Application Note LD16-02 : Analysis of hydrocarbons, CO2, N2O in Oxygen with the MultiDetek2 compact GC system using Nitrogen as carrier gas and the PlasmaDetek-E detection technology
The hydrocarbon analysis for the production of high purity Oxygen on air separation plants is essential for safety of the operations and quality of the product. For a very long time, the flame ionisation detector has been used for detection of trace hydrocarbons in different gas mixtures. This detector has now many different designs all based on carbon ions collection. The FIDs require a mixture of Air and Hydrogen to generate the flame used for ionisation. It is also necessary to have extra safety based on Hydrogen gas handling. All these points result in increase of operating and start-up costs as demonstrated in Figure 1.
LDetek has developed a detection system based on plasma emission detector (PlasmaDetek E) for the analysis of trace hydrocarbons in different gas mixtures. This PED technology offers enhanced sensitivity and selectivity to hydrocarbons using Nitrogen as single discharge/carrier gas. Other emission and ionisation detection technologies are known in the market for the analysis of hydrocarbons using Argon or Helium as discharge/carrier gas. However, these systems don’t offer the selectivity and sensitivity to allow running a single injection through a column without having interferences from residual Oxygen. Other techniques offering NMHC detection are also available and are sufficient in certain cases. Nevertheless, the NMHC detection doesn’t give the ability to focus on the measurement of critical impurities like low concentration acetylene in Oxygen production. Using the MultiDetek2 combined with the PlasmaDetek E with Nitrogen carrier gas, the system can be customized for the range and LDL that are specifically required for each impurity. This way, it is possible to configure the system according to each air separation plant specification. As shown in figures 2 and 3, low detection is possible using Nitrogen as carrier gas with PED technology. No need of complex valve and column chromatography configuration for flushing out the background gases.
Figure 1 : Comparison between FID based GC and MultiDetek2 compact GC with PlasmaDetek-E
Figure 2 : Chromatogram of trace impurities in balance Oxygen
Figure 3 : LDL based on 3 times noise ratio
With Nitrogen gas used as carrier, the MultiDetek2 with Plasmadetek-E becomes the ideal gas measuring instrument for trace detection of hydrocarbons on the air separation plants for high purity Oxygen monitoring. Keeping the start-up and operating costs low and offering enhanced hydrocarbon detection, LDetek is proud to offer its robust and easy to operate system.