Ozone Levels in Central Israel

Measurements performed during the early summer months of 1988–1991 at a rural site in central Israel, some 50 km east of the highly urbanized coastal region, have shown that during the afternoon hours the area was often under the influence of ozone mixing ratios above the Israel ambient standard (117 ppbv) and occasionally even above 150 ppbv. Analysis of air mass back trajectories has shown that only those air masses passing over the Tel Aviv metropolitan area cause elevated ozone mixing ratios at the rural site. This highly urbanized region emits large amounts of precursors which are entrapped in the air parcels entering Israel under the predominantly westerly wind flows. As these air masses travel inland, sufficient time is available (3–5 h) to allow the photochemical reactions to generate ozone before reaching the rural site. The above hypothesis is further supported by the fact that parallel to the increase of ozone at the rural site, elevated carbon monoxide (up to 0.8 ppmv) and other trace gases were also observed. A significant correlation (R² > 0.8) was found to exist between the ozone mixing ratio and the NO_x concentrations in photochemically aged air masses. In several cases an excess of up to 12 ozone molecules was formed for each NO_x molecule present.     

Effects of operational parameters on emission performance and combustion efficiency in small-scale CFBCs

A well-designed CFBC can burn coal with high efficiency and within acceptable levels of gaseous emissions. In this theoretical study effects of operational parameters on combustion efficiency and the pollutants emitted have been estimated using a developed dynamic 2D (two-dimensional) model for CFBCs. Model simulations have been carried out to examine the effect of different operational parameters such as excess air and gas inlet pressure and coal particle size on bed temperature, the overall CO, NO_x and SO₂ emissions and combustion efficiency from a small-scale CFBC. It has been observed that increasing excess air ratio causes fluidized bed temperature decrease and CO emission increase. Coal particle size has more significant effect on CO emissions than the gas inlet pressure at the entrance to fluidized bed. Increasing excess air ratio leads to decreasing SO₂ and NO_x emissions. The gas inlet pressure at the entrance to fluidized bed has a more significant effect on NO_x emission than the coal particle size. Increasing excess air causes decreasing combustion efficiency. The gas inlet pressure has more pronounced effect on combustion efficiency than the coal particle size, particularly at higher excess air ratios. The developed model is also validated in terms of combustion efficiency with experimental literature data obtained from 300 kW laboratory scale test unit. The present theoretical study also confirms that CFB combustion allows clean and efficient combustion of coal.     

Numerical Study of NOx Abatement Using Ozone Injection Integrated with Wet Absorption

Nitrogen oxides emitted from power plants and the chemical industry are poisonous to humans and animals, contribute to ozone depletion, and cause acid rain. More than 90% of nitrogen oxides (NO_x) consist of nitric oxide (NO), which is insoluble in water. Among the various available techniques of NO_x abatement, ozone injection is a promising method in which NO is oxidized to higher-order nitrogen oxides (NO₃, N₂O₃, N₂O₄, and N₂O₅), which can easily be absorbed in a wet scrubber. In this article, the ozone injection process integrated with an absorber column is numerically modeled and simulated at various operating conditions. The predicted results of NO_x oxidation with ozone injection and absorption in water agree with the published experimental results. The ozone injection process is modeled using a plug flow reactor, while the wet absorption is based on a rigorous rate-based RateFrac model. Detailed kinetic mechanisms of O₃-NO_x oxidation and absorption of nitrogen oxides in water are incorporated in the model to simultaneously predict the performance efficiency of the ozone reactor and absorber column. Thermodynamic properties of the components are estimated using an Electrolyte NRTL model. The influence of performance parameters (such as feed gas flow rate, inlet gas temperature, reactor configurations, ozone concentration, and NO/NO₂ molar ratio) on the oxidation efficiency of NO_x in the reactor and absorber column is investigated to predict the optimal operating conditions.     

