JPS6353500B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention provides the following advantages:
This paper relates to a method for calibrating a dissolved oxygen analyzer that continuously analyzes and measures the amount of dissolved oxygen in condensate/feed water or reactor water.

In thermal and nuclear power plants, the amount of dissolved oxygen in the condensate and feed water systems is important as a detection element for corrosion of piping systems, etc. For this reason, in this type of equipment, a dissolved oxygen amount monitoring device is provided to regulate the amount of dissolved oxygen.

Therefore, as this dissolved oxygen amount monitoring device, a dissolved oxygen analyzer having a polarographic type diaphragm electrode is mainly used.

By the way, in this type of dissolved oxygen analyzer, when oxygen exists in the sample water, a current flows according to the polarographic oxygen curve with respect to the potential difference between the two electrodes, and the amount of current is proportional to the oxygen partial pressure in the sample water. It is something to do. Further, when using this type of dissolved oxygen analyzer, calibration is required due to its operating characteristics, and a known quantity increase method, such as using a Faraday cell, is generally used as a calibration method. In other words, the known amount increase method is a method in which a known amount of oxygen is added to the sample water, and as a means for adding this known amount of oxygen, the sample water is electrolyzed and oxygen is generated by an anode reaction. . Therefore, the amount of oxygen generated in the anodic reaction caused by electrolysis can be known from the current value, assuming that the current efficiency is 100%.

However, according to the calibration method of the conventional dissolved oxygen analyzer mentioned above, when the amount of dissolved oxygen in the sample water is in a saturated state (6 to 8 ppm), such as at startup, the amount of dissolved oxygen in the sample water is Calibration is not possible because it is unclear. On the other hand, when starting operation after startup, when performing calibration to accurately measure trace oxygen, usually 10 to 100 ppb, separately prepare a calibration solution with a known trace oxygen amount and introduce it into the analyzer electrode. There is a need to. However, since it is virtually impossible to create a calibration solution with a known trace amount of dissolved oxygen, calibration must be performed after operation. The reliability of the measured values was extremely low.

Therefore, the present inventors conducted various studies and made prototypes in order to overcome all the problems in the conventional calibration method of dissolved oxygen analyzers mentioned above. As a result, the present inventors installed a degassing tank with a predetermined capacity and set up a degassing tank with a specified capacity. A predetermined amount of sample water with a concentration of dissolved oxygen is introduced into the deaeration tank, and then an inert gas is released from the bottom and middle part of the deaeration tank to bubble the sample water for a predetermined time. Dissolved oxygen in the water is exhausted to the outside to reduce the amount of dissolved oxygen, and then the sample water in the degassing tank is supplied to the analysis system including the Faraday cell and dissolved oxygen analyzer under the pressure of inert gas. It has been found that calibration can be performed properly and that the above problems can be solved at once.

In order to most effectively bubble the sample water in the deaeration tank, diffuser tubes made of porous sintered metal or ceramic should be arranged radially from the center of the deaeration tank, and It has been found that it is preferable to configure the air diffuser tube in the section so that the amount of discharge can be adjusted. Note that the deaeration tank can be used temporarily as mentioned above, such as during startup, and after calibration is completed, it can be separated from the sample water piping and connected to the piping to directly introduce the sample water into the analyzer. Calibration of an oxygen analyzer can be accomplished properly and smoothly using only a Faraday cell.

Therefore, it is an object of the present invention to detect dissolved oxygen during startup, etc. in a sample water dissolved oxygen analysis system in which a flow meter and a flow rate adjustment valve are installed in sample water piping, and a dissolved oxygen analyzer is connected via a Faraday cell or the like. To provide a calibration method that can smoothly and easily reduce the amount of dissolved oxygen in a sample water with a high concentration of oxygen, and can properly calibrate a dissolved oxygen analyzer using a known amount increase method. It is in.

