JP2001349812A - Method for reducing interference effect of gas analyser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply efficiently reduce the interference effect of an analyzer in a gas measuring apparatus. SOLUTION: The interference effect, corresponding to the characteristics of an analyzer, can be compensated by providing a cooling unit and a semipermeable membrane separator to a measuring gas sampling line for selectively removing a prescribed amount of alcohol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas measuring apparatus using a gas analyzer for continuously measuring the concentration of components such as automobile exhaust gas and various process gases.

[0002]

2. Description of the Related Art When continuously measuring the concentration of various components in exhaust gas and the concentration of components in various processes for producing and treating various compounds, a non-dispersive infrared gas analyzer (hereinafter referred to as "NDIR"). ) And non-dispersion type ultraviolet gas analyzers (hereinafter referred to as “NDUV”) are often used. In these gas analyzers, if the measurement gas is to be measured as it is, the interference of other components coexisting with the measurement component causes Correct concentration measurements may not be obtained.

Generally, in order to reduce such interference effects, a method of removing such coexisting components from a measurement gas is used. Specifically, a chemical treatment (e.g., removal of water with phosphorus pentoxide, calcium chloride, or the like corresponds to) by reacting with a specific chemical, or a physical treatment (e.g., removal by adsorption to a specific member) Activated alumina, molecular sieves and the like are used), and physical treatment of condensing and liquefying at a predetermined temperature to remove (for example, removal of water by low-temperature condensation by an electronic cooler).

As a method of reducing such interference effects in the gas analyzer itself, a method of compensating for the interference effects by using a plurality of detectors 4 is often adopted. Specifically, as shown in FIG. 2, a plurality of solid state detectors 4 (for example, a semiconductor detector,
An analyzer having an optical system in which a pyroelectric detector corresponds to the optical path is often used.
As shown in FIG. 3, there is an analyzer having an optical system in which a detector 7 (so-called "pneumatic detector") in which a plurality of measurement components and interference influence components are enclosed is arranged in series with the optical path. It is used. In the former, the signal of the measurement detector 4a combined with the optical filter 3 corresponding to the absorption wavelength unique to the measurement component is used to detect the interference compensation detector 4b combined with the optical filter 3 corresponding to the absorption wavelength unique to the interference influence component. The influence of interference can be reduced by subtracting the signals of .about.d. In the latter case, the signal of the interference compensation detector 5b in which the interference influence component is encapsulated from the signal of the measurement detector 5a in which the measurement component is encapsulated. Is subtracted by the computing unit 6 to reduce the influence of interference.

[0005]

However, in the case of a method for removing coexisting gas, in the case of a chemical treatment, it is necessary to dispose of the substance after the reaction, or the capacity of the chemical is reduced due to a limited quantity of the chemical. Because of its long life, it is difficult to adopt it as a pretreatment for a continuous measurement apparatus, and even in the case of treatment by physical adsorption, there is also a limit in terms of the life of adsorption capacity.
In the case of condensation removal, there is a case where the condensation temperature is limited due to the relation with other coexisting components and the target substance cannot be sufficiently removed. For example, when water and alcohol coexist, at normal pressure of 0 ° C. or less, icing occurs, and the risk of clogging of the measurement gas line is increased. For example, methyl alcohol has a vapor pressure of about 5 kPa, that is, 5% or more, as a coexisting component. The presence of such co-existing components, for example,
In some cases, interference in the analyzer for measurement of components such as CO, CO2 and CH4 in the processing gas (see FIG. 4) cannot be ignored.

Further, even when the analyzer itself is devised or coped with, it may not be possible to fully compensate for the type of coexisting components. In particular, when a plurality of coexisting components are present, there is a case where one of the compensations can be performed but the influence of the other cannot be completely compensated. For example, the interference effect on CH3OH, H2O, and CO2 in the NDIR / CO meter corresponds to this. In other words, when interference influence compensation is performed with H2O among the three components, specifically, the H2O interference output of the compensation detector is adjusted to match the H2O interference output of the measurement detector. In this case, the CH3OH interference is equivalent to 10 ppm, and the CH3OH interference output of the compensating detector is compared with the CH3OH interference of the measuring detector.
When adjusted to match the OH interference output, CO2
The interference is equivalent to -18 ppm, and any interference compensation cannot be sufficiently performed. In addition, even when the concentration of the coexisting gas is very high as compared with the measurement component, the effect may not be negligible. For example, when an interference-compensated NDIR is used as a measuring device for CO existing as a trace gas in the atmosphere,
Since the H2O concentration in the atmosphere changes in a wide range from about 0.6% (0 ° C saturation) to 4% (30 ° C saturation) at room temperature, the interference effect characteristics due to the H2O concentration of the measuring detector and the compensating detector. May be slightly shifted (see FIG. 6), and the compensation accuracy may be deteriorated.

