GB2192352A - Spiral separator - Google Patents

Abstract

A spiral separator 1 has a vibrator (4) mounted thereto and adapted to impart a vibratory effect to the spiral. The vibrator may be an eccentrically weighted (5,6) rotary motor which is mounted coaxially with a central take-off conduit (2) for the spiral. The resultant vibrations have a horizontal component. In another embodiment, a number of spiral separators is supported in a frame to which a vibrator is connected. <IMAGE>

Description

SPECIFICATION Spiral separator This invention relates to a spiral separator.

A spiral separator is an apparatus for the separation of particles of higher density from particles of lower density when a mixture of such particles suspended in a slurry is fed through the separator. The separator is in the form of a generally helical sluice or spiral supported with the helixal axis upright.

It is usual to feed a stream of slurry, for example water containing suspended solids, into the upper part of such a sluice and to permit the liquid and solids to flow down the sluice under gravity. If the shape of the sluice is correctly chosen, the higher density particules tend to travel more slowly than the lower density particles and under the influence of gravity tend to concentrate towards the inner edge of the sluice, whereat a fraction of concentrated heavy particles may be removed by means of a splitter and take-off.

A problem with prior art separators has been that heavy particles with a particle size less than about 75 Fm tend to be washed away with the transporting liquid rather than gravitating towards the centre of the separator. For many minerals which are separated with this type of separator this is not a particularly serious problem because only a low percentage of the mineral to be separated carried in the slurry have such a small particle size.However in the recovery of some minerals, such as gold for example, where the ore bearing rock must be crushed to a particularly small size in order to extract the mineral, a much greater percentage of the mineral to be extracted has a particle size less than 75 ,um. Indeed, about 90% of gold particles are below this size after the crushing process has been completed and thus prior art spiral separators are unsatisfactory for the upgrading of gold ores.

One way in which this problem can be alleviated to some extent is to decrease the gradient of the spiral. The advantage of this is that the slurry will travel at a slower speed thus providing more time for the heavier particles to gravitate towards the centre of the spiral. With the decreased gradient however, there is a tendency for the solids in the slurry to settle on the surface of the spiral resulting in poor separation.

It is an object of this invention to provide an efficient spiral separator.

SUMMARY OF THE INVENTION According to the invention there is provided a spiral separator comprising a spiral and a vibrator, vibration of the vibrator in use imparting a vibratory effect to the.spiral.

Further there is provided for the spiral to include an axially orientated central conduit which optionally may receive take-offs from the spiral and which, at least to some extent, supports the spiral, the vibrator being adapted to impart a vibratory effect to the conduit. In such instances the vibrator may be mounted to the conduit.

Where the spiral is supported in a frame, the vibrator may be mounted to the frame, or be linked to the frame, to impart a vibratory effect to the frame. The invention extends to a spiral separator assembly comprised of a plurality of spirals, each individual spiral having a vibrator mounted thereto adapted to impart a vibratory effect to the individual spirals.

The vibrator may comprise a rotary motor with an eccentric weight. In such an instance the vibrator will preferably be mounted with its axis of rotation substantially concentric with the spiral axis. The effect will be for the resulting vibration to have a horizontal component. The spiral may be mounted on a resilient support. The amplitude of the vibrations may be between 0,1 and 1,0 mm. The rotational speed of the rotary motor may be adjusted to meet the requirement of a particular separation and may for example be between 2000 and 3000 rpm.

The rotary motor may be a variable speed motor and the eccentric weight may be removable and replaceable with weights of different mass.

The invention also extends to a method of separating more dense particles from a slurry carrying particles with a range of densities, the method including the steps of: passing the slurry down the spiral of a spiral separator, vibrating the spiral with a vibrator, and separating out that part of the slurry near the inner edge of the spiral from the remainder of the slurry.

