GATE AG 2025 • Q60 NAT • 2 Marks

Section 6: Agricultural Process Engineering

Size Reduction and Material Handling

Subtopic: Mechanics and energy requirement in size reduction of agriculture produce

Question Statement:

Locust beans (avg. particle diameter 7 mm) are ground at 10 ton/h to 0.62 mm, consuming 6.7 kW. Using Rittinger's law, find the power (kW) to grind to 0.25 mm at the same rate. (Rounded to 2 decimal places)

Official Answer Key:

17.00 to 18.00

Step-by-Step Solution & Explanation

Rittinger's law: P/ṁ = Kr(1/d2 − 1/d1). From the first case: Kr = P1/(1/0.62 − 1/7) = 6.7/(1.6129−0.1429) = 6.7/1.4700 = 4.558 (kW per unit mass rate). For d2 = 0.25 mm: P2 = 4.558×(1/0.25 − 1/7) = 4.558×(4.0−0.1429) = 4.558×3.857 = 17.58 kW.

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