JP2014016252A - Hydrogen azide gas concentration measuring probe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrogen azide gas concentration measuring probe which can continuously monitor a hydrogen azide gas concentration regardless of humidity.SOLUTION: A hydrogen azide gas concentration measuring probe includes: a housing 2 having an optical fiber connection port 1; a metal mirror 3 reflecting infrared light R; a lens 4 which is provided between the optical fiber connection port 1 and the metal mirror 3 and which transmits the infrared light R; and a heater 5 heating the metal mirror 3.

Description

  The present invention relates to a probe, a measuring apparatus, and a measuring method that enable continuous monitoring of hydrogen azide gas concentration.

  Hydrogen azide is a highly volatile liquid generated by neutralizing sodium azide with an acid, and is a compound having explosiveness, extreme toxicity and metal corrosiveness. Therefore, appropriate equipment and strict management are required for handling hydrogen azide.

  Hydrogen azide is used as a raw material for synthesizing nitrogen-containing organic compounds such as tetrazole and triazole. At that time, hydrogen azide is not prepared and stored in advance. It is generated by contacting sodium chloride with an acid and immediately subjected to the reaction. In this case, it is preferable to control the amount of acid added while maintaining a balance between the amount of hydrogen azide consumed in the reaction and the amount generated, and it is desirable to continuously monitor the concentration of hydrogen azide in the system. It is.

  In recent years, the PUREX method has been adopted in each country as one of the nuclear fuel reprocessing methods. In this method, hydrogen azide is generated in a process of separating uranium and plutonium from a fuel rod dissolved in an acid. Therefore, in order to ensure safety, it is desirable to constantly monitor the hydrogen azide concentration in the separation process of uranium and plutonium.

  Thus, it is necessary in various situations to continuously grasp the concentration of hydrogen azide. However, until now, the measurement of the hydrogen azide concentration has been generally carried out by appropriately sampling and analyzing by high performance liquid chromatography, gas chromatography or the like, so that only intermittent monitoring has been possible at present.

  Therefore, the present inventors have conceived of measuring the hydrogen azide gas concentration by infrared spectroscopic analysis using a reflective cell probe. The infrared spectrum can be continuously generated by changing the copper mirror, which is widely used for general commercially available reflective cell probes, to aluminum mirrors or gold-plated mirrors to avoid the generation of copper azide. It was found and reported that the obtained absorbance and the hydrogen azide gas concentration correlate and can be quantified by preparing a calibration curve in advance (Non-patent Documents 1 and 2).

Hideo Fujiwara and 4 others, “Explosion Hazard of Hydrogen Azide”, 40th Safety Engineering Research Presentation, Proceedings p33-34, announced on December 6, 2007 Ken Okada and 5 others, “Study on synthesis, physical property evaluation and monitoring of hydrogen azide”, Atomic Energy Society of Japan “Autumn in 2011” (September 19-22, 2011, Kitakyushu International Conference Center, etc.), Proceedings p126

  However, the measurements reported in Non-Patent Documents 1 and 2 above were performed in an atmosphere with relatively low humidity. When attempting to monitor the hydrogen azide gas concentration in an atmosphere with relatively high humidity, azide In some cases, the infrared absorption spectrum of hydrogen could not be detected well.

  The present invention has been made paying attention to the above-described circumstances, and its purpose is to provide a probe, a measuring apparatus, and a measuring method capable of continuously monitoring the concentration of hydrogen azide gas regardless of humidity. There is to do.

  The probe for measuring the concentration of hydrogen azide gas of the present invention that has achieved the above object includes a housing having an optical fiber connection port, a metal mirror that reflects infrared light, and between the optical fiber connection port and the metal mirror. The present invention has a gist in that the lens includes a lens that transmits infrared light and a heater that heats the metal mirror. In the probe of the present invention, it is preferable that the material of the metal mirror is stainless steel because it is difficult to be corroded by hydrogen azide.

  The hydrogen azide gas concentration measuring apparatus of the present invention has a gist in that the probe of the present invention and an infrared spectrophotometer are connected by an optical fiber that transmits infrared light.

