Mixing effects in vertical upflow bubble columns

Abstract

The phenomenon of a rising macrovortex of preferentially aerated liquid was observed in large-scale bubble columns. A theoretical explanation of this phenomenon is presented, based on the theory of the turbulent free boundary layer. The description results in a single-parameter model, based on the coefficient of Prandtl's mixing length from the phenomenological theory of turbulence after introducing acceptable simplifications. The experimental procedure of measuring the coefficients of Prandtl's mixing length from the boundaries of jets forming after introduction of a tracer fluid into a macrovortex and into single-phase flow has been devised. Finally, a mixing coefficient is defined, relating the degree of mixing in the macrovortex to the turbulence created in singlephase flow alone. Thus a dimensionless single-parameter model of non-ideal flow in a part of the total flow in a bubble column, due essentially to gas maldistribution, has been formulated.