Use of computational fluid dynamics for simulating hydrodynamics and mass transfer in industrial ozonation towers

Ozonation is often used for drinking water disinfection. Ozonation lower is usually used to dissolve the ozonated gas in water by mass transfer betwee n the two phases. In particular, bubbly flow is chosen due to its high inte rfacial area. The main objective of the present paper is to upgrade industr ial ozonation tower by using the computational fluid dynamics software ASTR ID adapted to such flows. Hydrodynamics is simulated and numerical results are compared to global measurements of residence time distribution (RTD). T hen ozone mass transfer is simulated and results are compared to local meas urements of ozone concentration in water. A more complete validation of the methodology and the choice of closure relations has been done previously i n an airlift reactor (Cockx, Chemical Engineering Science, 1997, 52(21/22) 3787-3793). Numerical results are in good agreement with experimental measu rements. Accounting for the water quality and for the ozone consumption in the gas phase, it is possible to simulate in the two-phase flow reactor the zones with high ozone concentration and be able to predict the inactivatio n level for the micro-organisms. After validation, the same method is used to propose an upgraded tower allowing to double the efficiency of the disin fection process. (C) 1999 Elsevier Science Ltd. All rights reserved.