Simple substances refining: efficiency of distillation methods


National Scientific Center "Kharkiv Institute of Physics and Technology", National Academy of Sciences of Ukraine, 1 Akademicheskaya St., 61108 Kharkiv, Ukraine

Received November 11, 1998; in final form January 10, 2000

A method has been proposed to evaluate the efficiency of different distillation methods based on the efficiency, S, calculation as the ratio of the substance purification degree using a specific technique to that attainable by the simple distillation. The method peculiarities have been discussed associated with the S dependence on the temperature and impurity concentration. Literature data have been considered concerning different distillation techniques (condensation under a temperature gradient, distillation with the vapor chemical treatment, using of a chemically active admixture or chemically active filter, etc.). The S values for different distillation techniques have been found to vary from <<1 to 260 (S<<1 means that the result is worse than at the simple distillation). In some cases, the efficiency is very high and comparable to that of rectification; in other ones, the efficiency can be enhanced. The techniques combining the distillation with a chemical treatment are of somewhat higher efficiency. The efficiency of most techniques is better with respect to impurities having the separation coefficient close to 1. In each technique, S can exceed 1 for some impurities and be less than 1 for other ones. S can be concentration-dependent and decrease as the initial impurity concentration decreases.

Previous | Contents Next