Computation of the flow and reactive mixing in dual-Rushton ethoxylation reactor

Two ethoxylation reactors, powered with dual-Rushton impeller, were investigated in this paper using computational fluid dynamics (CFD). The flow was described as an incompressible, turbulent single-phase liquid (hydrophobe substrate) mixing with chemical species (ethylene oxide). The first reactor, simulated for the purpose of validation of hydrodynamics, was based on the literature with experimental (K. Rutherford, K.C. Lee, S.M. Mahmoudi, M. Yianneskis, Hydrodynamic characteristics of dual-Rushton impeller stirred vessel, AIChE J., 42 (1996) 332–346.) and numerical (G. Micale, A., Brucato, F., Grisafi, M., Ciofalo, Prediction of flow fields in a dual-impeller stirred vessel, AIChE J., 45 (1999), 445–464.) data on velocities and turbulent kinetic energy. After the successful validation exercise with reasonable accuracy, simulations were extended to predict the flow hydrodynamics and ethoxylation kinetic in a 6 m3 industrial ethoxylation reactor equipped with a dual-Rushton turbine. The ethoxylation kinetics were taken from the experiments previously conducted by the authors (Y.N. Chiu, A. Easton, K.F. Ngian, K.C. Pratt, Kinetics of a catalysed semi-batch ethoxylation of nonylphenol, in: Proceedings of the 4th Biennial Engineering Mathematics and Applications Conference, Melbourne, Australia, 2000.). Reasonably good agreement was obtained between the simulated and experimental data on the time-dependent changes of ethylene oxide mass fraction in the bulk liquid in the industrial ethoxylation operations.