Corporate Environment Affairs RECYCLING OF TETRA ... - Eko paket

Corporate Environment Affairs
RECYCLING OF TETRA PAK BEVERAGE CARTONS
Contents
March, 2000
Summary…………….…………………………………………………………………2
Introduction……………………………………………………………………………2
Collection and Sorting…………………………………………………………………3
Fiber Recycling Process –Hydrapulper………………………………………………4
Repulping…………………….………………………………………………….4
Process Data…………………………………….………………………………5
Washing of Polyethylene and Aluminum –Rejects………………………………5
Recycled Paper Characteristics…………………………………………………6
Tests and Methods……………………………………………………………………...8
Pulp Recycling Results and Discussion……………………………………………….8
Recycling of Aluminum and Polyethylene – Rejects…………………………………9
Conclusion………………………………….………………………………………….11
Glossary…………….………………………………………………………………….12

SUMMARY
This paper is based on many experimental trials at paper mills and shows the basic process to
recycle Tetra Pak post consumer cartons, from collection and sorting programs, on industrial level.
The mechanical characteristics showed excellent fibers for using in a number of papermaking
processes. Paper represents 75 % of the package, polyethylene 20 % and aluminum 5 %. The
repulping process takes about 35 minutes and separates pulp from aluminum and polyethylene
layers. Aluminum and polyethylene discharged after the repulping process can also be recovered in
three ways: burning to generate energy, Aluminum recuperation by pyrolysis or plasma kiln and
manufacturing of plastic products trays with thermo injection processes. For each ton of packaging
added to the system at least 650 Kg of good quality fiber can be recovered.
1.0 – INTRODUCTION
The utilization of recycled fibers from used cartons has grown substantially. While economic
factors are not always controllable and still a great concern, environmental demands for the use
of secondary fibers in the paper industry have increased. This subject has been the object of
several scientific papers, attempting to show the gains from the utilization of this kind of fiber. In
some countries, Belgium for instance, there is legislation, which requires the use of secondary
fibers in the composition of paper. Some countries have set the goal to include recycled fibers in
all printing paper sold.
The greatest gain in U.S. paper recycling for instance, was achieved in the corrugated board
sector, with an increase in annual growth to more than 11 million tons in less than eight years.
Within this segment, recycled corrugated board was the most successful venture. By the end of
the year 2000, the forecasted annual capacity for this segment will exceed 8.3 million tons, a
growth rate of 70 percent in the ‘90s.
Both recycled linerboard and corrugated medium (internal layer of the corrugated board) share
this rapid growth, a phenomenon based on the economic value of the recovered fiber. For
example, the increase in old corrugated container (OCC) consumption is influenced by the lower
capital cost of developing OCC recycling capacity versus the capital cost for virgin pulping
facilities. Also , recycled board mills often are located in close proximity to sources of recovered
materials and the targeted customers for the finished containers.
Tetra Brik Aseptic cartons, utilized in the aseptic filling of UHT processed products, are made up
of three raw materials: paper (Duplex, CTMP or Bleached), low density polyethylene and
aluminum foil. Tetra Brik Aseptic packaging (TBA) is composed of six layers starting from inside
out: polyethylene, polyethylene, aluminum, polyethylene, paper and polyethylene. The internal
polyethylene layers have the function of making the packaging impermeable and preventing food
contact with the aluminum. The aluminum layer prevents the penetration of air and light thus
assuring the preservation of food contents. Paper provides stiffness. The package is composed of
75% paper (long fiber), 20% polyethylene and 5% aluminum.
Tetra Brik packages (TB) are used for chilled products and are made of paper (Duplex or CTMP)
and low density polyethylene.
Tetra Rex packaging is composed of bleached paper and polyethylene. A layer of aluminum may
also be present in its composition. This packages material is used for pasteurized liquid food
such as juices and milk.
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Tetra Top packaging material is composed by duplex paper and low-density polyethylene and is
also used for pasteurized products.
Recycling of cartons is initially done at paper mills, which use its fibers in the manufacturing of
several types of papers. Recovery of polyethylene and aluminum can be accomplished in three
different ways: energy recovery through burning in cement kilns or incinerator thus saving fuels;
aluminum recovery by pyrolysis or plasma furnace; or in the manufacture of plastic objects by
extrusion or injection/molding processes.
