Nitrogen oxides from combustion processes

Nitrogen oxides from combustion processes (forklift trucks)... 

The OECD project showed that the acidification of precipitation was due to an increased content of sulphuric and nitric acid. The main cause was identified as the increased use of fossil fuels, including motor vehicle traffic. In the atmosphere, sulphur dioxide and nitrogen oxides from combustion processes are oxidized to sulphuric acid and nitric acid, which are taken up and deposited by the precipitation. 

Coal combustion for heating, as well as steel and power production, has been extensive in the United States, particularly in the north central and northeast portions of the country. Release of sulfur and nitrogen oxides from this process has resulted in a well-characterized impact downwind from the power plants in the northeastern US in the form of acid deposition (Husar etal., 1991 Shaw, 1984). Maps of sulfate (sulfuric acid) deposition show high values in parts of Ohio, West Virginia, and Pennsylvania as well as further to the northeast, into the New England states and Canada (Eilers and Selle, 1991 Shaw, 1984). The impact of acid deposition on lakes and soils is regionally detectible (Driscoll et al, 2001 Herlihy et ai, 1993) and is... 

A second important class of pollutant compounds resulting from combustion processes is the general class of the oxides of nitrogen (NO, NO2, NO3, N2O4, and so forth), typically denoted as NO . These NO molecules are key intermediates in the atmospheric conversion of VOCs into photochemical smog and ozone. There are three identified sources of NO molecules in combustion systems. 

As we have seen in earlier chapters, NO is the major form of nitrogen oxides emitted from combustion processes, but in the atmosphere it is oxidized to NOz and other oxides of nitrogen. The term NO, is used for the sum of (NO + N02). The term NOy denotes the sum of NO, N02 (i.e., NO.), plus all other oxides of nitrogen where the nitrogen is in an oxidation state of +2 or greater ... 

Emissions of nitrogen oxides and sulfur oxides from combustion systems constitute important environmental concerns. Sulfur oxides (SO ), formed from fuel-bound sulfur during oxidation, are largely unaffected by combustion reaction conditions, and need to be controlled by secondary measures. In contrast, nitrogen oxides (NO ) may be controlled by modification of the combustion process, and this fact has been an important incentive to study nitrogen chemistry. Below we briefly discuss the important mechanisms for NO formation and destruction. A more thorough treatment of nitrogen chemistry can be found in the literature (e.g., Refs. [39,138,149,274]). 

A.V. Joshi, An alternative method for the removal of oxides of nitrogen and sulfur from combustion processes. Final Report, US DOE contract DE-AC22-85PC81003,1986. 

Electrochemical sensors are also used to monitor the emissions from combustion processes. Because the oxidizer for most combustion processes is air, which contains 78% nitrogen, NO. gases are common components of the exhaust and their concentrations must be minimized [398, 399]. In addition, incomplete combustion can result in CO or hydrocarbon gaseous compounds in the exhaust gas, which both represent unconverted chemical energy and are hazardous to the environment. The use of sulfur-containing fuels can lead to the formation of SO gases [400], which have a detrimental impact on the environment, such as promoting acid rain. 

Legislation was passed in the 1970s to limit the release of sulfur and nitrogen oxides from power plants in Japan and later in Germany. This led to the investigation of new catalytic processes. Selective Catalytic Reduction (SCR) was developed to enable power companies to reduce NOX emissions from coal and oil based power plants. Since then another procedure has been developed to remove NOX from the gaseous effluent produced by several other combustion and chemical processes. 

Technological interest during these 30 years has focused on automotive air pollution and its control, on sulfur oxide pollution and its control by sulfur oxide removal from flue gases and fuel desulfurization, and on control of nitrogen oxides produced in combustion processes. 

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