MERCURY CHEMISTRY IN SIMULATED FLUE-GASES RELATED TO WASTE INCINERATION CONDITIONS

A flue gas generator has been built in order to study mercury reactions. The generator consists of a propanefueled furnace and a 12 m long temperature-controlled steel duct with a fabric filter. When vaporized (elemental) mercury was added to the propane flame in a concentration of 150 μg/m3 and with 8% excess of oxygen, 20–30% of the mercury was oxidized after 0.8 s residence time in the furnace and the duct (T > 500 °C). In the presence of HCl(g) in the flue gas, most of the elemental mercury was oxidized after 0.8 s. The reaction product is assumed to be mercuric chloride. A “rereduction” of the oxidized mercury occurs when the temperature has decreased below 200 °C. This reduction is probably a heterogeneous reaction at the surface of the flue gas duct. Experiments with mercury and activated carbon powder [0.5–1.0 g/m3, at NTP, specific surface 792 m2/g (BET)] in the flue gas duct have also been performed. The results indicate that activated carbon may act as a catalyst in the oxidation of mercury. © 1990, American Chemical Society. All rights reserved.