Numerical Simulation of Mass-Transfer Characteristics of External Loop Airlift Reactor (EALR)

摘要

The purpose of this work is to present results from numerical simulations of EALR. The model is taking into account the effect of the gas-liquid separator and variable liquid velocities In the riser and downcomer on the oxygen transfer rates. Axial dispersion and liquid circulation are primary reasons for different hydrodynamics in the riser, downcomer and separator and non-uniform mixing in the EALR. Therefore, a modified two phase dispersion model with axial mixing in both gas and liquid phases and well-mixing in gas-liquid separator is developed. Different operating conditions are used in order to establish the model response. The role of gas-liquid separator on the hydrodynamics and mass transfer is discussed. The model can be used as design tool to estimate the effective oxygen transfer rate and determination of volumetric transfer coefficient. The numerical solution is obtained by means of finite difference method with numerical procedure of exponential approximation. The model predicts well mass transfer in the reactor and can be used to determine the effects of parameter variation on the dynamic oxygen concentrations. The most importanl parameter affecting the mass transfer rate in the reactor was found to be value of K_(La). This model has been validated with experimental data. Qualitative agreement between experimental data and numerical results for O_2 concentration profiles in the reactor confirm the model adequacy.