JP6994376B2 - Pure water production equipment and its operation method - Google Patents

Description

The present invention relates to a pure water production apparatus and an operation method thereof.

Conventionally, as a device for producing pure water (purified water, water for injection, etc.) used for pharmaceutical production, etc., it has a back-penetration film (RO film) or nanofiltration film (NF film), and is used for industrial water and well water. , A membrane filtration device that separates raw water such as city water into permeated water and concentrated water, and an electric deionized water production device that produces deionized water (pure water) by passing the permeated water through an ion exchanger. A pure water production device in combination with is known.

Due to the nature of producing pure water used for manufacturing pharmaceuticals, such pure water production equipment reduces the number of viable bacteria in the system in order to meet the demands of the pharmacopoeia of each country such as the Japanese Pharmacopoeia. The sterilization process is performed regularly. This sterilization treatment is generally performed by passing hot water having a temperature of 60 ° C. or higher through the system.

Patent Document 1 describes hot water supplied from a membrane filtration device to an electric deionized water production device when water is passed by hot water for the purpose of stably maintaining the temperature and flow rate of hot water. A method of adjusting the pressure of permeated water) to the set pressure has been proposed. According to this method, it is expected that the sterilization treatment is surely carried out by maintaining the temperature and the flow rate of the hot water in a stable manner.

Japanese Unexamined Patent Publication No. 2014-124481

However, as described in Patent Document 1, even if the pressure of hot water from the membrane filtration device is adjusted to the set pressure, if the pressure loss on the downstream side of the membrane filtration device increases due to aging, the pressure loss on the downstream side of the membrane filtration device increases. The flow rate of hot water on the downstream side is lower than the initial flow rate. Therefore, there is a possibility that the temperature of the hot water will drop due to heat dissipation due to the decrease in the flow rate, and sufficient sterilization treatment will not be performed. Such an increase in pressure loss due to aging is particularly remarkable in an electric deionized water producing apparatus because the ion exchange membrane and the ion exchange resin are deformed by repeating expansion and contraction due to heat. This may occur similarly in an ion exchange device also equipped with an ion exchange resin, and further in a separation membrane such as a microfiltration membrane (MF membrane) or an ultrafiltration membrane (UF membrane). May occur in.

Therefore, an object of the present invention is to provide a pure water production apparatus capable of stably performing a sterilization treatment with hot water for a long period of time and an operation method thereof.

In order to achieve the above-mentioned object, the pure water production apparatus of the present invention is applied to a membrane filtration apparatus having a back-penetrating membrane or a nanofiltration membrane that separates the water to be treated into permeated water and concentrated water, and the membrane filtration apparatus. A supply line for supplying treated water, a permeated water line for circulating permeated water from the membrane filtering device, a concentrated water line for circulating concentrated water from the membrane filtering device, and a supply line provided for the membrane filtering device. A pressure adjusting means for adjusting the supply pressure of the water to be treated, a heating means provided on the upstream side of the pressure adjusting means of the supply line to heat the water to be treated supplied to the membrane filtration device, and a permeated water line. , Controls the pressure adjusting means based on the flow rate detecting means for detecting the flow rate of the permeated water flowing through the permeated water line and the flow rate of the permeated water detected by the flow rate detecting means, and sets the flow rate of the permeated water flowing through the permeated water line. It has a flow control means for adjusting the flow rate, and the flow control means is from the water to be treated and the membrane filtering device supplied to the membrane filtering device when the water to be treated is heated to 45 ° C. or higher by the heating means. The set flow rate of the permeated water flowing through the permeated water line is determined based on the water temperature of either the permeated water or the concentrated water from the membrane filtration device.

