| Studies of the liquid-liquid extraction equipment are increasingly popular in recent years. The operation method of alternating feeding between light and heavy phases (AFLHP) was proposed in order to solve the problems of the low productivity of the batch operation and the back-mixing of the countercurrent continuous operation in extraction. The mass transfer of a perforated-plate extraction column by means of alternating feeding between light and heavy phases was experimentally studied.Firstly, we apply the operation method of AFLHP in perforated-plate extraction column with the system of kerosene-benzoic acid-water. From these experiments, we have got the continuous phase concentration profile, and the overall mass transfer coefficient, Kod, based on dispersed phase, has been obtained using the single drops model. It is observed that the values of Kod are from 3.49·10-5 to 5.47·10-5m · s-1, and it has an excellent mass transfer performance when tray spacing is 5cm. The results show that the AFLHP Perforated-plate Extraction Column greatly reduces the back-mixing, which outperforms Pulsed Extraction Column.Secondly, the mass transfer performance of AFLHP technology with perforated-plate extraction column in the system of ethyl acetate-ethanol-water was studied. We got that the extraction rate is between 59% and 70% and the optimal tray spacing is 10cm. The results show by increasing the hole diameter the production capacity of ADLHP Perforated-plate Extraction Column is improved, its extraction rate is higher than Rotating Disc Columns.In this paper, the dispersed phase hold-up in two systems also have been analysed, the small total dispersed phase hold-up indicates that the flooding is difficult in the AFLHP Perforated-plate Extraction Column.Finally, based on laboratory and theoretical research, the mechanism of the AFLHP Perforated-plate Extraction Column to reduce the back-mixing has been stated through the analysis of the continuous phase concentration profile. |
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