Impact of Selective Catalytic Reduction on Exhaust Particle Formation over Excess Ammonia Events

While the NH3 – SCR technology has become the dominant method for the abatement of NOx emitted by diesel trucks and passenger vehicles, the impact of urea injection on particle emissions has not yet been thoroughly studied. In this paper we examine a typical NH3 – SCR configuration operating under a simulated malfunctioning condition and we study its impact on both solid and total particle number and size distribution. The tests were conducted on a light-duty diesel engine operating at both low and high load points. Its aftertreatment consisted of a commercial Fe-Zeolite SCR catalyst in series with alternatively a catalytic and an uncoated diesel particle filter. Hydrocarbon post-injection was conducted in some tests to investigate the combined effect of ammonia injection during active DPF regeneration. On average the post-DPF solid >23nm and total <23nm particle number emissions were increased 129% (range 80-193%) and 67% (range 26-136%), respectively, with 100 ppm ammonia slip. This was explicitly related with the NH3 excess concentration, while the count median diameter of the particle distribution remained unaffected. Based on NH3 – SCR kinetics, the particles formed should consist of ammonium sulfates or nitrates. No interaction with the unburned HCs emitted during active DPF regeneration in terms of particle formation was observed.

AMANATIDIS Stavros;  NTZIACHRISTOS Leonidas;  GIECHASKIEL Barouch;  BERGMANN Alexander;  SAMARAS Zissis; 

2014-11-13

AMER CHEMICAL SOC

JRC89136

0013-936X,   

http://pubs.acs.org/doi/pdf/10.1021/es502895v,    https://publications.jrc.ec.europa.eu/repository/handle/JRC89136,   

10.1021/es502895v,