JP5048592B2 - Fuel cell gas analyzer - Google Patents

Description

  The present invention relates to a fuel cell gas analyzer, and more particularly to a fuel cell gas analyzer for accurately analyzing the concentration of carbon monoxide gas (CO) discharged from a fuel cell (main body).

  In the course of developing a fuel cell system, off-gas (exhaust gas) from a fuel cell may be introduced as a sample gas (sample gas) into an exhaust gas analyzer and its gas composition components may be continuously measured. Here, since the off gas from the fuel cell contains a larger amount of water than the exhaust gas from the internal combustion engine, the flow rate of the off gas introduced into the analyzer as the sample gas is higher than the flow rate of the exhaust gas in the internal combustion engine. Must be considerably reduced.

  Conventionally, as an apparatus capable of accurately detecting a gas component contained in such a small flow rate of off-gas, for example, as described in JP-A-2002-98618, an exhaust gas analyzer using a mass spectrometer is known. (Patent Document 1). Gas analyzers that use mass spectrometry can measure a wide range of element abundances, that is, concentrations, depending on the mass-to-charge ratio and charge amount for each composition, as long as the sample gas molecules can be ionized. Therefore, it was preferable as a strict gas analyzer.

  Japanese Patent Application Laid-Open No. 2002-90271 describes a reaction gas analyzer using a distributed infrared densitometer (Patent Document 2).

A gas analyzer using a distributed infrared concentration meter measures components and concentrations in a sample gas based on the amount of absorption at a specific wavelength belonging to infrared light for a specific gas that exhibits suitable absorption characteristics for infrared light. Was done.

JP 2002-98618 A JP 2002-90271 A

  However, even a gas analyzer such as that described in Patent Document 1 may not be able to accurately analyze the gas composition depending on the gas composition to be measured. For example, when there are certain types of gas compositions (specifically, when carbon monoxide and nitrogen are included), it is difficult to separate the two because the masses of the gas molecules are the same. Therefore, only the ion current derived from one gas could not be measured with high accuracy.

  In particular, when the gas to be measured is off-gas from the fuel cell system, the carbon monoxide contained in the off-gas is low while the nitrogen is high. It was even more difficult.

  On the other hand, in the gas analyzer using the dispersion-type infrared concentration meter described in Patent Document 2, the measurable gas is limited to a specific gas exhibiting an absorption characteristic suitable for infrared rays. It was not enough to measure the correct gas.

  Accordingly, an object of the present invention is to provide a gas analyzer capable of measuring various gas compositions contained in a small flow rate of sample gas with high accuracy in order to solve the above problems.

  In order to solve the above problems, a gas analyzer of the present invention is a gas analyzer that measures a gas concentration contained in a sample gas, and the concentration of a specific gas having a specific infrared absorption wavelength contained in the sample gas. A non-dispersive infrared densitometer to be measured, a mass spectrometer to measure the abundance of each of a plurality of types of gases including a specific gas contained in a sample gas, and a specific gas measured by a non-dispersive infrared densitometer And a calculation unit that calculates the concentration of the gas contained in the sample gas based on the concentration of the gas and the abundance of each of the types of gases measured by the mass spectrometer, and the calculation unit is a non-dispersive type The concentration of the specific gas measured by the infrared densitometer was converted into the abundance of the specific gas, and the mass of the specific gas was measured out of the abundances of the masses of the plurality of types of gases measured by the mass spectrometer. Abundance Et subtracts the abundance of terms the particular gas, computing the abundance of different types of gases having the same mass as the specific gas, characterized by.

In order to solve the above problems, a gas analyzer of the present invention is a gas analyzer for measuring a gas concentration contained in a sample gas, the first supply path for supplying the sample gas, and the first A first mass flow controller provided in a supply path for adjusting the flow rate of the sample gas to a first amount; a second supply path for supplying a dilution gas for diluting the sample gas; and the second A second mass flow controller provided in the supply path for adjusting the flow rate of the dilution gas to a second amount; the sample gas from the first supply path; and the dilution gas from the second supply path; A mixed gas to be mixed gas, a non-dispersive infrared concentration meter for measuring the concentration of a specific gas having a specific infrared absorption wavelength contained in the mixed gas supplied from the inlet pipe, and the mixed gas included, aforementioned Japanese in A plurality of types of the mass spectrometer to measure the abundance of each mass of gas, the plurality of types of gas measured by the mass spectrometer and the concentration of the specific gas measured by the non-dispersive infrared densitometer comprises a gas on the basis of the abundance of each of the mass, and a calculator for calculating the concentration of the gas contained in the sample gas, the arithmetic unit, the concentration of the specific gas measured by the non-dispersive infrared densitometer was converted to the amount of the specific gas, out of the abundance of each mass of the plurality of types of gas measured by the mass spectrometer, the abundance measured for the mass of the specific gas, which is converted the by subtracting the abundance of a specific gas, characterized by calculating the abundance of different types of gases having the same mass as the specific gas.

