AU2011320001A1

AU2011320001A1 - Vibratory screening apparatus

Info

Publication number: AU2011320001A1
Application number: AU2011320001A
Authority: AU
Inventors: Gordon William Ashley; Simon Mann
Original assignee: Schenck Process Australia Pty Ltd
Current assignee: Sandvik Rock Processing Australia Pty Ltd
Priority date: 2010-10-28
Filing date: 2011-08-03
Publication date: 2013-05-30
Also published as: CL2013001177A1; WO2012054954A1; BR112013010452A2; CA2815684A1

Abstract

A vibratory screening apparatus for separating granulated material, the apparatus comprising: an inlet for receiving granulated material; a plurality of sampling outlets for sampling at least part of the granulated material; a first screen assembly for retaining a first portion of the granulated material for discharge at a first one of the plurality of sampling outlets and allowing a second portion of the granulated material to pass through the first screen assembly, wherein at least part of the second portion is discharged at a second one of the plurality of sampling outlets; and an actuator assembly adapted to actuate at an adjustable angle of actuation for causing vibration of the first screen assembly to facilitate passing of the second portion of the granulated material through the first screen assembly.

Description

WO 2012/054954 PCT/AU2011/000974 1 VIBRATORY SCREENING APPARATUS Field of the Invention The present invention relates generally to a vibratory screening apparatus, and particularly to a vibratory screening apparatus for separating granulated material. 5 Background of the Invention Vibratory screening apparatuses are typically used at mine sites to separate extracted granulated materials, such as iron ores, into multiple portions according to size. They generally have multiple decks, each including multiple mesh screens that have different mesh sizes and are placed at different screen angles along each deck, to separate the granulated 10 material for discharge at the end of an appropriate deck. Because of the variability of the operating parameters (such as the screen angles and the mesh sizes), there is often a set of optimised operating parameters for a particular granulated material. However it may be difficult to determine the optimised operating parameters merely by analysing the granulated material discharged at the end of each deck. 15 Summary of the Invention According to one aspect of the present invention there is provided a vibratory screening apparatus for separating granulated material, the apparatus comprising: an inlet for receiving granulated material; a plurality of sampling outlets for sampling at least part of the granulated material; 20 a first screen assembly for retaining a first portion of the granulated material for discharge at a first one of the plurality of sampling outlets and allowing a second portion of the granulated material to pass through the first screen assembly wherein at least part of the second portion is discharged at a second one of the plurality of sampling outlets; and an actuator assembly adapted to actuate at an adjustable angle of actuation for 25 causing vibration of the first screen assembly to facilitate passing of the second portion of the granulated material through the first screen assembly. Preferably the actuator assembly includes an angularly relocatable exciter for varying the adjustable angle of actuation. More preferably the angularly relocatable exciter is rotatably coupled to a frame of the vibratory screening apparatus. Even more preferably the frame 30 includes a fixed axis about which the exciter is rotatable. Preferably the adjustable angle of actuation includes discrete angles of actuation. More preferably the discrete angles of actuation include 40, 45 and 50 degrees to the horizontal.

WO 2012/054954 PCT/AU2011/000974 2 Preferably the first screen assembly includes a first mesh screen having a mesh size designed to allow granulated material of a predetermined maximum size to pass through. More preferably the first mesh screen is one of a plurality of first mesh screens each having a different mesh size. Even more preferably the plurality of first mesh screens are each placed 5 at a different first screen angle to the horizontal. Still more preferably the vibratory screening apparatus includes a replaceable support wedge member for simultaneously adjusting the first screen angle of each of the plurality of first mesh screens. Preferably the vibratory screening apparatus further comprises a second screen assembly for retaining said at least part of the second portion of the granulated material for discharge at the 10 second one of the plurality of sampling outlets and allowing a third portion of the granulated material to pass through the second screen assembly wherein at least part of the third portion is discharged at a third one of the plurality of sampling outlets. Preferably the second screen assembly includes a second mesh screen having a mesh size designed to allow granulated material of a predetermined maximum size to pass through. 15 More preferably the second mesh screen is one of a plurality of mesh screens each having a different mesh size. Even more preferably the plurality of second mesh screens are each placed at a different screen angle to the horizontal. Still more preferably the screen angle is adjustable. According to another aspect of the invention there is provided a vibratory screening apparatus 20 for separating granulated material, the apparatus comprising: an inlet for receiving granulated material; a plurality of sampling outlets for sampling at least part of the granulated material; a first screen assembly for retaining a first portion of the granulated material for discharge at a first one of the plurality of sampling outlets and allowing a second portion of the 25 granulated material to pass through the first screen assembly to a second screen assembly, the second screen assembly being adapted for retaining at least part of the second portion of the granulated material for discharge at a second one of the plurality of sampling outlets and allowing a third portion of the granulated material to pass through the second screen assembly; 30 a collector removably coupled to the second screen assembly and adapted to collect at least part of the third portion of the granulated material; an actuator assembly for causing vibration of the first screen assembly to facilitate passing of the second portion of the granulated material through the first screen assembly and for causing vibration of the second screen assembly to facilitate passing of the third 35 portion of the granulated material through the second screen assembly. Preferably the collector is adapted to be removed from an underside of the vibratory screening apparatus. More preferably the collector is adapted to be removed vertically from the underside of the vibratory screening apparatus.

