1984 Volume 17 Issue 5 Pages 486-490
To clarify the behavior of a trace component during distillation under reduced pressure, the vapor-liquid equilibrium ratio and the plate efficiency of the trace component are needed.
Vapor-liquid equilibria of aqueous ethanol solution containing about 0.05 wt % furfural (trace component) were measured at 25.3 kPa and 12.7 kPa by use of an Othmer-type still. The equilibrium ratio of furfural varys only slightly with the reduction of pressure.
Distillation experiments were carried out by use of an Oldershow-type column at atmospheric pressure, 25.3 kPa and 12.7 kPa. A method for calculating the plate efficiency from the concentrations of distillate and bottoms was derived. The calculated results show that the Murphree vapor efficiency is little affected by pressure in the range of 12.7 kPa to atmospheric pressure.
By reducing the pressures, the bubble point of the system decreases remarkably, but the change of behavior of a trace component in distillation becomes quite small.
