Abstract: A spray dryer apparatus for contacting a hot gas stream containing gaseous impurities with an aqueous medium containing an absorbent for the impurities to produce a gas stream of reduced impurity content and dried powder products. The apparatus includes a chamber formed symmetrically about a vertical axis and an atomizer means located in an upper portion of the chamber for introducing a finely dispersed spray of the aqueous medium, a conduit for delivering the hot gas stream to the chamber and a gas injection means for receiving a major portion of the hot gas stream from the conduit and introducing it circumferentially about the atomizer means. The gas injection means imparts both axial and angular velocity components to the major portion of the hot gas stream whereby the hot gas stream swirls downwardly through the chamber.The apparatus provides a bypass means for withdrawing a minor portion (about 5 to 25 vol.