Effect of Amplitude on Mass Transport, Void Fraction and Bubble Size in a Vertically Vibrating Liquid-Gas Bubble Column Reactor

Abstract

Two-phase and three-phase Bubble Column Reactors are used in many chemical, petroleum, and bio-systems processing applications such as the hydrogenation of coal slurry to produce synthetic fuels during the Fischer-Tropsch process. Vertical vibration of a BCR has previously been shown to increase mass transfer, increase void fraction, decrease bubble size and establish interesting flow phenomena through kinetic buoyancy or “Bjerknes force”. However, the effect of kinetic buoyancy on the flow field, mass transfer, and flow properties such as void fraction is not fully understood. While previous research has focused on the effect of vibration frequency (10 < f < 120 Hz) at low amplitudes, (A < 2.5 mm) very little attention has been given to the effect of larger amplitudes. Therefore, a new experimental set up was designed, built, verified by comparison to previous research, and used to collect mass transfer, void fraction, and bubble size data at high amplitude (2.5 mm < A < 9.5 mm) over a frequency range of 7.5–22.5 Hz. Comparison of the results with previous research shows similar local maxima occurring for void fraction and mass transfer, but that an optimum amplitude may exist for mass transfer which is independent of frequency. Statistical analysis and comparison of the results with data from the literature suggests a stronger relationship may exist between kinetic buoyancy and mass transfer than previously theorized.Copyright © 2013 by ASME