JP2019007796A - Gas sensor and gas alarm - Google Patents

Abstract

To provide a gas sensor in which sulfur poisoning that constitutes a catalyst poison in the gas sensor is suppressed and the improvement and long-term stability of environmental resistance of the sensor are established.SOLUTION: Provided is a gas sensor 1 comprising an inflow port 41 through which a detection object gas is introduced; a case body 40 located downstream of the inflow port and having a detection space 42 communicating with the inflow port; a filter provided in the detection space; and a gas sensor element 10 arranged in the detection space and downstream of the filter. The filter includes a sulfur adsorption filter, the sulfur adsorption filter being constituted by including a sulfur adsorbent 60 that contains a carrier selected from alumina, active carbon, zeolite and silica and an active ingredient selected from potassium permanganate and potassium carbonate supported by the carrier. Also provided is a gas alarm that includes the gas sensor 1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a gas sensor and a gas alarm using the same. In particular, the present invention relates to a gas sensor suitable for a gas containing sulfur-based gas and a gas alarm using the same.

Generally, a gas sensor is a device that is used for applications such as a gas leak alarm, and is selectively sensitive to a specific gas, for example, CO, CH ₄ , C ₃ H ₈ , CH ₃ OH, or the like. Due to the nature of gas sensors, high sensitivity, high selectivity, high response, and high reliability are necessary.

  However, because of its high sensitivity, it also has sensitivity to various gases generated in the home, and therefore a false alarm of a gas alarm that detects gases other than the target gas occurs. Examples of miscellaneous gases that cause false alarms include alcohol vapor, siloxane compounds, SOx, NOx, basic gas, and other VOCs. In order to protect the sensor from the influence of these miscellaneous gases and prevent false alarms, a filter package is usually installed on the gas sensor element, and the package is filled with a filter material such as activated carbon.

Conventionally, a technique is known in which a filter that absorbs NO, NO ₂ , and SO ₂ is arranged in a p-type metal oxide semiconductor CO gas sensor (see, for example, Patent Document 1). The filter disclosed in Patent Literature 1 includes a filter layer made of activated carbon and a filter layer made of an alkali metal carbonate aqueous solution impregnated in a base material as separate layers. And these filters, _NO, etc. NO 2, SO ₂ is prevented from contacting the sensing element.

  In addition, a technique for absorbing and removing sulfur oxide gas in the atmosphere mainly at room temperature is known (see, for example, Patent Document 2). The sulfur oxide absorbent disclosed in Patent Document 2 is a kneaded molding material mainly composed of zirconium hydroxide, activated carbon, an alkali material, and an inorganic cement material, and adsorbs sulfur oxide gas with activated carbon to produce an alkali material. It was made to react with zirconium hydroxide activated by the above and absorbed and removed at room temperature.

JP 2000-338072 A JP 2003-320246 A

  However, in the technique disclosed in Patent Document 1, since the gas sensor is intended for CO detection, activated carbon is used for the filter layer, and LP gas, which is a kind of target gas, is adsorbed to the filter layer made of activated carbon. There was a problem that the target gas could not be detected accurately. In addition, the technique disclosed in Patent Document 2 is specialized in the adsorption and removal of sulfur oxide gas, and there is a problem that other gas countermeasures for other sulfur-based gases are not taken. It is necessary to solve these problems, suppress sulfur poisoning as a catalyst poison in the gas sensor, improve the environmental resistance of the sensor, and establish long-term stability.

  As a result of intensive studies, the inventors have made it possible to adsorb and remove sulfur-based gas over a long period of time by using a gas sensor configured with a filter using a predetermined sulfur absorbent, and to suppress sulfur poisoning in the gas sensor element. As a result, the present invention has solved the problems of the present invention. That is, according to one embodiment of the present invention, a gas sensor is a case body having an inlet into which a detection target gas is introduced and a detection space that is downstream of the inlet and communicates with the inlet. And a filter provided in the detection space, and a gas sensor element disposed in the detection space and downstream of the filter, the filter comprising a sulfur adsorption filter, and the sulfur adsorption filter Gas sensor comprising a sulfur adsorbent comprising a support selected from alumina, activated carbon, zeolite, and silica, and an active component selected from potassium permanganate and potassium carbonate supported on the support About.

