JP2682882B2 - Method and apparatus for identifying gas type of combustible gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to soil for measuring and maintaining gas transportation pipelines in the city gas industry and LPG industry, which mainly use natural gas, coal gas, and petroleum gas. The present invention relates to a method and an apparatus for identifying whether the combustible gas component contained in the gas leaked to the ground or the surface of the earth via, for example, is derived from city gas, fermentation gas, or LPG. .

[Prior Art] As a conventional method and apparatus for identifying a gas type of a combustible gas, a specific component group is detected and identified based on it, or a gas chromatograph that is a component separation type analyzer for gas components. There is known a method in which the measurement is performed by an operator and identification is performed based on a chromatogram peak pattern which is an analog output of the analysis.

[Problems of Prior Art] FIG. 1 illustrates a conventional gas type identification method in the form of a graph. This is an example of a discriminating combustible gas detector that uses the contact combustion method as the operating principle of the detector.This detector is a detector element that is sensitive to all combustible gases including CH _4. It uses a two-element system of detection element B that is sensitive to all combustible gas components except A and CH _4, and calculates the output values of detection elements A and B, specifically, the output value of element A and A method of identifying the gas species based on the level of the ratio with the output value of the element B is adopted. In other words, this is nothing but a method of identifying gas species by the concentration ratio of CH ₄ in all combustible gas components, but when alcohols or esters are mixed in the combustible gas components, , It may not be possible to accurately identify gases. More specifically, when CH ₄ derived from the fermentation gas and alcohol are mixed, it may be erroneously recognized as city gas.

In addition, for example, the chromatogram peak pattern of the sample gas obtained using the gas chromatograph method is compared with the chromatogram peak pattern of city gas or LPG that has been measured in advance, and the measurer visually checks the degree of coincidence of the peak patterns. There is also a method to identify the gas type by judging with, etc., but this method is a relatively high concentration city gas,
It is a powerful method if the fermentation gas and LPG exist independently, but if the fermentation gas and LPG are mixed, it may be erroneously recognized as city gas, and the experience of the measurer There is an inconvenient aspect such that the identification result may differ from person to person due to the difference in the above.

Furthermore, none of the conventional methods and apparatuses for identifying the gas type of combustible gas has the disadvantage that accurate identification may not be possible because the atmospheric composition and the gas composition in soil are not taken into consideration. ing. Figure 2 shows the results of an investigation of atmospheric gas in the soil collected at more than 200 points in Tokyo. Soil atmosphere gas may contain a large amount of CH ₄ which is a combustible gas component and CO ₂ which is an inorganic gas component generated through the decomposition and fermentation process of organic substances contained in soil, and CH ₄ has the highest value. A value of about 50 ppm and a maximum value of about 10% for CO ₂ have been detected. In addition, CH ₄ is
It contains 1.6 ppm, and ignoring the background value of these flammable gas components contained in the soil or the atmosphere may lead to incorrect identification of the gas species from which the flammable gas component was derived. Table 1 shows an example of the composition of city gas, fermentation gas, LPG and dry air. For example, the concentration of combustible gas components in the sample gas collected at the point where a small amount of LPG leaked into the soil was CH. _{In the case of 4} , several tens of ppm, C ₃ H ₈ and C ₄ H ₁₀ may be several ppm each, but at this time, if the background value of CH ₄ is not taken into consideration, it is contained in this sample gas. There are some problems, such as the mistaken origin of combustible gas components as city gas.

The present invention is to solve the problems of the above conventional example,
The combustible gas components contained in the gas leaked to the ground or the surface via soil etc. are city gas, fermentation gas, LP
It proposes a method and an apparatus for identifying whether the gas is from any of G gas species.

[Means for Solving the Problems] As a means for achieving the above object, the present invention uses a gas of unknown origin that leaks into the ground or the surface of the earth via soil or the like, and is contained in this sample gas. Combustible gas components such as CH ₄ and inorganic gas components such as CO ₂ ,
Measuring the concentration of each individual component, said in the measured value of the concentration of the sample gas, to calculate the concentration ratio of each of the combustible gas component when relative to the CH ₄ concentration value, among the measured density values CH ₄
The concentration value, the concentration value of the combustible gas components other than CH ₄ and the CO ₂ concentration value, and the calculated value of the concentration ratio of the individual combustible gas components contained in the sample gas calculated above, the sample We propose a method to identify whether the source of flammable gas components in gas is city gas, fermentation gas, or LPG.

In addition, regarding the device that identifies the type of flammable gas,
In order to achieve the above-mentioned object, the combination of each component described below is proposed.

