JP2000055850A - Method for detecting failure in device for measuring concentration of ammonium nitrogen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the failure in a device for continuously performing measurement according to a time sequence even if the failure occurs. SOLUTION: In a device for continuously measuring the concentration of alkali nitrogen in inspection water, the inspection water is allowed to flow to the outside of a gas-permeable film 2 of a gas permeability separation column 1, a carrier liquid is allowed to flow to the inside by the pump, a strong alkali solution is added to the inspection water from the pump, and the reduction of the conductivity of the carrier liquid due to the neutralization reaction with the carrier liquid after the generation alkali gas permeates through the film 2 is measured by a cell. In the device, a calibration liquid is allowed to flow at a constant interval using the pump, the conductivity is measured, and a span value is calibrated in auto-span calibration, the span value of the auto-span calibration is compared with the upper-limit value being set with a width in advance, and the deterioration of the film 2 is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure in an ammonia-nitrogen-concentration measuring apparatus of a gas extraction displacement electric conductivity change measuring method for measuring the ammonia-nitrogen concentration in water such as sewage treatment plants, rivers, lakes and seawater. It relates to a detection method.

[0002]

2. Description of the Related Art Conventionally, a description will be given of an ammonia nitrogen concentration measuring apparatus of a gas extraction displacement electric conductivity change measuring method.

(1) Principle of Measurement Referring to FIG. 1, a tubular ammonia permeable separation column 1 has a tubular gas permeable membrane 2 inside, a measuring water (water sample) flows outside the membrane 2, and an inside of the membrane 2 The carrier liquid (sulfuric acid). When a strong alkaline solution such as sodium hydroxide is added to the measurement water flowing outside the gas permeable membrane 2, ammonium ions in the measurement water become ammonia gas and pass through the gas permeable membrane 2 and enter the carrier liquid.

On the carrier liquid side, a neutralization reaction occurs between ammonia and sulfuric acid, and the conductivity (rate) of sulfuric acid decreases accordingly. The apparatus measures the ammonia nitrogen concentration using the fact that the amount of decrease in the conductivity and the ammonia nitrogen concentration are in a proportional relationship.

(2) Configuration of Apparatus FIG. 2 shows the configuration of the flow path, and FIG. 3 shows an electric conductivity measuring circuit. In FIG. 2, 1 is an ammonia permeation separation column, 5 is a thermostat, 6 is a precooler, 7 is a mixer for mixing a test or calibration solution and a strong alkaline solution and supplying it to the column 1, and 8 is air in the carrier liquid. The air trap 9 to be removed is a conductivity detection cell for measuring the conductivity before and after the carrier liquid passes through the column 1.

[0006] P1 is an alkaline pump for supplying the strong alkaline solution 11, P2 is a sulfuric acid pump for delivering the carrier solution, and P3 is a test or calibration solution 14 or cleaning water 15 and a cleaning solution 16 from a test tank 13. Supply water pump, S
V1 to SV3 and SV8 are flow path switching valves, and SV4 to SV
V5, SV7 and BV1, BV2 indicate flow path valves.

The operation of the flow path configuration (FIG. 2) will be described. Upon the start of the measurement, the water test pump P3 sucks the water sample in the water test tank 13 through the valves SV8 and SV3, the sulfuric acid pump P2 sucks the sulfuric acid 12 through the valve SV2, and the alkali pump P1 sucks the strong alkaline solution 11. Suction is performed via the valve SV1.

After the suction, the sulfuric acid pump P2 discharges the sulfuric acid to discharge sulfuric acid into the valve SV2, the air trap 8, the electrode 9R of the conductivity detection cell 9, the inside of the gas permeable membrane 2, and the electrode 9 of the conductivity detection cell 9.
Flow through the S channel.

At the same time as the discharge of the sulfuric acid pump P2, the water sample pump S3 discharges, and the test water flows through the valves SV3, SV4, the mixer 7, and the gas permeation separation column 1.

When the electrical conductivity of the sulfuric acid detected by the electrodes 9S and 9R of the conductivity detecting cell 9 becomes stable, the alkaline pump P1
Is discharged, and the strong alkaline solution flows through the valve SV1, the mixer 7, and the flow path of the gas permeation separation column 1, and the strong alkali solution is mixed with the test water flowing through the gas permeation separation column 1.

In the gas permeable membrane separation column 1, the ammonia gas generated by the addition of the strong alkali solution moves to the sulfuric acid side flowing inside the gas permeable membrane 2, and the electric conductivity of the sulfuric acid flowing through the electrode 9S decreases.

