Fluid Dynamics, Mass Transfer, and Particle Formation in Supercritical Fluids

Abstract

FIGURE 1 (a) Schematic of a laser interferometer. Mirrors (M1 and M2) and cubic beam splitters (B1 and B2) constitute the Mach-Zehnder configuration. The interferometric fringes overlap the image of the flow or droplet within the optical cell created by the objective (O). The optical decoder (D) provides four parallel phase shift images, which are processed and stored by a computer to extract information on the dynamics of mass or heat transfer. (b) Optical cell, used for interferometry, laser diffraction, phase Doppler anemometry, or smallangle X-ray scattering (SAXS) measurements, manufactured by Thar Technologies Inc. (Pittsburgh, PA). This cell is equipped with single-crystal diamond windows for SAXS. FIGURE 2 P-T mixture critical curve (solid line) for ethanol-CO 2 modeled from the Peng-Robinson equation of state, also shown in relation to the extension of the gas-liquid coexistence curve for pure CO 2 (dashed line) (8).FIGURE 3 (a) Mean-square density fluctuation and (b) correlation length as functions of pressure at constant temperature 313.1 K for pure carbon dioxide and a mixture containing 1.6 mol % of ethanol.FIGURE 5 (a) Flow pattern in the precipitation vessel from a two-component mixing nozzle. (b) Distribution of fluid density in this system at 20 MPa and 323.1 K in the vessel.FIGURE 6 (a) Image of acetaminophen crystals (mean size f3 Am) obtained by precipitation from ethanol solution with CO 2 and used as seeds. (b) Jet flow pattern obtained by application of autocorrelation PIV algorithm to this image. The conditions correspond to those in Figure 5.

The Effect of System Temperature and Pressure on the Fluid-Dynamic Behavior of the Supercritical Antisolvent Micronization Process: A Numerical Approach

“…In this study, the energy variation due to the mixture enthalpy variation is accounted for in Eq. (11) by the source term S h (Jerzy et al, 2004):…”

“…01, pp. 73 -90, January -March, 2016  , can be understood as the deviation from the locally perfect mixture state, that is, the mixing process can be understood as the dissipation of such variance (Fox, 2003;Jerzy et al, 2004). The transport equations 2  are considered and inserted into the system of equations as user defined scalar -UDS -transport equations (ANSYS, 2010).…”

“…Among such techniques, one can highlight: the RESS -Rapid Expansion of Supercritical Solutions technique and its variants such as RESOLV, RESSAS (Türk and Bolten, 2010), and the SAS technique (Supercritical Antisolvent) and some variants such as SEDS, GAS and PCA (Bałdyga et al, 2010;Jerzy et al, 2004;Martín et al, 2007).…”

“…They are also designed for experimental adequacy to obtain good T 0 and P 0 limits for a determined system (for particular combinations of solutes and organic solvents), given the time expended to carry out several experimental runs and high material costs (Erriguible et al, 2013b). Beyond this, under high pressure, optical measurements to observe the flow patterns (as shadowgraphs or schlieren techniques) of the precipitation process may be obscured by temperature gradients, species concentration, and large numbers of very small particles that accompany flow in the precipitation chamber (Jerzy et al, 2004). This changes the way in which light passes through the flow, since the density variation may interfere with refractive indices and cause delay associated with non-homogeneity in the mid-section (Raffel et al, 1998).…”

“…However, within this scope there remains a lack of specific publications referring to the influence of operational temperature and pressure parameters upon the dynamics of the supercritical mixture. Some authors do consider the SAS process in the isothermal regime (Cardoso et al, 2008;Erriguible et al, 2013a;Martín and Cocero, 2004), while others have emphasized the influence of temperature variation (Jerzy et al, 2004;Sierra-Pallares et al, 2012).…”