Robert E. Moser

EFFECTS OF ALUMINUM/FLUORIDE CHEMISTRY IN WET LIMESTONE FLUE GAS DESULFURIZATION

Abstract In wet limestone flue gas desulfurization (FGD), elevated fly ash loadings can initiate the formation of liquid phase aluminum/fluoride (A1F n ) complexes which inhibit limestone dissolution, causing depressed slurry pH and reduced SO2 removal. This phenomenon was examined in a bench-scale pilot FGD scrubber system, and in batch reactor experiments, under conditions similar to those in full-scale utility FGD systems. It was shown that leachability of aluminum from fly ash is a critical factor, and depends on pH, fluoride concentration, and solid material properties. Reductions in limestone dissolution rate of more than an order of magnitude were measured at soluble aluminum concentrations as low as l0ppm. The implications for full-scale FGD systems reinforce the importance of maintaining efficient particulate removal upstream of the FGD scrubber.