1. The Reduction of Pollutants from
Diesel Engines
By Sean McSweeney

2. How A Diesel Engine Works
• Air is taken in and compressed by the piston.
• As the pressure of the air rises, so does the
temperature.
• When the temperature is over 200 C, fuel is
injected.
• The fuel is ignited by the hot air, and the energy
released pushes the piston.
• Exhaust is released, containg NOx and
particulate matter.

3. Diesel Engines vs. Petrol Engines
• Diesel engines are more efficient than petrol
engines
– It will give more torque at lower speeds
– It energy content is 38.6 MJ/L
– Lower auto ignition temperature
However, diesel engines produce higher levels of
particulate matter.

4. Major Pollutants
• Soluble Organic Fraction (SOF)
• Particulate Matter (PM)
• NOx

5. Diesel Oxidation Catalysts
• Honeycomb Monolith Structure
• Oxidation of CO, HC, SOF to less hazardous
components
• Coated with precious metals to help reduce
posionous emissions

6. Diesel Particulate Filter (DPF)

7. Regenerating the DPF
• Catalysed DPFs
Catalysing Washcoat on filter
• Fuel-Borne Catalysts
• Hydrogen Trap
• Hydrocarbon Dosing

8. Hydrogen trap
• Traps HC’s at lower temperatures
• Zeolites adsorb HC’s
Fuel Borne Catalyst
Advantages-
• Reduces combustion temperature
• Regeneration is faster and more complete
• FBC’s are more tolerant to high levels of fuel sulphur
• Regeneration is independent of engine NOx/PM ratios
• Do not produce additional NO2 emissions

9. Fuel – Borne Catalysts

10. Hydrocarbon Dosing

11. Reduction of NOx
Primary Methods
Delayed Injection, Miller Cycle
Secondary Methods
Exhaust Gas Recirculation (EGR)
Nitrogen Enriched Air (NEA)
Selective Catalytic Reuction (SCR)
Lean NOx Traps (LNT)

12. Exhaust Gas Recirculation
• Lowers temperature of
fuel ignition
• Up to 50% NOx
reduction
• NOx – PM trade off

13. Nitrogen-Enriched Air
• Some oxygen stripped
from air.
• NOx reduction of up to
50%
• Less adverse effects
than EGR

14. Selective Catalytic Reduction
• Ammonia used to convert NOx to N2 and water
• Usually using a V2O5 / TiO2 catalyst
• Can achieve an 80-90% reduction of NOx
• Problems with unburnt fuel, NH3 slippage

15. Selective Catalytic Reduction

16. Lean NOx Trap
• NO converted to NO2 using Pt oxidation
catalyst
• Alkaline metal oxide in washcoat of catalyst
traps NO2
• NO2 reduced by rhodium catalyst to N2
• Can reduce 60-70% NOx
• Problem with sulphur poisoning

17. Comparison of fossil fuel versus
biodiesel

18. References
• Lamas, M.I. and Rodriguez, C.G.
(2012) ‘Emissions from Marine Engines and NOx
Reduction Methods’, Journal of Maritime Research,
IX (1), 77-82
• Heck, R., Farrauto, R.J., Gulati, S. T. (2009)
Catalytic Air Pollution Control: Commercial
Technology, 3rd ed., USA: Wiley
• http://dieselnet.com/tech/dpf_cat.php
• Biodiesel: A realistic fuel alternative for diesel
engines. Ayhan Demirbas. 2008