JP2001165918A - Gas chromatograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the loss of a sample, and a sampling good in reproducibility is made performable when a high temperature gas sample containing a high- boiling point component is sampled by a sampling valve. SOLUTION: A pressure gauge 32 is provided on the outlet side of a sampling valve 3 of a flow passage of a sample gas passed through the sampling valve 3 to flow, and a resistance pipe 33 is provided in the sample discharge passage 7 on the downstream side from the sampling valve 3, to be housed in a thermostatic tank 34 along with the sampling valve 3. By this constitution, the pressure gauge 32 indicates the pressure of the sample gas in a metering pipe 31 and also shows the flow rate thereof because the pressure of the sample gas is generated by the flow rate of the sampling gas, which flows through the resistance pipe 33 and the pressure and flow rate of the sample gas can be monitored at the same time by one gauge. As a result, the sample gas can be charged surely at a proper flow rate while the loss of the sample gas is suppressed and a sampling good in reproducibility become possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas chromatograph particularly suitable for analyzing a high-temperature gas sample containing a high-boiling component.

[0002]

2. Description of the Related Art FIG. 2 shows a flow path configuration of a conventional gas chromatograph for analyzing a gas sample. In the figure, a carrier gas supplied from a gas cylinder 1 is adjusted to a predetermined flow rate by a flow controller 2, passes through a sampling valve 3, passes through a column 4 and a detector 5, and flows. The sample gas flows from the sample extraction valve 61 provided on the process line 60 or the like as the sample source, through the sample supply path 6, through the path indicated by the solid line of the sampling valve 3, flows through the measuring pipe 31, and passes through the sample discharge path 7. Released into the atmosphere from The sampling valve 3 is a 6-port rotary flow path switching valve, and when rotated by an angle of 60 degrees (clockwise in the figure) manually or by mechanical force, three paths indicated by solid lines inside the sampling valve 3 are formed. The flow paths are switched by moving to the positions indicated by the dotted lines, respectively.

When the sampling valve 3 is turned from the state of the flow path shown by the solid line in the drawing to the state of the flow path shown by the dotted line, the carrier gas which has been short-circuited inside the sampling valve 3 until then is metered. Flows through the column 4, so that a certain amount of the sample gas determined by the internal volume of the measuring tube 31 left in the measuring tube 31 is carried to the column 4 so as to be flushed by the carrier gas, where each component is separated. After being separated, it is converted into an electric signal by the detector 5 and output as data, whereby gas chromatograph analysis is performed.

The operation of introducing a predetermined amount of sample into the flow of the carrier gas as described above is called sampling. In general, sampling using a sampling valve is excellent in reproducibility because a fixed amount of sample can be introduced. However, it is important to ensure reproducibility that the process of flowing sample gas into the measuring tube prior to sampling (this Is called charging) to ensure a sufficient sample flow rate,
And keeping the sample pressure in the metering tube constant.

[0005] Usually, the sample flow rate during charging is 1 per minute.
About 100 to 500 mL is required. Since this flow rate does not affect the sample volume to be sampled, it is not necessary to control it accurately. However, if it is too small, the replacement of the sample will be insufficient or the air will flow back from the sample discharge channel 7 due to diffusion and will be reproduced. Sampling cannot be performed efficiently. If the charging flow rate is too large, the sample gas will be wasted. Therefore, the sample supply path 6
Usually, a flow meter 35 is provided to monitor the flow rate of the sample gas, and if necessary, the flow rate is adjusted by opening the sample extraction valve 61. As the flow meter 35 does not require much accuracy, a simple float type flow meter is often used.

On the other hand, the pressure inside the measuring pipe is normally open to the atmosphere at the end of the sample discharge path 7, and the inside of the measuring pipe 31 is also at atmospheric pressure. You will not be paid attention. However, when the sample gas is collected without being released to the atmosphere, a fluctuating back pressure may be applied to the sample discharge path 7, and in such a case, a back pressure adjusting valve (not shown) is applied to the sample discharge path 7. May be provided, but this is not common.

[0007]

If the sample gas contains a high-boiling component, it may condense at normal temperature or generate mist.
1 is kept in a constant temperature bath to keep the temperature high, and the temperature is kept by a method such as wrapping a heating wire around the sample supply path 6 or wrapping the sample supply path 6 with a steam tube and wrapping it with a heat insulating material. One thing to keep in mind when keeping the channel warm is to avoid creating cold spots. A cold spot is a place where the temperature is only partially insulated and the temperature is lower than that of other parts.In such a place, the high boiling components in the sample condense, It may cause troubles such as no longer flowing.

The above-mentioned flow meter 35 (especially a float type flow meter)
Can not be completely covered with heat insulator due to the necessity of visual observation, so it tends to be a cold spot. For this reason,
It is difficult to use a flow meter in a sample flow path requiring heat retention.When analyzing a high-temperature gas sample containing high boiling point components without necessity, charging is performed by a so-called blind control without a monitor instrument. Was. In practice, first connect a flow meter temporarily, and then adjust the flow rate by flowing a standard gas that is not likely to condense.
Thereafter, the actual sample gas is flowed without changing the setting.However, operators remain concerned about whether the sample gas is flowing sufficiently, and there is a strong tendency to flow the sample gas excessively for safety. The problem was that there was a large loss.

