GB1577325A

GB1577325A - Rotary air classifier

Info

Publication number: GB1577325A
Application number: GB3642376A
Authority: GB
Original assignee: Newell Dunford Engineering Ltd
Current assignee: Newell Dunford Engineering Ltd
Priority date: 1977-10-28
Filing date: 1977-10-28
Publication date: 1980-10-22

Description

(54) ROTARY AIR CLASSIFIER (71) We, NEWELL DUNFORD ENGINEER ING LIMITED, a British Company of Newell House, Portsmouth Road, Surbiton, Surrey KT6 5QF, England, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following state ment:- The present invention relates to classifiers for spearating light materials from a mixture of heavy and light materials or for separating large particles from small particles from a single material or a mixture of materials.

The classifier of the present invention is also suitable for separating mixtures of particles of different shapes, such as massive particles from plate-like particles of similar density e.g. tin from ferrous scrap.

It is often advantageous to be able to separate materials in the above manner and a particularly important application is in the separation of paper, plastics material and rags from domestic refuse in a raw or pulverised state, to enable the material to be fed to an incinerator apparatus.

According to the present invention there is provided a classifier comprising a vessel which is open at both ends, the axis of the vessel, in a direction transverse to the open ends, being inclined to the horizontal, means being provided to feed material to be classified into the vessel at or adjacent its upper end and means being provided to introduce air into the vessel, so as to cause the air to flow spirally within the vessel and axially out of the upper end.

With such an arrangement, the material to be sorted is fed into the vessel, and the lighter or smaller particles are caught up by the spiralling air stream and thrown out at the upper open end. Heavy or large particles remain in the vessel and roll or slide, by one path or another, down the slope and out of the lower end of the vessel.

By these means, the separation of light or small particles is achieved from the particles of greater density or of larger size.

Although it is advantageous for the vessel to have an internal surface which is formed by rotating a line about the axis, it is contemplated that the vessel could be made of generally polygonal cross-section, for example, having several i.e. ten or more sides.

In a preferred constuction of classifier according to the invention, the vessel is wider at the upper open end than at the lower open end. Thus, the most convenient construction of vessel is for it to be of frustoconical formation. The angle of the cone, however, should be such that the lower surface of the interior wall of the vessel still slopes downwardly towards the lower open end, to allow the heavier material to roll down within the vessel to the lower end and thus out of the vessel.

The air is advantageously fed into the vessel by means of one or more pipelines extending along the wall of the vessel, substantially parallel to the axis, the or each pipeline being provided with a jet which extends approximately along a tangent of the internal wall of the vessel.

Where more than one pipeline is provided, a manifold may be arranged to introduce air only at certain portions of the circumference of the classifier. If the vessel is wide at the upper end, this in itself would tend to cause the air to flow out of the upper end.

Advantageously, however, additional means may be provided to induce a flow of air from the lower to the upper end of the vessel. With such a construction, it is possible to provide further means to cause at least a major proportion of the air leaving the upper open end of the vessel to be recycled to flow back into the lower open end. With such an arrangement, an air filter may be provided for the passage of the remainder of the air which is not recycled. Such an arrangement has the advantage that the amount of air to be moved is greatly reduced, so that the power required to run the classifier is significantly reduced.

Desirably, the vessel is caused to rotate about its axis and the direction of rotation is advantageously the same as the direction of rotation of the spiral air flow. A deflector plate may be fitted behind the line of air jets to prevent the material catching on the tube or tubes holding the jets. In a preferred construction, however, the tubes are arranged, in effect, behind the wall of the vessel and have jets which project the air through openings in the wall.

If desired, the vessel may comprise two substantially coaxial vessels, in which the inner vessel is perforated and these perforations allow through fine, heavy particles, for example finely shredded grass. These particles would then be carried down the slope of the outer vessel and separately discharged at the lower end.

In another variation, the air jet positions may be arranged in non-regular pattern along the length of the pipelines, in order to achieve variation of the density of flow of the spiralling air stream. It is also contemplated that the inner wall of the vessel may be fitted with lifters, mechanically to raise the material to be separated up the side of the rotating vessel to allow its discharge at a higher level. One or more sets of air jets may be placed within the vessel to induce the spiral flow and the air may be fed either continuously or repulsed at various magnitudes.

A lance may extend into the open lower end of the vessel to project a high velocity air stream of air into the vessel to discharge the very light articles such as tin cans which can be thus separated from the remainder of the material. The lance is preferably directed at an angle to the axis of the drum and at an angle to the adjacent radius of the drum.

