Crystallizers: Design and Dimensions

Introduction

Qualities of a crystallized product

These qualities concern size, granulometry, purity and facies.

• 1) Size is the result of a compromise, since regular crystals of large size are expensive to produce. Typically, we accept a size that allows easy dewatering (or filtration), storage and transport. Occasionally, a small size is preferable (pigments and charges for plastic materials, later dissolution).
• 2) The size distribution required is often as tight as possible, though this is not always the case.
• 3) Purity is attained by the careful choice of bleeding.
• 4) Facies (shape) is influenced by both the impurities present and supersaturation (dendrite growth for high supersaturations).

Crystallizers

We will not attempt to apply a classification to crystallizers, which would be a futile exercise. However, we will review the main types of devices currently in use, with a particular focus on their operating mechanisms.

This study will lead us to establish several simple criteria for choosing the crystallizer best adapted to the work in question.