NOX pollution

Hydrodenitrogenation (HDN) is an important process in petroleum refining. It removes nitrogen from oil distillates, so that less NOx pollutes the air when oil is burned and poisoning of the subsequent refining catalysts is reduced when the oil is processed further. Although HDN has been studied intensively and different reaction mechanisms, catalytic active sites, and functions of the catalytic components have been proposed, there are stiU many questions to be answered in order to better mderstand the reaction and the catalyst (1-4). 

Power boilers at pulp and paper mills are sources of particulate emissions, S02, and NOx. Pollutants emitted from chemical recovery boilers include S02 and total reduced sulfur compounds (TRS). 

The American 1970 Clean Air Act defined ambient air quality standards (NAAQS) in the United States for atmospheric ozone, NO, lead, carbon monoxide, sulfur oxides, and PM-10 (particulate matter less than 10 p.m). The strategy to reduce levels of lead, NOx, PM-10, and to some extent carbon monoxide was to control emissions from automobiles that included the phasing-out of leaded fuel. As previously noted, ozone is a product of the photochemical reaction of volatile organic compounds with NOx (photochemical smog), so the balance between organic compounds and NOx pollutants is important in meeting target ozone levels (e.g., 0.12 ppm). Emissions from stationary sources is an important factor, and limits have been set for them. Because of low pressure drop requirements, coated monolithic catalysts... 

Supported copper-based catalysts are active for a great variety of reactions and there have been many fundamental studies of their catalytic and solid state properties. Among them, the oxidation of hydrocarbons and CO (1), alkanes (2) and alcohols (3) dehydrogenation, hydrogenation of ketones (4), allyl alcohols and a- and 6-unsaturated aldehydes and ketones (5), alcohol amination (6), low temperature water gas shift (7). methanol synthesis (8), oxidative condensation of methanol (9), hydrolysis of acrylonitrile to acrylamide (10), and removal of NOx pollutants (11). 

The transformation of NO and NO2 as main components of NOx pollution in exhaust gases, and N2O as stable intermediate in these reactions were investigated over the Cu- and Fe-con-taining ZSM-5 zeolite catalysts. 

Soderlund. R 1977 NOx pollutants and ammonia emissions-A mass balance for the atmosphere over NW Europe. Amhio 6, 118-122. 

Miyake, 1939). Several instances of rainwater pH values less than 3 were observed in the 1970s (Hashimoto, 1989 Hara, 1993). The incidence of acid rain seems to have declined in Japan due to the control of SO2 and NOx pollution (Hashimoto, 1989). 

Environmental Problems NOx Pollution and How to Remove NOx Using NP Catalysis... 

Oxygen enrichment (25-80% oxygen) in the air stream increases the O-ion availability and therefore worsens the NOx pollution, but oxy-fuel firing (96-100% oxygen as the air stream) practically eliminates the N-ions therefore, it is a good method of NOx control. 

The cost of NOx pollution abatement depends on the efficiency of the original absorption system estimated costs for a 365-tpd nitric acid unit are given in Table 19.4 [191. 

For salable byproduct processes, byproduct characteristics and purity are significant considerations. For disposable byproduct processes, the avaUabili oiF disposal sites, byproduct structural properties, and the landfill leachate properties are important factors. Hie need, or the potential need, to remove NOx and other pollutants should also be considoced in the selection process. Some processes have the capabili to remove NOx pollutants or... 

A high pressure level results in a higher energy requirement with possibly higher utility eosts. On the other hand, today s striet environmental pollution laws with regard to NOx diseharged into the atmosphere are easier to meet at higher pressures, and oxidation of NO to NO2 is favored by inereased pressure and low temperature. 

Catalytic combustion is a process in which a combustible compound and oxygen react on the surface of a catalyst, leading to complete oxidation of the compound. This process takes place without a flame and at much lower temperatures than those associated with conventional flame combustion. Due partly to the lower operating temperature, catalytic combustion produces lower emissions of nitrogen oxides (NOx) than conventional combustion. Catalytic combustion is now widely used to remove pollutants from... 

In April of 1998, the EPA published a final rule for emission of oxides of nitrogen (NOx), hydrocarbons (EIC), carbon monoxide (CO), particulate matter (PM), and smoke opacity for newly manufactured and rcmanufacturcd locomotives. The rulemaking took effect in 2000 and is estimated by the EPA to cost the railroads 80 million per year—about 163 per ton of NOx reduced, according to EPA figures. The emissions standards for the several pollutants will be implemented in three tiers—for locomotives... 

