Abstract: For additive-enhanced limestone flue gas desulfurization(FGD)process,the slurry solids settling time,supernate density and filter-cake soilds content were measured at different additives and different concentrations.The experimental results showed that when additives were used,the filter-cake solids content decreased,but no significant effects were obtained under the experiment conditions;the differences of slurry settling time had relation to the difference of the calcium sulfite solid product content and crystal size and form;the supernate densities also varied with different additives.For magnesium-enhanced lime FGD process,the slurry solids settling process could be divided into rapid period and slow period;the settling rate decreased as the calcium sulfite content increased in the solid phase;the filter-cake solids content was slightly lower in comparison with that of lime process without magnesium sulfate.Desulfurization tests showed that using additives could also abate scaling in the equipment.