Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METHOD AND DEVICE FOR PROCESSING WASTEP~PER
Back~round of the Invention
This invention relates to the processing of wastepaper, and more
s particularly to methods of and device for disintegrating a bulk of wastepaper
into individual fibers and separating these individual fibers from cont~min~nt.ssuch as metals, plastics and ink particles, etc.
The invention is especially concerned with the disintegration of bulks
of wastepaper, and more particularly old newspaper, old magazine, computer
printouts, mixed office wastepaper, paperboard, carton and any other types of
preconsumer and postconsumer paper product, to produce pulp fibers for
m~king new paper, paperboard or carton, etc.
Heretofore, conventional practice for processing wastepaper for paper
or board production has involved the mechanical disintegration of said
wastepaper using a pulper (an disintegrator used in the pulp and paper
industry for repulping wastepaper) equipped with revolving blades, water and
chemicals such as sodium hydroxide and dispersing agents, etc.; the screening
to remove coarse cont~min~nts such as metal and plastics, etc.; the high
density cleaning using hydrocyclone to elimin~te smaller contraries such as
20 metal, sands, grits, etc.; the flotation cell to remove ink particles; and the
washing to eliminate fine ink particles and fillers. Such a conventional method
requires large capital investment and high operating costs.
Industrial uses of high-pressure water jets for cleaning, mining and
debarking of wood logs, etc., are well known. In a Canadian patent
25 application (No. 2,098,515, June 16, 1993) Ali taught the use of liquid
stream with or without chemicals and temperatures to make pulp from
cellulosic materials like wood, waste papers and non-wood plants. Ali's
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technique teaches us how to disintegrate a primary cellulosic material into a
secondary material of different form and size for further treatment by
conventional means, but it does not teach us, for example in the case of waste
papers, how to separate useful fibers from cont~min~nts.
s One of the objects of this invention is the provision of an improved
method of more economically transforming wastepaper into individual fibers
for m~king new paper or any other kinds of fibrous products. Another object
is the provision of such methods that may effect improved economy by
reduction of initial equipment cost, reduction of energy consumption and
elimination of chemical cost. It is also the object of this invention to provide a
method that, in addition to the stated economic advantages, produces fibers of
requisite quality for manufacturing good quality paper and any other types of
paper product.
Theory of the Invention
Wood fibers are hygroscopic in nature; they form paper via the
chemical bonds called hydrogen bonds between individual fibers during a
drying process. Inversely, the inter-fiber bonds can be weakened and
removed by subjecting the paper to an environment of liquid water or water
vapor. When a sheet of paper, in which the fibers are de-bonded, is subjected
to an external force, such as a high pressure water jet, the individual fibers
can be released producing a pulp slurry.
When a bulk of wastepaper, which may contain various kinds of
cont~min~nts such as ink, adhesive tapes, plastics and metal, etc., is placed
on a screen with relatively large mesh size and subjected to a high-pressure
jet of water, which provides both the wetting effect and the mechanical force
required for de-bonding and liberating the fibers, de-fiberization takes place
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reducing the bulk of wastepaper into a pulp slurry or suspension. Under the
influence of such a high-pressure jet of water, the released individual fibers
and the small cont~min~nts, such as ink particles, are forced through the wire
meshes, leaving the coarse cont~min~nt~ on the screen. Such a method of
s treatment of wastepaper achieves three important functions of de-fiberization
of the bulk of wastepaper, dislodging ink particles from fiber surface and
screening out the large cont~min~nts. Using multiple combinations of high-
pressure water jets and screens of different mesh sizes, it is possible to
produce a clean pulp suitable for m~king paper or for further processing. In
o fact, one can achieve these three principal purposes, namely de-fiberization,
screening and washing, without the use of expensive equipment such as
pulpers, screens, hydrocyclones, flotation cells and press washers, etc. as in
conventional de-inking processes.
15 Brief Description of the Invention
In general, the method of this invention involves reducing a bulk of
wastepaper to individual fibers suitable for use in the manufacture of new
paper or any other kinds of paper product. The method comprises the
procedures of placing the bulk of wastepaper on an endless revolving screen
20 of suitable mesh size, subjecting it to a high-pressure liquid jet and affecting a
movement of the screen so that the liquid jets continuously impinge on the
bulk of wastepaper. As the liquid impacts onto the bulk of wastepaper, the
printed ink is reduced to fine particles and dislodged from the fiber surfaces,
while the individual fibers are simultaneously liberated from the bulk and
25 forced through the screen with meshes larger than the length of the liberated fibers. The resistant cont~min~nts such as plastic materials having a
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dimension larger than the mesh sizes remain on the revolving screen and are
removed by gravity and a water shower.
The liberated fibers and the smaller contaminants that passed through
the first coarse screen are retained on a second endless revolving screen of
s finer mesh size, located underneath the first coarse screen, and subjected to
high-pressure water jets that effect further de-fiberization, screening and
washing actions that may be further repeated using finer screens.
