JPH07103922A - Measuring device for gas odorant - Google Patents

Abstract

PURPOSE:To obtain a device and a method for measuring a gas odorant which measure accurately the concentration of the odorant in a city gas in an inexpensive manner and by an easy operation. CONSTITUTION:A passage 6 for supplying air as a carrier gas, a part 8 for introducing a gas to be inspected which can introduce intermittently a prescribed amount of the gas to be inspected, while making the air in a prescribed flow rate flow through the passage 6, a separating-removing part 22 which separates an odorant component and a coexistent component in the gas to be inspected from each other and removes the coexistent component by releasing it outside a device system, and a semiconductor gas sensor 30 which detects the odorant component separated from the gas to be inspected, are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for measuring an odorant added to a fuel gas such as city gas.

[0002]

2. Description of the Related Art Conventionally, city gas has been obliged to be odorized for the purpose of security such as prevention of accidents caused by gas leakage. Therefore, in the city gas business, a gas with almost no odor, such as natural gas or reformed gas, is added with an odorant of a sulfide compound that has a small amount of strong odor and is supplied as odorous gas. . Here, in order to reliably detect the smell of the added odorant from the leaked gas, conventionally, odor control was performed by an olfactory test of a plurality of panelists.

However, since odor management that relies on the human sense of smell requires time and labor, it is difficult to increase the frequency of tests to improve the odor management level, and it is difficult to secure such human resources. It is a burden for difficult local gas utilities. Therefore, in recent years, it has been confirmed that there is a correlation between the odorant concentration contained in gas and the odor concentration, and the odor intensity of city gas can be controlled by measuring the odorant concentration in city gas. The way to do is getting done. Here, as a method for measuring the odorant concentration, there are a gas chromatograph method, an absorptiometric method, a detector tube method and the like.

[0004]

However, these odorant measuring methods have the following drawbacks. (1) The gas chromatographic method has good accuracy and sensitivity, but the detector (Flame Photometoric Detector) is expensive. (2) Since the absorptiometry uses an organic solvent as an absorbing liquid, the running cost is high, the measurement operation is a little complicated, and the used organic solvent (waste liquid) needs to be treated. (3) The detector tube method is a simple method for measuring odorants, but it is easily affected by interfering components, lacks measurement accuracy, and currently there are few measurable components, and its use is limited. . Therefore, the present invention eliminates the drawbacks of the conventional odorant measurement, and a gas odorant measuring device and a gas odorant measuring device for accurately measuring the odorant concentration in city gas by an inexpensive and simple operation. It is intended to provide a method for measuring a drug.

[0005]

As a technical means for solving the above-mentioned problems, the inventors of the present invention flow a supply flow path of air as a carrier gas and a constant flow rate of air through the supply flow path. While separating a fixed amount of the test gas intermittently, the test gas introduction part separates the odorant component and the coexisting component in the test gas and releases the coexisting component to the outside of the system. A gas odorant measuring device having a semiconductor gas sensor for detecting an odorant component separated from a test gas was created.

As the semiconductor gas sensor (hereinafter, simply referred to as a sensor), a thin film metal oxide (Sn) having high sensitivity to a sulfur compound used as an odorant is used.
O ₂ ) is used. As a supply source of air as the carrier gas, purified air filled in a container may be used, or air in the atmosphere may be compressed by an air pump or the like to be used as an air source. However, in the latter case, a filter filled with an adsorbent for purifying air is attached to the pump discharge side. The flow rate of air as a carrier gas is 20 to 50 ml / min.

Gas detection by a sensor (n-type semiconductor) is
This is mainly because the change in the sensor resistance value due to the adsorption of gas on the semiconductor surface is measured. Therefore, it is desirable to measure an initial sensitive state change when the sensor comes into contact with the odorant component, and it is desirable that the introduction of the test gas be intermittent. Further, the sensor is regenerated by supplying oxygen to the semiconductor surface to release the odorant component adsorbed on the semiconductor surface. In the present invention, the sensor is in a state where it can always be regenerated by oxygen in the carrier gas.

