![]() ![]() The ratio between NO 2 and NO determines which reactions take place and how fast. The isocyanic acid reacts with the water vapor and hydrolyses to carbon dioxide and ammonia:Īmmonia, in the presence of oxygen and a catalyst, reduces two different nitrogen oxides: 4 NO + 4 NHĢ + 12 H 2O ("NO 2 SCR selective catalytic reduction") NO + NOĢ (NH 2) 2CO + 4 NO + O 2 → 4 N 2 + 4 H 2O + 2 CO 2 and 4 (NH 2) 2CO + 6 NO 2 → 7 N 2 + 8 H 2O + 4 CO 2 and (NH 2) 2CO + NO + NO 2 → 2 N 2 + 2 H 2O + CO 2 When it is injected into the hot exhaust gas stream, the water evaporates and the urea thermally decomposes to form ammonia ( NH An electronic control unit adjusts the addition of fluid in accordance with parameters such as NOx level in the exhaust gas (before catalytic converter, after catalytic converter, and possibly between catalytic converters if there is more than one), current ammonia filling level, engine operating temperature and speed. This low dosing rate ensures long fluid refill intervals and minimizes the tank's size and intrusion into vehicle packaging space. ![]() The injection rate of DEF into the exhaust depends on the specific after-treatment system, but is typically 2–6% of diesel consumption volume. In 2008, the concerns about compliance shifted to the infrastructure for DEF distribution. ![]() The 2007 EPA regulations were meant to be an interim solution to allow manufacturers time to prepare for the more stringent 2010 EPA regulations, which reduced NO After a brief transition period, ULSD fuel became common at fuel pumps in the United States and Canada. To achieve this standard, Cummins and other diesel engine manufacturers developed an aftertreatment system that includes the use of a diesel particulate filter (DPF).Īs the DPF does not function with low-sulfur diesel fuel, diesel engines that conform to 2007 EPA emissions standards require ultra-low-sulfur diesel (ULSD) fuel to prevent damage to the DPF. In 2007, the United States Environmental Protection Agency (EPA) enacted requirements to significantly reduce harmful exhaust emissions. With the cooperation of the oil and chemical industry, a 1,300-station infrastructure to supply DEF was prepared by September 2005 in Japan. SCR was applied to automobiles by Nissan Diesel Corporation, and the first practical product " Nissan Diesel Quon" was introduced in 2004. The water and nitrogen are then released into the atmosphere through the exhaust. X are reduced by the ammonia into water and nitrogen, which are both non-polluting. DEF from a separate tank is injected into the exhaust pipeline, and the exhaust heat decomposes it to ammonia. X, which are harmful pollutants, from nitrogen in the atmosphere. The excess air leads to the generation of NO Several brands of SCR systems use DEF: BlueHDI is used by PSA Group vehicles including Peugeot, Citroën, and DS Automobiles brands BlueTec by Daimler AG and FLENDS (Final Low Emission New Diesel System) by UD Trucks.ĭiesel engines are typically operated with a lean burn air-to-fuel ratio ( over-stoichiometric ratio) to ensure the full combustion of soot and to prevent them from exhausting unburnt fuel. DEF is also sold as AdBlue, a registered trademark of the German Association of the Automotive Industry. In the international standard defining DEF ( ISO 22241), it is referred to as AUS 32 (aqueous urea solution 32%). X) in the diesel exhaust emissions from a diesel engine. DEF is consumed in a selective catalytic reduction (SCR) that lowers the concentration of nitrogen oxides ( NO Specifically, DEF is an aqueous urea solution made with 32.5% urea and 67.5% deionized water. Diesel exhaust fluid ( DEF also known as AUS 32 and marketed as AdBlue ) is a liquid used to reduce the amount of air pollution created by a diesel engine. ![]()
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