WO 2012/054954 PCT/AU2011/000974 3 Preferably the second screen assembly includes a second mesh screen having a mesh size designed to allow granulated material of a predetermined maximum size to pass through. More preferably the second mesh screen is one of a plurality of second mesh screens each having a different mesh size. Even more preferably the plurality of second mesh screens are 5 each placed at a different second screen angle to the horizontal. Still more preferably the vibratory screening apparatus includes a replaceable support wedge member for simultaneously adjusting the second screen angle of each of the plurality of first mesh screens. Preferably the collector is one of a plurality of collectors each adapted to collect granulated 10 material having passed through a respective one of the plurality of second mesh screens of the second screen assembly. Preferably the vibratory screening apparatus includes a discharge chute coupled to the collector for discharging the third portion of the granulated material from the vibratory screen apparatus. More preferably the discharge chute is removably coupled to the collector. Even 15 more preferably the discharge chute is one of a pair of discharge chutes coupled to opposite sides of the collector. Preferably the first screening assembly includes a diverting chute for sampling the second portion of the granulated material having passed through the first screening assembly. More preferably the diverting chute is adapted to discharge a sample of the second portion of the 20 granulated material from the vibratory screening apparatus. Even more preferably the diverting chute is removably coupled to the first screen assembly. Preferably the first screen assembly is above the second screen assembly. Preferably the first screen assembly defines a first passageway for the first portion of the granulated material to travel to the first one of the plurality of sampling outlets. More 25 preferably the first passageway is formed by the plurality of first mesh screens. Preferably the second screen assembly defines a second passageway for said at least part of the second portion of the granulated material to travel to the second one of the plurality of sampling outlets. More preferably the second passageway is formed by the plurality of second mesh screens. 30 Preferably the first portion of granulated material includes oversized granulated material. Preferably said at least part of the second portion of granulated material includes middling granulated material. Preferably the third portion of granulated material includes undersized granulated material.

