Numerical Simulation And Experimental Study On Gas-Liquid Mixing Process For Non-Newtonian Fluids

Mechanically stirred tanks have been widely used in chemical industrial processes. In this paper, stirred tanks with multiple impellers were employed to study the hydrodynamics in gas-liquid flow with different media by experimental and CFD methods. The influences of CMC concentration, type of impeller, operation conditions on gas hold-up and power consumption were studied. The results show that the gas hold-up and kLa drops and power consumption increases with the increasing of the concentration of CMC. At the same power input, the impeller combinations with down-pumping produce higher gas holdup and lower power consumption than that of others. For BTD+2HDTd, higher mass transfer coefficient than BTD+2KSXd. Overall, mass transfer and mixing characteristics are quite good for the BTD+2HDTd combinations. The results provide useful clues for industrial process optimization.For the single-phase numerical simulation of BTD+2HDTd, the Np and power consumption obtained from simulation are 5% larger than experimental values. CFD coupled PBM model was employed for numerical simulation of aerated systems. The impeller is explicitly described in three dimensions using Multiple Reference Frame (MRF) Model. Dispersed gas and bubbles dynamics in the turbulent flow are modeled with dispersed SST turbulent model. Simulated gas holdup is low using default drag force model. The modified Symmetric drag model can obtain qualitatively similar gas holdup distribution was achieved when comparing the predicted result with experiments. Furthermore, a great deal of local experimental information which difficult to measure experimentally was obtained, such as macro-flow field, apparent viscosity, local gas holdup, etc. It helps to visually investigate the mixing state of fluid in tank.