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The downflow slurry bubble column reactor is gaining importance as a simple and inexpensive means of achieving efficient multiphase contact and mass-transfer operations. Knowledge about the effects of solids on gas–liquid–solid systems is minimal in the literature. In the present work, the effect of the presence of solids on the mass-transfer characteristics for gas–liquid–solid system is experimentally investigated in a downflow slurry bubble column with an internal diameter of 0.05 m. The mass-transfer coefficient was evaluated using the electroreduction of ferricyanide ions as the model reaction. The effects of superficial slurry velocity, gas velocity, slurry viscosity, and gas holdup on the mass-transfer coefficient were analyzed. The experimental results showed that the mass-transfer coefficient in the column is influenced more by the superficial slurry velocity than the superficial gas velocity. In this work, the mass-transfer efficiency in the gas–liquid–solid downflow bubble column reactor was analyzed for different concentrations of the slurry (0.1–1.0 wt %) and different sizes of the particles (2.21–96.0 μm). Empirical correlations were developed for the downflow slurry system with the different variables to interpret the mass-transfer phenomena. The developed correlation for mass-transfer efficiency as a function of quality of mixedness was also interpreted by the information entropy theory. The present analysis on mass-transfer characteristics and models for predicting the mass-transfer coefficient can provide insight into a further understanding of multiphase reactors in industrial applications.

This article presents the analysis of gas holdup, pressure drop and bubble size of gas-liquid-solid flow in a modified downflow slurry bubble column. The analysis is done based on the Lockhart-Martinelli principle. The Lockhart-Martinelli model is modified and incorporate to predict the frictional pressure drop and gas holdup of three-phase flow in the modified bubble column. The effects of operating variables such as slurry flow rate, gas flow rate, slurry concentration and particle diameter on frictional pressure drop and gas holdup are investigated. To predict the gas holdup, Sauter mean bubble diameter and pressure drop, correlations have also been developed as function of different dimensionless groups by introducing the operating variables and physical properties. The studies of the pressure drop in the downflow slurry bubble column may give insight into a further understanding and modeling of the three-phase flow characteristics in industrial applications.

In this paper, the flow of a viscous conducting liquid with uniform distribution of dust particles in a channel is considered under the influence of a uniform transverse magnetic field with pressure gradient varying linearly with time. The velocities of fluid and dust are found to decrease with the increase of the magnetic parameter. Further that the velocity of the fluid particles is observed to be more than that of dust particles.