JP3209489B2 - End point detection method for ion exchange type pure water production equipment - Google Patents

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 tube 24 is filled with an ion exchange resin 22 in which a cation exchange resin regenerated in an H form and an anion exchange resin regenerated in an OH form are mixed in advance. When the raw water passes through the ion exchange resin 22, treated water (pure water) is obtained. Such a cartridge-type pure water producing apparatus 20 is relatively small and is mainly used in a field requiring a relatively small amount of pure water, such as a laboratory or an analysis room.

[0003] When producing pure water with this apparatus 20,
When the capacity of the ion-exchange resin 22 filled therein is reduced and the predetermined water purity cannot be obtained, the ion-exchange resin 22 must be replaced immediately, and the resin 22 having the reduced capacity is required. Is taken out, and the regenerated ion exchange resin 22 is refilled and used, or the container (tube) 24 is replaced with a new one to restart the production of pure water.

[0004] Usually, to detect a decrease in the capacity of the ion exchange resin, as shown in FIG. 3, an electric conductivity meter 30 is installed at the outlet of the pure water to monitor the electric conductivity of the pure water. At the same time, when the measured value exceeds a predetermined value, for example, an alarm is issued to notify that the end point has been reached.

[0005] However, the ion-exchange apparatus stops production of pure water for a relatively long time and then resumes production.
As shown in the figure, the purity of pure water immediately after the restart temporarily deteriorated due to eluate from the resin and carbon dioxide in the air, even though the capacity of the ion exchange resin did not decrease until before the restart. Then, there is a characteristic that the water quality gradually becomes better with time and returns to the original electric conductivity. That is, in the ion exchange apparatus, the electric conductivity of water sampling is large at the beginning of flowing water, and the electric conductivity decreases exponentially with time when the water is kept flowing, and it takes about 15 seconds in a small pure water production apparatus. And characteristics that lead to a stable state. For this reason, when the operation of the apparatus is restarted after a long term stoppage, an alarm is issued based on the initial electric conductivity even though the end point of the ion exchange resin has not been reached.

Therefore, a conventionally used method is as follows.
The electric conductivity is measured after a certain period of time (about 15 seconds to 30 seconds) from the passage of water, and when the measured value exceeds the reference value in comparison with the reference electric conductivity, the end point of the ion exchange device is determined. We make a judgment and inform. That is, the apparatus is masked so that the alarm is not activated for a certain period of time after the water is passed.

Specifically, an end point detecting device as shown in FIG. 5 is used. In the figure, reference numeral 1 denotes an electric conductivity meter electrode, and 2 denotes an electric conductivity measuring circuit which amplifies, rectifies, smoothes, etc., a detected AC signal from the electrode 1 and outputs it as an analog electric conductivity signal. An analog comparator 3 compares the output of the electric conductivity measuring circuit 2 with a reference value set in advance by a reference electric conductivity setting circuit 4,
If the output of the electric conductivity measuring circuit 2 exceeds this reference value, a signal H (High) is output.

[0008] In the figure, reference numeral 5 denotes a water passage signal generation circuit.
It consists of a flow switch, etc., and outputs a signal H at the start of water flow and at that time. Reference numeral 6 denotes a digital delay element, and a water flow signal generator 5
The delay time is usually 15 to
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 an end point signal H to perform notification.
That is, in this apparatus, the electric conductivity of pure water after a certain period of time has passed since the passage of water is measured, and when the electric conductivity exceeds the reference value, it is notified that the life of the ion exchange apparatus has reached the end point.

[0009]

However, in recent years, the applications of the ion exchange device have been diversified, and the time for water passage and the time for stoppage have been diversified, so that 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 supply.
There is no chance for the end point to be determined, and there is a risk that poor quality pure water will continue to be produced without being noticed.

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

[0011]

DISCLOSURE OF THE INVENTION The present invention has been made to achieve the above-mentioned object, and produces pure water by ion exchange. 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 for measuring and detecting the end point of the ion-exchange resin from the electric conductivity, when it is detected that there has been a water stoppage for a first predetermined time or more, From the first water flow, the time is measured regardless of whether or not the water flow is stopped for less than the first predetermined time, and pure water is flowed at the time of the water flow after the measured time reaches the second predetermined time. When the measured value of the electric conductivity exceeds a predetermined electric conductivity reference value, it is determined that the end point of the ion exchange resin is determined and notified.

