Verfahrensentwicklung zur Minderung der Quecksilberkonzentration im REA-Abwasser aufbereitungsschlamm zur Mitverbrennung in Kraftwerksanlagen

The process described aims at the installation of an additional cleaning step in the FGD waste water treatment, which enables the preseparation of mercury compounds prior to the proper heavy metal precipitation. For this a precipitant (e.g. Na 2 S, TMT) is added to the FGD waste water and the emerging particulates are flocculated by an added aid (e.g. Praestol). The precipitates may be removed from the waste water stream by use of a special separation stage (e. g. a hydro cyclone). Through this a mercury enriched sludge is formed (approx. 10 to 20% of the total FGD sludge charge), that has to be disposed. The mercury depleted waste water stream provides - after neutralization with lime hydrate -a FGD sludge (approx. 80 to 90 % of the total FGD sludge charge) with lower mercury content, that may be introduced to the combustion again. This procedure provides the plant operator with a significant lowering of waste disposal costs for the FGD sludge and results in an obvious reduction of mercury emissions to the environment.