In order to achieve the above object, in the present invention, a dissolved oxygen analyzer is connected to the sample water piping via a main valve, a flow rate adjustment valve, a flow meter, and a Faraday cell, and the dissolved oxygen analyzer is In a dissolved oxygen analyzer configured to perform calibration, pipes for leading out sample water are connected to the upstream and downstream sides of the main valve of the sample water pipe through an inlet valve and an outlet valve, respectively, and these pipes are disconnected. A gas pipe is connected to the deaeration tank and communicated with an inert gas supply source to the deaeration tank, and a switching valve is provided in a part of this gas pipe to branch it into two directions, one branch being connected to the other. The gas pipe is extended into the bottom of the deaeration tank, a plurality of radially extending aeration pipes are provided at the tip thereof, and the other branch gas pipe is opened upward inside the deaeration tank to perform the deaeration process. After introducing an inert gas into the upper part of the degassing tank from the other branch gas pipe to purge the internal gas, inject the inert gas into the sample water from the one branch gas pipe to purge dissolved oxygen. Then, the outlet valve is opened while introducing an inert gas from the other branch gas pipe, and the degassed sample water is degassed with dissolved oxygen by the gas pressure in the degassing tank and the head of the degassed water. It is characterized by being supplied to an analyzer.

In the calibration method described above, the diffuser tube is made of porous sintered metal or ceramic, has a hollow space with a closed end, and is radially connected to the middle part of the branch gas pipe extending into the degassing tank. It is preferable to provide an adjustable air diffuser pipe that extends to.

Further, it is preferable to provide a vent pipe for deaeration at the top of the deaeration tank and a relief valve for protection against internal abnormal overpressure.

Next, an embodiment of the dissolved oxygen analyzer calibration method according to the present invention will be described in detail with reference to the accompanying drawings, illustrating a known quantity increase method using a Faraday cell.

FIG. 1 is a system diagram showing an embodiment of the system of the present invention. That is, in FIG.
0 is a sample water supply pipe, 12 is a sample water source valve, 14 is a flow rate adjustment valve, 16 is a flow meter, 18 is a Faraday cell, and 20 is a dissolved oxygen analyzer. However, by opening the sample water source valve 12 and supplying the sample water to the dissolved oxygen analyzer 20 via the Faraday cell 18 while adjusting the flow rate of the sample water using the flow rate adjustment valve 14 and the flow meter 16, the sample water It is configured to be able to perform continuous measurements. The analysis system having the above configuration is basically the same as a conventional dissolved oxygen analyzer.

Therefore, in the present invention, an inlet valve 22 and an outlet valve 2 are provided from the upstream side and the downstream side of the sample water source valve 12 connected to the sample water supply pipe 10, respectively.
4, a sample water inlet pipe 26 and a sample water outlet pipe 28 are led out, and these inlet pipe 26 and outlet pipe 28 are connected to a degassing tank 30. The deaeration tank 30 is generally a cylindrical sealed container, has an inlet pipe 26 connected to its upper side, an outlet pipe 28 connected to its lower side, and has a main valve 32 connected to one side as appropriate. A liquid level gauge 34 is provided therebetween. Further, an opening/closing lid 36 is detachably provided at the top of the deaeration tank 30, and a gas pipe 38 for aeration is inserted vertically into the deaeration tank 30 from the center of the opening/closing lid 36, and the lower end thereof is inserted into the deaeration tank 30 vertically. are connected to a plurality of air diffusers 40 arranged radially (see FIG. 2). Also,
In the middle part of the gas pipe 38 in the deaeration tank 30, adjustable aeration pipes 44 capable of adjusting the amount of released gas via an adjustment valve 42 are radially connected and arranged so as not to overlap with the aeration pipe 40. (See Figure 3).
Note that the diffuser pipes 40, 4 used in this example
4 is preferably made of porous sintered metal or ceramic and has a hollow tube structure with a closed tip.

