Mass Transfer Coefficients for a Bingham Fluid and Water With and Without Anti-Foam Agents

Abstract

The equations describing mass transfer coefficients are rather concise, but experimental data is required to determine the coefficients. Here, mass transfer rates were measured in a large scale system, which consisted of an 8.4 meter tall by 0.76 meter diameter column containing one of three fluids: water with an anti-foam agent, water without an anti-foam agent, and a Bingham plastic fluid, referred to as AZ101 simulant. The Bingham fluid differed from water since it required an applied yield stress to initiate flow. Newtonian fluids, like water, have a zero yield stress. Each of the fluids was saturated with oxygen, and the oxygen was removed from solution as air bubbled up, or sparged, through the solution from the bottom of the column. Air sparging was supplied by a single pipe which was co-axial to the column. The decrease in oxygen concentration was recorded, and the oxygen measurements were then used to determine the mass transfer coefficients to describe the rate of oxygen transfer from solution. Mass transfer data for 24 different test conditions were determined. Superficial sparging velocities of 2, 5, and 10 mm/second were applied to each of the simulants at three different column fill levels, where the superficial velocity is defined as the average volumetric flow rate divided by the liquid surface area in the column. Mass transfer coefficient test results are presented herein for each test combination of superficial velocity and fluid level.