JP7529268B2 - Detector tubes and detectors - Google Patents

Description

Embodiments of the present invention relate to detector tubes and detection devices.

In recent years, international efforts to prevent mercury pollution have been strengthened. Specifically, restrictions have been put in place on the manufacture, import and export of mercury and products that use mercury in order to prevent global-scale environmental pollution caused by mercury and mercury compounds and the resulting health damage. In Japan, the Minamata Convention on Mercury came into force in August 2017.

Mercury is sometimes used in batteries, lighting fixtures such as fluorescent lights, and measuring instruments such as thermometers and blood pressure monitors. Mercury is also sometimes used, for example, in detector tubes for detecting specific gases contained in the air. Detector tubes are primarily composed of a detector agent that reacts with a gas or other substance to be detected, and a glass tube in which the detector agent is enclosed (see, for example, Patent Document 1).

For example, some detector tubes that detect nitrile compounds such as acrylonitrile and 2-pentenenitrile use mercuric chloride as the detection agent. Some detector tubes of this type also use a reactant with hexavalent chromium added to react with nitrile compounds to produce easily detectable hydrogen cyanide.

JP 2014-92487 A

To prevent environmental pollution by harmful substances, there is hope for the emergence of detection technology that minimizes the use of harmful substances such as mercury compounds and hexavalent chromium compounds.

The present invention was made in light of the above circumstances, and aims to detect target substances while minimizing the use of harmful substances.

To solve the above problems, the detector tube according to the first invention is a detector tube for detecting acrylonitrile or 2-pentenenitrile contained in gas, and is equipped with a detector tube body having a gas inlet and outlet, and a detector agent that is filled in the detector tube body and contains potassium permanganate that reacts with the substance to be detected.

The detection device according to the second invention is a detection device for detecting acrylonitrile or 2-pentenenitrile contained in gas as a detection target substance, and includes a detection tube and a suction device. The detection tube has a detection tube body in which an inlet and an outlet for the gas are formed, and a detection agent that is filled in the detection tube body and contains potassium permanganate that reacts with the detection target substance. The suction device sucks in the gas through the detection tube body of the detection tube.

FIG. 2 is a plan view of the detector tube according to the embodiment. FIG. 2 is a cross-sectional view showing the XZ cross section of the detector tube. 11A to 11C are diagrams for explaining a manufacturing method of the detector tube. FIG. 1 is a diagram for explaining how to use a detector tube. FIG. 2 is a diagram showing a detector tube when detecting a detection target substance. FIG. 13 is a graph showing the relationship between the concentration of acrylonitrile as a detection target substance and the color change length of a detecting agent. FIG. 1 is a graph showing the relationship between the concentration of 2-pentenenitrile as a detection target substance and the color change length of a detection agent. FIG.

This embodiment will be described below with reference to the drawings. In the description, a coordinate system consisting of mutually orthogonal X-axis, Y-axis, and Z-axis will be used as appropriate.

Figure 1 is a plan view of a detector tube 10 according to this embodiment. The detector tube 10 is a detector tube that detects, for example, acrylonitrile or 2-pentenenitrile in the air as a substance to be detected. Acrylonitrile and 2-pentenenitrile are used as raw materials for acrylic synthetic fibers and synthetic resins such as synthetic rubber, ABS resin, and AS resin. The detector tube 10 is primarily used for analyzing the air environment in factories that manufacture acrylic synthetic fibers and synthetic resins.

As shown in FIG. 1, the detector tube 10 is a member whose longitudinal direction is the X-axis direction, and includes a detector tube body 11 and a detector agent 13 filled inside the detector tube body 11.

The detector tube body 11 is a cylindrical glass tube made of, for example, quartz glass, with the longitudinal direction being the X-axis direction. The length (dimension in the X-axis direction) of the detector tube body 11 is about 10 cm, and the inner diameter is about 2 to 3 mm. The two ends 11a, 11b of the detector tube body 11 are sealed, separating the internal space of the detector tube body 11 from the external space. A small diameter section 11c is formed about 20 mm away from the end 11b of the detector tube body 11, which is shaped so that the inner and outer diameters are small. In addition, a number M, for example 1 to 10, and an arrow A1 pointing in the direction from the end 11b to the end 11a are printed on the surface of the detector tube body 11.

