DeNOx experiments for the effects of hydrocarbon additives on diesel SNCR process were conducted under oxidizing diesel exhaust conditions. A diesel-fueled combustion system was set up to simulate the actual cylinder and head, exhaust pipe and combustion products, where the reducing agent NH3 and C2H6/diesel fuel additives were separately or simultaneously injected into the exhaust pipe, used as the SNCR flow reactor. A wide range of air/fuel ratios (A/F=20~40) were maintained, based on engine speeds where an initial NOx level was 530 ppm and the molar ratios (β=NH3/NOx) ranged between 1.0~2.0, together with adjusting the amounts of hydrocarbon additives. Temperature windows were normally formed in the range of 1200~1350K, which were shifted downwards by 50~100K with injecting C2H6/diesel fuel additives. About 50~68% NOx reduction was possible with the above molar ratios (β) at the optimum flow #1 (Tin=1260K). Injecting a small amount of C2H6 or diesel fuel (γ=hydrocarbon/NOx) gave the promising results, particularly in the lower exhaust temperatures, by contributing to the sufficient production of active radicals (OH/O/HO2/H) for NOx reduction. Unfortunately, the addition of hydrocarbons increased the concentrations of byproducts such as CO, UHC, N2O and NO2, and their emission levels are discussed. Among them, Injecting diesel fuel together with the primary reductant seems to be more encouraging for practical reason and could be suggested as an alternative SNCR DeNOx strategy under diesel exhaust systems, following further optimization of chemicals used for lower emission levels of byproducts.

Abstract
 1. Introduction
 2. Experimental
 3. Results and Discussion
  3.1. DeNOx characteristics without additive
  3.2. C2H6 additive
  3.3. Diesel fuel additive
  3.4. Emission Levels of CO, N2O and NO2
 4. Conclusions
 REFERENCES

• Changmo Nam(Division of Health and Science, Yeungnam University College) Corresponding author