(Cl) by addition of reagent grade Hg(NO3)2 and NaCl and validated
by atomic absorption spectrometry (AAS) and ion chromatography
respectively. S(IV) concentration is analyzed by iodometric titration.
In the first stage of the experiments, the FGD is operated under reference
conditions. Once steady state is reached, the slurry is
removed from the FGD and subsequently separated by filtration.
The liquid phase is directed immediately to the electrically heated
alkalization reactor, equipped with online ORP and pH-monitoring.
Alkalization is performed by step-wise addition of small quantities
of saturated Ca(OH)2 solution. An adjustable air flow is bubbled
through the liquid in the reactor. The total Hg concentration of the
exhaust air is continuously determined by AAS continuous emission
monitoring (CEM) with upstream reduction unit, utilizing SnCl2
solution as reducing agent. The speciation of Hg is determined by
a selective adsorption method for gaseous Hg2+ species by functionalized
ion exchange resin [16]. Due to the measurement range of the
Hg CEM, the threshold for the maximum Hg0 concentration in the
exhaust air for all experiments was set to 800 lg/m3
. The Hg-rich
exhaust air of the alkalization reactor is directed to a downstream
activated carbon adsorber. Absolute flow rates of gases and liquids
are controlled by MFCs and peristaltic pumps.