This work evaluates both the removal efficiencies of HCl and SO2 at different points in a spray dryer using Ca(OH)(2) as the absorbent. The operating conditions were specified in terms of the temperature of the flue gas (200-300 degreesC), the HCl concentration (120-1000 ppm), the SO2 concentration (150-500 ppm) and the amount of CaCl2 added (10-30 wt.%). The experimental results showed that the SO2 removal efficiencies were higher in the presence of HCl (120-500 ppm) than in the absence of HCl at 250 degreesC and 20% relative humidity (RH). However, the removal efficiency of SO2 decreased as the HCl concentration increased. The removal efficiency of SO2 also increased with the amount of CaCl2 in the spray dryer. (C) 2004 Elsevier Ltd. All rights reserved.