Reproducibility of the Hydrodynamic Performance and Measurements in a Liquid−Liquid Kühni Extraction ColumnRelevance to Theoretical Model Evaluation

Abstract

Liquid−liquid systems research increasingly concentrates on computer simulations. However, the possibility of adequately testing complex theoretical models against experiments is hindered by a lack of reliable reproducibility data for laboratory and pilot-plant measurements. This strongly limits meaningful evaluation of the increasingly complex process and equipment models/algorithms that are being developed. In this work, experimental data are obtained in a pilot-scale Kühni column, and model parameters and simulated data are generated using a drop population balance model and algorithm. The results can be summarized as follows: (i) As measured by the magnitude of careful random error and corresponding confidence limits estimates, the simulation results exhibit excellent agreement with experimental drop-size distributions and fair conformity with measured dispersed-phase hold-ups. (ii) Both experimental and simulated results show that interdrop coalescence is always present within a column extractor, even at low dispersed-phase hold-ups, and thus cannot be neglected in any physically realistic and accurate modeling.

Simulated and Experimental Dispersed-Phase Breakage and Coalescence Behavior in a Kühni Liquid−Liquid Extraction ColumnSteady State

“…Other details of these models and corresponding algorithms are given elsewhere by Ribeiro et al This algorithm, further adapted by Regueiras and co-workers , to model an agitated column, by stagewise solution of the population-balance equations under dynamic conditions, was designed to compute the drop-size distribution and local dispersed-phase holdup profiles along the column. Its use yielded an encouraging qualitative agreement with the experimental results obtained in a pilot-plant Kühni column …”

“…The experimental evidence presented and discussed in earlier works ,, by this team suggests that, even in agitated liquid−liquid extraction columns, like Kühni columns, interdrop coalescence cannot be neglected. The same applies to simple mixers …”

“…The target values for the local and overall dispersed-phase holdup and for the number-based drop-size distributions were tested against the confidence interval calculated from the actual experiments. 6 Following the experiment-based indication by Zamponi 14 that the agitation intensity stands out as the most sensitive operating variable, the simulations concentrated initially on the prediction of the steady state of experiments with two given sets of continuous-and dispersed-phase flows (standard operating conditions B12 and B16). Various sets of runs were made with the drop-interaction parameters values given in Table 2 and the three parameter values considered for the transport model.…”

“…Its use yielded an encouraging qualitative agreement with the experimental results obtained in a pilotplant Ku ¨hni column. 6 By taking into consideration the results of the error analysis performed 6 and their effect, the objective of this paper is to report and discuss the agreement obtained between the simulated and experimental data. Since the hydrodynamics alone was contemplated, all experiments were conducted in the absence of mass transfer, and therefore with no solute, for the purposes of this particular report.…”

Systematic Analysis of Single Droplet Coalescence

“…The DSD is of significant importance in extraction processes since it determines interfacial area (mass transfer) and drop rise velocities (residence time). As a result, extensive research on various apparatus like columns 1, mixer settlers 2, separators 3, and tank reactors 4 has been performed. Comparing breakage and coalescence phenomena, the coalescence is more complex due to two effects.…”