A sample introduction pipe for collecting a gas of unknown origin that leaks into the ground or the surface of the earth via soil etc. as a sample gas, and a sample introduction pump provided in the middle of the sample introduction pipe,
CH ₄ , C ₂ H ₆ , and C in the sample gas, which were provided in the middle of the sample introduction pipe and before or after the sampling pump.
_A separate detector for separately detecting ₃ H ₈ , C ₄ H ₁₀ and CO ₂ , a converter for converting the electric signal output from the separate detector into the concentration value of each component, and the converter From the concentration value of each of the components, the flammable gas component contained in the sample gas, city gas, fermentation gas, a determination circuit for determining whether from any gas species of LPG, and the determination circuit Display that displays the judgment result based on.

[Example] FIG. 3 shows an example of an apparatus for identifying a gas type of a combustible gas, and the reference numeral 1 is a sample of a gas of unknown origin that leaks to the ground or the surface via soil or the like. This is a sampling nozzle equipped with a filter for removing dust and water in the sample gas when collecting as a gas.

Reference numeral 2 is a separation detector inlet side sample introduction pipe which is connected to the sampling nozzle and through which the sample gas passes to the separation detector downstream.

Reference numeral 3 denotes a separation detector outlet-side sample introduction pipe which is connected to the separation detector output side and through which the sample gas passes to the downstream sampling pump.

Reference numeral 4 is a suction-type sampling pump for introducing the sample gas into the separation detector through the sampling nozzle and the sample introduction pipe.

Reference numeral 5 denotes CH ₄ , C ₂ H ₆ , C ₃ H ₈ , C ₄ H ₁₀ and CH ₄ contained in the sample gas introduced by the suction-type sampling pump, which passes through the sampling nozzle and the sample introduction pipe. CO
It is a separate detector that detects each component such as ₂ .

Reference numeral 6 denotes a converter for converting the electric signal output from the classification detector into the concentration value of each component.

7 determines whether the combustible gas component contained in the sample gas is derived from city gas, fermentation gas, or LPG based on the concentration values of the components converted by the converter. This is a determination circuit that does.

Reference numeral 8 is a display device that displays the determination result based on the determination circuit.

Reference numeral 9 is an electric signal corresponding to each of the components, which is an output of the classification detector.

10 is a density value corresponding to each of the components, which is the output of the converter.

Here, the separation detector is configured to detect each of the components, that is, CH.
_{4, C 2 H 6, C} 3 H 8, C 4 to detect the H ₁₀ and CO ₂ individually, can also be used which have any kind of detector as long as it is converted into an electrical signal , For example, a gas sensor sensitive only to CH ₄ , a gas sensor sensitive only to C ₂ H ₆ , a gas sensor sensitive only to C ₃ H ₈ , a gas sensor sensitive only to C ₄ H ₁₀ , and a CO ₂ only. A sensitive gas sensor may be arranged in the sample gas introduction pipe to be a separate detector, but the inventor used only two gas chromatograph type gas separation detectors having different lengths as separate detectors. .

FIG. 4 shows an embodiment of a classification detector, which is designated by reference numeral 2,
Reference numeral 2'denotes a sample introduction tube on the inlet side of the separation detector.

Reference numerals 11 and 11 'are sample gas line valves that are opened only when the sample adoption pump 4 is in operation.

Reference numerals 12 and 12 'are sample loops provided downstream of the sample gas line valve.

Reference numerals 13 and 13 'denote three-way valves, which connect the sample loop side and the downstream sample detector outlet side sample introduction pipe when the sampling pump 4 is in operation.

 Reference numerals 3 and 3 ′ are sample detector tubes on the outlet side of the separation detector.

14 is a carrier gas cylinder filled with He gas and made of stainless steel with an internal volume of 75 ml and a filling pressure of 150 kg / cm ² (gauge pressure).

Reference numeral 15 is a shutoff valve for preventing outside air from entering the inside of the classification detector when the carrier gas cylinder 14 is replaced.

Reference numeral 16 is a small primary pressure reducing valve for reducing the carrier gas pressure to 5 kg / cm ² (gauge pressure).

Reference numeral 17 is a small secondary pressure reducing valve for further reducing the carrier gas pressure reduced through the primary pressure reducing valve to 1 kg / cm ² (gauge pressure).

18 and 18 'are carrier gas lines made of stainless steel.

Reference numerals 19, 19 ', 20, and 20' are flow path resistance pipes provided downstream of the carrier gas line and made of stainless steel pipes that are narrowed down.

