Abstract: A method of treating a polluted gas e.g. desulphurizing a sulphur dioxide-containing flue gas is carried out by spraying the flue gas with a slurry of e.g. calcium hydroxide, under spray drying conditions. The spray device comprises a rotating cup comprising an extended surface on which a film of slurry is formed. On leaving the surface the slurry is immediately impacted with a high velocity stream of air supplied through an annular orifice.Arrangements for supplying the slurry to the rotating cup comprises a stationary distribution device adapted to direct the slurry onto the surface with a swirl component of motion.