JP5061393B2 - Fluorine gas concentration measuring method and concentration measuring apparatus - Google Patents

Description

  The present invention relates to a measurement method and a measurement apparatus for measuring the concentration of fluorine gas in a measurement target gas.

  Conventionally, various methods are known as methods for analyzing the fluorine concentration in a gas.

In Patent Document 1, oxygen gas is quantitatively generated by a reaction between fluorine gas and an alkali compound such as Ca (OH) ₂ , the oxygen gas is measured by gas chromatography, and the fluorine gas concentration is measured. A method has been proposed.

  Patent Document 2 proposes a method of indirectly measuring the fluorine concentration by converting fluorine in a sample gas into carbon dioxide or metal fluoride gas and measuring the concentration thereof.

  In Patent Document 3, the total of fluorine gas and oxygen in the sample gas is obtained by substituting fluorine with oxygen in the packed layer of the group 3 metal compound in the periodic table, while the fluorine in the sample is obtained. A method has been proposed in which a halogen component other than oxygen is substituted and the halogen component is adsorbed to obtain the oxygen content contained in the original sample gas, and the fluorine concentration is measured from the difference.

  In patent document 4, the apparatus which measures a fluorine gas density | concentration correctly is proposed by fluorinating the piping inner surface of a fluorine gas measuring apparatus beforehand.

JP-A-2-162257 JP-A-2-201160 JP 2001-165924 A JP 2007-107904 A

  However, each of the above conventional techniques has a problem that the concentration of fluorine gas cannot be measured with high detection accuracy because the concentration is measured by measuring the absorbance at a specific wavelength.

  An object of the present invention is to provide a fluorine gas concentration measuring method and measuring apparatus with high detection accuracy.

  The concentration measurement method of the present invention is a method for measuring the concentration of fluorine gas in a measurement target gas, wherein hydrogen gas is mixed with the measurement target gas, and hydrogen gas is added to all the fluorine gases in the measurement target gas. Mixing step of reacting to make hydrogen fluoride and making it a mixed gas containing hydrogen fluoride, and removing HF from the mixed gas by absorbing the hydrogen fluoride in the mixed gas with an alkaline agent And, after removing hydrogen fluoride, in order to remove water produced by the reaction between hydrogen fluoride and an alkaline agent, a drying step of obtaining a residual gas by drying a mixed gas, and the dried residual gas And a gas amount measuring step for measuring the amount of gas.

  In the present invention, hydrogen gas is mixed with the measurement target gas, and the hydrogen gas is reacted with all of the fluorine gas in the measurement target gas to form hydrogen fluoride. For this reason, in the reaction for completely converting the fluorine gas present in the measurement target gas to hydrogen fluoride, it is preferable to mix hydrogen gas in an amount equal to or greater than the fluorine gas into the measurement target gas. Therefore, in general, it is preferable to mix an equal amount or an equal amount or more of hydrogen gas with the measurement target gas.

  In the next step, hydrogen fluoride in the mixed gas is absorbed by an alkaline agent and removed from the mixed gas. As the alkaline chemical, an alkaline earth metal or an alkali metal hydroxide can be preferably used, and calcium hydroxide (soda lime) which is easy to handle is particularly preferably used.

  After removing the hydrogen fluoride, the mixed gas is dried to form a residual gas in order to remove the water generated by the reaction between the hydrogen fluoride and the alkaline chemical. Although it does not specifically limit as a method to dry, Since handling is easy, dehydration by reaction with calcium oxide (CaO: quicklime) is used preferably.

  Next, the concentration of the fluorine gas in the measurement target gas can be obtained by measuring the amount of the residual gas. Before mixing the gas to be measured and the hydrogen gas, the gas amounts of the gas to be measured, the hydrogen gas, and the residual gas are measured by measuring the gas amount of the gas to be measured and the gas amount of the hydrogen gas, respectively. From this, the concentration of fluorine gas in the gas to be measured can be determined. That is, the gas amount of hydrogen fluoride can be obtained by subtracting the gas amount of the residual gas from the total gas amount of the measurement target gas and the hydrogen gas. From the amount of hydrogen fluoride gas, the amount of fluoride gas in the measurement target gas can be determined.

  The method for measuring the amount of residual gas is not particularly limited. For example, the amount of residual gas can be measured by measuring the volume of the residual gas. When the measurement target gas is flowing, the concentration of the fluorine gas in the flowing measurement gas can be measured. In such a case, the amount of residual gas can be measured with a mass flow meter.

