Heterogeneous Modeling of Gas Absorption in Emulsions

Abstract

A heterogeneous, multilayer, mass-transfer model is proposed for explaining the effect of dispersed microparticles/microdroplets, which act as solubilizing and/or reactive agents, in enhancing the specific rate of interphase transport. The behavior of the mass-transfer rate with respect to the various parameters, such as microdispersed-phase holdup, partition coefficient of the solute between the microparticles and continuous phase, microparticle size, various rate constants, etc., has been modeled. Specific issues, such as the effect of multiple microparticle layers near the interphase boundary, the location of the first layer of microparticles closest to this boundary, and the incorporation of rate-retarding effects arising out of high apparent viscosities of the overall dispersion, have been addressed, for the first time. It is shown that the heterogeneous approach should be preferred when the dispersed-phase sizes are on the order of (but still less than) the diffusional lengths of the rate-limiting diffusant. The proposed model has been validated by analyzing experimental data from the literature, and it has been shown that it works well for the cases of high microphase holdups or large microparticle sizes.