WO 2012/054954 PCT/AU2011/000974 4 Preferably the actuator assembly is configured to cause acceleration of the granulated material relative to the screen assembly. More preferably the acceleration ranges from 2.6 to 6 times gravitational acceleration. Preferably the granulated material includes granulated ore material. More preferably the 5 granulated ore material includes iron ore. Mesh is to be understood as including screens having perforations of a variety of shapes and sizes. Brief Description of the Drawings Fig. 1 A cut-away, perspective view of an embodiment of the vibratory screening apparatus 10 according to the present invention. Fig. 2 A perspective view of a lower part of the embodiment of the vibratory screening apparatus shown in Fig. 1. Fig. 3 A perspective view of another embodiment of the vibratory screening apparatus according to the present invention. 15 Fig. 4 An internal perspective view of yet another embodiment of the vibratory screening apparatus according to the present invention. Detailed Description of the Preferred Embodiments The present invention relates to a vibratory screening apparatus with sampling capabilities. The sampling capabilities of the apparatus allow an operator of the apparatus to analyse the 20 effects of varying certain operating parameters (e.g. the angle of the exciter line of stroke, the angle of each mesh screen and the mesh size of each mesh screen) on the performance of the apparatus in separating any given extracted mineral, ore or granulated material into portions of differently sized material. The granulated material may be provided with or without some significant liquid fraction. It is envisaged that the apparatus may be used as a mobile 25 test facility transportable to different mine sites to determine a set of optimised operating parameters with which screen apparatuses may be set up for separating extracted minerals or ores at each particular mine site. Alternatively the apparatus may be located permanently at the mine site In one aspect of the invention, the vibratory screening apparatus comprises (i) an inlet for 30 receiving granulated material, (ii) a plurality of sampling outlets for sampling at least part of the granulated material, (iii) a screen assembly for retaining a first portion of the granulated material for discharge at one of the plurality of sampling outlets and allowing a second portion of the granulated material to pass through the first screen assembly for discharge at another WO 2012/054954 PCT/AU2011/000974 5 one of the plurality of sampling outlets, and (iv) an actuator assembly adapted to actuate at an adjustable angle of actuation for causing vibration of the first screen assembly to facilitate passing of the second portion of the granulated material through the first screen assembly. Fig. 1 shows a cut-away view of an embodiment of the vibratory screening apparatus 1. In 5 this embodiment, granulated material may enter the apparatus 1 at an inlet 10 and may be discharged at any one of a plurality of sampling outlets, such as 12a, 12b, 12c and 12d for sampling. Once the granulated material has entered the apparatus 1 through the inlet 10, the granulated material may be dropped on to an upper screen assembly 14 (the upper deck). Granulated material of a sufficiently large size may continue travelling along upper 10 passageway 15 to sampling outlet 12a. Conversely granulated material of a sufficiently small size may pass through the upper screen assembly 14 and drop on to a lower screen assembly 16 (the lower deck) and may continue travelling along lower passageway 17 leading to sampling outlet 12b. Granulated material of an even smaller size may pass through the lower screen assembly 16 and may be discharged and sampled at sampling outlet 12c. In 15 some embodiments, there may only be a single screening assembly and a single passageway (i.e. single deck). In other embodiments, there may be more than two screening assemblies and more than two passageways. The apparatus 1 includes an actuator assembly 18 for causing vibration of the screen assemblies 14 and 16 and, in particular, vibration of their mesh screens which in turn causes 20 acceleration of the granulated material relative to the screen assemblies, thereby facilitating passing of the appropriately sized portion of the granulated material through the screen assemblies 14 and 16. Typically the actuator assembly 18 can cause acceleration ranging from 2.6 to more than 6 times gravitational acceleration at a variety of vibration frequencies. Each of the two passageways 15 and 17 may be divided into sections each defined by a 25 mesh screen of a different mesh size and a different screen angle. In this embodiment, the passageways 15 and 17 are each divided into six sections respectively defined by six mesh screens. Going from the inlet 10 to the outlet 12a, the mesh size generally becomes progressively smaller and the screen angle to horizontal generally becomes progressively smaller. Each of the mesh screens in the lower screen assembly 16 also generally has a 30 smaller mesh size than the corresponding mesh screen in the upper screen assembly. The screen angle of each of the mesh screen in the lower screen assembly 16 may also be different from that of its corresponding mesh screen in the upper screen assembly 14. The different mesh sizes and different screen angles allow granulated material of predetermined maximum sizes to pass through the screen assemblies 14 and 16 at different 35 stages of the screening apparatus 1 (with each stage being defined by a particular combination of mesh angle and mesh size), and thus sampled or collected at different sampling outlets. For example, oversized granulated material may not be able to pass through the upper screen assembly 14 and may thus travel to sampling outlet 12a. Middling WO 2012/054954 PCT/AU2011/000974 6 granulated material may be able to pass through the upper screening assembly 14 but not the lower screening assembly 16 and may thus travel to sampling outlet 12b. Undersized granulated material may be able to pass through both the upper and the lower screening assemblies 14 and 16 and may thus be discharged to sampling outlet 12c. 5 In one embodiment the actuator assembly 18 includes an angularly relocatable exciter that actuates along a line of stroke at an angle that is fixed relative to the screening apparatus 1. The apparatus 1 may include a fixed axis 20 on which the exciter may rotate about a frame of the apparatus 1. The angle of actuation relative to the apparatus 1 can be varied