Hydrodynamic and mass transfer characteristics of single and multiple impeller hollow self-inducing reactors

Abstract

In the present work, hydrodynamics and mass transfer characteristics of a gas-liquid stirred tank provided with hollow self-inducing impellers were investigated. Critical impeller speed for the onset of gas induction, gas induction rate, power consumption, and mass transfer coefficient (k_La) were measured using two types of self-inducing impellers, viz., hollow pitched-blade downflow turbine and double-disk impeller. Experiments were carried out in 100 and 800 L tanks. Mass transfer coefficient was measured with steady-state hydrazine oxidation technique with air-water as the gas-liquid system. The impeller speed was varied from 2.5 to 14 rps, and power input per unit volume was varied from 0.5 to 10 kW/m³. Further, the performance of a multi-impeller hollow self-inducing system has been investigated. Four different hollow impellers in combination with three axial flow impellers have been studied in an 800 L tank using three impeller diameters and three liquid submergences. Suitable correlations have been proposed that also take into account all the published k_La data in the literature.