JPS602618B2 - Atmospheric fluorine concentration measurement method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for measuring fluorine concentration in the atmosphere.

More specifically, the present invention relates to an improved method for continuously measuring fluorine concentration in the atmosphere using a fluorine ion electrode method. Fluorine compounds (including fluorine gas, hereinafter the same) are contained in waste gas from factories, etc.! Well, even a small amount can cause damage to plants, so ultra-trace analysis is required to measure it.

Such fluorine compounds include, for example, fluorine gas "
Examples include so-called gaseous inorganic fluorine compounds such as hydrogen fluoride and silicon fluoride. Among these, ``Fluorine is a chemically very active compound, so its influence is extremely large, and measurement of ultra-trace quantities is required.Methods for measuring these fluorine compounds in the atmosphere include, for example, automated Continuous measurement methods such as fluorine ion electrode method and spectrophotometry are often used.

Among these measurement methods, the fluoride ion electrode method has the advantage of having a wide quantitative range and being able to perform simple and rapid analysis compared to other measurement methods such as spectrophotometry.

In particular, the automated fluorine ion electrode method is a method in which the fluorine compounds in the waste gas at the source are brought into contact with the absorption liquid, and the fluorine concentration in the absorption liquid is measured using the fluoride ion electrode method. Concentration changes can be measured directly.

By the way, fluorine compounds are fluorine gas (F2),
It is thought that the fluorine gas reacts immediately with water vapor in the atmosphere and changes to hydrogen fluoride (for example, see pages 15-16 of "Environmental Pollution Analysis Method 0" published by Dainippon Tosho ■). It was expected that the reaction would be fast, but ``As a result of various studies by the present inventors, we found that although fluorine gas has extremely high reactivity, it reacts surprisingly slowly with water. Continuous measurements using the method revealed that fluorine ions were not measured as fluorine ions.

Although JIS KKO 150-1967 describes a method for analyzing fluorine compounds in waste gas, it does not mention anything about the analysis of fluorine gas. Therefore, various studies were first conducted by changing the type of absorption liquid to one that is highly reactive with fluorine, but almost no performance was measured in any of the cases on the same aircraft as above.

However, as a result of extensive research by the present inventors, we found that the cause of this problem was surprisingly due to the absorption liquid contact flow rate of the detected gas containing fluorine gas.
At a rate of 10 to 300 so/min/10 (-absorption liquid), fluorine gas is hardly absorbed by the absorption liquid.In the reaction between fluorine gas and absorption liquid, the rate-determining rate is the dissolution of the fluorine gas into the absorption liquid. I finally figured out something. However, the present invention limits the flow rate of the gas to be detected to a low range, which was conventionally considered to be undesirable due to the long time required for measurement, so that the gas to be detected is brought into sufficient contact with the absorption liquid, and the fluorine gas is brought into contact with the absorption liquid. The object of the present invention is to provide an improved method for measuring fluorine concentration that can effectively measure the concentration of fluorine gas in the atmosphere by performing a dissolution reaction.

That is, in the present invention, when continuously measuring the fluorine concentration in the atmosphere using the fluorine ion electrode method, the gas to be detected is 1.

The present invention relates to a method for measuring fluorine concentration in the atmosphere, which is characterized by contacting an absorbent with an absorbent at a contact flow rate (hereinafter referred to as a "baker flow rate") of an absorbent at a flow rate of 5.0/min to 10.

In this specification, the contact flow rate of the gas to be detected refers to the flow rate of the gas to be detected through a nozzle having a hole with a hole diameter of 0.2 to 0.4 holes located close to the surface of the absorption liquid. The flow rate and the rate at which the height of the liquid level and the diameter of the nozzle hole change can be changed based on the above-mentioned conditions. This method has the remarkable effect of being able to measure concentrations of fluorine gas that were previously absent, even at levels as low as ppb.

Therefore, when applying the method of the present invention as described above to the actual measurement of fluorine concentration, it is necessary to measure the fluorine concentration of fluorine compounds such as hydrogen fluoride in the atmosphere as well as the fluorine concentration that was not detected by the conventional measurement method. It becomes possible to measure the so-called total fluorine concentration including gas.・However, it is difficult to measure only the fluorine gas concentration from various fluorine compounds.
Well, another measurement method based on the method described above must be provided. Therefore, the present invention also provides a novel method for measuring only the fluorine gas concentration in the atmosphere containing various fluorine compounds.

