JPH05322873A - Carbon content measuring instrument - Google Patents

Abstract

PURPOSE:To highly sensitively measure the carbon content of a sample liquid without damaging the instrument used for the measurement even when the sample liquid contains hydrochloric acid at a high concentration by passing a gas sent from an oxidizing reaction section through a solution containing bivalent tin ions. CONSTITUTION:When a flow passage change-over valve is switched to a chlorine gas absorbing section 18 side at the time of measuring the organic carbon content of a sample liquid containing hydrochloric acid at a high concentration, a gas to be measured containing a hydrochloric acid gas from an oxidizing reaction section (TC combustion tube) is sent to a scrubber 31 from the change-over valve and discharged into a stannous chloride solution 32 as small bubbles through a diffusing tube 33. As a result, the hydrochloric acid gas is reduced into a complex by the bivalent tin ions contained in the solution 32 and the complex is absorbed (into the solution 32. Since the solution containing bivalent tin ions has an extremely high absorbing ability against hydrochloric acid gases, such as the hydrogen chloride gas, etc., the full quantity of the hydrochloric acid gas generated in the TC combustion tube can be absorbed. Therefore, the corrosion of the flow passage and each part after the TC combustion tube can be prevented and carbon dioxide concentration can be accurately measured without disturbance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon content measuring device for measuring carbon content in a solution containing a high concentration of hydrochloric acid.

[0002]

2. Description of the Related Art A total organic carbon meter (TOC meter) has been conventionally used to measure the organic carbon concentration in a sample solution. The method for measuring the total organic carbon concentration by the TOC meter will be described with reference to FIG. The sample liquid 10 is sucked up from the sample container by the syringe 14, the four-way valve 13 is switched, and then a predetermined amount of the sample liquid 10 is delivered to the TC combustion tube 15. The carbon component (C) in the sample liquid is oxidized (combusted) at a high temperature by the high-purity air 11 under the oxidation catalyst in the TC combustion tube 15 to become all CO ₂ . The combustion gas (measurement gas) of the sample liquid containing CO ₂ passes through the IC reactor 16 and the dehumidification / gas processing unit 21 and is sent to the infrared gas analysis unit (NDIR) 22.
There, the CO ₂ concentration is measured. Based on the value of this CO ₂ concentration, the control unit 23 calculates the total carbon (TC) amount in the sample liquid. Next, the four-way valve 13 is switched to set a predetermined amount of the sample solution 10
Is then delivered to the IC reactor 16 by the syringe 14. In the IC reactor 16, the inorganic carbon (IC) in the sample solution reacts with the acid stored therein to become CO ₂ . After that, as in the case of the above TC amount measurement, this CO
The concentration of ₂ is measured by the NDIR 22, and the control unit 23 calculates the IC amount. T measured in this way
From the amount of C and the amount of IC, the amount of total organic carbon (TOC) is calculated as TOC = TC-IC.

Here, when hydrochloric acid is contained in the sample liquid such as, for example, a part of the waste liquid, a combustion oxidation reaction in the TC combustion pipe 15 (hereinafter, this portion is generically referred to as an oxidation reaction part). ), Hydrogen chloride (HCl), chlorine (C
l), corrosive gas such as chloric acid gas (ClO ₂ ) (hereinafter, referred to as hydrochloric acid gas) is generated. These hydrochloric acid gases affect the measured value when measuring the CO ₂ concentration by the NDIR22, and the flow path and the dehumidification / dehumidification after the oxidation reaction part.
It may corrode each part of the gas processing part 21 and the NDIR 22. In order to avoid such a situation, in the conventional TOC meter, (1) the sample solution is diluted in advance, (2) the gas discharged from the oxidation reaction part is a solution containing silver ions such as silver nitrate, or a first chloride solution. Measures were taken such as flushing with an iron solution and (3) passing the gas emitted from the oxidation reaction section through a column filled with pellets (small particles) of a metal such as silver or tin.

[0004]

The above-mentioned respective measures in the conventional TOC meter are effective for a sample liquid containing only a few percent of hydrochloric acid at most, such as an ordinary waste liquid, but the sample liquid However, these measures were completely inadequate when the solution contained hydrochloric acid at a higher concentration. For example,
In the electronics industry, a solution containing hydrochloric acid having a high purity and a high concentration (concentration of 10% or more) is used for etching a semiconductor substrate, but when trying to measure the TOC amount of such a sample solution with a TOC meter, oxidation occurs. A large amount of hydrochloric acid gas is generated in the reaction part and cannot be sufficiently removed by a conventional silver ion solution, ferrous chloride solution, silver, tin pellets, or the like. In addition, concentrated hydrochloric acid used in the electronics industry
Since the amount of C is generally an extremely small amount of 1 ppm or less, it is difficult to dilute the sample solution in advance in terms of measurement accuracy. Furthermore, since the TOC amount is so small that high-sensitivity measurement needs to be performed, it is necessary to inject a larger amount of sample than usual on the one hand, while on the other hand, a large amount of sample must be injected. A large amount of hydrochloric acid gas is generated, and the hydrochloric acid gas that cannot be completely removed by a silver ion solution or the like and enters the NDIR 22 becomes a disturbing component of the CO ₂ concentration measurement, resulting in a measurement error. There is also a problem of corroding the flow path and the like.
The present invention has been made to solve such a problem, and its object is to measure with high sensitivity without damaging the measuring device even with a sample solution containing a high concentration of hydrochloric acid. The object of the present invention is to provide a carbon content measuring device capable of carrying out.

