JPH07287002A - Gas chromatograph - Google Patents

Abstract

PURPOSE:To analyze a concn. component within a range from high concn. to low concn. and a low sensitivity component. CONSTITUTION:A stop valve 11, a pressure reducing valve 21 and a threeway valve 22 are arranged to a sample gas inflow passage 20 and a stop valve 23 is arranged to a sample gas discharge passage 12. When the usual separation and analysis of sample gas SG are performed, two stop valves 11, 23 are set to a full-open state and the pressure of the sample gas SG is adjusted by the pressure reducing valve 21 so as to become same to the pressure at the time of usual measurement and the sample gas SG is guided to a sample valve 2 to be separated and analyzed. When a low concn. component or a low sensitivity component is measured, the pressure of the sample gas SG is set to required pressure by the pressure reducing valve 21 and the stop valve 11 is closed to set two stop valves 11, 23 to a full-open state and, when the sample gas SG is guided to the sample valve 2, the pressure of the sample gas SG becomes high and the amt. of the sample taken by a weighing pipe 3 is increased.

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 separating gas into component gases by utilizing the difference in adsorptivity between a packing material packed as a stationary phase in a column and a sample gas, and particularly to a gas chromatograph. The present invention relates to a gas chromatograph capable of measuring low concentration components and low sensitivity components.

[0002]

2. Description of the Related Art In a petrochemical process, a steel process, etc., the concentration of each component of a process gas is analyzed, and as a detection device for monitoring each process step and performing various controls based on the analysis result. Gas chromatographs have been commonly used. This kind of industrial gas chromatograph collects a sample gas from a process line to be measured and sends it to a column by a carrier gas, and in the column, each component gas is adsorbed (affinity) of each component to a stationary phase and After separating using the difference in moving speed based on the difference in distribution coefficient, it is detected by the detector,
The electric signal is subjected to waveform processing by the controller, the process is controlled based on this, and the chromatogram waveform is printed out.

FIG. 2 is a diagram showing the basic construction of an industrial gas chromatograph of this type, wherein 1 is a predetermined temperature (60 ° C. to 12 ° C.).
It is a constant temperature bath heated and maintained at about 0 ° C., inside which a sample valve 2, a measuring pipe 3, a column 4, a detector 5,
A sample gas shutoff valve 11 and the like are provided. Column 4 is different depending on the sample gas SG,
Powders having a uniform particle size, such as activated carbon, activated alumina, and molecular sieve, are packed as the stationary phase. As the detector 5, a thermal conductivity detector, a hydrogen flame ionization detector or the like is used, and the detection signal thereof is sent to the controller 6 and subjected to waveform processing. During non-measurement, the flow path of the sample valve 2 is maintained in the state of a solid line so that the carrier gas CG made of an inert gas such as He supplied from the first carrier gas inlet 7 passes through the column 4 and the detector. On the other hand, the sample gas SG supplied to the sample valve 2 from the sample gas introduction port 8 is discharged to the sample gas discharge passage 12 via the metering pipe 3 and the vent port 9 while being led to 5. When the flow path of the sample valve 2 is switched from the solid line state to the broken line state during the measurement, the sample gas SG collected by the measuring pipe 3 is introduced into the column 4 by the carrier gas CG introduced from the second carrier gas introduction port 10. The gas is sent and separated into each component gas due to the difference in the adsorptivity with the stationary phase. Then, this component gas is detected by the detector 5 and converted into an electric signal. This electric signal is proportional to the component gas concentration, and this is subjected to waveform processing by the controller 6 to monitor the process steps and record the chromatogram waveform.

The concentration of each component gas is a standard gas (calibration sample gas) composed of the same component gas as the sample gas SG.
The output value is calibrated using HG and calculated by the CPU.

[0005]

