JPS6342787A - Automatic hot sterilizing device for ultrapure water feed line - Google Patents

Abstract

PURPOSE:To improve the durability and reliability of secondary side water feed lines by controlling the temp. of hot pure water to be used for sterilization automatically according to an ideal heatup and cooldown curve in a manner as not to affect the water feed lines. CONSTITUTION:The pure water 11 obtd. in a primary side pure water producing device is heated in a heat exchanger 18 of a device for subjecting the secondary side sater feed lines 12-15 for retreatment of the pure water 11 obtd. in the primary side pure water producing device just before a use point 16 to a hot water sterilization treatment. A heat medium is supplied to the heat exchanger 18 in a heat medium supply pipe 19 and a temp. control valve 20 is provided to the heat medium supply pipe 19 at the led to the heat exchanger 18. A temp. detector 21 for the pure water is provided at the proper point of the piping of the secondary side water feed lines. The control valve 20 is automatically controlled in accordance with the signal from the temp. detector 21 in the control circuit of an automatic controller 22. More specifically, the temp. of the hot pure water to be used for the sterilization is automatically controlled in a manner as not to exert an adverse influence to the piping lines, by which the durability of the secondary side water feed lines is improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention performs hot water sterilization treatment on a secondary water supply system in which pure water obtained in a primary water purification device is reprocessed immediately before the point of use. In particular, it improves the durability and reliability of the secondary water supply system by automatically controlling the temperature or temperature and pressure of hot pure water used for sterilization so as not to adversely affect the piping system. This invention relates to an automatic heat sterilizer for ultrapure water supply lines.

[Conventional technology]

In recent years, ultrapure water from which fine particles, colloidal substances, polymeric organic substances, exothermic substances, etc. have been removed as much as possible has been used as water for cleaning semiconductor wafers or chips (hereinafter referred to as semiconductor wafers) in the electronics industry that produces LSIs and VLSIs. is used.

Such water for cleaning semiconductor wafers is usually produced by the following method.

In other words, raw water is treated with a primary water supply device such as a coagulation sedimentation device, sand filter, activated carbon filter, reverse osmosis membrane device, two-bed three-column pure water production device, mixed-bed polisher, precision filter, etc. to produce pure water. immediately before cleaning the semiconductor wafer.
The primary pure water is treated with a secondary water supply device as shown in FIG.

In the secondary water supply system, pure water 2 once stored in a pure water tank 1 is transferred to a mixed bed polisher 3, an ultraviolet irradiation device 4, and a membrane device 5 such as a precision filtration membrane device, an ultrafiltration membrane device, or a reverse osmosis membrane device. This process removes as much as possible of ions, fine particles, colloidal substances, etc. remaining in the purified water for subsequent treatment, thereby producing ultrapure water suitable for cleaning semiconductor sea urchins.

Note that the ultraviolet irradiation device 4 may be installed before the mixed-bed polisher 3, and the ultrapure water that is the permeated water of the membrane device 5 is passed through the use point piping 6 as shown in the dashed line in Fig. 3. The permeated water is transported to a use point 7, where it is used as cleaning water, and the remaining permeated water is returned to the pure water tank 1 through a return pipe 8.

In this way, even though the water to be treated in the secondary water supply system is pure water obtained from the primary water supply system, and even though ultraviolet rays are irradiated just before the point of use, If the ultrapure water supply continues, the amount of raw chestnuts and fine particles leaking into the ultrapure water will increase and exceed the allowable limit.

The cause of this is a small amount of common bacteria that exist in ultrapure water and are resistant to ultraviolet rays.
This is thought to be because they gradually reproduce.

If the membrane device 5, use point piping 6, etc. are contaminated,
Since the water cannot be used for cleaning, it becomes necessary to perform some kind of sterilization treatment, but conventional sterilization methods include methods using oxidizing agents such as hydrogen peroxide solution and sodium hypochlorite solution, and a method using a patent application filed in 1983- No. 74265 discloses a cleaning method using hot water that also includes point-of-use piping.

[Problem that the invention seeks to solve]

When using the above-mentioned chemicals as a method of sterilizing the secondary water supply system, there is a problem of deterioration of the membrane device and piping system, and it is not economical because a large amount of pure water is used for cleaning after sterilization. There is a problem of being at a financial disadvantage.

On the other hand, when a hot water cleaning method is used including the point-of-use piping, it has the advantage of being able to solve the problems associated with chemical treatment, but new problems arise as shown below.

