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Lopes R.J.G.,GERSE Group on Environmental | Quinta-Ferreira R.M.,GERSE Group on Environmental
Chemical Engineering Journal | Year: 2010

Trickle-bed reactors (TBRs) are envisaged as a breakthrough technology in industrial wastewater treatment plants. According to the literature, the generous research in environmental reaction engineering has indicated that scale-up of TBR is erroneous if one considers isothermal operation and uses either a pseudo-homogeneous or a heterogeneous model with plug flow for gas and liquid phases. Even though axial dispersion model may account for liquid distribution non-uniformity, the reaction parameters are strongly dependent on the reactor fluid dynamics. In our case study, we develop an Eulerian CFD (computational fluid dynamics) framework based on empirical interphase coupling parameters in the momentum balance equation. After the hydrodynamic validation, the catalytic wet oxidation of phenolic wastewaters was taken as an example to evaluate axial and radial profiles for the total organic carbon depletion and temperature along the packed bed. The theoretical calculations were compared against experimental data taken from a trickle-bed reactor pilot plant. The Eulerian computations have shown promising results on how fluid dynamics can be correlated with chemical reaction, namely on the prediction of total organic carbon conversions attained at different temperatures. © 2010 Elsevier B.V. All rights reserved. Source


Lopes R.J.G.,GERSE Group on Environmental | Quinta-Ferreira R.M.,GERSE Group on Environmental
Chemical Engineering Science | Year: 2010

The present work encompasses an assessment of multiphase fluid modelling techniques to allow the prediction of reaction parameters in trickle-bed reactors (TBR). After the development of volume-of-fluid (VOF) and an Euler-Euler models, the catalytic wet air oxidation of phenolic acids was simulated under unsteady state evaluating axial and radial profiles for total organic carbon concentration and temperature for the bulk phase. For the purpose of code validation, theoretical results were compared with experimental data in terms of major hydrodynamic parameters, pressure drop and liquid holdup. The Euler-Euler model gave better predictions in comparison with VOF model since it used empirically based interphase coupling parameters in the momentum balance equation. After the hydrodynamic validation, both multiphase models were used to investigate the dynamic performance of TBR under reaction conditions for the pollutant decontamination of phenolic wastewaters. VOF exhibited the highest TOC conversion as well as the highest temperatures. The Euler-Euler model predictions gave rise also to the existence of hotspot formation in the first half of TBR being this fact related with poor radial mixing attained by means of CFD codes. © 2009 Elsevier Ltd. All rights reserved. Source

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