In the above configuration, the mass spectrometer measures the abundance corresponding to the masses of a plurality of types of gas, but if the mass of the specific gas is the same as the mass of another type of gas different from the specific gas, They cannot be measured separately, and the total amount of the specific gas and the different kinds of gases is measured. According to such a configuration, the non-dispersive infrared densitometer measures the concentration of a specific gas by a method different from mass spectrometry based on the mass of the charge amount and the mass, that is, the wavelength and absorption amount of the absorbed infrared ray. The abundance of the specific gas is calculated by converting from the concentration of the specific gas. Therefore, if the calculation is performed to remove the abundance of the specific gas from the abundance measured for the mass of the specific gas by the mass spectrometer (that is, the sum of the abundances of plural types of gases), the mass is the same as that of the specific gas The abundance of different kinds of gases can be calculated. Therefore, it compensates for the disadvantage of mass spectrometry that it is impossible to distinguish between multiple gas components with the same or close mass, by measuring with other parameters using a non-dispersive infrared densitometer. You can make measurements.
In addition, according to the above configuration, the mass flow controller adjusts the flow rate of both the sample gas and the dilution gas for diluting the sample gas, so there is a difference in viscosity for each gas composition contained in each gas. However, the flow rate can be accurately controlled without being affected by the difference in viscosity. Moreover, since the sample gas and the dilution gas whose flow rates are controlled are mixed in the introduction pipe, it is possible to generate a homogenized measurement gas. The mass flow controller also functions as a capillary (throttle valve), and can continuously maintain the pressure in the downstream of the mass flow controller by reducing the pressure continuously downstream.

  Here, in the present invention, a first supply path that supplies the sample gas, a first mass flow controller that is provided in the first supply path and adjusts the flow rate of the sample gas to the first amount, and the sample gas A second supply path for supplying a dilution gas for dilution; a second mass flow controller provided in the second supply path for adjusting the flow rate of the dilution gas to a second amount; and a first supply path It is preferable to provide an introduction pipe that mixes the sample gas and the dilution gas from the second supply path to form a mixed gas.

  According to such a configuration, it is possible to set an appropriate pressure according to each of the measuring devices in the first branch path and the second branch path.

  For example, it is preferable that the first branch path is provided with first decompression means for bringing the non-dispersive infrared densitometer into a first decompressed state.

  According to such a configuration, it is possible to perform measurement with the non-dispersive infrared densitometer in a negative pressure state. For example, when off gas from a fuel cell is introduced as a sample gas, it contains a large amount of water. However, by setting the first branch path to a reduced pressure state, the dew point temperature of the water is lowered and the water is solidified in the tube. Can be suppressed. In addition, by setting the reduced pressure state, the volume flow rate of the sample gas can be increased, the gas replacement inside the non-dispersive infrared concentration meter can be accelerated, and the response speed can be set to the factory.

  For example, the first decompression means may include a first vacuum pump that decompresses the closed space communicating with the non-dispersive infrared densitometer, and a negative pressure valve that maintains the closed space at a negative pressure. According to such a configuration, by continuously driving the first vacuum pump, a constant negative pressure state suitable for measurement in a closed space including the non-dispersive infrared concentration meter in the downstream region of the upstream mass flow controller. Can be. At this time, the negative pressure valve suppresses the pressure change inside the non-dispersive infrared densitometer, contributes to keeping the sensitivity constant and making the error insignificant. In addition, the negative pressure valve suppresses the change in pressure at the inlet of the mass spectrometer and makes the sample gas flow rate constant, which contributes to keeping the sensitivity of the mass spectrometer constant and minimizing errors. Furthermore, even if air is introduced to keep the negative pressure constant when the pressure in the closed space drops too much, if the negative pressure valve is installed downstream of the non-dispersive infrared densitometer, the concentration measurement value will be affected. Will not give.

  For example, it is preferable that the second branch path is provided with a second decompression unit that brings the mass spectrometer into the second decompression state. According to such a configuration, the mass spectrometer can be measured in an appropriate vacuum state. In particular, when the closed space including the mass spectrometer is in a high vacuum state, correct mass analysis can be performed in the mass spectrometer.

  For example, the second decompression unit may include a second vacuum pump that decompresses a closed space communicating with the mass spectrometer. According to such a configuration, by driving the second vacuum pump, the closed space including the mass spectrometer in the downstream area of the inlet orifice of the mass spectrometer can be brought into a vacuum state.