The method for measuring the concentration of hydrogen azide gas according to the present invention uses the above-described measuring apparatus according to the present invention to transmit infrared light from the infrared spectrophotometer through the optical fiber into the housing, pass through the lens, and pass through the metal. The present invention is summarized in that infrared light reflected by a mirror is transmitted again to the infrared spectrophotometer through the optical fiber. In the measurement method of the present invention, it is preferable to detect an infrared absorbance of 1163 ± 10 cm ⁻¹ because it is possible to reliably detect only absorption of hydrogen azide while avoiding the influence of water absorption.

A probe according to the present invention includes a housing having an optical fiber connection port, a metal mirror that reflects infrared light, a lens that transmits infrared light disposed between the optical fiber connection port and the metal mirror, Since the heater for heating the metal mirror is provided, the hydrogen azide gas concentration can be continuously monitored regardless of the humidity.
The reason for this is not necessarily elucidated, but when measuring the infrared absorption spectrum of hydrogen azide in a high-humidity atmosphere (ie, an atmosphere with a large amount of water vapor), the accuracy of the infrared spectrum can be reduced due to light scattering by water. Detection is not only prevented, but, for example, hydrogen azide dissolves in water adhering to the surface of mirrors and lenses and is adsorbed on the surface or promotes corrosion, resulting in accurate measurement of the infrared spectrum. It is considered that hydrogen azide poses unique problems, such as being inhibited. In any case, by providing a heater for heating the metal mirror, a good infrared spectrum was obtained regardless of humidity, and the hydrogen azide gas concentration could be measured.

  Moreover, since the probe of the present invention is a reflective probe provided with a metal mirror, it can be miniaturized. Since hydrogen azide gas is usually confined in a sealed space, downsizing the probe is advantageous when hydrogen azide gas is to be measured.

FIG. 1 is an external perspective view showing an embodiment of the probe of the present invention. FIG. 2 is a cross-sectional view of the probe 100 shown in FIG. 1 taken along line xx. FIG. 3 is a schematic diagram illustrating the experimental apparatus used in Example 1. 4 is a graph showing the relationship between infrared absorbance, beaker liquid temperature, and measurement time in Example 1. FIG. FIG. 5 is a graph showing a calibration curve obtained in the reference example.

(probe)
Hereinafter, the probe according to the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the illustrated examples, and appropriate modifications may be made within a range that can meet the purpose described above and below. In addition, it is possible to carry out, and they are all included in the technical scope of the present invention.

FIG. 1 is an external perspective view showing an embodiment of a probe 100 according to the present invention, and FIG. 2 is a cross-sectional view of the probe 100 shown in FIG. 1 taken along line xx.
As shown in FIGS. 1 and 2, the probe 100 is disposed between a housing 2 having an optical fiber connection port 1, a metal mirror 3 that reflects infrared light R, and an optical fiber connection port 1 and the metal mirror 3. The lens 4 that transmits the infrared light R and the heater 5 that heats the metal mirror 3 are provided.

  The housing 2 has, for example, a bottomed cylindrical shape. In the drawing, the right side of the paper is the bottom, and the left side of the paper is the opening 2 '. An optical fiber connection port 1 for connecting the optical fiber 6 at the time of measurement is provided at the bottom of the housing 2.

  On the opening 2 ′ side of the housing 2, a metal mirror 3 for reflecting the infrared light R irradiated from the optical fiber 6 and a heater 5 for heating the metal mirror 3 are provided. These are fixed to a part of the inner surface of the housing 2 so as not to completely block the opening 2 ′ of the housing 2. The hydrogen azide gas to be measured is introduced into the housing 2 through the opening 2 ′ of the housing 2.

  Furthermore, a lens 4 that transmits infrared light R is fixed inside the housing 2 at a predetermined interval from the metal mirror 3 and the optical fiber connection port 1. The lens 4 serves to change the infrared light R emitted from the optical fiber 6 into parallel light, converge the infrared light R reflected by the metal mirror 3 and return it to the optical fiber 6. For example, a convex lens is used. It is done.

