Stochastic modelling of axial dispersion in external-loop airlift bioreactors

The paper presents a model of the motion of a particle subjected to several transport processes in connection with mixing in two phase flow. A residen ce time distribution technique coupled with a one-dimensional dispersion mo del was used to obtain the axial dispersion coefficient in the Liquid phase , D-ax. The proposed model of D-ax for an external-loop airlift bioreactor is based on the stochastic analysis of the two-phase flow in a cocurrent bu bble column and modified for the specific how in the airlift reactor. The m odel takes into account the riser gas superficial velocity, the riser liqui d superficial velocity, the Sauter bubble diameter, the riser gas hold-up, the downcomer-to-riser cross sectional area ratio. The proposed model can b e applied with an average error of +/-20%.