JPH091138A - End point detection method for ion exchange type pure water production equipment - Google Patents

Abstract

(57) [Summary] [Purpose] The end point of the ion-exchange-type pure water production system that effectively detects the end point of the ion-exchange system even when it is used for applications in which water supply and water supply stop are repeated in a short time. Provide a detection method. [Constitution] In the ion-exchange-type pure water producing apparatus, for about 15 to 30 seconds from the start of the first passage of water after the passage of water for a long time, regardless of whether the performance of the ion-exchange resin is deteriorated or not, There is a period when the purity decreases. So long time (T1)
From the first water flow after the stop of water flow, the time is continuously measured regardless of whether the water flow is on or off for a short time thereafter, and the period (T2) during the time measurement is set as the alarm mask period. At (T2), the end point alarm is not output. When the measurement time exceeds the second predetermined period, the alarm monitoring period (T3) starts, and the measured value of the electric conductivity of the water flow during the alarm monitoring period (T3) exceeds the predetermined reference value of the electric conductivity. In this case, the end point of the ion exchange resin is determined and the notification is given. The end point of the ion exchange resin is detected stably and effectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an end point detecting method used in an apparatus for producing pure water by ion exchange.

[0002]

2. Description of the Related Art There are various types of pure water producing apparatuses, one of which is a cartridge type as shown in FIG. This is a type in which a cylinder 24 is filled with an ion exchange resin 22 which is a mixture of a cation exchange resin that has been regenerated in the H shape and an anion exchange resin that has been regenerated in the OH shape. Treated water (pure water) is obtained by passing the raw water through the ion exchange resin 22. The cartridge type pure water producing apparatus 20 as described above is of a relatively small size, and is mainly used in a field requiring a relatively small amount of pure water such as a laboratory or an analysis room.

When pure water is produced by this apparatus 20,
When the capacity of the ion-exchange resin 22 filled inside is lowered and the predetermined water purity cannot be obtained, the ion-exchange resin 22 must be immediately replaced, and the resin 22 with lowered capacity is required. Is taken out and used again by refilling the regenerated ion exchange resin 22, or the whole container (cylinder) 24 is replaced with a new one to restart the pure water production.

Usually, the deterioration of the capacity of the ion exchange resin is detected by installing an electric conductivity meter 30 at the outlet of pure water and monitoring the electric conductivity of pure water as shown in FIG. At the same time, when the measured value exceeds the predetermined value, for example, an alarm is issued to notify that the end point has been reached.

However, in the ion exchange apparatus, when the production of pure water is stopped for a relatively long time and then the production is restarted, as shown in FIG.
As shown in Fig. 6, the purity of the pure water immediately after the restart was temporarily deteriorated by the eluate from the resin and carbon dioxide gas in the air, etc., even though the capacity of the ion exchange resin did not decrease before the restart. After that, with the passage of time, the water quality gradually improves and the original electrical conductivity is restored. That is, in the ion exchange device, the electrical conductivity of the sampled water is large at the beginning of the flow of water, and the electrical conductivity exponentially decreases with time if the flow is continued, and it takes about 15 seconds in a small-sized pure water producing device. And there is a characteristic to reach a stable state. Therefore, when the operation of the device is restarted after a long period of stoppage, an alarm will be issued due to the initial electric conductivity even though the end point of the ion exchange resin has not been reached.

Therefore, the conventionally used method is as follows.
The electrical conductivity was measured after a lapse of a certain time (about 15 seconds to 30 seconds) from passing water, and compared with the reference electrical conductivity, and when the measured value exceeded the reference value, it was determined as the end point of the ion exchange device. It is decided and notified. In other words, the device is masked so that the alarm does not activate for a certain period of time after the passage of water.

Specifically, an end point detecting device as shown in FIG. 5 is used. In the figure, reference numeral 1 is an electric conductivity meter electrode, and 2 is a circuit for measuring an alternating current signal from the electrode 1 by an electric conductivity measuring circuit for amplifying, rectifying, smoothing, etc. and outputting as an analog electric conductivity signal. An analog comparator 3 compares the output of the electric conductivity measuring circuit 2 with a reference value preset by the reference electric conductivity setting circuit 4,
When the output of the electric conductivity measuring circuit 2 exceeds this reference value, the signal H (High) is output.