Referring to FIG. 3, the electrical conductivity measuring circuit inputs the output of the oscillator 21 to the electrode 9S via the buffer amplifier 22 and the output of the amplifier 22 to the electrode 9R via the compensation amplifier 23. and the output of 9S via respective amplifiers 24 and 25 is rectified by the rectifier 26 and 27, amplified by the differential amplifier 28, the ammonium nitrogen concentration detected from the amplifier 29 with a range adjustment resistor VR ₂ and span adjustment resistor VR ₃ The value is configured to output.

Various measures have been taken for the flow path (FIG. 2) of the apparatus. If air enters the measurement flow path, it greatly affects the measurement. Therefore, the gas permeation separation column 1,
The conductivity detection cell 9 and the like are installed in the low-temperature constant temperature bath 5 (about 10 ° C.), and each pipe is actively cooled by the precooler 6 to suppress water detection and generation of bubbles from the carrier.
Also, keeping the measurement system at a constant temperature has the effect of reducing the temperature dependence of the measured value.

In addition, an air trap 8 is provided in the carrier channel as a measure against bubbles. In addition, the air entering from the water test tank 13 is trapped in the water test pump P3, and is drained through the valve SV7 at the end of the measurement.

FIG. 4 shows a time sequence chart of the above apparatus. The contents of the symbols in the figure are as follows.

WAIT: Waiting time from the beginning of sulfuric acid flow until the indication stabilizes TIMES: Number of NaOH injections / measurement INJ-T: NaOH injection (= discharge) time MEAS. -T: Time for flowing (= discharging) the sample water Each value must be satisfied simultaneously.

(MEAS.-T)> (WAIT) +
((INJ-T) * 2) * (TIMES) HCL: Sets the suction time of the cleaning liquid (hydrochloric acid) in seconds.

WATER: Sets the dilution water suction time in seconds. The dilution ratio of the cleaning solution is determined by the values of [HCL] and [WATER].

AT-SPAN: When "0" is set, which sets the cycle of automatic span calibration in units of time, no calibration is performed. INTERVAL: Measurement cycle (30-minute unit) FIG. 5 shows an algorithm for detecting ammonia nitrogen concentration.

The peak height of the ammonia nitrogen concentration detection waveform obtained from the electric conductivity measuring circuit (FIG. 3) is obtained as shown in FIG. When determining the peak height [ZE
Although the measurement of the [RO] point is an important factor, here [ZE
[RO] point is determined as a value obtained by averaging the detection levels for 5 seconds immediately after [WAIT] is completed and alkali injection is started. Peak height [V] = Vertex voltage [V] −ZERO voltage [V] The span value is determined by measuring a standard solution (calibration solution) and obtaining the peak height of the obtained ammonia nitrogen concentration detection waveform. From [V]. (Span value) [ppm / V] = (Calibration solution concentration) [mg / L] /
(Peak height) [V] The method for obtaining the ammonia nitrogen concentration [mL / L] is as follows: the peak height [V] obtained by measuring the sample water and the span value obtained by measuring the calibration solution in advance. It is derived from [ppm / V]. Ammonia nitrogen concentration [mg / L] = span value [p
pm / V] * Peak height [V] Span calibration is to derive a span value by measuring the calibration solution 14 (FIG. 2) instead of the measurement of the sample. The calibration liquid 14 is flowed using the water sample pump P3.

The auto-span calibration is to correct the span value by measuring the calibration solution at regular intervals during the continuous measurement of the sample. The cycle of the autospan calibration is set in units of time using a switch (not shown) in the apparatus.

The washing of the above-mentioned flow path is performed by using a cleaning chemical solution (hydrochloric acid) 16 and cleaning water (distilled water) 15 in place of the water sample, using a water sample pump P3.
Then, the sample is passed through the flow path to clean the water detection flow path and the gas permeable membrane. Here, the hydrochloric acid concentration is as shown in FIG.
Dilute hydrochloric acid with suction time of washing water (distilled water) to adjust.

[0023]

In the conventional ammonia nitrogen concentration measuring apparatus described above, even if an abnormality such as deterioration or clogging of a gas permeable membrane, a failure of a flow path, or a failure of a valve occurs in the apparatus, it is possible to perform the measurement. 4 takes over the time sequence and continues the measurement.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to measure the concentration of ammoniacal nitrogen by using a method for measuring a change in the electric conductivity of a gas-exchange-substitute, which can detect an abnormality of the above-mentioned apparatus. An object of the present invention is to provide a method for detecting a failure in a device.

