JPH06160364A - Gas chromatograph device - Google Patents

Abstract

PURPOSE:To analyze compounds, C1-C12, in the exhausted gas with easy operation and at high sensitivity. CONSTITUTION:By making sample gas flow in multiple channels and also making switching timings for switching valves RV3 and RV4 for each channel different from each other, the sample gas is automatically separated into multiple gases, each containing the component of the range different from each other. After concentration columns 40 and 41 are cooled to absorb a to-be- analyze component in the sample gas, heating is done for desorption of the absorbed component, so that the sample gas is concentrated for higher sensitivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas chromatograph for highly sensitive (up to ppb order) analysis of exhaust gas discharged from an automobile, a combustion device or the like and other components of sample gas.

[0002]

2. Description of the Related Art For example, exhaust gas from an automobile (gasoline, diesel internal combustion engine) is converted from C1 (methane) to C1.
Since it contains a wide range of compounds up to about 2 (dodecane) and the other is that the content of each component is minute, conventionally, all the components must be measured with one gas chromatograph. Was impossible. for that reason,
Conventionally, four types of analysis are separately conducted: analysis mainly for methane (C1), analysis mainly for ethane and ethylene (C2), analysis mainly for C3 and C4, and analysis mainly for C5 to C12. I was doing.

[0003]

As described above, the conventional method has
In order to measure various kinds of exhaust gas, it was necessary to repeat the same measurement four times while exchanging the column and the like, and the operation was very complicated. Also, the analysis limit of each component is 100 ppb
However, it was not sufficient for the analysis of trace components.

The present invention has been made to solve the above problems, and its object is to analyze sample gas containing a wide range of components all at once with a simple operation. It is to provide a gas chromatograph device capable of performing with high sensitivity.

[0005]

Means for Solving the Problems The gas chromatograph apparatus according to the present invention made to solve the above problems comprises a) a sample gas measuring section provided with a measuring tube having a predetermined volume b) a precolumn and a flow A component separation unit equipped with a channel switching valve that separates only the analyte component that has passed through the pre-column from the sample gas before the channel switching valve is switched.c) Concentration column equipped with a concentration column, cooler and heater, and cooled with a cooler The gas concentration part that adsorbs the component to be analyzed in the sample gas by the above and desorbs the adsorbed component by heating the concentration column with a heater to concentrate the sample gas d) Each of the analysis part equipped with the main column and the detector In addition to providing multiple analysis flow paths with elements, e) By controlling the switching timing of the flow path switching valve of the component separation unit of each flow path, different analysis target It is characterized in that it comprises a control unit for concentrating the sample gas by was circulated to control the cooler and the heater of the gas concentration of each flow channel that the.

[0006]

The controller limits the sample gas flowing in each channel to an arbitrary range by changing the switching timing of the channel switching valve of the component separation section of each channel. Therefore, even if the sample gas contains a wide range of components, it is automatically divided into a plurality of sample gases containing different analysis targets (separating the analysis target components) without complicated operations, and each Perform analysis for each range. In addition, the control unit controls the cooler and the heater of the gas concentrating unit provided in each channel to concentrate the sample gas in each channel. For this reason,
Trace components can also be measured with high accuracy in the analysis unit.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A gas chromatograph for analyzing exhaust gas, which is an embodiment of the present invention, will be described with reference to FIGS. The gas chromatograph apparatus of this embodiment is roughly divided into a pretreatment unit 11, a concentration unit 12, a focusing unit 15, an analysis unit 16 and a control unit 17, as shown in FIG. In the pretreatment section 11, the sample gas (exhaust gas of automobile etc.) sucked from the sample introduction port 14 by the pump P is measured and supplied to the two flow paths, and the sample gas flowing in one of the flow paths is C1 to C1. The sample gas flowing through the other flow path is made to contain only the components of C1 to C6. The concentrating unit 12 is used during the process in the pretreatment unit 11, and condenses the sample gas in each flow path to increase the concentration of the hydrocarbon component to be analyzed in the sample gas. The focusing unit 15 further narrows the width of the peak of each component to be analyzed in each concentrated sample gas and increases the height. The analysis unit 16 detects each component contained in each concentrated sample gas by the column (main column) and the detector. The control unit 17 performs switching of the switching valve, control of the cooler and the heater, and the like in order to realize the operation of each unit described above.

