PROCESS AND APPARATUS FOR SORTING A MIXTURE OF PAPER

PROCEDE ET DISPOSITIF DE TRI D'UN MELANGE DE PAPIERS

English Abstract

The invention relates to a method for sorting a paper mixture according to
which the paper mixture is sorted into a fraction of mixed paper and a
fraction of deinking paper. The aim of the invention is to improve the sorting
process in such a way that the quality requirements of the deinking quality
can be reliably met and that the staff required for sorting is reduced. To
this end, the paper mixture is reduced to a grain size of approximately 40 to
100 mm and the reduced paper mixture is separated by air separation into a
heavy fraction that contains mixed paper and a light fraction that contains
deinking paper at a separation speed of approximately 1 to 5 m/sec. The
invention further relates to a device for sorting a paper mixture that allows
fulfillment of the quality requirements of the deinking quality and that can
be carried out with a reduced number of staff. To this end, a disintegrator
for disintegrating the paper mixture is provided. Downstream of said
disintegrator an air separator for separating the disintegrated paper mixture
into a heavy fraction and a light fraction is mounted. Said air separator has
a classification cross-section that can be adjusted to a separation speed of
between 1 and 5 m/sec.

French Abstract

La présente invention concerne un procédé de tri d'un mélange de papiers, dans lequel le mélange de papiers est séparé en une partie papier mixte et une partie papier apte au désencrage. Ce procédé permet de répondre aux exigences de qualité en ce qui concerne la qualité d'aptitude au désencrage et d'éviter d'avoir recours à trop de personnel pour effectuer le tri. Pour cela, le mélange de papiers est fractionné pour obtenir des morceaux dont la taille est comprise entre 40 et 100 mm et le mélange de papier fractionné est séparé par triage à vent en une fraction lourde composée de papier mixte et une fraction légère composée de papier apte au désencrage à une vitesse de séparation d'environ 1 à 5 m/s. L'invention concerne également un dispositif de tri d'un mélange de papiers permettant de répondre aux exigences de qualité en ce qui concerne la qualité d'aptitude au désencrage et d'éviter d'avoir recours à trop de personnel pour effectuer le tri. Pour cela, le dispositif comprend un élément de fractionnement destiné au fractionnement du mélange de papiers, et d'un séparateur à vent, situé en aval de l'élément de fractionnement, destiné à la séparation du mélange de papier fractionné en une fraction lourde et une fraction légère, présentant une vitesse de séparation réglable d'environ 1 à 5 m/s.

Claims

7
Claims
1. A process for sorting a mixture of paper, wherein the mixture is ground to
a particle size in a range of 40 to 100 mm and the ground mixture is
separated into a heavy material fraction containing mixed paper and into
a light material fraction containing a deinking fraction by means of
pneumatic sifting, characterised in that the separating speed of the
pneumatic sifting is 1 to 5 m/sec.
2. The process according to claim 1, characterised in that the mixture of
paper is ground to a particle size of approximately 60 to 90 mm.
3. The process according to claim 1 or 2, characterised in that the
separating speed is 1.5 to 4.5 m/sec and preferably 1.7 to 3.5 m/sec.
4. The process according to one of claims 1 to 3, characterised in that the
pneumatic sifting is carried out in a cone sifter.
5. The process according to one of claims 1 to 3, characterised in that the
pneumatic sifting is carried out in a Zigzag sifter.
6. The process according to one of claims 1 to 5, characterised in that the
mixture of paper is loosened by a loosening unit prior to grinding.
7. The process according to one of claims 1 to 6, characterised in that the
light material fraction is split into the deinking fraction and the air flow
in a
cyclone.

8
8. The process according to one of claims 1 to 7, characterised in that the
deinking fraction is re-sorted by means a colour and/or NIR detection.
9. An apparatus for sorting a mixture of paper, comprising a disintegrator
(1) for grinding the mixture of paper and a pneumatic sifter (2) arranged
behind the disintegrator (1) for separating the ground paper mix into a
heavy material fraction and into a light material fraction, characterised in
that the pneumatic sifter (2) has a sifting cross section, in which a
separating speed of between 1 to 5 m/sec can be adjusted.
10. The apparatus according to 9, characterised in that the disintegrator (1 )
is made up of a granulator or rotor shears.
11. The apparatus according to claim 9 or 10, characterised in that the
disintegrator (1) comprises grinding means for grinding the paper to a
particle size of approximately 40 to 100 mm.
12. The apparatus according to one of claims 9 to 11, characterised in that
the pneumatic sifter (2) is made up of a cone sifter.
13. The apparatus according to one of claims 9 to 11, characterised in that
the pneumatic sifter (2) is made up of a Zigzag sifter.
14. The apparatus according to one of claims 9 to 13, characterised in that a
cyclone (3) for separating the deinking fraction from the light particle
fraction is arranged behind the pneumatic sifter (2).
15. The apparatus according to one of claims 9 to 14, characterised in that a
loosening unit (5) is arranged in front of the disintegrator (1 ).

