Pulp and Paper Making in South Africa. Raw Materials Derived from Renewable Resources.

Pulp and Paper Makingin South Africa

Raw Materials Derived from Renewable Resources

Pulping Processes

bull Chemical Pulping

bull Mechanical Pulping

bull Chemo-Mechanical or Semi Chemical

bull Waste Repulping

Mechanical action breaks the ML which is morebrittle than the fibre wallbull The fibre wall is left intact but substantial fibre cutting occursbull Chemical composition is not altered very much

Mechanical Pulping

Mechanical Pulping

Wood physically taken apart ndash recovery highbull Dense species not usually used due to short thick walled fibres and high of vesselsbullResinous species can also present problems

bullYield - high but pulp unsuitable for many uses due to lignin content which stiffens fibresbull Lignin also results in yellowing of pulp with time

Mechanical Pulping ndash SWGPulp produced by pressing logsagainst rotating grindstone1048766 Fibres are compressed andloosened1048766 Friction creates heat to soften the lignin

Mechanical Pulping -SWG

Wood chips are broken down into fibres by bars ontwo rotating or one rotating and one stationary discs

Mechanical Pulping -Refiner Mechanical Pulp (RMP)

To decrease energy cost or to improve pulp quality chemical treatments (alkaline sulphite sodium sulphite) are often added to mechanical pulping1048766Pretreatment of chips (to lower energy)1048766Inter-stage treatment (lower energy increase fibre flexiblity)1048766Post-treatment (fibre flexiblity)

Chemi-thermomechanicalPulps (CTMP)

Chemical Pulping

Chemicals degrade amp dissolve the lignin1048766 Hemicellulose also removed1048766 Mainly secondary wall material remains

Chemical Pulping

bull Soda

bull Soda Anthra Quinone

bull Kraft = Caustic Soda + Sodium Sulphide (High strength efficient recovery of chemicals handles a variety of species tolerates bark)

bull Neutral Sulphite Semi Chemical = Sodium Carbonate + Sodium Sulphite

bull Sulphite ndash H2SO3 + bisulfite bright pulp amp easy to bleach higher yield easier to refine

Kraft Recovery Cycle

bull Black Liquor is Concentrated in Multiple Effect Evaporators to about 65 ndash 70 Solids

bull This Heavy Black Liquor is fired in a Soda Recovery Furnace

bull The Smelt is dissolved in water to form Green Liquor ndash Sodium Carbonate and Sodium Suphide

bull Green Liquor is causticised with un-slaked lime filtered and polished to form white liquor

bull The Calcium Carbonate sludge is burnt in Kilns

Soda Recovery

bull Soda or SodaAQ Liquor is concentrated to 55-60 Solids in Multiple Effect Evaporators

bull Strong Liquor is sprayed to form droplets in a Fluidized Bed Reactor

bull Further evaporation takes place as droplets fall

bull Organics burn in the fluidized bed

bull Inorganics recovered in the form of Sodium Carbonate

Washing

1048766 Aim is to

bull minimize black liquor carryover

bull recover dissolved solids

1048766 Solution contains

bull Lignin (30-45 )

bull Hemicellulose (28-36 )

bull Extractives (2-5 )

bull Na2O (25-40 )

Beating andRefining

1048766 Purpose

1048766 To flatten fibres to ensure maximum surface area for hydrogen bonding in paper

1048766 Beating also unravels fibres

1048766 Beating is done in refiners

1048766 Fluted plug rotates inside

similar shaped housing with ribs

Beating andRefiningFreeness

1048766 Freeness is term used to

describe pulp potential

1048766 Measured by rate of water passing through set amount of fibre formed on wire mesh

1048766 Well beaten fibre does not allow water to

pass so Freeness is low

1048766 Burst and tensile strength increased by

beating time ndash increases inter-fibre bonding

Chemical vs Mechanical Pulping


Bleaching ProcessesConventional

bull Chlorination ndash Elemental Chlorine (aromatic substitution of H and addition reactions over the C=C)

