THE EFFECT OF HYGROSCOPIC ADDITIVES ON CA(OH)(2) UTILIZATION IN SPRAYDRYER FLUE-GAS DESULFURIZATION

Soluble additives to enhance spray dryer performance for sulfur dioxid e (SO,) removal from flue gas have been evaluated in a pilot plant sys tem under controlled conditions. These additives have included NaOH, N aHCO3, NaCl and CaCl2. These additives were chosen because of their hy groscopicity as solids, and the understanding that SO2 reactivity is s ignificantly enhanced in the Liquid phase of the spray drying operatio n. All of the additives enhanced SO2 removal above baseline Ca(OH)(2) slurry usages, with NaOH providing the greatest degree of enhancement at approach to adiabatic saturation temperatures below 16.7 degrees C. The percent of enhancement per unit mass of additive was found to dec rease with additive concentrations above 100 mg l(-1). The enhancement effect may be explained by analyzing the vapor pressure lowering effe ct of the slurry droplets containing the additives. This procedure may by appropriate for estimating the enhancement by other hygroscopic so lids for spray dryer flue gas desulfurization improvement.