JPH06130030A - Automatic measuring apparatus of ammonia in water - Google Patents

Abstract

PURPOSE:To achieve that an acid whose cleaning power is high such as hydrochloric acid or nitric acid is used as a cleaning liquid by a method wherein, when a cleaning operation is performed, an inert gas is supplied and an ammonia-gas electrode is shut off from the contact with a gas volatilized from the cleaning liquid. CONSTITUTION:In a measuring mode, an arithmetic and control unit 9 closes solenoid valves 8, 4, 16 and opens solenoid valves 5, 6, 7. As a result, a pump 3 sends out water under test and an alkali agent into a measuring cell 2. The water under test in the cell 2 becomes strongly alkaline, an ammonia component in the water under test is shifted to a vapor phase part, and its concentration is detected by an ammonia-gas electrode 1. In a cleaning process, the control unit 9 opens the valve 16, it sends an inert gas to the vapor phase part in the cell 2 by a pump 15, it closes the valves 5, 7, 4, it opens the valves 8, 6 and it introduces an acid solution from a tank 12. During the period of the cleaning process, a gas generated from a cleaning liquid is discharged to the outside of the vapor phase part by the inert gas in the cell 2, and it does not come into contact with a diaphragm on the electrode 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic measuring device for ammonia in water of a type in which an alkaline agent is added to test water to transfer ammoniacal nitrogen in water as ammonia gas into the gas phase and the ammonia gas electrode is used for measurement.

[0002]

2. Description of the Related Art An alkaline agent is added to sample water to be measured to transfer ammonia nitrogen in water to the gas phase, and the concentration is measured with an ammonia gas electrode, so that the concentration of ammonia nitrogen in the sample water can be measured online. An automatic ammonia measuring device for measuring is disclosed in Japanese Patent Application Laid-Open No. 63-165.
It is known from 751 and JP-A-3-61856.

FIG. 3 shows the internal structure of the measuring cell section in the conventional device. In the conventional automatic ammonia measuring device having the structure of the measuring cell shown in FIG. 3, the measuring cell and the measuring device react with the calcium component of the sample water or the added alkaline component during the repeated measurement for a long time. It may deposit as scale in the piping and interfere with stable measurement.

Since the scale deposited in the measuring cell or the piping of the apparatus can be removed by flowing a high-concentration aqueous solution of an appropriate type of acid, in the conventional apparatus, the equilibrium acid component concentration in the gas phase is high even in a high-concentration aqueous solution. Sulfuric acid is selected as a type of acid that is low and does not affect the measurement by the ammonia gas electrode 1, and the measurement is interrupted periodically to allow the sulfuric acid aqueous solution to flow through the measurement cell or device piping, removing the scale in this part. Is being washed. However, when an aqueous solution of sulfuric acid is used as the cleaning liquid, when the calcium concentration in the test water is high, calcium sulfate whose solubility is not very high is newly generated and precipitated,
The required cleaning effect cannot be obtained, which hinders stable long-term measurement.

[0005]

As a cleaning liquid for deposits containing a large amount of calcium deposited in a measuring cell or a piping system of an apparatus for measuring test water having a high calcium concentration, the reaction product with calcium against water is used as a cleaning liquid. An aqueous solution of hydrochloric acid or nitric acid having high solubility is suitable. However, in an aqueous solution of a volatile acid such as hydrochloric acid or nitric acid, the concentration of the acid component in the vapor phase equilibrated with the aqueous solution is high, and such an acid solution is used as a cleaning liquid in the measuring cell of the conventional apparatus having the structure shown in FIG. When it is circulated, the gas phase portion 20 formed in the measurement cell 2
Also, a gaseous acid component is present, and the acid component in the gas phase passes through the diaphragm 19 of the ammonia gas electrode 1 whose sectional structure is shown in FIG. It dissolves in the solution and changes the pH value of the internal liquid 18. Since the diffusion rate of the volatile acid component once taken into the internal solution of the ammonia gas electrode 1 from the diaphragm 19 to the outside is very slow, the cleaning step is completed and the gaseous phase portion 20 of the measurement cell is in a gaseous state. The pH value of the internal solution does not recover to the original value for a long time even after the acid component of is absent.
At the ammonia gas electrode, the pH value of the gas phase detects the change in the pH value of the internal liquid when the ammonia component in the gas phase permeates the diaphragm and dissolves in the internal liquid. The presence of such a component that changes the pH value of the internal liquid greatly interferes with the ammonia concentration measurement. Due to such circumstances, the conventional apparatus cannot use an acid having a high cleaning ability such as hydrochloric acid or nitric acid as the cleaning liquid.