Figure 2 is a cross-sectional view showing the XZ section of the detector tube 10. As shown in Figure 2, inside the detector tube body 11, a plug 12 made of Teflon (registered trademark), a detector agent 13, a molecular sieve 14, and a cotton plug 15 are arranged.

The plug 12 is made of fluororesin with excellent chemical resistance. The plug 12 is breathable because the fluororesin material is made porous. The plug 12 is shaped into a sphere with a radius slightly smaller than the inside diameter of the detector tube body 11, and its position in the X-axis direction is determined by abutting against the inner wall surface of the small diameter section 11c.

The detection agent 13 is composed of a reactive agent that changes color by chemically reacting with the substance to be detected, and a carrier that supports this reactive agent. The carrier is a chemically stable granular material that is uniform in size and shape. For example, silica sand with an average particle size of 100 to 180 μm can be used as the carrier.

The reactant used is potassium permanganate, which reacts with acrylonitrile or 2-pentenenitrile. The reactant is attached to the surface of the carrier.

To prepare the detection agent 13, first prepare silica sand with an average particle size of 100 to 180 μm as a carrier.

Next, the surface of the silica sand is coated with alumina sol. Alumina sol is a colloidal solution of alumina hydrate with pure water as a dispersion medium. 50 g of colloidal solution is used per 1 kg of silica sand to coat the silica sand. Specifically, alumina sol is added to the silica sand, and the silica sand is dried under reduced pressure in a water bath at 100°C. The silica sand is then fired at 650°C for 4 hours. By firing the silica sand at 650°C, the alumina on the surface of the silica sand becomes γ-alumina, and the surface area increases. This increases the surface area of the support for the gas to be detected (detection target gas), and as a result, the physical adsorption of the detection target substance to the reactant is improved.

Next, potassium permanganate is added as a reactant to the carrier whose surface has been coated. To add potassium permanganate, 0.048 g of potassium permanganate is used per 1 kg of carrier. Specifically, a 1% aqueous solution of potassium permanganate is prepared. Then, 4.8 ml of the prepared 1% aqueous solution is added to the carrier, and the carrier is dried under reduced pressure in a water bath at 80°C. This completes the detection agent 13.

The molecular sieve 14 is a crystalline zeolite that functions as a desiccant. The cotton plug 15 is a member made of cotton.

As shown in FIG. 3, the plug 12, detection agent 13, molecular sieve 14, and cotton plug 15 are filled in the following order from the end 11a of the detector tube body 11: plug 12, detection agent 13, molecular sieve 14, and cotton plug 15.

The detecting agent 13 is filled between the plug 12 and the molecular sieve 14, and its length in the X-axis direction is about 70 mm. The length of the molecular sieve 14 is about 10 mm. The detecting agent 13 and the molecular sieve 14 are positioned by the plug 12 located in the small diameter portion 11c of the detector tube body 11 and the cotton plug 15 filled in the detector tube body 11. After the detector tube body 11 is filled with the plug 12, the detecting agent 13, the molecular sieve 14, and the cotton plug 15, the end 11a of the detector tube body 11 is sealed to complete the detector tube 10 shown in FIG. 1. In the detector tube 10, the both ends 11a and 11b of the detector tube body 11 are sealed, so that the detecting agent 13 is retained without its composition being changed by the influence of the external environment.

When using the detector tube 10 described above, both ends 11a, 11b of the detector tube body 11 are cut at the positions shown by the dashed lines in Figure 1. This forms openings 10a, 10b at both ends of the detector tube body 11 as shown in Figure 4, allowing gas such as air containing the substance to be detected (the gas to be detected) to pass through the inside of the detector tube body 11 through these openings 10a, 10b.

In the detector tube 10, when the target gas passes through the inside of the detector tube body 11 in the direction indicated by the arrow A1, the detector agent 13 changes color in accordance with the concentration of the target substance contained in the target gas. FIG. 5 is a diagram showing the detector tube 10 after target gas containing a predetermined concentration of the target substance has passed through. As shown in FIG. 5, the discoloration of the detector agent 13 occurs from the upstream side to the downstream side of the detector tube body 11. Therefore, the length of the discolored portion 13a of the detector agent 13 (discoloration length) corresponds to the concentration of the target substance contained in the target gas.

