AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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An Analysis of Fine Inorganic Aerosols Emitted by a Diesel Engine with Urea-Based Selective Catalytic Reduction
TERESA BARONE, Taekhee Lee, Jon Hummer, Sherri Friend, John Storey, Samuel Lewis, Aleksandar Bugarski, National Institute for Occupational Safety and Health
Abstract Number: 584 Working Group: Aerosol Exposure
Abstract Exposure to diesel exhaust may adversely affect cardiovascular health and increase risk of lung cancer. Diesel exhaust exposures can be reduced through the application of emissions control strategies. One strategy for diesel equipment in the construction, agriculture, and mining industries involves high-temperature combustion and urea-based selective catalytic reduction (urea-SCR). Adequate performance of the urea-SCR system is necessary to prevent worker exposure to acutely toxic NO2 in confined working spaces. Aerosol emissions that may hinder urea-SCR performance were investigated by size-separating and collecting 0.03-10 µm aerosols with an electrical low-pressure impactor. Aerosols were sampled isokinetically near the urea-SCR outlet and were analyzed by scanning electron microscopy and energy dispersive x-ray spectroscopy. The samples were collected from a medium-duty off-road engine, which was operated at mid-speed (1400 rpm) and high-load (530 ft-lbs) on an engine dynamometer. The system utilized commercially available diesel exhaust fluid (DEF) for urea-SCR operation that consisted of 32.5% urea in water. Aerosols collected after the urea-SCR system were predominately soot aggregates in the ultrafine size range (≤ 0.1 µm). However in the fine size range (≤ 2.5 µm), inorganic aerosols were abundant. They consisted of spherical particles of calcium, phosphorus and iron and irregularly shaped particles of sodium and iron. Fine inorganic aerosols may have originated from the use of DEF and engine lubricating oil. They are detrimental because they may deposit in the catalyst system and reduce catalyst performance. Their prevalence suggests that DEF impurities and lubricating oil additives should be limited to avoid urea-SCR catalyst fouling and consequently to prevent exposure to acutely toxic NO2 in confined working spaces.