Question Bank • QB_APE_EXP_093 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:

According to Bond's crushing law $W = 10 W_i \left(\frac{1}{\sqrt{d_2}} - \frac{1}{\sqrt{d_1}}\right)$, where $d$ is in $\mu\text{m}$, calculate the gross work required in $\text{kWh/tonne}$ to grind grain from $d_1 = 2500\text{ }\mu\text{m}$ to $d_2 = 100\text{ }\mu\text{m}$ if the Bond's Work Index is $W_i = 12.0\text{ kWh/tonne}$.

Answer Key:

9.6

Step-by-Step Solution & Explanation

$\frac{1}{\sqrt{d_2}} = \frac{1}{\sqrt{100}} = \frac{1}{10} = 0.10$ $\frac{1}{\sqrt{d_1}} = \frac{1}{\sqrt{2500}} = \frac{1}{50} = 0.02$ $W = 10 \times 12.0 \times (0.10 - 0.02) = 120 \times 0.08 = 9.6\text{ kWh/tonne}$
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