Figure 6 shows the relationship between the concentration of acrylonitrile, a target substance contained in the target gas, and the discoloration length of the detecting agent 13 used in the detecting tube 10. Line L1 in the figure shows the characteristics when 200 ml of the target gas passes through the detecting tube 10. Line L2 shows the characteristics when 100 ml of the target gas passes through the detecting tube 10. As shown in Figure 6, when the concentration of the target substance is about 2 ppm or more, the discoloration length of the detecting agent 13 increases linearly in proportion to the concentration of the target substance.

Figure 7 shows the relationship between the concentration of 2-pentenenitrile as a detection target substance contained in the detection target gas and the discoloration length of the detection agent 13 used in the detection tube 10. Line L3 in the figure shows the characteristics when 200 ml of the detection target gas passes through the detection tube 10. Line L4 shows the characteristics when 100 ml of the detection target gas passes through the detection tube 10. As shown in Figure 7, when the concentration of the detection target substance is approximately 2 ppm or more, it can be seen that the discoloration length of the detection agent 13 increases linearly in proportion to the concentration of the detection target substance.

As can be seen from Figures 6 and 7, the characteristics shown by lines L1 and L3 are almost identical, and the characteristics shown by lines L2 and L4 are almost identical. Therefore, the memory M of the detector tube 10 can be used in common whether the substance to be detected contained in the gas to be detected is acrylonitrile or 2-pentenenitrile. The detector tube 10 is capable of measuring in the range of 0.4 to 20 ppm with an air flow rate of 100 mL, and in the range of 0.2 to 10 ppm with an air flow rate of 200 mL.

The discoloration of the detecting agent 13 occurs when potassium permanganate _KMnO4 contained in the detecting agent 13 acts as an oxidizing agent for acrylonitrile and 2-pentenenitrile under acidic conditions, and the detecting agent 13 itself is reduced. Specifically, potassium permanganate is composed of potassium ions K ⁺ and permanganate ions _MnO4- (valence of Mn +7 ⁾ . When permanganate ions _MnO4- are present, the detecting agent 13 assumes a pink color. When the detecting agent 13 is reduced and the permanganate ^{ions MnO4-} are decomposed into manganese ions ^Mn2+ (valence of Mn +2) as shown in the following formula ( ₁ ), the detecting agent 13 assumes a white color.

MnO ₄ ^- +8H ⁺ +5e ^- →Mn ²⁺ +4H ₂ O...(1)

For example, the detector tube 10 is provided with a memory M on the assumption that 200 ml of the target gas will pass through it. As an example, as shown in FIG. 5, if the memory value at the +X end of the discolored portion 13a is 7.5, it can be seen that the concentration of the target substance contained in the target gas is 7.5 ppm.

When using the detector tube 10, both ends 11a, 11b are cut and the end 11a is attached to the suction device 50 as shown in FIG. 8. The suction device 50 consists of a cylindrical syringe 51 and a plunger 52 to which a gasket is fixed that moves back and forth inside the syringe 51. The +Z end of the syringe 51 is provided with a mounting part 53 to which the detector tube 10 is attached. The detector tube 10 can be attached to the suction device 50 by inserting the end 11a of the detector tube 10 into the opening 53a of the mounting part 53. The detector tube 10 is attached to the suction device 50, forming a detection device.

The suction device 50 can aspirate 100 ml of gas with one stroke of the plunger 52 into the syringe 51. Therefore, in a space filled with the target gas, by operating the suction device 50 to which the detector tube 10 is attached and performing two strokes of the plunger 52, 200 ml of the target gas can be ventilated into the detector tube 10. The value of the memory at the +X end of the discolored portion 13a after operating the suction device 50 indicates the concentration of the target substance contained in the target gas.

As explained above, in the detector tube 10 according to this embodiment, potassium permanganate is used as the detector agent 13 for acrylonitrile or 2-pentenenitrile contained in the gas to be detected. This makes it possible to detect the target substance without using harmful substances such as mercury compounds or hexavalent chromium compounds.