Further, in the operation method of the pure water production apparatus of the present invention, the membrane filtration apparatus having a back-penetrating membrane or a nanofiltration membrane that separates the water to be treated into permeated water and concentrated water, and the membrane filtration apparatus are supplied with the water to be treated. It is an operation method of a pure water production apparatus having a supply line, a permeated water line for circulating permeated water from the membrane filtration device, and a concentrated water line for circulating concentrated water from the membrane filtration device. Hot water of 45 ° C or higher is supplied to the membrane filtration device through the process, and the supply line, the membrane filtration device, the permeated water line, and the concentrated water line are sterilized by the hot water, and the hot water to the membrane filtration device during sterilization. The process of adjusting the flow rate of hot water including the step of adjusting the supply pressure of the hot water flowing through the permeated water line to the set flow rate is the step of adjusting the flow rate of hot water between the supply line, the permeated water line and the concentrated water line. It involves determining the set flow rate of hot water flowing through the permeated water line based on the water temperature of the hot water flowing through either.

According to such a pure water production device and its operation method, even if the pressure loss on the downstream side of the membrane filtration device fluctuates due to aging, the flow rate of permeated water (hot water) flowing through the permeated water line can be increased. It can be kept constant. As a result, it is possible to suppress the decrease in the water temperature of the hot water due to the decrease in the flow rate, and it is possible to stably carry out the sterilization treatment with the hot water.

As described above, according to the present invention, it is possible to provide a pure water production apparatus and an operation method thereof that can stably carry out sterilization treatment with hot water for a long period of time.

It is a schematic diagram which shows the structure of the pure water production apparatus which concerns on one Embodiment of this invention. It is a graph which shows the correspondence relationship between the water temperature of raw water and the set flow rate of permeation water in the membrane filtration apparatus provided with the reverse osmosis membrane.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view showing the configuration of a pure water production apparatus according to an embodiment of the present invention.

The pure water production device 1 has a raw water tank 2, a membrane filtration device 3, an electric deionized water production device 4, and a separation membrane 5, and sequentially treats the water to be treated (raw water) to produce pure water. It is manufactured. Further, the pure water production apparatus 1 has a control unit 6 that controls the operation of the pure water production apparatus 1.

The membrane filtration device 3 is a device that removes impurities in the raw water supplied from the raw water tank 2 to generate permeated water, and divides the raw water into concentrated water containing impurities and permeated water from which impurities have been removed. It has a reverse osmosis membrane (RO membrane) or a nanofiltration membrane (NF membrane) to be separated. The membrane filtration device 3 includes a supply line L1 for supplying raw water to the membrane filtration device 3, a permeation water line L2 for circulating permeated water from the membrane filtration device 3, and a concentration for circulating concentrated water from the membrane filtration device 3. It is connected to the water line L3. The concentrated water line L3 is branched into a drainage line L4 that discharges a part of the concentrated water flowing through the concentrated water line L3 to the outside, and a reflux water line L5 that returns the rest of the concentrated water to the supply line L1. A raw water supply line L6 is connected to the raw water tank 2, and raw water is supplied as needed.

The supply line L1 is provided with a temperature sensor 11, a water pump 12, a heat exchanger 13, a temperature sensor 14, an activated carbon filter 15, a pressurizing pump 16, and a flow rate adjusting valve 17. The activated carbon filter 15 does not necessarily have to be provided and may be omitted. The permeated water line L2 is provided with a flow rate adjusting valve 21 and a permeated water flow meter 22, and the concentrated water line L3 is provided with a constant flow rate valve 31 and a flow rate adjusting valve 32. The drainage line L4 is provided with a flow rate adjusting valve 41 and a drainage flow meter 42, and the recirculation water line L5 is provided with a manual valve 51. The reflux water line L5 is connected between the activated carbon 15 of the supply line L1 and the pressurizing pump 16.

