Emissions particulates

For other physical properties, the specification differences between diesel fuel and home-heating oil are minimal. Note only that there is no minimum distillation end point for heating oil, undoubtedly because tbe problem of particulate emissions is much less critical in domestic burners than in an engine. 

The main justification for diesel fuel desulfurization is related to particulate emissions which are subject to very strict rules. Part of the sulfur is transformed first into SO3, then into hydrated sulfuric acid on the filter designed to collect the particulates. Figure 5.21 gives an estimate of the variation of the particulate weights as a function of sulfur content of diesel fuel for heavy vehicles. The effect is greater when the test cycle contains more high temperature operating phases which favor the transformation of SO2 to SO3. This is particularly noticeable in the standard cycle used in Europe (ECE R49). 

Desulfurization will become mandatory when oxidizing catalysts are installed on the exhaust systems of diesel engines. At high temperatures this catalyst accelerates the oxidation of SO2 to SO3 and causes an increase in the weight of particulate emissions if the diesel fuel has not been desulfurized. As an illustrative example, Figure 5.22 shows that starting from a catalyst temperature of 400°C, the quantity of particulates increases very rapidly with the sulfur content. 

Influence of the sulfur content in diesel fuel on particulate emissions as a, function of the catalytic converter inlet temperature. 

Influence of hydrotreating a diesel fuel on particulate emissions. 

Diesel fuels, like gasoline, are formulated with additives that affect the process of combustion, in this case to improve the cetane number. Diesel fuels also contain detergents for irijection systems as well as compounds for improving the fuel s low tempierature rheology. Finally, decreasing particulate emissions is a problem of increasing concern, but the mechanism of action to promote this effect is not clearly understood. 

Moreover, the same surfactant structures that favor dispersion of fuel droplets in the combustion chamber most iikely play a role in reducing particulate emissions. (... 

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). 

E. Bakke, "The AppHcation of Wet Electrostatic Precipitators for Control of Eiue Particulate Matter," Preprint, Symposium on Control of Tine Particulate Emissions from Industrial Sources, Joint U.S.-USSR Working Group, Stationay Source Air Pollution ControlTechnology, San Francisco, Calif, Jan. 15—18, 1974. 

H. E. Hesketh, "Atomization and Cloud Behavior in Wet Sembbers," U.S.-USSR Symposium on Control of Fine Particulate Emissions,]an. 15—18,1974. 

Additional research for both ethanol and methanol showed that the amount of ignition improver could be reduced by systems increa sing engine compression (63). Going from 17 1 to 21 1 reduced the amount of TEGDN requited for methanol from 5% by volume to 3%. Ignition-improved methanol exhibited very low exhaust emissions compared to diesels particulate emissions were eliminated except for small amounts associated with engine oil, NO was even lower with increased compression, and CO and hydrocarbons were also below diesel levels. 

Formation of Airborne Emissions. Airborne emissions are formed from combustion of waste fuels as a function of certain physical and chemical reactions and mechanisms. In grate-fired systems, particulate emissions result from particles being swept through the furnace and boiler in the gaseous combustion products, and from incomplete oxidation of the soHd particles, with consequent char carryover. If pile burning is used, eg, the mass bum units employed for unprocessed MSW, typically only 20—25% of the unbumed soHds and inerts exit the combustion system as flyash. If spreader-stoker technologies are employed, between 75 and 90% of the unbumed soHds and inerts may exit the combustion system in the form of flyash. 

Methanol, a clean burning fuel relative to conventional industrial fuels other than natural gas, can be used advantageously in stationary turbines and boilers because of its low flame luminosity and combustion temperature. Low NO emissions and virtually no sulfur or particulate emissions have been observed (83). Methanol is also considered for dual fuel (methanol plus oil or natural gas) combustion power boilers (84) as well as to fuel gas turbines in combined methanol / electric power production plants using coal gasification (85) (see Power generation). 

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). 

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. 

These catalysts contained promoters to minimise SO2 oxidation. Second-generation systems are based on a combined oxidation catalyst and particulate trap to remove HC and CO, and to alleviate particulate emissions on a continuous basis. The next phase will be the development of advanced catalysts for NO removal under oxidising conditions. Low or 2ero sulfur diesel fuel will be an advantage in overall system development. 

In 1990, a test using scrap tires (2x2 in. I DE) to generate steam for electricity was conducted at the Elexsys plant. The I DE replaced 20% of the plant s coal. Results showed that IDE is an environmentally sound fuel. Particulate emissions were reduced by the lower ash content of IDE, volatile organic compounds (VOC) were reduced because of more efficient burning of I DE compared to coal, and carbon dioxide emissions were reduced because I DE contains half the fixed carbon found in coal. Nitrogen oxide, chlorine emissions, and metals were also reduced, and ferrous metals and dioxins were nondetectable (7). 

A considerable body of Hterature has been pubHshed on the distribution and detection methods of mbidium ia geological formations, the oceans, soils, iadustrial particulate emissions, and steUar/iatersteUar formations (2). 

Particulate emissions are controHed mainly through venting, baghouses and water scmbbers. Atmospheric zinc loss is estimated at 100 g/1 or zinc mines, mostly from handling dry ore and concentrate and wind erosion of tailing pHes. Sulfur dioxide emissions have been reduced by installing double absorption acid plants and improved containment of dilute gases. 

Heating value of the product (SRC) is ca 37 MJ/kg (16,000 Btu/lb). Sulfur contents have been reduced from 2—7% initially to 0.9% and possibly less. Ash contents have been reduced from 8—20% to 0.17% (102). These properties permit compliance with EPA requirements for SO2 and particulate emissions. The SRC is primarily intended to be used as a boiler fuel in either a soHd or molten form (heated to ca 315°C). The soHd has a Hardgrove index of 150 (103). Boiler tests have been successfully carried out using a utiHty boiler. 

EPA will closely examine particulate size distribution in particulate emission trades because finer particulates disperse more widely, remain in the air longer, and frequently are associated with more adverse health effects. 

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. 

There are four conventional types of equipment used for the control of particulate emissions ... 

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