In the present work, dispersed phase holdups have been measured in a Hanson mixer-settler extraction pilot plant with seven stages for two different liquid-liquid systems. The effects of agitation speed, dispersed and continuous phase flow rates have been investigated under a variety of operating conditions. Dispersed phase axial holdup profiles, determined by a sampling method, showed a strong nonuniformity. The results also showed that the dispersed phase holdup changes largely with the direction of mass transfer. Finally, an empirical correlation in terms of physical properties of liquid systems and operating variables was proposed to predict the holdup and good agreement between experimental data and calculated values of holdup was obtained.

This paper presents a methodology for calculation of a slug, two-phase flow hold-up in a horizontal pipe. The advantage of this method is that the slug unit hold up can be calculated directly from the solutions of flow field equations with no need to use correlations. An experimental apparatus to measure air-water hold up was setup. The flow pattern and liquid holdup in horizontal and inclined pipes, from angles 5o to 40o, for air-water two-phase flow, are experimentally observed. The test section, with an inside diameter of 30 mm and 3 m in length, was made of plexy-glass to permit visual observations of the flow patterns. The proposed model was tested extensively against experimentally collected data. Furthermore, other data sources for slug flow in horizontal pipes, for air-water and air-oil systems, were also used for comparison. The presented methodology was compared against four recently developed models of a two phase, slug flow holdup in horizontal pipes. Not only does the presented model demonstrate good agreement, with less than 6.8% error, compared to the experimental data, but also has less error compared to other models. These results substantiate the general validity of the model.

In this study, the effect of operating parameters on dispersed phase holdup in liquid-liquid extraction process has been investigated. Three chemical systems (Toluene/Water, Butyl acetate/Water, and n-Butanol/Water) were utilized and holdup was considered in a wide range of interfacial tensions through a Scheibel extraction column. Various rotor speeds were examined on the certain velocities of dispersed and continuous phases. It was found that with increasing rotor speed in a Scheibel extraction column, the drop size was reduced and drops were trapped inside the packed so that an increase in the dispersed phase holdup happened. An obvious increasing trend of dispersed phase holdup was observed as a result of increase in dispersed phase velocity for all systems operating under 2 different rotor speed, namely, 100 and 140rpm. However, the results showed that increase in the velocity of continuous phase would not make significant effect on the holdup. During examining the effect of both rotor speed and dispersed phase velocity, it was found that the holdup would be higher in the chemical system with the lowest interfacial tension compared with two other systems. An empirical correlation was also proposed to predict the dispersed phase holdup with AARE of 8.72%.

In this study, gas phase holdup in a gas-liquid bubble column reactor was experimentally studied. To conduct experiments, a bubble column with a height of 54 cm and a diameter of 10. 4 cm was applied. The studied systems include water-air, Gasoline-air, and Behran oil-air. Experiments were carried out in the range of 400-50 rpm agitator. Based on the Buckingham π,theorem, a semi-experimental model for gas phase holdup was presented. The results showed that with increasing viscosity from 0. 001 to 0. 0136 gas phase holdup loss due to high adhesion of bubbles at high viscosity and also the increase of bubble size at the output from the distributor decreases from 0. 41 to 0. 333. Among the selected systems, the gas phase holdup of the gas-air system was maximized. The results also showed that in materials with low viscosity, the gas phase reduction was due to the formation of liquid vortex movement and air canalization by the agitator. The best agitator speed to increase the gas phase holdup at water and oil are 150 and 400 rpm, respectively.

Bubble and slurry bubble column reactors usually work under pressures beyond the atmosphere in the industries. Although many studies have been done about bubble and slurry bubble column reactors, experimental studies under elevated pressure are very limited. In this study, the effects of pressure and slurry concentration on the gas holdup have been investigated by using pressure difference tests. The experiments of this study are made under pressures up to 18 bar and paraffin and silica are used as the liquid and solid contents. Increasing the operation pressure leads to an increase in gas holdup. It is also found out that the effect of pressure is vanished by increasing the slurry concentration. The experiments are performed in a column with a diameter of 16 cm and a height of 2.8 m. The gases used are nitrogen and air. Finally, a new experimental correlation is developed as a function of gas density (rg), superficial velocity of gas (Ug), slurry density (rSL), slurry viscosity (mSL), and liquid surface tension (sL); the correlation is obtained by using the data extracted from this investigation and is in good agreement with the experimental data.

Holdup was measured at various frequencies, amplitudes, continuous and dispersed phase flow rates for binary systems in a pulsed plate column capable of providing samples at various heights. The binary systems were so selected as to cover a wide spectrum of interfacial tensions. Dispersed phase holdup was found to increase with height in a logarithmic fashion at conditions away from the flooding point and to become almost invariant with height near flooding conditions.The interfacial tension of the binary system has a large effect on the dispersed phase holdup. In systems having low interfacial tension, a small increase in any of the parameters can increase the holdup significantly and lead to flooding. In systems having high interfacial tension, on the other hand, variations in system parameters do not affect system performance significantly.