(31d) The Formation Of Hot Zones In Packed Bed Reac

Local transversal hot spots may form in packed bed reactors., posing a safety hazard. The mechanism causing these hot spots in commercial reactors has not yet been established. We used infrared thermography to capture the formation and dynamics of transversal hot zones formed in a shallow reactor packed with several layers of spherical Pd on Al2O3 catalytic. We conducted in the same reactor the atmospheric oxidation of three different reactants feeds of CO, propylene and mixtures of propylene and CO to observe the impact of the chemical reaction on the dynamic features of the hot zones. The hot regions were separated from the colder ones by sharp fronts (?xT~75?aC). They exhibited characteristic motions such as back and forth (breathing), rapid transition from one side of reactor to another (anti-phase), and rotation around the bed. More intricate behavior due to interaction among these basic motions, has also been observed. We present a mathematical analysis that predicts the formation of transversal hot zones in both shallow and long, adiabatic packed bed reactors. The analysis predicts, in agreement with the experimental observations, that different types of hot zones may form under the same operating conditions. The increase of the reactor diameter or its length increases the number of qualitatively different hot zones. The interaction between different types of zones zones can lead to chaotic motion of the hot zones.