The opening/closing lid 36 of the deaeration tank 30 is provided with a vent pipe 48 for exhausting purge gas via a vent valve 46.
A relief valve 50 for protection against abnormal overpressure is also connected and arranged. Further, the gas pipe 38 inserted through the center of the opening/closing lid 36 is
As shown in FIG. 1, a three-way switching valve 52, a gas flow rate adjustment valve 54, a pressure adjustment valve 56, and a cylinder main valve 5
8, respectively, to an inert gas cylinder 60. A primary pressure gauge 62 and a secondary pressure gauge 64 are provided before and after the pressure regulating valve 56, respectively, to facilitate pressure regulation. Further, a bypass pipe 66 led out from the three-way switching valve 52 is connected to a nozzle 68 that opens into the top of the degassing tank 30 via the opening/closing lid 36. Furthermore, a drain pipe 72 is provided at the bottom of the deaeration tank 30 for discharging residual sample water via a drain valve 70.

Next, a procedure for calibrating the dissolved oxygen analyzer 20 using the degassing tank 30 having the above-described configuration will be described in relation to its operation.

1 Operation for introducing sample water into the deaeration tank at startup First, close the sample water source valve 12 and outlet valve 24, open the inlet valve 22 and vent valve 46, and introduce the sample water at startup into the inlet pipe 26. The gas is introduced into the deaeration tank 30 through the air. In this case, the deaeration tank 30
The total volume of the sample water is set to about 56, and the sample water is about 50
It is preferable to introduce it continuously. Deaeration tank 30
Level gauge 3 indicates that a predetermined amount of sample water has been introduced.
4 and close the inlet valve 22.

2 Degassing operation of sample water First, after operating the three-way switching valve 52 connected to the gas pipe 38 to communicate with the bypass pipe 66, the cylinder main valve 58 is opened and an inert gas such as nitrogen gas is introduced. The sample water is maintained at a predetermined pressure (1.4 kg/cm ² ) and supplied from the nozzle 68 to the gas phase portion of the degassing tank 30, and the oxygen in the gas phase when the sample water is introduced is purged through the bend pipe 48.

Next, the three-way switching valve 52 is switched to inject inert gas into the sample water from the aeration pipe 40. In this case, since the diffuser tube 40 is made of porous sintered metal or ceramic, the gas injected into the sample water becomes extremely fine bubbles, expanding the gas-liquid contact surface and efficiently purging dissolved oxygen. I can do it. In addition, by appropriately adjusting the amount of injected gas using the adjustable air diffuser 44, the partial pressure in the gas phase in the degassing tank 30 can be changed,
The amount of dissolved oxygen in sample water can be adjusted. By the way, the inert gas supply pressure is 1.4Kg/
cm ² , when using only the air diffuser 40, the amount of dissolved oxygen can be reduced to 10 ppb with about 30 minutes of deaeration treatment, whereas when the adjustable air diffuser 44 is fully opened and used together. The amount of dissolved oxygen can be reduced to 3 ppb under the same conditions.

3 Supply of sample water after degassing treatment and calibration operation When the degassing treatment process described above is completed, the outlet valve 2
4 is opened, and the degassed sample water is introduced into the analysis system under the pressure of the inert gas introduced into the degassing tank 30 from the bypass pipe 66 and nozzle 68 via the three-way switching valve 52 and by the water head of the degassed sample water. supply

In this way, if the sample water supplied to the analysis system generates dissolved oxygen of 10 to 30 ppb in the Faraday cell 18, the sample water is in the low concentration dissolved oxygen range of 13 to
The dissolved oxygen analyzer 20 can be calibrated within the range of 33 ppb.

4 Operations after calibration work When the above-mentioned calibration work is completed, close the main valve 58 and outlet valve 24 of the inert gas cylinder 60 to separate the deaeration tank 30 from the analysis system, and open the sample water main valve 12. and sample water supply piping 10
The sample water is directly supplied to the analysis system and the sample water is continuously measured. Further, the degassed sample water remaining in the deaeration tank 30 is released to the outside through the drain pipe 72 by opening the drain valve 70, in preparation for the calibration work of the analyzer at the next startup, etc.

