BlueTec the efficient NOx control technology
BlueTEC is Daimler AG’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.
Regulation and emission control technologies
Selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) reduce post combustion NOx by reacting the exhaust with urea or ammonia to produce nitrogen and water. SCR is now being used in ships, diesel trucks and in some diesel cars. The use of exhaust gas recirculation and catalytic converters in motor vehicle engines have significantly reduced vehicular emissions. NOx was the main focus of the Volkswagen emissions violations.
Other technologies such as flameless oxidation (FLOX) and staged combustion significantly reduce thermal NOx in industrial processes. Bowin low NOx technology is a hybrid of staged-premixed-radiant combustion technology with a major surface combustion preceded by a minor radiant combustion. In the Bowin burner, air and fuel gas are premixed at a ratio greater than or equal to the stoichiometric combustion requirement.Water Injection technology, whereby water is introduced into the combustion chamber, is also becoming an important means of NOx reduction through increased efficiency in the overall combustion process. Alternatively, the water (e.g. 10 to 50%) is emulsified into the fuel oil before the injection and combustion. This emulsification can either be made in-line (unstabilized) just before the injection or as a drop-in fuel with chemical additives for long term emulsion stability (stabilized). Inline emulsified fuel/water mixtures show NOx reductions between 4 and 83%.
BlueTec the efficient NOx control technology
Daimler introduced BlueTEC in the Mercedes E-Class (using the DeNOx system) and GL-Class (using SCR) at the 2006 North American International Auto Show. At that time, these BlueTEC vehicles were 45- and 50-state legal, respectively, in the United States (a 45-state vehicle does not meet the more stringent California emission standards that have also been adopted by four other states).
Daimler AG has entered into an agreement with Volkswagen and Audi to share BlueTEC technology with them in order to increase the Diesel passenger-vehicle market in the United States. VW introduced the Jetta Clean TDI, the Tiguan concept, and the Touareg BlueTDI as part of the BlueTec licensing program. The Jetta and the Tiguan use NOx adsorbers, while the Touareg uses a Selective Catalytic Reduction catalytic converter.
In August 2007 VW Group announced that cooperation on BlueTEC with Daimler AG would end. The reasoning for this change is due to the recognition of the VW TDI branding. VW did not want to use a competitor’s branding for a product they would introduce into the market. VW developed their own system, but it failed and they re-programmed the engine control to show false values during pollution tests.
By 2010 a BlueTEC version of the Mercedes Sprinter was released. The BlueTEC systems allowed the elimination of much of the EGR in that vehicle’s engine, which as a result gives 188 horsepower (140 kilowatts) compared to the non-BlueTec engine’s 154 horsepower (115 kilowatts).
Daimler Trucks uses BlueTEC on all its Freightliner and Western Star Trucks destined for highway use, as these vehicles are only available with diesel engines.
The BlueTEC system was created because the properties of the Diesel cycle that give diesel engines higher fuel efficiency also lead to relatively higher emissions of certain pollutants compared to Otto cycle engines. High compression ratios and lean air-fuel mixtures make high combustion temperatures, which results in more nitrogen oxides being produced during the combustion. While the particulate matter can be controlled with higher injection pressures and particulate filters, the big challenge is limiting NOx; Tier 2 regulations in the US are 0.07 grams per mile of NOx, which is ⅛ of the 0.40 limit in the European Union.
The emissions system works in a series of steps:
- A diesel oxidation catalyst reduces the amounts of carbon monoxide (CO) and hydrocarbons (HC) released from the exhaust.
- A DeNOx catalytic converter begins a preliminary removal of oxides of nitrogen.
- A particulate filter traps and stores soot particles, burning them off when the filter gets full.
- If the above are not sufficient to meet the prevailing emissions regulations, a Selective Catalytic Reduction (SCR) catalytic converter will convert the remaining nitrogen oxides to nitrogen and water; so-called diesel exhaust fluid (solution of urea and water) is injected into the exhaust gas stream to enable the conversion. In order to prevent vehicles from breaking emissions regulations, the engine may go into a limp-home-mode if the DEF tank is depleted; drivers are instructed to keep the tank refilled as necessary. Some commercial vehicles are equipped with a request or inhibit switch which allows the DEF injection to be “postponed” as it can reduce power output and increase temperatures temporarily; if the vehicle is climbing a grade, for example, it may be necessary to delay the cycle.
Emissions defeat device allegations
The Netherlands’ official automobile inspector TNO, on behalf on the Dutch Minister of the Environment, conducted an on-road tests of a C-Class Mercedes C220 TDi BlueTec diesel and determined it emitted more than 40 times the amount of cancer-causing NOx than in the lab test. The tests were done at temperatures below 10 degrees Celsius (50 °F). Mercedes says it is permissible for the BlueTec engine to emit 40 times more NOx when the temperature is less than 10 °C (50 °F).