[0007]

According to the present invention, in order to solve the above-mentioned problems, in a gas measuring apparatus, a cooling unit and a semi-permeable membrane separator are provided in a measuring gas sampling line to selectively remove a predetermined amount of alcohol. It is characterized by adopting a method of performing. (Claim 1) By using the method having such a characteristic, when alcohol is present as a coexisting gas, continuous measurement with high accuracy can be performed with almost no influence of alcohol interference on low concentration measurement of CO or the like.

In the gas measuring device, a cooling unit and a semi-permeable membrane separator are provided in a measuring gas sampling line, and the gas measuring device selectively removes a predetermined amount of alcohol to reduce interference effects. . (Claim 2) With the apparatus having such a feature, when alcohol is present as a coexisting gas, continuous measurement with high accuracy can be performed with almost no influence of alcohol interference on low concentration measurement of CO or the like.

Further, in the gas measuring apparatus, a cooling unit and a semi-permeable membrane separator are provided in a measuring gas sampling line, and alcohol is selectively removed by a predetermined amount. It is characterized by employing a reduction method. (Claim 3) By using the method having such a feature, when alcohol is present as a coexisting gas, continuous measurement with high accuracy can be performed with little influence of alcohol interference on low concentration measurement of CO or the like.

[0010] Further, the present invention is characterized in that a gas measuring apparatus is provided with a cooling unit and a semi-permeable membrane separator in a measurement gas sampling line to selectively remove a predetermined amount of alcohol to reduce the influence of interference in an interference compensation analyzer. I do. (Claim 4) With the device having such a feature, when alcohol is present as a coexisting gas, continuous measurement with high accuracy can be performed with almost no influence of alcohol interference on measurement of a low concentration of CO or the like.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on specific examples with reference to the drawings.

FIG. 1 shows a gas measuring apparatus comprising a sampling section and an analyzer according to an embodiment of the present invention. Here, the measurement gas is introduced into the heating sampling section 21 via the heating introduction pipe 12 and further introduced into the analyzer 20 via the preprocessing section 22. By continuously measuring the concentrations of various components in the measurement gas from which interference-influencing components have been removed,
Very high-accuracy continuous component analysis can be performed for the entire analyzer. At this time, the analyzer 20 which is not affected by interference even when moisture and alcohol coexist does not necessarily need to pass through the pre-processing unit, but in the following description, it passes through the pre-processing unit 22 related to the present invention. Only the lines of the analyzer to be described will be described.

Here, the configuration example shown in FIG. 1 will be described in detail. First, a measurement gas containing high-concentration water and alcohol as coexisting gases is introduced into the heating sampling unit 21 through the heating introduction pipe 12. The heating introduction pipe 12 controls heating at a temperature at which coexisting moisture and alcohol do not condense, prevents condensation of these substances, and also prevents a response delay of the analyzer due to adsorption of coexisting high-boiling substances and the like in the introduction pipe.

In the heating sampling unit 21, after the dust is removed by the filter 13, the measurement gas is branched and pumped by the suction pump 14 to the various analyzers 20 corresponding to the components to be measured or to the preprocessing unit 22 provided in the preceding stage thereof. Each branched line is adjusted to a predetermined flow rate by the valve 15. At this time, the heating sampling unit 12 employs a configuration in which each component is heated and the components are connected by a heating pipe, and a configuration in which each component is incorporated in a predetermined heating vessel and controlled at a predetermined temperature. There is. In any case, the material with which the measurement gas comes into contact needs to have heat resistance. The filter 13 treats dust and particulate matter contained in the measurement gas as early as possible, and aims to prevent a measurement error or a response delay due to contamination or corrosion of the sampling line thereafter. Those having a structure that can be replaced are used. Generally, a diaphragm pump is often used as the suction pump 14, but the present invention is not limited thereto, and a bellows pump or the like may be used. The valve 15 is generally a manual adjustment valve or a throttle, but is not limited thereto, and an automatic adjustment valve or the like may be used.

