Numerical simulation of reactive bubbly flows

Abstract

The interaction of numerous physical and chemical phenomena in bubble columns, a popular type of multiphase reactors, is studied numerically. The state of the art of gas-liquid flow modeling is reviewed, and a sophisticated mathematical model is assembled. It combines a detailed treatment of the two-phase flow hydrodynamics with consideration of mass transfer possibly enhanced by homogeneous chemical reaction in the liquid phase. Reasonable model simplifications are discussed. Approximate solution to the problem at hand is obtained by the finite element method. The numerical challenges to be faced are the tracking of moving boundaries, dominating convection and strong nonlinearities, to name just a few. Operator-splitting techniques are employed to decompose the original problem into a set of tractable subproblems. Proper solution tools are proposed in each case, and their performance is illustrated by application to benchmark problems. Notable accomplishments include a strategy for inflow /outflow boundary treatment within a Lagrangian spacetime finite element method, a pointwise limiter for pure convection problems and a simplified mass-conserving projection scheme for the intergrid transfer of data. These and other elemental components are embedded into a global numerical algorithm for dynamic numerical simulation of gas-driven flows in a bubble column reactor. The advocated approach is applied to investigate the startup behavior of a two-dimensional bubble column under a wide range of operating conditions. The role played by various model parameters is analyzed. The presented computational results are in good qualitative agreement with experimental data available in the literature.