GB2200859A

GB2200859A - Dry separation of solids

Info

Publication number: GB2200859A
Application number: GB08801705A
Authority: GB
Inventors: John Maxwell Lupton
Original assignee: National Research Development Corp UK
Current assignee: National Research Development Corp UK
Priority date: 1987-01-30
Filing date: 1988-01-26
Publication date: 1988-08-17
Anticipated expiration: 2008-01-26
Also published as: AU1092388A; DE3861799D1; AU3269789A; AU615533B2; CA1326648C; EP0278624A1; JPS63194752A; JPH0624644B2; GB2200859B; EP0278624B1; US4857177A; GB8801705D0; AU605542B2

Description

1 t11 1 C n r_. 0 0859 i- IL -131341 DRY SEPARATION OF SOLIDS The present

invention relates to a method and apparatus for dry separati.on of solids such as mineral ores, waste material or scrap metal.

Known dry media separators are disclosed in British Patents 1085810 and 1178235, In both. of which a mixture of materials of at least two different densities is Introduced Into a bed having a dry flotation medium which is vibrated and air-fluidised. The, principle of operation is that heavier particles of material sink to the bottom of the medium and lighter particles of material "float" towards the top of the medium. The materials, are effectively separated by having at one end of the flotation bed a weir over which only the lighter material flows and a ramp and inverted weir at the other end up which the heavier material flows. The apparatus is not found to be very efficient for a number of reasons. In particular the lighter material tends to.

circulate round within the bed and is notefficiently discharged. The lighter materi'al may also be discharged with.

the heavier material particularly if the separator is heavily loaded, considerably lowering the value of the sorted material.

It is an object of the present invention to provide a more efficient dry media separator.

According to the present Invention there i method of dry separation of solids, comprising:

vibration-driving a particulate material, finer than the solids.

to flow round a defined endless generally horizontal path; fluidising the material for a length of the path; adding the solids to the top of the flowing material; and depthwise partitioning the flowing material downstream of the solids-addition point and within the fluidised length, whereby to separate the solids which have not settled beyond the depth of the partition from those which settled faster.

1 s provided a The invention also provides a solids separator. comprising a trough defining an endless generally horizontal path, the trough having an air- permeable base over a length of the path; a distrib utor for sol-i ds onto the trough; and a depthwise partition In said trough at a point on said length. Preferably' means are provided to vibrate the separator with simu-1taneous horizontal and vertical components. The separator in use contains a particulate material as an entraining medium. and preferably the partition is perforated (to retain partitioned solids but to pass any entraining medium). An air supply upwardly through said base is in use present, to fluidise the medi um.

Preferably the solids-addition point (the distributor) is upstream.of the fluidised length, which preferably starts with an onset zone over which fluidisation progressively increases.

Preferably the defined path is rotary.

Preferably the rotary path is circular and the material and medium are constrained to move in the defined circular path by upstanding wall members.

Preferably the medium is fluidised over only a length of the rotary path.

The slower-settling material is preferably extracted by means of the -partition, which is in the form of a first ramp positioned along the rotary path at a position downstream from the commencement of the fluidised portion of the rotary path, and the faster.-settling material Is preferably extracted by means of a second ramp starting lower than the partition and preferably positioned along the rotary path at a position downstream from _the first ramp. Preferably the second ramp is positioned after the end of the fluidised length. Each ramp is preferably perforated such as to retain partitioned solids but to pass the particulate material, which can thereby continue flowing along said defined path.

t 1.

'V 1 ii 1 Ir e The present invention will now- be described by way of example with reference to the accompanying drawing, which shows a dry separation apparatus according to the present Invention in diagrammatic perspective.

