A spray nozzle assembly particularly adapted for directing a finely atomized slurry of hydrated lime for removing sulfur dioxide from flue gases. The nozzle assembly includes a nozzle body having a first pre-atomizing and mixing chamber into which pressurized liquid and air flow streams are directed for breaking down and pre-atomizing the liquid, an orifice plate at the downstream end of the first pre-atomization and mixing chamber for restricting the fluid flow into a second chamber defined by the orifice plate and spray tip, and a spray tip having a plurality of circumferentially spaced discharge orifices through which atomized liquid particles in the second chamber discharge. Each discharge orifice is inclined at a compound angle in order to cause the spray to discharge from the tip as a swirling annular curtain and thereby retard the build up of lime and fly ash on the tip.