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Modelling of catalytic aftertreatment of NOx emissions using hydrocarbon as a reductant

Sawatmongkhon, Boonlue (2012)
Ph.D. thesis, University of Birmingham.

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Abstract

Hydrocarbon selective catalytic reduction (HC-SCR) is emerging as one of the most practical methods for the removal of nitrogen oxides (NOx) from light-duty-diesel engine exhaust gas. In order to further promote the chemical reactions of NOx-SCR by hydrocarbons, an understanding of the HC-SCR process at the molecular level is necessary. In the present work, a novel surface-reaction mechanism for HC-SCR is set up with emphasis on microkinetic analysis aiming to investigate the chemical behaviour during the process at a molecular level via detailed elementary reaction steps. Propane (C3H8) is chosen as the reductant of HC-SCR. The simulation is designed for a single channel of a monolith, typical for automotive catalytic converters, coated with a silver alumina catalyst (Ag/Al2O3). The complicated physical and chemical details occurring in the catalytic converter are investigated by using the numerical method of computational fluid dynamics (CFD) coupled with the mechanism. The C3H8-SCR reaction mechanism consists of 94 elementary reactions, 24 gas-phase species and 24 adsorbed surface species. The mechanism is optimised by tuning some important reaction parameters against some measurable data from experiments. The optimised mechanism then is validated with another set of experimental data. The numerical simulation shows good agreements between the modelling and the experimental data. Finally, the numerical modelling also provides information that is difficult to measure for example, gas-phase concentration distribution, temperature profiles, wall temperatures and the occupation of adsorbed species on catalyst surface. Consequently, computational modelling can be used as an effective tool to design and/or optimise the catalytic exhaust aftertreatment system.

Type of Work:Ph.D. thesis.
Supervisor(s):Tsolakis, Athanasios and Wyszynski, Miroslaw L.
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Mechanical Engineering
Keywords:HC-SCR, Ag/Al2O3, Emissions, Modelling
Subjects:GE Environmental Sciences
QA76 Computer software
QD Chemistry
TD Environmental technology. Sanitary engineering
TP Chemical technology
Institution:University of Birmingham
ID Code:3138
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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