Abstract:-The volumetric overall mass transfer coefficients in a pilot plant Hanson mixer-settler extraction column of seven stages have been measured using toluene-acetone-water system. The effects of agitation speed and dispersed and continuous phases flow rates on volumetric overall mass transfer coefficients have been investigated. The results show that the volumetric overall mass transfer coefficient increases with increase in agitation speed and reaches a maximum. After having reached its maximum, it falls with f… Show more
“…In addition, experimental data for the overall mass transfer coefficient were compared with those obtained by the correlations that were proposed for other types of extraction column, which are presented in Table S1 †. 9,12,16,19,[29][30][31][32][33][34][35] A reliable correlation for predicting the mass transfer coefficient in a horizontalvertical pulsed packed extraction column is therefore required.…”
Section: Predictive Correlation Of the Overall Mass Transfer Coefficimentioning
In this study, hydrodynamic parameters and the mass transfer coefficient were investigated in a pilot version of a horizontal-vertical pulsed packed extraction column using a toluene-acetone-water system. The effects of the operational parameters on the volumetric overall mass transfer coefficient and hydrodynamic parameters away from the flooding point were studied, and it was found that the volumetric overall mass transfer coefficient, mean drop size and disperse phase holdup were significantly affected by the pulse intensity. However, the dispersed and continuous phase flow rates have a weaker effect. On the other hand, by increasing the pulse intensity the mean drop size and volumetric overall mass transfer coefficient were reduced and increased, respectively, in both sections of the column, but the disperse phase holdup displayed different behavior in the horizontal and vertical sections. By increasing the pulse intensity, the disperse phase holdup was first reduced and then increased in the horizontal section; however, an incremental trend was observed in the vertical section. The effect of the dispersed phase flow rate was significant for all the investigated parameters, but weaker. For instance, all the investigated parameters were increased by enhancing the dispersed phase flow rate. In contrast, the continuous phase flow rate has sometimes had no significant effect, for example, on the mean drop size in both sections of the column. Finally, two empirical correlations for the prediction of the volumetric overall mass transfer coefficient based on the continuous phase were derived in terms of the Sherwood number, Reynolds number and other dimensionless numbers. Good agreement between predictions and experiments was found for all operating conditions that were investigated.
“…In addition, experimental data for the overall mass transfer coefficient were compared with those obtained by the correlations that were proposed for other types of extraction column, which are presented in Table S1 †. 9,12,16,19,[29][30][31][32][33][34][35] A reliable correlation for predicting the mass transfer coefficient in a horizontalvertical pulsed packed extraction column is therefore required.…”
Section: Predictive Correlation Of the Overall Mass Transfer Coefficimentioning
In this study, hydrodynamic parameters and the mass transfer coefficient were investigated in a pilot version of a horizontal-vertical pulsed packed extraction column using a toluene-acetone-water system. The effects of the operational parameters on the volumetric overall mass transfer coefficient and hydrodynamic parameters away from the flooding point were studied, and it was found that the volumetric overall mass transfer coefficient, mean drop size and disperse phase holdup were significantly affected by the pulse intensity. However, the dispersed and continuous phase flow rates have a weaker effect. On the other hand, by increasing the pulse intensity the mean drop size and volumetric overall mass transfer coefficient were reduced and increased, respectively, in both sections of the column, but the disperse phase holdup displayed different behavior in the horizontal and vertical sections. By increasing the pulse intensity, the disperse phase holdup was first reduced and then increased in the horizontal section; however, an incremental trend was observed in the vertical section. The effect of the dispersed phase flow rate was significant for all the investigated parameters, but weaker. For instance, all the investigated parameters were increased by enhancing the dispersed phase flow rate. In contrast, the continuous phase flow rate has sometimes had no significant effect, for example, on the mean drop size in both sections of the column. Finally, two empirical correlations for the prediction of the volumetric overall mass transfer coefficient based on the continuous phase were derived in terms of the Sherwood number, Reynolds number and other dimensionless numbers. Good agreement between predictions and experiments was found for all operating conditions that were investigated.
“…Generally, mechanically agitated gas-liquid contractors are frequently applied in chemical processes or biochemical industries. Mechanical agitation can promote the mass transfer rate because it increases interfacial area between the liquid and gas phases (Garcia-Ochoa et al, 2009;Torab-Mostaedi et al, 2008).…”
The main objective of these experiments was to study the oxygen mass transfer rate through the volumetric mass transfer coefficient (k L a) for an experimental set-up equipped with a rotating magnetic field (RMF) generator and various liquids. The experimental results indicated that k L a increased along the magnetic strength and the superficial gas velocity. Mathematical correlations defining the influence of the considered factors on k L a were proposed.
“…Asymptotic cases, complete miscibility of bitumen fractions in pentane, and complete immiscibility provide upper and lower extrema for mass-transfer coefficient values and their dependence upon composition. Data treatment and analysis of forced mass-transfer measurements reported here follow established approaches applied to diverse mixtures in stirred vessels, − where the focus is on the identification of the transition from diffusion-controlled mass transfer (lower bound for mass-transfer rates) to another mass-transfer rate-limiting phenomenon (upper bound for mass transfer). This transition provides a basis for selecting operating conditions for industrial processes and informs the development of in-reservoir and surface-facility process models …”
Forced and diffusive mass transfer between pentane and Athabasca bitumen fractions was investigated at 297 K. Mutual diffusion coefficients were obtained using a free diffusion technique, where time-dependent composition profiles were jointly fit to obtain composition-dependent values. Because the density difference between pentane and Athabasca bitumen is significant, the density gradient was accounted for explicitly in the data analysis. Forced mass-transfer measurements were made by placing a high shear impeller in the pentane-rich phase adjacent to the pentane-feedstock interface. Mass-transfer coefficients were evaluated independently on the basis of the movement of the interface with time and changes in the bulk composition of the well-mixed pentane-rich phase above the interface. Because bitumen fractions are only partially soluble in pentane, the impact of the asymptotic assumptions, complete miscibility and complete immiscibility, on mass-transfer coefficient values obtained was assessed and found to fall within experimental error. The dependence of mass-transfer coefficients upon the shear rate and impeller-interface distance was also evaluated. Mass-transfer rates are shown to range from the diffusion limit at low shear rates and large impeller-interface distances to values consistent with those obtained from pertinent correlations for forced mass transfer under turbulent conditions at higher shear rates. The results suggest that bitumenpentane mass transfer in reservoirs and surface facilities is likely to be diffusion-limited.
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