AU606217B2

AU606217B2 - Separation of diamond particles from gangue

Info

Publication number: AU606217B2
Application number: AU23491/88A
Authority: AU
Inventors: Roberto De Pretto
Original assignee: De Beers Industrial Diamond Division Pty Ltd
Current assignee: De Beers Industrial Diamond Division Pty Ltd
Priority date: 1987-10-07
Filing date: 1988-10-06
Publication date: 1991-01-31
Anticipated expiration: 2008-10-06
Also published as: BR8805163A; GB8823489D0; GB2210686B; GB2210686A; AU2349188A

Description

_Y COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952- 0 62 1 COMPLETE SPECIFICATION (O ginal) This document contains the gamendments made under Section 49 and is correct for FOR OFFICE USE printing Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority: Related Art: 0 t 4 t t41n 4, II Ir i I I Name of Applicant: DE BEERS INDUSTRIAL DIAMOND DIVISION (PROPRIETARY) LIMITED Address of Applicant: 45 MAIN STREET, JOHANNESBURG, TRANSVAAL, SOUTH AFRICA Actual Inventor(s): ROBERTO DE PRETTO Address for Service: DAVIES COLLISON, ONE LITTLE COLLINS STREET, MELBOURNE, 3000, AUSTRALIA Complete Specification for the invention entitled: "SEPARATION OF DIAMOND PARTICLES FROM GANGUE" The following statement is a full description of this invention, including the best method of performing it known to me/us: Signature of dedarant(s) (no attestation required) Note: Initial all alterations. 2 BACKGROUND TO THE INVENTION- THIS invention relates to the separation of diamonds from gangue.

Diamonds may be separated from gangue using a variety of methods. One such method involves crushing the diamond-bearing ore to a predetermined size and making a suspension of the crushed mass with ferro-silicon particles in water. The suspension is pumped into a cyclone where it is separated into various fractions. The heavy fraction which issues from the bottom of the cyclone contains most of the heavy minerals and diamond.

The efficiency of a separation process of this kind is determined using tracer elements which have densities corresponding to the densities of the fractions produced by the separation process. In the case of separation of a i crushed diamond-bearing ore, the range of densities of the elements will correspond to the range of densities of the I fractions produced in the separation process, typically of 3 -3 3 -3 the order of 2,5 x 10 kgm to 3,5 x 10 kgm British patent specification 2,140,555 proposes an entirely different process for separating diamonds from gangue. In i this process, the particulate material which is to be sorted is subjected to incident laser radiation capable of causing Raman spectral activation. The scattered Raman radiation is detected using an appropriate detector and a determination is made as to whether or not the collected radiation is indicative of the presence of a diamond particle. Suitable ejection means are then actuated to separate the diamonds from the other particles.

I t (1 -i -3- The object of the present invention is to provide a tracer element which will be suitable for use in monitoring the efficiency of a separation process such as that proposed by the British specification referred to above.

A first aspect of the invention provides a method of monitoring the efficiency of a process in which diamond or diamond-containing particles are separated from gangue particles on the basis of Raman scattering of laser o radiation to which the particles are subjected, the ar o method comprising the steps of incorporating, in a mass on oo of particulate material which is to be sorted using the process, a plurality of tracer elements each of which on ia o comprises one or more diamonds at least partially o o embedded in a matrix.

The diamond or diamonds may be totally enclosed within the matrix, in which case the matrix should be transpareht to laser radiation. On the other hand, the o diamond or diamonds may be held in positions at the surface of the matrix so as to be exposed to the laser radiation. In the latter case, transparency to laser t i radiation is not essential and a material such as aluminium can be used for the matrix.

A second aspect of the invention provides a man-made tracer element for use in monitoring the efficiency of a process in which diamond or diamond-containing particles are separated from gangue particles on the basis of Raman scattering of laser radiation to which the particles are subjected, the tracer element comprising one or more diamonds at least partially embedded in a matrix which is not a naturally occurring diamond host.

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-3a- S '.ll further according to the invention, there is provided a man-made tracer element for use in monitoring the efficiency of a process in which diamond or diamondcontaining particles are separated from gangue particles on the basis of Raman scattering of laser radiation to which the particles are subjected, the tracer element comprising one or more diamonds at least partially embedded in a matrix.

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The diamond quality may vary from tracer element to tracer element, allowing the separation apparatus to be tuned to a high degree of accuracy.

It is proposed to convey the particles which are to be sorted on an endless conveyor belt. During their movement on the belt, the particles are subjected to the laser radiation and Raman scattering is detected. The invention proposes to incorporate tracer elements as specified above in the material of the belt in predetermined positions exposed to the laser radiation. As the belt moves in use, the particles in the belt will provide regular reference values permitting regular calibration of the detection apparatus to take place.

SPECIFI DSCeRIPTION Embodiments of the invention will now be described, by way of example only.