Emission characteristics using methyl soyate–ethanol–diesel fuel blends on a diesel engine

A blend of 20% (v/v) ethanol/methyl soyate was prepared and added to diesel fuel as an oxygenated additive at volume percent levels of 15 and 20% (denoted as BE15 and BE20). We also prepared a blend containing 20% methyl soyate in diesel fuel (denoted as B20). The fuel blends that did not have any other additive were stable for up to 3 months. Engine performance and emission characteristics of the three different fuels in a diesel engine were investigated and compared with the base diesel fuel. Observations showed that particulate matter (PM) emission decreased with increasing oxygenate content in the fuels but nitrogen oxides (NO_x) emissions increased. The diesel engine fueled by BE20 emitted significantly less PM and a lower Bosch smoke number but the highest NO_x among the fuel blends tested. All the oxygenate fuels produced moderately lower CO emissions relative to diesel fuel. The B20 blend emitted less total hydrocarbon (THC) emissions compared with base diesel fuel. This was opposite to the fuel blends containing ethanol (BE15, BE20), which produced much higher THC emission.     

Kinetic model of NOx ozonation and its experimental verification

The most of new technologies of reduction of NO_x emission, as literature survey (Skalska et al., 2010b) suggests is focused on NO_x emission control from power plants and mobile vehicles. Fewer investigations are conducted on the NO_x emission abatement from chemical industry. Recently, Chacuk et al. (2007) proposed the model for the nitrous acid oxidation with the use of ozone in gas–liquid contactor. It is well known that not all of NO_x can be totally absorbed in water or nitrous/nitric acid solution, as well as ozone is not totally consumed in the acidic liquid. The reaction between ozone and NO_x can take place also in the gas phase. The ozone injection into exhaust gas stream followed by absorption was proposed as the NO_x emission abatement. The objective of these studies was to propose kinetic model of the process and to determine the rate constants of NO_x ozonation in the laboratory scale batch reactor. The process was carried out in the 0.5 dm³ volume batch reactor for different concentrations of NO, and NO₂ and varying molar ratios of O₃/NO at temperature 25 °C. Gaseous reagents were analyzed using a Fourier Transform Infrared Spectrometer Jasco FTIR-4200. The kinetic model of NO_x ozonation process was proposed and rate constants were estimated based on experimental data.     

Impact of sulfur-in-gasoline on motor vehicle emissions in the metropolitan area of Mexico City

Light duty gasoline vehicles account for most of CO, hydrocarbons and NO_x emissions to the urban environment in Mexico City. From the beginning of year 2001, vehicles comply with Tier 1 emissions standards. Two types of Regular gasoline are available in the country. In those ozone non-attainment areas Regular oxygenated gasoline with an average of 450 ppm S is available, while on the rest of the country, a gasoline of 750 ppm S, is sold. It is anticipated then that many or all Tier 1 vehicles in ozone non-attainment zones would be occasionally or regularly fueled with high sulfur gasoline. In this work we evaluate the impact of sulfur on new, and in-use vehicles model years 1993-2001 with gasoline ranging from 90 to 815 ppm S. It is interesting to note that for Tier 0 vehicles, CO emissions are above the standard limits at all sulfur levels, while Tier 1 vehicles are very close to the limits for NO_x emissions.     

Improvement of combustion efficiency and reduction of NO x emission by external oscillation of reactants in an oil burner

The important requirement for the development of burners is the achievement of low emissions, particularly NO _x , while maintaining high combustion efficiency. In this work, an externally oscillated oil burner was developed which provides both high-efficiency combustion and low NO _x emission simultaneously. To investigate combustion characteristics and NO _x emission, parametric studies were carried out about oscillation frequency, forcing amplitude, and air velocity. Optimum combustion was achieved at frequency of 1,900 Hz, amplitude of 3 V _pp , and air velocity of 6.8 m/s. The NO _x and CO emissions were reduced by 47% and 22%, respectively. In particular, the mechanism responsible for the inherently low NO _x emission levels from an externally oscillated oil burner has been shown to be a short residence time at high temperature caused by rapid mixing with cooler residual gases.     

Prediction of NOx Emissions from a Transiently Operating Diesel Engine Using an Artificial Neural Network

For an adequate control of the reductant flow in selective catalytic reduction of NO_x in diesel exhaust, a tool has to be available to accurately and quickly predict the engine's NO_x emission. For these purposes, elaborate computer models and expensive NO_x analyzers are not feasible. The application of a neural network is proposed instead. Measurements were performed on a transient operating diesel engine. One part of the data was used to train the network for NO_x emission prediction, the other part was used to test. The average absolute deviation between the predicted and measured NO_x emission is 6.7 %. The reductant buffering capacity of the deNOx catalyst will diminish the effect of the deviation on the overall NO_x removal efficiency. The high accuracy of the neural network predictions, combined with the short computation times (0.2 ms/data point), makes the neural network a very promising tool in automotive NO_x control.     