The temperature sensor 11 is provided to detect the temperature of hot water for heat sterilization during the sterilization step described later. The water pump 12 is provided together with the pressurizing pump 16 to supply the raw water stored in the raw water tank 2 to the membrane filtration device 3, and the rotation speed is controlled by an inverter (not shown) as needed. It has become like. The heat exchanger 13 functions as a heating means for heating the raw water supplied to the membrane filtration device 3, and is provided to generate the hot water for heat sterilization described above. The temperature sensor 14 functions as a water temperature detecting means for detecting the temperature of the raw water supplied to the membrane filtration device 3. The activated carbon filter 15 is provided to remove chlorine from the raw water supplied to the membrane filtration device 3. The rotation speed of the pressurizing pump 16 is controlled by an inverter (not shown), and also functions as a pressure adjusting means for adjusting the supply pressure of raw water to the membrane filtration device 3.

The permeated water flow meter 22 has a function of detecting the flow rate of the permeated water flowing through the permeated water line L2, and the constant flow valve 31 has a function of keeping the flow rate of the concentrated water flowing through the concentrated water line L3 constant. ing. The flow rate adjusting valve 41 functions as a flow rate adjusting means for adjusting the flow rate of the concentrated water (hereinafter referred to as "concentrated drainage") flowing through the drainage line L4, and the drainage flow meter 42 has a function of detecting the flow rate of the concentrated drainage. is doing. The manual valve 51 functions as a pressure adjusting valve for adjusting the pressure balance between the concentrated water flowing through the drainage line L4 and the concentrated water flowing through the recirculation water line L5. The functions of the flow rate adjusting valves 17, 21, and 32 will be described later together with the explanation of the sterilization process.

The electric deionized water producing apparatus 4 is an apparatus that simultaneously performs a deionization (desalting) treatment of the water to be treated by an ion exchanger and a regeneration treatment of the ion exchanger. A permeated water line L2 is connected to the electric deionized water producing device 4, so that the permeated water from the membrane filtration device 3 is supplied as the water to be treated. Further, the electric deionized water production apparatus 4 is connected to a treated water line L7 that circulates the produced treated water (deionized water) and supplies it to the treated water tank or the point of use.

The electric deionized water production apparatus 4 is, for example, an anode and a cathode, a desalting chamber arranged between the anode and the cathode and filled with at least one of a cation exchanger and an anion exchanger, and an ion exchange membrane. It has a pair of concentration chambers arranged on both sides of the desalting chamber via the. The permeated water supplied from the membrane filtration device 3 is passed through the desalting chamber to remove ionic components, flows out of the desalting chamber as treated water (deionized water), and is passed through the treated water line L7 to the treated water tank or. Supplied to use points. On the other hand, the ionic component removed in the desalting chamber moves to the concentrating chamber adjacent to the desalting chamber due to the potential difference generated by applying a DC voltage between the two electrodes, and becomes concentrated water supplied to the concentrating chamber. It is captured. The electric deionized water production apparatus 4 is connected to a concentrated water discharge line L8 for discharging the concentrated water that has taken in the ionic component to the outside. In the desalting chamber, a water dissociation reaction (a reaction in which water dissociates into hydrogen ions and hydroxide ions) is continuously proceeding, and these hydrogen ions and hydroxide ions exchange ions in the desalting chamber. The ion exchanger in the desalting chamber is regenerated by being exchanged with the ion component adsorbed on the body.

The separation membrane 5 is a microfiltration membrane (MF membrane) or an ultrafiltration membrane (UF membrane), and is fine particles, microorganisms, and endotoxins in the treated water (deionized water) produced by the electric deionized water producing apparatus 4. It is provided in the treated water line L7 in order to remove such a substance. A cross-flow method can also be used as the filtration method for the UF membrane. A valve V1 is provided on the downstream side of the separation membrane 5 of the treated water line L7, and the treatment connected to the raw water tank 2 via the valve V2 between the separation membrane 5 and the valve V1 of the treated water line L7. The water recirculation line L9 is connected. As a result, the treated water produced by the electric deionized water producing apparatus 4 is returned to the raw water tank 2 at the time of starting the apparatus, restarting the operation, or when there is no demand for the treated water (pure water) at the point of use. It is also possible to perform circulation operation. Further, a valve V3 is provided in the concentrated water discharge line L8, and a concentrated water recirculation line L10 connected to the raw water tank 2 via the valve V4 is provided on the upstream side of the bubble V3 of the concentrated water discharge line L8. ing. Thereby, depending on the water quality of the concentrated water, a part or all of the concentrated water can be returned to the raw water tank 2.

