Simultaneous collection of sulfur dioxide and nitrogen oxides via spray drying: Using sodium-based and calcium-based sorbents with select additives

Several inorganic compounds including deliquescent compounds, catalysts, and an oxidant were added to the spray-dryer sorbents to evaluate their influence on the removal efficiencies of contaminant gases in a spray dryer. Two preliminary studies were conducted before the removal-efficiency tests. The experimental hygroscopicity tests evaluated the dependence of optical particle diameter on relative humidity, additive concentration, additive composition, and sorbent composition. The solubility calculations evaluated the dependence of sorbent's solubility on additive concentration and additive composition. The removal-efficiency tests were conducted by a laboratory-scale spray dryer using sodium-based and calcium-based sorbents with and without select additives. A mathematic model, SPRAYMOD-Y, accounting for the hygroscopicity and solubility of spray-dryer sorbents was developed to predict the simultaneous removal efficiencies of SO$\sb2$ and NO in a spray dryer. SPRAYMOD-Y considered the gas-phase resistance, liquid-phase resistance, and sorbent-dissolution resistance for the constant-rate period and the early stage of the falling rate period. The use of inorganic deliquescent additives decreased the saturation H$\sb2$O$\sb{\rm (g)}$ pressure over the surface of the droplet and thus reduced the rate of H$\sb2$O$\sb{(\ell)}$ evaporation. The decrease of the rate of H$\sb2$O$\sb{(\ell)}$ evaporation increased the drying time of the droplet and thus enhanced the removal efficiencies of SO$\sb2$ and NO in a spray dryer. The SPRAYMOD-Y predictions agreed well with the experimental results.U of I OnlyETDs are only available to UIUC Users without author permissio