For example, in the present invention, the specific gas is carbon monoxide, and the different kind of gas having the same mass to charge ratio as the specific gas is nitrogen. The mass-to-charge ratio of carbon monoxide (CO) and the mass-to-charge ratio of nitrogen (N ₂ ) are the same, and even if there is a difference in the exact mass number, it is not a mass difference that can be distinguished by a mass spectrometer. . For this reason, both abundances are measured as molecules with the same mass. Therefore, according to the present invention, the abundance of both molecules can be distinguished and measured.

  According to the present invention, the concentration of a specific gas is measured by a non-dispersive infrared densitometer based on a principle different from that of mass spectrometry, and the abundance of the specific gas is calculated by conversion from the measured concentration of the specific gas. A mass that cannot be distinguished from multiple gas components with the same or close mass, because the abundance of the specific gas is removed from the abundance measured based on the mass of the specific gas by the analyzer. The shortcomings of the analytical method can be compensated for by measurement using a non-dispersive infrared densitometer, and an accurate gas composition can be measured.

According to the present invention, the concentration of a specific gas is measured by a non-dispersive infrared densitometer based on a principle different from that of mass spectrometry, and the abundance of the specific gas is calculated by conversion from the measured concentration of the specific gas. A mass that cannot be distinguished from multiple gas components with the same or close mass, because the abundance of the specific gas is removed from the abundance measured based on the mass of the specific gas by the analyzer. The shortcomings of the analytical method can be compensated for by measurement using a non-dispersive infrared densitometer, and an accurate gas composition can be measured. Further, according to the present invention, since the mass flow controller adjusts the flow rate of the sample gas and the dilution gas for diluting the sample gas, there is a difference in viscosity for each gas composition contained in each gas. However, the flow rate can be accurately controlled without being affected by the difference in viscosity. Moreover, since the sample gas and the dilution gas whose flow rates are controlled are mixed in the introduction pipe, it is possible to generate a homogenized measurement gas. The mass flow controller also functions as a capillary (throttle valve), and can continuously maintain the pressure in the downstream of the mass flow controller by reducing the pressure continuously downstream.

(Embodiment 1)
FIG. 1 is a configuration diagram of a gas analyzer according to an embodiment of the present invention.
As shown in FIG. 1, the piping structure in the present gas analyzer includes a first supply path 1 into which a sample gas F1 is introduced, a second supply path 2 into which a dilution gas F2 is introduced, and a first supply path 1. The sample gas F1 from the second supply path 2 and the diluted gas F2 from the second supply path 2 are mixed to form a mixed gas, the first branch path 4 that branches the mixed gas F3 from the introduction pipe 3, and the introduction pipe 3 is provided with a second branch path 5 that branches the mixed gas F3 from 3 in parallel. The dilution gas F2 is not necessarily a necessary gas, and it is necessary to dilute the sample gas according to the composition of the sample gas F1, such as when the sample gas contains moisture or when it is desired to improve the measurement response speed. Provided in case. The dilution gas is an inert gas such as argon.

  The first supply path 1 is provided with a first mass flow controller 22 that adjusts the flow rate of the sample gas F1 to a first amount. The second supply path 2 is provided with a second mass flow controller 23 that adjusts the flow rate of the dilution gas F2 to a second amount.

  The first mass flow controller 21 and the second mass flow controller 22 can accurately measure the gas flow rate without being affected by the viscosity of the flowing gas composition. The specific configuration of the mass flow controller is not limited, but, for example, a flow rate detection sensor for detecting a mass flow rate, a metal thin tube into which gas flows, and two exothermic temperatures whose resistance values change depending on the temperatures upstream and downstream of the metal thin tube A bridge circuit that detects and outputs the difference between the resistance values of the resistance wire and the two heat-generating temperature sensing resistor wires as a difference between the sense voltage values, an amplifier circuit that amplifies the output voltage of the bridge circuit, a comparison control circuit that compares the sense voltage difference, A solenoid valve or the like controlled based on the result of the comparison control can be provided. By utilizing the fact that the temperature difference between the upstream and downstream of the metal thin tube corresponds to the flow rate of the flowing gas, the gas flow rate can be controlled to be constant. With the above operation, the first and second mass flow controllers 21 and 22 also function as orifices (throttle valves) for the downstream kneading passages.

  In the introduction pipe 3, the sample gas F1 controlled to the first flow rate and the dilution gas F2 controlled to the second flow rate join and flow upstream. By having a certain length, the sample gas F1 and the dilution gas F2 are uniformly mixed to become a mixed gas F3. The length of the introduction pipe 3 is set to a length capable of promoting gas mixing.

