Mixing Time, Homogenization Energy and Residence Time Distribution in a Gas-Induced Contactor

Mixing time, homogenization energy and residence time distribution (RTD) experiments have been carried out in a gas-induced contactor in order to determine mixing characteristics of the vessel. Effects of sensor location, impeller speed, gas induction, and gassing on mixing time have been studied. Experiments on a semi-technical scale vessel have identified optimal mixing time conditions and optimal impeller speeds for most efficient homogenization energy. The effects of liquid flow rate and impeller speed on liquid phase RTD have also been investigated. The contactor mixing behaviour was modelled by a continuous stirred tank reactor (CSTR) with dead zones and bypassing. Good agreement between experimental and model results was observed. Analysis shows that contactor performance is close to that of an ideal CSTR; however, dead zones (as large as 16.7%) at low liquid flow rates and bypassing (as large as 10%) at high liquid rates need to be considered.