[0025]

According to the present invention, there is provided a method for detecting a failure in an ammoniacal nitrogen concentration apparatus, wherein a test water and a carrier liquid are supplied to one and the other of a gas permeable membrane surface of a gas permeation separation column, respectively. Add the alkaline solution, measure the ammonia gas generated permeate the gas permeable membrane, neutralize and react with the carrier liquid and change the conductivity of the carrier liquid, and continuously measure the ammonia nitrogen concentration of the test sample In the apparatus, and during the continuous measurement, an auto-span calibration for calibrating a span value by measuring a change in the conductivity of the calibration solution by flowing a calibration solution instead of water at regular intervals and measuring the span value is performed. The span value of the span calibration is compared with an upper limit value having a predetermined width, and if the span value exceeds the upper limit value, it is determined that the gas permeable membrane is deteriorated.

When it is determined that the gas permeable membrane is deteriorated, the cleaning liquid is allowed to flow to wash the gas permeable membrane, and then the autospan calibration is performed to determine whether the gas permeable membrane has returned to normal.

Alternatively, during continuous measurement, an auto-span calibration for calibrating a span value by measuring a change in the conductivity of the calibration solution by flowing a calibration solution in place of the sample at regular intervals and measuring the change in conductivity is performed,
The span value of the auto span calibration is monitored, and when the span value approaches infinity, it is determined that the apparatus is abnormal.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 (Diagnosis Function of Deterioration of Gas-permeable Membrane) In the ammonia nitrogen concentration measuring apparatus shown in FIGS. When the nitrogen concentration is continuously measured, the permeation of the ammonia gas generated by the reaction between the ammonium nitrogen and sodium hydroxide contained in the test water deteriorates on the surface of the gas permeable membrane 2 of the gas permeation separation column 1, and the detection is performed. This causes a reduction in sensitivity.

The first embodiment is obtained at the time of auto-span calibration (see FIG. 4) in which the apparatus shown in FIG. 1 measures a calibration solution at regular intervals during continuous measurement for detection and corrects a span value. The deterioration diagnosis of the gas permeable membrane 2 is performed by the span value.

When the deterioration of the gas permeable membrane 2 causes deterioration of the ammonia gas permeation, the change in the electric conductivity of the fluid flowing from the gas permeation / separation column 1 to the electrode 9S of the conductivity detection cell 9 becomes smaller than in the normal state. and eventually cause a decrease in the output voltage of the electric conductivity measuring circuit (FIG. 3), span value to be adjusted by the variable resistor VR ₃ at the time of auto span calibration is increased. Span value [ppm / V] = Calibration solution concentration [ppm] / Peak height [V] Therefore, it is possible to diagnose the deterioration of the gas permeable membrane 2 by giving the span value a normal width in advance. a ≦ span value [ppm / V] ≦ b Here, if the span value is larger than b, it means that the gas permeable membrane 2 is deteriorated. If the span value is smaller than a, it means that the output voltage is abnormal, and it is necessary to adjust the range of the electric conductivity measuring circuit (FIG. 3).

The above-described function is referred to as a deterioration diagnosis function of the gas permeable membrane, which can be self-diagnosed in the CPU, and the spans a and b of the span value can be changed by a switch or the like.

Embodiment 2 (Degradation Diagnosis Function of Gas Permeable Membrane + Automatic Return Function) In Embodiment 2, when the deterioration diagnosis function of the gas permeable film detects deterioration of the gas permeable film, an automatic return function is provided. Work. The automatic return function here refers to the first embodiment.
Means that the gas permeable membrane is degraded, and is to clean the gas permeable membrane using hydrochloric acid.

The hydrochloric acid cleaning step will be described with reference to FIGS. First, the valve SV3 is NC, the valve SV
4 closes and opens the valve SV5, sucks hydrochloric acid by the water sample pump P3, closes the valve 5, opens the valve SV6, and sucks washing water (distilled water).

After the suction, the valve SV6 is closed and the valve SV6 is closed.
Reference numeral 3 denotes an NC, the valve SV4 is opened, and hydrochloric acid is discharged to the outside of the gas permeable membrane 2 by a water sampling pump P3.

After the discharge, the valve SV4 is closed and the valve SV3
Is NO, the valve SV8 is NC, and the calibration liquid 14 is sucked by the water sample pump P3. After the suction, the valve SV4 is opened, the valve SV3 is set to NC, and the calibration liquid 14 is discharged to the outside of the gas permeable membrane 2 by the water sampling pump 3. At this time, the operation of discharging and sucking the sodium hydroxide 11 is performed five times by the alkali pump P1, and the operation of restoring the gas permeable membrane 2 is performed.

After washing with hydrochloric acid, the auto-span calibration is performed by the function of diagnosing deterioration of the gas permeable membrane to determine whether or not the gas permeable membrane has returned to normal.

As a result of the above determination, if the gas permeable membrane is not returned to the normal state, the replacement of the gas permeable membrane is notified to the outside by an external output.

