Heat-Transfer Studies in Packed-Bed Catalytic Reactors of Low Tube/Particle Diameter Ratio

Abstract

This work describes a heat-transfer study conducted in two beds of low tube/particle diameter ratio (d t/d p ≈ 3) with almost the same diameter but different lengths, packed with catalyst spheres, operating in quasi-adiabatic and nonadiabatic modes. The operation in the short bed in a quasi-adiabatic mode provided independent sets of experiments to estimate the effective thermal conductivity at various Reynolds numbers. This information was transferred successfully to model the short and long beds operating in a nonadiabatic mode. The modeling compares the classical approach to model heat transfer in a packed bed with no hydrodynamics, against those which include the hydrodynamics and a radial voidage profile, as well as the boundary layer approximation of this model. Modeling results showed that very similar predictions of radial and axial temperature profiles are obtained in all cases, making it difficult to discriminate between both model approaches.

Combined wall and thermal effects during non-isothermal packed bed adsorption

“…However, in a highly loaded, exothermic packed bed sorption process, when it is necessity to effectively decrease the temperature by cooling jacket, hydrodynamics and heat factors could plays an important role. Some of the authors [3][4][5][6][7][8][9][10] indicate this fact, and problem became much more complicated. Hence, for relatively small D/d p ratio the tube wall has a considerable influence on porosity, fluid flow, heat transfer and mass transfer in the bed.…”

Modeling of oxidative dehydrogenation of ethane to ethylene on a MoVTeNbO/TiO2 catalyst in an industrial-scale packed bed catalytic reactor

“…Due to this, this work simulates the performance of the MoVTeNbO catalytic formulation during the ODH-Et in a single tube industrial-scale packed bed reactor operating in a non-isothermal and non-adiabatic mode. The reliability of the simulations is based on the modeling approach proposed by Castillo-Araiza and López-Isunza [33,34,45], which allows the prediction of the observed behavior of a wall-cooled packed bed catalytic reactor with low d t /d p . This methodology accounts for the role of void fraction and hydrodynamics on heat transport in the reactor through the proper determination, using experiments in absence of reaction, of the effective heat transport parameters (HTP) such as the radial and axial effective thermal conductivities, k effr and k effz, respectively, and the wall heat transfer coefficient, h w .…”

“…This methodology accounts for the role of void fraction and hydrodynamics on heat transport in the reactor through the proper determination, using experiments in absence of reaction, of the effective heat transport parameters (HTP) such as the radial and axial effective thermal conductivities, k effr and k effz, respectively, and the wall heat transfer coefficient, h w . Namely, these parameters are estimated using the boundary layer approximation that makes use of a two-dimensional heat transport model coupled to the Navier-Stokes-Darcy-Forchheimer equation and the existing void fraction profile [45]. The wall-cooled packed bed reactor model is based on averaged general conservation relations for mass and energy but considering effective transport parameters.…”

“…Some studies [33,34,45] suggest that the inclusion of velocity profiles improves heat transport description; however, others studies [68,[72][73][74] have neglected the influence of the hydrodynamics in the modeling of this type of reactors.…”

“…In fact, several researches [35][36][37][38][39][40][41] have considered the wall-cooled packed bed catalytic reactor for simulating the possible performance of the ODH-Et over catalytic systems different to the MoVTeNbO formulation. Nevertheless, these studies are questionable since they do not make use of reliable kinetic models and neglect the effect of the low d t /d p on the void fraction profile and, hence, on velocity field and its role on the heat transport [42][43][44][45][46].…”