GB2195559A - Process for treating a heterogeneous product, in particular domestic waste, and a shredding device for use therein - Google Patents

Abstract

In the treatment of any heterogeneous material such as domestic waste, involving the application to it of a sieving operation in order to separate it into two components, the sieving operation is preceded by one or several passages of the material to be treated in a shredder suitable for acting selectively on the components of the latter and comprising a drum 14 of at least 1 m diameter carrying fingers 15 whose tips preferably have a mean circumferential speed of 1800 m/min. The fingers 15 may be mounted on slidable bars. <IMAGE>

Description

SPECIFICATION Process for treating a heterogenous product in particular domestic waste and a shredding device suitable for use in such a process The present invention concerns in a general manner the treatment of any heterogeneous product, that is to say any product formed from at least two components, the said t?eat- ment involving the separation of one or other of the said components It is aimed more particularly, but not necessarily exclusively, at the case where the product to be treated consists of domestic waste.

As is known, domestic wastes in total are composed of two main categories of materials.

First of all there are the inert or scarcely fermentable materials which change little or not at all with time such as, for example, textiles, synthetic organic materials referred to subsequently simply as synthetic materials, glass and metals.

There are in addition non-synthetic or fermentable organic materials, that is to say substances which, as a result of a more or less slow degradation process, change with time.

These are in particular papers, cardboard, vegetable materials and animal materials.

Because of this second category of materials, domestic wastes have a nct insignificant importance in agriculture as organic soil improving products, and this is why they are now being more and more systematically made the object of a certain amount of recovery.

But, to be most suitable for agricultural requirements it is necessary to give them a preliminary treatment, on the one hand to favour a change towards a certain stabilization of the fermentable- fraction, and on the other hand to remove the inert fraction.

In a customary manner, the stabilization of the fermentable fraction is done by composting, for example by putting the material to be treated in swaths, that is elongated heaps, suitably moistened, and in turning at regular intervals these swaths in alternation with rest periods of the latter.

In an equally customary manner, elimination of inert materials is done with a screener.

In practice, the techniques of screening used exploit the physical characteristics which distinguish one or other of the materials to be separated.

If heavy materials are concerned, such as glass or metals for example, it is their density which is in effect taken into account.

If light materials are concerned, such as plastics for example, it is their dimensions, these materials occurring most often in the form of sacks of various sizes or of smaller or larger bottles or sheets.

The corresponding operation is.-therefore a simple sieving operation suitable for the separation of such components.

In a general manner the object of the present invention is an arrangement allowing the optimization of this sieving operation by exploiting another physical characteristic, namely the mechanical resistance, of the materials treated.

It is in fact based on the observation that, whilst the inert materials, such as the synthetic materials, usually show a significant mechanical resistance which is normally conserved with time, it is not the same with the fermentable materials either because they show from the start a relatively mediocre mechanical resistance or because, as a result of their moistening and their change by fermentation, the mechanical resistance decreases progressively with time.

A first aspect of the present invention provides a process of treatment of a heterogeneous product, of a type involving the application to this product of a screening operation in order to separate it into two components, this process being characterized in a general manner in that the said operation of screening is preceded by an operation of shredding conducted, in a manner to affect the said components selectively, with the aid of a shredder having a rotating drum of which the diameter is at least equal to 1 m and which carries projecting fingers.

A second aspect of the present invention provides a shredder to perform such a process, this shredder being characterized in a general manner in that it consists of a drum which, mounted to rotate in a frame, and being situated transversely at the far end of a conveyer, has a diameter at least equal to 1 m and carries projecting fingers.

Applied to domestic wastes, the shredding thus characteristic of the invention is selective since, in practice, because of their inherent mechanical resistance, it essentially only affects the fermentable materials which they contain.

In practice it has been found that since the substances in synthetic matter become only slightly moistened during composting and retain their mechanical resistance, a shredding carried out following the conditions of the invention hardly affects them and their size remains considerable, whilst the fermentable materials are shredded rapidly and so undergo a rapid and considerable decrease in their size, their large uptake of water, due to their great power of absorption, leading rapidly to a breakdown of their inherent mechanical resistance.

