Abstract: In a process involving contacting a gas with a liquid whereby to cool and/or clean the gas, the liquid is sprayed into the gas by a rotary-cup atomizer or other "air-assisted" atomizer in which the spray is produced by impacting a film of the liquid with a high pressure air stream. The atomizer has a low spray angle which is beneficial to ensuring good contact with the gas. The method is particularly applicable to processes where the liquid is an abrasive slurry or solution, as in a process of desulphurizing a hot flue gas by spray drying in a tower.