JP2009128177A - Gas analyzer and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas detector or the like capable of selectively measuring a desired gas component in a multi-component mixed gas sample with time. <P>SOLUTION: A detection side cavity 11 and a reference side cavity 12 are formed in a base block 1 of a thermal conductivity detector. A detection side filament 13 and a reference side filament 14 are disposed in the detection side cavity 11 and the reference side cavity 12, respectively. A molecule selecting membrane 41 that selectively allows only desired molecules to pass therethrough is disposed on the upstream side of the detection side cavity 11. This molecule selecting membrane 41 functions as a molecular sieve. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a gas analyzer that measures a gas concentration using a gas sensor, and a fuel cell that can measure the gas concentration in a gas flow path using the gas sensor.

  As a device for measuring the concentration of gas components, there is a gas chromatograph (GC) equipped with a thermal conductivity detector (TCD). In a gas chromatograph, a sample gas is mixed with a carrier gas and then introduced into a separation column, and analysis components are separated for each component when passing through the column. The separated components are measured by a thermal conductivity detector placed at the column outlet.

  In the gas chromatograph described in Japanese Patent Application Laid-Open No. 2002-228647, a carrier gas is introduced from a carrier gas introduction section, and is led as a continuous flow to a thermal conductivity detector through a sample vaporization chamber and a capillary column. The sample is introduced into the carrier gas in the sample vaporization chamber. Thereafter, the sample is carried to a carrier gas, separated for each component while passing through the capillary column, and then detected by a thermal conductivity detector. The capillary column is generally stored in a thermostat. In addition, the thermal conductivity detector is often stored in a thermostat separate from the capillary column so that the measurement sample is kept in a gaseous state and is not affected by changes in ambient temperature.

In the cell of the thermal conductivity detector made of a metal block, there are a detection side cavity and a reference side cavity that are gas flow paths, and filaments are installed in the detection side cavity and the reference side cavity. ing. As the material of the filament, tungsten or an alloy thereof is generally used. A constant direct current is applied to the filament. A mixed gas of the sample gas and the carrier gas flowing from the capillary column is introduced into the detection side cavity, and only the carrier gas is introduced into the reference side cavity. As the carrier gas, a gas having a relatively high thermal conductivity is often selected from gases such as helium gas. When the sample is not included, since the carrier gas has a relatively high thermal conductivity, the heat generated from the filament is transferred to the wall of the metal block of the thermal conductivity detector cell by heat conduction, and the temperature of the filament is relatively low. It reaches equilibrium at a low point. On the other hand, when the sample gas is introduced into the detection side cavity, the heat conductivity of the sample gas is smaller than that of helium gas, so the heat generated from the filament is less likely to be transferred to the wall of the metal block by heat conduction, As a result, the temperature of the filament increases. The temperature change of the filament can be taken out as a potential difference by passing a constant current through the filament, but a bridge circuit is used to take out a very small change in potential difference. At that time, a filament provided in the reference side cavity in which only the carrier gas flows is used as the reference resistance.
JP 2002-310971 A JP 2002-228647 A

  According to the above method, qualitative analysis and quantitative analysis can be performed at once according to the gas chromatograph. Further, even if the gas chromatograph is a multi-component mixed sample, since the concentration of each component is measured after being separated for each component, the measurement result is highly reliable. However, the gas chromatograph not only requires an analysis time corresponding to the component separation, but cannot proceed with the next analysis until the analysis result of the sample collected once becomes clear. That is, the gas chromatograph is an intermittent analyzer. For this reason, it is not an analysis apparatus suitable for the qualitative quantitative analysis application of the gas component in the process where the component concentration change is severe.

  On the other hand, as a gas sensor capable of continuously analyzing the concentration of a gas component, there is a heat conduction sensor that uses a detection principle of a heat conductivity detector that is a constituent element of a gas chromatograph. A heat conduction sensor is a filament that accompanies a change in thermal conductivity that occurs when the composition of the gas in contact with the filament is changed by heating a detection filament arranged to be exposed to the gas flow to be detected at a constant voltage or current. A change in temperature is detected as a potential difference by a bridge circuit via a change in electrical resistance value of the filament. However, although the heat conduction type sensor can detect a change with time of the measurement target gas, since it does not have a separation function, it is not possible to qualitatively determine only a specific component in a plurality of components.

