WO1998034737A1

WO1998034737A1 - Method and apparatus for removing lumps or agglomerates from granular or powdered material

Info

Publication number: WO1998034737A1
Application number: PCT/NZ1998/000016
Authority: WO
Inventors: Clive Eric Davies
Original assignee: Industrial Research Limited
Priority date: 1997-02-07
Filing date: 1998-02-09
Publication date: 1998-08-13
Also published as: WO1998034721A1; AU6007398A; AU6007598A

Abstract

A method of removing lumps or agglomerates from granular or powdered material, comprises causing a stream of the material to flow down an inclined surface (3) and spread to a thin dispersed layer (7) flowing over the surface and beneath a barrier (5) extending across the surface and spaced above the surface by a predetermined dimension. Lumps or agglomerates in the material larger than the dimension between the surface (3) and the barrier (5) do not pass beneath but are deflected by the barrier to one or other sides of the flow.

Description

METHOD AND APPARATUS FOR REMOVING LUMPS OR AGGLOMERATES FROM GRANULAR OR POWDERED MATERIAL

FIELD OF INVENTION

The invention comprises a method and apparatus for removing lumps or agglomerates from granular or powdered material.

BACKGROUND OF INVENTION

Lumps or large agglomerates in streams of flowing solids can seriously reduce process efficiency by causing blockages in flow channels or openings. This can be particularly serious when the minimum characteristic dimension of a flow conduit is of the same order of that of a lump, and can preclude the use of processing equipment containing narrow openings. The presence of lumps in a product can also cause processing and handling difficulties for users. There are therefore, a variety of incentives to ensure that process streams are kept lump-free.

SUMMARY OF INVENTION

The invention provides an improved or at least an alternative method and apparatus for removing lumps or agglomerates from granular or powdered material.

In broad terms in a first aspect the invention comprises a method of removing lumps or agglomerates from granular or powdered material, comprising causing a stream of the material to flow down an inclined surface and spread to a thin dispersed layer flowing over the surface and beneath a barrier extending across the surface substantially parallel to the plane of the surface and at an angle to the direction of flow of the thin dispersed layer and spaced above the surface by a predetermined dimension, such that lumps or agglomerates in the material larger than the dimension between the surface and the barrier do not pass beneath but are deflected by the barrier to one or other sides of the flow.

In one form the stream of material falls under gravity to impact the surface and flow over the surface spreading to said thin dispersed layer. In another form the stream of material flows from the outlet of a hopper positioned immediately above the surface onto the surface and over the surface spreading to said thin dispersed layer.

In broad terms in a second aspect the invention comprises apparatus for removing lumps or agglomerates from granular or powder material, comprising an inclined surface and a barrier extending across the surface substantially parallel to the plane of the surface and spaced above the surface by a predetermined dimension, and means arranged to direct a stream of the material onto the surface to spread to a thin dispersed layer flowing down the surface at an angle to and beneath the barrier, such that lumps or agglomerates in the material larger than the dimension between the surface and the barrier do not pass beneath but are deflected by the barrier to one or other sides of the flow.

BRIEF DESCRIPTION OF THE DRAWINGS

The method and apparatus of the invention are described further with reference to the accompanying drawings, by way of example and without intending to be limiting, wherein:

Figure 1 schematically shows apparatus of the invention in which a flowing stream of material falls onto an inclined surface from above,

Figure 2 schematically shows the apparatus of Fig 1 from one side,

Figure 3 schematically shows a portion of the surface and the barrier above the surface in cross-section,

Figure 4 schematically shows apparatus similar to that of Figures 1 to 3 in which the barrier extends at an angle to the direction of the flow, from above, and Figure 5 schematically shows another apparatus of the invention in which a stream of material flows from an outlet positioned immediately above the surface, of a hopper, down an inclined surface.

