Spray absorbers/spray dryers are chiefly used for removing gaseous pollutants from the flue gas. The pollutants are converted to solid salts by addition of an absorption solution. In addition, a large proportion of vaporous heavy metals condenses on the solid particle surfaces.
Turbulences in the incoming gas are achieved by means of deflector plates in the spray absorber. The absorption solution is introduced to the gas stream through annular nozzles. The solution is generally an aqueous lime solution nebulized to form a mist. The pollutants are bound to the lime after evaporation of the water. No waste water is therefore created.
A specific temperature gradient is required for the spray absorber to work. The lower the initial temperature of the flue gas on emergence, the better the condensation of the vaporous heavy metals on the surface of the solid particles.