How to operate a pure water production system

Abstract

To provide an operation method of a pure water production system capable of producing pure water at a prescribed temperature in a method of producing pure water by a pure water production system equipped with a chiller system.SOLUTION: In an operation method of a pure water production system, raw water is RO treated by an RO device 6 to obtain permeated water (intermediate water). The intermediate water is cooled by a heat exchanger 11 through an intermediate tank 8. Then it is treated by an ion exchanger 13 to obtain pure water, and pure water at a prescribed temperature is discharged from a pure water tank 15 through a pipe 17. When the temperature of the pure water exceeds a prescribed temperature, a part of the pure water is returned to a raw water tank 1 and tap water is supplied to the intermediate tank 8.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for operating a pure water production system, and more particularly to a method for operating a pure water production system equipped with a chiller system so as to produce pure water at a predetermined temperature. [Background technology]

[0002] A system for producing pure water using wastewater from semiconductor manufacturing processes as raw water is in use (Patent Document 1). This pure water production system includes an RO (reverse osmosis) device that treats the raw water with RO, an ion exchange device that treats the permeated water from the RO device with ion exchange, and other components. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-177326 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a method for producing pure water using a pure water production system equipped with a chiller system, which is capable of producing pure water at a predetermined temperature. [Means for solving the problem]

[0005] The method for operating the pure water production system of the present invention is summarized as follows.

[0006] [1] A raw water tank and an RO device that performs RO treatment on the water from the raw water tank; an intermediate tank for receiving permeated water (hereinafter referred to as intermediate water) from the RO device; a first heat exchanger that exchanges heat with the intermediate water from the intermediate tank; an ion exchange device through which the intermediate water that has undergone heat exchange in the first heat exchanger is passed; a pure water tank for receiving the pure water that has passed through the ion exchange device; a pure water extracting means for extracting pure water from the pure water tank; a pure water returning means for returning a portion of the pure water extracted by the pure water extracting means to the raw water tank or the intermediate tank; A receiving means for receiving concentrated water from the RO device; a second heat exchanger through which the water from the receiving means is circulated; a chiller system having a heat pump that transfers heat from the first heat exchanger to the second heat exchanger; A method for operating a pure water production system comprising: A method for operating a pure water production system, characterized in that when the temperature of the pure water taken out by the pure water tank or the pure water taking-out means rises above a specified temperature, the pure water taking-out means returns a portion of the pure water to the raw water tank.

[0007] [2] The method for operating the pure water production system according to [1], wherein the pure water returning means returns a portion of the pure water to the raw water tank and supplies industrial water to the intermediate tank.

[0008] [3] The above between [2] The method for operating a pure water production system, comprising adjusting the operating conditions of the ion exchange device in accordance with the supply of industrial water to the tank.

[0009] [4] A method for operating a pure water production system according to any one of [1] to [3], in which industrial water is supplied to the receiving means when the water temperature of the receiving means becomes higher than a predetermined temperature due to high-temperature wastewater flowing into the receiving means.

[0010] [5] Raw water tank and an RO device that performs RO treatment on the water from the raw water tank; an intermediate tank for receiving permeated water (hereinafter referred to as intermediate water) from the RO device; a first heat exchanger that exchanges heat with the intermediate water from the intermediate tank; an ion exchange device through which the intermediate water that has undergone heat exchange in the first heat exchanger is passed; a pure water tank for receiving the pure water that has passed through the ion exchange device; a pure water extracting means for extracting pure water from the pure water tank; a pure water returning means for returning a portion of the pure water extracted by the pure water extracting means to the raw water tank or the intermediate tank; A receiving means for receiving concentrated water from the RO device; a second heat exchanger through which the water from the receiving means is circulated; a chiller system having a heat pump that transfers heat from the first heat exchanger to the second heat exchanger; A method for operating a pure water production system comprising: A method for operating a pure water production system, comprising supplying industrial water to the receiving means when the water temperature of the receiving means becomes higher than a predetermined temperature due to high-temperature wastewater flowing into the receiving means.