  In the present embodiment, the heater 5 for heating the metal mirror 3 is provided on the back side of the infrared light reflecting surface of the metal mirror 3. By heating the metal mirror 3 with the heater 5, the hydrogen azide gas concentration can be measured even in a high humidity atmosphere. 1 and 2, the heater 5 is directly attached to the back surface of the metal mirror 3 by the heater attachment 10. However, as long as the temperature of the metal mirror 3 can be raised, the heater installation position is limited to this. It is not something. For example, a heater 5 is provided around (in part or all of) the inner or outer peripheral surface in the vicinity of the opening of the housing 2 to heat the metal mirror 3 directly or indirectly from the side surface, It is also possible to adopt a mode in which the heater 5 is provided in a state of being separated to the side (that is, leaving a certain space).

  The material of the metal mirror 3 may be any metal that can reflect infrared rays. For example, stainless steel, gold, aluminum, titanium, or the like can be used. Among these, stainless steel is preferable in that it is difficult to be corroded by hydrogen azide. For example, SUS304 is preferably used. Although the infrared reflectance of stainless steel is slightly inferior to that of gold or aluminum, it has the reflectance necessary for detecting the infrared absorbance in the present invention, and there is no practical problem.

  The metal mirror 3 can be provided with a thermocouple or a thermometer (not shown) for measuring the temperature when heated by the heater 5.

The material of the lens 4 may be any material that transmits infrared light. For example, zinc selenide (ZnSe), zinc sulfide (ZnS), germanium (Ge), silicon (Si), sapphire (Al ₂ O ₃ ), fluorine Examples thereof include calcium fluoride (CaF ₂ ), barium fluoride (BaF ₂ ), chalcogenide glass, and the like. Among these, zinc selenide (ZnSe) is preferable because it is less likely to absorb hydrogen azide gas and cause an error in the measured value.

  In FIGS. 1 and 2, the lens 4 is sandwiched between the ring-shaped rubber packing 7 and the ring-shaped spacer 8 from both sides, and a part of its circumference (on the left side in FIG. The metal mirror 3 is arranged so as to be in contact with one end (from the other end to the other end), and is fixed by pressing the metal mirror 3 from above (left side in FIG. 2) with a ring-shaped mirror holder 9 having an L-shaped cross section. Yes. The housing 2 is divided into two spaces with the lens 4 thus fixed as a boundary, and hydrogen azide gas is measured in the space on the metal mirror 3 side.

  In the present invention, the concentration of hydrogen azide gas between the fixed lens 4 and the metal mirror 3 is measured. The distance (distance) between the lens 4 and the metal mirror 3 may be set longer when measuring a relatively low concentration of hydrogen azide gas, and may be set shorter when measuring a relatively high concentration of hydrogen azide gas. desirable. Specifically, for example, the product of the optical path length (cm) and the hydrogen azide gas concentration (%) to be measured is set to be in the range of 1.6 to 6.0 [% · cm]. Is preferred. When the product of the optical path length and the hydrogen azide gas concentration is in the above range, the absorbance is in the range of about 0.1 to 0.8, and an infrared absorption spectrum suitable for calibration can be obtained. The value of the optical path length is twice the distance between the lens and the metal mirror. In addition, what is necessary is just to set the space | interval (distance) of the lens 4 and the metal mirror 3 with the thickness of the spacer 8, if it is an aspect shown to FIG.

  The material of the rubber packing 7 for fixing the lens 4 is not particularly limited, and for example, a known rubber packing material such as fluorine rubber, silicone rubber, ethylene propylene rubber, acrylic rubber, chlorosulfonated polyethylene rubber can be used. Among these, those that do not absorb hydrogen azide gas are preferable because they do not cause an error in measurement values, and fluororubbers such as Teflon (registered trademark) are preferably used.