  Further, the flow rate of the measurement target gas and the flow rate of the hydrogen gas mixed with the measurement target gas can be measured with a mass flow meter, respectively. Thereby, the mixing ratio of the hydrogen gas with respect to the measurement target gas can be obtained.

  In the present invention, it is preferable that a gas amount stabilization step for stabilizing the gas amount is further provided between the mixing step and the gas amount measurement step. In particular, when the gas to be measured is flowing, the gas flow rate is likely to fluctuate. Therefore, by providing the gas amount stabilization step, the concentration of the fluorine gas can be stably measured.

  The fluorine gas concentration measuring apparatus of the present invention is an apparatus for measuring the concentration of fluorine gas by the above-described measuring method of the present invention. The measurement object gas and hydrogen gas are introduced, mixed, reacted, and reacted with hydrogen fluoride. Reaction chamber for generating hydrogen, hydrogen fluoride removal chamber for removing hydrogen fluoride by absorbing hydrogen fluoride in the mixed gas discharged from the mixture reaction chamber with an alkaline agent, and hydrogen fluoride It is characterized by comprising a drying chamber for drying the mixed gas discharged from the removal chamber to obtain a residual gas, and a measuring means for measuring the amount of the residual gas discharged from the drying chamber.

  By using the concentration measuring apparatus of the present invention, the concentration of hydrogen gas in the measurement object can be easily measured with high detection accuracy.

  In the concentration measuring apparatus of the present invention, it is preferable that at least one buffer tank for stabilizing the gas amount is further provided between the mixing reaction chamber and the measuring means. By providing the buffer tank, fluctuations in the amount of gas to be measured can be stabilized, and the fluorine gas concentration in the measurement object gas can be stably measured.

  As the concentration measuring means for measuring the remaining amount, a mass flow meter can be used when the measurement target gas is flowing.

  In addition, when the measurement target gas is flowing, the amounts of the measurement target gas and hydrogen gas introduced into the mixing reaction chamber can be measured by the gas amount measuring means. As such a gas amount measuring means, for example, a mass flow meter can be used. If a mass flow meter is used, the fluorine gas concentration can be continuously measured.

  According to the present invention, the concentration of fluorine gas in the measurement target gas can be easily measured with high detection accuracy.

The schematic diagram which shows the fluorine gas concentration measuring apparatus of one Embodiment according to this invention. The figure which shows the relationship between the fluorine concentration (actual value) in measurement object gas, and a measured value. Sectional drawing which shows the piping for supplying the measuring object gas and hydrogen gas to the mixing reaction chamber in the fluorine gas concentration measuring apparatus of one Embodiment according to this invention. Sectional drawing which shows the state in which the water cooling pipe was provided around the piping shown in FIG.

  Hereinafter, the present invention will be described with reference to specific embodiments, but the present invention is not limited to the following embodiments.

  FIG. 1 is a schematic diagram showing a fluorine gas concentration measuring apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, the fluorine gas concentration measuring apparatus 10 of this embodiment includes mass flow meters 11 and 12, a mixing reaction chamber 13, a hydrogen fluoride removing chamber 14, a drying chamber 15, a buffer tank 16, and a mass flow meter 17. I have. The measurement target gas 1 passes through the mass flow meter 11 and is supplied to the mixing reaction chamber 13. The hydrogen gas 2 passes through the mass flow meter 12 and is supplied to the mixing reaction chamber 13. The mass flow meter 11 and the mass flow meter 12 are provided with a flow rate adjusting means so that an arbitrary flow rate can flow. Further, a mass flow controller may be additionally provided so that the set gas amount can be automatically flowed. The mass flow meters 11 and 12 use hydrogen gas or nitrogen gas set as a measurement standard. The mass flow meter 11 can measure the flow rate of the measurement target gas 1 to the mixed reaction chamber 13. In addition, the mass flow meter 12 can measure the flow rate of the hydrogen gas 2 to the mixed reaction chamber 13. From these flow rates measured by the mass flow meters 11 and 12, the mixing ratio of the hydrogen gas 2 to the measurement target gas 1 can be obtained. The display value of the flow rate of the measurement target gas 1 measured by the mass flow meter 11 is 100 ml / min. Moreover, the display value of the flow volume of the hydrogen gas 2 measured with the mass flow meter 12 is 100 ml / min.