  The gas sensor is preferably a gas sensor for liquefied petroleum gas, wherein the active component is potassium permanganate and the carrier is selected from alumina, zeolite, and silica. Alternatively, the gas sensor is preferably a gas sensor for methane gas in which the active component is potassium permanganate and the carrier is selected from activated carbon, alumina, zeolite, and silica.

  In the gas sensor, the active ingredient is preferably 1 to 10% by weight based on the total weight of the carrier and the active ingredient.

  In the gas sensor, the sulfur adsorbent is preferably a granular material having a diameter of about 0.1 mm to 0.5 mm.

  In the gas sensor, it is preferable that the sulfur adsorption filter has a thickness of 1.0 to 4.5 mm.

  In the gas sensor, it is preferable that the filter further includes a miscellaneous gas adsorption filter.

  In the gas sensor further including the miscellaneous gas adsorption filter, it is preferable that a total thickness of the sulfur adsorption filter and the miscellaneous gas adsorption filter is 4.0 to 6.0 mm.

  According to another embodiment, the present invention relates to a gas alarm device comprising the gas sensor according to any one of the foregoing.

  ADVANTAGE OF THE INVENTION According to this invention, the sulfur poison which can become a catalyst poison in a gas sensor is suppressed, and the gas sensor excellent in environmental resistance and long-term stability can be provided.

FIG. 1 is a conceptual diagram showing a cross-sectional structure of a gas sensor according to an embodiment of the present invention. FIG. 2 is a conceptual diagram showing a cross-sectional structure of a gas sensor element constituting a gas sensor according to an embodiment of the present invention. FIG. 3 is a conceptual diagram showing a cross-sectional structure of another gas sensor according to an embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the embodiments described below.

[First Embodiment: Gas Sensor]
The present invention relates to a gas sensor according to the first embodiment. FIG. 1 is a conceptual cross-sectional view showing an example of a gas sensor according to the first aspect of the present embodiment. Referring to FIG. 1, the gas sensor 1 mainly includes a gas sensor element 10, a sensor base 30, a case body 40, a metal mesh 50, a sulfur adsorbent 60, and lead terminals 80. And metal mesh 50a, b and the sulfur adsorption material 60 comprise a sulfur adsorption filter.

The gas sensor 1 according to the present embodiment detects a target gas for a detection target gas that can flow into the case body 40 from the outside. The detection target gas may be any gas, and is not particularly limited, and examples thereof include a gas containing a sulfur-based gas as an odorant. Examples of the detection target gas include, but are not limited to, liquefied petroleum gas (LP gas) and methane gas mainly containing methane. In the present invention, the methane gas refers to a gas containing methane as a main component and may contain ethane, propane, butane, etc., and is not limited to a gas composed only of methane. Here, the detection target gas generally contains a target gas and a miscellaneous gas. In the present specification, the miscellaneous gas refers to a gas that may cause a false alarm in the gas sensor, and may include sulfur-based gas (SO _{X and the} like), alcohol vapor, siloxane compounds, NOx, and VOCs. In the present specification, the sulfur-based gas may be described separately from the miscellaneous gas for the purpose of the invention, but generally the sulfur-based gas is included in the miscellaneous gas.

  Each configuration of the gas sensor 1 will be described. The case body 40 constituting the gas sensor 1 is a substantially cylindrical body, and has an inlet 41 having a smaller diameter than the case body diameter at one end thereof. The diameter of the inflow port 41 may be, for example, about 4 mm to 6 mm, but is not limited to a specific dimension. Further, the case body inner diameter is larger than the diameter of the inlet 41 and may be about 6 mm to 8 mm, and the case body outer diameter may be about 7.5 to 9 mm, but is limited to specific dimensions. Not. The other end of the case body 40 is fitted and fixed to the upper part of the sensor base 30, and a detection space 42 is formed inside the case body 40.

