Abstract
The Supercritical Antisolvent (SAS) technique allows for the precipitation of drugs and biopolymers in nanometer size in a wide range of industrial applications, while guaranteeing the physical and chemical integrity of such materials. However, a suitable combination of operating parameters is needed for each type of solute. The knowledge of fluid dynamics behavior plays a key role in the search for such parameter combinations. This work presents a numerical study concerning the impact of operating temperature and pressure upon the physical properties and mixture dynamics within the SAS process, because in supercritical conditions the radius of the droplets formed exhibits great sensitivity to these variables. For the conditions analyzed, to account for the heat of mixture in the energy balance, subtle variations in the temperature fields were observed, with almost negligible pressure drop. From analyses of the intensity of segregation, there is an enhancement of the mixture on the molecular scale when the system is operated at higher pressure. This corroborates experimental observations from the literature, related to smaller diameters of particles under higher pressures. Hence, the model resulted in a versatile tool for selecting conditions that may promote a better control over the performance of the SAS process.
Highlights
The supercritical state of a mixture is obtained when its temperature and pressure are above theirR
The model is represented by the system of Equations (1)-(19) in order to describe the flow from the SAS process in steady state, considering it as compressible, non-isothermal, and in the turbulent regime because the transition from a laminar jet to a turbulent jet occurs at low Reynolds numbers (Silveira-Neto, 2002)
A mathematical model to describe the flow of a supercritical CO2 and ethanol mixture in non-isothermal, compressible turbulent and permanent regime was employed to evaluate the effect of operating temperature and the operating pressure on the properties: density, viscosity, thermal conductivity and diffusivity
Summary
A suitable combination of operating parameters is needed for each type of solute. This work presents a numerical study concerning the impact of operating temperature and pressure upon the physical properties and mixture dynamics within the SAS process, because in supercritical conditions the radius of the droplets formed exhibits great sensitivity to these variables. From analyses of the intensity of segregation, there is an enhancement of the mixture on the molecular scale when the system is operated at higher pressure. This corroborates experimental observations from the literature, related to smaller diameters of particles under higher pressures.
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