Simple approaches to on-line and off-line speciation analysis of mercury in flue gases with detection by atomic absorption spectrometry: A pilot study
Abstract
Two simple approaches to speciation analysis of mercury in flue gases have been developed distinguishing between elemental mercury Hg-0 and oxidized form of mercury (often HgCl2) either in off-line or on-line measurement arrangements. Both approaches employ atomic absorption spectrometry (AAS) as a detector.
The offline approach combines a pair of sorbents from which the first one traps oxidized for of mercury (HgCl2) selectively on a raw alumina sorbent while the second one retains Hg-0 quantitatively on a gold-coated alumina filling. Trapped amount of Hg in both sorbents is subsequently determined by AAS employing the advanced mercury analyzer AMA-254.
Both sorbents can be regenerated for repeated use. Selectivity and capacity of both sorbents was investigated by means of model gases and compared to other materials.
The accuracy and precision of this approach have been proven by analysis of a model flue gas mixture. The on-line approach to speciation analysis is based on direct introduction of flue gases into the AAS spectrometer equipped with an externally heated quartz tube atomizer.
The temperature of the atomizer's optical arm or temperature of the gas line upstream the atomizer allow speciation analysis since Hg-0 as atomic Hg-vapor can be detected at ambient temperature while HgCl2 as a molecular species requires heating of the atomizer or gas line to 900 degrees C.