Segregation in liquid-liquid dispersions and its effect on chemical reactions

Segregation generally causes a spread in concentration in mass transfer and chemical reaction systems, but only when there is a spread in residence time, a spread in particle size, or in any other type of mass transfer or chemical activity determining factor. Interaction generally tends to eliminate these concentration differences. The segregation is complete when there is no interaction, while at infinite interaction rate there is no segregation. Coalescence and redispersion is the more general type of interaction that may occur in liquid–liquid two-phase systems and in gas–liquid systems where gas is the dispersed phase. When two drops or bubbles coalesce, the release of energy is so large that before break-up again occurs, the contents of the two dispersed particles may be assumed to be completely mixed. This chapter focuses on some of the effects of segregation on the kinetics of a chemical reaction between two liquid phases that is carried out in a continuous stirred tank reactor (CSTR). In the derivations of these effects, it is assumed that during the reaction the dispersed phase is maintained and that all dispersed drops have the same size. This means that when there is segregation, it is only the age distribution that causes a concentration distribution in the dispersed phase. When the interaction rate is measured in a particular way, it is possible to study the course of a chemical reaction that occurs in the dispersed phase between two components