Distributions emission from particles

In order to define the extent of emissions from automotive brakes and clutches, a study was carried out in which specially designed wear debris collectors were built for the dmm brake, the disk brake, and the clutch of a popular U.S. vehicle (1). The vehicle was driven through various test cycles to determine the extent and type of brake emissions generated under all driving conditions. Typical original equipment and aftermarket friction materials were evaluated. Brake relines were made to simulate consumer practices. The wear debris was analyzed by a combination of optical and electron microscopy to ascertain the asbestos content and its particle size distribution. It was found that more than 99.7% of the asbestos was converted to a nonfibrous form and... 

Airborne contaminant movement in the building depends upon the type of heat and contaminant sources, which can be classified as (1) buoyant (e.g., heat) sources, (2) nonbuoyant (diffusion) sources, and (d) dynamic sources.- With the first type of sources, contaminants move in the space primarily due to the heat energy as buoyant plumes over the heated surfaces. The second type of sources is characterized by cimtaminant diffusion in the room in all directions due to the concentration gradient in all directions (e.g., in the case of emission from painted surfaces). The emission rare in this case is significantly affected by the intensity of the ambient air turbulence and air velocity, dhe third type of sources is characterized by contaminant movement in the space with an air jet (e.g., linear jet over the tank with a push-pull ventilation), or particle flow (e.g., from a grinding wheel). In some cases, the above factors influencing contaminant distribution in the room are combined. 

A dust cloud comprising a distribution of particle sizes soon fractionates, e.g. visible matter settles to the ground in a few minutes. Hence the size distribution of airborne particles may differ significantly from that of the source material. (This is particularly relevant to occupational hygiene measurements involving toxic dust emissions.)... 

Whitby and Cantrell (16) report that aerosols collected near the surface of the earth are trimodal in nature. As listed in Table IV, these consist of distributions arising from (1) the irect emission of primary products from combustion having d = 0.02 un (2) coagulation of the aerosols from (1), or the c6ndensation of reaction products or water on the aerosols from (1), having = 0.16 and (3) larger particles arising from... 

As reported by Olmez and Gordon (University of Maryland), the concentration pattern of rare earth elements on fine airborne particles (less than 2.5 micrometers in diameter) is distorted from the crustal abundance pattern in areas influenced by emissions from oil-fired plants and refineries. The ratio of lanthanum (La) to samarium (Sm) is often greater than 20 (crustal ratio is less than 6). The unusual pattern apparently results from tlie distribution of rare earths in zeolite catalysts used in refining oil. Oil industry emissions have been found to perturb the rare earth pattern even in very remote locations, such as the Mauna Loa Observatory in Hawaii. 

Particulate emissions from the synthetic fuels were very low, on the order of 0.01 lb per million BTU, and approximately one order of magnitude less than particulate emissions from No. 6 fuel oil. Data on particulate morphology and submicron particle size distributions Indicate a unlmodal size distribution for the No. 6 fuel oil and the SRC-II fuels while Indicating a blmodal size distribution for the H-Coals. Burners out of service and low excess air (LEA) operation did not significantly contribute added particulate emissions although 1t did tend to shift the unlmodal distributions toward a larger number of smaller particles. 

Silicate dust in both the diffuse ISM as well as in dense protostellar envelopes has been observed to exhibit a nearly constant band profile dominated by small particles (Bouwman et al. 2001 Kemper et al. 2005). In sharp contrast, silicate bands observed in emission from protoplanetary disks exhibit a wide range of silicate band profiles, indicating a dominant presence of dust particles larger than the Rayleigh limit (Bouwman et al. 2001 van Boekel et al. 2005 Kessler-Silacci et al. 2006). The interpretation of this observation is that the characteristic size of the dust particles has grown either by a move to a shallower dust size distribution, or by the removal of smaller particles (cf. Fig. 7.1). Either way, the inference usually made is that small particles have been removed by a coagulation process not occuring in the ISM. 

Near rich limits of hydrocarbon flames, soot is sometimes produced in the flame. The carbonaceous particles—or any other solid particles— easily can be the most powerful radiators of energy from the flame. The function k(t) is difficult to compute for soot radiation for use in equation (21) because it depends on the histories of number densities and of size distributions of the particles produced for example, an approximate formula for Ip for spherical particles of radius with number density surface emissivity 6, and surface temperature is Ip = Tl nrle ns) [50]. These parameters depend on the chemical kinetics of soot production—a complicated subject. Currently it is uncertain whether any of the tabulated flammability limits are due mainly to radiant loss (since convective and diffusive phenomena will be seen below to represent more attractive alternatives), but if any of them are, then the rich limits of sooting hydrocarbon flames almost certainly can be attributed to radiant loss from soot. 

For measurement of particles and gaseous emissions the same equipment and methods were applied for the PDU as for the previously tested commercial wood chip boilers. The patterns of particle size distribution of emissions from the PDU showed similar characteristics as those from commercial boilers. The mode diameters (MD) are at sizes between 80 and 100 nm Figure 8). 

ABSTRACT The size distribution of polycyclic aromatic hydrocarbons (PAHs) on different particle size fractions in the fly ash emissions from biomass combustion have been measured by gas chromatography (GC) and mass spectrometer (MS). 

However, even with this limited data set it was possible to state that emissions from high-temperature sources are contained in particles which are in the (respirable) size range that can be trapped in the respiratory region. If the data contained in Table III and Table IV are compared for the elements that both techniques could detect (Fe and Zn), then the total atmospheric loading for Fe is 0.108 g/m by NAA and 0.098 g/m by AAS and for Zn is 0.037 g/m by NAA and 0.028 g/m by AAS. These samples were obtained on different days and yet the total loadings were comparable. However, the distribution of metals in the various particle... 

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