Exhaust emission limits

With reference to Figure 4, each piston down-stroke provides power, while each upstroke provides compression of the blower/turbo-supplied cylinder air. The actual number of degrees of both of these strokes will vary based on the specific engine make and model, and its year of manufacture needed to comply with U.S. Environmental Protection Agency (EPA) exhaust emission limits. 

EPA diesel exhaust emissions limits for 1998 on-highway diesel truck and bus engines in g/bhp-hr (grams/brake horscpowcr/hotir) when using existing... 

Table 2. Projected legislation on exhaust emission limits (g mile ) for passenger cars and light...

The diesel engine has many advantages when used as the power source in heavy transport vehicles, but a disadvantage is the emission of pollutants. As the exhaust emission limits become stricter, the need for more effective emission control systems becomes urgent. 

However, it should be noted that no information is available at present about the CEP of engines operating on unleaded gasolines or at more severe exhaust emission limits. 

TABLE 11.7. Exhaust Emission Limits for US and European Union. 

In 1957, Ethyl Corp. announced anew antiknock compound, methylcyclopentadienyknanganese tricarbonyl [12108-13-3] (MMT). MMT is almost as effective as lead on a per gram of metal basis, but because manganese was more expensive than lead, MMT was not widely used until limits were placed on the lead content of gasoline. MMT was used in unleaded fuel between 1975 and 1978. After a large fleet test suggested that MMT could increase exhaust emissions because it interfered with catalysts and oxygen sensors, EPA banned its use in unleaded fuel in 1978. MMT is used in Canada in unleaded fuel. 

RCRA incinerator regulations include adrninistrative as weU as performance standards. Administrative standards include procedures for waste analysis, inspection of equipment, monitoring, and facihty security. Steps needed to meet adrninistrative standards are outlined ia the permit apphcation performance standards are demonstrated during a trial bum. Trial bum operating conditions are included in the permit to assure ongoing compliance with the performance standards. Performance standards include destmction and removal efficiency (DRE), particulate emissions limits, products of incomplete combustion emission limits, metal emission limits, and HCl and Cl emission limits (see Exhaust CONTROL, INDUSTRIAL). 

Continuous Emissions Monitoring. A key aspect of the new CAAA is the requirement that plants prove their continued compHance to new emissions limits by installing continuous emissions monitoring systems (CEMs). The CAAA imposes new requirements for monitoring NO, SO2, and CO2 levels in a plant s exhaust gas stream. Affected plants typically must gather data from stack monitoring systems, gas analyzers, and the plant s data acquisition system and provide the data in a format approved by the EPA and state regulators. CEM systems must be in place by November 1993 for boilers affected by Phase I of the CAAA, and byjanuary 1995 for plants impacted by Phase II. 

Exhaust emissions of CO, unbumed hydrocarbons, and nitrogen oxides reflect combustion conditions rather than fuel properties. The only fuel component that degrades exhaust is sulfur the SO2 concentrations ia emissions are directly proportional to the content of bound sulfur ia the fuel. Sulfur concentrations ia fuel are determined by cmde type and desulfurization processes. Specifications for aircraft fuels impose limits of 3000 —4000 ppm total sulfur but the average is half of these values. Sulfur content ia heavier fuels is determined by legal limits on stack emissions. 

The first commercial supersonic transport, the Concorde, operates on Jet A1 kerosene but produces unacceptable noise and exhaust emissions. Moreover, it is limited in capacity to 100 passengers and to about 3000 miles in range. At supersonic speed of Mach 2, the surfaces of the aircraft are heated by ram air. These surfaces can raise the temperature of fuel held in the tanks to 80 °C. Since fuel is the coolant for airframe and engine subsystems, fuel to the engine can reach 150°C (26). An HSCT operated at Mach 3 would place much greater thermal stress on fuel. To minimize the formation of thermal oxidation deposits, it is likely that fuel deflvered to the HSCT would have to be deoxygenated. 

We have included in this volume two chapters specifically related to society s kinetic system. We have asked James Wei of the University of Delaware, recent Chairman of the consultant panel on Catalyst Systems for the National Academy of Sciences Committee on Motor Vehicle Emissions, to illustrate key problems and bridges between the catalytic science and the practical objectives of minimizing automobile exhaust emissions. We have also asked for a portrayal of the hard economic facts that constrain and guide what properties in a catalyst are useful to the catalytic practitioner. For this we have turned to Duncan S. Davies, General Manager of Research and Development, and John Dewing, Research Specialist in Heterogeneous Catalysts, both from Imperial Chemical Industries Limited. 

For similar motivations, there are limited incentives to develop an alternative SCR process for stationary sources based on methane (CH4-SCR) or other HCs, or based on NTP technologies, if not for specific, better applications. The situation is instead quite different for mobile sources, and in particular for diesel engine emissions. The catalytic removal of NO under lean conditions, e.g. when 02 during the combustion is in excess with respect to the stoichiometric one (diesel and lean-burn engines, natural gas or LPG-powered engines), is still a relevant target in catalysis research and an open problem to meet future exhaust emission regulations. 

If EuroV finally leads to a moderate reduction of the NOx emissions limit (s 20%), when regarding to US Tier 2-bin 5 levels3, we can presume that EuroVI will consist of much more stringent NOx limitation4. A NOx after-treatment system in combination with a DPF (which is mandatory since EuroV) in the exhaust line should become ordinary with EuroVI. The PM limit values will be unchanged from EuroV. 

In the EuroV context, the NO emissions limit, proposed by the European Commission at 200 mg/km, will impose for some heavy applications the implementation of a NO after-treatment system in the exhaust line. 

In summary, the NOx mass to convert (difference between engine-out NOx emissions and NOx emissions limit imposed by Diesel Euro standards) governs the requested duration for the rich conditions in the exhaust line (NOx regeneration duration), and thus dictates directly the quantity of methane released in the exhaust line. 

Ciambelli, P Corbo, P Migliardini, F. Potentialities and limitations of lean de-NOx catalysts in reducing automotive exhaust emissions, Catal. Today, 2000, Volume 59, Issues 3-4. 279-286... 

Recent developments and concern over the control of fuel exhaust emissions have led to the increased use of combustion system detergents, oxygenates and cetane improvers in fuel. Oxygenated blend components such as ethanol, methyl t-butyl ether (MTBE), ethyl t-butyl ether (ETBE), and /-amylmethyl ether (TAME) are also used to help limit the exhaust emissions from fuel. 

Pt-Rh/AROs catalysts are widely used in automotive-exhaust emission control. In these systems, Pt is generally used for the oxidation of CO and hydrocarbons and Rh is active for the reduction of nitric oxide to N2. HRTEM and AEM show two discrete particle morphologies and Pt-Rh alloy particles (Lakis et al 1995). EM studies aimed at understanding the factors leading to deactivation, surface segregation of one metal over the other and SMSI are limited. There are great opportunities for EM studies, in particular, of surface enrichment, and defects and dislocations in the complex alloy catalysts as sites for SMSI. 

Exhaust emission legislation has become more and more stringent over the last years, demanding for lower engine raw emissions and more efficient exhaust converters. Simultaneous low emission limits for different species, e.g. PM and NOx, lead to the development of combined aftertreatment systems, consisting of different catalyst technologies and particulate filter. Simulation can make a considerable contribution to shorten the time and lower the cost of the system development. In this publication, the current status of exhaust aftertreatment simulation tools used in automotive industry is reviewed. The developed models for DOC with HC adsorption, NSRC and catalyst for SCR of NOx by NH3 (urea) were included into the common simulation environment ExACT, which enables simulation of complete combined exhaust aftertreatment systems. 

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