As a treatment means for treating the permeated water from the membrane filtration device 3, instead of or together with the electric deionized water production device 4, ions such as a non-regenerative mixed bed type ion exchange device (cartridge polisher) are used. An exchange device may be provided. Further, another membrane filtration device may be added between the membrane filtration device 3 and the electric deionized water production device 4, or instead of the electric deionized water production device 4.

The control unit 6 controls the pressurizing pump 16 based on the flow rate of the permeated water detected by the permeated water flow meter 22 during the normal operation (pure water production) of the pure water production device 1 and flows through the permeated water line L2. It functions as a flow rate control means that adjusts the flow rate of permeated water to the set flow rate. Specifically, the control unit 7 controls the rotation speed of the pressurizing pump 16 so that the flow rate of the permeated water detected by the permeated water flow meter 22 becomes constant (a preset target flow rate). That is, as the water temperature decreases, the viscosity of the water increases, and as a result, the flow rate of the permeated water separated by the RO membrane or the NF membrane decreases. Therefore, the control unit 6 increases the supply pressure of the raw water by increasing the rotation speed of the pressurizing pump 16 so as to compensate for this decrease. Further, as the water temperature increases, the viscosity of the water decreases, and as a result, the flow rate of the permeated water separated by the RO membrane or the NF membrane increases. Therefore, the control unit 6 lowers the supply pressure of the raw water by lowering the rotation speed of the pressurizing pump 16 so as to cancel out this increase. In this way, the control unit 6 can maintain a constant flow rate of the permeated water from the membrane filtration device 3 by adjusting the rotation speed of the pressurizing pump 13, that is, the supply pressure of the raw water.

The flow rate of concentrated water separated by the RO membrane or NF membrane of the membrane filtration device 3 also changes according to the change in the supply pressure of raw water to the membrane filtration device 3 (change in the rotation speed of the pressurizing pump 16). However, the concentrated water line L3 is provided with a constant flow valve 31 as described above. As a result, even when the rotation speed of the pressurizing pump 16 changes and the supply pressure of the raw water changes, the flow rate of the concentrated water flowing through the concentrated water line L3 can be kept constant. As a result, the flow rate control of the permeated water does not affect the flow rate of the concentrated water flowing through the drainage line L4 and the recirculation water line L5. Therefore, for example, the flow rate control of the concentrated drainage for adjusting the recovery rate of the membrane filtration device 3, that is, the flow rate control for adjusting the opening degree of the flow rate adjusting valve 41 based on the flow rate of the concentrated drainage detected by the drainage flow meter 42. It is possible to prevent it from interfering with the flow rate control of the permeated water even when the above is performed.

The pure water production apparatus 1 of the present embodiment produces pure water used for manufacturing pharmaceuticals and the like, and therefore, it is necessary to periodically perform a sterilization treatment for reducing the viable cell count in the system. Therefore, the control unit 6 also periodically executes sterilization treatment in the system with hot water between the production of pure water during normal operation. Hereinafter, this hot water sterilization method will be described in detail.

(Sterilization preparation process)
The sterilization preparation step is a preparatory step for sterilizing the pure water production apparatus 1 with hot water, and is a step of replacing the raw water stored in the raw water tank 2 with treated water (pure water). However, when hot water sterilization is performed by heating raw water instead of pure water, the sterilization preparation step can be omitted.

