Thermal power plants nitrogen oxides

NO and NO2 are undesirable by-products of the combustion of coal, natural gas, or fuel oil in boilers of power plants. Nitrogen oxides are formed during combustion by the reaction of atmospheric N2 and O2 at temperatures > 1200 °C (thermal NO ). If nitrogen-containing fuels such as coal and heavy oils are burned, fuel NO, is produced by the combustion of the fuel-bound nitrogen. The third, usually small, source is prompt NO which is attributed to the reaction of N2 with radicals derived from the fuel. 

The atmosphere is an important conveyor belt for many pollutants. The atmosphere reacts most sensitively to anthropogenic disturbance because proportionally it represents a much smaller reservoir than land and water furthermore, the residence times of many constituents of the atmosphere are smaller than those that occur in the other exchange reservoirs. Water and atmosphere are interdependent systems. Many pollutants, especially precursors of acids and photooxidants, originate directiy or indirecdy from the combustion of fossil fuels. Hydrocarbons, carbon monoxide, and nitrogen oxides released by thermal power plants and, above all by automobile engines, can produce, under the influence of sunlight, ozone and other photooxidants. 

This NH3 is used mainly to manufacture nigrogen fertilizers. Furthermore, N2 is converted into nitrogen oxides in the combustion of gasoline and fossil fuel (automobile engines and thermal power plants) ... 

The burning of coal in thermal power plants results in major pollutants such as suspended particulate matter (SPM), sulphur dioxide (SO2), oxides of nitrogen (NOx) etc, of vdiich NOx is believed to be a key con nent responsible for several hazards associated with ecology and human health(l). Given the relative abundance of coal in India, coal-based thermal power plants will continue to play a dominant role in the power sector. Therefore NOx abatement through primary and secondary measures assumes great importance. Post combustion techniques such as selective catalytic reduction (SCR) can reduce NOx emissions by >95% (2). 

The narrow pulse energization of the flue gas of thermal power plants appears a promising technology for the abatement of solid particulates as well as the sulphur and nitrogen oxides. 

A process development known as NOXSO (DuPont) (165,166) uses sodium to purify power plant combustion flue gas for removal of nitrogen oxide, NO, and sulfur, SO compounds. This technology reHes on sodium metal generated in situ via thermal reduction of sodium compound-coated media contained within a flue-gas purification device, and subsequent flue-gas component reactions with sodium. The process also includes downstream separation and regeneration of spent media for recoating and circulation back to the gas purification device. A full-scale commercial demonstration project was under constmction in 1995. 

This is of considerable interest because of the key role of the reaction in the thermal de-NOr process involving the catalyzed reaction of ammonia with nitrogen oxides hence, in principle, the gaseous emissions from industrial plants and power stations can be purged of the... 

The main sources of harmful substances emissions, i.e., dust, SO and CO2 in the air, are the processing plants for coke, briquettes, coals, the thermal power stations, air, water, and road transport [9]. The exhaust gases contain also, CO, organic and inorganic compounds, etc. [10]. Dust, sulfur dioxide, carbon dioxide, nitrogen oxides and organic compounds, etc. are the main pollutants released in the environment from metallurgy. 

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