Maximizing impeller power efficiency in gas-solid-liquid stirred vessels through process intensification

In this work, suspension of ultrahigh concentration solids in the presence of gas at different solids concentrations, gas flow rates, and impeller types was studied in a mechanically agitated vessel. A term defined as the power efficiency factor (εjsg−1 (kg/W)) serves as an indication of the quantity of particles that could be suspended per unit of power consumed by the impeller. Accordingly, it was found that the εjsg−1 values can be maximized by operating the mixing tank with an optimum range of solids concentration, which is given as Cv ≈ 0.2−0.3 (v/v) for the systems studied in this work. It was observed that large mixed flow impellers were more energy-efficient when the tank was operated under aerated conditions with an optimum concentration of solids. A mathematical model was developed to predict the impeller specific power εjsg (W/kg), which can be used to determine the optimum solids concentration in three-phase stirred vessels, and its predictions exhibited reasonable agreement with the experimental results.