  As described above, in the conventional gas analysis method, a gas chromatograph capable of qualitative quantitative analysis of a plurality of gas component concentrations cannot be analyzed over time, whereas a heat conduction sensor capable of analyzing over time has a separation function. Therefore, there is a problem that it is unsuitable for a multi-component mixed sample. A method of performing pseudo continuous analysis by preparing a plurality of gas chromatographs and shifting the timing of sampling is also conceivable. However, in order to obtain a more continuous detection state, more gas chromatographs must be prepared, which is impractical and costly for continuous analysis applications. In the conventional gas analysis method, it is difficult to qualitatively and quantitatively select a single component or several components to be analyzed in a multi-component mixed sample, with high accuracy and economically.

  An object of the present invention is to provide a gas detection device or the like that can selectively measure a desired gas component in a multi-component mixed gas sample over time.

The gas analyzer of the present invention is characterized in that, in a gas analyzer that measures a gas concentration using a gas sensor, a molecule selection member that selectively passes only a measurement target component is disposed on the upstream side of the gas sensor.
According to this gas analyzer, since the molecule selection member that selectively passes only the measurement target component is arranged on the upstream side of the gas sensor, a desired gas component in the multi-component mixed gas sample can be selectively measured over time. .

  The gas sensor may be a thermal conductivity detector.

  A gas chromatograph column may be provided on the upstream side of the molecule selecting member.

The fuel cell of the present invention is a fuel cell in which the gas concentration in the gas flow path can be measured using a gas sensor, and a molecule selection member that selectively passes only a measurement target component is disposed upstream of the gas sensor. It is characterized by that.
According to this fuel cell, since the molecule selecting member that selectively passes only the component to be measured is disposed on the upstream side of the gas sensor, a desired gas component in the multi-component mixed gas sample can be selectively measured over time.

  According to the gas analyzer of the present invention, since the molecule selection member that selectively passes only the component to be measured is arranged upstream of the gas sensor, the desired gas component in the multi-component mixed gas sample is selectively and temporally changed. It can be measured.

  According to the fuel cell of the present invention, since the molecule selection member that selectively passes only the component to be measured is arranged upstream of the gas sensor, the desired gas component in the multi-component mixed gas sample is selectively measured over time. it can.

  Hereinafter, an embodiment of a gas analyzer according to the present invention will be described with reference to FIGS.

  Since the thermal conductivity detector does not have gas type selectivity, it is impossible to separate and detect only a specific component in a sample gas composed of a plurality of components.

  In the gas analyzer according to the present invention, a molecule selection member that selectively passes only the component to be measured is disposed upstream of the thermal conductivity detector, and the thermal conductivity detector and the molecule selection member are connected to organically. The above problem is solved by making it function. As the form of the molecule selecting member, a film form, a fiber form, a monolith form, and other forms can be selected. Preferably, a membranous form is selected.

  The desired component to be analyzed passes through the molecule selection member and is introduced into the thermal conductivity detector. On the other hand, since the non-measuring component contained in the sample cannot pass through the molecule selection member, it is guided to an exhaust line connected in the vicinity of the membrane surface. As a result of the sample gas undergoing such molecular sieving action, only the component to be measured flows into the vicinity of the filament of the thermal conductivity detector, which is a concentration detecting element. Therefore, only a specific component in the sample containing a plurality of components can be qualitatively determined over time with high selectivity. Of course, since the structure is such that a component group other than the desired component to be analyzed contained in the sample gas does not flow into the thermal conductivity detector, it is not affected by the contaminating component during detection.

  FIG. 1 is a block diagram illustrating a configuration of a gas analyzer according to an embodiment.

  As shown in FIG. 1, a detection-side cavity 11 and a reference-side cavity 12 are formed inside a base block 1 of a thermal conductivity detector formed of an inorganic material such as glass or ceramic or a temperature-resistant polymer such as PEEK resin. Is formed. A detection side filament 13 is disposed in the detection side cavity 11, and a reference side filament 14 is disposed in the reference side cavity 12.

