Crystallisation in concentrated systems: A modelling approach

AbstractWater crystallisation in concentrated systems has been studied using a combination of mathematical modelling and experimental work. Two different freezing models have been employed to describe primary and secondary mechanisms (i.e. non-seeded and seed-induced processes, respectively) in sucrose solutions up to 60% (w/w). Differential Scanning Calorimetry (DSC) has been employed to characterise the phase change of the binary water–sucrose system in primary processes, and the kinetic and thermodynamic parameters obtained were coupled to the heat transfer equation to obtain the product temperature distribution. A recently developed method has been also employed to measure crystal growth rates in seed-induced crystallisation systems. Simulated results for the secondary crystallisation mechanism were able to reproduce experimentally observed trends for growth rates. An evaluation of the energy consumption during freezing/crystallisation processes has been carried out to assess each mechanism performance (crystallisation will occur at temperatures approximately 20°C higher in seeded processes) considering different process conditions and product formulations (i.e. solids and air fractions)