JP3915280B2 - Gas sample introduction device for gas chromatograph - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas sample introduction device for a gas chromatograph, and more specifically, a gas chromatograph device for introducing a pure gas (a gas having a known single component of 100%) and performing a gas analysis in order to calibrate a calibration curve. The present invention relates to a gas sample introduction device for introducing the pure gas into a column.
[0002]
[Prior art]
In gas chromatographic analysis for a gas sample, a standard sample gas with a known component content is generally introduced into a column prior to analysis of the target sample gas, and quantitative analysis is performed based on the analysis result. A calibration curve is created. However, for fuel gas such as liquefied natural gas (LNG) and liquefied propane gas (LPG) produced overseas, the corresponding mixed standard gas is not available, so pure gas such as 100% methane and 100% ethane is used. Calibration curves may be created by pure gas analysis.
[0003]
In the pure gas analysis, pure gas is sampled in a measuring tube provided at the inlet of the column of the chromatograph apparatus so that a predetermined gas pressure is obtained, and the chromatogram analysis of the pure gas is performed to obtain a chromatogram on the acquired chromatogram. Find the peak area. Then, pure gas analysis is performed for a plurality of set gas pressures, and a calibration curve is created from the relationship between the gas pressures and peak areas.
[0004]
In such a pure gas analysis, in a conventional gas chromatograph gas sample introduction apparatus, it is necessary to introduce a pure gas into a column by the following procedure. That is, first, after closing the manual valve provided on the upstream side (pure gas inlet side) and the downstream side (column inlet side) of the metering tube, the pressure in the metering tube is reduced by suction. Next, the manual valve connected to the vacuum pump is closed, while the upstream manual valve is opened, and the needle valve is opened while monitoring the gas pressure in the measuring pipe, and pure gas is gradually introduced into the measuring pipe. When the gas pressure reaches the set gas pressure, the needle valve and the upstream manual valve are closed to hold the pure gas in the measuring pipe. Thereafter, the manual valve on the downstream side is opened and the carrier gas is introduced into the measuring tube from the upstream side, and the pure gas is expelled and introduced into the column.
[0005]
[Problems to be solved by the invention]
However, when trying to introduce pure gas after fully reducing the pressure of the metering tube, the pressure difference between the inside of the metering tube and the gas inlet is large, so that the pure gas is vigorously moved into the metering tube just by opening the needle valve slightly. The rate of increase in the gas pressure in the metering pipe increases. For this reason, it is difficult to set the gas pressure to the set gas pressure with high accuracy. Such operation requires a certain level of skill, and the accuracy depends on the skill of the analyst. There were many. In particular, when the set gas pressure is a small value, the pure gas often enters the measuring tube too much, and the measurement is repeated several times, resulting in a loss of time.
[0006]
The present invention has been made in view of these points, and the object of the present invention is to provide a gas chromatograph capable of increasing the accuracy of the gas pressure introduced into the measuring tube without depending on the experience and skill of the analyst. An object of the present invention is to provide a gas sample introduction device for a tomograph.
[0007]
[Means for Solving the Problems]
The gas sample introduction device for a gas chromatograph of the present invention, which has been made to solve the above problems,
a) a measuring tube;
b) a buffer tube in communication with the metering tube;
c) pressure measuring means for measuring the gas pressure in the flow passage in or near the measuring tube;
d) decompression means for decompressing the measuring tube and the buffer tube;
e) pure gas introduction means including an on-off valve capable of shutting off the flow of pure gas;
f) After reducing the pressure in the measuring pipe and the buffer pipe by the pressure reducing means, the pure gas is simultaneously introduced into the measuring pipe and the buffer pipe through the pure gas introducing means, and the measured value of the pressure measuring means rises to a predetermined value. Channel control means for closing the on-off valve when
It is characterized by having.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
In the gas sample introduction device according to the present invention, a buffer tube is provided in series or in parallel with the measuring tube. First, the flow path control means sucks down the gas remaining in both the measuring tube and the buffer tube by the pressure reducing means, and reduces the pressure. This decompression is not necessarily performed simultaneously. Thereafter, pure gas is simultaneously introduced into the metering tube and the buffer tube through the pure gas introduction means. When the metering tube and the buffer tube are connected in series, the introduced pure gas flows into the buffer tube through the metering tube in a reduced pressure state or into the buffer tube through the metering tube. When the metering tube and the buffer tube are connected in parallel, the introduced pure gas branches into the metering tube and the buffer tube that are in a reduced pressure state. In any case, since the volume of the portion where the pure gas is stored is larger than the volume of the measuring tube, if the flow rate of the introduced pure gas is constant, the volume in the measuring tube or The degree of increase in the gas pressure in the nearby flow path is moderate. The flow path control means closes the opening / closing valve of the pure gas introduction means and stops the introduction of the pure gas when the gas pressure measured by the pressure measurement means reaches a predetermined value. Since the rising speed of the measurement gas pressure is slow, the gas pressure of the pure gas in the measuring tube is close to a predetermined value.
