Improving the Performance of a 3-Stage Cyclic Crystallization Process Using a Hydrocyclone

Abstract

A dissolution process featuring a hydrocyclone for the selective removal of fine crystals, i.e., an operation analyzed through modeling and experiments in earlier studies, is implemented into a 3-stage cyclic crystallization process, which consists of repeated application of crystal growth, wet milling, and dissolution. For the selection of a hydrocyclone and of its operating conditions, experiments demonstrate that a mathematical model provides accurate estimates of the classification curve for different compounds and physical properties of the suspension, thus facilitating the process design. Two campaigns are conducted with two compounds, namely, γd-mannitol and β l-glutamic acid, where the selective dissolution strategy is compared to standard partial dissolution in terms of the attributes of the final product powder obtained from the 3-stage process. Crystal size, crystal shape, flowability, and filterability are measured, and it is shown that they are greatly influenced by the dissolution stages. Most remarkably, in the case of γd-mannitol, the experimental evidence shows that selective dissolution enables the removal of a greater amount of fines for the same mass of crystals being dissolved, thus improving the productivity of the process, as well as the measured flow and filtration performance.