  A sulfur adsorption filter is provided in the detection space 42 on the downstream side of the inflow port 41. In this specification, the terms “downstream” and “upstream” are defined with respect to the direction of gas flow indicated by g in the figure. The sulfur adsorption filter has a disk shape having substantially the same diameter as the detection space 42, and is composed of a sulfur adsorbent 60 held by metal meshes 50a and 50b. The metal mesh 50 is a stainless steel net. Examples of the metal mesh 50 include an opening of about 0.1 to 0.2 mm, a wire diameter of about 0.8 to 0.12 mm, and an opening ratio of about Although a 30 to 40% thing can be used, it is not limited to these. The metal mesh 50 a attached to the inlet 41 of the case body 40 functions as a presser for the sulfur adsorbent 60. The double metal meshes 50b and 50c on the downstream side of the sulfur adsorbent 60 (the lower side of the sulfur adsorbent 60 in FIG. 1) function as a presser for the sulfur adsorbent 60 and are legal as inspection regulations for the gas leak alarm. It is provided in order to meet the explosion-proof structure standards stipulated in 1.

  The sulfur adsorbent 60 includes a carrier and an active component carried on the carrier. The support is preferably at least one selected from alumina, activated carbon, zeolite, and silica. Moreover, as an active ingredient carry | supported by a support | carrier, it is preferable that it is 1 or more selected from potassium permanganate and potassium carbonate.

  The carrier can be selected depending on, for example, the target gas. When the target gas is LP gas mainly composed of propane and butane (isobutane), one or more selected from alumina, zeolite, and silica are used. It is preferable. When the target gas is a gas containing methane as a main component, it is preferably at least one selected from alumina, activated carbon, zeolite, and silica. Any of these carriers may be porous. The active ingredient may be potassium permanganate or potassium carbonate, or a mixture thereof. Both potassium permanganate and potassium carbonate can be supported on any of the above carriers. The ratio of the active ingredient is preferably 1 to 10% by weight when the total weight of the active ingredient and the carrier is 100%.

  As such a sulfur adsorbent 60 in which an active ingredient is supported on a predetermined carrier, a commercially available product can be used, or one prepared by an arbitrary method can be used. The sulfur adsorbent 60 is a granular material, and may be preferably in the form of powder, sphere, crushed or pellet, and the diameter or major axis thereof is preferably about 0.1 mm to 0.5 mm. Particles having a diameter in a predetermined range can be obtained by pulverizing a sulfur adsorbent having a larger particle size, for example, a particle size of 2 to 3 mm, using a mill or the like, and classifying using a sieve or the like. it can.

  The sulfur adsorbent 60 having a predetermined size and shape is preferably held by the metal mesh 50a and 50b in a granular state without being bound by a binder or the like, and constitutes a sulfur adsorption filter. The thickness of the sulfur adsorption filter is preferably 1.0 mm to 4.5 mm, and more preferably 1.5 mm to 4.5 mm. This is from the viewpoint of sufficiently adsorbing and removing sulfur, ensuring a sufficient diffusion rate of the target gas passing through the filter, and ensuring the response of the sensor. The thickness of the sulfur adsorption filter can be defined by the distance between the metal meshes 50a and 50b.

The sulfur adsorption filter can pass the target gas out of the detection gas and adsorb the sulfur-based gas. Examples of the sulfur-based gas include, but are not limited to, SOx gas and H ₂ S gas that can be generated from a compound mixed with the gas as an odorant. The sulfur adsorbent 60 constituting the present invention can adsorb any of these sulfur-based gases.

  The gas sensor element 10 is disposed in the detection space 42 and is fixed to the upper side of the sensor base 30 that is a stepped disk. The fixed position of the gas sensor element 10 is the downstream side of the sulfur adsorption filter. The gas sensor element 10 may be a thin film semiconductor gas sensor element. FIG. 2 shows a conceptual cross-sectional view of the gas sensor element 10. As shown in FIG. 2, the gas sensor element 10 includes a silicon substrate (hereinafter referred to as Si substrate) 11, a heat insulating support layer 12, a heater layer 13, an electric insulating layer 14, and a gas detection unit 15. FIG. 2 conceptually shows the configuration of a thin film semiconductor gas sensor element, and the size and thickness of each part are not strict, and the relative relationship and the like are shown in the drawing. It is not limited to the embodiment.

