JPH0645882Y2 - Carbon content measuring device - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention relates to a carbon content measuring device, and in particular, the concentration of total organic carbon (TOC) contained in ultrapure water used for applications such as semiconductors and nuclear power. The present invention relates to a carbon content measuring device suitable for use in the analysis of.

"Prior art" Generally, in a TOC meter, after removing carbon dioxide (inorganic carbon) contained in a sample solution, organic carbon is oxidized to generate carbon dioxide, and the amount of this carbon dioxide is measured by an infrared gas analyzer. It is being detected. Also, above
In the TOC measuring device, the TOC concentration is measured using a standard solution having a known TOC concentration, and the measurement result (infrared gas analyzer reading) is compared with the TOC concentration of the standard solution, It is necessary to calibrate the span of the TOC measuring device.

"Problems to be solved by the device" By the way, the standard solution on the market used for the span calibration is generally 1000 ppb or more, and the concentration to be measured by the device for the above application (about 50 ppb at full scale)
It cannot be used very high compared to.

Further, even if the user of the TOC meter tries to prepare a standard solution having a necessary concentration, it is very difficult to prepare an accurate standard solution having a low concentration of about several tens of ppb.

In other words, even if you try to obtain pure water, which is indispensable for preparing the standard solution, from a commercially available product, this pure water usually has a TOC
In addition, since it is necessary to maintain a high degree of cleanliness of the atmosphere of the container and equipment, it has been considered difficult to prepare a standard solution with a low TOC concentration.

The present invention has been proposed in view of the above circumstances, and an object thereof is to obtain a TOC meter capable of span calibration without using a low-concentration standard solution that is difficult to prepare.

[Means for Solving the Problems] In order to achieve the above object, the present invention mixes a reaction solution with a sample solution to oxidize organic carbon in the sample solution, and removes carbon dioxide generated by the oxidation reaction. In a carbon content measuring device that is extracted into a carrier gas in an extractor and is used to measure the extracted carbon dioxide by an infrared gas analyzer, in the pipe from the extractor to the infrared gas analyzer, the pipe is extracted. Or a first switching valve that is selectively connected to a gas supply source having zero carbon dioxide concentration, and the extractor is inactive in the pipe from the inert gas supply source to the extractor. A three-way switching valve that is selectively connected to a gas supply source or a carbon dioxide gas supply source of known concentration is provided.

[Operation] With the above configuration, by operating the three-way switching valve, a gas having a known carbon dioxide concentration can be supplied to the infrared gas analyzer as needed, and a carrier gas or a standard gas can be supplied to the extractor. Can be supplied as an alternative,
Therefore, before supplying the sample solution and the reaction solution to the device and starting the measurement, supply a known concentration of carbon dioxide and let the infrared gas analyzer measure the concentration, so that the span is calibrated and corrected. By switching the three-way switching valve, carbon dioxide can be extracted from the sample liquid after the reaction and the usual carbon amount measurement can be performed.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

Reference numeral 1 is a sample liquid supply pipe. A pump 2 is provided in the pipe 1, and the sample solution sent out by the pump 2 is a deaerator together with a reaction solution (a mixed solution of an oxidizing agent and an acidic solution) supplied from a tank 4 by the pump 3. 5
To be supplied to. The deaerator 5 supplies an inert gas such as helium or nitrogen from below to aerate a plurality of pipes connected in series, thereby aerating the inert gas and the inert gas in the sample solution and the reaction solution. It functions to remove carbon dioxide.

The liquid degassed by the degasser 5 is fed into the reactor 7 by the pump 6. In this reactor 7, a coil-shaped pipe line through which the liquid passes is heated by a heater arranged at the center of the coil to accelerate the oxidation reaction with the sample liquid, the reaction liquid and the reaction liquid. A throttle 8 is provided in the downstream pipe of the reactor 7 to apply a back pressure to the liquid in the reactor 7.

Further, the liquid passing through the reactor 7 and the throttle 8 is fed to the extractor 9. This extractor 9
Releases the pressurized liquid supplied from the pre-reactor 7 to the atmospheric pressure and also supplies the inert gas as the carrier gas to extract the carbon dioxide generated by the reaction into the carrier gas. There is.

Then, the carrier gas and the carbon dioxide extracted therein are passed through the dehumidifier 10 to be cooled to a temperature below the dew point to remove the water vapor content, and then supplied to the infrared gas analyzer 11 for concentration. Is being measured. This infrared gas analyzer 11 can output an electric signal of an output corresponding to the concentration of carbon dioxide according to the concentration, and this output is a concentration value calculated by a predetermined arithmetic expression in a control device (not shown). It is converted into and displayed. A three-way switching valve 12 is provided between the dehumidifier 10 and the infrared analyzer 11.

Further, reference numeral 13 is a gas cylinder as a supply source of the inert gas used for the aeration and the carrier. A pressure reducing valve 14 is provided on the discharge side of the supply source 13, a pipe 15 is connected, and the pipe 15 is connected to one port of a three-way switching valve 16. A pipe 17 leading to the deaerator 5 and a pipe 18 leading to the infrared analyzer 11 are connected to the other ports of the three-way switching valve 16, respectively.

