Question Bank • QB_APE_PROC_008 NAT • 2 Marks

Section 6: Agricultural Process Engineering

Processing of Agriculture Produce

Subtopic: Value addition of agriculture produce

Question Statement:

In a single-stage solid-liquid leaching process to extract oil from soybean flakes, $1000\text{ kg}$ of flakes containing $20.0\%\text{ (w/w)}$ oil and $80.0\%\text{ (w/w)}$ inert solids is mixed with $1000\text{ kg}$ of pure hexane. The underflow sludge retains $0.50\text{ kg}$ of solution per $\text{kg}$ of inert solid. Assuming complete dissolution and uniform concentration across extract and retained solution, the mass of oil extracted in the clear overflow solution in $\text{kg}$ is ________ (round off to two decimal places).

Answer Key:

133.33

Step-by-Step Solution & Explanation

Multi-Approach Solution: **Method 1: Solution Distribution Ratio** 1. Solute (oil) $A = 200\text{ kg}$. Pure hexane solvent $S = 1000\text{ kg}$. $\text{Total liquid solution} = 200 + 1000 = 1200\text{ kg}$ 2. Inert solid $B = 800\text{ kg}$. Underflow sludge retains $0.50\text{ kg solution / kg solid}$: $L_1 = \text{Solution retained in sludge} = 800 \times 0.50 = 400\text{ kg}$ 3. Clear overflow extract solution $V_1$: $V_1 = 1200 - 400 = 800\text{ kg}$ 4. Oil concentration in uniform solution: $x = \frac{200\text{ kg oil}}{1200\text{ kg solution}} = \frac{1}{6}\text{ kg oil/kg solution}$ 5. Oil in clear overflow $V_1$: $M_{\text{oil, overflow}} = V_1 \times x = 800 \times \frac{1}{6} = 133.33\text{ kg}$ **Method 2: Proportional Split** $\text{Fraction in overflow} = \frac{800}{1200} = \frac{2}{3}$ $M_{\text{oil}} = 200 \times \frac{2}{3} = 133.33\text{ kg}$
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