The most common air-pollution descriptor is the expression smoke . For the purposes of the 1956 and 1968 Acts, smoke includes soot, ash, grit and gritty particles emitted in smoke. Smoke is intended to mean the visible products of combustion and not the invisible ones (CO2, SO2, NOx, etc.) and is used to indicate the degree of completeness of combustion (if combustion is 100 per cent smoke is produced). 

The main pollutants in Diesel exhausts are NOx and particulate matter (PM), mostly soot, with lesser amounts of CO and light hydrocarbons (CH). Table 12.1 shows the corresponding emission standards in Europe and in the USA. These standards are becoming progressively stricter and Table 12.2 shows the needed conversion efficiency of the electrochemically promoted unit in order to meet the EUR04 2005 standards. 

Nitrogen forms several oxides, with oxidation numbers ranging from - -l to +5. All nitrogen oxides are acidic oxides and some are the acid anhydrides of the nitrogen oxoacids (Table 15.2). In atmospheric chemistry, where the oxides play an important two-edged role in both maintaining and polluting the atmosphere, the) are referred to collectively as NO (read nox ). 

Nitrogen Dioxide (NO2) Is a major pollutant originating from natural and man-made sources. It has been estimated that a total of about 150 million tons of NOx are emitted to the atmosphere each year, of which about 50% results from man-made sources (21). In urban areas, man-made emissions dominate, producing elevated ambient levels. Worldwide, fossil-fuel combustion accounts for about 75% of man-made NOx emissions, which Is divided equally between stationary sources, such as power plants, and mobile sources. These high temperature combustion processes emit the primary pollutant nitric oxide (NO), which Is subsequently transformed to the secondary pollutant NO2 through photochemical oxidation. 

Estimates of urban NOx emissions and trends are generally limited to those provided by the developed countries which have the detailed emission Inventories. As In the case of other pollutants, the USA contributes the most on a per-country basis to the global NOx emissions per year. Because of the Inaccuracy of the data base used. It Is difficult to discern trends In these emissions. However, with new control technologies being Implemented for both stationary and mobile sources, downward trends In the developed countries may be more prevalent In the future years. Unfortunately, the opposite trend Is likely to occur In the developing countries. 

FCC units, and in particular the catalyst regenerating section, may give rise to significant pollution. Sulfur in the coke oxidizes to SO2 and SO3, while the combustion also generates NOx compounds. In addition, the flue gas from the regenerator contains particulate matter from the catalyst. The FCC process is also the major source of sulfur in gasoline. Of all the sulfur in the feed, approximately 50% ends up as H2S in the light gas-LPG fraction, 43% in the liquid products and 7% in the coke on the spent catalysts. 

In the area of pollution control, file removal of NOx from stationary sources effluents, such as power plant stack gases, has been accomplished by use of titania-vanadia catal)rsts, which promote the reduction of NOx with NH3 to produce nitrogen and water. 

NCP National Oil and Hazardous Substances Pollution Contingency Plan NESHAP National Emission Standards for Hazardous Air Pollutants NOX Nitrogen oxides... 

The removal of a wide variety of pollutants by means of non-thermal plasma has been reported aliphatic hydrocarbons [1-3], aromatics [4-7], chlorinated hydrocarbons [4,8-10], as well as inorganic contaminants such as S02, H2S [11,12] and NOx, which will be discussed in detail in this chapter. 

Photocatalytic oxidation can be an effective way of removing pollutants in the gas phase, such as NOx, SOx, and volatile organic compounds (VOCs). 

S02 and NOx in flue gas from coal combustion contribute to smog and acid rain. Methods to remove these pollutants include alkaline wet scrubber systems that fix S02 to solid CaS04, and selective catalytic reduction by metal/metal oxide systems of NO/NOz to N2 and steam in the presence of ammonia. Particulate active carbons have also been used in flue gas decontamination, especially as they avoid costly scrubber processes and can operate at lower temperatures. The potential of active carbon fibers in this application has been explored by a... 

As member states of the European Union have been releasing new regulations to protect the environment by reducing pollutant emissions, the heating equipment industry as well as their customers is well aware of the need for a new sensor-con-trolled burner concept. The answer is continuous innovation in small burner technology. Burners with radiant surfaces, for example, reduce temperatures in the reaction zone of the flame, which in turn, reduces NOx emissions. Most modern furnaces use fully premixed burners. The stabilisation of the flame becomes more difficult, because a rise of the fluid flow yields a decrease of the burning velocity. 

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