Drop size distribution in agitated liquid‐liquid systems

Abstract

-The prediction of interfacial area in agitated dispersions is of considerable importance in heat and mass transfer operations and in certain heterogeneous reactions. Rietema (11) discusses control of reaction rate in a stirred-tank reactor through control of drop size and interfacial area. Interfacial area control also plays an important role in liquid-liquid extraction (15), dispersion polymerization (7, 8), and direct-contact heat transfer (18).When two immiscible liquids are agitated, a dispersion is formed in which continuous breakup and coalescence of drops occurs. After some time a dynamic equilibrium is established between breakup and coalescence and a spectrum of drop sizes results. The average drop size and the size distribution will depend upon conditions of agitation as well as hysical properties of the two liquids. Drops are believex (6) to be broken up by turbulent pressure fluctuations in the neighborhood of the drop surface. Coalescence may occur when drops collide. In a dilute dispersion coalescence will be minimal, and the e uilibrium ess alone.Despite the fact that the drop size distribution is a significant factor apart from its influence on the average particle size and the total interfacial area, no information exists from which one may predict the distribution function, and the manner in which it changes, with agitation parameters and physical properties of the immiscible phases. The goal of this work was to develop such information over a wide range of pertinent parameters and properties and to imbed these results within the framework of a rational theory.A fair1 extensive literature exists with regard to the average irop size obtained in dispersions. A critical discussion of this literature may be found in reference 2. Only the most pertinent references are reviewed here.

Drop behaviour characteristics in different operating regimes in an L‐shaped pulsed sieve‐plate column

“…Furthermore, it is found that drop size distributions shift to the left with the increase of pulsation intensity because smaller drops offered narrower and more homogeneous distributions due to smaller eddies of the liquid stream. [51,52] An increase in the flow rate of the dispersed and continuous phases leads to wider drop size distribution because of higher coalescence rate. However, the influence of continuous phase flow rate on size distribution is much weaker than that of the dispersed phase.…”

Microbial degradation kinetics of solid alkane dissolved in nondegradable oil phase

“…The portion of oil phase, pristane, which contained desired amount of heneicosane in the system was set as 1% (v/v). This value was selected from the consideration of available maximum value, where the oil phase could be dispersed stably fully enough to con®rm that there exists no coalescence of the oil drops [9]. Thus, this volume fraction of 1% of oil was thought to be rational to maintain hydrodynamic constant interfacial area between oil and aqueous phase.…”

Experimental investigation of liquid-liquid system drop size distribution in Taylor-Couette flow and its application in the CFD simulation

“…On one hand, some of these works are just focused on the single drop experiment [2][3][4] to define the break up kernel for the Population balance equation [5] . On the other hand, there are studies focused on the drop size distribution in the stirred tank reactor regardless of the event happens to each droplet [6,7]. The well-defined pattern of the Taylor-Couette flow enables the possibility to investigate DSD as a function of the local fluid dynamic properties, such as shear rate, which is in contrast to more complex devices such as stirred tank reactors.…”

“…Equation (1) is one of the first expressions to evaluate the Sauter mean diameter in a stirred tank reactor that was developed by the work of Shinnar and Church [8] and Chen and Middleman [6].…”