Special Distillation Applications

The field of distillation has existed for millennia and has evolved from simple batch stills for alcohol and perfume extraction in antiquity to some of the largest pieces of equipment on most modern chemical plants. For some separations, however, boiling the feed mixture, as in standard distillation, must be avoided as some of the components might be destroyed, and for these, short path distillation is now routinely used in industry. Some separations are better performed in completely different configurations that do not rely on gravity but rather on centrifugal forces, as in high gravity, or HiGee, units. The scale of distillation operation in industry is continuously increasing and has resulted in larger and larger distillation column configurations. In recent years, however, small-scale operations down to milli- and microscale have become of interest as means of separation for integrated and intensified micro plants, or labs-on-a-chip. Distillation can also be achieved with the use of a membrane in membrane distillation, a configuration that is finding increasing interest within desalination. These nonstandard modes of distillation will be considered in this chapter. The main principles of the operation will be outlined, and a summary will be given of current work that has considered these processes, as well as where the main applications either can be found today or might be found in the future.