Here, a gas obtained by diluting fluorine (F ₂ ) gas with nitrogen (N ₂ ) gas is used as the measurement target gas 1. Therefore, the gas component in the measurement target gas 1 is F ₂ + N ₂ , and the gas component in the hydrogen gas 2 is H ₂ . In the mixed reaction chamber 13, the measurement target gas 1 and the hydrogen gas 2 are mixed, and the fluorine (F ₂ ) gas in the measurement target gas 1 is converted into the hydrogen (H ₂ ) gas 2 and the following reaction formula. Reacts to produce hydrogen fluoride (HF) gas.

F ₂ + H ₂ → 2HF
In the present embodiment, the hydrogen gas 2 is mixed in an amount equal to the amount of fluorine gas in the measurement target gas 1, so that all the fluorine gas reacts with the hydrogen gas to become hydrogen fluoride gas. Further, since the amount of the hydrogen gas 2 is usually larger than the fluorine gas in the measurement target gas 1, unreacted hydrogen gas remains in the mixed gas. Furthermore, even when the concentration of the fluorine gas in the measurement target gas 1 is close to 100%, the fluorine gas is a display value at the time of measurement due to the characteristics of the mass flow meter in which hydrogen gas or nitrogen gas is set as the measurement standard. Is displayed about 7% more than the actual volume. The reason why the “display value” is attached in the above flow rate is because it does not indicate the “actual value” of the flow rate. Therefore, even if the amount of the hydrogen gas 2 is the same as that of the measurement target gas 1 in the “display value”, the fluorine gas is an “actual value” that is smaller than the “display value”, so there is no fear that the hydrogen gas 2 is insufficient. When the display value differs depending on the type of gas, such as a mass flow meter, “equal amount” blending can be replaced with the case where the concentration of the fluorine gas in the measurement target gas 1 is 100%. The mass flow meter measures the amount of fluid based on the temperature difference generated between upstream and downstream, and the generated temperature difference depends on the specific heat of the gas, which is a fluid. The mass flow meter used in this embodiment measures hydrogen gas and nitrogen gas, and there is no need for correction for these gases, but fluorine gas has a specific heat of about 7% larger than that of hydrogen gas or nitrogen gas. The numerical value displayed even when flowing an amount of gas is about 7% larger. Should Ru using 0.93 to the flow rate of the fluorine gas to correct the numerical value.

  When the fluorine gas and hydrogen gas in the measurement target gas 1 react with each other, ignition or heat generation may occur. It is preferable to prevent such ignition or heat generation from flowing back in the piping.

  FIG. 3 is a transverse cross-sectional view showing a pipe for preventing ignition or heat generation from flowing back in the pipe. As shown in FIG. 3, the pipe 20 is composed of an outer pipe 22 and an inner pipe 21 arranged inside the outer pipe 22. A gas to be measured is passed through the inside 21 a of the inner pipe 21, and hydrogen gas is passed through a portion 22 a between the outer pipe 22 and the inner pipe 21. The front ends of the inner pipe 21 and the outer pipe 22 are introduced into the mixing reaction chamber 13.

  The distal end of the inner pipe 21 and the distal end of the outer pipe 22 are formed in a tapered shape so that the pipe diameter is reduced and a tapered shape is formed. For this reason, when the measurement target gas and the hydrogen gas are discharged from the pipe 20, the flow velocity can be increased. Thereby, it can prevent that the ignition or heat_generation | fever which arises when the fluorine gas in measurement object gas and hydrogen gas contact and react flows back in the piping 20. FIG.

  In addition, the fluorine gas and the hydrogen gas come into contact with each other in the vicinity of the tip of the pipe 20 to cause a reaction, and the reaction can also be caused in the mixed reaction chamber 13. The reaction between the fluorine gas and the hydrogen gas can be performed in two stages. Can be reacted.

  Moreover, since fluorine gas is mixed so that hydrogen gas wraps in the front-end | tip part of the piping 20, fluorine gas and hydrogen gas can contact reliably and can be made to react reliably.

  A water cooling pipe is provided around at least a part of the pipe 20.