Evaluation of an artificial neural network for NOX emission prediction from a transient diesel engine as a base for NOX control

For an adequate control of the reductant flow in selective catalytic reduction of NO_x in diesel exhaust, a tool has to be available to predict accurately and fast the engine's NO_x emission. In this article the application of a neural network is proposed. Measurements were performed on a transient diesel engine. The average absolute deviation between the measured NO_x emission and the emission predicted by the neural network is 6.7%. The high accuracy of the neural network predictions, combined with the short computation times (0.2 ms/data point), makes the neural network a very promising tool in automotive NO_x control.     

Simultaneous Removal of NOx and SOx from Flue Gas of a Glass Melting Furnace using a Combined Ozone Injection and Semi-dry Chemical Process

In this study, we propose a plasma-chemical hybrid NO_x removal process using nonthermal plasma for the treatment of flue gases emitted from glass melting furnaces; the process is demonstrated through a laboratory-scale model experiment conducted using a semi-dry desulfurization apparatus. The performance of the system for simultaneous removal of SO₂ and NO_x is investigated. As a result, NO is effectively oxidized to NO₂ by injecting ozone into the spray region and the removal efficiencies of 90% and 50% were obtained for NO and NO_x, respectively. In addition, the SO₂ removal efficiency of 84% was achieved.     

Diesel engine performance and emission evaluation using emulsified fuels stabilized by conventional and gemini surfactants

Diesel engines exhausting gaseous emission and particulate matter have long been regarded as one of the major air pollution sources, particularly in metropolitan areas, and have been a source of serious public concern for a long time. The emulsification method is not only motivated by cost reduction but is also one of the potentially effective techniques to reduce exhaust emission from diesel engines. Water/diesel (W/D) emulsified formulations are reported to reduce the emissions of NO_x, SO_x, CO and particulate matter (PM) without compensating the engine’s performance. Emulsion fuels with varying contents of water and diesel were prepared and stabilized by conventional and gemini surfactant, respectively. Surfactant’s dosage, emulsification time, stirring intensity, emulsifying temperature and mixing time have been reported. Diesel engine performance and exhaust emission was also measured and analyzed with these indigenously prepared emulsified fuels. The obtained experimental results indicate that the emulsions stabilized by gemini surfactant have much finer and better-distributed water droplets as compared to those stabilized by conventional surfactant. A comparative study involving torque, engine brake mean effective pressure (BMEP), specific fuel consumption (SFC), particulate matter (PM), NO_x and CO emissions is also reported for neat diesel and emulsified formulations. It was found that there was an insignificant reduction in engine’s efficiency but on the other hand there are significant benefits associated with the incorporation of water contents in diesel regarding environmental hazards. The biggest reduction in PM, NO_x, CO and SO_x emission was achieved by the emulsion stabilized by gemini surfactant containing 15% water contents.     

Influence of CeO2 on NOx emission during iron ore sintering

The evolution of NO_x during coke combustion in the presence and absence of CeO₂ was studied in a quartz fixed bed reactor. The distribution of CeO₂ in the coke was examined by SEM, and the effects of CeO₂ loading and CeO₂ particle size on NO_x emission were discussed. NO_x emission was also investigated by sintering pot tests with CeO₂ modified coke as sintering fuel. The results showed that CeO₂ was catalytically active in promoting not only coke combustion but also NO_x reduction. SEM examination indicated that the CeO₂ particles were well distributed on the surface and in pore canals of coke. In coke combustion experiments, NO_x and CO emission decreased with increasing CeO₂ loading up to 2.0 wt.% and decreasing CeO₂ particle size (28–150 µm), while sintering pot tests showed that NO_x emission decreased by 18.8% with 2.0 wt.% CeO₂ modified coke as sintering fuel.     