[0011] [6] Raw water tank and an RO device that performs RO treatment on the water from the raw water tank; an intermediate tank for receiving permeated water (hereinafter referred to as intermediate water) from the RO device; a first heat exchanger that exchanges heat with the intermediate water from the intermediate tank; an ion exchange device through which the intermediate water that has undergone heat exchange in the first heat exchanger is passed; a pure water tank for receiving the pure water that has passed through the ion exchange device; a pure water extracting means for extracting pure water from the pure water tank; a pure water returning means for returning a portion of the pure water extracted by the pure water extracting means to the raw water tank or the intermediate tank; A receiving means for receiving concentrated water from the RO device; a second heat exchanger through which the water from the receiving means is circulated; a chiller system having a heat pump that transfers heat from the first heat exchanger to the second heat exchanger; A method for operating a pure water production system comprising: A method for operating a pure water production system, characterized in that industrial water is supplied to the receiving means when the temperature of the medium circulating through the condenser of the heat pump and the second heat exchanger becomes higher than a predetermined temperature.

[0012] [7] The method for operating a pure water production system according to any one of [4] to [6], wherein the industrial water supplied to the receiving means is well water.

[0013] [8] The receiving means includes a neutralization tank, a storage tank into which water from the neutralization tank flows, and an outlet means for discharging water from the storage tank, The method for operating a pure water production system according to any one of [4] to [7], wherein the concentrated water from the RO device and the high-temperature wastewater are introduced into the neutralization tank.

[0014] [9] The method for operating the pure water production system according to [8], wherein the water in the storage tank is circulated through the second heat exchanger.

[0015]

[10] The method for operating a pure water production system according to any one of [4] to [9], wherein the high-temperature wastewater is boiler drain water. [Effects of the Invention]

[0016] According to the present invention, a raw water tank, an RO device that performs RO treatment on water from the raw water tank, an intermediate tank that receives permeated water from the RO device, a first heat exchanger that exchanges heat with intermediate water from the intermediate tank, an ion exchange device through which the intermediate water that has undergone heat exchange in the first heat exchanger is passed, a pure water tank that receives pure water that has passed through the ion exchange device, and pure water removal means that removes pure water from the pure water tank. In a pure water production system having a pure water return means for returning a portion of the pure water extracted by the pure water extraction means to the raw water tank or intermediate tank, a receiving means for receiving concentrated water from the RO device, a second heat exchanger through which water from the receiving means is circulated, and a chiller system with a heat pump for transferring heat from the first heat exchanger to the second heat exchanger, pure water at a predetermined temperature can be produced without stopping the supply of pure water. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a configuration diagram of a pure water production system. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment will be described with reference to the drawings.

[0019] Raw water (in this embodiment, industrial wastewater or treated water thereof, but not limited to these) is introduced into raw water tank 1, and is sent to membrane filtration device 4 via pump 2 and piping 3, where it is subjected to membrane filtration. In this embodiment, an MF device is used as membrane filtration device 4, but any device capable of removing suspended solids and the like from the raw water is sufficient, and is not limited to an MF device, and filtration devices other than membrane filtration devices may also be used.

[0020] The filtered water filtered by the membrane filtration device 4 is sent to the RO device 6 through a pipe 5, and the RO treated water (permeated water) is sent to an intermediate tank 8 through a pipe 7 and stored therein.

[0021] The RO treated water in the intermediate tank 8 is sent to a first heat exchanger 11 via a pump 9 and a pipe 10, where it is heat exchanged to a predetermined temperature, and then sent to an ion exchanger 13 via a pipe 12. The pure water produced by the ion exchange treatment in the ion exchanger 13 is introduced into a pure water tank 15 via a pipe 14 and stored therein. The pure water in the pure water tank 15 is extracted by a pump 16 and a pipe 17 and sent to a pure water demand destination.

[0022] The ion exchange device 13 may have various configurations, such as a two-bed, three-tower type or a three-bed, four-tower type.

[0023] A pure water return pipe 18 branches off from the pipe 17. The downstream side of the pipe 18 branches off into pipes 19 and 21, and pure water can be introduced into the intermediate tank 8 via the pipe 19 and a valve 20, and into the raw water tank 1 via the pipe 21 and a valve 22.

[0024] Industrial water (industrial water, well water, tap water, etc.) can be introduced into the intermediate tank 8 via a pipe 23 and a valve 24.

[0025] The brine (concentrated water) from the RO device 6 is introduced into the neutralization tank 40 via a pipe 30. Industrial water (well water in this embodiment) can be introduced into the neutralization tank 40 via a pipe 31 and a valve 32. The industrial water supplied via the pipe 23 and the industrial water supplied via the pipe 31 may be the same type or different types.

