Gas hold-up and bubble diameters in a gassed pulsation reactor
Advancing the chemical engineering fundamentals
Multifase Flows (T2-5P)
Keywords: oscillatory flow, pulsation reactor,hold-up, bubble size, power dissipation
To intensify mass transfer in the liquid-gas phase, keeping sterility and uniform phase distribution in the reaction volume, reactors with oscillating baffles or pulsators of OBR, OBC or COBR type are used. A basic design problem is to relate elements of the reactor construction to the range of changes in the frequency and amplitude of pulsations for a liquid-gas system with specified physicochemical properties. As follows from literature survey, this topic is at the stage of preliminary studies. The studies are dedicated only to liquid-gas systems with physicochemical properties similar to those of water-air systems. There are no reports on the effect of the frequency and amplitude of pulsations on the hydrodynamics of gas flow through liquids with more complex rheological properties.
A model is proposed and its experimental verification is presented based on the authors’ research and literature data concerning the effect of frequency and amplitude of pulsations introduced to a continuous phase on gas hold-up and distribution of gas bubble diameters, for air flow through the layer of model Newtonian and non-Newtonian liquids in a model pulsation reactor. The experimental media were water, triethylene glycol, paraffin oil and PAA solutions as non-Newtonian liquids. Investigations were made for the frequency of pulsations introduced through a steel plate installed in the reactor bottom, ranging from 0 to 30 Hz, and at the amplitude from 0.3 to 2 mm. From 400 to 2000 dm3 air/h was introduced by means of a diffuser with six replaceable nozzles of diameters from 0.5 to 4 mm. A broad spectrum of experimental data allows us to state that an increase of the amplitude and frequency of pulsations causes a decrease of bubble diameter and an increase of the total gas hold-up. Additionally, extreme values of gas hold-up and minimum bubble diameters were observed locally along the reactor. The gas hold-up, bubble diameters and extreme points (nodes of standing wave) depended significantly on the rheological properties of a continuous liquid phase.
See the full pdf manuscript of the abstract.
Presented Tuesday 18, 13:30 to 15:00, in session Multifase Flows (T2-5P).