Conventionally, acrylonitrile (CH ₂ ═CHCN) has been detected by generating hydrogen cyanide (HCN) using a reactant containing hexavalent chromium (CrO ₃ ), as shown in the following reaction formula (2), and then detecting the hydrogen cyanide using a detector containing mercuric chloride (HgCl ₂ ), as shown in reaction formula (3).

_CH2 =CHCN+ _{CrO3 + H2SO4} →HCN...(2)
2HCN+HgCl ₂ →2HCl…(3)

In addition, to detect 2-pentenenitrile (CH ₃ CH ₂ CH═CHCN), a reactant using hexavalent chromium (CrO ₃ ) was used to generate hydrogen cyanide (HCN) as shown in the following reaction formula (4), and a detector containing mercuric chloride (HgCl ₂ ) was used to detect the hydrogen cyanide as shown in the reaction formula (5), thereby detecting 2-pentenenitrile.

_{CH3CH2CH =} CHCN+ _CrO3 + _H2SO4 →HCN...( ₄ )
2HCN+HgCl ₂ →2HCl...(5)

In the detector tube 10 according to this embodiment, acrylonitrile or 2-pentenenitrile is detected using potassium permanganate, as shown in the above reaction formula (1). This makes it possible to detect the target substance without using harmful substances such as mercury compounds or hexavalent chromium compounds.

The detector tube 10 according to this embodiment can detect acrylonitrile and 2-pentenenitrile using only the detector agent 13. This eliminates the need to pre-treat the target gas as in the past. This makes it possible to detect the target substance without using a pre-treatment tube or the like. In addition, there is no need to fill the detector tube body 11 with hexavalent chromium or the like, which simplifies the structure of the detector tube and ultimately reduces the manufacturing costs of the detector tube.

In the detector tube 10 according to this embodiment, the concentration of the target substance contained in the target gas is indicated by a memory. Therefore, the target substance contained in the target gas can be detected not only qualitatively but also quantitatively.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, in the above embodiment, silica sand is used as a carrier for the detecting agent 13. However, this is not limiting, and silica gel or the like may be used as the carrier.

In the detector tube 10 according to the above embodiment, the memory M is provided on the assumption that 200 ml of the gas to be detected will be passed through. This is not limiting, and the memory M may be provided on the assumption that, for example, 100 ml of the gas to be detected will be passed through. The memory M can be provided depending on the application of the detector tube 10.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention, and are included in the scope of the invention and its equivalents as set forth in the claims.

10 Detector tube 10a, 10b Opening 11 Detector tube body 11a, 11b End 11c Small diameter portion 12 Plug 13 Detector agent 13a Discolored portion 14 Molecular sieve 15 Cotton plug 50 Suction device 51 Syringe 52 Plunger 53 Mounting portion 53a Opening L1 to L4 Lines M Memory

Claims (7)

A detector tube for detecting acrylonitrile or 2-pentenenitrile contained in a gas as a detection target substance,
a detector tube body in which an inlet and an outlet for the gas are formed;
A detection agent that is filled in the detector tube body and contains potassium permanganate and reacts with the detection target substance;
A detector tube equipped with The detector tube according to claim 1, wherein the detector agent has a carrier that supports the potassium permanganate. The detector tube according to claim 2, wherein the carrier is made of granular material whose surface is coated with gamma-alumina. The detector tube according to any one of claims 1 to 3, wherein the detector tube body has a window through which the detector agent can be visually observed from the outside. The detector tube according to any one of claims 1 to 4, wherein the detector tube body is made of glass. The detector tube according to any one of claims 1 to 5, wherein the detector tube body is provided with a scale from the inlet to the outlet in the portion where the filled detector agent is located. A detection device for detecting acrylonitrile or 2-pentenenitrile contained in a gas as a detection target substance,
a detector tube having a detector tube body in which an inlet and an outlet for the gas are formed, and a detector agent containing potassium permanganate that is filled in the detector tube body and reacts with the detection target substance;
a suction device that sucks the gas through the detector tube body of the detector tube;
A detection device comprising:

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