[0026] Boiler drain water, which is steam condensate, can be introduced into the neutralization tank 40 from a drain tank and a drain pump (not shown) via piping 33. In addition, regenerated wastewater from the ion exchange device 13 is introduced into a pre-neutralization tank 35 via piping 34, and after being neutralized in the pre-neutralization tank 35, can be introduced into the neutralization tank 40. Note that the pre-neutralization tank 35 may be omitted, and the regenerated wastewater from the ion exchange device 13 may be introduced directly into the neutralization tank 40 via piping 34.

[0027] Neutralized water, which has been neutralized in neutralization tank 40 by adding a neutralizing agent such as an acid or alkali, is introduced into storage tank 42 via piping 41. The water in storage tank 42 is introduced into second heat exchanger 47 via pump 45 and piping 46, and after heat exchange in heat exchanger 47, returns to storage tank 42 via piping 48.

[0028] The water in the storage tank 42 is discharged via the pump 43 and the pipe 44 so that the water level in the storage tank 42 is within a predetermined range.

[0029] Second heat exchanger 47 constitutes part of a chiller system (heat pump-utilizing heat transfer system) 49 for circulating low-temperature water to first heat exchanger 11. Water-cooled chiller 50 of chiller system 49 is a heat pump configured to compress a heat medium such as a chlorofluorocarbon alternative from an evaporator 51 using a compressor 52 and introduce the compressed heat medium from condenser 53 into evaporator 51 via an expansion valve 54.

[0030] The second water medium from the second heat exchanger 47 is introduced into the condenser 53 via a pipe 57, and the second water medium heated in the condenser 53 is circulated to the heat exchanger 47 via a pump 55 and a pipe 56.

[0031] Meanwhile, the first medium water, which has been cooled by passing through the evaporator 51, is sent to the first heat exchanger 11 via piping 60, where it is heated by heat exchange with water (intermediate water) from the storage tank 8, and then circulated to the evaporator 51 via pump 61 and piping 62.

[0032] In this embodiment, temperature sensors T17, T56, and T40 are provided in the pipes 17 and 56 and the neutralization tank 40, but in practice temperature sensors are also provided in other locations. Temperature sensor T17 may also be provided in the pure water tank 15.

[0033] In the pure water production system configured as described above, during steady-state operation, raw water is RO treated in the RO device 6 to produce permeate (intermediate water), which passes through the intermediate tank 8, where it is cooled in the first heat exchanger 11, and then treated in the ion exchange device 13 to produce pure water, and the pure water at a predetermined temperature is extracted from the pure water tank 15 via the pipe 17. During steady-state operation, the valves 20 and 22 are closed, but the valve 20 may be slightly opened to return a small amount of pure water to the intermediate tank 8 via the pipes 18 and 19. During steady-state operation, the valves 24 and 32 are closed.

[0034] During steady operation, the brine in the RO unit 6 is discharged from the neutralization tank 40 to the outside of the system via the storage tank 42. Heat removed from the intermediate water in the first heat exchanger 11 passes through the chiller system 49, and is transferred (heat transferred) to the circulating water from the storage tank 42 in the second heat exchanger 47, and is discharged to the outside of the system via the piping 44 in the form of heated wastewater. During steady operation, the amount of heat transferred from the first heat exchanger 11 to the second heat exchanger 47 is sufficient, and the temperature of the pure water in the pure water tank 15 is maintained at a normal temperature (for example, 23°C ± 1°C).

[0035] In this pure water production system, a method for dealing with situations in which the temperature of the pure water rises above the steady temperature due to various causes will now be described.

[0036] [When the temperature of the pure water rises due to a significant rise in the raw water temperature or outside air temperature] When the temperature of the pure water (the temperature detected by temperature sensor T17) becomes higher than a first specified temperature (for example, 23.5°C) due to a significant increase in the raw water temperature or the outside air temperature, valve 22 is opened (slightly opened), and a portion of the pure water is returned to raw water tank 1 through pipe 17. This increases the amount of brine from RO device 6, lowers the water temperature in storage tank 42, and also lowers the temperature of the water circulated from storage tank 42 to second heat exchanger 47. A sufficient amount of heat is transferred from first heat exchanger 11 to second heat exchanger 47 via chiller system 49, allowing the intermediate water to be sufficiently lowered in first heat exchanger 11, and the pure water temperature (the temperature detected by temperature sensor T17) drops.