DETAILED DESCRIPTION

The apparatus of Figures 1 to 3 comprises a flow surface 3, two lump collectors 11, and a lump diverter comprising a barrier 5 and side walls 10.

The flow surface 3 is inclined from the horizontal such that a bulk flow of granular material 6 impacting near the top of the flow surface 3 spreads out or disperses and flows down the surface 3 in a thin dispersed layer 7. Viewed from above in Figure 1, the bulk flow 6 of granular material spreads out substantially parabolically as it flows down the flow surface 3 in a substantially uniform thin layer 7.

The barrier 5 extends across the flow surface 3 at an angle to the direction of the flow 7. The barrier 5 is supported above the flow surface 3 forming a gap of predetermined height such that normal granular material flows undiverted underneath the barrier 5. Lumps or agglomerates 8 of granular material however are unable to flow underneath the barriers 5 and are diverted to one side. The gap height between the barrier 5 and the flow surface 3 can be adjusted to divert different sizes of lumps 8 or for use with different sizes and types of granular material 6.

In the form shown the leading edge of the barrier 5 is in the form a symmetrical "V with its apex pointing into the oncoming flow 7. The point of impact of the bulk flow 6 and the apex of the V of the barrier 5 are preferably aligned on the longitudinal axis of the flow surface 3. Preferably the V angle is 90° or less. The barrier may take other forms such as a barrier extending directly across the flow surface 3 at right angles to the flow, a barrier 5 comprised of elements with different lengths and arranged at different angles to the oncoming flow 7. One alternative is shown in Figure 4 for example.

The barrier may comprise a single bar extending across the flow surface, or a wall extending downwardly with the gap of predetermined height being formed between the flow surface and the lower edge of the wall. In one form the barrier 5 is formed by two or more thin louvres 12 mounted one above the other and above the flow surface 3 as shown in Figure 3. The gaps between the louvres 12 are typically substantially equal.

The side walls 10 run parallel to the longitudinal axis of the flow surface 3 on either side of the barrier and prevent the re-mixing of normal granular material 9 and diverted lumps 8. Lump collectors 11 are located at each side wall 10 and either collect or redirect lumps 8 diverted by the barrier 5. The lump collectors 1 1 can include mesh portions to allow normal granular material which has inadvertently been diverted to re-enter the normal flow 9.

In practice it has been found that for a bulk flow rate of 26 tonnes per hour, it is advantageous to use a flow surface inclined by 45°, a barrier located 500mm downstream of the bulk flow impact point, and a barrier with three louvres positioned 15mm apart, the first louvre being 15mm above the flow surface, and the included angle of the V barrier being 90° or less.

In use, granular material 6 falls from the outlet of a hopper (not shown) or similar to impact on the upper region of the flow surface 3 of the apparatus. The flow surface 3 is inclined such that the bulk flow 6 of granular material spreads out and under gravity flows down the flow surface 3 in a thin dispersed layer 7. The flow 7 is substantially uniform when it reaches the barrier 5 positioned part way down the flow surface 3. The barrier 5 comprising the louvres 5 is arranged at a predetermined height above the flow surface 3 presenting a vertical gap for the flow 7 to flow through. Normal granular material 9 flows through the gap while lumps 8 within the flow layer 7 are diverted to one side of the barrier 5.

Figure 4 shows an alternative arrangement in which barrier 5 is angled across the entire material flow 7. This arrangement includes a single side wall 10 and lump collector 11. Preferably the barrier 5 includes two or more louvres 12 as shown in Figure 3.

Figure 5 shows a form of apparatus of the invention in which a stream of bulk material flows from outlet 13 positioned immediately above the surface, of a hopper 14. Optionally the hopper may be agitated, or the contents aerated or fluidised as appropriate, to encourage the flow of material from the outlet 13 as necessary, depending upon the characteristics of the particular powdered or particulate material in any case. The stream of material from the outlet 13 again forms a thin dispersed layer 7 of flowing material which passes beneath the barrier 5. Lumps or agglomerates are diverted to one or other side of the barrier.