  FIG. 4 is a cross-sectional view showing a cross section of the pipe 20 in a portion where the water-cooled pipe is provided. As shown in FIG. 4, a water cooling pipe 23 is provided around the pipe 20, and water for cooling the inside of the pipe 20 is provided in a portion 23 a between the outer pipe 22 and the water cooling pipe 23 of the pipe 20. Has been passed. By providing the water cooling pipe 23, the measurement target gas and the hydrogen gas in the pipe 20 can be cooled, and even if heat is generated due to the reaction between the fluorine gas and the hydrogen gas, it is possible to suppress an increase in temperature due to this. it can.

  Moreover, the mixing reaction chamber 13 can be immersed in water and cooled. By cooling, it is possible to prevent the gas from being heated and volume-expanding, so that highly accurate measurement can be performed.

The hydrogen fluoride (HF) gas generated by reacting in the mixed reaction chamber 13, the unreacted hydrogen (H ₂ ) gas, and the nitrogen (N ₂ ) gas as the dilution gas are then supplied to the hydrogen fluoride removal chamber. 14. Therefore, the gas component discharged from the mixing reaction chamber 13 and supplied to the hydrogen fluoride removal chamber 14 is HF + N ₂ + H ₂ . In the hydrogen fluoride removal chamber 14, calcium hydroxide (Ca (OH) ₂ ) is disposed, and this calcium hydroxide reacts with hydrogen fluoride (HF) gas as shown in the following reaction formula. Then, the fluorine component is taken in as calcium fluoride, and hydrogen fluoride (HF) gas is removed from the mixed gas.

2HF + Ca (OH) ₂ → CaF ₂ + 2H ₂ O
A large amount of calcium hydroxide is disposed in the hydrogen fluoride removal chamber 14 so that all the hydrogen fluoride (HF) gas contained in the mixed gas is removed.

As in the above reaction formula, hydrogen fluoride (HF) gas reacts with calcium hydroxide to generate calcium fluoride and water (H ₂ O). Therefore, the mixed gas contains water.

The mixed gas discharged from the hydrogen fluoride removing chamber 14 is then supplied to the drying chamber 15. The gas component discharged from the hydrogen fluoride removal chamber 14 is N ₂ + H ₂ + H ₂ O. Calcium oxide (CaO: quick lime) is arranged in the drying chamber 15. The calcium oxide absorbs water in the mixed gas and removes the water, whereby the mixed gas can be dried. Therefore, water (H ₂ O) is removed from the mixed gas to become a residual gas. The component in the residual gas is N ₂ + H ₂ .

The residual gas discharged from the drying chamber 15 contains unreacted hydrogen (H ₂ ) gas and nitrogen (N ₂ ) that is a dilution gas in the measurement target gas 1. The residual gas discharged from the drying chamber 15 is then sent to the buffer tank 16. By being sent to the buffer tank 16, fluctuations in the gas flow rate can be reduced and stabilized. By stabilizing the gas flow rate, the gas flow rate can be measured stably.

By measuring the flow rate of the residual gas discharged from the buffer tank 16 with the mass flow meter 17, the flow rates of nitrogen (N ₂ ) and unreacted hydrogen (H ₂ ) that are dilution gases in the measurement target gas 1 are measured. can do.

  By subtracting the flow rate of the residual gas measured by the mass flow meter 17 from the total flow rate of the measurement target gas 1 and the hydrogen gas 2 measured by the mass flow meter 12, the fluorine gas contained in the measurement target gas 1 and The amount of reacted hydrogen gas can be determined. From the amount of hydrogen gas that has reacted with the fluorine gas, the amount of fluorine gas that has reacted with this can be determined, and the amount of fluorine gas contained in the measurement target gas 1 can be calculated.

  As described above, when the flow rates of the measurement target gas 1 and the hydrogen gas 2 are set to 100 ml / min, the flow rate (display value) measured by the mass flow meter 17 is used to calculate the measurement target gas 1 in the measurement target gas 1. The amount of fluorine (%) can be determined.

Fluorine amount in measurement target gas (%) = [(207.5−display value) /1.93] × 0.93

When the fluorine gas amount (display value) in the measurement target gas 1 is X, the nitrogen gas amount Y is Y, the hydrogen gas 2 amount Z is the residual gas amount A, the measurement target gas 1 and the hydrogen gas 2 are respectively If it ’s 100ml,
X + Y = 100
Z = 100
A = Y + (Z-0.93X)
= (100-X) + (100-0.93X)
= 200-1.93X
X = (200−A) /1.93
However, since X is a display value here, the actual value needs to be multiplied by the conversion factor, so the actual value of fluorine gas = X × 0.93 = [(200−A) /1.93] × 0.93
It becomes.

