Diesel exhaust | EPFL Graph Search

Diesel exhaust is the gaseous exhaust produced by a diesel type of internal combustion engine, plus any contained particulates. Its composition may vary with the fuel type or rate of consumption, or speed of engine operation (e.g., idling or at speed or under load), and whether the engine is in an on-road vehicle, farm vehicle, locomotive, marine vessel, or stationary generator or other application. Diesel exhaust is a Group 1 carcinogen, which causes lung cancer and has a positive association with bladder cancer. It contains several substances that are also listed individually as human carcinogens by the IARC. Methods exist to reduce nitrogen oxides (NOx) and particulate matter (PM) in the exhaust. So, while diesel fuel contains slightly more carbon (2.68 kg CO₂/litre) than petrol (2.31 kg CO₂/litre), overall CO₂ emissions of a diesel car tend to be lower due to higher efficiency. In use, on average, this equates to around 200 g CO₂/km for petrol and 120 g CO₂/km for di

CFD Simulations Of Pollution Control Systems: DPF and SCR

Peter Loveday

New EU and US emissions regulations require the development of advanced after- treatment systems for non-road diesel engine exhausts. To help develop these at Liebherr Machines Bulle, the use of CFD has been adopted. The pro ject used two main models: one for the dosing of fuel for the regeneration of the Diesel Particulate Filter (HC Doser model) and one for the Selective Cataylitic Reduction system (SCR model). The HC Doser model was validated against published data and in-house experimental results. Good agreement was found in all cases. The SCR model was validated against published data only, showing good qualitative agreement -spatial distribution and spray formation- but the quantitative measures - N H3 and H N N C O concentrations- still need further adjustment. Validation against in-house experimental results was not possible as the necessary experiments have not yet been carried out. After validation, the DPF model was used to evaluate and improve specfic exhaust geometry configurations at LMB. Selected case studies are presented to show the appli- cability of the models to the design process, and the derived advantages. Using the DPF model, basic research was undertaken to investigate the ifluence of the static mixer's geometry on the performance of the system during regeneration. A new mixer geometry was designed which reduced the pressure drop and increased the uniformity of the HC distribution

2011

Polymer spiral film gas-liquid heat exchanger for waste heat recovery in exhaust gases

Antoine Breton

In this master thesis report the development of an innovative spiral heat exchanger based on polymer materials is described. Building prototypes, erection of a test bench and firsts tests of the heat exchanger are presented. The heat exchanger prototype survived all tests especially several days in contact with aggressive gases. A facility integrating a Diesel exhaust gases production has been developed to test this heat exchanger design. Performance results obtained during the tests are analysed. Measurement acquisition software developed with Labview was also used. Challenges have been overcome to run the facility in stable conditions in order to obtain reliable measurement. Heat load recovery achieved with the presented heat exchanger is in the range of 1.5 kW thermic but potential heat recovery about 3.5kW might be achievable. Overall heat transfer coefficient is improved compared to other polymer based heat exchanger design. Pressure drop on gas channel is in the range of several mbar and must be further improved and fouling must be minimized. Such a design based on polymer film technology provides better corrosion and chemical resistance compared to conventional metal heat exchangers. Due to the smooth surface of polymer film fouling is reduced. Series production and usage of such heat exchangers would allow operating low temperature waste heat recovery in gases at affordable costs. One promising application is heat recovery in soiled gases in combination with ORC power generation.

2012

Advances in Vanadium-Based Catalyst Research for the Selective Catalytic Reduction of NOx by NH₃

Adrian Marberger

The most efficient after-treatment technology for reducing harmful NOx emissions from stationary and mobile sources of diesel exhaust is the selective catalytic reduction (SCR) of NOx with ammonia (NH3). Vanadium-based SCR catalysts reduce NOx selectively between ca. 200 and 500°C. Low temperature activity and high temperature stability are important for the automotive sector because of the large temperature fluctuations in the exhaust gas. Additionally, SCR catalysts need to be resistant to water vapor, sulfur and potentially poi-soning elements. To date, V-based SCR catalysts of type V2O5/WO3/TiO2 (VWT) are the most widespread systems because of their activity over a broad temperature range, high sulfur tolerance and moderate production cost. Draw-backs are the moderate hydrothermal stability, poor low temperature activity and potential vanadium volatility which are the main research topics for V-based SCR catalysts. Exposure to different aging procedures of a V-loading optimized VWT catalyst (2 wt% V2O5) revealed that a hydrothermal environment affects the aging much more severely compared to a dry environment. Before deactivation, VWT catalysts have the capability to activate, which was correlated to changes in V and W surface coverage, the increased fraction of Lewis acid sites and SCR active vanadyl sites. The VWT catalyst with optimized V-loading was further investigated by means of transient experimentation, which revealed important insights into the mechanism of the SCR reaction: The active site was assigned to mono-oxo V5+ Lewis acid species, which were reduced only in presence of both NO and NH3. The formation of the nitrosamide intermediate, which is formed simultaneously to V5+ reduction, was also verified. The addition of 2 - 4 wt% SiO2 during the VWT catalyst synthesis increased the stability up to 650°C because it prevented anatase TiO2 particles from sin-tering by inhibiting their inter-particle contact. Using a SiO2 stabilized TiO2 support material, the potential of FeVO4 as a source of active redox centers was explored as a novel class of hydrothermally stable SCR catalyst. A loading of 4.5 wt% FeVO4 was found to be the optimum trade-off between stability and activity. Remarkable catalyst activation was observed after calcination at 600°C, which was correlated to the decomposition of FeVO4. Similar to FeVO4, it was shown that the catalytic activity of supported CeVO4, AlVO4 and ErVO4 is closely correlated to their degree of decomposition. The decomposition of metal vanadates generates dispersed VOx domains, which resemble those of VWT catalysts. This thesis demonstrates that research on V-based SCR catalysts is still crucial because their modification and optimization can result in enhanced perfor-mance and temperature stability. Metal vanadates can be envisaged as a reser-voir for active V-species as they decompose once supported on TiO2. Transient experimentation allowed in-depth mechanistic studies on V-based catalysts. This encourages further exploration of SCR catalysts in order to improve the fundamental knowledge of such systems that will assist the discovery of highly active and stable catalysts for the abatement of NOx.

EPFL2017

Advances in Vanadium-Based Catalyst Research for the Selective Catalytic Reduction of NOx by NH₃

Adrian Marberger

EPFL2017