WO2004082802A1

WO2004082802A1 - Thickener fitted with vibrator

Info

Publication number: WO2004082802A1
Application number: PCT/IB2004/000786
Authority: WO
Inventors: Walters Francois Du Toit
Original assignee: Wallie Se Trust
Priority date: 2003-03-17
Filing date: 2004-03-17
Publication date: 2004-09-30
Also published as: ZA200507477B

Abstract

A thickener includes a tank, at least one vibratable plate mounted within the tank, a frame located outside the tank and connected to the vibratable plate, and an offset mass rotatable about an axis by a motor for providing a rotatable vibrating force fixed to the frame. The frame is supported by damping means which is in turn fixed to a sidewall of the tank by a bracket.

Description

THICKENER FITTED WITH VIBRATOR

FIELD OF THE INVENTION

This invention relates to a thickener fitted with a vibrator.

BACKGROUND OF THE INVENTION

A thickener fitted with a vibrator is known. This vibrator includes a plate within the thickener. The plate is connected to a frame located outside the thickener. An air motor is located on the frame. The air motor has a piston which reciprocates at right angles to the adjacent sidewall of the thickener to which it is mounted. The air motor thus imparts a linear vibration to the plate causing the plate to vibrate in a linear direction at right angles to the sidewall of the thickener. A disadvantage of this separator is that the plate does not move in a direction substantially parallel to the sidewall of the thickener.

In this specification the term thickener includes clarifier, separator or settler.

SUMMARY OF THE INVENTION

According to the invention a thickener includes:

a tank;

at least one vibratable member mounted within the tank;

a frame located outside the tank and connected to the vibratable member; and means for providing a rotating vibrating force fixed to the frame.

The rotating vibrating force preferably imparts an omni-directional vibration to the vibratable member.

The means for providing the rotating vibrating force may be an offset or eccentri mass rotatable about an axis by a motor. The motor is preferably an electri motor. Preferably the extent to which the mass is offset from its axis adjustable. Preferably also the rotational speed of the motor can be varied.

The vibratable member may be a plate. If the plate is located in a conical section of the thickener the plate may be curved substantially to conform with the curvature of the conical section. The plate preferably tapers inwardly from its upper end to its lower end.

The frame may be supported by damping means which may be a spring which is in turn secured to a bracket fixed to the sidewall of the tank. Frame aligning means may be provided for adjusting the position of the frame relative to the sidewall of the tank to align mounting bolts and seals located between the frame and the plate. The frame aligning means may adjust the position of the spring. The frame aligning means may be a bolt which can compress the spring.

Offset mass adjusting means may be provided for adjusting the position of the offset mass relative to the frame. The offset mass adjusting means may comprise a groove in the frame and a bracket slidable relative to the groove.

According to another aspect of the invention a method of enhancing thickening of a slurry within a tank includes the steps of applying an omni-directional vibrating force to a plate located within the tank to cause the plate to vibrate at substantially right angles to, and substantially parallel to, an adjacent sidewall of the tank. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a diagrammatic cross-sectional side view of a thickener according to the invention;

Figure 2 is a cross-sectional side view of a vibrator;

Figure 3 is a front view of a vibratable plate of the vibrator.

Figure 4 is a plan view of figure 2.

DETAILED DESCRIPTION OF THE DRAWINGS

A thickener 10 includes a tank 12 with two vibrators 14. Each vibrator 14 has a curved vibratable plate 16 mounted within the tank 12. The plate 16 is located within the compaction zone of the thickener 10 which is a deep cone thickener, and the plate 16 is surrounded by the slurry in the tank 12. The plate 16 is connected by bolts 18 to a frame 20 in the form of a length of U-shaped channel iron. Rubber cones 22 are bolted to the tank 12 by bolts 24. The rubber cones 22 are located between the tank 12 and the plate 16 to reduce the amount of vibration transmitted to the tank 12.

An electric motor 26 with an eccentric weight 27 on either side of it is secured to a bracket 28 which is bolted to the frame 20. The position of the bracket 28, and hence the motor 26 and eccentric weights 27, can be altered relative to the frame 20 by sliding the bracket 28 along a groove 30 in the frame 20.

