(570ao) Low-Dimensional Models for Real Time Simulations of Catalytic Aftertreatment Systems

We present simplified averaged models for accurate design and real time simulations of catalytic monolith reactors. These are derived directly by averaging the governing equations and using the concept of inter and intra- phase transfer coefficients. They are described by a system of differential algebraic equations involving multiple concentration and temperature modes namely, cup-mixing concentration (Cfm) and temperature (Tfm), averaged concentrations and temperature in each phase, interfacial concentration (Cif) and temperature (Tif). With the use of multiple modes, the models capture all the important features involving exchange of mass and thermal energy within and between different phases. In the case of catalytic reactors, the multi-mode models couple the local or micro-scale length (or time) scales characterized by diffusion and reaction to macro scale problem of flow, heat and mass transfer at reactor scales. Specifically, to obtain the simplified models, we use recently developed concept of internal mass transfer coefficient (that is more general and fundamental than the classical effectiveness factor concept) to approximate the local diffusion and reaction problem, while the reactor scale problem of flow and diffusion in the fluid phase is simplified by using She and the inter-phase concentration/ temperature gradient. In the second part of this work, we demonstrate application of the models by simulating the transient non-isothermal behavior of a catalytic monolith in real time for various cases and comparing the predictions with detailed solutions. For the case of fluid-solid catalytic reactors, it is shown that the models are generalizations of the classical two-phase models and can account for the multi-component diffusion-reaction problem without using the concept of effectiveness factor. We conclude that these new models are robust and accurate with practically acceptable error, speed up the computations by orders of magnitude, and can be used with confidence for the real time simulation and design of catalytic reactors.