Quasi-static measurement of equilibrium solubilities in SC fluids: a mass transfer criterion

In this paper a continuous quasi-equilibrium method was used to determine the solubilities of α and β-naphthol in supercritical carbon dioxide. For the case of a packed bed extractor in which pure solid slabs were contacted with the flowing fluid, the approach to equilibrium is judged in terms of a modified Stanton number, in the region where free convection effects are dominant (low Reynolds number). Analysis of data from Tan and Weng [C.-S. Tan, J. Weng, Fluid Phase Equilib. 34 (1987) 37–48] and Anistescu-Tavlarides [G. Anitescu, L.L. Tavlarides, J. Supercrit. Fluids 10 (1997) 175–189;] for several solutes, as well as own data, show that quasi-static experiments provide the equilibrium solubility with negligible error.