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Crystallization Principle and Objectives

Crystallization is the (natural or artificial) process for the formation of solid crystals from a uniform solution.

More than 80% of the substances used in pharmaceuticals, fine chemicals, agrochemicals, food and cosmetics are isolated or formulated in their solid form. Crystallization is in general the last chemical purification step in the production of ingredients.

Since the properties of a solid material (polymorphism) can dramatically affect the process or the product’s compliance and effect (dissolution rate for example), monitoring and controlling the isolation of solids for the various applications through crystallization is of paramount interest.

Crystallization is also a chemical solid-liquid separation technique, in which mass transfer of a solute from the liquid solution to a pure solid crystalline phase occurs.

Crystallization Technologies

Draft tube baffle technology:

This type of crystallization is especially designed for low viscosity products when a narrow crystal size distribution is expected.
Super saturated product enters into a chamber containing the massecuite (mixture of solids and solution). Instantaneously, the product crystallizes around the crystals that are already inside the vessel so that the solution reaches the saturation point. Inside the chamber, a stirrer creates a high circulation flow in order to give a good repartition of the crystals in the massecuite.

On the side of the vessel, baffles create a quiet zone where an upward flow brings the smallest crystals out of the vessels. They are re-melted and put back in the vessel.

Forced circulation crystallization:

The design of such a crystallization unit is very similar to a forced circulation evaporator. A vertical tubular heat exchanger is only preferred due to the high viscosity of the massecuite.

This type of crystallization unit is designed for the crystallization of salts out of effluent.

Crystallization Plant

A complete crystallization plant includes a crystallization unit, centrifuge, vacuum group and condenser. The installation requires the integratation of crystallization technologies into a well adapted thermic scheme.

As with evaporation, it is also possible to organize different steps of crystallization in a multiple-effect crystallization unit to be combined with mechanical vapor compression or thermo-compression.

Browse the crystallization technology developed by Novasep for food applications.

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