By the way, in the conventional gas chromatograph using the sample valve 2 of the internal metering tube type in which the metering tube 3 is incorporated, the structure is such that the metering tube size cannot be changed. Further, since the sample conditioner has a built-in flow meter, the volume of the sample gas cannot be changed in a wide range. Therefore, the separation of the measurement components is limited, and there is a problem that a wide range of component analysis from high concentration components to low concentration components cannot be performed. That is, the sample gas SG is separated by the measuring pipe 3 and sequentially separated into each gas component in the column 4. Therefore, since the sample amount is always constant, it is difficult to analyze in a wide range from a high concentration component (% order) to a low concentration component having a concentration of about 1 ppm. For example, when a small measuring tube is used (2 to 20 micron liters), a high concentration component can be measured, but a low concentration component has a small output and measurement accuracy is poor or measurement is impossible. On the other hand, when using a large measuring pipe (20 to 20
(00 micron liter), the output of the high-concentration component is saturated and the separation from other components is poor, so that the high-concentration component cannot be analyzed, and instead the low-concentration component can be measured. In addition, it is difficult to measure a low-sensitivity component whose sensitivity to the detector is smaller than that of the carrier gas. As a method of solving such a problem, when measuring a low-concentration component or a low-sensitivity component, it is sufficient to replace the measuring tube to increase the sample amount and increase the output signal.
In that case, it is necessary to stop the device once, which is not practical.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to increase or decrease the sample amount regardless of the size of the measuring tube,
It is an object of the present invention to provide a gas chromatograph capable of measuring a wide range of components from high-concentration components to low-concentration components and measuring low-sensitivity components without replacing the measuring tube.

[0007]

In order to achieve such an object, the present invention provides a gas chromatograph equipped with a sample valve, a measuring tube, a column, a detector and the like, wherein the sample valve is provided in the sample gas inflow path. A stop valve, a pressure reducing valve, and a three-way valve that alternately introduces the sample gas and the standard gas from the side are provided, and a stop valve is provided in the sample gas discharge path, and an arithmetic unit that controls these four valves is provided. It is characterized by being provided.

[0008]

In the present invention, the pressure reducing valve arbitrarily sets the pressures of the sample gas and the standard gas introduced into the measuring pipe. The three-way valve switches between sample gas and standard gas. The stop valve on the sample gas inflow path side opens and closes the inflow path. The stop valve on the sample gas discharge passage side opens and closes the discharge passage. At the time of measurement, by controlling the opening and closing of these valves by the arithmetic unit, the sample amount of the sample gas (or standard gas) measured by the measuring pipe can be increased or decreased. That is,
The pressure of the sample gas is set to an arbitrary pressure while the stop valve on the sample gas discharge path side is closed by the pressure reducing valve. Next, the sample gas is caused to flow with the stop valves on the sample gas inflow side and the discharge path side opened. Next, about 10 seconds before the start of analysis, the stop valve on the sample gas discharge passage side is closed to make the pressure of the sample gas inside the measuring tube constant. Setting this pressure higher than during normal measurement increases the amount of sample to be metered by the metering tube. Therefore, when analyzing a low-concentration component or a low-sensitivity component having a small difference in sensitivity with respect to the detector as compared with the carrier gas, the pressure may be set higher than usual. Then, the stop valve on the sample gas inflow path side is closed, the sample gas inside the measuring pipe is guided to the column by the carrier gas, separated into each component gas, and detected by the detector. After the measurement of the sample gas is completed, open the three-way valve to introduce the standard gas into the measuring pipe, and then to the column and the detector at the same pressure as the sample gas to separate and detect it. Calibrate to calculate the concentration of the sample gas component.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on the embodiments shown in the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment of a gas chromatograph according to the present invention. In the figure, the same components as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, a sample gas shutoff valve (stop valve) 11, a pressure reducing valve 21, and a three-way valve 22 for alternately introducing the sample SG gas and the standard gas HG are arranged in the sample gas SG inflow passage 20 from the sample valve 2 side. At the same time, the stop valve 23 is provided in the discharge path 12 for the sample gas SG, and these four valves 11, 21,
2 and 23 are connected to a CPU electric board 24 as a calculation unit. 4 valves 11,2,1
2 and 23 are solenoid valves, and CPU electric board 24
Drive is controlled by a signal from. Other configurations are the same as the conventional structure shown in FIG.

In a gas chromatograph having such a structure, two stop valves 11 and 23 are used in the case of separating and analyzing a component gas which has a sensitivity to a detector at a normal concentration and is sufficient as compared with a carrier gas CG. The pressure is adjusted so that the pressure is the same as that during normal measurement by setting the fully opened state and the pressure reducing valve 21, and the sample gas SG is guided to the sample valve 2. When measuring the standard gas HG, the three-way valve 22 may be switched to guide the standard gas HG from the sample inflow passage 20 to the sample valve 2 side. Such sample gas SG
Since the measurement of the standard gas HG and the standard gas HG is exactly the same as the conventional apparatus described in FIG. 2, the description thereof will be omitted.

