Influence of the Nozzle Geometry on Spray-Dried Particle Formation Expanding Superheated Suspensions

摘要

Expanding a superheated solution or suspension to ambient atmosphere leads to a flash evaporation as a part of the pure liquid evaporates [1-3]. If a superheated solution or suspension is atomized into a spray dryer working under atmospheric conditions, the particles formed are smaller than the particles resulting from nonsuperheated suspensions. At hollow cone nozzles the generation of fines can nevertheless be kept within reasonable limits. The amount of air needed to dry the particles is reduced and the filters or cyclones installed for exhaust gas cleaning can be operated at lower pressure drop. Because of the decreased amount of drying air, the energy losses are also reduced. Another advantage is the reduced viscosity of the heated solution and improved atomization [4]. Of course, one has to make sure that the heated species are stable enough at high temperatures as, for example, suspensions of ceramics.