Surface area reference materials examples

Example 4 Calculation of Sample Weight for Surface Moisture Content An example is given with reference to material with minimal internal or pore-retained moisture such as mineral concentrates wherein physically adhering moisture is the sole consideration. With this simphfication, a moisture coefficient K is employed as miiltipher of nominal top-size particle size d taken to the third power to account for surface area. Adapting fundamental sampling theory to moisture sampling, variance is of a minimum sample quantity is expressed as... 

The as-method for surface area determination has been calibrated against certain non-porous reference materials. For example, for N2 adsorption on a non-porous hydroxylated silica, at 77 K, with aref=154m2g 1 and (nref)04 = 2387 pmol g"1, Equation (6.20) may be written as ... 

Particle-Size Analysis Methods for particle-size analysis are shown in Fig. 17-34, and examples of size-analysis methods are given in Table 17-1. More detailed information may be found in Lapple, Chem. Eng, 75(11), 140 (1968) L ple, Particle-Size Analysis, in Encyclopedia of Science and Technology, 5th ed., McGraw-Hill, New York, 1982 Cadle, The Measurement of Airborne Particles, Wiley, New York, 1975 Lowell, Introduction to Powder Surface Area, 2d ed., Wiley, New York, 1993 and Allen, Particle Size Measurement, 4th ed. Chapman and Hall, London, 1990. Particle-size distribution may be presented on either a frequency or a cumulative basis the various methods are discussed in the references just cited. The most common method presents a plot of particle size versus the cumulative weight percent of material larger or smaller than the indicated size, on logarithmic-probability graph paper. 

The two major costs associated with evaporators, as with any process equipment, are capital investment and operating costs. The best estimate of the installed cost of evaporation systems is, of course, a firm bid from a vendor. The installed cost, however, can be estimated based on the heat transfer surface area, as in Peters and Timmerhaus. Costs taken from published references must be adjusted for changes subsequent to the time of publication. To do this, one may use an index such as the Marshall and Swift allindustry index. The value of this index is published each month in Chemical Engineering, a McGraw-Hill publication. Further information on the use of this and other cost indices as well as their histories are available, for example, in Peters and Timmerhaus and Ulrich.f Variation of purchased evaporator costs with material of construction and pressure can also be found in Ulrich. ... 

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