A one-dimensional combined multifluid-population balance model for the simulation of batch bubble columns

Bubble columns are widely used as multiphase reactors for gas–liquid reactions in industrial applications. For the sensitivity and usability analysis of the bubble column in the process development, a model is needed that incorporates couplings between the fluid dynamics, the population balance equation (PBE) and the thermodynamics. Thereby the model should be as fast and reliable as possible. A suitable candidate is the kinetic theory approach with size resolution (KTAWSR), as one of the most rigorous combined multifluid-PBE models. A steady-state and one-dimensional version of the KTAWSR model was used and extended to batch bubble columns. For this purpose, a new approach for the determination of the integral gas holdup was developed which does not require additional empirical correlations. The spectral orthogonal collocation method was used to solve the model equations. Different breakage and coalescence model combinations were calibrated, compared and investigated on the basis of measured bubble size distributions. To validate the model, the integral gas holdup and the bubble size distribution were measured at four axial positions at three gas volume fluxes reaching the transition flow regime in a batch water–air bubble column. The novel integral gas holdup calculation approach could be predictively confirmed with measured data.