and adjusted by angularly relocating the actuator assembly 18 relative to the apparatus 1. The axis 20 is an 10 imaginary axis and located preferably at the mass centre of the screening machine so that rotating the exciter changes the vibration direction but not the balance of the machine. The angle of actuation may affect the acceleration value perpendicular to the screening surface and parallel to the screening surface to produce different and possibly beneficial trajectory of particle transport velocity and different flexure of the screening media. It is possible to test 15 this effect in isolation from changes to the angle of the screening media or passageways 15 and 17 relative to the horizontal and to test the effect of changing the angle of the screening media 15 and 17 without changing the excitation angle. It is envisaged that the angle of actuation may be adjusted to discrete excitation angles of 40, 45 and 50 degrees to the horizontal by rotation of the exciter 18 within the vibrating screening apparatus 1. 20 In this embodiment, the vibratory screening apparatus 1 is supported on a number of support members 22, each including a resilient element such as a spring 23 to allow for vibration of the apparatus 1 and a support wedge member 24 for tilting the frame of the apparatus and hence the entire screen assemblies 14 and 16. The support wedge member 24 may be replaced by another support wedge member having a different wedge angle so that the 25 screen angle of each mesh screen (relative to horizontal) can be adjustably tilted by the same amount. Since the actuator assembly 18 is angularly relocatable relative to the frame, any change in the angle of actuation (relative to the horizontal) of the actuator assembly 18 due to a change in tilt of the frame can be compensated by angularly reorienting the actuator assembly 18 to reach a desired angle of actuation (relative to the horizontal). Further 30 excitation angles may be achieved by altering the devices 23 and 24 or by other means such as altering the machine balance with mass addition or removal. In another aspect of the invention, the vibratory screening apparatus comprises: (i) an inlet for receiving granulated material, (ii) a plurality of sampling outlets for sampling at least part of the granulated material, (iii) a first screen assembly, (iv) a second screen assembly and (iv) 35 an actuator assembly for causing vibration of the first screen assembly and the second assembly. The first screen assembly, such as an upper screen assembly, is adapted to retain a first portion of the granulated material (such as oversized granulated material) for discharge at a first one of the plurality of sampling outlets and allowing a second portion of the WO 2012/054954 PCT/AU2011/000974 7 granulated material (such as middling granulated material) to pass through the first screen assembly to a second screen assembly, such as a lower screen assembly, which is adapted for retaining the second portion of the granulated material for discharge at a second one of the plurality of sampling outlets and allowing a third portion of the granulated material (such 5 as undersized granulated material) to pass through the second screen assembly to be collected by a collector removably coupled to the second screen assembly. The actuator assembly facilitates passing of the second portion of the granulated material through the first screen assembly and passing of the third portion of the granulated material through the second screen assembly. 10 Fig. 2, which shows a lower part of the vibratory screening apparatus 1 below the lower screen assembly 18, illustrates this aspect of the invention. This lower part includes a removable collector such as hopper 26 for each of the six sections of the lower passageway for collecting granulated material passing through the lower screening assembly 18. The hopper 26 may be removed vertically from the underside 29 of the apparatus 1. Each hopper 15 26 may be coupled to a pair of discharge chutes 28a and 28b disposed on opposite sides of the hopper 26 for discharging the collected granulated material. The discharge chutes 28a and 28b may be removably attached to the frame of the apparatus 1 or the hopper 26. In some embodiments, such as that shown in Fig. 3, the apparatus 2 may have some but not all of the hoppers and their corresponding discharge chutes removed from the apparatus 2. In 20 the example shown in Fig. 3, hopper 34 may collect granulated material having passed through the first stage of the apparatus section from the inlet 10 (i.e. both the first section of the upper screening assembly 14 and the first section of the lower screening assembly 16). The collected material, which may be discharged through discharge chute 30, can then be sampled at sampling outlet 36. The material sampled at sampling outlet 36 is expected to be 25 the finest portion of the granulated material. In some embodiments, the first screening assembly may include removable diverting chutes for sampling granulated material having passed through the first screening assembly. As shown in Figs. 1 and 4, there may be one or more diverting chutes (such as 38 and 39) underneath each mesh screen (i.e. each section) of the upper screening assembly 14. The 30 removable diverting chutes when in place may sample part of the granulated material having passed through the respective mesh screens of the first screening assembly 14 and may divert it to one of the sampling outlets such as 1 2e for sampling. For example, the embodiment shown in Fig. 4 includes two diverting chutes 38 and 39 for a particular section of the upper screening assembly. There is also room to add two more diverting chutes in the 35 same section to divert samples to the two remaining sampling outlets (12f and the other not shown) of that section. Now that the preferred embodiments of the vibratory screening apparatus have been described, it should be apparent that the present invention has the following advantages: WO 2012/054954 PCT/AU2011/000974 8 * The angularly relocatable actuator assembly allows for an adjustable angle of actuation; * The removable hoppers allow for sampling of undersized granulated material at different stages. 5 It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. For example, the screening apparatus may have fewer or more than two screen assemblies. There may be any number of mesh screens per screen assembly. There may be fewer or more than two 10 discharge chutes per collector or hopper. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

