A dilute aqueous slurry of viscosity 0.001 N-s/m² and density 1,000 kg/m³ is to be separated from the solid particles, which have a density of 3,000 kg/m³, by centrifugal sedimentation. Pilot-plant runs at a feed rate of 10 X10^–6 m³/s using a disc-stack centrifuge, shown in Figure 19.34, with n = 20 disks; a disk angle, u, of 45from the vertical; an outer radius R₀ = 0.075 m and an internal radius R₁ of 0.025 m; and operating at a bowl speed of 20,000 rpm, give satisfactory results. The same separation is to be carried out in a plant using a disc centrifuge with R₀ = 0.25 m and R₁ = 0.075 m, 100 disks, a disk angle of 50°, and rotating at 14,000 rpm. The sigma scale-up theory used in Example 19.10 with (19-33) applies, except that for a disc centrifuge [24],

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6 Ro Эт R1 Figure 19.34 Disc-stack centrifuge.