1. Pulp and Paper Making in South Africa

2. Raw Materials Derived from Renewable Resources

7. Pulping Processes Chemical Pulping Mechanical Pulping
Chemo-Mechanical or Semi Chemical
Waste Repulping

8. Mechanical Pulping Mechanical action breaks the ML which is more
brittle than the fibre wall.
The fibre wall is left intact, but substantial fibre cutting occurs
Chemical composition is not altered very much.

9. Mechanical Pulping Wood physically taken apart – recovery high
Dense species not usually used due to short thick walled fibres and high % of vessels
Resinous species can also present problems
Yield - high but pulp unsuitable for many uses due to lignin content which stiffens fibres
Lignin also results in yellowing of pulp with time

10. Mechanical Pulping -SWG
Pulp produced by pressing logs
against rotating grindstone
􀂾 Fibres are compressed, and
loosened
􀂾 Friction creates heat to soften the lignin

11. Mechanical Pulping -Refiner Mechanical Pulp (RMP)
Wood chips are broken down into fibres by bars on
two rotating or one rotating and one stationary discs

12. Chemi-thermomechanical Pulps (CTMP)
To decrease energy cost or to improve pulp quality, chemical treatments (alkaline sulphite, sodium sulphite) are often added to mechanical pulping
􀂾Pretreatment of chips (to lower energy)
􀂾Inter-stage treatment (lower energy, increase fibre flexiblity)
􀂾Post-treatment (fibre flexiblity)

13. Chemical Pulping Chemicals degrade & dissolve the lignin.
􀂾 Hemicellulose also removed.
􀂾 Mainly secondary wall material remains

14. Chemical Pulping Soda Soda Anthra Quinone
Kraft = Caustic Soda + Sodium Sulphide (High strength; efficient recovery of chemicals; handles a variety of species; tolerates bark)
Neutral Sulphite Semi Chemical = Sodium Carbonate + Sodium Sulphite
Sulphite – H2SO3 + bisulfite; bright pulp & easy to bleach; higher yield; easier to refine

15. Kraft Recovery Cycle
Black Liquor is Concentrated in Multiple Effect Evaporators to about 65 – 70% Solids
This Heavy Black Liquor is fired in a Soda Recovery Furnace
The Smelt is dissolved in water to form Green Liquor – Sodium Carbonate and Sodium Suphide
Green Liquor is causticised with un-slaked lime, filtered and polished to form white liquor
The Calcium Carbonate sludge is burnt in Kilns

16. Soda Recovery
Soda or Soda/AQ Liquor is concentrated to 55-60% Solids in Multiple Effect Evaporators
Strong Liquor is sprayed to form droplets in a Fluidized Bed Reactor
Further evaporation takes place as droplets fall
Organics burn in the fluidized bed
Inorganics recovered in the form of Sodium Carbonate

17. Washing 􀂾 Aim is to: • minimize black liquor carryover
• recover dissolved solids
􀂾 Solution contains
• Lignin (30-45 %)
• Hemicellulose (28-36 %)
• Extractives (2-5 %)
• Na2O (25-40 %)

18. Beating and Refining 􀂾 Purpose
􀂾 To flatten fibres to ensure maximum surface area for hydrogen bonding in paper
􀂾 Beating also unravels fibres
􀂾 Beating is done in refiners
􀂾 Fluted plug rotates inside
similar shaped housing with ribs

19. Beating and Refining Freeness 􀂾 Freeness is term used to
describe pulp potential
􀂾 Measured by rate of water passing through set amount of fibre formed on wire mesh
􀂾 Well beaten fibre does not allow water to
pass, so Freeness is low
􀂾 Burst and tensile strength increased by
beating time – increases inter-fibre bonding

20. Chemical vs. Mechanical Pulping

21. Chemical vs. Mechanical Pulping

22. Bleaching Processes Conventional
Chlorination – Elemental Chlorine (aromatic substitution of H and addition reactions over the C=C)
Alkali Extraction – Sodium Hydroxide
Chlorine Dioxide or Sodium Hypochlorite
Alkali Extraction

23. Bleaching Processes Modern Trends
Sulpher Dioxide
Oxygen (radical mechanism) or Ozone (addition over the C=C)
Chlorine Dioxide
Alkali Extraction
Hydrogen Peroxide
Exotics

24. Paper Making Chemicals
Cellulose Fibers – the bulk
Fillers – Clay, Calcium Carbonate – 0 to 25%
Strength Additives – Starch, CMC – 0 to 10%
Sizing Agents – Rosin + Alum, AKD, ASA
Wet Strength Additives – 0 to 2%
Dyes
Retention Agents

26. Major Grades of Paper

27. South African Pulp and paper Industry
Number of Paper & Board Mills – 17
Number of Pulp Mills – 9
Paper & Board Capacity = Mt – Local Consumption = 75%
Pulp Capacity = Mt – Local consumption = 60%
The Industry is a very important foreign exchange earner

28. Per Capita Paper Consumption kg

29. Pulp and Paper Making in South Africa