Seed of \( 1000 \) kg contains \( 42 \) per cent oil. Pressing leaves cake of \( 640 \) kg at \( 7 \) per cent oil. The oil recovered is
Answer: A
The seed holds \( 420 \) kg of oil and the cake retains \( 640 \times 0.07 = 44.8 \) kg, so \( 420 - 44.8 = 375 \) kg is recovered. The extraction efficiency is therefore about 89 per cent, which is typical of a well-set expeller on a high-oil seed.
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Soybean of \( 20 \) per cent oil is solvent extracted to leave meal at \( 0.6 \) per cent oil. From \( 1000 \) kg of seed the meal weighs about
Answer: B
Non-oil solids are \( 800 \) kg and they form \( 99.4 \) per cent of the meal, so the meal is \( 800/0.994 = 804.8 \) kg. Ignoring the residual oil and quoting 800 kg is the usual approximation and is very nearly right.
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Extraction efficiency is defined as oil recovered divided by oil present. With \( 420 \) kg present and \( 375 \) kg recovered it is
Answer: C
Correct answer: 89.3 per cent
Efficiency is recovered over present:
\[ \eta = \frac{375}{420} \times 100 = 89.3\% \]
The distractor 78.6 per cent comes from dividing by twice the difference, and 10.7 per cent is the fraction lost - the complement, and a useful check, since \( 89.3 + 10.7 = 100 \). A figure above 100 per cent is impossible by definition, so the fourth option can be eliminated without any arithmetic. Efficiency around 89 per cent is typical of pressing, well below the 99 per cent a solvent plant achieves.
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An oil has a free fatty acid content of \( 2.4 \) per cent as oleic acid. Neutralising \( 1000 \) kg with a 10 per cent excess of alkali requires soda equivalent to
Answer: D
Correct answer: 26.4 kg of free acid
The free acid present is 2.4 per cent of the charge:
\[ 0.024 \times 1000 = 24\ \mathrm{kg} \]
and the alkali is dosed against that figure plus a 10 per cent excess:
\[ 24 \times 1.10 = 26.4\ \mathrm{kg} \]
The excess is deliberate, ensuring the reaction goes to completion and the soap separates cleanly. It is not free: excess alkali saponifies some neutral oil as well, which is why refining loss always exceeds the acid actually removed, and why the excess is kept as small as the process will allow.
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A miscella contains \( 25 \) per cent oil by mass. To recover \( 200 \) kg of oil, the mass of miscella to be distilled is
Answer: A
Correct answer: 800 kg
The oil is a quarter of the miscella by mass, so the miscella needed is four times the oil wanted:
\[ m = \frac{200}{0.25} = 800\ \mathrm{kg} \]
The other 600 kg is solvent, which the distillation must evaporate and the condenser recover for reuse. That ratio is the reason miscella concentration matters so much to plant economics: a weaker miscella means more solvent circulated, more steam in the distillation and more cooling water, for the same oil.
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Flakes are rolled to \( 0.30 \) mm from a seed of \( 6.0 \) mm mean diameter. The reduction ratio in thickness is
Answer: B
Correct answer: 20 to 1
The ratio is the original dimension divided by the final one:
\[ \frac{6.0}{0.30} = 20 \]
so 20 to 1. The distractor 0.05 to 1 inverts it and 18 to 1 subtracts rather than divides. Such reductions are the point of flaking: a thin flake ruptures the oil-bearing cells and leaves the solvent only a very short path to diffuse in and out of, which is what makes near-complete extraction possible in a reasonable residence time.
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An oil of iodine value \( 130 \) is compared with one of \( 85 \). The first is
Answer: C
Correct answer: More unsaturated
Iodine value is the mass of iodine that adds across the double bonds, so a higher value means more of them. At 130 the first oil is markedly more unsaturated than the second at 85.
The figures identify the oils fairly closely - soybean and sunflower sit near 130, groundnut near 85 - and they predict behaviour: the more unsaturated oil stays liquid at lower temperatures but oxidises more readily and has the shorter shelf life. Free fatty acid content and wax content are measured by quite different determinations and are not implied by iodine value at all.
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Bran of \( 500 \) kg at \( 18 \) per cent oil is extracted to \( 1.0 \) per cent residual oil in the meal. The oil recovered is about
Answer: D
Solids are \( 410 \) kg and the meal weighs \( 410/0.99 = 414.1 \) kg holding \( 4.1 \) kg of oil, so \( 90 - 4.1 = 85.9 \) kg is recovered. Rice bran's oil content makes it a significant source despite the stabilisation it demands.
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A plant loses \( 1.2 \) litres of hexane per tonne of seed processed. Handling \( 300 \) tonnes a day, the daily loss is
Answer: A
Correct answer: 360 litres
The loss is a rate per tonne, so it scales with throughput:
\[ 1.2 \times 300 = 360\ \mathrm{litres\ per\ day} \]
The figure matters on three counts at once: hexane is bought and paid for, it is a fire and explosion hazard in the plant, and it is a regulated emission. Modern plants work to well under a litre per tonne, so 1.2 would prompt a survey of the desolventiser and the vent recovery system rather than being accepted as normal.
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An oil at \( 0.05 \) per cent free fatty acid rises to \( 3.5 \) per cent in storage. The increase is
Answer: B
Correct answer: 70-fold
The increase is expressed as a ratio of the two levels:
\[ \frac{3.5}{0.05} = 70 \]
The distractor 3.45-fold is the arithmetic difference mistaken for a ratio. A rise on this scale means severe hydrolysis in store - damp material, warm conditions, active lipase - and it is expensive: every point of acidity must be neutralised, and neutralisation removes neutral oil along with the acid, so refining loss rises faster than the acidity itself.
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