Aitor Cabezas Millán
Resumen
In these days, wine industry is reinventing itself by offering new products such as partial dealcoholized wines owing to the upward demand of these kinds of goods, which are having a significant acceptance amongst citizens, who find it better for their health and perceive it as luxurious articles. For these reasons, many attempts have been carried out so as to fulfill this increasing demand.
Amongst the most used techniques, postfermentation ones have drawn attention, however, many of them have resulted in unsuitable techniques that harm and lower excellent wines by affecting their aroma, which is the most appealing aspect of them. One technique that is gaining attention is evaporative pertraction (EP), which allows reducing these drawbacks.
EP is an isothermal and non-pressure driven membrane process which allows removing ethanol from wine without excessively affecting its properties, positioning itself as a groundbreaking field. Therefore, creating a model which represents reality as efficiently as it can is the main aim of this document. For this reason, a series resistances model has been developed using Aspen Custom Modeler (ACM), which has been used in order to create the model and run a dynamic simulation. The model consists of a dynamic system of PDEs (Partial Differential Equations) which is solved discretizing by the finite volume method and the method of lines for the time integration.
Several operation conditions have been studied, having obtained the experimental values from an equipment where two storage vessels containing the feed (wine) and stripping (water) phases were used in order to contact wine and water through a polypropylene hollow fiber membrane contactor, allowing ethanol transfer from wine to water. This contact is made by several pores filled with air, where the ethanol evaporates and gets in the pore matrix to finally abandon it and condense in the stripping phase. The driving force is the partial pressure difference at their respective interfaces.
In general, this model yields a positive outcome to predict both the alcohol degree as a function of time and the magnitude order of the ethanol global fluxes during the whole operation, having observed that an increase in the feed flow keeping the rest of the variables constant ($Q_{s}$=39 ml/min, $V_{f}/V_{s}=2$) and in the feed/stripping volume relation ($V_{f}$=375ml, $Q_{f}$=65 ml/min and $Q_{s}$=39 ml/min ) produces a greater ethanol removal. The optimal operation condition has turned out to be condition 4 ($Q_{f}$=74 ml/min, $Q_{s}$=39 ml/min and $V_{f}/V_{s}=2$), which allows reducing the time that wine is in contact with the membrane, preventing undesirable effects in wine quality.
Although many other components evaporate from wine, the model developed in this Final Degree Project (FDP) only considers wine as a mixture of wine and ethanol as a first approach. Nonetheless, this ACM model has an importance in order to set a benchmark, acting as a skeleton of more complex models due to the accuracy that it has shown in the outcomes predicted, and which is bound to be deeply developed in order to shed light on this innovative process.