Sizes analysis

Given tire a size dependence of tire settling rate, sedimentation can be used for particle size analysis. Indeed, a quick... 

Panicle Size Analysis", Proc. Conf. Analytical Div. Chem. Soc. 1977 (ed. M. J. Groves), Heyden, London (1978). 

J. H. Adair, A. J. Roese, and L. G. McCoy, "Particle Size Analysis of Ceramic Powders," in K. M. Nair, ed.,Hdrances in Ceramics, Vol. 2, The American Ceramic Society, Columbus, Ohio, 1984. 

Although performance curves are valuable in assessing classifier performance, frequently the cyclone overflow size analysis is used more than the d Q of the cyclone. In practice, clusters of cyclones (in parallel) are used to handle large capacities. Cyclones are manufactured in sizes ranging from 0.01 to 1.2 m in cyclone diameter, ie, the cylindrical section at the top (2,10). Capacities mn from 75 to 23,000 L/min. Materials of constmction vary widely. Rubber-lined or aH-polyurethane cyclones are used when abrasion is a problem. 

Analysis. Excellent reviews of phosphate analysis are available (28). SoHds characterization methods such as x-ray powder diffraction (xrd) and thermal gravimetric analysis (tga) are used for the identification of individual crystalline phosphates, either alone or in mixtures. These techniques, along with elemental analysis and phosphate species deterrnination, are used to identify unknown phosphates and their mixtures. Particle size analysis, surface area, microscopy, and other standard soHds characterizations are useful in relating soHds properties to performance. SoHd-state nmr is used with increasing frequency. 

Media Si. Media are suppHed in several size grades and the grade used varies at each plant. The finer grades improve media stabiUty, but finer particles are more difficult to recover and the feed rate of these finer-grade slurries should be reduced by a factor of 0.5—0.75 to maintain magnetic recovery. A typical size analysis as used in various heavy-media separation plants treating coal (qv) is given in Table 4. 

Raw material Approximate size analysis of raw material, less than indicated )J.m (mesh) Moisture content of balled product, wt % H2O... 

Talc producers most commonly use screens for particle size analysis of coarser products (+325 mesh (ca 44 -lm)) and the Micromeritics (Georgia)... 

Size Analysis. ASTM and BS (18) provide a number of methods dealing with the size specifications and size analysis procedures including D197, D410, D311, and D431. 

Surface Area and Permeability or Porosity. Gas or solute adsorption is typicaUy used to evaluate surface area (74,75), and mercury porosimetry is used, ia coajuactioa with at least oae other particle-size analysis, eg, electron microscopy, to assess permeabUity (76). Experimental techniques and theoretical models have been developed to elucidate the nature and quantity of pores (74,77). These iaclude the kinetic approach to gas adsorptioa of Bmaauer, Emmett, and TeUer (78), known as the BET method and which is based on Langmuir s adsorption model (79), the potential theory of Polanyi (25,80) for gas adsorption, the experimental aspects of solute adsorption (25,81), and the principles of mercury porosimetry, based on the Young-Duprn expression (24,25). 

R-6. Stockham and Fochtman, Fariicle Size Analysis, Ann Arbor Science Pubs., Ann Arbor, Michigan, 1977. 

For determination of the aerodynamic diameters of particles, the most commonly apphcable methods for particle-size analysis are those based on inertia aerosol centrifuges, cyclones, and inertial impactors (Lundgren et al.. Aerosol Measurement, University of Florida, Gainesville, 1979 and Liu, Fine Paiiicles—Aerosol Generation, Measurement, Sampling, and Analysis, Academic, New York, 1976). Impactors are the most commonly used. Nevertheless, impactor measurements are subject to numerous errors [Rao and Whitby, Am. Ind. Hyg. A.s.soc.]., 38, 174 (1977) Marple and WiUeke, "Inertial Impactors, in Lundgren et al.. Aerosol Measurement and Fuchs, "Aerosol Impactors, in Shaw, Fundamentals of Aerosol Sci-... 

TABLE 17-1 Particle Size Analysis Methods and Equipment... 

Particle-Size Distribution This is defined as the relative percentage by weight of grains of each of the different size fractious represented in the sample. It is one of the most important factors in evaluating a screening operation and is best determined by a complete size analysis using testing sieves. 

Terry Alletl/ Ph D / Senior Research Associate (retired), EkiPont Central Research and Development. (Particle Size Analysis)... 

Hall, 4th ed. 1990. Barth and Sun, Patiicle Size Analysis Review, Anal. Chem., 57, 151R, 1985. Miller and Lines, Ctitical Reviews in Analytical Chemistry, 20(2), 75-116, 1988. Herdan, Small Paiiicle Statistics, Biitterworths, London. OiT and DalleVaUe, Fine Patiicle Measurement, Macmillan, New York, 2d ed., 1960. Kaye, Direct Chatactetization of Fine Patiicles, Whey, New York, 1981. Van de Hiilst, Light Scattering hy Small Patiicles, Whey, New York, 1957. 

Heywood [Heywood, Symposium on Paiticle Size Analysis, lust. Chem. Engrs. (1 7), Suppl. 25, 14] recognized that the word shape refers to two distinc t charac teiistics of a particle—form and proportion. The first defines the degree to which the particle approaches a definite form such as cube, tetr edron, or sphere, and the second by the relative proportions of the particle which distinguish one cuboid, tetrahedron, or spheroid from another in the same class. He replaced historical quahtative definitions of shape by numerical shape coefficients. 

FIG. 20-4 Equipment used in the pipet method of size analysis. 

Microscope Methods In microscope methods of size analysis, direct measurements are made on enlarged images of the particles. In the simplest technique, linear measurements of particles are made by using a cahbrated scale on top of the particle image. Alternatively, the projected areas of the particles can be compared to areas of circles. 

In the Lasentec instruments a chord-length distribution is generated, from a rotating infrared beam, and this is converted to a size distribution. Since highly concentrated systems can be interrogated this system can be used for on-hne size analysis. 

In many cases, plants simply live with these problems. However, use of modern model-based control schemes in conjunction with improved methods for on-line moisture and particle size analysis can help overcome these effects [Ennis (ed.), Powder Tech., 82 (1995) Zhang et al., Control of Paiticulate Processes TV (1995)]. 

N.G. Stanley-Wood and R.W. Lines. Particle Size Analysis. Roy. Soc. Chem. Special Publication 102 (1992) TA 418.8 P32. 

Stanley-Wood, N. G., and Lines, R. W. (eds ), "Particle Size Analysis." Royal Society of Chemistry, Cambridge, UK, 1992. 

Several separating systems are used for particulate sampling. All rely on some principle of separating the aerosol from the gas stream. Many of the actual systems use more than one type of particulate collection device in series. If a size analysis is to be made on the collected material, it must be remembered that multiple collection devices in series will collect different size fractions. Therefore, size analyses must be made at each device and mathematically combined to obtain the size of the actual particulate in the effluent stream. In any system the probe itself removes some particulate before the carrying gas reaches the first separating device, so the probe must be cleaned and the weight of material added to that collected in the remainder of the train. 

A very important analytical tool that is overlooked by many sourcetesting personnel is the microscope. Microscopic analysis of a particulate sample can tell a great deal about the type of material collected as well as its size distribution. This analysis is necessary if the sample was collected to aid in the selechon of a piece of control equipment. All of the efficiency curves for particulate control devices are based on fractional sizes. One would not try to remove a submicron-size aerosol with a cyclone collector, but unless a size analysis is made on the sampled material, one is merely guessing at the actual size range. Figure 32-8 is a photomicrograph of material collected during a source test. 

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