Experimental study of dry HCl removal from simulated combustion flue gases using calcined limestone (CaO) is reported. The study was conducted in a unique fixed-bed reactor coupled with an online Fourier transform infrared (FTIR) spectrometer to investigate the effects of the presence of SO2, CO2 and O-2 on the chlorination reactivity of calcined limestone. The dechlorination efficiency, defined by the effluent HCl concentration, would be used to describe the HCl absorption history to gain a better understanding of the chlorination behavior. The experimental results indicated that the HCl uptake capacity remains less affected under various gas atmospheres at 650 degrees C although the chlorination is found to be faster when CO2 is present. At temperatures of 750 or 850 degrees C, the presence of SO2 or O-2 significantly decreases the reactivity of the calcined limestone toward HCl. The concurrent sulfation of chlorides, such as CaCl2 center dot H2O and/or CaClOH, causes the subsequent rerelease of HCl to the gas phase, thus reducing the attainable extent of the chlorination reaction. The presence of O-2 impedes the conversion of calcined limestone to chlorides, presumably through some type of reaction involving the dechlorination of the sorbent particles.