The Si substrate 11 is formed of silicon (Si), and a through hole is formed at a location where the gas detection unit 15 is located immediately above. The thermal insulating support layer 12 is stretched over the opening of the through hole and formed in a diaphragm shape, and is provided on the Si substrate 11. Specifically, the heat insulating support layer 12 has a three-layer structure of a thermally oxidized SiO ₂ layer 12a, a CVD-Si ₃ N ₄ layer 12b, and a CVD-SiO ₂ layer 12c. The thermally oxidized SiO ₂ layer 12a is formed as a heat insulating layer, and has a function of reducing heat capacity by preventing heat generated in the heater layer 13 from being conducted to the Si substrate 11 side. The thermally oxidized SiO ₂ layer 12a exhibits high resistance to plasma etching and facilitates formation of a through hole in the Si substrate 11 by plasma etching. The CVD-Si ₃ N ₄ layer 12b is formed above the thermally oxidized SiO ₂ layer 12a. The CVD-SiO ₂ layer 12c improves the adhesion with the heater layer 13 and ensures electrical insulation. The SiO ₂ layer formed by CVD (chemical vapor deposition) has a small internal stress.

The heater layer 13 is a thin-film Pt—W film, and is provided on the upper surface of the substantially center of the heat insulating support layer 12. The heater layer 13 is connected to a drive processing unit (not shown) and is supplied with power. The electrical insulating layer 14 is a sputtered SiO ₂ layer that ensures electrical insulation, and is provided so as to cover the heat insulating support layer 12 and the heater layer 13. The electrical insulating layer 14 can ensure electrical insulation between the heater layer 13 and the sensing layer electrode 15b. In addition, the electrical insulating layer 14 improves the adhesion with the gas sensing layer 15c.

Specifically, the gas detector 15 includes a pair of bonding layers 15a, a pair of sensing layer electrodes 15b, a gas sensing layer 15c, and a gas selective combustion layer 15d. The bonding layer 15 a is, for example, a Ta film (tantalum film) or a Ti film (titanium film), and is provided on the electrical insulating layer 14 in a pair of left and right. The bonding layer 15a is interposed between the sensing layer electrode 15b and the electrical insulating layer 14 to increase the bonding strength. The sensing layer electrodes 15b are, for example, a Pt film (platinum film) or an Au film (gold film), and are provided in a pair on the left and right sides so as to serve as sensing electrodes for the gas sensing layer 15c. The gas sensing layer 15c is a SnO ₂ layer, and is formed on the electrical insulating layer 14 so as to pass the pair of sensing layer electrodes 15b. The gas sensing layer 15c is a porous body or a columnar structure, and increases the specific surface area. Thereby, the contact area with the target gas to be detected is increased, and the sensitivity is increased. The gas sensing layer 15c is in addition to _{SnO 2, In 2 O 3,} WO 3, ZnO , or may be a layer of a thin film composed mainly of metal oxide such as TiO _2.

The gas selective combustion layer 15d is a sintered body supporting at least one kind of catalyst such as palladium (Pd), platinum (Pt), or palladium oxide (PdO), and is a catalyst-supported Al ₂ O ₃ sintered material. Since Al ₂ O _{3 is} also a porous body or a columnar structure, it is possible to increase the chance that the gas passing through the holes contacts the catalyst. And the combustion reaction of the reducible miscellaneous gas whose oxidation activity is stronger than the target gas to detect can be accelerated | stimulated, and the selectivity of target gas can be improved. That is, miscellaneous gas can be oxidized and removed with respect to the target gas. The gas concentration of the target gas reaching the gas sensing layer 15c is increased, and the gas sensor element 10 with higher sensitivity can be obtained. The gas selective combustion layer 15d is composed mainly of a metal oxide such as Cr ₂ O ₃ , Fe ₂ O ₃ , Ni ₂ O ₃ , ZrO ₂ , SiO ₂ , or zeolite in addition to the Al ₂ O _3. It is also good. The gas selective combustion layer 15d is provided so as to cover the surfaces of the electrical insulating layer 14, the pair of bonding layers 15a, the pair of sensing layer electrodes 15b, and the gas sensing layer 15c.

