Single-stage evaporation process

Next, distillation was used. I visited a primitive distillation plant in Peru. It was a single-stage evaporation process. The fermented grape juice is partially vaporized and the alcohol-water vapors are totally condensed. The resulting condensate is 40 to 44 percent alcohol. The higher alcohol content is obtained by vaporizing less of the still s content. 

This process is an evaporation that is conducted at such low pressures that the distance between the hot and condensing surfaces is less than the mean free path of the molecules. Each unit is a single stage, but several units in series are commonly employed. Molecular distillation is applied to thermally sensitive high molecular weight materials in the range of 250-1200 molecular... 

A thermodynamic analysis of the energy requirements of desalting processes is presented, to clarify the conditions under which such calculations are valid. The effects of departure from isothermal operation, finite product recovery, differential as opposed to single-stage operation, and salt concentration in the feed are examined. A comparison shows that there is essentially no difference between the energy requirements for a distillation and a freezing process. The minimum heat consumption and maximum number of efFects for a multiple-effect evaporation plant are calculated. The above analysis leads to the conclusion that efficiencies in the range 10 to 20% will be very difficult to achieve. 

FIG. 18-80 Swenson single-stage recompression evaporator. (Swenson Process Equipment, Inc.)... 

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