Mixing Characteristics in a Conical-based Pharmaceutical Reactor Fitted with a Retreat Curve Impeller

Abstract

Batch stirred tank reactors (STRs) equipped with non-standard impeller designs are commonly used in pharmaceutical industry. The non-standard impeller designs such as retreat curve impellor (RCI) or its modified versions are developed to fit in the irregular shaped STRs like the one with conical base. The non-standard base of STRs is designed to provide ease for final viscous product discharge, cleaning and improving fluid dynamics during the course of mixing and reaction. In this work, experiments have been conducted in a conical base non-standard STR having a diameter of 0.29 m and equipped with a modified RCI to measure the power number and mixing time by using water and glycerin as working fluids. Visualizations were also performed to gain an insight into the fluid dynamics during the course of the mixing process. Power numbers were measured for different impeller clearance ranges and baffling arrangements. Blending of liquid was observed and measured to occur rather quickly in these nonstandard STRs, which were mainly due to the use of a large RCI impeller.