Plant Volatile Organic Compounds (VOCs) in Ozone (O<Subscript>3</Subscript>) Polluted Atmospheres: The Ecological Effects

Tropospheric ozone (O₃) is an important secondary air pollutant formed as a result of photochemical reactions between primary pollutants, such as nitrogen oxides (NO_x), and volatile organic compounds (VOCs). O₃ concentrations in the lower atmosphere (troposphere) are predicted to continue increasing as a result of anthropogenic activity, which will impact strongly on wild and cultivated plants. O₃ affects photosynthesis and induces the development of visible foliar injuries, which are the result of genetically controlled programmed cell death. It also activates many plant defense responses, including the emission of phytogenic VOCs. Plant emitted VOCs play a role in many eco-physiological functions. Besides protecting the plant from abiotic stresses (high temperatures and oxidative stress) and biotic stressors (competing plants, micro- and macroorganisms), they drive multitrophic interactions between plants, herbivores and their natural enemies e.g., predators and parasitoids as well as interactions between plants (plant-to-plant communication). In addition, VOCs have an important role in atmospheric chemistry. They are O₃ precursors, but at the same time are readily oxidized by O₃, thus resulting in a series of new compounds that include secondary organic aerosols (SOAs). Here, we review the effects of O₃ on plants and their VOC emissions. We also review the state of current knowledge on the effects of ozone on ecological interactions based on VOC signaling, and propose further research directions.     

Atmospheric ammonia and ammonium transport in Europe and critical loads: a review

The atmosphere in Europe is polluted by easily available nitrogen (ammonium and nitrate) mainly from livestock (NH₃), traffic (NO_x) and stationary combustion sources (NO_x). The nitrogen emission from various European sources decreases in the order: agriculture, road traffic, stationary sources and other mobile sources (including vehicular emissions from agriculture), with annual emissions of approximately 4.9, 2.7, 2.7 and 0.8 Mt N respectively. The emissions have increased dramatically during the latest decades. In the atmosphere the pollutants are oxidised to more water soluble compounds that are washed out by clouds and eventually brought back to the earth's surface again. Since ammonia is emitted in a highly water soluble form it will also to a substantial degree be dry deposited near the source. Ammonia is, however, the dominant basic compound in the atmosphere and will form salts with acidic gases. These salt particles can be transported long distances especially in the absence of clouds.The deposition close to the source is substantial, but hard to estimate due to interaction with other pollutants. Far from the source the deposition of ammonium is on an annual average halved approximately every 400 km. This short transport distance and the substantial deposition near the source makes it possible for countries to control their ammonium deposition by decreasing their emissions, provided that there is no country with much higher emission in the direction of the prevailing wind trajectory. When the easily available nitrogen is deposited on natural ecosystems (lakes, forests), negative effect can occur. The effect is determined by the magnitude of the deposition and the type of ecosystems (its critical load for nitrogen). In order to reduce the negative effects by controlling the emissions in a cost-efficient way it is necessary to use atmospheric transport models and critical loads.     

Combustion performance test of a new fuel DME to adapt to a gas turbine for power generation

Recently, DME (dimethyl ether, CH₃OCH₃) has attracted a great deal of attention as an alternative fuel owing to its easy transportation and cleanliness. This study was conducted to verify the combustion performance and to identify potential problems when DME is fueled to a gas turbine. Combustion tests were conducted by comparing DME with methane, which is a major component of natural gas, in terms of combustion instability, NO_x and CO emissions, and the outlet temperature of the combustion chamber. The results of the performance tests show that DME combustion is very clean but hard to control. The CO emission level of DME is lower than that of methane, while the NO_x emission level of DME is as low as that of methane. When firing DME, the pressure fluctuation in the combustion chamber caused by combustion instability is lower than that occasioned when firing methane. From the results of the outlet temperature of combustor we have ascertained that DME combustion is more likely to flash back than methane combustion and this property should be considered when operating a gas turbine and retrofitting a burner.     

Performance, emission and combustion evaluation of soapnut oil-diesel blends in a compression ignition engine

Soapnut (Sapindus mukorossi) oil, a nonedible straight vegetable oil was blended with petroleum diesel in various proportions to evaluate the performance and emission characteristics of a single cylinder direct injection constant speed diesel engine. Diesel and soapnut oil (10%, 20%, 30% and 40%) fuel blends were used to conduct short-term engine performance and emission tests at varying loads in terms of 25% load increments from no load to full loads. Tests were carried out for engine operation and engine performance parameters such as fuel consumption, brake thermal efficiency, and exhaust emissions (smoke, CO, UBHC, NO_x, and O₂) were recorded. Among the blends SNO 10 has shown a better performance with respect to BTE and BSEC. All blends have shown higher HC emissions after about 75% load. SNO 10 and SNO 20 showed lower CO emissions at full load. NO_x emission for all blends was lower and SNO 40 blend achieved a 35% reduction in NO_x emission. SNO 10% has an overall better performance with regards to both engine performance and emission characteristics.     

