10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Chemical Characterization of Particles Emitted from Engine Operated by Natural Gas and Propane
SANNA SAARIKOSKI, Jenni Alanen, Hannu Vesala, Rasmus Pettinen, Mia Isotalo, Sampsa Martikainen, Matthew Bloss, Minna Aurela, Teuvo Maunula, Kauko Kallinen, Jan Torrkulla, Hilkka Timonen, Topi Rönkkö, Kati Lehtoranta, Finnish Meteorological Institute
Abstract Number: 1252 Working Group: Combustion
Abstract Natural gas (NG) is used globally as a fuel in engines because of its good availability, competitive cost and lower CO2 emissions compared to conventional liquid fossil fuels. However, also NG engines produce gas and particle emissions that can have effect on environment and human health. In terms of particle emissions, particle mass emissions from NG engines are small compared to conventional diesel engines because of lower soot particle formation in combustion but particle number emissions from NG engines, especially nanoparticle emissions, are not necessarily small. Although NG is most widely used fuel gas, in some power generation applications it is more advantageous to use other gas compositions, like ethane and propane, instead of NG that is composed mostly of methane. Changing the gas composition is likely to alter the emissions from gas combustion and also its environmental and health impacts. The first objective of this study was to examine particulate emissions from the engine operated by NG and propane. The second aim was to investigate the influence of different catalyst systems (oxidation catalysts and Selective Catalytic Reduction, SCR) on exhaust particles emitted from the gas engine.
Gas engine measurements were conducted at the engine test facility of VTT Technical Research Centre of Finland. A spark ignited passenger car engine adapted for NG and propane was used. Two different catalyst setups were tested of which the first one consisted of a combination of an oxidation and a Selective Catalytic Reduction (SCR) catalyst, and the other setup included only one oxidation reactor. Exhaust gas temperature was varied from 350 to 500 °C and exhaust gas flow was 80 kg/h or 40 kg/h. The chemical composition of exhaust particles was investigated by using a Soot Particle Aerosol Mass Spectrometer (SP-AMS, Aerodyne Research Inc.). Additionally, particle number concentration and particle size distribution were measured by a variety of instruments. The potential of gas engine exhaust to form secondary particles was examined by Potential Aerosol Mass (PAM) chamber.
Primary particulate mass emissions from the engine operated by NG and propane were very small. Primary particles were dominated by organic matter that consisted mostly of hydrocarbon compounds. Compared to primary emissions, secondary particulate mass emissions from gas engine were larger. Chemical composition of secondary particles was similar to NG and propane being dominated by sulfate (~50 %) and organic matter (~40 %), and followed by ammonium (~4 %) and nitrate (~2 %). However, the concentration and chemistry of secondary particles were dependent on the engine and catalyst conditions.
This work was funded by the Tekes – the Finnish Funding Agency for Innovation project no 770/31/2016 (New-Gas), Wärtsilä Finland Oy, Dinex-Ecocat Oy, Dekati Oy, Neste, Oilon Oy and Airmodus Oy.