1. A vibratory screening apparatus for separating granulated material, the apparatus comprising: an inlet for receiving granulated material; 5 a plurality of sampling outlets for sampling at least part of the granulated material; a first screen assembly for retaining a first portion of the granulated material for discharge at a first one of the plurality of sampling outlets and allowing a second portion of the granulated material to pass through the first screen assembly wherein 10 at least part of the second portion is discharged at a second one of the plurality of sampling outlets and an actuator assembly adapted to actuate at an adjustable angle of actuation for causing vibration of the first screen assembly to facilitate passing of the second portion of the granulated material through the first screen assembly. 15

2. A vibratory screening apparatus as claimed in claim 1 wherein the actuator assembly includes an angularly relocatable exciter for varying the adjustable angle of actuation.

3. A vibratory screening apparatus as claimed in claim 2 wherein the angularly relocatable exciter is rotatably coupled to a frame of the vibratory screening apparatus. 20

4. A vibratory screening apparatus as claimed in claim 3 wherein the frame includes a fixed axis about which the exciter is rotatable.

5. A vibratory screening apparatus as claimed in any one of the preceding claims wherein the adjustable angle of actuation includes discrete angles of actuation.

6. A vibratory screening apparatus as claimed in claim 5 wherein the discrete angles of 25 actuation include 40, 45 and 50 degrees to the horizontal.

7. A vibratory screening apparatus as claimed in any one of the preceding claims wherein the first screen assembly includes a first mesh screen having a mesh size designed to allow granulated material of a predetermined maximum size to pass through. 30

8. A vibratory screening apparatus as claimed in claim 7 wherein the first mesh screen is one of a plurality of first mesh screens each having a different mesh size.

9. A vibratory screening apparatus as claimed in claim 8 wherein the plurality of first mesh screens are each placed at a different first screen angle to the horizontal. WO 2012/054954 PCT/AU2011/000974 10

10. A vibratory screening apparatus as claimed in either of claims 8 or 9 also comprising a replaceable support wedge member for simultaneously adjusting the first screen angle of each of the plurality of first mesh screens.

11. A vibratory screening apparatus as claimed in any one of the preceding claims further 5 comprising a second screen assembly for retaining said at least part of the second portion of the granulated material for discharge at the second one of the plurality of sampling outlets and allowing a third portion of the granulated material to pass through the second screen assembly wherein at least part of the third portion is discharged at a third one of the plurality of sampling outlets. 10

12. A vibratory screening apparatus as claimed in claim 11 wherein the second screen assembly includes a second mesh screen having a mesh size designed to allow granulated material of a predetermined maximum size to pass through.

13. A vibratory screening apparatus as claimed in claim 12 wherein the second mesh screen is one of a plurality of mesh screens each having a different mesh size. 15

14. A vibratory screening apparatus as claimed in claim 13 wherein the plurality of second mesh screens are each placed at a different screen angle to the horizontal.

15. A vibratory screening apparatus as claimed in claim 14 wherein the screen angle is adjustable.

16. A vibratory screening apparatus for separating granulated material, the apparatus 20 comprising: an inlet for receiving granulated material; a plurality of sampling outlets for sampling at least part of the granulated material; a first screen assembly for retaining a first portion of the granulated material 25 for discharge at a first one of the plurality of sampling outlets and allowing a second portion of the granulated material to pass through the first screen assembly to a second screen assembly, the second screen assembly being adapted for retaining at least part of the second portion of the granulated material for discharge at a second one of the plurality of sampling outlets and allowing a third portion of the granulated 30 material to pass through the second screen assembly; a collector removably coupled to the second screen assembly and adapted to collect at least part of the third portion of the granulated material; an actuator assembly for causing vibration of the first screen assembly to facilitate passing of the second portion of the granulated material through the first 35 screen assembly and for causing vibration of the second screen assembly to facilitate WO 2012/054954 PCT/AU2011/000974 11 passing of the third portion of the granulated material through the second screen assembly.