2.0 COLLECTION and SORTING
The collection and sorting operations are an important part in the recycling system of cartons.
There is a tendency to establish collection by legislation as a way of solving the Municipal Solid
Waste problem. According to a World Bank book “ Solid Waste Landfills in Middle- and Lower-
Income Countries” , edited in l999, 76% of all solid waste collected in the developing countries is
disposed of in inadequate places (open dumps), 13% in managed landfills, 10% in waste landfills,
and only 1% is treated (composting, recycling and incineration).
Fig. 1 - Carton Sorting – Europe Fig. 2 - Carton Sorting
Fig. 3 - Carton Bales Fig. 4 - PET Bottles Sorting
The main collection schemes for Tetra Pak cartons are “Drop Off” system with other light
packaging or collection together with the paper stream (the cheapest solution) or “Curb Side
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Collection” where the “dry material” is collected directly in the households, as curb side collection
of cartons and other paper packages.
3.0 FIBER RECYCLING PROCESS - HYDRAPULPER
3.1 REPULPING
In order to recover the fiber from the packaging material, the various layers of materials, which
make up the package, must be separated. The separation of the materials is done in a high,
medium, or low consistency hydrapulper (big blender) with a volume from 5.000 to 40.000 liters.
A process time settling period of 30 to 40 minutes is necessary so that the fiber present in the
packages can be separated and remain in suspension allowing its removal by pumping action.
The separation process of this type of material does not require the utilization of any chemical
additive or hot water. The packaging is mixed with water in a concentration range from 3% (30 Kg
of packaging in 970 Kg of water) up to 15% (150 Kg of packaging in 850 Kg of water) by weight,
agitated during 30 to 40 minutes. Almost all fibers present in the carton will be separated from the
plastic/aluminum layers
Tetra Pak factory waste - laminated material – in general, must be shredded (20X10cm pieces)
before sending to the paper mill to be recycled. Shredding is necessary to improve repulping time
and also to facilitate discharge of the rejects (plastic/aluminum) from the hydrapulper.
Post consumer cartons do not need to be shredded before entering the pulper, except when
using a “Rotary Drum” pulper. In that case a cutting device is installed in the feeding conveyer
just before the pulper.
Tetra Pak’s carton fibers are utilized in the production of several types of products such as
corrugated board, cardboard, egg cartons, inner soles, tissue paper, paper core, etc.
Rotor and speed used in the pulper will determine some of the characteristics of the recovered
fiber. Low-consistency rotors (fig. 5) are used when a fast pulping is desired and cut fibers are
tolerated. High-consistency rotors (fig. 6) promote a high shear action among fibers and a smooth
pulping, but in a longer time than before. Medium-consistency rotors are seldom used as a
compromise solution between low and high consistencies. Speeds are directly linked to energy
consumption and both are usually optimized for best results in every application. Consistency is
mentioned on a percent basis of the amounts of fibers diluted per water volume. For pulping
purposes, low-consistencies are lower than 6%, medium-consistencies between 8 and 10%, highconsistencies
are from 12 to 15%.
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3.2 PROCESS DATA
Fig. 5 – Low consistency rotor
Fig. 6 - High consistency rotor
In tests conducted at paper mills, rotations from 280 to 450 rpm have been used in the
hydrapulpers. Hydrapulper mass filtering screens varied from 4 to 12 mm. Low consistency
processes have the advantage of making easier the discharge of the fibrous material. Processes
with high consistency require the reduction of the consistency by diluting with water before
sending the fibers to the storage tank.
Cartons can be recycled alone in the hydrapulper or mixed with others fibers sources like Old
Corrugated Container (OCC), Mixed Office Waste (MOW) or Old Magazines (OMG). The
maximum concentrations of Tetra Pak cartons in the pulper depend on the type of equipment
after the repulping process. Some recycling factories have a “rotary drum” after the pulper. With a
rotary drum they can use 100% batch of cartons with no majors problems. In general,
concentration up to 5% of cartons mixed with OCC (Old Corrugated Container) does not affect
the recycling process in the plant.
