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4.
5 Apparatus and equipment
5.
Figure 1 Absorption device
5.
5.
Figure 2 Absorption bottle
5.
5.
5.
5.
5.
5.
A gas chromatograph equipped with a hydrogen flame ionization detector.
5.
5.
5.
5.
5.
5.
4.
3 Recording device: integrator or chromatographic data processor
.
6 Sample preparation
6.
1 Sampling
Ethylene shall be conducted in accordance with the provisions of Article 2.
2 of GB 7715
.
Propylene shall be carried out in accordance with the provisions of GB 7716 in 2.
2
.
6.
2 Vaporization of the sample
Liquid propylene sample obtained from a sampling cylinder : it needs to be fully vaporized before it can be introduced into the sampling device or be subjected to water absorption and enrichment operations
.
Heat the water bath in the vaporization device (5.
3) to the required temperature, and connect one end of the heating coil (5.
3.
2) to the outlet valve of the sample cylinder, and the other end to the sampling device or absorption device, At this time, the exit valve of the steel cylinder is opened, and the sample enters the heating coil and is fully vaporized
.
When injecting with a gas injection valve, the sample injection device needs to be flushed sufficiently with the sample
.
6.
3 Enrichment of samples
For low-concentration samples or when the sensitivity of the instrument does not meet the requirements, the water absorption method should be used to enrich the methanol
.
Note: The absorption operation needs to be carried out in a fume hood, and the sample must be discharged to the vent system
.
6.
3.
1 Connect the absorption device (5.
1), immerse the three absorption bottles (A, B, and C) in the water bath (5.
2), and add 10.
0 mL of distilled water to each absorption bottle
.
6.
3.
2 Connect the absorption device (5.
1) to the vaporization device (5.
3), and ventilate the gaseous sample at a rate of 50L/h for about 2h.
Use a gas flowmeter to accurately measure the volume of the sample taken
.
6.
3.
3 Flush the sampling line with 2L nitrogen gas at a rate of 5-10L/h
.
6.
3.
4 Take the absorption liquid in absorption bottle C for chromatographic analysis to confirm that it does not contain methanol
.
6.
3.
5 Transfer the absorbing liquid of the first two absorbing flasks (A and B) to a 25mL volumetric flask, dilute to the mark with distilled water and mix well
.