17. A vibratory screening apparatus as claimed in claim 16 wherein the collector is adapted to be removed from an underside of the vibratory screening apparatus. 5

18. A vibratory screening apparatus as claimed in claim 17 wherein the collector is adapted to be removed vertically from the underside of the vibratory screening apparatus.

19. A vibratory screening apparatus as claimed in any one of claims 16 to 18 wherein the second screen assembly includes a second mesh screen having a mesh size 10 designed to allow granulated material of a predetermined maximum size to pass through.

20. A vibratory screening apparatus as claimed in claim 19 wherein the second mesh screen is one of a plurality of second mesh screens each having a different mesh size.

21. A vibratory screening apparatus as claimed in claim 20 wherein the plurality of 15 second mesh screens are each placed at a different second screen angle to the horizontal.

22. A vibratory screening apparatus as claimed in claim 21 wherein the vibratory screening apparatus includes a replaceable support wedge member for simultaneously adjusting the second screen angle of each of the plurality of first mesh 20 screens.

23. A vibratory screening apparatus as claimed in any one of claims 16 to 22 wherein the collector is one of a plurality of collectors each adapted to collect granulated material having passed through a respective one of the plurality of second mesh screens of the second screen assembly. 25

24. A vibratory screening apparatus as claimed in any one of claims 16 to 23 also comprising a discharge chute coupled to the collector for discharging the third portion of the granulated material from the vibratory screen apparatus.

25. A vibratory screening apparatus as claimed in claim 24 wherein the discharge chute is removably coupled to the collector. 30

26. A vibratory screening apparatus as claimed in either of claims 24 or 25 wherein the discharge chute is one of a pair of discharge chutes coupled to opposite sides of the collector. WO 2012/054954 PCT/AU2011/000974 12

27. A vibratory screening apparatus as claimed in any one of the preceding claims wherein the first screening assembly includes a diverting chute for sampling the second portion of the granulated material having passed through the first screening assembly. 5

28. A vibratory screening apparatus as claimed in claim 27 wherein the diverting chute is adapted to discharge a sample of the second portion of the granulated material from the vibratory screening apparatus.

29. A vibratory screening apparatus as claimed in either of claims 27 or 28 wherein the diverting chute is removably coupled to the first screen assembly. 10

30. A vibratory screening apparatus as claimed in any one of the preceding claims wherein the first screen assembly defines a first passageway for the first portion of the granulated material to travel to the first one of the plurality of sampling outlets.

31. A vibratory screening apparatus as claimed in claim 30 (when it depends on any one of claims 7 to 10) wherein the first passageway is formed by the plurality of first mesh 15 screens.

32. A vibratory screening apparatus as claimed in any one of claims 16 to 29 wherein the second screen assembly defines a second passageway for said at least part of the second portion of the granulated material to travel to the second one of the plurality of sampling outlets. 20

33. A vibratory screening apparatus as claimed in claim 32 wherein the second passageway is formed by the plurality of second mesh screens.

34. A vibratory screening apparatus as claimed in any one of claims 16 to 29 wherein the first screen assembly is above the second screen assembly.

35. A vibratory screening apparatus as claimed in any one of the preceding claims 25 wherein the first portion of granulated material includes oversized granulated material.

36. A vibratory screening apparatus as claimed in any one of the preceding claims wherein said at least part of the second portion of granulated material includes middling granulated material.

37. A vibratory screening apparatus as claimed in any one of claims 16 to 29 wherein the 30 third portion of granulated material includes undersized granulated material.

38. A vibratory screening apparatus as claimed in any one of the preceding claims wherein the actuator assembly is configured to cause acceleration of the granulated material relative to the screen assembly. WO 2012/054954 PCT/AU2011/000974 13

39. A vibratory screening apparatus as claimed in claim 38 wherein the acceleration is greater than 2.6 times gravitational acceleration.

40. A vibratory screening apparatus as claimed in any one of the preceding claims wherein the granulated material includes granulated ore material. 5

41. A vibratory screening apparatus as claimed in claim 40 wherein the granulated ore material includes iron ore.