solid mixing predicted mixture quality ; FPT Ch12 Q3

The basis for the worked solution for Question 3, Chapter 12 (available as free download at www.particles....) in Fundamentals of Particle Technology. The question asks for an analysis of mixture quality when mixing TWO solid powders together. The expected mixture quality comes from the Pool, Taylor and Wall equation which predicts the variance between samples withdrawn from an industrial mixer, at the point when the powder is randomly mixed. The cumulative particle size distribution functions (i.e. equations) are given for the two powders and the mean particle mass for each powder needs to be calculated, for use in the Pool equation. The variance between samples drawn from a mixer (i.e. variance in content of one of the components) is predicted for a fully mixed (i.e. Random) powder. From the variance the standard deviation can be calculated and the confidence in achieving the desired specification for this mixture can be assessed, using the Normal distribution. The mixer type still needs to be carefully considered, as some mixers may encourage segregation rather than mixing, the theory just tells us what should be possible (at best) in terms of a random mixture of the powder based on just the powder properties.