modmonster -
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Originally Posted by modmonster
whats wrong with NOx ?
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NOx is bad :
Facts on NOx Reduction
http://www.arvinmeritor.com/media_room/pdfs/gp0440.pdf
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What are the health and environmental impacts of NOx?
Human health concerns center on the respiratory system. NOx reacts with ammonia, moisture and other compounds to form nitric acid and related particles. These particles damage lung tissue. Small particles penetrate deeply into sensitive parts of the lungs, and can cause or worsen potentially fatal respiratory diseases such as emphysema and bronchitis. Ground-level ozone (smog) is formed when NOx and volatile organic compounds (VOCs) react with heat and sunlight. Children, asthmatics and people who work or exercise outside are susceptible to adverse effects such as lung tissue damage and decreased lung function. Ozone also damages vegetation and reduces crop yields.Acid rain forms when NOx and sulfur dioxide react with other substances in the air to form acids, which fall to earth with rain, fog, snow or dry particles. Acid rain damages or deteriorates cars, buildings and monuments, as well as causes lakes and streams to become unsuitable for fish.The accumulation of greenhouse gases in the atmosphere is thought to be a factor in global warming. One NOx element is a greenhouse gas.
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is it definatly created during lean burn or is there some lee-way
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(Same source as above)
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What is the best solution to reduce NOx?
There is no optimal solution for NOx at this time. Each solution has advantages and disadvantages. SCR has perceived environmental and societal concerns related to it, such as the need for a urea distribution network and the creation of ammonia within the reaction. However, it is a far more advanced solution than NOx traps. NOx traps do not carry the same societal issues, but they are not as advanced technically and in the field. The EPA is trying to balance the societal and technical issues to make sure the best solution is available for heavy-duty trucks for 2007 and 2010. The size of engine, duty cycle and application will all be factors in the ultimate solution.
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If you "go lean" of the stoichiometric ratio of 14.7 to 1, the good news is that your HC and CO emissions stay nice and low. The bad news is that your NOx emissions increase :
Automotive Electronics Handbook - Google Book Search
This is a conundrum of diesel engines, which "go lean" by design.
CarloSW2
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