JPS5930222B2 - Specific gas detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a specific gas detection method for detecting Co gas generated in the early stages of a fire, discovering incomplete combustion, or detecting Co gas for environmental control.

It is widely known that the resistance value of metal oxide semiconductors such as sno2 changes depending on various gases, and it has already been put into practical use to detect gases such as Co gas and methane gas using such gas detection elements. ing.

In the gas detection method, when detecting only a specific gas, that is, when detecting Co gas, it is necessary to provide a filter means to prevent other gases from coming into contact with the detection element.

Conventionally, activated carbon has been used as this filter.Although activated carbon has an excellent adsorption ability, it has the drawback that once adsorbed substances are not desorbed, saturation of adsorption occurs, resulting in a short service life. Adsorption-saturated activated carbon can be regenerated by heating it to 200°C or higher in an inert gas atmosphere, but gas detection is usually performed using equipment that is kept in place for a long period of time, so only the filter can be regenerated. It is inconvenient and impractical to frequently remove and regenerate.
In view of these points, the present invention provides a specific gas detection method that reliably removes organic gases that cause malfunctions and is equipped with a filter means that has a self-regeneration function.

When the test gas is Co gas, alcohol, ether,
Since other organic gases constitute miscellaneous gases, in order to detect only the target gas, it is necessary to remove only this organic gas with a filter.

The filter is also required to have a self-regeneration function. We have discovered that a rubber-like polymer material is suitable as a material that satisfies these requirements, and have completed the present invention based on this discovery. The present invention removes organic gases from the gas to be detected by absorbing organic gases in the air using a non-ventilating filter mainly made of rubber ash polymer that has the ability to absorb organic gases. The lCO gas is detected by a gas detection element made of an arsenic semiconductor with a metal part whose value changes.

Hereinafter, the present invention will be explained with reference to drawings of embodiments. In FIG. 1, reference numeral 1 denotes a case containing a metal oxide semiconductor gas detection element 10. At the top and bottom of the case 1, there is a filter 1 made of a rubber-like polymer J having the ability to absorb organic gas.
1 is held by a wire mesh 12. This filter 11 is made of an open-cell porous material or a rubber plate with many holes formed therein. The internal elements are made to come into sufficient contact with the air from the external atmosphere. Alternatively, as shown in FIG. 2, air from the outside atmosphere may be supplied into the case 1 from a suction pump 2 through a rubber-like polymer pipe 3.

In this case, the pipe 4 functions as a filter. 4 is an amplifier, and 5 is a meter, which amplifies and displays the detection signal from the gas detection element.

Examples of the polymers used for the filter include silicone rubber, vulcanized natural rubber, and low polymerization soft vinyl chloride rubber. When air containing the organic gas comes into contact with these, the organic gas is absorbed by the filter. This amount of absorption is proportional to the partial pressure of organic gas in the air and the weight of the filter material.
Furthermore, although the surface area of the filter is related to the absorption rate, there is no clear relationship with the absorption amount. This is considered to be because the filter 1 absorbs the gas rather than adsorbing it. When the atmosphere returns to clean air, the filter 1 gradually releases the absorbed gas to recover its absorption capacity and exhibits a self-regeneration function. Since this release is done very slowly, malfunctions do not occur due to the released gas. When we investigated the organic gas absorption capacity of silicone rubber, vulcanized natural rubber, and low-polymerized soft vinyl chloride rubber as filter materials, we found that:
The results are as shown in Table 1. The absorption rate decreased exponentially with time and reached saturation in about 30 minutes.

In addition, when the samples that reached saturation were left in clean air, all of the above materials released absorbed gas and recovered their absorption capacity. Next, according to the configuration shown in Fig. 2, a pipe 3 having an inner diameter of 4 m, an outer diameter of 8 wn, and a length of 10C771 was made from each material listed in Table 1 above, and contained ethanol vapor and n-hexane with a gas partial pressure of 10 t0r. When air is flowed at a flow rate of 30 cc/min and the air on the pipe outlet side is measured, the gas partial pressure is
The results shown in the table were obtained. As shown in Table 2 above, the organic gas was sufficiently absorbed by passing through the pipe 3, and in the above experiment, the flow rate (10 cc/out) normally supplied to the element was more than three times that of the organic gas. It can be seen that the filter function of the pipe 3 is sufficiently fulfilled because the water is flowing at a flow rate of .

In addition, when air containing CO gas was flowed under the same conditions,
No absorption by the filter was observed. Furthermore, when we look at the relationship with gas sensitivity when we used low-polymerized soft vinyl rubber among the pipes and varied the concentrations of ethanol gas and CO gas, the results were as shown in FIG. 3.

In the same figure, sensitivity is a value obtained by dividing the difference between the resistance of the element in clean air and the resistance of the element when gas is detected by the resistance of the element when gas is detected. In Fig. 3, curve 6 is the sensitivity characteristic to ethanol when filter 1 is not used, curve 7 is the sensitivity characteristic to ethanol when filter 1 is used, and curve 8 is the sensitivity characteristic to CO gas when filter 1 is not used. , curve 9 is the sensitivity characteristic to CO gas when filter 1 is used.

As is clear from this figure, by using the filter 1, the sensitivity to ethanol is lower than the sensitivity to CO gas, and therefore malfunctions due to ethanol can be prevented. As explained above, the present invention uses a rubber-like polymer material as a non-ventilation blocking filter to supply a sample gas from which organic gas has been removed to one element. Since it has a self-regeneration function, it is an extremely excellent gas detection method that can perform detection without maintenance for a long period of time.

It should be noted that the term "non-ventilation blocking filter 1" as used herein includes not only the filter 1 as a normally used porous body, but also the pipes shown in the above embodiments. It goes without saying that the rubber-like polymer may also be used as D coated by impregnating fibers or air permeable substrates. Furthermore, the scope of the present invention also includes a case where the inside of the device housing the gas sensing element is lined with a rubber-like polymer.

In this case, even though the rubber-like polymer does not have air permeability, the important thing is that the filter does not prevent the gas detection device from coming into contact with the air, and the rubber-like polymer itself does not have air permeability. It's not about being.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an apparatus implementing the present invention, FIG. 2 is a block diagram showing another example, and FIG. 3 is a sensitivity characteristic diagram. 1... Element case, 2... Suction pump, 3... Pipe (filter one), 10...
. . . Gas detection element, 11 . . . Non-ventilation blocking filter 1.

Claims (1)

[Claims] 1 A metal whose resistance value changes depending on the gas, by absorbing organic gas in the air and removing it from the gas to be detected using a non-ventilation barrier filter mainly made of a rubber-like polymer that has the ability to absorb organic gases. A specific gas detection method characterized by detecting CO gas using a gas detection element made of an oxide semiconductor.