CA1106821A - Apparatus for improving fibrous matter recovered from refuse - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Apparatus for recovering fibrous matter from refuse. The refuse is comminuted prior to drying.
Major portion of heavy particle components is removed from the refuse after the comminution step, whereupon excessive size particles of the accepted stock are further comminuted by shear cutting so that the maximum size of any particle still contained in the stock is equal to or smaller than the greatest size of the particles containing fibrous matter.
The step of drying is either simultaneous with or follows the step of decomposing the substances that are readily biologically decomposable such as albumen, sugar, fat and starch. The recovered fibrous matter is in the form of flakes, as opposed to the wool- or felt like appearance obtained in prior art, to facilitate subsequent porcessing of the recovered stock, e.g. gluing, and to improve properties such as mechanical strength of the products made from the recovered fibre stock.

Description

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"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 68;~1 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 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 ~61~

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, -3b-

2~i 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 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 82~

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 ~6821 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~

Claims (9)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An 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, said apparatus comprising in a conveyor path first comminuting means to comminute the refuse to form a first comminuted material; 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; 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 drying means following the second comminuting means to dry the second comminuted material, said second comminuted material containing more readily biologically degradable material which is reduced or removed or is converted into a more difficultly degradable form, during or after drying, so as to provide dried flaky material.

2. An apparatus according to Claim 1, wherein the first comminuting means comminutes the refuse to a particle size of at most 100 mm.

3. An apparatus according to claim 2, wherein the first comminuting means comminutes the refuse to a particle size of at most 80 mm.

4. An apparatus according to Claim 1 wherein separating means is so designed that the particle size of the second component which is removed from the first comminuted material lies above a predetermined limit value.

5. An apparatus according to Claim 4, wherein the said predetermined limit value is smaller than the predetermined maximum particle size of the flaky material.

6. An apparatus according to claim 1, wherein between the separating means and the second comminuting means there is disposed in the conveyor path a screen having a mesh size larger than the predetermined limit value and smaller than the predetermined maximum particle size.

7. An apparatus according to Claim 1, wherein downstream of the second comminuting means a screen is disposed having a mesh size equal to the predetermined maximum particle size and which in operation will provide a screen residue lying in the operative range of the second comminuting means.

8. An apparatus according to Claim 1, wherein between the first comminuting means and the separating means moisture equalisation means is provided.

9. An apparatus according to Claim 8, wherein the moisture equalisation means comprise at least one bunker.