  The material of the spacer 8 for fixing the lens 4 is not particularly limited. For example, a fluororesin, a combination of a fluororesin and a metal (a lens side made of fluororesin and a mirror side made of metal) is a lens. Is preferable in that it is not damaged.

(measuring device)
The hydrogen azide gas concentration measuring apparatus of the present invention is such that the probe of the present invention and an infrared spectrophotometer are connected by an optical fiber that transmits infrared light.
The infrared spectrophotometer includes a light source that emits infrared light and a detector that detects infrared light, and is a known infrared spectrometer, preferably a Fourier transform infrared spectrometer (FT-IR). Is used.

  The optical fiber includes an emission fiber that transmits infrared light R from an infrared spectrophotometer, and an incident fiber that transmits infrared light R reflected by a metal mirror and collected by a lens to the infrared spectrophotometer. It is formed. The emission fiber and the incident fiber can be appropriately combined. For example, by placing about 3 to 10 (preferably 6) incident fibers around one emission fiber, An optical fiber is formed.

(Measuring method)
The method for measuring the concentration of hydrogen azide gas according to the present invention uses the above-described measuring apparatus according to the present invention to transmit infrared light from the infrared spectrophotometer through the optical fiber into the housing, pass through the lens, and pass through the metal. The infrared light reflected by the mirror is transmitted again to the infrared spectrophotometer through the optical fiber.
In the measurement, the metal mirror is heated in advance by a probe heater. The temperature of the heated metal mirror is not particularly limited as long as it is at least higher than room temperature, and is, for example, 60 ° C. or higher, preferably 80 ° C. or higher, more preferably 100 ° C. or higher.

  In the measurement method of the present invention, the absorbance of a specific wavelength in an infrared absorption spectrum obtained by an infrared spectrophotometer is detected, and the concentration of hydrogen azide gas is obtained by a calibration curve of the concentration of hydrogen azide with respect to the absorbance of this specific wavelength. . The calibration curve may be obtained in advance by measuring the infrared spectrum of hydrogen azide gas whose concentration is known by known means such as gas chromatography. Since the absorbance of the infrared spectrum can be detected continuously over time, the method of the present invention makes it possible to measure the hydrogen azide concentration continuously over time.

In the infrared spectrum of hydrogen azide, absorption is observed mainly in the vicinity of a wavelength of 1163 ± 10 cm ^{−1 and in the} vicinity of a wavelength of 2152 ± 10 cm ⁻¹ . Therefore, in the measurement method of the present invention, it is preferable to detect the infrared absorbance at any of these wavelengths. In particular, in order to reliably detect only the absorption of hydrogen azide while avoiding the influence of water absorption, it is preferable to observe the absorbance at a wavelength of 1163 ± 10 cm ⁻¹ . However, when an organic compound having absorption near this (near 1163 ± 10 cm ⁻¹ ) is present in the atmosphere to be measured, it is possible to detect the absorbance near the wavelength 2152 ± 10 cm ⁻¹ . It is preferable to eliminate the influence of the above.

(Reference example-preparation of calibration curve)
For a plurality of hydrogen azide gases having different concentrations, the concentration is measured by gas chromatography (GC), while using the same probe, optical fiber, and infrared spectrophotometer as those used in Example 1 described later, The spectrum was measured. Then, the hydrogen azide concentration (%) by GC measurement on the horizontal axis, and plotting the absorbance at a wavelength of 1163cm ^-1 and a wavelength 2152cm ^-1 on the vertical axis, a calibration curve was prepared. This calibration curve is shown in FIG.

Example 1
1 and 2 shown in FIGS. 1 and 2 (the metal mirror 3 is made of stainless steel (SUS304), the lens 4 is made of zinc selenide, the distance from the metal mirror 3 to the lens 4 is 1 mm, and the optical path length is 2 mm), an optical fiber (injection). 1 fiber, 6 injection fibers) Connected to a Fourier transform infrared spectrophotometer (“VIR-9500” manufactured by JASCO Corporation) at the connection port 1, and as shown in FIG. The flask 11 was attached to one of the mouths so that the inside of the flask 11 was sealed through rubber packing. Further, a thermocouple 12 for measuring the mirror temperature was attached to the metal mirror 3, and the other end of the thermocouple 12 was led to the outside of the flask 11 so as to maintain a sealed state in the flask 11.