Next, a part of the measurement gas derived from the heating sampling unit 21 is introduced into a pre-processing unit 22 including the electronic cooler 16 and its related components and the semipermeable membrane separator 19. The measurement gas is supplied to the heating sampling unit 21 and the preprocessing unit 22.
Is cooled to near room temperature, and further cooled to a certain temperature, for example, 5 ° C. by the electronic cooler 16 of the pretreatment unit 22. At this time, the condensed water and alcohol fall into a drain pot 17 provided at a lower part of the electronic cooler 16, and when the storage amount of the drain in the pot 17 exceeds a certain amount, the electromagnetic valve 18 is opened to automatically operate. Is discharged. The removal efficiency of the electronic cooler 16 is determined not only by the capacity of the cooler but also by the set temperature of the cooler, the measured gas flow rate, the coexisting components, and the ambient temperature of the cooler. If there is a large amount of moisture as a gas,
In addition to the dissolution of alcohol in condensed water, stable separation and removal can be achieved. If the cooling between the pipe sections is insufficient due to the relationship between the measurement gas flow rate and the concentration of coexisting moisture, alcohol, etc., a cooling section having a certain space as a drain separator should be provided up to the electronic cooler 16. There is also. Similarly, the capacity of the drain pot 17 is determined by the measured gas flow rate, the coexisting component, the drainage interval, and the like.

Next, the measurement gas is introduced into the semipermeable membrane separator 19. At this time, moisture, alcohol, and the like in the measurement gas introduced into the separator 19 have been reduced to a predetermined concentration by the cooler 16 in advance, so that the load on the separator 19 is significantly reduced. Become. Semipermeable membrane separator 19
Is a material that uses the partial pressure difference between the two sides of a semipermeable membrane to move substances.In general, it is often used for desalination of seawater or for salt electrolyte membrane, but it is mainly used for the separation of water in the analysis. Used. In specific use, when separating a specific component from a measurement gas, a method of bundling a plurality of thin tubes, flowing the measurement gas into the tube and flowing a purge gas containing no specific component outside the tube, or the pressure of the measurement gas in the tube The method of making the pressure higher than the pressure outside the tube (including reducing the pressure outside the tube) and a combination thereof are often used. The separation capacity depends on the number and length of the thin tubes, the flow rates of the measurement gas and the purge gas, and the pressure difference and concentration difference between the inside and outside of the tubes. FIG. 1 shows a method of flowing a purge gas. However, the present invention is not limited to this, and any of the above methods can be used. A method is used. When a Nafion membrane (manufactured by DuPont) was used for the alcohol to be removed in the present invention, a separation effect as shown in FIG. 7 was obtained. In particular, when a large amount of moisture is present as a coexisting gas as in a fuel cell, the presence of moisture impregnated in the membrane works advantageously for the separation and removal of alcohol.

The measurement gas thus processed is introduced into the gas analyzer 20 corresponding to each measurement component. As the gas analyzer 20, various gas analyzers for continuous measurement, such as the aforementioned NDIR and NDUV, are optimal in terms of utilizing the effectiveness of the present invention.
Even if it is an analyzer for discontinuous measurement such as MS or MS (mass spectrometer), its function can be fully utilized. In other words, even when moisture and alcohol coexist in the measurement gas, since these are largely removed by the above-described processing, continuous measurement with high accuracy can be performed with almost no influence of interference. However, in the case of a very small measurement range such as CO 0-100 ppm, the influence of interference cannot be ignored yet, and a combination with the analyzer itself having the above-described interference compensation function is required.

