On the basis of the balance of forces acting on droplets falling down inside a co- or counter-current spray tower, a model of scrubber aerodynamic characteristics was developed. Relations between pressure drop caused by spray, droplet concentration and residence time distribution of the dispersed phase were found analytically for slurry droplet motion in the range of 400 < Re < 2500. The differences between the simplified model solutions and complete solutions are presented. The model was verified by the experimental data collected in two large pilot plant scrubbers applied for flue gas desulfurization (FGD).