Next, when the sample gas SG consisting of a low-concentration component or a low-sensitivity component is separated and analyzed, the output signal is small and the measurement is difficult. The sample gas S supplied from the sample inflow passage 20 to the sample valve 2 is driven by driving the pressure reducing valve 21 by a drive signal from the CPU electric board 24 to adjust the valve opening degree.
Set the G pressure to the required pressure. Stop valve 1 on the side of sample gas inlet 20 and the side of outlet 12
1 and 23 are opened, and the sample gas SG is caused to flow into the sample gas inflow path 20. Immediately before the start of analysis (about 10 seconds before) sample gas exhaust path 1
The stop valve 23 on the 2 side is closed. When the stop valve 23 is closed, the pressure of the sample gas SG in the sample gas inflow path 20, the sample valve 2 and the measuring pipe 3 becomes high, so that the amount of sample in the measuring pipe 3 increases. When the pressure of the sample gas SG inside the measuring pipe 3 reaches a predetermined pressure, the stop valve 11 on the sample gas inflow path 20 side is closed, and the sample valve 2 is switched from the solid line state to the broken line state. When the sample valve 2 is switched, the measuring tube 3
The sample gas SG separated by is sent to the column 4 by the carrier gas CG introduced from the second carrier gas inlet 10 and separated into each component gas. Then, this component gas is detected by the detector 5 and converted into an electric signal, which is subjected to waveform processing by the controller 6 to monitor a process step or recorded by a recorder. After the measurement of the sample gas SG is completed, the sample valve 2 is switched to the solid line state, the stop valve 23 is closed, and the three-way valve 22
Is switched to guide the standard gas HG from the sample gas inflow passage 20 to the measuring pipe 3, and the pressure of the standard gas HG is made the same as the pressure of the sample gas SG at the time of the above measurement. When the pressure of the standard gas HG inside the measuring pipe 3 reaches a predetermined pressure, the stop valve 11 on the sample gas inflow passage 20 side is closed,
The sample valve 2 is switched from the solid line state to the broken line state again. When the sample valve 2 is switched, the measuring tube 3
The standard gas HG separated by is sent to the column 4 by the carrier gas CG introduced from the second carrier gas inlet 10 and detected by the detector 5, and the output value of the sample SG is calibrated by the output value thereof. By doing so, the concentration of each component gas in the sample gas SG is calculated.

Thus, in the gas chromatograph having such a structure, the valves 11, 21, 22, and 23 are C
Since the opening / closing control is performed by the PU electric board 24 and the pressure of the sample gas SG supplied to the measuring pipe 3 is changed, the amount of sample to be measured and dispensed by the measuring pipe 3 is adjusted. It is not necessary to replace the sample gas depending on the sample gas, and it is possible to analyze gas in a wide range of concentrations from high concentration to low concentration and further to analyze gas components having low sensitivity to the detector. When measuring a high-concentration component, on the contrary, the pressure may be lowered to reduce the sample amount.

[0013]

As described above, according to the gas chromatograph of the present invention, a stop valve, a pressure reducing valve, and a three-way valve for alternately introducing the sample gas and the standard gas are introduced into the sample gas inflow path from the sample valve side. With the placement
Since stop valves are arranged in the sample gas discharge path and these four valves are configured to be driven and controlled by the arithmetic unit,
The amount of sample dispensed can be increased or decreased by pressure without changing the size of the metering tube. Therefore, if the pressure of the sample gas is increased to increase the sample amount, it becomes possible to measure low-concentration components and low-sensitivity components, which are difficult to measure by ordinary measurement, and a wide range of analysis can be performed. Further, unlike the replacement of the measuring pipe, the pressure adjustment does not require stopping the device, and since only four valves need to be incorporated, the structure is simple and the conventional device can be easily modified.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a gas chromatograph according to the present invention.

FIG. 2 is a diagram showing a schematic configuration of a conventional gas chromatograph.

[Explanation of symbols]

1 ... Constant temperature bath, 2 ... Sample valve, 3 ... Measuring pipe, 4 ... Column, 5 ... Detector, 6 ... Controller, 11 ... Sample shut-off valve (stop valve), 12 Sample gas discharge passage, 20 ... Sample gas supply Road, 21 ... Pressure reducing valve, 22 ...
Three-way valve.

Claims (1)

[Claims] 1. In a gas chromatograph equipped with a sample valve, a measuring tube, a column, a detector, etc., a stop valve, a pressure reducing valve, and a sample gas and a standard gas are alternately introduced into the sample gas inflow path from the sample valve side. A gas chromatograph characterized in that a three-way valve is provided, a stop valve is provided in a sample gas discharge path, and an arithmetic unit for controlling these four valves is provided.