Perlen adds a new twist! - Perlen Papier AG

TMP: Complete Technology for Good Paper.
Perlen adds a new twist!
A tradition we keep very much alive.

High-Tech TMP Plant
The TMP plant at Perlen represents in all respects today’s state-of-the-art
technology and contains a variety of technical and technological developments
that are all targeted to increase the efficiency of the system, to optimize
production cost – especially energy cost, and at the same time to
obtain an optimum pulp quality for the very demanding production program
of Perlen. As raw material chips from saw mill waste and forest thinnings
are used which are wet cleaned and conditioned at a temperature of approx.
85°C. The heart of the thermomechanical pulp production is the big refiner
which refines the chips fully automated to fiber material for paper production.
This Andritz pressurized refiner model TC 66 was installed for the first
time worldwide as a new development in the production in the year 1994.
This machine operates at a higher speed and therefore allows an energetically
more efficient refining process which results in reduced energy consumption.
All refining is accomplished under pressure, so that a major portion
of the heat losses is collected in the form of steam which is used at the
drying sections of the paper machines.
The RTS (R = retention time, T = temperature, S = speed) process, developed
by Andritz in Springfield, Ohio, was the first time realized at Perlen in the
year 1996. At this process the chips are heated for a very short time at the
feed to the refiner and thereafter defiberized at high speed. At the high temperature
(up to 180°C) the lumen of the chips is heated and the secondary
fiber walls are softened. This results in a reduced breakage of fibers at defiberizing
leading to better strength properties. This short time (10–12s)
avoids coloring and therefore loss in brightness. The fibers mechanically
treated in the refiner are strongly curled. This tension (latency) is removed
through intense agitation in the latency chest at about 85°C. The following
pressurized screening eliminates shives and fiber bundles. The screening is
effected at a consistency of more than 3%.
The applied screen baskets have a slot width of 0.15mm only. The shives
and fiber bundles have to be processed in a further refining stage. After
dewatering to a high consistency, this refining is accomplished in a reject
refiner model SB 150. After separation of steam thereby produced, the fiber
material is blown to the latency chest and mixed with the pulp from main
refining.
In order to comply with all requirements of the variety of paper grades in the
production program of Perlen, the pulp is thereafter individually bleached. To
increase the reaction efficiency with the bleaching agents, the pulp is dewatered
between two synthetic sieves. For papers with lower brightness the
pulp is brightened in medium consistency hydrosulfite bleaching. In a second
line thickening is accomplished to approx. 45% by means of a double-wire
press. In a high-consistency mixer hydroperoxide is added to obtain the required
brightness after the bleaching tower. After hydroperoxide bleaching,
the TMP is washed in a screw press. Thereby not fully integrated hydroperoxide
is recycled into the TMP process. The plant is equipped with a modern
process control system and fully automated quality and control facilities. At
various points within the process pulp samples are drawn on a regular basis
and sent to a central control station (Pulp Expert). The measurements are
fully automatic and serve the operator to maintain the quality requirements.
The average capacity of the plant is 350 tons/day of finished pulp and can
be increased to 380tons/day.

TMP – an important paper fiber
raw material
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TMP (Thermo Mechanical Pulp) is the most important and worldwide widely
used process to produce paper fiber material from wood. The raw material
exclusively consists of chips from saw mills (saw mill waste) and chips from
forest thinnings.
Quality of TMP
The quality of the produced TMP is a direct function of the applied energy and
the quality (freshness) of the used wood. Thanks to modern technology the
energy consumption in Perlen could be drastically reduced without changing the
decisive quality advantages of TMP. The TMP fiber pulp distinguishes itself
through various positive quality criteria.
High Volume
The higher volume of the TMP pulp compensates the loss of bulk from deinked
waste paper. For newsprint production the higher volume minimizes the ink
penetration and increases the paper stiffness.
Improved moisture uptake
The TMP pulp provides improved compressibility of the paper and therefore
facilitates ink uptake.
Higher Brightness
For improved newsprint papers as well as for LWC papers (light-weight coated
papers) the pulp can economically be bleached to the higher brightness level by
adding peroxide.

“TMP: a high quality paper fiber made from natural wood.“
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Chip Washing
The chips are cleaned from fines and
impurities. Since the washing process
is accomplished at a temperature of
85°C, the chips are simultaneously
heated and conditioned.
Presteaming Bin
The chip mixture of saw mill waste
and chips from forest thinnings are
fed to the preheating bin.
Chip Washer
The chip washer removes tramp material
such as sand, stones and metal
particles as well as knots. From the
washer the chips are pumped via a
cyclone to drain screw.
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Tramp Removal Conveyor
This dewatering screw separates
impurities from the washwater.
Cyclone
A hydrocyclone separates remaining
foreign particles and sand.
Dewatering Screw
After the cleaning process (washing)
the chips are separated from the
washwater.
Presteaming Bin
Washed and to 85°C preheated chips
are interim stored at the presteaming
bin.
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Main Refining
The heart of a modern TMP plant is
the main refining unit (refiner 7). The
chips are defiberized and refined between
rotating refining plates. The
heat generated during this process
evaporates excess water, and the
steam is led to the heat recovery
system.
Main Refining (Refiner TC 66)
The plug screw feeder after the presteaming
bin squeezes the chips into
the pressurized area of the refiner. By
heating the chips for a short, controlled
while to above 150°C, these are
strongly softened without, however,
coloring. The refining as such is effected
between two rotating discs. A
high energy input is required to loosen
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the fiber bond respectively to accomplish
fiber separation and treatment.
A large part of the applied energy is
transformed when the chips' humidity
is evaporated.
Pressurized Cyclone (Steam
Separator)
Together with the steam the fibers
are blown from the refiner to the
pressurized cyclone where steam and
fibers are separated. The steam is led
to the heat recovery system and the
pulp is discharged into the latency
chest.
Latency Chest
The mechanically pretreated fibers are
strongly curled. This tension (so-called
“latency“) is removed by intensive agi-

