JPH0718862B2 - Fluorine concentration measuring method and apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for measuring a fluorine concentration in a gas containing fluorine and an apparatus therefor, and particularly to an apparatus for measuring a fluorine concentration in an excimer gas laser.

[Prior Art] Conventionally, various methods are known as a method for analyzing the fluorine concentration in a gas, but generally, two methods, a wet method and a dry method, are known.

Known wet methods include (1) a method in which fluorine gas is passed through a LiCl solution to oxidize chlorine, and this is analyzed by an electrode.

[S.Kaye, M.Griggs: Anal.Chem., 40,2217, (1968)] Further, as a dry method, (2) after removing HF in the sample gas with NaF pellets, fluorine was passed through the NaCl layer. React, absorb the generated chlorine gas in NaOH solution,
Method of determining the generated hypochlorous acid by iodometric titration [A.
MGMacdonaldet al, “Fluoline”, Encyclopedia of Ind
ustrial Chemical Analsis, Vol.13, Newyork-London-S
ydney-Tronto, 1971], (3) As a gas chromatographic method, a special material such as nickel is used in the part where the sample contacts, and the thermoconductivity cell is coated with PTFE and the fluorine gas is directly analyzed. [E.Rudzitis: Anal.Chem.3
5,465, (1963)], etc. are known.

[Problems to be Solved by the Invention] However, in the above method, in (1), since it is necessary to completely absorb the fluorine gas into the liquid, setting of engineering conditions during blowing and adjustment of PH during analysis Etc., the apparatus and operation are complicated, and the reaction is complicated in two steps in (2), the accuracy is difficult to increase, and in (3), it is necessary to coat the thermal conductivity cell. There are various problems such as a decrease in sensitivity and an expensive material for the device.

The present invention has been made in order to solve the above-mentioned problems of the conventional method, and provides a method for analyzing the fluorine concentration in a gas very quickly and accurately using a simple device. .

[Means for Solving Problems] The method of the present invention has been made paying attention to the quantitative generation of oxygen gas by the reaction of fluorine gas with an alkali compound such as Ca (OH) _2. In this way, the highly toxic and active fluorine gas is converted into oxygen that is easy to handle, and then the oxygen concentration is quickly measured by the oxygen sensor.

That is, the present invention, in the method for measuring the fluorine concentration in a sample gas containing fluorine or the like, the step of passing the gas through a packed layer containing a packed layer containing a compound of an alkali metal or an alkaline earth metal, reacting with fluorine The gas passed through the step of passing a packed bed containing an element that forms a compound or the step of passing a packed bed consisting of the packed bed and two layers containing a compound of an alkali metal or an alkaline earth metal is detected by an oxygen sensor, respectively. The method for measuring the fluorine concentration in a gas, which is characterized by determining the fluorine concentration in a sample gas by comparing the oxygen concentrations of the two, a packed bed containing a compound of an alkali metal or an alkaline earth metal, and fluorine. A packed layer containing an element that reacts with the compound to form a compound or two layers containing the packed layer and a compound of an alkali metal or an alkaline earth metal Ranaru packed layer, and the fluorine concentration measuring apparatus characterized by being composed of detection portions consisting of oxygen sensor, and a fluorine concentration measuring device of the excimer laser gas composed of the apparatus.

In addition, after passing the above-mentioned gas of the present invention through a packed bed containing a compound of an alkali metal or an alkaline earth metal, it is led to a detection part consisting of an oxygen sensor, and the fluorine concentration in the sample gas is determined. Fluorine concentration measuring method, a packed bed containing a compound of an alkali metal or an alkaline earth metal and a detector comprising an oxygen sensor, and a device for measuring the fluorine concentration in a gas, and the above device. The device for measuring the concentration of fluorine in excimer laser gas is a method and device used for a gas containing no oxygen component.

Briefly explaining the principle of the present invention by a chemical reaction formula,
First, the reaction between fluorine in the gas and calcium hydroxide is represented by the following formula (a).

F ₂ + Ca (OH) ₂ → CaF ₂ + H ₂ O + 1 / 2O ₂ (a) By this reaction, with respect to fluorine and 2 atomic equivalents in the gas,
It is quantitatively converted into oxygen at a ratio of one atomic equivalent of oxygen. The above reaction is a reaction in the case of an alkaline earth metal. Alkali metal has a slightly different reaction coefficient, but the reaction mode is the same and the amount of oxygen generated is also the same.