As of 2016 April 22, Mercedes-Benz USA disclosed it is under investigation by the Department of Justice for potential discrepancies over its diesel emissions certifications, according to a Daimler statement. The DOJ effectively told MBUSA to begin an internal investigation “to review its certification and admissions process related to exhaust emissions in the United States,” Daimler said. The company “has agreed to cooperate fully with the DOJ.”
What is the NOx? Health and environmental effects of NOx
What is NOx?
In atmospheric chemistry, NOx is a generic term for the nitrogen oxides that are most relevant for air pollution, namely nitric oxide (NO) and nitrogen dioxide (NO2). These gases contribute to the formation of smog and acid rain, as well as tropospheric ozone.
NOx gases are usually produced from the reaction among nitrogen and oxygen during combustion of fuels, such as hydrocarbons, in air; especially at high temperatures, such as occur in car engines. In areas of high motor vehicle traffic, such as in large cities, the nitrogen oxides emitted can be a significant source of air pollution. NOx gases are also produced naturally by lightning.
The term NOx is chemistry shorthand for molecules containing one nitrogen and one or more oxygen atom. It is generally not meant to include nitrous oxide (N2O), a fairly inert oxide of nitrogen that has many uses as an oxidizer for rockets and car engines, an anesthetic, and a propellant for aerosol sprays and whipped cream. Nitrous oxide plays hardly any role in air pollution, although it may have a significant impact on the ozone layer.
NOy (reactive, odd nitrogen) is defined as the sum of NOx plus the compounds produced from the oxidation of NOx which include nitric acid.
Health and environment effects of NOx
NOx reacts with ammonia, moisture, and other compounds to form nitric acid vapor and related particles. Small particles can penetrate deeply into sensitive lung tissue and damage it, causing premature death in extreme cases. Inhalation of such particles may cause or worsen respiratory diseases, such as emphysema or bronchitis, or may also aggravate existing heart disease.
NOx reacts with volatile organic compounds in the presence of sunlight to form and to destroy ozone. Ozone can cause adverse effects such as damage to lung tissue and reduction in lung function mostly in susceptible populations (children, elderly, asthmatics). Ozone can be transported by wind currents and cause health impacts far from the original sources. The American Lung Association estimates that nearly 50 percent of United States inhabitants live in counties that are not in ozone compliance. In South East England, ground level ozone pollution tends to be highest in the countryside and in suburbs, while in central London and on major roads NO emissions are able to “mop up” ozone to form NO2 and oxygen.
NOx also readily reacts with common organic chemicals, and even ozone, to form a wide variety of toxic products: nitroarenes, nitrosamines and also the nitrate radical some of which may cause DNA mutations. Recently another pathway, via NOx, to ozone has been found that predominantly occurs in coastal areas via formation of nitryl chloride when NOx comes into contact with salt mist.
NOx emissions also cause global cooling through the formation of •OH radicals that destroy methane molecules, countering the effect of greenhouse gases. The effect can be significant. For instance, according to the OECD “the large NOx emissions from ship traffic lead to significant increases in hydroxyl (OH), which is the major oxidant in the lower atmosphere. Since reaction with OH is a major way of removing methane from the atmosphere, ship emissions decrease methane concentrations. (Reductions in methane lifetimes due to shipping-based NOx emissions vary between 1.5% and 5% in different calculations).” “In summary, most studies so far indicate that ship emissions actually lead to a net global cooling. However, it should be stressed that the uncertainties with this conclusion are large, in particular for indirect effects, and global temperature is only a first measure of the extent of climate change in any event.”
The ultimate destination of much NOx is to end up in the soil as nitrite or nitrate, which are useful to growing plants.
High Standard AdBlue Production Line
High Quality AdBlue (BlueTec Solution) Product
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AdBlue is introduced into the exhaust gases using an exhaust treatment system called selective catalytic reduction (SCR), where up to 90% of the nitrogen oxides (NOx) produced by the vehicle are converted into their environmentally friendly components: nitrogen and water.
HYUNDAI BLUE DRIVE, Our cars use a collection of innovative technologies we call ‘Blue Drive’ to help improve fuel consumption and reduce emissions. Together they can make a dramatic difference. The i20 Blue, for example, emits just 84 g/km of CO2 and returns impressive economy. Today’s Blue Drive technologies are just the beginning. But with Blue models throughout the Hyundai range offering leading eco-performance, our new thinking means we can offer real, practical ways to reduce emissions substantially, here and now.
DAIMLER ( MERCEDES BENZ), Daimler introduced BlueTEC in the Mercedes E-Class (using the DeNOx system) and GL-Class (using SCR) at the 2006 North American International Auto Show. The BlueTEC system was created because the properties of the Diesel cycle that give diesel engines higher fuel efficiency also lead to relatively higher emissions of certain pollutants compared to Otto cycle engines.