Gas‐phase backmixing in bubble‐column reactors

Abstract

Abstract Gas‐phase backmixing and holdup for the air‐water system were measured in 0.15‐ and 0.25‐m‐dia. bubble columns. Novel experimental and analytical techniques were used to analyze the gas‐phase residence time distribution. A Levenberg‐Marquardt‐type optimization scheme was used to obtain the two reactor model parameters: Peclet and Stanton numbers. Operating variables included the column diameter and the superficial gas‐ and liquid‐phase velocities. A two‐bubble‐class hydrodynamic model has been proposed to predict the gas‐phase backmixing in bubble column reactors. The model assumes a bimodal distribution of the gas phase with large bubbles flowing in a plug‐flow manner and the small bubbles partially backmixed. The model only needs easily measurable parameters and has been validated by comparing experimental as well as literature data on gas‐phase backmixing with the model predictions. The model is more realistic than the conventional single‐bubble‐class model and provides a rational approach to predict the gas‐phase backmixing in scaling‐up bubble‐column reactors.