Thin film drying on a permeable surface

A new drying technique for thin films of colloidal slurries and solutions has been proposed and evaluated. A bench top representation of the proposed drying system was constructed to test feasibility and performance of a mathematical model of the drying process. Preliminary tests showed that a water-vapor permeable drying surface could be an attractive alternative to traditional, thin-film drying methods. Four experiments, using modified corn, potato and rice starch films, were conducted.

The advantage of the new drying method is twofold: (1) the process of dehydration is up to 70 percent faster than traditional methods, and (2) the quality of the final product may be improved due to lower solids temperatures. Energy savings, a third possible advantage, remain undetermined in this study.

Shrinkage and heat and mass transfer of the proposed thin film drying system are described by the mathematical model. Physical properties of starch including moisture diffusivity, heat of sorption, modules of elasticity, bulk shrinkage, water activity, and thermal diffusivity have been taken from the literature and used in the model. The mathematical model accurately predicted drying curves for thin films of starches used in this study.