Solid dispersion in a viscous Newtonian phase using a dual shaft mixer

The goal of this work is to characterize in an experimental way the hydrodynamics of a dual-shaft mixer. This mixer is composed of a dispersing impeller and a Paravisc impeller mounted on two independent shafts. The dispersing turbine is located in an off-centered position rotating at high speed, while the other shaft rotating at low speed supports the wall-scraping Paravisc. The independence of each agitator drive makes it possible to operate the system at the desired rotational speed ratio; that is the rotational speed of the Deflo over the rotational speed of the Paravisc NDeflo/NParavisc ). This autonomy allows us to verify the homogenization of high viscosity Newtonian fluids and solid-liquid dispersion. In this work, it is proposed to characterize the power consumption and mixing efficiency in single phase and two phase flow in order to improve the knowledge about device performance and provide a scientifically-based design for scale up.; Although the dual-shaft mixer follows complex kinematics, it was possible to study the interaction between the impellers. It was demonstrated that, the Deflo rotational speed has great influence on the Paravisc power consumption. As the rotational speed of the Deflo increases, the power dissipated by the Paravisc decreases. However, no influence of the Paravisc was observed on the Deflo power consumption. Mixing times were measured using the IMAGE PRO-PLUS technique at various combinations of rotational speed ratios in different viscosities. It was found that the mixing process is mainly governed by the Paravisc; however, the Deflo shows a great pumping capacity especially at lower viscosities.; Power consumption and particle size measurements were carried out with a high viscosity solid-liquid dispersion of calcium carbonate and glass beads at 10 wt% solids concentration. Studying of the impellers power consumption showed the influence of impeller rotational speed on dispersion time. It was found that the Deflo disperser has a great ability to break up lumps and agglomerates within the vessel resulting in a homogenous dispersion.