9
16. The apparatus according to claim 14, characterised in that a sorting
means (4) for the deinking fraction is arranged behind the cyclone (3),
said sorting means working by means of a colour and/or NIR-detection
system.
17. Use of an apparatus according to one of claims 9 to 16 for sorting a
mixture of paper, in particular a mixture of used paper from a waste
paper collection.

Description

CA 02338553 2001-O1-24
Process and apparatus for sorting a mixture of paper
s The present invention relates to a process and apparatus for sorting a
mixture
of paper according to the preamble of claim 1 and/or claim 9.
At present, approx. 12 million tons of used paper are reutilised in production
processes in Germany each year. About 5.3 million tons of this amount are
io sorted each year into different categories by numerous facilities prior to
reutilisation.
The known apparatus and processes for sorting the collected mixtures of paper
use sorting staff for separating the contents of storage containers, paper
is collected in bins and/or paper bundles into the various qualities and to
achieve
the paper/cardboard quality, such as deinking quality, required for
reutilisation.
Prior apparatus for sorting mixtures of paper include transporting and sorting
conveyors with sorting staff who, in order to produce a deinking quality, also
manually remove interferents such as cardboard, cardboard articles and
Zo possibly books from the supplied mixture of paper. In this known sorting
procedure, cardboard and cardboard articles are also sorted for producing a
fraction predominantly containing cardboard.
In this way, a deinking fraction, a mixed paper fraction and a cardboard
fraction
2s is generated. The deinking fraction predominantly consits of newspapers and
magazines and contains, in accordance with the requirements, at least 60%
newspapers and no more than 3% of interferents such as cardboard and
cardboard articles, whilst the mixed paper fraction contains newspapers and
magazines (below 40%), cardboard, other papers and cardboard articles (over
30 60%) as well as plastic and other interferents to a lesser extent. The
cardboard

CA 02338553 2001-O1-24
2
board fraction contains predominantly (over 70%) of cardboard, cardboard
articles, solid board and similar material.
Apart from the known manual sorting, experiments concerning automation
s using sifting machines have been performed. The results did, however, not
live
up to the expectations as it is difficult to differentiate most of the
interferents
such as cardboard and cardboard articles from newspaper based on grain size,
so that sifting operations produced only inadequate qualities.
io It is object of the present invention to provide a process and an apparatus
according to the preamble of claim 1 and/or claim 9 that enable to reliably
fulfil
the deinking quality requirement and avoid labour-intensive sorting.
This object is achieved with a process and an apparatus with the features of
is claim 1 and/or claim 9.
As a result, no manual sorting is required and the maximum of 3% of
interferents and the minimum newspaper percentage of 60% can be reliably
obtained.
The combined grinding and pneumatic sifting operation also produces a high
throughput as a result of the high separating speed whilst at the same time
producing a continuously high quality of the resulting fractions.
2s If the mixture of paper is ground to a grain size of between approx. 60 and
90
mm, a particularly good separation can be achieved between mixed paper and
deinking with relatively little grinding effort.
With separating speeds in the range of 1.5 to 4.5 m/sec and preferably in the
3o range of 1.7 to 3.5 m/sec, a particularly high quality of the produced
fractions
can be guaranteed.

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By using a cone sifter for the pneumatic sifting, a near uninterrupted
operation
and a good separating performance can be guaranteed. If a Zigzag sifter is
used for pneumatic sifting, a particularly effective selectivity of mixed
paper and
s deinking can be achieved.
The light particle fraction, initially produced by pneumatic sifting and which
includes the deinking quality is advantageously separated in a cyclone into a
(transporting) air current and into deinking.
io
The quality of the deinking fraction can be increased by resorting - using
colour
and/or NIR detection - and a pneumatic ejection of the identified
interferents. In
this way, shreds of paper dyed throughout can, for instance, be effectively
separated based on their size and colour, allowing a deinking fraction, of
which
is most of the paper dyed throughout has been removed, to be produced.
Also a nearly 100% separation of adhesive backing from the deinking fraction
is
guaranteed which would normally interfere with further process stages during
reutilisation as a result of the adhesive sticking.
Other embodiments of the invention are specified in the dependent claims and
the description.
The invention is subsequently explained in more detail with reference to an
2s embodiment of an apparatus for sorting mixed used paper from collection
bins,
said embodiment being shown diagrammatically in the figure.
The apparatus for sorting a used paper mix shown in the figure comprises a
disintegrator in form of a granulator 1, a pneumatic sifter in form of cone
sifter 2,
3o said pneumatic sifter being arranged behind the granulator 1 and a cyclone
3
being arranged behind the cone sifter 2.

