Liquid back-mixing in packed-bubble column reactors: a state-of-the-art correlation

The extent of liquid back-mixing in gas-liquid concurrent upflow packed-bub ble column reactors is quantified in terms of an axial dispersion coefficie nt or its corresponding dimensionless Peclet number. Effects of reactor ope rating conditions on the axial dispersion coefficient are not properly acco unted for by the available literature correlations, wherein most often the Peclet number is expressed solely in terms of the gas and liquid Reynolds n umbers or superficial velocities. Based on the broadest experimental databa nk (1322 measurements, II liquids, four gases, 28 packing materials, 14 col umns diameters, Newtonian, non-Newtonian, aqueous, organic, coalescing and non-coalescing liquids, high pressure, bubble and pulsing how regime condit ions), a state-of-the-art liquid axial dispersion coefficient correlation i s obtained by combining neural network modeling and dimensional analysis. T horough qualitative and quantitative analyses of the constructed databank d emonstrate the robustness of the proposed correlation to restore the variet y of trend variations of liquid Peclet numbers reported in the literature. (C) 2001 Elsevier Science B.V. All rights reserved.