In the sterilization preparation step, normal operation is performed in the pure water production apparatus 1, and after the raw water in the raw water tank 2 is discharged to the outside, the pure water produced by the pure water production apparatus 1 is supplied to the raw water tank 2. It is stored. That is, when the sterilization preparation step is started, the supply of raw water from the raw water supply line L6 to the raw water tank 2 is stopped, and the raw water stored in the raw water tank 2 is supplied to the membrane filtration device 3 through the supply line L1. The separated concentrated water is discharged to the outside from the drainage line L4. On the other hand, the raw water supply line L6 and the supply line L1 are directly connected, the raw water is supplied from the raw water supply line L6 to the supply line L1, and the pure water production apparatus 1 performs normal operation. Then, the valve V1 of the treated water line L7 is closed, the valve V2 of the treated water recirculation line L9 is opened, and the treated water (pure water) flowing through the treated water line L7 is passed through the treated water recirculation line L9 to the raw water tank 2. Is stored in.

In the sterilization preparation step, the concentrated water of the electric deionized water production apparatus 4 is discharged to the outside through the concentrated water discharge line L8, or depending on the water quality of the concentrated water, the raw water tank is discharged through the concentrated water recirculation line L10. It is refluxed to 2. Further, the electrode water supplied to the electrode chamber (anode chamber provided with an anode and the cathode chamber provided with a cathode) of the electric deionized water producing apparatus 4 is discharged to the outside.

(Heating process and hot water sterilization process)
The temperature raising step is a step of heating the pure water stored in the raw water tank 2 to about 60 ° C. or higher, preferably about 90 ° C. by the heat exchanger 13 while circulating it in the system. In the hot water sterilization step, the supply line L1, the membrane filtration device 3, the permeated water line L2, the electric deionized water production device 4, the treated water line L8, and the treated water recirculation line L9 are formed by circulating the hot water thus generated. This is a step of sterilizing the inside of the system of the pure water production apparatus 1 including.

The temperature raising step is started when it is determined by the water level gauge (not shown) provided in the raw water tank 2 that the water level in the raw water tank 2 has reached a predetermined upper limit water level or higher in the sterilization preparation step. When the temperature raising step is started, the connection between the raw water supply line L6 and the supply line L1 is disconnected, and the supply of raw water from the raw water supply line L6 to the supply line L1 is stopped. Then, the pure water in the raw water tank 2 is circulated through the supply line L1, the permeated water line L2, the treated water line L7, and the treated water recirculation line L9. At the same time, the heat exchanger 13 heats the circulating pure water to 60 ° C to 90 ° C. By circulating the hot water thus generated, the hot water sterilization step is executed, and the inside of the system of the pure water production apparatus 1 is sterilized. In the hot water sterilization step, the flow control valve 41 of the drainage line L4 is closed and the manual valve 51 of the recirculation water line L5 is opened, so that the concentrated water line L3 and the recirculation water line L5 are also sterilized by hot water. To. Further, the valve V3 of the concentrated water discharge line L8 of the electric deionized water production apparatus 4 is closed, and the valve V4 of the concentrated water recirculation line L10 is opened, so that the concentrated water recirculation line L10 is also sterilized.

The rate of temperature rise in the temperature rise step is preferably about 1 to 2 ° C./min in order to reduce damage to the membrane filtration device 3 and the electric deionized water production device 4. The time required for the hot water sterilization step varies depending on the temperature of the hot water, but is preferably about 20 to 60 minutes for sufficient sterilization treatment. For example, it may take about 60 minutes to circulate hot water at 60 ° C, about 30 minutes to circulate hot water at 80 ° C, and about 20 minutes to circulate hot water at 90 ° C. preferable. Here, the temperature of the hot water in the hot water sterilization step is adjusted based on the value detected by the temperature sensor 11, but the position of the temperature sensor 11 is as far as possible from the heat exchanger 13 in the hot water circulation direction. The position is not particularly limited, and may be, for example, between the water supply pump 12 and the heat exchanger 13, or may be on the treated water recirculation line L9. In other words, it is not preferable to use the temperature sensor 14 installed immediately after the heat exchanger 13 in the hot water circulation direction instead of the temperature sensor 11, and in the present embodiment, the two temperature sensors 11 and 14 are separate. It is preferable that it is provided in.

