Investigation Of Mass Transfer Behavior Of Sieve Tray Extraction Column With Different Down Comer Structure By CFD Method

Sieve extraction column has a large work capacity, a simple structure, and a low manufacturing cost, so this column has been widely used in chemical engineering process. Both of the continuous and disperse phases'flowing pattern is one of the most important factors influencing extraction efficiency, and this flowing pattern has a close relation with the column structure. So in this paper, the structure of column has been modified to improve the continuous phase flowing pattern, which can also increase the efficiency. The modified sieve extraction column structures in this paper have not been reported before.The flowing pattern of continuous phase in traditional sieve extraction column has been simulated. Simulation results show that in traditional column the velocity of continuous phase on some parts of sieve plate is too fast, which can cause a big vortex in the area between two sieve plates in the column. The vortex area is not advantageous for two phase extraction process.In this paper, based on the traditional sieve extraction column structure, some modified structures of sieve extraction column have been proposed. The down comer structure has been modified and the baffle plates have been added, in order to improve the flowing pattern of continuous phase. The flowing pattern in the sieve tray extraction columns has been simulated, results of which are in good agreement with PIV investigation results. Both of them show that after the structure of down comer has been modified, the continuous phase flowing pattern has been improved. In the modified column, the velocity of continuous phase flowing has a more evenly distribution, the vortex between two sieve plates is weaken, the area of vortex is decreased, and almost 2/3 space between the two sieve plates in extraction column has been effectively used.Base on the investigation of continuous phase flowing, the extraction mass transfer process has been simulated. The mass transfer simulation system is Kerosene-acetic acid-water system. By comparison of the difference between inlet and outlet of the continuous phase in each column, the efficiency of each column can be compared. The mass transfer simulation results show that the efficiency of modified column is higher than the one in traditional column. In conclusion, by the preliminary study of computational mass transfer in each column, when the structure of down comer in traditional sieve extraction column has been modified, the continuous phase flowing pattern has been improved and the efficiency of extraction can be increased. In this paper, the efficiency has been highest increased to 66%.