Thus, the selective shredding according to the invention, which is associated in fact with a simple screening, is itself distinguished from a crushing which affects without differentiation the whole of the materials treated.

A fortion it is distinguished from a crushing which systematically reduces these indistinguishably into fragments of the same dimensions.

As indicated, the drum of the shredder used for this effect has a diameter at least equal to 1 m, and possibly substantially greater than such a dimension.

The diameter of the drum according to the invention is, therefore, relatively large.

Preferentially, for treatment of domestic wastes, the speed of rotation which is applied to it is, in contrast, moderate.

In practice, this speed of rotation is below 500 rpm, being for example about 200 to 300 rpm, so that the inert materials to be eliminated are not much affected by the operation of the corresponding shredding.

In any case it is much lower than the customary speeds of rotation of crushers, which are always above 500 rpm, being for example about 1000 to 1500 rpm.

Thus, as required, only the fermentable materials are affected by the operation of shredding and the particle size of these is progressively reduced to a relatively low value, of a kind to facilitate their selection during the subsequent sieving operation.

The weight of organic matter in the compost finally obtained is consequentiy advantageously increased.

Conjointly, the use for shredding, according to the invention, of a drum with relatively large diameter, avoids the progressive partial or total occlusion of this by the rolling round the drum of synthetic materials in sheets or as sacks, to the detriment of its efficacy.

Experience shows, in fact, that objects of synthetic matter having a length greater than would form a circumference with a diameter above 1 m are generally absent from domestic wastes.

Concerning the composting of domestic wastes, the operation of shredding according to the invention is advantageously associated with an operation for re-transfer of similar material, such as that necessary on the re-turning of a swath or that intervening between a feeding hopper and a refining chain.

In fact, in the one case or the other, the corresponding shredder integrates entirely in the logic of the corresponding treatment process.

Concerning domestic wastes in swaths, it facilitates the turning of them if the conveyer, at the extremity of which the drum is transversely placed, forms the floor of a vehicle the chassis of which carries the frame for the drum and the mobility of which permits the re-formation of such a swath during forward movement.

With regard to domestic wastes in hoppers, it facilitates breaking up of lumps before refining.

In practice several passages of the domestic wastes through such a shredder are envisaged, a first passage ensuring for example their preparation, whilst the several subsequent passages are each associated, as indicated, with a cycle in their composting.

In every case, where the densimetric screening necessary for the elimination of heavy substances intervenes before such passages, after the passages, or between two of them, the final screening by sieving allows separation of the domestic waste treated into the two components to be obtained, namely a component consisting of inert refuse to be eliminated, and a component consisting of a compost particularly rich in organic matter.

In practice, the content of organic matter of this compost can, thanks to the invention, usually be favourably above at least 65%.

The characteristics and advantages of the invention are further shown in the description which follows, by way of example, making reference to the schematic drawings attached in which: Figure 1 is a view in perspective of a shredder according to the invention, shown installed on a vehicle; Figure 2 is a side view in the direction of the arrow II in figure 1; Figure 3 is partial view in elevation in the direction of the arrow Ill in figure 2; Figure 4 shows, in enlargement, the detail in figure 3 marked by the insertion IV on it; Figure 5 is a partial view in transverse section along the line V-V in figure 4; Figure 6 is a diagram illustrating the results obtained with the shredder according to the invention; Figure 7 is a lateral view which, analogous to that of figure 2, corresponds to an alternative embodiment.

In the form for use illustrated in these figures, the shredder 10 according to the invention is installed on a vehicle 11.

This vehicle 11 is for instance a trailer with a movi-ng base, that is a trailer the floor of which is a conveyer.

This vehicle 11, not being itself part of the present invention, will not be described here.

It suffices to indicate that the shredder 10 according to the invention is situated at the far end of the conveyer forming the corresponding moving base.

In practice, therefore, it is situated at the rear end of the vehicle 11 concerned.

The shredder 10 according to the invention consists of, mounted on a frame 12 itself carried on a chassis 13 of a vehicle 11, a rotating drum 14, of which the diameter D is at least equal to 1 m, and which carries the projecting fingers 15.