The apparatus, which as will be seen can be considered as a' flowing media jigging separator, has a horizontal annular circular trough 2 which is vibrated through spring-supported mounts 4 with a motion which Is clockwise-and-uplanticlockwise and-down. Merely as a guide to indicate the general scale of one operable apparatus according to the invention, the diameter is 2m. The motion derives from eccentric cams or, preferably, two exciter units attached to diametrically opposite mounts 4 vibrating with opposed horizontal (i.e. net rotational) and in-phase vertical components, giving a reciprocating screw-twist is rising and falling at 'for example a resultant 450 to the horizontal.

The f requency and amplitude of vibration of the exciter units are selected according to the size and Intended throughput of the separator apparatus but again merely as a guide could be of the order of 50 Hz and 3mm.

The apparatus is fed by a chute 6 leading to a perforated track 8 adjoining part of the trough 2 at a higher level. The track 8 feeds a distributor 12 for discharging feed at a single angular location into the trough 2. Underneath the distributor 12 is an adjustable horizontal radial straight-edge (not shown) for levelling the contents of the trough 2.

About a radian clockwise from the distributor 12, a helical upwards perforated ramp 14 occupies the trough, starting with a strictly radial and horizontal splitter edge 14a. The edge is -30 about half-way down the depth of the trough; its exact height and distance from the distributor are determined by trial and error.

4 t A second perforated and upward helical ramp 16 otcupies the trough, starting at its base, at a (non-critical) later clockwise position. Both ramps 14 and 16 ris'e to the top of the trough and discharge their respective streams of material over the side to different collectors.

The base of the trough, from a point somewhat clockwise of the distributor 12 to a point somewhat clockwise of the splitter edge 14a, is an air-permeable membrane,_ the rest of the base being solid. The membrane passes air upwardly from a manifold 20a fed by a compressed air line 20. At the anticlockwise end of the membrane is a transition zone whereby the onset of fluidisation (to be described) is graduated over an area.

The trough is filled to a level well above the splitter edge 14a but below the brim with a dry particulate medium which is fine in comparison with the solids to be separated and which, unlike the solids, can pass through the perforated ramps 14 and 16. Sand i s suitable, the particle size and type being selected by trial and error to suit the specific separation. 20 The operational sequence of the separation apparatus is as follows. Typical solids to be separated comprise pieces of various materials obtained, for example, by crushing and fragmentising scrap cars, machines, 'white goods' and television sets. Ferrous metals are removed magnetically, leaving dust or dirt particles; rubber. plastic and glass; and pieces of light metals (magnesium, aluminium) and denser metals (zinc, brass). The solids are screened to exclude oversize chunks and then fed by the chute 6 to the track 8. The exciter units are activated and their vibratory action causes the material to move in a clockwise direction along the perf orated track 8, where undersize solids are lost, shaken through the perforations. As -f -c al 'I ii 1Y a guide, the perforations may lose solids of volumes up to 100 times the volume of a grain of sand. The remaining solids drop off the lip of the distributor 12 into the trough 2. The sand here has been levelled by the straight-edge and Is not fluidised.

Air through the line 20 fluidises the sand in the arc above the membrane, to a modest bed expansion (a few tens of percent) starting gradually over an area at the anticlockwise end. The vibratory action simultaneously causes all the sand In the trough 2 to advance slowly clockwise. The solids are entrained in this advance, and the very lightest solids "float" on the surface of the fluidised and advancing sand, while the remaining solids sink at varying_ rates, according to a phenomenon known as hindered settling induced by the combination of vertical (fluidised and vibrated) and horizontal (vibrated) motions.

Thus by the time that these solids have been conveyed the radian or so distance to the splitter edge 14a, some of them will have settled to its depth or deeper, while the r_est will have settled less deep.

This rest therefore moves up the ramp 14 (which is also being vibrated) and is discharged over the side, for example into an annular picking tray (not shown) round which those solids move, allowing unwanted material to be hand picked therefrom. The ramp 14 being perforated, the sand falls through back into the trough 2 and thereby continues on round the trough to be used again in the separation process.

