Ultrasound-assisted crystallization
is a promising process for
the production of crystals within a size distribution width. Toward
the direction of attaining high-quality crystals, this article proposes
and assesses a theoretical feedback control scheme that can be applied
in a continuous tubular crystallizer. In this crystallizer, the antisolvent
crystallization of aspirin (a pharmaceutical ingredient) in water
(an antisolvent) and ethanol (a solvent) takes place under ultrasound.
Initially, a dynamic model is developed and includes the aspirin concentration
variations while also taking into account temperature modifications
in the inlet. After model validation, a PI control scheme is finely
tuned, implemented theoretically, and critically assessed at the (i)
trajectory control of the crystal length (average size), (ii) alleviation
of suddenly emerged disturbances (e.g., solvent flow rate, inlet temperature),
and (iii) a combination of worst-case operating scenarios. As identified,
the proposed controller can offer a practical platform that can be
readily applied to different scales and geometries in continuous tubular
crystallizers operating with ultrasound. During all simulations, the
produced crystals maintained high quality.