The absorption of SO2 from an SO2/air mixture into CaCO3 slurry or NaOH aqueous solution was carried out using a new model of an air-lift tube (ALT)-type reactor in laboratory scale and in pilot scale. The aim of the study was to improve the efficiency of these processes, widely applied in industry, to find the optimal operation conditions in the new reactor type. The SO2-removal efficiency was measured by varying the gas velocity, the SO2 concentration and either the CaCO3 or the NaOH concentration according to experimental design. A computer program (Statgraphics/experimental design) was used to calculate the mathematical models of the SO2-removal efficiency, and the economic aspects of the two processes were compared.