The present invention provides a means for using an acid having a high cleaning ability, such as hydrochloric acid or nitric acid, as a cleaning liquid in an automatic ammonia measuring device without leaving an influence that interferes with the measurement of ammonia concentration. The objective is to enable stable operation for a long period of time and extend the maintenance cycle even when measuring test water containing a large amount of suspended matter.

[0007]

[Means for Solving the Problems] To achieve the above object,
In the present invention, in the liquid phase upper portion of the measurement cell in which the measurement liquid mixed with the test water and the alkaline agent flows, in the gas phase portion formed as the mounting location of the ammonia gas electrode, the ammonia electrode such as air or nitrogen gas On the other hand, a purge gas inlet for circulating an inert gas and a purge gas outlet are provided, and a solenoid valve which is closed at the time of measurement is connected to the purge gas outlet, and an air pump for supplying the inert gas to the measuring cell on the purge gas inlet side And an arithmetic controller for controlling the operations of the solenoid valve and the gas supply source in a preset order.

In this way, this arithmetic controller opens the electromagnetic valve at the purge outlet and operates the gas supply source connected to the purge inlet during the cleaning process, and calculates the value of the arithmetic processing output of the measurement result. The value shall be held at the value immediately before the start of the cleaning process. Further, the sample water and the alkaline agent to the measuring cell, the transfer of the cleaning acid solution in the cleaning cycle of the measuring cell and the piping system, and the arithmetic processing output of the detection signal of the ammonia gas electrode are also controlled through the above arithmetic controller. And

[0009]

In the automatic ammonia measuring device having the above-mentioned structure, the arithmetic controller shifts to the cleaning process control operation after a lapse of a certain measuring time, and is connected to the gas supply source such as an air pump connected to the purge gas inlet of the measuring cell. The solenoid valve at the outlet of the purge gas is driven, and an inert gas such as purge air is circulated in the vapor phase portion above the liquid layer of the measurement cell. At the same time, the arithmetic controller replaces the test water and sends the cleaning acid solution in the storage tank to the flow passage connected to the measurement cell and closes the alkali agent injection flow path.

The arithmetic controller also operates so as to hold the arithmetic processing output of the measurement result at the value immediately before the start of the cleaning step during the cleaning step. After the elapse of the preset cleaning time, the arithmetic and control unit returns the operation of the controlled device to the measurement mode. As described above, in the apparatus having the above configuration, the ammonia gas electrode of the measurement cell is protected by an inert gas such as clean air during the cleaning step, so even if a volatile acid solution is used as the cleaning liquid, Normal and stable operation can be started immediately after returning to the measurement mode.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of the structure of an automatic measuring device for ammonia in water based on the present invention, and FIG. 2 shows an example of the internal structure of a measuring cell section which is a component of the device. The operation will be described below with reference to the drawings. In the measurement mode, the arithmetic and control unit 9 closes the solenoid valves 8 and 4, and the solenoid valve 16 at the purge gas outlet of the measurement cell, while the solenoid valves 5, 6 and 7 related to the detection of water and the introduction of the alkaline agent are opened. . As a result, the liquid pump 3 pumps up the test water and the alkaline agent and sends them into the measuring cell. Since the test water in the measurement cell is strongly alkaline, the ammonia component in the test water moves to the gas phase section 20 in FIG. The concentration of the ammonia gas transferred to the gas phase portion is detected by the ammonia gas electrode 1, and the display is output as the ammonia concentration in the test water through the arithmetic processing in the arithmetic controller 9.

When entering the cleaning step, the arithmetic and control unit 9 opens the electromagnetic valve 16 at the purge gas outlet, starts the air pump 15 to supply the purge air to the gas phase portion 20 of the measuring cell, and at the same time, the electromagnetic valve 5, 7 and 4 are closed to stop the test water and the supply of the alkaline agent, and instead the electromagnetic valve 8 and the electromagnetic valve 6 are opened so that the acid solution stored in the cleaning acid solution tank 12 is introduced into the measurement system. To do. The air supply system including the air pump 15 may be composed of a gas cylinder of an inert gas such as nitrogen, a pressure reducing valve, and a solenoid valve.

