A coaxial mixer consisting of an anchor and a Rushton turbine was selected as the research object

whose solid suspension characteristics were studied with the help of Computational Fluid Dynamics (CFD) method. Based on the Eulerian-Eulerian method and modified Brucato drag model

the just-suspension speed of impeller was predicted

and the simulation results were in good agreement with the experimental data. The quality of solid suspension under different rotation modes was also compared

and the results showed the coaxial mixer operating under co-rotation mode could get the best performance

and a larger anchor speed was beneficial to solid suspension by enhancing the turbulent intensity at the bottom. Compared with the anchor

the inner Rushton turbine played a dominant role in solid suspension due to its high rotational speed

whereas an extremely high inner impeller speed would make the uniformity of solid distributions become worse. Additionally

the effects of solid phase properties were also investigated

the results revealed that the higher the overall solid volume fraction and the smaller the Shields number

the worse the performance of solid suspension

meanwhile the solid suspension was more susceptible to solid density compared with particle diameter within the same Shields number gradient.