The temperature of the sensor is set in consideration of the sensitivity to the odorant component and the adsorption / desorption rate of the odorant component. The detection sensitivity and response speed of the sensor are improved by adding a catalyst such as palladium or platinum.

As the method of introducing the test gas, there are a method of attaching a sample injection part wound with a heater to the air supply path and introducing it using a syringe, and a method of using a switching cock equipped with a measuring tube. In the introduction method in which the sample injection part around which the heater is wound is attached, the liquid can be gasified in the sample injection part, so that the liquid standard can be used.

The odorant component is a sulfide compound such as tetrahydrothiophene (hereinafter referred to as THT), tertiary butyl mercaptan (hereinafter referred to as TB).
It is called M. ), Dimethyl sulfide (hereinafter referred to as DMS), and the like. The separation / removal section is for separating the separation column filled with a separation packing material, and for releasing only the coexisting component of the coexisting component and the odorant separated by the separation column out of the apparatus system and introducing only the odorant to the sensor. It consists of a switching cock. With this switching cock, coexisting components in the test gas can be separated and removed, and the odorant concentration can be accurately measured.

By providing a blank column for the separation column, it is possible to prevent the influence of the column packing material and the pressure fluctuation in the sensor when switching the cock, and to always supply the carrier gas to the sensor. You can As the blank column, one having the same size as the separation column and packed with the same packing material is used.

[0012]

According to the odorant measuring apparatus of the present invention, the test gas is intermittently introduced into the carrier gas and separated and separated from the coexisting components in the test gas by the separation / removal section, and the odorant component is detected by the sensor. Detected by. The odorant component is detected by a decrease in electric resistance value of the sensor, that is, an increase in voltage. According to the device of the present invention, the sensor is always in the regenerated state by the oxygen in the carrier gas when measuring the odorant component.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of an apparatus 1 for measuring a gas odorant. Device 1 of this embodiment
Is an air cylinder 2, an air supply channel 6, a sample injection unit 8, 2
Book columns 22, 24, switching cock 26, sensor 30
Is mainly used, and these are connected by piping.

The air cylinder 2 is filled with purified air under pressure, and the filled air is introduced into the air supply passage 6 by opening the stop valve 4.

The air supply passage 6 is bifurcated through the stop valve 4 and is divided into a measurement side supply passage (hereinafter, simply referred to as measurement side passage) 6a and a blank side supply passage (hereinafter, simply referred to as blank side passage). 6b), and the air flow rate can be adjusted by the flow rate adjusting valves 7a and 7b provided in the middle of the flow paths 6a and 6b. The blank-side channel 6b is directly connected to the blank-side column (hereinafter, simply referred to as a blank column) 24, and the measurement-side channel 6a is connected to the measurement separation column (hereinafter, simply referred to as a separation column) via the sample injection unit 8. 22 is connected.

As shown in FIG. 2, the sample injecting section 8 is constituted by a sample injecting tube 10 which is opened upward and around which a heater coil 18 is wound. The sample injection tube 10 is
It has substantially the same inner diameter as the measurement-side flow channel 6a and forms a part of the measurement-side flow channel 6a, which is substantially L-shaped, and the test gas can be introduced into the measurement system via the carrier gas. There is. The upper portion of the sample injection tube 10 is a large diameter portion 12 that protrudes upward from the casing of the device 1 and is formed in a large diameter in an overhanging manner and opens upward. Is packed with a packing 14 made of silicon or the like. Further, the large diameter portion 12 is externally fitted by being screwed from above with a packing cap 16.
For this reason, the packing 14 elastically deforms and comes into close contact with the inside of the large-diameter portion 12 to elastically seal the upper opening of the sample injection tube 10. A syringe insertion hole 16a is formed in the center of the upper surface of the packing cap 16,
When the packing cap 16 is fitted on the large diameter portion 12, the syringe insertion hole 16a serves as a sample injection port.