The bracket 28 is bolted to a stand 32 which is supported on a spring 34 which isolates the tank and its supporting structure from vibration. The lower end of the spring 34 is supported on a bolt 36. The bolt 36 is adjustable relative to a bracket 38 to align the frame 20 relative to the tank 12. The bracket 38 is welded to the tank 12. The bolt 36 has lock nuts 40.

The electric motor 26 is connected to an inverter (not shown) so that the speed of rotation of the motor 26 can be adjusted. The position of the eccentric weight 27 rotated by the motor 26 can be varied as described above by varying the position of the bracket 28 relative to the frame 20. It will be appreciated that varying the speed of rotation of the motor 26, the oscillating frequency can be varied. By varying the position of the eccentric weights 27, the amplitude of the rotating vibrating force generated by the eccentric weights 27 can be varied. By varying the position of the eccentric weights 27 relative to the frame 20, the magnitude of the force applied at opposite ends of the plate 16 can be varied.

In use, rotation of the eccentric weights 27 by the motor 26 generates a rotating vibrating force which is applied to the contents of the tank 12 and not to the tank 12 or its supporting structure. This force is transmitted to the frame 20 and then to the plate 16 via the bolts 18 resulting in an omni-directional vibration of the plate 16. In particular, the plate 16 vibrates at right angles to the tank 12 in the direction of arrow 42, and parallel to the tank 12 in the direction of arrow 44.

Vibration of the plates 16 maintains the fluidity of slurry 46 within the tank 12 and enhances de-watering of the slurry 46 therefore increasing the density of the slurry 46. In particular, vibration of the plates 16 in the direction of arrow 44 facilitates downward settling of the slurry 46, in contact with the plate 16, towards an outlet 48 of the tank 12. This reduces the likelihood of hang-ups or blockages of the slurry 46 occurring within the tank 12.

The applicant has found that vibration or oscillation of the plates 16 accelerates the flow of the slurry down the cone of the thickener. This allows or forces freedom of movement of the individual solid particles and re-arrangement of them takes place. Because both the frequency of the vibration and the amplitude of the vibration can be adjusted, infinite combinations of frequency and amplitude are possible which allow a thickener to be tuned to obtain high underflow densities.

The applicant has also found thai the vibration from the plates 16 in the compaction zone extends to the consolidation zone, hindered settling and free settling zones in the tank. In the consolidation zone the vibration facilitates the release of excess or entrained water. The vibration also facilitates shear of solid/flocculant bonds to such an extent that ultrafines are released and allowed to displace water in the cavities between larger solid particles. Underflow density is thus rapidly increased. This lowers the height of the compaction zone and creates an extended free settling zone with a lower flux density and thus increases the settling rate.

The viscosity of the paste discharged from the thickener is measured and controlled. By controlling the viscosity of the paste, the pumpability of the paste is maintained. This is advantageous over measuring and controlling the density of the paste as the viscosity can vary greatly due to changes in the feed material, especially clays.

It will be appreciated that many modifications or variations of the invention are possible without departing from the spirit or scope of the invention.

Claims

1. A thickener including

a tank;

at least one vibratable member mounted within the tank;

a frame located outside the tank and connected to the vibratable member; and

means for providing a rotating vibrating force fixed to the fame.

2. The thickener of claim 1 wherein the means for providing the rotating vibrating force is an offset mass rotatable about an axis by a motor.

3. The thickener of claim 1 or claim 2 wherein the vibratable member is a plate.

4. The thickener of any one of the above claims wherein the frame is supported by a damping means which is in turn fixed to a sidewall of the tank.

5. The thickener of claim 4 wherein the damping means is a spring.

6. The thickener of claim 4 or claim 5 including frame aligning means for aligning the position of the frame relative to the sidewall of the tank.

7. The thickener of any one of the above claims including offset mass adjusting means for adjusting the position of the offset mass relative to the frame.

8. A thickener substantially as herein described and illustrated with reference to the drawings.

9. A method of enhancing thickening of a slurry within a tank including the steps of applying an omni-directional vibrating force to a frame located outside the tank and connected to a plate located within the tank to cause the plate to vibrate at least at substantially right angles to, and substantially parallel to, an adjacent sidewall of the tank.

10. A method of enhancing thickening of a slurry within a tank substantially as herein described and illustrated with reference to the drawings.