A semi-dry gas desulfurization method (mainly flue gases) based on the reaction between sulfur dioxide and alkaline sodium solution or lime slurry in a fluidized bed has been investigated. The bed consisted of inert (nonreactive) coarse particles of diameter not smaller than 1.00 mm. Alkaline reagents (sorbents) were trickled onto the surface of the fluidized bed, where the process gas desulfurization and drying of reaction products simultaneously occurred. The removal of the layer of the desulfurization products covering the bed particles occurred due to attrition during the fluidization, mainly by abrasion of the surface of particles as well as due to collisions of the parent solids in a bed. This allowed SO2 to contact continuously with the renewed sorbent surface and led to the increase of the values of sorbent utilization of over 90%. Then the products were removed from the bed by desulfurized gas and collected in a bag filter or electrofilter. A mathematical model referring to the processes of wet and dry desulfurization of a gas has been developed to predict absorption of SO2 in a fluidized bed. The investigation of fluidization of coarse particles revealed that the mass transfer between the gas and wet surface of the particles was the Controlling step in the overall mass exchange. The results of the experiments showed that the theoretical model adequately described the process under such conditions: the stoichiometric ratio of Ca/S of about 1, the degree of the gas humidity of 0.50-0.98 and by-product recycle ratio of low values. The relationship for desulfurization efficiency (1-eta(X))) = (1-eta(Y))(chi(0.5)phi) may be used to check (with relative accuracy) the degree of desulfurization of spray-dry scrubbing method.