Evaluating mercury transformation mechanisms in a laboratory - scale combustion system

Mercury speciation measurements during injections of 10 mgrm3 Hg0 g. into a 42-MJrh combustion system containing gaseous O ]Ar- and O ]N -rich mixtures indicate that 43 and 55% of the Hg0 g. spike was transformed 2 2 2 rapidly -0.1 s. to Hg2qX g. within a refractory-lined heat exchanger where gas temperatures decrease from f620 to 2008C. O2 g. is the probable Hg0 g. oxidant i.e. XsO2y.. The apparent formation of HgO g. involves a heterogeneous reaction with adsorbed Hg0 or O on refractory surfaces or a Hg0 g.]O g. reaction catalyzed by 2 2 corundum Al2O3. andror rutile TiO2. components of the refractory. The potential catalytic effects of Al2O3 and TiO on Hg0 g. oxidation were investigated by injecting Al O and TiO powders into f6508C subbituminous coal 2 2 3 2 Powder River Basin, Montana, USA. combustion flue gas. On-line Hg0 g. and total mercury measurements indicate, however, that Al O and TiO injections were ineffective in promoting the formation of additional Hg2qX g.. 2 3 2 Apparently, either the chemically complex flue gas hindered the catalytic effects of Al2O3 and TiO2, or these compounds are simply not Hg0 g. oxidation catalysts.