Dynamics of hot zones on top of packed-bed reactors

Marwaha, B.; Sundarram, Sandhya; Luss, Dan

doi:10.1016/j.ces.2004.07.090

Cited by 22 publications

(29 citation statements)

References 22 publications

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“…Wicke and Onken6, 7 noted different temperatures at two locations in the same cross‐section of a packed‐bed reactor. Infrared imaging revealed local hot regions on the exterior surface of a radial flow reactor,8–10 the top of shallow packed‐bed reactors,11–13 and a catalytic fiber cloth 10, 14. Sundarram et al15 found that global coupling between the effluents and the top of the reactor can affect the evolution, stability and shape of the temperature patterns.…”

Section: Introductionmentioning

confidence: 99%

“…PCA provides an objective characterization of the underlying dynamics in space and time. It has been successfully applied to the analysis of spatiotemporal patterns on catalytic surfaces13, 37 and the details are presented by Graham et al37 In this procedure, the spatiotemporal data u ( ξ , ϕ , τ ) are represented by the series \input amssym $$\font\abc=cmmib10\def\bi#1{\hbox{\abc #1}}{\bi u} (\xi, \phi, \tau)=\sum\limits_{i=1}^N {{\cal A}_i} (\tau) \varphi_i (\xi, \phi)$$ where ${\cal A}_i(\tau)$ are orthogonal time‐dependent amplitudes and φ i ( ξ , ϕ ) spatial modes. Thus, where λ i represent the energy captured by the principal modes, which correspond the relative contribution of the principal modes to the overall motion.…”

Section: Introductionmentioning

confidence: 99%

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Reactor diameter impact on hot zone dynamics in an adiabatic packed bed reactor

2007

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in Wiley InterScience (www.interscience.wiley.com).Recent analysis revealed that a pseudohomogeneous model of a uniformly active, adiabatic packed bed reactor can predict formation of stable hot zones in the crosssection of the reactor if the kinetic rate expression can lead to isothermal rate oscillations. This prediction was confirmed by simulations of CO oxidation. We show that hot zone formation in a shallow reactor can be predicted also for C 2 H 4 hydrogenation, the kinetic model of which is structurally different from that of CO oxidation. Qualitatively different spatiotemporal temperature patterns may form under the same operating conditions. Their number increases as the reactor diameter is increased. An increase in the reactor diameter increases the time constant of the transversal heat dispersion and decreases the temperature synchronization among points on the same reactor crosssection. The interaction and conjugation among qualitatively different moving temperature patterns can lead to formation of complex motions.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Reactor diameter impact on hot zone dynamics in an adiabatic packed bed reactor

2007

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“…Wicke and Onken3, 4 observed a transversal hot region in a laboratory packed‐bed reactor. Various types of transversal hot regions were observed in a shallow packed‐bed reactor by Marwaha et al5, 6 and on a catalytic glass fiber cloth by Digilov et al7 Transversal hot regions have a deleterious impact on the reactor performance and may pose severe safety hazards when present next to the reactor wall.…”

Section: Introductionmentioning

confidence: 99%

Model prediction of hot spots formation in shallow adiabatic packed‐bed reactors

Viswanathan¹,

Luss²

2005

AIChE Journal

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Transversal hot zones have been observed in many industrial and laboratory reactors. Yet, previous models which utilized rate expressions that depended only on the temperature and concentration of the limiting reactant failed to predict formation of stable hot zones. We previously proved that pseudohomogeneous models of a uniformly active shallow adiabatic packed‐bed reactor cannot predict a bifurcation to stable hot zones when the transversal heat dispersion is larger than that of the species, and the reaction rate depends only on the temperature and concentration of the limiting reactant. We prove here that the same is true also for a two‐phase model of a uniformly active shallow, adiabatic packed‐bed reactor. It is shown that a shallow reactor model, which uses more detailed kinetic expression, may attain stable, transversal hot zones. © 2005 American Institute of Chemical Engineers AIChE J, 2006

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“…At present, there is sufficient experimental evidence of SP formation in catalytic fluid-particle systems and reactors (Brown et al, 1985;Razon and Schmitz, 1987;Sant and Wolf, 1987;Sheintuch, 1996;Marwaha et al, 2004;Sundarram et al, 2005;Luss and Sheintuch, 2005). However, the theoretical analysis and interpretation of the conditions leading to pattern formation in catalytic reactors are rather confusing or misleading.…”

Section: Estimation Of the Range Of Parameter Values For Pattern Formmentioning

confidence: 92%

“…Balakotaiah et al (2002) demonstrated that transport limited patterns form in a catalytic monolith due to slow relative rate of heat and mass communication between the gas and the catalyst surface. Marwaha et al (2004) and Sundarram et al (2005) have shown that global coupling can lead to formation of hot zones on the top of a packed-bed reactor. Recently, Viswanathan et al (2005) and Viswanathan and Luss (2006) showed that a stable stationary hot zone can form in the cross-section of a packed-bed reactor only under the unrealistic assumption that the transversal species dispersion exceeded that of the temperature.…”

Section: Introductionmentioning

confidence: 98%