Research And Simulation On Droplet Distribution In φ38mm Pulsed Sieve-Plate Extraction Column

The production capacity and extraction efficiency of the sieve-plate extraction column are strongly influenced by many two-phase flow factors, particularly the dispersed phased droplet diameter and its distribution, which have both direct and indirect effects on the production capacity and the extraction efficiency and act as the foundation for the design and optimization of the sieve-plate extraction column. In this paper,30% TBP (kerosene)-water is adopted as the objective system, and the dispersed droplet diameter under different operation parameters is measured by photography in theφ38mm sieve-plate extraction column. Moreover, the effects of the continuous phase superficial velocity, the dispersed phase superficial velocity, the flow ratio, and the pulsation intensity on the dispersed droplet diameter and its distribution are systemically investigated. On the basis of the experiments, the numerical simulation of the two-phase flow hydrodynamics is carried out with the Fluent software.The experiment results indicate that in the emulsion operation region, the droplet diameter decreases with the increase of continuous phase superficial velocity, the dispersed phase superficial velocity or the pulsation intensity increase, however, the effect of flow ratio on the droplet diameter depends on the change way of the flow ratio. It is found by the qualitative comparison that the dispersed phase superficial velocity imposes smaller influences on the droplet diameter than the continuous phase superficial velocity, however, the influence of the pulse intensity on the droplet diameter is larger compared with the continuous phase superficial velocity. There are two methods to fit the droplet diameter formula. The first one only considers the influence of pulse intensity and ignores the effects of the continuous phase superficial velocity, the dispersed phase superficial velocity and the flow ratio, and the droplet diameter formula is d32=97.51×(Af)-0.86. The second one considers all the factors, and the droplet diameter formula is d32=177.68×Vc-0.09Vd-0.07(Af)-0.87. Both the formulas are in good agreement with the experimental data and their deviations are within±20%. However, the accuracy of the second formula is better than the first one because more operation parameters are considered. As far as the droplet diameter distribution is concerned,12 sets of data are selected at random from 118 sets of data because the operation parameters do not meet orthogonality. It is found that the droplet diameter can be well described by normal distribution function by the means of analysis and comparison of these droplet diameter data.Fluent is one of the specialized software for the computation fluid dynamics, and it can be applied to simulate the dispersed droplet diameter distribution, the distribution of the superficial velocity of the continuous phase and the dispersed phase, the volume fraction distribution of the continuous phase and the dispersed phase in pulsed sieve-plate extraction column. The simulation result of the dispersed droplet diameter distribution is in accord with experimental phenomenon, that is, the droplet diameter tends to be unified with the increase of the column height. The simulation results of the distribution of superficial velocity and volume fraction of two-phase fit well with the experimental results, and the wall and the sieve-plate of the column are also well simulated.The influence of various operation parameters on the droplet diameter is confirmed through experimental studies and two formulas for computation of the droplet diameter are raised. It is found that the operation parameters have no influence on the distribution of the drop diameter, and the distribution possesses normal distribution characteristics. The simulation result shows that the Fluent is a powerful tool to study the hydrodynamic properties in the sieve-plate extraction column. The combination of experiment and computer simulation improves the research level of the sieve-plate extraction column and benefits the optimization and the amplification of the sieve-plate extraction column.