Size-frequency distribution sieving

Weber and Moran Method of Calibration—Another method of calibrating sieves consists in measuring random openings in the sieve and obtaining size-frequency distributions as qutlined in Chapter 3. The openings are measured by filar micrometer or by projection methods. Two screens are then identical if the mean size of the openings and the standard deviations are the same. Weber and Moran (1938) use the coefficient of variation... 

Calculate the calibration size (weight basis) for a sand (p = 2.64) passing a 200-mesh and retained on a 325-mesh Tyler sieve, given the following size-frequency distribution ... 

The macroporosity and pore size distribution are commonly determined by mercury porosimetry as discussed in Section 2.6. The results of such measurements are commonly displayed either as a frequency distribution showing dV jdt- plotted against pore radius a as in Figure 1.2 or as a cumulative distribution shown as versus /. Pore size distribution data for a carbon molecular sieve and for two different commercial zeolite sieves are shown in Figure 1.14. 

Particle size is one of the principal determinants of powder behavior such as packing and consolidation, flow ability, compaction, etc., and it is therefore one of the most common and important areas of powder characterization. Typically, one refers to particle size or diameter as the largest dimension of its individual particles. Because a given powder consists of particles of many sizes, it is preferable to measure and describe the entire distribution. While many methods of size determination exist, no one method is perfect (5) two very common methods are sieve analysis and laser diffraction. Sieving is a very simple and inexpensive method, but it provides data at relatively few points within a distribution and is often very operator dependent. Laser diffraction is a very rapid technique and provides a detailed description of the distribution. However, its instrumentation is relatively expensive, the analytical results are subject to the unique and proprietary algorithms of the equipment manufacturer, and they often assume particle sphericity. The particle size distribution shown in Figure 1 was obtained by laser diffraction, where the curves represent frequency and cumulative distributions. 

Having the particle size distributions of the three streams, as well as two of their flow rates. Equation 9.8 can be used to evaluate efficiency. Fractions Xp, Xq, and Xpj can be determined from a plot of equivalent sieve diameter versus cumulative frequencies of the feed, overflow, and underflow, at the cut diameter Plotting data from Table 9.1, the graph in Figure 9.3 is obtained. 

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