Abstract
The most common NOx reduction technologies for diesel engine are urea selective catalytic reduction(Urea-SCR) and lean NOx trap(LNT) catalysts. Each technology has some advantages and disadvantages. There is another selective catalytic reduction that uses hydrocarbon(HC-SCR), specifically diesel fuel as reductants to reduce NOx emission. This work aims to discuss the possible implication of biodiesel blend fuels as reductants for NOx on the HC-SCR of heavy-duty diesel engine. The engine was fuelled with Ultra Low Sulfur Diesel(ULSD). And ULSD and blend fuels(volumetric 10% and 25% biodiesel) were used for secondary injection fuel as reductant. Reductants were injected upstream on HC-SCR. Diesel Oxidation Catalyst(DOC) for oxidizing slipped HC from a NOx reduction catalyst was equipped downstream with HC-SCR in a row. The exhaust gas temperature of upstream HC-SCR was maintained at 290℃, 320℃ and 350℃ and space velocity was kept at 23k(1/h) and 43k(1/h) during each test conditions.
This study showed that in general conversion efficiency of NOx on HC SCR decreased with increasing biodiesel contents in conventional diesel fuel. Also it was observed that the activity of a NOx catalyst was remarkably influenced at lower temperature for higher biodiesel contents, which was susceptible at high space velocity at 43k. Overall, biodiesel contents affect more NOx conversion in case of the low exhaust temperature and the high space velocity. If this HC SCR method was applied to heavy duty diesel engine and biodiesel content in diesel fuel would increase, it will not be to meet NOx emission regulations by WHTC and ETC mode which are low at average exhaust temperatures.
KEYWORDS – Selective Catalytic Reduction, Reductant, Biodiesel, Nitrogen oxides, Space Velocity