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Diesel exhaust fluid (DEF; also known as AUS 32 and marketed as AdBlue [3] ) is a liquid used to reduce the amount of air pollution created by a diesel engine. Specifically, DEF is an aqueous urea solution made with 32.5% urea and 67.5% deionized water. DEF is consumed in a selective catalytic reduction (SCR) that lowers the concentration of nitrogen oxides (NO
x) in the diesel exhaust emissions from a diesel engine. [4]
In the international standard defining DEF (ISO 22241), it is referred to as AUS 32 (aqueous urea solution 32%). [5] DEF is also sold as AdBlue, a registered trademark of the German Association of the Automotive Industry.
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.
Diesel 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. The excess air leads to the generation of NO
x, which are harmful pollutants, from nitrogen in the atmosphere. SCR is used to reduce the amount of NO
x released into the atmosphere. DEF from a separate tank is injected into the exhaust pipeline, and the exhaust heat decomposes it to ammonia. Within the SCR catalyst, the NO
x are reduced by the ammonia into water and nitrogen, which are both nonpolluting. The water and nitrogen are then released into the atmosphere through the exhaust. [6]
SCR was applied to automobiles by Nissan Diesel Corporation, and the first practical product "Nissan Diesel Quon" was introduced in 2004. With the cooperation of the oil and chemical industry, a 1,300-station infrastructure to supply DEF was prepared by September 2005 in Japan. [7]
In 2007, the United States Environmental Protection Agency (EPA) enacted requirements to significantly reduce harmful exhaust emissions. To achieve this standard, Cummins and other diesel engine manufacturers developed an aftertreatment system that includes the use of a diesel particulate filter (DPF).
As 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. After a brief transition period, ULSD fuel became common at fuel pumps in the United States and Canada.
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
x levels even further. [8] In 2008, the concerns about compliance shifted to the infrastructure for DEF distribution. [9]
The injection rate of DEF into the exhaust depends on the specific after-treatment system, but is typically 2–6% of diesel consumption volume. This low dosing rate ensures long fluid refill intervals and minimizes the tank's size and intrusion into vehicle packaging space. An electronic control unit adjusts the addition of fluid in accordance with parameters such as NO
x 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, [10] engine operating temperature and speed.[ citation needed ]
DEF is a 32.5% solution of urea, (NH
2)
2CO. When it is injected into the hot exhaust gas stream, the water evaporates and the urea thermally decomposes [11] to form ammonia (NH
3) and isocyanic acid (HNCO):
The isocyanic acid reacts with the water vapor and hydrolyses to carbon dioxide and ammonia:
Overall, thus far:
Ammonia, in the presence of oxygen and a catalyst, reduces two different nitrogen oxides: [12]
The overall reduction of NO
x by urea is then:
The ratio between NO2 and NO determines which reactions take place and how fast. The highest conversion rates are achieved if equal amounts of NO2 and NO are present, especially at temperatures between 200°C and 350°C. If there is more NO than NO2, fast SCR and standard SCR take place sequentially. If there is more NO2 than NO, fast SCR and NO2 SCR take place sequentially, however, NO2 SCR is slower than standard SCR, and ammonium nitrate can form and temporarily deactivate the catalytic converter. [13]
DEF freezes at −11 °C (12 °F). [14] [15] [16] For the SCR exhaust cleaning system to function at low temperatures, a sufficient amount of the frozen DEF must be melted in as short time as possible, preferably on the order of minutes. For example, 2010 EPA emissions requirements require full DEF coolant flow within 70 minutes. [17] [18]
In Europe, Regulation (EC) No 692/2008 [19] specified in Annex XVI point 10 that DEF from a frozen tank at a core temperature of −15 °C (5 °F) must become available within 20 minutes when starting the engine at −15 °C (5 °F).
Typically, the frozen DEF is melted by heat from the engine, e.g. engine coolant passing through the DEF tank, governed by a thermostatic coolant control valve. This method may take significant time before the SCR exhaust cleaning system is fully operational, often up to an hour. [4]
Another method to thaw DEF (and thus allow for full SCR operation) is to integrate an electric heater into the DEF tank. This heater must be sized, positioned, and powered adequately to rapidly melt sufficient frozen DEF. It should preferably be self regulating not to overheat if (part of) the heater is outside of the liquid. It should also preferably be self regulating to eliminate any complicated sensor and temperature regulating systems. Furthermore, the heater should not exceed 50–60 °C (122–140 °F), as DEF begins to decompose at around 60 °C (140 °F). PTC heaters are often used to achieve this.
The urea solution is clear, non-toxic and safe to handle. [20] Since urea has corrosive impact on metals like aluminium, DEF is stored and transported in special containers. [21] [22] These containers are typically made of stainless steel. [22] Vehicles' selective catalytic reduction (SCR) systems and DEF dispensers are designed in a manner that there is no corrosive impact of urea on them. [21] It is recommended that DEF be stored in a cool, dry, and well-ventilated area that is out of direct sunlight. Bulk volumes of DEF are compatible for storage within polyethylene containers (HDPE, XLPE), fiberglass reinforced plastic (FRP), and steel tanks. DEF is also often handled in intermediate bulk containers for storage and shipping.