In the hot water sterilization step, the flow rate is controlled by the control unit 6 as in the normal operation, and the flow rate of the permeated water (hot water) flowing through the permeated water line L2 is adjusted to the set flow rate. As a result, the flow rate of hot water flowing through the permeated water line L2, that is, the circulating flow rate of hot water can be kept constant regardless of the fluctuation of the pressure loss on the downstream side of the membrane filtration device 3. In other words, even when the pressure loss of the electric deionized water production apparatus 4 increases due to repeated sterilization treatment with hot water, or the pressure loss of the separation membrane 5 increases due to aging, the hot water also increases. It is possible to suppress a decrease in the circulating flow rate from the initial flow rate, and it is possible to suppress a decrease in the temperature of hot water due to heat dissipation accompanying the decrease in the flow rate. As a result, even when the sterilization treatment with hot water is repeatedly performed, the circulating flow rate of the hot water can be stably maintained, and the sterilization treatment can be stably carried out.

However, although the operating temperature range and operating pressure range recommended by the manufacturer are set for the RO membrane or NF membrane of the membrane filtration device 3, the temperature of hot water in the hot water sterilization step is generally the operating temperature. It will exceed the range. Therefore, in consideration of safety, in the hot water sterilization step, it is preferable to keep the supply pressure of the raw water to the membrane filtration device 3 within a safe pressure range that is lower than the above-mentioned operating pressure range. Therefore, in the present embodiment, the control unit 6 permeates the permeated water line L2 based on the temperature of the hot water detected by the temperature sensor 14 through the temperature raising step, the hot water sterilization step, and the temperature lowering step described later. The set flow rate of water (hot water) is determined. As a result, even if the water temperature deviates from the above-mentioned operating temperature range, the set flow rate of the permeated water (hot water) is set to a flow rate such that the supply pressure of the raw water to the membrane filtration device 3 falls within the safe pressure range. By doing so, it is possible to carry out safe driving. As a result, the pure water production apparatus 1 can be stably operated for a long period of time.

In order to determine the set flow rate of the permeated water (hot water), either the raw water supplied to the membrane filtration device 3, the permeated water from the membrane filtration device 3, or the concentrated water from the membrane filtration device 3 is determined. It suffices if the water temperature is detected. Therefore, the position of the temperature sensor 14 is not limited to the supply line L1 and may be on the permeated water line L2 or the concentrated water line L3.

The set flow rate of the permeated water (hot water) is preferably as large as possible in order to realize sufficient sterilization treatment and shorten the time required for sterilization treatment. Therefore, it is preferable that the set flow rate when the temperature of the raw water is within the operating temperature range is determined so that the supply pressure of the raw water to the membrane filtration device 3 becomes the maximum within the operating pressure range. On the other hand, when the temperature of the raw water exceeds the operating temperature range, the set flow rate is preferably determined so that the supply pressure of the raw water to the membrane filtration device 3 becomes maximum within the set pressure range. Here, the "set pressure range" is obtained by an experiment in advance separately from the above-mentioned operating pressure range, and the pressure range in which the film is not damaged is obtained for each temperature. As an example, FIG. 2 shows a graph showing the correspondence between the water temperature of raw water and the set flow rate of permeated water in the membrane filtration device 3 provided with the RO membrane.

In the example shown in FIG. 2, the operating temperature range of the RO membrane is less than 45 ° C., and the set flow rate of the permeated water in this temperature range is determined based on the operating pressure range and is constant regardless of the water temperature. On the other hand, when the water temperature of the raw water is 45 ° C. or higher, the set flow rate of the permeated water is determined based on the set pressure range and changes from 1300 L / h to 2170 L / h according to the water temperature. By changing the set flow rate of the permeated water according to the water temperature in this way, the supply pressure of the raw water to the membrane filtration device 3 can be adjusted to the operating pressure range of the RO membrane through the temperature raising step, the hot water sterilization step, and the temperature lowering step described later. Can be maintained in a safe pressure range below. In addition, in this specification, "hot water" means the temperature range to which this set pressure range is applied, that is, water of 45 degreeC or more. Further, the set flow rate of the permeated water shown in FIG. 2 is merely an example, and is not limited thereto.

