CLEERS Teleconference: Petr Kočí

Title: Multi-scale modeling of catalytic filters

Petr Kočí, Martin Isoz, Marie Plachá, Marek Václavík, Martin Leskovjan

University of Chemistry and Technology, Prague, Czech Republic

http://www.vscht.cz/monolith

Abstract:

Increasingly stringent legislation for particulate matter emissions in automotive applications requires the use of particulate filters not only for Diesel cars (DPF) but in Europe newly also for cars with gasoline engines (GPF). Current trend is the integration of catalytic coating for abatement of gaseous pollutants into the filter, making the system more compact. Typical examples are DOC or SCR coating on DPF (CDPF or SCRF, respectively) and TWC coating on GPF (4-way catalyst). Distribution of the catalytic coating in/ on the porous filter wall affects the catalytic activity, soot trapping efficiency and pressure drop.

In this talk, a methodology for pore-scale modeling of flow, diffusion and reaction combined with soot particles filtration will be presented. The models work with 3D-reconstruction of porous filter wall obtained from X-ray tomography (XRT) scans, describing pore morphology as well as detailed spatial distribution of solid phases (substrate and coating). The XRT images are transformed into simulation mesh suitable for computations in OpenFOAM simulation environment. Processes in the filter wall are decoupled and solved by in-house developed models: (i) gas flow through filter wall, (ii) gas component convection, diffusion and reaction in the coated zones, and (iii) soot particle transport and filtration, including Brownian motion.

Spatially averaged permeability and filtration efficiency predicted from the micro-scale simulations are then employed in a full-scale model of filter channels, which enables prediction of the overall pressure drop and performance of the entire device, depending on its geometry as well as microstructure. The simulation results are compared to measurements with several filter samples possessing different in/on-wall distribution of the catalytic coating.

References 

Kočí P., Isoz M., Plachá M., Arvajová A., Václavík M., Svoboda M., Price E., Novák V., Thompsett D. 3D reconstruction and pore-scale modeling of coated catalytic filters for automotive exhaust gas aftertreatment. Catalysis Today (2018) in press, http://dx.doi.org/10.1016/j.cattod.2017.12.025

Václavík M., Plachá M., Kočí P., Svoboda M., Hotchkiss T., Novák V., Thompsett D. Structure characterisation of catalytic particulate filters for automotive exhaust gas aftertreatment. Materials Characterization 134 (2017), 311-318. http://dx.doi.org/10.1016/j.matchar.2017.11.011

Schejbal M., Štěpánek J., Marek M., Kočí P., Kubíček M. Modelling of soot oxidation by NO2 in various types of Diesel particulate filters, Fuel 89 (2010), 2365-2375. http://dx.doi.org/10.1016/j.fuel.2010.04.018