Meanwhile, the faster-settling solids are conveyed under the splitter edge 14a and along or near the base of the trough 2 until they meet the second ramp 16 the end of which Is at or close to the bottom of the trough. These solids move up the ramp 16 which is perforated to allow the sand to be shaken through, leaving these solids to proceed up the ramp to an outlet chute (not shown). That chute may lead to a picking tray (e.g. a further section of the said annular picking tray, for hand picking), and thence to a collecting hopper. The bottom of this ramp 16 Is in the non-fluidised section of the trough.

v The ^ sand flows on round the trough 2 as shown by the hollow arrows to receive a fresh load of solids from 12 in its turn.

For a more discriminating separation, two apparati can operate in series, the second receiving as feed one of the exiting solids streams of the first, and the two apparati. operating with appropriately differing parameters such as splitter edge depth or grade of sand.

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Claims

- 7 CLAIMS

1. A method of dry separatibn of solids, comprising: vibration-driving a particulate material, finer than the solids, to -flow round a defined endless generally horizontal path; add i ng the so] i ds to the top of the f 1 owing mater 1 al; fluidising the material; and depthwise partitioning the flowing fluidised material downstream of the solids-addition point, whereby to separate the solids which have not settled beyond the depth of the partition from those which settled faster, characterised in that the material is fluidised for only a portion of the length of the path, and the solids-addition point is upstream of the fluidised portion.

2. A method according to Claim 1, wherein the top of the material is levelled before the solids are added.

3. A method according to Claim 1 or 2, wherein said fluidised portion starts wi th an onset zone over which f 1 ui d i sati on progressively increases.

4. A method according to any preceding claim, wherein the defined path is rotary.

5. A method according to any preceding claim, wherein the slower-settling material is extracted by means of the partition, whi ch i S i n the form of a first ramp starting within the fVuidised portion of the endless path.

6. A method according to Claim 5, wherein the faster-settling material is extracted by means of a second ramp starting lower than the partition and positioned along the endless path at a position downstream from the first ramp.

7. A solids separator, comprising a trough defining an endless generally horizontal path, the trough having an air-permeable base and in use containing a particulate material as an entraining medium; a distributor for solids onto the trough; and a depthwise partition in said trough, characterised in that 1 1 1 8 the base is air-permeable for only a' portion of the length of the trough, the partition being situated over said portion and the distributor being situated off said portion.

8. A solids separator according to Claim 7, further comprising 05 means to vibrate the-separator with simultaneous horizontal and vertical components.

9. A solids separator according to Claim 7 or 8, wherein the airpermeable portion of the base, at its end facing the distributor, has- an onset zone over which the air-permeability progressively increases.

10. A solids separator according to Claim 7, 8 or 9, further comp ising an air supply upwardly through said base, to fluidise the medium.

11. A solids separator according to any of Claims 7 to 10, 15 wherein the endless path is rotary.

12. A solids separator according to Claim 11, wherein the rotary path is circular and the material and medium are constrained to move in the defined circular path by upstanding wall members.

13. A solids separator according to any of Claims 7 to 12, 20 further comprising means for levelling the entraining medium before it reaches the distributor.

14. A solids 'separator according to any of Claims 7 to 13, wherein the partition is-in the form of a first ramp starting over the said airpermeable portion of the base.

15. A solids separator according to Claim 14, further comprising a second ramp starting lower than the first ramp ris-ing in the same sense from.a position beyond that end of the air-permeable portion distant from the distri butor.

16. A solids separator according to Claim 14 or 15, wherein the or each ramp is perforated such as to retain partitioned solids but to pass the particulate material, which can thereby continue flowing along said defined path.

Published 1988 W. The Patent Office. Staw House. 6671 Hi6h Holbori., Lo.. don WClFL 4TP. Further copies may be obtained from The Patent O."Ice. Sales Branch.. St Ma:-y Cray. Orp_,ng%,on, Kent BR5 3RD Printed by Multaplex techniques Itd. St M&r_v Cray, Kent. Con. 1/87, Z