JPH03251744A - Measuring apparatus of concentration of organic substance provided with washing function - Google Patents

Abstract

PURPOSE:To prevent occurrence of abnormality in measurement and to enable realization of a stable operation by washing automatically by detecting sticking of an extraneous substance to a measuring cell of a COD meter. CONSTITUTION:A comparator 122 comparing the quantity of transmitted visible light with a set level and delivering an output when the quantity of the transmitted visible light exceeds the set level, and a determining device 124 outputting an operation signal to a washing device 115 at least on condition that a comparison output continues for a prescribed time or longer and that washing is not executed, are equipped. Lights transmitted through a measuring sample, which are based on two wavelengths of a visible light and an ultraviolet light, are detected 100, 101, a difference between them is taken and the concentration of an organic substance is measured therefrom while the effect of the suspension of the sample, floating solids therein, etc. is prevented. Besides, the presence or absence of sticking of an extraneous substance is subjected to self-diagnosis by discriminating the quantity of the visible light, and when the result of diagnosis shows the sticking of the extraneous substance, automatic washing 115 is executed. Thereby the occurrence of abnormality in measurement is prevented and a stable operation can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for measuring the concentration of dissolved organic matter in sample water.

[Conventional technology]

Generally, a COD meter is used as a device for measuring the concentration of organic matter contained in water. COD (Chemica)
1 Oxygen Demand) is chemical oxygen demand, and the amount of oxygen consumed by chemical oxidation is used as an index of the amount of organic substances contained therein.

FIGS. 6 and 7 show conventional COD meters.

In FIG. 6, water flowing through a water pipe 1 is extracted by a sampling pump 2, guided to a measuring cell 3, and then transported to a low-pressure mercury lamp 7.
Then, light including ultraviolet rays is irradiated through the cell window 8. As shown in FIG. 7, the measurement cell 3 is designed such that sample water is supplied from a sample inlet 28, passes through the cell, and is discharged from an outlet hole 27 and a sample outlet 29. The cell window wiper 6 is periodically moved up and down via the rod 21 by the drive motor 5 so as not to be exposed to the windshield 8.
At the same time, cleaning chemicals and clean water are sent to clean the inside, and the zero point is calibrated using clean water. The light that is irradiated into the measurement cell and transmitted through the sample water is transmitted through window 8.
It is divided into two light east by half mirror 10.

One of them passes through an ultraviolet optical filter 12 that transmits only ultraviolet light (254 nm) and is converted into an electrical signal by a measurement side detector 13 consisting of a photodiode, etc., and the other passes through a visible light optical filter 11 that transmits only visible light. and is detected by the comparison side detector 14. Ultraviolet light changes exponentially in response to the concentration of dissolved organic substances and suspended substances in the sample water, while visible light does not respond to the concentration of dissolved organic substances in the sample water and remains unchanged. It changes exponentially in response only to the concentration of turbid substances. Therefore, the signals detected by each detector are converted into linear outputs by logarithmic amplifiers 15 and 16, respectively.
A differential amplifier 17 takes the difference between the two, and a voltage-current converter 1
When converted into a current value in step 8, a COD output signal proportional only to the concentration of dissolved organic matter in the sample water is obtained. Note that if the data during cleaning is extracted as a COD output signal, the data will be abnormal, so the data before cleaning is held as a sample.

[Problem to be solved by the invention]

By the way, the sample measured by a COD meter contains a large amount of foreign matter, and no effective method for removing it with a pretreatment device has been developed at present, and even if you try using a filter or a static tank, It quickly becomes occluded and no lasting effect can be obtained. Currently, in most cases, automatic cleaning and manual disassembly cleaning are carried out periodically at set intervals, but since foreign matter gets caught in the measurement cell suddenly, it cannot be dealt with by regular cleaning etc. Can not. Furthermore, cleaning using conventional cleaning chemicals or clean water is not effective in removing foreign substances. Factories and plants are required to report the COD measurement results of the water they use to relevant government agencies, and abnormal data reporting or missing data may occur due to abnormal COD meter measurements. Additionally, there is a problem in that it takes a lot of effort to respond to abnormalities and perform recovery work.

The present invention is intended to solve the above problems, and by detecting foreign matter adhering to the COD meter measurement cell and automatically cleaning it, it is possible to prevent measurement abnormalities and achieve stable operation. The purpose of the present invention is to provide an organic substance concentration measuring device with a cleaning function.

