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A new process consisting of a combination of crystallization, milling, and dissolution stages is presented. At first, a mathematical model for the different unit operations, as well as their coupling, is developed, based on the basic phenomena characterizing the evolution of the ensemble of particles in terms of both size and shape. Because of the broad design space and the plethora of interparticle phenomena, the mathematical model stands out as a vital tool for an in silico assessment of process feasibility. Subsequently, computer simulations can be exploited for a thorough understanding of the effect of the different operating conditions. The results collected are discussed considering the particle size and shape distribution in its entirety and by means of its properties, such as the average sizes and the variance. A final assessment is performed by comparing the combined process with a single cooling crystallization stage, both with and without a milling of the final products.

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In this work, thorough experimental characterization and theoretical investigation for the quantitative description of the breakage of needlelike crystals of βl-glutamic acid in a continuous rotor-stator wet mill are performed. The constitutive equations of the newly developed model rely on the physics of the phenomena occurring at the single crystal and at the process scale. The fundamental equations consider not only the operating conditions adopted for the grinding device but also the morphology of the crystals. First, a comprehensive experimental campaign is performed to investigate the effect of the different operating conditions, namely, the suspension density, the rotor speed, and the residence time in the grinding chamber, on the product properties, in particular, the average sizes and the particle size and shape distribution. Measurements are collected using an in-house developed double-camera stereoscopic measurement device, the μ-DISCO, capable of quantitatively measuring the particle size and shape distribution. The data collected shed light on aspects previously hardly accessible, providing a set of robust quantitative information for a thorough experimental characterization of a continuous milling process. Furthermore, these data can be used to estimate the kinetic parameters and to obtain a model, which is able to quantitatively predict the product properties.

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