Suchergebnisse

This paper reviews the regulatory history for nitrogen oxides (NOx) pollutant emissions from stationary sources,primarily in coal-fired power plants. Nitrogen dioxide (NO2) is one of the six criteria pollutants regulated by the 1970 Clean Air Act where National Ambient Air Quality Standards were established to protect public health and welfare. We use patent data to show that in the cases of Japan, Germany, and the United States, innovations in NOx control technologies did not occur until stringent government regulations were in place, thus "forcing" innovation. We also demonstrate that reductions in the capital and operation and maintenance (O&M) costs of new generations of high-efficiency NOx control technologies, selective catalytic reduction (SCR), are consistently associated with the increasing adoption of the control technology: the so-called learning-by-doing phenomena. The results show that as cumulative world coal-fired SCR capacity doubles, capital costs decline to 86% and O&M costs to 58% of their original values. The observed changes in SCR technology reflect the impact of technological advance as well as other factors, such as market competition and economies of scale.

Denitrification losses of nitrogen-containing gases in the biome of boreal forests are discussed. In the soils of coniferous and deciduous forests of Western Europe, 0.57 ± 0.2 and 1.0 ± 0.2 kg N-N2O/ha/ year are lost during denitrification. In North America this figure was 0.35 ± 0.29 kg N-N2O/ha/yr for all stands. The emission of N2O from forest soils correlated with the input of nitrogen from the atmosphere withr= 0.47 in coniferous forests and withr= 0.68 in deciduous plantations, returning to the atmosphere up to 30% of the nitrogen supplied with atmospheric precipitation. With a high input of nitrogen from the atmosphere, the emission of nitrogen-containing gases reached 20 kg N /ha /yr. Of these, NO, N2O, and N2accounted for 21, 15, and 64%. Measurements of NO and especially N2emissions remain very rare, leading to incomplete estimates of denitrification losses. Denitrification remains the most complex process in the nitrogen cycle, with no definitive methods for measuring it.

A theoretical model of emission reductions is specified that accounts for voluntary and non‐voluntary behaviour regarding the adherence to the Helsinki and Sofia Protocols, which mandated emission reductions for sulphur (S) and nitrogen oxides (NOx), respectively. From this model, we derive an econometric specification for the demand for emission reductions that adjusts for the spatial dispersion of the pollutant. When tested for 25 European nations, the model performs well for sulphur cutbacks. Less satisfying results are obtained for NOx, because the model's assumption of a unitary actor at the national level is less descriptive. Collective action considerations indicate that sulphur emissions are easier to control than those of NOx.

Fuel vapors are released from storage tanks through vent pipes and from filling pumps fuel dispensary stations. These petroleum-based by-products are introduced into ambient atmospheres and neighboring areas and may become potential health risk. With aim to investigate quantity of benzene, toluene, ethylbenzene, and xylene (BTEX) and nitrogen oxides (NOx) concentrations at selected fuel dispensing stations within Kuwaiti residential areas, passive samplers were deployed within selected fuel stations and also several residential areas for one week. Findings reveal that concentration of BTEX at the filling stations were significantly elevated than it were for the breathing pipe in residential areas. In short, concentrations of benzene and NOx at both, the fuel stations and the residential areas were slightly above the permissible limit of what organization standard. Emissions escalate during weather change because meteorological variables like temperature and wind direction influence dispersion (R2 = 0.91) of noxious compounds in the ambient air. With significant additions of harmful petroleum products into Kuwaiti air, a weary for respiratory and digestive implications may be paving way to cause an ecological uproar. Hence, the government should use this baseline data and provide guidance to fuel dispensary stations for improved method of fuel dispense, improvising fuel storing to minimise temperature change for fuel state preservation and, use of nozzles that increase dispensary speeds while minimising vapour production.

With increasing legislative demands to remove nitrogen oxides (NOx) from automotive diesel exhaust, new catalyst systems are investigated and intensely studied in industry as well in academia. The most prevailing catalytic method of choice is the selective catalytic reduction (SCR) where non-toxic urea is used as a reductant for practical reasons. Usually urea is stored in a separate tank and once injected into the exhaust system it hydrolyses into the more aggressive reductant NH3 and CO2. 4 NH3 + 4 NO + O2 -> 4 N2 + 6 H2O (NH3-SCR reaction) In regions where vanadium is not banned cost effective V2O5/WO3/TiO2 NH3-SCR catalyst systems can be used. Vanadium based are well understood, but they do however not provide stability above ca. 550 °C for longer periods of time. In exhaust treatment systems where the temperature is either high or where high temperature excursions are experienced from e.g. regeneration of particulate filters, zeolite based catalysts are therefore today the most promising candidates as high-temperature stable and non-toxic catalysts for the NH3-SCR reaction. Among the most promising candidates are the Cu- and Fe-based zeolites. Usually Fe based zeolites show good performance in the temperature range 250-500 °C and reasonable stability, whereas Cu-based zeolites show good low-temperature activity in the 180-400 °C range. The presence of copper does however also lead to a lower stability of the catalyst material. Since the low-temperature activity is of paramount importance it is necessary to improve this behavior. Therefore the purpose of this project is to investigate: - The deactivation mechanism of copper based zeolites - The influence of the zeolite framework on stability and activity These investigations should mostly be carried out on model systems such as Cu-ZSM-5 and Cu-IM-5. Recently it was found that zeolite materials with the CHA-type structure show increased hydrothermal stability, most likely originating from the small 8-MR window openings in the structure. Part of the project ...

Ziel dieser Untersuchung war es, verschiedene Messgeräte und Analysentechniken zur Ermittlung der Stickoxidkonzentrationen (NOx-Konzentrationen) so zu vergleichen, wie sie zurzeit in Messstellen eingesetzt werden. Dazu wurden sie verschiedenen Prüfgaskonzentrationen ausgesetzt, die sich an den aktuellen Arbeitsplatzgrenzwerten (AGW) orientierten. Ein Nebenaspekt betraf NOx-Prüfgase aus Druckgasflaschen, um Aussagen zur Abweichung zwischen Soll- und Istwerten zu treffen. Zum Einsatz kamen mehrere Chemolumineszenz-Analysatoren, direktanzeigende Warngeräte auf Basis elektrochemischer Sensorik und elektrochemische Sensorelemente, die nicht in einem Gerät verbaut waren. Die Vergleichsmessungen fanden 2019 im Institut für Prävention und Arbeitsmedizin der Deutschen Gesetzlichen Unfallversicherung (IPA) statt. Während die Messergebnisse der Chemolumineszenz-Geräte geringe Abweichungen zeigten, ergaben sich bei den elektrochemischen Sensoren teilweise erhebliche Spannbreiten. Die Messergebnisse der Warngeräte können als orientierende Konzentrationsbestimmungen im AGW-Bereich verwendet werden. Zusätzlich wurde gezeigt, dass die gemessenen NOx-Konzentrationen der Prüfgasflaschen teilweise deutlich von den zertifizierten Werten abwichen.