Continuous Sugar Crystallization: A Chemical Engineer’s Viewpoint

Abstract

From the standpoint of a chemical engineer, the crystallization of both salt and sugar are by far the oldest and probably still among the most important of crystallization activities. The crystallization of sugar was known in prehistoric times, and records from 500 A.D. in Persia show that people collected syrups and boiled them to produce a purified form of crystalline sugar. This same general procedure seems to have been in use for a thousand years or more until roughly the beginning of the nineteenth century, when a French inventor developed the vacuum pan. The use of vacuum evaporation permitted operation at temperatures much lower than had been the practice previously and led to less discoloration of the syrups and solutions of much lower concentration from which the separation of crystalline material was easier.

Although sugar crystallization is one of the oldest and most important crystallization activities, it is still accomplished by batch methods. A chemical engineer has much to offer in possible improvements in the current process and in the design of possible continuous processes. A workable continuous process is described, along with a discussion of the economics engendered.