  The gas sensor element 10 having such a diaphragm structure is a structure that can have high heat insulation and low heat capacity. Further, the gas sensor element 10 can reduce the heat capacity of each component of the sensing layer electrode 15b, the gas sensing layer 15c, the gas selective combustion layer 15d, and the heater layer 13 by a technique such as MEMS (micro electromechanical system). Therefore, the time change of the temperature when the heater is driven becomes fast, and the thermal desorption can be caused in a very short time.

The heater layer 13 of the gas sensor element 10 is electrically connected to a drive processing unit (not shown), and the drive processing unit drives the heater layer 13 with a heater. The gas detection unit 15 of the gas sensor element 10 (specifically, the gas detection layer 15c via the detection layer electrode 15b) is also electrically connected to a drive processing unit (not shown), and the drive processing unit is connected to the gas detection layer 15c. The electrical resistance value (referred to as sensor resistance value) can be read out. The gas sensor element 10 is a sensor that utilizes a phenomenon in which the sensor resistance value of the gas sensing layer 15c, which is a SnO ₂ layer, is changed by contact with various gas components. The detailed mechanism is as described in JP-A-2016-200547 by the present applicant. In the present embodiment, the semiconductor type gas sensor element has been illustrated and described. However, a gas sensor equipped with a catalytic combustion type gas sensor element or an electrochemical gas sensor element can also be used.

  The lead terminal 80 is an electrode that protrudes from the sensor base 30. The two lead terminals 80 are electrodes for driving the heater layer 13 (see FIG. 2) constituting the gas sensor element 10, and the other two lead terminals 80 are the gas sensing layer 15c (see FIG. 2). It is an electrode for measuring a sensor resistance value. Both are connected to a drive processing unit (not shown).

  According to the gas sensor 1 according to the present embodiment, the detection gas that has flowed into the detection space 42 from the inflow port 41 passes and diffuses between the particulates of the sulfur adsorbent 60. In the meantime, the sulfur-based gas is adsorbed and removed from the detection gas by the sulfur adsorbent 60. With this action, the target gas can be selectively brought into contact with the gas sensor element 10. And the gas sensor element 10 can perform the removal which removes the miscellaneous gas which passed the sulfur adsorption material 60, and the object gas as object. According to the gas sensor 1 according to the present embodiment, sulfur poisoning of the gas sensor element 10 can be suppressed, and the environmental resistance and long-term reliability of the gas sensor 1 can be improved.

  Next, the gas sensor of the 2nd mode by this embodiment is explained. FIG. 3 is a conceptual cross-sectional view showing an example of a gas sensor according to the second aspect of the present embodiment. Referring to FIG. 3, the gas sensor 2 mainly includes a gas sensor element 10, a sensor base 30, a case body 40, a metal mesh 50, a sulfur adsorbent 60, a miscellaneous gas adsorbent 70, and a lead terminal 80.

  In the gas sensor 2 of the second aspect, the members denoted by the same reference numerals as those in FIGS. 1 and 2 may have the same configuration as the gas sensor 1 of the first aspect described with reference to FIGS. 1 and 2. Omitted. In the gas sensor 2 of the second aspect, a two-layer filter is provided downstream of the inflow port 41. Specifically, with respect to the direction of detection gas inflow, a sulfur adsorption filter is provided on the upstream side, and a miscellaneous gas adsorption filter is further provided on the downstream side.