In the above reaction, as the alkali metal and alkaline earth metal compounds corresponding to calcium hydroxide, hydroxides of alkaline earth metals and alkali metals (for example, lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, water Strontium oxide, barium hydroxide, etc., oxides (eg lithium oxide, sodium oxide,
Potassium oxide, calcium oxide, magnesium oxide, barium oxide, etc.), carbonate (for example, lithium carbonate, sodium carbonate, potassium carbonate, magnesium carbonate, calcium strontium carbonate, barium carbonate, etc.), bicarbonate, sulfate, nitrate or Soda lime (a mixture of calcium hydroxide, calcium oxide, sodium hydroxide, water, etc.) can be used, but a mixture of calcium hydroxide, calcium oxide and sodium hydroxide, which is called soda lime, is a quantitative oxygen. It is preferable considering the generation of gas.

Although a description of the device will be given later, a layer filled with these materials is shown as a filled layer in FIG.

Although the packed bed can be used even at room temperature, it is more preferably kept at 100 ° C. or higher in consideration of efficiency and the like.

On the other hand, an oxygen sensor is used as a method for measuring the oxygen concentration in the gas that has passed through the packed bed.

The oxygen sensor used in the detector is an oxygen ion conductor,
Any material can be used as long as it forms a concentration cell by the oxygen concentration gradient at both ends, but especially so-called stabilized zirconium obtained by solid solution of calcium oxide, yttrium oxide, etc. in zirconia becomes an oxygen ion conductor at high temperature. By using this sintered body, it is possible to accurately measure the oxygen concentration of an unknown sample in a few tens of seconds after starting the measurement.

The zirconia oxygen sensor used in the present invention is used at a temperature of 500 ° or higher and uses the atmosphere as a reference gas.

The zirconia oxygen sensor has a wide dynamic range because its output is proportional to the logarithm of the oxygen partial pressure.
It is also possible to measure low concentrations on the order of m.

Further, based on the principle of the present invention, in order to measure the concentration of fluorine in the gas, it is necessary to know in advance the concentration of oxygen existing in the gas. Since the sensor may be destroyed if introduced, the concentration of oxygen contained in the gas from the beginning is measured by fixing fluorine to the packed bed by the following reaction and then introducing it into the zircoia sensor. be able to.

As a fixing method, a case where it is directly reacted with fluorine to be fixed as a solid fluoride and a case where it is made into a fluoride gas and then a packed layer of the same material as that used for the packed layer is provided later and fixed as a fluoride There are two possible cases.

Any element that reacts with fluorine to form a compound by reacting with fluorine may be used, such as Si, Ge,
P, Sb, Te, S, W, Mo, V, Fe, Cr, Mn, Co, Zn, Pb, Ti, Zr, Se and the like can be mentioned.

In this case, Fe, Cr, Mn, Co, Zn, Ti, Zr, Sn, Pb, etc. react with fluorine to produce solid fluorides such as FeF ₃ , CrF ₃ , MnF _4, ... Be converted.

In this case, in FIG. 1, the filling layer is only the filling layer.

On the other hand, Si, Ge, P, Sb, S, Se, Te, W, Mo, V, etc. generate a gaseous fluoride by reaction with fluorine, and therefore the following reaction is used in this case.

2F ₂ + Si → SiF ₄ (b) SiF ₄ + 2Ca (OH) ₂ → 2CaF ₂ + SiO ₂ + 2H ₂ O (c) In the reaction of the above formula (b), since the valences of the respective elements are different, fluoride The valences of are slightly different, but the reaction forms are the same.

On the other hand, in the reaction of the formula (c), the compound used for the reaction with the fluoride gas is exactly the same as the compound used in the formula (a).

Here, the layers in which the reactions (b) and (c) are carried out are filled layers in FIG. 1, respectively.

In this case as well, the column can be used at room temperature, but it is preferable to keep it at 100 ° C. or higher with a heater or the like (not shown in FIG. 1).

The column used in the present invention has a diameter of 10 mm and a length of about 100 mn, and may be any as long as it has durability against fluorine gas, but as a practical material, SUS-31
6. A material such as monel that has been so-called passivated by flowing fluorine gas before using the device may be used.

Further, the amount of the compound to be filled varies depending on the fluorine concentration of the gas to be measured, but may be an amount sufficient to be able to measure about 2000 times or more, for example, in the case of fluorine concentration measurement in an excimer gas laser, soda It is enough to fill about 10g of lime.

Thus, the method of converting the fluorine in the gas into oxygen and measuring the oxygen concentration by the oxygen sensor makes it possible for the first time to measure the fluorine concentration in the gas very quickly.

