At-Line Analysis of Polycyclic Aromatic Hydrocarbons in Aluminium Primary Production

Emissions of Polycyclic Aromatic Hydrocarbons (PAH) from prebake anode production are closely monitored. The PAH concentrations downstream the gas treatment facility are normally in the ultra-trace range[1]. Rigorous sampling and analytical procedures are required in order to estimate the PAH release. The time from sampling to analytical result is therefore long. It is often of interest to study the dynamic gas composition. In this work, the applicability of Thermal Desorption (TD) combined with a transportable Gas Chromatography/Mass Spectrometry (GC/MS) instrument was investigated. The analytical setup was found to be capable of PAH quantification in the parts per trillion range. With short sampling times required, the total analytical time required was about 30 minutes. The limiting factor was the GC elution time. The analytical methodology was used to evaluate the efficiency of a prebake anode factory dry scrubber. At-line analysis made possible the direct evaluation of PAH emission as function of the operational set points.