WO2002047803A2

WO2002047803A2 - A method and system for recovering diamonds from diamond bearing material

Info

Publication number: WO2002047803A2
Application number: PCT/ZA2001/000198
Authority: WO
Inventors: Colin Glyn Jones
Original assignee: Siemens Limited
Priority date: 2000-12-11
Filing date: 2001-12-10
Publication date: 2002-06-20
Also published as: WO2002047803A3; AU2002220289A1

Abstract

A method and system for recovering diamonds (45) from diamond bearing material sich as kimberlite ore or sea shells, comprises the steps of subjecting the material to a contactless disintegration stage (26). By convecting electrical energy into a pressure pulse (33) in an energy converter (34.1), the propagating pressure pulse (33) causes the material to disintegrate into particles (47) smaller than the diamonds. The particles and diamonds are then separated by known techniques.

Description

A METHOD AND SYSTEM FOR RECOVERING DIAMONDS FROM DIAMOND BEARING MATERIAL

TECHNICAL FIELD

THIS invention relates to a system for and a method of enhancing

recovery of diamonds from bodies of foreign host materials, such as

kimberlite ore or sea shells in the case of off-shore mining operations.

BACKGROUND ART

It is well known that diamonds are mined from the sea bed in certain

parts of the world such as the South African and Namibian west

coasts. These diamonds may be trapped in sea shells and further

processing of the shells are required to prevent such entrapped

diamonds from being treated as waste together with the shells.

Up to now, these shells are processed through a preparation plant and

in some cases are mechanically disintegrated or crushed whereafter

the material is sieved to separate the resulting waste in the form of

disintegrated shells from the diamonds. A problem with this process is

that the diamonds are damaged or destroyed during the necessary

communitioh step, to liberate the diamonds. OBJECT OF THE INVENTION

Accordingly, it is an object of the present invention to provide an

alternative method and system for disintegrating diamond bearing

material to recover the diamonds therefrom and with which the

applicant believes the aforementioned disadvantages may at least be

alleviated.

SUMMARY OF THE INVENTION

According to the invention there is provided a method of recovering

diamonds from diamond bearing material, the method comprising the

steps of:

subjecting the material to a contactless disintegration stage; and

causing the material to be disintegrated into particles smaller

than the diamonds, thereby facilitating separation of the

particles and the diamonds.

The method may also include a further step of separating the particles

and the diamonds. The separating step may be performed by a

screening or size classification step.

In some embodiments the material may be kimberlite ore and in other

embodiments it may be sea shells. The material may be subjected to at least one pressure pulse,- to

disintegrate the material.

The at least one pressure pulse may be a Shockwave or burst of ultra-

sound and may be generated by applying high voltage signals between

electrodes in an energy converter.

The method may also include the step of repeatedly subjecting the

material to pressure pulses, thereby to disintegrate the material while

the diamonds remain intact.

According to another aspect of the present invention there is provided

a system for recovering diamonds from diamond bearing material, the

system comprising:

- means for generating pressure pulses;

means for subjecting the diamond bearing material to the pulses

to disintegrate the material into particles, while leaving the

diamonds intact; and

means for separating the particles and the diamonds.

The means for generating pressure pulses may comprise an electricity

to pressure pulse converter. The pressure pulses may comprise be high voltage generated

Shockwaves.

The system may comprise a train of converters and means for feeding

batches of the material in sequential manner past the converters.

Each converter may comprise an electrode arrangement which may be

submerged in a body of water in a suitable vessel.

BRIEF DESCRIPTION OF THE ACCOMPANYING DIAGRAMS

The invention will now further be described, by way of example only,

with reference to the accompanying diagrams wherein:

figure 1 is a schematic representation of a first embodiment of a

diamond recovery plant;

figure 2 is a diagrammatic representation of a contactless

disintegration stage according to the invention and

forming part of the diamond recovery plant; and

figure 3 is a schematic representation of a second embodiment of

the plant according to the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

A first embodiment of a marine diamond recovery system is generally designated by the reference numeral 10 in figure 1 .

The system comprises a first screening stage 12 where mined alluvium

14 comprising sea shells, some of which may entrap diamonds, is

received. Particles bigger than a first size S_T (S, = 19mm say) are

separated from smaller particles and the bigger particles 1 6 are fed to

waste.

The particles 18 equal to and smaller than the first size is fed to a

second screening stage 20. Here particles smaller than a second size

S₂ (S₂ = 2mm say) are separated from a product 24 which has a

particle size p wherein:

S₂ < p < S,.

In a conventional marine diamond recovery system, the

aforementioned product 24 would have been fed to a mechanical

disintegration or crushing stage (not shown) or directly to a FeSi

addition stage, thereafter to a dense media separation stage and then

to a final recovery stage, as will hereinafter be described. These

conventional systems have the disadvantages referred to in the

introduction of this specification. The system 10 according to the invention comprises a contactless

disintegration stage 26 for the product 24. The contactless

disintegration 26 stage is shown in more detail in figure 2.

The stage 26 comprises an endless conveyor 28 carrying a plurality of

equi-spaced containers 30.1 to 30. n for batches of the product 24. As

stated hereinbefore, the product 24 comprises shells having a particle

size p wherein

S_T < p < S₂

and some of which may entrap marine diamonds.

