Pulp and Paper Industry Questions and Answers

Answer: A

Correct answer: 2 - 4 - 1 - 3

The stock arrives at about one per cent consistency and water is removed in order of increasing cost. The headbox spreads it evenly across the width, the wire drains most of the water by gravity and suction, the presses squeeze out more mechanically, and only the last few per cent is evaporated in the dryers. Evaporation is by far the most expensive route, which is why so much effort goes into the sections before it.

Answer: B

Both are true and the reason gives the economics: a small gain in press dryness translates into a large saving in steam, which is why press design receives so much attention. Shoe presses were developed for exactly this gain.

Answer: C

One part of fibre carries about one hundred and ninety-nine parts of water at the headbox and four parts at the couch, so about ninety-eight per cent has gone. Most of the water leaves in the very first section of the machine.

Answer: D

Correct answer: control penetration of water and ink

Cellulose fibres are hydrophilic, so an unsized sheet wicks liquid like blotting paper. Internal sizing adds a hydrophobic agent to the stock so that water and ink stay on the surface long enough to be controlled - which is what allows printing without feathering and writing without spreading. It does not affect brightness, thickness or lignin.

Answer: A

They scatter light and are cheaper than fibre, so both properties and economics improve up to a limit. Beyond that limit the sheet loses strength because the filler interferes with fibre bonding. Filler levels of twenty per cent are common.

Answer: B

Correct answer: 1 and 2 only

Statements 1 and 2 are correct: dissolved organics give the effluent a high biochemical oxygen demand, and lignin fragments from the bleach plant give it a dark colour that is visible far downstream. Statement 3 is wrong and would be economically absurd - black liquor is the mill’s fuel and chemical stock, and discharging it would mean buying fresh chemicals while overwhelming the treatment plant.