Simulation of the semicontinuous supercritical antisolvent recrystallization process

A model is developed for simulating semicontinuous supercritical antisolvent recrystallization processes. Thermodynamics, hydrodynamics, and mass-transfer issues are addressed. The model makes it possible to calculate the composition and flow-rate profiles of the vapor and liquid phases and the amount of the solid product along the precipitator. The effect of the operating variables is discussed. With reference to a CO2-toluene-naphthalene-phenanthrene system, it is shown that the dissolution of the antisolvent in the liquid phase is usually faster than the evaporation of the solvent, that the two solutes may behave in completely different ways at the same process conditions (for example, phenanthrene can be easily precipitated, while for naphthalene a higher gas-to-liquid flow-rate ratio is needed, to force solvent evaporation), and that under proper operating conditions it is possible to selectively precipitate phenanthrene from a phenanthrene + naphthalene solution.