JP2003149100A - Filter for removing disturbance gas for gas detecting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filter for removing disturbance gases for a gas detecting apparatus capable of removing hydrogen sulfide and organic solvents by a single filter. SOLUTION: Silver salt is dissolved in a moisture retaining agent. The silver salt in this state is carried by an air permeable sheet 2 made of activated carbon. The organic solvents are adsorbed and removed by the activated carbon, and the hydrogen sulfide is removed by the reaction between the silver salt dissolved in the moisture retaining agent carried by the sheet and the hydrogen sulfide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter for removing interfering gases such as hydrogen sulfide and organic solvents from a test gas flowing into a gas detector.

[0002]

2. Description of the Related Art In petrochemical and oil drilling sites, for example, dangerous gases such as hydrogen sulfide (H ₂ S), sulfur dioxide (SO ₂ ) and carbon monoxide (CO) are present in high concentrations. It is necessary to constantly monitor the concentrations of these gases. Among these gases, when measuring sulfur dioxide or carbon monoxide, usually, a constant potential is applied between the working electrode that forms a boundary surface with the electrolytic solution and the counter electrode immersed in the electrolytic solution, A potentiostatic electrochemical sensor that utilizes the fact that the electrolytic current changes depending on the gas concentration is used.

When a potentiostatic electrolysis type electrochemical sensor is used in an environment in which hydrogen sulfide is present, hydrogen sulfide acts as an interfering component, so that the target gas such as sulfur dioxide or carbon monoxide is detected. Will be difficult to do. In order to solve such a problem, Japanese Patent Laid-Open No. 6-18614
As shown in the publication, a sheet-like carrier having gas permeability holds polyhydric alcohol and silver salt, and a silver salt dissolved in polyhydric alcohol and hydrogen sulfide contained in a test gas are selected. It has been proposed that the hydrogen sulfide be removed by a reactive reaction.

[0004]

On the other hand, depending on the environment, not only hydrogen sulfide but also an organic solvent such as ethanol to which the potentiostatic electrochemical sensor responds with high sensitivity may exist. In such an environment, the above-mentioned hydrogen sulfide removing filter and the activated carbon sheet are placed one on top of the other at the gas inlet. However, since the case is small, especially for a small gas detector that is used while being worn on clothes, the task of exchanging two filters and a sheet is troublesome, and it is necessary to attach either a filter or a sheet. There are problems such as forgetting. The present invention has been made in view of such a problem, and an object thereof is to provide a filter for gas detector interfering gas removal capable of removing hydrogen sulfide and an organic solvent with a single filter. Is to provide.

[0005]

In order to solve such a problem, in the present invention, a breathable sheet made of activated carbon is loaded with a silver salt dissolved in a moisturizing agent.

[0006]

The organic solvent is adsorbed and removed by the activated carbon forming the sheet, and the hydrogen sulfide is removed by the reaction between the silver salt dissolved in the humectant carried on the sheet and the hydrogen sulfide.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The details of the present invention will be described below with reference to illustrated embodiments. FIG. 1A shows an embodiment of the filter of the present invention, which is denoted by reference numeral 1 in the drawing.
Is a filter characterized by the present invention, in which a permeative sheet 2 composed of activated carbon fibers is provided with silver perchlorate as a silver salt in an amount of 25 to 50 g / m 2 per square meter and glycerin as a moisturizing agent. It is configured to carry 20 grams.

This filter 1 contains 5 to 1 silver perchlorate.
0 grams w / v percent, glycerin 5 grams w / v
It can be produced by immersing an activated carbon sheet in a solution in which each of the above percentages is dissolved in methanol to impregnate the solution between the fibers, and then pulling up the activated carbon sheet to evaporate the methanol at room temperature.

FIG. 1 (b) is an enlarged view showing the fibers 3 forming the activated carbon sheet forming the filter, and silver paratoluenesulfonate is shown in the pores of the fibers having large openings. Glycerin 4 in which is dissolved is adsorbed, but an opening 5 small enough to adsorb molecules having a small molecular weight such as methanol is opened. With such a structure, the organic solvent contained in the test gas, especially ethanol, is adsorbed at the openings 5 of the activated carbon constituting the sheet, and silver perchlorate dissolved in the water held by the glycerin 4 is absorbed. Reacts with hydrogen sulfide to retain it in glycerin.