This method can be applied to various gases including fluorine, and the detection range of F ₂ is very wide, from several tens of ppm to several%.

An apparatus to which this method is applied is as shown in FIG. That is, not only the laser device indicated by 1, but also a gas containing fluorine can be applied to the measurement of the fluorine gas concentration by this device.

Therefore, the measuring method of this apparatus will be described with reference to FIG. First, open valves 13, 15, 16 and 18 and measure a constant flow rate of the measurement gas with a flow meter for several tens of seconds to several minutes through the packed bed to measure p ₁ (fluorine gas concentration + oxygen gas concentration) You can

On the other hand, in order to check whether or not oxygen is contained in the gas, the valves 13, 14, 17 and 18 are opened, and the gas for measurement is flowed through the packed bed at the same flow rate to obtain p ₂ (oxygen gas Concentration) can be measured.

In this case, since the concentration is directly displayed on the indicator, the concentration can be immediately known if correction and conversion are performed in advance with fluorine gas or oxygen gas having a known concentration. That is, as can be seen from the formula (a), 1 mol of F ₂
Since the gas is converted to 1/2 molar O ₂ gas, the original fluorine gas concentration is considered to be twice the oxygen gas concentration, and 2n (p ₁
Calculate with −p ₂ ). In this case, n is a correction coefficient.

Also, if it is known that the gas does not contain oxygen, it is not necessary to measure the oxygen gas concentration originally contained in the gas, so it is necessary to use a packed bed, or a packed bed and a packed bed. Instead, a device having only a packed bed may be used. When measuring with this device, the gas containing fluorine can be measured irrespective of the pressure, and the flow rate of the gas flowing through the detection unit may be constant (several tens cc / min to several hundreds cc / min).

In addition, this device is very effective especially as a fluorine concentration analyzer for excimer laser gas.

Generally, an excimer laser has Ar-F ₂ -He, Ne or Kr-F.
A gas having a composition of _2- He and Ne is used, and the proportion of fluorine contained in the gas is usually about 0.1 to 1%.
The output of this excimer gas laser device may decrease during operation, and the cause is considered to be the decrease in the fluorine concentration in the gas and the generation of oxygen and other impurity gases.

Impurities can be removed by adsorption method or cold trap method, but the concentration of fluorine in the laser gas can be monitored.
Currently, this is not done because of the complexity of the analysis and the difficulty of handling. Therefore, it was not possible to determine whether the decrease in laser output was due to the generation of impurity gas or the decrease in fluorine gas concentration.

According to the present apparatus, such a problem can be solved, and the fluorine concentration in the laser gas can be measured almost on-time, which enables efficient laser oscillation.

[Examples] Hereinafter, examples will be described in more detail, but the present invention is not limited to these examples.

Example 1 First, Monel's 8φ × 100 L shown by the packed bed in FIG.
Using a column packed with 8 g of soda lime, it was investigated whether fluorine was completely converted to oxygen. The pipe through which the fluorine gas passes was used after being passivated with fluorine gas made of SUS-316.

A gas containing 0.5% of fluorine was passed through helium under the conditions shown in Table 1, and it was examined whether or not fluorine was detected after passing through the column. For detection, a layer filled with potassium iodide powder was used, and it was examined whether the color of the powder changed. It has been known in advance that this method can detect a fluorine concentration of 100 ppb or more.

As a result, as shown in Table 1, at 150 ° C or higher, fluorine was not detected and there was no problem even if it was passed through the column at a flow rate much faster than the flow rate (100 cc / min) normally flown. I understood.

Example 2 The packing layer shown in FIG. 1 was a column of Monel 10φ × 100 L, which was passivated with fluorine, packed with 5 g of Si powder, and the packing layer used was the same as the packing layer of Example 1. Was fixed in this column. The method is the same as in Example 1.

As a result, as can be seen from Table 2, it was found that at a flow rate of 150 ° C. or higher, the flow rate was fixed at a normal flow rate without any problem.

Example 3 In the apparatus shown in FIG. 1, instead of the laser apparatus of 1, the concentration of fluorine gas was changed to 0.1%, 0.2%, 0.3%, 0.4%, respectively.
A helium gas cylinder adjusted to 0.5% (both vol%) was used. The flow rate of the gas was set to 100 cc / min, the above gas was passed through the packed bed, and the values in the indicator at that time were read. The same packing layer as in Example 1 was used.

The results are shown in Table 3 and FIG.

As can be seen from this result, for the introduced gas, the oxygen concentration indicated value of the zirconia sensor converted to fluorine was almost the same, and a linear relationship was obtained, and the value obtained by converting the sensor indicated value to fluorine was unchanged. It turns out that it can be considered as the fluorine concentration.

