This content is not included in your SAE MOBILUS subscription, or you are not logged in.
Investigation of Crystalline Powder Precipitates Observed in Engine Exhaust Emission Measurement Systems and NOx Exhaust Gas Analyzers
ISSN: 0148-7191, e-ISSN: 2688-3627
Published April 05, 2016 by SAE International in United States
Annotation ability available
The application of Selective Catalytic Reduction (SCR) to control nitric oxides (NOx) in diesel engines (2010, Tier 2, Bin5) introduced significant amounts of Ammonia (NH3) and Urea to the NOx exhaust gas analyzers and sampling systems. Under some test conditions, reactions in the sampling system precipitate a white powder, which can accumulate to block sample lines, rendering the exhaust emission sampling inoperable. NOx gas analyzers used for exhaust measurement are also susceptible to precipitation within the sample path and detector components. The contamination requires immediate maintenance for powder removal to restore baseline performance.
The results of experiments to eliminate the powder are presented. Analysis of the powder identifies it as ammonium nitrate (NH4NO3) and ammonium sulfate ((NH4)2SO4), which is consistent with the white crystalline precipitate. Techniques to eliminate or minimize the condensation of the ammonia salts are presented, including removing gaseous ammonia on a phosphoric acid (scrubbing) filter, and maintaining the NOx analyzer and sample lines at a temperature greater than the melting point of the ammonia salts. A review of the temperature dependent crystallization of ammonium nitrate provides an estimate of the condensation rate based on gas concentrations and temperatures.
CitationZummer, R., Nevius, T., and Porter, S., "Investigation of Crystalline Powder Precipitates Observed in Engine Exhaust Emission Measurement Systems and NOx Exhaust Gas Analyzers," SAE Technical Paper 2016-01-0990, 2016, https://doi.org/10.4271/2016-01-0990.
- Environmental Protection Agency Emission Standards Reference Guide http://www3.epa.gov/otaq/standards/light-duty/tier2stds.htm
- Nakatani , S. , Yoshimura , T. , Mori , Y. , Kihara , N. et al. Development of a Real-time NH3 Gas Analyzer Utilizing Chemi-luminescence Detection for Vehicle Emission Measurement SAE Technical Paper 2004-01-2907 2004 10.4271/2004-01-2907
- Tennison , P. , Lambert , C. , and Levin , M. NOx Control Development with Urea SCR on a Diesel Passenger Car SAE Technical Paper 2004-01-1291 2004 10.4271/2004-01-1291
- Lambert , C. , Hammerle , R. , McGill , R. , Khair , M. et al. Technical Advantages of Urea SCR for Light-Duty and Heavy-Duty Diesel Vehicle Applications SAE Technical Paper 2004-01-1292 2004 10.4271/2004-01-1292
- US Patent 4259302
- Suzuki H. et al. Evaluation of ammonia continuous measurement techniques for automobile exhaust gas JSAE 20045287
- Cavataio , G. , Girard , J. , Patterson , J. , Montreuil , C. et al. Laboratory Testing of Urea-SCR Formulations to Meet Tier 2 Bin 5 Emissions SAE Technical Paper 2007-01-1575 2007 10.4271/2007-01-1575
- The dissociation constant of ammonium nitrate and its dependence on temperature, relative humidity and particle size Mozurkewich Michael 10.1016/0960-1686(93)90356-4
- Properties of Ammonium Nitrate. III Bowen N. L. J. Phys. Chem. 1926 30 6 736 737 DOI: 10.1021/j150264a003
- Cotton , F.A. , and Wilkinson G.W. 1980 Advanced Inorganic Chemistry Wiley Interscience New York 342
- Falk , F. 1954 Stoichiometry and Kinetics of the Gas Phase Reaction of Nitrogen Dioxide and Ammonia J. Am. Chem. Soc. 76 4746 4747
- Mearns , A.M. , and Ofosu-Asiedu K. 1984 Kinetics of reaction of Low Concentration Mixtures of Oxides of Nitrogen, Ammonia, and Water J. Chem. Tech. Biotechnol. 34A 341 349
- Naser , A.J. 1983 Ammonium Nitrate HEPA Filter Loading Study Results, SD-WM-TRP-003 Rockwell Hanford Operations Richland, Washington