As is clear from the embodiments described above, according to the present invention, sample water whose dissolved oxygen content reaches a saturated state at the time of startup etc. is collected in advance into a deaeration tank to obtain sample water with a constant trace amount of dissolved oxygen. In this case, the degassed sample water can be supplied from the deaeration tank to the analysis system using the pressure of the inert gas used to purge dissolved oxygen, and the dissolved oxygen analyzer can be properly calibrated using the Faraday cell. be able to.

Furthermore, the deaeration tank used in the present invention has an extremely simple configuration, and can be connected between the sample water supply system and the analysis system by operating the inlet and outlet valves, allowing for efficient deaeration of the sample water. This can be achieved well and tunably. In particular, when degassing and supplying degassed sample water, it can be easily operated using inert gas pressure without using drive means such as motors and pumps, making handling and maintenance easier. It has advantages such as being easy to use.

Although the preferred embodiments of the present invention have been described above, it goes without saying that various design changes can be made without departing from the spirit of the present invention.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing one embodiment of the calibration method for a dissolved oxygen analyzer according to the present invention, Fig. 2 is a cross-sectional explanatory diagram of a degassing tank used in the method of the present invention, and Fig. 3 is similar to Fig. 2. It is a top view which shows the attachment state of the air diffuser shown in FIG. 10... Sample water supply piping, 12... Sample water source valve, 14... Flow rate adjustment valve, 16... Flow meter, 18
... Farade cell, 20 ... Dissolved oxygen analyzer,
22... Inlet valve, 24... Outlet valve, 26... Inlet piping, 28... Outlet piping, 30... Deaeration tank, 32
... Main valve, 34 ... Liquid level gauge, 36 ... Opening/closing lid, 3
8...Gas piping, 40...Diffuser pipe, 42...Adjustment valve, 44...Adjustable air diffuser pipe, 46...Vent valve,
48... Vent pipe, 50... Relief valve, 52... Three-way switching valve, 54... Gas flow rate adjustment valve, 56... Pressure adjustment valve, 58... Cylinder main valve, 60... Inert gas cylinder, 62... ...Primary pressure gauge, 64...Secondary pressure gauge, 66...Bypass pipe, 68...Nozzle,
70...Drain valve, 72...Drain pipe.

Claims (1)

[Scope of Claims] 1. A dissolved oxygen analyzer is connected to the sample water piping via a main valve, a flow rate adjustment valve, a flow meter, and a Faraday cell, and the dissolved oxygen analyzer is calibrated by a known amount increase method. In the dissolved oxygen analyzer, pipes for extracting sample water are connected to the upstream and downstream sides of the main valve of the sample water pipe through an inlet valve and an outlet valve, respectively, and these pipes are connected to a degassing tank. , A gas pipe communicating with an inert gas supply source is introduced into the deaeration tank, and a switching valve is provided in a part of this gas pipe to branch it into two directions, and one branched gas pipe is connected to the deaeration tank. A plurality of aeration pipes are provided extending in the bottom of the tank and extending radially at the tips thereof, and the other branch gas pipe is opened upwardly inside the deaeration tank, and the other branch gas is removed in the deaeration treatment process. After introducing an inert gas into the upper part of the degassing tank through the piping to purge the internal gas, inject the inert gas into the sample water from one of the branched gas piping to purge dissolved oxygen and perform the degassing process. Then, while introducing an inert gas from the other branch gas pipe, open the outlet valve and supply degassed sample water to the dissolved oxygen analyzer using the gas pressure in the degassing tank and the head of the degassed water. A method for calibrating a dissolved oxygen analyzer, characterized in that: 2. In the method for calibrating a dissolved oxygen analyzer according to claim 1, the aeration tube is a hollow tube made of porous sintered metal or ceramic and has a closed tip, and further includes a degassing tank. A method for calibrating a dissolved oxygen analyzer in which an adjustable air diffuser pipe that extends radially is provided in the middle part of a branch gas pipe that extends within the interior. 3. In the method for calibrating a dissolved oxygen analyzer as set forth in claim 1, a deaeration vent pipe is provided at the top of the deaeration tank, and a relief valve is provided to protect against internal abnormal overpressure. A method for calibrating a dissolved oxygen analyzer according to paragraph 1.