Further, in FIG. 2, the air cylinder 2 is provided at a predetermined position slightly below the large diameter portion 12 of the sample injection tube 10.
The measurement side supply pipe 6a from the side is connected. Further, a heater coil 18 is wound around the outer periphery of the sample injection tube 10 from below the large diameter portion 12 toward the separation column 22 for a predetermined length. The sample injection tube 10 around which the heater coil 18 is wound is wrapped in a heat insulating material 20 and arranged in the apparatus 1.

The separation column 22 is composed of a thin glass or stainless steel tube filled with a filler capable of separating the odorant component and the coexisting component in the city gas. Further, the separation column 22 is arranged in a thermostat (not shown). The blank column 24 has the same size as the separation column 22 and is filled with the same packing material.

Separation column 22 and blank column 24
Are further connected to the switching cock 26 via the flow paths 6a and 6b, respectively. The switching cock 26 discharges the outflow gas from the separation column 22 to the outside of the system at the outflow timing of the coexisting component so that the coexisting component other than the odorant component in the sample gas is not introduced into the sensor 30. It is for introducing only the component into the sensor 30. When the coexisting component flows out from the separation column 22, the switching cock 26 shown in FIG. 1 causes the outflow gas containing the coexisting component to flow through the discharge channel 29b through the channel shown by the solid line in FIG. The carrier gas from the column 24 is introduced into the sensor 30 by flowing through the sensor channel 29a through the channel indicated by the solid line.
On the other hand, when the odorant component flows out from the separation column 22, the sample side flow path 6a is connected to the sensor flow path 29a by the flow path shown by the dotted line of the switching cock 26 in FIG.
And the carrier gas from the blank column 24 is
The discharge flow path 29b is connected through the flow path indicated by the dotted line and is discharged to the outside of the device system.

The temperature of the sensor 30 can be controlled by a heater (not shown) so that it can be set to a temperature suitable for measuring the odorant component. The flow path exiting the sensor 30 is a flow meter F for further measuring the carrier gas flow rate.
It is connected to the.

Next, using this device 1, T was used as an odorant.
A method for measuring TBM in city gas added with BM will be described. The TBM measurement conditions are as follows.

[0022]

[Table 1]

Further, the sensor 30 is set to the heater voltage or the like most suitable for detecting the TBM, and the measurement is started after the column and the sensor are in a sufficiently stable state.

The sample gas (city gas) is separated and detected according to the flow chart shown in FIG. First, a fixed amount (0.2 to 2 ml) of sample gas is sampled with a gas tight syringe,
The sample is introduced into the device 1 from the sample injection unit 8. It should be noted that the injection is performed by piercing the needle of the syringe through the syringe insertion hole 16a of the packing cap 16 into the packing 14,
Insert the needle until the tip of the needle reaches the connecting portion of the measurement-side flow path 6a, and push the rod of the syringe at this position. Further, the city gas to which the odorant is added at a normal concentration can be injected as it is without being diluted and can be measured.

Next, the injected sample gas passes through the separation column 22 by the air supplied from the cylinder 2 through the measurement side flow path 6a, and while coexisting with the packing material, the coexisting component is present. Separation column 22 separated into W and TBM
Spilled from. FIG. 4 shows a chromatogram obtained from the sensor 30 when the total outflow gas of the sample gas is directly introduced into the sensor 30 without operating the switching cock 26 in the middle of the outflow timing. The vertical axis of the chromatogram is the output signal of the sensor 30, and the horizontal axis is the time elapsed after the sample injection. From this chromatogram, it can be seen that under the conditions of this example, the coexisting component W flows out within about 1 minute after the sample injection and the TBM flows out within about 2 minutes.

Therefore, in the present embodiment, the switching cock 2
The effluent gas 50 to 60 seconds after the sample injection is discharged to the outside of the system of the apparatus 1 by the operation of 6, and the effluent gas after that is introduced into the sensor 30 (see the measurement conditions of the TBM), and is displayed on the chromatogram. The peak of TBM only is obtained (see FIG. 5).

