Wrong‐way behavior of packed‐bed reactors: II. Impact of thermal dispersion

Pinjala, V.; Chen, Y. C.; Luss, Dan

doi:10.1002/aic.690341010

Cited by 77 publications

(64 citation statements)

References 15 publications

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“…Consider, for example, a sudden and persistent decrease of feed temperature. The resulting wrong-way response (Boreskov and Slinko, 1965;Pinjala et al, 1988;Luss, 1997) illustrated in Fig. 2a, consists of a transient temperature rise.…”

Section: Introductionmentioning

confidence: 99%

Dynamic responses of packed bed reactors

Menzinger

Yakhnin

Jaree

et al. 2004

Chemical Engineering Science

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Section: Introductionmentioning

confidence: 99%

Dynamic responses of packed bed reactors

Menzinger

Yakhnin

Jaree

et al. 2004

Chemical Engineering Science

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“…The physical mechanism for thermal spike formation is akin to wrong-way Ž . behavior Oh and Cavendish, 1982;Pinjala et al, 1988 . If the rich fuel persists, thermal runaway can occur quite read- The time elapsed between snapshots of the simulated thermal profile is 1r13 th of a half-cycle.…”

Section: Reverse-flow Reactor Operationmentioning

confidence: 97%

Novel scheme for delaying reverse‐flow reactor runaway

Keith

2002

AIChE Journal

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The reverse-flow packed-bed reactor has been proposed for use in the chemical process industries because of its ability to Ž store thermal energy within the bed Boreskov and Matros, . 1983 . During periods of high fuel concentration, large thermal spikes may form within the reactor upon flow reversal. If the duration of high fuel concentration is large, thermal runaway may result since the spikes grow in magnitude upon each other. A new scheme is proposed here which strategically reduces the flow reversal time with each half-cycle in order to utilize the entire bed to store thermal spike energy. Alternatively, the principles outlined here can be used to reduce the startup time of reverse-flow reactors.

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“…In both cases, we have assumed constant wall temperature, constant physical properties and no radial pro"les. According to Pinjala et al (1988) and Chen and Luss (1989), when the inlet variables are changed, if axial dispersion is not taken into account, discontinuities in state variables will be observed, which do not correspond to the physical reality. On the other hand, the terms of axial dispersion allow the transformation of hyperbolic partial di!erential equations into parabolic partial di!erential equations, which are much easier to solve.…”

Section: Mathematical Modelsmentioning

confidence: 99%

“…Metha, Sams and Luss (1981) found analytical criteria to predict that behavior, for zero-order reactions. Pinjala, Chen and Luss (1988) analyzed the importance of the thermal dispersion on the transient response, and concluded that the ignition of the reactor during the transient period is possible to occur. They suggested that axial dispersion terms should be included in the mathematical models, when the transient response of the system is studied.…”

Section: Introductionmentioning

confidence: 99%

“…Under some circumstances this behavior can lead to undesired results, such as promotion of side reactions, catalyst deactivation and thermal runaway. Moreover, if the system operates in a multiplicity zone, the increase of the temperature during the transient period can lead to a jump from a lowertemperature steady-state to a higher-temperature steadystate (Sharma & Hughes, 1979b;Pinjala, Chen & Luss, 1988), which is known as the ignition of the reactor.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Start-up and wrong-way behavior in a tubular reactor: dilution effect of the catalytic bed

Quina

Quinta‐Ferreira

2000

Chemical Engineering Science

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The start-up and the wrong-way behavior of a "xed-bed reactor were analyzed through one-dimensional heterogeneous and pseudo-homogeneous models. The simulation work was based on the methanol oxidation to formaldehyde, which takes place in a "xed-bed reactor with two distinct zones. In the "rst part of the reactor, the catalyst was diluted with inert, and in the second zone the catalyst is pure. This activity pro"le leads to new features on the start-up and wrong-way behavior of the system when compared with a uniform catalytic bed. For a partially diluted bed, when the inlet temperature is increased (decreased), the "nal steady state can show a hot spot lower (higher) than the initial one. This behavior is not observed in a one-zone bed, where the "nal steady-state maximum temperature is always higher (lower) than the initial one if the inlet temperature is submitted to a positive (negative) change. During the dynamic period, the transient pro"les are closer to the initial steady states in the case of the two-zone bed, pointing out that the catalyst dilution in the upstream section of the reactor can decrease the system sensitivity in both steady state and dynamic period. The di!erences between the predictions obtained through the pseudo-homogeneous and the heterogeneous models can be more signi"cant on the transient responses than on the steady state situations and the wall temperature is the most important parameter on the reactor dynamic response. Moreover, signi"cant wrong-way behavior can occur for step changes and ramp variations in feed and wall temperatures.

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Wrong‐way behavior of packed‐bed reactors: II. Impact of thermal dispersion

Cited by 77 publications

References 15 publications

Dynamic responses of packed bed reactors

Dynamic responses of packed bed reactors

Novel scheme for delaying reverse‐flow reactor runaway

Start-up and wrong-way behavior in a tubular reactor: dilution effect of the catalytic bed

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