Fluid effective extraction rate, factors

The extraction of toluene and 1,2 dichlorobenzene from shallow packed beds of porous particles was studied both experimentally and theoretically at various operating conditions. Mathematical extraction models, based on the shrinking core concept, were developed for three different particle geometries. These models contain three adjustable parameters an effective diffusivity, a volumetric fluid-to-particle mass transfer coefficient, and an equilibrium solubility or partition coefficient. K as well as Kq were first determined from initial extraction rates. Then, by fitting experimental extraction data, values of the effective diffusivity were obtained. Model predictions compare well with experimental data and the respective value of the tortuosity factor around 2.5 is in excellent agreement with related literature data. 

Removing an analyte from a matrix using supercritical fluid extraction (SEE) requires knowledge about the solubiUty of the solute, the rate of transfer of the solute from the soHd to the solvent phase, and interaction of the solvent phase with the matrix (36). These factors collectively control the effectiveness of the SEE process, if not of the extraction process in general. The range of samples for which SEE has been appHed continues to broaden. Apphcations have been in the environment, food, and polymers (37). 

Effect of Solvent Concentration on Reaction Rate. In the kinetic modeling of chemical (such as kraTt) pulping, the effect of cooking liquor on delignificatlon rate Is sometimes considered. For example, the alkali concentration [0H ] can be Included In the rate equation (12,13,32). Since the extraction experiments In this study have been conducted under constant solvent flow (1 g/mln) and the solvent ratios In binary fluid extractions have been maintained at a constant, one can combine the solvent concentration factor Into an effective rate constant (keff). Therefore, Equation 13 can be rewritten as ... 

Most importantly for computational viscoelastic fluid mechanics, most of the charmel DNS calculations are not performed for a constant flux (which would have naturally resulted in a constant bulk Reynolds number) but for a constant pressure drop per unit length that results in a constant zero shear rate friction Reynolds number. These runs lead to substantial variations in the (instantaneous and average) bulk Reynolds number from which the drag reduction needs to be estimated. Knowing roughly the relationship between the friction and the average bulk Reynolds number for a Newtonian fluid (from the experimentally determined and DNS confirmed empirical relationships for the skin friction factor - see, for example. Ref [34]), one can extract such a relationship that also takes into account the already mentioned (in Section 1.2) shear thinning effect in association with viscoelastic results [78]. 

---