NOX emission reduction

A simple explanation of why the trends are more pronounced for the stations with the highest initial episodic peak levels would be that these stations show the highest ozone responses to VOC and NOx emission reductions. Whilst this is certainly feasible, it is not a common finding in photochemical ozone modelling. Ozone responses to changing VOC and NOx emissions in photochemical models are usually illustrated as isopleth plots. Ozone isopleths are commonly seen as a set of parallel curves, see Fig. 5 for one such isopleths diagram constructed from a European photochemical trajectory model [23]. It is not at all common for the isopleths to become closer together as would be implied by the ozone responses to... 

VOC and NOx emission reductions increasing with increasing ozone levels and decreasing with decreasing ozone levels. 

Kim SW, Heckel A, McKeen SA, Frost GJ, Hsie EY, Trainer MK, Richter A, Burrows JP, Peckham SE, Grell GA (2006) Satellite-observed US power plant NOx emission reductions and their impact on air quality. Geophys Res Lett 33(L22812) 5 Kulmala M, Laaksonen A, Pirjola L (1998) Parametrization for sulphuric acid/water nucleation rates. J Geophys Res 103 8301-8307... 

The typical configuration of the model set is shown in Figure 12.1. This modelling set was used in several studies for the Polish government in which official energy or emission projections were developed. It was also used to calculate the potential and costs of CO2, SO2 or NOx emission reduction. 

Typical NOx reductions required can vary between 30 and 90%. In ozone nonattainment areas, NOx emission reductions of greater than 80% can be required. The South Coast Air Quality Management District (SCAQMD) in Southern California has regulations that are among the most stringent in the world. Similar local regulations... 

The primary purpose of the acid rain NOx emission reduction program is to reduce the adverse effects of acidic deposition on natural resources, ecosystems, visibility, materials, and public health by substantially reducing annual emissions of NOx- NOx emissions are a principal acidic deposition precursor. Although sulfate deposition is considered to be the major contributor to long-term aquatic acidification, nitric acidic deposition plays a dominant role in the "acid pulses" associated with the fish kills observed during the springtime meltdown of the snowpack in sensitive watersheds. 

Johannessen T (2010) Compact ammonia storage systems for fuelefficient NOx emissions reduction. In CTI conference on SCR Systems, Stuttgart... 

Reduced CO, SOx, and NOx emissions. Reduction of carbon monoxide emissions requires improved efficiency in the CO boilers of FCC units. SOx emissions from FCC units are being reduced by the hydrotreating of feedstocks, the use of SOx-transfer additives, and the addition of flue-gas scrubbing. At some plants, limitations on NOx may require the addition of post-combustion NOx-removal on boilers and heaters. 

NOx emissions reductions occurred as a function of cofiring, and the integration of the biomass injection system with the SOFA system. The following regression equation has been developed to describe the NOx reduction phenomenon (r = 0.87) [47,58] ... 

Chen, S. K. Yanakiev, O. (2005). Transient NOx emissions reduction using exhaust oxygen concentration based control for a diesel engine, SAE. No. 2005-01-0372. 

Table 1 NOx emissions reduction targets for existing plants over 50 MWt in the EC (Official Journal of the European Communities, 1988)...

Many GTL-derived fuels are being considered for blending with gasoline and diesel to achieve emission reductions of particulate matter (PM), carbon monoxide (CO), nitrogen compounds (NOx) and nonmethane hydrocarbons (NMHC). The most promising fuels converted from natural gas are methanol and ethers such as dimethyl ether (DME) and mcthyl-t-bntyl ether (MTBE). 

The placement of the NOx bed ahead of the oxidation bed causes a delay of the warm-up of the oxidation bed from a cold start. Since many of the materials considered for the reduction of NO are also excellent oxidation catalysts, the NOx bed is often used as the oxidation bed by the injection of secondary air during the first two minutes from a cold start. After the oxidation bed is warmed up, the secondary air is diverted from upstream of the first bed to upstream of the second bed. This procedure helps the emission reduction when the catalysts are fresh, but hastens the aging of the NOx catalyst as it is being exposed repeatedly to oxidation and reduction conditions. 

