The Research And Development Of Novel Extraction Hybrid Packing

In liquid-liquid extraction process, the breakage and coalescence of the dispersedphase has an important effect on mass transfer efficiency. Previous studies suggestedthat the mass transfer efficiency improved dramatically when dispersed phase dropletswas broken and coalesced alternately and repeatedly. Based on this finding, theconcept of dispersed phase’s droplet-film flow pattern was proposed, and a hybridstructured packing named PY-1hybrid packing was developed by our research group.In this investigation, a series of hybrid packings for extraction were developed, andthe mass transfer performance and hydrodynamic performance of the packings werestudied. The liquid system is30%tributyl phosphate-kerosene/acetic/water system.Firstly, the breakage and coalescence of the dispersed phase in extractionpacking column was observed, and the flow patterns of the dispersed phase throughdifferent packing elements were photographed by high-speed camera. The resultsshowed that the dispersed phase was broken into small and uniform droplet swarm in700Y rhombus mesh frame packing (RMFP), and the droplet swarm coalesced intofilms in350Y polypropylene corrugated sheet packing (PPCSP), and then developedbig droplets with uniform diameter. Besides, some droplets were broken into smallerones, and the other coalesced into bigger ones when went through plum flower miniring (PFMR). In addition,350Y corrugated sheet packing and polypropylene pall ringhad some positive effect on coalescence of droplets, but less than350Y PPCSP. Basedon these findings, PY-2~PY-7hybrid packing were developed in this research.Secondly, the mass transfer performance of these hybrid packings wasinvestigated in a packing column with an internal diameter of150mm. It was foundthat the mass transfer efficiency of700Y RMFP, PFMR and PY-1hybrid packing wasclose. Besides, PY-2and PY-3had similar results but their mass transfer efficiencywas far less than that of PFMR. The mass transfer efficiency of PY-4, PY-5, and PY-6hybrid packings was close, but slight lower than that of PFMR. PY-7had anadvantage over PFMR in mass transfer performance, and the apparent height of masstransfer unit of the hybrid structured packing is21%smaller than that of PMFR inaverage.Thirdly, the hydrodynamic performance of PFMR and PY-7hybrid packing wasinvestigated in the same packing column. It was found that the holdup of PFMR was less than that of PY-7hybrid packing in the same experimental condition, and theflooding velocity of PFMR is13.47%larger than that of PY-7hybrid packing inaverage at the same continuous phase flow rate. The holdup, in the process withoutmass transfer, is larger than that in the process with mass transfer from dispersedphase to continuous phase. Besides, the experiment data was used to calculate theflow parameters, and the results could provide reference for the design of extractionpacking column.