When an interference-compensating gas analyzer is used, generally, the output of the measuring detector and the output of the interference-compensating detector for the coexisting component having the largest interference effect in the measuring detector are determined. A method of adjusting so as to match them is adopted. However, for example, CH3O
When the concentration of H or H2O is high, it is necessary to compensate for a plurality of components having a large influence of interference. However, as shown in FIG. 5, even if one compensation is performed, the other compensation may be insufficient. is there. In this case, if the concentration of CH3OH or H2O in the measurement gas introduced into the analyzer is low, these effects become negligible, and adjustments are made mainly to compensate for interference effects of coexisting components other than CH3OH and H2O. by doing,
The overall interference effect can be reduced. Similarly, when the concentrations of CH3OH and H2O greatly vary depending on the operating conditions, it is necessary to make the output characteristics (linearity) of the detectors equal to each other for the influence of interference of such components and compensate for them. However, as shown in FIG. 6, the output characteristics of the measurement detector and the interference compensation detector may be slightly shifted. Similarly, in this case, if the concentration of CH3OH or H2O in the measurement gas introduced into the analyzer is low, these effects can be neglected.

By adopting the above configuration example, it is possible to obtain a highly accurate measurement with little influence of interference by a simple method. The present inventor has found that this semipermeable membrane is effective for removing alcohol that has not been used conventionally, and that the effect is particularly enhanced when moisture coexists. Also, by using the interference compensation type gas analyzer as shown in FIG. 2 or FIG. 3, the load on the analyzer can be reduced by the processing effect in the sampling unit, and
The load on the sampling section can be reduced by the interference compensation effect of the analyzer, and continuous measurement with higher accuracy can be performed due to the synergistic effect of both.

[0020]

According to the present invention, the selective removal of alcohol from a measurement gas containing a large amount of alcohol or water, such as a fuel cell, can be continuously performed with very stable efficiency. By effectively utilizing the interference compensation capability of the analyzer, it is possible to make use of the features of both, and to realize a device capable of maximizing the mutual capability. In other words, in the sampling unit, it is possible to determine the load on each component to be minimized as long as the interference compensation capability of the gas analyzer can be complemented. Since it is possible to determine the constituent elements of the detector for the purpose of reducing the interference effect only for, it is possible to perform highly accurate continuous measurement with very little interference effect in a simple and efficient method as a whole device. You can do it.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an implementation method of a sampling unit in the present invention.

FIG. 2 is an explanatory diagram showing an example of an NDIR optical system.

FIG. 3 is an explanatory diagram showing another example of the NDIR optical system.

FIG. 4 is an explanatory diagram showing a methanol reforming system for a fuel cell.

FIG. 5 is an explanatory diagram showing an example of interference influence data in NDIR.

FIG. 6 is an explanatory diagram showing an example of interference influence characteristics in NDIR.

FIG. 7 is an explanatory diagram showing an example of alcohol separation characteristics in a semipermeable membrane separator.

[Explanation of symbols]

 Reference Signs List 1 light source 2 cell 3 optical filter 4 detector 4a measurement detector, 4b interference compensation detector 5 preamplifier 6 arithmetic unit 7a measurement detector, 7b interference compensation detector 11 inlet 12 heating inlet tube 13 filter 14 suction Pump 15 Valve 16 Electronic cooler 17 Drain pot 18 Solenoid valve 19 Semi-permeable membrane separator 20 Analyzer 21 Heat sampling unit 22 Pretreatment unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G01N 21/35 G01N 21/61 21/61 1/28 K

Claims (4)

[Claims] In a gas measuring device, a cooling unit and a semi-permeable membrane separator are provided in a measurement gas sampling line,
A method for reducing interference effects in a gas analyzer, comprising selectively removing a predetermined amount of alcohol. 2. A gas measuring apparatus comprising a cooling unit and a semi-permeable membrane separator provided on a measurement gas sampling line to selectively remove a predetermined amount of alcohol to reduce the influence of interference in a gas analyzer. 3. A gas measuring device, wherein a cooling unit and a semi-permeable membrane separator are provided on a measurement gas sampling line,
A method for reducing the influence of interference in an interference-compensated gas analyzer, comprising selectively removing a predetermined amount of alcohol. 4. A gas characterized in that a cooling unit and a semi-permeable membrane separator are provided in a measurement gas sampling line, and alcohol is selectively removed by a predetermined amount to reduce interference effects in an interference-compensated gas analyzer. measuring device.