[0037] In this way, if the pure water temperature does not decrease even when a portion of the pure water is returned, the amount of pure water returned is increased. When the pure water temperature reaches a second specified temperature (e.g., 24.0°C) higher than the first specified temperature, the valve 24 is opened and industrial water such as well water is supplied to the intermediate tank 8 to decrease the temperature of the intermediate water. This decreases the pure water temperature (the temperature detected by the temperature sensor T17).

[0038] Even if the temperature of the pure water does not rise, when the water level in the intermediate tank 8 drops below a specified water level, the valve 24 may be opened to supply industrial water to the intermediate tank 8.

[0039] Furthermore, if the water level in the raw water tank 1 drops for some reason, the valve 24 may be opened to supply industrial water to the intermediate tank 8.

[0040] The ion concentration of the industrial water is higher than that of the RO permeate from the RO device 6. Therefore, when industrial water is supplied to the intermediate tank 8 for operation, it is preferable to adjust the water flow conditions of the ion exchange device 13 (the timing of regeneration of the ion exchange resin), and it is preferable to introduce a program that automatically controls the timing of regeneration of the ion exchange resin according to the amount of industrial water supplied.

[0041] [When the temperature of the pure water rises due to the inflow of boiler drain water into the neutralization tank 40] The boiler drain water has a higher temperature than the RO brine. Therefore, when the drain pump is operated and the boiler drain water is introduced into the neutralization tank 40, the temperature of the water flowing from the intermediate tank 40 into the storage tank 42 rises. This increases the temperature of the stored water in the storage tank 42, increases the temperature of the water circulated from the storage tank 42 to the second heat exchanger 47, and increases the temperature of the medium water flowing through the pipe 56 (the temperature detected by the temperature sensor T56). As a result, the amount of heat transferred from the first heat exchanger 11 to the second heat exchanger 47 via the chiller system 49 decreases, making it impossible to sufficiently lower the temperature of the intermediate water in the first heat exchanger 11, which may result in an increase in the temperature of the pure water produced.

[0042] Therefore, when boiler drain water flows into the neutralization tank 40 and the water temperature of the neutralization tank 40 (the temperature detected by the temperature sensor T40) rises above a predetermined temperature, the valve 32 is opened, industrial water (well water in this embodiment) is introduced into the neutralization tank 40, and the temperature of the water flowing from the neutralization tank 40 into the storage tank 42 is brought to a normal temperature. As a result, a sufficient amount of heat is transferred from the first heat exchanger 11 to the second heat exchanger 47 via the chiller system 49, the temperature of the intermediate water in the first heat exchanger 11 is sufficiently lowered, and pure water at a steady temperature is produced.

[0043] [When the temperature of the medium water in pipe 56 (temperature detected by temperature sensor T56) rises due to other reasons] The intermediate water temperature detected by temperature sensor T56 may rise above the specified temperature due to some cause other than the inflow of boiler drain water into the neutralization tank 40. In such a case, valve 32 is opened, industrial water is introduced into the neutralization tank 40, and the temperature of the water flowing from the neutralization tank 40 into the storage tank 42 is set to the normal temperature. This allows a sufficient amount of heat to be transferred from the first heat exchanger 11 to the second heat exchanger 47 via the chiller system 49, causing the temperature of the intermediate water in the first heat exchanger 11 to drop sufficiently, producing pure water at a steady temperature.

[0044] In the above embodiment, when the supply of pure water to the pure water demander becomes temporarily unnecessary, the entire amount of pure water from the pipe 17 is returned to the raw water tank 1. In this case, the quality of the water supplied to the RO device 6 improves and the amount of RO brine decreases, so it is preferable to open the valve 32 and replenish industrial water from the pipe 31 to the neutralization tank 40.

