Flow Pattern Optimization Of A Sieve Plate Extraction Column Using CFD Simulations And PIV Measurements

Sieve plate extraction columns (SPEC) are widely used in different industryprocesses because of its simple structure, low cost, large capacity and high efficiency.The flow patterns of fluids in chemical equipment such as distillation columns andextractors are of great importance in determining their process performances.Meanwhile, the flow pattern of the continuous phase is closely related to the internalstructure of the column. Hence, our research project aims at optimizing the flowpattern of a SPEC by modifying the internal structure of the column.Flow pattern optimization of the continuous phase with the modification of theinternal structure of a SPEC was studied using computational fluid dynamics (CFD)simulations and particle image velocimetry (PIV) measurements. Simulationsrevealed a large reverse flow area between every two plates in the traditional SPEC.The reverse flow of the continuous phase wasted the internal space, increased theresistance on the two phase mass transfer process and finally decreased the masstransfer efficiency. The flow pattern was optimized with the objective of minimizingreverse flow area. Four new generations of SPECs with different internal structureswere proposed. Structure modifications included inclining and slotting thedowncomers, adding baffles, adjusting the number of slots and fixing small, leveledbaffles at some slots. An optimal flow pattern almost without reverse flow area wasevolved. PIV measurements were carried out on three SPECs and the results ofsimulations and measurements were in good agreement. At last,3d CFD simulationswere conducted to comprehensively reveal the flow patterns of different internalstructured columns.Results of CFD simulation and PIV measurement consistently show that flowpattern was optimized with the modification of the internal structure of a SPEC.Reverse flow area decreased and the velocity distribution became uniform and thewhole flow pattern tend to be reasonable. Finally, column5C was obtained and itturned out that the flow pattern of this special column was the optimal. Reverse flowarea disappeared in most of the region only expect for few small dead zones at thecorners of the plates. The axial back-mixing phenomenon was reduced greatly and the flow pattern through the entire column was very close to the ideal piston flow model.Meanwhile, the result of computational mass transfer performance showed that inColumn5C there was no concentration reverse flow area except for very small masstransfer dead zones in the corners of the plates. The entire concentration distributionresembled the ideal piston model. Under these conditions, the interphase contactsurface could be fully updated and the contact time could be prolonged to enable themass transfer process to be intensified.