[CCoE Notice] Dissertation Defense: Spatio-temporal Dynamics of Reaction Zones in Catalytic Monolith Reactors

[Grayson, Audrey A]

PhD DEFENSE STUDENT: Tian Gu
DATE: Friday, August 5, 2016
TIME: 10:00 AM
PLACE: Chemical Engineering Conference Room
DISSERTATION CHAIR: Dr. Vemuri Balakotaiah
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TITLE:

Spatio-temporal Dynamics of Reaction Zones in Catalytic Monolith Reactors
Catalytic monolith reactors are widely used in exhaust after-treatment systems. Unlike traditional chemical reactors which are commonly operated around certain steady-states, these monolith reactors are almost always in transient states due to the nature of their applications. In order to meet the increasingly challenging emissions requirements, it is desired to understand dynamic behaviors of monolith reactors. The main goal of this work is to analyze some of the important spatio-temporal dynamics of monolith reactors.
In the first part, a physics based one-dimensional transient model is proposed to study the oxygen storage dynamics of a three-way catalytic converter (TWC). The model uses a simplified kinetic model, is computationally efficient, and may be used for online TWC outer loop controller design and validation.
Monolith reactors are often studied in laboratory experiments using monolith samples of the same cell density, washcoat thickness, and catalyst loading but with a smaller length compared to the full-scale reactor. In the second part of this work, it is shown that when thermal effects are significant and heat and mass dispersion effects are not negligible, similarity may not exist and the ignition/extinction behavior of the two systems can be qualitatively different.
One major challenge in exhaust after-treatment is reducing cold-start emissions. Back-end ignition followed by a fast upstream creeping reaction zone provides a feasible way to reduce cold-start emissions. In the third part of this work, the upstream creeping reaction zone is investigated in detail using modeling approach. The influence of various design parameters and operating conditions on the creep velocity is determined and summarized.
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