The Impact of Heat and Mass Dispersion and Thermal Effects on the Scale-up of Monolith Reactors Used in Catalytic After-treatment

Tian  Gu, University of Houston

Monolith reactors are used in many catalytic after-treatment systems (e.g. TWC, DOC, LNT and SCR). These systems are often studied in laboratory experiments using monolith samples of the same cell density, washcoat thickness and catalyst loading but of a smaller length compared to the full scale systems. The flow rate in the laboratory scale operation is selected so that the same space velocity is maintained as in the full scale system. However, matching space velocity between laboratory scale and full scale reactor leads to similar performance only under ideal conditions such as isothermal operation and negligible heat and mass dispersion (i.e. plug flow conditions). In this paper, it is shown that when thermal effects are significant (or adiabatic temperature rise is large) and heat and mass transfer and dispersion effects are not negligible, the similarity does not exist and the ignition/extinction behavior of the two systems can be qualitatively different. Further, when lab scale data is used for kinetic parameter estimation, failure to consider these effects in the reactor model can lead to false kinetic parameters and inaccurate prediction of reactor performances. We present both simulations and analytical results quantifying the impact of these effects on the scale-up of monolith reactors.

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