21 and 21 'are CH ₄ , C ₂ H ₆ , and C contained in the sample gas.
₃ H _8, a n-C ₄ H _10, gas separation tube to separate i-C ₄ H ₁₀ and CO _2, 21 is, CH ₄ in the sample gas, C ₂ H ₆ preliminary CO ₂
Have a function of separating each other and other gas components. Further, 21 'has a function of separating the _{C 3 H 8, n-C} 4 H 10 and i-C ₄ to H ₁₀ together and the other gas components in the sample gas. Here, the n-C ₄ H ₁₀ and the i-C ₄ H ₁₀ is a compound having a relationship of structural mutually isomers, especially in the case where no distinction is expressed as C ₄ H _10.

Reference numerals 22 and 22 'are reference gas separation tubes having the same flow resistance as the gas separation tubes 21 and 21'.
Only carrier gas flows through 2 and 22 '.

23, 23 'is a thermal conductivity type detector, the components separated by the gas separation tubes 21, 21' and the reference gas separation tube 22,
It has the function of converting the difference in thermal conductivity from the carrier gas flowing through 22 'into an electric signal.

24 and 24 'are sample gas injection valves, one end of which is connected between the sample gas line valve and the sample loop, and the other end of which is connected to the flow path resistance tube (19, 19') and It is connected between the gas separation pipes 21 and 21 '.

Here, as the gas separation tubes 21 and 21 ′, commercially available fused silica capillary columns can be used, but in the experiments of the inventor, columns in which porous polymer beads were applied to the inner surface of the fused silica capillary columns were suitable for the purpose of use. It was something to do. The column length is 8 m in the gas separation pipe 21 for separating CH ₄ , C ₂ H ₆ and CO ₂ , C ₃ H ₈ , nC ₄ H ₁₀ and iC.
₄ H ₁₀ in the gas separation tube 21 separates' 2m was optimal.
The analog outputs of the thermal conductivity type detectors 23 and 23 'obtained under these conditions are shown in FIGS. 5 (1) and 5 (2). Also, the exchange 6
The calibration, a known concentration of _{CH 4, C 2 H 6,} C 3 H 8, n-C 4 H 10, i
Although a standard gas containing -C ₄ H ₁₀ and CO ₂ may be prepared and the standard gas may be measured, the conversion factor of the concentration of each component to the electric signal and the detection time may be obtained in advance. , The thermal conductivity type detectors 23 and 23 'used for the separation detector 6 are also sensitive to O ₂ and N ₂ in the atmosphere, and the concentration of the sum of O ₂ and N ₂ is used. Always uses a constant atmosphere as standard gas, and by analyzing the atmosphere, CH ₄ , C ₂ H ₆ , C
_{3 H 8, n-C 4} H 10, i-C 4 H 10 and CO _2, since the determination of the detection time and said it is possible to obtain a conversion factor of concentration versus electrical signals of each component, provides a special standard gas cylinder Moreover, the measurement work can be extremely simplified.

If it is desired to minimize the separation detector 5, the "small gas chromatograph device" described in Japanese Patent Publication No. 58-195149 may be used.

The example has the above-mentioned configuration, and from the measurement data of CH ₄ , C ₂ H ₆ , C ₃ H ₈ , C ₄ H ₁₀ and CO ₂ contained in the sample gas, these combustible gas components are , Fermentation gas,
The gas parameter of the LPG is determined, and the measurement parameters and measurement flow used in the determination circuit 7 for gas type identification will be described below.

A) Extraction of sample gas derived from air Since some combustible gas components of the sample gas may contain only combustible gas below the background level of the atmospheric gas in the soil, this is extracted as the sample gas derived from air. Necessary and sufficient parameters for performing this measurement, the CH ₄ concentration value is two parameters of the density values of the _{C 2 H 6 + C 3 H} 8 + C 4 H 10. Specifically, when CH ₄ is contained below the background level and does not contain C ₂ H ₆ + C ₃ H ₈ + C ₄ H ₁₀ , that is, the sample gas containing no combustible gas component is identified as air.

B) Extraction of sample gas derived from LPG Since some sample gas may contain only combustible gas components derived from LPG, this is extracted as sample gas derived from LPG. The parameters necessary and sufficient for making this determination are the same as those in the previous item (a). Specifically, it contains CH ₄ below the background level and C ₂ H
Sample gas containing ₆ + C ₃ H ₈ + C ₄ H ₁₀ above a certain concentration level
Identify as LPG.

C) Identification of sample gas derived from city gas and fermented gas As shown in Table 1, both fermented gas and city gas are gas species containing CH ₄ as the main combustible gas component. In order to distinguish between the two while considering them, there are two points: ・ whether a combustible gas component other than CH ₄ is contained ・ whether it contains a large amount of CO ₂ produced in the fermentation process. It will be a point.

