Emission standards particulate

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). 

Pa.rticula.te Emission Limits. Particulate emissions, including condensables, must be demonstrated during the bum to be on a dry basis less than 0.18 g/m (0.08 grain per dry standard cubic foot (gr/DSCF)) at the iaciaerator s stack, or lower depending on state regulations. 

Other Emissions. Tide 3 of the CAAA also impacts power plant particulate matter (ash) emissions. In June of 1994, the EPA actually relaxed its standards for emissions of particulate smaller than 10 micrometers (PMIO). This revision was in response to the EPA s mandate to review health-based poUution standards every dve years (12). However, it is uncertain as of this writing (1996) if states will indeed implement less stringent regulations for PMIO emissions. 

Cement plants in the United States are now carehiUy monitored for compliance with Environmental Protection Agency (EPA) standards for emissions of particulates, SO, NO, and hydrocarbons. AH plants incorporate particulate collection devices such as baghouses and electrostatic precipitators (see Air POLLUTION CONTROL methods). The particulates removed from stack emissions are called cement kiln dust (CKD). It has been shown that CKD is characterized by low concentrations of metals which leach from the CKD at levels far below regulatory limits (63,64). Environmental issues continue to be of concern as the use of waste fuel in cement kilns becomes more widespread. 

In addition, the PMio NAAQS will continue to place emphasis on quantifying and reducing particulate emissions in the less than 10- Im particle-size range. Particle size-specific emission factors have been developed for many sources, and size-specific emission standards have been developed in a number of states. These standards are addressing concerns related to HAP emissions of hea y metals, which are generaUy associated with the submicron particles. 

Explain why stringent emission standards for particulate matter based on mass/heat input will do little to improve visual air quality. 

In the past, for many air pollution control situations, a change to a less polluting fuel offered the ideal solution to the problem. If a power plant was emitting large quantities of SO2 and fly ash, conversion to natural gas was cheaper than instaUing the necessary control equipment to reduce the pollutant emissions to the permitted values. If the drier at an asphalt plant was emitting 350 mg of particulate matter per standard cubic meter of effluent when fired with heavy oil of 4% ash, it was probable that a switch to either oil of a lower ash content or natural gas would allow the operation to meet an emission standard of 250 mg per standard cubic meter. 

Effective with the 1982 model year, particulate matter from diesel vehicles was regulated by the U.S. Environmental Protection Agency for the first time, at a level of 0.37 gm km . Diesel vehicles were allowed to meet an NO level of 0.93 gm km under an Environmental Protection Agency waiver. These standards were met by a combination of control systems, primarily exhaust gas recirculation and improvements in the combustion process. For the 1985 model year, the standards decreased to 0.12 gm of particulate matter per kilometer and 0.62 gm of NO per kilometer. This required the use of much more extensive control systems (1). The Clean Air Act Amendments of 1990 (2) have kept the emission standards at the 1985 model level with one exception diesel-fueled heavy trucks shall be required to meet an NO standard of 4.0 gm per brake horsepower hour. 

Emissions monitoring is essential in controlling industrial environments and processes to ensure good air quality standards are maintained. It is also required in order that the various regulations and guidelines related to air quality are met. In addition to gaseous emissions, such as sulfur dioxide, carbon monoxide, nitrogen oxides, hydrocarbons, and many others, the emissions of particulate material and heavy metals must also be controlled. 

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 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. 

Understanding particulate emissions, their formation and control, is another key issue in meeting the new particulate emission Hmits set by the new EURO emission standards. The particulate emissions formed in diesel engines have a mass median diameter of 0.05-1.0 gm. Particle consists of carbon with various HCs adsorbed on it including polyaromatic hydrocarbon (PAH) as well as nitro-PAH compounds. 

At pulp and paper mills, air emissions from both process and combustion units are regulated under the National Ambient Air Quality Standards (NAAQS) and the State Implementation Plans (SIP) that enforce the standards. States may implement controls to limit emissions of particulate matter (PM), nitrogen oxides (NO ), volatile organic compounds (VOCs), and sulfur dioxide (S02). 

The last point is worth considering in more detail. Most hydrocarbon diffusion flames are luminous, and this luminosity is due to carbon particulates that radiate strongly at the high combustion gas temperatures. As discussed in Chapter 6, most flames appear yellow when there is particulate formation. The solid-phase particulate cloud has a very high emissivity compared to a pure gaseous system thus, soot-laden flames appreciably increase the radiant heat transfer. In fact, some systems can approach black-body conditions. Thus, when the rate of heat transfer from the combustion gases to some surface, such as a melt, is important—as is the case in certain industrial furnaces—it is beneficial to operate the system in a particular diffusion flame mode to ensure formation of carbon particles. Such particles can later be burned off with additional air to meet emission standards. But some flames are not as luminous as others. Under certain conditions the very small particles that form are oxidized in the flame front and do not create a particulate cloud. 

In commercial vehicle engines, by means of cooled exhaust gas recirculation, in-cylinder temperatures are reduced, leading to lower NOx, but mostly also to higher particulate emissions. To fulfill future emission standards, a combination of raw emission reduction and exhaust gas aftertreatment is necessary. Decreasing fuel economy with raw emission reduction has to be weighed against catalyst—and especially noble metal—price for exhaust gas aftertreatment. 

Emission studies show that lead is only a small part of the automotive pollution problem. Prior to control, hydrocarbon emissions were more than 40 times and the oxides of nitrogen emissions more than 15 times the emission of the lead compounds. Obviously, however, legislation will result in the eventual elimination of lead from gasoline. The removal of lead, besides eliminating a possible toxic pollutant, simplifies the problem of handling other automotive exhaust pollutants in that catalytic exhaust chambers perform much better in the absence of lead contaminant. All emission standards become particularly severe in 1975 and 1980. The particulate standards are equivalent to 1 gram Pb/gal in 1975 and 0.3 gram Pb/gal in 1980. Since the particulates include all solid materials, tolerable lead levels will be less than indicated above. 

Coal is not a viable option in many urban areas because of very stringent emission standards for nitrogen oxides and particulate emissions. However, coal derived liquid feuls with tailored properties could be used to meet these requirements. 

There are stringent controls over emissions of particulate matter and solvent vapours—not only must a factory be of standard sufficient to meet the relevant exposure limits (which are controlled under the Health and Safety at Work Act, 1974, and subsequent regulations) but manufacturers have a legal duty to ensure that exposure and emissions are (in the official phrase) as low as is reasonably practicable . Specific values as limits for emissions of particulates and vapours are laid down under the Environmental Protection Act, 1990. In effect this means that there must be continuing attention to the maintenance of operating standards, and to the improvement of formulations—and on the latter, paint technologists are following two main lines of advance ... 

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