In other words, thermally purified water heated by a heating means such as a heat exchanger reaches a high temperature of 70°C or higher, but this temperature and the pressure inside the pipes have traditionally been controlled manually by operators. In addition to excessive expansion and contraction of piping due to rapid temperature rises and falls, the durability of piping may be adversely affected due to increases in pressure inside the pipes due to rapid temperature rises.
There was a drawback to that. In addition, there is a risk of operator error occurring due to manual operation, and there is a problem that it is not labor-saving.

An object of the present invention is to eliminate the problems associated with the conventional hot water sterilization treatment described above, and to automatically control the temperature or temperature and pressure of hot pure water used for sterilization so as not to affect the piping system. An object of the present invention is to provide an automatic heat sterilizer for an ultrapure water supply system that improves the durability of a secondary water supply system and eliminates operator errors through automation.

[Means for solving problems]

To describe the present invention in detail, in an apparatus for hot water sterilization of a secondary water supply system in which pure water obtained in a primary pure water production apparatus is reprocessed immediately before the point of use, A heat exchanger for heating pure water obtained in a manufacturing device, a heat medium supply pipe that supplies a heat medium to this heat exchanger, and a temperature control valve attached to the heat medium supply pipe leading to the heat exchanger. , equipped with a pure water temperature detector attached to an appropriate position in the piping of the secondary water supply system line, and an automatic regulator having a control circuit that automatically controls the temperature control valve based on a signal from the temperature detector. This is an automatic heat sterilizer for an ultrapure water supply system, and in some cases, a pressure control valve and a pressure detector are attached to appropriate positions in the piping of the secondary side water supply system to control the pressure. A valve and a pressure detector are connected to the automatic regulator in an instrumentation manner. [Function] Hereinafter, the specific structure and function of the device of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is an explanatory diagram showing a flow of an example of an embodiment of the present invention, and in the figure, 10 is pure water 11 obtained from a primary side pure water production device.
This shows a pure water tank that stores water.

The secondary water supply system starting from this pure water tank 10 first passes the pure water in the pure water tank 10 through piping to the mixed bed polisher 12.
, the ultraviolet irradiation device 13 and the membrane device 14, and the permeated water is sent to the use point 1 via the use point piping 15.
6, where it is used as water for cleaning semiconductor wafers. The unconsumed ultrapure water is returned to the pure water tank 10 via the return pipe 17 and is used repeatedly.

Although not shown, the structure is such that the non-permeated water in the membrane device 14 is also returned to the pure water tank 10 via the non-permeated water circulation piping.

The device for hot water sterilization treatment of the secondary water supply system includes a heat exchanger 18 for heating the pure water 11 obtained by the primary pure water production device, and a heat exchanger 18 for heating the pure water 11 obtained by the primary pure water production device, and for supplying hot water or steam to the heat exchanger 18. The heat medium supply pipe 19 that supplies the heat medium, the temperature control valve 20 attached to the heat medium supply pipe 19 leading to the heat exchanger 18, and the temperature control valve 20 of pure water attached to the appropriate position of the piping of the secondary water supply system path. The heat exchanger 1 in this embodiment consists of a detector 21 and an automatic regulator 22 having a control circuit that automatically controls the temperature control valve 20 based on a signal from the temperature detector 21.
8 is attached in a conduit leading from the pure water tank 10 to the mixed bed type polisher 12.

In addition, in order to control the pressure inside the piping as necessary, a pure water is added to the appropriate place in the piping of the secondary water supply system, that is, in this embodiment, in the piping of the use point piping 15 from the membrane device 14 to the use point 16. A water pressure regulating valve 23 and a pressure detector 24 are attached, and the pressure regulating valve 23 is automatically controlled by the automatic regulator 22 based on a signal from the pressure detector 24. Note that if the piping used has excellent pressure resistance, such as a difluoride resin pipe (TVDF), the pressure adjustment mechanism can be omitted.

In addition, 25 in the figure is an automatic valve attached to the heat medium supply pipe 19, 26 is a refrigerant supply pipe arranged to join the heat medium supply pipe 19 as necessary, for example, using room temperature water as a refrigerant, 27 is an automatic valve attached to the refrigerant supply pipe, and opening and closing of both the automatic valves 25 and 27 are controlled by the automatic regulator 22.

