Experiments for HCl sorption by calcium and sodium sorbents have been carried out with simulated gases of compositions typical for "air-blown" and "oxygen-blown" IGCC fuel gases. The concentration of CO2 affects the behaviour of HCl sorption by Ca-sorbents but does not influence the performance of Na-sorbents in the temperature range 300-600 degrees C. The sorbent panicle size has a slight effect on HCl sorption by Na2CO3 in the range 90-250 mu m. The optimum temperature for the reaction was found to be between 400 and 500 degrees C. This has been attributed to a combination of reaction kinetics and sintering. A mathematical model has been developed to simulate gas solid reactions in fixed beds. The coefficient of gas diffusion through the product layer (NaCl) was obtained at 300-600 degrees C.