Note: Descriptions are shown in the official language in which they were submitted.
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11~68~
"M,ethod of imProvina a fibrous material made from refuse"
The present invention relates to a method of improving
a fibrous material made from refuse, wherein the refuse is
comminuted and dried and before and/or during the drying
the more easily biologically degradable substances, such
as albumen, sugar, fat, and starch are removed from the
comminuted refuse or are converted into a more difficultly
biologically degradable form, and the invention further re-
lates to an apparatus for carrying out the method, to a
fibro~ls material produced by the method> and to a utilisation
of th~. fibrous material.
~ iethods of this kind are known and are described, for
example, in Swiss Patent Specification No. 503,576 and in
US Patent Specifications No. 3,892,706 and No. 3,951,731.
In these methods the refuse is comminuted by hammer mills,
impact mills, and beater mills in accordance with theparticle
size desired in the fibrous material or fibrous granulate.
The more readily biologically degradable components of the
refuse .are thereupon removed or decomposed, and this can be
done before and/or during the dryiny of the refuse.
In these known methods the heavy Parts are separated
only after the drying. Drying and sterilisation yield either
a fibrous material in granulate form or a fibrous material
in fibre form which looks like a wool or felt. This external
form may give rise to difficulties in further processing,
such as gluing to form molded products; it may also impair
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the mechanical strength properties of the moulded products.
The problem ~derlying the present invention is that
of improving the methods of the kind first mentloned above
in such a manner that the fibrous material obtained consists
essentially of particles which in their external form are
similar to flaxes~ that is to say re~semble in aPPearance
a flake of wood.
According to the invention this problem is solved in
that the refuse is precomminuted before the drying, that at
least the major proportion of heavy parts are removed from
the precomminuted refuse, whereupon at least those particles
of refuse which are larger than the largest particles of the
fibrous material are further comminuted bY cuttinq until they
are equal in size to or smaller than the largest particles
of the fibrous material.
The invention provides for the apparatus used to com-
prise, in a conveyor path, a precomminution apparatus followed
by a heavy Part separator, the latter being followed by a
cutting aPParatus, and the cutting apparatus preceding a
drying apparatus.
According to the invention the fibrous material produced
according to the method is used to produce moulded products.
The invention, that is to say the flake-like form of
the individual fibres of the fibrous material,provides the
advantage that the fibrous material contains a smaller pro-
portion of mineral dust. Another advantage consists in that
both mineral dust and organic dust can be removed more
easily from the fibrous material. Another advantage consists
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in that the fibrous material can be more effectively
divided into fractions by screening, since a wool-like or
fe:Lt-like material rapidly clogs the screens.
~ n apparatus suitable for preparing from
refuse, which consists of a first component comprising
relatively light and soft materials and a second component
comprising relatively heavy and hard materials, a flaky
material which comprises particles having a predetermined
maximum particle size and which simulates a wood flake-
like material. The apparatus comprise$ ina conveyor path
(a) first comminuting means to comminute the refuse to
form a first comminuted material, the particle size of
which is preferably at most 100 mm and more preferably at
most 80 mm, (b) separating means following the first
comminuting means to remove at least a major portion of
the second component from the first comminuted material to
form a residual material; (c) second comminuting means
following the separating means to comminute the residual
material by cutting particles of the residual material
which are larger than the predetermined maximum particle
size such as to yield particles equal to or smaller than
the predetermined maximum particle size, thus forming a
second comminuted material, and (d) drying means follow-
ing the second comminuting means to dry the second comminuted
material. The second comminuted material contains more
readily bio]ogically degradable material which is reduced
or removed or is converted into a more difficultly
- degradable form, durillg or after drying, so as to provide
dried fla~y material. The separating means is preferably
so designed that the particle size of the second component
which is removed from the first comminuted material
lies a~ove a predetermined limit value. The predetermined
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limit value is preferably smaller than the predetermined
maximum particle size of the flaky material.
In a preferred embodiment a screen having
a mesh size larger than the predetermined limit value
and smaller than the predetermined maximum particle
size is disposed in the conveyor path between the
separating means and second comminuting means. Furthermore,
a screen having a mesh size equal to the predetermined
maximum particle size may be disposed downstream of the
second comminuting means. In operation, this screen
will provide a screen residue lying in the operative
range of the second comminuting means. Between the first
comminuting means and the separating means moisture
equalization means which preferably comprise at least one
bunker may be provided.