  In addition, you may comprise so that stirring with the sample gas F1 and the dilution gas F2 may be promoted by providing the introduction piping 3 with a stirring structure. The stirring structure is, for example, a flow path structure in which the other gas generates a turbulent flow with respect to one gas flow. Mixing of gas is also promoted by arranging a stirring member such as glass wool.

  A non-dispersive infrared densitometer 23 is disposed in the first branch path 4, and a mass spectrometer 24 is disposed in the second branch path 5. The first branch path 4 and the second branch path 5 are configured such that the pressure state of each branch path can be changed. Specifically, in this embodiment, the first branch path 4 is configured to be at atmospheric pressure, and the second branch path 5 is configured to be in a constant vacuum state. The non-dispersive infrared densitometer 23 is preferably measured in a state slightly depressurized from the atmospheric pressure, but the mass spectrometer 24 is not capable of accurate measurement unless the degree of vacuum is increased to a considerable extent.

  Specifically, a negative pressure valve V for keeping the pressure at a constant negative pressure downstream of the non-dispersion type infrared densitometer 23 and a non-dispersion type infrared ray are provided in the first branch path 4 as a first pressure reducing means. And a first vacuum pump 25 that depressurizes a closed space communicating with the densitometer 23. The negative pressure valve V opens and introduces air when the pressure becomes lower than the set pressure, and closes when the pressure becomes higher than the set pressure. Therefore, the closed space including the non-dispersive infrared densitometer 23 is closed to a desired negative pressure. It is possible to maintain the state (for example, −50 KPa). By driving the first vacuum pump 25, the first mass flow controller 21 and the second mass flow controller 22 function as orifices (throttle valves), and a closed space from the introduction pipe 3 to the first branch path 4 is formed. Maintain negative pressure. At this time, since the negative pressure valve V is connected to this closed space, it is possible to maintain a constant pressure in an optical path 232 (described later) which is a detection unit of the non-dispersive infrared densitometer 23.

  In the second branch 5, as a second decompression means, a second vacuum that decompresses a closed space downstream of an inlet capillary 240 (described later) of the mass spectrometer 24 on the downstream side of the mass spectrometer 24. A pump 26 is provided. By driving the second vacuum pump 26, the space after the inlet capillary 240 is decompressed, and the mass spectrometer 24 can be maintained in a constant high vacuum state.

  The non-dispersive infrared concentration meter 23 provided in the first branch 4 is configured to measure the concentration of a specific gas having a specific infrared absorption wavelength contained in the sample gas F1. For example, the concentration of carbon monoxide (CO) as a specific gas can be measured.

FIG. 2 shows the structure of the non-dispersive infrared densitometer 23.
As shown in FIG. 2, the non-dispersive infrared densitometer 23 has an optical path 232 having an introduction path 231 and an outlet path 233, and an infrared ray L is emitted from the light source 234 to the optical path 232 and passes through the optical path 232. The light beam L is detected by the light receiving element 235 and is output as a detection signal D1. However, the structure shown in FIG. 2 is merely an example, and may have another configuration based on a known technique.

  The non-dispersive infrared densitometer 23 utilizes the property that many kinds of gases each absorb a specific infrared wavelength, and based on the absorbed infrared wavelength and the amount absorbed, The gas composition is specified, and the concentration of the gas composition is measured.

  Specifically, a non-dispersive infrared ray, that is, an infrared ray including all wavelength components is emitted from the light source 234 (for example, nichrome wire). The infrared ray L introduced into the optical path 232 is constant in proportion to the concentration of a specific gas (hereinafter referred to as carbon monoxide CO) contained in the mixed gas F3 introduced from the introduction path 231 and filled in the optical path 232. The infrared ray having the wavelength is absorbed and attenuated, and reaches the light receiving element 235. The light receiving element 235 is set to be highly sensitive to infrared rays in a narrow wavelength band centered on the absorption wavelength of a specific gas to be detected, and generates an electrical signal (detection signal D1) proportional to the amount of received infrared rays. And output. It shows that the larger the signal level of the output detection signal D1, the smaller the amount of light absorption, and thus the lower the density. Conversely, the smaller the signal level of the detection signal D1, the greater the amount of light absorption, and thus the higher the density. Therefore, if the correspondence between the concentration of the reference specific gas and the level of the detection signal D1 is held as a relation table or a relational expression, the concentration of the specific gas contained in the mixed gas F3 according to the level of the detection signal D1. Can be measured.

  Although it depends on the structure of the non-dispersion infrared densitometer, the detection accuracy of the non-dispersion infrared densitometer may increase if the non-dispersion infrared densitometer is in a slightly negative pressure state, for example, a negative pressure of several tens kPa. In the present embodiment, the pressure is reduced by the first vacuum pump 25 and can be maintained at a constant negative pressure state by the negative pressure valve V.

