Nitric oxide combustion

At the high temperatures found in MHD combustors, nitrogen oxides, NO, are formed primarily by gas-phase reactions, rather than from fuel-bound nitrogen. The principal constituent is nitric oxide [10102-43-9] NO, and the amount formed is generally limited by kinetics. Equilibrium values are reached only at very high temperatures. NO decomposes as the gas cools, at a rate which decreases with temperature. If the combustion gas cools too rapidly after the MHD channel the NO has insufficient time to decompose and excessive amounts can be released to the atmosphere. Below about 1800 K there is essentially no thermal decomposition of NO. 

Nitric oxide, NO, results from high-temperature combustion, both in stationary sources such as power plants or industrial plants in the production of process heat and in internal combustion engines in vehicles. The NO is oxidized in the atmosphere, usually rather slowly, or more rapidly if there is ozone present, to nitrogen dioxide, NO2. NO2 also reacts further with other constituents, forming nitrates, which is also in fine parhculate form. 

A substantial portion of fhe gas and vapors emitted to the atmosphere in appreciable quantity from anthropogenic sources tends to be relatively simple in chemical structure carbon dioxide, carbon monoxide, sulfur dioxide, and nitric oxide from combustion processes hydrogen sulfide, ammonia, hydrogen chloride, and hydrogen fluoride from industrial processes. The solvents and gasoline fractions that evaporate are alkanes, alkenes, and aromatics with relatively simple structures. In addition, more complex... 

The advantages of thermal incineration are that it is simple in concept, has a wide application, and results in almost complete destruction of pollutants with no liquid or solid residue. Thermal incineration provides an opportunity for heat recovery and has low maintenance requirements and low capital cost. Thermal incineration units for small or moderate exhaust streams are generally compact and light. Such units can be installed on a roof when the plant area is limited. = The main disadvantage is the auxiliary fuel cost, which is partly offset with an efficient heat-recovery system. The formation of nitric oxides during the combustion processes must be reduced by control of excess air temperature, fuel supply, and combustion air distribution at the burner inlet, The formation of thermal NO increases dramatically above 980 Table 13.10)... 

Suppose we are interested in the heat of combustion of nitric oxide, NO ... 

Nitric oxide is the most stable oxide of nitrogen. It decomps above 1000° and will not support combustion below this temp. When mixed with hydrogen, it can be expld by a long duration, intense electric spark (Ref 8). It is very endothermic, its Qf being —21,575cal/g at RT (Ref 5)... 

Originally prepd by the spontaneous combustion of nitric oxide In an atm of fluorine 4NO+Fj- N2+2N02F (Ref 1). More easily prepd by mixing nitrogen dioxide with fluorine 2N02+F2 -+2N02F (Ref 2)... 

Nitrogen Dioxide (NO2) Is a major pollutant originating from natural and man-made sources. It has been estimated that a total of about 150 million tons of NOx are emitted to the atmosphere each year, of which about 50% results from man-made sources (21). In urban areas, man-made emissions dominate, producing elevated ambient levels. Worldwide, fossil-fuel combustion accounts for about 75% of man-made NOx emissions, which Is divided equally between stationary sources, such as power plants, and mobile sources. These high temperature combustion processes emit the primary pollutant nitric oxide (NO), which Is subsequently transformed to the secondary pollutant NO2 through photochemical oxidation. 

Nitric oxide (NO) is severely irritating to eyes and respiratory system. Effects may be delayed for several hours following exposure. Corrosive. Inhalation may result in chemical pneumonitis and pulmonary edema. Nonflammable. Oxidizer. This product accelerates the combustion of combustible material. 

Barlow, R. S., N. S. A. Smith, J.-Y. Chen, and R. W. Bilger (1999). Nitric oxide formation in dilute hydrogen jet flames Isolation of the effects of radiation and turbulence-chemistry submodels. Combustion and Flame 117, 4—31. 

Flagan, R. C. and J. P. Appleton (1974). A stochastic model of turbulent mixing with chemical reaction Nitric oxide formation in a plug-flow burner. Combustion and Flame 23, 249-267. 

Some oxidation of combined nitrogen to nitric oxide may take place when measurements are made low in a range, so that an excess of oxygen is available for combustion. 

As mentioned, the addition of a small amount of water to the bomb ensures that the vapor phase remains saturated throughout the experiment, so that liquid water is produced in the combustion reaction. It also ensures that the mixture of nitric oxides formed by the oxidation of the N2 will be converted to NOjT(aq), which is simple to determine. 

During combustion processes the molecular nitrogen in the combustion air and the fuel nitrogen that may be present in the fuel is converted into nitric oxide and some nitrogen dioxide4 when NO and residual O2 are cooled together. The NO formation is also controlled by (1) thermal NO, (2) prompt NO and (3) N2O to NO routes5-7. 

The amount of prompt NO produced in combustion systems is relatively small compared with the total NO formation. However, prompt NO is still formed at low temperatures and is one of the features in producing ultra-low NO burners. The nitric oxide reacts with other species in the atmosphere to give various other nitrogen oxides, namely NO2 and nitrogen pollutants. 

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