Therefore, the concentration ratio of C ₂ H ₆ , C ₃ H ₈ , and C ₄ H ₁₀ when CH ₄ is 100, which is the combustible gas component contained in the sample gas other than the sample gas identified as air or LPG. To obtain y (C ₂ H ₆ ), y (C ₃ H ₈ ), y (C ₄ H ₁₀ ),
y (C ₂ H ₆ ) + y (C ₃ H ₈ ) + y (C ₄ H ₁₀ ) and CO ₂ concentration are also used as parameters to distinguish between city gas and fermentation gas.

Specifically, y (C ₂ H ₆ ) + y (C ₃ H ₈ ) + y (C ₄ H ₁₀ ).
Is a value within a certain level range, and y (C
₂ H ₆ ) is above a certain level and does not contain CO ₂ , in other words, the gas component contained in the sample gas
When CH ₄ is the main component and C ₂ H ₆ , C ₃ H ₈ and C ₄ H ₁₀ are contained at a certain level and CO ₂ is not contained, the composition of the flammable gas component in the sample gas is It can be judged that it matches very well with city gas, and this sample gas and city gas are distinguished.

In addition, when y (C ₂ H ₆ ) + y (C ₃ H ₈ ) + y (C ₄ H ₁₀ ) is less than a certain level, that is, the combustible gas component contained in the sample gas is CH ₄ As the main component, C ₂ H ₆ , C ₃ H
_{8 When it} contains almost no C ₄ H ₁₀ , it can be judged that it is in agreement with the fermentation gas, and this sample gas is distinguished from the fermentation gas.

D) Identification of sample gas in which two or more types of city gas, fermentation gas, and LPG are mixed According to the above-mentioned a), b), and c), if the sample gas contains combustible gas components, it is the source. It is possible to identify whether the gas species is city gas, fermentation gas, or LPG. If it does not contain combustible gas components,
Differentiate from air. However, in some cases, the combustible gas component contained in the sample gas may be derived from two or more gas species. In this case, the gas species identification should be in addition to the parameters used in (c) above, and y (C ₂ H It is achieved by introducing ₆ ). The target of this identification is a sample gas other than the sample gas identified as air or LPG.

Identification of sample gas in which fermentation gas and LPG are mixed y (C
₂ H ₆ ) + y (C ₃ H ₈ ) + y (C ₄ H ₁₀ ) is a large value above a certain level, and y (C ₂ H ₆ ) is below a certain level, in the sample gas Since it is a case where only CH ₄ , C ₃ H ₈ and C ₄ H ₁₀ are contained as the combustible gas component contained in
Judging from the gas composition in Table 1, this sample gas is identified as a mixture of fermentation gas and LPG.

Identification of sample gas in which city gas and LPG are mixed y (C
₂ H ₆ ) + y (C ₃ H ₈ ) + y (C ₄ H ₁₀ ) is a large value above a certain level, y (C ₂ H ₆ ) is above a certain level, and CO ₂ otherwise the a combustible gas component contained in the sample _{gas, CH 4, C 2 H 6} , C 3 H 8, C 4 H
Means that ₁₀ exists, as the gas species derived from,
This is the case when city gas and LPG are mixed.

Identification of sample gas in which city gas and fermentation gas are mixed y (C ₂ H ₆ ) + y (C ₃ H ₈ ) + y (C ₄ H ₁₀ ) is a value within a certain level range, and y (C ₂ H ₆ ) exceeds a certain level and contains CO ₂ , in other words, the components contained in the sample gas are CH ₄ as the main component, and C ₂ H ₆ , C ₃ H ₈ , C
_{When 4} H ₁₀ is contained at a certain level or higher and contains CO ₂ , it can be judged that the composition of the combustible gas component in the sample gas is in very good agreement with city gas, and since CO ₂ is contained, This sample gas is identified as a mixture of city gas and fermentation gas.

Identification of sample gas in which city gas, fermentation gas, and LPG are mixed y (C ₂ H ₆ ) + y (C ₃ H ₈ ) + y (C ₄ H ₁₀ ) is a large value above a certain level, and y (C C ₂ H ₆₎ is not less a certain level or higher, and if it contains CO _2, as a combustible gas component contained in the sample _{gas, CH 4, C 2 H 6} , C
_{Since 3} H ₈ and C ₄ H ₁₀ are present and CO ₂ is included, the gas species derived from are 3 types of city gas, fermentation gas, and LPG. This is the case.

