Numerical investigation of the effect of slurry viscosity on centrifugal classification of pseudo-boehmite in continuous-carbonation preparation process

The monodisperse pseudo-boehmite (PB) is an essential raw material for the preparation of the hydrogenation catalyst carrier, γ-Al2O3, which is of great significance for the efficient conversion of heavy crude oil and the development of the residue hydrotreating technology. The introduction of hydrocyclone has been proved to better improve the grade efficiency of PB particles. However, in the actual production process, it is found that the change of slurry viscosity will have a serious impact on particle size control and centrifugal classification of PB particles. Therefore, in this paper, based on the computational fluid dynamics (CFD), the internal flow field characteristics of the hydrocyclone and the effect of continuous phase viscosity on particle classification efficiency were systematically studied. The results demonstrated that hydrocyclone not only participated in particles classification, but also indirectly promoted particle growth. Satisfied classification efficiency was obtained in practical industrial applications by adopting the optimized condition parameter (Na2CO3 concentration of slurry 5 wt%). The average PB particles size increased from 12.9 µm to 40.3 µm, and the corresponding separation efficiency was improved to 74.9%. The obtained results can provide a feasible reference and theoretical basis for optimization of continuous-carbonization preparation process of PB particles.