[0005]

According to the present invention made to solve the above problems, carbon in a sample solution is oxidized and converted into carbon dioxide in an oxidation reaction section, and a carbon dioxide concentration is measured in a carbon dioxide measurement section. In a carbon amount measuring device for measuring the amount of carbon in a sample solution by measuring, the gas sent from the oxidation reaction part is passed through a solution containing divalent tin ions, and then the carbon dioxide measurement part The feature is that it is sent out.

[0006]

When the sample solution contains hydrochloric acid, a gas (hydrochloric acid gas) such as hydrogen chloride (HCl), chlorine (Cl), and chloric acid gas (Cl0 ₂ ) is generated from hydrochloric acid in the oxidation reaction part. The term "oxidation reaction section" as used herein refers to a high temperature oxidation section (TC combustion tube 15 in the above TOC meter example) that oxidizes (burns) the sample liquid at a high temperature in the presence of a catalyst. These hydrochloric acid gases are reduced in a solution containing divalent tin ions and absorbed in the solution. Since the ability of this solution containing divalent tin ions to absorb hydrochloric acid gas such as hydrogen chloride gas is 10 times or more that of conventional solutions containing silver ions or ferrous chloride solutions, high concentration hydrochloric acid is used. Even with a sample liquid containing, the total amount of hydrochloric acid gas generated in the oxidation reaction part is absorbed, and those gases are not sent to the carbon dioxide measurement part. Therefore, corrosion of each part such as the flow path and the carbon dioxide part after the oxidation reaction part can be prevented, and the carbon dioxide measuring part can accurately measure the carbon dioxide concentration without interference.

[0007]

EXAMPLE An all-organic carbon meter (T
The OC meter will be described with reference to FIGS. 1 and 2. T of this embodiment
The OC meter is similar to the conventional basic TOC meter shown in FIG.
The hydrochloric acid gas absorption part 18 as shown in FIG. 2 is added, and the IC reactor 16 and the dehumidification / gas treatment part 21 can be switched to use or not to use the hydrochloric acid gas absorption part 18. A flow path switching valve 20 is provided between and.

As shown in FIG. 1, the hydrochloric acid gas absorption section 18 is provided with a scrubber 31, a detection tube 34, a solid absorption tube 36, and a scrubber liquid exchange system such as a pump 39. The scrubber 31 is installed inside the glass container.
% Stannous chloride (SnCl ₂ ) solution (scrubber solution) 3
2 into the scrubber liquid 32 from the top, and the air diffuser 33
Is inserted. It should be noted that a small amount of hydrochloric acid may be added to the stannous chloride solution 32 in order to prevent the stannous chloride crystal (SnCl ₂ .2H ₂ O) from being hydrolyzed to form a white precipitate. The detection tube 34 is formed by fixing a hydrochloric acid gas detection agent 35 containing an organic dye inside a glass tube. The solid absorption tube 36 has a diameter of about 1 to 2 m inside the glass tube.
It is filled with m granular copper (copper pellets) 37, and a gas inlet is provided at the bottom of the tube and an outlet is provided at the top.

The TOC meter has a high hydrochloric acid concentration (concentration is several%.
When measuring the amount of organic carbon in the sample liquid 10 (above),
The flow path switching valve 20 is connected to the hydrochloric acid gas absorption section 18 side (solid line in FIG. 1)
Switch to. The sample solution 10 sucked from the sample container by the syringe 14 is sent to the TC combustion tube 15 or the IC reactor 16 by switching the four-way valve 13, and the sample solution 1 is there.
The carbon component in 0 (total carbon in the TC combustion tube 15 and inorganic carbon in the IC reactor 16) is converted into carbon dioxide (CO ₂ ). However, when the sample liquid 10 contains hydrochloric acid when burned in the TC combustion tube 15, hydrogen chloride (HCl),
Gas (hydrochloric acid gas) such as chlorine (Cl) and chloric acid gas (ClO ₂ ) is generated and sent to the dehumidifying / gas processing unit 21 and the NDIR 22 together with CO ₂ which is the original measurement target. In this embodiment, in order to prevent this, the hydrochloric acid gas absorption unit 18 removes the hydrochloric acid gas in advance.

The measurement gas containing hydrochloric acid gas is first sent from the flow path switching valve 20 to the scrubber 31, and its diffusing pipe 3
3 is discharged as fine bubbles into the stannous chloride solution 32. The hydrochloric acid gas contained in the measurement gas is reduced by the divalent tin ions in the stannous chloride solution 32 on the surface of the foam, forms a complex, and is absorbed in the stannous chloride solution 32. The measurement gas is then fed to the detection tube 34 and the solid absorption tube 3
6 through the flow path switching valve 20 to dehumidify / gas treatment unit 2
1 and NDIR 22.

