No abstract

Axial mixing measurements in single phase (water) flow have been taken in open-type reciprocating plate columns of diameters 25.4 and 508 mm. In the case of the smaller column, two-phase axial mixing was measured, both in the dispersed phase (water dispersed in n-heptane) and the continuous phase (with n-heptane dispersed in water). Pulse injection of a tracer solution of ammonium chloride and methanol in water was used.Under single phase conditions, the axial dispersion coefficients were found to go through a minimum as the agitation level was increased from zero. The coefficients were nearly an order of magnitude higher in the 508 m m column than in the 25.4 m m column. In two phase flow in the 25.4 m m column, the continuous phase axial dispersion coefficients

Liquid–liquid extraction, also known as solvent extracting, is a well‐established separation technique that depends on the unequal distribution of a solute between two immiscible liquids. The initial feed liquid containing the solute is brought into contact with a solvent that is selected to have a greater affinity for the solute. The partition of the solute can be enhanced by adding a chemical extractant to the solvent; this practice is widespread in the hydrometallurgical and nuclear industries. Most industrial extractors operate continuously with countercurrent flow of the two phases. In mixer–settlers, the phases are contacted as a well‐agitated dispersion of drops, which are then sent to settling tanks for phase disengagement. In extraction columns, the dispersed drops move countercurrently against the flow of the second (continuous) phase. The physics, chemistry, and practice of extraction, with brief descriptions of important industrial extraction processes and equipment, are presented. Research on hydrodynamic aspects of process design, eg, axial mixing, drop dispersion, and coalescence, is reviewed. New extraction techniques, eg, membrane extraction, supercritical exctraction, and two‐phase aqueous extraction, are discussed.

ConclusionsDesign equations which are similar t o those for Newtonian fluids have been developed for low Reynolds number heat transfer for pseudoplastic and Bingham plastic fluids. The correlation method is based on methods used for correlating rates of viscous dissipation of energy in non-Newtonian fluids. The variation in heat transfer coefficient with impellervessel wall clearance was investigated. The data obtained show a minimum in the heat transfer coefficient with wall clearance and indicate a n optimum clearance to tank diameter ratio to be greater than 0.06. Scale-up relationships for heat transfer to both pseudoplastic and Bingham plastic fluids have been derived for two common design criteria. AcknowledgmentThe statistical analysis of the data was facilitated by the provision of computer time by the Nomenclature a = exponent on Reynolds number, Equation 3 A = area for heat transfer, ft2 A , = proportionality constant defined by Equation 5 c = exponent on viscosity ratio number, Equation 3 C = constant defined by Equation 3 C l = clearance between impeller and wall, ft C, = heat capacity a t constant pressure, Btu/lb OF 1 = full-scale model 2 = prototype literature Cited effective viscosity, defined by Equation 4, lb, see ft Calderbank, P. H., Moo-Young, M. B., Trans. Inst. Chem. Eng.,

Liquid‐liquid extraction, also known as solvent extracting, is a well‐established separation technique that depend on the unequal distribution of a solute between two immiscible liquids. The initial feed liquid containing the solute is brought into contact with a solvent which is selected to have a greater affinity for the solute. The partition of the solute can be enhanced by adding a chemical extractant to the solvent; this practice is widespread in the hydrometallurgical and nuclear industries. Most industrial extractors operate continuously with countercurrent flow of the two phases. In mixer‐settlers, the phases are contacted as a well‐agitated dispersion of drops, which are then sent to settling tanks for phase disengagement. In extraction columns, the dispersed drops move countercurrently against the flow of the second (continuous) phase. The physics, chemistry, and practice of extraction, with brief descriptions of important industrial extraction processes and equipment, are presented. Research on hydrodynamic aspects of process design such as axial mixing, drop dispersion, and coalescence is reviewed. New extraction techniques such as membrane extraction, supercritical exctraction, and two‐phase aqueous extraction are discussed.