[0009]
Moreover, in the gas sample introducing device according to the present invention, the pure gas introducing means can be configured such that a resistance tube for limiting the flow rate can be selectively inserted. When the resistance tube is inserted, the pure gas introduction flow rate itself decreases, so that the degree of increase in the gas pressure in the measuring tube or in the flow path in the vicinity thereof becomes even slower. Therefore, accurate measurement of pure gas becomes easier.
[0010]
In addition, since the increase rate of the gas pressure in the measuring tube becomes slower as the volume of the buffer tube is larger, accurate pure gas measurement can be easily performed. On the other hand, since the time required for measurement becomes longer and the amount of pure gas required increases, it is better to set the volume appropriately according to the balance.
[0011]
【The invention's effect】
As described above, according to the gas sample introduction device for a gas chromatograph according to the present invention, the gas pressure of the pure gas collected in the measuring tube does not greatly exceed the set gas pressure, and the pure gas can be accurately measured. . In addition, since pure gas can be collected automatically, no experience or skill is required for operation, and there is no measurement failure, so no time is wasted.
[0012]
【Example】
An embodiment of a gas sample introduction device for gas chromatography according to the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram centering on the flow path of a gas chromatograph apparatus provided with the gas sample introduction apparatus of the present embodiment. This gas chromatograph apparatus is roughly divided into a selection unit 1 for selecting and supplying a pure gas used when preparing a calibration curve and a sample gas to be analyzed, and a predetermined amount of gas (pure gas or sample gas) is collected. A gas sample introduction unit including a measuring unit 2 and an analysis unit 3 including two separation columns. Hereinafter, the configuration of the selection unit 1, the measurement unit 2, and the analysis unit 3 will be described.
[0013]
(1) The first six-way solenoid valve V1 is installed in the center of the selector 1 and the first six-way solenoid valve V1 can be switched between two connection states indicated by solid lines and dotted lines in FIG. Yes. Between the pure gas inlet 11 and the port a of the first six-way solenoid valve V1, a first two-way solenoid valve SV1 and a first resistance pipe 13 connected in parallel and a second two-way solenoid valve SV2 are connected in series. It is connected to the. A third two-way solenoid valve SV3 is connected between the sample gas inlet 12 and the port e of the first six-way solenoid valve V1. The port b of the first six-way solenoid valve V1 reaches the discharge port (VENT) through the second resistance tube 14 and the diaphragm pump 15. Further, the port d of the first six-way solenoid valve V1 reaches the discharge port via the vacuum pump 16.
[0014]
(2) The first and second ten-way solenoid valves V2 and V3 are placed at the center of the metering section metering section 2, and the first and second ten-way solenoid valves V2 and V3 are shown by solid lines in FIG. And can be switched to two connection states indicated by dotted lines. The first and second precolumns PC1 and PC2 are connected between the ports a and e of the two-way solenoid valves V2 and V3, respectively, and the first and second measuring pipes 23 are connected between the ports g and j, respectively. 24 are connected to each other. The volume of the first and second measuring tubes 23 and 24 is, for example, about 2 mL. The ports f of the first and second ten-way solenoid valves V2 and V3 are connected to the carrier gas inlet 25, respectively, and the port c is connected to the carrier gas inlet 25 via the first and third dummy columns DC1 and DC3, respectively. Has been. The port i of the first ten-way solenoid valve V2 is connected to the port f of the first six-way solenoid valve V1, and the port h of the first ten-way solenoid valve V2 is connected to the port i of the second ten-way solenoid valve V3. ing. The port h of the second ten-way solenoid valve V3 is connected to the port c of the first six-way solenoid valve V1 through the buffer tube 21 and the fourth two-way solenoid valve SV4 together with the fifth two-way solenoid valve SV5 reaching the discharge port. ing. Further, a pressure gauge 22 is also connected to the port h of the twentieth electromagnetic valve V3. The volume of the buffer tube 21 is preferably about ten times or more that of the first and second measuring tubes 23 and 24. When the volume of the measuring tubes 23 and 24 is about 2 mL, the volume may be set to 20 to 30 mL.
