AU612071B1 - Separation of mixtures in a wind tunnel - Google Patents

Description

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To the Comm 1n-- -e 0 Commonwei ADDITIONAL APPLICATION No 7E o

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COMMONWEALTH OF AUSTRALIA6 Patents Act 1952 COMPLETE SPECIFICATION (Original) FOR OFFICE USE Application Number: Lodged: Class Int. Class Complete Specification Lodged: Accepted: Published: Priority: Related Art: pap.

0000 app', 00 0 a p 40000 pa a00 TO BE COMPLETED BY APPLICANT S.T. aeOL AplQS PG G LTRD Name of Applicant: -ROB-ERT-GE ORGE-S TAF-FORD I-i+ t r{ri Address of Applicant: a 0 p0 p 90000 0 (Q papa 4-Unw-i-n-Gre ent-i--Mann-i-ng, -i-n-t-he-State -of-Western-Austra-l-i-a, .Commonwealth-o f.-Austra-l-i-a-.

ROBERT GEORGE STAFFORD Actual Inventor: 0 p p p 0 p0 0 0 0. ai Address for Service:- Wray Associates Primary Industry House 239 Adelaide Terrace Perth Western Australia 6000.

Complete Specification for the invention entitled: "SEPARATION OF MIXTURES IN A WIND TUNNEL" The following statement is a full description of this invention, including the best method of performing it known to me:- -1- To the Commissioner of Patents Commonwea.th of Australia 1 2 ."SEPARATION OF MIXTURES IN A WIND TUNNEL" THIS INVENTION relates to apparatus for the classifying of particles in a wind tunnel.

A particular application of the invention relates to the classification of ores which may include gold ores, iron ,re, coal, vermiculite, mica, metallurgical slag or other such material and tailings, classification of grain, classification of sand, and like applications.

According to the present invention, -there is provided an apparatus for the classification of a mixture of 10 particulate material, said apparatus comprising a wind 0000 0o 0 tunnel having an entry section an exit section and a main o0oo section, fan means communicating with said exit section 00 for creating a flow of air through the wind tunnel from 00 .oo the atmosphere into the entry section through the main 000ooo0 0° section to the exit section, inlet means provided at a top side of the main section for introducing the particulate material into the main section across substantially the full width of the air flow for free fall under the 0000 °o0o* influence of gravity and a plurality of collectors spaced 0""0 :20 axially along a bottom side of the main section, each of Q0 0 said collectors extending transversely across the main o0ooo section, the main section being co-linear, of substantially uniform cross sectional width and height from the entry section to beyond the collectors and the 0o0 o entry section being open and of a flared configuration converging in the direction of the air flow into the wind o tunnel, the end of the entry section and the end of the exit section adjacent the main section being of corresponding cross-section to the cross section of the main section whereby the air flow through the main section is of substantially constant velocity across the cross- -3 3 section of the main section and is substantially laminar in nature wherein the inlet means is provided with a flow path for such particulate material said flow path having an inlet associated with a source for such particulate material and an outlet opening into wind tunnel and being directed downwardly said flow path beipg configured to control the flow of particulate material between the inlet and outlet and whereby the particulate material falling from the outlet is principally under the influence of gravity.

According to a preferred feature of the invention said outlet is variable as to degree of opening in a direction °0o parallel to the main axis of the wind tunnel.

0000 0 00 0 0 0oo According to a preferred feature of the invention the o 0 degree of opening is directly proportic al to the size of 00 Sooo the particles flowing therethrough.

0000 0000 The invention will be more fully understood in the light of the following description of one specific embodiment.

'The description is made with reference to the accompanying o0 20 drawings of which:- 000 0 oo 0 Figure 1 is a plan view of the embodiment, 0 000 00 0 0 Figure 2 is a sectional view along line 2-2 of Figure 1; 0 0 0 00 Figure 3 is a sectional view along line 3-3 of Figure 2; Figure 4 illustrates a variati 6 n to the embodiment in which two wind tunnels are employed; V S, 4 Figure 5 illustrates a further variation in which three wind tunnels are employed; Figure 6 is a plan view of part of the embodiment, showing particularly a conveyor for conveying particulate material along a discharge orifice opening into the wind tunnel; Figure 7 is an end view of the conveyor shown in Figure 6; Figure 8 is a view similar to Figure 6, showing another form of conveyor; and Figure 9 is also a view similar to Figure 6, showing still another form of conveyor.