3.3 WASHING OF POLYETHYLENE AND ALUMINUM - REJECTS
The first separation of the fiber from the rejects containing aluminum and polyethylene is done in
the hydrapulper discharge. The fibrous material that is suspended in water is removed by
pumping. During the pumping the fiber goes through a perforated plate which prevents the
passage of the polyethylene and the aluminum. These materials are removed laterally by gravity
and go through a washing process where the residual fibers, the polyethylene and aluminum are
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washed with water (Fig. 7). After washing the recovered fibers return to the process of paper
making while the polyethylene and aluminum are pressed in a bale.
The type of separator or plastic washer that has proven efficient is the rotating and nonpressurized
cylindrical screen or rotary drum (Fig. 8). The recovered fibers that return to the white
water system can be recovered by Thickeners or Side Hill Static screens.
Fig. 7 - Rejects After Rotary Drum
Fig. 8 - Rotary Drum (Trommel) for Rejects Cleaning
3.4 RECYCLED PAPER CHARACTERISTICS
The recycling of Tetra Pak’s cartons packaging a high consistency process was studied by
Bowser (l996) where post-consumer milk and juice cartons were used. The cartons were
separated in a high consistency hydrapulper for 35 minutes with helicoidal rotor and were
extracted through a perforated plate with 3\8 inch holes. The plastic and aluminum were
removed and put through a plastic/aluminum separator to recover remaining fibers in the material.
After the contaminant removal from fibers using pressurized screens and cleaners, samples were
taken for tests. The results are shown on Table l.
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TEST Units I II III IV
Burst index kPa m 2 /g 3,36 3,72 3,91 4,14
Tear index mNm 2 /g 12,42 12,71 11,53 11,48
Tensile index Nm/g 44,18 52,75 55,22 64,59
Rupture strain % 3,31 3,60 3,38 3,39
CSF ml 430 397 327 257
Bulk cm 3 /g 1,69 1,64 1,56 1,53
TABLE 1 – Results obtained in high consistency pulper recycling 100% cartons.
Wastewater
Treatment
Sludge
Fiber Recycling Process
Process Flow Scheme
Water
Water
Water
Pulper
Coarse Filter
Fibers
Cleaner
Paper
Machine
Paper
Packaging
Plastic
Aluminium
Water
Fig. 9 - Recycling of beverage cartons (Process Flow Scheme)
Fig. 10 - Paper Machine (250 ton/day)
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Water
Extractor
Boiler
Al 2 O 3
Refractories
)
Injection/Extrusion /
CO 2 /H 2 O
Pyrolisis
Plasma
Al
Plastic
Objects
Boiler
Methane/
Propane
STEAM

4.0 TESTS AND METHODS
Industrial tests were conducted in accordance with the production processes of several recycling
plants. Bales, weighing on average 300 kg each used in the various tests, were obtained from
sorting centers. The material used for tests was disintegrated in 35 minutes in low consistency
hydrapulper using rotor speed between 280 and 300 rpm with consistencies between 3% to 4%.
After the carton disintegration, pulp samples were collected for physical analyses. The obtained
samples were refined with a laboratory Valley beater and afterwards, sheets were manufactured
for the physical tests in compliance with TAPPI Test Methods.
5.0 PULP RECYCLING RESULTS AND DISCUSSION
Tests Units I II III IV
Burst index kPa m 2 /g 0,95 2,86 3,53 4,03
Tear index Nm 2 /g 11,77 14,02 12,97 12,13
Tensile index Nm/g 20,34 57,45 65,91 65,51
Rupture strain % 0,93 1,85 2,20 2,00
Thickness mm 0,1600 0,1355 0,1330 0,1290
Schopper Riegler SR 20 29 41 50
Dry gramature g/m 2 60,68 57,91 65,91 65,51
Dry fibers contend % 91,60 93,25 93,16 93,07
Bulk cm 3 /g 2,64 2,34 2,02 1,97
TABLE 2 – Results of physical tests- fibrous materials obtained in industrial tests with low
Consistency hydrapulpers.
During the testing, it was observed that cutting rotors caused a shredding effect on the aluminum
and polyethylene that had passed through the hydrapulper screen together with the fiber, making
difficult the aluminum removal. In these cases, the recommendation was either reduce rotation or
change the rotor.
