Hydrodynamics and mass transfer prediction in a three-phase airlift reactor for marine sediment biotreatment

Fluid dynamic and mass transfer characteristics of a three-phase airlift re actor were studied in a rectangular split-vessel reactor. The gas-liquid-so lid system consisted of air, seawater and marine sediment, respectively. Ex periments were conducted over a range of downcomer to riser cross-sectional area ratios (A(D)/A(R) = 1.0-0.65) and for five sediment concentrations (5 -25% w/v). Simple models were used to simulate the fluid dynamic and mass t ransfer behavior for all experimental conditions examined. The fluid dynami c model was based on an energy balance which takes into account the energy dissipated at the phases interfaces. The mass transfer model was based on a two-phase fluid dynamic model, the Higbie's penetration theory and Kolmogo roff's theory of isotropic turbulence. Experimental data of gas holdup, liq uid velocity and volumetric mass transfer coefficient were simulated with s atisfactory accuracy (differences less than 20% for most cases) when assump tions regarding to gas recirculation on the overall gas holdup and the volu metric mass transfer coefficient were made. (C) 1999 Elsevier Science Ltd, All rights reserved.