Concentrazione di mosto d' uva mediante distillazione osmotica: effetto dei parametri operativi sul flusso di evaporazione

In this work the effect of various operating parameters on the evaporation fluxes obtained in the concentration of grape must by osmotic distillation (OD) was studied. Evaporation fluxes in the range of 0.1 to 2.0 kg/m2h were obtained by modifying several operating parameters such as the solute content, the circulation velocity and the temperature of brine solution (calcium chloride dehydrate) and grape must. The analyses of the results indicates that the solute content, either salt or total soluble solids (TSS) content, is the most influencing variable involved in the process. An increasing of the circulation velocity of the salt solution, in the range of the velocities investigated, determined a significant improvement (43%) of the water transport. On the contrary, the contribute of the feed velocity to the improvement of the evaporation flux was insignificant. Consequently, the control of the hydrodynamic circulation conditions on the brine side can lead to a significant flux improvement that must be considered in a process optimization study. The evaporation flux was improved by 2.2 times when the temperature of the solutions, under isothermal conditions, increased by 15 degrees. Finally, the evaporation flux was significantly increased by combining a temperature gradient with a concentration gradient between the grape must and the brine solution.