bull Alkali Extraction ndash Sodium Hydroxide

bull Chlorine Dioxide or Sodium Hypochlorite

bull Alkali Extraction

Bleaching ProcessesModern Trends

bull Sulpher Dioxide

bull Oxygen (radical mechanism) or Ozone (addition over the C=C)

bull Chlorine Dioxide



bull Hydrogen Peroxide

bull Exotics

Paper Making Chemicals

bull Cellulose Fibers ndash the bulk

bull Fillers ndash Clay Calcium Carbonate ndash 0 to 25

bull Strength Additives ndash Starch CMC ndash 0 to 10

bull Sizing Agents ndash Rosin + Alum AKD ASA

bull Wet Strength Additives ndash 0 to 2

bull Dyes

bull Retention Agents

Major Grades of Paper

South African Pulp and paper Industry

bull Number of Paper amp Board Mills ndash 17

bull Number of Pulp Mills ndash 9

bull Paper amp Board Capacity = 2421 Mt ndash Local Consumption = 75

bull Pulp Capacity = 2472 Mt ndash Local consumption = 60

bull The Industry is a very important foreign exchange earner

Per Capita Paper Consumption kg

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USA Europe RSA WORLD AFRICA

1993199920022004


Pulp and Paper Making in South Africa


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Pulping Processes

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Chemical Pulping


Soda Recovery

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Bleaching Processes Conventional

Bleaching Processes Modern Trends


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Pulping Processes






Mechanical Pulping

Mechanical Pulping









Chemical Pulping


Chemical Pulping

bull Soda











Soda Recovery






Washing

1048766 Aim is to







bull Na2O (25-40 )

Beating andRefining

1048766 Purpose




























bull Exotics







bull Dyes










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Pulping Processes

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Chemical Pulping


Soda Recovery

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Mechanical Pulping

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Chemical Pulping


Chemical Pulping

bull Soda











Soda Recovery






Washing

1048766 Aim is to







bull Na2O (25-40 )

Beating andRefining

1048766 Purpose




























bull Exotics







bull Dyes










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Pulping Processes

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Chemical Pulping


Soda Recovery

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Mechanical Pulping









Chemical Pulping


Chemical Pulping

bull Soda











Soda Recovery






Washing

1048766 Aim is to







bull Na2O (25-40 )

Beating andRefining

1048766 Purpose




























bull Exotics







bull Dyes










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Pulping Processes

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Chemical Pulping


Soda Recovery

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Chemical Pulping


Chemical Pulping

bull Soda











Soda Recovery






Washing

1048766 Aim is to







bull Na2O (25-40 )

Beating andRefining

1048766 Purpose




























bull Exotics







bull Dyes










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Pulping Processes

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Chemical Pulping


Soda Recovery

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Chemical Pulping

bull Soda











Soda Recovery






Washing

1048766 Aim is to







bull Na2O (25-40 )

Beating andRefining

1048766 Purpose




























bull Exotics







bull Dyes










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Pulping Processes

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Chemical Pulping


Soda Recovery

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Soda Recovery






Washing

1048766 Aim is to







bull Na2O (25-40 )

Beating andRefining

1048766 Purpose




























bull Exotics







bull Dyes










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Chemical Pulping


Soda Recovery

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Washing

1048766 Aim is to







bull Na2O (25-40 )

Beating andRefining

1048766 Purpose




























bull Exotics







bull Dyes










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Pulping Processes

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Chemical Pulping


Soda Recovery

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Beating andRefining

1048766 Purpose




























bull Exotics







bull Dyes










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Pulping Processes

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Chemical Pulping


Soda Recovery

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bull Exotics







bull Dyes










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Pulping Processes

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Chemical Pulping


Soda Recovery

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bull Dyes










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Chemical Pulping


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Pulping Processes

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Chemical Pulping


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Pulping Processes

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Chemical Pulping


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Pulp and Paper Making in South Africa. Raw Materials Derived from Renewable Resources.

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Transcript of Pulp and Paper Making in South Africa. Raw Materials Derived from Renewable Resources.