Abstract
A mathematical model to predict separation rates of two phase liquid dispersions coalescing under a.c. fields has been developed. The model consists of a procedural algorithm that includes the effects of film drainage, drop-drop coalescence, drop terminal velocity, and coalescer fluid-dynamic characteristics, on the separation rate. Two adjustable parameters approximate the predicted response to experimental data. Agreement between predicted and experimental data was obtained for field strengths up to 7 kV(peak-peak)/cm and frequency above 100 Hz. A dispersion of Isopar M and distilled water was used for model validation, and to assess the effect of applied voltage, frequency, and conductivity of the continuum on separation rate. A dispersion of guayule resins and water, was used to evaluate the combined effect of phase contacting and electrical separation on the removal of water soluble components from the resinous phase. Maximum rates of separation were assessed by measuring output flow rates, under steady state conditions. Steady conditions were attained by adjusting the input/output flow rates to maintain the interface at a constant level and avoid accumulation of unresolved emulsion in the coalescer. In general, a linear dependence between maximum rate of separation of Isopar M/water and field strength was found for most of the experimental conditions evaluated. For the same frequency and field strength, pulsed d.c. fields yielded a higher separation rate than a.c. fields. Analysis of droplet size distribution showed that entrainment of water drops in the oil phase occurred. This analysis also showed that there is a input flow rate that produces a maximum mean droplet diameter in the separated oil phase. When the separation rate for guayule resins and Isopar M were compared, the major difference was found on the magnitude of the separation rate for a pulsed d.c. signal. For this signal, separation rate of guayule resin almost tripled that obtained for Isopar M. Additionally, the resin-water mixing process in combination with electrostatic coalescence contributed to the removal of several different metallic species from the resin phase. This is apparently the first demonstration of removal of solubilized or ionized species from resinous plant extracts.
Figueroa, Crescente E. (1993). Electrostatic separation of liquid dispersions : a working model and application to guayule processing technology. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -1518983.