BRIEF DESCRIPTION. OF THIE DRA WINGS An embodiment Qf the invention is described below by way of example, reference being made to the accompanying drawings in which: Figure 1 shows a side elevation of a spiral with a vibrator mounted thereto, and Figure 2 shows a plan view of a spiral, and Figure 3 shows a side view of frame and spiral assembly.

DETAILED DESCRIPTION OF THE DRA WINGS As shown, a spiral separator comprises a spiral or helical sluice 1 which defines a downwardly spiraling flowpath around a central conduit 2. At various points along the length of the spiral, openings (not shown) are formed in the conduit 2 and, optionally, splitters including a vertically extending blade, are used to separate the inner portion of slurry flowing down the spiral and direct it into the openings. The cross-sectional shape of the sluice may take any convenient form and a form which includes a low central ridge, dividing the sluice into two channels is well known. That part of the slurry directed into the central conduit 1 discharges through outlet 3, and will include a high percentage of the heavier particles carried in the slurry.

Mounted below the spiral 1 and concentric with the central conduit 2 is a vibrator 4 in the form of a rotary motor. The motor has flywheel 5 which rotates therewith, the flywheel having an eccentric weight 6 on one side thereof. Due to this eccentricity, rotation of the motor will set up a vibration which is transmitted to the central conduit 2 through a connecting rod 7. A rubber mounting block 8 is interposed between the rod 7 and the conduit 2 to damp the vibrations to some extent. This block may be omitted if necessary.

The vibrations resulting from a vibrator of this nature which is located concentrically with the spiral axis will be circular in form in a substantially horizontal plane. It is envisaged that this form of vibration will be most effective in moving the heavier particles towards the central conduit.

The circular-vibrations will, it is believed, urge the solid particles to move in a circular path.

However, due to the configuration of the spiral surface the heavier particles will tend only to move towards the centre of the spiral and will thus not complete a full circle of movement.

Although-vertically orientated vibrations of the spiral will have the effect of lifting the heavier particles off the spiral surface, the slurry travelling downwards will tend to carry these particles downwards rather than towards the central conduit. It must be emphasized however that even vertical vibrations will to some extent assist in the separation process because these vibrations will cause the heavier particles to move and they will, due to the form of the spiral, tend to gravitate towards the take off openings in the conduit. The actual form of the vibrations will be selected with consideration of the shape of the spiral and the material to be separated to thereby provide the most efficient vibration profile.

It has been found that vibrations having an amplitude of about 0,25 mm and a frequency of about 46 Hz are effective in improving the efficiency of a separator.

In the preferred form of the invention the rotary motor will be a variable speed type motor enabiing the frequency of vibrations to be varied to suit the particular operating conditions at any one time. A motor which has a variable speed of between about 1500 to 4000 rpm will be ideal for the vibration of the spiral.

The eccentric weight on the flywheel should - be removable and replaceable with a weight of different mass. This will enable the amplitude of the vibrations to be varied. Experimentation will soon determine the amplitude of vibration which is most efficient for a particular slurry mix. The actual mass of the weight will of course depend on the configuration of flywheel selected.

Generally, an amplitude of between about 0,1 and 1,0 mm is envisaged.

Experimentation using a Reichert LD 10 coal spiral and vibrated with vibrations having an amplitude of about 0,25 mm produced by an eccentrically weighted rotary motor rotating at about 2760 rpm produced in the following comparative results in separating SnO2 from a slurry, the SnO2 having been crushed to a particle size of less than 75 ,um:: With Vibration

|Fraction Sample Mass Kg Assay $ 1% Mass Distribution Wet Dry %Sn02 Solids |Solids l Mineral Sn02 Product 0,498 1 0,297 4,22 59,64 1 4,7 86,78 Midlings 1,686 1 0,893 0,04 52,97 14,0 2,47 Tailings 4,238 5,173 0,03 15,11 81,3 10,i5 Calculated ~ . ~ ~ Head )6,422 6,363 0,23 17,47 100,0 l 100,00 Recovery of Sn02 to Products was 86.78 WITHOUT VIBRATION

Fraction Sample ass Kg Assay % Mass Distribution Wet Dry %Sn02 Solids Solids Mineral Sn02 Product 0,464 0,291 2,24 62,72 4,0 65,97 Midlings 1,715 0,908 0,04 52,94 12,6 3,68 Tailings 37,860 5,998 0,05 15,84 83,3 30,35 Calculated ~~ Head j40,039 7,197 0,14 17,97 100,0 | 100,00 Recovery of Sn02 to Products was 65.97 In both tests the same slurry was used.