FIG. 2 shows an example of a gas detection device in which the filter of the present invention is used, in which a power supply unit, a signal processing unit and a sounding element are housed in a case 10 formed by polymer injection molding. Further, the display panel 11 is provided on the surface, and the band fixing portions 10a at both ends are configured to be worn on the arm by bands (not shown).

A plurality of gas inlets 12 are formed on the side of the case 10, and a plurality of button type gas sensors 13 for detecting different gases are housed as shown in FIG. On the outside of the gas sensor 13, a sensor fixing frame 14 having a window 14a for allowing gas to flow into each sensor is attached to the case 10 by the claws 15 at both ends.

On the surface of the sensor fixing frame 14, a filter fixing frame 17 having a gas inlet 12 with a common dustproof filter 16 for removing atmospheric dust flowing into each sensor 13 is attached and detached. It is installed as possible. Recesses 18 and 19 for housing the above-described filter 1 and other types of filters 1 ′ are formed around the window 14 a of the sensor fixing frame 14 facing the specific gas sensor.

According to this embodiment, the filter fixing frame 17
It is possible to prevent hydrogen sulfide and the organic solvent from entering the gas sensor by simply removing the filter, setting the single filter 1 and filling the filter fixing frame 17.

Although silver perchlorate is used as the silver salt in the above-mentioned examples, a silver salt that easily reacts with hydrogen sulfide and is soluble in water, such as silver nitrate or silver p-toluenesulfonate, is used. Even if it is used, the same effect is obtained.
Further, in the above-mentioned examples, glycerin, which has a low degree of reducing the adsorption capacity of the activated carbon sheet, is used as a moisturizing agent, but other moisturizing agents, for example, polyhydric alcohols such as ethylene glycol may be used. it can.

Further, the larger the amount of silver salt supported on the activated carbon sheet, the higher the ability to remove hydrogen sulfide, but if the concentration exceeds the saturated concentration with respect to the polyhydric alcohol, the air permeability is impeded by the precipitation of metallic silver. , The upper limit is naturally limited. When the amount of glycerin is increased, it is possible to increase the upper limit of the silver salt that can be supported without precipitating metallic silver, but the air permeability is impaired, and therefore the upper limit is naturally limited.

Further, although the case of using one kind of silver salt has been described in the above embodiment, the same effect can be obtained even if a plurality of kinds of silver salts are used in combination as long as the moisturizer is not saturated. It is clear that Also,
In this embodiment, the case of applying to an electrochemical gas sensor which is relatively susceptible to hydrogen sulfide has been described, but the same applies when used as a filter for removing an interfering gas of another type of gas sensor such as a semiconductor gas sensor. It is clear that the action of

[0017]

As described above, according to the present invention,
The organic solvent is adsorbed and removed by the activated carbon of the sheet constituting the filter body, and hydrogen sulfide can be removed by the reaction between the silver salt dissolved in the moisturizer carried on the sheet and hydrogen sulfide.

[Brief description of drawings]

1A and 1B are respectively a cross-sectional view showing an embodiment of a filter for removing an interfering gas for a gas detection device of the present invention, and an enlarged view of fibers constituting a sheet. .

FIG. 2 is a perspective view showing an embodiment of a small gas measuring device to which the filter of the present invention is applied.

FIG. 3 is a cross-sectional view showing a disassembled mounting portion of the gas sensor of the same apparatus.

[Explanation of symbols]

1 filter 2 Breathable sheet of activated carbon

Claims (3)

[Claims] 1. A filter for removing an interfering gas for a gas detection device, comprising a breathable sheet made of activated carbon and a silver salt dissolved in a moisturizing agent. 2. The filter for removing an interfering gas for a gas detection device according to claim 1, wherein the silver salt is one of silver perchlorate, silver paratoluenesulfonate, silver nitrate, or a mixture thereof. 3. The filter for removing an interfering gas for a gas detection device according to claim 1, wherein the humectant is glycerin or a polyhydric alcohol.