Chemical Engineering Journal 321 (2017) 584–599
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A simple approach to describe hydrodynamics and its effect on heat and mass transport in an industrial wall-cooled fixed bed catalytic reactor: ODH of ethane on a MoVNbTeO formulation Gustavo Aparicio-Mauricio a, Richard S. Ruiz a, Felipe López-Isunza b, Carlos O. Castillo-Araiza a,⇑ a Grupo de Procesos de Transporte y Reacción en Sistemas Multifásicos, Departamento. de IPH, Área de Ingeniería Química, Universidad Autónoma Metropolitana-Iztapalapa, Apartado Postal 55-534, Mexico City 09340, Mexico b Depto. de IPH, Universidad Autónoma Metropolitana-Iztapalapa, Apartado Postal 55-534, Mexico City 09340, Mexico
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g r a p h i c a l a b s t r a c t
! This work proposes a new
hydrodynamic approach (PHA) for modeling packed beds. ! The effect of hydrodynamics on heat transfer and reaction is elucidated. ! Wall-cooled packed-bed reactor seems an ideal design for the ODH-Et on MoVTeNbO. ! Industrial reactor model accounts for the effect of hydrodynamics on heat transfer. ! The PHA leads to significantly lower CPU times than the conventional approach.
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Article history: Received 14 October 2016 Received in revised form 10 March 2017 Accepted 13 March 2017 Available online 16 March 2017 Keywords: Packed bed reactor Hydrodynamics Heat transfer Oxidative dehydrogenation of ethane MoVNbTeO formulation
a b s t r a c t The incorporation of hydrodynamics in an industrial wall-cooled packed bed reactor model is essential to describe the performance of highly exothermic oxidation reactions. Although the conventional hydrodynamic approach (CHA), Navier-Stokes equations coupled to Darcy-Forchheimer terms, has been the most used approximation to describe velocity profiles in these packed bed reactors, it is itself inconsistent and the computation time for its numerical solution, when coupled to the reactor model, is still demanding. This work is aimed at developing a practical but reliable hydrodynamic approach (PHA) to describe velocity profiles in packed bed reactors presenting a low tube to particle diameter ratio. In this approach, velocity profiles are described at the core and close to the wall of the reactor. The core model makes use of the Darcy-Forchheimer equation (DFE), and the wall model makes use of Navier-Stokes equations (NSE) using an effective viscosity to account for turbulence. The PHA predicts similar results to those obtained by the CHA and properly fits velocity observations from packed beds with a tube to particle diameter ratio (dt/dp) ranging from 3 to 6. The PHA allows the estimation of both turbulent viscosity (lt) involved in the viscous term of the NSE and parameters influencing viscous (a) and inertial (b) flow resistances in Darcy and Forchheimer terms, respectively. Then, hydrodynamics is coupled to a heat transport model accounting for conductive anisotropy to fit temperature observations in absence of reaction from a pilot-scale packed bed reactor with a dt/dp = 3.048. Hydrodynamics and heat transfer results are, then, transferred to a pseudo heterogeneous reactor model to simulate the behavior of a novel
Abbreviations: CFD, computational fluid dynamics; PHA, proposed hydrodynamic approach; CHA, conventional hydrodynamic approach; CPU, central processing unit; dt/dp, tube-to-particle diameter ratio; ODH, oxidative dehydrogenation; NSE, Navier-Stokes equations; 3D, three-dimensional space; 2D, two-dimensional space; WR, wall region; CR, core region. ⇑ Corresponding author. E-mail address:
[email protected] (C.O. Castillo-Araiza). http://dx.doi.org/10.1016/j.cej.2017.03.043 1385-8947/! 2017 Published by Elsevier B.V.