“Papers with extraordinary quality properties are based on perfect raw
materials (pulp).“
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tation and pumping at about 85°C to
obtain maximum fiber flexibility.
Screening
Fiber bundles that are not yet completely
loosened are separated.
Screening System
Fibers that are not yet completely refined
are separated in the screening
(consistency 3–4%). The accepted
fibers (finished fibers) are pumped to
the prethickening.
Treatment of Rejects
The fiber bundles separated in the
screening are dewatered and treated
in a refiner.
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Rejects Chest
The rejects (coarse fibers and shives)
from the screening are stored in an
intermediary rejects chest.
Rejects Screw Press
The screw press thickens the rejects
up to the consistency required for refining
which is about 30% (30%
fibers, balance water).
Rejects Refining (Refiner SB
150)
A sophisticated conveying system
feeds the rejects onwards to a further
refining process. The fiber bundles
and shives are treated (analogous to
the main refining 7) between one
rotating and one stationary disc.
Pressurized Cyclone (Steam
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Separator)
Together with the steam generated in
the refiner the fibers are blown to the
pressurized cyclone. The separated
fiber stream is led into the latency
chest and is mixed with the pulp from
main refining while the steam is recycled
to the heat recovery system.
Hydrosulf Bleaching
The brightness of the TMP pulp is
slightly increased with marginal Nahydrosulfite
addition to obtain a
brightness level required for newsprint.
The ready pulp is conveyed to a
interim storage tower.
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Prethickener
Dewatering to about 12% is carried
out on a Wedge Thickener between
two synthetic wires. A continuous
fiber mat is formed. This fiber mat is
desintegrated in a shredder conveyor.
SF-Pump
Na-hydrosulfite is added at a consistency
of 12% by means of a pump.
Bleaching Standpipe
The reaction in the bleaching standpipe
is accomplished during a retention
time of about 20 minutes under
air exemption.
Storage Tower
At a consistency of 12% the final pulp
is stored in a tower (1000 m 3 ) and

“The TMP system of Perlen Papier AG processes wood chips into ready TMP.“
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subsequently pumped to the paper
machines.
Peroxide Bleaching
For brighter papers (LWC) the TMP
pulp is bleached to a higher brightness
level. High consistency improves
the chemical reaction.
SF pump
The SF pump supplies the pulp to the
peroxide bleaching system.
Double-Wire Press
The pulp is dewatered in the doublewire
press between two synthetic
wire sieves up to a consistency of
45% (45% fibers, balance water).
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High Consistency Mixer
The fiber mat leaving the double-wire
press is size-reduced in a fluffer conveyor
and conveyed to the high consistency
mixer where the required
bleaching agents are added.
Bleaching Tower
The bleaching of the pulp is accomplished
within 2 hours at about 70°C
in the bleaching tower. In the following
conveying system the bleached
pulp is diluted with filtrate from the
paper machine and fed to the high
consistency pump.
Screw Press (Pulp Washing)
In the screw press the bleached TMP
is again dewatered to about 30% consistency.
Thereby loosened substances
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resulting from the bleaching process
and residual peroxide are washed out.
SF pump
After pulp washing, the TMP again is
diluted with paper machine filtrate to
a consistency of about 12%. The following
medium consistency pump conveys
the bleached TMP (occasionally
by adding Na-hydrosulfite) through the
bleaching standpipe to the storage
tower.
Bleaching Standpipe
Na-Hydrosulfite can be added to
obtain the highest possible brightness.
The reaction in the bleaching standpipe
is accomplished during a retention
time of about 20 minutes
under air exemption.
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Storage Tower
The bleached TMP is stored at the
storage tower (1300m 3 ) and thereafter
pumped to the paper machines.
Heat Recovery
In the heat recovery system most of
the excess heat from the TMP plant is
converted into clean steam which is
utilized at the paper machines for
paper drying.
Heat Recovery System

Technical Data
Project History
Start of construction August 1993
Start-up June 1994
Modification to RTS process May 1996
Rebuild (capacity/1-stage process) April 2000
Capacities
Storage capacity – chips (Silos) 11,500 m 3
Storage capacity – low brightness TMP 1,000 m 3
Storage capacity – bleached TMP 1,300 m 3
Installed Power at Refining
Main refiner (TC 66)
Rejects refiner (SB 150)
22 MW
8 MW
Raw Material
Chips
Chip quality
Chips of spruce (spruce fir and silver fir)
Length 20–25mm, thickness 6–8mm
Bark content max. 0.6%
Fresh wood (natural humidity, no coloring)
Supply
60% from saw mills
40% own chips from thinnings
Production
TMP production
Steam production
up to 380 tons/day
up to 450 tons/day