In the drawing which illustrates, by way of
example, a particular embodiment of the present invention:
Figure 1 shows a diagram of one embodiment of
the apparatus and process according to the invention.
In this exampIe the refuse is worked up into
fibrous material which is finally produced in three
fractions. The fractions are:
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coarse fraction: screen mesh 2 to 8 mm (bunker 26)
middle fraction: screen mesh about 0.1 to 2 mm (bunker 25)
dust fraction (bunker 27).
Refuse produced in populated areas is usually delivered
in sacks of plastics materials, boxes or other containers,
or loose.Cn the average it has the following composition:
about 10 to 15 ~ glass, sand, and stones
about 0.5 % non-ferrous metals
about 3 to 5 % iron
about 2 to 3 % residues of fabric and other tex~iles,
synthetic resins, plastics, leatner, and
wood
about 20 ~ kitchen refuse in general
about 15 % garden refuse, agricultural and forestry
refuse
about 40 % papers and packing materials
The refuse collecting vehicles tip the refuse directly
into a crude refuse pit 2 at the discharge point 1. The refuse
lying in the crude refuse pit is delivered into a well by
means of a pit conveyor belt 3. From the well the refuse is
delivered by means of a grab crane 4 into a precomminution
apparatus which consists of a mill 5, a vibration trough 6,
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a second mill 8, and a second vibration trough 9. The mills
5 and 8 are preferably commercially available units in which
the refuse is crushed or broken up between two cutter shafts.
They are for example marketed by Herbold AG, Neckersheim,
Federal Republic of Germany, under the name "Messerscheiben-
zerkleinerer'l (cutter disc grinders). However, it is also
possible to use commercially available beater, hammer, or
impact mills, provided that a small proportion of particles
resembling wool or felt in appearance is accepted in the
fibrous material. Instead of two mills 5 and 8 it is also
possible to use only one~ In the mills 5 and 8 the refuse
is precomminuted to a maximum particle size corresponding
to a screen mesh of 80 mm. It is inadvisable to select a
s~reen mesh of more than lO0 mm. The refuse comminuted in
the mill 5 falls onto the vibration trough 6, which carries
it to the second mill 8. Above the vibration trough 6 is dis-
posed a magnetic separator 7 which throws the magnetic metal
parts onto a mechanical conveyor system, which passes them
to a scrap metal bundling device 11 which produces bundles
12. The refuse precomminuted in the mill 8 is delivered past
a second magnetic separator 10 and to a heavy part separator
13 by means of the vibration trough 9. The magnetic metal
parts separated by the magnetic separator 10 are liXewise
delivered to the scrap metal bundling apparatus 11.
From the vibration trough 9 the precomminuted refuse
passes into the heavy part separatOr 13, which separates all
heavy parts of a diameter of more than 1.5 mm. The heavy part
separator 13 is a commercially available apparatus ~nown
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E~r se and is marketed by Simpelkamp KG, Penzberg, Federal
~epublic of Germany, under the name "Rotationswindsichter"
(rotary air sifter).
The heavy parts separated in the heavy part separator
13 drop into a conveyor trough 14. The refuse leaving the
heavy part separator 13 is substantially freed of heavy parts. _
grain
The ~X~ /size of the heavy parts still contained therein
corresponds at most to a screen mesh o~ 1.5 mm. The refuse
is then delivered onto a vibration screen 15 having a mesh
of 6 mm; the mesh of the vibration screen 15 is thus larger
than the largest heavy parts still contained in the refuse,
so that the latter fall through the screen 15 together with
the smaller particles of refuse. In addition. the mesh of
the vibration screen 15 is equal to or smaller than the
largest fraction of the fibrous material which is desired
at the end of the process. The refuse fraction falling
through the vibration screen 15 is delivered to an inter-
media~e bunker 17 and the fraction of refuse which does
not all through the vibration screen 15 is delivered to a
cutter mill 16. In the cutter mill 16 the mill is finally
comminuted by cutking. The cutters of the fine cutter mill
16 are subjected to only slight wearJ because the refuse now
contains no heavy parts. The fine cutter mill 16 is a
commercially available unit (Pallmann KG, Zweibrucken,
Federal Republic of Germany) and consists of a steel casing,
a cutter rotor, inbuilt stator cutters, and a square hole
screen with a screen mesh of 8 x 8 mm. The size of the
screen mesh of the square hole screen determines the size of
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the largest fraction of the vibrous material produced. The
refuse falls directly onto the cutter rotor, which recei~es
the material and throws it to the cutter statOr, The material
comes to lie on the stationary cutter and by means of the
rotor cutters rotating with a cutting action past the stator
cutter is cut into small chips having clean cut edges. The
cut parts then fall into the screen chamber. The particles
w~ch do not fall through the square hole screen are again
thrown by the rotor cutters into the feed chamber and sub-
jected to further comminution~ The material leaving the fine
cutter mill 16 has an appearance similar to wood flakes with
clean cut edges and is passed on to intermediate~bunker 17.