[0015]
(3) The first choke column CC1 and the first main column MC1 are connected to the port b and the port d of the analysis unit first ten-way solenoid valve V2, respectively, and the port b and the port d of the second ten-way solenoid valve V3. The second choke column CC2 and the fourth main column MC4 are connected to each other, and the outlet of the first main column MC1 is connected to the port f of the second six-way solenoid valve V4. The second and third main columns MC2 and MC3 are connected to the port a and the port e of the second six-way solenoid valve V4, respectively, and the outlets of both the main columns MC2 and MC3 merge to form the first TCD (thermal conductivity type detection). Container) 31 is introduced into the sample-side cell s1. Further, the outlets of the second choke column CC2 and the fourth main column MC4 are joined and introduced into the sample side cell s2 of the second TCD 32. The port b and the port d of the second six-way solenoid valve V4 are directly connected, and the port c is connected to the carrier gas inlet 25 via the second dummy column DC2. The carrier gas flows through the reference column RC1 in the reference side cells r1 and r2 of the first and second TCDs 31 and 32. The detection signals of the first and second TCDs 31 and 32 are input to the signal processing unit 33, where signal processing as described below is performed.
[0016]
In addition, a control unit 41 is provided to control the electromagnetic valves SV1 to SV5, V1 to V4 and other parts, and the control unit 41 is provided with an operation unit 42 including a keyboard and various switches. The control unit 41 is embodied by, for example, a personal computer, and controls the operation of the solenoid valves SV1 to SV5 and V1 to V4 according to a predetermined control program while monitoring the gas pressure with the pressure gauge 22 to be described later. Perform gas analysis. The function of the signal processing unit 33 can also be realized by the same personal computer.
[0017]
Next, the operation when performing a pure gas analysis for calibration prior to the analysis of the sample gas in this gas chromatograph apparatus will be described. In the pure gas analysis, the analyzer sets 3 to 5 points of the set gas pressure for creating a calibration curve via the operation unit 42.
[0018]
When the pure gas analysis is started, first, the second and fifth two-way solenoid valves SV2 and SV5 are closed, the fourth two-way solenoid valve SV4 is opened, and the first six-way solenoid valve V1 is indicated by a dotted line in FIG. The connected state, the first and second ten-way solenoid valves V2, V3 are brought into a connected state indicated by a solid line. At this time, the vacuum pump 16-fourth two-way solenoid valve SV4-buffer pipe 21-second metering pipe 24-first metering pipe 23-second two-way solenoid valve SV2 communicate with each other, and the second two-way solenoid valve SV2. In FIG. Therefore, when the vacuum pump 16 is driven, the residual gas in the flow path is sucked by the vacuum pump 16 and discharged to the outside, and the buffer pipe 21 and the first and second measuring pipes 23 and 24 are depressurized. It becomes a state.
[0019]
After a predetermined time has elapsed since the vacuum pump 16 was driven, the fourth two-way solenoid valve SV4 is closed and the first and second two-way solenoid valves SV1 and SV2 are opened. Then, the pure gas inlet 11-first two-way solenoid valve SV1-second two-way solenoid valve SV2-first six-way solenoid valve V1-first metering pipe 23-second metering pipe 24-buffer pipe 21-fourth second. The one-way solenoid valve SV4 communicates, and the flow path is closed at the fourth two-way solenoid valve SV4. Since the gas pressure in the pure gas inlet 11 is much higher than the gas pressure in the buffer pipe 21 and the first and second metering pipes 23, 24, the pure gas supplied to the pure gas inlet 11 is The first and second two-way solenoid valves SV1 and SV2 are filled into the first and second measuring pipes 23 and 24 and the buffer pipe 21.
[0020]
By repeating the above-described decompression and introduction of pure gas a plurality of times, undesired gas remaining in the first and second measuring pipes 23 and 24 and the buffer pipe 21 or the pipes connecting them can be removed. Replace with pure gas.
[0021]
When collecting the pure gas in an amount corresponding to the set gas pressure in the first and second measuring pipes 23 and 24 after a predetermined number of repeated operations, the control unit 41 monitors the gas pressure with the pressure gauge 22 and monitors the gas pressure. The opening and closing of the first and second two-way solenoid valves SV1 and SV2 are controlled. That is, when the set gas pressure is high, that is, when a relatively large amount of pure gas is introduced into the first and second measuring pipes 23 and 24, both the first and second two-way solenoid valves SV1 and SV2 are opened. . Then, the pure gas flows into the first and second measuring tubes 23 and 24 with a large flow rate without passing through the resistance tube 13, passes through them, and flows into the buffer tube 21. The volume of the buffer tube 21 is much larger than the sum of the volumes of the two measuring tubes 23 and 24 and the volumes in the other pipes. For this reason, since the pure gas that has flowed in is most consumed to fill the buffer tube 21, the degree of increase in the gas pressure at the measurement point by the pressure gauge 22 is relatively gradual. Therefore, the first two-way solenoid valve SV1 is closed when the measured gas pressure reaches an appropriate gas pressure set to be lower than the set gas pressure. Then, the flow rate of the pure gas passing through the second two-way solenoid valve SV2 is limited by the resistance tube 13 and is remarkably reduced, so that the degree of increase in the gas pressure becomes more gradual. Then, the second two-way solenoid valve SV2 is closed at the time when the gas pressure reaches the set gas pressure or immediately before reaching the set gas pressure. Thereby, the gas pressure in the 1st, 2nd measuring pipes 23 and 24 becomes substantially the set gas pressure.