On the other hand, reference numeral 19 is a supply source of carbon dioxide as a standard gas having a known concentration, and this supply source 19 is connected to one port of a three-way switching valve 21 via a pressure reducing valve 20. This 3
A branch of a pipe from the inert gas supply source 13 to the deaerator 5 is connected to the other port of the one-way switching valve 21 to supply the inert gas supply source 13 or the standard gas to the extractor 9. Source 19 is adapted to be connected. Reference numeral 22 is a mass flow controller for adjusting the flow rate of the gas supplied to the extractor 9.

Next, referring to FIG. 4, the control device (not shown) for switching the three-way switching valves will be described together with the operation of the TOC meter having the above configuration. In the following description, step n is the fourth
It corresponds to each step labeled Sn in the figure.

Step 1 Calibration is started by operating a calibration switch (not shown) provided in the control device.

Step 2 When the pumps 2, 3, 6 are stopped and the switching valves 12 and 16 are energized as shown in FIG. 2 to switch the state shown in FIG. 1 to the state shown in FIG. A source 13 of inert gas is connected to the infrared gas analyzer 11.

Step 3 When a high-purity inert gas (gas having a CO ₂ concentration of zero) is supplied from the supply source 13, the infrared gas analyzer 11 to which this inert gas has been supplied has a signal corresponding to a concentration of zero (for example, a signal corresponding to zero). 4 mA when the span is 4 to 20 mA, 0 to 1 VDC
In the case of, the signal a of a level corresponding to a predetermined error is output even though 0 V) should be output. Therefore, the difference between this signal and the signal corresponding to the original zero concentration is zero point drift. The value M is stored in the control device.

Step 4 Turn off the switching valves 12 and 16.

Step 5 When the switching valve 21 is further turned on, the inert gas supply source 13 is connected to the original deaerator 5 and the standard gas having a known CO ₂ concentration is supplied as shown in FIG. 19 to mass flow controller 22, extractor 9, dehumidifier 10 and switching valve
It is supplied to the infrared gas analyzer 11 via 12. Further, the mass flow controller 22 controls the flow rate of the standard gas so that the flow rate becomes equal to that during the TOC meter operation.

Step 6 The infrared gas analyzer 11 detects a gas having a known CO ₂ concentration and outputs a signal of level a. Further, the difference from the output corresponding to the known CO ₂ is stored as a drift value N in the concentration in the control device.

Step 7 When the switching valve 21 is turned off, each valve is opened and closed as shown in FIG.

Step 8 The span drift correction coefficient κ is calculated from the detection values M and N for the zero concentration and the known concentration S measured in the above Steps 3 and 6, respectively, by the formula (N−M) / S = κ, and the controller To memorize.

By the above steps, the zero point correction value M and the span calibration value N are stored in the control device, respectively, and the TOC is measured based on these values in the valve open / close state of FIG.

That is, the pumps 2 and 3 are driven to feed the sample liquid and the reaction liquid to the deaerator 5, and the inert gas is supplied to the deaerator 5 to release the dissolved carbon dioxide, and the degassed liquid is pumped. After being sent to the reactor 7 by 6 and reacted under heating, the reacted liquid is extracted into an inert gas as a carrier in the extractor 9, and further cooled to below the dew point in the dehumidifier 10 to remove water vapor. The carbon dioxide concentration is measured by the infrared gas analyzer 11. Further, the output of the infrared gas analyzer 11 has its span properly corrected by a constant κ preset in the control device, and the carbon dioxide concentration is detected.

It should be noted that the switching direction depending on ON-OFF of the three-way switching valve is not limited to the above-described embodiment, but may be the same switching state as in the embodiment by the operation in which ON-OFF is reversed. Of course.

Further, in the above embodiment, the carrier gas and the inert gas as the aeration gas are supplied from a single supply source, but it is needless to say that they may be supplied as separate supply sources.

“Effect of device” As is clear from the above description, according to the present invention, a normal TO
A switching valve can be installed at a predetermined position of the piping system of the C meter to supply a carrier gas with a carbon dioxide concentration of zero or a carbon dioxide gas of a known concentration to the infrared gas analyzer. The effect that the highly accurate span calibration can be easily performed using the carrier gas essential to the meter and the carbon dioxide gas that is easily available.

[Brief description of drawings]

The drawings show one embodiment of the present invention. Fig. 1 is a piping diagram showing the open / closed state of the valve during measurement, Fig. 2 is a piping diagram showing the open / closed state of the valve at zero point correction, and Fig. 3 Is a piping diagram showing the open / closed state of the valve at the time of span adjustment, and FIG. 4 is a control flowchart. 5 ... Deaerator, 9 ... Extractor, 11 ... Infrared gas analyzer, 13 ... Inert gas supply source, 19 ... Carbon dioxide gas supply source, 22 ... Mass flow controller, 12.16.21 ......
3-way switching valve.

Claims (1)

[Scope of utility model registration request] 1. A reaction solution is mixed with a sample solution to oxidize organic carbon in the sample solution, and carbon dioxide generated by this oxidation reaction is extracted into a carrier gas in an extractor to extract carbon dioxide. In the carbon content measuring device adapted to measure the gas by an infrared gas analyzer, a pipe from the extractor to the infrared gas analyzer is selected, and the pipe is selected as the extractor or a gas supply source of zero carbon dioxide concentration. A first switching valve that is integrally connected is provided, and the extractor is supplied to the inert gas supply source or a carbon dioxide gas having a known concentration in a pipe from the inert gas supply source to the extractor. A carbon content measuring device, characterized in that a three-way switching valve that is selectively connected to the source is provided.