  The configuration of the sulfur adsorption filter may be the same as in the first embodiment, and the sulfur adsorbent 60 is held by the metal mesh 50a, 50d. The miscellaneous gas adsorption filter mainly adsorbs miscellaneous gases other than the sulfur-based gas and removes them from the detection gas. As with the sulfur adsorption filter, the miscellaneous gas adsorption filter can also be configured by sandwiching and holding the particulate miscellaneous gas adsorbent 70 between the metal meshes 50b and 50d. The miscellaneous gas adsorbent 70 may be a general adsorbent capable of adsorbing and removing miscellaneous gas. When the detection gas is LP gas, alumina, zeolite, silica gel, molecular sieve, gas selective permeable membrane , Kaolinite, silicic acid component, etc. can be used as a base material, and catalyst etc. are supported on them to remove only miscellaneous gases. In the case of methane gas, activated carbon, alumina, zeolite, silica gel, molecular sieve, gas selection Although an organic permeable membrane, kaolinite, and a silicic acid component can be used, it is not limited to these. The particle shape, particle diameter, etc. of the miscellaneous gas adsorbent may be the same as or different from those of the sulfur adsorbent. The thickness of the miscellaneous gas adsorption filter is preferably 3 mm to 4.5 mm. The thickness of the miscellaneous gas adsorption filter can be defined by the distance between the metal meshes 50b and 50d. By setting the total thickness of the sulfur adsorption filter and the miscellaneous gas adsorption filter to 4.0 to 6.0 mm, it is possible to ensure the removal of miscellaneous gas and the diffusibility of the target gas, and to ensure good response of the gas sensor. This is because it can.

  In the illustrated embodiment, a sulfur adsorption filter is provided on the upstream side and a miscellaneous gas adsorption filter is provided on the downstream side with respect to the inflow direction of the detection gas, but the order of installation is not particularly limited, A sulfur adsorption filter may be provided on the downstream side, and a miscellaneous gas adsorption filter may be provided on the upstream side. Further, the miscellaneous gas adsorption filter may be composed of two or more different filter layers, and each may hold different types of adsorbents. Even in this case, the total thickness of the sulfur adsorption filter and the plurality of miscellaneous gas adsorption filters is preferably 4.0 to 6.0 mm as described above.

  According to the gas sensor 2 according to the present embodiment, not only the compound containing sulfur but also other gas removal performance is excellent, and the reliability of the sensor particularly for a specific substance that is poisoned by the sensor. There is an advantage that can be improved.

[Second Embodiment: Gas Alarm]
The present invention is a gas alarm device according to the second embodiment. The gas alarm device according to the present embodiment includes the gas sensor described in detail in the first embodiment, a drive processing unit of the gas sensor, an alarm generation unit that issues an alarm based on a sensing result by the gas sensor, and a power supply unit. The power supply unit may be a battery-type power supply that can be built in the alarm device or a mechanism that can be connected to a commercial power supply. The gas alarm device according to the present embodiment suppresses sulfur poisoning in the sensor, has high responsiveness, is stable over a long period, and has high reliability.

  Hereinafter, the present invention will be described in more detail with reference to examples of the present invention. However, the present invention is not limited to the scope of the following examples.

[Test example: Selection of sulfur adsorbent]
The sulfur adsorbent constituting the sulfur adsorption filter was selected. In Test Example 1, alumina adsorbing KMnO ₂ (Purafil (registered trademark) SelectChemisorbant manufactured by Purafil) was pulverized, and a sulfur adsorbent classified to a diameter of about 0.1 mm to 0.5 mm was used. In this sulfur adsorbent, the proportion of KMnO ₂ relative to the total weight of the alumina support and KMnO ₂ was 8 wt%. In Test Example 2, a sulfur adsorbent obtained by pulverizing activated carbon / alumina (Purafil Puracarb (registered trademark) manufactured by Purafil) carrying KCO ₃ and classifying it to a diameter of about 0.1 mm to 0.5 mm was used. In this sulfur adsorbent, the ratio of KCO _{3 to} the activated carbon / alumina carrier was 1 to 5% by weight. The weight ratio of activated carbon to alumina was 1: 1. In Comparative Test Example 1, a sulfur adsorbent obtained by classifying silica gel supporting Ca into a diameter of about 0.1 mm to 0.5 mm was used. In Comparative Test Example 2, a sulfur adsorbent obtained by classifying zeolite supporting Ag into a diameter of about 0.1 mm to 0.5 mm was used. In Comparative Test Example 3, a sulfur adsorbent obtained by pulverizing alumina (PurafilSP (registered trademark)) supported by NaMnO ₂ and classifying it to a diameter of about 0.1 mm to 0.5 mm was used.