By the way, in the hot water sterilization step, even if the rotation speed of the pressurizing pump 16 is adjusted to the lower limit value, the supply pressure of the raw water to the membrane filtration device 3 may exceed the set pressure range described above. Even in this case, the supply pressure of the raw water to the membrane filtration device 3 can be kept within the set pressure range by reducing the opening degree of the flow rate adjusting valve 17 provided in the supply line L1. Further, when the pressure loss is extremely low in the permeated water line L2 and its downstream side, hot water flows too much in the permeated water line L2, which makes it difficult for hot water to flow in the concentrated water line L3, resulting in. As a result, the concentrated water line L3 may not be sufficiently sterilized. Even in that case, the flow rate of the hot water flowing through the permeated water line L2 can be reduced by reducing the opening degree of the flow rate adjusting valve 21 provided in the permeated water line L2, and therefore, the flow rate flows through the concentrated water line L3. The flow rate of hot water can be increased.

On the other hand, when the pressure loss is extremely low in the concentrated water line L3 and its downstream side, hot water flows too much in the concentrated water line L3, which makes it difficult for hot water to flow in the permeated water line L2. As a result, the sterilization treatment may not be sufficiently performed on the downstream side of the permeated water line L2. On the other hand, in the present embodiment, since the constant flow valve 31 is provided in the concentrated water line L3, the flow rate of the hot water flowing through the concentrated water line L3 can be kept constant even in the hot water sterilization step. can. However, when the pressure loss is extremely high on the permeated water line L2 and its downstream side, the pressure difference between the primary side and the secondary side of the constant flow rate valve 31 is within the operating differential pressure range (primary side and secondary side of the constant flow rate valve). The allowable range of the pressure difference on the side) may be exceeded, and hot water may flow too much to the concentrated water line L3. Even in that case, by narrowing the opening degree of the flow rate adjusting valve 32 provided in the concentrated water line L3, the pressure difference between the primary side and the secondary side of the constant flow rate valve 31 can be kept within the operating differential pressure range. The constant flow valve 31 can be operated normally.

(Temperature lowering process)
The temperature lowering step is a step of cooling the hot water to a temperature suitable for pure water production in order to restart the normal operation after the hot water sterilization step is completed.

In the temperature lowering step, the heat exchanger 13 cools the circulating hot water to less than 45 ° C., and then the normal operation of the pure water production apparatus 1 is restarted. Then, the valve V2 of the treated water recirculation line L9 is closed, the valve V1 of the treated water line L7 is opened, and the pure water produced by the pure water production apparatus 1 is supplied to the treated water tank or the point of use. At this time, the raw water tank 2 and the raw water supply line L6 are connected, and raw water is supplied to the raw water tank 2 through the raw water supply line L6 as needed.

In the temperature lowering step, in addition to cooling the hot water with the heat exchanger 13, for example, the hot water can be cooled by mixing the unheated raw water with the hot water. That is, the temperature of the circulating hot water is obtained by supplying unheated raw water to the raw water tank 2 through the raw water supply line L6 while discharging a part of the circulating hot water to the outside through, for example, the concentrated water discharge line L8. Can be lowered. In any case, the temperature lowering rate in the temperature lowering step is 1 to 2 ° C./1 in order to reduce the influence of temperature fluctuations on the members constituting the membrane filtration device 3 and the electric deionized water production device 4. It is preferably about a minute.

