**2.5 Spinning cone column**

*Advances in Grape and Wine Biotechnology*

K values of the respective substances [32, 34]:

Distillation is a thermal separation process in which liquids are vaporized and the vapor then condensed. Generally, distillation is a process that separates substances according to their relative volatility. The relative volatility is a measure of the separability of a distillation with respect to two components to be separated. The relative volatility of two components (α) is calculated from the quotient of the

<sup>∝</sup> *<sup>i</sup>*,*<sup>j</sup>* <sup>=</sup> <sup>K</sup> <sup>−</sup> Value Substance <sup>i</sup> \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ K <sup>−</sup> Value Substance <sup>j</sup> (2)

The volatility of a substance, in turn, depends on the K value. The K value of a

The higher the *K* value, the higher the amount of the respective substance in the vapor phase. The *K* value depends on the temperature, pressure, and composition

Higher temperatures greatly increase the vapor pressure, so the K value of the substance increases as well. If the vapor pressure of the liquid mixture is equal to the ambient pressure in the distillation unit, the liquid begins to boil. The vapor pressure of the liquid mixture is composed according to Dalton's law from the vapor pressures of the individual components, also called partial pressures together. Depending on the nature of the composition of the liquid mixture, the boiling point

The alcohol content of the rising vapors during distillation increases when the boiling liquid contains more alcohol. In addition, the boiling point is lower with increasing alcohol content of the liquid. On the other hand, it can be seen that the gain factor decreases as the alcohol content of the solution increases. The gain factor describes the amount in which the alcohol content increases from the starting liquid until the distillate. The vacuum distillation achieves lower boiling points by applying a vacuum in the column. By lowering the pressure inside the plant, the volatility of the components is increased, and thus the boiling point of the ethanol is reduced. Consequently, the energy required to boil from the ethanol decreases. As a result, the thermal load on the ingredients of the treated liquid is minimized. Alcohol

To increase the alcohol content in the distillate, the rising vapors in the distillation column are amplified. This is done by allowing the ascending vapors to flow through the so-called caps of the column against an incoming liquid. The vapor is enriched with volatile components such as ethanol, while the incoming liquid is enriched with high-boiling components from the steam. Depending on the field of application, the columns have different numbers of amplifier caps. This countercurrent distillation or rectification mentioned method is cheaper and less expensive

(mole fraction substance <sup>i</sup> in liquid phase) (3)

substance describes the tendency of a substance to volatilize [32]:

reduction of wine takes place at around 26–35°C [14].

further concentration is realized [34].

apparatus, as multiple repetitions of single-stage distillation [30].

In general, the alcohol content in the distillate can be up to a content of 97.2 vol.% increase. Then a so-called azeotrope occurs. With an aqueous alcohol solution of 97.2 vol.%, the boiling point at atmospheric pressure is 78.15°C and thus below the usual boiling point of ethanol. Since the rising vapors from this mixture have the same composition as the starting liquid, the gain factor is 1.0, and so no

Ki = (mole fraction substance i in vapor phase)/

**2.4 Vacuum rectification**

of the liquid [32].

shifts [34].

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A special form of vacuum rectification is the spinning cone column. This unit is used in the food and beverage industry in various areas for aroma separation and aroma recovery [8].

Unlike conventional columns for vacuum rectification, no static installations are used. Within the cylinder of the spinning cone, there are pairs of a fixed and a movable cone installed. The wine running down the column from the top forms a thin film due to the rotation of the cones. On the underside of the movable cones, there are fins, which swirl the rising vapors and thus allow an increased exchange between the wine and the so-called strip phase.

The special design of the spinning cone column helps to overcome the disadvantage of conventional columns for vacuum rectification. The mass transfer in the column is reduced by the application of the vacuum that instead of turbulent flow, only a laminar flow of the boiling gases prevails. This general disadvantage of distillation under vacuum is qualified by the fact that rotating inserts are mounted in the column. The liquid running down is transformed by its rotation into a thin liquid film. On average, this liquid film is less than 1 mm thick. This results in a very efficient contact between vapors and liquid, whereby the necessary residence time is reduced in the column. In addition, the construction of the spinning cone column, unlike columns for vacuum rectification, can also work with viscous or slurries with a high solid matter content [9, 35].
