JPH0450073B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method of controlling an ultrapure water production apparatus.

[Background of the invention]

Generally, ultrapure water production systems connect multiple stages of pure water production equipment in series to increase the purity one after another, and the final stage subsystem, the so-called ultrapure water production equipment, produces ultrapure water close to theoretical purity. Ultrapure water is usually produced using raw water such as industrial water, tap water, or a mixture of raw water and recovered water, and is used, for example, as cleaning water for semiconductors such as ICs and LSIs.

FIG. 2 shows a typical flow of a conventional ultrapure water production device (subsystem).

The ultrapure water production device 1 includes a pure water tank 2, a circulation pump 3, a flow rate setting valve 4, a flow meter 5, an ultraviolet irradiation device 6, a cartridge polisher 7 filled with ion exchange resin, and a reverse osmosis membrane or ultrafiltration. Membrane processing device 8 consisting of membrane etc., point of use 9, pressure detector 1
0, a pressure control valve 11, and the pure water tank 2 receives pure water from the make-up water pump 12 in the pure water production device (hereinafter referred to as the primary pure water production device) in the previous stage of the ultrapure water production device 1. In addition to being supplied with water, it is also filled with high-purity nitrogen gas to prevent environmental pollution caused by fluctuations in the liquid level. The pure water in the pure water tank 2 is
The circulating pump 3 sequentially passes through an ultraviolet irradiation device 6, a cartridge polisher 7, and a membrane treatment device 8, and the water is sterilized and processed to remove impurities such as fine particles, organic matter, and ions to become ultrapure, and the water is supplied to a use point 9. consumed. At this time, the pure water supplied from the circulation pump 3 to the ultraviolet irradiation device 6 is adjusted to a preset flow rate by the flow rate setting valve 4 while the flow rate is detected by the flow meter 5.

On the other hand, the remaining ultrapure water consumed at the use point 9 returns to the pure water tank 2 through the pressure control valve 11, but even if the amount of ultrapure water consumed changes, the discharge pressure of the ultrapure water at the use point 9 is To maintain the required pressure,
The pressure is detected by the pressure detector 10 and the pressure regulating valve 1 is
1 adjusts the pressure to the set pressure.

Then, pure water is replenished from the make-up water pump 12 by the amount that the liquid level in the deionized water tank 2 falls below a predetermined value.

By the way, in such an ultrapure water production apparatus 1, if pure water or ultrapure water stagnates, viable bacteria will propagate, which will lead to a decrease in the purity of the ultrapure water. However, it has been pointed out that piping alone cannot solve the problem of stagnation.

In other words, the ultrapure water production equipment 1 is equipped with a pure water tank 2 that constantly stores pure water in order to absorb fluctuations in the amount of ultrapure water consumed at the point of use 9. Purified water stagnates in the deionized water tank 2, and as the operating time increases, viable bacteria and fine particles in the deionized water tank 2 increase.

In addition to the above-mentioned retention problem, the pure water tank 2
It has also been pointed out that high purity nitrogen is constantly consumed due to fluctuations in the liquid level, and that the area occupied by the pure water tank 2 occupies a considerable proportion of the ultrapure water production apparatus 1.

Therefore, when the pure water tank 2 is removed from the ultrapure water production equipment 1, the amount of ultrapure water consumed at the use point 9 is not always constant, and there are times when a large amount is consumed and times when it is not consumed at all. Therefore, it is necessary to quickly correct the flow rate and pressure in accordance with fluctuations in consumption.

[Purpose of the invention]

The present invention was made in view of this point of view, and is an ultrapure water production device that does not have a pure water tank and can always meet the required consumption of ultrapure water at the point of use. The purpose of this invention is to provide a control method for the following.

[Summary of the invention]

The gist of the present invention for achieving the purpose of the present invention is that it consists of an ultraviolet irradiation device, an ion exchange resin tower, a membrane treatment device, a circulation pump placed upstream of the ultraviolet irradiation device, etc. A first system that sequentially passes pure water through these to produce ultrapure water and supplies it to the use point, and returns unused ultrapure water at the use point to the inlet side of the circulation pump of the first system. and a second system to which primary pure water is supplied from the water supply pump of the primary pure water manufacturing apparatus disposed in the preceding stage, in which the flow rate of the first system is detected. , the rotation speed of the circulation pump of the first system is controlled so that the flow rate of the first system becomes a preset flow rate, the flow rate of the second system is detected, and the flow rate of the first system is controlled. Ultrapure water characterized by controlling the rotation speed of the water supply pump of the primary pure water production device so that the second system is supplied with primary pure water by the difference in flow rate between the flow rate and the second system. It is in the manufacturing method of the manufacturing equipment.

[Embodiments of the invention]

The present invention will be described in detail below based on embodiments shown in the drawings.

FIG. 1 shows the flow of one embodiment of the present invention.

The ultrapure water production device 20 of this embodiment has a closed-loop circulation system by connecting a circulation pump 3, an ultraviolet irradiation device 6, a cartridge polisher 7, and a membrane treatment device 8 in series, and the water is consumed at a point of use 9. The remaining ultrapure water is returned to the inlet side of the circulation pump 3, and pure water from the make-up water pump 12 of the primary pure water production device is directly supplied to the circulation pump 3.