DEF is offered to consumers in a variety of quantities ranging from containers for single or repeated small usage, up to bulk carriers for consumers requiring a large amount of DEF. As of 2013, many truck stops have added DEF pumps. These are usually adjacent to fuel pumps so the driver can fill both tanks without moving the truck.
In Europe, increasing numbers of fuel stations offer AdBlue pumps, not only for large commercial vehicles but also for passenger cars.
At airports, where DEF can sometimes be required for diesel ground service vehicles, its labelling and storage must be carefully managed to avoid accidentally servicing jet aircraft with DEF instead of fuel system icing inhibitor, a mistake that has been blamed for multiple in-flight engine failure and grounding incidents. [23] [24] [25]
As of December 2021 [update] , a shortage of DEF in South Korea was continuing and brought havoc to its economy. As most of the urea used is supplied by China, imports have slowed since China introduced mandatory inspections of urea exports in September. [26] Nearly 97% of South Korea's urea imports came from China between January and September. In 2015, South Korea had made it mandatory for diesel cars to use urea solutions to control emissions, a move that now impacts 40% of registered vehicles. Diesel vehicles made since 2015 were required to be fitted with SCR systems. [27] The South Korean government started rationing urea solution, and banned its resale as panic buying by drivers exacerbated an acute shortage that could cause transport and industry to grind to a halt. [28] A KC-330 Cygnus was sent to import Diesel exhaust fluid from Australia to ease a supply shortage of the key material used in diesel vehicles. [29]
In early December 2021, the Australian National Road Transport Association also raised concerns about a shortage of DEF in the country due to the shortage of urea in China. [30] China capped exports to protect its domestic supplies and rising DEF prices. By mid-December there was approximately 7 weeks’ supply of AdBlue left in Australia. [31] On 14 December, an Australian company stated that it would build a new plant. [32]
Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the formula NH3. A stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pungent smell. Biologically, it is a common nitrogenous waste, and it contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to fertilisers. Around 70% of ammonia produced industrially is used to make fertilisers in various forms and composition, such as urea and diammonium phosphate. Ammonia in pure form is also applied directly into the soil.
Urea, also called carbamide, is an organic compound with chemical formula CO(NH2)2. This amide has two amino groups joined by a carbonyl functional group. It is thus the simplest amide of carbamic acid.
A catalytic converter is an exhaust emission control device which converts toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalyzing a redox reaction. Catalytic converters are usually used with internal combustion engines fueled by gasoline or diesel, including lean-burn engines, and sometimes on kerosene heaters and stoves.
Vehicle emissions control is the study of reducing the emissions produced by motor vehicles, especially internal combustion engines.
Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline (petrol), diesel fuel, fuel oil, biodiesel blends, or coal. According to the type of engine, it is discharged into the atmosphere through an exhaust pipe, flue gas stack, or propelling nozzle. It often disperses downwind in a pattern called an exhaust plume.
Diesel exhaust is the gaseous exhaust produced by a diesel type of internal combustion engine, plus any contained particulates. Its composition may vary with the fuel type or rate of consumption, or speed of engine operation, and whether the engine is in an on-road vehicle, farm vehicle, locomotive, marine vessel, or stationary generator or other application.
Selective catalytic reduction (SCR) means of converting nitrogen oxides, also referred to as NO
x with the aid of a catalyst into diatomic nitrogen, and water. A reductant, typically anhydrous ammonia, aqueous ammonia, or a urea solution, is added to a stream of flue or exhaust gas and is reacted onto a catalyst. As the reaction drives toward completion, nitrogen, and carbon dioxide, in the case of urea use, are produced.
A nitrogen oxide sensor or NOx sensor is typically a high-temperature device built to detect nitrogen oxides in combustion environments such as an automobile, truck tailpipe or smokestack.
In atmospheric chemistry, NOx is shorthand for nitric oxide and nitrogen dioxide, the nitrogen oxides that are most relevant for air pollution. These gases contribute to the formation of smog and acid rain, as well as affecting tropospheric ozone.
A diesel particulate filter (DPF) is a device designed to remove diesel particulate matter or soot from the exhaust gas of a diesel engine.
BlueTEC is Mercedes-Benz Group's marketing name for engines equipped with advanced NOx reducing technology for vehicle emissions control in diesel-powered vehicles. The technology in BlueTec vehicles includes a selective catalytic reduction (SCR) system that uses diesel exhaust fluid, and a system of NOx adsorbers the automaker calls DeNOx, which uses an oxidizing catalytic converter and diesel particulate filter combined with other NOx reducing systems.