From the intermediate bunker 17 the refuse passes into a
drying drum 18. The commercially available drying drum 18
(W. Kunz AG, Dintikon, Switzerland) consists of a rotating
cylinder into which the combustion gases of an oil burner
are blown ~xially from one side and drawn off axially on the
opposite side. In the drying d~um 18 a temperature is selected
which is above 100C but below the ignition point of the
refuse. Surrounded by a cushion of vapour the incoming
refuse is therefore dried within a residence time of about
2 minutes to a final water content of less than 5 %. The
temperatures selected in the drying drum 18 effect sterilisat:
of the refuse simultaneously with the drying. ~n the drying
drum 18 the refuse is converted into a sterile fibrous
material which contains no readily biologically degradable
substances such as albumen, starch, sugar, and the liXe,
since these are converted by the heat into a low molecular
form. The m dividual particles retain their appearance
similar to wood flakes with sharp cut edges. The fibrous
material together with the outgoing gases then passes into
a separating cyclone. The outgoing gases are partly returned
by means of a pressure fan into the combustion chamber for
recirculation. The remainder passes into an exhaust gas
purifying system 21 (venturi system)~ ~
From the separating cyclone the fibrous material passes
into an ozone-fibre mixer 20, in which the fibrous material
is mixed with ozone gas. Any butyric acid and fatty acid,
or residues thereof, which are still present and which impart
a peculiar but harmless odour to the fibrous material, are
completely eliminated or split. As the fibrous material
treated with ozone is discharged the excess ozone is drawn
off and passed to the hot exhaust gases. Ozone is continuously
produced in the ozonizer 19. The fibrous material leavin~
the ozone-fibre mixer 20 is passed to a screening machine
22. The screening machine 22 comprises an upper screen with
a mesh of 2 mm and a lower screen of a mesh of 1 x 1 mm. The
fibrous material which does not pass through the upper screen
forms the largest fraction and is delivered by way of a
cyclone to a silo 26. The fractions of fibrous material
passing through the upper screen fall onto the lower screen
with a mesh of 1 mm. The fraction of fibrous material with a
mesh of 1 to 2 mm remains on the lower screen, from which it
is passed to a fine screening system 24. The fraction of
fibrous material falling through the lower screen, with a
size of from O to 1 mm, is passed to a fine screening system
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23. In the two fine screening systems 23 and 24 the heavy
part;s still present in the fibrous material are separated.
The heavy parts are separated in the fine screening systems
23 ànd 24 because they correspond to a screen mesh of at most
1.5 mm and therefore must be contained in these two fractions
of fibrous material. The heavy parts separated are passed to
the trough 14. The fibrous material passing out or the fine
screening systems 23 and 24 is delivered by way of a cyclone
to a bunker 25. The dust separated in the bunkers preceding
the bunkers 25 and 26 is passed to a bunker 27. From the
bunker 27 dust-laden air is drawn off by way of a dust filter
28. The three fractions of fibrous material which are stored
separately in the bunkers 25, 26, and 27 can be passed on
separately or in planned m-xtures for further processing.
In the refuse treated the distribution of water may vary,
for example if rotten fruits lie side by side with dry news-
paper. This may have the consequence that very wet refuse
components may be separated together with the heavy parts in
the heavy parts separator 13; the amount of fibrous material
obtained at the end of the process would thereby be reduced,
which is undesirable. It has therefore been found expedient
for moisture equalisation to be effected in the refuse up-
stream of the heavy part separator 13; as indicated in dot-
dash lines, this can be achieved by intermediate storage of
the refuse in a bunker Sl or S2 for from four to twenty-four
hours. After being filled with refuse the bunkers Sl, S2 are
-preferably closed. In order to ensure continuous operation J
at least two bunkers should be provided. ~'hen two bunkers are
available, the refuse can be taken off from one of them for
further processing while the other is being filled. This
intermediate storage takes place most expediently downstream
of 1he precomminution apparatuS 5, 6, 8,9, since moisture
equalisation is achieved most quickly in the comminuted
refuse~