[0045] The above embodiment is merely an example of the present invention, and the present invention may be embodied in other forms. For example, in the above embodiment, the neutralization tank 40 receives boiler drain water, but it may also receive high-temperature water other than boiler drain water. [Explanation of symbols]

[0046] 1 Raw water tank 4 Membrane filtration device 6 RO equipment 8 Intermediate tank 11 1st heat exchanger 13 Ion exchange device 15 Pure water tank 40 Neutralization tank 42 Reservoir 47 Second heat exchanger 49 Chiller System 50 Water-cooled chiller

Claims

1. Raw water tank and an RO device that performs RO treatment on the water from the raw water tank; an intermediate tank for receiving permeated water (hereinafter referred to as intermediate water) from the RO device; a first heat exchanger that exchanges heat with the intermediate water from the intermediate tank; an ion exchange device through which the intermediate water that has undergone heat exchange in the first heat exchanger is passed; a pure water tank for receiving the pure water that has passed through the ion exchange device; a pure water extracting means for extracting pure water from the pure water tank; a pure water returning means for returning a portion of the pure water extracted by the pure water extracting means to the raw water tank or the intermediate tank; A receiving means for receiving concentrated water from the RO device; a second heat exchanger through which the water from the receiving means is circulated; a chiller system having a heat pump that transfers heat from the first heat exchanger to the second heat exchanger; A method for operating a pure water production system comprising: A method for operating a pure water production system, characterized in that when the temperature of the pure water taken out by the pure water tank or the pure water taking-out means rises above a specified temperature, the pure water taking-out means returns a portion of the pure water to the raw water tank.

2. 2. A method for operating a pure water producing system according to claim 1, wherein said pure water returning means returns a portion of the pure water to the raw water tank and also supplies well water to said intermediate tank.

3. 3. The method for operating a pure water production system according to claim 2, wherein the operating conditions of said ion exchange unit are adjusted in accordance with the supply of well water to said intermediate tank.

4. 4. A method for operating a pure water production system according to any one of claims 1 to 3, wherein well water is supplied to said receiving means when the water temperature of said receiving means becomes higher than a predetermined temperature due to high-temperature wastewater flowing into said receiving means.

5. Raw water tank and an RO device that performs RO treatment on the water from the raw water tank; an intermediate tank for receiving permeated water (hereinafter referred to as intermediate water) from the RO device; a first heat exchanger that exchanges heat with the intermediate water from the intermediate tank; an ion exchange device through which the intermediate water that has undergone heat exchange in the first heat exchanger is passed; a pure water tank for receiving the pure water that has passed through the ion exchange device; a pure water extracting means for extracting pure water from the pure water tank; a pure water returning means for returning a portion of the pure water extracted by the pure water extracting means to the raw water tank or the intermediate tank; A receiving means for receiving concentrated water from the RO device; a second heat exchanger through which the water from the receiving means is circulated; a chiller system having a heat pump that transfers heat from the first heat exchanger to the second heat exchanger; A method for operating a pure water production system comprising: A method for operating a pure water production system, comprising the steps of: supplying well water to said receiving means when the water temperature of said receiving means becomes higher than a predetermined temperature;

6. Raw water tank and an RO device that performs RO treatment on the water from the raw water tank; an intermediate tank for receiving permeated water (hereinafter referred to as intermediate water) from the RO device; a first heat exchanger that exchanges heat with the intermediate water from the intermediate tank; an ion exchange device through which the intermediate water that has undergone heat exchange in the first heat exchanger is passed; a pure water tank for receiving the pure water that has passed through the ion exchange device; a pure water extracting means for extracting pure water from the pure water tank; a pure water returning means for returning a portion of the pure water extracted by the pure water extracting means to the raw water tank or the intermediate tank; A receiving means for receiving concentrated water from the RO device; a second heat exchanger through which the water from the receiving means is circulated; a chiller system having a heat pump that transfers heat from the first heat exchanger to the second heat exchanger; A method for operating a pure water production system comprising: a heat pump condenser and a second heat exchanger, the second heat exchanger being connected to the heat pump condenser; a heat pump condenser and a second heat exchanger being connected to the second heat exchanger;

7. the receiving means includes a neutralization tank, a storage tank into which water from the neutralization tank flows, and an outlet means for discharging water from the storage tank; 5. The method for operating a pure water production system according to claim 4, wherein the concentrated water from the RO device and the high-temperature wastewater are introduced into the neutralization tank.

8. 8. The method for operating a pure water producing system according to claim 7, wherein the water in the storage tank is circulated through the second heat exchanger.

9. 9. The method for operating a pure water production system according to claim 4, 7 or 8, wherein the high-temperature wastewater is boiler drain water.

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