Improvement of De-NOx Performance of a SCR System by Dual-Point Ammonia Injection in a Diesel Engine

Selective catalytic reduction (SCR) catalysts is used widely to reduce NOx emissions from diesel engines. However, improvements in de-NOx performance are required to meet future standards of near-zero NOx emissions. This study examines the effectiveness of dual-point NH₃ injection technology, in which gaseous NH₃ is injected into both closed coupled and under floor SCR catalysts. The NOx removal efficiency of dual-point NH₃ injection is compared with that of single-point injection in a World Harmonized Transient Cycle test. The results show that dual-point injection of NH₃ gas can effectively reduce NOx emissions from diesel engines due to superior temporal and spatial distribution of NH₃ gas in an SCR catalyst.