Basics of wood, pulp and paper november 2012
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Transcript of Basics of wood, pulp and paper november 2012
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Wood, pulp and paper
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Summary
From Tree to Pulp
From Pulp to Paper
Different kinds of paper
Paper characteristics
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Summary
From Tree to Pulp
From Pulp to Paper
Different kinds of paper
Paper characteristics
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Wood is use for ……..
World production by area - source FAO 2009
http://www.twosides.info/#page=Latest-5
More info about the sustainability of the paper industry:
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57%
87%
49%
8%
22%
14%
5%
1%
8%
14%17%
7% 7%
0%3%
6%
14%
49%
19%
10%
34%
55%
38%
16%
12%
1%
6%
17%
9%
14%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Europe Asia & Pacific Afrique Latin America &
Caribbean
North America Western & Central Asia
woodfuel sawnwood
wood based panels industrial roundwood
pulp, paper & paperboard
Wood is used for….by continent
Production by area by
continent - source FAO 2009
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Which part of a tree does the paper industry use ?
Construction wood :
for carpentry,
furniture or
construction
Wood left-overs,
wood shavings :
for pulp and
panelling
Bark :
for energy
or compost
Sawdust :
for panelling or energy
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Hardwood and Softwood…
hardwood
softwood
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Hardwood and Softwood…
hardwood
softwood
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Chemical composition of wood
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Pulp making : practically : Debarking
Cutting logs with
rotating saws
Logs rotated in
drum with water
Debarked logs
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Pulp making : practically : Chipping
Chipper
Chip Screen
Chips Chips Chips!
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From Tree to Pulp : Mechanical Pulp
The wood is only mechanically
treated (grounded)
The yield is about 98%, rests
products (barks) are used as
fertilizer or for heating
1 ton of wood produces 980kg
mechanical pulp
All the lignin remains in the pulp
2 Major processes :
Mechanical pulp
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Stonegroundwood process
Grinding
Debarking
Bark is used to produce energy Pine
(bleaching) Washing
water
logs
exit of the fibres
rotating stone
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From Tree to Pulp : Chemical Pulp
The wood is treated :
• mechanically (grounded),
• thermally (heated up in boiling water)
• chemically
All the lignin is removed from the
wood
The yield is about 50%:
With 1 ton of wood, we
produce about 500kg chemical pulp
Chemical pulp
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Chemical pulp process
pine/birch
debarking
cooking
sorting
bleaching
washing
chips
steam
production of electricity
Cooking liquor
evaporation
Causticising
Chemical recovery
Liqueur de cuisson fraiche
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Chemical pulp mill
Cooking vessel
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Different types of pulp…..
Trees
Logs
Debarking
Steaming
Grinding
Thermo-
Mechanical
Pulp
Trees
Logs
Debarking
Chemical pre-
softening
Grinding
Chemi -
Thermo -
Mechanical
Pulp
Trees
Logs
Debarking
Chemical
cooking
Chemical
Pulp
Secondary fibre
Deinking
Washing
Recycled
Pulp
Trees
Logs
Debarking
Grinding
Mechanical
Pulp
Between Mechanical process & Chemical process, we have intermediate processes :
TMP and CTMP. These processes only remove part of the lignin, up to the level desired.
Wood Containing Papers
Light Wood Containing Papers
Wood Free
Papers
Recycled
Papers
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Under the microscope…
Pine Birch
Birch
Chemical pulp Mechanical pulp Recycled pulp
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Different pulp for different kinds of paper
100 % chemical pulp 100% mechanical pulp
Strength is higher
Less stiffness
Less bulk
Easy to bleach
Lower opacity
Smooth surface
Brightness stable with time
Less strength
Higher stiffness
High bulk
Lower brightness
High opacity
Rougher surface
Trend to yellowing
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Bleaching of the pulp Without bleaching, the pulp is brown
Therefore, depending on the level of brightness we want to achieve, we need to « bleach »
the pulp with chemicals. We can make it step by step with different chemicals :
2nd step 3rd step 4th step
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Bleaching of the pulp
No
Total
Chlorine
Free
And
No
No Elemental
Chlorine
Free (Cl2)
(Cl2)
(ClO2)
1
2
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Summary
From Tree to Pulp
From Pulp to Paper
Different kinds of paper
Paper characteristics
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Integrated or not integrated…… Papermills do not always make their own pulp
they are so called “non integrated mills” (those who produce their own pulp are … integrated
mills); they received the pulp in units with a dryness of around 90%....
