Effect of Hydrocarbon Additives on SNCR DeNOx Characteristics under Oxidizing Diesel Exhaust Gas Conditions

  • Nam, Changmo (Division of Health and Science, Yeungnam University College)
  • Received : 2018.05.28
  • Accepted : 2018.07.06
  • Published : 2018.10.31


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 $NH_3$ and $C_2H_6/diesel$ 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 (${\beta}=NH_3/NOx$) 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 $C_2H_6/diesel$ fuel additives. About 50~68% NOx reduction was possible with the above molar ratios (${\beta}$) at the optimum flow #1 ($T_{in}=1260K$). Injecting a small amount of $C_2H_6$ or diesel fuel (${\gamma}=hydrocarbon/NOx$) gave the promising results, particularly in the lower exhaust temperatures, by contributing to the sufficient production of active radicals ($OH/O/HO_2/H$) for NOx reduction. Unfortunately, the addition of hydrocarbons increased the concentrations of byproducts such as CO, UHC, $N_2O$ and $NO_2$, 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.


Supported by : Yeungnam University College


  1. An, H., Yang, W., Li, J., Zhou, D., 2015, Modeling analysis of urea direct injection on the NOx emission reduction of biodiesel fueled diesel engines, Ener. Conv. Manage., 101, 442-449.
  2. Anderson, J. A., Marquez-Alvarez, C., Lopez-Munoz, M. J., Guerrero-Ruiz, A., 1997, Reduction of NOx in $C_3H_6$/air mixtures over Cu/$Al_2O_3$ catalysts, Appl. Catal. B, 14, 189-202.
  3. Lyon, R. K., 1987, Thermal DeNOx controlling nitrogen oxides emissions by a noncatalytic process, Environ. Sci. Tech., 21(3), 231-236.
  4. Miller, J. A., Bowman, C. T., 1989, Mechanism and modeling of nitrogen chemistry in combustion, Prog. Ener. Combust. Sci., 15, 287-338.
  5. Capener, L., 2008, Advanced overfire air/SNCR and sorbent injection system, Power Eng., 112, 192-198.
  6. Duo, W., Dam-Johansen, K., Ostergaard, K., 1990, Widening the temperature range of the Thermal DeNOx process; an experimental investigation, Proc. Combust. Inst., 23, 297-303.
  7. Glarborg, P., Dam-Johansen, K., Miller, J. A., Kee, R. J., Coltrin, M. E., 1994, Modeling the Thermal DeNOx process in flow reactors, Inter. J. Chem. Kinet., 26, 421-4213.
  8. Heimrich, M. J., Deviney, M. L., 1993, Lean NOx catalysts evaluation and characterization, SAE paper 930736.
  9. Jodal, M., Neilsen, C., Hulgaard, T., Ostergaard, K., 1990, Pilot-scale experiments with $NH_3$ and urea as reductants in SNCR of NO, Proc. Combust. Inst., 23, 237-243.
  10. Miyamoto, N., Ogawa, H., Wang, J., Shudo, T., Yamazaki, K., 1995, Diesel NOx reduction with ammonium deoxidizing agents directly injected into the cylinder, Int. J. Vehi. Desi., 16(1), 71-79.
  11. Nakatsuji, T., Yamaguchi, T., Sato, N., Ohno, H., 2008, A selective NOx reduction on Rh-based catalysts in lean conditions using CO as a main reductant, Appl. Catal. B, 85, 61-70.
  12. Nam, C. M., Gibbs, B. M., 2002, Application of the Thermal DeNOx process to diesel engine DeNOx: an experimental and kinetic modeling study, FUEL, 81, 1359-1367.
  13. Nam, C. M., Gibbs, B. M., 2012, SNCR application to diesel engine DeNOx under combustion-driven flow reactor conditions, J. Environ. Sci., 21(7), 769-778.
  14. Niu, S., Han, K., Lu, C., 2010, Experimental study on the effect of urea and additive injection for controlling NOx emissions, Environ. Eng. Sci., 27, 47-53.
  15. Ostberg, M., Dam-Johansen, K., 1994, Empirical modeling of the SNCR of NO: comparison with large-scale experiments and detailed kinetic modeling, Chem. Eng. Sci., 49(12), 1897-1904.
  16. Palash, S., Masjuki, H., Kalam, M., Masum, B., Sanjid, A., Abedin, M., 2013, State of the art of NOx mitigation technologies and their effects on the performance and emission characteristics of biodiesel-fueled compression ignition engines, Ener. Conv. Manage., 76, 400-420.
  17. Quang Dao, D., Gasnot, L., Marschallek, K., Bakali, A., Pauwels, J. F., 2009, Experimental study of NO removal by gas reburning and selective noncatalytic reduction using ammonia in a lab-scale reactor, Ener. Fuels, 24, 1696-1703.
  18. Raj, A., Zainuddin, Z., Sander, M., Kraft, M., 2011, A mechanistic study on the simultaneous elimination of soot and NO from engine exhaust, Carbon, 49, 1516-1531.
  19. Srivastava, R. K., Hall, R. E., Khan, S., Culligan, K., Lani, B. W., 2005, NOx emission control options for coal-fired electric utility boilers, J. Air & Waste Manage. Assoc., 55, 1367-1388.
  20. Stohr, M., Schutz, M., Kruger, H., 1997, Status of and experience with NOx reduction in coal-fired power plants, Proc. Inst. Mech. Eng., 211, 27-41.
  21. Toops, T., Nguyen, K., Foster, A., Bunting, B., Ottinger, N., Pihl, J., Hagaman, E., Jiao, J., 2010, Deactivation of accelerated engine-aged and field-aged Fe-zeolite SCR catalysts, Catal. Today, 151, 257-265.
  22. U.S. Environmental Protection Agency (EPA), 2018,
  23. Vedharaj, S., Vallinayagam, R., Yang, W., Saravanan, C., Chou, S., Chua, K., Lee, P., 2014, Reduction of harmful emissions from a diesel engine fueled by kapok methyl ester using combined coating and SNCR technology, Ener. Conv. Manage., 79, 581-589.
  24. Weijuan, Y., Zhijun, Z., Junhu, Z., Hongkun, L., Jianzhong, L., Kefa, C., 2009, Application of hybrid coal reburning/SNCR processes for NOx reduction in a coal-fired boiler, Environ. Eng. Sci., 26, 311-318.
  25. Xu, B., Tian, H., Yang, J., Sun, D., Cai, S., 2011, A system of selective non catalytic reduction of NOx for diesel engine, Adv. Mater. Res., Vols. 201-203, 643-646.
  26. Yang, S., Wang, C., Li, J., Ma, L., Chang, H., 2011, Low temperature selective catalytic reduction of NO with $NH_3$ over Mn-Fe spinel: performance, mechanism and kinetic study, Appl. Catal. B, 110, 71-80.
  27. Yao, T., Duan, Y., Yang, Z., Li, Y., Wang, L., Zhu, C., Zhou, Q., Xhang, J., She, M., Lie, M., 2017, Experimental characterization of enhanced SNCR process with carbonaceous gas additives, Chemosphere, 177, 149-156.