Such measurement methods include a parallel method in which two types of measurement systems are arranged in parallel, and a series method in which they are arranged in series. First, in the parallel method, when continuously measuring the fluorine concentration in the atmosphere using the fluorine ion electrode method, two types of measurement systems are arranged in parallel, and one measurement system is used to measure the gas to be detected at 12
The fluorine concentration of other fluorine compounds other than fluorine gas is measured by contacting the absorption liquid at a contact flow rate higher than 1/min/10 pm, and in the other measurement system, the gas to be detected is The fluorine gas concentration is determined by contacting the absorption liquid at a contact flow rate less than or equal to the absorption liquid, measuring the total fluorine concentration, and subtracting the fluorine concentration of the other fluorine compound from the total fluorine concentration.

In addition, in the series method, when continuously measuring the fluorine concentration in the atmosphere using the fluoride ion electrode method, two types of measurement systems are arranged in series, and the gas to be detected is first measured at 12/min/10 in the previous measurement system. The fluorine concentration of other fluorine compounds other than fluorine gas is measured by contacting the absorption liquid at a contact flow rate higher than that of the secretion-absorption liquid, and then in the subsequent measurement system, the gas to be detected that has passed through the previous measurement system is 1. The fluorine gas concentration is measured by bringing the sample into contact with the absorption liquid at a contact flow rate of less than 5 minutes/minute/10' of the absorption liquid.

In both of these parallel and series methods, when the contact flow rate of the gas to be detected is 12 days/minute/10 days - absorption liquid or more, the fluorine gas hardly reacts with the absorption liquid, but when the contact flow rate is 1.
This was completed based on the new finding that when the absorption liquid is below 5〆/min/10, it reacts well with fluorine gas.

The fluorine ion electrode method is a conventional method in which gaseous inorganic fluorine compounds contained in a certain amount of gas to be detected are collected in an absorption liquid, and the fluorine ion concentration in this liquid is measured by the ion electrode method. The parallel method and the serial method of the present invention will be explained with reference to the drawings.

FIG. 1 is a schematic explanatory diagram showing an embodiment of the parallel method in the present invention, and FIG. 2 is a schematic explanatory diagram showing an embodiment of the serial method in the present invention.

1 and 2, 1 and 2 are absorbers having absorption liquids 3 and 31 therein, respectively;
Hydrogen ion electrodes 4 and 41 are inserted into absorption liquids 3 and 31, respectively.

In the parallel method shown in FIG. 1, the absorbers 1 and 2 are arranged in parallel by feed pipes 5 and 51 for feeding the gas to be detected (atmosphere) into the absorption liquid and 31. In the series method shown in FIG. 2, absorbers 1 and 2 are arranged in series by connecting an exhaust pipe 6 connected to absorber 1 and an inlet pipe 51 connected to absorber 2. . In FIG. 1, the gas to be detected (atmosphere) passes through the inlet pipe 5
Absorber 1 with a contact flow rate of 2 min/min/10 [-absorbing liquid or higher]
and brought into contact with the absorbing liquid 3.

In the absorption liquid 3, the fluorine concentration of fluorine compounds other than fluorine gas is measured by the fluorine ion electrode 4.
On the other hand, a part of the gas to be detected passes through another feed pipe 51 to 1.5
The absorbent is sent to the absorber 2 at a contact flow rate of less than 1/10' of the absorption liquid, is brought into contact with the absorption liquid 31, and the total fluorine concentration including fluorine gas is measured by the fluorine ion electrode method 41. The hydrogen ion electrodes 4 and 41 are connected to the computer 8 via amplifiers 7 and 71, and are slowly generated so that the indicator meter 9 automatically displays the fluorine concentration in the gas to be detected (atmosphere) and the fluorine gas concentration. is preferable. The gas discharged from the absorbers 1 and 2, respectively, is exhausted to the outside of the system through exhaust pipes 6 and 61 each having an air pump 12 at its tip, through rotameters 10 and 11, and then through valves 3 and 4. In Figure 2,
The gas to be detected (atmosphere) is first sent to the absorber 1 through the inlet pipe 5 at a contact flow rate of 12Z/min.
The fluorine concentration of a fluorine compound other than fluorine gas that is brought into contact with the absorption liquid 3 is measured by a fluorine ion electrode 4 .

