Agro Processing Plant Design Questions and Answers

Answer: C

Correct answer: Land, buildings and equipment

Fixed capital is what is spent once to create the plant: land, buildings, equipment, installation, piping, instrumentation and engineering. Raw material, wages and utilities are recurring operating costs, and interest is a financing charge.

Answer: D

Correct answer: Stocks, work in progress and receivables

Working capital is the money tied up in running the plant: raw material stocks, work in progress, finished goods, receivables and cash, less what is owed to suppliers. It is recovered at the end of the project rather than depreciated - and in a seasonal plant it is unusually large, since a year’s raw material may have to be bought in one season.

Answer: A

Correct answer: Total revenue equals total cost

At breakeven the plant makes neither profit nor loss:

The denominator is the contribution per tonne - what each tonne contributes towards the fixed costs once its own variable cost has been met.

Answer: B

Correct answer: Time for cumulative inflow to equal the outlay

The payback period is how long the investment takes to return its own cost:

It is simple and widely used as a first screen, but it ignores everything after the payback point and takes no account of the time value of money.

Answer: C

Correct answer: A high biochemical oxygen demand

Fruit and vegetable effluent carries sugars, starches, pulp and washings - all readily biodegradable - so its BOD is high, often several thousand mg/l. That makes biological treatment the natural choice, and it also makes the effluent a candidate for anaerobic digestion, since the organic load is an energy source.

Answer: D

Correct answer: Steam, electricity, water, air, refrigeration

A processing plant needs the whole set: steam for blanching, cooking and sterilising; electricity for drives; water for washing and cooling; compressed air for controls and pneumatics; and refrigeration for chilling and cold storage. Each has to be sized, and each is a running cost.

Answer: A

Correct answer: Consumers do not all peak together

The diversity factor recognises that the sum of individual peak demands overstates the real maximum, because the consumers do not all peak at the same instant. Sizing a boiler or a transformer on the simple sum would mean paying for capacity that is never used at once.

Answer: B

Correct answer: Delivered equipment cost times a factor

The Lang factor method estimates fixed capital as

with \(f_L\) around 3 for a solids plant, 4 to 5 for a mixed one and above 5 for a fluid processing plant. The factor covers installation, piping, instrumentation, buildings and engineering - everything the equipment alone does not.

Answer: C

Correct answer: Scale a plant cost to another capacity

The six-tenths rule scales cost with capacity:

The exponent below one is the economy of scale: a vessel’s cost follows its surface area while its capacity follows its volume, so doubling the throughput costs about 52 per cent more, not 100.

Answer: D

Correct answer: Test the process at intermediate scale

A pilot plant tests at a scale between the laboratory and the works, where the problems of continuous operation, heat transfer, handling and fouling first appear. It is far cheaper to discover them there than in a full-scale plant, and the data it gives is what makes a confident scale-up possible.