Hydrodynamic Behavior of a Rotating Disc Contactor Under Low Agitation Conditions

Abstract

The hydrodynamics of a rotating disc contactor (76.2 mm diameter, 19 stages, and operating height of 815 mm) has been investigated at limiting operational conditions of low holdup (/ 3%) and low agitation (Re R 22,000) for the water=n-heptane system in the absence of mass transfer. Water was chosen as the continuous phase, and it was kept stagnant inside the column. Local drop size distribution, local mean drop diameter, and total holdup have been measured at different flow rates of the dispersed phase (70 to 640 mL=min) and rotor speeds (0 to 700 rpm). Drop size distributions along the column were suitably described using the log-normal probability density function, and empirical expressions were derived to predict the parameters of the distribution curve as a function of operating conditions. An empirical expression was also proposed to predict the Sauter mean drop diameter along the column with a mean deviation of 3.4%. Statistical analysis has revealed no significant effect of the rotor speed on the total holdup, which changed solely with the dispersed phase flow rate for the operating conditions investigated.

New Predictive Correlations for the Drop Size in a Rotating Disc Contactor Liquid‐Liquid Extraction Column

“…2 reveals that care was taken to design distributors that have approximately the same total hole area (0.088-0.095 cm 2 ). This provides all of the runs with the same range of flow rate, but with different jet hole velocities.…”

“…It is well known that the mean drop diameter is an important factor in the study and design of the liquid-liquid extraction column [1][2][3][4]. It is a vital variable required to determine the relationship between the interfacial area, the disperse phase holdup, the drop velocity, and effectiveness of mass transfer inside the column.…”

Mass transfer performance in pulsed disc and doughnut extraction columns

“…Insofar as liquors from hydrometallurgical industries are concerned, on account of the slow extraction rates exhibited by most metal systems of practical interest, mixer-settlers have been frequently adopted. However, in recent years, the development of new extractants with superior selectivity and efficiency characteristics has led to an increasing interest in the use of agitated columns for the treatment of hydrometallurgical liquors (Moreira et al, 2005).…”

Modified correlations for the first and second critical rotor speeds, as well as break up probability in a rotary disc contactor

“…The performance of an RDC depends largely on the geometry of the column internals and rotor speed (Kamath and Subba Rau, 1985). Indeed, mass transfer rates and, accordingly, unit separation efficiencies are closely related to the interfacial area, which in turn, depends upon the contactor hydrodynamic parameters (Moreira et al, 2005).…”