The sulfur adsorbents of Test Examples 1 and 2 and Comparative Test Examples 1 to 3 were subjected to a breakage test using a flow method when SO ₂ gas was used. Specifically, 6 ml of sulfur adsorbent is filled in an adsorption tube having an inner diameter of 20 mm installed in a constant temperature bath at 50 ° C., and 100 ppm of SO ₂ gas is 0.5 NL using base gas as dry air. / Min for 48 hours through the adsorbent. Every hour from the start of the flow, the flow gas was sampled at the inlet upstream of the adsorption tube and the outlet downstream, and the SO ₂ gas concentration was measured. As a result, the time until the outlet concentration of SO ₂ reaches 50% or more of the inlet concentration is “Break (×)” when the time is less than 48 hours, ) ”. The results are shown in Table 1. Although all of the sulfur adsorbents of Comparative Test Examples 1 to 3 were broken, the sulfur adsorbents of Test Examples 1 and ₂ maintained the adsorptivity to SO ₂ gas even after 48 hours. From this result, in the gas sensor according to the present invention, it was found that the adsorption amount for the sulfur-based gas can be improved by using the sulfur adsorbents of Test Examples 1 and 2.

[Example 1: Change in LP gas sensor alarm concentration due to SO ₂ exposure]
The gas sensor of Example 1-1 was assembled according to FIG. 1, and the gas sensor of Examples 1-2 to 1-5 was assembled according to FIG. All gas sensors used the KMnO ₂ / alumina catalyst of Test Example 1 as a sulfur adsorbent. As the miscellaneous gas adsorbing material filled in the miscellaneous gas adsorption filter, a general-purpose adsorbing material not containing activated carbon was used. Table 2 below shows the layer thicknesses of the sulfur adsorption filter and the miscellaneous gas adsorption filter of each sensor.

  In these sensors, a durability test was performed by exposure to a gas containing sulfur, and the alarm concentrations before and after the durability test were compared. The alarm concentration is a gas concentration at which a gas alarm device including a gas sensor to be tested issues an alarm. In this example, with the LP gas detection sensor in mind, the isobutane gas concentration was used as the alarm concentration. The initial alarm concentration at 20 ° C. was set to 2000 ppm for all the sensors of Examples 1-1 to 1-5. The alarm concentration at −10 ° C. of the sensor before the durability test is within the range of 500 ppm to 4500 ppm, which is the standard concentration range of LP gas determined by national standards for all the sensors of Examples 1-1 to 1-5. Met.

The sensor of Example 1-1 to 1-5 were subjected to SO ₂ exposure test. The base gas was humidified air and 6.6 ppm of SO ₂ gas was supplied over 96 hours. Separately from the SO ₂ exposure test, the H ₂ S exposure test was performed on the sensors of Examples 1-1 and 1-2. The base gas was humidified air, and 5 ppm of H ₂ S gas was supplied over 27.6 hours.

When the alarm concentration was measured for the sensor after the SO ₂ exposure test and the sensor after the H ₂ S exposure test, the alarm concentrations at −10 ° C. and 20 ° C. were both within the above-mentioned standard concentration range defined by national standards. From this, it was confirmed that the LP gas sensor provided with the sulfur adsorption filter according to the present invention can suppress sulfur poisoning and can provide a stable sensor according to the present invention.

