2. Introduction
• Pulp is a lignocellulosic fibrous material
prepared by chemically or mechanically
separating cellulose fibres from wood,
fiber crops or waste paper.
• The wood fiber sourcer require for
pulping are approximately 45% Saw Mill
residue, 21% Logs and Chips, 34%
Recycled Paper.
• First mechanical and then chemical
methods have been developed to
produce pulp from wood.
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3. Paper Production Prrocesses
The production process can be divided
into 5 types.
Forestry
Debarking
Chipping
Pulp Preparation
Paper Formation
Paper Finishing
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4. Forestry
• Typically, trees used for papermaking
are specifically grown and harvested
like a crop for that purpose. To meet
tomorrow's demand, forest products
companies and private landowners in
Wisconsin plant millions of new
seedlings every year.
5. Raw Material Process
• Debarking is the process of removing
bark from wood.
• Debarking generally involves the use of
industrial machinery into which the log
or stake is placed. These machines can
be either stationary or portable.
Generally they are powered by hydraulic
motors.
• The log is pressed against blades or
knives which remove the bark.
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6. • Chipping- are a medium-sized solid
material made by cutting, or chipping,
larger pieces of wood.
• Woodchips are raw material for
producing wood pulp.
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7. Pulping processes
Pulping aims to separate cellulose
fibers from the wood structure.
Those wood chips are then pressure-
cooked with a mixture of water and
chemicals in a digester.
Kraft process The kraft process entails
treatment of wood chips with a hot
mixture of water, sodium hydroxide,
and sodium sulfide, known as white
liquor, that breaks the bonds that link
lignin, hemicellulose, and cellulose.
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8. Recovery process
• The excess black liquor contains about
15% solids and is concentrated in a
multiple effect evaporator.
• The weak black liquor is further
evaporated to 65% or even 80% solids
(heavy black liquor)and burned in the
recovery boiler to recover the inorganic
chemicals for reuse in the pulping
process.
9. • Bleaching of Wood Pulp
• In a modern mill, brownstock (cellulose
fibers containing approximately 5%
residual lignin) produced by the pulping
is first washed to remove some of the
dissolved organic material and then
further delignified by a variety of
bleaching stages.
• After Bleaching of pulp the pulp is stored
into the Headbox.
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10. Paper Formation
• Paper Machine (Fourdrinier Machine)
• Paper machines have four distinct
operational sections
• Forming section- commonly called the
wet end, is where the slurry of fibres
filters out fluid a continuous fabric loop
to form a wet web of fibre.
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11. • Press section -Where the wet fibre
web passes between large rolls loaded
under high pressure to squeeze out as
much water as possible.
• Drying section, where the pressed
sheet passes partly around, in a
serpentine manner, a series of steam
heated drying cylinders. Drying
removes the water content down to a
level of about 6%, where it will remain
at typical indoor atmospheric
conditions.
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12. • Calender section - Where the dried
paper is smoothened under high
loading and pressure. Only one nip
(where the sheet is pressed between
two rolls) is necessary in order to hold
the sheet, which shrinks through the
drying section and is held in tension
between the press section (or breaker
stack if used) and the calender. Extra
nips give more smoothing but at some
expense to paper strength.
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13. Paper Finishing
• The characteristics, appearance and
properties of paper and board are
supplemented and enhanced by their
final treatments. These may be simple
processes where the reel is slit into a
number of more narrow reels or cut
into sheets or more complicated
processes such as coating or super-
calendering.
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14. • Coating improves the opacity,
lightness, surface smoothness, lustre
and colour-absorption ability of paper.
• Coating means that a layer is applied to
the paper
• The coat consists of a mix of pigments,
extenders such as china clay and chalk
• For Even Smoother Paper Super-
Calendering is Required (for
magazines paper)
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