Subtopic: Drying and milling of cereals, pulses and oilseeds
Question Statement:
Mustard seeds containing $35\%$ oil and $65\%$ oil-free solid residue are crushed in a continuous mechanical expeller. The resulting oil cake contains $7\%$ residual oil. Assuming no loss of oil-free dry solids during crushing, the mass of oil extracted from $1000\text{ kg}$ of mustard seed in $\text{kg}$ is ________ (round off to 1 decimal place).
Answer Key:
301.1
Step-by-Step Solution & Explanation
1. Oil-free dry solid residue in feed:
$S = 1000 \times (1 - 0.35) = 650\text{ kg}$
2. The oil cake contains $7\%$ oil, so $93\%$ is solid residue. Mass of cake produced $W_{cake}$:
$W_{cake} = \frac{S}{1 - 0.07} = \frac{650}{0.93} = 698.925\text{ kg}$
3. Mass of oil remaining in cake:
$O_{cake} = 698.925 \times 0.07 = 48.925\text{ kg}$
4. Initial oil in feed:
$O_{feed} = 1000 \times 0.35 = 350.0\text{ kg}$
5. Mass of oil extracted:
$O_{ext} = 350.0 - 48.925 = 301.075\text{ kg} \approx 301.1\text{ kg}$