Emission fine particulate

To examine a sample by inductively coupled plasma mass spectrometry (ICP/MS) or inductively coupled plasma atomic-emission spectroscopy (ICP/AES) the sample must be transported into the flame of a plasma torch. Once in the flame, sample molecules are literally ripped apart to form ions of their constituent elements. These fragmentation and ionization processes are described in Chapters 6 and 14. To introduce samples into the center of the (plasma) flame, they must be transported there as gases, as finely dispersed droplets of a solution, or as fine particulate matter. The various methods of sample introduction are described here in three parts — A, B, and C Chapters 15, 16, and 17 — to cover gases, solutions (liquids), and solids. Some types of sample inlets are multipurpose and can be used with gases and liquids or with liquids and solids, but others have been designed specifically for only one kind of analysis. However, the principles governing the operation of inlet systems fall into a small number of categories. This chapter discusses specifically substances that are normally liquids at ambient temperatures. This sort of inlet is the commonest in analytical work. 

For inductively coupled plasma atomic emission spectroscopy (ICP-AES) the sample is normally in solution but may be a fine particulate solid or even a gas. If it is a solution, this is nebulized, resulting in a fine spray or aerosol, in flowing argon gas. The aerosol is introduced into a plasma torch, illustrated in Figure 3.21. 

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

Opacity reduction is the control of fine particulate matter less than 1 ixm). It can be accomplished through the application of the systems and devices discussed for control of particulate matter and by use of combustion control systems to reduce smoke and aerosol emission. In addition, operational practices such as continuous soot blowing and computerized fuel and air systems should be considered. 

Particulate emissions have their greatest impact on terrestrial ecosystems in the vicinity of emissions sources. Ecological alterations may be the result of particulate emissions that include toxic elements. Furthermore, the presence of fine particulates may cause light scattering, known as atmospheric haze, reducing visibility and adversely affecting transport safety, property values, and aesthetics. 

Precipitation Pamphlet, Western Precipitation Company C-103R-1, Los Angeles, Calif., 1952, p. 3, E. Bakke The Application of Wet Electrostatic Precipitators for Control of Fine Particulate Matter, Paper presented at Symposium on Control of Fine Particulate Emissions from Industrial Sources for the Joint U.S.-U.S.S.R. Working Group, Stationary Source Air Pollution Control Technology, San Francisco, Calif., January 15-18, 1974, pp. 6-7. 

Figure 17-46 shows such a performance curve for the collection of coal fly ash by a pilot-plant venturi scrubber (Raben "Use of Scrubbers for Control of Emissions from Power Boilers, United States-U.S.S.R. Symposium on Control of Fine-Particulate Emissions from Industrial Sources, San Francisco, 1974). The scatter in the data reflects not merely experimental errors but actual variations in the particle-size characteristics of the dust. Because the characteristics of an industrial dust vary with time, the scrubber performance curve necessarily must represent an average material, and the scatter in the data is frequently greater than is shown in Fig. 17-46. For best definition, the curve should cover as wide a range of contacting power as possible. Obtaining the data thus requires pilot-plant equipment with the flexibility to operate over a wide range of conditions. Because scrubber performance is not greatly affected by the size of the unit, it is feasible to conduct the tests with a unit handling no more than 170 m3/h (100 ftVmin) of gas.

Excerpt 4E is taken from an article in Chemical Research in Toxicology and involves the toxicity of fine particulate matter, airborne particles with effective diameters <2.5 pm (also known as PM2 5). The fine particulate was collected using a PM2 5 monitor. Ambient air is pulled through the monitor, diverting the larger particles (>2.5 pm) and capturing only the smaller ones onto a filter. Such fine particles arise from a number of sources including industrial emissions, vehicle exhaust, and forest fires and may lead to asthma, bronchitis, and possibly cancer. 

A balance between control of fugative dust emissions and sources of fine particulates is perhaps the most appropriate approach to standard attainment. 

One unit firing low-sulfur western coal and utilizing a hot precipitator is described in Table V. This unit was unable to meet particulate emissions and opacity requirements consistently due to an excessive amount of fine particulate which was not being collected. The unit load had to be controlled so that the opacity limit was not exceeded. A chemical treatment program was established and several different chemical formulations were evaluated for their ability to reduce opacity since electrical response was not deemed to be the problem. 

To do this, the paper first explained the operation of existing particulate control devices, notably the electrostatic precipitator (ESP). It described how particulate capturability can be improved by chemical treatment and then illustrated how proprietary formulation has led to the treatment of a wide variety of fuels in both cold and hot side ESP units. Evidence was also presented showing fine particulate emissions, i.e., those implicated in health effects, could be significantly reduced. A description was made of the specific marketing problems that had to be solved when a chemical company sought to develop an industrial market where the customer has little or no chemical capability. 

In an analysis of airborne coal fly ash, Natusch and co-workers (50) found that 12 elements, i.e., Pb, Tl, Sb, Cd, Se, Zn, As, Ni, Cr, S, Be, and Mn, were concentrated in the smallest diameter particles. Mercury, although not studied, was expected to follow suit because of its high volatility and probable deposition on small particles. Toca and Berry reported similar findings for lead and cadmium (5). Atmospheric vanadium (59, 60) as well as selenium, antimony, and zinc (61) arising principally from residual fuel combustion also showed a similar pattern. The health risk of this concentration phenomenon is enhanced because of the magnitude of fine particulate emissions and the ease with which these particles bypass particle collection devices, resist fallout, and readily disseminate (50). 

FIG. 17-46 Performance of pilot-plant venturi scrubber on fly ash. Liquid-to-gas ratio, gal/1000 ft O, lOj A, 15 , 20. Raben, United States-U. S. S.R. Symposium on Fine-Particulate Emissions from Industrial Sources, San Francisco, 1974.)... 

Biological, chemical, and physical effects of airborne metals are a direct function of particle size, concentration, and composition. The major parameter governing the significance of natural and anthropogenic emissions of environmentally important metals is particle size. Metals associated with fine particulates are of concern particles larger than about 3-fjim aerodynamic equivalent diameter are minimally respirable, are ineffective in atmospheric interactions, and have a short air residence time. Seventeen environmentally important metals are identified arsenic, beryllium, cadmium, chromium, copper, iron, mercury, magnesium, manganese, nickel, lead, antimony, selenium, tin, vanadium, and zinc. This report reviews the major sources of these metals with emphasis on fine particulate emissions. 

Table III. Estimates of Total and Fine Particulate Airborne Emissions from Various Sources in the United States...

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