As a result, since the coexisting component W is not introduced into the sensor 30, the sensitivity of the sensor 30 is maintained in the optimum state. Therefore, the sensor 30
Without being affected by the degree of desorption of the coexisting component W from
It is possible to measure TBM with good accuracy, precision and reproducibility. That is, by a simple measurement operation of injecting a sample, it is possible to easily eliminate the influence of interfering components and perform accurate measurement. Also, by changing the measurement conditions without using a large amount of organic solvent,
It is possible to measure a wide range of odorant components.

Further, during the outflow gas elimination operation by the switching cock 26, no carrier gas is introduced into the sensor 30 through the separation column 22, but the blank column 24 and the switching cock 26 keep the sensor 30 in the meantime.
The carrier gas is always introduced in the
It is possible to eliminate the influence of pressure fluctuations and obtain a stable baseline on the chromatogram.

The detection of TBM by the sensor 30 is
This is due to the adsorption of TBM on the surface of the sensor 30,
By desorbing the BM from the surface of the sensor 30 under oxygen, the sensor 30 is regenerated and good sensitivity to the TBM is restored again. In the device 1 of this example, the sensor 3 is always
Since air as a carrier gas is supplied to 0,
The sensor 30 after the adsorption of the TBM is quickly regenerated by oxygen in the air. Therefore, in the present device 1, the sensor 30 can be reproduced without providing a special sensor reproducing means. Further, since the sensor 30 in this device 1 is rapidly regenerated at the same time as TBM is adsorbed by the carrier gas, it can react sensitively to the TBM concentration. Further, since the quick regeneration is possible and the carrier gas is constantly in the regeneration state, the sensitivity of the sensor 30 can be maintained for a long time, and the sensor 30 which is a consumable item.
It also extends the service life (replacement time) of the.

As a standard for TBM, a fixed amount of TBM was diluted with n-hexane as a solvent to 0.4 ng / μl,
Two kinds of solutions of 2.0 ng / μl are prepared, and 2 μl and 10 ng of each are used as a TBM in a microsyringe of 5 μL. A chromatogram can be similarly obtained for the standard solution by the same operation as for the sample gas.

Two calibration curves were created from the TBM peaks of the chromatograms of the standard solutions of the two concentrations thus obtained, and the TBM concentration in the sample gas was calculated from the TBM peaks on the chromatogram of the sample gas. To calculate.

FIG. 6 shows the result of comparison between the TBM concentration measured by this method using the same sample gas and the concentration measured by the conventional gas chromatograph method. As is clear from FIG. 6, the measured value by the present device 1 and the measured value by the gas chromatograph method (detector: FPD) are in good agreement,
The accuracy of the measuring method by the present device 1 was confirmed, and it was found that this method can replace the conventional gas chromatograph method.

In the apparatus 1 and method of this example, inexpensive air is used without using nitrogen gas as a carrier gas,
Further, since hydrogen gas is not used as the fuel gas, the running cost for odorant measurement can be reduced. In addition, since hydrogen gas is not used at the time of detection unlike the conventional gas chromatograph method using an FPD detector,
The odorant component can be safely measured.

In this example, the measurement of the concentration of TBM as an odorant has been described, but the other odorant T
For HT and DMS, the concentration in city gas can be similarly measured.

Next, a modified example of the device 1 will be described. Device 1
The sample injection part 8 of the switching cock 4 is equipped with a measuring pipe 42 as an introduction part of the sample gas and the standard gas as shown in FIG.
4 can be used. In the apparatus 31 of FIG. 7, the sample gas is introduced from the sample gas sampling pipe 33 by opening the stop valve 32. Sample gas sampling tube 3
3 is connected to a city gas supply conduit or the like. In addition, the standard gas used for the quantification is gas cylinders 34 and 36 filled with standard gas of two predetermined concentrations, respectively.
Is introduced by opening the stop valves 38, 40.