Next, the gas to be detected exhausted from the absorber 3 passes through an exhaust pipe 6 and an inlet pipe 51 connected to the exhaust pipe 6 to a
min/10'-contact flow rate of the absorption liquid to the absorber 2,
It is brought into contact with the absorption liquid 31 and the fluorine gas concentration is measured by a fluorine ion electrode method. As the absorption liquids 3 and 31 used in the present invention, the absorption liquids conventionally used in the fluorine ion electrode method as described above can be used as they are. Such absorption liquids 3 and 31 may contain, for example, a certain amount of fluorine ions with a known concentration in advance, and p
Buffers with H between about 5.4 and 7.5 are preferably used. The fluorine ions are added to the buffer solution in order to stabilize the electromotive force generated by the ion electrode, and usually sodium fluoride is added to the buffer solution at a concentration of about 1 x 10-5M (about 0.1 egg/ml).
wppm). As the buffer solution,
Higher organic acid salt-sodium hydroxide-based buffers are generally used, but specific examples include citric acid-citrate (e.g. trisodium citrate, potassium hydrogen citrate, etc.)-based buffers, citrate ( (same as above)-sodium hydroxide-based buffer, maleate (for example, sodium hydrogen maleate, etc.)-sodium hydroxide-based buffer, and the like. In addition to these buffers, examples include phosphate buffers, glacial acetic acid-sodium chloride-sodium hydroxide buffers, and sodium acetate-sodium chloride-acetic acid buffers. In the present invention, when measuring the fluorine concentration in a gas to be detected containing fluorine gas or other fluorine compounds, the contact flow rate of the gas to be detected is 1.5 m/min/1.
Below 0w'-absorbing liquid, especially 1 to 0.1Z/min/1
It is preferable that the absorption liquid is 0. If the contact flow rate is larger than this, the fluorine gas will not be sufficiently absorbed by the absorption liquid 31.

On the other hand, when the contact flow rate is too small, it takes a long time to measure a gas with a low concentration of fluorine, which is not preferable. This contact flow rate of the gas to be detected is applied to the measurement of the other total fluorine concentration in the parallel method and the subsequent measurement of the fluorine gas concentration in the series method, so that the target total fluorine concentration or fluorine gas concentration can be determined with high accuracy. It is measured in

In addition, in the series method, the fluorine concentration of other fluorine compounds other than fluorine, which is measured concurrently or continuously with the total fluorine concentration and fluorine gas concentration, is determined by measuring the fluorine concentration of the detected gas at 12 days/minute/10 hours. It is contacted with the absorption liquid 3 at a contact flow rate higher than that of the absorption liquid. As described above, the present invention provides a method for measuring the concentration of a mixture of gaseous inorganic fluorine compounds such as fluorine, hydrogen fluoride, and silicon fluoride contained in the atmosphere, or of fluorine gas alone, using a fluorine ion electrode method. In measuring fluorine concentration using the fluorine ion electrode method, it is possible to measure fluorine gas concentration, which has not been previously measured, with high sensitivity (ppb order), and it is remarkable that the total fluorine concentration in the atmosphere can be measured accurately. This method has excellent effects and can be suitably used as a method for measuring fluorine concentration in the atmosphere.

Next, the method of the present invention will be explained with reference to Examples and Comparative Examples.

