Coherent flow structures in bubble column reactors

Abstract

This paper reviews the flow patterns in bubble columns with a focus on transient flow structures. The subject of mean flow pattern has not been covered in view of the earlier publication (Chemical Engineering Science 56 (2001) 5893-5933), which also deals with the subject of the formulation of governing equations and the description of interface force terms for gas-liquid dispersions. The published literature in the last ten years has been analyzed on a coherent basis and the present status has been brought out for (i) Euler-Euler versus Euler-Lagrange approach, (ii) closure formulation for eddy diffusivity in gas-liquid dispersions, (iii) numerical issues such as grid size, discretization scheme and the solution algorithms and (iv) two-dimensional versus three-dimensional formulation. The following geometries of bubble columns have been investigated in the past: (i) two-dimensional column with off-center sparging, (ii) two-dimensional column with central sparging, (iii) two-dimensional column with uniform sparging and (iv) cylindrical columns with uniform sparging. All these cases have been covered in the present paper. A critical account of the predictive capability of all the models for transient flow structures has been presented. This paper also includes the application of multiresolution analysis of velocity-time series for the identification of coherent flow structures.