Oxygen transfer in a three-phase bubble column using solid polymers as mass transfer vectors

Abstract

Three solid polymers; Kraton, Elvax, and Desmopan, previously suggested to be used in three-phase reactors, were evaluated for their ability to enhance oxygen transfer in a bubble column. These vectors were first characterized, including; particle size distribution, specific surface area, density, void fraction and thermal stability. Oxygen transfer was then determined with a noncoalescing medium using polymer volume fractions from 0 to 75% in a 4 L bubble column operated at air flow rates ranging from 1 to 6 L/min. The results showed that in most of the cases, particles clusters were formed at the surface of the bulk water phase, which caused a decrease of the oxygen transfer capacity. Kraton, was the polymer vector more easily dispersible in the air/water bulk phase of the bubble column, and used at a proportion of 10% with an aeration flowrate of 2 L/min, it allowed an oxygen transfer enhancement by 90-100%, compared to a control with no vector. This enhancement was a result of constant collisions between vector particles and bubbles, decreasing their rising speed, while not altering their mean size, thus resulting in a significantly higher gas holdup and air/water exchange area.