Evaluation of exhaust after-treatment device effectiveness in reducing regulated and unregulated emissions from natural gas fueled heavy duty transit bus

Evaluation of Exhaust After-Treatment Device Effectiveness in Reducing Regulated and Unregulated Emissions from Natural Gas Fueled Heavy Duty Transit Bus Arvind Thiruvengadam Padmavathy The promulgation of the public transit fleet rule by the California Air Resources Board (CARB) in 2000, has given transit fleet operators the option of choosing the alternative fuel path in order to reduce their fleet average NOx and PM emissions. Natural gas being an abundant domestic fuel, has found its way as an economically and technologically feasible alternative fuel option. Many studies have shown the clean burning nature of natural gas with lower NOx and near zero Particulate Matter (PM) emissions from heavy duty natural gas vehicles. Though natural gas fueled vehicles emit lower NOx and PM than their diesel counterparts, the emissions of carbon monoxide (CO) and total hydrocarbons (THC) are higher. This necessitates the use of a suitable exhaust after-treatment device to attain complete emission benefits. The objective of the study was to measure regulated and unregulated emissions from CNG fueled heavy-duty transit bus with and without the after-treatment device present. The study conducted in Riverside, California utilized two CNG fueled transit buses one from Riverside Transit Authority (RTA) and the other from Los Angeles County Metro Transit Authority (LACMTA). The study required the complete chemical speciation of exhaust from the RTA bus with and without the after-treatment device so as to evaluate the effectiveness of the after-treatment device in reducing both regulated and unregulated emissions. The buses were retrofitted with an oxidation catalytic converter manufactured by Engine Control Systems (ECS). The buses were tested on a heavy duty chassis dynamometer part of the West Virginia University Transportable Heavy Duty Vehicle Emissions Testing Laboratory (WVTHDVETL). The transit buses were exercised over a double length Orange County Transit Authority (OCTA) cycle to characterize its emission levels. The analysis of the unregulated sample, which included Poly Aromatic Hydrocarbons (PAH), aldehydes, Volatile Organic Compounds (VOC), metals and elemental/organic carbon was done by Desert Research Institute (DRI). The results of the regulated emissions showed a 99% reduction in CO and 62% reduction in THC with the after-treatment device present. The unregulated speciation results showed 96% reduction in carbonyl compounds with formaldehyde being the major contributor, 46% reduction in PAH compounds, 60% reduction in nitro-PAH compounds and 93% reduction in VOC. There was an overall 27% increase in metal content in exhaust with the after-treatment device present. There was no effect on the organic carbon concentration with the after-treatment device present.

[1]  Kevin Barraclough,et al.  I and i , 2001, BMJ : British Medical Journal.

[2]  UNDERSTANDING THE HEALTH EFFECTS OF COMPONENTS OF THE PARTICULATE MATTER MIX : PROGRESS AND NEXT STEPS , 2002 .

[3]  Nigel N. Clark,et al.  Speciation of Organic Compounds from the Exhaust of Trucks and Buses: Effect of Fuel and After-Treatment on Vehicle Emission Profiles , 2002 .

[4]  Nigel N. Clark,et al.  Energy consumption analysis of heavy-duty vehicles for transient emissions evaluation on chassis dynamometer , 1999 .

[5]  David B. Kittelson,et al.  Exhaust particulate emissions from two port fuel injected spark ignition engines , 1999 .

[6]  Paul Zelenka,et al.  Reduction of Diesel Exhaust Emissions by Using Oxidation Catalysts , 1990 .

[7]  David B. Kittelson,et al.  Diesel Aerosol Sampling in the Atmosphere , 2000 .

[8]  I. Glassman.  Soot formation in combustion processes , 1989 .

[9]  Kimmo Erkkilae,et al.  TRANSIT BUS EMISSION STUDY: COMPARISON OF EMISSIONS FROM DIESEL AND NATURAL GAS BUSES , 2004 .

[10]  Kent Nord,et al.  Particles and unregulated emissions from CI engines subjected to emission control , 2005 .

[11]  John B. Heywood,et al.  Internal combustion engine fundamentals , 1988 .

[12]  Robert W. Dibble,et al.  Quantifying the contribution of lubrication oil carbon to particulate emissions from a diesel engine , 2003 .