Example 4 Using the same apparatus as in Example 3, the gas cylinder used in Example 3 was further diluted, and the oxygen concentration was measured in the same manner with helium gas having a fluorine concentration of 50 ppm, 100 ppm, 150 ppm, and converted to a fluorine concentration. As a result, it was 46 ppm, 110 ppm, and 150 ppm, and it was found that the fluorine concentration of this level could be sufficiently measured.

Example 5 About 0.05% of oxygen was further added to the cylinder used in Example 3, and the same measurement method as in Example 3 and the packed bed were measured. In this case, the same equipment as in Example 2 was used for the packed bed and the packed bed. The results are shown in Table 4.

As can be seen from these results, the fluorine concentration can be measured without problems even in a system containing oxygen.

Comparative Example 1 Fluorine concentration was analyzed by a method in which fluorine in gas was converted to chlorine with NaCl and the amount was detected with a corrosion-resistant gas chromatograph (detector HID). A tube filled with NaCl (made of nickel, inner diameter 10 mm, outer diameter 12 mm, length 20
0mm), connect a gas sampler containing helium gas with a fluorine concentration of 0.5vol%, and let the carrier gas flow.
The integrated intensity was measured. FIG. 3 shows the relationship between the volume of helium gas taken in the gas sampler converted to 1 atm and the integrated intensity of gas chromatograph. As can be seen from this graph, it was found that there is a problem in reproducibility and accuracy when the amount of chlorine gas is small.

[Effects of the Invention] According to the present invention, by using a simple method, operation and device,
Since the fluorine concentration in the gas can be measured quickly and accurately, and especially the fluorine concentration in the excimer laser gas can be measured rapidly, the fluorine concentration can be kept constant, which is a very effective method.

[Brief description of drawings]

FIG. 1 is a schematic view of the apparatus of the present invention, FIG. 2 is a graph showing the relationship between the theoretical oxygen amount and the indicated value of the zirconia oxygen sensor when the fluorine concentration is changed, and FIG. 3 is a fluorine gas. Is a graph showing the results of measurement with a corrosion-resistant gas chromatograph after converting to chlorine gas with NaCl. 2 ... Packing layer, 3 ... Packing layer 4 ... Packing layer, 6 ... Oxygen gas sensor 10 ... Indicator

Claims (6)

[Claims] 1. A method for measuring the concentration of fluorine in a sample gas containing fluorine or the like, the step of passing the gas through a packed bed containing a compound of an alkali metal or an alkaline earth metal, and reacting with fluorine to produce a compound. The gas passed through the step of passing through the packed bed containing the element or the step of passing through the packed bed filled with the two components of the element and the compound of the alkali metal or the alkaline earth metal in this order is guided to the detection part including the oxygen sensor. A method for measuring the fluorine concentration in a gas, wherein the fluorine concentration in the sample gas is obtained by comparing the oxygen concentrations of the two. 2. A method for measuring the fluorine concentration in a sample gas containing fluorine or the like, wherein the gas is passed through a packed bed containing a compound of an alkali metal or an alkaline earth metal, and then led to a detection section composed of an oxygen sensor. A method for measuring the fluorine concentration in a gas, which comprises determining the fluorine concentration in the sample gas. 3. A packing layer containing an element that reacts with fluorine to form a compound in parallel with a packing layer containing a compound of an alkali metal or an alkaline earth metal, or a compound of the element and an alkali metal or an alkaline earth metal. An apparatus for measuring fluorine concentration in a gas, comprising a structure in which a packed bed filled with two components in this order is arranged, and a detection unit composed of an oxygen sensor arranged on the downstream side thereof. 4. An apparatus for measuring the concentration of fluorine in gas, comprising a packed bed containing a compound of an alkali metal or an alkaline earth metal and a detection part composed of an oxygen sensor arranged downstream of the packed bed. 5. A packing layer containing an element that reacts with fluorine to form a compound in parallel with a packing layer containing a compound of an alkali metal or an alkaline earth metal, or a compound of the element and an alkali metal or an alkaline earth metal. 1. A device for measuring the concentration of fluorine in excimer laser gas, which comprises a packed layer in which two components are packed in this order, and a detection unit composed of an oxygen sensor arranged on the downstream side thereof. 6. A device for measuring the concentration of fluorine in excimer laser gas, comprising a packed bed containing a compound of an alkali metal or an alkaline earth metal and a detector composed of an oxygen sensor arranged downstream of the packed bed.