Note that the rotational speed of the circulation pump 3 and the make-up water pump 12 of this embodiment is controlled by an inverter, respectively.

Reference numeral 21 denotes a first flow rate detector that detects the discharge flow rate Q ₁ of the circulation pump 3. The detected discharge flow rate Q ₁ of the circulation pump 3 is output to a control device 22 consisting of a microcomputer or the like.

The control device 22 has the target flow rate _Q2 of the circulation system set in advance, and the discharge flow rate _Q1 of the circulation pump 3 and the target flow rate.
The rotation speed of the circulation pump 3 is controlled so as to correct the variation (Q ₂ -Q ₁ ) by comparing Q ₂ with Q 2 .

23 is a second flow rate detector that detects the flow rate Q ₃ of ultrapure water returning from the use point 9 to the circulation pump 3;
The detected flow rate _Q3 is output to the control device 22. In addition,
24 is a connection from the make-up water pump 12 to the ultrapure water production device 20
This is a check valve to prevent the pure water supplied to the pump from accidentally flowing directly to the point of use 9 without passing through the circulation pump 3, the ultraviolet irradiation device 6, etc.

In addition to controlling the rotation speed of the circulation pump 3 described above, the control device 22 compares the flow rate Q ₁ detected by the first flow rate detector 21 and the flow rate Q ₃ detected by the second flow rate detector 23, and calculates the difference ( The rotation speed of the make-up water pump 12 is controlled so as to replenish water (Q ₁ -Q ₃ ).

That is, when ultrapure water is consumed at use point 9, the flow rate returning from use point 9 to circulation pump 3 decreases, and accordingly, the flow rate from use point 9 to circulation pump 3 decreases.
However, since the amount of pure water equivalent to the consumed amount is supplied from the make-up water pump 12 to the circulation pump 3, the pressure on the inlet side of the circulation pump 3 increases, and the supply pressure decreases. This will prevent a drop in pressure.

In addition, even if the consumption amount of ultrapure water at use point 9 fluctuates, the circulation pump 3 will maintain the target flow rate.
Since the discharge flow rate is controlled so that Q ₂ is achieved, the required flow rate can be fully satisfied.

In the above embodiments, only the make-up water pump 12 has been described for the primary water purification apparatus, but for example, an ion exchange resin column, reverse osmosis membrane, ultrafiltration membrane, etc. may be installed before or after the make-up water pump 12. A membrane treatment device may also be provided.

In addition, the ultrapure water production apparatus 20 has an ultraviolet irradiation device 6 disposed after the circulation pump 3, a cartridge polisher 7 is disposed after the circulation pump 3, and an ultraviolet irradiation device 6 and an ultraviolet irradiation device 6 are arranged after the circulation pump 3. A membrane treatment device 8 may also be arranged.

〔Effect of the invention〕

As explained above, according to the present invention, the amount of ultrapure water required at the point of use can be obtained without equipping a pure water tank to absorb fluctuations in the amount of ultrapure water consumed at the point of use. It is possible to always supply in a stable state, and the entire system has 1
Since there is no accumulation of secondary pure water, it is possible to supply highly pure ultrapure water, and the ultrapure water production equipment can be made more compact. Moreover, the nitrogen gas that was previously supplied to the pure water tank is no longer necessary. It will be done.

[Brief explanation of drawings]

FIG. 1 shows the flow of an embodiment of an ultrapure water production apparatus that implements the method of the present invention, and FIG. 2 shows the flow of a conventional ultrapure water production apparatus. DESCRIPTION OF SYMBOLS 1... Ultrapure water production device, 2... Pure water tank, 3... Circulation pump, 4... Flow rate setting valve, 5... Flow meter, 6... Ultraviolet irradiation device, 7... Cartridge polisher, 8... Membrane treatment device, 9... Point of use, 10...Pressure detector, 11...Pressure control valve, 12...Makeup water pump, 2
0... Ultrapure water production equipment, 21, 23 flow rate detector, 2
2...Control device.

Claims (1)

[Scope of Claims] 1 Consists of an ultraviolet irradiation device, an ion-exchange resin tower, a membrane treatment device, and a circulation pump placed upstream of the ultraviolet irradiation device, and the circulation pump sequentially passes primary pure water through these. a first system that produces ultrapure water and supplies it to the use point, and a first system that returns unused ultrapure water at the use point to the inlet side of the circulation pump of the first system, and a and a second system to which primary pure water is supplied from a water supply pump of the secondary pure water manufacturing apparatus, the flow rate of the first system is detected, and the flow rate of the first system is detected. The rotation speed of the circulation pump of the first system is controlled so that the flow rate is a preset flow rate, and the flow rate of the second system is detected, and the flow rate of the first system and the second system are controlled. A method for controlling an ultrapure water production apparatus, characterized in that the rotation speed of a water supply pump of the primary pure water production apparatus is controlled so that primary pure water is supplied to a second system by a flow rate difference of .