[0012]

The operation will be described with reference to FIG. In the figure, the horizontal axis indicates time, the vertical axis indicates measured electric conductivity (μS / cm), and further illustrates water supply and water supply stop period. If water supply and stop are repeated in a short time of several seconds after stopping water supply for a certain period (T1), the electrical conductivity repeats a fall and a rise like a wave, but as a whole the basic tone is The electrical conductivity at the beginning of the water sharply decreases, gradually becoming a gentle gradient with the passage of time, and eventually reaches a stable state. Since the present invention is configured as described above, a short period of time that is shorter than the first predetermined time after the first water flow that occurs after a long-term stoppage for the first predetermined time (T1) or more. The time is continuously measured irrespective of the presence or absence of the water stop, 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, an alarm monitoring period (T
3), 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. Is determined to be the end point of the notification. In addition, 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]

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

In FIG. 1, reference numeral 1 denotes an electric conductivity meter electrode, and 2 denotes an electric conductivity measuring circuit which amplifies, rectifies, smoothes, etc. the detected AC signal from the electrode 1 and outputs it as an analog electric conductivity signal. . Reference numeral 3 denotes an analog comparator.
Is compared with a reference value set in advance by a reference electric conductivity setting circuit 4, 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 denotes a water passage signal generation 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 denotes an alarm monitoring timing generation circuit, which starts measuring time when the first water flow signal H is received from the water flow signal generator 5 after a long water flow stop period longer than a first predetermined time (several hours). The measurement of time is continued regardless of the presence / absence of on / off (H, L) of the short-time water passing signal thereafter, and when the measurement time reaches a second predetermined time (several tens of seconds), an H signal is generated. Then, the state is held, and the hold state is cleared when the water flow signal becomes L (off) for several hours. Note that, when the water stoppage for the first predetermined time or more occurs during the measurement of the second predetermined time, the state returns to the initial state, and the time is measured again from the first water flow thereafter. Alarm monitoring timing generation circuit 15
When the output signal of the comparator 3 is H and the output signal of the comparator 3 is also H, the end point signal H is output and the notification is performed.

The operation of this circuit will be further described. First, when the power is turned on after the water supply is stopped for a long time (T1 in FIG. 2) to start water supply, a signal H (Hig
h) is output to the alarm monitoring timing generation circuit 15. The alarm monitoring timing generation circuit 15 is configured by, for example, a timer, an RS / FF, or the like. When the first water flow signal H from the water flow signal generation circuit 5 is received after a water flow stop period of several hours, the subsequent alarm monitoring time generation circuit 15 is Regardless of ON / OFF (H, L) of the water flow signal for a short time, that is, for example, even if water flow and water flow stop are repeated at intervals of several seconds, the water flow signal is counted from the first water flow signal regardless of that fact. Ten seconds (T2 in FIG. 2) is an alarm mask timing, and thereafter, an alarm monitoring timing (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.

The detection signal from the electric conductivity meter electrode 1 arranged at the water sampling outlet of the apparatus is supplied to an electric conductivity measuring circuit 2.
Are amplified, rectified, smoothed, etc., and output as an analog electric conductivity signal. And this electrical conductivity signal is
The signal is inputted to the non-inverting input terminal (+) of the analog comparator 3 and compared with the reference value from the reference electric conductivity setting circuit 4 inputted to the inverting input terminal (-). The signal 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 an end point signal.

That is, the end point detection method of the above embodiment is as follows.
Instead of measuring the electrical conductivity after a certain period of time at the start of water supply as before, the time from the first water supply start after a long-term water supply stop is used for water supply and short-term water supply stop. Are accumulated and measured, and the electric conductivity of pure water is determined after a lapse of a certain period from the first passage of water. This makes it possible to effectively detect the end point of the ion exchange resin even when the on / off operation of the water flow is repeated in a short period of time. In addition, this detection method can effectively detect the end point of the ion-exchange resin not only in applications where water is repeatedly supplied and stopped in a short time, but also in applications where ordinary long-time water supply and water supply are stopped. it can.

[0019]

As described above, according to the method for detecting the end point of the ion-exchange type pure water producing apparatus of the present invention, not only the usual use but also the use where water supply and water supply stop are repeated in a short time such as several seconds. In this case, the end point of the ion exchange resin can be effectively detected and reported. Therefore, the stability of the quality of 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 one embodiment of an end point detecting device of an ion exchange type pure water producing apparatus according to the present invention.

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

FIG. 3 is a schematic view of a cartridge type pure water production apparatus.

FIG. 4 is a diagram showing a change in electrical conductivity when water is once stopped and restarted after a long time has elapsed.

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

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Electric conductivity meter electrode 2 Electric conductivity meter measurement circuit 3 Analog comparator 4 Electric conductivity reference value setting circuit 5 Water flow signal generation circuit 7 AND circuit 15 Alarm monitoring time generation circuit 20 Pure water production device 22 Ion exchange resin 24 cylinder 30 Electricity Conductivity meter

Claims (1)

(57) [Claims] 1. Ion-exchange pure water production wherein pure water is produced by ion exchange, the purity of the produced pure water is measured by an electric conductivity meter, and the end point of the ion exchange resin is detected from the electric conductivity. In the end point detection method of the apparatus, when it is detected that there is a water stoppage for a first predetermined time or more, from the first water supply thereafter, regardless of the presence or absence of the water supply stop for less than the first predetermined time. The time is measured, and when the measured value of the electric conductivity of the pure water exceeds a predetermined electric conductivity reference value at the time of passing water after the measured time reaches the second predetermined time, the ion A method for detecting an end point of an ion-exchange type pure water producing apparatus, wherein the end point of an exchange resin is determined and notified.