Power number and hydrodynamic characterization of a stirred vessel equipped with a Retreat-Blade Impeller and different types of pharmaceutical single baffles

Many operations conducted in the pharmaceutical industry take place in glass-lined vessels provided with a Retreat-Blade Impeller (RBI) and one of different types of single baffles. Little information is available on the power dissipated by the RBI and on the hydrodynamic of such systems. Here, the turbulent Power Numbers, Po's, for an RBI in a scaled-down vessel equipped with one of the different types of single baffles used in the pharmaceutical industry (beavertail, D-type, H-type, finger-type, fin-type baffles) were experimentally determined for different positions of the baffles and computationally obtained, together with the velocity distribution. Vortex formation, occurring with the beavertail baffle, was also quantified experimentally and computationally. The experimental Po values were in close agreement with the computational predictions. Additionally, a simple power-law correlation was established between Po and the dimensionless vertical cross-sectional area of the baffles, resulting in an equation with a good fit with the experimental data.