Molecular distillation thermal efficiency

Distillation processes may be operated continuously or batchwise. The operating pressure may be low (10 Pa-100 Pa), medium (10 Pa-0.1 Pa) or even high vacuum (0.1 Pa-10 Pa) (molecular distillation) to avoid thermal damage to the mixture, or to increase efficiency. Special types of distillation are equilibrium or flash distillation (flash evaporation) and carrier distillation processes. 

The thermal efficiency of a molecular distillation is low. Fawcett (Ref. 2) has given a heat balance on a unit distilling triolein at 240 C. with the condenser at 25°C. The data are summarized in the following table ... 

The maj ority of these new plants are corn dry-grind ethanol plants. Approximately 2.5-2.7 gal of ethanol, 17.5 lb of dried distiller s grain (DDG), and 17 lb of carbon dioxide are produced from each bushel of corn processed through a corn dry mill (2). Since 1980, process improvements in enzymes, thermal-tolerant yeasts, molecular sieves, and cogeneration have achieved a 50% reduction in the energy required to produce ethanol from corn (2). Further improvements in efficiencies and reductions in production costs can be expected in the future. 

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