A tracer element is formed which is composed of one or more diamonds of the same or essentially the same quality Scompletely enclosed in a matrix which is transparent to the laser radiation used in the separation process described in i British patent specification 2,140,555. The diamonds can be natural or synthetic and the overall size of the tracer element will usually be in the range 2mm to 38mm. Any suitable robust matrix which is transparent to laser Sradiation can be used, toughened glass or an appropriate plastics being possibilities. The diamond(s) will typically t,,c occupy about 40% by volume of the total volume of the tracer element.

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J.2A A plurality of tracer elements are formed in this way and

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are mixed into particulate material which is to be sorted using the method described in the British patent specification. The effect of the separation process on the tracer elements is then monitored, for example by counting the tracer elements present in the separated fractions and in this way a determination can be made as to the efficiency of the process.

I The invention also proposes that batches of tracer elements i be formed, in the manner described above, with the diamonds i enclosed in the matrices in the different batches varying in quality. By determining which fractions the tracer elements having enclosed diamonds of different qualities are assigned to by the separation process, a more exact determination of the efficiency of the separation process, particularly as regards diamond quality, can be obtained. Using such batches, it would be possible to "tune" the separation apparatus to a fine degree of accuracy.

In another version of the invention, the diamond or diamonds are not completely enclosed in the matrix, but are partially *0t, embedded so as to be exposed at the surface of the matrix t4 St for laser irradiation. In this case, a suitable matrix would be of aluminium.

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Claims

1. A method of monitoring the efficiency of a process in which diamond or diamond-containing particles are separated from gangue particles on the basis of Raman scattering of laser radiation to which the particles are subjected, the method comprising the steps of incorporating, in a mass of particulate material which is to be sorted using the process, a plurality of tracer elements each of which comprises one or more diamonds at least partially embedded in a matrix. t

2. A method according to claim 1 when used to monitor the efficiency of a separation process as described in British patent specification 2,140,555.

3. A method according to either one of the preceding claims wherein each individual tracer element contains one or more diamonds of the same or essentially the same quality and wherein some of the tracer elements contain a diamond or diamonds differing in quality from the diamond or diamonds contained by other tracer elements.

4. A man-made tracer element for use in monitoring the efficiency of a process in which diamond or diamond- containing particles are separated from gangue particles on the basis of Raman scattering of laser radiation to 11 which the particles are subjected, the tracer element comprising one or more diamonds at least partially embedded in a matrix which is not a naturally occurring diamond host.

A tracer element according to claim 4, wherein the matrix is of aluminium. |1 U 901030,csspe.002,debeersspc,6 IS O I -7-

6. A man-made tracer element for use in monitoring the efficiency of a process in which diamond or diamond- I containing particles are separated from gangue particles on the basis of Raman scattering of laser radiation to which the particles are subjected, the tracer element comprising one or more diamonds at least partially ii embedded in a matrix. i

7. A tracer element according to claim 6, wherein the I jmatrix consists of aluminium, glass, or plastics. f

8. A tracer element according to any one of claims 4 to "7 wherein the diamond or diamonds occupy about 40% by volume of the tracer element. t I 1

9. A tracer element according to any one of claims 4 to 8 wherein the diamond or diamonds are natural.

A tracer elen.ent according to any one of claims 4 to 8 wherein the diamond or diamonds are synthetic.

11. A tracer element according to any one of claims 4 to wherein the element contains more than one diamond and the diamonds in the element are of the same or essentially the same quality.

12. A tracer element according to any one of claims 4 to 11 wherein the diamond or diamonds are completely I enclosed within a matrix which is transparent to laser radiation.

13. A tracer element according to any one of claims 4 to 11 wherein the diamond or diamonds are partially embedded in the matrix so as to be exposed at the surface of the matrix for laser radiation. S901030,c sspc.002,debccr,spc,7 /V T -8-

14. Apparatus for monitoring the efficiency of a process in which diamonds or diamond-containing particles are separated from gangue particles on the basis of Raman scattering of laser radiation to which the particles are subjected, the apparatus comprising a plurality of tracer i elements according to any one of claims 4 to 13 for j incorporation into a mass of particulate material which Sis to be sorted using the process, wherein the diamond or j diamonds in each individual tracer element are of the Ssame or essentially the same quality and wherein some of the tracer elements contain a diamond or diamonds differing in quality to the diamond or diamonds contained by other tracer elements. A fli ftI I

15. A tracer element according to any one of claims 4 to 13 when used to monitor the efficiency of a separation S i process as described in British patent specification 2,140,555.

16. Apparatus according to claim 14 when used to monitor o, the efficiency of a separation process as described in British patent specification 2,140,555. tctt

17. A tracer element according to any one of claims 4 to 13 when incorporated in predetermined, exposed positions on a conveyor belt on which particles to be sorted are conveyed in a separation process as described in British A patent specification 2,140,555, thereby to provide reference values for calibration purposes. 901030,c~sspc002,debeers.spc,8 2 -9

18. A man-made tracer element substantially as hereinbef ore described. with, e~ferenee te the aeeempany... DATED this 30th day of October, 1990 DE BEER INDUSTRIAL DIAMOND DIVISION (PROPRIETARY) LIMITED By its Patent Attorneys: DAVIES COLLISON IL 11 ii 4 901030,csSpe.002,dcbccrs,spc,9