The screens used in Prob. 29.1 are shaking screens with a capacity of 4 metric tons/m²-h-mm mesh size. How many square meters of screen are needed for each of the screens in Prob. 29.1 if the feed to the first screen is 100 tons/h?

Prob. 29.1

It is desired to separate a mixture of crystals into three fractions, a coarse fraction retained on an 8-mesh screen, a middle fraction passing an 8-mesh but retained on a 14-mesh screen, and a fine fraction passing a 14-mesh. Two screens in series areused, an 8-mesh and a 14-mesh, conforming to the Tyler standard, Screen analyses of feed, coarse, medium, and fine fractions are given in Table 29.5. Assuming the analyses are accurate, what do they show about the ratio by weight of each of the three fractions actually obtained?

Table 29.5

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TABLE 29.5 Screen analyses for Prob. 29.1 Screen 3/4 4/6 8/10 10/14 14/20 20/28 28/35 35/48 Total Feed 3.5 15.0 27.5 23.5 16.0 9.1 1.3 0.7 100,0 Coarse fraction 14.0 50.0 24.0 8.0 4.0 100.0 Middle fraction 4.2 35.8 30.8 18.3 10.2 0.7 100.0 Fine fraction 20.0 26.7 20.2 19.6 8.9 4.6 100.0