In the embodiment shown, the frame 12 consists of two lateral uprights 16, which are suitably fixed at their lower ends to the chassis 13 of the vehicle 11, for example by being bolted, and which at their upper ends are joined one to the other by a cross member 17.

The uprights 16 and the cross member 17 can for example be made of lengths of box section as shown.

In a variant they may well be U-shaped iron pieces.

Whatever they are, each lateral upright 16 carries the respective bearing necessary to support the drum 14, and the installation of the assembly on the chassis 13 of the vehicle 11 is such that the drum 14, with its fingers 15, is situated largely above the conveyer forming the moving bottom of the vehicle 11, at a distance for example of about 10 cm from it, being of course arranged transversely with respect to the conveyer.

Also provided in the embodiment shown in figures 1 to 5, are two lateral deflectors 20, made of metal for example, each of which is respectively joined to the corresponding lateral upright 16, an upper hood 21 which, joined to the cross member 17, is like the latter, inclined to the horizontal, sloping towards the moving base of the vehicle 11 in the direction of the front of the latter, and a lower protecting sheet 22, which, suspended at the bottom part of the assembly is designed to protect any projections of the rear axle of a vehicle 11.

The whole assembly which can be made for example by welding, can be made by a man practiced in the art, and this will therefore not be described in detail here.

Similarly, according to the arrangements relevant to a man skilled in the art, the lateral deflectors 20 and/or the upper hood 21 can, if desired, be reinforced by stiffeners.

Preferably, as shown schematically by a broken line in figures 1 and 2, the lower part of the deflectors is removable, to facilitate access to the shaft 24 of the drum 14 in order for example to clean it.

Externally, the shaft 24 of the drum 14 carries laterally, at one of its ends, a sprocket wheel 25 round which is passed a chain 26 which also passes in an endless ring round a driving sprocket wheel 27 fixed to a motor shaft 28.

Internally, each of the lateral deflectors 20 carries, projecting around the corresponding end of the drum 14, a mudguard 30 which, formed for example from a simple iron plate suitably welded on such a lateral deflector 20, serves to protect against any wrapping of the product around the shaft 24 of the said drum 14.

If the diameter D of the drum 14 is, in accordance with the invention, at least equal to 1 m, being for example precisely equal to 1 m, its length L is immaterial.

In practice it is obviously adapted to the size of the vehicle 11 concerned.

It is therefore for example about 2 m.

Of course these numerical values are given here only by way of example and are not necessarily limiting for the invention.

The same applies to the other numerical values which will be given below.

In practice, the fingers 15 of the drum 14 are arranged in rows following the generatrices of this.

In the embodiments shown, eight rows of fingers 15 are provided, being regularly distributed circularly around the axis of the drum 14 and the fingers 15 are staggered from one row to another.

In practice, the fingers 15 of one row are carried on a bar 32, which is common to them, and which is fixed removably on the drum 14.

For example, as shown, a bar 32 bearing a row of fingers 15 is held by sliding into guide blocks 33 which, formed in practice from simple clamps, are fixed to the drum 14 by being arranged in steps at intervals along the generatrix corresponding to this, and, in order to hold such a bar 32 longitudinally on the drum 14, it is provided with appropriate means of fixing it, for example bolts with lock nuts, at at least one of its ends, and preferably at both ends.

In the embodiment shown, each bar 32 thus used carries seventeen fingers 15, and the gap between the latter is about 10 cm.

Preferably, as shown, the fingers 15 are each inclined in the same direction with respect to the radial direction R of the drum 14 passing their origin, diverging from this radial direction R upstream from this with respect to the direction of rotation of the drum 14.

This direction of rotation has been marked by an arrow F in the figures 2 and 5.

In practice it is a clockwise direction as viewed in Figure 2.

The angle of inclination of the fingers 15 with respect to the corresponding radial direction is between 0 and 90".

For example, it is about 45 , as shown.

Whatever it is, it is the same for all the fingers 15.

In the embodiment shown, each of these fingers 15 takes the form of a small plate with a paralielepipedic contour the plane of which is transverse to the axis of the drum 14.

In practice the fingers are metal plates having a thickness of, for example, about 1 cm.