[Example 2: Change in alarm concentration of methane gas sensor due to SO ₂ exposure]
The gas sensor of Example 2-1 was assembled according to FIG. 1, and the gas sensor of Examples 2-2 to 2-5 was assembled according to FIG. All gas sensors used the KMnO ₂ / alumina catalyst of Test Example 1 as a sulfur adsorbent. Activated carbon was used as the miscellaneous gas adsorbing material to be filled in the miscellaneous gas adsorption filter. Table 3 below shows the layer thicknesses of the sulfur adsorption filter and the miscellaneous gas adsorption filter of each sensor.

  In these sensors, a durability test was performed by exposure to a gas containing sulfur, and the alarm concentrations before and after the durability test were compared. The alarm concentration is a gas concentration at which a gas alarm device including a gas sensor to be tested issues an alarm. In this example, the methane gas concentration was set as the alarm concentration with the methane gas detection sensor in mind. The initial alarm concentration at 20 ° C. was set to 3000 ppm for all the sensors of Examples 2-1 to 2-5. The alarm concentration at −10 ° C. in the sensor before the durability test is within the range of 1000 ppm to 12500 ppm, which is the standard concentration range of methane gas determined by the national standards for all the sensors of Examples 2-1 to 2-5. there were.

The sensor of Example 2-1 to 2-5 were subjected to SO ₂ exposure test. Further, from those performed SO ₂ exposure test Separately, the sensor of Example 2-1 and 2-2 were subjected to _{H 2} S exposure test. In both the SO ₂ exposure test and the H ₂ S exposure test, the test conditions were the same as in Example 1.

When the alarm concentration was measured for the sensor after the SO ₂ exposure test and the sensor after the H ₂ S exposure test, the alarm concentrations at −10 ° C. and 20 ° C. were both within the above-mentioned standard concentration range defined by national standards. From this, it was confirmed that the methane gas sensor provided with the sulfur adsorption filter according to the present invention can suppress sulfur poisoning and can provide a stable sensor according to the present invention.

  The gas sensor according to the present invention is useful as a low power consumption gas sensor with battery driving in mind.

DESCRIPTION OF SYMBOLS 1 Gas sensor 2 Gas sensor 10 Gas sensor element 11 Si substrate 12 Thermal insulation support layer 13 Heater layer 14 Electrical insulation layer 15 Gas detection part 15a Joining layer 15b Sensing layer electrode 15c Gas sensing layer 15d Gas selective combustion layer 30 Sensor base 40 Case body 41 Flow Inlet 42 Detection space 50 Metal mesh 60 Sulfur adsorbent 70 Miscellaneous gas adsorbent 80 Lead terminal g Detection gas

Claims (9)

An inlet into which the gas to be detected is introduced;
A case body having a detection space on the downstream side of the inlet and communicating with the inlet;
A filter provided in the detection space;
A gas sensor comprising: a gas sensor element disposed in the detection space and downstream of the filter;
The filter includes a sulfur adsorption filter;
The sulfur adsorption filter includes a sulfur adsorbent containing a support selected from alumina, activated carbon, zeolite, and silica, and an active component selected from potassium permanganate and potassium carbonate supported on the support. Configured gas sensor.   The gas sensor according to claim 1, for liquefied petroleum gas, wherein the active ingredient is potassium permanganate and the carrier is selected from alumina, zeolite, and silica.   The gas sensor according to claim 1, for methane gas, wherein the active ingredient is potassium permanganate and the carrier is selected from activated carbon, alumina, zeolite, and silica.   The gas sensor according to any one of claims 1 to 3, wherein the active ingredient is 1 to 10% by weight based on a total weight of the carrier and the active ingredient.   The gas sensor according to any one of claims 1 to 4, wherein the sulfur adsorbent is a granular material having a diameter of about 0.1 mm to 0.5 mm.   The gas sensor according to any one of claims 1 to 5, wherein the sulfur adsorption filter has a thickness of 1.0 to 4.5 mm.   The gas sensor according to claim 1, wherein the filter further includes a miscellaneous gas adsorption filter.   The gas sensor according to claim 7 whose total thickness of said sulfur adsorption filter and said miscellaneous gas adsorption filter is 4.0-6.0 mm.   A gas alarm device comprising the gas sensor according to claim 1.

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