1 Pure water production equipment 2 Raw water tank 3 Film filtration equipment 4 Electric deionized water production equipment 5 Separation membrane 6 Control unit 11, 14 Temperature sensor 12 Water supply pump 13 Heat exchanger 15 Activated charcoal filter 16 Pressurized pump 17, 21, 32, 41 Flow control valve 22 Permeation water flow meter 31 Constant flow valve 42 Drainage flow meter 51 Manual valve L1 Supply line L2 Permeation water line L3 Concentrated water line L4 Drainage line L5 Recirculated water line L6 Raw water supply line L7 Treated water line L8 Concentration Water discharge line L9 Treated water recirculation line L10 Concentrated water recirculation line V1 to V4 Valve

Claims (7)

A membrane filtration device having a reverse osmosis membrane or a nanofiltration membrane that separates the water to be treated into permeated water and concentrated water,
A supply line that supplies water to be treated to the membrane filtration device,
A permeated water line that circulates permeated water from the membrane filtration device,
A concentrated water line that distributes concentrated water from the membrane filtration device,
A pressure adjusting means provided in the supply line to adjust the supply pressure of the water to be treated to the membrane filtration device, and
A heating means provided on the upstream side of the pressure adjusting means of the supply line to heat the water to be treated supplied to the membrane filtration device, and a heating means.
A flow rate detecting means provided in the permeated water line and detecting the flow rate of the permeated water flowing through the permeated water line.
It has a flow rate control means that controls the pressure adjusting means based on the flow rate of the permeated water detected by the flow rate detecting means and adjusts the flow rate of the permeated water flowing through the permeated water line to a set flow rate.
When the water to be treated is heated to 45 ° C. or higher by the heating means, the flow control means includes the water to be treated supplied to the membrane filtration device, the permeated water from the membrane filtration device, and the membrane filtration device. A pure water production apparatus that determines the set flow rate of permeated water flowing through the permeated water line based on the water temperature of any of the concentrated water. The pure water production apparatus according to claim 1, further comprising a reflux water line that branches from the concentrated water line, is connected to the supply line, and returns at least a part of the concentrated water flowing through the concentrated water line to the supply line. .. The pure water production apparatus according to claim 2, further comprising a constant flow rate valve provided in the concentrated water line and maintaining a constant flow rate of concentrated water flowing through the concentrated water line. A treatment means for treating permeated water from the membrane filtration apparatus, the present invention comprising at least one of an electric deionized water production apparatus, an ion exchange apparatus, an ultrafiltration membrane, and a microfiltration membrane. Item 5. The pure water production apparatus according to any one of Items 1 to 3. A treated water line for circulating treated water from the treated means and a treated water branched from the treated water line and connected to the upstream side of the heating means of the supply line and flowing through the treated water line to the supply line. It has a treated water recirculation line to recirculate,
The pure water production apparatus according to claim 4, wherein the treated water heated by the heating means and supplied to the membrane filtration device is the treated water that is refluxed from the treated water recirculation line to the supply line. It has a flow rate adjusting valve provided between the pressure adjusting means of the supply line and the membrane filtration device.
The pure water production apparatus according to any one of claims 1 to 5, wherein the flow rate control means controls the pressure adjusting means and the flow rate adjusting valve based on the flow rate detected by the flow rate detecting means. .. A membrane filtration device having a back-penetration membrane or nanofiltration membrane that separates the water to be treated into permeated water and concentrated water, a supply line that supplies the water to be treated to the membrane filtration device, and permeated water from the membrane filtration device. A method of operating a pure water production apparatus having a permeated water line for circulating water and a concentrated water line for circulating concentrated water from the membrane filtration device.
A step of supplying hot water having a temperature of 45 ° C. or higher to the membrane filtration device through the supply line and sterilizing the supply line, the membrane filtration device, the permeated water line, and the concentrated water line with the hot water.
During the sterilization, a step of adjusting the supply pressure of hot water to the membrane filtration device to adjust the flow rate of hot water flowing through the permeated water line to a set flow rate is included.
The step of adjusting the flow rate of the hot water is the set flow rate of the hot water flowing through the permeated water line based on the water temperature of the hot water flowing through any of the supply line, the permeated water line and the concentrated water line. How to operate a pure water production device, including determining.

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