Standards emission

National Emission Standards for Hazardous Air Pollutants (NESITAP)... 

Once a substance is designated by EPA as a ha2ardous air pollutant (HAP), EPA has to promulgate a NESHAP (National Emission Standard for Ha2ardous Air Pollutants), designed to protect pubHc health with an ample margin of safety. 

The physical state of a pollutant is obviously important a particulate coUector cannot remove vapor. Pollutant concentration and carrier gas quantity ate necessary to estimate coUector si2e and requited efficiency and knowledge of a poUutant s chemistry may suggest alternative approaches to treatment. Emission standards may set coUection efficiency, but specific regulations do not exist for many trace emissions. In such cases emission targets must be set by dose—exposure time relationships obtained from effects on vegetation, animals, and humans. With such information, a Ust of possible treatment methods can be made (see Table 1). 

The benefits of alcohol fuels include increased energy diversification in the transportation sector, accompanied by some energy security and balance of payments benefits, and potential air quaUty improvements as a result of the reduced emissions of photochemically reactive products (see Air POLLUTION). The Clean Air Act of 1990 and emission standards set out by the State of California may serve to encourage the substantial use of alcohol fuels, unless gasoline and diesel technologies can be developed that offer comparable advantages. 

In the late 1980s attempts were made in California to shift fuel use to methanol in order to capture the air quaHty benefits of the reduced photochemical reactivity of the emissions from methanol-fueled vehicles. Proposed legislation would mandate that some fraction of the sales of each vehicle manufacturer be capable of using methanol, and that fuel suppHers ensure that methanol was used in these vehicles. The legislation became a study of the California Advisory Board on Air QuaHty and Fuels. The report of the study recommended a broader approach to fuel quaHty and fuel choice that would define environmental objectives and allow the marketplace to determine which vehicle and fuel technologies were adequate to meet environmental objectives at lowest cost and maximum value to consumers. The report directed the California ARB to develop a regulatory approach that would preserve environmental objectives by using emissions standards that reflected the best potential of the cleanest fuels. 

Table 7. Federal Light-Duty Exhaust Emission Standards...

Table 12. Federal Heavy-Duty Truck Exhaust Emission Standards, g/(kWh) ...

The future use of lead may be decided by the resolution of an environmental paradox. Some markets for lead are being phased out because of environmental concerns, eg, the use of tetraethyllead as a gasoline additive. However, a 1990 State of California law and similar laws in nine eastern U.S. states require that 2% of new cars meet 2ero-emission standards in 1998. By 2003 this requirement rises to 10% of new vehicles. Zero emission vehicles are generally accepted to mean electric, ie, battery powered cars, and there is considerable research effort to bring suitable electric vehicles to market by 1998. 

The lignitic coals of the northern United States tend to have low sulfur contents, making them attractive for boilet fuels to meet sulfur-emission standards. However, low sulfur content coals have impaired the performance of electrostatic precipitators. The ash of these coals tends to be high in alkaline earths (Ca, Mg) and alkaUes (Na, K). As a result, the ash can trap sulfur as sulfites and sulfates (see Airpollution control methods). 

Review of National Emission Standards forMercuy, EPA-450/3-84-014b, U.S. Environmental Protection Agency, Washington, D.C., 1987. 

Emission Standards. In order to have a nationwide basis for air pollution emission controls and to set a minimum emission limit, the EPA developed New Source Performance Standards (NSPS). The NSPS set specific poUutant emission limits or describe the best available control technology (BACT) that should be appUed at that source. The EPA has issued NSPS, which apply to new constmction as weU as to large modifications, for many different sources. Sources in the chemical industry include the foUowing. 

In the early 1970s, air pollution requirements led to the adoption of the double contact or double absorption process, which provides overall conversions of better than 99.7%. The double absorption process employs the principle of intermediate removal of the reaction product, ie, SO, to obtain favorable equiUbria and kinetics in later stages of the reaction. A few single absorption plants are stiU being built in some areas of the world, or where special circumstances exist, but most industriali2ed nations have emission standards that cannot be achieved without utili2ing double absorption or tad-gas scmbbers. A discussion of sulfuric acid plant air emissions, control measures, and emissions calculations can be found in Reference 98. 

U.S. Environmental Protection Ageny Report No. EPA-450/2-75-009, Environmental Protection Agency, Research Triangle Park, N.C., Oct. 1975. EPA Regulations, 40 CFR 61, Subpart F—National Emission Standard for Viayl Chloride, Aug. 27, 1993. 

To add surface area, the supports are uniformly coated with a slurry of gamma-alumina and recalcined under moderate conditions. The wash coat acts to accept the active metals, typically low levels of platinum and palladium, in a conventional impregnation process. In the United States in passenger car apphcations the spherical catalyst is used almost exclusively, and methods have been developed to replace the catalyst without removing the converter shell when vehicle inspection reveals that emission standards are not met. 

In the United States, federal regulations require automobile manufacturers to certify that vehicles are ia compliance with exhaust emission standards when tested under specific test procedures. 

Table 1. Federal Exhaust Emission Standards for Conventionally Fueled Passenger Cars and Light Trucks, g/km...

Test Procedure. To comply with emission standards, representative vehicles must be mn for 80,000 km (Appendix IV of the Eederal Test Procedure (ETP)) (3). The first 6,400 km are considered a break-in portion. Exhaust emissions are measured each 8,000 km between approximately 6,400 and 80,000 km of accumulation and a deterioration factor (DE) of emissions is calculated. A DE of 1.15 for HC indicates that HC emissions increased by 15% between 6,400 and 80,000 km, and were within the 80,000 km standard. This DE is appHed to the 6,400 km emission test data points for all other model variations of the family of vehicles represented by the 80,000 km durabiUty car. 

Catalytic oxidation systems are normally designed for destmction efficiencies that range from 90 to 98% (27). In the early 1980s, typical design requirements were for 90% or higher VOC conversions. More recently, however, an increasing number of appHcations require 95 to 98% conversions to meet the more stringent emission standards (20). 

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