Figure 4 illustrates the use of flow guides to direct the material flow. In particular, flow guides may be utilised to reduce any thickening of the flow which may occur at the edges of the flow. Two flow guides, such as short barriers or walls 33, positioned immediately above the point of impact of the stream of material flow onto the inclined surface and each to one side of the point of impact have been found to assist in achieving a uniform thickness of flow down the inclined surface. Guides so positioned tend to redirect the material pushed upwardly from the point of impact, which naturally tends to flow towards the outer edges of the flow, down the inclined surface to spread more centrally into the material flow. Guides at the sides of the flow below the point of impact may also be utilised to direct any thickening of material at the sides of the flow towards the centre of the flow, to again assist in achieving layer flow down the surface which is as uniform in thickness as possible. Flow guides may be provided at other points in relation to the flow in addition to or alternative to those shown in Figure 4.

In the invention a thin layer of flowing granular or powdered material is created and caused to flow down an inclined surface and between a barrier extending across the surface such that normal granular material flows unhindered but lumps or agglomerates in the material cannot pass through the gap and are diverted away from the normal granular flow.

The foregoing describes the invention including preferred forms thereof, and alterations and modifications will be obvious to those skilled in the art are intended to be incorporated in the scope hereof as defined in the following claims.

Claims

1. A method of removing lumps or agglomerates from granular or powdered material, comprising causing a stream of the material to flow down an inclined surface and spread to a thin dispersed layer flowing over the surface and beneath a barrier extending across the surface substantially parallel to the plane of the surface and at an angle to the direction of flow of the thin dispersed layer and spaced above the surface by a predetermined dimension, such that lumps or agglomerates in the material larger than the dimension between the surface and the barrier do not pass beneath but are deflected by the barrier to one or other sides of the flow.

2. A method according to claim 1 including causing the stream of material to fall under gravity to impact the surface and flow over the surface spreading to said thin dispersed layer.

3. A method according to claim 1 including causing the stream of material to flow from the outlet of a hopper positioned immediately above the surface onto the surface and to flow over the surface spreading to said thin dispersed layer.

4. A method according to claim 3 including agitating said hopper to assist said flow.

5. A method according to any one of the preceding claims wherein the leading edge of the barrier has a V shape when viewed from above the surface.

6. A method according to any one of the preceding claims wherein the barrier comprises two or more louvres extending one above the other across the surface.

7. Apparatus for removing lumps or agglomerates from granular or powder material, comprising an inclined surface and a barrier extending across the surface substantially parallel to the plane of the surface and spaced above the surface by a predetermined dimension, and means arranged to direct a stream of the material onto the surface to spread to a thin dispersed layer flowing down the surface at an angle to and beneath the barrier, such that lumps or agglomerates in the material larger than the dimension between the surface and the barrier do not pass beneath but are deflected by the barrier to one or other sides of the flow.

8. Apparatus according to claim 9 wherein the stream of material is arranged to fall under gravity to impact the surface and flow over the surface spreading to said thin dispersed layer.

9. Apparatus according to claim 7 wherein the apparatus comprises a hopper having an outlet positioned immediately above the surface from which the stream of material flows from the outlet over the surface spreading to said thin dispersed layer.

10. Apparatus according to claim 9 including means arranged to agitate the hopper to assist the flow of bulk material from the hopper.

11. Apparatus according to any one of claims 7 to 10 wherein the leading edge of the barrier has a V shape when viewed from above the surface.

12. Apparatus according to any one of claims 7 to 11 wherein the barrier comprises two or more louvres extending one above the other across the surface.

13. A method of removing lumps or agglomerates from granular or powdered material, substantially as herein described with reference to any one or more of the accompanying drawings.

14. Apparatus for removing lumps or agglomerates from granular or powdered material, substantially as herein described with reference to any one or more of the accompanying drawings.