Effect of adding aluminum salts to wet FGD systems upon the stabilization of mercury

This paper evaluates the effect of using aluminum salts in wet Flue Gas Desulphurization Plants (FGD) upon mercury reemission. Aluminum sulfate is employed to increase the SO2 retention capacity of low porosity limestone. However, its presence in the FGD system also influences the chemical reactions of the species in the scrubber. This study, performed at lab-scale to assess the reduction of mercury from aqueous solutions and gypsum slurries, has demonstrated that the addition of aluminum sulfate mainly affects the pH of the solution and the formation of sulfite ions, which in turn affects the mechanisms of mercury re-emission.