In order that the invention may more readily be understood, the following description is given, merely by way of example, reference being made to the accompanying drawings, in which: Figure 1 is a schematic side elevation, in section, of one embodiment of classifier according to the invention; Figure 2 is a section taken along the line Il-Il of Figure 1; Figure 3 is a section taken along the line IIIIII of Figure 1; Figure 4 is a view similar to Figure 1 of a second embodiment; and Figure 5 is a section taken along the line V-V of Figure 4.

Referring first to Figures 1, 2 and 3, the classifier indicated therein comprises a vessel 10 in the form of a frustum of a cone, the vessel being open at its lower end 11 and at its upper end 12. As can be seen, the axis 13 of the vessel 10 is inclined at an angle to the horizontal which is sufficiently large for the lower interior surface 14 of the vessel also to be inclined to the horizontal.

The vessel 10 is mounted within an outer cylindrical casing 15 which itself has the same axis 13 and is provided with running rings 16 and 17 which enable the casing 15 and drum 10 to rotate about the axis 13, the running rings being supported by rollers 18 and 19, a thrust flange 20 extending radially outwardly from the housing 15 and engaging a further thrust roller 21. Structural members 22 support the vessel 10 within the casing 15.

The upper open end 12 is mounted within a first collection chamber 23 which is connected, via a recycle duct 24 having a fan 25 therin, with a second chamber 26 which has the lower end 11 of the vessel 15 opening thereinto. An air discharge vent 27 provided with an air filter indicated schematically at 28 is connected to the duct 24.

The first chamber 23 is tapered at its lower end so that materials discharged therefrom can leave and be collected on a discharge conveyor 29 whilst a similar arrangement is provided in the second chamber 26, material flowing therethrough being collected on discharge conveyor 30.

As indicated more clearly in Figures 2 and 3, three air pipelines 31 extend parallel to the axis 13 at circumferentially spaced locations.

These air pipelines are provided along their length with a plurality of spaced apart nozzles 32 which are arranged to project air along the inner wall surface of the vessel 10 as generally tangential flow. Air is supplied to the pipelines 31 via a rotary coupling structure 33, 34. Alternatively a manifold, which is fixed in space, may arranged selectively to feed air from an air supply to the pipelines 31 at such times as the latter are aligned with the outlet of the manifold.

A rotating inlet conveyor tube 35 extends along the axis of the vessel 10 and into the upper end 12 thereof, this tube being supported by a spider arrangement 36 on the inner wall of the vessel 10.

In operation of the above described classifier, the casing 15 and thus the vessel 10 are caused to rotate in a clockwise direction, as viewed in Figure 2, and air under pressure is introduced via air supply 34 so that air is discharged into the vessel along the direction illustrated by the arrows in Figure 2, that is to say again in a generally clockwise direction thus inducing spiral flow from the lower to the upper end of the vessel. This induces, along the axis, a vortex. Material to be classified is fed down along the conveyor 35, which is caused to rotate at the same speed as the vessel by the spider 36 and the material is therefore drawn in by the vortex action. At the same time, the fan 25 is switched on, thus causing a flow from the first chamber 23 to the second chamber 26 and, it will be appreciated, a flow from the lower end 11 to the upper end 12 of the vessel 10.

The air, particularly air induced by the nozzles 32, entrains the lighter and/or smaller particles and projects these out of the upper end 12 so that they fall downwardly in the chamber 23 onto the conveyor 29. The heavier and/or larger particles are not entrained by the air to such an extent, and therefore roll or slide down the interior wall 14 of the vessel and out of the open lower end 11 to fall within the chamber 26 and thence onto the discharge conveyor 30.

The construction illustrated in Figures 4 and 5 is generally similar to that illustrated in Figures 1, 2 and 3 and like parts have been indicated by like reference numerals. The main change is in the method of introducing the air to cause the sprial flow and the method of introducing the material to be treated. In the construction shown in Figures 4 and 5, the air inlet pipeline 31A is arranged within the vessel and spaced from the wall thereof. This is a simpler construction than that illustrated in Figure 1. Instead of having the inlet conveyor 35 as a rotating tube, a simple belt conveyor 35A is illustrated in Figure 4. The apparatus, in fact, operates in precisely the same way as the apparatus of the ealier embodiment.