Figure 10 is a cross-section bf the inlet means.

Figure 11 is an elevation of the inlet means; and Figure 12 is a sectional plan view of the inlet means along line 12-12 of Figure 11.

embodiment is directed to an apparatus for effecting classification of particle mixtures.

0..0 10 10 0000 o 0 00 0000 tt0 0 00 to o 0 000 000 00o a p 0 0 a 0 0 00 0 0 00 0 0 a a The the The separating means of the embodiment comprises a wind 20 tunnel 10 having an entry section 11, a main section 12 and an exit section 13. The main section 12 is rectangular in cross-section. The exit section 13 is formed to converge and is connected at its outer end to adust extraction cyclone 15 the air outlet of which is connected by ducting 16 to a bag filter 17.

Communicating with the filter 17 is a fan housing 14 which may accommodate an axial or centrifugal fan or any other suitable means. If desired the cyclone or filter may be located to the outlet side of the fan. The entry section 11 of the wind tunnel is of a flared configuration, converging in the direction of air flow to define an inlet bell. Since the air flow into the wind tunnel 10 is effected through the full cross-section of the wind tunnel, there is less manipulation required of the air flow than would be required if the air flow were induced from the entry side of the wind tunnel and therefore the losses and inconsistencies created are less.

0000 The wind tunnel 10 is associated with a feed material inlet means 18 at its upper side which delivers the oo° particulate material into the wind tunnel 10. The inlet 00 means 18 extends transversely across the top of the wind 0 S tunnel 10 for substantially the full width of the wind 0000 tunnel 10 and the particulate material is allowed to fall freely under the influence of gravity across the wind tunnel. The particular configuration of the inlet means 0.0 Ooo 18 will be described in detail later in the specification.

00 0 aQ The floor of the wind tunnel 10 is associated with a plurality of longitudinally spaced collectors 20 which are located below and down stream from the inlet means 18.

Each of the collectors 20 extends the full transverse width of the wind tunnel 10. The collectors are o, separated from each other by partitions 21 each of which is pivotally mounted atits lower edge about a transverse axis of the wind tunnel 10. The pivotal action of the partitions 21 of the collectors 20 enables the collection of the particulate material to be accommodated according i, j 6 to the degree of air flow through the wind tunnel 10 and the characteristics of the feed material being delivered into the wind tunnel 10. In addition, the pivotal movement of the partitions facilitates a variation in the angle of the partition to the stream of material in order to select the material collected at ,each' chamber.

Furthermore, if desired the collectors 20 can be jointly supported from the floor of the wind tunnel from a track 22 to be slidable axially thereon in order that the position of the collectors can be adjusted according to the trajectory and size of the material and the velocity of the air stream through the wind tunnel.

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3 As a result of the air flow through the wind tunnel the particulate material being deposited into the wind tunnel 10 is classified according to size, or shape or specific gravity or any combination of such properties.

Where a separator according to th6 embodiment is to process only material having little or no dust content, the cyclone 15, and in certain cases the filter 17, need not be provided. The provision of a. cyclone 15 and filter 17 is however, of particular importance when separating material having a particle size less than 180 microns.

As a result of the construction of the embodiment, the degree of manipulation of the air flow required to produce a streamline laminar air flow through the wind tunnel is less than that required in installations having a fan 0 located at the inlet of the wind tunnel and therefore the construction of the separating device is less complicated than that of the prior art proposals'discussed previously.