  On the upstream side of the detection-side cavity 11, a molecule selection film 41 that can selectively pass only desired molecules is disposed. This molecular selective membrane 41 functions as a molecular sieve.

  A gas introduction pipe 21 for introducing a sample containing an analysis target component is connected to the upstream side of the molecule selection film 41, and an analysis gas pipe 23 is connected to the downstream side of the detection side cavity 11. Further, an exhaust gas pipe 31 branched from the gas introduction pipe 21 is provided in the vicinity of the molecule selection film 41.

  A reference gas introduction pipe 22 for introducing a reference gas is connected to the upstream side of the reference side cavity 12, and a reference gas exhaust pipe 24 is connected to the downstream side of the reference side cavity 12.

  The sample gas containing the component to be analyzed is introduced by the sample gas introduction tube 21, and the specific molecule (or the gas having a component ratio rich in the specific molecule as compared with the sample gas) is selected according to the functional characteristics of the molecule selective film 41. It is guided to the detection side cavity 11 via 41 and detected by the detection side filament 13.

  The gas component that has not passed through the molecule selective membrane 41 is exhausted to the outside through the exhaust gas pipe 31. In FIG. 1, the gas flow of the sample gas, the exhaust gas, and the gas passing through the molecule selection film 41 can be controlled by the control valve 32, but the control valve 32 may be omitted.

  In this way, by constituting a detector in which the molecular selective membrane 41 functioning as a molecular sieve and the thermal conductivity detector are integrated, component separation by a gas chromatograph becomes unnecessary, and a desired gas in a multi-component mixed gas sample is obtained. Components can be measured selectively and over time, and high-accuracy measurement can be performed without being affected by contaminant components.

  As the material of the molecule selection film 41, a material having a function of allowing a desired chemical species to pass through with high selectivity and suppressing the passage of other chemical species in the sample can be widely used.

Examples of the combination of the analysis target component and the molecule selection member include the following.
(1) When the component to be analyzed is hydrogen ・ Separation that selectively allows hydrogen to permeate on a porous support (aluminum, silica, zeolite, titania, silica-alumina ceramic tubular body, flat body, etc.) A hydrogen permeable membrane having a structure provided with a functional layer. Materials having a separation function for selectively permeating hydrogen (film-like, layer-like) include Pd or Pd, Ag, Au, Pt, Rh, Ru, Cu, Sn, Se, Te, Y, Si, Zn Alloy of at least one of Ir, Ta, Nb, V, Ni, Zr, etc., Alloy of V or V and at least one of Ni, Co, Mo, etc., V _α Ni _β Co _γ Mo _δ alloy (Metal ratio is not limited. _Α , β, γ, and δ are arbitrary values including zero.), Amorphous Zr _α Ni _β alloy (Although α and β are arbitrary values including zero, Zr ₃₆ Ni ₆₄ alloy Is preferred.)
A material or member comprising a metal base layer containing at least one metal of V, Zr, Nb, and Ta, and a tantalum oxide layer formed on at least a part of the outermost layer of the metal base layer.
・ Syria acetate hollow fiber ・ Amorphous silica (2) When analysis component is nitrogen ・ Polyimide hollow fiber ・ Polyolefin hollow composite membrane ・ Polyethylene, polypropylene, polyvinylidene fluoride, polyphenylene oxide ・ Syria acetate hollow fiber (3) Analysis component When oxygen is ・ Polyethylene film, polypropylene film, polyphenylene oxide, silicone film, silicone polycarbonate film, polytrimethylsilylpropyne film, polyimide hollow fiber, polyolefin hollow composite film, two or more kinds of vinyl aromatic amine polymers, And oxygen-permeable polymer membrane, polyurethane-based polymer hollow fiber, polysulfone non-porous membrane hollow fiber, and polyvinylidene fluoride comprising mesotetrakis (α, α, α, α-o-pivalamidophenyl) porphyrinatocobalt Hollow fiber with cellulose polymer coating on porous membrane ・ Cellulose acetate hollow composite membrane (3) When the component to be analyzed is carbon monoxide ・ Dendrimer (4) When the component to be analyzed is carbon dioxide ・ Polyimide hollow fiber, Fluorine-based polyimide hollow composite membrane / Polyurethane polymer hollow fiber / Composite alkoxide membrane of silicon alkoxide and zirconium alkoxide and hollow fiber / lithium zirconate, composite membrane of zirconia and support membrane (5) Analytical components are volatile organic compounds Case ・ Silicone rubber-polyimide composite membrane ・ Porous support membrane and ionic group-containing polymer hollow fiber