FIG. 6 shows, as an example, CH ₄ , C ₂ H ₆ , and C ₃ H in the sample gas.
₈ , C ₄ H ₁₀ and CO ₂ were measured, and the above five parameters were measured: CH ₄ concentration, C ₂ H ₆ + C ₃ H ₈ + C ₄ H ₁₀ concentration, CO ₂ concentration,
It is a determination flow for gas type identification configured using y (C ₂ H ₆ ) + y (C ₃ H ₈ ) + y (C ₄ H ₁₀ ), y (C ₂ H ₆ ). Using this flow, CH ₄ , C ₂ H ₆ , and C ₃ H in the sample gas
_The combustible gas components contained in the sample gas can be measured by simply measuring ₈ , C ₄ H ₁₀ and CO ₂ and obtaining the concentration ratio by a simple calculation.
It is possible to identify whether the gas is derived from city gas, fermentation gas, or LPG.

[Effects of the Present Invention] The effects obtained by the method of identifying the gas species of the combustible gas, which is one of the present invention, are as described below.

a. Anyone can clearly and clearly identify whether the combustible gas component contained in the sample gas originates from city gas, fermentation gas, or LPG.

b. Leakage investigation work that occurs due to misidentification of gas species can be reduced.

Subsequently, the effect obtained by the device for identifying the gas species of the combustible gas is as described below.

c. Since it is extremely easy to assemble it as an on-site portable automatic analysis / identification device, the use of this device can reduce the burden of leak investigation on site.

d. Even if the operator has no knowledge of analysis and no experience of leak investigation, it will be possible to identify the gas species without error and in a short time.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a graph of a conventional gas type identification method. Figure 2 is a graph showing the analysis results of atmospheric gas in the soil collected at more than 200 points in Tokyo. FIG. 3 is an explanatory diagram of an apparatus for identifying a gas type of combustible gas. FIG. 4 is an explanatory diagram of the classification detector. FIGS. 5 (1) and 5 (2) are explanatory diagrams of the analog output of the thermal conductivity type detector. FIG. 6 is an explanatory diagram of the determination flow. 1 …… Sampling nozzle 2 …… Separation detector inlet side sample introduction pipe 3 …… Separation detector outlet side sample introduction pipe 4 …… Pump 5 …… Separation detector 6 …… Exchanger 7 …… Judgment circuit 8 …… Indicator 9 …… Electrical signal 10 …… Concentration value 11, 11 ′ …… Sample gas line valve 12, 12 ′ …… Sample loop 13, 13 ′ …… Three-way valve 14 …… Carrier gas bomb 15 …… Cutoff valve 16 ...... Primary pressure reducing valve 17 ...... Secondary pressure reducing valve 18,18 '...... Carrier gas lines 19, 19', 20,20 '...... Flow resistance pipes 21,21' ...... Gas separation pipes 22,22 ' ...... Reference gas separation pipe 23,23 '...... Thermal conductivity type detector 24,24' …… Sample gas injection valve

Claims (2)

(57) [Claims] 1. A sample gas is a gas of unknown origin that leaks into the ground or the surface of the earth via soil or the like, and combustible gas components such as CH ₄ contained in this sample gas and CO ₂ Inorganic gas components and the concentration of each individual component is measured, among the concentration measurement values of the sample gas, the concentration ratio of each combustible gas component when the CH ₄ concentration value is used as a reference is calculated, The CH ₄ concentration value in the measured concentration value, the magnitude of the concentration value of the combustible gas component other than CH ₄ and the CO ₂ concentration value, and the concentration ratio of the individual combustible gas components contained in the calculated sample gas From the magnitude of the calculated value, the origin of the combustible gas components contained in the sample gas is city gas, fermentation gas, LP
A method of identifying whether the gas type is G. 2. A sample introduction pipe for collecting, as a sample gas, a gas of unknown origin that leaks into the ground or the surface of the earth via soil or the like, and a sample adoption pump provided in the middle of the sample introduction pipe, a middle of the sample inlet tube and provided before or after the sampling pump, CH ₄ in the sample gas, C ₂ H _6, C
_A separation detector for separately detecting ₃ H ₈ , C ₄ H ₁₀ and CO ₂ , a converter for converting the electric signal output from the separation detector into the concentration value of each component, and the conversion by the converter. From the concentration value of each of the components, the flammable gas component contained in the sample gas, the city gas, the fermentation gas, a determination circuit for determining whether from any gas species of LPG, the determination circuit A device for identifying the gas type of combustible gas, which consists of an indicator that displays the judgment result based on.