It will be appreciated that the recovery of SnO2 with the vibratory enhanced separation was substantially better than the test where no vibration was present.

Referring now to Figure 3, a plurality of spirals 10 are shown mounted in a frame 11. The frame 11 is mounted on elastomeric footings 12 and is vibrated by means of a vibrator 13 mounted to a suitable foundation 14 and connected to one side of the frame. It will be appreciated that vibrations imparted to the frame will be imparted to the spirals mounted to the frame. Thus only one vibrator need be used to vibrate all the spirals mounted in the frame.

The vibrator itself may be in the form of a rotary motor with some form of cam connection 15 linking the motor to the frame. The cam connection 15 will be designed to impart much the same amplitude of vibrations to the frame as hereinbefore described with reference to a single spiral and vibrator assembly.

Many variations may be made to the above described embodiments without departing from the scope of the invention. In applications where large flowrates need to be separated it is often the practice to mount a whole bank of spiral separators to a single frame structure. The configuration of the vibrator may also taken any convenient form and the invention is not limited to a rotary motor with an eccentrically weighted flywheel.

Claims (16)

1. A spiral separator comprising a spiral and a vibrator, vibration of the vibrator in use imparting a vibratory effect to the spiral.

2. A spiral separator as claimed in claim 1 wherein the separator includes an axially orientated central conduit which is optionally in communication with the spiral through tubes or conduits and which, at least to some extent, supports the spiral, the vibrator being adapted to impart a vibratory effect to the conduit.

3. A spiral separator as claimed in claim 1 wherein the spiral is supported in a frame, the vibrator being mounted on, or linked to, the frame to impart in use a vibratory effect to the spiral through the frame.

4. A spiral separator as claimed in any preceding claim wherein the vibrator comprises an eccentrically weighted rotary motor.

5. A spiral separator as claimed in claim 4 wherein the eccentric weight is removable and replaceable with a weight of different mass.

6. A spiral separator as claimed in claim 4 or 5 wherein the motor is mounted with its axis of rotation substantially concentric with the spiral axis.

7. A spiral separator as claimed in any preceding claim wherein the amplitude of the vibrations are adapted to be between 0,1 and 1,0 mm.

8. A spiral separator as claimed in any preceding claim wherein the vibrator is adapted to impart vibrations at a frequency of between 30 and 50 cycles per second.

9. A spiral separator as claimed in any preceding claim wherein the vibrator includes means for varying the frequency or vibrations.

10. A spiral separator as claimed in claim 9 wherein the means is a variable speed rotary motor.

11. A spiral separator assembly comprising a plurality of spiral separators mounted in a frame, and a vibrator mounted to or connected to the frame, the vibrator adapted to impart vibrations through the frame to the spiral separators.

12. A spiral separator substantially as hereinbefore described with reference to the drawings.

13. A method of separating more dense particles from a slurry carrying particles with a range of densities, the method including the steps of: passing the slurry down the spiral of a spiral separator, vibrating the spiral with a vibrator, and separating out that part of the slurry near the inner edge of the spiral from the remainder of the slurry.

14. A method as claimed in claim 13 wherein the spiral is vibrated with vibrations having an amplitude of between 0,1 and 1,0 mm.

15. A method as claimed in either claim 13 or 14 wherein the spiral is vibrated with vibrations at a vibratory speed of between 30 and 50 cycles per second.

16. A method of separating more dense particles from a slurry carrying particles with a range of densities, substantially as hereinbfore described with reference to the accompanying drawings.