Experimental study on the mixing and dispersing of floating particles in viscous system

Abstract

The effects of baffle configuration, impeller type, impeller diameter ratio, and immersion depth on the critical drawdown speed and power of floating particles were investigated by experiment, and the advantageous stirred vessel was determined on the basis of the low energy consumption principle. Furthermore, the effects of system viscosity, mean solid concentration, and particle size on the dispersing characteristic of floating particles were also researched with the advantageous stirred vessel. The results show that, (1) when the stirred vessel is equipped with a single baffle, the critical drawdown speed and power of floating particles are lower than those of others. (2) Among the propeller, six flat‐blade disc turbine (Rushton), and six 45° pitched‐blade turbine (PBT‐6), the Rushton turbine has the lowest critical drawdown speed, and the down‐pumping propeller (TXL) has the lowest critical drawdown power. (3) The critical drawdown speed and power are lower with a larger impeller diameter and a smaller immersion depth. (4) The critical drawdown speed and power increase with increasing system viscosity, mean solid concentration, and particle size. The experimental results provide useful guidelines for the advantageous design of the stirred vessel used for the dispersing of floating particles in a viscous system.

CFD simulation of the mixing and dispersing of floating particles in a viscous system

“…It was mixed with the tangential flow near the center and generated the eccentric vortex. The position of the vortex observed in experiment (Liu et al, 2016), as shown in Figure 10, was basically the same where the largest intensity appeared in the simulation (Chen, 2015). 3The turbulence intensity near the surface in the vessel equipped with a Rushton turbine was larger than those in the vessels equipped with other impellers.…”

Mechanisms for drawdown of floating particles in a laminar stirred tank flow

“…This process is quite different from previous results in the literature. For example, Özcan-Taşkin et al [28] found that the drawdown position of floating particles is close to the vessel walls when a downward pumping impeller is mounted close to the vessel base, and Liu et al [40] found that an eccentric vortex is able to generate a strong vertical force to draw down floating particles. The main reason for the difference in drawdown positions and patterns is that the investigated flow conditions vary greatly; the flow fields in the literature are mainly turbulent, while they are laminar in this study.…”

Effect of inside Surface Baffle Conditions on Just Drawdown Impeller Rotational Speed

“…Te study by Atibeni et al [30], in which the width and shape of the bafes were varied, found that triangle bafes were more efective in suspending foating solids. Liu et al [31] studied the efect of the number of bafes on N JD and reported that N JD was lowest when one bafe was used. Furukawa et al [32] reported that N JD was reduced by placing a partial bafe away from the wall surface.…”