A NOx adsorber or NOx trap (also called Lean NOx trap, abbr. LNT) is a device that is used to reduce oxides of nitrogen (NO and NO2) emissions from a lean burn internal combustion engine by means of adsorption.
Selective non-catalytic reduction (SNCR) is a method to lessen nitrogen oxide emissions in conventional power plants that burn biomass, waste and coal. The process involves injecting either ammonia or urea into the firebox of the boiler at a location where the flue gas is between 1,400 and 2,000 °F (760 and 1,090 °C) to react with the nitrogen oxides formed in the combustion process. The resulting product of the chemical redox reaction is molecular nitrogen (N2), carbon dioxide (CO2), and water (H2O).
Cerium(III) oxide, also known as cerium oxide, cerium trioxide, cerium sesquioxide, cerous oxide or dicerium trioxide, is an oxide of the rare-earth metal cerium. It has chemical formula Ce2O3 and is gold-yellow in color.
The Cummins X-series engine is an Inline (Straight)-6 diesel engine produced by Cummins for heavy duty trucks and motorcoaches, replacing the N14 in 2001 when emissions regulations passed by the EPA made the engine obsolete. Originally called the "Signature" series engine, the ISX uses the "Intellect System" to further improve the engine. This engine is widely used in on highway and vocational trucks and is available in power ranging from 430 hp all the way to 620 hp 2050 lb-ft. The QSX is the off-highway version of the ISX with the Q standing for Quantum. The QSX is used for industrial, marine, oil & gas and other off-highway applications. Cummins also produced a 650 hp and 1950 lb-ft version for the RV market.
Ammonium carbamate is a chemical compound with the formula [NH4][H2NCO2] consisting of ammonium cation NH+4 and carbamate anion NH2COO−. It is a white solid that is extremely soluble in water, less so in alcohol. Ammonium carbamate can be formed by the reaction of ammonia NH3 with carbon dioxide CO2, and will slowly decompose to those gases at ordinary temperatures and pressures. It is an intermediate in the industrial synthesis of urea (NH2)2CO, an important fertilizer.
The Eberspächer Group of Companies is a privately owned international automotive supplier, headquartered in Esslingen am Neckar, Germany. Customers include almost all major manufacturers of passenger cars and commercial vehicles. It is one of the leading system developers and suppliers of exhaust technology, vehicle heaters and air-conditioning systems worldwide and is also involved in automotive electronics for electronic networking in the vehicles.
The Medium Diesel Engine (MDE) is a four-cylinder diesel engine developed by Adam Opel AG and branded "1.6 CDTI Ecotec" in most markets. Opel also adds the marketing term "Whisper Diesel" in some markets, claiming relatively low levels of noise, vibration, and harshness. Production commenced in late 2013 at Szentgotthárd, Hungary. The MDE is Opel's first all-aluminum diesel engine and offers a power density of 85 hp (63 kW) per liter 136 PS in its most powerful version. Maximum power and torque have been increased versus the previous-generation 1.7-liter engine, while fuel consumption has been reduced by up to 10 percent compared with a 2.0-liter CDTI engine of similar power output. This new 1.6 CDTI engine will replace the current 1.7-liter and lower-powered 2.0-liter diesel engines in a wide range of Opel models, with more- and less-powerful versions to come. The most powerful version of this engine, delivering 136 PS at 3,500–4,000 rpm and 320 N⋅m (236 lb⋅ft) at 2,000 rpm, was first introduced in the 2013 Opel Zafira Tourer, and later in the 2014 Opel Astra J and restyled 2014 Opel Meriva B. In 2014, versions were released with power outputs of 110 and 95 PS.
The EMD 1010 or EMD 265 is a line of four-stroke diesel engines manufactured by Electro-Motive Diesel. The precursor to the 1010 was introduced around 1998 as the 265H or H-Engine. The H-engine was initially designed for use as a 6,300 hp (4,700 kW) 16 cylinder, the EMD SD90MAC; however, the early engines were found to be unreliable, and unsuccessful in the market, with the proven EMD 710 2-stroke design being preferred. The EMD four-stroke engine was resurrected in 2015 to meet EPA Tier 4 emissions regulations.
Urine patches in cattle pastures generate large concentrations of the greenhouse gas nitrous oxide through nitrification and denitrification processes in urine-contaminated soils. Over the past few decades, the cattle population has increased more rapidly than the human population. Between the years 2000 and 2050, the cattle population is expected to increase from 1.5 billion to 2.6 billion. When large populations of cattle are packed into pastures, excessive amounts of urine soak into soils. This increases the rate at which nitrification and denitrification occur and produce nitrous oxide. Currently, nitrous oxide is one of the single most important ozone-depleting emissions and is expected to remain the largest throughout the 21st century.
3.1– For Human Health … The product has a low toxicity and it is not considered that it could be harmful to health. … 3.1.5. – Long-term effects: … Urea is a substance that appears in the body as a result of proteins during metabolism, it is eliminated with the urine.