Development of Online Monitoring Method for Ambient VOCs at ppb Level at Air Separation Plant

摘要

An online GC(Gas Chromatography) method for monitoring ambient VOCs (Volatile Organic Compounds) specified as C2-C6 hydrocarbons around the air separation plant is described. Instead of the traditional process monitoring GC, this method employs a pre-concentration system equipped with a crvofocusing and thermal desorption device to dynamically pre-conccntrate the VOCs. This technique provides enhanced detecting sensitivity that makes it possible to monitor ambient VOCs at low ppb levels by a general FID (Flame Ionization Detector). The results showed that a moderately modified thermal desorption time could influence peak shape, and improve peak integration by shortening thermal desorption time bv 0.5 seconds Good results were obtained with 94~118ppb standards in the precision and accuracv test with MDL (Method Detection Limit) at 0.15~1.52ppb, which resulted in the maximum standard deviation of repeatability and reproducibility of 4.6% and 6.5%, respectively, with an accuracy of 19.2%.