Reference numeral 5 in the figure is a water flow signal generating circuit,
It consists of a flow switch, etc., and outputs signal H at the start of water flow and at that time. 6 is a digital delay element, which is a water flow signal generator 5
It delays the signal from, and the delay time is usually 15 ~
It is set to about 30 seconds. 7 is an AND circuit,
When the output signal of the digital delay element 6 is H and the output signal of the comparator 3 is also H, the AND circuit 7 is configured to output the end point signal H for notification.
That is, in this device, the electrical conductivity of pure water after a lapse of a certain time from the passage of water is measured, and if it exceeds a reference value, it is notified that the life of the ion exchange device has reached the end point.

[0009]

However, in recent years, the applications of ion exchangers have been diversified, and the water passage time and stoppage time have also become diversified, and the water passage time may be several seconds. In this case, in the conventional end point detection method, the end point is determined after 15 seconds from the start of water flow,
There is no opportunity to determine the end point, and there is a risk that unqualified pure water will continue to be produced.

The present invention provides an ion-exchange type pure water producing apparatus capable of effectively detecting the end point of the ion-exchange apparatus even when it is used for a purpose in which water supply and water supply stop are repeated in a short time. The purpose is to provide an endpoint detection method.

[0011]

The present invention has been made in order to achieve the above-mentioned object, in which pure water is produced by ion exchange and the purity of the produced pure water is measured by an electric conductivity meter. In the end point detection method of the ion exchange type pure water production apparatus which measures the end point of the ion exchange resin from the electric conductivity and detects that the water flow has stopped for the first predetermined time or longer, From the time of the first passage of water, the time is measured regardless of whether or not the passage of water is stopped for less than the first predetermined time, and the pure water is passed during the passage of water after the measured time reaches the second predetermined time. When the measured value of the electric conductivity exceeds a predetermined reference value of the electric conductivity, the end point of the ion exchange resin is determined and the notification is made.

[0012]

The operation will be described with reference to FIG. The figure shows time on the horizontal axis and electric conductivity (μS / cm) measured on the vertical axis, and further exemplarily shows water supply and water supply stop periods. After the water flow is stopped for a certain period (T1), if water is repeatedly passed through the ion exchange device in a short time of several seconds and then stopped, the electric conductivity repeatedly drops and rises like a wave. The electrical conductivity at the beginning of the water drops sharply, gradually becomes a gradual slope with the passage of time, and eventually reaches a stable state. Since the present invention is configured as described above, from the first passage of water that occurs after a long-term suspension for the first predetermined time (T1) or more, the short-term passage of less than the first predetermined time thereafter. The time is continuously measured regardless of whether or not the water is stopped, and the alarm mask period is set until the measured time reaches the second predetermined time (T2). After the measured time exceeds the second predetermined time, the alarm monitoring period (T
3) is entered, the measured value of the electric conductivity within the alarm monitoring period (T3) is compared with a predetermined electric conductivity reference value, and when the measured value exceeds the end point reference value, the ion exchange resin is used. It is judged that it is the end point of No. and is notified. In the case shown in FIG. 2, since the electric conductivity does not exceed the reference value within the alarm monitoring period (T3), the end point has not been reached.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in more detail based on the embodiments of the present invention with reference to the drawings. The same or corresponding elements as those described in the section of the related art are designated by the same reference numerals. FIG. 1 is a block diagram showing an embodiment of an end point detecting device used in the end point detecting method of an ion exchange type pure water producing apparatus according to the present invention.

In the figure, 1 is an electric conductivity meter electrode, and 2 is an electric conductivity measuring circuit for amplifying, rectifying, smoothing, etc. the detected AC signal from the electrode 1 and outputting it as an analog electric conductivity signal. . Reference numeral 3 is an analog comparator, which allows the electric conductivity measuring circuit 2
And the reference value preset by the reference electric conductivity setting circuit 4 are compared, and if the output of the electric conductivity measuring circuit 2 exceeds this reference value, a signal H (High) is output. Is configured.

Reference numeral 5 in the figure is a water flow signal generating circuit,
It consists of a flow switch etc. and outputs a signal H at the same time as the start of water flow. Reference numeral 15 is an alarm monitoring time generation circuit, which starts time measurement when it receives the first water flow signal H from the water flow signal generator 5 after a long water flow stop period of a first predetermined time (several hours) or more. , Continues to measure time regardless of whether the water flow signal is turned on or off (H, L) for a short period of time thereafter, and generates an H signal when the measured time reaches the second predetermined time (tens of seconds) Then, the state is kept held, and the hold state is cleared when the water flow signal becomes L (OFF) for several hours. In addition, when water stoppage for more than the first predetermined time occurs while measuring the second predetermined time, it returns to the initial state and measures the time again from the first water flow thereafter. 7 is an AND circuit, Alarm monitoring time generation circuit 15
When the output signal of is H and the output signal of the comparator 3 is also H, the end point signal H is output to notify.