[Means to solve the problem]

The present invention irradiates light onto a liquid sample introduced into a measurement cell that is periodically cleaned by a cleaning device, detects two wavelengths of light in the ultraviolet region and visible region that have passed through the liquid sample, and both detection signals are detected. In a device that measures dissolved organic matter concentration from the difference between The present invention is characterized in that it is provided with a determination device that outputs a cleaning device activation signal on the condition that cleaning is not in progress.

[Effect]

The present invention detects the light transmitted through the measurement sample using two wavelengths of visible light and ultraviolet light, and by taking the difference between the two, prevents the influence of sample turbidity, suspended solids, etc., and measures the concentration of organic substances. It self-diagnoses the presence or absence of foreign matter by discriminating the amount of visible light, and when a diagnosis of foreign matter is found, automatic cleaning is performed to prevent measurement abnormalities and achieve stable operation.

〔Example〕

Examples will be described below.

FIG. 1 is a block diagram showing the configuration of an organic matter concentration measuring device with a cleaning function according to the present invention, FIG. 2 is a flowchart for determining cleaning conditions, FIG. 3 is a diagram for explaining the cleaning operation, and FIG. FIG. 4 is a diagram showing an example of a measurement signal when a foreign object passes through the cell, and FIG. 5 is a diagram showing an example of the self-diagnosis function operation when a foreign object is attached to the cell or the cell is clogged. In the figure, 100 is a measurement side detector;
101 is a comparison side detector, 102.103 is a 1/V converter, 104 is a balance adjuster, 105.10ε is a logarithmic amplifier, 107.108 is an amplifier, 109 is a zero point adjuster,
110 is a zero point coarse adjuster, 111 is a differential amplifier, 112 is a gain adjuster, 113 is a signal holder, 114 is a V/I converter, 115 is a cleaning device, 116 is an automatic calibrator, and 120 is a self-diagnosis function. Block 121 is a detection level setter, 1
22 is a comparator, 123 is a buffer amplifier, 124 is a determiner,
125 is a cleaning condition setting section.

The measuring principle of the device shown in FIG. 1 is the same as that of the measuring device shown in FIG. It is converted into a signal, balanced by a balance adjuster 104, converted into a linear output by logarithmic amplifiers 105 and 106, amplified by amplifiers 109 and 110, the difference between the two is taken by a differential amplifier 111, and the gain is adjusted. /I conversion to obtain a COD output signal, and during cleaning, a hold signal is output to the automatic calibrator 116 and signal holder 113 according to the signal from the cleaning device 115 to detect abnormal data during cleaning.
l: I try not to emit it as a force signal.

The light entering the measuring instrument side detector 100 is absorbed or reflected by organic matter in the sample, foreign matter, dirt, etc. within its optical axis. On the other hand, the light entering the comparative detector 101 is absorbed or reflected by foreign matter in the sample or dirt on the cell window within its optical axis.

Therefore, dirt or foreign matter accumulation on the cell window can be detected from changes in the amount of light entering the comparison side detector 101. Therefore, when a foreign object passes through the measurement cell, the output of the comparison side detector lO1 (visible light) changes greatly as shown by Pi, P2, and P3 in the figure, as shown as an example in FIG. If the foreign matter passes through without staying, the indication will immediately return to its original value without cleaning, as shown in the figure. On the other hand, if foreign matter remains, large changes as shown in Pl, P2, P3, etc. remain, and measurement abnormalities continue.