It has been found in the case of the embodiment, a laminar ,.0

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0~a 0~ LI 0 6 7 air flow is automatically established where there is an inlet bell of approximate dimensions which may equate to 4:1 area with that of the wind tunnel in which the separation occurs. This avoids the need for trial and error distribution plates as in the case of the prior art wind tunnels and a laminar air flow occurs at any set velocity from 0.5 m/s to 15.0 m/s both vertically from the top of the tunnel to the bottom and laterally from side to side with the exception of minor drag on the internal walls. This also obviates the need for screen meshes which are used in the prior wind tunnels to redistribute the air after straightening.

In addition, the capacity of the wind tunnel separation method can be increased more readily with the embodiment in comparison to prior art devices due to difficulties in the latter devices in achieving laminar flow in a wide wind tunnel which utilises a multiplicity of fans.

Indeed, the wind tunnel separation'method performed by the embodiment can be increased in capacity to achieve operation outside the known limits (as mentioned hereinbefore) of the pripr art separators.

To increase the capacity of the embodiment a number of wind tunnel main sections 12 may be located side by side as shown in Figures 4 and 5 which each utilise a common entry section 11, exit section 13 and fan. In the instance of a triple wind tunnel, as shown at Figure 5, if the velocity of the air is greater in the central wind tunnel section 12B, the collectors associated with that tunnel can be adjusted to compensate. Additionally, the entry section 11 may also be provided with inlet dampers 16 to regulate the air flow through the central tunnel section to provide for a complete shut off of inlet air if desired and to vary inlet air flow precisely to the desired velocity.

me" 8 The delivery of material to the inlet 18 is such that a substantially uniform curtain of material is delivered into the wind tunn6 across substantially the full width of the tunnel. More particularly, the curtain of material is delivered across that part of the tunnel where streamlined air flow exists. There is a region immediately adjacent to each wall of the wind tunnel where the flow is not uniform owing to drag arising from the effect of the boundary surface on the air flow. The curtain of material preferably terminates inwardly of each side wall of the tunnel so as not to extend into the affected region of the air flow.

o 00 00 0 0 040 0000 a o o 00 0 00 0 0000 00 0 0 0 0 00 0 0 4 The inlet means 18 of the embodiment is shown at Figures 11 and 12 and comprises a slot shaped flow passageway 51 which extends substantially the full width of the wind tunnel but which terminates short of each side wall.

When a set of wind tunnels are located, side by side as is described later in relation to Figures 4 and 5 the flow passageway if desired extend the full width of the set of 20 wind tunnels however jit is closed in the region located above the walls of adjacent wind tunnels in order that no material is delivered into the region adjacent each wall .where the airflow is affected by the wall. The flow path has an inlet 52 which communicates with a source of particulate material. Examples of such sources are described later in the specification in relation to Figures 6, 7, 8 and 9. It has been found to be important that the source of the particulate material is able to provide a substantially constant flow of material to the inlet means.

The inlet means has an outlet 53 which provides a slot 9 shaped opening in the top wall of the wind tunnel extending substantially the full width of the wind tunnel and which is directed vertically downwardly. The flow passageway 51 is convoluted and comprises an upper 4 vertical portion 54 a lower vertical portion 55 and an intermediate oblique portion 56. As a result particulate material entering the flow passageway is prevented from free fall through the passageway and is slowed in its travel whereby free fall of the particles commences in the lower vertical section. As a result on the particulate material exiting the outlet there has been substantially no high velocity impact with the walls of the passageway or between particles which is likely to introduce a °"e 1 significant horizontal component to the path of the o °°particles and as a result the particles enter the wind .oa tunnel. in a state of vertical free fall principally under 0 M 0 0 the influence of gravity. Without the control created by 00 00 the convoluted floor passageway it has been found that the 00ooo0 0000 material flowing from the outlet has a significant lateral component in its motion.