Next, the structure of the exhaust gas analyzing gas chromatograph apparatus of this embodiment will be described in detail with reference to the detailed system diagram of FIG.

(1) Pretreatment unit 11 Between the sample inlet 14 and the pump P, a first switching valve RV1 and a second switching valve RV2 are connected. Both the first and second switching valves RV1 and RV2 are eight-way valves, and measuring pipes 30 and 31 are connected between the two ports of each valve. The sample gas taken into the gas chromatograph apparatus of this embodiment from the sample inlet 14 is measured and collected by the measuring pipes 30 and 31 of the first and second switching valves RV1 and RV2, respectively. The sample gas sampled by each of the measuring pipes 30 and 31 is the flow path (hereinafter, referred to as the first switching valve RV) provided in parallel in the gas chromatograph device of this embodiment thereafter.
The flow passage corresponding to 1 is called the first flow passage, and the flow passage corresponding to the second switching valve RV2 is called the second flow passage). In the pretreatment unit 11, a third switching valve RV3 and a fourth switching valve RV4 are provided in the first and second flow paths, respectively. Third and fourth switching valve R
V3 and RV4 are both 10-way valves.
Pre-columns 32, 35, choke columns 33, 36, dummy columns 34, 37, mass flow controller MFC
1, MFC2, pressure controller PC1, PC2
Are connected.

(2) Concentrating section 12 As shown in FIG. 2, the concentrating section 12 is composed of two columns 40 and 41 filled with a usual packing material, and each column 40, 4 is provided.
1 is connected to the two ports of the third switching valve RV3 and the fourth switching valve RV4, respectively. As shown in FIG. 4, a heat-insulating closed space is provided around both columns 40 and 41 of the concentrating unit 12. By opening the valve LNV1 and flowing liquid nitrogen (LN ₂ ) there, the column is closed. Four
0 and 41 can be cooled to about -170 ° C.
Further, each of the columns 40 and 41 is made of metal and can be electrically heated by the power source HT1.

(3) Focusing Section 15 One focusing column 51, 52 is provided for each of the first and second flow paths. As shown in FIG. 5, the focusing columns 51 and 52 are formed by capillary columns, and a thermally insulated space 53 and a heater HT3 are provided around the focusing columns 51 and 52. Like the concentrating unit 12, by opening the valve LNV2 and flowing liquid nitrogen (LN ₂ ) into the heat insulating space 53, the focusing columns 51 and 52 can be cooled, and by supplying a current to the heater 56 by the power supply HT2. , Can be heated. Both columns 51, 52
The entire focusing section 15 in which the column is housed can also be heated by another heater HT3, and the columns 51, 52
The internal temperature can be changed from about 40 to 180 ° C. according to the temperature.

(4) Analytical section 16 Main columns 61 and 62 and detectors 63 and 64 are provided for the first and second flow paths, respectively. In this embodiment, capillary columns are used as the main columns 61 and 62, but they may be packed columns.
A flame ion detector (FID) is generally used as the detector, but other detectors may be used. Like the focusing unit 15, this analyzing unit 16 also has a heater HT4 for heating the entire room, and can be changed from about 40 to 180 ° C.

(5) Control unit 17 As shown in FIG. 3, the control unit 17 includes the pump P, the switching valves RV1 to RV4, and the mass flow controller MFC.
1, MFC2, pressure controller PC1, PC
2. Liquid nitrogen valves LNV1 and LNV2, heaters (or heater power supplies) HT1 to HT4, etc. are connected and driven at each timing described later. The control unit 17 may be configured by a microcomputer, or a sequencer and a relay.

Next, the procedure of analyzing the exhaust gas by the gas chromatograph of this embodiment will be described step by step.

(1) Metering First, the flow paths of the first and second switching valves RV1 and RV2 are set at the positions indicated by the solid line in FIG. The sample gas (exhaust gas of automobile, etc.) sucked in through the inlet 14 is the first switching valve R.
V1-metering pipe 30-first switching valve RV1-second switching valve RV2-metering pipe 31-second switching valve RV2-valve 28 is discharged by pump P.