Some conventional TOC meters also use a scrubber similar to the above in order to remove the hydrochloric acid gas generated by considering the case where the sample contains a small amount of hydrochloric acid. A solution or ferrous chloride solution was used. However, since the hydrochloric acid gas absorption capacity of the silver nitrate solution and the ferrous chloride solution is not high, when measuring a sample containing a high concentration of hydrochloric acid, the hydrochloric acid gas in the measurement gas cannot be sufficiently absorbed, and the NDIR22 When measuring the CO ₂ concentration, there arises a problem that interference is caused and a flow path, parts and the like are corroded. On the other hand, in the TOC meter of the present embodiment, the stannous chloride solution 32 is used as the solution in the scrubber 31, but the divalent tin ion in the stannous chloride solution 32 has conventionally used the ability to absorb hydrochloric acid gas. It is 10 times more than that of silver ions. Therefore, the hydrochloric acid gas in the measurement gas is almost completely removed by the scrubber 31 of this embodiment.

In order to compare the hydrochloric acid gas absorption capacity of the TOC meter of this embodiment with that of the conventional TOC meter, the TOC was set to 0.3.
A reagent grade hydrochloric acid having a concentration of 36% containing 0.8 ppm was prepared as the sample solution 10, and the measurement was performed by both TOC meters.
Since the conventional TOC meter cannot sufficiently remove the hydrochloric acid gas in the measurement gas, the CO ₂ in the NDIR 22 cannot be removed.
An interference peak was generated during the concentration measurement, and the CO ₂ concentration could not be measured accurately. On the other hand, the TO of this embodiment
With the C meter, even if TOC measurement of 40 ml (250 μl × 160 times) of the sample liquid 10 in total was performed, the NDIR22
No interference occurred, and no corrosion of the flow path or parts occurred.

However, since the stannous chloride solution 32 also changes in quality by absorbing hydrochloric acid gas, its ability to absorb hydrochloric acid gas eventually disappears. In this case, hydrochloric acid gas may remain in the measurement gas discharged from the scrubber 31, but the copper pellet 37 in the solid absorption tube 36 surely captures it, and the dehumidification / gas treatment unit 21 and the NDIR 22. To be sent to. In addition, at this time, the color of the hydrochloric acid gas detecting agent 35 in the detecting tube 34 changes to notify that the stannous chloride solution 32 in the scrubber 31 should be replaced. The deteriorated solution 32 is discharged to the drain 41 through the solenoid valve 38, and a new stannous chloride solution (supplementary scrubber solution) 40 is pumped up from the storage tank by the pump 39, and the scrubber 3
Sent to 1.

As shown in FIG. 3, the scrubber 31
A potentiometer 44 is installed in the stannous chloride solution 32
Deterioration of the stannous chloride solution 32 may be detected by detecting a change in potential when a valent tin ion reacts with hydrochloric acid gas and changes into a tetravalent tin ion. In this case, the solenoid valve 38 and the pump 39 are operated by the control unit 43 (may be shared with the control unit 23 of FIG. 2) to automatically update the stannous chloride solution 32 in the scrubber 31. You can

[0015]

EFFECTS OF THE INVENTION The ability of the solution containing divalent tin ions used in the carbon content measuring apparatus of the present invention to absorb a gas such as hydrogen chloride gas is higher than that of conventional solutions containing silver ions or ferrous chloride solutions. 10 times or more. Therefore, even a sample liquid containing high-concentration hydrochloric acid can absorb all the corrosive gas such as hydrogen chloride gas generated in the oxidation reaction part, and does not send the gas to the carbon dioxide measurement part. .. Therefore, corrosion of each part such as the flow path and the carbon dioxide part after the oxidation reaction part is prevented, and the carbon dioxide measuring part can accurately measure the carbon dioxide concentration without interference.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a total organic carbon content measuring apparatus (TOC meter) which is an embodiment of the present invention.

FIG. 2 is a configuration diagram of a hydrochloric acid gas absorption unit of the TOC meter of the embodiment.

FIG. 3 is a configuration diagram of a scrubber equipped with a device for automatically updating the scrubber liquid.

[Explanation of symbols]

10 ... Sample solution 15 ... TC combustion tube 16 ... IC reactor 18 ... Hydrochloric acid gas absorption section 20 ... Flow path switching valve 31 ... Scrubber 32 ... Stannous chloride solution (scrubber solution) 33 ... Diffuser tube 34 ... Detection tube 35 ... Hydrochloric acid gas detecting agent 36 ... Solid absorption tube 37 ... Copper pellet 38 ... Electromagnetic valve 39 ... Pump 44 ... Potentiometer

Claims (1)

[Claims] 1. A carbon amount measurement for measuring the carbon amount in a sample liquid by oxidizing carbon in the sample liquid in the oxidation reaction part to convert it into carbon dioxide and measuring the carbon dioxide concentration in the carbon dioxide measuring part. In the apparatus, the gas delivered from the oxidation reaction section is passed through a solution containing divalent tin ions, and then delivered to a carbon dioxide measurement section.