N ITROGEN O XIDES The term nitrogen oxide typically refers to any binary compound of oxygen and nitrogen, or to a mixture of such compounds: Nitric oxide (NO) Nitrogen dioxide (NO 2 ) Nitrous oxide (N 2 O)

At ambient temperatures, the oxygen and nitrogen gases in air will not react with each other. In an internal combustion engine, combustion of a mixture of air and fuel produces combustion temperatures high enough to cause chemical reactions between atmospheric nitrogen and oxygen in the flame, producing various oxides of nitrogen. In areas of high motor vehicle traffic, such as in large cities, the amount of nitrigen oxides given out into the atmosphere can be quite significant. Nitrogen Oxide Nitrogen Dioxide

S OURCES : One of the primary sources of nitrogen oxides in combustion processes is the fuel nitrogen oxide. During combustion, the nitrogen bound in the fuel is released and forms N 2 or NO. Fuel nitrogen oxide can contribute as much as 50% of total pollutants when combusting oil and as much as 80% when combusting coal. The process of formation involves the oxidation of volatile nitrogen (low boiling point) species during the first stages of combustion. During the release and before the oxidation of the volatiles, nitrogen reacts to form several chemicals which are then oxidized into NO.

E FFECTS : Nitrogen oxides leave harmful effects on us. When NO and volatile organic compounds react in the presence of sunlight, they form smog, a significant form of air pollution, especially in the summer. People with lung diseases such as asthma and people who work or exercise outside, are more likely to be effected by the adverse effects of smog such as damage to lung tissue and reduction in lung function.

E FFECTS : NO 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 bronchitis. It may also worsen existing heart diseases.

E FFECTS : Nitrogen oxides eventually form nitric acid when dissolved in atmospheric moisture, forming a component of acid rain. Acid rain is rain or any other form of precipitation that is unusually acidic. It has harmful effects on plants, aquatic animals and infrastructure. Acid rain is mostly caused by human pollutants of sulfur and nitrogen compounds which react in the atmosphere to produce acids. Different Effects of Acid Rain

P OSSIBLE M ETHODS O F C ONTROL : Atmospheric NO eventually forms nitric acid, which contributes to acid rain. NO pollutants are regulated in the United States by the Environmental Protection Agency and in the UK by the Department for Environment, Food and Rural Affairs

P OSSIBLE M ETHODS O F C ONTROL : Technologies such as flameless oxidation and staged combustion, significantly reduce NO in industrial processes. Bowin low NO technology is a combination of staged-premixed-radiant combustion technology with a major surface combustion preceded by a minor radiant combustion. Staged Combustion

P OSSIBLE M ETHODS O F C ONTROL : Water Injection technology is also becoming an important means of NO reduction through increased efficiency in the overall combustion process. The water is mixed with the fuel oil before the injection and combustion. Other technologies, such as selective catalytic reduction and selective non-catalytic reduction reduce post combustion NO. The use of Exhaust gas recirculation and catalytic converters in motor vehicle engines have decreased significantly pollutants. Catalytic Converter