[13]  David Kittelson,et al.  Formation of Nanoparticles during Exhaust Dilution , 1999 .

[14]  H. Burtscher.  Tailpipe Particulate Emission Measurement for Diesel Engines , 2001 .

[15]  Peter Eastwood,et al.  Critical topics in exhaust gas aftertreatment , 2000 .

[16]  Peter Wiesen,et al.  Smog chamber studies on the influence of diesel exhaust on photosmog formation , 2002 .

[17]  Patrick Burk,et al.  Cold Start Hydrocarbon Emissions Control , 1995 .

[18]  Byung-Chul Choi,et al.  Unburned fuel and formaldehyde purification characteristics of catalytic converters for natural gas fueled automotive engine , 1991 .

[19]  Lawrence R. Smith,et al.  Comparison of Exhaust Emissions, Including Toxic Air Contaminants, from School Buses in Compressed Natural Gas, Low Emitting Diesel, and Conventional Diesel Engine Configurations , 2003 .

[20]  Hannu Vesala,et al.  Comparison of Different Dilution Methods for Measuring Diesel Particle Emissions , 2004 .

[21]  John H. Johnson,et al.  The Effect of Fuel and Engine Design on Diesel Exhaust Particle Size Distributions , 1996 .

[22]  Martin Mohr,et al.  TEM analysis of volatile nanoparticles from particle trap equipped diesel and direct-injection spark-ignition vehicles , 2004 .

[23]  J. Raub,et al.  Health effects of exposure to ambient carbon monoxide , 1999 .

[24]  S. M. Shahed,et al.  The Effect of Mixing Rate, End of Injection, and Sac Volume on Hydrocarbon Emissions from a D.I. Diesel Engine , 1983 .

[25]  Frank R. Hartley,et al.  Chemistry of the platinum group metals : recent developments , 1991 .

[26]  Alan Brown,et al.  EFFECTS OF LUBRICATION SYSTEM PARAMETERS ON DIESEL PARTICULATE EMISSION CHARACTERISTICS , 1996 .

[27]  Thomas Kreuzer,et al.  Catalyst Development for Stoichiometric and Lean Bum Natural Gas Engines , 1994 .

[28]  Marko Tainio,et al.  Health Effects Caused by Primary Fine Particulate Matter (PM2.5) Emitted from Buses in the Helsinki Metropolitan Area, Finland , 2005, Risk analysis : an official publication of the Society for Risk Analysis.

[29]  Timothy S. Burlingame.  Reduction of natural gas engine emissions using a novel aftertreatment system , 2004 .

[30]  Hiroshi Matsuzaki,et al.  Oxygen Sensor for CNG Application as ULEV or Tighter Emission Vehicle , 1998 .

[31]  Wen-Yinn Lin,et al.  Characteristics of metals in nano/ultrafine/fine/coarse particles collected beside a heavily trafficked road. , 2005, Environmental science & technology.

[32]  Alberto Ayala,et al.  Diesel and CNG Heavy-duty Transit Bus Emissions over Multiple Driving Schedules: Regulated Pollutants and Project Overview , 2002 .

[33]  B. Holmén,et al.  Ultrafine PM emissions from natural gas, oxidation-catalyst diesel, and particle-trap diesel heavy-duty transit buses. , 2002, Environmental science & technology.

[34]  David B. Kittelson,et al.  Physical Factors Affecting Hydrocarbon Oxidation in a Diesel Oxidation Catalyst , 1994 .

[35]  J. Zuboy,et al.  Emission Testing of Washington Metropolitan Area Transit Authority (WMATA) Natural Gas and Diesel Transit Buses , 2005 .

[36]  Takuji Ishiyama,et al.  Fundamental Investigation of NOx Formation in Diesel Combustion Under Supercharged and EGR Conditions , 2005 .

[37]  Kaoru Fujimoto,et al.  Direct synthesis of acetylene from methane by direct current pulse discharge , 1999 .

[38]  Takayuki Sakai,et al.  Characteristics of formaldehyde formation from catalytic reaction of methane in the presence of No , 1994 .

[39]  Takeyuki Kamimoto,et al.  Fast Burning and Reduced Soot Formation via Ultra-High Pressure Diesel Fuel Injection , 1991 .

[40]  Timothy J. Callahan,et al.  Engine Knock Rating of Natural Gases—Methane Number , 1993 .