FIG. 3 shows the configuration of the mass spectrometer 24.
As shown in FIG. 3, the mass spectrometer 24 is provided with an inlet capillary 240, an ionization unit 241, an analysis unit 242, and a detection unit 243 along the flow path. However, the structure shown in FIG. 3 is merely an example, and other configurations based on known techniques may be provided.

  The mass spectrometer 24 applies a high voltage to gas molecules contained in the sample gas to ionize and fly, and the ions are electrically and electromagnetically acted on by a mass-to-charge ratio (molecular mass m and charge amount z). Is a device that detects the amount of each ion after separation. Finally, in the calculation unit, it is possible to measure a mass spectrum having the mass-to-charge ratio on the horizontal axis and the detection intensity (ion count) on the vertical axis. The gas composition concentration can be calculated from the amount of ions.

  Specifically, the inlet capillary 240 has a constant flow path resistance, and can drive the second vacuum pump 26 to maintain the pressure in the closed space including the mass spectrometer 24 in a high vacuum state. It is a throttle valve.

  The ionization unit 241 is a part that applies energy to gas molecules contained in the sample gas and ionizes them. An electron ionization method in which ionization is performed by colliding thermal electrons, gas molecules that are ionized in advance, and target gas molecules Chemical ionization method that causes ionization by causing a charge exchange reaction, electric field separation method that generates a high electric field by a saddle electrode and ionizes using the tunnel effect, fast atom collision method that ionizes by colliding neutral atoms at high speed, etc. Known methods can be applied.

  The analysis unit 242 is a part that separates ionized gas molecules, and a known method such as a magnetic field deflection method, a quadrupole method, an ion trap method, or a time-of-flight method can be applied. In the magnetic field deflection method, ionized gas molecules are supplied into a magnetic field, and specific gas molecules are separated and detected by Lorentz force using a difference in flight path determined by the relationship between the mass and velocity of the gas molecules. In the quadrupole method, ionized gas molecules are passed through four electrodes, a high frequency is applied between the electrodes to perturb the gas molecules, and only ions to be detected are passed. The ion trap method is a method in which ions are held in a trap chamber provided with electrodes, and selectively released by changing potential to separate them. The time-of-flight method is a method of separating ions by accelerating ionized gas molecules and detecting a time difference until reaching a detector that changes according to the mass-to-charge ratio.

  The detection unit 243 is a part that detects ionized and separated gas molecules, and sensitizes and detects them with an electron multiplier tube, a microchannel plate, or the like. A value corresponding to the number of gas molecules will be detected. It can be said that the number of gas molecules per unit volume corresponds to the total amount of gas molecules, that is, the gas concentration.

(Description of operation)
Next, a gas analysis method in the gas analyzer according to this embodiment will be described.
The gas analysis method of this embodiment will be described based on the flowchart of FIG.

  First, in step S10, the flow rate of the first mass flow controller 21 is set to be the first flow rate Q1. The first flow rate Q1 is selected to be a flow rate at which the detection accuracy is relatively high based on the concentration of the specific gas (carbon monoxide CO) contained in the sample gas F1. Subsequently, in step S11, the flow rate of the second mass flow controller 22 is set to be the second flow rate Q2. This second flow rate Q2 is selected as a flow rate of a dilution gas suitable for diluting the sample gas F1.

  Next, in step S12, the first vacuum pump 25 provided in the first branch path 4 is driven at a predetermined rotational speed. Along with this driving, the inlet of the first vacuum pump 25 including the introduction pipe 3 and the first branch path 4 disposed downstream of the first mass flow controller 21 and the second mass flow controller 22 that function as capillaries. The closed space up to is decompressed. At this time, since the negative pressure valve V is provided in the first branch path 4, the pressure is reduced to the set pressure (for example, −50 kPa) set in the negative pressure valve V. Air is introduced from the outside when the pressure in the branch path 4 is lowered below the set pressure. By such an action, the first branch path 4 including the non-dispersive infrared densitometer 23 is maintained in a constant negative pressure state.

  In step S13, the second vacuum pump 26 provided in the second branch path 5 is driven at a predetermined rotational speed. With this driving, the closed space downstream of the inlet capillary 240 of the mass spectrometer 24 and to the inlet of the second vacuum pump 26 is depressurized. By controlling the rotation speed of the second vacuum pump 26, the pressure in the closed space is maintained in a considerably high vacuum state. At this time, when the pressure in the vicinity of the inlet of the mass spectrometer 24 to the inlet capillary 240 (that is, the internal pressure of the second branch 5) varies, the flow rate of the sample gas passing through the inlet capillary 240 varies, and the mass spectrometer. The sensitivity of 24 varies and an error occurs. However, in this embodiment, the second branch path 5 communicates with the first branch path 4, and the internal pressure of the first branch path 4 is maintained at a constant negative pressure by the function of the negative pressure valve V. Therefore, the internal pressure of the second branch path 5 is also stable. Therefore, the possibility of generating an error in the mass spectrometer 24 is suppressed.