The operation of this circuit will be further explained. First, when the power is turned on after the water supply is stopped for a long time (T1 in FIG. 2) to start the water supply, the signal H (Hig
h) is output to the alarm monitoring time generation circuit 15. The alarm monitoring time generation circuit 15 is composed of, for example, a timer, RS / FF, and the like, and when the first water flow signal H from the water flow signal generation circuit 5 is received after the water flow stop period of several hours, the subsequent Regardless of whether the water signal is on or off (H, L) for a short period of time, that is, even if water flow and water flow stop are repeated at intervals of several seconds, regardless of that, the number of signals from the first water signal is counted. The alarm mask time is set for 10 seconds (T2 in FIG. 2), and then the alarm monitoring time (T3 in FIG. 2) is entered and the H signal is set to AN.
Output to D circuit 7. Then, the output state of the H signal remains held, and when the water flow signal becomes L (OFF) for several hours, the hold state is cleared for the first time.

Further, the detection signal from the electric conductivity meter electrode 1 arranged at the water sampling outlet of the apparatus is the electric conductivity measuring circuit 2.
Then, the signal is amplified, rectified, smoothed, and output as an analog electric conductivity signal. And this electrical conductivity signal is
The signal H is input to the non-inverting input terminal (+) of the analog comparator 3 and compared with the reference value from the reference electrical conductivity setting circuit 4 input to the inverting input terminal (−). It is output from the comparator 3 to the AND circuit 7. When both input signals of the AND circuit 7 become H, the output of the AND circuit 7 becomes H and is notified as the end point signal.

That is, the end point detection method of the above embodiment is
Rather than measuring the electrical conductivity after a certain period of time each time the water flow is started as in the past, the time from the start of the first water flow after the long-term water flow stop is changed to the water flow and the short-term water flow stop. Each period is accumulated and measured, and the electrical conductivity of pure water is determined after a certain period of time has passed since the first passage of water. As a result, the end point of the ion exchange resin can be effectively detected even when water is turned on and off repeatedly for a short period of time. Further, with this detection method, it is possible to effectively detect the end point of the ion exchange resin not only in applications where water supply and water supply stop are repeated in a short time, but also in applications where water supply and water supply stoppage are normally performed for a long time. it can.

[0019]

As described above, according to the end point detecting method of the ion exchange type pure water producing apparatus of the present invention, not only the usual application but also the application of repeating water supply and water supply stop in a short time such as several seconds. Also in this case, it is possible to effectively detect the end point of the ion exchange resin and notify it. Therefore, the stability of the quality of the pure water to be produced can be maintained, and the number of defective products can be reduced in various industries using pure water.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an end point detecting device of an ion exchange type pure water producing device according to the present invention.

FIG. 2 is an example showing a change in electric conductivity of pure water when water passing and stopping are repeated in a short time.

FIG. 3 is a schematic view of a cartridge-type pure water producing device.

FIG. 4 is a diagram showing a change in electric conductivity when water sampling is once stopped and then restarted after a long time.

FIG. 5 is a block diagram of a conventional end point detection device.

[Explanation of symbols]

 1 Electric Conductor Electrode 2 Electric Conductor Measuring Circuit 3 Analog Comparator 4 Electric Conductivity Reference Value Setting Circuit 5 Water Flow Signal Generation Circuit 7 AND Circuit 15 Alarm Monitoring Timing Generation Circuit 20 Pure Water Production Device 22 Ion Exchange Resin 24 Cylinder 30 Electric Conductivity meter

Claims (1)

[Claims] 1. An ion exchange pure water production method for producing pure water by ion exchange, measuring the purity of the produced pure water with an electric conductivity meter, and detecting the end point of the ion exchange resin from the electric conductivity. In the end point detection method of the device, when it is detected that the water flow has stopped for the first predetermined time or longer, regardless of whether the water flow has been stopped for less than the first predetermined time since the first water flow thereafter. When the time is measured and the measured value of the electric conductivity of pure water exceeds a predetermined electric conductivity reference value during water flow after the time when the measured time reaches the second predetermined time, A method for detecting an end point of an ion exchange type pure water producing apparatus, which is characterized in that the end point of the exchange resin is judged and notified.