The fingers 15 are suitably set on the bar 32 which carries them, for example by welding, and the height of the projection which they form on the surface of the drum 14, and which is the same for them all, is, including the support bar 32 and the slide box 33, of course, less than the distance separating the drum 14 from the moving base of the vehicle 11. This height, therefore, is less than 10 cm.

Finally, in the embodiment shown in figures 1 to 5, the drum 14 also carries, following a generatrix, between two bars 32, a U-shaped piece of iron suitable for guiding a cutting blade if the use of such a cutting blade appears to be necessary because of a partial wrapping of any material around the drum 14.

In operation, and using as example the turning of a swath, such a transfering machine attacks the swath, throwing the material onto the moving base of the vehicle 11, which, following the arrow F' in figure 2 systematically directs it towards the rear of the latter for its discharge.

During passage, this material is worked upon by the fingers 15 of the drum 14 of the shredder 10 in accordance with the invention.

Thus as will be noted, as a result of the clockwise direction of rotation of the drum 14 the fingers 15 work in a counter current manner.

In practice, they essentially ensure the shredding only of the fermentable materials in the matter worked upon, without significantly affecting the objects of synthetic material contained amongst them.

Moreover, as a result of the suitable inclination of the fingers 15, which are in a sense in "fleeting" contact with the matter which they pass through, the tendency which they could have to entrain prematurely the objects of synthetic materials in it, with the risk of encouraging them to wrap around the drum 14, is minimized. Thanks to this obliqueness these objects made of synthetic material fall more easily by gravity before reaching the summit of the said drum 14.

Because of the advance of the vehicle 11, the swath worked upon reforms itself at the exit from the former.

In practice, preferably several passages of.

the shredder according to the invention are applied to the mass of such a swath.

For example, the chain of treatment stages of a collection of domestic waste forming such a swath could be the following: -a first passage of preparation in the shredder 10 according to the invention; -the elimination by densimetric sorting of heavy materials initially present; -three new successive passages in the shredder 10 according to the invention, alternating with rest periods of the waste, for example, of a week; -the elimination by an operation of sieving of voluminous objects of synthetic matter still present.

However, alternatively, the densimetric sorting could also be done at the start or, on the contrary, could be done after the sieving.

It has been found that in the latter case, among the heavy materials concerned, glass keeps at any rate a size distribution sufficient for such a densimetric sorting to remain effective.

The results obtained are illustrated by the diagram of figure 6.

This, which concerns the size distribution analysis of a compost the treatment processes of which have involved three successive passages in a shredder according to the invention, shows on the abscissa the dimension, in mm for example, of the sieve mesh used for the sieving operation in these treatment processes, and on the ordinate the percentage, in dry weight, of the products retained on such a sieve.

Curves I and I' relate to light and voluminous synthetic material, curve I for a mean circumferential speed at the point of the fingers 15 of the drum 14 equal to 375 m/min, and the curve I' for a mean circumferential speed at the point of these fingers 15 equal to 750 m/min.

Curves II and II' relate, under the same conditions, to the desired organic materials, that is to say to non-synthetic or fermentable organic matter, and curves Ill and III' to heavy materials, these being essentially glass.

With a square sieve with a 20 mm side for example, almost all, that is more than 95%, of the synthetic material is retained whatever the speed of rotation of the drum 14, whilst 45% of the fermentable matter passes when this speed of rotation is 100 rpm which is 325 m/min at the points of the fingers 15, and 60% when it is 200 rpm which is 750 m/min at the points of the fingers 15, and in both cases almost all, that is 90%, of the glass passes through.

These results which concern only one case given here by way of example, show that shredding according to the invention facilitates the selection of the desired fermentable matter, for whilst reducing their size it leaves that of the synthetic material to be eliminated almost unchanged, and that, from a certain point of view, it is of interest to increase the speed of operation of the shredding drum.

However, in practice, an increase in this speed of operation risks extending prematurely the corresponding shredding effects to the light and voluminous synthetic materials.

This is why, according to the invention, it is preferably limited to at the most 1800 m/min at the points of the fingers 15, being preferably about 750 to 1100 m/min, and, for example, close to 1000 m/min.

In the embodiment illustrated by figure 7, the drum 14 of the shredder 10 according to the invention is placed in the shelter of a more developed hood than before.