Examples 1 to 7 and Comparative Examples 1 to 4 A sample gas inlet pipe (polytetrafluorocarbon Made of ethylene, outer seat 3.5
Pork ◇, inner diameter 2.5 mm, the tip is melt-sealed, and a box with 1 small hole with a diameter of 0.2 to 0.4 mm is provided at the tip) and gas outlet pipe (trifluorochloride) Made of ethylene resin, outer diameter 6.
5 ribs? , inner diameter 3.8 ribs ◇) attached to a diamond-shaped gas absorber (made of polytetrafluoroethylene) (after installation, the tip of the gas outlet pipe will be one kite from the bottom of the container), Measure the fluorine sample gas (F2: 5 mm/vppm) with a flowmeter [
Hastings Mass Flow Meter (HASTIN)
GSMASS FLOWMETER, manufactured by Hastings), ALL-IK type, transducer H-IKM type (Orion manufactured)], and further diluent gas (nitrogen) is supplied as necessary. In an absorption device in which the amount of gas passing through the absorber is measured using a wet gas meter in the rear layer, the fluorine sample gas and nitrogen gas are fed into the gas absorber, and the fluorine gas concentration in the sample gas is adjusted. , A polyethylene container containing a certain amount of sodium citrate buffer A as an absorption liquid (a container containing 50% of the absorption liquid), the liquid height is 2 ships, and the gas outlet pipe end and the liquid level are (The distance was 19 ships), and absorption was carried out at various fluorine gas concentrations.

After absorption, add the same volume of TISAB to the absorbent sample as the absorbent.
Add the solution and use a fluorine ion meter (Orion's "
Orion Ion'Analyzer (ORlONIONA)
Concentration obtained by subtracting the blank value from the measured fluorine ion concentration in each absorption liquid using NALIZER) (40-ship type)
and the fluorine scavenging rate was measured. The results are shown in Table 1. Preparation of fluorine sample gas: Using fluorine gas filled in a cylinder (purity of 99.5 v/vppm or higher), it was prepared by repeating nitrogen pressurization (dilution and release) five times.

'2' Sodium citrate buffer A: 1 x 10-5M with the addition of citric acid (monohydrate) 2 t/d, trisodium citrate (dihydrate) 20 t/d and 0.0075 t/d.
- Sodium fluoride aqueous solution.

[3' TFSAB solution (ionic strength adjustment buffer):
Sodium chloride 58M, acetic acid 57M and sodium citrate 0.3M were dissolved in water to give a pH above 500*, then neutralized to pH 5.5 with sodium hydroxide solution, and after cooling, distilled water was added. Add and reduce the total amount by 1.

Table 1 From the measurement results of Examples 1 to 7 and Comparative Examples 1 to 4, when the contact flow rate of the gas to be detected is greater than 1.5 m/min/10 M-absorbing liquid, the collection rate of fluorine gas increases rapidly. It can be seen that the value decreases to .

Comparative Examples 5 to 8 Fluorination using hydrogen fluoride instead of fluorine gas. Fluorine ion concentration in the absorption liquid (same as above) and fluorine collection rate when the contact flow rate was variously changed in the same manner as in Example 1 except that a polyhydrogen sample gas (HF: 5 vppm) was used. was measured.

The results are shown in Table 2. From these Comparative Examples 5 to 8 in Table 2, it can be seen that when the measurement gas is hydrogen fluoride, the fluorine collection rate does not change much even though the contact flow rate changes considerably.

Example 8 Using the same absorption apparatus and method used in Example 1, 52
, 5.2, and 3.1 v/vppm were absorbed into the absorption liquid at each contact flow rate shown in Table 3, and the fluorine ion concentration and fluorine collection rate in the liquid were measured.

The results are shown in Table 3. The main absorption liquids used in Example 8 are as follows.

■Sodium citrate buffer A Same as Example 1 above.

■Sodium citrate buffer B O. IM sodium citrate solution (C6 is 07/day 20
21.0 min of sodium hydroxide solution 200'
(solution) 60' and 0.1N
- Sodium fluoride was added to a mixed aqueous solution of 40' of sodium hydroxide solution to a concentration of 1 x 10-5M.

■Potassium hydrogen citrate buffer 0.1M Potassium hydrogen citrate (KC 6th 707, 23. Tanok) Its concentration is 1×10-
It was prepared by adding it to a concentration of 5M.

■ Sodium hydrogen maleate buffer 0.1M - Sodium hydrogen maleate solution (NaC4 is 04 13.8 times a day) Mix 50 [ and 0.1N - sodium hydroxide solution 26.9' o TISAB solution prepared by adding sodium fluoride to a concentration of 1 x 10-5M to an aqueous solution diluted with 100% of the total volume. Same as in Example 1 above.

(2) From Ship Example 8, it can be seen that the collection rate of fluorine hardly changes even if the type of absorption liquid is changed, and the collection rate of fluorine changes greatly with the contact flow rate of the gas to be detected.

