Design and Durability of Vanadium-SCR Catalyst Systems in Mobile Off-Road Applications Ecocat Oy

Format:

Conference/Event

Author/Creator:

Maunula, Maunula, author.

Contributor:

Iivonen, Markus

Kinnunen, Toni

Conference Name:

SAE 2011 World Congress & Exhibition (2011-04-12 : Detroit, Michigan, United States)

Language:

English

Physical Description:

1 online resource

Place of Publication:

Warrendale, PA SAE International 2011

Summary:

The emission regulations for mobile off-road applications arefollowing on-road trends by a short delay. The latest Stage 3B and4 emission limits mean a gradual implementation of oxidation andSCR catalysts as well as particulate filters with off-roadmachines/vehicles in the 2010s. The driving conditions and testcycles differ from on-road truck applications which have been thefirst design base for off-road aftertreatment technologies.Aftertreatment systems for Stage 4 were first analyzed and theywill include oxidation catalysts, a NOx reductioncatalyst (SCR or LNT), a particulate filter and possibly units forurea hydrolysis and ammonia slip removal. The design and durabilityof V₂O₅/TiO₂-WO₃ catalysts based on metallic substrates wereinvestigated by engine bench and field experiments. NOxemissions were measured with 6.6 and 8.4 liters engines designedfor agricultural and industrial machinery. The criteriaNOx conversions with NH₃ slip below 20 ppm and variedcatalyst volumes were used as a design base for dosing strategiesover the lifetime of the system. The target NOxconversion over ISO 8178 cycle was about 50% for Stage 3A withfirst SCR engines and will be 80-95% for Stage 4, which highconversion target has a crucial effect on the required catalystamount and dosing strategy margins, particularly after ageing.NOx conversions were stable in the designed urea dosingvalues after engine bench ageing for 3000 hours and field ageingfor 8000 hours. Durability and reaction studies were applied to theSCR catalyst design for Stage 3B and 4.In thermogravimetric and mass spectrometric (TGA-MS) analysis,no vanadium evaporation was detected below 1000°C but near to themelting point (690°C) of V₂O₅, the catalytic activity ofvanadium-SCR catalyst was dropped due to sintering of active sites.The commercial vanadium-SCR systems were designed to the maximumtemperatures of 600C. The characterization of 3000 and 8000 hoursaged catalysts revealed the axial accumulation of elements (P, Zn,Ca, Na, K, S, Si, Fe) originating from lubrication oil and fuel.However, only the short front part of the catalyst had a higherconcentration of deactivating compounds correlating to a decreasedNOx performance by laboratory experiments. Thislong-term deactivation has also been included into the SCR catalystdesign for off-road applications by the target NOxconversions

Notes:

Vendor supplied data

Publisher Number:

2011-01-1316

Access Restriction:

Restricted for use by site license