Hot zones formation in packed bed reactors

Marwaha, B.; Luss, Dan

doi:10.1016/s0009-2509(02)00602-4

Cited by 39 publications

(29 citation statements)

References 10 publications

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“…Our previous experiments with a shallow radial flow reactor (Marwaha et al, 2001;Marwaha and Luss, 2002) revealed breathing motions, while experiments in a shallow packed bed (Marwaha and Luss, 2003) showed that in addition a splitting and recombination of the hot zone may occur. The current experiments, using smaller (2-3 mm) diameter pellets, revealed a much richer and complex dynamics than when using larger (3-4 mm) diameter pellets.…”

Section: Discussionmentioning

confidence: 92%

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Dynamics of hot zones on top of packed-bed reactors

Marwaha

Sundarram

Luss

2004

Chemical Engineering Science

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Section: Discussionmentioning

confidence: 92%

“…A detailed description of experimental set-up and procedure is presented by Marwaha and Luss (2003). In all the experiments reported here, unless stated otherwise, the feed composition was CO -6 vol%, O 2 -70 vol% and N 2 -24 vol% and the total flow rate was 1600 cm 3 / min.…”

Section: Experimental Set-up and Proceduresmentioning

confidence: 99%

Dynamics of hot zones on top of packed-bed reactors

Marwaha

Sundarram

Luss

2004

Chemical Engineering Science

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“…These include formation of hot spots in commercial PBRs 10 and infrared imaging of thermal patterns in Correspondence concerning this article should be addressed to O. Nekhamkina at aermwon@tx.technion.ac.il. V V C 2012 American Institute of Chemical Engineers various laboratory reactors including the exterior surface of a radial flow reactor, 11 the shallow packed-bed reactors 12 or the surface of a catalytic cloth under oscillatory conditions. 13 Technologies that monitor 3-D states are quite expensive and at this stage the 3-D patterns can be inferred from theory only.…”

Section: Introductionmentioning

confidence: 99%

Are 3‐D models necessary to simulate packed bed reactors? analysis and 3‐D simulations of adiabatic and cooled reactors

Nekhamkina¹,

Sheintuch²

2012

AIChE Journal

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Simulations and analysis of transversal patterns in a homogeneous three‐dimensional (3‐D) model of adiabatic or cooled packed bed reactors (PBRs) catalyzing a first‐order exothermic reaction were presented. In the adiabatic case the simulation verify previous criteria, claiming the emergence of such patterns when (ΔTad/ΔTm)/(PeC/PeT) surpasses a critical value larger than unity, where ΔTad and ΔTm are adiabatic and maximal temperature rise, respectively. The reactor radius required for such patterns should be larger than a bifurcation value, calculated here from the linear analysis. With increasing radius new patterned branches, corresponding to eigenfunction of the problem emerge, whereas other branches become unstable. The maximal temperature of the 3‐D simulations may exceed the 1‐D prediction, which may affect design procedures. Cooled reactor may exhibit patterns, usually axisymmetric ones that can be characterized by two anomalies: the peak temperature may exceed the corresponding value of an adiabatic reactor and may increase with wall heat‐transfer coefficient, and the peak temperature in a sufficiently wide reactor need not lie at the center but rather on a ring away from it. In conclusions, we argue that transversal patterns are highly unlikely to emerge in practical adiabatic PBRs with a single exothermic reaction, as in practice PeC/PeT > 1. That eliminates patterns in stationary and downstream‐moving fronts, whereas patterns may emerge in upstream‐moving fronts, as shown here. This conclusion may not hold for microkinetic models, for which stationary modes may be established over a domain of parameters. This suggests that a 1‐D model may be sufficient to analyze a single reaction in an adiabatic reactor and a 2‐D axisymmetric model is sufficient for a cooled reactor. The predictions of a 2‐D cylindrical thin reactor with those of a 3‐D reactor were compared, to show many similarities but some notable differences. © 2012 American Institute of Chemical Engineers AIChE J, 2012

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“…Obviously, tracking such symmetry breaking is difficult in large commercial reactors. Infrared imaging revealed temperature pattern formation in various laboratory reactors including the exterior surface of a radial flow reactor6 and the top of shallow packed‐bed reactors7 or the surface of a catalytic cloth8 under oscillatory conditions.…”

Section: Introductionmentioning

confidence: 99%

Transversal patterns in three‐dimensional packed bed reactors: Oscillatory kinetics

Nekhamkina¹,

Sheintuch²

2010

AIChE Journal

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in Wiley Online Library (wileyonlinelibrary.com).Formation of transversal patterns in a 3D cylindrical reactor is studied with a catalytic reactor model in which an exothermic first-order reaction of Arrhenius kinetics occurs with a variable catalytic activity. Under these oscillatory kinetics, the system exhibits a planar front (1D) solution with the front position oscillating in the axial direction. Three types of patterns were simulated in the 3D system: rotating fronts, oscillating fronts with superimposed transversal (nonrotating) oscillations, and mixed rotating-oscillating fronts. These solutions coexist with the planar front solution and require special initial conditions. We map bifurcation diagrams showing domains of different modes using the reactor radius as a bifurcation parameter. The possible reduction of the 3D model to the 2D cylindrical shell model is discussed.

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Hot zones formation in packed bed reactors

Cited by 39 publications

References 10 publications

Dynamics of hot zones on top of packed-bed reactors

Dynamics of hot zones on top of packed-bed reactors

Are 3‐D models necessary to simulate packed bed reactors? analysis and 3‐D simulations of adiabatic and cooled reactors

Transversal patterns in three‐dimensional packed bed reactors: Oscillatory kinetics

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