In addition one side, wall 60 of the flow passageway is 0oo oo.. capable of displacement relative to the other fixed side OSo wall 57. Thus relative movement'is facilitated by a pair of tubes 62 supported from the outer face of a fixed 0 S""0"0 member 61 at horizontally spaced locations. The movable wall 60 is slidable movable towards and away from the fixed wall 57 and is provided with a pair of rods 58 fixed o to the outer face of the movable wall 60 and interconnected at their outer end by a bracket 59. The rods 58 are slidably received .through the tubes 62. The tubes 62 are interconnected by a support 63 and a threaded rod 64 is mounted between the bracket 59 and a support 63 to be threadedly receivable on both the bracket and support. A crank handle 65 is provided on the outer end of the threaded rod whereby rotation of the threaded shaft causes relative displacement between the fixed and movable walls 60 and 57.

i- 10 In use the width of the outlet and flow passageway is varied in direct dependence on the average size of the particulate material in order that the ratio of particles to volume is substantially constant in order that each particle has substantially equal opportunity of being influenced by the air stream in the wind tunnel.

One means of delivering particulate material to the inlet means is illustrated in Figure 6 of the drawings and comprises a conveyor 31 extending across the wind tunnel and having a discharge slot opening into the inlet of the inlet means (not shown in Figure The conveyor °S°o includes an intake end 30 and a discharge end 32. The 0000ooo o conveyor 31 carries material along the full length of the o..o discharge slot 33 and excess material is discharged at the discharge end of the conveyor. Where a multiplicity of ao 0 0o. wind tunnels are used, as shown in Figures 4 and 5, the oo00 conveyor may if desired carry material-across the width of the set of tunnels.

o°oo 20 0 0 0 00 o o 0 o 0o 0 00 In the arrangement illustrated in Figures 6 and 7, the conveyor 31 is in the form of a screw conveyor comprising a feed screw 35 within a casing 34. A slot in the lower end of the casing 37 provides the discharge slot 33.

In another arrangement, which is shown in Figure 8, the conveyor 31 comprises an endless band 41 movable through a circuitous path in a casing 43 having a slot 33 in its lower base which defines the discharge orifice for the discharge of particulate material to the inlet means.

The endless band 41 has paddles 45 spaced along its length to convey material through the housing.

11 In still another arrangement, which is shown in Figure 9, the conveyor 31 comprises a pair of opposed flat belt conveyor runs 47 which are angled to define a trough therebetween to receive and convey material and which are spaced to provide a discharge opening 49 communicating with the discharge slot 33 which communicates with the inlet means.

The embodiment provides a method and apparatus for the separation of a mixture of particles according to:- Size, when the particles have substantially the same shape and specific gravity, or shape and 0o0 specific gravity combinations that make them 0o°° capable of substantially equal settling in ooo air.

00o 00 0o 0 00 Shape, when the particles have substantially the 000ooo 0oo same size and t secific gravity, or size and specific gravity combinations that make them capable of substantially equal settling in air.

0 0 0000 o 20 Specific gravity, when the particles have substantially the same size and shape or size o 0o and shape combinations that make them capable of substantially equal settling in air.

00 0 0 Equal settling combinations of size and shape, when the specific gravity\ is substantially constant.

Equal settling combinations' of size and specific gravity, when the shape is substantially constant.

12 Equal settling combination of shape and specific gravity, when the size is substantially constant.

For the purpose of this patent, equal settling particles are those which because of their combination of size, shape and specific gravity, have substantially the same terminal velocity or settling velocity when falling through a static fluid medium.

It should be appreciated that the scope of the present 10 invention need not be limited to the particular scope of 0000 Sthe embodiment described above.

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Claims (14)

1. An apparatus for the classification of a mixture of particulate material, said apparatus comprising a wind tunnel having an entry section an exit section and a main section, fan means communicating with said exit section for creating a flow of air through the wind tunnel from the atmosphere into the entry section through the main section to the exit section, inlet means provided at a top side of the main section for introducing the particulate material into the main section across substantially the full width of the air flow for free fall under the oo influence of gravity and a plurality of collectors spaced S0° axially along a bottom side of the main section, each of 0oo00o .oo. said collectors extending transversely across the main o0 0 0 o section, the main section being co-linear, of 0 0 o .o substantially uniform cross sectional width and height 0ooo from the entry section to beyond the .collectors and the entry section being open and of a flared configuration converging in the direction of the air flow into the wind tunnel, the end of the entry section and the end of the °°oooo exit section adjacent the main section being of 0o,° o corresponding cross-section to the cross section of the main section whereby the air flow through the main section 0 0o 0°0o is of substantially constant velocity across the cross- section of the main section and is substantially laminar in nature wherein the inlet means is provided with a flow 0 00 co path for such particulate material said flow path having o0o an inlet associated with a source for such particulate material and an outlet opening.into wind tunnel and being directed downwardly said flow path being configured to control the flow of particulate mat6rial between the inlet and outlet and whereby the particulate material falling from the outlet is principally under the influence of gravity. Si h r~~u~~-yrcr* u au~ 1 i; 14

