LONGITUDINAL DISPERSION IN PACKED EXTRACTION COLUMNS

Technical Report · Mon Mar 18 04:00:00 EST 1963

OSTI ID:4704318

Hennico, A; Jacques, G; Vermeulen, T

Axial dispersion in packed beds is investigated with particular reference to extraction-tower design. A new model for dispersion behavior, based upon segmented laminar flow, is derived for analysis of breakthrough curves at low flowrates; its applicability is discussed in comparison with other theoretical models of mixing. Axial dispersion coefficients in single-phase flow were measured by a step-input method over a wide range of Reynolds numbers (3 to 2000). Nine different types of packings were used, involving regular and random arrangements of spheres, and random arrangements of Raschig rings, Berl saddles, and Intalox saddles. Different constant values of axial Peclet number are found in the turbulent range and the iaminar range, which are separated by a fairly sharp transition region. Viscosity is found to have a large effect upon axial dispersion, for two solutions of different viscosity, the Peclet-number values are identical at the same Reynolds number. The axial Peclet number is found to vary inversely with bed porosity. No effect of packing arrangement is observed. For two-phase countercurrent flow of water and kerosene, axial-dispersion coefficients were measured for the continuous phase, they were also measured for the dispersed phase, both where the current does and does not wet the packing material. The continuous-phase Peclet number appears to increase with decreasing continuous-phase Reynolds number, and also with an increasing ratio of dispersed- phase flowrate to continuous-phase flowrate. For a nonwetting dispersed phase, the Peclet number remains practically constant, whereas for a wetting discontinuous phase it decreases somewhat with an increasing ratio of discontinuous-phase flowrate to continuous-phase flowrate. On the basis of typical calculations of mass-transfer rates from experimental extraction data, longitudinal dispersion is an important effect and should be calculated as an independent factor in extraction column design. (auth)

• Research Organization: California. Univ., Berkeley. Lawrence Radiation Lab.
• DOE Contract Number: W-7405-ENG-48
• NSA Number: NSA-17-027544
• OSTI ID: 4704318
• Report Number(s): UCRL-10696
• Country of Publication: United States
• Language: English

Related Subjects

ADHESION
BERL SADDLES
CONFIGURATION
COUNTER CURRENT
DIAGRAMS
DISPERSIONS
EFFICIENCY
ENGINEERING AND EQUIPMENT
EXTRACTION COLUMNS
FLOW MODELS
FLUID FLOW
MATHEMATICS
MEASURED VALUES
MIXING
PACKED BED
PETROLEUM
PLANNING
RASCHIG RINGS
REYNOLDS NUMBER
SPHERES
STANDARDS
THERMAL DIFFUSION
TURBULENCE
VELOCITY
VISCOSITY