Examples of multi-disciplinary innovation can also be found in the field of environmental catalysis such as a newly developed catalyst system for exhaust emission control in lean burn automobiles. Japanese workers [17] have successfully merged the disciplines of catalysis, adsorption and process control to develop a so-called NOx-Storage-Reduction (NSR) lean burn emission control system. This NSR catalyst employs barium oxide as an adsorbent which stores NOx as a nitrate under lean burn conditions. The adsorbent is regenerated in a very short fuel rich cycle during which the released NOx is reduced to nitrogen over a conventional three-way catalyst. A process control system ensures for the correct cycle times and minimizes the effect on motor performance. 

The previous section has evidenced that NH3-SCR technology has been used successfully for more than two decades, to reduce NOx emissions from power stations fired by coal, oil and gas, from marine vessels and stationary diesel engines. NH3-SCR technology for high-duty diesel (HDD) vehicles has also been developed to the commercialization stage and is already available as an option in the series production of several European truck-manufacturing companies starting from 2001. For mobile source applications, the preferred reductant source is aqueous urea, which rapidly hydrolyses to produce ammonia in the exhaust stream. 

SCR for heavy-duty vehicles reduces NOx emissions by 80%, HC emissions by 90% and PM emissions by 40% in the EU test cycles, using current diesel fuel (<350 ppm sulphur) [27], Fleet tests with SCR technology show excellent NOx reduction performance for more than 500000 km of truck operation. This experience is based on over 6 000 000 km of accumulated commercial fleet operation [82], The combination of SCR with a pre-oxidation catalyst, a hydrolysis catalyst and an oxidation catalyst enables higher NOx reduction under low-load and low-temperature conditions [83],... 

If EuroV finally leads to a moderate reduction of the NOx emissions limit (s 20%), when regarding to US Tier 2-bin 5 levels3, we can presume that EuroVI will consist of much more stringent NOx limitation4. A NOx after-treatment system in combination with a DPF (which is mandatory since EuroV) in the exhaust line should become ordinary with EuroVI. The PM limit values will be unchanged from EuroV. 

The SCR-NH3 system consists in reducing engine-out NOx emissions with NH3 as key-reductant. 

Aromatics are typically included in gasolines to increase octane number. However, high aromatic content increases engine-out hydrocarbons and NOx emissions.16 Moreover, aromatics are the main precursors of exhaust benzene, a known carcinogenic, via dealkylation of substituted aromatics.17 Therefore, reduction of total aromatic content, together with olefin content, is an important part of California phase III reformulated gasoline specifications,18 with respect to the current allowed concentrations of benzene and total aromatics of 0.8 and 25 percent of volume, respectively. 

Calcined LDHs have been investigated as potential materials for the reduction of SOx and NOx emissions from FCCU in oil refineries [75,76]. Corma et al. found that mixed oxides obtained from a Cu/Mg/Al LDH precursor were the most effective at catalyzing both the oxidation of SO2 to S04 in the FCC regenerator and the reduction of sulfates to H2S, which may be recovered, in the reducing atmosphere of the cracking zone [76]. Calcined Cu/Mg/Al LDHs [77] and Co/Mg/Al LDHs [78], subsequently activated by heating under H2, can simultaneously remove SOx and NOx. In both cases, reduced transition metal species have been proposed as the active sites. 

Iwamoto, M. and Mizimo, N. NOx emission control in oxygen-rich exhaust through selective catalytic reduction by hydrocarbon. Proceedings - IMechE Part D, J. Automobile Eng., 1993, Volume 207, Issue Dl, 23-33. 

Weaver, E. H., and Confuorto, N. An Evaluation of Add-On Technologies for the Reduction of NOx Emissions from the Regenerator. Singapore ARTC Management, 2004. 

Several modifications in plant design and process conditions for ammonia oxidation processes have taken place in recent years. These variations are more or less based on operating pressures and temperatures, reduction of NOx emission and other environmental regulations, and the desired plant production capacity. 

In a similar vein, Kuklin and Seinfeld (1995) have shown that the predicted reductions in VOC needed to attain the federal air quality standard of 0.12 ppm for 03 in the Los Angeles area for a given level of NOx emissions can differ by almost a factor of two, depending on the initial boundary conditions assumed. 

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