Example 9 Using a wet collection type atmospheric fluorine compound automatic measuring device (having a fairlift type absorber) as an automatic measuring device using a fluorine ion electrode method, and using the above-mentioned sodium citrate buffer solution A as an absorption liquid, this Fluorine sample gas (F2: 5/vppm) at a predetermined contact flow rate using a flowmeter.
was absorbed together with a predetermined flow rate of air (air dried with silica gel after washing with alkaline solution).

At this time, the amount of evaporated water in the absorption liquid in the absorption tube was automatically replenished using an attached liquid level gauge, so that the amount of liquid remained constant. After allowing the absorption liquid to absorb the atmosphere containing the sample gas for 50 minutes, the absorption liquid in the absorption tube was taken out, and the fluorine ion concentration in the nuclear absorption liquid was measured in the same manner as in Example 1 to determine the fluorine construction rate. . The results of these measurements are shown in Table 4. Comparative Example 9 Fluorine ions in the absorption liquid were removed in the same manner as in Example 9, except that a fluorine sample gas (HF: 5Y/vppm) was used instead of the fluorine sample gas, and it was sucked into the absorption tube together with the atmosphere at a predetermined flow rate. The concentration and fluorine scavenging rate were determined.

The results are shown in Table 4. Shipboard Example 10 (Parallel Method) Air is passed through a filter and a gas mixer at a constant flow rate by a suction pump, and two types of gas suction devices are arranged in parallel (the same airlift type absorber as described in Example 9). Hydrogen fluoride and fluorine gas were collected as fluorine ions using a 100-board absorber (hereinafter referred to as absorber 0) made of the same tetrafluoroethylene resin as described in Example 1 (hereinafter referred to as absorber 1). Afterwards, using an absorption device that exhausts air with a suction pump through each flow meter, absorber 1 and potassium citrate buffer A are each charged at 17 m, and atmospheric air is sucked in at a rate of 22 m/min using the suction pump. 100' of each of fluorine sample gas (5 vppm) and hydrogen fluoride sample gas (5 vppm) were introduced into this suction atmospheric flow.
The mixed sample gas (F2 concentration 0.23/vppm, HF concentration 0.2$/
vppm) was flowed into absorber 1 at a rate of 20.8 pm/min and into absorber RO at a rate of 1.2 pm/min, and contacted for 30 minutes.

The contact flow rate in absorber 1 is 12.2 mm/min/10 secretions.
The catalytic flow rate of the absorption liquid in the absorber D' is 0.71 mm/min. After absorbing the mixture gas, the fluorine ion concentration in absorber 1 is 6.5 w/wpp.
m, and the fluorine ion concentration in the absorption liquid of absorber 0 was 1.1 w/WPPm. The fluorine ions measured in the absorption liquid of absorber 1 are due to the absorption of hydrogen fluoride, and the hydrogen fluoride concentration in the mixed sample gas is 0.2/
vppm, fluorine scavenging rate for incoming hydrogen fluoride is 96
%.

In addition, the fluorine ions measured in absorber 0 are due to absorption of hydrogen fluoride and fluorine gas, and the fluorine ion concentration measured in absorber 1 was converted from the fluorine ion concentration measured in absorber 0 to the flow rate. By subtracting the above, the fluorine gas concentration in the mixed sample gas is 1.2/vp
pm, and the fluorine scavenging rate with respect to the supplied fluorine gas was found to be 96%. Example 11 (Series method) Example 1
In the gas absorption device in 0, absorbers 1 and 2 are connected in series, and a flow path having a flow meter placed in parallel with absorber 0 from the middle of absorbers 1 and 0 is provided. The absorber 1 and sodium citrate buffer A were each charged at 17 ml, and the air was sucked in at a flow rate of 22 ml/min using a suction pump, and a fluorine sample gas (5 ml/vppm) was added into the sucked atmosphere. ) and hydrogen fluoride sample gas (5 ppm/vppm) are each fed at a flow rate of 100 cells/min, and the entire amount of the mixed sample gas obtained by mixing is passed through the absorber 1. A portion of the mixed sample gas was flowed at a flow rate of 1.7 som/min, which was adjusted using a flow meter and a valve.

