JPH09248568A - Production of purified water and purified water reduction device used therefore - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration of water quality of purified water when water level control for maintaining the purified water level in a purified water tank in a constant range is performed. SOLUTION: When raw water supplied from a raw water tank 1 is made into purified water with a water purifying tower 2 and the purified water is stored in the purified water tank 3 the purified water 18 produced with the water purifying tower 2 is circulate to the raw water tank 1 during a period that the water level of the purified water 18 stored in the purified water tank 3 reaches an upper limit, value and then the water level decreases to a prescribed value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pure water producing method and a pure water producing apparatus used therefor,
In particular, it is intended to prevent fluctuations in the amount of raw water supplied to the pure water tower, and consequently to prevent deterioration of the quality of pure water.

[0002]

2. Description of the Related Art For example, in a deionized water cleaning process in a continuous cold-rolled steel sheet manufacturing facility, it is essential to continuously supply deionized water, but the deionized water tower that forms the basis of the deionized water manufacturing apparatus has a fixed amount. Since it is necessary to perform a process for regenerating the ion-exchange resins for each of the Yin and Yang after the production of pure water, it is impossible to continuously produce pure water by one pure water tower. Therefore, conventionally, in a pure water production apparatus in which two pure water towers that are arranged in parallel to each other are connected to a raw water tank, when one of the pure water towers is subjected to regeneration treatment, the other pure water tower is operated in an operating cycle. Is adopted to enable continuous production of pure water.

[0003]

By the way, in such a conventional technique, pure water produced in order to ensure continuous feed of pure water even when the pure water tower to be used is switched. It is necessary to install a buffer tank that stores a certain amount of water, that is, a pure water tank. Here, in such a deionized water tank, it is inevitable to control the water surface level of the deionized water within a certain range. Therefore, in general, a pure water tank having a pure water production capacity larger than the amount of pure water used is required. When the amount of pure water produced by the water production device stored in the pure water tank reaches a specified value, the operation of the device is stopped, while when the amount of stored water decreases to a specified value, the operation of the device is stopped. The water level was controlled by restarting.

However, according to such a water level control, since the raw water supply to the pure water tower is turned on and off, the respective negative and positive ion exchange resins mixed and accommodated in the pure water tower have a difference in specific gravity. There was a problem that the water quality of the pure water produced immediately after the resumption of water flow was significantly reduced. Therefore, in order to solve such a problem, a flow rate adjusting valve that maintains a constant water surface level in the pure water tank is installed on the outlet side of the pure water tower, and pure water in an amount suitable for the amount of pure water delivered from that valve is installed. A technique has been proposed in which the deionized water is introduced into the deionized water tank. However, according to this technique, an expensive flow rate measuring device and an adjusting device are required, and the deionized water supply amount is rapidly increased by stopping the deionized water washing process. When it fluctuates, the opening degree of the flow rate control valve also changes rapidly, so that the same problem as in the water surface level control arises, and there is the inconvenience that the deterioration of the quality of pure water cannot be sufficiently prevented.

The present invention advantageously solves the above-mentioned problems of the prior art. By controlling the water level of the pure water tank by changing the flow path of the pure water produced, the expensive flow rate can be controlled. The quality of pure water can be made sufficiently steady without the need to use a measuring device or adjusting device.
It is another object of the present invention to provide a pure water production method and a pure water production apparatus used for the same, which can maintain high water quality even with a rapid change in the pure water feed rate.

[0006]

A method for producing pure water according to the present invention is a pure water producing apparatus comprising a raw water tank, a plurality of deionized water towers arranged in parallel, and a pure water tank. In producing water, the pure water produced in the pure water tower is charged with the pure water produced in the pure water tower until the water surface level of the pure water stored in the pure water tank reaches the upper limit and the water surface level decreases to a predetermined value. It is to recirculate in a water tank. With this method, regardless of the water level of the pure water tank, the raw water in the raw water tank is constantly supplied to the pure water tower to prevent fluctuations in the amount of raw water supplied to the pure water tower, thus reducing the quality of pure water. In addition, the water level can be effectively controlled by circulating part or all of the pure water that is constantly produced to the raw water tank, depending on the storage amount in the pure water tank. Easy to do.

Further, the pure water producing apparatus of the present invention is a pure water producing apparatus comprising a raw water tank connected in sequence, a plurality of pure water towers arranged in parallel with each other, and a pure water tank. A circulation passage opening to the raw water tank is branched from the water tank. With this device, the method can be carried out with a simple and inexpensive structure in which only a circulation passage is provided.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing one embodiment of the invented apparatus, in which 1 is a raw water tank, 2 is each of two pure water towers in a diagram in which they are arranged in parallel with each other, and 3 is The pure water tank which stores the pure water manufactured by each pure water tower 2 is shown. Here, the raw water tank 1 and each of the pure water towers 2 are connected by a raw water feed passage 4, a raw water pump 5 is provided near the raw water tank, and a raw water pump 5 is provided near the pure water tower. , Each raw water switching valve 6 is provided. Further, the pure water tower 2 and the pure water tank 3 are connected by a pure water passage 7, and the pure water switching valve 8 and the conductivity meter 9 are sequentially provided in the pure water passage 7 from the upstream side. Further, a pure water delivery passage 11 provided with a pure water delivery pump 10 is connected to the pure water tank 3, and this pure water delivery passage 11 is connected.
At, the pure water once stored in the pure water tank 3 is guided to a required cleaning facility or the like. In addition, the water level detection device 1 is provided inside the pure water tank 3.
2 and the ultraviolet sterilizer 13 are provided. Here, in this device, at a position downstream of the conductivity meter 9,
A reflux passage 14 is provided to branch from the pure water passage 7, the tip of the reflux passage 14 is opened to the raw water tank 1, a reflux switching valve 15 is provided at the branch base of the reflux passage 14, and a reflux flow of the pure water passage 7 is controlled. Pure water discharge valves 16 are provided at the downstream side of the passage branching position.