  In the example of FIG. 1, the molecule selection film 41 is fitted in the gas flow path connected to the detection-side cavity 11 of the thermal conductivity detector. However, using MEMS (Micro Electro Mechanical Systems) technology, glass or the like is used. A gas flow path and a thermal conductivity detecting element are formed on the base substrate, and a thin film-like molecular selective film is formed on the upstream side of the thermal conductivity detecting element, whereby a single chip can be obtained.

  FIG. 2A is a block diagram showing a configuration in which the molecular selective membrane and the thermal conductivity detector are separate units and are connected to each other. The same elements as those in FIG. 1 are denoted by the same reference numerals.

  In the example of FIG. 2A, a molecule selection film 42 is connected in the middle of the sample gas introduction pipe 21 connected upstream of the detection-side cavity 11 of the thermal conductivity detector, and the base of the thermal conductivity detector. The block 1 and the molecular selective membrane 42 are configured as separate units.

  In the gas analyzer of the present invention, the volume (dead volume) between the molecular selective membrane and the detection filament creates a dilution effect and a diffusion effect, and deteriorates the limit of quantification. Therefore, it is better that the capacity between the molecular selective membrane and the detection filament is small, and it is better to integrate the molecular selective membrane and the thermal conductivity detector as shown in FIG. However, as long as the influence of the dilution effect and diffusion effect on the analysis result is within a practical range, the molecular selective membrane and the thermal conductivity detector can be made independent as shown in FIG. Can be used in conjunction. In this way, by adopting a structure for connecting individual units, it is possible to make only the molecular selective membrane unit detachable without destroying the connection state of the other components of the analysis system. Accordingly, the molecular selective membrane unit can be selectively exchanged as appropriate.

  The configuration shown in FIG. 2A is suitable when the sample gas has a relatively high pressure. Here, the pressure of the sample gas itself is used as the driving force, and the analysis target component in the sample passes through the molecule selection film 42 and is introduced into the detection-side cavity 11 of the thermal conductivity detector. Components that do not pass through the molecule selection membrane 42 in the sample are exhausted to the outside through the exhaust gas pipe 31 by the operation of the control valve 32.

  FIG. 2B is a block diagram showing a configuration in which a function for sucking gas is added.

  As shown in FIG. 2B, the analysis gas pipe 23 connected to the downstream side of the detection side cavity 11 is provided with a suction pump 23a, and the exhaust gas pipe 31 is provided with a suction pump 33. By operating the suction pump, the sample gas can be efficiently flowed. As these suction pumps, for example, diaphragm type or piston type pumps are effective.

  The sample gas is guided to the vicinity of the molecular selective membrane 42 by the action of the suction pump 33 installed in the exhaust gas pipe 31. The analysis target component passes through the molecule selection film 42 and flows into the detection-side cavity 11, and the non-analysis target component that does not pass through the molecule selection film 42 is exhausted to the outside through the exhaust gas pipe 31. By making the downstream side of the molecular selective membrane 42 in a reduced pressure state by the suction pump 23 a provided in the analysis gas pipe 23, the analysis target component is efficiently flowed into the detection side cavity 11 and the membrane permeability of the analysis target component is increased. We can expect effect to raise. In addition, it is preferable to control the flow velocity when the analysis target component that has passed through the molecule selective membrane 42 passes through the vicinity of the detection filament by means such as a differential pressure method.

