Wall Temperature Modulates Transversal Spatiotemporal Pattern Selection in Shallow, Nonadiabatic Packed-Bed Reactors

Abstract

Transversal temperature pattern formation has been observed in laboratory and industrial catalytic packed-bed reactors (PBRs) used for conducting exothermic reactions. These patterns or nonuniform states can strongly affect reactor performance and pose severe safety issues. Recent studies show that symmetry-breaking bifurcations may cause transversal pattern formation in a reactor operated under nonadiabatic conditions. In this study, we show that wall temperature, which dictates the instantaneous and overall heat exchange rate, strongly influences the selection and dynamics of various target and rotating patterns exhibited in a shallow nonadiabatic PBR. We demonstrate this by linear stability analysis-guided extensive numerical simulations of a shallow reactor model assuming periodic blocking-reactivation kinetics for the catalytic reaction. Transversal spatiotemporal patterns predicted in lab-scale (∼6 cm diameter) and/or bench-scale (∼60 cm) reactors, include rotating patterns, inward/outward/multi-ring targets, quasi-stationary moving patterns, and symmetric and asymmetric spirals. We show that wall temperature modulates the transition between these targets and rotating transversal nonuniform states at both scales. We argue that rich and intricate patterns observed much more in bench-scale reactors than those in lab-scale reactors are possibly due to reduction in the heat removal time upon increase in diameter by 10-fold. We further classify the simulated transversal patterns into three regimes, viz., (i) heating, (ii) heating and cooling, and (iii) cooling, based on the nature of wall heat exchange rate dynamics dictated by the (instantaneous) local temperature near the reactor wall. Wall heat exchange rate dynamics being an experimental observable makes it a signature of a nonuniform state present inside the reactor.

NASCRE-4 Editorial

“…The excellent participation from the next generation of chemical reaction engineers was a particularly exciting aspect of the meeting and is reflected in the contributions to this special issue. The papers in this VSI () reflect the diverse topics of the meeting, centered on several key unifying themes, including biomass conversion, − catalysis, including catalyst design and modeling, − environmental remediation, , membrane reactors, , novel reactor design, , polymerization, and process intensification and optimization. − …”