When the sample gas is sufficiently introduced into both metering pipes 30 and 31, the control unit 17 controls both switching valves RV1 and RV2.
Is rotated 45 ° to bring the flow path to the position indicated by the dotted line, and the mass flow controllers MFC1 and MFC2 are activated to feed the carrier gas to the first and second switching valves RV1 and RV2. Accordingly, the mass flow controller MFC1-first switching valve RV1-metering pipe 30-first switching valve RV
1-Third switching valve RV3 flow path is configured, measuring pipe 3
A predetermined amount (for example, 50 ml) of the sample gas stored in 0 is pushed by the carrier gas from the mass flow controller MFC1 and sent to the third switching valve RV3. The sample gas in the measuring pipe 31 is also sent to the fourth switching valve RV4 by the mass flow controller MFC2.

(2) Concentration The flow paths of the third and fourth switching valves RV3, RV4 are initially placed at the positions indicated by the dotted lines in FIG. 1, and the first switching valve RV1
A predetermined amount of sample gas from is sent to the column 40 of the concentrating section 12 from the third switching valve RV3. In the concentrating section 12, the valve LNV1 is opened before that by the control section 17, and the column 40 is cooled by liquid nitrogen (LN ₂ ). The sample gas from the third switching valve RV3 is caused to flow from the end A to the end B of the column 40, and during that time, the hydrocarbon component in the sample gas is adsorbed on the surface of the filler having a low temperature. The sample gas that has passed through the column 40 of the concentrating unit 12 (which does not already contain the hydrocarbon component for analysis) returns to the third switching valve RV3 and is discharged to the outside (VENT on the left side of FIG. 1). The same applies to the second flow path (fourth switching valve RV4 and column 41).

After delivering a predetermined amount of carrier gas by the mass flow controller MFC1, the controller 17 rotates the third switching valve RV3 by 36 ° to bring the flow path to the position indicated by the solid line. Then, the liquid nitrogen valve LNV1 of the concentrating section 12 is closed, and the columns 40 and 41 are heated by supplying a current from the power source HT1 to the columns 40 and 41, and at the same time, the pressure controller PC1 is activated to carry the carrier gas of a predetermined pressure. Via the third switching valve RV3
Send to 2. At this time, contrary to the above, the carrier gas flows from the end portion B of the column 40 toward the end portion A. As a result, the components adsorbed on the packing material of the column 40 in the low temperature state are desorbed from the packing material, but since the temperature of the column 40 is sufficiently high, the components are desorbed at a high speed and the sample The gas is concentrated. The same applies to the second flow path (fourth switching valve RV4 and column 41).

(3) Separation The concentrated sample gas returned to the third switching valve RV3 passes through the precolumn 32. In this pre-column 32, the concentrated sample gas is separated according to the number of carbons, and the components having the smaller number of carbons exit the pre-column in order, and the focusing unit 15
Sent to. The control unit 17 sets the third switching valve RV3 to 3 when the components up to C12 have just passed through the pre-column 32.
Rotate 6 ° to switch the flow path to the dotted position. At this time, the high carbon number component of C13 or higher exists in the pre-column 32 or in the flow path before it. The carrier gas from the pressure controller PC1 flows through the third switching valve RV3 in the pre-column 32 in the opposite direction to the above direction, pushes back those high carbon number components (those with C13 or higher), and then the choke column 33 to the outside ( VENT). Choke column 33
Is a kind of dummy column having the same flow resistance as the main column 61 described later.

The concentrated sample gas returned from the concentrating section 12 to the fourth switching valve RV4 is basically separated in the same manner as described above, but in this case (second flow path), the fourth switching valve is used. RV4 flow path switching timing 3rd
By advancing earlier than the switching valve RV3, only the low carbon number component of C6 or less is sent to the focusing unit 15, and the high carbon number component of more than that (C7 or more) is discharged from the pre-column 35 to the outside. Thus, in the first flow path C1 to C12
To C6 in the second flow path, and only components from C1 to C6 are sent to the focusing unit 15. The timing of switching the third switching valve RV3 and the fourth switching valve RV4 described above is determined in advance by performing preliminary measurement.