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The design of the disintegrator 1 mainly has to ensure that the disintegrating
means prevent several pages from sticking during the disintegration so that
only a small amount of sticking paper shreds, i.e. because of block punching,
s are created. A swing-hammer crusher can for instance be used as
disintegrator
1, a relative high amount of dust caused by said swing-hammer crusher being
acceptable.
A colour sorting means 4 is arranged after the cyclone 3 at the discharge side
io of the deinking fraction. A loosening unit in form of a drum 5 is arranged
before
the granulator 1. In order to be able to separate cardboard articles and
cardboard that is considerably larger and more bulky than paper pages, a sieve
in form of a corrugated sieve can be arranged in front of or behind the drum.
is For processing or sorting, the used paper mix supplied in drums, after
possibly
being sifted, is loosened in the drum 5 and fed into the granulator 1 where it
is
ground to a particle size of approx. 70 mm.
The ground, used paper mix is then separated by means of an air current into a
2o heavy material fraction and a light material fraction in the cone sifter 2,
the
speed of the air flow being set to approx. 3 m/sec. The heavy material
fraction
includes the mixed paper fraction consisting mainly of bits of cardboard,
cardboard articles and other paper shreds as well as a low amount of
interferents. The light material fraction contains the deinking fraction and
the
2s transporting air current.
Whilst the mixed paper fraction is deposited in a bunker not shown in the
figure,
the light particle fraction is forwarded to cyclone 3 where it is separated
into
deinking and the air current.

CA 02338553 2001-O1-24
The deinking fraction can be fed to the sorting means 4, where paper shreds
dyed throughout can been removed. In case of the deinking fraction only
containing a small amount of paper shreds dyed throughout, the fraction can be
forwarded directly to a collection bunker.
5
In order to achieve a good separation and at the same time a high throughput
with pneumatic sifting, the pneumatic sifter 2 has a sifting cross section of
approximately 0.01 to 0.4 m2 and preferably of 0.05 to 0.3 m2. The volume flow
of the air is adjusted in such a way that a separating speed of approx. 1 to 5
io m/sec and preferably 1.5 to 4.5 m/sec and particularly preferably of 1.7 to
3.5
m/sec is achieved.
During a test, a supplied mixture of used paper fed through a disintegrator 1,
cone sifter 2 and cyclone 3, produced approx. 40.5% of mixed paper and
is approx. 59.5% of deinking. Significantly more than 97.5% of the deinking
fraction consisted of thin paper with only a low percentage of thin cardboard
and other interferents.
In a test in which the cone sifter was replaced by a Zigzag sifter, the
process
2o yielded approx. 36% mixed paper and approx. 64% deinking in relation to the
original used paper mix.
At the specified separating speeds, the percentage of interferents produced in
the tests, said interferents having a significant adverse effect on the
quality of
2s the papers produced from deinking, such as cardboard, adhesive backing,
packaging paper and paper dyed throughout, amounted to less than 1.5%
(mass % compared to the input).
Interferents which are removed as rejects in paper plants, such as plastic and
3o wet-strength paper, amounted to less than 1 % (mass % compared to the
input).
This means that the amount of interferents adversely affecting the quality of
the

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produced deinking fraction was significantly reduced - by more than 30% -
compared to the prior art.
By equipping the system with a corrugated sieve, large cardboard can be
s automatically separated and a high-quality card fraction can be produced in
a
cost-effective manner. One of the important parts of the system is the
loosening
unit, ensuring, as far as possible, that individual sheets are forwarded to
the
disintegrator, to prevent multi-layer newspaper / magazines to be pressed
together at the cutting edges. This significantly increases the deinking
yield.
io Without a loosening unit a respectively lower yield is has to be accepted
as the
paper shreds pressed together may be get into the heavy material fraction.
Where, in variation to the aforementioned tests, pneumatic sifting is carried
out
by means of a cross-flow sifter, a compact and low-cost pneumatic sifting
stage
is can be realised.