28 is a bypass pipe that connects the inlet side and the outlet side of the mixed bed type polisher 12, and the bypass pipe 28 and the mixed bed type polisher 1
Valves 29 and 30 are disposed on the inlet sides of the valves 2 and 2, respectively. In addition, 31 is the return pipe 1 after the use point 16
Pure water return valve attached to 7, 32 is hot water blow piping 33
Each figure shows the hot water blow valve installed inside.

Next, sterilization treatment using hot water in the apparatus of the present invention is performed as follows.

First, the pure water return valve 3 is activated by a signal from the automatic regulator 22.
1 is closed, the hot water blow valve 32 is opened, and the heating process begins.

In the heating process, the heat medium automatic valve 25 is automatically opened in response to a signal from the automatic controller 22 and the heat medium is supplied to the heat exchanger 18. The temperature control valve 20 is automatically controlled by the calculation command from the regulator 22 so that the pure water is heated along a preset temperature increase curve. In order to protect the mixed bed polisher 12 from hot pure water, valve 3 must be closed during hot water sterilization.
Needless to say, the valve 29 is opened to allow hot pure water to pass through the bypass pipe 28.

The pressure in the water supply system gradually rises due to the flow of hot pure water, but this pressure change is transmitted to the automatic regulator 22 by the pressure detector 24, and if the pressure exceeds a predetermined value, For protection, a pressure regulating valve 23 is used to control the pressure as necessary. By passing hot pure water,
Living bacteria, particles, etc. adhering to the membrane device 14 and the piping section of the use point 16 are sterilized and removed, and are discharged to the outside of the system through the hot water blow piping 33.

The cleaning time must be at least 30 minutes or longer, and the heat sterilization treatment is usually continued for about 60 minutes. After a predetermined period of time has elapsed, in the case of the embodiment shown in FIG. Cool the water down to the pure water supply temperature.

All of the above operations are automatically processed using the automatic regulator 22. Note that if the pure water can be cooled along a predetermined temperature drop curve by simply reducing the supply amount of the heat medium using the temperature control valve 20, the supply of the refrigerant can be omitted.

〔Example〕

Hot water sterilization treatment was performed according to the flow shown in FIG. 1 and along the temperature rise/fall curve shown in FIG. 2.

In the heating process, the constant P (proportional band) and I (integral time) values of the calculation command to the temperature control valve 20 of the automatic controller 22 differ depending on each temperature, so the process is divided into three stages, and the heating I
, heating ■, and heating ■.

The values of P for each stage are 80%, 100%, and 12, respectively.
It was set to 0%. Also, the values of I are set to 5 seconds, 20 seconds, and 2, respectively.
It was set to 0 seconds.

The pressure was always maintained at 1.2 kg/cd.

As a result, no abnormality was observed in the piping even if hot water sterilization was performed under the same conditions each time, and it became possible to perform sufficient hot water sterilization automatically.

〔effect〕

As explained above, according to the device of the present invention, the temperature of the hot pure water used for sterilization can be automatically controlled according to the ideal temperature rise/fall curve so as not to affect the water supply line. This dramatically improves the durability of the next water supply system.

In addition, since the pressure inside the pipes is automatically adjusted, it is possible to eliminate the problem of damage to the pipes due to operational errors, which was the case in the past.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of a flow showing an example of an embodiment of the device of the present invention, Fig. 2 is a graph showing temperature rise and fall curves in the heating process of pure water, and Fig. 3 is a diagram of a conventional secondary water supply device. It is an explanatory diagram of a flow. 10: Pure water tank 11: Pure water 12; Mixed bed polisher 13: Ultraviolet irradiation device 14: Membrane device 15 News point piping 16: Use point

Claims (2)

[Claims] (1) In a device for hot water sterilization of the secondary water supply system where the pure water obtained from the primary pure water production equipment is treated again just before the point of use, the pure water obtained from the primary pure water production equipment is A heat exchanger for heating pure water, a heat medium supply pipe that supplies a heat medium to this heat exchanger, a temperature control valve attached to the heat medium supply pipe leading to the heat exchanger, and a secondary side water supply. The system is equipped with a pure water temperature detector attached to a proper place in the piping of the system, and an automatic regulator having a control circuit that automatically controls the temperature control valve based on a signal from the temperature detector. Features: Automatic heat sterilization equipment for ultrapure water supply lines. (2) A pressure regulating valve and a pressure detector are attached to appropriate positions in the piping of the secondary water supply system, and the pressure regulating valve and the pressure detector are instrumentedly connected to the automatic regulator. Automatic heat sterilization device for ultrapure water supply system according to item 1.