Backmixing in gas‐liquid reactors

Abstract

This review evaluates the present state of the art on backmixing in gas‐liquid and gas‐liquid‐solid reactors. A brief outline of numerous techniques for measuring residence time distribution (RTD) of various phases in a multiphase reactor is presented. This is followed by a brief description of differential and stagewise models for characterizing backmixing from RTD measurements. Both simple (that is, single‐parameter axial dispersion model) and more complex (that is, two‐, three‐, or four‐parameter models) models are evaluated. Backmixing characteristics of various gas‐liquid columns such as trickle beds, spray columns, mechanically agitated columns, plate columns, fluidized bed columns, etc., are subsequently evaluated. The performance of a bubble column under various reaction conditions is analyzed. Criteria for the elimination of backmixing in packed‐bed reactors are presented, and the effect of backmixing on the multiple steady states in a gas‐liquid reactor is briefly reviewed. Finally, the scale‐up problems associated with gas‐liquid reactors with various degrees of backmixing and the recommendations for the future work in RTD and macromixing models are outlined. Copyright © 1978 American Institute of Chemical Engineers