Nitric oxide combustion systems

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)... 

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. 

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. 

On a different front, one of the first successful modelings of a practical combustion system was achieved, that of the formation of NO in a jet engine combustor.227 The method proposed for nitric oxide abatement is being incorporated into the next generation of aircraft jet engines. Later, essentially complete agreement between experiment and numerical modeling was achieved for the thermal explosions of methyl isocyanide in spherical vessels.228... 

Greater than equilibrium concentrations of intermediate species have been observed in the combustion products of several reactant systems. Examples are the concentrations of ammonia in the products of the decomposition of hydrazine (32), the concentration of CH4 in ethylene oxide decomposition (33), nitric oxide and ammonia in the products of the reaction of hydrazine and nitrogen tetroxide (34), and chlorine monofluoride in the products of the reaction of hydrazine and chlorine pentafluorlde (35). 

Baukal, C. E., and Dalton, A. I. "Nitric Oxide Measurements in Oxygen Enriched Air-Natural Gas Gombustion Systems." Proceedings of the Fossil Fuel Combustion Symposium, edited by S. N. Singh, New York ASME, 1990. 

When a reaction resuits in the evolution of heat, it is said to be exothermic (exo- is a prefix meaning "out of") that is, energy flows out of the system. For example, in the combustion of methane, energy flows out of the system as heat. Reactions that absorb energy from the surroundings are said to be endothermic. When the heat flow is into a system, the process is endothermic. For example, the formation of nitric oxide from nitrogen and oxygen is endothermic ... 

The primary form of NOx for a combustion source is nitric oxide (NO). The NOx removal system to be considered is Selective Catalytic Reduction (SCR). 

The chemistry of photochemical smog is still not crystal clear (pun intended), but scientists do know the basics that go into creating the smog. Nitrogen from the atmosphere is oxidized to nitric oxide in internal combustion engines and then released into the atmosphere through the engines exhaust systems ... 

The Thermal De-NOx process was developed by Richard Lyon at Exxon in the early 1970 s and patented in 1975 [1]. It is one of three SNCR (selective non-catalytic reduction) schemes for nitrogen oxides (the others are RAPRENOx, or cyanuric acid injection, and urea injection). Such after-treatment processes are commonly used on stationary combustion systems to control NOx emissions. The Thermal De-NOx process uses ammonia as the additive, and the complex reaction by which the ammonia reacts with nitric oxide has a number of fascinating properties that have prompted considerable research over the past 15 years or so. 

Nitric oxide (NOx) is one of the main pollutants in combustion systems and rotary kilns are no exception particularly for pulverized fuel combustion. NOx formation depends on three factors, namely (i) the amount of nitrogen present in the fuel, (ii) the combustion temperature, and (iii) the stoichiometric conditions for the combustion reaction. Hence NOx production is classified into fuel NOx, thermal NOx, and prompt NOx. Some of the mechanisms for the formation of these species during pulverized coal combustion in rotary cement kilns have been described in commercial CFD packages (e.g., FLUENT, CINAR). 

M. Gehring, K. Hoyermann, H. Schacke, J. Wolf rum Direct studies of some elementary steps for the formation and destruction of nitric oxide in the H-N-0 system. 14th Symp. on Combustion (Combustion Institute, Pittsburgh, PA 1973)... 

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