In the application a spray dryer absorption apparatus for treating a stream of flue gas containing acidic components is disclosed. The apparatus comprises a chamber having vertical cylindrical walls, said chamber comprises (i) an inlet for a flue gas stream containing an acidic component, (ii) an atomizer for spraying droplets of an absorbent slurry into said flue gas stream to effect a chemical reaction between the droplets and the acidic component of the flue gas, thereby forming a particulate reaction product, and (iii) an outlet for the treated flue gas and entrained particulate reaction product, wherein the bottom of the chamber having vertical cylindrical walls is substantially horizontal and impervious to gases. The apparatus of the invention has the advantage of a simplified geometry accounting for lower building and maintenance costs.