Crystallization of Organic Compounds, 2nd Edition

Chapter 5Mixing and Crystallization

5.1 INTRODUCTION

Mixing in crystallization involves all elements of transport phenomena: momentum transport, energy transport, and material transport in both the solution phase and the solid phase. In many cases, the interactions of these elements can affect every aspect of a crystallization operation including nucleation, growth, and maintenance of a crystal slurry. To further complicate the problem, mixing optimization for one aspect of an operation may require different parameters than for another aspect even though both requirements must be satisfied simultaneously. In addition, these operations are intrinsically scale dependent. For these and other reasons to be discussed below, it might be stated that crystallization is the most difficult of the common unit operations to scale up successfully.

Successful operations depend on identifying the mixing parameters for the most critical aspects of the process and then evaluating whether those parameters will be satisfactory for the others. Although this approach may be satisfactory in most cases, there will be crystallization procedures that require operation under conditions that are not optimum for mixing for some aspects of the operation, as discussed below.

Successful scale‐up implies that both physical and chemical properties have been duplicated between pilot plant and plant operations. These rigid criteria are not always required but are, for example, for final bulk active pharmaceutical ...