Introduction of the sample gas and the standard gas into the separation column 22 in the apparatus 31 of this embodiment is carried out as follows.
When the sample gas is introduced, by operating the switching cock 44, the flow path shown by the solid line of the switching cock 44 in FIG. As a result, a fixed amount of the sample gas is collected in the measuring pipe 42. After the sample gas is collected, the stop valve 3
2 is closed and the switching cock 44 is operated to cause the carrier gas from the air cylinder 2 to push out the sample gas in the measuring pipe 42 through the flow path 45 by the flow path shown by the dotted line of the switching cock 44 in FIG. 7. The sample gas, together with the carrier gas, reaches the separation column 22 through the column flow path 47. The separation column 22 and the subsequent steps are the same as those of the device 1 of the first embodiment described above.

On the other hand, also when introducing the standard gas, similarly, the standard gas is sampled into the measuring pipe 42 by the operation of the switching cock 44, and then the carrier gas is introduced into the measuring pipe 42 to the separation column 22. Guide the standard gas.

This device 31 has the advantage that the sample gas or standard gas can be introduced into the separation column without using a microsyringe or a gas tight syringe. Further, it is possible to save the trouble of collecting the sample gas and the standard gas.

Further, stop valves 32, 38 for supplying the sample gas and the standard gas in the above-mentioned device 31 are provided.
The opening / closing operation of 40 is performed by the solenoid valves 48, 4 of the device 55 shown in FIG.
9 and 50, the switching operation of the switching cocks 26 and 44 can be performed by the pneumatically driven valve by the electromagnetic switches 52 and 54. Solenoid valves 48, 4 in FIG.
8, 50 and electromagnetic switches 52, 54 are controlled by a computer, respectively, and operate according to a timer or a predetermined program. Therefore, the stop valve opening / closing operation and the cock switching operation can be automated.
The automatic operation of No. 5 becomes possible, and further labor saving of odorant measurement can be achieved. In particular, the device 5 of FIG.
In No. 5, since no dangerous hydrogen gas is used, unattended continuous automatic operation can be performed at night and the odor control can be improved. In addition, no complicated measurement operation or cock operation is required, and odor management can be simplified.

[0040]

According to the present invention, the test gas is introduced into the air flow passage as the carrier gas, and the coexisting component other than the odorant component is separated by the separation column and the switching cock to remove only the odorant. Is introduced into the sensor to measure the odorant component. Therefore, it is possible to measure the concentration of the odorant with accuracy and accuracy by a simple measurement operation. Also, without using expensive detectors and reagents, the sensor is constantly regenerated by oxygen in the air as a carrier gas, and the detection sensitivity of the sensor is good for a long period of time without providing a sensor regenerating means. Therefore, the measurement cost can be reduced.

[Brief description of drawings]

FIG. 1 is a piping diagram of the device of the present invention.

FIG. 2 is an enlarged cross-sectional view of a sample injection part of the device of the present invention.

FIG. 3 is a flow chart of TBM measurement in the apparatus of the present invention.

FIG. 4 is an example of a chromatogram obtained by TBM measurement.

FIG. 5 is an example of a chromatogram obtained by TBM measurement.

FIG. 6 is a graph showing the correlation between the measurement results of TBM concentration by the method using the device of the present invention and the conventional gas chromatography method.

FIG. 7 is a diagram showing another example of the device of the present invention.

FIG. 8 is a diagram showing another example of the device of the present invention.

[Explanation of symbols]

 6 ... Air supply flow path 8 ... Test gas introduction section 22 ... Separation and removal section 30 ... Sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Setoguchi 1-3-5 Senba Nishi, Minoh City, Osaka Prefecture Figaro Giken Co., Ltd.

Claims (1)

[Claims] 1. A supply flow path for air as a carrier gas, and a test gas introduction section capable of intermittently introducing a fixed amount of a test gas while allowing a constant flow rate of air to flow through the supply flow path. A separation / removal unit that separates the odorant component and the coexisting component in the test gas to release the coexisting component out of the system, and a semiconductor gas sensor that detects the odorant component separated from the test gas. A gas odorant measuring device characterized by being provided.