The conveyor is mounted about rollers 32.1 , 32.2 and 32.3 and has a

top run 28.1 and a return run 28.2. Just below the top run 28.1 there

are provided a plurality of spaced electric to pressure pulse energy

converters 34.1 to 34.4. The spacing between adjacent converters is

equal to the spacing between adjacent containers 30.1 to 30. n.

Each converter comprises a steel vessel 36 and an electrode

arrangement 38 extending into a body of water 40 in the vessel. A top

end of the vessel is closed by a membrane 42. The electrode

arrangements are energized by respective capacitors (not shown) in a

capacitor bank 31 . When energized, an arc is formed between the electrodes of an arrangement. This generates a pressure pulse 33

propagating through the water towards the membrane 42 and the

aforementioned containers holding the product 24. The pressure pulse

may be in the form of a Shockwave or burst of ultra-sound. The

converters may be of the kind described in a pamphlet of a company

TZN of Unterlϋss, Germany and entitled "High Performance Pulsed

Power Technology (HP³T) - Contactless disintegration of compound

materials."

The top ends of containers 30.2 to 30.5 are closed off by a lid

arrangement 35.

In use, the conveyor moves in a clockwise direction. As the containers

30.1 to 30. n move past charging point A, batches of product 24 are

charged into the containers.

When a container 30.2 is located opposite converter 34.1 , the

electrode arrangement of that converter is energized. The resulting

pulse 33 causes the shells at least partially to disintegrate. The

conveyor then moves on, so that container 30.1 is opposite converter

34.1 , container 30.2 is opposite converter 34.2 and container 30. n is

opposite changing point A The electrode arrangements of converters 34.1 and 34.2 are then energized either simultaneously or

sequentially, to further disintegrate the shells. This procedure is

repeated until each batch of the product 24 has been subjected to a

desired number of pulses. The number of pulses will depend on the

diamond bearing material. For sea shells, it is presently believed that

four to five pulses or stages should suffice.

As shown in the container 30.6, with the apparatus 26 hereinbefore

described and the method, the shells are disintegrated to particles 47

having a size of less than 1 mm or even 0.5mm, depending on the

parameters of the pulse such as frequency, repetition rate, energy,

pulse shape etc. The diamonds 45 remain intact and are released by

the disintegrated shells.

Referring again to figure 1 , the product 44 of the disintegration stage

26 is fed to a third screening stage 46. Here particles smaller than a

third size S₃ (S₃ = 2mm say) are separated from larger particles. The

smaller particles 48 are fed to waste.

The larger particles 50 are fed to the aforementioned and known FeSi

addition stage 52. Thereafter a dense media separation stage 54 is

used to separate particles that float and particles that sink. The floating particles 56 are fed to waste and the particles 58 that sank

are fed to an X-ray sorter and final recovery stage 60. Between

stages 54 and 60, the FeSi is recovered for recycling. It is believed

that the system and method according to the invention would use less

FeSi than the known systems and methods.

In stage 60 the diamonds 45 are separated from waste 64 in known

manner.

In the second embodiment of the plant shown at 100 in figure 3, the

contactless disintegration stage 26 is provided downstream of the FeSi

stage 52 and the dense media separation stage 54. A return path for

recovered FeSi is shown at 102 in figure 3.

It will be appreciated that there are many variations in detail on the

system and method according to the invention without departing from

the scope and spirit of the appended claims.

Claims

1 . A method of recovering diamonds from diamond bearing

material, the method comprising the steps of:

subjecting the material to a contactless disintegration

stage; and

causing the material to be disintegrated, thereby

facilitating separation of the particles and the diamonds.

2. A method as claimed in claim 1 wherein the material is

disintegrated into particles smaller than the diamonds.

3. A method as claimed in claim 1 or claim 2 including a further

step of separating the particles and the diamonds.

4. A method as claimed in claim 3 wherein the separating step

comprises a screening or size classification step.

5. A method as claimed in any one of the preceding steps wherein

the material comprises kimberlite ore.

6. A method as claimed in any one of claims 1 to 4 wherein the

material comprises sea shells.

7. A method as claimed in any one of the preceding claims wherein

the material is subjected to at least one pressure pulse in the

disintegration stage.

8. A method as claimed in claim 7 wherein the at least one

pressure pulse comprises a Shockwave or burst of ultra-sound.

9. A method as claimed in claim 7 or claim 8 wherein the at least

one pulse is generated by applying a high voltage signal

between spaced electrodes in an energy converter.

10. A method as claimed in any one of claims 7 to 9 wherein the

material is repeatedly subjected to pressure pulses, thereby to

disintegrate the material while the diamonds remain intact.

1 1 . A system for recovering diamonds from diamond bearing

material, the system comprising:

means for generating pressure pulses;

means for subjecting the diamond bearing material to at

least one pulse, to disintegrate the material into particles,

while leaving the diamonds intact; and

means for separating the particles and the diamonds.

12. A system as claimed in claim 1 1 wherein the means for

generating pressure pulses comprises at least one electricity to

pressure pulse converter.

13. A system as claimed in claim 1 1 or claim 12 wherein the

pressure pulses comprise high voltage generated Shockwaves.

14. A system as claimed in any one of claims 12 and 13 comprising

a train of converters and means for feeding batches of the

material in sequential manner past the converters.

1 5. A system as claimed in any one of claims 12 to 14 wherein

each converter comprises an electrode arrangement submerged

in a body of water in a suitable vessel.