Intensification on drawdown process of floating particles by circle package fractal impellers

Abstract

Abstract The floating particle drawdown and dispersion characteristics in a stirred tank with four pitched-blade impellers, fractal impellers, and circle package fractal impellers were studied using computational fluid dynamics (CFD) simulation. The effects of impeller type, impeller speed, impeller spacing, impeller submergence, initial floating particle concentration, and floating particle diameter on the floating particle dispersion quality were investigated. Results showed that the floating particle dispersion degree was improved with an increment in the impeller speed, in term of axial solid concentration profile, solid concentration distribution, and cloud height. The impeller spacing of T2/3 and impeller submergence of T/6 were appropriate for the floating particle drawdown process in this work. Higher initial floating particle concentration was easier to achieve a higher floating particle dispersion degree. Smaller particle diameter resulted in smaller buoyancy and more uniform distribution. Meanwhile, circle package fractal impeller can reduce the power consumption compared with four pitched-blade impeller and fractal impeller at the same impeller speed, and enhance the solid integrated velocity and the level of homogeneity for floating particle dispersion process under the constant power consumption. In addition, the just drawdown speed (Njd) and correlation equation for Njd in the three different impeller systems were obtained.