An investigation of gas-liquid flow in a kenics mixer

Motionless mixers are pipe insets which generate high rates of energy dissipationëmpared to an empty pipe, and more miformly than in a stirred tank. A range of experimental technique ¬ _ ` _ , 'id to study the effects of flow parameters and liquid viscosity on gas-liquid mixing and mass transfer within a 6 element Kenics mixer (manufactured by Chemineer) operating in a vertical downflow mode. Four major experimental techniques were developed: a bre-optic probe technique for determining flow pattern; a gamma-ray transmission and a, conductivity technique for measuring liquid residence times to obtain local and average holdup respectively; and a photographic technique for measuring bubble size. New data is presented on performance parameters such as the flow pattern, pressure drop, bubble size and gas holdup at a range of gas and liquid flow conditions up to 4 1 s'1 each, at viscosities up to 32 mPas and their effect on the mass transfer rate within the mixer is discussed. Experimental results show that viscosity does not appear to affect holdup for liquid superficial velocities less than or equal to 1.52 m s'1, and flow pattern is affected only slightly. Pressure drop increases as viscosity is increased up to 12 mPas but is increased very little above 12 mPas. The pressure drop can be predicted reasonably well using the mixer manufacturer's correlation.