In the apparatus constructed as described above, the raw water switching valve 6 and the pure water switching valve 8 of either one of the pure water towers 2 are arranged.
The raw water in the raw water tank is made to flow down into the pure water tower 2 by operating the raw water pump 5 under the open condition of the raw water. Pure water is exchanged and adsorbed by the ion exchange resin 17 of FIG.
Be washed away. The pure water 18 that has flowed into the pure water tank in this manner is stored therein, and the ultraviolet sterilizer 1
3 is sterilized, and water is sent through the pure water delivery pump 10 according to the required amount of pure water in the cleaning equipment or the like.

In the pure water production process as described above, when the water level detecting device 12 detects that the amount of pure water in the pure water tank has increased and the water surface level has reached the upper limit value, the pure water is detected. By continuing the steady production of the above, the circulation switch valve 15 is opened and the pure water discharge valve 16 is closed, so that the produced pure water is circulated to the raw water tank 1 through the circulation passage 14. Here, the amount of the circulating pure water may be not only all of the manufactured pure water but also a part thereof.

On the other hand, when the water surface level in the pure water tank drops to a predetermined value, the pure water discharge valve 16 is opened and the return flow switching valve 15 is closed while the pure water is still produced. The flow of the water 18 into the pure water tank 3 is restarted. By the way, also in this case, it is possible to continue the circulation of a part of the produced pure water in relation to the production amount of the pure water and the increasing rate of the water surface level in the pure water tank.

According to this, the water surface level of the pure water tank 3 can be controlled without causing substantial fluctuations in the amount of raw water supplied by the raw water pump 5 and the amount of pure water produced by the pure water tower 2. Therefore, the deterioration of the quality of the pure water 18 produced can be extremely effectively prevented with a simple equipment structure.

In order to suppress fluctuations in the flow rate passing through the deionized water tower 2 as much as possible when performing such water surface level control, each of the valves 15 and 16 is opened and closed by taking a time of 2 seconds or more. It is preferable to perform the sequence control in which the pure water discharge valve 16 is closed after a certain period of time after opening the reflux switch valve 15 and the reflux switch valve 15 is closed after a period of time from the opening of the pure water discharge valve 16. Is preferably performed.

[0014]

EXAMPLE A change in the quality of pure water by the water surface level control of the present invention described above was measured with a conductivity meter.
As shown by the solid line in FIG. The broken line in the figure shows the water quality change due to the conventional water surface level control for stopping and restarting the operation of the raw water pump. According to the graph shown in FIG. 2, in both the present invention and the prior art, the quality of the water is inevitably deteriorated when the pure water is re-supplied to the pure water tank. It can be seen that the maximum value can be suppressed to about 3 times that in the steady state, whereas in the conventional technique, the maximum value of the conductivity is increased to about 30 times.

[0015]

Therefore, according to the method of the present invention, it is possible to effectively prevent the deterioration of the water quality during the control of the water surface level, and according to the apparatus of the present invention, only the circulation passage 14 is provided. The invention method can be easily implemented with a simple and inexpensive structure.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of an inventive device.

FIG. 2 is a graph showing a change in conductivity when pure water is re-supplied to a pure water tank.

[Explanation of symbols]

 1 Raw water tank 2 Pure water tower 3 Pure water tank 4 Raw water feed passage 5 Raw water pump 7 Pure water passage 8 Pure water switching valve 9 Conductivity meter 10 Pure water delivery pump 11 Pure water delivery passage 12 Water level detector 14 Recirculation passage 15 Recirculation switching Valve 16 Pure water discharge valve 17 Ion exchange resin 18 Pure water

Claims (2)

[Claims] 1. Pure water stored in a pure water tank when pure water is manufactured by a pure water manufacturing apparatus in which a raw water tank, a plurality of pure water towers arranged in parallel, and a pure water tank are sequentially arranged. The method for producing pure water, characterized in that, after the water surface level of the water reaches the upper limit value, the pure water produced in the pure water tower is refluxed to the raw water tank until the water surface level decreases to a predetermined value. . 2. A pure water production apparatus comprising a raw water tank which is sequentially connected, a plurality of pure water towers arranged in parallel with each other, and a pure water tank, wherein the raw water tank is provided between the pure water tower and the pure water tank. A pure water producing device, characterized in that a circulation passage opening to the side is branched.