Nitrogen Oxides Ozonation as a Method for NOx Emission Abatement

Attempts to develop new technologies of reduction of NO_x emission are still carried out all around the world. However, most of them as literature survey suggests is focused on NO_x emission control from power plants and mobile vehicles. Fewer investigations are conducted on the NO_x emission abatement from the chemical industry. One of the relatively new approaches is the application of ozone injection into exhaust gas stream followed by an absorption process. Ozone is used to transform NO_x to higher nitrogen oxides that are more soluble in water, and therefore the higher yield of nitric acid is expected. The main objective of this article is to present results of our studies in which the effectiveness of the ozonation process, as well as the dependence of the conversion rate and the selectivities of NO ozonation into NO₂, N₂O₅ and HNO₃ on the residence time of reagents in the reactor space were studied. Results of laboratory investigations were confirmed during ozonation experiments with real exhaust gases from a nitric acid pilot plant in Fertilizers Research Institute in Pulawy, Poland.     

PCDD/PCDF emissions from co-combustion of coal and PVC in a bubbling fluidised bed boiler

This paper reports on the results obtained in the study of the co-combustion of PVC with hard coal from South Africa in a 0,5 MW_th Bubbling Fluidised Bed Boiler. The research has included the study of the effect of combustion temperature, fluidisation velocity and PVC content. The addition of urea to the raw fuel, as a dioxin-preventing compound has also been evaluated. Results have been analysed in terms of combustion efficiency, major pollutants emission (NO_x, CO), and PCDD/Fs formation in the flue gas and in the fly ash. Under the experimental conditions tested, co-combustion of coal and PVC has proved to be feasible from the combustion efficiency and emission of PCDD/Fs points of view, whose levels remained below limits set by existing legislation on persistent organic pollutants. The addition of solid urea to the fuel blend reduces the amount of chlorinated compounds emitted. However, it has a negative impact on nitrogen pollutants formation     

NOx emission from soils and its consequences for the atmosphere and biosphere: critical gaps and research directions for the future

Since the first paper on soil NO_x emissions was published in 1978, the understanding of NO_x flux from soil has grown enormously. While rapid strides have been made, progress across the suite of disciplines required to understand NO_x emission, transport, chemistry, and deposition has been uneven and has resulted in gaps in knowledge and, indeed, somewhat conflicting ideas about the regional and global importance of NO_x from soils. This paper summarizes some of the findings of the papers presented at the 1996 Tsukuba NO_x workshop and suggests gaps in knowledge that may limit estimation and management of NO_x emissions from soils. I discuss the causes and consequences of uncertainties in global estimates of soil NO_x emissions and argue for use of process simulation models for NO_x estimates. I also suggest three other missing pieces that limit our understanding of and ability to predict or manage NO_x fluxes: 1) information on canopy uptake of NO_x emitted from soils; 2) information on NO_x response to agricultural management practices and approaches for simulating those high resolution effects; and 3) information on the consequences of atmospheric transport and deposition of anthropogenic nitrogen on NO_x emissions from soils.     

Katalysatoren für den Umweltschutz

Catalysts for environmental protection. The main emitters of anthropogenic air pollution are internal combustion engines, power plants, and production processes. Components of exhaust gases which are regarded as pollutants are hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NO_x), sulfur dioxide (SO₂), and dust. Three main types of catalyst are understood to improve the environment; namely automotive emission control, NO_x abatement and oxidation. To reduce the pollutants HC, CO, and NO_x in automobile exhaust gas, three-way catalysts are currently applied. The reduction of particle emissions in diesel exhaust gas is achieved by diesel filters and oxidation catalysts. Pollutants from power plants are mainly the inorganic components NO_x and SO₂. In the SCR process, NO_x is catalytically reduced to nitrogen and water. The DESONOX process is suited for the simultaneous catalytic abatement of NO_x and SO_x. Exhaust gases from production processes in many areas require after-treatment. Therefore catalyst formulations depend on process parameters and exhaust gas components. This overview presents and explains catalyst types, design, mode of operation, and processes.