PSE 200 Example Questions

In a TCF (Totally Chlorine-free) bleaching sequence, chlorine dioxide can be used as a
bleaching agent

False

What is the primary purpose of oxygen delignification in the pulp production process?

To selectively remove lignin while preserving pulp yield.

Global production of pulp sourced from non-wood biomass has decreased since 2010

True

What percentage of global pulp production in 2022 was attributed to chemical pulp?

79.6%

What are the structural differences between softwood and hardwood fibers?

Softwood are longer and have greater strength while hardwood are longer with less strength

When would you choose to use softwood/hardwood fibers? What properties do they create in paper made with them?

Softwood = Use in applications requiring high strength

Hardwood = Smoothness, Opacity, used in many specialty papers and magazine/newspaper

What are the disadvantages/benefits to using non-wood fiber sources?

Disadvantages include lack of supply chain and processing difficulties

Benefits include lower cost and easier access in certain environmentsWhat part of the tree contains the strongest/most commonly used fibers?

What part of the tree contains the strongest/most commonly used fibers?

Heartwood

Put the following terms in the order they occur in the drying and baling process: Wet end, dryer, cutter layboy, bailing

Wet end, dryer, cutter, bailing

Why would a plant choose to bale pulp rather than storing it as sheets?

So it can be cut later into specific shapes for specific purposes

Name at least three of the five main reasons why debarking is critical for woodprocessing and provide an explanation for each reason

a. Low Yield of Fiber from Bark (Only about 20% of fiber is usable per slides)
b. Potential Equipment Damage (Particulates found in bark like sand)
c. High Extractives Content (Requires more processing chemicals)
d. Drainage Obstacles (Small cells in bark can inhibit dewatering)
e. Dirty Paper (Some bark cells will not degrade, and will appear as dirt-like

What are the benefits of implementing a recovery boiler within the wood handling
process?

a. Reduces waste
b. Produces usable energy

A

Acid Wash

C

Chlorine Gas

E

Alkaline Extraction

Q

Celating Agent

Y

Dithionite

When is Oxygen Delignification used in the Bleaching process?

First Stages of the Bleaching Process

Briefly explain one reason why Oxygen Delignification is preferred over other
methods of delignification

More selective cooking to reduce Kappa number without degrading fibers

Explain the difference between TCF and ECF in the pulp bleaching process

ECF = Elemental Chlorine Free (Chlorine Dioxide can be used)

TCF = Totally Chlorine Free

List a primary and secondary goal of the pulp bleaching process

a. Primary: Bright paper product

b. Secondary: Stable brightness, Clean Pulp

What is the ideal pH of a bleaching chemical? Explain why.

The ideal pH of a bleaching chemical is alkaline (high pH). An alkaline solution is best
because alkaline conditions aid in dissolving and removing lignin

Briefly explain the floatation deinking process.

Air bubbles are injected into the pulp in a floatation cell. With the aid of certain chemicals,
the ink particles attach to the air bubbles and rise to the surface where they can be skimmed off.

Briefly explain the washing deinking process

The small ink particles are separated from the fiber suspension by the use of wires or
screens.

As the Kappa number increases the lignin content…

increases

As the pulp viscosity decreases, the degree of polymerization…

Decreases

White Liquor mainly consists of…

NaOH and Na2S