  By using the apparatus of the above embodiment, a high detection accuracy of about ± 1% can be obtained as the fluorine gas detection accuracy.

  FIG. 2 is a diagram showing the relationship between the fluorine concentration (actual value) in the measurement target gas and the measurement value measured by the measurement apparatus of the present embodiment. As shown in FIG. 2, the actual value of the concentration of the fluorine gas actually contained in the measurement target gas and the measurement value measured by the measurement apparatus of the present embodiment have a substantially proportional relationship and are good. It can be seen that accurate detection accuracy can be obtained.

  In the above embodiment, nitrogen gas is used as the dilution gas in the measurement target gas 1, but measurement is similarly performed when an inert gas that does not react with fluorine, such as argon (Ar) gas, is used as the dilution gas. can do. Further, when hydrogen fluoride is contained in the measurement target gas 1, a measurement error occurs due to the presence of hydrogen fluoride. Therefore, it is preferable to remove hydrogen fluoride with NaF or the like in advance.

DESCRIPTION OF SYMBOLS 1 ... Measurement object gas 2 ... Hydrogen gas 10 ... Fluorine gas concentration measuring device 11, 12, 17 ... Mass flow meter 13 ... Mixing reaction chamber 14 ... Hydrogen fluoride removal chamber 15 ... Drying chamber 16 ... Buffer tank 20 ... Piping 21 ... Inside Pipe 21a ... Inside of inner pipe 22 ... Outer pipe 22a ... Part between inner pipe and outer pipe 23 ... Water-cooled pipe 23a ... Part between outer pipe and water-cooled pipe

Claims (9)

A method for measuring the concentration of fluorine gas in a measurement target gas,
A mixing step of mixing hydrogen gas with the measurement target gas, causing hydrogen gas to react with all the fluorine gas in the measurement target gas to form hydrogen fluoride, and to form a mixed gas containing the hydrogen fluoride;
An HF removing step of removing the hydrogen fluoride from the mixed gas by absorbing the hydrogen fluoride in the mixed gas with an alkaline agent;
After removing the hydrogen fluoride, in order to remove water generated by the reaction between the hydrogen fluoride and the alkaline chemical, a drying step of drying the mixed gas to obtain a residual gas;
A method for measuring the concentration of fluorine gas, comprising: a gas amount measuring step for measuring the amount of the dried residual gas.   The method for measuring the concentration of fluorine gas according to claim 1, wherein the hydrogen gas is mixed in an equal amount with the measurement target gas.   The gas amount of the measurement target gas and the gas amount of the hydrogen gas are measured in advance before mixing, and the concentration of fluorine gas in the measurement target gas is determined from the gas amounts of the measurement target gas, the hydrogen gas, and the residual gas. The method for measuring the concentration of fluorine gas according to claim 1 or 2, wherein:   The fluorine gas according to any one of claims 1 to 3, further comprising a gas amount stabilization step for stabilizing the gas amount between the mixing step and the gas amount measurement step. Concentration measurement method.   The method for measuring the concentration of fluorine gas according to claim 1, wherein the amount of the residual gas is measured with a mass flow meter. An apparatus for measuring the concentration of fluorine gas by the measurement method according to any one of claims 1 to 5,
A mixed reaction chamber for introducing and mixing the gas to be measured and the hydrogen gas and reacting them to generate hydrogen fluoride;
A hydrogen fluoride removing chamber for removing the hydrogen fluoride by absorbing the hydrogen fluoride in the mixed gas discharged from the mixed reaction chamber into an alkaline agent;
A drying chamber for drying the mixed gas discharged from the hydrogen fluoride removal chamber to obtain a residual gas;
A fluorine gas concentration measuring device comprising: a measuring means for measuring the amount of the residual gas discharged from the drying chamber.   The fluorine gas concentration measuring device according to claim 6, further comprising at least one buffer tank for stabilizing a gas amount between the mixing reaction chamber and the measuring means.   The fluorine gas concentration measuring device according to claim 6 or 7, wherein the measuring means is a mass flow meter.   The fluorine according to any one of claims 6 to 8, further comprising gas amount measuring means for measuring respective amounts of the measurement object gas and the hydrogen gas introduced into the mixed reaction chamber. Gas concentration measuring device.

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