Wood for Pulp and Paper Production

Question 1

What production is more common, sulphate or sulphite pulping?

Answer 1

Sulphate.
Production in 2022 was about 25X that of sulphite pulp

Question 2

Examples of softwood trees (long fibres)

Answer 2

Pine
Spruce
Fir
Cedar
Hemlock

Question 3

Examples of hardwood trees (short fibres)

Answer 3

Birch
Beech
Eucalyptus
Aspen
oak

Question 4

List some cellulose preparation techniques (pulping processes)

Answer 4

Groundwood
TMP/CTMP
Sulphate/Kraft process
Sulphite
Soda
Organosolv

Question 5

What is another name for the sulphate pulping process?

Answer 5

Kraft process

Question 6

What is the general structure of a tree? (3 parts)

Answer 6

1 - Crown - needles/leaves and branches, these are responsible for energy supply via photosynthesis
2 - Stem - responsible for transport
3 - Root system

Question 6

What is the scientific name for hardwoods? And list a few

Answer 6

Angiosperms
Eucalyptus. Birch. Beech. Aspen. Oaks

Question 6

What is the scientific name for softwoods? And list a few

Answer 6

Gymnosperms
Pine. Spruce. Fir. Cedar. Hemlock.

Question 7

What is the cambium of the tree?

Answer 7

The thin layer of cells between bark and inner sapwood where cell growth takes place

Question 7

How is wood produced?

Answer 7

Not directly through photosynthesis - this creates carbohydrates that aid the process though.
The tree grows though cell divisions in growth points. Then each cells goes through development phases. (enlargement, wall thickening, lignification, death)

Question 8

Draw a cross section of a tree stem. Label the parts

Answer 8

Outer bark: Protection
Inner bark: Conduction and storage
Cambium: Layer of cells where cell growth occurs
Growth ring: Early wood for conduction and latewood for strength
Heartwood – mechanical support

Question 9

What is the earlywood’s primary function? (springwood)

Answer 9

Conduction

Question 10

What is the latewood’s primary function? (Summerwood)

Answer 10

Strength

Question 11

What is the outer bark for?

Answer 11

Protection

Question 12

What is sapwood for?

Answer 12

For transporting (conduction) of sap up the stem to the leaves

Question 13

What is the function of heartwood?

Answer 13

Mechanical support

Question 14

What is a clear difference in cell structure between hardwoods and softwoods?

Answer 14

Hardwoods contain vessel cells, softwoods do not. Vessel cells are for conduction

Question 15

What are the 2 broad categories of wood cell?

Answer 15

Prosenchyma cells - long and thin with tapered edges - fibres
Parenchyma cells - rectangular short cells

Question 16

Fibre length range for softwoods?

Answer 16

2 to 6mm

Question 17

List the layers of a fibre (7)

Answer 17

Middle lamella - acts as a glue between fibres - mainly lignin
Primary wall
secondary wall - makes bulk of cell there are 3 layers to this
S1 outer layer of secondary wall
S2 main body of the fibre
S3 inner layer of the secondary wall
Lumen - central cavity of the fibre

Question 18

What are the major cell types? (3 cells) and their function

Answer 18

Trachieds/ Fibres (for support)
Ray cells (for storage or conduction)
Vessel elements (only in hardwoods for conduction)

Question 19

What are the 3 principal functions of cells and give an example of the cell

Answer 19

Support (fibres)
Conduction (vessel cells in hardwoods and ray trachieds in softwoods)
Storage (ray cells)

Question 20

What are typical cell types in hardwoods?

Answer 20

Fibres
Vessel elements
Ray and longitudinal parenchyma cells

Question 21

What is the correlation between wood density and papermaking properties?

Answer 21

A high wood density gives a slower beating response, lower tensile, burst and folding strength. But greater bulk and higher tear strength

Question 22

What is the benefit of thinner cell walls?

Answer 22

They collapse easier during sheet formation and form good inter fibre bonding surfaces

Question 23

What properties do thick cell walls give to a paper sheet?

Answer 23

More open absorbent and bulkier sheet

Question 24

What is the correlation between wood density and papermaking properties

Answer 24

High wood density means lower tensile, burst, and fold. But greater bulk and tear. We also have a slower beating response. Additionally the yield is directly related to the density.