The γ-CT Measurement Of Gas Holdup Distribution And Cfd Simulation Of Gas-liquid Mixing In Rushton Stirred Tank

Rushton stirred tank are extensively used in many industry processes such as petrochemical industry, pharmacy, chemical engineering and biological chemistry etc. Based on gamma-CT measuring experiment, the gas-liquid mixing process in Rushton stirred tank has been simulated. Two response function models of both negative accumulative distribution and density distribution are proposed and established.The Eulerian-Eulerian two-fluid model coupling with the bubbles'coalescence and break-up models, and drag coefficient model were established to make CFD simulation of gas hold-up distributions for the gas-liquid stirred Rushton tank under different gas flow rates and impeller rotating speeds. Gas holdup increased both with gas flow rate and impeller rotating speed, but gas flow rate had more influence on gas holdup than impeller rotating speed. The dense area of gas holdup distribution appeared in the upper space of impeller blades.Reynolds stress model combined with the multiple reference frame (MRF) approach was developed to simulate gas-liquid flow characteristics in a stirred vessel which was agitated by a Rushton turbine, obtained an array of gas hold-up distribution in different cross sectional places. The numerical simulated results were compared with the gamma-CT measurement results. It was shown that CFD simulated results reasonable agreement with the experimental data for all the circulation regions except the discharge flow region. It was indicated that the gas hold-up distribution in discharge flow region was higher than other regions. Under high-speed rotary agitator, the fluid discharge rapidly along the surface of blade-tips. Radial distribution profile and axial distribution profile of the liquid phase speed under different experimental conditions were discussed. It was demonstrated that the maximum of radial velocity of single-phase flow was closer to mixing blade-tips, while the maximum of radial velocity of two phase flow had a little outward translation. Compared the distribution profile of turbulent kinetic energy, it was found that there was a peak value of turbulent kinetic energy on the plane of the impeller in both the radial distribution and the axial distribution.