In some cases, it was noticed that, during the disintegration, Tetra Brik Aseptic packages
separated more easily than the Tetra Rex packages. This is explained by the humidity resistance
products (wet strength) contained in Tetra Rex packages material. In industrial terms, without
use of chemical products or heating the pulper water, a the period of 35 minutes is enough to
disintegrate cartons and unbind the polyethylene.
The values obtained in the tests are those required by market standards for all types of paper.
Part of the trials presented was carried out in plants for producing corrugated paper and the fiber
tests show values that are within market requirements.
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6.0 RECYCLING OF ALUMINUM AND POLYETHYLENE - REJECTS
One of the ways to recover aluminum and polyethylene, generated in the recycling process of
carton packages, is incineration with energy recovery in boilers or cement kiln. This process is
utilized in European countries where the material is used as fuel in cement kilns, thus reducing
the use of fossil fuels. In this process the boiler or kiln should have washing gases systems or
electrostatic precipitators to guarantee the retention of aluminum particles. In the combustion
process the aluminum reacts with oxygen producing aluminum trioxide that can be used in the
production of polyeletrolites for water treatment.
One process for the recovery of aluminum is a pyrolysis furnace where a low percentage of
oxygen is maintained in order to prevent the oxidation of aluminum. In this process the
polyethylene reacts with the oxygen providing energy to the process. Plasma technology has
been developed to recover metallic aluminum. In the Plasma process, polyethylene degrades in
short molecules that can be burnt as a fuel.
Processing polyethylene/aluminun in plastic recycling industries is very interesting commercially
speaking. Polyethylene is a thermoplastic and can be processed over and over again. The
aluminum present does not interfere in the injection or extrusion process and is incorporated in
the plastic products.
Aluminum and polyethylene are bound in bales, as shown in figure 11, and sent to plastic
recyclers where they will undergo a new cleaning process in a washing machine for plastics
that is able to remove all residual fibers from the material. After cleaning, polyethylene with
aluminum is centrifuged and dried.
FIG.11- Polyethylene with aluminum bale
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FIG. 12 - Rejects Cleaner
The cleaning of polyethylene containing aluminum is made in an equipment (Fig. 12) fitted with a
non-cutting or dull rotor (Fig. 13), operating above 1000 rpm. This allows to completely removing
any trace of fibers that can harm the extrusion of the material. The separation of the fibers takes
place inside the washing device by means of a perforated sieve which has two compartments. In
the inner compartment, the polyethylene with aluminum is retained and in the outer compartment
the paper pulp is retained. Water is injected tangentially into the walls of the washing equipment.
Fig. 13 - Non-cutting or dull rotor
The agglutination process consists of a thermo-mechanic treatment where a rotor agitates the dry
plastic until it reaches the plastic transition temperature. The objective of this is to increase the
material density, in order to make it easier to feed the extruder and remove residual moisture.
Installing an exhauster where gases exit the agglutinator can optimize the moisture removal.
The amount of aluminum present in the material is on average 18% to 20%. When the material
goes into the agglutinator, humidity is an important factor since agglutinated material should have
low humidity with the objective of eliminating possible air bubbles during extrusion. This process
allows that aluminum be dispersed thus guaranteeing a homogeneous material.
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After the agglutination process, the material goes through extrusion where pellets are obtained.
These pellets are the raw material for injection or lamination of plastic parts. In the extrusion
process, the material is heated in an extruder (Fig. 14) and then is cut into small pellets.
7.0 CONCLUSION
Fig. 14 - Extrusion of Rejects (plastic/aluminium)
Post-consumer cartons represent an attractive source of high quality raw material, which
contributes to the improvement of the characteristics of the paper. The test results have shown
that tensile index, tearing index, rupture strain, burst index and concora mediu test values are
within those demanded by the market with considerable potential of gains by optimization of
refining.
As a commodity, the recycled paper market can easily change from US$250/ ton to US$450/ton
in a period of a few months and therefore, affecting the raw material (OCC, Cartons, MOW, etc)
price as well.
The utilization of high consistency rotors prevent excessive cutting in the beating process and
improve fiber fibrillation which represents an energy save at paper manufacture. On the other
hand, most of the equipments for the production of recycled paper installed in many countries
operate with low consistency hydrapulpers and low investment in production modifications is
necessary in order to recycle that material. In addition is easier to discharge the pulp from low
consistency hydrapulper system.
