CFD Simulation Of Hydrodynamics In The Bubble Column

In this thesis, we investigated the liquid flow in the bubble column, another bubble column with the baffles, the structure cells of structured packing and slice structure of structured packing by the method of CFD (computational fluid dynamics), and studied their backmixing phenomena by using pulse tracer injection techniques. Moreover, researches on their mixing characteristic have been conducted by using backmixing model to regress the RTD curves which are attained in CFD simulation.At present, a few CFD simulations of countercurrent of liquid and gas in the bubble column are found. In this article, we present a new quasi single-fluid model according to the flow characteristic of bubble column of countercurrent of liquid and gas. Three flow regions are found in the bubble column: core region along the column center, backflow region near the column wall and zero velocity region between the two regions. Furthermore, the main reason of the axial backmixing of the liquid is the liquid backflow which induced by the reverse flow of the bubbles.According to the liquid flow characteristic of bubble column, we hope to decrease axial backmixing of the liquid by putting some baffles which have certain distribution rule in the bubble column. As result, the liquid flow changes from three flow regions to four flow form (the vortex, the backflow around the baffles, the distributary and the backflow around the wall of the column). Comparing with that of bubble column, the liquid axial backmixing apparently decreases after inserting the baffles.Because of the complicated structure in structured packing, it will definitely be unattained to simulate the fluid flow of the whole bubble column with structured packing on the present conditions. So we investigate every characteristics of bubble column containing structured packing by the ways of the cells of structured packing and slice structure of structured packing. As result, different cell has different contribution to axial backmixing of the liquid. Moreover, cross-over cell is the basic cell of mass transfer. Therefore, the performance of mass transfer of different structured packing directly relate to the number of cross-over cells in unit volume.