Gas Absorption Enhancement Mechanism in Mechanically Agitated Multiphase System: Effect of Fine Solid Particles and Interfacial Turbulence

To probe the particle effect on gas-liquid mass transfer in three-phase flow, a series of comparative tests was conducted in a stirred reactor with flat gas-liquid interface in which four kinds of solid particles, i.e., powdered activated carbon (PAC), kieselguhr, barium sulfate (${\mathrm{BaSO}}_4$), and granular activated carbon (GAC) were introduced, respectively. The enhancement factor ($E^p$) for oxygen transfer could be controlled by both the interfacial turbulence and particle species. Either low film mobility or turbulent interphase would limit the particle-induced promotion of mass transfer, which could not be explained by the so-called shuttle effect. The effect of fine particles on $E^p$ follows the order of $\mathrm{PAC}>\text{kieselguhr}>{\mathrm{BaSO}}_4$ opposite to the sequence of particle densities (i.e., ${\rho }_{\mathrm{PAC}}<{\rho }_{\text{kieselguhr}}<{\rho }_{{\text{BaSO}}_4}$), suggesting the key role of particle density on its interfacial performance. The particle impact on mass transfer intensity would militate only when the size was small enough. It was assumed that the collision between particles and the gas-liquid interface and the particle interactions might have played the decisive role on altering the efficiency of oxygen transfer, and an $E^p$ model was developed accordingly to describe this process as a function of particle concentration. Experimental data fit well with the model, which confirms the validity of the assumption for the enhancement effect functioned by particles.