Gas chromatographic analysis method for refinery gas components
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Which approach is better for the full analysis of refinery gas components by gas chromatography? What are the advantages and disadvantages of using FID and TCD, as well as helium and argon, as carrier gases?
A FID can only detect hydrocarbons; if gases from refineries contain nitrogen, hydrogen, carbon monoxide, carbon dioxide, etc., a FID cannot detect them, and a TCD is required instead. It is recommended that this chromatograph be equipped with a dual detector: the TCD should be used for components with higher concentrations and those that are not detected by the FID, while the FID should be used for hydrocarbon gases with lower concentrations. It is better to determine it using two separate chromatographs. Regarding the choice of carrier gas, if a TCD detector is used, helium has high sensitivity but is expensive ； Argon has poor sensitivity but is slightly cheaper. If hydrogen detection is not required, hydrogen can be used in place of helium; it offers high sensitivity and is inexpensive. If detecting hydrogen, it can be detected separately using nitrogen as the carrier gas.
All of these hydrocarbons, along with H2, O2, N2, CO, and CO2, need to be detected. Currently, gas chromatographs are available in configurations with three valves and four columns or four valves and five columns; some models use a TCD, while others employ two types of detectors, and there are also those with three detectors. I’m not sure which configuration is the best I would appreciate advice from experts or experienced seniors.
The components of refinery gas generally come from catalytic cracking dry gas, coking gas, as well as high-pressure gases from hydrogenation and reforming units. The composition of this refinery gas can be divided into two main categories. A large category consists of permanent gases other than hydrocarbons, such as hydrogen, nitrogen, carbon monoxide, carbon dioxide, small amounts of ammonia, hydrogen sulfide, and water. Another major category consists of hydrocarbons with up to six carbon atoms, including some alkenes and even trace amounts of alkynes. There should be a wealth of mature experience and reference materials available regarding chromatographic analysis methods for refinery gases; this can be learned by visiting the Beijing Research Institute of Petrochemical Technology (RIPP). Moreover, there are likely many research papers and application reports in various journals dedicated to chromatography and analysis.
Which is better: a mixture of coal-derived hydrogen and refinery gas?