NOx

About: NOx is a research topic. Over the lifetime, 26367 publications have been published within this topic receiving 496555 citations.

Reducing NOx emissions from an engine by selective catalytic reduction utilizing solid reagents

Abstract: Urea or other solid NO x -reducing reagent is employed in a selective catalytic reduction process on emissions from diesel and lean-burn gasoline engines. The solid reagent is fed to a gas generator that produces a reactant gas by heating. In one embodiment the reactant gas is maintained at elevated temperatures to prevent condensation products from forming. The reactant gas contains ammonia and is fed to the exhaust on an as-needed basis.

Formation of sulfuric and nitric acid in the atmosphere during long-range transport

Abstract: A simple photochemical model has been used to simulate the formation of sulfuric and nitric acid during long-range transport through the atmosphere. Comparisons have been made with observations of sulfate and nitrate in precipitation at various distances from the source areas in northern Europe. Both observations and model calculations indicate that HNO 3 is formed at a faster rate than H 2 SO 4 and that the long-range transport of HNO 3 is thus somewhat less pronounced than that of H 2 SO4. Mainly because of the common dependence of the oxidation of SO 2 and NOx on the concentration of the OH radical, the concentration of NOx has a significant influence on the rate of formation of H 2 SO 4 : A higher emission of NOx tends to reduce the levels of OH and H 2 O 2 close to the source area thereby delaying and decreasing the transformation of SO 2 to H 2 SO 4 . Because of the interactions of the chemical species, the dependence of the concentrations on emission rates is not linear. Our model suggests that the concentrations of H 2 SO 4 at travel distances up to a few tens of hours should have increased significantly less over the last 20 years than the rates of emission of SO 2 . This also seems to be brought out by observations of sulfate in precipitation. DOI: 10.1111/j.2153-3490.1981.tb01739.x

Transient behaviour of tropospheric ozone precursors in a global 3-d ctm and their indirect greenhouse effects

Abstract: The global three-dimensional Lagrangian chemistry-transport model STOCHEM has been used to follow the changes in the tropospheric distributions of the two major radiatively-active trace gases, methane and tropospheric ozone, following the emission of pulses of the short-lived tropospheric ozone precursor species, methane, carbon monoxide, NOx and hydrogen. The radiative impacts of NOx emissionswere dependent on the location chosen for the emission pulse, whether at the surface or in the upper troposphere or whether in the northern or southern hemispheres. Global warming potentials were derived for each of the short-lived tropospheric ozone precursor species by integrating the methane and tropospheric ozone responses over a 100 year time horizon. Indirect radiative forcing due to methane and tropospheric ozone changes appear to be significant for all of the tropospheric ozone precursor species studied. Whereas the radiative forcing from methane changes is likely to be dominated by methane emissions, that from tropospheric ozone changes is controlled by all the tropospheric ozone precursor gases, particularly NOxemissions. The indirect radiative forcing impacts of tropospheric ozone changes may be large enough such that ozone precursors should be considered in the basket of trace gases through which policy-makers aim to combat global climate change.

Comparative study of diesel and biodiesel on CI engine with emphasis to emissions - a review.

Abstract: Biodiesel is a renewable, nontoxic, eco-friendly and sustainable alternative fuel for compression ignition engines. In spite of having some application problems, biodiesel, in recent times, being considered as one of the most promising alternative fuels in internal combustion engine. It has been proven that the pollutants in the vehicular emissions have significant impacts on the ecological systems and on the health of human beings. Thus there is an increasing demand on tightening the emission standards of motor vehicles, as well as an ever increasing need for developing means of reducing emissions from in service motor vehicles. Biofuel, such as alcohol and biodiesel, could partly replace petroleum fuel, reduce toxic emissions and more importantly restrain the life-cycle emission of CO. In the present paper, earlier studies have been collected and analyzed. The aim of the present study is to evaluate the feasibility of biodiesel in automobiles, with special emphasis on emission aspects. Few aspects on durability and performance are also included. Evaluation is done on both conventional and CRDI engines, though literature on the latter are few and insufficient when compared to the former. Biodiesel use, when compared to diesel as a fuel, in conventional diesel engines with little or no modification leads to the substantial reduction in particulate matter (PM), hydro carbon (HC) and carbon monoxide (CO) emissions. This is accompanied by a light power loss, increase in fuel consumption and an increase in nitrogen oxide (NOx) emission.