(4) Focusing In the focusing unit 15, the concentrated sample gas is further concentrated by a method similar to that of the above-described concentration unit 12. That is,
Explaining the first flow path, first, the liquid nitrogen valve L
The column 51 is cooled to a low temperature with liquid nitrogen by opening the NV2 (FIG. 5), and the concentrated sample gas is passed through it. As a result, the analysis target component in the sample gas is adsorbed on the inner wall of the column (capillary column) 51. After that, the adsorbed component is desorbed at high speed by heating the column 51 with the heater 56. The same applies to the second channel.

(5) Analysis The sample gas in the first flow path containing only C12 or lower components sent from the focusing unit 15 via the connector 60 passes through the main column 61, where each component is separated. . Of the separated components, the detector 63 mainly measures the late separated components, that is, the C6 to C12 components. In the second flow path, the sample gas contains only the component of C6 or less, and thus the component separated by passing through the main column 62 is highly accurately measured by the detector 64 from the beginning. As a result, the low carbon number components C1 to C6 are measured with high accuracy by the detector 64 in the second flow path, and the high carbon number components C6 to C12 are measured with high accuracy by the detector 63 in the first flow path. Done.

FIG. 6 shows a chromatogram of the standard gas containing only the C1 to C12 components measured by the gas chromatograph of this embodiment, and FIG. 7 shows a chromatogram of the result of measuring the exhaust gas of an actual automobile. As a result of analysis by comparing the area of each peak of the graph of FIG. 7 with the area of the corresponding peak of the graph of FIG. 6, it was found that in the gas chromatograph apparatus of this example, 2.5 ppb (* 1 peak at the center of the upper part of FIG. 7). ) And
It is possible to measure trace components as low as 0.5 ppb (* 2 peak).

[0024]

In the gas chromatograph apparatus according to the present invention, since the control unit automatically separates the sample gas in each arbitrary range, even if the sample gas contains a wide range of components, a complicated operation is required. It is possible to perform analysis for each component range without requiring. In addition, since the sample gas in each flow path is concentrated, trace components can be measured with high accuracy.

[Brief description of drawings]

FIG. 1 is a flow path diagram of a high-sensitivity gas chromatograph for exhaust gas analysis which is an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a gas chromatograph device of an example.

FIG. 3 is a control system diagram of the gas chromatograph apparatus of the embodiment.

FIG. 4 is a sectional view showing the structure of a gas concentrating section.

FIG. 5 is a configuration diagram of a focusing unit.

FIG. 6 is a chromatogram of a standard gas created by the gas chromatograph of the example.

FIG. 7 is a chromatogram of automobile exhaust gas created by the gas chromatograph of the embodiment.

[Explanation of symbols]

11 ... Pretreatment part 12 ... Concentration part 14 ... Sample introduction port 15 ... Focusing part 16 ... Analysis part 17 ... Control part RV1, RV2 ... Switching valve (8-way valve) RV3, RV4 ... Switching valve (10-way valve) MFC1, MFC2 Mass flow controller PC1, PC2 Pressure controller HT1, HT2 Heater power supply HT3, HT4
... Heater LNV1, LNV2 ... Liquid nitrogen valve 30, 31 ... Measuring pipe 32, 35 ... Pre-column 33, 36 ... Choke column 34, 37 ... Dummy column 40, 41 ... Concentration column 51, 52 ... Focusing column 61, 62 ... Main column 63, 64 ... Detector

Claims (1)

[Claims] 1. A sample gas metering unit provided with a) a metering tube having a predetermined volume b) A precolumn and a channel switching valve, and the sample gas passed through the precolumn before the channel switching valve was switched. Component separation part that separates only the analysis target component c) Equipped with a concentration column, cooler, and heater, the analysis target component in the sample gas is adsorbed by the concentration column cooled by the cooler, and it is adsorbed by heating the concentration column with a heater. Gas concentrator for desorbing components and concentrating sample gas d) Along with multiple analytical flow channels that have each element of the analysis unit with main column and detector, e) Flow of the component separation unit of each flow channel By controlling the switching timing of the channel switching valve, different analytes are circulated in each channel, and the sample gas is concentrated by controlling the cooler and heater of the gas concentrating section of each channel. Gas chromatography apparatus, characterized in that it comprises a control unit.