  In the example of FIG. 2B, the suction pumps are arranged in two places, but only one of them may be installed depending on the situation.

  FIG. 2C is a block diagram illustrating a configuration example of a carrier gas type.

  In this configuration, a carrier gas (for example, nitrogen, helium, argon, hydrogen, or the like) in which the pressure is controlled by the pressure regulator 21a and the flow rate 21b is controlled by using a flow meter is supplied to the gas introduction pipe 21. Note that only one of the pressure and flow rate of the carrier gas may be controlled.

  Further, the sample gas is introduced from the sample gas introduction pipe 25 through the sample introduction valve 21c and mixed with the carrier gas. The sample gas is guided to the vicinity of the molecule selective film 42 by the flow of the carrier gas. Components to be analyzed pass through the molecule selection membrane 42 and flow into the detection-side cavity 11, and components not to be analyzed that do not pass through the molecule selection membrane 42 are exhausted to the outside through the exhaust gas pipe 31. The analysis gas pipe 23 is provided with a suction pump (not shown), and the downstream side of the molecule selection film 42 is in a decompressed state, whereby the analysis target component is efficiently allowed to flow into the detection side cavity 11 and the analysis target component film The transmittance may be increased. In addition, it is preferable to control the flow velocity when the analysis target component that has passed through the molecule selective membrane 42 passes through the vicinity of the detection filament by means such as a differential pressure method.

  As described above, by combining the molecular selective membrane and the thermal conductivity detector, the entire apparatus can be used as a sensor capable of selectively quantifying only a specific component in a sample containing a plurality of components. As a result, it is possible to selectively measure only the desired component in the multi-component mixed sample with time, and with high accuracy.

  FIG. 3 is a block diagram showing a configuration in which a thermal conductivity detector with a molecular selective film is used as a detector for a gas chromatograph. In this configuration, a capillary column 5 is added to the gas analyzer shown in FIG.

  In this configuration, a continuous flow of a carrier gas (for example, nitrogen, helium, argon, hydrogen, or the like) in which the pressure is controlled by the pressure regulator 21a and the flow rate 21b using a flow meter is formed in the gas introduction pipe 21. Note that only one of the pressure and flow rate of the carrier gas may be controlled.

  Further, the sample gas is introduced from the sample gas introduction pipe 25 through the sample introduction valve 21c and mixed with the carrier gas. The sample gas is introduced into the capillary column 5 by the flow of the carrier gas, separated for each component, and then guided to the vicinity of the molecule selective film 42. Components to be analyzed pass through the molecule selection membrane 42 and flow into the detection-side cavity 11, and components not to be analyzed that do not pass through the molecule selection membrane 42 are exhausted to the outside through the exhaust gas pipe 31. The analysis gas pipe 23 is provided with a suction pump (not shown), and the downstream side of the molecule selection film 42 is in a decompressed state, whereby the analysis target component is efficiently allowed to flow into the detection side cavity 11 and the analysis target component film The transmittance may be increased. In addition, it is preferable to control the flow velocity when the analysis target component that has passed through the molecule selective membrane 42 passes through the vicinity of the detection filament by means such as a differential pressure method.

  On the other hand, on the reference side, a reference gas whose pressure is controlled by the pressure regulator 22 a and whose flow rate is controlled by the flow meter 22 b is introduced into the reference-side cavity 12 by the reference gas introduction pipe 22 and passes through the reference gas exhaust pipe 24. It is discharged outside.

  The capillary column 5 shown in FIG. 3 is accommodated in a thermostat (not shown). Further, the base block 1 of the thermal conductivity detector is accommodated in a thermostat (not shown) separate from the capillary column 5 so that the measurement sample is kept in a gaseous state and is not affected by ambient temperature changes. desirable.

  In view of the dilution diffusion theory of chromatography, in order to minimize the influence of dead volume, it is desirable to integrate the molecular selective membrane and the thermal conductivity detector. However, as long as the influence of dilution diffusion is within a practically allowable range, as shown in FIG. 3, each component may be an individual unit, and both may be connected.

  FIG. 4 is a cross-sectional view showing the configuration of a fuel cell incorporating a thermal conductivity detector with a molecular selective membrane according to the present invention.