In practice, in this embodiment, the hood carries a rigid part 38 which, to the rear of the upper hood 21 and the lateral deflectors 20, is joined to them to form an open canopy.

The hood also carries laterally suspended from the sides of this rigid part 38, as well as from the lateral deflectors 20 to which it forms a continuation, flaps 39 of flexible material.

Flaps 40 are provided in a similar manner at the rear along the edge of the upper end of the rigid part 38.

To facilitate access, if desired, to the drum 14, certain at least of these flaps 39, 40, perhaps even all of them, can be removed.

For example their suspension can be made very simply by the use of screws and nuts.

In addition, in the embodiment shown, a flap 42 is also provided in front, along the corresponding edge of the upper hood 21.

Finally, in this embodiment, a hood is also provided around the transmission which ensures the connection between the shaft of the drum 14 and the shaft of the corresponding motor.

Of course, the present invention is not limited by the forms of representation described and shown, but includes all variants of execution.

In particular, whilst preferentially put to use on a vehicle or other mobile engine, since it involves treatment of domestic waste the composting of which is done in swaths, the shredder according to the invention can equally well be used in a fixed installation, and more particularly that can be the case when domestic wastes to be transferred from a storage hopper to a treatment chain are concerned.

Equally, of course, the field of application of the invention is not necessarily limited just to domestic wastes, but extends in the most general manner to all other heterogeneous materials composed of a mixture of products whose rigidity can not hinder the functioning of the shredder to be used.

Claims (15)

1. Process of treatment of a heterogeneous product involving the application to it of an operation of sieving in order to separate it into two components characterized in that an operation of shredding is made to take place before the said operation of sieving, conducted in a manner to affect the said components selectively, by use of a shredder (10) bearing a rotating drum (14) the diameter of which is at least equal to 1 m and which carries projecting fingers (15).

2. Process according to claim 1 characterized in that, with regard to the composting of domestic wastes, the operation of shredding is associated with an operation of transfer of such a material such as, for example, that necessary when turning a swath, or that occurring between a feeding hopper and a refining chain.

3. Shredder suitable to be used in a process according to either of the claims 1 or 2, characterized in that it carries a drum (14) which, mounted to rotate in a frame (12) and being situated transversely at the rear end of a conveyer, has a diameter at least equal to 1 m and carries projecting fingers (15).

4. Shredder according to claim 3 characterized in that the fingers (15) which the drum (14) carries are all of the same length.

5. Shredder according to either of claims 3 or 4 characterized in that the fingers (15) of its drum (14) are arranged in rows following the generatrices of the said drum (14).

6. Shredder according to claim 5 characterized in that the fingers (15) of its drum (14) are staggered from one row to another.

7. Shredder according to either of claims 5 or 6 characterized in that the fingers (15) of the same row of its drum (14) are carried on a bar (32) which is common to them and which is fixed in a removable manner on the said drum (14).

8. Shredder according to claim 7 characterized in that a bar (32) carrying a row of fingers (15) is held by sliding in sliding blocks (33) joined to the drum (14).

9. Shredder according to any of claims 3 to 8 characterized in that the fingers (15) of the drum (14) are each inclined in the same direction with respect to the radial direction (R) of such a drum (14) passing their origin, and diverging from this radial direction (R) on the upstream side of this with respect to the direction of rotation of the said drum (14).

10. Shredder according to any one of claims 3 to 9 characterized in that each of the fingers is in the shape of a small plate with a parallelepipedic contour.

11. Shredder according to any one of claims 3 to 10 characterized in that the conveyer, at the far end of which its drum (14) is situated, forms the floor of a vehicle (11) the chassis (13) of which carries the corresponding frame (12).

12. Shredder according to any one of claims 3 to 11 characterized in that its drum (14) is placed in the shelter of a hood.

13. Shredder according to any one of claims 3 to 12 characterized in that the mean circumferential speed of the points of the fingers (15) of its drum (14) is restricted to at most 1800 m/min and preferably is about 750 to 1100 m/min.

14. A process for the treatment of a heterogeneous product substantially as described herein.

15. A shredder substantially as described herein with reference to the accompanying drawings.