Physical Simulation on Mixing Uniformity in Seed Precipitation Tank

The suspension and dispersion of Al(OH)3 particles in seed precipitation tank, which may affect the quality and output of alumina besides the deposit on the bottom of the tank, is one of the key steps in Bayer process. In order to solve these problems, the solids concentration profiles of Al(OH)3 particles were investigated by cold water experiments under simulated industrial conditions. The results showed that, the mixing uniformity in the whole tank was improved with the increase of impeller off-bottom clearance when the impeller of small diameter (D/T=0.5~0.6) was used, and it deteriorated when the impeller (D/T=0.65~0.7) was enlarged. The mixing effects can be improved by increasing the impeller diameter and stirring speed, meanwhile the influence of impeller off bottom clearance was weakened. But the impeller diameter and stirring speed should be controlled in appropriate ranges for the consideration of power consumption and mixing efficiency.