PULP PRODUCTION within SFPE
ALFELD
EHINGEN
GRATKORN
KIRKNIEMI
LANAKEN
STOCKSTADT
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Just before the paper machine
Dyes/Filler
Water
Hardwood pulp
Hydrapulper Refining Cleaning & Screening
Waste Filter System
Recycled Water
Softwood pulp
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Pulper
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Refining
Slide
26
Drawing of a refiner
discs
Admission of the pulp
Outflow of the pulp
Refiner discs
Feeding screw
Refining chamber
Fibres are cut, frayed and hydrated
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Refining
Fibres before refining fibers after refining
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Cleaning and screening
Rejected material
Pulp entry
Cleaned pulp
Pulp entry
Rejected
material
Screened pulp
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Just before the paper machine Before the pulp is sent to the papermaking machine various additives are included.
Water
Papermaking uses a lot of water and this is why mills are built next to rivers.
A kilo of paper will use 100 litres of water.
The water systems are virtually closed where excess water is continuously recycled.
Colouring
Optical Brightening Agents are added that react with ultra violet light and give the paper a
blue whiteness.
Dyers are also added.
Binders
Both latex and starch are used to keep the fillers bound with the pulp. Starch also adds
stiffness.
Other additives
Anti bacterial, retention aids, pH buffers, …etc
Fillers
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Fillers
Titane dioxyde Talc
Clay
Gypsum
Calcium carbonate
Clay
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Paper machine
Up to 80 km/hour
Up to 10 meters wide,
430 meters long
Cost: a few hundreds
millions €
18 months to be built
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Paper machine
The function of the paper machine is mainly to remove water
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Wire section
Moisture
content
99.9%
Moisture
content
80%
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Wire section
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Forming the web
Fourdrinier former
Twin wire
hybrid former
Duo former
Twin wire
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Press section
water
water
Press felts
paperweb
about 50% of the water is removed
in the press section
The water is removed
by pressure of the sheet in the nip
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Press section
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Pre - drying section
The water is removed by
evaporation
The moisture content of the
paper is around 5-8%
The basis paper is ready to be
coated (for coated papers) or
sized (for uncoated papers)
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Pre drying section
Water
content
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Fibrous support Fibrous support + sizing = uncoated paper
Fibrous support + (sizing) + coating = coated paper
~ 0.1 mm
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Size press
A few g/m²/face is applied;
the layer is mainly made of starch
Absorption
Hydrodynamic pressure
Mechanical pressure
Split of the starch layer
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Post - drying section
The water is removed by
evaporation
The moisture content of the
paper is around 5-8%
The basis paper is ready to be
coated (for coated papers) or
calendered/rewinded for
uncoated papers
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Why coating papers ?
Uncoated Coated
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Why coating papers ?
uncoated paper light weight coated high weight coated
Print quality improves
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Why coating papers ?
Slide
45
base paper
More and more coating
light weight coated high weight coated
BRIGHTNESS
SMOOTHNESS
GLOSS
PRINTING QUALITY
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Le couchage Coating is made of
Mineral pigments
Binders
Additives
Water (35-45%)
+ or – coating will lead to different kind of papers :
LWC, MWC, modern, classic
On-line or Off-line coating
Single, double, triple coated
What is coating ? What is the coating colour made of ?
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Coating
Blade
Base paper
Coating tank
How do we coat ? Blade coating
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Infra red dryers Scanner Hot air dryer Scanner Hot air dryer
Blade coating heads
How do we coat ? Blade coating
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Blade coater
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Cross section of a coated paper
coating fillers
fibres
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Surface of the coated paper
Satin?
Silk?
Satimat? Demi-mat?
Gloss?
Matt?
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Satin or Mat ?