  Steps S10 to S13 related to the above measurement preparation may be performed in any order. When this measurement preparation is completed, it is determined in step S14 whether or not it is time to start gas analysis. If it is not the measurement timing as a result of the determination (NO), the standby state is continued. As a result of the determination, if it is the measurement timing (YES), the process proceeds to step S15.

  In step S15, first, mass spectrometry measurement is performed in the mass spectrometer 24. By this measurement, the gas molecules are counted according to the mass-to-charge ratio, and the detection intensity according to the mass-to-charge ratio, that is, the count value corresponding to the ionization current value of the gas molecules is detected. This count value corresponds to the gas concentration. The detected count value is supplied to the calculation unit 30 as the detection signal D2.

  In step S <b> 16, the arithmetic unit 30 records the gas molecule count value in correspondence with the mass-to-charge ratio. When the detection for all the gas molecules is completed, a mass spectrum in which the detection intensity corresponding to the mass to charge ratio is plotted is obtained.

FIG. 5 shows an example of a mass spectrum showing the relationship between the mass-to-charge ratio and the detected intensity. It is a mass spectrum in which a characteristic S1 indicated by a solid line is detected. Here, as can be seen from FIG. 5, at the peak P, the mass-to-charge ratio of nitrogen N _{2 and} the mass-to-charge ratio of carbon monoxide CO, which is the specific gas to be detected, are substantially the same. Therefore, nitrogen and carbon monoxide are detected as gases having the same mass-to-charge ratio, and the count amount of both gases is added at the peak of the characteristic S1. Therefore, even with mass spectrometry alone, the detection intensities of other gas compositions can be measured, but the detection intensities of nitrogen and carbon monoxide cannot be measured.

  Therefore, in step S17, the concentration of the specific gas, that is, carbon monoxide is detected by the non-dispersive infrared densitometer 23 this time. Since the light receiving element 235 in the non-dispersive infrared densitometer 23 is specialized for the infrared absorption wavelength of carbon monoxide, the absorption state of other gas compositions containing nitrogen is not detected. The detection signal D1 from the light receiving element 23 is supplied to the calculation unit 30.

  In step S18, the computing unit 30 computes the concentration of carbon monoxide, which is a specific gas, using a relation table or relational expression prepared in advance based on the detection signal D1. Furthermore, the calculating part 30 converts into gas molecule number Cco per unit volume based on the density | concentration of the gas in gas.

Next, the process proceeds to step S19, and the calculation unit 30 reads the count value Cmix at the peak P from the recorded mass spectrum. Then the process proceeds to step S20, the arithmetic unit 30, the number of molecules Cco of carbon monoxide converted from the read count value Cmix is subtracted to calculate the number of molecules C _N2 nitrogen. In order to convert the count value into the concentration of the gas composition, specifically, the gas composition in the sample gas F1 includes a predetermined gas (for example, carbon monoxide CO, carbon dioxide CO ₂ , oxygen O ₂ , hydrogen Assuming that only H ₂ , moisture H ₂ O, and nitrogen N ₂ ) exist, the count value corresponding to the ionization current value is converted into a concentration for each gas composition so that the total gas composition ratio is 100 wt%. To do. When the sample gas F1 is diluted with the dilution gas F2 as in the present embodiment, the concentration conversion calculation is performed on the assumption that the dilution rate does not affect the concentration of each gas component.

That is, in FIG. 5, the count value Cmix at the peak P detected by the mass spectrometer 24 is the total number of molecules of nitrogen and carbon monoxide. Therefore, the concentration of carbon monoxide is detected by a non-dispersive infrared densitometer 23 that is different in principle and can extract only carbon monoxide, converted into the number of molecules Cco, and subtracted from the count value Cmix, thereby reducing the nitrogen concentration. They succeeded in obtaining the molecular number C _N2 .

  In the above embodiment, the case where the mass-to-charge ratio of nitrogen and carbon monoxide was the same was exemplified, but similarly, the gas composition that cannot be separated by mass spectrometry as a result of the mass-to-charge ratio being very close. At the same time, by applying the present invention, it is possible to measure both separately.

As described above, according to the gas analyzer of the first embodiment, since the mass spectrometer 24 is provided first, carbon monoxide CO, carbon dioxide CO ₂ , oxygen O ₂ , hydrogen, which are gas compositions that can be discharged from the fuel cell system. It is possible to continuously analyze many kinds of gases such as H ₂ , moisture H ₂ O, and nitrogen N ₂ .

