Maximizing power efficiency in gas-solid-liquid stirred vessels handling high solids concentrations

This study focuses on determining the optimum operating and geometrical conditions that will enhance the agitator energy efficiency in a gas-liquid-solid agitated vessel. A term defined as the power efficiency factor (epsilon jsg -1 (kg/W)) served as an indication of the quantity of solid particles that could be suspended per unit of power consumed by the impeller. By varying operational parameters like solids concentration and gas flow rate and design parameters like impeller type and baffling condition, it was found that the epsilon jsg -1 values can be maximized by operating the tank with an optimum range of solids concentration, which is around Cv = 0.2 - 0.3 v/v for the systems studied in this work. Another term, known as baffling efficiency factor, 'R epsilon', was used to study how baffle removal influences the energy efficiency of impellers in three-phase systems. It was observed that absence of baffles could exert negative effects on energy efficiency of axial-flow impellers at particular operating conditions. Moreover, the gas-liquid interfacial area 'ɑ' was studied by determining the gas holdup and Sauter mean bubble diameter (d32) at 'just-suspended condition' Njsg, for a wide range of solids concentrations. It was observed that increasing solids concentration is an effective strategy for maximization of contact area between gas and liquid phases in three-phase stirred tanks