Industrial Difluorochloromethane (HCFC-22) (4)

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Using gas chromatography, under selected working conditions, make the gas-phase non-condensable gas in the product packaging container pass through the packed chromatographic column, detect with a thermal conductivity detector, and calculate the content of the non-condensable gas by an external standard method

Among the typical refrigerant samples, air is the only non-condensable gas with an exact amount, and other gases are not subject to daily analysis

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The recommended chromatographic operating conditions are shown in Table 2

Table 2 Recommended chromatographic operating conditions

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5 Analysis steps

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1 Calibration

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1 Connect the outlet valve of the standard gas cylinder to the injection valve of the gas chromatograph, pass the tail gas of the six-way valve into the gas washing bottle filled with a small amount of water, and slowly open the valve of the standard gas cylinder to 1mL/ The standard gas is released at the speed of s through the injection valve to clean the injection system.
After about 10 seconds, the standard gas cylinder valve is closed, and the injection valve is immediately rotated to the "injection" position for sample analysis
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Repeat the injection three times, and any absolute difference of the three determinations shall not be greater than 0.
1% of the arithmetic mean of the consecutive determinations
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2 The response factor f of standard gas air is calculated according to formula (3):

Where:

A _s —the peak area of ​​air;

V _s —The volume fraction of air in the standard gas, %
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Take the arithmetic average of three measurements as the measurement result
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Any absolute difference of the three measurement plants shall not be greater than 1.
6% of the arithmetic mean of the continuous measurement values
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3 Perform calibration before each analysis
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2 Sample analysis

Before measuring the sample, record the temperature of the environment where the sample is located to the nearest 0.
1°C, which is the temperature of the liquid phase of the sample
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Connect the vacuum-dried sampling cylinder to the gas-phase outlet valve of the product packaging container, open the outlet valve of the product packaging container, and then open the inlet and outlet valves of the sampling cylinder.
After fully replacing the air in the system, close the outlet valve of the sampling cylinder.
Make the gas in the upper part of the product packaging container enter the sampling cylinder and fill it
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The sampling cylinder is disconnected from the product packaging container and connected to the inlet of the injection valve of the chromatograph.
The following operations are the same as 4.
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Continuously repeat the injection until the measured air peak area is repeated, indicating that the air in the system is exhausted
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Then the samples were injected for 2 to 3 consecutive times, and the arithmetic mean was taken as the peak area measurement result
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6 Result calculation

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1 The volume fraction φ of the non-condensable gas content in difluorochloromethane at the sampling ambient temperature T℃ , the value is expressed in %, calculated according to formula (4):

Where:

A—The peak area of ​​air;

f—Response factor of standard gas air
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2 The volume fraction φ1 of non-condensable gas content corrected to 25℃, the value is expressed in %, calculated according to formula (5):

Where:

φ—volume fraction of non-condensable gas (%) (at temperature t);

p—the saturated vapor pressure of the sample at the temperature t, in kilopascals (kPa), this value is found in Appendix B;

t—the ambient temperature of the sample at the time of sampling, in degrees Celsius (°C);

P ₂₅ - sample at saturation vapor pressure at 25 ℃, kilopascals (kPa), the value is made to Appendix B Richard
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Take the arithmetic mean of the continuous measurement results as the measurement result, and any absolute difference of the continuous measurement results shall not be greater than 10% of the arithmetic mean of the continuous measurement values
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10 Determination of oxygen content in the gas phase

Carry out according to the provisions of GB/T5831, in which sampling is carried out according to the following steps
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Clean the analyzer and fill it with water, turn on all the pistons of the analyzer, and connect the branch pipe of the gas piston of the analyzer with a rubber tube and the metal sampling tube tightly
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Open the sampling cylinder outlet valve to vaporize the sample, adjust the sample gas flow rate to (1000～5000) mL/min, replace all the water in the analyzer with the sample gas, reduce the sample gas flow rate, and close the pistons of the analyzer , Remove the analyzer
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Use the piston to adjust the balance of the gas pressure in the analyzer to normal pressure
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Read and record the room temperature and atmospheric pressure
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