In particular, according to the gas analyzer of the first embodiment, the concentration of the specific gas is measured by the non-dispersive infrared densitometer 23 on the principle different from the mass analysis by the mass spectrometer 24, and the calculation unit 30 performs this measurement. The specific gas abundance was calculated by converting from the concentration of the specific gas, and the calculation was made to remove the specific gas abundance from the abundance measured for the mass-to-charge ratio of the specific gas by the mass spectrometer. A plurality of gas components (for example, carbon monoxide CO and nitrogen N ₂ ) whose masses are close to each other can be accurately identified and detected.

  In other words, according to the first embodiment, two items of measurement data (more specifically, concentration composition data and mass composition data) are measured for the sample gas, and the measurement data (concentration) based on these measurement data. Since the error included in the composition data is calculated and the error is removed from the measurement data, the concentration of the specific gas can be accurately measured.

  In a fuel cell system, if a large amount of sample gas is sampled from the exhaust gas, the characteristics of the fuel cell change. Therefore, in order to analyze the gas composition of the exhaust gas continuously, only a small amount of sample gas should be sampled. I can't. At this time, if the measuring device is configured to feed the sample gas with the pump, the pump is interposed upstream of the measuring means, so a time lag occurs between the sampling time and the measuring time due to the volume of the pump. The measurement result cannot be reflected in the control of the fuel cell system.

  In this regard, according to the gas analyzer of the first embodiment, since the vacuum pump is provided on the downstream side of the measuring means, even if it is a measurement object that can sample only a small amount of sample gas as in the fuel cell system. Further, it is possible to suppress a delay in measurement response speed due to the pump volume and the like. Further, since the sample gas is measured in a reduced pressure state by being sucked by a vacuum pump, the flow rate of the sample gas can be increased and the measurement response speed can be increased as compared with the case of measuring at atmospheric pressure. Furthermore, since the sample gas F1 is further diluted with the diluent gas F2, it is possible to increase the measurement response speed by increasing the flow rate of the sample gas.

  Exhaust gas discharged from the fuel system may contain a large amount of moisture. However, if such exhaust gas is introduced into the gas analyzer as a sample gas at the same pressure, moisture aggregates. Measurement errors may increase or the analyzer may malfunction. In order to suppress such inconvenience, it is necessary to maintain the gas analyzer at a temperature at which moisture aggregation does not occur (for example, 100 ° C. or higher). At such a high temperature, the durability of the analyzer is lowered, and another failure occurs. It becomes the cause of.

  In this regard, according to the gas analyzer of the first embodiment, the mass flow controllers 21 and 22 functioning as capillaries are provided at the inlet portion, and suction is performed by the vacuum pumps 25 and 26, and the sample gas is measured in a reduced pressure state. Therefore, even if a large amount of water is contained in the sample gas, water aggregation does not occur, and it is not necessary to maintain a high temperature in order to suppress the aggregation, and the above-described disadvantage does not occur. In addition, since the sample gas F1 is further diluted with the dilution gas F2, the moisture concentration in the sample gas is further reduced and the dew point temperature is lowered, so that condensation of moisture in the gas analyzer can be further effectively suppressed. It is.

  Furthermore, according to the gas analyzer of the first embodiment, the first mass flow controller 21 for the sample gas F1, and the second mass flow controller 22 for the dilution gas F2 for diluting the sample gas F1, respectively. Therefore, even if there is a difference in viscosity for each gas composition contained in each gas, the flow rate can be accurately controlled without being affected by the difference in viscosity.

  According to the gas analyzer of the first embodiment, since the sample gas F1 and the dilution gas F2 whose flow rates are controlled are mixed in the introduction pipe 3, it is possible to generate a homogenized measurement gas. .

  According to the first embodiment, since measurement is performed with the non-dispersive infrared densitometer 23 in a negative pressure state, the concentration of the specific gas can be detected more accurately.

  According to the gas analyzer of the first embodiment, since the negative pressure valve V is provided, the internal pressure of the non-dispersive infrared concentration meter 23 and the inlet pressure of the mass spectrometer 24 can be stabilized. Therefore, both the measurement error in the non-dispersive infrared densitometer 23 and the measurement error in the mass spectrometer 24 can be effectively suppressed.

(Embodiment 2)
FIG. 6 is a configuration diagram of a gas analyzer according to Embodiment 2 of the present invention.
As shown in FIG. 6, the piping structure in the present gas analyzer has substantially the same configuration as that of the first embodiment, but the first decompression means for maintaining the first branch path 4 in a decompressed state, that is, The difference is that the negative pressure valve V and the first vacuum pump 25 are not provided.

