Coupling cellular substrates and radial flow reactors for enhanced exhaust abatement in automotive DeNOx-SCR

Abstract

Cellular materials, such as open-cell foams and POCS, are envisioned as alternative structured substrates to the standard honeycomb monoliths for improving automotive DeNOx-SCR abatement efficiency thanks to their superior gas-to-solid mass transfer properties. The innovative substrates are numerically assessed through Computational Fluid Dynamics simulations to parametrically investigate their performances in terms of pressure drop and abatement efficiency in full-scale geometries as a function of cell size and operating conditions. Cellular substrates (open-cell foams and 3D printed POCS) are tested first as a direct replacement of the monolith preserving the catalyst loading and the standard device geometry. An increment in NO conversion is observed due to the enhanced gas–solid transfer. However, a concomitant unacceptable increase in the pressure drop across the device is apparent in all the conditions for both commercial foams and POCS. To avoid this issue, a radial flow configuration of the reactor is hereby proposed for the first time for mobile ATS systems to reduce the pressure drop. Such a configuration is only possible for cellular substrates, since they are characterized by isotropic permeability. The simulations revealed that the new reactor loaded with cellular materials is a compelling solution granting comparable or lower pressure drops than honeycomb monoliths with a concomitant improvement of the abatement efficiency. The best reactor configuration offered up to a 5% conversion increase and up to a 5-fold pressure drops reduction compared to the state-of-the-art. Even so, better performances than the honeycomb were found for other reactor configurations, allowing for a flexible choice of the final design.