supply pumps, and it can be composed of one or two types selected from reverse osmosis membranes, ultraviolet oxidation devices, degassing membranes, electrodeionization devices, regenerative ion exchange devices, non-regenerative ion exchange devices, etc. Moreover, it can be applied not only when supplying primary pure water W2 to a subsystem of an ultrapure water production apparatus, but also when supplying primary pure water W2 to a use point. [Examples]

[0042] The present invention will be described more specifically 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 supplied, the amount of circulating water, the amount of water used, the number of operating pumps, and the amount of reduced power consumption when the water supply amount is controlled only by starting and stopping the water supply pumps 32A to 32C without inverter control, as in the second embodiment shown in Figure 2. Note that the power consumption per water supply 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 circulating water, the amount of water used, the number of operating pumps, and the amount of reduced power consumption when the third water supply pumps 32A to 32C are operated at their maximum design 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 apparatus of Example 1 can reduce power consumption by controlling the number of operating pumps, and the amount of circulating water can also be reduced, compared to the control method for the pure water production apparatus of Comparative Example 1. [Explanation of symbols]

[0048] 1 Ultrapure water production equipment 2 Pre-treatment device 21. Aggregation treatment device 22 Turbidity removal UF membrane device 3 Primary water purification equipment (pure water production equipment) 30 Water treatment equipment 31. Water tank to be treated 32 Water supply pump 32A, 32B, 32C Water supply pumps 33 Reverse osmosis membrane equipment 34 Membrane degassing device 35. Ultraviolet oxidation apparatus 36 Electrodeionizer 37 Sub-tank 4. Secondary pure water production system (subsystem) 41 pumps 42. Ultraviolet oxidation apparatus 43 Membrane degassing device 44 Non-regenerative mixed-bed ion exchange system 45 Ultrafiltration (UF) membrane 5 Youth 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 Pre-treated water (water to be treated) W2 Primary Pure Water W3 Ultrapure water (secondary pure water)

Claims

1. A control method for an ultrapure water production apparatus comprising a primary pure water system and a subsystem located downstream of the primary pure water system, The primary pure water system comprises a storage tank for water to be treated, three or more series of water pumps for supplying the water to be treated stored in the storage tank, one or more water treatment devices located downstream of the three or more series of water pumps, a water supply channel for supplying the primary pure water produced by the water treatment device to the subsystem, and a circulation channel for returning any surplus primary pure water branched from the water supply channel to the storage tank. In accordance with the primary pure water requirements of the subsystem, the number of operating water pumps (three or more series) and / or the output of the three or more water pumps are controlled, and, The number of operating water pumps in the three or more water pumps and / or the output of the three or more water pumps are controlled so that the amount of water circulated in the circulation path is 20% or less of the sum of the maximum design discharge volumes of the three or more water pumps. A control method for an ultrapure water production apparatus, wherein the output of the three or more water supply pumps is controlled to 60-100% of the design maximum discharge volume.

2. A control method for an ultrapure water production apparatus according to claim 1, wherein the number of operating water supply pumps is controlled so that the number of pumps is obtained by dividing the amount of primary pure water supplied by the design maximum discharge rate of each water supply pump, and then rounding up the result up to a natural number.

3. The control method for an ultrapure water production apparatus according to claim 1 or 2, wherein the primary pure water apparatus is equipped with a chemical injection device in the water supply channel of the primary pure water produced by the primary pure water apparatus, and the amount of chemicals added from the chemical injection device is adjusted according to the amount of primary pure water supplied by the primary pure water apparatus.

4. The control method for an ultrapure water production apparatus according to claim 1 or 2, wherein the water treatment apparatus comprises a reverse osmosis membrane apparatus, a membrane degasser, an ultraviolet oxidation apparatus, and an electrodeionizer.

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