  As shown in FIG. 4, the fuel cell 6 is configured by laminating an electrolyte membrane 61, an anode side catalyst diffusion layer 62a, a cathode side catalyst diffusion layer 62c, an anode side separator 63a, and a cathode side separator 63c, and an anode side separator 63a. Is formed with a gas channel 64a, and a cathode channel 63c is formed with a gas channel 64c.

  As shown in FIG. 4, in the vicinity of the gas flow path 64a and the gas flow path 64c, a thermal conductivity detector 7a with a molecular selective film is interposed between the separator 63a and the separator 63c via an insulating layer (not shown). , 7a,... And thermal conductivity detectors 7c, 7c,. Each thermal conductivity detector is connected to an exhaust gas pipe 71 for discharging a sample after measurement.

  In the fuel cell 6, the thermal conductivity detectors 7a, 7a,... And the thermal conductivity detectors 7c, 7c,. The gas concentration inside can be measured over time pinpoint. Further, in the configuration shown in FIG. 4, since a plurality of measurement points are provided along the gas flow path, the gas concentration distribution inside the fuel cell can be grasped in detail. By using the gas concentration distribution for the operation control of the fuel cell 6, an optimum operation state can be obtained.

  When measuring the gas concentration distribution in the fuel cell, hydrogen or carbon monoxide is mainly the object to be measured on the anode side, and oxygen or nitrogen is mainly the object to be measured on the cathode side. In the conductivity detector 7c, a molecular selective membrane corresponding to each component may be used.

  In each of the above-described embodiments, the device using a combination of a molecular selective membrane and a thermal conductivity detector has been described. However, depending on the component to be detected, the molecular selective membrane is combined with a gas sensor based on a principle other than the thermal conductivity detector. May be used. For example, a semiconductor sensor, a contact combustion sensor, a surface potential sensor, an infrared absorption sensor, a light wave interference sensor, or the like can be used as the gas sensor.

  As described above, according to the gas analyzer of the present invention, since the molecule selection member that selectively passes only the component to be measured is arranged upstream of the gas sensor, the desired gas component in the multi-component mixed gas sample can be obtained. Can be measured selectively and over time. In addition, according to the fuel cell of the present invention, the molecule selection member that selectively passes only the component to be measured is arranged upstream of the gas sensor, so that a desired gas component in the multi-component mixed gas sample can be selectively and time-lapsed. Therefore, the optimum operation control of the fuel cell becomes possible.

  The scope of application of the present invention is not limited to the above embodiment. The present invention can be widely applied to a gas analyzer that measures a gas concentration using a gas sensor, and a fuel cell that can measure the gas concentration in a gas flow path using the gas sensor.

The block diagram which shows the structure of the gas analyzer of one Embodiment. It is a figure which shows the structure of the gas analyzer of other embodiment, (a) is a block diagram which shows the structure which made the molecule | numerator selective membrane and the thermal conductivity detector another unit, and connected both, (b) is The block diagram which shows the structure which added the function which attracts | sucks gas, (c) is a block diagram which shows the structural example of a carrier gas type | mold. The block diagram which shows the structure which uses the thermal conductivity detector with a molecule | numerator selective film as a detector of a gas chromatograph. Sectional drawing which shows the structure of the fuel cell which incorporated the thermal conductivity detector with the molecule | numerator selective membrane.

Explanation of symbols

1 Base block (gas sensor)
41 Molecular selective membrane (member for molecular selection)

Claims (4)

In a gas analyzer that measures the gas concentration using a gas sensor,
A gas analyzer comprising a molecule selection member that selectively passes only a measurement target component upstream of the gas sensor. The gas analyzer according to claim 1, wherein the gas sensor is a thermal conductivity detector. The gas analyzer according to claim 1, wherein a gas chromatograph column is provided upstream of the molecule selecting member. A fuel cell capable of measuring a gas concentration in a gas flow path using a gas sensor,
A fuel cell, wherein a molecule selection member that selectively passes only a measurement target component is disposed upstream of the gas sensor.

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