[0022]
When the set gas pressure is low, the first two-way solenoid valve SV1 is closed from the beginning to introduce pure gas into the first and second measuring pipes 23 and 24 and the buffer pipe 21 with a small flow rate. In this case, since the increase in the gas pressure is very gradual, the second two-way solenoid valve SV2 is closed at the time when the gas pressure reaches the set gas pressure or immediately before reaching the set gas pressure.
[0023]
If pure gas in an amount corresponding to the set gas pressure is collected in the first and second measuring pipes 23 and 24 in this way, the first and second ten-way solenoid valves V2 and V3 are indicated by dotted lines in FIG. Switch to the connection state shown. Then, the pure gas collected in the first and second measuring tubes 23 and 24 is pushed out by the carrier gas supplied from the carrier gas inlet 25 to the ports f of the first and second ten-way solenoid valves V2 and V3. Are introduced into the first and fourth main columns MC1 and MC4 through the first and second precolumns PC1 and PC2, respectively. The pure gas that has passed through the first main column MC1 is introduced into either the second main column MC2 or the third main column MC3 according to the connection state of the second six-way solenoid valve V4, passes through it, and passes through the first TCD31. To the sample side cell s1. On the other hand, since the carrier gas always flows through the reference-side cell r1 of the first TCD 31, a detection signal corresponding to the difference in thermal conductivity between the two is extracted from the first TCD 31.
[0024]
In the second TCD 32, the pure gas that has passed through the fourth main column MC4 flows into the sample side cell s2, and the carrier gas flows through the reference side cell r2. Therefore, the second TCD 32 takes out a detection signal corresponding to the difference in thermal conductivity between the two. The signal processing unit 33 receives the detection signals from the first and second TCDs 31 and 32, creates a chromatogram, detects a peak due to pure gas, and obtains the peak area.
[0025]
When a series of analyzes as described above is completed for one set gas pressure, pure gas analysis is performed for the other set gas pressures in the same procedure, and the peak area is obtained. When the analysis for all the set gas pressures is completed, a calibration curve is created from the relationship between the set gas pressure and the peak area, and this is stored in the memory. FIG. 2 is an example of a calibration curve obtained in this way.
[0026]
When the sample gas supplied to the sample gas inlet 12 is introduced, the first and second measuring pipes 23 and 24 are depressurized, and then the first six-way solenoid valve V1, first, and twentyth. One-way solenoid valves V2 and V3 may be connected to each other as shown by a solid line in FIG. 1, and sample gas may be poured into the first and second measuring tubes 23 and 24.
[0027]
The above embodiment is merely an example, and it is obvious that appropriate modifications and corrections can be made in accordance with the spirit of the present invention.
[Brief description of the drawings]
FIG. 1 is a configuration diagram centering on a flow path of a gas chromatograph apparatus provided with a gas sample introduction apparatus according to an embodiment of the present invention.
FIG. 2 is a view showing an example of a calibration curve obtained by this gas chromatograph apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Selection part 2 ... Metering part 3 ... Analysis part 11 ... Pure gas inlet 13 ... Resistance pipe 16 ... Vacuum pump 21 ... Buffer pipe 22 ... Pressure gauge 23, 24 ... Metering pipe 25 ... Carrier gas introduction port 31, 32 ... TCD
33 ... Signal processing unit 41 ... Control unit 42 ... Operating units SV1 to SV5 ... Two-way solenoid valves V1, V4 ... Six-way solenoid valves V2, V3 ... Ten-way solenoid valves MC1-MC4 ... Main columns PC1, PC2 ... Pre-columns

Claims (1)

a) a measuring tube;
b) a buffer tube in communication with the metering tube;
c) pressure measuring means for measuring the gas pressure in the flow passage in or near the measuring tube;
d) decompression means for decompressing the measuring tube and the buffer tube;
e) pure gas introduction means including an on-off valve capable of shutting off the flow of pure gas;
f) After reducing the pressure in the measuring pipe and the buffer pipe by the pressure reducing means, the pure gas is simultaneously introduced into the measuring pipe and the buffer pipe through the pure gas introducing means, and the measured value of the pressure measuring means rises to a predetermined value. Channel control means for closing the on-off valve when
A gas sample introduction device for a gas chromatograph, comprising:

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