One of the embodiments of this invention comprises a series of three or
more endless revolving screens configured in such a way that the screens with
larger mesh sizes are positioned above those of smaller mesh sizes; the
coarsest one being on the top of all the others and the finest one at the
bottom.
In another aspect of the invention, means are provided to recover, treat
and re-utilize the white water used in the system, to minimi7e the
consumption of water.
Specific Description of the Invention
The invention, as exemplified by a preferred embodiment, is described
with reference to the drawings in which:
Figure 1 is a sectional view of an embodiment of an apparatus of the
invention;
Figure 2 is a perspective view of part of the apparatus shown in Figure
l;
Figure 3 is a perspective view of part of the apparatus shown in Figure
2.
Referring to drawings, the embodiment of the invention shown, an
apparatus 2 comprises a conveyor 18, four endless screens 10, 12, 14 and 16,
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one narrow angle high-impact water jet 22, four high-pressure washing jets
24, 26,28 30, four intermediate-pressure washing jets 32, 34, 36, 38, three
white waters (used water) collectors 40, 42, 44, one accept collector 46, and
three reject collectors 48, 50, 52.
The conveyor 18, located at the top end of the coarsest screen 10, is
used to continuously feed the apparatus 2 with wastepaper 58, and it revolves
in the same direction as the screens 10, 12, 14, 16 do.
The screens 10, 12, 14 16 are configured in such as way that the finer
ones are positioned below the coarser ones, with the coarsest one 10 on the
o top and the finest one 16 at the bottom. The screens 10, 12, 14, 16 are
supported by motorized rolls 20.
The high-impact water jet 22 is located near the feeding end of the
coarsest screen 10, while the high-pressure washing jet 24 is located
immediately after the high-impact water jet 22. The high-pressure washing
S jets 26, 28, 30 are, respectively, located above the screens 12, 14, 16. These
high-pressure washing jets 24, 26, 28, 30 are positioned in series without
overlapping each other. The high-pressure washing jets 24, 26, 28 are used to
washed the fibrous material through meshes 56 of the screens 10, 12, 14,
while the high-pressure washing jet 30 is used to wash off the fine
cont~min~nts, such as ink particles, from the de-fiberized wastepaper.
The intermediate-pressure washing jets 32, 34, 36, 38, are located,
respectively, above the lower part of the screens 16, 14, 12, 10. The washing
jets 32 is used to remove the accept of fibers from the finest screen 16 into
the accept collector 46, while the washing jets 34, 36, 38 are used to wash off
the cont;~min~nts on the respective screens 14, 12, 10 into the respective
reject collectors 48, 50, 52.
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The white water collectors 40, 42, 44 are, respectively, located under
the screens 12, 14, 16. The white water collectors 40, 42 under the screens 12
and 14, respectively, are positioned immediately before, but not directly
under, their respective high-pressure washing jets 26, 28. However, the white
5 water collector 44 located under the finest screen 16 is extended to cover the area directly under the high-pressure washing jet 30.
In order to disclose more clearly the nature of the present invention, the
following example illustrating the invention is given. It should be understood,
however, that this is done solely by way of example and is intended neither to
delineate the scope of the invention nor limit the ambit of the appended
claims.
This example illustrates the de-fiberization of a bulk of wastepaper 58
on a revolving coarse screen 10 under a mechanical force of the high-impact
water jet 22. As the wastepaper 58 moves forward it is subjected to the action
of the high-impact water jet 22. The highly concentrated water particles 54
strike onto the fibers 60 stretching across the meshes 56 of the screen 10.
With the wires 62 of the screen 10 acting in opposite direction of the water
particles 54, the fibers 60 of the bulk of wastepaper 58 are de-bonded and
liberated either individually or in bundles, or in flakes. Under the mechanical
20 force of the high-impact water jet 22, the partially de-fiberized wastepaper
passes through the meshes 56 of the coarse screen 10 and onto the revolving
finer screen 12, while larger bundles of fibers will be further de-fiberized by
the high-pressure washing jet 24 and forced through the meshes 56 of the
coarse screen 10. The fully liberated fibers and the partially de-fiberized
25 wastepaper (or fiber bundles) deposited onto the finer screen 12 are subjected
to the action of the high-pressure washing jet 26. These de-fiberization and
washing actions are repeated on screens of finer mesh sizes 14, 16. The
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accept of pulp fibers is doctored off by means of the intermediate-pressure
washing jet 32 and collected by the accept collector 46. Any large
contaminants that cannot be broken down by the high-impact water jet 22 and
the high-pressure washing jets 24, 26, 28 are removed by the intermediate-
s pressure washing jets 34, 36, 38 and collected by the respective rejectcollectors 48, 50, 52. The fine ink particles are received by the white water
collectors 40, 42, 44.
A feature of the apparatus combination 2 of this invention is its ability
to disintegrate a bulk of wastepaper into individual fibers suitable for
o manufacturing new paper products and remove the cont~min~nts from the
usable fibers.
Although only a single embodiment of the present invention has been
described and illustrated, the present invention is not limited to the feature of
this embodiment, but includes all variations and modifications within the
scope of the claims.
