Paper IndustyThe manufacturing process

Pulping processWood chips are cooked in pressurized

digesters with strong basic solution and high temperature

Deliginification of wood chips gives cellulose pulp that are free from lignins

Some chemicals used in Kraft’s process includes

❖Caustic Soda

❖Sodium Sulfide

❖Sodium Sulfate

Pulping process

Recovery processBlack liquor formed as a byproduct of

pulping, containing excess pulping chemicals that can be reused

This process encourages 97% chemical efficiency for Kraft’s chemical pulping process

Some chemicals used include

❖Soda Ash

❖Lime or Hydrated Lime

Recovery process

Bleaching processWood pulp retain their brownish parent

color if untreated

This is due to residual ligins still present in the pulp

Bleaching usually involves using chemicals with strong reacting properties to whiten the pulps

Some chemicals used include

❖Sodium Hypochlorite

❖Sodium Chlorite

❖Sodium Thiosulphate (anti-chlor agent)

❖Hydrogen Peroxide

❖Sodium Dithonite (Radical stabilizer)

Bleaching process

Finishing ProcessAdditives are added in this process to

modify the physical properties of paper

Some properties includes opacity, optical brightness, strength and density of the final paper product

Some chemicals used include

❖Calcium Carbonate

❖Titanium Dioxide

❖Talc

Finishing Process