  In addition, a sodium azide aqueous solution is accommodated in the flask 11, and a syringe and a polyethylene tube (not shown) are provided so that 10% by mass sulfuric acid can be injected while maintaining the sealed state in the flask 11. It was. At this time, the hydrogen azide solution produced by the addition of sulfuric acid was adjusted to a concentration of 5% by mass so that the amount of the produced solution was about 1/6 of the total volume of the flask 11. Further, in order to measure the temperature of the solution, a Teflon (registered trademark) -coated thermocouple 13 was attached to the flask 11 so as to maintain a sealed state in the flask. The flask 11 was placed on a hot stirrer 14 and a stirrer 15 was placed inside.

  In the experimental apparatus described above, the metal mirror was first heated to 105 ° C. by the heater 5 of the probe. At this time, the temperature of the lens 4 was at least 50 ° C. or higher. And the infrared spectrum measurement was started and sulfuric acid was inject | poured 4 minutes after the measurement start, and the hydrogen azide solution was produced | generated. Next, 20 minutes after the start of the measurement, the surface temperature of the hot stirrer 14 was set to 105 ° C., heating of the solution was started, and the temperature of the solution was raised to 82 ° C. Thereafter, heating by the hot stirrer 14 was stopped 70 minutes after the start of measurement.

The vertical axis on the horizontal axis the time from the start of the infrared spectrum measurement, absorbance at a wavelength 1163cm ^-1 and a wavelength 2152cm ^-1 in the infrared spectrum obtained, or the temperature of the solution in the flask 11 (liquid temperature) The graph taken is shown in FIG. As can be seen from FIG. 4, the liquid temperature of the hydrogen azide solution and the absorbance at the wavelength of 1163 cm ⁻¹ or the wavelength of 2152 cm ⁻¹ are correlated. In view of the fact that the amount of hydrogen azide vaporization (in other words, hydrogen azide gas concentration) increases or decreases according to the liquid temperature of the hydrogen azide solution, the fact that the infrared absorbance and the hydrogen azide gas concentration are correlated is Since it is clear, the hydrogen azide gas concentration over time can be known based on the calibration curve obtained in the reference example. For example, since the absorbance at a wavelength of 1163 cm ⁻¹ is about 0.44 at the time point of 50 minutes from the start of measurement, the hydrogen azide gas concentration in the flask 11 is about 28%.

DESCRIPTION OF SYMBOLS 100 Probe 1 Optical fiber connection port 2 Case 3 Metal mirror 4 Lens 5 Heater 6 Optical fiber 7 Rubber packing 8 Spacer 9 Mirror holder 10 Heater attachment 11 Flask 12 Thermocouple 13 Thermocouple 14 Hot stirrer 15 Stirrer

Claims (5)

  A housing having an optical fiber connection port, a metal mirror that reflects infrared light, a lens that transmits infrared light disposed between the optical fiber connection port and the metal mirror, and a heater that heats the metal mirror; A probe for measuring hydrogen azide gas concentration, comprising:   The hydrogen azide gas concentration measuring probe according to claim 1, wherein the metal mirror is made of stainless steel.   3. A hydrogen azide gas concentration measuring apparatus, wherein the probe according to claim 1 and an infrared spectrophotometer are connected by an optical fiber that transmits infrared light.   Using the measuring apparatus according to claim 3, infrared light is transmitted from the infrared spectrophotometer through the optical fiber into the housing, and the infrared light transmitted through the lens and reflected by a metal mirror is again transmitted to the optical fiber. And transmitting the hydrogen azide gas concentration to the infrared spectrophotometer. The method for measuring a hydrogen azide gas concentration according to claim 4, wherein an infrared absorbance of 1163 ± 10 cm ⁻¹ is detected.