Clean air

Clays, activated Clay treatment C1CH2CHC1CH20H C1CH2CHOHCH3 C1CH2CHOHCH2C1 1990 Clean Air Act Clean Air Act... 

Although the majority of molecules in cmde oils and refined products are hydrocarbons, the U.S. Clean Air Act amendment of 1990 mandated the addition of oxygenated compounds to gasoline in many parts of the United States. The requirement is usually that 2% (w/w) of the fuel be oxygen, which... 

The 1990 Clean Air Act regulates the production and use of CFCs, hydrochlorocarbons, hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbon (HFC) substitutes. CFC and halon (Class I substances) usage is to be phased out in steps until total phaseout occurs on January 1,... 

Large sources of SO2 and NO may also require additional emission reductions because of the 1990 Clean Air Act Amendments. To reduce acid... 

Since SO2 and NO2 are criteria pollutants, their emissions are regulated. In addition, for the purposes of abating acid deposition in the United States, the 1990 Clean Air Act Amendments require that nationwide SO2 and NO emissions be reduced by approximately 10 million and 2 million t/yr, respectively, by the year 2000. Reasons for these reductions are based on concerns which include acidification of lakes and streams, acidification of poorly buffered soils, and acid damage to materials. An additional major concern is that acid deposition is contributing to the die-back of forests at high elevations in the eastern United States and in Europe. 

In 1976 the United States banned the use of CFCs as aerosol propellants. No further steps were taken until 1987 when the United States and some 50 other countries adopted the Montreal Protocol, specifing a 50% reduction of fully halogenated CFCs by 1999. In 1990, an agreement was reached among 93 nations to accelerate the discontinuation of CFCs and completely eliminate production by the year 2000. The 1990 Clean Air Act Amendments contain a phaseout schedule for CFCs, halons, carbon tetrachloride, and methylchloroform. Such steps should stop the iacrease of CFCs ia the atmosphere but, because of the long lifetimes, CFCs will remain ia the atmosphere for centuries. 

There has been considerable improvement, especially in industrial areas, in U.S. air quaUty since the adoption of the Clean Air Act of 1972. Appreciable reductions in particulate emissions and in SO2 levels ate especially evident. In 1990, however, almost every metropoUtan area was in nonattainment status on o2one air quaUty standards 50 metropoUtan areas exceeded the CO standard and between 50 and 100 exceeded the PM q standard for particulate level (29). 

Cyclone Pressure Drop. Typical cyclone pressure drops range from 250 to 2000 Pa. Most data are reported for clean air flowing through the cyclone and these data are conservative for design purposes. Many investigators have unsuccessfully attempted to relate pressure drops to inlet and oudet dimension ratios. Manufacturers caUbration curves or experimental measurements on cyclones of similar dimension should be used where possible. If a rehable experimental measurement is available, however, the pressure drop at other conditions can be estimated by first evaluating the constant i in equation 17. 

Some empirical equations to predict cyclone pressure drop have been proposed (165,166). One (166) rehably predicts pressure drop under clean air flow for a cyclone having the API model dimensions. Somewhat surprisingly, pressure drop decreases with increasing dust loading. One reasonable explanation for this phenomenon is that dust particles approaching the cyclone wall break up the boundary layer film (much like spoiler knobs on an airplane wing) and reduce drag forces. 

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. 

K. Boekhaus and co-workers, "Reformulated GasoHne for Clean Air An ARCO Assessment," 2nd Biennial U.C. Davis Conf. on yiltemative Fuels (July 12, 1990). 

The Clean Air Act Amendments of 1990 limit the amount of benzene in gasoline in the United States to 1% (7). Initially there was some concern that this would dismpt the benzene supply and demand balance in the chemical industry because at that time gasoline contained benzene above 1%. If refiners had to extract all of the benzene above 1%, substantial additional benzene would be produced. However, only modest increases in the quantity of benzene produced from reformer sources is expected as most refiners can adjust the composition of reformer feed and reformer severity to produce less benzene. 

United States Congress, Public Eaw 101-549, MnMct toMmend the Clean Air Met to Provide for Attainment and Maintenance of Health Protective National Ambient Air Quality Standards, andfor Other Purposes, Nov. 15,1990. 

In the United States, the Clean Air Act of 1970 imposed limitations on composition of new fuels, and as such methanol-containing fuels were required to obtain Environmental Protection Agency (EPA) waivers. Upon enactment of the Clean Air Act Amendments of 1977, EPA set for waiver unleaded fuels containing 2 wt % maximum oxygenates excluding methanol (0.3 vol % maximum). Questions regarding methanol s influence on emissions, water separation, and fuel system components were raised (80). 

In the winter, the Clean Air Act mandates that gasoline in all areas which exceed the NAAQS for CO must contain at least 2.7% oxygen. This is based on the assumption that adding oxygen to the fuel reduces CO emissions. 

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