A mill grinds locust beans from mean diameter 7 mm to .62 mm at 10 ton/hour, using 6.7 kW. At the same throughput, find power to grind to .25 mm using Rittinger’s law, in kW, to two decimals.
Rittinger’s law gives specific energy proportional to $1/d_p-1/d_f$. Throughput and material are unchanged, so $$P_2=6.7\frac{1/.25-1/7}{1/.62-1/7}=17.57962\ldots\ \mathrm{kW}.$$ Thus **17.58 kW**. All particle diameters may remain in millimetres because the length-unit factor cancels in the ratio.
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