The volume mean diameter,, can be quantified by: The mean particle size by volume is important when dealing with topics such as material transport, storage and hindered particle settling velocities. There is special graph paper available to help determine the correct values of R and b over any size range.The modified equation to predict the % finer is:.The Rosin-Rammler model is typically used to predict the % retained.The values of k and m can be determined by linear regression: Gates-Gaudin-Schumann Model The GGS model predicts the cumulative percent passing distribution: It may be needed to perform model fits over more than 2 particle size rangers.The GGS model is generally considered more precise for fine particle size distributions.The RR model is typically satisfactory for coarse distributions.The desired particle size may not have been included in the original particle size analysis.There is a common need to determine the amount of material in the feed at a given particle size.The mean size of the material passing the 0.15mm screen can be estimated assuming the bottom size is 1 micron.95% of the feed is finer than 1mm and 20% is finer than 0.15mm.If the total feed was directed to the 0.3mm screen, 40% of the feed would be retained on the screen.There is 5% retained on the 1mm screen.The top size was estimated to be the square root of two times the top sieve size or 1.4mm.Particle Size Analysis Sieve Opening Size (mm) N = number of particles or size fractions The geometric mean is typically preferred when segregation of the particles into various fraction were achieved by passing particles through an opening having a given shape and area, e.g., screening.The arithmetic mean is most accurate for symmetric particles such as spheres or cubes.The mean particle size of a distribution is typically measured by either the arithmetic or geometric mean of the maximum (dmax) and minimum (dmin) particle sizes.Optical (Laser deflection or reflection).Particle size characterization can be determined by:.However, the majority of particles are often neither of these two shape types.Particles that are either spherical or cubical are relatively easy to characterize.Quantifying the amount of material within a given size fraction is often important for design and operational considerations.Particles within a given process stream vary in size and shape.Explain the different convention followed in measuring particle size.Differentiate between the different models used for predicting particle size.Explain the importance of particle size analysis and its application.Demonstrate understanding of various method involved in measuring particle size.After completing this lesson students should be able to:
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