The present invention has been made in view of such circumstances, and when analyzing a high-temperature gas sample containing a high-boiling component, means for monitoring the pressure in the measuring pipe simultaneously with the charging flow rate is provided. Accordingly, it is an object of the present invention to provide a gas chromatograph which can perform sampling with a small sample loss and good reproducibility.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a gas chromatograph for sampling a gas sample using a sampling valve. A pressure gauge is provided on the side, and a resistance is further provided in the sample gas discharge channel downstream thereof, and this resistance is accommodated in a thermostat together with the sampling valve.

With this configuration, the sample flow rate can be monitored at the same time as the sample pressure in the measuring tube at the time of charging, so that charging can be reliably performed at an appropriate flow rate while suppressing sample loss. Good sampling becomes possible.

[0012]

FIG. 1 shows an embodiment of the present invention. In the figure, the configuration of a flow controller 2, a sampling valve 3, a column 4, a detector 5, and the like arranged along the flow of a carrier gas from a gas cylinder 1, that is, the basic configuration as a gas chromatograph is the same as the conventional one, In the present embodiment, a new design is added to a sample flow path system for charging the sample gas into the measuring tube.

That is, a pressure gauge 32 is provided on the outlet side of the sampling valve 3 in the flow path of the sample gas, and a resistance pipe 33 is further provided on the sample discharge path 7 on the downstream side. It is housed in a thermostat 34. The resistance tube 33 has an inner diameter of about 3 mm and a length of several tens cm.
A metal tube filled with glass beads or the like, or a thin tube having an inner diameter of about 0.5 mm and a length of several meters and a pressure of 30 to
The resistance was adjusted so that the flow rate was 200 to 500 mL per minute at 50 kPa.

With this configuration, the pressure gauge 3
Reference numeral 2 indicates the pressure in the metering tube 31 during charging, and since this pressure is generated by the flow of the sample gas through the resistance tube 33, it also indicates the flow rate of the sample gas. In other words, with this one instrument,
The pressure and flow rate of the sample gas necessary for performing sampling with good reproducibility can be monitored simultaneously. This allows the operator to perform charging while adjusting the sample flow rate to an appropriate value with a small loss, check the sample pressure, and perform sampling.

Since the pressure gauge 32 is mounted facing a window provided in a part of the thermostat for the necessity of visual observation, it may be a cold spot.
Since the gas does not flow through the inside of the pressure gauge 2, the flow of the sample gas does not hinder the liquefaction of some components in the pressure gauge 32.

Since the temperature of the thermostat 34 is set at a temperature at which the high-boiling components in the sample are not condensed, the sample does not liquefy in the resistance tube 33 and clogs the flow path. Since the temperature is maintained, there is no change in the resistance of the resistance tube 33 due to temperature, and stable and reliable monitoring can be performed. Constant temperature bath 34
Is determined in consideration of not only the properties of the sample but also the heat resistance of the sampling valve 3 (the upper limit is about 200 ° C.). Although not particularly shown, the column 4 and the detector 5 are housed in separate thermostats as a general configuration of a gas chromatograph. The temperature of a thermostat (not shown) for accommodating the column 4 is determined by the necessity for analysis and is usually different from the temperature of the thermostat 34 such as a sampling valve.
When both temperatures are the same, the thermostat may be shared.

Although not explicitly shown in FIG. 1, the removal of a sample from a process line or the like is the same as in FIG. 2, and the sample supply path 6 is connected to a thermostat using a heating wire as described above. It is assumed that the temperature is kept substantially the same as the temperature of 34. In addition, the numerical value in the above description is an example,
The present invention is not limited to this.

[0018]

As described above in detail, according to the present invention, a pressure gauge is provided at an outlet side of a sampling valve, and a resistance tube is inserted into a sample discharge passage on the downstream side thereof. Since the sample is accommodated in the tank, the sample flow rate can be monitored simultaneously with the sample pressure in the measuring tube 31 at the time of charging, so that charging can be performed reliably while suppressing sample loss, and the reproducibility is good. Analysis is possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the present invention.

FIG. 2 is a diagram showing an example of a channel configuration of a conventional gas chromatograph for gas sample analysis.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Gas cylinder 2 ... Flow rate controller 3 ... Sampling valve 4 ... Column 5 ... Detector 6 ... Sample supply path 7 ... Sample discharge path 31 ... Measuring pipe 32 ... Pressure gauge 33 ... Resistance pipe 34 ... Constant temperature bath

Claims (1)

[Claims] In a gas chromatograph for sampling a gas sample by a sampling valve, a pressure gauge is provided at an outlet side of the sampling valve in a flow path of the sample gas flowing through the sampling valve, and a sample gas discharge flow further downstream thereof is provided. A gas chromatograph, wherein a resistance is provided in a path, and the resistance is housed in a thermostat together with the sampling valve.