The study, conducted in a fixed bed multilayer reactor, investigates the influence of temperature (200 - 600 degrees C), HCl concentration (3000, 6000 and 9000 ppm) and particle size (120 and 209 mu m) on the HCl collection efficiency of sodium carbonate. Results show that the carbonate conversion and the HCl collection efficiency reach the maximum values in the temperature range of 400 - 500 degrees C, while the HCl concentration and the humidity of the gas have negligible influence on the sodium carbonate conversion efficiency. Furthermore results show that the neutralization reaction is weakly influenced by the sorbent particle size, although some differences are appreciable only at low temperature. The experimental data were interpreted by using the particle grain model implemented in a fixed bed reactor model. A first order reaction with respect to hydrogen chloride concentration has been found adequate to describe the neutralization reaction, which is governed by a combination of chemical reaction and product layer diffusion. An optimization procedure carried out in the gPROMS (TM) environment allowed to calculate the Arrhenius parameters for the reaction rate constant and the diffusion coefficient in the product layer. (c) 2006 Elsevier Ltd. All rights reserved.