Embodiment 3 (Method of Detecting Failure of Apparatus) This failure detection method is a method of detecting by a span value at the time of auto span. Here, the failure of the device is 1) clogging of the gas permeable membrane 2) clogging of the flow path 3) failure of the pump 4) failure of the valve.

When such a phenomenon occurs in the apparatus, a change in electrical conductivity cannot be obtained, the output voltage of the electrical conductivity measuring circuit (FIG. 3) approaches zero infinitely, and the span value becomes infinite. Become. Span value [ppm / V] = Calibration solution concentration [ppm] / Peak height [V] The failure (abnormality) of the apparatus is detected by monitoring the infinity of this span value.

[0040]

Since the present invention is configured as described above, the following effects can be obtained.

(1) Since deterioration diagnosis of the gas permeable membrane can be performed, a decrease in measurement sensitivity can be detected.

(2) After the deterioration diagnosis of the gas permeable film in the above (1), the gas permeable film is washed and the auto-span calibration is performed to determine whether the gas permeable film has returned to the normal state.

(3) It is possible to detect a failure of the device based on the span value in the auto span calibration, and to stop the device that continues to move in the sequence. Further, since the failure output of the device can be performed, the failure of the device can be immediately known.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of measuring the concentration of ammonia nitrogen.

FIG. 2 is a flow chart of an ammoniacal nitrogen concentration measuring device.

FIG. 3 is an electric conductivity measurement circuit diagram in the ammonia nitrogen concentration measurement device.

FIG. 4 is a time sequence chart of the ammonia nitrogen concentration measuring device.

FIG. 5 is an algorithm for detecting an ammonia nitrogen concentration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ammonia gas permeation | separation column 2 ... Gas permeable membrane 5 ... Constant temperature bath 6 ... Precooler 7 ... Mixer 8 ... Air trap 9 ... Conductivity detection cell 9R, 9S ... Electrode 11 ... Strong alkali solution (sodium hydroxide) 12 ... Carrier Liquid (sulfuric acid) 13 ... Test tank 14 ... Calibration liquid (standard solution) 15 ... Cleaning liquid 16 ... Cleaning liquid (hydrochloric acid) P1 to P3 ... Pump BV1, BV2, SV1 to SV8 ... Valve (valve).

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Nagatake Takatake 2-1-1-17 Osaki, Shinagawa-ku, Tokyo F-term in Meidensha Co., Ltd. (reference) 2G058 AA01 BA07 BB15 DA02 DA03 EA03 EA05 EC01 FB02 FB12 GA12 GD01 GE01 2G060 AA06 AB04 AB07 AC03 AE17 AE21 AE26 AF03 AF08 AG08 AG11 EA08 FA01 FA15 FB02 FB03 FB07 HA02 HA06 HA07 HA09 HC07 HC10 HC15 HC24

Claims (3)

[Claims] Claims: 1. A sample and a carrier liquid are passed through one and the other of a gas permeable membrane surface of a gas permeable separation column.
A strong alkaline solution was added to the test water, and the generated ammonia gas permeated through the gas permeable membrane and neutralized with the carrier liquid to measure the change in the conductivity of the carrier liquid. In the device for continuous measurement, during the continuous measurement, perform auto span calibration to calibrate the span value by measuring the change in the conductivity of the calibration solution by flowing a calibration solution instead of water at regular intervals and measuring the change in the conductivity. The failure of the ammonia nitrogen concentration measuring device is characterized in that the span value of the auto span calibration is compared with an upper limit value with a predetermined width, and if the span value exceeds the upper limit value, it is determined that the gas permeable membrane has deteriorated. Detection method. 2. The gas permeable membrane according to claim 1, wherein, when it is determined that the gas permeable membrane is deteriorated, the gas permeable membrane is washed by flowing a cleaning agent solution, and thereafter, autospan calibration is performed to determine whether the gas permeable membrane has returned to normal. A method for detecting a failure in an ammonia nitrogen concentration measuring device, characterized in that: 3. A test liquid and a carrier liquid are respectively passed to one and the other of the gas permeable membrane surfaces of the gas permeable separation column,
A strong alkaline solution was added to the test water, and the generated ammonia gas permeated through the gas permeable membrane and neutralized with the carrier liquid to measure the change in the conductivity of the carrier liquid. In the device for continuous measurement, during the continuous measurement, perform auto span calibration to calibrate the span value by measuring the change in the conductivity of the calibration solution by flowing a calibration solution instead of water at regular intervals and measuring the change in the conductivity. A method for detecting a failure in an ammonia nitrogen concentration measuring device, wherein a span value of an auto span calibration is monitored, and when the span value approaches infinity, it is determined that the device is abnormal.