2. An apparatus as claimed at claim 1 wherein said outlet is variable as to degree of opening in a direction parallel to the main axis of the wind tunnel.

3. An apparatus as claimed at claim 1 or 2 wherein the degree of opening is directly proportional to the size of the particles flowing therethrough.

4. An apparatus as claimed at any one of the preceding claims wherein a dust collection means is provided in association with the exit section. ao 5. An apparatus as claimed at claim 4 wherein the dust o 00 collection means comprises a cyclone. oo o 0 0 00 0 o 6. An apparatus as claimed at claim 4 wherein the dust collection means comprises a filter. 00oo.o0 ooo000

7. An apparatus as claimed at claim 5 wherein the dust collection means includes a filter between the cyclone and the fan means. ooo 0 0 00 0000 S 8. An apparatus as claimed at any one of the preceding claims wherein the entry section is provided with a 0o000o plurality of damper blades located across the entry section to be movable to control the magnitude and uniformity of the air flow through the entry section. o 00 o0 oo 9. An apparatus as claimed at any one of the preceding claims wherein the inlet means.is located adjacent to the entry section and is provided with a discharge orifice 'i extending transversely across and opening into the main section. ~ci airsari-aa~mu-i 15 0000 00 0 0 (000 An apparatus as claimed at claim 9 wherein a conveyor is provided above the discharge orifice for conveying particulate material along the length of the discharge orifice.

11. An apparatus as claimed at claim 9 wherein means are provided for varying the width of the discharge orifice.

12. An apparatus as claimed at claim 10 or 11 wherein the conveyor comprises a screw conveyor having a feed screw within a casing, the casing being provided with a slot defining the discharge orifice.

13. An apparatus as claimed at claim 10 or 11 wherein the conveyor comprises an endless elongate member such as a chain, cable, rope or the like having a portion passing through a casing, the endless elongate member being adapted to move particulate material ,through the casing and the casing having a slot defining the discharge orifice.

14. An apparatus as claimed at claim 13 wherein members are provided on the endless elong'ate member to facilitate movement of the particulate material through the casing.

15. An apparatus as claimed at claim 10 or 11 wherein the conveyor comprises a pair of opposed belt conveyor runs defining a trough therebetween to receive and convey particulate material, the belt conveyor runs being space& to define a discharge opening at the bottom of the trough. 00 0 3.0 0 aO~ 03 0 0 b'Od 00 0 o

16. An apparatus as claims wherein the members which extend and are pivotable claimed at any' one of the preceding collectors are separated by partition transversely across the main section to vary the available area of each 16- collector to the stream of particulate material.

17. An apparatus as claimed at any one of the preceding claims wherein the collectors are movable axially with respect to the main section.

18. An apparatus for the classification of a mixture of particulate material substantially as herein described with reference to the accompanying drawings.

19. A method of classifying a mixture of particulate material comprising utilizing an apparatus of the form as claimed at any one of the preceding claims and introducing the mixture of particulate material into the inlet and So*o removing the classified fractions from the collectors and controlling the width of the inlet means according to the GO e I U, average particle size of the mixture. o a 0 DATED this TWELFTH day of JANUARY 1990. S.T. PT4o1Df fiT p TP ROBERT- GEORGE- -S'TAFFORD- IA 0 Applicant. 4c Wray Associates IK SPerth, Western Australia, Patent Attorneys for the Applicant. 0 6 e i 0 0