The contact flow rate in absorber 1 is 12.9/min.
The contact flow rate of absorption liquid and absorber 0 is 1.0/min.
0 machine - becomes absorption liquid.

After the mixed sample gas was absorbed by three vessels, the fluorine ion concentration in the absorption liquid in each absorber was measured in the same manner as in the previous example.

As a result, the fluorine ion concentration in the absorption liquid of absorber 1 was 6.7w/wppm, the hydrogen fluoride concentration in the mixed sample gas was 0.2f/vppm, and the fluorine collection rate was 96%.
The fluorine ion concentration in the absorption liquid of absorber D is 1.5 w/wppm, the fluorine gas concentration in the mixed sample gas is 0.21 v/vppm, and the fluorine collection rate is 91%.
Met.

[Brief explanation of the drawing]

FIG. i is a schematic explanatory diagram showing an embodiment of the parallel method in the present invention, and FIG. 2 is a schematic explanatory diagram showing an embodiment of the serial method in the present invention. Main symbols in the drawings: 1, 2: absorber, 3, 31: absorption liquid,
4,14: Fluorine ion electrode. 1 figure, 2 figures

Claims (1)

[Claims] 1. In order to continuously measure the fluorine concentration in the atmosphere using the fluorine ion electrode method,
1.5 l/min/10 m when the gas to be detected is fed from a nozzle with a hole diameter of 0.2 to 0.4 mm located at
A method for measuring the concentration of fluorine in the atmosphere, characterized in that a gas to be detected is brought into contact with an absorbent at a flow rate of contact with the absorbent such that the flow rate is less than or equal to 1-absorbent. 2. The method according to claim 1, wherein the gas to be detected is brought into contact with the absorption liquid at an absorption liquid contact flow rate of 1 to 0.1 l/min/10 ml of the absorption liquid. 3. When continuously measuring the fluorine concentration in the atmosphere using the fluorine ion electrode method, two types of measurement systems are arranged in parallel, and one measurement system is placed 19 mm below the surface of the absorption liquid.
12 l/min/10 m when the gas to be detected is fed from a nozzle with a hole diameter of 0.2 to 0.4 mm located at
The gas to be detected is brought into contact with the absorbing liquid at a flow rate of the absorbing liquid at a rate equal to or higher than that of the absorbing liquid, and the fluorine concentration of other fluorine compounds other than fluorine gas is measured. Pore diameter 0.2-0 located 19mm below the liquid surface
．． When the gas to be detected is fed through a nozzle with a 4 mm hole, the gas to be detected is brought into contact with the absorption liquid at a flow rate of 1.5 l/min/10 ml or less. By measuring the fluorine concentration and subtracting the fluorine concentration of the other fluorine compound from the total fluorine concentration,
A method for measuring the concentration of fluorine in the atmosphere, which is characterized by determining the concentration of fluorine gas. 4 In the other measurement system, detect the gas to be detected from 1 to 0.
．． 4. A method according to claim 3, characterized in that the absorption liquid is brought into contact with the absorption liquid at an absorption liquid contacting flow rate of 1 l/min/10 ml. 5. To continuously measure the fluorine concentration in the atmosphere using the fluorine ion electrode method, two types of measurement systems are arranged in series, and the first measurement system is placed 19 meters below the surface of the absorption liquid.
12 l/min/10 when the gas to be detected is fed from a nozzle with a hole diameter of 0.2 to 0.4 mm located at
The gas to be detected is brought into contact with the absorption liquid at a rate of contact flow rate of the absorption liquid or higher, and the fluorine concentration of other fluorine compounds other than fluorine gas is measured, and then in the subsequent measurement system. The pore size located 19 mm below the surface of the absorption liquid is 0.
When the gas to be detected is introduced through a nozzle having a hole of 2 to 0.4 mm, the sample was passed through the measurement system at a rate of contact flow rate of the absorbent such that the gas was 1.5 l/min/10 ml or less. A method for measuring fluorine concentration in the atmosphere, which is characterized by bringing a gas to be detected into contact with an absorption liquid and measuring the fluorine gas concentration. 6. In the measurement system after the above, the gas to be detected is 1 to 0.
6. A method according to claim 5, characterized in that the absorption is brought into contact with the absorbent at an absorbent contacting flow rate of 1 l/min/10 ml of absorbent.