IE42556B1 - Plant for the classification of heterogenous materials, e.g.for the treatment of city solid wastes - Google Patents

Abstract

The present invention provides a method of and an apparatus for separating heterogeneously sized and shaped solid waste particles. The particles are introduced into a vertical duct, under an accelerating force provided from behind the material, against a slanted wall in the duct. Depending on the slant of the wall, particles of different sizes and shapes striking the wall will be deflected downward. Some particles though will not receive sufficient force from the air to hit the wall and will be pulled up the duct by a vaccuum system located at the top thereof. In this manner, materials can be separated according to their physical characteristics. In contrast, known separating systems rely simply on the buoyancy of the different materials in order to separate them. This means that the particles must be generally homogeneous in size and shape to achieve a proper separation.

Description

The invention relates to a plant for classifying heterogeneous materials, for example urban solid wastes.

It is known that when it is needed to classify materials that are heterogenous as regards their shape and weight, air classifiers are often used.

However, these classifiers generally can only accomplish their task satisfactorily, when there is a substantial uniformity, at least in the size of the materia].

Also conventional classifiers often depend on the use of a rising air stream which provides within the duct in which it flows, a different buoyancy of the different materials as determined by their particular specific weight.

In the case of city solid wastes, it is very difficult to obtain a size that can be defined as uniform, whereas the treated material has very frequently a nearly uniform weight.

It is an object of the invention to provide an improved plant for the classification of heterogenous materials for example city solid wastes. The plant seeks to obtain a substantially complete and efficient separation of the said wastes.

According to the invention there is provided a plant for the classification of heterogeneous material comprising a duct open at one end to the atmosphere and in fluid flow connection at the other end with means for reducing the air pressure within the duct and for creating an air flow there-through, an opening -242556 in the duct, upstream of the said other end, for receiving the material to be classified, means for feeding the material to the opening so that the material enters the duct substantially transversely to the said air flow; and a wall positioned in the duct on the side of the duct opposite the said opening and having a surface facing the opening, the wall surface being inclined at an acute angle to the duct axis, the plant being constructed and adapted to operate such that secondary air is drawn into the duct through the said opening by the reduced pressure within the duct, this secondary air causing the material being fed through the opening to be accelerated whereby heavier components of the material impact on the said wall surface and are detected by the surface towards the end of the duct open to atmosphere and lighter components of the material are carried by the air flow towards the dowstream end of the duct.

On the basis of this plant, and in connection with the different weights and volumes of the materials, the acceleration of the said materials is undergone in different ways so that whereas some materials are lifted within the duct by the air flow, others fall. Indeed, the fall of these materials is helped by their impact against the wall surface which is suitably slanted as to provide a component of Velocity to the falling body.

Preferably, the material feeding means comprises a shakable or vibratable conveyor.

This duct is preferably under reduced pressure through an exhauster, and a cyclone separator may be provided with an outlet valve having a star-shape, the cyclone separator being connected to the duct upstream of the exhauster. Bodies of the material hitting the wall surface are deflected downwards.

A construction of a plant embodying the invention is diagrammatically illustrated, by way of example, in the accompanying drawing, which shows a side elevational view of the plant.

With reference to the drawing, the material coming from a primary separator (not shown) and thus already pre-selected -and this for the purpose of obtaining a better output from the plant-is discharged onto a shakable or vibratable conveyor 11. It is fed from the conveyor 11 to a duct 12 under reduced pressure. -3The duct 12 leads to a centrifugal decanter 13 (cyclone separator) provided with a star outlet valve 14. The reduced pressure in the duct 12 is obtained by an exhauster 15.

The air classifier is subjected to air suction by the exhauster 15 and sucks 5 in air between an upper surface 16 of a material charging mouth for the duct 12.

Indeed, the charging mouth 16, through v/hich the material is introduced to the duct 12 under vacuum, is not airtight. In other words, and in contradistinction to what is usual in customary classifiers, a certain amount of secondary air can penetrate within the duct 12 through the material to be classified and the inlet TO mouth.

The air entering in through the mouth even though present in a very little amount has the purpose of accelerating the bodies of material that the conveyor is feeding to the duct.

The duct 12 has opposite the material inlet mouth, and therefore opposite 15 the feeder 11, a wall 18, slanted relative to the vertical. The slant of the wall T8 must be such that the material going into duct 12, fed by tho feeder 11 and accelerated by the secondary air, if it has suitable weight and shape characteristics, hits the wall 18 in such a v/ay that the resultant of the force acting on the said material assists the material to fall downwards, whereas the material, that according its characteristics, has no substantial weight and it is not sufficiently accelerated, is lifted by the air suction and therefore reaches the cyclone separator or centrifugal decanter 13. From the cyclone separator 13 this material is afterwards removed through valve 14. The material removed through the valve T4 may comprise paper and plastics material contained in city solid wastes feed to the duct 12 by the conveyor 11.

As it is possible to observe, the slanted wall 18 has an important function, together the secondary air, for the classification of the material. As the material can be of different qualities, and be different as its size and weight, the wall 18 can be suitably hinged at 19 in such a way as to change its slanting 30 relative to the axis of the duct 12.

It will also be observed that as a consequence of the air suction and of -4- 4 25 5 the space between the upper edge 16 of the inlet mouth of the duct and the feed ing plane of the feeder 11, the material, at its entry into the duct 12, is subjected, as already mentioned, to an acceleration and either hits or does not hit the wall 18, the component of such an impinging force when it does hit ensuring the downwards fall of the material. If such an acceleration is not great enough to produce the hit, the material is lifted and carried to the separator 13.

It is evident that with a plant as the one just described it is possible to use as starting material, materials which are extremely heretogenous, such as the ones that are comprised in city solid wastes, and to obtain a separation of the different components of the starting material which are different with respect to their weight and their shape.

Claims (7)

1. A plant for the classification of heterogenous material comprising a duct open at one end to the atmosphere and in fluid flow connection at the other end with means for reducing the air pressure within the duct and for creating an air 5 flow there-through, an opening in the duct, upstream of the said other end, for receiving the material to be classified, means for feeding the material to the opening so that the material enters the duct substantially transversely to the said air flow, and a wall positioned in the duct on the side of the duct opposite the said opening and having a surface facing the opening, the wall surface being io inclined at an acute angle to the duct axis, the plant being constructed and adapted to operate such that secondary air is drawn into the duct through the said opening by the reduced pressure within the duct, this secondary air causing the material being fed through the opening to be accelerated whereby heavier components of the material impact on the said wall surface and are 15 deflected by the surface towards the end of the duct open to atmosphere and lighter components of the material are carried by the air flow towards the downstream end of the duct.

2. A plant, according to Claim 1, in which the material feeding means comprises a shakeable or vibratable conveyor and the secondary air enters the duct 20 through a space defined at least in part by an upper edge surface of the opening - and by the material on the conveyor.

3. A plant, according to Claim 1 or Claim 2, in which the said wall is adjustably mounted within the duct to enable the angle of inclination of the wall surface to be varied. 25

4. A plant, according to any preceding claim, comprising a cyclone separator having its inlet connected to the duct at a position downstream of the said opening and upstream of the means for reducing the air pressure within the duct and for creating the air flow.

5. A plant, according to any preceding claim, in which the means for reducing θ the air pressure within the duct and for creating the air flow comprises an -642556 exhauster.

6. A plant, according to any preceding claim for the classification of city solid wastes.

7. A plant for the classification of heterogenous material substantially as 5 hereinbefore described with reference to, and as illustrated in, the accompanying drawing.