Therefore, in the self-diagnosis function block 120, first, the output of the comparison side detector 101 in a normal measurement state and the output of the comparison side detector lot in a state where a measurement abnormality occurs due to dirt or foreign matter accumulation on the cell window are determined. The level to be determined as abnormal among the surface outputs is determined empirically and set as a reference value in the comparator 122 by the setter 121. In addition, the comparator 122
The output of the comparison side detector 101 is connected to the comparison side human power. The comparator 122 turns ON when the input on the comparison side exceeds a reference value, and determines that an abnormal state has occurred. Incidentally, in order to prevent interference between the self-diagnosis function block side and the detection section side, a buffer amplifier 123 is inserted between the comparison side detector output and the comparison side input of the comparator 122 as necessary. Then, when the output signal of the comparator 122 is turned ON, the determiner 124 determines whether or not there is any foreign matter attached. Then, as shown in FIG. 2, when an ON signal is received from the comparator 122, the cleaning is not in progress (step ■), the comparator is ON for a certain period of time, for example, 30 seconds or more (step ■), and the overheat sensor is normal (step ■). Cleaning is started on the condition that step (2) is met, and no cleaning trigger signal is issued if the conditions of steps (2) to (2) are not met. Note that the reason why it is determined in step (2) whether or not it is ON for a certain period of time or more is to prevent unnecessary cleaning in the case where a foreign object passes by setting a certain period of time. In step ■, it is determined whether the overheat sensor is normal or not.
This is to check to limit the number of consecutive washes. In this way, when the determiner 124 determines that foreign matter has adhered, the cleaning device 115 operates to automatically perform cleaning, and the automatic calibrator 116 performs zero calibration. During cleaning and calibration, the signal holder 113 holds and outputs the indicated value immediately before cleaning so that abnormal signals are not output during cleaning and calibration.

Fig. 5 is an example of the self-diagnosis function operation. When an abnormal value is detected by the visible light detector at timing T1 in the figure, automatic cleaning is performed at timing T2 other than regular cleaning, and as a result, subsequent visible light The detected value of light becomes stable and COD
Measurements will continue. In addition, in the figure, the timing of holding the measured value and the timing of automatic cleaning by self-diagnosis are displayed as being out of sync. This is because there is a deviation, but there is no actual deviation. The same applies to FIG. 4 as well.

In addition, in the cleaning process in this embodiment, as shown in FIG. 3, when the cell foreign matter adhesion signal continues for 30 seconds, the measured value is held, and the cell window wiper is driven as in the case of FIG. 6 to start cleaning. Then, cleaning is performed by sending cleaning chemicals (for example, 5 to 8% HNO) and bubbling air (cleaning air), which is a feature of the present invention, using an air pump (not shown), and clean water for cleaning. and perform zero point calibration. These cleaning steps are controlled by a sequence controller (not shown) by sequentially controlling the sample and clean water flow valve, a bubbling air supply device for enhancing the cleaning effect, a cleaning chemical supply device, and the like. Note that bubbling air is activated in two steps.

The first time is to remove the foreign matter that caused the measurement abnormality, and the second time is to forcibly discharge the foreign matter due to a large amount of foreign matter accumulated in the pipe due to valve shock etc. when switching to the sample.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to self-diagnose the presence or absence of foreign matter adhesion and effectively eliminate foreign matter in the cell by combining bubbling, thereby improving the reliability of COD measurement and making maintenance free. It becomes possible to aim for

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an organic matter concentration measuring device with a cleaning function according to the present invention, FIG. 2 is a flowchart for determining cleaning conditions, FIG. 3 is a diagram for explaining the cleaning operation, and FIG. Figure 4 is a diagram showing an example of a measurement signal when a foreign object passes through a cell, Figure 5 is a diagram showing an example of the self-diagnosis function operation when a foreign object is attached or clogged in a cell, and Figure 6 is a diagram showing the configuration of a conventional COD meter. , FIG. 7 is a diagram showing the structure of the measurement cell. 100... Measurement side detector, 101... Comparison side detector, 105.106... Logarithmic amplifier, 111... Differential amplifier, 113... Signal holder, 115... Cleaning device, 120... Self-diagnosis function block, 121...
Detection level setter, 122... Comparator, 123...
Buffer amplifier, 124... Judgment device, 125... Cleaning condition setting section. Tail 2 Figure 3 Figure 5 Figure 4 Figure 6

Claims (2)

[Claims] (1) Light is irradiated onto a liquid sample introduced into a measurement cell that is regularly cleaned by a cleaning device, and the two wavelengths of ultraviolet and visible light transmitted through the liquid sample are detected, and both detection signals are detected. A device that measures dissolved organic matter concentration from the difference has a comparator that compares the amount of transmitted visible light with a set level and outputs an output when the amount of transmitted visible light exceeds the set level, and the comparator output continues for at least a predetermined period of time. 1. An organic matter concentration measuring device having a cleaning function, comprising: a determining device that outputs a cleaning device activation signal on the condition that cleaning is not in progress. (2) The organic matter concentration measuring device with a cleaning function according to claim 1, wherein the cleaning device has means for supplying bubbling air together with the cleaning liquid.