The operation in the second embodiment is the same as that in the first embodiment (FIG. 4).
However, in the second embodiment, the non-dispersive infrared concentration meter 23 is configured to detect a specific gas while being maintained at atmospheric pressure. Unlike the mass spectrometer, the non-dispersive infrared densitometer can detect the gas concentration even at atmospheric pressure, and thus can adopt such a configuration. In the second embodiment, since the first branch 4 is maintained at substantially atmospheric pressure, the second branch 5 serving as the inlet pressure of the mass spectrometer 24 is also maintained at substantially atmospheric pressure. Therefore, the measurement error in the mass spectrometer 24 can be suppressed.

(Other embodiments)
The present invention can be applied with various modifications other than the above embodiment.
For example, the gas analyzer of this embodiment is applicable to any gas analysis. In particular, in a fuel cell system, since air is used as one of the fuel gases, a large amount of nitrogen is contained in the exhaust gas, which is suitable for accurately analyzing the gas composition in the exhaust gas.

  In the above embodiment, the mass flow controllers 21 and / or 22 are used. However, if the amount of sample gas supplied is stable, and if the sample gas does not contain a large amount of moisture, the mass flow controller is It may not be used.

  In the above embodiment, the dilution gas is used. However, the dilution gas is not necessarily used if the concentration of the specific gas to be detected in the supplied sample gas is appropriate.

Configuration diagram of a gas analyzer according to Embodiment 1 Configuration diagram of non-dispersive infrared densitometer Mass spectrometer configuration diagram Flowchart of gas analysis method according to embodiment 1 Example of mass spectrum measurement Configuration diagram of a gas analyzer according to Embodiment 2

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... 1st supply path, 2 ... 2nd supply path, 3 ... Introductory piping, 4 ... 1st branch path, 5 ... 2nd branch path, 21 ... 1st mass flow controller, 22 ... 2nd Mass flow controller, 23 ... Non-dispersion type infrared densitometer, 24 ... Mass spectrometer, 25 ... First vacuum pump, 26 ... Second vacuum pump, 30 ... Calculation unit, V1 ... First shut-off valve, V2 ... First 2 shutoff valve, F1 ... sample gas, F2 ... dilution gas, F3 ... mixed gas

Claims (7)

A gas analyzer for measuring a gas concentration contained in a sample gas,
A first supply path for supplying the sample gas;
A first mass flow controller provided in the first supply path for adjusting the flow rate of the sample gas to a first amount;
A second supply path for supplying a dilution gas for diluting the sample gas;
A second mass flow controller, provided in the second supply path, for adjusting the flow rate of the dilution gas to a second amount;
An introduction pipe that mixes the sample gas from the first supply path and the dilution gas from the second supply path to form a mixed gas;
A non-dispersive infrared concentration meter that measures the concentration of a specific gas having a specific infrared absorption wavelength contained in the mixed gas supplied from the introduction pipe ;
A mass spectrometer for measuring the abundance of each mass of a plurality of types of gas the mixed contained in the gas, containing the specific gas,
On the basis of the abundance of each of the non-dispersive infrared concentration plural types which are measured by the concentration and the mass spectrometer of the specific gas measured by meter gas mass, the concentration of the gas contained in the sample gas A computing unit for computing,
The computing unit is
Converting the concentration of the specific gas measured by the non-dispersive infrared densitometer abundance of the specific gas,
Wherein among the abundance of each mass of the plurality of types of gas measured by the mass spectrometer, said the abundance measured for mass of the specific gas, by subtracting the abundance of the specific gas that is converted, the Calculating the abundance of different types of gas with the same mass as the specific gas,
Gas analyzer characterized by. A first branch path for branching the mixed gas from the introduction pipe to the non-dispersive infrared densitometer;
A second branch path for branching the mixed gas from the introduction pipe to the mass spectrometer,
The pressure state in the first branch path or the second branch path is configured to be changeable.
The gas analyzer according to claim 1 . The first branch path includes first decompression means for bringing the non-dispersive infrared densitometer into a first decompressed state,
The gas analyzer according to claim 2 . The first decompression means includes
A first vacuum pump for depressurizing a closed space communicating with the non-dispersive infrared densitometer;
A negative pressure valve that maintains the closed space at a constant negative pressure,
The gas analyzer according to claim 3 . The second branch path includes second decompression means for bringing the mass spectrometer into a second decompressed state,
The gas analyzer according to claim 2 . The second decompression means includes
A second vacuum pump for depressurizing a closed space communicating with the mass spectrometer;
The gas analyzer according to claim 5 .   The gas analyzer according to claim 1, wherein the specific gas is carbon monoxide, and the different kind of gas having the same mass-to-charge ratio as the specific gas is nitrogen.

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