When the cleaning process is started, the arithmetic controller 9 operates so as to hold the arithmetic processing output of the measurement result at the value immediately before the start of the cleaning process. After the lapse of a predetermined washing time, the arithmetic and control unit 9 returns the opening and closing of the electromagnetic valve in the liquid flow path of the water test reagent or the like to the state of the measurement mode, and the cleaning liquid in the measurement cell is replaced with the mixed liquid of the test water and the alkaline agent. After a lapse of the time required for the operation, a command to stop the air pump 15 and to close the electromagnetic valve 16 at the purge gas outlet is issued, and then the hold state of the calculation processing output of the measurement result is released, and the mode returns to the measurement mode. When returning to the measurement mode, when the electromagnetic valves 7 and 6 connected to the water sampling tank 14 are closed and the electromagnetic valve 4 is opened, the standard liquid tank 10
The standard solution is supplied, and the instrument is calibrated.

In the apparatus of the present invention having the above-described structure and operation, the gas generated from the cleaning liquid during the cleaning process is not sent to the measuring cell 2 from the purge gas inlet shown in FIG. Gas phase 20 by active gas
Since it is discharged to the outside, it does not touch the diaphragm 19 of the ammonia gas electrode 1.

[0015]

According to the present invention, in the automatic ammonia measuring device using the ammonia gas electrode as the detection end, the purge gas flow port is provided in the gas phase portion above the measurement cell, and the cleaning liquid is flown through the test water flow system such as the measurement cell. During the cleaning process, the gas phase part of the measuring cell was purged with an inert gas such as clean air to block the contact between the ammonia gas electrode and the gas generated from the cleaning liquid, so it had a high cleaning ability as a cleaning liquid. It allows the use of concentrated aqueous solutions of volatile acids such as hydrochloric acid or nitric acid. As a result, it is possible to perform efficient cleaning without leaving the measurement gas obstruction effect on the ammonia gas electrode by volatile gas components, ensuring stable operation of the device for a long period of time, and disassembling and cleaning mainly on the measurement cell part. The effect of reducing the frequency of requiring heavy maintenance including replacement of parts is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the structure of a measurement cell section of the device shown in FIG.

FIG. 3 is a cross-sectional view showing the structure of a measuring cell section in a conventional device.

[Explanation of symbols]

 1 Ammonia gas electrode 2 Measuring cell 3 Liquid pump 4 Solenoid valve (energized open) 5 Solenoid valve (energized open) 6 Solenoid valve (energized close) 7 Solenoid valve (energized close) 8 Solenoid valve (energized open) 9 Operation controller 10 Standard Addition Liquid Tank 11 Alkaline Agent Tank 12 Cleaning Acid Solution Tank 13 Stirrer 14 Water Collection Tank 15 Air Pump 16 Electromagnetic Valve (energized Open) 17 pH Electrode 18 Internal Liquid 19 Septum 20 Gas Phase 21 21 Thermometer

Claims (4)

[Claims] 1. A gas phase portion, which is provided above a liquid phase of a measurement cell in which a measurement liquid obtained by mixing test water and an alkaline agent flows, and which is inert to an ammonia gas electrode is flowed. A purge gas inlet, a purge gas outlet, a solenoid valve coupled to the purge gas outlet side and closed during a measurement operation, a gas supply source coupled to the purge gas inlet side to supply the inert gas, the measurement cell and the measurement cell When the cleaning liquid is circulated in the flow passage of the measurement liquid connected to the cleaning liquid, the solenoid valve is opened to block the contact between the ammonia gas electrode and the gas volatilized from the cleaning liquid, and the gas supply source is connected. An arithmetic controller for controlling the supply of the inert gas to the gas phase part of the measurement cell, and an automatic measuring device for ammonia in water, comprising: 2. The apparatus for automatically measuring ammonia in water according to claim 1, wherein the gas supply source is an air pump for supplying air as an inert gas. 3. The automatic measuring device for ammonia in water according to claim 1, wherein the gas supply source comprises a high pressure gas cylinder of an inert gas and a pressure reducing valve. 4. The period from the start of the washing step of the measuring cell to the equilibrium of the ammonia gas concentration in the gas phase due to the measuring liquid introduced into the measuring cell after the washing is completed,
The apparatus for automatically measuring ammonia in water according to claim 1, wherein the display output of the measurement is held at a value immediately before the start of the cleaning step.