NOx

Abstract: The present status of knowledge of the gas-phase reactions of inorganic Ox, HOx and NOx species and of selected classes of volatile organic compounds (VOCs) [alkanes, alkenes, aromatic hydrocarbons, oxygen-containing VOCs and nitrogen-containing VOCs] and their degradation products in the troposphere is discussed. There is now a good qualitative and, in a number of areas, quantitative understanding of the tropospheric chemistry of NOx and VOCs involved in the photochemical formation of ozone. During the past five years much progress has been made in elucidating the reactions of alkoxy radicals, the mechanisms of the gas-phase reactions of O3 with alkenes, and the mechanisms and products of the OH radical-initiated reactions of aromatic hydrocarbons, and further progress is expected. However, there are still areas of uncertainty which impact the ability to accurately model the formation of ozone in urban, rural and regional areas, and these include a need for: rate constants and mechanisms of the reactions of organic peroxy ( R O 2 ) radicals with NO, NO3 radicals, HO2 radicals and other R O 2 radicals; organic nitrate yields from the reactions of R O 2 radicals with NO, preferably as a function of temperature and pressure; the reaction rates of alkoxy radicals for decomposition, isomerization, and reaction with O2, especially for alkoxy radicals other than those formed from alkanes and alkenes; the detailed mechanisms of the reactions of O3 with alkenes and VOCs containing >CC

Abstract: In this article, the status of fat and oil derived diesel fuels with respect to fuel properties, engine performance, and emissions is reviewed The fuels considered are primarily the methyl esters of fatty acids derived from a variety of vegetable oils and animal fats, and referred to as biodiesel The major obstacle to widespread use of biodiesel is the high cost relative to petroleum Economics of biodiesel production are discussed, and it is concluded that the price of the feedstock fat or oil is the major factor determining biodiesel priceBiodiesel is completely miscible with petroleum diesel fuel, and is generally tested as a blend The use of biodiesel in neat or blended form has no effect on the energy based engine fuel economy The lubricity of these fuels is superior to conventional diesel, and this property is imparted to blends at levels above 20 vol% Emissions of PM can be reduced dramatically through use of biodiesel in engines that are not high lube oil emitters Emissions of NOx increase significantly for both neat and blended fuels in both two- and four-stroke engines The increase may be lower in newer, lower NOx emitting four-strokes, but additional data are needed to confirm this conclusion A discussion of available data on unregulated air toxins is presented, and it is concluded that definitive studies have yet to be performed in this area A detailed discussion of important biodiesel properties and recommendations for future research is presented Among the most important recommendations is the need for all future studies to employ biodiesel of well-known composition and purity, and to report detailed analyses The purity levels necessary for achieving adequate engine endurance, compatibility with coatings and elastomers, cold flow properties, stability, and emissions performance must be better defined

Abstract: The awareness of the increase in greenhouse gas emissions has resulted in the development of new technologies with lower emissions and technologies that can accommodate capture and sequestration of carbon dioxide. For existing coal-fired combustion plants there are two main options for CO2 capture: removal of nitrogen from flue gases or removal of nitrogen from air before combustion to obtain a gas stream ready for geo-sequestration. In oxy-fuel combustion, fuel is combusted in pure oxygen rather than air. This technology recycles flue gas back into the furnace to control temperature and makeup the volume of the missing N2 to ensure there is sufficient gas to maintain the temperature and heat flux profiles in the boiler. A further advantage of the technology revealed in pilot-scale tests is substantially reduced NOx emissions. For coal-fired combustion, the technology was suggested in the eighties, however, recent developments have led to a renewed interest in the technology. This paper provides a comprehensive review of research that has been undertaken, gives the status of the technology development and assessments providing comparisons with other power generation options, and suggests research needs.

Abstract: This paper outlines the history of air pollution in the UK, describes the types of pollutant now in the atmosphere, and discusses the relation between air pollution and health. The primary pollutants, which are directly discharged into the atmosphere, often from vehicle exhaust emissions, are: (1) sulphur dioxide (SO2); (2) nitrogen oxides (NOx); (3) smoke and particulates; (4) carbon monoxide (CO); (5) carbon dioxide (CO2); (6) organic compounds; and (7) metals, especially lead and calcium. The secondary pollutants, derived from primary pollutants, by chemical changes, include: (1) ground ozone, an important constituent of photochemical smog; and (2) acid aerosols. It is now proved beyond reasonable doubt that sufficiently high concentrations of atmospheric pollution have severe health effects. Various biological and medical methodologies can be used to evaluate their effects on health. Asthma and rhinitis are two important respiratory diseases, whose causes include air pollution. For the covering abstract see IRRD 869702.

Abstract: Biodiesel is a domestic and renewable alternative with the potential to replace some of the petrodiesel market. It is obtained from vegetable oils, animal fats, or other sources with a significant content of triacylglycerols by means of a transesterification reaction. The fatty acid profile of biodiesel thus corresponds to that of the parent oil or fat and is a major factor influencing fuel properties. Besides being renewable and of domestic origin, advantages of biodiesel compared to petrodiesel include biodegradability, higher flash point, reduction of most regulated exhaust emissions, miscibility in all ratios with petrodiesel, compatibility with the existing fuel distribution infrastructure, and inherent lubricity. Technical problems with biodiesel include oxidative stability, cold flow, and increased NOx exhaust emissions. Solutions to one of these problems often entail increasing the problematic behavior of another property and have included the use of additives or modifying the fatty acid compositi...