As an additional feature of the invention which may be employed either in a structure as shown in Figure 1 or the structure of Figure 4, an air lance 40 is provided which is directed at an angle to the axis of the drum and at angle to the radius of the drum. The lance 40 extends slightly downwardly. The effect of providing this lance, through which a jet of air can be projected at high speed, is to blow light articles, such as cans, out of the upper end of the vessel. Since the tin available in cans is recuperable and of high commercial value, this form of separation is very effective.

WHAT WE CLAIM IS: 1. A classifier comprising a vessel which is open at both ends, the axis of the vessel, in a direction transverse to the open ends, being inclined to the horizontal, means being provided to feed material to be classified into the vessel at or adjacent its upper end and means being provided to introduce air into the vessel, so as to cause the air to flow spirally within the vessel and axially out of the upper end.

2. A classifier according to claim 1, wherein the vessel has an internal surface which is formed by rotating a line about said axis.

3. A classifier according to claim 2, wherein the vessel is of frusto-conical form, the angle of the cone being such that the lower surface of the interior wall of the vessel slopes downardly towards the lower open end.

4. A classifier according to claim 3, wherein the wider end of the vessel is the upper end.

5. A classifier according to any preceding claim, wherein the means for introducing air include at least one pipeline extending along the wall of the vessel, substantially parallel to the axis, the or each pipeline being provided with at least one jet which extends approximately along a tangent of the internal wall of the vessel.

6. A classifier according to claim 5, wherein a plurality of pipelines are provided and a manifold arranged to introduce air only at certain portions of the circumference of the classifier.

7. A classifier according to any preceding claim, wherein the vessel is mounted to rotate about its axis.

8. A classifier according to claim 5 or 6 and 7, wherein the vessel is caused to rotate about its axis in the same direction as the direction of rotation of the spiralling air.

9. A classifier according to any preceding claim, wherein additional means are provided to induce a flow of air from the lower to the upper end of the vessel.

10. A classifier according to claim 9, wherein means are provided to cause at least a major proportion of the air leaving the upper open end of the vessel to be recycled to flow back into the lower open end.

11. A classifier according to claim 10, wherein an air filter is provided for the passage of the remainder of the air which is not recycled.

12. A classifier according to any preceding claim, wherein the means to feed material to be classified to the upper open end comprise a rotary conveyor adapted to feed the material to be classified to a location adjacent the axis of the conveyor.

13. A classifier according to any preceding claim, and comprising a lance extending into the open lower end of the vessel to project a high velocity stream of air into the vessel.

14. A classifier according to claim 13, wherein the lance is directed at an angle to the axis of the drum and at an angle to the adjacent radius of the drum.

15. A classifier substantially as hereinbefore described with reference to and as illustrated in Figures 1, 2 and 3 of the accompanying drawings.

16. A classifier substantially as hereinbefore described with reference to and as illustrated in Figures 4 and 5 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. entrained by the air to such an extent, and therefore roll or slide down the interior wall 14 of the vessel and out of the open lower end 11 to fall within the chamber 26 and thence onto the discharge conveyor 30. The construction illustrated in Figures 4 and 5 is generally similar to that illustrated in Figures 1, 2 and 3 and like parts have been indicated by like reference numerals. The main change is in the method of introducing the air to cause the sprial flow and the method of introducing the material to be treated. In the construction shown in Figures 4 and 5, the air inlet pipeline 31A is arranged within the vessel and spaced from the wall thereof. This is a simpler construction than that illustrated in Figure 1. Instead of having the inlet conveyor 35 as a rotating tube, a simple belt conveyor 35A is illustrated in Figure 4. The apparatus, in fact, operates in precisely the same way as the apparatus of the ealier embodiment. As an additional feature of the invention which may be employed either in a structure as shown in Figure 1 or the structure of Figure 4, an air lance 40 is provided which is directed at an angle to the axis of the drum and at angle to the radius of the drum. The lance 40 extends slightly downwardly. The effect of providing this lance, through which a jet of air can be projected at high speed, is to blow light articles, such as cans, out of the upper end of the vessel. Since the tin available in cans is recuperable and of high commercial value, this form of separation is very effective. WHAT WE CLAIM IS:

1. A classifier comprising a vessel which is open at both ends, the axis of the vessel, in a direction transverse to the open ends, being inclined to the horizontal, means being provided to feed material to be classified into the vessel at or adjacent its upper end and means being provided to introduce air into the vessel, so as to cause the air to flow spirally within the vessel and axially out of the upper end.