Satin Mat
150x
5000x
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Classification of paper surfaces
Gloss
Gloss > 70 % 30 - 40 % <15% Smoothness 1500 - 3000 sec 300 - 900 sec 50 - 200 sec
Satin / Silk
Matt
5000x
Marketing evaluation, no strict rule/norm
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How do me make the surface ? Calendering
MAT, BRILLANT, DEMI MAT, SILK, ...
Pressure
Temperature
Moisture
Hardness of the rolls
Number of rolls
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Supercalendering
Steel
Steel
Steel
Steel
Soft
Soft
Soft
Soft
Soft
Bottom
driver roll
The soft
rolls can
be of a
cotton,
paper or
synthetic
covering
Steel
Steel
Steel
Steel
Soft
Soft
Soft
Soft
Soft
Bottom
driver roll
Reversing nip
Blow rolls to
cool sheet and
prevent
wrinkling in nip
Uncalendered
Paper
Calendered
Paper
The soft rolls
are usually
made of
synthetic
covering
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Rewinding
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Rewinding
Slitting
Drop 3
Drop 2
Drop 1
Mother Reel
Pos. 1/A Pos. 2/B Pos. 3/C Pos. 4/D Pos. 5/E Pos. 1/A
Reels for
delivery or
sheeting
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Reels packaging
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Sheeting
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Sheeting
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Sheeting - slitting
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Sheeting - cutting
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Sheets packaging
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Summary
From Tree to Pulp
From Pulp to Paper
Different kinds of paper
Paper characteristics
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Publication papers & end-uses
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Summary
From Tree to Pulp
From Pulp to Paper
Different kinds of paper
Paper characteristics
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Grammage (g/m²), Thickness (µm), Bulk (cm³/g)
Substance or basis weight :
weight in grams of 1 m² paper
Thickness or Caliper :
Distance between one face of the paper
and the other
Bulk (cm³/g) = Thickness (µm) / grammage (g/m²)
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ISO-brightness (%) and CIE whiteness
ISO brightness is a measurement of reflected blue light off the paper surface.
This is expressed as a percentage in comparison with an ultimate reference.
The ISO standard only measures a portion of the reflected light.
The CIE whiteness measures the reflected light of the whole spectrum.
For both measures, the higher the value, the brighter or whiter the paper is.
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Opacity (%)
Opacity is related to the ability of light to
pass through paper.
The higher the percentage, the more
opaque the paper is.
Opacity isn't always determined by thickness or weight; a thinner paper may have more opacity than a thicker paper if opacifying agents are used.
High opacity
Low opacity
Opacity (ISO 2471) can be defined as the ratio of reflectance
from a paper sheet backed by a perfect black and from a
sufficiently thick stack of identical sheets of paper.
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Gloss (%)
Gloss is an optical phenomenon caused when evaluating the appearance of a surface.
The evaluation of gloss describes the capacity of a
surface to reflect directed light.
The measure can be made on the paper itself (paper gloss) or on a printed area (print
gloss). Gloss papers are generally the most calendered
and thus the thinnest.
Please note we cannot compare gloss measures made
according to different norms (Tappi T480 & DIN 54502
are the most common).
Gloss
paper
Mat paper Gloss paper => smooth => high gloss
Matt paper => rough => low gloss
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Smoothness Bekk. (sec)
This method measures how long it takes for a certain amount of air to escape from
between the paper surface and a smooth metal disc.
The smoother the paper, the less openings there are between paper surface and metal
disc, so the longer it will take for the air to escape.
The higher the figure is, the rougher the surface is.
Known also as “roughness”
Mat paper Silk paper
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Fiber orientation
The paper fibers naturally take up
alignment roughly parallel to the
direction of travel of the web on
the PM :
this becomes the grain direction or
the Machine Direction (MD).
the other direction is called Cross Direction (CD).
This influences the strength characteristics of the finished paper.
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Grain direction
LG
SG
Jumbo-reel 45
64
64
45
• Long Grain: fibres // long side (LG) : 45 X 64
• Short Grain: fibres // short side (SG) : 64 x 45
The first dimension is by convention always the dimension cross the web
64 x 45
45 x 64
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Questions ?
Will be happy to answer your technical questions :
Françoise Accou
+32 492.582.287