The type of rotor and its rotating speed affect the final characteristics of the fiber. Cutting rotors
cause the negative effect of cutting the aluminum and the polyethylene and thus contaminating
the pulp and making more difficult to remove the contaminant. For processes that shred material
in very fine pieces, at the point where the material goes through the hydrapulper screen, it is
recommended changing the rotor or reducing the rotation.
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To summarize we can say that with minor’s investment it is possible to adapt an existing paper
recycling factory to use Tetra Pak Cartons as a raw material and recovery the investment in a
short period of time.
Regarding the Poly/aluminum rejects the type of separator, after the pulper, that has shown the
best results is the cylindrical depressurized rotating screen (Rotary Drum or Trommel). After the
rejects from the separation goes through the washing in the screen mentioned above, it can be
baled and sold for the recycling of plastics or incinerated in cement kilns to recovery the energy.
8.0 – GLOSSARY
Bleached Board - Board made with pulp that has been bleached to a high level of brightness
using chemical products. Bleaching is a whitening process carried out on pulps by selective
chemical removal of residual lignin and other colored materials, and with minimal degradation of
the cellulosic constituents.
Bulk – Volume per unit weight of paper product. Bulk is the reciprocal of apparent density.
Burst index (strength) - resistance of paper to rupture under pressure, as indicated on a
"Mullen" or "pop" tester.
Chemical pulp - pulp obtained by cooking wood with solutions of various chemicals. The
principal chemical processes are the sulfite (acid), sulfate or kraft (alkaline) and soda processes.
Cleaner - Cyclone device which removes unwanted particles from fiber suspension in the paper
recycling factories.
Consistency – Mass Concentration – Solids Content - Mass or weight percentage of dry fiber
in the hydrapulper. Consistency is often described qualitatively as low, medium or high.
Corrugated Medium – Lightweight board used for the fluted inner plies (undulations) of
corrugated container board, having requirements only of stiffness and runnability through the
fluter.
CTMP – Chemi Thermo Mechanical Pulp – A mechanical pulping process in which chips are
given a chemical pretreatment whith sodium hydroxide and sodium sulphite in water. After the
short chemical treatment the chips are fed into large refiners (milling machines) under pressure
and defibrated at around 120 o C. Compared to chemical fibers the CTMP fibers are shorter and
less flexible which results in higher stiffness. Conditions are usually controlled to produce a pulp
above 90% yield.
Hydrapulper – Batch or continuous equipment for dispersing waste paper or Tetra Pak cartons
in water to prepare papermaking stock. It is a big blender used in recycling plants with volume
from 5 m 3 up to 40 m 3 .
Linerboard – Lightweight board used as the liners or facing for corrugated container. The main
requirements are stiffness and strength.
OCC – Old Corrugated Container – Post-consumer packaging used as raw material to recycling
mills to produce corrugated board.
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Paper - a homogeneous formation of primarily cellulose fibers which are formed in water
suspension on the machine wire and bound together by weaving of the fibers and by bonding
agents.
Plasma Kiln – Process used to separate polyethylene from aluminum foil using high temperature
and in the absence of oxygen.
Pressure Screen – Pulp screening equipment with some form of perforated barrier to remove
oversize, troublesome and unwanted particles from good fiber.
Pulp - papermaking material existing in a disintegrated fibrous wet or dry state. Before it is
dispersed onto the paper machine, it is mixed, beaten, and diluted to a suitable consistency for
fabrication of paper.
Pyrolyses – Chemical decomposition of the polyethylene by the action of heat.
Rotary Drum – Rotary Screen – Trommel – Coarse stock screen consisting of a large rotary
shell fitted with perforated screen plates and having an internal spiral arrangement. It is installed
in the reject exit of the pulper. Rejects enter at one end and the fiber is washed through the
screen plates by high volume showers. The reject material travels to the opposite end of the
cylinder (assisted by the spiral) where it is discharged. See figure 8.
Stiffness – Bending resistance, a desirable property of certain paper and board grades (rigidity).
Tear Index – Measure of tear strength that is independent of sheet grammage.
Tensile Strength (Index) – Force required to break a narrow strip of paper when both the length
of strip and rate of loading are closely specified.
Wet Strength – Chemical compounds used to avoid water penetration in the paper board.
White Water – General term for any stock filtrate or process water that contains fiber fines.
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