Spray Drying of Aqueous Solutions of Inorganic and Organic Materials

Since the characteristics of the solution and the hot drying air have major influence on the physical, structural, and granulometric properties of the powders obtained by spray drying, it is very important to properly select the process conditions which will result with the formation of a powder of desired properties. For that reason, the influence of process conditions on the properties of the powders produced by spray drying has been investigated on a laboratory scale. The aqueous solutions of two organic (glycine and pentaerythritol) and three inorganic (sodium chloride, potassium chloride and potassium sulfate) materials have been chosen. During very fast spray drying it is impossible to distinguish individual steps of simultaneous processes (crystallization and drying). Knowledge of solubility data and crystallization kinetics of selected materials may help to explain what happens during spray drying. The experiments have been performed at different drying air temperature, flow rate of the solution and of the spraying air. The obtained powders are mostly crystalline and agglomerated. Investigated process conditions influence the polymorphic composition of glycine obtained by spray drying. In order to have real information about the granulometric composition of powders it is necessary to perform microscopic analysis of the obtained crystals.