Nitrous oxides : emissions control

Public concerns about air quality led to the passage of the Clean Air Act in 1970 to amendments to that act in 1977 and 1990. The 1990 amendments contained seven separate titles covering different regula-toiy programs and include requirements to install more advanced pollution control equipment and make other changes in industrial operations to reduce emissions of air pollutants. The 1990 amendments address sulfur dioxide emissions and acid rain deposition, nitrous oxide emissions, ground-level ozone, carbon monoxide emissions, particulate emissions, tail pipe emissions, evaporative emissions, reformulated gasoline, clean-fueled vehicles and fleets, hazardous air pollutants, solid waste incineration, and accidental chemical releases. 

Dobbie KE, Smith KA (2003) Nitrous oxide emission factors for agricultural soils in Great Britain the impact of soil water-filled pore space and other controlling variables. Glob Change Biol 9 204-218... 

Oonk, H., Kroeze, C. (1999). Nitrous oxide emissions and control. In R. A. Meyers (Ed.). Encyclopedia of Environmental Pollution and Cleanup. The Wiley, 1055-1069. 

AFG Industries, in Victorville, CA, a manufacturer of flat glass, formerly used an ammonia injection system to control nitrous oxide emissions. This system required storing anhydrous ammonia. To further reduce air emissions from glass furnaces, the company adopted a natural gas process (Pilkington 3R technology). The change eliminated a vulnerability zone of 82,000 people. 

Emissions of nitric and nitrous oxides are the result of microbial nitrification and denitrification in soils, controlled principally by soil water and mineral N contents, labile organic carbon, and temperature. Nitric oxide is a direct intermediate of both nitrification... 

Recent emission control system development in the automotive industry has been directed mainly towards the use of three-way or dual bed catalytic converters, This type of converter system not only oxidizes the hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas but will also reduce the nitrous oxides (NO ). An integral part of this type of system is the exhaust oxygen sensor which is used to provide feedback for closed loop control of the air-fuel ratio. This is necessary since this type of catalytic converter system operates efficiently only when the composition of the exhaust gas is very near the stoichiometric point. 

Often, the rates of fertilization in intensively managed agriculture are intended to satiate the needs of crop plants for these chemicals, so their productivity will not be limited by nutrient availability. However, excessive rates of fertilization have important environmental costs. These include the contamination of ground water with nitrate eutrophication of surface waters caused by nutrient inputs (especially phosphate) acidification of soil because of the nitrification of ammonium to nitrate large emissions of nitrous oxide and other nitrogen gases to the atmosphere, with implications for acid rain and Earth s greenhouse effect and the need to use herbicides to control the weeds that flourish under artificially nutrient-rich conditions. 

In the review by Armor [1] a variety of pollutants are discussed with a focus on commercially applied processes using catalysis as a solution. Issues such as the removal of NO.v, SO.v, chlorofluorohydrocarbons (CFC), VOC, carbon monoxide, auto exhaust emission, ozone, nitrous oxide, byproducts from chemicals production, odor control, and toxic gas removal are discussed. In another review Armor [2] discusses specific topics such as monolith technology, new catalytic materials, and specific processes. Additionally, key suggestions for future research effort are given. 

There are several consistent themes that run through this volume that indicate what we still need to do. One of the highest priorities is to find a more effective way to reduce major sources of acid deposition other than sulfur dioxide. This means reducing emissions of nitrous oxides and ammonia that are derived from dispersed sources (vehicles and farming activities, respectively) and so are more difficult to control. Another theme is that we need to understand and monitor the ecological effects of acid deposition in a wide range of ecosystems, and determine if there are ways to speed their recovery from decades of acid deposition. 

Emission control is of the greatest importance in energy generation, and new high-performance catalysts play a key role here. For example, new catalysts that can decompose nitrous oxides into N2 and O2 would be of interest because the use of... 

An array of many individual burner elements is used in industrial boilers, and various postflame combustion control systems, such as overfire air, staging air, re-buming systems, and selective non-catalytic reduction systems, can be employed in the post-flame zone to enhance the efficiency. Emissions of carbon monoxide, unbumt carbon, nitrous oxides, or sulfur dioxide are monitored to ensure the compliance with... 

To date, no emission regulations exist for fuel cell systems. European legislation has directives for heating systems based on natural gas or Liquified Petroleum Gas (LPG). They limit nitrous oxides (NO,) to 200 ppm and carbon monoxide to 100 ppm. However, the legislation in some EU member countries are well below these values, German emission control regulations limit NO to 80 ppm and carbon monoxide to 60 ppm. 

Elkins, J., 1990, Current Uncertainties in the Global Atmospheric N2O Budget, European Workshop on the Emission of Nitrous Oxide, Lisbon, Portugal, June 6-8, 1990. (Prom Hofmann, J. E., Johnson, R. A., Schumacher, P. D., Sload, A., Afonso, R., 1993, Post Combustion NO, Control for Coal-Fired Utility Boilers, paper presented at the 1993 Joint Symposium on Stationary Combustion NO, Control—EPRI/EPA, Bal Harbour, FL, May 24-27.)... 

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